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Schlessinger A, Zatorski N, Hutchinson K, Colas C. Targeting SLC transporters: small molecules as modulators and therapeutic opportunities. Trends Biochem Sci 2023; 48:801-814. [PMID: 37355450 PMCID: PMC10525040 DOI: 10.1016/j.tibs.2023.05.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 05/24/2023] [Accepted: 05/25/2023] [Indexed: 06/26/2023]
Abstract
Solute carrier (SLCs) transporters mediate the transport of a broad range of solutes across biological membranes. Dysregulation of SLCs has been associated with various pathologies, including metabolic and neurological disorders, as well as cancer and rare diseases. SLCs are therefore emerging as key targets for therapeutic intervention with several recently approved drugs targeting these proteins. Unlocking this large and complex group of proteins is essential to identifying unknown SLC targets and developing next-generation SLC therapeutics. Recent progress in experimental and computational techniques has significantly advanced SLC research, including drug discovery. Here, we review emerging topics in therapeutic discovery of SLCs, focusing on state-of-the-art approaches in structural, chemical, and computational biology, and discuss current challenges in transporter drug discovery.
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Affiliation(s)
- Avner Schlessinger
- Department of Pharmacological Sciences Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
| | - Nicole Zatorski
- Department of Pharmacological Sciences Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Keino Hutchinson
- Department of Pharmacological Sciences Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Claire Colas
- University of Vienna, Department of Pharmaceutical Chemistry, Vienna, Austria.
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2
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Rosenhouse-Dantsker A, Gazgalis D, Logothetis DE. PI(4,5)P 2 and Cholesterol: Synthesis, Regulation, and Functions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:3-59. [PMID: 36988876 DOI: 10.1007/978-3-031-21547-6_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is the most abundant membrane phosphoinositide and cholesterol is an essential component of the plasma membrane (PM). Both lipids play key roles in a variety of cellular functions including as signaling molecules and major regulators of protein function. This chapter provides an overview of these two important lipids. Starting from a brief description of their structure, synthesis, and regulation, the chapter continues to describe the primary functions and signaling processes in which PI(4,5)P2 and cholesterol are involved. While PI(4,5)P2 and cholesterol can act independently, they often act in concert or affect each other's impact. The chapters in this volume on "Cholesterol and PI(4,5)P2 in Vital Biological Functions: From Coexistence to Crosstalk" focus on the emerging relationship between cholesterol and PI(4,5)P2 in a variety of biological systems and processes. In this chapter, the next section provides examples from the ion channel field demonstrating that PI(4,5)P2 and cholesterol can act via common mechanisms. The chapter ends with a discussion of future directions.
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Affiliation(s)
| | - Dimitris Gazgalis
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA
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3
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Barbera N, Granados ST, Vanoye CG, Abramova TV, Kulbak D, Ahn SJ, George AL, Akpa BS, Levitan I. Cholesterol-induced suppression of Kir2 channels is mediated by decoupling at the inter-subunit interfaces. iScience 2022; 25:104329. [PMID: 35602957 PMCID: PMC9120057 DOI: 10.1016/j.isci.2022.104329] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/29/2022] [Accepted: 04/26/2022] [Indexed: 12/29/2022] Open
Abstract
Cholesterol is a major regulator of multiple types of ion channels. Although there is increasing information about cholesterol binding sites, the molecular mechanisms through which cholesterol binding alters channel function are virtually unknown. In this study, we used a combination of Martini coarse-grained simulations, a network theory-based analysis, and electrophysiology to determine the effect of cholesterol on the dynamic structure of the Kir2.2 channel. We found that increasing membrane cholesterol reduced the likelihood of contact between specific regions of the cytoplasmic and transmembrane domains of the channel, most prominently at the subunit-subunit interfaces of the cytosolic domains. This decrease in contact was mediated by pairwise interactions of specific residues and correlated to the stoichiometry of cholesterol binding events. The predictions of the model were tested by site-directed mutagenesis of two identified residues-V265 and H222-and high throughput electrophysiology.
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Affiliation(s)
- Nicolas Barbera
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Sara T. Granados
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Carlos Guillermo Vanoye
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Tatiana V. Abramova
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Danielle Kulbak
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Sang Joon Ahn
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Alfred L. George
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Belinda S. Akpa
- Division of Biosciences, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA
- Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Irena Levitan
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
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4
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Bobkov D, Semenova S. Impact of lipid rafts on transient receptor potential channel activities. J Cell Physiol 2022; 237:2034-2044. [PMID: 35014032 DOI: 10.1002/jcp.30679] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 12/06/2021] [Accepted: 12/23/2021] [Indexed: 11/06/2022]
Abstract
Members of the transient receptor potential (TRP) superfamily are cation channels that are expressed in nearly every mammalian cell type and respond as cellular sensors to various environmental stimuli. Light, pressure, osmolarity, temperature, and other stimuli can induce TRP calcium conductivity and correspondingly trigger many signaling processes in cells. Disruption of TRP channel activity, as a rule, harms cellular function. Despite numerous studies, the mechanisms of TRP channel regulation are not yet sufficiently clear, in part, because TRP channels are regulated by a broad set of ligands having diverse physical and chemical features. It is now known that some TRP members are located in membrane microdomains termed lipid rafts. Moreover, interaction between specific raft-associated lipids with channels may be a key regulation mechanism. This review examines recent findings related to the roles of lipid rafts in regulation of TRP channel activity. The mechanistic events of channel interactions with the main lipid raft constituent, cholesterol, are being clarified. Better understanding of mechanisms behind such interactions would help establish the key elements of TRP channel regulation and hence allow control of cellular responses to environmental stimuli.
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Affiliation(s)
- Danila Bobkov
- Laboratory of Ionic Mechanisms of Cell Signaling, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Svetlana Semenova
- Laboratory of Ionic Mechanisms of Cell Signaling, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
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5
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Gutiérrez-García L, Arró M, Altabella T, Ferrer A, Boronat A. Structural and functional analysis of tomato sterol C22 desaturase. BMC PLANT BIOLOGY 2021; 21:141. [PMID: 33731007 PMCID: PMC7972189 DOI: 10.1186/s12870-021-02898-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 02/21/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Sterols are structural and functional components of eukaryotic cell membranes. Plants produce a complex mixture of sterols, among which β-sitosterol, stigmasterol, campesterol, and cholesterol in some Solanaceae, are the most abundant species. Many reports have shown that the stigmasterol to β-sitosterol ratio changes during plant development and in response to stresses, suggesting that it may play a role in the regulation of these processes. In tomato (Solanum lycopersicum), changes in the stigmasterol to β-sitosterol ratio correlate with the induction of the only gene encoding sterol C22-desaturase (C22DES), the enzyme specifically involved in the conversion of β-sitosterol to stigmasterol. However, despite the biological interest of this enzyme, there is still a lack of knowledge about several relevant aspects related to its structure and function. RESULTS In this study we report the subcellular localization of tomato C22DES in the endoplasmic reticulum (ER) based on confocal fluorescence microscopy and cell fractionation analyses. Modeling studies have also revealed that C22DES consists of two well-differentiated domains: a single N-terminal transmembrane-helix domain (TMH) anchored in the ER-membrane and a globular (or catalytic) domain that is oriented towards the cytosol. Although TMH is sufficient for the targeting and retention of the enzyme in the ER, the globular domain may also interact and be retained in the ER in the absence of the N-terminal transmembrane domain. The observation that a truncated version of C22DES lacking the TMH is enzymatically inactive revealed that the N-terminal membrane domain is essential for enzyme activity. The in silico analysis of the TMH region of plant C22DES revealed several structural features that could be involved in substrate recognition and binding. CONCLUSIONS Overall, this study contributes to expand the current knowledge on the structure and function of plant C22DES and to unveil novel aspects related to plant sterol metabolism.
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Affiliation(s)
- Laura Gutiérrez-García
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
| | - Montserrat Arró
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028, Barcelona, Spain
| | - Teresa Altabella
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
- Department of Biology, Healthcare and the Environment, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028, Barcelona, Spain
| | - Albert Ferrer
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028, Barcelona, Spain
| | - Albert Boronat
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain.
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, 08028, Barcelona, Spain.
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6
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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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7
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Fancher IS, Levitan I. Endothelial inwardly-rectifying K + channels as a key component of shear stress-induced mechanotransduction. CURRENT TOPICS IN MEMBRANES 2020; 85:59-88. [PMID: 32402645 DOI: 10.1016/bs.ctm.2020.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
It has been recognized for decades that fluid shear stress plays a major role in vascular function. Acting on the endothelium shear stress induces vasorelaxation of resistance arteries and plays a major role in the propensity of the major arteries to atherosclerosis. Many elements of shear-induced signaling have been identified yet we are just beginning to decipher the roles that mechanosensitive ion channels may play in the signaling pathways initiated by shear stress. Endothelial inwardly-rectifying K+ channels were identified as potential primary mechanosensors in the late 1980s yet until our recent works, highlighted in the forthcoming chapter, the functional effect of a shear-activated K+ current was completely unknown. In this chapter, we present the physiological effects of shear stress in arteries in health and disease and highlight the most prevalent of today's investigated mechanosensitive ion channels. Ultimately, we focus on Kir2.1 channels and discuss in detail our findings regarding the downstream signaling events that are induced by shear-activated endothelial Kir2.1 channels. Most importantly, we examine our findings regarding hypercholesterolemia-induced inhibition of Kir channel shear-sensitivity and the impact on endothelial function in the context of flow (shear)-mediated vasodilation and atherosclerosis.
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Affiliation(s)
- Ibra S Fancher
- Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, IL, United States.
| | - Irena Levitan
- Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, IL, United States
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8
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Gutorov R, Peters M, Katz B, Brandwine T, Barbera NA, Levitan I, Minke B. Modulation of Transient Receptor Potential C Channel Activity by Cholesterol. Front Pharmacol 2019; 10:1487. [PMID: 31920669 PMCID: PMC6923273 DOI: 10.3389/fphar.2019.01487] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 11/15/2019] [Indexed: 12/11/2022] Open
Abstract
Changes of cholesterol level in the plasma membrane of cells have been shown to modulate ion channel function. The proposed mechanisms underlying these modulations include association of cholesterol to a single binding site at a single channel conformation, association to a highly flexible cholesterol binding site adopting multiple poses, and perturbation of lipid rafts. These perturbations have been shown to induce reversible targeting of mammalian transient receptor potential C (TRPC) channels to the cholesterol-rich membrane environment of lipid rafts. Thus, the observed inhibition of TRPC channels by methyl-β-cyclodextrin (MβCD), which induces cholesterol efflux from the plasma membrane, may result from disruption of lipid rafts. This perturbation was also shown to disrupt multimolecular signaling complexes containing TRPC channels. The Drosophila TRP and TRP-like (TRPL) channels belong to the TRPC channel subfamily. When the Drosophila TRPL channel was expressed in S2 or HEK293 cells and perfused with MβCD, the TRPL current was abolished in less than 100 s, fitting well the fast kinetic phase of cholesterol sequestration experiments in cells. It was thus suggested that the fast kinetics of TRPL channel suppression by MβCD arise from disruption of lipid rafts. Accordingly, lipid raft perturbation by cholesterol sequestration could give clues to the function of lipid environment in TRPC channel activity and its mechanism.
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Affiliation(s)
- Rita Gutorov
- Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Maximilian Peters
- Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Ben Katz
- Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Tal Brandwine
- Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Nicolas A Barbera
- Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, IL, United States
| | - Irena Levitan
- Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, IL, United States
| | - Baruch Minke
- Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, The Hebrew University, Jerusalem, Israel
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9
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Lee AG. Interfacial Binding Sites for Cholesterol on TRP Ion Channels. Biophys J 2019; 117:2020-2033. [PMID: 31672270 DOI: 10.1016/j.bpj.2019.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 10/11/2019] [Accepted: 10/15/2019] [Indexed: 12/24/2022] Open
Abstract
Transient receptor potential (TRP) channels are members of a large family of ion channels located in membranes rich in cholesterol, some of whose functions are affected by the cholesterol content of the membrane. Here, cholesterol binding to TRPs is studied using a docking procedure that allows the transmembrane surface of a TRP to be swept rapidly for potential binding sites at the interfaces on the two sides of the membrane. Cholesterol docking poses determined in this way match 89% of the cholesterol hemisuccinate molecules in published TRP structures when cholesterol hemisuccinate molecules unlikely to represent typical bound cholesterols are excluded. TRPs are tetrameric, with large clefts at the interfaces between subunits; cholesterol poses are located in hollows, largely within these clefts. Comparison of cholesterol poses with phospholipid binding sites suggests that binding of cholesterol to a TRP need not result in displacement of phospholipid molecules from the TRP surface.
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Affiliation(s)
- Anthony G Lee
- School of Biological Sciences, University of Southampton, Southampton, United Kingdom.
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10
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Molecular Determinants of Cholesterol Binding to Soluble and Transmembrane Protein Domains. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1135:47-66. [PMID: 31098810 DOI: 10.1007/978-3-030-14265-0_3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Cholesterol-protein interactions play a critical role in lipid metabolism and maintenance of cell integrity. To elucidate the molecular mechanisms underlying these interactions, a growing number of studies have focused on determining the crystal structures of a variety of proteins complexed with cholesterol. These include structures in which cholesterol binds to transmembrane domains, and structures in which cholesterol interacts with soluble ones. However, it remains unknown whether there are differences in the prerequisites for cholesterol binding to these two types of domains. Thus, to define the molecular determinants that characterize the binding of cholesterol to these two distinct protein domains, we employed the database of crystal structures of proteins complexed with cholesterol. Our analysis suggests that cholesterol may bind more strongly to soluble domains than to transmembrane domains. The interactions between cholesterol and the protein in both cases critically depends on hydrophobic and aromatic residues. In addition, cholesterol binding sites in both types of domains involve polar and/or charged residues. However, the percentage of appearance of the different types of polar/charged residues in cholesterol binding sites differs between soluble and transmembrane domains. No differences were observed in the conformational characteristics of the cholesterol molecules bound to soluble versus transmembrane protein domains suggesting that cholesterol is insensitive to the environment provided by the different protein domains.
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11
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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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12
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Rosenhouse-Dantsker A. Cholesterol Binding Sites in Inwardly Rectifying Potassium Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1135:119-138. [DOI: 10.1007/978-3-030-14265-0_7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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13
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Liu H, Kabrah A, Ahuja M, Muallem S. CRAC channels in secretory epithelial cell function and disease. Cell Calcium 2018; 78:48-55. [PMID: 30641249 DOI: 10.1016/j.ceca.2018.12.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/28/2018] [Accepted: 12/29/2018] [Indexed: 02/08/2023]
Abstract
The receptor-evoked Ca2+ signal in secretory epithelia mediate many cellular functions essential for cell survival and their most fundamental functions of secretory granules exocytosis and fluid and electrolyte secretion. Ca2+ influx is a key component of the receptor-evoked Ca2+ signal in secretory cell and is mediated by both TRPC and the STIM1-activated Orai1 channels that mediates the Ca2+ release-activated current (CRAC) Icrac. The core components of the receptor-evoked Ca2+ signal are assembled at the ER/PM junctions where exchange of materials between the plasma membrane and internal organelles take place, including transfer of lipids and Ca2+. The Ca2+ signal generated at the confined space of the ER/PM junctions is necessary for activation of the Ca2+-regulated proteins and ion channels that mediate exocytosis with high fidelity and tight control. In this review we discuss the general properties of Ca2+ signaling, PI(4,5)P2 and other lipids at the ER/PM junctions with regard to secretory cells function and disease caused by uncontrolled Ca2+ influx.
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Affiliation(s)
- Haiping Liu
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, United States
| | - Ahmed Kabrah
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, United States
| | - Malini Ahuja
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, United States
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, United States.
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14
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Dergunov AD, Savushkin EV, Dergunova LV, Litvinov DY. Significance of Cholesterol-Binding Motifs in ABCA1, ABCG1, and SR-B1 Structure. J Membr Biol 2018; 252:41-60. [DOI: 10.1007/s00232-018-0056-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 11/29/2018] [Indexed: 10/27/2022]
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15
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Bukiya AN, Blank PS, Rosenhouse-Dantsker A. Cholesterol intake and statin use regulate neuronal G protein-gated inwardly rectifying potassium channels. J Lipid Res 2018; 60:19-29. [PMID: 30420402 DOI: 10.1194/jlr.m081240] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 11/10/2018] [Indexed: 12/31/2022] Open
Abstract
Cholesterol, a critical component of the cellular plasma membrane, is essential for normal neuronal function. Cholesterol content is highest in the brain, where most cholesterol is synthesized de novo; HMG-CoA reductase controls the synthesis rate. Despite strict control, elevated blood cholesterol levels are common and are associated with various neurological disorders. G protein-gated inwardly rectifying potassium (GIRK) channels mediate the actions of inhibitory brain neurotransmitters. Loss of GIRK function enhances neuron excitability; gain of function reduces neuronal activity. However, the effect of dietary cholesterol or HMG-CoA reductase inhibition (i.e., statin therapy) on GIRK function remains unknown. Using a rat model, we compared the effects of a high-cholesterol versus normal diet both with and without atorvastatin, a widely prescribed HMG-CoA reductase inhibitor, on neuronal GIRK currents. The high-cholesterol diet increased hippocampal CA1 region cholesterol levels and correspondingly increased neuronal GIRK currents. Both phenomena were reversed by cholesterol depletion in vitro. Atorvastatin countered the high-cholesterol diet effects on neuronal cholesterol content and GIRK currents; these effects were reversed by cholesterol enrichment in vitro. Our findings suggest that high-cholesterol diet and atorvastatin therapy affect ion channel function in the brain by modulating neuronal cholesterol levels.
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Affiliation(s)
- Anna N Bukiya
- Department of Pharmacology, The University of Tennessee Health Science Center, Memphis, TN 38163
| | - Paul S Blank
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
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16
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Jaipuria G, Giller K, Leonov A, Becker S, Zweckstetter M. Insights into Cholesterol/Membrane Protein Interactions Using Paramagnetic Solid-State NMR. Chemistry 2018; 24:17606-17611. [PMID: 30255522 DOI: 10.1002/chem.201804550] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Indexed: 11/10/2022]
Abstract
Cholesterol is an essential component of animal cell membranes and impacts the structure and function of membrane proteins. But how cholesterol exerts its functions remains often enigmatic. Here, high-resolution solid-state NMR in combination with paramagnetic cholesterol analogues was shown to be a powerful approach to study the interaction of membrane proteins with cholesterol. Application of the method to the 169-residue translocator protein TSPO provides residue-specific information about its interaction with cholesterol. Comparison with NMR signal perturbations induced by diamagnetic cholesterol furthermore supports changes in the structure of mammalian TSPO caused by cholesterol binding.
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Affiliation(s)
- Garima Jaipuria
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Von-Siebold-Str. 3a, 37075, Göttingen, Germany
| | - Karin Giller
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Andrei Leonov
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Stefan Becker
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Markus Zweckstetter
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Von-Siebold-Str. 3a, 37075, Göttingen, Germany.,Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
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17
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Barbera N, Ayee MAA, Akpa BS, Levitan I. Molecular Dynamics Simulations of Kir2.2 Interactions with an Ensemble of Cholesterol Molecules. Biophys J 2018; 115:1264-1280. [PMID: 30205899 PMCID: PMC6170799 DOI: 10.1016/j.bpj.2018.07.041] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 07/12/2018] [Accepted: 07/31/2018] [Indexed: 11/16/2022] Open
Abstract
Cholesterol is a major regulator of multiple types of ion channels, but the specific mechanisms and the dynamics of its interactions with the channels are not well understood. Kir2 channels were shown to be sensitive to cholesterol through direct interactions with "cholesterol-sensitive" regions on the channel protein. In this work, we used Martini coarse-grained simulations to analyze the long (μs) timescale dynamics of cholesterol with Kir2.2 channels embedded into a model membrane containing POPC phospholipid with 30 mol% cholesterol. This approach allows us to simulate the dynamic, unbiased migration of cholesterol molecules from the lipid membrane environment to the protein surface of Kir2.2 and explore the favorability of cholesterol interactions at both surface sites and recessed pockets of the channel. We found that the cholesterol environment surrounding Kir channels forms a complex milieu of different short- and long-term interactions, with multiple cholesterol molecules concurrently interacting with the channel. Furthermore, utilizing principles from network theory, we identified four discrete cholesterol-binding sites within the previously identified cholesterol-sensitive region that exist depending on the conformational state of the channel-open or closed. We also discovered that a twofold decrease in the cholesterol level of the membrane, which we found earlier to increase Kir2 activity, results in a site-specific decrease of cholesterol occupancy at these sites in both the open and closed states: cholesterol molecules at the deepest of these discrete sites shows no change in occupancy at different cholesterol levels, whereas the remaining sites showed a marked decrease in occupancy.
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Affiliation(s)
- Nicolas Barbera
- Department of Chemical Engineering; Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Manuela A A Ayee
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Belinda S Akpa
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, North Carolina.
| | - Irena Levitan
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois.
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Rosenhouse-Dantsker A. Cholesterol-Binding Sites in GIRK Channels: The Devil is in the Details. Lipid Insights 2018; 11:1178635317754071. [PMID: 29467578 PMCID: PMC5815411 DOI: 10.1177/1178635317754071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 11/14/2017] [Indexed: 11/17/2022] Open
Abstract
In recent years, it has become evident that cholesterol plays a direct role in the modulation of a variety of ion channels. In most cases, cholesterol downregulates channel activity. In contrast, our earlier studies have demonstrated that atrial G protein inwardly rectifying potassium (GIRK) channels are upregulated by cholesterol. Recently, we have shown that hippocampal GIRK currents are also upregulated by cholesterol. A combined computational-experimental approach pointed to putative cholesterol-binding sites in the transmembrane domain of the GIRK2 channel, the primary subunit in hippocampal GIRK channels. In particular, the principal cholesterol-binding site was located in the center of the transmembrane domain in between the inner and outer α-helices of 2 adjacent subunits. Further studies pointed to a similar cholesterol-binding site in GIRK4, a major subunit in atrial GIRK channels. However, a close look at a sequence alignment of the transmembrane helices of the 2 channels reveals surprising differences among the residues that interact with the cholesterol molecule in these 2 channels. Here, we compare the residues that form putative cholesterol-binding sites in GIRK2 and GIRK4 and discuss the similarities and differences among them.
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