1
|
Feng W, Lopez JR, Antrobus S, Zheng J, Uryash A, Dong Y, Beqollari D, Bannister RA, Hopkins PM, Beam KG, Allen PD, Pessah IN. Putative malignant hyperthermia mutation Ca V1.1-R174W is insufficient to trigger a fulminant response to halothane or confer heat stress intolerance. J Biol Chem 2023; 299:104992. [PMID: 37392848 PMCID: PMC10413282 DOI: 10.1016/j.jbc.2023.104992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/16/2023] [Accepted: 06/20/2023] [Indexed: 07/03/2023] Open
Abstract
Malignant hyperthermia susceptibility (MHS) is an autosomal dominant pharmacogenetic disorder that manifests as a hypermetabolic state when carriers are exposed to halogenated volatile anesthetics or depolarizing muscle relaxants. In animals, heat stress intolerance is also observed. MHS is linked to over 40 variants in RYR1 that are classified as pathogenic for diagnostic purposes. More recently, a few rare variants linked to the MHS phenotype have been reported in CACNA1S, which encodes the voltage-activated Ca2+ channel CaV1.1 that conformationally couples to RyR1 in skeletal muscle. Here, we describe a knock-in mouse line that expresses one of these putative variants, CaV1.1-R174W. Heterozygous (HET) and homozygous (HOM) CaV1.1-R174W mice survive to adulthood without overt phenotype but fail to trigger with fulminant malignant hyperthermia when exposed to halothane or moderate heat stress. All three genotypes (WT, HET, and HOM) express similar levels of CaV1.1 by quantitative PCR, Western blot, [3H]PN200-110 receptor binding and immobilization-resistant charge movement densities in flexor digitorum brevis fibers. Although HOM fibers have negligible CaV1.1 current amplitudes, HET fibers have similar amplitudes to WT, suggesting a preferential accumulation of the CaV1.1-WT protein at triad junctions in HET animals. Never-the-less both HET and HOM have slightly elevated resting free Ca2+ and Na+ measured with double barreled microelectrode in vastus lateralis that is disproportional to upregulation of transient receptor potential canonical (TRPC) 3 and TRPC6 in skeletal muscle. CaV1.1-R174W and upregulation of TRPC3/6 alone are insufficient to trigger fulminant malignant hyperthermia response to halothane and/or heat stress in HET and HOM mice.
Collapse
Affiliation(s)
- Wei Feng
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Jose R Lopez
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA; Department of Research, Mount Sinai Medical Center, Miami Beach, Florida, USA
| | - Shane Antrobus
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Jing Zheng
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Arkady Uryash
- Department of Research, Mount Sinai Medical Center, Miami Beach, Florida, USA
| | - Yao Dong
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA
| | - Donald Beqollari
- Department of Medicine-Cardiology Division, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Philip M Hopkins
- Institute of Medical Research at St James's, University of Leeds, Leeds, United Kingdom
| | - Kurt G Beam
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Paul D Allen
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA; Institute of Medical Research at St James's, University of Leeds, Leeds, United Kingdom
| | - Isaac N Pessah
- Department of Molecular Biosciences, University of California Davis, Davis, California, USA.
| |
Collapse
|
2
|
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.
Collapse
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.
| |
Collapse
|
3
|
Lin C, Fesi BD, Marquis M, Bosak NP, Lysenko A, Koshnevisan MA, Duke FF, Theodorides ML, Nelson TM, McDaniel AH, Avigdor M, Arayata CJ, Shaw L, Bachmanov AA, Reed DR. Burly1 is a mouse QTL for lean body mass that maps to a 0.8-Mb region of chromosome 2. Mamm Genome 2018; 29:325-343. [PMID: 29737391 DOI: 10.1007/s00335-018-9746-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Accepted: 04/26/2018] [Indexed: 11/25/2022]
Abstract
To fine map a mouse QTL for lean body mass (Burly1), we used information from intercross, backcross, consomic, and congenic mice derived from the C57BL/6ByJ (host) and 129P3/J (donor) strains. The results from these mapping populations were concordant and showed that Burly1 is located between 151.9 and 152.7 Mb (rs33197365 to rs3700604) on mouse chromosome 2. The congenic region harboring Burly1 contains 26 protein-coding genes, 11 noncoding RNA elements (e.g., lncRNA), and 4 pseudogenes, with 1949 predicted functional variants. Of the protein-coding genes, 7 have missense variants, including genes that may contribute to lean body weight, such as Angpt41, Slc52c3, and Rem1. Lean body mass was increased by the B6-derived variant relative to the 129-derived allele. Burly1 influenced lean body weight at all ages but not food intake or locomotor activity. However, congenic mice with the B6 allele produced more heat per kilogram of lean body weight than did controls, pointing to a genotype effect on lean mass metabolism. These results show the value of integrating information from several mapping populations to refine the map location of body composition QTLs and to identify a short list of candidate genes.
Collapse
Affiliation(s)
- Cailu Lin
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Brad D Fesi
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Michael Marquis
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Natalia P Bosak
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Anna Lysenko
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | | | - Fujiko F Duke
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | | | - Theodore M Nelson
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Amanda H McDaniel
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Mauricio Avigdor
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Charles J Arayata
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | - Lauren Shaw
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA
| | | | - Danielle R Reed
- Monell Chemical Senses Center, 3500 Market St, Philadelphia, PA, 19104, USA.
| |
Collapse
|
4
|
Beqollari D, Romberg CF, Dobrowolny G, Martini M, Voss AA, Musarò A, Bannister RA. Progressive impairment of CaV1.1 function in the skeletal muscle of mice expressing a mutant type 1 Cu/Zn superoxide dismutase (G93A) linked to amyotrophic lateral sclerosis. Skelet Muscle 2016; 6:24. [PMID: 27340545 PMCID: PMC4918102 DOI: 10.1186/s13395-016-0094-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 06/03/2016] [Indexed: 11/24/2022] Open
Abstract
Background Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disorder that is typically fatal within 3–5 years of diagnosis. While motoneuron death is the defining characteristic of ALS, the events that underlie its pathology are not restricted to the nervous system. In this regard, ALS muscle atrophies and weakens significantly before presentation of neurological symptoms. Since the skeletal muscle L-type Ca2+ channel (CaV1.1) is a key regulator of both mass and force, we investigated whether CaV1.1 function is impaired in the muscle of two distinct mouse models carrying an ALS-linked mutation. Methods We recorded L-type currents, charge movements, and myoplasmic Ca2+ transients from dissociated flexor digitorum brevis (FDB) fibers to assess CaV1.1 function in two mouse models expressing a type 1 Cu/Zn superoxide dismutase mutant (SOD1G93A). Results In FDB fibers obtained from “symptomatic” global SOD1G93A mice, we observed a substantial reduction of SR Ca2+ release in response to depolarization relative to fibers harvested from age-matched control mice. L-type current and charge movement were both reduced by ~40 % in symptomatic SOD1G93A fibers when compared to control fibers. Ca2+ transients were not significantly reduced in similar experiments performed with FDB fibers obtained from “early-symptomatic” SOD1G93A mice, but L-type current and charge movement were decreased (~30 and ~20 %, respectively). Reductions in SR Ca2+ release (~35 %), L-type current (~20 %), and charge movement (~15 %) were also observed in fibers obtained from another model where SOD1G93A expression was restricted to skeletal muscle. Conclusions We report reductions in EC coupling, L-type current density, and charge movement in FDB fibers obtained from symptomatic global SOD1G93A mice. Experiments performed with FDB fibers obtained from early-symptomatic SOD1G93A and skeletal muscle autonomous MLC/SOD1G93A mice support the idea that events occurring locally in the skeletal muscle contribute to the impairment of CaV1.1 function in ALS muscle independently of innervation status. Electronic supplementary material The online version of this article (doi:10.1186/s13395-016-0094-6) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Donald Beqollari
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, 12700 East 19th Avenue, B-139, Aurora, CO 80045 USA
| | - Christin F Romberg
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, 12700 East 19th Avenue, B-139, Aurora, CO 80045 USA
| | - Gabriella Dobrowolny
- Institute Pasteur Cenci-Bolognetti, DAHFMO-Unit of Histology and Medical Embryology, La Sapienza University, Via A. Scarpa, 14, 00161 Rome, Italy ; Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Martina Martini
- Institute Pasteur Cenci-Bolognetti, DAHFMO-Unit of Histology and Medical Embryology, La Sapienza University, Via A. Scarpa, 14, 00161 Rome, Italy ; Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - 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
| | - Antonio Musarò
- Institute Pasteur Cenci-Bolognetti, DAHFMO-Unit of Histology and Medical Embryology, La Sapienza University, Via A. Scarpa, 14, 00161 Rome, Italy ; Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Roger A Bannister
- Department of Medicine-Cardiology Division, University of Colorado School of Medicine, 12700 East 19th Avenue, B-139, Aurora, CO 80045 USA
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
Hernández-Ochoa EO, Vanegas C, Iyer SR, Lovering RM, Schneider MF. Alternating bipolar field stimulation identifies muscle fibers with defective excitability but maintained local Ca(2+) signals and contraction. Skelet Muscle 2016; 6:6. [PMID: 26855765 PMCID: PMC4743112 DOI: 10.1186/s13395-016-0076-8] [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] [Received: 10/14/2015] [Accepted: 01/05/2016] [Indexed: 11/25/2022] Open
Abstract
Background Most cultured enzymatically dissociated adult myofibers exhibit spatially uniform (UNI) contractile responses and Ca2+ transients over the entire myofiber in response to electric field stimuli of either polarity applied via bipolar electrodes. However, some myofibers only exhibit contraction and Ca2+ transients at alternating (ALT) ends in response to alternating polarity field stimulation. Here, we present for the first time the methodology for identification of ALT myofibers in primary cultures and isolated muscles, as well as a study of their electrophysiological properties. Results We used high-speed confocal microscopic Ca2+ imaging, electric field stimulation, microelectrode recordings, immunostaining, and confocal microscopy to characterize the properties of action potential-induced Ca2+ transients, contractility, resting membrane potential, and staining of T-tubule voltage-gated Na+ channel distribution applied to cultured adult myofibers. Here, we show for the first time, with high temporal and spatial resolution, that normal control myofibers with UNI responses can be converted to ALT response myofibers by TTX addition or by removal of Na+ from the bathing medium, with reappearance of the UNI response on return of Na+. Our results suggest disrupted excitability as the cause of ALT behavior and indicate that the ALT response is due to local depolarization-induced Ca2+ release, whereas the UNI response is triggered by action potential propagation over the entire myofiber. Consistent with this interpretation, local depolarizing monopolar stimuli give uniform (propagated) responses in UNI myofibers, but only local responses at the electrode in ALT myofibers. The ALT responses in electrically inexcitable myofibers are consistent with expectations of current spread between bipolar stimulating electrodes, entering (hyperpolarizing) one end of a myofiber and leaving (depolarizing) the other end of the myofiber. ALT responses were also detected in some myofibers within intact isolated whole muscles from wild-type and MDX mice, demonstrating that ALT responses can be present before enzymatic dissociation. Conclusions We suggest that checking for ALT myofiber responsiveness by looking at the end of a myofiber during alternating polarity stimuli provides a test for compromised excitability of myofibers, and could be used to identify inexcitable, damaged or diseased myofibers by ALT behavior in healthy and diseased muscle. Electronic supplementary material The online version of this article (doi:10.1186/s13395-016-0076-8) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, 108 N. Greene Street, Baltimore, MD 21201 USA
| | - Camilo Vanegas
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, 108 N. Greene Street, Baltimore, MD 21201 USA
| | - Shama R Iyer
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Martin F Schneider
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, 108 N. Greene Street, Baltimore, MD 21201 USA
| |
Collapse
|
7
|
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.
Collapse
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
| |
Collapse
|
8
|
Functional assessment of three Rem residues identified as critical for interactions with Ca(2+) channel β subunits. Pflugers Arch 2015; 467:2299-306. [PMID: 25771954 DOI: 10.1007/s00424-015-1700-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 03/04/2015] [Indexed: 12/18/2022]
Abstract
Members of the Rem, Rem2, Rad, Gem/Kir (RGK) family of small GTP-binding proteins inhibit high-voltage-activated (HVA) Ca(2+) channels through interactions with both the principal α1 and the auxiliary β subunits of the channel complex. Three highly conserved residues of Rem (R200, L227, and H229) have been shown in vitro to be critical for interactions with β subunits. However, the functional significance of these residues is not known. To investigate the contributions of R200, L227, and H229 to β subunit-mediated RGK protein-dependent inhibition of HVA channels, we introduced alanine substitutions into all three positions of Venus fluorescent protein-tagged Rem (V-Rem AAA) and made three other V-Rem constructs with an alanine introduced at only one position (V-Rem R200A, V-Rem L227A, and V-Rem H229A). Confocal imaging and immunoblotting demonstrated that each Venus-Rem mutant construct had comparable expression levels to Venus-wild-type Rem when heterologously expressed in tsA201 cells. In electrophysiological experiments, V-Rem AAA failed to inhibit N-type Ca(2+) currents in tsA201 cells coexpressing CaV2.2 α1B, β3, and α2δ-1 channel subunits. The V-Rem L227A single mutant also failed to reduce N-type currents conducted by coexpressed CaV2.2 channels, a finding consistent with the previous observation that a leucine at position 227 is critical for Rem-β interactions. Rem-dependent inhibition of CaV2.2 channels was impaired to a much lesser extent by the R200A substitution. In contrast to the earlier work demonstrating that Rem H229A was unable to interact with β3 subunits in vitro, V-Rem H229A produced nearly complete inhibition of CaV2.2-mediated currents.
Collapse
|
9
|
Buraei Z, Lumen E, Kaur S, Yang J. RGK regulation of voltage-gated calcium channels. SCIENCE CHINA-LIFE SCIENCES 2015; 58:28-38. [PMID: 25576452 PMCID: PMC9074095 DOI: 10.1007/s11427-014-4788-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 09/02/2014] [Indexed: 01/01/2023]
Abstract
Voltage-gated calcium channels (VGCCs) play critical roles in cardiac and skeletal muscle contractions, hormone and neurotransmitter release, as well as slower processes such as cell proliferation, differentiation, migration and death. Mutations in VGCCs lead to numerous cardiac, muscle and neurological disease, and their physiological function is tightly regulated by kinases, phosphatases, G-proteins, calmodulin and many other proteins. Fifteen years ago, RGK proteins were discovered as the most potent endogenous regulators of VGCCs. They are a family of monomeric GTPases (Rad, Rem, Rem2, and Gem/Kir), in the superfamily of Ras GTPases, and they have two known functions: regulation of cytoskeletal dynamics including dendritic arborization and inhibition of VGCCs. Here we review the mechanisms and molecular determinants of RGK-mediated VGCC inhibition, the physiological impact of this inhibition, and recent evidence linking the two known RGK functions.
Collapse
Affiliation(s)
- Zafir Buraei
- Department of Biology, Pace University, New York, NY, 10038, USA,
| | | | | | | |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Yarotskyy V, Dirksen RT. RGK proteins: fashioning muscle with “Rad” new brakes. Channels (Austin) 2014; 8:286-7. [PMID: 25478619 PMCID: PMC5210512 DOI: 10.4161/chan.29982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 06/27/2014] [Indexed: 11/19/2022] Open
Affiliation(s)
- Viktor Yarotskyy
- Department of Pharmacology and Physiology; University of Rochester Medical Center; Rochester, NY USA
| | - Robert T Dirksen
- Department of Pharmacology and Physiology; University of Rochester Medical Center; Rochester, NY USA
| |
Collapse
|