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Ke LY, Chan HC, Chen CC, Chang CF, Lu PL, Chu CS, Lai WT, Shin SJ, Liu FT, Chen CH. Increased APOE glycosylation plays a key role in the atherogenicity of L5 low-density lipoprotein. FASEB J 2020; 34:9802-9813. [PMID: 32501643 DOI: 10.1096/fj.202000659r] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 12/22/2022]
Abstract
Low-density lipoprotein (LDL) is heterogeneous, composed of particles with variable atherogenicity. Electronegative L5 LDL exhibits atherogenic properties in vitro and in vivo, and its levels are elevated in patients with increased cardiovascular risk. Apolipoprotein E (APOE) content is increased in L5, but what role APOE plays in L5 function remains unclear. Here, we characterized the contributions of APOE posttranslational modification to L5's atherogenicity. Using two-dimensional electrophoresis and liquid chromatography-mass spectrometry, we studied APOE's posttranslational modification in L5 from human plasma. APOE structures with various glycan residues were predicted. Molecular docking and molecular dynamics simulation were performed to examine the functional changes of APOE resulting from glycosylation. We also examined the effects of L5 deglycosylation on endothelial cell apoptosis. The glycan sequence N-acetylgalactosamine, galactose, and sialic acid was consistently expressed on serine 94, threonine 194, and threonine 289 of APOE in L5 and was predicted to contribute to L5's negative surface charge and hydrophilicity. The electrostatic force between the negatively charged sialic acid-containing glycan residue of APOE and positively charged amino acids at the receptor-binding area suggested that glycosylation interferes with APOE's attraction to receptors, lipid-binding ability, and lipid transportation and metabolism functions. Importantly, L5 containing glycosylated APOE induced apoptosis in cultured endothelial cells through lectin-like oxidized LDL receptor-1 (LOX-1) signaling, and glycosylation removal from L5 attenuated L5-induced apoptosis. APOE glycosylation may contribute to the atherogenicity of L5 and be a useful biomarker for rapidly quantifying L5.
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Affiliation(s)
- Liang-Yin Ke
- Vascular and Medicinal Research, Texas Heart Institute, Houston, TX, USA.,Center for Lipid Biosciences, Kaohsiung Medical University Hospital, Lipid Science and Aging Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Medical Laboratory Science and Biotechnology, College of Health Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan.,Graduate Institute of Medicine, College of Medicine, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Hua-Chen Chan
- Vascular and Medicinal Research, Texas Heart Institute, Houston, TX, USA.,Center for Lipid Biosciences, Kaohsiung Medical University Hospital, Lipid Science and Aging Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Chih-Chieh Chen
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Chuan-Fa Chang
- Department of Medical Laboratory Science and Biotechnology, College of Health Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Po-Liang Lu
- Center for Lipid Biosciences, Kaohsiung Medical University Hospital, Lipid Science and Aging Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Chih-Sheng Chu
- Center for Lipid Biosciences, Kaohsiung Medical University Hospital, Lipid Science and Aging Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Wen-Ter Lai
- Graduate Institute of Medicine, College of Medicine, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Shyi-Jang Shin
- Graduate Institute of Medicine, College of Medicine, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Fu-Tong Liu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.,Department of Dermatology, University of California, Davis, School of Medicine, Sacramento, CA, USA
| | - Chu-Huang Chen
- Vascular and Medicinal Research, Texas Heart Institute, Houston, TX, USA.,New York Heart Research Foundation, New York, NY, USA
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Fruhwürth S, Kovacs WJ, Bittman R, Messner S, Röhrl C, Stangl H. Differential basolateral-apical distribution of scavenger receptor, class B, type I in cultured cells and the liver. Histochem Cell Biol 2014; 142:645-55. [PMID: 25059650 PMCID: PMC4241236 DOI: 10.1007/s00418-014-1251-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2014] [Indexed: 12/11/2022]
Abstract
The high-density lipoprotein (HDL) receptor, scavenger receptor class B, type I (SR-BI), mediates selective cholesteryl ester uptake into the liver, which finally results in cholesterol secretion into the bile. Despite several reports, the distribution of hepatic SR-BI between the sinusoidal and canalicular membranes is still under debate. We present immunohistological data using specific markers showing that the bulk of SR-BI is present in sinusoidal membranes and, to a lesser extent, in canalicular membranes in murine and human liver sections. In addition, SR-BI was detected in preparations of rat liver canalicular membranes. We also compared the in vivo findings to HepG2 cells, a widely used in vitro hepatocyte model. Interestingly, SR-BI was enriched in bile canalicular-like (BC-like) structures in polarized HepG2 cells, which were cultivated either conventionally to form a monolayer or in Matrigel to form three-dimensional structures. Fluorescently labeled HDL was transported into close proximity of BC-like structures, whereas HDL labeled with the fluorescent cholesterol analog BODIPY-cholesterol was clearly detected within these structures. Importantly, similarly to human and mouse liver, SR-BI was localized in basolateral membranes in three-dimensional liver microtissues from primary human liver cells. Our results demonstrate that SR-BI is highly enriched in sinusoidal membranes and is also found in canalicular membranes. There was no significant basolateral-apical redistribution of hepatic SR-BI in fasting and refeeding experiments in mice. Furthermore, in vitro studies in polarized HepG2 cells showed explicit differences as SR-BI was highly enriched in BC-like structures. These structures are, however, functional and accumulated HDL-derived cholesterol. Thus, biological relevant model systems should be employed when investigating SR-BI distribution in vitro.
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Affiliation(s)
- Stefanie Fruhwürth
- Center for Pathobiochemistry and Genetics, Department of Medical Chemistry, Medical University of Vienna, Währingerstraße 10, 1090 Vienna, Austria
| | - Werner J. Kovacs
- Institute of Molecular Health Sciences, Swiss Federal Institute of Technology Zurich (ETHZ), Zurich, Switzerland
| | - Robert Bittman
- Department of Chemistry and Biochemistry, Queens College of the City University of New York, Flushing, NY USA
| | | | - Clemens Röhrl
- Center for Pathobiochemistry and Genetics, Department of Medical Chemistry, Medical University of Vienna, Währingerstraße 10, 1090 Vienna, Austria
| | - Herbert Stangl
- Center for Pathobiochemistry and Genetics, Department of Medical Chemistry, Medical University of Vienna, Währingerstraße 10, 1090 Vienna, Austria
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Dantas SA, Ficker ES, Vinagre CGC, Ianni BM, Maranhão RC, Mady C. Metabolism of a lipid nanoemulsion resembling low-density lipoprotein in patients with grade iii obesity. Clinics (Sao Paulo) 2010; 65:23-7. [PMID: 20126342 PMCID: PMC2815278 DOI: 10.1590/s1807-59322010000100005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 10/11/2009] [Indexed: 11/22/2022] Open
Abstract
INTRODUCTION Obesity increases triglyceride levels and decreases high-density lipoprotein concentrations in plasma. Artificial emulsions resembling lipidic plasma lipoprotein structures have been used to evaluate low-density lipoprotein metabolism. In grade III obesity, low density lipoprotein metabolism is poorly understood. OBJECTIVE To evaluate the kinetics with which a cholesterol-rich emulsion (called a low-density emulsion) binds to low-density lipoprotein receptors in a group of patients with grade III obesity by the fractional clearance rate. METHODS A low-density emulsion was labeled with [(14)C]-cholesterol ester and [(3)H]-triglycerides and injected intravenously into ten normolipidemic non-diabetic patients with grade III obesity [body mass index higher than 40 kg/m(2)] and into ten non-obese healthy controls. Blood samples were collected over 24 hours to determine the plasma decay curve and to calculate the fractional clearance rate. RESULTS There was no difference regarding plasma levels of total cholesterol or low-density lipoprotein cholesterol between the two groups. The fractional clearance rate of triglycerides was 0.086 +/- 0.044 in the obese group and 0.122 +/- 0.026 in the controls (p = 0.040), and the fractional clearance rate of cholesterol ester (h(-1)) was 0.052 +/- 0.021 in the obese subjects and 0.058 +/- 0.015 (p = 0.971) in the controls. CONCLUSION Grade III obese subjects exhibited normal low-density lipoprotein removal from plasma as tested by the nanoemulsion method, but triglyceride removal was slower.
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Affiliation(s)
- Simone Alves Dantas
- Unidade Clínica de Miocardiopatias - Instituto do Coração - Hospital das Clinicas, Faculdade de Medicina da Universidade de São Paulo,São Paulo/SP,Brazil.
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4
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Mullick AE, Powers AF, Kota RS, Tetali SD, Eiserich JP, Rutledge JC. Apolipoprotein E3- and Nitric Oxide–Dependent Modulation of Endothelial Cell Inflammatory Responses. Arterioscler Thromb Vasc Biol 2007; 27:339-45. [PMID: 17138935 DOI: 10.1161/01.atv.0000253947.70438.99] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Objective—
Although apolipoprotein E3 (apoE3) is known to be atheroprotective, its mechanisms of protection in endothelial cells remain unclear.
Methods and Results—
Cultured human aortic endothelial cells were stimulated with tumor necrosis factor (TNF)-α in the presence of human recombinant apoE3 solubilized in dimyristoyl phosphatidylcholine liposomes. Using flow cytometry and real-time polymerase chain reaction, a significant increase of inflammatory cell adhesion proteins (vascular cell adhesion molecule-1 and E-Selectin), and MCP-1, interleukin-8, and intercellular adhesion molecule-1 gene expression was observed within 5 hours of TNF-α exposure, which was markedly attenuated in cells coincubated with apoE3. Treatment with apoE4 resulted in increased inflammatory gene expression relative to either TNF treatment alone or TNF + apoE3 treatment. NO synthase inhibition experiments demonstrated NO to be an active participant in the actions of both TNF and apoE. To clarify the role of NO, dose-response experiments were performed with 0.03 to 300 μmol/L DEA-NONOate. Using flow cytometry and real-time polymerase chain reaction, a modulatory role of NO in TNF-induced endothelial cell activation was observed.
Conclusions—
These data suggest a role of vascular wall apoE3 to balance the intracellular redox state in injured endothelial cells via NO-dependent pathways.
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Affiliation(s)
- Adam E Mullick
- Department of Internal Medicine, Division of Endocrinology, Clinical Nutrition, and Vascular Medicine, School of Medicine, University of California, Davis, USA.
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Pagler TA, Rhode S, Neuhofer A, Laggner H, Strobl W, Hinterndorfer C, Volf I, Pavelka M, Eckhardt ERM, van der Westhuyzen DR, Schütz GJ, Stangl H. SR-BI-mediated high density lipoprotein (HDL) endocytosis leads to HDL resecretion facilitating cholesterol efflux. J Biol Chem 2006; 281:11193-204. [PMID: 16488891 DOI: 10.1074/jbc.m510261200] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The high density lipoprotein (HDL) receptor, scavenger receptor class B, type I (SR-BI), mediates selective cholesteryl ester uptake from lipoproteins into liver and steroidogenic tissues but also cholesterol efflux from macrophages to HDL. Recently, we demonstrated the uptake of HDL particles in SR-BI overexpressing Chinese hamster ovarian cells (ldlA7-SRBI) using ultrasensitive microscopy. In this study we show that this uptake of entire HDL particles is followed by resecretion. After uptake, HDL is localized in endocytic vesicles and organelles en route to the perinuclear area; many HDL-positive compartments were classified as multivesiculated and multilamellated organelles by electron microscopy. By using 125I-labeled HDL, we found that approximately 0.8% of the HDL added to the media is taken up by the ldlA7-SRBI cells within 1 h, and almost all HDL is finally resecreted. 125I-Labeled low density lipoprotein showed a very similar association, uptake, and resecretion pattern in ldlA7-SRBI cells that do not express any low density lipoprotein receptor. Moreover, we demonstrate that the process of HDL cell association, uptake, and resecretion occurs in three physiologically relevant cell systems, the liver cell line HepG2, the adrenal cell line Y1BS1, and phorbol myristate acetate-differentiated THP-1 cells as a model for macrophages. Finally, we present evidence that HDL retroendocytosis represents one of the pathways for cholesterol efflux.
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Affiliation(s)
- Tamara A Pagler
- Center for Physiology and Pathophysiology, Department of Medical Chemistry, Medical University of Vienna, Währingerstrasse 10, A-1090 Vienna, Austria
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Takahashi Y, Zhu H, Xu W, Murakami T, Iwasaki T, Hattori H, Yoshimoto T. Selective uptake and efflux of cholesteryl linoleate in LDL by macrophages expressing 12/15-lipoxygenase. Biochem Biophys Res Commun 2005; 338:128-35. [PMID: 16105647 DOI: 10.1016/j.bbrc.2005.07.182] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Accepted: 07/30/2005] [Indexed: 01/08/2023]
Abstract
Oxidation of low density lipoprotein (LDL) is a critical step for atherogenesis, and the role of the 12/15-lipoxygenase (12/15-LOX) as well as LDL receptor-related protein (LRP) expressed in macrophages in this process has been suggested. The oxygenation of cholesteryl linoleate in LDL by mouse macrophage-like J774A.1 cells overexpressing 12/15-LOX was inhibited by an anti-LRP antibody but not by an anti-LDL receptor antibody. When the cells were incubated with LDL double-labeled by [3H]cholesteryl linoleate and [125I]apoB, association with the cells of [3H]cholesteryl linoleate expressed as LDL protein equivalent exceeded that of [125I]apoB, indicating selective uptake of [3H]cholesteryl linoleate from LDL to these cells. An anti-LRP antibody inhibited the selective uptake of [3H]cholesteryl ester by 62% and 81% with the 12/15-LOX-expressing cells and macrophages, respectively. Furthermore, addition of LDL to the culture medium of the [3H]cholesteryl linoleate-labeled 12/15-LOX-expressing cells increased the release of [3H]cholesteryl linoleate to the medium in LDL concentration- and time-dependent manners. The transport of [3H]cholesteryl linoleate from the cells to LDL was also inhibited by an anti-LRP antibody by 75%. These results strongly suggest that LRP contributes to the LDL oxidation by 12/15-LOX in macrophages by selective uptake and efflux of cholesteryl ester in the LDL particle.
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Affiliation(s)
- Yoshitaka Takahashi
- Department of Nutritional Science, Faculty of Health and Welfare Science, Okayama Prefectural University, Soja, Okayama 719-1197, Japan.
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7
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Huard K, Bourgeois P, Rhainds D, Falstrault L, Cohn JS, Brissette L. Apolipoproteins C-II and C-III inhibit selective uptake of low- and high-density lipoprotein cholesteryl esters in HepG2 cells. Int J Biochem Cell Biol 2005; 37:1308-18. [PMID: 15778093 DOI: 10.1016/j.biocel.2005.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2004] [Accepted: 01/18/2005] [Indexed: 01/26/2023]
Abstract
Plasma low- and high-density lipoproteins (LDL and HDL) are cleared from the circulation by specific receptors and are either totally degraded or their cholesteryl esters (CE) are selectively delivered to cells by receptors such as the scavenger receptor class B type I (SR-BI). The aim of the present study was to define the effect of apoC-II and apoC-III on the uptake of LDL and HDL by HepG2 cells. Stable transformants were obtained with sense or antisense strategies that secrete 47-294% the normal level of apoC-II or 60-200% that of apoC-III. Different levels of secreted apoC-II or apoC-III had little effect on LDL and HDL protein degradation by HepG2 cells. However, compared to controls, cells under-expressing apoC-II showed a 160% higher capacity to selectively take up HDL-CE, while cells under-expressing apoC-III demonstrated 70 and 160% higher capacity to take up CE from LDL and HDL, respectively. In experiments conducted with exogenously added apoC-II or apoC-III, no significant effect was observed on lipoprotein-protein association/degradation; however, LDL-CE and HDL-CE selective uptake was significantly reduced in a dose-dependent manner. These results indicate that apoC-II and apoC-III inhibit CE-selective uptake.
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Affiliation(s)
- Karine Huard
- Département des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888, Succ. Centre-ville, Montréal, Que., Canada H3C 3P8
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8
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Seo T, Qi K, Chang C, Liu Y, Worgall TS, Ramakrishnan R, Deckelbaum RJ. Saturated fat-rich diet enhances selective uptake of LDL cholesteryl esters in the arterial wall. J Clin Invest 2005; 115:2214-22. [PMID: 16041409 PMCID: PMC1177997 DOI: 10.1172/jci24327] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2004] [Accepted: 05/24/2005] [Indexed: 11/17/2022] Open
Abstract
Plasma LDL levels and atherosclerosis both increase on a saturated fat-rich (SAT) diet. LDL cholesterol delivery to tissue may occur via uptake of the LDL particles or via selective uptake (SU), wherein cholesteryl ester (CE) enters cells without concomitant whole-particle uptake. It is not known how dietary fats might directly affect arterial LDL-CE uptake and whether SU is involved. Thus, mice that are relatively atherosclerosis resistant (C57BL/6) or susceptible to atherosclerosis (apoE) were fed a chow or SAT diet and injected with double radiolabeled or fluorescent-labeled human LDL to independently trace LDL-CE core and whole-particle uptake, respectively. Our results show that a SAT diet increased contributions of SU to total arterial LDL-CE delivery in C57BL/6 and apoE mice. The SAT diet increased plasma fatty acid and cholesterol levels; cholesterol, but not fatty acid, levels correlated with SU, as did the degree of atherosclerosis. Increased SU did not correlate with arterial scavenger receptor class B type I levels but paralleled increased lipoprotein lipase (LPL) levels and LPL distribution in the arterial wall. These studies suggest that arterial LDL-CE delivery via SU can be an important mechanism in vivo and that dietary influences on arterial LPL levels and atherogenesis modulate arterial LDL-CE delivery, cholesterol deposition, and SU.
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Affiliation(s)
- Toru Seo
- Department of Pediatrics, Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
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Zhao Y, Thorngate FE, Weisgraber KH, Williams DL, Parks JS. Apolipoprotein E is the major physiological activator of lecithin-cholesterol acyltransferase (LCAT) on apolipoprotein B lipoproteins. Biochemistry 2005; 44:1013-25. [PMID: 15654758 DOI: 10.1021/bi0481489] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Our previous studies have indicated that lecithin-cholesterol acyltransferase (LCAT) contributes significantly to the apoB lipoprotein cholesteryl ester (CE) pool. Cholesterol esterification rate (CER) in apoA-I(-)(/)(-) apoE(-)(/)(-) mouse plasma was <7% that of C57Bl/6 (B6) mouse plasma, even though apoA-I(-)(/)(-) apoE(-)(/)(-) plasma retained (1)/(3) the amount of B6 LCAT activity. This suggested that lack of LCAT enzyme did not explain the low CER in apoA-I(-)(/)(-) apoE(-)(/)(-) mice and indicated that apoE and apoA-I are the only major activators of LCAT in mouse plasma. Deleting apoE on low-density lipoprotein (LDL) reduced CER (1% free cholesterol (FC) esterified/h) compared to B6 (6% FC esterified/h) and apoA-I(-)(/)(-) (11% FC esterified/h) LDL. Similar sized LDL particles from all four genotypes were isolated by fast protein liquid chromatography (FPLC) after radiolabeling with [(3)H]-free cholesterol (FC). LDLs (1 microg FC) from each genotype were incubated with purified recombinant mouse LCAT; LDL particles from B6 and apoA-I(-)(/)(-) plasma were much better substrates for CE formation (5.7% and 6.3% CE formed/30 min, respectively) than those from apoE(-)(/)(-) and apoE(-)(/)(-) apoA-I(-)(/)(-) plasma (1.2% and 1.1% CE formed/30 min). Western blot analysis showed that the amount of apoA-I on apoE(-)(/)(-) LDLs was higher compared to B6 LDL. Adding apoE to incubations of apoA-I(-)(/)(-) apoE(-)(/)(-) very low density lipoprotein (VLDL) resulted in a 3-fold increase in LCAT CER, whereas addition of apoA-I resulted in a more modest 80% increase. We conclude that apoE is a more significant activator of LCAT than apoA-I on mouse apoB lipoproteins.
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Affiliation(s)
- Yue Zhao
- Department of Pathology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
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10
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Rhainds D, Brissette L. The role of scavenger receptor class B type I (SR-BI) in lipid trafficking. defining the rules for lipid traders. Int J Biochem Cell Biol 2004; 36:39-77. [PMID: 14592533 DOI: 10.1016/s1357-2725(03)00173-0] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The scavenger receptor class B type I (SR-BI) is a 509-amino acid, 82 kDa glycoprotein, with two cytoplasmic C- and N-terminal domains separated by a large extracellular domain. The aim of this review is to define the role of SR-BI as a lipoprotein receptor responsible for selective uptake of cholesteryl esters (CE) from high density lipoprotein (HDL) and low density lipoprotein (LDL) and free cholesterol (FC) efflux to lipoprotein acceptors. These activities depend on lipoprotein binding to its extracellular domain and subsequent lipid exchange at the plasma membrane. CE selective uptake supplies cholesterol to liver and steroidogenic tissues, for biliary cholesterol secretion and steroid hormone synthesis. Genetically modified mice have confirmed SR-BI's major role in tissue cholesterol uptake and in reverse cholesterol transport, i.e. cholesterol turnover. Accordingly, cellular cholesterol level, estrogens and trophic hormones regulate SR-BI expression by both transcriptional and post-transcriptional mechanisms. Importantly, mouse SR-BI overexpression has both corrective and preventive effects on atherosclerosis. Human SR-BI has very similar tissue distribution, binding properties and lipid transfer activities compared to rodent SR-BI. However, human plasma has most of its cholesterol in LDL. Thus, there is considerable interest to develop anti-atherogenic strategies involving human SR-BI-mediated increases in reverse cholesterol transport through HDL and/or LDL.
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MESH Headings
- Amino Acid Sequence
- Animals
- Biological Transport, Active
- CD36 Antigens
- Cell Membrane/chemistry
- Cell Membrane/genetics
- Cell Membrane/metabolism
- Cell Membrane/physiology
- Humans
- Lipid Metabolism
- Lipoproteins/metabolism
- Models, Biological
- Promoter Regions, Genetic
- Protein Structure, Tertiary
- Receptors, Immunologic/chemistry
- Receptors, Immunologic/genetics
- Receptors, Immunologic/metabolism
- Receptors, Immunologic/physiology
- Receptors, Scavenger
- Scavenger Receptors, Class B
- Tissue Distribution
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Affiliation(s)
- David Rhainds
- Département des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montreal, Que., Canada H3C 3P8.
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Vassiliou G, McPherson R. A novel efflux-recapture process underlies the mechanism of high-density lipoprotein cholesteryl ester-selective uptake mediated by the low-density lipoprotein receptor-related protein. Arterioscler Thromb Vasc Biol 2004; 24:1669-75. [PMID: 15178567 DOI: 10.1161/01.atv.0000134295.09932.60] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To determine the mechanism of low-density lipoprotein (LDL) receptor-related protein (LRP)-mediated selective uptake of high-density lipoprotein (HDL)-derived cholesteryl esters (CE). METHODS AND RESULTS Apolipoprotein E (apoE) and heparin sulfate proteoglycans are required for LRP-mediated selective uptake in adipocytes. Furthermore, 2-deoxyglucose and NaN(3) abolish this process, indicating that cellular energy is required. LRP-mediated selective uptake is also abolished by monensin or when clathrin-mediated internalization is inhibited (using hypotonic, K(+)-free medium or hyperosmolar sucrose), clearly implicating receptor endocytosis. The receptor-associated protein (RAP), an inhibitor of ligand binding to LRP, reduced the transport of CE into an intracellular compartment but not into the plasma membrane. Remarkably, the CE that is ultimately transported by LRP first enters the plasma membrane then undergoes apoE-mediated CE efflux before being recaptured and internalized by LRP. CONCLUSIONS According to this "efflux-recapture" model, LRP contributes to selective uptake because it recovers CE that would normally be lost by efflux mediated by apoE. In adipocytes, the LDL receptor-related protein contributes to selective uptake when it recaptures and internalizes HDL-derived cholesteryl esters that are otherwise lost by apoE-mediated efflux. This novel "efflux-recapture" process explains some conflicting observations of selective uptake and underscores the bi-directional nature of efflux.
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Affiliation(s)
- Gerard Vassiliou
- Lipoprotein and Atherosclerosis Group, Lab H453, University of Ottawa Heart Institute, Ottawa ON K1Y 4W7, Canada.
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12
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Corbo RM, Scacchi R, Cresta M. Differential reproductive efficiency associated with common apolipoprotein e alleles in postreproductive-aged subjects. Fertil Steril 2004; 81:104-7. [PMID: 14711551 DOI: 10.1016/j.fertnstert.2003.05.029] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE To investigate the possible impact of apolipoprotein E (APOE) polymorphism on reproductive efficiency. DESIGN Population study. SETTING University Departments and a Laboratory of National Research Council. PATIENT(S) One hundred sixty healthy unrelated subjects of postreproductive age. INTERVENTION(S) Peripheral blood collection and questionnaire administration. MAIN OUTCOME MEASURE(S) Apolipoprotein E genotypes were detected after PCR amplification and CfoI digestion; plasma total cholesterol was assayed. RESULT(S) The mean number of children of e*2 allele carriers (2.4) was lower than that of e*3/e*3 and e*4/e*3 subjects (3.9). The trend was similar (2.8 vs. 4.8) when the number of pregnancies was considered. Moreover, there was a clear inverse relationship between number of children and e*2-carrying genotype proportions (chi(2) for trend = 6.3). Conversely, the e*3/e*3 genotype was associated with the highest number of children and pregnancies (3.9 and 4.9, respectively), and the e*4/e*3 genotype, with intermediate values (3.7 and 4.4). Carriers of e*2 allele also showed the lowest levels of total cholesterol. CONCLUSION(S) The e*2 allele seems to be associated with the lowest reproductive efficiency and the e*3 allele, with the highest. The different total cholesterol levels associated with APOE genotypes could have an effect on steroidogenesis and determine as a consequence the observed differential fertility.
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Affiliation(s)
- Rosa M Corbo
- Department of Genetics and Molecular Biology, University "La Sapienza,", Rome, Italy.
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Kraemer FB, Shen WJ, Harada K, Patel S, Osuga JI, Ishibashi S, Azhar S. Hormone-sensitive lipase is required for high-density lipoprotein cholesteryl ester-supported adrenal steroidogenesis. Mol Endocrinol 2003; 18:549-57. [PMID: 14657254 DOI: 10.1210/me.2003-0179] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Steroid hormones are synthesized using cholesterol as precursor, with a substantial portion supplied by the selective uptake of lipoprotein-derived cholesteryl esters. Adrenals express a high level of neutral cholesteryl ester hydrolase activity, and recently hormone-sensitive lipase (HSL) was shown to be responsible for most adrenal neutral cholesteryl ester hydrolase activity. To determine the functional importance of HSL in adrenal steroidogenesis, adrenal cells were isolated from control and HSL-/- mice, and the in vitro production of corticosterone was quantified. Results show that, even though adrenal cholesteryl ester content was substantially elevated in both male and female HSL-/- mice, basal corticosterone production was reduced approximately 50%. The maximum corticosterone production induced by dibutyryl cAMP, and lipoproteins was approximately 75-85% lower in adrenal cells from HSL-/- mice compared with control. There is no intrinsic defect in the conversion of cholesterol into steroids in HSL-/- mice. Dibutyryl cAMP-stimulated conversion of high-density lipoprotein cholesteryl esters into corticosterone was reduced 97% in HSL-/- mice. An increase in low-density lipoprotein receptor expression appears to be one of the compensatory mechanisms for cholesterol delivery in HSL-/- mice. These findings suggest that HSL is functionally linked to the selective pathway and is critically involved in the intracellular processing and availability of cholesterol for adrenal steroidogenesis.
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Affiliation(s)
- Fredric B Kraemer
- Veterans Affairs Palo Alto Health Care System, California 94304, USA.
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14
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Thuahnai ST, Lund-Katz S, Anantharamaiah GM, Williams DL, Phillips MC. A quantitative analysis of apolipoprotein binding to SR-BI: multiple binding sites for lipid-free and lipid-associated apolipoproteins. J Lipid Res 2003; 44:1132-42. [PMID: 12671027 DOI: 10.1194/jlr.m200429-jlr200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Competitive binding experiments were performed using Y1-BS1 adrenal cells to provide information about the interaction of HDL apolipoproteins with scavenger receptor class B, type I (SR-BI). Exchangeable apolipoproteins apolipoprotein A-I (apoA-I), apoA-II, apoE-2, apoE-3, and apoE-4 as phospholipid complexes bind like HDL3 to SR-BI via their multiple amphipathic alpha-helices; the concentrations required to reduce the binding of HDL3 to SR-BI by 50% (IC50) were similar and in the range of 35-50 microgram protein/ml. In the case of apoA-I, peptides corresponding to segments 1-85, 44-65, 44-87, 149-243, and 209-241 all had the same IC50 as each other (P = 0.86), showing that a specific amino acid sequence in apoA-I is not responsible for the interaction with SR-BI. The distribution of charged residues in the amphipathic alpha-helix affects the interaction, with class A and Y helices binding better than class G* helices. Synthetic alpha-helical peptides composed of either l or d amino acids can bind equally to the receptor. Association with phospholipid increases the amount of apolipoprotein binding to SR-BI without altering the affinity of binding. Lipid-free apolipoproteins compete only partially with the binding of HDL to SR-BI, whereas lipidated apolipoproteins compete fully. These results are consistent with the existence of more than one type of apolipoprotein binding site on SR-BI.
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Affiliation(s)
- Stephen T Thuahnai
- Division of GI/Nutrition, Lipid Research Group, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, 19104-4318, USA
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15
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Santos RD, Hueb W, Oliveira AA, Ramires JAF, Maranhão RC. Plasma kinetics of a cholesterol-rich emulsion in subjects with or without coronary artery disease. J Lipid Res 2003; 44:464-9. [PMID: 12562871 DOI: 10.1194/jlr.m200331-jlr200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A cholesterol-rich emulsion (LDE) that resembles the LDL lipidic structure is taken-up by LDL receptors after intravenous injection by means of apolipoprotein E it acquires in the circulation and can be used to probe LDL metabolism. In this study, LDE was labeled with [14C]cholesteryl oleate and [3H]cholesterol and injected into 19 patients with coronary artery disease (CAD) and into 14 subjects without CAD to verify whether the kinetic behavior of the radioactive lipids is different in CAD. Blood was sampled over 24 h for radioactivity measurement after lipid extraction and separation by thin-layer chromatography. Fractional clearance rate (FCR, in h-1) of [14C]cholesteryl ester was not different in CAD and nonCAD expressed as median (25%; 75%): 0.08 (0.062; 0.134) h-1 versus 0.06 (0.04; 0.083) h-1, P = 0.167. However, [3H]cholesterol FCR was greater in CAD than in nonCAD (mean +/- SEM): 0.163 +/- 0.016 h-1 versus 0.077 +/- 0.014 h-1, P < 0.001. Esterification of the LDE [3H]cholesterol was also greater in CAD subjects than nonCAD at 10 h and 24 h after emulsion injection (P = 0.029 and 0.024 respectively). In conclusion, both removal from the plasma and esterification of the LDE-cholesterol were increased in CAD. These findings may contribute for unraveling pro-atherogenic mechanisms and the establishment of novel CAD markers.
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Affiliation(s)
- Raul D Santos
- Lipid Metabolism Laboratory, the Heart Institute (INCOR), Medical School Hospital (InCor-HCFMUSP), University of São Paulo, São Paulo, Brazil
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16
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Thorngate FE, Strockbine PA, Erickson SK, Williams DL. Altered adrenal gland cholesterol metabolism in the apoE-deficient mouse. J Lipid Res 2002; 43:1920-6. [PMID: 12401891 DOI: 10.1194/jlr.m200205-jlr200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies suggest the hypothesis that apoE produced by adrenocortical cells modulates cellular cholesterol metabolism to enhance the storage of esterified cholesterol (EC) at the expense of cholesterol delivery to the steroidogenic pathway. In the present study, parameters of adrenal cholesterol metabolism and corticosteroid production were examined in wild type and apoE-deficient (apoe(-/-)) mice. Adrenal gland EC content and the EC/free cholesterol (FC) ratio in mice stressed by adrenocorticotropin (ACTH) treatment or saline injection were reduced in apoe(-/-) compared to apoe(+/+) mice. Relative to apoe(+/+) mice, apoE deficiency also resulted in increased levels of plasma corticosterone in the basal state, in response to acute or long-term ACTH treatment, and after a swim-induced neuroendocrine-directed stress test. Measurements of adrenal gland scavenger receptor class B, type I (SR-BI), LDL receptor, and LDL receptor related protein (LRP) levels and the activities of ACAT or HMG-CoA reductase showed no difference between genotypes. Apoe(-/-) and apoe(+/+) mice showed similar quantitative increases in LDL receptors, SR-BI, adrenal weight gain, and ACAT activities in response to ACTH, and both genotypes had similar basal plasma ACTH concentrations. These results suggest that the effects of apoE deficiency reflect events at the level of the adrenal gland and are specific to changes in cholesterol accumulation and corticosterone production. Further, these findings support the hypothesis that apoE acts to enhance adrenocortical EC accumulation and diminish corticosterone production.
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Affiliation(s)
- Fayanne E Thorngate
- Department of Pharmacological Sciences, University Medical Center, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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17
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Azhar S, Reaven E. Scavenger receptor class BI and selective cholesteryl ester uptake: partners in the regulation of steroidogenesis. Mol Cell Endocrinol 2002; 195:1-26. [PMID: 12354669 DOI: 10.1016/s0303-7207(02)00222-8] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The steroidogenic tissues have a special requirement for cholesterol, which is used as a substrate for steroid hormone biosynthesis. In many species this cholesterol is obtained from plasma lipoproteins by a unique pathway in which circulating lipoproteins bind to the surface of the steroidogenic cells and contribute their cholesteryl esters to the cells by a 'selective' process in which the whole lipoprotein particle does not enter the cell. This review describes the lipoprotein selective cholesteryl ester uptake process and its specific partnership with the HDL receptor, scavenger receptor class BI (SR-BI). It describes the characteristics of the selective pathway, and the molecular properties, localization, regulation, anchoring sites and potential mechanisms of action of SR-BI in facilitating cholesteryl ester uptake by steroidogenic cells.
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Affiliation(s)
- Salman Azhar
- Geriatric Research, Education and Clinical Center, GRECC-182B, VA Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, CA 94304, USA.
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18
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Bultel-Brienne S, Lestavel S, Pilon A, Laffont I, Tailleux A, Fruchart JC, Siest G, Clavey V. Lipid free apolipoprotein E binds to the class B Type I scavenger receptor I (SR-BI) and enhances cholesteryl ester uptake from lipoproteins. J Biol Chem 2002; 277:36092-9. [PMID: 12138091 DOI: 10.1074/jbc.m201943200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Class B type I scavenger receptor I (SR-BI) is a physiologically relevant high density lipoprotein (HDL) receptor that can mediate selective cholesteryl ester (CE) uptake by cells. Direct interaction of apolipoprotein E (apoE) with this receptor has never been demonstrated, and its implication in CE uptake is still controversial. By using a human adrenal cell line (NCI-H295R), we have addressed the role of apoE in binding to SR-BI and in selective CE uptake from lipoproteins to cells. This cell line does not secrete apoE and SR-BI is its major HDL-binding protein. We can now provide evidence that 1) free apoE is a ligand for SR-BI, 2) apoE associated to lipids or in lipoproteins does not modulate binding or CE-selective uptake by the SR-BI pathway, and 3) the direct interaction of free apoE to SR-BI leads to an increase in CE uptake from lipoproteins of both low and high densities. We propose that this direct interaction could modify SR-BI structure in cell membranes and potentiate CE uptake.
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MESH Headings
- Apolipoproteins E/metabolism
- Binding Sites
- Binding, Competitive
- CD36 Antigens/chemistry
- CD36 Antigens/metabolism
- Cell Line
- Cell Membrane/metabolism
- Cholesterol Esters/pharmacokinetics
- Dose-Response Relationship, Drug
- Electrophoresis, Polyacrylamide Gel
- Enzyme-Linked Immunosorbent Assay
- Glycosides/metabolism
- Humans
- Hydrolysis
- Ligands
- Lipid Metabolism
- Lipoproteins/metabolism
- Lipoproteins, HDL/metabolism
- Lipoproteins, LDL/metabolism
- Membrane Proteins
- Protein Binding
- Receptors, Immunologic
- Receptors, Lipoprotein
- Receptors, Scavenger
- Recombinant Proteins/metabolism
- Scavenger Receptors, Class B
- Thrombin/metabolism
- Tumor Cells, Cultured
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Affiliation(s)
- Stéphanie Bultel-Brienne
- Unité INSERM U 545, Institut Pasteur de Lille, Faculté de Pharmacie, Université Lille 2, 1 rue du Professeur Calmette, 59019 Lille cedex, France
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19
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Webb NR, de Beer MC, Yu J, Kindy MS, Daugherty A, van der Westhuyzen DR, de Beer FC. Overexpression of SR-BI by adenoviral vector promotes clearance of apoA-I, but not apoB, in human apoB transgenic mice. J Lipid Res 2002; 43:1421-8. [PMID: 12235173 DOI: 10.1194/jlr.m200026-jlr200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Scavenger receptor BI (SR-BI) is a multi-ligand lipoprotein receptor that mediates selective lipid uptake from HDL, and plays a central role in hepatic HDL metabolism. In this report, we investigated the extent to which SR-BI selective lipid uptake contributes to LDL metabolism. As has been reported for human LDL, mouse SR-BI expressed in transfected cells mediated selective lipid uptake from mouse LDL. However, LDL-cholesteryl oleoyl ester (CE) transfer relative to LDL-CE bound to the cell surface (fractional transfer) was approximately 18-fold lower compared with HDL-CE. Adenoviral vector-mediated SR-BI overexpression in livers of human apoB transgenic mice ( approximately 10-fold increased expression) reduced plasma HDL-cholesterol (HDL-C) and apolipoprotein (apo)A-I concentrations to nearly undetectable levels 3 days after adenovirus infusion. Increased hepatic SR-BI expression resulted in only a modest depletion in LDL-C that was restricted to large LDL particles, and no change in steady-state concentrations of human apoB. Kinetic studies showed a 19% increase in the clearance rate of LDL-CE in mice with increased SR-BI expression, but no change in LDL apolipoprotein clearance. Quantification of hepatic uptake of LDL-CE and LDL-apolipoprotein showed selective uptake of LDL-CE in livers of human apo B transgenic mice. However, such uptake was not significantly increased in mice over-expressing SR-BI. We conclude that SR-BI-mediated selective uptake from LDL plays a minor role in LDL metabolism in vivo.
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Affiliation(s)
- Nancy R Webb
- Department of Internal Medicine, University of Kentucky Medical Center, Lexington, KY 40536.
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20
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Vassiliou G, Benoist F, Lau P, Kavaslar GN, McPherson R. The low density lipoprotein receptor-related protein contributes to selective uptake of high density lipoprotein cholesteryl esters by SW872 liposarcoma cells and primary human adipocytes. J Biol Chem 2001; 276:48823-30. [PMID: 11604390 DOI: 10.1074/jbc.m103954200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The concept that selective transfer of high density lipoprotein (HDL)-derived cholesteryl esters (CE) does not require lipoprotein internalization has been challenged recently by evidence that implicates HDL recycling during the selective uptake process. This has prompted us to examine the role of the low density lipoprotein receptor-related protein (LRP) in selective uptake. LRP is an endocytic receptor for lipoprotein lipase (LpL) and apolipoprotein E (apoE) ligands that are able to mediate selective uptake. We report that molecules that interfere with ligand binding to LRP, such as the receptor-associated protein (RAP), suramin, alpha(2)-macroglobulin, or lactoferrin, inhibit HDL-CE selective uptake by human primary adipocytes and SW872 liposarcoma cells by 35-50%. This partial inhibition of selective uptake from total HDL was not due to preferential inhibition of the HDL(2) or HDL(3) subfractions. Selective uptake by the scavenger receptor BI was not inhibited by RAP, excluding its involvement. Furthermore, in SW872 cells in which LRP was reduced to 14% of control levels by stable antisense expression, selective uptake was attenuated by at least 33%, confirming a role for LRP in this process. RAP, alpha(2)-macroglobulin, lactoferrin, and suramin (individually or in paired combinations) also attenuated selective uptake of HDL-CE by primary human adipocytes by about 40%. On the other hand, human skin fibroblasts express LRP abundantly but lack the capacity for selective uptake, demonstrating that other molecules are required. In SW872 cells, exogenous apoE or LpL can facilitate selective uptake but only the apoE-enhanced uptake can be inhibited by RAP, implicating apoE as a likely co-mediator. We discuss the possible mechanisms by which the endocytic receptor, LRP, can mediate selective uptake.
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Affiliation(s)
- G Vassiliou
- Lipoprotein and Atherosclerosis Group, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4E9, Canada.
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21
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Swarnakar S, Beers J, Strickland DK, Azhar S, Williams DL. The apolipoprotein E-dependent low density lipoprotein cholesteryl ester selective uptake pathway in murine adrenocortical cells involves chondroitin sulfate proteoglycans and an alpha 2-macroglobulin receptor. J Biol Chem 2001; 276:21121-8. [PMID: 11274190 DOI: 10.1074/jbc.m101691200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cells acquire lipoprotein cholesterol by receptor-mediated endocytosis and selective uptake pathways. In the latter case, lipoprotein cholesteryl ester (CE) is transferred to the plasma membrane without endocytosis and degradation of the lipoprotein particle. Previous studies with Y1/E/tet/2/3 murine adrenocortical cells that were engineered to express apolipoprotein (apo) E demonstrated that apoE expression enhances low density lipoprotein (LDL) CE uptake by both selective and endocytic pathways. The present experiments test the hypothesis that apoE-dependent LDL CE selective uptake is mediated by scavenger receptor, class B, type I (SR-BI). Surprisingly, SR-BI expression was not detected in the Y1/E/tet/2/3 clone of Y1 adrenocortical cells, indicating the presence of a distinct apoE-dependent pathway for LDL CE selective uptake. ApoE-dependent LDL CE selective uptake in Y1/E/tet/2/3 cells was inhibited by receptor-associated protein and by activated alpha(2)-macroglobulin (alpha(2)M), suggesting the participation of the LDL receptor-related protein/alpha(2)M receptor. Reagents that inhibited proteoglycan synthesis or removed cell surface chondroitin sulfate proteoglycan completely blocked apoE-dependent LDL CE selective uptake. None of these reagents inhibited SR-BI-mediated LDL CE selective uptake in the Y1-BS1 clone of Y1 cells in which LDL CE selective uptake is mediated by SR-BI. We conclude that LDL CE selective uptake in adrenocortical cells occurs via SR-BI-independent and SR-BI-dependent pathways. The SR-BI-independent pathway is an apoE-dependent process that involves both chondroitin sulfate proteoglycans and an alpha(2)M receptor.
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Affiliation(s)
- S Swarnakar
- Department of Pharmacological Sciences, University Medical Center, State University of New York, Stony Brook, New York 11794, USA
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22
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Monks J, Huey PU, Hanson L, Eckel RH, Neville MC, Gavigan S. A lipoprotein-containing particle is transferred from the serum across the mammary epithelium into the milk of lactating mice. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31630-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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23
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Auger A, Truong TQ, Rhainds D, Lapointe J, Letarte F, Brissette L. Low and high density lipoprotein metabolism in primary cultures of hepatic cells from normal and apolipoprotein E knockout mice. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:2322-30. [PMID: 11298750 DOI: 10.1046/j.1432-1327.2001.02115.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Apolipoprotein E (apoE) plays a major role in lipoprotein metabolism by mediating the binding of apoE-containing lipoproteins to receptors. The role of hepatic apoE in the catabolism of apoE-free lipoproteins such as low density lipoprotein (LDL) and high density lipoprotein-3 (HDL(3)) is however, unclear. We analyzed the importance of hepatic apoE by comparing human LDL and HDL(3) metabolism in primary cultures of hepatic cells from control C57BL/6J and apoE knockout (KO) mice. Binding analysis showed that the maximal binding capacity (Bmax) of LDL, but not of HDL(3), is increased by twofold in the absence of apoE synthesis/secretion. Compared to control hepatic cells, LDL and HDL(3) holoparticle uptake by apoE KO hepatic cells, as monitored by protein degradation, is reduced by 54 and 77%, respectively. Cleavage of heparan sulfate proteoglycans (HSPG) by treatment with heparinase I reduces LDL association by 21% in control hepatic cells. Thus, HSPG alone or a hepatic apoE-HSPG complex is partially involved in LDL association with mouse hepatic cells. In apoE KO, but not in normal hepatic cells, the same treatment increases LDL uptake/degradation by 2.4-fold suggesting that in normal hepatic cells, hepatic apoE increases LDL degradation by masking apoB-100 binding sites on proteoglycans. Cholesteryl ester (CE) association and CE selective uptake (CE/protein association ratio) from LDL and HDL(3) by mouse hepatic cells were not affected by the absence of apoE expression. We also show that 69 and 72% of LDL-CE hydrolysis in control and apoE KO hepatic cells, respectively, is sensitive to chloroquine revealing the importance of a pathway linked to lysosomes. In contrast, HDL(3)-CE hydrolysis is only mediated by a nonlysosomal pathway in both control and apoE KO hepatic cells. Overall, our results indicate that hepatic apoE increases the holoparticle uptake pathway of LDL and HDL(3) by mouse hepatic cells, that HSPG devoid of apoE favors LDL binding/association but impairs LDL uptake/degradation and that apoE plays no significant role in CE selective uptake from either human LDL or HDL(3) lipoproteins.
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MESH Headings
- Animals
- Apolipoproteins E/genetics
- Binding Sites
- CD36 Antigens/metabolism
- Cells, Cultured
- Cholesterol Esters/metabolism
- Dose-Response Relationship, Drug
- Female
- Heparan Sulfate Proteoglycans/metabolism
- Homozygote
- Humans
- Immunoblotting
- Kinetics
- Lipoproteins, HDL/metabolism
- Lipoproteins, LDL/metabolism
- Liver/cytology
- Liver/metabolism
- Male
- Membrane Proteins
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Protein Binding
- Receptors, Immunologic
- Receptors, LDL/metabolism
- Receptors, Lipoprotein
- Receptors, Scavenger
- Scavenger Receptors, Class B
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Affiliation(s)
- A Auger
- Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Québec, Canada
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24
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Charpentier D, Tremblay C, Rassart E, Rhainds D, Auger A, Milne RW, Brissette L. Low- and high-density lipoprotein metabolism in HepG2 cells expressing various levels of apolipoprotein E. Biochemistry 2000; 39:16084-91. [PMID: 11123936 DOI: 10.1021/bi001436u] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To determine the importance of hepatic apolipoprotein (apo) E in lipoprotein metabolism, HepG2 cells were transfected with a constitutive expression vector (pRc/CMV) containing either the complete or the first 474 base pairs of the human apoE cDNA inserted in an antisense orientation, for apoE gene inactivation, or the full-length human apoE cDNA inserted in a sense orientation for overexpression of apoE. Stable transformants were obtained that expressed 15, 24, 226, and 287% the apoE level of control HepG2 cells. The metabolism of low-density lipoprotein (LDL) and high-density lipoprotein-3 (HDL(3)), two lipoprotein classes following both holoparticle and cholesteryl esters (CE)-selective uptake pathways, was compared between all these cells. LDL-protein degradation, an indicator of the holoparticle uptake, was greater in low apoE expressing cells than in control or high expressing cells, while HDL(3)-protein degradation paralleled the apoE levels of the cells (r(2) = 0.989). LDL- and HDL(3)-protein association was higher in low apoE expressing cells compared to control cells. In opposition, LDL- and HDL(3)-CE association was not different from control cells in low apoE expressing cells but rose in high apoE expressing cells. In consequence, the CE-selective uptake (CE/protein association ratio) was positively correlated with the level of apoE expression in all cells for both LDL (r(2) = 0.977) and HDL(3) (r(2) = 0.998). We also show that, although in normal and low apoE expressor cells, 92% of LDL- and 80% HDL(3)-CE hydrolysis is sensitive to chloroquine suggesting a pathway linked to lysosomes for both lipoproteins, cells overexpressing apoE lost 60% of chloroquine-sensitive HDL(3)-CE hydrolysis without affecting that of LDL-CE. Thus, the level of apoE expression in HepG2 cells determines the fate of LDL and HDL(3).
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Affiliation(s)
- D Charpentier
- Département des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888, Succ. Centre-ville, Montréal, Québec, Canada
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25
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Fisher CA, Narayanaswami V, Ryan RO. The lipid-associated conformation of the low density lipoprotein receptor binding domain of human apolipoprotein E. J Biol Chem 2000; 275:33601-6. [PMID: 10906325 DOI: 10.1074/jbc.m002643200] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein E (apoE) is a 34-kDa exchangeable apolipoprotein that regulates metabolism of plasma lipoproteins by functioning as a ligand for members of the LDL receptor family. The receptor-binding region localizes to the vicinity of residues 130-150 within its independently folded 22-kDa N-terminal domain. In the absence of lipid, this domain exists as a receptor-inactive, globular four-helix bundle. Receptor recognition properties of this domain are manifest upon lipid association, which is accompanied by a conformational change in the protein. Fluorescence resonance energy transfer has been used to monitor helix repositioning, which accompanies lipid association of the apoE N-terminal domain. Site-directed mutagenesis was used to replace naturally occurring Trp residues with phenylalanine, creating a Trp-null apoE3 N-terminal domain (residues 1-183). Subsequently, tyrosine residues in helix 2, helix 3, or helix 4 were converted to Trp, generating single Trp mutant proteins. The lone cysteine at position 112 was covalently modified with N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine, which serves as an energy acceptor from excited tryptophan residues. Fluorescence resonance energy transfer analysis of apoE N-terminal domain variants in phospholipid disc complexes suggests that the helix bundle opens to adopt a partially extended conformation. A model is presented that depicts a tandem arrangement of the receptor-binding region of the protein in the disc complex, corresponding to its low density lipoprotein receptor-active conformation.
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Affiliation(s)
- C A Fisher
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
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26
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Seo T, Al-Haideri M, Treskova E, Worgall TS, Kako Y, Goldberg IJ, Deckelbaum RJ. Lipoprotein lipase-mediated selective uptake from low density lipoprotein requires cell surface proteoglycans and is independent of scavenger receptor class B type 1. J Biol Chem 2000; 275:30355-62. [PMID: 10896681 DOI: 10.1074/jbc.m910327199] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Lipoprotein lipase (LpL) hydrolyzes chylomicron and very low density lipoprotein triglycerides to provide fatty acids to tissues. Aside from its lipolytic activity, LpL promotes lipoprotein uptake by increasing the association of these particles with cell surfaces allowing for the internalization by receptors and proteoglycans. Recent studies also indicate that LpL stimulates selective uptake of lipids from high density lipoprotein (HDL) and very low density lipoprotein. To study whether LpL can mediate selective uptake of lipids from low density lipoprotein (LDL), LpL was incubated with LDL receptor negative fibroblasts, and the uptake of LDL protein, labeled with (125)I, and cholesteryl esters traced with [(3)H]cholesteryl oleoyl ether, was compared. LpL mediated greater uptake of [(3)H]cholesteryl oleoyl ether than (125)I-LDL protein, a result that indicated selective lipid uptake. Lipid enrichment of cells was confirmed by measuring cellular cholesterol mass. LpL-mediated LDL selective uptake was not affected by the LpL inhibitor tetrahydrolipstatin but was nearly abolished by heparin, monoclonal anti-LpL antibodies, or chlorate treatment of cells and was not found using proteoglycan-deficient Chinese hamster ovary cells. Selective uptake from HDL, but not LDL, was 2-3-fold greater in scavenger receptor class B type I overexpressing cells (SR-BI cells) than compared control cells. LpL, however, induced similar increases in selective uptake from LDL and HDL in either control or SR-BI cells, indicative of the SR-BI-independent pathway. This was further supported by ability of LpL to promote selective uptake from LDL in human embryonal kidney 293 cells, cells that do not express SR-BI. In Chinese hamster ovary cell lines that overexpress LpL, we also found that selective uptake from LDL was induced by both endogenous and exogenous LpL. Transgenic mice that overexpress human LpL via a muscle creatine kinase promoter had more LDL selective uptake in muscle than did wild type mice. In summary LpL stimulates selective uptake of cholesteryl esters from LDL via pathways that are distinct from SR-BI. Moreover this process also occurs in vivo in tissues where abundant LpL is present.
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Affiliation(s)
- T Seo
- Departments of Pediatrics and Medicine, Institute of Human Nutrition, Columbia University, New York, New York 10032, USA
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27
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Pussinen PJ, Karten B, Wintersperger A, Reicher H, McLean M, Malle E, Sattler W. The human breast carcinoma cell line HBL-100 acquires exogenous cholesterol from high-density lipoprotein via CLA-1 (CD-36 and LIMPII analogous 1)-mediated selective cholesteryl ester uptake. Biochem J 2000; 349:559-66. [PMID: 10880355 PMCID: PMC1221179 DOI: 10.1042/0264-6021:3490559] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Aberrant cell proliferation is one of the hallmarks of carcinogenesis, and cholesterol is thought to play an important role during cell proliferation and cancer progression. In the present study we examined the pathways that could contribute to enhanced proliferation rates of HBL-100 cells in the presence of apolipoprotein E-depleted high-density lipoprotein subclass 3 (HDL(3)). When HBL-100 cells were cultivated in the presence of HDL(3) (up to 200 microg/ml HDL(3) protein), the growth rates and cellular cholesterol content were directly related to the concentrations of HDL(3) in the culture medium. In principle, two pathways can contribute to cholesterol/cholesteryl ester (CE) uptake from HDL(3), (i) holoparticle- and (ii) scavenger-receptor BI (SR-BI)-mediated selective uptake of HDL(3)-associated CEs. Northern- and Western-blot analyses revealed the expression of CLA-1 (CD-36 and LIMPII analogous 1), the human homologue of the rodent HDL receptor SR-BI. In line with CLA-1 expression, selective uptake of HDL(3)-CEs exceeded HDL(3)-holoparticle uptake between 12- and 58-fold. Competition experiments demonstrated that CLA-1 ligands (oxidized HDL, oxidized and acetylated low-density lipoprotein and phosphatidylserine) inhibited selective HDL(3)-CE uptake. In line with the ligand-binding specificity of CLA-1, phosphatidylcholine did not compete for selective HDL(3)-CE uptake. Selective uptake was regulated by the availability of exogenous cholesterol and PMA, but not by adrenocorticotropic hormone. HPLC analysis revealed that a substantial part of HDL(3)-CE, which was taken up selectively, was subjected to intracellular hydrolysis. A potential candidate facilitating extralysosomal hydrolysis of HDL(3)-CE is hormone-sensitive lipase, an enzyme which was identified in HBL-100 cells by Western blots. Our findings demonstrate that HBL-100 cells are able to acquire HDL-CEs via selective uptake. Subsequent partial hydrolysis by hormone-sensitive lipase could provide 'free' cholesterol that is available for the synthesis of cellular membranes during proliferation of cancer cells.
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Affiliation(s)
- P J Pussinen
- Institute of Medical Biochemistry and Molecular Biology, University of Graz, Harrachgasse 21, 8010 Graz, Austria
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28
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Swarnakar S, Temel RE, Connelly MA, Azhar S, Williams DL. Scavenger receptor class B, type I, mediates selective uptake of low density lipoprotein cholesteryl ester. J Biol Chem 1999; 274:29733-9. [PMID: 10514447 DOI: 10.1074/jbc.274.42.29733] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Scavenger receptor, class B, type I (SR-BI) is a cell-surface glycoprotein that mediates selective uptake of high density lipoprotein cholesteryl ester (CE) without the concomitant uptake and degradation of the particle. We have investigated the endocytic and selective uptake of low density lipoprotein (LDL)-CE by SR-BI using COS-7 cells transiently transfected with mouse SR-BI. Analysis of lipoprotein uptake data showed a concentration-dependent LDL-CE-selective uptake when doubly labeled LDL particles were incubated with SR-BI-expressing COS-7 cells. In contrast to vector-transfected cells, SR-BI-expressing COS-7 cells showed marked increases in LDL cell association and CE uptake by the selective uptake pathway, but only a modest increase in CE uptake by the endocytic pathway. SR-BI-mediated LDL-CE-selective uptake exceeded LDL endocytic uptake by 50-100-fold. SR-BI-mediated LDL-CE-selective uptake was not inhibited by the proteoglycan synthesis inhibitor, p-nitrophenyl-beta-D-xylopyranoside or by the sulfation inhibitor sodium chlorate, indicating that SR-BI-mediated LDL-CE uptake occurs independently of LDL interaction with cell-surface proteoglycan. Analyses with subclones of Y1 adrenocortical cells showed that LDL-CE-selective uptake was proportional to the level of SR-BI expression. Furthermore, antibody directed to the extracellular domain of SR-BI blocked LDL-CE-selective uptake in adrenocortical cells. Thus, in cells that normally express SR-BI and in transfected COS-7 cells SR-BI mediates the efficient uptake of LDL-CE via the selective uptake mechanism. These results suggest that SR-BI may influence the metabolism of apoB-containing lipoproteins in vivo by mediating LDL-CE uptake into SR-BI-expressing cells.
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Affiliation(s)
- S Swarnakar
- Department of Pharmacological Sciences, University Medical Center, State University of New York, Stony Brook, New York 11794, USA
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29
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Arai T, Rinninger F, Varban L, Fairchild-Huntress V, Liang CP, Chen W, Seo T, Deckelbaum R, Huszar D, Tall AR. Decreased selective uptake of high density lipoprotein cholesteryl esters in apolipoprotein E knock-out mice. Proc Natl Acad Sci U S A 1999; 96:12050-5. [PMID: 10518574 PMCID: PMC18410 DOI: 10.1073/pnas.96.21.12050] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Scavenger receptor BI (SR-BI) mediates the selective uptake of high density lipoprotein (HDL) cholesteryl esters (CE) by cells, i.e., the uptake of CE without degradation of HDL protein. Mice with attenuated expression of SR-BI, because of targeted gene mutation (SR-BIatt mice), have increased plasma HDL levels as a result of decreased selective uptake in the liver. To further evaluate the role of SR-BI in lipoprotein metabolism, compound apolipoprotein E knock-out (apoE0)/SR-BIatt mice were bred. Hepatic SR-BI protein was increased (2.3-fold) in apoE0 mice compared with wild type (wt) and was reduced significantly in apoE0/SR-BIatt mice. However, the plasma lipoprotein profile of apoE0 and apoE0/SR-BIatt mice was identical. This was explained by HDL turnover studies that revealed that the selective clearance of HDL CE by the liver and adrenal was already profoundly impaired in apoE0 mice compared with wt (28% of wt in liver). A similar decrease in selective uptake was seen when apoE0 HDL was incubated with isolated apoE0 hepatocytes. The results suggest that apoE plays a major role in the selective clearance of HDL CE by the liver and adrenal gland, possibly by facilitating the presentation of HDL to SR-BI at the cell surface.
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Affiliation(s)
- T Arai
- Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY 10032, USA.
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30
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Rhainds D, Brissette L. Low density lipoprotein uptake: holoparticle and cholesteryl ester selective uptake. Int J Biochem Cell Biol 1999; 31:915-31. [PMID: 10533283 DOI: 10.1016/s1357-2725(99)00046-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Low density lipoproteins (LDL) contain apolipoprotein B-100 and are cholesteryl ester-rich, triglyceride-poor macromolecules, arising from the lipolysis of very low density lipoproteins. This review will describe the receptors responsible for uptake of whole LDL particles (holoparticle uptake), and the selective uptake of LDL cholesteryl ester. The LDL-receptor mediates the internalization of whole LDL through an endosomal-lysosomal pathway, leading to complete degradation of LDL. Increasing LDL-receptor expression by pharmacological intervention efficiently reduces blood LDL concentrations. The lipolysis stimulated receptor and LDL-receptor related protein may also lead to complete degradation of LDL in presence of free fatty acids and apolipoprotein E- or lipase-LDL complexes, respectively. Selective uptake of LDL cholesteryl ester has been demonstrated in the liver, especially in rodents and humans. This activity brings five times more LDL cholesteryl ester than the LDL-receptor to human hepatoma cells, suggesting that it is a physiologically significant pathway. The lipoprotein binding site of HepG2 cells mediates this process and recognizes all lipoprotein classes. Scavenger receptor class B type I and CD36, which mediate the selective uptake of high density lipoprotein cholesteryl ester, are potentially involved in LDL cholesteryl ester selective uptake, since they both bind LDL with high affinity. It is not known whether they are identical to the uncloned lipoprotein binding site and if the selective uptake of LDL cholesteryl ester produces a less atherogenic particle. If this is verified, pharmacological up-regulation of LDL cholesteryl ester selective uptake may become another therapeutic approach for reducing blood LDL-cholesterol levels and the risk of atherosclerosis.
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Affiliation(s)
- D Rhainds
- Département des Sciences Biologiques, Université du Québec à Montréal, Canada
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31
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Holwell TA, Schweitzer SC, Reyland ME, Evansk RM. Vimentin-dependent utilization of LDL-cholesterol in human adrenal tumor cells is not associated with the level of expression of apoE, sterol carrier protein-2, or caveolin. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33386-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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32
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Finch CE, Sapolsky RM. The evolution of Alzheimer disease, the reproductive schedule, and apoE isoforms. Neurobiol Aging 1999; 20:407-28. [PMID: 10604433 DOI: 10.1016/s0197-4580(99)00053-6] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Alzheimer disease (AD)-like neuropathology increases progressively during aging in most primates, and, in some species, is concurrent with reproductive decline in females and cognitive impairments. We consider how the schedule of AD may have evolved in early humans in relation to the apolipoprotein E (apoE) allele system, which is not found in other primates, and to the increasing duration of postnatal care. The delay of independence and the increasing length of maturation required that the schedule of AD-like neurodegeneration be slowed, otherwise parental caregivers would already have become impaired. We hypothesize that the uniquely human apoE epsilon3 allele evolved from the epsilon4 of primate ancestors during human evolution in relation to the rapid increases of brain size and the emergence of grandmothering. In discussing theses possibilities, we review the diverse bioactivities of apoE, which include involvement in hormone systems. The evolution of menopause is also considered in relation to the protective effect of estrogen on AD.
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Affiliation(s)
- C E Finch
- Neurogerontology Division, Andrus Gerontology Center and University of Southern California, Los Angeles 90089-0191, USA.
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33
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Affiliation(s)
- L Liscum
- Department of Physiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
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34
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Seo T, Deckelbaum RJ. Lipid metabolism. Curr Opin Lipidol 1998; 9:605-7. [PMID: 10075480 DOI: 10.1097/00041433-199812000-00014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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35
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Amar MJ, Dugi KA, Haudenschild CC, Shamburek RD, Foger B, Chase M, Bensadoun A, Hoyt RF, Brewer HB, Santamarina-Fojo S. Hepatic lipase facilitates the selective uptake of cholesteryl esters from remnant lipoproteins in apoE-deficient mice. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)33323-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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