1
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Kok M, Brodsky JL. The biogenesis of potassium transporters: implications of disease-associated mutations. Crit Rev Biochem Mol Biol 2024:1-45. [PMID: 38946646 DOI: 10.1080/10409238.2024.2369986] [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: 03/29/2024] [Accepted: 06/16/2024] [Indexed: 07/02/2024]
Abstract
The concentration of intracellular and extracellular potassium is tightly regulated due to the action of various ion transporters, channels, and pumps, which reside primarily in the kidney. Yet, potassium transporters and cotransporters play vital roles in all organs and cell types. Perhaps not surprisingly, defects in the biogenesis, function, and/or regulation of these proteins are linked to range of catastrophic human diseases, but to date, few drugs have been approved to treat these maladies. In this review, we discuss the structure, function, and activity of a group of potassium-chloride cotransporters, the KCCs, as well as the related sodium-potassium-chloride cotransporters, the NKCCs. Diseases associated with each of the four KCCs and two NKCCs are also discussed. Particular emphasis is placed on how these complex membrane proteins fold and mature in the endoplasmic reticulum, how non-native forms of the cotransporters are destroyed in the cell, and which cellular factors oversee their maturation and transport to the cell surface. When known, we also outline how the levels and activities of each cotransporter are regulated. Open questions in the field and avenues for future investigations are further outlined.
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Affiliation(s)
- Morgan Kok
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
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2
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Delpire E, Terker AS, Gagnon KB. Pharmacology of Compounds Targeting Cation-Chloride Cotransporter Physiology. Handb Exp Pharmacol 2024; 283:249-284. [PMID: 37563251 PMCID: PMC10823342 DOI: 10.1007/164_2023_692] [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: 08/12/2023]
Abstract
Transporters of the solute carrier family 12 (SLC12) carry inorganic cations such as Na+ and/or K+ alongside Cl across the plasma membrane of cells. These tightly coupled, electroneutral, transporters are expressed in almost all tissues/organs in the body where they fulfil many critical functions. The family includes two key transporters participating in salt reabsorption in the kidney: the Na-K-2Cl cotransporter-2 (NKCC2), expressed in the loop of Henle, and the Na-Cl cotransporter (NCC), expressed in the distal convoluted tubule. NCC and NKCC2 are the targets of thiazides and "loop" diuretics, respectively, drugs that are widely used in clinical medicine to treat hypertension and edema. Bumetanide, in addition to its effect as a loop diuretic, has recently received increasing attention as a possible therapeutic agent for neurodevelopmental disorders. This chapter also describes how over the past two decades, the pharmacology of Na+ independent transporters has expanded significantly to provide novel tools for research. This work has indeed led to the identification of compounds that are 100-fold to 1000-fold more potent than furosemide, the first described inhibitor of K-Cl cotransport, and identified compounds that possibly directly stimulate the function of the K-Cl cotransporter. Finally, the recent cryo-electron microscopy revolution has begun providing answers as to where and how pharmacological agents bind to and affect the function of the transporters.
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Affiliation(s)
- Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN, USA.
| | - Andrew S Terker
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Kenneth B Gagnon
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
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3
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Trejo F, Elizalde S, Mercado A, Gamba G, de losHeros P. SLC12A cryo-EM: analysis of relevant ion binding sites, structural domains, and amino acids. Am J Physiol Cell Physiol 2023; 325:C921-C939. [PMID: 37545407 DOI: 10.1152/ajpcell.00089.2023] [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: 03/13/2023] [Revised: 07/24/2023] [Accepted: 07/24/2023] [Indexed: 08/08/2023]
Abstract
The solute carrier family 12A (SLC12A) superfamily of membrane transporters modulates the movement of cations coupled with chloride across the membrane. In doing so, these cotransporters are involved in numerous aspects of human physiology: cell volume regulation, ion homeostasis, blood pressure regulation, and neurological action potential via intracellular chloride concentration modulation. Their physiological characterization has been largely studied; however, understanding the mechanics of their function and the relevance of structural domains or specific amino acids has been a pending task. In recent years, single-particle cryogenic electron microscopy (cryo-EM) has been successfully applied to members of the SLC12A family including all K+:Cl- cotransporters (KCCs), Na+:K+:2Cl- cotransporter NKCC1, and recently Na+:Cl- cotransporter (NCC); revealing structural elements that play key roles in their function. The present review analyzes the data provided by these cryo-EM reports focusing on structural domains and specific amino acids involved in ion binding, domain interactions, and other important SCL12A structural elements. A comparison of cryo-EM data from NKCC1 and KCCs is presented in the light of the two recent NCC cryo-EM studies, to propose insight into structural elements that might also be found in NCC and are necessary for its proper function. In the final sections, the importance of key coordination residues for substrate specificity and their implication on various pathophysiological conditions and genetic disorders is reviewed, as this could provide the basis to correlate structural elements with the development of novel and selective treatments, as well as mechanistic insight into the function and regulation of cation-coupled chloride cotransporters (CCCs).
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Affiliation(s)
- Fátima Trejo
- Unidad de Investigación UNAM-INC, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Stephanie Elizalde
- Departamento de Nefrología y Metabolismo Mineral, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
| | - Adriana Mercado
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico
| | - Gerardo Gamba
- Departamento de Nefrología y Metabolismo Mineral, 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
| | - Paola de losHeros
- Unidad de Investigación UNAM-INC, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
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4
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Abstract
PURPOSE OF REVIEW We recently localized a new K-Cl cotransporters-3 (KCC3) transporter to the apical membrane of type-B intercalated cells. This gives us an opportunity to revisit the roles of the KCC3 in kidney and integrate the new findings to our current knowledge of the biology of the bicarbonate secreting cells. RECENT FINDINGS Here, we review the basic properties of the K-Cl cotransporter with a particular attention to the responsiveness of the transporter to cell swelling. We summarize what is already known about KCC3b and discuss new information gained from our localizing of KCC3a in type-B intercalated cells. We integrate the physiology of KCC3a with the main function of the type-B cell, that is, bicarbonate secretion through the well characterized apical Cl-/HCO3- exchanger and the basolateral Na-HCO3 cotransporter. SUMMARY Both KCC3b and KCC3a seem to be needed for maintaining cell volume during enhanced inward cotransport of Na-glucose in proximal tubule and Na-HCO3 in intercalated cells. In addition, apical KCC3a might couple to pendrin function to recycle Cl-, particularly in conditions of low salt diet and therefore low Cl- delivery to the distal tubule. This function is critical in alkalemia, and KCC3a function in the pendrin-expressing cells may contribute to the K+ loss which is observed in alkalemia.
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Affiliation(s)
- Mohammed Z Ferdaus
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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5
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Pressey JC, de Saint-Rome M, Raveendran VA, Woodin MA. Chloride transporters controlling neuronal excitability. Physiol Rev 2023; 103:1095-1135. [PMID: 36302178 DOI: 10.1152/physrev.00025.2021] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Synaptic inhibition plays a crucial role in regulating neuronal excitability, which is the foundation of nervous system function. This inhibition is largely mediated by the neurotransmitters GABA and glycine that activate Cl--permeable ion channels, which means that the strength of inhibition depends on the Cl- gradient across the membrane. In neurons, the Cl- gradient is primarily mediated by two secondarily active cation-chloride cotransporters (CCCs), NKCC1 and KCC2. CCC-mediated regulation of the neuronal Cl- gradient is critical for healthy brain function, as dysregulation of CCCs has emerged as a key mechanism underlying neurological disorders including epilepsy, neuropathic pain, and autism spectrum disorder. This review begins with an overview of neuronal chloride transporters before explaining the dependent relationship between these CCCs, Cl- regulation, and inhibitory synaptic transmission. We then discuss the evidence for how CCCs can be regulated, including by activity and their protein interactions, which underlie inhibitory synaptic plasticity. For readers who may be interested in conducting experiments on CCCs and neuronal excitability, we have included a section on techniques for estimating and recording intracellular Cl-, including their advantages and limitations. Although the focus of this review is on neurons, we also examine how Cl- is regulated in glial cells, which in turn regulate neuronal excitability through the tight relationship between this nonneuronal cell type and synapses. Finally, we discuss the relatively extensive and growing literature on how CCC-mediated neuronal excitability contributes to neurological disorders.
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Affiliation(s)
- Jessica C Pressey
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Miranda de Saint-Rome
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Vineeth A Raveendran
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Melanie A Woodin
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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6
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Nan J, Yuan Y, Yang X, Shan Z, Liu H, Wei F, Zhang W, Zhang Y. Cryo-EM structure of the human sodium-chloride cotransporter NCC. SCIENCE ADVANCES 2022; 8:eadd7176. [PMID: 36351028 PMCID: PMC9645730 DOI: 10.1126/sciadv.add7176] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/21/2022] [Indexed: 05/29/2023]
Abstract
The sodium-chloride cotransporter NCC mediates the coupled import of sodium and chloride across the plasma membrane, playing vital roles in kidney extracellular fluid volume and blood pressure control. Here, we present the full-length structure of human NCC, with 2.9 Å for the transmembrane domain and 3.8 Å for the carboxyl-terminal domain. NCC adopts an inward-open conformation and a domain-swap dimeric assembly. Conserved ion binding sites among the cation-chloride cotransporters and the Na2 site are observed in our structure. A unique His residue in the substrate pocket in NCC potentially interacts with Na1 and Cl1 and might also mediate the coordination of Na2 through a Ser residue. Putative observed water molecules are indicated to participate in the coordination of ions and TM coupling. Together with transport activity assays, our structure provides the first glimpse of NCC and defines ion binding sites, promoting drug development for hypertension targeting on NCC.
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Affiliation(s)
- Jing Nan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yafei Yuan
- Beijing Frontier Research Center for Biological Structure, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xuemei Yang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Ziyang Shan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Huihui Liu
- Warshel Institute for Computational Biology, School of Life and Health Sciences, The Chinese University of Hong Kong, Shenzhen 518172, Guangdong, China
| | - Feiwen Wei
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Wei Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yanqing Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
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7
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Beijer D, Baets J. The expanding genetic landscape of hereditary motor neuropathies. Brain 2021; 143:3540-3563. [PMID: 33210134 DOI: 10.1093/brain/awaa311] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/15/2020] [Accepted: 07/27/2020] [Indexed: 12/12/2022] Open
Abstract
Hereditary motor neuropathies are clinically and genetically diverse disorders characterized by length-dependent axonal degeneration of lower motor neurons. Although currently as many as 26 causal genes are known, there is considerable missing heritability compared to other inherited neuropathies such as Charcot-Marie-Tooth disease. Intriguingly, this genetic landscape spans a discrete number of key biological processes within the peripheral nerve. Also, in terms of underlying pathophysiology, hereditary motor neuropathies show striking overlap with several other neuromuscular and neurological disorders. In this review, we provide a current overview of the genetic spectrum of hereditary motor neuropathies highlighting recent reports of novel genes and mutations or recent discoveries in the underlying disease mechanisms. In addition, we link hereditary motor neuropathies with various related disorders by addressing the main affected pathways of disease divided into five major processes: axonal transport, tRNA aminoacylation, RNA metabolism and DNA integrity, ion channels and transporters and endoplasmic reticulum.
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Affiliation(s)
- Danique Beijer
- Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium.,Laboratory of Neuromuscular Pathology, Institute Born-Bunge, University of Antwerp, Belgium
| | - Jonathan Baets
- Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium.,Laboratory of Neuromuscular Pathology, Institute Born-Bunge, University of Antwerp, Belgium.,Neuromuscular Reference Centre, Department of Neurology, Antwerp University Hospital, Belgium
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8
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Shi J, Zhao F, Pang X, Huang S, Wang J, Chang X, Zhang J, Liu Y, Guo J, Zhang W. Whole-exome sequencing identifies a heterozygous mutation in SLC12A6 associated with hereditary sensory and motor neuropathy. Neuromuscul Disord 2020; 31:149-157. [PMID: 33323309 DOI: 10.1016/j.nmd.2020.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 10/20/2020] [Accepted: 11/04/2020] [Indexed: 10/22/2022]
Abstract
Charcot-Marie-Tooth disease (CMT) represents a phenotypically and genetically heterogeneous disorder of the peripheral nervous system. Biallelic variants in SLC12A6 have been reported as the cause of autosomal-recessive (AR) hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC). Here we identified an autosomal-dominant (AD) heterozygous mutation in SLC12A6 in a Chinese patient with intermediate CMT. The patient presented with slowly progressive distal muscle weakness and atrophy. Electrophysiological examination showed a mixed axonal/demyelinating neuropathy. Cognition and brain MRI were normal. A single heterozygous missense mutation c.620G>A (p.R207H) in exon 5 of SLC12A6 was identified as the likely pathogenic mutation by whole-exome sequencing consistent with two previously published cases. It affects evolutionarily highly conserved amino acid residue and is predicted to be deleterious by using in silico tools. Modelling of the mutant KCC3 cotransporter showed altered formation of hydrogen bonds and weakened interaction force between the mutated site and its surrounding amino acid residues. Our findings expand the genotypic and phenotypic spectrum associated with SLC12A6 mutations from AR-HMSN/ACC to AD-CMT. The differences in the inheritance pattern might be associated with a dominant-negative pathomechanism.
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Affiliation(s)
- Jiaying Shi
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Fei Zhao
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Xiaomin Pang
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Shan Huang
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Juan Wang
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Xueli Chang
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Jing Zhang
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Yanming Liu
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Junhong Guo
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China
| | - Wei Zhang
- Department of Neurology, First Hospital, Shanxi Medical University, Taiyuan 030000, PR China.
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9
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Xie Y, Chang S, Zhao C, Wang F, Liu S, Wang J, Delpire E, Ye S, Guo J. Structures and an activation mechanism of human potassium-chloride cotransporters. SCIENCE ADVANCES 2020; 6:eabc5883. [PMID: 33310850 PMCID: PMC7732191 DOI: 10.1126/sciadv.abc5883] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Accepted: 10/21/2020] [Indexed: 05/07/2023]
Abstract
Potassium-chloride cotransporters KCC1 to KCC4 mediate the coupled export of potassium and chloride across the plasma membrane and play important roles in cell volume regulation, auditory system function, and γ-aminobutyric acid (GABA) and glycine-mediated inhibitory neurotransmission. Here, we present 2.9- to 3.6-Å resolution structures of full-length human KCC2, KCC3, and KCC4. All three KCCs adopt a similar overall architecture, a domain-swap dimeric assembly, and an inward-facing conformation. The structural and functional studies reveal that one unexpected N-terminal peptide binds at the cytosolic facing cavity and locks KCC2 and KCC4 at an autoinhibition state. The C-terminal domain (CTD) directly interacts with the N-terminal inhibitory peptide, and the relative motions between the CTD and the transmembrane domain (TMD) suggest that CTD regulates KCCs' activities by adjusting the autoinhibitory effect. These structures provide the first glimpse of full-length structures of KCCs and an autoinhibition mechanism among the amino acid-polyamine-organocation transporter superfamily.
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Affiliation(s)
- Yuan Xie
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Shenghai Chang
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
- Center of Cryo Electron Microscopy, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Cheng Zhao
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Feng Wang
- Wuxi Biortus Biosciences Co. Ltd., 6 Dongsheng West Road, Jiangyin, 214437, China
| | - Si Liu
- Tianjin Key Laboratory of Function and Application of Biological Macromolecular Structures, School of Life Sciences, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Jin Wang
- Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Sheng Ye
- Tianjin Key Laboratory of Function and Application of Biological Macromolecular Structures, School of Life Sciences, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China.
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Jiangtao Guo
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.
- Department of Cardiology, Key Laboratory of Cardiovascular Intervention and Regenerative Medicine of Zhejiang Province, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, 310016, China
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10
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Park J, Flores BR, Scherer K, Kuepper H, Rossi M, Rupprich K, Rautenberg M, Deininger N, Weichselbaum A, Grimm A, Sturm M, Grasshoff U, Delpire E, Haack TB. De novo variants in SLC12A6 cause sporadic early-onset progressive sensorimotor neuropathy. J Med Genet 2020; 57:283-288. [PMID: 31439721 PMCID: PMC11074718 DOI: 10.1136/jmedgenet-2019-106273] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/26/2019] [Accepted: 07/20/2019] [Indexed: 12/28/2022]
Abstract
BACKGROUND Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous disorder of the peripheral nervous system. Biallelic variants in SLC12A6 have been associated with autosomal-recessive hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC). We identified heterozygous de novo variants in SLC12A6 in three unrelated patients with intermediate CMT. METHODS We evaluated the clinical reports and electrophysiological data of three patients carrying de novo variants in SLC12A6 identified by diagnostic trio exome sequencing. For functional characterisation of the identified variants, potassium influx of mutated KCC3 cotransporters was measured in Xenopus oocytes. RESULTS We identified two different de novo missense changes (p.Arg207His and p.Tyr679Cys) in SLC12A6 in three unrelated individuals with early-onset progressive CMT. All presented with axonal/demyelinating sensorimotor neuropathy accompanied by spasticity in one patient. Cognition and brain MRI were normal. Modelling of the mutant KCC3 cotransporter in Xenopus oocytes showed a significant reduction in potassium influx for both changes. CONCLUSION Our findings expand the genotypic and phenotypic spectrum associated with SLC12A6 variants from autosomal-recessive HMSN/ACC to dominant-acting de novo variants causing a milder clinical presentation with early-onset neuropathy.
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Affiliation(s)
- Joohyun Park
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Bianca R Flores
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Katalin Scherer
- Neuromuscular Clinic, Children's Clinic for Rehabilitative Services, Tucson, Arizona, USA
| | - Hanna Kuepper
- Department of Neuropediatrics, University of Tübingen, Tübingen, Germany
| | - Mari Rossi
- Department of Clinical Diagnostics, Ambry Genetics, Aliso Viejo, California, USA
| | - Katrin Rupprich
- Department of Neuropediatrics, Essen University Hospital, Essen, Germany
| | - Maren Rautenberg
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | - Natalie Deininger
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | | | - Alexander Grimm
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Marc Sturm
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | - Ute Grasshoff
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Tobias B Haack
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
- Centre for Rare Diseases, University of Tübingen, Tübingen, Germany
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11
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Delpire E, Guo J. Cryo-EM structures of DrNKCC1 and hKCC1: a new milestone in the physiology of cation-chloride cotransporters. Am J Physiol Cell Physiol 2020; 318:C225-C237. [PMID: 31747317 PMCID: PMC7052613 DOI: 10.1152/ajpcell.00465.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/20/2019] [Accepted: 11/20/2019] [Indexed: 01/29/2023]
Abstract
New milestones have been reached in the field of cation-Cl- cotransporters with the recently released cryo-electron microscopy (EM) structures of the Danio rerio (zebrafish) Na+-K+-2Cl- cotransporter (DrNKCC1) and the human K+-Cl- cotransporter (hKCC1). In this review we provide a brief timeline that identifies the multiple breakthroughs in the field of solute carrier 12 transporters that led to the structure resolution of two of its key members. While cation-Cl- cotransporters share the overall architecture of carriers belonging to the amino acid-polyamine-organocation (APC) superfamily and some of their substrate binding sites, several new insights are gained from the two individual structures. A first major feature relates to the largest extracellular domain between transmembrane domain (TMD) 5 and TMD6 of KCC1, which stabilizes the dimer and forms a cap that likely participates in extracellular gating. A second feature is the conservation of the K+ and Cl- binding sites in both structures and evidence of an unexpected second Cl- coordination site in the KCC1 structure. Structural data are discussed in the context of previously published studies that examined the basic and kinetics properties of these cotransport mechanisms. A third characteristic is the evidence of an extracellular gate formed by conserved salt bridges between charged residues located toward the end of TMD3 and TMD4 in both transporters and the existence of an additional neighboring bridge in the hKCC1 structure. A fourth feature of these newly solved structures relates to the multiple points of contacts between the monomer forming the cotransporter homodimer units. These involve the TMDs, the COOH-terminal domains, and the large extracellular loop for hKCC1.
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Affiliation(s)
- Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jiangtao Guo
- Department of Biophysics, Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
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12
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Jin SC, Furey CG, Zeng X, Allocco A, Nelson‐Williams C, Dong W, Karimy JK, Wang K, Ma S, Delpire E, Kahle KT. SLC12A ion transporter mutations in sporadic and familial human congenital hydrocephalus. Mol Genet Genomic Med 2019; 7:e892. [PMID: 31393094 PMCID: PMC6732308 DOI: 10.1002/mgg3.892] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 06/15/2019] [Accepted: 07/07/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Congenital hydrocephalus (CH) is a highly morbid disease that features enlarged brain ventricles and impaired cerebrospinal fluid homeostasis. Although early linkage or targeted sequencing studies in large multigenerational families have localized several genes for CH, the etiology of most CH cases remains unclear. Recent advances in whole exome sequencing (WES) have identified five new bona fide CH genes, implicating impaired regulation of neural stem cell fate in CH pathogenesis. Nonetheless, in the majority of CH cases, the pathological etiology remains unknown, suggesting more genes await discovery. METHODS WES of family members of a sporadic and familial form of severe L1CAM mutation-negative CH associated with aqueductal stenosis was performed. Rare genetic variants were analyzed, prioritized, and validated. De novo copy number variants (CNVs) were identified using the XHMM algorithm and validated using qPCR. Xenopus oocyte experiments were performed to access mutation impact on protein function and expression. RESULTS A novel inherited protein-damaging mutation (p.Pro605Leu) in SLC12A6, encoding the K+ -Cl- cotransporter KCC3, was identified in both affected members of multiplex kindred CHYD110. p.Pro605 is conserved in KCC3 orthologs and among all human KCC paralogs. The p.Pro605Leu mutation maps to the ion-transporting domain, and significantly reduces KCC3-dependent K+ transport. A novel de novo CNV (deletion) was identified in SLC12A7, encoding the KCC3 paralog and binding partner KCC4, in another family (CHYD130) with sporadic CH. CONCLUSION These findings identify two novel, related genes associated with CH, and implicate genetically encoded impairments in ion transport for the first time in CH pathogenesis.
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Affiliation(s)
- Sheng Chih Jin
- Department of GeneticsYale University School of MedicineNew HavenCTUSA
- Laboratory of Human Genetics and GenomicsThe Rockefeller UniversityNew YorkNYUSA
| | - Charuta G. Furey
- Department of GeneticsYale University School of MedicineNew HavenCTUSA
- Department of NeurosurgeryYale University School of MedicineNew HavenCTUSA
| | - Xue Zeng
- Department of GeneticsYale University School of MedicineNew HavenCTUSA
| | - August Allocco
- Department of NeurosurgeryYale University School of MedicineNew HavenCTUSA
| | | | - Weilai Dong
- Department of GeneticsYale University School of MedicineNew HavenCTUSA
| | - Jason K. Karimy
- Department of NeurosurgeryYale University School of MedicineNew HavenCTUSA
| | - Kevin Wang
- Department of NeurosurgeryYale University School of MedicineNew HavenCTUSA
| | - Shaojie Ma
- Department of GeneticsYale University School of MedicineNew HavenCTUSA
| | - Eric Delpire
- Department of AnesthesiologyVanderbilt University School of MedicineNashvilleTNUSA
| | - Kristopher T. Kahle
- Department of GeneticsYale University School of MedicineNew HavenCTUSA
- Department of NeurosurgeryYale University School of MedicineNew HavenCTUSA
- Department of Cellular & Molecular PhysiologyYale University School of MedicineNew HavenCTUSA
- NIH‐Yale Centers for Mendelian Genomics, Yale School of MedicineNew HavenCTUSA
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13
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Abstract
K+-Cl- co-transporter 2 (KCC2/SLC12A5) is a neuronal specific cation chloride co-transporter which is active under isotonic conditions, and thus a key regulator of intracellular Cl- levels. It also has an ion transporter-independent structural role in modulating the maturation and regulation of excitatory glutamatergic synapses. KCC2 levels are developmentally regulated, and a postnatal upregulation of KCC2 generates a low intracellular chloride concentration that allows the neurotransmitters γ-aminobutyric acid (GABA) and glycine to exert inhibitory neurotransmission through its Cl- permeating channel. Functional expression of KCC2 at the neuronal cell surface is necessary for its activity, and impairment in KCC2 cell surface transport and/or internalization may underlie a range of neuropathological conditions. Although recent advances have shed light on a range of cellular mechanisms regulating KCC2 activity, little is known about its membrane trafficking itinerary and regulatory proteins. In this review, known membrane trafficking signals, pathways and mechanisms pertaining to KCC2's functional surface expression are discussed.
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Affiliation(s)
- Bor Luen Tang
- a Department of Biochemistry, Yong Loo Lin School of Medicine , National University Health System , Singapore.,b NUS Graduate School for Integrative Sciences and Engineering , National University of Singapore , Singapore
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14
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Garneau AP, Marcoux AA, Frenette-Cotton R, Mac-Way F, Lavoie JL, Isenring P. Molecular insights into the normal operation, regulation, and multisystemic roles of K +-Cl - cotransporter 3 (KCC3). Am J Physiol Cell Physiol 2017; 313:C516-C532. [PMID: 28814402 DOI: 10.1152/ajpcell.00106.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 07/26/2017] [Accepted: 08/14/2017] [Indexed: 12/12/2022]
Abstract
Long before the molecular identity of the Na+-dependent K+-Cl- cotransporters was uncovered in the mid-nineties, a Na+-independent K+-Cl- cotransport system was also known to exist. It was initially observed in sheep and goat red blood cells where it was shown to be ouabain-insensitive and to increase in the presence of N-ethylmaleimide (NEM). After it was established between the early and mid-nineties, the expressed sequence tag (EST) databank was found to include a sequence that was highly homologous to those of the Na+-dependent K+-Cl- cotransporters. This sequence was eventually found to code for the Na+-independent K+-Cl- cotransport function that was described in red blood cells several years before. It was termed KCC1 and led to the discovery of three isoforms called KCC2, KCC3, and KCC4. Since then, it has become obvious that each one of these isoforms exhibits unique patterns of distribution and fulfills distinct physiological roles. Among them, KCC3 has been the subject of great attention in view of its important role in the nervous system and its association with a rare hereditary sensorimotor neuropathy (called Andermann syndrome) that affects many individuals in Quebec province (Canada). It was also found to play important roles in the cardiovascular system, the organ of Corti, and circulating blood cells. As will be seen in this review, however, there are still a number of uncertainties regarding the transport properties, structural organization, and regulation of KCC3. The same is true regarding the mechanisms by which KCC3 accomplishes its numerous functions in animal cells.
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Affiliation(s)
- A P Garneau
- Nephrology Research Group, Department of Medicine, Laval University, Quebec City, Quebec, Canada; and
- Cardiometabolic Axis, Kinesiology Department, University of Montréal, Montreal, Quebec, Canada
| | - A A Marcoux
- Nephrology Research Group, Department of Medicine, Laval University, Quebec City, Quebec, Canada; and
| | - R Frenette-Cotton
- Nephrology Research Group, Department of Medicine, Laval University, Quebec City, Quebec, Canada; and
| | - F Mac-Way
- Nephrology Research Group, Department of Medicine, Laval University, Quebec City, Quebec, Canada; and
| | - J L Lavoie
- Cardiometabolic Axis, Kinesiology Department, University of Montréal, Montreal, Quebec, Canada
| | - P Isenring
- Nephrology Research Group, Department of Medicine, Laval University, Quebec City, Quebec, Canada; and
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15
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Kahle KT, Flores B, Bharucha-Goebel D, Zhang J, Donkervoort S, Hegde M, Hussain G, Duran D, Liang B, Sun D, Bönnemann CG, Delpire E. Peripheral motor neuropathy is associated with defective kinase regulation of the KCC3 cotransporter. Sci Signal 2016; 9:ra77. [PMID: 27485015 PMCID: PMC5506493 DOI: 10.1126/scisignal.aae0546] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Using exome sequencing, we identified a de novo mutation (c.2971A>G; T991A) in SLC12A6, the gene encoding the K(+)-Cl(-) cotransporter KCC3, in a patient with an early-onset, progressive, and severe peripheral neuropathy primarily affecting motor neurons. Normally, the WNK kinase-dependent phosphorylation of T(991) tonically inhibits KCC3; however, cell swelling triggers Thr(991) dephosphorylation to activate the transporter and restore cell volume. KCC3 T991A mutation in patient cells abolished Thr(991) phosphorylation, resulted in constitutive KCC3 activity, and compromised cell volume homeostasis. KCC3(T991A/T991A) mutant mice exhibited constitutive KCC3 activity and recapitulated aspects of the clinical, electrophysiological, and histopathological findings of the patient. These results suggest that the function of the peripheral nervous system depends on finely tuned, kinase-regulated KCC3 activity and implicate abnormal cell volume homeostasis as a previously unreported mechanism of axonal degeneration.
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Affiliation(s)
- Kristopher T Kahle
- Departments of Neurosurgery and Pediatrics and Cellular and Molecular Physiology, Centers for Mendelian Genomics, Yale School of Medicine, New Haven, CT 06510, USA
| | - Bianca Flores
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Diana Bharucha-Goebel
- Neuromuscular and Neurogenetic Disorders of Childhood Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20814, USA. Department of Neurology, Children's National Health System, Washington, DC 20010, USA
| | - Jinwei Zhang
- Departments of Neurosurgery and Pediatrics and Cellular and Molecular Physiology, Centers for Mendelian Genomics, Yale School of Medicine, New Haven, CT 06510, USA. MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Sandra Donkervoort
- Neuromuscular and Neurogenetic Disorders of Childhood Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20814, USA
| | - Madhuri Hegde
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
| | - Gulnaz Hussain
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA. Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center Pittsburgh, PA 15240, USA
| | - Daniel Duran
- Departments of Neurosurgery and Pediatrics and Cellular and Molecular Physiology, Centers for Mendelian Genomics, Yale School of Medicine, New Haven, CT 06510, USA
| | - Bo Liang
- Departments of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02114, USA
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA. Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center Pittsburgh, PA 15240, USA
| | - Carsten G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20814, USA.
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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16
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Saitsu H, Watanabe M, Akita T, Ohba C, Sugai K, Ong WP, Shiraishi H, Yuasa S, Matsumoto H, Beng KT, Saitoh S, Miyatake S, Nakashima M, Miyake N, Kato M, Fukuda A, Matsumoto N. Impaired neuronal KCC2 function by biallelic SLC12A5 mutations in migrating focal seizures and severe developmental delay. Sci Rep 2016; 6:30072. [PMID: 27436767 PMCID: PMC4951812 DOI: 10.1038/srep30072] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 06/28/2016] [Indexed: 11/09/2022] Open
Abstract
Epilepsy of infancy with migrating focal seizures (EIMFS) is one of the early-onset epileptic syndromes characterized by migrating polymorphous focal seizures. Whole exome sequencing (WES) in ten sporadic and one familial case of EIMFS revealed compound heterozygous SLC12A5 (encoding the neuronal K(+)-Cl(-) co-transporter KCC2) mutations in two families: c.279 + 1G > C causing skipping of exon 3 in the transcript (p.E50_Q93del) and c.572 C >T (p.A191V) in individuals 1 and 2, and c.967T > C (p.S323P) and c.1243 A > G (p.M415V) in individual 3. Another patient (individual 4) with migrating multifocal seizures and compound heterozygous mutations [c.953G > C (p.W318S) and c.2242_2244del (p.S748del)] was identified by searching WES data from 526 patients and SLC12A5-targeted resequencing data from 141 patients with infantile epilepsy. Gramicidin-perforated patch-clamp analysis demonstrated strongly suppressed Cl(-) extrusion function of E50_Q93del and M415V mutants, with mildly impaired function of A191V and S323P mutants. Cell surface expression levels of these KCC2 mutants were similar to wildtype KCC2. Heterologous expression of two KCC2 mutants, mimicking the patient status, produced a significantly greater intracellular Cl(-) level than with wildtype KCC2, but less than without KCC2. These data clearly demonstrated that partially disrupted neuronal Cl(-) extrusion, mediated by two types of differentially impaired KCC2 mutant in an individual, causes EIMFS.
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Affiliation(s)
- Hirotomo Saitsu
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan
| | - Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan
| | - Tenpei Akita
- Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan
| | - Chihiro Ohba
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan
| | - Kenji Sugai
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8551, Japan
| | - Winnie Peitee Ong
- Department of Genetics, Hospital Kuala Lumpur, Jalan Pahang, Kuala Lumpur 50586, Malaysia
| | - Hideaki Shiraishi
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, North 15 West 7, Sapporo 060-8638, Japan
| | - Shota Yuasa
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8551, Japan
| | - Hiroshi Matsumoto
- Department of Pediatrics, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan
| | - Khoo Teik Beng
- Department of Pediatrics, Institute of Pediatrics, Hospital Kuala Lumpur, Jalan Pahang, Kuala Lumpur 50586, Malaysia
| | - Shinji Saitoh
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-Cho, Nagoya 467-8601, Japan
| | - Satoko Miyatake
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan
| | - Mitsuko Nakashima
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan
| | - Noriko Miyake
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan
| | - Mitsuhiro Kato
- Department of Pediatrics, Showa University School of Medicine, 1-5-8 Hatanodai, Tokyo 142-8666, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan
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17
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Kahle KT, Delpire E. Kinase-KCC2 coupling: Cl- rheostasis, disease susceptibility, therapeutic target. J Neurophysiol 2016; 115:8-18. [PMID: 26510764 PMCID: PMC4760510 DOI: 10.1152/jn.00865.2015] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 10/25/2015] [Indexed: 01/06/2023] Open
Abstract
The intracellular concentration of Cl(-) ([Cl(-)]i) in neurons is a highly regulated variable that is established and modulated by the finely tuned activity of the KCC2 cotransporter. Despite the importance of KCC2 for neurophysiology and its role in multiple neuropsychiatric diseases, our knowledge of the transporter's regulatory mechanisms is incomplete. Recent studies suggest that the phosphorylation state of KCC2 at specific residues in its cytoplasmic COOH terminus, such as Ser940 and Thr906/Thr1007, encodes discrete levels of transporter activity that elicit graded changes in neuronal Cl(-) extrusion to modulate the strength of synaptic inhibition via Cl(-)-permeable GABAA receptors. In this review, we propose that the functional and physical coupling of KCC2 to Cl(-)-sensitive kinase(s), such as the WNK1-SPAK kinase complex, constitutes a molecular "rheostat" that regulates [Cl(-)]i and thereby influences the functional plasticity of GABA. The rapid reversibility of (de)phosphorylation facilitates regulatory precision, and multisite phosphorylation allows for the control of KCC2 activity by different inputs via distinct or partially overlapping upstream signaling cascades that may become more or less important depending on the physiological context. While this adaptation mechanism is highly suited to maintaining homeostasis, its adjustable set points may render it vulnerable to perturbation and dysregulation. Finally, we suggest that pharmacological modulation of this kinase-KCC2 rheostat might be a particularly efficacious strategy to enhance Cl(-) extrusion and therapeutically restore GABA inhibition.
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Affiliation(s)
- Kristopher T Kahle
- Departments of Neurosurgery and Pediatrics, Yale School of Medicine, New Haven, Connecticut; Yale Neurogenetics Program, Yale School of Medicine, New Haven, Connecticut; and
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee
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18
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Impact of Hybrid and Complex N-Glycans on Cell Surface Targeting of the Endogenous Chloride Cotransporter Slc12a2. Int J Cell Biol 2015; 2015:505294. [PMID: 26351455 PMCID: PMC4553341 DOI: 10.1155/2015/505294] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/29/2015] [Accepted: 07/07/2015] [Indexed: 11/21/2022] Open
Abstract
The Na+K+2Cl− cotransporter-1 (Slc12a2, NKCC1) is widely distributed and involved in cell volume/ion regulation. Functional NKCC1 locates in the plasma membrane of all cells studied, particularly in the basolateral membrane of most polarized cells. Although the mechanisms involved in plasma membrane sorting of NKCC1 are poorly understood, it is assumed that N-glycosylation is necessary. Here, we characterize expression, N-glycosylation, and distribution of NKCC1 in COS7 cells. We show that ~25% of NKCC1 is complex N-glycosylated whereas the rest of it corresponds to core/high-mannose and hybrid-type N-glycosylated forms. Further, ~10% of NKCC1 reaches the plasma membrane, mostly as core/high-mannose type, whereas ~90% of NKCC1 is distributed in defined intracellular compartments. In addition, inhibition of the first step of N-glycan biosynthesis with tunicamycin decreases total and plasma membrane located NKCC1 resulting in almost undetectable cotransport function. Moreover, inhibition of N-glycan maturation with swainsonine or kifunensine increased core/hybrid-type NKCC1 expression but eliminated plasma membrane complex N-glycosylated NKCC1 and transport function. Together, these results suggest that (i) NKCC1 is delivered to the plasma membrane of COS7 cells independently of its N-glycan nature, (ii) most of NKCC1 in the plasma membrane is core/hybrid-type N-glycosylated, and (iii) the minimal proportion of complex N-glycosylated NKCC1 is functionally active.
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19
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Kahle KT, Khanna AR, Alper SL, Adragna NC, Lauf PK, Sun D, Delpire E. K-Cl cotransporters, cell volume homeostasis, and neurological disease. Trends Mol Med 2015; 21:513-23. [PMID: 26142773 PMCID: PMC4834970 DOI: 10.1016/j.molmed.2015.05.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Revised: 05/10/2015] [Accepted: 05/29/2015] [Indexed: 11/24/2022]
Abstract
K(+)-Cl(-) cotransporters (KCCs) were originally characterized as regulators of red blood cell (RBC) volume. Since then, four distinct KCCs have been cloned, and their importance for volume regulation has been demonstrated in other cell types. Genetic models of certain KCCs, such as KCC3, and their inhibitory WNK-STE20/SPS1-related proline/alanine-rich kinase (SPAK) serine-threonine kinases, have demonstrated the evolutionary necessity of these molecules for nervous system cell volume regulation, structure, and function, and their involvement in neurological disease. The recent characterization of a swelling-activated dephosphorylation mechanism that potently stimulates the KCCs has pinpointed a potentially druggable switch of KCC activity. An improved understanding of WNK/SPAK-mediated KCC cell volume regulation in the nervous system might reveal novel avenues for the treatment of multiple neurological diseases.
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Affiliation(s)
- Kristopher T Kahle
- Department of Neurosurgery, Boston Children's Hospital and Harvard Medical School, Boston, MA 02114, USA; Manton Center for Orphan Disease Research, Children's Hospital Boston, 300 Longwood Avenue, Boston, MA 02114, USA.
| | - Arjun R Khanna
- Department of Neurosurgery, Boston Children's Hospital and Harvard Medical School, Boston, MA 02114, USA
| | - Seth L Alper
- Renal Division and Molecular and Vascular Medicine Division, Beth Israel Deaconess Medical Center; Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
| | - Norma C Adragna
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA
| | - Peter K Lauf
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA; Department of Pathology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15217, USA; Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center, Pittsburgh, PA 15213, USA
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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