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Li YE, Norris DM, Xiao FN, Pandzic E, Whan RM, Fok S, Zhou M, Du G, Liu Y, Du X, Yang H. Phosphatidylserine regulates plasma membrane repair through tetraspanin-enriched macrodomains. J Cell Biol 2024; 223:e202307041. [PMID: 38530252 PMCID: PMC10964951 DOI: 10.1083/jcb.202307041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 11/30/2023] [Accepted: 03/11/2024] [Indexed: 03/27/2024] Open
Abstract
The integrity of the plasma membrane is critical to cell function and survival. Cells have developed multiple mechanisms to repair damaged plasma membranes. A key process during plasma membrane repair is to limit the size of the damage, which is facilitated by the presence of tetraspanin-enriched rings surrounding damage sites. Here, we identify phosphatidylserine-enriched rings surrounding damaged sites of the plasma membrane, resembling tetraspanin-enriched rings. Importantly, the formation of both the phosphatidylserine- and tetraspanin-enriched rings requires phosphatidylserine and its transfer proteins ORP5 and ORP9. Interestingly, ORP9, but not ORP5, is recruited to the damage sites, suggesting cells acquire phosphatidylserine from multiple sources upon plasma membrane damage. We further demonstrate that ORP9 contributes to efficient plasma membrane repair. Our results thus unveil a role for phosphatidylserine and its transfer proteins in facilitating the formation of tetraspanin-enriched macrodomains and plasma membrane repair.
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Affiliation(s)
- Yang E. Li
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Dougall M. Norris
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Fanqian N. Xiao
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Elvis Pandzic
- Katerina Gaus Light Microscopy Facility, Mark Wainwright Analytical Center, University of New South Wales, Sydney, Australia
| | - Renee M. Whan
- Katerina Gaus Light Microscopy Facility, Mark Wainwright Analytical Center, University of New South Wales, Sydney, Australia
| | - Sandra Fok
- Katerina Gaus Light Microscopy Facility, Mark Wainwright Analytical Center, University of New South Wales, Sydney, Australia
| | - Ming Zhou
- Verna and Marrs McLean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Guangwei Du
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Yang Liu
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Ximing Du
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA
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2
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Oqua AI, Manchanda Y, McGlone ER, Jones B, Rouse S, Tomas A. Lipid regulation of the glucagon receptor family. J Endocrinol 2024; 261:e230335. [PMID: 38614123 PMCID: PMC11103681 DOI: 10.1530/joe-23-0335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 04/09/2024] [Indexed: 04/15/2024]
Abstract
The glucagon receptor family are typical class B1 G protein-coupled receptors (GPCRs) with important roles in metabolism, including the control of pancreas, brain, and liver function. As proteins with seven transmembrane domains, GPCRs are intimately in contact with lipid bilayers and therefore can be putatively regulated by interactions with their lipidic components, including cholesterol, sphingolipids, and other lipid species. Additionally, these receptors, as well as the agonists they bind to, can undergo lipid modifications, which can influence their binding capacity and/or elicit modified or biased signalling profiles. While the effect of lipids, and in particular cholesterol, has been widely studied for other GPCR classes, information about their role in regulating the glucagon receptor family is only beginning to emerge. Here we summarise our current knowledge on the effects of cholesterol modulation of glucagon receptor family signalling and trafficking profiles, as well as existing evidence for specific lipid-receptor binding and indirect effects of lipids via lipid modification of cognate agonists. Finally, we discuss the different methodologies that can be employed to study lipid-receptor interactions and summarise the importance of this area of investigation to increase our understanding of the biology of this family of metabolically relevant receptors.
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Affiliation(s)
- Affiong Ika Oqua
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
| | - Yusman Manchanda
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
| | - Emma Rose McGlone
- Department of Surgery and Cancer, Imperial College London, London, UK
| | - Ben Jones
- Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
| | - Sarah Rouse
- Department of Life Sciences, Imperial College, London, UK
| | - Alejandra Tomas
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
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3
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Moore MP, Wang X, Kennelly JP, Shi H, Ishino Y, Kano K, Aoki J, Cherubini A, Ronzoni L, Guo X, Chalasani NP, Khalid S, Saleheen D, Mitsche MA, Rotter JI, Yates KP, Valenti L, Kono N, Tontonoz P, Tabas I. Low MBOAT7 expression, a genetic risk for MASH, promotes a profibrotic pathway involving hepatocyte TAZ upregulation. Hepatology 2024:01515467-990000000-00886. [PMID: 38776184 DOI: 10.1097/hep.0000000000000933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 04/03/2024] [Indexed: 05/24/2024]
Abstract
BACKGROUND AND AIMS The common genetic variant rs641738 C>T is a risk factor for metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis (MASH), including liver fibrosis, and is associated with decreased expression of the phospholipid-remodeling enzyme MBOAT7 (LPIAT1). However, whether restoring MBOAT7 expression in established metabolic dysfunction-associated steatotic liver disease dampens the progression to liver fibrosis and, importantly, the mechanism through which decreased MBOAT7 expression exacerbates MASH fibrosis remain unclear. APPROACH AND RESULTS We first showed that hepatocyte MBOAT7 restoration in mice with diet-induced steatohepatitis slows the progression to liver fibrosis. Conversely, when hepatocyte-MBOAT7 was silenced in mice with established hepatosteatosis, liver fibrosis but not hepatosteatosis was exacerbated. Mechanistic studies revealed that hepatocyte-MBOAT7 restoration in MASH mice lowered hepatocyte-TAZ (WWTR1), which is known to promote MASH fibrosis. Conversely, hepatocyte-MBOAT7 silencing enhanced TAZ upregulation in MASH. Finally, we discovered that changes in hepatocyte phospholipids due to MBOAT7 loss-of-function promote a cholesterol trafficking pathway that upregulates TAZ and the TAZ-induced profibrotic factor Indian hedgehog (IHH). As evidence for relevance in humans, we found that the livers of individuals with MASH carrying the rs641738-T allele had higher hepatocyte nuclear TAZ, indicating higher TAZ activity and increased IHH mRNA. CONCLUSIONS This study provides evidence for a novel mechanism linking MBOAT7-LoF to MASH fibrosis, adds new insight into an established genetic locus for MASH, and, given the druggability of hepatocyte TAZ for MASH fibrosis, suggests a personalized medicine approach for subjects at increased risk for MASH fibrosis due to inheritance of variants that lower MBOAT7.
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Affiliation(s)
- Mary P Moore
- Department of Medicine, Columbia University Irving Medical Center, New York, New York, USA
| | - Xiaobo Wang
- Department of Medicine, Columbia University Irving Medical Center, New York, New York, USA
| | - John Paul Kennelly
- Department of Pathology and Laboratory Medicine, Molecular Biology Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - Hongxue Shi
- Department of Medicine, Columbia University Irving Medical Center, New York, New York, USA
| | - Yuki Ishino
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Kuniyuki Kano
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Junken Aoki
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Alessandro Cherubini
- Precisione Medicine Lab, Biological Resource Center and Department of Transfusion Medicine, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico Milano, Milan, Italy
| | - Luisa Ronzoni
- Precisione Medicine Lab, Biological Resource Center and Department of Transfusion Medicine, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico Milano, Milan, Italy
| | - Xiuqing Guo
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA
| | - Naga P Chalasani
- Division of Gastroenterology and Hepatology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Shareef Khalid
- Department of Medicine, Columbia University Irving Medical Center, New York, New York, USA
- Center for Non-Communicable Disease, Karachi, Karachi City, Sindh, Pakistan
| | - Danish Saleheen
- Department of Medicine, Columbia University Irving Medical Center, New York, New York, USA
- Center for Non-Communicable Disease, Karachi, Karachi City, Sindh, Pakistan
| | - Matthew A Mitsche
- Center for Human Nutrition and Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Jerome I Rotter
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA
| | - Katherine P Yates
- Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
| | - Luca Valenti
- Precisione Medicine Lab, Biological Resource Center and Department of Transfusion Medicine, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico Milano, Milan, Italy
- Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milano, Italy
| | - Nozomu Kono
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, Molecular Biology Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
| | - Ira Tabas
- Department of Medicine, Columbia University Irving Medical Center, New York, New York, USA
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, New York, USA
- Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, New York, USA
- Columbia University Digestive and Liver Disease Research Center, New York, NY
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4
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Yalcinkaya M, Liu W, Xiao T, Abramowicz S, Wang R, Wang N, Westerterp M, Tall AR. Cholesterol trafficking to the ER leads to the activation of CaMKII/JNK/NLRP3 and promotes atherosclerosis. J Lipid Res 2024; 65:100534. [PMID: 38522750 PMCID: PMC11031842 DOI: 10.1016/j.jlr.2024.100534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 03/12/2024] [Accepted: 03/14/2024] [Indexed: 03/26/2024] Open
Abstract
The deposition of cholesterol-rich lipoproteins in the arterial wall triggers macrophage inflammatory responses, which promote atherosclerosis. The NLRP3 inflammasome aggravates atherosclerosis; however, cellular mechanisms connecting macrophage cholesterol accumulation to inflammasome activation are poorly understood. We investigated the mechanisms of NLRP3 inflammasome activation in cholesterol-loaded macrophages and in atherosclerosis-prone Ldlr-/- mice with defects in macrophage cholesterol efflux. We found that accumulation of cholesterol in macrophages treated with modified LDL or cholesterol crystals, or in macrophages defective in the cholesterol efflux promoting transporters ABCA1 and ABCG1, leads to activation of NLRP3 inflammasomes as a result of increased cholesterol trafficking from the plasma membrane to the ER, via Aster-B. In turn, the accumulation of cholesterol in the ER activates the inositol triphosphate-3 receptor, CaMKII/JNK, and induces NLRP3 deubiquitylation by BRCC3. An NLRP3 deubiquitylation inhibitor or deficiency of Abro1, an essential scaffolding protein in the BRCC3-containing cytosolic complex, suppressed inflammasome activation, neutrophil extracellular trap formation (NETosis), and atherosclerosis in vivo. These results identify a link between the trafficking of cholesterol to the ER, NLRP3 deubiquitylation, inflammasome activation, and atherosclerosis.
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Affiliation(s)
- Mustafa Yalcinkaya
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA.
| | - Wenli Liu
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Tong Xiao
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Sandra Abramowicz
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Ranran Wang
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Nan Wang
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Marit Westerterp
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA; Department of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Alan R Tall
- Division of Molecular Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA.
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5
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Gao Y, Kennelly JP, Xiao X, Whang E, Ferrari A, Bedard AH, Mack JJ, Nguyen AH, Weston T, Uchiyama LF, Lee MS, Young SG, Bensinger SJ, Tontonoz P. T cell cholesterol transport is a metabolic checkpoint that links intestinal immune responses to dietary lipid absorption. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.08.584164. [PMID: 38559079 PMCID: PMC10979874 DOI: 10.1101/2024.03.08.584164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The intrinsic pathways that control membrane organization in immune cells and the impact of such pathways on cellular function are not well defined. Here we report that the non-vesicular cholesterol transporter Aster-A links plasma membrane (PM) cholesterol availability in T cells to immune signaling and systemic metabolism. Aster-A is recruited to the PM during T-cell receptor (TCR) activation, where it facilitates the removal of newly generated "accessible" membrane cholesterol. Loss of Aster-A leads to excess PM cholesterol accumulation, resulting in enhanced TCR nano-clustering and signaling, and Th17 cytokine production. Finally, we show that the mucosal Th17 response is restrained by PM cholesterol remodeling. Ablation of Aster-A in T cells leads to enhanced IL-22 production, reduced intestinal fatty acid absorption, and resistance to diet-induced obesity. These findings delineate a multi-tiered regulatory scheme linking immune cell lipid flux to nutrient absorption and systemic physiology.
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6
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Rong S, Xia M, Vale G, Wang S, Kim CW, Li S, McDonald JG, Radhakrishnan A, Horton JD. DGAT2 inhibition blocks SREBP-1 cleavage and improves hepatic steatosis by increasing phosphatidylethanolamine in the ER. Cell Metab 2024; 36:617-629.e7. [PMID: 38340721 PMCID: PMC10939742 DOI: 10.1016/j.cmet.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 11/28/2023] [Accepted: 01/18/2024] [Indexed: 02/12/2024]
Abstract
Diacylglycerol acyltransferase 2 (DGAT2) catalyzes the final step of triglyceride (TG) synthesis. DGAT2 deletion in mice lowers liver TGs, and DGAT2 inhibitors are under investigation for the treatment of fatty liver disease. Here, we show that DGAT2 inhibition also suppressed SREBP-1 cleavage, reduced fatty acid synthesis, and lowered TG accumulation and secretion from liver. DGAT2 inhibition increased phosphatidylethanolamine (PE) levels in the endoplasmic reticulum (ER) and inhibited SREBP-1 cleavage, while DGAT2 overexpression lowered ER PE concentrations and increased SREBP-1 cleavage in vivo. ER enrichment with PE blocked SREBP-1 cleavage independent of Insigs, which are ER proteins that normally retain SREBPs in the ER. Thus, inhibition of DGAT2 shunted diacylglycerol into phospholipid synthesis, increasing the PE content of the ER, resulting in reduced SREBP-1 cleavage and less hepatic steatosis. This study reveals a new mechanism that regulates SREBP-1 activation and lipogenesis that is independent of sterols and SREBP-2 in liver.
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Affiliation(s)
- Shunxing Rong
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA; Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Mingfeng Xia
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA; Department of Endocrinology and Metabolism, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Goncalo Vale
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA; Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Simeng Wang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Chai-Wan Kim
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA; Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Shili Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Jeffrey G McDonald
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA; Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Arun Radhakrishnan
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA
| | - Jay D Horton
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA; Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA.
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7
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Gillard BK, Rosales C, Gotto AM, Pownall HJ. The pathophysiology of excess plasma-free cholesterol. Curr Opin Lipidol 2023; 34:278-286. [PMID: 37732779 PMCID: PMC10624414 DOI: 10.1097/mol.0000000000000899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
PURPOSE OF REVIEW Several large studies have shown increased mortality due to all-causes and to atherosclerotic cardiovascular disease. In most clinical settings, plasma HDL-cholesterol is determined as a sum of free cholesterol and cholesteryl ester, two molecules with vastly different metabolic itineraries. We examine the evidence supporting the concept that the pathological effects of elevations of plasma HDL-cholesterol are due to high levels of the free cholesterol component of HDL-C. RECENT FINDINGS In a small population of humans, a high plasma HDL-cholesterol is associated with increased mortality. Similar observations in the HDL-receptor deficient mouse (Scarb1 -/- ), a preclinical model of elevated HDL-C, suggests that the pathological component of HDL in these patients is an elevated plasma HDL-FC. SUMMARY Collective consideration of the human and mouse data suggests that clinical trials, especially in the setting of high plasma HDL, should measure free cholesterol and cholesteryl esters and not just total cholesterol.
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Affiliation(s)
- Baiba K. Gillard
- Center for Bioenergetics, Houston Methodist, Houston, Texas
- Weill Cornell Medicine, New York, New York, USA
| | - Corina Rosales
- Center for Bioenergetics, Houston Methodist, Houston, Texas
- Weill Cornell Medicine, New York, New York, USA
| | - Antonio M. Gotto
- Center for Bioenergetics, Houston Methodist, Houston, Texas
- Weill Cornell Medicine, New York, New York, USA
| | - Henry J. Pownall
- Center for Bioenergetics, Houston Methodist, Houston, Texas
- Weill Cornell Medicine, New York, New York, USA
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8
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Shaw TR, Wisser KC, Schaffner TA, Gaffney AD, Machta BB, Veatch SL. Chemical potential measurements constrain models of cholesterol-phosphatidylcholine interactions. Biophys J 2023; 122:1105-1117. [PMID: 36785512 PMCID: PMC10111267 DOI: 10.1016/j.bpj.2023.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 12/12/2022] [Accepted: 02/01/2023] [Indexed: 02/15/2023] Open
Abstract
Bilayer membranes composed of cholesterol and phospholipids exhibit diverse forms of nonideal mixing. In particular, many previous studies document macroscopic liquid-liquid phase separation as well as nanometer-scale heterogeneity in membranes of phosphatidylcholine (PC) lipids and cholesterol. Here, we present experimental measurements of cholesterol chemical potential (μc) in binary membranes containing dioleoyl PC (DOPC), 1-palmitoyl-2-oleoyl PC (POPC), or dipalmitoyl PC (DPPC), and in ternary membranes of DOPC and DPPC, referenced to crystalline cholesterol. μc is the thermodynamic quantity that dictates the availability of cholesterol to bind other factors, and notably must be equal between coexisting phases of a phase separated mixture. It is simply related to concentration under conditions of ideal mixing, but is far from ideal for the majority of lipid mixtures investigated here. Measurements of μc can vary with phospholipid composition by 1.5 kBT at constant cholesterol mole fraction implying a more than fivefold change in its availability for binding receptors and other reactions. Experimental measurements are fit to thermodynamic models including cholesterol-DPPC complexes or pairwise interactions between lipid species to provide intuition about the magnitude of interactions. These findings reinforce that μc depends on membrane composition overall, suggesting avenues for cells to alter the availability of cholesterol without varying cholesterol concentration.
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Affiliation(s)
- Thomas R Shaw
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan; Program in Applied Physics, University of Michigan, Ann Arbor, Michigan
| | | | | | - Anna D Gaffney
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan
| | | | - Sarah L Veatch
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan; Program in Applied Physics, University of Michigan, Ann Arbor, Michigan.
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9
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Lange Y, Tabei SMA, Steck TL. A basic model for the association of ligands with membrane cholesterol: application to cytolysin binding. J Lipid Res 2023; 64:100344. [PMID: 36791915 PMCID: PMC10119614 DOI: 10.1016/j.jlr.2023.100344] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/19/2023] [Accepted: 02/07/2023] [Indexed: 02/16/2023] Open
Abstract
Almost all the cholesterol in cellular membranes is associated with phospholipids in simple stoichiometric complexes. This limits the binding of sterol ligands such as filipin and Perfringolysin O (PFO) to a small fraction of the total. We offer a simple mathematical model that characterizes this complexity. It posits that the cholesterol accessible to ligands has two forms: active cholesterol, which is that not complexed with phospholipids; and extractable cholesterol, that which ligands can capture competitively from the phospholipid complexes. Simulations based on the model match published data for the association of PFO oligomers with liposomes, plasma membranes and the isolated endoplasmic reticulum. The model shows how the binding of a probe greatly underestimates cholesterol abundance when its affinity for the sterol is so weak that it competes poorly with the membrane phospholipids. Two examples are the under-staining of plasma membranes by filipin and the failure of domain D4 of PFO to label their cytoplasmic leaflets. Conversely, the exaggerated staining of endolysosomes suggests that their cholesterol, being uncomplexed, is readily available. The model is also applicable to the association of cholesterol with intrinsic membrane proteins. For example, it supports the hypothesis that the sharp threshold in the regulation of homeostatic ER proteins by cholesterol derives from the cooperativity of their binding to the sterol weakly held by the phospholipid. § Thus, the model explicates the complexity inherent in the binding of ligands like PFO and filipin to the small accessible fraction of membrane cholesterol.
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Affiliation(s)
- Yvonne Lange
- 1Department of Pathology, Rush University Medical Center, Chicago, Il 60612, USA.
| | - S M Ali Tabei
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614, USA
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Il 60637, USA
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10
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Heisler DB, Johnson KA, Ma DH, Ohlson MB, Zhang L, Tran M, Corley CD, Abrams ME, McDonald JG, Schoggins JW, Alto NM, Radhakrishnan A. A concerted mechanism involving ACAT and SREBPs by which oxysterols deplete accessible cholesterol to restrict microbial infection. eLife 2023; 12:e83534. [PMID: 36695568 PMCID: PMC9925056 DOI: 10.7554/elife.83534] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 01/25/2023] [Indexed: 01/26/2023] Open
Abstract
Most of the cholesterol in the plasma membranes (PMs) of animal cells is sequestered through interactions with phospholipids and transmembrane domains of proteins. However, as cholesterol concentration rises above the PM's sequestration capacity, a new pool of cholesterol, called accessible cholesterol, emerges. The transport of accessible cholesterol between the PM and the endoplasmic reticulum (ER) is critical to maintain cholesterol homeostasis. This pathway has also been implicated in the suppression of both bacterial and viral pathogens by immunomodulatory oxysterols. Here, we describe a mechanism of depletion of accessible cholesterol from PMs by the oxysterol 25-hydroxycholesterol (25HC). We show that 25HC-mediated activation of acyl coenzyme A: cholesterol acyltransferase (ACAT) in the ER creates an imbalance in the equilibrium distribution of accessible cholesterol between the ER and PM. This imbalance triggers the rapid internalization of accessible cholesterol from the PM, and this depletion is sustained for long periods of time through 25HC-mediated suppression of SREBPs and continued activation of ACAT. In support of a physiological role for this mechanism, 25HC failed to suppress Zika virus and human coronavirus infection in ACAT-deficient cells, and Listeria monocytogenes infection in ACAT-deficient cells and mice. We propose that selective depletion of accessible PM cholesterol triggered by ACAT activation and sustained through SREBP suppression underpins the immunological activities of 25HC and a functionally related class of oxysterols.
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Affiliation(s)
- David B Heisler
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Kristen A Johnson
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Duo H Ma
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Maikke B Ohlson
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Lishu Zhang
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Michelle Tran
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Chase D Corley
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Michael E Abrams
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Jeffrey G McDonald
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - John W Schoggins
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Neal M Alto
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Arun Radhakrishnan
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
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Kinnebrew M, Luchetti G, Sircar R, Frigui S, Viti LV, Naito T, Beckert F, Saheki Y, Siebold C, Radhakrishnan A, Rohatgi R. Patched 1 reduces the accessibility of cholesterol in the outer leaflet of membranes. eLife 2021; 10:e70504. [PMID: 34698632 PMCID: PMC8654371 DOI: 10.7554/elife.70504] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 10/25/2021] [Indexed: 11/13/2022] Open
Abstract
A long-standing mystery in vertebrate Hedgehog signaling is how Patched 1 (PTCH1), the receptor for Hedgehog ligands, inhibits the activity of Smoothened, the protein that transmits the signal across the membrane. We previously proposed (Kinnebrew et al., 2019) that PTCH1 inhibits Smoothened by depleting accessible cholesterol from the ciliary membrane. Using a new imaging-based assay to directly measure the transport activity of PTCH1, we find that PTCH1 depletes accessible cholesterol from the outer leaflet of the plasma membrane. This transport activity is terminated by binding of Hedgehog ligands to PTCH1 or by dissipation of the transmembrane potassium gradient. These results point to the unexpected model that PTCH1 moves cholesterol from the outer to the inner leaflet of the membrane in exchange for potassium ion export in the opposite direction. Our study provides a plausible solution for how PTCH1 inhibits SMO by changing the organization of cholesterol in membranes and establishes a general framework for studying how proteins change cholesterol accessibility to regulate membrane-dependent processes in cells.
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Affiliation(s)
- Maia Kinnebrew
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Giovanni Luchetti
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
- Department of Physiological Chemistry, GenentechSouth San FranciscoUnited States
| | - Ria Sircar
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Sara Frigui
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Lucrezia Vittoria Viti
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of OxfordOxfordUnited Kingdom
| | - Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological UniversitySingaporeSingapore
| | - Francis Beckert
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological UniversitySingaporeSingapore
| | - Christian Siebold
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of OxfordOxfordUnited Kingdom
| | - Arun Radhakrishnan
- Department of Molecular Genetics, University of Texas Southwestern Medical CenterDallasUnited States
| | - Rajat Rohatgi
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
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