1
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Yao X, Gao S, Yan N. Structural biology of voltage-gated calcium channels. Channels (Austin) 2024; 18:2290807. [PMID: 38062897 PMCID: PMC10761187 DOI: 10.1080/19336950.2023.2290807] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 11/27/2023] [Indexed: 12/18/2023] Open
Abstract
Voltage-gated calcium (Cav) channels mediate Ca2+ influx in response to membrane depolarization, playing critical roles in diverse physiological processes. Dysfunction or aberrant regulation of Cav channels can lead to life-threatening consequences. Cav-targeting drugs have been clinically used to treat cardiovascular and neuronal disorders for several decades. This review aims to provide an account of recent developments in the structural dissection of Cav channels. High-resolution structures have significantly advanced our understanding of the working and disease mechanisms of Cav channels, shed light on the molecular basis for their modulation, and elucidated the modes of actions (MOAs) of representative drugs and toxins. The progress in structural studies of Cav channels lays the foundation for future drug discovery efforts targeting Cav channelopathies.
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Affiliation(s)
- Xia Yao
- TaiKang Center for Life and Medical Sciences, School of Pharmaceutical Sciences, Wuhan University, Wuhan, China
| | - Shuai Gao
- TaiKang Center for Life and Medical Sciences, School of Pharmaceutical Sciences, Wuhan University, Wuhan, China
| | - Nieng Yan
- Beijing Frontier Research Center for Biological Structures, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
- Shenzhen Medical Academy of Research and Translation, Shenzhen, China
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2
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Catacuzzeno L, Conti F, Franciolini F. Fifty years of gating currents and channel gating. J Gen Physiol 2023; 155:e202313380. [PMID: 37410612 PMCID: PMC10324510 DOI: 10.1085/jgp.202313380] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/12/2023] [Accepted: 06/02/2023] [Indexed: 07/08/2023] Open
Abstract
We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This retrospective tries to illustrate the context knowledge on channel gating and the impact gating-current recording had then, and how it continued to clarify concepts, elaborate new ideas, and steer the scientific debate in these 50 years. The notion of gating particles and gating currents was first put forward by Hodgkin and Huxley in 1952 as a necessary assumption for interpreting the voltage dependence of the Na and K conductances of the action potential. 20 years later, gating currents were actually recorded, and over the following decades have represented the most direct means of tracing the movement of the gating charges and gaining insights into the mechanisms of channel gating. Most work in the early years was focused on the gating currents from the Na and K channels as found in the squid giant axon. With channel cloning and expression on heterologous systems, other channels as well as voltage-dependent enzymes were investigated. Other approaches were also introduced (cysteine mutagenesis and labeling, site-directed fluorometry, cryo-EM crystallography, and molecular dynamics [MD] modeling) to provide an integrated and coherent view of voltage-dependent gating in biological macromolecules. The layout of this retrospective reflects the past 50 years of investigations on gating currents, first addressing studies done on Na and K channels and then on other voltage-gated channels and non-channel structures. The review closes with a brief overview of how the gating-charge/voltage-sensor movements are translated into pore opening and the pathologies associated with mutations targeting the structures involved with the gating currents.
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Affiliation(s)
- Luigi Catacuzzeno
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Franco Conti
- Department of Physics, University of Genova, Genova, Italy
| | - Fabio Franciolini
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
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3
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Contreras GF, Saavedra J, Navarro-Quezada N, Mellado G, Gonzalez C, Neely A. Direct inhibition of Ca V2.3 by Gem is dynamin dependent and does not require a direct alfa/beta interaction. Biochem Biophys Res Commun 2022; 586:107-113. [PMID: 34837834 DOI: 10.1016/j.bbrc.2021.11.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/21/2021] [Accepted: 11/14/2021] [Indexed: 11/17/2022]
Abstract
The Rad, Rem, Rem2, and Gem/Kir (RGK) sub-family of small GTP-binding proteins are crucial in regulating high voltage-activated (HVA) calcium channels. RGK proteins inhibit calcium current by either promoting endocytosis or reducing channel activity. They all can associate directly with Ca2+ channel β subunit (CaVβ), and the binding between CaVα1/CaVβ appears essential for the endocytic promotion of CaV1.X, CaV2.1, and CaV2.2 channels. In this study, we investigated the inhibition of CaV2.3 channels by RGK proteins in the absence of CaVβ. To this end, Xenopus laevis oocytes expressing CaV2.3 channels devoid of auxiliary subunit were injected with purified Gem and Rem and found that only Gem had an effect. Ca currents and charge movements were reduced by injection of Gem, pointing to a reduction in the number of channels in the plasma membrane. Since this reduction was ablated by co-expression of the dominant-negative mutant of dynamin K44A, enhanced endocytosis appears to mediate this reduction in the number of channels. Thus, Gem inhibition of CaV2.3 channels would be the only example of a CaVβ independent promotion of dynamin-dependent endocytosis.
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Affiliation(s)
- Gustavo F Contreras
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile
| | - Jonathan Saavedra
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile; Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Nieves Navarro-Quezada
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile
| | - Guido Mellado
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile; Doctorado en Ciencias Mención Biofisica y Biología Computacional, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carlos Gonzalez
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile; Cardiovascular Research, Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Alan Neely
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile
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4
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Conrad R, Kortzak D, Guzman GA, Miranda-Laferte E, Hidalgo P. Ca V β controls the endocytic turnover of Ca V 1.2 L-type calcium channel. Traffic 2021; 22:180-193. [PMID: 33890356 DOI: 10.1111/tra.12788] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 03/17/2021] [Accepted: 04/17/2021] [Indexed: 01/10/2023]
Abstract
Membrane depolarization activates the multisubunit CaV 1.2 L-type calcium channel initiating various excitation coupling responses. Intracellular trafficking into and out of the plasma membrane regulates the channel's surface expression and stability, and thus, the strength of CaV 1.2-mediated Ca2+ signals. The mechanisms regulating the residency time of the channel at the cell membrane are unclear. Here, we coexpressed the channel core complex CaV 1.2α1 pore-forming and auxiliary CaV β subunits and analyzed their trafficking dynamics from single-particle-tracking trajectories. Speed histograms obtained for each subunit were best fitted to a sum of diffusive and directed motion terms. The same mean speed for the highest-mobility state underlying directed motion was found for all subunits. The frequency of this component increased by covalent linkage of CaV β to CaV 1.2α1 suggesting that high-speed transport occurs in association with CaV β. Selective tracking of CaV 1.2α1 along the postendocytic pathway failed to show the highly mobile state, implying CaV β-independent retrograde transport. Retrograde speeds of CaV 1.2α1 are compatible with myosin VI-mediated backward transport. Moreover, residency time at the cell surface was significantly prolonged when CaV 1.2α1 was covalently linked to CaV β. Thus, CaV β promotes fast transport speed along anterograde trafficking and acts as a molecular switch controlling the endocytic turnover of L-type calcium channels.
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Affiliation(s)
- Rachel Conrad
- Institute of Biological Information Processing (IBI-1), Molecular and Cellular Physiology, Forschungszentrum Jülich, Jülich, Germany
| | - Daniel Kortzak
- Institute of Biological Information Processing (IBI-1), Molecular and Cellular Physiology, Forschungszentrum Jülich, Jülich, Germany
| | - Gustavo A Guzman
- Institute of Biological Information Processing (IBI-1), Molecular and Cellular Physiology, Forschungszentrum Jülich, Jülich, Germany
| | - Erick Miranda-Laferte
- Institute of Biological Information Processing (IBI-1), Molecular and Cellular Physiology, Forschungszentrum Jülich, Jülich, Germany
| | - Patricia Hidalgo
- Institute of Biological Information Processing (IBI-1), Molecular and Cellular Physiology, Forschungszentrum Jülich, Jülich, Germany.,Institute of Biochemistry, Heinrich-Heine University, Düsseldorf, Germany
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5
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Neumaier F, Schneider T, Albanna W. Ca v2.3 channel function and Zn 2+-induced modulation: potential mechanisms and (patho)physiological relevance. Channels (Austin) 2020; 14:362-379. [PMID: 33079629 PMCID: PMC7583514 DOI: 10.1080/19336950.2020.1829842] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Voltage-gated calcium channels (VGCCs) are critical for Ca2+ influx into all types of excitable cells, but their exact function is still poorly understood. Recent reconstruction of homology models for all human VGCCs at atomic resolution provides the opportunity for a structure-based discussion of VGCC function and novel insights into the mechanisms underlying Ca2+ selective flux through these channels. In the present review, we use these data as a basis to examine the structure, function, and Zn2+-induced modulation of Cav2.3 VGCCs, which mediate native R-type currents and belong to the most enigmatic members of the family. Their unique sensitivity to Zn2+ and the existence of multiple mechanisms of Zn2+ action strongly argue for a role of these channels in the modulatory action of endogenous loosely bound Zn2+, pools of which have been detected in a number of neuronal, endocrine, and reproductive tissues. Following a description of the different mechanisms by which Zn2+ has been shown or is thought to alter the function of these channels, we discuss their potential (patho)physiological relevance, taking into account what is known about the magnitude and function of extracellular Zn2+ signals in different tissues. While still far from complete, the picture that emerges is one where Cav2.3 channel expression parallels the occurrence of loosely bound Zn2+ pools in different tissues and where these channels may serve to translate physiological Zn2+ signals into changes of electrical activity and/or intracellular Ca2+ levels.
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Affiliation(s)
- Felix Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5) , Jülich, Germany.,University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging , Cologne, Germany
| | - Toni Schneider
- Institute of Neurophysiology , Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Walid Albanna
- Department of Neurosurgery, RWTH Aachen University , Aachen, Germany
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6
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Wie J, Bharthur A, Wolfgang M, Narayanan V, Ramsey K, Aranda K, Zhang Q, Zhou Y, Ren D. Intellectual disability-associated UNC80 mutations reveal inter-subunit interaction and dendritic function of the NALCN channel complex. Nat Commun 2020; 11:3351. [PMID: 32620897 PMCID: PMC7335163 DOI: 10.1038/s41467-020-17105-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 06/11/2020] [Indexed: 01/08/2023] Open
Abstract
The sodium-leak channel NALCN forms a subthreshold sodium conductance that controls the resting membrane potentials of neurons. The auxiliary subunits of the channel and their functions in mammals are largely unknown. In this study, we demonstrate that two large proteins UNC80 and UNC79 are subunits of the NALCN complex. UNC80 knockout mice are neonatal lethal. The C-terminus of UNC80 contains a domain that interacts with UNC79 and overcomes a soma-retention signal to achieve dendritic localization. UNC80 lacking this domain, as found in human patients, still supports whole-cell NALCN currents but lacks dendritic localization. Our results establish the subunit composition of the NALCN complex, uncover the inter-subunit interaction domains, reveal the functional significance of regulation of dendritic membrane potential by the sodium-leak channel complex, and provide evidence supporting that genetic variations found in individuals with intellectual disability are the causes for the phenotype observed in patients.
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Affiliation(s)
- Jinhong Wie
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Apoorva Bharthur
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Morgan Wolfgang
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, 85012, USA
| | - Vinodh Narayanan
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, 85012, USA
| | - Keri Ramsey
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, 85012, USA
| | - Kimberly Aranda
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Qi Zhang
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Yandong Zhou
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Dejian Ren
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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7
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Overexpression of Kif1A in the Developing Drosophila Heart Causes Valvar and Contractility Defects: Implications for Human Congenital Heart Disease. J Cardiovasc Dev Dis 2020; 7:jcdd7020022. [PMID: 32498427 PMCID: PMC7345553 DOI: 10.3390/jcdd7020022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 05/23/2020] [Accepted: 05/26/2020] [Indexed: 11/24/2022] Open
Abstract
Left-sided congenital heart defects (CHDs) are among the most common forms of congenital heart disease, but a disease-causing gene has only been identified in a minority of cases. Here, we identified a candidate gene for CHDs, KIF1A, that was associated with a chromosomal balanced translocation t(2;8)(q37;p11) in a patient with left-sided heart and aortic valve defects. The breakpoint was in the 5′ untranslated region of the KIF1A gene at 2q37, which suggested that the break affected the levels of Kif1A gene expression. Transgenic fly lines overexpressing Kif1A specifically in the heart muscle (or all muscles) caused diminished cardiac contractility, myofibrillar disorganization, and heart valve defects, whereas cardiac knockdown had no effect on heart structure or function. Overexpression of Kif1A also caused increased collagen IV deposition in the fibrous network that normally surrounds the fly heart. Kif1A overexpression in C2C12 myoblasts resulted in specific displacement of the F-actin fibers, probably through a direct interaction with G-actin. These results point to a Kif1A-mediated disruption of F-actin organization as a potential mechanism for the pathogenesis in at least some human CHDs.
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8
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Guerra MJ, González‐Jamett AM, Báez‐Matus X, Navarro‐Quezada N, Martínez AD, Neely A, Cárdenas AM. The Ca2+channel subunit CaVβ2a‐subunit down‐regulates voltage‐activated ion current densities by disrupting actin‐dependent traffic in chromaffin cells. J Neurochem 2019; 151:703-715. [DOI: 10.1111/jnc.14851] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 05/01/2019] [Accepted: 08/05/2019] [Indexed: 12/11/2022]
Affiliation(s)
- María J. Guerra
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia Universidad de Valparaíso Valparaíso Chile
| | - Arlek M. González‐Jamett
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia Universidad de Valparaíso Valparaíso Chile
| | - Ximena Báez‐Matus
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia Universidad de Valparaíso Valparaíso Chile
| | - Nieves Navarro‐Quezada
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia Universidad de Valparaíso Valparaíso Chile
| | - Agustín D. Martínez
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia Universidad de Valparaíso Valparaíso Chile
| | - Alan Neely
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia Universidad de Valparaíso Valparaíso Chile
| | - Ana M. Cárdenas
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia Universidad de Valparaíso Valparaíso Chile
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9
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Tammineni ER, Carrillo ED, Soto-Acosta R, Angel-Ambrocio AH, García MC, Bautista-Carbajal P, del Angel RM, Sánchez JA. The β
4
subunit of Ca
v
1.2 channels is required for an optimal interferon response in cardiac muscle cells. Sci Signal 2018; 11:11/560/eaaj1676. [DOI: 10.1126/scisignal.aaj1676] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Eshwar R. Tammineni
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Elba D. Carrillo
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Rubén Soto-Acosta
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Antonio H. Angel-Ambrocio
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - María C. García
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Patricia Bautista-Carbajal
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Rosa M. del Angel
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Jorge A. Sánchez
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
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10
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Rosa N, Triffaux E, Robert V, Mars M, Klein M, Bouchaud G, Canivet A, Magnan A, Guéry JC, Pelletier L, Savignac M. The β and α2δ auxiliary subunits of voltage-gated calcium channel 1 (Ca v1) are required for T H2 lymphocyte function and acute allergic airway inflammation. J Allergy Clin Immunol 2017; 142:892-903.e8. [PMID: 29129580 DOI: 10.1016/j.jaci.2017.09.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/04/2017] [Accepted: 09/08/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND T lymphocytes express not only cell membrane ORAI calcium release-activated calcium modulator 1 but also voltage-gated calcium channel (Cav) 1 channels. In excitable cells these channels are composed of the ion-forming pore α1 and auxiliary subunits (β and α2δ) needed for proper trafficking and activation of the channel. Previously, we disclosed the role of Cav1.2 α1 in mouse and human TH2 but not TH1 cell functions and showed that knocking down Cav1 α1 prevents experimental asthma. OBJECTIVE We investigated the role of β and α2δ auxiliary subunits on Cav1 α1 function in TH2 lymphocytes and on the development of acute allergic airway inflammation. METHODS We used Cavβ antisense oligonucleotides to knock down Cavβ and gabapentin, a drug that binds to and inhibits α2δ1 and α2δ2, to test their effects on TH2 functions and their capacity to reduce allergic airway inflammation. RESULTS Mouse and human TH2 cells express mainly Cavβ1, β3, and α2δ2 subunits. Cavβ antisense reduces T-cell receptor-driven calcium responses and cytokine production by mouse and human TH2 cells with no effect on TH1 cells. Cavβ is mainly involved in restraining Cav1.2 α1 degradation through the proteasome because a proteasome inhibitor partially restores the α1 protein level. Gabapentin impairs the T-cell receptor-driven calcium response and cytokine production associated with the loss of α2δ2 protein in TH2 cells. CONCLUSIONS These results stress the role of Cavβ and α2δ2 auxiliary subunits in the stability and activation of Cav1.2 channels in TH2 lymphocytes both in vitro and in vivo, as demonstrated by the beneficial effect of Cavβ antisense and gabapentin in allergic airway inflammation.
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Affiliation(s)
- Nicolas Rosa
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Emily Triffaux
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Virginie Robert
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Marion Mars
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Martin Klein
- Institut du Thorax, INSERM CNRS, UNIV Nantes, France
| | | | - Astrid Canivet
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Antoine Magnan
- Institut du Thorax, INSERM CNRS, UNIV Nantes, France; Centre Hospitalier Universitaire de Nantes, Service de Pneumologie, Nantes, France
| | - Jean-Charles Guéry
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Lucette Pelletier
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France.
| | - Magali Savignac
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France.
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11
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Findeisen F, Campiglio M, Jo H, Abderemane-Ali F, Rumpf CH, Pope L, Rossen ND, Flucher BE, DeGrado WF, Minor DL. Stapled Voltage-Gated Calcium Channel (Ca V) α-Interaction Domain (AID) Peptides Act As Selective Protein-Protein Interaction Inhibitors of Ca V Function. ACS Chem Neurosci 2017; 8:1313-1326. [PMID: 28278376 PMCID: PMC5481814 DOI: 10.1021/acschemneuro.6b00454] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
![]()
For many voltage-gated
ion channels (VGICs), creation of a properly functioning ion channel
requires the formation of specific protein–protein interactions
between the transmembrane pore-forming subunits and cystoplasmic accessory
subunits. Despite the importance of such protein–protein interactions
in VGIC function and assembly, their potential as sites for VGIC modulator
development has been largely overlooked. Here, we develop meta-xylyl (m-xylyl) stapled peptides that
target a prototypic VGIC high affinity protein–protein interaction,
the interaction between the voltage-gated calcium channel (CaV) pore-forming subunit α-interaction domain (AID) and
cytoplasmic β-subunit (CaVβ). We show using
circular dichroism spectroscopy, X-ray crystallography, and isothermal
titration calorimetry that the m-xylyl staples enhance
AID helix formation are structurally compatible with native-like AID:CaVβ interactions and reduce the entropic penalty associated
with AID binding to CaVβ. Importantly, electrophysiological
studies reveal that stapled AID peptides act as effective inhibitors
of the CaVα1:CaVβ interaction
that modulate CaV function in an CaVβ
isoform-selective manner. Together, our studies provide a proof-of-concept
demonstration of the use of protein–protein interaction inhibitors
to control VGIC function and point to strategies for improved AID-based
CaV modulator design.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Daniel L. Minor
- Molecular Biophysics & Integrated Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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12
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Chi CH, Tang CY, Pan CY. Calmodulin modulates the Ca 2+-dependent inactivation and expression level of bovine Ca V2.2 expressed in HEK293T cells. IBRO Rep 2017; 2:63-71. [PMID: 30135934 PMCID: PMC6084911 DOI: 10.1016/j.ibror.2017.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 02/27/2017] [Accepted: 03/10/2017] [Indexed: 01/31/2023] Open
Abstract
Ca2+ influx through voltage-gated Ca2+ channels (CaVs) at the plasma membrane is the major pathway responsible for the elevation of the intracellular Ca2+ concentration ([Ca2+]i), which activates various physiological activities. Calmodulin (CaM) is known to be involved in the Ca2+-dependent inactivation (CDI) of several types of CaVs; however, little is known about how CaM modulates CaV2.2. Here, we expressed CaV2.2 with CaM or CaM mutants with a Ca2+-binding deficiency in HEK293T cells and measured the currents to characterize the CDI. The results showed that CaV2.2 displayed a fast inactivation with Ca2+ but not Ba2+ as the charge carrier; when CaV2.2 was co-expressed with CaM mutants with a Ca2+-binding deficiency, the level of inactivation decreased. Using glutathione S-transferase-tagged CaM or CaM mutants as the bait, we found that CaM could interact with the intracellular C-terminal fragment of CaV2.2 in the presence or absence of Ca2+. However, CaM and its mutants could not interact with this fragment when mutations were generated in the conserved amino acid residues of the CaM-binding site. CaV2.2 with mutations in the CaM-binding site showed a greatly reduced current that could be rescued by CaM12 (Ca2+-binding deficiency at the N-lobe) overexpression; in addition, CaM12 enhanced the total expression level of CaV2.2, but the ratio of CaV2.2 present in the membrane to the total fraction remained unchanged. Together, our data suggest that CaM, with different Ca2+-binding abilities, modulates not only the inactivation of CaV2.2 but also its expression to regulate Ca2+-related physiological activities.
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Affiliation(s)
- Chih-Hung Chi
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Chih-Yung Tang
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.,Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan
| | - Chien-Yuan Pan
- Department of Life Science, National Taiwan University, Taipei, Taiwan.,Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan
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13
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Karmažínová M, Jašková K, Griac P, Perez-Reyes E, Lacinová Ľ. Contrasting the roles of the I-II loop gating brake in CaV3.1 and CaV3.3 calcium channels. Pflugers Arch 2015; 467:2519-27. [PMID: 26306541 DOI: 10.1007/s00424-015-1728-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 08/16/2015] [Accepted: 08/18/2015] [Indexed: 01/23/2023]
Abstract
Low-voltage-activated CaV3 channels are distinguished among other voltage-activated calcium channels by the most negative voltage activation threshold. The voltage dependence of current activation is virtually identical in all three CaV3 channels while the current kinetics of the CaV3.3 current is one order slower than that of the CaV3.1 and CaV3.2 channels. We have analyzed the voltage dependence and kinetics of charge (Q) movement in human recombinant CaV3.3 and CaV3.1 channels. The voltage dependence of voltage sensor activation (Qon-V) of the CaV3.3 channel was significantly shifted with respect to that of the CaV3.1 channel by +18.6 mV and the kinetic of Qon activation in the CaV3.3 channel was significantly slower than that of the CaV3.1 channel. Removal of the gating brake in the intracellular loop connecting repeats I and II in the CaV3.3 channel in the ID12 mutant channel shifted the Qon-V relation to a value even more negative than that for the CaV3.1 channel. The kinetic of Qon activation was not significantly different between ID12 and CaV3.1 channels. Deletion of the gating brake in the CaV3.1 channel resulted in a GD12 channel with the voltage dependence of the gating current activation significantly shifted toward more negative potentials. The Qon kinetic was not significantly altered. ID12 and GD12 mutants did not differ significantly in voltage dependence nor in the kinetic of voltage sensor activation. In conclusion, the putative gating brake in the intracellular loop connecting repeats I and II controls the gating current of the CaV3 channels. We suggest that activation of the voltage sensor in domain I is limiting both the voltage dependence and the kinetics of CaV3 channel activation.
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Affiliation(s)
- Mária Karmažínová
- Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, 833 34, Bratislava, Slovakia
| | - Katarína Jašková
- Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, 833 34, Bratislava, Slovakia
| | - Peter Griac
- Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Ivanka pri Dunaji, Slovakia
| | - Edward Perez-Reyes
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22908, USA
| | - Ľubica Lacinová
- Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, 833 34, Bratislava, Slovakia.
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Intramolecular ex vivo Fluorescence Resonance Energy Transfer (FRET) of Dihydropyridine Receptor (DHPR) β1a Subunit Reveals Conformational Change Induced by RYR1 in Mouse Skeletal Myotubes. PLoS One 2015; 10:e0131399. [PMID: 26114725 PMCID: PMC4482598 DOI: 10.1371/journal.pone.0131399] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 06/02/2015] [Indexed: 11/29/2022] Open
Abstract
The dihydropyridine receptor (DHPR) β1a subunit is essential for skeletal muscle excitation-contraction coupling, but the structural organization of β1a as part of the macromolecular DHPR-ryanodine receptor type I (RyR1) complex is still debatable. We used fluorescence resonance energy transfer (FRET) to probe proximity relationships within the β1a subunit in cultured skeletal myotubes lacking or expressing RyR1. The fluorescein biarsenical reagent FlAsH was used as the FRET acceptor, which exhibits fluorescence upon binding to specific tetracysteine motifs, and enhanced cyan fluorescent protein (CFP) was used as the FRET donor. Ten β1a reporter constructs were generated by inserting the CCPGCC FlAsH binding motif into five positions probing the five domains of β1a with either carboxyl or amino terminal fused CFP. FRET efficiency was largest when CCPGCC was positioned next to CFP, and significant intramolecular FRET was observed for all constructs suggesting that in situ the β1a subunit has a relatively compact conformation in which the carboxyl and amino termini are not extended. Comparison of the FRET efficiency in wild type to that in dyspedic (lacking RyR1) myotubes revealed that in only one construct (H458 CCPGCC β1a -CFP) FRET efficiency was specifically altered by the presence of RyR1. The present study reveals that the C-terminal of the β1a subunit changes conformation in the presence of RyR1 consistent with an interaction between the C-terminal of β1a and RyR1 in resting myotubes.
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15
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Voltage Sensing in Membranes: From Macroscopic Currents to Molecular Motions. J Membr Biol 2015; 248:419-30. [PMID: 25972106 DOI: 10.1007/s00232-015-9805-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/24/2015] [Indexed: 01/06/2023]
Abstract
Voltage-sensing domains (VSDs) are integral membrane protein units that sense changes in membrane electric potential, and through the resulting conformational changes, regulate a specific function. VSDs confer voltage-sensitivity to a large superfamily of membrane proteins that includes voltage-gated Na[Formula: see text], K[Formula: see text], Ca[Formula: see text] ,and H[Formula: see text] selective channels, hyperpolarization-activated cyclic nucleotide-gated channels, and voltage-sensing phosphatases. VSDs consist of four transmembrane segments (termed S1 through S4). Their most salient structural feature is the highly conserved positions for charged residues in their sequences. S4 exhibits at least three conserved triplet repeats composed of one basic residue (mostly arginine) followed by two hydrophobic residues. These S4 basic side chains participate in a state-dependent internal salt-bridge network with at least four acidic residues in S1-S3. The signature of voltage-dependent activation in electrophysiology experiments is a transient current (termed gating or sensing current) upon a change in applied membrane potential as the basic side chains in S4 move across the membrane electric field. Thus, the unique structural features of the VSD architecture allow for competing requirements: maintaining a series of stable transmembrane conformations, while allowing charge motion, as briefly reviewed here.
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16
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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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17
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Stölting G, de Oliveira RC, Guzman RE, Miranda-Laferte E, Conrad R, Jordan N, Schmidt S, Hendriks J, Gensch T, Hidalgo P. Direct interaction of CaVβ with actin up-regulates L-type calcium currents in HL-1 cardiomyocytes. J Biol Chem 2015; 290:4561-4572. [PMID: 25533460 PMCID: PMC4335199 DOI: 10.1074/jbc.m114.573956] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 12/05/2014] [Indexed: 12/14/2022] Open
Abstract
Expression of the β-subunit (CaVβ) is required for normal function of cardiac L-type calcium channels, and its up-regulation is associated with heart failure. CaVβ binds to the α1 pore-forming subunit of L-type channels and augments calcium current density by facilitating channel opening and increasing the number of channels in the plasma membrane, by a poorly understood mechanism. Actin, a key component of the intracellular trafficking machinery, interacts with Src homology 3 domains in different proteins. Although CaVβ encompasses a highly conserved Src homology 3 domain, association with actin has not yet been explored. Here, using co-sedimentation assays and FRET experiments, we uncover a direct interaction between CaVβ and actin filaments. Consistently, single-molecule localization analysis reveals streaklike structures composed by CaVβ2 that distribute over several micrometers along actin filaments in HL-1 cardiomyocytes. Overexpression of CaVβ2-N3 in HL-1 cells induces an increase in L-type current without altering voltage-dependent activation, thus reflecting an increased number of channels in the plasma membrane. CaVβ mediated L-type up-regulation, and CaVβ-actin association is prevented by disruption of the actin cytoskeleton with cytochalasin D. Our study reveals for the first time an interacting partner of CaVβ that is directly involved in vesicular trafficking. We propose a model in which CaVβ promotes anterograde trafficking of the L-type channels by anchoring them to actin filaments in their itinerary to the plasma membrane.
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Affiliation(s)
- Gabriel Stölting
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | | | - Raul E Guzman
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Erick Miranda-Laferte
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Rachel Conrad
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Nadine Jordan
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Silke Schmidt
- the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Johnny Hendriks
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Thomas Gensch
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Patricia Hidalgo
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and.
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18
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Liu F, Zhou Q, Zhou J, Sun H, Wang Y, Zou X, Feng L, Hou Z, Zhou A, Zhou Y, Li Y. 14-3-3τ promotes surface expression of Cav2.2 (α1B) Ca2+ channels. J Biol Chem 2014; 290:2689-98. [PMID: 25516596 DOI: 10.1074/jbc.m114.567800] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Surface expression of voltage-gated Ca(2+) (Cav) channels is important for their function in calcium homeostasis in the physiology of excitable cells, but whether or not and how the α1 pore-forming subunits of Cav channels are trafficked to plasma membrane in the absence of the known Cav auxiliary subunits, β and α2δ, remains mysterious. Here we showed that 14-3-3 proteins promoted functional surface expression of the Cav2.2 α1B channel in transfected tsA-201 cells in the absence of any known Cav auxiliary subunit. Both the surface to total ratio of the expressed α1B protein and the current density of voltage step-evoked Ba(2+) current were markedly suppressed by the coexpression of a 14-3-3 antagonist construct, pSCM138, but not its inactive control, pSCM174, as determined by immunofluorescence assay and whole cell voltage clamp recording, respectively. By contrast, coexpression with 14-3-3τ significantly enhanced the surface expression and current density of the Cav2.2 α1B channel. Importantly, we found that between the two previously identified 14-3-3 binding regions at the α1B C terminus, only the proximal region (amino acids 1706-1940), closer to the end of the last transmembrane domain, was retained by the endoplasmic reticulum and facilitated by 14-3-3 to traffic to plasma membrane. Additionally, we showed that the 14-3-3/Cav β subunit coregulated the surface expression of Cav2.2 channels in transfected tsA-201 cells and neurons. Altogether, our findings reveal a previously unidentified regulatory function of 14-3-3 proteins in promoting the surface expression of Cav2.2 α1B channels.
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Affiliation(s)
- Feng Liu
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Qin Zhou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Jie Zhou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Hao Sun
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Yan Wang
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Xiuqun Zou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Lingling Feng
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Zhaoyuan Hou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Aiwu Zhou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Yi Zhou
- the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306
| | - Yong Li
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
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19
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Functional heterogeneity of the four voltage sensors of a human L-type calcium channel. Proc Natl Acad Sci U S A 2014; 111:18381-6. [PMID: 25489110 DOI: 10.1073/pnas.1411127112] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Excitation-evoked Ca(2+) influx is the fastest and most ubiquitous chemical trigger for cellular processes, including neurotransmitter release, muscle contraction, and gene expression. The voltage dependence and timing of Ca(2+) entry are thought to be functions of voltage-gated calcium (CaV) channels composed of a central pore regulated by four nonidentical voltage-sensing domains (VSDs I-IV). Currently, the individual voltage dependence and the contribution to pore opening of each VSD remain largely unknown. Using an optical approach (voltage-clamp fluorometry) to track the movement of the individual voltage sensors, we discovered that the four VSDs of CaV1.2 channels undergo voltage-evoked conformational rearrangements, each exhibiting distinct voltage- and time-dependent properties over a wide range of potentials and kinetics. The voltage dependence and fast kinetic components in the activation of VSDs II and III were compatible with the ionic current properties, suggesting that these voltage sensors are involved in CaV1.2 activation. This view is supported by an obligatory model, in which activation of VSDs II and III is necessary to open the pore. When these data were interpreted in view of an allosteric model, where pore opening is intrinsically independent but biased by VSD activation, VSDs II and III were each found to supply ∼50 meV (∼2 kT), amounting to ∼85% of the total energy, toward stabilizing the open state, with a smaller contribution from VSD I (∼16 meV). VSD IV did not appear to participate in channel opening.
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20
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Neely A, Hidalgo P. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels. Front Physiol 2014; 5:209. [PMID: 24917826 PMCID: PMC4042065 DOI: 10.3389/fphys.2014.00209] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 05/15/2014] [Indexed: 11/13/2022] Open
Abstract
Openings of high-voltage-activated (HVA) calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, HVA calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1) associated with four additional polypeptide chains β, α2, δ, and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of HVA calcium channels.
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Affiliation(s)
- Alan Neely
- Centro Interdisciplinario de Neurociencia de Valparaíso and Facultad de Ciencias, Universidad de Valparaíso Valparaíso, Chile
| | - Patricia Hidalgo
- Forschungszentrum Jülich, Institute of Complex Systems 4, Zelluläre Biophysik Jülich, Germany
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Functional exofacially tagged N-type calcium channels elucidate the interaction with auxiliary α2δ-1 subunits. Proc Natl Acad Sci U S A 2014; 111:8979-84. [PMID: 24889613 DOI: 10.1073/pnas.1403731111] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CaV1 and CaV2 voltage-gated calcium channels are associated with β and α2δ accessory subunits. However, examination of cell surface-associated CaV2 channels has been hampered by the lack of antibodies to cell surface-accessible epitopes and of functional exofacially tagged CaV2 channels. Here we report the development of fully functional CaV2.2 constructs containing inserted surface-accessible exofacial tags, which allow visualization of only those channels at the plasma membrane, in both a neuronal cell line and neurons. We first examined the effect of the auxiliary subunits. Although α2δ subunits copurify with CaV2 channels, it has recently been suggested that this interaction is easily disrupted and nonquantitative. We have now tested whether α2δ subunits are associated with these channels at the cell surface. We found that, whereas α2δ-1 is readily observed at the plasma membrane when expressed alone, it appears absent when coexpressed with CaV2.2/β1b, despite our finding that α2δ-1 increases plasma-membrane CaV2.2 expression. However, this was due to occlusion of the antigenic epitope by association with CaV2.2, as revealed by antigen retrieval; thus, our data provide evidence for a tight interaction between α2δ-1 and the α1 subunit at the plasma membrane. We further show that, although CaV2.2 cell-surface expression is reduced by gabapentin in the presence of wild-type α2δ-1 (but not a gabapentin-insensitive α2δ-1 mutant), the interaction between CaV2.2 and α2δ-1 is not disrupted by gabapentin. Altogether, these results demonstrate that CaV2.2 and α2δ-1 are intimately associated at the plasma membrane and allow us to infer a region of interaction.
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22
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Felix R, Calderón-Rivera A, Andrade A. Regulation of high-voltage-activated Ca 2+ channel function, trafficking, and membrane stability by auxiliary subunits. ACTA ACUST UNITED AC 2013; 2:207-220. [PMID: 24949251 DOI: 10.1002/wmts.93] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Voltage-gated Ca2+ (CaV) channels mediate Ca2+ ions influx into cells in response to depolarization of the plasma membrane. They are responsible for initiation of excitation-contraction and excitation-secretion coupling, and the Ca2+ that enters cells through this pathway is also important in the regulation of protein phosphorylation, gene transcription, and many other intracellular events. Initial electrophysiological studies divided CaV channels into low-voltage-activated (LVA) and high-voltage-activated (HVA) channels. The HVA CaV channels were further subdivided into L, N, P/Q, and R-types which are oligomeric protein complexes composed of an ion-conducting CaVα1 subunit and auxiliary CaVα2δ, CaVβ, and CaVγ subunits. The functional consequences of the auxiliary subunits include altered functional and pharmacological properties of the channels as well as increased current densities. The latter observation suggests an important role of the auxiliary subunits in membrane trafficking of the CaVα1 subunit. This includes the mechanisms by which CaV channels are targeted to the plasma membrane and to appropriate regions within a given cell. Likewise, the auxiliary subunits seem to participate in the mechanisms that remove CaV channels from the plasma membrane for recycling and/or degradation. Diverse studies have provided important clues to the molecular mechanisms involved in the regulation of CaV channels by the auxiliary subunits, and the roles that these proteins could possibly play in channel targeting and membrane Stabilization.
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Affiliation(s)
- Ricardo Felix
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav-IPN), Mexico City, Mexico
| | - Aida Calderón-Rivera
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav-IPN), Mexico City, Mexico
| | - Arturo Andrade
- Department of Neuroscience, Brown University, Providence, RI, USA
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23
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Adams DJ, Callaghan B, Berecki G. Analgesic conotoxins: block and G protein-coupled receptor modulation of N-type (Ca(V) 2.2) calcium channels. Br J Pharmacol 2012; 166:486-500. [PMID: 22091786 DOI: 10.1111/j.1476-5381.2011.01781.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Conotoxins (conopeptides) are small disulfide bonded peptides from the venom of marine cone snails. These peptides target a wide variety of membrane receptors, ion channels and transporters, and have enormous potential for a range of pharmaceutical applications. Structurally related ω-conotoxins bind directly to and selectively inhibit neuronal (N)-type voltage-gated calcium channels (VGCCs) of nociceptive primary afferent neurones. Among these, ω-conotoxin MVIIA (Prialt) is approved by the Food and Drug Administration (FDA) as an alternative intrathecal analgesic for the management of chronic intractable pain, particularly in patients refractory to opioids. A series of newly discovered ω-conotoxins from Conus catus, including CVID-F, are potent and selective antagonists of N-type VGCCs. In spinal cord slices, these peptides reversibly inhibit excitatory synaptic transmission between primary afferents and dorsal horn superficial lamina neurones, and in the rat partial sciatic nerve ligation model of neuropathic pain, significantly reduce allodynic behaviour. Another family of conotoxins, the α-conotoxins, are competitive antagonists of mammalian nicotinic acetylcholine receptors (nAChRs). α-Conotoxins Vc1.1 and RgIA possess two disulfide bonds and are currently in development as a treatment for neuropathic pain. It was initially proposed that the primary target of these peptides is the α9α10 neuronal nAChR. Surprisingly, however, α-conotoxins Vc1.1, RgIA and PeIA more potently inhibit N-type VGCC currents via a GABA(B) GPCR mechanism in rat sensory neurones. This inhibition is largely voltage-independent and involves complex intracellular signalling. Understanding the molecular mechanisms of conotoxin action will lead to new ways to regulate VGCC block and modulation in normal and diseased states of the nervous system.
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Affiliation(s)
- David J Adams
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria, Australia.
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24
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Miranda-Laferte E, Schmidt S, Jara AC, Neely A, Hidalgo P. A short polybasic segment between the two conserved domains of the β2a-subunit modulates the rate of inactivation of R-type calcium channel. J Biol Chem 2012; 287:32588-97. [PMID: 22851179 DOI: 10.1074/jbc.m112.362509] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Besides opening and closing, high voltage-activated calcium channels transit to a nonconducting inactivated state from which they do not re-open unless the plasma membrane is repolarized. Inactivation is critical for temporal regulation of intracellular calcium signaling and prevention of a deleterious rise in calcium concentration. R-type high voltage-activated channels inactivate fully in a few hundred milliseconds when expressed alone. However, when co-expressed with a particular β-subunit isoform, β(2a), inactivation is partial and develops in several seconds. Palmitoylation of a unique di-cysteine motif at the N terminus anchors β(2a) to the plasma membrane. The current view is that membrane-anchored β(2a) immobilizes the channel inactivation machinery and confers slow inactivation phenotype. β-Subunits contain one Src homology 3 and one guanylate kinase domain, flanked by variable regions with unknown structures. Here, we identified a short polybasic segment at the boundary of the guanylate kinase domain that slows down channel inactivation without relocating a palmitoylation-deficient β(2a) to the plasma membrane. Substitution of the positively charged residues within this segment by alanine abolishes its slow inactivation-conferring phenotype. The linker upstream from the polybasic segment, but not the N- and C-terminal variable regions, masks the effect of this determinant. These results reveal a novel mechanism for inhibiting voltage-dependent inactivation of R-type calcium channels by the β(2a)-subunit that might involve electrostatic interactions with an unknown target on the channel's inactivation machinery or its modulatory components. They also suggest that intralinker interactions occlude the action of the polybasic segment and that its functional availability is regulated by the palmitoylated state of the β(2a)-subunit.
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Affiliation(s)
- Erick Miranda-Laferte
- Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
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Calcium channel auxiliary α2δ and β subunits: trafficking and one step beyond. Nat Rev Neurosci 2012; 13:542-55. [PMID: 22805911 DOI: 10.1038/nrn3311] [Citation(s) in RCA: 264] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The voltage-gated calcium channel α(2)δ and β subunits are traditionally considered to be auxiliary subunits that enhance channel trafficking, increase the expression of functional calcium channels at the plasma membrane and influence the channels' biophysical properties. Accumulating evidence indicates that these subunits may also have roles in the nervous system that are not directly linked to calcium channel function. For example, β subunits may act as transcriptional regulators, and certain α(2)δ subunits may function in synaptogenesis. The aim of this Review is to examine both the classic and novel roles for these auxiliary subunits in voltage-gated calcium channel function and beyond.
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Gonzalez C, Contreras GF, Peyser A, Larsson P, Neely A, Latorre R. Voltage sensor of ion channels and enzymes. Biophys Rev 2012; 4:1-15. [PMID: 28509999 PMCID: PMC5425699 DOI: 10.1007/s12551-011-0061-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 11/17/2011] [Indexed: 10/14/2022] Open
Abstract
Placed in the cell membrane (a two-dimensional environment), ion channels and enzymes are able to sense voltage. How these proteins are able to detect the difference in the voltage across membranes has attracted much attention, and at times, heated debate during the last few years. Sodium, Ca2+ and K+ voltage-dependent channels have a conserved positively charged transmembrane (S4) segment that moves in response to changes in membrane voltage. In voltage-dependent channels, S4 forms part of a domain that crystallizes as a well-defined structure consisting of the first four transmembrane (S1-S4) segments of the channel-forming protein, which is defined as the voltage sensor domain (VSD). The VSD is tied to a pore domain and VSD movements are allosterically coupled to the pore opening to various degrees, depending on the type of channel. How many charges are moved during channel activation, how much they move, and which are the molecular determinants that mediate the electromechanical coupling between the VSD and the pore domains are some of the questions that we discuss here. The VSD can function, however, as a bona fide proton channel itself, and, furthermore, the VSD can also be a functional part of a voltage-dependent phosphatase.
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Affiliation(s)
- Carlos Gonzalez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso, 2360103, Chile
| | - Gustavo F Contreras
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso, 2360103, Chile
| | - Alexander Peyser
- Department of Physiology and Biophysics, University of Miami, Miami, FL, USA
| | - Peter Larsson
- Department of Physiology and Biophysics, University of Miami, Miami, FL, USA
| | - Alan Neely
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso, 2360103, Chile
| | - Ramón Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Pasaje Harrington 287, Valparaíso, 2360103, Chile.
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Fang K, Colecraft HM. Mechanism of auxiliary β-subunit-mediated membrane targeting of L-type (Ca(V)1.2) channels. J Physiol 2011; 589:4437-55. [PMID: 21746784 DOI: 10.1113/jphysiol.2011.214247] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Ca(2+) influx via Ca(V)1/Ca(V)2 channels drives processes ranging from neurotransmission to muscle contraction. Association of a pore-forming α(1) and cytosolic β is necessary for trafficking Ca(V)1/Ca(V)2 channels to the cell surface through poorly understood mechanisms. A prevalent idea suggests β binds the α(1) intracellular I-II loop, masking an endoplasmic reticulum (ER) retention signal as the dominant mechanism for Ca(V)1/Ca(V)2 channel membrane trafficking. There are hints that other α(1) subunit cytoplasmic domains may play a significant role, but the nature of their potential contribution is unclear. We assessed the roles of all intracellular domains of Ca(V)1.2-α(1C) by generating chimeras featuring substitutions of all possible permutations of intracellular loops/termini of α(1C) into the β-independent Ca(V)3.1-α(1G) channel. Surprisingly, functional analyses demonstrated α(1C) I-II loop strongly increases channel surface density while other cytoplasmic domains had a competing opposing effect. Alanine-scanning mutagenesis identified an acidic-residue putative ER export motif responsible for the I-II loop-mediated increase in channel surface density. β-dependent increase in current arose as an emergent property requiring four α(1C) intracellular domains, with the I-II loop and C-terminus being essential. The results suggest β binding to the α(1C) I-II loop causes a C-terminus-dependent rearrangement of intracellular domains, shifting a balance of power between export signals on the I-II loop and retention signals elsewhere.
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Affiliation(s)
- Kun Fang
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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Waithe D, Ferron L, Page KM, Chaggar K, Dolphin AC. Beta-subunits promote the expression of Ca(V)2.2 channels by reducing their proteasomal degradation. J Biol Chem 2011; 286:9598-611. [PMID: 21233207 PMCID: PMC3059031 DOI: 10.1074/jbc.m110.195909] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 12/22/2010] [Indexed: 02/03/2023] Open
Abstract
The β-subunits of voltage-gated calcium channels regulate their functional expression and properties. Two mechanisms have been proposed for this, an effect on gating and an enhancement of expression. With respect to the effect on expression, β-subunits have been suggested to enhance trafficking by masking an unidentified endoplasmic reticulum (ER) retention signal. Here we have investigated whether, and how, β-subunits affect the level of Ca(V)2.2 channels within somata and neurites of cultured sympathetic neurons. We have used YFP-Ca(V)2.2 containing a mutation (W391A), that prevents binding of β-subunits to its I-II linker and found that expression of this channel was much reduced compared with WT CFP-Ca(V)2.2 when both were expressed in the same neuron. This effect was particularly evident in neurites and growth cones. The difference between the levels of YFP-Ca(V)2.2(W391A) and CFP-Ca(V)2.2(WT) was lost in the absence of co-expressed β-subunits. Furthermore, the relative reduction of expression of Ca(V)2.2(W391A) compared with the WT channel was reversed by exposure to two proteasome inhibitors, MG132 and lactacystin, particularly in the somata. In further experiments in tsA-201 cells, we found that proteasome inhibition did not augment the cell surface Ca(V)2.2(W391A) level but resulted in the observation of increased ubiquitination, particularly of mutant channels. In contrast, we found no evidence for selective retention of Ca(V)2.2(W391A) in the ER, in either the soma or growth cones. In conclusion, there is a marked effect of β-subunits on Ca(V)2.2 expression, particularly in neurites, but our results point to protection from proteasomal degradation rather than masking of an ER retention signal.
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Affiliation(s)
- Dominic Waithe
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Laurent Ferron
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Karen M. Page
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Kanchan Chaggar
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
| | - Annette C. Dolphin
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower St., London WC1E 6BT, United Kingdom
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Karmažínová M, Baumgart JP, Perez-Reyes E, Lacinová L. The voltage dependence of gating currents of the neuronal CA(v)3.3 channel is determined by the gating brake in the I-II loop. Pflugers Arch 2011; 461:461-8. [PMID: 21340458 DOI: 10.1007/s00424-011-0937-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 02/06/2011] [Accepted: 02/08/2011] [Indexed: 01/10/2023]
Abstract
Low-voltage-activated Ca(v)3 Ca(2+) channels have an activation threshold around -60 mV, which is lower than the activation threshold of other voltage-dependent calcium channels (VDCCs). The kinetics of their activation at membrane voltages just above the activation threshold is much slower than the activation kinetics of other VDCCs. It was demonstrated recently that the intracellular loop connecting repeats I and II of all three Ca(v)3 channels contains a so-called gating brake. Disruption of this brake yields channels that activate at even more hyperpolarized potentials with significantly accelerated kinetics. We have compared gating of a wild-type Ca(v)3.3 channel and a mutated ID12 channel, in which the putative gating brake at the proximal part of the I-II loop was removed. Voltage dependence of the gating current activation was shifted by 34.6 mV towards more hyperpolarized potentials in ID12 channel. ON-charge movement was significantly faster in the ID12 channel, while the kinetics of the off-charge was not altered by the mutation. We conclude that the putative gating brake in I-II loop hinders not only the opening of the conducting pore but also the activating movement of voltage-sensing S4 segments, stabilizing the channel in its closed state.
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Affiliation(s)
- Mária Karmažínová
- Institute of Molecular Physiology and Genetics, Centre of Excellence for Cardiovascular Research, Slovak Academy of Sciences, Bratislava, Slovakia
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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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Dai S, Hall DD, Hell JW. Supramolecular assemblies and localized regulation of voltage-gated ion channels. Physiol Rev 2009; 89:411-52. [PMID: 19342611 DOI: 10.1152/physrev.00029.2007] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
This review addresses the localized regulation of voltage-gated ion channels by phosphorylation. Comprehensive data on channel regulation by associated protein kinases, phosphatases, and related regulatory proteins are mainly available for voltage-gated Ca2+ channels, which form the main focus of this review. Other voltage-gated ion channels and especially Kv7.1-3 (KCNQ1-3), the large- and small-conductance Ca2+-activated K+ channels BK and SK2, and the inward-rectifying K+ channels Kir3 have also been studied to quite some extent and will be included. Regulation of the L-type Ca2+ channel Cav1.2 by PKA has been studied most thoroughly as it underlies the cardiac fight-or-flight response. A prototypical Cav1.2 signaling complex containing the beta2 adrenergic receptor, the heterotrimeric G protein Gs, adenylyl cyclase, and PKA has been identified that supports highly localized via cAMP. The type 2 ryanodine receptor as well as AMPA- and NMDA-type glutamate receptors are in close proximity to Cav1.2 in cardiomyocytes and neurons, respectively, yet independently anchor PKA, CaMKII, and the serine/threonine phosphatases PP1, PP2A, and PP2B, as is discussed in detail. Descriptions of the structural and functional aspects of the interactions of PKA, PKC, CaMKII, Src, and various phosphatases with Cav1.2 will include comparisons with analogous interactions with other channels such as the ryanodine receptor or ionotropic glutamate receptors. Regulation of Na+ and K+ channel phosphorylation complexes will be discussed in separate papers. This review is thus intended for readers interested in ion channel regulation or in localization of kinases, phosphatases, and their upstream regulators.
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Affiliation(s)
- Shuiping Dai
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242-1109, USA
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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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Chen RS, Best PM. A Small Peptide Inhibitor of the Low Voltage-Activated Calcium Channel Cav3.1. Mol Pharmacol 2009; 75:1042-51. [DOI: 10.1124/mol.108.052654] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Gonzalez-Gutierrez G, Miranda-Laferte E, Naranjo D, Hidalgo P, Neely A. Mutations of nonconserved residues within the calcium channel alpha1-interaction domain inhibit beta-subunit potentiation. ACTA ACUST UNITED AC 2008; 132:383-95. [PMID: 18725532 PMCID: PMC2518731 DOI: 10.1085/jgp.200709901] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Voltage-dependent calcium channels consist of a pore-forming subunit (Ca(V)alpha(1)) that includes all the molecular determinants of a voltage-gated channel, and several accessory subunits. The ancillary beta-subunit (Ca(V)beta) is a potent activator of voltage-dependent calcium channels, but the mechanisms and structural bases of this regulation remain elusive. Ca(V)beta binds reversibly to a conserved consensus sequence in Ca(V)alpha(1), the alpha(1)-interaction domain (AID), which forms an alpha-helix when complexed with Ca(V)beta. Conserved aromatic residues face to one side of the helix and strongly interact with a hydrophobic pocket on Ca(V)beta. Here, we studied the effect of mutating residues located opposite to the AID-Ca(V)beta contact surface in Ca(V)1.2. Substitution of AID-exposed residues by the corresponding amino acids present in other Ca(V)alpha(1) subunits (E462R, K465N, D469S, and Q473K) hinders Ca(V)beta's ability to increase ionic-current to charge-movement ratio (I/Q) without changing the apparent affinity for Ca(V)beta. At the single channel level, these Ca(V)1.2 mutants coexpressed with Ca(V)beta(2a) visit high open probability mode less frequently than wild-type channels. On the other hand, Ca(V)1.2 carrying either a mutation in the conserved tryptophan residue (W470S, which impairs Ca(V)beta binding), or a deletion of the whole AID sequence, does not exhibit Ca(V)beta-induced increase in I/Q. In addition, we observed a shift in the voltage dependence of activation by +12 mV in the AID-deleted channel in the absence of Ca(V)beta, suggesting a direct participation of these residues in the modulation of channel activation. Our results show that Ca(V)beta-dependent potentiation arises primarily from changes in the modal gating behavior. We envision that Ca(V)beta spatially reorients AID residues that influence the channel gate. These findings provide a new framework for understanding modulation of VDCC gating by Ca(V)beta.
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The guanylate kinase domain of the beta-subunit of voltage-gated calcium channels suffices to modulate gating. Proc Natl Acad Sci U S A 2008; 105:14198-203. [PMID: 18776052 DOI: 10.1073/pnas.0806558105] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Inactivation of voltage-gated calcium channels is crucial for the spatiotemporal coordination of calcium signals and prevention of toxic calcium buildup. Only one member of the highly conserved family of calcium channel beta-subunits--Ca(V)beta--inhibits inactivation. This unique property has been attributed to short variable regions of the protein; however, here we report that this inhibition actually is conferred by a conserved guanylate kinase (GK) domain and, moreover, that this domain alone recapitulates Ca(V)beta-mediated modulation of channel activation. We expressed and refolded the GK domain of Ca(V)beta(2a), the unique variant that inhibits inactivation, and of Ca(V)beta(1b), an isoform that facilitates it. The refolded domains of both Ca(V)beta variants were found to inhibit inactivation of Ca(V)2.3 channels expressed in Xenopus laevis oocytes. These findings suggest that the GK domain endows calcium channels with a brake restraining voltage-dependent inactivation, and thus facilitation of inactivation by full-length Ca(V)beta requires additional structural determinants to antagonize the GK effect. We found that Ca(V)beta can switch the inactivation phenotype conferred to Ca(V)2.3 from slow to fast after posttranslational modifications during channel biogenesis. Our findings provide a framework within which to understand the modulation of inactivation and a new functional map of Ca(V)beta in which the GK domain regulates channel gating and the other conserved domain (Src homology 3) may couple calcium channels to other signaling pathways.
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Alanine-scanning mutagenesis defines a conserved energetic hotspot in the CaValpha1 AID-CaVbeta interaction site that is critical for channel modulation. Structure 2008; 16:280-94. [PMID: 18275819 DOI: 10.1016/j.str.2007.11.010] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 11/19/2007] [Accepted: 11/24/2007] [Indexed: 11/21/2022]
Abstract
Voltage-gated calcium channels (CaVs) are large, multisubunit complexes that control cellular calcium entry. CaV pore-forming (CaValpha1) and cytoplasmic (CaVbeta) subunits associate through a high-affinity interaction between the CaValpha1 alpha interaction domain (AID) and CaVbeta alpha binding pocket (ABP). Here we analyze AID-ABP interaction thermodynamics using isothermal titration calorimetry. We find that commensurate with their strong sequence similarity, all CaV1 and CaV2 AID peptides bind CaVbeta with similar nanomolar affinities. Although the AID-ABP interface encompasses 24 side chains, alanine-scanning mutagenesis reveals that the binding energy is focused in two complementary hotspots comprising four deeply conserved residues. Electrophysiological experiments show that hotspot interaction disruption prevents trafficking and functional modulation of CaV1.2 by CaVbeta. Together, the data support the primacy of the AID-ABP interface for CaValpha1-CaVbeta association, underscore the idea that hotspots dominate protein-protein interaction affinities, and uncover a target for strategies to control cellular excitability by blocking CaValpha1-CaVbeta complex formation.
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Hering S, Beyl S, Stary A, Kudrnac M, Hohaus A, Guy HR, Timin E. Pore stability and gating in voltage-activated calcium channels. Channels (Austin) 2008; 2:61-9. [PMID: 18849656 DOI: 10.4161/chan.2.2.5999] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Calcium channel family members activate at different membrane potentials, which enables tissue specific calcium entry. Pore mutations affecting this voltage dependence are associated with channelopathies. In this review we analyze the link between voltage sensitivity and corresponding kinetic phenotypes of calcium channel activation. Systematic changes in hydrophobicity in the lower third of S6 segments gradually shift the activation curve thereby determining the voltage sensitivity. Homology modeling suggests that hydrophobic residues that are located in all four S6 segments close to the inner channel mouth might form adhesion points stabilizing the closed gate. Simulation studies support a scenario where voltage sensors and the pore are essentially independent structural units. We speculate that evolution designed the voltage sensing machinery as robust "all-or-non" device while the varietys of voltage sensitivities of different channel types was accomplished by shaping pore stability.
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Affiliation(s)
- Steffen Hering
- Institute of Pharmacology and Toxicology, University of Vienna, Vienna, Austria.
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38
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Temperature dependence of Cav1.4 calcium channel gating. Neuroscience 2008; 151:1066-83. [DOI: 10.1016/j.neuroscience.2007.11.053] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 11/29/2007] [Accepted: 12/07/2007] [Indexed: 11/23/2022]
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Nguemo F, Fleischmann BK, Schunkert H, Hescheler J, Reppel M. Functional Expression and Inactivation of L-type Ca 2+ Currents During Murine Heart Development -Implications for Cardiac Ca 2+ Homeostasis. Cell Physiol Biochem 2007; 20:809-24. [DOI: 10.1159/000110441] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/09/2007] [Indexed: 11/19/2022] Open
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Gudzenko V, Shiferaw Y, Savalli N, Vyas R, Weiss JN, Olcese R. Influence of channel subunit composition on L-type Ca2+ current kinetics and cardiac wave stability. Am J Physiol Heart Circ Physiol 2007; 293:H1805-15. [PMID: 17545475 DOI: 10.1152/ajpheart.01160.2006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have demonstrated that the slope of the function relating the action potential duration (APD) and the diastolic interval, known as the APD restitution curve, plays an important role in the initiation and maintenance of ventricular fibrillation. Since the APD restitution slope critically depends on the kinetics of the L-type Ca(2+) current, we hypothesized that manipulation of the subunit composition of these channels may represent a powerful strategy to control cardiac arrhythmias. We studied the kinetic properties of the human L-type Ca(2+) channel (Ca(v)1.2) coexpressed with the alpha(2)delta-subunit alone (alpha(1C) + alpha(2)delta) or in combination with beta(2a), beta(2b), or beta(3) subunits (alpha(1C) + alpha(2)delta + beta), using Ca(2+) as the charge carrier. We then incorporated the kinetic properties observed experimentally into the L-type Ca(2+) current mathematical model of the cardiac action potential to demonstrate that the APD restitution slope can be selectively controlled by altering the subunit composition of the Ca(2+) channel. Assuming that beta(2b) most closely resembles the native cardiac L-type Ca(2+) current, the absence of beta, as well as the coexpression of beta(2a), was found to flatten restitution slope and stabilize spiral waves. These results imply that subunit modification of L-type Ca(2+) channels can potentially be used as an antifibrillatory strategy.
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Affiliation(s)
- Vadim Gudzenko
- Division of Molecular Medicine, Department of Anesthesiology, David Geffen School of Medicine, University of California Los Angeles 90095-7115, USA
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Chen RS, Deng TC, Garcia T, Sellers ZM, Best PM. Calcium channel γ subunits: a functionally diverse protein family. Cell Biochem Biophys 2007; 47:178-86. [PMID: 17652770 DOI: 10.1007/s12013-007-0002-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 10/23/2022]
Abstract
The calcium channel gamma subunits comprise an eight-member protein family that share a common topology consisting of four transmembrane domains and intracellular N- and C-termini. Although the first gamma subunit was identified as an auxiliary subunit of a voltage-dependent calcium channel, a review of phylogenetic, bioinformatic, and functional studies indicates that they are a functionally diverse protein family. A cluster containing gamma1 and gamma6 conforms to the original description of the protein family as they seem to act primarily as subunits of calcium channels expressed in muscle. Members of a second cluster (gamma2, gamma3, gamma4, gamma8) function as regulators of AMPA receptor localization and function in the brain and are collectively known as TARPs. The function of members of the third cluster (gamma5, gamma7) remains unclear. Our analysis shows that the members of each cluster contain conserved regulatory motifs that help to differentiate the groups. However, the physiological significance of these motifs in many cases remains to be demonstrated.
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Affiliation(s)
- Ren-Shiang Chen
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, 524 Burrill Hall, 407 S Goodwin Avenue, Urbana, IL 61801, USA
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43
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Abstract
Triggered activity in cardiac muscle and intracellular Ca2+ have been linked in the past. However, today not only are there a number of cellular proteins that show clear Ca2+ dependence but also there are a number of arrhythmias whose mechanism appears to be linked to Ca2+-dependent processes. Thus we present a systematic review of the mechanisms of Ca2+ transport (forward excitation-contraction coupling) in the ventricular cell as well as what is known for other cardiac cell types. Second, we review the molecular nature of the proteins that are involved in this process as well as the functional consequences of both normal and abnormal Ca2+ cycling (e.g., Ca2+ waves). Finally, we review what we understand to be the role of Ca2+ cycling in various forms of arrhythmias, that is, those associated with inherited mutations and those that are acquired and resulting from reentrant excitation and/or abnormal impulse generation (e.g., triggered activity). Further solving the nature of these intricate and dynamic interactions promises to be an important area of research for a better recognition and understanding of the nature of Ca2+ and arrhythmias. Our solutions will provide a more complete understanding of the molecular basis for the targeted control of cellular calcium in the treatment and prevention of such.
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Affiliation(s)
- Henk E D J Ter Keurs
- Department of Medicine, Physiology and Biophysics, University of Calgary, Alberta, Canada
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44
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Gonzalez-Gutierrez G, Miranda-Laferte E, Neely A, Hidalgo P. The Src Homology 3 Domain of the β-Subunit of Voltage-gated Calcium Channels Promotes Endocytosis via Dynamin Interaction. J Biol Chem 2007; 282:2156-62. [PMID: 17110381 DOI: 10.1074/jbc.m609071200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
High voltage-gated calcium channels enable calcium entry into cells in response to membrane depolarization. Association of the auxiliary beta-subunit to the alpha-interaction-domain in the pore-forming alpha1-subunit is required to form functional channels. The beta-subunit belongs to the membrane-associated guanylate kinase class of scaffolding proteins containing a Src homology 3 and a guanylate kinase domain. Although the latter is responsible for the high affinity binding to the alpha-interaction domain, the functional significance of the Src homology 3 domain remains elusive. Here, we show that injection of isolated beta-subunit Src homology 3 domain into Xenopus laevis oocytes expressing the alpha1-subunit reduces the number of channels in the plasma membrane. This effect is reverted by coexpressing alpha1 with a dominant-negative mutant of dynamin, a GTPase involved in receptor-mediated endocytosis. Full-length beta-subunit also down-regulates voltage-gated calcium channels but only when lacking the alpha-interaction domain. Moreover, isolated Src homology 3 domain and the full-length beta-subunit were found to interact in vitro with dynamin and to internalize the distantly related Shaker potassium channel. These results demonstrate that the beta-subunit regulates the turnover of voltage-gated calcium channels and other proteins in the cell membrane. This effect is mediated by dynamin and depends on the association state of the beta-subunit to the alpha1-pore-forming subunit. Our findings define a novel function for the beta-subunit through its Src homology 3 domain and establish a link between voltage-gated calcium channel activity and the cell endocytic machinery.
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45
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Affiliation(s)
- Annette C Dolphin
- Laboratory of Cellular and Molecular Neuroscience, Department of Pharmacology, University College London, Gower St, London WC1E6BT.
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46
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Kanevsky N, Dascal N. Regulation of maximal open probability is a separable function of Ca(v)beta subunit in L-type Ca2+ channel, dependent on NH2 terminus of alpha1C (Ca(v)1.2alpha). ACTA ACUST UNITED AC 2006; 128:15-36. [PMID: 16801381 PMCID: PMC2151559 DOI: 10.1085/jgp.200609485] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
β subunits (Cavβ) increase macroscopic currents of voltage-dependent Ca2+ channels (VDCC) by increasing surface expression and modulating their gating, causing a leftward shift in conductance–voltage (G-V) curve and increasing the maximal open probability, Po,max. In L-type Cav1.2 channels, the Cavβ-induced increase in macroscopic current crucially depends on the initial segment of the cytosolic NH2 terminus (NT) of the Cav1.2α (α1C) subunit. This segment, which we term the “NT inhibitory (NTI) module,” potently inhibits long-NT (cardiac) isoform of α1C that features an initial segment of 46 amino acid residues (aa); removal of NTI module greatly increases macroscopic currents. It is not known whether an NTI module exists in the short-NT (smooth muscle/brain type) α1C isoform with a 16-aa initial segment. We addressed this question, and the molecular mechanism of NTI module action, by expressing subunits of Cav1.2 in Xenopus oocytes. NT deletions and chimeras identified aa 1–20 of the long-NT as necessary and sufficient to perform NTI module functions. Coexpression of β2b subunit reproducibly modulated function and surface expression of α1C, despite the presence of measurable amounts of an endogenous Cavβ in Xenopus oocytes. Coexpressed β2b increased surface expression of α1C approximately twofold (as demonstrated by two independent immunohistochemical methods), shifted the G-V curve by ∼14 mV, and increased Po,max 2.8–3.8-fold. Neither the surface expression of the channel without Cavβ nor β2b-induced increase in surface expression or the shift in G-V curve depended on the presence of the NTI module. In contrast, the increase in Po,max was completely absent in the short-NT isoform and in mutants of long-NT α1C lacking the NTI module. We conclude that regulation of Po,max is a discrete, separable function of Cavβ. In Cav1.2, this action of Cavβ depends on NT of α1C and is α1C isoform specific.
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Affiliation(s)
- Nataly Kanevsky
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Israel
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47
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Yang SN, Berggren PO. The role of voltage-gated calcium channels in pancreatic beta-cell physiology and pathophysiology. Endocr Rev 2006; 27:621-76. [PMID: 16868246 DOI: 10.1210/er.2005-0888] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Voltage-gated calcium (CaV) channels are ubiquitously expressed in various cell types throughout the body. In principle, the molecular identity, biophysical profile, and pharmacological property of CaV channels are independent of the cell type where they reside, whereas these channels execute unique functions in different cell types, such as muscle contraction, neurotransmitter release, and hormone secretion. At least six CaValpha1 subunits, including CaV1.2, CaV1.3, CaV2.1, CaV2.2, CaV2.3, and CaV3.1, have been identified in pancreatic beta-cells. These pore-forming subunits complex with certain auxiliary subunits to conduct L-, P/Q-, N-, R-, and T-type CaV currents, respectively. beta-Cell CaV channels take center stage in insulin secretion and play an important role in beta-cell physiology and pathophysiology. CaV3 channels become expressed in diabetes-prone mouse beta-cells. Point mutation in the human CaV1.2 gene results in excessive insulin secretion. Trinucleotide expansion in the human CaV1.3 and CaV2.1 gene is revealed in a subgroup of patients with type 2 diabetes. beta-Cell CaV channels are regulated by a wide range of mechanisms, either shared by other cell types or specific to beta-cells, to always guarantee a satisfactory concentration of Ca2+. Inappropriate regulation of beta-cell CaV channels causes beta-cell dysfunction and even death manifested in both type 1 and type 2 diabetes. This review summarizes current knowledge of CaV channels in beta-cell physiology and pathophysiology.
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Affiliation(s)
- Shao-Nian Yang
- The Rolf Luft Research Center for Diabetes and Endocrinology L1:03, Karolinska University Hospital Solna, SE-171 76 Stockholm, Sweden.
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48
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Hidalgo P, Gonzalez-Gutierrez G, Garcia-Olivares J, Neely A. The alpha1-beta-subunit interaction that modulates calcium channel activity is reversible and requires a competent alpha-interaction domain. J Biol Chem 2006; 281:24104-10. [PMID: 16793763 DOI: 10.1074/jbc.m605930200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
High voltage-gated calcium channels consist of a pore-forming subunit (alpha(1)) and three nonhomologous subunits (alpha(2)/delta, beta, and gamma). Although it is well established that the beta-subunit promotes traffic of channels to the plasma membrane and modifies their activity, the reversible nature of the interaction with the alpha(1)-subunit remains controversial. Here, we address this issue by examining the effect of purified beta(2a) protein on Ca(V)1.2 and Ca(V)2.3 channels expressed in Xenopus oocytes. The beta(2a)-subunit binds to the alpha(1)-interaction domain (AID) in vitro, and when injected into oocytes, it shifts the voltage dependence of activation and increases charge movement to ionic current coupling of Ca(V)1.2 channels. This increase depended on the integrity of AID but was not abolished by bafilomycin, demonstrating that the alpha(1)-beta interaction through the AID site can take place at the plasma membrane. Furthermore, injection of beta(2a) protein inhibited inactivation of Ca(V)2.3 channels and converted fast inactivating Ca(V)2.3/beta(1b) channels to slow inactivating channels. Inhibition of inactivation required larger concentration of beta(2a) in oocytes expressing Ca(V)2.3/beta(1b) channels than expressing Ca(V)2.3 alone but reached the same maximal level as expected for a competitive interaction through a single binding site. Together, our data show that the alpha(1)-beta interaction is reversible in intact cells and defines calcium channels beta-subunits as regulatory proteins rather than stoichiometric subunits.
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Affiliation(s)
- Patricia Hidalgo
- Abteilung Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
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49
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Butcher AJ, Leroy J, Richards MW, Pratt WS, Dolphin AC. The importance of occupancy rather than affinity of CaV(beta) subunits for the calcium channel I-II linker in relation to calcium channel function. J Physiol 2006; 574:387-98. [PMID: 16627564 PMCID: PMC1817768 DOI: 10.1113/jphysiol.2006.109744] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The Ca(V)beta subunits of voltage-gated calcium channels regulate the trafficking and biophysical properties of these channels. We have taken advantage of mutations in the tyrosine residue within the alpha interaction domain (AID) in the I-II linker of Ca(V)2.2 which reduce, but do not abolish, the binding of beta1b to the AID of Ca(V)2.2. We have found that the mutation Y388S decreased the affinity of Ca(V)beta1b binding to the Ca(V)2.2 I-II linker from 14 to 329 nm. However, the Y388S mutation had no effect on current density and cell surface expression of Ca(V)2.2/alpha2delta-2/beta1b channels expressed in human embryonic kidney tsA-201 cells, when equivalent proportions of cDNA were used. Furthermore, despite the 24-fold reduced affinity of Ca(V)beta1b for the Y388S I-II linker of Ca(V)2.2, all the key features of modulation as well as trafficking by Ca(V)beta subunits remained intact. This is in contrast to the much more marked effect of the W391A mutation, which abolished interaction with the Ca(V)2.2 I-II linker, and very markedly affected the trafficking of the channels. However, using the Xenopus oocyte expression system, where expression levels can be accurately titrated, when Ca(V)beta1b cDNA was diluted 50-fold, all evidence of interaction with Ca(V)2.2 Y388S was lost, although wild-type Ca(V)2.2 was still normally modulated by the reduced concentration of beta1b. These results indicate that high affinity interaction with the alpha1 subunit is not necessary for any of the modulatory effects of Ca(V)beta subunits, but occupancy of the interaction site is important, and this will occur, despite the reduced affinity, if the Ca(V)beta subunit is present in sufficient excess.
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Affiliation(s)
- Adrian J Butcher
- Laboratory of Cellular and Molecular Neuroscience, Department of Pharmacology, Andrew Huxley Building, University College London, UK
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50
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Boyden PA, ter Keurs H. Would modulation of intracellular Ca2+ be antiarrhythmic? Pharmacol Ther 2005; 108:149-79. [PMID: 16038982 DOI: 10.1016/j.pharmthera.2005.03.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Accepted: 03/22/2005] [Indexed: 01/10/2023]
Abstract
Under several types of conditions, reversal of steps of excitation-contraction coupling (RECC) can give rise to nondriven electrical activity. In this review we explore those conditions for several cardiac cell types (SA, atrial, Purkinje, ventricular cells). We find that abnormal spontaneous Ca2+ release from intracellular Ca2+ stores, aberrant Ca2+ influx from sarcolemmal channels or abnormal Ca2+ surges in nonuniform muscle can be the initiators of the RECC. Often, with such increases in Ca2+, spontaneous Ca2+ waves occur and lead to membrane depolarizations. Because the change in membrane voltage is produced by Ca2+-dependent changes in ion channel function, we also review here what is known about the molecular interaction of Ca2+ and several Ca2+-dependent processes, including the intracellular Ca2+ release channels implicated in the genetic basis of some forms of human arrhythmias. Finally, we review what is known about the effectiveness of several agents in modifying such Ca2+-dependent arrhythmias.
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Affiliation(s)
- Penelope A Boyden
- Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, NY 10032, USA.
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