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Zaidi SAH, Lemtalsi T, Xu Z, Santana I, Sandow P, Labazi L, Caldwell RW, Caldwell RB, Rojas MA. Role of acyl-coenzyme A: cholesterol transferase 1 (ACAT1) in retinal neovascularization. J Neuroinflammation 2023; 20:14. [PMID: 36691048 PMCID: PMC9869542 DOI: 10.1186/s12974-023-02700-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 01/13/2023] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND We have investigated the efficacy of a new strategy to limit pathological retinal neovascularization (RNV) during ischemic retinopathy by targeting the cholesterol metabolizing enzyme acyl-coenzyme A: cholesterol transferase 1 (ACAT1). Dyslipidemia and cholesterol accumulation have been strongly implicated in promoting subretinal NV. However, little is known about the role of cholesterol metabolism in RNV. Here, we tested the effects of inhibiting ACAT1 on pathological RNV in the mouse model of oxygen-induced retinopathy (OIR). METHODS In vivo studies used knockout mice that lack the receptor for LDL cholesterol (LDLR-/-) and wild-type mice. The wild-type mice were treated with a specific inhibitor of ACAT1, K604 (10 mg/kg, i.p) or vehicle (PBS) during OIR. In vitro studies used human microglia exposed to oxygen-glucose deprivation (OGD) and treated with the ACAT1 inhibitor (1 μM) or PBS. RESULTS Analysis of OIR retinas showed that increased expression of inflammatory mediators and pathological RNV were associated with significant increases in expression of the LDLR, increased accumulation of neutral lipids, and formation of toxic levels of cholesterol ester (CE). Deletion of the LDLR completely blocked OIR-induced RNV and significantly reduced the AVA. The OIR-induced increase in CE formation was accompanied by significant increases in expression of ACAT1, VEGF and inflammatory factors (TREM1 and MCSF) (p < 0.05). ACAT1 was co-localized with TREM1, MCSF, and macrophage/microglia makers (F4/80 and Iba1) in areas of RNV. Treatment with K604 prevented retinal accumulation of neutral lipids and CE formation, inhibited RNV, and decreased the AVA as compared to controls (p < 0.05). The treatment also blocked upregulation of LDLR, ACAT1, TREM1, MCSF, and inflammatory cytokines but did not alter VEGF expression. K604 treatment of microglia cells also blocked the effects of OGD in increasing expression of ACAT1, TREM1, and MCSF without altering VEGF expression. CONCLUSIONS OIR-induced RNV is closely associated with increases in lipid accumulation and CE formation along with increased expression of LDLR, ACAT1, TREM1, and MCSF. Inhibiting ACAT1 blocked these effects and limited RNV independently of alterations in VEGF expression. This pathway offers a novel strategy to limit vascular injury during ischemic retinopathy.
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Affiliation(s)
- Syed A H Zaidi
- Vascular Biology Center, Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912-2500, USA.,Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Tahira Lemtalsi
- Vascular Biology Center, Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912-2500, USA.,Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Zhimin Xu
- Vascular Biology Center, Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912-2500, USA.,Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Isabella Santana
- Vascular Biology Center, Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912-2500, USA
| | - Porsche Sandow
- Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA.,Department of Pharmacology and Toxicology, Augusta University, Augusta, GA, USA
| | - Leila Labazi
- Vascular Biology Center, Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912-2500, USA
| | - Robert W Caldwell
- Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA.,Department of Pharmacology and Toxicology, Augusta University, Augusta, GA, USA
| | - Ruth B Caldwell
- Vascular Biology Center, Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912-2500, USA. .,Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA. .,Department of Cellular Biology and Anatomy, Augusta University, Augusta, GA, USA.
| | - Modesto A Rojas
- Vascular Biology Center, Augusta University, 1460 Laney Walker Blvd, Augusta, GA, 30912-2500, USA. .,Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA. .,Department of Pharmacology and Toxicology, Augusta University, Augusta, GA, USA.
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Neumann B, Chao K, Chang CCY, Chang TY. Nanodisc scaffold peptide (NSP r) replaces detergent by reconstituting acyl-CoA:cholesterol acyltransferase 1 into peptidiscs. Arch Biochem Biophys 2020; 691:108518. [PMID: 32735863 PMCID: PMC7507747 DOI: 10.1016/j.abb.2020.108518] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/20/2020] [Accepted: 07/25/2020] [Indexed: 12/19/2022]
Abstract
To conduct biochemical studies in vitro, membrane proteins (MPs) must be solubilized with detergents. While detergents are great tools, they can also inhibit the biological activity and/or perturb oligomerization of individual MPs. Nanodisc scaffold peptide (NSPr), an amphipathic peptide analog of ApoA1, was recently shown to reconstitute detergent solubilized MPs into peptidiscs in vitro. Acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT1), also known as sterol O-acyltransferase 1 (SOAT1), plays a key role in cellular cholesterol storage in various cell types and is a drug target to treat multiple human diseases. ACAT1 contains nine transmembrane domains (TMDs) and primarily forms a homotetramer in vitro and in intact cells; deletion of the N-terminal dimerization domain produces a homodimer with full retention in catalytic activity. ACAT1 is prone to inactivation by numerous detergents. Here we pursued the use of NSPr to overcome the detergent-induced inactivation of ACAT1 by generating near detergent-free ACAT1 peptidiscs. Based on native-PAGE analysis, we showed that NSPr reconstitutes ACAT1 into soluble peptidiscs, in which ACAT1 exists predominantly in oligomeric states greater than a homotetramer. The formation of these higher-order oligomeric states was independent of the N-terminal dimerization domain, suggesting that the oligomerization is mediated through hydrophobic interactions of multiple ACAT1 subunits. ACAT1 peptidiscs were still susceptible to heat-mediated inactivation, presumably due to the residual detergent (CHAPS) bound to ACAT1. We then conditioned ACAT1 with phosphatidylcholine (PC) to replace CHAPS prior to the formation of ACAT1 peptidiscs. The results showed, when PC was included, ACAT1 was present mainly in higher-order oligomeric states with greater enzymatic activity. With PC present, the enzymatic activity of ACAT1 peptidiscs was protected from heat-mediated inactivation. These results support the use of NSPr to create a near detergent-free solution of ACAT1 in peptidiscs for various in vitro studies. Our current results also raise the possibility that, under certain conditions, ACAT1 may form higher-order oligomeric states in vivo.
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Affiliation(s)
- Bryan Neumann
- Department of Biochemistry & Cell Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH, 03755, USA
| | - Kevin Chao
- College of Medicine, SUNY Downstate Health Sciences University, Brooklyn, NY, 11203, USA
| | - Catherine C Y Chang
- Department of Biochemistry & Cell Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH, 03755, USA.
| | - Ta-Yuan Chang
- Department of Biochemistry & Cell Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH, 03755, USA.
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3
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Acidic extracellular pH promotes accumulation of free cholesterol in human monocyte-derived macrophages via inhibition of ACAT1 activity. Atherosclerosis 2020; 312:1-7. [PMID: 32942042 DOI: 10.1016/j.atherosclerosis.2020.08.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 08/14/2020] [Accepted: 08/27/2020] [Indexed: 12/12/2022]
Abstract
BACKGROUND AND AIMS In focal areas of advanced human atherosclerotic lesions, the intimal fluid is acidic. An acidic medium impairs the ABCA1-mediated cholesterol efflux from macrophages, so tending to increase their content of free cholesterol, which is then available for esterification by the macrophage enzyme ACAT1. Here we investigated whether low extracellular pH would affect the activity of ACAT1. METHODS - Human monocyte-derived macrophages were first incubated with acetyl-LDL at neutral and acidic conditions (pH 7.5, 6.5, and 5.5) to generate foam cells, and then the foam cells were incubated with [3H]oleate-BSA complexes, and the formation of [3H]oleate-labeled cholesteryl esters was measured. ACAT1 activity was also measured in cell-free macrophage extracts. RESULTS - In acidic media, ACAT1-dependent cholesteryl [3H]oleate generation became compromised in the developing foam cells and their content of free cholesterol increased. In line with this finding, ACAT1 activity in the soluble cell-free fraction derived from macrophage foam cells peaked at pH 7, and gradually decreased under acidic pH with a rapid drop below pH 6.5. Incubation of macrophages under progressively more acidic conditions (until pH 5.5) lowered the cytosolic pH of macrophages (down to pH 6.0). Such intracellular acidification did not affect macrophage gene expression of ACAT1 or the neutral CEH. CONCLUSIONS Exposure of human macrophage foam cells to acidic conditions lowers their intracellular pH with simultaneous decrease in ACAT1 activity. This reduces cholesterol esterification and thus leads to accumulation of potentially toxic levels of free cholesterol, a contributing factor to macrophage foam cell death.
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Adenovirus Reveals New Pathway for Cholesterol Egress from the Endolysosomal System. Int J Mol Sci 2020; 21:ijms21165808. [PMID: 32823559 PMCID: PMC7460884 DOI: 10.3390/ijms21165808] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 08/11/2020] [Accepted: 08/12/2020] [Indexed: 12/15/2022] Open
Abstract
In addition to providing invaluable insights to the host response to viral infection, adenovirus continues to be an important model system for discovering basic aspects of cell biology. This is especially true for products of early region three (E3), which have provided the foundation for understanding many new mechanisms regulating intracellular trafficking of host cell proteins involved in the host immune response. Cholesterol homeostasis is vital for proper cellular physiology, and disturbances in cholesterol balance are increasingly recognized as important factors in human disease. Despite its central role in numerous aspects of cellular functions, the mechanisms responsible for delivery of dietary cholesterol to the endoplasmic reticulum, where the lipid metabolic and regulatory machinery reside, remain poorly understood. In this review, we describe a novel intracellular pathway for cholesterol trafficking that has been co-opted by an adenovirus E3 gene product. We describe what is known about the molecular regulation of this pathway, how it might benefit viral replication, and its potential involvement in normal cell physiology. Finally, we make a case that adenovirus has co-opted a cellular pathway that may be dysregulated in various human diseases.
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Saadane A, Mast N, Dao T, Ahmad B, Pikuleva IA. Retinal Hypercholesterolemia Triggers Cholesterol Accumulation and Esterification in Photoreceptor Cells. J Biol Chem 2016; 291:20427-39. [PMID: 27514747 DOI: 10.1074/jbc.m116.744656] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Indexed: 01/01/2023] Open
Abstract
The process of vision is impossible without the photoreceptor cells, which have a unique structure and specific maintenance of cholesterol. Herein we report on the previously unrecognized cholesterol-related pathway in the retina discovered during follow-up characterizations of Cyp27a1(-/-)Cyp46a1(-/-) mice. These animals have retinal hypercholesterolemia and convert excess retinal cholesterol into cholesterol esters, normally present in the retina in very small amounts. We established that in the Cyp27a1(-/-)Cyp46a1(-/-) retina, cholesterol esters are generated by and accumulate in the photoreceptor outer segments (OS), which is the retinal layer with the lowest cholesterol content. Mouse OS were also found to express the cholesterol-esterifying enzyme acyl-coenzyme A:cholesterol acyltransferase (ACAT1), but not lecithin-cholesterol acyltransferase (LCAT), and to differ from humans in retinal expression of ACAT1. Nevertheless, cholesterol esters were discovered to be abundant in human OS. We suggest a mechanism for cholesterol ester accumulation in the OS and that activity impairment of ACAT1 in humans may underlie the development of subretinal drusenoid deposits, a hallmark of age-related macular degeneration, which is a common blinding disease. We generated Cyp27a1(-/-)Cyp46a1(-/-)Acat1(-/-) mice, characterized their retina by different imaging modalities, and confirmed that unesterified cholesterol does accumulate in their OS and that there is photoreceptor apoptosis and OS degeneration in this line. Our results provide insights into the retinal response to local hypercholesterolemia and the retinal significance of cholesterol esterification, which could be cell-specific and both beneficial and detrimental for retinal structure and function.
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Affiliation(s)
- Aicha Saadane
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
| | - Natalia Mast
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
| | - Tung Dao
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
| | - Baseer Ahmad
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and the University Hospitals, Cleveland, Ohio 44106
| | - Irina A Pikuleva
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
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Huang LH, Melton EM, Li H, Sohn P, Rogers MA, Mulligan-Kehoe MJ, Fiering SN, Hickey WF, Chang CCY, Chang TY. Myeloid Acyl-CoA:Cholesterol Acyltransferase 1 Deficiency Reduces Lesion Macrophage Content and Suppresses Atherosclerosis Progression. J Biol Chem 2016; 291:6232-44. [PMID: 26801614 DOI: 10.1074/jbc.m116.713818] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2016] [Indexed: 01/03/2023] Open
Abstract
Acyl-CoA:cholesterol acyltransferase 1 (Acat1) converts cellular cholesterol to cholesteryl esters and is considered a drug target for treating atherosclerosis. However, in mouse models for atherosclerosis, global Acat1 knockout (Acat1(-/-)) did not prevent lesion development. Acat1(-/-) increased apoptosis within lesions and led to several additional undesirable phenotypes, including hair loss, dry eye, leukocytosis, xanthomatosis, and a reduced life span. To determine the roles of Acat1 in monocytes/macrophages in atherosclerosis, we produced a myeloid-specific Acat1 knockout (Acat1(-M/-M)) mouse and showed that, in the Apoe knockout (Apoe(-/-)) mouse model for atherosclerosis, Acat1(-M/-M) decreased the plaque area and reduced lesion size without causing leukocytosis, dry eye, hair loss, or a reduced life span. Acat1(-M/-M) enhanced xanthomatosis in apoe(-/-) mice, a skin disease that is not associated with diet-induced atherosclerosis in humans. Analyses of atherosclerotic lesions showed that Acat1(-M/-M) reduced macrophage numbers and diminished the cholesterol and cholesteryl ester load without causing detectable apoptotic cell death. Leukocyte migration analysis in vivo showed that Acat1(-M/-M) caused much fewer leukocytes to appear at the activated endothelium. Studies in inflammatory (Ly6C(hi)-positive) monocytes and in cultured macrophages showed that inhibiting ACAT1 by gene knockout or by pharmacological inhibition caused a significant decrease in integrin β 1 (CD29) expression in activated monocytes/macrophages. The sparse presence of lesion macrophages without Acat1 can therefore, in part, be attributed to decreased interaction between inflammatory monocytes/macrophages lacking Acat1 and the activated endothelium. We conclude that targeting ACAT1 in a myeloid cell lineage suppresses atherosclerosis progression while avoiding many of the undesirable side effects caused by global Acat1 inhibition.
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Affiliation(s)
- Li-Hao Huang
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | - Elaina M Melton
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | - Haibo Li
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | - Paul Sohn
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | - Maximillian A Rogers
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | | | | | - William F Hickey
- Pathology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire 03756
| | - Catherine C Y Chang
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | - Ta-Yuan Chang
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
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Yamauchi Y, Yokoyama S, Chang TY. ABCA1-dependent sterol release: sterol molecule specificity and potential membrane domain for HDL biogenesis. J Lipid Res 2015; 57:77-88. [PMID: 26497474 DOI: 10.1194/jlr.m063784] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Indexed: 01/28/2023] Open
Abstract
Mammalian cells synthesize various sterol molecules, including the C30 sterol, lanosterol, as cholesterol precursors in the endoplasmic reticulum. The build-up of precursor sterols, including lanosterol, displays cellular toxicity. Precursor sterols are found in plasma HDL. How these structurally different sterols are released from cells is poorly understood. Here, we show that newly synthesized precursor sterols arriving at the plasma membrane (PM) are removed by extracellular apoA-I in a manner dependent on ABCA1, a key macromolecule for HDL biogenesis. Analysis of sterol molecules by GC-MS and tracing the fate of radiolabeled acetate-derived sterols in normal and mutant Niemann-Pick type C cells reveal that ABCA1 prefers newly synthesized sterols, especially lanosterol, as the substrates before they are internalized from the PM. We also show that ABCA1 resides in a cholesterol-rich membrane domain resistant to the mild detergent, Brij 98. Blocking ACAT activity increases the cholesterol contents of this domain. Newly synthesized C29/C30 sterols are transiently enriched within this domain, but rapidly disappear from this domain with a half-life of less than 1 h. Our work shows that substantial amounts of precursor sterols are transported to a certain PM domain and are removed by the ABCA1-dependent pathway.
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Affiliation(s)
- Yoshio Yamauchi
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Shinji Yokoyama
- Nutritional Health Science Research Center and Department of Food and Nutritional Sciences, Chubu University, Kasugai 487-8501, Japan
| | - Ta-Yuan Chang
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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8
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He X, Leow KY, Yang H, Heng CK. Functional characterization of two single nucleotide polymorphisms of acyl-coenzyme A:cholesterol acyltransferase 2. Gene 2015; 566:236-41. [PMID: 25917363 DOI: 10.1016/j.gene.2015.04.061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 03/20/2015] [Accepted: 04/21/2015] [Indexed: 11/24/2022]
Abstract
BACKGROUND Acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) plays a critical role in the formation of cholesteryl esters from cholesterol and fatty acids, and is a potential target for treating hypercholesterolemia. We recently reported the significant effects of two human ACAT2 gene polymorphisms, 41A>G (Glu(14)Gly, rs9658625) and 734C>T (Thr(254)Ile, rs2272296), on plasma lipid levels and coronary artery disease susceptibility in a case-control association study. In the present study, we evaluated the possible biological influence of the two polymorphism using two approaches. METHODS In the first approach, the functional impact of the two polymorphisms was predicted in-silico using available web-based software, and in the second approach, the varying functions of the two polymorphisms were characterized in in vitro experiments, using ACAT2-deficient AC-29 cells. RESULTS Our results show that the enzymatic activity of mutant Glu(14)Gly is approximately two times higher than wildtype, and that this increase is primarily due to the increased expression and/or stability of the mutant ACAT2 protein. CONCLUSIONS These results suggest that the genetic variation at Glu(14)Gly is functionally important and may contribute to ACAT2 protein expression and stability.
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Affiliation(s)
- Xuelian He
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore; Central Laboratory, Wuhan Children's Hospital, China.
| | - Koon-Yeow Leow
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore
| | - Hongyuan Yang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Chew-Kiat Heng
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore.
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Kamikawa M, Lei X, Fujiwara Y, Nishitsuji K, Mizuta H, Takeya M, Sakashita N. ACAT1-associated Late Endosomes/Lysosomes Significantly Improve Impaired Intracellular Cholesterol Metabolism and the Survival of Niemann-Pick Type C Mice. Acta Histochem Cytochem 2014; 47:35-43. [PMID: 25221362 PMCID: PMC4105798 DOI: 10.1267/ahc.13033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 01/15/2014] [Indexed: 11/22/2022] Open
Abstract
We previously demonstrated that macrophages exhibit endoplasmic reticulum fragmentation under cholesterol-rich conditions, which results in the generation of acyl-coenzyme A: cholesterol acyltransferase 1 (ACAT1)-associated late endosomes/lysosomes (ACAT1-LE). ACAT1-LE efficiently esterify free cholesterol in loco, even with abnormal egress of free cholesterol from late endosomes. Because impaired free cholesterol transport from late endosomes results in Niemann-Pick type C disease (NPC), the induction of ACAT1-LE is a potential therapeutic intervention for NPC. To examine the effects of ACAT1-LE induction on intracellular cholesterol metabolism, we incubated bone marrow-derived macrophages possessing NPC phenotype (npc1–/–) with methyl-β-cyclodextrin-cholesterol complex (mβCD-cho), a cholesterol donor. Immunofluorescence confocal microscopy revealed that mβCD-cho treatment of npc1–/– macrophages resulted in significant colocalization of signals from ACAT1 and lysosome-associated membrane protein 2, a late endosome/lysosome marker. npc1–/– macrophages contained significant amounts of free cholesterol with negligible amounts of cholesteryl ester, while wild-type macrophages possessed the same amounts of both cholesterols. mβCD-cho treatment also induced marked restoration of cholesterol esterification activity. mβCD-cho administration in neonate npc1–/– mice improved survival. These results indicate that ACAT1-LE induction in npc1–/– mice corrects impaired intracellular cholesterol metabolism and that restoring cholesterol esterification improves prognosis of npc1–/–. These data suggest that ACAT1-LE induction is a potential alternative therapeutic strategy for NPC.
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Affiliation(s)
- Masashi Kamikawa
- Department of Cell Pathology, Graduate School of Medical Sciences, Kumamoto University
- Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kumamoto University
| | - XiaoFeng Lei
- Department of Biochemistry, Showa University School of Medicine
| | - Yukio Fujiwara
- Department of Cell Pathology, Graduate School of Medical Sciences, Kumamoto University
| | - Kazuchika Nishitsuji
- Department of Human Pathology, Institute of Health Biosciences, The University of Tokushima Graduate School
| | - Hiroshi Mizuta
- Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kumamoto University
| | - Motohiro Takeya
- Department of Cell Pathology, Graduate School of Medical Sciences, Kumamoto University
| | - Naomi Sakashita
- Department of Cell Pathology, Graduate School of Medical Sciences, Kumamoto University
- Department of Human Pathology, Institute of Health Biosciences, The University of Tokushima Graduate School
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Luquain-Costaz C, Lefai E, Arnal-Levron M, Markina D, Sakaï S, Euthine V, Makino A, Guichardant M, Yamashita S, Kobayashi T, Lagarde M, Moulin P, Delton-Vandenbroucke I. Bis(monoacylglycero)phosphate accumulation in macrophages induces intracellular cholesterol redistribution, attenuates liver-X receptor/ATP-Binding cassette transporter A1/ATP-binding cassette transporter G1 pathway, and impairs cholesterol efflux. Arterioscler Thromb Vasc Biol 2013; 33:1803-11. [PMID: 23788762 DOI: 10.1161/atvbaha.113.301857] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Endosomal signature phospholipid bis(monoacylglycero)phosphate (BMP) has been involved in the regulation of cellular cholesterol homeostasis. Accumulation of BMP is a hallmark of lipid storage disorders and was recently reported as a noticeable feature of oxidized low-density lipoprotein-laden macrophages. This study was designed to delineate the consequences of macrophage BMP accumulation on intracellular cholesterol distribution, metabolism, and efflux and to unravel the underlying molecular mechanisms. APPROACH AND RESULTS We have developed an experimental design to specifically increase BMP content in RAW 264.7 macrophages. After BMP accumulation, cell cholesterol distribution was markedly altered, despite no change in low-density lipoprotein uptake and hydrolysis, cholesterol esterification, or total cell cholesterol content. The expression of cholesterol-regulated genes sterol regulatory element-binding protein 2 and hydroxymethylglutaryl-coenzyme A reductase was decreased by 40%, indicative of an increase of endoplasmic reticulum-associated cholesterol. Cholesterol delivery to plasma membrane was reduced as evidenced by the 20% decrease of efflux by cyclodextrin. Functionally, BMP accumulation reduced cholesterol efflux to both apolipoprotein A1 and high-density lipoprotein by 40% and correlated with a 40% decrease in mRNA contents of ATP-binding cassette transporter A1, ATP-binding cassette transporter G1, and liver-X receptor α and β. Foam cell formation induced by oxidized low-density lipoprotein exposure was exacerbated in BMP-enriched cells. CONCLUSIONS The present work shows for the first time a strong functional link between BMP and cholesterol-regulating genes involved in both intracellular metabolism and efflux. We propose that accumulation of cellular BMP might contribute to the deregulation of cholesterol homeostasis in atheromatous macrophages.
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Affiliation(s)
- Céline Luquain-Costaz
- Université de Lyon, UMR 1060 Inserm, CarMeN, Institut National des Sciences Appliquées-Lyon, Villeurbanne, France
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11
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Apolipoprotein A-I Helsinki promotes intracellular acyl-CoA cholesterol acyltransferase (ACAT) protein accumulation. Mol Cell Biochem 2013; 377:197-205. [DOI: 10.1007/s11010-013-1585-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 01/30/2013] [Indexed: 10/27/2022]
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12
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Jamwal S, Midha MK, Verma HN, Basu A, Rao KVS, Manivel V. Characterizing virulence-specific perturbations in the mitochondrial function of macrophages infected with Mycobacterium tuberculosis. Sci Rep 2013; 3:1328. [PMID: 23435464 PMCID: PMC3580321 DOI: 10.1038/srep01328] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 02/07/2013] [Indexed: 02/03/2023] Open
Abstract
To probe how the pathogen Mycobacterium tuberculosis controls host cellular death pathways, we compared mitochondrial responses in human macrophages infected either with the avirulent mycobacterial strain H37Ra, or its virulent counterpart H37Rv. Following H37Ra infection, induction of the apoptotic response was foreshadowed by the early suppression of stress-induced mitochondrial activity. In contrast, mitochondria in H37Rv-infected cells displayed robust activity with increased membrane potential and ATP synthesis. An examination of the mitochondrial proteome revealed that attenuation of mitochondrial function was also coupled with the vigorous activation of bactericidal mechanisms in H37Ra-infected cells. In contrast, augmentation of mitochondrial activity by H37Rv enabled manipulation of host cellular mechanisms to inhibit apoptosis on the one hand, while ensuring fortification against anti-microbial pathways on the other. These results thus provide novel insights into the molecular interplay that facilitates adaptation of virulent mycobacteria within the hostile intracellular milieu of the host macrophage.
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Affiliation(s)
- Shilpa Jamwal
- Immunology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi – 110067, India
- School of Life Sciences, Jaipur National University, Jaipur – 302025, India
| | - Mukul Kumar Midha
- Immunology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi – 110067, India
- School of Life Sciences, Jaipur National University, Jaipur – 302025, India
| | | | - Atanu Basu
- National Institute of Virology, Dr. Ambedkar Road, Pune – 411001, India
| | - Kanury V. S. Rao
- Immunology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi – 110067, India
| | - Venkatasamy Manivel
- Immunology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi – 110067, India
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The dynamin chemical inhibitor dynasore impairs cholesterol trafficking and sterol-sensitive genes transcription in human HeLa cells and macrophages. PLoS One 2011; 6:e29042. [PMID: 22205993 PMCID: PMC3242776 DOI: 10.1371/journal.pone.0029042] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 11/19/2011] [Indexed: 11/19/2022] Open
Abstract
Intracellular transport of cholesterol contributes to the regulation of cellular cholesterol homeostasis by mechanisms that are yet poorly defined. In this study, we characterized the impact of dynasore, a recently described drug that specifically inhibits the enzymatic activity of dynamin, a GTPase regulating receptor endocytosis and cholesterol trafficking. Dynasore strongly inhibited the uptake of low-density lipoprotein (LDL) in HeLa cells, and to a lower extent in human macrophages. In both cell types, dynasore treatment led to the abnormal accumulation of LDL and free cholesterol (FC) within the endolysosomal network. The measure of cholesterol esters (CE) further showed that the delivery of regulatory cholesterol to the endoplasmic reticulum (ER) was deficient. This resulted in the inhibition of the transcriptional control of the three major sterol-sensitive genes, sterol-regulatory element binding protein 2 (SREBP-2), 3-hydroxy-3-methyl-coenzymeA reductase (HMGCoAR), and low-density lipoprotein receptor (LDLR). The sequestration of cholesterol in the endolysosomal compartment impaired both the active and passive cholesterol efflux in HMDM. Our data further illustrate the importance of membrane trafficking in cholesterol homeostasis and validate dynasore as a new pharmacological tool to study the intracellular transport of cholesterol.
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Rodriguez-Agudo D, Calderon-Dominguez M, Ren S, Marques D, Redford K, Medina-Torres MA, Hylemon P, Gil G, Pandak WM. Subcellular localization and regulation of StarD4 protein in macrophages and fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1811:597-606. [PMID: 21767660 PMCID: PMC3156897 DOI: 10.1016/j.bbalip.2011.06.028] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 06/07/2011] [Accepted: 06/30/2011] [Indexed: 10/18/2022]
Abstract
StarD4 is a member of the StarD4 subfamily of START domain proteins with a characteristic lipid binding pocket specific for cholesterol. The objective of this study was to define StarD4 subcellular localization, regulation, and function. Immunobloting showed that StarD4 is highly expressed in the mouse fibroblast cell line 3T3-L1, in human THP-1 macrophages, Kupffer cells (liver macrophages), and hepatocytes. In 3T3-L1 cells and THP-1 macrophages, StarD4 protein appeared localized to the cytoplasm and the endoplasmic reticulum (ER). More specifically, in THP-1 macrophages StarD4 co-localized to areas of the ER enriched in Acyl-CoA:cholesterol acyltransferase-1 (ACAT-1), and was closely associated with budding lipid droplets. The addition of purified StarD4 recombinant protein to an in vitro assay increased ACAT activity 2-fold, indicating that StarD4 serves as a rate-limiting step in cholesteryl ester formation by delivering cholesterol to ACAT-1-enriched ER. In addition, StarD4 protein was found to be highly regulated and to redistribute in response to sterol levels. In summary, these observations, together with our previous findings demonstrating the ability of increased StarD4 expression to increase bile acid synthesis and cholesteryl ester formation, provide strong evidence for StarD4 as a highly regulated, non-vesicular, directional, intracellular transporter of cholesterol which plays a key role in the maintenance of intracellular cholesterol homeostasis.
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Affiliation(s)
| | - Maria Calderon-Dominguez
- Department of Medicine, Veterans Affairs Medical Center and Virginia Commonwealth University; Richmond, Virginia,Department of Molecular Biology and Biochemistry, Universidad de Malaga, Spain
| | - Shunlin Ren
- Department of Medicine, Veterans Affairs Medical Center and Virginia Commonwealth University; Richmond, Virginia
| | - Dalila Marques
- Department of Medicine, Veterans Affairs Medical Center and Virginia Commonwealth University; Richmond, Virginia
| | - Kaye Redford
- Department of Medicine, Veterans Affairs Medical Center and Virginia Commonwealth University; Richmond, Virginia
| | | | - Phillip Hylemon
- Department of Microbiology/Immunology, Veterans Affairs Medical Center and Virginia Commonwealth University; Richmond, Virginia
| | - Gregorio Gil
- Department of Biochemistry and Molecular Biology, Veterans Affairs Medical Center and Virginia Commonwealth University; Richmond, Virginia
| | - William M. Pandak
- Department of Medicine, Veterans Affairs Medical Center and Virginia Commonwealth University; Richmond, Virginia
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