1
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Freitas FP, Alborzinia H, Dos Santos AF, Nepachalovich P, Pedrera L, Zilka O, Inague A, Klein C, Aroua N, Kaushal K, Kast B, Lorenz SM, Kunz V, Nehring H, Xavier da Silva TN, Chen Z, Atici S, Doll SG, Schaefer EL, Ekpo I, Schmitz W, Horling A, Imming P, Miyamoto S, Wehman AM, Genaro-Mattos TC, Mirnics K, Kumar L, Klein-Seetharaman J, Meierjohann S, Weigand I, Kroiss M, Bornkamm GW, Gomes F, Netto LES, Sathian MB, Konrad DB, Covey DF, Michalke B, Bommert K, Bargou RC, Garcia-Saez A, Pratt DA, Fedorova M, Trumpp A, Conrad M, Friedmann Angeli JP. 7-Dehydrocholesterol is an endogenous suppressor of ferroptosis. Nature 2024; 626:401-410. [PMID: 38297129 DOI: 10.1038/s41586-023-06878-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/17/2023] [Indexed: 02/02/2024]
Abstract
Ferroptosis is a form of cell death that has received considerable attention not only as a means to eradicate defined tumour entities but also because it provides unforeseen insights into the metabolic adaptation that tumours exploit to counteract phospholipid oxidation1,2. Here, we identify proferroptotic activity of 7-dehydrocholesterol reductase (DHCR7) and an unexpected prosurvival function of its substrate, 7-dehydrocholesterol (7-DHC). Although previous studies suggested that high concentrations of 7-DHC are cytotoxic to developing neurons by favouring lipid peroxidation3, we now show that 7-DHC accumulation confers a robust prosurvival function in cancer cells. Because of its far superior reactivity towards peroxyl radicals, 7-DHC effectively shields (phospho)lipids from autoxidation and subsequent fragmentation. We provide validation in neuroblastoma and Burkitt's lymphoma xenografts where we demonstrate that the accumulation of 7-DHC is capable of inducing a shift towards a ferroptosis-resistant state in these tumours ultimately resulting in a more aggressive phenotype. Conclusively, our findings provide compelling evidence of a yet-unrecognized antiferroptotic activity of 7-DHC as a cell-intrinsic mechanism that could be exploited by cancer cells to escape ferroptosis.
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Affiliation(s)
- Florencio Porto Freitas
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Hamed Alborzinia
- Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM gGmbH), Heidelberg, Germany
- Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Ancély Ferreira Dos Santos
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Palina Nepachalovich
- Center of Membrane Biochemistry and Lipid Research, University Hospital and Faculty of Medicine Carl Gustav Carus of TU Dresden, Dresden, Germany
| | - Lohans Pedrera
- Institute of Genetics, CECAD, University of Cologne, Cologne, Germany
| | - Omkar Zilka
- Department of Chemistry & Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Alex Inague
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
- Instituto de Química, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - Corinna Klein
- Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM gGmbH), Heidelberg, Germany
- Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Nesrine Aroua
- Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM gGmbH), Heidelberg, Germany
- Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Kamini Kaushal
- Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM gGmbH), Heidelberg, Germany
- Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Bettina Kast
- Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM gGmbH), Heidelberg, Germany
- Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Svenja M Lorenz
- Institute of Metabolism and Cell Death, Helmholtz Zentrum München, Neuherberg, Germany
| | - Viktoria Kunz
- Comprehensive Cancer Center Mainfranken, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Helene Nehring
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Thamara N Xavier da Silva
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Zhiyi Chen
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Sena Atici
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Sebastian G Doll
- Institute of Metabolism and Cell Death, Helmholtz Zentrum München, Neuherberg, Germany
| | - Emily L Schaefer
- Department of Chemistry & Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Ifedapo Ekpo
- Department of Chemistry & Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Werner Schmitz
- Department of Biochemistry and Molecular Biology, Theodor Boveri Institute, Biocenter, University of Würzburg, Würzburg, Germany
| | - Aline Horling
- Institute of Pharmacy, Martin Luther University Halle Wittenberg, Halle, Germany
| | - Peter Imming
- Institute of Pharmacy, Martin Luther University Halle Wittenberg, Halle, Germany
| | - Sayuri Miyamoto
- Instituto de Química, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - Ann M Wehman
- Department of Biological Sciences, University of Denver, Denver, CO, USA
| | - Thiago C Genaro-Mattos
- Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, NE, USA
| | - Karoly Mirnics
- Munroe-Meyer Institute for Genetics and Rehabilitation, University of Nebraska Medical Center, Omaha, NE, USA
| | - Lokender Kumar
- Faculty of Applied Sciences and Biotechnology, Shoolini University, Himachal Pradesh, India
| | - Judith Klein-Seetharaman
- Department of Physics, Colorado School of Mines, Golden, CO, USA
- School of Molecular Sciences, Arizona State University, Phoenix, AZ, USA
| | | | - Isabel Weigand
- Medizinische Klinik und Poliklinik IV, Ludwig Maximillian University, Munich, Germany
| | - Matthias Kroiss
- Medizinische Klinik und Poliklinik IV, Ludwig Maximillian University, Munich, Germany
| | - Georg W Bornkamm
- Institute of Experimental Cancer Research, University Hospital Ulm, Ulm, Germany
| | - Fernando Gomes
- Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | | | - Manjima B Sathian
- Department of Pharmacy, Ludwig Maximilian University of Munich, Munich, Germany
| | - David B Konrad
- Department of Pharmacy, Ludwig Maximilian University of Munich, Munich, Germany
| | - Douglas F Covey
- Department of Developmental Biology, Washington University in St. Louis, St. Louis, MO, USA
- Taylor Family Institute for Innovative Psychiatric Research, Washington University, St. Louis, MO, USA
| | - Bernhard Michalke
- Research Unit Analytical BioGeoChemistry, Helmholtz Center München (HMGU), Neuherberg, Germany
| | - Kurt Bommert
- Comprehensive Cancer Center Mainfranken, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Ralf C Bargou
- Comprehensive Cancer Center Mainfranken, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Ana Garcia-Saez
- Institute of Genetics, CECAD, University of Cologne, Cologne, Germany
| | - Derek A Pratt
- Department of Chemistry & Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Maria Fedorova
- Center of Membrane Biochemistry and Lipid Research, University Hospital and Faculty of Medicine Carl Gustav Carus of TU Dresden, Dresden, Germany
| | - Andreas Trumpp
- Heidelberg Institute for Stem Cell Technology and Experimental Medicine (HI-STEM gGmbH), Heidelberg, Germany
- Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and DKFZ-ZMBH Alliance, Heidelberg, Germany
- German Cancer Consortium (DKTK), Heidelberg, Germany
| | - Marcus Conrad
- Institute of Metabolism and Cell Death, Helmholtz Zentrum München, Neuherberg, Germany
| | - José Pedro Friedmann Angeli
- Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany.
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Samhan-Arias AK, Poejo J, Marques-da-Silva D, Martínez-Costa OH, Gutierrez-Merino C. Are There Lipid Membrane-Domain Subtypes in Neurons with Different Roles in Calcium Signaling? Molecules 2023; 28:7909. [PMID: 38067638 PMCID: PMC10708093 DOI: 10.3390/molecules28237909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 11/24/2023] [Accepted: 11/29/2023] [Indexed: 12/18/2023] Open
Abstract
Lipid membrane nanodomains or lipid rafts are 10-200 nm diameter size cholesterol- and sphingolipid-enriched domains of the plasma membrane, gathering many proteins with different roles. Isolation and characterization of plasma membrane proteins by differential centrifugation and proteomic studies have revealed a remarkable diversity of proteins in these domains. The limited size of the lipid membrane nanodomain challenges the simple possibility that all of them can coexist within the same lipid membrane domain. As caveolin-1, flotillin isoforms and gangliosides are currently used as neuronal lipid membrane nanodomain markers, we first analyzed the structural features of these components forming nanodomains at the plasma membrane since they are relevant for building supramolecular complexes constituted by these molecular signatures. Among the proteins associated with neuronal lipid membrane nanodomains, there are a large number of proteins that play major roles in calcium signaling, such as ionotropic and metabotropic receptors for neurotransmitters, calcium channels, and calcium pumps. This review highlights a large variation between the calcium signaling proteins that have been reported to be associated with isolated caveolin-1 and flotillin-lipid membrane nanodomains. Since these calcium signaling proteins are scattered in different locations of the neuronal plasma membrane, i.e., in presynapses, postsynapses, axonal or dendritic trees, or in the neuronal soma, our analysis suggests that different lipid membrane-domain subtypes should exist in neurons. Furthermore, we conclude that classification of lipid membrane domains by their content in calcium signaling proteins sheds light on the roles of these domains for neuronal activities that are dependent upon the intracellular calcium concentration. Some examples described in this review include the synaptic and metabolic activity, secretion of neurotransmitters and neuromodulators, neuronal excitability (long-term potentiation and long-term depression), axonal and dendritic growth but also neuronal cell survival and death.
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Affiliation(s)
- Alejandro K. Samhan-Arias
- Departamento de Bioquímica, Universidad Autónoma de Madrid (UAM), C/Arturo Duperier 4, 28029 Madrid, Spain;
- Instituto de Investigaciones Biomédicas ‘Sols-Morreale’ (CSIC-UAM), C/Arturo Duperier 4, 28029 Madrid, Spain
| | - Joana Poejo
- Instituto de Biomarcadores de Patologías Moleculares, Universidad de Extremadura, 06006 Badajoz, Spain;
| | - Dorinda Marques-da-Silva
- LSRE—Laboratory of Separation and Reaction Engineering and LCM—Laboratory of Catalysis and Materials, School of Management and Technology, Polytechnic Institute of Leiria, Morro do Lena-Alto do Vieiro, 2411-901 Leiria, Portugal;
- ALiCE—Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
- School of Technology and Management, Polytechnic Institute of Leiria, Morro do Lena-Alto do Vieiro, 2411-901 Leiria, Portugal
| | - Oscar H. Martínez-Costa
- Departamento de Bioquímica, Universidad Autónoma de Madrid (UAM), C/Arturo Duperier 4, 28029 Madrid, Spain;
- Instituto de Investigaciones Biomédicas ‘Sols-Morreale’ (CSIC-UAM), C/Arturo Duperier 4, 28029 Madrid, Spain
| | - Carlos Gutierrez-Merino
- Instituto de Biomarcadores de Patologías Moleculares, Universidad de Extremadura, 06006 Badajoz, Spain;
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3
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Covey DF, Evers AS, Izumi Y, Maguire JL, Mennerick SJ, Zorumski CF. Neurosteroid enantiomers as potentially novel neurotherapeutics. Neurosci Biobehav Rev 2023; 149:105191. [PMID: 37085023 PMCID: PMC10750765 DOI: 10.1016/j.neubiorev.2023.105191] [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: 12/14/2022] [Revised: 04/17/2023] [Accepted: 04/18/2023] [Indexed: 04/23/2023]
Abstract
Endogenous neurosteroids and synthetic neuroactive steroids (NAS) are important targets for therapeutic development in neuropsychiatric disorders. These steroids modulate major signaling systems in the brain and intracellular processes including inflammation, cellular stress and autophagy. In this review, we describe studies performed using unnatural enantiomers of key neurosteroids, which are physiochemically identical to their natural counterparts except for rotation of polarized light. These studies led to insights in how NAS interact with receptors, ion channels and intracellular sites of action. Certain effects of NAS show high enantioselectivity, consistent with actions in chiral environments and likely direct interactions with signaling proteins. Other effects show no enantioselectivity and even reverse enantioselectivity. The spectrum of effects of NAS enantiomers raises the possibility that these agents, once considered only as tools for preclinical studies, have therapeutic potential that complements and in some cases may exceed their natural counterparts. Here we review studies of NAS enantiomers from the perspective of their potential development as novel neurotherapeutics.
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Affiliation(s)
- Douglas F Covey
- Departments of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA; Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA; Anesthesiology Washington University School of Medicine, St. Louis, MO, USA; The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Alex S Evers
- Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA; Anesthesiology Washington University School of Medicine, St. Louis, MO, USA; The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Yukitoshi Izumi
- Departments of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA; The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Jamie L Maguire
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Steven J Mennerick
- Departments of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA; The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Charles F Zorumski
- Departments of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA; The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA.
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4
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Sarkar P, Chattopadhyay A. Membrane Dipole Potential: An Emerging Approach to Explore Membrane Organization and Function. J Phys Chem B 2022; 126:4415-4430. [PMID: 35696090 DOI: 10.1021/acs.jpcb.2c02476] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biological membranes are complex organized molecular assemblies of lipids and proteins that provide cells and membrane-bound intracellular organelles their individual identities by morphological compartmentalization. Membrane dipole potential originates from the electrostatic potential difference within the membrane due to the nonrandom arrangement (orientation) of amphiphile and solvent (water) dipoles at the membrane interface. In this Feature Article, we will focus on the measurement of dipole potential using electrochromic fluorescent probes and highlight interesting applications. In addition, we will focus on ratiometric fluorescence microscopic imaging technique to measure dipole potential in cellular membranes, a technique that can be used to address novel problems in cell biology which are otherwise difficult to address using available approaches. We envision that membrane dipole potential could turn out to be a convenient tool in exploring the complex interplay between membrane lipids and proteins and could provide novel insights in membrane organization and function.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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5
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Direct and indirect cholesterol effects on membrane proteins with special focus on potassium channels. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158706. [DOI: 10.1016/j.bbalip.2020.158706] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 03/19/2020] [Accepted: 03/30/2020] [Indexed: 12/16/2022]
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6
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Hanashima S, Yano Y, Murata M. Enantiomers of phospholipids and cholesterol: A key to decipher lipid‐lipid interplay in membrane. Chirality 2020; 32:282-298. [DOI: 10.1002/chir.23171] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 12/23/2019] [Accepted: 12/26/2019] [Indexed: 12/13/2022]
Affiliation(s)
- Shinya Hanashima
- Department of Chemistry, Graduate School of ScienceOsaka University Toyonaka Japan
| | - Yo Yano
- Department of Chemistry, Graduate School of ScienceOsaka University Toyonaka Japan
| | - Michio Murata
- Department of Chemistry, Graduate School of ScienceOsaka University Toyonaka Japan
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7
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Surface interactions determined by stereostructure on the example of 7-hydroxycholesterol epimers – The Langmuir monolayer study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1275-1283. [DOI: 10.1016/j.bbamem.2019.05.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 12/20/2018] [Accepted: 01/06/2019] [Indexed: 01/06/2023]
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8
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Solsona-Vilarrasa E, Fucho R, Torres S, Nuñez S, Nuño-Lámbarri N, Enrich C, García-Ruiz C, Fernández-Checa JC. Cholesterol enrichment in liver mitochondria impairs oxidative phosphorylation and disrupts the assembly of respiratory supercomplexes. Redox Biol 2019; 24:101214. [PMID: 31108462 PMCID: PMC6526464 DOI: 10.1016/j.redox.2019.101214] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 04/24/2019] [Accepted: 05/06/2019] [Indexed: 12/20/2022] Open
Abstract
Mitochondrial cholesterol accumulation is a hallmark of alcoholic and non-alcoholic fatty liver diseases and impairs the function of specific solute carriers through changes in membrane physical properties. However, its impact on mitochondrial respiration and organization of respiratory supercomplexes has not been determined so far. Here we fed mice a cholesterol-enriched diet (HC) supplemented with sodium cholate to examine the effect of cholesterol in mitochondrial function. HC feeding increased liver cholesterol content, which downregulated Srebp2 and Hmgcr expression, while sodium cholate administration decreased Cyp7a1 and Cyp8b1 mRNA levels, suggesting the downregulation of bile acid synthesis through the classical pathway. HC-fed mice exhibited increased expression of Stard1 and Mln64 and enhanced mitochondrial free cholesterol levels (2–3 fold), leading to decreased membrane fluidity. Mitochondria from HC-fed mice displayed increased cholesterol loading in both outer and inner mitochondrial membranes. Cholesterol loading decreased complex I and complex II-driven state 3 respiration and mitochondrial membrane potential. Decreased respiratory and uncoupling control ratio from complex I was also observed after in situ enrichment of mouse liver mitochondria with cholesterol or enantiomer cholesterol, the mirror image of natural cholesterol. Moreover, in vivo cholesterol loading decreased the level of complex III2 and the assembly of respiratory supercomplexes I1+III2+IV and I1+III2. Moreover, HC feeding caused oxidative stress and mitochondrial GSH (mGSH) depletion, which translated in hepatic steatosis and liver injury, effects that were rescued by replenishing mGSH with GSH ethyl ester. Overall, mitochondrial cholesterol accumulation disrupts mitochondrial functional performance and the organization of respiratory supercomplexes assembly, which can contribute to oxidative stress and liver injury. Hepatic mitochondrial cholesterol enrichment impairs oxidative phosphorylation. Cholesterol accumulation perturbs mitochondrial membrane physical properties and morphology. Cholesterol loading disrupts the assembly of mitochondrial respiratory supercomplexes. In vivo mitochondrial cholesterol accumulation induces liver injury, which is prevented by GSH ethyl ester administration.
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Affiliation(s)
- Estel Solsona-Vilarrasa
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain; Liver Unit, Hospital Clinic I Provincial de Barcelona, Instituto de Investigaciones Biomédicas August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Centro de Investigación Biomédica en Red (CIBEREHD), Barcelona, Spain; Department of Biomedical Sciences, Medicine Faculty, Universitat de Barcelona (UB), Spain
| | - Raquel Fucho
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain; Liver Unit, Hospital Clinic I Provincial de Barcelona, Instituto de Investigaciones Biomédicas August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Centro de Investigación Biomédica en Red (CIBEREHD), Barcelona, Spain
| | - Sandra Torres
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain; Liver Unit, Hospital Clinic I Provincial de Barcelona, Instituto de Investigaciones Biomédicas August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Centro de Investigación Biomédica en Red (CIBEREHD), Barcelona, Spain
| | - Susana Nuñez
- Centro de Investigación Biomédica en Red (CIBEREHD), Barcelona, Spain
| | - Natalia Nuño-Lámbarri
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain; Liver Unit, Hospital Clinic I Provincial de Barcelona, Instituto de Investigaciones Biomédicas August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Traslational Research Unit, Medica Sur Clinic & Foundation, Mexico City, Mexico
| | - Carlos Enrich
- Liver Unit, Hospital Clinic I Provincial de Barcelona, Instituto de Investigaciones Biomédicas August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Department of Biomedical Sciences, Medicine Faculty, Universitat de Barcelona (UB), Spain
| | - Carmen García-Ruiz
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain; Liver Unit, Hospital Clinic I Provincial de Barcelona, Instituto de Investigaciones Biomédicas August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Centro de Investigación Biomédica en Red (CIBEREHD), Barcelona, Spain; (e)Research Center for ALPD, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States.
| | - José C Fernández-Checa
- Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), CSIC, Barcelona, Spain; Liver Unit, Hospital Clinic I Provincial de Barcelona, Instituto de Investigaciones Biomédicas August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Centro de Investigación Biomédica en Red (CIBEREHD), Barcelona, Spain; (e)Research Center for ALPD, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States.
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9
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Oakes V, Domene C. Influence of Cholesterol and Its Stereoisomers on Members of the Serotonin Receptor Family. J Mol Biol 2019; 431:1633-1649. [PMID: 30857969 DOI: 10.1016/j.jmb.2019.02.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 02/27/2019] [Accepted: 02/28/2019] [Indexed: 01/24/2023]
Abstract
Despite the ubiquity of cholesterol within the cell membrane, the mechanism by which it influences embedded proteins remains elusive. Numerous G-protein coupled receptors exhibit dramatic responses to membrane cholesterol with regard to the ligand-binding affinity and functional properties, including the 5-HT receptor family. Here, we use over 25 μs of unbiased atomistic molecular dynamics simulations to identify cholesterol interaction sites in the 5-HT1B and 5-HT2B receptors and evaluate their impact on receptor structure. Susceptibility to membrane cholesterol is shown to be subtype dependent and determined by the quality of interactions between the extracellular loops. Charged residues are essential for maintaining the arrangement of the extracellular surface in 5-HT2B; in the absence of such interactions, the extracellular surface of the 5-HT1B is malleable, populating a number of distinct conformations. Elevated cholesterol density near transmembrane helix 4 is considered to be conducive to the conformation of extracellular loop 2. Occupation of this site is also shown to be stereospecific, illustrated by differential behavior of nat-cholesterol isomers, ent- and epi-cholesterol. In simulations containing the endogenous agonist, serotonin, cholesterol binding at transmembrane helix 4 biases bound serotonin molecules toward an unexpected binding mode in the extended binding pocket. The results highlight the capability of membrane cholesterol to influence the mobility of the extracellular surface in the 5-HT1 receptor family and manipulate the architecture of the extracellular ligand-binding pocket.
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Affiliation(s)
- Victoria Oakes
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Carmen Domene
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK; Department of Chemistry, University of Oxford, Oxford, OX1 3TA, Oxford, UK.
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10
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Barbera N, Levitan I. Chiral Specificity of Cholesterol Orientation Within Cholesterol Binding Sites in Inwardly Rectifying K+ Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:77-95. [DOI: 10.1007/978-3-030-04278-3_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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11
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Bukiya AN, Dopico AM. Regulation of BK Channel Activity by Cholesterol and Its Derivatives. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:53-75. [DOI: 10.1007/978-3-030-04278-3_3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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12
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A Critical Analysis of Molecular Mechanisms Underlying Membrane Cholesterol Sensitivity of GPCRs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:21-52. [PMID: 30649754 DOI: 10.1007/978-3-030-04278-3_2] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G protein-coupled receptors (GPCRs) are the largest and a diverse family of proteins involved in signal transduction across biological membranes. GPCRs mediate a wide range of physiological processes and have emerged as major targets for the development of novel drug candidates in all clinical areas. Since GPCRs are integral membrane proteins, regulation of their organization, dynamics, and function by membrane lipids, in particular membrane cholesterol, has emerged as an exciting area of research. Cholesterol sensitivity of GPCRs could be due to direct interaction of cholesterol with the receptor (specific effect). Alternately, GPCR function could be influenced by the effect of cholesterol on membrane physical properties (general effect). In this review, we critically analyze the specific and general mechanisms of the modulation of GPCR function by membrane cholesterol, taking examples from representative GPCRs. While evidence for both the proposed mechanisms exists, there appears to be no clear-cut distinction between these two mechanisms, and a combination of these mechanisms cannot be ruled out in many cases. We conclude that classifying the mechanism underlying cholesterol sensitivity of GPCR function merely into these two mutually exclusive classes could be somewhat arbitrary. A more holistic approach could be suitable for analyzing GPCR-cholesterol interaction.
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13
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Qian L, Cui F, Yang Y, Liu Y, Qi S, Wang C. Mechanisms of developmental toxicity in zebrafish embryos (Danio rerio) induced by boscalid. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 634:478-487. [PMID: 29631138 DOI: 10.1016/j.scitotenv.2018.04.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 03/09/2018] [Accepted: 04/01/2018] [Indexed: 06/08/2023]
Abstract
Boscalid has been widely used for controlling various plant diseases. It is one of the most frequently detected pesticides in main coastal estuaries in California, with concentrations as high as 36μg/L, but its ecotoxicology information is scarce. To assess the aquatic risk of boscalid, acute toxicity and sub-lethal developmental toxicity toward zebrafish embryos were determined in the present study. In the acute toxicity test, a series of toxic symptoms of embryos were observed, including abnormal spontaneous movement, slow heartbeat, yolk sac oedema, pericardial oedema, spine deformation and hatching inhibition, and 96-h-LC50 (50% lethal concentration) of boscalid toward zebrafish embryos was 2.65 (2.506-2.848)mg/L. From the results of the sub-lethal developmental toxicity test, boscalid was confirmed to have a great impact on development mechanisms of zebrafish embryos. Cell apoptosis in embryos was induced by boscalid with upregulation of genes in the cell apoptosis and an increase of capspase-3 and caspase-9 activity in the present study. Lipid metabolism was affected in embryos due to changes in gene expression and the contents of total triacylglyceride and cholesterol. Melanin synthesis and deposition was caused in embryos due to alterations in related gene expression. Overall, changes in cell apoptosis, lipid metabolism and melanin synthesis and deposition might be responsible for developmental toxicity of boscalid to zebrafish embryos.
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Affiliation(s)
- Le Qian
- College of Sciences, China Agricultural University, Beijing, China
| | - Feng Cui
- College of Sciences, China Agricultural University, Beijing, China
| | - Yang Yang
- College of Sciences, China Agricultural University, Beijing, China
| | - Yuan Liu
- College of Sciences, China Agricultural University, Beijing, China
| | - Suzhen Qi
- Risk Assessment Laboratory for Bee Products Quality and Safety of Ministry of Agriculture, Institute of Agricultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, China
| | - Chengju Wang
- College of Sciences, China Agricultural University, Beijing, China.
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14
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Stereospecific Interactions of Cholesterol in a Model Cell Membrane: Implications for the Membrane Dipole Potential. J Membr Biol 2018; 251:507-519. [DOI: 10.1007/s00232-018-0016-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 01/25/2018] [Indexed: 12/11/2022]
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15
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Fantini J, J. Barrantes F. How membrane lipids control the 3D structure and function of receptors. AIMS BIOPHYSICS 2018. [DOI: 10.3934/biophy.2018.1.22] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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16
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Discrimination of Stereoisomers by Their Enantioselective Interactions with Chiral Cholesterol-Containing Membranes. Molecules 2017; 23:molecules23010049. [PMID: 29295605 PMCID: PMC5943951 DOI: 10.3390/molecules23010049] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 12/22/2017] [Accepted: 12/22/2017] [Indexed: 12/02/2022] Open
Abstract
Discrimination between enantiomers is an important subject in medicinal and biological chemistry because they exhibit markedly different bioactivity and toxicity. Although stereoisomers should vary in the mechanistic interactions with chiral targets, their discrimination associated with the mode of action on membrane lipids is scarce. The aim of this study is to reveal whether enantiomers selectively act on chiral lipid membranes. Different classes of stereoisomers were subjected at 5–200 μM to reactions with biomimetic phospholipid membranes containing ~40 mol % cholesterol to endow the lipid bilayers with chirality and their membrane interactions were comparatively evaluated by measuring fluorescence polarization. All of the tested compounds interacted with cholesterol-containing membranes to modify their physicochemical property with different potencies between enantiomers, correlating to those of their experimental and clinical effects. The rank order of membrane interactivity was reversed by changing cholesterol to C3-epimeric α-cholesterol. The same selectivity was also obtained from membranes prepared with 5α-cholestan-3β-ol and 5β-cholestan-3α-ol diastereomers. The opposite configuration allows molecules to interact with chiral sterol-containing membranes enantioselectively, and the specific β configuration of cholesterol’s 3-hydroxyl group is responsible for such selectivity. The enantioselective membrane interaction has medicinal implications for the characterization of the stereostructures with higher bioactivity and lower toxicity.
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17
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Kang L, Lubensky TC. Chiral twist drives raft formation and organization in membranes composed of rod-like particles. Proc Natl Acad Sci U S A 2017; 114:E19-E27. [PMID: 27999184 PMCID: PMC5224397 DOI: 10.1073/pnas.1613732114] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lipid rafts are hypothesized to facilitate protein interaction, tension regulation, and trafficking in biological membranes, but the mechanisms responsible for their formation and maintenance are not clear. Insights into many other condensed matter phenomena have come from colloidal systems, whose micron-scale particles mimic basic properties of atoms and molecules but permit dynamic visualization with single-particle resolution. Recently, experiments showed that bidisperse mixtures of filamentous viruses can self-assemble into colloidal monolayers with thermodynamically stable rafts exhibiting chiral structure and repulsive interactions. We quantitatively explain these observations by modeling the membrane particles as chiral liquid crystals. Chiral twist promotes the formation of finite-sized rafts and mediates a repulsion that distributes them evenly throughout the membrane. Although this system is composed of filamentous viruses whose aggregation is entropically driven by dextran depletants instead of phospholipids and cholesterol with prominent electrostatic interactions, colloidal and biological membranes share many of the same physical symmetries. Chiral twist can contribute to the behavior of both systems and may account for certain stereospecific effects observed in molecular membranes.
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Affiliation(s)
- Louis Kang
- Department of Physics & Astronomy, University of Pennsylvania, Philadelphia, PA 19104
| | - Tom C Lubensky
- Department of Physics & Astronomy, University of Pennsylvania, Philadelphia, PA 19104
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18
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Barbera N, Ayee MA, Akpa BS, Levitan I. Differential Effects of Sterols on Ion Channels: Stereospecific Binding vs Stereospecific Response. CURRENT TOPICS IN MEMBRANES 2017; 80:25-50. [DOI: 10.1016/bs.ctm.2017.06.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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19
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Jafurulla M, Chattopadhyay A. Structural Stringency of Cholesterol for Membrane Protein Function Utilizing Stereoisomers as Novel Tools: A Review. Methods Mol Biol 2017; 1583:21-39. [PMID: 28205164 DOI: 10.1007/978-1-4939-6875-6_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Cholesterol is an important lipid in the context of membrane protein function. The function of a number of membrane proteins, including G protein-coupled receptors (GPCRs) and ion channels, has been shown to be dependent on membrane cholesterol. However, the molecular mechanism underlying such regulation is still being explored. In some cases, specific interaction between cholesterol and the protein has been implicated. In other cases, the effect of cholesterol on the membrane properties has been attributed for the regulation of protein function. In this article, we have provided an overview of experimental approaches that are useful for determining the degree of structural stringency of cholesterol for membrane protein function. In the process, we have highlighted the role of immediate precursors in cholesterol biosynthetic pathway in the function of membrane proteins. Special emphasis has been given to the application of stereoisomers of cholesterol in deciphering the structural stringency required for regulation of membrane protein function. A comprehensive examination of these processes would help in understanding the molecular basis of cholesterol regulation of membrane proteins in subtle details.
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Affiliation(s)
- Md Jafurulla
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India
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20
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Wei X, Song H, Yin L, Rizzo MG, Sidhu R, Covey DF, Ory DS, Semenkovich CF. Fatty acid synthesis configures the plasma membrane for inflammation in diabetes. Nature 2016; 539:294-298. [PMID: 27806377 DOI: 10.1038/nature20117] [Citation(s) in RCA: 194] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 09/23/2016] [Indexed: 12/19/2022]
Abstract
Dietary fat promotes pathological insulin resistance through chronic inflammation. The inactivation of inflammatory proteins produced by macrophages improves diet-induced diabetes, but how nutrient-dense diets induce diabetes is unknown. Membrane lipids affect the innate immune response, which requires domains that influence high-fat-diet-induced chronic inflammation and alter cell function based on phospholipid composition. Endogenous fatty acid synthesis, mediated by fatty acid synthase (FAS), affects membrane composition. Here we show that macrophage FAS is indispensable for diet-induced inflammation. Deleting Fasn in macrophages prevents diet-induced insulin resistance, recruitment of macrophages to adipose tissue and chronic inflammation in mice. We found that FAS deficiency alters membrane order and composition, impairing the retention of plasma membrane cholesterol and disrupting Rho GTPase trafficking-a process required for cell adhesion, migration and activation. Expression of a constitutively active Rho GTPase, however, restored inflammatory signalling. Exogenous palmitate was partitioned to different pools from endogenous lipids and did not rescue inflammatory signalling. However, exogenous cholesterol, as well as other planar sterols, did rescue signalling, with cholesterol restoring FAS-induced perturbations in membrane order. Our results show that the production of endogenous fat in macrophages is necessary for the development of exogenous-fat-induced insulin resistance through the creation of a receptive environment at the plasma membrane for the assembly of cholesterol-dependent signalling networks.
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Affiliation(s)
- Xiaochao Wei
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Haowei Song
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Li Yin
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Michael G Rizzo
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Rohini Sidhu
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Douglas F Covey
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Daniel S Ory
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA.,Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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21
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Bisen S, Seleverstov O, Belani J, Rychnovsky S, Dopico AM, Bukiya AN. Distinct mechanisms underlying cholesterol protection against alcohol-induced BK channel inhibition and resulting vasoconstriction. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1861:1756-1766. [PMID: 27565113 PMCID: PMC5274633 DOI: 10.1016/j.bbalip.2016.08.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 07/21/2016] [Accepted: 08/22/2016] [Indexed: 02/01/2023]
Abstract
Alcohol (ethanol) at concentrations reached in blood following moderate to heavy drinking (30-80mM) reduces cerebral artery diameter via inhibition of voltage- and calcium-gated potassium channels of large conductance (BK) in cerebral artery smooth muscle. These channels consist of channel-forming α and regulatory β1 subunits. A high-cholesterol diet protects against ethanol-induced constriction via accumulation of cholesterol within the vasculature. The molecular mechanisms of this protection remain unknown. In the present work, we demonstrate that in vitro cholesterol enrichment of rat middle cerebral arteries significantly increased cholesterol within arterial tissues and blunted constriction by 50mM of ethanol. Ethanol-induced BK channel inhibition in inside-out patches excised from freshly isolated cerebral artery myocytes was also abolished by cholesterol enrichment. Enrichment of arteries with enantiomeric cholesterol (ent-cholesterol) also blunted BK channel inhibition and cerebral artery constriction in response to ethanol. The similar protection of cholesterol and ent-cholesterol against ethanol action indicates that this protection does not require protein site(s) that specifically sense natural cholesterol. Cholesterol-driven protection against ethanol-induced BK channel inhibition and vasoconstriction was replicated in myocytes and middle cerebral arteries of C57BL/6 mice. BK β1 subunits are known to regulate vascular diameter and its modification by ethanol. However, blunting of an ethanol effect by in vitro cholesterol enrichment was observed in arteries and myocyte membrane patches from BK β1 (KCNMB1) knockout mice. Thus, BK β1 subunits are not needed for cholesterol protection against ethanol effect on BK channel function and cerebral artery diameter.
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Affiliation(s)
- Shivantika Bisen
- Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Olga Seleverstov
- Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Jitendra Belani
- Department of Chemistry, School of Physical Sciences, University of California, Irvine, 3038B FRH, Mail Code: 2025, Irvine, CA 92697, USA
| | - Scott Rychnovsky
- Department of Chemistry, School of Physical Sciences, University of California, Irvine, 3038B FRH, Mail Code: 2025, Irvine, CA 92697, USA
| | - Alex M Dopico
- Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Anna N Bukiya
- Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA.
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22
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Howe V, Sharpe LJ, Alexopoulos SJ, Kunze SV, Chua NK, Li D, Brown AJ. Cholesterol homeostasis: How do cells sense sterol excess? Chem Phys Lipids 2016; 199:170-178. [PMID: 26993747 DOI: 10.1016/j.chemphyslip.2016.02.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 02/27/2016] [Indexed: 12/23/2022]
Abstract
Cholesterol is vital in mammals, but toxic in excess. Consequently, elaborate molecular mechanisms have evolved to maintain this sterol within narrow limits. How cells sense excess cholesterol is an intriguing area of research. Cells sense cholesterol, and other related sterols such as oxysterols or cholesterol synthesis intermediates, and respond to changing levels through several elegant mechanisms of feedback regulation. Cholesterol sensing involves both direct binding of sterols to the homeostatic machinery located in the endoplasmic reticulum (ER), and indirect effects elicited by sterol-dependent alteration of the physical properties of membranes. Here, we examine the mechanisms employed by cells to maintain cholesterol homeostasis.
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Affiliation(s)
- Vicky Howe
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Stephanie J Alexopoulos
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Sarah V Kunze
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Ngee Kiat Chua
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Dianfan Li
- National Center for Protein Sciences, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia.
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23
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Using Sterol Substitution to Probe the Role of Membrane Domains in Membrane Functions. Lipids 2015; 50:721-34. [PMID: 25804641 DOI: 10.1007/s11745-015-4007-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 03/03/2015] [Indexed: 02/04/2023]
Abstract
Ordered membrane lipid domains rich in sphingolipids and sterols ("lipid rafts") are thought to be important in many biological processes. However, it is often difficult to distinguish domain-dependent biological functions from ones that have a specific dependence on sterol, e.g. are dependent upon a protein with a function that is dependent upon its binding to sterol. Removing cholesterol and replacing it with various sterols with varying abilities to form membrane domains or otherwise alter membrane properties has the potential to help distinguish these cases. This review describes this strategy, and how it has been applied by various investigators to understand cellular functions.
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24
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Bandari S, Chakraborty H, Covey DF, Chattopadhyay A. Membrane dipole potential is sensitive to cholesterol stereospecificity: implications for receptor function. Chem Phys Lipids 2014; 184:25-9. [PMID: 25219773 DOI: 10.1016/j.chemphyslip.2014.09.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/05/2014] [Accepted: 09/08/2014] [Indexed: 12/25/2022]
Abstract
Dipole potential is the potential difference within the membrane bilayer, which originates due to the nonrandom arrangement of lipid dipoles and water molecules at the membrane interface. Cholesterol, an essential lipid in higher eukaryotic membranes, has previously been shown to increase membrane dipole potential. In this work, we explored the effect of stereoisomers of cholesterol, ent-cholesterol and epi-cholesterol, on membrane dipole potential, monitored by the dual wavelength ratiometric approach utilizing the probe di-8-ANEPPS. Our results show that cholesterol and ent-cholesterol share comparable ability in increasing membrane dipole potential. In contrast, epi-cholesterol displays a slight reduction in membrane dipole potential. Our results constitute the first report on the effect of stereoisomers of cholesterol on membrane dipole potential, and imply that an extremely subtle change in sterol structure can significantly alter the dipolar field at the membrane interface. These results assume relevance in the context of differential abilities of these stereoisomers of cholesterol in supporting the activity of the serotonin1A receptor, a representative G protein-coupled receptor. The close correlation between membrane dipole potential and receptor activity provides new insight in receptor-cholesterol interaction in terms of stereospecificity. We envision that membrane dipole potential could prove to be a sensitive indicator of lipid-protein interactions in biological membranes.
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Affiliation(s)
- Suman Bandari
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Hirak Chakraborty
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Douglas F Covey
- Departments of Developmental Biology, Anesthesiology, Psychiatry and The Taylor Family Institute for Innovative Psychiatry Research, WA University in St. Louis Medical School, St. Louis, MO 63110, USA
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25
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Levitan I, Singh DK, Rosenhouse-Dantsker A. Cholesterol binding to ion channels. Front Physiol 2014; 5:65. [PMID: 24616704 PMCID: PMC3935357 DOI: 10.3389/fphys.2014.00065] [Citation(s) in RCA: 136] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 02/03/2014] [Indexed: 11/13/2022] Open
Abstract
Numerous studies demonstrated that membrane cholesterol is a major regulator of ion channel function. The goal of this review is to discuss significant advances that have been recently achieved in elucidating the mechanisms responsible for cholesterol regulation of ion channels. The first major insight that comes from growing number of studies that based on the sterol specificity of cholesterol effects, show that several types of ion channels (nAChR, Kir, BK, TRPV) are regulated by specific sterol-protein interactions. This conclusion is supported by demonstrating direct saturable binding of cholesterol to a bacterial Kir channel. The second major advance in the field is the identification of putative cholesterol binding sites in several types of ion channels. These include sites at locations associated with the well-known cholesterol binding motif CRAC and its reversed form CARC in nAChR, BK, and TRPV, as well as novel cholesterol binding regions in Kir channels. Notably, in the majority of these channels, cholesterol is suggested to interact mainly with hydrophobic residues in non-annular regions of the channels being embedded in between transmembrane protein helices. We also discuss how identification of putative cholesterol binding sites is an essential step to understand the mechanistic basis of cholesterol-induced channel regulation. Clearly, however, these are only the first few steps in obtaining a general understanding of cholesterol-ion channels interactions and their roles in cellular and organ functions.
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Affiliation(s)
- Irena Levitan
- Division of Pulmonary, Critical Care, Sleep, and Allergy, Department of Medicine, University of Illinois at ChicagoChicago, IL, USA
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26
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Wong A. Chemical and microbiological considerations of phytosterols and their relative efficacies in functional foods for the lowering of serum cholesterol levels in humans: A review. J Funct Foods 2014. [DOI: 10.1016/j.jff.2013.10.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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27
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Jafurulla M, Rao BD, Sreedevi S, Ruysschaert JM, Covey DF, Chattopadhyay A. Stereospecific requirement of cholesterol in the function of the serotonin1A receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:158-63. [PMID: 24008092 DOI: 10.1016/j.bbamem.2013.08.015] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/16/2013] [Accepted: 08/23/2013] [Indexed: 01/04/2023]
Abstract
The serotonin1A receptor is an important member of the G protein-coupled receptor (GPCR) family. It is involved in the generation and modulation of a variety of cognitive and behavioral functions and serves as a drug target. Previous work from our laboratory has established the sensitivity of the function of the serotonin1A receptor to membrane cholesterol. Solubilization of the hippocampal serotonin1A receptor utilizing the zwitterionic detergent CHAPS is accompanied by loss of cholesterol and results in reduction in specific ligand binding. Replenishment of cholesterol to solubilized membranes restores specific ligand binding to the receptor. We utilized this strategy of sterol replenishment of solubilized membranes to explore the stereospecific stringency of cholesterol for receptor function. We used two stereoisomers of cholesterol, ent-cholesterol (enantiomer of cholesterol) and epi-cholesterol (a diastereomer of cholesterol), for this purpose. Importantly, we show here that while ent-cholesterol could replace cholesterol in supporting receptor function, epi-cholesterol could not. These results imply that the requirement of membrane cholesterol for the serotonin1A receptor function is diastereospecific, yet not enantiospecific. Our results extend and help define specificity of the interaction of membrane cholesterol with the serotonin1A receptor, and represent the first report utilizing ent-cholesterol to examine stereospecificity of GPCR-cholesterol interaction.
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Affiliation(s)
- Md Jafurulla
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
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28
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Kristiana I, Luu W, Stevenson J, Cartland S, Jessup W, Belani JD, Rychnovsky SD, Brown AJ. Cholesterol through the looking glass: ability of its enantiomer also to elicit homeostatic responses. J Biol Chem 2012; 287:33897-904. [PMID: 22869373 DOI: 10.1074/jbc.m112.360537] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
How cholesterol is sensed to maintain homeostasis has been explained by direct binding to a specific protein, Scap, or through altering the physical properties of the membrane. The enantiomer of cholesterol (ent-cholesterol) is a valuable tool in distinguishing between these two models because it shares nonspecific membrane effects with native cholesterol (nat-cholesterol), but not specific binding interactions. This is the first study to compare ent- and nat-cholesterol directly on major molecular parameters of cholesterol homeostasis. We found that ent-cholesterol suppressed activation of the master transcriptional regulator of cholesterol metabolism, SREBP-2, almost as effectively as nat-cholesterol. Importantly, ent-cholesterol induced a conformational change in the cholesterol-sensing protein Scap in isolated membranes in vitro, even when steps were taken to eliminate potential confounding effects from endogenous cholesterol. Ent-cholesterol also accelerated proteasomal degradation of the key cholesterol biosynthetic enzyme, squalene monooxygenase. Together, these findings provide compelling evidence that cholesterol maintains its own homeostasis not only via direct protein interactions, but also by altering membrane properties.
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Affiliation(s)
- Ika Kristiana
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
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29
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Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol. Pharmacol Ther 2012; 135:133-50. [PMID: 22584144 DOI: 10.1016/j.pharmthera.2012.05.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/09/2012] [Indexed: 11/21/2022]
Abstract
Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease.
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30
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Bielska AA, Schlesinger P, Covey DF, Ory DS. Oxysterols as non-genomic regulators of cholesterol homeostasis. Trends Endocrinol Metab 2012; 23:99-106. [PMID: 22244444 PMCID: PMC3294026 DOI: 10.1016/j.tem.2011.12.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 11/21/2011] [Accepted: 12/05/2011] [Indexed: 12/31/2022]
Abstract
Tight regulation of cellular and plasma cholesterol is crucial to proper cellular functioning because excess free cholesterol is toxic to cells and is associated with atherosclerosis and heart disease. Cellular cholesterol homeostasis is regulated by enzymatically formed oxygenated cholesterol derivatives termed oxysterols. Although the effects of oxysterols on transcriptional pathways are well described, the non-transcriptional mechanisms through which oxysterols acutely modulate cellular cholesterol levels are less well understood. We present emerging evidence suggesting that the membrane biophysical properties of oxysterols underlie their acute cholesterol-regulatory functions and discuss the relevance of these acute effects to cholesterol overload in physiological and pathophysiological states.
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Affiliation(s)
- Agata A Bielska
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St Louis, MO 63110, USA
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Yuan C, Chen M, Covey DF, Johnston LJ, Treistman SN. Cholesterol tuning of BK ethanol response is enantioselective, and is a function of accompanying lipids. PLoS One 2011; 6:e27572. [PMID: 22140451 PMCID: PMC3226590 DOI: 10.1371/journal.pone.0027572] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 10/19/2011] [Indexed: 12/22/2022] Open
Abstract
In the search to uncover ethanol's molecular mechanisms, the calcium and voltage activated, large conductance potassium channel (BK) has emerged as an important molecule. We examine how cholesterol content in bilayers of 1,2-dioleoyl-3-phosphatidylethanolamine (DOPE)/sphingomyelin (SPM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine (POPE)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine (POPS) affect the function and ethanol sensitivity of BK. In addition, we examine how manipulation of cholesterol in biological membranes modulates ethanol's actions on BK. We report that cholesterol levels regulate the change in BK channel open probability elicited by 50 mM ethanol. Low levels of cholesterol (<20%, molar ratio) supports ethanol activation, while high levels of cholesterol leads to ethanol inhibition of BK. To determine if cholesterol affects BK and its sensitivity to ethanol through a direct cholesterol-protein interaction or via an indirect action on the lipid bilayer, we used the synthetic enantiomer of cholesterol (ent-CHS). We found that 20% and 40% ent-CHS had little effect on the ethanol sensitivity of BK, when compared with the same concentration of nat-CHS. We accessed the effects of ent-CHS and nat-CHS on the molecular organization of DOPE/SPM monolayers at the air/water interface. The isotherm data showed that ent-CHS condensed DOPE/SPM monolayer equivalently to nat-CHS at a 20% concentration, but slightly less at a 40% concentration. Atomic force microscopy (AFM) images of DOPE/SPM membranes in the presence of ent-CHS or nat-CHS prepared with LB technique or vesicle deposition showed no significant difference in topographies, supporting the interpretation that the differences in actions of nat-CHS and ent-CHS on BK channel are not likely from a generalized action on bilayers. We conclude that membrane cholesterol influences ethanol's modulation of BK in a complex manner, including an interaction with the channel protein. Finally, our results suggest that an understanding of membrane protein function and modulation is impossible unless protein and surrounding lipid are considered as a functional unit.
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Affiliation(s)
- Chunbo Yuan
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico
| | - Maohui Chen
- Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Douglas F. Covey
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Linda J. Johnston
- Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Steven N. Treistman
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico
- * E-mail:
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32
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Bielska AA, Ory DS, Covey DF. Synthesis of the enantiomer of the oxysterol-antagonist LY295427. Steroids 2011; 76:986-90. [PMID: 21470559 PMCID: PMC3139699 DOI: 10.1016/j.steroids.2011.03.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 03/14/2011] [Accepted: 03/17/2011] [Indexed: 11/20/2022]
Abstract
Cellular cholesterol homeostasis is regulated by oxygenated cholesterol metabolites called oxysterols. While the importance of oxysterols in the acute regulation of cholesterol homeostasis is known, the precise molecular mechanisms through which oxysterols exert their effects remain to be elucidated. LY295427 (1) is a known antagonist of the cholesterol-homeostatic effects of 25-hydroxycholesterol (25-HC), a biologically active oxysterol. In order to examine the mechanism of action of this antagonism, and to further explore recent evidence suggesting that the membrane effects of 25-HC contribute to acute cholesterol regulation, we synthesized the enantiomer of LY295427 (ent-LY295427). ent-LY295427 (2) will serve as a unique probe to provide insight into the role of transcription-independent mechanisms in regulation of cholesterol homeostasis.
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Affiliation(s)
- Agata A. Bielska
- Departments of Medicine, Washington University School of Medicine, 660 S. Euclid, St. Louis, MO 63110, United States
| | - Daniel S. Ory
- Departments of Medicine, Washington University School of Medicine, 660 S. Euclid, St. Louis, MO 63110, United States
| | - Douglas F. Covey
- Developmental Biology, Washington University School of Medicine, 660 S. Euclid, St. Louis, MO 63110, United States
- Corresponding author. Department of Developmental Biology, Washington University School of Medicine, Box 8103, 660 S. Euclid, St. Louis, MO 63110, United States, Tel.: +1 314 362 1726; fax: +1 314 362 7058;
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Tsuchiya H, Ueno T, Mizogami M. Stereostructure-based differences in the interactions of cardiotoxic local anesthetics with cholesterol-containing biomimetic membranes. Bioorg Med Chem 2011; 19:3410-5. [PMID: 21550810 DOI: 10.1016/j.bmc.2011.04.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 04/12/2011] [Accepted: 04/13/2011] [Indexed: 01/09/2023]
Abstract
Amide-type pipecoloxylidide local anesthetics, bupivacaine, and ropivacaine, show cardiotoxic effects with the potency depending on stereostructures. Cardiotoxic drugs not only bind to cardiomyocyte membrane channels to block them but also modify the physicochemical property of membrane lipid bilayers in which channels are embedded. The opposite configurations allow enantiomers to be discriminated by their enantiospecific interactions with another chiral molecule in membranes. We compared the interactions of local anesthetic stereoisomers with biomimetic membranes consisting of chiral lipid components, the differences of which might be indicative of the drug design for reducing cardiotoxicity. Fluorescent probe-labeled biomimetic membranes were prepared with cardiolipin and cholesterol of varying compositions and different phospholipids. Local anesthetics were reacted with the membrane preparations at a cardiotoxically relevant concentration of 200 μM. The potencies to interact with biomimetic membranes and change their fluidity were compared by measuring fluorescence polarization. All local anesthetics acted on lipid bilayers to increase membrane fluidity. Chiral cardiolipin was ineffective in discriminating S(-)-enantiomers from their antipodes. On the other hand, cholesterol produced the enantiospecific membrane interactions of bupivacaine and ropivacaine with increasing its composition in membranes. In 40 mol% and more cholesterol-containing membranes, the membrane-interacting potency was S(-)-bupivacaine<racemic bupivacaine<R(+)-bupivacaine, and S(-)-ropivacaine<R(+)-ropivacaine. Ropivacaine (S(-)-enantiomer), levobupivacaine (S(-)-enantiomeric), and bupivacaine (racemic) interacted with biomimetic membranes in increasing order of intensity. The rank order of membrane interactivity agreed with that of known cardiotoxicity. The stereoselective membrane interactions determined by cholesterol with higher chirality appears to be associated with the stereoselective cardiotoxic effects of local anesthetics. The stereostructure and membrane interactivity relationship supports the clinical use and development of S(-)-enantiomers to decrease the adverse effects of pipecoloxylidide local anesthetics on the cardiovascular system.
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Affiliation(s)
- Hironori Tsuchiya
- Department of Dental Basic Education, Asahi University School of Dentistry, Mizuho, Gifu 501-0296, Japan.
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34
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Bukiya AN, Belani JD, Rychnovsky S, Dopico AM. Specificity of cholesterol and analogs to modulate BK channels points to direct sterol-channel protein interactions. J Gen Physiol 2011; 137:93-110. [PMID: 21149543 PMCID: PMC3010061 DOI: 10.1085/jgp.201010519] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 11/22/2010] [Indexed: 11/26/2022] Open
Abstract
The activity (Po) of large-conductance voltage/Ca(2+)-gated K(+) (BK) channels is blunted by cholesterol levels within the range found in natural membranes. We probed BK channel-forming α (cbv1) subunits in phospholipid bilayers with cholesterol and related monohydroxysterols and performed computational dynamics to pinpoint the structural requirements for monohydroxysterols to reduce BK Po and obtain insights into cholesterol's mechanism of action. Cholesterol, cholestanol, and coprostanol reduced Po by shortening mean open and lengthening mean closed times, whereas epicholesterol, epicholestanol, epicoprostanol, and cholesterol trisnorcholenic acid were ineffective. Thus, channel inhibition by monohydroxysterols requires the β configuration of the C3 hydroxyl and is favored by the hydrophobic nature of the side chain, while having lax requirements on the sterol A/B ring fusion. Destabilization of BK channel open state(s) has been previously interpreted as reflecting increased bilayer lateral stress by cholesterol. Lateral stress is controlled by the sterol molecular area and lipid monolayer lateral tension, the latter being related to the sterol ability to adopt a planar conformation in lipid media. However, we found that the differential efficacies of monohydroxysterols to reduce Po (cholesterol≥coprostanol≥cholestanol>>>epicholesterol) did not follow molecular area rank (coprostanol>>epicholesterol>cholesterol>cholestanol). In addition, computationally predicted energies for cholesterol (effective BK inhibitor) and epicholesterol (ineffective) to adopt a planar conformation were similar. Finally, cholesterol and coprostanol reduced Po, yet these sterols have opposite effects on tight lipid packing and, likely, on lateral stress. Collectively, these findings suggest that an increase in bilayer lateral stress is unlikely to underlie the differential ability of cholesterol and related steroids to inhibit BK channels. Remarkably, ent-cholesterol (cholesterol mirror image) failed to reduce Po, indicating that cholesterol efficacy requires sterol stereospecific recognition by a protein surface. The BK channel phenotype resembled that of α homotetramers. Thus, we hypothesize that a cholesterol-recognizing protein surface resides at the BK α subunit itself.
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Affiliation(s)
- Anna N. Bukiya
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163
| | | | - Scott Rychnovsky
- Department of Chemistry, University of California, Irvine, CA 92697
| | - Alex M. Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163
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35
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Chang CCY, Miyazaki A, Dong R, Kheirollah A, Yu C, Geng Y, Higgs HN, Chang TY. Purification of recombinant acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT1) from H293 cells and binding studies between the enzyme and substrates using difference intrinsic fluorescence spectroscopy. Biochemistry 2010; 49:9957-63. [PMID: 20964445 DOI: 10.1021/bi1013936] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT1) is a membrane-bound enzyme utilizing long-chain fatty acyl-coenzyme A and cholesterol to form cholesteryl esters and coenzyme A. Previously, we had expressed tagged human ACAT1 (hACAT1) in CHO cells and purified it to homogeneity; however, only a sparse amount of purified protein could be obtained. Here we report that the hACAT1 expression level in H293 cells is 18-fold higher than that in CHO cells. We have developed a milder purification procedure to purify the enzyme to homogeneity. The abundance of the purified protein enabled us to conduct difference intrinsic fluorescence spectroscopy to study the binding between the enzyme and its substrates in CHAPS/phospholipid mixed micelles. The results show that oleoyl-CoA binds to ACAT1 with K(d) = 1.9 μM and elicits significant structural changes of the protein as manifested by the significantly positive changes in its fluorescence spectrum; stearoyl-CoA elicits a similar spectrum change but much lower in magnitude. Previously, kinetic studies had shown that cholesterol is an efficient substrate and an allosteric activator of ACAT1, while its diastereomer epicholesterol is neither a substrate nor an activator. Here we show that both cholesterol and epicholesterol induce positive changes in the ACAT1 fluorescence spectrum; however, the magnitude of spectrum changes induced by cholesterol is much larger than epicholesterol. These results show that stereospecificity, governed by the 3β-OH moiety in steroid ring A, plays an important role in the binding of cholesterol to ACAT1.
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Affiliation(s)
- Catherine C Y Chang
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, United States.
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36
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Chisari M, Eisenman LN, Covey DF, Mennerick S, Zorumski CF. The sticky issue of neurosteroids and GABA(A) receptors. Trends Neurosci 2010; 33:299-306. [PMID: 20409596 DOI: 10.1016/j.tins.2010.03.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Revised: 03/10/2010] [Accepted: 03/25/2010] [Indexed: 01/01/2023]
Abstract
Endogenous neurosteroids and their synthetic analogs (neuroactive steroids) are potent modulators of GABA(A) receptors. Thus, they are of physiological and clinical relevance for their ability to modulate inhibitory function in the CNS. Despite their importance, fundamental issues of neurosteroid actions remain unresolved. Recent evidence suggests that glutamatergic principal neurons, rather than glia, are the major sources of neurosteroid synthesis. Other recent studies have identified putative neurosteroid binding sites on GABA(A) receptors. In this Opinion, we argue that neurosteroids require a membranous route of access to transmembrane-domain binding sites within GABA(A) receptors. This has implications for the design of future neuroactive steroids because the lipid solubility and related accessibility properties of the ligand are likely to be key determinants of receptor modulation.
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Affiliation(s)
- Mariangela Chisari
- Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave, St. Louis, MO 63110, USA
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37
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Minogue S, Chu KME, Westover EJ, Covey DF, Hsuan JJ, Waugh MG. Relationship between phosphatidylinositol 4-phosphate synthesis, membrane organization, and lateral diffusion of PI4KIIalpha at the trans-Golgi network. J Lipid Res 2010; 51:2314-24. [PMID: 20388919 DOI: 10.1194/jlr.m005751] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Type II phosphatidylinositol 4-kinase IIalpha (PI4KIIalpha) is the dominant phosphatidylinositol kinase activity measured in mammalian cells and has important functions in intracellular vesicular trafficking. Recently PI4KIIalpha has been shown to have important roles in neuronal survival and tumorigenesis. This study focuses on the relationship between membrane cholesterol levels, phosphatidylinositol 4-phosphate (PI4P) synthesis, and PI4KIIalpha mobility. Enzyme kinetic measurements, sterol substitution studies, and membrane fragmentation analyses all revealed that cholesterol regulates PI4KIIalpha activity indirectly through effects on membrane structure. In particular, we found that cholesterol levels determined the distribution of PI4KIIalpha to biophysically distinct membrane domains. Imaging studies on cells expressing enhanced green fluorescent protein (eGFP)-tagged PI4KIIalpha demonstrated that cholesterol depletion resulted in morphological changes to the juxtanuclear membrane pool of the enzyme. Lateral membrane diffusion of eGFP-PI4KIIalpha was assessed by fluorescence recovery after photobleaching (FRAP) experiments, which revealed the existence of both mobile and immobile pools of the enzyme. Sterol depletion decreased the size of the mobile pool of PI4KIIalpha. Further measurements revealed that the reduction in the mobile fraction of PI4KIIalpha correlated with a loss of trans-Golgi network (TGN) membrane connectivity. We conclude that cholesterol modulates PI4P synthesis through effects on membrane organization and enzyme diffusion.
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Affiliation(s)
- Shane Minogue
- Department of Inflammation, Division of Medicine, University College London, Centre for Molecular Cell Biology, London, United Kingdom
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38
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Akk G, Covey DF, Evers AS, Steinbach JH, Zorumski CF, Mennerick S. The influence of the membrane on neurosteroid actions at GABA(A) receptors. Psychoneuroendocrinology 2009; 34 Suppl 1:S59-66. [PMID: 19541427 PMCID: PMC2794963 DOI: 10.1016/j.psyneuen.2009.05.020] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 05/26/2009] [Accepted: 05/26/2009] [Indexed: 11/27/2022]
Abstract
Modern views of anesthetic neurosteroid interaction with the GABA(A) receptor conceptualize steroid ligands interacting with a protein binding site on the receptor. It has generally been assumed that the steroid interaction/binding site is contained in an extracellular domain of the receptor, and that steroid interactions are of high potency, evidenced by the low aqueous ligand concentrations required to achieve potentiation of channel function. We have been considering implications of the observations that steroids are quite lipophilic and that recently identified putative steroid binding sites are in transmembrane domains of the receptor. Accordingly, we expect that both the effective plasma membrane steroid concentration and steroid pharmacophore properties will contribute to steady-state potency and to the lifetime of steroid actions following removal of free aqueous steroid. Here we review our recent studies that address the evidence that membrane partitioning and intracellular accumulation are non-specific contributors to the effects of anesthetic steroids at GABA(A) receptors. We compare and contrast the profile of anesthetic steroids with that of sulfated steroids that negatively regulate GABA(A) receptor function. These studies give rise to the view that the inherent affinity of anesthetic steroid for GABA(A) receptors is very low; low effective aqueous concentrations are accounted for by lipid partitioning. This yields a very different picture of the interaction of neurosteroids with the GABA(A) receptor than that of steroid interactions with classical intracellular steroid receptors, which exhibit inherently high affinity. These considerations have practical implications for actions of endogenous neurosteroids. Lipophilicity will tend to promote autocrine actions of neurosteroids at GABA(A) receptors within cells that synthesize neurosteroids, and lipophilic retention will limit intercellular diffusion from the source of steroid synthesis. Lipophilicity and steroid access to the receptor binding sites also must be considerations in drug design if drugs are to effectively reach the target GABA(A) receptor site.
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Affiliation(s)
- Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110
| | - Douglas F. Covey
- Department of Developmental Biology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110
| | - Alex S. Evers
- Department of Anesthesiology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110,Department of Developmental Biology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110
| | - Joe Henry Steinbach
- Department of Anesthesiology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110,Department of Anatomy & Neurobiology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110
| | - Charles F. Zorumski
- Department of Anatomy & Neurobiology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110,Department of Psychiatry, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110
| | - Steven Mennerick
- Department of Anatomy & Neurobiology, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110,Department of Psychiatry, Washington University School of Medicine 660 S. Euclid Ave. St. Louis, MO 63110
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39
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Alakoskela JM, Vitovic P, Kinnunen PKJ. Screening for the drug-phospholipid interaction: correlation to phospholipidosis. ChemMedChem 2009; 4:1224-51. [PMID: 19551800 DOI: 10.1002/cmdc.200900052] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Phospholipid bilayers represent a complex, anisotropic environment fundamentally different from bulk oil or octanol, for instance. Even "simple" drug association to phospholipid bilayers can only be fully understood if the slab-of-hydrocarbon approach is abandoned and the complex, anisotropic properties of lipid bilayers reflecting the chemical structures and organization of the constituent phospholipids are considered. The interactions of drugs with phospholipids are important in various processes, such as drug absorption, tissue distribution, and subcellular distribution. In addition, drug-lipid interactions may lead to changes in lipid-dependent protein activities, and further, to functional and morphological changes in cells, a prominent example being the phospholipidosis (PLD) induced by cationic amphiphilic drugs. Herein we briefly review drug-lipid interactions in general and the significance of these interactions in PLD in particular. We also focus on a potential causal connection between drug-induced PLD and steatohepatitis, which is induced by some cationic amphiphilic drugs.
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Affiliation(s)
- Juha-Matti Alakoskela
- Division of Biochemistry, Institute of Biomedicine, University of Helsinki, Haartmaninkatu 8, 00014 Helsinki, Finland.
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40
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Lange Y, Ye J, Duban ME, Steck TL. Activation of membrane cholesterol by 63 amphipaths. Biochemistry 2009; 48:8505-15. [PMID: 19655814 DOI: 10.1021/bi900951r] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A few membrane-intercalating amphipaths have been observed to stimulate the interaction of cholesterol with cholesterol oxidase, saponin and cyclodextrin, presumably by displacing cholesterol laterally from its phospholipid complexes. We now report that this effect, referred to as cholesterol activation, occurs with dozens of other amphipaths, including alkanols, saturated and cis- and trans-unsaturated fatty acids, fatty acid methyl esters, sphingosine derivatives, terpenes, alkyl ethers, ketones, aromatics and cyclic alkyl derivatives. The apparent potency of the agents tested ranged from 3 microM to 7 mM and generally paralleled their octanol/water partition coefficients, except that relative potency declined for compounds with >10 carbons. Some small amphipaths activated cholesterol at a membrane concentration of approximately 3 mol per 100 mol of bilayer lipids, about equimolar with the cholesterol they displaced. Lysophosphatidylserine countered the effects of all these agents, consistent with its ability to reduce the pool of active membrane cholesterol. Various amphipaths stabilized red cells against the hemolysis elicited by cholesterol depletion, presumably by substituting for the extracted sterol. The number and location of cis and trans fatty acid unsaturations and the absolute stereochemistry of enantiomer pairs had only small effects on amphipath potency. Nevertheless, potency varied approximately 7-fold within a group of diverse agents with similar partition coefficients. We infer that a wide variety of amphipaths can displace membrane cholesterol by competing stoichiometrically but with only limited specificity for weak association with phospholipids. Any number of other drugs and experimental agents might do the same.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois 60612, USA.
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41
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Covey DF. ent-Steroids: novel tools for studies of signaling pathways. Steroids 2009; 74:577-85. [PMID: 19103212 PMCID: PMC2668732 DOI: 10.1016/j.steroids.2008.11.019] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 11/21/2008] [Accepted: 11/24/2008] [Indexed: 12/24/2022]
Abstract
Membrane receptors are often modulated by steroids and it is necessary to distinguish the effects of steroids at these receptors from effects occurring at nuclear receptors. Additionally, it may also be mechanistically important to distinguish between direct effects caused by binding of steroids to membrane receptors and indirect effects on membrane receptor function caused by steroid perturbation of the membrane containing the receptor. In this regard, ent-steroids, the mirror images of naturally occurring steroids, are novel tools for distinguishing between these various actions of steroids. The review provides a background for understanding the different actions that can be expected of steroids and ent-steroids in biological systems, references for the preparation of ent-steroids, a short discussion about relevant forms of stereoisomerism and the requirements that need to be fulfilled for the interaction between two molecules to be enantioselective. The review then summarizes results of biophysical, biochemical and pharmacological studies published since 1992 in which ent-steroids have been used to investigate the actions of steroids in membranes and/or receptor-mediated signaling pathways.
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Affiliation(s)
- Douglas F Covey
- Department of Developmental Biology, Campus Box 8103, Washington Univ. in St. Louis, School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, United States.
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42
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Chisari M, Eisenman LN, Krishnan K, Bandyopadhyaya AK, Wang C, Taylor A, Benz A, Covey DF, Zorumski CF, Mennerick S. The influence of neuroactive steroid lipophilicity on GABAA receptor modulation: evidence for a low-affinity interaction. J Neurophysiol 2009; 102:1254-64. [PMID: 19553485 DOI: 10.1152/jn.00346.2009] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Anesthetic steroids with actions at gamma-aminobutyric acid type A receptors (GABA(A)Rs) may access transmembrane domain binding site(s) directly from the plasma cell membrane. Accordingly, the effective concentration in lipid phase and the ability of the steroid to meet pharmacophore requirements for activity will both contribute to observed steady-state potency. Furthermore, onset and offset of receptor effects may be rate limited by lipid partitioning. Here we show that several GABA-active steroids, including naturally occurring neurosteroids, of different lipophilicity differ in kinetics and potency at GABA(A)Rs. The hydrophobicity ranking predicted relative potency of GABA(A)R potentiation and predicted current offset kinetics. Kinetic offset differences among steroids were largely eliminated by gamma-cyclodextrin, a scavenger of unbound steroid, suggesting that affinity differences among the analogues are dwarfed by the contributions of nonspecific accumulation. A 7-nitrobenz-2-oxa-1,3-diazole (NBD)-tagged fluorescent analogue of the low-lipophilicity alphaxalone (C17-NBD-alphaxalone) exhibited faster nonspecific accumulation and departitioning than those of a fluorescent analogue of the high-lipophilicity (3alpha,5alpha)-3-hydroxypregnan-20-one (C17-NBD-3alpha5alphaA). These differences were paralleled by differences in potentiation of GABA(A)R function. The enantiomer of C17-NBD-3alpha5alphaA, which does not satisfy pharmacophore requirements for steroid potentiation, exhibited identical fluorescence kinetics and distribution to C17-NBD-3alpha5alphaA, but was inactive at GABA(A)Rs. Simple simulations supported our major findings, which suggest that neurosteroid binding affinity is low. Therefore both specific (e.g., fulfilling pharmacophore requirements) and nonspecific (e.g., lipid solubility) properties contribute to the potency and longevity of anesthetic steroid action.
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Affiliation(s)
- Mariangela Chisari
- Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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43
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Cerný I, Budesínský M, Pouzar V, Drasar P. Steroids linked with amide bond-extended cholesterol. Steroids 2009; 74:88-94. [PMID: 18950651 DOI: 10.1016/j.steroids.2008.09.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 09/16/2008] [Accepted: 09/19/2008] [Indexed: 11/16/2022]
Abstract
New type of linear cholesterol-like molecules based on cholesterol extended by attachment of etienic acid derivatives was designed and oligosteroids with two to four units were synthesized. Amide bond was used for inter steroid connections and 1-hydroxybenzotriazole active ester method was adapted for their formations. Use of disteroids as larger building blocks was applied.
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Affiliation(s)
- Ivan Cerný
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., 166 10 Prague 6, Czech Republic.
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44
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Gale SE, Westover EJ, Dudley N, Krishnan K, Merlin S, Scherrer DE, Han X, Zhai X, Brockman HL, Brown RE, Covey DF, Schaffer JE, Schlesinger P, Ory DS. Side chain oxygenated cholesterol regulates cellular cholesterol homeostasis through direct sterol-membrane interactions. J Biol Chem 2008; 284:1755-64. [PMID: 18996837 DOI: 10.1074/jbc.m807210200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Side chain oxysterols exert cholesterol homeostatic effects by suppression of sterol regulatory element-binding protein maturation and promoting degradation of hydroxymethylglutaryl-CoA reductase. To examine whether oxysterol-membrane interactions contribute to the regulation of cellular cholesterol homeostasis, we synthesized the enantiomer of 25-hydroxycholesterol. Using this unique oxysterol probe, we provide evidence that oxysterol regulation of cholesterol homeostatic responses is not mediated by enantiospecific oxysterol-protein interactions. We show that side chain oxysterols, but not steroid ring-modified oxysterols, exhibit membrane expansion behavior in phospholipid monolayers and bilayers in vitro. This behavior is non-enantiospecific and is abrogated by increasing the saturation of phospholipid acyl chain constituents. Moreover, we extend these findings into cultured cells by showing that exposure to saturated fatty acids at concentrations that lead to endoplasmic reticulum membrane phospholipid remodeling inhibits oxysterol activity. These studies implicate oxysterol-membrane interactions in acute regulation of sterol homeostatic responses and provide new insights into the mechanism through which oxysterols regulate cellular cholesterol balance.
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Affiliation(s)
- Sarah E Gale
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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45
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Christenson E, Merlin S, Saito M, Schlesinger P. Cholesterol effects on BAX pore activation. J Mol Biol 2008; 381:1168-83. [PMID: 18590739 DOI: 10.1016/j.jmb.2008.06.037] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 06/11/2008] [Accepted: 06/13/2008] [Indexed: 01/29/2023]
Abstract
The importance of BCL-2 family proteins in the control of cell death has been clearly established. One of the key members of this family, BAX, has soluble, membrane-bound, and membrane-integrated forms that are central to the regulation of apoptosis. Using purified monomeric human BAX, defined liposomes, and isolated human mitochondria, we have characterized the soluble to membrane transition and pore formation by this protein. For the purified protein, activation, but not oligomerization, is required for membrane binding. The transition to the membrane environment includes a binding step that is reversible and distinct from the membrane integration step. Oligomerization and pore activation occur after the membrane integration. In cells, BAX targets several intracellular membranes but notably does not target the plasma membrane while initiating apoptosis. When cholesterol was added to either the liposome bilayer or mitochondrial membranes, we observed increased binding but markedly reduced integration of BAX into both membranes. This cholesterol inhibition of membrane integration accounts for the reduction of BAX pore activation in liposomes and mitochondrial membranes. Our results indicate that the presence of cholesterol in membranes inhibits the pore-forming activity of BAX by reducing the ability of BAX to transition from a membrane-associated protein to a membrane-integral protein.
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Affiliation(s)
- Eric Christenson
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Pöyry S, Róg T, Karttunen M, Vattulainen I. Significance of Cholesterol Methyl Groups. J Phys Chem B 2008; 112:2922-9. [DOI: 10.1021/jp7100495] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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47
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Atkinson J, Epand RF, Epand RM. Tocopherols and tocotrienols in membranes: a critical review. Free Radic Biol Med 2008; 44:739-64. [PMID: 18160049 DOI: 10.1016/j.freeradbiomed.2007.11.010] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 11/09/2007] [Accepted: 11/12/2007] [Indexed: 12/14/2022]
Abstract
The familiar role of tocols (tocopherols and tocotrienols) as lipid-soluble chain-terminating inhibitors of lipid peroxidation is currently in the midst of a reinterpretation. New biological activities have been described for tocols that apparently are not dependent on their well-established antioxidant behaviour. These activities could well be real, but there remain large gaps in our understanding of the behaviour of tocols in membranes, especially when it comes to the alpha-, beta-, gamma-, delta-chroman methylation patterns and the seemingly special nature of tocotrienols. It is inappropriate to make conclusions and develop models based on in vivo (or cell culture) results with reference to in vitro measurements of antioxidant activity. When present in biological membranes, tocols will experience a large variation in the local composition of phospholipids and the presence of neutral lipids such as cholesterol, both of which would be expected to change the efficiency of antioxidant action. It is likely that tocols are not homogeneously dispersed in a membrane, but it is still not known whether any specific combination of lipid head group and acyl chains are conferred special protection from peroxidation, nor do we currently appreciate the structural role that tocols play in membranes. Tocols may enhance curvature stress or counteract similar stresses generated by other lipids such as lysolipids. This review will outline what is known about the location and behaviour of tocols in phospholipid bilayers. We will draw mainly from the biophysical literature, but will attempt to extend the discussion to biologically relevant phenomena when appropriate. We hope that it will assist researchers when designing new experiments and when critically assessing the results, in turn providing a more thorough understanding of the biochemistry of tocols.
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Affiliation(s)
- Jeffrey Atkinson
- Department of Chemistry and Centre for Biotechnology, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada.
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48
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Alakoskela JM, Sabatini K, Jiang X, Laitala V, Covey DF, Kinnunen PKJ. Enantiospecific interactions between cholesterol and phospholipids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:830-836. [PMID: 18171092 DOI: 10.1021/la702909q] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The effects of cholesterol on various membrane proteins have received considerable attention. An important question regarding each of these effects is whether the cholesterol exerts its influence by binding directly to membrane proteins or by changing the properties of lipid bilayers. Recently it was suggested that a difference in the effects of natural cholesterol and its enantiomer, ent-cholesterol, would originate from direct binding of cholesterol to a target protein. This strategy rests on the fact that ent-cholesterol has appeared to have effects on lipid films similar to those of cholesterol, yet fluorescence microscopy studies of phospholipid monolayers have provided striking demonstrations of the enantiomer effects, showing opposite chirality of domain shapes for phospholipid enantiomer pairs. We observed the shapes of ordered domains in phospholipid monolayers containing either cholesterol or ent-cholesterol and found that the phospholipid chirality had a great effect on the domain chirality, whereas a minor (quantitative) effect of cholesterol chirality could be observed only in monolayers with racemic dipalmitoylphosphatidylcholine. The latter is likely to derive from cholesterol-cholesterol interactions. Accordingly, cholesterol chirality has only a modest effect that is highly likely to require the presence of solidlike domains and, accordingly, is unlikely to play a role in biological membranes.
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Affiliation(s)
- Juha-Matti Alakoskela
- Helsinki Biophysics and Biomembrane Group, Institute of Biomedicine/Biochemistry, P.O. Box 63, University of Helsinki, 00014 Helsinki, Finland.
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49
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Akk G, Covey DF, Evers AS, Steinbach JH, Zorumski CF, Mennerick S. Mechanisms of neurosteroid interactions with GABA(A) receptors. Pharmacol Ther 2007; 116:35-57. [PMID: 17524487 PMCID: PMC2047817 DOI: 10.1016/j.pharmthera.2007.03.004] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Accepted: 03/29/2007] [Indexed: 11/20/2022]
Abstract
Neuroactive steroids have some of their most potent actions by augmenting the function of GABA(A) receptors. Endogenous steroid actions on GABA(A) receptors may underlie important effects on mood and behavior. Exogenous neuroactive steroids have potential as anesthetics, anticonvulsants, and neuroprotectants. We have taken multiple approaches to understand more completely the interaction of neuroactive steroids with GABA(A) receptors. We have developed many novel steroid analogues in this effort. Recent work has resulted in synthesis of new enantiomer analogue pairs, novel ligands that probe various properties of the steroid pharmacophore, fluorescent neuroactive steroid analogues, and photoaffinity labels. Using these tools, combined with receptor binding and electrophysiological assays, we have begun to untangle the complexity of steroid actions at this important class of ligand-gated ion channel.
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Affiliation(s)
- Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
| | - Douglas F. Covey
- Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
| | - Alex S. Evers
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
- Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
| | - Joe Henry Steinbach
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
- Department of Anatomy & Neurobiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
| | - Charles F. Zorumski
- Department of Anatomy & Neurobiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
- Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
| | - Steven Mennerick
- Department of Anatomy & Neurobiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
- Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
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Cerf E, Gasper R, Belani JD, Rychnovsky S, Chang XB, Buyse F, Ruysschaert JM. Multidrug resistance protein 1 is not associated to detergent-resistant membranes. Biochem Biophys Res Commun 2007; 355:1025-30. [PMID: 17336270 DOI: 10.1016/j.bbrc.2007.02.075] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Accepted: 02/14/2007] [Indexed: 11/26/2022]
Abstract
Multidrug resistance protein 1 (MRP1) is a member of the ATP-binding cassette superfamily. Using the energy provided by ATP hydrolysis, it transports a broad spectrum of substrates across the plasma membrane, including hormones, leukotriene C(4), bile salts, and anti-cancer drugs. Recent works have suggested that P-glycoprotein is associated to cholesterol and sphingolipid-rich membrane microdomains and that cholesterol upregulates its ATPase and drug transport activities. Confocal microscopy experiments and Triton X-100 extraction of detergent-resistant membranes provide evidence that MRP1 is not located in raft-like structures and that its activity is downregulated by cholesterol. The data are discussed in terms of cholesterol-protein interaction and topology.
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Affiliation(s)
- Emilie Cerf
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles, Boulevard du Triomphe, B-1050 Brussels, Belgium
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