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Mammalian ABCG-transporters, sterols and lipids: To bind perchance to transport? Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1866:158860. [PMID: 33309976 DOI: 10.1016/j.bbalip.2020.158860] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 11/15/2020] [Accepted: 12/08/2020] [Indexed: 02/08/2023]
Abstract
Members of the ATP binding cassette (ABC) transporter family perform a critical function in maintaining lipid homeostasis in cells as well as the transport of drugs. In this review, we provide an update on the ABCG-transporter subfamily member proteins, which include the homodimers ABCG1, ABCG2 and ABCG4 as well as the heterodimeric complex formed between ABCG5 and ABCG8. This review focusses on progress made in this field of research with respect to their function in health and disease and the recognised transporter substrates. We also provide an update on post-translational regulation, including by transporter substrates, and well as the involvement of microRNA as regulators of transporter expression and activity. In addition, we describe progress made in identifying structural elements that have been recognised as important for transport activity. We furthermore discuss the role of lipids such as cholesterol on the transport function of ABCG2, traditionally thought of as a drug transporter, and provide a model of potential cholesterol binding sites for ABCG2.
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2
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Castaño D, Rattanasopa C, Monteiro-Cardoso VF, Corlianò M, Liu Y, Zhong S, Rusu M, Liehn EA, Singaraja RR. Lipid efflux mechanisms, relation to disease and potential therapeutic aspects. Adv Drug Deliv Rev 2020; 159:54-93. [PMID: 32423566 DOI: 10.1016/j.addr.2020.04.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 02/06/2023]
Abstract
Lipids are hydrophobic and amphiphilic molecules involved in diverse functions such as membrane structure, energy metabolism, immunity, and signaling. However, altered intra-cellular lipid levels or composition can lead to metabolic and inflammatory dysfunction, as well as lipotoxicity. Thus, intra-cellular lipid homeostasis is tightly regulated by multiple mechanisms. Since most peripheral cells do not catabolize cholesterol, efflux (extra-cellular transport) of cholesterol is vital for lipid homeostasis. Defective efflux contributes to atherosclerotic plaque development, impaired β-cell insulin secretion, and neuropathology. Of these, defective lipid efflux in macrophages in the arterial walls leading to foam cell and atherosclerotic plaque formation has been the most well studied, likely because a leading global cause of death is cardiovascular disease. Circulating high density lipoprotein particles play critical roles as acceptors of effluxed cellular lipids, suggesting their importance in disease etiology. We review here mechanisms and pathways that modulate lipid efflux, the role of lipid efflux in disease etiology, and therapeutic options aimed at modulating this critical process.
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Wang Y, Li Z, Bie X, Liu F, Yao Q, Liu Y, Zhang Z, Yang S, Luan Y, Jia J, Xu Y, Yang D, He Y, Zheng H. A Promoter Polymorphism (Rs57137919) of ABCG1 Gene Influence on Blood Lipoprotein in Chinese Han Population. Ann Vasc Surg 2020; 68:460-467. [PMID: 32339682 DOI: 10.1016/j.avsg.2020.04.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/30/2020] [Accepted: 04/07/2020] [Indexed: 10/24/2022]
Abstract
BACKGROUND Adenosine triphosphate-binding cassette subfamily G member 1 (ABCG1) has the function of transporting free intracellular cholesterol to extracellular high-density lipoprotein (HDL) particles, which play a crucial role in atherosclerosis. The goal of this study is to examine the relationship between the polymorphisms of the ABCG1 gene promoter region and ischemic stroke. METHODS In the present study, a case-control association study was designed to identify 3 single-nucleotide polymorphisms (SNPs; rs5713919, rs1378577, and rs1893590), which were located in the promoter region of ABCG1 gene by kompetitive allele-specific polymerase chain reaction genotyping approach. The in vitro luciferase assay was done to estimate the effect of rs5713919 on gene expression. Finally, the relationships of 3 SNPs of ABCG1 gene with plasma lipids and lipoproteins were investigated in this Chinese cohort. RESULTS The correlation analysis between lipids and genotypes showed that the rs57137919 locus genotype was significantly associated with HDL cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels (P = 0.021 and P = 0.017, respectively), and the GA and AA genotypes had higher HDL-C levels than the GG genotype. CONCLUSIONS Our study provides evidence that ABCG1 promoter region polymorphism rs57137919 has an influence on plasma HDL-C and LDL-C levels in Chinese Han population.
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Affiliation(s)
- Yuanli Wang
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Zheng Li
- Clinical Laboratory, Henan Provincial Chest Hospital, Zhengzhou, China
| | - Xiaoshuai Bie
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Fuyong Liu
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Qihui Yao
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Yang Liu
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Zhaojing Zhang
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Shangdong Yang
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Yingying Luan
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Jing Jia
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Yan Xu
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Dongzhi Yang
- School of Life Sciences, Zhengzhou University, Zhengzhou, China
| | - Ying He
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China.
| | - Hong Zheng
- Department of Medical Genetics & Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China.
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Yu XH, Zhang DW, Zheng XL, Tang CK. Cholesterol transport system: An integrated cholesterol transport model involved in atherosclerosis. Prog Lipid Res 2018; 73:65-91. [PMID: 30528667 DOI: 10.1016/j.plipres.2018.12.002] [Citation(s) in RCA: 129] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 10/30/2018] [Accepted: 12/01/2018] [Indexed: 02/07/2023]
Abstract
Atherosclerosis, the pathological basis of most cardiovascular disease (CVD), is closely associated with cholesterol accumulation in the arterial intima. Excessive cholesterol is removed by the reverse cholesterol transport (RCT) pathway, representing a major antiatherogenic mechanism. In addition to the RCT, other pathways are required for maintaining the whole-body cholesterol homeostasis. Thus, we propose a working model of integrated cholesterol transport, termed the cholesterol transport system (CTS), to describe body cholesterol metabolism. The novel model not only involves the classical view of RCT but also contains other steps, such as cholesterol absorption in the small intestine, low-density lipoprotein uptake by the liver, and transintestinal cholesterol excretion. Extensive studies have shown that dysfunctional CTS is one of the major causes for hypercholesterolemia and atherosclerosis. Currently, several drugs are available to improve the CTS efficiently. There are also several therapeutic approaches that have entered into clinical trials and shown considerable promise for decreasing the risk of CVD. In recent years, a variety of novel findings reveal the molecular mechanisms for the CTS and its role in the development of atherosclerosis, thereby providing novel insights into the understanding of whole-body cholesterol transport and metabolism. In this review, we summarize the latest advances in this area with an emphasis on the therapeutic potential of targeting the CTS in CVD patients.
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Affiliation(s)
- Xiao-Hua Yu
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Medical Research Experiment Center, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, Hunan 421001, China
| | - Da-Wei Zhang
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, University of Alberta, Alberta, Canada
| | - Xi-Long Zheng
- Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Health Sciences Center, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Chao-Ke Tang
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Medical Research Experiment Center, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, Hunan 421001, China.
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Cholesterol Efflux: Does It Contribute to Aortic Stiffening? J Cardiovasc Dev Dis 2018; 5:jcdd5020023. [PMID: 29724005 PMCID: PMC6023341 DOI: 10.3390/jcdd5020023] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 04/20/2018] [Accepted: 04/25/2018] [Indexed: 12/12/2022] Open
Abstract
Aortic stiffness during cardiac contraction is defined by the rigidity of the aorta and the elastic resistance to deformation. Recent studies suggest that aortic stiffness may be associated with changes in cholesterol efflux in endothelial cells. This alteration in cholesterol efflux may directly affect endothelial function, extracellular matrix composition, and vascular smooth muscle cell function and behavior. These pathological changes favor an aortic stiffness phenotype. Among all of the proteins participating in the cholesterol efflux process, ATP binding cassette transporter A1 (ABCA1) appears to be the main contributor to arterial stiffness changes in terms of structural and cellular function. ABCA1 is also associated with vascular inflammation mediators implicated in aortic stiffness. The goal of this mini review is to provide a conceptual hypothesis of the recent advancements in the understanding of ABCA1 in cholesterol efflux and its role and association in the development of aortic stiffness, with a particular emphasis on the potential mechanisms and pathways involved.
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Endothelial ATP-binding cassette G1 in mouse endothelium protects against hemodynamic-induced atherosclerosis. Biochem Biophys Res Commun 2016; 477:247-54. [DOI: 10.1016/j.bbrc.2016.06.050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 06/09/2016] [Indexed: 12/26/2022]
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7
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Westerterp M, Tsuchiya K, Tattersall IW, Fotakis P, Bochem AE, Molusky MM, Ntonga V, Abramowicz S, Parks JS, Welch CL, Kitajewski J, Accili D, Tall AR. Deficiency of ATP-Binding Cassette Transporters A1 and G1 in Endothelial Cells Accelerates Atherosclerosis in Mice. Arterioscler Thromb Vasc Biol 2016; 36:1328-37. [PMID: 27199450 DOI: 10.1161/atvbaha.115.306670] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 05/10/2016] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Plasma high-density lipoproteins have several putative antiatherogenic effects, including preservation of endothelial functions. This is thought to be mediated, in part, by the ability of high-density lipoproteins to promote cholesterol efflux from endothelial cells (ECs). The ATP-binding cassette transporters A1 and G1 (ABCA1 and ABCG1) interact with high-density lipoproteins to promote cholesterol efflux from ECs. To determine the impact of endothelial cholesterol efflux pathways on atherogenesis, we prepared mice with endothelium-specific knockout of Abca1 and Abcg1. APPROACH AND RESULTS Generation of mice with EC-ABCA1 and ABCG1 deficiency required crossbreeding Abca1(fl/fl)Abcg1(fl/fl)Ldlr(-/-) mice with the Tie2Cre strain, followed by irradiation and transplantation of Abca1(fl/fl)Abcg1(fl/fl) bone marrow to abrogate the effects of macrophage ABCA1 and ABCG1 deficiency induced by Tie2Cre. After 20 to 22 weeks of Western-type diet, both single EC-Abca1 and Abcg1 deficiency increased atherosclerosis in the aortic root and whole aorta. Combined EC-Abca1/g1 deficiency caused a significant further increase in lesion area at both sites. EC-Abca1/g1 deficiency dramatically enhanced macrophage lipid accumulation in the branches of the aorta that are exposed to disturbed blood flow, decreased aortic endothelial NO synthase activity, and increased monocyte infiltration into the atherosclerotic plaque. Abca1/g1 deficiency enhanced lipopolysaccharide-induced inflammatory gene expression in mouse aortic ECs, which was recapitulated by ABCG1 deficiency in human aortic ECs. CONCLUSIONS These studies provide direct evidence that endothelial cholesterol efflux pathways mediated by ABCA1 and ABCG1 are nonredundant and atheroprotective, reflecting preservation of endothelial NO synthase activity and suppression of endothelial inflammation, especially in regions of disturbed arterial blood flow.
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MESH Headings
- ATP Binding Cassette Transporter 1/deficiency
- ATP Binding Cassette Transporter 1/genetics
- ATP Binding Cassette Transporter, Subfamily G, Member 1/deficiency
- ATP Binding Cassette Transporter, Subfamily G, Member 1/genetics
- Animals
- Aorta, Thoracic/metabolism
- Aorta, Thoracic/pathology
- Aorta, Thoracic/physiopathology
- Aortic Diseases/genetics
- Aortic Diseases/metabolism
- Aortic Diseases/pathology
- Atherosclerosis/genetics
- Atherosclerosis/metabolism
- Atherosclerosis/pathology
- Atherosclerosis/physiopathology
- Bone Marrow Transplantation
- Cholesterol/metabolism
- Diet, High-Fat
- Disease Models, Animal
- Disease Progression
- Endothelial Cells/metabolism
- Endothelial Cells/pathology
- Genetic Predisposition to Disease
- Inflammation Mediators/metabolism
- Macrophages/metabolism
- Male
- Mice, Knockout
- Monocytes/metabolism
- Neovascularization, Physiologic
- Nitric Oxide Synthase Type III/metabolism
- Phenotype
- Plaque, Atherosclerotic
- Receptors, LDL/deficiency
- Receptors, LDL/genetics
- Regional Blood Flow
- Retinal Neovascularization/genetics
- Retinal Neovascularization/metabolism
- Time Factors
- Tissue Culture Techniques
- Whole-Body Irradiation
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Affiliation(s)
- Marit Westerterp
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.).
| | - Kyoichiro Tsuchiya
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Ian W Tattersall
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Panagiotis Fotakis
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Andrea E Bochem
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Matthew M Molusky
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Vusisizwe Ntonga
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Sandra Abramowicz
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - John S Parks
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Carrie L Welch
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Jan Kitajewski
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Domenico Accili
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
| | - Alan R Tall
- From the Division of Molecular Medicine, Department of Medicine (M.W., P.F., A.E.B., M.M.M., V.N., S.A., C.L.W., A.R.T.), Naomi Berrie Diabetes Center (K.T., D.A.), and Department of Pathology, Obstetrics, and Gynaecology (I.W.T., J.K.), Columbia University, New York, NY; Section on Molecular Genetics, Department of Pediatrics, University Medical Center Groningen, Groningen, The Netherlands (M.W.); Department of Diabetes, Endocrinology, and Metabolism, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan (K.T.); and Section on Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC (J.S.P.)
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8
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Al-Sharea A, Lee MKS, Moore XL, Fang L, Sviridov D, Chin-Dusting J, Andrews KL, Murphy AJ. Native LDL promotes differentiation of human monocytes to macrophages with an inflammatory phenotype. Thromb Haemost 2015; 115:762-72. [PMID: 26676845 DOI: 10.1160/th15-07-0571] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 11/13/2015] [Indexed: 11/05/2022]
Abstract
Recruitment of monocytes in atherosclerosis is dependent upon increased levels of plasma lipoproteins which accumulate in the blood vessel wall. The extracellular milieu can influence the phenotype of monocyte subsets (classical: CD14++CD16-, intermediate: CD14+CD16+ and non-classical: CD14dimCD16++) and macrophages (M1 or M2) and consequently the initiation, progression and/or regression of atherosclerosis. However, it is not known what effect lipoproteins, in particular native low-density lipoproteins (nLDL), have on the polarisation of monocyte-derived macrophages. Monocytes were differentiated into macrophages in the presence of nLDL. nLDL increased gene expression of the inflammatory cytokines TNFα and IL-6 in macrophages polarised towards the M1 phenotype while decreasing the M2 surface markers, CD206 and CD200R and the anti-inflammatory cytokines TGFβ and IL-10. Compared to the classical and intermediate subsets, the non-classical subset-derived macrophages had a reduced ability to respond to M1 stimuli (LPS and IFNγ). nLDL enhanced the TNFα and IL-6 gene expression in macrophages from all monocyte subsets, indicating an inflammatory effect of nLDL. Further, the classical and intermediate subsets both responded to M2 stimuli (IL-4) with upregulation of TGFβ and SR-B1 mRNA; an effect, which was reduced by nLDL. In contrast, the non-classical subset failed to respond to IL-4 or nLDL, suggesting it may be unable to polarise into M2 macrophages. Our data suggests that monocyte interaction with nLDL significantly affects macrophage polarisation and that this interaction appears to be subset dependent.
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Affiliation(s)
| | | | | | | | | | | | | | - Andrew J Murphy
- Dr. Andrew J. Murphy, Baker IDI Heart and Diabetes Institute, PO Box 6492, St Kilda Road central, Melbourne, VIC 8008, Australia, Tel.: +61 3 8532 1292, Fax: +61 3 8532 1100, E-mail:
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9
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Affiliation(s)
- Federico Oldoni
- From the Departments of Molecular Genetics (F.O., J.A.K.) and Genetics (R.J.S.), University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Richard J. Sinke
- From the Departments of Molecular Genetics (F.O., J.A.K.) and Genetics (R.J.S.), University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Jan Albert Kuivenhoven
- From the Departments of Molecular Genetics (F.O., J.A.K.) and Genetics (R.J.S.), University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
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10
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Westerterp M, Bochem AE, Yvan-Charvet L, Murphy AJ, Wang N, Tall AR. ATP-Binding Cassette Transporters, Atherosclerosis, and Inflammation. Circ Res 2014; 114:157-70. [DOI: 10.1161/circresaha.114.300738] [Citation(s) in RCA: 184] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Marit Westerterp
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Andrea E. Bochem
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Laurent Yvan-Charvet
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Andrew J. Murphy
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Nan Wang
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Alan R. Tall
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
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11
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Xue J, Wei J, Dong X, Zhu C, Li Y, Song A, Liu Z. ABCG1 deficiency promotes endothelial apoptosis by endoplasmic reticulum stress-dependent pathway. J Physiol Sci 2013; 63:435-44. [PMID: 23897420 PMCID: PMC10717156 DOI: 10.1007/s12576-013-0281-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 07/12/2013] [Indexed: 10/26/2022]
Abstract
The present study was focused on whether ABCG1 deficiency was involved in endothelial apoptosis and its possible mechanism. Human umbilical artery endothelial cells were transfected with ABCG1 siRNA and/or ABCG1 expression plasmid. We observed that silencing of endothelial ABCG1 reduced cholesterol efflux to HDL and increased intracellular lipid content. Moreover, reduction of ABCG1 promoted endothelial apoptosis and expression of endoplasmic reticulum (ER) stress-related molecules GRP78 and CHOP. In contrast, transfection of ABCG1 overexpression plasmid reversed endothelial apoptosis and intracellular lipid accumulation as well as decreased expression of GRP78 and CHOP in ABCG1-deficient endothelial cells. Furthermore, endothelial apoptosis and ER stress-related molecules were induced by repletion of endothelial cells with cholesterol-loaded cyclodextrin, otherwise endothelial apoptotic response and expression of GRP78 and CHOP were suppressed by depletion of cellular cholesterol in ABCG1-deficient endothelial cells. The present results suggest that reduction of ABCG1 induces endothelial apoptosis, which seems associated with intracellular free cholesterol accumulation and subsequent ER stress.
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Affiliation(s)
- Jiahong Xue
- Department of Cardiovascular Medicine, Second Affiliated Hospital of Medical School, Xi'an Jiaotong University, 157 West Five Road, Xi'an, 710004, Shaanxi, China,
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12
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Abstract
At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.
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Affiliation(s)
- Paul N Hopkins
- Cardiovascular Genetics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, USA.
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13
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Tawakol A, Fayad ZA, Mogg R, Alon A, Klimas MT, Dansky H, Subramanian SS, Abdelbaky A, Rudd JH, Farkouh ME, Nunes IO, Beals CR, Shankar SS. Intensification of Statin Therapy Results in a Rapid Reduction in Atherosclerotic Inflammation. J Am Coll Cardiol 2013; 62:909-17. [DOI: 10.1016/j.jacc.2013.04.066] [Citation(s) in RCA: 279] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 03/27/2013] [Accepted: 04/09/2013] [Indexed: 10/26/2022]
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14
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Miller JD, Chu Y, Castaneda LE, Serrano KM, Brooks RM, Heistad DD. Vascular function during prolonged progression and regression of atherosclerosis in mice. Arterioscler Thromb Vasc Biol 2013; 33:459-65. [PMID: 23307875 PMCID: PMC3960951 DOI: 10.1161/atvbaha.112.252700] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Endothelial dysfunction is associated with atherosclerosis in mice, but it is difficult to reduce cholesterol levels enough to study regression of atherosclerosis in genetically modified mice. The goal of this study was to examine vascular structure and function before and after reducing elevated plasma lipid levels with a genetic switch in Reversa mice, and identify novel mechanisms contributing to structural and functional improvements in the vasculature after reduction of blood lipids. METHODS AND RESULTS After 6 months of hypercholesterolemia, endothelial function (maximum relaxation to acetylcholine) in aorta was impaired and responses to nitric oxide were unaffected. Further impairment in endothelial function was observed after 12 months of hypercholesterolemia and was associated with reductions in sensitivity to nitric oxide. Expression of dihydrofolate reductase was reduced at 6 and 12 months, and addition of the tetrahydrobiopterin precursor sepiapterin significantly improved endothelial function. Reducing cholesterol levels at 6 months normalized dihydrofolate reductase expression and prevented further impairment in endothelial function. Similar functional changes were observed after 12 months of hypercholesterolemia followed by 2 months of lipid lowering. CONCLUSIONS Our data suggest that endothelial dysfunction after prolonged hypercholesterolemia is the result of both impairment of sensitivity to nitric oxide and reduced nitric oxide synthase cofactor bioavailability. Both of these changes can be prevented by normalizing blood lipids during moderately severe or advanced atherosclerosis.
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Affiliation(s)
- Jordan D. Miller
- Departments of Internal Medicine, University of Iowa Carver College of Medicine
| | | | - Lauren E. Castaneda
- Departments of Internal Medicine, University of Iowa Carver College of Medicine
| | - Kristine M. Serrano
- Departments of Internal Medicine, University of Iowa Carver College of Medicine
| | - Robert M. Brooks
- Departments of Internal Medicine, University of Iowa Carver College of Medicine
| | - Donald D. Heistad
- Departments of Internal Medicine, University of Iowa Carver College of Medicine
- Departments of Pharmacology, University of Iowa Carver College of Medicine
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15
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Characterization of palmitoylation of ATP binding cassette transporter G1: effect on protein trafficking and function. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1067-78. [PMID: 23388354 DOI: 10.1016/j.bbalip.2013.01.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 01/14/2013] [Accepted: 01/25/2013] [Indexed: 12/12/2022]
Abstract
ATP-binding cassette transporter G1 (ABCG1) mediates cholesterol efflux onto lipidated apolipoprotein A-I and HDL and plays a role in various important physiological functions. However, the mechanism by which ABCG1 mediates cholesterol translocation is unclear. Protein palmitoylation regulates many functions of proteins such as ABCA1. Here we investigated if ABCG1 is palmitoylated and the subsequent effects on ABCG1-mediated cholesterol efflux. We demonstrated that ABCG1 is palmitoylated in both human embryonic kidney 293 cells and in mouse macrophage, J774. Five cysteine residues located at positions 26, 150, 311, 390 and 402 in the NH2-terminal cytoplasmic region of ABCG1 were palmitoylated. Removal of palmitoylation at Cys311 by mutating the residue to Ala (C311A) or Ser significantly decreased ABCG1-mediated cholesterol efflux. On the other hand, removal of palmitoylation at sites 26, 150, 390 and 402 had no significant effect. We further demonstrated that mutations of Cys311 affected ABCG1 trafficking from the endoplasmic reticulum. Therefore, our data suggest that palmitoylation plays a critical role in ABCG1-mediated cholesterol efflux through the regulation of trafficking.
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16
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Abstract
PURPOSE OF REVIEW HDL and their main apolipoprotein (apo) constituent apoA-I are antiatherogenic. This has been predominantly attributed to the ability of apoA-I/HDL to efflux cholesterol from macrophages within atherosclerotic plaques. It is now emerging that a number of the protective properties of HDL may be due to their effects on the endothelium. RECENT FINDINGS In addition to their well characterized anti-inflammatory and antioxidant effects, apoA-I and HDL regulate several other key biological pathways known to preserve endothelial function and promote vascular repair. The ATP-binding cassette (ABC) transporters ABCA1 and ABCG1, and the scavenger receptor B type 1 mediate multiple intracellular signaling pathways as well as the efflux of cholesterol and/or oxysterols in response to apoA-I/HDL. Although cholesterol efflux triggers a host of signaling events in endothelial cells, there is evidence that some of the beneficial actions of HDL may occur independently of efflux. SUMMARY Current data suggest that in endothelial cells ABCA1 and ABCG1 mediate the activation of intracellular signaling pathways primarily through the efflux of cholesterol and oxysterols to apoA-I/HDL. Interaction between HDL and scavenger receptor B type 1 initiates the greatest number of known signaling pathways and there is evidence that some of these are activated independent of efflux.
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Affiliation(s)
- Hamish C Prosser
- Translational Research Group, Heart Research Institute Department of Cardiology, Royal Prince Alfred Hospital Department of Medicine, University of Sydney, Sydney, New South Wales, Australia Immunobiology Unit, Heart Research Institute
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17
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Meurs I, Lammers B, Zhao Y, Out R, Hildebrand RB, Hoekstra M, Van Berkel TJ, Van Eck M. The effect of ABCG1 deficiency on atherosclerotic lesion development in LDL receptor knockout mice depends on the stage of atherogenesis. Atherosclerosis 2012; 221:41-7. [DOI: 10.1016/j.atherosclerosis.2011.11.024] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 10/25/2011] [Accepted: 11/17/2011] [Indexed: 01/01/2023]
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18
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Shearn AIU, Deswaerte V, Gautier EL, Saint-Charles F, Pirault J, Bouchareychas L, Rucker EB, Beliard S, Chapman J, Jessup W, Huby T, Lesnik P. Bcl-x inactivation in macrophages accelerates progression of advanced atherosclerotic lesions in Apoe(-/-) mice. Arterioscler Thromb Vasc Biol 2012; 32:1142-9. [PMID: 22383704 DOI: 10.1161/atvbaha.111.239111] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Bcl-x is the most abundantly expressed member of the Bcl-2 gene family in macrophages, but its role in macrophage apoptosis during atherogenesis is unknown. METHODS AND RESULTS We previously reported dual pro- and antiatherogenic effects of macrophage survival in early versus advanced atherosclerotic lesions, respectively, potentially reflecting growing impairment of efferocytosis during plaque progression. Here, we specifically inactivated Bcl-x in macrophages and evaluated its impact on atherosclerotic lesion formation in Apoe(-/-) mice at various stages of the disease. Bcl-x deficiency in macrophages increased their susceptibility to apoptosis, resulting in the depletion of tissue macrophages in vivo, including its major pool, Küppfer cells in the liver. We also observed increased cholesterol levels that were, however, not associated with any acceleration of early atherosclerotic plaque progression. This observation suggests that the atheroprotective effect of macrophage apoptosis at that stage of disease was counterbalanced by enhanced cholesterol levels. Bcl-x KO(mac)/Apoe(-/-) mice exhibited significantly larger advanced lesions than control mice. These lesions showed vulnerable traits. Such enhanced lesion size may occur as a result not only of apoptotic cell accumulation but also of elevated cholesterol levels. CONCLUSIONS Modulation of macrophage resistance to apoptosis through targeted deletion of Bcl-x has a major impact on the entire macrophage cell population in the body, including Küpffer cells. Macrophage survival may, therefore, not only influence atherosclerotic plaque development and vulnerability but also cholesterol metabolism.
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Schou J, Frikke-Schmidt R, Kardassis D, Thymiakou E, Nordestgaard BG, Jensen G, Grande P, Tybjærg-Hansen A. Genetic variation in ABCG1 and risk of myocardial infarction and ischemic heart disease. Arterioscler Thromb Vasc Biol 2011; 32:506-15. [PMID: 22155456 DOI: 10.1161/atvbaha.111.234872] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE ATP binding cassette transporter G1 (ABCG1) facilitates cholesterol efflux from macrophages to mature high-density lipoprotein particles. Whether genetic variation in ABCG1 affects risk of atherosclerosis in humans remains to be determined. METHODS AND RESULTS We resequenced the core promoter and coding regions of ABCG1 in 380 individuals from the general population. Next, we genotyped 10 237 individuals from the Copenhagen City Heart Study for the identified variants and determined the effect on lipid and lipoprotein levels and on risk of myocardial infarction (MI) and ischemic heart disease (IHD). g.-376C>T, g.-311T>A, and Ser630Leu predicted risk of MI in the Copenhagen City Heart Study, with hazard ratios of 2.2 (95% confidence interval: 1.2-4.3), 1.7 (1.0-2.9), and 7.5 (1.9-30), respectively. These results were confirmed for g.-376C>T in a case-control study comprising 4983 independently ascertained IHD cases and 7489 controls. Expression levels of ABCG1 mRNA were decreased by approximately 40% in g.-376C>T heterozygotes versus noncarriers (probability values: 0.005-0.009). Finally, in vitro specificity protein 1 (Sp1) bound specifically to a putative Sp1 binding site at position -382 to -373 in the ABCG1 promoter, and the presence of the -376 T allele reduced binding and transactivation of the promoter by Sp1. CONCLUSIONS This is the first report of a functional variant in ABCG1 that associates with increased risk of MI and IHD in the general population.
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Affiliation(s)
- Jesper Schou
- Department of Clinical Biochemistry KB3011, Section for Molecular Genetics, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, DK-2100 Copenhagen, Denmark
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Mukhamedova N, D’Souza W, Low H, Kesani R, Chimini G, Sviridov D. Global functional knockdown of ATP binding cassette transporter A1 stimulates development of atherosclerosis in apoE K/O mice. Biochem Biophys Res Commun 2011; 412:446-9. [DOI: 10.1016/j.bbrc.2011.07.113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 07/27/2011] [Indexed: 10/17/2022]
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Identification of an amino acid residue in ATP-binding cassette transport G1 critical for mediating cholesterol efflux. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:552-9. [PMID: 21821149 DOI: 10.1016/j.bbalip.2011.07.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 07/07/2011] [Accepted: 07/15/2011] [Indexed: 01/31/2023]
Abstract
The ATP-binding cassette transporter G1 (ABCG1) mediates free cholesterol efflux onto lipidated apolipoprotein A-I (apoA-I) and plays an important role in macrophage reverse cholesterol transport thereby reducing atherosclerosis. However, how ABCG1 mediates the efflux of cholesterol onto lipidated apoA-I is unclear. Since the crystal structure of ABCG family is not available, other approaches such as site-directed mutagenesis have been widely used to identify amino acid residues important for protein functions. We noticed that ABCG1 contains a single cysteine residue in its putative transmembrane domains. This cysteine residue locates at position 514 (Cys(514)) within the third putative transmembrane domain and is highly conserved. Replacement of Cys(514) with Ala (C514A) essentially abolished ABCG1-mediated cholesterol efflux onto lipidated apoA-I. Substitution of Cys(514) with more conserved amino acid residues, Ser or Thr, also significantly decreased cholesterol efflux. However, mutation C514A had no detectable effect on protein stability and trafficking. Mutation C514A also did not affect the dimerization of ABCG1. Our findings demonstrated that the sulfhydryl group of Cys residue located at position 514 plays a critical role in ABCG1-mediated cholesterol efflux. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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Abstract
The lipoprotein HDL has two important roles: first, it promotes reverse cholesterol transport, and second, it modulates inflammation. Epidemiological studies show that HDL-cholesterol levels are inversely correlated with the risk of cardiovascular events. However, many patients who experience a clinical event have normal, or even high, levels of HDL cholesterol. Measuring HDL-cholesterol levels provides information about the size of the HDL pool, but does not predict HDL composition or function. The main component of HDL, apolipoprotein A-I (apo A-I), is largely responsible for reverse cholesterol transport through the macrophage ATP-binding cassette transporter ABCA1. Apo A-I can be damaged by oxidative mechanisms, which render the protein less able to promote cholesterol efflux. HDL also contains a number of other proteins that are affected by the oxidative environment of the acute-phase response. Modification of the protein components of HDL can convert it from an anti-inflammatory to a proinflammatory particle. Small peptides that mimic some of the properties of apo A-I have been shown in preclinical models to improve HDL function and reduce atherosclerosis without altering HDL-cholesterol levels. Robust assays to evaluate the function of HDL are needed to supplement the measurement of HDL-cholesterol levels in the clinic.
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