1
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Lory P. The good company of T-type calcium channels : Commentary on: "T-type calcium channelosome," a review by N. Weiss and G. W. Zamponi. Pflugers Arch 2024; 476:149-150. [PMID: 38191755 DOI: 10.1007/s00424-023-02903-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 12/21/2023] [Accepted: 12/28/2023] [Indexed: 01/10/2024]
Affiliation(s)
- Philippe Lory
- IGF, Univ Montpellier, CNRS, INSERM, Montpellier, France.
- LabEx 'Ion Channel Science and Therapeutics', Montpellier, France.
- Institut de Génomique Fonctionnelle - CNRS, 141 rue de la Cardonille, 34094, Montpellier, France.
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2
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Weiss N, Zamponi GW. The T-type calcium channelosome. Pflugers Arch 2024; 476:163-177. [PMID: 38036777 DOI: 10.1007/s00424-023-02891-z] [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: 10/27/2023] [Revised: 11/21/2023] [Accepted: 11/23/2023] [Indexed: 12/02/2023]
Abstract
T-type calcium channels perform crucial physiological roles across a wide spectrum of tissues, spanning both neuronal and non-neuronal system. For instance, they serve as pivotal regulators of neuronal excitability, contribute to cardiac pacemaking, and mediate the secretion of hormones. These functions significantly hinge upon the intricate interplay of T-type channels with interacting proteins that modulate their expression and function at the plasma membrane. In this review, we offer a panoramic exploration of the current knowledge surrounding these T-type channel interactors, and spotlight certain aspects of their potential for drug-based therapeutic intervention.
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Affiliation(s)
- Norbert Weiss
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic.
| | - Gerald W Zamponi
- Department of Clinical Neurosciences, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Canada
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3
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The life cycle of voltage-gated Ca 2+ channels in neurons: an update on the trafficking of neuronal calcium channels. Neuronal Signal 2021; 5:NS20200095. [PMID: 33664982 PMCID: PMC7905535 DOI: 10.1042/ns20200095] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 02/10/2021] [Accepted: 02/15/2021] [Indexed: 01/26/2023] Open
Abstract
Neuronal voltage-gated Ca2+ (CaV) channels play a critical role in cellular excitability, synaptic transmission, excitation-transcription coupling and activation of intracellular signaling pathways. CaV channels are multiprotein complexes and their functional expression in the plasma membrane involves finely tuned mechanisms, including forward trafficking from the endoplasmic reticulum (ER) to the plasma membrane, endocytosis and recycling. Whether genetic or acquired, alterations and defects in the trafficking of neuronal CaV channels can have severe physiological consequences. In this review, we address the current evidence concerning the regulatory mechanisms which underlie precise control of neuronal CaV channel trafficking and we discuss their potential as therapeutic targets.
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4
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Striessnig J. Voltage-Gated Ca 2+-Channel α1-Subunit de novo Missense Mutations: Gain or Loss of Function - Implications for Potential Therapies. Front Synaptic Neurosci 2021; 13:634760. [PMID: 33746731 PMCID: PMC7966529 DOI: 10.3389/fnsyn.2021.634760] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Accepted: 02/02/2021] [Indexed: 12/12/2022] Open
Abstract
This review summarizes our current knowledge of human disease-relevant genetic variants within the family of voltage gated Ca2+ channels. Ca2+ channelopathies cover a wide spectrum of diseases including epilepsies, autism spectrum disorders, intellectual disabilities, developmental delay, cerebellar ataxias and degeneration, severe cardiac arrhythmias, sudden cardiac death, eye disease and endocrine disorders such as congential hyperinsulinism and hyperaldosteronism. A special focus will be on the rapidly increasing number of de novo missense mutations identified in the pore-forming α1-subunits with next generation sequencing studies of well-defined patient cohorts. In contrast to likely gene disrupting mutations these can not only cause a channel loss-of-function but can also induce typical functional changes permitting enhanced channel activity and Ca2+ signaling. Such gain-of-function mutations could represent therapeutic targets for mutation-specific therapy of Ca2+-channelopathies with existing or novel Ca2+-channel inhibitors. Moreover, many pathogenic mutations affect positive charges in the voltage sensors with the potential to form gating-pore currents through voltage sensors. If confirmed in functional studies, specific blockers of gating-pore currents could also be of therapeutic interest.
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Affiliation(s)
- Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
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5
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Tyagi S, Ribera AB, Bannister RA. Zebrafish as a Model System for the Study of Severe Ca V2.1 (α 1A) Channelopathies. Front Mol Neurosci 2020; 12:329. [PMID: 32116539 PMCID: PMC7018710 DOI: 10.3389/fnmol.2019.00329] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 12/23/2019] [Indexed: 02/02/2023] Open
Abstract
The P/Q-type CaV2.1 channel regulates neurotransmitter release at neuromuscular junctions (NMJ) and many central synapses. CACNA1A encodes the pore-containing α1A subunit of CaV2.1 channels. In humans, de novo CACNA1A mutations result in a wide spectrum of neurological, neuromuscular, and movement disorders, such as familial hemiplegic migraine type 1 (FHM1), episodic ataxia type 2 (EA2), as well as a more recently discovered class of more severe disorders, which are characterized by ataxia, hypotonia, cerebellar atrophy, and cognitive/developmental delay. Heterologous expression of CaV2.1 channels has allowed for an understanding of the consequences of CACNA1A missense mutations on channel function. In contrast, a mechanistic understanding of how specific CACNA1A mutations lead in vivo to the resultant phenotypes is lacking. In this review, we present the zebrafish as a model to both study in vivo mechanisms of CACNA1A mutations that result in synaptic and behavioral defects and to screen for effective drug therapies to combat these and other CaV2.1 channelopathies.
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Affiliation(s)
- Sidharth Tyagi
- Medical Scientist Training Program, Yale University School of Medicine, New Haven, CT, United States
| | - Angeles B Ribera
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO, United States
| | - Roger A Bannister
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, United States.,Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
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6
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Ahuja AS, Rozen TD, Atwal PS. A sleep modulated Channelopathy: a novel CACNA1A pathogenic variant identified in episodic Ataxia type 2 and a potential link to sleep alleviated migraine. BMC Neurol 2019; 19:246. [PMID: 31640633 PMCID: PMC6806495 DOI: 10.1186/s12883-019-1491-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 10/01/2019] [Indexed: 11/25/2022] Open
Abstract
Background To describe a patient with sleep alleviated episodic ataxia type 2 with a novel CACNA1A pathogenic variant and provide a possible link to sleep responsive migraine. Case presentation A 26-year-old woman with recurrent attacks of dizziness, nausea, vomiting, ataxia and dysarthria presented for a possible diagnosis of vestibular migraine. Unique to her attacks was if she could fall asleep for as little as 15 min the spells would subside. If however she remained awake the attacks would continue unabated. A presumed diagnosis of episodic ataxia type 2 was made and she became attack free on acetazolamide without recurrence. Genetic testing demonstrated a novel pathogenic variant in CACNA1A on chromosome 19. This pathogenic variant has not been previously reported in the literature and is suggested to truncate the CACNA1A polypeptide by introducing a premature stop codon. Conclusion A case of episodic ataxia type 2 with a novel pathogenic variant in CACNA1A is described. Interestingly, the patient’s symptoms would completely alleviate with sleep which suggests a sleep modulated channelopathy. The mechanisms by which sleep could potentially alter this pathogenic variant are hypothesized. A potential link to sleep alleviated migraine is suggested. Further study of this novel pathogenic variant may help us understand not only how sleep can modulate episodic ataxia type 2, but also migraine.
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7
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Bar C, Barcia G, Jennesson M, Le Guyader G, Schneider A, Mignot C, Lesca G, Breuillard D, Montomoli M, Keren B, Doummar D, Billette de Villemeur T, Afenjar A, Marey I, Gerard M, Isnard H, Poisson A, Dupont S, Berquin P, Meyer P, Genevieve D, De Saint Martin A, El Chehadeh S, Chelly J, Guët A, Scalais E, Dorison N, Myers CT, Mefford HC, Howell KB, Marini C, Freeman JL, Nica A, Terrone G, Sekhara T, Lebre A, Odent S, Sadleir LG, Munnich A, Guerrini R, Scheffer IE, Kabashi E, Nabbout R. Expanding the genetic and phenotypic relevance of
KCNB1
variants in developmental and epileptic encephalopathies: 27 new patients and overview of the literature. Hum Mutat 2019; 41:69-80. [DOI: 10.1002/humu.23915] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 08/28/2019] [Accepted: 09/09/2019] [Indexed: 12/28/2022]
Affiliation(s)
- Claire Bar
- Department of Pediatric Neurology, Reference Centre for Rare EpilepsiesHôpital Necker‐Enfants MaladesParis France
- Imagine institute, laboratory of Translational Research for Neurological Disorders, INSERM UMR 1163Imagine InstituteParis France
- Université Paris Descartes‐Sorbonne Paris CitéParis France
| | - Giulia Barcia
- Imagine institute, laboratory of Translational Research for Neurological Disorders, INSERM UMR 1163Imagine InstituteParis France
- Université Paris Descartes‐Sorbonne Paris CitéParis France
- Department of genetics, Necker Enfants Malades hospitalAssistance Publique‐Hôpitaux de ParisParis France
| | | | - Gwenaël Le Guyader
- Department of geneticsUniversity hospital PoitiersPoitiers Cedex France
- EA3808‐NEUVACOD Unité Neurovasculaire et Troubles Cognitifs, Pôle Biologie SantéUniversité de PoitiersPoitiers France
| | - Amy Schneider
- Department of Medicine, Epilepsy Research Centre, Austin HealthThe University of MelbourneHeidelberg Victoria Australia
| | - Cyril Mignot
- Institut du Cerveau et de la Moelle épinière, INSERM, U 1127, CNRS UMR 7225Sorbonne Universités UPMC Univ Paris 06 UMR S 1127 Paris France
- Département de Génétique et de Cytogénétique, Centre de Reference Déficience Intellectuelle de Causes Rares, APHP, Hôpital Pitié‐SalpêtrièreGRC UPMC (Déficience Intellectuelle et Autisme)Paris France
| | - Gaetan Lesca
- Department of geneticsHospices Civils de LyonLyon France
- Neurosciences centre of Lyon, INSERM U1028, UMR CNRS 5292Université Claude Bernard Lyon 1Bron Cedex France
| | - Delphine Breuillard
- Department of Pediatric Neurology, Reference Centre for Rare EpilepsiesHôpital Necker‐Enfants MaladesParis France
| | - Martino Montomoli
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Department of Neuroscience, A Meyer Children's HospitalUniversity of FlorenceFlorence Italy
| | - Boris Keren
- Département de Génétique et de Cytogénétique, Centre de Reference Déficience Intellectuelle de Causes Rares, APHP, Hôpital Pitié‐SalpêtrièreGRC UPMC (Déficience Intellectuelle et Autisme)Paris France
| | - Diane Doummar
- Department of Pediatric Neurology, Hôpital Armand TrousseauAP‐HPParis France
| | | | - Alexandra Afenjar
- Département de Génétique et Embryologie Médicale, Pathologies Congénitales du Cervelet‐LeucoDystrophies, Centre de Référence déficiences intellectuelles de causes rares, AP‐HP, Hôpital Armand Trousseau, GRC n°19Sorbonne UniversitéParis France
| | - Isabelle Marey
- Département de Génétique et de Cytogénétique, Centre de Reference Déficience Intellectuelle de Causes Rares, APHP, Hôpital Pitié‐SalpêtrièreGRC UPMC (Déficience Intellectuelle et Autisme)Paris France
| | | | | | - Alice Poisson
- Reference Center for Diagnosis and Management of Genetic Psychiatric Disorders, Centre Hospitalier le Vinatier and EDR‐Psy TeamCentre National de la Recherche Scientifique & Lyon 1 Claude Bernard UniversityVilleurbanne France
| | - Sophie Dupont
- Institut du Cerveau et de la Moelle épinière, INSERM, U 1127, CNRS UMR 7225Sorbonne Universités UPMC Univ Paris 06 UMR S 1127 Paris France
- Epileptology and Rehabilitation department, GH Pitie‐Salpêtrière‐Charles FoixAP‐HPParis France
| | - Patrick Berquin
- Department of pediatric neurology Amiens‐Picardie university hospitalUniversité de Picardie Jules VerneAmiens France
| | - Pierre Meyer
- Department of pediatric neurologyMontpellier university hospitalMontpellier France
- PhyMedExp, U1046 INSERMUMR9214 CNRSMontpellier France
| | - David Genevieve
- Service de génétique clinique et du Département de Génétique Médicale, Maladies Rares et Médecine Personnalisée, Centre de référence maladies rares anomalies du développementCHU MontpellierMontpellier France
| | - Anne De Saint Martin
- Department of Pediatric NeurologyStrasbourg University HospitalStrasbourg France
| | - Salima El Chehadeh
- Department of genetics, Hôpital de HautepierreHôpitaux Universitaires de StrasbourgStrasbourg France
| | - Jamel Chelly
- Department of genetics, Hôpital de HautepierreHôpitaux Universitaires de StrasbourgStrasbourg France
| | - Agnès Guët
- Department of PediatricLouis‐Mourier HospitalColombes France
| | - Emmanuel Scalais
- Department of Pediatric Neurology, Centre Hospitalier de LuxembourgLuxembourg CityLuxembourg City Luxembourg
| | - Nathalie Dorison
- Department of pediatric NeurosurgeryRothschild Foundation HospitalParis France
| | - Candace T. Myers
- Department of PediatricsUniversity of WashingtonSeattle Washington
| | - Heather C. Mefford
- Department of Pediatrics, Division of Genetic MedicineUniversity of WashingtonSeattle Washington
| | - Katherine B. Howell
- Departments of Neurology and Paediatrics, Royal Children's HospitalUniversity of MelbourneMelbourne Victoria Australia
- Murdoch Children's Research InstituteMelbourne Victoria Australia
| | - Carla Marini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Department of Neuroscience, A Meyer Children's HospitalUniversity of FlorenceFlorence Italy
| | - Jeremy L. Freeman
- Departments of Neurology and Paediatrics, Royal Children's HospitalUniversity of MelbourneMelbourne Victoria Australia
- Murdoch Children's Research InstituteMelbourne Victoria Australia
| | - Anca Nica
- Department of Neurology, Center for Clinical Research (CIC 1414)Rennes University HospitalRennes France
| | - Gaetano Terrone
- Department of Translational Medical Sciences, Section of Pediatrics‐Child Neurology UnitFederico II UniversityNaples Italy
| | - Tayeb Sekhara
- Department of Pediatric NeurologyC.H.I.R.E.CBrussels Belgium
| | - Anne‐Sophie Lebre
- Department of genetics, Maison Blanche hospitalUniversity hospital, ReimsReims France
| | - Sylvie Odent
- Reference Centre for Rare Developmental AbnormalitiesCLAD‐Ouest, CHU RennesRennes France
- Institute of genetics and developmentCNRS UMR 6290, Rennes universityRennes France
| | - Lynette G. Sadleir
- Department of Paediatrics and Child HealthUniversity of OtagoWellington New Zealand
| | - Arnold Munnich
- Université Paris Descartes‐Sorbonne Paris CitéParis France
- Department of genetics, Necker Enfants Malades hospitalAssistance Publique‐Hôpitaux de ParisParis France
| | - Renzo Guerrini
- Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Department of Neuroscience, A Meyer Children's HospitalUniversity of FlorenceFlorence Italy
| | - Ingrid E. Scheffer
- Department of Medicine, Epilepsy Research Centre, Austin HealthThe University of MelbourneHeidelberg Victoria Australia
- Departments of Neurology and Paediatrics, Royal Children's HospitalUniversity of MelbourneMelbourne Victoria Australia
- The Florey Institute of Neurosciences and Mental HealthHeidelberg Victoria Australia
| | - Edor Kabashi
- Imagine institute, laboratory of Translational Research for Neurological Disorders, INSERM UMR 1163Imagine InstituteParis France
- Université Paris Descartes‐Sorbonne Paris CitéParis France
| | - Rima Nabbout
- Department of Pediatric Neurology, Reference Centre for Rare EpilepsiesHôpital Necker‐Enfants MaladesParis France
- Imagine institute, laboratory of Translational Research for Neurological Disorders, INSERM UMR 1163Imagine InstituteParis France
- Université Paris Descartes‐Sorbonne Paris CitéParis France
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8
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Huang YC, Pirri JK, Rayes D, Gao S, Mulcahy B, Grant J, Saheki Y, Francis MM, Zhen M, Alkema MJ. Gain-of-function mutations in the UNC-2/CaV2α channel lead to excitation-dominant synaptic transmission in Caenorhabditis elegans. eLife 2019; 8:e45905. [PMID: 31364988 PMCID: PMC6713474 DOI: 10.7554/elife.45905] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 07/30/2019] [Indexed: 01/17/2023] Open
Abstract
Mutations in pre-synaptic voltage-gated calcium channels can lead to familial hemiplegic migraine type 1 (FHM1). While mammalian studies indicate that the migraine brain is hyperexcitable due to enhanced excitation or reduced inhibition, the molecular and cellular mechanisms underlying this excitatory/inhibitory (E/I) imbalance are poorly understood. We identified a gain-of-function (gf) mutation in the Caenorhabditis elegans CaV2 channel α1 subunit, UNC-2, which leads to increased calcium currents. unc-2(zf35gf) mutants exhibit hyperactivity and seizure-like motor behaviors. Expression of the unc-2 gene with FHM1 substitutions R192Q and S218L leads to hyperactivity similar to that of unc-2(zf35gf) mutants. unc-2(zf35gf) mutants display increased cholinergic and decreased GABAergic transmission. Moreover, increased cholinergic transmission in unc-2(zf35gf) mutants leads to an increase of cholinergic synapses and a TAX-6/calcineurin-dependent reduction of GABA synapses. Our studies reveal mechanisms through which CaV2 gain-of-function mutations disrupt excitation-inhibition balance in the nervous system.
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Affiliation(s)
- Yung-Chi Huang
- Department of NeurobiologyUniversity of Massachusetts Medical SchoolWorcesterUnited States
| | - Jennifer K Pirri
- Department of NeurobiologyUniversity of Massachusetts Medical SchoolWorcesterUnited States
| | - Diego Rayes
- Department of NeurobiologyUniversity of Massachusetts Medical SchoolWorcesterUnited States
| | - Shangbang Gao
- Lunenfeld-Tanenbaum Research InstituteMount Sinai HospitalTorontoCanada
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research InstituteMount Sinai HospitalTorontoCanada
| | - Jeff Grant
- Department of NeurobiologyUniversity of Massachusetts Medical SchoolWorcesterUnited States
| | - Yasunori Saheki
- Lulu and Anthony Wang Laboratory of Neural Circuits and BehaviorThe Rockefeller UniversityNew YorkUnited States
| | - Michael M Francis
- Department of NeurobiologyUniversity of Massachusetts Medical SchoolWorcesterUnited States
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research InstituteMount Sinai HospitalTorontoCanada
- Department of Molecular GeneticsUniversity of TorontoTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
| | - Mark J Alkema
- Department of NeurobiologyUniversity of Massachusetts Medical SchoolWorcesterUnited States
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9
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Nanou E, Catterall WA. Calcium Channels, Synaptic Plasticity, and Neuropsychiatric Disease. Neuron 2019; 98:466-481. [PMID: 29723500 DOI: 10.1016/j.neuron.2018.03.017] [Citation(s) in RCA: 265] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 03/06/2018] [Accepted: 03/09/2018] [Indexed: 12/14/2022]
Abstract
Voltage-gated calcium channels couple depolarization of the cell-surface membrane to entry of calcium, which triggers secretion, contraction, neurotransmission, gene expression, and other physiological responses. They are encoded by ten genes, which generate three voltage-gated calcium channel subfamilies: CaV1; CaV2; and CaV3. At synapses, CaV2 channels form large signaling complexes in the presynaptic nerve terminal, which are responsible for the calcium entry that triggers neurotransmitter release and short-term presynaptic plasticity. CaV1 channels form signaling complexes in postsynaptic dendrites and dendritic spines, where their calcium entry induces long-term potentiation. These calcium channels are the targets of mutations and polymorphisms that alter their function and/or regulation and cause neuropsychiatric diseases, including migraine headache, cerebellar ataxia, autism, schizophrenia, bipolar disorder, and depression. This article reviews the molecular properties of calcium channels, considers their multiple roles in synaptic plasticity, and discusses their potential involvement in this wide range of neuropsychiatric diseases.
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Affiliation(s)
- Evanthia Nanou
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA
| | - William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA.
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10
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Bartels P, Yu D, Huang H, Hu Z, Herzig S, Soong TW. Alternative Splicing at N Terminus and Domain I Modulates Ca V1.2 Inactivation and Surface Expression. Biophys J 2019; 114:2095-2106. [PMID: 29742403 DOI: 10.1016/j.bpj.2018.03.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 03/12/2018] [Accepted: 03/27/2018] [Indexed: 10/17/2022] Open
Abstract
The CaV1.2 L-type calcium channel is a key conduit for Ca2+ influx to initiate excitation-contraction coupling for contraction of the heart and vasoconstriction of the arteries and for altering membrane excitability in neurons. Its α1C pore-forming subunit is known to undergo extensive alternative splicing to produce many CaV1.2 isoforms that differ in their electrophysiological and pharmacological properties. Here, we examined the structure-function relationship of human CaV1.2 with respect to the inclusion or exclusion of mutually exclusive exons of the N-terminus exons 1/1a and IS6 segment exons 8/8a. These exons showed tissue selectivity in their expression patterns: heart variant 1a/8a, one smooth-muscle variant 1/8, and a brain isoform 1/8a. Overall, the 1/8a, when coexpressed with CaVβ2a, displayed a significant and distinct shift in voltage-dependent activation and inactivation and inactivation kinetics as compared to the other three splice variants. Further analysis showed a clear additive effect of the hyperpolarization shift in V1/2inact of CaV1.2 channels containing exon 1 in combination with 8a. However, this additive effect was less distinct for V1/2act. However, the measured effects were β-subunit-dependent when comparing CaVβ2a with CaVβ3 coexpression. Notably, calcium-dependent inactivation mediated by local Ca2+-sensing via the N-lobe of calmodulin was significantly enhanced in exon-1-containing CaV1.2 as compared to exon-1a-containing CaV1.2 channels. At the cellular level, the current densities of the 1/8a or 1/8 variants were significantly larger than the 1a/8a and 1a/8 variants when coexpressed either with CaVβ2a or CaVβ3 subunit. This finding correlated well with a higher channel surface expression for the exon 1-CaV1.2 isoform that we quantified by protein surface-expression levels or by gating currents. Our data also provided a deeper molecular understanding of the altered biophysical properties of alternatively spliced human CaV1.2 channels by directly comparing unitary single-channel events with macroscopic whole-cell currents.
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Affiliation(s)
- Peter Bartels
- Department of Physiology, National University of Singapore, Singapore, Singapore
| | - Dejie Yu
- Department of Physiology, National University of Singapore, Singapore, Singapore
| | - Hua Huang
- Department of Physiology, National University of Singapore, Singapore, Singapore
| | - Zhenyu Hu
- Department of Physiology, National University of Singapore, Singapore, Singapore
| | - Stefan Herzig
- Department of Pharmacology, University of Cologne, Cologne, Germany
| | - Tuck Wah Soong
- Department of Physiology, National University of Singapore, Singapore, Singapore; NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore; Neurobiology/Ageing Programme, National University of Singapore, Singapore, Singapore; National Neuroscience Institute, Singapore, Singapore.
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11
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Samant RS, Livingston CM, Sontag EM, Frydman J. Distinct proteostasis circuits cooperate in nuclear and cytoplasmic protein quality control. Nature 2018; 563:407-411. [PMID: 30429547 PMCID: PMC6707801 DOI: 10.1038/s41586-018-0678-x] [Citation(s) in RCA: 115] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 09/04/2018] [Indexed: 11/09/2022]
Abstract
Protein misfolding is linked to a wide array of human disorders, including Alzheimer's disease, Parkinson's disease and type II diabetes1,2. Protective cellular protein quality control (PQC) mechanisms have evolved to selectively recognize misfolded proteins and limit their toxic effects3-9, thus contributing to the maintenance of the proteome (proteostasis). Here we examine how molecular chaperones and the ubiquitin-proteasome system cooperate to recognize and promote the clearance of soluble misfolded proteins. Using a panel of PQC substrates with distinct characteristics and localizations, we define distinct chaperone and ubiquitination circuitries that execute quality control in the cytoplasm and nucleus. In the cytoplasm, proteasomal degradation of misfolded proteins requires tagging with mixed lysine 48 (K48)- and lysine 11 (K11)-linked ubiquitin chains. A distinct combination of E3 ubiquitin ligases and specific chaperones is required to achieve each type of linkage-specific ubiquitination. In the nucleus, however, proteasomal degradation of misfolded proteins requires only K48-linked ubiquitin chains, and is thus independent of K11-specific ligases and chaperones. The distinct ubiquitin codes for nuclear and cytoplasmic PQC appear to be linked to the function of the ubiquilin protein Dsk2, which is specifically required to clear nuclear misfolded proteins. Our work defines the principles of cytoplasmic and nuclear PQC as distinct, involving combinatorial recognition by defined sets of cooperating chaperones and E3 ligases. A better understanding of how these organelle-specific PQC requirements implement proteome integrity has implications for our understanding of diseases linked to impaired protein clearance and proteostasis dysfunction.
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Affiliation(s)
- Rahul S Samant
- Department of Biology, Stanford University, Stanford, CA, USA.
| | - Christine M Livingston
- Department of Biology, Stanford University, Stanford, CA, USA. .,Janssen Research and Development, Spring House, PA, USA.
| | - Emily M Sontag
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Judith Frydman
- Department of Biology, Stanford University, Stanford, CA, USA. .,Department of Genetics, Stanford University, Stanford, CA, USA.
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12
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Dorgans K, Salvi J, Bertaso F, Bernard L, Lory P, Doussau F, Mezghrani A. Characterization of the dominant inheritance mechanism of Episodic Ataxia type 2. Neurobiol Dis 2017; 106:110-123. [PMID: 28688851 DOI: 10.1016/j.nbd.2017.07.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 06/30/2017] [Accepted: 07/04/2017] [Indexed: 12/01/2022] Open
Abstract
Episodic Ataxia type 2 (EA2) is an autosomal dominant neuronal disorder linked to mutations in the Cav2.1 subunit of P/Q-type calcium channels. In vitro studies have established that EA2 mutations induce loss of channel activity and that EA2 mutants can exert a dominant negative effect, suppressing normal Cav2.1 activity through protein misfolding and trafficking defects. To date, the role of this mechanism in the disease pathogenesis is unknown because no animal model exists. To address this issue, we have generated a mouse bearing the R1497X nonsense mutation in Cav2.1 (Cav2.1R1497X). Phenotypic analysis of heterozygous Cav2.1R1497X mice revealed ataxia associated with muscle weakness and generalized absence epilepsy. Electrophysiological studies of the cerebellar circuits in heterozygous Cav2.1R1497X mice highlighted severe dysregulations in synaptic transmission of the two major excitatory inputs as well as alteration of the spontaneous activity of Purkinje cells. Moreover, these neuronal dysfunctions were associated with a strong suppression of Cav2.1 channel expression in the cerebellum of heterozygous Cav2.1R1497X mice. Finally, the presence of Cav2.1 in cerebellar lipid raft microdomains was strongly impaired in heterozygous Cav2.1R1497X mice. Altogether, these results reveal a pathogenic mechanism for EA2 based on a dominant negative activity of mutant channels.
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Affiliation(s)
- Kevin Dorgans
- Institut des Neurosciences Cellulaires et Intégratives-INCI CNRS-UPR 3212, 5 rue Blaise Pascal, 67084 Strasbourg, France
| | - Julie Salvi
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U1191, Université de Montpellier, LabEx 'Ion Channel Science and Therapeutics', 141 rue de la Cardonille, 34094 Montpellier, France
| | - Federica Bertaso
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U1191, Université de Montpellier, LabEx 'Ion Channel Science and Therapeutics', 141 rue de la Cardonille, 34094 Montpellier, France
| | - Ludivine Bernard
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U1191, Université de Montpellier, LabEx 'Ion Channel Science and Therapeutics', 141 rue de la Cardonille, 34094 Montpellier, France
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U1191, Université de Montpellier, LabEx 'Ion Channel Science and Therapeutics', 141 rue de la Cardonille, 34094 Montpellier, France.
| | - Frederic Doussau
- Institut des Neurosciences Cellulaires et Intégratives-INCI CNRS-UPR 3212, 5 rue Blaise Pascal, 67084 Strasbourg, France
| | - Alexandre Mezghrani
- Institut des Neurosciences de Montpellier, INSERM U1051, Hôpital Saint Eloi - Bâtiment INM, 80 rue Augustin Fliche, 34091 Montpellier, France.
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13
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Kabir ZD, Martínez-Rivera A, Rajadhyaksha AM. From Gene to Behavior: L-Type Calcium Channel Mechanisms Underlying Neuropsychiatric Symptoms. Neurotherapeutics 2017; 14:588-613. [PMID: 28497380 PMCID: PMC5509628 DOI: 10.1007/s13311-017-0532-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The L-type calcium channels (LTCCs) Cav1.2 and Cav1.3, encoded by the CACNA1C and CACNA1D genes, respectively, are important regulators of calcium influx into cells and are critical for normal brain development and plasticity. In humans, CACNA1C has emerged as one of the most widely reproduced and prominent candidate risk genes for a range of neuropsychiatric disorders, including bipolar disorder (BD), schizophrenia (SCZ), major depressive disorder, autism spectrum disorder, and attention deficit hyperactivity disorder. Separately, CACNA1D has been found to be associated with BD and autism spectrum disorder, as well as cocaine dependence, a comorbid feature associated with psychiatric disorders. Despite growing evidence of a significant link between CACNA1C and CACNA1D and psychiatric disorders, our understanding of the biological mechanisms by which these LTCCs mediate neuropsychiatric-associated endophenotypes, many of which are shared across the different disorders, remains rudimentary. Clinical studies with LTCC blockers testing their efficacy to alleviate symptoms associated with BD, SCZ, and drug dependence have provided mixed results, underscoring the importance of further exploring the neurobiological consequences of dysregulated Cav1.2 and Cav1.3. Here, we provide a review of clinical studies that have evaluated LTCC blockers for BD, SCZ, and drug dependence-associated symptoms, as well as rodent studies that have identified Cav1.2- and Cav1.3-specific molecular and cellular cascades that underlie mood (anxiety, depression), social behavior, cognition, and addiction.
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Affiliation(s)
- Zeeba D Kabir
- Pediatric Neurology, Pediatrics, Weill Cornell Medicine, New York, NY, USA
- Weill Cornell Autism Research Program, Weill Cornell Medicine, New York, NY, USA
| | - Arlene Martínez-Rivera
- Pediatric Neurology, Pediatrics, Weill Cornell Medicine, New York, NY, USA
- Weill Cornell Autism Research Program, Weill Cornell Medicine, New York, NY, USA
| | - Anjali M Rajadhyaksha
- Pediatric Neurology, Pediatrics, Weill Cornell Medicine, New York, NY, USA.
- Weill Cornell Autism Research Program, Weill Cornell Medicine, New York, NY, USA.
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA.
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14
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Mutation Spectrum in the CACNA1A Gene in 49 Patients with Episodic Ataxia. Sci Rep 2017; 7:2514. [PMID: 28566750 PMCID: PMC5451382 DOI: 10.1038/s41598-017-02554-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 04/13/2017] [Indexed: 11/08/2022] Open
Abstract
Episodic ataxia is an autosomal dominant ion channel disorder characterized by episodes of imbalance and incoordination. The disease is genetically heterogeneous and is classified as episodic ataxia type 2 (EA2) when it is caused by a mutation in the CACNA1A gene, encoding the α1A subunit of the P/Q-type voltage-gated calcium channel Cav2.1. The vast majority of EA2 disease-causing variants are loss-of-function (LoF) point changes leading to decreased channel currents. CACNA1A exonic deletions have also been reported in EA2 using quantitative approaches. We performed a mutational screening of the CACNA1A gene, including the promoter and 3'UTR regions, in 49 unrelated patients diagnosed with episodic ataxia. When pathogenic variants were not found by sequencing, we performed a copy number variant (CNV) analysis to screen for duplications or deletions. Overall, sequencing screening allowed identification of six different point variants (three nonsense and three missense changes) and two coding indels, one of them found in two unrelated patients. Additionally, CNV analysis identified a deletion in a patient spanning exon 35 as a result of a recombination event between flanking intronic Alu sequences. This study allowed identification of potentially pathogenic alterations in our sample, five of them novel, which cover 20% of the patients (10/49). Our data suggest that most of these variants are disease-causing, although functional studies are required.
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15
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Terragni B, Scalmani P, Franceschetti S, Cestèle S, Mantegazza M. Post-translational dysfunctions in channelopathies of the nervous system. Neuropharmacology 2017; 132:31-42. [PMID: 28571716 DOI: 10.1016/j.neuropharm.2017.05.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 05/12/2017] [Accepted: 05/26/2017] [Indexed: 12/23/2022]
Abstract
Channelopathies comprise various diseases caused by defects of ion channels. Modifications of their biophysical properties are common and have been widely studied. However, ion channels are heterogeneous multi-molecular complexes that are extensively modulated and undergo a maturation process comprising numerous steps of structural modifications and intracellular trafficking. Perturbations of these processes can give rise to aberrant channels that cause pathologies. Here we review channelopathies of the nervous system associated with dysfunctions at the post-translational level (folding, trafficking, degradation, subcellular localization, interactions with associated proteins and structural post-translational modifications). We briefly outline the physiology of ion channels' maturation and discuss examples of defective mechanisms, focusing in particular on voltage-gated sodium channels, which are implicated in numerous neurological disorders. We also shortly introduce possible strategies to develop therapeutic approaches that target these processes. This article is part of the Special Issue entitled 'Channelopathies.'
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Affiliation(s)
- Benedetta Terragni
- U.O. Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Paolo Scalmani
- U.O. Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Silvana Franceschetti
- U.O. Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Sandrine Cestèle
- Institute of Molecular and Cellular Pharmacology (IPMC), CNRS UMR7275, 06560, Valbonne-Sophia Antipolis, France; University Côte d'Azur (UCA), 06560, Valbonne-Sophia Antipolis, France
| | - Massimo Mantegazza
- Institute of Molecular and Cellular Pharmacology (IPMC), CNRS UMR7275, 06560, Valbonne-Sophia Antipolis, France; University Côte d'Azur (UCA), 06560, Valbonne-Sophia Antipolis, France.
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16
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Ubiquitin Ligase RNF138 Promotes Episodic Ataxia Type 2-Associated Aberrant Degradation of Human Ca v2.1 (P/Q-Type) Calcium Channels. J Neurosci 2017; 37:2485-2503. [PMID: 28167673 DOI: 10.1523/jneurosci.3070-16.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 01/09/2017] [Accepted: 01/31/2017] [Indexed: 11/21/2022] Open
Abstract
Voltage-gated CaV2.1 channels comprise a pore-forming α1A subunit with auxiliary α2δ and β subunits. CaV2.1 channels play an essential role in regulating synaptic signaling. Mutations in the human gene encoding the CaV2.1 subunit are associated with the cerebellar disease episodic ataxia type 2 (EA2). Several EA2-causing mutants exhibit impaired protein stability and exert dominant-negative suppression of CaV2.1 wild-type (WT) protein expression via aberrant proteasomal degradation. Here, we set out to delineate the protein degradation mechanism of human CaV2.1 subunit by identifying RNF138, an E3 ubiquitin ligase, as a novel CaV2.1-binding partner. In neurons, RNF138 and CaV2.1 coexist in the same protein complex and display notable subcellular colocalization at presynaptic and postsynaptic regions. Overexpression of RNF138 promotes polyubiquitination and accelerates protein turnover of CaV2.1. Disrupting endogenous RNF138 function with a mutant (RNF138-H36E) or shRNA infection significantly upregulates the CaV2.1 protein level and enhances CaV2.1 protein stability. Disrupting endogenous RNF138 function also effectively rescues the defective protein expression of EA2 mutants, as well as fully reversing EA2 mutant-induced excessive proteasomal degradation of CaV2.1 WT subunits. RNF138-H36E coexpression only partially restores the dominant-negative effect of EA2 mutants on CaV2.1 WT functional expression, which can be attributed to defective membrane trafficking of CaV2.1 WT in the presence of EA2 mutants. We propose that RNF138 plays a critical role in the homeostatic regulation of CaV2.1 protein level and functional expression and that RNF138 serves as the primary E3 ubiquitin ligase promoting EA2-associated aberrant degradation of human CaV2.1 subunits.SIGNIFICANCE STATEMENT Loss-of-function mutations in the human CaV2.1 subunit are linked to episodic ataxia type 2 (EA2), a dominantly inherited disease characterized by paroxysmal attacks of ataxia and nystagmus. EA2-causing mutants may exert dominant-negative effects on the CaV2.1 wild-type subunit via aberrant proteasomal degradation. The molecular nature of the CaV2.1 ubiquitin-proteasome degradation pathway is currently unknown. The present study reports the first identification of an E3 ubiquitin ligase for CaV2.1, RNF138. CaV2.1 protein stability is dynamically regulated by RNF138 and auxiliary α2δ and β subunits. We provide a proof of concept that protecting the human CaV2.1 subunit from excessive proteasomal degradation with specific interruption of endogenous RNF138 function may partially contribute to the future development of a novel therapeutic strategy for EA2 patients.
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17
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Hu Z, Wang JW, Yu D, Soon JL, de Kleijn DPV, Foo R, Liao P, Colecraft HM, Soong TW. Aberrant Splicing Promotes Proteasomal Degradation of L-type Ca V1.2 Calcium Channels by Competitive Binding for Ca Vβ Subunits in Cardiac Hypertrophy. Sci Rep 2016; 6:35247. [PMID: 27731386 PMCID: PMC5059693 DOI: 10.1038/srep35247] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 09/27/2016] [Indexed: 12/13/2022] Open
Abstract
Decreased expression and activity of CaV1.2 calcium channels has been reported in pressure overload-induced cardiac hypertrophy and heart failure. However, the underlying mechanisms remain unknown. Here we identified in rodents a splice variant of CaV1.2 channel, named CaV1.2e21+22, that contained the pair of mutually exclusive exons 21 and 22. This variant was highly expressed in neonatal hearts. The abundance of this variant was gradually increased by 12.5-folds within 14 days of transverse aortic banding that induced cardiac hypertrophy in adult mouse hearts and was also elevated in left ventricles from patients with dilated cardiomyopathy. Although this variant did not conduct Ca2+ ions, it reduced the cell-surface expression of wild-type CaV1.2 channels and consequently decreased the whole-cell Ca2+ influx via the CaV1.2 channels. In addition, the CaV1.2e21+22 variant interacted with CaVβ subunits significantly more than wild-type CaV1.2 channels, and competition of CaVβ subunits by CaV1.2e21+22 consequently enhanced ubiquitination and subsequent proteasomal degradation of the wild-type CaV1.2 channels. Our findings show that the resurgence of a specific neonatal splice variant of CaV1.2 channels in adult heart under stress may contribute to heart failure.
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Affiliation(s)
- Zhenyu Hu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore 117597, Singapore
| | - Jiong-Wei Wang
- Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.,Cardiovascular Research Institute, National University Health Systems, Centre for Translational Medicine, 117599, Singapore
| | - Dejie Yu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore 117597, Singapore
| | - Jia Lin Soon
- National Heart Centre Singapore, 5 hospital drive, 169609, Singapore
| | - Dominique P V de Kleijn
- Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.,Cardiovascular Research Institute, National University Health Systems, Centre for Translational Medicine, 117599, Singapore.,Dept of Cardiology, University Medical Center Utrecht, 3584CX Utrecht, The Netherlands
| | - Roger Foo
- Cardiovascular Research Institute, National University Health Systems, Centre for Translational Medicine, 117599, Singapore
| | - Ping Liao
- Calcium Signaling Laboratory, National Neuroscience Institute, 11 Jalan Tan Tock Seng 308433, Singapore
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
| | - Tuck Wah Soong
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore 117597, Singapore.,NUS Graduate School for Integrative Sciences and Engineering, 117456, Singapore.,Neurobiology/Ageing Programme, National University of Singapore, 117456, Singapore
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18
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Mark MD, Schwitalla JC, Groemmke M, Herlitze S. Keeping Our Calcium in Balance to Maintain Our Balance. Biochem Biophys Res Commun 2016; 483:1040-1050. [PMID: 27392710 DOI: 10.1016/j.bbrc.2016.07.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 07/04/2016] [Indexed: 01/13/2023]
Abstract
Calcium is a key signaling molecule and ion involved in a variety of diverse processes in our central nervous system (CNS) which include gene expression, synaptic transmission and plasticity, neuronal excitability and cell maintenance. Proper control of calcium signaling is not only vital for neuronal physiology but also cell survival. Mutations in fundamental channels, transporters and second messenger proteins involved in orchestrating the balance of our calcium homeostasis can lead to severe neurodegenerative disorders, such as Spinocerebellar (SCA) and Episodic (EA) ataxias. Hereditary ataxias make up a remarkably diverse group of neurological disorders clinically characterized by gait ataxia, nystagmus, dysarthria, trunk and limb ataxia and often atrophy of the cerebellum. The largest family of hereditary ataxias is SCAs which consists of a growing family of 42 members. A relatively smaller family of 8 members compose the EAs. The gene mutations responsible for half of the EA members and over 35 of the SCA subtypes have been identified, and several have been found to be responsible for cerebellar atrophy, abnormal intracellular calcium levels, dysregulation of Purkinje cell pacemaking, altered cerebellar synaptic transmission and/or ataxia in mouse models. Although the genetic diversity and affected cellular pathways of hereditary ataxias are broad, one common theme amongst these genes is their effects on maintaining calcium balance in primarily the cerebellum. There is emerging evidence that the pathogenesis of hereditary ataxias may be caused by imbalances in intracellular calcium due to genetic mutations in calcium-mediating proteins. In this review we will discuss the current evidence supporting the role of deranged calcium as the culprit to neurodegenerative diseases with a primary focus on SCAs and EAs.
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Affiliation(s)
- Melanie D Mark
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
| | - Jan Claudius Schwitalla
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Michelle Groemmke
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Stefan Herlitze
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
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19
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Dahimene S, Page KM, Nieto-Rostro M, Pratt WS, D'Arco M, Dolphin AC. A CaV2.1 N-terminal fragment relieves the dominant-negative inhibition by an Episodic ataxia 2 mutant. Neurobiol Dis 2016; 93:243-56. [PMID: 27260834 PMCID: PMC4940211 DOI: 10.1016/j.nbd.2016.05.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 05/30/2016] [Indexed: 02/08/2023] Open
Abstract
Episodic ataxia 2 (EA2) is an autosomal dominant disorder caused by mutations in the gene CACNA1A that encodes the pore-forming CaV2.1 calcium channel subunit. The majority of EA2 mutations reported so far are nonsense or deletion/insertion mutations predicted to form truncated proteins. Heterologous expression of wild-type CaV2.1, together with truncated constructs that mimic EA2 mutants, significantly suppressed wild-type calcium channel function, indicating that the truncated protein produces a dominant-negative effect (Jouvenceau et al., 2001; Page et al., 2004). A similar finding has been shown for CaV2.2 (Raghib et al., 2001). We show here that a highly conserved sequence in the cytoplasmic N-terminus is involved in this process, for both CaV2.1 and CaV2.2 channels. Additionally, we were able to interfere with the suppressive effect of an EA2 construct by mutating key N-terminal residues within it. We postulate that the N-terminus of the truncated channel plays an essential part in its interaction with the full-length CaV2.1, which prevents the correct folding of the wild-type channel. In agreement with this, we were able to disrupt the interaction between EA2 and the full length channel by co-expressing a free N-terminal peptide.
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Affiliation(s)
- Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
| | - Karen M Page
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Manuela Nieto-Rostro
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Marianna D'Arco
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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20
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Moshfegh Y, Velez G, Li Y, Bassuk AG, Mahajan VB, Tsang SH. BESTROPHIN1 mutations cause defective chloride conductance in patient stem cell-derived RPE. Hum Mol Genet 2016; 25:2672-2680. [PMID: 27193166 DOI: 10.1093/hmg/ddw126] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/13/2016] [Accepted: 04/18/2016] [Indexed: 12/20/2022] Open
Abstract
Bestrophin1 (BEST1) is expressed in human retinal pigment epithelium (RPE) and mutations in the BEST1 gene commonly cause retinal dysfunction and macular degeneration. BEST1 is presumed to assemble into a calcium-activated chloride channel and be involved in chloride transport but there is no direct evidence in live human RPE cells to support this idea. To test whether BEST1 functions as a chloride channel in living tissue, BEST1-mutant RPE (R218H, L234P, A243T) were generated from patient-derived induced pluripotent stem cells and compared with wild-type RPE in a retinal environment, using a biosensor that visualizes calcium-induced chloride ion flux in the cell. Calcium stimulation elicited chloride ion export in normal RPE but not in RPE derived from three patients with BEST1 mutations. These data, along with three-dimensional modeling, provide evidence that BEST1 assembles into a key calcium-sensing chloride channel in human RPE.
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Affiliation(s)
- Yasmin Moshfegh
- Barbara & Donald Jonas Laboratory of Regenerative Medicine, and Bernard & Shirlee Brown Glaucoma Laboratory, Department of Pathology & Cell Biology, Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.,Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY 10032, USA
| | - Gabriel Velez
- Omics Lab.,Department of Ophthalmology and Visual Sciences.,Medical Scientist Training Program
| | - Yao Li
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY 10032, USA
| | | | - Vinit B Mahajan
- Department of Ophthalmology and Visual Sciences.,Medical Scientist Training Program
| | - Stephen H Tsang
- Barbara & Donald Jonas Laboratory of Regenerative Medicine, and Bernard & Shirlee Brown Glaucoma Laboratory, Department of Pathology & Cell Biology, Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA .,Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY 10032, USA
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21
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Sottas V, Abriel H. Negative-dominance phenomenon with genetic variants of the cardiac sodium channel Nav1.5. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1791-8. [PMID: 26907222 DOI: 10.1016/j.bbamcr.2016.02.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/15/2016] [Accepted: 02/19/2016] [Indexed: 02/07/2023]
Abstract
During the past two decades, many pathological genetic variants in SCN5A, the gene encoding the pore-forming subunit of the cardiac (monomeric) sodium channel Na(v)1.5, have been described. Negative dominance is a classical genetic concept involving a "poison" mutant peptide that negatively interferes with the co-expressed wild-type protein, thus reducing its cellular function. This phenomenon has been described for genetic variants of multimeric K(+) channels, which mechanisms are well understood. Unexpectedly, several pathologic SCN5A variants that are linked to Brugada syndrome also demonstrate such a dominant-negative (DN) effect. The molecular determinants of these observations, however, are not yet elucidated. This review article summarizes recent findings that describe the mechanisms underlying the DN phenomenon of genetic variants of K(+), Ca(2+), Cl(-) and Na(+) channels, and in particular Brugada syndrome variants of Na(v)1.5. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.
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Affiliation(s)
- Valentin Sottas
- Department of Clinical Research, Ion Channel Research Group, University of Bern, Switzerland
| | - Hugues Abriel
- Department of Clinical Research, Ion Channel Research Group, University of Bern, Switzerland.
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22
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Weyhrauch DL, Ye D, Boczek NJ, Tester DJ, Gavrilova RH, Patterson MC, Wieben ED, Ackerman MJ. Whole Exome Sequencing and Heterologous Cellular Electrophysiology Studies Elucidate a Novel Loss-of-Function Mutation in the CACNA1A-Encoded Neuronal P/Q-Type Calcium Channel in a Child With Congenital Hypotonia and Developmental Delay. Pediatr Neurol 2016; 55:46-51. [PMID: 26739101 DOI: 10.1016/j.pediatrneurol.2015.10.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 10/30/2015] [Accepted: 10/31/2015] [Indexed: 01/09/2023]
Abstract
BACKGROUND A 4-year-old boy born at 37 weeks' gestation with intrauterine growth retardation presented with developmental delay with pronounced language and gross motor delay, axial hypotonia, and dynamic hypertonia of the extremities. Investigations including the Minnesota Newborn Screen, thyroid stimulating hormone/thyroxin, and inborn errors of metabolism screening were negative. Cerebral magnetic resonance imaging and spectroscopy were normal. Genetic testing was negative for coagulopathy, Smith-Lemli-Opitz, fragile X, and Prader-Willi/Angelman syndromes. Whole genome array analysis was unremarkable. METHODS Whole exome sequencing was performed through a commercial testing laboratory to elucidate the underlying etiology for the child's presentation. A de novo mutation was hypothesized. In attempt to establish pathogenicity of our candidate variant, cellular electrophysiologic functional analysis of the putative de novo mutation was performed using patch-clamp technology. RESULTS Whole exome sequencing revealed a p.P1353L variant in the CACNA1A gene, which encodes for the α1-subunit of the brain-specific P/Q-type calcium channel (CaV2.1). This presynaptic high-voltage-gated channel couples neuronal excitation to the vesicular release of neurotransmitter and is implicated in several neurologic disorders. DNA Sanger sequencing confirmed that the de novo mutation was absent in both parents and present in the child only. Electrophysiologic analysis of P1353L-CACNA1A demonstrated near complete loss of function, with a 95% reduction in peak current density. CONCLUSIONS Whole exome sequencing coupled with cellular electrophysiologic functional analysis of a de novoCACNA1A missense mutation has elucidated the probable underlying pathophysiologic mechanism responsible for the child's phenotype. Genetic testing of CACNA1A in patients with congenital hypotonia and developmental delay may be warranted.
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Affiliation(s)
- Derek L Weyhrauch
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota
| | - Dan Ye
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota
| | - Nicole J Boczek
- Department of Health Science Research, Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
| | - David J Tester
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota
| | - Ralitza H Gavrilova
- Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota; Department of Neurology, Mayo Clinic, Rochester, Minnesota
| | - Marc C Patterson
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota; Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota; Department of Neurology, Mayo Clinic, Rochester, Minnesota
| | - Eric D Wieben
- Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota; Departments of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota
| | - Michael J Ackerman
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota; Department of Pediatric and Adolescent Medicine (Division of Pediatric Cardiology), Mayo Clinic, Rochester, Minnesota; Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota.
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Frolov RV, Weckström M. Harnessing the Flow of Excitation: TRP, Voltage-Gated Na(+), and Voltage-Gated Ca(2+) Channels in Contemporary Medicine. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2015; 103:25-95. [PMID: 26920687 DOI: 10.1016/bs.apcsb.2015.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cellular signaling in both excitable and nonexcitable cells involves several classes of ion channels. Some of them are of minor importance, with very specialized roles in physiology, but here we concentrate on three major channel classes: TRP (transient receptor potential channels), voltage-gated sodium channels (Nav), and voltage-gated calcium channels (Cav). Here, we first propose a conceptual framework binding together all three classes of ion channels, a "flow-of-excitation model" that takes into account the inputs mediated by TRP and other similar channels, the outputs invariably provided by Cav channels, and the regenerative transmission of signals in the neural networks, for which Nav channels are responsible. We use this framework to examine the function, structure, and pharmacology of these channel classes both at cellular and also at whole-body physiological level. Building on that basis we go through the pathologies arising from the direct or indirect malfunction of the channels, utilizing ion channel defects, the channelopathies. The pharmacological interventions affecting these channels are numerous. Part of those are well-established treatments, like treatment of hypertension or some forms of epilepsy, but many other are deeply problematic due to poor drug specificity, ion channel diversity, and widespread expression of the channels in tissues other than those actually targeted.
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Affiliation(s)
- Roman V Frolov
- Division of Biophysics, Department of Physics, University of Oulu, Oulun Yliopisto, Finland.
| | - Matti Weckström
- Division of Biophysics, Department of Physics, University of Oulu, Oulun Yliopisto, Finland
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Zamponi GW, Striessnig J, Koschak A, Dolphin AC. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential. Pharmacol Rev 2015; 67:821-70. [PMID: 26362469 PMCID: PMC4630564 DOI: 10.1124/pr.114.009654] [Citation(s) in RCA: 704] [Impact Index Per Article: 78.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and anxiety. Use-dependent N-type calcium channel blockers are likely to be of therapeutic use in chronic pain conditions. Thus, more selective calcium channel blockers hold promise for therapeutic intervention.
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Affiliation(s)
- Gerald W Zamponi
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Joerg Striessnig
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Alexandra Koschak
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Annette C Dolphin
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
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Heyes S, Pratt WS, Rees E, Dahimene S, Ferron L, Owen MJ, Dolphin AC. Genetic disruption of voltage-gated calcium channels in psychiatric and neurological disorders. Prog Neurobiol 2015; 134:36-54. [PMID: 26386135 PMCID: PMC4658333 DOI: 10.1016/j.pneurobio.2015.09.002] [Citation(s) in RCA: 164] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/08/2015] [Accepted: 09/08/2015] [Indexed: 12/15/2022]
Abstract
Voltage-gated calcium channel classification—genes and proteins. Genetic analysis of neuropsychiatric syndromes. Calcium channel genes identified from GWA studies of psychiatric disorders. Rare mutations in calcium channel genes in psychiatric disorders. Pathophysiological sequelae of CACNA1C mutations and polymorphisms. Monogenic disorders resulting from harmful mutations in other voltage-gated calcium channel genes. Changes in calcium channel gene expression in disease. Involvement of voltage-gated calcium channels in early brain development.
This review summarises genetic studies in which calcium channel genes have been connected to the spectrum of neuropsychiatric syndromes, from bipolar disorder and schizophrenia to autism spectrum disorders and intellectual impairment. Among many other genes, striking numbers of the calcium channel gene superfamily have been implicated in the aetiology of these diseases by various DNA analysis techniques. We will discuss how these relate to the known monogenic disorders associated with point mutations in calcium channels. We will then examine the functional evidence for a causative link between these mutations or single nucleotide polymorphisms and the disease processes. A major challenge for the future will be to translate the expanding psychiatric genetic findings into altered physiological function, involvement in the wider pathology of the diseases, and what potential that provides for personalised and stratified treatment options for patients.
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Affiliation(s)
- Samuel Heyes
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Elliott Rees
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Michael J Owen
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
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Monteil A, Chausson P, Boutourlinsky K, Mezghrani A, Huc-Brandt S, Blesneac I, Bidaud I, Lemmers C, Leresche N, Lambert RC, Lory P. Inhibition of Cav3.2 T-type Calcium Channels by Its Intracellular I-II Loop. J Biol Chem 2015; 290:16168-76. [PMID: 25931121 DOI: 10.1074/jbc.m114.634261] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Indexed: 11/06/2022] Open
Abstract
Voltage-dependent calcium channels (Cav) of the T-type family (Cav3.1, Cav3.2, and Cav3.3) are activated by low threshold membrane depolarization and contribute greatly to neuronal network excitability. Enhanced T-type channel activity, especially Cav3.2, contributes to disease states, including absence epilepsy. Interestingly, the intracellular loop connecting domains I and II (I-II loop) of Cav3.2 channels is implicated in the control of both surface expression and channel gating, indicating that this I-II loop plays an important regulatory role in T-type current. Here we describe that co-expression of this I-II loop or its proximal region (Δ1-Cav3.2; Ser(423)-Pro(542)) together with recombinant full-length Cav3.2 channel inhibited T-type current without affecting channel expression and membrane incorporation. Similar T-type current inhibition was obtained in NG 108-15 neuroblastoma cells that constitutively express Cav3.2 channels. Of interest, Δ1-Cav3.2 inhibited both Cav3.2 and Cav3.1 but not Cav3.3 currents. Efficacy of Δ1-Cav3.2 to inhibit native T-type channels was assessed in thalamic neurons using viral transduction. We describe that T-type current was significantly inhibited in the ventrobasal neurons that express Cav3.1, whereas in nucleus reticularis thalami neurons that express Cav3.2 and Cav3.3 channels, only the fast inactivating T-type current (Cav3.2 component) was significantly inhibited. Altogether, these data describe a new strategy to differentially inhibit Cav3 isoforms of the T-type calcium channels.
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Affiliation(s)
- Arnaud Monteil
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, Plateforme de Vectorologie, Biocampus Montpellier CNRS UMS 3426, INSERM US009, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Patrick Chausson
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Katia Boutourlinsky
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Alexandre Mezghrani
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Sylvaine Huc-Brandt
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Iulia Blesneac
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Isabelle Bidaud
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Céline Lemmers
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, Plateforme de Vectorologie, Biocampus Montpellier CNRS UMS 3426, INSERM US009, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France
| | - Nathalie Leresche
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Régis C Lambert
- Sorbonne Universités, Université Pierre et Marie Curie Université Paris 06, UM 119, Neuroscience Paris Seine (NPS), Paris F-75005, France, CNRS UMR 8246, NPS, Paris F-75005, France, and INSERM, U1130, NPS, Paris F-75005, France
| | - Philippe Lory
- From the Université de Montpellier, CNRS UMR 5203, Département de Physiologie, Institut de Génomique Fonctionnelle, Montpellier, F-34094 France, INSERM, U1191, Montpellier, F-34094 France, LabEx "Ion Channel Science and Therapeutics," Montpellier, F-34094 France,
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Chong J, McMillin M, Shively K, Beck A, Marvin C, Armenteros J, Buckingham K, Nkinsi N, Boyle E, Berry M, Bocian M, Foulds N, Uzielli M, Haldeman-Englert C, Hennekam R, Kaplan P, Kline A, Mercer C, Nowaczyk M, Klein Wassink-Ruiter J, McPherson E, Moreno R, Scheuerle A, Shashi V, Stevens C, Carey J, Monteil A, Lory P, Tabor H, Smith J, Shendure J, Nickerson D, Bamshad MJ, Bamshad M, Shendure J, Nickerson D, Abecasis G, Anderson P, Blue E, Annable M, Browning B, Buckingham K, Chen C, Chin J, Chong J, Cooper G, Davis C, Frazar C, Harrell T, He Z, Jain P, Jarvik G, Jimenez G, Johanson E, Jun G, Kircher M, Kolar T, Krauter S, Krumm N, Leal S, Luksic D, Marvin C, McMillin M, McGee S, O’Reilly P, Paeper B, Patterson K, Perez M, Phillips S, Pijoan J, Poel C, Reinier F, Robertson P, Santos-Cortez R, Shaffer T, Shephard C, Shively K, Siegel D, Smith J, Staples J, Tabor H, Tackett M, Underwood J, Wegener M, Wang G, Wheeler M, Yi Q. De novo mutations in NALCN cause a syndrome characterized by congenital contractures of the limbs and face, hypotonia, and developmental delay. Am J Hum Genet 2015; 96:462-73. [PMID: 25683120 DOI: 10.1016/j.ajhg.2015.01.003] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/07/2015] [Indexed: 12/13/2022] Open
Abstract
Freeman-Sheldon syndrome, or distal arthrogryposis type 2A (DA2A), is an autosomal-dominant condition caused by mutations in MYH3 and characterized by multiple congenital contractures of the face and limbs and normal cognitive development. We identified a subset of five individuals who had been putatively diagnosed with "DA2A with severe neurological abnormalities" and for whom congenital contractures of the limbs and face, hypotonia, and global developmental delay had resulted in early death in three cases; this is a unique condition that we now refer to as CLIFAHDD syndrome. Exome sequencing identified missense mutations in the sodium leak channel, non-selective (NALCN) in four families affected by CLIFAHDD syndrome. We used molecular-inversion probes to screen for NALCN in a cohort of 202 distal arthrogryposis (DA)-affected individuals as well as concurrent exome sequencing of six other DA-affected individuals, thus revealing NALCN mutations in ten additional families with "atypical" forms of DA. All 14 mutations were missense variants predicted to alter amino acid residues in or near the S5 and S6 pore-forming segments of NALCN, highlighting the functional importance of these segments. In vitro functional studies demonstrated that NALCN alterations nearly abolished the expression of wild-type NALCN, suggesting that alterations that cause CLIFAHDD syndrome have a dominant-negative effect. In contrast, homozygosity for mutations in other regions of NALCN has been reported in three families affected by an autosomal-recessive condition characterized mainly by hypotonia and severe intellectual disability. Accordingly, mutations in NALCN can cause either a recessive or dominant condition characterized by varied though overlapping phenotypic features, perhaps based on the type of mutation and affected protein domain(s).
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Béziau DM, Barc J, O'Hara T, Le Gloan L, Amarouch MY, Solnon A, Pavin D, Lecointe S, Bouillet P, Gourraud JB, Guicheney P, Denjoy I, Redon R, Mabo P, le Marec H, Loussouarn G, Kyndt F, Schott JJ, Probst V, Baró I. Complex Brugada syndrome inheritance in a family harbouring compound SCN5A and CACNA1C mutations. Basic Res Cardiol 2014; 109:446. [PMID: 25341504 DOI: 10.1007/s00395-014-0446-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/19/2014] [Accepted: 10/09/2014] [Indexed: 12/19/2022]
Abstract
Brugada syndrome (BrS) is characterized by ST-segment elevation in the right precordial leads and is associated with increased risk of sudden cardiac death. We have recently reported families with BrS and SCN5A mutations where some affected members do not carry the familial mutation. We evaluated the involvement of additional genetic determinants for BrS in an affected family. We identified three distinct gene variants within a family presenting BrS (5 individuals), cardiac conduction defects (CCD, 3 individuals) and shortened QT interval (4 individuals). The first mutation is nonsense, p.Q1695*, lying within the SCN5A gene, which encodes for NaV1.5, the α-subunit of the cardiac Na(+) channel. The second mutation is missense, p.N300D, and alters the CACNA1C gene, which encodes the α-subunit CaV1.2 of the L-type cardiac Ca(2+) channel. The SCN5A mutation strictly segregates with CCD. Four out of the 5 BrS patients carry the CACNA1C variant, and three of them present shortened QT interval. One of the BrS patients carries none of these mutations but a rare variant located in the ABCC9 gene as well as his asymptomatic mother. Patch-clamp studies identified a loss-of-function of the mutated CaV1.2 channel. Western-blot experiments showed a global expression defect while increased mobility of CaV1.2 channels on cell surface was revealed by FRAP experiments. Finally, computer simulations of the two mutations recapitulated patient phenotypes. We report a rare CACNA1C mutation as causing BrS and/or shortened QT interval in a family also carrying a SCN5A stop mutation, but which does not segregate with BrS. This study underlies the complexity of BrS inheritance and its pre-symptomatic genetic screening interpretation.
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Affiliation(s)
- Delphine M Béziau
- INSERM, UMR 1087, l'institut du thorax, 8 Quai Moncousu, BP 70721, 44007, Nantes cedex 1, France
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Rose SJ, Kriener LH, Heinzer AK, Fan X, Raike RS, van den Maagdenberg AMJM, Hess EJ. The first knockin mouse model of episodic ataxia type 2. Exp Neurol 2014; 261:553-62. [PMID: 25109669 DOI: 10.1016/j.expneurol.2014.08.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 07/07/2014] [Accepted: 08/01/2014] [Indexed: 12/28/2022]
Abstract
Episodic ataxia type 2 (EA2) is an autosomal dominant disorder associated with attacks of ataxia that are typically precipitated by stress, ethanol, caffeine or exercise. EA2 is caused by loss-of-function mutations in the CACNA1A gene, which encodes the α1A subunit of the CaV2.1 voltage-gated Ca(2+) channel. To better understand the pathomechanisms of this disorder in vivo, we created the first genetic animal model of EA2 by engineering a mouse line carrying the EA2-causing c.4486T>G (p.F1406C) missense mutation in the orthologous mouse Cacna1a gene. Mice homozygous for the mutated allele exhibit a ~70% reduction in CaV2.1 current density in Purkinje cells, though surprisingly do not exhibit an overt motor phenotype. Mice hemizygous for the knockin allele (EA2/- mice) did exhibit motor dysfunction measurable by rotarod and pole test. Studies using Cre-flox conditional genetics explored the role of cerebellar Purkinje cells or cerebellar granule cells in the poor motor performance of EA2/- mice and demonstrate that manipulation of either cell type alone did not cause poor motor performance. Thus, it is possible that subtle dysfunction arising from multiple cell types is necessary for the expression of certain ataxia syndromes.
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Affiliation(s)
- Samuel J Rose
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Lisa H Kriener
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Ann K Heinzer
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Xueliang Fan
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Robert S Raike
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Arn M J M van den Maagdenberg
- Department of Human Genetics, Leiden University Medical Centre, 2300 RC Leiden, The Netherlands; Department of Neurology, Leiden University Medical Centre, 2300 RC Leiden, The Netherlands
| | - Ellen J Hess
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA; Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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Age-related homeostatic midchannel proteolysis of neuronal L-type voltage-gated Ca²⁺ channels. Neuron 2014; 82:1045-57. [PMID: 24908485 DOI: 10.1016/j.neuron.2014.04.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/01/2014] [Indexed: 12/11/2022]
Abstract
Neural circuitry and brain activity depend critically on proper function of voltage-gated calcium channels (VGCCs), whose activity must be tightly controlled. We show that the main body of the pore-forming α1 subunit of neuronal L-type VGCCs, Cav1.2, is proteolytically cleaved, resulting in Cav1.2 fragment channels that separate but remain on the plasma membrane. This "midchannel" proteolysis is regulated by channel activity, involves the Ca(2+)-dependent protease calpain and the ubiquitin-proteasome system, and causes attenuation and biophysical alterations of VGCC currents. Recombinant Cav1.2 fragment channels mimicking the products of midchannel proteolysis do not form active channels on their own but, when properly paired, produce currents with distinct biophysical properties. Midchannel proteolysis increases dramatically with age and can be attenuated with an L-type VGCC blocker in vivo. Midchannel proteolysis represents a novel form of homeostatic negative-feedback processing of VGCCs that could profoundly affect neuronal excitability, neurotransmission, neuroprotection, and calcium signaling in physiological and disease states.
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Pavlovic Z, Singh RK, Bakovic M. A novel murine CTP:phosphoethanolamine cytidylyltransferase splice variant is a post-translational repressor and an indicator that both cytidylyltransferase domains are required for activity. Gene 2014; 543:58-68. [PMID: 24703999 DOI: 10.1016/j.gene.2014.04.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/20/2014] [Accepted: 04/01/2014] [Indexed: 11/27/2022]
Abstract
CTP:phosphoethanolamine cytidylyltransferase (Pcyt2) has an important regulatory function in biosynthesis of the membrane phospholipid phosphatidylethanolamine. We previously determined that the full-length Pcyt2α and its splice variant Pcyt2β are the main active isoforms of this enzyme. Here we report that mouse Pcyt2 could be spliced at Introns 7 and 8 to produce a unique third isoform, Pcyt2γ, in which the second cytidylyltransferase domain at the C-terminus becomes deleted. Pcyt2γ is ubiquitously expressed in embryonic and adult mouse tissues, and is the most abundant in the kidney, skeletal muscle and testis. Pcyt2γ splicing mechanism dominates over Pcyt2β exon-skipping mechanism in most examined tissues. Although Pcyt2γ maintains the N-terminal cytidylyltransferase domain as most cytidylyltransferases, the lack of the C-terminal cytidylyltransferase domain causes a complete loss of catalytic activity. However, Pcyt2γ interacts with the active isoform, Pcyt2α, and significantly reduces Pcyt2α homodimerization and activity. The inactive N-domain (H35Y, H35A) and C-domain (H244Y, H244A) mutants of Pcyt2α also reduce Pcyt2α homodimerization and activity. This study revealed the importance of both cytidylyltransferase (35)HYGH and (244)HIGH motifs for the activity of murine Pcyt2α and established that the naturally occurring splice variant Pcyt2γ has a function to restrain the enzyme activity through the formation of unproductive enzyme complexes.
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Affiliation(s)
- Zvezdan Pavlovic
- Department of Human Health and Nutritional Sciences, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G2W1, Canada.
| | - Ratnesh Kumar Singh
- Department of Human Health and Nutritional Sciences, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G2W1, Canada
| | - Marica Bakovic
- Department of Human Health and Nutritional Sciences, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G2W1, Canada
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Simms BA, Zamponi GW. Neuronal voltage-gated calcium channels: structure, function, and dysfunction. Neuron 2014; 82:24-45. [PMID: 24698266 DOI: 10.1016/j.neuron.2014.03.016] [Citation(s) in RCA: 420] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Voltage-gated calcium channels are the primary mediators of depolarization-induced calcium entry into neurons. There is great diversity of calcium channel subtypes due to multiple genes that encode calcium channel α1 subunits, coassembly with a variety of ancillary calcium channel subunits, and alternative splicing. This allows these channels to fulfill highly specialized roles in specific neuronal subtypes and at particular subcellular loci. While calcium channels are of critical importance to brain function, their inappropriate expression or dysfunction gives rise to a variety of neurological disorders, including, pain, epilepsy, migraine, and ataxia. This Review discusses salient aspects of voltage-gated calcium channel function, physiology, and pathophysiology.
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Affiliation(s)
- Brett A Simms
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada.
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Simms BA, Souza IA, Rehak R, Zamponi GW. The amino-terminus of high voltage activated calcium channels: CaM you or can't you? Channels (Austin) 2014; 8:370-5. [PMID: 24875328 DOI: 10.4161/chan.29313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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RNAi silencing of P/Q-type calcium channels in Purkinje neurons of adult mouse leads to episodic ataxia type 2. Neurobiol Dis 2014; 68:47-56. [PMID: 24768804 DOI: 10.1016/j.nbd.2014.04.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 04/04/2014] [Accepted: 04/12/2014] [Indexed: 01/05/2023] Open
Abstract
Episodic ataxia type-2 (EA2) is a dominantly inherited human neurological disorder caused by loss of function mutations in the CACNA1A gene, which encodes the CaV2.1 subunit of P/Q-type voltage-gated calcium channels. It remains however unknown whether the deficit of cerebellar CaV2.1 in adult is in direct link with the disease. To address this issue, we have used lentiviral based-vector RNA interference (RNAi) to knock-down CaV2.1 expression in the cerebellum of adult mice. We show that suppression of the P/Q-type channels in Purkinje neurons induced motor abnormalities, such as imbalance and ataxic gait. Interestingly, moderate channel suppression caused no basal ataxia, while β-adrenergic activation and exercise mimicked stress induced motor disorders. Moreover, stress-induced ataxia was stable, non-progressive and totally abolished by acetazolamide, a carbonic anhydrase inhibitor used to treat EA2. Altogether, these data reveal that P/Q-type channel suppression in adult mice supports the episodic status of EA2 disease.
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Cox RH, Fromme SJ. A naturally occurring truncated Cav1.2 α1-subunit inhibits Ca2+ current in A7r5 cells. Am J Physiol Cell Physiol 2013; 305:C896-905. [PMID: 23926129 DOI: 10.1152/ajpcell.00217.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Alternative splicing of the voltage-gated Ca(2+) (CaV) α1-subunit adds to the functional diversity of Ca(2+) channels. A variant with a 73-nt deletion in exon 15 of the Cav1.2 α1-subunit (Cav1.2Δ73) produced by alternative splicing that predicts a truncated protein has been described, but its function, if any, is unknown. We sought to determine if, by analogy to other truncated CaV α1-subunits, Cav1.2Δ73 acts as an inhibitor of wild-type Cav1.2 currents. HEK-293 cells were transfected with Cav1.2Δ73 in a pIRES vector with CD8 or in pcDNA3.1 with a V5/his COOH-terminal tag plus β2 and α2δ1 accessory subunits and pEGFP. Production of Cav1.2Δ73 protein was confirmed by Western blotting and immunofluorescence. Voltage-clamp studies revealed the absence of functional channels in transfected cells. In contrast, cells transfected with full-length Cav1.2 plus accessory subunits and pEGFP exhibited robust Ca(2+) currents. A7r5 cells exhibited endogenous Cav1.2-based currents that were greatly reduced (>80%) without a change in voltage-dependent activation when transfected with Cav1.2Δ73-IRES-CD8 compared with empty vector or pIRES-CD8 controls. Transfection of A7r5 cells with an analogous Cav2.3Δ73-IRES-CD8 had no effect on Ca(2+) currents. Immunofluorescence showed intracellular, but not plasma membrane, localization of Cav1.2Δ73-V5/his, as well as colocalization with an endoplasmic reticulum marker, ER Organelle Lights. Expression of Cav1.2Δ73 α1-subunits in A7r5 cells inhibits endogenous Cav1.2 currents. The fact that this variant arises naturally by alternative splicing raises the possibility that it may represent a physiological mechanism to modulate Cav1.2 functional activity.
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Affiliation(s)
- Robert H Cox
- Program in Cardiovascular Studies, Lankenau Institute for Medical Research, Main Line Health System, Wynnewood, Pennsylvania
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Duarri A, Jezierska J, Fokkens M, Meijer M, Schelhaas HJ, den Dunnen WFA, van Dijk F, Verschuuren-Bemelmans C, Hageman G, van de Vlies P, Küsters B, van de Warrenburg BP, Kremer B, Wijmenga C, Sinke RJ, Swertz MA, Kampinga HH, Boddeke E, Verbeek DS. Mutations in potassium channel kcnd3 cause spinocerebellar ataxia type 19. Ann Neurol 2013; 72:870-80. [PMID: 23280838 DOI: 10.1002/ana.23700] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 05/21/2012] [Accepted: 06/13/2012] [Indexed: 01/15/2023]
Abstract
OBJECTIVE To identify the causative gene for the neurodegenerative disorder spinocerebellar ataxia type 19 (SCA19) located on chromosomal region 1p21-q21. METHODS Exome sequencing was used to identify the causal mutation in a large SCA19 family. We then screened 230 ataxia families for mutations located in the same gene (KCND3, also known as Kv4.3) using high-resolution melting. SCA19 brain autopsy material was evaluated, and in vitro experiments using ectopic expression of wild-type and mutant Kv4.3 were used to study protein localization, stability, and channel activity by patch-clamping. RESULTS We detected a T352P mutation in the third extracellular loop of the voltage-gated potassium channel KCND3 that cosegregated with the disease phenotype in our original family. We identified 2 more novel missense mutations in the channel pore (M373I) and the S6 transmembrane domain (S390N) in 2 other ataxia families. T352P cerebellar autopsy material showed severe Purkinje cell degeneration, with abnormal intracellular accumulation and reduced protein levels of Kv4.3 in their soma. Ectopic expression of all mutant proteins in HeLa cells revealed retention in the endoplasmic reticulum and enhanced protein instability, in contrast to wild-type Kv4.3 that was localized on the plasma membrane. The regulatory β subunit Kv channel interacting protein 2 was able to rescue the membrane localization and the stability of 2 of the 3 mutant Kv4.3 complexes. However, this either did not restore the channel function of the membrane-located mutant Kv4.3 complexes or restored it only partially. INTERPRETATION KCND3 mutations cause SCA19 by impaired protein maturation and/or reduced channel function.
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Affiliation(s)
- Anna Duarri
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen
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Hu Y, Jiang H, Wang Q, Xie Z, Pan S. Identification of a novel nonsense mutation p.Tyr1957Ter of CACNA1A in a Chinese family with episodic ataxia 2. PLoS One 2013; 8:e56362. [PMID: 23441182 PMCID: PMC3575407 DOI: 10.1371/journal.pone.0056362] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 01/08/2013] [Indexed: 11/19/2022] Open
Abstract
Type 2 episodic ataxia (EA2) is the most common subtype among a group of rare hereditary syndromes characterized by recurrent attacks of ataxia. More than 60 mutations and several gene rearrangements due to large deletions in CACNA1A gene have been reported so far for the cause of EA2. Because CACNA1A gene is a large gene containing 47 exons and there is no hot spot mutation, direct sequencing will be a challenge in clinical genetic testing. In this study, we used next generation sequencing technology to identify a novel nonsense mutation of CACNA1A (p.Tyr1957Ter, NP_001120693.1) resulting in truncated protein without 305 amino acids in the c-terminus. Sanger sequencing confirmed the heterozygous mutation of CACNA1A in a Chinese family with 11 affected individuals. Affected individuals experienced recurrent attacks with or without nystagmus, dysarthria, seizure, myokymia, dystonia, weakness, blurred vision, visual field defects, diplopia, migraine, dizziness, nausea and vomiting, sweating and abdominal pain. This is the first report of EA2 in a Chinese family that carries a novel mutation in CACNA1A gene and had abdominal pain as a novel phenotype associated with EA2.
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Affiliation(s)
- Yafang Hu
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of China
| | - Haishan Jiang
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of China
| | - Qun Wang
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of China
| | - Zuoshan Xie
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of China
| | - Suyue Pan
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of China
- * E-mail:
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Mercier A, Clément R, Harnois T, Bourmeyster N, Faivre JF, Findlay I, Chahine M, Bois P, Chatelier A. The β1-subunit of Na(v)1.5 cardiac sodium channel is required for a dominant negative effect through α-α interaction. PLoS One 2012; 7:e48690. [PMID: 23133651 PMCID: PMC3486797 DOI: 10.1371/journal.pone.0048690] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 10/01/2012] [Indexed: 12/03/2022] Open
Abstract
Brugada syndrome (BrS) is an inherited autosomal dominant cardiac channelopathy. Several mutations on the cardiac sodium channel Nav1.5 which are responsible for BrS lead to misfolded proteins that do not traffic properly to the plasma membrane. In order to mimic patient heterozygosity, a trafficking defective mutant, R1432G was co-expressed with Wild Type (WT) Nav1.5 channels in HEK293T cells. This mutant significantly decreased the membrane Na current density when it was co-transfected with the WT channel. This dominant negative effect did not result in altered biophysical properties of Nav1.5 channels. Luminometric experiments revealed that the expression of mutant proteins induced a significant reduction in membrane expression of WT channels. Interestingly, we have found that the auxiliary Na channel β1-subunit was essential for this dominant negative effect. Indeed, the absence of the β1-subunit prevented the decrease in WT sodium current density and surface proteins associated with the dominant negative effect. Co-immunoprecipitation experiments demonstrated a physical interaction between Na channel α-subunits. This interaction occurred only when the β1-subunit was present. Our findings reveal a new role for β1-subunits in cardiac voltage-gated sodium channels by promoting α-α subunit interaction which can lead to a dominant negative effect when one of the α-subunits shows a trafficking defective mutation.
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Affiliation(s)
- Aurélie Mercier
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Romain Clément
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Thomas Harnois
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- CHU de Poitiers, Poitiers, France
| | - Nicolas Bourmeyster
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- CHU de Poitiers, Poitiers, France
| | - Jean-François Faivre
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Ian Findlay
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- Laboratoire de Physiologie des Cellules Cardiaques et Vasculaires, Institut de Physiologie et Biologie Cellulaires, FRE 3511 CNRS, Université François-Rabelais, Faculté des Sciences, Tours, France
| | - Mohamed Chahine
- Institut universitaire en santé mentale de Québec, Université Laval, Québec, Québec, Canada
| | - Patrick Bois
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
| | - Aurélien Chatelier
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Pôle Biologie Santé, Poitiers, France
- * E-mail:
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Balse E, Steele DF, Abriel H, Coulombe A, Fedida D, Hatem SN. Dynamic of Ion Channel Expression at the Plasma Membrane of Cardiomyocytes. Physiol Rev 2012; 92:1317-58. [DOI: 10.1152/physrev.00041.2011] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cardiac myocytes are characterized by distinct structural and functional entities involved in the generation and transmission of the action potential and the excitation-contraction coupling process. Key to their function is the specific organization of ion channels and transporters to and within distinct membrane domains, which supports the anisotropic propagation of the depolarization wave. This review addresses the current knowledge on the molecular actors regulating the distinct trafficking and targeting mechanisms of ion channels in the highly polarized cardiac myocyte. In addition to ubiquitous mechanisms shared by other excitable cells, cardiac myocytes show unique specialization, illustrated by the molecular organization of myocyte-myocyte contacts, e.g., the intercalated disc and the gap junction. Many factors contribute to the specialization of the cardiac sarcolemma and the functional expression of cardiac ion channels, including various anchoring proteins, motors, small GTPases, membrane lipids, and cholesterol. The discovery of genetic defects in some of these actors, leading to complex cardiac disorders, emphasizes the importance of trafficking and targeting of ion channels to cardiac function. A major challenge in the field is to understand how these and other actors work together in intact myocytes to fine-tune ion channel expression and control cardiac excitability.
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Affiliation(s)
- Elise Balse
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David F. Steele
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Hugues Abriel
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Alain Coulombe
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - David Fedida
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
| | - Stéphane N. Hatem
- Institute of Cardiometabolism and Nutrition, Paris, France; Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Heart and Metabolism Division, Paris, France; Institut National de la Santé et de la Recherche Médicale UMR_S956, Paris, France; Université Pierre et Marie Curie, Paris, France; Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, Canada; and Department of Clinical Research University of Bern, Bern, Switzerland
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Clatot J, Ziyadeh-Isleem A, Maugenre S, Denjoy I, Liu H, Dilanian G, Hatem SN, Deschênes I, Coulombe A, Guicheney P, Neyroud N. Dominant-negative effect of SCN5A N-terminal mutations through the interaction of Na(v)1.5 α-subunits. Cardiovasc Res 2012; 96:53-63. [PMID: 22739120 DOI: 10.1093/cvr/cvs211] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
AIMS Brugada syndrome (BrS) is an autosomal-inherited cardiac arrhythmia characterized by an ST-segment elevation in the right precordial leads of the electrocardiogram and an increased risk of syncope and sudden death. SCN5A, encoding the cardiac sodium channel Na(v)1.5, is the main gene involved in BrS. Despite the fact that several mutations have been reported in the N-terminus of Na(v)1.5, the functional role of this region remains unknown. We aimed to characterize two BrS N-terminal mutations, R104W and R121W, a construct where this region was deleted, ΔNter, and a construct where only this region was present, Nter. METHODS AND RESULTS Patch-clamp recordings in HEK293 cells demonstrated that R104W, R121W, and ΔNter abolished the sodium current I(Na). Moreover, R104W and R121W mutations exerted a strong dominant-negative effect on wild-type (WT) channels. Immunocytochemistry of rat neonatal cardiomyocytes revealed that both mutants were mostly retained in the endoplasmic reticulum and that their co-expression with WT channels led to WT channel retention. Furthermore, co-immunoprecipitation experiments showed that Na(v)1.5-subunits were interacting with each other, even when mutated, deciphering the mutation dominant-negative effect. Both mutants were mostly degraded by the ubiquitin-proteasome system, while ΔNter was addressed to the membrane, and Nter expression induced a two-fold increase in I(Na). In addition, the co-expression of N-terminal mutants with the gating-defective but trafficking-competent R878C-Na(v)1.5 mutant gave rise to a small I(Na). CONCLUSION This study reports for the first time the critical role of the Na(v)1.5 N-terminal region in channel function and the dominant-negative effect of trafficking-defective channels occurring through α-subunit interaction.
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Senatore A, Spafford JD. Gene transcription and splicing of T-type channels are evolutionarily-conserved strategies for regulating channel expression and gating. PLoS One 2012; 7:e37409. [PMID: 22719839 PMCID: PMC3376122 DOI: 10.1371/journal.pone.0037409] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/19/2012] [Indexed: 01/17/2023] Open
Abstract
T-type calcium channels operate within tightly regulated biophysical constraints for supporting rhythmic firing in the brain, heart and secretory organs of invertebrates and vertebrates. The snail T-type gene, LCa(v)3 from Lymnaea stagnalis, possesses alternative, tandem donor splice sites enabling a choice of a large exon 8b (201 aa) or a short exon 25c (9 aa) in cytoplasmic linkers, similar to mammalian homologs. Inclusion of optional 25c exons in the III-IV linker of T-type channels speeds up kinetics and causes hyperpolarizing shifts in both activation and steady-state inactivation of macroscopic currents. The abundant variant lacking exon 25c is the workhorse of embryonic Ca(v)3 channels, whose high density and right-shifted activation and availability curves are expected to increase pace-making and allow the channels to contribute more significantly to cellular excitation in prenatal tissue. Presence of brain-enriched, optional exon 8b conserved with mammalian Ca(v)3.1 and encompassing the proximal half of the I-II linker, imparts a ~50% reduction in total and surface-expressed LCa(v)3 channel protein, which accounts for reduced whole-cell calcium currents of +8b variants in HEK cells. Evolutionarily conserved optional exons in cytoplasmic linkers of Ca(v)3 channels regulate expression (exon 8b) and a battery of biophysical properties (exon 25c) for tuning specialized firing patterns in different tissues and throughout development.
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Rajakulendran S, Kaski D, Hanna MG. Neuronal P/Q-type calcium channel dysfunction in inherited disorders of the CNS. Nat Rev Neurol 2012; 8:86-96. [PMID: 22249839 DOI: 10.1038/nrneurol.2011.228] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The past two decades have witnessed the emergence of a new and expanding field of neurological diseases--the genetic ion channelopathies. These disorders arise from mutations in genes that encode ion channel subunits, and manifest as paroxysmal attacks involving the brain or spinal cord, and/or muscle. The voltage-gated P/Q-type calcium channel (P/Q channel) is highly expressed in the cerebellum, hippocampus and cortex of the mammalian brain. The P/Q channel has a fundamental role in mediating fast synaptic transmission at central and peripheral nerve terminals. Autosomal dominant mutations in the CACNA1A gene, which encodes voltage-gated P/Q-type calcium channel subunit α(1) (the principal pore-forming subunit of the P/Q channel) are associated with episodic and progressive forms of cerebellar ataxia, familial hemiplegic migraine, vertigo and epilepsy. This Review considers, from both a clinical and genetic perspective, the various neurological phenotypes arising from inherited P/Q channel dysfunction, with a focus on recent advances in the understanding of the pathogenetic mechanisms underlying these disorders.
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Affiliation(s)
- Sanjeev Rajakulendran
- Medical Research Council Center for Neuromuscular Diseases, Box 102, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK
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Bechi G, Scalmani P, Schiavon E, Rusconi R, Franceschetti S, Mantegazza M. Pure haploinsufficiency for Dravet syndrome Na(V)1.1 (SCN1A) sodium channel truncating mutations. Epilepsia 2011; 53:87-100. [PMID: 22150645 DOI: 10.1111/j.1528-1167.2011.03346.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
PURPOSE Dravet syndrome (DS), a devastating epileptic encephalopathy, is mostly caused by mutations of the SCN1A gene, coding for the voltage-gated Na(+) channel Na(V)1.1 α subunit. About 50% of SCN1A DS mutations truncate Na(V)1.1, possibly causing complete loss of its function. However, it has not been investigated yet if Na(V)1.1 truncated mutants are dominant negative, if they impair expression or function of wild-type channels, as it has been shown for truncated mutants of other proteins (e.g., Ca(V) channels). We studied the effect of two DS truncated Na(V)1.1 mutants, R222* and R1234*, on coexpressed wild-type Na(+) channels. METHODS We engineered R222* or R1234* in the human cDNA of Na(V)1.1 (hNa(V)1.1) and studied their effect on coexpressed wild-type hNa(V)1.1, hNa(V)1.2 or hNa(V)1.3 cotransfecting tsA-201 cells, and on hNa(V)1.6 transfecting an human embryonic kidney (HEK) cell line stably expressing this channel. We also studied hippocampal neurons dissociated from Na(V)1.1 knockout (KO) mice, an animal model of DS expressing a truncated Na(V)1.1 channel. KEY FINDINGS We found no modifications of current amplitude coexpressing the truncated mutants with hNa(V)1.1, hNa(V)1.2, or hNa(V)1.3, but a 30% reduction coexpressing them with hNa(V)1.6. However, we showed that also coexpression of functional full-length hNa(V)1.1 caused a similar reduction. Therefore, this effect should not be involved in the pathomechanism of DS. Some gating properties of hNa(V)1.1, hNa(V)1.3, and hNa(V)1.6 were modified, but recordings of hippocampal neurons dissociated from Na(V)1.1 KO mice did not show any significant modifications of these properties. Therefore, Na(V)1.1 truncated mutants are not dominant negative, consistent with haploinsufficiency as the cause of DS. SIGNIFICANCE We have better clarified the pathomechanism of DS, pointed out an important difference between pathogenic truncated Ca(V)2.1 mutants and hNa(V)1.1 ones, and shown that hNa(V)1.6 expression can be reduced in physiologic conditions by coexpression of hNa(V)1.1. Moreover, our data may provide useful information for the development of therapeutic approaches.
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Affiliation(s)
- Giulia Bechi
- Department of Neurophysiopathology, Besta Foundation Neurological Institute, Milan, Italy
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Baylis HA, Vázquez-Manrique RP. Genetic analysis of IP3 and calcium signalling pathways in C. elegans. Biochim Biophys Acta Gen Subj 2011; 1820:1253-68. [PMID: 22146231 DOI: 10.1016/j.bbagen.2011.11.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 11/15/2011] [Accepted: 11/16/2011] [Indexed: 01/02/2023]
Abstract
BACKGROUND The nematode, Caenorhabditis elegans is an established model system that is particularly well suited to genetic analysis. C. elegans is easily manipulated and we have an in depth knowledge of many aspects of its biology. Thus, it is an attractive system in which to pursue integrated studies of signalling pathways. C. elegans has a complement of calcium signalling molecules similar to that of other animals. SCOPE OF REVIEW We focus on IP3 signalling. We describe how forward and reverse genetic approaches, including RNAi, have resulted in a tool kit which enables the analysis of IP3/Ca2+ signalling pathways. The importance of cell and tissue specific manipulation of signalling pathways and the use of epistasis analysis are highlighted. We discuss how these tools have increased our understanding of IP3 signalling in specific developmental, physiological and behavioural roles. Approaches to imaging calcium signals in C. elegans are considered. MAJOR CONCLUSIONS A wide selection of tools is available for the analysis of IP3/Ca2+ signalling in C. elegans. This has resulted in detailed descriptions of the function of IP3/Ca2+ signalling in the animal's biology. Nevertheless many questions about how IP3 signalling regulates specific processes remain. GENERAL SIGNIFICANCE Many of the approaches described may be applied to other calcium signalling systems. C. elegans offers the opportunity to dissect pathways, perform integrated studies and to test the importance of the properties of calcium signalling molecules to whole animal function, thus illuminating the function of calcium signalling in animals. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling.
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Affiliation(s)
- Howard A Baylis
- Department of Zoology, University of Cambridge, Cambridge, UK.
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Wan J, Mamsa H, Johnston JL, Spriggs EL, Singer HS, Zee DS, Al-Bayati AR, Baloh RW, Jen JC. Large Genomic Deletions in CACNA1A Cause Episodic Ataxia Type 2. Front Neurol 2011; 2:51. [PMID: 21927611 PMCID: PMC3169784 DOI: 10.3389/fneur.2011.00051] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 07/26/2011] [Indexed: 11/13/2022] Open
Abstract
Episodic ataxia (EA) syndromes are heritable diseases characterized by dramatic episodes of imbalance and incoordination. EA type 2 (EA2), the most common and the best characterized subtype, is caused by mostly nonsense, splice site, small indel, and sometimes missense mutations in CACNA1A. Direct sequencing of CACNA1A fails to identify mutations in some patients with EA2-like features, possibly due to incomplete interrogation of CACNA1A or defects in other EA genes not yet defined. Previous reports described genomic deletions between 4 and 40 kb in EA2. In 47 subjects with EA (26 with EA2-like features) who tested negative for mutations in the known EA genes, we used multiplex ligation-dependent probe amplification to analyze CACNA1A for exonic copy number variations. Breakpoints were further defined by long-range PCR. We identified distinct multi-exonic deletions in three probands with classic EA2-like features: episodes of prolonged vertigo and ataxia triggered by stress and fatigue, interictal nystagmus, with onset during infancy or early childhood. The breakpoints in all three probands are located in Alu sequences, indicating errors in homologous recombination of Alu sequences as the underlying mechanism. The smallest deletion spanned exons 39 and 40, while the largest deletion spanned 200 kb, missing all but the first three exons. One deletion involving exons 39 through 47 arose spontaneously. The search for mutations in CACNA1A appears most fruitful in EA patients with interictal nystagmus and onset early in life. The finding of large heterozygous deletions suggests haploinsufficiency as a possible pathomechanism of EA2.
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Affiliation(s)
- Jijun Wan
- Department of Neurology, University of California, Los Angeles Los Angeles, CA, USA
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Veneziano L, Albertosi S, Pesci D, Mantuano E, Frontali M, Jodice C. Dramatically different levels of Cacna1a gene expression between pre-weaning wild type and leaner mice. J Neurol Sci 2011; 305:71-4. [PMID: 21440913 DOI: 10.1016/j.jns.2011.03.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 02/28/2011] [Accepted: 03/03/2011] [Indexed: 10/18/2022]
Abstract
Loss of function mutations of the CACNA1A gene, coding for the α1A subunit of P/Q type voltage-gated calcium channel (Ca(V)2.1), are responsible for Episodic Ataxia type 2 (EA2), an autosomal dominant disorder. A dominant negative effect of the EA2 mutated protein, rather than a haploinsufficiency mechanism, has been hypothesised both for protein-truncating and missense mutations. We analysed the cacna1a mRNA expression in leaner mice carrying a cacna1a mutation leading to a premature stop codon. The results showed a very low mutant mRNA expression compared to the wild type allele. Although the mutant mRNA slightly increases with age, its low level is likely due to degradation by nonsense mediated decay, a quality control mechanism that selectively degrades mRNA harbouring premature stop codons. These data have implications for EA2 in humans, suggesting a haploinsufficiency mechanism at least for some of the CACNA1A mutations leading to a premature stop codon.
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Affiliation(s)
- Liana Veneziano
- Istituto di Farmacologia Traslazionale, CNR, Via Fosso del Cavaliere, 00133 Roma, Italy
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Bidaud I, Lory P. Hallmarks of the channelopathies associated with L-type calcium channels: a focus on the Timothy mutations in Ca(v)1.2 channels. Biochimie 2011; 93:2080-6. [PMID: 21664226 DOI: 10.1016/j.biochi.2011.05.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Accepted: 05/19/2011] [Indexed: 11/29/2022]
Abstract
Within the voltage-gated calcium channels (Cav channels) family, there are four genes coding for the L-type Cav channels (Cav1). The Cav1 channels underly many important physiological functions like excitation-contraction coupling, hormone secretion, neuronal excitability and gene transcription. Mutations found in the genes encoding the Cav channels define a wide variety of diseases called calcium channelopathies and all four genes coding the Cav1 channels are carrying such mutations. L-type calcium channelopathies include muscular, neurological, cardiac and vision syndromes. Among them, the Timothy syndrome (TS) is linked to missense mutations in CACNA1C, the gene that encodes the Ca(v)1.2 subunit. Here we review the important features of the Cav1 channelopathies. We also report on the specific properties of TS-Ca(v)1.2 channels, which display non-inactivating calcium current as well as higher plasma membrane expression. Overall, we conclude that both electrophysiological and surface expression properties must be investigated to better account for the functional consequences of mutations linked to calcium channelopathies.
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Affiliation(s)
- Isabelle Bidaud
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, Montpellier, France
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Abstract
Voltage-gated calcium channels are a family of integral membrane calcium-selective proteins found in all excitable and many nonexcitable cells. Calcium influx affects membrane electrical properties by depolarizing cells and generally increasing excitability. Calcium entry further regulates multiple intracellular signaling pathways as well as the biochemical factors that mediate physiological functions such as neurotransmitter release and muscle contraction. Small changes in the biophysical properties or expression of calcium channels can result in pathophysiological changes leading to serious chronic disorders. In humans, mutations in calcium channel genes have been linked to a number of serious neurological, retinal, cardiac, and muscular disorders.
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Affiliation(s)
- Stuart M Cain
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
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Riant F, Vahedi K, Tournier-Lasserve E. [Hereditary episodic ataxia]. Rev Neurol (Paris) 2011; 167:401-7. [PMID: 21492892 DOI: 10.1016/j.neurol.2010.10.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/31/2010] [Accepted: 10/13/2010] [Indexed: 12/29/2022]
Abstract
INTRODUCTION Episodic ataxia (EA) designates a group of autosomal dominant channelopathies that manifest as paroxysmal attacks of imbalance and incoordination. EA conditions are clinically and genetically heterogeneous. Seven types of EA have been reported so far but the majority of clinical cases result from two recognized entities. STATE OF ART Episodic ataxia type 1 (EA1) is characterized by brief episodes of ataxia and dysarthria, and interictal myokymia. Onset occurs during the first two decades of life. Associated epilepsy has been reported in some EA1 patients. EA1 is caused by mutations of the KCNA1 gene coding for the voltage-gated potassium channel Kv1.1. Mutation is mostly missense mutations. Acetazolamide, a carbonic-anhydrase inhibitor, may reduce the frequency and severity of the attacks in some but not all affected individuals. Episodic ataxia type 2 (EA2) is characterized by episodes lasting longer than in EA1, that manifest by ataxia, dysarthria, vertigo, and also, in most of the cases, an interictal nystagmus. Other clinical features as developmental delay or epilepsy can be present in some patients. Brain MRI shows frequently a vermian atrophy. Onset occurs typically in childhood or early adolescence, but can sometimes be in adulthood. EA2 is caused by mutations in CACNA1A, a gene coding for the neuronal voltage-gated calcium channel Cav1.1. For two-thirds of the cases, mutations lead to a stop codon. This type is most often responsive to acetazolamide that reduces the frequency and severity of attacks, but does not appear to prevent the progression of interictal symptoms. PERSPECTIVES This article summarizes current knowledge on episodic ataxia type 1 and 2 and describes briefly the other types of EA. CONCLUSION Molecular analysis of KCNA1 or CACNA1A provides a confirmation of the diagnosis of EA1 and EA2. Other types remain rare phenotypic variants. Among them, only two genes have been identified: CACNB4 in EA5 and SLC1A3 in EA6 and mutations have been found in a very few cases. No mutation can be detected in some familial cases of episodic ataxia, suggesting further heterogeneity.
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Affiliation(s)
- F Riant
- Laboratoire de génétique, groupe hospitalier Lariboisière-Fernand-Widal, AP-HP, 2, rue Ambroise-Paré, 75010 Paris, France.
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