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Kwon HC, Fairclough RH, Chen TY. Insights into CLC-0's Slow-Gating from Intracellular Proton Inhibition. Int J Mol Sci 2024; 25:7796. [PMID: 39063037 PMCID: PMC11276645 DOI: 10.3390/ijms25147796] [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: 05/15/2024] [Revised: 06/27/2024] [Accepted: 07/03/2024] [Indexed: 07/28/2024] Open
Abstract
The opening of the Torpedo CLC-0 chloride (Cl-) channel is known to be regulated by two gating mechanisms: fast gating and slow (common) gating. The structural basis underlying the fast-gating mechanism is better understood than that of the slow-gating mechanism, which is still largely a mystery. Our previous study on the intracellular proton (H+i)-induced inhibition of the CLC-0 anionic current led to the conclusion that the inhibition results from the slow-gate closure (also called inactivation). The conclusion was made based on substantial evidence such as a large temperature dependence of the H+i inhibition similar to that of the channel inactivation, a resistance to the H+i inhibition in the inactivation-suppressed C212S mutant, and a similar voltage dependence between the current recovery from the H+i inhibition and the recovery from the channel inactivation. In this work, we further examine the mechanism of the H+i inhibition of wild-type CLC-0 and several mutants. We observe that an anion efflux through the pore of CLC-0 accelerates the recovery from the H+i-induced inhibition, a process corresponding to the slow-gate opening. Furthermore, various inactivation-suppressed mutants exhibit different current recovery kinetics, suggesting the existence of multiple inactivated states (namely, slow-gate closed states). We speculate that protonation of the pore of CLC-0 increases the binding affinity of permeant anions in the pore, thereby generating a pore blockage of ion flow as the first step of inactivation. Subsequent complex protein conformational changes further transition the CLC-0 channel to deeper inactivated states.
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Affiliation(s)
- Hwoi Chan Kwon
- Biophysics Graduate Program, University of California, Davis, CA 95618, USA; (H.C.K.); (R.H.F.)
| | - Robert H. Fairclough
- Biophysics Graduate Program, University of California, Davis, CA 95618, USA; (H.C.K.); (R.H.F.)
- Department of Neurology, University of California, Davis, CA 95618, USA
| | - Tsung-Yu Chen
- Biophysics Graduate Program, University of California, Davis, CA 95618, USA; (H.C.K.); (R.H.F.)
- Department of Neurology, University of California, Davis, CA 95618, USA
- Center for Neuroscience, University of California, 1544 Newton Court, Davis, CA 95618, USA
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2
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Lee C, Chang Y, Lin H, Lee H, Yeh T, Fang L, Lee N, Tsai J, Lin S. Multisystem disorder associated with a pathogenic variant in CLCN7 in the absence of osteopetrosis. Mol Genet Genomic Med 2024; 12:e2494. [PMID: 39056574 PMCID: PMC11273547 DOI: 10.1002/mgg3.2494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 05/08/2024] [Accepted: 07/02/2024] [Indexed: 07/28/2024] Open
Abstract
BACKGROUND We clinically and genetically evaluated a Taiwanese boy presenting with developmental delay, organomegaly, hypogammaglobulinemia and hypopigmentation without osteopetrosis. Whole-exome sequencing revealed a de novo gain-of-function variant, p.Tyr715Cys, in the C-terminal domain of ClC-7 encoded by CLCN7. METHODS Nicoli et al. (2019) assessed the functional impact of p.Tyr715Cys by heterologous expression in Xenopus oocytes and evaluating resulting currents. RESULTS The variant led to increased outward currents, indicating it underlies the patient's phenotype of lysosomal hyperacidity, storage defects and vacuolization. This demonstrates the crucial physiological role of ClC-7 antiporter activity in maintaining appropriate lysosomal pH. CONCLUSION Elucidating mechanisms by which CLCN7 variants lead to lysosomal dysfunction will advance understanding of genotype-phenotype correlations. Identifying modifier genes and compensatory pathways may reveal therapeutic targets. Ongoing functional characterization of variants along with longitudinal clinical evaluations will continue advancing knowledge of ClC-7's critical roles and disease mechanisms resulting from its dysfunction. Expanded cohort studies are warranted to delineate the full spectrum of associated phenotypes.
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Affiliation(s)
- Chung‐Lin Lee
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
- Department and Institute of Clinical MedicineNational Yang‐Ming Chiao‐Tung UniversityTaipeiTaiwan
- Department of Rare Disease CenterMacKay Memorial HospitalTaipeiTaiwan
- Department of MedicineMackay Medical CollegeNew Taipei CityTaiwan
- Mackay Junior College of Medicine, Nursing, and ManagementTaipeiTaiwan
| | - Yeun‐Wen Chang
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
- Department of PediatricsTaipei Tzu Chi Hospital, Buddhist Tzu Chi Medical FoundationNew Taipei CityTaiwan
| | - Hsiang‐Yu Lin
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
- Department of Rare Disease CenterMacKay Memorial HospitalTaipeiTaiwan
- Department of MedicineMackay Medical CollegeNew Taipei CityTaiwan
- Mackay Junior College of Medicine, Nursing, and ManagementTaipeiTaiwan
- Division of Genetics and Metabolism, Department of Medical ResearchMacKay Memorial HospitalTaipeiTaiwan
- Department of Medical ResearchChina Medical University Hospital, China Medical UniversityTaichungTaiwan
| | - Hung‐Chang Lee
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
| | - Ting‐Chi Yeh
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
| | - Li‐Ching Fang
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
| | - Ni‐Chung Lee
- Department of PediatricsNational Taiwan University HospitalTaipeiTaiwan
| | - Jeng‐Daw Tsai
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
- Department of MedicineMackay Medical CollegeNew Taipei CityTaiwan
| | - Shuan‐Pei Lin
- Department of PediatricsMacKay Memorial HospitalTaipeiTaiwan
- Department of Rare Disease CenterMacKay Memorial HospitalTaipeiTaiwan
- Department of MedicineMackay Medical CollegeNew Taipei CityTaiwan
- Division of Genetics and Metabolism, Department of Medical ResearchMacKay Memorial HospitalTaipeiTaiwan
- Department of Infant and Child CareNational Taipei University of Nursing and Health SciencesTaipeiTaiwan
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3
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Duan S, Li B, Cui S, Chen Y, He Y, Fan L. Clcn3 deficiency ameliorates high-fat diet-induced obesity and improves metabolism in mice. Front Nutr 2024; 11:1387806. [PMID: 38784133 PMCID: PMC11111939 DOI: 10.3389/fnut.2024.1387806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Accepted: 04/11/2024] [Indexed: 05/25/2024] Open
Abstract
Objective Obesity is defined as excess body fat and is a current health epidemic associated with increased risk for type 2 diabetes and cardiovascular disease. The ClC-3 chloride channel/antiporter, encoded by the Clcn3, is associated with some diseases, like carcinoma, nervous system diseases, and metabolic diseases. To verify the relationship between the Clcn3 and weight including metabolic changes, searching for a new target for metabolic therapy of obesity, we designed the experiment. Methods The mice were divided into 4 different groups: Clcn3+/+ mice + high-fat diet (HFD), Clcn3-/- mice + HFD, Clcn3+/+ mice + normal diet (ND), Clcn3-/- mice + ND, and fed for 16 weeks. After the glucose tolerance test and insulin tolerance test, peripheral blood and adipose tissues were collected. Moreover, we performed transcriptome sequencing for the epididymal white adipose tissue from Clcn3+/+ and Clcn3-/- mice with the high-fat diet. Western blotting verified the changes in protein levels of relevant metabolic genes. Results We found that the Clcn3-/- mice had lower body weight and visceral fat, refining glucose and lipid metabolism in HFD-induced mice, but had no effect in normal diet mice. RNA-seq and Western blotting indicated that Clcn3 deficiency may inhibit obesity through the AMPK-UCP1 axis. Conclusion Modulation of Clcn3 may provide an appealing therapeutic target for obesity and associated metabolic syndrome.
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Affiliation(s)
- Sirui Duan
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Bo Li
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
- Department of Cardiology, Ninth Hospital of Xi’an, Xi’an, China
| | - Shiyu Cui
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
- Department of Pathology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an Jiaotong University, Xi’an, China
| | - Yaoyao Chen
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Ying He
- Graduate Students Teaching Experiment Center, Xi’an Jiaotong University Health Science Center, Xi’an, China
| | - Lihong Fan
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
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4
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Langner E, Puapatanakul P, Pudlowski R, Alsabbagh DY, Miner JH, Horani A, Dutcher SK, Brody SL, Wang JT, Suleiman HY, Mahjoub MR. Ultrastructure expansion microscopy (U-ExM) of mouse and human kidneys for analysis of subcellular structures. Cytoskeleton (Hoboken) 2024. [PMID: 38715433 DOI: 10.1002/cm.21870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 04/11/2024] [Accepted: 04/22/2024] [Indexed: 05/21/2024]
Abstract
Ultrastructure expansion microscopy (U-ExM) involves the physical magnification of specimens embedded in hydrogels, which allows for super-resolution imaging of subcellular structures using a conventional diffraction-limited microscope. Methods for expansion microscopy exist for several organisms, organs, and cell types, and used to analyze cellular organelles and substructures in nanoscale resolution. Here, we describe a simple step-by-step U-ExM protocol for the expansion, immunostaining, imaging, and analysis of cytoskeletal and organellar structures in kidney tissue. We detail the critical modified steps to optimize isotropic kidney tissue expansion, and preservation of the renal cell structures of interest. We demonstrate the utility of the approach using several markers of renal cell types, centrioles, cilia, the extracellular matrix, and other cytoskeletal elements. Finally, we show that the approach works well on mouse and human kidney samples that were preserved using different fixation and embedding conditions. Overall, this protocol provides a simple and cost-effective approach to analyze both preclinical and clinical renal samples in high detail, using conventional lab supplies and standard widefield or confocal microscopy.
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Affiliation(s)
- Ewa Langner
- Department of Medicine, Washington University, St. Louis, Missouri, USA
| | - Pongpratch Puapatanakul
- Department of Medicine, Washington University, St. Louis, Missouri, USA
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Rachel Pudlowski
- Department of Biology, Washington University, St. Louis, Missouri, USA
| | | | - Jeffrey H Miner
- Department of Medicine, Washington University, St. Louis, Missouri, USA
| | - Amjad Horani
- Department of Pediatrics, Washington University, St. Louis, Missouri, USA
| | - Susan K Dutcher
- Department of Genetics, Washington University, St. Louis, Missouri, USA
| | - Steven L Brody
- Department of Medicine, Washington University, St. Louis, Missouri, USA
| | - Jennifer T Wang
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Hani Y Suleiman
- Department of Medicine, Washington University, St. Louis, Missouri, USA
| | - Moe R Mahjoub
- Department of Medicine, Washington University, St. Louis, Missouri, USA
- Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri, USA
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5
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Langner E, Puapatanakul P, Pudlowski R, Alsabbagh DY, Miner JH, Horani A, Dutcher SK, Brody SL, Wang JT, Suleiman HY, Mahjoub MR. Ultrastructure expansion microscopy (U-ExM) of mouse and human kidneys for analysis of subcellular structures. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.16.580708. [PMID: 38405695 PMCID: PMC10889020 DOI: 10.1101/2024.02.16.580708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Ultrastructure expansion microscopy (U-ExM) involves the physical magnification of specimens embedded in hydrogels, which allows for super-resolution imaging of subcellular structures using a conventional diffraction-limited microscope. Methods for expansion microscopy exist for several organisms, organs, and cell types, and used to analyze cellular organelles and substructures in nanoscale resolution. Here, we describe a simple step-by-step U-ExM protocol for the expansion, immunostaining, imaging, and analysis of cytoskeletal and organellar structures in kidney tissue. We detail the critical modified steps to optimize isotropic kidney tissue expansion, and preservation of the renal cell structures of interest. We demonstrate the utility of the approach using several markers of renal cell types, centrioles, cilia, the extracellular matrix, and other cytoskeletal elements. Finally, we show that the approach works well on mouse and human kidney samples that were preserved using different fixation and storage conditions. Overall, this protocol provides a simple and cost-effective approach to analyze both pre-clinical and clinical renal samples in high detail, using conventional lab supplies and standard widefield or confocal microscopy.
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6
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Xu M, Neelands T, Powers AS, Liu Y, Miller SD, Pintilie GD, Bois JD, Dror RO, Chiu W, Maduke M. CryoEM structures of the human CLC-2 voltage-gated chloride channel reveal a ball-and-chain gating mechanism. eLife 2024; 12:RP90648. [PMID: 38345841 PMCID: PMC10942593 DOI: 10.7554/elife.90648] [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] [Indexed: 02/15/2024] Open
Abstract
CLC-2 is a voltage-gated chloride channel that contributes to electrical excitability and ion homeostasis in many different tissues. Among the nine mammalian CLC homologs, CLC-2 is uniquely activated by hyperpolarization, rather than depolarization, of the plasma membrane. The molecular basis for the divergence in polarity of voltage gating among closely related homologs has been a long-standing mystery, in part because few CLC channel structures are available. Here, we report cryoEM structures of human CLC-2 at 2.46 - 2.76 Å, in the presence and absence of the selective inhibitor AK-42. AK-42 binds within the extracellular entryway of the Cl--permeation pathway, occupying a pocket previously proposed through computational docking studies. In the apo structure, we observed two distinct conformations involving rotation of one of the cytoplasmic C-terminal domains (CTDs). In the absence of CTD rotation, an intracellular N-terminal 15-residue hairpin peptide nestles against the TM domain to physically occlude the Cl--permeation pathway. This peptide is highly conserved among species variants of CLC-2 but is not present in other CLC homologs. Previous studies suggested that the N-terminal domain of CLC-2 influences channel properties via a "ball-and-chain" gating mechanism, but conflicting data cast doubt on such a mechanism, and thus the structure of the N-terminal domain and its interaction with the channel has been uncertain. Through electrophysiological studies of an N-terminal deletion mutant lacking the 15-residue hairpin peptide, we support a model in which the N-terminal hairpin of CLC-2 stabilizes a closed state of the channel by blocking the cytoplasmic Cl--permeation pathway.
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Affiliation(s)
- Mengyuan Xu
- Department of Molecular and Cellular Physiology, Stanford UniversityStanfordUnited States
| | - Torben Neelands
- Department of Molecular and Cellular Physiology, Stanford UniversityStanfordUnited States
| | - Alexander S Powers
- Department of Chemistry, Stanford UniversityStanfordUnited States
- Department of Computer Science, Stanford UniversityStanfordUnited States
- Department of Structural Biology, Stanford UniversityStanfordUnited States
- Institute for Computational and Mathematical Engineering, Stanford UniversityStanfordUnited States
| | - Yan Liu
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford UniversityStanfordUnited States
| | - Steven D Miller
- Department of Chemistry, Stanford UniversityStanfordUnited States
| | - Grigore D Pintilie
- Department of Bioengineering and Department of Microbiology and Immunology, Stanford UniversityStanfordUnited States
| | - J Du Bois
- Department of Chemistry, Stanford UniversityStanfordUnited States
| | - Ron O Dror
- Department of Molecular and Cellular Physiology, Stanford UniversityStanfordUnited States
- Department of Computer Science, Stanford UniversityStanfordUnited States
- Department of Structural Biology, Stanford UniversityStanfordUnited States
- Institute for Computational and Mathematical Engineering, Stanford UniversityStanfordUnited States
| | - Wah Chiu
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford UniversityStanfordUnited States
- Department of Bioengineering and Department of Microbiology and Immunology, Stanford UniversityStanfordUnited States
| | - Merritt Maduke
- Department of Molecular and Cellular Physiology, Stanford UniversityStanfordUnited States
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7
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Langner E, Cheng T, Kefaloyianni E, Gluck C, Wang B, Mahjoub MR. Cep120 is essential for kidney stromal progenitor cell growth and differentiation. EMBO Rep 2024; 25:428-454. [PMID: 38177914 PMCID: PMC10897188 DOI: 10.1038/s44319-023-00019-z] [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: 07/07/2023] [Revised: 11/15/2023] [Accepted: 11/22/2023] [Indexed: 01/06/2024] Open
Abstract
Mutations in genes that disrupt centrosome structure or function can cause congenital kidney developmental defects and lead to fibrocystic pathologies. Yet, it is unclear how defective centrosome biogenesis impacts renal progenitor cell physiology. Here, we examined the consequences of impaired centrosome duplication on kidney stromal progenitor cell growth, differentiation, and fate. Conditional deletion of the ciliopathy gene Cep120, which is essential for centrosome duplication, in the stromal mesenchyme resulted in reduced abundance of interstitial lineages including pericytes, fibroblasts and mesangial cells. These phenotypes were caused by a combination of delayed mitosis, activation of the mitotic surveillance pathway leading to apoptosis, and changes in both Wnt and Hedgehog signaling that are key for differentiation of stromal cells. Cep120 ablation resulted in small hypoplastic kidneys with medullary atrophy and delayed nephron maturation. Finally, Cep120 and centrosome loss in the interstitium sensitized kidneys of adult mice, causing rapid fibrosis after renal injury via enhanced TGF-β/Smad3-Gli2 signaling. Our study defines the cellular and developmental defects caused by loss of Cep120 and aberrant centrosome biogenesis in the embryonic kidney stroma.
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Affiliation(s)
- Ewa Langner
- Department of Medicine (Nephrology Division), Washington University, St Louis, MO, USA
| | - Tao Cheng
- Department of Medicine (Nephrology Division), Washington University, St Louis, MO, USA
| | - Eirini Kefaloyianni
- Department of Medicine (Rheumatology Division), Washington University, St Louis, MO, USA
| | - Charles Gluck
- Department of Medicine (Nephrology Division), Washington University, St Louis, MO, USA
| | - Baolin Wang
- Department of Genetic Medicine, Weill Medical College of Cornell University, New York, NY, USA
| | - Moe R Mahjoub
- Department of Medicine (Nephrology Division), Washington University, St Louis, MO, USA.
- Department of Cell Biology and Physiology, Washington University, St Louis, MO, USA.
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Andrini O, Eladari D, Picard N. ClC-K Kidney Chloride Channels: From Structure to Pathology. Handb Exp Pharmacol 2024; 283:35-58. [PMID: 36811727 DOI: 10.1007/164_2023_635] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
The molecular basis of chloride transport varies all along the nephron depending on the tubular segments especially in the apical entry of the cell. The major chloride exit pathway during reabsorption is provided by two kidney-specific ClC chloride channels ClC-Ka and ClC-Kb (encoded by CLCNKA and CLCNKB gene, respectively) corresponding to rodent ClC-K1 and ClC-K2 (encoded by Clcnk1 and Clcnk2). These channels function as dimers and their trafficking to the plasma membrane requires the ancillary protein Barttin (encoded by BSND gene). Genetic inactivating variants of the aforementioned genes lead to renal salt-losing nephropathies with or without deafness highlighting the crucial role of ClC-Ka, ClC-Kb, and Barttin in the renal and inner ear chloride handling. The purpose of this chapter is to summarize the latest knowledge on renal chloride structure peculiarity and to provide some insight on the functional expression on the segments of the nephrons and on the related pathological effects.
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Affiliation(s)
- Olga Andrini
- Univ Lyon, University Claude Bernard Lyon 1, CNRS UMR 5284, INSERM U 1314, Melis, Lyon, France.
| | - Dominique Eladari
- CHU Amiens Picardie, Service de Médecine de Précision des maladies Métaboliques et Rénales, Université de Picardie Jules Verne, Amiens, France
| | - Nicolas Picard
- CNRS, LBTI UMR5305, Université Claude Bernard Lyon 1, Lyon, France
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9
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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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10
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Xu M, Neelands T, Powers AS, Liu Y, Miller SD, Pintilie G, Bois JD, Dror RO, Chiu W, Maduke M. CryoEM structures of the human CLC-2 voltage gated chloride channel reveal a ball and chain gating mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.13.553136. [PMID: 37645939 PMCID: PMC10462068 DOI: 10.1101/2023.08.13.553136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
CLC-2 is a voltage-gated chloride channel that contributes to electrical excitability and ion homeostasis in many different mammalian tissues and cell types. Among the nine mammalian CLC homologs, CLC-2 is uniquely activated by hyperpolarization, rather than depolarization, of the plasma membrane. The molecular basis for the divergence in polarity of voltage gating mechanisms among closely related CLC homologs has been a long-standing mystery, in part because few CLC channel structures are available, and those that exist exhibit high conformational similarity. Here, we report cryoEM structures of human CLC-2 at 2.46 - 2.76 Å, in the presence and absence of the potent and selective inhibitor AK-42. AK-42 binds within the extracellular entryway of the Cl--permeation pathway, occupying a pocket previously proposed through computational docking studies. In the apo structure, we observed two distinct apo conformations of CLC-2 involving rotation of one of the cytoplasmic C-terminal domains (CTDs). In the absence of CTD rotation, an intracellular N-terminal 15-residue hairpin peptide nestles against the TM domain to physically occlude the Cl--permeation pathway from the intracellular side. This peptide is highly conserved among species variants of CLC-2 but is not present in any other CLC homologs. Previous studies suggested that the N-terminal domain of CLC-2 influences channel properties via a "ball-and-chain" gating mechanism, but conflicting data cast doubt on such a mechanism, and thus the structure of the N-terminal domain and its interaction with the channel has been uncertain. Through electrophysiological studies of an N-terminal deletion mutant lacking the 15-residue hairpin peptide, we show that loss of this short sequence increases the magnitude and decreases the rectification of CLC-2 currents expressed in mammalian cells. Furthermore, we show that with repetitive hyperpolarization WT CLC-2 currents increase in resemblance to the hairpin-deleted CLC-2 currents. These functional results combined with our structural data support a model in which the N-terminal hairpin of CLC-2 stabilizes a closed state of the channel by blocking the cytoplasmic Cl--permeation pathway.
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Affiliation(s)
- Mengyuan Xu
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305
| | - Torben Neelands
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305
| | - Alexander S. Powers
- Department of Chemistry, Stanford University, Stanford, CA 94305
- Department of Computer Science, Stanford University, Stanford, CA 94305
- Department of Structural Biology, Stanford University, Stanford, CA 94305
- Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305
| | - Yan Liu
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park 94025
| | - Steven D. Miller
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Grigore Pintilie
- Department of Bioengineering and Department of Microbiology and Immunology, Stanford University, Stanford, 94305
| | - J. Du Bois
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Ron O. Dror
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305
- Department of Computer Science, Stanford University, Stanford, CA 94305
- Department of Structural Biology, Stanford University, Stanford, CA 94305
- Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305
| | - Wah Chiu
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park 94025
- Department of Bioengineering and Department of Microbiology and Immunology, Stanford University, Stanford, 94305
| | - Merritt Maduke
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305
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Coppola MA, Pusch M, Imbrici P, Liantonio A. Small Molecules Targeting Kidney ClC-K Chloride Channels: Applications in Rare Tubulopathies and Common Cardiovascular Diseases. Biomolecules 2023; 13:biom13040710. [PMID: 37189456 DOI: 10.3390/biom13040710] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/15/2023] [Accepted: 04/19/2023] [Indexed: 05/17/2023] Open
Abstract
Given the key role played by ClC-K chloride channels in kidney and inner ear physiology and pathology, they can be considered important targets for drug discovery. Indeed, ClC-Ka and ClC-Kb inhibition would interfere with the urine countercurrent concentration mechanism in Henle's loop, which is responsible for the reabsorption of water and electrolytes from the collecting duct, producing a diuretic and antihypertensive effect. On the other hand, ClC-K/barttin channel dysfunctions in Bartter Syndrome with or without deafness will require the pharmacological recovery of channel expression and/or activity. In these cases, a channel activator or chaperone would be appealing. Starting from a brief description of the physio-pathological role of ClC-K channels in renal function, this review aims to provide an overview of the recent progress in the discovery of ClC-K channel modulators.
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Affiliation(s)
| | - Michael Pusch
- Institute of Biophysics, National Research Council, 16149 Genova, Italy
| | - Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", 70125 Bari, Italy
| | - Antonella Liantonio
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", 70125 Bari, Italy
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Langner E, Cheng T, Kefaloyianni E, Gluck C, Wang B, Mahjoub MR. Impaired centrosome biogenesis in kidney stromal progenitors reduces abundance of interstitial lineages and accelerates injury-induced fibrosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.04.535583. [PMID: 37066241 PMCID: PMC10104024 DOI: 10.1101/2023.04.04.535583] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Defective centrosome function can disrupt embryonic kidney development, by causing changes to the renal interstitium that leads to fibrocystic disease pathologies. Yet, it remains unknown how mutations in centrosome genes impact kidney interstitial cells. Here, we examined the consequences of defective centrosome biogenesis on stromal progenitor cell growth, differentiation and fate. Conditional deletion of Cep120 , a ciliopathy gene essential for centrosome duplication, in the stromal mesenchyme resulted in reduced abundance of pericytes, interstitial fibroblasts and mesangial cells. This was due to delayed mitosis, increased apoptosis, and changes in Wnt and Hedgehog signaling essential for differentiation of stromal lineages. Cep120 ablation resulted in hypoplastic kidneys with medullary atrophy and delayed nephron maturation. Finally, centrosome loss in the interstitium sensitized kidneys of adult mice, causing rapid fibrosis via enhanced TGF-β/Smad3-Gli2 signaling after renal injury. Our study defines the cellular and developmental defects caused by centrosome dysfunction in embryonic kidney stroma. Highlights Defective centrosome biogenesis in kidney stroma causes:Reduced abundance of stromal progenitors, interstitial and mesangial cell populationsDefects in cell-autonomous and paracrine signalingAbnormal/delayed nephrogenesis and tubular dilationsAccelerates injury-induced fibrosis via defective TGF-β/Smad3-Gli2 signaling axis.
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13
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Modus operandi of ClC-K2 Cl - Channel in the Collecting Duct Intercalated Cells. Biomolecules 2023; 13:biom13010177. [PMID: 36671562 PMCID: PMC9855527 DOI: 10.3390/biom13010177] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/10/2023] [Accepted: 01/13/2023] [Indexed: 01/18/2023] Open
Abstract
The renal collecting duct is known to play a critical role in many physiological processes, including systemic water-electrolyte homeostasis, acid-base balance, and the salt sensitivity of blood pressure. ClC-K2 (ClC-Kb in humans) is a Cl--permeable channel expressed on the basolateral membrane of several segments of the renal tubule, including the collecting duct intercalated cells. ClC-Kb mutations are causative for Bartters' syndrome type 3 manifested as hypotension, urinary salt wasting, and metabolic alkalosis. However, little is known about the significance of the channel in the collecting duct with respect to the normal physiology and pathology of Bartters' syndrome. In this review, we summarize the available experimental evidence about the signaling determinants of ClC-K2 function and the regulation by systemic and local factors as well as critically discuss the recent advances in understanding the collecting-duct-specific roles of ClC-K2 in adaptations to changes in dietary Cl- intake and maintaining systemic acid-base homeostasis.
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14
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Ye S, Wu P, Gao Z, Wang M, Zhou L, Qi Z. Inhibitory effect of S-nitroso-N-acetylpenicillamine on the basolateral 10-pS Cl- channel in thick ascending limb. PLoS One 2023; 18:e0284707. [PMID: 37083928 PMCID: PMC10121052 DOI: 10.1371/journal.pone.0284707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 04/05/2023] [Indexed: 04/22/2023] Open
Abstract
We have previously reported that L-arginine, a nitric oxide synthase substrate, inhibits the basolateral 10-pS Cl- channel through the cGMP/PKG signaling pathway in the thick ascending limb (TAL). As a NO releasing agent, the effect of S-nitroso-N-acetyl-penicillamine (SNAP) on the channel activity was examined in thick ascending limb of C57BL/6 mice in the present study. SNAP inhibited the basolateral 10-pS Cl- channel in a dose-dependent manner with an IC50 value of 6.6 μM. The inhibitory effect of SNAP was abolished not only by NO scavenger (carboxy-PTIO) but also by blockers of soluble guanylate cyclase (ODQ or LY-83583), indicating that the cGMP-dependent signaling pathway is involved. Moreover, the inhibitory effect of SNAP on the channel was strongly attenuated by a protein kinase G (PKG)-specific inhibitor, KT-5823, but not by the PDE2 inhibitor, BAY-60-7550. We concluded that SNAP inhibited the basolateral 10-pS Cl- channels in the TAL through a cGMP/PKG signaling pathway. As the 10-pS Cl- channel is important for regulation of NaCl absorption along the nephron, these data suggest that SNAP might be served as a regulator to prevent high-salt absorption related diseases, such as hypertension.
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Affiliation(s)
- Shiwei Ye
- Department of Basic Medical Sciences, School of Medicine, Xiamen University, Xiamen, China
| | - Peng Wu
- Department of Basic Medical Sciences, School of Medicine, Xiamen University, Xiamen, China
- Department of Nephrology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Zhongxiuzi Gao
- Department of Basic Medical Sciences, School of Medicine, Xiamen University, Xiamen, China
- Department of Nephrology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Mingyan Wang
- Department of Basic Medical Sciences, School of Medicine, Xiamen University, Xiamen, China
| | - Li Zhou
- Department of Basic Medical Sciences, School of Medicine, Xiamen University, Xiamen, China
| | - Zhi Qi
- Department of Basic Medical Sciences, School of Medicine, Xiamen University, Xiamen, China
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15
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Kelkar S, Nailwal N, Bhatia NY, Doshi G, Sathaye S, Godad AP. An Update On Proficiency of Voltage-gated Ion Channel Blockers in the Treatment of Inflammation-associated Diseases. Curr Drug Targets 2022; 23:1290-1303. [PMID: 35996239 DOI: 10.2174/1389450123666220819141827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 05/24/2022] [Accepted: 06/21/2022] [Indexed: 01/25/2023]
Abstract
Inflammation is the body's mechanism to trigger the immune system, thereby preventing bacteria and viruses from manifesting their toxic effect. Inflammation plays a vital role in regulating inflammatory mediator levels to initiate the wound healing process depending on the nature of the stimuli. This process occurs due to chemical release from white blood cells by elevating blood flow to the site of action, leading to redness and increased body temperature. Currently, there are numerous Non-steroidal anti-inflammatory drugs (NSAIDs) available, but these drugs are reported with adverse effects such as gastric bleeding, progressive kidney damage, and increased risk of heart attacks when prolonged use. For such instances, alternative options need to be adopted. The introduction of voltage-gated ion channel blockers can be a substantial alternative to mask the side effects of these currently available drugs. Chronic inflammatory disorders such as rheumatoid and osteoarthritis, cancer and migraine, etc., can cause dreadful pain, which is often debilitating for the patient. The underlying mechanism for both acute and chronic inflammation involves various complex receptors, different types of cells, receptors, and proteins. The working of voltage-gated sodium and calcium channels is closely linked to both inflammatory and neuropathic pain. Certain drugs such as carbamazepine and gabapentin, which are ion channel blockers, have greater pharmacotherapeutic activity for sodium and calcium channel blockers for the treatment of chronic inflammatory pain states. This review intends to provide brief information on the mechanism of action, latest clinical trials, and applications of these blockers in treating inflammatory conditions.
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Affiliation(s)
- Siddesh Kelkar
- MET Institute of Pharmacy, Bhujbal Knowledge City, Reclamation, Bandra West, Mumbai, Maharashtra 400050, India
| | - Namrata Nailwal
- SVKM's Dr. Bhanuben Nanavati College of Pharmacy, Mithibai College Campus, Vaikunthlal Mehta Rd, Vile Parle West, Mumbai, Maharashtra 400056, India
| | - Nirav Yogesh Bhatia
- SVKM's Dr. Bhanuben Nanavati College of Pharmacy, Mithibai College Campus, Vaikunthlal Mehta Rd, Vile Parle West, Mumbai, Maharashtra 400056, India
| | - Gaurav Doshi
- SVKM's Dr. Bhanuben Nanavati College of Pharmacy, Mithibai College Campus, Vaikunthlal Mehta Rd, Vile Parle West, Mumbai, Maharashtra 400056, India
| | - Sadhana Sathaye
- Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, Mumbai, India
| | - Angel Pavalu Godad
- SVKM's Dr. Bhanuben Nanavati College of Pharmacy, Mithibai College Campus, Vaikunthlal Mehta Rd, Vile Parle West, Mumbai, Maharashtra 400056, India.,Department of Pharmaceutical Sciences and Technology, Institute of Chemical Technology, Mumbai, India
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16
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Pyrshev K, Khayyat NH, Stavniichuk A, Tomilin VN, Zaika O, Ramkumar N, Pochynyuk O. ClC-K2 Cl - channel allows identification of A- and B-type of intercalated cells in split-opened collecting ducts. FASEB J 2022; 36:e22275. [PMID: 35349181 PMCID: PMC9014849 DOI: 10.1096/fj.202200160r] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/01/2022] [Accepted: 03/14/2022] [Indexed: 11/11/2022]
Abstract
The collecting duct is a highly adaptive terminal part of the nephron, which is essential for maintaining systemic homeostasis. Principal and intercalated cells perform different physiological tasks and exhibit distinctive morphology. However, acid-secreting A- and base secreting B-type of intercalated cells cannot be easily separated in functional studies. We used BCECF-sensitive intracellular pH (pHi ) measurements in split-opened collecting ducts followed by immunofluorescent microscopy in WT and intercalated cell-specific ClC-K2-/- mice to demonstrate that ClC-K2 inhibition enables to distinguish signals from A- and B-intercalated cells. We show that ClC-K2 Cl- channel is expressed on the basolateral side of intercalated cells, where it governs Cl- -dependent H+ /HCO3 - transport. ClC-K2 blocker, NPPB, caused acidification or alkalization in different subpopulations of intercalated cells in WT but not ClC-K2-/- mice. Immunofluorescent assessment of the same collecting ducts revealed that NPPB increased pHi in AE1-positive A-type and decreased pHi in pendrin-positive B-type of intercalated cells. Induction of metabolic acidosis led to a significantly augmented abundance and H+ secretion in A-type and decreased proton transport in B-type of intercalated cells, whereas metabolic alkalosis caused the opposite changes in intercalated cell function, but did not substantially change their relative abundance. Overall, we show that inhibition of ClC-K2 can be employed to discriminate between A- and B-type of intercalated cells in split-opened collecting duct preparations. We further demonstrate that this method can be used to independently monitor changes in the functional status and abundance of A- and B-type in response to systemic acid/base stimuli.
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Affiliation(s)
- Kyrylo Pyrshev
- Department of Integrative Biology and Pharmacology, the University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Naghmeh Hassanzadeh Khayyat
- Department of Integrative Biology and Pharmacology, the University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Anna Stavniichuk
- Department of Integrative Biology and Pharmacology, the University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Viktor N Tomilin
- Department of Integrative Biology and Pharmacology, the University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Oleg Zaika
- Department of Integrative Biology and Pharmacology, the University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Nirupama Ramkumar
- Division of Nephrology and Hypertension, University of Utah Health, Salt Lake City, Utah, USA
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology, the University of Texas Health Science Center at Houston, Houston, Texas, USA
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17
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Kouyoumdzian NM, Kim G, Rudi MJ, Rukavina Mikusic NL, Fernández BE, Choi MR. Clues and new evidences in arterial hypertension: unmasking the role of the chloride anion. Pflugers Arch 2021; 474:155-176. [PMID: 34966955 DOI: 10.1007/s00424-021-02649-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 12/02/2021] [Accepted: 12/03/2021] [Indexed: 02/06/2023]
Abstract
The present review will focus on the role of chloride anion in cardiovascular disease, with special emphasis in the development of hypertensive disease and vascular inflammation. It is known that acute and chronic overload of sodium chloride increase blood pressure and have pro-inflammatory and pro-fibrotic effects on different target organs, but it is unknown how chloride may influence these processes. Chloride anion is the predominant anion in the extracellular fluid and its intracellular concentration is dynamically regulated. As the queen of the electrolytes, it is of crucial importance to understand the physiological mechanisms that regulate the cellular handling of this anion including the different transporters and cellular chloride channels, which exert a variety of functions, such as regulation of cellular proliferation, differentiation, migration, apoptosis, intracellular pH and cellular redox state. In this article, we will also review the relationship between dietary, serum and intracellular chloride and how these different sources of chloride in the organism are affected in hypertension and their impact on cardiovascular disease. Additionally, we will discuss the approach of potential strategies that affect chloride handling and its potential effect on cardiovascular system, including pharmacological blockade of chloride channels and non-pharmacological interventions by replacing chloride by another anion.
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Affiliation(s)
- Nicolás Martín Kouyoumdzian
- Universidad de Buenos Aires, CONICET, Instituto Alberto C. Taquini de Investigaciones en Medicina Traslacional (IATIMET), Buenos Aires, Argentina.
| | - Gabriel Kim
- Facultad de Farmacia Y Bioquímica, Departamento de Ciencias Biológicas, Cátedra de Anatomía e Histología, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - María Julieta Rudi
- Facultad de Farmacia Y Bioquímica, Departamento de Ciencias Biológicas, Cátedra de Anatomía e Histología, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Natalia Lucía Rukavina Mikusic
- Facultad de Farmacia Y Bioquímica, Departamento de Ciencias Biológicas, Cátedra de Anatomía e Histología, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | - Marcelo Roberto Choi
- Universidad de Buenos Aires, CONICET, Instituto Alberto C. Taquini de Investigaciones en Medicina Traslacional (IATIMET), Buenos Aires, Argentina.,Facultad de Farmacia Y Bioquímica, Departamento de Ciencias Biológicas, Cátedra de Anatomía e Histología, Universidad de Buenos Aires, Buenos Aires, Argentina.,Instituto Universitario de Ciencias de La Salud, Fundación H.A. Barceló, Buenos Aires, Argentina
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18
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Marcoux AA, Tremblay LE, Slimani S, Fiola MJ, Mac-Way F, Haydock L, Garneau AP, Isenring P. Anatomophysiology of the Henle's Loop: Emphasis on the Thick Ascending Limb. Compr Physiol 2021; 12:3119-3139. [PMID: 34964111 DOI: 10.1002/cphy.c210021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The loop of Henle plays a variety of important physiological roles through the concerted actions of ion transport systems in both its apical and basolateral membranes. It is involved most notably in extracellular fluid volume and blood pressure regulation as well as Ca2+ , Mg2+ , and acid-base homeostasis because of its ability to reclaim a large fraction of the ultrafiltered solute load. This nephron segment is also involved in urinary concentration by energizing several of the steps that are required to generate a gradient of increasing osmolality from cortex to medulla. Another important role of the loop of Henle is to sustain a process known as tubuloglomerular feedback through the presence of specialized renal tubular cells that lie next to the juxtaglomerular arterioles. This article aims at describing these physiological roles and at discussing a number of the molecular mechanisms involved. It will also report on novel findings and uncertainties regarding the realization of certain processes and on the pathophysiological consequences of perturbed salt handling by the thick ascending limb of the loop of Henle. Since its discovery 150 years ago, the loop of Henle has remained in the spotlight and is now generating further interest because of its role in the renal-sparing effect of SGLT2 inhibitors. © 2022 American Physiological Society. Compr Physiol 12:1-21, 2022.
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Affiliation(s)
- Andrée-Anne Marcoux
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Laurence E Tremblay
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Samira Slimani
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Marie-Jeanne Fiola
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Fabrice Mac-Way
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Ludwig Haydock
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
| | - Alexandre P Garneau
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada.,Cardiometabolic Axis, School of Kinesiology and Physical Activity Sciences, University of Montréal, Montréal, QC, Canada
| | - Paul Isenring
- Nephrology Research Group, Department of Medicine, Laval University, Québec, QC, Canada
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19
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Lin MH, Chen JC, Tian X, Lee CM, Yu IS, Lo YF, Uchida S, Huang CL, Chen BC, Cheng CJ. Impairment in renal medulla development underlies salt wasting in Clc-k2 channel deficiency. JCI Insight 2021; 6:e151039. [PMID: 34499620 PMCID: PMC8564913 DOI: 10.1172/jci.insight.151039] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 09/08/2021] [Indexed: 12/13/2022] Open
Abstract
The prevailing view is that the ClC-Ka chloride channel (mouse Clc-k1) functions in the thin ascending limb to control urine concentration, whereas the ClC-Kb channel (mouse Clc-k2) functions in the thick ascending limb (TAL) to control salt reabsorption. Mutations of ClC-Kb cause classic Bartter syndrome, characterized by renal salt wasting, with perinatal to adolescent onset. We studied the roles of Clc-k channels in perinatal mouse kidneys using constitutive or inducible kidney-specific gene ablation and 2D and advanced 3D imaging of optically cleared kidneys. We show that Clc-k1 and Clc-k2 were broadly expressed and colocalized in perinatal kidneys. Deletion of Clc-k1 and Clc-k2 revealed that both participated in NKCC2- and NCC-mediated NaCl reabsorption in neonatal kidneys. Embryonic deletion of Clc-k2 caused tubular injury and impaired renal medulla and TAL development. Inducible deletion of Clc-k2 beginning after medulla maturation produced mild salt wasting resulting from reduced NCC activity. Thus, both Clc-k1 and Clc-k2 contributed to salt reabsorption in TAL and distal convoluted tubule (DCT) in neonates, potentially explaining the less-severe phenotypes in classic Bartter syndrome. As opposed to the current understanding that salt wasting in adult patients with Bartter syndrome is due to Clc-k2 deficiency in adult TAL, our results suggest that it originates mainly from defects occurring in the medulla and TAL during development.
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Affiliation(s)
- Meng-Hsuan Lin
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, and.,Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
| | - Jen-Chi Chen
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, and
| | - Xuejiao Tian
- Brain Research Center, National Tsing Hua University, Hsinchu, Taiwan
| | - Chia-Ming Lee
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - I-Shing Yu
- Laboratory Animal Center, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yi-Fen Lo
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, and
| | - Shinichi Uchida
- Department of Nephrology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Chou-Long Huang
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Bi-Chang Chen
- Brain Research Center, National Tsing Hua University, Hsinchu, Taiwan.,Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Chih-Jen Cheng
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, and.,Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan.,Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
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20
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Murillo-de-Ozores AR, Chávez-Canales M, de los Heros P, Gamba G, Castañeda-Bueno M. Physiological Processes Modulated by the Chloride-Sensitive WNK-SPAK/OSR1 Kinase Signaling Pathway and the Cation-Coupled Chloride Cotransporters. Front Physiol 2020; 11:585907. [PMID: 33192599 PMCID: PMC7606576 DOI: 10.3389/fphys.2020.585907] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 09/29/2020] [Indexed: 12/15/2022] Open
Abstract
The role of Cl- as an intracellular signaling ion has been increasingly recognized in recent years. One of the currently best described roles of Cl- in signaling is the modulation of the With-No-Lysine (K) (WNK) - STE20-Proline Alanine rich Kinase (SPAK)/Oxidative Stress Responsive Kinase 1 (OSR1) - Cation-Coupled Cl- Cotransporters (CCCs) cascade. Binding of a Cl- anion to the active site of WNK kinases directly modulates their activity, promoting their inhibition. WNK activation due to Cl- release from the binding site leads to phosphorylation and activation of SPAK/OSR1, which in turn phosphorylate the CCCs. Phosphorylation by WNKs-SPAK/OSR1 of the Na+-driven CCCs (mediating ions influx) promote their activation, whereas that of the K+-driven CCCs (mediating ions efflux) promote their inhibition. This results in net Cl- influx and feedback inhibition of WNK kinases. A wide variety of alterations to this pathway have been recognized as the cause of several human diseases, with manifestations in different systems. The understanding of WNK kinases as Cl- sensitive proteins has allowed us to better understand the mechanistic details of regulatory processes involved in diverse physiological phenomena that are reviewed here. These include cell volume regulation, potassium sensing and intracellular signaling in the renal distal convoluted tubule, and regulation of the neuronal response to the neurotransmitter GABA.
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Affiliation(s)
- Adrián Rafael Murillo-de-Ozores
- Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
- Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - María Chávez-Canales
- Unidad de Investigación UNAM-INC, Instituto Nacional de Cardiología Ignacio Chávez and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Paola de los Heros
- Unidad de Investigación UNAM-INC, Research Division, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Gerardo Gamba
- Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - María Castañeda-Bueno
- Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
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21
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Empitu MA, Kadariswantiningsih IN. Modelling salt transport disorders of human kidney in zebrafish: the grain of salt. J Physiol 2019; 597:5529-5530. [PMID: 31571217 DOI: 10.1113/jp278802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 09/26/2019] [Indexed: 11/08/2022] Open
Affiliation(s)
- Maulana A Empitu
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan.,Faculty of Medicine, Universitas Airlangga, Surabaya, East Java, Indonesia
| | - Ika N Kadariswantiningsih
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan.,Faculty of Medicine, Universitas Airlangga, Surabaya, East Java, Indonesia
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22
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Nicoli ER, Weston MR, Hackbarth M, Becerril A, Larson A, Zein WM, Baker PR, Burke JD, Dorward H, Davids M, Huang Y, Adams DR, Zerfas PM, Chen D, Markello TC, Toro C, Wood T, Elliott G, Vu M, Zheng W, Garrett LJ, Tifft CJ, Gahl WA, Day-Salvatore DL, Mindell JA, Malicdan MCV, Acosta MT, Adams DR, Agrawal P, Alejandro ME, Allard P, Alvey J, Andrews A, Ashley EA, Azamian MS, Bacino CA, Bademci G, Baker E, Balasubramanyam A, Baldridge D, Bale J, Barbouth D, Batzli GF, Bayrak-Toydemir P, Beggs AH, Bejerano G, Bellen HJ, Bernstein JA, Berry GT, Bican A, Bick DP, Birch CL, Bivona S, Bohnsack J, Bonnenmann C, Bonner D, Boone BE, Bostwick BL, Botto L, Briere LC, Brokamp E, Brown DM, Brush M, Burke EA, Burrage LC, Butte MJ, Carey J, Carrasquillo O, Chang TCP, Chao HT, Clark GD, Coakley TR, Cobban LA, Cogan JD, Cole FS, Colley HA, Cooper CM, Cope H, Craigen WJ, D'Souza P, Dasari S, Davids M, Dayal JG, Dell'Angelica EC, Dhar SU, Dorrani N, Dorset DC, Douine ED, Draper DD, Duncan L, Eckstein DJ, Emrick LT, Eng CM, Esteves C, Estwick T, Fernandez L, Ferreira C, Fieg EL, Fisher PG, Fogel BL, Forghani I, Fresard L, Gahl WA, Godfrey RA, Goldman AM, Goldstein DB, Gourdine JPF, Grajewski A, Groden CA, Gropman AL, Haendel M, Hamid R, Hanchard NA, Hayes N, High F, Holm IA, Hom J, Huang A, Huang Y, Isasi R, Jamal F, Jiang YH, Johnston JM, Jones AL, Karaviti L, Kelley EG, Kiley D, Koeller DM, Kohane IS, Kohler JN, Krakow D, Krasnewich DM, Korrick S, Koziura M, Krier JB, Kyle JE, Lalani SR, Lam B, Lanpher BC, Lanza IR, Lau CC, Lazar J, LeBlanc K, Lee BH, Lee H, Levitt R, Levy SE, Lewis RA, Lincoln SA, Liu P, Liu XZ, Longo N, Loo SK, Loscalzo J, Maas RL, Macnamara EF, MacRae CA, Maduro VV, Majcherska MM, Malicdan MCV, Mamounas LA, Manolio TA, Mao R, Markello TC, Marom R, Marth G, Martin BA, Martin MG, Martínez-Agosto JA, Marwaha S, May T, McCauley J, McConkie-Rosell A, McCormack CE, McCray AT, Metz TO, Might M, Morava-Kozicz E, Moretti PM, Morimoto M, Mulvihill JJ, Murdock DR, Nath A, Nelson SF, Newberry JS, Newman JH, Nicholas SK, Novacic D, Oglesbee D, Orengo JP, Pace L, Pak S, Pallais JC, Palmer CG, Papp JC, Parker NH, Phillips JA, Posey JE, Postlethwait JH, Potocki L, Pusey BN, Quinlan A, Raja AN, Renteria G, Reuter CM, Rives L, Robertson AK, Rodan LH, Rosenfeld JA, Rowley RK, Ruzhnikov M, Sacco R, Sampson JB, Samson SL, Saporta M, Schaechter J, Schedl T, Schoch K, Scott DA, Shakachite L, Sharma P, Shashi V, Shields K, Shin J, Signer R, Sillari CH, Silverman EK, Sinsheimer JS, Sisco K, Smith KS, Solnica-Krezel L, Spillmann RC, Stoler JM, Stong N, Sullivan JA, Sutton S, Sweetser DA, Tabor HK, Tamburro CP, Tan QKG, Tekin M, Telischi F, Thorson W, Tifft CJ, Toro C, Tran AA, Urv TK, Velinder M, Viskochil D, Vogel TP, Wahl CE, Walley NM, Walsh CA, Walker M, Wambach J, Wan J, Wang LK, Wangler MF, Ward PA, Waters KM, Webb-Robertson BJM, Wegner D, Westerfield M, Wheeler MT, Wise AL, Wolfe LA, Woods JD, Worthey EA, Yamamoto S, Yang J, Yoon AJ, Yu G, Zastrow DB, Zhao C, Zuchner S. Lysosomal Storage and Albinism Due to Effects of a De Novo CLCN7 Variant on Lysosomal Acidification. Am J Hum Genet 2019; 104:1127-1138. [PMID: 31155284 PMCID: PMC6562152 DOI: 10.1016/j.ajhg.2019.04.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 04/10/2019] [Indexed: 12/15/2022] Open
Abstract
Optimal lysosome function requires maintenance of an acidic pH maintained by proton pumps in combination with a counterion transporter such as the Cl-/H+ exchanger, CLCN7 (ClC-7), encoded by CLCN7. The role of ClC-7 in maintaining lysosomal pH has been controversial. In this paper, we performed clinical and genetic evaluations of two children of different ethnicities. Both children had delayed myelination and development, organomegaly, and hypopigmentation, but neither had osteopetrosis. Whole-exome and -genome sequencing revealed a de novo c.2144A>G variant in CLCN7 in both affected children. This p.Tyr715Cys variant, located in the C-terminal domain of ClC-7, resulted in increased outward currents when it was heterologously expressed in Xenopus oocytes. Fibroblasts from probands displayed a lysosomal pH approximately 0.2 units lower than that of control cells, and treatment with chloroquine normalized the pH. Primary fibroblasts from both probands also exhibited markedly enlarged intracellular vacuoles; this finding was recapitulated by the overexpression of human p.Tyr715Cys CLCN7 in control fibroblasts, reflecting the dominant, gain-of-function nature of the variant. A mouse harboring the knock-in Clcn7 variant exhibited hypopigmentation, hepatomegaly resulting from abnormal storage, and enlarged vacuoles in cultured fibroblasts. Our results show that p.Tyr715Cys is a gain-of-function CLCN7 variant associated with developmental delay, organomegaly, and hypopigmentation resulting from lysosomal hyperacidity, abnormal storage, and enlarged intracellular vacuoles. Our data supports the hypothesis that the ClC-7 antiporter plays a critical role in maintaining lysosomal pH.
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Gonzalez-Vicente A, Saez F, Monzon CM, Asirwatham J, Garvin JL. Thick Ascending Limb Sodium Transport in the Pathogenesis of Hypertension. Physiol Rev 2019; 99:235-309. [PMID: 30354966 DOI: 10.1152/physrev.00055.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The thick ascending limb plays a key role in maintaining water and electrolyte balance. The importance of this segment in regulating blood pressure is evidenced by the effect of loop diuretics or local genetic defects on this parameter. Hormones and factors produced by thick ascending limbs have both autocrine and paracrine effects, which can extend prohypertensive signaling to other structures of the nephron. In this review, we discuss the role of the thick ascending limb in the development of hypertension, not as a sole participant, but one that works within the rich biological context of the renal medulla. We first provide an overview of the basic physiology of the segment and the anatomical considerations necessary to understand its relationship with other renal structures. We explore the physiopathological changes in thick ascending limbs occurring in both genetic and induced animal models of hypertension. We then discuss the racial differences and genetic defects that affect blood pressure in humans through changes in thick ascending limb transport rates. Throughout the text, we scrutinize methodologies and discuss the limitations of research techniques that, when overlooked, can lead investigators to make erroneous conclusions. Thus, in addition to advancing an understanding of the basic mechanisms of physiology, the ultimate goal of this work is to understand our research tools, to make better use of them, and to contextualize research data. Future advances in renal hypertension research will require not only collection of new experimental data, but also integration of our current knowledge.
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Affiliation(s)
| | - Fara Saez
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Casandra M Monzon
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jessica Asirwatham
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jeffrey L Garvin
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
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24
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Lagostena L, Zifarelli G, Picollo A. New Insights into the Mechanism of NO 3 - Selectivity in the Human Kidney Chloride Channel ClC-Ka and the CLC Protein Family. J Am Soc Nephrol 2019; 30:293-302. [PMID: 30635372 DOI: 10.1681/asn.2018060593] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 12/01/2018] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND The mechanism of anion selectivity in the human kidney chloride channels ClC-Ka and ClC-Kb is unknown. However, it has been thought to be very similar to that of other channels and antiporters of the CLC protein family, and to rely on anions interacting with a conserved Ser residue (Sercen) at the center of three anion binding sites in the permeation pathway Scen. In both CLC channels and antiporters, mutations of Sercen alter the anion selectivity. Structurally, the side chain of Sercen of CLC channels and antiporters typically projects into the pore and coordinates the anion bound at Scen. METHODS To investigate the role of several residues in anion selectivity of ClC-Ka, we created mutations that resulted in amino acid substitutions in these residues. We also used electrophysiologic techniques to assess the properties of the mutants. RESULTS Mutations in ClC-Ka that change Sercen to Gly, Pro, or Thr have only minor effects on anion selectivity, whereas the mutations in residues Y425A, F519A, and Y520A increase the NO3 -/Cl- permeability ratio, with Y425A having a particularly strong effect. CONCLUSION s ClC-Ka's mechanism of anion selectivity is largely independent of Sercen, and it is therefore unique in the CLC protein family. We identified the residue Y425 in ClC-Ka-and the corresponding residue (A417) in the chloride channel ClC-0-as residues that contribute to NO3 - discrimination in these channels. This work provides important and timely insight into the relationship between structure and function for the kidney chloride channels ClC-Ka and ClC-Kb, and for CLC proteins in general.
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Affiliation(s)
- Laura Lagostena
- Dulbecco Telethon Laboratory, Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy; and
| | - Giovanni Zifarelli
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Alessandra Picollo
- Dulbecco Telethon Laboratory, Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy; and
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25
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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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26
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Abstract
Since its discovery, aldosterone and ion modulation have been entwined. While scientific investigations throughout the decades have emphasized aldosterone's connection to Na+, K+, and H+ homeostasis, more recent research has demonstrated a relationship between aldosterone and Mg2+, Ca2+, and Cl- homeostasis. The mechanisms connecting aldosterone to ion regulation frequently involve ion channels; the membrane localized proteins containing at least one aqueous pore for ion conduction. In order to precisely control intracellular or intraorganelle ion concentrations, ion channels have evolved highly specific regions within the conduction pore that select ions by charge, size, and/or dehydration energy requirement, meaning aldosterone must be able to modulate multiple ion channels to regulate the many ions described above. The list of ion channels presently connected to aldosterone includes ENaC (Na+), ROMK/BK (K+), TRPV4/5/6 (Ca2+), TRPM7/6 (Mg2+), and ClC-K/CFTR (Cl-), among others. This list is only expected to grow over time, as the promiscuity of aldosterone becomes more understood.
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Affiliation(s)
| | - Rhian M Touyz
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Alvin Shrier
- Department of Physiology, McGill University, Montreal, QC, Canada.
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27
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Wang C, Chen Y, Zheng B, Zhu M, Fan J, Wang J, Jia Z, Huang S, Zhang A. Novel compound heterozygous CLCNKB gene mutations (c.1755A>G/c.848_850delTCT) cause classic Bartter syndrome. Am J Physiol Renal Physiol 2018; 315:F844-F851. [PMID: 29442545 DOI: 10.1152/ajprenal.00077.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inactivated variants in CLCNKB gene encoding the basolateral chloride channel ClC-Kb cause classic Bartter syndrome characterized by hypokalemic metabolic alkalosis and hyperreninemic hyperaldosteronism. Here, we identified two cBS siblings presenting hypokalemia in a Chinese family due to novel compound heterozygous CLCNKB mutations (c.848_850delTCT/c.1755A>G). Compound heterozygosity was confirmed by amplifying and sequencing the patient's genomic DNA. The synonymous mutation c.1755A>G (Thr585Thr) was located at +2 bp from the 5' splice donor site in exon 15. Further transcript analysis demonstrated that this single nucleotide mutation causes exclusion of exon 15 in the cDNA from the proband and his mother. Furthermore, we investigated the expression and protein trafficking change of c.848_850delTCT (ΔTCT) and exon 15 deletion (ΔE15) mutation in vitro. The ΔE15 mutation markedly decreased the expression of ClC-Kb and resulted in a low-molecular-weight band (~55 kDa) trapping in the endoplasmic reticulum, while the ΔTCT mutant only decreased the total and plasma membrane ClC-Kb protein expression but did not affect the subcellular localization. Finally, we studied the physiological functions of mutations by using whole cell patch-clamp and found that the ΔE15 or ΔTCT mutation decreased the current of the ClC-Kb/barttin channel. These results suggested that the compound defective mutations of the CLCNKB gene are the molecular mechanism of the two cBS siblings.
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Affiliation(s)
- Chunli Wang
- Nanjing Key Laboratory of Pediatrics, Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Ying Chen
- Department of Nephrology, Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Bixia Zheng
- Nanjing Key Laboratory of Pediatrics, Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Mengshu Zhu
- Nanjing Key Laboratory of Pediatrics, Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Jia Fan
- Department of Physiology, Nanjing Medical University , Nanjing , China
| | - Juejin Wang
- Department of Physiology, Nanjing Medical University , Nanjing , China
| | - Zhanjun Jia
- Nanjing Key Laboratory of Pediatrics, Children's Hospital of Nanjing Medical University , Nanjing , China
| | - Songming Huang
- Department of Nephrology, Children's Hospital of Nanjing Medical University , Nanjing , China.,Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University , Nanjing , China
| | - Aihua Zhang
- Department of Nephrology, Children's Hospital of Nanjing Medical University , Nanjing , China.,Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University , Nanjing , China
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28
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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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Differential localizations of the myo-inositol transporters HMIT and SMIT1 in the cochlear stria vascularis. Neurosci Lett 2018; 674:88-93. [PMID: 29551423 DOI: 10.1016/j.neulet.2018.03.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 02/28/2018] [Accepted: 03/13/2018] [Indexed: 11/22/2022]
Abstract
The cochlear stria vascularis produces endolymph and thereby plays an active role in inner ear homeostasis. We recently reported that the H+/myo-inositol cotransporter (HMIT) gene is expressed in the stria vascularis. Here, we examined the protein localization of HMIT and Na+/myo-inositol cotransporter 1 (SMIT1) in the stria vascularis by immunohistochemistry. HMIT and SMIT1 were detected in the lateral wall of the cochlear duct. HMIT was widely detected throughout the stria vascularis, while SMIT1 was enriched in the strial basal cells. To examine the localization of HMIT in the stria vascularis in more detail, dissociated strial cells were immunostained, which resulted in the detection of HMIT immunoreactivity in marginal cells. These results indicate that HMIT is expressed in marginal cells and basal cells of the stria vascularis, while SMIT1 expression is enriched in basal cells. We speculate that HMIT and SMIT1 may play important roles in the homeostasis of cochlear fluids, for example by participating in pH regulation and osmoregulation.
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30
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Wingo CS, Stockand JD. Alkaline activation of ClC-K2 chloride channels switches renal cells from reabsorbing to secreting. J Gen Physiol 2018; 148:195-9. [PMID: 27574289 PMCID: PMC5004340 DOI: 10.1085/jgp.201611669] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 08/05/2016] [Indexed: 12/28/2022] Open
Affiliation(s)
- Charles S Wingo
- Department of Medicine, University of Florida, Gainesville, FL 32610 Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32610 Nephrology Section, Department of Veteran Affairs Medical Center, Gainesville, FL 32608
| | - James D Stockand
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
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31
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Aldosterone, SGK1, and ion channels in the kidney. Clin Sci (Lond) 2018; 132:173-183. [PMID: 29352074 PMCID: PMC5817097 DOI: 10.1042/cs20171525] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 12/15/2017] [Accepted: 12/19/2017] [Indexed: 12/14/2022]
Abstract
Hyperaldosteronism, a common cause of hypertension, is strongly connected to Na+, K+, and Mg2+ dysregulation. Owing to its steroidal structure, aldosterone is an active transcriptional modifier when bound to the mineralocorticoid receptor (MR) in cells expressing the enzyme 11β-hydroxysteroid dehydrogenase 2, such as those comprising the aldosterone-sensitive distal nephron (ASDN). One such up-regulated protein, the ubiquitous serum and glucocorticoid regulated kinase 1 (SGK1), has the capacity to modulate the surface expression and function of many classes of renal ion channels, including those that transport Na+ (ENaC), K+ (ROMK/BK), Ca2+ (TRPV4/5/6), Mg2+ (TRPM7/6), and Cl− (ClC-K, CFTR). Here, we discuss the mechanisms by which ASDN expressed channels are up-regulated by SGK1, while highlighting newly discovered pathways connecting aldosterone to nonselective cation channels that are permeable to Mg2+ (TRPM7) or Ca2+ (TRPV4).
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32
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Pinelli L, Nissant A, Edwards A, Lourdel S, Teulon J, Paulais M. Dual regulation of the native ClC-K2 chloride channel in the distal nephron by voltage and pH. J Gen Physiol 2017; 148:213-26. [PMID: 27574292 PMCID: PMC5004338 DOI: 10.1085/jgp.201611623] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 07/07/2016] [Indexed: 12/23/2022] Open
Abstract
ClC-K2 is present on the basolateral membrane of kidney epithelial cells, but little is known about its single channel properties. Pinelli et al. record unitary ClC-K2 currents from intercalated cells of mouse connecting tubules and investigate their regulation by voltage, pH, Cl−, and Ca2+. ClC-K2, a member of the ClC family of Cl− channels and transporters, forms the major basolateral Cl− conductance in distal nephron epithelial cells and therefore plays a central role in renal Cl− absorption. However, its regulation remains largely unknown because of the fact that recombinant ClC-K2 has not yet been studied at the single-channel level. In the present study, we investigate the effects of voltage, pH, Cl−, and Ca2+ on native ClC-K2 in the basolateral membrane of intercalated cells from the mouse connecting tubule. The ∼10-pS channel shows a steep voltage dependence such that channel activity increases with membrane depolarization. Intracellular pH (pHi) and extracellular pH (pHo) differentially modulate the voltage dependence curve: alkaline pHi flattens the curve by causing an increase in activity at negative voltages, whereas alkaline pHo shifts the curve toward negative voltages. In addition, pHi, pHo, and extracellular Ca2+ strongly increase activity, mainly because of an increase in the number of active channels with a comparatively minor effect on channel open probability. Furthermore, voltage alters both the number of active channels and their open probability, whereas intracellular Cl− has little influence. We propose that changes in the number of active channels correspond to them entering or leaving an inactivated state, whereas modulation of open probability corresponds to common gating by these channels. We suggest that pH, through the combined effects of pHi and pHo on ClC-K2, might be a key regulator of NaCl absorption and Cl−/HCO3− exchange in type B intercalated cells.
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Affiliation(s)
- Laurent Pinelli
- Sorbonne Universités, Université Pierre-et-Marie-Curie Paris 06, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Centre National de la Recherche Scientifique ERL 8228, Centre de Recherche des Cordeliers, F-75006 Paris, France
| | - Antoine Nissant
- Sorbonne Universités, Université Pierre-et-Marie-Curie Paris 06, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Centre National de la Recherche Scientifique ERL 8228, Centre de Recherche des Cordeliers, F-75006 Paris, France
| | - Aurélie Edwards
- Sorbonne Universités, Université Pierre-et-Marie-Curie Paris 06, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Centre National de la Recherche Scientifique ERL 8228, Centre de Recherche des Cordeliers, F-75006 Paris, France
| | - Stéphane Lourdel
- Sorbonne Universités, Université Pierre-et-Marie-Curie Paris 06, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Centre National de la Recherche Scientifique ERL 8228, Centre de Recherche des Cordeliers, F-75006 Paris, France
| | - Jacques Teulon
- Sorbonne Universités, Université Pierre-et-Marie-Curie Paris 06, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Centre National de la Recherche Scientifique ERL 8228, Centre de Recherche des Cordeliers, F-75006 Paris, France
| | - Marc Paulais
- Sorbonne Universités, Université Pierre-et-Marie-Curie Paris 06, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Université Paris Descartes, Sorbonne Paris Cité, UMR_S 1138, Centre de Recherche des Cordeliers, F-75006 Paris, France Centre National de la Recherche Scientifique ERL 8228, Centre de Recherche des Cordeliers, F-75006 Paris, France
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Cheng CJ, Lo YF, Chen JC, Huang CL, Lin SH. Functional severity of CLCNKB mutations correlates with phenotypes in patients with classic Bartter's syndrome. J Physiol 2017; 595:5573-5586. [PMID: 28555925 PMCID: PMC5556149 DOI: 10.1113/jp274344] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Accepted: 05/08/2017] [Indexed: 12/28/2022] Open
Abstract
KEY POINTS The highly variable phenotypes observed in patients with classic Bartter's syndrome (BS) remain unsatisfactorily explained. The wide spectrum of functional severity of CLCNKB mutations may contribute to the phenotypic variability, and the genotype-phenotype association has not been established. Low-level expression of the human ClC-Kb channel in mammalian cells impedes the functional study of CLCNKB mutations, and the underlying cause is still unclear. The human ClC-Kb channel is highly degraded by proteasome in human embryonic kidney cells. The C-terminal in-frame green fluorescent protein fusion may slow down the proteasome-mediated proteolysis. Barttin co-expression necessarily improves the stability, membrane trafficking and gating of ClC-Kb. CLCNKB mutations in barttin-binding sites, dimer interface or selectivity filter often have severe functional consequences. The remaining chloride conductance of the ClC-Kb mutant channel significantly correlates with the phenotypes, such as age at diagnosis, plasma chloride concentration, and the degree of calciuria in patients with classic BS. ABSTRACT Mutations in the CLCNKB gene encoding the human voltage-gated chloride ClC-Kb (hClC-Kb) channel cause classic Bartter's syndrome (BS). In contrast to antenatal BS, classic BS manifests with highly variable phenotypes. The functional severity of the mutant channel has been proposed to explain this phenomenon. Due to difficulties in the expression of hClC-Kb in heterologous expression systems, the functional consequences of mutant channels have not been thoroughly examined, and the genotype-phenotype association has not been established. In this study, we found that hClC-Kb, when expressed in human embryonic kidney (HEK) cells, was unstable due to degradation by proteasome. In-frame fusion of green fluorescent protein (GFP) to the C-terminus of the channel may ameliorate proteasome degradation. Co-expression of barttin increased protein abundance and membrane trafficking of hClC-Kb and markedly increased functional chloride current. We then functionally characterized 18 missense mutations identified in our classic BS cohort and others using HEK cells expressing hClC-Kb-GFP. Most CLCNKB mutations resulted in marked reduction in protein abundance and chloride current, especially those residing at barttin binding sites, dimer interface and selectivity filter. We enrolled classic BS patients carrying homozygous missense mutations with well-described functional consequences and clinical presentations for genotype-phenotype analysis. We found significant correlations of mutant chloride current with the age at diagnosis, plasma chloride concentration and urine calcium excretion rate. In conclusion, hClC-Kb expression in HEK cells is susceptible to proteasome degradation, and fusion of GFP to the C-terminus of hClC-Kb improves protein expression. The functional severity of the CLCNKB mutation is an important determinant of the phenotype in classic BS.
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Affiliation(s)
- Chih-Jen Cheng
- Department of Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan
| | - Yi-Fen Lo
- Department of Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan
| | - Jen-Chi Chen
- Department of Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan
| | - Chou-Long Huang
- Department of Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-8856, USA
| | - Shih-Hua Lin
- Department of Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan
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Poroca DR, Pelis RM, Chappe VM. ClC Channels and Transporters: Structure, Physiological Functions, and Implications in Human Chloride Channelopathies. Front Pharmacol 2017; 8:151. [PMID: 28386229 PMCID: PMC5362633 DOI: 10.3389/fphar.2017.00151] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/09/2017] [Indexed: 02/04/2023] Open
Abstract
The discovery of ClC proteins at the beginning of the 1990s was important for the development of the Cl- transport research field. ClCs form a large family of proteins that mediate voltage-dependent transport of Cl- ions across cell membranes. They are expressed in both plasma and intracellular membranes of cells from almost all living organisms. ClC proteins form transmembrane dimers, in which each monomer displays independent ion conductance. Eukaryotic members also possess a large cytoplasmic domain containing two CBS domains, which are involved in transport modulation. ClC proteins function as either Cl- channels or Cl-/H+ exchangers, although all ClC proteins share the same basic architecture. ClC channels have two gating mechanisms: a relatively well-studied fast gating mechanism, and a slow gating mechanism, which is poorly defined. ClCs are involved in a wide range of physiological processes, including regulation of resting membrane potential in skeletal muscle, facilitation of transepithelial Cl- reabsorption in kidneys, and control of pH and Cl- concentration in intracellular compartments through coupled Cl-/H+ exchange mechanisms. Several inherited diseases result from C1C gene mutations, including myotonia congenita, Bartter's syndrome (types 3 and 4), Dent's disease, osteopetrosis, retinal degeneration, and lysosomal storage diseases. This review summarizes general features, known or suspected, of ClC structure, gating and physiological functions. We also discuss biophysical properties of mammalian ClCs that are directly involved in the pathophysiology of several human inherited disorders, or that induce interesting phenotypes in animal models.
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Affiliation(s)
- Diogo R Poroca
- Department of Physiology and Biophysics, Dalhousie University, Halifax NS, Canada
| | - Ryan M Pelis
- Department of Pharmacology, Dalhousie University, Halifax NS, Canada
| | - Valérie M Chappe
- Department of Physiology and Biophysics, Dalhousie University, Halifax NS, Canada
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Palygin O, Pochynyuk O, Staruschenko A. Role and mechanisms of regulation of the basolateral K ir 4.1/K ir 5.1K + channels in the distal tubules. Acta Physiol (Oxf) 2017; 219:260-273. [PMID: 27129733 PMCID: PMC5086442 DOI: 10.1111/apha.12703] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 01/28/2016] [Accepted: 04/28/2016] [Indexed: 12/11/2022]
Abstract
Epithelial K+ channels are essential for maintaining electrolyte and fluid homeostasis in the kidney. It is recognized that basolateral inward-rectifying K+ (Kir ) channels play an important role in the control of resting membrane potential and transepithelial voltage, thereby modulating water and electrolyte transport in the distal part of nephron and collecting duct. Monomeric Kir 4.1 (encoded by Kcnj10 gene) and heteromeric Kir 4.1/Kir 5.1 (Kir 4.1 together with Kir 5.1 (Kcnj16)) channels are abundantly expressed at the basolateral membranes of the distal convoluted tubule and the cortical collecting duct cells. Loss-of-function mutations in KCNJ10 cause EAST/SeSAME tubulopathy in humans associated with salt wasting, hypomagnesaemia, metabolic alkalosis and hypokalaemia. In contrast, mice lacking Kir 5.1 have severe renal phenotype that, apart from hypokalaemia, is the opposite of the phenotype seen in EAST/SeSAME syndrome. Experimental advances using genetic animal models provided critical insights into the physiological role of these channels in electrolyte homeostasis and the control of kidney function. Here, we discuss current knowledge about K+ channels at the basolateral membrane of the distal tubules with specific focus on the homomeric Kir 4.1 and heteromeric Kir 4.1/Kir 5.1 channels. Recently identified molecular mechanisms regulating expression and activity of these channels, such as cell acidification, dopamine, insulin and insulin-like growth factor-1, Src family protein tyrosine kinases, as well as the role of these channels in NCC-mediated transport in the distal convoluted tubules, are also described.
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Affiliation(s)
- Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
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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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Grill A, Schießl IM, Gess B, Fremter K, Hammer A, Castrop H. Salt-losing nephropathy in mice with a null mutation of the Clcnk2 gene. Acta Physiol (Oxf) 2016; 218:198-211. [PMID: 27421685 DOI: 10.1111/apha.12755] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 05/03/2016] [Accepted: 07/11/2016] [Indexed: 12/19/2022]
Abstract
AIM The basolateral chloride channel ClC-Kb facilitates Cl reabsorption in the distal nephron of the human kidney. Functional mutations in CLCNKB are associated with Bartter's syndrome type 3, a hereditary salt-losing nephropathy. To address the function of ClC-K2 in vivo, we generated ClC-K2-deficient mice. METHODS ClC-K2-deficient mice were generated using TALEN technology. RESULTS ClC-K2-deficient mice were viable and born in a Mendelian ratio. ClC-K2-/- mice showed no gross anatomical abnormalities, but they were growth retarded. The 24-h urine volume was increased in ClC-K2-/- mice (4.4 ± 0.6 compared with 0.9 ± 0.2 mL per 24 h in wild-type littermates; P = 0.001). Accordingly, ambient urine osmolarity was markedly reduced (590 ± 39 vs. 2216 ± 132 mosmol L-1 in wild types; P < 0.0001). During water restriction (24 h), urinary osmolarity increased to 1633 ± 153 and 3769 ± 129 mosmol L-1 in ClC-K2-/- and wild-type mice (n = 12; P < 0.0001), accompanied by a loss of body weight of 12 ± 0.4 and 8 ± 0.2% respectively (P < 0.0001). ClC-K2-/- mice showed an increased renal sodium excretion and compromised salt conservation during a salt-restricted diet. The salt-losing phenotype of ClC-K2-/- mice was associated with a reduced plasma volume, hypotension, a slightly reduced glomerular filtration rate, an increased renal prostaglandin E2 generation and a massively stimulated renin-angiotensin system. Clckb-/- mice showed a reduced sensitivity to furosemide and were completely resistant to thiazides. CONCLUSION Loss of ClC-K2 compromises TAL function and abolishes salt reabsorption in the distal convoluted tubule. Our data suggest that ClC-K2 is crucial for renal salt reabsorption and concentrating ability. ClC-K2-deficient mice in most aspects mimic patients with Bartter's syndrome type 3.
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Affiliation(s)
- A. Grill
- Institute of Physiology; University of Regensburg; Regensburg Germany
| | - I. M. Schießl
- Institute of Physiology; University of Regensburg; Regensburg Germany
| | - B. Gess
- Institute of Physiology; University of Regensburg; Regensburg Germany
| | - K. Fremter
- Institute of Physiology; University of Regensburg; Regensburg Germany
| | - A. Hammer
- Institute of Physiology; University of Regensburg; Regensburg Germany
| | - H. Castrop
- Institute of Physiology; University of Regensburg; Regensburg Germany
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Molecular bases of K + secretory cells in the inner ear: shared and distinct features between birds and mammals. Sci Rep 2016; 6:34203. [PMID: 27680950 PMCID: PMC5041087 DOI: 10.1038/srep34203] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 09/08/2016] [Indexed: 11/08/2022] Open
Abstract
In the cochlea, mammals maintain a uniquely high endolymphatic potential (EP), which is not observed in other vertebrate groups. However, a high [K+] is always present in the inner ear endolymph. Here, we show that Kir4.1, which is required in the mammalian stria vascularis to generate the highly positive EP, is absent in the functionally equivalent avian tegmentum vasculosum. In contrast, the molecular repertoire required for K+ secretion, specifically NKCC1, KCNQ1, KCNE1, BSND and CLC-K, is shared between the tegmentum vasculosum, the vestibular dark cells and the marginal cells of the stria vascularis. We further show that in barn owls, the tegmentum vasculosum is enlarged and a higher EP (~+34 mV) maintained, compared to other birds. Our data suggest that both the tegmentum vasculosum and the stratified stria vascularis evolved from an ancestral vestibular epithelium that already featured the major cell types of the auditory epithelia. Genetic recruitment of Kir4.1 specifically to strial melanocytes was then a crucial step in mammalian evolution enabling an increase in the cochlear EP. An increased EP may be related to high-frequency hearing, as this is a hallmark of barn owls among birds and mammals among amniotes.
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Luan H, Wu P, Wang M, Sui H, Fan L, Gu R. Effects of adenosine stimulation on the mRNA expression of CLCNKB in the basolateral medullary thick ascending limb of the rat kidney. Mol Med Rep 2016; 14:4391-4398. [PMID: 27748841 DOI: 10.3892/mmr.2016.5781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 08/06/2016] [Indexed: 11/06/2022] Open
Abstract
Adenosine is a molecule produced by several organs within the body, including the kidneys, where it acts as an autoregulatory factor. It mediates ion transport in several nephron segments, including the proximal tubule and the thick ascending limb (TAL). Ion transport is dictated in part by anionic chloride channels, which regulate crucial kidney functions, including the reabsorption of Na+ and Cl‑, urine concentration, and establishing and maintaining the corticomedullary osmotic gradient. The present study investigated the effects of adenosine on the mRNA expression of chloride voltage‑gated channel Kb (CLCNKB), a candidate gene involved in hypertension, which encodes for the ClC‑Kb channel. Medullary thick ascending limb (mTAL) tubules were isolated from the rat kidney, and primary cultures of mTAL cells from the mTAL tubules were established. The cells were treated with adenosine and the mRNA expression of CLCNKB was detected by reverse transcription‑quantitative polymerase chain reaction. The cells were also treated with pathways inhibitors (H8 and AACOCF3), and the protein expression of cyclic adenosine 3',5'‑monophosphate (cAMP)‑protein kinase A (PKA) and phospholipase A2 (PLA2) by were analyzed by western blotting. The findings indicated that adenosine increased the mRNA expression of CLCNKB in primary cultures of medullary TAL cells, and this stimulatory effect was regulated by the cAMP‑PKA and PLA2‑arachidonic acid (AA) pathways. The present study showed that adenosine affected the mRNA expression of CLCNKB, initially through the cAMP‑PKA pathway and then the PLA2‑AA pathway.
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Affiliation(s)
- Haiyan Luan
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Peng Wu
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Mingxiao Wang
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Hongyu Sui
- Department of Physiology, Basic Medical School, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Lili Fan
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Ruimin Gu
- Department of Pharmacology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
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Abstract
Myotonia (muscle stiffness) is a symptom of several inherited diseases in humans and also in animals. It is due to muscle membrane hyperexcitability, which, in turn, can be caused by mutations in plasma membrane ion channels. The skeletal muscle chloride channel CLC-1 provides the major part of muscle membrane conductance and is important for keeping this membrane close to its resting voltage. Mutations in CLC-1 can cause both recessive (Becker) and dominant (Thomsen) forms of myotonia. Some of these mutations have been introduced into the functional cDNA and analyzed in the Xenopus oocyte expression system. From these studies, it was concluded that CLC-1 functions as a homooligomer with probably four subunits. Dominant mutant subunits are assumed to associate with wild-type ones, leading to their inactivation. The principle disease-causing mechanism of dominant mutations is a drastic alteration in the voltage dependence of CLC-1 gating. Some mutations in CLC-1 can be inherited either recessively or dominantly, probably depending on the genetic background. These studies point to the important role of CLC-1 in muscle physiology and provide interesting insights into the structure and function of this gene family of voltage-gated chloride channels. NEUROSCIENTIST 2:225-232, 1996
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Affiliation(s)
- Klaus Steinmeyer
- Institute for Molecular Neuropathobiology Center for
Molecular Neurobiology (ZMNH) Hamburg University Hamburg
| | - Thomas J. Jentsch
- Institute for Molecular Neuropathobiology Center for
Molecular Neurobiology (ZMNH) Hamburg University Hamburg
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41
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Hennings JC, Andrini O, Picard N, Paulais M, Huebner AK, Cayuqueo IKL, Bignon Y, Keck M, Cornière N, Böhm D, Jentsch TJ, Chambrey R, Teulon J, Hübner CA, Eladari D. The ClC-K2 Chloride Channel Is Critical for Salt Handling in the Distal Nephron. J Am Soc Nephrol 2016; 28:209-217. [PMID: 27335120 DOI: 10.1681/asn.2016010085] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/04/2016] [Indexed: 11/03/2022] Open
Abstract
Chloride transport by the renal tubule is critical for blood pressure (BP), acid-base, and potassium homeostasis. Chloride uptake from the urinary fluid is mediated by various apical transporters, whereas basolateral chloride exit is thought to be mediated by ClC-Ka/K1 and ClC-Kb/K2, two chloride channels from the ClC family, or by KCl cotransporters from the SLC12 gene family. Nevertheless, the localization and role of ClC-K channels is not fully resolved. Because inactivating mutations in ClC-Kb/K2 cause Bartter syndrome, a disease that mimics the effects of the loop diuretic furosemide, ClC-Kb/K2 is assumed to have a critical role in salt handling by the thick ascending limb. To dissect the role of this channel in detail, we generated a mouse model with a targeted disruption of the murine ortholog ClC-K2. Mutant mice developed a Bartter syndrome phenotype, characterized by renal salt loss, marked hypokalemia, and metabolic alkalosis. Patch-clamp analysis of tubules isolated from knockout (KO) mice suggested that ClC-K2 is the main basolateral chloride channel in the thick ascending limb and in the aldosterone-sensitive distal nephron. Accordingly, ClC-K2 KO mice did not exhibit the natriuretic response to furosemide and exhibited a severely blunted response to thiazide. We conclude that ClC-Kb/K2 is critical for salt absorption not only by the thick ascending limb, but also by the distal convoluted tubule.
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Affiliation(s)
- J Christopher Hennings
- Institut für Humangenetik, University Hospital Jena, Friedrich-Schiller-Universität, Jena, Germany
| | - Olga Andrini
- Centre National de la Recherche Scientifique Equipe de Recherche Labelisée 8228, Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 1138, Université Pierre et Marie Curie, Centre de Recherche des Cordeliers, Paris, France
| | - Nicolas Picard
- Centre National de la Recherche Scientifique Equipe de Recherche Labelisée 8228, Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 1138, Université Pierre et Marie Curie, Centre de Recherche des Cordeliers, Paris, France
| | - Marc Paulais
- Centre National de la Recherche Scientifique Equipe de Recherche Labelisée 8228, Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 1138, Université Pierre et Marie Curie, Centre de Recherche des Cordeliers, Paris, France
| | - Antje K Huebner
- Institut für Humangenetik, University Hospital Jena, Friedrich-Schiller-Universität, Jena, Germany
| | - Irma Karen Lopez Cayuqueo
- Institut National de la Santé et de la Recherche Médicale U970, Paris Cardiovascular Research Center, Paris, France.,Centro de Estudios Científicos, Valdivia, Chile
| | - Yohan Bignon
- Centre National de la Recherche Scientifique Equipe de Recherche Labelisée 8228, Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 1138, Université Pierre et Marie Curie, Centre de Recherche des Cordeliers, Paris, France
| | - Mathilde Keck
- Centre National de la Recherche Scientifique Equipe de Recherche Labelisée 8228, Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 1138, Université Pierre et Marie Curie, Centre de Recherche des Cordeliers, Paris, France
| | - Nicolas Cornière
- Service de Néphrologie, Hôpital Felix Guyon, Centre Hospitalier Universitaire de la Réunion, St Denis, Ile de la Réunion, France
| | - David Böhm
- Institut für Humangenetik, University Hospital Jena, Friedrich-Schiller-Universität, Jena, Germany
| | - Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie and Max-Delbrück Centrum für Molekulare Medizin, Berlin, Germany
| | - Régine Chambrey
- Institut National de la Santé et de la Recherche Médicale U970, Paris Cardiovascular Research Center, Paris, France.,Faculté de Médecine, Université Paris-Descartes, Paris, France.,Centre National de la Recherche Scientifique, Paris, France; and
| | - Jacques Teulon
- Centre National de la Recherche Scientifique Equipe de Recherche Labelisée 8228, Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 1138, Université Pierre et Marie Curie, Centre de Recherche des Cordeliers, Paris, France;
| | - Christian A Hübner
- Institut für Humangenetik, University Hospital Jena, Friedrich-Schiller-Universität, Jena, Germany
| | - Dominique Eladari
- Institut National de la Santé et de la Recherche Médicale U970, Paris Cardiovascular Research Center, Paris, France; .,Faculté de Médecine, Université Paris-Descartes, Paris, France.,Département de Physiologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
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Barrallo-Gimeno A, Gradogna A, Zanardi I, Pusch M, Estévez R. Regulatory-auxiliary subunits of CLC chloride channel-transport proteins. J Physiol 2016; 593:4111-27. [PMID: 25762128 DOI: 10.1113/jp270057] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 02/15/2015] [Indexed: 02/06/2023] Open
Abstract
The CLC family of chloride channels and transporters is composed by nine members, but only three of them, ClC-Ka/b, ClC-7 and ClC-2, have been found so far associated with auxiliary subunits. These CLC regulatory subunits are small proteins that present few common characteristics among them, both structurally and functionally, and their effects on the corresponding CLC protein are different. Barttin, a protein with two transmembrane domains, is essential for the membrane localization of ClC-K proteins and their activity in the kidney and inner ear. Ostm1 is a protein with a single transmembrane domain and a highly glycosylated N-terminus. Unlike the other two CLC auxiliary subunits, Ostm1 shows a reciprocal relationship with ClC-7 for their stability. The subcellular localization of Ostm1 depends on ClC-7 and not the other way around. ClC-2 is active on its own, but GlialCAM, a transmembrane cell adhesion molecule with two extracellular immunoglobulin (Ig)-like domains, regulates its subcellular localization and activity in glial cells. The common theme for these three proteins is their requirement for a proper homeostasis, since their malfunction leads to distinct diseases. We will review here their properties and their role in normal chloride physiology and the pathological consequences of their improper function.
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Affiliation(s)
- Alejandro Barrallo-Gimeno
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, University of Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
| | | | - Ilaria Zanardi
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genoa, Italy
| | - Michael Pusch
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genoa, Italy
| | - Raúl Estévez
- Sección de Fisiología, Departamento de Ciencias Fisiológicas II, University of Barcelona, Barcelona, Spain.,U-750, Centro de investigación en red de enfermedades raras (CIBERER), ISCIII, Barcelona, Spain
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Zaika O, Tomilin V, Mamenko M, Bhalla V, Pochynyuk O. New perspective of ClC-Kb/2 Cl- channel physiology in the distal renal tubule. Am J Physiol Renal Physiol 2016; 310:F923-30. [PMID: 26792067 PMCID: PMC5002062 DOI: 10.1152/ajprenal.00577.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 01/14/2016] [Indexed: 12/17/2022] Open
Abstract
Since its identification as the underlying molecular cause of Bartter's syndrome type 3, ClC-Kb (ClC-K2 in rodents, henceforth it will be referred as ClC-Kb/2) is proposed to play an important role in systemic electrolyte balance and blood pressure regulation by controlling basolateral Cl(-) exit in the distal renal tubular segments from the cortical thick ascending limb to the outer medullary collecting duct. Considerable experimental and clinical effort has been devoted to the identification and characterization of disease-causing mutations as well as control of the channel by its cofactor, barttin. However, we have only begun to unravel the role of ClC-Kb/2 in different tubular segments and to reveal the regulators of its expression and function, e.g., insulin and IGF-1. In this review we discuss recent experimental evidence in this regard and highlight unexplored questions critical to understanding ClC-Kb/2 physiology in the kidney.
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Affiliation(s)
- Oleg Zaika
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas; and
| | - Viktor Tomilin
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas; and
| | - Mykola Mamenko
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas; and
| | - Vivek Bhalla
- Division of Nephrology, Department of Medicine, Stanford University, Stanford, California
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas; and
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44
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45
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Stölting G, Bungert-Plümke S, Franzen A, Fahlke C. Carboxyl-terminal Truncations of ClC-Kb Abolish Channel Activation by Barttin Via Modified Common Gating and Trafficking. J Biol Chem 2015; 290:30406-16. [PMID: 26453302 DOI: 10.1074/jbc.m115.675827] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Indexed: 12/21/2022] Open
Abstract
ClC-K chloride channels are crucial for auditory transduction and urine concentration. Mutations in CLCNKB, the gene encoding the renal chloride channel hClC-Kb, cause Bartter syndrome type III, a human genetic condition characterized by polyuria, hypokalemia, and alkalosis. In recent years, several Bartter syndrome-associated mutations have been described that result in truncations of the intracellular carboxyl terminus of hClC-Kb. We here used a combination of whole-cell patch clamp, confocal imaging, co-immunoprecipitation, and surface biotinylation to study the functional consequences of a frequent CLCNKB mutation that creates a premature stop codon at Trp-610. We found that W610X leaves the association of hClC-Kb and the accessory subunit barttin unaffected, but impairs its regulation by barttin. W610X attenuates hClC-Kb surface membrane insertion. Moreover, W610X results in hClC-Kb channel opening in the absence of barttin and prevents further barttin-mediated activation. To describe how the carboxyl terminus modifies the regulation by barttin we used V166E rClC-K1. V166E rClC-K1 is active without barttin and exhibits prominent, barttin-regulated voltage-dependent gating. Electrophysiological characterization of truncated V166E rClC-K1 demonstrated that the distal carboxyl terminus is necessary for slow cooperative gating. Since barttin modifies this particular gating process, channels lacking the distal carboxyl-terminal domain are no longer regulated by the accessory subunit. Our results demonstrate that the carboxyl terminus of hClC-Kb is not part of the binding site for barttin, but functionally modifies the interplay with barttin. The loss-of-activation of truncated hClC-Kb channels in heterologous expression systems fully explains the reduced basolateral chloride conductance in affected kidneys and the clinical symptoms of Bartter syndrome patients.
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Affiliation(s)
- Gabriel Stölting
- From the Institute of Complex Systems 4 (ICS-4), Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich
| | - Stefanie Bungert-Plümke
- From the Institute of Complex Systems 4 (ICS-4), Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich
| | - Arne Franzen
- From the Institute of Complex Systems 4 (ICS-4), Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich
| | - Christoph Fahlke
- From the Institute of Complex Systems 4 (ICS-4), Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich
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Fong P. Twenty-five years of CLC chloride transport proteins. J Physiol 2015; 593:4083-4. [PMID: 26372836 DOI: 10.1113/jp271325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 07/22/2015] [Indexed: 11/08/2022] Open
Affiliation(s)
- Peying Fong
- Kansas State University College of Veterinary Medicine, 1600 Denison Ave, 129 Coles Hall, Manhattan, KS, 66506, USA
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Jentsch TJ. Discovery of CLC transport proteins: cloning, structure, function and pathophysiology. J Physiol 2015; 593:4091-109. [PMID: 25590607 DOI: 10.1113/jp270043] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/11/2015] [Indexed: 02/06/2023] Open
Abstract
After providing a personal description of the convoluted path leading 25 years ago to the molecular identification of the Torpedo Cl(-) channel ClC-0 and the discovery of the CLC gene family, I succinctly describe the general structural and functional features of these ion transporters before giving a short overview of mammalian CLCs. These can be categorized into plasma membrane Cl(-) channels and vesicular Cl(-) /H(+) -exchangers. They are involved in the regulation of membrane excitability, transepithelial transport, extracellular ion homeostasis, endocytosis and lysosomal function. Diseases caused by CLC dysfunction include myotonia, neurodegeneration, deafness, blindness, leukodystrophy, male infertility, renal salt loss, kidney stones and osteopetrosis, revealing a surprisingly broad spectrum of biological roles for chloride transport that was unsuspected when I set out to clone the first voltage-gated chloride channel.
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Affiliation(s)
- Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
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Wei G, Rosen S, Dantzler WH, Pannabecker TL. Architecture of the human renal inner medulla and functional implications. Am J Physiol Renal Physiol 2015; 309:F627-37. [PMID: 26290371 DOI: 10.1152/ajprenal.00236.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/10/2015] [Indexed: 11/22/2022] Open
Abstract
The architecture of the inner stripe of the outer medulla of the human kidney has long been known to exhibit distinctive configurations; however, inner medullary architecture remains poorly defined. Using immunohistochemistry with segment-specific antibodies for membrane fluid and solute transporters and other proteins, we identified a number of distinctive functional features of human inner medulla. In the outer inner medulla, aquaporin-1 (AQP1)-positive long-loop descending thin limbs (DTLs) lie alongside descending and ascending vasa recta (DVR, AVR) within vascular bundles. These vascular bundles are continuations of outer medullary vascular bundles. Bundles containing DTLs and vasa recta lie at the margins of coalescing collecting duct (CD) clusters, thereby forming two regions, the vascular bundle region and the CD cluster region. Although AQP1 and urea transporter UT-B are abundantly expressed in long-loop DTLs and DVR, respectively, their expression declines with depth below the outer medulla. Transcellular water and urea fluxes likely decline in these segments at progressively deeper levels. Smooth muscle myosin heavy chain protein is also expressed in DVR of the inner stripe and the upper inner medulla, but is sparsely expressed at deeper inner medullary levels. In rodent inner medulla, fenestrated capillaries abut CDs along their entire length, paralleling ascending thin limbs (ATLs), forming distinct compartments (interstitial nodal spaces; INSs); however, in humans this architecture rarely occurs. Thus INSs are relatively infrequent in the human inner medulla, unlike in the rodent where they are abundant. UT-B is expressed within the papillary epithelium of the lower inner medulla, indicating a transcellular pathway for urea across this epithelium.
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Affiliation(s)
- Guojun Wei
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - Seymour Rosen
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - William H Dantzler
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
| | - Thomas L Pannabecker
- Department of Physiology, University of Arizona Health Sciences Center, Tucson, Arizona; and
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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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Andrini O, Keck M, Briones R, Lourdel S, Vargas-Poussou R, Teulon J. ClC-K chloride channels: emerging pathophysiology of Bartter syndrome type 3. Am J Physiol Renal Physiol 2015; 308:F1324-34. [DOI: 10.1152/ajprenal.00004.2015] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 03/23/2015] [Indexed: 02/08/2023] Open
Abstract
The mutations in the CLCNKB gene encoding the ClC-Kb chloride channel are responsible for Bartter syndrome type 3, one of the four variants of Bartter syndrome in the genetically based nomenclature. All forms of Bartter syndrome are characterized by hypokalemia, metabolic alkalosis, and secondary hyperaldosteronism, but Bartter syndrome type 3 has the most heterogeneous presentation, extending from severe to very mild. A relatively large number of CLCNKB mutations have been reported, including gene deletions and nonsense or missense mutations. However, only 20 CLCNKB mutations have been functionally analyzed, due to technical difficulties regarding ClC-Kb functional expression in heterologous systems. This review provides an overview of recent progress in the functional consequences of CLCNKB mutations on ClC-Kb chloride channel activity. It has been observed that 1) all ClC-Kb mutants have an impaired expression at the membrane; and 2) a minority of the mutants combines reduced membrane expression with altered pH-dependent channel gating. Although further investigation is needed to fully characterize disease pathogenesis, Bartter syndrome type 3 probably belongs to the large family of conformational diseases, in which the mutations destabilize channel structure, inducing ClC-Kb retention in the endoplasmic reticulum and accelerated channel degradation.
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Affiliation(s)
- Olga Andrini
- UPMC Université Paris 06, UMR_S 1138, Team 3, Paris, France
- INSERM, UMR_S 872, Paris, France
| | - Mathilde Keck
- UPMC Université Paris 06, UMR_S 1138, Team 3, Paris, France
- INSERM, UMR_S 872, Paris, France
| | - Rodolfo Briones
- Department of Theoretical and Computational Biophysics, Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Stéphane Lourdel
- UPMC Université Paris 06, UMR_S 1138, Team 3, Paris, France
- INSERM, UMR_S 872, Paris, France
| | - Rosa Vargas-Poussou
- Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Département de Génétique, Paris, France; and
- Université Paris-Descartes, Faculté de Médecine, Paris, France
| | - Jacques Teulon
- UPMC Université Paris 06, UMR_S 1138, Team 3, Paris, France
- INSERM, UMR_S 872, Paris, France
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