1
|
Bassila C, Kluck GEG, Thyagarajan N, Chathely KM, Gonzalez L, Trigatti BL. Ligand-dependent interactions between SR-B1 and S1PR1 in macrophages and atherosclerotic plaques. J Lipid Res 2024; 65:100541. [PMID: 38583587 PMCID: PMC11087725 DOI: 10.1016/j.jlr.2024.100541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 03/16/2024] [Accepted: 04/01/2024] [Indexed: 04/09/2024] Open
Abstract
HDLs carry sphingosine-1-phosphate (S1P) and stimulate signaling pathways in different cells including macrophages and endothelial cells, involved in atherosclerotic plaque development. HDL signaling via S1P relies on the HDL receptor scavenger receptor class B, type I (SR-B1) and the sphingosine-1-phosphate receptor 1 (S1PR1), which interact when both are heterologously overexpressed in the HEK293 cell line. In this study, we set out to test if SR-B1 and S1PR1 interacted in primary murine macrophages in culture and atherosclerotic plaques. We used knock-in mice that endogenously expressed S1PR1 tagged with eGFP-(S1pr1eGFP/eGFP mice), combined with proximity ligation analysis to demonstrate that HDL stimulates the physical interaction between SR-B1 and S1PR1 in primary macrophages, that this is dependent on HDL-associated S1P and can be blocked by an inhibitor of SR-B1's lipid transfer activity or an antagonist of S1PR1. We also demonstrate that a synthetic S1PR1-selective agonist, SEW2871, stimulates the interaction between SR-B1 and S1PR1 and that this was also blocked by an inhibitor of SR-B1's lipid transport activity. Furthermore, we detected abundant SR-B1/S1PR1 complexes in atherosclerotic plaques of S1pr1eGFP/eGFP mice that also lacked apolipoprotein E. Treatment of mice with the S1PR1 antagonist, Ex26, for 12 h disrupted the SR-B1-S1PR1 interaction in atherosclerotic plaques. These findings demonstrate that SR-B1 and S1PR1 form ligand-dependent complexes both in cultured primary macrophages and within atherosclerotic plaques in mice and provide mechanistic insight into how SR-B1 and S1PR1 participate in mediating HDL signaling to activate atheroprotective responses in macrophages.
Collapse
Affiliation(s)
- Christine Bassila
- Department of Biochemistry and Biomedical Sciences, Thrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences, McMaster University, Hamilton, ON, Canada
| | - George E G Kluck
- Department of Biochemistry and Biomedical Sciences, Thrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences, McMaster University, Hamilton, ON, Canada
| | - Narmadaa Thyagarajan
- Department of Biochemistry and Biomedical Sciences, Thrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences, McMaster University, Hamilton, ON, Canada
| | - Kevin M Chathely
- Department of Biochemistry and Biomedical Sciences, Thrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences, McMaster University, Hamilton, ON, Canada
| | - Leticia Gonzalez
- Department of Biochemistry and Biomedical Sciences, Thrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences, McMaster University, Hamilton, ON, Canada
| | - Bernardo L Trigatti
- Department of Biochemistry and Biomedical Sciences, Thrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences, McMaster University, Hamilton, ON, Canada.
| |
Collapse
|
2
|
Powers HR, Jenjak SE, Volkman BF, Sahoo D. Development and validation of a purification system for functional full-length human SR-B1 and CD36. J Biol Chem 2023; 299:105187. [PMID: 37625590 PMCID: PMC10509710 DOI: 10.1016/j.jbc.2023.105187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 07/31/2023] [Accepted: 08/18/2023] [Indexed: 08/27/2023] Open
Abstract
Scavenger receptor class B type 1 (SR-B1) and CD36 are both members of the class B scavenger receptor family that play important roles in lipoprotein metabolism and atherosclerotic disease. SR-B1 is the primary receptor for high-density lipoproteins, while CD36 is the receptor responsible for the internalization of oxidized low-density lipoproteins. Despite their importance, class B scavenger receptor structure has only been studied by functional domain or peptide fragments-there are currently no reports of utilizing purified full-length protein. Here we report the successful expression and purification of full-length human SR-B1 and CD36 using an Spodoptera frugiperda insect cell system. We demonstrate that both SR-B1 and CD36 retained their normal functions in Spodoptera frugiperda cells, including lipoprotein binding, lipid transport, and the formation of higher order oligomers in the plasma membrane. Purification schemes for both scavenger receptors were optimized and their purity was confirmed by SDS-PAGE. Both purified scavenger receptors were assessed for stability by thermal shift assay and shown to maintain stable melting temperatures up to 6 weeks post-purification. Microscale thermophoresis was used to demonstrate that purified SR-B1 and CD36 were able to bind their native lipoprotein ligands. Further, there was no difference in affinity of SR-B1 for high-density lipoprotein or CD36 for oxidized low-density lipoprotein, when comparing glycosylated and deglycosylated receptors. These studies mark a significant step forward in creating physiologically relevant tools to study scavenger receptor function and lay the groundwork for future functional studies and determination of receptor structure.
Collapse
Affiliation(s)
- Hayley R Powers
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Shawn E Jenjak
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Brian F Volkman
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Daisy Sahoo
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Division of Endocrinology & Molecular Medicine, Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
| |
Collapse
|
3
|
Hayakawa S, Tamura A, Nikiforov N, Koike H, Kudo F, Cheng Y, Miyazaki T, Kubekina M, Kirichenko TV, Orekhov AN, Yui N, Manabe I, Oishi Y. Activated cholesterol metabolism is integral for innate macrophage responses by amplifying Myd88 signaling. JCI Insight 2022; 7:138539. [PMID: 36509286 DOI: 10.1172/jci.insight.138539] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 10/07/2022] [Indexed: 11/22/2022] Open
Abstract
Recent studies have shown that cellular metabolism is tightly linked to the regulation of immune cells. Here, we show that activation of cholesterol metabolism, involving cholesterol uptake, synthesis, and autophagy/lipophagy, is integral to innate immune responses in macrophages. In particular, cholesterol accumulation within endosomes and lysosomes is a hallmark of the cellular cholesterol dynamics elicited by Toll-like receptor 4 activation and is required for amplification of myeloid differentiation primary response 88 (Myd88) signaling. Mechanistically, Myd88 binds cholesterol via its CLR recognition/interaction amino acid consensus domain, which promotes the protein's self-oligomerization. Moreover, a novel supramolecular compound, polyrotaxane (PRX), inhibited Myd88‑dependent inflammatory macrophage activation by decreasing endolysosomal cholesterol via promotion of cholesterol trafficking and efflux. PRX activated liver X receptor, which led to upregulation of ATP binding cassette transporter A1, thereby promoting cholesterol efflux. PRX also inhibited atherogenesis in Ldlr-/- mice. In humans, cholesterol levels in circulating monocytes correlated positively with the severity of atherosclerosis. These findings demonstrate that dynamic changes in cholesterol metabolism are mechanistically linked to Myd88‑dependent inflammatory programs in macrophages and support the notion that cellular cholesterol metabolism is integral to innate activation of macrophages and is a potential therapeutic and diagnostic target for inflammatory diseases.
Collapse
Affiliation(s)
- Sumio Hayakawa
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Atsushi Tamura
- Department of Organic Biomaterials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Nikita Nikiforov
- National Medical Research Center of Cardiology, Institute of Experimental Cardiology, Moscow, Russia.,Institute of Gene Biology, Centre of Collective Usage, Moscow, Russia.,Laboratory of Angiopathology, Institute of General Pathology and Pathophysiology, Moscow, Russia
| | - Hiroyuki Koike
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Fujimi Kudo
- Department of Systems Medicine, Chiba University Graduate School of Medicine, Chiba, Japan
| | - Yinglan Cheng
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Takuro Miyazaki
- Department of Biochemistry, Showa University School of Medicine, Tokyo, Japan
| | - Marina Kubekina
- Institute of Gene Biology, Centre of Collective Usage, Moscow, Russia
| | - Tatiana V Kirichenko
- National Medical Research Center of Cardiology, Institute of Experimental Cardiology, Moscow, Russia.,Laboratory of Angiopathology, Institute of General Pathology and Pathophysiology, Moscow, Russia
| | - Alexander N Orekhov
- Laboratory of Angiopathology, Institute of General Pathology and Pathophysiology, Moscow, Russia.,Institute for Atherosclerosis Research, Moscow, Russia
| | - Nobuhiko Yui
- Department of Organic Biomaterials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ichiro Manabe
- Department of Systems Medicine, Chiba University Graduate School of Medicine, Chiba, Japan
| | - Yumiko Oishi
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| |
Collapse
|
4
|
Powers HR, Sahoo D. SR-B1's Next Top Model: Structural Perspectives on the Functions of the HDL Receptor. Curr Atheroscler Rep 2022; 24:277-288. [PMID: 35107765 PMCID: PMC8809234 DOI: 10.1007/s11883-022-01001-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2021] [Indexed: 02/04/2023]
Abstract
PURPOSE OF REVIEW The binding of high-density lipoprotein (HDL) to its primary receptor, scavenger receptor class B type 1 (SR-B1), is critical for lowering plasma cholesterol levels and reducing cardiovascular disease risk. This review provides novel insights into how the structural elements of SR-B1 drive efficient function with an emphasis on bidirectional cholesterol transport. RECENT FINDINGS We have generated a new homology model of full-length human SR-B1 based on the recent resolution of the partial structures of other class B scavenger receptors. Interrogating this model against previously published observations allows us to generate structurally informed hypotheses about SR-B1's ability to mediate HDL-cholesterol (HDL-C) transport. Furthermore, we provide a structural perspective as to why human variants of SR-B1 may result in impaired HDL-C clearance. A comprehensive understanding of SR-B1's structure-function relationships is critical to the development of therapeutic agents targeting SR-B1 and modulating cardiovascular disease risk.
Collapse
Affiliation(s)
- Hayley R. Powers
- grid.30760.320000 0001 2111 8460Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI USA
| | - Daisy Sahoo
- grid.30760.320000 0001 2111 8460Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI USA ,grid.30760.320000 0001 2111 8460Department of Medicine, Division of Endocrinology & Molecular Medicine, Medical College of Wisconsin, Milwaukee, WI USA ,grid.30760.320000 0001 2111 8460Cardiovascular Center, H4930 Health Research Center, Medical College of Wisconsin, 8701 W. Watertown Plank Road, Milwaukee, WI 53226 USA
| |
Collapse
|
5
|
Binding of liposomes composed of phosphatidylcholine to scavenger receptor class B type 1 and its modulation by phosphatidic acid in HEK293T cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119043. [PMID: 33862056 DOI: 10.1016/j.bbamcr.2021.119043] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 04/11/2021] [Indexed: 12/29/2022]
Abstract
In this study, we developed a method to analyze liposomal binding to a cell membrane receptor using fluorescence-labeled liposomes and demonstrated that scavenger class B type 1 (SR-B1) plays a crucial role in binding of liposomes containing phosphatidylcholine (PC) to HEK293T cell membrane and phosphatidic acid (PA) can modulate it. Site-directed mutagenesis of SR-B1 revealed that S112F and T175A mutations in its ectodomain abrogated binding and endocytosis of PC liposomes in HEK293T cells. K151A and K156A mutations attenuated their binding and endocytosis too. Although the effects of mutations on binding and endocytosis were similar between PC liposomes and PC/PA and PA liposomes, SR-B1 dependency appeared to be PC > PC/PA > PA liposomes. Our data indicate that (i) nanoparticles including high-density lipoprotein (HDL), silica, and liposomes bind to a common or close site of SR-B1, and (ii) PC/PA and PA liposomes bind not only to SR-B1 but also other receptor(s) in HEK293T cells. In addition, PC/PA liposomes induced lipid droplet (LD) formation in HEK293T cells more than PC liposomes. Treatment of HEK293T cells with SR-B1 siRNA suppressed PC/PA liposome-induced LD formation. Taken together, our results demonstrate that SR-B1 plays an essential role in binding PC-containing liposomes and the subsequent induction of cellular responses, while PA can modulate them.
Collapse
|
6
|
Xin L, Gao J, Lin H, Qu Y, Shang C, Wang Y, Lu Y, Cui X. Regulatory Mechanisms of Baicalin in Cardiovascular Diseases: A Review. Front Pharmacol 2020; 11:583200. [PMID: 33224035 PMCID: PMC7667240 DOI: 10.3389/fphar.2020.583200] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 09/15/2020] [Indexed: 12/17/2022] Open
Abstract
Cardiovascular diseases (CVDs) is the leading cause of high morbidity and mortality worldwide, which emphasizes the urgent necessity to develop new pharmacotherapies. In eastern countries, traditional Chinese medicine Scutellaria baicalensis Georgi has been used clinically for thousands of years. Baicalin is one of the main active ingredients extracted from Chinese herbal medicine S. baicalensis. Emerging evidence has established that baicalin improves chronic inflammation, immune imbalance, disturbances in lipid metabolism, apoptosis and oxidative stress. Thereby it offers beneficial roles against the initiation and progression of CVDs such as atherosclerosis, hypertension, myocardial infarction and reperfusion, and heart failure. In this review, we summarize the pharmacological features and relevant mechanisms by which baicalin regulates CVDs in the hope to reveal its application for CVDs prevention and/or therapy.
Collapse
Affiliation(s)
- Laiyun Xin
- The First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China.,Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Jialiang Gao
- Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Hongchen Lin
- Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yi Qu
- Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Chang Shang
- Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yuling Wang
- Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yingdong Lu
- Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Xiangning Cui
- Department of Cardiology, Guang' anmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| |
Collapse
|
7
|
Current Understanding of the Relationship of HDL Composition, Structure and Function to Their Cardioprotective Properties in Chronic Kidney Disease. Biomolecules 2020; 10:biom10091348. [PMID: 32967334 PMCID: PMC7564231 DOI: 10.3390/biom10091348] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/15/2020] [Accepted: 09/17/2020] [Indexed: 12/27/2022] Open
Abstract
In the general population, the ability of high-density lipoproteins (HDLs) to promote cholesterol efflux is a predictor of cardiovascular events, independently of HDL cholesterol levels. Although patients with chronic kidney disease (CKD) have a high burden of cardiovascular morbidity and mortality, neither serum levels of HDL cholesterol, nor cholesterol efflux capacity associate with cardiovascular events. Important for the following discussion on the role of HDL in CKD is the notion that traditional atherosclerotic cardiovascular risk factors only partially account for this increased incidence of cardiovascular disease in CKD. As a potential explanation, across the spectrum of cardiovascular disease, the relative contribution of atherosclerotic cardiovascular disease becomes less important with advanced CKD. Impaired renal function directly affects the metabolism, composition and functionality of HDL particles. HDLs themselves are a heterogeneous population of particles with distinct sizes and protein composition, all of them affecting the functionality of HDL. Therefore, a more specific approach investigating the functional and compositional features of HDL subclasses might be a valuable strategy to decipher the potential link between HDL, cardiovascular disease and CKD. This review summarizes the current understanding of the relationship of HDL composition, metabolism and function to their cardio-protective properties in CKD, with a focus on CKD-induced changes in the HDL proteome and reverse cholesterol transport capacity. We also will highlight the gaps in the current knowledge regarding important aspects of HDL biology.
Collapse
|
8
|
Fujita K, Koide N, Somiya M, Kuroda S, Hinuma S. A regulatory role of scavenger receptor class B type 1 in endocytosis and lipid droplet formation induced by liposomes containing phosphatidylethanolamine in HEK293T cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1868:118859. [PMID: 32956759 DOI: 10.1016/j.bbamcr.2020.118859] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 09/03/2020] [Accepted: 09/16/2020] [Indexed: 12/16/2022]
Abstract
We have recently reported that phosphatidylethanolamine (PE)-containing liposomes are endocytosed and then induce lipid droplets (LDs) in HEK293T cells. In this study, we elucidated a mechanism responsible for endocytosis of PE-containing liposomes and induction of LDs. By using fluorescence-labeled liposomes and flow cytometry, we found that PE-containing liposomes were very efficiently internalized in HEK293T cells. However, Block lipid transporter-1 (BLT-1) only marginally suppressed the uptake of these liposomes, indicating that entire liposomes were mostly taken up in these cells. They were therefore inferred to express abundant PE receptors responsible for endocytosis of PE-containing liposomes. We examined the expression of 52 candidate genes through transcriptomic analyses and eventually narrowed it down to four candidate genes, which were abundantly expressed in HEK293T cells. Among siRNAs targeting these candidates, scavenger receptor class B type 1 (SR-B1) siRNA showed the most profound reduction in PE liposomal uptake. Conversely, the expression of SR-B1 by transfection of an expression plasmid enhanced the uptake of PE-containing liposomes. After the internalization of PE-containing liposomes, they were colocalized with endosomes/lysosomes and SR-B1, which indicates that these liposomes are taken up in HEK293T cells at least partially through the endosomal/lysosomal pathway. A specific anti-SR-B1-antibody blocked the uptake of PE-containing liposomes in HEK293T cells while LD formation in these cells induced by PE-containing liposomes was suppressed by treatment with SR-B1 siRNA. These results demonstrate that SR-B1 functions as a receptor for the endocytosis of PE-containing liposomes and regulates the formation of LDs induced by PE-containing liposomes in HEK293T cells.
Collapse
Affiliation(s)
- Kazuyo Fujita
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan; Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; Faculty of Human Life Science, Senri Kinran University, Suita, Osaka 565-0873, Japan.
| | - Narumi Koide
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
| | - Masaharu Somiya
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
| | - Shun'ichi Kuroda
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan; Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
| | - Shuji Hinuma
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
| |
Collapse
|
9
|
Jeries H, Volkova N, Grajeda-Iglesias C, Najjar M, Rosenblat M, Aviram M, Hayek T. Prednisone and Its Active Metabolite Prednisolone Attenuate Lipid Accumulation in Macrophages. J Cardiovasc Pharmacol Ther 2019; 25:174-186. [PMID: 31648564 DOI: 10.1177/1074248419883591] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Synthetic forms of glucocorticoids (GCs; eg, prednisone, prednisolone) are anti-inflammatory drugs that are widely used in clinical practice. The role of GCs in cardiovascular diseases, including atherosclerosis, is highly controversial, and their impact on macrophage foam cell formation is still unknown. We investigated the effects of prednisone and prednisolone on macrophage oxidative stress and lipid metabolism. METHODS AND RESULTS C57BL/6 mice were intraperitoneally injected with prednisone or prednisolone (5 mg/kg) for 4 weeks, followed by lipid metabolism analyses in the aorta and peritoneal macrophages. We also analyzed the effect of serum samples obtained from 9 healthy human volunteers before and after oral administration of prednisone (20 mg for 5 days) on J774A.1 macrophage atherogenicity. Finally, J774A.1 macrophages, human monocyte-derived macrophages, and fibroblasts were incubated with increasing concentrations (0-200 ng/mL) of prednisone or prednisolone, followed by determination of cellular oxidative status, and triglyceride and cholesterol metabolism. Prednisone and prednisolone treatment resulted in a significant reduction in triglyceride and cholesterol accumulation in macrophages, as observed in vivo, ex vivo, and in vitro. These effects were associated with GCs' inhibitory effect on triglyceride- and cholesterol-biosynthesis rates, through downregulation of diacylglycerol acyltransferase 1 and HMG-CoA reductase expression. Glucocorticoid-induced reduction of cellular lipid accumulation was mediated by the GC receptors on the macrophages, because the GC-receptor antagonist (RU486) abolished these effects. In fibroblasts, unlike macrophages, GCs showed no effects. CONCLUSION Prednisone and prednisolone exhibit antiatherogenic activity by protecting macrophages from lipid accumulation and foam cell formation.
Collapse
Affiliation(s)
- Helana Jeries
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Nina Volkova
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Claudia Grajeda-Iglesias
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Mahmoud Najjar
- Department of Internal Medicine E, Rambam Health Care Campus, Haifa, Israel
| | - Mira Rosenblat
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Michael Aviram
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Tony Hayek
- Department of Internal Medicine E, Rambam Health Care Campus, Haifa, Israel
| |
Collapse
|
10
|
Abstract
The reduction of plasma apolipoprotein B (apoB) containing lipoproteins has long been pursued as the main modifiable risk factor for the development of cardiovascular disease (CVD). This has led to an intense search for strategies aiming at reducing plasma apoB-lipoproteins, culminating in reduction of overall CV risk. Despite 3 decades of progress, CVD remains the leading cause of morbidity and mortality worldwide and, as such, new therapeutic targets are still warranted. Clinical and preclinical research has moved forward from the original concept, under which some lipids must be accumulated and other removed to achieve the ideal condition in disease prevention, into the concept that mechanisms that orchestrate lipid movement between lipoproteins, cells and organelles is equally involved in CVD. As such, this review scrutinizes potentially atherogenic changes in lipid trafficking and assesses the molecular mechanisms behind it. New developments in risk assessment and new targets for the mitigation of residual CVD risk are also addressed.
Collapse
Affiliation(s)
- Andrei C Sposito
- Atherosclerosis and Vascular Biology Laboratory (Aterolab), State University of Campinas (Unicamp), São Paulo, Brazil.
| | | | - Joaquim Barreto
- Atherosclerosis and Vascular Biology Laboratory (Aterolab), State University of Campinas (Unicamp), São Paulo, Brazil
| | - Ilaria Zanotti
- Department of Food and Drug, University of Parma, Parma, Italy
| |
Collapse
|
11
|
Orekhov AN, Pushkarsky T, Oishi Y, Nikiforov NG, Zhelankin AV, Dubrovsky L, Makeev VJ, Foxx K, Jin X, Kruth HS, Sobenin IA, Sukhorukov VN, Zakiev ER, Kontush A, Le Goff W, Bukrinsky M. HDL activates expression of genes stimulating cholesterol efflux in human monocyte-derived macrophages. Exp Mol Pathol 2018; 105:202-207. [PMID: 30118702 DOI: 10.1016/j.yexmp.2018.08.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 08/09/2018] [Accepted: 08/13/2018] [Indexed: 12/24/2022]
Abstract
High density lipoproteins (HDL) are key components of reverse cholesterol transport pathway. HDL removes excessive cholesterol from peripheral cells, including macrophages, providing protection from cholesterol accumulation and conversion into foam cells, which is a key event in pathogenesis of atherosclerosis. The mechanism of cellular cholesterol efflux stimulation by HDL involves interaction with the ABCA1 lipid transporter and ensuing transfer of cholesterol to HDL particles. In this study, we looked for additional proteins contributing to HDL-dependent cholesterol efflux. Using RNAseq, we analyzed mRNAs induced by HDL in human monocyte-derived macrophages and identified three genes, fatty acid desaturase 1 (FADS1), insulin induced gene 1 (INSIG1), and the low-density lipoprotein receptor (LDLR), expression of which was significantly upregulated by HDL. We individually knocked down these genes in THP-1 cells using gene silencing by siRNA, and measured cellular cholesterol efflux to HDL. Knock down of FADS1 did not significantly change cholesterol efflux (p = 0.70), but knockdown of INSIG1 and LDLR resulted in highly significant reduction of the efflux to HDL (67% and 75% of control, respectively, p < 0.001). Importantly, the suppression of cholesterol efflux was independent of known effects of these genes on cellular cholesterol content, as cells were loaded with cholesterol using acetylated LDL. These results indicate that HDL particles stimulate expression of genes that enhance cellular cholesterol transfer to HDL.
Collapse
Affiliation(s)
- Alexander N Orekhov
- Institute of General Pathology and Pathophysiology, Moscow, Russia; Institute for Atherosclerosis Research, Skolkovo Innovative Center, Moscow, Russia
| | - Tatiana Pushkarsky
- The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Yumiko Oishi
- Department of Cellular and Molecular Medicine, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Nikita G Nikiforov
- Institute of General Pathology and Pathophysiology, Moscow, Russia; Laboratory of Medical Genetics, Institute of Experimental Cardiology, National Medical Research Center of Cardiology, Moscow, Russia; Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - Andrey V Zhelankin
- Laboratory of postgenomic research, Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, Russia
| | - Larisa Dubrovsky
- The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Vsevolod J Makeev
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia; Scientific Center "Kurchatov Institute", Research Institute for Genetics and Selection of Industrial Microorganisms, Moscow, Russia; Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow, Region, Russia; Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Kathy Foxx
- Kalen Biomedical LLC, Montgomery Village, MD, USA
| | - Xueting Jin
- Experimental Atherosclerosis Section, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Howard S Kruth
- Experimental Atherosclerosis Section, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Igor A Sobenin
- Institute of General Pathology and Pathophysiology, Moscow, Russia; Laboratory of Medical Genetics, Institute of Experimental Cardiology, National Medical Research Center of Cardiology, Moscow, Russia
| | - Vasily N Sukhorukov
- Institute of General Pathology and Pathophysiology, Moscow, Russia; Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Hôpital de la Pitié, Paris, France
| | - Emile R Zakiev
- Institute of General Pathology and Pathophysiology, Moscow, Russia; Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Hôpital de la Pitié, Paris, France
| | - Anatol Kontush
- Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Hôpital de la Pitié, Paris, France
| | - Wilfried Le Goff
- Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Hôpital de la Pitié, Paris, France
| | - Michael Bukrinsky
- The George Washington University School of Medicine and Health Sciences, Washington, DC, USA.
| |
Collapse
|
12
|
Shen WJ, Asthana S, Kraemer FB, Azhar S. Scavenger receptor B type 1: expression, molecular regulation, and cholesterol transport function. J Lipid Res 2018; 59:1114-1131. [PMID: 29720388 DOI: 10.1194/jlr.r083121] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/26/2018] [Indexed: 12/16/2022] Open
Abstract
Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many cellular functions. Cellular cholesterol can be obtained from lipoproteins in a selective pathway of HDL-cholesteryl ester (CE) uptake without parallel apolipoprotein uptake. Scavenger receptor B type 1 (SR-B1) is a cell surface HDL receptor that mediates HDL-CE uptake. It is most abundantly expressed in liver, where it provides cholesterol for bile acid synthesis, and in steroidogenic tissues, where it delivers cholesterol needed for storage or steroidogenesis in rodents. SR-B1 transcription is regulated by trophic hormones in the adrenal gland, ovary, and testis; in the liver and elsewhere, SR-B1 is subject to posttranscriptional and posttranslational regulation. SR-B1 operates in several metabolic processes and contributes to pathogenesis of atherosclerosis, inflammation, hepatitis C virus infection, and other conditions. Here, we summarize characteristics of the selective uptake pathway and involvement of microvillar channels as facilitators of selective HDL-CE uptake. We also present the potential mechanisms of SR-B1-mediated selective cholesterol transport; the transcriptional, posttranscriptional, and posttranslational regulation of SR-B1; and the impact of gene variants on expression and function of human SR-B1. A better understanding of this unique pathway and SR-B1's role may yield improved therapies for a wide variety of conditions.
Collapse
Affiliation(s)
- Wen-Jun Shen
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Shailendra Asthana
- Drug Discovery Research Center (DDRC), Translational Health Science and Technology Institute (THSTI), NCR Biotech Science Cluster, Faridabad 121001, Haryana, India
| | - Fredric B Kraemer
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Salman Azhar
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| |
Collapse
|
13
|
Grajeda-Iglesias C, Rom O, Hamoud S, Volkova N, Hayek T, Abu-Saleh N, Aviram M. Leucine supplementation attenuates macrophage foam-cell formation: Studies in humans, mice, and cultured macrophages. Biofactors 2018; 44:245-262. [PMID: 29399895 DOI: 10.1002/biof.1415] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 01/06/2018] [Accepted: 01/09/2018] [Indexed: 01/07/2023]
Abstract
Whereas atherogenicity of dietary lipids has been largely studied, relatively little is known about the possible contribution of dietary amino acids to macrophage foam-cell formation, a hallmark of early atherogenesis. Recently, we showed that leucine has antiatherogenic properties in the macrophage model system. In this study, an in-depth investigation of the role of leucine in macrophage lipid metabolism was conducted by supplementing humans, mice, or cultured macrophages with leucine. Macrophage incubation with serum obtained from healthy adults supplemented with leucine (5 g/d, 3 weeks) significantly decreased cellular cholesterol mass by inhibiting the rate of cholesterol biosynthesis and increasing cholesterol efflux from macrophages. Similarly, leucine supplementation to C57BL/6 mice (8 weeks) resulted in decreased cholesterol content in their harvested peritoneal macrophages (MPM) in relation with reduced cholesterol biosynthesis rate. Studies in J774A.1 murine macrophages revealed that leucine dose-dependently decreased cellular cholesterol and triglyceride mass. Macrophages treated with leucine (0.2 mM) showed attenuated uptake of very low-density lipoproteins and triglyceride biosynthesis rate, with a concurrent down-regulation of diacylglycerol acyltransferase-1, a key enzyme catalyzing triglyceride biosynthesis in macrophages. Similar effects were observed when macrophages were treated with α-ketoisocaproate, a key leucine metabolite. Finally, both in vivo and in vitro leucine supplementation significantly improved macrophage mitochondrial respiration and ATP production. The above studies, conducted in human, mice, and cultured macrophages, highlight a protective role for leucine attenuating macrophage foam-cell formation by mechanisms related to the metabolism of cholesterol, triglycerides, and energy production. © 2018 BioFactors, 44(3):245-262, 2018.
Collapse
Affiliation(s)
- Claudia Grajeda-Iglesias
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Oren Rom
- Department of Internal Medicine, Cardiovascular Center, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Shadi Hamoud
- Department of Internal Medicine E, Rambam Health Care Campus and Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Nina Volkova
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Tony Hayek
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
- Department of Internal Medicine E, Rambam Health Care Campus and Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Niroz Abu-Saleh
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Michael Aviram
- The Lipid Research Laboratory, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| |
Collapse
|
14
|
Marín D, Taborda NA, Urcuqui S, Hernandez JC. Inflamación y respuesta inmune innata: participación de las lipoproteínas de alta densidad. IATREIA 2017. [DOI: 10.17533/udea.iatreia.v30n4a06] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
15
|
Zannis VI, Su S, Fotakis P. Role of apolipoproteins, ABCA1 and LCAT in the biogenesis of normal and aberrant high density lipoproteins. J Biomed Res 2017; 31:471. [PMID: 29109329 PMCID: PMC6307667 DOI: 10.7555/jbr.31.20160082] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 08/30/2016] [Indexed: 12/28/2022] Open
Abstract
In this review, we focus on the pathway of biogenesis of HDL, the essential role of apoA-I, ATP binding cassette transporter A1 (ABCA1), and lecithin: cholesterol acyltransferase (LCAT) in the formation of plasma HDL; the generation of aberrant forms of HDL containing mutant apoA-I forms and the role of apoA-IV and apoE in the formation of distinct HDL subpopulations. The biogenesis of HDL requires functional interactions of the ABCA1 with apoA-I (and to a lesser extent with apoE and apoA-IV) and subsequent interactions of the nascent HDL species thus formed with LCAT. Mutations in apoA-I, ABCA1 and LCAT either prevent or impair the formation of HDL and may also affect the functionality of the HDL species formed. Emphasis is placed on three categories of apoA-I mutations. The first category describes a unique bio-engineered apoA-I mutation that disrupts interactions between apoA-I and ABCA1 and generates aberrant preβ HDL subpopulations that cannot be converted efficiently to α subpopulations by LCAT. The second category describes natural and bio-engineered apoA-I mutations that generate preβ and small size α4 HDL subpopulations, and are associated with low plasma HDL levels. These phenotypes can be corrected by excess LCAT. The third category describes bio-engineered apoA-I mutations that induce hypertriglyceridemia that can be corrected by excess lipoprotein lipase and also have defective maturation of HDL. The HDL phenotypes described here may serve in the future for diagnosis, prognoses and potential treatment of abnormalities that affect the biogenesis and functionality of HDL.
Collapse
Affiliation(s)
- Vassilis I. Zannis
- . Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA
- . Department University of Crete, School of Medicine, Heraklion, Crete, Greece
| | - Shi Su
- . Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA
| | - Panagiotis Fotakis
- . Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA
- . Department University of Crete, School of Medicine, Heraklion, Crete, Greece
| |
Collapse
|
16
|
Leiva A, Contreras-Duarte S, Amigo L, Sepúlveda E, Boric M, Quiñones V, Busso D, Rigotti A. Gugulipid causes hypercholesterolemia leading to endothelial dysfunction, increased atherosclerosis, and premature death by ischemic heart disease in male mice. PLoS One 2017; 12:e0184280. [PMID: 28910310 PMCID: PMC5598962 DOI: 10.1371/journal.pone.0184280] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 08/21/2017] [Indexed: 12/29/2022] Open
Abstract
For proper cholesterol metabolism, normal expression and function of scavenger receptor class B type I (SR-BI), a high-density lipoprotein (HDL) receptor, is required. Among the factors that regulate overall cholesterol homeostasis and HDL metabolism, the nuclear farnesoid X receptor plays an important role. Guggulsterone, a bioactive compound present in the natural product gugulipid, is an antagonist of this receptor. This natural product is widely used globally as a natural lipid-lowering agent, although its anti-atherogenic cardiovascular benefit in animal models or humans is unknown. The aim of this study was to determine the effects of gugulipid on cholesterol homeostasis and development of mild and severe atherosclerosis in male mice. For this purpose, we evaluated the impact of gugulipid treatment on liver histology, plasma lipoprotein cholesterol, endothelial function, and development of atherosclerosis and/or ischemic heart disease in wild-type mice; apolipoprotein E knockout mice, a model of atherosclerosis without ischemic complications; and SR-B1 knockout and atherogenic–diet-fed apolipoprotein E hypomorphic (SR-BI KO/ApoER61h/h) mice, a model of lethal ischemic heart disease due to severe atherosclerosis. Gugulipid administration was associated with histological abnormalities in liver, increased alanine aminotransferase levels, lower hepatic SR-BI content, hypercholesterolemia due to increased HDL cholesterol levels, endothelial dysfunction, enhanced atherosclerosis, and accelerated death in animals with severe ischemic heart disease. In conclusion, our data show important adverse effects of gugulipid intake on HDL metabolism and atherosclerosis in male mice, suggesting potential and unknown deleterious effects on cardiovascular health in humans. In addition, these findings reemphasize the need for rigorous preclinical and clinical studies to provide guidance on the consumption of natural products and regulation of their use in the general population.
Collapse
Affiliation(s)
- Andrea Leiva
- Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail: (AL); (AR)
| | - Susana Contreras-Duarte
- Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Ludwig Amigo
- Department of Gastroenterology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Esteban Sepúlveda
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Mauricio Boric
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Verónica Quiñones
- Department of Nutrition, Diabetes and Metabolism, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Dolores Busso
- Department of Nutrition, Diabetes and Metabolism, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Attilio Rigotti
- Department of Nutrition, Diabetes and Metabolism, Pontificia Universidad Católica de Chile, Santiago, Chile
- Center of Molecular Nutrition and Chronic Diseases, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail: (AL); (AR)
| |
Collapse
|
17
|
High-density lipoprotein receptor SCARB1 is required for carotenoid coloration in birds. Proc Natl Acad Sci U S A 2017; 114:5219-5224. [PMID: 28465440 DOI: 10.1073/pnas.1700751114] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Yellow, orange, and red coloration is a fundamental aspect of avian diversity and serves as an important signal in mate choice and aggressive interactions. This coloration is often produced through the deposition of diet-derived carotenoid pigments, yet the mechanisms of carotenoid uptake and transport are not well-understood. The white recessive breed of the common canary (Serinus canaria), which carries an autosomal recessive mutation that renders its plumage pure white, provides a unique opportunity to investigate mechanisms of carotenoid coloration. We carried out detailed genomic and biochemical analyses comparing the white recessive with yellow and red breeds of canaries. Biochemical analysis revealed that carotenoids are absent or at very low concentrations in feathers and several tissues of white recessive canaries, consistent with a genetic defect in carotenoid uptake. Using a combination of genetic mapping approaches, we show that the white recessive allele is due to a splice donor site mutation in the scavenger receptor B1 (SCARB1; also known as SR-B1) gene. This mutation results in abnormal splicing, with the most abundant transcript lacking exon 4. Through functional assays, we further demonstrate that wild-type SCARB1 promotes cellular uptake of carotenoids but that this function is lost in the predominant mutant isoform in white recessive canaries. Our results indicate that SCARB1 is an essential mediator of the expression of carotenoid-based coloration in birds, and suggest a potential link between visual displays and lipid metabolism.
Collapse
|
18
|
Yu R, Lv Y, Wang J, Pan N, Zhang R, Wang X, Yu H, Tan L, Zhao Y, Li B. Baicalin promotes cholesterol efflux by regulating the expression of SR-BI in macrophages. Exp Ther Med 2016; 12:4113-4120. [PMID: 28105139 DOI: 10.3892/etm.2016.3884] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 10/05/2016] [Indexed: 01/22/2023] Open
Abstract
Intake of a high dosage of baicalin has previously been shown to attenuate hyperlipidemia induced by a high-fat diet. Baicalin functions as an activator of peroxisome proliferator-activated receptor-γ (PPAR-γ), which is the key regulator of reverse cholesterol transport (RCT). The present study aimed to test the hypothesis that baicalin could promote cholesterol efflux in macrophages through activating PPAR-γ. Phorbol 12-myristate 13-acetate-stimulated THP-1 cells were treated with oxidized low-density lipoprotein and (3H)-cholesterol for 24 h, and the effects of baicalin on cholesterol efflux were evaluated in the presence of apolipoprotein A-1 (ApoA-1), or high-density lipoprotein subfraction 2 (HDL2) or subfraction 3 (HDL3). The expression levels of scavenger receptor class B type I (SR-BI), PPAR-γ and liver X receptor-α (LXRα) were detected and specific inhibitors or activators of SR-BI, PPAR-γ and LXRα were applied to investigate the mechanism. Treatment of THP-1 macrophages with baicalin significantly accelerated HDL-mediated, but not ApoA-1-mediated cholesterol efflux. However, baicalin treatment increased the expression of SR-BI at the mRNA and protein levels in a dose- and time-dependent manner, and pre-treatment with the SR-BI inhibitor BLT-1 and SR-BI small interfering RNA significantly inhibited baicalin-induced cholesterol efflux. Furthermore, baicalin increased the expression of PPAR-γ and LXRα, and the application of specific agonists and inhibitors of PPAR-γ and LXRα changed the expression of SR-BI, as well as cholesterol efflux. It may be concluded that baicalin induced cholesterol efflux from THP-1 macrophages via the PPAR-γ/LXRα/SR-BI pathway.
Collapse
Affiliation(s)
- Renchao Yu
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China
| | - Yuexia Lv
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China
| | - Juanling Wang
- Clinical Skill Training Center, People's Hospital of Weifang, Weifang, Shandong 261041, P.R. China
| | - Nana Pan
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China
| | - Rui Zhang
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China
| | - Xiaxia Wang
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China
| | - Haichu Yu
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China
| | - Lijuan Tan
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266555, P.R. China
| | - Yunhe Zhao
- Department of Cardiology, Central Hospital of Zibo, Zibo, Shandong 255036, P.R. China
| | - Bo Li
- Department of Cardiology, Central Hospital of Zibo, Zibo, Shandong 255036, P.R. China
| |
Collapse
|
19
|
Pal R, Ke Q, Pihan GA, Yesilaltay A, Penman ML, Wang L, Chitraju C, Kang PM, Krieger M, Kocher O. Carboxy-terminal deletion of the HDL receptor reduces receptor levels in liver and steroidogenic tissues, induces hypercholesterolemia, and causes fatal heart disease. Am J Physiol Heart Circ Physiol 2016; 311:H1392-H1408. [PMID: 27694217 DOI: 10.1152/ajpheart.00463.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 09/13/2016] [Indexed: 01/15/2023]
Abstract
The HDL receptor SR-BI mediates the transfer of cholesteryl esters from HDL to cells and controls HDL abundance and structure. Depending on the genetic background, loss of SR-BI causes hypercholesterolemia, anemia, reticulocytosis, splenomegaly, thrombocytopenia, female infertility, and fatal coronary heart disease (CHD). The carboxy terminus of SR-BI (505QEAKL509) must bind to the cytoplasmic adaptor PDZK1 for normal hepatic-but not steroidogenic cell-expression of SR-BI protein. To determine whether SR-BI's carboxy terminus is also required for normal protein levels in steroidogenic cells, we introduced into SR-BI's gene a 507Ala/STOP mutation that produces a truncated receptor (SR-BIΔCT). As expected, the dramatic reduction of hepatic receptor protein in SR-BIΔCT mice was similar to that in PDZK1 knockout (KO) mice. Unlike SR-BI KO females, SR-BIΔCT females were fertile. The severity of SR-BIΔCT mice's hypercholesterolemia was intermediate between those of SR-BI KO and PDZK1 KO mice. Substantially reduced levels of the receptor in adrenal cortical cells, ovarian cells, and testicular Leydig cells in SR-BIΔCT mice suggested that steroidogenic cells have an adaptor(s) functionally analogous to hepatic PDZK1. When SR-BIΔCT mice were crossed with apolipoprotein E KO mice (SR-BIΔCT/apoE KO), pathologies including hypercholesterolemia, macrocytic anemia, hepatic and splenic extramedullary hematopoiesis, massive splenomegaly, reticulocytosis, thrombocytopenia, and rapid-onset and fatal occlusive coronary arterial atherosclerosis and CHD (median age of death: 9 wk) were observed. These results provide new insights into the control of SR-BI in steroidogenic cells and establish SR-BIΔCT/apoE KO mice as a new animal model for the study of CHD.
Collapse
Affiliation(s)
- Rinku Pal
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Qingen Ke
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - German A Pihan
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Ayce Yesilaltay
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Marsha L Penman
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Li Wang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Chandramohan Chitraju
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts
| | - Peter M Kang
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Monty Krieger
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Olivier Kocher
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts;
| |
Collapse
|
20
|
Okuda K, Tong M, Dempsey B, Moore KJ, Gazzinelli RT, Silverman N. Leishmania amazonensis Engages CD36 to Drive Parasitophorous Vacuole Maturation. PLoS Pathog 2016; 12:e1005669. [PMID: 27280707 PMCID: PMC4900624 DOI: 10.1371/journal.ppat.1005669] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 05/10/2016] [Indexed: 11/19/2022] Open
Abstract
Leishmania amastigotes manipulate the activity of macrophages to favor their own success. However, very little is known about the role of innate recognition and signaling triggered by amastigotes in this host-parasite interaction. In this work we developed a new infection model in adult Drosophila to take advantage of its superior genetic resources to identify novel host factors limiting Leishmania amazonensis infection. The model is based on the capacity of macrophage-like cells, plasmatocytes, to phagocytose and control the proliferation of parasites injected into adult flies. Using this model, we screened a collection of RNAi-expressing flies for anti-Leishmania defense factors. Notably, we found three CD36-like scavenger receptors that were important for defending against Leishmania infection. Mechanistic studies in mouse macrophages showed that CD36 accumulates specifically at sites where the parasite contacts the parasitophorous vacuole membrane. Furthermore, CD36-deficient macrophages were defective in the formation of the large parasitophorous vacuole typical of L. amazonensis infection, a phenotype caused by inefficient fusion with late endosomes and/or lysosomes. These data identify an unprecedented role for CD36 in the biogenesis of the parasitophorous vacuole and further highlight the utility of Drosophila as a model system for dissecting innate immune responses to infection.
Collapse
Affiliation(s)
- Kendi Okuda
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (KO); (NS)
| | - Mei Tong
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Brian Dempsey
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Kathryn J. Moore
- Department of Medicine, New York University School of Medicine, Langone Medical Center, New York, New York, United States of America
| | - Ricardo T. Gazzinelli
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Neal Silverman
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (KO); (NS)
| |
Collapse
|
21
|
Mutharasan RK, Foit L, Thaxton CS. High-Density Lipoproteins for Therapeutic Delivery Systems. J Mater Chem B 2016; 4:188-197. [PMID: 27069624 PMCID: PMC4825811 DOI: 10.1039/c5tb01332a] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
High-density lipoproteins (HDL) are a class of natural nanostructures found in the blood and are composed of lipids, proteins, and nucleic acids (e.g. microRNA). Their size, which appears to be well-suited for both tissue penetration/retention as well as payload delivery, long circulation half-life, avoidance of endosomal sequestration, and potential low toxicity are all excellent properties to model in a drug delivery vehicle. In this review, we consider high-density lipoproteins for therapeutic delivery systems. First we discuss the structure and function of natural HDL, describing in detail its biogenesis and transformation from immature, discoidal forms, to more mature, spherical forms. Next we consider features of HDL making them suitable vehicles for drug delivery. We then describe the use of natural HDL, discoidal HDL analogs, and spherical HDL analogs to deliver various classes of drugs, including small molecules, lipids, and oligonucleotides. We briefly consider the notion that the drug delivery vehicles themselves are therapeutic, constituting entities that exhibit "theralivery." Finally, we discuss challenges and future directions in the field.
Collapse
Affiliation(s)
- R. Kannan Mutharasan
- Feinberg Cardiovascular Research Institute, 303 E. Chicago Ave., Tarry 14-725, Chicago, IL 60611 United States
| | - Linda Foit
- Feinberg School of Medicine, Department of Urology, Northwestern University, Tarry 16-703, 303 E. Chicago Ave, Chicago, IL 60611, USA
| | - C. Shad Thaxton
- Feinberg School of Medicine, Department of Urology, Northwestern University, Tarry 16-703, 303 E. Chicago Ave, Chicago, IL 60611, USA
- Simpson Querrey Institute for BioNanotechnology, Northwestern University, 303 E. Superior St, Chicago, IL 60611, USA
- International Institute for Nanotechnology (IIN), 2145 Sheridan Road, Evanston, IL 60208, USA
- Robert H Lurie Comprehensive Cancer Center (RHLCCC), Northwestern University, Feinberg School of Medicine, 303 E Superior, Chicago, IL 60611, USA
| |
Collapse
|
22
|
Cohen E, Aviram M, Khatib S, Volkova N, Vaya J. Human carotid atherosclerotic plaque protein(s) change HDL protein(s) composition and impair HDL anti-oxidant activity. Biofactors 2016; 42:115-28. [PMID: 26662883 DOI: 10.1002/biof.1254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/16/2015] [Accepted: 11/16/2015] [Indexed: 11/09/2022]
Abstract
High density lipoprotein (HDL) anti-atherogenic functions are closely associated with cardiovascular disease risk factor, and are dictated by its composition, which is often affected by environmental factors. The present study investigates the effects of the human carotid plaque constituents on HDL composition and biological functions. To this end, human carotid plaques were homogenized and incubated with HDL. Results showed that after incubation, most of the apolipoprotein A1 (Apo A1) protein was released from the HDL, and HDL diameter increased by an average of approximately 2 nm. In parallel, HDL antioxidant activity was impaired. In response to homogenate treatment HDL could not prevent the accelerated oxidation of LDL caused by the homogenate. Boiling of the homogenate prior to its incubation with HDL abolished its effects on HDL composition changes. Moreover, tryptophan fluorescence quenching assay revealed an interaction between plaque component(s) and HDL, an interaction that was reduced by 50% upon using pre-boiled homogenate. These results led to hypothesize that plaque protein(s) interacted with HDL-associated Apo A1 and altered the HDL composition. Immuno-precipitation of Apo A1 that was released from the HDL after its incubation with the homogenate revealed a co-precipitation of three isomers of actin. However, beta-actin alone did not significantly affect the HDL composition, and yet the active protein within the plaque was elusive. In conclusion then, protein(s) in the homogenate interact with HDL protein(s), leading to release of Apo A1 from the HDL particle, a process that was associated with an increase in HDL diameter and with impaired HDL anti-oxidant activity.
Collapse
Affiliation(s)
- Elad Cohen
- Department of Oxidative Stress and Human Diseases, MIGAL - Galilee Research Institute, , P.O. Box 831, Kiryat Shmona, 11016, Israel
- Tel-Hai College, Upper Galilee, 12210, Israel
- Lipid Research Laboratory Technion Rappaport Faculty of Medicine, Rappaport Family Institute for Research in the Medical Sciences, and Rambam Medical Center, Haifa, 31096, Israel
| | - Michael Aviram
- Lipid Research Laboratory Technion Rappaport Faculty of Medicine, Rappaport Family Institute for Research in the Medical Sciences, and Rambam Medical Center, Haifa, 31096, Israel
| | - Soliman Khatib
- Department of Oxidative Stress and Human Diseases, MIGAL - Galilee Research Institute, , P.O. Box 831, Kiryat Shmona, 11016, Israel
- Tel-Hai College, Upper Galilee, 12210, Israel
| | - Nina Volkova
- Lipid Research Laboratory Technion Rappaport Faculty of Medicine, Rappaport Family Institute for Research in the Medical Sciences, and Rambam Medical Center, Haifa, 31096, Israel
| | - Jacob Vaya
- Department of Oxidative Stress and Human Diseases, MIGAL - Galilee Research Institute, , P.O. Box 831, Kiryat Shmona, 11016, Israel
- Tel-Hai College, Upper Galilee, 12210, Israel
| |
Collapse
|
23
|
Rosenblat M, Volkova N, Aviram M. Selective oxidative stress and cholesterol metabolism in lipid-metabolizing cell classes: Distinct regulatory roles for pro-oxidants and antioxidants. Biofactors 2015; 41:273-88. [PMID: 26228307 DOI: 10.1002/biof.1223] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 06/21/2015] [Indexed: 12/13/2022]
Abstract
Atherogenesis is associated with macrophage cholesterol and oxidized lipids accumulation and foam cell formation. However, two other major lipid-metabolizing cell classes, namely intestinal and liver cells, are also associated with atherogenesis. This study demonstrates that manipulations of cellular oxidative stress (by fatty acids, glucose, low-density lipoprotein, angiotensin II, polyphenolic antioxidants, or the glutathione/paraoxonase 1 systems) have some similar, but also some different effects on cholesterol metabolism in macrophages (J774A.1) versus intestinal cells (HT-29) versus liver cells (HuH7). Cellular oxidative stress was ≈3.5-folds higher in both intestinal and liver cells versus macrophages. In intestinal cells or liver cells versus macrophages, the cholesterol biosynthesis rate was increased by 9- or 15-fold, respectively. In both macrophages and intestinal cells C-18:1 and C-18:2 but not C-18:0, fatty acids significantly increased oxidative stress, whereas in liver cells oxidative stress was significantly decreased by all three fatty acids. In liver cells, trans C-18:1 versus cis C-18:1, unlike intestinal cells or macrophages, significantly increased cellular oxidative stress and cellular cholesterol biosynthesis rate. Pomegranate juice (PJ), red wine, or their phenolics gallic acids or quercetin significantly reduced cellular oxidation mostly in macrophages. Recombinant PON1 significantly decreased macrophage (but not the other cells) oxidative stress by ≈30%. We conclude that cellular atherogenesis research should look at atherogenicity, not only in macrophages but also in intestinal and liver cells, to advance our understanding of the complicated mechanisms behind atherogenesis. © 2015 BioFactors, 41(4):273-288, 2015.
Collapse
Affiliation(s)
- Mira Rosenblat
- The Lipid Research Laboratory, Technion Rappaport Faculty of Medicine, Haifa, Israel
| | - Nina Volkova
- The Lipid Research Laboratory, Technion Rappaport Faculty of Medicine, Haifa, Israel
| | - Michael Aviram
- The Lipid Research Laboratory, Technion Rappaport Faculty of Medicine, Haifa, Israel
| |
Collapse
|
24
|
Rosenblat M, Volkova N, Abassi Z, Britton SL, Koch LG, Aviram M. High intrinsic aerobic capacity and pomegranate juice are protective against macrophage atherogenecity: studies in high- vs. low-capacity runner (HCR vs. LCR) rats. J Nutr Biochem 2015; 26:1015-21. [PMID: 26004903 DOI: 10.1016/j.jnutbio.2015.04.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 04/06/2015] [Accepted: 04/13/2015] [Indexed: 12/16/2022]
Abstract
We studied the rat model system of high- vs. low-capacity runner (HCR vs. LCR) rats to question the atherogenic properties (oxidative stress, triglycerides and cholesterol metabolism) in the rat macrophages, serum, liver and heart. Half of the LCR or HCR rats consumed pomegranate juice (PJ; 15 μmol of gallic acid equivalents/rat/day) for 3 weeks and were compared to placebo-treated rats. At the end of the study blood samples, peritoneal macrophages (RPM), livers, and hearts were harvested from the rats. RPM harvested from HCR vs. LCR demonstrated reduced cellular oxidation (21%), increased paraoxonase 2 activity (28%) and decreased triglycerides mass (44%). Macrophage uptake rates of fluorescein-isothiocyanate-labeled low-density lipoprotein (LDL) or oxidized LDL were significantly lower, by 37% or by 18%, respectively, in HCR vs. LCR RPM. PJ consumption significantly decreased all the above atherogenic parameters with more substantial beneficial effects observed in the LCR vs. the HCR rats (~80% vs. ~40% improvement, respectively). Similar hypo-triglyceridemic pattern was noted in serum from HCR vs. LCR. In contrast to the above results, liver oxidation and triglycerides mass were both minimally increased in HCR vs. LCR rats by 31% and 28%, respectively. In the heart, lipid content was very low, and interestingly, an absence of any significant oxidative stress, along with modest triglyceride accumulation, was observed. We conclude that HCR vs. LCR rats demonstrate reduced atherogenicity, mostly in their macrophages. PJ exerts a further improvement, mostly in macrophages from LCR rats.
Collapse
Affiliation(s)
- Mira Rosenblat
- The Lipid Research Laboratory, Rambam Health Care Campus, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
| | - Nina Volkova
- The Lipid Research Laboratory, Rambam Health Care Campus, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
| | - Zaid Abassi
- Department of Physiology and Biophysics, Technion Rappaport Faculty of Medicine, Haifa, Israel
| | - Steven L Britton
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Lauren G Koch
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Michael Aviram
- The Lipid Research Laboratory, Rambam Health Care Campus, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel.
| |
Collapse
|
25
|
Borochov-Neori H, Judeinstein S, Greenberg A, Volkova N, Rosenblat M, Aviram M. Antioxidant and antiatherogenic properties of phenolic acid and flavonol fractions of fruits of 'Amari' and 'Hallawi' date (Phoenix dactylifera L.) varieties. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:3189-3195. [PMID: 25765921 DOI: 10.1021/jf506094r] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Date (Phoenix dactylifera L.) fruit phenolic-acid or flavonol fractions were examined in vitro for antioxidant and antiatherogenic properties. Two fractions of each subgroup were prepared from two date varieties, 'Amari' and 'Hallawi', by solid phase extraction on C18. The fractions were analyzed for phenolics composition by RP-HPLC and tested for ferric-reducing antioxidant power, free radical scavenging capacity, inhibition of Cu(2+)-induced LDL oxidation, and enhancement of HDL-mediated cholesterol efflux from macrophages. All four fractions exhibited variable capacities to reduce ferric ions, scavenge radicals, and inhibit LDL oxidation. Flavonol fractions were considerably better inhibitors of LDL oxidation compared to phenolic acid fractions, with IC50's of 9-31 nmol GAE mL(-1) compared to 85-116 nmol GAE mL(-1), respectively. Only the flavonol fractions stimulated cholesterol removal from macrophages. Within each subgroup, the levels of all the activities varied with fraction composition. The results demonstrated strong structure-activity relationships for date phenolics and identified date flavonols as potential antiatherogenic bioactives.
Collapse
Affiliation(s)
| | - Sylvie Judeinstein
- †Southern Arava Research and Development, M. P. Hevel Eilot 88820, Israel
| | - Amnon Greenberg
- †Southern Arava Research and Development, M. P. Hevel Eilot 88820, Israel
| | - Nina Volkova
- ‡The Lipid Research Laboratory, Rappaport Faculty of Medicine and the Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Rambam Medical Center, Haifa 31096, Israel
| | - Mira Rosenblat
- ‡The Lipid Research Laboratory, Rappaport Faculty of Medicine and the Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Rambam Medical Center, Haifa 31096, Israel
| | - Michael Aviram
- ‡The Lipid Research Laboratory, Rappaport Faculty of Medicine and the Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Rambam Medical Center, Haifa 31096, Israel
| |
Collapse
|
26
|
Zhao Y, Hoekstra M, Korporaal SJA, Van Berkel TJC, Van Eck M. HDL Receptor Scavenger Receptor BI. Atherosclerosis 2015. [DOI: 10.1002/9781118828533.ch25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
27
|
Zannis VI, Fotakis P, Koukos G, Kardassis D, Ehnholm C, Jauhiainen M, Chroni A. HDL biogenesis, remodeling, and catabolism. Handb Exp Pharmacol 2015; 224:53-111. [PMID: 25522986 DOI: 10.1007/978-3-319-09665-0_2] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this chapter, we review how HDL is generated, remodeled, and catabolized in plasma. We describe key features of the proteins that participate in these processes, emphasizing how mutations in apolipoprotein A-I (apoA-I) and the other proteins affect HDL metabolism. The biogenesis of HDL initially requires functional interaction of apoA-I with the ATP-binding cassette transporter A1 (ABCA1) and subsequently interactions of the lipidated apoA-I forms with lecithin/cholesterol acyltransferase (LCAT). Mutations in these proteins either prevent or impair the formation and possibly the functionality of HDL. Remodeling and catabolism of HDL is the result of interactions of HDL with cell receptors and other membrane and plasma proteins including hepatic lipase (HL), endothelial lipase (EL), phospholipid transfer protein (PLTP), cholesteryl ester transfer protein (CETP), apolipoprotein M (apoM), scavenger receptor class B type I (SR-BI), ATP-binding cassette transporter G1 (ABCG1), the F1 subunit of ATPase (Ecto F1-ATPase), and the cubulin/megalin receptor. Similarly to apoA-I, apolipoprotein E and apolipoprotein A-IV were shown to form discrete HDL particles containing these apolipoproteins which may have important but still unexplored functions. Furthermore, several plasma proteins were found associated with HDL and may modulate its biological functions. The effect of these proteins on the functionality of HDL is the topic of ongoing research.
Collapse
Affiliation(s)
- Vassilis I Zannis
- Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, 02118, USA,
| | | | | | | | | | | | | |
Collapse
|
28
|
Kartz GA, Holme RL, Nicholson K, Sahoo D. SR-BI/CD36 chimeric receptors define extracellular subdomains of SR-BI critical for cholesterol transport. Biochemistry 2014; 53:6173-82. [PMID: 25211142 PMCID: PMC4188264 DOI: 10.1021/bi500706x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
High-density lipoproteins (HDLs) are athero-protective, primarily because of their ability to promote cholesterol flux from peripheral tissues to the liver by reverse cholesterol transport (RCT). The delivery of HDL-cholesteryl esters (CE) into cells is mediated by the HDL receptor, scavenger receptor class B type I (SR-BI), a promising target for enhancing whole body cholesterol disposal and preventing cardiovascular disease. A detailed understanding of the structural determinants underlying proper SR-BI/HDL alignment that supports the selective uptake of HDL-CE into cells remains lacking. To this end, we exploited CD36, a class B scavenger receptor with a predicted topology similar to that of SR-BI that binds HDL but is unable to mediate efficient selective uptake of HDL-CE. We generated a series of SR-BI/CD36 chimeric receptors that span the extracellular (EC) domain of SR-BI to delineate regions that are essential for SR-BI's cholesterol transport functions. All 16 SR-BI/CD36 chimeras were transiently expressed in COS-7 cells, and their plasma membrane localization was confirmed. The majority of SR-BI/CD36 chimeric receptors displayed significant reductions in their ability to (i) bind HDL, (ii) deliver HDL-CE to cells, (iii) mediate efflux of free cholesterol (FC) to HDL, and (iv) redistribute plasma membrane domains of FC. We also demonstrated that changes in SR-BI function were independent of receptor oligomerization. Altogether, we have identified discrete subdomains, particularly in the N-terminal and C-terminal regions of the EC domain of SR-BI, that are critical for productive receptor-ligand interactions and the various cholesterol transport functions of SR-BI.
Collapse
Affiliation(s)
- Gabriella A Kartz
- Departments of Pharmacology & Toxicology, ‡Biochemistry, and §Medicine, Medical College of Wisconsin , Milwaukee, Wisconsin 53226, United States
| | | | | | | |
Collapse
|
29
|
Al-Jarallah A, Chen X, González L, Trigatti BL. High density lipoprotein stimulated migration of macrophages depends on the scavenger receptor class B, type I, PDZK1 and Akt1 and is blocked by sphingosine 1 phosphate receptor antagonists. PLoS One 2014; 9:e106487. [PMID: 25188469 PMCID: PMC4154704 DOI: 10.1371/journal.pone.0106487] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 08/04/2014] [Indexed: 01/12/2023] Open
Abstract
HDL carries biologically active lipids such as sphingosine-1-phosphate (S1P) and stimulates a variety of cell signaling pathways in diverse cell types, which may contribute to its ability to protect against atherosclerosis. HDL and sphingosine-1-phosphate receptor agonists, FTY720 and SEW2871 triggered macrophage migration. HDL-, but not FTY720-stimulated migration was inhibited by an antibody against the HDL receptor, SR-BI, and an inhibitor of SR-BI mediated lipid transfer. HDL and FTY720-stimulated migration was also inhibited in macrophages lacking either SR-BI or PDZK1, an adaptor protein that binds to SR-BI's C-terminal cytoplasmic tail. Migration in response to HDL and S1P receptor agonists was inhibited by treatment of macrophages with sphingosine-1-phosphate receptor type 1 (S1PR1) antagonists and by pertussis toxin. S1PR1 activates signaling pathways including PI3K-Akt, PKC, p38 MAPK, ERK1/2 and Rho kinases. Using selective inhibitors or macrophages from gene targeted mice, we demonstrated the involvement of each of these pathways in HDL-dependent macrophage migration. These data suggest that HDL stimulates the migration of macrophages in a manner that requires the activities of the HDL receptor SR-BI as well as S1PR1 activity.
Collapse
Affiliation(s)
- Aishah Al-Jarallah
- Department of Biochemistry and Biomedical Sciences, and the Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Xing Chen
- Department of Biochemistry and Biomedical Sciences, and the Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Leticia González
- Department of Biochemistry and Biomedical Sciences, and the Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Bernardo L. Trigatti
- Department of Biochemistry and Biomedical Sciences, and the Thrombosis and Atherosclerosis Research Institute, McMaster University, Hamilton, Ontario, Canada
- * E-mail:
| |
Collapse
|
30
|
Rosenblat M, Volkova N, Aviram M. HDL3 stimulates paraoxonase 1 antiatherogenic catalytic and biological activities in a macrophage model system: in vivo and in vitro studies. Biofactors 2014; 40:536-45. [PMID: 25230879 DOI: 10.1002/biof.1184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 08/28/2014] [Accepted: 09/03/2014] [Indexed: 11/07/2022]
Abstract
We analyzed in-vivo and in-vitro high density lipoprotein (HDL) effects on paraoxonase 1 (PON1) antiatherogenic properties in serum and in macrophages. Intraperitoneal injection to C57BL/6 mice of recombinant PON1 (rePON1) + HDL, in comparison to HDL or to rePON1 alone, significantly increased serum PON1 arylesterase activity (by 20%), and serum-mediated cholesterol efflux from J774A.1 macrophages (by 18%). Similarly, in peritoneal macrophages (MPM) harvested from mice injected with HDL + rePON1 versus rePON1 alone, we observed reduction in oxidative stress (by 11%), increase in cellular PON1 activity (by 14%) and in HDL-mediated cholesterol efflux (by 38%). Incubation of serum or HDL with rePON1, substantially increased PON1 arylesterase activity, two-fold more than the expected additive values. HDL2 and HDL3 increased PON1 activity by 199% or 274%, respectively. Macrophage (J774A.1) cholesterol efflux rate significantly increased by HDL3 + rePON1 versus HDL3 alone (by 19%), but not by HDL2 + rePON1 versus HDL2 alone. Oxidation of HDL3 reduced its ability to induce macrophage cholesterol efflux, and abolished HDL3 stimulatory effects on rePON1. Addition of exogenous polyphenol quercetin (60 µM), but not phosphatidylcholine or apolipoprotein A1, to HDL + rePON1 increased PON1 activity (by 404%), increased the ability to reduce oxidative stress in J774A.1 macrophages (by 53%) and to stimulate macrophage cholesterol efflux (by 14%). Upon adding the hypocholesterolemic drug simvastatin (15 µg/mL) to HDL + rePON1, PON1 activity and the ability to induce macrophage cholesterol efflux increased, in comparison to HDL + rePON1. We thus concluded that HDL (mostly HDL3), stimulates PON1 antiatherogenic activities in macrophages, and these PON1 activities were further stimulated by quercetin, or by simvastatin.
Collapse
Affiliation(s)
- Mira Rosenblat
- The Lipid Research Laboratory, the Technion Rappaport Faculty of Medicine and Research Institute, Rambam Health Care Campus, Technion- Israel Institute of Technology, Haifa, Israel
| | | | | |
Collapse
|
31
|
Abstract
Most types of cells in the body do not express the capability of catabolizing cholesterol, so cholesterol efflux is essential for homeostasis. For instance, macrophages possess four pathways for exporting free (unesterified) cholesterol to extracellular high density lipoprotein (HDL). The passive processes include simple diffusion via the aqueous phase and facilitated diffusion mediated by scavenger receptor class B, type 1 (SR-BI). Active pathways are mediated by the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1, which are membrane lipid translocases. The efflux of cellular phospholipid and free cholesterol to apolipoprotein A-I promoted by ABCA1 is essential for HDL biogenesis. Current understanding of the molecular mechanisms involved in these four efflux pathways is presented in this minireview.
Collapse
Affiliation(s)
- Michael C Phillips
- From the Division of Translational Medicine and Human Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104-5158
| |
Collapse
|
32
|
The Impact of Lipoproteins on Wound Healing: Topical HDL Therapy Corrects Delayed Wound Healing in Apolipoprotein E Deficient Mice. Pharmaceuticals (Basel) 2014; 7:419-32. [PMID: 24705596 PMCID: PMC4014700 DOI: 10.3390/ph7040419] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 03/06/2014] [Accepted: 03/26/2014] [Indexed: 12/22/2022] Open
Abstract
Chronic non-healing wounds lead to considerable morbidity and mortality. Pleiotropic effects of high density lipoproteins (HDL) may beneficially affect wound healing. The objectives of this murine study were: (1) to investigate the hypothesis that hypercholesterolemia induces impaired wound healing and (2) to study the effect of topical HDL administration in a model of delayed wound healing. A circular full thickness wound was created on the back of each mouse. A silicone splint was used to counteract wound contraction. Coverage of the wound by granulation tissue and by epithelium was quantified every 2 days. Re-epithelialization from day 0 till day 10 was unexpectedly increased by 21.3% (p < 0.05) in C57BL/6 low density lipoprotein (LDLr) deficient mice with severe hypercholesterolemia (489 ± 14 mg/dL) compared to C57BL/6 mice and this effect was entirely abrogated following cholesterol lowering adenoviral LDLr gene transfer. In contrast, re-epithelialization in hypercholesterolemic (434 ± 16 mg/dL) C57BL/6 apolipoprotein (apo) E−/− mice was 22.6% (p < 0.0001) lower than in C57BL/6 mice. Topical HDL gel administered every 2 days increased re-epithelialization by 25.7% (p < 0.01) in apo E−/− mice. In conclusion, topical HDL application is an innovative therapeutic strategy that corrects impaired wound healing in apo E−/− mice.
Collapse
|
33
|
Zhu Y, Huang X, Zhang Y, Wang Y, Liu Y, Sun R, Xia M. Anthocyanin supplementation improves HDL-associated paraoxonase 1 activity and enhances cholesterol efflux capacity in subjects with hypercholesterolemia. J Clin Endocrinol Metab 2014; 99:561-9. [PMID: 24285687 DOI: 10.1210/jc.2013-2845] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
CONTEXT AND OBJECTIVE Paraoxonase 1 (PON1), an enzyme associated with high-density lipoprotein (HDL-PON1), is reported to have antioxidant and cardioprotective properties. The aim of the present study was to investigate the effects of anthocyanins on the HDL-PON1 activity and cholesterol efflux capacity in hypercholesterolemic subjects. DESIGN AND PARTICIPANTS A total of 122 hypercholesterolemic subjects were given 160 mg of anthocyanins twice daily or placebo (n = 61 of each group) for 24 weeks in a double-blind, randomized, placebo-controlled trial. Participants and investigators were masked to treatment allocation. RESULTS Anthocyanin consumption significantly increased HDL cholesterol and decreased low -density lipoprotein cholesterol concentrations compared with placebo (P < .018 and P < .001, respectively). Anthocyanin supplementation also increased the activity of HDL-PON1 compared with placebo (P < .001). Furthermore, cholesterol efflux capacity was increased more in the anthocyanin group (20.0% increase) than in the placebo group (0.2% increase) (P < .001). The negative correlations established between HDL-PON1 activity and the levels of lipid hydroperoxides associated with HDL confirm the relationship between PON1 activity and lipid peroxidation of lipoproteins. Furthermore, a strong positive correlation was noted between increased HDL-PON1 activity and improved cholesterol efflux capacity both before and after adjustment for HDL cholesterol and apolipoprotein AI in anthocyanin-treated subjects (both P < .001). Inhibition of HDL-PON1 activity strongly prevented the antioxidant ability of HDL and attenuated the cholesterol efflux capacity of subjects from anthocyanin group. CONCLUSIONS Our observations suggest that the alterations of PON1 activity by anthocyanin observed in hypercholesterolemic HDL reflect a shift to an improvement of cholesterol efflux capacity of HDL and may provide a link between anthocyanin and cardioprotective effects.
Collapse
Affiliation(s)
- Yanna Zhu
- Guangdong Provincial Key Laboratory of Food, Nutrition, and Health, Department of Nutrition, School of Public Health, Sun Yat-sen University (Northern Campus), Guangzhou, Guangdong Province 510080, People's Republic of China
| | | | | | | | | | | | | |
Collapse
|
34
|
Hamoud S, Hayek T, Volkova N, Attias J, Moscoviz D, Rosenblat M, Aviram M. Pomegranate extract (POMx) decreases the atherogenicity of serum and of human monocyte-derived macrophages (HMDM) in simvastatin-treated hypercholesterolemic patients: A double-blinded, placebo-controlled, randomized, prospective pilot study. Atherosclerosis 2014; 232:204-10. [DOI: 10.1016/j.atherosclerosis.2013.11.037] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 11/04/2013] [Accepted: 11/04/2013] [Indexed: 01/27/2023]
|
35
|
Abstract
Cardiovascular disease (CVD) is the leading cause of death globally. For close to four decades, we have known that high density lipoprotein (HDL) levels are inversely correlated with the risk of CVD. HDL is a complex particle that consists of proteins, phospholipids, and cholesterol and has the ability to carry micro-RNAs. HDL is constantly undergoing remodelling throughout its life-span and carries out many functions. This review summarizes many of the different aspects of HDL from its assembly, the receptors it interacts with, along with the functions it performs and how it can be altered in disease. While HDL is a key cholesterol efflux particle, this review highlights the many other important functions of HDL in the innate immune system and details the potential therapeutic uses of HDL outside of CVD.
Collapse
|
36
|
Neculai D, Schwake M, Ravichandran M, Zunke F, Collins RF, Peters J, Neculai M, Plumb J, Loppnau P, Pizarro JC, Seitova A, Trimble WS, Saftig P, Grinstein S, Dhe-Paganon S. Structure of LIMP-2 provides functional insights with implications for SR-BI and CD36. Nature 2013; 504:172-6. [PMID: 24162852 DOI: 10.1038/nature12684] [Citation(s) in RCA: 207] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Accepted: 09/20/2013] [Indexed: 11/09/2022]
Abstract
Members of the CD36 superfamily of scavenger receptor proteins are important regulators of lipid metabolism and innate immunity. They recognize normal and modified lipoproteins, as well as pathogen-associated molecular patterns. The family consists of three members: SR-BI (which delivers cholesterol to the liver and steroidogenic organs and is a co-receptor for hepatitis C virus), LIMP-2/LGP85 (which mediates lysosomal delivery of β-glucocerebrosidase and serves as a receptor for enterovirus 71 and coxsackieviruses) and CD36 (a fatty-acid transporter and receptor for phagocytosis of effete cells and Plasmodium-infected erythrocytes). Notably, CD36 is also a receptor for modified lipoproteins and β-amyloid, and has been implicated in the pathogenesis of atherosclerosis and of Alzheimer's disease. Despite their prominent roles in health and disease, understanding the function and abnormalities of the CD36 family members has been hampered by the paucity of information about their structure. Here we determine the crystal structure of LIMP-2 and infer, by homology modelling, the structure of SR-BI and CD36. LIMP-2 shows a helical bundle where β-glucocerebrosidase binds, and where ligands are most likely to bind to SR-BI and CD36. Remarkably, the crystal structure also shows the existence of a large cavity that traverses the entire length of the molecule. Mutagenesis of SR-BI indicates that the cavity serves as a tunnel through which cholesterol(esters) are delivered from the bound lipoprotein to the outer leaflet of the plasma membrane. We provide evidence supporting a model whereby lipidic constituents of the ligands attached to the receptor surface are handed off to the membrane through the tunnel, accounting for the selective lipid transfer characteristic of SR-BI and CD36.
Collapse
Affiliation(s)
- Dante Neculai
- Cell Biology Program, The Hospital for Sick Children, Toronto M5G 1X8, Canada
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Challenges in using cultured primary rodent hepatocytes or cell lines to study hepatic HDL receptor SR-BI regulation by its cytoplasmic adaptor PDZK1. PLoS One 2013; 8:e69725. [PMID: 23936087 PMCID: PMC3720616 DOI: 10.1371/journal.pone.0069725] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 06/12/2013] [Indexed: 12/15/2022] Open
Abstract
Background PDZK1 is a four PDZ-domain containing cytoplasmic protein that binds to a variety of membrane proteins via their C-termini and can influence the abundance, localization and/or function of its target proteins. One of these targets in hepatocytes in vivo is the HDL receptor SR-BI. Normal hepatic expression of SR-BI protein requires PDZK1 - <5% of normal hepatic SR-BI is seen in the livers of PDZK1 knockout mice. Progress has been made in identifying features of PDZK1 required to control hepatic SR-BI in vivo using hepatic expression of wild-type and mutant forms of PDZK1 in wild-type and PDZK1 KO transgenic mice. Such in vivo studies are time consuming and expensive, and cannot readily be used to explore many features of the underlying molecular and cellular mechanisms. Methodology/Principal Findings Here we have explored the potential to use either primary rodent hepatocytes in culture using 2D collagen gels with newly developed optimized conditions or PDZK1/SR-BI co-transfected cultured cell lines (COS, HEK293) for such studies. SR-BI and PDZK1 protein and mRNA expression levels fell rapidly in primary hepatocyte cultures, indicating this system does not adequately mimic hepatocytes in vivo for analysis of the PDZK1 dependence of SR-BI. Although PDZK1 did alter SR-BI protein expression in the cell lines, its influence was independent of SR-BI’s C-terminus, and thus is not likely to occur via the same mechanism as that which occurs in hepatocytes in vivo. Conclusions/Significance Caution must be exercised in using primary hepatocytes or cultured cell lines when studying the mechanism underlying the regulation of hepatic SR-BI by PDZK1. It may be possible to use SR-BI and PDZK1 expression as sensitive markers for the in vivo-like state of hepatocytes to further improve primary hepatocyte cell culture conditions.
Collapse
|
38
|
Borochov-Neori H, Judeinstein S, Greenberg A, Volkova N, Rosenblat M, Aviram M. Date (Phoenix dactylifera L.) fruit soluble phenolics composition and anti-atherogenic properties in nine Israeli varieties. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2013; 61:4278-4286. [PMID: 23587027 DOI: 10.1021/jf400782v] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Date (Phoenix dactylifera L.) fruit soluble phenolics composition and anti-atherogenic properties were examined in nine diverse Israeli grown varieties. Ethanol and acetone extracts of 'Amari', 'Barhi', 'Deglet Noor', 'Deri', 'Hadrawi', 'Hallawi', 'Hayani', 'Medjool', and 'Zahidi' fruit were analyzed for phenolics composition by RP-HPLC and tested for anti-atherogenicity by measuring their effects on LDL susceptibility to copper ion- and free radical-induced oxidation, and on serum-mediated cholesterol efflux from macrophages. The most frequently detected phenolics were hydroxybenzoates, hydroxycinnamates, and flavonols. Significant differences in phenolics composition were established between varieties as well as extraction solvents. All extracts inhibited LDL oxidation, and most extracts also stimulated cholesterol removal from macrophages. Considerable varietal differences were measured in the levels of the bioactivities. Also, acetone extracts exhibited a significantly higher anti-atherogenic potency for most varieties. The presence of soluble ingredients with anti-atherogenic capacities in dates and the possible involvement of phenolics are discussed.
Collapse
|
39
|
Yu M, Lau TY, Carr SA, Krieger M. Contributions of a disulfide bond and a reduced cysteine side chain to the intrinsic activity of the high-density lipoprotein receptor SR-BI. Biochemistry 2012. [PMID: 23205738 DOI: 10.1021/bi301203x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The high-density lipoprotein (HDL) receptor scavenger receptor class B, type I (SR-BI), binds HDL and mediates selective cholesteryl ester uptake. SR-BI's structure and mechanism are poorly understood. We used mass spectrometry to assign the two disulfide bonds in SR-BI that connect cysteines within the conserved Cys(321)-Pro(322)-Cys(323) (CPC) motif and connect Cys(280) to Cys(334). We used site-specific mutagenesis to evaluate the contributions of the CPC motif and the side chain of extracellular Cys(384) to HDL binding and lipid uptake. The effects of CPC mutations on activity were context-dependent. Full wild-type (WT) activity required Pro(322) and Cys(323) only when Cys(321) was present. Reduced intrinsic activities were observed for CXC and CPX, but not XXC, XPX, or XXX mutants (X ≠ WT residue). Apparently, a free thiol side chain at position 321 that cannot form an intra-CPC disulfide bond with Cys(323) is deleterious, perhaps because of aberrant disulfide bond formation. Pro(322) may stabilize an otherwise strained CPC disulfide bond, thus supporting WT activity, but this disulfide bond is not absolutely required for normal activity. C(384)X (X = S, T, L, Y, G, or A) mutants exhibited altered activities that varied with the side chain's size: larger side chains phenocopied WT SR-BI treated with its thiosemicarbazone inhibitor BLT-1 (enhanced binding, weakened uptake); smaller side chains produced almost inverse effects (increased uptake:binding ratio). C(384)X mutants were BLT-1-resistant, supporting the proposal that Cys(384)'s thiol interacts with BLT-1. We discuss the implications of our findings on the functions of the extracellular loop cysteines in SR-BI and compare our results to those presented by other laboratories.
Collapse
Affiliation(s)
- Miao Yu
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | | | | | | |
Collapse
|
40
|
Duka A, Fotakis P, Georgiadou D, Kateifides A, Tzavlaki K, von Eckardstein L, Stratikos E, Kardassis D, Zannis VI. ApoA-IV promotes the biogenesis of apoA-IV-containing HDL particles with the participation of ABCA1 and LCAT. J Lipid Res 2012; 54:107-15. [PMID: 23132909 DOI: 10.1194/jlr.m030114] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The objective of this study was to establish the role of apoA-IV, ABCA1, and LCAT in the biogenesis of apoA-IV-containing HDL (HDL-A-IV) using different mouse models. Adenovirus-mediated gene transfer of apoA-IV in apoA-I(-/-) mice did not change plasma lipid levels. ApoA-IV floated in the HDL2/HDL3 region, promoted the formation of spherical HDL particles as determined by electron microscopy, and generated mostly α- and a few pre-β-like HDL subpopulations. Gene transfer of apoA-IV in apoA-I(-/-) × apoE(-/-) mice increased plasma cholesterol and triglyceride levels, and 80% of the protein was distributed in the VLDL/IDL/LDL region. This treatment likewise generated α- and pre-β-like HDL subpopulations. Spherical and α-migrating HDL particles were not detectable following gene transfer of apoA-IV in ABCA1(-/-) or LCAT(-/-) mice. Coexpression of apoA-IV and LCAT in apoA-I(-/-) mice restored the formation of HDL-A-IV. Lipid-free apoA-IV and reconstituted HDL-A-IV promoted ABCA1 and scavenger receptor BI (SR-BI)-mediated cholesterol efflux, respectively, as efficiently as apoA-I and apoE. Our findings are consistent with a novel function of apoA-IV in the biogenesis of discrete HDL-A-IV particles with the participation of ABCA1 and LCAT, and may explain previously reported anti-inflammatory and atheroprotective properties of apoA-IV.
Collapse
Affiliation(s)
- Adelina Duka
- Molecular Genetics, Boston University School of Medicine, Boston, MA, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Chadwick AC, Sahoo D. Functional characterization of newly-discovered mutations in human SR-BI. PLoS One 2012; 7:e45660. [PMID: 23029167 PMCID: PMC3448639 DOI: 10.1371/journal.pone.0045660] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 08/20/2012] [Indexed: 12/27/2022] Open
Abstract
In rodents, SR-BI has been firmly established as a physiologically relevant HDL receptor that mediates removal of HDL-cholesteryl esters (CE). However, its role in human lipoprotein metabolism is less defined. Recently, two unique point mutations in human SR-BI - S112F or T175A - were identified in subjects with high HDL-cholesterol (HDL-C) levels. We hypothesized that mutation of these conserved residues would compromise the cholesterol-transport functions of SR-BI. To test this hypothesis, S112F- and T175A-SR-BI were generated by site-directed mutagenesis. Cell surface expression was confirmed for both mutant receptors in COS-7 cells upon transient transfection, albeit at lower levels for T175A-SR-BI. Both mutant receptors displayed defective HDL binding, selective uptake of HDL-CE and release of free cholesterol (FC) from cells to HDL. Mutant receptors were also unable to re-organize plasma membrane pools of FC. While these impaired functions were independent of receptor oligomerization, inability of T175A-SR-BI to mediate cholesterol-transport functions could be related to altered N-linked glycosylation status. In conclusion, high HDL-C levels observed in carriers of S112F- or T175A-SR-BI mutant receptors are consistent with the inability of these SR-BI receptors to mediate efficient selective uptake of HDL-CE, and suggest that increased plasma HDL concentrations in these settings may not be associated with lower risk of cardiovascular disease.
Collapse
Affiliation(s)
- Alexandra C Chadwick
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA
| | | |
Collapse
|
42
|
Dao Thi VL, Granier C, Zeisel MB, Guérin M, Mancip J, Granio O, Penin F, Lavillette D, Bartenschlager R, Baumert TF, Cosset FL, Dreux M. Characterization of hepatitis C virus particle subpopulations reveals multiple usage of the scavenger receptor BI for entry steps. J Biol Chem 2012; 287:31242-57. [PMID: 22767607 PMCID: PMC3438956 DOI: 10.1074/jbc.m112.365924] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Revised: 06/29/2012] [Indexed: 12/21/2022] Open
Abstract
Hepatitis C virus (HCV) particles assemble along the very low density lipoprotein pathway and are released from hepatocytes as entities varying in their degree of lipid and apolipoprotein (apo) association as well as buoyant densities. Little is known about the cell entry pathway of these different HCV particle subpopulations, which likely occurs by regulated spatiotemporal processes involving several cell surface molecules. One of these molecules is the scavenger receptor BI (SR-BI), a receptor for high density lipoprotein that can bind to the HCV glycoprotein E2. By studying the entry properties of infectious virus subpopulations differing in their buoyant densities, we show that these HCV particles utilize SR-BI in a manifold manner. First, SR-BI mediates primary attachment of HCV particles of intermediate density to cells. These initial interactions involve apolipoproteins, such as apolipoprotein E, present on the surface of HCV particles, but not the E2 glycoprotein, suggesting that lipoprotein components in the virion act as host-derived ligands for important entry factors such as SR-BI. Second, we found that in contrast to this initial attachment, SR-BI mediates entry of HCV particles independent of their buoyant density. This function of SR-BI does not depend on E2/SR-BI interaction but relies on the lipid transfer activity of SR-BI, probably by facilitating entry steps along with other HCV entry co-factors. Finally, our results underscore a third function of SR-BI governed by specific residues in hypervariable region 1 of E2 leading to enhanced cell entry and depending on SR-BI ability to bind to E2.
Collapse
Affiliation(s)
- Viet Loan Dao Thi
- From the INSERM, U758, Human Virology Laboratory, EVIR team, Lyon, F-69007, France
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, UCB-Lyon1, Lyon, F-69007, France
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
| | - Christelle Granier
- From the INSERM, U758, Human Virology Laboratory, EVIR team, Lyon, F-69007, France
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, UCB-Lyon1, Lyon, F-69007, France
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
| | - Mirjam B. Zeisel
- INSERM, U748, 67000, Strasbourg, France
- Université de Strasbourg, 67000, Strasbourg, France
| | | | - Jimmy Mancip
- From the INSERM, U758, Human Virology Laboratory, EVIR team, Lyon, F-69007, France
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, UCB-Lyon1, Lyon, F-69007, France
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
| | - Ophélia Granio
- From the INSERM, U758, Human Virology Laboratory, EVIR team, Lyon, F-69007, France
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, UCB-Lyon1, Lyon, F-69007, France
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
| | - François Penin
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
- Institut de Biologie et Chimie des Protéines, UMR 5086 CNRS, Université de Lyon, Lyon, F-69367, France
| | - Dimitri Lavillette
- From the INSERM, U758, Human Virology Laboratory, EVIR team, Lyon, F-69007, France
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, UCB-Lyon1, Lyon, F-69007, France
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
| | - Ralf Bartenschlager
- the Department of Infectious Diseases, Molecular Virology, University of Heidelberg, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany, and
| | - Thomas F. Baumert
- INSERM, U748, 67000, Strasbourg, France
- Université de Strasbourg, 67000, Strasbourg, France
- Pôle Hepato-digestif, Hôpitaux Universitaires de Strasbourg, 67000, Strasbourg, France
| | - François-Loïc Cosset
- From the INSERM, U758, Human Virology Laboratory, EVIR team, Lyon, F-69007, France
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, UCB-Lyon1, Lyon, F-69007, France
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
| | - Marlène Dreux
- From the INSERM, U758, Human Virology Laboratory, EVIR team, Lyon, F-69007, France
- Ecole Normale Supérieure de Lyon, Lyon, F-69007, France
- Université de Lyon, UCB-Lyon1, Lyon, F-69007, France
- LabEx Ecofect, Université de Lyon, Lyon, F-69007, France
| |
Collapse
|
43
|
Rosenblat M, Ward S, Volkova N, Hayek T, Aviram M. VLDL triglycerides inhibit HDL-associated paraoxonase 1 (PON1) activity: in vitro and in vivo studies. Biofactors 2012; 38:292-9. [PMID: 22674772 DOI: 10.1002/biof.1021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Accepted: 04/02/2012] [Indexed: 01/31/2023]
Abstract
We analyzed, for the first time, both in vitro and in vivo, the effect of very low density lipoprotein (VLDL), or of pure triglycerides, on high-density lipoprotein (HDL)-associated paraoxonase1 (PON1) catalytic activities. Incubation of serum or HDL from healthy subjects with VLDL (0-330 μg protein/mL) significantly decreased serum PON1 lactonase or arylesterase activities by up to 11% or 24%, and HDL-associated PON1 lactonase or arylesterase activities by up to 32% or 46%, respectively, in a VLDL dose-dependent manner. VLDL (0-660 μg protein/mL) also inhibited recombinant PON1 (rePON1) lactonase or arylesterase activities by up to 20% or 42%, respectively. Similar inhibitory effect was noted upon rePON1 incubation with pure triglyceride emulsion. Bezafibrate therapy to three hypertriglyceridemic patients (400 mg/day, for one month) significantly decreased serum triglyceride concentration by 67%, and increased serum HDL cholesterol levels by 48%. PON1 arylesterase or paraoxonase activities in the patients' HDL fractions after drug therapy were significantly increased by 86-88%, as compared to PON1 activities before treatment. Similarly, HDL-PON1 protein levels significantly increased after bezafibrate therapy. Finally, bezafibrate therapy improved HDL biological activity, as HDL obtained after drug therapy showed increased ability to induce cholesterol efflux from J774A.1 macrophages, by 19%, as compared to HDL derived before therapy. We thus conclude that VLDL triglycerides inhibit PON1 catalytic activities, and bezafibrate therapy significantly improved HDL-PON1 catalytic and biological activities.
Collapse
Affiliation(s)
- Mira Rosenblat
- The Lipid Research Laboratory, Technion Faculty of Medicine, the Rappaport Family Institute for Research in the Medical Sciences, Rambam Medical Center, Haifa, Israel
| | | | | | | | | |
Collapse
|
44
|
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.
Collapse
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
| | | | | |
Collapse
|
45
|
Ballantyne CM, Miller M, Niesor EJ, Burgess T, Kallend D, Stein EA. Effect of dalcetrapib plus pravastatin on lipoprotein metabolism and high-density lipoprotein composition and function in dyslipidemic patients: results of a phase IIb dose-ranging study. Am Heart J 2012; 163:515-21, 521.e1-3. [PMID: 22424025 DOI: 10.1016/j.ahj.2011.11.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 11/30/2011] [Indexed: 10/28/2022]
Abstract
BACKGROUND Cholesteryl ester transfer protein (CETP) is involved in high-density lipoprotein (HDL) remodeling and transfer of lipids between HDL particles and other lipoproteins. Epidemiologic studies show that both elevated HDL-cholesterol (HDL-C) and reduced CETP activity attenuate cardiovascular risk, making inhibition or modulation of CETP a potential therapeutic target. This study analyzed the effect of dalcetrapib on lipoprotein profile, CETP activity, and cellular cholesterol efflux when co-administered with pravastatin in patients with low or average HDL-C. METHODS Patients were randomized in a double-blind fashion to receive placebo or dalcetrapib 300, 600, or 900 mg once daily for 12 weeks. All patients were concomitantly treated to their low-density lipoprotein cholesterol target with pravastatin. Lipoprotein profile was analyzed by nuclear magnetic resonance spectroscopy and polyacrylamide gradient gel electrophoresis. Composition of the HDL fraction was assessed after polyethylene glycol precipitation. Contribution of this fraction to cholesterol efflux was assessed using radiolabeled donor cells. RESULTS Co-administration of dalcetrapib with pravastatin increased HDL-C, apolipoproteins (apo) A-I and A-II, and CETP mass, and decreased CETP activity. A relative increase in large HDL and low-density lipoprotein subparticle fractions was observed. High-density lipoprotein composition showed increased association of esterified cholesterol, free cholesterol, phospholipids, apo A-I, and apo E. Adenosine 5'-triphosphate-binding cassette A1- and scavenger receptor type BI-mediated cholesterol efflux increased. CONCLUSIONS Dalcetrapib up to 600 mg, combined with pravastatin, increased HDL-C and altered lipoprotein profile, HDL composition, and HDL function, with little further change at a 900-mg dose. The impact on cardiovascular events in dyslipidemic patients is being evaluated.
Collapse
|
46
|
Rosenblat M, Volkova N, Aviram M. Injection of paraoxonase 1 (PON1) to mice stimulates their HDL and macrophage antiatherogenicity. Biofactors 2011; 37:462-7. [PMID: 22162319 DOI: 10.1002/biof.188] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 09/08/2011] [Indexed: 11/08/2022]
Abstract
We analyzed, for the first time, the effects of recombinant PON1 (rePON1) intraperitoneal injection to C₅₇BL/6 mice on their HDL and macrophage antiatherogenic properties. Thioglycolate-treated mice were injected with either saline (Control), or rePON1 (50 μg/mouse), and 20 H post injection, their blood samples and peritoneal macrophages (MPM) were collected. A significant increase in serum and HDL-PON1 arylesterase and lactonase activities was noted. Similarly, a significant increment, by 3.8 and 2.8 fold, in MPM-PON1 arylesterase and lactonase activities, respectively, as compared to the activities in control MPM was observed. The HDL from rePON1-injected mice was resistant to oxidation by copper ions as compared to control HDL. Furthermore, enrichment of the mouse HDL with rePON1 increased its ability to induce cholesterol efflux from J774A.1 macrophage cell line, and to inhibit macrophage-mediated LDL oxidation. In MPM from rePON1-injected mice vs. control MPM, there was a significant reduction in cholesterol mass, by 42%, in association with inhibition in cellular cholesterol biosynthesis rate, by 33%, and with significant stimulation, by 65%, of human HDL-mediated cholesterol efflux from the cells. We conclude that rePON1 injection to mice improved the mice HDL and MPM antiatherogenic properties, and these effects could probably lead to attenuation of atherosclerosis development.
Collapse
Affiliation(s)
- Mira Rosenblat
- The Lipid Research Laboratory, Technion Faculty of Medicine, the Rappaport Family Institute for Research in the Medical Sciences, Rambam Medical Center, Haifa, Israel
| | | | | |
Collapse
|
47
|
Valacchi G, Sticozzi C, Lim Y, Pecorelli A. Scavenger receptor class B type I: a multifunctional receptor. Ann N Y Acad Sci 2011; 1229:E1-7. [DOI: 10.1111/j.1749-6632.2011.06205.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
48
|
Exoplasmic cysteine Cys384 of the HDL receptor SR-BI is critical for its sensitivity to a small-molecule inhibitor and normal lipid transport activity. Proc Natl Acad Sci U S A 2011; 108:12243-8. [PMID: 21746906 DOI: 10.1073/pnas.1109078108] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The HDL receptor, scavenger receptor, class B, type I (SR-BI), is a homooligomeric cell surface glycoprotein that controls HDL structure and metabolism by mediating the cellular selective uptake of lipids, mainly cholesteryl esters, from HDL. The mechanism underlying SR-BI-mediated lipid transfer, which differs from classic receptor-mediated endocytosis, involves a two-step process (binding followed by lipid transport) that is poorly understood. Our previous structure/activity analysis of the small-molecule inhibitor blocker of lipid transport 1 (BLT-1), which potently (IC(50) ∼ 50 nM) blocks SR-BI-mediated lipid transport, established that the sulfur in BLT-1's thiosemicarbazone moiety was essential for activity. Here we show that BLT-1 is an irreversible inhibitor of SR-BI, raising the possibility that cysteine(s) in SR-BI interact with BLT-1. Mass spectrometric analysis of purified SR-BI showed two of its six exoplasmic cysteines have free thiol groups (Cys251 and Cys384). Converting Cys384 (but not Cys251) to serine resulted in complete BLT-1 insensitivity, establishing that the unique molecular target of BLT-1 inhibition of cellular SR-BI dependent lipid transport is SR-BI itself. The C384S substitution reduced the receptor's intrinsic lipid uptake activity by approximately 60% without dramatically altering its surface expression, homooligomerization, or HDL binding. Thus, a small-molecule screening approach identified a key residue in SR-BI involved in lipid transport, providing a powerful springboard into the analyses of the structure and mechanism of SR-BI, and highlighting the power of this approach for such analyses.
Collapse
|
49
|
Gaidukov L, Nager AR, Xu S, Penman M, Krieger M. Glycine dimerization motif in the N-terminal transmembrane domain of the high density lipoprotein receptor SR-BI required for normal receptor oligomerization and lipid transport. J Biol Chem 2011; 286:18452-64. [PMID: 21454587 PMCID: PMC3099662 DOI: 10.1074/jbc.m111.229872] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 03/23/2011] [Indexed: 12/15/2022] Open
Abstract
Scavenger receptor class B, type I (SR-BI), a CD36 superfamily member, is an oligomeric high density lipoprotein (HDL) receptor that mediates negatively cooperative HDL binding and selective lipid uptake. We identified in the N-terminal transmembrane (N-TM) domain of SR-BI a conserved glycine dimerization motif, G(15)X(2)G(18)X(3)AX(2)G(25), of which the submotif G(18)X(3)AX(2)G(25) significantly contributes to homodimerization and lipid uptake activity. SR-BI variants were generated by mutations (single or multiple Gly → Leu substitutions) or by replacing the N-TM domain with those from other CD36 superfamily members containing (croquemort) or lacking (lysosomal integral membrane protein (LIMP) II) this glycine motif (chimeras). None of the SR-BI variants exhibited altered surface expression (based on antibody binding) or HDL binding. However, the G15L/G18L/G25L triple mutant exhibited reductions in cell surface homo-oligomerization (>10-fold) and the rate of selective lipid uptake (∼ 2-fold). Gly(18) and Gly(25) were necessary for normal lipid uptake activity of SR-BI and the SR-BI/croquemort chimera. The lipid uptake activity of the glycine motif-deficient SR-BI/LIMP II chimera was low but could be increased by introducing glycines at positions 18 and 25. The rate of lipid uptake mediated by SR-BI/LIMP II chimeras was proportional to the extent of receptor oligomerization. Thus, the glycine dimerization motif G(18)X(3)AX(2)G(25) in the N-TM domain of SR-BI contributes substantially to the homo-oligomerization and lipid transport activity of SR-BI but does not influence the negative cooperativity of HDL binding. Oligomerization-independent binding cooperativity suggests that classic allostery is not involved and that the negative cooperativity is probably the consequence of a "lattice effect" (interligand steric interference accompanying binding to adjacent receptors).
Collapse
Affiliation(s)
- Leonid Gaidukov
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Andrew R. Nager
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Shangzhe Xu
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Marsha Penman
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Monty Krieger
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| |
Collapse
|
50
|
Nieland TJ, Xu S, Penman M, Krieger M. Negatively cooperative binding of high-density lipoprotein to the HDL receptor SR-BI. Biochemistry 2011; 50:1818-30. [PMID: 21254782 PMCID: PMC3065119 DOI: 10.1021/bi101657j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Scavenger receptor class B, type I (SR-BI), is a high-density lipoprotein (HDL) receptor, which also binds low-density lipoprotein (LDL), and mediates the cellular selective uptake of cholesteryl esters from lipoproteins. SR-BI also is a coreceptor for hepatitis C virus and a signaling receptor that regulates cell metabolism. Many investigators have reported that lipoproteins bind to SR-BI via a single class of independent (not interacting), high-affinity binding sites (one site model). We have reinvestigated the ligand concentration dependence of (125)I-HDL binding to SR-BI and SR-BI-mediated specific uptake of [(3)H]CE from [(3)H]CE-HDL using an expanded range of ligand concentrations (<1 μg of protein/mL, lower than previously reported). Scatchard and nonlinear least-squares model fitting analyses of the binding and uptake data were both inconsistent with a single class of independent binding sites binding univalent lipoprotein ligands. The data are best fit by models in which SR-BI has either two independent classes of binding sites or one class of sites exhibiting negative cooperativity due to either classic allostery or ensemble effects ("lattice model"). Similar results were observed for LDL. Application of the "infinite dilution" dissociation rate method established that the binding of (125)I-HDL to SR-BI at 4 °C exhibits negative cooperativity. The unexpected complexity of the interactions of lipoproteins with SR-BI should be taken into account when interpreting the results of experiments that explore the mechanism(s) by which SR-BI mediates ligand binding, lipid transport, and cell signaling.
Collapse
Affiliation(s)
- Thomas J.F. Nieland
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
- Broad Institute of Harvard and MIT, 7 Cambridge Center, Cambridge, MA 02142
| | - Shangzhe Xu
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Marsha Penman
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Monty Krieger
- Department of Biology, Massachusetts Institute of Technology, Room 68-483, 77 Massachusetts Avenue, Cambridge, MA 02139
| |
Collapse
|