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Cases M, Dorca-Arévalo J, Blanch M, Rodil S, Terni B, Martín-Satué M, Llobet A, Blasi J, Solsona C. The epsilon toxin from Clostridium perfringens stimulates calcium-activated chloride channels, generating extracellular vesicles in Xenopus oocytes. Pharmacol Res Perspect 2024; 12:e70005. [PMID: 39320019 PMCID: PMC11423345 DOI: 10.1002/prp2.70005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 07/18/2024] [Accepted: 08/08/2024] [Indexed: 09/26/2024] Open
Abstract
The epsilon toxin (Etx) from Clostridium perfringens has been identified as a potential trigger of multiple sclerosis, functioning as a pore-forming toxin that selectively targets cells expressing the plasma membrane (PM) myelin and lymphocyte protein (MAL). Previously, we observed that Etx induces the release of intracellular ATP in sensitive cell lines. Here, we aimed to re-examine the mechanism of action of the toxin and investigate the connection between pore formation and ATP release. We examined the impact of Etx on Xenopus laevis oocytes expressing human MAL. Extracellular ATP was assessed using the luciferin-luciferase reaction. Activation of calcium-activated chloride channels (CaCCs) and a decrease in the PM surface were recorded using the two-electrode voltage-clamp technique. To evaluate intracellular Ca2+ levels and scramblase activity, fluorescent dyes were employed. Extracellular vesicles were imaged using light and electron microscopy, while toxin oligomers were identified through western blots. Etx triggered intracellular Ca2+ mobilization in the Xenopus oocytes expressing hMAL, leading to the activation of CaCCs, ATP release, and a reduction in PM capacitance. The toxin induced the activation of scramblase and, thus, translocated phospholipids from the inner to the outer leaflet of the PM, exposing phosphatidylserine outside in Xenopus oocytes and in an Etx-sensitive cell line. Moreover, Etx caused the formation of extracellular vesicles, not derived from apoptotic bodies, through PM fission. These vesicles carried toxin heptamers and doughnut-like structures in the nanometer size range. In conclusion, ATP release was not directly attributed to the formation of pores in the PM, but to scramblase activity and the formation of extracellular vesicles.
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Affiliation(s)
- Mercè Cases
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
- Laboratory of Molecular and Cellular Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - Jonatan Dorca-Arévalo
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
- Laboratory of Molecular and Cellular Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - Marta Blanch
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
- Laboratory of Molecular and Cellular Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat, Spain
| | - Sergi Rodil
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
| | - Beatrice Terni
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
- Laboratory of Molecular and Cellular Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - Mireia Martín-Satué
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
| | - Artur Llobet
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
- Laboratory of Molecular and Cellular Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - Juan Blasi
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
- Laboratory of Molecular and Cellular Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - Carles Solsona
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences-Campus Bellvitge, University of Barcelona, Barcelona, Spain
- Laboratory of Molecular and Cellular Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat, Spain
- Institute of Neuroscience, University of Barcelona, Barcelona, Spain
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2
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Sebinelli HG, Syska C, Čopič A, Lenoir G. Established and emerging players in phospholipid scrambling: A structural perspective. Biochimie 2024:S0300-9084(24)00218-9. [PMID: 39304020 DOI: 10.1016/j.biochi.2024.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Revised: 09/16/2024] [Accepted: 09/17/2024] [Indexed: 09/22/2024]
Abstract
The maintenance of a diverse and non-homogeneous lipid composition in cell membranes is crucial for a multitude of cellular processes. One important example is transbilayer lipid asymmetry, which refers to a difference in lipid composition between the two leaflets of a cellular membrane. Transbilayer asymmetry is especially pronounced at the plasma membrane, where at resting state, negatively-charged phospholipids such as phosphatidylserine (PS) are almost exclusively restricted to the cytosolic leaflet, whereas sphingolipids are mostly found in the exoplasmic leaflet. Transbilayer movement of lipids is inherently slow, and for a fast cellular response, for example during apoptosis, transmembrane proteins termed scramblases facilitate the movement of polar/charged lipid headgroups through the membrane interior. In recent years, an expanding number of proteins from diverse families have been suggested to possess a lipid scramblase activity. Members of TMEM16 and XKR proteins have been implicated in blood clotting and apoptosis, whereas the scrambling activity of ATG9 and TMEM41B/VMP1 proteins contributes to the synthesis of autophagosomal membrane during autophagy. Structural studies, in vitro reconstitution of lipid scrambling, and molecular dynamics simulations have significantly advanced our understanding of the molecular mechanisms of lipid scrambling and helped delineate potential lipid transport pathways through the membrane. A number of examples also suggest that lipid scrambling activity can be combined with another activity, as is the case for TMEM16 proteins, which also function as ion channels, rhodopsin in the photoreceptor membrane, and possibly other G-protein coupled receptors.
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Affiliation(s)
- Heitor Gobbi Sebinelli
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell, Gif-sur-Yvette, France
| | - Camille Syska
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293, Montpellier, Cedex 05, France
| | - Alenka Čopič
- Centre de Recherche en Biologie Cellulaire de Montpellier (CRBM), Université de Montpellier, CNRS, 34293, Montpellier, Cedex 05, France
| | - Guillaume Lenoir
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell, Gif-sur-Yvette, France.
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3
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Arreola J, López-Romero AE, Huerta M, Guzmán-Hernández ML, Pérez-Cornejo P. Insights into the function and regulation of the calcium-activated chloride channel TMEM16A. Cell Calcium 2024; 121:102891. [PMID: 38772195 DOI: 10.1016/j.ceca.2024.102891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 05/23/2024]
Abstract
The TMEM16A channel, a member of the TMEM16 protein family comprising chloride (Cl-) channels and lipid scramblases, is activated by the free intracellular Ca2+ increments produced by inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release after GqPCRs or Ca2+ entry through cationic channels. It is a ubiquitous transmembrane protein that participates in multiple physiological functions essential to mammals' lives. TMEM16A structure contains two identical 10-segment monomers joined at their transmembrane segment 10. Each monomer harbours one independent hourglass-shaped pore gated by Ca2+ ligation to an orthosteric site adjacent to the pore and controlled by two gates. The orthosteric site is created by assembling negatively charged glutamate side chains near the pore´s cytosolic end. When empty, this site generates an electrostatic barrier that controls channel rectification. In addition, an isoleucine-triad forms a hydrophobic gate at the boundary of the cytosolic vestibule and the inner side of the neck. When the cytosolic Ca2+ rises, one or two Ca2+ ions bind to the orthosteric site in a voltage (V)-dependent manner, thus neutralising the electrostatic barrier and triggering an allosteric gating mechanism propagating via transmembrane segment 6 to the hydrophobic gate. These coordinated events lead to pore opening, allowing the Cl- flux to ensure the physiological response. The Ca2+-dependent function of TMEM16A is highly regulated. Anions with higher permeability than Cl- facilitate V dependence by increasing the Ca2+ sensitivity, intracellular protons can replace Ca2+ and induce channel opening, and phosphatidylinositol 4,5-bisphosphate bound to four cytosolic sites likely maintains Ca2+ sensitivity. Additional regulation is afforded by cytosolic proteins, most likely by phosphorylation and protein-protein interaction mechanisms.
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Affiliation(s)
- Jorge Arreola
- Jorge Arreola, Physics Institute of Universidad Autónoma de San Luis Potosí. Av. Parque Chapultepec 1570, Privadas del Pedregal, 78295 San Luis Potosí, SLP., Mexico.
| | - Ana Elena López-Romero
- Jorge Arreola, Physics Institute of Universidad Autónoma de San Luis Potosí. Av. Parque Chapultepec 1570, Privadas del Pedregal, 78295 San Luis Potosí, SLP., Mexico
| | - Miriam Huerta
- Jorge Arreola, Physics Institute of Universidad Autónoma de San Luis Potosí. Av. Parque Chapultepec 1570, Privadas del Pedregal, 78295 San Luis Potosí, SLP., Mexico
| | - María Luisa Guzmán-Hernández
- Catedrática CONAHCYT, Department of Physiology and Biophysics, School of Medicine, Universidad Autónoma de San Luis Potosí. Ave. V. Carranza 2905, Los Filtros, San Luis Potosí, SLP 78210, Mexico
| | - Patricia Pérez-Cornejo
- Department of Physiology and Biophysics, School of Medicine, Universidad Autónoma de San Luis Potosí. Ave. V. Carranza 2905, Los Filtros, San Luis Potosí, SLP 78210, Mexico
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Ye Z, Galvanetto N, Puppulin L, Pifferi S, Flechsig H, Arndt M, Triviño CAS, Di Palma M, Guo S, Vogel H, Menini A, Franz CM, Torre V, Marchesi A. Structural heterogeneity of the ion and lipid channel TMEM16F. Nat Commun 2024; 15:110. [PMID: 38167485 PMCID: PMC10761740 DOI: 10.1038/s41467-023-44377-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 12/11/2023] [Indexed: 01/05/2024] Open
Abstract
Transmembrane protein 16 F (TMEM16F) is a Ca2+-activated homodimer which functions as an ion channel and a phospholipid scramblase. Despite the availability of several TMEM16F cryogenic electron microscopy (cryo-EM) structures, the mechanism of activation and substrate translocation remains controversial, possibly due to restrictions in the accessible protein conformational space. In this study, we use atomic force microscopy under physiological conditions to reveal a range of structurally and mechanically diverse TMEM16F assemblies, characterized by variable inter-subunit dimerization interfaces and protomer orientations, which have escaped prior cryo-EM studies. Furthermore, we find that Ca2+-induced activation is associated to stepwise changes in the pore region that affect the mechanical properties of transmembrane helices TM3, TM4 and TM6. Our direct observation of membrane remodelling in response to Ca2+ binding along with additional electrophysiological analysis, relate this structural multiplicity of TMEM16F to lipid and ion permeation processes. These results thus demonstrate how conformational heterogeneity of TMEM16F directly contributes to its diverse physiological functions.
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Affiliation(s)
- Zhongjie Ye
- International School for Advanced Studies (SISSA), 34136, Trieste, Italy
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, China
| | - Nicola Galvanetto
- Department of Physics, University of Zurich, 8057, Zurich, Switzerland
- Department of Biochemistry, University of Zurich, 8057, Zurich, Switzerland
| | - Leonardo Puppulin
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, I-30172 Mestre, Venice, Italy
- WPI Nano Life Science Institute, Kanazawa University, Kakuma-machi, 920-1192, Kanazawa, Japan
| | - Simone Pifferi
- International School for Advanced Studies (SISSA), 34136, Trieste, Italy
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, 60126, Ancona, Italy
| | - Holger Flechsig
- WPI Nano Life Science Institute, Kanazawa University, Kakuma-machi, 920-1192, Kanazawa, Japan
| | - Melanie Arndt
- Department of Biochemistry, University of Zurich, 8057, Zurich, Switzerland
| | | | - Michael Di Palma
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, 60126, Ancona, Italy
| | - Shifeng Guo
- Shenzhen Key Laboratory of Smart Sensing and Intelligent Systems, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
- Guangdong Provincial Key Lab of Robotics and Intelligent System, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Horst Vogel
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, China
- Institut des Sciences et Ingénierie Chimiques (ISIC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Anna Menini
- International School for Advanced Studies (SISSA), 34136, Trieste, Italy
| | - Clemens M Franz
- WPI Nano Life Science Institute, Kanazawa University, Kakuma-machi, 920-1192, Kanazawa, Japan
| | - Vincent Torre
- International School for Advanced Studies (SISSA), 34136, Trieste, Italy.
- Institute of Materials (ION-CNR), Area Science Park, Basovizza, 34149, Trieste, Italy.
- BIoValley Investments System and Solutions (BISS), 34148, Trieste, Italy.
| | - Arin Marchesi
- WPI Nano Life Science Institute, Kanazawa University, Kakuma-machi, 920-1192, Kanazawa, Japan.
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, 60126, Ancona, Italy.
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5
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Zheng W, Rawson S, Shen Z, Tamilselvan E, Smith HE, Halford J, Shen C, Murthy SE, Ulbrich MH, Sotomayor M, Fu TM, Holt JR. TMEM63 proteins function as monomeric high-threshold mechanosensitive ion channels. Neuron 2023; 111:3195-3210.e7. [PMID: 37543036 PMCID: PMC10592209 DOI: 10.1016/j.neuron.2023.07.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 05/12/2023] [Accepted: 07/08/2023] [Indexed: 08/07/2023]
Abstract
OSCA/TMEM63s form mechanically activated (MA) ion channels in plants and animals, respectively. OSCAs and related TMEM16s and transmembrane channel-like (TMC) proteins form homodimers with two pores. Here, we uncover an unanticipated monomeric configuration of TMEM63 proteins. Structures of TMEM63A and TMEM63B (referred to as TMEM63s) revealed a single highly restricted pore. Functional analyses demonstrated that TMEM63s are bona fide mechanosensitive ion channels, characterized by small conductance and high thresholds. TMEM63s possess evolutionary variations in the intracellular linker IL2, which mediates dimerization in OSCAs. Replacement of OSCA1.2 IL2 with TMEM63A IL2 or mutations to key variable residues resulted in monomeric OSCA1.2 and MA currents with significantly higher thresholds. Structural analyses revealed substantial conformational differences in the mechano-sensing domain IL2 and gating helix TM6 between TMEM63s and OSCA1.2. Our studies reveal that mechanosensitivity in OSCA/TMEM63 channels is affected by oligomerization and suggest gating mechanisms that may be shared by OSCA/TMEM63, TMEM16, and TMC channels.
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Affiliation(s)
- Wang Zheng
- Departments of Otolaryngology & Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
| | - Shaun Rawson
- Harvard Cryo-Electron Microscopy Center for Structural Biology, Harvard Medical School, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Zhangfei Shen
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USA
| | - Elakkiya Tamilselvan
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Biophysics Program, The Ohio State University, Columbus, OH 43210, USA
| | - Harper E Smith
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Biophysics Program, The Ohio State University, Columbus, OH 43210, USA
| | - Julia Halford
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Chen Shen
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Swetha E Murthy
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Maximilian H Ulbrich
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany; Internal Medicine IV, University of Freiburg Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marcos Sotomayor
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Biophysics Program, The Ohio State University, Columbus, OH 43210, USA
| | - Tian-Min Fu
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USA.
| | - Jeffrey R Holt
- Departments of Otolaryngology & Neurology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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Filep JG. Two to tango: endothelial cell TMEM16 scramblases drive coagulation and thrombosis. J Clin Invest 2023; 133:170643. [PMID: 37259922 DOI: 10.1172/jci170643] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023] Open
Abstract
Endothelial cells form a constitutively anticoagulant surface under homeostasis. While loss of this anticoagulant property is a hallmark of many cardiovascular diseases, the molecular mechanisms underlying the procoagulant transition remain incompletely understood. In this issue of the JCI, Schmaier et al. identify the phospholipid scramblases TMEM16E and TMEM16F, which support endothelial procoagulant activity through phosphatidylserine (PS) externalization. Genetic deletion of TMEM16E or TMEM16F or treatment with TMEM16 inhibitors prevented PS externalization and reduced fibrin formation in the vessel wall independently of platelets in a murine laser-injury model of thrombosis. These findings reveal a role for endothelial TMEM16E in thrombosis and identify TMEM16E as a potential therapeutic target for preventing thrombus formation.
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Affiliation(s)
- János G Filep
- Department of Pathology and Cell Biology, University of Montreal, Montreal, Quebec, Canada
- Research Center, Maisonneuve-Rosemont Hospital, Montreal, Quebec, Canada
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7
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Li RC, Molday LL, Lin CC, Ren X, Fleischmann A, Molday RS, Yau KW. Low signaling efficiency from receptor to effector in olfactory transduction: A quantified ligand-triggered GPCR pathway. Proc Natl Acad Sci U S A 2022; 119:e2121225119. [PMID: 35914143 PMCID: PMC9371729 DOI: 10.1073/pnas.2121225119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 07/11/2022] [Indexed: 02/03/2023] Open
Abstract
G protein-coupled receptor (GPCR) signaling is ubiquitous. As an archetype of this signaling motif, rod phototransduction has provided many fundamental, quantitative details, including a dogma that one active GPCR molecule activates a substantial number of downstream G protein/enzyme effector complexes. However, rod phototransduction is light-activated, whereas GPCR pathways are predominantly ligand-activated. Here, we report a detailed study of the ligand-triggered GPCR pathway in mammalian olfactory transduction, finding that an odorant-receptor molecule when (one-time) complexed with its most effective odorants produces on average much less than one downstream effector. Further experiments gave a nominal success probability of tentatively ∼10-4 (more conservatively, ∼10-2 to ∼10-5). This picture is potentially more generally representative of GPCR signaling than is rod phototransduction, constituting a paradigm shift.
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Affiliation(s)
- Rong-Chang Li
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Laurie L. Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Chih-Chun Lin
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Neuroscience Graduate Program, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Xiaozhi Ren
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | | | - Robert S. Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - King-Wai Yau
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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8
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Tembo M, Bainbridge RE, Lara-Santos C, Komondor KM, Daskivich GJ, Durrant JD, Rosenbaum JC, Carlson AE. Phosphate position is key in mediating transmembrane ion channel TMEM16A-phosphatidylinositol 4,5-bisphosphate interaction. J Biol Chem 2022; 298:102264. [PMID: 35843309 PMCID: PMC9396059 DOI: 10.1016/j.jbc.2022.102264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 07/10/2022] [Accepted: 07/11/2022] [Indexed: 02/07/2023] Open
Abstract
TransMEMbrane 16A (TMEM16A) is a Ca2+-activated Cl- channel that plays critical roles in regulating diverse physiologic processes, including vascular tone, sensory signal transduction, and mucosal secretion. In addition to Ca2+, TMEM16A activation requires the membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). However, the structural determinants mediating this interaction are not clear. Here, we interrogated the parts of the PI(4,5)P2 head group that mediate its interaction with TMEM16A by using patch- and two-electrode voltage-clamp recordings on oocytes from the African clawed frog Xenopus laevis, which endogenously express TMEM16A channels. During continuous application of Ca2+ to excised inside-out patches, we found that TMEM16A-conducted currents decayed shortly after patch excision. Following this rundown, we show that the application of a synthetic PI(4,5)P2 analog produced current recovery. Furthermore, inducible dephosphorylation of PI(4,5)P2 reduces TMEM16A-conducted currents. Application of PIP2 analogs with different phosphate orientations yielded distinct amounts of current recovery, and only lipids that include a phosphate at the 4' position effectively recovered TMEM16A currents. Taken together, these findings improve our understanding of how PI(4,5)P2 binds to and potentiates TMEM16A channels.
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Affiliation(s)
- Maiwase Tembo
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Rachel E Bainbridge
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Crystal Lara-Santos
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Kayla M Komondor
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Grant J Daskivich
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jacob D Durrant
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Joel C Rosenbaum
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Anne E Carlson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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9
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Herta T, Kersten R, Chang JC, Hubers L, Go S, Tolenaars D, Paulusma CC, Nathanson MH, Elferink RO, van de Graaf SFJ, Beuers U. Role of the IgG4-related cholangitis autoantigen annexin A11 in cholangiocyte protection. J Hepatol 2022; 76:319-331. [PMID: 34718050 PMCID: PMC10804347 DOI: 10.1016/j.jhep.2021.10.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 09/20/2021] [Accepted: 10/11/2021] [Indexed: 01/01/2023]
Abstract
BACKGROUND & AIMS Annexin A11 was identified as autoantigen in IgG4-related cholangitis (IRC), a B-cell driven disease. Annexin A11 modulates calcium-dependent exocytosis, a crucial mechanism for insertion of proteins into their target membranes. Human cholangiocytes form an apical 'biliary bicarbonate umbrella' regarded as defense against harmful hydrophobic bile acid influx. The bicarbonate secretory machinery comprises the chloride/bicarbonate exchanger AE2 and the chloride channel ANO1. We aimed to investigate the expression and function of annexin A11 in human cholangiocytes and a potential role of IgG1/IgG4-mediated autoreactivity against annexin A11 in the pathogenesis of IRC. METHODS Expression of annexin A11 in human liver was studied by immunohistochemistry and immunofluorescence. In human control and ANXA11 knockdown H69 cholangiocytes, intracellular pH, AE2 and ANO1 surface expression, and bile acid influx were examined using ratio microspectrofluorometry, cell surface biotinylation, and 22,23-3H-glycochenodeoxycholic acid permeation, respectively. The localization of annexin A11-mEmerald and ANO1-mCherry was investigated by live-cell microscopy in H69 cholangiocytes after incubation with IRC patient serum containing anti-annexin A11 IgG1/IgG4-autoantibodies or disease control serum. RESULTS Annexin A11 was strongly expressed in human cholangiocytes, but not hepatocytes. Knockdown of ANXA11 led to reduced plasma membrane expression of ANO1, but not AE2, alkalization of intracellular pH and uncontrolled bile acid influx. High intracellular calcium conditions led to annexin A11 membrane shift and colocalization with ANO1. Incubation with IRC patient serum inhibited annexin A11 membrane shift and reduced ANO1 surface expression. CONCLUSION Cholangiocellular annexin A11 mediates apical membrane abundance of the chloride channel ANO1, thereby supporting biliary bicarbonate secretion. Insertion is inhibited by IRC patient serum containing anti-annexin A11 IgG1/IgG4-autoantibodies. Anti-annexin A11 autoantibodies may contribute to the pathogenesis of IRC by weakening the 'biliary bicarbonate umbrella'. LAY SUMMARY We previously identified annexin A11 as a specific autoantigen in immunoglobulin G4-related cholangitis (IRC), a B-cell driven disease affecting the bile ducts. Human cholangiocytes are protected against harmful hydrophobic bile acid influx by a defense mechanism referred to as the 'biliary bicarbonate umbrella'. We found that annexin A11 is required for the formation of a robust bicarbonate umbrella. Binding of patient-derived annexin A11 autoantibodies inhibits annexin A11 function, possibly contributing to bile duct damage by weakening the biliary bicarbonate umbrella in patients with IRC.
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Affiliation(s)
- Toni Herta
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Remco Kersten
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands; Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, USA
| | - Jung-Chin Chang
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Lowiek Hubers
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Simei Go
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Dagmar Tolenaars
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Coen C Paulusma
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Michael H Nathanson
- Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, USA
| | - Ronald Oude Elferink
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Stan F J van de Graaf
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands
| | - Ulrich Beuers
- Department of Gastroenterology and Hepatology and Tytgat Institute for Liver and Intestinal Research, AGEM, Amsterdam University Medical Centers, location AMC, Amsterdam, The Netherlands.
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10
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Differential Regulation of Ca 2+-Activated Cl - Channel TMEM16A Splice Variants by Membrane PI(4,5)P 2. Int J Mol Sci 2021; 22:ijms22084088. [PMID: 33920953 PMCID: PMC8071329 DOI: 10.3390/ijms22084088] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/08/2021] [Accepted: 04/13/2021] [Indexed: 12/24/2022] Open
Abstract
TMEM16A is a Ca2+-activated Cl− channel that controls broad cellular processes ranging from mucus secretion to signal transduction and neuronal excitability. Recent studies have reported that membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is an important cofactor that allosterically regulates TMEM16A channel activity. However, the detailed regulatory actions of PIP2 in splice variants of TMEM16A remain unclear. Here, we demonstrated that the attenuation of membrane phosphoinositide levels selectively inhibited the current amplitude of the TMEM16A(ac) isoform by decreasing the slow, but not instantaneous, Cl− currents, which are independent of the membrane potential and specific to PI(4,5)P2 depletion. The attenuation of endogenous PI(4,5)P2 levels by the activation of Danio rerio voltage-sensitive phosphatase (Dr-VSP) decreased the Cl− currents of TMEM16A(ac) but not the TMEM16A(a) isoform, which was abolished by the co-expression of PIP 5-kinase type-1γ (PIPKIγ). Using the rapamycin-inducible dimerization of exogenous phosphoinositide phosphatases, we further revealed that the stimulatory effects of phosphoinositide on TMEM16A(ac) channels were similar in various membrane potentials and specific to PI(4,5)P2, not PI4P and PI(3,4,5)P3. Finally, we also confirmed that PI(4,5)P2 resynthesis is essential for TMEM16A(ac) recovery from Dr-VSP-induced current inhibition. Our data demonstrate that membrane PI(4,5)P2 selectively modulates the gating of the TMEM16A(ac) channel in an agonistic manner, which leads to the upregulation of TMEM16A(ac) functions in physiological conditions.
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11
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The Groovy TMEM16 Family: Molecular Mechanisms of Lipid Scrambling and Ion Conduction. J Mol Biol 2021; 433:166941. [PMID: 33741412 DOI: 10.1016/j.jmb.2021.166941] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/09/2021] [Accepted: 03/09/2021] [Indexed: 12/28/2022]
Abstract
The TMEM16 family of membrane proteins displays a remarkable functional dichotomy - while some family members function as Ca2+-activated anion channels, the majority of characterized TMEM16 homologs are Ca2+-activated lipid scramblases, which catalyze the exchange of phospholipids between the two membrane leaflets. Furthermore, some TMEM16 scramblases can also function as channels. Due to their involvement in important physiological processes, the family has been actively studied ever since their molecular identity was unraveled. In this review, we will summarize the recent advances in the field and how they influenced our view of TMEM16 family function and evolution. Structural, functional and computational studies reveal how relatively small rearrangements in the permeation pathway are responsible for the observed functional duality: while TMEM16 scramblases can adopt both ion- and lipid conductive conformations, TMEM16 channels can only populate the former. Recent data further provides the molecular details of a stepwise activation mechanism, which is initiated by Ca2+ binding and modulated by various cellular factors, including lipids. TMEM16 function and the surrounding membrane properties are inextricably intertwined, with the protein inducing bilayer deformations associated with scrambling, while the surrounding lipids modulate TMEM16 conformation and activity.
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12
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Le SC, Yang H. Structure-Function of TMEM16 Ion Channels and Lipid Scramblases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:87-109. [PMID: 35138612 PMCID: PMC11020148 DOI: 10.1007/978-981-16-4254-8_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The TMEM16 protein family comprises two novel classes of structurally conserved but functionally distinct membrane transporters that function as Ca2+-dependent Cl- channels (CaCCs) or dual functional Ca2+-dependent ion channels and phospholipid scramblases. Extensive functional and structural studies have advanced our understanding of TMEM16 molecular mechanisms and physiological functions. TMEM16A and TMEM16B CaCCs control transepithelial fluid transport, smooth muscle contraction, and neuronal excitability, whereas TMEM16 phospholipid scramblases mediate the flip-flop of phospholipids across the membrane to allow phosphatidylserine externalization, which is essential in a plethora of important processes such as blood coagulation, bone development, and viral and cell fusion. In this chapter, we summarize the major methods in studying TMEM16 ion channels and scramblases and then focus on the current mechanistic understanding of TMEM16 Ca2+- and voltage-dependent channel gating as well as their ion and phospholipid permeation.
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Affiliation(s)
- Son C Le
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, USA
| | - Huanghe Yang
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, USA.
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13
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Liu CZ, Li FY, Lv XF, Ma MM, Li XY, Lin CX, Wang GL, Guan YY. Endophilin A2 regulates calcium-activated chloride channel activity via selective autophagy-mediated TMEM16A degradation. Acta Pharmacol Sin 2020; 41:208-217. [PMID: 31484993 PMCID: PMC7470808 DOI: 10.1038/s41401-019-0298-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Accepted: 08/06/2019] [Indexed: 02/05/2023] Open
Abstract
TMEM16A Ca2+-activated chloride channel (CaCC) plays an essential role in vascular homeostasis. In this study we investigated the molecular mechanisms underlying downregulation of TMEM16A CaCC activity during hypertension. In cultured basilar artery smooth muscle cells (BASMCs) isolated from 2k2c renohypertesive rats, treatment with angiotensin II (0.125-1 μM) dose-dependently increased endophilin A2 levels and decreased TMEM16A expression. Similar phenomenon was observed in basilar artery isolated from 2k2c rats. We then used whole-cell recording to examine whether endophilin A2 could regulate TMEM16A CaCC activity in BASMCs and found that knockdown of endophilin A2 significantly enhanced CaCC activity, whereas overexpression of endophilin A2 produced the opposite effect. Overexpression of endophilin A2 did not affect the TMEM16A mRNA level, but markedly decreased TMEM16A protein level in BASMCs by inducing ubiquitination and autophagy of TMEM16A. Ubiquitin-binding receptor p62 (SQSTM1) could bind to ubiquitinated TMEM16A and resulted in a process of TMEM16A proteolysis in autophagosome/lysosome. These data provide new insights into the regulation of TMEM16A CaCC activity by endophilin A2 in BASMCs, which partly explains the mechanism of angiotensin-II-induced TMEM16A inhibition during hypertension-induced vascular remodeling.
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Affiliation(s)
- Can-Zhao Liu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China.
| | - Fei-Ya Li
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
- Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Xiao-Fei Lv
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Ming-Ming Ma
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Xiang-Yu Li
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Cai-Xia Lin
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Guan-Lei Wang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Yong-Yuan Guan
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China.
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14
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Nguyen DM, Chen LS, Yu WP, Chen TY. Comparison of ion transport determinants between a TMEM16 chloride channel and phospholipid scramblase. J Gen Physiol 2019; 151:518-531. [PMID: 30670476 PMCID: PMC6445582 DOI: 10.1085/jgp.201812270] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 01/02/2019] [Indexed: 01/03/2023] Open
Abstract
The I-V relation of the TMEM16A channel is linear, whereas that of the TMEM16F scramblase is outwardly rectifying. Nguyen et al. show that rectification of TMEM16A is regulated by the charge of residue 584 but that rectification of TMEM16F is affected by aromatic residues at the equivalent position. Two TMEM16 family members, TMEM16A and TMEM16F, have different ion transport properties. Upon activation by intracellular Ca2+, TMEM16A—a Ca2+-activated Cl− channel—is more selective for anions than cations, whereas TMEM16F—a phospholipid scramblase—appears to transport both cations and anions. Under saturating Ca2+ conditions, the current–voltage (I-V) relationships of these two proteins also differ; the I-V curve of TMEM16A is linear, while that of TMEM16F is outwardly rectifying. We previously found that mutating a positively charged lysine residue (K584) in the ion transport pathway to glutamine converted the linear I-V curve of TMEM16A to an outwardly rectifying curve. Interestingly, the corresponding residue in the outwardly rectifying TMEM16F is also a glutamine (Q559). Here, we examine the ion transport functions of TMEM16 molecules and compare the roles of K584 of TMEM16A and Q559 of TMEM16F in controlling the rectification of their respective I-V curves. We find that rectification of TMEM16A is regulated electrostatically by the side-chain charge on the residue at position 584, whereas the charge on residue 559 in TMEM16F has little effect. Unexpectedly, mutation of Q559 to aromatic amino acid residues significantly alters outward rectification in TMEM16F. These same mutants show reduced Ca2+-induced current rundown (or desensitization) compared with wild-type TMEM16F. A mutant that removes the rundown of TMEM16F could facilitate the study of ion transport mechanisms in this phospholipid scramblase in the same way that a CLC-0 mutant in which inactivation (or closure of the slow gate) is suppressed was used in our previous studies.
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Affiliation(s)
- Dung M Nguyen
- Graduate Group of Pharmacology and Toxicology, University of California, Davis, Davis, CA
| | - Louisa S Chen
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Wei-Ping Yu
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Tsung-Yu Chen
- Center for Neuroscience, University of California, Davis, Davis, CA .,Department of Neurology, University of California, Davis, Davis, CA
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15
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Choi J, Jang Y, Kim H, Wee J, Cho S, Son WS, Kim SM, Yang YD. Functional roles of glutamic acid E143 and E705 residues in the N-terminus and transmembrane domain 7 of Anoctamin 1 in calcium and noxious heat sensing. BMB Rep 2018; 51:236-241. [PMID: 29335069 PMCID: PMC5988578 DOI: 10.5483/bmbrep.2018.51.5.199] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Indexed: 01/12/2023] Open
Abstract
Anoctamin 1 (ANO1) is an anion channel that is activated by changes in cytosolic Ca2+ concentration and noxious heat. Although the critical roles of ANO1 have been elucidated in various cell types, the control of its gating mechanisms by Ca2+ and heat remain more elusive. To investigate critical amino acid residues for modulation of Ca2+ and heat sensing, we constructed a randomized mutant library for ANO1. Among 695 random mutants, reduced Ca2+ sensitivity was observed in two mutants (mutant 84 and 87). Consequently, the E143A mutant showed reduced sensitivity to Ca2+ but not to high temperatures, whereas the E705V mutant exhibited reduced sensitivity to both Ca2+ and noxious heat. These results suggest that the glutamic acids (E) at 143 and 705 residues in ANO1 are critical for modulation of Ca2+ and/or heat responses. Furthermore, these findings help to provide a better understanding of the Ca2+-mediated activation and heat-sensing mechanism of ANO1.
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Affiliation(s)
- Jonghyun Choi
- College of Pharmacy, CHA University, Sungnam 13488, Korea
| | - Yongwoo Jang
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
| | - Haedong Kim
- College of Pharmacy, CHA University, Sungnam 13488, Korea
| | - Jungwon Wee
- Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Korea
| | - Sinyoung Cho
- College of Pharmacy, CHA University, Sungnam 13488, Korea
| | - Woo Sung Son
- College of Pharmacy, CHA University, Sungnam 13488, Korea
| | - Sung Min Kim
- Department of Physical Education, College of Performing Arts and Sport, Hanyang University, Seoul 04763; Department of Active Aging Industry, Graduate School, Hanyang University, Seoul 04763, Korea
| | - Young Duk Yang
- College of Pharmacy, CHA University, Sungnam 13488, Korea
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16
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Falzone ME, Malvezzi M, Lee BC, Accardi A. Known structures and unknown mechanisms of TMEM16 scramblases and channels. J Gen Physiol 2018; 150:933-947. [PMID: 29915161 PMCID: PMC6028493 DOI: 10.1085/jgp.201711957] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 05/29/2018] [Indexed: 12/25/2022] Open
Abstract
Falzone et al. interpret the mechanisms underlying the activity of TMEM16 family members from recent structural and functional work. The TMEM16 family of membrane proteins is composed of both Ca2+-gated Cl− channels and Ca2+-dependent phospholipid scramblases. The functional diversity of TMEM16s underlies their involvement in numerous signal transduction pathways that connect changes in cytosolic Ca2+ levels to cellular signaling networks. Indeed, defects in the function of several TMEM16s cause a variety of genetic disorders, highlighting their fundamental pathophysiological importance. Here, we review how our mechanistic understanding of TMEM16 function has been shaped by recent functional and structural work. Remarkably, the recent determination of near-atomic-resolution structures of TMEM16 proteins of both functional persuasions has revealed how relatively minimal rearrangements in the substrate translocation pathway are sufficient to precipitate the dramatic functional differences that characterize the family. These structures, when interpreted in the light of extensive functional analysis, point to an unusual mechanism for Ca2+-dependent activation of TMEM16 proteins in which substrate permeation is regulated by a combination of conformational rearrangements and electrostatics. These breakthroughs pave the way to elucidate the mechanistic bases of ion and lipid transport by the TMEM16 proteins and unravel the molecular links between these transport activities and their function in human pathophysiology.
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Affiliation(s)
- Maria E Falzone
- Department of Biochemistry, Weill Cornell Medical School, New York, NY
| | - Mattia Malvezzi
- Department of Anesthesiology, Weill Cornell Medical School, New York, NY
| | - Byoung-Cheol Lee
- Department of Anesthesiology, Weill Cornell Medical School, New York, NY
| | - Alessio Accardi
- Department of Biochemistry, Weill Cornell Medical School, New York, NY .,Department of Anesthesiology, Weill Cornell Medical School, New York, NY.,Department of Physiology, Biophysics and Systems Biology, Weill Cornell Medical School, New York, NY
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17
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Rottgen TS, Nickerson AJ, Rajendran VM. Calcium-Activated Cl - Channel: Insights on the Molecular Identity in Epithelial Tissues. Int J Mol Sci 2018; 19:E1432. [PMID: 29748496 PMCID: PMC5983713 DOI: 10.3390/ijms19051432] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/07/2018] [Accepted: 05/08/2018] [Indexed: 12/25/2022] Open
Abstract
Calcium-activated chloride secretion in epithelial tissues has been described for many years. However, the molecular identity of the channel responsible for the Ca2+-activated Cl− secretion in epithelial tissues has remained a mystery. More recently, TMEM16A has been identified as a new putative Ca2+-activated Cl− channel (CaCC). The primary goal of this article will be to review the characterization of TMEM16A, as it relates to the physical structure of the channel, as well as important residues that confer voltage and Ca2+-sensitivity of the channel. This review will also discuss the role of TMEM16A in epithelial physiology and potential associated-pathophysiology. This will include discussion of developed knockout models that have provided much needed insight on the functional localization of TMEM16A in several epithelial tissues. Finally, this review will examine the implications of the identification of TMEM16A as it pertains to potential novel therapies in several pathologies.
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Affiliation(s)
- Trey S Rottgen
- Department of Physiology, Pharmacology, and Neuroscience, West Virginia University School of Medicine, Morgantown, WV 26506, USA.
- Department of Biochemistry and Molecular Pharmacology, West Virginia University School of Medicine, Morgantown, WV 26506, USA.
| | - Andrew J Nickerson
- Department of Physiology, Pharmacology, and Neuroscience, West Virginia University School of Medicine, Morgantown, WV 26506, USA.
- Department of Biochemistry and Molecular Pharmacology, West Virginia University School of Medicine, Morgantown, WV 26506, USA.
| | - Vazhaikkurichi M Rajendran
- Department of Physiology, Pharmacology, and Neuroscience, West Virginia University School of Medicine, Morgantown, WV 26506, USA.
- Department of Biochemistry and Molecular Pharmacology, West Virginia University School of Medicine, Morgantown, WV 26506, USA.
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18
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Peters CJ, Gilchrist JM, Tien J, Bethel NP, Qi L, Chen T, Wang L, Jan YN, Grabe M, Jan LY. The Sixth Transmembrane Segment Is a Major Gating Component of the TMEM16A Calcium-Activated Chloride Channel. Neuron 2018; 97:1063-1077.e4. [PMID: 29478917 DOI: 10.1016/j.neuron.2018.01.048] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 12/03/2017] [Accepted: 01/26/2018] [Indexed: 11/29/2022]
Abstract
Calcium-activated chloride channels (CaCCs) formed by TMEM16A or TMEM16B are broadly expressed in the nervous system, smooth muscles, exocrine glands, and other tissues. With two calcium-binding sites and a pore within each monomer, the dimeric CaCC exhibits voltage-dependent calcium sensitivity. Channel activity also depends on the identity of permeant anions. To understand how CaCC regulates neuronal signaling and how CaCC is, in turn, modulated by neuronal activity, we examined the molecular basis of CaCC gating. Here, we report that voltage modulation of TMEM16A-CaCC involves voltage-dependent occupancy of calcium- and anion-binding site(s) within the membrane electric field as well as a voltage-dependent conformational change intrinsic to the channel protein. These gating modalities all critically depend on the sixth transmembrane segment.
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Affiliation(s)
- Christian J Peters
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - John M Gilchrist
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jason Tien
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Neville P Bethel
- Department of Pharmaceutical Chemistry and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Lijun Qi
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Tingxu Chen
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Lynn Wang
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Yuh Nung Jan
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Michael Grabe
- Department of Pharmaceutical Chemistry and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Lily Y Jan
- Departments of Physiology, Biophysics and Biochemistry, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA.
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19
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Affiliation(s)
- H Criss Hartzell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
| | - Jarred M Whitlock
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
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20
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Yamamura H, Nishimura K, Hagihara Y, Suzuki Y, Imaizumi Y. TMEM16A and TMEM16B channel proteins generate Ca 2+-activated Cl - current and regulate melatonin secretion in rat pineal glands. J Biol Chem 2017; 293:995-1006. [PMID: 29187602 DOI: 10.1074/jbc.ra117.000326] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 11/28/2017] [Indexed: 11/06/2022] Open
Abstract
Pinealocytes regulate circadian rhythm by synthesizing and secreting melatonin. These cells generate action potentials; however, the contribution of specific ion channels to melatonin secretion from pinealocytes remains unclear. In this study, the involvement and molecular identity of Ca2+-activated Cl- (ClCa) channels in the regulation of melatonin secretion were examined in rat pineal glands. Treatment with the ClCa channel blockers, niflumic acid or T16Ainh-A01, significantly reduced melatonin secretion in pineal glands. After pineal K+ currents were totally blocked under whole-cell patch clamp conditions, depolarization and subsequent repolarization induced a slowly activating outward current and a substantial inward tail current, respectively. Both of these current changes were dependent on intracellular Ca2+ concentration and inhibited by niflumic acid and T16Ainh-A01. Quantitative real-time PCR, Western blotting, and immunocytochemical analyses revealed that TMEM16A and TMEM16B were highly expressed in pineal glands. siRNA knockdown of TMEM16A and/or TMEM16B showed that both channels contribute to ClCa currents in pinealocytes. Conversely, co-expression of TMEM16A and TMEM16B channels or the expression of this tandem channel in HEK293 cells mimicked the electrophysiological characteristics of ClCa currents in pinealocytes. Moreover, bimolecular fluorescence complementation, FRET, and co-immunoprecipitation experiments suggested that TMEM16A and TMEM16B can form heteromeric channels, as well as homomeric channels. In conclusion, pineal ClCa channels are composed of TMEM16A and TMEM16B subunits, and these fluxes regulate melatonin secretion in pineal glands.
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Affiliation(s)
- Hisao Yamamura
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Kaori Nishimura
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Yumiko Hagihara
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Yoshiaki Suzuki
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Yuji Imaizumi
- From the Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
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21
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Wang L, Wang K. Highlights for the 6th International Ion Channel Conference: ion channel structure, function, disease and therapeutics. Acta Pharm Sin B 2017; 7:665-669. [PMID: 29159026 PMCID: PMC5687311 DOI: 10.1016/j.apsb.2017.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 08/15/2017] [Indexed: 11/17/2022] Open
Abstract
To foster communication and interactions amongst international scholars and scientists in the field of ion channel research, the 6th International Ion Channel Conference (IICC-2017) was held between June 23–27, 2017 in the eastern coastal city of Qingdao, China. The meeting consisted of 450 attendees and 130 speakers and poster presenters. The program consisted of research progress, new findings and ongoing studies that were focused on (1) Ion channel structure and function; (2) Ion channel physiology and human diseases; (3) Ion channels as targets for drug discovery; (4) Technological advances in ion channel research. An insightful overview was presented on the structure and function of the mechanotransduction channel Drosophila NOMPC (No mechanoreceptor potential C), a member of the transient receptor potential (TRP) channel family. Recent studies on Transmembrane protein 16 or Anoctamin-1 (TMEM16A, a member of the calcium-activated chloride channel [CaCC] family) were summarized as well. In addition, topics for ion channel regulation, homeostatic feedback and brain disorders were thoroughly discussed. The presentations at the IICC-2017 offer new insights into our understanding of ion channel structures and functions, and ion channels as targets for drug discovery.
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22
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Truong EC, Phuan PW, Reggi AL, Ferrera L, Galietta LJ, Levy SE, Moises AC, Cil O, Diez-Cecilia E, Lee S, Verkman AS, Anderson MO. Substituted 2-Acylaminocycloalkylthiophene-3-carboxylic Acid Arylamides as Inhibitors of the Calcium-Activated Chloride Channel Transmembrane Protein 16A (TMEM16A). J Med Chem 2017; 60:4626-4635. [PMID: 28493701 PMCID: PMC5516794 DOI: 10.1021/acs.jmedchem.7b00020] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Transmembrane protein 16A (TMEM16A), also called anoctamin 1 (ANO1), is a calcium-activated chloride channel expressed widely mammalian cells, including epithelia, vascular smooth muscle tissue, electrically excitable cells, and some tumors. TMEM16A inhibitors have been proposed for treatment of disorders of epithelial fluid and mucus secretion, hypertension, asthma, and possibly cancer. Herein we report, by screening, the discovery of 2-acylaminocycloalkylthiophene-3-carboxylic acid arylamides (AACTs) as inhibitors of TMEM16A and analysis of 48 synthesized analogs (10ab-10bw) of the original AACT compound (10aa). Structure-activity studies indicated the importance of benzene substituted as 2- or 4-methyl, or 4-fluoro, and defined the significance of thiophene substituents and size of the cycloalkylthiophene core. The most potent compound (10bm), which contains an unusual bromodifluoroacetamide at the thiophene 2-position, had IC50 of ∼30 nM, ∼3.6-fold more potent than the most potent previously reported TMEM16A inhibitor 4 (Ani9), and >10-fold improved metabolic stability. Direct and reversible inhibition of TMEM16A by 10bm was demonstrated by patch-clamp analysis. AACTs may be useful as pharmacological tools to study TMEM16A function and as potential drug development candidates.
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Affiliation(s)
- Eric C. Truong
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco CA, 94132-4136 USA
| | - Puay W. Phuan
- Departments of Medicine and Physiology, University of California, San Francisco CA, 94143-0521 USA
| | - Amanda L. Reggi
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco CA, 94132-4136 USA
| | - Loretta Ferrera
- U.O.C. Genetica Medica, Istituto Giannina Gaslini, Genova, ITALY
| | - Luis J.V. Galietta
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli (NA), ITALY
| | - Sarah E. Levy
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco CA, 94132-4136 USA
| | - Alannah C. Moises
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco CA, 94132-4136 USA
| | - Onur Cil
- Departments of Medicine and Physiology, University of California, San Francisco CA, 94143-0521 USA
| | - Elena Diez-Cecilia
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco CA, 94132-4136 USA
| | - Sujin Lee
- Departments of Medicine and Physiology, University of California, San Francisco CA, 94143-0521 USA
| | - Alan S. Verkman
- Departments of Medicine and Physiology, University of California, San Francisco CA, 94143-0521 USA
| | - Marc O. Anderson
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco CA, 94132-4136 USA
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23
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Paulino C, Neldner Y, Lam AKM, Kalienkova V, Brunner JD, Schenck S, Dutzler R. Structural basis for anion conduction in the calcium-activated chloride channel TMEM16A. eLife 2017; 6:e26232. [PMID: 28561733 PMCID: PMC5470873 DOI: 10.7554/elife.26232] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 04/11/2017] [Indexed: 12/11/2022] Open
Abstract
The calcium-activated chloride channel TMEM16A is a member of a conserved protein family that comprises ion channels and lipid scramblases. Although the structure of the scramblase nhTMEM16 has defined the architecture of the family, it was unknown how a channel has adapted to cope with its distinct functional properties. Here we have addressed this question by the structure determination of mouse TMEM16A by cryo-electron microscopy and a complementary functional characterization. The protein shows a similar organization to nhTMEM16, except for changes at the site of catalysis. There, the conformation of transmembrane helices constituting a membrane-spanning furrow that provides a path for lipids in scramblases has changed to form an enclosed aqueous pore that is largely shielded from the membrane. Our study thus reveals the structural basis of anion conduction in a TMEM16 channel and it defines the foundation for the diverse functional behavior in the TMEM16 family.
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Affiliation(s)
- Cristina Paulino
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Yvonne Neldner
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Andy KM Lam
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | | | | | - Stephan Schenck
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Raimund Dutzler
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
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24
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Peckys DB, Stoerger C, Latta L, Wissenbach U, Flockerzi V, de Jonge N. The stoichiometry of the TMEM16A ion channel determined in intact plasma membranes of COS-7 cells using liquid-phase electron microscopy. J Struct Biol 2017; 199:102-113. [PMID: 28559167 DOI: 10.1016/j.jsb.2017.05.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 05/24/2017] [Accepted: 05/25/2017] [Indexed: 11/29/2022]
Abstract
TMEM16A is a membrane protein forming a calcium-activated chloride channel. A homodimeric stoichiometry of the TMEM16 family of proteins has been reported but an important question is whether the protein resides always in a dimeric configuration in the plasma membrane or whether monomers of the protein are also present in its native state within in the intact plasma membrane. We have determined the stoichiometry of the human (h)TMEM16A within whole COS-7 cells in liquid. For the purpose of detecting TMEM16A subunits, single proteins were tagged by the streptavidin-binding peptide within extracellular loops accessible by streptavidin coated quantum dot (QD) nanoparticles. The labeled proteins were then imaged using correlative light microscopy and environmental scanning electron microscopy (ESEM) using scanning transmission electron microscopy (STEM) detection. The locations of 19,583 individual proteins were determined of which a statistical analysis using the pair correlation function revealed the presence of a dimeric conformation of the protein. The amounts of detected label pairs and single labels were compared between experiments in which the TMEM16A SBP-tag position was varied, and experiments in which tagged and non-tagged TMEM16A proteins were present. It followed that hTMEM16A resides in the plasma membrane as dimer only and is not present as monomer. This strategy may help to elucidate the stoichiometry of other membrane protein species within the context of the intact plasma membrane in future.
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Affiliation(s)
- Diana B Peckys
- Department of Biophysics, Saarland University, 66421 Homburg, Germany
| | - Christof Stoerger
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, 66421 Homburg, Germany
| | - Lorenz Latta
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, 66421 Homburg, Germany
| | - Ulrich Wissenbach
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, 66421 Homburg, Germany
| | - Veit Flockerzi
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, 66421 Homburg, Germany
| | - Niels de Jonge
- INM - Leibniz Institute for New Materials, Saarland University, 66123 Saarbrücken, Germany; Department of Physics, Saarland University, 66123 Saarbrücken, Germany.
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25
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Kamaleddin MA. Molecular, biophysical, and pharmacological properties of calcium-activated chloride channels. J Cell Physiol 2017; 233:787-798. [PMID: 28121009 DOI: 10.1002/jcp.25823] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 01/24/2017] [Indexed: 12/15/2022]
Abstract
Calcium-activated chloride channels (CaCCs) are a family of anionic transmembrane ion channels. They are mainly responsible for the movement of Cl- and other anions across the biological membranes, and they are widely expressed in different tissues. Since the Cl- flow into or out of the cell plays a crucial role in hyperpolarizing or depolarizing the cells, respectively, the impact of intracellular Ca2+ concentration on these channels is attracting a lot of attentions. After summarizing the molecular, biophysical, and pharmacological properties of CaCCs, the role of CaCCs in normal cellular functions will be discussed, and I will emphasize how dysregulation of CaCCs in pathological conditions can account for different diseases. A better understanding of CaCCs and a pivotal regulatory role of Ca2+ can shed more light on the therapeutic strategies for different neurological disorders that arise from chloride dysregulation, such as asthma, cystic fibrosis, and neuropathic pain.
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Affiliation(s)
- Mohammad Amin Kamaleddin
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.,Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada
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26
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Sala-Rabanal M, Yurtsever Z, Berry KN, Nichols CG, Brett TJ. Modulation of TMEM16A channel activity by the von Willebrand factor type A (VWA) domain of the calcium-activated chloride channel regulator 1 (CLCA1). J Biol Chem 2017; 292:9164-9174. [PMID: 28420732 DOI: 10.1074/jbc.m117.788232] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 04/18/2017] [Indexed: 11/06/2022] Open
Abstract
Calcium-activated chloride channels (CaCCs) are key players in transepithelial ion transport and fluid secretion, smooth muscle constriction, neuronal excitability, and cell proliferation. The CaCC regulator 1 (CLCA1) modulates the activity of the CaCC TMEM16A/Anoctamin 1 (ANO1) by directly engaging the channel at the cell surface, but the exact mechanism is unknown. Here we demonstrate that the von Willebrand factor type A (VWA) domain within the cleaved CLCA1 N-terminal fragment is necessary and sufficient for this interaction. TMEM16A protein levels on the cell surface were increased in HEK293T cells transfected with CLCA1 constructs containing the VWA domain, and TMEM16A-like currents were activated. Similar currents were evoked in cells exposed to secreted VWA domain alone, and these currents were significantly knocked down by TMEM16A siRNA. VWA-dependent TMEM16A modulation was not modified by the S357N mutation, a VWA domain polymorphism associated with more severe meconium ileus in cystic fibrosis patients. VWA-activated currents were significantly reduced in the absence of extracellular Mg2+, and mutation of residues within the conserved metal ion-dependent adhesion site motif impaired the ability of VWA to potentiate TMEM16A activity, suggesting that CLCA1-TMEM16A interactions are Mg2+- and metal ion-dependent adhesion site-dependent. Increase in TMEM16A activity occurred within minutes of exposure to CLCA1 or after a short treatment with nocodazole, consistent with the hypothesis that CLCA1 stabilizes TMEM16A at the cell surface by preventing its internalization. Our study hints at the therapeutic potential of the selective activation of TMEM16A by the CLCA1 VWA domain in loss-of-function chloride channelopathies such as cystic fibrosis.
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Affiliation(s)
- Monica Sala-Rabanal
- From the Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology and Physiology
| | - Zeynep Yurtsever
- Biochemistry Program.,Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine
| | - Kayla N Berry
- Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.,Medical Scientist Training Program, and
| | - Colin G Nichols
- From the Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology and Physiology
| | - Tom J Brett
- From the Center for the Investigation of Membrane Excitability Diseases, .,Department of Cell Biology and Physiology.,Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine.,Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110
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27
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Dibattista M, Pifferi S, Boccaccio A, Menini A, Reisert J. The long tale of the calcium activated Cl - channels in olfactory transduction. Channels (Austin) 2017; 11:399-414. [PMID: 28301269 DOI: 10.1080/19336950.2017.1307489] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ca2+-activated Cl- currents have been implicated in many cellular processes in different cells, but for many years, their molecular identity remained unknown. Particularly intriguing are Ca2+-activated Cl- currents in olfactory transduction, first described in the early 90s. Well characterized electrophysiologically, they carry most of the odorant-induced receptor current in the cilia of olfactory sensory neurons (OSNs). After many attempts to determine their molecular identity, TMEM16B was found to be abundantly expressed in the cilia of OSNs in 2009 and having biophysical properties like those of the native olfactory channel. A TMEM16B knockout mouse confirmed that TMEM16B was indeed the olfactory Cl- channel but also suggested a limited role in olfactory physiology and behavior. The question then arises of what the precise role of TMEM16b in olfaction is. Here we review the long story of this channel and its possible roles.
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Affiliation(s)
- Michele Dibattista
- a Department of Basic Medical Sciences, Neuroscience and Sensory Organs , University of Bari A. Moro , Bari , Italy
| | - Simone Pifferi
- b Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati , Trieste , Italy
| | | | - Anna Menini
- b Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati , Trieste , Italy
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28
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Pifferi S. Permeation Mechanisms in the TMEM16B Calcium-Activated Chloride Channels. PLoS One 2017; 12:e0169572. [PMID: 28046119 PMCID: PMC5207786 DOI: 10.1371/journal.pone.0169572] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Accepted: 12/18/2016] [Indexed: 12/03/2022] Open
Abstract
TMEM16A and TMEM16B encode for Ca2+-activated Cl− channels (CaCC) and are expressed in many cell types and play a relevant role in many physiological processes. Here, I performed a site-directed mutagenesis study to understand the molecular mechanisms of ion permeation of TMEM16B. I mutated two positive charged residues R573 and K540, respectively located at the entrance and inside the putative channel pore and I measured the properties of wild-type and mutant TMEM16B channels expressed in HEK-293 cells using whole-cell and excised inside-out patch clamp experiments. I found evidence that R573 and K540 control the ion permeability of TMEM16B depending both on which side of the membrane the ion substitution occurs and on the level of channel activation. Moreover, these residues contribute to control blockage or activation by permeant anions. Finally, R573 mutation abolishes the anomalous mole fraction effect observed in the presence of a permeable anion and it alters the apparent Ca2+-sensitivity of the channel. These findings indicate that residues facing the putative channel pore are responsible both for controlling the ion selectivity and the gating of the channel, providing an initial understanding of molecular mechanism of ion permeation in TMEM16B.
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Affiliation(s)
- Simone Pifferi
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy
- * E-mail:
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29
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Banerjee J, Leung CT, Li A, Peterson-Yantorno K, Ouyang H, Stamer WD, Civan MM. Regulatory Roles of Anoctamin-6 in Human Trabecular Meshwork Cells. Invest Ophthalmol Vis Sci 2017; 58:492-501. [PMID: 28125837 PMCID: PMC5283088 DOI: 10.1167/iovs.16-20188] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 12/07/2016] [Indexed: 12/19/2022] Open
Abstract
Purpose Trabecular meshwork (TM) cell volume is a determinant of aqueous humor outflow resistance, and thereby IOP. Regulation of TM cell volume depends on chloride ion (Cl-) release through swelling-activated channels (ICl,Swell), whose pore is formed by LRRC8 proteins. Chloride ion release through swelling-activated channels has been reported to be regulated by calcium-activated anoctamins, but this finding is controversial. Particularly uncertain has been the effect of anoctamin Ano6, reported as a Ca2+-activated Cl- (CaCC) or cation channel in other cells. The current study tested whether anoctamin activity modifies volume regulation of primary TM cell cultures and cell lines. Methods Gene expression was studied with quantitative PCR, supplemented by reverse-transcriptase PCR and Western immunoblots. Currents were measured by ruptured whole-cell patch clamping and volume by electronic cell sizing. Results Primary TM cell cultures and the TM5 and GTM3 cell lines expressed Ano6 3 to 4 orders of magnitude higher than the other anoctamin CaCCs (Ano1 and Ano2). Ionomycin increased cell Ca2+ and activated macroscopic currents conforming to CaCCs in other cells, but displayed significantly more positive mean reversal potentials (+5 to +12 mV) than those displayed by ICl,Swell (-14 to -21 mV) in the same cells. Nonselective CaCC inhibitors (tannic acid>CaCCinh-A01) and transient Ano6 knockdown strongly inhibited ionomycin-activated currents, ICl,Swell and the regulatory volume response to hyposmotic swelling. Conclusions Ionomycin activates CaCCs associated with net cation movement in TM cells. These currents, ICl,Swell, and cell volume are regulated by Ano6. The findings suggest a novel clinically-relevant approach for altering cell volume, and thereby outflow resistance, by targeting Ano6.
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Affiliation(s)
- Juni Banerjee
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - Chi-Ting Leung
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - Ang Li
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States
- Guangdong-Hong Kong - Macau Institute of CNS Regeneration, Guangdong Key Laboratory of Brain Function and Diseases, Jinan University, Guangzhou, China
| | - Kim Peterson-Yantorno
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States
| | - Huan Ouyang
- Guangdong-Hong Kong - Macau Institute of CNS Regeneration, Guangdong Key Laboratory of Brain Function and Diseases, Jinan University, Guangzhou, China
| | - W. Daniel Stamer
- Departments of Ophthalmology and Biomedical Engineering, Duke University, DUMC 3802, Durham, North Carolina, United States
| | - Mortimer M. Civan
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States
- Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States
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30
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Jeng G, Aggarwal M, Yu WP, Chen TY. Independent activation of distinct pores in dimeric TMEM16A channels. J Gen Physiol 2016; 148:393-404. [PMID: 27799319 PMCID: PMC5089935 DOI: 10.1085/jgp.201611651] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 09/30/2016] [Indexed: 01/16/2023] Open
Abstract
The TMEM16 family encompasses Ca2+-activated Cl- channels (CaCCs) and lipid scramblases. These proteins are formed by two identical subunits, as confirmed by the recently solved crystal structure of a TMEM16 lipid scramblase. However, the high-resolution structure did not provide definitive information regarding the pore architecture of the TMEM16 channels. In this study, we express TMEM16A channels constituting two covalently linked subunits with different Ca2+ affinities. The dose-response curve of the heterodimer appears to be a weighted sum of two dose-response curves-one corresponding to the high-affinity subunit and the other to the low-affinity subunit. However, fluorescence resonance energy transfer experiments suggest that the covalently linked heterodimeric proteins fold and assemble as one molecule. Together these results suggest that activation of the two TMEM16A subunits likely activate independently of each other. The Ca2+ activation curve for the heterodimer at a low Ca2+ concentration range ([Ca2+] < 5 µM) is similar to that of the wild-type channel-the Hill coefficients in both cases are significantly greater than one. This suggests that Ca2+ binding to one subunit of TMEM16A is sufficient to activate the channel and that each subunit contains more than one Ca2+-binding site. We also take advantage of the I-V curve rectification that results from mutation of a pore residue to address the pore architecture of the channel. By introducing the pore mutation and the mutation that alters Ca2+ affinity in the same or different subunits, we demonstrate that activation of different subunits appears to be associated with the opening of different pores. These results suggest that the TMEM16A CaCC may also adopt a "double-barrel" pore architecture, similar to that found in CLC channels and transporters.
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Affiliation(s)
- Grace Jeng
- Center for Neuroscience, University of California, Davis, Davis, CA 95618
| | - Muskaan Aggarwal
- Center for Neuroscience, University of California, Davis, Davis, CA 95618
| | - Wei-Ping Yu
- Center for Neuroscience, University of California, Davis, Davis, CA 95618
| | - Tsung-Yu Chen
- Center for Neuroscience, University of California, Davis, Davis, CA 95618 .,Department of Neurology, University of California, Davis, Davis, CA 95618
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31
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Ma K, Wang H, Yu J, Wei M, Xiao Q. New Insights on the Regulation of Ca 2+ -Activated Chloride Channel TMEM16A. J Cell Physiol 2016; 232:707-716. [PMID: 27682822 DOI: 10.1002/jcp.25621] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 09/27/2016] [Indexed: 12/16/2022]
Abstract
TMEM16A, also known as anoctamin 1, is a recently identified Ca2+ -activated chloride channel and the first member of a 10-member TMEM16 family. TMEM16A dysfunction is implicated in many diseases such as cancer, hypertension, and cystic fibrosis. TMEM16A channels are well known to be dually regulated by voltage and Ca2+ . In addition, recent studies have revealed that TMEM16A channels are regulated by many molecules such as calmodulin, protons, cholesterol, and phosphoinositides, and a diverse range of stimuli such as thermal and mechanical stimuli. A better understanding of the regulatory mechanisms of TMEM16A is important to understand its physiological and pathological role. Recently, the crystal structure of a TMEM16 family member from the fungus Nectria haematococcaten (nhTMEM16) is discovered, and provides valuable information for studying the structure and function of TMEM16A. In this review, we discuss the structure and function of TMEM16A channels based on the crystal structure of nhTMEM16A and focus on the regulatory mechanisms of TMEM16A channels. J. Cell. Physiol. 232: 707-716, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Ke Ma
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Hui Wang
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Jiankun Yu
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Minjie Wei
- Department of Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
| | - Qinghuan Xiao
- Department of Ion Channel Pharmacology, School of Pharmacy, China Medical University, Shenyang, P. R. China
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32
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Structural basis for phospholipid scrambling in the TMEM16 family. Curr Opin Struct Biol 2016; 39:61-70. [PMID: 27295354 DOI: 10.1016/j.sbi.2016.05.020] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/28/2016] [Accepted: 05/30/2016] [Indexed: 11/21/2022]
Abstract
Upon activation, lipid scramblases dissipate the lipid asymmetry of membranes, in an ATP-independent manner, by catalyzing flip-flop of lipids between the leaflets. The molecular identities of these proteins long remained obscure, but in recent years the TMEM16 family of proteins has been found to constitute Ca2+-activated scramblases. Recently, the X-ray structure of a fungal TMEM16 homologue has provided insight into the architecture of this protein family and into potential scrambling mechanisms. The protein forms homodimers with each subunit containing a membrane-spanning hydrophilic cleft. This region is of sufficient size to harbor polar headgroups on their way across the membrane and thus may lower the energetic barrier for the diffusion of lipids between the two leaflets of the bilayer. A regulatory Ca2+ binding site located within the membrane adjacent to this hydrophobic cleft is responsible for activation by yet unknown mechanisms.
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33
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Andreeva TV, Tyazhelova TV, Rykalina VN, Gusev FE, Goltsov AY, Zolotareva OI, Aliseichik MP, Borodina TA, Grigorenko AP, Reshetov DA, Ginter EK, Amelina SS, Zinchenko RA, Rogaev EI. Whole exome sequencing links dental tumor to an autosomal-dominant mutation in ANO5 gene associated with gnathodiaphyseal dysplasia and muscle dystrophies. Sci Rep 2016; 6:26440. [PMID: 27216912 PMCID: PMC4877638 DOI: 10.1038/srep26440] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 04/29/2016] [Indexed: 12/19/2022] Open
Abstract
Tumors of the jaws may represent different human disorders and frequently associate with pathologic bone fractures. In this report, we analyzed two affected siblings from a family of Russian origin, with a history of dental tumors of the jaws, in correspondence to original clinical diagnosis of cementoma consistent with gigantiform cementoma (GC, OMIM: 137575). Whole exome sequencing revealed the heterozygous missense mutation c.1067G > A (p.Cys356Tyr) in ANO5 gene in these patients. To date, autosomal-dominant mutations have been described in the ANO5 gene for gnathodiaphyseal dysplasia (GDD, OMIM: 166260), and multiple recessive mutations have been described in the gene for muscle dystrophies (OMIM: 613319, 611307); the same amino acid (Cys) at the position 356 is mutated in GDD. These genetic data and similar clinical phenotypes demonstrate that the GC and GDD likely represent the same type of bone pathology. Our data illustrate the significance of mutations in single amino-acid position for particular bone tissue pathology. Modifying role of genetic variations in another gene on the severity of the monogenic trait pathology is also suggested. Finally, we propose the model explaining the tissue-specific manifestation of clinically distant bone and muscle diseases linked to mutations in one gene.
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Affiliation(s)
- T V Andreeva
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.,Center for Brain Neurobiology and Neurogenetics, Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - T V Tyazhelova
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia
| | - V N Rykalina
- Max-Planck Institute for Molecular Genetics, Berlin 14195, Germany.,Alacris Theranostics GmbH, Berlin 14195, Germany.,Freie Universitaät Berlin, Berlin 14195, Germany
| | - F E Gusev
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.,Center for Brain Neurobiology and Neurogenetics, Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - A Yu Goltsov
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia
| | - O I Zolotareva
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.,Faculty of Bioengineering and Bioinformatics, Center of Genetics and Genetic Technologies, Lomonosov Moscow State University, Moscow 119234, Russia
| | - M P Aliseichik
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia
| | - T A Borodina
- Max-Planck Institute for Molecular Genetics, Berlin 14195, Germany.,Alacris Theranostics GmbH, Berlin 14195, Germany.,Freie Universitaät Berlin, Berlin 14195, Germany
| | - A P Grigorenko
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.,Center for Brain Neurobiology and Neurogenetics, Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia.,Department of Psychiatry, Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01604, USA
| | - D A Reshetov
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia
| | - E K Ginter
- Federal State Budgetary Institution «Research Centre for Medical Genetics», Moscow 115478, Russia
| | - S S Amelina
- The Rostov State Medical University, Rostov-on-Don 344022, Russia
| | - R A Zinchenko
- Federal State Budgetary Institution «Research Centre for Medical Genetics», Moscow 115478, Russia.,Pirogov Russian National Research Medical University, Moscow 117997, Russia
| | - E I Rogaev
- Department of Genomics and Human Genetics, Laboratory of Evolutionary Genomics, Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 119991, Russia.,Center for Brain Neurobiology and Neurogenetics, Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia.,Faculty of Bioengineering and Bioinformatics, Center of Genetics and Genetic Technologies, Lomonosov Moscow State University, Moscow 119234, Russia.,Department of Psychiatry, Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01604, USA
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Lee YS, Lee JK, Bae Y, Lee BS, Kim E, Cho CH, Ryoo K, Yoo J, Kim CH, Yi GS, Lee SG, Lee CJ, Kang SS, Hwang EM, Park JY. Suppression of 14-3-3γ-mediated surface expression of ANO1 inhibits cancer progression of glioblastoma cells. Sci Rep 2016; 6:26413. [PMID: 27212225 PMCID: PMC4876403 DOI: 10.1038/srep26413] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 05/03/2016] [Indexed: 01/03/2023] Open
Abstract
Anoctamin-1 (ANO1) acts as a Ca2+-activated Cl− channel in various normal tissues, and its expression is increased in several different types of cancer. Therefore, understanding the regulation of ANO1 surface expression is important for determining its physiological and pathophysiological functions. However, the trafficking mechanism of ANO1 remains elusive. Here, we report that segment a (N-terminal 116 amino acids) of ANO1 is crucial for its surface expression, and we identified 14-3-3γ as a binding partner for anterograde trafficking using yeast two-hybrid screening. The surface expression of ANO1 was enhanced by 14-3-3γ, and the Thr9 residue of ANO1 was critical for its interaction with 14-3-3γ. Gene silencing of 14-3-3γ and/or ANO1 demonstrated that suppression of ANO1 surface expression inhibited migration and invasion of glioblastoma cells. These findings provide novel therapeutic implications for glioblastomas, which are associated with poor prognosis.
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Affiliation(s)
- Young-Sun Lee
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Republic of Korea.,Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 52727, Republic of Korea.,Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Jae Kwang Lee
- Neuroscience Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Yeonju Bae
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Republic of Korea
| | - Bok-Soon Lee
- Department of Otolaryngology, Ajou University School of Medicine, Suwon 16499, Republic of Korea
| | - Eunju Kim
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Republic of Korea.,Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Chang-Hoon Cho
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Republic of Korea
| | - Kanghyun Ryoo
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Republic of Korea
| | - Jiyun Yoo
- Division of Applied Life Science (BK21 plus), Research Institute of Life Sciences, Gyeongsang National University, Jinju 52828, Korea
| | - Chul-Ho Kim
- Department of Otolaryngology, Ajou University School of Medicine, Suwon 16499, Republic of Korea
| | - Gwan-Su Yi
- Department of Bio and Brain Engineering, KAIST, Daejeon 34141, Republic of Korea
| | - Seok-Geun Lee
- Department of Science in Korean Medicine, College of Korean Medicine, KHU-KIST department of Convergging Science and Technology, Kyung Hee University, Seoul 02447, Republic of Korea
| | - C Justin Lee
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.,Neuroscience Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Sang Soo Kang
- Department of Anatomy and Convergence Medical Science, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 52727, Republic of Korea
| | - Eun Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.,Neuroscience Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Jae-Yong Park
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 02841, Republic of Korea
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Horváth B, Váczi K, Hegyi B, Gönczi M, Dienes B, Kistamás K, Bányász T, Magyar J, Baczkó I, Varró A, Seprényi G, Csernoch L, Nánási PP, Szentandrássy N. Sarcolemmal Ca(2+)-entry through L-type Ca(2+) channels controls the profile of Ca(2+)-activated Cl(-) current in canine ventricular myocytes. J Mol Cell Cardiol 2016; 97:125-39. [PMID: 27189885 DOI: 10.1016/j.yjmcc.2016.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 04/20/2016] [Accepted: 05/10/2016] [Indexed: 12/15/2022]
Abstract
Ca(2+)-activated Cl(-) current (ICl(Ca)) mediated by TMEM16A and/or Bestrophin-3 may contribute to cardiac arrhythmias. The true profile of ICl(Ca) during an actual ventricular action potential (AP), however, is poorly understood. We aimed to study the profile of ICl(Ca) systematically under physiological conditions (normal Ca(2+) cycling and AP voltage-clamp) as well as in conditions designed to change [Ca(2+)]i. The expression of TMEM16A and/or Bestrophin-3 in canine and human left ventricular myocytes was examined. The possible spatial distribution of these proteins and their co-localization with Cav1.2 was also studied. The profile of ICl(Ca), identified as a 9-anthracene carboxylic acid-sensitive current under AP voltage-clamp conditions, contained an early fast outward and a late inward component, overlapping early and terminal repolarizations, respectively. Both components were moderately reduced by ryanodine, while fully abolished by BAPTA, but not EGTA. [Ca(2+)]i was monitored using Fura-2-AM. Setting [Ca(2+)]i to the systolic level measured in the bulk cytoplasm (1.1μM) decreased ICl(Ca), while application of Bay K8644, isoproterenol, and faster stimulation rates increased the amplitude of ICl(Ca). Ca(2+)-entry through L-type Ca(2+) channels was essential for activation of ICl(Ca). TMEM16A and Bestrophin-3 showed strong co-localization with one another and also with Cav1.2 channels, when assessed using immunolabeling and confocal microscopy in both canine myocytes and human ventricular myocardium. Activation of ICl(Ca) in canine ventricular cells requires Ca(2+)-entry through neighboring L-type Ca(2+) channels and is only augmented by SR Ca(2+)-release. Substantial activation of ICl(Ca) requires high Ca(2+) concentration in the dyadic clefts which can be effectively buffered by BAPTA, but not EGTA.
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Affiliation(s)
- Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Faculty of Pharmacy, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Krisztina Váczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Bence Hegyi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Mónika Gönczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; MTA-DE Momentum, Laboratory of Protein Dynamics, Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Beatrix Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary; MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, H-6720 Szeged, Dóm tér 12, P.O. Box 427, Hungary
| | - György Seprényi
- Department of Medical Biology, Faculty of Medicine, University of Szeged, H-6720 Szeged, Somogyi Béla utca 4, P.O. Box 427, Hungary
| | - László Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary
| | - Norbert Szentandrássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary; Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, P.O. Box 22, Hungary.
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36
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Bevers EM, Williamson PL. Getting to the Outer Leaflet: Physiology of Phosphatidylserine Exposure at the Plasma Membrane. Physiol Rev 2016; 96:605-45. [PMID: 26936867 DOI: 10.1152/physrev.00020.2015] [Citation(s) in RCA: 298] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Phosphatidylserine (PS) is a major component of membrane bilayers whose change in distribution between inner and outer leaflets is an important physiological signal. Normally, members of the type IV P-type ATPases spend metabolic energy to create an asymmetric distribution of phospholipids between the two leaflets, with PS confined to the cytoplasmic membrane leaflet. On occasion, membrane enzymes, known as scramblases, are activated to facilitate transbilayer migration of lipids, including PS. Recently, two proteins required for such randomization have been identified: TMEM16F, a scramblase regulated by elevated intracellular Ca(2+), and XKR8, a caspase-sensitive protein required for PS exposure in apoptotic cells. Once exposed at the cell surface, PS regulates biochemical reactions involved in blood coagulation, and bone mineralization, and also regulates a variety of cell-cell interactions. Exposed on the surface of apoptotic cells, PS controls their recognition and engulfment by other cells. This process is exploited by parasites to invade their host, and in specialized form is used to maintain photoreceptors in the eye and modify synaptic connections in the brain. This review discusses what is known about the mechanism of PS exposure at the surface of the plasma membrane of cells, how actors in the extracellular milieu sense surface exposed PS, and how this recognition is translated to downstream consequences of PS exposure.
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Affiliation(s)
- Edouard M Bevers
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands; and Department of Biology, Amherst College, Amherst, Massachusetts
| | - Patrick L Williamson
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands; and Department of Biology, Amherst College, Amherst, Massachusetts
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37
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Novel Roles for Chloride Channels, Exchangers, and Regulators in Chronic Inflammatory Airway Diseases. Mediators Inflamm 2015; 2015:497387. [PMID: 26612971 PMCID: PMC4647060 DOI: 10.1155/2015/497387] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 10/13/2015] [Indexed: 01/14/2023] Open
Abstract
Chloride transport proteins play critical roles in inflammatory airway diseases, contributing to the detrimental aspects of mucus overproduction, mucus secretion, and airway constriction. However, they also play crucial roles in contributing to the innate immune properties of mucus and mucociliary clearance. In this review, we focus on the emerging novel roles for a chloride channel regulator (CLCA1), a calcium-activated chloride channel (TMEM16A), and two chloride exchangers (SLC26A4/pendrin and SLC26A9) in chronic inflammatory airway diseases.
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38
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TMEM16, LRRC8A, bestrophin: chloride channels controlled by Ca2+ and cell volume. Trends Biochem Sci 2015; 40:535-43. [DOI: 10.1016/j.tibs.2015.07.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 07/10/2015] [Accepted: 07/10/2015] [Indexed: 01/13/2023]
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Dam VS, Boedtkjer DMB, Aalkjaer C, Matchkov V. The bestrophin- and TMEM16A-associated Ca(2+)- activated Cl(–) channels in vascular smooth muscles. Channels (Austin) 2015; 8:361-9. [PMID: 25478625 PMCID: PMC4203738 DOI: 10.4161/chan.29531] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The presence of Ca2+-activated Cl– currents (ICl(Ca)) in vascular smooth muscle cells (VSMCs) is well established. ICl(Ca) are supposedly important for arterial contraction by linking changes in [Ca2+]i and membrane depolarization. Bestrophins and some members of the TMEM16 protein family were recently associated with ICl(Ca). Two distinct ICl(Ca) are characterized in VSMCs; the cGMP-dependent ICl(Ca) dependent upon bestrophin expression and the ‘classical’ Ca2+-activated Cl– current, which is bestrophin-independent. Interestingly, TMEM16A is essential for both the cGMP-dependent and the classical ICl(Ca). Furthermore, TMEM16A has a role in arterial contraction while bestrophins do not. TMEM16A’s role in the contractile response cannot be explained however only by a simple suppression of the depolarization by Cl– channels. It is suggested that TMEM16A expression modulates voltage-gated Ca2+ influx in a voltage-independent manner and recent studies also demonstrate a complex role of TMEM16A in modulating other membrane proteins.
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40
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Yang T, Colecraft HM. Calmodulin regulation of TMEM16A and 16B Ca(2+)-activated chloride channels. Channels (Austin) 2015; 10:38-44. [PMID: 26083059 DOI: 10.1080/19336950.2015.1058455] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Ca(2+)-activated chloride channels encoded by TMEM16A and 16B are important for regulating epithelial mucus secretion, cardiac and neuronal excitability, smooth muscle contraction, olfactory transduction, and cell proliferation. Whether and how the ubiquitous Ca(2+) sensor calmodulin (CaM) regulates the activity of TMEM16A and 16B channels has been controversial and the subject of an ongoing debate. Recently, using a bioengineering approach termed ChIMP (Channel Inactivation induced by Membrane-tethering of an associated Protein) we argued that Ca(2+)-free CaM (apoCaM) is pre-associated with functioning TMEM16A and 16B channel complexes in live cells. Further, the pre-associated apoCaM mediates Ca(2+)-dependent sensitization of activation (CDSA) and Ca(2+)-dependent inactivation (CDI) of some TMEM16A splice variants. In this review, we discuss these findings in the context of previous and recent results relating to Ca(2+)-dependent regulation of TMEM16A/16B channels and the putative role of CaM. We further discuss potential future directions for these nascent ideas on apoCaM regulation of TMEM16A/16B channels, noting that such future efforts will benefit greatly from the pioneering work of Dr. David T. Yue and colleagues on CaM regulation of voltage-dependent calcium channels.
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Affiliation(s)
- Tingting Yang
- a Department of Physiology and Cellular Biophysics ; Columbia University; College of Physicians and Surgeons ; New York , NY USA
| | - Henry M Colecraft
- a Department of Physiology and Cellular Biophysics ; Columbia University; College of Physicians and Surgeons ; New York , NY USA
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Leblanc N, Forrest AS, Ayon RJ, Wiwchar M, Angermann JE, Pritchard HAT, Singer CA, Valencik ML, Britton F, Greenwood IA. Molecular and functional significance of Ca(2+)-activated Cl(-) channels in pulmonary arterial smooth muscle. Pulm Circ 2015; 5:244-68. [PMID: 26064450 DOI: 10.1086/680189] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 07/22/2014] [Indexed: 12/31/2022] Open
Abstract
Increased peripheral resistance of small distal pulmonary arteries is a hallmark signature of pulmonary hypertension (PH) and is believed to be the consequence of enhanced vasoconstriction to agonists, thickening of the arterial wall due to remodeling, and increased thrombosis. The elevation in arterial tone in PH is attributable, at least in part, to smooth muscle cells of PH patients being more depolarized and displaying higher intracellular Ca(2+) levels than cells from normal subjects. It is now clear that downregulation of voltage-dependent K(+) channels (e.g., Kv1.5) and increased expression and activity of voltage-dependent (Cav1.2) and voltage-independent (e.g., canonical and vanilloid transient receptor potential [TRPC and TRPV]) Ca(2+) channels play an important role in the functional remodeling of pulmonary arteries in PH. This review focuses on an anion-permeable channel that is now considered a novel excitatory mechanism in the systemic and pulmonary circulations. It is permeable to Cl(-) and is activated by a rise in intracellular Ca(2+) concentration (Ca(2+)-activated Cl(-) channel, or CaCC). The first section outlines the biophysical and pharmacological properties of the channel and ends with a description of the molecular candidate genes postulated to encode for CaCCs, with particular emphasis on the bestrophin and the newly discovered TMEM16 and anoctamin families of genes. The second section provides a review of the various sources of Ca(2+) activating CaCCs, which include stimulation by mobilization from intracellular Ca(2+) stores and Ca(2+) entry through voltage-dependent and voltage-independent Ca(2+) channels. The third and final section summarizes recent findings that suggest a potentially important role for CaCCs and the gene TMEM16A in PH.
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Affiliation(s)
- Normand Leblanc
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Abigail S Forrest
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Ramon J Ayon
- Department of Medicine, University of Illinois, Chicago, Illinois, USA
| | - Michael Wiwchar
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Jeff E Angermann
- School of Community Health Sciences, University of Nevada, Reno, Nevada, USA
| | - Harry A T Pritchard
- Vascular Biology Research Centre, Institute of Cardiovascular and Cell Sciences, St. George's University of London, London, United Kingdom
| | - Cherie A Singer
- Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Maria L Valencik
- Department of Biochemistry and Molecular Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Fiona Britton
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Iain A Greenwood
- Vascular Biology Research Centre, Institute of Cardiovascular and Cell Sciences, St. George's University of London, London, United Kingdom
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42
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Matchkov VV, Boedtkjer DM, Aalkjaer C. The role of Ca2+ activated Cl− channels in blood pressure control. Curr Opin Pharmacol 2015; 21:127-37. [DOI: 10.1016/j.coph.2015.02.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 02/02/2015] [Accepted: 02/04/2015] [Indexed: 12/17/2022]
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43
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Sala-Rabanal M, Yurtsever Z, Nichols CG, Brett TJ. Secreted CLCA1 modulates TMEM16A to activate Ca(2+)-dependent chloride currents in human cells. eLife 2015; 4. [PMID: 25781344 PMCID: PMC4360653 DOI: 10.7554/elife.05875] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 02/12/2015] [Indexed: 12/22/2022] Open
Abstract
Calcium-activated chloride channel regulator 1 (CLCA1) activates calcium-dependent chloride currents; neither the target, nor mechanism, is known. We demonstrate that secreted CLCA1 activates calcium-dependent chloride currents in HEK293T cells in a paracrine fashion, and endogenous TMEM16A/Anoctamin1 conducts the currents. Exposure to exogenous CLCA1 increases cell surface levels of TMEM16A and cellular binding experiments indicate CLCA1 engages TMEM16A on the surface of these cells. Altogether, our data suggest that CLCA1 stabilizes TMEM16A on the cell surface, thus increasing surface expression, which results in increased calcium-dependent chloride currents. Our results identify the first Cl− channel target of the CLCA family of proteins and establish CLCA1 as the first secreted direct modifier of TMEM16A activity, delineating a unique mechanism to increase currents. These results suggest cooperative roles for CLCA and TMEM16 proteins in influencing the physiology of multiple tissues, and the pathology of multiple diseases, including asthma, COPD, cystic fibrosis, and certain cancers. DOI:http://dx.doi.org/10.7554/eLife.05875.001 Many biological processes that are important for our health involve the movement of ions into, and out of, our cells. For example, the flow of chloride ions out of cells controls the production of the sticky mucus that lines our windpipe and other airways. This mucus helps trap pollution and other foreign particles before they reach our lungs, and thus protects the lungs from harm. However in some diseases—such as cystic fibrosis and asthma—excessive amounts of thick mucus are produced; this can lead to breathing difficulties and an increased risk of infection. Proteins belonging to the CLCA protein family were first thought to act as channels that allow chloride ions to flow through cell membranes. Later studies then revealed that these proteins are not channels; instead they trigger the movement of chloride ions across cell membranes by activating other channel proteins. However, the identity of these channel proteins was unknown, and it was unclear how CLCA proteins might activate these channels. Sala-Rabanal, Yurtsever et al. have now shown that a member of the CLCA protein family, called CLCA1, is released from human cells and causes nearby cells to release chloride ions when the channel detects calcium ions. The movement of chloride ions triggered by CLCA1 looked very similar to the way chloride ions flow through a channel protein called TMEM16A, and so Sala-Rabanal, Yurtsever et al. asked whether these two proteins interact. TMEM16A was discovered several years ago, but remains the only calcium-dependent chloride channel known in mammals. Sala-Rabanal, Yurtsever et al. showed that adding CLCA1 to cells caused more TMEM16A channels to appear in the cell surface membrane and thereby increased the flow of chloride ions. The CLCA protein also physically interacted with the chloride channel in the membrane to stabilize it; no other protein has been shown to regulate ion channels in this way before. The findings of Sala-Rabanal, Yurtsever et al. provide a much clearer understanding of how the CLCA protein and the chloride channel work. Both of these proteins are known to contribute to excess mucus production in airway diseases; and both have been linked to cardiovascular diseases and certain cancers. These new findings may therefore also help researchers to target these proteins and develop treatments for these diseases. DOI:http://dx.doi.org/10.7554/eLife.05875.002
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Affiliation(s)
- Monica Sala-Rabanal
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, United States
| | - Zeynep Yurtsever
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St Louis, United States
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, United States
| | - Tom J Brett
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, United States
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Stolz M, Klapperstück M, Kendzierski T, Detro-Dassen S, Panning A, Schmalzing G, Markwardt F. Homodimeric anoctamin-1, but not homodimeric anoctamin-6, is activated by calcium increases mediated by the P2Y1 and P2X7 receptors. Pflugers Arch 2015; 467:2121-40. [PMID: 25592660 DOI: 10.1007/s00424-015-1687-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 12/23/2014] [Accepted: 01/06/2015] [Indexed: 01/14/2023]
Abstract
The P2X7 receptor (P2X7R) is a ligand-gated ion channel that conducts Na(+), K(+), and Ca(2+) when activated by extracellular ATP. In various cell types, such as secretory epithelia, the P2X7R is co-expressed with Ca(2+)-dependent Cl(-) channels of the TMEM16/anoctamin family. Here, we studied whether the P2X7R and TMEM16A/anoctamin-1 (Ano1) or TMEM16F/anoctamin-6 (Ano6) interact functionally and physically, using oocytes of Xenopus laevis and Ambystoma mexicanum (Axolotl) for heterologous expression. As a control, we co-expressed anoctamin-1 with the P2Y1 receptor (P2Y1R), which induces the release of Ca(2+) from intracellular stores via activating phospholipase C through coupling to Gαq. We found that co-expression of anoctamin-1 with the P2Y1R resulted in a small transient increase in Cl(-) conductance in response to ATP. Co-expression of anoctamin-1 with the P2X7R resulted in a large sustained increase in Cl(-) conductance via Ca(2+) influx through the ATP-opened P2X7R in Xenopus and in Axolotl oocytes, which lack endogenous Ca(2+)-dependent Cl(-) channels. P2Y1R- or P2X7R-mediated stimulation of Ano1 was primarily functional, as demonstrated by the absence of a physically stable interaction between Ano1 and the P2X7R. In the pancreatic cell line AsPC-1, we found the same functional Ca(2+)-dependent interaction of P2X7R and Ano1. The P2X7R-mediated sustained activation of Ano1 may be physiologically relevant to the time course of stimulus-secretion coupling in secretory epithelia. No such increase in Cl(-) conductance could be elicited by activating the P2X7 receptor in either Xenopus oocytes or Axolotl oocytes co-expressing Ano6. The lack of function of Ano6 can, at least in part, be explained by its poor cell-surface expression, resulting from a relatively inefficient exit of the homodimeric Ano6 from the endoplasmic reticulum.
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Affiliation(s)
- Michaela Stolz
- Molecular Pharmacology, RWTH Aachen University, Wendlingweg 2, D-52074, Aachen, Germany
| | - Manuela Klapperstück
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle-Wittenberg, Magdeburger Str. 6, D-06097, Halle/Saale, Germany
| | - Thomas Kendzierski
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle-Wittenberg, Magdeburger Str. 6, D-06097, Halle/Saale, Germany
| | - Silvia Detro-Dassen
- Molecular Pharmacology, RWTH Aachen University, Wendlingweg 2, D-52074, Aachen, Germany
| | - Anna Panning
- Molecular Pharmacology, RWTH Aachen University, Wendlingweg 2, D-52074, Aachen, Germany
| | - Günther Schmalzing
- Molecular Pharmacology, RWTH Aachen University, Wendlingweg 2, D-52074, Aachen, Germany
| | - Fritz Markwardt
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle-Wittenberg, Magdeburger Str. 6, D-06097, Halle/Saale, Germany.
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Henkel B, Drose DR, Ackels T, Oberland S, Spehr M, Neuhaus EM. Co-expression of anoctamins in cilia of olfactory sensory neurons. Chem Senses 2014; 40:73-87. [PMID: 25500808 DOI: 10.1093/chemse/bju061] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Vertebrates can sense and identify a vast array of chemical cues. The molecular machinery involved in chemodetection and transduction is expressed within the cilia of olfactory sensory neurons. Currently, there is only limited information available on the distribution and density of individual signaling components within the ciliary compartment. Using super-resolution microscopy, we show here that cyclic-nucleotide-gated channels and calcium-activated chloride channels of the anoctamin family are localized to discrete microdomains in the ciliary membrane. In addition to ANO2, a second anoctamin, ANO6, also localizes to ciliary microdomains. This observation, together with the fact that ANO6 and ANO2 co-localize, indicates a role for ANO6 in olfactory signaling. We show that both ANO2 and ANO6 can form heteromultimers and that this heteromerization alters the recombinant channels' physiological properties. Thus, we provide evidence for interaction of ANO2 and ANO6 in olfactory cilia, with possible physiological relevance for olfactory signaling.
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Affiliation(s)
- Bastian Henkel
- Department of Pharmacology and Toxicology, University Hospital Jena, Drackendorfer Strasse 1, 07747 Jena, Germany, Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany, FU Berlin, Fachbereich Biologie, Chemie und Pharmazie , Takustr. 3, 14195 Berlin, Germany and
| | - Daniela R Drose
- Department of Chemosensation, Institute for Biology II, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany
| | - Tobias Ackels
- Department of Chemosensation, Institute for Biology II, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany
| | - Sonja Oberland
- Department of Pharmacology and Toxicology, University Hospital Jena, Drackendorfer Strasse 1, 07747 Jena, Germany, Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany, FU Berlin, Fachbereich Biologie, Chemie und Pharmazie , Takustr. 3, 14195 Berlin, Germany and
| | - Marc Spehr
- Department of Chemosensation, Institute for Biology II, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany
| | - Eva M Neuhaus
- Department of Pharmacology and Toxicology, University Hospital Jena, Drackendorfer Strasse 1, 07747 Jena, Germany, Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany,
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Kodigepalli KM, Bowers K, Sharp A, Nanjundan M. Roles and regulation of phospholipid scramblases. FEBS Lett 2014; 589:3-14. [PMID: 25479087 DOI: 10.1016/j.febslet.2014.11.036] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 11/22/2014] [Accepted: 11/24/2014] [Indexed: 02/06/2023]
Abstract
Phospholipid scramblase activity is involved in the collapse of phospholipid (PL) asymmetry at the plasma membrane leading to externalization of phosphatidylserine. This activity is crucial for initiation of the blood coagulation cascade and for recognition/elimination of apoptotic cells by macrophages. Efforts to identify gene products associated with this activity led to the characterization of PL scramblase (PLSCR) and XKR family members which contribute to phosphatidylserine exposure in response to apoptotic stimuli. Meanwhile, TMEM16 family members were identified to externalize phosphatidylserine in response to elevated calcium in Scott syndrome platelets, which is critical for activation of the coagulation cascade. Herein, we report their mechanisms of gene regulation, molecular functions independent of their scrambling activity, and their potential roles in pathogenic conditions.
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Affiliation(s)
- Karthik M Kodigepalli
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, United States
| | - Kiah Bowers
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, United States
| | - Arielle Sharp
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, United States
| | - Meera Nanjundan
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, United States.
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Bill A, Popa MO, van Diepen MT, Gutierrez A, Lilley S, Velkova M, Acheson K, Choudhury H, Renaud NA, Auld DS, Gosling M, Groot-Kormelink PJ, Gaither LA. Variomics screen identifies the re-entrant loop of the calcium-activated chloride channel ANO1 that facilitates channel activation. J Biol Chem 2014; 290:889-903. [PMID: 25425649 DOI: 10.1074/jbc.m114.618140] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The calcium-activated chloride channel ANO1 regulates multiple physiological processes. However, little is known about the mechanism of channel gating and regulation of ANO1 activity. Using a high-throughput, random mutagenesis-based variomics screen, we generated and functionally characterized ∼6000 ANO1 mutants and identified novel mutations that affected channel activity, intracellular trafficking, or localization of ANO1. Mutations such as S741T increased ANO1 calcium sensitivity and rendered ANO1 calcium gating voltage-independent, demonstrating a critical role of the re-entrant loop in coupling calcium and voltage sensitivity of ANO1 and hence in regulating ANO1 activation. Our data present the first unbiased and comprehensive study of the structure-function relationship of ANO1. The novel ANO1 mutants reported have diverse functional characteristics, providing new tools to study ANO1 function in biological systems, paving the path for a better understanding of the function of ANO1 and its role in health and diseases.
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Affiliation(s)
- Anke Bill
- From the Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139
| | - M Oana Popa
- the Novartis Institutes for Biomedical Research, Horsham, West Sussex RH12 5AB, United Kingdom, and
| | - Michiel T van Diepen
- the Novartis Institutes for Biomedical Research, Horsham, West Sussex RH12 5AB, United Kingdom, and
| | - Abraham Gutierrez
- From the Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139
| | - Sarah Lilley
- the Novartis Institutes for Biomedical Research, Horsham, West Sussex RH12 5AB, United Kingdom, and
| | - Maria Velkova
- the Novartis Institutes for Biomedical Research, Horsham, West Sussex RH12 5AB, United Kingdom, and
| | - Kathryn Acheson
- the Novartis Institutes for Biomedical Research, Horsham, West Sussex RH12 5AB, United Kingdom, and
| | - Hedaythul Choudhury
- the Novartis Institutes for Biomedical Research, Horsham, West Sussex RH12 5AB, United Kingdom, and
| | - Nicole A Renaud
- From the Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139
| | - Douglas S Auld
- From the Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139
| | - Martin Gosling
- the Novartis Institutes for Biomedical Research, Horsham, West Sussex RH12 5AB, United Kingdom, and
| | | | - L Alex Gaither
- From the Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139,
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Brunner JD, Lim NK, Schenck S, Duerst A, Dutzler R. X-ray structure of a calcium-activated TMEM16 lipid scramblase. Nature 2014; 516:207-12. [DOI: 10.1038/nature13984] [Citation(s) in RCA: 339] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 10/20/2014] [Indexed: 12/11/2022]
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49
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TMEM16 proteins: unknown structure and confusing functions. J Mol Biol 2014; 427:94-105. [PMID: 25451786 DOI: 10.1016/j.jmb.2014.09.028] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 09/24/2014] [Accepted: 09/29/2014] [Indexed: 11/23/2022]
Abstract
The TMEM16 family of membrane proteins, also known as anoctamins, plays key roles in a variety of physiological functions that range from ion transport to phospholipid scrambling and to regulating other ion channels. The first two family members to be functionally characterized, TMEM16A (ANO1) and TMEM16B (ANO2), form Ca(2+)-activated Cl(-) channels and are important for transepithelial ion transport, olfaction, phototransduction, smooth muscle contraction, nociception, cell proliferation and control of neuronal excitability. The roles of other family members, such as TMEM16C (ANO3), TMEM16D (ANO4), TMEM16F (ANO6), TMEM16G (ANO7) and TMEM16J (ANO9), remain poorly understood and controversial. These homologues were reported to be phospholipid scramblases, ion channels, to have both functions or to be regulatory subunits of other channels. Mutations in TMEM16F cause Scott syndrome, a bleeding disorder caused by impaired Ca(2+)-dependent externalization of phosphatidylserine in activated platelets, suggesting that this homologue might be a scramblase. However, overexpression of TMEM16F has also been associated with a remarkable number of different ion channel types, raising the possibility that this protein might be involved in both ion and lipid transports. The recent identification of an ancestral TMEM16 homologue with intrinsic channel and scramblase activities supports this hypothesis. Thus, the TMEM16 family might have diverged in two or three different subclasses, channels, scramblases and dual-function channel/scramblases. The structural bases and functional implication of such a functional diversity within a single protein family remain to be elucidated and the links between TMEM16 functions and human physiology and pathologies need to be investigated.
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50
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Ertongur-Fauth T, Hochheimer A, Buescher JM, Rapprich S, Krohn M. A novel TMEM16A splice variant lacking the dimerization domain contributes to calcium-activated chloride secretion in human sweat gland epithelial cells. Exp Dermatol 2014; 23:825-31. [PMID: 25220078 DOI: 10.1111/exd.12543] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2014] [Indexed: 12/13/2022]
Abstract
Sweating is an important physiological process to regulate body temperature in humans, and various disorders are associated with dysregulated sweat formation. Primary sweat secretion in human eccrine sweat glands involves Ca(2+) -activated Cl(-) channels (CaCC). Recently, members of the TMEM16 family were identified as CaCCs in various secretory epithelia; however, their molecular identity in sweat glands remained elusive. Here, we investigated the function of TMEM16A in sweat glands. Gene expression analysis revealed that TMEM16A is expressed in human NCL-SG3 sweat gland cells as well as in isolated human eccrine sweat gland biopsy samples. Sweat gland cells express several previously described TMEM16A splice variants, as well as one novel splice variant, TMEM16A(acΔe3) lacking the TMEM16A-dimerization domain. Chloride flux assays using halide-sensitive YFP revealed that TMEM16A is functionally involved in Ca(2+) -dependent Cl(-) secretion in NCL-SG3 cells. Recombinant expression in NCL-SG3 cells showed that TMEM16A(acΔe3) is forming a functional CaCC, with basal and Ca(2+) -activated Cl(-) permeability distinct from canonical TMEM16A(ac). Our results suggest that various TMEM16A isoforms contribute to sweat gland-specific Cl(-) secretion providing opportunities to develop sweat gland-specific therapeutics for treatment of sweating disorders.
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