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Jeong S, Lee BY, Rhee JS, Lee JH. G protein β subunits regulate Ca v3.3 T-type channel activity and current kinetics via interaction with the Ca v3.3 C-terminus. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184337. [PMID: 38763272 DOI: 10.1016/j.bbamem.2024.184337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 05/06/2024] [Accepted: 05/13/2024] [Indexed: 05/21/2024]
Abstract
Ca2+ influx through Cav3.3 T-type channel plays crucial roles in neuronal excitability and is subject to regulation by various signaling molecules. However, our understanding of the partners of Cav3.3 and the related regulatory pathways remains largely limited. To address this quest, we employed the rat Cav3.3 C-terminus as bait in yeast-two-hybrid screenings of a cDNA library, identifying rat Gβ2 as an interaction partner. Subsequent assays revealed that the interaction of Gβ2 subunit was specific to the Cav3.3 C-terminus. Through systematic dissection of the C-terminus, we pinpointed a 22 amino acid sequence (amino acids 1789-1810) as the Gβ2 interaction site. Coexpression studies of rat Cav3.3 with various Gβγ compositions were conducted in HEK-293 cells. Patch clamp recordings revealed that coexpression of Gβ2γ2 reduced Cav3.3 current density and accelerated inactivation kinetics. Interestingly, the effects were not unique to Gβ2γ2, but were mimicked by Gβ2 alone as well as other Gβγ dimers, with similar potencies. Deletion of the Gβ2 interaction site abolished the effects of Gβ2γ2. Importantly, these Gβ2 effects were reproduced in human Cav3.3. Overall, our findings provide evidence that Gβ(γ) complexes inhibit Cav3.3 channel activity and accelerate the inactivation kinetics through the Gβ interaction with the Cav3.3 C-terminus.
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Affiliation(s)
- Sua Jeong
- Department of Life Science, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Republic of Korea
| | - Bo-Young Lee
- Department of Life Science, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Republic of Korea
| | - Jeong Seop Rhee
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Synaptic Physiology Group, Hermann-Rein-Str. 3, 37075 Göttingen, Germany
| | - Jung-Ha Lee
- Department of Life Science, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Republic of Korea.
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Wardas B, Schneider JG, Klugbauer N, Flockerzi V, Beck A. Englerin A Inhibits T-Type Voltage-Gated Calcium Channels at Low Micromolar Concentrations. Mol Pharmacol 2023; 104:144-153. [PMID: 37399325 DOI: 10.1124/molpharm.122.000651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 05/31/2023] [Accepted: 06/08/2023] [Indexed: 07/05/2023] Open
Abstract
Englerin A (EA) is a potent agonist of tetrameric transient receptor potential canonical (TRPC) ion channels containing TRPC4 and TRPC5 subunits. TRPC proteins form cation channels that are activated by plasma membrane receptors. They convert extracellular signals such as angiotensin II into cellular responses, whereupon Na+ and Ca2+ influx and depolarization of the plasma membrane occur. Via depolarization, voltage-gated Ca2+ (CaV) channels can be activated, further increasing Ca2+ influx. We investigated the extent to which EA also affects the functions of CaV channels using the high-voltage-activated L-type Ca2+ channel CaV1.2 and the low-voltage-activated T-type Ca2+ channels CaV3.1, CaV3.2, and CaV3.3. After expression of cDNAs in human embryonic kidney (HEK293) cells, EA inhibited currents through all T-type channels at half-maximal inhibitory concentrations (IC50) of 7.5 to 10.3 μM. In zona glomerulosa cells of the adrenal gland, angiotensin II-induced elevation of cytoplasmic Ca2+ concentration leads to aldosterone release. We identified transcripts of low- and high-voltage-activated CaV channels and of TRPC1 and TRPC5 in the human adrenocortical (HAC15) zona glomerulosa cell line. Although no EA-induced TRPC activity was measurable, Ca2+ channel blockers distinguished T- and L-type Ca2+ currents. EA blocked 60% of the CaV current in HAC15 cells and T- and L-type channels analyzed at -30 mV and 10 mV were inhibited with IC50 values of 2.3 and 2.6 μM, respectively. Although the T-type blocker Z944 reduced basal and angiotensin II-induced 24-hour aldosterone release, EA was not effective. In summary, we show here that EA blocks CaV1.2 and T-type CaV channels at low-micromolar concentrations. SIGNIFICANCE STATEMENT: In this study we showed that englerin A (EA), a potent agonist of tetrameric transient receptor potential canonical (TRPC)4- or TRPC5-containing channels and currently under investigation to treat certain types of cancer, also inhibits the L-type voltage-gated Ca2+ (CaV) channel CaV1.2 and the T-type CaV channels CaV3.1, CaV3.2, and CaV3.3 channels at low micromolar concentrations.
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Affiliation(s)
- Barbara Wardas
- Experimentelle und Klinische Pharmakologie und Toxikologie/PZMS, Universität des Saarlandes, Homburg, Germany (B.W., V.F., A.B.); Department of Internal Medicine II, Universitätsklinikum des Saarlandes und Medizinische Fakultät der Universität des Saarlandes, Homburg, Germany (J.G.S.); Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg, Luxembourg (J.G.S.); and Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany (N.K.)
| | - Jochen G Schneider
- Experimentelle und Klinische Pharmakologie und Toxikologie/PZMS, Universität des Saarlandes, Homburg, Germany (B.W., V.F., A.B.); Department of Internal Medicine II, Universitätsklinikum des Saarlandes und Medizinische Fakultät der Universität des Saarlandes, Homburg, Germany (J.G.S.); Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg, Luxembourg (J.G.S.); and Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany (N.K.)
| | - Norbert Klugbauer
- Experimentelle und Klinische Pharmakologie und Toxikologie/PZMS, Universität des Saarlandes, Homburg, Germany (B.W., V.F., A.B.); Department of Internal Medicine II, Universitätsklinikum des Saarlandes und Medizinische Fakultät der Universität des Saarlandes, Homburg, Germany (J.G.S.); Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg, Luxembourg (J.G.S.); and Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany (N.K.)
| | - Veit Flockerzi
- Experimentelle und Klinische Pharmakologie und Toxikologie/PZMS, Universität des Saarlandes, Homburg, Germany (B.W., V.F., A.B.); Department of Internal Medicine II, Universitätsklinikum des Saarlandes und Medizinische Fakultät der Universität des Saarlandes, Homburg, Germany (J.G.S.); Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg, Luxembourg (J.G.S.); and Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany (N.K.)
| | - Andreas Beck
- Experimentelle und Klinische Pharmakologie und Toxikologie/PZMS, Universität des Saarlandes, Homburg, Germany (B.W., V.F., A.B.); Department of Internal Medicine II, Universitätsklinikum des Saarlandes und Medizinische Fakultät der Universität des Saarlandes, Homburg, Germany (J.G.S.); Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg, Luxembourg (J.G.S.); and Experimentelle und Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany (N.K.)
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3
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El Ghaleb Y, Flucher BE. Ca V3.3 Channelopathies. Handb Exp Pharmacol 2023; 279:263-288. [PMID: 36592228 DOI: 10.1007/164_2022_631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
CaV3.3 is the third member of the low-voltage-activated calcium channel family and the last to be recognized as disease gene. Previously, CACNA1I, the gene encoding CaV3.3, had been described as schizophrenia risk gene. More recently, de novo missense mutations in CACNA1I were identified in patients with variable degrees of neurodevelopmental disease with and without epilepsy. Their functional characterization indicated gain-of-function effects resulting in increased calcium load and hyperexcitability of neurons expressing CaV3.3. The amino acids mutated in the CaV3.3 disease variants are located in the vicinity of the channel's activation gate and thus are classified as gate-modifying channelopathy mutations. A persistent calcium leak during rest and prolonged calcium spikes due to increased voltage sensitivity of activation and slowed kinetics of channel inactivation, respectively, may be causal for the neurodevelopmental defects. The prominent expression of CaV3.3 in thalamic reticular nucleus neurons and its essential role in generating the rhythmic thalamocortical network activity are consistent with a role of the mutated channels in the etiology of epileptic seizures and thus suggest T-type channel blockers as a viable treatment option.
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Affiliation(s)
- Yousra El Ghaleb
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria.
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McArthur JR, Wen J, Hung A, Finol-Urdaneta RK, Adams DJ. µ-Theraphotoxin-Pn3a inhibition of Ca V3.3 channels reveals a novel isoform-selective drug binding site. eLife 2022; 11:74040. [PMID: 35858123 PMCID: PMC9342953 DOI: 10.7554/elife.74040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 07/19/2022] [Indexed: 11/13/2022] Open
Abstract
Low voltage-activated calcium currents are mediated by T-type calcium channels CaV3.1, CaV3.2, and CaV3.3, which modulate a variety of physiological processes including sleep, cardiac pace-making, pain, and epilepsy. CaV3 isoforms’ biophysical properties, overlapping expression, and lack of subtype-selective pharmacology hinder the determination of their specific physiological roles in health and disease. We have identified μ-theraphotoxin Pn3a as the first subtype-selective spider venom peptide inhibitor of CaV3.3, with >100-fold lower potency against the other T-type isoforms. Pn3a modifies CaV3.3 gating through a depolarizing shift in the voltage dependence of activation thus decreasing CaV3.3-mediated currents in the normal range of activation potentials. Paddle chimeras of KV1.7 channels bearing voltage sensor sequences from all four CaV3.3 domains revealed preferential binding of Pn3a to the S3-S4 region of domain II (CaV3.3DII). This novel T-type channel pharmacological site was explored through computational docking simulations of Pn3a, site-directed mutagenesis, and full domain II swaps between CaV3 channels highlighting it as a subtype-specific pharmacophore. This research expands our understanding of T-type calcium channel pharmacology and supports the suitability of Pn3a as a molecular tool in the study of the physiological roles of CaV3.3 channels.
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Affiliation(s)
- Jeffrey R McArthur
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
| | - Jierong Wen
- School of Science, RMIT University, Melbourne, Australia
| | - Andrew Hung
- School of Science, RMIT University, Melbourne, Australia
| | - Rocio K Finol-Urdaneta
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
| | - David J Adams
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
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5
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Baez-Nieto D, Allen A, Akers-Campbell S, Yang L, Budnik N, Pupo A, Shin YC, Genovese G, Liao M, Pérez-Palma E, Heyne H, Lal D, Lipscombe D, Pan JQ. Analysing an allelic series of rare missense variants of CACNA1I in a Swedish schizophrenia cohort. Brain 2022; 145:1839-1853. [PMID: 34919654 PMCID: PMC9166571 DOI: 10.1093/brain/awab443] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 10/23/2021] [Accepted: 11/11/2021] [Indexed: 11/14/2022] Open
Abstract
CACNA1I is implicated in the susceptibility to schizophrenia by large-scale genetic association studies of single nucleotide polymorphisms. However, the channelopathy of CACNA1I in schizophrenia is unknown. CACNA1I encodes CaV3.3, a neuronal voltage-gated calcium channel that underlies a subtype of T-type current that is important for neuronal excitability in the thalamic reticular nucleus and other regions of the brain. Here, we present an extensive functional characterization of 57 naturally occurring rare and common missense variants of CACNA1I derived from a Swedish schizophrenia cohort of more than 10 000 individuals. Our analysis of this allelic series of coding CACNA1I variants revealed that reduced CaV3.3 channel current density was the dominant phenotype associated with rare CACNA1I coding alleles derived from control subjects, whereas rare CACNA1I alleles from schizophrenia patients encoded CaV3.3 channels with altered responses to voltages. CACNA1I variants associated with altered current density primarily impact the ionic channel pore and those associated with altered responses to voltage impact the voltage-sensing domain. CaV3.3 variants associated with altered voltage dependence of the CaV3.3 channel and those associated with peak current density deficits were significantly segregated across affected and unaffected groups (Fisher's exact test, P = 0.034). Our results, together with recent data from the SCHEMA (Schizophrenia Exome Sequencing Meta-Analysis) cohort, suggest that reduced CaV3.3 function may protect against schizophrenia risk in rare cases. We subsequently modelled the effect of the biophysical properties of CaV3.3 channel variants on thalamic reticular nucleus excitability and found that compared with common variants, ultrarare CaV3.3-coding variants derived from control subjects significantly decreased thalamic reticular nucleus excitability (P = 0.011). When all rare variants were analysed, there was a non-significant trend between variants that reduced thalamic reticular nucleus excitability and variants that either had no effect or increased thalamic reticular nucleus excitability across disease status. Taken together, the results of our functional analysis of an allelic series of >50 CACNA1I variants in a schizophrenia cohort reveal that loss of function of CaV3.3 is a molecular phenotype associated with reduced disease risk burden, and our approach may serve as a template strategy for channelopathies in polygenic disorders.
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Affiliation(s)
- David Baez-Nieto
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Andrew Allen
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Seth Akers-Campbell
- Carney Institute for Brain Science & Department of Neuroscience, Brown University, Providence, RI 02912, USA
| | - Lingling Yang
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Nikita Budnik
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Amaury Pupo
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506, USA
| | - Young-Cheul Shin
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Giulio Genovese
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - Maofu Liao
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Eduardo Pérez-Palma
- Genomic Medicine Institute, Lerner Research institute, Cleveland Clinic, OH 44195, USA
- Centro de Genética y Genómica, Universidad del Desarrollo, Centro de Genética y Genómica, Facultad de Medicina Clínica Alemana, Chile
| | - Henrike Heyne
- Genomic Medicine, Hasso Plattner Institute, Potsdam, 14482, Germany
| | - Dennis Lal
- Genomic Medicine Institute, Lerner Research institute, Cleveland Clinic, OH 44195, USA
- Cologne Center for Genomics, University of Cologne, Cologne 50931, Germany
- Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Diane Lipscombe
- Carney Institute for Brain Science & Department of Neuroscience, Brown University, Providence, RI 02912, USA
| | - Jen Q. Pan
- Stanley Center for Psychiatric Research, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
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Papazoglou A, Arshaad MI, Henseler C, Daubner J, Broich K, Hescheler J, Ehninger D, Haenisch B, Weiergräber M. Ca v3 T-Type Voltage-Gated Ca 2+ Channels and the Amyloidogenic Environment: Pathophysiology and Implications on Pharmacotherapy and Pharmacovigilance. Int J Mol Sci 2022; 23:ijms23073457. [PMID: 35408817 PMCID: PMC8998330 DOI: 10.3390/ijms23073457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 03/17/2022] [Accepted: 03/18/2022] [Indexed: 12/07/2022] Open
Abstract
Voltage-gated Ca2+ channels (VGCCs) were reported to play a crucial role in neurotransmitter release, dendritic resonance phenomena and integration, and the regulation of gene expression. In the septohippocampal system, high- and low-voltage-activated (HVA, LVA) Ca2+ channels were shown to be involved in theta genesis, learning, and memory processes. In particular, HVA Cav2.3 R-type and LVA Cav3 T-type Ca2+ channels are expressed in the medial septum-diagonal band of Broca (MS-DBB), hippocampal interneurons, and pyramidal cells, and ablation of both channels was proven to severely modulate theta activity. Importantly, Cav3 Ca2+ channels contribute to rebound burst firing in septal interneurons. Consequently, functional impairment of T-type Ca2+ channels, e.g., in null mutant mouse models, caused tonic disinhibition of the septohippocampal pathway and subsequent enhancement of hippocampal theta activity. In addition, impairment of GABA A/B receptor transcription, trafficking, and membrane translocation was observed within the septohippocampal system. Given the recent findings that amyloid precursor protein (APP) forms complexes with GABA B receptors (GBRs), it is hypothesized that T-type Ca2+ current reduction, decrease in GABA receptors, and APP destabilization generate complex functional interdependence that can constitute a sophisticated proamyloidogenic environment, which could be of potential relevance in the etiopathogenesis of Alzheimer’s disease (AD). The age-related downregulation of T-type Ca2+ channels in humans goes together with increased Aβ levels that could further inhibit T-type channels and aggravate the proamyloidogenic environment. The mechanistic model presented here sheds new light on recent reports about the potential risks of T-type Ca2+ channel blockers (CCBs) in dementia, as observed upon antiepileptic drug application in the elderly.
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Affiliation(s)
- Anna Papazoglou
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (A.P.); (M.I.A.); (C.H.); (J.D.)
| | - Muhammad Imran Arshaad
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (A.P.); (M.I.A.); (C.H.); (J.D.)
| | - Christina Henseler
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (A.P.); (M.I.A.); (C.H.); (J.D.)
| | - Johanna Daubner
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (A.P.); (M.I.A.); (C.H.); (J.D.)
| | - Karl Broich
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (K.B.); (B.H.)
| | - Jürgen Hescheler
- Faculty of Medicine, Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, 50931 Cologne, Germany;
- Center of Physiology and Pathophysiology, Faculty of Medicine, University of Cologne, Robert-Koch-Str. 39, 50931 Cologne, Germany
| | - Dan Ehninger
- Translational Biogerontology, German Center for Neurodegenerative Diseases (Deutsches Zentrum für Neurodegenerative Erkrankungen, DZNE), Venusberg-Campus 1/99, 53127 Bonn, Germany;
- German Center for Neurodegenerative Diseases (Deutsches Zentrum für Neurodegenerative Erkrankungen, DZNE), Venusberg-Campus 1/99, 53127 Bonn, Germany
| | - Britta Haenisch
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (K.B.); (B.H.)
- German Center for Neurodegenerative Diseases (Deutsches Zentrum für Neurodegenerative Erkrankungen, DZNE), Venusberg-Campus 1/99, 53127 Bonn, Germany
- Center for Translational Medicine, Medical Faculty, University of Bonn, 53113 Bonn, Germany
| | - Marco Weiergräber
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (A.P.); (M.I.A.); (C.H.); (J.D.)
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany; (K.B.); (B.H.)
- Faculty of Medicine, Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, 50931 Cologne, Germany;
- Center of Physiology and Pathophysiology, Faculty of Medicine, University of Cologne, Robert-Koch-Str. 39, 50931 Cologne, Germany
- Correspondence: ; Tel.: +49-228-99307-4358
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Targeting the T-type calcium channel Cav3.2 in GABAergic arcuate nucleus neurons to treat obesity. Mol Metab 2021; 54:101391. [PMID: 34767997 PMCID: PMC8640109 DOI: 10.1016/j.molmet.2021.101391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 10/20/2021] [Accepted: 11/02/2021] [Indexed: 01/16/2023] Open
Abstract
OBJECTIVE Cav3.2, a T-type low voltage-activated calcium channel widely expressed throughout the central nervous system, plays a vital role in neuronal excitability and various physiological functions. However, the effects of Cav3.2 on energy homeostasis remain unclear. Here, we examined the role of Cav3.2 expressed by hypothalamic GABAergic neurons in the regulation of food intake and body weight in mice and explored the underlying mechanisms. METHODS Male congenital Cana1h (the gene coding for Cav3.2) global knockout (Cav3.2KO) mice and their wild type (WT) littermates were first used for metabolic phenotyping studies. By using the CRISPR-Cas9 technique, Cav3.2 was selectively deleted from GABAergic neurons in the arcuate nucleus of the hypothalamus (ARH) by specifically overexpressing Cas9 protein and Cav3.2-targeting sgRNAs in ARH Vgat (VgatARH) neurons. These male mutants (Cav3.2KO-VgatARH) were used to determine whether Cav3.2 expressed by VgatARH neurons is required for the proper regulation of energy balance. Subsequently, we used an electrophysiological patch-clamp recording in ex vivo brain slices to explore the impact of Cav3.2KO on the cellular excitability of VgatARH neurons. RESULTS Male Cav3.2KO mice had significantly lower food intake than their WT littermate controls when fed with either a normal chow diet (NCD) or a high-fat diet (HFD). This hypophagia phenotype was associated with increased energy expenditure and decreased fat mass, lean mass, and total body weight. Selective deletion of Cav3.2 in VgatARH neurons resulted in similar feeding inhibition and lean phenotype without changing energy expenditure. These data provides an intrinsic mechanism to support the previous finding on ARH non-AgRP GABA neurons in regulating diet-induced obesity. Lastly, we found that naringenin extract, a predominant flavanone found in various fruits and herbs and known to act on Cav3.2, decreased the firing activity of VgatARH neurons and reduced food intake and body weight. These naringenin-induced inhibitions were fully blocked in Cav3.2KO-VgatARH mice. CONCLUSION Our results identified Cav3.2 expressed by VgatARH neurons as an essential intrinsic modulator for food intake and energy homeostasis, which is a potential therapeutic target in the treatment of obesity.
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8
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El Ghaleb Y, Schneeberger PE, Fernández-Quintero ML, Geisler SM, Pelizzari S, Polstra AM, van Hagen JM, Denecke J, Campiglio M, Liedl KR, Stevens CA, Person RE, Rentas S, Marsh ED, Conlin LK, Tuluc P, Kutsche K, Flucher BE. CACNA1I gain-of-function mutations differentially affect channel gating and cause neurodevelopmental disorders. Brain 2021; 144:2092-2106. [PMID: 33704440 PMCID: PMC8422349 DOI: 10.1093/brain/awab101] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 12/11/2022] Open
Abstract
T-type calcium channels (Cav3.1 to Cav3.3) regulate low-threshold calcium spikes, burst firing and rhythmic oscillations of neurons and are involved in sensory processing, sleep, and hormone and neurotransmitter release. Here, we examined four heterozygous missense variants in CACNA1I, encoding the Cav3.3 channel, in patients with variable neurodevelopmental phenotypes. The p.(Ile860Met) variant, affecting a residue in the putative channel gate at the cytoplasmic end of the IIS6 segment, was identified in three family members with variable cognitive impairment. The de novo p.(Ile860Asn) variant, changing the same amino acid residue, was detected in a patient with severe developmental delay and seizures. In two additional individuals with global developmental delay, hypotonia, and epilepsy, the variants p.(Ile1306Thr) and p.(Met1425Ile), substituting residues at the cytoplasmic ends of IIIS5 and IIIS6, respectively, were found. Because structure modelling indicated that the amino acid substitutions differentially affect the mobility of the channel gate, we analysed possible effects on Cav3.3 channel function using patch-clamp analysis in HEK293T cells. The mutations resulted in slowed kinetics of current activation, inactivation, and deactivation, and in hyperpolarizing shifts of the voltage-dependence of activation and inactivation, with Cav3.3-I860N showing the strongest and Cav3.3-I860M the weakest effect. Structure modelling suggests that by introducing stabilizing hydrogen bonds the mutations slow the kinetics of the channel gate and cause the gain-of-function effect in Cav3.3 channels. The gating defects left-shifted and increased the window currents, resulting in increased calcium influx during repetitive action potentials and even at resting membrane potentials. Thus, calcium toxicity in neurons expressing the Cav3.3 variants is one likely cause of the neurodevelopmental phenotype. Computer modelling of thalamic reticular nuclei neurons indicated that the altered gating properties of the Cav3.3 disease variants lower the threshold and increase the duration and frequency of action potential firing. Expressing the Cav3.3-I860N/M mutants in mouse chromaffin cells shifted the mode of firing from low-threshold spikes and rebound burst firing with wild-type Cav3.3 to slow oscillations with Cav3.3-I860N and an intermediate firing mode with Cav3.3-I860M, respectively. Such neuronal hyper-excitability could explain seizures in the patient with the p.(Ile860Asn) mutation. Thus, our study implicates CACNA1I gain-of-function mutations in neurodevelopmental disorders, with a phenotypic spectrum ranging from borderline intellectual functioning to a severe neurodevelopmental disorder with epilepsy.
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Affiliation(s)
- Yousra El Ghaleb
- Institute of Physiology, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Pauline E Schneeberger
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg 20251, Germany
| | - Monica L Fernández-Quintero
- Institute of Physiology, Medical University Innsbruck, Innsbruck 6020, Austria
- Institute of Theoretical Chemistry, University of Innsbruck, Innsbruck 6020, Austria
| | - Stefanie M Geisler
- Department of Pharmacology, University of Innsbruck, Innsbruck 6020, Austria
| | - Simone Pelizzari
- Institute of Physiology, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Abeltje M Polstra
- Department of Clinical Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, 1012 WX, The Netherlands
| | - Johanna M van Hagen
- Department of Clinical Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, 1012 WX, The Netherlands
| | - Jonas Denecke
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg 20251, Germany
| | - Marta Campiglio
- Institute of Physiology, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Klaus R Liedl
- Institute of Theoretical Chemistry, University of Innsbruck, Innsbruck 6020, Austria
| | - Cathy A Stevens
- Department of Pediatrics, University of Tennessee College of Medicine, Chattanooga, TN 37403, USA
| | | | - Stefan Rentas
- Division of Genomic Diagnostics, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Eric D Marsh
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Laura K Conlin
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Petronel Tuluc
- Department of Pharmacology, University of Innsbruck, Innsbruck 6020, Austria
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg 20251, Germany
| | - Bernhard E Flucher
- Institute of Physiology, Medical University Innsbruck, Innsbruck 6020, Austria
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9
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Ferron L, Novazzi CG, Pilch KS, Moreno C, Ramgoolam K, Dolphin AC. FMRP regulates presynaptic localization of neuronal voltage gated calcium channels. Neurobiol Dis 2020; 138:104779. [PMID: 31991246 PMCID: PMC7152798 DOI: 10.1016/j.nbd.2020.104779] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 01/09/2020] [Accepted: 01/24/2020] [Indexed: 12/31/2022] Open
Abstract
Fragile X syndrome (FXS), the most common form of inherited intellectual disability and autism, results from the loss of fragile X mental retardation protein (FMRP). We have recently identified a direct interaction of FMRP with voltage-gated Ca2+ channels that modulates neurotransmitter release. In the present study we used a combination of optophysiological tools to investigate the impact of FMRP on the targeting of voltage-gated Ca2+ channels to the active zones in neuronal presynaptic terminals. We monitored Ca2+ transients at synaptic boutons of dorsal root ganglion (DRG) neurons using the genetically-encoded Ca2+ indicator GCaMP6f tagged to synaptophysin. We show that knock-down of FMRP induces an increase of the amplitude of the Ca2+ transient in functionally-releasing presynaptic terminals, and that this effect is due to an increase of N-type Ca2+ channel contribution to the total Ca2+ transient. Dynamic regulation of CaV2.2 channel trafficking is key to the function of these channels in neurons. Using a CaV2.2 construct with an α-bungarotoxin binding site tag, we further investigate the impact of FMRP on the trafficking of CaV2.2 channels. We show that forward trafficking of CaV2.2 channels from the endoplasmic reticulum to the plasma membrane is reduced when co-expressed with FMRP. Altogether our data reveal a critical role of FMRP on localization of CaV channels to the presynaptic terminals and how its defect in a context of FXS can profoundly affect synaptic transmission. Loss of FMRP increases presynaptic Ca2+ transients. FMRP is a negative regulator of presynaptic Cav2.2 channel abundance. FMRP reduces the forward trafficking of Cav2.2 channels from ER to plasma membrane. Distal part of FMRP carboxy terminus is key for interaction with Cav2.2 channels.
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Affiliation(s)
- Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
| | - Cesare G Novazzi
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Kjara S Pilch
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Cristian Moreno
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Krishma Ramgoolam
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
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10
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A novel phospho-modulatory mechanism contributes to the calcium-dependent regulation of T-type Ca 2+ channels. Sci Rep 2019; 9:15642. [PMID: 31666636 PMCID: PMC6821770 DOI: 10.1038/s41598-019-52194-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 10/13/2019] [Indexed: 11/08/2022] Open
Abstract
Cav3 / T-type Ca2+ channels are dynamically regulated by intracellular Ca2+ ions, which inhibit Cav3 availability. Here, we demonstrate that this inhibition becomes irreversible in the presence of non-hydrolysable ATP analogs, resulting in a strong hyperpolarizing shift in the steady-state inactivation of the residual Cav3 current. Importantly, the effect of these ATP analogs was prevented in the presence of intracellular BAPTA. Additional findings obtained using intracellular dialysis of inorganic phosphate and alkaline phosphatase or NaN3 treatment further support the involvement of a phosphorylation mechanism. Contrasting with Cav1 and Cav2 Ca2+ channels, the Ca2+-dependent modulation of Cav3 channels appears to be independent of calmodulin, calcineurin and endocytic pathways. Similar findings were obtained for the native T-type Ca2+ current recorded in rat thalamic neurons of the central medial nucleus. Overall, our data reveal a new Ca2+ sensitive phosphorylation-dependent mechanism regulating Cav3 channels, with potentially important physiological implications for the multiple cell functions controlled by T-type Ca2+ channels.
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11
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Mäki-Marttunen T, Devor A, Phillips WA, Dale AM, Andreassen OA, Einevoll GT. Computational Modeling of Genetic Contributions to Excitability and Neural Coding in Layer V Pyramidal Cells: Applications to Schizophrenia Pathology. Front Comput Neurosci 2019; 13:66. [PMID: 31616272 PMCID: PMC6775251 DOI: 10.3389/fncom.2019.00066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 09/09/2019] [Indexed: 11/13/2022] Open
Abstract
Pyramidal cells in layer V of the neocortex are one of the most widely studied neuron types in the mammalian brain. Due to their role as integrators of feedforward and cortical feedback inputs, they are well-positioned to contribute to the symptoms and pathology in mental disorders-such as schizophrenia-that are characterized by a mismatch between the internal perception and external inputs. In this modeling study, we analyze the input/output properties of layer V pyramidal cells and their sensitivity to modeled genetic variants in schizophrenia-associated genes. We show that the excitability of layer V pyramidal cells and the way they integrate inputs in space and time are altered by many types of variants in ion-channel and Ca2+ transporter-encoding genes that have been identified as risk genes by recent genome-wide association studies. We also show that the variability in the output patterns of spiking and Ca2+ transients in layer V pyramidal cells is altered by these model variants. Importantly, we show that many of the predicted effects are robust to noise and qualitatively similar across different computational models of layer V pyramidal cells. Our modeling framework reveals several aspects of single-neuron excitability that can be linked to known schizophrenia-related phenotypes and existing hypotheses on disease mechanisms. In particular, our models predict that single-cell steady-state firing rate is positively correlated with the coding capacity of the neuron and negatively correlated with the amplitude of a prepulse-mediated adaptation and sensitivity to coincidence of stimuli in the apical dendrite and the perisomatic region of a layer V pyramidal cell. These results help to uncover the voltage-gated ion-channel and Ca2+ transporter-associated genetic underpinnings of schizophrenia phenotypes and biomarkers.
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Affiliation(s)
| | - Anna Devor
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States.,Department of Radiology, University of California San Diego, La Jolla, CA, United States.,Martinos Center for Biomedical Imaging, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States
| | - William A Phillips
- Psychology, Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom
| | - Anders M Dale
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States.,Department of Radiology, University of California San Diego, La Jolla, CA, United States
| | - Ole A Andreassen
- NORMENT, Division of Mental Health and Addiction, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Gaute T Einevoll
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway.,Department of Physics, University of Oslo, Oslo, Norway
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12
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McArthur JR, Finol-Urdaneta RK, Adams DJ. Analgesic transient receptor potential vanilloid-1-active compounds inhibit native and recombinant T-type calcium channels. Br J Pharmacol 2019; 176:2264-2278. [PMID: 30927254 DOI: 10.1111/bph.14676] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 03/07/2019] [Accepted: 03/21/2019] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE T-type calcium (Cav 3) and transient receptor potential vanilloid-1 (TRPV1) channels play central roles in the control of excitability in the peripheral nervous system and are regarded as potential therapeutic pain targets. Modulators that either activate or inhibit TRPV1-mediated currents display analgesic properties in various pain models despite opposing effects on their connate target, TRPV1. We explored the effects of TRPV1-active compounds on Cav 3-mediated currents. EXPERIMENTAL APPROACH Whole-cell patch clamp recordings were used to examine the effects of TRPV1-active compounds on rat dorsal root ganglion low voltage-activated calcium currents and recombinant Cav 3 isoforms in expression systems. KEY RESULTS The classical TRPV1 agonist capsaicin as well as TRPV1 antagonists A-889425, BCTC, and capsazepine directly inhibited Cav 3 channels. These compounds altered the voltage-dependence of activation and inactivation of Cav 3 channels and delayed their recovery from inactivation, leading to a concomitant decrease in T-type current availability. The TRPV1 antagonist capsazepine potently inhibited Cav 3.1 and 3.2 channels (KD < 120 nM), as demonstrated by its slow off rate. In contrast, neither the TRPV1 agonists, Palvanil and resiniferatoxin, nor the TRPV1 antagonist AMG9810 modulated Cav 3-mediated currents. CONCLUSIONS AND IMPLICATIONS Analgesic TRPV1-active compounds inhibit Cav 3 currents in native and heterologous systems. Hence, their analgesic effects may not be exclusively attributed to their actions on TRPV1, which has important implications in the current understanding of nociceptive pathways. Importantly, our results highlight the need for attention in the experimental design used to address the analgesic properties of Cav 3 channel inhibitors.
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Affiliation(s)
- Jeffrey R McArthur
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
| | - Rocio K Finol-Urdaneta
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
| | - David J Adams
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
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13
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Schaub C, Uebachs M. Scaling of recovery rates influences T-type Ca 2+ channel availability following IPSPs. Heliyon 2019; 5:e01278. [PMID: 30886927 PMCID: PMC6395784 DOI: 10.1016/j.heliyon.2019.e01278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 12/21/2018] [Accepted: 02/22/2019] [Indexed: 11/24/2022] Open
Abstract
The excitability of neuronal membranes is crucially modulated by T-type Ca2+ channels (ICaT) due to their low threshold of activation. ICaT inactivates steeply at potentials close to the resting membrane potential. Therefore, the availability of ICaT following changes in membrane potential depends on the time course of the onset of inactivation as well as on the time course of recovery from inactivation. It was previously shown that the time course of recovery from inactivation depends on the duration of the conditioning pulse in cloned T-type Ca2+ channel subunits (Cav3.1-Cav3.3(Uebachs et al., 2006)). This provides a potential mechanism for an intrinsic form of short term plasticity. Here, we address the question, whether this mechanism results in altered availability of ICaT following physiological changes in membrane potential. We found that the recovery of ICaT during an IPSP depends on the duration of a preceding depolarized period.
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Affiliation(s)
- Christina Schaub
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, Life & Brain Center, Sigmund Freud Str. 2, 53121, Bonn, Germany.,Department of Neurology, University of Bonn, Sigmund Freud Str. 2, 53121, Bonn, Germany
| | - Mischa Uebachs
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, Life & Brain Center, Sigmund Freud Str. 2, 53121, Bonn, Germany.,Department of Neurology, University of Bonn, Sigmund Freud Str. 2, 53121, Bonn, Germany
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14
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Mäki-Marttunen T, Krull F, Bettella F, Hagen E, Næss S, Ness TV, Moberget T, Elvsåshagen T, Metzner C, Devor A, Edwards AG, Fyhn M, Djurovic S, Dale AM, Andreassen OA, Einevoll GT. Alterations in Schizophrenia-Associated Genes Can Lead to Increased Power in Delta Oscillations. Cereb Cortex 2019; 29:875-891. [PMID: 30475994 PMCID: PMC6319172 DOI: 10.1093/cercor/bhy291] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 10/03/2018] [Indexed: 12/13/2022] Open
Abstract
Genome-wide association studies have implicated many ion channels in schizophrenia pathophysiology. Although the functions of these channels are relatively well characterized by single-cell studies, the contributions of common variation in these channels to neurophysiological biomarkers and symptoms of schizophrenia remain elusive. Here, using computational modeling, we show that a common biomarker of schizophrenia, namely, an increase in delta-oscillation power, may be a direct consequence of altered expression or kinetics of voltage-gated ion channels or calcium transporters. Our model of a circuit of layer V pyramidal cells highlights multiple types of schizophrenia-related variants that contribute to altered dynamics in the delta-frequency band. Moreover, our model predicts that the same membrane mechanisms that increase the layer V pyramidal cell network gain and response to delta-frequency oscillations may also cause a deficit in a single-cell correlate of the prepulse inhibition, which is a behavioral biomarker highly associated with schizophrenia.
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Affiliation(s)
- Tuomo Mäki-Marttunen
- Simula Research Laboratory, Oslo, Norway
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Florian Krull
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Francesco Bettella
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Espen Hagen
- Department of Physics, University of Oslo, Oslo, Norway
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Solveig Næss
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Torbjørn V Ness
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Torgeir Moberget
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Torbjørn Elvsåshagen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Department of Neurology, Oslo University Hospital, Oslo, Norway
| | - Christoph Metzner
- Centre for Computer Science and Informatics Research, University of Hertfordshire, Hatfield, UK
| | - Anna Devor
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | | | - Marianne Fyhn
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Srdjan Djurovic
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
- NORMENT, KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Anders M Dale
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
| | - Ole A Andreassen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
| | - Gaute T Einevoll
- Department of Physics, University of Oslo, Oslo, Norway
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
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15
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Arteaga-Tlecuitl R, Sanchez-Sandoval AL, Ramirez-Cordero BE, Rosendo-Pineda MJ, Vaca L, Gomora JC. Increase of Ca V3 channel activity induced by HVA β1b-subunit is not mediated by a physical interaction. BMC Res Notes 2018; 11:810. [PMID: 30428904 PMCID: PMC6236959 DOI: 10.1186/s13104-018-3917-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 11/09/2018] [Indexed: 01/13/2023] Open
Abstract
Objective Low voltage-activated (LVA) calcium channels are crucial for regulating oscillatory behavior in several types of neurons and other excitable cells. LVA channels dysfunction has been implicated in epilepsy, neuropathic pain, cancer, among other diseases. Unlike for High Voltage-Activated (HVA) channels, voltage-dependence and kinetics of currents carried by recombinant LVA, i.e., CaV3 channels, are quite similar to those observed in native currents. Therefore, whether these channels are regulated by HVA auxiliary subunits, remain controversial. Here, we used the α1-subunits of CaV3.1, CaV3.2, and CaV3.3 channels, together with HVA auxiliary β-subunits to perform electrophysiological, confocal microscopy and immunoprecipitation experiments, in order to further explore this possibility. Results Functional expression of CaV3 channels is up-regulated by all four β-subunits, although most consistent effects were observed with the β1b-subunit. The biophysical properties of CaV3 channels were not modified by any β-subunit. Furthermore, although β1b-subunits increased colocalization of GFP-tagged CaV3 channels and the plasma membrane of HEK-293 cells, western blots analysis revealed the absence of physical interaction between CaV3.3 and β1b-subunits as no co-immunoprecipitation was observed. These results provide solid evidence that the up-regulation of LVA channels in the presence of HVA-β1b subunit is not mediated by a high affinity interaction between both proteins. Electronic supplementary material The online version of this article (10.1186/s13104-018-3917-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Rogelio Arteaga-Tlecuitl
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Ana Laura Sanchez-Sandoval
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Belen Ernestina Ramirez-Cordero
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Margarita Jacaranda Rosendo-Pineda
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Luis Vaca
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Juan Carlos Gomora
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico.
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16
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Wang D, Ragnarsson L, Lewis RJ. T-type Calcium Channels in Health and Disease. Curr Med Chem 2018; 27:3098-3122. [PMID: 30277145 DOI: 10.2174/0929867325666181001112821] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 08/28/2018] [Accepted: 08/30/2018] [Indexed: 12/12/2022]
Abstract
Low Voltage-Activated (LVA) T-type calcium channels are characterized by transient current and Low Threshold Spikes (LTS) that trigger neuronal firing and oscillatory behavior. Combined with their preferential localization in dendrites and their specific "window current", T-type calcium channels are considered to be key players in signal amplification and synaptic integration. Assisted by the emerging pharmacological tools, the structural determinants of channel gating and kinetics, as well as novel physiological and pathological functions of T-type calcium channels, are being uncovered. In this review, we provide an overview of structural determinants in T-type calcium channels, their involvement in disorders and diseases, the development of novel channel modulators, as well as Structure-Activity Relationship (SAR) studies that lead to rational drug design.
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Affiliation(s)
- Dan Wang
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane Qld 4072, Australia
| | - Lotten Ragnarsson
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane Qld 4072, Australia
| | - Richard J Lewis
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, the University of Queensland, Brisbane Qld 4072, Australia
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17
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Hazzaz Abouamal T, Choukairi Z, Taoufiq F. Functional Exploration Of T-Type Calcium Channels (Cav3.2 And Cav3.3) And Their Sensitivity To Zinc. Open Microbiol J 2018; 12:280-287. [PMID: 30197701 PMCID: PMC6110071 DOI: 10.2174/1874285801812010280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 06/28/2018] [Accepted: 07/02/2018] [Indexed: 11/22/2022] Open
Abstract
Introduction: T-type Ca2+ channels (TTCC) are low Voltage-gated calcium channels, expressed in various tissues such as the brain and heart, and contribute to a variety of physiological functions including neuronal excitability, hormone secretion, muscle contraction, and pacemaker activity. At high concentrations, Zinc (Zn2+) is naturally attached to cell membranes and is therefore considered a reversible inhibitor of calcium. Zinc is also involved in the kinetics of sodium and potassium currents. Zinc is essential for many functions. A low zinc tenor is associated with emotional instability, digestive disorders, slow-growing and alteration of protein synthesis. Material and Methods: For the Cell Culture we used HEK-293/tsA-201, and for transfection, the pCDNA3 plasmid constructs encoding human CaV3.2, and CaV3.3 subunits. Electrophysiological experiments were performed using the whole cell configuration of the patch-clamp technique. T-type currents were recorded using a test pulse from a holding potential at (-100mV) to (-30 mV), data Acquisition and Analysis for Current-voltage relationships (I-V curves) were recorded for the two cloned T-type Ca2+ channels (Cav3.2, Cav3.3). Results: Our studies describe the behavior of these channels Cav3.2 and Cav3.3 and also their current sensitivity to Zinc (Zn2+) in transfected HEK-293/tsA-201cells. Our results show that Zn2+ applies a modulatory effect on T-type calcium channels. We observe that Zn2+ differentially modulates the CaV3.2 and CaV3.3 channels. Zn2+ preferably inhibits Cav3.2. Conclusion: We have demonstrated that Zn2+ differentially modulates two CaV3 channels (Cav3.2 and Cav3.3): It is a preferential blocker of CaV3.2 channels and it alters the gating behaviour of CaV3.3 channels.
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Affiliation(s)
- Tahar Hazzaz Abouamal
- Department of Biology, Laboratory of Biosciences, Faculty of Sciences and Technology of Mohammedia, Casablanca, Morocco
| | - Zineb Choukairi
- Department of Biology, Laboratory of Biosciences, Faculty of Sciences and Technology of Mohammedia, Casablanca, Morocco
| | - Fechtali Taoufiq
- Department of Biology, Laboratory of Biosciences, Faculty of Sciences and Technology of Mohammedia, Casablanca, Morocco
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18
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Sanchez-Sandoval AL, Herrera Carrillo Z, Díaz Velásquez CE, Delgadillo DM, Rivera HM, Gomora JC. Contribution of S4 segments and S4-S5 linkers to the low-voltage activation properties of T-type CaV3.3 channels. PLoS One 2018; 13:e0193490. [PMID: 29474447 PMCID: PMC5825144 DOI: 10.1371/journal.pone.0193490] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 02/12/2018] [Indexed: 11/25/2022] Open
Abstract
Voltage-gated calcium channels contain four highly conserved transmembrane helices known as S4 segments that exhibit a positively charged residue every third position, and play the role of voltage sensing. Nonetheless, the activation range between high-voltage (HVA) and low-voltage (LVA) activated calcium channels is around 30–40 mV apart, despite the high level of amino acid similarity within their S4 segments. To investigate the contribution of S4 voltage sensors for the low-voltage activation characteristics of CaV3.3 channels we constructed chimeras by swapping S4 segments between this LVA channel and the HVA CaV1.2 channel. The substitution of S4 segment of Domain II in CaV3.3 by that of CaV1.2 (chimera IIS4C) induced a ~35 mV shift in the voltage-dependence of activation towards positive potentials, showing an I-V curve that almost overlaps with that of CaV1.2 channel. This HVA behavior induced by IIS4C chimera was accompanied by a 2-fold decrease in the voltage-dependence of channel gating. The IVS4 segment had also a strong effect in the voltage sensing of activation, while substitution of segments IS4 and IIIS4 moved the activation curve of CaV3.3 to more negative potentials. Swapping of IIS4 voltage sensor influenced additional properties of this channel such as steady-state inactivation, current decay, and deactivation. Notably, Domain I voltage sensor played a major role in preventing CaV3.3 channels to inactivate from closed states at extreme hyperpolarized potentials. Finally, site-directed mutagenesis in the CaV3.3 channel revealed a partial contribution of the S4-S5 linker of Domain II to LVA behavior, with synergic effects observed in double and triple mutations. These findings indicate that IIS4 and, to a lesser degree IVS4, voltage sensors are crucial in determining the LVA properties of CaV3.3 channels, although the accomplishment of this function involves the participation of other structural elements like S4-S5 linkers.
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Affiliation(s)
- Ana Laura Sanchez-Sandoval
- Departamento de Neuropatología Molecular, División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Mexico City, México
| | - Zazil Herrera Carrillo
- Departamento de Neuropatología Molecular, División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Mexico City, México
| | - Clara Estela Díaz Velásquez
- Programa de Neurociencias, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Tlalnepantla de Baz, Estado de México, México
| | - Dulce María Delgadillo
- Laboratorios Nacionales de Servicios Experimentales Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico City, México
| | - Heriberto Manuel Rivera
- Facultad de Medicina, Universidad Autónoma del Estado de Morelos Cuernavaca, Morelos, México
| | - Juan Carlos Gomora
- Departamento de Neuropatología Molecular, División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Mexico City, México
- * E-mail:
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19
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Mäki-Marttunen T, Lines GT, Edwards AG, Tveito A, Dale AM, Einevoll GT, Andreassen OA. Pleiotropic effects of schizophrenia-associated genetic variants in neuron firing and cardiac pacemaking revealed by computational modeling. Transl Psychiatry 2017; 7:5. [PMID: 30446648 PMCID: PMC5802468 DOI: 10.1038/s41398-017-0007-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 07/07/2017] [Accepted: 07/14/2017] [Indexed: 01/01/2023] Open
Abstract
Schizophrenia patients have an increased risk of cardiac dysfunction. A possible factor underlying this comorbidity are the common variants in the large set of genes that have recently been discovered in genome-wide association studies (GWASs) as risk genes of schizophrenia. Many of these genes control the cell electrogenesis and calcium homeostasis. We applied biophysically detailed models of layer V pyramidal cells and sinoatrial node cells to study the contribution of schizophrenia-associated genes on cellular excitability. By including data from functional genomics literature to simulate the effects of common variants of these genes, we showed that variants of voltage-gated Na+ channel or hyperpolarization-activated cation channel-encoding genes cause qualitatively similar effects on layer V pyramidal cell and sinoatrial node cell excitability. By contrast, variants of Ca2+ channel or transporter-encoding genes mostly have opposite effects on cellular excitability in the two cell types. We also show that the variants may crucially affect the propagation of the cardiac action potential in the sinus node. These results may help explain some of the cardiac comorbidity in schizophrenia, and may facilitate generation of effective antipsychotic medications without cardiac side-effects such as arrhythmia.
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Affiliation(s)
- Tuomo Mäki-Marttunen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway. .,Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway.
| | - Glenn T. Lines
- Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway
| | - Andrew G. Edwards
- Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway
| | - Aslak Tveito
- Simula Research Laboratory and Center for Cardiological Innovation, Oslo, Norway
| | - Anders M. Dale
- 0000 0001 2107 4242grid.266100.3Multimodal Imaging Laboratory, UC San Diego, La Jolla, CA USA ,0000 0001 2107 4242grid.266100.3Department of Neurosciences, University of California San Diego, La Jolla, CA USA ,0000 0001 2107 4242grid.266100.3Department of Radiology, University of California, San Diego, La Jolla, CA USA
| | - Gaute T. Einevoll
- 0000 0004 0607 975Xgrid.19477.3cDepartment of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway ,0000 0004 1936 8921grid.5510.1Department of Physics, University of Oslo, Oslo, Norway
| | - Ole A. Andreassen
- 0000 0004 1936 8921grid.5510.1NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway ,0000 0004 0389 8485grid.55325.34Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
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20
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Zhao Y, Sivaji S, Chiang MC, Ali H, Zukowski M, Ali S, Kennedy B, Sklyar A, Cheng A, Guo Z, Reed AK, Kodali R, Borowski J, Frost G, Beukema P, Wills ZP. Amyloid Beta Peptides Block New Synapse Assembly by Nogo Receptor-Mediated Inhibition of T-Type Calcium Channels. Neuron 2017; 96:355-372.e6. [PMID: 29024660 DOI: 10.1016/j.neuron.2017.09.041] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 07/27/2017] [Accepted: 09/22/2017] [Indexed: 01/07/2023]
Abstract
Compelling evidence links amyloid beta (Aβ) peptide accumulation in the brains of Alzheimer's disease (AD) patients with the emergence of learning and memory deficits, yet a clear understanding of the events that drive this synaptic pathology are lacking. We present evidence that neurons exposed to Aβ are unable to form new synapses, resulting in learning deficits in vivo. We demonstrate the Nogo receptor family (NgR1-3) acts as Aβ receptors mediating an inhibition of synapse assembly, plasticity, and learning. Live imaging studies reveal Aβ activates NgRs on the dendritic shaft of neurons, triggering an inhibition of calcium signaling. We define T-type calcium channels as a target of Aβ-NgR signaling, mediating Aβ's inhibitory effects on calcium, synapse assembly, plasticity, and learning. These studies highlight deficits in new synapse assembly as a potential initiator of cognitive pathology in AD, and pinpoint calcium dysregulation mediated by NgRs and T-type channels as key components. VIDEO ABSTRACT.
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Affiliation(s)
- Yanjun Zhao
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Sivaprakash Sivaji
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Michael C Chiang
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA; Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Haadi Ali
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Monica Zukowski
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Sareen Ali
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Bryan Kennedy
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Alex Sklyar
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Alice Cheng
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Zihan Guo
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Alexander K Reed
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Ravindra Kodali
- Department of Structural Biology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Jennifer Borowski
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Georgia Frost
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA
| | - Patrick Beukema
- Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, PA 15213, USA; Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Zachary P Wills
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213, USA; Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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21
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McArthur JR, Motin L, Gleeson EC, Spiller S, Lewis RJ, Duggan PJ, Tuck KL, Adams DJ. Inhibition of human N- and T-type calcium channels by an ortho-phenoxyanilide derivative, MONIRO-1. Br J Pharmacol 2017; 175:2284-2295. [PMID: 28608537 DOI: 10.1111/bph.13910] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 03/24/2017] [Accepted: 06/05/2017] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND AND PURPOSE Voltage-gated calcium channels are involved in nociception in the CNS and in the periphery. N-type (Cav 2.2) and T-type (Cav 3.1, Cav 3.2 and Cav 3.3) voltage-gated calcium channels are particularly important in studying and treating pain and epilepsy. EXPERIMENTAL APPROACH In this study, whole-cell patch clamp electrophysiology was used to assess the potency and mechanism of action of a novel ortho-phenoxylanilide derivative, MONIRO-1, against a panel of voltage-gated calcium channels including Cav 1.2, Cav 1.3, Cav 2.1, Cav 2.2, Cav 2.3, Cav 3.1, Cav 3.2 and Cav 3.3. KEY RESULTS MONIRO-1 was 5- to 20-fold more potent at inhibiting human T-type calcium channels, hCav 3.1, hCav 3.2 and hCav 3.3 (IC50 : 3.3 ± 0.3, 1.7 ± 0.1 and 7.2 ± 0.3 μM, respectively) than N-type calcium channel, hCav 2.2 (IC50 : 34.0 ± 3.6 μM). It interacted with L-type calcium channels Cav 1.2 and Cav 1.3 with significantly lower potency (IC50 > 100 μM) and did not inhibit hCav 2.1 or hCav 2.3 channels at concentrations as high as 100 μM. State- and use-dependent inhibition of hCav 2.2 channels was observed, whereas stronger inhibition occurred at high stimulation frequencies for hCav 3.1 channels suggesting a different mode of action between these two channels. CONCLUSIONS AND IMPLICATIONS Selectivity, potency, reversibility and multi-modal effects distinguish MONIRO-1 from other low MW inhibitors acting on Cav channels involved in pain and/or epilepsy pathways. High-frequency firing increased the affinity for MONIRO-1 for both hCav 2.2 and hCav 3.1 channels. Such Cav channel modulators have potential clinical use in the treatment of epilepsies, neuropathic pain and other nociceptive pathophysiologies. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.
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Affiliation(s)
- Jeffrey R McArthur
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia.,Health Innovations Research Institute, RMIT University, Melbourne, VIC, Australia
| | - Leonid Motin
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia.,Health Innovations Research Institute, RMIT University, Melbourne, VIC, Australia
| | - Ellen C Gleeson
- CSIRO Manufacturing, Bag 10, Clayton South, VIC, Australia.,School of Chemistry, Monash University, Clayton, VIC, Australia
| | - Sandro Spiller
- School of Chemistry, Monash University, Clayton, VIC, Australia
| | - Richard J Lewis
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Peter J Duggan
- CSIRO Manufacturing, Bag 10, Clayton South, VIC, Australia.,School of Chemical and Physical Sciences, Flinders University, Adelaide, SA, Australia
| | - Kellie L Tuck
- School of Chemistry, Monash University, Clayton, VIC, Australia
| | - David J Adams
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia.,Health Innovations Research Institute, RMIT University, Melbourne, VIC, Australia
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22
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Smith CL, Abdallah S, Wong YY, Le P, Harracksingh AN, Artinian L, Tamvacakis AN, Rehder V, Reese TS, Senatore A. Evolutionary insights into T-type Ca 2+ channel structure, function, and ion selectivity from the Trichoplax adhaerens homologue. J Gen Physiol 2017; 149:483-510. [PMID: 28330839 PMCID: PMC5379919 DOI: 10.1085/jgp.201611683] [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: 08/28/2016] [Accepted: 02/07/2017] [Indexed: 12/31/2022] Open
Abstract
The role of T-type calcium channels in animals without nervous systems is unknown. Smith et al. characterize TCav3 from Trichoplax adhaerens, finding expression in neurosecretory-like cells and preference for Ca2+ over Na+ via strong extracellular Ca2+ block, despite low selectivity for Ca2+ in the pore. Four-domain voltage-gated Ca2+ (Cav) channels play fundamental roles in the nervous system, but little is known about when or how their unique properties and cellular roles evolved. Of the three types of metazoan Cav channels, Cav1 (L-type), Cav2 (P/Q-, N- and R-type) and Cav3 (T-type), Cav3 channels are optimized for regulating cellular excitability because of their fast kinetics and low activation voltages. These same properties permit Cav3 channels to drive low-threshold exocytosis in select neurons and neurosecretory cells. Here, we characterize the single T-type calcium channel from Trichoplax adhaerens (TCav3), an early diverging animal that lacks muscle, neurons, and synapses. Co-immunolocalization using antibodies against TCav3 and neurosecretory cell marker complexin labeled gland cells, which are hypothesized to play roles in paracrine signaling. Cloning and in vitro expression of TCav3 reveals that, despite roughly 600 million years of divergence from other T-type channels, it bears the defining structural and biophysical features of the Cav3 family. We also characterize the channel’s cation permeation properties and find that its pore is less selective for Ca2+ over Na+ compared with the human homologue Cav3.1, yet it exhibits a similar potent block of inward Na+ current by low external Ca2+ concentrations (i.e., the Ca2+ block effect). A comparison of the permeability features of TCav3 with other cloned channels suggests that Ca2+ block is a locus of evolutionary change in T-type channel cation permeation properties and that mammalian channels distinguish themselves from invertebrate ones by bearing both stronger Ca2+ block and higher Ca2+ selectivity. TCav3 is the most divergent metazoan T-type calcium channel and thus provides an evolutionary perspective on Cav3 channel structure–function properties, ion selectivity, and cellular physiology.
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Affiliation(s)
- Carolyn L Smith
- National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Salsabil Abdallah
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Yuen Yan Wong
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Phuong Le
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | | | | | | | | | - Thomas S Reese
- National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Adriano Senatore
- University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
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23
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Zhu MH, Sung TS, Kurahashi M, O'Kane LE, O'Driscoll K, Koh SD, Sanders KM. Na+-K+-Cl- cotransporter (NKCC) maintains the chloride gradient to sustain pacemaker activity in interstitial cells of Cajal. Am J Physiol Gastrointest Liver Physiol 2016; 311:G1037-G1046. [PMID: 27742704 PMCID: PMC5206290 DOI: 10.1152/ajpgi.00277.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 10/11/2016] [Indexed: 01/31/2023]
Abstract
Interstitial cells of Cajal (ICC) generate electrical slow waves by coordinated openings of ANO1 channels, a Ca2+-activated Cl- (CaCC) conductance. Efflux of Cl- during slow waves must be significant, as there is high current density during slow-wave currents and slow waves are of sufficient magnitude to depolarize the syncytium of smooth muscle cells and PDGFRα+ cells to which they are electrically coupled. We investigated how the driving force for Cl- current is maintained in ICC. We found robust expression of Slc12a2 (which encodes an Na+-K+-Cl- cotransporter, NKCC1) and immunohistochemical confirmation that NKCC1 is expressed in ICC. With the use of the gramicidin permeabilized-patch technique, which is reported to not disturb [Cl-]i, the reversal potential for spontaneous transient inward currents (ESTICs) was -10.5 mV. This value corresponds to the peak of slow waves when they are recorded directly from ICC in situ. Inhibition of NKCC1 with bumetanide shifted ESTICs to more negative potentials within a few minutes and reduced pacemaker activity. Bumetanide had no direct effects on ANO1 or CaV3.2 channels expressed in HEK293 cells or L-type Ca2+ currents. Reducing extracellular Cl- to 10 mM shifted ESTICs to positive potentials as predicted by the Nernst equation. The relatively rapid shift in ESTICs when NKCC1 was blocked suggests that significant changes in the transmembrane Cl- gradient occur during the slow-wave cycle, possibly within microdomains formed between endoplasmic reticulum and the plasma membrane in ICC. Recovery of Cl- via NKCC1 might have additional consequences on shaping the waveforms of slow waves via Na+ entry into microdomains.
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Affiliation(s)
- Mei Hong Zhu
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Tae Sik Sung
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Masaaki Kurahashi
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Lauren E. O'Kane
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Kate O'Driscoll
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Sang Don Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
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24
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Andrade A, Hope J, Allen A, Yorgan V, Lipscombe D, Pan JQ. A rare schizophrenia risk variant of CACNA1I disrupts Ca V3.3 channel activity. Sci Rep 2016; 6:34233. [PMID: 27756899 PMCID: PMC5069464 DOI: 10.1038/srep34233] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 09/07/2016] [Indexed: 02/04/2023] Open
Abstract
CACNA1I is a candidate schizophrenia risk gene. It encodes the pore-forming human CaV3.3 α1 subunit, a subtype of voltage-gated calcium channel that contributes to T-type currents. Recently, two de novo missense variations, T797M and R1346H, of hCaV3.3 were identified in individuals with schizophrenia. Here we show that R1346H, but not T797M, is associated with lower hCaV3.3 protein levels, reduced glycosylation, and lower membrane surface levels of hCaV3.3 when expressed in human cell lines compared to wild-type. Consistent with our biochemical analyses, whole-cell hCaV3.3 currents in cells expressing the R1346H variant were ~50% of those in cells expressing WT hCaV3.3, and neither R1346H nor T797M altered channel biophysical properties. Employing the NEURON simulation environment, we found that reducing hCaV3.3 current densities by 22% or more eliminates rebound bursting in model thalamic reticular nucleus (TRN) neurons. Our analyses suggest that a single copy of Chr22: 39665939G > A CACNA1I has the capacity to disrupt CaV3.3 channel-dependent functions, including rebound bursting in TRN neurons, with potential implications for schizophrenia pathophysiology.
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Affiliation(s)
- A Andrade
- Department of Biological Sciences, College of Life Sciences and Agriculture, University of New Hampshire, Durham, NH 03824, USA.,Brown Institute for Brain Science, Providence, RI 02912, USA
| | - J Hope
- Stanley Center of Psychiatric Research, Broad Institute of Harvard and MIT, 75 Ames Street, Cambridge, MA 02142, USA
| | - A Allen
- Stanley Center of Psychiatric Research, Broad Institute of Harvard and MIT, 75 Ames Street, Cambridge, MA 02142, USA
| | - V Yorgan
- Brown Institute for Brain Science, Providence, RI 02912, USA
| | - D Lipscombe
- Brown Institute for Brain Science, Providence, RI 02912, USA
| | - J Q Pan
- Stanley Center of Psychiatric Research, Broad Institute of Harvard and MIT, 75 Ames Street, Cambridge, MA 02142, USA
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25
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Liu XP, Wooltorton JRA, Gaboyard-Niay S, Yang FC, Lysakowski A, Eatock RA. Sodium channel diversity in the vestibular ganglion: NaV1.5, NaV1.8, and tetrodotoxin-sensitive currents. J Neurophysiol 2016; 115:2536-55. [PMID: 26936982 DOI: 10.1152/jn.00902.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 02/02/2016] [Indexed: 01/02/2023] Open
Abstract
Firing patterns differ between subpopulations of vestibular primary afferent neurons. The role of sodium (NaV) channels in this diversity has not been investigated because NaV currents in rodent vestibular ganglion neurons (VGNs) were reported to be homogeneous, with the voltage dependence and tetrodotoxin (TTX) sensitivity of most neuronal NaV channels. RT-PCR experiments, however, indicated expression of diverse NaV channel subunits in the vestibular ganglion, motivating a closer look. Whole cell recordings from acutely dissociated postnatal VGNs confirmed that nearly all neurons expressed NaV currents that are TTX-sensitive and have activation midpoints between -30 and -40 mV. In addition, however, many VGNs expressed one of two other NaV currents. Some VGNs had a small current with properties consistent with NaV1.5 channels: low TTX sensitivity, sensitivity to divalent cation block, and a relatively negative voltage range, and some VGNs showed NaV1.5-like immunoreactivity. Other VGNs had a current with the properties of NaV1.8 channels: high TTX resistance, slow time course, and a relatively depolarized voltage range. In two NaV1.8 reporter lines, subsets of VGNs were labeled. VGNs with NaV1.8-like TTX-resistant current also differed from other VGNs in the voltage dependence of their TTX-sensitive currents and in the voltage threshold for spiking and action potential shape. Regulated expression of NaV channels in primary afferent neurons is likely to selectively affect firing properties that contribute to the encoding of vestibular stimuli.
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Affiliation(s)
- Xiao-Ping Liu
- Speech and Hearing Bioscience and Technology Program, Harvard-Massachusetts Institute of Technology Health Sciences and Technology Program, Cambridge, Massachusetts; Eaton-Peabody Laboratories, Massachusetts Eye and Ear, and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
| | | | - Sophie Gaboyard-Niay
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois
| | - Fu-Chia Yang
- Dana-Farber Cancer Institute, Boston, Massachusetts; Department of Neurobiology, Harvard Medical School, Boston, Massachusetts; and
| | - Anna Lysakowski
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois; Department of Otolaryngology-Head and Neck Surgery, University of Illinois at Chicago, Chicago, Illinois
| | - Ruth Anne Eatock
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts; Department of Neurobiology, Harvard Medical School, Boston, Massachusetts; and Department of Otolaryngology-Head and Neck Surgery, University of Illinois at Chicago, Chicago, Illinois
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26
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Bonner TI. Should pharmacologists care about alternative splicing? IUPHAR Review 4. Br J Pharmacol 2014; 171:1231-40. [PMID: 24670145 DOI: 10.1111/bph.12526] [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: 08/26/2013] [Revised: 10/27/2013] [Accepted: 11/13/2013] [Indexed: 11/29/2022] Open
Abstract
Alternative splicing of mRNAs occurs in the majority of human genes, and most differential splicing results in different protein isoforms with possibly different functional properties. However, there are many reported splicing variations that may be quite rare, and not all combinatorially possible variants of a given gene are expressed at significant levels. Genes of interest to pharmacologists are frequently expressed at such low levels that they are not adequately represented in genome-wide studies of transcription. In single-gene studies, data are commonly available on the relative abundance and functional significance of individual alternatively spliced exons, but there are rarely data that quantitate the relative abundance of full-length transcripts and define which combinations of exons are significant. A number of criteria for judging the significance of splice variants and suggestions for their nomenclature are discussed.
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Affiliation(s)
- T I Bonner
- National Institute of Mental Health, Bethesda, MD, USA
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27
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Gangarossa G, Laffray S, Bourinet E, Valjent E. T-type calcium channel Cav3.2 deficient mice show elevated anxiety, impaired memory and reduced sensitivity to psychostimulants. Front Behav Neurosci 2014; 8:92. [PMID: 24672455 PMCID: PMC3957728 DOI: 10.3389/fnbeh.2014.00092] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 03/03/2014] [Indexed: 01/28/2023] Open
Abstract
The fine-tuning of neuronal excitability relies on a tight control of Ca2+ homeostasis. The low voltage-activated (LVA) T-type calcium channels (Cav3.1, Cav3.2 and Cav3.3 isoforms) play a critical role in regulating these processes. Despite their wide expression throughout the central nervous system, the implication of T-type Cav3.2 isoform in brain functions is still poorly characterized. Here, we investigate the effect of genetic ablation of this isoform in affective disorders, including anxiety, cognitive functions as well as sensitivity to drugs of abuse. Using a wide range of behavioral assays we show that genetic ablation of the cacna1h gene results in an anxiety-like phenotype, whereas novelty-induced locomotor activity is unaffected. Deletion of the T-type channel Cav3.2 also triggers impairment of hippocampus-dependent recognition memories. Acute and sensitized hyperlocomotion induced by d-amphetamine and cocaine are dramatically reduced in T-type Cav3.2 deficient mice. In addition, the administration of the T-type blocker TTA-A2 prevented the expression of locomotor sensitization observed in wildtype mice. In conclusion, our data reveal that physiological activity of this specific Ca2+ channel is required for affective and cognitive behaviors. Moreover, our work highlights the interest of T-type channel blockers as therapeutic strategies to reverse drug-associated alterations.
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Affiliation(s)
- Giuseppe Gangarossa
- Institut de Génomique Fonctionnelle, CNRS UMR-5203, Montpellier, France ; INSERM U661, Montpellier, France ; Universités de Montpellier 1 and 2 UMR-5203, Montpellier, France
| | - Sophie Laffray
- Institut de Génomique Fonctionnelle, CNRS UMR-5203, Montpellier, France ; INSERM U661, Montpellier, France ; Universités de Montpellier 1 and 2 UMR-5203, Montpellier, France ; Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle Montpellier, France
| | - Emmanuel Bourinet
- Institut de Génomique Fonctionnelle, CNRS UMR-5203, Montpellier, France ; INSERM U661, Montpellier, France ; Universités de Montpellier 1 and 2 UMR-5203, Montpellier, France ; Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle Montpellier, France
| | - Emmanuel Valjent
- Institut de Génomique Fonctionnelle, CNRS UMR-5203, Montpellier, France ; INSERM U661, Montpellier, France ; Universités de Montpellier 1 and 2 UMR-5203, Montpellier, France
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28
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Exposure to extremely low-frequency electromagnetic fields inhibits T-type calcium channels via AA/LTE4 signaling pathway. Cell Calcium 2014; 55:48-58. [DOI: 10.1016/j.ceca.2013.11.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 10/26/2013] [Accepted: 11/27/2013] [Indexed: 11/22/2022]
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29
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Eckle VS, Shcheglovitov A, Vitko I, Dey D, Yap CC, Winckler B, Perez-Reyes E. Mechanisms by which a CACNA1H mutation in epilepsy patients increases seizure susceptibility. J Physiol 2013; 592:795-809. [PMID: 24277868 DOI: 10.1113/jphysiol.2013.264176] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
T-type calcium channels play essential roles in regulating neuronal excitability and network oscillations in the brain. Mutations in the gene encoding Cav3.2 T-type Ca(2+) channels, CACNA1H, have been found in association with various forms of idiopathic generalized epilepsy. We and others have found that these mutations may influence neuronal excitability either by altering the biophysical properties of the channels or by increasing their surface expression. The goals of the present study were to investigate the excitability of neurons expressing Cav3.2 with the epilepsy mutation, C456S, and to elucidate the mechanisms by which it influences neuronal properties. We found that expression of the recombinant C456S channels substantially increased the excitability of cultured neurons by increasing the spontaneous firing rate and reducing the threshold for rebound burst firing. Additionally, we found that molecular determinants in the I-II loop (the region in which most childhood absence epilepsy-associated mutations are found) substantially increase the surface expression of T-channels but do not alter the relative distribution of channels into dendrites of cultured hippocampal neurons. Finally, we discovered that expression of C456S channels promoted dendritic growth and arborization. These effects were reversed to normal by either the absence epilepsy drug ethosuximide or a novel T-channel blocker, TTA-P2. As Ca(2+)-regulated transcription factors also increase dendritic development, we tested a transactivator trap assay and found that the C456S variant can induce changes in gene transcription. Taken together, our findings suggest that gain-of-function mutations in Cav3.2 T-type Ca(2+) channels increase seizure susceptibility by directly altering neuronal electrical properties and indirectly by changing gene expression.
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Affiliation(s)
- Veit-Simon Eckle
- Jordan Hall 800735, 1340 Jefferson Park Avenue, Charlottesville, VA 22908, USA.
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Lipscombe D, Allen SE, Toro CP. Control of neuronal voltage-gated calcium ion channels from RNA to protein. Trends Neurosci 2013; 36:598-609. [PMID: 23907011 DOI: 10.1016/j.tins.2013.06.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Revised: 06/27/2013] [Accepted: 06/28/2013] [Indexed: 12/22/2022]
Abstract
Voltage-gated calcium ion (CaV) channels convert neuronal activity into rapid intracellular calcium signals to trigger a myriad of cellular responses. Their involvement in major neurological and psychiatric diseases, and importance as therapeutic targets, has propelled interest in subcellular-specific mechanisms that align CaV channel activity to specific tasks. Here, we highlight recent studies that delineate mechanisms controlling the expression of CaV channels at the level of RNA and protein. We discuss the roles of RNA editing and alternative pre-mRNA splicing in generating CaV channel isoforms with activities specific to the demands of individual cells; the roles of ubiquitination and accessory proteins in regulating CaV channel expression; and the specific binding partners that contribute to both pre- and postsynaptic CaV channel function.
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Affiliation(s)
- Diane Lipscombe
- Department of Neuroscience, Brown University, Providence, RI 02912, USA.
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Gilmore AJ, Heblinski M, Reynolds A, Kassiou M, Connor M. Inhibition of human recombinant T-type calcium channels by N-arachidonoyl 5-HT. Br J Pharmacol 2013; 167:1076-88. [PMID: 22624680 DOI: 10.1111/j.1476-5381.2012.02047.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
BACKGROUND AND PURPOSE N-arachidonoyl 5-HT (NA-5HT) has anti-nociceptive effects reported to be mediated by inhibitory actions at the transient receptor potential vanilloid receptor 1 (TRPV1) and fatty acid amide hydrolase (FAAH). Anandamide and N-arachidonoyl dopamine (NA-DA), endocannabinoids that activate TRPV1 or are metabolized by FAAH, also inhibit T-type calcium channels (I(Ca) ). T-type I(Ca) are expressed by many excitable cells, including neurons involved in pain detection and processing. We sought to determine whether NA-5HT also modulates T-type I(Ca) . EXPERIMENTAL APPROACH Human recombinant T-type I(Ca) (Ca(V) 3 channels) expressed in HEK 293 cells were examined using standard whole-cell voltage-clamp electrophysiology techniques. KEY RESULTS NA-5HT completely inhibited Ca(V) 3 channels with a rank order of potency (pEC(50) ) of Ca(V) 3.1 (7.4) > Ca(V) 3.3 (6.8) ≥ Ca(V) 3.2 (6.6). The effects of NA-5HT were voltage-dependent, and it produced significant hyperpolarizing shifts in Ca(V) 3 steady-state inactivation relationships. NA-5HT selectively affected Ca(V) 3.3 channel kinetics. CONCLUSIONS AND IMPLICATIONS NA-5HT increases the steady-state inactivation of Ca(V) 3 channels, reducing the number of channels available to open during depolarization. These effects occur at NA-5HT concentrations at or below those at which NA-5HT affects TRPV1 receptors and FAAH. NA-5HT is one of the most potent inhibitors of T-type I(Ca) described to date, and it is likely to exert some of its biological effects, including anti-nociception, via inhibition of these channels.
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Affiliation(s)
- Andrew J Gilmore
- Pain Management Research Institute, Kolling Institute, University of Sydney at Royal North Hospital St Leonards, Australia
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Albéri L, Lintas A, Kretz R, Schwaller B, Villa AEP. The calcium-binding protein parvalbumin modulates the firing 1 properties of the reticular thalamic nucleus bursting neurons. J Neurophysiol 2013; 109:2827-41. [PMID: 23486206 DOI: 10.1152/jn.00375.2012] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The reticular thalamic nucleus (RTN) of the mouse is characterized by an overwhelming majority of GABAergic neurons receiving afferences from both the thalamus and the cerebral cortex and sending projections mainly on thalamocortical neurons. The RTN neurons express high levels of the "slow Ca(2+) buffer" parvalbumin (PV) and are characterized by low-threshold Ca(2+) currents, I(T). We performed extracellular recordings in ketamine/xylazine anesthetized mice in the rostromedial portion of the RTN. In the RTN of wild-type and PV knockout (PVKO) mice we distinguished four types of neurons characterized on the basis of their firing pattern: irregular firing (type I), medium bursting (type II), long bursting (type III), and tonically firing (type IV). Compared with wild-type mice, we observed in the PVKOs the medium bursting (type II) more frequently than the long bursting type and longer interspike intervals within the burst without affecting the number of spikes. This suggests that PV may affect the firing properties of RTN neurons via a mechanism associated with the kinetics of burst discharges. Ca(v)3.2 channels, which mediate the I(T) currents, were more localized to the somatic plasma membrane of RTN neurons in PVKO mice, whereas Ca(v)3.3 expression was similar in both genotypes. The immunoelectron microscopy analysis showed that Ca(v)3.2 channels were localized at active axosomatic synapses, thus suggesting that the differential localization of Ca(v)3.2 in the PVKOs may affect bursting dynamics. Cross-correlation analysis of simultaneously recorded neurons from the same electrode tip showed that about one-third of the cell pairs tended to fire synchronously in both genotypes, independent of PV expression. In summary, PV deficiency does not affect the functional connectivity between RTN neurons but affects the distribution of Ca(v)3.2 channels and the dynamics of burst discharges of RTN cells, which in turn regulate the activity in the thalamocortical circuit.
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Affiliation(s)
- Lavinia Albéri
- Unit of Anatomy, Department of Medicine, University of Fribourg, Fribourg, Switzerland
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Lopez-Charcas O, Rivera M, Gomora JC. Block of Human CaV3 Channels by the Diuretic Amiloride. Mol Pharmacol 2012; 82:658-67. [DOI: 10.1124/mol.112.078923] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Karmažínová M, Baumgart JP, Perez-Reyes E, Lacinová L. The voltage dependence of gating currents of the neuronal CA(v)3.3 channel is determined by the gating brake in the I-II loop. Pflugers Arch 2011; 461:461-8. [PMID: 21340458 DOI: 10.1007/s00424-011-0937-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 02/06/2011] [Accepted: 02/08/2011] [Indexed: 01/10/2023]
Abstract
Low-voltage-activated Ca(v)3 Ca(2+) channels have an activation threshold around -60 mV, which is lower than the activation threshold of other voltage-dependent calcium channels (VDCCs). The kinetics of their activation at membrane voltages just above the activation threshold is much slower than the activation kinetics of other VDCCs. It was demonstrated recently that the intracellular loop connecting repeats I and II of all three Ca(v)3 channels contains a so-called gating brake. Disruption of this brake yields channels that activate at even more hyperpolarized potentials with significantly accelerated kinetics. We have compared gating of a wild-type Ca(v)3.3 channel and a mutated ID12 channel, in which the putative gating brake at the proximal part of the I-II loop was removed. Voltage dependence of the gating current activation was shifted by 34.6 mV towards more hyperpolarized potentials in ID12 channel. ON-charge movement was significantly faster in the ID12 channel, while the kinetics of the off-charge was not altered by the mutation. We conclude that the putative gating brake in I-II loop hinders not only the opening of the conducting pore but also the activating movement of voltage-sensing S4 segments, stabilizing the channel in its closed state.
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Affiliation(s)
- Mária Karmažínová
- Institute of Molecular Physiology and Genetics, Centre of Excellence for Cardiovascular Research, Slovak Academy of Sciences, Bratislava, Slovakia
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35
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David LS, Garcia E, Cain SM, Thau E, Tyson JR, Snutch TP. Splice-variant changes of the Ca(V)3.2 T-type calcium channel mediate voltage-dependent facilitation and associate with cardiac hypertrophy and development. Channels (Austin) 2010; 4:375-89. [PMID: 20699644 DOI: 10.4161/chan.4.5.12874] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Low voltage-activated T-type calcium (Ca) channels contribute to the normal development of the heart and are also implicated in pathophysiological states such as cardiac hypertrophy. Functionally distinct T-type Ca channel isoforms can be generated by alternative splicing from each of three different T-type genes (Ca(V)3.1, Ca(V)3.2,Ca(V)3.3), although it remains to be described whether specific splice variants are associated with developmental states and pathological conditions. We aimed to identify and functionally characterize Ca(V)3.2 T-type Ca channel alternatively spliced variants from newborn animals and to compare with adult normotensive and spontaneously hypertensive rats (SHR). DNA sequence analysis of full-length Ca(V)3.2 cDNA generated from newborn heart tissue identified ten major regions of alternative splicing, the more common variants of which were analyzed by quantitative real-time PCR (qRT-PCR) and also subject to functional examination by whole-cell patch clamp. The main findings are that: (1) cardiac Ca(V)3.2 T-type Ca channels are subject to considerable alternative splicing, (2) there is preferential expression of Ca(V)3.2(-25) splice variant channels in newborn rat heart with a developmental shift in adult heart that results in approximately equal levels of expression of both (+25) and (-25) exon variants, (3) in the adult stage of hypertensive rats there is a both an increase in overall Ca(V)3.2 expression and a shift towards expression of Ca(V)3.2(+25) containing channels as the predominant form, and (4) alternative splicing confers a variant-specific voltage-dependent facilitation of Ca(V)3.2 channels. We conclude that Ca(V)3.2 alternative splicing generates significant T-type Ca channel structural and functional diversity with potential implications relevant to cardiac developmental and pathophysiological states.
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Strege PR, Sha L, Beyder A, Bernard CE, Perez-Reyes E, Evangelista S, Gibbons SJ, Szurszewski JH, Farrugia G. T-type Ca(2+) channel modulation by otilonium bromide. Am J Physiol Gastrointest Liver Physiol 2010; 298:G706-13. [PMID: 20203058 PMCID: PMC2867415 DOI: 10.1152/ajpgi.00437.2009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Antispasmodics are used clinically to treat a variety of gastrointestinal disorders by inhibition of smooth muscle contraction. The main pathway for smooth muscle Ca(2+) entry is through L-type channels; however, there is increasing evidence that T-type Ca(2+) channels also play a role in regulating contractility. Otilonium bromide, an antispasmodic, has previously been shown to inhibit L-type Ca(2+) channels and colonic contractile activity. The objective of this study was to determine whether otilonium bromide also inhibits T-type Ca(2+) channels. Whole cell currents were recorded by patch-clamp technique from HEK293 cells transfected with cDNAs encoding the T-type Ca(2+) channels, Ca(V)3.1 (alpha1G), Ca(V)3.2 (alpha1H), or Ca(V)3.3 (alpha1I) alpha subunits. Extracellular solution was exchanged with otilonium bromide (10(-8) to 10(-5) M). Otilonium bromide reversibly blocked all T-type Ca(2+) channels with a significantly greater affinity for Ca(V)3.3 than Ca(V)3.1 or Ca(V)3.2. Additionally, the drug slowed inactivation in Ca(V)3.1 and Ca(V)3.3. Inhibition of T-type Ca(2+) channels may contribute to inhibition of contractility by otilonium bromide. This may represent a new mechanism of action for antispasmodics and may contribute to the observed increased clinical effectiveness of antispasmodics compared with selective L-type Ca(2+) channel blockers.
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Affiliation(s)
- Peter R. Strege
- 1Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota;
| | - Lei Sha
- 1Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota;
| | - Arthur Beyder
- 1Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota;
| | - Cheryl E. Bernard
- 1Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota;
| | - Edward Perez-Reyes
- 2Department of Pharmacology, University of Virginia, Charlottesville, Virginia; and
| | | | - Simon J. Gibbons
- 1Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota;
| | - Joseph H. Szurszewski
- 1Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota;
| | - Gianrico Farrugia
- 1Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota;
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Kovács K, SÃk A, Ricketts C, Timofeev I. Subcellular distribution of low-voltage activated T-type Ca2+ channel subunits (Cav3.1 and Cav3.3) in reticular thalamic neurons of the cat. J Neurosci Res 2010; 88:448-60. [DOI: 10.1002/jnr.22200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Senatore A, Spafford JD. Transient and big are key features of an invertebrate T-type channel (LCav3) from the central nervous system of Lymnaea stagnalis. J Biol Chem 2010; 285:7447-58. [PMID: 20056611 DOI: 10.1074/jbc.m109.090753] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here we describe features of the first non-mammalian T-type calcium channel (LCa(v)3) expressed in vitro. This molluscan channel possesses combined biophysical properties that are reminiscent of all mammalian T-type channels. It exhibits T-type features such as "transient" kinetics, but the "tiny" label, usually associated with Ba(2+) conductance, is hard to reconcile with the "bigness" of this channel in many respects. LCa(v)3 is 25% larger than any voltage-gated ion channel expressed to date. It codes for a massive, 322-kDa protein that conducts large macroscopic currents in vitro. LCa(v)3 is also the most abundant Ca(2+) channel transcript in the snail nervous system. A window current at typical resting potentials appears to be at least as large as that reported for mammalian channels. This distant gene provides a unique perspective to analyze the structural, functional, drug binding, and evolutionary aspects of T-type channels.
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Affiliation(s)
- Adriano Senatore
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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39
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Kang HW, Vitko I, Lee SS, Perez-Reyes E, Lee JH. Structural determinants of the high affinity extracellular zinc binding site on Cav3.2 T-type calcium channels. J Biol Chem 2009; 285:3271-81. [PMID: 19940152 DOI: 10.1074/jbc.m109.067660] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(v)3.2 T-type channels contain a high affinity metal binding site for trace metals such as copper and zinc. This site is occupied at physiologically relevant concentrations of these metals, leading to decreased channel activity and pain transmission. A histidine at position 191 was recently identified as a critical determinant for both trace metal block of Ca(v)3.2 and modulation by redox agents. His(191) is found on the extracellular face of the Ca(v)3.2 channel on the IS3-S4 linker and is not conserved in other Ca(v)3 channels. Mutation of the corresponding residue in Ca(v)3.1 to histidine, Gln(172), significantly enhances trace metal inhibition, but not to the level observed in wild-type Ca(v)3.2, implying that other residues also contribute to the metal binding site. The goal of the present study is to identify these other residues using a series of chimeric channels. The key findings of the study are that the metal binding site is composed of a Asp-Gly-His motif in IS3-S4 and a second aspartate residue in IS2. These results suggest that metal binding stabilizes the closed conformation of the voltage-sensor paddle in repeat I, and thereby inhibits channel opening. These studies provide insight into the structure of T-type channels, and identify an extracellular motif that could be targeted for drug development.
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Affiliation(s)
- Ho-Won Kang
- Department of Life Science, Sogang University, Seoul 121-742, Korea
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40
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Ross HR, Gilmore AJ, Connor M. Inhibition of human recombinant T-type calcium channels by the endocannabinoid N-arachidonoyl dopamine. Br J Pharmacol 2009; 156:740-50. [PMID: 19226289 DOI: 10.1111/j.1476-5381.2008.00072.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE N-arachidonoyl dopamine (NADA) has complex effects on nociception mediated via cannabinoid CB(1) receptors and the transient receptor potential vanilloid receptor 1 (TRPV1). Anandamide, the prototypic CB(1)/TRPV1 agonist, also inhibits T-type voltage-gated calcium channel currents (I(Ca)). These channels are expressed by many excitable cells, including neurons involved in pain detection and processing. We sought to determine whether NADA and the prototypic arachidonoyl amino acid, N-arachidonoyl glycine (NAGly) modulate T-type I(Ca) EXPERIMENTAL APPROACH Human recombinant T-type I(Ca) (Ca(V)3 channels) expressed in HEK 293 cells and native mouse T-type I(Ca) were examined using standard whole-cell voltage clamp electrophysiology techniques. KEY RESULTS N-arachidonoyl dopamine completely inhibited Ca(V)3 channels with a rank order of potency (pEC(50)) of Ca(V)3.3 (6.45) > or = Ca(V)3.1 (6.29) > Ca(V)3.2 (5.95). NAGly (10 micromol.L(-1)) inhibited Ca(V)3 I(Ca) by approximately 50% or less. The effects of NADA and NAGly were voltage- but not use-dependent, and both compounds produced significant hyperpolarizing shifts in Ca(V)3 channel steady-state inactivation relationships. By contrast with anandamide, NADA and NAGly had modest effects on Ca(V)3 channel kinetics. Both NAGly and NADA inhibited native T-type I(Ca) in mouse sensory neurons. CONCLUSIONS AND IMPLICATIONS N-arachidonoyl dopamine and NAGly increase the steady-state inactivation of Ca(V)3 channels, reducing the number of channels available to open during depolarization. These effects occur at NADA concentrations at or below to those affecting CB(1) and TRPV1 receptors. Together with anandamide, the arachidonoyl neurotransmitter amides, NADA and NAGly, represent a new family of endogenous T-type I(Ca) modulators.
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Affiliation(s)
- Hamish R Ross
- Pain Management Research Institute, Kolling Institute, University of Sydney at Royal North Hospital, St Leonards, NSW, Australia, and
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41
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Transcriptional upregulation of Cav3.2 mediates epileptogenesis in the pilocarpine model of epilepsy. J Neurosci 2009; 28:13341-53. [PMID: 19052226 DOI: 10.1523/jneurosci.1421-08.2008] [Citation(s) in RCA: 155] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In both humans and animals, an insult to the brain can lead, after a variable latent period, to the appearance of spontaneous epileptic seizures that persist for life. The underlying processes, collectively referred to as epileptogenesis, include multiple structural and functional neuronal alterations. We have identified the T-type Ca(2+) channel Ca(v)3.2 as a central player in epileptogenesis. We show that a transient and selective upregulation of Ca(v)3.2 subunits on the mRNA and protein levels after status epilepticus causes an increase in cellular T-type Ca(2+) currents and a transitional increase in intrinsic burst firing. These functional changes are absent in mice lacking Ca(v)3.2 subunits. Intriguingly, the development of neuropathological hallmarks of chronic epilepsy, such as subfield-specific neuron loss in the hippocampal formation and mossy fiber sprouting, was virtually completely absent in Ca(v)3.2(-/-) mice. In addition, the appearance of spontaneous seizures was dramatically reduced in these mice. Together, these data establish transcriptional induction of Ca(v)3.2 as a critical step in epileptogenesis and neuronal vulnerability.
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Perez-Reyes E, Van Deusen AL, Vitko I. Molecular pharmacology of human Cav3.2 T-type Ca2+ channels: block by antihypertensives, antiarrhythmics, and their analogs. J Pharmacol Exp Ther 2008; 328:621-7. [PMID: 18974361 DOI: 10.1124/jpet.108.145672] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Antihypertensive drugs of the "calcium channel blocker" or "calcium antagonist" class have been used to establish the physiological role of L-type Ca(2+) channels in vascular smooth muscle. In contrast, there has been limited progress on the pharmacology T-type Ca(2+) channels. T-type channels play a role in cardiac pacemaking, aldosterone secretion, and renal hemodynamics, leading to the hypothesis that mixed T- and L-type blockers may have therapeutic advantages over selective L-type blockers. The goal of this study was to identify compounds that block the Ca(v)3.2 T-type channel with high affinity, focusing on two classes of compounds: phenylalkylamines (e.g., mibefradil) and dihydropyridines (e.g., efonidipine). Compounds were tested using a validated Ca(2+) influx assay into a cell line expressing recombinant Ca(v)3.2 channels. This study identified four clinically approved antihypertensive drugs (efonidipine, felodipine, isradipine, and nitrendipine) as potent T-channel blockers (IC(50) < 3 microM). In contrast, other widely prescribed dihydropyridines, such as amlodipine and nifedipine, were 10-fold less potent, making them a more appropriate choice in research studies on the role of L-type currents. In summary, the present results support the notion that many available antihypertensive drugs block a substantial fraction of T-current at therapeutically relevant concentrations, contributing to their mechanism of action.
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Affiliation(s)
- Edward Perez-Reyes
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia, USA.
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43
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Ross HR, Napier I, Connor M. Inhibition of recombinant human T-type calcium channels by Delta9-tetrahydrocannabinol and cannabidiol. J Biol Chem 2008; 283:16124-34. [PMID: 18390906 PMCID: PMC3259625 DOI: 10.1074/jbc.m707104200] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Revised: 03/27/2008] [Indexed: 11/06/2022] Open
Abstract
Delta(9)-Tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most prevalent biologically active constituents of Cannabis sativa. THC is the prototypic cannabinoid CB1 receptor agonist and is psychoactive and analgesic. CBD is also analgesic, but it is not a CB1 receptor agonist. Low voltage-activated T-type calcium channels, encoded by the Ca(V)3 gene family, regulate the excitability of many cells, including neurons involved in nociceptive processing. We examined the effects of THC and CBD on human Ca(V)3 channels stably expressed in human embryonic kidney 293 cells and T-type channels in mouse sensory neurons using whole-cell, patch clamp recordings. At moderately hyperpolarized potentials, THC and CBD inhibited peak Ca(V)3.1 and Ca(V)3.2 currents with IC(50) values of approximately 1 mum but were less potent on Ca(V)3.3 channels. THC and CBD inhibited sensory neuron T-type channels by about 45% at 1 mum. However, in recordings made from a holding potential of -70 mV, 100 nm THC or CBD inhibited more than 50% of the peak Ca(V)3.1 current. THC and CBD produced a significant hyperpolarizing shift in the steady state inactivation potentials for each of the Ca(V)3 channels, which accounts for inhibition of channel currents. Additionally, THC caused a modest hyperpolarizing shift in the activation of Ca(V)3.1 and Ca(V)3.2. THC but not CBD slowed Ca(V)3.1 and Ca(V)3.2 deactivation and inactivation kinetics. Thus, THC and CBD inhibit Ca(V)3 channels at pharmacologically relevant concentrations. However, THC, but not CBD, may also increase the amount of calcium entry following T-type channel activation by stabilizing open states of the channel.
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MESH Headings
- Analgesics, Non-Narcotic/chemistry
- Analgesics, Non-Narcotic/pharmacology
- Animals
- Calcium/metabolism
- Calcium Channels, T-Type/metabolism
- Cannabidiol/chemistry
- Cannabidiol/pharmacology
- Cannabis/chemistry
- Cell Line
- Dose-Response Relationship, Drug
- Dronabinol/chemistry
- Dronabinol/pharmacology
- Gene Expression
- Humans
- Kinetics
- Membrane Potentials/drug effects
- Mice
- Neurons, Afferent/cytology
- Neurons, Afferent/physiology
- Receptor, Cannabinoid, CB1/agonists
- Receptor, Cannabinoid, CB1/genetics
- Receptor, Cannabinoid, CB1/metabolism
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Affiliation(s)
| | | | - Mark Connor
- Pain Management Research Institute, Kolling Institute, University of
Sydney at Royal North Shore Hospital, St Leonards, New South Wales 2065,
Australia
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44
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Xie X, Van Deusen AL, Vitko I, Babu DA, Davies LA, Huynh N, Cheng H, Yang N, Barrett PQ, Perez-Reyes E. Validation of High Throughput Screening Assays Against Three Subtypes of Cav3 T-Type Channels Using Molecular and Pharmacologic Approaches. Assay Drug Dev Technol 2007; 5:191-203. [PMID: 17477828 DOI: 10.1089/adt.2006.054] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
T-type Ca(2+) channels encoded by voltage-gated Ca(2+) channel (Ca(v)) 3.1, 3.2, and 3.3 genes play important physiological roles and serve as therapeutic targets for neurological and cardiovascular disorders. Currently there is no selective T-channel blocker. To screen for such a blocker, we developed three stable cell lines expressing human recombinant Ca(v)3.1, 3.2, or 3.3 channels and then examined their usefulness in high throughput screens. All three cell lines displayed an increase in intracellular Ca(2+) in response to changes in extracellular Ca(2+) as detected with Ca(2+)-sensitive dyes using a fluorometric imaging plate reader (FLIPR [Molecular Devices, Sunnyvale, CA] or FlexStation [Molecular Devices]). The signal-to-noise ratio was 2-4. Co-expression of Ca(v)3.2 with a mouse leak K(+) channel, which by virtue of being open at rest hyperpolarizes the cell membrane, blocked the fluorescent signal. Co-addition of KCl to these cells induced a Ca(2+) signal that was similar to that observed in the cell line expressing Ca(v)3.2 alone. These results confirm that the detection of intracellular Ca(2+) increase in cells expressing Ca(v)3.2 alone results from Ca(2+) entry through channels that are open at the resting membrane potential of each cell line (i.e., window currents). Testing known drugs on Ca(v)3 channels showed that block could be reliably detected using the FlexStation assay, FLIPR assay, or voltage clamp recordings using the IonWorks HT system (Molecular Devices). These results support the use of the FLIPR window current assay for primary drug screening and high throughput patch recordings for secondary screening of novel T-channel blockers.
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Affiliation(s)
- Xinmin Xie
- Bioscience Division, SRI International, Menlo Park, CA 94250, USA.
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Coste B, Crest M, Delmas P. Pharmacological dissection and distribution of NaN/Nav1.9, T-type Ca2+ currents, and mechanically activated cation currents in different populations of DRG neurons. J Gen Physiol 2007; 129:57-77. [PMID: 17190903 PMCID: PMC2151607 DOI: 10.1085/jgp.200609665] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Accepted: 12/04/2006] [Indexed: 02/04/2023] Open
Abstract
Low voltage-activated (LVA) T-type Ca(2+) (I(Ca)T) and NaN/Nav1.9 currents regulate DRG neurons by setting the threshold for the action potential. Although alterations in these channels have been implicated in a variety of pathological pain states, their roles in processing sensory information remain poorly understood. Here, we carried out a detailed characterization of LVA currents in DRG neurons by using a method for better separation of NaN/Nav1.9 and I(Ca)T currents. NaN/Nav1.9 was inhibited by inorganic I(Ca) blockers as follows (IC(50), microM): La(3+) (46) > Cd(2+) (233) > Ni(2+) (892) and by mibefradil, a non-dihydropyridine I(Ca)T antagonist. Amiloride, however, a preferential Cav3.2 channel blocker, had no effects on NaN/Nav1.9 current. Using these discriminative tools, we showed that NaN/Nav1.9, Cav3.2, and amiloride- and Ni(2+)-resistant I(Ca)T (AR-I(Ca)T) contribute differentially to LVA currents in distinct sensory cell populations. NaN/Nav1.9 carried LVA currents into type-I (CI) and type-II (CII) small nociceptors and medium-Adelta-like nociceptive cells but not in low-threshold mechanoreceptors, including putative Down-hair (D-hair) and Aalpha/beta cells. Cav3.2 predominated in CII-nociceptors and in putative D-hair cells. AR-I(Ca)T was restricted to CII-nociceptors, putative D-hair cells, and Aalpha/beta-like cells. These cell types distinguished by their current-signature displayed different types of mechanosensitive channels. CI- and CII-nociceptors displayed amiloride-sensitive high-threshold mechanical currents with slow or no adaptation, respectively. Putative D-hair and Aalpha/beta-like cells had low-threshold mechanical currents, which were distinguished by their adapting kinetics and sensitivity to amiloride. Thus, subspecialized DRG cells express specific combinations of LVA and mechanosensitive channels, which are likely to play a key role in shaping responses of DRG neurons transmitting different sensory modalities.
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Affiliation(s)
- Bertrand Coste
- Laboratoire de Neurophysiologie Cellulaire, Centre National de la Recherche Scientifique, UMR 6150, Faculté de Médecine, IFR Jean Roche, 13916 Marseille Cedex 20, France
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46
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Traboulsie A, Chemin J, Chevalier M, Quignard JF, Nargeot J, Lory P. Subunit-specific modulation of T-type calcium channels by zinc. J Physiol 2006; 578:159-71. [PMID: 17082234 PMCID: PMC2075129 DOI: 10.1113/jphysiol.2006.114496] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Zinc (Zn2+) functions as a signalling molecule in the nervous system and modulates many ionic channels. In this study, we have explored the effects of Zn2+ on recombinant T-type calcium channels (CaV3.1, CaV3.2 and CaV3.3). Using tsA-201 cells, we demonstrate that CaV3.2 current (IC50, 0.8 microm) is significantly more sensitive to Zn2+ than are CaV3.1 and CaV3.3 currents (IC50, 80 microm and approximately 160 microm, respectively). This inhibition of CaV3 currents is associated with a shift to more negative membrane potentials of both steady-state inactivation for CaV3.1, CaV3.2 and CaV3.3 and steady-state activation for CaV3.1 and CaV3.3 currents. We also document changes in kinetics, especially a significant slowing of the inactivation kinetics for CaV3.1 and CaV3.3, but not for CaV3.2 currents. Notably, deactivation kinetics are significantly slowed for CaV3.3 current (approximately 100-fold), but not for CaV3.1 and CaV3.2 currents. Consequently, application of Zn2+ results in a significant increase in CaV3.3 current in action potential clamp experiments, while CaV3.1 and CaV3.2 currents are significantly reduced. In neuroblastoma NG 108-15 cells, the duration of CaV3.3-mediated action potentials is increased upon Zn2+ application, indicating further that Zn2+ behaves as a CaV3.3 channel opener. These results demonstrate that Zn2+ exhibits differential modulatory effects on T-type calcium channels, which may partly explain the complex features of Zn2+ modulation of the neuronal excitability in normal and disease states.
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Affiliation(s)
- Achraf Traboulsie
- Département de Physiologie, Institut de Génomique Fonctionnelle (IGF), CNRS UMR 5203, INSERM U661, Universités de Montpellier I and II, 141 rue de la Cardonille, 34094 Montpellier cedex 05, France
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47
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Abstract
The voltage-gated calcium channels (VGCCs) are a large and functionally diverse group of ion channels found throughout the central nervous system (CNS) and the periphery. Neuronal functions include the control of neurotransmitter release and neuronal excitability in important pain pathways. In the current review we will give an overview of the data that has been generated in support of these channels performing a pivotal role in the pain pathway.
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Affiliation(s)
- Valentin K Gribkoff
- Knopp Neurosciences, Inc., 100 Technology Drive, Suite 400, Pittsburgh, PA 15219, USA.
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48
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Talavera K, Nilius B. Evidence for common structural determinants of activation and inactivation in T-type Ca2+ channels. Pflugers Arch 2006; 453:189-201. [PMID: 16955311 DOI: 10.1007/s00424-006-0129-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Revised: 05/30/2006] [Accepted: 06/22/2006] [Indexed: 12/19/2022]
Abstract
One of the most distinctive features of T-type Ca(2+) channels is their fast inactivation. Recent structure-function studies indicate that the rate of macroscopic inactivation of these channels is influenced by several structural components, including intracellular linkers, transmembrane segments, and pore loops. The macroscopic inactivation of T-type channels is partially coupled to activation. It is therefore possible that changes in the rate of macroscopic inactivation after alteration in the structure of these channels might actually result from changes in activation kinetics. In this study, we use kinetic simulations to illustrate how the alteration of the rate of channel activation may lead to changes in the rate of macroscopic inactivation. By examining data pooled from several structure-function studies we demonstrate that gating modifications induced by alteration in the channel structure unveils a correlation between the time constants of macroscopic inactivation and activation. This analysis underscores the relevance of considering the inactivation-activation coupling when analyzing the structural determinants of T-type channel inactivation. Furthermore, we demonstrate that slow-inactivating mutants, with modifications in the IIIS6 segment and the proximal C terminus, display significant alterations in the voltage dependencies of activation and deactivation with respect to the wild type channel Ca(V)3.1. Our results indicate that common structures, most likely the S6 transmembrane segments, are involved in the conformational changes occurring during both channel activation and inactivation.
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Affiliation(s)
- Karel Talavera
- Laboratorium voor Fysiologie, KU Leuven, Campus Gasthuisberg, LEUVEN, Belgium.
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Wang J, Zhang Y, Liang J, Pan H, Wu H, Xu K, Liu X, Jiang Y, Shen Y, Wu X. CACNA1I is not associated with childhood absence epilepsy in the Chinese Han population. Pediatr Neurol 2006; 35:187-90. [PMID: 16939858 DOI: 10.1016/j.pediatrneurol.2006.03.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Revised: 02/02/2006] [Accepted: 03/14/2006] [Indexed: 10/24/2022]
Abstract
This study investigated whether the T-type calcium channel gene CACNA1I causes susceptibility in the Chinese Han population to childhood absence epilepsy, a form of idiopathic generalized seizure disorder. For this investigation, we searched for mutations in the 35 exons and exon-intron boundaries of the CACNA1I gene in 50 Han Chinese patients with childhood absence epilepsy. Seventeen single nucleotide polymorphisms were identified in the 35 exons. Using six single nucleotide polymorphisms as markers, the allele and genotype distributions of all of the identified single nucleotide polymorphisms were examined; there was no significant difference between the childhood absence epilepsy cases and the control groups. Thus, we do not consider the CACNA1I gene to be an important susceptibility gene for childhood absence epilepsy in the Chinese Han population.
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Affiliation(s)
- Juli Wang
- Department of Pediatrics, Peking University First Hospital, Beijing, PR China
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50
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Choi S, Na HS, Kim J, Lee J, Lee S, Kim D, Park J, Chen CC, Campbell KP, Shin HS. Attenuated pain responses in mice lacking Ca(V)3.2 T-type channels. GENES BRAIN AND BEHAVIOR 2006; 6:425-31. [PMID: 16939637 DOI: 10.1111/j.1601-183x.2006.00268.x] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Although T-type Ca(2+) channels are implicated in nociception, the function of specific subtypes has not been well defined. Here, we compared pain susceptibility in mice lacking Ca(V)3.2 subtype of T-type Ca(2+) channels (Ca(V)3.2(-/-)) with wild-type littermates in various behavioral models of pain to explore the roles of Ca(V)3.2 in the processing of noxious stimuli in vivo. In acute mechanical, thermal and chemical pain tests, Ca(V)3.2(-/-) mice showed decreased pain responses compared to wild-type mice. Ca(V)3.2(-/-) mice also displayed attenuated pain responses to tonic noxious stimuli such as intraperitoneal injections of irritant agents and intradermal injections of formalin. In spinal nerve ligation-induced neuropathic pain, however, behavioral responses of Ca(V)3.2(-/-) mice were not different from those of wild-type mice. The present study reveals that the Ca(V)3.2 subtype of T-type Ca(2+) channels are important in the peripheral processing of noxious signals, regardless of modality, duration or affected tissue type.
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Affiliation(s)
- S Choi
- Center for Neural Science, Division of Life Sciences, Korea Institute of Science and Technology, Seoul, Korea
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