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Kimura T, Miyashita K, Fukamachi I, Fukamachi K, Ogura K, Yokoyama E, Tsunekawa K, Nagasawa T, Ploug M, Yang Y, Song W, Young SG, Beigneux AP, Nakajima K, Murakami M. Quantification of lipoprotein lipase in mouse plasma with a sandwich enzyme-linked immunosorbent assay. J Lipid Res 2024; 65:100532. [PMID: 38608546 PMCID: PMC11017283 DOI: 10.1016/j.jlr.2024.100532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 03/03/2024] [Accepted: 03/06/2024] [Indexed: 04/14/2024] Open
Abstract
To support in vivo and in vitro studies of intravascular triglyceride metabolism in mice, we created rat monoclonal antibodies (mAbs) against mouse LPL. Two mAbs, mAbs 23A1 and 31A5, were used to develop a sandwich ELISA for mouse LPL. The detection of mouse LPL by the ELISA was linear in concentrations ranging from 0.31 ng/ml to 20 ng/ml. The sensitivity of the ELISA made it possible to quantify LPL in serum and in both pre-heparin and post-heparin plasma samples (including in grossly lipemic samples). LPL mass and activity levels in the post-heparin plasma were lower in Gpihbp1-/- mice than in wild-type mice. In both groups of mice, LPL mass and activity levels were positively correlated. Our mAb-based sandwich ELISA for mouse LPL will be useful for any investigator who uses mouse models to study LPL-mediated intravascular lipolysis.
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Affiliation(s)
- Takao Kimura
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan; Clinical Laboratory Center, Gunma University Hospital, Maebashi, Gunma, Japan.
| | | | | | | | - Kazumi Ogura
- Immuno-Biological Laboratories, Fujioka, Gunma, Japan
| | | | - Katsuhiko Tsunekawa
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan; Clinical Laboratory Center, Gunma University Hospital, Maebashi, Gunma, Japan
| | - Takumi Nagasawa
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan; Clinical Laboratory Center, Gunma University Hospital, Maebashi, Gunma, Japan
| | - Michael Ploug
- Finsen Laboratory, Copenhagen University Hospital - Rigshospitalet, Copenhagen, Denmark; Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan; Clinical Laboratory Center, Gunma University Hospital, Maebashi, Gunma, Japan
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2
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Yang Y, Beigneux AP, Song W, Nguyen LP, Jung H, Tu Y, Weston TA, Tran CM, Xie K, Yu RG, Tran AP, Miyashita K, Nakajima K, Murakami M, Chen YQ, Zhen EY, Kim JR, Kim PH, Birrane G, Tontonoz P, Ploug M, Konrad RJ, Fong LG, Young SG. Hypertriglyceridemia in Apoa5-/- mice results from reduced amounts of lipoprotein lipase in the capillary lumen. J Clin Invest 2023; 133:e172600. [PMID: 37824203 PMCID: PMC10688983 DOI: 10.1172/jci172600] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 10/05/2023] [Indexed: 10/14/2023] Open
Abstract
Why apolipoprotein AV (APOA5) deficiency causes hypertriglyceridemia has remained unclear, but we have suspected that the underlying cause is reduced amounts of lipoprotein lipase (LPL) in capillaries. By routine immunohistochemistry, we observed reduced LPL staining of heart and brown adipose tissue (BAT) capillaries in Apoa5-/- mice. Also, after an intravenous injection of LPL-, CD31-, and GPIHBP1-specific mAbs, the binding of LPL Abs to heart and BAT capillaries (relative to CD31 or GPIHBP1 Abs) was reduced in Apoa5-/- mice. LPL levels in the postheparin plasma were also lower in Apoa5-/- mice. We suspected that a recent biochemical observation - that APOA5 binds to the ANGPTL3/8 complex and suppresses its capacity to inhibit LPL catalytic activity - could be related to the low intracapillary LPL levels in Apoa5-/- mice. We showed that an ANGPTL3/8-specific mAb (IBA490) and APOA5 normalized plasma triglyceride (TG) levels and intracapillary LPL levels in Apoa5-/- mice. We also showed that ANGPTL3/8 detached LPL from heparan sulfate proteoglycans and GPIHBP1 on the surface of cells and that the LPL detachment was blocked by IBA490 and APOA5. Our studies explain the hypertriglyceridemia in Apoa5-/- mice and further illuminate the molecular mechanisms that regulate plasma TG metabolism.
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Affiliation(s)
- Ye Yang
- Department of Medicine and
- Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | | | | | | | | | | | | | | | | | | | | | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Yan Q. Chen
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Eugene Y. Zhen
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | | | | | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - Michael Ploug
- Finsen Laboratory, Copenhagen University Hospital–Rigshospitalet, Copenhagen, Denmark
- Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Robert J. Konrad
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | | | - Stephen G. Young
- Department of Medicine and
- Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
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Song W, Beigneux AP, Weston TA, Chen K, Yang Y, Nguyen LP, Guagliardo P, Jung H, Tran AP, Tu Y, Tran C, Birrane G, Miyashita K, Nakajima K, Murakami M, Tontonoz P, Jiang H, Ploug M, Fong LG, Young SG. The lipoprotein lipase that is shuttled into capillaries by GPIHBP1 enters the glycocalyx where it mediates lipoprotein processing. Proc Natl Acad Sci U S A 2023; 120:e2313825120. [PMID: 37871217 PMCID: PMC10623010 DOI: 10.1073/pnas.2313825120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 09/19/2023] [Indexed: 10/25/2023] Open
Abstract
Lipoprotein lipase (LPL), the enzyme that carries out the lipolytic processing of triglyceride-rich lipoproteins (TRLs), is synthesized by adipocytes and myocytes and secreted into the interstitial spaces. The LPL is then bound by GPIHBP1, a GPI-anchored protein of endothelial cells (ECs), and transported across ECs to the capillary lumen. The assumption has been that the LPL that is moved into capillaries remains attached to GPIHBP1 and that GPIHBP1 serves as a platform for TRL processing. In the current studies, we examined the validity of that assumption. We found that an LPL-specific monoclonal antibody (mAb), 88B8, which lacks the ability to detect GPIHBP1-bound LPL, binds avidly to LPL within capillaries. We further demonstrated, by confocal microscopy, immunogold electron microscopy, and nanoscale secondary ion mass spectrometry analyses, that the LPL detected by mAb 88B8 is located within the EC glycocalyx, distant from the GPIHBP1 on the EC plasma membrane. The LPL within the glycocalyx mediates the margination of TRLs along capillaries and is active in TRL processing, resulting in the delivery of lipoprotein-derived lipids to immediately adjacent parenchymal cells. Thus, the LPL that GPIHBP1 transports into capillaries can detach and move into the EC glycocalyx, where it functions in the intravascular processing of TRLs.
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Affiliation(s)
- Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Anne P. Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Thomas A. Weston
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Kai Chen
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
- School of Molecular Sciences, The University of Western Australia, Perth6009, Australia
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Le Phuong Nguyen
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Paul Guagliardo
- Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Perth6009, Australia
| | - Hyesoo Jung
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Anh P. Tran
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Caitlyn Tran
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA02215
| | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University School of Medicine, Maebashi371-8511, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University School of Medicine, Maebashi371-8511, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University School of Medicine, Maebashi371-8511, Japan
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA90095
| | - Haibo Jiang
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Michael Ploug
- Finsen Laboratory, Copenhagen University Hospital-Rigshospitalet, Copenhagen NDK–2200, Denmark
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen NDK-2200, Denmark
| | - Loren G. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Stephen G. Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA90095
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4
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Song W, Yang Y, Heizer P, Tu Y, Weston TA, Kim JR, Munguia P, Jung H, Fong JLC, Tran C, Ploug M, Beigneux AP, Young SG, Fong LG. Intracapillary LPL levels in brown adipose tissue, visualized with an antibody-based approach, are regulated by ANGPTL4 at thermoneutral temperatures. Proc Natl Acad Sci U S A 2023; 120:e2219833120. [PMID: 36787365 PMCID: PMC9974459 DOI: 10.1073/pnas.2219833120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 01/18/2023] [Indexed: 02/15/2023] Open
Abstract
Lipoprotein lipase (LPL) is secreted into the interstitial spaces by parenchymal cells and then transported into capillaries by GPIHBP1. LPL carries out the lipolytic processing of triglyceride (TG)-rich lipoproteins (TRLs), but the tissue-specific regulation of LPL is incompletely understood. Plasma levels of TG hydrolase activity after heparin injection are often used to draw inferences about intravascular LPL levels, but the validity of these inferences is unclear. Moreover, plasma TG hydrolase activity levels are not helpful for understanding LPL regulation in specific tissues. Here, we sought to elucidate LPL regulation under thermoneutral conditions (30 °C). To pursue this objective, we developed an antibody-based method to quantify (in a direct fashion) LPL levels inside capillaries. At 30 °C, intracapillary LPL levels fell sharply in brown adipose tissue (BAT) but not heart. The reduced intracapillary LPL levels were accompanied by reduced margination of TRLs along capillaries. ANGPTL4 expression in BAT increased fourfold at 30 °C, suggesting a potential explanation for the lower intracapillary LPL levels. Consistent with that idea, Angptl4 deficiency normalized both LPL levels and TRL margination in BAT at 30 °C. In Gpihbp1-/- mice housed at 30 °C, we observed an ANGPTL4-dependent decrease in LPL levels within the interstitial spaces of BAT, providing in vivo proof that ANGPTL4 regulates LPL levels before LPL transport into capillaries. In conclusion, our studies have illuminated intracapillary LPL regulation under thermoneutral conditions. Our approaches will be useful for defining the impact of genetic variation and metabolic disease on intracapillary LPL levels and TRL processing.
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Affiliation(s)
- Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Patrick Heizer
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Thomas A. Weston
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Joonyoung R. Kim
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Priscilla Munguia
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Hyesoo Jung
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Jared L.-C. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Caitlyn Tran
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Michael Ploug
- Finsen Laboratory, RigshospitaletDK-2200Copenhagen N, Denmark
- Biotech Research and Innovation Centre, University of CopenhagenDK-220Copenhagen N, Denmark
| | - Anne P. Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Stephen G. Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Loren G. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
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5
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Young SG, Song W, Yang Y, Birrane G, Jiang H, Beigneux AP, Ploug M, Fong LG. A protein of capillary endothelial cells, GPIHBP1, is crucial for plasma triglyceride metabolism. Proc Natl Acad Sci U S A 2022; 119:e2211136119. [PMID: 36037340 PMCID: PMC9457329 DOI: 10.1073/pnas.2211136119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 07/18/2022] [Indexed: 11/18/2022] Open
Abstract
GPIHBP1, a protein of capillary endothelial cells (ECs), is a crucial partner for lipoprotein lipase (LPL) in the lipolytic processing of triglyceride-rich lipoproteins. GPIHBP1, which contains a three-fingered cysteine-rich LU (Ly6/uPAR) domain and an intrinsically disordered acidic domain (AD), captures LPL from within the interstitial spaces (where it is secreted by parenchymal cells) and shuttles it across ECs to the capillary lumen. Without GPIHBP1, LPL remains stranded within the interstitial spaces, causing severe hypertriglyceridemia (chylomicronemia). Biophysical studies revealed that GPIHBP1 stabilizes LPL structure and preserves LPL activity. That discovery was the key to crystallizing the GPIHBP1-LPL complex. The crystal structure revealed that GPIHBP1's LU domain binds, largely by hydrophobic contacts, to LPL's C-terminal lipid-binding domain and that the AD is positioned to project across and interact, by electrostatic forces, with a large basic patch spanning LPL's lipid-binding and catalytic domains. We uncovered three functions for GPIHBP1's AD. First, it accelerates the kinetics of LPL binding. Second, it preserves LPL activity by inhibiting unfolding of LPL's catalytic domain. Third, by sheathing LPL's basic patch, the AD makes it possible for LPL to move across ECs to the capillary lumen. Without the AD, GPIHBP1-bound LPL is trapped by persistent interactions between LPL and negatively charged heparan sulfate proteoglycans (HSPGs) on the abluminal surface of ECs. The AD interrupts the HSPG interactions, freeing LPL-GPIHBP1 complexes to move across ECs to the capillary lumen. GPIHBP1 is medically important; GPIHBP1 mutations cause lifelong chylomicronemia, and GPIHBP1 autoantibodies cause some acquired cases of chylomicronemia.
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Affiliation(s)
- Stephen G. Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - Haibo Jiang
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Anne P. Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen 2200N, Denmark
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Loren G. Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
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6
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Song W, Beigneux AP, Winther AML, Kristensen KK, Grønnemose AL, Yang Y, Tu Y, Munguia P, Morales J, Jung H, de Jong PJ, Jung CJ, Miyashita K, Kimura T, Nakajima K, Murakami M, Birrane G, Jiang H, Tontonoz P, Ploug M, Fong LG, Young SG. Electrostatic sheathing of lipoprotein lipase is essential for its movement across capillary endothelial cells. J Clin Invest 2022; 132:157500. [PMID: 35229724 PMCID: PMC8884915 DOI: 10.1172/jci157500] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 01/19/2022] [Indexed: 12/18/2022] Open
Abstract
GPIHBP1, an endothelial cell (EC) protein, captures lipoprotein lipase (LPL) within the interstitial spaces (where it is secreted by myocytes and adipocytes) and transports it across ECs to its site of action in the capillary lumen. GPIHBP1’s 3-fingered LU domain is required for LPL binding, but the function of its acidic domain (AD) has remained unclear. We created mutant mice lacking the AD and found severe hypertriglyceridemia. As expected, the mutant GPIHBP1 retained the capacity to bind LPL. Unexpectedly, however, most of the GPIHBP1 and LPL in the mutant mice was located on the abluminal surface of ECs (explaining the hypertriglyceridemia). The GPIHBP1-bound LPL was trapped on the abluminal surface of ECs by electrostatic interactions between the large basic patch on the surface of LPL and negatively charged heparan sulfate proteoglycans (HSPGs) on the surface of ECs. GPIHBP1 trafficking across ECs in the mutant mice was normalized by disrupting LPL-HSPG electrostatic interactions with either heparin or an AD peptide. Thus, GPIHBP1’s AD plays a crucial function in plasma triglyceride metabolism; it sheathes LPL’s basic patch on the abluminal surface of ECs, thereby preventing LPL-HSPG interactions and freeing GPIHBP1-LPL complexes to move across ECs to the capillary lumen.
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Affiliation(s)
- Wenxin Song
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Anne-Marie L Winther
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Kristian K Kristensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Anne L Grønnemose
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Ye Yang
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Priscilla Munguia
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Jazmin Morales
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Hyesoo Jung
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Pieter J de Jong
- Children's Hospital Oakland Research Institute, Oakland, California, USA
| | - Cris J Jung
- Children's Hospital Oakland Research Institute, Oakland, California, USA
| | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan.,Immuno-Biological Laboratories (IBL), Fujioka, Gunma, Japan
| | - Takao Kimura
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Haibo Jiang
- Department of Chemistry, The University of Hong Kong, Hong Kong
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California, USA.,Department of Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
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7
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Lutz J, Dunaj-Kazmierowska M, Arcan S, Kassner U, Miyashita K, Murakami M, Ploug M, Fong LG, Young SG, Nakajima K, Beigneux AP. Chylomicronemia From GPIHBP1 Autoantibodies Successfully Treated With Rituximab: A Case Report. Ann Intern Med 2020; 173:764-765. [PMID: 32777186 PMCID: PMC8174005 DOI: 10.7326/l20-0327] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Jens Lutz
- Central Rhine Hospital Group, Koblenz, Germany (J.L., M.D., S.A.)
| | | | - Sven Arcan
- Central Rhine Hospital Group, Koblenz, Germany (J.L., M.D., S.A.)
| | - Ursula Kassner
- Charité University Medicine Campus Virchow, Berlin, Germany (U.K.)
| | - Kazuya Miyashita
- Gunma University Graduate School of Medicine, Maebashi, Japan (K.M., M.M., K.N.)
| | - Masami Murakami
- Gunma University Graduate School of Medicine, Maebashi, Japan (K.M., M.M., K.N.)
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (M.P.)
| | - Loren G Fong
- University of California, Los Angeles, Los Angeles, California (L.G.F., S.G.Y., A.P.B.)
| | - Stephen G Young
- University of California, Los Angeles, Los Angeles, California (L.G.F., S.G.Y., A.P.B.)
| | - Katsuyuki Nakajima
- Gunma University Graduate School of Medicine, Maebashi, Japan (K.M., M.M., K.N.)
| | - Anne P Beigneux
- University of California, Los Angeles, Los Angeles, California (L.G.F., S.G.Y., A.P.B.)
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8
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Miyashita K, Lutz J, Hudgins LC, Toib D, Ashraf AP, Song W, Murakami M, Nakajima K, Ploug M, Fong LG, Young SG, Beigneux AP. Chylomicronemia from GPIHBP1 autoantibodies. J Lipid Res 2020; 61:1365-1376. [PMID: 32948662 PMCID: PMC7604722 DOI: 10.1194/jlr.r120001116] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Some cases of chylomicronemia are caused by autoantibodies against glycosylphosphatidylinositol-anchored HDL binding protein 1 (GPIHBP1), an endothelial cell protein that shuttles LPL to the capillary lumen. GPIHBP1 autoantibodies prevent binding and transport of LPL by GPIHBP1, thereby disrupting the lipolytic processing of triglyceride-rich lipoproteins. Here, we review the "GPIHBP1 autoantibody syndrome" and summarize clinical and laboratory findings in 22 patients. All patients had GPIHBP1 autoantibodies and chylomicronemia, but we did not find a correlation between triglyceride levels and autoantibody levels. Many of the patients had a history of pancreatitis, and most had clinical and/or serological evidence of autoimmune disease. IgA autoantibodies were present in all patients, and IgG4 autoantibodies were present in 19 of 22 patients. Patients with GPIHBP1 autoantibodies had low plasma LPL levels, consistent with impaired delivery of LPL into capillaries. Plasma levels of GPIHBP1, measured with a monoclonal antibody-based ELISA, were very low in 17 patients, reflecting the inability of the ELISA to detect GPIHBP1 in the presence of autoantibodies (immunoassay interference). However, GPIHBP1 levels were very high in five patients, indicating little capacity of their autoantibodies to interfere with the ELISA. Recently, several GPIHBP1 autoantibody syndrome patients were treated successfully with rituximab, resulting in the disappearance of GPIHBP1 autoantibodies and normalization of both plasma triglyceride and LPL levels. The GPIHBP1 autoantibody syndrome should be considered in any patient with newly acquired and unexplained chylomicronemia.
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Affiliation(s)
- Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
- Immuno-Biological Laboratories (IBL), Fujioka, Gunma, Japan
| | - Jens Lutz
- Medical Clinic, Nephrology-Infectious Diseases, Central Rhine Hospital Group, Koblenz, Germany
| | - Lisa C Hudgins
- Rogosin Institute, Weill Cornell Medical College, New York, NY, USA
| | - Dana Toib
- Department of Pediatrics, Drexel University, Philadelphia, PA, USA
- Section of Pediatric Rheumatology, St. Christopher's Hospital for Children, Philadelphia, PA, USA
| | - Ambika P Ashraf
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark
- Biotechnology Research Innovation Center, Copenhagen University, Copenhagen, Denmark
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
- Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
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9
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Luz JG, Beigneux AP, Asamoto DK, He C, Song W, Allan CM, Morales J, Tu Y, Kwok A, Cottle T, Meiyappan M, Fong LG, Kim JE, Ploug M, Young SG, Birrane G. The structural basis for monoclonal antibody 5D2 binding to the tryptophan-rich loop of lipoprotein lipase. J Lipid Res 2020; 61:1347-1359. [PMID: 32690595 DOI: 10.1194/jlr.ra120000993] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
For three decades, the LPL-specific monoclonal antibody 5D2 has been used to investigate LPL structure/function and intravascular lipolysis. 5D2 has been used to measure LPL levels, block the triglyceride hydrolase activity of LPL, and prevent the propensity of concentrated LPL preparations to form homodimers. Two early studies on the location of the 5D2 epitope reached conflicting conclusions, but the more convincing report suggested that 5D2 binds to a tryptophan (Trp)-rich loop in the carboxyl terminus of LPL. The same loop had been implicated in lipoprotein binding. Using surface plasmon resonance, we showed that 5D2 binds with high affinity to a synthetic LPL peptide containing the Trp-rich loop of human (but not mouse) LPL. We also showed, by both fluorescence and UV resonance Raman spectroscopy, that the Trp-rich loop binds lipids. Finally, we used X-ray crystallography to solve the structure of the Trp-rich peptide bound to a 5D2 Fab fragment. The Trp-rich peptide contains a short α-helix, with two Trps projecting into the antigen recognition site. A proline substitution in the α-helix, found in mouse LPL, is expected to interfere with several hydrogen bonds, explaining why 5D2 cannot bind to mouse LPL.
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Affiliation(s)
- John G Luz
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - DeeAnn K Asamoto
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, CA, USA
| | - Cuiwen He
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Wenxin Song
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Christopher M Allan
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Jazmin Morales
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Yiping Tu
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Adam Kwok
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Thomas Cottle
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Muthuraman Meiyappan
- Analytical Development, Pharmaceutical Sciences, Takeda Pharmaceutical Company, Lexington, MA, USA
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Judy E Kim
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, CA, USA
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA .,Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
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10
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Ashraf AP, Miyashita K, Nakajima K, Murakami M, Hegele RA, Ploug M, Fong LG, Young SG, Beigneux AP. Intermittent chylomicronemia caused by intermittent GPIHBP1 autoantibodies. J Clin Lipidol 2020; 14:197-200. [PMID: 32107180 DOI: 10.1016/j.jacl.2020.01.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 01/22/2020] [Accepted: 01/27/2020] [Indexed: 02/06/2023]
Abstract
Chylomicronemia caused by a deficiency in lipoprotein lipase (LPL) or GPIHBP1 (the endothelial cell protein that transports LPL to the capillary lumen) is typically diagnosed during childhood and represents a serious, lifelong medical problem. Affected patients have high plasma triglyceride levels (>1500 mg/dL) and a high risk of acute pancreatitis. However, chylomicronemia frequently presents later in life in the absence of an obvious monogenic cause. In these cases, the etiology for the chylomicronemia is presumed to be "multifactorial" (involving diabetes, drugs, alcohol, or polygenic factors), but on a practical level, the underlying cause generally remains a mystery. Here, we describe a 15-year-old female with chylomicronemia caused by GPIHBP1 autoantibodies (which abolish LPL transport to the capillary lumen). Remarkably, chylomicronemia in this patient was intermittent, interspersed between periods when the plasma triglyceride levels were normal. GPIHBP1 autoantibodies were easily detectable during episodes of chylomicronemia but were undetectable during periods of normotriglyceridemia. During the episodes of chylomicronemia (when GPIHBP1 autoantibodies were present), plasma LPL levels were low, consistent with impaired LPL transport into capillaries. During periods of normotriglyceridemia, when GPIHBP1 autoantibodies were absent, plasma LPL levels normalized. Because the chylomicronemia in this patient was accompanied by debilitating episodes of acute pancreatitis, the patient was ultimately treated with immunosuppressive drugs, which resulted in disappearance of GPIHBP1 autoantibodies and normalization of plasma triglyceride levels. GPIHBP1 autoantibodies need to be considered in patients who present with unexplained acquired cases of chylomicronemia.
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Affiliation(s)
- Ambika P Ashraf
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA.
| | | | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Robert A Hegele
- Robarts Research Institute, Western University, London, Ontario, Canada
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen N, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen N, Denmark
| | - Loren G Fong
- Departments of Medicine and Human Genetics, David Geffen School of Medicine, University of California Los Angeles, CA, USA
| | - Stephen G Young
- Departments of Medicine and Human Genetics, David Geffen School of Medicine, University of California Los Angeles, CA, USA; Departments of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
| | - Anne P Beigneux
- Departments of Medicine and Human Genetics, David Geffen School of Medicine, University of California Los Angeles, CA, USA.
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11
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Young SG, Fong LG, Beigneux AP, Allan CM, He C, Jiang H, Nakajima K, Meiyappan M, Birrane G, Ploug M. GPIHBP1 and Lipoprotein Lipase, Partners in Plasma Triglyceride Metabolism. Cell Metab 2019; 30:51-65. [PMID: 31269429 PMCID: PMC6662658 DOI: 10.1016/j.cmet.2019.05.023] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Lipoprotein lipase (LPL), identified in the 1950s, has been studied intensively by biochemists, physiologists, and clinical investigators. These efforts uncovered a central role for LPL in plasma triglyceride metabolism and identified LPL mutations as a cause of hypertriglyceridemia. By the 1990s, with an outline for plasma triglyceride metabolism established, interest in triglyceride metabolism waned. In recent years, however, interest in plasma triglyceride metabolism has awakened, in part because of the discovery of new molecules governing triglyceride metabolism. One such protein-and the focus of this review-is GPIHBP1, a protein of capillary endothelial cells. GPIHBP1 is LPL's essential partner: it binds LPL and transports it to the capillary lumen; it is essential for lipoprotein margination along capillaries, allowing lipolysis to proceed; and it preserves LPL's structure and activity. Recently, GPIHBP1 was the key to solving the structure of LPL. These developments have transformed the models for intravascular triglyceride metabolism.
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Affiliation(s)
- Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Christopher M Allan
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Cuiwen He
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Haibo Jiang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; School of Molecular Sciences, University of Western Australia, Crawley 6009, Australia
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Department of Medicine, Maebashi, Gunma 371-0805, Japan
| | - Muthuraman Meiyappan
- Discovery Therapeutics, Takeda Pharmaceutical Company Ltd., Cambridge, MA 02142, USA
| | - Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen DK-2200, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen DK-2200, Denmark.
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12
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Hu X, Matsumoto K, Jung RS, Weston TA, Heizer PJ, He C, Sandoval NP, Allan CM, Tu Y, Vinters HV, Liau LM, Ellison RM, Morales JE, Baufeld LJ, Bayley NA, He L, Betsholtz C, Beigneux AP, Nathanson DA, Gerhardt H, Young SG, Fong LG, Jiang H. GPIHBP1 expression in gliomas promotes utilization of lipoprotein-derived nutrients. eLife 2019; 8:e47178. [PMID: 31169500 PMCID: PMC6594755 DOI: 10.7554/elife.47178] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 06/05/2019] [Indexed: 12/25/2022] Open
Abstract
GPIHBP1, a GPI-anchored protein of capillary endothelial cells, binds lipoprotein lipase (LPL) within the subendothelial spaces and shuttles it to the capillary lumen. GPIHBP1-bound LPL is essential for the margination of triglyceride-rich lipoproteins (TRLs) along capillaries, allowing the lipolytic processing of TRLs to proceed. In peripheral tissues, the intravascular processing of TRLs by the GPIHBP1-LPL complex is crucial for the generation of lipid nutrients for adjacent parenchymal cells. GPIHBP1 is absent from the capillaries of the brain, which uses glucose for fuel; however, GPIHBP1 is expressed in the capillaries of mouse and human gliomas. Importantly, the GPIHBP1 in glioma capillaries captures locally produced LPL. We use NanoSIMS imaging to show that TRLs marginate along glioma capillaries and that there is uptake of TRL-derived lipid nutrients by surrounding glioma cells. Thus, GPIHBP1 expression in gliomas facilitates TRL processing and provides a source of lipid nutrients for glioma cells.
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Affiliation(s)
- Xuchen Hu
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Ken Matsumoto
- VIB-KU Leuven Center for Cancer Biology (CCB)LeuvenBelgium
| | - Rachel S Jung
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Thomas A Weston
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Patrick J Heizer
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Cuiwen He
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Norma P Sandoval
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Christopher M Allan
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Yiping Tu
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Harry V Vinters
- Department of Pathology and Laboratory Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Linda M Liau
- Department of Neurosurgery, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
- Jonsson Comprehensive Cancer Center (JCCC), David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Rochelle M Ellison
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Jazmin E Morales
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Lynn J Baufeld
- Department of Molecular and Medical Pharmacology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
- Ahmanson Translational Imaging Division, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Nicholas A Bayley
- Department of Molecular and Medical Pharmacology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
- Ahmanson Translational Imaging Division, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Liqun He
- Department of Immunology, Genetics and Pathology, Rudbeck LaboratoryUppsala UniversityUppsalaSweden
| | - Christer Betsholtz
- Department of Immunology, Genetics and Pathology, Rudbeck LaboratoryUppsala UniversityUppsalaSweden
- Integrated Cardio Metabolic Centre (ICMC)Karolinska InstitutetHuddingeSweden
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - David A Nathanson
- Department of Molecular and Medical Pharmacology, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
- Ahmanson Translational Imaging Division, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Holger Gerhardt
- VIB-KU Leuven Center for Cancer Biology (CCB)LeuvenBelgium
- Max Delbrück Center for Molecular MedicineBerlinGermany
| | - Stephen G Young
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
- Department of Human Genetics, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Loren G Fong
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
| | - Haibo Jiang
- Department of Medicine, David Geffen School of MedicineUniversity of California, Los AngelesLos AngelesUnited States
- School of Molecular SciencesUniversity of Western AustraliaPerthAustralia
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13
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Allan CM, Heizer PJ, Tu Y, Sandoval NP, Jung RS, Morales JE, Sajti E, Troutman TD, Saunders TL, Cusanovich DA, Beigneux AP, Romanoski CE, Fong LG, Young SG. An upstream enhancer regulates Gpihbp1 expression in a tissue-specific manner. J Lipid Res 2019; 60:869-879. [PMID: 30598475 PMCID: PMC6446700 DOI: 10.1194/jlr.m091322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 12/02/2018] [Indexed: 01/22/2023] Open
Abstract
Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1), the protein that shuttles LPL to the capillary lumen, is essential for plasma triglyceride metabolism. When GPIHBP1 is absent, LPL remains stranded within the interstitial spaces and plasma triglyceride hydrolysis is impaired, resulting in severe hypertriglyceridemia. While the functions of GPIHBP1 in intravascular lipolysis are reasonably well understood, no one has yet identified DNA sequences regulating GPIHBP1 expression. In the current studies, we identified an enhancer element located ∼3.6 kb upstream from exon 1 of mouse Gpihbp1. To examine the importance of the enhancer, we used CRISPR/Cas9 genome editing to create mice lacking the enhancer (Gpihbp1Enh/Enh). Removing the enhancer reduced Gpihbp1 expression by >90% in the liver and by ∼50% in heart and brown adipose tissue. The reduced expression of GPIHBP1 was insufficient to prevent LPL from reaching the capillary lumen, and it did not lead to hypertriglyceridemia-even when mice were fed a high-fat diet. Compound heterozygotes (Gpihbp1Enh/- mice) displayed further reductions in Gpihbp1 expression and exhibited partial mislocalization of LPL (increased amounts of LPL within the interstitial spaces of the heart), but the plasma triglyceride levels were not perturbed. The enhancer element that we identified represents the first insight into DNA sequences controlling Gpihbp1 expression.
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Affiliation(s)
- Christopher M Allan
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Patrick J Heizer
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Yiping Tu
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Norma P Sandoval
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Rachel S Jung
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Jazmin E Morales
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Eniko Sajti
- Department of Pediatrics, Division of Neurology, Rady Children's Hospital, University of California, San Diego, San Diego, CA 92123
| | - Ty D Troutman
- Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Thomas L Saunders
- University of Michigan Transgenic Animal Model Core, Department of Medicine, University of Michigan Medical School, Ann Arbor, MI 48109
| | - Darren A Cusanovich
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721
| | - Anne P Beigneux
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095
| | - Casey E Romanoski
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721.
| | - Loren G Fong
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095.
| | - Stephen G Young
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA 90095; Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095.
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14
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Miyashita K, Fukamachi I, Machida T, Nakajima K, Young SG, Murakami M, Beigneux AP, Nakajima K. An ELISA for quantifying GPIHBP1 autoantibodies and making a diagnosis of the GPIHBP1 autoantibody syndrome. Clin Chim Acta 2018; 487:174-178. [PMID: 30287259 DOI: 10.1016/j.cca.2018.09.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 09/27/2018] [Accepted: 09/28/2018] [Indexed: 01/04/2023]
Abstract
BACKGROUND Autoantibodies against GPIHBP1, the endothelial cell transporter for lipoprotein lipase (LPL), cause severe hypertriglyceridemia ("GPIHBP1 autoantibody syndrome"). Affected patients have low serum GPIHBP1 and LPL levels. We report the development of a sensitive and specific ELISA, suitable for routine clinical use, to detect GPIHBP1 autoantibodies in serum and plasma. METHODS Serum and plasma samples were added to wells of an ELISA plate that had been coated with recombinant human GPIHBP1. GPIHBP1 autoantibodies bound to GPIHBP1 were detected with an HRP-labeled antibody against human immunoglobulin. Sensitivity, specificity, and reproducibility of the ELISA was evaluated with plasma or serum samples from patients with the GPIHBP1 autoantibody syndrome. RESULTS A solid-phase ELISA to detect and quantify GPIHBP1 autoantibodies in human plasma and serum was developed. Spiking recombinant human GPIHBP1 into the samples reduced the ability of the ELISA to detect GPIHBP1 autoantibodies. The ELISA is reproducible and sensitive; it can detect GPIHBP1 autoantibodies in samples diluted by >1000-fold. CONCLUSION We have developed a sensitive and specific ELISA for detecting GPIHBP1 autoantibodies in human serum and plasma; this assay will make it possible to rapidly diagnose the GPIHBP1 autoantibody syndrome.
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Affiliation(s)
| | | | - Tetsuo Machida
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Kiyomi Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Stephen G Young
- Department of Medicine and David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90025, United States; Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90025, United States
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Anne P Beigneux
- Department of Medicine and David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90025, United States.
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
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15
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He C, Weston TA, Jung RS, Heizer P, Larsson M, Hu X, Allan CM, Tontonoz P, Reue K, Beigneux AP, Ploug M, Holme A, Kilburn M, Guagliardo P, Ford DA, Fong LG, Young SG, Jiang H. NanoSIMS Analysis of Intravascular Lipolysis and Lipid Movement across Capillaries and into Cardiomyocytes. Cell Metab 2018; 27:1055-1066.e3. [PMID: 29719224 PMCID: PMC5945212 DOI: 10.1016/j.cmet.2018.03.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 02/16/2018] [Accepted: 03/24/2018] [Indexed: 10/17/2022]
Abstract
The processing of triglyceride-rich lipoproteins (TRLs) in capillaries provides lipids for vital tissues, but our understanding of TRL metabolism is limited, in part because TRL processing and lipid movement have never been visualized. To investigate the movement of TRL-derived lipids in the heart, mice were given an injection of [2H]triglyceride-enriched TRLs, and the movement of 2H-labeled lipids across capillaries and into cardiomyocytes was examined by NanoSIMS. TRL processing and lipid movement in tissues were extremely rapid. Within 30 s, TRL-derived lipids appeared in the subendothelial spaces and in the lipid droplets and mitochondria of cardiomyocytes. Enrichment of 2H in capillary endothelial cells was not greater than in cardiomyocytes, implying that endothelial cells may not be a control point for lipid movement into cardiomyocytes. Remarkably, a deficiency of the putative fatty acid transport protein CD36, which is expressed highly in capillary endothelial cells, did not impede entry of TRL-derived lipids into cardiomyocytes.
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Affiliation(s)
- Cuiwen He
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Thomas A Weston
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Rachel S Jung
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Patrick Heizer
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mikael Larsson
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Xuchen Hu
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Christopher M Allan
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Karen Reue
- Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Anne P Beigneux
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark; Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Andrea Holme
- Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Perth 6009, Australia
| | - Matthew Kilburn
- Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Perth 6009, Australia
| | - Paul Guagliardo
- Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Perth 6009, Australia
| | - David A Ford
- Department of Biochemistry and Molecular Biology, Center for Cardiovascular Research, Saint Louis University, St. Louis, MO 63104, USA
| | - Loren G Fong
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Stephen G Young
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Haibo Jiang
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Perth 6009, Australia.
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16
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Larsson M, Allan CM, Heizer PJ, Tu Y, Sandoval NP, Jung RS, Walzem RL, Beigneux AP, Young SG, Fong LG. Impaired thermogenesis and sharp increases in plasma triglyceride levels in GPIHBP1-deficient mice during cold exposure. J Lipid Res 2018; 59:706-713. [PMID: 29449313 DOI: 10.1194/jlr.m083832] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Indexed: 01/11/2023] Open
Abstract
Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1), an endothelial cell protein, binds LPL in the subendothelial spaces and transports it to the capillary lumen. In Gpihbp1-/- mice, LPL remains stranded in the subendothelial spaces, causing hypertriglyceridemia, but how Gpihbp1-/- mice respond to metabolic stress (e.g., cold exposure) has never been studied. In wild-type mice, cold exposure increases LPL-mediated processing of triglyceride-rich lipoproteins (TRLs) in brown adipose tissue (BAT), providing fuel for thermogenesis and leading to lower plasma triglyceride levels. We suspected that defective TRL processing in Gpihbp1-/- mice might impair thermogenesis and blunt the fall in plasma triglyceride levels. Indeed, Gpihbp1-/- mice exhibited cold intolerance, but the effects on plasma triglyceride levels were paradoxical. Rather than falling, the plasma triglyceride levels increased sharply (from ∼4,000 to ∼15,000 mg/dl), likely because fatty acid release by peripheral tissues drives hepatic production of TRLs that cannot be processed. We predicted that the sharp increase in plasma triglyceride levels would not occur in Gpihbp1-/-Angptl4-/- mice, where LPL activity is higher and baseline plasma triglyceride levels are lower. Indeed, the plasma triglyceride levels in Gpihbp1-/-Angptl4-/- mice fell during cold exposure. Metabolic studies revealed increased levels of TRL processing in the BAT of Gpihbp1-/-Angptl4-/- mice.
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Affiliation(s)
- Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095.
| | - Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Patrick J Heizer
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Yiping Tu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Norma P Sandoval
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Rosemary L Walzem
- Department of Poultry Science and Faculty of Nutrition, Texas A&M University, College Station, TX 77843
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095; Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095.
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095.
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Miyashita K, Fukamachi I, Nagao M, Ishida T, Kobayashi J, Machida T, Nakajima K, Murakami M, Ploug M, Beigneux AP, Young SG, Nakajima K. An enzyme-linked immunosorbent assay for measuring GPIHBP1 levels in human plasma or serum. J Clin Lipidol 2017; 12:203-210.e1. [PMID: 29246728 DOI: 10.1016/j.jacl.2017.10.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 10/23/2017] [Accepted: 10/24/2017] [Indexed: 12/17/2022]
Abstract
BACKGROUND Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), a glycosylphosphatidylinositol (GPI)-anchored protein of capillary endothelial cells, transports lipoprotein lipase to the capillary lumen and is essential for the lipolytic processing of triglyceride-rich lipoproteins. OBJECTIVE Because some GPI-anchored proteins have been detected in plasma, we tested whether GPIHBP1 is present in human blood and whether GPIHBP1 deficiency or a history of cardiovascular disease affected GPIHBP1 circulating levels. METHODS We developed 2 monoclonal antibodies against GPIHBP1 and used the antibodies to establish a sandwich enzyme-linked immunosorbent assay (ELISA) to measure GPIHBP1 levels in human blood. RESULTS The GPIHBP1 ELISA was linear in the 8 to 500 pg/mL range and allowed the quantification of GPIHBP1 in serum and in pre- and post-heparin plasma (including lipemic samples). GPIHBP1 was undetectable in the plasma of subjects with null mutations in GPIHBP1. Serum GPIHBP1 median levels were 849 pg/mL (range: 740-1014) in healthy volunteers (n = 28) and 1087 pg/mL (range: 877-1371) in patients with a history of cardiovascular or metabolic disease (n = 415). There was an extremely small inverse correlation between GPIHBP1 and triglyceride levels (r = 0.109; P < .0275). GPIHBP1 levels tended to be slightly higher in patients who had a major cardiovascular event after revascularization. CONCLUSION We developed an ELISA for quantifying GPIHBP1 in human blood. This assay will be useful to identify patients with GPIHBP1 deficiency and patients with GPIHBP1 autoantibodies. The potential of plasma GPIHBP1 as a biomarker for metabolic or cardiovascular disease is yet questionable but needs additional testing.
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Affiliation(s)
| | | | - Manabu Nagao
- Division of Cardiovascular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tatsuro Ishida
- Division of Cardiovascular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Junji Kobayashi
- Department of General Internal Medicine, Kanazawa Medical University, Kanazawa, Ishikawa, Japan
| | - Tetsuo Machida
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Kiyomi Nakajima
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Katsuyuki Nakajima
- Department of General Internal Medicine, Kanazawa Medical University, Kanazawa, Ishikawa, Japan; Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
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18
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He C, Hu X, Jung RS, Larsson M, Tu Y, Duarte-Vogel S, Kim P, Sandoval NP, Price TR, Allan CM, Raney B, Jiang H, Bensadoun A, Walzem RL, Kuo RI, Beigneux AP, Fong LG, Young SG. Lipoprotein lipase reaches the capillary lumen in chickens despite an apparent absence of GPIHBP1. JCI Insight 2017; 2:96783. [PMID: 29046479 DOI: 10.1172/jci.insight.96783] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 09/11/2017] [Indexed: 12/17/2022] Open
Abstract
In mammals, GPIHBP1 is absolutely essential for transporting lipoprotein lipase (LPL) to the lumen of capillaries, where it hydrolyzes the triglycerides in triglyceride-rich lipoproteins. In all lower vertebrate species (e.g., birds, amphibians, reptiles, fish), a gene for LPL can be found easily, but a gene for GPIHBP1 has never been found. The obvious question is whether the LPL in lower vertebrates is able to reach the capillary lumen. Using purified antibodies against chicken LPL, we showed that LPL is present on capillary endothelial cells of chicken heart and adipose tissue, colocalizing with von Willebrand factor. When the antibodies against chicken LPL were injected intravenously into chickens, they bound to LPL on the luminal surface of capillaries in heart and adipose tissue. LPL was released rapidly from chicken hearts with an infusion of heparin, consistent with LPL being located inside blood vessels. Remarkably, chicken LPL bound in a specific fashion to mammalian GPIHBP1. However, we could not identify a gene for GPIHBP1 in the chicken genome, nor could we identify a transcript for GPIHBP1 in a large chicken RNA-seq data set. We conclude that LPL reaches the capillary lumen in chickens - as it does in mammals - despite an apparent absence of GPIHBP1.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Tara R Price
- Department of Poultry Science and Faculty of Nutrition, Texas A&M University, College Station, Texas, USA
| | | | - Brian Raney
- University of California, Santa Cruz Genomics Institute and
| | - Haibo Jiang
- Department of Medicine and.,Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia, Western Australia, Perth, Australia
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, New York, USA
| | - Rosemary L Walzem
- Department of Poultry Science and Faculty of Nutrition, Texas A&M University, College Station, Texas, USA
| | - Richard I Kuo
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | | | | | - Stephen G Young
- Department of Medicine and.,Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
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19
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Allan CM, Heizer PJ, Jung CJ, Tu Y, Tran D, Young LC, Fong LG, de Jong PJ, Beigneux AP, Young SG. Palmoplantar keratoderma in Slurp1/Slurp2 double-knockout mice. J Dermatol Sci 2017; 89:85-87. [PMID: 29017797 DOI: 10.1016/j.jdermsci.2017.08.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 08/24/2017] [Indexed: 12/18/2022]
Affiliation(s)
- Christopher M Allan
- From the Divisions of Cardiology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Patrick J Heizer
- From the Divisions of Cardiology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Cris J Jung
- Children's Hospital Oakland Research Institute, Oakland, CA 94609, United States
| | - Yiping Tu
- From the Divisions of Cardiology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Deanna Tran
- From the Divisions of Cardiology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Lorraine C Young
- From the Divisions of Dermatology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Loren G Fong
- From the Divisions of Cardiology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Pieter J de Jong
- Children's Hospital Oakland Research Institute, Oakland, CA 94609, United States
| | - Anne P Beigneux
- From the Divisions of Cardiology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Stephen G Young
- From the Divisions of Cardiology in the Department of Medicine , David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
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20
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Allan CM, Tran D, Tu Y, Heizer PJ, Young LC, Fong LG, Beigneux AP, Young SG. A hypomorphic Egfr allele does not ameliorate the palmoplantar keratoderma caused by SLURP1 deficiency. Exp Dermatol 2017; 26:1134-1136. [PMID: 28418591 DOI: 10.1111/exd.13363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2017] [Indexed: 01/25/2023]
Abstract
Mutations in SLURP1, a secreted protein of keratinocytes, cause a palmoplantar keratoderma (PPK) known as mal de Meleda. Slurp1 deficiency in mice faithfully recapitulates the human disease, with increased keratinocyte proliferation and thickening of the epidermis on the volar surface of the paws. There has long been speculation that SLURP1 serves as a ligand for a receptor that regulates keratinocyte growth and differentiation. We were intrigued that mutations leading to increased signalling through the epidermal growth factor receptor (EGFR) cause PPK. Here, we sought to determine whether reducing EGFR signalling would ameliorate the PPK associated with SLURP1 deficiency. To address this issue, we bred Slurp1-deficient mice that were homozygous for a hypomorphic Egfr allele. The hypomorphic Egfr allele, which leads to reduced EGFR signalling in keratinocytes, did not ameliorate the PPK elicited by SLURP1 deficiency, suggesting that SLURP1 deficiency causes PPK independently (or downstream) from the EGFR pathway.
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Affiliation(s)
- Christopher M Allan
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Deanna Tran
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Yiping Tu
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Patrick J Heizer
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Lorraine C Young
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Loren G Fong
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Anne P Beigneux
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Stephen G Young
- Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
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21
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Larsson M, Allan CM, Jung RS, Heizer PJ, Beigneux AP, Young SG, Fong LG. Apolipoprotein C-III inhibits triglyceride hydrolysis by GPIHBP1-bound LPL. J Lipid Res 2017; 58:1893-1902. [PMID: 28694296 DOI: 10.1194/jlr.m078220] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/05/2017] [Indexed: 12/13/2022] Open
Abstract
apoC-III is often assumed to retard the intravascular processing of triglyceride-rich lipoproteins (TRLs) by inhibiting LPL, but that view is based largely on studies of free LPL. We now recognize that intravascular LPL is neither free nor loosely bound, but instead is tightly bound to glycosylphosphatidylinositol-anchored HDL-binding protein 1 (GPIHBP1) on endothelial cells. Here, we revisited the effects of apoC-III on LPL, focusing on apoC-III's capacity to affect the activity of GPIHBP1-bound LPL. We found that TRLs from APOC3 transgenic mice bound normally to GPIHBP1-bound LPL on cultured cells in vitro and to heart capillaries in vivo. However, the triglycerides in apoC-III-enriched TRLs were hydrolyzed more slowly by free LPL, and the inhibitory effect of apoC-III on triglyceride lipolysis was exaggerated when LPL was bound to GPIHBP1 on the surface of agarose beads. Also, recombinant apoC-III reduced triglyceride hydrolysis by free LPL only modestly, but the inhibitory effect was greater when the LPL was bound to GPIHBP1. A mutant apoC-III associated with low plasma triglyceride levels (p.A23T) displayed a reduced capacity to inhibit free and GPIHBP1-bound LPL. Our results show that apoC-III potently inhibits triglyceride hydrolysis when LPL is bound to GPIHBP1.
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Affiliation(s)
- Mikael Larsson
- Departments of Medicine and Human Genetics, University of California Los Angeles, Los Angeles, CA 90095
| | - Christopher M Allan
- Departments of Medicine and Human Genetics, University of California Los Angeles, Los Angeles, CA 90095
| | - Rachel S Jung
- Departments of Medicine and Human Genetics, University of California Los Angeles, Los Angeles, CA 90095
| | - Patrick J Heizer
- Departments of Medicine and Human Genetics, University of California Los Angeles, Los Angeles, CA 90095
| | - Anne P Beigneux
- Departments of Medicine and Human Genetics, University of California Los Angeles, Los Angeles, CA 90095
| | - Stephen G Young
- Departments of Medicine and Human Genetics, University of California Los Angeles, Los Angeles, CA 90095 .,David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095
| | - Loren G Fong
- Departments of Medicine and Human Genetics, University of California Los Angeles, Los Angeles, CA 90095
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22
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Allan CM, Jung CJ, Larsson M, Heizer PJ, Tu Y, Sandoval NP, Dang TLP, Jung RS, Beigneux AP, de Jong PJ, Fong LG, Young SG. Mutating a conserved cysteine in GPIHBP1 reduces amounts of GPIHBP1 in capillaries and abolishes LPL binding. J Lipid Res 2017; 58:1453-1461. [PMID: 28476858 DOI: 10.1194/jlr.m076943] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 05/04/2017] [Indexed: 12/22/2022] Open
Abstract
Mutation of conserved cysteines in proteins of the Ly6 family cause human disease-chylomicronemia in the case of glycosylphosphatidylinositol-anchored HDL binding protein 1 (GPIHBP1) and paroxysmal nocturnal hemoglobinuria in the case of CD59. A mutation in a conserved cysteine in CD59 prevented the protein from reaching the surface of blood cells. In contrast, mutation of conserved cysteines in human GPIHBP1 had little effect on GPIHBP1 trafficking to the surface of cultured CHO cells. The latter findings were somewhat surprising and raised questions about whether CHO cell studies accurately model the fate of mutant GPIHBP1 proteins in vivo. To explore this concern, we created mice harboring a GPIHBP1 cysteine mutation (p.C63Y). The p.C63Y mutation abolished the ability of mouse GPIHBP1 to bind LPL, resulting in severe chylomicronemia. The mutant GPIHBP1 was detectable by immunohistochemistry on the surface of endothelial cells, but the level of expression was ∼70% lower than in WT mice. The mutant GPIHBP1 protein in mouse tissues was predominantly monomeric. We conclude that mutation of a conserved cysteine in GPIHBP1 abolishes the ability of GPIHBP1 to bind LPL, resulting in mislocalization of LPL and severe chylomicronemia. The mutation reduced but did not eliminate GPIHBP1 on the surface of endothelial cells in vivo.
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Affiliation(s)
- Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Cris J Jung
- Children's Hospital Oakland Research Institute, Oakland, CA 94609
| | - Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Patrick J Heizer
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Yiping Tu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Norma P Sandoval
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Tiffany Ly P Dang
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095.
| | - Pieter J de Jong
- Children's Hospital Oakland Research Institute, Oakland, CA 94609
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095.
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095; Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095.
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23
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Beigneux AP, Miyashita K, Ploug M, Blom DJ, Ai M, Linton MF, Khovidhunkit W, Dufour R, Garg A, McMahon MA, Pullinger CR, Sandoval NP, Hu X, Allan CM, Larsson M, Machida T, Murakami M, Reue K, Tontonoz P, Goldberg IJ, Moulin P, Charrière S, Fong LG, Nakajima K, Young SG. Autoantibodies against GPIHBP1 as a Cause of Hypertriglyceridemia. N Engl J Med 2017; 376:1647-1658. [PMID: 28402248 PMCID: PMC5555413 DOI: 10.1056/nejmoa1611930] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
BACKGROUND A protein that is expressed on capillary endothelial cells, called GPIHBP1 (glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1), binds lipoprotein lipase and shuttles it to its site of action in the capillary lumen. A deficiency in GPIHBP1 prevents lipoprotein lipase from reaching the capillary lumen. Patients with GPIHBP1 deficiency have low plasma levels of lipoprotein lipase, impaired intravascular hydrolysis of triglycerides, and severe hypertriglyceridemia (chylomicronemia). During the characterization of a monoclonal antibody-based immunoassay for GPIHBP1, we encountered two plasma samples (both from patients with chylomicronemia) that contained an interfering substance that made it impossible to measure GPIHBP1. That finding raised the possibility that those samples might contain GPIHBP1 autoantibodies. METHODS Using a combination of immunoassays, Western blot analyses, and immunocytochemical studies, we tested the two plasma samples (as well as samples from other patients with chylomicronemia) for the presence of GPIHBP1 autoantibodies. We also tested the ability of GPIHBP1 autoantibodies to block the binding of lipoprotein lipase to GPIHBP1. RESULTS We identified GPIHBP1 autoantibodies in six patients with chylomicronemia and found that these autoantibodies blocked the binding of lipoprotein lipase to GPIHBP1. As in patients with GPIHBP1 deficiency, those with GPIHBP1 autoantibodies had low plasma levels of lipoprotein lipase. Three of the six patients had systemic lupus erythematosus. One of these patients who had GPIHBP1 autoantibodies delivered a baby with plasma containing maternal GPIHBP1 autoantibodies; the infant had severe but transient chylomicronemia. Two of the patients with chylomicronemia and GPIHBP1 autoantibodies had a response to treatment with immunosuppressive agents. CONCLUSIONS In six patients with chylomicronemia, GPIHBP1 autoantibodies blocked the ability of GPIHBP1 to bind and transport lipoprotein lipase, thereby interfering with lipoprotein lipase-mediated processing of triglyceride-rich lipoproteins and causing severe hypertriglyceridemia. (Funded by the National Heart, Lung, and Blood Institute and the Leducq Foundation.).
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Affiliation(s)
- Anne P Beigneux
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Kazuya Miyashita
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Michael Ploug
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Dirk J Blom
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Masumi Ai
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - MacRae F Linton
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Weerapan Khovidhunkit
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Robert Dufour
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Abhimanyu Garg
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Maureen A McMahon
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Clive R Pullinger
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Norma P Sandoval
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Xuchen Hu
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Christopher M Allan
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Mikael Larsson
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Tetsuo Machida
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Masami Murakami
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Karen Reue
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Peter Tontonoz
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Ira J Goldberg
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Philippe Moulin
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Sybil Charrière
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Loren G Fong
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Katsuyuki Nakajima
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
| | - Stephen G Young
- From the Departments of Medicine (A.P.B., M.A.M., N.P.S., X.H., C.M.A., M.L., L.G.F., S.G.Y.), Rheumatology (M.A.M.), Human Genetics (K.R., S.G.Y.), and Pathology and Laboratory Medicine (P.T.), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, and the Cardiovascular Research Institute and Department of Physiological Nursing, University of California, San Francisco, San Francisco (C.R.P.); the Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi (K.M., T.M., M.M., K.N.), and the Department of Insured Medical Care Management, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo (M.A.) - both in Japan; the Finsen Laboratory, Rigshospitalet, Copenhagen (M.P.); the Department of Medicine, University of Cape Town, Cape Town, South Africa (D.J.B.); the Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville (M.F.L.); the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok, Thailand (W.K.); Clinique de Prévention Cardiovasculaire, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal (R.D.); the Department of Medicine, University of Texas Southwestern Medical Center, Dallas (A.G.); the Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, New York University School of Medicine, New York (I.J.G.); and Fédération d'Endocrinologie, Groupement Hospitalier Est, Hospices Civils de Lyon, INSERM UMR-1060 Carmen, Université de Lyon, Lyon, France (P.M., S.C.)
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24
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Hu X, Sleeman MW, Miyashita K, Linton MF, Allan CM, He C, Larsson M, Tu Y, Sandoval NP, Jung RS, Mapar A, Machida T, Murakami M, Nakajima K, Ploug M, Fong LG, Young SG, Beigneux AP. Monoclonal antibodies that bind to the Ly6 domain of GPIHBP1 abolish the binding of LPL. J Lipid Res 2016; 58:208-215. [PMID: 27875259 DOI: 10.1194/jlr.m072462] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 10/31/2016] [Indexed: 01/18/2023] Open
Abstract
GPIHBP1, an endothelial cell protein, binds LPL in the interstitial spaces and shuttles it to its site of action inside blood vessels. For years, studies of human GPIHBP1 have been hampered by an absence of useful antibodies. We reasoned that monoclonal antibodies (mAbs) against human GPIHBP1 would be useful for 1) defining the functional relevance of GPIHBP1's Ly6 and acidic domains to the binding of LPL; 2) ascertaining whether human GPIHBP1 is expressed exclusively in capillary endothelial cells; and 3) testing whether GPIHBP1 is detectable in human plasma. Here, we report the development of a panel of human GPIHBP1-specific mAbs. Two mAbs against GPIHBP1's Ly6 domain, RE3 and RG3, abolished LPL binding, whereas an antibody against the acidic domain, RF4, did not. Also, mAbs RE3 and RG3 bound with reduced affinity to a mutant GPIHBP1 containing an Ly6 domain mutation (W109S) that abolishes LPL binding. Immunohistochemistry studies with the GPIHBP1 mAbs revealed that human GPIHBP1 is expressed only in capillary endothelial cells. Finally, we created an ELISA that detects GPIHBP1 in human plasma. That ELISA should make it possible for clinical lipidologists to determine whether plasma GPIHBP1 levels are a useful biomarker of metabolic or vascular disease.
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Affiliation(s)
- Xuchen Hu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Mark W Sleeman
- Monash Biomedicine Discovery Institute and Antibody Technologies Facility, Monash University, Victoria, Australia
| | - Kazuya Miyashita
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - MacRae F Linton
- Departments of Medicine and Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Cuiwen He
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Yiping Tu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Norma P Sandoval
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Alaleh Mapar
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Tetsuo Machida
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - Katsuyuki Nakajima
- Department of Clinical Laboratory Medicine, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA .,Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
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25
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Allan CM, Larsson M, Jung RS, Ploug M, Bensadoun A, Beigneux AP, Fong LG, Young SG. Mobility of "HSPG-bound" LPL explains how LPL is able to reach GPIHBP1 on capillaries. J Lipid Res 2016; 58:216-225. [PMID: 27811232 DOI: 10.1194/jlr.m072520] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 10/31/2016] [Indexed: 12/22/2022] Open
Abstract
In mice lacking glycosylphosphatidylinositol-anchored high density lipoprotein binding protein 1 (GPIHBP1), the LPL secreted by adipocytes and myocytes remains bound to heparan sulfate proteoglycans (HSPGs) on all cells within tissues. That observation raises a perplexing issue: Why isn't the freshly secreted LPL in wild-type mice captured by the same HSPGs, thereby preventing LPL from reaching GPIHBP1 on capillaries? We hypothesized that LPL-HSPG interactions are transient, allowing the LPL to detach and move to GPIHBP1 on capillaries. Indeed, we found that LPL detaches from HSPGs on cultured cells and moves to: 1) soluble GPIHBP1 in the cell culture medium; 2) GPIHBP1-coated agarose beads; and 3) nearby GPIHBP1-expressing cells. Movement of HSPG-bound LPL to GPIHBP1 did not occur when GPIHBP1 contained a Ly6 domain missense mutation (W109S), but was almost normal when GPIHBP1's acidic domain was mutated. To test the mobility of HSPG-bound LPL in vivo, we injected GPIHBP1-coated agarose beads into the brown adipose tissue of GPIHBP1-deficient mice. LPL moved quickly from HSPGs on adipocytes to GPIHBP1-coated beads, thereby depleting LPL stores on the surface of adipocytes. We conclude that HSPG-bound LPL in the interstitial spaces of tissues is mobile, allowing the LPL to move to GPIHBP1 on endothelial cells.
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Affiliation(s)
- Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, DK-2200 Copenhagen N, Denmark and Biotech Research and Innovation Centre (BRIC), University of Copenhagen, DK-220 Copenhagen N, Denmark
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA 90095 .,Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095
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26
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Allan CM, Larsson M, Hu X, He C, Jung RS, Mapar A, Voss C, Miyashita K, Machida T, Murakami M, Nakajima K, Bensadoun A, Ploug M, Fong LG, Young SG, Beigneux AP. An LPL-specific monoclonal antibody, 88B8, that abolishes the binding of LPL to GPIHBP1. J Lipid Res 2016; 57:1889-1898. [PMID: 27494936 DOI: 10.1194/jlr.m070813] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Indexed: 12/26/2022] Open
Abstract
LPL contains two principal domains: an amino-terminal catalytic domain (residues 1-297) and a carboxyl-terminal domain (residues 298-448) that is important for binding lipids and binding glycosylphosphatidylinositol-anchored high density lipoprotein binding protein 1 (GPIHBP1) (an endothelial cell protein that shuttles LPL to the capillary lumen). The LPL sequences required for GPIHBP1 binding have not been examined in detail, but one study suggested that sequences near LPL's carboxyl terminus (residues ∼403-438) were crucial. Here, we tested the ability of LPL-specific monoclonal antibodies (mAbs) to block the binding of LPL to GPIHBP1. One antibody, 88B8, abolished LPL binding to GPIHBP1. Consistent with those results, antibody 88B8 could not bind to GPIHBP1-bound LPL on cultured cells. Antibody 88B8 bound poorly to LPL proteins with amino acid substitutions that interfered with GPIHBP1 binding (e.g., C418Y, E421K). However, the sequences near LPL's carboxyl terminus (residues ∼403-438) were not sufficient for 88B8 binding; upstream sequences (residues 298-400) were also required. Additional studies showed that these same sequences are required for LPL binding to GPIHBP1. In conclusion, we identified an LPL mAb that binds to LPL's GPIHBP1-binding domain. The binding of both antibody 88B8 and GPIHBP1 to LPL depends on large segments of LPL's carboxyl-terminal domain.
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Affiliation(s)
- Christopher M Allan
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Mikael Larsson
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Xuchen Hu
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Cuiwen He
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Rachel S Jung
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Alaleh Mapar
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | - Constance Voss
- Departments of Medicine University of California Los Angeles, Los Angeles, CA
| | | | - Tetsuo Machida
- Gunma University, Graduate School of Medicine, Maebashi, Japan
| | - Masami Murakami
- Gunma University, Graduate School of Medicine, Maebashi, Japan
| | | | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen N, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen N, Denmark
| | - Loren G Fong
- Departments of Medicine University of California Los Angeles, Los Angeles, CA.
| | - Stephen G Young
- Departments of Medicine University of California Los Angeles, Los Angeles, CA; Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA.
| | - Anne P Beigneux
- Departments of Medicine University of California Los Angeles, Los Angeles, CA.
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27
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Fong LG, Young SG, Beigneux AP, Bensadoun A, Oberer M, Jiang H, Ploug M. GPIHBP1 and Plasma Triglyceride Metabolism. Trends Endocrinol Metab 2016; 27:455-469. [PMID: 27185325 PMCID: PMC4927088 DOI: 10.1016/j.tem.2016.04.013] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 10/21/2022]
Abstract
GPIHBP1, a GPI-anchored protein in capillary endothelial cells, is crucial for the lipolytic processing of triglyceride-rich lipoproteins (TRLs). GPIHBP1 shuttles lipoprotein lipase (LPL) to its site of action in the capillary lumen and is essential for the margination of TRLs along capillaries - such that lipolytic processing can proceed. GPIHBP1 also reduces the unfolding of the LPL catalytic domain, thereby stabilizing LPL catalytic activity. Many different GPIHBP1 mutations have been identified in patients with severe hypertriglyceridemia (chylomicronemia), the majority of which interfere with folding of the protein and abolish its capacity to bind and transport LPL. The discovery of GPIHBP1 has substantially revised our understanding of intravascular triglyceride metabolism but has also raised many new questions for future research.
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Affiliation(s)
- Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, USA
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz and BioTechMed, Graz, Austria
| | - Haibo Jiang
- Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, 2200 Copenhagen N, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, 220 Copenhagen N, Denmark.
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28
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Dijk W, Beigneux AP, Larsson M, Bensadoun A, Young SG, Kersten S. Angiopoietin-like 4 promotes intracellular degradation of lipoprotein lipase in adipocytes. J Lipid Res 2016; 57:1670-83. [PMID: 27034464 DOI: 10.1194/jlr.m067363] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Indexed: 01/17/2023] Open
Abstract
LPL hydrolyzes triglycerides in triglyceride-rich lipoproteins along the capillaries of heart, skeletal muscle, and adipose tissue. The activity of LPL is repressed by angiopoietin-like 4 (ANGPTL4) but the underlying mechanisms have not been fully elucidated. Our objective was to study the cellular location and mechanism for LPL inhibition by ANGPTL4. We performed studies in transfected cells, ex vivo studies, and in vivo studies with Angptl4(-/-) mice. Cotransfection of CHO pgsA-745 cells with ANGPTL4 and LPL reduced intracellular LPL protein levels, suggesting that ANGPTL4 promotes LPL degradation. This conclusion was supported by studies of primary adipocytes and adipose tissue explants from wild-type and Angptl4(-/-) mice. Absence of ANGPTL4 resulted in accumulation of the mature-glycosylated form of LPL and increased secretion of LPL. Blocking endoplasmic reticulum (ER)-Golgi transport abolished differences in LPL abundance between wild-type and Angptl4(-/-) adipocytes, suggesting that ANGPTL4 acts upon LPL after LPL processing in the ER. Finally, physiological changes in adipose tissue ANGPTL4 expression during fasting and cold resulted in inverse changes in the amount of mature-glycosylated LPL in wild-type mice, but not Angptl4(-/-) mice. We conclude that ANGPTL4 promotes loss of intracellular LPL by stimulating LPL degradation after LPL processing in the ER.
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Affiliation(s)
- Wieneke Dijk
- Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
| | - Anne P Beigneux
- Departments of Medicine David Geffen School of Medicine, University of California, Los Angeles, CA
| | - Mikael Larsson
- Departments of Medicine David Geffen School of Medicine, University of California, Los Angeles, CA
| | - André Bensadoun
- Division of Nutritional Sciences, Cornell University, Ithaca, NY
| | - Stephen G Young
- Departments of Medicine David Geffen School of Medicine, University of California, Los Angeles, CA Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - Sander Kersten
- Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands Division of Nutritional Sciences, Cornell University, Ithaca, NY
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29
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Mysling S, Kristensen KK, Larsson M, Beigneux AP, Gårdsvoll H, Fong LG, Bensadouen A, Jørgensen TJ, Young SG, Ploug M. The acidic domain of the endothelial membrane protein GPIHBP1 stabilizes lipoprotein lipase activity by preventing unfolding of its catalytic domain. eLife 2016; 5:e12095. [PMID: 26725083 PMCID: PMC4755760 DOI: 10.7554/elife.12095] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 01/02/2016] [Indexed: 12/19/2022] Open
Abstract
GPIHBP1 is a glycolipid-anchored membrane protein of capillary endothelial cells that binds lipoprotein lipase (LPL) within the interstitial space and shuttles it to the capillary lumen. The LPL•GPIHBP1 complex is responsible for margination of triglyceride-rich lipoproteins along capillaries and their lipolytic processing. The current work conceptualizes a model for the GPIHBP1•LPL interaction based on biophysical measurements with hydrogen-deuterium exchange/mass spectrometry, surface plasmon resonance, and zero-length cross-linking. According to this model, GPIHBP1 comprises two functionally distinct domains: (1) an intrinsically disordered acidic N-terminal domain; and (2) a folded C-terminal domain that tethers GPIHBP1 to the cell membrane by glycosylphosphatidylinositol. We demonstrate that these domains serve different roles in regulating the kinetics of LPL binding. Importantly, the acidic domain stabilizes LPL catalytic activity by mitigating the global unfolding of LPL's catalytic domain. This study provides a conceptual framework for understanding intravascular lipolysis and GPIHBP1 and LPL mutations causing familial chylomicronemia. DOI:http://dx.doi.org/10.7554/eLife.12095.001 Fat is an important part of our diet. The intestines absorb fats and package them into particles called lipoproteins. After reaching the bloodstream, the fat molecules (lipids) in the lipoproteins are broken down by an enzyme called lipoprotein lipase (LPL), which is located along the surface of small blood vessels. This releases nutrients that can be used by vital tissues – mainly the heart, skeletal muscle, and adipose tissues. LPL is produced by muscle and adipose tissue, but it is quickly swept up by a protein called GPIHBP1 and shuttled to its site of action inside the blood vessels. Mutations that alter the structure of LPL or GPIHBP1 can prevent the breakdown of lipids, resulting in high levels of lipids in the blood. This can lead to inflammation in the pancreas and also increases the risk of heart attacks and strokes. Many earlier studies have examined the properties of LPL, but our understanding of GPIHBP1 has been limited, mainly because it has been difficult to purify GPIHBP1 for analysis. Using genetically altered insect cells, Mysling et al. were able to purify two different forms of GPIHBP1 – a full-length version and a shorter version that lacked a small section at the end of the molecule known as the acidic domain. This revealed that the opposite end of the molecule – called the carboxyl-terminal domain – is primarily responsible for binding LPL and anchoring it inside blood vessels. Once LPL is bound to GPIHBP1, the acidic domain of GPIHBP1 helps to stabilize LPL. If GPIHBP1’s acidic domain is missing then LPL is more susceptible to losing its structure, rendering it incapable of breaking down the lipids in the blood. Mysling et al. describe a new model for how LPL and GPIHBP1 interact that explains how specific mutations in the genes that encode these proteins interfere with the delivery of LPL to small blood vessels. In the future, this could help researchers to develop new strategies to treat people with high levels of lipids in their blood. DOI:http://dx.doi.org/10.7554/eLife.12095.002
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Affiliation(s)
- Simon Mysling
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.,Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Kristian Kølby Kristensen
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Mikael Larsson
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Anne P Beigneux
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Henrik Gårdsvoll
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
| | - Loren G Fong
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - André Bensadouen
- Division of Nutritional Science, Cornell University, Ithaca, United States
| | - Thomas Jd Jørgensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Stephen G Young
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States.,Department of Human Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Michael Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark.,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
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Allan CM, Procaccia S, Tran D, Tu Y, Barnes RH, Larsson M, Allan BB, Young LC, Hong C, Tontonoz P, Fong LG, Young SG, Beigneux AP. Palmoplantar Keratoderma in Slurp2-Deficient Mice. J Invest Dermatol 2015; 136:436-443. [PMID: 26967477 PMCID: PMC4789766 DOI: 10.1016/j.jid.2015.11.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 09/29/2015] [Accepted: 10/12/2015] [Indexed: 01/13/2023]
Abstract
SLURP1, a member of the Ly6 protein family, is secreted by suprabasal keratinocytes. Mutations in SLURP1 cause a palmoplantar keratoderma (PPK) known as mal de Meleda. Another secreted Ly6 protein, SLURP2, is encoded by a gene located ~20 kb downstream from SLURP1. SLURP2 is produced by suprabasal keratinocytes. To investigate the importance of SLURP2, we first examined Slurp2 knockout mice in which exon 2–3 sequences had been replaced with lacZ and neo cassettes. Slurp2−/− mice exhibited hyperkeratosis on the volar surface of the paws (i.e., PPK), increased keratinocyte proliferation, and an accumulation of lipid droplets in the stratum corneum. They also exhibited reduced body weight and hind limb clasping. These phenotypes are very similar to those of Slurp1−/− mice. To solidify a link between Slurp2 deficiency and PPK and to be confident that the disease phenotypes in Slurp2−/− mice were not secondary to the effects of the lacZ and neo cassettes on Slurp1 expression, we created a new line of Slurp2 knockout mice (Slurp2X−/−) in which Slurp2 was inactivated with a simple nonsense mutation. Slurp2X−/− mice exhibited the same disease phenotypes. Thus, Slurp2 deficiency and Slurp1 deficiencies cause the same disease phenotypes.
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Affiliation(s)
- Christopher M Allan
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Shiri Procaccia
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Deanna Tran
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Yiping Tu
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Richard H Barnes
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Mikael Larsson
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Bernard B Allan
- Department of Molecular Biology, Genentech, South San Francisco, California, USA
| | - Lorraine C Young
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Cynthia Hong
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA; Howard Hughes Medical Institute, University of California, Los Angeles, California, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA; Howard Hughes Medical Institute, University of California, Los Angeles, California, USA
| | - Loren G Fong
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
| | - Stephen G Young
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
| | - Anne P Beigneux
- Department of Medicine, Divisions of Cardiology and Dermatology, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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Adeyo O, Oberer M, Ploug M, Fong LG, Young SG, Beigneux AP. Heterogeneity in the properties of mutant secreted lymphocyte antigen 6/urokinase receptor-related protein 1 (SLURP1) in Mal de Meleda. Br J Dermatol 2015; 173:1066-9. [PMID: 25919322 DOI: 10.1111/bjd.13868] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- O Adeyo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
| | - M Oberer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, A-8010, Graz, Austria
| | - M Ploug
- Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark
| | - L G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
| | - S G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A.,Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
| | - A P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, 90095, CA, U.S.A
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Beigneux AP, Fong LG, Bensadoun A, Davies BSJ, Oberer M, Gårdsvoll H, Ploug M, Young SG. GPIHBP1 missense mutations often cause multimerization of GPIHBP1 and thereby prevent lipoprotein lipase binding. Circ Res 2014; 116:624-32. [PMID: 25387803 DOI: 10.1161/circresaha.116.305085] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
RATIONALE GPIHBP1, a GPI-anchored protein of capillary endothelial cells, binds lipoprotein lipase (LPL) in the subendothelial spaces and shuttles it to the capillary lumen. GPIHBP1 missense mutations that interfere with LPL binding cause familial chylomicronemia. OBJECTIVE We sought to understand mechanisms by which GPIHBP1 mutations prevent LPL binding and lead to chylomicronemia. METHODS AND RESULTS We expressed mutant forms of GPIHBP1 in Chinese hamster ovary cells, rat and human endothelial cells, and Drosophila S2 cells. In each expression system, mutation of cysteines in GPIHBP1's Ly6 domain (including mutants identified in patients with chylomicronemia) led to the formation of disulfide-linked dimers and multimers. GPIHBP1 dimerization/multimerization was not unique to cysteine mutations; mutations in other amino acid residues, including several associated with chylomicronemia, also led to protein dimerization/multimerization. The loss of GPIHBP1 monomers is relevant to the pathogenesis of chylomicronemia because only GPIHBP1 monomers-and not dimers or multimers-are capable of binding LPL. One GPIHBP1 mutant, GPIHBP1-W109S, had distinctive properties. GPIHBP1-W109S lacked the ability to bind LPL but had a reduced propensity for forming dimers or multimers, suggesting that W109 might play a more direct role in binding LPL. In support of that idea, replacing W109 with any of 8 other amino acids abolished LPL binding-and often did so without promoting the formation of dimers and multimers. CONCLUSIONS Many amino acid substitutions in GPIHBP1's Ly6 domain that abolish LPL binding lead to protein dimerization/multimerization. Dimerization/multimerization is relevant to disease pathogenesis, given that only GPIHBP1 monomers are capable of binding LPL.
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Affiliation(s)
- Anne P Beigneux
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles.
| | - Loren G Fong
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - André Bensadoun
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Brandon S J Davies
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Monika Oberer
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Henrik Gårdsvoll
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Michael Ploug
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
| | - Stephen G Young
- From the Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles (A.P.B., L.G.F., S.G.Y.); Division of Nutritional Science, Cornell University, Ithaca, NY (A.B.); Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City (B.S.J.D.); Institute of Molecular Biosciences, University of Graz, Graz, Austria (M.O.); Finsen Laboratory, Rigshospitalet, Copenhagen, Denmark (H.G., M.P.); and Molecular Biology Institute (S.G.Y.), Department of Human Genetics, David Geffen School of Medicine (S.G.Y.), University of California at Los Angeles
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Jiang H, Goulbourne CN, Tatar A, Turlo K, Wu D, Beigneux AP, Grovenor CRM, Fong LG, Young SG. High-resolution imaging of dietary lipids in cells and tissues by NanoSIMS analysis. J Lipid Res 2014; 55:2156-66. [PMID: 25143463 DOI: 10.1194/jlr.m053363] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nanoscale secondary ion MS (NanoSIMS) imaging makes it possible to visualize stable isotope-labeled lipids in cells and tissues at 50 nm lateral resolution. Here we report the use of NanoSIMS imaging to visualize lipids in mouse cells and tissues. After administering stable isotope-labeled fatty acids to mice by gavage, NanoSIMS imaging allowed us to visualize neutral lipids in cytosolic lipid droplets in intestinal enterocytes, chylomicrons at the basolateral surface of enterocytes, and lipid droplets in cardiomyocytes and adipocytes. After an injection of stable isotope-enriched triglyceride-rich lipoproteins (TRLs), NanoSIMS imaging documented delivery of lipids to cytosolic lipid droplets in parenchymal cells. Using a combination of backscattered electron (BSE) and NanoSIMS imaging, it was possible to correlate the chemical data provided by NanoSIMS with high-resolution BSE images of cell morphology. This combined imaging approach allowed us to visualize stable isotope-enriched TRLs along the luminal face of heart capillaries and the lipids within heart capillary endothelial cells. We also observed examples of TRLs within the subendothelial spaces of heart capillaries. NanoSIMS imaging provided evidence of defective transport of lipids from the plasma LPs to adipocytes and cardiomyocytes in mice deficient in glycosylphosphatidylinositol-anchored HDL binding protein 1.
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Affiliation(s)
- Haibo Jiang
- Materials Department, Oxford University, Oxford, United Kingdom
| | - Chris N Goulbourne
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Angelica Tatar
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Kirsten Turlo
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Daniel Wu
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Anne P Beigneux
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | | | - Loren G Fong
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA
| | - Stephen G Young
- Departments of Medicine University of California, Los Angeles, Los Angeles, CA Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
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Turlo K, Leung CS, Seo JJ, Goulbourne CN, Adeyo O, Gin P, Voss C, Bensadoun A, Fong LG, Young SG, Beigneux AP. Equivalent binding of wild-type lipoprotein lipase (LPL) and S447X-LPL to GPIHBP1, the endothelial cell LPL transporter. Biochim Biophys Acta 2014; 1841:963-9. [PMID: 24704550 PMCID: PMC4212522 DOI: 10.1016/j.bbalip.2014.03.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 03/18/2014] [Accepted: 03/27/2014] [Indexed: 02/05/2023]
Abstract
The S447X polymorphism in lipoprotein lipase (LPL), which shortens LPL by two amino acids, is associated with low plasma triglyceride levels and reduced risk for coronary heart disease. S447X carriers have higher LPL levels in the pre- and post-heparin plasma, raising the possibility that the S447X polymorphism leads to higher LPL levels within capillaries. One potential explanation for increased amounts of LPL in capillaries would be more avid binding of S447X-LPL to GPIHBP1 (the protein that binds LPL dimers and shuttles them to the capillary lumen). This explanation seems plausible because sequences within the carboxyl terminus of LPL are known to mediate LPL binding to GPIHBP1. To assess the impact of the S447X polymorphism on LPL binding to GPIHBP1, we compared the ability of internally tagged versions of wild-type LPL (WT-LPL) and S447X-LPL to bind to GPIHBP1 in both cell-based and cell-free binding assays. In the cell-based assay, we compared the binding of WT-LPL and S447X-LPL to GPIHBP1 on the surface of cultured cells. This assay revealed no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1. In the cell-free assay, we compared the binding of internally tagged WT-LPL and S447X-LPL to soluble GPIHBP1 immobilized on agarose beads. Again, no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1 were observed. We conclude that increased binding of S447X-LPL to GPIHBP1 is unlikely to be the explanation for more efficient lipolysis and lower plasma triglyceride levels in S447X carriers.
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Affiliation(s)
- Kirsten Turlo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Calvin S Leung
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Jane J Seo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Chris N Goulbourne
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Oludotun Adeyo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Peter Gin
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Constance Voss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, United States
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States; Department of Human Genetics, University of California, Los Angeles, CA 90095, United States.
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
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Plengpanich W, Young SG, Khovidhunkit W, Bensadoun A, Karnman H, Ploug M, Gårdsvoll H, Leung CS, Adeyo O, Larsson M, Muanpetch S, Charoen S, Fong LG, Niramitmahapanya S, Beigneux AP. Multimerization of glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) and familial chylomicronemia from a serine-to-cysteine substitution in GPIHBP1 Ly6 domain. J Biol Chem 2014; 289:19491-9. [PMID: 24847059 DOI: 10.1074/jbc.m114.558528] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
GPIHBP1, a glycosylphosphatidylinositol-anchored glycoprotein of microvascular endothelial cells, binds lipoprotein lipase (LPL) within the interstitial spaces and transports it across endothelial cells to the capillary lumen. The ability of GPIHBP1 to bind LPL depends on the Ly6 domain, a three-fingered structure containing 10 cysteines and a conserved pattern of disulfide bond formation. Here, we report a patient with severe hypertriglyceridemia who was homozygous for a GPIHBP1 point mutation that converted a serine in the GPIHBP1 Ly6 domain (Ser-107) to a cysteine. Two hypertriglyceridemic siblings were homozygous for the same mutation. All three homozygotes had very low levels of LPL in the preheparin plasma. We suspected that the extra cysteine in GPIHBP1-S107C might prevent the trafficking of the protein to the cell surface, but this was not the case. However, nearly all of the GPIHBP1-S107C on the cell surface was in the form of disulfide-linked dimers and multimers, whereas wild-type GPIHBP1 was predominantly monomeric. An insect cell GPIHBP1 expression system confirmed the propensity of GPIHBP1-S107C to form disulfide-linked dimers and to form multimers. Functional studies showed that only GPIHBP1 monomers bind LPL. In keeping with that finding, there was no binding of LPL to GPIHBP1-S107C in either cell-based or cell-free binding assays. We conclude that an extra cysteine in the GPIHBP1 Ly6 motif results in multimerization of GPIHBP1, defective LPL binding, and severe hypertriglyceridemia.
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Affiliation(s)
- Wanee Plengpanich
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | - Stephen G Young
- the Departments of Medicine and Human Genetics, UCLA, Los Angeles, California 90095
| | - Weerapan Khovidhunkit
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand,
| | - André Bensadoun
- the Division of Nutritional Science, Cornell University, Ithaca, New York 14853
| | - Hirankorn Karnman
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | - Michael Ploug
- the Finsen Laboratory and Biotech Research and Innovation Center, Rigshospitalet, DK-2200 Copenhagen, Denmark
| | - Henrik Gårdsvoll
- the Finsen Laboratory and Biotech Research and Innovation Center, Rigshospitalet, DK-2200 Copenhagen, Denmark
| | | | | | - Mikael Larsson
- the Department of Medical Biosciences and Physiological Chemistry, Umeå University, SE-901 87 Umeå, Sweden, and
| | - Suwanna Muanpetch
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | - Supannika Charoen
- From the Department of Medicine, Faculty of Medicine, Chulalongkorn University and Thai Red Cross Society, Bangkok 10330, Thailand
| | | | - Sathit Niramitmahapanya
- the Department of Medicine, Rajavithi Hospital, College of Medicine, Rangsit University, Bangkok 10400, Thailand
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Goulbourne CN, Gin P, Tatar A, Nobumori C, Hoenger A, Jiang H, Grovenor CRM, Adeyo O, Esko JD, Goldberg IJ, Reue K, Tontonoz P, Bensadoun A, Beigneux AP, Young SG, Fong LG. The GPIHBP1-LPL complex is responsible for the margination of triglyceride-rich lipoproteins in capillaries. Cell Metab 2014; 19:849-60. [PMID: 24726386 PMCID: PMC4143151 DOI: 10.1016/j.cmet.2014.01.017] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 12/06/2013] [Accepted: 01/17/2014] [Indexed: 12/16/2022]
Abstract
Triglyceride-rich lipoproteins (TRLs) undergo lipolysis by lipoprotein lipase (LPL), an enzyme that is transported to the capillary lumen by an endothelial cell protein, GPIHBP1. For LPL-mediated lipolysis to occur, TRLs must bind to the lumen of capillaries. This process is often assumed to involve heparan sulfate proteoglycans (HSPGs), but we suspected that TRL margination might instead require GPIHBP1. Indeed, TRLs marginate along the heart capillaries of wild-type but not Gpihbp1⁻/⁻ mice, as judged by fluorescence microscopy, quantitative assays with infrared-dye-labeled lipoproteins, and EM tomography. Both cell-culture and in vivo studies showed that TRL margination depends on LPL bound to GPIHBP1. Notably, the expression of LPL by endothelial cells in Gpihbp1⁻/⁻ mice did not restore defective TRL margination, implying that the binding of LPL to HSPGs is ineffective in promoting TRL margination. Our studies show that GPIHBP1-bound LPL is the main determinant of TRL margination.
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Affiliation(s)
- Chris N Goulbourne
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Peter Gin
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Angelica Tatar
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Chika Nobumori
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Andreas Hoenger
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Haibo Jiang
- Department of Materials, University of Oxford, Oxford OX13PH, UK
| | | | - Oludotun Adeyo
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Jeffrey D Esko
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ira J Goldberg
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Karen Reue
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Peter Tontonoz
- Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, USA
| | - Anne P Beigneux
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Stephen G Young
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Loren G Fong
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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Bensadoun A, Mottler CD, Pelletier C, Wu D, Seo JJ, Leung CS, Adeyo O, Goulbourne CN, Gin P, Fong LG, Young SG, Beigneux AP. A new monoclonal antibody, 4-1a, that binds to the amino terminus of human lipoprotein lipase. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:970-6. [PMID: 24681165 DOI: 10.1016/j.bbalip.2014.03.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/17/2014] [Accepted: 03/21/2014] [Indexed: 10/25/2022]
Abstract
Lipoprotein lipase (LPL) has been highly conserved through vertebrate evolution, making it challenging to generate useful antibodies. Some polyclonal antibodies against LPL have turned out to be nonspecific, and the available monoclonal antibodies (Mabs) against LPL, all of which bind to LPL's carboxyl terminus, have drawbacks for some purposes. We report a new LPL-specific monoclonal antibody, Mab 4-1a, which binds to the amino terminus of LPL (residues 5-25). Mab 4-1a binds human and bovine LPL avidly; it does not inhibit LPL catalytic activity nor does it interfere with the binding of LPL to heparin. Mab 4-1a does not bind to human hepatic lipase. Mab 4-1a binds to GPIHBP1-bound LPL and does not interfere with the ability of the LPL-GPIHBP1 complex to bind triglyceride-rich lipoproteins. Mab 4-1a will be a useful reagent for both biochemists and clinical laboratories.
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Affiliation(s)
- André Bensadoun
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, USA.
| | - Charlene D Mottler
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, USA
| | - Chris Pelletier
- Division of Nutritional Science, Cornell University, Ithaca, NY 14853, USA
| | - Daniel Wu
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Jane J Seo
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Calvin S Leung
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Oludotun Adeyo
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Chris N Goulbourne
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Peter Gin
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Loren G Fong
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA.
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Adeyo O, Goulbourne CN, Bensadoun A, Beigneux AP, Fong LG, Young SG. Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 and the intravascular processing of triglyceride-rich lipoproteins. J Intern Med 2012; 272:528-40. [PMID: 23020258 PMCID: PMC3940157 DOI: 10.1111/joim.12003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lipoprotein lipase (LPL) is produced by parenchymal cells, mainly adipocytes and myocytes, but is involved in hydrolysing triglycerides in plasma lipoproteins at the capillary lumen. For decades, the mechanism by which LPL reaches its site of action in capillaries was unclear, but this mystery was recently solved. Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells, 'picks up' LPL from the interstitial spaces and shuttles it across endothelial cells to the capillary lumen. When GPIHBP1 is absent, LPL is mislocalized to the interstitial spaces, leading to severe hypertriglyceridaemia. Some cases of hypertriglyceridaemia in humans are caused by GPIHBP1 mutations that interfere with the ability of GPIHBP1 to bind to LPL, and some are caused by LPL mutations that impair the ability of LPL to bind to GPIHBP1. Here, we review recent progress in understanding the role of GPIHBP1 in health and disease and discuss some of the remaining unresolved issues regarding the processing of triglyceride-rich lipoproteins.
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Affiliation(s)
- O Adeyo
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
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Davies BSJ, Goulbourne CN, Barnes RH, Turlo KA, Gin P, Vaughan S, Vaux DJ, Bensadoun A, Beigneux AP, Fong LG, Young SG. Assessing mechanisms of GPIHBP1 and lipoprotein lipase movement across endothelial cells. J Lipid Res 2012; 53:2690-7. [PMID: 23008484 DOI: 10.1194/jlr.m031559] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein lipase (LPL) is secreted into the interstitial spaces by adipocytes and myocytes but then must be transported to the capillary lumen by GPIHBP1, a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells. The mechanism by which GPIHBP1 and LPL move across endothelial cells remains unclear. We asked whether the transport of GPIHBP1 and LPL across endothelial cells was uni- or bidirectional. We also asked whether GPIHBP1 and LPL are transported across cells in vesicles and whether this transport process requires caveolin-1. The movement of GPIHBP1 and LPL across cultured endothelial cells was bidirectional. Also, GPIHBP1 moved bidirectionally across capillary endothelial cells in live mice. The transport of LPL across endothelial cells was inhibited by dynasore and genistein, consistent with a vesicular transport process. Also, transmission electron microscopy (EM) and dual-axis EM tomography revealed GPIHBP1 and LPL in invaginations of the plasma membrane and in vesicles. The movement of GPIHBP1 across capillary endothelial cells was efficient in the absence of caveolin-1, and there was no defect in the internalization of LPL by caveolin-1-deficient endothelial cells in culture. Our studies show that GPIHBP1 and LPL move bidirectionally across endothelial cells in vesicles and that transport is efficient even when caveolin-1 is absent.
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Affiliation(s)
- Brandon S J Davies
- Department of Medicine, University of California, Los Angeles, CA 90095, USA.
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Gin P, Goulbourne CN, Adeyo O, Beigneux AP, Davies BSJ, Tat S, Voss CV, Bensadoun A, Fong LG, Young SG. Chylomicronemia mutations yield new insights into interactions between lipoprotein lipase and GPIHBP1. Hum Mol Genet 2012; 21:2961-72. [PMID: 22493000 DOI: 10.1093/hmg/dds127] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Lipoprotein lipase (LPL) is a 448-amino-acid head-to-tail dimeric enzyme that hydrolyzes triglycerides within capillaries. LPL is secreted by parenchymal cells into the interstitial spaces; it then binds to GPIHBP1 (glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1) on the basolateral face of endothelial cells and is transported to the capillary lumen. A pair of amino acid substitutions, C418Y and E421K, abolish LPL binding to GPIHBP1, suggesting that the C-terminal portion of LPL is important for GPIHBP1 binding. However, a role for LPL's N terminus has not been excluded, and published evidence has suggested that only full-length homodimers are capable of binding GPIHBP1. Here, we show that LPL's C-terminal domain is sufficient for GPIHBP1 binding. We found, serendipitously, that two LPL missense mutations, G409R and E410V, render LPL susceptible to cleavage at residue 297 (a known furin cleavage site). The C terminus of these mutants (residues 298-448), bound to GPIHBP1 avidly, independent of the N-terminal fragment. We also generated an LPL construct with an in-frame deletion of the N-terminal catalytic domain (residues 50-289); this mutant was secreted but also was cleaved at residue 297. Once again, the C-terminal domain (residues 298-448) bound GPIHBP1 avidly. The binding of the C-terminal fragment to GPIHBP1 was eliminated by C418Y or E421K mutations. After exposure to denaturing conditions, the C-terminal fragment of LPL refolds and binds GPIHBP1 avidly. Thus, the binding of LPL to GPIHBP1 requires only the C-terminal portion of LPL and does not depend on full-length LPL homodimers.
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Affiliation(s)
- Peter Gin
- Department of Medicine, David Geffen School of Medicine, University of California-Los Angeles, CA 90095, USA
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Abstract
PURPOSE OF REVIEW We summarize recent progress on GPIHBP1, a molecule that transports lipoprotein lipase (LPL) to the capillary lumen, and discuss several newly studied molecules that appear important for the regulation of LPL activity. RECENT FINDINGS LPL, the enzyme responsible for the lipolytic processing of triglyceride-rich lipoproteins, interacts with multiple proteins and is regulated at multiple levels. Several regulators of LPL activity have been known for years and have been investigated thoroughly, but several have been identified only recently, including an endothelial cell protein that transports LPL to the capillary lumen, a microRNA that reduces LPL transcript levels, a sorting protein that targets LPL for uptake and degradation, and a transcription factor that increases the expression of apolipoproteins that regulate LPL activity. SUMMARY Proper regulation of LPL is important for controlling the delivery of lipid nutrients to tissues. Recent studies have identified GPIHBP1 as the molecule that transports LPL to the capillary lumen, and have also identified other molecules that are potentially important for regulating LPL activity. These new discoveries open new doors for understanding basic mechanisms of lipolysis and hyperlipidemia.
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Affiliation(s)
- Brandon S J Davies
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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Weinstein MM, Goulbourne CN, Davies BSJ, Tu Y, Barnes RH, Watkins SM, Davis R, Reue K, Tontonoz P, Beigneux AP, Fong LG, Young SG. Reciprocal metabolic perturbations in the adipose tissue and liver of GPIHBP1-deficient mice. Arterioscler Thromb Vasc Biol 2011; 32:230-5. [PMID: 22173228 DOI: 10.1161/atvbaha.111.241406] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Gpihbp1-deficient (Gpihbp1-/-) mice lack the ability to transport lipoprotein lipase to the capillary lumen, resulting in mislocalization of lipoprotein lipase within tissues, defective lipolysis of triglyceride-rich lipoproteins, and chylomicronemia. We asked whether GPIHBP1 deficiency and mislocalization of catalytically active lipoprotein lipase would alter the composition of triglycerides in adipose tissue or perturb the expression of lipid biosynthetic genes. We also asked whether perturbations in adipose tissue composition and gene expression, if they occur, would be accompanied by reciprocal metabolic changes in the liver. METHODS AND RESULTS The chylomicronemia in Gpihbp1-/- mice was associated with reduced levels of essential fatty acids in adipose tissue triglycerides and increased expression of lipid biosynthetic genes. The liver exhibited the opposite changes: increased levels of essential fatty acids in triglycerides and reduced expression of lipid biosynthetic genes. CONCLUSIONS Defective lipolysis in Gpihbp1-/- mice causes reciprocal metabolic perturbations in adipose tissue and liver. In adipose tissue, the essential fatty acid content of triglycerides is reduced and lipid biosynthetic gene expression is increased, whereas the opposite changes occur in the liver.
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Young SG, Davies BSJ, Voss CV, Gin P, Weinstein MM, Tontonoz P, Reue K, Bensadoun A, Fong LG, Beigneux AP. GPIHBP1, an endothelial cell transporter for lipoprotein lipase. J Lipid Res 2011; 52:1869-84. [PMID: 21844202 DOI: 10.1194/jlr.r018689] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Interest in lipolysis and the metabolism of triglyceride-rich lipoproteins was recently reignited by the discovery of severe hypertriglyceridemia (chylomicronemia) in glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1)-deficient mice. GPIHBP1 is expressed exclusively in capillary endothelial cells and binds lipoprotein lipase (LPL) avidly. These findings prompted speculation that GPIHBP1 serves as a binding site for LPL in the capillary lumen, creating "a platform for lipolysis." More recent studies have identified a second and more intriguing role for GPIHBP1-picking up LPL in the subendothelial spaces and transporting it across endothelial cells to the capillary lumen. Here, we review the studies that revealed that GPIHBP1 is the LPL transporter and discuss which amino acid sequences are required for GPIHBP1-LPL interactions. We also discuss the human genetics of LPL transport, focusing on cases of chylomicronemia caused by GPIHBP1 mutations that abolish GPIHBP1's ability to bind LPL, and LPL mutations that prevent LPL binding to GPIHBP1.
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Affiliation(s)
- Stephen G Young
- Department of Medicine, University of California, Los Angeles, CA 90095, USA.
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Beigneux AP, Davies BSJ, Tat S, Chen J, Gin P, Voss CV, Weinstein MM, Bensadoun A, Pullinger CR, Fong LG, Young SG. Assessing the role of the glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) three-finger domain in binding lipoprotein lipase. J Biol Chem 2011; 286:19735-43. [PMID: 21478160 PMCID: PMC3103352 DOI: 10.1074/jbc.m111.242024] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 04/07/2011] [Indexed: 11/06/2022] Open
Abstract
Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) is an endothelial cell protein that transports lipoprotein lipase (LPL) from the subendothelial spaces to the capillary lumen. GPIHBP1 contains two main structural motifs, an amino-terminal acidic domain enriched in aspartates and glutamates and a lymphocyte antigen 6 (Ly6) motif containing 10 cysteines. All of the cysteines in the Ly6 domain are disulfide-bonded, causing the protein to assume a three-fingered structure. The acidic domain of GPIHBP1 is known to be important for LPL binding, but the involvement of the Ly6 domain in LPL binding requires further study. To assess the importance of the Ly6 domain, we created a series of GPIHBP1 mutants in which each residue of the Ly6 domain was changed to alanine. The mutant proteins were expressed in Chinese hamster ovary (CHO) cells, and their expression level on the cell surface and their ability to bind LPL were assessed with an immunofluorescence microscopy assay and a Western blot assay. We identified 12 amino acids within GPIHBP1, aside from the conserved cysteines, that are important for LPL binding; nine of those were clustered in finger 2 of the GPIHBP1 three-fingered motif. The defective GPIHBP1 proteins also lacked the ability to transport LPL from the basolateral to the apical surface of endothelial cells. Our studies demonstrate that the Ly6 domain of GPIHBP1 is important for the ability of GPIHBP1 to bind and transport LPL.
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Affiliation(s)
- Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, California 90095, USA.
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Gin P, Beigneux AP, Voss C, Davies BSJ, Beckstead JA, Ryan RO, Bensadoun A, Fong LG, Young SG. Binding preferences for GPIHBP1, a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells. Arterioscler Thromb Vasc Biol 2010; 31:176-82. [PMID: 20966398 DOI: 10.1161/atvbaha.110.214718] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To define the ability of GPIHBP1 to bind other lipase family members and other apolipoproteins (apos) and lipoproteins. METHODS AND RESULTS GPIHBP1, a GPI-anchored lymphocyte antigen (Ly)6 protein of capillary endothelial cells, binds lipoprotein lipase (LPL) avidly, but its ability to bind related lipase family members has never been evaluated. As judged by cell-based and cell-free binding assays, LPL binds to GPIHBP1, but other members of the lipase family do not. We also examined the binding of apoAV-phospholipid disks to GPIHBP1. ApoAV binds avidly to GPIHBP1-transfected cells; this binding requires GPIHBP1's amino-terminal acidic domain and is independent of its cysteine-rich Ly6 domain (the latter domain is essential for LPL binding). GPIHBP1-transfected cells did not bind high-density lipoprotein. Chylomicrons bind avidly to GPIHBP1-transfected Chinese hamster ovary cells, but this binding is dependent on GPIHBP1's ability to bind LPL within the cell culture medium. CONCLUSIONS GPIHBP1 binds LPL but does not bind other lipase family members. GPIHBP1 binds apoAV but does not bind apoAI or high-density lipoprotein. The ability of GPIHBP1-transfected Chinese hamster ovary cells to bind chylomicrons is mediated by LPL; chylomicron binding does not occur unless GPIHBP1 first captures LPL from the cell culture medium.
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Affiliation(s)
- Peter Gin
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
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Olafsen T, Young SG, Davies BSJ, Beigneux AP, Kenanova VE, Voss C, Young G, Wong KP, Barnes RH, Tu Y, Weinstein MM, Nobumori C, Huang SC, Goldberg IJ, Bensadoun A, Wu AM, Fong LG. Unexpected expression pattern for glycosylphosphatidylinositol-anchored HDL-binding protein 1 (GPIHBP1) in mouse tissues revealed by positron emission tomography scanning. J Biol Chem 2010; 285:39239-48. [PMID: 20889497 DOI: 10.1074/jbc.m110.171041] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1), a GPI-anchored endothelial cell protein, binds lipoprotein lipase (LPL) and transports it into the lumen of capillaries where it hydrolyzes triglycerides in lipoproteins. GPIHBP1 is assumed to be expressed mainly within the heart, skeletal muscle, and adipose tissue, the sites where most lipolysis occurs, but the tissue pattern of GPIHBP1 expression has never been evaluated systematically. Because GPIHBP1 is found on the luminal face of capillaries, we predicted that it would be possible to define GPIHBP1 expression patterns with radiolabeled GPIHBP1-specific antibodies and positron emission tomography (PET) scanning. In Gpihbp1(-/-) mice, GPIHBP1-specific antibodies were cleared slowly from the blood, and PET imaging showed retention of the antibodies in the blood pools (heart and great vessels). In Gpihbp1(+/+) mice, the antibodies were cleared extremely rapidly from the blood and, to our surprise, were taken up mainly by lung and liver. Immunofluorescence microscopy confirmed the presence of GPIHBP1 in the capillary endothelium of both lung and liver. In most tissues with high levels of Gpihbp1 expression, Lpl expression was also high, but the lung was an exception (very high Gpihbp1 expression and extremely low Lpl expression). Despite low Lpl transcript levels, however, LPL protein was readily detectable in the lung, suggesting that some of that LPL originates elsewhere and then is captured by GPIHBP1 in the lung. In support of this concept, lung LPL levels were significantly lower in Gpihbp1(-/-) mice than in Gpihbp1(+/+) mice. In addition, Lpl(-/-) mice expressing human LPL exclusively in muscle contained high levels of human LPL in the lung.
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Affiliation(s)
- Tove Olafsen
- Department of Molecular and Medical Pharmacology, California NanoSystems Institute, Los Angeles, California 90095, USA
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Weinstein MM, Tu Y, Beigneux AP, Davies BSJ, Gin P, Voss C, Walzem RL, Reue K, Tontonoz P, Bensadoun A, Fong LG, Young SG. Cholesterol intake modulates plasma triglyceride levels in glycosylphosphatidylinositol HDL-binding protein 1-deficient mice. Arterioscler Thromb Vasc Biol 2010; 30:2106-13. [PMID: 20814015 DOI: 10.1161/atvbaha.110.214403] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To determine whether plasma triglyceride levels in adult Glycosylphosphatidylinositol HDL-binding protein 1 (GPIHBP1)-deficient (Gpihbp1(-/-)) mice would be sensitive to cholesterol intake. METHODS AND RESULTS Gpihbp1(-/-) mice were fed a Western diet containing 0.15% cholesterol. After 4 to 8 weeks, their plasma triglyceride levels were 113 to 135 mmol/L. When 0.005% ezetimibe was added to the diet to block cholesterol absorption, Lpl expression in the liver was reduced significantly, and the plasma triglyceride levels were significantly higher (>170 mmol/L). We also assessed plasma triglyceride levels in Gpihbp1(-/-) mice fed Western diets containing either high (1.3%) or low (0.05%) amounts of cholesterol. The high-cholesterol diet significantly increased Lpl expression in the liver and lowered plasma triglyceride levels. CONCLUSIONS Treatment of Gpihbp1(-/-) mice with ezetimibe lowers Lpl expression in the liver and increases plasma triglyceride levels. A high-cholesterol diet had the opposite effects. Thus, cholesterol intake modulates plasma triglyceride levels in Gpihbp1(-/-) mice.
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Affiliation(s)
- Michael M Weinstein
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, USA
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Abstract
GPIHBP1 is a new addition to a group of proteins required for the lipolysis of triglyceride-rich lipoproteins. GPIHBP1 contains an acidic domain and an Ly6 domain with ten cysteines. GPIHBP1 binds lipoprotein lipase (LPL) avidly and likely tethers LPL to the luminal surface of capillaries.Inactivation of Gpihbp1 in mice is associated with milky plasma and severe chylomicronemia, even on a low-fat chow diet. Recently, four missense mutations in GPIHBP1 were identified in humans with severe chylomicronemia (C65Y, C65S, C68G, and Q115P). All four mutations involve highly conserved residues within GPIHBP1's Ly6 domain.This review will provide an update on GPIHBP1's role in the processing of chylomicrons and the pathogenesis of chylomicronemia.
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Affiliation(s)
- Anne P Beigneux
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095
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49
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Davies BSJ, Beigneux AP, Barnes RH, Tu Y, Gin P, Weinstein MM, Nobumori C, Nyrén R, Goldberg I, Olivecrona G, Bensadoun A, Young SG, Fong LG. GPIHBP1 is responsible for the entry of lipoprotein lipase into capillaries. Cell Metab 2010; 12:42-52. [PMID: 20620994 PMCID: PMC2913606 DOI: 10.1016/j.cmet.2010.04.016] [Citation(s) in RCA: 273] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 03/05/2010] [Accepted: 04/28/2010] [Indexed: 12/18/2022]
Abstract
The lipolytic processing of triglyceride-rich lipoproteins by lipoprotein lipase (LPL) is the central event in plasma lipid metabolism, providing lipids for storage in adipose tissue and fuel for vital organs such as the heart. LPL is synthesized and secreted by myocytes and adipocytes, but then finds its way into the lumen of capillaries, where it hydrolyzes lipoprotein triglycerides. The mechanism by which LPL reaches the lumen of capillaries has remained an unresolved problem of plasma lipid metabolism. Here, we show that GPIHBP1 is responsible for the transport of LPL into capillaries. In Gpihbp1-deficient mice, LPL is mislocalized to the interstitial spaces surrounding myocytes and adipocytes. Also, we show that GPIHBP1 is located at the basolateral surface of capillary endothelial cells and actively transports LPL across endothelial cells. Our experiments define the function of GPIHBP1 in triglyceride metabolism and provide a mechanism for the transport of LPL into capillaries.
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Affiliation(s)
- Brandon S J Davies
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
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Franssen R, Young SG, Peelman F, Hertecant J, Sierts JA, Schimmel AWM, Bensadoun A, Kastelein JJP, Fong LG, Dallinga-Thie GM, Beigneux AP. Chylomicronemia with low postheparin lipoprotein lipase levels in the setting of GPIHBP1 defects. ACTA ACUST UNITED AC 2010; 3:169-78. [PMID: 20124439 DOI: 10.1161/circgenetics.109.908905] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Recent studies in mice have established that an endothelial cell protein, glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), is essential for the lipolytic processing of triglyceride-rich lipoproteins. METHODS AND RESULTS We report the discovery of a homozygous missense mutation in GPIHBP1 in a young boy with severe chylomicronemia. The mutation, p.C65Y, replaces a conserved cysteine in the GPIHBP1 lymphocyte antigen 6 domain with a tyrosine and is predicted to perturb protein structure by interfering with the formation of a disulfide bond. Studies with transfected Chinese hamster ovary cells showed that GPIHBP1-C65Y reaches the cell surface but has lost the ability to bind lipoprotein lipase (LPL). When the GPIHBP1-C65Y homozygote was given an intravenous bolus of heparin, only trace amounts of LPL entered the plasma. We also observed very low levels of LPL in the postheparin plasma of a subject with chylomicronemia who was homozygous for a different GPIHBP1 mutation (p.Q115P). When the GPIHBP1-Q115P homozygote was given a 6-hour infusion of heparin, a significant amount of LPL appeared in the plasma, resulting in a fall in the plasma triglyceride levels from 1780 to 120 mg/dL. CONCLUSIONS We identified a novel GPIHBP1 missense mutation (p.C65Y) associated with defective LPL binding in a young boy with severe chylomicronemia. We also show that homozygosity for the C65Y or Q115P mutations is associated with low levels of LPL in the postheparin plasma, demonstrating that GPIHBP1 is important for plasma triglyceride metabolism in humans.
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Affiliation(s)
- Remco Franssen
- Department of Vascular Medicine, Academic Medical Center Amsterdam, The Netherlands
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