1
|
Allam S, Levenson-Palmer R, Chia Chang Z, Kaur S, Cernuda B, Raman A, Booth A, Dobbins S, Suppa G, Yang J, Buraei Z. Inactivation influences the extent of inhibition of voltage-gated Ca +2 channels by Gem-implications for channelopathies. Front Physiol 2023; 14:1155976. [PMID: 37654674 PMCID: PMC10466392 DOI: 10.3389/fphys.2023.1155976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 07/21/2023] [Indexed: 09/02/2023] Open
Abstract
Voltage-gated Ca2+ channels (VGCC) directly control muscle contraction and neurotransmitter release, and slower processes such as cell differentiation, migration, and death. They are potently inhibited by RGK GTP-ases (Rem, Rem2, Rad, and Gem/Kir), which decrease Ca2+ channel membrane expression, as well as directly inhibit membrane-resident channels. The mechanisms of membrane-resident channel inhibition are difficult to study because RGK-overexpression causes complete or near complete channel inhibition. Using titrated levels of Gem expression in Xenopus oocytes to inhibit WT P/Q-type calcium channels by ∼50%, we show that inhibition is dependent on channel inactivation. Interestingly, fast-inactivating channels, including Familial Hemiplegic Migraine mutants, are more potently inhibited than WT channels, while slow-inactivating channels, such as those expressed with the Cavβ2a auxiliary subunit, are spared. We found similar results in L-type channels, and, remarkably, Timothy Syndrome mutant channels were insensitive to Gem inhibition. Further results suggest that RGKs slow channel recovery from inactivation and further implicate RGKs as likely modulating factors in channelopathies.
Collapse
Affiliation(s)
- Salma Allam
- Department of Biology, Pace University, New York, NY, United States
| | - Rose Levenson-Palmer
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | | | - Sukhjinder Kaur
- Department of Biology, Pace University, New York, NY, United States
| | - Bryan Cernuda
- Department of Biology, Pace University, New York, NY, United States
| | - Ananya Raman
- Department of Biology, Pace University, New York, NY, United States
| | - Audrey Booth
- Department of Biology, Pace University, New York, NY, United States
| | - Scott Dobbins
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | - Gabrielle Suppa
- Department of Biology, Pace University, New York, NY, United States
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, NY, United States
| | - Zafir Buraei
- Department of Biology, Pace University, New York, NY, United States
| |
Collapse
|
2
|
Cunningham KL, Littleton JT. Mechanisms controlling the trafficking, localization, and abundance of presynaptic Ca 2+ channels. Front Mol Neurosci 2023; 15:1116729. [PMID: 36710932 PMCID: PMC9880069 DOI: 10.3389/fnmol.2022.1116729] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 12/26/2022] [Indexed: 01/14/2023] Open
Abstract
Voltage-gated Ca2+ channels (VGCCs) mediate Ca2+ influx to trigger neurotransmitter release at specialized presynaptic sites termed active zones (AZs). The abundance of VGCCs at AZs regulates neurotransmitter release probability (Pr ), a key presynaptic determinant of synaptic strength. Given this functional significance, defining the processes that cooperate to establish AZ VGCC abundance is critical for understanding how these mechanisms set synaptic strength and how they might be regulated to control presynaptic plasticity. VGCC abundance at AZs involves multiple steps, including channel biosynthesis (transcription, translation, and trafficking through the endomembrane system), forward axonal trafficking and delivery to synaptic terminals, incorporation and retention at presynaptic sites, and protein recycling. Here we discuss mechanisms that control VGCC abundance at synapses, highlighting findings from invertebrate and vertebrate models.
Collapse
Affiliation(s)
- Karen L. Cunningham
- The Picower Institute for Learning and Memory, Department of Biology, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| | | |
Collapse
|
3
|
Abstract
D2 dopamine receptor-mediated suppression of synaptic transmission from interneurons plays a key role in neurobiological functions across species, ranging from respiration to memory formation. In this study, we investigated the mechanisms of D2 receptor-dependent suppression using soma-soma synapse between respiratory interneuron VD4 and LPeD1 in the mollusk Lymnaea stagnalis (L. stagnalis). We studied the effects of dopamine on voltage-dependent Ca2+ current and synaptic vesicle release from the VD4. We report that dopamine inhibits voltage-dependent Ca2+ current in the VD4 by both voltage-dependent and -independent mechanisms. Dopamine also suppresses synaptic vesicle release downstream of activity-dependent Ca2+ influx. Our study demonstrated that dopamine acts through D2 receptors to inhibit interneuron synaptic transmission through both voltage-dependent Ca2+ channel-dependent and -independent pathways. Taken together, these findings expand our understanding of dopamine function and fundamental mechanisms that shape the dynamics of neural circuit.
Collapse
Affiliation(s)
- Nancy Dong
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
| | - David W K Lee
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
| | - Hong-Shuo Sun
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
| | - Zhong-Ping Feng
- a Department of Physiology, Faculty of Medicine , University of Toronto , Toronto , ON , Canada
| |
Collapse
|
4
|
Visa A, Shaikh S, Alza L, Herreros J, Cantí C. The Hard-To-Close Window of T-Type Calcium Channels. Trends Mol Med 2019; 25:571-584. [PMID: 31031178 DOI: 10.1016/j.molmed.2019.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 03/04/2019] [Accepted: 03/06/2019] [Indexed: 01/03/2023]
Abstract
T-Type calcium channels (TTCCs) are key regulators of membrane excitability, which is the reason why TTCC pharmacology is subject to intensive research in the neurological and cardiovascular fields. TTCCs also play a role in cancer physiology, and pharmacological blockers such as tetralols and dihydroquinazolines (DHQs) reduce the viability of cancer cells in vitro and slow tumor growth in murine xenografts. However, the available compounds are better suited to blocking TTCCs in excitable membranes rather than TTCCs contributing window currents at steady potentials. Consistently, tetralols and dihydroquinazolines exhibit cytostatic/cytotoxic activities at higher concentrations than those required for TTCC blockade, which may involve off-target effects. Gene silencing experiments highlight the targetability of TTCCs, but further pharmacological research is required for TTCC blockade to become a chemotherapeutic option.
Collapse
Affiliation(s)
- Anna Visa
- Laboratory of Calcium Cell Signaling, IRBLleida-Universitat de Lleida, Rovira Roure, 80, 25198-Lleida, Spain
| | - Soni Shaikh
- Laboratory of Calcium Cell Signaling, IRBLleida-Universitat de Lleida, Rovira Roure, 80, 25198-Lleida, Spain
| | - Lía Alza
- Laboratory of Calcium Cell Signaling, IRBLleida-Universitat de Lleida, Rovira Roure, 80, 25198-Lleida, Spain
| | - Judit Herreros
- Laboratory of Calcium Cell Signaling, IRBLleida-Universitat de Lleida, Rovira Roure, 80, 25198-Lleida, Spain
| | - Carles Cantí
- Laboratory of Calcium Cell Signaling, IRBLleida-Universitat de Lleida, Rovira Roure, 80, 25198-Lleida, Spain.
| |
Collapse
|
5
|
Mäki-Marttunen T, Krull F, Bettella F, Hagen E, Næss S, Ness TV, Moberget T, Elvsåshagen T, Metzner C, Devor A, Edwards AG, Fyhn M, Djurovic S, Dale AM, Andreassen OA, Einevoll GT. Alterations in Schizophrenia-Associated Genes Can Lead to Increased Power in Delta Oscillations. Cereb Cortex 2019; 29:875-891. [PMID: 30475994 PMCID: PMC6319172 DOI: 10.1093/cercor/bhy291] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 10/03/2018] [Indexed: 12/13/2022] Open
Abstract
Genome-wide association studies have implicated many ion channels in schizophrenia pathophysiology. Although the functions of these channels are relatively well characterized by single-cell studies, the contributions of common variation in these channels to neurophysiological biomarkers and symptoms of schizophrenia remain elusive. Here, using computational modeling, we show that a common biomarker of schizophrenia, namely, an increase in delta-oscillation power, may be a direct consequence of altered expression or kinetics of voltage-gated ion channels or calcium transporters. Our model of a circuit of layer V pyramidal cells highlights multiple types of schizophrenia-related variants that contribute to altered dynamics in the delta-frequency band. Moreover, our model predicts that the same membrane mechanisms that increase the layer V pyramidal cell network gain and response to delta-frequency oscillations may also cause a deficit in a single-cell correlate of the prepulse inhibition, which is a behavioral biomarker highly associated with schizophrenia.
Collapse
Affiliation(s)
- Tuomo Mäki-Marttunen
- Simula Research Laboratory, Oslo, Norway
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Florian Krull
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Francesco Bettella
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Espen Hagen
- Department of Physics, University of Oslo, Oslo, Norway
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Solveig Næss
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Torbjørn V Ness
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Torgeir Moberget
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Torbjørn Elvsåshagen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Department of Neurology, Oslo University Hospital, Oslo, Norway
| | - Christoph Metzner
- Centre for Computer Science and Informatics Research, University of Hertfordshire, Hatfield, UK
| | - Anna Devor
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | | | - Marianne Fyhn
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Srdjan Djurovic
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
- NORMENT, KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Anders M Dale
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Department of Radiology, University of California, San Diego, La Jolla, CA, USA
| | - Ole A Andreassen
- NORMENT, KG Jebsen Centre for Psychosis Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
| | - Gaute T Einevoll
- Department of Physics, University of Oslo, Oslo, Norway
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| |
Collapse
|
6
|
Arteaga-Tlecuitl R, Sanchez-Sandoval AL, Ramirez-Cordero BE, Rosendo-Pineda MJ, Vaca L, Gomora JC. Increase of Ca V3 channel activity induced by HVA β1b-subunit is not mediated by a physical interaction. BMC Res Notes 2018; 11:810. [PMID: 30428904 PMCID: PMC6236959 DOI: 10.1186/s13104-018-3917-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 11/09/2018] [Indexed: 01/13/2023] Open
Abstract
Objective Low voltage-activated (LVA) calcium channels are crucial for regulating oscillatory behavior in several types of neurons and other excitable cells. LVA channels dysfunction has been implicated in epilepsy, neuropathic pain, cancer, among other diseases. Unlike for High Voltage-Activated (HVA) channels, voltage-dependence and kinetics of currents carried by recombinant LVA, i.e., CaV3 channels, are quite similar to those observed in native currents. Therefore, whether these channels are regulated by HVA auxiliary subunits, remain controversial. Here, we used the α1-subunits of CaV3.1, CaV3.2, and CaV3.3 channels, together with HVA auxiliary β-subunits to perform electrophysiological, confocal microscopy and immunoprecipitation experiments, in order to further explore this possibility. Results Functional expression of CaV3 channels is up-regulated by all four β-subunits, although most consistent effects were observed with the β1b-subunit. The biophysical properties of CaV3 channels were not modified by any β-subunit. Furthermore, although β1b-subunits increased colocalization of GFP-tagged CaV3 channels and the plasma membrane of HEK-293 cells, western blots analysis revealed the absence of physical interaction between CaV3.3 and β1b-subunits as no co-immunoprecipitation was observed. These results provide solid evidence that the up-regulation of LVA channels in the presence of HVA-β1b subunit is not mediated by a high affinity interaction between both proteins. Electronic supplementary material The online version of this article (10.1186/s13104-018-3917-1) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Rogelio Arteaga-Tlecuitl
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Ana Laura Sanchez-Sandoval
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Belen Ernestina Ramirez-Cordero
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Margarita Jacaranda Rosendo-Pineda
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Luis Vaca
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - Juan Carlos Gomora
- Departamento de Neuropatología Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico.
| |
Collapse
|
7
|
Chen X, Liu D, Zhou D, Si Y, Xu D, Stamatkin CW, Ghozayel MK, Ripsch MS, Obukhov AG, White FA, Meroueh SO. Small-molecule Ca Vα 1⋅Ca Vβ antagonist suppresses neuronal voltage-gated calcium-channel trafficking. Proc Natl Acad Sci U S A 2018; 115:E10566-75. [PMID: 30355767 DOI: 10.1073/pnas.1813157115] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Extracellular calcium flow through neuronal voltage-gated CaV2.2 calcium channels converts action potential-encoded information to the release of pronociceptive neurotransmitters in the dorsal horn of the spinal cord, culminating in excitation of the postsynaptic central nociceptive neurons. The CaV2.2 channel is composed of a pore-forming α1 subunit (CaVα1) that is engaged in protein-protein interactions with auxiliary α2/δ and β subunits. The high-affinity CaV2.2α1⋅CaVβ3 protein-protein interaction is essential for proper trafficking of CaV2.2 channels to the plasma membrane. Here, structure-based computational screening led to small molecules that disrupt the CaV2.2α1⋅CaVβ3 protein-protein interaction. The binding mode of these compounds reveals that three substituents closely mimic the side chains of hot-spot residues located on the α-helix of CaV2.2α1 Site-directed mutagenesis confirmed the critical nature of a salt-bridge interaction between the compounds and CaVβ3 Arg-307. In cells, compounds decreased trafficking of CaV2.2 channels to the plasma membrane and modulated the functions of the channel. In a rodent neuropathic pain model, the compounds suppressed pain responses. Small-molecule α-helical mimetics targeting ion channel protein-protein interactions may represent a strategy for developing nonopioid analgesia and for treatment of other neurological disorders associated with calcium-channel trafficking.
Collapse
|
8
|
Yeon JH, Park CG, Hille B, Suh BC. Translocatable voltage-gated Ca 2+ channel β subunits in α1-β complexes reveal competitive replacement yet no spontaneous dissociation. Proc Natl Acad Sci U S A 2018; 115:E9934-43. [PMID: 30257950 DOI: 10.1073/pnas.1809762115] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
β subunits of high voltage-gated Ca2+ (CaV) channels promote cell-surface expression of pore-forming α1 subunits and regulate channel gating through binding to the α-interaction domain (AID) in the first intracellular loop. We addressed the stability of CaV α1B-β interactions by rapamycin-translocatable CaV β subunits that allow drug-induced sequestration and uncoupling of the β subunit from CaV2.2 channel complexes in intact cells. Without CaV α1B/α2δ1, all modified β subunits, except membrane-tethered β2a and β2e, are in the cytosol and rapidly translocate upon rapamycin addition to anchors on target organelles: plasma membrane, mitochondria, or endoplasmic reticulum. In cells coexpressing CaV α1B/α2δ1 subunits, the translocatable β subunits colocalize at the plasma membrane with α1B and stay there after rapamycin application, indicating that interactions between α1B and bound β subunits are very stable. However, the interaction becomes dynamic when other competing β isoforms are coexpressed. Addition of rapamycin, then, switches channel gating and regulation by phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] lipid. Thus, expression of free β isoforms around the channel reveals a dynamic aspect to the α1B-β interaction. On the other hand, translocatable β subunits with AID-binding site mutations are easily dissociated from CaV α1B on the addition of rapamycin, decreasing current amplitude and PI(4,5)P2 sensitivity. Furthermore, the mutations slow CaV2.2 current inactivation and shift the voltage dependence of activation to more positive potentials. Mutated translocatable β subunits work similarly in CaV2.3 channels. In sum, the strong interaction of CaV α1B-β subunits can be overcome by other free β isoforms, permitting dynamic changes in channel properties in intact cells.
Collapse
|
9
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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.
| |
Collapse
|
10
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | - Daniel L. Minor
- Molecular Biophysics & Integrated Imaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| |
Collapse
|
11
|
Oz S, Pankonien I, Belkacemi A, Flockerzi V, Klussmann E, Haase H, Dascal N. Protein kinase A regulates C-terminally truncated Ca V 1.2 in Xenopus oocytes: roles of N- and C-termini of the α 1C subunit. J Physiol 2017; 595:3181-3202. [PMID: 28194788 DOI: 10.1113/jp274015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 02/08/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS β-Adrenergic stimulation enhances Ca2+ entry via L-type CaV 1.2 channels, causing stronger contraction of cardiac muscle cells. The signalling pathway involves activation of protein kinase A (PKA), but the molecular details of PKA regulation of CaV 1.2 remain controversial despite extensive research. We show that PKA regulation of CaV 1.2 can be reconstituted in Xenopus oocytes when the distal C-terminus (dCT) of the main subunit, α1C , is truncated. The PKA upregulation of CaV 1.2 does not require key factors previously implicated in this mechanism: the clipped dCT, the A kinase-anchoring protein 15 (AKAP15), the phosphorylation sites S1700, T1704 and S1928, or the β subunit of CaV 1.2. The gating element within the initial segment of the N-terminus of the cardiac isoform of α1C is essential for the PKA effect. We propose that the regulation described here is one of two or several mechanisms that jointly mediate the PKA regulation of CaV 1.2 in the heart. ABSTRACT β-Adrenergic stimulation enhances Ca2+ currents via L-type, voltage-gated CaV 1.2 channels, strengthening cardiac contraction. The signalling via β-adrenergic receptors (β-ARs) involves elevation of cyclic AMP (cAMP) levels and activation of protein kinase A (PKA). However, how PKA affects the channel remains controversial. Recent studies in heterologous systems and genetically engineered mice stress the importance of the post-translational proteolytic truncation of the distal C-terminus (dCT) of the main (α1C ) subunit. Here, we successfully reconstituted the cAMP/PKA regulation of the dCT-truncated CaV 1.2 in Xenopus oocytes, which previously failed with the non-truncated α1C . cAMP and the purified catalytic subunit of PKA, PKA-CS, injected into intact oocytes, enhanced CaV 1.2 currents by ∼40% (rabbit α1C ) to ∼130% (mouse α1C ). PKA blockers were used to confirm specificity and the need for dissociation of the PKA holoenzyme. The regulation persisted in the absence of the clipped dCT (as a separate protein), the A kinase-anchoring protein AKAP15, and the phosphorylation sites S1700 and T1704, previously proposed as essential for the PKA effect. The CaV β2b subunit was not involved, as suggested by extensive mutagenesis. Using deletion/chimeric mutagenesis, we have identified the initial segment of the cardiac long-N-terminal isoform of α1C as a previously unrecognized essential element involved in PKA regulation. We propose that the observed regulation, that exclusively involves the α1C subunit, is one of several mechanisms underlying the overall PKA action on CaV 1.2 in the heart. We hypothesize that PKA is acting on CaV 1.2, in part, by affecting a structural 'scaffold' comprising the interacting cytosolic N- and C-termini of α1C .
Collapse
Affiliation(s)
- Shimrit Oz
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Ines Pankonien
- Max Delbrück Center for Molecular Medicine (MDC), D-13092, and the German Centre for Cardiovascular Research (DZHK) partner site, Berlin, Germany
| | - Anouar Belkacemi
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421, Homburg, Germany
| | - Veit Flockerzi
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421, Homburg, Germany
| | - Enno Klussmann
- Max Delbrück Center for Molecular Medicine (MDC), D-13092, and the German Centre for Cardiovascular Research (DZHK) partner site, Berlin, Germany
| | - Hannelore Haase
- Max Delbrück Center for Molecular Medicine (MDC), D-13092, and the German Centre for Cardiovascular Research (DZHK) partner site, Berlin, Germany
| | - Nathan Dascal
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 6997801, Israel.,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 6997801, Israel
| |
Collapse
|
12
|
Cox RH, Fromme S. Comparison of Voltage Gated K + Currents in Arterial Myocytes with Heterologously Expressed K v Subunits. Cell Biochem Biophys 2016; 74:499-511. [PMID: 27638047 DOI: 10.1007/s12013-016-0763-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 08/31/2016] [Indexed: 01/06/2023]
Abstract
We have shown that three components contribute to functional voltage gated K+ (K v) currents in rat small mesenteric artery myocytes: (1) Kv1.2 plus Kv1.5 with Kvβ1.2 subunits, (2) Kv2.1 probably associated with Kv9.3 subunits, and (3) Kv7.4 subunits. To confirm and address subunit stoichiometry of the first two, we have compared the biophysical properties of K v currents in small mesenteric artery myocytes with those of Kv subunits heterologously expressed in HEK293 cells using whole cell voltage clamp methods. Selective inhibitors of Kv1 (correolide, COR) and Kv2 (stromatoxin, ScTx) channels were used to separate these K v current components. Conductance-voltage and steady state inactivation data along with time constants of activation, inactivation, and deactivation of native K v components were generally well represented by those of Kv1.2-1.5-β1.2 and Kv2.1-9.3 channels. The slope of the steady state inactivation-voltage curve (availability slope) proved to be the most sensitive measure of accessory subunit presence. The availability slope curves exhibited a single peak for both native K v components. Availability slope curves for Kv1.2-1.5-β1.2 and Kv2.1-9.3 channels expressed in human embryonic kidney cells also exhibited a single peak that shifted to more depolarized voltages with increasing accessory to α subunit transfection ratio. Availability slope curves for SxTc-insensitive currents were similar to those of Kv1.2-1.5 expressed with Kvβ1.2 at a 1:5 molar ratio while curves for COR-insensitive currents closely resembled those of Kv2.1 expressed with Kv9.3 at a 1:1 molar ratio. These results support the suggested Kv subunit combinations in small mesenteric artery, and further suggest that Kv1 α and Kvβ1.2 but not Kv2.1 and Kv9.3 subunits are present in a saturated (4:4) stoichiometry.
Collapse
|
13
|
Dolphin AC. Voltage-gated calcium channels and their auxiliary subunits: physiology and pathophysiology and pharmacology. J Physiol 2016; 594:5369-90. [PMID: 27273705 PMCID: PMC5043047 DOI: 10.1113/jp272262] [Citation(s) in RCA: 201] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/09/2016] [Indexed: 12/22/2022] Open
Abstract
Voltage‐gated calcium channels are essential players in many physiological processes in excitable cells. There are three main subdivisions of calcium channel, defined by the pore‐forming α1 subunit, the CaV1, CaV2 and CaV3 channels. For all the subtypes of voltage‐gated calcium channel, their gating properties are key for the precise control of neurotransmitter release, muscle contraction and cell excitability, among many other processes. For the CaV1 and CaV2 channels, their ability to reach their required destinations in the cell membrane, their activation and the fine tuning of their biophysical properties are all dramatically influenced by the auxiliary subunits that associate with them. Furthermore, there are many diseases, both genetic and acquired, involving voltage‐gated calcium channels. This review will provide a general introduction and then concentrate particularly on the role of auxiliary α2δ subunits in both physiological and pathological processes involving calcium channels, and as a therapeutic target.
![]()
Collapse
Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
| |
Collapse
|
14
|
Heyes S, Pratt WS, Rees E, Dahimene S, Ferron L, Owen MJ, Dolphin AC. Genetic disruption of voltage-gated calcium channels in psychiatric and neurological disorders. Prog Neurobiol 2015; 134:36-54. [PMID: 26386135 PMCID: PMC4658333 DOI: 10.1016/j.pneurobio.2015.09.002] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/08/2015] [Accepted: 09/08/2015] [Indexed: 12/15/2022]
Abstract
Voltage-gated calcium channel classification—genes and proteins. Genetic analysis of neuropsychiatric syndromes. Calcium channel genes identified from GWA studies of psychiatric disorders. Rare mutations in calcium channel genes in psychiatric disorders. Pathophysiological sequelae of CACNA1C mutations and polymorphisms. Monogenic disorders resulting from harmful mutations in other voltage-gated calcium channel genes. Changes in calcium channel gene expression in disease. Involvement of voltage-gated calcium channels in early brain development.
This review summarises genetic studies in which calcium channel genes have been connected to the spectrum of neuropsychiatric syndromes, from bipolar disorder and schizophrenia to autism spectrum disorders and intellectual impairment. Among many other genes, striking numbers of the calcium channel gene superfamily have been implicated in the aetiology of these diseases by various DNA analysis techniques. We will discuss how these relate to the known monogenic disorders associated with point mutations in calcium channels. We will then examine the functional evidence for a causative link between these mutations or single nucleotide polymorphisms and the disease processes. A major challenge for the future will be to translate the expanding psychiatric genetic findings into altered physiological function, involvement in the wider pathology of the diseases, and what potential that provides for personalised and stratified treatment options for patients.
Collapse
Affiliation(s)
- Samuel Heyes
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Elliott Rees
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Michael J Owen
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
| |
Collapse
|
15
|
Neumaier F, Dibué-Adjei M, Hescheler J, Schneider T. 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] [What about the content of this article? (0)] [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.
Collapse
|
16
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
17
|
Béguin P, Nagashima K, Mahalakshmi RN, Vigot R, Matsunaga A, Miki T, Ng MY, Ng YJA, Lim CH, Tay HS, Hwang LA, Firsov D, Tang BL, Inagaki N, Mori Y, Seino S, Launey T, Hunziker W. BARP suppresses voltage-gated calcium channel activity and Ca2+-evoked exocytosis. ACTA ACUST UNITED AC 2014; 205:233-49. [PMID: 24751537 PMCID: PMC4003244 DOI: 10.1083/jcb.201304101] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Voltage-gated calcium channels (VGCCs) are key regulators of cell signaling and Ca(2+)-dependent release of neurotransmitters and hormones. Understanding the mechanisms that inactivate VGCCs to prevent intracellular Ca(2+) overload and govern their specific subcellular localization is of critical importance. We report the identification and functional characterization of VGCC β-anchoring and -regulatory protein (BARP), a previously uncharacterized integral membrane glycoprotein expressed in neuroendocrine cells and neurons. BARP interacts via two cytosolic domains (I and II) with all Cavβ subunit isoforms, affecting their subcellular localization and suppressing VGCC activity. Domain I interacts at the α1 interaction domain-binding pocket in Cavβ and interferes with the association between Cavβ and Cavα1. In the absence of domain I binding, BARP can form a ternary complex with Cavα1 and Cavβ via domain II. BARP does not affect cell surface expression of Cavα1 but inhibits Ca(2+) channel activity at the plasma membrane, resulting in the inhibition of Ca(2+)-evoked exocytosis. Thus, BARP can modulate the localization of Cavβ and its association with the Cavα1 subunit to negatively regulate VGCC activity.
Collapse
Affiliation(s)
- Pascal Béguin
- Epithelial Cell Biology Laboratory and 2 Monoclonal Antibody Unit, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore 138673
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Alvarez-Laviada A, Kadurin I, Senatore A, Chiesa R, Dolphin AC. The inhibition of functional expression of calcium channels by prion protein demonstrates competition with α2δ for GPI-anchoring pathways. Biochem J 2014; 458:365-74. [PMID: 24329154 DOI: 10.1042/BJ20131405] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
It has been shown recently that PrP (prion protein) and the calcium channel auxiliary α2δ subunits interact in neurons and expression systems [Senatore, Colleoni, Verderio, Restelli, Morini, Condliffe, Bertani, Mantovani, Canovi, Micotti, Forloni, Dolphin, Matteoli, Gobbi and Chiesa (2012) Neuron 74, 300-313]. In the present study we examined whether there was an effect of PrP on calcium currents. We have shown that when PrP is co-expressed with calcium channels formed from CaV2.1/β and α2δ-1 or α2δ-2, there is a consistent decrease in calcium current density. This reduction was absent when a PrP construct was used lacking its GPI (glycosylphosphatidylinositol) anchor. We have reported previously that α2δ subunits are able to form GPI-anchored proteins [Davies, Kadurin, Alvarez-Laviada, Douglas, Nieto-Rostro, Bauer, Pratt and Dolphin (2010) Proc. Natl. Acad. Sci. U.S.A. 107, 1654-1659] and show further evidence in the present paper. We have characterized recently a C-terminally truncated α2δ-1 construct, α2δ-1ΔC, and found that, despite loss of its membrane anchor, it still shows a partial ability to increase calcium currents [Kadurin, Alvarez-Laviada, Ng, Walker-Gray, D'Arco, Fadel, Pratt and Dolphin (2012) J. Biol. Chem. 1287, 33554-33566]. We now find that PrP does not inhibit CaV2.1/β currents formed with α2δ-1ΔC, rather than α2δ-1. It is possible that PrP and α2δ-1 compete for GPI-anchor intermediates or trafficking pathways, or that interaction between PrP and α2δ-1 requires association in cholesterol-rich membrane microdomains. Our additional finding that CaV2.1/β1b/α2δ-1 currents were inhibited by GPI-GFP, but not cytosolic GFP, indicates that competition for limited GPI-anchor intermediates or trafficking pathways may be involved in PrP suppression of α2δ subunit function.
Collapse
|
19
|
Dawson TF, Boone AN, Senatore A, Piticaru J, Thiyagalingam S, Jackson D, Davison A, Spafford JD. Gene splicing of an invertebrate beta subunit (LCavβ) in the N-terminal and HOOK domains and its regulation of LCav1 and LCav2 calcium channels. PLoS One 2014; 9:e92941. [PMID: 24690951 PMCID: PMC3972191 DOI: 10.1371/journal.pone.0092941] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 02/27/2014] [Indexed: 01/31/2023] Open
Abstract
The accessory beta subunit (Ca(v)β) of calcium channels first appear in the same genome as Ca(v)1 L-type calcium channels in single-celled coanoflagellates. The complexity of this relationship expanded in vertebrates to include four different possible Ca(v)β subunits (β1, β2, β3, β4) which associate with four Ca(v)1 channel isoforms (Ca(v)1.1 to Ca(v)1.4) and three Ca(v)2 channel isoforms (Ca(v)2.1 to Ca(v)2.3). Here we assess the fundamentally-shared features of the Ca(v)β subunit in an invertebrate model (pond snail Lymnaea stagnalis) that bears only three homologous genes: (LCa(v)1, LCa(v)2, and LCa(v)β). Invertebrate Ca(v)β subunits (in flatworms, snails, squid and honeybees) slow the inactivation kinetics of Ca(v)2 channels, and they do so with variable N-termini and lacking the canonical palmitoylation residues of the vertebrate β2a subunit. Alternative splicing of exon 7 of the HOOK domain is a primary determinant of a slow inactivation kinetics imparted by the invertebrate LCa(v)β subunit. LCa(v)β will also slow the inactivation kinetics of LCa(v)3 T-type channels, but this is likely not physiologically relevant in vivo. Variable N-termini have little influence on the voltage-dependent inactivation kinetics of differing invertebrate Ca(v)β subunits, but the expression pattern of N-terminal splice isoforms appears to be highly tissue specific. Molluscan LCa(v)β subunits have an N-terminal "A" isoform (coded by exons: 1a and 1b) that structurally resembles the muscle specific variant of vertebrate β1a subunit, and has a broad mRNA expression profile in brain, heart, muscle and glands. A more variable "B" N-terminus (exon 2) in the exon position of mammalian β3 and has a more brain-centric mRNA expression pattern. Lastly, we suggest that the facilitation of closed-state inactivation (e.g. observed in Ca(v)2.2 and Ca(v)β3 subunit combinations) is a specialization in vertebrates, because neither snail subunit (LCa(v)2 nor LCa(v)β) appears to be compatible with this observed property.
Collapse
Affiliation(s)
- Taylor F. Dawson
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Adrienne N. Boone
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Adriano Senatore
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Joshua Piticaru
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | | | - Daniel Jackson
- Institute of Genetics, School of Biology, University of Nottingham, Nottingham, United Kingdom
| | - Angus Davison
- Institute of Genetics, School of Biology, University of Nottingham, Nottingham, United Kingdom
| | - J. David Spafford
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| |
Collapse
|
20
|
Tevoufouet EE, Nembo EN, Dibué-Adjei M, Hescheler J, Nguemo F, Schneider T. Cardiac functions of voltage-gated Ca(2+) channels: role of the pharmacoresistant type (E-/R-Type) in cardiac modulation and putative implication in sudden unexpected death in epilepsy (SUDEP). Rev Physiol Biochem Pharmacol 2014; 167:115-39. [PMID: 25280639 DOI: 10.1007/112_2014_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Voltage-gated Ca(2+) channels (VGCCs) are ubiquitous in excitable cells. These channels play key roles in many physiological events like cardiac regulation/pacemaker activity due to intracellular Ca(2+) transients. In the myocardium, the Cav1 subfamily (L-type: Cav1.2 and Cav1.3) is the main contributor to excitation-contraction coupling and/or pacemaking, whereas the Cav3 subfamily (T-type: Cav3.1 and Cav3.2) is important in rhythmically firing of the cardiac nodal cells. No established cardiac function has been attributed to the Cav2 family (E-/R-type: Cav2.3) despite accumulating evidence of cardiac dysregulation observed upon deletion of the Cav2.3 gene, the only member of this family so far detected in cardiomyocytes. In this review, we summarize the pathophysiological changes observed after ablation of the E-/R-type VGCC and propose a cardiac mechanism of action for this channel. Also, considering the role played by this channel in epilepsy and its reported sensitivity to antiepileptic drugs, a putative involvement of this channel in the cardiac mechanism of sudden unexpected death in epilepsy is also discussed.
Collapse
|
21
|
|
22
|
Buraei Z, Yang J. Structure and function of the β subunit of voltage-gated Ca²⁺ channels. Biochim Biophys Acta 2012; 1828:1530-40. [PMID: 22981275 DOI: 10.1016/j.bbamem.2012.08.028] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 08/22/2012] [Accepted: 08/25/2012] [Indexed: 12/31/2022]
Abstract
The voltage-gated Ca²⁺ channel β subunit (Ca(v)β) is a cytosolic auxiliary subunit that plays an essential role in regulating the surface expression and gating properties of high-voltage activated (HVA) Ca²⁺ channels. It is also crucial for the modulation of HVA Ca²⁺ channels by G proteins, kinases, Ras-related RGK GTPases, and other proteins. There are indications that Ca(v)β may carry out Ca²⁺ channel-independent functions. Ca(v)β knockouts are either non-viable or result in a severe pathophysiology, and mutations in Ca(v)β have been implicated in disease. In this article, we review the structure and various biological functions of Ca(v)β, as well as recent advances. This article is part of a Special Issue entitled: Calcium channels.
Collapse
Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | | |
Collapse
|
23
|
Kadurin I, Alvarez-Laviada A, Ng SFJ, Walker-Gray R, D'Arco M, Fadel MG, Pratt WS, Dolphin AC. Calcium currents are enhanced by α2δ-1 lacking its membrane anchor. J Biol Chem 2012; 287:33554-66. [PMID: 22869375 PMCID: PMC3460456 DOI: 10.1074/jbc.m112.378554] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The accessory α(2)δ subunits of voltage-gated calcium channels are membrane-anchored proteins, which are highly glycosylated, possess multiple disulfide bonds, and are post-translationally cleaved into α(2) and δ. All α(2)δ subunits have a C-terminal hydrophobic, potentially trans-membrane domain and were described as type I transmembrane proteins, but we found evidence that they can be glycosylphosphatidylinositol-anchored. To probe further the function of membrane anchoring in α(2)δ subunits, we have now examined the properties of α(2)δ-1 constructs truncated at their putative glycosylphosphatidylinositol anchor site, located before the C-terminal hydrophobic domain (α(2)δ-1ΔC-term). We find that the majority of α(2)δ-1ΔC-term is soluble and secreted into the medium, but unexpectedly, some of the protein remains associated with detergent-resistant membranes, also termed lipid rafts, and is extrinsically bound to the plasma membrane. Furthermore, heterologous co-expression of α(2)δ-1ΔC-term with Ca(V)2.1/β1b results in a substantial enhancement of the calcium channel currents, albeit less than that produced by wild-type α(2)δ-1. These results call into question the role of membrane anchoring of α(2)δ subunits for calcium current enhancement.
Collapse
Affiliation(s)
- Ivan Kadurin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Jangsangthong W, Kuzmenkina E, Böhnke AK, Herzig S. Single-channel monitoring of reversible L-type Ca(2+) channel Ca(V)α(1)-Ca(V)β subunit interaction. Biophys J 2011; 101:2661-70. [PMID: 22261054 DOI: 10.1016/j.bpj.2011.09.063] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 09/06/2011] [Indexed: 11/24/2022] Open
Abstract
Voltage-dependent Ca(2+) channels are heteromultimers of Ca(V)α(1) (pore), Ca(V)β- and Ca(V)α(2)δ-subunits. The stoichiometry of this complex, and whether it is dynamically regulated in intact cells, remains controversial. Fortunately, Ca(V)β-isoforms affect gating differentially, and we chose two extremes (Ca(V)β(1a) and Ca(V)β(2b)) regarding single-channel open probability to address this question. HEK293α(1C) cells expressing the Ca(V)1.2 subunit were transiently transfected with Ca(V)α(2)δ1 alone or with Ca(V)β(1a), Ca(V)β(2b), or (2:1 or 1:1 plasmid ratio) combinations. Both Ca(V)β-subunits increased whole-cell current and shifted the voltage dependence of activation and inactivation to hyperpolarization. Time-dependent inactivation was accelerated by Ca(V)β(1a)-subunits but not by Ca(V)β(2b)-subunits. Mixtures induced intermediate phenotypes. Single channels sometimes switched between periods of low and high open probability. To validate such slow gating behavior, data were segmented in clusters of statistically similar open probability. With Ca(V)β(1a)-subunits alone, channels mostly stayed in clusters (or regimes of alike clusters) of low open probability. Increasing Ca(V)β(2b)-subunits (co-)expressed (1:2, 1:1 ratio or alone) progressively enhanced the frequency and total duration of high open probability clusters and regimes. Our analysis was validated by the inactivation behavior of segmented ensemble averages. Hence, a phenotype consistent with mutually exclusive and dynamically competing binding of different Ca(V)β-subunits is demonstrated in intact cells.
Collapse
|
25
|
Pankonien I, Otto A, Dascal N, Morano I, Haase H. Ahnak1 interaction is affected by phosphorylation of Ser-296 on Cavβ₂. Biochem Biophys Res Commun 2012; 421:184-9. [PMID: 22497893 DOI: 10.1016/j.bbrc.2012.03.132] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 03/26/2012] [Indexed: 10/28/2022]
Abstract
Ahnak1 has been implicated in protein kinase A (PKA)-mediated control of cardiac L-type Ca(2+) channels (Cav1.2) through its interaction with the Cavβ(2) regulatory channel subunit. Here we corroborate this functional linkage by immunocytochemistry on isolated cardiomyocytes showing co-localization of ahnak1 and Cavβ(2) in the T-tubule system. In previous studies Cavβ(2) attachment sites which impacted the channel's PKA regulation have been located to ahnak1's proximal C-terminus (ahnak1(4889-5535), ahnak1(5462-5535)). In this study, we mapped the ahnak1-interacting regions in Cavβ(2) and investigated whether Cavβ(2) phosphorylation affects its binding behavior. In vitro binding assays with Cavβ(2) truncation mutants and ahnak1(4889-5535) revealed that the core region of Cavβ(2) consisting of Src-homology 3 (SH3), HOOK, and guanylate kinase (GK) domains was important for ahnak1 interaction while the C- and N-terminal regions were dispensable. Furthermore, Ser-296 in the GK domain of Cavβ(2) was identified as novel PKA phosphorylation site by mass spectrometry. Surface plasmon resonance (SPR) binding analysis showed that Ser-296 phosphorylation did not affect the high affinity interaction (K(D)≈35 nM) between Cavβ(2) and the α(1C) I-II linker, but affected ahnak1 interaction in a complex manner. SPR experiments with ahnak1(5462-5535) revealed that PKA phosphorylation of Cavβ(2) significantly increased the binding affinity and, in parallel, it reduced the binding capacity. Intriguingly, the phosphorylation mimic substitution Glu-296 fully reproduced both effects, increased the affinity by ≈2.4-fold and reduced the capacity by ≈60%. Our results are indicative for the release of a population of low affinity interaction sites following Cavβ(2) phosphorylation on Ser-296. We propose that this phosphorylation event is one mechanism underlying ahnak1's modulator function on Cav1.2 channel activity.
Collapse
Affiliation(s)
- Ines Pankonien
- Max Delbrück Center for Molecular Medicine, Department of Molecular Muscle Physiology, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
| | | | | | | | | |
Collapse
|
26
|
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.
Collapse
Affiliation(s)
- Kun Fang
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
| | | |
Collapse
|
27
|
Radhakrishnan K, Kamp MA, Siapich SA, Hescheler J, Lüke M, Schneider T. Ca(v)2.3 Ca2+ channel interacts with the G1-subunit of V-ATPase. Cell Physiol Biochem 2011; 27:421-32. [PMID: 21691059 DOI: 10.1159/000329963] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2011] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Calcium channels are essential in coupling action potential to signal transduction in cells. There are several types of calcium channels, which can be pharmacologically classified as L-, N-, P/Q-, R- and T-type. But molecular basis of R-type channels is less clearly understood compared the other channel types. Therefore the current study aims at understanding the molecular functions of R-type calcium channels by identifying interaction partners of the channel. METHODS In order to do so, a yeast two hybrid (Y2H) screen, with carboxy terminus of α1 subunit of the channel, as the bait, was performed. G1 subunit of v-ATPase was identified as a putative interaction partner of human Ca(v)2.3 by using the Y2H screening. The interaction was confirmed by immunoprecipitation. To study the functional importance of the interaction, bafilomycin A(1), a potent and specific inhibitor of v-ATPase was used in patch-clamp recordings in Ca(v)2.3 stably-transfected HEK-293 cells (2C6) as well as in electroretinography of the isolated bovine retina expressing R-type Ca(2+) channels. RESULTS G1 subunit of v-ATPase interacts with C-terminal tail of Ca(v)2.3 and bafilomycin A(1) reduces Ca(v)2.3 mediated calcium currents. Additionally peak I(Ca) is inhibited in retinal signal transduction when recorded as ERG b-wave. CONCLUSIONS The results suggest that v-ATPase interacts physically and also functionally with Ca(v)2.3. This is the first demonstration of association of Ca(v)2.3 C-terminus with a protein complex which is involved in transmembrane signalling.
Collapse
Affiliation(s)
- Kayalvizhi Radhakrishnan
- Institute of Neurophysiology, Center of Molecular Medicine Cologne, University of Cologne, Robert-Koch-Strasse 39, Cologne, Germany
| | | | | | | | | | | |
Collapse
|
28
|
Minor DL, Findeisen F. Progress in the structural understanding of voltage-gated calcium channel (CaV) function and modulation. Channels (Austin) 2011; 4:459-74. [PMID: 21139419 DOI: 10.4161/chan.4.6.12867] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Voltage-gated calcium channels (CaVs) are large, transmembrane multiprotein complexes that couple membrane depolarization to cellular calcium entry. These channels are central to cardiac action potential propagation, neurotransmitter and hormone release, muscle contraction, and calcium-dependent gene transcription. Over the past six years, the advent of high-resolution structural studies of CaV components from different isoforms and CaV modulators has begun to reveal the architecture that underlies the exceptionally rich feedback modulation that controls CaV action. These descriptions of CaV molecular anatomy have provided new, structure-based insights into the mechanisms by which particular channel elements affect voltage-dependent inactivation (VDI), calcium‑dependent inactivation (CDI), and calcium‑dependent facilitation (CDF). The initial successes have been achieved through structural studies of soluble channel domains and modulator proteins and have proven most powerful when paired with biochemical and functional studies that validate ideas inspired by the structures. Here, we review the progress in this growing area and highlight some key open challenges for future efforts.
Collapse
Affiliation(s)
- Daniel L Minor
- Cardiovascular Research Institute, University of California-San Francisco, CA, USA.
| | | |
Collapse
|
29
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
30
|
Meissner M, Weissgerber P, Londoño JEC, Prenen J, Link S, Ruppenthal S, Molkentin JD, Lipp P, Nilius B, Freichel M, Flockerzi V. Moderate calcium channel dysfunction in adult mice with inducible cardiomyocyte-specific excision of the cacnb2 gene. J Biol Chem 2011; 286:15875-82. [PMID: 21357697 DOI: 10.1074/jbc.m111.227819] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The major L-type voltage-gated calcium channels in heart consist of an α1C (Ca(V)1.2) subunit usually associated with an auxiliary β subunit (Ca(V)β2). In embryonic cardiomyocytes, both the complete and the cardiac myocyte-specific null mutant of Ca(V)β2 resulted in reduction of L-type calcium currents by up to 75%, compromising heart function and causing defective remodeling of intra- and extra-embryonic blood vessels followed by embryonic death. Here we conditionally excised the Ca(V)β2 gene (cacnb2) specifically in cardiac myocytes of adult mice (KO). Upon gene deletion, Ca(V)β2 protein expression declined by >96% in isolated cardiac myocytes and by >74% in protein fractions from heart. These latter protein fractions include Ca(V)β2 proteins expressed in cardiac fibroblasts. Surprisingly, mice did not show any obvious impairment, although cacnb2 excision was not compensated by expression of other Ca(V)β proteins or changes of Ca(V)1.2 protein levels. Calcium currents were still dihydropyridine-sensitive, but current density at 0 mV was reduced by <29%. The voltage for half-maximal activation was slightly shifted to more depolarized potentials in KO cardiomyocytes when compared with control cells, but the difference was not significant. In summary, Ca(V)β2 appears to be a much stronger modulator of L-type calcium currents in embryonic than in adult cardiomyocytes. Although essential for embryonic survival, Ca(V)β2 down-regulation in cardiomyocytes is well tolerated by the adult mice.
Collapse
Affiliation(s)
- Marcel Meissner
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Lao QZ, Kobrinsky E, Liu Z, Soldatov NM. Oligomerization of Ca vβ subunits is an essential correlate of Ca 2+channel activity. FASEB J 2010. [DOI: 10.1096/fj.10.165381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Qi Zong Lao
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
| | - Evgeny Kobrinsky
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
| | - Zhuo Liu
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
| | - Nikolai M. Soldatov
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
| |
Collapse
|
32
|
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.
Collapse
Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | | |
Collapse
|
33
|
Bae J, Suh EJ, Lee C. Interaction of T-type calcium channel Ca(V)3.3 with the β-subunit. Mol Cells 2010; 30:185-91. [PMID: 20803093 DOI: 10.1007/s10059-010-0106-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 05/12/2010] [Accepted: 05/27/2010] [Indexed: 11/24/2022] Open
Abstract
The β-subunit of high-voltage-activated (HVA) calcium channels is essential for the regulation of expression and gating. On the other hand, various reports have suggested that β subunits play no role in the regulation of low-voltage-activated T-type channels. In addition there has been no clear demonstration of a physical interaction between the α-subunit of T-type channel with β-subunit. In this study, we systematically investigated the interaction between Ca(V)α and Ca(V)β. The four Ca(V)β isoforms were expressed in a bacterial system and purified into homogeneity, whereas the ten types of Ca(V)α alpha interaction domain (AID) peptides were chemically synthesized. All possible combinations of Ca(V)α and Ca(V)β were then tested for by in vitro immunoassays. We describe here the identification of a new interaction between Ca(V)3.3 and Ca(V)β proteins. This interaction is of low affinity compared to that between the AID of the HVA α-subunit and the alpha-binding pocket (ABP) site of the β-subunit. The AID peptide of HVA channel exerted no effect on the Ca(V)3.3-Ca(V)β interaction, thus demonstrating that another site not in the ABP of Ca(V)β protein played a role in binding with Ca(V)3.3. This is the first demonstration of an α-β subunit interaction in a T-type calcium channel.
Collapse
Affiliation(s)
- Jinhee Bae
- Life Sciences Division, Korea Institute of Science and Technology, Seoul, 136-791, Korea
| | | | | |
Collapse
|
34
|
Abstract
Voltage-gated calcium channels conduct Ca(2+) ions in response to membrane depolarization. The resulting transient increase in cytoplasmic free calcium concentration is a critical trigger for the initiation of such vital responses as muscle contraction and transcription. L-type Ca(v)1.2 calcium channels are complexes of the pore-forming α(1C) subunit associated with cytosolic Ca(v)β subunits. All major Ca(v)βs share a highly homologous membrane associated guanylate kinase-like (MAGUK) domain that binds to α(1C) at the α-interaction domain (AID), a short motif in the linker between transmembrane repeats I and II. In this study we show that Ca(v)β subunits form multimolecular homo- and heterooligomeric complexes in human vascular smooth muscle cells expressing native calcium channels and in Cos7 cells expressing recombinant Ca(v)1.2 channel subunits. Ca(v)βs oligomerize at the α(1C) subunits residing in the plasma membrane and bind to the AID. However, Ca(v)β oligomerization occurs independently on the association with α(1C). Molecular structures responsible for Ca(v)β oligomerization reside in 3 regions of the guanylate kinase subdomain of MAGUK. An augmentation of Ca(v)β homooligomerization significantly increases the calcium current density, while heterooligomerization may also change the voltage-dependence and inactivation kinetics of the channel. Thus, oligomerization of Ca(v)β subunits represents a novel and essential aspect of calcium channel regulation.
Collapse
Affiliation(s)
- Qi Zong Lao
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA
| | | | | | | |
Collapse
|
35
|
|
36
|
Bourdin B, Marger F, Wall-Lacelle S, Schneider T, Klein H, Sauvé R, Parent L. Molecular determinants of the CaVbeta-induced plasma membrane targeting of the CaV1.2 channel. J Biol Chem 2010; 285:22853-63. [PMID: 20478999 DOI: 10.1074/jbc.m110.111062] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Ca(V)beta subunits modulate cell surface expression and voltage-dependent gating of high voltage-activated (HVA) Ca(V)1 and Ca(V)2 alpha1 subunits. High affinity Ca(V)beta binding onto the so-called alpha interaction domain of the I-II linker of the Ca(V)alpha1 subunit is required for Ca(V)beta modulation of HVA channel gating. It has been suggested, however, that Ca(V)beta-mediated plasma membrane targeting could be uncoupled from Ca(V)beta-mediated modulation of channel gating. In addition to Ca(V)beta, Ca(V)alpha2delta and calmodulin have been proposed to play important roles in HVA channel targeting. Indeed we show that co-expression of Ca(V)alpha2delta caused a 5-fold stimulation of the whole cell currents measured with Ca(V)1.2 and Ca(V)beta3. To gauge the synergetic role of auxiliary subunits in the steady-state plasma membrane expression of Ca(V)1.2, extracellularly tagged Ca(V)1.2 proteins were quantified using fluorescence-activated cell sorting analysis. Co-expression of Ca(V)1.2 with either Ca(V)alpha2delta, calmodulin wild type, or apocalmodulin (alone or in combination) failed to promote the detection of fluorescently labeled Ca(V)1.2 subunits. In contrast, co-expression with Ca(V)beta3 stimulated plasma membrane expression of Ca(V)1.2 by a 10-fold factor. Mutations within the alpha interaction domain of Ca(V)1.2 or within the nucleotide kinase domain of Ca(V)beta3 disrupted the Ca(V)beta3-induced plasma membrane targeting of Ca(V)1.2. Altogether, these data support a model where high affinity binding of Ca(V)beta to the I-II linker of Ca(V)alpha1 largely accounts for Ca(V)beta-induced plasma membrane targeting of Ca(V)1.2.
Collapse
Affiliation(s)
- Benoîte Bourdin
- Institute of Neurophysiology and Center for Molecular Medicine, Cologne University, D-50931 Cologne, Germany
| | | | | | | | | | | | | |
Collapse
|
37
|
Tselnicker I, Tsemakhovich VA, Dessauer CW, Dascal N. Stargazin modulates neuronal voltage-dependent Ca(2+) channel Ca(v)2.2 by a Gbetagamma-dependent mechanism. J Biol Chem 2010; 285:20462-71. [PMID: 20435886 DOI: 10.1074/jbc.m110.121277] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of neuronal protein stargazin (gamma(2)) is associated with recurrent epileptic seizures and ataxia in mice. Initially, due to homology to the skeletal muscle calcium channel gamma(1) subunit, stargazin and other family members (gamma(3-8)) were classified as gamma subunits of neuronal voltage-gated calcium channels (such as Ca(V)2.1-Ca(V)2.3). Here, we report that stargazin interferes with G protein modulation of Ca(V)2.2 (N-type) channels expressed in Xenopus oocytes. Stargazin counteracted the Gbetagamma-induced inhibition of Ca(V)2.2 channel currents, caused either by coexpression of the Gbetagamma dimer or by activation of a G protein-coupled receptor. Expression of high doses of Gbetagamma overcame the effects of stargazin. High affinity Gbetagamma scavenger proteins m-cbetaARK and m-phosducin produced effects similar to stargazin. The effects of stargazin and m-cbetaARK were not additive, suggesting a common mechanism of action, and generally independent of the presence of the Ca(V)beta(3) subunit. However, in some cases, coexpression of Ca(V)beta(3) blunted the modulation by stargazin. Finally, the Gbetagamma-opposing action of stargazin was not unique to Ca(V)2.2, as stargazin also inhibited the Gbetagamma-mediated activation of the G protein-activated K(+) channel. Purified cytosolic C-terminal part of stargazin bound Gbetagamma in vitro. Our results suggest that the regulation by stargazin of biophysical properties of Ca(V)2.2 are not exerted by direct modulation of the channel but via a Gbetagamma-dependent mechanism.
Collapse
Affiliation(s)
- Isabella Tselnicker
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
| | | | | | | |
Collapse
|
38
|
Mitra-Ganguli T, Vitko I, Perez-Reyes E, Rittenhouse AR. Orientation of palmitoylated CaVbeta2a relative to CaV2.2 is critical for slow pathway modulation of N-type Ca2+ current by tachykinin receptor activation. ACTA ACUST UNITED AC 2010; 134:385-96. [PMID: 19858358 PMCID: PMC2768804 DOI: 10.1085/jgp.200910204] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The G(q)-coupled tachykinin receptor (neurokinin-1 receptor [NK-1R]) modulates N-type Ca(2+) channel (Ca(V)2.2 or N channel) activity at two distinct sites by a pathway involving a lipid metabolite, most likely arachidonic acid (AA). In another study published in this issue (Heneghan et al. 2009. J. Gen Physiol. doi:10.1085/jgp.200910203), we found that the form of modulation observed depends on which Ca(V)beta is coexpressed with Ca(V)2.2. When palmitoylated Ca(V)beta2a is coexpressed, activation of NK-1Rs by substance P (SP) enhances N current. In contrast, when Ca(V)beta3 is coexpressed, SP inhibits N current. However, exogenously applied palmitic acid minimizes this inhibition. These findings suggested that the palmitoyl groups of Ca(V)beta2a may occupy an inhibitory site on Ca(V)2.2 or prevent AA from interacting with that site, thereby minimizing inhibition. If so, changing the orientation of Ca(V)beta2a relative to Ca(V)2.2 may displace the palmitoyl groups and prevent them from antagonizing AA's actions, thereby allowing inhibition even in the presence of Ca(V)beta2a. In this study, we tested this hypothesis by deleting one (Bdel1) or two (Bdel2) amino acids proximal to the alpha interacting domain (AID) of Ca(V)2.2's I-II linker. Ca(V)betas bind tightly to the AID, whereas the rigid region proximal to the AID is thought to couple Ca(V)beta's movements to Ca(V)2.2 gating. Although Bdel1/beta2a currents exhibited more variable enhancement by SP, Bdel2/beta2a current enhancement was lost at all voltages. Instead, inhibition was observed that matched the profile of N-current inhibition from Ca(V)2.2 coexpressed with Ca(V)beta3. Moreover, adding back exogenous palmitic acid minimized inhibition of Bdel2/beta2a currents, suggesting that when palmitoylated Ca(V)beta2a is sufficiently displaced, endogenously released AA can bind to the inhibitory site. These findings support our previous hypothesis that Ca(V)beta2a's palmitoyl groups directly interact with an inhibitory site on Ca(V)2.2 to block N-current inhibition by SP.
Collapse
Affiliation(s)
- Tora Mitra-Ganguli
- Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | | | | | | |
Collapse
|
39
|
Page KM, Heblich F, Margas W, Pratt WS, Nieto-Rostro M, Chaggar K, Sandhu K, Davies A, Dolphin AC. N terminus is key to the dominant negative suppression of Ca(V)2 calcium channels: implications for episodic ataxia type 2. J Biol Chem 2009; 285:835-44. [PMID: 19903821 PMCID: PMC2801285 DOI: 10.1074/jbc.m109.065045] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Expression of the calcium channels CaV2.1 and CaV2.2 is markedly suppressed by co-expression with truncated constructs containing Domain I. This is the basis for the phenomenon of dominant negative suppression observed for many of the episodic ataxia type 2 mutations in CaV2.1 that predict truncated channels. The process of dominant negative suppression has been shown previously to stem from interaction between the full-length and truncated channels and to result in downstream consequences of the unfolded protein response and endoplasmic reticulum-associated protein degradation. We have now identified the specific domain that triggers this effect. For both CaV2.1 and CaV2.2, the minimum construct producing suppression was the cytoplasmic N terminus. Suppression was enhanced by tethering the N terminus to the membrane with a CAAX motif. The 11-amino acid motif (including Arg52 and Arg54) within the N terminus, which we have previously shown to be required for G protein modulation, is also essential for dominant negative suppression. Suppression is prevented by addition of an N-terminal tag (XFP) to the full-length and truncated constructs. We further show that suppression of CaV2.2 currents by the N terminus-CAAX construct is accompanied by a reduction in CaV2.2 protein level, and this is also prevented by mutation of Arg52 and Arg54 to Ala in the truncated construct. Taken together, our evidence indicates that both the extreme N terminus and the Arg52, Arg54 motif are involved in the processes underlying dominant negative suppression.
Collapse
Affiliation(s)
- Karen M Page
- Department of Neuroscience, Physiology, and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Berecki G, Motin L, Haythornthwaite A, Vink S, Bansal P, Drinkwater R, Wang CI, Moretta M, Lewis RJ, Alewood PF, Christie MJ, Adams DJ. Analgesic ω-Conotoxins CVIE and CVIF Selectively and Voltage-Dependently Block Recombinant and Native N-Type Calcium Channels. Mol Pharmacol 2009; 77:139-48. [DOI: 10.1124/mol.109.058834] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
41
|
Abstract
Ca2+ release from the sarcoplasmic reticulum (SR) into the cytosol is a crucial part of excitation-contraction (E-C) coupling. Excitation-contraction uncoupling, a deficit in Ca2+ release from the SR, is thought to be responsible for at least some of the loss in specific force observed in aging skeletal muscle. Excitation-contraction uncoupling may be caused by alterations in expression of the voltage-dependent calcium channel alpha1s (CaV1.1) and beta1a (CaVbeta1a) subunits, both of which are necessary for E-C coupling to occur. While previous studies have found CaV1.1 expression declines in old rodents, CaVbeta1a expression has not been previously examined in aging models. Western blot analysis shows a substantial increase of CaVbeta1a expression over the full lifespan of Friend Virus B (FVB) mice. To examine the specific effects of CaVbeta1a overexpression, a CaVbeta1a-YFP plasmid was electroporated in vivo into young animals. The resulting increase in expression of CaVbeta1a corresponded to decline of CaV1.1 over the same time period. YFP fluorescence, used as a measure of CaVbeta1a-YFP expression in individual fibers, also showed an inverse relationship with charge movement, measured using the whole-cell patch-clamp technique. Specific force was significantly reduced in young CaVbeta1a-YFP electroporated muscle fibers compared with sham-electroporated, age-matched controls. siRNA interference of CaVbeta1a in young muscles reduced charge movement, while charge movement in old was restored to young control levels. These studies imply CaVbeta1a serves as both a positive and negative regulator CaV1.1 expression, and that endogenous overexpression of CaVbeta1a during old age may play a role in the loss of specific force.
Collapse
Affiliation(s)
- Jackson R Taylor
- Department of Internal Medicine-Gerontology, Wake Forest University School of Medicine, 1 Medical Center Boulvard, Winston Salem, NC 27157, USA
| | | | | | | | | | | |
Collapse
|
42
|
Abstract
G-protein (Gbetagamma)-mediated voltage-dependent inhibition of N- and P/Q-type Ca(2+) channels contributes to presynaptic inhibition and short-term synaptic plasticity. The voltage dependence derives from the dissociation of Gbetagamma from the inhibited channels, but the underlying molecular and biophysical mechanisms remain largely unclear. In this study we investigated the role in this process of Ca(2+) channel beta subunit (Ca(v)beta) and a rigid alpha-helical structure between the alpha-interacting domain (AID), the primary Ca(v)beta docking site on the channel alpha(1) subunit, and the pore-lining IS6 segment. Gbetagamma inhibition of P/Q-type channels was reconstituted in giant inside-out membrane patches from Xenopus oocytes. Large populations of channels devoid of Ca(v)beta were produced by washing out a mutant Ca(v)beta with a reduced affinity for the AID. These beta-less channels were still inhibited by Gbetagamma, but without any voltage dependence, indicating that Ca(v)beta is indispensable for voltage-dependent Gbetagamma inhibition. A truncated Ca(v)beta containing only the AID-binding guanylate kinase (GK) domain could fully confer voltage dependence to Gbetagamma inhibition. Gbetagamma did not alter inactivation properties, and channels recovered from Gbetagamma inhibition exhibited the same activation property as un-inhibited channels, indicating that Gbetagamma does not dislodge Ca(v)beta from the inhibited channel. Furthermore, voltage-dependent Gbetagamma inhibition was abolished when the rigid alpha-helix between the AID and IS6 was disrupted by insertion of multiple glycines, which also eliminated Ca(v)beta regulation of channel gating, revealing a pivotal role of this rigid alpha-helix in both processes. These results suggest that depolarization-triggered movement of IS6, coupled to the subsequent conformational change of the Gbetagamma-binding pocket through a rigid alpha-helix induced partly by the Ca(v)beta GK domain, causes the dissociation of Gbetagamma and is fundamental to voltage-dependent Gbetagamma inhibition.
Collapse
Affiliation(s)
- Yun Zhang
- 1Department of Biological Sciences, Columbia University, New York, New York 10027, and
| | - Yu-hang Chen
- 1Department of Biological Sciences, Columbia University, New York, New York 10027, and
| | - Saroja D. Bangaru
- 1Department of Biological Sciences, Columbia University, New York, New York 10027, and
| | - Linling He
- 1Department of Biological Sciences, Columbia University, New York, New York 10027, and
| | - Kathryn Abele
- 1Department of Biological Sciences, Columbia University, New York, New York 10027, and
| | - Shihori Tanabe
- 2Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois 60612
| | - Tohru Kozasa
- 2Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois 60612
| | - Jian Yang
- 1Department of Biological Sciences, Columbia University, New York, New York 10027, and
| |
Collapse
|
43
|
Ferron L, Davies A, Page KM, Cox DJ, Leroy J, Waithe D, Butcher AJ, Sellaturay P, Bolsover S, Pratt WS, Moss FJ, Dolphin AC. The stargazin-related protein gamma 7 interacts with the mRNA-binding protein heterogeneous nuclear ribonucleoprotein A2 and regulates the stability of specific mRNAs, including CaV2.2. J Neurosci 2008; 28:10604-17. [PMID: 18923037 DOI: 10.1523/JNEUROSCI.2709-08.2008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The role(s) of the novel stargazin-like gamma-subunit proteins remain controversial. We have shown previously that the neuron-specific gamma7 suppresses the expression of certain calcium channels, particularly Ca(V)2.2, and is therefore unlikely to operate as a calcium channel subunit. We now show that the effect of gamma7 on Ca(V)2.2 expression is via an increase in the degradation rate of Ca(V)2.2 mRNA and hence a reduction of Ca(V)2.2 protein level. Furthermore, exogenous expression of gamma7 in PC12 cells also decreased the endogenous Ca(V)2.2 mRNA level. Conversely, knockdown of endogenous gamma7 with short-hairpin RNAs produced a reciprocal enhancement of Ca(V)2.2 mRNA stability and an increase in endogenous calcium currents in PC12 cells. Moreover, both endogenous and expressed gamma7 are present on intracellular membranes, rather than the plasma membrane. The cytoplasmic C terminus of gamma7 is essential for all its effects, and we show that gamma7 binds directly via its C terminus to a heterogeneous nuclear ribonucleoprotein (hnRNP A2), which also binds to a motif in Ca(V)2.2 mRNA, and is associated with native Ca(V)2.2 mRNA in PC12 cells. The expression of hnRNP A2 enhances Ca(V)2.2 I(Ba), and this enhancement is prevented by a concentration of gamma7 that alone has no effect on I(Ba). The effect of gamma7 is selective for certain mRNAs because it had no effect on alpha2delta-2 mRNA stability, but it decreased the mRNA stability for the potassium-chloride cotransporter, KCC1, which contains a similar hnRNP A2 binding motif to that in Ca(V)2.2 mRNA. Our results indicate that gamma7 plays a role in stabilizing Ca(V)2.2 mRNA.
Collapse
|
44
|
Dresviannikov AV, Page KM, Leroy J, Pratt WS, Dolphin AC. Determinants of the voltage dependence of G protein modulation within calcium channel beta subunits. Pflugers Arch 2008; 457:743-56. [PMID: 18651169 PMCID: PMC2686087 DOI: 10.1007/s00424-008-0549-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Accepted: 06/17/2008] [Indexed: 11/21/2022]
Abstract
CaVβ subunits of voltage-gated calcium channels contain two conserved domains, a src-homology-3 (SH3) domain and a guanylate kinase-like (GK) domain with an intervening HOOK domain. We have shown in a previous study that, although Gβγ-mediated inhibitory modulation of CaV2.2 channels did not require the interaction of a CaVβ subunit with the CaVα1 subunit, when such interaction was prevented by a mutation in the α1 subunit, G protein modulation could not be removed by a large depolarization and showed voltage-independent properties (Leroy et al., J Neurosci 25:6984–6996, 2005). In this study, we have investigated the ability of mutant and truncated CaVβ subunits to support voltage-dependent G protein modulation in order to determine the minimal domain of the CaVβ subunit that is required for this process. We have coexpressed the CaVβ subunit constructs with CaV2.2 and α2δ-2, studied modulation by the activation of the dopamine D2 receptor, and also examined basal tonic modulation. Our main finding is that the CaVβ subunit GK domains, from either β1b or β2, are sufficient to restore voltage dependence to G protein modulation. We also found that the removal of the variable HOOK region from β2a promotes tonic voltage-dependent G protein modulation. We propose that the absence of the HOOK region enhances Gβγ binding affinity, leading to greater tonic modulation by basal levels of Gβγ. This tonic modulation requires the presence of an SH3 domain, as tonic modulation is not supported by any of the CaVβ subunit GK domains alone.
Collapse
Affiliation(s)
- Andriy V Dresviannikov
- Laboratory of Cellular and Molecular Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | | | | | | | | |
Collapse
|
45
|
Mich PM, Horne WA. Alternative Splicing of the Ca2+ Channel β4 Subunit Confers Specificity for Gabapentin Inhibition of Cav2.1 Trafficking. Mol Pharmacol 2008; 74:904-12. [DOI: 10.1124/mol.108.045153] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
|
46
|
Van Petegem F, Duderstadt KE, Clark KA, Wang M, Minor DL Jr. 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] [What about the content of this article? (0)] [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.
Collapse
|
47
|
Dai G, Haedo RJ, Warren VA, Ratliff KS, Bugianesi RM, Rush A, Williams ME, Herrington J, Smith MM, McManus OB, Swensen AM. A High-Throughput Assay for Evaluating State Dependence and Subtype Selectivity of Cav2 Calcium Channel Inhibitors. Assay Drug Dev Technol 2008; 6:195-212. [DOI: 10.1089/adt.2008.136] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Affiliation(s)
- Ge Dai
- Merck Research Laboratories, Rahway, NJ
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
|
49
|
Milstein AD, Zhou W, Karimzadegan S, Bredt DS, Nicoll RA. TARP subtypes differentially and dose-dependently control synaptic AMPA receptor gating. Neuron 2007; 55:905-18. [PMID: 17880894 PMCID: PMC3167227 DOI: 10.1016/j.neuron.2007.08.022] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2007] [Revised: 08/01/2007] [Accepted: 08/28/2007] [Indexed: 10/22/2022]
Abstract
A family of transmembrane AMPA receptor regulatory proteins (TARPs) profoundly affects the trafficking and gating of AMPA receptors (AMPARs). Although TARP subtypes are differentially expressed throughout the CNS, it is unclear whether this imparts functional diversity to AMPARs in distinct neuronal populations. Here, we examine the effects of each TARP subtype on the kinetics of AMPAR gating in heterologous cells and in neurons. We report a striking heterogeneity in the effects of TARP subtypes on AMPAR deactivation and desensitization, which we demonstrate controls the time course of synaptic transmission. In addition, we find that some TARP subtypes dramatically slow AMPAR activation kinetics. Synaptic AMPAR kinetics also depend on TARP expression level, suggesting a variable TARP/AMPAR stoichiometry. Analysis of quantal synaptic transmission in a TARP gamma-4 knockout (KO) mouse corroborates our expression data and demonstrates that TARP subtype-specific gating of AMPARs contributes to the kinetics of native AMPARs at central synapses.
Collapse
Affiliation(s)
- Aaron D. Milstein
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143
- Department of Physiology, University of California, San Francisco, CA 94143
- Neuroscience Graduate Program, University of California, San Francisco, CA 94143
| | - Wei Zhou
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143
| | | | - David S. Bredt
- Department of Physiology, University of California, San Francisco, CA 94143
| | - Roger A. Nicoll
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143
- Department of Physiology, University of California, San Francisco, CA 94143
- Address correspondence to: Roger A. Nicoll, Dept. of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143, , Phone: (415) 476-2018
| |
Collapse
|
50
|
Abstract
The importance of voltage-gated calcium channels is underscored by the multitude of intracellular processes that depend on calcium, notably gene regulation and neurotransmission. Given their pivotal roles in calcium (and hence, cellular) homeostasis, voltage-gated calcium channels have been the subject of intense research, much of which has focused on channel regulation. While ongoing research continues to delineate the myriad of interactions that govern calcium channel regulation, an increasing amount of work has focused on the trafficking of voltage-gated calcium channels. This includes the mechanisms by which calcium channels are targeted to the plasma membrane, and, more specifically, to their appropriate loci within a given cell. In addition, we are beginning to gain some insights into the mechanisms by which calcium channels can be removed from the plasma membrane for recycling and/or degradation. Here we highlight recent advances in our understanding of these fundamentally important mechanisms.
Collapse
Affiliation(s)
- Scott E Jarvis
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Dr. NW, Calgary T2N 4N1, Canada
| | | |
Collapse
|