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Endo Y, Groom L, Wang SM, Pannia E, Griffiths NW, Van Gennip JLM, Ciruna B, Laporte J, Dirksen RT, Dowling JJ. Two zebrafish cacna1s loss-of-function variants provide models of mild and severe CACNA1S-related myopathy. Hum Mol Genet 2024; 33:254-269. [PMID: 37930228 PMCID: PMC10800018 DOI: 10.1093/hmg/ddad178] [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: 07/03/2023] [Revised: 09/25/2023] [Accepted: 10/09/2023] [Indexed: 11/07/2023] Open
Abstract
CACNA1S-related myopathy, due to pathogenic variants in the CACNA1S gene, is a recently described congenital muscle disease. Disease associated variants result in loss of gene expression and/or reduction of Cav1.1 protein stability. There is an incomplete understanding of the underlying disease pathomechanisms and no effective therapies are currently available. A barrier to the study of this myopathy is the lack of a suitable animal model that phenocopies key aspects of the disease. To address this barrier, we generated knockouts of the two zebrafish CACNA1S paralogs, cacna1sa and cacna1sb. Double knockout fish exhibit severe weakness and early death, and are characterized by the absence of Cav1.1 α1 subunit expression, abnormal triad structure, and impaired excitation-contraction coupling, thus mirroring the severe form of human CACNA1S-related myopathy. A double mutant (cacna1sa homozygous, cacna1sb heterozygote) exhibits normal development, but displays reduced body size, abnormal facial structure, and cores on muscle pathologic examination, thus phenocopying the mild form of human CACNA1S-related myopathy. In summary, we generated and characterized the first cacna1s zebrafish loss-of-function mutants, and show them to be faithful models of severe and mild forms of human CACNA1S-related myopathy suitable for future mechanistic studies and therapy development.
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Affiliation(s)
- Yukari Endo
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Linda Groom
- Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - Sabrina M Wang
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Emanuela Pannia
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
- Zebrafish Genetics and Disease Models Core Facility, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Nigel W Griffiths
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Jenica L M Van Gennip
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Brian Ciruna
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
| | - Jocelyn Laporte
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Inserm U1258, Cnrs UMR7104, Université de Strasbourg, 1 Rue Laurent Fries, Illkirch 67400, France
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY 14642, United States
| | - James J Dowling
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
- Division of Neurology, Hospital for Sick Children, 555 University Ave, Toronto, ON M5G 1X8, Canada
- Department of Paediatrics, University of Toronto, 555 University Ave, Toronto, ON M5G 1X8, Canada
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Lei PJ, Ruscic KJ, Roh K, Rajotte JJ, O'Melia MJ, Bouta EM, Marquez M, Pereira ER, Kumar AS, Arroyo-Ataz G, Razavi MS, Zhou H, Menzel L, Kumra H, Duquette M, Huang P, Baish JW, Munn LL, Ubellacker JM, Jones D, Padera TP. Lymphatic muscle cells are unique cells that undergo aging induced changes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.18.567621. [PMID: 38014141 PMCID: PMC10680808 DOI: 10.1101/2023.11.18.567621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Lymphatic muscle cells (LMCs) within the wall of collecting lymphatic vessels exhibit tonic and autonomous phasic contractions, which drive active lymph transport to maintain tissue-fluid homeostasis and support immune surveillance. Damage to LMCs disrupts lymphatic function and is related to various diseases. Despite their importance, knowledge of the transcriptional signatures in LMCs and how they relate to lymphatic function in normal and disease contexts is largely missing. We have generated a comprehensive transcriptional single-cell atlas-including LMCs-of collecting lymphatic vessels in mouse dermis at various ages. We identified genes that distinguish LMCs from other types of muscle cells, characterized the phenotypical and transcriptomic changes in LMCs in aged vessels, and uncovered a pro-inflammatory microenvironment that suppresses the contractile apparatus in advanced-aged LMCs. Our findings provide a valuable resource to accelerate future research for the identification of potential drug targets on LMCs to preserve lymphatic vessel function as well as supporting studies to identify genetic causes of primary lymphedema currently with unknown molecular explanation.
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Rossi D, Pierantozzi E, Amadsun DO, Buonocore S, Rubino EM, Sorrentino V. The Sarcoplasmic Reticulum of Skeletal Muscle Cells: A Labyrinth of Membrane Contact Sites. Biomolecules 2022; 12:488. [PMID: 35454077 PMCID: PMC9026860 DOI: 10.3390/biom12040488] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/14/2022] [Accepted: 03/18/2022] [Indexed: 12/17/2022] Open
Abstract
The sarcoplasmic reticulum of skeletal muscle cells is a highly ordered structure consisting of an intricate network of tubules and cisternae specialized for regulating Ca2+ homeostasis in the context of muscle contraction. The sarcoplasmic reticulum contains several proteins, some of which support Ca2+ storage and release, while others regulate the formation and maintenance of this highly convoluted organelle and mediate the interaction with other components of the muscle fiber. In this review, some of the main issues concerning the biology of the sarcoplasmic reticulum will be described and discussed; particular attention will be addressed to the structure and function of the two domains of the sarcoplasmic reticulum supporting the excitation-contraction coupling and Ca2+-uptake mechanisms.
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Affiliation(s)
- Daniela Rossi
- Department of Molecular and Developmental Medicine, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy; (E.P.); (D.O.A.); (S.B.); (E.M.R.); (V.S.)
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Lilliu E, Koenig S, Koenig X, Frieden M. Store-Operated Calcium Entry in Skeletal Muscle: What Makes It Different? Cells 2021; 10:cells10092356. [PMID: 34572005 PMCID: PMC8468011 DOI: 10.3390/cells10092356] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/03/2021] [Accepted: 09/04/2021] [Indexed: 01/26/2023] Open
Abstract
Current knowledge on store-operated Ca2+ entry (SOCE) regarding its localization, kinetics, and regulation is mostly derived from studies performed in non-excitable cells. After a long time of relative disinterest in skeletal muscle SOCE, this mechanism is now recognized as an essential contributor to muscle physiology, as highlighted by the muscle pathologies that are associated with mutations in the SOCE molecules STIM1 and Orai1. This review mainly focuses on the peculiar aspects of skeletal muscle SOCE that differentiate it from its counterpart found in non-excitable cells. This includes questions about SOCE localization and the movement of respective proteins in the highly organized skeletal muscle fibers, as well as the diversity of expressed STIM isoforms and their differential expression between muscle fiber types. The emerging evidence of a phasic SOCE, which is activated during EC coupling, and its physiological implication is described as well. The specific issues related to the use of SOCE modulators in skeletal muscles are discussed. This review highlights the complexity of SOCE activation and its regulation in skeletal muscle, with an emphasis on the most recent findings and the aim to reach a current picture of this mesmerizing phenomenon.
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Affiliation(s)
- Elena Lilliu
- Center for Physiology and Pharmacology, Department of Neurophysiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria;
| | - Stéphane Koenig
- Department of Cell Physiology and Metabolism, University of Geneva, 1201 Geneva, Switzerland;
| | - Xaver Koenig
- Center for Physiology and Pharmacology, Department of Neurophysiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria;
- Correspondence: (X.K.); (M.F.)
| | - Maud Frieden
- Department of Cell Physiology and Metabolism, University of Geneva, 1201 Geneva, Switzerland;
- Correspondence: (X.K.); (M.F.)
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Perni S, Beam K. Neuronal junctophilins recruit specific Ca V and RyR isoforms to ER-PM junctions and functionally alter Ca V2.1 and Ca V2.2. eLife 2021; 10:64249. [PMID: 33769283 PMCID: PMC8046434 DOI: 10.7554/elife.64249] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 03/19/2021] [Indexed: 12/15/2022] Open
Abstract
Junctions between the endoplasmic reticulum and plasma membrane that are induced by the neuronal junctophilins are of demonstrated importance, but their molecular architecture is still poorly understood and challenging to address in neurons. This is due to the small size of the junctions and the multiple isoforms of candidate junctional proteins in different brain areas. Using colocalization of tagged proteins expressed in tsA201 cells, and electrophysiology, we compared the interactions of JPH3 and JPH4 with different calcium channels. We found that JPH3 and JPH4 caused junctional accumulation of all the tested high-voltage-activated CaV isoforms, but not a low-voltage-activated CaV. Also, JPH3 and JPH4 noticeably modify CaV2.1 and CaV2.2 inactivation rate. RyR3 moderately colocalized at junctions with JPH4, whereas RyR1 and RyR2 did not. By contrast, RyR1 and RyR3 strongly colocalized with JPH3, and RyR2 moderately. Likely contributing to this difference, JPH3 binds to cytoplasmic domain constructs of RyR1 and RyR3, but not of RyR2.
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Affiliation(s)
- Stefano Perni
- Department of Physiology and Biophysics, Anschutz Medical Campus, University of Colorado, Aurora, United States
| | - Kurt Beam
- Department of Physiology and Biophysics, Anschutz Medical Campus, University of Colorado, Aurora, United States
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Lawal TA, Wires ES, Terry NL, Dowling JJ, Todd JJ. Preclinical model systems of ryanodine receptor 1-related myopathies and malignant hyperthermia: a comprehensive scoping review of works published 1990-2019. Orphanet J Rare Dis 2020; 15:113. [PMID: 32381029 PMCID: PMC7204063 DOI: 10.1186/s13023-020-01384-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 04/14/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Pathogenic variations in the gene encoding the skeletal muscle ryanodine receptor (RyR1) are associated with malignant hyperthermia (MH) susceptibility, a life-threatening hypermetabolic condition and RYR1-related myopathies (RYR1-RM), a spectrum of rare neuromuscular disorders. In RYR1-RM, intracellular calcium dysregulation, post-translational modifications, and decreased protein expression lead to a heterogenous clinical presentation including proximal muscle weakness, contractures, scoliosis, respiratory insufficiency, and ophthalmoplegia. Preclinical model systems of RYR1-RM and MH have been developed to better understand underlying pathomechanisms and test potential therapeutics. METHODS We conducted a comprehensive scoping review of scientific literature pertaining to RYR1-RM and MH preclinical model systems in accordance with the PRISMA Scoping Reviews Checklist and the framework proposed by Arksey and O'Malley. Two major electronic databases (PubMed and EMBASE) were searched without language restriction for articles and abstracts published between January 1, 1990 and July 3, 2019. RESULTS Our search yielded 5049 publications from which 262 were included in this review. A majority of variants tested in RYR1 preclinical models were localized to established MH/central core disease (MH/CCD) hot spots. A total of 250 unique RYR1 variations were reported in human/rodent/porcine models with 95% being missense substitutions. The most frequently reported RYR1 variant was R614C/R615C (human/porcine total n = 39), followed by Y523S/Y524S (rabbit/mouse total n = 30), I4898T/I4897T/I4895T (human/rabbit/mouse total n = 20), and R163C/R165C (human/mouse total n = 18). The dyspedic mouse was utilized by 47% of publications in the rodent category and its RyR1-null (1B5) myotubes were transfected in 23% of publications in the cellular model category. In studies of transfected HEK-293 cells, 57% of RYR1 variations affected the RyR1 channel and activation core domain. A total of 15 RYR1 mutant mouse strains were identified of which ten were heterozygous, three were compound heterozygous, and a further two were knockout. Porcine, avian, zebrafish, C. elegans, canine, equine, and drosophila model systems were also reported. CONCLUSIONS Over the past 30 years, there were 262 publications on MH and RYR1-RM preclinical model systems featuring more than 200 unique RYR1 variations tested in a broad range of species. Findings from these studies have set the foundation for therapeutic development for MH and RYR1-RM.
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Affiliation(s)
- Tokunbor A Lawal
- National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Emily S Wires
- National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Nancy L Terry
- National Institutes of Health Library, National Institutes of Health, Bethesda, MD, USA
| | - James J Dowling
- Program for Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Joshua J Todd
- National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, 20892, USA.
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Zhang J, Li X, Ismail F, Xu S, Wang Z, Peng X, Yang C, Chang H, Wang H, Gao Y. Priority Strategy of Intracellular Ca 2+ Homeostasis in Skeletal Muscle Fibers During the Multiple Stresses of Hibernation. Cells 2019; 9:cells9010042. [PMID: 31877883 PMCID: PMC7016685 DOI: 10.3390/cells9010042] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 12/19/2019] [Accepted: 12/19/2019] [Indexed: 01/16/2023] Open
Abstract
: Intracellular calcium (Ca2+) homeostasis plays a vital role in the preservation of skeletal muscle. In view of the well-maintained skeletal muscle found in Daurian ground squirrels (Spermophilus dauricus) during hibernation, we hypothesized that hibernators possess unique strategies of intracellular Ca2+ homeostasis. Here, cytoplasmic, sarcoplasmic reticulum (SR), and mitochondrial Ca2+ levels, as well as the potential Ca2+ regulatory mechanisms, were investigated in skeletal muscle fibers of Daurian ground squirrels at different stages of hibernation. The results showed that cytoplasmic Ca2+ levels increased in the skeletal muscle fibers during late torpor (LT) and inter-bout arousal (IBA), and partially recovered when the animals re-entered torpor (early torpor, ET). Furthermore, compared with levels in the summer active or pre-hibernation state, the activity and protein expression levels of six major Ca2+ channels/proteins were up-regulated during hibernation, including the store-operated Ca2+ entry (SOCE), ryanodine receptor 1 (RyR1), leucine zipper-EF-hand containing transmembrane protein 1 (LETM1), SR Ca2+ ATPase 1 (SERCA1), mitochondrial calcium uniporter complex (MCU complex), and calmodulin (CALM). Among these, the increased extracellular Ca2+ influx mediated by SOCE, SR Ca2+ release mediated by RyR1, and mitochondrial Ca2+ extrusion mediated by LETM1 may be triggers for the periodic elevation in cytoplasmic Ca2+ levels observed during hibernation. Furthermore, the increased SR Ca2+ uptake through SERCA1, mitochondrial Ca2+ uptake induced by MCU, and elevated free Ca2+ binding capacity mediated by CALM may be vital strategies in hibernating ground squirrels to attenuate cytoplasmic Ca2+ levels and restore Ca2+ homeostasis during hibernation. Compared with that in LT or IBA, the decreased extracellular Ca2+ influx mediated by SOCE and elevated mitochondrial Ca2+ uptake induced by MCU may be important mechanisms for the partial cytoplasmic Ca2+ recovery in ET. Overall, under extreme conditions, hibernating ground squirrels still possess the ability to maintain intracellular Ca2+ homeostasis.
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Affiliation(s)
- Jie Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
| | - Xiaoyu Li
- Human Functional Genomics Laboratory, Northwest University, Xi’an 710069, China;
| | - Fazeela Ismail
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
| | - Shenhui Xu
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
| | - Zhe Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
| | - Xin Peng
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
| | - Chenxi Yang
- College of Biological Science and Engineering, North Minzu University, Yinchuan 750021, China;
| | - Hui Chang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
- Correspondence: (H.C.); (Y.G.)
| | - Huiping Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
| | - Yunfang Gao
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Northwest University, Ministry of Education, Xi’an 710069, China; (J.Z.); (F.I.); (S.X.); (Z.W.); (X.P.); (H.W.)
- Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi’an 710069, China
- Correspondence: (H.C.); (Y.G.)
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Sanchez C, Berthier C, Allard B, Perrot J, Bouvard C, Tsutsui H, Okamura Y, Jacquemond V. Tracking the sarcoplasmic reticulum membrane voltage in muscle with a FRET biosensor. J Gen Physiol 2018; 150:1163-1177. [PMID: 29899059 PMCID: PMC6080890 DOI: 10.1085/jgp.201812035] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 05/16/2018] [Indexed: 11/20/2022] Open
Abstract
The sarcoplasmic reticulum membrane contains ion channels, but it is unknown whether it experiences voltage changes during cellular activity. By expressing voltage-sensitive fluorescence biosensors in this membrane, Sanchez et al. suggest that it remains electrically silent during muscle activation. Ion channel activity in the plasma membrane of living cells generates voltage changes that are critical for numerous biological functions. The membrane of the endoplasmic/sarcoplasmic reticulum (ER/SR) is also endowed with ion channels, but whether changes in its voltage occur during cellular activity has remained ambiguous. This issue is critical for cell functions that depend on a Ca2+ flux across the reticulum membrane. This is the case for contraction of striated muscle, which is triggered by opening of ryanodine receptor Ca2+ release channels in the SR membrane in response to depolarization of the transverse invaginations of the plasma membrane (the t-tubules). Here, we use targeted expression of voltage-sensitive fluorescence resonance energy transfer (FRET) probes of the Mermaid family in differentiated muscle fibers to determine whether changes in SR membrane voltage occur during depolarization–contraction coupling. In the absence of an SR targeting sequence, FRET signals from probes present in the t-tubule membrane allow calibration of the voltage sensitivity and amplitude of the response to voltage-clamp pulses. Successful SR targeting of the probes was achieved using an N-terminal domain of triadin, which completely eliminates voltage-clamp–activated FRET signals from the t-tubule membrane of transfected fibers. In fibers expressing SR-targeted Mermaid probes, activation of SR Ca2+ release in the presence of intracellular ethyleneglycol-bis(β-amino-ethyl ether)-N,N,N′,N′-tetra acetic acid (EGTA) results in an accompanying FRET signal. We find that this signal results from pH sensitivity of the probe, which detects cytosolic acidification because of the release of protons upon Ca2+ binding to EGTA. When EGTA is substituted with either 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid or the contraction blocker N-benzyl-p-toluene sulfonamide, we find no indication of a substantial change in the FRET response caused by a voltage change. These results suggest that the ryanodine receptor–mediated SR Ca2+ efflux is well balanced by concomitant counterion currents across the SR membrane.
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Affiliation(s)
- Colline Sanchez
- Université Claude Bernard Lyon 1, Institut NeuroMyoGène, Villeurbanne, France
| | - Christine Berthier
- Université Claude Bernard Lyon 1, Institut NeuroMyoGène, Villeurbanne, France
| | - Bruno Allard
- Université Claude Bernard Lyon 1, Institut NeuroMyoGène, Villeurbanne, France
| | - Jimmy Perrot
- Université Claude Bernard Lyon 1, Institut NeuroMyoGène, Villeurbanne, France
| | - Clément Bouvard
- Université Claude Bernard Lyon 1, Institut NeuroMyoGène, Villeurbanne, France
| | - Hidekazu Tsutsui
- Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan.,Bioscience and Bioengineering, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, Japan
| | - Yasushi Okamura
- Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Vincent Jacquemond
- Université Claude Bernard Lyon 1, Institut NeuroMyoGène, Villeurbanne, France
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Franzini-Armstrong C. The relationship between form and function throughout the history of excitation-contraction coupling. J Gen Physiol 2018; 150:189-210. [PMID: 29317466 PMCID: PMC5806676 DOI: 10.1085/jgp.201711889] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Franzini-Armstrong reviews the development of the excitation–contraction coupling field over time. The concept of excitation–contraction coupling is almost as old as Journal of General Physiology. It was understood as early as the 1940s that a series of stereotyped events is responsible for the rapid contraction response of muscle fibers to an initial electrical event at the surface. These early developments, now lost in what seems to be the far past for most young investigators, have provided an endless source of experimental approaches. In this Milestone in Physiology, I describe in detail the experiments and concepts that introduced and established the field of excitation–contraction coupling in skeletal muscle. More recent advances are presented in an abbreviated form, as readers are likely to be familiar with recent work in the field.
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Affiliation(s)
- Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA
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10
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Polster A, Perni S, Filipova D, Moua O, Ohrtman JD, Bichraoui H, Beam KG, Papadopoulos S. Junctional trafficking and restoration of retrograde signaling by the cytoplasmic RyR1 domain. J Gen Physiol 2017; 150:293-306. [PMID: 29284662 PMCID: PMC5806685 DOI: 10.1085/jgp.201711879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/07/2017] [Indexed: 11/20/2022] Open
Abstract
The type 1 ryanodine receptor (RyR1) in skeletal muscle is a homotetrameric protein that releases Ca2+ from the sarcoplasmic reticulum (SR) in response to an "orthograde" signal from the dihydropyridine receptor (DHPR) in the plasma membrane (PM). Additionally, a "retrograde" signal from RyR1 increases the amplitude of the Ca2+ current produced by CaV1.1, the principle subunit of the DHPR. This bidirectional signaling is thought to depend on physical links, of unknown identity, between the DHPR and RyR1. Here, we investigate whether the isolated cytoplasmic domain of RyR1 can interact structurally or functionally with CaV1.1 by producing an N-terminal construct (RyR11:4300) that lacks the C-terminal membrane domain. In CaV1.1-null (dysgenic) myotubes, RyR11:4300 is diffusely distributed, but in RyR1-null (dyspedic) myotubes it localizes in puncta at SR-PM junctions containing endogenous CaV1.1. Fluorescence recovery after photobleaching indicates that diffuse RyR11:4300 is mobile, whereas resistance to being washed out with a large-bore micropipette indicates that the punctate RyR11:4300 stably associates with PM-SR junctions. Strikingly, expression of RyR11:4300 in dyspedic myotubes causes an increased amplitude, and slowed activation, of Ca2+ current through CaV1.1, which is almost identical to the effects of full-length RyR1. Fast protein liquid chromatography indicates that ∼25% of RyR11:4300 in diluted cytosolic lysate of transfected tsA201 cells is present in complexes larger in size than the monomer, and intermolecular fluorescence resonance energy transfer implies that RyR11:4300 is significantly oligomerized within intact tsA201 cells and dyspedic myotubes. A large fraction of these oligomers may be homotetramers because freeze-fracture electron micrographs reveal that the frequency of particles arranged like DHPR tetrads is substantially increased by transfecting RyR-null myotubes with RyR11:4300 In summary, the RyR1 cytoplasmic domain, separated from its SR membrane anchor, retains a tendency toward oligomerization/tetramerization, binds to SR-PM junctions in myotubes only if CaV1.1 is also present and is fully functional in retrograde signaling to CaV1.1.
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Affiliation(s)
- Alexander Polster
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Stefano Perni
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Dilyana Filipova
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
| | - Ong Moua
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Joshua D Ohrtman
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Hicham Bichraoui
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Kurt G Beam
- Department of Physiology and Biophysics, University of Colorado Denver Anschutz Medical Campus, Denver, CO
| | - Symeon Papadopoulos
- Institute of Vegetative Physiology, University Hospital of Cologne, Cologne, Germany
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Takeshima H, Hoshijima M, Song LS. Ca²⁺ microdomains organized by junctophilins. Cell Calcium 2015; 58:349-56. [PMID: 25659516 PMCID: PMC5159448 DOI: 10.1016/j.ceca.2015.01.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/15/2015] [Accepted: 01/16/2015] [Indexed: 11/21/2022]
Abstract
Excitable cells typically possess junctional membrane complexes (JMCs) constructed by the plasma membrane and the endo/sarcoplasmic reticulum (ER/SR) for channel crosstalk. These JMCs are termed triads in skeletal muscle, dyads in cardiac muscle, peripheral couplings in smooth and developing striated muscles, and subsurface cisterns in neurons. Junctophilin subtypes contribute to the formation and maintenance of JMCs by serving as a physical bridge between the plasma membrane and ER/SR membrane in different cell types. In muscle cells, junctophilin deficiency prevents JMC formation and functional crosstalk between cell-surface Ca2+ channels and ER/SR Ca2+ release channels. Human genetic mutations in junctophilin subtypes are linked to congenital hypertrophic cardiomyopathy and neurodegenerative diseases. Furthermore, growing evidence suggests that dysregulation of junctophilins induces pathological alterations in skeletal and cardiac muscle.
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Affiliation(s)
- Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
| | - Masahiko Hoshijima
- Department of Medicine and Center for Research in Biological Systems, University of California, San Diego, CA 92093, USA.
| | - Long-Sheng Song
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
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12
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Distinct regions of triadin are required for targeting and retention at the junctional domain of the sarcoplasmic reticulum. Biochem J 2014; 458:407-17. [DOI: 10.1042/bj20130719] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Three regions contribute to triadin localization to the junctional sarcoplasmic reticulum. Dynamics studies revealed that TR3 mediates triadin stability at junctional sites. The stable association of triadin at the junctional sites is facilitated by interactions with calsequestrin-1.
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13
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Fourest-Lieuvin A, Rendu J, Osseni A, Pernet-Gallay K, Rossi D, Oddoux S, Brocard J, Sorrentino V, Marty I, Fauré J. Role of triadin in the organization of reticulum membrane at the muscle triad. J Cell Sci 2012; 125:3443-53. [PMID: 22505613 DOI: 10.1242/jcs.100958] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The terminal cisternae represent one of the functional domains of the skeletal muscle sarcoplasmic reticulum (SR). They are closely apposed to plasma membrane invaginations, the T-tubules, with which they form structures called triads. In triads, the physical interaction between the T-tubule-anchored voltage-sensing channel DHPR and the SR calcium channel RyR1 is essential because it allows the depolarization-induced calcium release that triggers muscle contraction. This interaction between DHPR and RyR1 is based on the peculiar membrane structures of both T-tubules and SR terminal cisternae. However, little is known about the molecular mechanisms governing the formation of SR terminal cisternae. We have previously shown that ablation of triadins, a family of SR transmembrane proteins that interact with RyR1, induced skeletal muscle weakness in knockout mice as well as a modification of the shape of triads. Here we explore the intrinsic molecular properties of the longest triadin isoform Trisk 95. We show that when ectopically expressed, Trisk 95 can modulate reticulum membrane morphology. The membrane deformations induced by Trisk 95 are accompanied by modifications of the microtubule network organization. We show that multimerization of Trisk 95 by disulfide bridges, together with interaction with microtubules, are responsible for the ability of Trisk 95 to structure reticulum membrane. When domains responsible for these molecular properties are deleted, anchoring of Trisk 95 to the triads in muscle cells is strongly decreased, suggesting that oligomers of Trisk 95 and microtubules contribute to the organization of the SR terminal cisternae in a triad.
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Affiliation(s)
- Anne Fourest-Lieuvin
- INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble 38042, France
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14
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Measurement of calcium release due to inositol trisphosphate receptors in skeletal muscle. Methods Mol Biol 2012; 798:383-93. [PMID: 22130849 DOI: 10.1007/978-1-61779-343-1_22] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Calcium transients elicited by IP(3) receptors upon electrical stimulation of skeletal muscle cells (slow calcium signals) are often hard to visualize due to their relatively small amplitude compared to the large transient originated from ryanodine receptors associated to excitation-contraction coupling. The study of slow calcium transients, however, is relevant due to their function in regulation of muscle gene expression and in the process of excitation-transcription coupling. Discussed here are the procedures used to record slow calcium signals from both cultured mouse myotubes and from cultured adult skeletal muscle fibers.
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15
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Al-Qusairi L, Laporte J. T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases. Skelet Muscle 2011; 1:26. [PMID: 21797990 PMCID: PMC3156648 DOI: 10.1186/2044-5040-1-26] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 07/13/2011] [Indexed: 12/25/2022] Open
Abstract
In skeletal muscle, the excitation-contraction (EC) coupling machinery mediates the translation of the action potential transmitted by the nerve into intracellular calcium release and muscle contraction. EC coupling requires a highly specialized membranous structure, the triad, composed of a central T-tubule surrounded by two terminal cisternae from the sarcoplasmic reticulum. While several proteins located on these structures have been identified, mechanisms governing T-tubule biogenesis and triad formation remain largely unknown. Here, we provide a description of triad structure and plasticity and review the role of proteins that have been linked to T-tubule biogenesis and triad formation and/or maintenance specifically in skeletal muscle: caveolin 3, amphiphysin 2, dysferlin, mitsugumins, junctophilins, myotubularin, ryanodine receptor, and dihydhropyridine Receptor. The importance of these proteins in triad biogenesis and subsequently in muscle contraction is sustained by studies on animal models and by the direct implication of most of these proteins in human myopathies.
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Affiliation(s)
- Lama Al-Qusairi
- Department of Translational Medecine and Neurogenetics, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), 1 rue Laurent Fries, 67404 Illkirch, France.
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16
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Woo JS, Cho CH, Kim DH, Lee EH. TRPC3 cation channel plays an important role in proliferation and differentiation of skeletal muscle myoblasts. Exp Mol Med 2011; 42:614-27. [PMID: 20644344 DOI: 10.3858/emm.2010.42.9.061] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
During membrane depolarization associated with skeletal excitation-contraction (EC) coupling, dihydropyridine receptor [DHPR, a L-type Ca(2+) channel in the transverse (t)-tubule membrane] undergoes conformational changes that are transmitted to ryanodine receptor 1 [RyR1, an internal Ca(2+)-release channel in the sarcoplasmic reticulum (SR) membrane] causing Ca(2+) release from the SR. Canonical-type transient receptor potential cation channel 3 (TRPC3), an extracellular Ca(2+)-entry channel in the t-tubule and plasma membrane, is required for full-gain of skeletal EC coupling. To examine additional role(s) for TRPC3 in skeletal muscle other than mediation of EC coupling, in the present study, we created a stable myoblast line with reduced TRPC3 expression and without alpha1((S))DHPR (MDG/TRPC3 KD myoblast) by knock-down of TRPC3 in alpha1((S))DHPR-null muscular dysgenic (MDG) myoblasts using retrovirus-delivered small interference RNAs in order to eliminate any DHPR-associated EC coupling-related events. Unlike wild-type or alpha1((S))DHPR-null MDG myoblasts, MDG/TRPC3 KD myoblasts exhibited dramatic changes in cellular morphology (e.g., unusual expansion of both cell volume and the plasma membrane, and multi-nuclei) and failed to differentiate into myotubes possibly due to increased Ca(2+) content in the SR. These results suggest that TRPC3 plays an important role in the maintenance of skeletal muscle myoblasts and myotubes.
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Affiliation(s)
- Jin Seok Woo
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
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17
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Pirone A, Schredelseker J, Tuluc P, Gravino E, Fortunato G, Flucher BE, Carsana A, Salvatore F, Grabner M. Identification and functional characterization of malignant hyperthermia mutation T1354S in the outer pore of the Cavalpha1S-subunit. Am J Physiol Cell Physiol 2010; 299:C1345-54. [PMID: 20861472 PMCID: PMC3006335 DOI: 10.1152/ajpcell.00008.2010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Accepted: 09/16/2010] [Indexed: 11/22/2022]
Abstract
To identify the genetic locus responsible for malignant hyperthermia susceptibility (MHS) in an Italian family, we performed linkage analysis to recognized MHS loci. All MHS individuals showed cosegregation of informative markers close to the voltage-dependent Ca(2+) channel (Ca(V)) α(1S)-subunit gene (CACNA1S) with logarithm of odds (LOD)-score values that matched or approached the maximal possible value for this family. This is particularly interesting, because so far MHS was mapped to >178 different positions on the ryanodine receptor (RYR1) gene but only to two on CACNA1S. Sequence analysis of CACNA1S revealed a c.4060A>T transversion resulting in amino acid exchange T1354S in the IVS5-S6 extracellular pore-loop region of Ca(V)α(1S) in all MHS subjects of the family but not in 268 control subjects. To investigate the impact of mutation T1354S on the assembly and function of the excitation-contraction coupling apparatus, we expressed GFP-tagged α(1S)T1354S in dysgenic (α(1S)-null) myotubes. Whole cell patch-clamp analysis revealed that α(1S)T1354S produced significantly faster activation of L-type Ca(2+) currents upon 200-ms depolarizing test pulses compared with wild-type GFP-α(1S) (α(1S)WT). In addition, α(1S)T1354S-expressing myotubes showed a tendency to increased sensitivity for caffeine-induced Ca(2+) release and to larger action-potential-induced intracellular Ca(2+) transients under low (≤ 2 mM) caffeine concentrations compared with α(1S)WT. Thus our data suggest that an additional influx of Ca(2+) due to faster activation of the α(1S)T1354S L-type Ca(2+) current, in concert with higher caffeine sensitivity of Ca(2+) release, leads to elevated muscle contraction under pharmacological trigger, which might be sufficient to explain the MHS phenotype.
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Affiliation(s)
- Antonella Pirone
- Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria
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18
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Franzini-Armstrong C. RyRs: Their Disposition, Frequency, and Relationships with Other Proteins of Calcium Release Units. CURRENT TOPICS IN MEMBRANES 2010; 66:3-26. [PMID: 22353474 DOI: 10.1016/s1063-5823(10)66001-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
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19
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Abstract
JPs (junctophilins) contribute to the formation of junctional membrane complexes in muscle cells by physically linking the t-tubule (transverse-tubule) and SR (sarcoplasmic reticulum) membranes. In humans with HCM (hypertrophic cardiomyopathy), mutations in JP2 are linked to altered Ca2+ signalling in cardiomyocytes; however, the effects of these mutations on skeletal muscle function have not been examined. In the present study, we investigated the role of the dominant-negative JP2-S165F mutation (which is associated with human HCM) in skeletal muscle. Consistent with the hypertrophy observed in human cardiac muscle, overexpression of JP2-S165F in primary mouse skeletal myotubes led to a significant increase in myotube diameter and resting cytosolic Ca2+ concentration. Single myotube Ca2+ imaging experiments showed reductions in both the excitation-contraction coupling gain and RyR (ryanodine receptor) 1-mediated Ca2+ release from the SR. Immunoprecipitation assays revealed defects in the PKC (protein kinase C)-mediated phosphorylation of the JP2-S165F mutant protein at Ser165 and in binding of JP2-S165F to the Ca2+ channel TRPC3 (transient receptor potential cation canonical-type channel 3) on the t-tubule membrane. Therefore both the hypertrophy and altered intracellular Ca2+ signalling in the JP2-S165F-expressing skeletal myotubes can be linked to altered phosphorylation of JP2 and/or altered cross-talk among Ca2+ channels on the t-tubule and SR membranes.
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20
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Rigoard P, Buffenoir K, Wager M, Bauche S, Giot JP, Lapierre F. [Molecular architecture of the sarcoplasmic reticulum and its role in the ECC]. Neurochirurgie 2009; 55 Suppl 1:S83-91. [PMID: 19233437 DOI: 10.1016/j.neuchi.2008.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 05/09/2008] [Indexed: 11/16/2022]
Abstract
The sarcoplasmic reticulum (SR) plays a fundamental role in excitation-contraction coupling, which propagates the electric signal conversion along the muscle fiber's plasmic membrane to a mechanical event manifested as a muscle contraction. It plays a crucial role in calcium homeostasis and intracellular calcium storage control (storage, liberation and uptake) necessary for fiber muscle contraction and then relaxation. These functions take place at the triad, made up of individualized SR subdomains where the protein-specific organization provides efficient and fast coupling. Ryanodine receptors (RyR) and dihydropyridine receptors (DHPR) mainly act in calcium exchanges in the SR. This particular structural and molecular architecture must be correlated to its functional specificity.
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Affiliation(s)
- P Rigoard
- Service de neurochirurgie, CHU La Milétrie, 2, rue de la Milétrie, BP 577, 86021 Poitiers cedex, France.
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21
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Payne AM, Jimenez-Moreno R, Wang ZM, Messi ML, Delbono O. Role of Ca2+, membrane excitability, and Ca2+ stores in failing muscle contraction with aging. Exp Gerontol 2008; 44:261-73. [PMID: 18948183 DOI: 10.1016/j.exger.2008.09.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Revised: 09/18/2008] [Accepted: 09/21/2008] [Indexed: 10/21/2022]
Abstract
Excitation-contraction (EC) coupling in a population of skeletal muscle fibers of aged mice becomes dependent on the presence of external Ca(2+) ions (Payne, A.M., Zheng, Z., Gonzalez, E., Wang, Z.M., Messi, M.L., Delbono, O., 2004b. External Ca(2+)-dependent excitation - contraction coupling in a population of aging mouse skeletal muscle fibers. J. Physiol. 560, 137-155.). However, the mechanism(s) underlying this process remain unknown. In this work, we examined the role of (1) extracellular Ca(2+); (2) voltage-induced influx of external Ca(2+) ions; (3) sarcoplasmic reticulum (SR) Ca(2+) depletion during repeated contractions; (4) store-operated Ca(2+) entry (SOCE); (5) SR ultrastructure; (6) SR subdomain localization of the ryanodine receptor; and (7) sarcolemmal excitability in muscle force decline with aging. These experiments show that external Ca(2+), but not Ca(2+) influx, is needed to maintain force upon repetitive fiber electrical stimulation. Decline in fiber force is associated with depressed SR Ca(2+) release. SR Ca(2+) depletion, SOCE, and the putative segregated Ca(2+) release store do not play a significant role in external Ca(2+)-dependent contraction. More importantly, a significant number of action potentials fail in senescent mouse muscle fibers subjected to a stimulation frequency. These results indicate that failure to generate action potentials accounts for decreased intracellular Ca(2+) mobilization and tetanic force in aging muscle exposed to a Ca(2+)-free medium.
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Affiliation(s)
- Anthony Michael Payne
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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22
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Abstract
The expression of TRPC3 (canonical-type transient receptor potential cation channel type 3) is tightly regulated during skeletal muscle cell differentiation, and a functional interaction between TRPC3 and RyR1 [(ryanodine receptor type 1), an SR (sarcoplasmic reticulum) Ca2+-release channel] regulates the gain of SR Ca2+ release during EC (excitation–contraction) coupling. However, it has not been possible to demonstrate direct protein–protein interactions between TRPC3 and RyR1. To identify possible candidate(s) for a linker protein(s) between TRPC3 and RyR1 in skeletal muscle, in the present study we performed MALDI–TOF (matrix-assisted laser-desorption ionization–time-of-flight) MS analysis of a cross-linked triadic protein complex from rabbit skeletal triad vesicles and co-immunoprecipitation assays using primary mouse skeletal myotubes. From these studies, we found that six triadic proteins, that are known to regulate RyR1 function and/or EC coupling [TRPC1, JP2 (junctophilin 2), homer, mitsugumin 29, calreticulin and calmodulin], interacted directly with TRPC3 in a Ca2+-independent manner. However we again found no direct interaction between TRPC3 and RyR1. TRPC1 was identified as a potential physical link between TRPC3 and RyR1, as it interacted with both TRPC3 and RyR1, and JPs showed subtype-specific interactions with both RyR1 and TRPC3 (JP1–RyR1 and JP2–TRPC3). These results support the hypothesis that TRPC3 and RyR1 are functionally engaged via linker proteins in skeletal muscle.
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23
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Rossi D, Barone V, Giacomello E, Cusimano V, Sorrentino V. The sarcoplasmic reticulum: an organized patchwork of specialized domains. Traffic 2008; 9:1044-9. [PMID: 18266914 DOI: 10.1111/j.1600-0854.2008.00717.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The sarcoplasmic reticulum (SR) of skeletal muscle cells is a convoluted structure composed of a variety of tubules and cisternae, which share a continuous lumen delimited by a single continuous membrane, branching to form a network that surrounds each myofibril. In this network, some specific domains basically represented by the longitudinal SR and the junctional SR can be distinguished. These domains are mainly dedicated to Ca(2+) homeostasis in relation to regulation of muscle contraction, with the longitudinal SR representing the sites of Ca(2+) uptake and storage and the junctional SR representing the sites of Ca(2+) release. To perform its functions, the SR takes contact with other cellular elements, the sarcolemma, the contractile apparatus and the mitochondria, giving rise to a number of interactions, most of which are still to be defined at the molecular level. This review will describe some of the most recent advancements in understanding the organization of this complex network and its specific domains. Furthermore, we shall address initial evidence on how SR proteins are retained at distinct SR domains.
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Affiliation(s)
- Daniela Rossi
- Molecular Medicine Section, Department of Neuroscience and Interuniversitary Institute of Myology, University of Siena, 53100 Siena, Italy
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24
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Ma L, Zhu B, Chen X, Liu J, Guan Y, Ren J. Abnormalities of sarcoplasmic reticulum Ca2+ mobilization in aortic smooth muscle cells from streptozotocin-induced diabetic rats. Clin Exp Pharmacol Physiol 2007; 35:568-73. [PMID: 18067595 DOI: 10.1111/j.1440-1681.2007.04832.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Previously, we found that contractions in response to receptor-dependent (i.e. a(1)-adrenoceptor agonist phenylephrine) and -independent (i.e. cyclopiazonic acid) stimuli are decreased in rat aorta during late diabetes. The aim of the present study was to further investigate the changes of intracellular Ca(2+) homeostasis in diabetic aortic smooth muscle cells. Functional changes of inositol 1,4,5-trisphosphate (IP(3))- and ryanodine-sensitive Ca(2+) stores of the sarcoplasmic reticulum (SR) were evaluated using Fluo-3 acetoxymethyl ester fluorescence, western blot and organ bath techniques. 2. In aortic smooth muscle cells from diabetic rats, the Ca(2+) release and Ca(2+) influx caused by both 10 mmol/L phenylephrine (depletion of IP(3)-sensitive Ca(2+) stores) and 1 mmol/L ryanodine (depletion of ryanodine-sensitive Ca(2+) stores) were both significantly decreased compared with control. Moreover, protein expression levels of IP(3) (260 kDa) and ryanodine receptors (500 kDa) were reduced by 31.8 +/- 7.7 and 69.2 +/- 8.4%, respectively, in aortas from diabetic rats compared with those from control rats. 3. In diabetic rat aorta, phenylephrine-induced contractility was decreased to approximately two-thirds of that in controls, whereas ryanodine alone did not cause obvious contraction in aortas from either control or diabetic rats. 4. The present results suggest that the hyporeactivity of aortic smooth muscle to vasoconstrictors in diabetes results mainly from changes to the IP(3)-sensitive Ca(2+) release pathway. The SR Ca(2+) signalling pathway plays a crucial role in the development of diabetic vascular complications.
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Affiliation(s)
- Li Ma
- Department of Pharmacology, Cardiac and Cerebral Vascular Research Center, Zhongshan Medical College, Sun Yat-Sen University, Guangzhou, China
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25
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Bannister RA. Bridging the myoplasmic gap: recent developments in skeletal muscle excitation–contraction coupling. J Muscle Res Cell Motil 2007; 28:275-83. [PMID: 17899404 DOI: 10.1007/s10974-007-9118-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Accepted: 08/28/2007] [Indexed: 01/17/2023]
Abstract
Conformational coupling between the L-type voltage-gated Ca(2+) channel (or 1,4-dihydropyridine receptor; DHPR) and the ryanodine-sensitive Ca(2+) release channel of the sarcoplasmic reticulum (RyR1) is the mechanistic basis for excitation-contraction (EC) coupling in skeletal muscle. In this article, recent findings regarding the roles of the individual cytoplasmic domains (the amino- and carboxyl-termini, cytoplasmic loops I-II, II-III, and III-IV) of the DHPR alpha(1S) subunit in bi-directional communication with RyR1 will be discussed.
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Affiliation(s)
- Roger A Bannister
- Department of Physiology and Biophysics, School of Medicine, University of Colorado at Denver and Health Sciences Center, RC-1, North Tower, P18-7130, Mail Stop F8307, 12800 E. 19th St, Aurora, CO 80045, USA.
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26
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Sheridan DC, Takekura H, Franzini-Armstrong C, Beam KG, Allen PD, Perez CF. Bidirectional signaling between calcium channels of skeletal muscle requires multiple direct and indirect interactions. Proc Natl Acad Sci U S A 2006; 103:19760-5. [PMID: 17172444 PMCID: PMC1750873 DOI: 10.1073/pnas.0609473103] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have defined regions of the skeletal muscle ryanodine receptor (RyR1) essential for bidirectional signaling with dihydropyridine receptors (DHPRs) and for the organization of DHPR into tetrad arrays by expressing RyR1-RyR3 chimerae in dyspedic myotubes. RyR1-RyR3 constructs bearing RyR1 residues 1-1681 restored wild-type DHPR tetrad arrays and, in part, skeletal-type excitation-contraction (EC) coupling (orthograde signaling) but failed to enhance DHPR Ca(2+) currents (retrograde signaling) to WT RyR1 levels. Within this region, the D2 domain (amino acids 1272-1455), although ineffective on its own, dramatically enhanced the formation of tetrads and EC coupling rescue by constructs that otherwise are only partially effective. These findings suggest that the orthograde signal and DHPR tetrad formation require the contributions of numerous RyR regions. Surprisingly, we found that RyR3, although incapable of supporting EC coupling or tetrad formation, restored a significant level of Ca(2+) current, revealing a functional interaction with the skeletal muscle DHPR. Thus, our data support the hypotheses that (i) the structural/functional link between RyR1 and the skeletal muscle DHPR requires multiple interacting regions, (ii) the D2 domain of RyR1 plays a key role in stabilizing this interaction, and (iii) a form of retrograde signaling from RyR3 to the DHPR occurs in the absence of direct protein-protein interactions.
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Affiliation(s)
- David C. Sheridan
- *University of Colorado Health and Sciences Center, Aurora, CO 80045
| | - Hiroaki Takekura
- National Institute of Fitness and Sports, Kanoya, Kagoshima 891-2393, Japan
| | - Clara Franzini-Armstrong
- University of Pennsylvania, Philadelphia, PA 19104; and
- To whom correspondence may be addressed. E-mail:
or
| | - Kurt G. Beam
- *University of Colorado Health and Sciences Center, Aurora, CO 80045
| | - Paul D. Allen
- Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115
| | - Claudio F. Perez
- Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115
- To whom correspondence may be addressed. E-mail:
or
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27
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Miller G, Peter AK, Espinoza E, Heighway J, Crosbie RH. Over-expression of Microspan, a novel component of the sarcoplasmic reticulum, causes severe muscle pathology with triad abnormalities. J Muscle Res Cell Motil 2006; 27:545-58. [PMID: 16823602 DOI: 10.1007/s10974-006-9069-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2005] [Accepted: 04/25/2006] [Indexed: 11/27/2022]
Abstract
Sarcospan (SSPN) is a core component of the dystrophin-glycoprotein complex (DGC). Multiple SSPN transcripts are ubiquitously expressed and SSPN splicing is disrupted in many lung tumors, suggesting the importance of SSPN-related mRNAs. We describe the isolation of an alternatively spliced isoform of SSPN, which we designate 'microspan' based on its small size relative to SSPN. Microspan has two transmembrane domains and a novel C-terminus. We demonstrate that microspan is not an integral component of the DGC and is not perturbed by the loss of dystrophin. Microspan protein is detected at the sarcoplasmic reticulum (SR) using indirect immunofluorescence and immunoelectron microscopy. Furthermore, microspan purifies with skeletal muscle SR membranes and not transverse tubules. Mice engineered to over-express microspan display severe kyphosis and die at approximately 8 weeks of age. Levels of ryanodine receptor, dihydropyridine receptor, and SERCA-1 are greatly reduced in microspan transgenic muscle. Furthermore, electron microscopy reveals that microspan over-expression causes a dramatic perturbation in triad structure. Our findings suggest that microspan is an important component of the SR and may contribute to excitation-contraction coupling.
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MESH Headings
- 3' Untranslated Regions
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Calcium Channels, L-Type/analysis
- Carrier Proteins/biosynthesis
- Carrier Proteins/chemistry
- Carrier Proteins/genetics
- Carrier Proteins/isolation & purification
- Chromosomes, Human, Pair 12
- Dystrophin/chemistry
- Exons
- Fluorescent Antibody Technique
- Glycoproteins/chemistry
- Humans
- Introns
- Membrane Proteins/biosynthesis
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/isolation & purification
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Models, Biological
- Molecular Sequence Data
- Molecular Weight
- Muscle Contraction/physiology
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiology
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/chemistry
- Neoplasm Proteins/genetics
- Neoplasm Proteins/isolation & purification
- Protein Isoforms/chemistry
- Protein Isoforms/genetics
- Protein Isoforms/isolation & purification
- Protein Isoforms/metabolism
- Protein Structure, Secondary
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- Rabbits
- Ryanodine Receptor Calcium Release Channel/analysis
- Sarcoplasmic Reticulum/chemistry
- Sarcoplasmic Reticulum Calcium-Transporting ATPases/analysis
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Affiliation(s)
- Gaynor Miller
- Department of Physiological Science, University of California Los Angeles, Los Angeles, CA 90095, USA
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Lee EH, Cherednichenko G, Pessah IN, Allen PD. Functional coupling between TRPC3 and RyR1 regulates the expressions of key triadic proteins. J Biol Chem 2006; 281:10042-8. [PMID: 16484216 DOI: 10.1074/jbc.m600981200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown that TRPC3 (transient receptor potential channel canonical type 3) is sharply up-regulated during the early part of myotube differentiation and remains elevated in mature myotubes compared with myoblasts. To examine its functional roles in muscle, TRPC3 was "knocked down" in mouse primary skeletal myoblasts using retroviral-delivered small interference RNAs and single cell cloning. TRPC3 knockdown myoblasts (97.6 +/- 1.9% reduction in mRNA) were differentiated into myotubes (TRPC3 KD) and subjected to functional and biochemical assays. By measuring rates of Mn(2+) influx with Fura-2 and Ca(2+) transients with Fluo-4, we found that neither excitation-coupled Ca(2+) entry nor thapsigargin-induced store-operated Ca(2+) entry was significantly altered in TRPC3 KD, indicating that expression of TRPC3 is not required for engaging either Ca(2+) entry mechanism. In Ca(2+) imaging experiments, the gain of excitation-contraction coupling and the amplitude of the Ca(2+) release seen after direct RyR1 activation with caffeine was significantly reduced in TRPC3 KD. The decreased gain appears to be due to a decrease in RyR1 Ca(2+) release channel activity, because sarcoplasmic reticulum (SR) Ca(2+) content was not different between TRPC3 KD and wild-type myotubes. Immunoblot analysis demonstrated that TRPC1, calsequestrin, triadin, and junctophilin 1 were up-regulated (1.46 +/- 1.91-, 1.42 +/- 0.08-, 2.99 +/- 0.32-, and 1.91 +/- 0.26-fold, respectively) in TRPC3 KD. Based on these data, we conclude that expression of TRPC3 is tightly regulated during muscle cell differentiation and propose that functional interaction between TRPC3 and RyR1 may regulate the gain of SR Ca(2+) release independent of SR Ca(2+) load.
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Affiliation(s)
- Eun Hui Lee
- Laboratory of Calcium Communication, Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea
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29
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Sanyal S, Jennings T, Dowse H, Ramaswami M. Conditional mutations in SERCA, the Sarco-endoplasmic reticulum Ca2+-ATPase, alter heart rate and rhythmicity in Drosophila. J Comp Physiol B 2005; 176:253-63. [PMID: 16320060 DOI: 10.1007/s00360-005-0046-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Revised: 09/27/2005] [Accepted: 10/10/2005] [Indexed: 10/25/2022]
Abstract
To analyze the role of cytosolic calcium in regulating heart beat frequency and rhythm, we studied conditional mutations in Drosophila Sarco-endoplasmic reticulum Ca2+-ATPase, believed to be predominantly responsible for sequestering free cytosolic calcium. Abnormalities in the amount or structure of the SERCA protein have been linked to cardiac malfunction in mammals. Drosophila SERCA protein (dSERCA) is highly enriched in Drosophila larval heart with a distinct membrane distribution of SERCA at cardiac Z-lines, suggesting evolutionarily conserved zones for calcium uptake into the sarcoplasmic reticulum. Heart beat frequency is strikingly reduced in mutant animals following dSERCA inactivation, (achieved by a brief exposure of these conditional mutants to non-permissive temperature). Cardiac contractions also show abnormal rhythmicity and electrophysiological recordings from the heart muscle reveal dramatic alterations in electrical activity. Overall, these studies underscore the utility of the Drosophila heart to model SERCA dysfunction dependent cardiac disorders and constitute an initial step towards developing Drosophila as a viable genetic model system to study conserved molecular determinants of cardiac physiology.
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Affiliation(s)
- Subhabrata Sanyal
- Molecular and Cellular Biology Department and ARL Division of Neurobiology, University of Arizona, 1007 E. Lowell Street, Life Sciences South, AZ, Tucson, USA.
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30
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Weiss RG, O'Connell KMS, Flucher BE, Allen PD, Grabner M, Dirksen RT. Functional analysis of the R1086H malignant hyperthermia mutation in the DHPR reveals an unexpected influence of the III-IV loop on skeletal muscle EC coupling. Am J Physiol Cell Physiol 2004; 287:C1094-102. [PMID: 15201141 DOI: 10.1152/ajpcell.00173.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Malignant hyperthermia (MH) is an inherited pharmacogenetic disorder caused by mutations in the skeletal muscle ryanodine receptor (RyR1) and the dihydropyridine receptor (DHPR) alpha(1S)-subunit. We characterized the effects of an MH mutation in the DHPR cytoplasmic III-IV loop of alpha(1S) (R1086H) on DHPR-RyR1 coupling after reconstitution in dysgenic (alpha(1S) null) myotubes. Compared with wild-type alpha(1S), caffeine-activated Ca(2+) release occurred at approximately fivefold lower concentrations in nonexpressing and R1086H-expressing myotubes. Although maximal voltage-gated Ca(2+) release was similar in alpha(1S)- and R1086H-expressing myotubes, the voltage dependence of Ca(2+) release was shifted approximately 5 mV to more negative potentials in R1086H-expressing myotubes. Our results demonstrate that alpha(1S) functions as a negative allosteric modulator of release channel activation by caffeine/voltage and that the R1086H MH mutation in the intracellular III-IV linker disrupts this negative regulatory influence. Moreover, a low caffeine concentration (2 mM) caused a similar shift in voltage dependence of Ca(2+) release in alpha(1S)- and R1086H-expressing myotubes. Compared with alpha(1S)-expressing myotubes, maximal L channel conductance (G(max)) was reduced in R1086H-expressing myotubes (alpha(1S) 130 +/- 10.2, R1086H 88 +/- 6.8 nS/nF; P < 0.05). The decrease in G(max) did not result from a change in retrograde coupling with RyR1 as maximal conductance-charge movement ratio (G(max)/Q(max)) was similar in alpha(1S)- and R1086H-expressing myotubes and a similar decrease in G(max) was observed for an analogous mutation engineered into the cardiac L channel (R1217H). In addition, both R1086H and R1217H DHPRs targeted normally and colocalized with RyR1 in sarcoplasmic reticulum (SR)-sarcolemmal junctions. These results indicate that the R1086H MH mutation in alpha(1S) enhances RyR1 sensitivity to activation by both endogenous (voltage sensor) and exogenous (caffeine) activators.
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Affiliation(s)
- Regina G Weiss
- Department of Biochemical Pharmacology, Innsbruck Medical Univ., Peter-Mayr-Strasse 1, A-6020 Innsbruck, Austria
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Beard NA, Laver DR, Dulhunty AF. Calsequestrin and the calcium release channel of skeletal and cardiac muscle. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2004; 85:33-69. [PMID: 15050380 DOI: 10.1016/j.pbiomolbio.2003.07.001] [Citation(s) in RCA: 201] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Calsequestrin is by far the most abundant Ca(2+)-binding protein in the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle. It allows the Ca2+ required for contraction to be stored at total concentrations of up to 20mM, while the free Ca2+ concentration remains at approximately 1mM. This storage capacity confers upon muscle the ability to contract frequently with minimal run-down in tension. Calsequestrin is highly acidic, containing up to 50 Ca(2+)-binding sites, which are formed simply by clustering of two or more acidic residues. The Kd for Ca2+ binding is between 1 and 100 microM, depending on the isoform, species and the presence of other cations. Calsequestrin monomers have a molecular mass of approximately 40 kDa and contain approximately 400 residues. The monomer contains three domains each with a compact alpha-helical/beta-sheet thioredoxin fold which is stable in the presence of Ca2+. The protein polymerises when Ca2+ concentrations approach 1mM. The polymer is anchored at one end to ryanodine receptor (RyR) Ca2+ release channels either via the intrinsic membrane proteins triadin and junctin or by binding directly to the RyR. It is becoming clear that calsequestrin has several functions in the lumen of the SR in addition to its well-recognised role as a Ca2+ buffer. Firstly, it is a luminal regulator of RyR activity. When triadin and junctin are present, calsequestrin maximally inhibits the Ca2+ release channel when the free Ca2+ concentration in the SR lumen is 1mM. The inhibition is relieved when the Ca2+ concentration alters, either because of small changes in the conformation of calsequestrin or its dissociation from the junctional face membrane. These changes in calsequestrin's association with the RyR amplify the direct effects of luminal Ca2+ concentration on RyR activity. In addition, calsequestrin activates purified RyRs lacking triadin and junctin. Further roles for calsequestrin are indicated by the kinase activity of the protein, its thioredoxin-like structure and its influence over store operated Ca2+ entry. Clearly, calsequestrin plays a major role in calcium homeostasis that extends well beyond its ability to buffer Ca2+ ions.
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Affiliation(s)
- N A Beard
- John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra 2601, Australia
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Lee EH, Lopez JR, Li J, Protasi F, Pessah IN, Kim DH, Allen PD. Conformational coupling of DHPR and RyR1 in skeletal myotubes is influenced by long-range allosterism: evidence for a negative regulatory module. Am J Physiol Cell Physiol 2003; 286:C179-89. [PMID: 13679303 DOI: 10.1152/ajpcell.00176.2003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Four ryanodine receptor type 1 and 2 chimeras (R4, R9, R10, and R16) and their respective wild-type ryanodine receptors (type 1 and 2; wtRyR1 and wtRyR2) were expressed in dyspedic 1B5 to identify possible negative regulatory modules of the Ca2+ release channel that are under the influence of the dihydropyridine receptor (DHPR). Responses of intact 1B5 myotubes expressing each construct to caffeine in the absence or presence of either La3+ and Cd2+ or the organic DHPR blocker nifedipine were determined by imaging single 1B5 myotubes loaded with fluo 4. The presence of La3+ and Cd2+ or nifedipine in the external medium at concentrations known to block Ca2+ entry through the DHPRs significantly decreased the caffeine EC50 of wtRyR1 (2.80 +/- 0.12 to 0.83 +/- 0.09 mM; P < 0.05). On the other hand, DHPR blockade did not significantly alter the caffeine EC50 values of wtRyR2, chimeras R10 and R16, whereas the caffeine EC50 values of chimeras R4 and R9 were significantly increased (1.27 +/- 0.05 to 2.60 +/- 0.16 mM, and 1.15 +/- 0.03 to 2.11 +/- 0.32 mM, respectively; P < 0.05). Despite the fact that all the chimeras form fully functional Ca2+ release channels in situ, sarcoplasmic reticulum (SR) containing R4, R10, and R16 did not possess high-affinity binding of [3H]ryanodine regardless of Ca2+ concentration. These results suggest the presence of an interaction between RyR1 and the DHPR, which is not present in RyR2, that contributes negative control of SR Ca2+ release induced by direct agonists such as caffeine. Although we were unable to define the negative module using RyR1-RyR2 chimeras, they further demonstrated that the RyR is very sensitive to long-range allosterism.
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Affiliation(s)
- Eun Hui Lee
- Department of Anesthesia Research, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Launikonis BS, Barnes M, Stephenson DG. Identification of the coupling between skeletal muscle store-operated Ca2+ entry and the inositol trisphosphate receptor. Proc Natl Acad Sci U S A 2003; 100:2941-4. [PMID: 12601149 PMCID: PMC151445 DOI: 10.1073/pnas.0536227100] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Examination of store-operated Ca(2+) entry (SOC) in single, mechanically skinned skeletal muscle cells by confocal microscopy shows that the inositol 1,4,5-trisphosphate (IP(3)) receptor acts as a sarcoplasmic reticulum [Ca(2+)] sensor and mediates SOC by physical coupling without playing a key role in Ca(2+) release from internal stores, as is the case with various cell types in which SOC was investigated previously. The results have broad implications for understanding the mechanism of SOC that is essential for cell function in general and muscle function in particular. Moreover, the study ascribes an important role to the IP(3) receptors in skeletal muscle, the role of which with respect to Ca(2+) homeostasis was ill defined until now.
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Tijskens P, Meissner G, Franzini-Armstrong C. Location of ryanodine and dihydropyridine receptors in frog myocardium. Biophys J 2003; 84:1079-92. [PMID: 12547789 PMCID: PMC1302685 DOI: 10.1016/s0006-3495(03)74924-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2002] [Accepted: 10/17/2002] [Indexed: 11/16/2022] Open
Abstract
Frog myocardium depends almost entirely on calcium entry from extracellular spaces for its beat-to-beat activation. Atrial myocardium additionally shows internal calcium release under certain conditions, but internal release in the ventricle is absent or very low. We have examined the content and distribution of the sarcoplasmic reticulum (SR) calcium release channels (ryanodine receptors, RyRs) and the surface membrane calcium channels (dihydropyridine receptors, DHPRs) in myocardium from the two atria and the ventricle of the frog heart using binding of radioactive ryanodine, immunolabeling of RyR and DHPR, and thin section and freeze-fracture electron microscopy. In cells from both types of chambers, the SR forms peripheral couplings and in both chambers peripheral couplings colocalize with clusters of DHPRs. However, although a low level of high affinity binding of ryanodine is detectable and RyRs are present in peripheral couplings of the atrium, the ventricle shows essentially no ryanodine binding and RyRs are not detectable either by electron microscopy or immunolabeling. The results are consistent with the lack of internal calcium release in the ventricle, and raise questions regarding the significance of DHPR at peripheral couplings in the absence of RyR. Interestingly, the free SR membrane in both heart chambers shows a low but equal density of intramembrane particles representing the Ca(2+) ATPase.
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Affiliation(s)
- Pierre Tijskens
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6058, USA
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Araya R, Liberona JL, Cárdenas JC, Riveros N, Estrada M, Powell JA, Carrasco MA, Jaimovich E. Dihydropyridine receptors as voltage sensors for a depolarization-evoked, IP3R-mediated, slow calcium signal in skeletal muscle cells. J Gen Physiol 2003; 121:3-16. [PMID: 12508050 PMCID: PMC2217318 DOI: 10.1085/jgp.20028671] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The dihydropyridine receptor (DHPR), normally a voltage-dependent calcium channel, functions in skeletal muscle essentially as a voltage sensor, triggering intracellular calcium release for excitation-contraction coupling. In addition to this fast calcium release, via ryanodine receptor (RYR) channels, depolarization of skeletal myotubes evokes slow calcium waves, unrelated to contraction, that involve the cell nucleus (Jaimovich, E., R. Reyes, J.L. Liberona, and J.A. Powell. 2000. Am. J. Physiol. Cell Physiol. 278:C998-C1010). We tested the hypothesis that DHPR may also be the voltage sensor for these slow calcium signals. In cultures of primary rat myotubes, 10 micro M nifedipine (a DHPR inhibitor) completely blocked the slow calcium (fluo-3-fluorescence) transient after 47 mM K(+) depolarization and only partially reduced the fast Ca(2+) signal. Dysgenic myotubes from the GLT cell line, which do not express the alpha(1) subunit of the DHPR, did not show either type of calcium transient following depolarization. After transfection of the alpha(1) DNA into the GLT cells, K(+) depolarization induced slow calcium transients that were similar to those present in normal C(2)C(12) and normal NLT cell lines. Slow calcium transients in transfected cells were blocked by nifedipine as well as by the G protein inhibitor, pertussis toxin, but not by ryanodine, the RYR inhibitor. Since slow Ca(2+) transients appear to be mediated by IP(3), we measured the increase of IP(3) mass after K(+) depolarization. The IP(3) transient seen in control cells was inhibited by nifedipine and was absent in nontransfected dysgenic cells, but alpha(1)-transfected cells recovered the depolarization-induced IP(3) transient. In normal myotubes, 10 micro M nifedipine, but not ryanodine, inhibited c-jun and c-fos mRNA increase after K(+) depolarization. These results suggest a role for DHPR-mediated calcium signals in regulation of early gene expression. A model of excitation-transcription coupling is presented in which both G proteins and IP(3) appear as important downstream mediators after sensing of depolarization by DHPR.
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Affiliation(s)
- Roberto Araya
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 6530499, Chile
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