1
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del Rivero Morfin PJ, Kochiss AL, Liedl KR, Flucher BE, Fernández-Quintero ML, Ben-Johny M. Asymmetric contribution of a selectivity filter gate in triggering inactivation of CaV1.3 channels. J Gen Physiol 2024; 156:e202313365. [PMID: 38175169 PMCID: PMC10771039 DOI: 10.1085/jgp.202313365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 10/08/2023] [Accepted: 12/14/2023] [Indexed: 01/05/2024] Open
Abstract
Voltage-dependent and Ca2+-dependent inactivation (VDI and CDI, respectively) of CaV channels are two biologically consequential feedback mechanisms that fine-tune Ca2+ entry into neurons and cardiomyocytes. Although known to be initiated by distinct molecular events, how these processes obstruct conduction through the channel pore remains poorly defined. Here, focusing on ultrahighly conserved tryptophan residues in the interdomain interfaces near the selectivity filter of CaV1.3, we demonstrate a critical role for asymmetric conformational changes in mediating VDI and CDI. Specifically, mutagenesis of the domain III-IV interface, but not others, enhanced VDI. Molecular dynamics simulations demonstrate that mutations in distinct selectivity filter interfaces differentially impact conformational flexibility. Furthermore, mutations in distinct domains preferentially disrupt CDI mediated by the N- versus C-lobes of CaM, thus uncovering a scheme of structural bifurcation of CaM signaling. These findings highlight the fundamental importance of the asymmetric arrangement of the pseudotetrameric CaV pore domain for feedback inhibition.
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Affiliation(s)
| | - Audrey L. Kochiss
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - Klaus R. Liedl
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innsbruck, Austria
| | - Bernhard E. Flucher
- Department of Physiology and Medical Physics, Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | | | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
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2
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del Rivero Morfin PJ, Kochiss AL, Liedl KR, Flucher BE, Fernández-Quintero ML, Ben-Johny M. Asymmetric Contribution of a Selectivity Filter Gate in Triggering Inactivation of Ca V1.3 Channels. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.21.558864. [PMID: 37790368 PMCID: PMC10542529 DOI: 10.1101/2023.09.21.558864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Voltage-dependent and Ca2+-dependent inactivation (VDI and CDI, respectively) of CaV channels are two biologically consequential feedback mechanisms that fine-tune Ca2+ entry into neurons and cardiomyocytes. Although known to be initiated by distinct molecular events, how these processes obstruct conduction through the channel pore remains poorly defined. Here, focusing on ultra-highly conserved tryptophan residues in the inter-domain interfaces near the selectivity filter of CaV1.3, we demonstrate a critical role for asymmetric conformational changes in mediating VDI and CDI. Specifically, mutagenesis of the domain III-IV interface, but not others, enhanced VDI. Molecular dynamics simulations demonstrate that mutations in distinct selectivity filter interfaces differentially impact conformational flexibility. Furthermore, mutations in distinct domains preferentially disrupt CDI mediated by the N- versus C-lobes of CaM, thus uncovering a scheme of structural bifurcation of CaM signaling. These findings highlight the fundamental importance of the asymmetric arrangement of the pseudo-tetrameric CaV pore domain for feedback inhibition.
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Affiliation(s)
| | - Audrey L. Kochiss
- Department of Physiology and Cellular Biophysics, Columbia University
| | - Klaus R. Liedl
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innsbruck, Austria
| | - Bernhard E. Flucher
- Institute of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | | | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, Columbia University
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3
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Allam S, Levenson-Palmer R, Chia Chang Z, Kaur S, Cernuda B, Raman A, Booth A, Dobbins S, Suppa G, Yang J, Buraei Z. Inactivation influences the extent of inhibition of voltage-gated Ca +2 channels by Gem-implications for channelopathies. Front Physiol 2023; 14:1155976. [PMID: 37654674 PMCID: PMC10466392 DOI: 10.3389/fphys.2023.1155976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 07/21/2023] [Indexed: 09/02/2023] Open
Abstract
Voltage-gated Ca2+ channels (VGCC) directly control muscle contraction and neurotransmitter release, and slower processes such as cell differentiation, migration, and death. They are potently inhibited by RGK GTP-ases (Rem, Rem2, Rad, and Gem/Kir), which decrease Ca2+ channel membrane expression, as well as directly inhibit membrane-resident channels. The mechanisms of membrane-resident channel inhibition are difficult to study because RGK-overexpression causes complete or near complete channel inhibition. Using titrated levels of Gem expression in Xenopus oocytes to inhibit WT P/Q-type calcium channels by ∼50%, we show that inhibition is dependent on channel inactivation. Interestingly, fast-inactivating channels, including Familial Hemiplegic Migraine mutants, are more potently inhibited than WT channels, while slow-inactivating channels, such as those expressed with the Cavβ2a auxiliary subunit, are spared. We found similar results in L-type channels, and, remarkably, Timothy Syndrome mutant channels were insensitive to Gem inhibition. Further results suggest that RGKs slow channel recovery from inactivation and further implicate RGKs as likely modulating factors in channelopathies.
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Affiliation(s)
- Salma Allam
- Department of Biology, Pace University, New York, NY, United States
| | - Rose Levenson-Palmer
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | | | - Sukhjinder Kaur
- Department of Biology, Pace University, New York, NY, United States
| | - Bryan Cernuda
- Department of Biology, Pace University, New York, NY, United States
| | - Ananya Raman
- Department of Biology, Pace University, New York, NY, United States
| | - Audrey Booth
- Department of Biology, Pace University, New York, NY, United States
| | - Scott Dobbins
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | - Gabrielle Suppa
- Department of Biology, Pace University, New York, NY, United States
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | - Zafir Buraei
- Department of Biology, Pace University, New York, NY, United States
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4
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Gao Y, Xu S, Cui X, Xu H, Qiu Y, Wei Y, Dong Y, Zhu B, Peng C, Liu S, Zhang XC, Sun J, Huang Z, Zhao Y. Molecular insights into the gating mechanisms of voltage-gated calcium channel Ca V2.3. Nat Commun 2023; 14:516. [PMID: 36720859 PMCID: PMC9889812 DOI: 10.1038/s41467-023-36260-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 01/23/2023] [Indexed: 02/02/2023] Open
Abstract
High-voltage-activated R-type CaV2.3 channel plays pivotal roles in many physiological activities and is implicated in epilepsy, convulsions, and other neurodevelopmental impairments. Here, we determine the high-resolution cryo-electron microscopy (cryo-EM) structure of human CaV2.3 in complex with the α2δ1 and β1 subunits. The VSDII is stabilized in the resting state. Electrophysiological experiments elucidate that the VSDII is not required for channel activation, whereas the other VSDs are essential for channel opening. The intracellular gate is blocked by the W-helix. A pre-W-helix adjacent to the W-helix can significantly regulate closed-state inactivation (CSI) by modulating the association and dissociation of the W-helix with the gate. Electrostatic interactions formed between the negatively charged domain on S6II, which is exclusively conserved in the CaV2 family, and nearby regions at the alpha-interacting domain (AID) and S4-S5II helix are identified. Further functional analyses indicate that these interactions are critical for the open-state inactivation (OSI) of CaV2 channels.
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Affiliation(s)
- Yiwei Gao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Shuai Xu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China
| | - Xiaoli Cui
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.,Chinese Institute for Brain Research, Beijing, China
| | - Hao Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Yunlong Qiu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yiqing Wei
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yanli Dong
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Boling Zhu
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Chao Peng
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China
| | - Shiqi Liu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China
| | - Xuejun Cai Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jianyuan Sun
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.,Sino-Danish College, University of Chinese Academy of Sciences, Beijing, China.,The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China
| | - Zhuo Huang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China. .,IDG/McGovern Institute for Brain Research, Peking University, Beijing, China.
| | - Yan Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China. .,State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, China. .,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.
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5
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Zong P, Yue L. Regulation of Presynaptic Calcium Channels. ADVANCES IN NEUROBIOLOGY 2023; 33:171-202. [PMID: 37615867 DOI: 10.1007/978-3-031-34229-5_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Voltage-gated calcium channels (VGCCs), especially Cav2.1 and Cav2.2, are the major mediators of Ca2+ influx at the presynaptic membrane in response to neuron excitation, thereby exerting a predominant control on synaptic transmission. To guarantee the timely and precise release of neurotransmitters at synapses, the activity of presynaptic VGCCs is tightly regulated by a variety of factors, including auxiliary subunits, membrane potential, G protein-coupled receptors (GPCRs), calmodulin (CaM), Ca2+-binding proteins (CaBP), protein kinases, various interacting proteins, alternative splicing events, and genetic variations.
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Affiliation(s)
- Pengyu Zong
- Department of Cell Biology, Calhoun Cardiology Center, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Lixia Yue
- Department of Cell Biology, Calhoun Cardiology Center, University of Connecticut School of Medicine, Farmington, CT, USA.
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6
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Abstract
The CACNA1C gene encodes the pore-forming subunit of the CaV1.2 L-type Ca2+ channel, a critical component of membrane physiology in multiple tissues, including the heart, brain, and immune system. As such, mutations altering the function of these channels have the potential to impact a wide array of cellular functions. The first mutations identified within CACNA1C were shown to cause a severe, multisystem disorder known as Timothy syndrome (TS), which is characterized by neurodevelopmental deficits, long-QT syndrome, life-threatening cardiac arrhythmias, craniofacial abnormalities, and immune deficits. Since this initial description, the number and variety of disease-associated mutations identified in CACNA1C have grown tremendously, expanding the range of phenotypes observed in affected patients. CACNA1C channelopathies are now known to encompass multisystem phenotypes as described in TS, as well as more selective phenotypes where patients may exhibit predominantly cardiac or neurological symptoms. Here, we review the impact of genetic mutations on CaV1.2 function and the resultant physiological consequences.
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Affiliation(s)
- Kevin G Herold
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - John W Hussey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Ivy E Dick
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.
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7
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Bamgboye MA, Herold KG, Vieira DC, Traficante MK, Rogers PJ, Ben-Johny M, Dick IE. CaV1.2 channelopathic mutations evoke diverse pathophysiological mechanisms. J Gen Physiol 2022; 154:e202213209. [PMID: 36167061 PMCID: PMC9524202 DOI: 10.1085/jgp.202213209] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 08/09/2022] [Accepted: 09/13/2022] [Indexed: 01/17/2023] Open
Abstract
The first pathogenic mutation in CaV1.2 was identified in 2004 and was shown to cause a severe multisystem disorder known as Timothy syndrome (TS). The mutation was localized to the distal S6 region of the channel, a region known to play a major role in channel activation. TS patients suffer from life-threatening cardiac symptoms as well as significant neurodevelopmental deficits, including autism spectrum disorder (ASD). Since this discovery, the number and variety of mutations identified in CaV1.2 have grown tremendously, and the distal S6 regions remain a frequent locus for many of these mutations. While the majority of patients harboring these mutations exhibit cardiac symptoms that can be well explained by known pathogenic mechanisms, the same cannot be said for the ASD or neurodevelopmental phenotypes seen in some patients, indicating a gap in our understanding of the pathogenesis of CaV1.2 channelopathies. Here, we use whole-cell patch clamp, quantitative Ca2+ imaging, and single channel recordings to expand the known mechanisms underlying the pathogenesis of CaV1.2 channelopathies. Specifically, we find that mutations within the S6 region can exert independent and separable effects on activation, voltage-dependent inactivation (VDI), and Ca2+-dependent inactivation (CDI). Moreover, the mechanisms underlying the CDI effects of these mutations are varied and include altered channel opening and possible disruption of CDI transduction. Overall, these results provide a structure-function framework to conceptualize the role of S6 mutations in pathophysiology and offer insight into the biophysical defects associated with distinct clinical manifestations.
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Affiliation(s)
- Moradeke A. Bamgboye
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Kevin G. Herold
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Daiana C.O. Vieira
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Maria K. Traficante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Philippa J. Rogers
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Manu Ben-Johny
- Department of Physiology and Biophysics, Columbia University, New York, NY
| | - Ivy E. Dick
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
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8
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Yeow SQZ, Loh KWZ, Soong TW. Calcium Channel Splice Variants and Their Effects in Brain and Cardiovascular Function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:67-86. [DOI: 10.1007/978-981-16-4254-8_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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9
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Marcantoni A, Calorio C, Hidisoglu E, Chiantia G, Carbone E. Cav1.2 channelopathies causing autism: new hallmarks on Timothy syndrome. Pflugers Arch 2020; 472:775-789. [PMID: 32621084 DOI: 10.1007/s00424-020-02430-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 06/23/2020] [Accepted: 06/26/2020] [Indexed: 02/07/2023]
Abstract
Cav1.2 L-type calcium channels play key roles in long-term synaptic plasticity, sensory transduction, muscle contraction, and hormone release. De novo mutations in the gene encoding Cav1.2 (CACNA1C) causes two forms of Timothy syndrome (TS1, TS2), characterized by a multisystem disorder inclusive of cardiac arrhythmias, long QT, autism, and adrenal gland dysfunction. In both TS1 and TS2, the missense mutation G406R is on the alternatively spliced exon 8 and 8A coding for the IS6-helix of Cav1.2 and is responsible for the penetrant form of autism in most TS individuals. The mutation causes specific gain-of-function changes to Cav1.2 channel gating: a "leftward shift" of voltage-dependent activation, reduced voltage-dependent inactivation, and a "leftward shift" of steady-state inactivation. How this occurs and how Cav1.2 gating changes alter neuronal firing and synaptic plasticity is still largely unexplained. Trying to better understanding the molecular basis of Cav1.2 gating dysfunctions leading to autism, here, we will present and discuss the properties of recently reported typical and atypical TS phenotypes and the effective gating changes exhibited by missense mutations associated with long QTs without extracardiac symptoms, unrelated to TS. We will also discuss new emerging views achieved from using iPSCs-derived neurons and the newly available autistic TS2-neo mouse model, both appearing promising for understanding neuronal mistuning in autistic TS patients. We will also analyze and describe recent proposals of molecular pathways that might explain mistuned Ca2+-mediated and Ca2+-independent excitation-transcription signals to the nucleus. Briefly, we will also discuss possible pharmacological approaches to treat autism associated with L-type channelopathies.
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Affiliation(s)
- Andrea Marcantoni
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy
| | - Chiara Calorio
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy
| | - Enis Hidisoglu
- Department of Biophysics, Faculty of Medicine, Akdeniz University, Antalya, Turkey
| | - Giuseppe Chiantia
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy
| | - Emilio Carbone
- Department of Drug Science, Laboratory of Cellular and Molecular Neuroscience, N.I.S. Centre, Corso Raffaello 30, 10125, Torino, Italy.
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10
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Balleza D, Rosas ME, Romero-Romero S. Voltage vs. Ligand I: Structural basis of the intrinsic flexibility of S3 segment and its significance in ion channel activation. Channels (Austin) 2019; 13:455-476. [PMID: 31647368 PMCID: PMC6833973 DOI: 10.1080/19336950.2019.1674242] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
We systematically predict the internal flexibility of the S3 segment, one of the most mobile elements in the voltage-sensor domain. By analyzing the primary amino acid sequences of V-sensor containing proteins, including Hv1, TPC channels and the voltage-sensing phosphatases, we established correlations between the local flexibility and modes of activation for different members of the VGIC superfamily. Taking advantage of the structural information available, we also assessed structural aspects to understand the role played by the flexibility of S3 during the gating of the pore. We found that S3 flexibility is mainly determined by two specific regions: (1) a short NxxD motif in the N-half portion of the helix (S3a), and (2) a short sequence at the beginning of the so-called paddle motif where the segment has a kink that, in some cases, divide S3 into two distinct helices (S3a and S3b). A good correlation between the flexibility of S3 and the reported sensitivity to temperature and mechanical stretch was found. Thus, if the channel exhibits high sensitivity to heat or membrane stretch, local S3 flexibility is low. On the other hand, high flexibility of S3 is preferentially associated to channels showing poor heat and mechanical sensitivities. In contrast, we did not find any apparent correlation between S3 flexibility and voltage or ligand dependence. Overall, our results provide valuable insights into the dynamics of channel-gating and its modulation.
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Affiliation(s)
- Daniel Balleza
- Departamento de Química ICET, Universidad Autónoma de Guadalajara , Zapopan Jalisco , Mexico
| | - Mario E Rosas
- Departamento de Química ICET, Universidad Autónoma de Guadalajara , Zapopan Jalisco , Mexico
| | - Sergio Romero-Romero
- Facultad de Medicina, Departamento de Bioquímica, Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico. Current address: Department of Biochemistry, University of Bayreuth , Bayreuth , Germany
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11
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Korkosh VS, Kiselev AM, Mikhaylov EN, Kostareva AA, Zhorov BS. Atomic Mechanisms of Timothy Syndrome-Associated Mutations in Calcium Channel Cav1.2. Front Physiol 2019; 10:335. [PMID: 30984024 PMCID: PMC6449482 DOI: 10.3389/fphys.2019.00335] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 03/13/2019] [Indexed: 12/22/2022] Open
Abstract
Timothy syndrome (TS) is a very rare multisystem disorder almost exclusively associated with mutations G402S and G406R in helix IS6 of Cav1.2. Recently, mutations R518C/H in helix IIS0 of the voltage sensing domain II (VSD-II) were described as a cause of cardiac-only TS. The three mutations are known to decelerate voltage-dependent inactivation (VDI). Here, we report a case of cardiac-only TS caused by mutation R518C. To explore possible impact of the three mutations on interdomain contacts, we modeled channel Cav1.2 using as templates Class Ia and Class II cryo-EM structures of presumably inactivated channel Cav1.1. In both models, R518 and several other residues in VSD-II donated H-bonds to the IS6-linked α1-interaction domain (AID). We further employed steered Monte Carlo energy minimizations to move helices S4–S5, S5, and S6 from the inactivated-state positions to those seen in the X-ray structures of the open and closed NavAb channel. In the open-state models, positions of AID and VSD-II were similar to those in Cav1.1. In the closed-state models, AID moved along the β subunit (Cavβ) toward the pore axis and shifted AID-bound VSD-II. In all the models R518 retained strong contacts with AID. Our calculations suggest that conformational changes in VSD-II upon its deactivation would shift AID along Cavβ toward the pore axis. The AID-linked IS6 would bend at flexible G402 and G406, facilitating the activation gate closure. Mutations R518C/H weakened the IIS0-AID contacts and would retard the AID shift. Mutations G406R and G402S stabilized the open state and would resist the pore closure. Several Cav1.2 mutations associated with long QT syndromes are consistent with this proposition. Our results provide a mechanistic rationale for the VDI deceleration caused by TS-associated mutations and suggest targets for further studies of calcium channelopathies.
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Affiliation(s)
- Vyacheslav S Korkosh
- Almazov National Medical Research Centre, Saint Petersburg, Russia.,I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Artem M Kiselev
- Almazov National Medical Research Centre, Saint Petersburg, Russia
| | | | - Anna A Kostareva
- Almazov National Medical Research Centre, Saint Petersburg, Russia.,Department of Woman and Child Health, Karolinska Institute, Stockholm, Sweden
| | - Boris S Zhorov
- Almazov National Medical Research Centre, Saint Petersburg, Russia.,I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg, Russia.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
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12
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Ozawa J, Ohno S, Saito H, Saitoh A, Matsuura H, Horie M. A novel CACNA1C mutation identified in a patient with Timothy syndrome without syndactyly exerts both marked loss- and gain-of-function effects. HeartRhythm Case Rep 2018; 4:273-277. [PMID: 30023270 PMCID: PMC6050422 DOI: 10.1016/j.hrcr.2018.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Junichi Ozawa
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan.,Department of Pediatrics, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Seiko Ohno
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan.,Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Otsu, Japan
| | - Hideki Saito
- Department of Cardiology, Seirei Hamamatsu General Hospital, Hamamatsu, Japan
| | - Akihiko Saitoh
- Department of Pediatrics, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Hiroshi Matsuura
- Department of Physiology, Shiga University of Medical Science, Otsu, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
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13
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Lyons JJ, Stotz SC, Chovanec J, Liu Y, Lewis KL, Nelson C, DiMaggio T, Jones N, Stone KD, Sung H, Biesecker LG, Colicos MA, Milner JD. A common haplotype containing functional CACNA1H variants is frequently coinherited with increased TPSAB1 copy number. Genet Med 2017; 20:503-512. [DOI: 10.1038/gim.2017.136] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 06/27/2017] [Indexed: 12/19/2022] Open
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14
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Lead poisoning: acute exposure of the heart to lead ions promotes changes in cardiac function and Cav1.2 ion channels. Biophys Rev 2017; 9:807-825. [PMID: 28836190 DOI: 10.1007/s12551-017-0303-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/28/2017] [Indexed: 01/02/2023] Open
Abstract
Lead ions (Pb2+) possess characteristics similar to Ca2+. Because of this and its redox capabilities, lead causes different toxic effects. The neurotoxic effects have been well documented; however, the toxic effects on cardiac tissues remain allusive. We utilized isolated guinea pig hearts and measured the effects of Pb2+ on their contractility and excitability. Acute exposure to extracellular Pb2+ had a negative inotropic effect and increased diastolic tension. The speed of contraction and relaxation were affected, though the effects were more dramatic on the speed of contraction. Excitability was also altered. Heart beat frequency increased and later diminished after lead ion exposure. Pro-arrhytmic events, such as early after-depolarization and a reduction of the action potential plateau, were also observed. In isolated cardiomyocytes and tsA 201 cells, extracellular lead blocked currents through Cav1.2 channels, diminished their activation, and enhanced their fast inactivation, negatively affecting their gating currents. Thus, Pb2+ was cardiotoxic and reduced cardiac contractility, making the heart prone to arrhythmias. This was due, in part, to Pb2+ effects on the Cav1.2 channels; however, other channels, transporters or pathways may also be involved. Acute cardiotoxic effects were observed at Pb2+ concentrations achievable during acute lead poisoning. The results suggest how Cav1.2 gating can be affected by divalent cations, such as Pb2, and also suggest a more thorough evaluation of heart function in individuals affected by lead poisoning.
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Xiao J, Wang T, Li P, Liu R, Li Q, Bi K. Development of two step liquid-liquid extraction tandem UHPLC-MS/MS method for the simultaneous determination of Ginkgo flavonoids, terpene lactones and nimodipine in rat plasma: Application to the pharmacokinetic study of the combination of Ginkgo biloba dispersible tablets and Nimodipine tablets. J Chromatogr B Analyt Technol Biomed Life Sci 2016; 1028:33-41. [PMID: 27318642 DOI: 10.1016/j.jchromb.2016.06.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 04/29/2016] [Accepted: 06/03/2016] [Indexed: 12/26/2022]
Abstract
A sensitive, reliable and accurate UHPLC-MS/MS method has been firstly established and validated for the simultaneous quantification of ginkgo flavonoids, terpene lactones and nimodipine in rat plasma after oral administration of Ginkgo biloba dispersible tablets, Nimodipine tablets and the combination of the both, respectively. The plasma samples were extracted by two step liquid-liquid extraction, nimodipine was extracted by hexane-ether (3:1, v/v) at the first step, after that ginkgo flavonoids and terpene lactones were extracted by ethyl acetate. Then the analytes were successfully separated by running gradient elution with the mobile phase consisting of 0.1% formic acid in water and methanol at a flow rate of 0.6mL/min. The detection of the analytes was performed on a UHPLC-MS/MS system with turbo ion spray source in the negative ion and multiple reaction monitoring (MRM) mode. The calibration curves for the determination of all the analytes showed good linearity (R(2)>0.99), and the lower limits of quantification were 0.50-4.00ng/mL. Intra-day and inter-day precisions were in the range of 3.6%-9.2% and 3.2%-13.1% for all the analytes. The mean extraction recoveries of the analytes were within 69.82%-103.5% and the matrix were within 82.8%-110.0%. The validated method had been successfully applied to compare the pharmacokinetic parameters of ginkgo flavonoids, terpene lactones and nimodipine in rat plasma after oral administration of Ginkgo biloba dispersible tablets, Nimodipine tablets with the combination of the both. There were no statistically significant differences on the pharmacokinetic behaviors of all the analytes between the combined and single administration groups. Results showed that the combination of the two agents may avoid dosage adjustments in clinic and the combination is more convenient as well as efficient on different pathogenesis of cerebral ischemia.
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Affiliation(s)
- Jie Xiao
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang 110016, China
| | - Tianyang Wang
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang 110016, China
| | - Pei Li
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang 110016, China
| | - Ran Liu
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang 110016, China
| | - Qing Li
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang 110016, China
| | - Kaishun Bi
- School of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang 110016, China.
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Limpitikul WB, Dick IE, Ben-Johny M, Yue DT. An autism-associated mutation in CaV1.3 channels has opposing effects on voltage- and Ca(2+)-dependent regulation. Sci Rep 2016; 6:27235. [PMID: 27255217 PMCID: PMC4891671 DOI: 10.1038/srep27235] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 05/13/2016] [Indexed: 01/07/2023] Open
Abstract
CaV1.3 channels are a major class of L-type Ca(2+) channels which contribute to the rhythmicity of the heart and brain. In the brain, these channels are vital for excitation-transcription coupling, synaptic plasticity, and neuronal firing. Moreover, disruption of CaV1.3 function has been associated with several neurological disorders. Here, we focus on the de novo missense mutation A760G which has been linked to autism spectrum disorder (ASD). To explore the role of this mutation in ASD pathogenesis, we examined the effects of A760G on CaV1.3 channel gating and regulation. Introduction of the mutation severely diminished the Ca(2+)-dependent inactivation (CDI) of CaV1.3 channels, an important feedback system required for Ca(2+) homeostasis. This reduction in CDI was observed in two major channel splice variants, though to different extents. Using an allosteric model of channel gating, we found that the underlying mechanism of CDI reduction is likely due to enhanced channel opening within the Ca(2+)-inactivated mode. Remarkably, the A760G mutation also caused an opposite increase in voltage-dependent inactivation (VDI), resulting in a multifaceted mechanism underlying ASD. When combined, these regulatory deficits appear to increase the intracellular Ca(2+) concentration, thus potentially disrupting neuronal development and synapse formation, ultimately leading to ASD.
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Affiliation(s)
- Worawan B Limpitikul
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Ivy E Dick
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Manu Ben-Johny
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
| | - David T Yue
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
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Voltage-gated calcium channels: Determinants of channel function and modulation by inorganic cations. Prog Neurobiol 2015; 129:1-36. [PMID: 25817891 DOI: 10.1016/j.pneurobio.2014.12.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 12/15/2014] [Accepted: 12/27/2014] [Indexed: 11/20/2022]
Abstract
Voltage-gated calcium channels (VGCCs) represent a key link between electrical signals and non-electrical processes, such as contraction, secretion and transcription. Evolved to achieve high rates of Ca(2+)-selective flux, they possess an elaborate mechanism for selection of Ca(2+) over foreign ions. It has been convincingly linked to competitive binding in the pore, but the fundamental question of how this is reconcilable with high rates of Ca(2+) transfer remains unanswered. By virtue of their similarity to Ca(2+), polyvalent cations can interfere with the function of VGCCs and have proven instrumental in probing the mechanisms underlying selective permeation. Recent emergence of crystallographic data on a set of Ca(2+)-selective model channels provides a structural framework for permeation in VGCCs, and warrants a reconsideration of their diverse modulation by polyvalent cations, which can be roughly separated into three general mechanisms: (I) long-range interactions with charged regions on the surface, affecting the local potential sensed by the channel or influencing voltage-sensor movement by repulsive forces (electrostatic effects), (II) short-range interactions with sites in the ion-conducting pathway, leading to physical obstruction of the channel (pore block), and in some cases (III) short-range interactions with extracellular binding sites, leading to non-electrostatic modifications of channel gating (allosteric effects). These effects, together with the underlying molecular modifications, provide valuable insights into the function of VGCCs, and have important physiological and pathophysiological implications. Allosteric suppression of some of the pore-forming Cavα1-subunits (Cav2.3, Cav3.2) by Zn(2+) and Cu(2+) may play a major role for the regulation of excitability by endogenous transition metal ions. The fact that these ions can often traverse VGCCs can contribute to the detrimental intracellular accumulation of metal ions following excessive release of endogenous Cu(2+) and Zn(2+) or exposure to non-physiological toxic metal ions.
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Simms BA, Zamponi GW. Neuronal voltage-gated calcium channels: structure, function, and dysfunction. Neuron 2014; 82:24-45. [PMID: 24698266 DOI: 10.1016/j.neuron.2014.03.016] [Citation(s) in RCA: 396] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Voltage-gated calcium channels are the primary mediators of depolarization-induced calcium entry into neurons. There is great diversity of calcium channel subtypes due to multiple genes that encode calcium channel α1 subunits, coassembly with a variety of ancillary calcium channel subunits, and alternative splicing. This allows these channels to fulfill highly specialized roles in specific neuronal subtypes and at particular subcellular loci. While calcium channels are of critical importance to brain function, their inappropriate expression or dysfunction gives rise to a variety of neurological disorders, including, pain, epilepsy, migraine, and ataxia. This Review discusses salient aspects of voltage-gated calcium channel function, physiology, and pathophysiology.
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Affiliation(s)
- Brett A Simms
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada.
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Simms BA, Souza IA, Zamponi GW. A novel calmodulin site in the Cav1.2 N-terminus regulates calcium-dependent inactivation. Pflugers Arch 2013; 466:1793-803. [DOI: 10.1007/s00424-013-1423-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 12/05/2013] [Accepted: 12/06/2013] [Indexed: 01/04/2023]
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Two mechanistically distinct effects of dihydropyridine nifedipine on CaV1.2 L-type Ca²⁺ channels revealed by Timothy syndrome mutation. Eur J Pharmacol 2012; 685:15-23. [PMID: 22554770 DOI: 10.1016/j.ejphar.2012.04.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Revised: 04/10/2012] [Accepted: 04/12/2012] [Indexed: 01/28/2023]
Abstract
Dihydropyridine Ca(2+) channel antagonists (DHPs) block Ca(V)1.2 L-type Ca(2+) channels (LTCCs) by stabilizing their voltage-dependent inactivation (VDI); however, it is still not clear how DHPs allosterically interact with the kinetically distinct (fast and slow) VDI. Thus, we analyzed the effect of a prototypical DHP, nifedipine on LTCCs with or without the Timothy syndrome mutation that resides in the I-II linker (L(I)-(II)) of Ca(V)1.2 subunits and impairs VDI. Whole-cell Ba(2+) currents mediated by rabbit Ca(V)1.2 with or without the Timothy mutation (G436R) (analogous to the human G406R mutation) were analyzed in the presence and absence of nifedipine. In the absence of nifedipine, the mutation significantly impaired fast closed- and open-state VDI (CSI and OSI) at -40 and 0 mV, respectively, but did not affect channels' kinetics at -100 mV. Nifedipine equipotently blocked these channels at -80 mV. In wild-type LTCCs, nifedipine promoted fast CSI and OSI at -40 and 0 mV and promoted or stabilized slow CSI at -40 and -100 mV, respectively. In LTCCs with the mutation, nifedipine resumed the impaired fast CSI and OSI at -40 and 0 mV, respectively, and had the same effect on slow CSI as in wild-type LTCCs. Therefore, nifedipine has two mechanistically distinct effects on LTCCs: the promotion of fast CSI/OSI caused by L(I-II) at potentials positive to the sub-threshold potential and the promotion or stabilization of slow CSI caused by different mechanisms at potentials negative to the sub-threshold potential.
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Complex distribution patterns of voltage-gated calcium channel α-subunits in the spiral ganglion. Hear Res 2011; 278:52-68. [PMID: 21281707 DOI: 10.1016/j.heares.2011.01.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 01/21/2011] [Accepted: 01/21/2011] [Indexed: 01/10/2023]
Abstract
As with other elements of the peripheral auditory system, spiral ganglion neurons display specializations that vary as a function of location along the tonotopic axis. Previous work has shown that voltage-gated K(+) channels and synaptic proteins show graded changes in their density that confers rapid responsiveness to neurons in the high frequency, basal region of the cochlea and slower, more maintained responsiveness to neurons in the low frequency, apical region of the cochlea. In order to understand how voltage-gated calcium channels (VGCCs) may contribute to these diverse phenotypes, we identified the VGCC α-subunits expressed in the ganglion, investigated aspects of Ca(2+)-dependent neuronal firing patterns, and mapped the intracellular and intercellular distributions of seven VGCC α-subunits in the spiral ganglion in vitro. Initial experiments with qRT-PCR showed that eight of the ten known VGCC α-subunits were expressed in the ganglion and electrophysiological analysis revealed firing patterns that were consistent with the presence of both LVA and HVA Ca(2+) channels. Moreover, we were able to study seven of the α-subunits with immunocytochemistry, and we found that all were present in spiral ganglion neurons, three of which were neuron-specific (Ca(V)1.3, Ca(V)2.2, and Ca(V)3.3). Further characterization of neuron-specific α-subunits showed that Ca(V)1.3 and Ca(V)3.3 were tonotopically-distributed, whereas Ca(V)2.2 was uniformly distributed in apical and basal neurons. Multiple VGCC α-subunits were also immunolocalized to Schwann cells, having distinct intracellular localizations, and, significantly, appearing to distinguish putative compact (Ca(V)2.3, Ca(V)3.1) from loose (Ca(V)1.2) myelin. Electrophysiological evaluation of spiral ganglion neurons in the presence of TEA revealed Ca(2+) plateau potentials with slopes that varied proportionately with the cochlear region from which neurons were isolated. Because afterhyperpolarizations were minimal or absent under these conditions, we hypothesize that differential density and/or kinetics of one or more of the VGCC α-subunits could account for observed tonotopic differences. These experiments have set the stage for defining the clear multiplicity of functional control in neurons and Schwann cells of the spiral ganglion.
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Bähring R, Covarrubias M. Mechanisms of closed-state inactivation in voltage-gated ion channels. J Physiol 2010; 589:461-79. [PMID: 21098008 DOI: 10.1113/jphysiol.2010.191965] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Inactivation of voltage-gated ion channels is an intrinsic auto-regulatory process necessary to govern the occurrence and shape of action potentials and establish firing patterns in excitable tissues. Inactivation may occur from the open state (open-state inactivation, OSI) at strongly depolarized membrane potentials, or from pre-open closed states (closed-state inactivation, CSI) at hyperpolarized and modestly depolarized membrane potentials. Voltage-gated Na(+), K(+), Ca(2+) and non-selective cationic channels utilize both OSI and CSI. Whereas there are detailed mechanistic descriptions of OSI, much less is known about the molecular basis of CSI. Here, we review evidence for CSI in voltage-gated cationic channels (VGCCs) and recent findings that shed light on the molecular mechanisms of CSI in voltage-gated K(+) (Kv) channels. Particularly, complementary observations suggest that the S4 voltage sensor, the S4S5 linker and the main S6 activation gate are instrumental in the installment of CSI in Kv4 channels. According to this hypothesis, the voltage sensor may adopt a distinct conformation to drive CSI and, depending on the stability of the interactions between the voltage sensor and the pore domain, a closed-inactivated state results from rearrangements in the selectivity filter or failure of the activation gate to open. Kv4 channel CSI may efficiently exploit the dynamics of the subthreshold membrane potential to regulate spiking properties in excitable tissues.
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Affiliation(s)
- Robert Bähring
- Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
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23
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Abstract
Calcium regulates a wide spectrum of physiological processes such as heartbeat, muscle contraction, neuronal communication, hormone release, cell division, and gene transcription. Major entryways for Ca(2+) in excitable cells are high-voltage activated (HVA) Ca(2+) channels. These are plasma membrane proteins composed of several subunits, including α(1), α(2)δ, β, and γ. Although the principal α(1) subunit (Ca(v)α(1)) contains the channel pore, gating machinery and most drug binding sites, the cytosolic auxiliary β subunit (Ca(v)β) plays an essential role in regulating the surface expression and gating properties of HVA Ca(2+) channels. Ca(v)β is also crucial for the modulation of HVA Ca(2+) channels by G proteins, kinases, and the Ras-related RGK GTPases. New proteins have emerged in recent years that modulate HVA Ca(2+) channels by binding to Ca(v)β. There are also indications that Ca(v)β may carry out Ca(2+) channel-independent functions, including directly regulating gene transcription. All four subtypes of Ca(v)β, encoded by different genes, have a modular organization, consisting of three variable regions, a conserved guanylate kinase (GK) domain, and a conserved Src-homology 3 (SH3) domain, placing them into the membrane-associated guanylate kinase (MAGUK) protein family. Crystal structures of Ca(v)βs reveal how they interact with Ca(v)α(1), open new research avenues, and prompt new inquiries. In this article, we review the structure and various biological functions of Ca(v)β, with both a historical perspective as well as an emphasis on recent advances.
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Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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Salvador-Recatalà V, Greenberg RM. The N terminus of a schistosome beta subunit regulates inactivation and current density of a Cav2 channel. J Biol Chem 2010; 285:35878-88. [PMID: 20826800 DOI: 10.1074/jbc.m110.144725] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The β subunit of high voltage-activated Ca(2+) (Ca(v)) channels targets the pore-forming α(1) subunit to the plasma membrane and tunes the biophysical phenotype of the Ca(v) channel complex. We used a combination of molecular biology and whole-cell patch clamp to investigate the functional role of a long N-terminal polyacidic motif (NPAM) in a Ca(v)β subunit of the human parasite Schistosoma mansoni (β(Sm)), a motif that does not occur in other known Ca(v)β subunits. When expressed in human embryonic kidney cells stably expressing Ca(v)2.3, β(Sm) accelerates Ca(2+)/calmodulin-independent inactivation of Ca(v)2.3. Deleting the first 44 amino acids of β(Sm), a region that includes NPAM, significantly slows the predominant time constant of inactivation (τ(fast)) under conditions that prevent Ca(2+)/CaM-dependent inactivation (β(Sm): τ(fast) = 66 ms; β(SmΔ2-44): τ(fast) = 111 ms, p < 0.01). Interestingly, deleting the amino acids that are N-terminal to NPAM (2-24 or 2-17) results in faster inactivation than with an intact N terminus (τ(fast) = 42 ms with β(SmΔ2-17); τ(fast) = 40 ms with β(SmΔ2-24), p < 0.01). This suggests that NPAM is the structural determinant for accelerating Ca(2+)/calmodulin-independent inactivation. We also created three chimeric subunits that contain the first 44 amino acids of β(Sm) attached to mammalian β(1b), β(2a), and β(3) subunits. For any given mammalian β subunit, inactivation was faster if it contained the N terminus of β(Sm) than if it did not. Co-expression of the mammalian α(2)δ-1 subunit resulted in doubling of the inactivation rate, but the effects of NPAM persisted. Thus, it appears that the schistosome Ca(v) channel complex has acquired a new function that likely contributes to reducing the amount of Ca(2+) that enters the cells in vivo. This feature is of potential interest as a target for new antihelminthics.
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Affiliation(s)
- Vicenta Salvador-Recatalà
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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Tadross MR, Ben Johny M, Yue DT. Molecular endpoints of Ca2+/calmodulin- and voltage-dependent inactivation of Ca(v)1.3 channels. ACTA ACUST UNITED AC 2010; 135:197-215. [PMID: 20142517 PMCID: PMC2828906 DOI: 10.1085/jgp.200910308] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ca2+/calmodulin- and voltage-dependent inactivation (CDI and VDI) comprise vital prototypes of Ca2+ channel modulation, rich with biological consequences. Although the events initiating CDI and VDI are known, their downstream mechanisms have eluded consensus. Competing proposals include hinged-lid occlusion of channels, selectivity filter collapse, and allosteric inhibition of the activation gate. Here, novel theory predicts that perturbations of channel activation should alter inactivation in distinctive ways, depending on which hypothesis holds true. Thus, we systematically mutate the activation gate, formed by all S6 segments within CaV1.3. These channels feature robust baseline CDI, and the resulting mutant library exhibits significant diversity of activation, CDI, and VDI. For CDI, a clear and previously unreported pattern emerges: activation-enhancing mutations proportionately weaken inactivation. This outcome substantiates an allosteric CDI mechanism. For VDI, the data implicate a “hinged lid–shield” mechanism, similar to a hinged-lid process, with a previously unrecognized feature. Namely, we detect a “shield” in CaV1.3 channels that is specialized to repel lid closure. These findings reveal long-sought downstream mechanisms of inactivation and may furnish a framework for the understanding of Ca2+ channelopathies involving S6 mutations.
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Affiliation(s)
- Michael R Tadross
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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26
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Liao P, Soong TW. CaV1.2 channelopathies: from arrhythmias to autism, bipolar disorder, and immunodeficiency. Pflugers Arch 2009; 460:353-9. [PMID: 19916019 DOI: 10.1007/s00424-009-0753-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 10/22/2009] [Accepted: 10/23/2009] [Indexed: 11/28/2022]
Abstract
Mutations of human CaV1.2 channel gene were identified only recently. The gain-of-function mutations were found at two mutually exclusive exons in patients with Timothy syndrome (TS). These patients exhibit prolonged QT interval and lethal cardiac arrhythmias. In contrast, the loss-of-function mutations of CaV1.2 channel in patients with Brugada syndrome produce short QT interval that could result in sudden cardiac death. TS patients also suffer from multi-organ dysfunction that includes neurological disorder such as autism and mental retardation reflecting the wide tissue distribution of CaV1.2 channel. Mutations found on different mutually exclusive exons determine the severity of the disease. Unexpectedly, TS patients may develop recurrent infections and bronchitis that suggests a role of CaV1.2 channel in the immune system. Furthermore, recent reports revealed a linkage of CaV1.2 channel polymorphism with multiple central nervous system disorders including bipolar disorder, depression, and schizophrenia. Here, we will discuss how alternative splicing modulates CaV1.2 channelopathy and the role of CaV1.2 channel in both excitable and non-excitable tissues.
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Affiliation(s)
- Ping Liao
- National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433, Singapore.
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Findeisen F, Minor DL. Disruption of the IS6-AID linker affects voltage-gated calcium channel inactivation and facilitation. ACTA ACUST UNITED AC 2009; 133:327-43. [PMID: 19237593 PMCID: PMC2654080 DOI: 10.1085/jgp.200810143] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Two processes dominate voltage-gated calcium channel (CaV) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The CaVβ/CaVα1-I-II loop and Ca2+/calmodulin (CaM)/CaVα1–C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6–α-interaction domain (AID) linker provides a rigid connection between the pore and CaVβ/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate CaV1.2 (L-type) and CaV2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt CaVβ/I-II association sharply decelerate CDI and reduce a second Ca2+/CaM/CaVα1–C-terminal–mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, CaVβ and the IS6-AID linker, are essential for calcium-dependent modulation, and that both CaVβ-dependent and CaM-dependent components couple to the pore by a common mechanism requiring CaVβ and an intact IS6-AID linker.
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Affiliation(s)
- Felix Findeisen
- Cardiovascular Research Institute, Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA
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Dresviannikov AV, Page KM, Leroy J, Pratt WS, Dolphin AC. Determinants of the voltage dependence of G protein modulation within calcium channel beta subunits. Pflugers Arch 2008; 457:743-56. [PMID: 18651169 PMCID: PMC2686087 DOI: 10.1007/s00424-008-0549-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Accepted: 06/17/2008] [Indexed: 11/21/2022]
Abstract
CaVβ subunits of voltage-gated calcium channels contain two conserved domains, a src-homology-3 (SH3) domain and a guanylate kinase-like (GK) domain with an intervening HOOK domain. We have shown in a previous study that, although Gβγ-mediated inhibitory modulation of CaV2.2 channels did not require the interaction of a CaVβ subunit with the CaVα1 subunit, when such interaction was prevented by a mutation in the α1 subunit, G protein modulation could not be removed by a large depolarization and showed voltage-independent properties (Leroy et al., J Neurosci 25:6984–6996, 2005). In this study, we have investigated the ability of mutant and truncated CaVβ subunits to support voltage-dependent G protein modulation in order to determine the minimal domain of the CaVβ subunit that is required for this process. We have coexpressed the CaVβ subunit constructs with CaV2.2 and α2δ-2, studied modulation by the activation of the dopamine D2 receptor, and also examined basal tonic modulation. Our main finding is that the CaVβ subunit GK domains, from either β1b or β2, are sufficient to restore voltage dependence to G protein modulation. We also found that the removal of the variable HOOK region from β2a promotes tonic voltage-dependent G protein modulation. We propose that the absence of the HOOK region enhances Gβγ binding affinity, leading to greater tonic modulation by basal levels of Gβγ. This tonic modulation requires the presence of an SH3 domain, as tonic modulation is not supported by any of the CaVβ subunit GK domains alone.
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Affiliation(s)
- Andriy V Dresviannikov
- Laboratory of Cellular and Molecular Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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Cens T, Leyris JP, Charnet P. Introduction into Cav2.1 of the homologous mutation of Cav1.2 causing the Timothy syndrome questions the role of V421 in the phenotypic definition of P-type Ca2+ channel. Pflugers Arch 2008; 457:417-30. [DOI: 10.1007/s00424-008-0534-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Revised: 04/17/2008] [Accepted: 05/15/2008] [Indexed: 01/06/2023]
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The Timothy syndrome mutation differentially affects voltage- and calcium-dependent inactivation of CaV1.2 L-type calcium channels. Proc Natl Acad Sci U S A 2008; 105:2157-62. [PMID: 18250309 DOI: 10.1073/pnas.0710501105] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Calcium entry into excitable cells is an important physiological signal, supported by and highly sensitive to the activity of voltage-gated Ca2+ channels. After membrane depolarization, Ca2+ channels first open but then undergo various forms of negative feedback regulation including voltage- and calcium-dependent inactivation (VDI and CDI, respectively). Inactivation of Ca2+ channel activity is perturbed in a rare yet devastating disorder known as Timothy syndrome (TS), whose features include autism or autism spectrum disorder along with severe cardiac arrhythmia and developmental abnormalities. Most cases of TS arise from a sporadic single nucleotide change that generates a mutation (G406R) in the pore-forming subunit of the L-type Ca2+ channel Ca(V)1.2. We found that the TS mutation powerfully and selectively slows VDI while sparing or possibly speeding the kinetics of CDI. The deceleration of VDI was observed when the L-type channels were expressed with beta1 subunits prominent in brain, as well as beta2 subunits of importance for the heart. Dissociation of VDI and CDI was further substantiated by measurements of Ca2+ channel gating currents and by analysis of another channel mutation (I1624A) that hastens VDI, acting upstream of the step involving Gly406. As highlighted by the TS mutation, CDI does not proceed to completeness but levels off at approximately 50%, consistent with a change in gating modes and not an absorbing inactivation process. Thus, the TS mutation offers a unique perspective on mechanisms of inactivation as well as a promising starting point for exploring the underlying pathophysiology of autism.
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Yamashita M, Navarro-Borelly L, McNally BA, Prakriya M. Orai1 mutations alter ion permeation and Ca2+-dependent fast inactivation of CRAC channels: evidence for coupling of permeation and gating. ACTA ACUST UNITED AC 2008; 130:525-40. [PMID: 17968026 PMCID: PMC2151669 DOI: 10.1085/jgp.200709872] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ca(2+) entry through store-operated Ca(2+) release-activated Ca(2+) (CRAC) channels is an essential trigger for lymphocyte activation and proliferation. The recent identification of Orai1 as a key CRAC channel pore subunit paves the way for understanding the molecular basis of Ca(2+) selectivity, ion permeation, and regulation of CRAC channels. Previous Orai1 mutagenesis studies have indicated that a set of conserved acidic amino acids in trans membrane domains I and III and in the I-II loop (E106, E190, D110, D112, D114) are essential for the CRAC channel's high Ca(2+) selectivity. To further dissect the contribution of Orai1 domains important for ion permeation and channel gating, we examined the role of these conserved acidic residues on pore geometry, properties of Ca(2+) block, and channel regulation by Ca(2+). We find that alteration of the acidic residues lowers Ca(2+) selectivity and results in striking increases in Cs(+) permeation. This is likely the result of enlargement of the unusually narrow pore of the CRAC channel, thus relieving steric hindrance for Cs(+) permeation. Ca(2+) binding to the selectivity filter appears to be primarily affected by changes in the apparent on-rate, consistent with a rate-limiting barrier for Ca(2+) binding. Unexpectedly, the mutations diminish Ca(2+)-mediated fast inactivation, a key mode of CRAC channel regulation. The decrease in fast inactivation in the mutant channels correlates with the decrease in Ca(2+) selectivity, increase in Cs(+) permeability, and enlargement of the pore. We propose that the structural elements involved in ion permeation overlap with those involved in the gating of CRAC channels.
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Affiliation(s)
- Megumi Yamashita
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
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Kiyonaka S, Wakamori M, Miki T, Uriu Y, Nonaka M, Bito H, Beedle AM, Mori E, Hara Y, De Waard M, Kanagawa M, Itakura M, Takahashi M, Campbell KP, Mori Y. RIM1 confers sustained activity and neurotransmitter vesicle anchoring to presynaptic Ca2+ channels. Nat Neurosci 2007; 10:691-701. [PMID: 17496890 PMCID: PMC2687938 DOI: 10.1038/nn1904] [Citation(s) in RCA: 176] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Accepted: 04/02/2007] [Indexed: 12/20/2022]
Abstract
The molecular organization of presynaptic active zones is important for the neurotransmitter release that is triggered by depolarization-induced Ca2+ influx. Here, we demonstrate a previously unknown interaction between two components of the presynaptic active zone, RIM1 and voltage-dependent Ca2+ channels (VDCCs), that controls neurotransmitter release in mammalian neurons. RIM1 associated with VDCC beta-subunits via its C terminus to markedly suppress voltage-dependent inactivation among different neuronal VDCCs. Consistently, in pheochromocytoma neuroendocrine PC12 cells, acetylcholine release was significantly potentiated by the full-length and C-terminal RIM1 constructs, but membrane docking of vesicles was enhanced only by the full-length RIM1. The beta construct beta-AID dominant negative, which disrupts the RIM1-beta association, accelerated the inactivation of native VDCC currents, suppressed vesicle docking and acetylcholine release in PC12 cells, and inhibited glutamate release in cultured cerebellar neurons. Thus, RIM1 association with beta in the presynaptic active zone supports release via two distinct mechanisms: sustaining Ca2+ influx through inhibition of channel inactivation, and anchoring neurotransmitter-containing vesicles in the vicinity of VDCCs.
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Affiliation(s)
- Shigeki Kiyonaka
- Department of Synthetic Chemistry and Biological Chemistry
Kyoto UniversityGraduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510,JP
| | - Minoru Wakamori
- Department of Synthetic Chemistry and Biological Chemistry
Kyoto UniversityGraduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510,JP
| | - Takafumi Miki
- Department of Synthetic Chemistry and Biological Chemistry
Kyoto UniversityGraduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510,JP
| | - Yoshitsugu Uriu
- Department of Synthetic Chemistry and Biological Chemistry
Kyoto UniversityGraduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510,JP
| | - Mio Nonaka
- Department of Neurochemistry
University of TokyoUniversity of Tokyo Graduate School of Medicine, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033,JP
| | - Haruhiko Bito
- Department of Neurochemistry
University of TokyoUniversity of Tokyo Graduate School of Medicine, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033,JP
| | - Aaron M. Beedle
- Departments of Physiology and Biophysics, Internal Medicine, and Neurology
University of IowaUniversity of Iowa Roy J. and Lucille A. Carver College of Medicine, 285 Newton Road, Iowa City, Iowa 52242-1101,US
- HHMI, Howard Hughes Medical Institute
Howard Hugues Institute Howard Hughes Medical Institute,US
| | - Emiko Mori
- Department of Synthetic Chemistry and Biological Chemistry
Kyoto UniversityGraduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510,JP
| | - Yuji Hara
- Department of Synthetic Chemistry and Biological Chemistry
Kyoto UniversityGraduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510,JP
- Departments of Physiology and Biophysics, Internal Medicine, and Neurology
University of IowaUniversity of Iowa Roy J. and Lucille A. Carver College of Medicine, 285 Newton Road, Iowa City, Iowa 52242-1101,US
- HHMI, Howard Hughes Medical Institute
Howard Hugues Institute Howard Hughes Medical Institute,US
| | - Michel De Waard
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Motoi Kanagawa
- Departments of Physiology and Biophysics, Internal Medicine, and Neurology
University of IowaUniversity of Iowa Roy J. and Lucille A. Carver College of Medicine, 285 Newton Road, Iowa City, Iowa 52242-1101,US
- HHMI, Howard Hughes Medical Institute
Howard Hugues Institute Howard Hughes Medical Institute,US
| | - Makoto Itakura
- Department of Biochemistry
Kitasato University School of MedicineKitasato University School of Medicine, Kitasato 1-15-1, Sagamihara, Kanagawa 228-8555,JP
| | - Masami Takahashi
- Department of Biochemistry
Kitasato University School of MedicineKitasato University School of Medicine, Kitasato 1-15-1, Sagamihara, Kanagawa 228-8555,JP
| | - Kevin P. Campbell
- Departments of Physiology and Biophysics, Internal Medicine, and Neurology
University of IowaUniversity of Iowa Roy J. and Lucille A. Carver College of Medicine, 285 Newton Road, Iowa City, Iowa 52242-1101,US
- HHMI, Howard Hughes Medical Institute
Howard Hugues Institute Howard Hughes Medical Institute,US
| | - Yasuo Mori
- Department of Synthetic Chemistry and Biological Chemistry
Kyoto UniversityGraduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510,JP
- * Correspondence should be adressed to: Yasuo Mori
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Minezaki Y, Homma K, Nishikawa K. Intrinsically Disordered Regions of Human Plasma Membrane Proteins Preferentially Occur in the Cytoplasmic Segment. J Mol Biol 2007; 368:902-13. [PMID: 17368479 DOI: 10.1016/j.jmb.2007.02.033] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 01/29/2007] [Accepted: 02/09/2007] [Indexed: 12/30/2022]
Abstract
A systematic survey of intrinsically disordered (ID) regions was carried out in 2109 human plasma membrane proteins with full assignment of the transmembrane topology with respect to the lipid bilayer. ID regions with 30 consecutive residues or more were detected in 41.0% of the human proteins, a much higher percentage than the corresponding figure (4.7%) for inner membrane proteins of Escherichia coli. The domain organization of each of the membrane protein in terms of transmembrane helices, structural domains, ID, and unassigned regions as well as the distinction of inside or outside of the cell was determined. Long ID regions constitute 13.3 and 3.5% of the human plasma membrane proteins on the inside and outside of the cell, respectively, showing that they preferentially occur on the cytoplasmic side. We interpret this phenomenon as a reflection of the general scarcity of ID regions on the extracellular side and their relative abundance on the cytoplasmic side in multicellular eukaryotic organisms.
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Affiliation(s)
- Yoshiaki Minezaki
- Laboratory of Gene-Product Informatics, Center for Information Biology and DNA Data Bank of Japan, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 311-8540, Japan
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Pitt GS. Calmodulin and CaMKII as molecular switches for cardiac ion channels: Fig. 1. Cardiovasc Res 2007; 73:641-7. [PMID: 17137569 DOI: 10.1016/j.cardiores.2006.10.019] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 10/20/2006] [Accepted: 10/25/2006] [Indexed: 10/23/2022] Open
Abstract
Because changes in intracellular Ca(2+) concentration are the final signals of electrical activity in excitable cells, many mechanisms have evolved to regulate Ca(2+) influx. Among the most important are those pathways that directly regulate the ion channels responsible for regulating and generating the Ca(2+) influx signal. Recent work has demonstrated that the Ca(2+) binding protein calmodulin (CaM) and the Ca(2+)/CaM-sensitive kinase CaMKII are important modulators of cardiac ion channels. Thus, Ca(2+) participates in feedback modulation to control electrical activity. This review highlights various mechanisms by which CaM and CaMKII regulate cardiovascular ion channel activity and presents a novel model for CaMKII regulation of Ca(V)1.2 Ca(2+) channel function.
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Affiliation(s)
- Geoffrey S Pitt
- Department of Medicine, Division of Cardiology, College of Physicians and Surgeons of Columbia University, 630 W 168th St, PH 7W 318, New York, NY 10032, USA.
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35
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McDavid S, Currie KPM. G-proteins modulate cumulative inactivation of N-type (Cav2.2) calcium channels. J Neurosci 2007; 26:13373-83. [PMID: 17182788 PMCID: PMC6675003 DOI: 10.1523/jneurosci.3332-06.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Precise regulation of N-type (Ca(V)2.2) voltage-gated calcium channels (Ca-channels) controls many cellular functions including neurotransmitter and hormone release. One important mechanism that inhibits Ca2+ entry involves binding of G-protein betagamma subunits (Gbetagamma) to the Ca-channels. This shifts the Ca-channels from "willing" to "reluctant" gating states and slows activation. Voltage-dependent reversal of the inhibition (facilitation) is thought to reflect transient dissociation of Gbetagamma from the Ca-channels and can occur during high-frequency bursts of action potential-like waveforms (APW). Inactivation of Ca-channels will also limit Ca2+ entry, but it remains unclear whether G-proteins can modulate inactivation. In part this is because of the complex nature of inactivation, and because facilitation of Ca-channel currents (I(Ca)) masks the extent and kinetics of inactivation during typical stimulation protocols. We used low-frequency trains of APW to activate I(Ca). This more closely mimics physiological stimuli and circumvents the problem of facilitation which does not occur at < or = 5 Hz. Activation of endogenous G-proteins reduced both Ca2+-dependent, and voltage-dependent inactivation of recombinant I(Ca) in human embryonic kidney 293 cells. This was mimicked by expression of wild-type Gbetagamma, but not by a point mutant of Gbetagamma with reduced affinity for Ca-channels. A similar decrease in the inactivation of I(Ca) was produced by P2Y receptors in adrenal chromaffin cells. Overall, our data identify and characterize a novel effect of G-proteins on I(Ca), and could have important implications for understanding how G-protein-coupled receptors control Ca2+ entry and Ca2+-dependent events such as neurotransmitter and hormone release.
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Affiliation(s)
- Sarah McDavid
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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36
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Voltage-gated calcium channels, calcium signaling, and channelopathies. CALCIUM - A MATTER OF LIFE OR DEATH 2007. [DOI: 10.1016/s0167-7306(06)41005-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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37
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Weiss N, Tadmouri A, Mikati M, Ronjat M, De Waard M. Importance of voltage-dependent inactivation in N-type calcium channel regulation by G-proteins. Pflugers Arch 2006; 454:115-29. [PMID: 17171365 PMCID: PMC2703660 DOI: 10.1007/s00424-006-0184-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Accepted: 10/29/2006] [Indexed: 10/23/2022]
Abstract
Direct regulation of N-type calcium channels by G-proteins is essential to control neuronal excitability and neurotransmitter release. Binding of the G(betagamma) dimer directly onto the channel is characterized by a marked current inhibition ("ON" effect), whereas the pore opening- and time-dependent dissociation of this complex from the channel produce a characteristic set of biophysical modifications ("OFF" effects). Although G-protein dissociation is linked to channel opening, the contribution of channel inactivation to G-protein regulation has been poorly studied. Here, the role of channel inactivation was assessed by examining time-dependent G-protein de-inhibition of Ca(v)2.2 channels in the presence of various inactivation-altering beta subunit constructs. G-protein activation was produced via mu-opioid receptor activation using the DAMGO agonist. Whereas the "ON" effect of G-protein regulation is independent of the type of beta subunit, the "OFF" effects were critically affected by channel inactivation. Channel inactivation acts as a synergistic factor to channel activation for the speed of G-protein dissociation. However, fast inactivating channels also reduce the temporal window of opportunity for G-protein dissociation, resulting in a reduced extent of current recovery, whereas slow inactivating channels undergo a far more complete recovery from inhibition. Taken together, these results provide novel insights on the role of channel inactivation in N-type channel regulation by G-proteins and contribute to the understanding of the physiological consequence of channel inactivation in the modulation of synaptic activity by G-protein coupled receptors.
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Affiliation(s)
- Norbert Weiss
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Abir Tadmouri
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Mohamad Mikati
- Department of Pediatrics
American University of Beirut Medical CenterBeyrouth,LB
| | - Michel Ronjat
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
| | - Michel De Waard
- Canaux calciques , fonctions et pathologies
INSERM : U607CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble I17, rue des martyrs 38054 Grenoble,FR
- * Correspondence should be adressed to: Michel De Waard
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38
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Raybaud A, Dodier Y, Bissonnette P, Simoes M, Bichet DG, Sauvé R, Parent L. The Role of the GX9GX3G Motif in the Gating of High Voltage-activated Ca2+ Channels. J Biol Chem 2006; 281:39424-36. [PMID: 17038321 DOI: 10.1074/jbc.m607405200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The putative hinge point revealed by the crystal structure of the MthK potassium channel is a glycine residue that is conserved in many ion channels. In high voltage-activated (HVA) Ca(V) channels, the mid-S6 glycine residue is only present in IS6 and IIS6, corresponding to G422 and G770 in Ca(V)1.2. Two additional glycine residues are found in the distal portion of IS6 (Gly(432) and Gly(436) in Ca(V)1.2) to form a triglycine motif unique to HVA Ca(V) channels. Lethal arrhythmias are associated with mutations of glycine residues in the human L-type Ca(2+) channel. Hence, we undertook a mutational analysis to investigate the role of S6 glycine residues in channel gating. In Ca(V)1.2, alpha-helix-breaking proline mutants (G422P and G432P) as well as the double G422A/G432A channel did not produce functional channels. The macroscopic inactivation kinetics were significantly decreased with Ca(V)1.2 wild type > G770A > G422A congruent with G436A >> G432A (from the fastest to the slowest). Mutations at position Gly(432) produced mostly nonfunctional mutants. Macroscopic inactivation kinetics were markedly reduced by mutations of Gly(436) to Ala, Pro, Tyr, Glu, Arg, His, Lys, or Asp residues with stronger effects obtained with charged and polar residues. Mutations within the distal GX(3)G residues blunted Ca(2+)-dependent inactivation kinetics and prevented the increased voltage-dependent inactivation kinetics brought by positively charged residues in the I-II linker. In Ca(V)2.3, mutation of the distal glycine Gly(352) impacted significantly on the inactivation gating. Altogether, these data highlight the role of the GX(3)G motif in the voltage-dependent activation and inactivation gating of HVA Ca(V) channels with the distal glycine residue being mostly involved in the inactivation gating.
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Affiliation(s)
- Alexandra Raybaud
- Département de Physiologie and the Membrane Protein Research Group, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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Wahl-Schott C, Baumann L, Cuny H, Eckert C, Griessmeier K, Biel M. Switching off calcium-dependent inactivation in L-type calcium channels by an autoinhibitory domain. Proc Natl Acad Sci U S A 2006; 103:15657-62. [PMID: 17028172 PMCID: PMC1622877 DOI: 10.1073/pnas.0604621103] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The retinal L-type Ca2+ channel Cav1.4 is distinguished from all other members of the high voltage-activated (HVA) Ca2+ channel family by lacking Ca2+-calmodulin-dependent inactivation. In synaptic terminals of photoreceptors and bipolar cells, this feature is essential to translate graded membrane depolarizations into sustained Ca2+ influx and tonic glutamate release. The sequences conferring Ca2+-dependent inactivation (CDI) are conserved throughout the HVA calcium channel family, raising the question of how Cav1.4 manages to switch off CDI. Here, we identify an autoinhibitory domain in the distal C terminus of Cav1.4 that serves to abolish CDI. We show that this domain (ICDI, inhibitor of CDI) uncouples the molecular machinery conferring CDI from the inactivation gate by binding to the EF hand motif in the proximal C terminus. Deletion of ICDI completely restores Ca2+-calmodulin-mediated CDI in Cav1.4. CDI can be switched off again in the truncated Cav1.4 channel by coexpression of ICDI, indicating that ICDI works as an autonomous unit. Furthermore, we show that in the Cav1.2 l-type Ca2+-channel replacement of the distal C terminus by the corresponding sequence of Cav1.4 is sufficient to block CDI. This finding suggests that autoinhibition of CDI can be introduced principally into other Ca2+ channel types. Our data provide a previously undescribed perspective on the regulation of HVA calcium channels by Ca2+.
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Affiliation(s)
- Christian Wahl-Schott
- Department Pharmazie – Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstrasse 7, 81377 Munich, Germany
| | - Ludwig Baumann
- Department Pharmazie – Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstrasse 7, 81377 Munich, Germany
| | - Hartmut Cuny
- Department Pharmazie – Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstrasse 7, 81377 Munich, Germany
| | - Christian Eckert
- Department Pharmazie – Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstrasse 7, 81377 Munich, Germany
| | - Kristina Griessmeier
- Department Pharmazie – Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstrasse 7, 81377 Munich, Germany
| | - Martin Biel
- Department Pharmazie – Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität München, Butenandtstrasse 7, 81377 Munich, Germany
- *To whom correspondence should be addressed. E-mail:
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40
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Hamid J, Peloquin JB, Monteil A, Zamponi GW. Determinants of the differential gating properties of Cav3.1 and Cav3.3 T-type channels: a role of domain IV? Neuroscience 2006; 143:717-28. [PMID: 16996222 DOI: 10.1016/j.neuroscience.2006.08.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Revised: 08/11/2006] [Accepted: 08/15/2006] [Indexed: 11/24/2022]
Abstract
We have investigated the channel structural determinants that underlie the difference in gating properties of Cav3.1 and Cav3.3 T-type channels, by creating a series of chimeric channel constructs in which the major transmembrane domains were swapped. The chimeras were then expressed in tsA-201 cells and subjected to whole cell patch clamp analysis. Our data reveal that domains I and IV are major determinants of the half-activation potential. Substitution of domain IV was the most important determinant of activation time constant and time constant for recovery from inactivation, with domains I and II mediating a smaller role. In contrast, the carboxy terminal region did not appear to be involved. Determinants of the time constant for inactivation could not be localized to a specific transmembrane domain, but the concomitant substitution of domains I+IV was able to partially confer the inactivation kinetics among the two wild type channels. Our data indicate that the domain IV region mediates an important role in T-type channel activation, whereas multiple channel structural determinants appear to control T-type channel inactivation.
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Affiliation(s)
- J Hamid
- Hotchkiss Brain Institute and Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive Northwest, Calgary, Canada T2N 4N1
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41
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Pitt GS, Dun W, Boyden PA. Remodeled cardiac calcium channels. J Mol Cell Cardiol 2006; 41:373-88. [PMID: 16901502 DOI: 10.1016/j.yjmcc.2006.06.071] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Revised: 05/26/2006] [Accepted: 06/22/2006] [Indexed: 10/24/2022]
Abstract
Cardiac calcium channels play a pivotal role in the proper functioning of cardiac cells. In response to various pathologic stimuli, they become remodeled, changing how they function, as they adapt to their new environment. Specific features of remodeled channels depend upon the particular disease state. This review will summarize what is known about remodeled cardiac calcium channels in three disease states: hypertrophy, heart failure and atrial fibrillation. In addition, it will review the recent advances made in our understanding of the function of the various molecular building blocks that contribute to the proper functioning of the cardiac calcium channel.
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Affiliation(s)
- Geoffrey S Pitt
- Department of Medicine, Columbia University, New York, NY, USA
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42
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Iftinca M, McKay BE, Snutch TP, McRory JE, Turner RW, Zamponi GW. Temperature dependence of T-type calcium channel gating. Neuroscience 2006; 142:1031-42. [PMID: 16935432 DOI: 10.1016/j.neuroscience.2006.07.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 07/11/2006] [Accepted: 07/14/2006] [Indexed: 10/24/2022]
Abstract
T-type calcium channel isoforms are expressed in a multitude of tissues and have a key role in a variety of physiological processes. To fully appreciate the physiological role of distinct channel isoforms it is essential to determine their kinetic properties under physiologically relevant conditions. We therefore characterized the gating behavior of expressed rat voltage-dependent calcium channels (Ca(v)) 3.1, Ca(v)3.2, and Ca(v)3.3, as well as human Ca(v)3.3 at 21 degrees C and 37 degrees C in saline that approximates physiological conditions. Exposure to 37 degrees C caused significant increases in the rates of activation, inactivation, and recovery from inactivation, increased the current amplitudes, and induced a hyperpolarizing shift of half-activation for Ca(v)3.1 and Ca(v)3.2. At 37 degrees C the half-inactivation showed a hyperpolarizing shift for Ca(v)3.1 and Ca(v)3.2 and human Ca(v)3.3, but not rat Ca(v)3.3. The observed changes in the kinetics were significant but not identical for the three isoforms, showing that the ability of T-type channels to conduct calcium varies with both channel isoform and temperature.
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Affiliation(s)
- M Iftinca
- Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Drive Northwest, Calgary, Canada T2N 4N1
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Livneh A, Cohen R, Atlas D. A novel molecular inactivation determinant of voltage-gated CaV1.2 L-type Ca2+ channel. Neuroscience 2006; 139:1275-87. [PMID: 16533566 DOI: 10.1016/j.neuroscience.2006.01.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Revised: 01/26/2006] [Accepted: 01/26/2006] [Indexed: 11/16/2022]
Abstract
The inactivation of voltage-gated L-type Ca(2+) channels (Ca(V)1) regulates Ca(2+) entry and controls intracellular Ca(2+) levels that are essential for cellular activity. The molecular entities implicated in L-channel (Ca(V)1.2) inactivation are not fully identified. Here we show for the first time the functional impact of one of the two highly conserved clusters of six negatively charged glutamates and aspartate (802-807; poly ED motif) at the II-III loop of the alpha 1 subunits of rabbit of Ca(v)1.2, alpha(1)1.2 and alpha(1)1.2 DeltaN60-Delta1733) on voltage-dependent inactivation. Mutation of the poly ED motif to alanine or glutamine/asparagine greatly enhanced voltage-dependent inactivation, shifting the voltage dependence to negative potentials by >50 mV and conferring a neuronal like inactivation kinetics onto Ca(V)1.2. The large shift in the midpoint of inactivation of the steady-state inactivation kinetics was observed also in Ca(2+) or Ba(2+) and was not altered by the beta2A subunit. Missing from the fast inactivating neuronal P/Q (Ca(V)2.1)-, N (Ca(V)2.2)- or R (Ca(V)2.3)-type channels and modulating Ca(V)1.2 inactivation kinetics, the poly ED motif is likely to be a specific L-type Ca(2+) channels inactivating domain. Our results fit a model in which the poly ED either by itself or as part of a larger inactivating motif acts as Ca(V)1.2 specific built-in "stopper." In this model, Ca(V)1 accomplishes a large Ca(2+) influx during depolarization, possibly by the poly ED hindering occlusion at the pore. Furthermore, the selective designed poly ED perhaps clarifies major inactivation differences between L- and non-L-type calcium channels.
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Affiliation(s)
- A Livneh
- Department of Biological Chemistry, The Silverman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat Ram, Jerusalem, Israel
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Markevich NI, Pimenov OY, Kokoz YM. Analysis of the modal hypothesis of Ca2+-dependent inactivation of L-type Ca2+ channels. Biophys Chem 2005; 117:173-90. [PMID: 15936868 DOI: 10.1016/j.bpc.2005.04.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Revised: 04/28/2005] [Accepted: 04/28/2005] [Indexed: 10/25/2022]
Abstract
A kinetic model of Ca2+-dependent inactivation (CDI) of L-type Ca2+ channels was developed. The model is based on the hypothesis that postulates the existence of four short-lived modes with lifetimes of a few hundreds of milliseconds. Our findings suggest that the transitions between the modes is primarily determined by the binding of Ca2+ to two intracellular allosteric sites located in different motifs of the CI region, which have greatly differing binding rates for Ca2+ (different k(on)). The slow-binding site is controlled by local Ca2+ near a single open channel that is consistent with the "domain" CDI model, and Ca2+ binding to the fast-binding site(s) depends on Ca2+ arising from distant sources that is consistent with the "shell" CDI model. The model helps to explain numerous experimental findings that are poorly understood so far.
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Affiliation(s)
- Nick I Markevich
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow 142290, Russia.
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Abstract
Calmodulin, a highly versatile and ubiquitously expressed Ca2+ sensor, regulates the function of many enzymes and ion channels. Both Ca2+-dependent inactivation and Ca2+-dependent facilitation of the voltage-gated Ca2+ channels Cav1.2 and Cav2.1 are regulated through an interaction with Ca2+-bound calmodulin. This review addresses the functional regulation of Cav1.2 and Cav2.1 by calmodulin and discusses how Ca2+ binding to a single calmodulin molecule can regulate opposing functions of the voltage-gated Ca2+ channels.
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Affiliation(s)
- D Brent Halling
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
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46
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Zhou H, Yu K, McCoy KL, Lee A. Molecular Mechanism for Divergent Regulation of Cav1.2 Ca2+ Channels by Calmodulin and Ca2+-binding Protein-1. J Biol Chem 2005; 280:29612-9. [PMID: 15980432 DOI: 10.1074/jbc.m504167200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)-binding protein-1 (CaBP1) and calmodulin (CaM) are highly related Ca(2+)-binding proteins that directly interact with, and yet differentially regulate, voltage-gated Ca(2+) channels. Whereas CaM enhances inactivation of Ca(2+) currents through Ca(v)1.2 (L-type) Ca(2+) channels, CaBP1 completely prevents this process. How CaBP1 and CaM mediate such opposing effects on Ca(v)1.2 inactivation is unknown. Here, we identified molecular determinants in the alpha(1)-subunit of Ca(v)1.2 (alpha(1)1.2) that distinguish the effects of CaBP1 and CaM on inactivation. Although both proteins bind to a well characterized IQ-domain in the cytoplasmic C-terminal domain of alpha(1)1.2, mutations of the IQ-domain that significantly weakened CaM and CaBP1 binding abolished the functional effects of CaM, but not CaBP1. Pulldown binding assays revealed Ca(2+)-independent binding of CaBP1 to the N-terminal domain (NT) of alpha(1)1.2, which was in contrast to Ca(2+)-dependent binding of CaM to this region. Deletion of the NT abolished the effects of CaBP1 in prolonging Ca(v)1.2 Ca(2+) currents, but spared Ca(2+)-dependent inactivation due to CaM. We conclude that the NT and IQ-domains of alpha(1)1.2 mediate functionally distinct interactions with CaBP1 and CaM that promote conformational alterations that either stabilize or inhibit inactivation of Ca(v)1.2.
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Affiliation(s)
- Hong Zhou
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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47
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Winquist RJ, Pan JQ, Gribkoff VK. Use-dependent blockade of Cav2.2 voltage-gated calcium channels for neuropathic pain. Biochem Pharmacol 2005; 70:489-99. [PMID: 15950195 DOI: 10.1016/j.bcp.2005.04.035] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 04/11/2005] [Accepted: 04/11/2005] [Indexed: 11/28/2022]
Abstract
The translocation of extracellular calcium (Ca(2+)) via voltage-gated Ca(2+) channels (VGCCs) in neurons is involved in triggering multiple physiological cell functions but also the abnormal, pathophysiological responses that develop as a consequence of injury. In conditions of neuropathic pain, VGCCs are involved in supplying the signal Ca(2+) important for the sustained neuronal firing and neurotransmitter release characteristic of these syndromes. Preclinical data have identified N-type VGCCs (Ca(v)2.2) as key participants in contributing to these Ca(2+) signaling events and clinical data with the peptide blocker Prialt have now validated Ca(v)2.2 as a bona fide target for future drug discovery efforts to identify new and novel therapeutics for neuropathic pain. Imperative for the success of such an endeavor will be the ability to identify compounds selective for Ca(v)2.2, versus other VGCCs, but also compounds which demonstrate effective blockade during the pathophysiological states of neuropathic pain without compromising channel activity associated with sustaining normal housekeeping cellular functions. An approach to obtain this research target profile is to identify compounds, which are more potent in blocking Ca(v)2.2 during higher frequencies of firing as compared to the slower more physiologically-relevant frequencies. This may be achieved by identifying compounds with enhanced potency for the inactivated state of Ca(v)2.2. This commentary explores the rationale and options for engineering a use-dependent blocker of Ca(v)2.2. It is anticipated that this use-dependent profile of channel blockade will result in new chemical entities with an improved therapeutic ratio for neuropathic pain.
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Affiliation(s)
- Raymond J Winquist
- Department of Pharmacology, Scion Pharmaceuticals Inc., 200 Boston Avenue, Suite 3600, Medford, MA 02155, USA.
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Brette F, Leroy J, Le Guennec JY, Sallé L. Ca2+ currents in cardiac myocytes: Old story, new insights. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2005; 91:1-82. [PMID: 16503439 DOI: 10.1016/j.pbiomolbio.2005.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Calcium is a ubiquitous second messenger which plays key roles in numerous physiological functions. In cardiac myocytes, Ca2+ crosses the plasma membrane via specialized voltage-gated Ca2+ channels which have two main functions: (i) carrying depolarizing current by allowing positively charged Ca2+ ions to move into the cell; (ii) triggering Ca2+ release from the sarcoplasmic reticulum. Recently, it has been suggested than Ca2+ channels also participate in excitation-transcription coupling. The purpose of this review is to discuss the physiological roles of Ca2+ currents in cardiac myocytes. Next, we describe local regulation of Ca2+ channels by cyclic nucleotides. We also provide an overview of recent studies investigating the structure-function relationship of Ca2+ channels in cardiac myocytes using heterologous system expression and transgenic mice, with descriptions of the recently discovered Ca2+ channels alpha(1D) and alpha(1E). We finally discuss the potential involvement of Ca2+ currents in cardiac pathologies, such as diseases with autoimmune components, and cardiac remodeling.
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Affiliation(s)
- Fabien Brette
- School of Biomedical Sciences, University of Leeds, Worsley Building Leeds, LS2 9NQ, UK.
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Ishiguro M, Wellman TL, Honda A, Russell SR, Tranmer BI, Wellman GC. Emergence of a R-type Ca2+ channel (CaV 2.3) contributes to cerebral artery constriction after subarachnoid hemorrhage. Circ Res 2005; 96:419-26. [PMID: 15692089 DOI: 10.1161/01.res.0000157670.49936.da] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cerebral aneurysm rupture and subarachnoid hemorrhage (SAH) inflict disability and death on thousands of individuals each year. In addition to vasospasm in large diameter arteries, enhanced constriction of resistance arteries within the cerebral vasculature may contribute to decreased cerebral blood flow and the development of delayed neurological deficits after SAH. In this study, we provide novel evidence that SAH leads to enhanced Ca2+ entry in myocytes of small diameter cerebral arteries through the emergence of R-type voltage-dependent Ca2+ channels (VDCCs) encoded by the gene CaV 2.3. Using in vitro diameter measurements and patch clamp electrophysiology, we have found that L-type VDCC antagonists abolish cerebral artery constriction and block VDCC currents in cerebral artery myocytes from healthy animals. However, 5 days after the intracisternal injection of blood into rabbits to mimic SAH, cerebral artery constriction and VDCC currents were enhanced and partially resistant to L-type VDCC blockers. Further, SNX-482, a blocker of R-type Ca2+ channels, reduced constriction and membrane currents in cerebral arteries from SAH animals, but was without effect on cerebral arteries of healthy animals. Consistent with our biophysical and functional data, cerebral arteries from healthy animals were found to express only L-type VDCCs (CaV 1.2), whereas after SAH, cerebral arteries were found to express both CaV 1.2 and CaV 2.3. We propose that R-type VDCCs may contribute to enhanced cerebral artery constriction after SAH and may represent a novel therapeutic target in the treatment of neurological deficits after SAH.
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MESH Headings
- Animals
- Blood
- Calcium/metabolism
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/physiology
- Calcium Channels, R-Type/drug effects
- Calcium Channels, R-Type/physiology
- Cerebral Arteries/drug effects
- Cerebral Arteries/metabolism
- Cerebral Arteries/pathology
- Cerebral Arteries/physiopathology
- Cisterna Magna
- Dihydropyridines/pharmacology
- Diltiazem/pharmacology
- Disease Models, Animal
- Drug Resistance
- Injections
- Ion Transport/drug effects
- Male
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Nifedipine/pharmacology
- Patch-Clamp Techniques
- Rabbits
- Spider Venoms/pharmacology
- Subarachnoid Hemorrhage/etiology
- Subarachnoid Hemorrhage/physiopathology
- Vasoconstriction/drug effects
- Vasoconstriction/physiology
- Vasospasm, Intracranial/etiology
- Vasospasm, Intracranial/physiopathology
- omega-Agatoxin IVA/pharmacology
- omega-Conotoxin GVIA/pharmacology
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Affiliation(s)
- Masanori Ishiguro
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, VT 05405-0068, USA
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50
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Isaev D, Solt K, Gurtovaya O, Reeves JP, Shirokov R. Modulation of the voltage sensor of L-type Ca2+ channels by intracellular Ca2+. ACTA ACUST UNITED AC 2004; 123:555-71. [PMID: 15111645 PMCID: PMC2234499 DOI: 10.1085/jgp.200308876] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Both intracellular calcium and transmembrane voltage cause inactivation, or spontaneous closure, of L-type (CaV1.2) calcium channels. Here we show that long-lasting elevations of intracellular calcium to the concentrations that are expected to be near an open channel (>/=100 microM) completely and reversibly blocked calcium current through L-type channels. Although charge movements associated with the opening (ON) motion of the channel's voltage sensor were not altered by high calcium, the closing (OFF) transition was impeded. In two-pulse experiments, the blockade of calcium current and the reduction of gating charge movements available for the second pulse developed in parallel during calcium load. The effect depended steeply on voltage and occurred only after a third of the total gating charge had moved. Based on that, we conclude that the calcium binding site is located either in the channel's central cavity behind the voltage-dependent gate, or it is formed de novo during depolarization through voltage-dependent rearrangements just preceding the opening of the gate. The reduction of the OFF charge was due to the negative shift in the voltage dependence of charge movement, as previously observed for voltage-dependent inactivation. Elevation of intracellular calcium concentration from approximately 0.1 to 100-300 microM sped up the conversion of the gating charge into the negatively distributed mode 10-100-fold. Since the "IQ-AA" mutant with disabled calcium/calmodulin regulation of inactivation was affected by intracellular calcium similarly to the wild-type, calcium/calmodulin binding to the "IQ" motif apparently is not involved in the observed changes of voltage-dependent gating. Although calcium influx through the wild-type open channels does not cause a detectable negative shift in the voltage dependence of their charge movement, the shift was readily observable in the Delta1733 carboxyl terminus deletion mutant, which produces fewer nonconducting channels. We propose that the opening movement of the voltage sensor exposes a novel calcium binding site that mediates inactivation.
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Affiliation(s)
- Dmytro Isaev
- Department of Pharmacology and Physiology, New Jersey Medical School, UMDNJ, 185 South Orange Avenue, Newark, NJ 07101-1709, USA
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