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Romer SH, Metzger S, Peraza K, Wright MC, Jobe DS, Song LS, Rich MM, Foy BD, Talmadge RJ, Voss AA. A mouse model of Huntington's disease shows altered ultrastructure of transverse tubules in skeletal muscle fibers. J Gen Physiol 2021; 153:211860. [PMID: 33683318 PMCID: PMC7931643 DOI: 10.1085/jgp.202012637] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 11/05/2020] [Accepted: 01/26/2021] [Indexed: 12/12/2022] Open
Abstract
Huntington’s disease (HD) is a fatal and progressive condition with severe debilitating motor defects and muscle weakness. Although classically recognized as a neurodegenerative disorder, there is increasing evidence of cell autonomous toxicity in skeletal muscle. We recently demonstrated that skeletal muscle fibers from the R6/2 model mouse of HD have a decrease in specific membrane capacitance, suggesting a loss of transverse tubule (t-tubule) membrane in R6/2 muscle. A previous report also indicated that Cav1.1 current was reduced in R6/2 skeletal muscle, suggesting defects in excitation–contraction (EC) coupling. Thus, we hypothesized that a loss and/or disruption of the skeletal muscle t-tubule system contributes to changes in EC coupling in R6/2 skeletal muscle. We used live-cell imaging with multiphoton confocal microscopy and transmission electron microscopy to assess the t-tubule architecture in late-stage R6/2 muscle and found no significant differences in the t-tubule system density, regularity, or integrity. However, electron microscopy images revealed that the cross-sectional area of t-tubules at the triad were 25% smaller in R6/2 compared with age-matched control skeletal muscle. Computer simulation revealed that the resulting decrease in the R6/2 t-tubule luminal conductance contributed to, but did not fully explain, the reduced R6/2 membrane capacitance. Analyses of bridging integrator-1 (Bin1), which plays a primary role in t-tubule formation, revealed decreased Bin1 protein levels and aberrant splicing of Bin1 mRNA in R6/2 muscle. Additionally, the distance between the t-tubule and sarcoplasmic reticulum was wider in R6/2 compared with control muscle, which was associated with a decrease in junctophilin 1 and 2 mRNA levels. Altogether, these findings can help explain dysregulated EC coupling and motor impairment in Huntington’s disease.
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Affiliation(s)
- Shannon H Romer
- Department of Biological Sciences, Wright State University, Dayton, OH.,Odyssey Systems, Environmental Health Effects Laboratory, Navy Medical Research Unit, Dayton, Wright-Patterson Air Force Base, Dayton, OH
| | - Sabrina Metzger
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, OH
| | - Kristiana Peraza
- Department of Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA
| | - Matthew C Wright
- Department of Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA
| | - D Scott Jobe
- Department of Biological Sciences, Wright State University, Dayton, OH
| | - Long-Sheng Song
- Division of Cardiovascular Medicine, Department of Internal Medicine, Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA
| | - Mark M Rich
- Department of Neuroscience, Cell Biology, and Physiology, Wright State University, Dayton, OH
| | - Brent D Foy
- Department of Physics, Wright State University, Dayton, OH
| | - Robert J Talmadge
- Department of Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA
| | - Andrew A Voss
- Department of Biological Sciences, Wright State University, Dayton, OH
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2
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Gibbs ZA, Reza LC, Cheng CC, Westcott JM, McGlynn K, Whitehurst AW. The testis protein ZNF165 is a SMAD3 cofactor that coordinates oncogenic TGFβ signaling in triple-negative breast cancer. eLife 2020; 9:57679. [PMID: 32515734 PMCID: PMC7302877 DOI: 10.7554/elife.57679] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 06/09/2020] [Indexed: 12/19/2022] Open
Abstract
Cancer/testis (CT) antigens are proteins whose expression is normally restricted to germ cells yet aberrantly activated in tumors, where their functions remain relatively cryptic. Here we report that ZNF165, a CT antigen frequently expressed in triple-negative breast cancer (TNBC), associates with SMAD3 to modulate transcription of transforming growth factor β (TGFβ)-dependent genes and thereby promote growth and survival of human TNBC cells. In addition, we identify the KRAB zinc finger protein, ZNF446, and its associated tripartite motif protein, TRIM27, as obligate components of the ZNF165-SMAD3 complex that also support tumor cell viability. Importantly, we find that TRIM27 alone is necessary for ZNF165 transcriptional activity and is required for TNBC tumor growth in vivo using an orthotopic xenograft model in immunocompromised mice. Our findings indicate that aberrant expression of a testis-specific transcription factor is sufficient to co-opt somatic transcriptional machinery to drive a pro-tumorigenic gene expression program in TNBC.
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Affiliation(s)
- Zane A Gibbs
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, United States
| | - Luis C Reza
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, United States
| | - Chun-Chun Cheng
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, United States
| | - Jill M Westcott
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, United States
| | - Kathleen McGlynn
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, United States
| | - Angelique W Whitehurst
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, United States
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Beqollari D, Dockstader K, Bannister RA. A skeletal muscle L-type Ca 2+ channel with a mutation in the selectivity filter (Ca V1.1 E1014K) conducts K<sup/>. J Biol Chem 2018; 293:3126-3133. [PMID: 29326166 DOI: 10.1074/jbc.m117.812446] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 01/04/2018] [Indexed: 12/17/2022] Open
Abstract
A glutamate-to-lysine substitution at position 1014 within the selectivity filter of the skeletal muscle L-type Ca2+ channel (CaV1.1) abolishes Ca2+ flux through the channel pore. Mice engineered to exclusively express the mutant channel display accelerated muscle fatigue, changes in muscle composition, and altered metabolism relative to wildtype littermates. By contrast, mice expressing another mutant CaV1.1 channel that is impermeable to Ca2+ (CaV1.1 N617D) have shown no detectable phenotypic differences from wildtype mice to date. The major biophysical difference between the CaV1.1 E1014K and CaV1.1 N617D mutants elucidated thus far is that the former channel conducts robust Na+ and Cs+ currents in patch-clamp experiments, but neither of these monovalent conductances seems to be of relevance in vivo Thus, the basis for the different phenotypes of these mutants has remained enigmatic. We now show that CaV1.1 E1014K readily conducts 1,4-dihydropyridine-sensitive K+ currents at depolarizing test potentials, whereas CaV1.1 N617D does not. Our observations, coupled with a large body of work by others regarding the role of K+ accumulation in muscle fatigue, raise the possibility that the introduction of an additional K+ flux from the myoplasm into the transverse-tubule lumen accelerates the onset of fatigue and precipitates the metabolic changes observed in CaV1.1 E1014K muscle. These results, highlighting an unexpected consequence of a channel mutation, may help define the complex mechanisms underlying skeletal muscle fatigue and related dysfunctions.
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Affiliation(s)
- Donald Beqollari
- From the Department of Medicine, Cardiology Division, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Karen Dockstader
- From the Department of Medicine, Cardiology Division, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Roger A Bannister
- From the Department of Medicine, Cardiology Division, University of Colorado School of Medicine, Aurora, Colorado 80045
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Xing W, Gao C, Qi D, Zhang Y, Hao P, Dai G, Yan G. Enhanced effect of VEGF165 on L-type calcium currents in guinea-pig cardiac ventricular myocytes. Biomed Pharmacother 2017; 85:697-703. [DOI: 10.1016/j.biopha.2016.11.082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 11/09/2016] [Accepted: 11/18/2016] [Indexed: 02/08/2023] Open
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Beqollari D, Romberg CF, Filipova D, Papadopoulos S, Bannister RA. 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] [What about the content of this article? (0)] [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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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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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] [What about the content of this article? (0)] [Affiliation(s)] [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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