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Segura É, Zhao J, Broszczak M, Audet F, Sauvé R, Parent L. Investigating the Impact of Electrostatic Interactions on Calmodulin Binding and Ca 2+-Dependent Activation of the Calcium-Gated Potassium SK4 Channel. Int J Mol Sci 2024; 25:4255. [PMID: 38673845 PMCID: PMC11050286 DOI: 10.3390/ijms25084255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/03/2024] [Accepted: 04/09/2024] [Indexed: 04/28/2024] Open
Abstract
Ca2+ binding to the ubiquitous Ca2+ sensing protein calmodulin (CaM) activates the intermediate conductance Ca2+-activated SK4 channel. Potential hydrophilic pockets for CaM binding have been identified at the intracellular HA and HB helices in the C-terminal of SK4 from the three published cryo-EM structures of SK4. Single charge reversal substitutions at either site, significantly weakened the pull-down of SK4 by CaM wild-type (CaM), and decreased the TRAM-34 sensitive outward K+ current densities in native HEK293T cells when compared with SK4 WT measured under the same conditions. Only the doubly substituted SK4 R352D/R355D (HB helix) obliterated the CaM-mediated pull-down and thwarted outward K+ currents. However, overexpression of CaM E84K/E87K, which had been predicted to face the arginine doublet, restored the CaM-mediated pull-down of SK4 R352D/R355D and normalized its whole-cell current density. Virtual analysis of the putative salt bridges supports a unique role for the positively charged arginine doublet at the HB helix into anchoring the interaction with the negatively charged CaM glutamate 84 and 87 CaM. Our findings underscore the unique contribution of electrostatic interactions in carrying CaM binding onto SK4 and support the role of the C-terminal HB helix to the Ca2+-dependent gating process.
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Affiliation(s)
- Émilie Segura
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (É.S.); (F.A.)
| | - Juan Zhao
- Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (J.Z.); (M.B.)
| | - Marlena Broszczak
- Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (J.Z.); (M.B.)
| | - Frédéric Audet
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (É.S.); (F.A.)
| | - Rémy Sauvé
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, 2900 Bd Édouard-Montpetit, Montréal, QC H3T 1J4, Canada;
| | - Lucie Parent
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (É.S.); (F.A.)
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Zhao J, Segura E, Marsolais M, Parent L. A CACNA1C variant associated with cardiac arrhythmias provides mechanistic insights in the calmodulation of L-type Ca 2+ channels. J Biol Chem 2022; 298:102632. [PMID: 36273583 PMCID: PMC9691931 DOI: 10.1016/j.jbc.2022.102632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 10/12/2022] [Accepted: 10/15/2022] [Indexed: 11/07/2022] Open
Abstract
We recently reported the identification of a de novo single nucleotide variant in exon 9 of CACNA1C associated with prolonged repolarization interval. Recombinant expression of the glycine to arginine variant at position 419 produced a gain in the function of the L-type CaV1.2 channel with increased peak current density and activation gating but without significant decrease in the inactivation kinetics. We herein reveal that these properties are replicated by overexpressing calmodulin (CaM) with CaV1.2 WT and are reversed by exposure to the CaM antagonist W-13. Phosphomimetic (T79D or S81D), but not phosphoresistant (T79A or S81A), CaM surrogates reproduced the impact of CaM WT on the function of CaV1.2 WT. The increased channel activity of CaV1.2 WT following overexpression of CaM was found to arise in part from enhanced cell surface expression. In contrast, the properties of the variant remained unaffected by any of these treatments. CaV1.2 substituted with the α-helix breaking proline residue were more reluctant to open than CaV1.2 WT but were upregulated by phosphomimetic CaM surrogates. Our results indicate that (1) CaM and its phosphomimetic analogs promote a gain in the function of CaV1.2 and (2) the structural properties of the first intracellular linker of CaV1.2 contribute to its CaM-induced modulation. We conclude that the CACNA1C clinical variant mimics the increased activity associated with the upregulation of CaV1.2 by Ca2+-CaM, thus maintaining a majority of channels in a constitutively active mode that could ultimately promote ventricular arrhythmias.
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Affiliation(s)
- Juan Zhao
- Centre de recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec, Canada
| | - Emilie Segura
- Centre de recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec, Canada,Département de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec, Canada
| | - Mireille Marsolais
- Centre de recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec, Canada,Département de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec, Canada
| | - Lucie Parent
- Centre de recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec, Canada,Département de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec, Canada,For correspondence: Lucie Parent
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Al Katat A, Zhao J, Calderone A, Parent L. Sympathetic Stimulation Upregulates the Ca 2+ Channel Subunit, Ca Vα2δ1, via the β1 and ERK 1/2 Pathway in Neonatal Ventricular Cardiomyocytes. Cells 2022; 11:188. [PMID: 35053304 PMCID: PMC8774121 DOI: 10.3390/cells11020188] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 12/29/2021] [Accepted: 01/03/2022] [Indexed: 02/04/2023] Open
Abstract
Intracellular Ca2+ overload secondary to chronic hemodynamic stimuli promotes the recruitment of Ca2+-dependent signaling implicated in cardiomyocyte hypertrophy. The present study tested the hypothesis that sympathetic-mediated hypertrophy of neonatal rat ventricular cardiomyocytes (NRVMs) translated to an increase in calcium influx secondary to the upregulation of CaV1.2 channel subunits. Confocal imaging of norepinephrine (NE)-treated NRVMs revealed a hypertrophic response compared to untreated NRVMs. L-type CaV1.2 peak current density was increased 4-fold following a 24-h stimulation with NE. NE-treated NRVMs exhibited a significant upregulation of CaVα2δ1 and CaVβ3 protein levels without significant changes of CaVα1C and CaVβ2 protein levels. Pre-treatment with the β1-blocker metoprolol failed to inhibit hypertrophy or CaVβ3 upregulation whereas CaVα2δ1 protein levels were significantly reduced. NE promoted the phosphorylation of ERK 1/2, and the response was attenuated by the β1-blocker. U0126 pre-treatment suppressed NE-induced ERK1/2 phosphorylation but failed to attenuate hypertrophy. U0126 inhibition of ERK1/2 phosphorylation prevented NE-mediated upregulation of CaVα2δ1, whereas CaVβ3 protein levels remained elevated. Thus, β1-adrenergic receptor-mediated recruitment of the ERK1/2 plays a seminal role in the upregulation of CaVα2δ1 in NRVMs independent of the concomitant hypertrophic response. However, the upregulation of CaVβ3 protein levels may be directly dependent on the hypertrophic response of NRVMs.
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Affiliation(s)
- Aya Al Katat
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, Montréal, QC H3T 1J4, Canada; (A.A.K.); (A.C.)
- Research Center, Montreal Heart Institute, 5000 Rue Belanger, Montréal, QC H1T 1C8, Canada;
| | - Juan Zhao
- Research Center, Montreal Heart Institute, 5000 Rue Belanger, Montréal, QC H1T 1C8, Canada;
| | - Angelino Calderone
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, Montréal, QC H3T 1J4, Canada; (A.A.K.); (A.C.)
- Research Center, Montreal Heart Institute, 5000 Rue Belanger, Montréal, QC H1T 1C8, Canada;
| | - Lucie Parent
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, Montréal, QC H3T 1J4, Canada; (A.A.K.); (A.C.)
- Research Center, Montreal Heart Institute, 5000 Rue Belanger, Montréal, QC H1T 1C8, Canada;
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Segura E, Mehta A, Marsolais M, Quan XR, Zhao J, Sauvé R, Spafford JD, Parent L. An ancestral MAGUK protein supports the modulation of mammalian voltage-gated Ca 2+ channels through a conserved Ca Vβ-like interface. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183439. [PMID: 32814116 DOI: 10.1016/j.bbamem.2020.183439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 07/11/2020] [Accepted: 08/03/2020] [Indexed: 01/09/2023]
Abstract
Eukaryote voltage-gated Ca2+ channels of the CaV2 channel family are hetero-oligomers formed by the pore-forming CaVα1 protein assembled with auxiliary CaVα2δ and CaVβ subunits. CaVβ subunits are formed by a Src homology 3 (SH3) domain and a guanylate kinase (GK) domain connected through a HOOK domain. The GK domain binds a conserved cytoplasmic region of the pore-forming CaVα1 subunit referred as the "AID". Herein we explored the phylogenetic and functional relationship between CaV channel subunits in distant eukaryotic organisms by investigating the function of a MAGUK protein (XM_004990081) cloned from the choanoflagellate Salpingoeca rosetta (Sro). This MAGUK protein (Sroβ) features SH3 and GK structural domains with a 25% primary sequence identity to mammalian CaVβ. Recombinant expression of its cDNA with mammalian high-voltage activated Ca2+ channel CaV2.3 in mammalian HEK cells produced robust voltage-gated inward Ca2+ currents with typical activation and inactivation properties. Like CaVβ, Sroβ prevents fast degradation of total CaV2.3 proteins in cycloheximide assays. The three-dimensional homology model predicts an interaction between the GK domain of Sroβ and the AID motif of the pore-forming CaVα1 protein. Substitution of AID residues Trp (W386A) and Tyr (Y383A) significantly impaired co-immunoprecipitation of CaV2.3 with Sroβ and functional upregulation of CaV2.3 currents. Likewise, a 6-residue deletion within the GK domain of Sroβ, similar to the locus found in mammalian CaVβ, significantly reduced peak current density. Altogether our data demonstrate that an ancestor MAGUK protein reconstitutes the biophysical and molecular features responsible for channel upregulation by mammalian CaVβ through a minimally conserved molecular interface.
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Affiliation(s)
- Emilie Segura
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Amrit Mehta
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Mireille Marsolais
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Xin R Quan
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Juan Zhao
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Rémy Sauvé
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Canada
| | - J David Spafford
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
| | - Lucie Parent
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada.
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CACHD1 is an α2δ-Like Protein That Modulates Ca V3 Voltage-Gated Calcium Channel Activity. J Neurosci 2018; 38:9186-9201. [PMID: 30181139 DOI: 10.1523/jneurosci.3572-15.2018] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 06/03/2018] [Accepted: 06/13/2018] [Indexed: 11/21/2022] Open
Abstract
The putative cache (Ca2+ channel and chemotaxis receptor) domain containing 1 (CACHD1) protein has predicted structural similarities to members of the α2δ voltage-gated Ca2+ channel auxiliary subunit family. CACHD1 mRNA and protein were highly expressed in the male mammalian CNS, in particular in the thalamus, hippocampus, and cerebellum, with a broadly similar tissue distribution to CaV3 subunits, in particular CaV3.1. In expression studies, CACHD1 increased cell-surface localization of CaV3.1, and these proteins were in close proximity at the cell surface, consistent with the formation of CACHD1-CaV3.1 complexes. In functional electrophysiological studies, coexpression of human CACHD1 with CaV3.1, CaV3.2, and CaV3.3 caused a significant increase in peak current density and corresponding increases in maximal conductance. By contrast, α2δ-1 had no effect on peak current density or maximal conductance in CaV3.1, CaV3.2, or CaV3.3. A comparison of CACHD1-mediated increases in CaV3.1 current density and gating currents revealed an increase in channel open probability. In hippocampal neurons from male and female embryonic day 19 rats, CACHD1 overexpression increased CaV3-mediated action potential firing frequency and neuronal excitability. These data suggest that CACHD1 is structurally an α2δ-like protein that functionally modulates CaV3 voltage-gated calcium channel activity.SIGNIFICANCE STATEMENT This is the first study to characterize the Ca2+ channel and chemotaxis receptor domain containing 1 (CACHD1) protein. CACHD1 is widely expressed in the CNS, in particular in the thalamus, hippocampus, and cerebellum. CACHD1 distribution is similar to that of low voltage-activated (CaV3, T-type) calcium channels, in particular to CaV3.1, a protein that regulates neuronal excitability and is a potential therapeutic target in conditions such as epilepsy and pain. CACHD1 is structurally an α2δ-like protein that functionally increases CaV3 calcium current. CACHD1 increases the presence of CaV3.1 at the cell surface, forms complexes with CaV3.1 at the cell surface, and causes an increase in channel open probability. In hippocampal neurons, CACHD1 causes increases in neuronal firing. Thus, CACHD1 represents a novel protein that modulates CaV3 activity.
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Briot J, Mailhot O, Bourdin B, Tétreault MP, Najmanovich R, Parent L. A three-way inter-molecular network accounts for the Ca Vα2δ1-induced functional modulation of the pore-forming Ca V1.2 subunit. J Biol Chem 2018; 293:7176-7188. [PMID: 29588365 DOI: 10.1074/jbc.ra118.001902] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 03/09/2018] [Indexed: 12/17/2022] Open
Abstract
L-type CaV1.2 channels are essential for the excitation-contraction coupling in cardiomyocytes and are hetero-oligomers of a pore-forming CaVα1C assembled with CaVβ and CaVα2δ1 subunits. A direct interaction between CaVα2δ1 and Asp-181 in the first extracellular loop of CaVα1 reproduces the native properties of the channel. A 3D model of the von Willebrand factor type A (VWA) domain of CaVα2δ1 complexed with the voltage sensor domain of CaVα1C suggests that Ser-261 and Ser-263 residues in the metal ion-dependent adhesion site (MIDAS) motif are determinant in this interaction, but this hypothesis is untested. Here, coimmunoprecipitation assays and patch-clamp experiments of single-substitution variants revealed that CaVα2δ1 Asp-259 and Ser-261 are the two most important residues in regard to protein interactions and modulation of CaV1.2 currents. In contrast, mutating the side chains of CaVα2δ1 Ser-263, Thr-331, and Asp-363 with alanine did not completely prevent channel function. Molecular dynamics simulations indicated that the carboxylate side chain of CaVα2δ1 Asp-259 coordinates the divalent cation that is further stabilized by the oxygen atoms from the hydroxyl side chain of CaVα2δ1 Ser-261 and the carboxylate group of CaVα1C Asp-181. In return, the hydrogen atoms contributed by the side chain of Ser-261 and the main chain of Ser-263 bonded the oxygen atoms of CaV1.2 Asp-181. We propose that CaVα2δ1 Asp-259 promotes Ca2+ binding necessary to produce the conformation of the VWA domain that locks CaVα2δ1 Ser-261 and Ser-263 within atomic distance of CaVα1C Asp-181. This three-way network appears to account for the CaVα2δ1-induced modulation of CaV1.2 currents.
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Affiliation(s)
- Julie Briot
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Olivier Mailhot
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Biochimie et Médecine Moléculaire, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada
| | - Benoîte Bourdin
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Marie-Philippe Tétreault
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Rafael Najmanovich
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada
| | - Lucie Parent
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada.
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Rosa N, Triffaux E, Robert V, Mars M, Klein M, Bouchaud G, Canivet A, Magnan A, Guéry JC, Pelletier L, Savignac M. The β and α2δ auxiliary subunits of voltage-gated calcium channel 1 (Ca v1) are required for T H2 lymphocyte function and acute allergic airway inflammation. J Allergy Clin Immunol 2017; 142:892-903.e8. [PMID: 29129580 DOI: 10.1016/j.jaci.2017.09.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/04/2017] [Accepted: 09/08/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND T lymphocytes express not only cell membrane ORAI calcium release-activated calcium modulator 1 but also voltage-gated calcium channel (Cav) 1 channels. In excitable cells these channels are composed of the ion-forming pore α1 and auxiliary subunits (β and α2δ) needed for proper trafficking and activation of the channel. Previously, we disclosed the role of Cav1.2 α1 in mouse and human TH2 but not TH1 cell functions and showed that knocking down Cav1 α1 prevents experimental asthma. OBJECTIVE We investigated the role of β and α2δ auxiliary subunits on Cav1 α1 function in TH2 lymphocytes and on the development of acute allergic airway inflammation. METHODS We used Cavβ antisense oligonucleotides to knock down Cavβ and gabapentin, a drug that binds to and inhibits α2δ1 and α2δ2, to test their effects on TH2 functions and their capacity to reduce allergic airway inflammation. RESULTS Mouse and human TH2 cells express mainly Cavβ1, β3, and α2δ2 subunits. Cavβ antisense reduces T-cell receptor-driven calcium responses and cytokine production by mouse and human TH2 cells with no effect on TH1 cells. Cavβ is mainly involved in restraining Cav1.2 α1 degradation through the proteasome because a proteasome inhibitor partially restores the α1 protein level. Gabapentin impairs the T-cell receptor-driven calcium response and cytokine production associated with the loss of α2δ2 protein in TH2 cells. CONCLUSIONS These results stress the role of Cavβ and α2δ2 auxiliary subunits in the stability and activation of Cav1.2 channels in TH2 lymphocytes both in vitro and in vivo, as demonstrated by the beneficial effect of Cavβ antisense and gabapentin in allergic airway inflammation.
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Affiliation(s)
- Nicolas Rosa
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Emily Triffaux
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Virginie Robert
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Marion Mars
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Martin Klein
- Institut du Thorax, INSERM CNRS, UNIV Nantes, France
| | | | - Astrid Canivet
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Antoine Magnan
- Institut du Thorax, INSERM CNRS, UNIV Nantes, France; Centre Hospitalier Universitaire de Nantes, Service de Pneumologie, Nantes, France
| | - Jean-Charles Guéry
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Lucette Pelletier
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France.
| | - Magali Savignac
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France.
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Bourdin B, Briot J, Tétreault MP, Sauvé R, Parent L. Negatively charged residues in the first extracellular loop of the L-type Ca V1.2 channel anchor the interaction with the Ca Vα2δ1 auxiliary subunit. J Biol Chem 2017; 292:17236-17249. [PMID: 28864774 PMCID: PMC5655503 DOI: 10.1074/jbc.m117.806893] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/18/2017] [Indexed: 12/20/2022] Open
Abstract
Voltage-gated L-type CaV1.2 channels in cardiomyocytes exist as heteromeric complexes. Co-expression of CaVα2δ1 with CaVβ/CaVα1 proteins reconstitutes the functional properties of native L-type currents, but the interacting domains at the CaV1.2/CaVα2δ1 interface are unknown. Here, a homology-based model of CaV1.2 identified protein interfaces between the extracellular domain of CaVα2δ1 and the extracellular loops of the CaVα1 protein in repeats I (IS1S2 and IS5S6), II (IIS5S6), and III (IIIS5S6). Insertion of a 9-residue hemagglutinin epitope in IS1S2, but not in IS5S6 or in IIS5S6, prevented the co-immunoprecipitation of CaV1.2 with CaVα2δ1. IS1S2 contains a cluster of three conserved negatively charged residues Glu-179, Asp-180, and Asp-181 that could contribute to non-bonded interactions with CaVα2δ1. Substitutions of CaV1.2 Asp-181 impaired the co-immunoprecipitation of CaVβ/CaV1.2 with CaVα2δ1 and the CaVα2δ1-dependent shift in voltage-dependent activation gating. In contrast, single substitutions in CaV1.2 in neighboring positions in the same loop (179, 180, and 182–184) did not significantly alter the functional up-regulation of CaV1.2 whole-cell currents. However, a negatively charged residue at position 180 was necessary to convey the CaVα2δ1-mediated shift in the activation gating. We also found a more modest contribution from the positively charged Arg-1119 in the extracellular pore region in repeat III of CaV1.2. We conclude that CaV1.2 Asp-181 anchors the physical interaction that facilitates the CaVα2δ1-mediated functional modulation of CaV1.2 currents. By stabilizing the first extracellular loop of CaV1.2, CaVα2δ1 may up-regulate currents by promoting conformations of the voltage sensor that are associated with the channel's open state.
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Affiliation(s)
- Benoîte Bourdin
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Julie Briot
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada.,From the Département de Pharmacologie et Physiologie, Faculté de Médecine, and
| | - Marie-Philippe Tétreault
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Rémy Sauvé
- From the Département de Pharmacologie et Physiologie, Faculté de Médecine, and
| | - Lucie Parent
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada .,From the Département de Pharmacologie et Physiologie, Faculté de Médecine, and
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