1
|
Neumaier F, Alpdogan S, Hescheler J, Schneider T. Protein phosphorylation maintains the normal function of cloned human Ca v2.3 channels. J Gen Physiol 2018; 150:491-510. [PMID: 29453293 PMCID: PMC5839719 DOI: 10.1085/jgp.201711880] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Revised: 12/22/2017] [Accepted: 01/24/2018] [Indexed: 11/30/2022] Open
Abstract
Cav2.3 Ca2+ channels are subject to cytosolic regulation, which has been difficult to characterize in native cells. Neumaier et al. demonstrate the role of phosphorylation in the function of these channels and suggest a close relationship between voltage dependence and the phosphorylation state. R-type currents mediated by native and recombinant Cav2.3 voltage-gated Ca2+ channels (VGCCs) exhibit facilitation (run-up) and subsequent decline (run-down) in whole-cell patch-clamp recordings. A better understanding of the two processes could provide insight into constitutive modulation of the channels in intact cells, but low expression levels and the need for pharmacological isolation have prevented investigations in native systems. Here, to circumvent these limitations, we use conventional and perforated-patch-clamp recordings in a recombinant expression system, which allows us to study the effects of cell dialysis in a reproducible manner. We show that the decline of currents carried by human Cav2.3+β3 channel subunits during run-down is related to adenosine triphosphate (ATP) depletion, which reduces the number of functional channels and leads to a progressive shift of voltage-dependent gating to more negative potentials. Both effects can be counteracted by hydrolysable ATP, whose protective action is almost completely prevented by inhibition of serine/threonine but not tyrosine or lipid kinases. Protein kinase inhibition also mimics the effects of run-down in intact cells, reduces the peak current density, and hyperpolarizes the voltage dependence of gating. Together, our findings indicate that ATP promotes phosphorylation of either the channel or an associated protein, whereas dephosphorylation during cell dialysis results in run-down. These data also distinguish the effects of ATP on Cav2.3 channels from those on other VGCCs because neither direct nucleotide binding nor PIP2 synthesis is required for protection from run-down. We conclude that protein phosphorylation is required for Cav2.3 channel function and could directly influence the normal features of current carried by these channels. Curiously, some of our findings also point to a role for leupeptin-sensitive proteases in run-up and possibly ATP protection from run-down. As such, the present study provides a reliable baseline for further studies on Cav2.3 channel regulation by protein kinases, phosphatases, and possibly proteases.
Collapse
Affiliation(s)
- Felix Neumaier
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
| | - Serdar Alpdogan
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
| | - Jürgen Hescheler
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
| | - Toni Schneider
- Institute for Neurophysiology, University of Cologne, Cologne, Germany
| |
Collapse
|
2
|
Manning JR, Chelvarajan L, Levitan BM, Withers CN, Nagareddy PR, Haggerty CM, Fornwalt BK, Gao E, Tripathi H, Abdel-Latif A, Andres DA, Satin J. Rad GTPase deletion attenuates post-ischemic cardiac dysfunction and remodeling. ACTA ACUST UNITED AC 2018; 3:83-96. [PMID: 29732439 PMCID: PMC5931223 DOI: 10.1016/j.jacbts.2017.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Rad-GTPase is an LTCC component that functions to govern calcium current in the myocardium. Deletion of Rad increases myocardial contractility secondary to increased trigger calcium entry. AMI induces heart failure, including reduced calcium homeostasis, but deletion of Rad prevents AMI myocardial calcium alterations. Rad deletion prevents post-MI scar spread by attenuating the inflammatory response. Future studies will explore whether Rad deletion is an effective therapeutic direction for providing combined safe, stable inotropic support to the failing heart in concert with protection against inflammatory signaling.
The protein Rad interacts with the L-type calcium channel complex to modulate trigger Ca2+ and hence to govern contractility. Reducing Rad levels increases cardiac output. Ablation of Rad also attenuated the inflammatory response following acute myocardial infarction. Future studies to target deletion of Rad in the heart could be conducted to establish a novel treatment paradigm whereby pathologically stressed hearts would be given safe, stable positive inotropic support without arrhythmias and without pathological structural remodeling. Future investigations will also focus on establishing inhibitors of Rad and testing the efficacy of Rad deletion in cardioprotection relative to the time of onset of acute myocardial infarction.
Collapse
Affiliation(s)
- Janet R Manning
- Department of Physiology, University of Kentucky, Lexington KY.,Department of Biochemistry, University of Kentucky, Lexington KY
| | - Lakshman Chelvarajan
- Saha Cardiovascular Research Center, Department of Medicine, University of Kentucky, Lexington, KY
| | - Bryana M Levitan
- Department of Physiology, University of Kentucky, Lexington KY.,Gill Heart and Vascular Institute, University of Kentucky, Lexington KY
| | | | | | - Christopher M Haggerty
- Saha Cardiovascular Research Center, Department of Medicine, University of Kentucky, Lexington, KY.,Department of Imaging Science and Innovation, Geisinger, Danville PA
| | - Brandon K Fornwalt
- Saha Cardiovascular Research Center, Department of Medicine, University of Kentucky, Lexington, KY.,Department of Imaging Science and Innovation, Geisinger, Danville PA
| | - Erhe Gao
- Department of Physiology, University of Kentucky, Lexington KY.,Center for Translational Medicine, Temple University School of Medicine, Philadelphia PA
| | - Himi Tripathi
- Saha Cardiovascular Research Center, Department of Medicine, University of Kentucky, Lexington, KY
| | - Ahmed Abdel-Latif
- Saha Cardiovascular Research Center, Department of Medicine, University of Kentucky, Lexington, KY.,Gill Heart and Vascular Institute, University of Kentucky, Lexington KY
| | - Douglas A Andres
- Department of Biochemistry, University of Kentucky, Lexington KY
| | - Jonathan Satin
- Department of Physiology, University of Kentucky, Lexington KY
| |
Collapse
|
3
|
Manning JR, Withers CN, Levitan B, Smith JD, Andres DA, Satin J. Loss of Rad-GTPase produces a novel adaptive cardiac phenotype resistant to systolic decline with aging. Am J Physiol Heart Circ Physiol 2015; 309:H1336-45. [PMID: 26371164 DOI: 10.1152/ajpheart.00389.2015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/02/2015] [Indexed: 12/26/2022]
Abstract
Rad-GTPase is a regulator of L-type calcium current (LTCC), with increased calcium current observed in Rad knockout models. While mouse models that result in elevated LTCC have been associated with heart failure, our laboratory and others observe a hypercontractile phenotype with enhanced calcium homeostasis in Rad(-/-). It is currently unclear whether this observation represents an early time point in a decompensatory progression towards heart failure or whether Rad loss drives a novel phenotype with stable enhanced function. We test the hypothesis that Rad(-/-) drives a stable nonfailing hypercontractile phenotype in adult hearts, and we examine compensatory regulation of sarcoplasmic reticulum (SR) loading and protein changes. Heart function was measured in vivo with echocardiography. In vivo heart function was significantly improved in adult Rad(-/-) hearts compared with wild type. Heart wall dimensions were significantly increased, while heart size was decreased, and cardiac output was not changed. Cardiac function was maintained through 18 mo of age with no decompensation. SR releasable Ca(2+) was increased in isolated Rad(-/-) ventricular myocytes. Higher Ca(2+) load was accompanied by sarco/endoplasmic reticulum Ca(2+) ATPase 2a (SERCA2a) protein elevation as determined by immunoblotting and a rightward shift in the thapsigargan inhibitor-response curve. Rad(-/-) promotes morphological changes accompanied by a stable increase in contractility with aging and preserved cardiac output. The Rad(-/-) phenotype is marked by enhanced systolic and diastolic function with increased SR uptake, which is consistent with a model that does not progress into heart failure.
Collapse
Affiliation(s)
- Janet R Manning
- Department of Physiology, University of Kentucky, Lexington, Kentucky; Department of Biochemistry, University of Kentucky, Lexington, Kentucky; and
| | - Catherine N Withers
- Department of Biochemistry, University of Kentucky, Lexington, Kentucky; and
| | - Bryana Levitan
- Gill Heart Institute, University of Kentucky, Lexington, Kentucky
| | - Jeffrey D Smith
- Department of Biochemistry, University of Kentucky, Lexington, Kentucky; and
| | - Douglas A Andres
- Department of Biochemistry, University of Kentucky, Lexington, Kentucky; and
| | - Jonathan Satin
- Department of Physiology, University of Kentucky, Lexington, Kentucky;
| |
Collapse
|
4
|
Functional assessment of three Rem residues identified as critical for interactions with Ca(2+) channel β subunits. Pflugers Arch 2015; 467:2299-306. [PMID: 25771954 DOI: 10.1007/s00424-015-1700-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 03/04/2015] [Indexed: 12/18/2022]
Abstract
Members of the Rem, Rem2, Rad, Gem/Kir (RGK) family of small GTP-binding proteins inhibit high-voltage-activated (HVA) Ca(2+) channels through interactions with both the principal α1 and the auxiliary β subunits of the channel complex. Three highly conserved residues of Rem (R200, L227, and H229) have been shown in vitro to be critical for interactions with β subunits. However, the functional significance of these residues is not known. To investigate the contributions of R200, L227, and H229 to β subunit-mediated RGK protein-dependent inhibition of HVA channels, we introduced alanine substitutions into all three positions of Venus fluorescent protein-tagged Rem (V-Rem AAA) and made three other V-Rem constructs with an alanine introduced at only one position (V-Rem R200A, V-Rem L227A, and V-Rem H229A). Confocal imaging and immunoblotting demonstrated that each Venus-Rem mutant construct had comparable expression levels to Venus-wild-type Rem when heterologously expressed in tsA201 cells. In electrophysiological experiments, V-Rem AAA failed to inhibit N-type Ca(2+) currents in tsA201 cells coexpressing CaV2.2 α1B, β3, and α2δ-1 channel subunits. The V-Rem L227A single mutant also failed to reduce N-type currents conducted by coexpressed CaV2.2 channels, a finding consistent with the previous observation that a leucine at position 227 is critical for Rem-β interactions. Rem-dependent inhibition of CaV2.2 channels was impaired to a much lesser extent by the R200A substitution. In contrast to the earlier work demonstrating that Rem H229A was unable to interact with β3 subunits in vitro, V-Rem H229A produced nearly complete inhibition of CaV2.2-mediated currents.
Collapse
|
5
|
Buraei Z, Lumen E, Kaur S, Yang J. RGK regulation of voltage-gated calcium channels. SCIENCE CHINA-LIFE SCIENCES 2015; 58:28-38. [PMID: 25576452 PMCID: PMC9074095 DOI: 10.1007/s11427-014-4788-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 09/02/2014] [Indexed: 01/01/2023]
Abstract
Voltage-gated calcium channels (VGCCs) play critical roles in cardiac and skeletal muscle contractions, hormone and neurotransmitter release, as well as slower processes such as cell proliferation, differentiation, migration and death. Mutations in VGCCs lead to numerous cardiac, muscle and neurological disease, and their physiological function is tightly regulated by kinases, phosphatases, G-proteins, calmodulin and many other proteins. Fifteen years ago, RGK proteins were discovered as the most potent endogenous regulators of VGCCs. They are a family of monomeric GTPases (Rad, Rem, Rem2, and Gem/Kir), in the superfamily of Ras GTPases, and they have two known functions: regulation of cytoskeletal dynamics including dendritic arborization and inhibition of VGCCs. Here we review the mechanisms and molecular determinants of RGK-mediated VGCC inhibition, the physiological impact of this inhibition, and recent evidence linking the two known RGK functions.
Collapse
Affiliation(s)
- Zafir Buraei
- Department of Biology, Pace University, New York, NY, 10038, USA,
| | | | | | | |
Collapse
|
6
|
Beqollari D, Romberg CF, Meza U, Papadopoulos S, Bannister RA. Differential effects of RGK proteins on L-type channel function in adult mouse skeletal muscle. Biophys J 2014; 106:1950-7. [PMID: 24806927 DOI: 10.1016/j.bpj.2014.03.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Revised: 02/24/2014] [Accepted: 03/25/2014] [Indexed: 11/19/2022] Open
Abstract
Work in heterologous systems has revealed that members of the Rad, Rem, Rem2, Gem/Kir (RGK) family of small GTP-binding proteins profoundly inhibit L-type Ca(2+) channels via three mechanisms: 1), reduction of membrane expression; 2), immobilization of the voltage-sensors; and 3), reduction of Po without impaired voltage-sensor movement. However, the question of which mode is the critical one for inhibition of L-type channels in their native environments persists. To address this conundrum in skeletal muscle, we overexpressed Rad and Rem in flexor digitorum brevis (FDB) fibers via in vivo electroporation and examined the abilities of these two RGK isoforms to modulate the L-type Ca(2+) channel (CaV1.1). We found that Rad and Rem both potently inhibit L-type current in FDB fibers. However, intramembrane charge movement was only reduced in fibers transfected with Rad; charge movement for Rem-expressing fibers was virtually identical to charge movement observed in naïve fibers. This result indicated that Rem supports inhibition solely through a mechanism that allows for translocation of CaV1.1's voltage-sensors, whereas Rad utilizes at least one mode that limits voltage-sensor movement. Because Rad and Rem differ significantly only in their amino-termini, we constructed Rad-Rem chimeras to probe the structural basis for the distinct specificities of Rad- and Rem-mediated inhibition. Using this approach, a chimera composed of the amino-terminus of Rem and the core/carboxyl-terminus of Rad inhibited L-type current without reducing charge movement. Conversely, a chimera having the amino-terminus of Rad fused to the core/carboxyl-terminus of Rem inhibited L-type current with a concurrent reduction in charge movement. Thus, we have identified the amino-termini of Rad and Rem as the structural elements dictating the specific modes of inhibition of CaV1.1.
Collapse
Affiliation(s)
- D Beqollari
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, Colorado
| | - C F Romberg
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, Colorado
| | - U Meza
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, Colorado; Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
| | - S Papadopoulos
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
| | - R A Bannister
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, Colorado.
| |
Collapse
|
7
|
Weiss S, Oz S, Benmocha A, Dascal N. Regulation of cardiac L-type Ca²⁺ channel CaV1.2 via the β-adrenergic-cAMP-protein kinase A pathway: old dogmas, advances, and new uncertainties. Circ Res 2013; 113:617-31. [PMID: 23948586 DOI: 10.1161/circresaha.113.301781] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the heart, adrenergic stimulation activates the β-adrenergic receptors coupled to the heterotrimeric stimulatory Gs protein, followed by subsequent activation of adenylyl cyclase, elevation of cyclic AMP levels, and protein kinase A (PKA) activation. One of the main targets for PKA modulation is the cardiac L-type Ca²⁺ channel (CaV1.2) located in the plasma membrane and along the T-tubules, which mediates Ca²⁺ entry into cardiomyocytes. β-Adrenergic receptor activation increases the Ca²⁺ current via CaV1.2 channels and is responsible for the positive ionotropic effect of adrenergic stimulation. Despite decades of research, the molecular mechanism underlying this modulation has not been fully resolved. On the contrary, initial reports of identification of key components in this modulation were later refuted using advanced model systems, especially transgenic animals. Some of the cardinal debated issues include details of specific subunits and residues in CaV1.2 phosphorylated by PKA, the nature, extent, and role of post-translational processing of CaV1.2, and the role of auxiliary proteins (such as A kinase anchoring proteins) involved in PKA regulation. In addition, the previously proposed crucial role of PKA in modulation of unstimulated Ca²⁺ current in the absence of β-adrenergic receptor stimulation and in voltage-dependent facilitation of CaV1.2 remains uncertain. Full reconstitution of the β-adrenergic receptor signaling pathway in heterologous expression systems remains an unmet challenge. This review summarizes the past and new findings, the mechanisms proposed and later proven, rejected or disputed, and emphasizes the essential issues that remain unresolved.
Collapse
Affiliation(s)
- Sharon Weiss
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel-Aviv, Israel.
| | | | | | | |
Collapse
|
8
|
Magyar J, Kiper CE, Sievert G, Cai W, Shi GX, Crump SM, Li L, Niederer S, Smith N, Andres DA, Satin J. Rem-GTPase regulates cardiac myocyte L-type calcium current. Channels (Austin) 2012; 6:166-73. [PMID: 22854599 DOI: 10.4161/chan.20192] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
RATIONALE The L-type calcium channels (LTCC) are critical for maintaining Ca(2+)-homeostasis. In heterologous expression studies, the RGK-class of Ras-related G-proteins regulates LTCC function; however, the physiological relevance of RGK-LTCC interactions is untested. OBJECTIVE In this report we test the hypothesis that the RGK protein, Rem, modulates native Ca(2+) current (I(Ca,L)) via LTCC in murine cardiomyocytes. METHODS AND RESULTS Rem knockout mice (Rem(-/-)) were engineered, and I(Ca,L) and Ca(2+) -handling properties were assessed. Rem(-/-) ventricular cardiomyocytes displayed increased I(Ca,L) density. I(Ca,L) activation was shifted positive on the voltage axis, and β-adrenergic stimulation normalized this shift compared with wild-type I(Ca,L). Current kinetics, steady-state inactivation, and facilitation was unaffected by Rem(-/-) . Cell shortening was not significantly different. Increased I(Ca,L) density in the absence of frank phenotypic differences motivated us to explore putative compensatory mechanisms. Despite the larger I(Ca,L) density, Rem(-/-) cardiomyocyte Ca(2+) twitch transient amplitude was significantly less than that compared with wild type. Computer simulations and immunoblot analysis suggests that relative dephosphorylation of Rem(-/-) LTCC can account for the paradoxical decrease of Ca(2+) transients. CONCLUSIONS This is the first demonstration that loss of an RGK protein influences I(Ca,L) in vivo in cardiac myocytes.
Collapse
Affiliation(s)
- Janos Magyar
- Department of Physiology, University of Kentucky College of Medicine, Lexington, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Crump SM, Andres DA, Sievert G, Satin J. The cardiac L-type calcium channel distal carboxy terminus autoinhibition is regulated by calcium. Am J Physiol Heart Circ Physiol 2012. [PMID: 23203963 DOI: 10.1152/ajpheart.00396.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The L-type calcium channel (LTCC) provides trigger Ca(2+) for sarcoplasmic reticulum Ca-release, and LTCC function is influenced by interacting proteins including the LTCC distal COOH terminus (DCT) and calmodulin. DCT is proteolytically cleaved and reassociates with the LTCC complex to regulate calcium channel function. DCT reduces LTCC barium current (I(Ba,L)) in reconstituted channel complexes, yet the contribution of DCT to LTCC Ca(2+) current (I(Ca,L)) in cardiomyocyte systems is unexplored. This study tests the hypothesis that DCT attenuates cardiomyocyte I(Ca,L). We measured LTCC current and Ca(2+) transients with DCT coexpressed in murine cardiomyocytes. We also heterologously coexpressed DCT and Ca(V)1.2 constructs with truncations corresponding to the predicted proteolytic cleavage site, Ca(V)1.2Δ1801, and a shorter deletion corresponding to well-studied construct, Ca(V)1.2Δ1733. DCT inhibited I(Ba,L) in cardiomyocytes, and in human embryonic kidney (HEK) 293 cells expressing Ca(V)1.2Δ1801 and Ca(V)1.2Δ1733. Ca(2+)-CaM relieved DCT block in cardiomyocytes and HEK cells. The selective block of I(Ba,L) combined with Ca(2+)-CaM effects suggested that DCT-mediated blockade may be relieved under conditions of elevated Ca(2+). We therefore tested the hypothesis that DCT block is dynamic, increasing under relatively low Ca(2+), and show that DCT reduced diastolic Ca(2+) at low stimulation frequencies but spared high frequency Ca(2+) entry. DCT reduction of diastolic Ca(2+) and relief of block at high pacing frequencies and under conditions of supraphysiological bath Ca(2+) suggests that a physiological function of DCT is to increase the dynamic range of Ca(2+) transients in response to elevated pacing frequencies. Our data motivate the new hypothesis that DCT is a native reverse use-dependent inhibitor of LTCC current.
Collapse
Affiliation(s)
- Shawn M Crump
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky 40536-0298, USA
| | | | | | | |
Collapse
|
10
|
Yang T, Colecraft HM. Regulation of voltage-dependent calcium channels by RGK proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1644-54. [PMID: 23063948 DOI: 10.1016/j.bbamem.2012.10.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 10/04/2012] [Accepted: 10/05/2012] [Indexed: 12/28/2022]
Abstract
RGK proteins belong to the Ras superfamily of monomeric G-proteins, and currently include four members - Rad, Rem, Rem2, and Gem/Kir. RGK proteins are broadly expressed, and are the most potent known intracellular inhibitors of high-voltage-activated Ca²⁺ (Ca(V)1 and Ca(V)2) channels. Here, we review and discuss the evidence in the literature regarding the functional mechanisms, structural determinants, physiological role, and potential practical applications of RGK-mediated inhibition of Ca(V)1/Ca(V)2 channels. This article is part of a Special Issue entitled: Calcium channels.
Collapse
Affiliation(s)
- Tingting Yang
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, 1150 St. Nicholas Avenue, New York, NY 10032, USA
| | | |
Collapse
|
11
|
Naranjo JR, Mellström B. Ca2+-dependent transcriptional control of Ca2+ homeostasis. J Biol Chem 2012; 287:31674-80. [PMID: 22822058 DOI: 10.1074/jbc.r112.384982] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Intracellular free Ca(2+) ions regulate many cellular functions, and in turn, the cell devotes many genes/proteins to keep tight control of the level of intracellular free Ca(2+). Here, we review recent work on Ca(2+)-dependent mechanisms and effectors that regulate the transcription of genes encoding proteins involved in the maintenance of the homeostasis of Ca(2+) in the cell.
Collapse
Affiliation(s)
- Jose R Naranjo
- National Center of Biotechnology, Consejo Superior de Investigaciones Científicas (CSIC) and the Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 28049 Madrid, Spain.
| | | |
Collapse
|
12
|
Activity-dependent subcellular cotrafficking of the small GTPase Rem2 and Ca2+/CaM-dependent protein kinase IIα. PLoS One 2012; 7:e41185. [PMID: 22815963 PMCID: PMC3399833 DOI: 10.1371/journal.pone.0041185] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Accepted: 06/18/2012] [Indexed: 11/19/2022] Open
Abstract
Background Rem2 is a small monomeric GTP-binding protein of the RGK family, whose known functions are modulation of calcium channel currents and alterations of cytoskeletal architecture. Rem2 is the only RGK protein found predominantly in the brain, where it has been linked to synaptic development. We wished to determine the effect of neuronal activity on the subcellular distribution of Rem2 and its interacting partners. Results We show that Rem2 undergoes activity-and N-Methyl-D-Aspartate Receptor (NMDAR)-dependent translocation in rat hippocampal neurons. This redistribution of Rem2, from a diffuse pattern to one that is highly punctate, is dependent on Ca2+ influx, on binding to calmodulin (CaM), and also involves an auto-inhibitory domain within the Rem2 distal C-terminus region. We found that Rem2 can bind to Ca2+/CaM-dependent protein kinase IIα (CaMKII) a in Ca2+/CaM-dependent manner. Furthermore, our data reveal a spatial and temporal correlation between NMDAR-dependent clustering of Rem2 and CaMKII in neurons, indicating co-assembly and co-trafficking in neurons. Finally, we show that inhibiting CaMKII aggregation in neurons and HEK cells reduces Rem2 clustering, and that Rem2 affects the baseline distribution of CaMKII in HEK cells. Conclusions Our data suggest a novel function for Rem2 in co-trafficking with CaMKII, and thus potentially expose a role in neuronal plasticity.
Collapse
|
13
|
Parks RJ, Howlett SE. H-89 decreases the gain of excitation-contraction coupling and attenuates calcium sparks in the absence of beta-adrenergic stimulation. Eur J Pharmacol 2012; 691:163-72. [PMID: 22796673 DOI: 10.1016/j.ejphar.2012.07.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/27/2012] [Accepted: 07/03/2012] [Indexed: 01/11/2023]
Abstract
This study used the selective protein kinase A (PKA) inhibitor H-89 (N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide) to determine the role of basal PKA activity in modulating cardiac excitation-contraction coupling in the absence of β-adrenergic stimulation. Basal intracellular cyclic AMP (cAMP) levels measured in isolated murine ventricular myocytes with an enzyme immunoassay were increased upon adenylyl cyclase activation (forskolin; 1 and 10 μM) or phosphodiesterase inhibition (3-isobutyl-1-methylxanthine, IBMX; 300 μM). Forskolin and IBMX also caused concentration-dependent increases in peak Ca(2+) transients (fura-2) and cell shortening (edge-detector) measured simultaneously in field-stimulated myocytes (37 °C). Similar effects were seen upon application of dibutyryl cAMP. In voltage-clamped myocytes, H-89 (2 μM) decreased basal Ca(2+) transients, contractions and underlying Ca(2+) currents. H-89 also decreased diastolic Ca(2+) and the gain of excitation-contraction coupling (Ca(2+) release/Ca(2+) current), especially at negative membrane potentials. This was independent of alterations in sarcoplasmic reticulum (SR) Ca(2+) loading, as SR stores were unchanged by PKA inhibition. H-89 also decreased the frequency, amplitude and width of spontaneous Ca(2+) sparks measured in quiescent myocytes (loaded with fluo-4), but increased time-to-peak. Thus, H-89 suppressed SR Ca(2+) release by decreasing Ca(2+) current and by reducing the gain of excitation-contraction coupling, in part by decreasing the size of individual Ca(2+) release units. These data suggest that basal PKA activity enhances SR Ca(2+) release in the absence of ß-adrenergic stimulation. This may depress contractile function in models such as aging, where the cAMP/PKA pathway is altered due to low basal cAMP levels.
Collapse
Affiliation(s)
- Randi J Parks
- Departments of Pharmacology, 1459 Oxford Street, PO Box 15000 Dalhousie University Halifax, Nova Scotia, Canada B3H 4R2.
| | | |
Collapse
|
14
|
Gunton JE, Sisavanh M, Stokes RA, Satin J, Satin LS, Zhang M, Liu SM, Cai W, Cheng K, Cooney GJ, Laybutt DR, So T, Molero JC, Grey ST, Andres DA, Rolph MS, Mackay CR. Mice deficient in GEM GTPase show abnormal glucose homeostasis due to defects in beta-cell calcium handling. PLoS One 2012; 7:e39462. [PMID: 22761801 PMCID: PMC3386271 DOI: 10.1371/journal.pone.0039462] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/21/2012] [Indexed: 11/29/2022] Open
Abstract
Aims and Hypothesis Glucose-stimulated insulin secretion from beta-cells is a tightly regulated process that requires calcium flux to trigger exocytosis of insulin-containing vesicles. Regulation of calcium handling in beta-cells remains incompletely understood. Gem, a member of the RGK (Rad/Gem/Kir) family regulates calcium channel handling in other cell types, and Gem over-expression inhibits insulin release in insulin-secreting Min6 cells. The aim of this study was to explore the role of Gem in insulin secretion. We hypothesised that Gem may regulate insulin secretion and thus affect glucose tolerance in vivo. Methods Gem-deficient mice were generated and their metabolic phenotype characterised by in vivo testing of glucose tolerance, insulin tolerance and insulin secretion. Calcium flux was measured in isolated islets. Results Gem-deficient mice were glucose intolerant and had impaired glucose stimulated insulin secretion. Furthermore, the islets of Gem-deficient mice exhibited decreased free calcium responses to glucose and the calcium oscillations seen upon glucose stimulation were smaller in amplitude and had a reduced frequency. Conclusions These results suggest that Gem plays an important role in normal beta-cell function by regulation of calcium signalling.
Collapse
Affiliation(s)
- Jenny E Gunton
- Diabetes and Transcription Factors Group, Garvan Institute of Medical Research, Sydney, Australia.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Yang T, Puckerin A, Colecraft HM. Distinct RGK GTPases differentially use α1- and auxiliary β-binding-dependent mechanisms to inhibit CaV1.2/CaV2.2 channels. PLoS One 2012; 7:e37079. [PMID: 22590648 PMCID: PMC3349659 DOI: 10.1371/journal.pone.0037079] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 04/13/2012] [Indexed: 11/30/2022] Open
Abstract
CaV1/CaV2 channels, comprised of pore-forming α1 and auxiliary (β,α2δ) subunits, control diverse biological responses in excitable cells. Molecules blocking CaV1/CaV2 channel currents (ICa) profoundly regulate physiology and have many therapeutic applications. Rad/Rem/Rem2/Gem GTPases (RGKs) strongly inhibit CaV1/CaV2 channels. Understanding how RGKs block ICa is critical for insights into their physiological function, and may provide design principles for developing novel CaV1/CaV2 channel inhibitors. The RGK binding sites within CaV1/CaV2 channel complexes responsible for ICa inhibition are ambiguous, and it is unclear whether there are mechanistic differences among distinct RGKs. All RGKs bind β subunits, but it is unknown if and how this interaction contributes to ICa inhibition. We investigated the role of RGK/β interaction in Rem inhibition of recombinant CaV1.2 channels, using a mutated β (β2aTM) selectively lacking RGK binding. Rem blocked β2aTM-reconstituted channels (74% inhibition) less potently than channels containing wild-type β2a (96% inhibition), suggesting the prevalence of both β-binding-dependent and independent modes of inhibition. Two mechanistic signatures of Rem inhibition of CaV1.2 channels (decreased channel surface density and open probability), but not a third (reduced maximal gating charge), depended on Rem binding to β. We identified a novel Rem binding site in CaV1.2 α1C N-terminus that mediated β-binding-independent inhibition. The CaV2.2 α1B subunit lacks the Rem binding site in the N-terminus and displays a solely β-binding-dependent form of channel inhibition. Finally, we discovered an unexpected functional dichotomy amongst distinct RGKs— while Rem and Rad use both β-binding-dependent and independent mechanisms, Gem and Rem2 use only a β-binding-dependent method to inhibit CaV1.2 channels. The results provide new mechanistic perspectives, and reveal unexpected variations in determinants, underlying inhibition of CaV1.2/CaV2.2 channels by distinct RGK GTPases.
Collapse
Affiliation(s)
- Tingting Yang
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, New York, New York, United States of America
- * E-mail: (HMC); (TY)
| | - Akil Puckerin
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, New York, New York, United States of America
| | - Henry M. Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, New York, New York, United States of America
- * E-mail: (HMC); (TY)
| |
Collapse
|
16
|
Jhun BS, O-Uchi J, Wang W, Ha CH, Zhao J, Kim JY, Wong C, Dirksen RT, Lopes CMB, Jin ZG. Adrenergic signaling controls RGK-dependent trafficking of cardiac voltage-gated L-type Ca2+ channels through PKD1. Circ Res 2011; 110:59-70. [PMID: 22076634 DOI: 10.1161/circresaha.111.254672] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
RATIONALE The Rad-Gem/Kir-related family (RGKs) consists of small GTP-binding proteins that strongly inhibit the activity of voltage-gated calcium channels. Among RGKs, Rem1 is strongly and specifically expressed in cardiac tissue. However, the physiological role and regulation of RGKs, and Rem1 in particular, are largely unknown. OBJECTIVE To determine if Rem1 function is physiologically regulated by adrenergic signaling and thus impacts voltage-gated L-type calcium channel (VLCC) activity in the heart. METHODS AND RESULTS We found that activation of protein kinase D1, a protein kinase downstream of α(1)-adrenergic signaling, leads to direct phosphorylation of Rem1 at Ser18. This results in an increase of the channel activity and plasma membrane expression observed by using a combination of electrophysiology, live cell confocal microscopy, and immunohistochemistry in heterologous expression system and neonatal cardiomyocytes. In addition, we show that stimulation of α(1)-adrenergic receptor-protein kinase D1-Rem1 signaling increases transverse-tubule VLCC expression that results in increased L-type Ca(2+) current density in adult ventricular myocytes. CONCLUSION The α(1)-adrenergic stimulation releases Rem1 inhibition of VLCCs through direct phosphorylation of Rem1 at Ser18 by protein kinase D1, resulting in an increase of the channel activity and transverse-tubule expression. Our results uncover a novel molecular regulatory mechanism of VLCC trafficking and function in the heart and provide the first demonstration of physiological regulation of RGK function.
Collapse
Affiliation(s)
- Bong Sook Jhun
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Jin O-Uchi
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Weiye Wang
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Chang Hoon Ha
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Jinjing Zhao
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Ji Young Kim
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Chelsea Wong
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Coeli M B Lopes
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| | - Zheng Gen Jin
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester NY, 14642 USA
| |
Collapse
|
17
|
Sasson Y, Navon-Perry L, Huppert D, Hirsch JA. RGK family G-domain:GTP analog complex structures and nucleotide-binding properties. J Mol Biol 2011; 413:372-89. [PMID: 21903096 DOI: 10.1016/j.jmb.2011.08.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Revised: 08/08/2011] [Accepted: 08/09/2011] [Indexed: 11/26/2022]
Abstract
The RGK family of small G-proteins, including Rad, Gem, Rem1, and Rem2, is inducibly expressed in various mammalian tissues and interacts with voltage-dependent calcium channels and Rho kinase. Many questions remain regarding their physiological roles and molecular mechanism. Previous crystallographic studies reported RGK G-domain:guanosine di-phosphate structures. To test whether RGK proteins undergo a nucleotide-induced conformational change, we determined the crystallographic structures of Rad:GppNHp and Rem2:GppNHp to 1.7 and 1.8 Å resolutions, respectively. Also, we characterized the nucleotide-binding properties and conformations for Gem, Rad, and several structure-based mutants using fluorescence spectroscopy. The results suggest that RGK G-proteins may not behave as Ras-like canonical nucleotide-induced molecular switches. Further, the RGK proteins have differing structures and nucleotide-binding properties, which may have implications for their varied action on effectors.
Collapse
Affiliation(s)
- Yehezkel Sasson
- Department of Biochemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | | | | | | |
Collapse
|
18
|
Satin J, Schroder EA, Crump SM. L-type calcium channel auto-regulation of transcription. Cell Calcium 2011; 49:306-13. [PMID: 21295347 DOI: 10.1016/j.ceca.2011.01.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/06/2011] [Accepted: 01/07/2011] [Indexed: 01/24/2023]
Abstract
L-type calcium channels (LTCC) impact the function of nearly all excitable cells. The classical LTCC function is to mediate trans-sarcolemmal Ca(2+) flux. This review focuses on the contribution of a mobile segment of the LTCC that regulates ion channel function, and also serves as a regulator of transcription in the nucleus. Specifically we highlight recent work demonstrating an auto-feedback regulatory pathway whereby the LTCC transcription factor regulates the LTCC. Also discussed is acute and long-term regulation of function by the LTCC-transcription regulator.
Collapse
Affiliation(s)
- Jonathan Satin
- Department of Physiology, MS-508, University of Kentucky College of Medicine, 800 Rose Street, Lexington, KY 40536-0298, USA.
| | | | | |
Collapse
|
19
|
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
|
20
|
Abstract
l-Type calcium channels (LTCCs) are major contributors to electrical and contractile function of the heart. They regulate action potential duration, enable calcium entry into cardiac myocytes for contraction, and regulate growth-related signaling in the heart. In cardiac development and in mature heart disease, LTCCs are regulated at levels of acute function and transcription. In addition, LTCCs are clinically relevant therapeutic targets for antihypertensive medications. In this review, we discuss LTCC homeostasis whereby cardiac myocytes maintain LTCC expression via a novel transcriptionally regulated pathway that includes a segment of the LTCC that moves between surface membrane and nucleus.
Collapse
Affiliation(s)
- Jonathan Satin
- Department of Physiology, MS508 University of Kentucky College of Medicine, Lexington, KY 40536-0298, USA.
| | | |
Collapse
|
21
|
Direct inhibition of P/Q-type voltage-gated Ca2+ channels by Gem does not require a direct Gem/Cavbeta interaction. Proc Natl Acad Sci U S A 2010; 107:14887-92. [PMID: 20679232 DOI: 10.1073/pnas.1007543107] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The Rem, Rem2, Rad, and Gem/Kir (RGK) family of small GTP-binding proteins potently inhibits high voltage-activated (HVA) Ca(2+) channels, providing a powerful means of modulating neural, endocrine, and muscle functions. The molecular mechanisms of this inhibition are controversial and remain largely unclear. RGK proteins associate directly with Ca(2+) channel beta subunits (Ca(v)beta), and this interaction is widely thought to be essential for their inhibitory action. In this study, we investigate the molecular underpinnings of Gem inhibition of P/Q-type Ca(2+) channels. We find that a purified Gem protein markedly and acutely suppresses P/Q channel activity in inside-out membrane patches, that this action requires Ca(v)beta but not the Gem/Ca(v)beta interaction, and that Gem coimmunoprecipitates with the P/Q channel alpha(1) subunit (Ca(v)alpha(1)) in a Ca(v)beta-independent manner. By constructing chimeras between P/Q channels and Gem-insensitive low voltage-activated T-type channels, we identify a region encompassing transmembrane segments S1, S2, and S3 in the second homologous repeat of Ca(v)alpha(1) critical for Gem inhibition. Exchanging this region between P/Q and T channel Ca(v)alpha(1) abolishes Gem inhibition of P/Q channels and confers Ca(v)beta-dependent Gem inhibition to a chimeric T channel that also carries the P/Q I-II loop (a cytoplasmic region of Ca(v)alpha(1) that binds Ca(v)beta). Our results challenge the prevailing view regarding the role of Ca(v)beta in RGK inhibition of high voltage-activated Ca(2+) channels and prompt a paradigm in which Gem directly binds and inhibits Ca(v)beta-primed Ca(v)alpha(1) on the plasma membrane.
Collapse
|
22
|
Pang C, Crump SM, Jin L, Correll RN, Finlin BS, Satin J, Andres DA. Rem GTPase interacts with the proximal CaV1.2 C-terminus and modulates calcium-dependent channel inactivation. Channels (Austin) 2010; 4:192-202. [PMID: 20458179 DOI: 10.4161/chan.4.3.11867] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Rem, Rem2, Rad, and Gem/Kir (RGK) GTPases, comprise a subfamily of small Ras-related GTP-binding proteins, and have been shown to potently inhibit high voltage-activated Ca(2+) channel current following overexpression. Although the molecular mechanisms underlying RGK-mediated Ca(2+) channel regulation remains controversial, recent studies suggest that RGK proteins inhibit Ca(2+) channel currents at the plasma membrane in part by interactions with accessory channel β subunits. In this paper, we extend our understanding of the molecular determinants required for RGK-mediated channel regulation by demonstrating a direct interaction between Rem and the proximal C-terminus of Ca(V)1.2 (PCT), including the CB/IQ domain known to contribute to Ca(2+)/calmodulin (CaM)-mediated channel regulation. The Rem2 and Rad GTPases display similar patterns of PCT binding, suggesting that the Ca(V)1.2 C-terminus represents a common binding partner for all RGK proteins. In vitro Rem:PCT binding is disrupted by Ca(2+)/CaM, and this effect is not due to Ca(2+)/CaM binding to the Rem C-terminus. In addition, co-overexpression of CaM partially relieves Rem-mediated L-type Ca(2+) channel inhibition and slows the kinetics of Ca(2+)-dependent channel inactivation. Taken together, these results suggest that the association of Rem with the PCT represents a crucial molecular determinant in RGK-mediated Ca(2+) channel regulation and that the physiological function of the RGK GTPases must be re-evaluated. Rather than serving as endogenous inhibitors of Ca(2+) channel activity, these studies indicate that RGK proteins may play a more nuanced role, regulating Ca(2+) currents via modulation of Ca(2+)/CaM-mediated channel inactivation kinetics.
Collapse
Affiliation(s)
- Chunyan Pang
- Department of Molecular and Cellular Biochemistry and Physiology, University of Kentucky College of Medicine, Lexington, USA
| | | | | | | | | | | | | |
Collapse
|
23
|
Wang G, Zhu X, Xie W, Han P, Li K, Sun Z, Wang Y, Chen C, Song R, Cao C, Zhang J, Wu C, Liu J, Cheng H. Rad As a Novel Regulator of Excitation–Contraction Coupling and β-Adrenergic Signaling in Heart. Circ Res 2010; 106:317-27. [DOI: 10.1161/circresaha.109.208272] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Rationale
:
Rad (Ras associated with diabetes) GTPase, a monomeric small G protein, binds to Ca
v
β subunit of the L-type Ca
2+
channel (LCC) and thereby regulates LCC trafficking and activity. Emerging evidence suggests that Rad is an important player in cardiac arrhythmogenesis and hypertrophic remodeling. However, whether and how Rad involves in the regulation of excitation–contraction (EC) coupling is unknown.
Objective
:
This study aimed to investigate possible role of Rad in cardiac EC coupling and β-adrenergic receptor (βAR) inotropic mechanism.
Methods and Results
:
Adenoviral overexpression of Rad by 3-fold in rat cardiomyocytes suppressed LCC current (
I
Ca
), [Ca
2+
]
i
transients, and contractility by 60%, 42%, and 38%, respectively, whereas the “gain” function of EC coupling was significantly increased, due perhaps to reduced “redundancy” of LCC in triggering sarcoplasmic reticulum release. Conversely, ≈70% Rad knockdown by RNA interference increased
I
Ca
(50%), [Ca
2+
]
i
transients (52%) and contractility (58%) without altering EC coupling efficiency; and the dominant negative mutant RadS105N exerted a similar effect on
I
Ca
. Rad upregulation caused depolarizing shift of LCC activation and hastened time-dependent LCC inactivation; Rad downregulation, however, failed to alter these attributes. The Na
+
/Ca
2+
exchange activity, sarcoplasmic reticulum Ca
2+
content, properties of Ca
2+
sparks and propensity for Ca
2+
waves all remained unperturbed regardless of Rad manipulation. Rad overexpression, but not knockdown, negated βAR effects on
I
Ca
and Ca
2+
transients.
Conclusion
:
These results establish Rad as a novel endogenous regulator of cardiac EC coupling and βAR signaling and support a parsimonious model in which Rad buffers Ca
v
β to modulate LCC activity, EC coupling, and βAR responsiveness.
Collapse
Affiliation(s)
- Gang Wang
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Xiaojun Zhu
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Wenjun Xie
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Peidong Han
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Kaitao Li
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Zhongcui Sun
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Yanru Wang
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Chunlei Chen
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Ruisheng Song
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Chunmei Cao
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Jifeng Zhang
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Caihong Wu
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Jie Liu
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Heping Cheng
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| |
Collapse
|
24
|
Leyris JP, Gondeau C, Charnet A, Delattre C, Rousset M, Cens T, Charnet P. RGK GTPase-dependent CaV2.1 Ca2+ channel inhibition is independent of CaVbeta-subunit-induced current potentiation. FASEB J 2009; 23:2627-38. [PMID: 19332647 DOI: 10.1096/fj.08-122135] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
RGK (Rad-Gem-Rem) GTPases have been described as potent negative regulators of the Ca(2+) influx via high-threshold voltage-activated Ca(2+) channels. Recent work, mostly performed on Ca(V)1.2 Ca(2+) channels, has highlighted the crucial role played by the channel auxiliary Ca(V)beta subunits and identified several GTPase and beta-subunit protein domains involved in this regulation. We now extend these conclusions by producing the first complete characterization of the effects of Gem, Rem, and Rem2 on the neuronal Ca(V)2.1 Ca(2+) channels expressed with Ca(V)beta(1) or Ca(V)beta(2) subunits. Current inhibition is limited to a decrease in amplitude with no modification in the voltage dependence or kinetics of the current. We demonstrate that this inhibition can occur for Ca(V)beta constructs with impaired capacity to induce current potentiation, but that it is lost for Ca(V)beta constructs deleted for their beta-interaction domain. The RGK C-terminal last approximately 80 amino acids are sufficient to allow potent current inhibition and in vivo beta-subunit/Gem interaction. Interestingly, although Gem and Gem carboxy-terminus induce a completely different pattern of beta-subunit cellular localization, they both potently inhibit Ca(V)2.1 channels. These data therefore set the status of neuronal Ca(V)2.1 Ca(2+) channel inhibition by RGK GTPases, emphasizing the role of short amino acid sequences of both proteins in beta-subunit binding and channel inhibition and revealing a new mechanism for channel inhibition.
Collapse
Affiliation(s)
- J-P Leyris
- CRBM, CNRS UMR 5237, Université de Montpellier 1, 34293 Montpellier cedex, France
| | | | | | | | | | | | | |
Collapse
|
25
|
Steady-state coupling of plasma membrane calcium entry to extrusion revealed by novel L-type calcium channel block. Cell Calcium 2008; 44:353-62. [DOI: 10.1016/j.ceca.2008.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
26
|
Correll RN, Pang C, Niedowicz DM, Finlin BS, Andres DA. The RGK family of GTP-binding proteins: regulators of voltage-dependent calcium channels and cytoskeleton remodeling. Cell Signal 2008; 20:292-300. [PMID: 18042346 PMCID: PMC2254326 DOI: 10.1016/j.cellsig.2007.10.028] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 10/30/2007] [Indexed: 02/05/2023]
Abstract
RGK proteins constitute a novel subfamily of small Ras-related proteins that function as potent inhibitors of voltage-dependent (VDCC) Ca(2+) channels and regulators of actin cytoskeletal dynamics. Within the larger Ras superfamily, RGK proteins have distinct regulatory and structural characteristics, including nonconservative amino acid substitutions within regions known to participate in nucleotide binding and hydrolysis and a C-terminal extension that contains conserved regulatory sites which control both subcellular localization and function. RGK GTPases interact with the VDCC beta-subunit (Ca(V)beta) and inhibit Rho/Rho kinase signaling to regulate VDCC activity and the cytoskeleton respectively. Binding of both calmodulin and 14-3-3 to RGK proteins, and regulation by phosphorylation controls cellular trafficking and the downstream signaling of RGK proteins, suggesting that a complex interplay between interacting protein factors and trafficking contribute to their regulation.
Collapse
Affiliation(s)
- Robert N Correll
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536, United States
| | | | | | | | | |
Collapse
|
27
|
Rem inhibits skeletal muscle EC coupling by reducing the number of functional L-type Ca2+ channels. Biophys J 2008; 94:2631-8. [PMID: 18192376 DOI: 10.1529/biophysj.107.116467] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In skeletal muscle, the L-type voltage-gated Ca(2+) channel (1,4-dihydropyridine receptor) serves as the voltage sensor for excitation-contraction (EC) coupling. In this study, we examined the effects of Rem, a member of the RGK (Rem, Rem2, Rad, Gem/Kir) family of Ras-related monomeric GTP-binding proteins, on the function of the skeletal muscle L-type Ca(2+) channel. EC coupling was found to be weakened in myotubes expressing Rem tagged with enhanced yellow fluorescent protein (YFP-Rem), as assayed by electrically evoked contractions and myoplasmic Ca(2+) transients. This impaired EC coupling was not a consequence of altered function of the type 1 ryanodine receptor, or of reduced Ca(2+) stores, since the application of 4-chloro-m-cresol, a direct type 1 ryanodine receptor activator, elicited myoplasmic Ca(2+) release in YFP-Rem-expressing myotubes that was not distinguishable from that in control myotubes. However, YFP-Rem reduced the magnitude of L-type Ca(2+) current by approximately 75% and produced a concomitant reduction in membrane-bound charge movements. Thus, our results indicate that Rem negatively regulates skeletal muscle EC coupling by reducing the number of functional L-type Ca(2+) channels in the plasma membrane.
Collapse
|
28
|
Correll RN, Pang C, Niedowicz DM, Satin J, Andres DA. Calmodulin binding is dispensable for Rem-mediated Ca2+ channel inhibition. Mol Cell Biochem 2007; 310:103-10. [DOI: 10.1007/s11010-007-9670-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 11/22/2007] [Indexed: 10/25/2022]
|
29
|
Correll RN, Pang C, Finlin BS, Dailey AM, Satin J, Andres DA. Plasma membrane targeting is essential for Rem-mediated Ca2+ channel inhibition. J Biol Chem 2007; 282:28431-28440. [PMID: 17686775 PMCID: PMC3063359 DOI: 10.1074/jbc.m706176200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The small GTPase Rem is a potent negative regulator of high voltage-activated Ca(2+) channels and a known interacting partner for Ca(2+) channel accessory beta subunits. The mechanism for Rem-mediated channel inhibition remains controversial, although it has been proposed that Ca(V)beta association is required. Previous work has shown that a C-terminal truncation of Rem (Rem-(1-265)) displays reduced in vivo binding to membrane-localized beta 2a and lacks channel regulatory function. In this paper, we describe a role for the Rem C terminus in plasma membrane localization through association with phosphatidylinositol lipids. Moreover, Rem-(1-265) can associate with beta 2a in vitro and beta 1b in vivo, suggesting that the C terminus does not directly participate in Ca(V)beta association. Despite demonstrated beta 1b binding, Rem-(1-265) was not capable of regulating a Ca(V)1.2-beta 1b channel complex, indicating that beta subunit binding is not sufficient for channel regulation. However, fusion of the CAAX domain from K-Ras4B or H-Ras to the Rem-(1-265) C terminus restored membrane localization and Ca(2+) channel regulation, suggesting that beta binding and membrane localization are independent events required for channel inhibition.
Collapse
Affiliation(s)
| | - Chunyan Pang
- Departments of Molecular and Cellular Biochemistry
| | | | | | - Jonathan Satin
- Departments of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky 40536-0509
| | | |
Collapse
|
30
|
Kobayashi T, Yamada Y, Fukao M, Tsutsuura M, Tohse N. Regulation of Cav1.2 current: interaction with intracellular molecules. J Pharmacol Sci 2007; 103:347-53. [PMID: 17409629 DOI: 10.1254/jphs.cr0070012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Ca(V)1.2 (alpha(1c)) is a pore-forming subunit of the voltage-dependent L-type calcium channel and is expressed in many tissues. The beta and alpha(2)/delta subunits are auxiliary subunits that affect the kinetics and the expression of Ca(V)1.2. In addition to the beta and alpha(2)/delta subunits, several molecules have been reported to be involved in the regulation of Ca(V)1.2 current. Calmodulin, CaBP1 (calcium-binding protein-1), CaMKII (calcium/calmodulin-dependent protein kinase II), AKAPs (A-kinase anchoring proteins), phosphatases, Caveolin-3, beta(2)-adrenergic receptor, PDZ domain proteins, sorcin, SNARE proteins, synaptotagmin, CSN5, RGK family, and AHNAK1 have all been reported to interact with Ca(V)1.2 and the beta subunit. This review focuses on the effect of these molecules on Ca(V)1.2 current.
Collapse
Affiliation(s)
- Takeshi Kobayashi
- Department of Cellular Physiology and Signal Transduction, Sapporo Medical University School of Medicine, Sapporo, Japan.
| | | | | | | | | |
Collapse
|
31
|
Schroder E, Magyar J, Burgess D, Andres D, Satin J. Chronic verapamil treatment remodelsICa,Lin mouse ventricle. Am J Physiol Heart Circ Physiol 2007; 292:H1906-16. [PMID: 17158651 DOI: 10.1152/ajpheart.00793.2006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study we tested the hypothesis that ventricular homeostasis of L-type Ca2+current ( ICa,L) minimally involves regulation of the main pore-forming α-subunit (CaV1.2) and auxiliary proteins that serve as positive or negative regulators of ICa,L. We treated animals for 24 h with verapamil (Ver, 3.6 mg·kg−1·day−1), isoproterenol (Iso, 30 mg·kg−1·day−1), or Iso + Ver via osmotic minipumps. To test for alterations of Ca2+channel complex components we performed real-time PCR and Western blot analysis on ventricle. In addition, cardiac myocytes (CMs) were dispersed and current was recorded in the whole cell configuration to evaluate ICa,L. Surprisingly, 24- to 48-h Ver increased CaV1.2 mRNA and protein and ICa,Lcurrent (Ver 11 ± 1pA/pF vs. control 7 ± 0.5pA/pF; P < 0.01). ICa,Lfrom CMs in Ver mice showed no change in whole cell capacitance. To examine the in vivo effects of a physiologically relevant Ca2+channel agonist, we treated mice with Iso. Twenty-four-hour Iso infusion increased heart rate; CaV1.2- and CaVβ2mRNA levels were constant, but the Ca2+channel subunit mRNA Rem was increased twofold. Cells isolated from 24-h Iso hearts showed no change in basal ICa,Ldensity and diminished responsiveness to acute 1 μM Iso. To further examine the homeostatic regulation of the Ca2+channel, we treated animals for 24 h with Iso + Ver. The influence of Iso + Ver was similar that of to Iso alone on Ca2+channel mRNAs and ICa,L, with the exception that it prevented the increase in Rem seen with Iso treatment. Long-term Ca2+channel blockade induces an increase of CaV1.2 mRNA and protein and significantly increases ICa,L.
Collapse
Affiliation(s)
- Elizabeth Schroder
- Department of Physiology, University of Kentucky, Lexington, Kentucky 40536-0298, USA.
| | | | | | | | | |
Collapse
|
32
|
Abstract
Although inhibition of voltage-gated calcium channels by RGK GTPases (RGKs) represents an important mode of regulation to control Ca2+ influx in excitable cells, their exact mechanism of inhibition remains controversial. This has prevented an understanding of how RGK regulation can be significant in a physiological context. Here we show that RGKs—Gem, Rem, and Rem2—decreased CaV1.2 Ca2+ current amplitude in a dose-dependent manner. Moreover, Rem2, but not Rem or Gem, produced dose-dependent alterations on gating kinetics, uncovering a new mode by which certain RGKs can precisely modulate Ca2+ currents and affect Ca2+ influx during action potentials. To explore how RGKs influence gating kinetics, we separated the roles mediated by the Ca2+ channel accessory β subunit's interaction with its high affinity binding site in the pore-forming α1C subunit (AID) from its other putative contact sites by utilizing an α1C•β3 concatemer in which the AID was mutated to prevent β subunit interaction. This mutant concatemer generated currents with all the hallmarks of β subunit modulation, demonstrating that AID-β–independent interactions are sufficient for β subunit modulation. Using this construct we found that although inhibition of current amplitude was still partially sensitive to RGKs, Rem2 no longer altered gating kinetics, implicating different determinants for this specific mode of Rem2-mediated regulation. Together, these results offer new insights into the molecular mechanism of RGK-mediated Ca2+ channel current modulation.
Collapse
Affiliation(s)
- Lillian Seu
- Department of Pharmacology, Division of Cardiology, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA
| | | |
Collapse
|