1
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Loh KWZ, Liu C, Soong TW, Hu Z. β subunits of voltage-gated calcium channels in cardiovascular diseases. Front Cardiovasc Med 2023; 10:1119729. [PMID: 36818347 PMCID: PMC9931737 DOI: 10.3389/fcvm.2023.1119729] [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: 12/09/2022] [Accepted: 01/16/2023] [Indexed: 02/05/2023] Open
Abstract
Calcium signaling is required in bodily functions essential for survival, such as muscle contractions and neuronal communications. Of note, the voltage-gated calcium channels (VGCCs) expressed on muscle and neuronal cells, as well as some endocrine cells, are transmembrane protein complexes that allow for the selective entry of calcium ions into the cells. The α1 subunit constitutes the main pore-forming subunit that opens in response to membrane depolarization, and its biophysical functions are regulated by various auxiliary subunits-β, α2δ, and γ subunits. Within the cardiovascular system, the γ-subunit is not expressed and is therefore not discussed in this review. Because the α1 subunit is the pore-forming subunit, it is a prominent druggable target and the focus of many studies investigating potential therapeutic interventions for cardiovascular diseases. While this may be true, it should be noted that the direct inhibition of the α1 subunit may result in limited long-term cardiovascular benefits coupled with undesirable side effects, and that its expression and biophysical properties may depend largely on its auxiliary subunits. Indeed, the α2δ subunit has been reported to be essential for the membrane trafficking and expression of the α1 subunit. Furthermore, the β subunit not only prevents proteasomal degradation of the α1 subunit, but also directly modulates the biophysical properties of the α1 subunit, such as its voltage-dependent activities and open probabilities. More importantly, various isoforms of the β subunit have been found to differentially modulate the α1 subunit, and post-translational modifications of the β subunits further add to this complexity. These data suggest the possibility of the β subunit as a therapeutic target in cardiovascular diseases. However, emerging studies have reported the presence of cardiomyocyte membrane α1 subunit trafficking and expression in a β subunit-independent manner, which would undermine the efficacy of β subunit-targeting drugs. Nevertheless, a better understanding of the auxiliary β subunit would provide a more holistic approach when targeting the calcium channel complexes in treating cardiovascular diseases. Therefore, this review focuses on the post-translational modifications of the β subunit, as well as its role as an auxiliary subunit in modulating the calcium channel complexes.
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Affiliation(s)
- Kelvin Wei Zhern Loh
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Cong Liu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Tuck Wah Soong
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,NUS Graduate School for Integrative Sciences and Engineering, Singapore, Singapore,Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,*Correspondence: Tuck Wah Soong,
| | - Zhenyu Hu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Zhenyu Hu,
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2
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Cai D, Zheng Z, Jin X, Fu Y, Cen L, Ye J, Song Y, Lian J. The Advantages, Challenges, and Future of Human-Induced Pluripotent Stem Cell Lines in Type 2 Long QT Syndrome. J Cardiovasc Transl Res 2023; 16:209-220. [PMID: 35976484 DOI: 10.1007/s12265-022-10298-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 07/23/2022] [Indexed: 02/05/2023]
Abstract
Type 2 long QT syndrome (LQT2) is the second most common subtype of long QT syndrome and is caused by mutations in KCHN2 encoding the rapidly activating delayed rectifier potassium channel vital for ventricular repolarization. Sudden cardiac death is a sentinel event of LQT2. Preclinical diagnosis by genetic testing is potentially life-saving.Traditional LQT2 models cannot wholly recapitulate genetic and phenotypic features; therefore, there is a demand for a reliable experimental model. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) meet this challenge. This review introduces the advantages of the hiPSC-CM model over the traditional model and discusses how hiPSC-CM and gene editing are used to decipher mechanisms of LQT2, screen for cardiotoxicity, and identify therapeutic strategies, thus promoting the realization of precision medicine for LQT2 patients.
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Affiliation(s)
- Dihui Cai
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo University, Zhejiang Province, Ningbo, China
| | - Zequn Zheng
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo University, Zhejiang Province, Ningbo, China
- Department of Cardiovascular, First Affiliated Hospital of Shantou University Medical College, Shantou, China
| | - Xiaojun Jin
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo University, Zhejiang Province, Ningbo, China
| | - Yin Fu
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo University, Zhejiang Province, Ningbo, China
| | - Lichao Cen
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo University, Zhejiang Province, Ningbo, China
| | - Jiachun Ye
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo University, Zhejiang Province, Ningbo, China
| | - Yongfei Song
- Department of Cardiovascular, Ningbo Institute of Innovation for Combined Medicine and Engineering, Ningbo, China
| | - Jiangfang Lian
- Department of Cardiovascular, Lihuili Hospital Affiliated to Ningbo University, Ningbo University, Zhejiang Province, Ningbo, China.
- Department of Cardiovascular, Ningbo Institute of Innovation for Combined Medicine and Engineering, Ningbo, China.
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3
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Del Rivero Morfin PJ, Marx SO, Ben-Johny M. Sympathetic Nervous System Regulation of Cardiac Calcium Channels. Handb Exp Pharmacol 2023. [PMID: 36592229 DOI: 10.1007/164_2022_632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Calcium influx through voltage-gated calcium channels, Cav1.2, in cardiomyocytes initiates excitation-contraction coupling in the heart. The force and rate of cardiac contraction are modulated by the sympathetic nervous system, mediated substantially by changes in intracellular calcium. Norepinephrine released from sympathetic neurons innervating the heart and epinephrine secreted by the adrenal chromaffin cells bind to β-adrenergic receptors on the sarcolemma of cardiomyocytes initiating a signaling cascade that generates cAMP and activates protein kinase A, the targets of which control calcium influx. For decades, the mechanisms by which PKA regulated calcium channels in the heart were not known. Recently, these mechanisms have been elucidated. In this chapter, we will review the history of the field and the studies that led to the identification of the evolutionarily conserved process.
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Affiliation(s)
- Pedro J Del Rivero Morfin
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Steven O Marx
- Division of Cardiology, Department of Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA. .,Department of Pharmacology and Molecular Signaling, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
| | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
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4
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Hu XQ, Zhang L. Oxidative Regulation of Vascular Ca v1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders. Antioxidants (Basel) 2022; 11:antiox11122432. [PMID: 36552639 PMCID: PMC9774363 DOI: 10.3390/antiox11122432] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 11/28/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022] Open
Abstract
Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca2+ (Cav1.2) channel in small arteries and arterioles plays an essential role in regulating Ca2+ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Cav1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Cav1.2 and potential roles of ROS-mediated Cav1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.
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5
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Morgenstern TJ, Nirwan N, Hernández-Ochoa EO, Bibollet H, Choudhury P, Laloudakis YD, Ben Johny M, Bannister RA, Schneider MF, Minor DL, Colecraft HM. Selective posttranslational inhibition of Ca Vβ 1-associated voltage-dependent calcium channels with a functionalized nanobody. Nat Commun 2022; 13:7556. [PMID: 36494348 PMCID: PMC9734117 DOI: 10.1038/s41467-022-35025-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 11/15/2022] [Indexed: 12/13/2022] Open
Abstract
Ca2+ influx through high-voltage-activated calcium channels (HVACCs) controls diverse cellular functions. A critical feature enabling a singular signal, Ca2+ influx, to mediate disparate functions is diversity of HVACC pore-forming α1 and auxiliary CaVβ1-CaVβ4 subunits. Selective CaVα1 blockers have enabled deciphering their unique physiological roles. By contrast, the capacity to post-translationally inhibit HVACCs based on CaVβ isoform is non-existent. Conventional gene knockout/shRNA approaches do not adequately address this deficit owing to subunit reshuffling and partially overlapping functions of CaVβ isoforms. Here, we identify a nanobody (nb.E8) that selectively binds CaVβ1 SH3 domain and inhibits CaVβ1-associated HVACCs by reducing channel surface density, decreasing open probability, and speeding inactivation. Functionalizing nb.E8 with Nedd4L HECT domain yielded Chisel-1 which eliminated current through CaVβ1-reconstituted CaV1/CaV2 and native CaV1.1 channels in skeletal muscle, strongly suppressed depolarization-evoked Ca2+ influx and excitation-transcription coupling in hippocampal neurons, but was inert against CaVβ2-associated CaV1.2 in cardiomyocytes. The results introduce an original method for probing distinctive functions of ion channel auxiliary subunit isoforms, reveal additional dimensions of CaVβ1 signaling in neurons, and describe a genetically-encoded HVACC inhibitor with unique properties.
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Affiliation(s)
- Travis J. Morgenstern
- grid.239585.00000 0001 2285 2675Department of Molecular Pharmacology and Therapeutics, Columbia University Irving Medical Center, New York, NY USA
| | - Neha Nirwan
- grid.266102.10000 0001 2297 6811Cardiovascular Research Institute, University of California, San Francisco, CA USA
| | - Erick O. Hernández-Ochoa
- grid.411024.20000 0001 2175 4264Department of Biochemistry and Biology, University of Maryland School of Medicine, Baltimore, MD USA
| | - Hugo Bibollet
- grid.411024.20000 0001 2175 4264Department of Biochemistry and Biology, University of Maryland School of Medicine, Baltimore, MD USA
| | - Papiya Choudhury
- grid.239585.00000 0001 2285 2675Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, NY USA
| | - Yianni D. Laloudakis
- grid.239585.00000 0001 2285 2675Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY USA
| | - Manu Ben Johny
- grid.239585.00000 0001 2285 2675Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, NY USA
| | - Roger A. Bannister
- grid.411024.20000 0001 2175 4264Department of Biochemistry and Biology, University of Maryland School of Medicine, Baltimore, MD USA ,grid.411024.20000 0001 2175 4264Department of Pathology, University of Maryland School of Medicine, Baltimore, MD USA
| | - Martin F. Schneider
- grid.411024.20000 0001 2175 4264Department of Biochemistry and Biology, University of Maryland School of Medicine, Baltimore, MD USA
| | - Daniel L. Minor
- grid.266102.10000 0001 2297 6811Cardiovascular Research Institute, University of California, San Francisco, CA USA ,grid.266102.10000 0001 2297 6811Department of Biochemistry and Biophysics, University of California, San Francisco, CA USA ,grid.266102.10000 0001 2297 6811Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA USA ,grid.266102.10000 0001 2297 6811California Institute for Quantitative Biomedical Research, University of California, San Francisco, CA USA ,grid.266102.10000 0001 2297 6811Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, CA USA ,grid.184769.50000 0001 2231 4551Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
| | - Henry M. Colecraft
- grid.239585.00000 0001 2285 2675Department of Molecular Pharmacology and Therapeutics, Columbia University Irving Medical Center, New York, NY USA ,grid.239585.00000 0001 2285 2675Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, NY USA
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6
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Despang P, Salamon S, Breitenkamp A, Kuzmenkina E, Matthes J. Inhibitory effects on L- and N-type calcium channels by a novel Ca Vβ 1 variant identified in a patient with autism spectrum disorder. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2022; 395:459-470. [PMID: 35122502 PMCID: PMC8873119 DOI: 10.1007/s00210-022-02213-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 01/25/2022] [Indexed: 12/01/2022]
Abstract
Voltage-gated calcium channel (VGCC) subunits have been genetically associated with autism spectrum disorders (ASD). The properties of the pore-forming VGCC subunit are modulated by auxiliary β-subunits, which exist in four isoforms (CaVβ1-4). Our previous findings suggested that activation of L-type VGCCs is a common feature of CaVβ2 subunit mutations found in ASD patients. In the current study, we functionally characterized a novel CaVβ1b variant (p.R296C) identified in an ASD patient. We used whole-cell and single-channel patch clamp to study the effect of CaVβ1b_R296C on the function of L- and N-type VGCCs. Furthermore, we used co-immunoprecipitation followed by Western blot to evaluate the interaction of the CaVβ1b-subunits with the RGK-protein Gem. Our data obtained at both, whole-cell and single-channel levels, show that compared to a wild-type CaVβ1b, the CaVβ1b_R296C variant inhibits L- and N-type VGCCs. Interaction with and modulation by the RGK-protein Gem seems to be intact. Our findings indicate functional effects of the CaVβ1b_R296C variant differing from that attributed to CaVβ2 variants found in ASD patients. Further studies have to detail the effects on different VGCC subtypes and on VGCC expression.
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Affiliation(s)
- Patrick Despang
- Center of Pharmacology, Institute II, University of Cologne, Gleueler Strasse 24, 50931, Köln, Cologne, Germany
| | - Sarah Salamon
- Center of Pharmacology, Institute II, University of Cologne, Gleueler Strasse 24, 50931, Köln, Cologne, Germany
| | - Alexandra Breitenkamp
- Center of Pharmacology, Institute II, University of Cologne, Gleueler Strasse 24, 50931, Köln, Cologne, Germany
| | - Elza Kuzmenkina
- Center of Pharmacology, Institute II, University of Cologne, Gleueler Strasse 24, 50931, Köln, Cologne, Germany
| | - Jan Matthes
- Center of Pharmacology, Institute II, University of Cologne, Gleueler Strasse 24, 50931, Köln, Cologne, Germany.
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7
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Abstract
Optogenetics combines light and genetics to enable precise control of living cells, tissues, and organisms with tailored functions. Optogenetics has the advantages of noninvasiveness, rapid responsiveness, tunable reversibility, and superior spatiotemporal resolution. Following the initial discovery of microbial opsins as light-actuated ion channels, a plethora of naturally occurring or engineered photoreceptors or photosensitive domains that respond to light at varying wavelengths has ushered in the next chapter of optogenetics. Through protein engineering and synthetic biology approaches, genetically-encoded photoswitches can be modularly engineered into protein scaffolds or host cells to control a myriad of biological processes, as well as to enable behavioral control and disease intervention in vivo. Here, we summarize these optogenetic tools on the basis of their fundamental photochemical properties to better inform the chemical basis and design principles. We also highlight exemplary applications of opsin-free optogenetics in dissecting cellular physiology (designated "optophysiology"), and describe the current progress, as well as future trends, in wireless optogenetics, which enables remote interrogation of physiological processes with minimal invasiveness. This review is anticipated to spark novel thoughts on engineering next-generation optogenetic tools and devices that promise to accelerate both basic and translational studies.
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Affiliation(s)
- Peng Tan
- Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University, Houston, Texas, United States.,Klarman Cell Observatory, Broad Institute of MIT and Harvard, Cambridge, MA, United States
| | - Lian He
- Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University, Houston, Texas, United States
| | - Yun Huang
- Center for Epigenetics and Disease Prevention, Institute of Biosciences and Technology, Texas A&M University, Houston, TX, United States.,Department of Translational Medical Sciences, College of Medicine, Texas A&M University, Houston, Texas, United States
| | - Yubin Zhou
- Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University, Houston, Texas, United States.,Department of Translational Medical Sciences, College of Medicine, Texas A&M University, Houston, Texas, United States
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8
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Contreras GF, Saavedra J, Navarro-Quezada N, Mellado G, Gonzalez C, Neely A. Direct inhibition of Ca V2.3 by Gem is dynamin dependent and does not require a direct alfa/beta interaction. Biochem Biophys Res Commun 2022; 586:107-113. [PMID: 34837834 DOI: 10.1016/j.bbrc.2021.11.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/21/2021] [Accepted: 11/14/2021] [Indexed: 11/17/2022]
Abstract
The Rad, Rem, Rem2, and Gem/Kir (RGK) sub-family of small GTP-binding proteins are crucial in regulating high voltage-activated (HVA) calcium channels. RGK proteins inhibit calcium current by either promoting endocytosis or reducing channel activity. They all can associate directly with Ca2+ channel β subunit (CaVβ), and the binding between CaVα1/CaVβ appears essential for the endocytic promotion of CaV1.X, CaV2.1, and CaV2.2 channels. In this study, we investigated the inhibition of CaV2.3 channels by RGK proteins in the absence of CaVβ. To this end, Xenopus laevis oocytes expressing CaV2.3 channels devoid of auxiliary subunit were injected with purified Gem and Rem and found that only Gem had an effect. Ca currents and charge movements were reduced by injection of Gem, pointing to a reduction in the number of channels in the plasma membrane. Since this reduction was ablated by co-expression of the dominant-negative mutant of dynamin K44A, enhanced endocytosis appears to mediate this reduction in the number of channels. Thus, Gem inhibition of CaV2.3 channels would be the only example of a CaVβ independent promotion of dynamin-dependent endocytosis.
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Affiliation(s)
- Gustavo F Contreras
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile
| | - Jonathan Saavedra
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile; Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Nieves Navarro-Quezada
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile
| | - Guido Mellado
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile; Doctorado en Ciencias Mención Biofisica y Biología Computacional, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carlos Gonzalez
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile; Centro Interdisciplinario de Neurociencias Valparaíso, Chile; Cardiovascular Research, Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, USA
| | - Alan Neely
- Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaiso, Chile
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9
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Ahern BM, Sebastian A, Levitan BM, Goh J, Andres DA, Satin J. L-type channel inactivation balances the increased peak calcium current due to absence of Rad in cardiomyocytes. J Gen Physiol 2021; 153:212476. [PMID: 34269819 PMCID: PMC8289690 DOI: 10.1085/jgp.202012854] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 06/25/2021] [Indexed: 12/15/2022] Open
Abstract
The L-type Ca2+ channel (LTCC) provides trigger calcium to initiate cardiac contraction in a graded fashion that is regulated by L-type calcium current (ICa,L) amplitude and kinetics. Inactivation of LTCC is controlled to fine-tune calcium flux and is governed by voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). Rad is a monomeric G protein that regulates ICa,L and has recently been shown to be critical to β-adrenergic receptor (β-AR) modulation of ICa,L. Our previous work showed that cardiomyocyte-specific Rad knockout (cRadKO) resulted in elevated systolic function, underpinned by an increase in peak ICa,L, but without pathological remodeling. Here, we sought to test whether Rad-depleted LTCC contributes to the fight-or-flight response independently of β-AR function, resulting in ICa,L kinetic modifications to homeostatically balance cardiomyocyte function. We recorded whole-cell ICa,L from ventricular cardiomyocytes from inducible cRadKO and control (CTRL) mice. The kinetics of ICa,L stimulated with isoproterenol in CTRL cardiomyocytes were indistinguishable from those of unstimulated cRadKO cardiomyocytes. CDI and VDI are both enhanced in cRadKO cardiomyocytes without differences in action potential duration or QT interval. To confirm that Rad loss modulates LTCC independently of β-AR stimulation, we crossed a β1,β2-AR double-knockout mouse with cRadKO, resulting in a Rad-inducible triple-knockout mouse. Deletion of Rad in cardiomyocytes that do not express β1,β2-AR still yielded modulated ICa,L and elevated basal heart function. Thus, in the absence of Rad, increased Ca2+ influx is homeostatically balanced by accelerated CDI and VDI. Our results indicate that the absence of Rad can modulate the LTCC without contribution of β1,β2-AR signaling and that Rad deletion supersedes β-AR signaling to the LTCC to enhance in vivo heart function.
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Affiliation(s)
- Brooke M Ahern
- Department of Physiology, 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
| | - Jensen Goh
- Department of Physiology, University of Kentucky, Lexington, KY
| | - Douglas A Andres
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY
| | - Jonathan Satin
- Department of Physiology, University of Kentucky, Lexington, KY
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10
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Pickel S, Cruz-Garcia Y, Bandleon S, Barkovits K, Heindl C, Völker K, Abeßer M, Pfeiffer K, Schaaf A, Marcus K, Eder-Negrin P, Kuhn M, Miranda-Laferte E. The β 2-Subunit of Voltage-Gated Calcium Channels Regulates Cardiomyocyte Hypertrophy. Front Cardiovasc Med 2021; 8:704657. [PMID: 34307509 PMCID: PMC8292724 DOI: 10.3389/fcvm.2021.704657] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 06/09/2021] [Indexed: 12/16/2022] Open
Abstract
L-type voltage-gated calcium channels (LTCCs) regulate crucial physiological processes in the heart. They are composed of the Cavα1 pore-forming subunit and the accessory subunits Cavβ, Cavα2δ, and Cavγ. Cavβ is a cytosolic protein that regulates channel trafficking and activity, but it also exerts other LTCC-independent functions. Cardiac hypertrophy, a relevant risk factor for the development of congestive heart failure, depends on the activation of calcium-dependent pro-hypertrophic signaling cascades. Here, by using shRNA-mediated Cavβ silencing, we demonstrate that Cavβ2 downregulation enhances α1-adrenergic receptor agonist-induced cardiomyocyte hypertrophy. We report that a pool of Cavβ2 is targeted to the nucleus in cardiomyocytes and that the expression of this nuclear fraction decreases during in vitro and in vivo induction of cardiac hypertrophy. Moreover, the overexpression of nucleus-targeted Cavβ2 in cardiomyocytes inhibits in vitro-induced hypertrophy. Quantitative proteomic analyses showed that Cavβ2 knockdown leads to changes in the expression of diverse myocyte proteins, including reduction of calpastatin, an endogenous inhibitor of the calcium-dependent protease calpain. Accordingly, Cavβ2-downregulated cardiomyocytes had a 2-fold increase in calpain activity as compared to control cells. Furthermore, inhibition of calpain activity in Cavβ2-downregulated cells abolished the enhanced α1-adrenergic receptor agonist-induced hypertrophy observed in these cells. Our findings indicate that in cardiomyocytes, a nuclear pool of Cavβ2 participates in cellular functions that are independent of LTCC activity. They also indicate that a downregulation of nuclear Cavβ2 during cardiomyocyte hypertrophy promotes the activation of calpain-dependent hypertrophic pathways.
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Affiliation(s)
- Simone Pickel
- Institute of Physiology, University of Würzburg, Würzburg, Germany
| | | | - Sandra Bandleon
- Comprehensive Heart Failure Center, University Hospital Würzburg, Würzburg, Germany
| | - Katalin Barkovits
- Medizinisches Proteom-Center, Medical Faculty, Ruhr-University Bochum, Bochum, Germany.,Medical Proteome Analysis, Center for Proteindiagnostics (PRODI), Ruhr-University Bochum, Bochum, Germany
| | - Cornelia Heindl
- Institute of Physiology, University of Würzburg, Würzburg, Germany
| | - Katharina Völker
- Institute of Physiology, University of Würzburg, Würzburg, Germany
| | - Marco Abeßer
- Institute of Physiology, University of Würzburg, Würzburg, Germany
| | - Kathy Pfeiffer
- Medizinisches Proteom-Center, Medical Faculty, Ruhr-University Bochum, Bochum, Germany.,Medical Proteome Analysis, Center for Proteindiagnostics (PRODI), Ruhr-University Bochum, Bochum, Germany
| | - Alice Schaaf
- Comprehensive Heart Failure Center, University Hospital Würzburg, Würzburg, Germany
| | - Katrin Marcus
- Medizinisches Proteom-Center, Medical Faculty, Ruhr-University Bochum, Bochum, Germany.,Medical Proteome Analysis, Center for Proteindiagnostics (PRODI), Ruhr-University Bochum, Bochum, Germany
| | - Petra Eder-Negrin
- Comprehensive Heart Failure Center, University Hospital Würzburg, Würzburg, Germany
| | - Michaela Kuhn
- Institute of Physiology, University of Würzburg, Würzburg, Germany.,Comprehensive Heart Failure Center, University Hospital Würzburg, Würzburg, Germany
| | - Erick Miranda-Laferte
- Institute of Physiology, University of Würzburg, Würzburg, Germany.,Institut für Biologische Informationsprozesse, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Jülich, Germany
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11
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Miranda DR, Voss AA, Bannister RA. Into the spotlight: RGK proteins in skeletal muscle. Cell Calcium 2021; 98:102439. [PMID: 34261001 DOI: 10.1016/j.ceca.2021.102439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 06/24/2021] [Accepted: 06/26/2021] [Indexed: 10/20/2022]
Abstract
The RGK (Rad, Rem, Rem2 and Gem/Kir) family of small GTPases are potent endogenous inhibitors of voltage-gated Ca2+ channels (VGCCs). While the impact of RGK proteins on cardiac physiology has been investigated extensively, much less is known regarding their influence on skeletal muscle biology. Thus, the purpose of this article is to establish a basis for future investigation into the role of RGK proteins in regulating the skeletal muscle excitation-contraction (EC) coupling complex via modulation of the L-type CaV1.1 VGCC. The pathological consequences of elevated muscle RGK protein expression in Type II Diabetes, Amyotrophic Lateral Sclerosis (ALS), Duchenne's Muscular Dystrophy and traumatic nerve injury are also discussed.
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Affiliation(s)
- Daniel R Miranda
- Department of Biological Sciences, College of Science and Mathematics, Wright State University, 235A Biological Sciences, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA
| | - Andrew A Voss
- Department of Biological Sciences, College of Science and Mathematics, Wright State University, 235A Biological Sciences, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
| | - Roger A Bannister
- Departments of Pathology and Biochemistry & Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, MD 21201, USA.
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12
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Reconstitution of β-adrenergic regulation of Ca V1.2: Rad-dependent and Rad-independent protein kinase A mechanisms. Proc Natl Acad Sci U S A 2021; 118:2100021118. [PMID: 34001616 DOI: 10.1073/pnas.2100021118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
L-type voltage-gated CaV1.2 channels crucially regulate cardiac muscle contraction. Activation of β-adrenergic receptors (β-AR) augments contraction via protein kinase A (PKA)-induced increase of calcium influx through CaV1.2 channels. To date, the full β-AR cascade has never been heterologously reconstituted. A recent study identified Rad, a CaV1.2 inhibitory protein, as essential for PKA regulation of CaV1.2. We corroborated this finding and reconstituted the complete pathway with agonist activation of β1-AR or β2-AR in Xenopus oocytes. We found, and distinguished between, two distinct pathways of PKA modulation of CaV1.2: Rad dependent (∼80% of total) and Rad independent. The reconstituted system reproduces the known features of β-AR regulation in cardiomyocytes and reveals several aspects: the differential regulation of posttranslationally modified CaV1.2 variants and the distinct features of β1-AR versus β2-AR activity. This system allows for the addressing of central unresolved issues in the β-AR-CaV1.2 cascade and will facilitate the development of therapies for catecholamine-induced cardiac pathologies.
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13
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Ferron L, Koshti S, Zamponi GW. The life cycle of voltage-gated Ca 2+ channels in neurons: an update on the trafficking of neuronal calcium channels. Neuronal Signal 2021; 5:NS20200095. [PMID: 33664982 PMCID: PMC7905535 DOI: 10.1042/ns20200095] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 02/10/2021] [Accepted: 02/15/2021] [Indexed: 01/26/2023] Open
Abstract
Neuronal voltage-gated Ca2+ (CaV) channels play a critical role in cellular excitability, synaptic transmission, excitation-transcription coupling and activation of intracellular signaling pathways. CaV channels are multiprotein complexes and their functional expression in the plasma membrane involves finely tuned mechanisms, including forward trafficking from the endoplasmic reticulum (ER) to the plasma membrane, endocytosis and recycling. Whether genetic or acquired, alterations and defects in the trafficking of neuronal CaV channels can have severe physiological consequences. In this review, we address the current evidence concerning the regulatory mechanisms which underlie precise control of neuronal CaV channel trafficking and we discuss their potential as therapeutic targets.
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Affiliation(s)
- Laurent Ferron
- Department of Physiology and Pharmacology, Alberta Children’s Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Saloni Koshti
- Department of Physiology and Pharmacology, Alberta Children’s Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, Alberta Children’s Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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14
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Gandini MA, Zamponi GW. Voltage‐gated calcium channel nanodomains: molecular composition and function. FEBS J 2021; 289:614-633. [DOI: 10.1111/febs.15759] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/05/2021] [Accepted: 02/10/2021] [Indexed: 12/16/2022]
Affiliation(s)
- Maria A. Gandini
- Department of Physiology and Pharmacology Alberta Children’s Hospital Research Institute Hotchkiss Brain Institute Cumming School of Medicine University of Calgary AB Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology Alberta Children’s Hospital Research Institute Hotchkiss Brain Institute Cumming School of Medicine University of Calgary AB Canada
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15
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Abstract
The identification of a gain-of-function mutation in CACNA1C as the cause of Timothy syndrome, a rare disorder characterized by cardiac arrhythmias and syndactyly, highlighted roles for the L-type voltage-gated Ca2+ channel CaV1.2 in nonexcitable cells. Previous studies in cells and animal models had suggested that several voltage-gated Ca2+ channels (VGCCs) regulated critical signaling events in various cell types that are not expected to support action potentials, but definitive data were lacking. VGCCs occupy a special position among ion channels, uniquely able to translate membrane excitability into the cytoplasmic Ca2+ changes that underlie the cellular responses to electrical activity. Yet how these channels function in cells not firing action potentials and what the consequences of their actions are in nonexcitable cells remain critical questions. The development of new animal and cellular models and the emergence of large data sets and unbiased genome screens have added to our understanding of the unanticipated roles for VGCCs in nonexcitable cells. Here, we review current knowledge of VGCC regulation and function in nonexcitable tissues and cells, with the goal of providing a platform for continued investigation.
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Affiliation(s)
- Geoffrey S Pitt
- Cardiovascular Research Institute, Weill Cornell Medicine, New York, NY 10021, USA;
| | - Maiko Matsui
- Cardiovascular Research Institute, Weill Cornell Medicine, New York, NY 10021, USA;
| | - Chike Cao
- Cardiovascular Research Institute, Weill Cornell Medicine, New York, NY 10021, USA;
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16
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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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17
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Stiegler AL, Boggon TJ. The pseudoGTPase group of pseudoenzymes. FEBS J 2020; 287:4232-4245. [PMID: 32893973 PMCID: PMC7544640 DOI: 10.1111/febs.15554] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/21/2020] [Accepted: 09/01/2020] [Indexed: 12/14/2022]
Abstract
Pseudoenzymes are emerging as significant mediators and regulators of signal transduction. These proteins maintain enzyme folds and topologies, but are disrupted in the conserved motifs required for enzymatic activity. Among the pseudoenzymes, the pseudoGTPase group of atypical GTPases has recently expanded and includes the Rnd and RGK groups, RhoH and the RhoBTB proteins, mitochondrial RhoGTPase and centaurin-γ groups, CENP-M, dynein LIC, Entamoeba histolytica RabX3, leucine-rich repeat kinase 2, and the p190RhoGAP proteins. The wide range of cellular functions associated with pseudoGTPases includes cell migration and adhesion, membrane trafficking and cargo transport, mitosis, mitochondrial activity, transcriptional control, and autophagy, placing the group in an expanding portfolio of signaling pathways. In this review, we examine how the pseudoGTPases differ from canonical GTPases and consider their mechanistic and functional roles in signal transduction. We review the amino acid differences between the pseudoGTPases and discuss how these proteins can be classified based on their ability to bind nucleotide and their enzymatic activity. We discuss the molecular and structural consequences of amino acid divergence from canonical GTPases and use comparison with the well-studied pseudokinases to illustrate the classifications. PseudoGTPases are fast becoming recognized as important mechanistic components in a range of cellular roles, and we provide a concise discussion of the currently identified members of this group. ENZYMES: small GTPases; EC number: EC 3.6.5.2.
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Affiliation(s)
- Amy L. Stiegler
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
| | - Titus J. Boggon
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
- Departments of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
- Yale Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
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18
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Ohara-Imaizumi M, Aoyagi K, Ohtsuka T. Role of the active zone protein, ELKS, in insulin secretion from pancreatic β-cells. Mol Metab 2020; 27S:S81-S91. [PMID: 31500835 PMCID: PMC6768504 DOI: 10.1016/j.molmet.2019.06.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Background Insulin is stored within large dense-core granules in pancreatic beta (β)-cells and is released by Ca2+-triggered exocytosis with increasing blood glucose levels. Polarized and targeted secretion of insulin from β-cells in pancreatic islets into the vasculature has been proposed; however, the mechanisms related to cellular and molecular localization remain largely unknown. Within nerve terminals, the Ca2+-dependent release of a polarized transmitter is limited to the active zone, a highly specialized area of the presynaptic membrane. Several active zone-specific proteins have been characterized; among them, the CAST/ELKS protein family members have the ability to form large protein complexes with other active zone proteins to control the structure and function of the active zone for tight regulation of neurotransmitter release. Notably, ELKS but not CAST is also expressed in β-cells, implying that ELKS may be involved in polarized insulin secretion from β-cells. Scope of review This review provides an overview of the current findings regarding the role(s) of ELKS and other active zone proteins in β-cells and focuses on the molecular mechanism underlying ELKS regulation within polarized insulin secretion from islets. Major conclusions ELKS localizes at the vascular-facing plasma membrane of β-cells in mouse pancreatic islets. ELKS forms a potent insulin secretion complex with L-type voltage-dependent Ca2+ channels on the vascular-facing plasma membrane of β-cells, enabling polarized Ca2+ influx and first-phase insulin secretion from islets. This model provides novel insights into the functional polarity observed during insulin secretion from β-cells within islets at the molecular level. This active zone-like region formed by ELKS at the vascular side of the plasma membrane is essential for coordinating physiological insulin secretion and may be disrupted in diabetes.
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Affiliation(s)
- Mica Ohara-Imaizumi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan.
| | - Kyota Aoyagi
- Department of Cellular Biochemistry, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Graduate School of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
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19
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Regulation of cardiovascular calcium channel activity by post-translational modifications or interacting proteins. Pflugers Arch 2020; 472:653-667. [PMID: 32435990 DOI: 10.1007/s00424-020-02398-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 05/04/2020] [Accepted: 05/06/2020] [Indexed: 02/08/2023]
Abstract
Voltage-gated calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alterations of calcium channel function have been implicated in multiple cardiovascular diseases, such as hypertension, atrial fibrillation, and long QT syndrome. Post-translational modifications do expand cardiovascular calcium channel structure and function to affect processes such as channel trafficking or polyubiquitination by two E3 ubiquitin ligases, Ret finger protein 2 (Rfp2) or murine double minute 2 protein (Mdm2). Additionally, biophysical property such as Ca2+-dependent inactivation (CDI) could be altered through binding of calmodulin, or channel activity could be modulated via S-nitrosylation by nitric oxide and phosphorylation by protein kinases or by interacting protein partners, such as galectin-1 and Rem. Understanding how cardiovascular calcium channel function is post-translationally remodeled under distinctive disease conditions will provide better information about calcium channel-related disease mechanisms and improve the development of more selective therapeutic agents for cardiovascular diseases.
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20
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Colecraft HM. Designer genetically encoded voltage-dependent calcium channel inhibitors inspired by RGK GTPases. J Physiol 2020; 598:1683-1693. [PMID: 32104913 PMCID: PMC7195252 DOI: 10.1113/jp276544] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 02/07/2020] [Indexed: 12/28/2022] Open
Abstract
High‐voltage‐activated calcium (CaV1/CaV2) channels translate action potentials into Ca2+ influx in excitable cells to control essential biological processes that include; muscle contraction, synaptic transmission, hormone secretion and activity‐dependent regulation of gene expression. Modulation of CaV1/CaV2 channel activity is a powerful mechanism to regulate physiology, and there are a host of intracellular signalling molecules that tune different aspects of CaV channel trafficking and gating for this purpose. Beyond normal physiological regulation, the diverse CaV channel modulatory mechanisms may potentially be co‐opted or interfered with for therapeutic benefits. CaV1/CaV2 channels are potently inhibited by a four‐member sub‐family of Ras‐like GTPases known as RGK (Rad, Rem, Rem2, Gem/Kir) proteins. Understanding the mechanisms by which RGK proteins inhibit CaV1/CaV2 channels has led to the development of novel genetically encoded CaV channel blockers with unique properties; including, chemo‐ and optogenetic control of channel activity, and blocking channels either on the basis of their subcellular localization or by targeting an auxiliary subunit. These genetically encoded CaV channel inhibitors have outstanding utility as enabling research tools and potential therapeutics.
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Affiliation(s)
- Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Department of Pharmacology and Molecular Signaling, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
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21
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ELKS/Voltage-Dependent Ca 2+ Channel-β Subunit Module Regulates Polarized Ca 2+ Influx in Pancreatic β Cells. Cell Rep 2020; 26:1213-1226.e7. [PMID: 30699350 DOI: 10.1016/j.celrep.2018.12.106] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 10/29/2018] [Accepted: 12/27/2018] [Indexed: 12/14/2022] Open
Abstract
Pancreatic β cells secrete insulin by Ca2+-triggered exocytosis. However, there is no apparent secretory site similar to the neuronal active zones, and the cellular and molecular localization mechanism underlying polarized exocytosis remains elusive. Here, we report that ELKS, a vertebrate active zone protein, is used in β cells to regulate Ca2+ influx for insulin secretion. β cell-specific ELKS-knockout (KO) mice showed impaired glucose-stimulated first-phase insulin secretion and reduced L-type voltage-dependent Ca2+ channel (VDCC) current density. In situ Ca2+ imaging of β cells within islets expressing a membrane-bound G-CaMP8b Ca2+ sensor demonstrated initial local Ca2+ signals at the ELKS-localized vascular side of the β cell plasma membrane, which were markedly decreased in ELKS-KO β cells. Mechanistically, ELKS directly interacted with the VDCC-β subunit via the GK domain. These findings suggest that ELKS and VDCCs form a potent insulin secretion complex at the vascular side of the β cell plasma membrane for polarized Ca2+ influx and first-phase insulin secretion from pancreatic islets.
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22
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Autism-associated mutations in the CaVβ2 calcium-channel subunit increase Ba2+-currents and lead to differential modulation by the RGK-protein Gem. Neurobiol Dis 2020; 136:104721. [DOI: 10.1016/j.nbd.2019.104721] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 12/06/2019] [Accepted: 12/26/2019] [Indexed: 12/26/2022] Open
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23
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Cerrone M, Remme CA, Tadros R, Bezzina CR, Delmar M. Beyond the One Gene-One Disease Paradigm: Complex Genetics and Pleiotropy in Inheritable Cardiac Disorders. Circulation 2019; 140:595-610. [PMID: 31403841 DOI: 10.1161/circulationaha.118.035954] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Inheritable cardiac disorders, which may be associated with cardiomyopathic changes, are often associated with increased risk of sudden death in the young. Early linkage analysis studies in Mendelian forms of these diseases, such as hypertrophic cardiomyopathy and long-QT syndrome, uncovered large-effect genetic variants that contribute to the phenotype. In more recent years, through genotype-phenotype studies and methodological advances in genetics, it has become evident that most inheritable cardiac disorders are not monogenic but, rather, have a complex genetic basis wherein multiple genetic variants contribute (oligogenic or polygenic inheritance). Conversely, studies on genes underlying these disorders uncovered pleiotropic effects, with a single gene affecting multiple and apparently unrelated phenotypes. In this review, we explore these 2 phenomena: on the one hand, the evidence that variants in multiple genes converge to generate one clinical phenotype, and, on the other, the evidence that variants in one gene can lead to apparently unrelated phenotypes. Although multiple conditions are addressed to illustrate these concepts, the experience obtained in the study of long-QT syndrome, Brugada syndrome, and arrhythmogenic cardiomyopathy, and in the study of functions related to SCN5A (the gene coding for the α-subunit of the most abundant sodium channel in the heart) and PKP2 (the gene coding for the desmosomal protein plakophilin-2), as well, is discussed in more detail.
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Affiliation(s)
- Marina Cerrone
- Leon H. Charney Division of Cardiology (M.C., M.D.), NYU School of Medicine, New York.,Inherited Arrhythmias Clinic and Heart Rhythm Center, Leon H. Charney Division of Cardiology (M.C.), NYU School of Medicine, New York
| | - Carol Ann Remme
- Inherited Arrhythmias Clinic and Heart Rhythm Center, Leon H. Charney Division of Cardiology (M.C.), NYU School of Medicine, New York
| | - Rafik Tadros
- Amsterdam UMC, University of Amsterdam, Clinical and Experimental Cardiology, Amsterdam Cardiovascular Sciences, AMC Heart Center, The Netherlands (C.A.R., C.R.B.)
| | - Connie R Bezzina
- Inherited Arrhythmias Clinic and Heart Rhythm Center, Leon H. Charney Division of Cardiology (M.C.), NYU School of Medicine, New York
| | - Mario Delmar
- Leon H. Charney Division of Cardiology (M.C., M.D.), NYU School of Medicine, New York
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24
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Morgenstern TJ, Park J, Fan QR, Colecraft HM. A potent voltage-gated calcium channel inhibitor engineered from a nanobody targeted to auxiliary Ca Vβ subunits. eLife 2019; 8:49253. [PMID: 31403402 PMCID: PMC6701945 DOI: 10.7554/elife.49253] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 08/10/2019] [Indexed: 12/15/2022] Open
Abstract
Inhibiting high-voltage-activated calcium channels (HVACCs; CaV1/CaV2) is therapeutic for myriad cardiovascular and neurological diseases. For particular applications, genetically-encoded HVACC blockers may enable channel inhibition with greater tissue-specificity and versatility than is achievable with small molecules. Here, we engineered a genetically-encoded HVACC inhibitor by first isolating an immunized llama nanobody (nb.F3) that binds auxiliary HVACC CaVβ subunits. Nb.F3 by itself is functionally inert, providing a convenient vehicle to target active moieties to CaVβ-associated channels. Nb.F3 fused to the catalytic HECT domain of Nedd4L (CaV-aβlator), an E3 ubiquitin ligase, ablated currents from diverse HVACCs reconstituted in HEK293 cells, and from endogenous CaV1/CaV2 channels in mammalian cardiomyocytes, dorsal root ganglion neurons, and pancreatic β cells. In cardiomyocytes, CaV-aβlator redistributed CaV1.2 channels from dyads to Rab-7-positive late endosomes. This work introduces CaV-aβlator as a potent genetically-encoded HVACC inhibitor, and describes a general approach that can be broadly adapted to generate versatile modulators for macro-molecular membrane protein complexes.
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Affiliation(s)
- Travis J Morgenstern
- Department of Pharmacology, Columbia University, Vagelos College of Physicians and Surgeons, New York, United States
| | - Jinseo Park
- Department of Pharmacology, Columbia University, Vagelos College of Physicians and Surgeons, New York, United States
| | - Qing R Fan
- Department of Pharmacology, Columbia University, Vagelos College of Physicians and Surgeons, New York, United States
| | - Henry M Colecraft
- Department of Pharmacology, Columbia University, Vagelos College of Physicians and Surgeons, New York, United States.,Department of Physiology and Cellular Biophysics, Columbia University, Vagelos College of Physicians and Surgeons, New York, United States
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25
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Ahern BM, Levitan BM, Veeranki S, Shah M, Ali N, Sebastian A, Su W, Gong MC, Li J, Stelzer JE, Andres DA, Satin J. Myocardial-restricted ablation of the GTPase RAD results in a pro-adaptive heart response in mice. J Biol Chem 2019; 294:10913-10927. [PMID: 31147441 PMCID: PMC6635439 DOI: 10.1074/jbc.ra119.008782] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 05/16/2019] [Indexed: 12/25/2022] Open
Abstract
Existing therapies to improve heart function target β-adrenergic receptor (β-AR) signaling and Ca2+ handling and often lead to adverse outcomes. This underscores an unmet need for positive inotropes that improve heart function without any adverse effects. The GTPase Ras associated with diabetes (RAD) regulates L-type Ca2+ channel (LTCC) current (ICa,L). Global RAD-knockout mice (gRAD-/-) have elevated Ca2+ handling and increased cardiac hypertrophy, but RAD is expressed also in noncardiac tissues, suggesting the possibility that pathological remodeling is due also to noncardiac effects. Here, we engineered a myocardial-restricted inducible RAD-knockout mouse (RADΔ/Δ). Using an array of methods and techniques, including single-cell electrophysiological and calcium transient recordings, echocardiography, and radiotelemetry monitoring, we found that RAD deficiency results in a sustained increase of inotropy without structural or functional remodeling of the heart. ICa,L was significantly increased, with RAD loss conferring a β-AR-modulated phenotype on basal ICa,L Cardiomyocytes from RADΔ/Δ hearts exhibited enhanced cytosolic Ca2+ handling, increased contractile function, elevated sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2a) expression, and faster lusitropy. These results argue that myocardial RAD ablation promotes a beneficial elevation in Ca2+ dynamics, which would obviate a need for increased β-AR signaling to improve cardiac function.
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Affiliation(s)
| | - Bryana M Levitan
- Department of Physiology,; Gill Heart and Vascular Institute, and
| | - Sudhakar Veeranki
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536 and
| | | | - Nemat Ali
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536 and
| | | | | | | | - Jiayang Li
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Julian E Stelzer
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Douglas A Andres
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536 and.
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26
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Xu Q, Wang Y, Zhu J, Zhao Y, Lin Y. Molecular characterization of GTP binding protein overexpressed in skeletal muscle (GEM) and its role in promoting adipogenesis in goat intramuscular preadipocytes. Anim Biotechnol 2018; 31:17-24. [PMID: 30570352 DOI: 10.1080/10495398.2018.1523796] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
GTP binding protein overexpressed in skeletal muscle (GEM) is an important gene with many functions, such as regulating the rearrangement of cytoskeleton and the activity of voltage-dependent calcium channel, and GEM was regarded as a candidate gene for obesity. However, little investigation has been carried out to explore whether GEM affected the intramuscular fat (IMF) deposition of goat. To explore the role of GEM gene in goat, this gene was cloned and its tissue and temporal expression profile were detected. Effect of GEM on adipogenesis was examined by losing function of GEM in vitro. Thereafter, several lipid metabolism-related genes were examined, including CCAAT/enhancing-binding protein α (C/EBPα), CCAAT/enhancing-binding protein β (C/EBPβ), lipoprotein lipase (LPL), preadipocyte factor 1 (Pref-1), peroxisome proliferator activated receptor γ (PPARγ) and sterol regulatory element binding protein 1 (SREBP1). We found that the goat GEM gene consisted of 936 bp, which encoded a protein of 311 amino acids. The expression of GEM was higher in spleen, lung and large intestine and it appeared sharp in the interim stage of differentiation. Furthermore, GEM knockdown blocked adipogenesis and the expression of C/EBPα, C/EBPβ, LPL, PPARγ and SREBP1. These results indicated that GEM might promote lipid accumulation and adipogenesis.
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Affiliation(s)
- Qing Xu
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China
| | - Yong Wang
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China.,Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Exploitation, Chengdu, Sichuan, P.R. China
| | - Jiangjiang Zhu
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China.,Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Exploitation, Chengdu, Sichuan, P.R. China
| | - Yanying Zhao
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China
| | - Yaqiu Lin
- School of Life Science and Technology, Southwest Minzu University, Chengdu, P.R. China.,Key Laboratory of Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Ministry of Education, Southwest Minzu UniversityChengdu, Sichuan, P.R. China
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27
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Engineering selectivity into RGK GTPase inhibition of voltage-dependent calcium channels. Proc Natl Acad Sci U S A 2018; 115:12051-12056. [PMID: 30397133 PMCID: PMC6255209 DOI: 10.1073/pnas.1811024115] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genetically encoded inhibitors for voltage-dependent Ca2+ (CaV) channels (GECCIs) are useful research tools and potential therapeutics. Rad/Rem/Rem2/Gem (RGK) proteins are Ras-like G proteins that potently inhibit high voltage-activated (HVA) Ca2+ (CaV1/CaV2 family) channels, but their nonselectivity limits their potential applications. We hypothesized that nonselectivity of RGK inhibition derives from their binding to auxiliary CaVβ-subunits. To investigate latent CaVβ-independent components of inhibition, we coexpressed each RGK individually with CaV1 (CaV1.2/CaV1.3) or CaV2 (CaV2.1/CaV2.2) channels reconstituted in HEK293 cells with either wild-type (WT) β2a or a mutant version (β2a,TM) that does not bind RGKs. All four RGKs strongly inhibited CaV1/CaV2 channels reconstituted with WT β2a By contrast, when channels were reconstituted with β2a,TM, Rem inhibited only CaV1.2, Rad selectively inhibited CaV1.2 and CaV2.2, while Gem and Rem2 were ineffective. We generated mutant RGKs (Rem[R200A/L227A] and Rad[R208A/L235A]) unable to bind WT CaVβ, as confirmed by fluorescence resonance energy transfer. Rem[R200A/L227A] selectively blocked reconstituted CaV1.2 while Rad[R208A/L235A] inhibited CaV1.2/CaV2.2 but not CaV1.3/CaV2.1. Rem[R200A/L227A] and Rad[R208A/L235A] both suppressed endogenous CaV1.2 channels in ventricular cardiomyocytes and selectively blocked 25 and 62%, respectively, of HVA currents in somatosensory neurons of the dorsal root ganglion, corresponding to their distinctive selectivity for CaV1.2 and CaV1.2/CaV2.2 channels. Thus, we have exploited latent β-binding-independent Rem and Rad inhibition of specific CaV1/CaV2 channels to develop selective GECCIs with properties unmatched by current small-molecule CaV channel blockers.
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β-Subunit of the voltage-gated Ca 2+ channel Cav1.2 drives signaling to the nucleus via H-Ras. Proc Natl Acad Sci U S A 2018; 115:E8624-E8633. [PMID: 30150369 DOI: 10.1073/pnas.1805380115] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Depolarization-induced signaling to the nucleus by the L-type voltage-gated calcium channel Cav1.2 is widely assumed to proceed by elevating intracellular calcium. The apparent lack of quantitative correlation between Ca2+ influx and gene activation suggests an alternative activation pathway. Here, we demonstrate that membrane depolarization of HEK293 cells transfected with α11.2/β2b/α2δ subunits (Cav1.2) triggers c-Fos and MeCP2 activation via the Ras/ERK/CREB pathway. Nuclear signaling is lost either by absence of the intracellular β2 subunit or by transfecting the cells with the channel mutant α11.2W440A/β2b/α2δ, a mutation that disrupts the interaction between α11.2 and β2 subunits. Pulldown assays in neuronal SH-SY5Y cells and in vitro binding of recombinant H-Ras and β2 confirmed the importance of the intracellular β2 subunit for depolarization-induced gene activation. Using a Ca2+-impermeable mutant channel α11.2L745P/β2b/α2δ or disrupting Ca2+/calmodulin binding to the channel using the channel mutant α11.2I1624A/β2b/α2δ, we demonstrate that depolarization-induced c-Fos and MeCP2 activation does not depend on Ca2+ transport by the channel. Thus, in contrast to the paradigm that elevated intracellular Ca2+ drives nuclear signaling, we show that Cav1.2-triggered c-Fos or MeCP2 is dependent on extracellular Ca2+ and Ca2+ occupancy of the open channel pore, but is Ca2+-influx independent. An indispensable β-subunit interaction with H-Ras, which is triggered by conformational changes at α11.2 independently of Ca2+ flux, brings to light a master regulatory role of β2 in transcriptional activation via the ERK/CREB pathway. This mode of H-Ras activation could have broad implications for understanding the coupling of membrane depolarization to the rapid induction of gene transcription.
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29
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Royer L, Herzog JJ, Kenny K, Tzvetkova B, Cochrane JC, Marr MT, Paradis S. The Ras-like GTPase Rem2 is a potent inhibitor of calcium/calmodulin-dependent kinase II activity. J Biol Chem 2018; 293:14798-14811. [PMID: 30072381 DOI: 10.1074/jbc.ra118.003560] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 07/20/2018] [Indexed: 02/05/2023] Open
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a well-characterized, abundant protein kinase that regulates a diverse set of functions in a tissue-specific manner. For example, in heart muscle, CaMKII regulates Ca2+ homeostasis, whereas in neurons, CaMKII regulates activity-dependent dendritic remodeling and long-term potentiation (LTP), a neurobiological correlate of learning and memory. Previously, we identified the GTPase Rem2 as a critical regulator of dendrite branching and homeostatic plasticity in the vertebrate nervous system. Here, we report that Rem2 directly interacts with CaMKII and potently inhibits the activity of the intact holoenzyme, a previously unknown Rem2 function. Our results suggest that Rem2 inhibition involves interaction with both the CaMKII hub domain and substrate recognition domain. Moreover, we found that Rem2-mediated inhibition of CaMKII regulates dendritic branching in cultured hippocampal neurons. Lastly, we report that substitution of two key amino acid residues in the Rem2 N terminus (Arg-79 and Arg-80) completely abolishes its ability to inhibit CaMKII. We propose that our biochemical findings will enable further studies unraveling the functional significance of Rem2 inhibition of CaMKII in cells.
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Affiliation(s)
| | | | | | | | - Jesse C Cochrane
- Department of Molecular Biology and Genetics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Michael T Marr
- From the Department of Biology, .,Rosenstiel Basic Medical Sciences Research Center
| | - Suzanne Paradis
- From the Department of Biology, .,Volen Center for Complex Systems, and.,National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454 and
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30
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Optogenetic Control of Voltage-Gated Calcium Channels. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201713080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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31
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Ma G, Liu J, Ke Y, Liu X, Li M, Wang F, Han G, Huang Y, Wang Y, Zhou Y. Optogenetic Control of Voltage-Gated Calcium Channels. Angew Chem Int Ed Engl 2018; 57:7019-7022. [PMID: 29569306 PMCID: PMC6032918 DOI: 10.1002/anie.201713080] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Indexed: 11/11/2022]
Abstract
Voltage‐gated Ca2+ (CaV) channels mediate Ca2+ entry into excitable cells to regulate a myriad of cellular events following membrane depolarization. We report the engineering of RGK GTPases, a class of genetically encoded CaV channel modulators, to enable photo‐tunable modulation of CaV channel activity in excitable mammalian cells. This optogenetic tool (designated optoRGK) tailored for CaV channels could find broad applications in interrogating a wide range of CaV‐mediated physiological processes.
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Affiliation(s)
- Guolin Ma
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, 2121 W Holcombe Blvd, Houston, TX, 77030, USA
| | - Jindou Liu
- Beijing Key Laboratory of Gene Resource and Molecular, Development, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Yuepeng Ke
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, 2121 W Holcombe Blvd, Houston, TX, 77030, USA
| | - Xin Liu
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, 2121 W Holcombe Blvd, Houston, TX, 77030, USA
| | - Minyong Li
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, School of Pharmacy, Shandong University, Jinan, Shandong, 250012, China
| | - Fen Wang
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, 2121 W Holcombe Blvd, Houston, TX, 77030, USA
| | - Gang Han
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, 01605, USA
| | - Yun Huang
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, 2121 W Holcombe Blvd, Houston, TX, 77030, USA
| | - Youjun Wang
- Beijing Key Laboratory of Gene Resource and Molecular, Development, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
| | - Yubin Zhou
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, 2121 W Holcombe Blvd, Houston, TX, 77030, USA.,Department of Medical Physiology, College of Medicine, Texas A&M University, Temple, TX, 76504, USA
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32
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Meza U, Beqollari D, Bannister RA. Molecular mechanisms and physiological relevance of RGK proteins in the heart. Acta Physiol (Oxf) 2018; 222:e13016. [PMID: 29237245 DOI: 10.1111/apha.13016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 12/05/2017] [Accepted: 12/06/2017] [Indexed: 12/19/2022]
Abstract
The primary route of Ca2+ entry into cardiac myocytes is via 1,4-dihydropyridine-sensitive, voltage-gated L-type Ca2+ channels. Ca2+ influx through these channels influences duration of action potential and engages excitation-contraction (EC) coupling in both the atria and the myocardium. Members of the RGK (Rad, Rem, Rem2 and Gem/Kir) family of small GTP-binding proteins are potent, endogenously expressed inhibitors of cardiac L-type channels. Although much work has focused on the molecular mechanisms by which RGK proteins inhibit the CaV 1.2 and CaV 1.3 L-type channel isoforms that expressed in the heart, their impact on greater cardiac function is only beginning to come into focus. In this review, we summarize recent findings regarding the influence of RGK proteins on normal cardiac physiology and the pathological consequences of aberrant RGK activity.
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Affiliation(s)
- U. Meza
- Departamento de Fisiología y Biofísica; Facultad de Medicina; Universidad Autónoma de San Luis Potosí; San Luis Potosí México
| | - D. Beqollari
- Department of Medicine-Cardiology Division; University of Colorado School of Medicine; Aurora CO USA
| | - R. A. Bannister
- Department of Medicine-Cardiology Division; University of Colorado School of Medicine; Aurora CO USA
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33
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Chai S, Wan X, Ramirez-Navarro A, Tesar PJ, Kaufman ES, Ficker E, George AL, Deschênes I. Physiological genomics identifies genetic modifiers of long QT syndrome type 2 severity. J Clin Invest 2018; 128:1043-1056. [PMID: 29431731 DOI: 10.1172/jci94996] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 01/02/2018] [Indexed: 12/11/2022] Open
Abstract
Congenital long QT syndrome (LQTS) is an inherited channelopathy associated with life-threatening arrhythmias. LQTS type 2 (LQT2) is caused by mutations in KCNH2, which encodes the potassium channel hERG. We hypothesized that modifier genes are partly responsible for the variable phenotype severity observed in some LQT2 families. Here, we identified contributors to variable expressivity in an LQT2 family by using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and whole exome sequencing in a synergistic manner. We found that iPSC-CMs recapitulated the clinical genotype-phenotype discordance in vitro. Importantly, iPSC-CMs derived from the severely affected LQT2 patients displayed prolonged action potentials compared with cells from mildly affected first-degree relatives. The iPSC-CMs derived from all patients with hERG R752W mutation displayed lower IKr amplitude. Interestingly, iPSC-CMs from severely affected mutation-positive individuals exhibited greater L-type Ca2+ current. Whole exome sequencing identified variants of KCNK17 and the GTP-binding protein REM2, providing biologically plausible explanations for this variable expressivity. Genome editing to correct a REM2 variant reversed the enhanced L-type Ca2+ current and prolonged action potential observed in iPSC-CMs from severely affected individuals. Thus, our findings showcase the power of combining complementary physiological and genomic analyses to identify genetic modifiers and potential therapeutic targets of a monogenic disorder. Furthermore, we propose that this strategy can be deployed to unravel myriad confounding pathologies displaying variable expressivity.
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Affiliation(s)
- Sam Chai
- Department of Physiology and Biophysics.,Heart and Vascular Research Center, Department of Medicine, and
| | - Xiaoping Wan
- Heart and Vascular Research Center, Department of Medicine, and
| | | | - Paul J Tesar
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio, USA
| | | | - Eckhard Ficker
- Heart and Vascular Research Center, Department of Medicine, and
| | - Alfred L George
- Department of Pharmacology, Northwestern University, Chicago, Illinois, USA
| | - Isabelle Deschênes
- Department of Physiology and Biophysics.,Heart and Vascular Research Center, Department of Medicine, and
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34
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Belkacemi A, Hui X, Wardas B, Laschke MW, Wissenbach U, Menger MD, Lipp P, Beck A, Flockerzi V. IP3 Receptor-Dependent Cytoplasmic Ca2+ Signals Are Tightly Controlled by Cavβ3. Cell Rep 2018; 22:1339-1349. [DOI: 10.1016/j.celrep.2018.01.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/10/2017] [Accepted: 01/03/2018] [Indexed: 12/11/2022] Open
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35
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Kenny K, Royer L, Moore AR, Chen X, Marr MT, Paradis S. Rem2 signaling affects neuronal structure and function in part by regulation of gene expression. Mol Cell Neurosci 2017; 85:190-201. [PMID: 29066292 DOI: 10.1016/j.mcn.2017.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 09/27/2017] [Accepted: 10/11/2017] [Indexed: 12/12/2022] Open
Abstract
The central nervous system has the remarkable ability to convert changes in the environment in the form of sensory experience into long-term alterations in synaptic connections and dendritic arborization, in part through changes in gene expression. Surprisingly, the molecular mechanisms that translate neuronal activity into changes in neuronal connectivity and morphology remain elusive. Rem2, a member of the Rad/Rem/Rem2/Gem/Kir (RGK) subfamily of small Ras-like GTPases, is a positive regulator of synapse formation and negative regulator of dendritic arborization. Here we identify that one output of Rem2 signaling is the regulation of gene expression. Specifically, we demonstrate that Rem2 signaling modulates the expression of genes required for a variety of cellular processes from neurite extension to synapse formation and synaptic function. Our results highlight Rem2 as a unique molecule that transduces changes in neuronal activity detected at the cell membrane to morphologically relevant changes in gene expression in the nucleus.
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Affiliation(s)
- Katelyn Kenny
- Department of Biology, Brandeis University, Waltham, MA 02454, United States
| | - Leandro Royer
- Department of Biology, Brandeis University, Waltham, MA 02454, United States
| | - Anna R Moore
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, United States; National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, United States
| | - Xiao Chen
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, United States
| | - Michael T Marr
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, United States
| | - Suzanne Paradis
- Department of Biology, Brandeis University, Waltham, MA 02454, United States; Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, United States; National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, United States.
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36
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Aromolaran AS, Boutjdir M. Cardiac Ion Channel Regulation in Obesity and the Metabolic Syndrome: Relevance to Long QT Syndrome and Atrial Fibrillation. Front Physiol 2017; 8:431. [PMID: 28680407 PMCID: PMC5479057 DOI: 10.3389/fphys.2017.00431] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 06/06/2017] [Indexed: 01/03/2023] Open
Abstract
Obesity and its associated metabolic dysregulation leading to metabolic syndrome is an epidemic that poses a significant public health problem. More than one-third of the world population is overweight or obese leading to enhanced risk of cardiovascular disease (CVD) incidence and mortality. Obesity predisposes to atrial fibrillation, ventricular, and supraventricular arrhythmias; conditions that are underlain by dysfunction in electrical activity of the heart. To date, current therapeutic options for cardiomyopathy of obesity are limited, suggesting that there is considerable room for development of therapeutic interventions with novel mechanisms of action that will help normalize rhythm in obese patients. Emerging candidates for modulation by obesity are cardiac ion channels and Ca handling proteins. However, the underlying molecular mechanisms of the impact of obesity on these channels/Ca handling proteins remain incompletely understood. Obesity is marked by accumulation of adipose tissue associated with a variety of adverse adaptations including dyslipidemia (or abnormal levels of serum free fatty acids), increased secretion of pro-inflammatory cytokines, fibrosis, hyperglycemia, and insulin resistance, that will cause electrical remodeling and thus predispose to arrhythmias. Further, adipose tissue is also associated with the accumulation of subcutaneous and visceral fat, which are marked by distinct signaling mechanisms. Thus, there may also be functional differences in the outcome of regional distribution of fat deposits on ion channel/Ca handling proteins expression. Evaluating alterations in their functional expression in obesity will lead to progress in the knowledge about the mechanisms responsible for obesity-related arrhythmias. These advances are likely to reveal new targets for pharmacological modulation. The objective of this article is to review cardiac ion channel/Ca handling proteins remodeling that predispose to arrhythmias. Understanding how obesity and related mechanisms lead to cardiac electrical remodeling is likely to have a significant medical and economic impact.
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Affiliation(s)
- Ademuyiwa S Aromolaran
- Cardiovascular Research Program, VA New York Harbor Healthcare SystemBrooklyn, NY, United States.,Departments of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Medical CenterBrooklyn, NY, United States
| | - Mohamed Boutjdir
- Cardiovascular Research Program, VA New York Harbor Healthcare SystemBrooklyn, NY, United States.,Departments of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Medical CenterBrooklyn, NY, United States.,Department of Medicine, New York University School of MedicineNew York, NY, United States
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37
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Two Components of Aversive Memory in Drosophila, Anesthesia-Sensitive and Anesthesia-Resistant Memory, Require Distinct Domains Within the Rgk1 Small GTPase. J Neurosci 2017; 37:5496-5510. [PMID: 28416593 DOI: 10.1523/jneurosci.3648-16.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Revised: 03/12/2017] [Accepted: 04/12/2017] [Indexed: 12/17/2022] Open
Abstract
Multiple components have been identified that exhibit different stabilities for aversive olfactory memory in Drosophila These components have been defined by behavioral and genetic studies and genes specifically required for a specific component have also been identified. Intermediate-term memory generated after single cycle conditioning is divided into anesthesia-sensitive memory (ASM) and anesthesia-resistant memory (ARM), with the latter being more stable. We determined that the ASM and ARM pathways converged on the Rgk1 small GTPase and that the N-terminal domain-deleted Rgk1 was sufficient for ASM formation, whereas the full-length form was required for ARM formation. Rgk1 is specifically accumulated at the synaptic site of the Kenyon cells (KCs), the intrinsic neurons of the mushroom bodies, which play a pivotal role in olfactory memory formation. A higher than normal Rgk1 level enhanced memory retention, which is consistent with the result that Rgk1 suppressed Rac-dependent memory decay; these findings suggest that rgk1 bolsters ASM via the suppression of forgetting. We propose that Rgk1 plays a pivotal role in the regulation of memory stabilization by serving as a molecular node that resides at KC synapses, where the ASM and ARM pathway may interact.SIGNIFICANCE STATEMENT Memory consists of multiple components. Drosophila olfactory memory serves as a fundamental model with which to investigate the mechanisms that underlie memory formation and has provided genetic and molecular means to identify the components of memory, namely short-term, intermediate-term, and long-term memory, depending on how long the memory lasts. Intermediate memory is further divided into anesthesia-sensitive memory (ASM) and anesthesia-resistant memory (ARM), with the latter being more stable. We have identified a small GTPase in Drosophila, Rgk1, which plays a pivotal role in the regulation of olfactory memory stability. Rgk1 is required for both ASM and ARM. Moreover, N-terminal domain-deleted Rgk1 was sufficient for ASM formation, whereas the full-length form was required for ARM formation.
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38
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Chang DD, Colecraft HM. Rad and Rem are non-canonical G-proteins with respect to the regulatory role of guanine nucleotide binding in Ca(V)1.2 channel regulation. J Physiol 2016; 593:5075-90. [PMID: 26426338 DOI: 10.1113/jp270889] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 09/27/2015] [Indexed: 12/15/2022] Open
Abstract
Rad and Rem are Ras-like G-proteins linked to diverse cardiovascular functions and pathophysiology. Understanding how Rad and Rem are regulated is important for deepened insights into their pathophysiological roles. As in other Ras-like G-proteins, Rad and Rem contain a conserved guanine-nucleotide binding domain (G-domain). Canonically, G-domains are key control modules, functioning as nucleotide-regulated switches of G-protein activity. Whether Rad and Rem G-domains conform to this canonical paradigm is ambiguous. Here, we used multiple functional measurements in HEK293 cells and cardiomyocytes (Ca(V)1.2 currents, Ca(2+) transients, Ca(V)β binding) as biosensors to probe the role of the G-domain in regulation of Rad and Rem function. We utilized Rad(S105N) and Rem(T94N), which are the cognate mutants to Ras(S17N), a dominant-negative variant of Ras that displays decreased nucleotide binding affinity. In HEK293 cells, over-expression of either Rad(S105N) or Rem(T94N) strongly inhibited reconstituted Ca(V)1.2 currents to the same extent as their wild-type (wt) counterparts, contrasting with reports that Rad(S105N) is functionally inert in HEK293 cells. Adenovirus-mediated expression of either wt Rad or Rad(S105N) in cardiomyocytes dramatically blocked L-type calcium current (I(Ca,L)) and inhibited Ca(2+)-induced Ca(2+) release, contradicting reports that Rad(S105N) acts as a dominant negative in heart. By contrast, Rem(T94N) was significantly less effective than wt Rem at inhibiting I(Ca,L) and Ca(2+) transients in cardiomyocytes. FRET analyses in cardiomyocytes revealed that both Rad(S105N) and Rem(T94N) had moderately reduced binding affinity for Ca(V)βs relative to their wt counterparts. The results indicate Rad and Rem are non-canonical G-proteins with respect to the regulatory role of their G-domain in Ca(V)1.2 regulation.
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Affiliation(s)
- Donald D Chang
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
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39
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Rusconi F, Ceriotti P, Miragoli M, Carullo P, Salvarani N, Rocchetti M, Di Pasquale E, Rossi S, Tessari M, Caprari S, Cazade M, Kunderfranco P, Chemin J, Bang ML, Polticelli F, Zaza A, Faggian G, Condorelli G, Catalucci D. Peptidomimetic Targeting of Cavβ2 Overcomes Dysregulation of the L-Type Calcium Channel Density and Recovers Cardiac Function. Circulation 2016; 134:534-46. [PMID: 27486162 DOI: 10.1161/circulationaha.116.021347] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 06/27/2016] [Indexed: 02/07/2023]
Abstract
BACKGROUND L-type calcium channels (LTCCs) play important roles in regulating cardiomyocyte physiology, which is governed by appropriate LTCC trafficking to and density at the cell surface. Factors influencing the expression, half-life, subcellular trafficking, and gating of LTCCs are therefore critically involved in conditions of cardiac physiology and disease. METHODS Yeast 2-hybrid screenings, biochemical and molecular evaluations, protein interaction assays, fluorescence microscopy, structural molecular modeling, and functional studies were used to investigate the molecular mechanisms through which the LTCC Cavβ2 chaperone regulates channel density at the plasma membrane. RESULTS On the basis of our previous results, we found a direct linear correlation between the total amount of the LTCC pore-forming Cavα1.2 and the Akt-dependent phosphorylation status of Cavβ2 both in a mouse model of diabetic cardiac disease and in 6 diabetic and 7 nondiabetic cardiomyopathy patients with aortic stenosis undergoing aortic valve replacement. Mechanistically, we demonstrate that a conformational change in Cavβ2 triggered by Akt phosphorylation increases LTCC density at the cardiac plasma membrane, and thus the inward calcium current, through a complex pathway involving reduction of Cavα1.2 retrograde trafficking and protein degradation through the prevention of dynamin-mediated LTCC endocytosis; promotion of Cavα1.2 anterograde trafficking by blocking Kir/Gem-dependent sequestration of Cavβ2, thus facilitating the chaperoning of Cavα1.2; and promotion of Cavα1.2 transcription by the prevention of Kir/Gem-mediated shuttling of Cavβ2 to the nucleus, where it limits the transcription of Cavα1.2 through recruitment of the heterochromatin protein 1γ epigenetic repressor to the Cacna1c promoter. On the basis of this mechanism, we developed a novel mimetic peptide that, through targeting of Cavβ2, corrects LTCC life-cycle alterations, facilitating the proper function of cardiac cells. Delivery of mimetic peptide into a mouse model of diabetic cardiac disease associated with LTCC abnormalities restored impaired calcium balance and recovered cardiac function. CONCLUSIONS We have uncovered novel mechanisms modulating LTCC trafficking and life cycle and provide proof of concept for the use of Cavβ2 mimetic peptide as a novel therapeutic tool for the improvement of cardiac conditions correlated with alterations in LTCC levels and function.
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Affiliation(s)
- Francesca Rusconi
- From Humanitas Clinical and Research Center, Rozzano, Milan, Italy (F.R., P. Ceriotti, M.M., P. Carullo, N.S., E.D.P., P.K., M.-L.B., G.C., D.C.); Institute of Genetic and Biomedical Research UOS Milan National Research Council, Milan, Italy (F.R., P. Carullo, N.S., E.D.P., M.-L.B., D.C.); Department of Biotechnologies and Biosciences, University of Milan-Bicocca, Milan, Italy (M.R., A.Z.); Departments of Life Sciences (S.R.) and Clinical and Experimental Medicine (M.M.), University of Parma, Parma, Italy; University Hospital of Verona, Division of Cardiac Surgery, Verona, Italy (M.T., G.F.); Department of Sciences, University of Roma Tre, Rome, Italy (S.C., F.P.); University of Montpellier, CNRS UMR 5203, INSERM, Department of Neuroscience, Institute for Functional Genomics, LabEx Ion Channel Science and Therapeutics, Montpellier, France (M.C., J.C.); and National Institute of Nuclear Physics, Rome Tre Section, Rome, Italy (F.P.)
| | - Paola Ceriotti
- From Humanitas Clinical and Research Center, Rozzano, Milan, Italy (F.R., P. Ceriotti, M.M., P. Carullo, N.S., E.D.P., P.K., M.-L.B., G.C., D.C.); Institute of Genetic and Biomedical Research UOS Milan National Research Council, Milan, Italy (F.R., P. Carullo, N.S., E.D.P., M.-L.B., D.C.); Department of Biotechnologies and Biosciences, University of Milan-Bicocca, Milan, Italy (M.R., A.Z.); Departments of Life Sciences (S.R.) and Clinical and Experimental Medicine (M.M.), University of Parma, Parma, Italy; University Hospital of Verona, Division of Cardiac Surgery, Verona, Italy (M.T., G.F.); Department of Sciences, University of Roma Tre, Rome, Italy (S.C., F.P.); University of Montpellier, CNRS UMR 5203, INSERM, Department of Neuroscience, Institute for Functional Genomics, LabEx Ion Channel Science and Therapeutics, Montpellier, France (M.C., J.C.); and National Institute of Nuclear Physics, Rome Tre Section, Rome, Italy (F.P.)
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Liput DJ, Lu VB, Davis MI, Puhl HL, Ikeda SR. Rem2, a member of the RGK family of small GTPases, is enriched in nuclei of the basal ganglia. Sci Rep 2016; 6:25137. [PMID: 27118437 PMCID: PMC4846870 DOI: 10.1038/srep25137] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 11/09/2022] Open
Abstract
Rem2 is a member of the RGK subfamily of RAS small GTPases. Rem2 inhibits high voltage activated calcium channels, is involved in synaptogenesis, and regulates dendritic morphology. Rem2 is the primary RGK protein expressed in the nervous system, but to date, the precise expression patterns of this protein are unknown. In this study, we characterized Rem2 expression in the mouse nervous system. In the CNS, Rem2 mRNA was detected in all regions examined, but was enriched in the striatum. An antibody specific for Rem2 was validated using a Rem2 knockout mouse model and used to show abundant expression in striatonigral and striatopallidal medium spiny neurons but not in several interneuron populations. In the PNS, Rem2 was abundant in a subpopulation of neurons in the trigeminal and dorsal root ganglia, but was absent in sympathetic neurons of superior cervical ganglia. Under basal conditions, Rem2 was subject to post-translational phosphorylation, likely at multiple residues. Further, Rem2 mRNA and protein expression peaked at postnatal week two, which corresponds to the period of robust neuronal maturation in rodents. This study will be useful for elucidating the functions of Rem2 in basal ganglia physiology.
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Affiliation(s)
- Daniel J. Liput
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Van B. Lu
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Margaret I. Davis
- Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Henry L. Puhl
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
| | - Stephen R. Ikeda
- Laboratories of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, 20892-9411, USA
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41
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Puckerin AA, Chang DD, Subramanyam P, Colecraft HM. Similar molecular determinants on Rem mediate two distinct modes of inhibition of Ca V1.2 channels. Channels (Austin) 2016; 10:379-394. [PMID: 27115600 PMCID: PMC4988437 DOI: 10.1080/19336950.2016.1180489] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Rad/Rem/Rem2/Gem (RGK) proteins are Ras-like GTPases that potently inhibit all high-voltage-gated calcium (CaV1/CaV2) channels and are, thus, well-positioned to tune diverse physiological processes. Understanding how RGK proteins inhibit CaV channels is important for perspectives on their (patho)physiological roles and could advance their development and use as genetically-encoded CaV channel blockers. We previously reported that Rem can block surface CaV1.2 channels in 2 independent ways that engage distinct components of the channel complex: (1) by binding auxiliary β subunits (β-binding-dependent inhibition, or BBD); and (2) by binding the pore-forming α1C subunit N-terminus (α1C-binding-dependent inhibition, or ABD). By contrast, Gem uses only the BBD mechanism to block CaV1.2. Rem molecular determinants required for BBD CaV1.2 inhibition are the distal C-terminus and the guanine nucleotide binding G-domain which interact with the plasma membrane and CaVβ, respectively. However, Rem determinants for ABD CaV1.2 inhibition are unknown. Here, combining fluorescence resonance energy transfer, electrophysiology, systematic truncations, and Rem/Gem chimeras we found that the same Rem distal C-terminus and G-domain also mediate ABD CaV1.2 inhibition, but with different interaction partners. Rem distal C-terminus interacts with α1C N-terminus to anchor the G-domain which likely interacts with an as-yet-unidentified site. In contrast to some previous studies, neither the C-terminus of Rem nor Gem was sufficient to inhibit CaV1/CaV2 channels. The results reveal that similar molecular determinants on Rem are repurposed to initiate 2 independent mechanisms of CaV1.2 inhibition.
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Affiliation(s)
- Akil A Puckerin
- a Department of Pharmacology & Molecular Signaling , Columbia University , New York , NY , USA
| | - Donald D Chang
- b Department of Physiology & Cellular Biophysics , Columbia University , New York , NY , USA
| | - Prakash Subramanyam
- b Department of Physiology & Cellular Biophysics , Columbia University , New York , NY , USA
| | - Henry M Colecraft
- a Department of Pharmacology & Molecular Signaling , Columbia University , New York , NY , USA.,b Department of Physiology & Cellular Biophysics , Columbia University , New York , NY , USA
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Campiglio M, Flucher BE. The role of auxiliary subunits for the functional diversity of voltage-gated calcium channels. J Cell Physiol 2015; 230:2019-31. [PMID: 25820299 PMCID: PMC4672716 DOI: 10.1002/jcp.24998] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 03/23/2015] [Indexed: 11/18/2022]
Abstract
Voltage-gated calcium channels (VGCCs) represent the sole mechanism to convert membrane depolarization into cellular functions like secretion, contraction, or gene regulation. VGCCs consist of a pore-forming α1 subunit and several auxiliary channel subunits. These subunits come in multiple isoforms and splice-variants giving rise to a stunning molecular diversity of possible subunit combinations. It is generally believed that specific auxiliary subunits differentially regulate the channels and thereby contribute to the great functional diversity of VGCCs. If auxiliary subunits can associate and dissociate from pre-existing channel complexes, this would allow dynamic regulation of channel properties. However, most auxiliary subunits modulate current properties very similarly, and proof that any cellular calcium channel function is indeed modulated by the physiological exchange of auxiliary subunits is still lacking. In this review we summarize available information supporting a differential modulation of calcium channel functions by exchange of auxiliary subunits, as well as experimental evidence in support of alternative functions of the auxiliary subunits. At the heart of the discussion is the concept that, in their native environment, VGCCs function in the context of macromolecular signaling complexes and that the auxiliary subunits help to orchestrate the diverse protein–protein interactions found in these calcium channel signalosomes. Thus, in addition to a putative differential modulation of current properties, differential subcellular targeting properties and differential protein–protein interactions of the auxiliary subunits may explain the need for their vast molecular diversity. J. Cell. Physiol. 999: 00–00, 2015. © 2015 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc. J. Cell. Physiol. 230: 2019–2031, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Marta Campiglio
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
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Beqollari D, Romberg CF, Filipova D, Meza U, Papadopoulos S, Bannister RA. Rem uncouples excitation-contraction coupling in adult skeletal muscle fibers. ACTA ACUST UNITED AC 2015; 146:97-108. [PMID: 26078055 PMCID: PMC4485024 DOI: 10.1085/jgp.201411314] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 05/18/2015] [Indexed: 12/14/2022]
Abstract
The RGK protein Rem uncouples the voltage sensors of CaV1.1 from RYR1-mediated sarcoplasmic reticulum Ca2+ release via its ability to interact with the auxiliary β1a subunit. In skeletal muscle, excitation–contraction (EC) coupling requires depolarization-induced conformational rearrangements in L-type Ca2+ channel (CaV1.1) to be communicated to the type 1 ryanodine-sensitive Ca2+ release channel (RYR1) of the sarcoplasmic reticulum (SR) via transient protein–protein interactions. Although the molecular mechanism that underlies conformational coupling between CaV1.1 and RYR1 has been investigated intensely for more than 25 years, the question of whether such signaling occurs via a direct interaction between the principal, voltage-sensing α1S subunit of CaV1.1 and RYR1 or through an intermediary protein persists. A substantial body of evidence supports the idea that the auxiliary β1a subunit of CaV1.1 is a conduit for this intermolecular communication. However, a direct role for β1a has been difficult to test because β1a serves two other functions that are prerequisite for conformational coupling between CaV1.1 and RYR1. Specifically, β1a promotes efficient membrane expression of CaV1.1 and facilitates the tetradic ultrastructural arrangement of CaV1.1 channels within plasma membrane–SR junctions. In this paper, we demonstrate that overexpression of the RGK protein Rem, an established β subunit–interacting protein, in adult mouse flexor digitorum brevis fibers markedly reduces voltage-induced myoplasmic Ca2+ transients without greatly affecting CaV1.1 targeting, intramembrane gating charge movement, or releasable SR Ca2+ store content. In contrast, a β1a-binding–deficient Rem triple mutant (R200A/L227A/H229A) has little effect on myoplasmic Ca2+ release in response to membrane depolarization. Thus, Rem effectively uncouples the voltage sensors of CaV1.1 from RYR1-mediated SR Ca2+ release via its ability to interact with β1a. Our findings reveal Rem-expressing adult muscle as an experimental system that may prove useful in the definition of the precise role of the β1a subunit in skeletal-type EC coupling.
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Affiliation(s)
- Donald Beqollari
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045
| | - Christin F Romberg
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045
| | - Dilyana Filipova
- Institute of Vegetative Physiology, University Hospital of Köln, D-50931 Köln, Germany
| | - Ulises Meza
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045 Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, 78210 San Luis Potosí, Mexico
| | - Symeon Papadopoulos
- Institute of Vegetative Physiology, University Hospital of Köln, D-50931 Köln, Germany
| | - Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado Denver-Anschutz Medical Campus, Aurora, CO 80045
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Rousset M, Cens T, Menard C, Bowerman M, Bellis M, Brusés J, Raoul C, Scamps F, Charnet P. Regulation of neuronal high-voltage activated Ca(V)2 Ca(2+) channels by the small GTPase RhoA. Neuropharmacology 2015; 97:201-9. [PMID: 26044639 DOI: 10.1016/j.neuropharm.2015.05.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 05/12/2015] [Accepted: 05/16/2015] [Indexed: 11/29/2022]
Abstract
High-Voltage-Activated (HVA) Ca(2+) channels are known regulators of synapse formation and transmission and play fundamental roles in neuronal pathophysiology. Small GTPases of Rho and RGK families, via their action on both cytoskeleton and Ca(2+) channels are key molecules for these processes. While the effects of RGK GTPases on neuronal HVA Ca(2+) channels have been widely studied, the effects of RhoA on the HVA channels remains however elusive. Using heterologous expression in Xenopus laevis oocytes, we show that RhoA activity reduces Ba(2+) currents through CaV2.1, CaV2.2 and CaV2.3 Ca(2+) channels independently of CaVβ subunit. This inhibition occurs independently of RGKs activity and without modification of biophysical properties and global level of expression of the channel subunit. Instead, we observed a marked decrease in the number of active channels at the plasma membrane. Pharmacological and expression studies suggest that channel expression at the plasma membrane is impaired via a ROCK-sensitive pathway. Expression of constitutively active RhoA in primary culture of spinal motoneurons also drastically reduced HVA Ca(2+) current amplitude. Altogether our data revealed that HVA Ca(2+) channels regulation by RhoA might govern synaptic transmission during development and potentially contribute to pathophysiological processes when axon regeneration and growth cone kinetics are impaired.
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Affiliation(s)
- Matthieu Rousset
- IBMM, CNRS UMR 5247, Université de Montpellier, 1919 route de Mende, 34293 Montpellier, France
| | - Thierry Cens
- IBMM, CNRS UMR 5247, Université de Montpellier, 1919 route de Mende, 34293 Montpellier, France
| | - Claudine Menard
- IBMM, CNRS UMR 5247, Université de Montpellier, 1919 route de Mende, 34293 Montpellier, France
| | - Melissa Bowerman
- Institut des Neurosciences, INSERM U1051, 80 rue Augustin Fliche, 34091 Montpellier, France
| | - Michel Bellis
- IBMM, CNRS UMR 5247, Université de Montpellier, 1919 route de Mende, 34293 Montpellier, France
| | - Juan Brusés
- Department of Natural Sciences, Mercy College, Dobbs Ferry, NY 10522, USA; Institute for Cell Biology and Neuroscience (CONICET-UBA), Buenos Aires, Argentina
| | - Cedric Raoul
- Institut des Neurosciences, INSERM U1051, 80 rue Augustin Fliche, 34091 Montpellier, France
| | - Frédérique Scamps
- Institut des Neurosciences, INSERM U1051, 80 rue Augustin Fliche, 34091 Montpellier, France
| | - Pierre Charnet
- IBMM, CNRS UMR 5247, Université de Montpellier, 1919 route de Mende, 34293 Montpellier, France.
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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.
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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.
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Affiliation(s)
- Zafir Buraei
- Department of Biology, Pace University, New York, NY, 10038, USA,
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Xu X, Zhang F, Zamponi GW, Horne WA. Solution NMR and calorimetric analysis of Rem2 binding to the Ca2+ channel β4 subunit: a low affinity interaction is required for inhibition of Cav2.1 Ca2+ currents. FASEB J 2015; 29:1794-804. [PMID: 25563298 DOI: 10.1096/fj.14-264499] [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: 09/30/2014] [Accepted: 12/22/2014] [Indexed: 12/20/2022]
Abstract
Rem, Rad, Kir/Gem (RGK) proteins, including Rem2, mediate profound inhibition of high-voltage activated Ca(2+) channels containing intracellular regulatory β subunits. All RGK proteins bind to voltage-gated Ca(2+) channel β subunit (Cavβ) subunits in vitro, but the necessity of the interaction for current inhibition remains controversial. This study applies NMR and calorimetric techniques to map the binding site for Rem2 on human Cavβ4a and measure its binding affinity. Our experiments revealed 2 binding surfaces on the β4 guanylate kinase domain contributing to a 156 ± 18 µM Kd interaction: a hydrophobic pocket lined by 4 critical residues (L173, N261, H262, and V303), mutation of any of which completely disrupted binding, and a nearby surface containing 3 residues (D206, L209, and D258) that when individually mutated decreased affinity. Voltage-gated Ca(2+) channel α1A subunit (Cav2.1) Ca(2+) currents were completely inhibited by Rem2 when co-expressed with wild-type Cavβ4a, but were unaffected by Rem2 when coexpressed with a Cavβ4a site 1 (L173A/V303A) or site 2 (D258A) mutant. These results provide direct evidence for a low-affinity Rem2/Cavβ4 interaction and show definitively that the interaction is required for Cav2.1 inhibition.
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Affiliation(s)
- Xingfu Xu
- *Department of Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA; and Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Fangxiong Zhang
- *Department of Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA; and Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Gerald W Zamponi
- *Department of Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA; and Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - William A Horne
- *Department of Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA; and Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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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.
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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.
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Adachi-Akahane S. [Regulation of L-type Ca(2+) channels via cross-talk of Ca(2+) signaling in cardiac myocytes]. Nihon Yakurigaku Zasshi 2014; 144:211-216. [PMID: 25381889 DOI: 10.1254/fpj.144.211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
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50
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Electrophysiological changes in laterodorsal tegmental neurons associated with prenatal nicotine exposure: implications for heightened susceptibility to addict to drugs of abuse. J Dev Orig Health Dis 2014; 6:182-200. [PMID: 25339425 DOI: 10.1017/s204017441400049x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Prenatal nicotine exposure (PNE) is a risk factor for developing an addiction to nicotine at a later stage in life. Understanding the neurobiological changes in reward related circuitry induced by exposure to nicotine prenatally is vital if we are to combat the heightened addiction liability in these vulnerable individuals. The laterodorsal tegmental nucleus (LDT), which is comprised of cholinergic, GABAergic and glutamatergic neurons, is importantly involved in reward mediation via demonstrated excitatory projections to dopamine-containing ventral tegmental neurons. PNE could lead to alterations in LDT neurons that would be expected to alter responses to later-life nicotine exposure. To examine this issue, we monitored nicotine-induced responses of LDT neurons in brain slices of PNE and drug naive mice using calcium imaging and whole-cell patch clamping. Nicotine was found to induce rises in calcium in a smaller proportion of LDT cells in PNE mice aged 7-15 days and smaller rises in calcium in PNE animals from postnatal ages 11-21 days when compared with age-matched control animals. While inward currents induced by nicotine were not found to be different, nicotine did induce larger amplitude excitatory postsynaptic currents in PNE animals in the oldest age group when compared with amplitudes induced in similar-aged control animals. Immunohistochemically identified cholinergic LDT cells from PNE animals exhibited slower spike rise and decay slopes, which likely contributed to the wider action potential observed. Further, PNE was associated with a more negative action potential afterhyperpolarization in cholinergic cells. Interestingly, the changes found in these parameters in animals exposed prenatally to nicotine were age related, in that they were not apparent in animals from the oldest age group examined. Taken together, our data suggest that PNE induces changes in cholinergic LDT cells that would be expected to alter cellular excitability. As the changes are age related, these PNE-associated alterations could contribute differentially across ontogeny to nicotine-mediated reward and may contribute to the particular susceptibility of in utero nicotine exposed individuals to addict to nicotine upon nicotine exposure in the juvenile period.
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