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Gaitán-Peñas H, Pérez-Rius C, Muhaisen A, Castellanos A, Errasti-Murugarren E, Barrallo-Gimeno A, Alcaraz-Pérez F, Estévez R. Characterization of ClC-1 chloride channels in zebrafish: a new model to study myotonia. J Physiol 2024; 602:3975-3994. [PMID: 39031529 DOI: 10.1113/jp286530] [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: 03/08/2024] [Accepted: 07/01/2024] [Indexed: 07/22/2024] Open
Abstract
The function of the chloride channel ClC-1 is crucial for the control of muscle excitability. Thus, reduction of ClC-1 functions by CLCN1 mutations leads to myotonia congenita. Many different animal models have contributed to understanding the myotonia pathophysiology. However, these models do not allow in vivo screening of potentially therapeutic drugs, as the zebrafish model does. In this work, we identified and characterized the two zebrafish orthologues (clc-1a and clc-1b) of the ClC-1 channel. Both channels are mostly expressed in the skeletal muscle as revealed by RT-PCR, western blot, and electrophysiological recordings of myotubes, and clc-1a is predominantly expressed in adult stages. Characterization in Xenopus oocytes shows that the zebrafish channels display similar anion selectivity and voltage dependence to their human counterparts. However, they show reduced sensitivity to the inhibitor 9-anthracenecarboxylic acid (9-AC), and acidic pH inverts the voltage dependence of activation. Reduction of clc-1a/b expression hampers spontaneous and mechanically stimulated movement, which could be reverted by expression of human ClC-1 but not by some ClC-1 containing myotonia mutations. Treatment of clc-1-depleted zebrafish with mexiletine, a typical drug used in human myotonia, improves the motor behaviour. Our work extends the repertoire of ClC channels to evolutionary structure-function studies and proposes the zebrafish clcn1 crispant model as a simple tool to find novel therapies for myotonia. KEY POINTS: We have identified two orthologues of ClC-1 in zebrafish (clc-1a and clc-1b) which are mostly expressed in skeletal muscle at different developmental stages. Functional characterization of the activity of these channels reveals many similitudes with their mammalian counterparts, although they are less sensitive to 9-AC and acidic pH inverts their voltage dependence of gating. Reduction of clc-1a/b expression hampers spontaneous and mechanically stimulated movement which could be reverted by expression of human ClC-1. Myotonia-like symptoms caused by clc-1a/b depletion can be reverted by mexiletine, suggesting that this model could be used to find novel therapies for myotonia.
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Affiliation(s)
- Héctor Gaitán-Peñas
- Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona-IDIBELL, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
| | - Carla Pérez-Rius
- Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona-IDIBELL, Barcelona, Spain
| | - Ashraf Muhaisen
- Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona-IDIBELL, Barcelona, Spain
| | - Aida Castellanos
- Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona-IDIBELL, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
| | - Ekaitz Errasti-Murugarren
- Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona-IDIBELL, Barcelona, Spain
| | - Alejandro Barrallo-Gimeno
- Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona-IDIBELL, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
| | - Francisca Alcaraz-Pérez
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
- Department of Surgery, Telomerase, Cancer and Aging Group (TCAG), Hospital Clínico Universitario Virgen de la Arrixaca, Murcia, Spain
- Instituto Murciano de Investigación Biosanitaria-Arrixaca (IMIB-Arrixaca), Murcia, Spain
| | - Raúl Estévez
- Physiology Unit, Department of Physiological Sciences, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona-IDIBELL, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
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2
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Nelson TS, Duran P, Calderon-Rivera A, Gomez K, Loya-Lopez S, Khanna R. Mouse models of non-dystrophic and dystrophic myotonia exhibit nociplastic pain-like behaviors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.19.599732. [PMID: 38948724 PMCID: PMC11212949 DOI: 10.1101/2024.06.19.599732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Pain is a prominent and debilitating symptom in myotonic disorders, yet its physiological mechanisms remain poorly understood. This study assessed preclinical pain-like behavior in murine models of pharmacologically induced myotonia and myotonic dystrophy type 1 (DM1). In both myotonia congenita and DM1, impairment of the CLCN1 gene, which encodes skeletal muscle voltage-gated CLC-1 chloride channels, reduces chloride ion conductance in skeletal muscle cells, leading to prolonged muscle excitability and delayed relaxation after contraction. We used the CLC-1 antagonist anthracene-9-carboxylic acid (9-AC) at intraperitoneal doses of 30 or 60 mg/kg and HSA LR20b DM1 mice to model CLC-1-induced myotonia. Our experimental approach included in vivo pain behavioral testing, ex vivo calcium imaging, and whole-cell current-clamp electrophysiology in mouse dorsal root ganglion (DRG) neurons. A single injection of 9-AC induced myotonia in mice, which persisted for several hours and resulted in long-lasting allodynic pain-like behavior. Similarly, HSA LR20b mice exhibited both allodynia and hyperalgesia. Despite these pain-like behaviors, DRG neurons did not show signs of hyperexcitability in either myotonic model. These findings suggest that myotonia induces nociplastic pain-like behavior in preclinical rodents, likely through central sensitization mechanisms rather than peripheral sensitization. This study provides insights into the pathophysiology of pain in myotonic disorders and highlights the potential of using myotonic mouse models to explore pain mechanisms and assess novel analgesics. Future research should focus on the central mechanisms involved in myotonia-induced pain and develop targeted therapies to alleviate this significant clinical burden.
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Affiliation(s)
- Tyler S. Nelson
- Department of Pharmacology and Therapeutics, McKnight Brain Institute, and Pain and Addiction Therapeutics (PATH) Collaboratory, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Paz Duran
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA
| | - Aida Calderon-Rivera
- Department of Pharmacology and Therapeutics, McKnight Brain Institute, and Pain and Addiction Therapeutics (PATH) Collaboratory, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Kimberly Gomez
- Department of Pharmacology and Therapeutics, McKnight Brain Institute, and Pain and Addiction Therapeutics (PATH) Collaboratory, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Santiago Loya-Lopez
- Department of Pharmacology and Therapeutics, McKnight Brain Institute, and Pain and Addiction Therapeutics (PATH) Collaboratory, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Rajesh Khanna
- Department of Pharmacology and Therapeutics, McKnight Brain Institute, and Pain and Addiction Therapeutics (PATH) Collaboratory, University of Florida College of Medicine, Gainesville, FL 32610, USA
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3
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Kwon HC, Fairclough RH, Chen TY. Biophysical and Pharmacological Insights to CLC Chloride Channels. Handb Exp Pharmacol 2024; 283:1-34. [PMID: 35768555 DOI: 10.1007/164_2022_594] [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] [Indexed: 06/15/2023]
Abstract
The CLC family encompasses two functional categories of transmembrane proteins: chloride conducting channels and proton-chloride antiporters. All members in this chloride channel/transporter family consist of two identical protein subunits, and each subunit forms an independent ion-transport pathway, a structural architecture known as "double barrel." These CLC proteins serve biological functions ranging from membrane excitability and cell volume regulation to acidification of endosomes. Despite their ubiquitous expression, physiological significance, and resolved molecular structures of some of the family members, the mechanisms governing these molecules' biophysical functions are still not completely settled. However, a series of functional and structural studies have brought insights into interesting questions related to these proteins. This chapter explores the functional peculiarities underlying CLC channels aided by information observed from the chloride-proton antiporters in the CLC family. The overall structural features of these CLC proteins will be presented, and the biophysical functions will be addressed. Finally, the mechanism of pharmacological agents that interact with CLC channels will also be discussed.
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Affiliation(s)
- Hwoi Chan Kwon
- Center for Neuroscience and Biophysics Graduate Group, University of California, Davis, CA, USA
| | - Robert H Fairclough
- Department of Neurology and the Biophysics Graduate Group, University of California, Davis, CA, USA
| | - Tsung-Yu Chen
- Center for Neuroscience, Department of Neurology, and Biophysics Graduate Group, University of California, Davis, CA, USA.
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4
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Ma T, Wang L, Chai A, Liu C, Cui W, Yuan S, Wing Ngor Au S, Sun L, Zhang X, Zhang Z, Lu J, Gao Y, Wang P, Li Z, Liang Y, Vogel H, Wang YT, Wang D, Yan K, Zhang H. Cryo-EM structures of ClC-2 chloride channel reveal the blocking mechanism of its specific inhibitor AK-42. Nat Commun 2023; 14:3424. [PMID: 37296152 PMCID: PMC10256776 DOI: 10.1038/s41467-023-39218-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 06/02/2023] [Indexed: 06/12/2023] Open
Abstract
ClC-2 transports chloride ions across plasma membranes and plays critical roles in cellular homeostasis. Its dysfunction is involved in diseases including leukodystrophy and primary aldosteronism. AK-42 was recently reported as a specific inhibitor of ClC-2. However, experimental structures are still missing to decipher its inhibition mechanism. Here, we present cryo-EM structures of apo ClC-2 and its complex with AK-42, both at 3.5 Å resolution. Residues S162, E205 and Y553 are involved in chloride binding and contribute to the ion selectivity. The side-chain of the gating glutamate E205 occupies the putative central chloride-binding site, indicating that our structure represents a closed state. Structural analysis, molecular dynamics and electrophysiological recordings identify key residues to interact with AK-42. Several AK-42 interacting residues are present in ClC-2 but not in other ClCs, providing a possible explanation for AK-42 specificity. Taken together, our results experimentally reveal the potential inhibition mechanism of ClC-2 inhibitor AK-42.
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Grants
- National Natural Science Foundation of China (National Science Foundation of China)
- National Science and Technology Innovation 2030 Major Program (No. 2022ZD0211900)
- the Science and Technology Innovation Committee of Shenzhen(No. JCYJ20200109150700942), the Key-Area Research and Development Program of Guangdong Province (2019B030335001), the Shenzhen Fund for Guangdong Provincial High Level Clinical Key Specialties (No. SZGSP013), and the Shenzhen Key Medical Discipline Construction Fund (No. SZXK042)
- The Shenzhen Key Laboratory of Computer Aided Drug Discovery, Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, 518055, China, Funding number: ZDSYS20201230165400001. The Chinese Academy of Science President’s International Fellowship Initiative (PIFI) (No. 2020FSB0003), Guangdong Retired Expert (granted by Guangdong Province), National Overseas High Level Talent Introduction Plan-Foreign Expert from Organization Department of the CPC Central Committee (1000 talent project), Shenzhen Pengcheng Scientist, NSFC-SNSF Funding (No. 32161133022), AlphaMol & SIAT Joint Laboratory, Shenzhen Government Top-talent Working Funding and Guangdong Province Academician Work Funding.
- NSFC-Guangdong Joint Fund-U20A6005, Shenzhen Key Laboratory of Translational Research for Brain Diseases (ZDSYS20200828154800001)
- Shenzhen Science and Technology Program (No. JCYJ20220530115214033 and No. KQTD20210811090115021)
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Affiliation(s)
- Tao Ma
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, China
- Department of Biomedical Engineering, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Lei Wang
- School of Life Sciences, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Anping Chai
- Shenzhen Key Laboratory of Translational Research for Brain Diseases, The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
- Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, 518055, Shenzhen, Guangdong, China
| | - Chao Liu
- Department of Biomedical Engineering, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Wenqiang Cui
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Shuguang Yuan
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, China
| | - Shannon Wing Ngor Au
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - Liang Sun
- Shenzhen Shuli Tech Co., Ltd, 518126, Shenzhen, Guangdong, China
| | - Xiaokang Zhang
- Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, 518055, Shenzhen, Guangdong, China
- Interdisciplinary Center for Brain Information, The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, Guangdong, China
- Faculty of Life and Health Sciences, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, Guangdong, China
| | - Zhenzhen Zhang
- Department of Biomedical Engineering, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Jianping Lu
- Department of Child and Adolescent Psychiatry, Shenzhen Kangning Hospital, Shenzhen Mental Health Center, Shenzhen, 518020, China
| | - Yuanzhu Gao
- Cryo-EM Facility Center, Southern University of Science and Technology, 518055, Shenzhen, Guangdong, China
| | - Peiyi Wang
- Cryo-EM Facility Center, Southern University of Science and Technology, 518055, Shenzhen, Guangdong, China
| | - Zhifang Li
- Department of Biomedical Engineering, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Yujie Liang
- Department of Child and Adolescent Psychiatry, Shenzhen Kangning Hospital, Shenzhen Mental Health Center, Shenzhen, 518020, 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.
| | - Yu Tian Wang
- Shenzhen Key Laboratory of Translational Research for Brain Diseases, The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.
- Faculty of Life and Health Sciences, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, Guangdong, China.
| | - Daping Wang
- Department of Biomedical Engineering, Southern University of Science and Technology, 518055, Shenzhen, China.
- Department of Orthopedics, Shenzhen Intelligent Orthopaedics and Biomedical Innovation Platform, Guangdong Provincial Research Center for Artificial Intelligence and Digital Orthopedic Technology, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, 518000, Shenzhen, China.
| | - Kaige Yan
- School of Life Sciences, Southern University of Science and Technology, 518055, Shenzhen, China.
| | - Huawei Zhang
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, 518055, Shenzhen, China.
- Department of Biomedical Engineering, Southern University of Science and Technology, 518055, Shenzhen, China.
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5
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Álvarez-Abril MC, García-Alcover I, Colonques-Bellmunt J, Garijo R, Pérez-Alonso M, Artero R, López-Castel A. Natural Compound Boldine Lessens Myotonic Dystrophy Type 1 Phenotypes in DM1 Drosophila Models, Patient-Derived Cell Lines, and HSA LR Mice. Int J Mol Sci 2023; 24:9820. [PMID: 37372969 PMCID: PMC10298378 DOI: 10.3390/ijms24129820] [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: 04/28/2023] [Revised: 05/25/2023] [Accepted: 06/01/2023] [Indexed: 06/29/2023] Open
Abstract
Myotonic dystrophy type 1 (DM1) is a complex rare disorder characterized by progressive muscle dysfunction, involving weakness, myotonia, and wasting, but also exhibiting additional clinical signs in multiple organs and systems. Central dysregulation, caused by an expansion of a CTG trinucleotide repeat in the DMPK gene's 3' UTR, has led to exploring various therapeutic approaches in recent years, a few of which are currently under clinical trial. However, no effective disease-modifying treatments are available yet. In this study, we demonstrate that treatments with boldine, a natural alkaloid identified in a large-scale Drosophila-based pharmacological screening, was able to modify disease phenotypes in several DM1 models. The most significant effects include consistent reduction in nuclear RNA foci, a dynamic molecular hallmark of the disease, and noteworthy anti-myotonic activity. These results position boldine as an attractive new candidate for therapy development in DM1.
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Affiliation(s)
| | - Irma García-Alcover
- Valentia BioPharma S.L., 46980 Paterna, Spain (R.A.)
- Human Translational Genomics Group, Institute for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, 46100 Burjasot, Spain
| | | | - Raquel Garijo
- Valentia BioPharma S.L., 46980 Paterna, Spain (R.A.)
| | - Manuel Pérez-Alonso
- Valentia BioPharma S.L., 46980 Paterna, Spain (R.A.)
- Human Translational Genomics Group, Institute for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, 46100 Burjasot, Spain
- Incliva Biomedical Research Institute, 46010 Valencia, Spain
| | - Rubén Artero
- Valentia BioPharma S.L., 46980 Paterna, Spain (R.A.)
- Human Translational Genomics Group, Institute for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, 46100 Burjasot, Spain
- Incliva Biomedical Research Institute, 46010 Valencia, Spain
| | - Arturo López-Castel
- Valentia BioPharma S.L., 46980 Paterna, Spain (R.A.)
- Human Translational Genomics Group, Institute for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, 46100 Burjasot, Spain
- Incliva Biomedical Research Institute, 46010 Valencia, Spain
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6
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De Bellis M, Boccanegra B, Cerchiara AG, Imbrici P, De Luca A. Blockers of Skeletal Muscle Na v1.4 Channels: From Therapy of Myotonic Syndrome to Molecular Determinants of Pharmacological Action and Back. Int J Mol Sci 2023; 24:ijms24010857. [PMID: 36614292 PMCID: PMC9821513 DOI: 10.3390/ijms24010857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 12/28/2022] [Accepted: 12/30/2022] [Indexed: 01/05/2023] Open
Abstract
The voltage-gated sodium channels represent an important target for drug discovery since a large number of physiological processes are regulated by these channels. In several excitability disorders, including epilepsy, cardiac arrhythmias, chronic pain, and non-dystrophic myotonia, blockers of voltage-gated sodium channels are clinically used. Myotonia is a skeletal muscle condition characterized by the over-excitability of the sarcolemma, resulting in delayed relaxation after contraction and muscle stiffness. The therapeutic management of this disorder relies on mexiletine and other sodium channel blockers, which are not selective for the Nav1.4 skeletal muscle sodium channel isoform. Hence, the importance of deepening the knowledge of molecular requirements for developing more potent and use-dependent drugs acting on Nav1.4. Here, we review the available treatment options for non-dystrophic myotonia and the structure-activity relationship studies performed in our laboratory with a focus on new compounds with potential antimyotonic activity.
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Altamura C, Conte E, Campanale C, Laghetti P, Saltarella I, Camerino GM, Imbrici P, Desaphy JF. Chaperone activity of niflumic acid on ClC-1 chloride channel mutants causing myotonia congenita. Front Pharmacol 2022; 13:958196. [PMID: 36034862 PMCID: PMC9403836 DOI: 10.3389/fphar.2022.958196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 07/08/2022] [Indexed: 11/14/2022] Open
Abstract
Myotonia congenita (MC) is an inherited rare disease characterized by impaired muscle relaxation after contraction, resulting in muscle stiffness. It is caused by loss-of-function mutations in the skeletal muscle chloride channel ClC-1, important for the stabilization of resting membrane potential and for the repolarization phase of action potentials. Thanks to in vitro functional studies, the molecular mechanisms by which ClC-1 mutations alter chloride ion influx into the cell have been in part clarified, classifying them in “gating-defective” or “expression-defective” mutations. To date, the treatment of MC is only palliative because no direct ClC-1 activator is available. An ideal drug should be one which is able to correct biophysical defects of ClC-1 in the case of gating-defective mutations or a drug capable to recover ClC-1 protein expression on the plasma membrane for trafficking-defective ones. In this study, we tested the ability of niflumic acid (NFA), a commercial nonsteroidal anti-inflammatory drug, to act as a pharmacological chaperone on trafficking-defective MC mutants (A531V, V947E). Wild-type (WT) or MC mutant ClC-1 channels were expressed in HEK293 cells and whole-cell chloride currents were recorded with the patch-clamp technique before and after NFA incubation. Membrane biotinylation assays and western blot were performed to support electrophysiological results. A531V and V947E mutations caused a decrease in chloride current density due to a reduction of ClC-1 total protein level and channel expression on the plasma membrane. The treatment of A531V and V947E-transfected cells with 50 µM NFA restored chloride currents, reaching levels similar to those of WT. Furthermore, no significant difference was observed in voltage dependence, suggesting that NFA increased protein membrane expression without altering the function of ClC-1. Indeed, biochemical experiments confirmed that V947E total protein expression and its plasma membrane distribution were recovered after NFA incubation, reaching protein levels similar to WT. Thus, the use of NFA as a pharmacological chaperone in trafficking defective ClC-1 channel mutations could represent a good strategy in the treatment of MC. Because of the favorable safety profile of this drug, our study may easily open the way for confirmatory human pilot studies aimed at verifying the antimyotonic activity of NFA in selected patients carrying specific ClC-1 channel mutations.
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Affiliation(s)
- Concetta Altamura
- Dept. of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
- *Correspondence: Concetta Altamura,
| | - Elena Conte
- Dept. of Pharmacy-Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Carmen Campanale
- Dept. of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Paola Laghetti
- Dept. of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Ilaria Saltarella
- Dept. of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | | | - Paola Imbrici
- Dept. of Pharmacy-Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Jean-François Desaphy
- Dept. of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
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Abstract
TMEM16A Ca2+-activated chloride channels are involved in multiple cellular functions and are proposed targets for diseases such as hypertension, stroke, and cystic fibrosis. This therapeutic endeavor, however, suffers from paucity of selective and potent modulators. Here, exploiting a synthetic small molecule with a biphasic effect on the TMEM16A channel, anthracene-9-carboxylic acid (A9C), we shed light on sites of the channel amenable for pharmacological intervention. Mutant channels with the intracellular gate constitutively open were generated. These channels were entirely insensitive to extracellular A9C when intracellular Ca2+ was omitted. However, when physiological Ca2+ levels were reestablished, the mutants regained sensitivity to A9C. Thus, intracellular Ca2+ is mandatory for the channel response to an extracellular modulator. The underlying mechanism is a conformational change in the outer pore that enables A9C to enter the pore to reach its binding site. The explanation of this structural rearrangement highlights a critical site for pharmacological intervention and reveals an aspect of Ca2+ gating in the TMEM16A channel.
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9
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Hosotani S, Yamauchi S, Kobayashi H, Fuji S, Koya S, Shimazaki KI, Takemiya A. A BLUS1 kinase signal and a decrease in intercellular CO2 concentration are necessary for stomatal opening in response to blue light. THE PLANT CELL 2021; 33:1813-1827. [PMID: 33665670 PMCID: PMC8254492 DOI: 10.1093/plcell/koab067] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 02/20/2021] [Indexed: 05/20/2023]
Abstract
Light-induced stomatal opening stimulates CO2 uptake and transpiration in plants. Weak blue light under strong red light effectively induces stomatal opening. Blue light-dependent stomatal opening initiates light perception by phototropins, and the signal is transmitted to a plasma membrane H+-ATPase in guard cells via BLUE LIGHT SIGNALING 1 (BLUS1) kinase. However, it is unclear how BLUS1 transmits the signal to H+-ATPase. Here, we characterized BLUS1 signaling in Arabidopsis thaliana, and showed that the BLUS1 C-terminus acts as an auto-inhibitory domain and that phototropin-mediated Ser-348 phosphorylation within the domain removes auto-inhibition. C-Terminal truncation and phospho-mimic Ser-348 mutation caused H+-ATPase activation in the dark, but did not elicit stomatal opening. Unexpectedly, the plants exhibited stomatal opening under strong red light and stomatal closure under weak blue light. A decrease in intercellular CO2 concentration via red light-driven photosynthesis together with H+-ATPase activation caused stomatal opening. Furthermore, phototropins caused H+-ATPase dephosphorylation in guard cells expressing constitutive signaling variants of BLUS1 in response to blue light, possibly for fine-tuning stomatal opening. Overall, our findings provide mechanistic insights into the blue light regulation of stomatal opening.
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Affiliation(s)
- Sakurako Hosotani
- Department of Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan
| | - Shota Yamauchi
- Department of Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan
| | - Haruki Kobayashi
- Department of Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan
| | - Saashia Fuji
- Department of Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan
| | - Shigekazu Koya
- Department of Biology, Kyushu University, Fukuoka 819-0395, Japan
| | | | - Atsushi Takemiya
- Department of Biology, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan
- Author for correspondence:
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Hoff A, Rath N, Lisko J, Zeller M, Balendiran GK. Signature of Glycylglutamic Acid Structure. INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND BIOPHYSICS 2021; 9:8-15. [PMID: 34660846 PMCID: PMC8515908 DOI: 10.13189/ijbb.2021.090102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Glutamate (Glu) is of great interest in biomedical research. It is considered a biomarker in diabetes, which may potentially contribute to the development of autism in genetically vulnerable human populations, and it is found in relation to advanced glycation end products (AGEs) [1]. Additionally, Glu plays an active role in the function of ligand-gated ion channel glutamate receptors, chloride channels capable of filtering glutamate, as well as Potassium (K+)-channel [2]. Glu attains α [3] and β [4] crystal forms and Cβ-CH2 show asymmetric 1H signal pattern in NMR spectra. OBJECTIVES The current study was undertaken to understand the signal patterns of Cβ-CH2 in Glu of the smallest dipeptide, Glycylglutamic Acid (GlyGlu), as well as the order, and planarity of the amide bond in the molecule. MATERIALS AND METHODS NMR spectra of GlyGlu were measured in D2O to deduce 1H and 13C chemical shifts and coupling constants. GlyGlu was crystallized from MeOH and the structure was determined by single crystal X-ray diffraction techniques. RESULTS The sidechain of Glu in the dipeptide dissimilates the β form. The amino group of Gly (Glycine) is protonated and exhibits hydrogen bonding with the main chain carboxylate group of a symmetry-related Glu that is deprotonated in the crystal packing of GlyGlu. The deprotonated main chain carboxylate of Glu is also in hydrogen-bonding distance from the side chain carboxylic acid group that is in the protonated form of a symmetry-related Glu of the dipeptide. The Cβ-CH2 geminal protons on the side chain of Glu have different chemical shifts and splitting pattern in 1H NMR reflecting their dissymmetric environment. CONCLUSION The results reported will be useful for monitoring changes that Glu and/or molecules in connection to Glu may undergo in in vivo, in situ, and in vitro conditions. This provides a valuable metric which will enable the examination of the metabolites relevant to the detection and diagnosis of disease or developmental conditions, as well as scrutinizing the effectiveness of treatment options.
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Affiliation(s)
- Amanda Hoff
- Department of Chemistry, Youngstown State University,
Youngstown, OH 44555, USA
- Northwestern Medicine Central DuPage Hospital, Winfield, IL
60190, USA
| | - Nigam Rath
- Department of Chemistry and Biochemistry and Center for
Nanoscience, University of Missouri, St. Louis, MO 63121, USA
| | - John Lisko
- Department of Chemistry, Youngstown State University,
Youngstown, OH 44555, USA
| | - Matthias Zeller
- Department of Chemistry, Youngstown State University,
Youngstown, OH 44555, USA
- Department of Chemistry, Purdue University, West Lafayette,
Indiana 47907, USA
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11
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Di Zanni E, Palagano E, Lagostena L, Strina D, Rehman A, Abinun M, De Somer L, Martire B, Brown J, Kariminejad A, Balasubramaniam S, Baynam G, Gurrieri F, Pisanti MA, De Maggio I, Abboud MR, Chiesa R, Burren CP, Villa A, Sobacchi C, Picollo A. Pathobiologic Mechanisms of Neurodegeneration in Osteopetrosis Derived From Structural and Functional Analysis of 14 ClC-7 Mutants. J Bone Miner Res 2021; 36:531-545. [PMID: 33125761 DOI: 10.1002/jbmr.4200] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 10/21/2020] [Accepted: 10/22/2020] [Indexed: 12/18/2022]
Abstract
ClC-7 is a chloride-proton antiporter of the CLC protein family. In complex with its accessory protein Ostm-1, ClC-7 localizes to lysosomes and to the osteoclasts' ruffled border, where it plays a critical role in acidifying the resorption lacuna during bone resorption. Gene inactivation in mice causes severe osteopetrosis, neurodegeneration, and lysosomal storage disease. Mutations in the human CLCN7 gene are associated with diverse forms of osteopetrosis. The functional evaluation of ClC-7 variants might be informative with respect to their pathogenicity, but the cellular localization of the protein hampers this analysis. Here we investigated the functional effects of 13 CLCN7 mutations identified in 13 new patients with severe or mild osteopetrosis and a known ADO2 mutation. We mapped the mutated amino acid residues in the homology model of ClC-7 protein, assessed the lysosomal colocalization of ClC-7 mutants and Ostm1 through confocal microscopy, and performed patch-clamp recordings on plasma-membrane-targeted mutant ClC-7. Finally, we analyzed these results together with the patients' clinical features and suggested a correlation between the lack of ClC-7/Ostm1 in lysosomes and severe neurodegeneration. © 2020 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Eleonora Di Zanni
- Consiglio Nazionale delle Ricerche, Istituto di Biofisica (CNR-IBF), Dulbecco Telethon Laboratory, Genoa, Italy
| | - Eleonora Palagano
- Consiglio Nazionale delle Ricerche-Istituto di Ricerca Genetica e Biomedica (CNR-IRGB), Milan, Italy.,Humanitas Clinical and Research Center, Rozzano, Italy
| | - Laura Lagostena
- Consiglio Nazionale delle Ricerche, Istituto di Biofisica (CNR-IBF), Dulbecco Telethon Laboratory, Genoa, Italy
| | - Dario Strina
- Consiglio Nazionale delle Ricerche-Istituto di Ricerca Genetica e Biomedica (CNR-IRGB), Milan, Italy.,Humanitas Clinical and Research Center, Rozzano, Italy
| | - Asma Rehman
- UMB Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD, USA
| | - Mario Abinun
- Department of Pediatric Immunology, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK.,Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Lien De Somer
- Department of Pediatric Rheumatology, University Hospital Leuven, Leuven, Belgium
| | | | - Justin Brown
- Department of Pediatrics, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Australia.,Department of Pediatric Endocrinology and Diabetes, Monash Children's Hospital, Monash Health, Clayton, Australia
| | | | - Shanti Balasubramaniam
- Department of Metabolic Medicine and Rheumatology, Perth Children's Hospital, Perth, Australia
| | - Gareth Baynam
- Western Australian Register of Developmental Anomalies, King Edward Memorial Hospital, Subiaco, Australia.,Genetic Services of Western Australia, King Edward Memorial Hospital, Perth, Australia.,Telethon Kids Institute and Division of Pediatrics, School of Health and Medical Sciences, University of Western Australia, Perth, Australia.,Faculty of Medicine, Notre Dame University, Fremantle, Australia
| | | | - Maria A Pisanti
- Medical Genetics Unit, "Antonio Cardarelli" Hospital, Naples, Italy
| | - Ilaria De Maggio
- Medical Genetics Unit, "Antonio Cardarelli" Hospital, Naples, Italy
| | - Miguel R Abboud
- Department of Pediatrics and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Robert Chiesa
- Bone Marrow Transplantation Department, Great Ormond Street Hospital for Children, London, UK
| | - Christine P Burren
- Department of Pediatric Endocrinology and Diabetes, Bristol Royal Hospital for Children, University Hospitals Bristol and Weston NHS Foundation Trust, Bristol, UK.,Bristol Medical School, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
| | - Anna Villa
- Consiglio Nazionale delle Ricerche-Istituto di Ricerca Genetica e Biomedica (CNR-IRGB), Milan, Italy.,San Raffaele Telethon Institute for Gene Therapy SR-Tiget, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Cristina Sobacchi
- Consiglio Nazionale delle Ricerche-Istituto di Ricerca Genetica e Biomedica (CNR-IRGB), Milan, Italy.,Humanitas Clinical and Research Center, Rozzano, Italy
| | - Alessandra Picollo
- Consiglio Nazionale delle Ricerche, Istituto di Biofisica (CNR-IBF), Dulbecco Telethon Laboratory, Genoa, Italy
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12
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Brenes O, Barbieri R, Vásquez M, Vindas-Smith R, Roig J, Romero A, del Valle G, Bermúdez-Guzmán L, Bertelli S, Pusch M, Morales F. Functional and Structural Characterization of ClC-1 and Na v1.4 Channels Resulting from CLCN1 and SCN4A Mutations Identified Alone and Coexisting in Myotonic Patients. Cells 2021; 10:cells10020374. [PMID: 33670307 PMCID: PMC7918176 DOI: 10.3390/cells10020374] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 01/13/2021] [Accepted: 01/13/2021] [Indexed: 11/25/2022] Open
Abstract
Non-dystrophic myotonias have been linked to loss-of-function mutations in the ClC-1 chloride channel or gain-of-function mutations in the Nav1.4 sodium channel. Here, we describe a family with members diagnosed with Thomsen’s disease. One novel mutation (p.W322*) in CLCN1 and one undescribed mutation (p.R1463H) in SCN4A are segregating in this family. The CLCN1-p.W322* was also found in an unrelated family, in compound heterozygosity with the known CLCN1-p.G355R mutation. One reported mutation, SCN4A-p.T1313M, was found in a third family. Both CLCN1 mutations exhibited loss-of-function: CLCN1-p.W322* probably leads to a non-viable truncated protein; for CLCN1-p.G355R, we predict structural damage, triggering important steric clashes. The SCN4A-p.R1463H produced a positive shift in the steady-state inactivation increasing window currents and a faster recovery from inactivation. These gain-of-function effects are probably due to a disruption of interaction R1463-D1356, which destabilizes the voltage sensor domain (VSD) IV and increases the flexibility of the S4-S5 linker. Finally, modelling suggested that the p.T1313M induces a strong decrease in protein flexibility on the III-IV linker. This study demonstrates that CLCN1-p.W322* and SCN4A-p.R1463H mutations can act alone or in combination as inducers of myotonia. Their co-segregation highlights the necessity for carrying out deep genetic analysis to provide accurate genetic counseling and management of patients.
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Affiliation(s)
- Oscar Brenes
- Departamento de Fisiología, Escuela de Medicina, Universidad de Costa Rica, 11501 San José, Costa Rica;
- Centro de Investigación en Neurociencias (CIN), Universidad de Costa Rica, 11501 San José, Costa Rica
| | | | - Melissa Vásquez
- Instituto de Investigaciones en Salud (INISA), Universidad de Costa Rica, 11501 San José, Costa Rica; (M.V.); (R.V.-S.); (J.R.)
| | - Rebeca Vindas-Smith
- Instituto de Investigaciones en Salud (INISA), Universidad de Costa Rica, 11501 San José, Costa Rica; (M.V.); (R.V.-S.); (J.R.)
| | - Jeffrey Roig
- Instituto de Investigaciones en Salud (INISA), Universidad de Costa Rica, 11501 San José, Costa Rica; (M.V.); (R.V.-S.); (J.R.)
| | - Adarli Romero
- Escuela de Biología, Universidad de Costa Rica, 11501 San José, Costa Rica;
| | - Gerardo del Valle
- Laboratorio de Neurofisiología (Neurolab), 11801 San José, Costa Rica;
| | - Luis Bermúdez-Guzmán
- Sección de Genética y Biotecnología, Escuela de Biología, Universidad de Costa Rica, 11501 San José, Costa Rica;
| | - Sara Bertelli
- Istituto di Biofisica, CNR, 16149 Genova, Italy; (R.B.); (S.B.)
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
| | - Michael Pusch
- Istituto di Biofisica, CNR, 16149 Genova, Italy; (R.B.); (S.B.)
- Correspondence: (M.P.); (F.M.); Tel.: +39-0106475-553/522 (M.P.); +506-2511-2124 (F.M.)
| | - Fernando Morales
- Instituto de Investigaciones en Salud (INISA), Universidad de Costa Rica, 11501 San José, Costa Rica; (M.V.); (R.V.-S.); (J.R.)
- Correspondence: (M.P.); (F.M.); Tel.: +39-0106475-553/522 (M.P.); +506-2511-2124 (F.M.)
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13
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Desaphy JF, Altamura C, Vicart S, Fontaine B. Targeted Therapies for Skeletal Muscle Ion Channelopathies: Systematic Review and Steps Towards Precision Medicine. J Neuromuscul Dis 2021; 8:357-381. [PMID: 33325393 PMCID: PMC8203248 DOI: 10.3233/jnd-200582] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Skeletal muscle ion channelopathies include non-dystrophic myotonias (NDM), periodic paralyses (PP), congenital myasthenic syndrome, and recently identified congenital myopathies. The treatment of these diseases is mainly symptomatic, aimed at reducing muscle excitability in NDM or modifying triggers of attacks in PP. OBJECTIVE This systematic review collected the evidences regarding effects of pharmacological treatment on muscle ion channelopathies, focusing on the possible link between treatments and genetic background. METHODS We searched databases for randomized clinical trials (RCT) and other human studies reporting pharmacological treatments. Preclinical studies were considered to gain further information regarding mutation-dependent drug effects. All steps were performed by two independent investigators, while two others critically reviewed the entire process. RESULTS For NMD, RCT showed therapeutic benefits of mexiletine and lamotrigine, while other human studies suggest some efficacy of various sodium channel blockers and of the carbonic anhydrase inhibitor (CAI) acetazolamide. Preclinical studies suggest that mutations may alter sensitivity of the channel to sodium channel blockers in vitro, which has been translated to humans in some cases. For hyperkalemic and hypokalemic PP, RCT showed efficacy of the CAI dichlorphenamide in preventing paralysis. However, hypokalemic PP patients carrying sodium channel mutations may have fewer benefits from CAI compared to those carrying calcium channel mutations. Few data are available for treatment of congenital myopathies. CONCLUSIONS These studies provided limited information about the response to treatments of individual mutations or groups of mutations. A major effort is needed to perform human studies for designing a mutation-driven precision medicine in muscle ion channelopathies.
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Affiliation(s)
- Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Savine Vicart
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
| | - Bertrand Fontaine
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
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14
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Altamura C, Desaphy JF, Conte D, De Luca A, Imbrici P. Skeletal muscle ClC-1 chloride channels in health and diseases. Pflugers Arch 2020; 472:961-975. [PMID: 32361781 DOI: 10.1007/s00424-020-02376-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/18/2020] [Accepted: 03/31/2020] [Indexed: 12/14/2022]
Abstract
In 1970, the study of the pathomechanisms underlying myotonia in muscle fibers isolated from myotonic goats highlighted the importance of chloride conductance for skeletal muscle function; 20 years later, the human ClC-1 chloride channel has been cloned; last year, the crystal structure of human protein has been solved. Over the years, the efforts of many researchers led to significant advances in acknowledging the role of ClC-1 in skeletal muscle physiology and the mechanisms through which ClC-1 dysfunctions lead to impaired muscle function. The wide spectrum of pathophysiological conditions associated with modification of ClC-1 activity, either as the primary cause, such as in myotonia congenita, or as a secondary adaptive mechanism in other neuromuscular diseases, supports the idea that ClC-1 is relevant to preserve not only for skeletal muscle excitability, but also for skeletal muscle adaptation to physiological or harmful events. Improving this understanding could open promising avenues toward the development of selective and safe drugs targeting ClC-1, with the aim to restore normal muscle function. This review summarizes the most relevant research on ClC-1 channel physiology, associated diseases, and pharmacology.
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Affiliation(s)
- Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari "Aldo Moro", Bari, Italy
| | - Jean-Francois Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari "Aldo Moro", Bari, Italy
| | - Diana Conte
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy
| | - Annamaria De Luca
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy
| | - Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy.
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15
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Leisle L, Xu Y, Fortea E, Lee S, Galpin JD, Vien M, Ahern CA, Accardi A, Bernèche S. Divergent Cl - and H + pathways underlie transport coupling and gating in CLC exchangers and channels. eLife 2020; 9:e51224. [PMID: 32343228 PMCID: PMC7274781 DOI: 10.7554/elife.51224] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 04/28/2020] [Indexed: 12/12/2022] Open
Abstract
The CLC family comprises H+-coupled exchangers and Cl- channels, and mutations causing their dysfunction lead to genetic disorders. The CLC exchangers, unlike canonical 'ping-pong' antiporters, simultaneously bind and translocate substrates through partially congruent pathways. How ions of opposite charge bypass each other while moving through a shared pathway remains unknown. Here, we use MD simulations, biochemical and electrophysiological measurements to identify two conserved phenylalanine residues that form an aromatic pathway whose dynamic rearrangements enable H+ movement outside the Cl- pore. These residues are important for H+ transport and voltage-dependent gating in the CLC exchangers. The aromatic pathway residues are evolutionarily conserved in CLC channels where their electrostatic properties and conformational flexibility determine gating. We propose that Cl- and H+ move through physically distinct and evolutionarily conserved routes through the CLC channels and transporters and suggest a unifying mechanism that describes the gating mechanism of both CLC subtypes.
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Affiliation(s)
- Lilia Leisle
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Yanyan Xu
- SIB Swiss Institute of Bioinformatics, University of BaselBaselSwitzerland
- Biozentrum, University of BaselBaselSwitzerland
| | - Eva Fortea
- Department of Physiology and Biophysics, Weill Cornell Medical CollegeNew YorkUnited States
| | - Sangyun Lee
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Jason D Galpin
- Department of Molecular Physiology and Biophysics, University of Iowa Carver College of MedicineIowa CityUnited States
| | - Malvin Vien
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa Carver College of MedicineIowa CityUnited States
| | - Alessio Accardi
- Department of Anesthesiology, Weill Cornell Medical CollegeNew YorkUnited States
- Department of Physiology and Biophysics, Weill Cornell Medical CollegeNew YorkUnited States
- Department of Biochemistry, Weill Cornell Medical CollegeNew YorkUnited States
| | - Simon Bernèche
- SIB Swiss Institute of Bioinformatics, University of BaselBaselSwitzerland
- Biozentrum, University of BaselBaselSwitzerland
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16
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Chavan TS, Cheng RC, Jiang T, Mathews II, Stein RA, Koehl A, Mchaourab HS, Tajkhorshid E, Maduke M. A CLC-ec1 mutant reveals global conformational change and suggests a unifying mechanism for the CLC Cl -/H + transport cycle. eLife 2020; 9:53479. [PMID: 32310757 PMCID: PMC7253180 DOI: 10.7554/elife.53479] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 04/18/2020] [Indexed: 12/16/2022] Open
Abstract
Among coupled exchangers, CLCs uniquely catalyze the exchange of oppositely charged ions (Cl– for H+). Transport-cycle models to describe and explain this unusual mechanism have been proposed based on known CLC structures. While the proposed models harmonize with many experimental findings, gaps and inconsistencies in our understanding have remained. One limitation has been that global conformational change – which occurs in all conventional transporter mechanisms – has not been observed in any high-resolution structure. Here, we describe the 2.6 Å structure of a CLC mutant designed to mimic the fully H+-loaded transporter. This structure reveals a global conformational change to improve accessibility for the Cl– substrate from the extracellular side and new conformations for two key glutamate residues. Together with DEER measurements, MD simulations, and functional studies, this new structure provides evidence for a unified model of H+/Cl– transport that reconciles existing data on all CLC-type proteins. Cells are shielded from harmful molecules and other threats by a thin, flexible layer called the membrane. However, this barrier also prevents chloride, sodium, protons and other ions from moving in or out of the cell. Channels and transporters are two types of membrane proteins that form passageways for these charged particles. Channels let ions flow freely from one side of the membrane to the other. To do so, these proteins change their three-dimensional shape to open or close as needed. On the other hand, transporters actively pump ions across the membrane to allow the charged particles to accumulate on one side. The shape changes needed for that type of movement are different: the transporters have to open a passageway on one side of the membrane while closing it on the other side, alternating openings to one side or the other. In general, channels and transporters are not related to each other, but one exception is a group called CLCs proteins. Present in many organisms, this family contains a mixture of channels and transporters. For example, humans have nine CLC proteins: four are channels that allow chloride ions in and out, and five are ‘exchange transporters’ that make protons and chloride ions cross the membrane in opposite directions. These proteins let one type of charged particle move freely across the membrane, which generates energy that the transporter then uses to actively pump the other ion in the direction needed by the cell. Yet, the exact three-dimensional changes required for CLC transporters and channels to perform their roles are still unknown. To investigate this question, Chavan, Cheng et al. harnessed a technique called X-ray crystallography, which allows scientists to look at biological molecules at the level of the atom. This was paired with other methods to examine a CLC mutant that adopts the shape of a normal CLC transporter when it is loaded with a proton. The experiments revealed how various elements in the transporter move relative to each other to adopt a structure that allows protons and chloride ions to enter the protein from opposite sides of the membrane, using separate pathways. While obtained on a bacterial CLC, these results can be applied to other CLC channels and transporters (including those in humans), shedding light on how this family transports charged particles across membranes. From bone diseases to certain types of seizures, many human conditions are associated with poorly functioning CLCs. Understanding the way these structures change their shapes to perform their roles could help to design new therapies for these health problems.
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Affiliation(s)
- Tanmay S Chavan
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, United States
| | - Ricky C Cheng
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, United States
| | - Tao Jiang
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, United States
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, United States
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States
| | - Antoine Koehl
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, United States
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, United States
| | - Merritt Maduke
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, United States
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17
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McKiernan KA, Koster AK, Maduke M, Pande VS. Dynamical model of the CLC-2 ion channel reveals conformational changes associated with selectivity-filter gating. PLoS Comput Biol 2020; 16:e1007530. [PMID: 32226009 PMCID: PMC7145265 DOI: 10.1371/journal.pcbi.1007530] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 04/09/2020] [Accepted: 11/05/2019] [Indexed: 12/18/2022] Open
Abstract
This work reports a dynamical Markov state model of CLC-2 "fast" (pore) gating, based on 600 microseconds of molecular dynamics (MD) simulation. In the starting conformation of our CLC-2 model, both outer and inner channel gates are closed. The first conformational change in our dataset involves rotation of the inner-gate backbone along residues S168-G169-I170. This change is strikingly similar to that observed in the cryo-EM structure of the bovine CLC-K channel, though the volume of the intracellular (inner) region of the ion conduction pathway is further expanded in our model. From this state (inner gate open and outer gate closed), two additional states are observed, each involving a unique rotameric flip of the outer-gate residue GLUex. Both additional states involve conformational changes that orient GLUex away from the extracellular (outer) region of the ion conduction pathway. In the first additional state, the rotameric flip of GLUex results in an open, or near-open, channel pore. The equilibrium population of this state is low (∼1%), consistent with the low open probability of CLC-2 observed experimentally in the absence of a membrane potential stimulus (0 mV). In the second additional state, GLUex rotates to occlude the channel pore. This state, which has a low equilibrium population (∼1%), is only accessible when GLUex is protonated. Together, these pathways model the opening of both an inner and outer gate within the CLC-2 selectivity filter, as a function of GLUex protonation. Collectively, our findings are consistent with published experimental analyses of CLC-2 gating and provide a high-resolution structural model to guide future investigations.
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Affiliation(s)
- Keri A. McKiernan
- Department of Chemistry, Stanford University, Stanford, California, United States of America
| | - Anna K. Koster
- Department of Chemistry, Stanford University, Stanford, California, United States of America
- Department of Molecular & Cellular Physiology, Stanford University, Stanford, California, United States of America
| | - Merritt Maduke
- Department of Molecular & Cellular Physiology, Stanford University, Stanford, California, United States of America
| | - Vijay S. Pande
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
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18
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Morales F, Pusch M. An Up-to-Date Overview of the Complexity of Genotype-Phenotype Relationships in Myotonic Channelopathies. Front Neurol 2020; 10:1404. [PMID: 32010054 PMCID: PMC6978732 DOI: 10.3389/fneur.2019.01404] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/23/2019] [Indexed: 12/11/2022] Open
Abstract
Myotonic disorders are inherited neuromuscular diseases divided into dystrophic myotonias and non-dystrophic myotonias (NDM). The latter is a group of dominant or recessive diseases caused by mutations in genes encoding ion channels that participate in the generation and control of the skeletal muscle action potential. Their altered function causes hyperexcitability of the muscle membrane, thereby triggering myotonia, the main sign in NDM. Mutations in the genes encoding voltage-gated Cl− and Na+ channels (respectively, CLCN1 and SCN4A) produce a wide spectrum of phenotypes, which differ in age of onset, affected muscles, severity of myotonia, degree of hypertrophy, and muscle weakness, disease progression, among others. More than 200 CLCN1 and 65 SCN4A mutations have been identified and described, but just about half of them have been functionally characterized, an approach that is likely extremely helpful to contribute to improving the so-far rather poor clinical correlations present in NDM. The observed poor correlations may be due to: (1) the wide spectrum of symptoms and overlapping phenotypes present in both groups (Cl− and Na+ myotonic channelopathies) and (2) both genes present high genotypic variability. On the one hand, several mutations cause a unique and reproducible phenotype in most patients. On the other hand, some mutations can have different inheritance pattern and clinical phenotypes in different families. Conversely, different mutations can be translated into very similar phenotypes. For these reasons, the genotype-phenotype relationships in myotonic channelopathies are considered complex. Although the molecular bases for the clinical variability present in myotonic channelopathies remain obscure, several hypotheses have been put forward to explain the variability, which include: (a) differential allelic expression; (b) trans-acting genetic modifiers; (c) epigenetic, hormonal, or environmental factors; and (d) dominance with low penetrance. Improvements in clinical tests, the recognition of the different phenotypes that result from particular mutations and the understanding of how a mutation affects the structure and function of the ion channel, together with genetic screening, is expected to improve clinical correlation in NDMs.
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Affiliation(s)
- Fernando Morales
- Instituto de Investigaciones en Salud, Universidad de Costa, San José, Costa Rica
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19
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Bignon Y, Sakhi I, Bitam S, Bakouh N, Keck M, Frachon N, Paulais M, Planelles G, Teulon J, Andrini O. Analysis of CLCNKB mutations at dimer-interface, calcium-binding site, and pore reveals a variety of functional alterations in ClC-Kb channel leading to Bartter syndrome. Hum Mutat 2019; 41:774-785. [PMID: 31803959 DOI: 10.1002/humu.23962] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 11/14/2019] [Accepted: 11/29/2019] [Indexed: 12/12/2022]
Abstract
Pathological missense mutations in CLCNKB gene give a wide spectrum of clinical phenotypes in Bartter syndrome type III patients. Molecular analysis of the mutated ClC-Kb channels can be helpful to classify the mutations according to their functional alteration. We investigated the functional consequences of nine mutations in the CLCNKB gene causing Bartter syndrome. We first established that all tested mutations lead to decreased ClC-Kb currents. Combining electrophysiological and biochemical methods in Xenopus laevis oocytes and in MDCKII cells, we identified three classes of mutations. One class is characterized by altered channel trafficking. p.A210V, p.P216L, p.G424R, and p.G437R are totally or partially retained in the endoplasmic reticulum. p.S218N is characterized by reduced channel insertion at the plasma membrane and altered pH-sensitivity; thus, it falls in the second class of mutations. Finally, we found a novel class of functionally inactivated mutants normally present at the plasma membrane. Indeed, we found that p.A204T alters the pH-sensitivity, p.A254V abolishes the calcium-sensitivity. p.G219C and p.G465R are probably partially inactive at the plasma membrane. In conclusion, most pathogenic mutants accumulate partly or totally in intracellular compartments, but some mutants are normally present at the membrane surface and simultaneously show a large range of altered channel gating properties.
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Affiliation(s)
- Yohan Bignon
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | - Imene Sakhi
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | - Sara Bitam
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | - Naziha Bakouh
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | - Mathilde Keck
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | | | - Marc Paulais
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | - Gabrielle Planelles
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | - Jacques Teulon
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Laboratoire Physiologie Rénale et Tubulopathies, Paris, France.,CNRS ERL8228, Paris, France
| | - Olga Andrini
- Institut NeuroMyoGène, Univ Lyon, Université Claude Bernard Lyon 1, Lyon, France
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20
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Wang K, Preisler SS, Zhang L, Cui Y, Missel JW, Grønberg C, Gotfryd K, Lindahl E, Andersson M, Calloe K, Egea PF, Klaerke DA, Pusch M, Pedersen PA, Zhou ZH, Gourdon P. Structure of the human ClC-1 chloride channel. PLoS Biol 2019; 17:e3000218. [PMID: 31022181 PMCID: PMC6483157 DOI: 10.1371/journal.pbio.3000218] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 03/22/2019] [Indexed: 11/18/2022] Open
Abstract
ClC-1 protein channels facilitate rapid passage of chloride ions across cellular membranes, thereby orchestrating skeletal muscle excitability. Malfunction of ClC-1 is associated with myotonia congenita, a disease impairing muscle relaxation. Here, we present the cryo-electron microscopy (cryo-EM) structure of human ClC-1, uncovering an architecture reminiscent of that of bovine ClC-K and CLC transporters. The chloride conducting pathway exhibits distinct features, including a central glutamate residue ("fast gate") known to confer voltage-dependence (a mechanistic feature not present in ClC-K), linked to a somewhat rearranged central tyrosine and a narrower aperture of the pore toward the extracellular vestibule. These characteristics agree with the lower chloride flux of ClC-1 compared with ClC-K and enable us to propose a model for chloride passage in voltage-dependent CLC channels. Comparison of structures derived from protein studied in different experimental conditions supports the notion that pH and adenine nucleotides regulate ClC-1 through interactions between the so-called cystathionine-β-synthase (CBS) domains and the intracellular vestibule ("slow gating"). The structure also provides a framework for analysis of mutations causing myotonia congenita and reveals a striking correlation between mutated residues and the phenotypic effect on voltage gating, opening avenues for rational design of therapies against ClC-1-related diseases.
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Affiliation(s)
- Kaituo Wang
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Microbiology, Immunology & Molecular Genetics, University of California at Los Angeles, Los Angeles, California
- California NanoSystems Institute, University of California at Los Angeles, Los Angeles, California
| | | | - Liying Zhang
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Yanxiang Cui
- Department of Microbiology, Immunology & Molecular Genetics, University of California at Los Angeles, Los Angeles, California
- California NanoSystems Institute, University of California at Los Angeles, Los Angeles, California
| | - Julie Winkel Missel
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Christina Grønberg
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kamil Gotfryd
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Erik Lindahl
- Department of Biochemistry & Biophysics, Stockholm University, Stockholm, Sweden
| | | | - Kirstine Calloe
- Department of Veterinary and Animal Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Pascal F. Egea
- Department of Biological Chemistry, University of California at Los Angeles, Los Angeles, California
| | - Dan Arne Klaerke
- Department of Veterinary and Animal Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Michael Pusch
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | | | - Z. Hong Zhou
- Department of Microbiology, Immunology & Molecular Genetics, University of California at Los Angeles, Los Angeles, California
- California NanoSystems Institute, University of California at Los Angeles, Los Angeles, California
| | - Pontus Gourdon
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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21
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Teulon J, Planelles G, Sepúlveda FV, Andrini O, Lourdel S, Paulais M. Renal Chloride Channels in Relation to Sodium Chloride Transport. Compr Physiol 2018; 9:301-342. [DOI: 10.1002/cphy.c180024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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22
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Kasimova MA, Lindahl E, Delemotte L. Determining the molecular basis of voltage sensitivity in membrane proteins. J Gen Physiol 2018; 150:1444-1458. [PMID: 30150239 PMCID: PMC6168238 DOI: 10.1085/jgp.201812086] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 08/07/2018] [Indexed: 12/31/2022] Open
Abstract
The identification of voltage-sensing elements in membrane proteins is challenging due to the diversity of voltage-sensing mechanisms. Kasimova et al. present a computational approach to predict the elements involved in voltage sensing, which they validate using voltage-gated ion channels. Voltage-sensitive membrane proteins are united by their ability to transform changes in membrane potential into mechanical work. They are responsible for a spectrum of physiological processes in living organisms, including electrical signaling and cell-cycle progression. Although the mechanism of voltage-sensing has been well characterized for some membrane proteins, including voltage-gated ion channels, even the location of the voltage-sensing elements remains unknown for others. Moreover, the detection of these elements by using experimental techniques is challenging because of the diversity of membrane proteins. Here, we provide a computational approach to predict voltage-sensing elements in any membrane protein, independent of its structure or function. It relies on an estimation of the propensity of a protein to respond to changes in membrane potential. We first show that this property correlates well with voltage sensitivity by applying our approach to a set of voltage-sensitive and voltage-insensitive membrane proteins. We further show that it correctly identifies authentic voltage-sensitive residues in the voltage-sensor domain of voltage-gated ion channels. Finally, we investigate six membrane proteins for which the voltage-sensing elements have not yet been characterized and identify residues and ions that might be involved in the response to voltage. The suggested approach is fast and simple and enables a characterization of voltage sensitivity that goes beyond mere identification of charges. We anticipate that its application before mutagenesis experiments will significantly reduce the number of potential voltage-sensitive elements to be tested.
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Affiliation(s)
- Marina A Kasimova
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Erik Lindahl
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden.,Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Lucie Delemotte
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, Stockholm, Sweden
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23
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Jentsch TJ, Pusch M. CLC Chloride Channels and Transporters: Structure, Function, Physiology, and Disease. Physiol Rev 2018; 98:1493-1590. [DOI: 10.1152/physrev.00047.2017] [Citation(s) in RCA: 214] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion translocation parthway, assemble to homo- or heteromeric dimers that sometimes require accessory β-subunits for function. CLC proteins come in two flavors: anion channels and anion/proton exchangers. Structures of these two CLC protein classes are surprisingly similar. Extensive structure-function analysis identified residues involved in ion permeation, anion-proton coupling and gating and led to attractive biophysical models. In mammals, ClC-1, -2, -Ka/-Kb are plasma membrane Cl−channels, whereas ClC-3 through ClC-7 are 2Cl−/H+-exchangers in endolysosomal membranes. Biological roles of CLCs were mostly studied in mammals, but also in plants and model organisms like yeast and Caenorhabditis elegans. CLC Cl−channels have roles in the control of electrical excitability, extra- and intracellular ion homeostasis, and transepithelial transport, whereas anion/proton exchangers influence vesicular ion composition and impinge on endocytosis and lysosomal function. The surprisingly diverse roles of CLCs are highlighted by human and mouse disorders elicited by mutations in their genes. These pathologies include neurodegeneration, leukodystrophy, mental retardation, deafness, blindness, myotonia, hyperaldosteronism, renal salt loss, proteinuria, kidney stones, male infertility, and osteopetrosis. In this review, emphasis is laid on biophysical structure-function analysis and on the cell biological and organismal roles of mammalian CLCs and their role in disease.
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Affiliation(s)
- Thomas J. Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Michael Pusch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
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24
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Altamura C, Mangiatordi GF, Nicolotti O, Sahbani D, Farinato A, Leonetti F, Carratù MR, Conte D, Desaphy JF, Imbrici P. Mapping ligand binding pockets in chloride ClC-1 channels through an integrated in silico and experimental approach using anthracene-9-carboxylic acid and niflumic acid. Br J Pharmacol 2018; 175:1770-1780. [PMID: 29500929 DOI: 10.1111/bph.14192] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 02/19/2018] [Accepted: 02/23/2018] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Although chloride channels are involved in several physiological processes and acquired diseases, the availability of compounds selectively targeting CLC proteins is limited. ClC-1 channels are responsible for sarcolemma repolarization after an action potential in skeletal muscle and have been associated with myotonia congenita and myotonic dystrophy as well as with other muscular physiopathological conditions. To date only a few ClC-1 blockers have been discovered, such as anthracene-9-carboxylic acid (9-AC) and niflumic acid (NFA), whereas no activator exists. The absence of a ClC-1 structure and the limited information regarding the binding pockets in CLC channels hamper the identification of improved modulators. EXPERIMENTAL APPROACH Here we provide an in-depth characterization of drug binding pockets in ClC-1 through an integrated in silico and experimental approach. We first searched putative cavities in a homology model of ClC-1 built upon an eukaryotic CLC crystal structure, and then validated in silico data by measuring the blocking ability of 9-AC and NFA on mutant ClC-1 channels expressed in HEK 293 cells. KEY RESULTS We identified four putative binding cavities in ClC-1. 9-AC appears to interact with residues K231, R421 and F484 within the channel pore. We also identified one preferential binding cavity for NFA and propose R421 and F484 as critical residues. CONCLUSIONS AND IMPLICATIONS This study represents the first effort to delineate the binding sites of ClC-1. This information is fundamental to discover compounds useful in the treatment of ClC-1-associated dysfunctions and might represent a starting point for specifically targeting other CLC proteins.
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Affiliation(s)
- C Altamura
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
| | - G F Mangiatordi
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
| | - O Nicolotti
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
| | - D Sahbani
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
| | - A Farinato
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
| | - F Leonetti
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
| | - M R Carratù
- Department of Biomedical Sciences and Human Oncology, University of Bari 'Aldo Moro', Bari, Italy
| | - D Conte
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
| | - J-F Desaphy
- Department of Biomedical Sciences and Human Oncology, University of Bari 'Aldo Moro', Bari, Italy
| | - P Imbrici
- Department of Pharmacy - Drug Sciences, University of Bari 'Aldo Moro', Bari, Italy
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25
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Wang CH, Duster AW, Aydintug BO, Zarecki MG, Lin H. Chloride Ion Transport by the E. coli CLC Cl -/H + Antiporter: A Combined Quantum-Mechanical and Molecular-Mechanical Study. Front Chem 2018; 6:62. [PMID: 29594103 PMCID: PMC5859129 DOI: 10.3389/fchem.2018.00062] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 02/26/2018] [Indexed: 01/05/2023] Open
Abstract
We performed steered molecular dynamics (SMD) and umbrella sampling simulations of Cl- ion migration through the transmembrane domain of a prototypical E. coli CLC Cl-/H+ antiporter by employing combined quantum-mechanical (QM) and molecular-mechanical (MM) calculations. The SMD simulations revealed interesting conformational changes of the protein. While no large-amplitude motions of the protein were observed during pore opening, the side chain rotation of the protonated external gating residue Glu148 was found to be critical for full access of the channel entrance by Cl-. Moving the anion into the external binding site (Sext) induced small-amplitude shifting of the protein backbone at the N-terminal end of helix F. As Cl- traveled through the pore, rigid-body swinging motions of helix R separated it from helix D. Helix R returned to its original position once Cl- exited the channel. Population analysis based on polarized wavefunction from QM/MM calculations discovered significant (up to 20%) charge loss for Cl- along the ion translocation pathway inside the pore. The delocalized charge was redistributed onto the pore residues, especially the functional groups containing π bonds (e.g., the Tyr445 side chain), while the charges of the H atoms coordinating Cl- changed almost negligibly. Potentials of mean force computed from umbrella sampling at the QM/MM and MM levels both displayed barriers at the same locations near the pore entrance and exit. However, the QM/MM PMF showed higher barriers (~10 kcal/mol) than the MM PMF (~2 kcal/mol). Binding energy calculations indicated that the interactions between Cl- and certain pore residues were overestimated by the semi-empirical PM3 Hamiltonian and underestimated by the CHARMM36 force fields, both of which were employed in the umbrella sampling simulations. In particular, CHARMM36 underestimated binding interactions for the functional groups containing π bonds, missing the stabilizations of the Cl- ion due to electron delocalization. The results suggested that it is important to explore these quantum effects for accurate descriptions of the Cl- transport.
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Affiliation(s)
- Chun-Hung Wang
- Department of Chemistry, University of Colorado Denver, Denver, CO, United States
| | - Adam W Duster
- Department of Chemistry, University of Colorado Denver, Denver, CO, United States
| | - Baris O Aydintug
- Department of Chemistry, University of Colorado Denver, Denver, CO, United States
| | - MacKenzie G Zarecki
- Department of Chemistry, University of Colorado Denver, Denver, CO, United States
| | - Hai Lin
- Department of Chemistry, University of Colorado Denver, Denver, CO, United States
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26
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Gaitán-Peñas H, Apaja PM, Arnedo T, Castellanos A, Elorza-Vidal X, Soto D, Gasull X, Lukacs GL, Estévez R. Leukoencephalopathy-causing CLCN2 mutations are associated with impaired Cl - channel function and trafficking. J Physiol 2017; 595:6993-7008. [PMID: 28905383 DOI: 10.1113/jp275087] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 09/11/2017] [Indexed: 01/30/2023] Open
Abstract
KEY POINTS Characterisation of most mutations found in CLCN2 in patients with CC2L leukodystrophy show that they cause a reduction in function of the chloride channel ClC-2. GlialCAM, a regulatory subunit of ClC-2 in glial cells and involved in the leukodystrophy megalencephalic leukoencephalopathy with subcortical cysts (MLC), increases the activity of a ClC-2 mutant by affecting ClC-2 gating and by stabilising the mutant at the plasma membrane. The stabilisation of ClC-2 at the plasma membrane by GlialCAM depends on its localisation at cell-cell junctions. The membrane protein MLC1, which is defective in MLC, also contributes to the stabilisation of ClC-2 at the plasma membrane, providing further support for the view that GlialCAM, MLC1 and ClC-2 form a protein complex in glial cells. ABSTRACT Mutations in CLCN2 have been recently identified in patients suffering from a type of leukoencephalopathy involving intramyelinic oedema. Here, we characterised most of these mutations that reduce the function of the chloride channel ClC-2 and impair its plasma membrane (PM) expression. Detailed biochemical and electrophysiological analyses of the Ala500Val mutation revealed that defective gating and increased cellular and PM turnover contributed to defective A500V-ClC-2 functional expression. Co-expression of the adhesion molecule GlialCAM, which forms a tertiary complex with ClC-2 and megalencephalic leukoencephalopathy with subcortical cysts 1 (MLC1), rescued the functional expression of the mutant by modifying its gating properties. GlialCAM also restored the PM levels of the channel by impeding its turnover at the PM. This rescue required ClC-2 localisation to cell-cell junctions, since a GlialCAM mutant with compromised junctional localisation failed to rescue the impaired stability of mutant ClC-2 at the PM. Wild-type, but not mutant, ClC-2 was also stabilised by MLC1 overexpression. We suggest that leukodystrophy-causing CLCN2 mutations reduce the functional expression of ClC-2, which is partly counteracted by GlialCAM/MLC1-mediated increase in the gating and stability of the channel.
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Affiliation(s)
- Héctor Gaitán-Peñas
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
| | - Pirjo M Apaja
- Department of Physiology, McGill University, Montréal, Quebec, H3E 1Y6, Canada.,Research Group Focused on Protein Structure, McGill University, Montréal, Quebec, H3E 1Y6, Canada.,South Australian Health and Medical Research Institute, Nutrition and Metabolism Theme and EMBL Australia, 5000, Adelaide, Australia
| | - Tanit Arnedo
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
| | - Aida Castellanos
- Neurophysiology Laboratory, Physiology Unit, Department of Biomedicine, Medical School, Institute of Neurosciences, IDIBAPS, University of Barcelona, Barcelona, Spain
| | - Xabier Elorza-Vidal
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
| | - David Soto
- Neurophysiology Laboratory, Physiology Unit, Department of Biomedicine, Medical School, Institute of Neurosciences, IDIBAPS, University of Barcelona, Barcelona, Spain
| | - Xavier Gasull
- Neurophysiology Laboratory, Physiology Unit, Department of Biomedicine, Medical School, Institute of Neurosciences, IDIBAPS, University of Barcelona, Barcelona, Spain
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Montréal, Quebec, H3E 1Y6, Canada.,Research Group Focused on Protein Structure, McGill University, Montréal, Quebec, H3E 1Y6, Canada
| | - Raúl Estévez
- Unitat de Fisiología, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Spain
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27
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Skov M, de Paoli FV, Nielsen OB, Pedersen TH. The anti-convulsants lacosamide, lamotrigine, and rufinamide reduce myotonia in isolated human and rat skeletal muscle. Muscle Nerve 2017; 56:136-142. [PMID: 27783415 DOI: 10.1002/mus.25452] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Revised: 10/14/2016] [Accepted: 10/19/2016] [Indexed: 11/11/2022]
Abstract
INTRODUCTION In myotonia congenita, loss of ClC-1 Cl- channel function results in skeletal muscle hyperexcitability and myotonia. Anti-myotonic treatment has typically targeted the voltage-gated sodium channel in skeletal muscle (Nav1.4). In this study we explored whether 3 sodium channel-modulating anti-epileptics can reduce myotonia in isolated rat and human muscle. METHODS Dissected muscles were rendered myotonic by ClC-1 channel inhibition. The ability of the drugs to suppress myotonia was then assessed from subclinical to maximal clinical concentrations. Drug synergy was determined using isobole plots. RESULTS All drugs were capable of abolishing myotonia in both rat and human muscles. Lamotrigine and rufinamide completely suppressed myotonia at submaximal clinical concentrations, whereas lacosamide had to be raised above the maximal clinical concentration to suppress myotonia completely. A synergistic effect of lamotrigine and rufinamide was observed. CONCLUSION These findings suggest that lamotrigine and rufinamide could be considered for anti-myotonic treatment in myotonia congenita. Muscle Nerve 56: 136-142, 2017.
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Affiliation(s)
- Martin Skov
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark
| | - Frank V de Paoli
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark.,Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital Skejby, Aarhus, Denmark
| | - Ole B Nielsen
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark
| | - Thomas H Pedersen
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000, Aarhus C, Denmark
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28
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Structure of a CLC chloride ion channel by cryo-electron microscopy. Nature 2016; 541:500-505. [PMID: 28002411 PMCID: PMC5576512 DOI: 10.1038/nature20812] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 11/18/2016] [Indexed: 12/18/2022]
Abstract
CLC proteins transport chloride (Cl-) ions across cellular membranes to regulate muscle excitability, electrolyte movement across epithelia, and acidification of intracellular organelles. Some CLC proteins are channels that conduct Cl- ions passively, whereas others are secondary active transporters that exchange two Cl- ions for one H+. The structural basis underlying these distinctive transport mechanisms is puzzling because CLC channels and transporters are expected to share the same architecture on the basis of sequence homology. Here we determined the structure of a bovine CLC channel (CLC-K) using cryo-electron microscopy. A conserved loop in the Cl- transport pathway shows a structure markedly different from that of CLC transporters. Consequently, the cytosolic constriction for Cl- passage is widened in CLC-K such that the kinetic barrier previously postulated for Cl-/H+ transporter function would be reduced. Thus, reduction of a kinetic barrier in CLC channels enables fast flow of Cl- down its electrochemical gradient.
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Seong JY, Ha K, Hong C, Myeong J, Lim HH, Yang D, So I. Helix O modulates voltage dependency of CLC-1. Pflugers Arch 2016; 469:183-193. [PMID: 27921211 DOI: 10.1007/s00424-016-1907-5] [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: 09/13/2016] [Revised: 10/14/2016] [Accepted: 11/14/2016] [Indexed: 11/25/2022]
Abstract
The chloride channel (CLC) family of proteins consists of channels and transporters that share similarities in architecture and play essential roles in physiological functions. Among the CLC family, CLC-1 channels have the representative homodimeric double-barreled structure carrying two gating processes. One is protopore gating that acts on each pore independently by glutamate residue (Eext). The other is common gating that closes both pores simultaneously in association with large conformational changes across each subunit. In skeletal muscle, CLC-1 is associated with maintaining normal sarcolemmal excitability, and a number of myotonic mutants were reported to modify the channel gating of CLC-1. In this study, we characterized highly conserved helix O as a key determinant of structural stability in CLC-1. Supporting this hypothesis, myotonic mutant (G523D) at N-terminal of helix O showed the activation at hyperpolarizing membrane potentials with a reversed voltage dependency. However, introducing glutamate at serine residue (S537) at the C-terminal of the helix O on G523D restored WT-like voltage dependency of the common gate and showed proton insensitive voltage dependency. To further validate this significant site, site-specific mutagenesis experiments was performed on V292 that is highly conserved as glutamate in antiporter and closely located to S537 and showed that this area is essential for channel function. Taken together, the results of our study suggest the importance of helix O as the main contributor for stable structure of evolutionary conserved CLC proteins and its key role in voltage dependency of the CLC-1. Furthermore, the C-terminal of the helix O can offer a clue for possible proton involvement in CLC-1 channel.
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Affiliation(s)
- Ju Yong Seong
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Kotdaji Ha
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Chansik Hong
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Jongyun Myeong
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Hyun-Ho Lim
- Korea Brain Research Institute (KBRI), Daegu, 41068, Republic of Korea
| | - Dongki Yang
- Department of Physiology, College of Medicine, Gachon University, Incheon, 461-701, Republic of Korea
| | - Insuk So
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea.
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30
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Harasztosi C, Gummer AW. The chloride-channel blocker 9-anthracenecarboxylic acid reduces the nonlinear capacitance of prestin-associated charge movement. Eur J Neurosci 2016; 43:1062-74. [PMID: 26869218 PMCID: PMC5111741 DOI: 10.1111/ejn.13209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 02/09/2016] [Accepted: 02/09/2016] [Indexed: 02/01/2023]
Abstract
The basis of the extraordinary sensitivity and frequency selectivity of the cochlea is a chloride-sensitive protein called prestin which can produce an electromechanical response and which resides in the basolateral plasma membrane of outer hair cells (OHCs). The compound 9-anthracenecarboxylic acid (9-AC), an inhibitor of chloride channels, has been found to reduce the electromechanical response of the cochlea and the OHC mechanical impedance. To elucidate these 9-AC effects, the functional electromechanical status of prestin was assayed by measuring the nonlinear capacitance of OHCs from the guinea-pig cochlea and of prestin-transfected human embryonic kidney 293 (HEK 293) cells. Extracellular application of 9-AC caused reversible, dose-dependent and chloride-sensitive reduction in OHC nonlinear charge transfer, Qmax . Prestin-transfected cells also showed reversible reduction in Qmax . For OHCs, intracellular 9-AC application as well as reduced intracellular pH had no detectable effect on the reduction in Qmax by extracellularly applied 9-AC. In the prestin-transfected cells, cytosolic application of 9-AC approximately halved the blocking efficacy of extracellularly applied 9-AC. OHC inside-out patches presented the whole-cell blocking characteristics. Disruption of the cytoskeleton by preventing actin polymerization with latrunculin A or by decoupling of spectrin from actin with diamide did not affect the 9-AC-evoked reduction in Qmax . We conclude that 9-AC acts on the electromechanical transducer principally by interaction with prestin rather than acting via the cytoskeleton, chloride channels or pH. The 9-AC block presents characteristics in common with salicylate, but is almost an order of magnitude faster. 9-AC provides a new tool for elucidating the molecular dynamics of prestin function.
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Affiliation(s)
- Csaba Harasztosi
- Section of Physiological Acoustics and Communication, Faculty of Medicine, Eberhard Karls University Tübingen, 72076, Tübingen, Germany
| | - Anthony W Gummer
- Section of Physiological Acoustics and Communication, Faculty of Medicine, Eberhard Karls University Tübingen, 72076, Tübingen, Germany
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31
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Ta CM, Adomaviciene A, Rorsman NJG, Garnett H, Tammaro P. Mechanism of allosteric activation of TMEM16A/ANO1 channels by a commonly used chloride channel blocker. Br J Pharmacol 2016; 173:511-28. [PMID: 26562072 PMCID: PMC4728427 DOI: 10.1111/bph.13381] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 09/15/2015] [Accepted: 10/29/2015] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE Calcium-activated chloride channels (CaCCs) play varied physiological roles and constitute potential therapeutic targets for conditions such as asthma and hypertension. TMEM16A encodes a CaCC. CaCC pharmacology is restricted to compounds with relatively low potency and poorly defined selectivity. Anthracene-9-carboxylic acid (A9C), an inhibitor of various chloride channel types, exhibits complex effects on native CaCCs and cloned TMEM16A channels providing both activation and inhibition. The mechanisms underlying these effects are not fully defined. EXPERIMENTAL APPROACH Patch-clamp electrophysiology in conjunction with concentration jump experiments was employed to define the mode of interaction of A9C with TMEM16A channels. KEY RESULTS In the presence of high intracellular Ca(2+) , A9C inhibited TMEM16A currents in a voltage-dependent manner by entering the channel from the outside. A9C activation, revealed in the presence of submaximal intracellular Ca(2+) concentrations, was also voltage-dependent. The electric distance of A9C inhibiting and activating binding site was ~0.6 in each case. Inhibition occurred according to an open-channel block mechanism. Activation was due to a dramatic leftward shift in the steady-state activation curve and slowed deactivation kinetics. Extracellular A9C competed with extracellular Cl(-) , suggesting that A9C binds deep in the channel's pore to exert both inhibiting and activating effects. CONCLUSIONS AND IMPLICATIONS A9C is an open TMEM16A channel blocker and gating modifier. These effects require A9C to bind to a region within the pore that is accessible from the extracellular side of the membrane. These data will aid the future drug design of compounds that selectively activate or inhibit TMEM16A channels.
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Affiliation(s)
- Chau M Ta
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Aiste Adomaviciene
- Department of Pharmacology, University of Oxford, Oxford, UK.,Faculty of Life Sciences, The University of Manchester, Manchester, UK
| | - Nils J G Rorsman
- Department of Pharmacology, University of Oxford, Oxford, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK
| | - Hannah Garnett
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Paolo Tammaro
- Department of Pharmacology, University of Oxford, Oxford, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK
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Vindas-Smith R, Fiore M, Vásquez M, Cuenca P, del Valle G, Lagostena L, Gaitán-Peñas H, Estevez R, Pusch M, Morales F. Identification and Functional Characterization ofCLCN1Mutations Found in Nondystrophic Myotonia Patients. Hum Mutat 2015; 37:74-83. [DOI: 10.1002/humu.22916] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 09/25/2015] [Indexed: 10/22/2022]
Affiliation(s)
- Rebeca Vindas-Smith
- Instituto de Investigaciones en Salud (INISA); Universidad de Costa Rica; San José Costa Rica
| | - Michele Fiore
- Istituto di Biofisica; CNR; Via De Marini 6 Genova Italy
| | - Melissa Vásquez
- Instituto de Investigaciones en Salud (INISA); Universidad de Costa Rica; San José Costa Rica
- Centro de Investigación en Neurociencias (CIN); Universidad de Costa Rica; San José Costa Rica
| | - Patricia Cuenca
- Instituto de Investigaciones en Salud (INISA); Universidad de Costa Rica; San José Costa Rica
- Centro de Investigación en Neurociencias (CIN); Universidad de Costa Rica; San José Costa Rica
- Escuela de Medicina; Universidad de Costa Rica; Curridabat San José Costa Rica
| | - Gerardo del Valle
- Laboratorio de Neurofisiología (Neurolab); Curridabat San José Costa Rica
| | | | - Héctor Gaitán-Peñas
- Departament de Ciències Fisiològiques II; Unitat de Fisiologia; Universitat de Barcelona; Carrer Feixa Llarga s/n, L'Hospitalet de Llobregat Barcelona Spain
- U-750, Centro de Investigación en red de enfermedades raras (CIBERER); ISCIII; Barcelona Spain
| | - Raúl Estevez
- Departament de Ciències Fisiològiques II; Unitat de Fisiologia; Universitat de Barcelona; Carrer Feixa Llarga s/n, L'Hospitalet de Llobregat Barcelona Spain
- U-750, Centro de Investigación en red de enfermedades raras (CIBERER); ISCIII; Barcelona Spain
| | - Michael Pusch
- Istituto di Biofisica; CNR; Via De Marini 6 Genova Italy
| | - Fernando Morales
- Instituto de Investigaciones en Salud (INISA); Universidad de Costa Rica; San José Costa Rica
- Centro de Investigación en Neurociencias (CIN); Universidad de Costa Rica; San José Costa Rica
- Escuela de Medicina; Universidad de Costa Rica; Curridabat San José Costa Rica
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33
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Imbrici P, Maggi L, Mangiatordi GF, Dinardo MM, Altamura C, Brugnoni R, Alberga D, Pinter GL, Ricci G, Siciliano G, Micheli R, Annicchiarico G, Lattanzi G, Nicolotti O, Morandi L, Bernasconi P, Desaphy JF, Mantegazza R, Camerino DC. ClC-1 mutations in myotonia congenita patients: insights into molecular gating mechanisms and genotype-phenotype correlation. J Physiol 2015; 593:4181-99. [PMID: 26096614 DOI: 10.1113/jp270358] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 06/04/2015] [Indexed: 12/31/2022] Open
Abstract
KEY POINTS Loss-of-function mutations of the skeletal muscle ClC-1 channel cause myotonia congenita with variable phenotypes. Using patch clamp we show that F484L, located in the conducting pore, probably induces mild dominant myotonia by right-shifting the slow gating of ClC-1 channel, without exerting a dominant-negative effect on the wild-type (WT) subunit. Molecular dynamics simulations suggest that F484L affects the slow gate by increasing the frequency and the stability of H-bond formation between E232 in helix F and Y578 in helix R. Three other myotonic ClC-1 mutations are shown to produce distinct effects on channel function: L198P shifts the slow gate to positive potentials, V640G reduces channel activity, while L628P displays a WT-like behaviour (electrophysiology data only). Our results provide novel insight into the molecular mechanisms underlying normal and altered ClC-1 function. ABSTRACT Myotonia congenita is an inherited disease caused by loss-of-function mutations of the skeletal muscle ClC-1 chloride channel, characterized by impaired muscle relaxation after contraction and stiffness. In the present study, we provided an in-depth characterization of F484L, a mutation previously identified in dominant myotonia, in order to define the genotype-phenotype correlation, and to elucidate the contribution of this pore residue to the mechanisms of ClC-1 gating. Patch-clamp recordings showed that F484L reduced chloride currents at every tested potential and dramatically right-shifted the voltage dependence of slow gating, thus contributing to the mild clinical phenotype of affected heterozygote carriers. Unlike dominant mutations located at the dimer interface, no dominant-negative effect was observed when F484L mutant subunits were co-expressed with wild type. Molecular dynamics simulations further revealed that F484L affected the slow gate by increasing the frequency and stability of the H-bond formation between the pore residue E232 and the R helix residue Y578. In addition, using patch-clamp electrophysiology, we characterized three other myotonic ClC-1 mutations. We proved that the dominant L198P mutation in the channel pore also right-shifted the voltage dependence of slow gating, recapitulating mild myotonia. The recessive V640G mutant drastically reduced channel function, which probably accounts for myotonia. In contrast, the recessive L628P mutant produced currents very similar to wild type, suggesting that the occurrence of the compound truncating mutation (Q812X) or other muscle-specific mechanisms accounted for the severe symptoms observed in this family. Our results provide novel insight into the molecular mechanisms underlying normal and altered ClC-1 function.
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Affiliation(s)
- P Imbrici
- Department of Pharmacy - Drug Sciences, University of Bari, Bari, Italy
| | - L Maggi
- Neuroimmunology and Neuromuscular Diseases Unit, IRCCS Fondazione Istituto Neurologico 'Carlo Besta', Milano, Italy
| | - G F Mangiatordi
- Department of Pharmacy - Drug Sciences, University of Bari, Bari, Italy
| | - M M Dinardo
- Department of Pharmacy - Drug Sciences, University of Bari, Bari, Italy
| | - C Altamura
- Department of Pharmacy - Drug Sciences, University of Bari, Bari, Italy
| | - R Brugnoni
- Neuroimmunology and Neuromuscular Diseases Unit, IRCCS Fondazione Istituto Neurologico 'Carlo Besta', Milano, Italy
| | - D Alberga
- Department of Physics 'M. Merlin', INFN and TIRES, University of Bari, Bari, Italy
| | - G Lauria Pinter
- Neuroalgology and Headache Unit, IRCCS Fondazione Istituto Neurologico 'Carlo Besta', Milano, Italy
| | - G Ricci
- Department of Clinical and Experimental Medicine, Section of Neurology, University of Pisa, Pisa, Italy
| | - G Siciliano
- Department of Clinical and Experimental Medicine, Section of Neurology, University of Pisa, Pisa, Italy
| | - R Micheli
- Unit of Child Neurology and Psychiatry, Spedali Civili, Brescia, Italy
| | - G Annicchiarico
- Regional Coordination for Rare Diseases, A. Re. S. Puglia, Bari, Italy
| | - G Lattanzi
- Department of Physics 'M. Merlin', INFN and TIRES, University of Bari, Bari, Italy
| | - O Nicolotti
- Department of Pharmacy - Drug Sciences, University of Bari, Bari, Italy
| | - L Morandi
- Neuroimmunology and Neuromuscular Diseases Unit, IRCCS Fondazione Istituto Neurologico 'Carlo Besta', Milano, Italy
| | - P Bernasconi
- Neuroimmunology and Neuromuscular Diseases Unit, IRCCS Fondazione Istituto Neurologico 'Carlo Besta', Milano, Italy
| | - J-F Desaphy
- Department of Pharmacy - Drug Sciences, University of Bari, Bari, Italy
| | - R Mantegazza
- Neuroimmunology and Neuromuscular Diseases Unit, IRCCS Fondazione Istituto Neurologico 'Carlo Besta', Milano, Italy
| | - D Conte Camerino
- Department of Pharmacy - Drug Sciences, University of Bari, Bari, Italy
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34
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Zifarelli G. A tale of two CLCs: biophysical insights toward understanding ClC-5 and ClC-7 function in endosomes and lysosomes. J Physiol 2015; 593:4139-50. [PMID: 26036722 DOI: 10.1113/jp270604] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Accepted: 05/22/2015] [Indexed: 11/08/2022] Open
Abstract
The CLC protein family comprises both Cl(-) channels and H(+) -coupled anion transporters. The understanding of the critical role of CLC proteins in a number of physiological functions has greatly contributed to a revision of the classical paradigm that attributed to Cl(-) ions only a marginal role in human physiology. The endosomal ClC-5 and the lysosomal ClC-7 are the best characterized human CLC transporters. Their dysfunction causes Dent's disease and osteopetrosis, respectively. It had been originally proposed that they would provide a Cl(-) shunt conductance allowing efficient acidification of intracellular compartments. However, this model seems to conflict with the transport properties of these proteins and with recent physiological evidence. Currently, there is no consensus on their specific physiological role. CLC proteins present also a number of peculiar biophysical properties, such as the dimeric architecture, the co-existence of intrinsically different thermodynamic modes of transport based on similar structural principles, and the gating mechanism recently emerging for the transporters, just to name a few. This review focuses on the biophysical properties and physiological roles of ClC-5 and ClC-7.
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Affiliation(s)
- Giovanni Zifarelli
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
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35
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Capdevila-Nortes X, Jeworutzki E, Elorza-Vidal X, Barrallo-Gimeno A, Pusch M, Estévez R. Structural determinants of interaction, trafficking and function in the ClC-2/MLC1 subunit GlialCAM involved in leukodystrophy. J Physiol 2015; 593:4165-80. [PMID: 26033718 DOI: 10.1113/jp270467] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/22/2015] [Indexed: 02/03/2023] Open
Abstract
KEY POINTS The extracellular domain of GlialCAM is necessary for its targeting to cell junctions, as well as for interactions with itself and MLC1 and ClC-2. The C-terminus of GlialCAM is not necessary for interaction but is required for targeting to cell junctions. The first three residues of the transmembrane segment of GlialCAM are required for GlialCAM-mediated ClC-2 activation. ABSTRACT Mutations in the genes encoding the astrocytic protein MLC1, the cell adhesion molecule GlialCAM or the Cl(-) channel ClC-2 underlie human leukodystrophies. GlialCAM binds to itself, to MLC1 and to ClC-2, and directs these proteins to cell-cell contacts. In addition, GlialCAM dramatically activates ClC-2 mediated currents. In the present study, we used mutagenesis studies combined with functional and biochemical analyses to determine which parts of GlialCAM are required to perform these cellular functions. We found that the extracellular domain of GlialCAM is necessary for cell junction targeting and for mediating interactions with itself or with MLC1 and ClC-2. The C-terminus is also necessary for proper targeting to cell-cell junctions but is not required for the biochemical interaction. Finally, we identified the first three amino acids of the transmembrane segment of GlialCAM as being essential for the activation of ClC-2 currents but not for targeting or biochemical interaction. Our results provide new mechanistic insights concerning the regulation of the cell biology and function of MLC1 and ClC-2 by GlialCAM.
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Affiliation(s)
- Xavier Capdevila-Nortes
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain
| | - Elena Jeworutzki
- Istituto di Biofisica, CNR, Genoa, Italy.,Present address IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, Münster, Germany
| | - Xabier Elorza-Vidal
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
| | - Alejandro Barrallo-Gimeno
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain
| | | | - Raúl Estévez
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
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36
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Imbrici P, Altamura C, Pessia M, Mantegazza R, Desaphy JF, Camerino DC. ClC-1 chloride channels: state-of-the-art research and future challenges. Front Cell Neurosci 2015; 9:156. [PMID: 25964741 PMCID: PMC4410605 DOI: 10.3389/fncel.2015.00156] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/08/2015] [Indexed: 01/06/2023] Open
Abstract
The voltage-dependent ClC-1 chloride channel belongs to the CLC channel/transporter family. It is a homodimer comprising two individual pores which can operate independently or simultaneously according to two gating modes, the fast and the slow gate of the channel. ClC-1 is preferentially expressed in the skeletal muscle fibers where the presence of an efficient Cl(-) homeostasis is crucial for the correct membrane repolarization and propagation of action potential. As a consequence, mutations in the CLCN1 gene cause dominant and recessive forms of myotonia congenita (MC), a rare skeletal muscle channelopathy caused by abnormal membrane excitation, and clinically characterized by muscle stiffness and various degrees of transitory weakness. Elucidation of the mechanistic link between the genetic defects and the disease pathogenesis is still incomplete and, at this time, there is no specific treatment for MC. Still controversial is the subcellular localization pattern of ClC-1 channels in skeletal muscle as well as its modulation by some intracellular factors. The expression of ClC-1 in other tissues such as in brain and heart and the possible assembly of ClC-1/ClC-2 heterodimers further expand the physiological properties of ClC-1 and its involvement in diseases. A recent de novo CLCN1 truncation mutation in a patient with generalized epilepsy indeed postulates an unexpected role of this channel in the control of neuronal network excitability. This review summarizes the most relevant and state-of-the-art research on ClC-1 chloride channels physiology and associated diseases.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | - Concetta Altamura
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | - Mauro Pessia
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | - Renato Mantegazza
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | | | - Diana Conte Camerino
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
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37
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Identification and characterization of the zebrafish ClC-2 chloride channel orthologs. Pflugers Arch 2014; 467:1769-81. [DOI: 10.1007/s00424-014-1614-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/09/2014] [Accepted: 09/09/2014] [Indexed: 12/31/2022]
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38
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Gradogna A, Imbrici P, Zifarelli G, Liantonio A, Camerino DC, Pusch M. I-J loop involvement in the pharmacological profile of CLC-K channels expressed in Xenopus oocytes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2745-56. [PMID: 25073071 PMCID: PMC4331650 DOI: 10.1016/j.bbamem.2014.07.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 07/13/2014] [Accepted: 07/21/2014] [Indexed: 12/19/2022]
Abstract
CLC-K chloride channels and their subunit, barttin, are crucial for renal NaCl reabsorption and for inner ear endolymph production. Mutations in CLC-Kb and barttin cause Bartter syndrome. Here, we identified two adjacent residues, F256 and N257, that when mutated hugely alter in Xenopus oocytes CLC-Ka's biphasic response to niflumic acid, a drug belonging to the fenamate class, with F256A being potentiated 37-fold and N257A being potently blocked with a KD~1μM. These residues are localized in the same extracellular I-J loop which harbors a regulatory Ca(2+) binding site. This loop thus can represent an ideal and CLC-K specific target for extracellular ligands able to modulate channel activity. Furthermore, we demonstrated the involvement of the barttin subunit in the NFA potentiation. Indeed the F256A mutation confers onto CLC-K1 a transient potentiation induced by NFA which is found only when CLC-K1/F256A is co-expressed with barttin. Thus, in addition to the role of barttin in targeting and gating, the subunit participates in the pharmacological modulation of CLC-K channels and thus represents a further target for potential drugs.
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Affiliation(s)
| | - Paola Imbrici
- Dipartimento di Farmacia-Scienze del farmaco, Università degli Studi di Bari, Via Orabona 4, 70125 Bari, Italy
| | | | - Antonella Liantonio
- Dipartimento di Farmacia-Scienze del farmaco, Università degli Studi di Bari, Via Orabona 4, 70125 Bari, Italy
| | - Diana Conte Camerino
- Dipartimento di Farmacia-Scienze del farmaco, Università degli Studi di Bari, Via Orabona 4, 70125 Bari, Italy
| | - Michael Pusch
- Istituto di Biofisica, CNR, Via De Marini 6, 16149 Genoa, Italy.
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39
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Sirisi S, Folgueira M, López-Hernández T, Minieri L, Pérez-Rius C, Gaitán-Peñas H, Zang J, Martínez A, Capdevila-Nortes X, De La Villa P, Roy U, Alia A, Neuhauss S, Ferroni S, Nunes V, Estévez R, Barrallo-Gimeno A. Megalencephalic leukoencephalopathy with subcortical cysts protein 1 regulates glial surface localization of GLIALCAM from fish to humans. Hum Mol Genet 2014; 23:5069-86. [DOI: 10.1093/hmg/ddu231] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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40
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ClC-1 and ClC-2 form hetero-dimeric channels with novel protopore functions. Pflugers Arch 2014; 466:2191-204. [DOI: 10.1007/s00424-014-1490-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 02/19/2014] [Indexed: 10/25/2022]
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Pusch M, Zifarelli G. Thermal sensitivity of CLC and TMEM16 chloride channels and transporters. CURRENT TOPICS IN MEMBRANES 2014; 74:213-31. [PMID: 25366238 DOI: 10.1016/b978-0-12-800181-3.00008-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cl(-) transport is of fundamental importance in the most diverse physiological contexts and it is mediated by a variety of ion channels and transporters belonging to different protein families. In particular, the recently identified TMEM16 protein family comprises the long sought Ca(2+)-activated Cl(-) channel (CaCC) and the activity of one of its members, TMEM16A, is highly dependent on temperature and is involved in thermal nociception. Among the other protein families mediating Cl(-) transport, CLC proteins are also regulated by temperature although so far the physiological implications of this dependence are unknown.
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Stauber T, Weinert S, Jentsch TJ. Cell biology and physiology of CLC chloride channels and transporters. Compr Physiol 2013; 2:1701-44. [PMID: 23723021 DOI: 10.1002/cphy.c110038] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Proteins of the CLC gene family assemble to homo- or sometimes heterodimers and either function as Cl(-) channels or as Cl(-)/H(+)-exchangers. CLC proteins are present in all phyla. Detailed structural information is available from crystal structures of bacterial and algal CLCs. Mammals express nine CLC genes, four of which encode Cl(-) channels and five 2Cl(-)/H(+)-exchangers. Two accessory β-subunits are known: (1) barttin and (2) Ostm1. ClC-Ka and ClC-Kb Cl(-) channels need barttin, whereas Ostm1 is required for the function of the lysosomal ClC-7 2Cl(-)/H(+)-exchanger. ClC-1, -2, -Ka and -Kb Cl(-) channels reside in the plasma membrane and function in the control of electrical excitability of muscles or neurons, in extra- and intracellular ion homeostasis, and in transepithelial transport. The mainly endosomal/lysosomal Cl(-)/H(+)-exchangers ClC-3 to ClC-7 may facilitate vesicular acidification by shunting currents of proton pumps and increase vesicular Cl(-) concentration. ClC-3 is also present on synaptic vesicles, whereas ClC-4 and -5 can reach the plasma membrane to some extent. ClC-7/Ostm1 is coinserted with the vesicular H(+)-ATPase into the acid-secreting ruffled border membrane of osteoclasts. Mice or humans lacking ClC-7 or Ostm1 display osteopetrosis and lysosomal storage disease. Disruption of the endosomal ClC-5 Cl(-)/H(+)-exchanger leads to proteinuria and Dent's disease. Mouse models in which ClC-5 or ClC-7 is converted to uncoupled Cl(-) conductors suggest an important role of vesicular Cl(-) accumulation in these pathologies. The important functions of CLC Cl(-) channels were also revealed by human diseases and mouse models, with phenotypes including myotonia, renal loss of salt and water, deafness, blindness, leukodystrophy, and male infertility.
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Affiliation(s)
- Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie FMP and Max-Delbrück-Centrum für Molekulare Medizin MDC, Berlin, Germany
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CLCNKB mutations causing mild Bartter syndrome profoundly alter the pH and Ca2+ dependence of ClC-Kb channels. Pflugers Arch 2013; 466:1713-23. [DOI: 10.1007/s00424-013-1401-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 10/30/2013] [Accepted: 11/01/2013] [Indexed: 10/26/2022]
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De Stefano S, Pusch M, Zifarelli G. A single point mutation reveals gating of the human ClC-5 Cl-/H+ antiporter. J Physiol 2013; 591:5879-93. [PMID: 24099800 PMCID: PMC3872759 DOI: 10.1113/jphysiol.2013.260240] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
ClC-5 is a 2Cl−/1H+ antiporter highly expressed in endosomes of proximal tubule cells. It is essential for endocytosis and mutations in ClC-5 cause Dent's disease, potentially leading to renal failure. However, the physiological role of ClC-5 is still unclear. One of the main issues is whether the strong rectification of ClC-5 currents observed in heterologous systems, with currents elicited only at positive voltages, is preserved in vivo and what is the origin of this rectification. In this work we identified a ClC-5 mutation, D76H, which, besides the typical outward currents of the wild-type (WT), shows inward tail currents at negative potentials that allow the estimation of the reversal of ClC-5 currents for the first time. A detailed analysis of the dependence of these inward tail currents on internal and external pH and [Cl−] shows that they are generated by a coupled transport of Cl− and H+ with a 2 : 1 stoichiometry. From this result we conclude that the inward tail currents are caused by a gating mechanism that regulates ClC-5 transport activity and not by a major alteration of the transport mechanism itself. This implies that the strong rectification of the currents of WT ClC-5 is at least in part caused by a gating mechanism that activates the transporter at positive potentials. These results elucidate the biophysical properties of ClC-5 and contribute to the understanding of its physiological role.
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Affiliation(s)
- Silvia De Stefano
- G. Zifarelli: Istituto di Biofisica, CNR, Via De Marini 6, I-16149 Genova, Italy.
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Molecular determinants of common gating of a ClC chloride channel. Nat Commun 2013; 4:2507. [DOI: 10.1038/ncomms3507] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 08/27/2013] [Indexed: 11/08/2022] Open
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Abstract
Despite the role of chloride channels and anion/proton antiporters of the CLC protein family in physiological processes and different genetic diseases, their pharmacology has been under-developed. In this issue of Chemistry & Biology, Howery et al. report the synthesis of 4'-octanamidostilbene-2,2'-disulfonate, the first high-affinity inhibitor of a CLC antiporter, a critical step toward reviving the CLC pharmacology.
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Abstract
The lack of small-molecule inhibitors for anion-selective transporters and channels has impeded our understanding of the complex mechanisms that underlie ion passage. The ubiquitous CLC "Chloride Channel" family represents a unique target for biophysical and biochemical studies because its distinctive protein fold supports both passive chloride channels and secondary-active chloride-proton transporters. Here, we describe the synthesis and characterization of a specific small-molecule inhibitor directed against a CLC antiporter (ClC-ec1). This compound, 4,4'-octanamidostilbene-2,2'-disulfonate (OADS), inhibits ClC-ec1 with low micromolar affinity and has no specific effect on a CLC channel (ClC-1). Inhibition of ClC-ec1 occurs by binding to two distinct intracellular sites. The location of these sites and the lipid dependence of inhibition suggest potential mechanisms of action. This compound will empower research to elucidate differences between antiporter and channel mechanisms and to develop treatments for CLC-mediated disorders.
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Nieto-Delgado P, Arreola J, Guirado-López R. Atomic charges of Cl− ions confined in a model Escherichia coli ClC−Cl−/H+ ion exchanger: a density functional theory study. Mol Phys 2013. [DOI: 10.1080/00268976.2013.776709] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Cortes C, Galindo F, Galicia S, Cebada J, Flores A. Excitatory actions of GABA in developing chick vestibular afferents: effects on resting electrical activity. Synapse 2013; 67:374-81. [PMID: 23401185 DOI: 10.1002/syn.21646] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Accepted: 01/31/2013] [Indexed: 11/09/2022]
Abstract
The aim of this study was to characterize the effect of γ-aminobutyric acid (GABA) in the resting multiunit activity of the vestibular afferents during development using the isolated inner ear of embryonic and postnatal chickens (E15-E21 and P5). GABA (10(-3) to 10(-5) M; n = 133) and muscimol (10(-3) M) elicited an increase in the frequency of the basal discharge of the vestibular afferents. We found that GABA action was dose-dependent and inversely related to animal age. Thus, the largest effect was observed in embryonic ages such as E15 and E17 and decreases in E21 and P5. The GABAA receptor antagonists, bicuculline (10(-5) M; n = 10) and picrotoxin (10(-4) M; n = 10), significantly decreased the excitatory action of GABA and muscimol (10(-3) M). Additionally, CNQX 10(-6) M, MCPG 10(-5) M and 7ClKyn 10(-5) M (n = 5) were co-applied by bath substitution (n = 5). Both the basal discharge and the GABA action significantly decreased in these experimental conditions. The chloride channel blocker 9-AC 0.5 mM produced an important reduction in the effect of GABA 10(-3) (n = 5) and 10(-4) M (n = 5). Thus, our results suggest an excitatory role of GABA in the resting activity of the vestibular afferents that can be explained by changes in the gradient of concentration of Cl(-) during development. We show for the first time that the magnitude of this GABA effect decreases at later stages of embryonic and early postnatal development. Taking into account the results with glutamatergic antagonists, we conclude that GABA has a presynaptic action but is not the neurotransmitter in the vestibular afferent synapses, although it could act as a facilitator of the spontaneous activity and may regulate glutamate release.
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Affiliation(s)
- Celso Cortes
- Facultad de Medicina, Benemérita Universidad Autónoma de Puebla, Av. 13 Sur 2702 Colonia Volcanes CP, 72410, Puebla, Pue., México
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Zanardi I, Zifarelli G, Pusch M. An optical assay of the transport activity of ClC-7. Sci Rep 2013; 3:1231. [PMID: 23390581 PMCID: PMC3565172 DOI: 10.1038/srep01231] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 01/21/2013] [Indexed: 11/09/2022] Open
Abstract
Osteoporosis, characterized by excessive osteoclast mediated bone resorption, affects millions of people worldwide representing a major public health problem. ClC-7 is a chloride-proton exchanger localized in lysosomes and in the resorption lacuna in osteoclasts where it is essential for bone resorption. Thus, drugs targeted at ClC-7 have been proposed for ameliorating osteoporosis. However, functional assays suited for high throughput screening (HTS) of ClC-7 function are lacking. Here we describe two complementary variants of purely optical assays of the transport activity of ClC-7, redirected to the plasma membrane employing a genetically encoded fluorescent Cl−/pH indicator fused to the ClC-7 protein. These simple and robust functional assays of ClC-7 transport are well-suited to be applied in HTS of small-molecule inhibitors and may help to develop drugs suited for the treatment of osteoporosis.
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Affiliation(s)
- Ilaria Zanardi
- Istituto di Biofisica, CNR, Via De Marini 6, 16149 Genoa, Italy
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