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Pal-Ghosh S, Tadvalkar G, Stepp MA. Alterations in Corneal Sensory Nerves During Homeostasis, Aging, and After Injury in Mice Lacking the Heparan Sulfate Proteoglycan Syndecan-1. Invest Ophthalmol Vis Sci 2017; 58:4959-4975. [PMID: 28973369 PMCID: PMC5627677 DOI: 10.1167/iovs.17-21531] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Purpose To determine the impact of the loss of syndecan 1 (SDC1) on intraepithelial corneal nerves (ICNs) during homeostasis, aging, and in response to 1.5-mm trephine and debridement injury. Methods Whole-mount corneas are used to quantify ICN density and thickness over time after birth and in response to injury in SDC1-null and wild-type (WT) mice. High-resolution three-dimensional imaging is used to visualize intraepithelial nerve terminals (INTs), axon fragments, and lysosomes in corneal epithelial cells using antibodies against growth associated protein 43 (GAP43), βIII tubulin, and LAMP1. Quantitative PCR was performed to quantify expression of SDC1, SDC2, SDC3, and SDC4 in corneal epithelial mRNA. Phagocytosis was assessed by quantifying internalization of fluorescently labeled 1-μm latex beads. Results Intraepithelial corneal nerves innervate the corneas of SDC1-null mice more slowly. At 8 weeks, ICN density is less but thickness is greater. Apically projecting intraepithelial nerve terminals and lysosome-associated membrane glycoprotein 1 (LAMP1) are also reduced in unwounded SDC1-null corneas. Quantitative PCR and immunofluorescence studies show that SDC3 expression and localization are increased in SDC1-null ICNs. Wild-type and SDC1-null corneas lose ICN density and thickness as they age. Recovery of axon density and thickness after trephine but not debridement wounds is slower in SDC1-null corneas compared with WT. Experiments assessing phagocytosis show reduced bead internalization by SDC1-null epithelial cells. Conclusions Syndecan-1 deficiency alters ICN morphology and homeostasis during aging, reduces epithelial phagocytosis, and impairs reinnervation after trephine but not debridement injury. These data provide insight into the mechanisms used by sensory nerves to reinnervate after injury.
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Affiliation(s)
- Sonali Pal-Ghosh
- Department of Anatomy and Regenerative Biology, The George Washington University Medical School, Washington, D.C., United States
| | - Gauri Tadvalkar
- Department of Anatomy and Regenerative Biology, The George Washington University Medical School, Washington, D.C., United States
| | - Mary Ann Stepp
- Department of Anatomy and Regenerative Biology, The George Washington University Medical School, Washington, D.C., United States.,Department of Ophthalmology, The George Washington University Medical School, Washington, D.C., United States
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Leonova EI, Sadovnikova ES, Shaykhutdinova ER, Galzitskaya OV, Murashev AN, Solonin AS. Hepatic and Aortic Arch Expression and Serum Levels of Syndecan-1 in ApoE -/- Mice. Open Biochem J 2017; 11:77-93. [PMID: 29151984 PMCID: PMC5676011 DOI: 10.2174/1874091x01711010077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 05/03/2017] [Accepted: 06/09/2017] [Indexed: 12/17/2022] Open
Abstract
Background: Heparan sulfate proteoglycan (HSPG) syndecan-1 (Sdc1) acts as a receptor for triglyceride-rich lipoproteins (TRLs), growth factors, chemokines and enzymes. Due to the disordered structure, its function is as diverse as its ligands. In this paper, we have analyzed hepatic and aortic arch expression of Sdc1 in ApoE-/- mice and examined their association with biochemical changes in plasma during the atheroma formation. Methods: ApoE knockout (ApoE-/-) mice as a model of atherosclerosis were used. Plasma chemistry parameters were estimated by automatic biochemical analyzer. The ELISA test was used to detect soluble Sdc1. The mRNA level of syndecan-1 in liver cells and aortic arch was determined by real time PCR. Results: The Sdc1 mRNA level in liver cells was 1.5-2.5 times higher in ApoE-/- mice compared to the wild-type species and increased with age, whereas it remained at the same level in wild-type mice upon aging. Furthermore, the plasma cholesterol level was 4-6 times higher in ApoE-/- mice compared to the wild type; in contrast, triglyceride (TG) remained at the same level. Simultaneously, the expression of Sdc1 in the aortic arch of ApoE-/- mice decreases with age; however, it increases in wild-type mice of the same age. We determined that the Sdc1 mRNA expression in liver cells is significantly higher compared to the cells of aortic arch. In addition, our research demonstrated that the level of soluble Sdc1 slightly increased with age and did not depend on mouse genotype; yet, the total amount of soluble Sdc1 was higher in ApoE-/- mice. Conclusion: Our data suggest that the level of soluble Sdc1 in serum of mice can be associated with chronic inflammation. In addition, we hypothesized that a compensatory increase in the Sdc1 expression in ApoE-/- mice may prevent accumulation of triglycerides in serum, yet having no effect on cholesterol accumulation.
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Affiliation(s)
- Elena I Leonova
- Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Moscow Region, Pushchino, 142290, Russia
| | - Elena S Sadovnikova
- Branch of Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Pushchino 142290, Russia
| | - Elvira R Shaykhutdinova
- Branch of Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Pushchino 142290, Russia
| | - Oxana V Galzitskaya
- Institute of Protein Research, Russian Academy of Sciences, Moscow Region, Pushchino, Russia
| | - Arkady N Murashev
- Branch of Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Pushchino 142290, Russia
| | - Alexandr S Solonin
- Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Moscow Region, Pushchino, 142290, Russia
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Heparan sulfate proteoglycans present PCSK9 to the LDL receptor. Nat Commun 2017; 8:503. [PMID: 28894089 PMCID: PMC5593881 DOI: 10.1038/s41467-017-00568-7] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 07/11/2017] [Indexed: 11/08/2022] Open
Abstract
Coronary artery disease is the main cause of death worldwide and accelerated by increased plasma levels of cholesterol-rich low-density lipoprotein particles (LDL). Circulating PCSK9 contributes to coronary artery disease by inducing lysosomal degradation of the LDL receptor (LDLR) in the liver and thereby reducing LDL clearance. Here, we show that liver heparan sulfate proteoglycans are PCSK9 receptors and essential for PCSK9-induced LDLR degradation. The heparan sulfate-binding site is located in the PCSK9 prodomain and formed by surface-exposed basic residues interacting with trisulfated heparan sulfate disaccharide repeats. Accordingly, heparan sulfate mimetics and monoclonal antibodies directed against the heparan sulfate-binding site are potent PCSK9 inhibitors. We propose that heparan sulfate proteoglycans lining the hepatocyte surface capture PCSK9 and facilitates subsequent PCSK9:LDLR complex formation. Our findings provide new insights into LDL biology and show that targeting PCSK9 using heparan sulfate mimetics is a potential therapeutic strategy in coronary artery disease.PCSK9 interacts with LDL receptor, causing its degradation, and consequently reduces the clearance of LDL. Here, Gustafsen et al. show that PCSK9 interacts with heparan sulfate proteoglycans and this binding favors LDLR degradation. Pharmacological inhibition of this binding can be exploited as therapeutic intervention to lower LDL levels.
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Abstract
Heparin and heparan sulfate glycosaminoglycans are long, linear polysaccharides that are made up of alternating dissacharide sequences of sulfated uronic acid and amino sugars. Unlike heparin, which is only found in mast cells, heparan sulfate is ubiquitously expressed on the cell surface and in the extracellular matrix of all animal cells. These negatively-charged glycans play essential roles in important cellular functions such as cell growth, adhesion, angiogenesis, and blood coagulation. These biomolecules are also involved in pathophysiological conditions such as pathogen infection and human disease. This review discusses past and current methods for targeting these complex biomolecules as a novel therapeutic strategy to treating disorders such as cancer, neurodegenerative diseases, and infection.
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Affiliation(s)
- Ryan J Weiss
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA 92093-0358, USA
| | - Jeffrey D Esko
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA 92093-0358, USA
| | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0358, USA.
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Palomino R, Lee HW, Millhauser GL. The agouti-related peptide binds heparan sulfate through segments critical for its orexigenic effects. J Biol Chem 2017; 292:7651-7661. [PMID: 28264929 DOI: 10.1074/jbc.m116.772822] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 03/03/2017] [Indexed: 12/20/2022] Open
Abstract
Syndecans potently modulate agouti-related peptide (AgRP) signaling in the central melanocortin system. Through heparan sulfate moieties, syndecans are thought to anchor AgRP near its receptor, enhancing its orexigenic effects. Original work proposed that the N-terminal domain of AgRP facilitates this interaction. However, this is not compatible with evidence that this domain is posttranslationally cleaved. Addressing this long-standing incongruity, we used calorimetry and magnetic resonance to probe interactions of AgRP peptides with glycosaminoglycans, including heparan sulfate. We show that mature, cleaved, C-terminal AgRP, not the N-terminal domain, binds heparan sulfate. NMR shows that the binding site consists of regions distinct from the melanocortin receptor-binding site. Using a library of designed AgRP variants, we find that the strength of the syndecan interaction perfectly tracks orexigenic action. Our data provide compelling evidence that AgRP is a heparan sulfate-binding protein and localizes critical regions in the AgRP structure required for this interaction.
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Affiliation(s)
- Rafael Palomino
- From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
| | - Hsiau-Wei Lee
- From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
| | - Glenn L Millhauser
- From the Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
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Gordts PLSM, Nock R, Son NH, Ramms B, Lew I, Gonzales JC, Thacker BE, Basu D, Lee RG, Mullick AE, Graham MJ, Goldberg IJ, Crooke RM, Witztum JL, Esko JD. ApoC-III inhibits clearance of triglyceride-rich lipoproteins through LDL family receptors. J Clin Invest 2016; 126:2855-66. [PMID: 27400128 DOI: 10.1172/jci86610] [Citation(s) in RCA: 181] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 05/12/2016] [Indexed: 02/05/2023] Open
Abstract
Hypertriglyceridemia is an independent risk factor for cardiovascular disease, and plasma triglycerides (TGs) correlate strongly with plasma apolipoprotein C-III (ApoC-III) levels. Antisense oligonucleotides (ASOs) for ApoC-III reduce plasma TGs in primates and mice, but the underlying mechanism of action remains controversial. We determined that a murine-specific ApoC-III-targeting ASO reduces fasting TG levels through a mechanism that is dependent on low-density lipoprotein receptors (LDLRs) and LDLR-related protein 1 (LRP1). ApoC-III ASO treatment lowered plasma TGs in mice lacking lipoprotein lipase (LPL), hepatic heparan sulfate proteoglycan (HSPG) receptors, LDLR, or LRP1 and in animals with combined deletion of the genes encoding HSPG receptors and LDLRs or LRP1. However, the ApoC-III ASO did not lower TG levels in mice lacking both LDLR and LRP1. LDLR and LRP1 were also required for ApoC-III ASO-induced reduction of plasma TGs in mice fed a high-fat diet, in postprandial clearance studies, and when ApoC-III-rich or ApoC-III-depleted lipoproteins were injected into mice. ASO reduction of ApoC-III had no effect on VLDL secretion, heparin-induced TG reduction, or uptake of lipids into heart and skeletal muscle. Our data indicate that ApoC-III inhibits turnover of TG-rich lipoproteins primarily through a hepatic clearance mechanism mediated by the LDLR/LRP1 axis.
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Gandley RE, Althouse A, Jeyabalan A, Bregand-White JM, McGonigal S, Myerski AC, Gallaher M, Powers RW, Hubel CA. Low Soluble Syndecan-1 Precedes Preeclampsia. PLoS One 2016; 11:e0157608. [PMID: 27299886 PMCID: PMC4907460 DOI: 10.1371/journal.pone.0157608] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 06/01/2016] [Indexed: 12/18/2022] Open
Abstract
INTRODUCTION Syndecan-1 (Sdc1; CD138) is a major transmembrane heparan sulfate proteoglycan expressed on the extracellular, luminal surface of epithelial cells and syncytiotrophoblast, thus comprising a major component of the glycocalyx of these cells. The "soluble" (shed) form of Sdc1 has paracrine and autocrine functions and is normally produced in a regulated fashion. We compared plasma soluble Sdc1 concentrations, in relation to placental Sdc1 expression, in uncomplicated (control) and preeclamptic pregnancies. METHODS We evaluated soluble Sdc1 across uncomplicated pregnancy, and between preeclamptic, gestational hypertensive and control patients at mid-pregnancy (20 weeks) and 3rd trimester by ELISA. Placental expression level of Sdc1 was compared between groups in relation to pre-delivery plasma soluble Sdc1. Participants were recruited from Magee-Womens Hospital. RESULTS In uncomplicated pregnancy, plasma soluble Sdc1 rose significantly in the 1st trimester, and reached an approximate 50-fold increase at term compared to post pregnancy levels. Soluble Sdc1 was lower at mid-pregnancy in women who later developed preeclampsia (P<0.05), but not gestational hypertension, compared to controls, and remained lower at late pregnancy in preeclampsia (P<0.01) compared to controls. Sdc1 was prominently expressed on syncytiotrophoblast of microvilli. Syncytiotrophoblast Sdc1 immunostaining intensities, and mRNA content in villous homogenates, were lower in preeclampsia vs. controls (P<0.05). Soluble Sdc1 and Sdc1 immunostaining scores were inversely associated with systolic blood pressures, and positively correlated with infant birth weight percentile. CONCLUSION Soluble Sdc1 is significantly lower before the clinical onset of preeclampsia, with reduced expression of Sdc1 in the delivered placenta, suggesting a role for glycocalyx disturbance in preeclampsia pathophysiology.
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Affiliation(s)
- Robin E Gandley
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.,Department of Obstetrics, Gynecology & Reproductive Sciences, Division of Maternal Fetal Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Andrew Althouse
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Arundhathi Jeyabalan
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.,Department of Obstetrics, Gynecology & Reproductive Sciences, Division of Maternal Fetal Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.,Clinical and Translational Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Julia M Bregand-White
- Department of Obstetrics, Gynecology & Reproductive Sciences, Division of Maternal Fetal Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Stacy McGonigal
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Ashley C Myerski
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Marcia Gallaher
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Robert W Powers
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.,Department of Obstetrics, Gynecology & Reproductive Sciences, Division of Maternal Fetal Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Carl A Hubel
- Department of Obstetrics, Gynecology & Reproductive Sciences, Division of Maternal Fetal Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
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Ricard-Blum S, Gondelaud F. [Shuttling from the extracellular matrix to the nucleus]. Biol Aujourdhui 2016; 210:37-44. [PMID: 27286579 DOI: 10.1051/jbio/2016007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Indexed: 01/03/2023]
Abstract
Several enzymes secreted in the extracellular space, such as matrix metalloproteinases and lysyl oxidase, are internalized and translocated to the nucleus, where they may act as proteases and transcription factors to regulate gene expression and enhance apoptosis. Membrane proteoglycan syndecans, glycosaminoglycans and an anti-angiogenic matricryptin of collagen XVIII have also been identified in the nucleus. The nuclear entry of most extracellular proteins is likely mediated by nuclear localizing sequences. The molecular mechanisms of nuclear import, the physiopathological contexts, which induce it, and the biological roles played in vivo by extracellular proteins and proteoglycans are still underexplored.
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Abstract
Glycosaminoglycans (GAGs) are complex linear polysaccharides expressed in intracellular compartments, at the cell surface, and in the extracellular environment where they interact with various molecules to regulate many cellular processes implicated in health and disease. Subversion of GAGs is a pathogenic strategy shared by a wide variety of microbial pathogens, including viruses, bacteria, parasites, and fungi. Pathogens use GAGs at virtually every major portals of entry to promote their attachment and invasion of host cells, movement from one cell to another, and to protect themselves from immune attack. Pathogens co-opt fundamental activities of GAGs to accomplish these tasks. This ingenious strategy to subvert essential activities of GAGs likely prevented host organisms from deleting or inactivating these mechanisms during their evolution. The goal of this review is to provide a mechanistic overview of our current understanding of how microbes subvert GAGs at major steps of pathogenesis, using select GAG-pathogen interactions as representative examples.
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Affiliation(s)
- Rafael S Aquino
- Division of Respiratory Diseases and 2Division of Newborn Medicine, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Pyong Woo Park
- Division of Respiratory Diseases Children's Hospital, Harvard Medical School, Boston, MA 02115, USA and Division of Newborn Medicine, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA,
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Gowd V, Gurukar A, Chilkunda ND. Glycosaminoglycan remodeling during diabetes and the role of dietary factors in their modulation. World J Diabetes 2016; 7:67-73. [PMID: 26962410 PMCID: PMC4766247 DOI: 10.4239/wjd.v7.i4.67] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Revised: 11/23/2015] [Accepted: 01/04/2016] [Indexed: 02/06/2023] Open
Abstract
Glycosaminoglycans (GAGs) play a significant role in various aspects of cell physiology. These are complex polymeric molecules characterized by disaccharides comprising of uronic acid and amino sugar. Compounded to the heterogeneity, these are variously sulfated and epimerized depending on the class of GAG. Among the various classes of GAG, namely, chondroitin/dermatan sulfate, heparin/heparan sulfate, keratan sulfate and hyaluronic acid (HA), only HA is non-sulfated. GAGs are known to undergo remodeling in various tissues during various pathophysiological conditions, diabetes mellitus being one among them. These changes will likely affect their structure thereby impinging on their functionality. Till date, diabetes has been shown to affect GAGs in organs such as kidney, liver, aorta, skin, erythrocytes, etc. to name a few, with deleterious consequences. One of the mainstays in the treatment of diabetes is though dietary means. Various dietary factors are known to play a significant role in regulating glucose homeostasis. Furthermore, in recent years, there has been a keen interest to decipher the role of dietary factors on GAG metabolism. This review focuses on the remodeling of GAGs in various organs during diabetes and their modulation by dietary factors. While effect of diabetes on GAG metabolism has been worked out quite a bit, studies on the role of dietary factors in their modulation has been few and far between. We have tried our best to give the latest reports available on this subject.
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Pugh RJ, Slee JB, Farwell SLN, Li Y, Barthol T, Patton WA, Lowe-Krentz LJ. Transmembrane Protein 184A Is a Receptor Required for Vascular Smooth Muscle Cell Responses to Heparin. J Biol Chem 2016; 291:5326-41. [PMID: 26769966 DOI: 10.1074/jbc.m115.681122] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Indexed: 11/06/2022] Open
Abstract
Vascular cell responses to exogenous heparin have been documented to include decreased vascular smooth muscle cell proliferation following decreased ERK pathway signaling. However, the molecular mechanism(s) by which heparin interacts with cells to induce those responses has remained unclear. Previously characterized monoclonal antibodies that block heparin binding to vascular cells have been found to mimic heparin effects. In this study, those antibodies were employed to isolate a heparin binding protein. MALDI mass spectrometry data provide evidence that the protein isolated is transmembrane protein 184A (TMEM184A). Commercial antibodies against three separate regions of the TMEM184A human protein were used to identify the TMEM184A protein in vascular smooth muscle cells and endothelial cells. A GFP-TMEM184A construct was employed to determine colocalization with heparin after endocytosis. Knockdown of TMEM184A eliminated the physiological responses to heparin, including effects on ERK pathway activity and BrdU incorporation. Isolated GFP-TMEM184A binds heparin, and overexpression results in additional heparin uptake. Together, these data support the identification of TMEM184A as a heparin receptor in vascular cells.
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Affiliation(s)
- Raymond J Pugh
- Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015
| | - Joshua B Slee
- From the Departments of Biological Sciences and the Department of Natural Sciences, DeSales University, Center Valley, Pennsylvania 18034
| | | | - Yaqiu Li
- From the Departments of Biological Sciences and
| | | | - Walter A Patton
- the Department of Chemistry, Lebanon Valley College, Annville, Pennsylvania 17003, and
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Baghy K, Tátrai P, Regős E, Kovalszky I. Proteoglycans in liver cancer. World J Gastroenterol 2016; 22:379-393. [PMID: 26755884 PMCID: PMC4698501 DOI: 10.3748/wjg.v22.i1.379] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 09/14/2015] [Accepted: 11/09/2015] [Indexed: 02/06/2023] Open
Abstract
Proteoglycans are a group of molecules that contain at least one glycosaminoglycan chain, such as a heparan, dermatan, chondroitin, or keratan sulfate, covalently attached to the protein core. These molecules are categorized based on their structure, localization, and function, and can be found in the extracellular matrix, on the cell surface, and in the cytoplasm. Cell-surface heparan sulfate proteoglycans, such as syndecans, are the primary type present in healthy liver tissue. However, deterioration of the liver results in overproduction of other proteoglycan types. The purpose of this article is to provide a current summary of the most relevant data implicating proteoglycans in the development and progression of human and experimental liver cancer. A review of our work and other studies in the literature indicate that deterioration of liver function is accompanied by an increase in the amount of chondroitin sulfate proteoglycans. The alteration of proteoglycan composition interferes with the physiologic function of the liver on several levels. This article details and discusses the roles of syndecan-1, glypicans, agrin, perlecan, collagen XVIII/endostatin, endocan, serglycin, decorin, biglycan, asporin, fibromodulin, lumican, and versican in liver function. Specifically, glypicans, agrin, and versican play significant roles in the development of liver cancer. Conversely, the presence of decorin could potentially provide protective effects.
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Springer SA, Gagneux P. Glycomics: revealing the dynamic ecology and evolution of sugar molecules. J Proteomics 2015; 135:90-100. [PMID: 26626628 DOI: 10.1016/j.jprot.2015.11.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Revised: 11/11/2015] [Accepted: 11/23/2015] [Indexed: 01/11/2023]
Abstract
Sugars are the most functionally and structurally diverse molecules in the biological world. Glycan structures range from tiny single monosaccharide units to giant chains thousands of units long. Some glycans are branched, their monosaccharides linked together in many different combinations and orientations. Some exist as solitary molecules; others are conjugated to proteins and lipids and alter their collective functional properties. In addition to structural and storage roles, glycan molecules participate in and actively regulate physiological and developmental processes. Glycans also mediate cellular interactions within and between individuals. Their roles in ecology and evolution are pivotal, but not well studied because glycan biochemistry requires different methods than standard molecular biology practice. The properties of glycans are in some ways convenient, and in others challenging. Glycans vary on organismal timescales, and in direct response to physiological and ecological conditions. Their mature structures are physical records of both genetic and environmental influences during maturation. We describe the scope of natural glycan variation and discuss how studying glycans will allow researchers to further integrate the fields of ecology and evolution.
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Affiliation(s)
- Stevan A Springer
- Glycobiology Research and Training Center, University of California San Diego, La Jolla, CA 92039, USA; Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92039, USA.
| | - Pascal Gagneux
- Glycobiology Research and Training Center, University of California San Diego, La Jolla, CA 92039, USA; Department of Pathology, University of California San Diego, La Jolla, CA 92039, USA.
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Hepatocyte Heparan Sulfate Is Required for Adeno-Associated Virus 2 but Dispensable for Adenovirus 5 Liver Transduction In Vivo. J Virol 2015; 90:412-20. [PMID: 26491162 DOI: 10.1128/jvi.01939-15] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Accepted: 10/12/2015] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED Adeno-associated virus 2 (AAV2) and adenovirus 5 (Ad5) are promising gene therapy vectors. Both display liver tropism and are currently thought to enter hepatocytes in vivo through cell surface heparan sulfate proteoglycans (HSPGs). To test directly this hypothesis, we created mice that lack Ext1, an enzyme required for heparan sulfate biosynthesis, in hepatocytes. Ext1(HEP) mutant mice exhibit an 8-fold reduction of heparan sulfate in primary hepatocytes and a 5-fold reduction of heparan sulfate in whole liver tissue. Conditional hepatocyte Ext1 gene deletion greatly reduced AAV2 liver transduction following intravenous injection. Ad5 transduction requires blood coagulation factor X (FX); FX binds to the Ad5 capsid hexon protein and bridges the virus to HSPGs on the cell surface. Ad5.FX transduction was abrogated in primary hepatocytes from Ext1(HEP) mice. However, in contrast to the case with AAV2, Ad5 transduction was not significantly reduced in the livers of Ext1(HEP) mice. FX remained essential for Ad5 transduction in vivo in Ext1(HEP) mice. We conclude that while AAV2 requires HSPGs for entry into mouse hepatocytes, HSPGs are dispensable for Ad5 hepatocyte transduction in vivo. This study reopens the question of how adenovirus enters cells in vivo. IMPORTANCE Our understanding of how viruses enter cells, and how they can be used as therapeutic vectors to manage disease, begins with identification of the cell surface receptors to which viruses bind and which mediate viral entry. Both adeno-associated virus 2 and adenovirus 5 are currently thought to enter hepatocytes in vivo through heparan sulfate proteoglycans (HSPGs). However, direct evidence for these conclusions is lacking. Experiments presented herein, in which hepatic heparan sulfate synthesis was genetically abolished, demonstrated that HSPGs are not likely to function as hepatocyte Ad5 receptors in vivo. The data also demonstrate that HSPGs are required for hepatocyte transduction by AAV2. These results reopen the question of the identity of the Ad5 receptor in vivo and emphasize the necessity of demonstrating the nature of the receptor by genetic means, both for understanding Ad5 entry into cells in vivo and for optimization of Ad5 vectors as therapeutic agents.
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Pasqualon T, Pruessmeyer J, Weidenfeld S, Babendreyer A, Groth E, Schumacher J, Schwarz N, Denecke B, Jahr H, Zimmermann P, Dreymueller D, Ludwig A. A transmembrane C-terminal fragment of syndecan-1 is generated by the metalloproteinase ADAM17 and promotes lung epithelial tumor cell migration and lung metastasis formation. Cell Mol Life Sci 2015; 72:3783-801. [PMID: 25912030 PMCID: PMC11114049 DOI: 10.1007/s00018-015-1912-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 03/30/2015] [Accepted: 04/20/2015] [Indexed: 12/27/2022]
Abstract
Syndecan-1 is a heparan sulfate proteoglycan expressed by endothelial and epithelial cells and involved in wound healing and tumor growth. Surface-expressed syndecan-1 undergoes proteolytic shedding leading to the release of the soluble N-terminal ectodomain from a transmembrane C-terminal fragment (tCTF). We show that the disintegrin and metalloproteinase (ADAM) 17 generates a syndecan-1 tCTF, which can then undergo further intra-membrane proteolysis by γ-secretase. Scratch-induced wound closure of cultured lung epithelial A549 tumor cells associates with increased syndecan-1 cleavage as evidenced by the release of shed syndecan-1 ectodomain and enhanced generation of the tCTF. Both wound closure and the associated syndecan-1 shedding can be suppressed by inhibition of ADAM family proteases. Cell proliferation, migration and invasion into matrigel as well as several signaling pathways implicated in these responses are suppressed by silencing of syndecan-1. These defects of syndecan-1 deficient cells can be overcome by overexpression of syndecan-1 tCTF or a corresponding tCTF of syndecan-4 but not by overexpression of a tCTF lacking the transmembrane domain. Finally, lung metastasis formation of A549 cells in SCID mice was found to be dependent on syndecan-1, and the presence of syndecan-1 tCTF was sufficient for this activity. Thus, the syndecan-1 tCTF by itself is capable of mediating critical syndecan-1-dependent functions in cell proliferation, migration, invasion and metastasis formation and therefore can replace full length syndecan-1 in the situation of increased syndecan-1 shedding during cell migration and tumor formation.
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Affiliation(s)
- Tobias Pasqualon
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Jessica Pruessmeyer
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Sarah Weidenfeld
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Aaron Babendreyer
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Esther Groth
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Julian Schumacher
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Nicole Schwarz
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany
| | - Bernd Denecke
- Interdisciplinary Center for Clinical Research, RWTH Aachen University, Aachen, Germany
| | - Holger Jahr
- Department of Orthopaedic Surgery, RWTH Aachen University, Aachen, Germany
| | - Pascale Zimmermann
- Centre de Recherche en Cancérologie de Marseille (CRCM), Inserm, U1068-CNRS UMR7258, Aix-Marseille Université, Institut Paoli-Calmettes, Marseille, France
- Department of Human Genetics, KU Leuven, 3000, Louvain, Belgium
| | - Daniela Dreymueller
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany
| | - Andreas Ludwig
- Institute of Pharmacology and Toxicology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany.
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66
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Gopal S, Søgaard P, Multhaupt HAB, Pataki C, Okina E, Xian X, Pedersen ME, Stevens T, Griesbeck O, Park PW, Pocock R, Couchman JR. Transmembrane proteoglycans control stretch-activated channels to set cytosolic calcium levels. J Cell Biol 2015; 210:1199-211. [PMID: 26391658 PMCID: PMC4586746 DOI: 10.1083/jcb.201501060] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 08/25/2015] [Indexed: 02/07/2023] Open
Abstract
Syndecans regulate members of the transient receptor potential family to control cytosolic calcium levels with impact on cell adhesion, junction formation, and neuronal guidance. Transmembrane heparan sulfate proteoglycans regulate multiple aspects of cell behavior, but the molecular basis of their signaling is unresolved. The major family of transmembrane proteoglycans is the syndecans, present in virtually all nucleated cells, but with mostly unknown functions. Here, we show that syndecans regulate transient receptor potential canonical (TRPCs) channels to control cytosolic calcium equilibria and consequent cell behavior. In fibroblasts, ligand interactions with heparan sulfate of syndecan-4 recruit cytoplasmic protein kinase C to target serine714 of TRPC7 with subsequent control of the cytoskeleton and the myofibroblast phenotype. In epidermal keratinocytes a syndecan–TRPC4 complex controls adhesion, adherens junction composition, and early differentiation in vivo and in vitro. In Caenorhabditis elegans, the TRPC orthologues TRP-1 and -2 genetically complement the loss of syndecan by suppressing neuronal guidance and locomotory defects related to increases in neuronal calcium levels. The widespread and conserved syndecan–TRPC axis therefore fine tunes cytoskeletal organization and cell behavior.
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Affiliation(s)
- Sandeep Gopal
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Pernille Søgaard
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Hinke A B Multhaupt
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Csilla Pataki
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Elena Okina
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Xiaojie Xian
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Mikael E Pedersen
- Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Troy Stevens
- Department of Pharmacology, Center for Lung Biology, University of South Alabama, Mobile, AL 36688 Department of Medicine, Center for Lung Biology, University of South Alabama, Mobile, AL 36688
| | - Oliver Griesbeck
- Max Planck Institute of Neurobiology, 82152 Martinsried, Germany
| | - Pyong Woo Park
- Division of Newborn Medicine, Children's Hospital, Harvard Medical School, Boston, MA 02115 Division of Respiratory Diseases, Children's Hospital, Harvard Medical School, Boston, MA 02115
| | - Roger Pocock
- Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
| | - John R Couchman
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark Biotech Research and Innovation Center, University of Copenhagen, 2200 Copenhagen, Denmark
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67
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Meen AJ, Drevon CA, Pejler G, Jenssen TG, Olstad OK, Åbrink M, Kolset SO. Serglycin protects against high fat diet-induced increase in serum LDL in mice. Glycoconj J 2015; 32:703-14. [PMID: 26391682 DOI: 10.1007/s10719-015-9621-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 09/02/2015] [Accepted: 09/08/2015] [Indexed: 12/21/2022]
Abstract
Proteoglycans have been implicated in regulation of lipoprotein metabolism. However, the impact of serglycin, the major proteoglycan expressed by many hematopoietic- and endothelial cells, on lipoprotein metabolism has not been explored. Here we addressed this issue by comparing several parameters of lipid metabolism in wild type (WT) and serglycin-/- mice, both at baseline and after feeding mice the Paigen diet. We show that, after feeding this diet for 20 weeks, serglycin deficient mice exhibited elevated concentrations of serum LDL in comparison with WT mice, thus suggesting that serglycin protects against an elevation of serum LDL levels after intake of a high-fat diet. Body weight increased in both groups, but only significantly in the serglycin-/- group. To explore the mechanism underlying this phenotype, genome-wide expression analysis was performed on liver tissues from WT and serglycin-/- mice. This analysis showed that serglycin-deficiency is associated with differential expression of numerous genes involved in the regulation of lipid metabolism, suggesting that the impact of serglycin on LDL levels may be related to effects at the gene expression level. In particular, several members of the CYP gene family were differently regulated in serglycin-/- compared with WT mice. Moreover, upstream regulator analysis suggested that several pro-inflammatory pathways, including the NFκB pathway, could contribute to the impact of serglycin on LDL. Hence, the elevation of serum LDL seen in serglycin-/- mice may be linked to dysregulated inflammatory responses. Taken together, our findings introduce serglycin as a novel player in processes that regulate lipid metabolism.
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Affiliation(s)
- Astri J Meen
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Pb. 1046, Blindern, 0317, Oslo, Norway.
| | - Christian A Drevon
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Pb. 1046, Blindern, 0317, Oslo, Norway
| | - Gunnar Pejler
- Department of Anatomy, Physiology, and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden.,Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Trond G Jenssen
- Department of Transplant Medicine, Section of Nephrology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Health Science, University of Tromsø, Tromsø, Norway
| | - Ole Kristoffer Olstad
- Department of Medical Biochemistry, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Magnus Åbrink
- Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Svein O Kolset
- Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Pb. 1046, Blindern, 0317, Oslo, Norway
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68
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Dai H, Rahman A, Saxena A, Jaiswal AK, Mohamood A, Ramirez L, Noel S, Rabb H, Jie C, Hamad ARA. Syndecan-1 identifies and controls the frequency of IL-17-producing naïve natural killer T (NKT17) cells in mice. Eur J Immunol 2015; 45:3045-51. [PMID: 26300525 DOI: 10.1002/eji.201545532] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 07/21/2015] [Accepted: 08/19/2015] [Indexed: 02/06/2023]
Abstract
Invariant natural killer T (iNKT) cells recognize glycolipids as antigens and diversify into NKT1 (IFN-γ), NKT2 (IL-4), and NKT17 (IL-17) functional subsets while developing in the thymus. Mechanisms that govern the balance between these functional subsets are poorly understood due, partly, to the lack of distinguishing surface markers. Here we identify the heparan sulfate proteoglycan syndecan-1 (sdc1) as a specific marker of naïve thymic NKT17 cells in mice and show that sdc1 deficiency significantly increases thymic NKT17 cells at the expense of NKT1 cells, leading to impaired iNKT cell-derived IFN-γ, both in vitro and in vivo. Using surface expression of sdc1 to identify NKT17 cells, we confirm differential tissue localization and interstrain variability of NKT17 cells, and reveal that NKT17 cells express high levels of TCR-β, preferentially use Vβ8, and are more highly sensitive to ɑ-GalCer than to CD3/CD28 stimulation. These findings provide a novel, noninvasive, simple method for identification, and viable sorting of naïve NKT17 cells from unmanipulated mice, and suggest that sdc1 expression negatively regulates homeostasis in iNKT cells. In addition, these findings lay the groundwork for investigating the mechanisms by which sdc1 regulates NKT17 cells.
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Affiliation(s)
- Hong Dai
- Department of Pathology, Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ayesha Rahman
- Department of Pathology, Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ankit Saxena
- Department of Pathology, Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Anil K Jaiswal
- Department of Pathology, Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Abdiaziz Mohamood
- Department of Pathology, Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Lourdes Ramirez
- Department of Pathology, Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sanjeev Noel
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hamid Rabb
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Chunfa Jie
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, USA
| | - Abdel Rahim A Hamad
- Department of Pathology, Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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69
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Amaya R, Pierides A, Tarbell JM. The Interaction between Fluid Wall Shear Stress and Solid Circumferential Strain Affects Endothelial Gene Expression. PLoS One 2015; 10:e0129952. [PMID: 26147292 PMCID: PMC4492743 DOI: 10.1371/journal.pone.0129952] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 05/14/2015] [Indexed: 11/19/2022] Open
Abstract
Endothelial cells lining the walls of blood vessels are exposed simultaneously to wall shear stress (WSS) and circumferential stress (CS) that can be characterized by the temporal phase angle between WSS and CS (stress phase angle - SPA). Regions of the circulation with highly asynchronous hemodynamics (SPA close to -180°) such as coronary arteries are associated with the development of pathological conditions such as atherosclerosis and intimal hyperplasia whereas more synchronous regions (SPA closer to 0°) are spared of disease. The present study evaluates endothelial cell gene expression of 42 atherosclerosis-related genes under asynchronous hemodynamics (SPA=-180 °) and synchronous hemodynamics (SPA=0 °). This study used a novel bioreactor to investigate the cellular response of bovine aortic endothelial cells (BAECS) exposed to a combination of pulsatile WSS and CS at SPA=0 or SPA=-180. Using a PCR array of 42 genes, we determined that BAECS exposed to non-reversing sinusoidal WSS (10±10 dyne/cm2) and CS (4 ± 4%) over a 7 hour testing period displayed 17 genes that were up regulated by SPA = -180 °, most of them pro-atherogenic, including NFκB and other NFκB target genes. The up regulation of NFκB p50/p105 and p65 by SPA =-180° was confirmed by Western blots and immunofluorescence staining demonstrating the nuclear translocation of NFκB p50/p105 and p65. These data suggest that asynchronous hemodynamics (SPA=-180 °) can elicit proatherogenic responses in endothelial cells compared to synchronous hemodynamics without shear stress reversal, indicating that SPA may be an important parameter characterizing arterial susceptibility to disease.
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Affiliation(s)
- Ronny Amaya
- Department of Biomedical Engineering, City College of New York, City University of New York, New York, New York, 10031, United States of America
| | - Alexis Pierides
- Department of Biomedical Engineering, City College of New York, City University of New York, New York, New York, 10031, United States of America
| | - John M. Tarbell
- Department of Biomedical Engineering, City College of New York, City University of New York, New York, New York, 10031, United States of America
- * E-mail:
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70
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Lillis AP, Muratoglu SC, Au DT, Migliorini M, Lee MJ, Fried SK, Mikhailenko I, Strickland DK. LDL Receptor-Related Protein-1 (LRP1) Regulates Cholesterol Accumulation in Macrophages. PLoS One 2015; 10:e0128903. [PMID: 26061292 PMCID: PMC4463855 DOI: 10.1371/journal.pone.0128903] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 05/03/2015] [Indexed: 11/18/2022] Open
Abstract
Within the circulation, cholesterol is transported by lipoprotein particles and is taken up by cells when these particles associate with cellular receptors. In macrophages, excessive lipoprotein particle uptake leads to foam cell formation, which is an early event in the development of atherosclerosis. Currently, mechanisms responsible for foam cell formation are incompletely understood. To date, several macrophage receptors have been identified that contribute to the uptake of modified forms of lipoproteins leading to foam cell formation, but the in vivo contribution of the LDL receptor-related protein 1 (LRP1) to this process is not known [corrected]. To investigate the role of LRP1 in cholesterol accumulation in macrophages, we generated mice with a selective deletion of LRP1 in macrophages on an LDL receptor (LDLR)-deficient background (macLRP1-/-). After feeding mice a high fat diet for 11 weeks, peritoneal macrophages isolated from Lrp+/+ mice contained significantly higher levels of total cholesterol than those from macLRP1-/- mice. Further analysis revealed that this was due to increased levels of cholesterol esters. Interestingly, macLRP1-/- mice displayed elevated plasma cholesterol and triglyceride levels resulting from accumulation of large, triglyceride-rich lipoprotein particles in the circulation. This increase did not result from an increase in hepatic VLDL biosynthesis, but rather results from a defect in catabolism of triglyceride-rich lipoprotein particles in macLRP1-/- mice. These studies reveal an important in vivo contribution of macrophage LRP1 to cholesterol homeostasis.
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Affiliation(s)
- Anna P. Lillis
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
- Department of Pathology, Duke University Medical Center, Durham, NC 27710, United States of America
| | - Selen Catania Muratoglu
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
| | - Dianaly T. Au
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
| | - Mary Migliorini
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
| | - Mi-Jeong Lee
- Department of Medicine, Section of Endocrinology, Diabetes and Nutrition, Boston University School of Medicine, Boston, MA 02118, United States of America
| | - Susan K. Fried
- Department of Medicine, Section of Endocrinology, Diabetes and Nutrition, Boston University School of Medicine, Boston, MA 02118, United States of America
| | - Irina Mikhailenko
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
| | - Dudley K. Strickland
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, United States of America
- * E-mail:
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71
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Hopkins PN, Brinton EA, Nanjee MN. Hyperlipoproteinemia type 3: the forgotten phenotype. Curr Atheroscler Rep 2015; 16:440. [PMID: 25079293 DOI: 10.1007/s11883-014-0440-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Hyperlipoproteinemia type 3 (HLP3) is caused by impaired removal of triglyceride-rich lipoproteins (TGRL) leading to accumulation of TGRL remnants with abnormal composition. High levels of these remnants, called β-VLDL, promote lipid deposition in tuberous xanthomas, atherosclerosis, premature coronary artery disease, and early myocardial infarction. Recent genetic and molecular studies suggest more genes than previously appreciated may contribute to the expression of HLP3, both through impaired hepatic TGRL processing or removal and increased TGRL production. HLP3 is often highly amenable to appropriate treatment. Nevertheless, most HLP3 probably goes undiagnosed, in part because of lack of awareness of the relatively high prevalence (about 0.2% in women and 0.4-0.5% in men older than 20 years) and largely because of infrequent use of definitive diagnostic methods.
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Affiliation(s)
- Paul N Hopkins
- Cardiovascular Genetics, Department of Internal Medicine, University of Utah, 420 Chipeta Way, Room 1160, Salt Lake City, UT, 84108, USA,
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72
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Wang Y, Gusarova V, Banfi S, Gromada J, Cohen JC, Hobbs HH. Inactivation of ANGPTL3 reduces hepatic VLDL-triglyceride secretion. J Lipid Res 2015; 56:1296-307. [PMID: 25954050 DOI: 10.1194/jlr.m054882] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Indexed: 02/01/2023] Open
Abstract
Humans and mice lacking angiopoietin-like protein 3 (ANGPTL3) have pan-hypolipidemia. ANGPTL3 inhibits two intravascular lipases, LPL and endothelial lipase, and the low plasma TG and HDL-cholesterol levels in ANGPTL3 deficiency reflect increased activity of these enzymes. The mechanism responsible for the low LDL-cholesterol levels associated with ANGPTL3 deficiency is not known. Here we used an anti-ANGPTL3 monoclonal antibody (REGN1500) to inactivate ANGPTL3 in mice with genetic deficiencies in key proteins involved in clearance of ApoB-containing lipoproteins. REGN1500 treatment consistently reduced plasma cholesterol levels in mice in which Apoe, Ldlr, Lrp1, and Sdc1 were inactivated singly or in combination, but did not alter clearance of rabbit (125)I-βVLDL or mouse (125)I-LDL. Despite a 61% reduction in VLDL-TG production, VLDL-ApoB-100 production was unchanged in REGN1500-treated animals. Hepatic TG content, fatty acid synthesis, and fatty acid oxidation were similar in REGN1500 and control antibody-treated animals. Taken together, our findings indicate that inactivation of ANGPTL3 does not affect the number of ApoB-containing lipoproteins secreted by the liver but alters the particles that are made such that they are cleared more rapidly from the circulation via a noncanonical pathway(s). The increased clearance of lipolytic remnants results in decreased production of LDL in ANGPTL3-deficient animals.
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Affiliation(s)
- Yan Wang
- Departments of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX
| | | | - Serena Banfi
- Departments of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX
| | | | - Jonathan C Cohen
- Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX
| | - Helen H Hobbs
- Departments of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX
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73
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Stepp MA, Pal-Ghosh S, Tadvalkar G, Pajoohesh-Ganji A. Syndecan-1 and Its Expanding List of Contacts. Adv Wound Care (New Rochelle) 2015; 4:235-249. [PMID: 25945286 DOI: 10.1089/wound.2014.0555] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 06/01/2014] [Indexed: 12/13/2022] Open
Abstract
Significance: The binding of cytokines and growth factors to heparan sulfate (HS) chains on proteoglycans generates gradients that control development and regulate wound healing. Syndecan-1 (sdc1) is an integral membrane HS proteoglycan. Its structure allows it to bind with cytosolic, transmembrane, and extracellular matrix (ECM) proteins. It plays important roles in mediating key events during wound healing because it regulates a number of important processes, including cell adhesion, cell migration, endocytosis, exosome formation, and fibrosis. Recent Advances: Recent studies reveal that sdc1 regulates wound healing by altering integrin activation. Differences in integrin activation lead to cell-type-specific changes in the rate of cell migration and ECM assembly. Sdc1 also regulates endocytosis and the formation and release of exosomes. Critical Issues: Understanding how sdc1 facilitates wound healing and resolution will improve treatment options for elderly and diabetic patients with delayed wound healing. Studies showing that sdc1 function is altered in cancer are relevant to those interested in controlling fibrosis and scarring. Future Directions: The key to understanding the various functions ascribed to sdc1 is resolving how it interacts with its numerous binding partners. The role played by chondroitin sulfate glycosaminoglycan (GAG) chains on the ability of sdc1 to associate with its ligands needs further investigation. At wound sites heparanase can cleave the HS GAG chains of sdc1, alter its ability to bind cytokines, and induce shedding of the ectodomain. This review will discuss how the unique structure of sdc1 allows it to play key roles in cell signaling, ECM assembly, and wound healing.
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Affiliation(s)
- Mary Ann Stepp
- Department of Anatomy and Regenerative Biology, George Washington University Medical School, Washington, District of Columbia
- Department of Ophthalmology, George Washington University Medical School, Washington, District of Columbia
| | - Sonali Pal-Ghosh
- Department of Anatomy and Regenerative Biology, George Washington University Medical School, Washington, District of Columbia
| | - Gauri Tadvalkar
- Department of Anatomy and Regenerative Biology, George Washington University Medical School, Washington, District of Columbia
| | - Ahdeah Pajoohesh-Ganji
- Department of Anatomy and Regenerative Biology, George Washington University Medical School, Washington, District of Columbia
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74
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Mooij HL, Bernelot Moens SJ, Gordts PSM, Stanford K, Foley E, van den Boogert MW, Witjes J, Hassing HC, Tanck M, van de Sande MJ, Levels JH, Kastelein JP, Stroes EG, Dallinga-Thie G, Esko J, Nieuwdorp M. Ext1 heterozygosity causes a modest effect on postprandial lipid clearance in humans. J Lipid Res 2015; 56:665-673. [PMID: 25568062 DOI: 10.1194/jlr.m053504] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Elevated nonfasting TG-rich lipoprotein levels are a risk factor for CVD. To further evaluate the relevance of LDL-receptor (LDLr) pathway and heparan sulfate proteoglycans (HSPGs) in TG homeostasis, we analyzed fasting and postprandial TG levels in mice bearing combined heterozygous mutations in both Exostosin (Ext) 1 and Ldlr, in subjects with hereditary multiple exostosis (HME) due to a heterozygous loss-of-function mutation in EXT1 or EXT2 (N = 13), and in patients with heterozygous mutations in LDLR [familial hypercholesterolemia (FH)] and SNPs in major HSPG-related genes (n = 22). Mice bearing a homozygous mutation in hepatic Ext1 exhibited elevated plasma TGs similar to mice lacking other key enzymes involved in HSPG assembly. Compound heterozygous mice lacking Ldlr and Ext1 showed synergy on plasma TG accumulation and postprandial clearance. In human subjects, a trend was observed in HME patients toward reduced postprandial TG clearance with a concomitant reduction in chylomicron clearance [area under the curve (AUC)-retinyl ester (RE) HME, 844 ± 127 vs. controls, 646 ± 119 nM/h, P = 0.09]. Moreover, in FH subjects with a high HSPG gene score, retinyl palmitate excursions were higher (AUC-RE, 2,377 ± 293 vs. 1,565 ± 181 nM/h, P < 0.05). Incremental AUC-apoB48 was similar between the groups. In conclusion, the data are supportive for a minor yet additive role of HSPG in human postprandial TG clearance, and further studies are warranted.
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Affiliation(s)
| | | | - PhilipL S M Gordts
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA
| | - KristinI Stanford
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA
| | - ErinM Foley
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA
| | | | | | | | - MichaelW Tanck
- Department of Clinical Epidemiology, Biostatistics and Bioinformatics
| | | | - J Han Levels
- Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
| | | | | | - GeesjeM Dallinga-Thie
- Department of Vascular Medicine; Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
| | - JeffD Esko
- Department of Cellular and Molecular Medicine, University of California San Diego, San Diego, CA
| | - Max Nieuwdorp
- Department of Vascular Medicine; Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands.
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75
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Anantharamaiah GM, Goldberg D. Novel method for reducing plasma cholesterol: a ligand replacement therapy. CLINICAL LIPIDOLOGY 2015; 10:83-90. [PMID: 25937835 PMCID: PMC4415983 DOI: 10.2217/clp.14.63] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Despite wide use of statins, significant cardiovascular disease risk persists. High-density lipoprotein based therapy has not yielded any positive results in combating this disease. Newer methods to rapidly decrease plasma cholesterol are much needed. While apolipoprotein B is a ligand for low-density lipoprotein receptor, which clears low-density lipoprotein cholesterol in a highly regulated pathway, apolipoprotein E (apoE) is a ligand for clearing other apolipoprotein B containing atherogenic lipoproteins via an alternate receptor pathway, especially the heparin sulfate proteoglycans on the liver cell surface. We describe here a novel method that replaces apoE as a ligand to clear all of the atherogenic lipoproteins via the heparin sulfate proteoglycans pathway. This ligand replacement apoE mimetic peptide therapy, having been designated as an orphan drug by the US FDA, is in clinical trials.
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Affiliation(s)
- GM Anantharamaiah
- Department of Medicine, Biochemistry & Molecular Genetics; University of Alabama at Birmingham, Birmingham, AL 35294, USA
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76
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Reducing macrophage proteoglycan sulfation increases atherosclerosis and obesity through enhanced type I interferon signaling. Cell Metab 2014; 20:813-826. [PMID: 25440058 PMCID: PMC4254584 DOI: 10.1016/j.cmet.2014.09.016] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Revised: 08/30/2014] [Accepted: 09/26/2014] [Indexed: 01/05/2023]
Abstract
Heparan sulfate proteoglycans (HSPGs) are an important constituent of the macrophage glycocalyx and extracellular microenvironment. To examine their role in atherogenesis, we inactivated the biosynthetic gene N-acetylglucosamine N-deacetylase-N-sulfotransferase 1 (Ndst1) in macrophages and crossbred the strain to Ldlr(-/-) mice. When placed on an atherogenic diet, Ldlr(-/-)Ndst1(f/f)LysMCre(+) mice had increased atherosclerotic plaque area and volume compared to Ldlr(-/-) mice. Diminished sulfation of heparan sulfate resulted in enhanced chemokine expression; increased macrophages in plaques; increased expression of ACAT2, a key enzyme in cholesterol ester storage; and increased foam cell conversion. Motif analysis of promoters of upregulated genes suggested increased type I interferon signaling, which was confirmed by elevation of STAT1 phosphorylation induced by IFN-β. The proinflammatory macrophages derived from Ndst1(f/f)LysMCre(+) mice also sensitized the animals to diet-induced obesity. We propose that macrophage HSPGs control basal activation of macrophages by maintaining type I interferon reception in a quiescent state through sequestration of IFN-β.
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77
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Kim J, Yoon H, Basak J, Kim J. Apolipoprotein E in synaptic plasticity and Alzheimer's disease: potential cellular and molecular mechanisms. Mol Cells 2014; 37:767-76. [PMID: 25358504 PMCID: PMC4255096 DOI: 10.14348/molcells.2014.0248] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 09/14/2014] [Indexed: 01/12/2023] Open
Abstract
Alzheimer's disease (AD) is clinically characterized with progressive memory loss and cognitive decline. Synaptic dysfunction is an early pathological feature that occurs prior to neurodegeneration and memory dysfunction. Mounting evidence suggests that aggregation of amyloid-β (Aβ) and hyperphosphorylated tau leads to synaptic deficits and neurodegeneration, thereby to memory loss. Among the established genetic risk factors for AD, the ɛ4 allele of apolipoprotein E (APOE) is the strongest genetic risk factor. We and others previously demonstrated that apoE regulates Aβ aggregation and clearance in an isoform-dependent manner. While the effect of apoE on Aβ may explain how apoE isoforms differentially affect AD pathogenesis, there are also other underexplored pathogenic mechanisms. They include differential effects of apoE on cerebral energy metabolism, neuroinflammation, neurovascular function, neurogenesis, and synaptic plasticity. ApoE is a major carrier of cholesterols that are required for neuronal activity and injury repair in the brain. Although there are a few conflicting findings and the underlying mechanism is still unclear, several lines of studies demonstrated that apoE4 leads to synaptic deficits and impairment in long-term potentiation, memory and cognition. In this review, we summarize current understanding of apoE function in the brain, with a particular emphasis on its role in synaptic plasticity and the underlying cellular and molecular mechanisms, involving low-density lipoprotein receptor-related protein 1 (LRP1), syndecan, and LRP8/ApoER2.
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Affiliation(s)
- Jaekwang Kim
- Department of Neuroscience, Mayo Clinic College of Medicine, Jacksonville, FL 32224,
USA
| | - Hyejin Yoon
- Department of Neuroscience, Mayo Clinic College of Medicine, Jacksonville, FL 32224,
USA
- Neurobiology of Disease Graduate Program, Mayo Graduate School, Jacksonville, FL 32224,
USA
| | - Jacob Basak
- Department of Neurology, Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110,
USA
| | - Jungsu Kim
- Department of Neuroscience, Mayo Clinic College of Medicine, Jacksonville, FL 32224,
USA
- Neurobiology of Disease Graduate Program, Mayo Graduate School, Jacksonville, FL 32224,
USA
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78
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Manunza A, Casellas J, Quintanilla R, González-Prendes R, Pena RN, Tibau J, Mercadé A, Castelló A, Aznárez N, Hernández-Sánchez J, Amills M. A genome-wide association analysis for porcine serum lipid traits reveals the existence of age-specific genetic determinants. BMC Genomics 2014; 15:758. [PMID: 25189197 PMCID: PMC4164741 DOI: 10.1186/1471-2164-15-758] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 07/25/2014] [Indexed: 01/07/2023] Open
Abstract
Background The genetic determinism of blood lipid concentrations, the main risk factor for atherosclerosis, is practically unknown in species other than human and mouse. Even in model organisms, little is known about how the genetic determinants of lipid traits are modulated by age-specific factors. To gain new insights into this issue, we have carried out a genome-wide association study (GWAS) for cholesterol (CHOL), triglyceride (TRIG) and low (LDL) and high (HDL) density lipoprotein concentrations measured in Duroc pigs at two time points (45 and 190 days). Results Analysis of data with mixed-model methods (EMMAX, GEMMA, GenABEL) and PLINK showed a low positional concordance between trait-associated regions (TARs) for serum lipids at 45 and 190 days. Besides, the proportion of phenotypic variance explained by SNPs at these two time points was also substantially different. The four analyses consistently detected two regions on SSC3 (124 Mb, CHOL and LDL at 190 days) and SSC6 (135 Mb, CHOL and TRIG at 190 days) with highly significant effects on the porcine blood lipid profile. Moreover, we have found that SNP variation within SSC3, SSC6, SSC10, SSC13 and SSC16 TARs is associated with the expression of several genes mapping to other chromosomes and related to lipid metabolism. Conclusions Our data demonstrate that the effects of genomic determinants influencing lipid concentrations in pigs, as well as the amount of phenotypic variance they explain, are influenced by age-related factors. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-758) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Marcel Amills
- Department of Animal Genetics, Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Universitat Autònoma de Barcelona, Bellaterra 08193, Spain.
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van Golen RF, Reiniers MJ, Vrisekoop N, Zuurbier CJ, Olthof PB, van Rheenen J, van Gulik TM, Parsons BJ, Heger M. The mechanisms and physiological relevance of glycocalyx degradation in hepatic ischemia/reperfusion injury. Antioxid Redox Signal 2014; 21:1098-118. [PMID: 24313895 PMCID: PMC4123469 DOI: 10.1089/ars.2013.5751] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
SIGNIFICANCE Hepatic ischemia/reperfusion (I/R) injury is an inevitable side effect of major liver surgery that can culminate in liver failure. The bulk of I/R-induced liver injury results from an overproduction of reactive oxygen and nitrogen species (ROS/RNS), which inflict both parenchymal and microcirculatory damage. A structure that is particularly prone to oxidative attack and modification is the glycocalyx (GCX), a meshwork of proteoglycans and glycosaminoglycans (GAGs) that covers the lumenal endothelial surface and safeguards microvascular homeostasis. ROS/RNS-mediated degradation of the GCX may exacerbate I/R injury by, for example, inducing vasoconstriction, facilitating leukocyte adherence, and directly activating innate immune cells. RECENT ADVANCES Preliminary experiments revealed that hepatic sinusoids contain a functional GCX that is damaged during murine hepatic I/R and major liver surgery in patients. There are three ROS that mediate GCX degradation: hydroxyl radicals, carbonate radical anions, and hypochlorous acid (HOCl). HOCl converts GAGs in the GCX to GAG chloramides that become site-specific targets for oxidizing and reducing species and are more efficiently fragmented than the parent molecules. In addition to ROS/RNS, the GAG-degrading enzyme heparanase acts at the endothelial surface to shed the GCX. CRITICAL ISSUES The GCX seems to be degraded during major liver surgery, but the underlying cause remains ill-defined. FUTURE DIRECTIONS The relative contribution of the different ROS and RNS intermediates to GCX degradation in vivo, the immunogenic potential of the shed GCX fragments, and the role of heparanase in liver I/R injury all warrant further investigation.
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Affiliation(s)
- Rowan F van Golen
- 1 Department of Surgery, Surgical Laboratory, Academic Medical Center, University of Amsterdam , Amsterdam, The Netherlands
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80
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Kasza I, Suh Y, Wollny D, Clark RJ, Roopra A, Colman RJ, MacDougald OA, Shedd TA, Nelson DW, Yen MI, Yen CLE, Alexander CM. Syndecan-1 is required to maintain intradermal fat and prevent cold stress. PLoS Genet 2014; 10:e1004514. [PMID: 25101993 PMCID: PMC4125098 DOI: 10.1371/journal.pgen.1004514] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 06/05/2014] [Indexed: 02/07/2023] Open
Abstract
Homeostatic temperature regulation is fundamental to mammalian physiology and is controlled by acute and chronic responses of local, endocrine and nervous regulators. Here, we report that loss of the heparan sulfate proteoglycan, syndecan-1, causes a profoundly depleted intradermal fat layer, which provides crucial thermogenic insulation for mammals. Mice without syndecan-1 enter torpor upon fasting and show multiple indicators of cold stress, including activation of the stress checkpoint p38α in brown adipose tissue, liver and lung. The metabolic phenotype in mutant mice, including reduced liver glycogen, is rescued by housing at thermoneutrality, suggesting that reduced insulation in cool temperatures underlies the observed phenotypes. We find that syndecan-1, which functions as a facultative lipoprotein uptake receptor, is required for adipocyte differentiation in vitro. Intradermal fat shows highly dynamic differentiation, continuously expanding and involuting in response to hair cycle and ambient temperature. This physiology probably confers a unique role for Sdc1 in this adipocyte sub-type. The PPARγ agonist rosiglitazone rescues Sdc1−/− intradermal adipose tissue, placing PPARγ downstream of Sdc1 in triggering adipocyte differentiation. Our study indicates that disruption of intradermal adipose tissue development results in cold stress and complex metabolic pathology. All mammals strive to maintain a fixed body temperature, and do so using a remarkable array of different strategies, which vary depending upon the degree of cold challenge. Physiologists many decades ago observed that a fat layer right underneath the epidermis (and above the dermal muscle layer) thickens in response to colder ambient temperatures. This “intradermal fat” provided insulation within days of climate changes. We have found that syndecan-1, which functions as a facultative lipoprotein uptake receptor, is required for intradermal fat expansion in response to cold exposure. This is a highly specific phenotype not shared by other adipocytes. When intradermal fat is absent, mice do not adapt normally to cold stress, and show altered systemic physiologies, including increased brown adipose tissue thermogenesis and hyper-activation of a stress checkpoint (p38α), designed to protect the body against mutagenic and oxidative stressors. The phenotypes associated with loss of Sdc1 function are reversed when mice are housed in warm temperatures, where defense of body temperature is not required. This study is the first to show that intradermal fat can be genetically regulated, with systemic effects on physiology.
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Affiliation(s)
- Ildiko Kasza
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Yewseok Suh
- Department of Dermatology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Damian Wollny
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Rod J. Clark
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Avtar Roopra
- Department of Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Ricki J. Colman
- Wisconsin National Primate Research Center, Madison, Wisconsin, United States of America
| | - Ormond A. MacDougald
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Timothy A. Shedd
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - David W. Nelson
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Mei-I Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Caroline M. Alexander
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail:
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81
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Leonova EI, Galzitskaya OV. Cell communication using intrinsically disordered proteins: what can syndecans say? J Biomol Struct Dyn 2014; 33:1037-50. [PMID: 24956062 DOI: 10.1080/07391102.2014.926256] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Because intrinsically disordered proteins are incapable of forming unique tertiary structures in isolation, their interaction with partner structures enables them to play important roles in many different biological functions. Therefore, such proteins are usually multifunctional, and their ability to perform their major function, as well as accessory functions, depends on the characteristics of a given interaction. The present paper demonstrates, using predictions from two programs, that the transmembrane proteoglycans syndecans are natively disordered because of their diverse functions and large number of interaction partners. Syndecans perform multiple functions during development, damage repair, tumor growth, angiogenesis, and neurogenesis. By mediating the binding of a large number of extracellular ligands to their receptors, these proteoglycans trigger a cascade of reactions that subsequently regulate various cell processes: cytoskeleton formation, proliferation, differentiation, adhesion, and migration. The occurrences of 20 amino acids in syndecans 1-4 from 25 animals were compared with those in 17 animal proteomes. Gly + Ala, Thr, Glu, and Pro were observed to predominate in the syndecans, contributing to the lack of an ordered structure. In contrast, there were many fewer amino acids in syndecans that promote an ordered structure, such as Cys, Trp, Asn, and His. In addition, a region rich in Asp has been identified between two heparan sulfate-binding sites in the ectodomains, and a region rich in Lys has been identified in the conserved C1 site of the cytoplasmic domain. These particular regions play an essential role in the various functions of syndecans due to their lack of structure.
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Affiliation(s)
- Elena I Leonova
- a Institute of Protein Research, Russian Academy of Sciences , Moscow Region, Pushchino 142290 , Russia
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82
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Hassing HC, Surendran RP, Derudas B, Verrijken A, Francque SM, Mooij HL, Bernelot Moens SJ, ’t Hart LM, Nijpels G, Dekker JM, Williams KJ, Stroes ESG, Van Gaal LF, Staels B, Nieuwdorp M, Dallinga-Thie GM. SULF2 strongly prediposes to fasting and postprandial triglycerides in patients with obesity and type 2 diabetes mellitus. Obesity (Silver Spring) 2014; 22:1309-16. [PMID: 24339435 PMCID: PMC4008695 DOI: 10.1002/oby.20682] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 12/05/2013] [Accepted: 12/09/2013] [Indexed: 01/15/2023]
Abstract
OBJECTIVE Hepatic overexpression of sulfatase-2 (SULF2), a heparan sulfate remodeling enzyme, strongly contributes to high triglyceride (TG) levels in obese, type 2 diabetic (T2DM) db/db mice. Nevertheless, data in humans are lacking. Here, the association of human hepatic SULF2 expression and SULF2 gene variants with TG metabolism in patients with obesity and/or T2DM was investigated. METHODS Liver biopsies from 121 obese subjects were analyzed for relations between hepatic SULF2 mRNA levels and plasma TG. Associations between seven SULF2 tagSNPs and TG levels were assessed in 210 obese T2DM subjects with dyslipidemia. Replication of positive findings was performed in 1,316 independent obese T2DM patients. Postprandial TRL clearance was evaluated in 29 obese T2DM subjects stratified by SULF2 genotype. RESULTS Liver SULF2 expression was significantly associated with fasting plasma TG (r = 0.271; P = 0.003) in obese subjects. The SULF2 rs2281279(A>G) SNP was reproducibly associated with lower fasting plasma TG levels in obese T2DM subjects (P < 0.05). Carriership of the minor G allele was associated with lower levels of postprandial plasma TG (P < 0.05) and retinyl esters levels (P < 0.001). CONCLUSIONS These findings implicate SULF2 as potential therapeutic target in the atherogenic dyslipidemia of obesity and T2DM.
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Affiliation(s)
- H. Carlijne Hassing
- Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
| | - R. Preethi Surendran
- Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
| | - Bruno Derudas
- University of Lille 2; INSERM U1011; EGID; Institute Pasteur de Lille, France
| | - An Verrijken
- Department of Endocrinology, Diabetology and Metabolism, Antwerp University Hospital, University of Antwerp, Belgium
| | - Sven M. Francque
- Department of Gastroenterology and Hepatology, Antwerp University Hospital, University of Antwerp, Belgium
| | - Hans L. Mooij
- Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
| | | | - Leen M. ’t Hart
- Departments of Molecular Epidemiology and Molecular Cell Biology, Leiden University Medical Center
| | - Giel Nijpels
- Department of General Practice, EMGO Institute for Health and Care Research, VU University Medical Center
| | - Jacqueline M. Dekker
- Department of Epidemiology and Biostatistics, EMGO Institute for Health and Care Research, VU University Medical Center
| | - Kevin Jon Williams
- Section of Endocrinology, Diabetes and Metabolism, Temple University School of Medicine, Philadelphia, PA USA
- Department of Molecular and Clinical Medicine, Sahlgrenska Center for Cardiovascular and Metabolic Research, University of Göthenborg, Sweden
| | - Erik S. G. Stroes
- Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
| | - Luc F. Van Gaal
- Department of Endocrinology, Diabetology and Metabolism, Antwerp University Hospital, University of Antwerp, Belgium
| | - Bart Staels
- University of Lille 2; INSERM U1011; EGID; Institute Pasteur de Lille, France
| | - Max Nieuwdorp
- Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
| | - Geesje M. Dallinga-Thie
- Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
- Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands
- Corresponding author: G.M.Dallinga-Thie, PhD Department of Vascular Medicine, Academic Medical Center, Meibergdreef 9, room K1.262, 1105 AZ Amsterdam, the Netherlands,
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83
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Lefèvre M, Felmlee DJ, Parnot M, Baumert TF, Schuster C. Syndecan 4 is involved in mediating HCV entry through interaction with lipoviral particle-associated apolipoprotein E. PLoS One 2014; 9:e95550. [PMID: 24751902 PMCID: PMC3994096 DOI: 10.1371/journal.pone.0095550] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 03/28/2014] [Indexed: 12/16/2022] Open
Abstract
Hepatitis C virus (HCV) is a major cause of liver disease worldwide and HCV infection represents a major health problem. HCV associates with host lipoproteins forming host/viral hybrid complexes termed lipoviral particles. Apolipoprotein E (apoE) is a lipoprotein component that interacts with heparan sulfate proteoglycans (HSPG) to mediate hepatic lipoprotein uptake, and may likewise mediate HCV entry. We sought to define the functional regions of apoE with an aim to identify critical apoE binding partners involved in HCV infection. Using adenoviral vectors and siRNA to modulate apoE expression we show a direct correlation of apoE expression and HCV infectivity, whereas no correlation exists with viral protein expression. Mutating the HSPG binding domain (HSPG-BD) of apoE revealed key residues that are critical for mediating HCV infection. Furthermore, a novel synthetic peptide that mimics apoE’s HSPG-BD directly and competitively inhibits HCV infection. Genetic knockdown of the HSPG proteins syndecan (SDC) 1 and 4 revealed that SDC4 principally mediates HCV entry. Our data demonstrate that HCV uses apoE-SDC4 interactions to enter hepatoma cells and establish infection. Targeting apoE-SDC interactions could be an alternative strategy for blocking HCV entry, a critical step in maintaining chronic HCV infection.
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Affiliation(s)
- Mathieu Lefèvre
- Inserm, U1110, Research Institute on Viral and Hepatic Disease, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
| | - Daniel J. Felmlee
- Inserm, U1110, Research Institute on Viral and Hepatic Disease, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
| | - Marie Parnot
- Inserm, U1110, Research Institute on Viral and Hepatic Disease, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
| | - Thomas F. Baumert
- Inserm, U1110, Research Institute on Viral and Hepatic Disease, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
- Pôle hépato-digestif, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Catherine Schuster
- Inserm, U1110, Research Institute on Viral and Hepatic Disease, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
- * E-mail:
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Abstract
Numerous proteins, including cytokines and chemokines, enzymes and enzyme inhibitors, extracellular matrix proteins, and membrane receptors, bind heparin. Although they are traditionally classified as heparin-binding proteins, under normal physiological conditions these proteins actually interact with the heparan sulfate chains of one or more membrane or extracellular proteoglycans. Thus, they are more appropriately classified as heparan sulfate-binding proteins (HSBPs). This review provides an overview of the various modes of interaction between heparan sulfate and HSBPs, emphasizing biochemical and structural insights that improve our understanding of the many biological functions of heparan sulfate.
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Affiliation(s)
- Ding Xu
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, California 92093; ,
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85
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Chaterji S, Lam CH, Ho DS, Proske DC, Baker AB. Syndecan-1 regulates vascular smooth muscle cell phenotype. PLoS One 2014; 9:e89824. [PMID: 24587062 PMCID: PMC3934950 DOI: 10.1371/journal.pone.0089824] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Accepted: 01/24/2014] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVE We examined the role of syndecan-1 in modulating the phenotype of vascular smooth muscle cells in the context of endogenous inflammatory factors and altered microenvironments that occur in disease or injury-induced vascular remodeling. METHODS AND RESULTS Vascular smooth muscle cells (vSMCs) display a continuum of phenotypes that can be altered during vascular remodeling. While the syndecans have emerged as powerful and complex regulators of cell function, their role in controlling vSMC phenotype is unknown. Here, we isolated vSMCs from wild type (WT) and syndecan-1 knockout (S1KO) mice. Gene expression and western blotting studies indicated decreased levels of α-smooth muscle actin (α-SMA), calponin, and other vSMC-specific differentiation markers in S1KO relative to WT cells. The spread area of the S1KO cells was found to be greater than WT cells, with a corresponding increase in focal adhesion formation, Src phosphorylation, and alterations in actin cytoskeletal arrangement. In addition, S1KO led to increased S6RP phosphorylation and decreased AKT and PKC-α phosphorylation. To examine whether these changes were present in vivo, isolated aortae from aged WT and S1KO mice were stained for calponin. Consistent with our in-vitro findings, the WT mice aortae stained higher for calponin relative to S1KO. When exposed to the inflammatory cytokine TNF-α, WT vSMCs had an 80% reduction in syndecan-1 expression. Further, with TNF-α, S1KO vSMCs produced increased pro-inflammatory cytokines relative to WT. Finally, inhibition of interactions between syndecan-1 and integrins αvβ3 and αvβ5 using the inhibitory peptide synstatin appeared to have similar effects on vSMCs as knocking out syndecan-1, with decreased expression of vSMC differentiation markers and increased expression of inflammatory cytokines, receptors, and osteopontin. CONCLUSIONS Taken together, our results support that syndecan-1 promotes vSMC differentiation and quiescence. Thus, the presence of syndecan-1 would have a protective effect against vSMC dedifferentiation and this activity is linked to interactions with integrins αvβ3 and αvβ5.
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Affiliation(s)
- Somali Chaterji
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States of America
| | - Christoffer H. Lam
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States of America
| | - Derek S. Ho
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States of America
| | - Daniel C. Proske
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States of America
| | - Aaron B. Baker
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States of America
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86
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Abstract
The identification and validation of gene–gene interactions is a major challenge in human studies. Here, we explore an approach for studying epistasis in humans using a Drosophila melanogaster model of neonatal diabetes mellitus. Expression of the mutant preproinsulin (hINSC96Y) in the eye imaginal disc mimics the human disease: it activates conserved stress-response pathways and leads to cell death (reduction in eye area). Dominant-acting variants in wild-derived inbred lines from the Drosophila Genetics Reference Panel produce a continuous, highly heritable distribution of eye-degeneration phenotypes in a hINSC96Y background. A genome-wide association study (GWAS) in 154 sequenced lines identified a sharp peak on chromosome 3L, which mapped to a 400-bp linkage block within an intron of the gene sulfateless (sfl). RNAi knockdown of sfl enhanced the eye-degeneration phenotype in a mutant-hINS-dependent manner. RNAi against two additional genes in the heparan sulfate (HS) biosynthetic pathway (ttv and botv), in which sfl acts, also modified the eye phenotype in a hINSC96Y-dependent manner, strongly suggesting a novel link between HS-modified proteins and cellular responses to misfolded proteins. Finally, we evaluated allele-specific expression difference between the two major sfl-intronic haplotypes in heterozygtes. The results showed significant heterogeneity in marker-associated gene expression, thereby leaving the causal mutation(s) and its mechanism unidentified. In conclusion, the ability to create a model of human genetic disease, map a QTL by GWAS to a specific gene, and validate its contribution to disease with available genetic resources and the potential to experimentally link the variant to a molecular mechanism demonstrate the many advantages Drosophila holds in determining the genetic underpinnings of human disease.
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Matikainen N, Burza MA, Romeo S, Hakkarainen A, Adiels M, Folkersen L, Eriksson P, Lundbom N, Ehrenborg E, Orho-Melander M, Taskinen MR, Borén J. Genetic variation in SULF2 is associated with postprandial clearance of triglyceride-rich remnant particles and triglyceride levels in healthy subjects. PLoS One 2013; 8:e79473. [PMID: 24278138 PMCID: PMC3835823 DOI: 10.1371/journal.pone.0079473] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 09/21/2013] [Indexed: 11/18/2022] Open
Abstract
Context Nonfasting (postprandial) triglyceride concentrations have emerged as a clinically significant cardiovascular disease risk factor that results from accumulation of remnant triglyceride-rich lipoproteins (TRLs) in the circulation. The remnant TRLs are cleared from the circulation by hepatic uptake, but the specific mechanisms involved are unclear. The syndecan-1 heparan sulfate proteoglycan (HSPG) pathway is important for the hepatic clearance of remnant TRLs in mice, but its relevance in humans is unclear. Objective We sought to determine whether polymorphisms of the genes responsible for HSPG assembly and disassembly contribute to atherogenic dyslipoproteinemias in humans. Patients And Design We performed an oral fat load in 68 healthy subjects. Lipoproteins (chylomicrons and very low density lipoproteins 1 and 2) were isolated from blood, and the area under curve and incremental area under curve for postprandial variables were calculated. Single nucleotide polymorphisms in genes encoding syndecan-1 and enzymes involved in the synthesis or degradation of HSPG were genotyped in the study subjects. Results Our results indicate that the genetic variation rs2281279 in SULF2 associates with postprandial clearance of remnant TRLs and triglyceride levels in healthy subjects. Furthermore, the SNP rs2281279 in SULF2 associates with hepatic SULF2 mRNA levels. Conclusions In humans, mild but clinically relevant postprandial hyperlipidemia due to reduced hepatic clearance of remnant TRLs may result from genetic polymorphisms that affect hepatic HSPG.
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Affiliation(s)
- Niina Matikainen
- HUCH Heart and Lung Centre, Cardiovascular Research Group, Helsinki University Central Hospital, Diabetes & Obesity, University of Helsinki, Helsinki, Finland
| | - Maria Antonella Burza
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Stefano Romeo
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Antti Hakkarainen
- Medical Imaging Center, Helsinki University Central Hospital, Department of Radiology, University of Helsinki, Helsinki, Finland
| | - Martin Adiels
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Lasse Folkersen
- Atherosclerosis Research Unit, Department of Medicine, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
| | - Per Eriksson
- Atherosclerosis Research Unit, Department of Medicine, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
| | - Nina Lundbom
- Medical Imaging Center, Helsinki University Central Hospital, Department of Radiology, University of Helsinki, Helsinki, Finland
| | - Ewa Ehrenborg
- Atherosclerosis Research Unit, Department of Medicine, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
| | | | - Marja-Riitta Taskinen
- HUCH Heart and Lung Centre, Cardiovascular Research Group, Helsinki University Central Hospital, Diabetes & Obesity, University of Helsinki, Helsinki, Finland
| | - Jan Borén
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
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88
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Haas ME, Attie AD, Biddinger SB. The regulation of ApoB metabolism by insulin. Trends Endocrinol Metab 2013; 24:391-7. [PMID: 23721961 PMCID: PMC3810413 DOI: 10.1016/j.tem.2013.04.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 04/10/2013] [Accepted: 04/12/2013] [Indexed: 01/07/2023]
Abstract
The leading cause of death in diabetic patients is cardiovascular disease. Apolipoprotein B (ApoB)-containing lipoprotein particles, which are secreted and cleared by the liver, are essential for the development of atherosclerosis. Insulin plays a key role in the regulation of ApoB. Insulin decreases ApoB secretion by promoting ApoB degradation in the hepatocyte. In parallel, insulin promotes clearance of circulating ApoB particles by the liver via the low-density lipoprotein receptor (LDLR), LDLR-related protein 1 (LRP1), and heparan sulfate proteoglycans (HSPGs). Consequently, the insulin-resistant state of type 2 diabetes (T2D) is associated with increased secretion and decreased clearance of ApoB. Here, we review the mechanisms by which insulin controls the secretion and uptake of ApoB in normal and diabetic livers.
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Affiliation(s)
- Mary E Haas
- Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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89
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Foley EM, Gordts PLSM, Stanford KI, Gonzales JC, Lawrence R, Stoddard N, Esko JD. Hepatic remnant lipoprotein clearance by heparan sulfate proteoglycans and low-density lipoprotein receptors depend on dietary conditions in mice. Arterioscler Thromb Vasc Biol 2013; 33:2065-74. [PMID: 23846497 DOI: 10.1161/atvbaha.113.301637] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Chylomicron and very low-density lipoprotein remnants are cleared from the circulation in the liver by heparan sulfate proteoglycan (HSPG) receptors (syndecan-1), the low-density lipoprotein receptor (LDLR), and LDLR-related protein-1 (LRP1), but the relative contribution of each class of receptors under different dietary conditions remains unclear. APPROACH AND RESULTS Triglyceride-rich lipoprotein clearance was measured in AlbCre(+)Ndst1(f/f), Ldlr(-/-), and AlbCre(+)Lrp1(f/f) mice and mice containing combinations of these mutations. Triglyceride measurements in single and double mutant mice showed that HSPGs and LDLR dominate clearance under fasting conditions and postprandial conditions, but LRP1 contributes significantly when LDLR is absent. Mice lacking hepatic expression of all 3 receptors (AlbCre(+)Ndst1(f/f) Lrp1(f/f) Ldlr(-/-)) displayed dramatic hyperlipidemia (870 ± 270 mg triglyceride/dL; 1300 ± 350 mg of total cholesterol/dL) and exhibited persistent elevated postprandial triglyceride levels because of reduced hepatic clearance. Analysis of the particles accumulating in mutants showed that HSPGs preferentially clear a subset of small triglyceride-rich lipoproteins (≈ 20-40 nm diameter), whereas LDLR and LRP1 clear larger particles (≈ 40-60 nm diameter). Finally, we show that HSPGs play a major role in clearance of triglyceride-rich lipoproteins in mice fed normal chow or under postprandial conditions but seem to play a less significant role on a high-fat diet. CONCLUSIONS These data show that HSPGs, LDLR, and LRP1 clear distinct subsets of particles, that HSPGs work independently of LDLR and LRP1, and that HSPGs, LDLR, and LRP1 are the 3 major hepatic triglyceride-rich lipoprotein clearance receptors in mice.
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Affiliation(s)
- Erin M Foley
- Department of Cellular and Molecular Medicine University of California San Diego, La Jolla, California, USA.,Department of Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California, USA
| | - Philip L S M Gordts
- Department of Cellular and Molecular Medicine University of California San Diego, La Jolla, California, USA
| | - Kristin I Stanford
- Department of Cellular and Molecular Medicine University of California San Diego, La Jolla, California, USA
| | - Jon C Gonzales
- Department of Cellular and Molecular Medicine University of California San Diego, La Jolla, California, USA.,Department of Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California, USA
| | - Roger Lawrence
- Department of Cellular and Molecular Medicine University of California San Diego, La Jolla, California, USA
| | - Nicole Stoddard
- Department of Cellular and Molecular Medicine University of California San Diego, La Jolla, California, USA.,Department of Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California, USA
| | - Jeffrey D Esko
- Department of Cellular and Molecular Medicine University of California San Diego, La Jolla, California, USA.,Department of Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California, USA
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90
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Bi X, Zhu X, Duong M, Boudyguina EY, Wilson MD, Gebre AK, Parks JS. Liver ABCA1 deletion in LDLrKO mice does not impair macrophage reverse cholesterol transport or exacerbate atherogenesis. Arterioscler Thromb Vasc Biol 2013; 33:2288-96. [PMID: 23814116 DOI: 10.1161/atvbaha.112.301110] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Hepatic ATP binding cassette transporter A1 (ABCA1) expression is critical for maintaining plasma high-density lipoprotein (HDL) concentrations, but its role in macrophage reverse cholesterol transport and atherosclerosis is not fully understood. We investigated atherosclerosis development and reverse cholesterol transport in hepatocyte-specific ABCA1 knockout (HSKO) mice in the low-density lipoprotein (LDL) receptor KO (LDLrKO) C57BL/6 background. APPROACH AND RESULTS Male and female LDLrKO and HSKO/LDLrKO mice were switched from chow at 8 weeks of age to an atherogenic diet (10% palm oil, 0.2% cholesterol) for 16 weeks. Chow-fed HSKO/LDLrKO mice had HDL concentrations 10% to 20% of LDLrKO mice, but similar very low-density lipoprotein and LDL concentrations. Surprisingly, HSKO/LDLrKO mice fed the atherogenic diet had significantly lower (40% to 60%) very low-density lipoprotein, LDL, and HDL concentrations (50%) compared with LDLrKO mice. Aortic surface lesion area and cholesterol content were similar for both genotypes of mice, but aortic root intimal area was significantly lower (20% to 40%) in HSKO/LDLrKO mice. Although macrophage (3)H-cholesterol efflux to apoB lipoprotein-depleted plasma was 24% lower for atherogenic diet-fed HSKO/LDLrKO versus LDLrKO mice, variation in percentage efflux among individual mice was <2-fold compared with a 10-fold variation in plasma HDL concentrations, suggesting that HDL levels, per se, were not the primary determinant of plasma efflux capacity. In vivo reverse cholesterol transport, resident peritoneal macrophage sterol content, biliary lipid composition, and fecal cholesterol mass were similar between both genotypes of mice. CONCLUSIONS The markedly reduced plasma HDL pool in HSKO/LDLrKO mice is sufficient to maintain macrophage reverse cholesterol transport, which, along with reduced plasma very low-density lipoprotein and LDL concentrations, prevented the expected increase in atherosclerosis.
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Affiliation(s)
- Xin Bi
- From the Section on Lipid Sciences, Department of Pathology (X.B., X.Z., M.D., E.Y.B., M.D.W., A.K.G., J.S.P.), and Department of Biochemistry (J.S.P.), Wake Forest School of Medicine, Winston-Salem, NC
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91
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Hepatitis C virus, cholesterol and lipoproteins--impact for the viral life cycle and pathogenesis of liver disease. Viruses 2013; 5:1292-324. [PMID: 23698400 PMCID: PMC3712309 DOI: 10.3390/v5051292] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 04/10/2013] [Accepted: 04/27/2013] [Indexed: 02/07/2023] Open
Abstract
Hepatitis C virus (HCV) is a leading cause of chronic liver disease, including chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Hepatitis C infection associates with lipid and lipoprotein metabolism disorders such as hepatic steatosis, hypobetalipoproteinemia, and hypocholesterolemia. Furthermore, virus production is dependent on hepatic very-low-density lipoprotein (VLDL) assembly, and circulating virions are physically associated with lipoproteins in complexes termed lipoviral particles. Evidence has indicated several functional roles for the formation of these complexes, including co-opting of lipoprotein receptors for attachment and entry, concealing epitopes to facilitate immune escape, and hijacking host factors for HCV maturation and secretion. Here, we review the evidence surrounding pathogenesis of the hepatitis C infection regarding lipoprotein engagement, cholesterol and triglyceride regulation, and the molecular mechanisms underlying these effects.
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92
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Gonzales JC, Gordts PLSM, Foley EM, Esko JD. Apolipoproteins E and AV mediate lipoprotein clearance by hepatic proteoglycans. J Clin Invest 2013; 123:2742-51. [PMID: 23676495 DOI: 10.1172/jci67398] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 03/14/2013] [Indexed: 11/17/2022] Open
Abstract
The heparan sulfate proteoglycan (HSPG) syndecan-1 (SDC1) acts as a major receptor for triglyceride-rich lipoprotein (TRL) clearance in the liver. We sought to identify the relevant apolipoproteins on TRLs that mediate binding to SDC1 and determine their clinical relevance. Evidence supporting ApoE as a major determinant arose from its enrichment in TRLs from mice defective in hepatic heparan sulfate (Ndst1f/fAlbCre⁺ mice), decreased binding of ApoE-deficient TRLs to HSPGs on human hepatoma cells, and decreased clearance of ApoE-deficient [³H]TRLs in vivo. Evidence for a second ligand was suggested by the faster clearance of ApoE-deficient TRLs after injection into WT Ndst1f/fAlbCre⁻ versus mutant Ndst1f/fAlbCre⁺ mice and elevated fasting and postprandial plasma triglycerides in compound Apoe⁻/⁻Ndst1f/fAlbCre⁺ mice compared with either single mutant. ApoAV emerged as a candidate based on 6-fold enrichment of ApoAV in TRLs accumulating in Ndst1f/fAlbCre⁺ mice, decreased binding of TRLs to proteoglycans after depletion of ApoAV or addition of anti-ApoAV mAb, and decreased heparan sulfate-dependent binding of ApoAV-deficient particles to hepatocytes. Importantly, disruption of hepatic heparan sulfate-mediated clearance increased atherosclerosis. We conclude that clearance of TRLs by hepatic HSPGs is atheroprotective and mediated by multivalent binding to ApoE and ApoAV.
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Affiliation(s)
- Jon C Gonzales
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, UCSD, La Jolla, California 92093-0687, USA
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93
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Chen K, Williams KJ. Molecular mediators for raft-dependent endocytosis of syndecan-1, a highly conserved, multifunctional receptor. J Biol Chem 2013; 288:13988-13999. [PMID: 23525115 DOI: 10.1074/jbc.m112.444737] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endocytosis via rafts has attracted considerable recent interest, but the molecular mediators remain incompletely characterized. Here, we focused on the syndecan-1 heparan sulfate proteoglycan, a highly conserved, multifunctional receptor that we previously showed to undergo raft-dependent endocytosis upon clustering. Alanine scanning mutagenesis of three to five consecutive cytoplasmic residues at a time revealed that a conserved juxtamembrane motif, MKKK, was the only region required for efficient endocytosis after clustering. Endocytosis of clustered syndecan-1 occurs in two phases, each requiring a kinase and a corresponding cytoskeletal partner. In the initial phase, ligands trigger rapid MKKK-dependent activation of ERK and the localization of syndecan-1 into rafts. Activation of ERK drives the dissociation of syndecan-1 from α-tubulin, a molecule that may act as an anchor for syndecan-1 at the plasma membrane in the basal state. In the second phase, Src family kinases phosphorylate tyrosyl residues within the transmembrane and cytoplasmic regions of syndecan-1, a process that also requires MKKK. Tyrosine phosphorylation of syndecan-1 triggers the robust recruitment of cortactin, which we found to be an essential mediator of efficient actin-dependent endocytosis. These findings represent the first detailed characterization of the molecular events that drive endocytosis of a raft-dependent receptor and identify a novel endocytic motif, MKKK. Moreover, the results provide new tools to study syndecan function and regulation during uptake of its biologically and medically important ligands, such as HIV-1, atherogenic postprandial remnant lipoproteins, and molecules implicated in Alzheimer disease.
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Affiliation(s)
- Keyang Chen
- Division of Endocrinology, Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Kevin Jon Williams
- Division of Endocrinology, Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
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94
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Savery MD, Jiang JX, Park PW, Damiano ER. The endothelial glycocalyx in syndecan-1 deficient mice. Microvasc Res 2013; 87:83-91. [PMID: 23428342 DOI: 10.1016/j.mvr.2013.02.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 02/05/2013] [Accepted: 02/07/2013] [Indexed: 01/28/2023]
Abstract
The existence of a hydrodynamically relevant endothelial glycocalyx has been established in capillaries, venules, and arterioles in vivo. The glycocalyx is thought to consist primarily of membrane-bound proteoglycans with glycosaminoglycan side-chains, membrane-bound glypicans, and adsorbed plasma proteins. The proteoglycans found on the luminal surface of endothelial cells are syndecans-1, -2, and -4, and glypican-1. The extent to which any of these proteins might serve to anchor the glycocalyx to the endothelium has not yet been determined. To test whether syndecan-1, in particular, is an essential anchoring protein, we performed experiments to determine the hydrodynamically relevant glycocalyx thickness in syndecan-1 deficient (Sdc1(-/-)) mice. Micro-particle image velocimetry data were collected using a previously described method. Microviscometric analysis of these data consistently revealed the existence of a hydrodynamically relevant endothelial glycocalyx in Sdc1(-/-) mice in vivo. The mean glycocalyx thickness found in Sdc1(-/-) mice was 0.45±0.10 μm (N=15), as compared with 0.54±0.12 μm (N=11) in wild-type (WT) mice (p=0.03). The slightly thinner glycocalyx observed in Sdc1(-/-) mice relative to WT mice may be due to the absence of syndecan-1. These findings show that healthy Sdc1(-/-) mice are able to synthesize and maintain a hydrodynamically relevant glycocalyx, which indicates that syndecan-1 is not an essential anchoring protein for the glycocalyx in Sdc1(-/-) mice. This may also be the case for WT mice; however, Sdc1(-/-) mice might adapt to the lack of syndecan-1 by increasing the expression of other proteoglycans. In any case, syndecan-1 does not appear to be a prerequisite for the existence of an endothelial glycocalyx.
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Affiliation(s)
- Michele D Savery
- Boston University, Department of Biomedical Engineering, Boston, MA 02215, USA.
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95
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Mendoza-Barberá E, Julve J, Nilsson SK, Lookene A, Martín-Campos JM, Roig R, Lechuga-Sancho AM, Sloan JH, Fuentes-Prior P, Blanco-Vaca F. Structural and functional analysis of APOA5 mutations identified in patients with severe hypertriglyceridemia. J Lipid Res 2013; 54:649-661. [PMID: 23307945 DOI: 10.1194/jlr.m031195] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
During the diagnosis of three unrelated patients with severe hypertriglyceridemia, three APOA5 mutations [p.(Ser232_Leu235)del, p.Leu253Pro, and p.Asp332ValfsX4] were found without evidence of concomitant LPL, APOC2, or GPIHBP1 mutations. The molecular mechanisms by which APOA5 mutations result in severe hypertriglyceridemia remain poorly understood, and the functional impairment/s induced by these specific mutations was not obvious. Therefore, we performed a thorough structural and functional analysis that included follow-up of patients and their closest relatives, measurement of apoA-V serum concentrations, and sequencing of the APOA5 gene in 200 nonhyperlipidemic controls. Further, we cloned, overexpressed, and purified both wild-type and mutant apoA-V variants and characterized their capacity to activate LPL. The interactions of recombinant wild-type and mutated apoA-V variants with liposomes of different composition, heparin, LRP1, sortilin, and SorLA/LR11 were also analyzed. Finally, to explore the possible structural consequences of these mutations, we developed a three-dimensional model of full-length, lipid-free human apoA-V. A complex, wide array of impairments was found in each of the three mutants, suggesting that the specific residues affected are critical structural determinants for apoA-V function in lipoprotein metabolism and, therefore, that these APOA5 mutations are a direct cause of hypertriglyceridemia.
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Affiliation(s)
| | - Josep Julve
- Institute for Biomedical Research (IIB) Sant Pau, 08025 Barcelona, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas, 08017 Barcelona, Spain
| | - Stefan K Nilsson
- Department of Medical Biosciences/Physiological Chemistry, Umeå University, SE90187, Sweden
| | - Aivar Lookene
- Department of Chemistry, Tallinn Technical University, Tallinn 12618, Estonia
| | | | - Rosa Roig
- Institute for Biomedical Research (IIB) Sant Pau, 08025 Barcelona, Spain
| | | | | | | | - Francisco Blanco-Vaca
- Institute for Biomedical Research (IIB) Sant Pau, 08025 Barcelona, Spain; CIBER de Diabetes y Enfermedades Metabólicas Asociadas, 08017 Barcelona, Spain; Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08025 Barcelona, Spain
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96
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Scilabra SD, Troeberg L, Yamamoto K, Emonard H, Thøgersen I, Enghild JJ, Strickland DK, Nagase H. Differential regulation of extracellular tissue inhibitor of metalloproteinases-3 levels by cell membrane-bound and shed low density lipoprotein receptor-related protein 1. J Biol Chem 2013; 288:332-42. [PMID: 23166318 PMCID: PMC3537031 DOI: 10.1074/jbc.m112.393322] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 10/10/2012] [Indexed: 11/06/2022] Open
Abstract
Tissue inhibitor of metalloproteinases-3 (TIMP-3) plays a key role in regulating extracellular matrix turnover by inhibiting matrix metalloproteinases (MMPs), adamalysins (ADAMs), and adamalysins with thrombospondin motifs (ADAMTSs). We demonstrate that levels of this physiologically important inhibitor can be regulated post-translationally by endocytosis. TIMP-3 was endocytosed and degraded by a number of cell types including chondrocytes, fibroblasts, and monocytes, and we found that the endocytic receptor low density lipoprotein receptor-related protein-1 (LRP-1) plays a major role in TIMP-3 internalization. However, the cellular uptake of TIMP-3 significantly slowed down after 10 h due to shedding of LRP-1 from the cell surface and formation of soluble LRP-1 (sLRP-1)-TIMP-3 complexes. Addition of TIMP-3 to HTB94 human chondrosarcoma cells increased the release of sLRP-1 fragments of 500, 215, 160, and 110 kDa into the medium in a concentration-dependent manner, and all of these fragments were able to bind to TIMP-3. TIMP-3 bound to sLRP-1, which was resistant to endocytosis, retained its inhibitory activity against metalloproteinases. Extracellular levels of sLRP-1 can thus increase the half-life of TIMP-3 in the extracellular space, controlling the bioavailability of TIMP-3 to inhibit metalloproteinases.
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Affiliation(s)
- Simone D. Scilabra
- From the Department of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
- the Kennedy Institute of Rheumatology, University of Oxford, London W6 8LH, United Kingdom
| | - Linda Troeberg
- From the Department of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
- the Kennedy Institute of Rheumatology, University of Oxford, London W6 8LH, United Kingdom
| | - Kazuhiro Yamamoto
- the Kennedy Institute of Rheumatology, University of Oxford, London W6 8LH, United Kingdom
| | - Hervé Emonard
- the University of Reims Champagne-Ardenne, FRE 3481 CNRS, 51100 Reims, France
| | - Ida Thøgersen
- the Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark, and
| | - Jan J. Enghild
- the Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark, and
| | | | - Hideaki Nagase
- From the Department of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
- the Kennedy Institute of Rheumatology, University of Oxford, London W6 8LH, United Kingdom
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97
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98
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Altemeier WA, Schlesinger SY, Buell CA, Brauer R, Rapraeger AC, Parks WC, Chen P. Transmembrane and extracellular domains of syndecan-1 have distinct functions in regulating lung epithelial migration and adhesion. J Biol Chem 2012; 287:34927-34935. [PMID: 22936802 DOI: 10.1074/jbc.m112.376814] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Syndecan-1 is a cell surface proteoglycan that can organize co-receptors into a multimeric complex to transduce intracellular signals. The syndecan-1 core protein has multiple domains that confer distinct cell- and tissue-specific functions. Indeed, the extracellular, transmembrane, and cytoplasmic domains have all been found to regulate specific cellular processes. Our previous work demonstrated that syndecan-1 controls lung epithelial migration and adhesion. Here, we identified the necessary domains of the syndecan-1 core protein that modulate its function in lung epithelial repair. We found that the syndecan-1 transmembrane domain has a regulatory function in controlling focal adhesion disassembly, which in turn controls cell migration speed. In contrast, the extracellular domain facilitates cell adhesion through affinity modulation of α(2)β(1) integrin. These findings highlight the fact that syndecan-1 is a multidimensional cell surface receptor that has several regulatory domains to control various biological processes. In particular, the lung epithelium requires the syndecan-1 transmembrane domain to govern cell migration and is independent from its ability to control cell adhesion via the extracellular domain.
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Affiliation(s)
- William A Altemeier
- Division of Pulmonary and Critical Care Medicine, Center for Lung Biology, University of Washington, Seattle, Washington 98109-4752
| | - Saundra Y Schlesinger
- Division of Pulmonary and Critical Care Medicine, Center for Lung Biology, University of Washington, Seattle, Washington 98109-4752
| | - Catherine A Buell
- Division of Pulmonary and Critical Care Medicine, Center for Lung Biology, University of Washington, Seattle, Washington 98109-4752
| | - Rena Brauer
- Division of Pulmonary and Critical Care Medicine, Center for Lung Biology, University of Washington, Seattle, Washington 98109-4752
| | - Alan C Rapraeger
- Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin 53792
| | - William C Parks
- Division of Pulmonary and Critical Care Medicine, Center for Lung Biology, University of Washington, Seattle, Washington 98109-4752
| | - Peter Chen
- Division of Pulmonary and Critical Care Medicine, Center for Lung Biology, University of Washington, Seattle, Washington 98109-4752.
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99
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Strong A, Ding Q, Edmondson AC, Millar JS, Sachs KV, Li X, Kumaravel A, Wang MY, Ai D, Guo L, Alexander ET, Nguyen D, Lund-Katz S, Phillips MC, Morales CR, Tall AR, Kathiresan S, Fisher EA, Musunuru K, Rader DJ. Hepatic sortilin regulates both apolipoprotein B secretion and LDL catabolism. J Clin Invest 2012; 122:2807-16. [PMID: 22751103 DOI: 10.1172/jci63563] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 05/21/2012] [Indexed: 01/05/2023] Open
Abstract
Genome-wide association studies (GWAS) have identified a genetic variant at a locus on chromosome 1p13 that is associated with reduced risk of myocardial infarction, reduced plasma levels of LDL cholesterol (LDL-C), and markedly increased expression of the gene sortilin-1 (SORT1) in liver. Sortilin is a lysosomal sorting protein that binds ligands both in the Golgi apparatus and at the plasma membrane and traffics them to the lysosome. We previously reported that increased hepatic sortilin expression in mice reduced plasma LDL-C levels. Here we show that increased hepatic sortilin not only reduced hepatic apolipoprotein B (APOB) secretion, but also increased LDL catabolism, and that both effects were dependent on intact lysosomal targeting. Loss-of-function studies demonstrated that sortilin serves as a bona fide receptor for LDL in vivo in mice. Our data are consistent with a model in which increased hepatic sortilin binds intracellular APOB-containing particles in the Golgi apparatus as well as extracellular LDL at the plasma membrane and traffics them to the lysosome for degradation. We thus provide functional evidence that genetically increased hepatic sortilin expression both reduces hepatic APOB secretion and increases LDL catabolism, providing dual mechanisms for the very strong association between increased hepatic sortilin expression and reduced plasma LDL-C levels in humans.
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Affiliation(s)
- Alanna Strong
- Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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Gordts PL, Bartelt A, Nilsson SK, Annaert W, Christoffersen C, Nielsen LB, Heeren J, Roebroek AJ. Impaired LDL receptor-related protein 1 translocation correlates with improved dyslipidemia and atherosclerosis in apoE-deficient mice. PLoS One 2012; 7:e38330. [PMID: 22701627 PMCID: PMC3368875 DOI: 10.1371/journal.pone.0038330] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 05/03/2012] [Indexed: 01/20/2023] Open
Abstract
Objective Determination of the in vivo significance of LDL receptor-related protein 1 (LRP1) dysfunction on lipid metabolism and atherosclerosis development in absence of its main ligand apoE. Methods and Results LRP1 knock-in mice carrying an inactivating mutation in the NPxYxxL motif were crossed with apoE-deficient mice. In the absence of apoE, relative to LRP1 wild-type animals, LRP1 mutated mice showed an increased clearance of postprandial lipids despite a compromised LRP1 endocytosis rate and inefficient insulin-mediated translocation of the receptor to the plasma membrane, likely due to inefficient slow recycling of the mutated receptor. Postprandial lipoprotein improvement was explained by increased hepatic clearance of triglyceride-rich remnant lipoproteins and accompanied by a compensatory 1.6-fold upregulation of LDLR expression in hepatocytes. One year-old apoE-deficient mice having the dysfunctional LRP1 revealed a 3-fold decrease in spontaneous atherosclerosis development and a 2-fold reduction in LDL-cholesterol levels. Conclusion These findings demonstrate that the NPxYxxL motif in LRP1 is important for insulin-mediated translocation and slow perinuclear endosomal recycling. These LRP1 impairments correlated with reduced atherogenesis and cholesterol levels in apoE-deficient mice, likely via compensatory LDLR upregulation.
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Affiliation(s)
- Philip L.S.M. Gordts
- Laboratory for Experimental Mouse Genetics, Center for Human Genetics, KU Leuven, Leuven, Belgium
| | - Alexander Bartelt
- Department of Biochemistry and Molecular Cell Biology
- Department of Orthopedics University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Stefan K. Nilsson
- Department of Medical Biosciences/Physiological Chemistry, Umeå University, Umeå, Sweden
| | - Wim Annaert
- Laboratory of Membrane Trafficking, Department of Molecular and Developmental Genetics, VIB, Leuven, Belgium
- Laboratory of Membrane Trafficking, Center for Human Genetics, KU Leuven, Leuven, Belgium
| | | | - Lars Bo Nielsen
- Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology
- * E-mail: (AJMR); (JH)
| | - Anton J.M. Roebroek
- Laboratory for Experimental Mouse Genetics, Center for Human Genetics, KU Leuven, Leuven, Belgium
- * E-mail: (AJMR); (JH)
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