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Liimatta J, Curschellas E, Altinkilic EM, Naamneh Elzenaty R, Augsburger P, du Toit T, Voegel CD, Breault DT, Flück CE, Pignatti E. Adrenal Abcg1 Controls Cholesterol Flux and Steroidogenesis. Endocrinology 2024; 165:bqae014. [PMID: 38301271 PMCID: PMC10863561 DOI: 10.1210/endocr/bqae014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 01/14/2024] [Accepted: 01/30/2024] [Indexed: 02/03/2024]
Abstract
Cholesterol is the precursor of all steroids, but how cholesterol flux is controlled in steroidogenic tissues is poorly understood. The cholesterol exporter ABCG1 is an essential component of the reverse cholesterol pathway and its global inactivation results in neutral lipid redistribution to tissue macrophages. The function of ABCG1 in steroidogenic tissues, however, has not been explored. To model this, we inactivated Abcg1 in the mouse adrenal cortex, which led to an adrenal-specific increase in transcripts involved in cholesterol uptake and de novo synthesis. Abcg1 inactivation did not affect adrenal cholesterol content, zonation, or serum lipid profile. Instead, we observed a moderate increase in corticosterone production that was not recapitulated by the inactivation of the functionally similar cholesterol exporter Abca1. Altogether, our data imply that Abcg1 controls cholesterol uptake and biosynthesis and regulates glucocorticoid production in the adrenal cortex, introducing the possibility that ABCG1 variants may account for physiological or subclinical variation in stress response.
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Affiliation(s)
- Jani Liimatta
- Division of Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, Bern 3010, Switzerland
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
- Kuopio Pediatric Research Unit (KuPRU), University of Eastern Finland and Kuopio University Hospital, Kuopio 70200, Finland
| | - Evelyn Curschellas
- Department of Chemistry, Biochemistry and Pharmacy, Medical Faculty, University of Bern, Bern 3010, Switzerland
| | - Emre Murat Altinkilic
- Division of Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, Bern 3010, Switzerland
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
| | - Rawda Naamneh Elzenaty
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
| | - Philipp Augsburger
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
| | - Therina du Toit
- Division of Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, Bern 3010, Switzerland
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern 3010, Switzerland
| | - Clarissa D Voegel
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern 3010, Switzerland
| | - David T Breault
- Department of Pediatrics, Harvard Medical School, Boston Children's Hospital, Boston, MA 02115, USA
- Harvard Stem Cell Institute, Cambridge, MA 02138, USA
| | - Christa E Flück
- Division of Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, Bern 3010, Switzerland
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
| | - Emanuele Pignatti
- Division of Pediatric Endocrinology, Diabetology and Metabolism, Department of Pediatrics, Inselspital, Bern University Hospital, Bern 3010, Switzerland
- Department for BioMedical Research, University Hospital Inselspital, University of Bern, Bern 3010, Switzerland
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2
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Structure and transport mechanism of the human cholesterol transporter ABCG1. Cell Rep 2022; 38:110298. [PMID: 35081353 DOI: 10.1016/j.celrep.2022.110298] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 12/13/2021] [Accepted: 01/04/2022] [Indexed: 12/31/2022] Open
Abstract
The reverse cholesterol transport pathway is responsible for the maintenance of human cholesterol homeostasis, an imbalance of which usually leads to atherosclerosis. As a key component of this pathway, the ATP-binding cassette transporter ABCG1 forwards cellular cholesterol to the extracellular acceptor nascent high-density lipoprotein (HDL). Here, we report a 3.26-Å cryo-electron microscopy structure of cholesterol-bound ABCG1 in an inward-facing conformation, which represents a turnover condition upon ATP binding. Structural analyses combined with functional assays reveals that a cluster of conserved hydrophobic residues, in addition to two sphingomyelins, constitute a well-defined cholesterol-binding cavity. The exit of this cavity is closed by three pairs of conserved Phe residues, which constitute a hydrophobic path for the release of cholesterol in an acceptor concentration-dependent manner. Overall, we propose an ABCG1-driven cholesterol transport cycle initiated by sphingomyelin-assisted cholesterol recruitment and accomplished by the release of cholesterol to HDL.
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May SC, Dron JS, Hegele RA, Sahoo D. Human variant of scavenger receptor BI (R174C) exhibits impaired cholesterol transport functions. J Lipid Res 2021; 62:100045. [PMID: 33577783 PMCID: PMC7985710 DOI: 10.1016/j.jlr.2021.100045] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 01/22/2021] [Indexed: 11/29/2022] Open
Abstract
HDL and its primary receptor, scavenger receptor class B type I (SR-BI), work together to promote the clearance of excess plasma cholesterol, thereby protecting against atherosclerosis. Human variants of SR-BI have been identified in patients with high HDL-cholesterol levels, and at least one variant has been linked to cardiovascular disease. Therefore, while often regarded as beneficial, very high levels of HDL-cholesterol may result from impaired cholesterol clearance through SR-BI and contribute to cardiovascular risk. In this study, we characterized the function of a rare human variant of SR-BI, resulting in the substitution of arginine-174 with cysteine (R174C), which was previously identified in a heterozygous individual with high levels of HDL-cholesterol. We hypothesized that the R174C-SR-BI variant has impaired cholesterol transport functions, which were assessed in COS-7 cells after transient transfection with full-length WT or R174C-SR-BI. Although R174C-SR-BI was expressed at levels comparable to the WT receptor, HDL binding, cholesteryl hexadecyl ether uptake, free cholesterol efflux, and modulation of membrane cholesterol were disrupted in the presence of R174C-SR-BI. We further examined the role of salt bridges as a potential mechanism for R174C-SR-BI dysfunction. If translatable, this human variant could lead to increased plasma HDL-cholesterol levels, impaired cholesterol clearance, and increased cardiovascular disease risk.
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Affiliation(s)
- Sarah C May
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Jacqueline S Dron
- Robarts Research Institute, Western University, London, Ontario, Canada; Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Robert A Hegele
- Robarts Research Institute, Western University, London, Ontario, Canada; Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Daisy Sahoo
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, USA; Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, USA.
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4
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Jang E, Robert J, Rohrer L, von Eckardstein A, Lee WL. Transendothelial transport of lipoproteins. Atherosclerosis 2020; 315:111-125. [PMID: 33032832 DOI: 10.1016/j.atherosclerosis.2020.09.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/15/2020] [Accepted: 09/18/2020] [Indexed: 02/06/2023]
Abstract
The accumulation of low-density lipoproteins (LDL) in the arterial wall plays a pivotal role in the initiation and pathogenesis of atherosclerosis. Conversely, the removal of cholesterol from the intima by cholesterol efflux to high density lipoproteins (HDL) and subsequent reverse cholesterol transport shall confer protection against atherosclerosis. To reach the subendothelial space, both LDL and HDL must cross the intact endothelium. Traditionally, this transit is explained by passive filtration. This dogma has been challenged by the identification of several rate-limiting factors namely scavenger receptor SR-BI, activin like kinase 1, and caveolin-1 for LDL as well as SR-BI, ATP binding cassette transporter G1, and endothelial lipase for HDL. In addition, estradiol, vascular endothelial growth factor, interleukins 6 and 17, purinergic signals, and sphingosine-1-phosphate were found to regulate transendothelial transport of either LDL or HDL. Thorough understanding of transendothelial lipoprotein transport is expected to elucidate new therapeutic targets for the treatment or prevention of atherosclerotic cardiovascular disease and the development of strategies for the local delivery of drugs or diagnostic tracers into diseased tissues including atherosclerotic lesions.
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Affiliation(s)
- Erika Jang
- Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada
| | - Jerome Robert
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland
| | - Lucia Rohrer
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland
| | - Arnold von Eckardstein
- Institute of Clinical Chemistry, University of Zurich and University Hospital of Zurich, Switzerland.
| | - Warren L Lee
- Keenan Centre for Biomedical Research, St. Michael's Hospital, Toronto, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada; Interdepartmental Division of Critical Care, Department of Medicine, University of Toronto, Canada; Department of Biochemistry, University of Toronto, Canada; Institute of Medical Science, University of Toronto, Canada.
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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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Mechanisms and regulation of cholesterol homeostasis. Nat Rev Mol Cell Biol 2019; 21:225-245. [DOI: 10.1038/s41580-019-0190-7] [Citation(s) in RCA: 450] [Impact Index Per Article: 90.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2019] [Indexed: 12/14/2022]
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Wen X, Zhao WH, Chen LZ, Qu W, Liu HX, Yan HY, Hou LF, Ping J. Attenuated cholesterol metabolism pathway suppresses regulatory T cell development in prenatal nicotine exposed female mice. Toxicology 2019; 428:152309. [PMID: 31629012 DOI: 10.1016/j.tox.2019.152309] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 10/10/2019] [Accepted: 10/15/2019] [Indexed: 12/21/2022]
Abstract
The recession of regulatory T cells (Tregs) contributes to development of autoimmune disease. Our previous study suggested that prenatal nicotine exposure (PNE) inhibited Tregs frequency in offspring, but the mechanisms are still uncertain. This study aimed to explore the molecular mechanisms of PNE-induced Tregs inhibition from the perspective of cellular cholesterol homeostasis both in vivo and in vitro. PNE mice model were established by 3 mg/kg/d nicotine administration in Balb/c strain from gestational day (GD) 9 to GD 18. The results showed that PNE significantly decreased thymic Tregs frequency in neonatal offspring. The activation of mTOR and downregulation of p-STAT5/Foxp3 pathway of Tregs were observed in PNE offspring. Mechanism study found that PNE elevated ATP-binding cassette transporter G1 (ABCG1) expression and decreased intracellular cholesterol content of Tregs in offspring, indicating impaired intracellular cholesterol homeostasis. Similar results were observed in 1 μM nicotine-treated primary thymocytes in vitro. Further, cholesterol-replenishment can abrogate nicotine-induced mTOR activation and the following suppression of p-STAT5/Foxp3 pathway and Tregs frequency. In addition, Abcg1 siRNA transfection can partly reverse the nicotine-decreased intracellular cholesterol content and cell frequency of Tregs. In conclusion, this study showed that PNE could suppress Tregs development in female mice by up-regulating ABCG1-dependent cholesterol efflux, and suggested that PNE-induced thymic Tregs recession of offspring at early life was the developmental origin mechanism of immune dysfunction in later life.
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Affiliation(s)
- Xiao Wen
- Department of Pharmacology, Wuhan University School of Basic Medical Sciences, Wuhan 430071, China
| | - Wen-Hao Zhao
- Department of Pharmacology, Wuhan University School of Basic Medical Sciences, Wuhan 430071, China
| | - Lan-Zhou Chen
- Hubei Key Laboratory of Biomass-Resources Chemistry and Environmental Biotechnology, Wuhan University School of Resource and Environmental Sciences, Wuhan, 430079, China
| | - Wen Qu
- Department of Pharmacology, Wuhan University School of Basic Medical Sciences, Wuhan 430071, China
| | - Han-Xiao Liu
- Department of Pharmacology, Wuhan University School of Basic Medical Sciences, Wuhan 430071, China
| | - Hui-Yi Yan
- Department of Pharmacology, Wuhan University School of Basic Medical Sciences, Wuhan 430071, China
| | - Li-Fang Hou
- Department of Pharmacology, Wuhan University School of Basic Medical Sciences, Wuhan 430071, China
| | - Jie Ping
- Department of Pharmacology, Wuhan University School of Basic Medical Sciences, Wuhan 430071, China.
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8
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Lu HS, Schmidt AM, Hegele RA, Mackman N, Rader DJ, Weber C, Daugherty A. Reporting Sex and Sex Differences in Preclinical Studies. Arterioscler Thromb Vasc Biol 2019; 38:e171-e184. [PMID: 30354222 DOI: 10.1161/atvbaha.118.311717] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Hong S Lu
- From the Department of Physiology, Saha Cardiovascular Research Center, University of Kentucky, Lexington (H.S.L., A.D.)
| | - Ann Marie Schmidt
- Diabetes Research Program, Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, New York University Langone Medical Center, New York, NY (A.M.S.)
| | - Robert A Hegele
- Department of Medicine and Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada (R.A.H.)
| | - Nigel Mackman
- Department of Medicine, University of North Carolina at Chapel Hill (N.M.)
| | - Daniel J Rader
- Department of Medicine (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia.,Department of Genetics (D.J.R.), Perelman School of Medicine, University of Pennsylvania, Philadelphia
| | - Christian Weber
- Department of Medicine, Institute for Cardiovascular Prevention, Ludwig-Maximilians-Universität, Munich, Germany (C.W.).,German Centre for Cardiovascular Research, Partner Site Munich Heart Alliance, Munich, Germany (C.W.)
| | - Alan Daugherty
- From the Department of Physiology, Saha Cardiovascular Research Center, University of Kentucky, Lexington (H.S.L., A.D.)
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9
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He Y, Kothari V, Bornfeldt KE. High-Density Lipoprotein Function in Cardiovascular Disease and Diabetes Mellitus. Arterioscler Thromb Vasc Biol 2019; 38:e10-e16. [PMID: 29367232 DOI: 10.1161/atvbaha.117.310222] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Yi He
- From the Division of Metabolism, Endocrinology and Nutrition, Department of Medicine (Y.H., V.K., K.E.B.) and Department of Pathology (K.E.B.), University of Washington Medicine Diabetes Institute, University of Washington School of Medicine, Seattle
| | - Vishal Kothari
- From the Division of Metabolism, Endocrinology and Nutrition, Department of Medicine (Y.H., V.K., K.E.B.) and Department of Pathology (K.E.B.), University of Washington Medicine Diabetes Institute, University of Washington School of Medicine, Seattle
| | - Karin E Bornfeldt
- From the Division of Metabolism, Endocrinology and Nutrition, Department of Medicine (Y.H., V.K., K.E.B.) and Department of Pathology (K.E.B.), University of Washington Medicine Diabetes Institute, University of Washington School of Medicine, Seattle.
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10
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Hoekstra M, Ouweneel AB, Nahon JE, van der Geest R, Kröner MJ, van der Sluis RJ, Van Eck M. ATP-binding cassette transporter G1 deficiency is associated with mild glucocorticoid insufficiency in mice. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:443-451. [PMID: 30633988 DOI: 10.1016/j.bbalip.2019.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 12/06/2018] [Accepted: 01/07/2019] [Indexed: 10/27/2022]
Abstract
OBJECTIVE Since cholesterol is the sole precursor for glucocorticoid synthesis, it is hypothesized that genetic defects in proteins that impact the cellular cholesterol pool may underlie glucocorticoid insufficiency in humans. In the current study, we specifically focused on the cholesterol efflux mediator ATP-binding cassette transporter G1 (ABCG1) as gene candidate. METHODS The adrenal transcriptional response to fasting stress was measured in wild-type mice to identify putative novel gene candidates. Subsequently, the adrenal glucocorticoid function was compared between ABCG1 knockout mice and wild-type controls. RESULTS Overnight food deprivation induced a change in relative mRNA expression levels of cholesterol metabolism-related proteins previously linked to steroidogenesis, i.e. scavenger receptor class B type I (+149%; P < 0.001), LDL receptor (-70%; P < 0.001) and apolipoprotein E (-41%; P < 0.01). Strikingly, ABCG1 transcript levels were also markedly decreased (-61%; P < 0.05). In contrast to our hypothesis that decreasing cholesterol efflux would increase the adrenal cholesterol pool and enhance glucocorticoid output, ABCG1 knockout mice as compared to wild-type mice exhibited a reduced ability to secrete corticosterone in response to an ACTH challenge (two-way ANOVA: P < 0.001 for genotype) or fasting stress. As a result, glucocorticoid target gene expression levels in liver and hypothalamus were reduced and blood lymphocyte concentrations and spleen weights increased in ABCG1 knockout mice under fasting stress conditions. This was paralleled by a 48% reduction in adrenal cholesteryl ester stores and stimulation of adrenal NPC intracellular cholesterol transporter 2 (+37%; P < 0.05) and apolipoprotein E (+59%; P < 0.01) mRNA expression. CONCLUSION ABCG1 deficiency is associated with mild glucocorticoid insufficiency in mice.
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Affiliation(s)
- Menno Hoekstra
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands.
| | - Amber B Ouweneel
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Joya E Nahon
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Rick van der Geest
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Mara J Kröner
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Ronald J van der Sluis
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Miranda Van Eck
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
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11
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Affiliation(s)
- Jacqueline S Dron
- From the Department of Biochemistry (J.S.D., J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
- Robarts Research Institute (J.S.D., J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Julieta Lazarte
- From the Department of Biochemistry (J.S.D., J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
- Robarts Research Institute (J.S.D., J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
- Department of Medicine (J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Robert A Hegele
- From the Department of Biochemistry (J.S.D., J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
- Robarts Research Institute (J.S.D., J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
- Department of Medicine (J.L., R.A.H.), Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
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12
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Intracellular and Plasma Membrane Events in Cholesterol Transport and Homeostasis. J Lipids 2018; 2018:3965054. [PMID: 30174957 PMCID: PMC6106919 DOI: 10.1155/2018/3965054] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 07/26/2018] [Indexed: 12/13/2022] Open
Abstract
Cholesterol transport between intracellular compartments proceeds by both energy- and non-energy-dependent processes. Energy-dependent vesicular traffic partly contributes to cholesterol flux between endoplasmic reticulum, plasma membrane, and endocytic vesicles. Membrane contact sites and lipid transfer proteins are involved in nonvesicular lipid traffic. Only “active" cholesterol molecules outside of cholesterol-rich regions and partially exposed in water phase are able to fast transfer. The dissociation of partially exposed cholesterol molecules in water determines the rate of passive aqueous diffusion of cholesterol out of plasma membrane. ATP hydrolysis with concomitant conformational transition is required to cholesterol efflux by ABCA1 and ABCG1 transporters. Besides, scavenger receptor SR-B1 is involved also in cholesterol efflux by facilitated diffusion via hydrophobic tunnel within the molecule. Direct interaction of ABCA1 with apolipoprotein A-I (apoA-I) or apoA-I binding to high capacity binding sites in plasma membrane is important in cholesterol escape to free apoA-I. ABCG1-mediated efflux to fully lipidated apoA-I within high density lipoprotein particle proceeds more likely through the increase of “active” cholesterol level. Putative cholesterol-binding linear motifs within the structure of all three proteins ABCA1, ABCG1, and SR-B1 are suggested to contribute to the binding and transfer of cholesterol molecules from cytoplasmic to outer leaflets of lipid bilayer. Together, plasma membrane events and intracellular cholesterol metabolism and traffic determine the capacity of the cell for cholesterol efflux.
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Temporary sequestration of cholesterol and phosphatidylcholine within extracellular domains of ABCA1 during nascent HDL generation. Sci Rep 2018; 8:6170. [PMID: 29670126 PMCID: PMC5906560 DOI: 10.1038/s41598-018-24428-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 04/03/2018] [Indexed: 02/06/2023] Open
Abstract
The quality and quantity of high-density lipoprotein (HDL) in blood plasma are important for preventing coronary artery disease. ATP-binding cassette protein A1 (ABCA1) and apolipoprotein A-I (apoA-I) play essential roles in nascent HDL formation, but controversy persists regarding the mechanism by which nascent HDL is generated. In the “direct loading model”, apoA-I acquires lipids directly from ABCA1 while it is bound to the transporter. By contrast, in the “indirect model”, apoA-I acquires lipids from the specific membrane domains created by ABCA1. In this study, we found that trypsin treatment causes rapid release of phosphatidylcholine (PC) and cholesterol from BHK/ABCA1 cells, and that the time course of lipid release coincides with those of trypsin digestion of extracellular domains (ECDs) of surface ABCA1 and of release of ECD fragments into the medium. This trypsin-dependent lipid release was dependent on ABCA1 ATPase activity, and did not occur in cells that express ABCG1, which exports lipids like ABCA1 but does not have large ECDs. These results suggest that the trypsin-sensitive sites on the cell surface are the large ECDs of ABCA1, and that lipids transported by ABCA1 are temporarily sequestered within the ECDs during nascent HDL formation.
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14
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Kober AC, Manavalan APC, Tam-Amersdorfer C, Holmér A, Saeed A, Fanaee-Danesh E, Zandl M, Albrecher NM, Björkhem I, Kostner GM, Dahlbäck B, Panzenboeck U. Implications of cerebrovascular ATP-binding cassette transporter G1 (ABCG1) and apolipoprotein M in cholesterol transport at the blood-brain barrier. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:573-588. [PMID: 28315462 DOI: 10.1016/j.bbalip.2017.03.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/07/2017] [Accepted: 03/12/2017] [Indexed: 02/03/2023]
Abstract
Impaired cholesterol/lipoprotein metabolism is linked to neurodegenerative diseases such as Alzheimer's disease (AD). Cerebral cholesterol homeostasis is maintained by the highly efficient blood-brain barrier (BBB) and flux of the oxysterols 24(S)-hydroxycholesterol and 27-hydroxycholesterol, potent liver-X-receptor (LXR) activators. HDL and their apolipoproteins are crucial for cerebral lipid transfer, and loss of ATP binding cassette transporters (ABC)G1 and G4 results in toxic accumulation of oxysterols in the brain. The HDL-associated apolipoprotein (apo)M is positively correlated with pre-β HDL formation in plasma; its presence and function in the brain was thus far unknown. Using an in vitro model of the BBB, we examined expression, regulation, and functions of ABCG1, ABCG4, and apoM in primary porcine brain capillary endothelial cells (pBCEC). RT Q-PCR analyses and immunoblotting revealed that in addition to ABCA1 and scavenger receptor, class B, type I (SR-BI), pBCEC express high levels of ABCG1, which was up-regulated by LXR activation. Immunofluorescent staining, site-specific biotinylation and immunoprecipitation revealed that ABCG1 is localized both to early and late endosomes and on apical and basolateral plasma membranes. Using siRNA interference to silence ABCG1 (by 50%) reduced HDL-mediated [3H]-cholesterol efflux (by 50%) but did not reduce [3H]-24(S)-hydroxycholesterol efflux. In addition to apoA-I, pBCEC express and secrete apoM mainly to the basolateral (brain) compartment. HDL enhanced expression and secretion of apoM by pBCEC, apoM-enriched HDL promoted cellular cholesterol efflux more efficiently than apoM-free HDL, while apoM-silencing diminished cellular cholesterol release. We suggest that ABCG1 and apoM are centrally involved in regulation of cholesterol metabolism/turnover at the BBB.
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Affiliation(s)
| | | | | | - Andreas Holmér
- Department of Translational Medicine, University Hospital SUS, Malmö, Lund University, Sweden
| | - Ahmed Saeed
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institute Huddinge, Huddinge, Sweden
| | - Elham Fanaee-Danesh
- Institute of Pathophysiology and Immunology, Medical University of Graz, Graz, Austria
| | - Martina Zandl
- Institute of Pathophysiology and Immunology, Medical University of Graz, Graz, Austria
| | | | - Ingemar Björkhem
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institute Huddinge, Huddinge, Sweden
| | - Gerhard M Kostner
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Björn Dahlbäck
- Department of Translational Medicine, University Hospital SUS, Malmö, Lund University, Sweden
| | - Ute Panzenboeck
- Institute of Pathophysiology and Immunology, Medical University of Graz, Graz, Austria.
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15
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de Aguiar Vallim TQ, Lee E, Merriott DJ, Goulbourne CN, Cheng J, Cheng A, Gonen A, Allen RM, Palladino END, Ford DA, Wang T, Baldán Á, Tarling EJ. ABCG1 regulates pulmonary surfactant metabolism in mice and men. J Lipid Res 2017; 58:941-954. [PMID: 28264879 DOI: 10.1194/jlr.m075101] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/03/2017] [Indexed: 12/27/2022] Open
Abstract
Idiopathic pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by accumulation of surfactant. Surfactant synthesis and secretion are restricted to epithelial type 2 (T2) pneumocytes (also called T2 cells). Clearance of surfactant is dependent upon T2 cells and macrophages. ABCG1 is highly expressed in both T2 cells and macrophages. ABCG1-deficient mice accumulate surfactant, lamellar body-loaded T2 cells, lipid-loaded macrophages, B-1 lymphocytes, and immunoglobulins, clearly demonstrating that ABCG1 has a critical role in pulmonary homeostasis. We identify a variant in the ABCG1 promoter in patients with PAP that results in impaired activation of ABCG1 by the liver X receptor α, suggesting that ABCG1 basal expression and/or induction in response to sterol/lipid loading is essential for normal lung function. We generated mice lacking ABCG1 specifically in either T2 cells or macrophages to determine the relative contribution of these cell types on surfactant lipid homeostasis. These results establish a critical role for T2 cell ABCG1 in controlling surfactant and overall lipid homeostasis in the lung and in the pathogenesis of human lung disease.
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Affiliation(s)
- Thomas Q de Aguiar Vallim
- Department of Medicine, University of California Los Angeles, Los Angeles, CA 90095.,Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095.,Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095.,Johnson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, CA 90095
| | - Elinor Lee
- Department of Medicine, University of California Los Angeles, Los Angeles, CA 90095.,Division of Pulmonary and Critical Care Medicine, University of California Los Angeles, Los Angeles, CA 90095
| | - David J Merriott
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095
| | | | - Joan Cheng
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095
| | - Angela Cheng
- Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095
| | - Ayelet Gonen
- Department of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Ryan M Allen
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University, St. Louis, MO 63104
| | - Elisa N D Palladino
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University, St. Louis, MO 63104.,Center for Cardiovascular Research, School of Medicine, Saint Louis University, St. Louis, MO 63104
| | - David A Ford
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University, St. Louis, MO 63104.,Center for Cardiovascular Research, School of Medicine, Saint Louis University, St. Louis, MO 63104
| | - Tisha Wang
- Department of Medicine, University of California Los Angeles, Los Angeles, CA 90095.,Division of Pulmonary and Critical Care Medicine, University of California Los Angeles, Los Angeles, CA 90095
| | - Ángel Baldán
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University, St. Louis, MO 63104
| | - Elizabeth J Tarling
- Department of Medicine, University of California Los Angeles, Los Angeles, CA 90095 .,Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA 90095.,Johnson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, CA 90095
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16
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Chai AB, Ammit AJ, Gelissen IC. Examining the role of ABC lipid transporters in pulmonary lipid homeostasis and inflammation. Respir Res 2017; 18:41. [PMID: 28241820 PMCID: PMC5330150 DOI: 10.1186/s12931-017-0526-9] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 02/21/2017] [Indexed: 01/03/2023] Open
Abstract
Respiratory diseases including asthma and chronic obstructive pulmonary disease (COPD) are characterised by excessive and persistent inflammation. Current treatments are often inadequate for symptom and disease control, and hence new therapies are warranted. Recent emerging research has implicated dyslipidaemia in pulmonary inflammation. Three ATP-binding cassette (ABC) transporters are found in the mammalian lung – ABCA1, ABCG1 and ABCA3 – that are involved in movement of cholesterol and phospholipids from lung cells. The aim of this review is to corroborate the current evidence for the role of ABC lipid transporters in pulmonary lipid homeostasis and inflammation. Here, we summarise results from murine knockout studies, human diseases associated with ABC transporter mutations, and in vitro studies. Disruption to ABC transporter activity results in lipid accumulation and elevated levels of inflammatory cytokines in lung tissue. Furthermore, these ABC-knockout mice exhibit signs of respiratory distress. ABC lipid transporters appear to have a crucial and protective role in the lung. However, our knowledge of the underlying molecular mechanisms for these benefits requires further attention. Understanding the relationship between cholesterol and inflammation in the lung, and the role that ABC transporters play in this may illuminate new pathways to target for the treatment of inflammatory lung diseases.
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Affiliation(s)
- Amanda B Chai
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, 2006, Australia
| | - Alaina J Ammit
- Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Camperdown, NSW, Australia. .,School of Life Sciences, University of Technology, Sydney, NSW, Australia.
| | - Ingrid C Gelissen
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, 2006, Australia
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17
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Hoekstra M, Van Berkel TJ. Functionality of High-Density Lipoprotein as Antiatherosclerotic Therapeutic Target. Arterioscler Thromb Vasc Biol 2016; 36:e87-e94. [DOI: 10.1161/atvbaha.116.308262] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Menno Hoekstra
- From the Division of Biopharmaceutics, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, The Netherlands
| | - Theo J.C. Van Berkel
- From the Division of Biopharmaceutics, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, The Netherlands
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