1
|
Youhanna S, Bruton J, Jardemark K, Westerblad H, Lauschke VM. Calcium measurements in enzymatically dissociated or mechanically microdissected mouse primary skeletal muscle fibers. STAR Protoc 2023; 4:102260. [PMID: 37126446 PMCID: PMC10165447 DOI: 10.1016/j.xpro.2023.102260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/23/2023] [Accepted: 03/30/2023] [Indexed: 05/02/2023] Open
Abstract
Here, we provide a protocol for isolation of mouse primary skeletal muscle fibers using two alternative approaches-enzymatic dissociation or mechanical microdissection. We describe the procedures for surgical removal of muscle of interest and isolation of intact single-muscle fibers by either collagenase digestion or mechanical microdissection. We then detail intracellular calcium measurements by microinjecting or loading the isolated muscle fibers with membrane permeable calcium dyes. Finally, we outline steps for intracellular calcium quantification by fluorescent measurement. For complete details on the use and execution of this protocol, please refer to Gineste et al.1.
Collapse
Affiliation(s)
- Sonia Youhanna
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Joseph Bruton
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Kent Jardemark
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden.
| | - Volker M Lauschke
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden; Dr Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany; University of Tuebingen, Tuebingen, Germany.
| |
Collapse
|
2
|
Idoux R, Bretaud S, Berthier C, Ruggiero F, Jacquemond V, Allard B. Superfast excitation-contraction coupling in adult zebrafish skeletal muscle fibers. J Gen Physiol 2022; 154:213310. [PMID: 35767225 PMCID: PMC9247716 DOI: 10.1085/jgp.202213158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 06/15/2022] [Indexed: 12/16/2022] Open
Abstract
The zebrafish has emerged as a very relevant animal model for probing the pathophysiology of human skeletal muscle disorders. This vertebrate animal model displays a startle response characterized by high-frequency swimming activity powered by contraction of fast skeletal muscle fibers excited at extremely high frequencies, critical for escaping predators and capturing prey. Such intense muscle performance requires extremely fast properties of the contractile machinery but also of excitation-contraction coupling, the process by which an action potential spreading along the sarcolemma induces a change in configuration of the dihydropyridine receptors, resulting in intramembrane charge movements, which in turn triggers the release of Ca2+ from the sarcoplasmic reticulum. However, thus far, the fastest Ca2+ transients evoked by vertebrate muscle fibers has been described in muscles used to produce sounds, such as those in the toadfish swim bladder, but not in muscles used for locomotion. By performing intracellular Ca2+ measurements under voltage control in isolated fast skeletal muscle fibers from adult zebrafish and mouse, we demonstrate that fish fast muscle fibers display superfast kinetics of action potentials, intramembrane charge movements, and action potential-evoked Ca2+ transient, allowing fusion and fused sustained Ca2+ transients at frequencies of excitation much higher than in mouse fast skeletal muscle fibers and comparable to those recorded in muscles producing sounds. The present study is the first demonstration of superfast kinetics of excitation-contraction coupling in skeletal muscle allowing superfast locomotor behaviors in a vertebrate.
Collapse
Affiliation(s)
- Romane Idoux
- Institut de Physiopathologie et Génétique du Neurone et du Muscle (PGNM), Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR 5261, INSERM U1315, Faculté de Médecine Rockefeller, Lyon, France
| | - Sandrine Bretaud
- Institut de Génomique Fonctionnelle de Lyon (IGFL), École normale supérieure de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR 5242, Lyon, France
| | - Christine Berthier
- Institut de Physiopathologie et Génétique du Neurone et du Muscle (PGNM), Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR 5261, INSERM U1315, Faculté de Médecine Rockefeller, Lyon, France
| | - Florence Ruggiero
- Institut de Génomique Fonctionnelle de Lyon (IGFL), École normale supérieure de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR 5242, Lyon, France
| | - Vincent Jacquemond
- Institut de Physiopathologie et Génétique du Neurone et du Muscle (PGNM), Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR 5261, INSERM U1315, Faculté de Médecine Rockefeller, Lyon, France
| | - Bruno Allard
- Institut de Physiopathologie et Génétique du Neurone et du Muscle (PGNM), Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR 5261, INSERM U1315, Faculté de Médecine Rockefeller, Lyon, France,Correspondence to Bruno Allard:
| |
Collapse
|
3
|
Chan S, Kueh SLL, Morley JW, Head SI. Sarcoplasmic reticulum calcium handling in unbranched, immediately post-necrotic fast-twitch mdx fibres is similar to wild-type littermates. Exp Physiol 2022; 107:601-614. [PMID: 35471703 DOI: 10.1113/ep090057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 04/19/2022] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS Central question: What are the early effects of dystrophin deficiency on SR Ca2+ handling in the mdx mouse? MAIN FINDING In the mdx mouse, Ca2+ handling by the SR is little affected by the absence of dystrophin when looking at fibres without branches that have just regenerated following massive myonecrosis. This has important implications for our understanding of Ca2+ pathology in the mdx mouse. ABSTRACT There is a variety of results in the literature regarding the effects of dystrophin deficiency on the Ca2+ -handling properties of the SR in mdx mice, an animal model of Duchenne muscular dystrophy. One possible source of variation is the presence of branched fibres. Fibre branching, a consequence of degenerative-regenerative processes such as muscular dystrophy, has in itself a significant influence on the function of the SR. In our present study we attempt to detect early effects of dystrophin deficiency on SR Ca2+ handling by using unbranched fibres from the immediate post-necrotic stage in mdx mice (just regenerated following massive necrosis). Using kinetically-corrected Fura-2 fluorescence signals measured during twitch and tetanus, we analysed the amplitude, rise time and decay time of Δ[Ca2+ ]i in unfatigued and fatigued fibres. Decay was also resolved into SR pump and SR leak components. Fibres from mdx mice were similar in all respects to fibres from wt littermates apart from: (i) a smaller amplitude of the initial spike of Δ[Ca2+ ]i during a tetanus; and (ii) a mitigation of the fall in Δ[Ca2+ ]i amplitude during the course of fatigue. Our findings suggest that the early effects of a loss of dystrophin on SR Ca2+ handling in mdx mice are subtle, and emphasise the importance of distinguishing between Ca2+ pathology that is due to lack of dystrophin and Ca2+ pathology that is due to muscle degeneration. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Stephen Chan
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia.,Department of Physiology, Faculty of Science, Mahidol University, Ratchatewi, Bangkok, Thailand
| | - Sindy L L Kueh
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia
| | - Stewart I Head
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia
| |
Collapse
|
4
|
Mareedu S, Million ED, Duan D, Babu GJ. Abnormal Calcium Handling in Duchenne Muscular Dystrophy: Mechanisms and Potential Therapies. Front Physiol 2021; 12:647010. [PMID: 33897454 PMCID: PMC8063049 DOI: 10.3389/fphys.2021.647010] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 03/02/2021] [Indexed: 12/18/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked muscle-wasting disease caused by the loss of dystrophin. DMD is associated with muscle degeneration, necrosis, inflammation, fatty replacement, and fibrosis, resulting in muscle weakness, respiratory and cardiac failure, and premature death. There is no curative treatment. Investigations on disease-causing mechanisms offer an opportunity to identify new therapeutic targets to treat DMD. An abnormal elevation of the intracellular calcium (Cai2+) concentration in the dystrophin-deficient muscle is a major secondary event, which contributes to disease progression in DMD. Emerging studies have suggested that targeting Ca2+-handling proteins and/or mechanisms could be a promising therapeutic strategy for DMD. Here, we provide an updated overview of the mechanistic roles the sarcolemma, sarcoplasmic/endoplasmic reticulum, and mitochondria play in the abnormal and sustained elevation of Cai2+ levels and their involvement in DMD pathogenesis. We also discuss current approaches aimed at restoring Ca2+ homeostasis as potential therapies for DMD.
Collapse
Affiliation(s)
- Satvik Mareedu
- Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers University, Newark, NJ, United States
| | - Emily D Million
- Department of Molecular Microbiology and Immunology, The University of Missouri, Columbia, MO, United States
| | - Dongsheng Duan
- Department of Molecular Microbiology and Immunology, The University of Missouri, Columbia, MO, United States.,Department of Biomedical, Biological & Chemical Engineering, The University of Missouri, Columbia, MO, United States
| | - Gopal J Babu
- Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers University, Newark, NJ, United States
| |
Collapse
|
5
|
Saüc S, Frieden M. Neurological and Motor Disorders: TRPC in the Skeletal Muscle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:557-575. [PMID: 28900933 DOI: 10.1007/978-3-319-57732-6_28] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Transient receptor potential canonical (TRPC) channels belong to the large family of TRPs that are mostly nonselective cation channels with a great variety of gating mechanisms. TRPC are composed of seven members that can all be activated downstream of agonist-induced phospholipase C stimulation, but some members are also stretch-activated and/or are part of the store-operated Ca2+ entry (SOCE) pathway. Skeletal muscles generate contraction via an explosive increase of cytosolic Ca2+ concentration resulting almost exclusively from sarcoplasmic reticulum Ca2+ channel opening. Even if neglected for a long time, it is now commonly accepted that Ca2+ entry via SOCE and other routes is essential to sustain contractions of the skeletal muscle. In addition, Ca2+ influx is required during muscle regeneration, and alteration of the influx is associated with myopathies. In this chapter, we review the implication of TRPC channels at different stages of muscle regeneration, in adult muscle fibers, and discuss their implication in myopathies.
Collapse
Affiliation(s)
- Sophie Saüc
- Department of Cell Physiology and Metabolism, University of Geneva, 1 rue Michel Servet, 1211, Geneva, Switzerland
| | - Maud Frieden
- Department of Cell Physiology and Metabolism, University of Geneva, 1 rue Michel Servet, 1211, Geneva, Switzerland.
| |
Collapse
|
6
|
Farini A, Sitzia C, Cassinelli L, Colleoni F, Parolini D, Giovanella U, Maciotta S, Colombo A, Meregalli M, Torrente Y. Inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ signaling mediates delayed myogenesis in Duchenne muscular dystrophy fetal muscle. Development 2016; 143:658-69. [DOI: 10.1242/dev.126193] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disorder characterized by muscle wasting and premature death. The defective gene is dystrophin, a structural protein, absence of which causes membrane fragility and myofiber necrosis. Several lines of evidence showed that in adult DMD patients dystrophin is involved in signaling pathways that regulate calcium homeostasis and differentiation programs. However, secondary aspects of the disease, such as inflammation and fibrosis development, might represent a bias in the analysis. Because fetal muscle is not influenced by gravity and does not suffer from mechanical load and/or inflammation, we investigated 12-week-old fetal DMD skeletal muscles, highlighting for the first time early alterations in signaling pathways mediated by the absence of dystrophin itself. We found that PLC/IP3/IP3R/Ryr1/Ca2+ signaling is widely active in fetal DMD skeletal muscles and, through the calcium-dependent PKCα protein, exerts a fundamental regulatory role in delaying myogenesis and in myofiber commitment. These data provide new insights into the origin of DMD pathology during muscle development.
Collapse
Affiliation(s)
- Andrea Farini
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| | - Clementina Sitzia
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| | - Letizia Cassinelli
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| | - Federica Colleoni
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| | - Daniele Parolini
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| | - Umberto Giovanella
- Consiglio Nazionale delle Ricerche, Istituto per lo Studio delle Macromolecole (CNR-ISMAC), via Bassini 15, Milano 20133, Italy
| | - Simona Maciotta
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| | - Augusto Colombo
- Servizio ‘Legge 194’ Dipartimento BDN-Fondazione IRCCS, Policlinico Mangiagalli-Regina Elena, Via Francesco Sforza 35, Milan 20122, Italy
| | - Mirella Meregalli
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| | - Yvan Torrente
- Laboratorio di Cellule Staminali, Dipartimento di Fisiopatologia medico-chirurgica e dei Trapianti, Università degli Studi di Milano, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Centro Dino Ferrari, Via Francesco Sforza 35, Milan 20122, Centro Dino Ferrari, Italy
| |
Collapse
|
7
|
Hernández-Ochoa EO, Pratt SJP, Lovering RM, Schneider MF. Critical Role of Intracellular RyR1 Calcium Release Channels in Skeletal Muscle Function and Disease. Front Physiol 2016; 6:420. [PMID: 26793121 PMCID: PMC4709859 DOI: 10.3389/fphys.2015.00420] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 12/21/2015] [Indexed: 01/25/2023] Open
Abstract
The skeletal muscle Ca2+ release channel, also known as ryanodine receptor type 1 (RyR1), is the largest ion channel protein known and is crucial for effective skeletal muscle contractile activation. RyR1 function is controlled by Cav1.1, a voltage gated Ca2+ channel that works mainly as a voltage sensor for RyR1 activity during skeletal muscle contraction and is also fine-tuned by Ca2+, several intracellular compounds (e.g., ATP), and modulatory proteins (e.g., calmodulin). Dominant and recessive mutations in RyR1, as well as acquired channel alterations, are the underlying cause of various skeletal muscle diseases. The aim of this mini review is to summarize several current aspects of RyR1 function, structure, regulation, and to describe the most common diseases caused by hereditary or acquired RyR1 malfunction.
Collapse
Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine Baltimore, MD, USA
| | - Stephen J P Pratt
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Martin F Schneider
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine Baltimore, MD, USA
| |
Collapse
|
8
|
Burr AR, Molkentin JD. Genetic evidence in the mouse solidifies the calcium hypothesis of myofiber death in muscular dystrophy. Cell Death Differ 2015; 22:1402-12. [PMID: 26088163 PMCID: PMC4532779 DOI: 10.1038/cdd.2015.65] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 04/03/2015] [Accepted: 04/17/2015] [Indexed: 01/19/2023] Open
Abstract
Muscular dystrophy (MD) refers to a clinically and genetically heterogeneous group of degenerative muscle disorders characterized by progressive muscle wasting and often premature death. Although the primary defect underlying most forms of MD typically results from a loss of sarcolemmal integrity, the secondary molecular mechanisms leading to muscle degeneration and myofiber necrosis is debated. One hypothesis suggests that elevated or dysregulated cytosolic calcium is the common transducing event, resulting in myofiber necrosis in MD. Previous measurements of resting calcium levels in myofibers from dystrophic animal models or humans produced equivocal results. However, recent studies in genetically altered mouse models have largely solidified the calcium hypothesis of MD, such that models with artificially elevated calcium in skeletal muscle manifest fulminant dystrophic-like disease, whereas models with enhanced calcium clearance or inhibited calcium influx are resistant to myofiber death and MD. Here, we will review the field and the recent cadre of data from genetically altered mouse models, which we propose have collectively mostly proven the hypothesis that calcium is the primary effector of myofiber necrosis in MD. This new consensus on calcium should guide future selection of drugs to be evaluated in clinical trials as well as gene therapy-based approaches.
Collapse
Affiliation(s)
- A R Burr
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, 240 Albert Sabin Way, Cincinnati, OH, USA
| | - J D Molkentin
- 1] Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, 240 Albert Sabin Way, Cincinnati, OH, USA [2] Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Molecular Cardiovascular Biology, 240 Albert Sabin Way, Cincinnati, OH, USA
| |
Collapse
|
9
|
Hernández-Ochoa EO, Pratt SJP, Garcia-Pelagio KP, Schneider MF, Lovering RM. Disruption of action potential and calcium signaling properties in malformed myofibers from dystrophin-deficient mice. Physiol Rep 2015; 3:3/4/e12366. [PMID: 25907787 PMCID: PMC4425971 DOI: 10.14814/phy2.12366] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Duchenne muscular dystrophy (DMD), the most common and severe muscular dystrophy, is caused by the absence of dystrophin. Muscle weakness and fragility (i.e., increased susceptibility to damage) are presumably due to structural instability of the myofiber cytoskeleton, but recent studies suggest that the increased presence of malformed/branched myofibers in dystrophic muscle may also play a role. We have previously studied myofiber morphology in healthy wild-type (WT) and dystrophic (MDX) skeletal muscle. Here, we examined myofiber excitability using high-speed confocal microscopy and the voltage-sensitive indicator di-8-butyl-amino-naphthyl-ethylene-pyridinium-propyl-sulfonate (di-8-ANEPPS) to assess the action potential (AP) properties. We also examined AP-induced Ca2+ transients using high-speed confocal microscopy with rhod-2, and assessed sarcolemma fragility using elastimetry. AP recordings showed an increased width and time to peak in malformed MDX myofibers compared to normal myofibers from both WT and MDX, but no significant change in AP amplitude. Malformed MDX myofibers also exhibited reduced AP-induced Ca2+ transients, with a further Ca2+ transient reduction in the branches of malformed MDX myofibers. Mechanical studies indicated an increased sarcolemma deformability and instability in malformed MDX myofibers. The data suggest that malformed myofibers are functionally different from myofibers with normal morphology. The differences seen in AP properties and Ca2+ signals suggest changes in excitability and remodeling of the global Ca2+ signal, both of which could underlie reported weakness in dystrophic muscle. The biomechanical changes in the sarcolemma support the notion that malformed myofibers are more susceptible to damage. The high prevalence of malformed myofibers in dystrophic muscle may contribute to the progressive strength loss and fragility seen in dystrophic muscles.
Collapse
Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Stephen J P Pratt
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
| | - Karla P Garcia-Pelagio
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Martin F Schneider
- Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
| |
Collapse
|
10
|
Mázala DAG, Grange RW, Chin ER. The role of proteases in excitation-contraction coupling failure in muscular dystrophy. Am J Physiol Cell Physiol 2014; 308:C33-40. [PMID: 25298424 DOI: 10.1152/ajpcell.00267.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Duchenne muscular dystrophy (DMD) is one of the most frequent types of muscular dystrophy. Alterations in intracellular calcium (Ca(2+)) handling are thought to contribute to the disease severity in DMD, possibly due to the activation of Ca(2+)-activated proteases. The purpose of this study was twofold: 1) to determine whether prolonged excitation-contraction (E-C) coupling disruption following repeated contractions is greater in animals lacking both dystrophin and utrophin (mdx/Utr(-/-)) compared with mice lacking only dystrophin (mdx); and 2) to assess whether protease inhibition can prevent E-C coupling failure following repeated tetani in these dystrophic mouse models. Excitation-contraction coupling was assessed using Fura-2 ratio, as an index of intracellular free Ca(2+) concentration, in response to electrical stimulation of single muscle fibers from the flexor digitorum brevis muscle. Resting Fura-2 ratio was higher in dystrophic compared with control (Con) fibers, but peak Fura-2 ratios during stimulation were similar in dystrophic and Con fibers. One hour after a series of repeated tetani, peak Fura-2 ratios were reduced by 30 ± 5.6%, 23 ± 2%, and 36 ± 3.1% in mdx, mdx/Utr(+/-), and mdx/Utr(-/-), respectively, with the greatest reduction in mdx/Utr(-/-) fibers (P < 0.05). Protease inhibition attenuated this decrease in peak Fura-2 ratio. These data indicate that E-C coupling impairment after repeated contractions is greatest in fibers lacking both dystrophin and utrophin and that prevention of protease activation can mitigate the prolonged E-C coupling impairment. These data further suggest that acute protease inhibition may be useful in reducing muscle weakness in DMD.
Collapse
Affiliation(s)
- Davi A G Mázala
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland; and
| | - Robert W Grange
- Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Eva R Chin
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland; and
| |
Collapse
|
11
|
Barnabei MS, Martindale JM, Townsend D, Metzger JM. Exercise and muscular dystrophy: implications and analysis of effects on musculoskeletal and cardiovascular systems. Compr Physiol 2013; 1:1353-63. [PMID: 23733645 DOI: 10.1002/cphy.c100062] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The muscular dystrophies are a heterogeneous collection of progressive, inherited diseases of muscle weakness and degeneration. Although these diseases can vary widely in their etiology and presentation, nearly all muscular dystrophies cause exercise intolerance to some degree. Here, we focus on Duchenne muscular dystrophy (DMD), the most common form of muscular dystrophy, as a paradigm for the effects of muscle disease on exercise capacity. First described in the mid-1800s, DMD is a rapidly progressive and lethal muscular dystrophy caused by mutations in the dystrophin gene. Dystrophin is a membrane-associated cytoskeletal protein, the loss of which causes numerous cellular defects including mechanical instability of the sarcolemma, increased influx of extracellular calcium, and cell signaling defects. Here, we discuss the physiological basis for exercise intolerance in DMD, focusing on the molecular and cellular defects caused by loss of dystrophin and how these manifest as organ-level dysfunction and reduced exercise capacity. The main focus of this article is the defects present in dystrophin-deficient striated muscle. However, discussion regarding the effects of dystrophin loss on other tissues, including vascular smooth muscle is also included. Collectively, the goal of this article is to summarize the current state of knowledge regarding the mechanistic basis for exercise intolerance in DMD, which may serve as an archetype for other muscular dystrophies and diseases of muscle wasting.
Collapse
Affiliation(s)
- Matthew S Barnabei
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | | | | | | |
Collapse
|
12
|
Schneider JS, Shanmugam M, Gonzalez JP, Lopez H, Gordan R, Fraidenraich D, Babu GJ. Increased sarcolipin expression and decreased sarco(endo)plasmic reticulum Ca2+ uptake in skeletal muscles of mouse models of Duchenne muscular dystrophy. J Muscle Res Cell Motil 2013; 34:349-56. [DOI: 10.1007/s10974-013-9350-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 05/27/2013] [Indexed: 02/02/2023]
|
13
|
Robin G, Berthier C, Allard B. Sarcoplasmic reticulum Ca2+ permeation explored from the lumen side in mdx muscle fibers under voltage control. ACTA ACUST UNITED AC 2012; 139:209-18. [PMID: 22371362 PMCID: PMC3289961 DOI: 10.1085/jgp.201110738] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Under resting conditions, external Ca2+ is known to enter skeletal muscle cells, whereas Ca2+ stored in the sarcoplasmic reticulum (SR) leaks into the cytosol. The nature of the pathways involved in the sarcolemmal Ca2+ entry and in the SR Ca2+ leak is still a matter of debate, but several lines of evidence suggest that these Ca2+ fluxes are up-regulated in Duchenne muscular dystrophy. We investigated here SR calcium permeation at resting potential and in response to depolarization in voltage-controlled skeletal muscle fibers from control and mdx mice, the mouse model of Duchenne muscular dystrophy. Using the cytosolic Ca2+ dye Fura2, we first demonstrated that the rate of Ca2+ increase in response to cyclopiazonic acid (CPA)–induced inhibition of SR Ca2+-ATPases at resting potential was significantly higher in mdx fibers, which suggests an elevated SR Ca2+ leak. However, removal of external Ca2+ reduced the rate of CPA-induced Ca2+ increase in mdx and increased it in control fibers, which indicates an up-regulation of sarcolemmal Ca2+ influx in mdx fibers. Fibers were then loaded with the low-affinity Ca2+ dye Fluo5N-AM to measure intraluminal SR Ca2+ changes. Trains of action potentials, chloro-m-cresol, and depolarization pulses evoked transient Fluo5N fluorescence decreases, and recovery of voltage-induced Fluo5N fluorescence changes were inhibited by CPA, demonstrating that Fluo5N actually reports intraluminal SR Ca2+ changes. Voltage dependence and magnitude of depolarization-induced SR Ca2+ depletion were found to be unchanged in mdx fibers, but the rate of the recovery phase that followed depletion was found to be faster, indicating a higher SR Ca2+ reuptake activity in mdx fibers. Overall, CPA-induced SR Ca2+ leak at −80 mV was found to be significantly higher in mdx fibers and was potentiated by removal of external Ca2+ in control fibers. The elevated passive SR Ca2+ leak may contribute to alteration of Ca2+ homeostasis in mdx muscle.
Collapse
Affiliation(s)
- Gaëlle Robin
- Université Lyon 1, Centre National de la Recherche Scientifique UMR 5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, 69622 Villeurbanne Cedex, France
| | | | | |
Collapse
|
14
|
Goodall MH, Ward CW, Pratt SJP, Bloch RJ, Lovering RM. Structural and functional evaluation of branched myofibers lacking intermediate filaments. Am J Physiol Cell Physiol 2012; 303:C224-32. [PMID: 22592402 DOI: 10.1152/ajpcell.00136.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intermediate filaments (IFs), composed of desmin and keratins, link myofibrils to each other and to the sarcolemma in skeletal muscle. Fast-twitch muscle of mice lacking the IF proteins, desmin and keratin 19 (K19), showed reduced specific force and increased susceptibility to injury in earlier studies. Here we tested the hypothesis that the number of malformed myofibers in mice lacking desmin (Des(-/-)), keratin 19 (K19(-/-)), or both IF proteins (double knockout, DKO) is increased and is coincident with altered excitation-contraction (EC) coupling Ca(2+) kinetics, as reported for mdx mice. We quantified the number of branched myofibers, characterized their organization with confocal and electron microscopy (EM), and compared the Ca(2+) kinetics of EC coupling in flexor digitorum brevis myofibers from adult Des(-/-), K19(-/-), or DKO mice and compared them to age-matched wild type (WT) and mdx myofibers. Consistent with our previous findings, 9.9% of mdx myofibers had visible malformations. Des(-/-) myofibers had more malformations (4.7%) than K19(-/-) (0.9%) or DKO (1.3%) myofibers. Confocal and EM imaging revealed no obvious changes in sarcomere misalignment at the branch points, and the neuromuscular junctions in the mutant mice, while more variably located, were limited to one per myofiber. Global, electrically evoked Ca(2+) signals showed a decrease in the rate of Ca(2+) uptake (decay rate) into the sarcoplasmic reticulum after Ca(2+) release, with the most profound effect in branched DKO myofibers (44% increase in uptake relative to WT). Although branched DKO myofibers showed significantly faster rates of Ca(2+) clearance, the milder branching phenotype observed in DKO muscle suggests that the absence of K19 corrects the defect created by the absence of desmin alone. Thus, there are complex roles for desmin-based and K19-based IFs in skeletal muscle, with the null and DKO mutations having different effects on Ca(2+) reuptake and myofiber branching.
Collapse
Affiliation(s)
- Mariah H Goodall
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, 21201, USA
| | | | | | | | | |
Collapse
|
15
|
Baylor SM, Hollingworth S. Calcium indicators and calcium signalling in skeletal muscle fibres during excitation-contraction coupling. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 105:162-79. [PMID: 20599552 DOI: 10.1016/j.pbiomolbio.2010.06.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 06/14/2010] [Indexed: 11/25/2022]
Abstract
During excitation-contraction coupling in skeletal muscle, calcium ions are released into the myoplasm by the sarcoplasmic reticulum (SR) in response to depolarization of the fibre's exterior membranes. Ca(2+) then diffuses to the thin filaments, where Ca(2+) binds to the Ca(2+) regulatory sites on troponin to activate muscle contraction. Quantitative studies of these events in intact muscle preparations have relied heavily on Ca(2+)-indicator dyes to measure the change in the spatially-averaged myoplasmic free Ca(2+) concentration (Δ[Ca(2+)]) that results from the release of SR Ca(2+). In normal fibres stimulated by an action potential, Δ[Ca(2+)] is large and brief, requiring that an accurate measurement of Δ[Ca(2+)] be made with a low-affinity rapidly-responding indicator. Some low-affinity Ca(2+) indicators monitor Δ[Ca(2+)] much more accurately than others, however, as reviewed here in measurements in frog twitch fibres with sixteen low-affinity indicators. This article also examines measurements and simulations of Δ[Ca(2+)] in mouse fast-twitch fibres. The simulations use a multi-compartment model of the sarcomere that takes into account Ca(2+)'s release from the SR, its diffusion and binding within the myoplasm, and its re-sequestration by the SR Ca(2+) pump. The simulations are quantitatively consistent with the measurements and appear to provide a satisfactory picture of the underlying Ca(2+) movements.
Collapse
Affiliation(s)
- Stephen M Baylor
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA.
| | | |
Collapse
|
16
|
Weiss N, Legrand C, Pouvreau S, Bichraoui H, Allard B, Zamponi GW, De Waard M, Jacquemond V. In vivo expression of G-protein beta1gamma2 dimer in adult mouse skeletal muscle alters L-type calcium current and excitation-contraction coupling. J Physiol 2010; 588:2945-60. [PMID: 20547679 DOI: 10.1113/jphysiol.2010.191593] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A number of G-protein-coupled receptors are expressed in skeletal muscle but their roles in muscle physiology and downstream effector systems remain poorly investigated. Here we explored the functional importance of the G-protein betagamma (Gbetagamma) signalling pathway on voltage-controlled Ca(2+) homeostasis in single isolated adult skeletal muscle fibres. A GFP-tagged Gbeta(1)gamma(2) dimer was expressed in vivo in mice muscle fibres. The GFP fluorescence pattern was consistent with a Gbeta(1)gamma(2) dimer localization in the transverse-tubule membrane. Membrane current and indo-1 fluorescence measurements performed under voltage-clamp conditions reveal a drastic reduction of both L-type Ca(2+) current density and of peak amplitude of the voltage-activated Ca(2+) transient in Gbeta(1)gamma(2)-expressing fibres. These effects were not observed upon expression of Gbeta(2)gamma(2), Gbeta(3)gamma(2) or Gbeta(4)gamma(2). Our data suggest that the G-protein beta(1)gamma(2) dimer may play an important regulatory role in skeletal muscle excitation-contraction coupling.
Collapse
Affiliation(s)
- Norbert Weiss
- Université Lyon 1, UMR CNRS 5123, Physiologie Intégrative Cellulaire et Moléculaire, Bâtiment R. Dubois, 43 boulevard du 11 novembre 1918, Villeurbanne, France.
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Wooddell CI, Zhang G, Griffin JB, Hegge JO, Huss T, Wolff JA. Use of Evans blue dye to compare limb muscles in exercised young and old mdx mice. Muscle Nerve 2010; 41:487-99. [PMID: 19813196 DOI: 10.1002/mus.21527] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Evans blue dye (EBD) is used to mark damaged and permeable muscle fibers in mouse models of muscular dystrophy and as an endpoint in therapeutic trials. We counted EBD-positive muscle fibers and extracted EBD from muscles sampled throughout the hindlimbs in young adult and old mdx mice to determine if the natural variability in morphology would allow measurement of a functional improvement in one limb compared to the contralateral limb. Following one bout of rotarod or treadmill exercise that greatly increased serum creatine kinase levels, the number of EBD(+) muscle fibers in 12-19-month-old mdx mice increased 3-fold, EBD in the muscles increased, and, importantly, contralateral pairs of muscles contained similar amounts of EBD. In contrast, the intra- and interlimb amounts of EBD in 2-7-month-old mdx mice were much too variable. A therapeutic effect can more readily be measured in old mdx mice. These results will be useful in the design of therapy protocols using the mdx mouse.
Collapse
|
18
|
Berbey C, Weiss N, Legrand C, Allard B. Transient receptor potential canonical type 1 (TRPC1) operates as a sarcoplasmic reticulum calcium leak channel in skeletal muscle. J Biol Chem 2009; 284:36387-36394. [PMID: 19875453 DOI: 10.1074/jbc.m109.073221] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Extensive studies performed in nonexcitable cells and expression systems have shown that type 1 transient receptor potential canonical (TRPC1) channels operate mainly in plasma membranes and open through phospholipase C-dependent processes, membrane stretch, or depletion of Ca(2+) stores. In skeletal muscle, it is proposed that TRPC1 channels are involved in plasmalemmal Ca(2+) influx and stimulated by store depletion or membrane stretch, but direct evidence for TRPC1 sarcolemmal channel activity is not available. We investigated here the functional role of TRPC1 using an overexpressing strategy in adult mouse muscle fibers. Immunostaining for endogenous TRPC1 revealed a striated expression pattern that matched sarcoplasmic reticulum (SR) Ca(2+) pump immunolabeling. In cells expressing TRPC1-yellow fluorescent protein (YFP), the same pattern of expression was observed, compatible with a longitudinal SR localization. Resting electric properties, action potentials, and resting divalent cation influx were not altered in TRPC1-YFP-positive cells. Poisoning with the SR Ca(2+) pump blocker cyclopiazonic acid elicited a contracture of the fiber at the level of the overexpression site in presence and absence of external Ca(2+) which was not observed in control cells. Ca(2+) measurements indicated that resting Ca(2+) and the rate of Ca(2+) increase induced by cyclopiazonic acid were higher in the TRPC1-YFP-positive zone than in the TRPC1-YFP-negative zone and control cells. Ca(2+) transients evoked by 200-ms voltage clamp pulses decayed slower in TRPC1-YFP-positive cells. In contrast to previous hypotheses, these data demonstrate that TRPC1 operates as a SR Ca(2+) leak channel in skeletal muscle.
Collapse
Affiliation(s)
- Céline Berbey
- Laboratoire de Physiologie Intégrative, Cellulaire, et Moléculaire, Université de Lyon, Université Lyon 1, CNRS Unité Mixte de Recherche 5123, 69622 Villeurbanne Cedex, France
| | - Norbert Weiss
- Laboratoire de Physiologie Intégrative, Cellulaire, et Moléculaire, Université de Lyon, Université Lyon 1, CNRS Unité Mixte de Recherche 5123, 69622 Villeurbanne Cedex, France
| | - Claude Legrand
- Laboratoire de Physiologie Intégrative, Cellulaire, et Moléculaire, Université de Lyon, Université Lyon 1, CNRS Unité Mixte de Recherche 5123, 69622 Villeurbanne Cedex, France
| | - Bruno Allard
- Laboratoire de Physiologie Intégrative, Cellulaire, et Moléculaire, Université de Lyon, Université Lyon 1, CNRS Unité Mixte de Recherche 5123, 69622 Villeurbanne Cedex, France.
| |
Collapse
|
19
|
Calcium influx is sufficient to induce muscular dystrophy through a TRPC-dependent mechanism. Proc Natl Acad Sci U S A 2009; 106:19023-8. [PMID: 19864620 DOI: 10.1073/pnas.0906591106] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Muscular dystrophy is a general term encompassing muscle disorders that cause weakness and wasting, typically leading to premature death. Membrane instability, as a result of a genetic disruption within the dystrophin-glycoprotein complex (DGC), is thought to induce myofiber degeneration, although the downstream mechanism whereby membrane fragility leads to disease remains controversial. One potential mechanism that has yet to be definitively proven in vivo is that unregulated calcium influx initiates disease in dystrophic myofibers. Here we demonstrate that calcium itself is sufficient to cause a dystrophic phenotype in skeletal muscle independent of membrane fragility. For example, overexpression of transient receptor potential canonical 3 (TRPC3) and the associated increase in calcium influx resulted in a phenotype of muscular dystrophy nearly identical to that observed in DGC-lacking dystrophic disease models, including a highly similar molecular signature of gene expression changes. Furthermore, transgene-mediated inhibition of TRPC channels in mice dramatically reduced calcium influx and dystrophic disease manifestations associated with the mdx mutation (dystrophin gene) and deletion of the delta-sarcoglycan (Scgd) gene. These results demonstrate that calcium itself is sufficient to induce muscular dystrophy in vivo, and that TRPC channels are key disease initiators downstream of the unstable membrane that characterizes many types of muscular dystrophy.
Collapse
|
20
|
T-tubule disorganization and defective excitation-contraction coupling in muscle fibers lacking myotubularin lipid phosphatase. Proc Natl Acad Sci U S A 2009; 106:18763-8. [PMID: 19846786 DOI: 10.1073/pnas.0900705106] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Skeletal muscle contraction is triggered by the excitation-contraction (E-C) coupling machinery residing at the triad, a membrane structure formed by the juxtaposition of T-tubules and sarcoplasmic reticulum (SR) cisternae. The formation and maintenance of this structure is key for muscle function but is not well characterized. We have investigated the mechanisms leading to X-linked myotubular myopathy (XLMTM), a severe congenital disorder due to loss of function mutations in the MTM1 gene, encoding myotubularin, a phosphoinositide phosphatase thought to have a role in plasma membrane homeostasis and endocytosis. Using a mouse model of the disease, we report that Mtm1-deficient muscle fibers have a decreased number of triads and abnormal longitudinally oriented T-tubules. In addition, SR Ca(2+) release elicited by voltage-clamp depolarizations is strongly depressed in myotubularin-deficient muscle fibers, with myoplasmic Ca(2+) removal and SR Ca(2+) content essentially unaffected. At the molecular level, Mtm1-deficient myofibers exhibit a 3-fold reduction in type 1 ryanodine receptor (RyR1) protein level. These data reveal a critical role of myotubularin in the proper organization and function of the E-C coupling machinery and strongly suggest that defective RyR1-mediated SR Ca(2+) release is responsible for the failure of muscle function in myotubular myopathy.
Collapse
|
21
|
Lovering RM, Michaelson L, Ward CW. Malformed mdx myofibers have normal cytoskeletal architecture yet altered EC coupling and stress-induced Ca2+ signaling. Am J Physiol Cell Physiol 2009; 297:C571-80. [PMID: 19605736 DOI: 10.1152/ajpcell.00087.2009] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle function is dependent on its highly regular structure. In studies of dystrophic (dy/dy) mice, the proportion of malformed myofibers decreases after prolonged whole muscle stimulation, suggesting that the malformed myofibers are more prone to injury. The aim of this study was to assess morphology and to measure excitation-contraction (EC) coupling (Ca(2+) transients) and susceptibility to osmotic stress (Ca(2+) sparks) of enzymatically isolated muscle fibers of the extensor digitorum longus (EDL) and flexor digitorum brevis (FDB) muscles from young (2-3 mo) and old (8-9 mo) mdx and age-matched control mice (C57BL10). In young mdx EDL, 6% of the myofibers had visible malformations (i.e., interfiber splitting, branched ends, midfiber appendages). In contrast, 65% of myofibers in old mdx EDL contained visible malformations. In the mdx FDB, malformation occurred in only 5% of young myofibers and 11% of old myofibers. Age-matched control mice did not display the altered morphology of mdx muscles. The membrane-associated and cytoplasmic cytoskeletal structures appeared normal in the malformed mdx myofibers. In mdx FDBs with significantly branched ends, an assessment of global, electrically evoked Ca(2+) signals (indo-1PE-AM) revealed an EC coupling deficit in myofibers with significant branching. Interestingly, peak amplitude of electrically evoked Ca(2+) release in the branch of the bifurcated mdx myofiber was significantly decreased compared with the trunk of the same myofiber. No alteration in the basal myoplasmic Ca(2+) concentration (i.e., indo ratio) was seen in malformed vs. normal mdx myofibers. Finally, osmotic stress induced the occurrence of Ca(2+) sparks to a greater extent in the malformed portions of myofibers, which is consistent with deficits in EC coupling control. In summary, our data show that aging mdx myofibers develop morphological malformations. These malformations are not associated with gross disruptions in cytoskeletal or t-tubule structure; however, alterations in myofiber Ca(2+) signaling are evident.
Collapse
Affiliation(s)
- Richard M Lovering
- Univ. of Maryland School of Medicine, Dept. of Physiology, 685 W. Baltimore St., HSF-1, Rm, 580, Baltimore, MD 21201, USA.
| | | | | |
Collapse
|
22
|
Csernoch L, Pouvreau S, Ronjat M, Jacquemond V. Voltage-activated elementary calcium release events in isolated mouse skeletal muscle fibers. J Membr Biol 2008; 226:43-55. [PMID: 19015802 PMCID: PMC2796304 DOI: 10.1007/s00232-008-9138-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 10/20/2008] [Indexed: 10/21/2022]
Abstract
The elementary Ca(2+)-release events underlying voltage-activated myoplasmic Ca(2+) transients in mammalian muscle remain elusive. Here, we looked for such events in confocal line-scan (x,t) images of fluo-3 fluorescence taken from isolated adult mouse skeletal muscle fibers held under voltage-clamp conditions. In response to step depolarizations, spatially segregated fluorescence signals could be detected that were riding on a global increase in fluorescence. These discrete signals were separated using digital filtering in the spatial domain; mean values for their spatial half-width and amplitude were 1.99 +/- 0.09 microm and 0.16 +/- 0.005 DeltaF/F(0) (n = 151), respectively. Under control conditions, the duration of the events was limited by the pulse duration. In contrast, in the presence of maurocalcine, a scorpion toxin suspected to disrupt the process of repolarization-induced ryanodine receptor (RyR) closure, events uninterrupted by the end of the pulse were readily detected. Overall results establish these voltage-activated low-amplitude local Ca(2+) signals as inherent components of the physiological Ca(2+)-release process of mammalian muscle and suggest that they result from the opening of either one RyR or a coherently operating group of RyRs, under the control of the plasma membrane polarization.
Collapse
Affiliation(s)
- Laszlo Csernoch
- Department of Physiology
Medical and Health Science CentreUniversity of DebrecenDebrecen,HU
| | - Sandrine Pouvreau
- PICM, Physiologie intégrative, cellulaire et moléculaire
CNRS : UMR5123Université Claude Bernard - Lyon IBât. R. Dubois 43, Bvd du 11 Novembre 1918 69622 VILLEURBANNE CEDEX,FR
| | - Michel Ronjat
- GIN, Grenoble Institut des Neurosciences
INSERM : U836CEAUniversité Joseph Fourier - Grenoble ICHU GrenobleUJF - Site Santé La Tronche BP 170 38042 Grenoble Cedex 9,FR
| | - Vincent Jacquemond
- PICM, Physiologie intégrative, cellulaire et moléculaire
CNRS : UMR5123Université Claude Bernard - Lyon IBât. R. Dubois 43, Bvd du 11 Novembre 1918 69622 VILLEURBANNE CEDEX,FR
| |
Collapse
|
23
|
Hollingworth S, Zeiger U, Baylor SM. Comparison of the myoplasmic calcium transient elicited by an action potential in intact fibres of mdx and normal mice. J Physiol 2008; 586:5063-75. [PMID: 18772198 DOI: 10.1113/jphysiol.2008.160507] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The myoplasmic free [Ca2+] transient elicited by an action potential (Delta[Ca2+]) was compared in fast-twitch fibres of mdx (dystrophin null) and normal mice. Methods were used that maximized the likelihood that any detected differences apply in vivo. Small bundles of fibres were manually dissected from extensor digitorum longus muscles of 7- to 14-week-old mice. One fibre within a bundle was microinjected with furaptra, a low-affinity rapidly responding fluorescent calcium indicator. A fibre was accepted for study if it gave a stable, all-or-nothing fluorescence response to an external shock. In 18 normal fibres, the peak amplitude and the full-duration at half-maximum (FDHM) of Delta[Ca2+] were 18.4 +/- 0.5 microm and 4.9 +/- 0.2 ms, respectively (mean +/- s.e.m.; 16 degrees C). In 13 mdx fibres, the corresponding values were 14.5 +/- 0.6 microm and 4.7 +/- 0.2 ms. The difference in amplitude is statistically highly significant (P = 0.0001; two-tailed t test), whereas the difference in FDHM is not (P = 0.3). A multi-compartment computer model was used to estimate the amplitude and time course of the sarcoplasmic reticulum (SR) calcium release flux underlying Delta[Ca2+]. Estimates were made based on several differing assumptions: (i) that the resting myoplasmic free Ca2+ concentration ([Ca2+]R) and the total concentration of parvalbumin ([Parv(T)]) are the same in mdx and normal fibres, (ii) that [Ca2+](R) is larger in mdx fibres, (iii) that [Parv(T)] is smaller in mdx fibres, and (iv) that [Ca2+]R is larger and [Parv(T)] is smaller in mdx fibres. According to the simulations, the 21% smaller amplitude of Delta[Ca2+] in mdx fibres in combination with the unchanged FDHM of Delta[Ca2+] is consistent with mdx fibres having a approximately 25% smaller flux amplitude, a 6-23% larger FDHM of the flux, and a 9-20% smaller total amount of released Ca2+ than normal fibres. The changes in flux are probably due to a change in the gating of the SR Ca2+-release channels and/or in their single channel flux. The link between these changes and the absence of dystrophin remains to be elucidated.
Collapse
Affiliation(s)
- Stephen Hollingworth
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA
| | | | | |
Collapse
|
24
|
Ram N, Weiss N, Texier-Nogues I, Aroui S, Andreotti N, Pirollet F, Ronjat M, Sabatier JM, Darbon H, Jacquemond V, De Waard M. Design of a disulfide-less, pharmacologically inert, and chemically competent analog of maurocalcine for the efficient transport of impermeant compounds into cells. J Biol Chem 2008; 283:27048-56. [PMID: 18621738 DOI: 10.1074/jbc.m804727200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Maurocalcine is a 33-mer peptide initially isolated from the venom of a Tunisian scorpion. It has proved itself valuable as a pharmacological activator of the ryanodine receptor and has helped the understanding of the molecular basis underlying excitation-contraction coupling in skeletal muscles. Because of its positively charged nature, it is also an innovative vector for the cell penetration of various compounds. We report a novel maurocalcine analog with improved properties: (i) the complete loss of pharmacological activity, (ii) preservation of the potent ability to carry cargo molecules into cells, and (iii) coupling chemistries not affected by the presence of internal cysteine residues of maurocalcine. We did this by replacing the six internal cysteine residues of maurocalcine by isosteric 2-aminobutyric acid residues and by adding an additional N-terminal biotinylated lysine (for a proof of concept analog) or an N-terminal cysteine residue (for a chemically competent coupling analogue). Additional replacement of a glutamate residue by alanyl at position 12 further improves the potency of these analogues. Coupling to several cargo molecules or nanoparticles are presented to illustrate the cell penetration potency and usefulness of these pharmacologically inactive analogs.
Collapse
Affiliation(s)
- Narendra Ram
- Research Group 3 Calcium Channels, Functions, and Pathologies, Unité Inserm 836, Grenoble Institute of Neuroscience, Université Joseph Fourier, Site Santé, BP 170, 38042 Grenoble Cedex 09, France
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Weiss N, Couchoux H, Legrand C, Berthier C, Allard B, Jacquemond V. Expression of the muscular dystrophy-associated caveolin-3(P104L) mutant in adult mouse skeletal muscle specifically alters the Ca(2+) channel function of the dihydropyridine receptor. Pflugers Arch 2008; 457:361-75. [PMID: 18509671 DOI: 10.1007/s00424-008-0528-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Revised: 04/30/2008] [Accepted: 05/07/2008] [Indexed: 12/11/2022]
Abstract
Caveolins are plasma-membrane-associated proteins potentially involved in a variety of signalling pathways. Different mutations in CAV3, the gene encoding for the muscle-specific isoform caveolin-3 (Cav-3), lead to muscle diseases, but the underlying molecular mechanisms remain largely unknown. Here, we explored the functional consequences of a Cav-3 mutation (P104L) inducing the 1C type limb-girdle muscular dystrophy (LGMD 1C) in human on intracellular Ca(2+) regulation of adult skeletal muscle fibres. A YFP-tagged human Cav-3(P104L) mutant was expressed in vivo in muscle fibres from mouse. Western blot analysis revealed that expression of this mutant led to an approximately 80% drop of the level of endogenous Cav-3. The L-type Ca(2+) current density was found largely reduced in fibres expressing the Cav-3(P104L) mutant, with no change in the voltage dependence of activation and inactivation. Interestingly, the maximal density of intramembrane charge movement was unaltered in the Cav-3(P104L)-expressing fibres, suggesting no change in the total amount of functional voltage-sensing dihydropyridine receptors (DHPRs). Also, there was no obvious alteration in the properties of voltage-activated Ca(2+) transients in the Cav-3(P104L)-expressing fibres. Although the actual role of the Ca(2+) channel function of the DHPR is not clearly established in adult skeletal muscle, its specific alteration by the Cav-3(P104L) mutant suggests that it may be involved in the physiopathology of LGMD 1C.
Collapse
Affiliation(s)
- Norbert Weiss
- Physiologie Intégrative Cellulaire et Moléculaire, Université Claude Bernard-Lyon 1,Villeurbanne Cedex, France
| | | | | | | | | | | |
Collapse
|
26
|
Yazawa M, Ferrante C, Feng J, Mio K, Ogura T, Zhang M, Lin PH, Pan Z, Komazaki S, Kato K, Nishi M, Zhao X, Weisleder N, Sato C, Ma J, Takeshima H. TRIC channels are essential for Ca2+ handling in intracellular stores. Nature 2007; 448:78-82. [PMID: 17611541 DOI: 10.1038/nature05928] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Accepted: 05/14/2007] [Indexed: 11/08/2022]
Abstract
Cell signalling requires efficient Ca2+ mobilization from intracellular stores through Ca2+ release channels, as well as predicted counter-movement of ions across the sarcoplasmic/endoplasmic reticulum membrane to balance the transient negative potential generated by Ca2+ release. Ca2+ release channels were cloned more than 15 years ago, whereas the molecular identity of putative counter-ion channels remains unknown. Here we report two TRIC (trimeric intracellular cation) channel subtypes that are differentially expressed on intracellular stores in animal cell types. TRIC subtypes contain three proposed transmembrane segments, and form homo-trimers with a bullet-like structure. Electrophysiological measurements with purified TRIC preparations identify a monovalent cation-selective channel. In TRIC-knockout mice suffering embryonic cardiac failure, mutant cardiac myocytes show severe dysfunction in intracellular Ca2+ handling. The TRIC-deficient skeletal muscle sarcoplasmic reticulum shows reduced K+ permeability, as well as altered Ca2+ 'spark' signalling and voltage-induced Ca2+ release. Therefore, TRIC channels are likely to act as counter-ion channels that function in synchronization with Ca2+ release from intracellular stores.
Collapse
Affiliation(s)
- Masayuki Yazawa
- Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Collet C, Belzunces L. Excitable properties of adult skeletal muscle fibres from the honeybeeApis mellifera. J Exp Biol 2007; 210:454-64. [PMID: 17234615 DOI: 10.1242/jeb.02667] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYIn the hive, a wide range of honeybees tasks such as cell cleaning,nursing, thermogenesis, flight, foraging and inter-individual communication(waggle dance, antennal contact and trophallaxy) depend on proper muscle activity. However, whereas extensive electrophysiological studies have been undertaken over the past ten years to characterize ionic currents underlying the physiological neuronal activity in honeybee, ionic currents underlying skeletal muscle fibre activity in this insect remain, so far, unexplored. Here, we show that, in contrast to many other insect species, action potentials in muscle fibres isolated from adult honeybee metathoracic tibia,are not graded but actual all-or-none responses. Action potentials are blocked by Cd2+ and La3+ but not by tetrodotoxin (TTX) in current-clamp mode of the patch-clamp technique, and as assessed under voltage-clamp, both Ca2+ and K+ currents are involved in shaping action potentials in single muscle fibres. The activation threshold potential for the voltage-dependent Ca2+ current is close to–40 mV, its mean maximal amplitude is –8.5±1.9 A/F and the mean apparent reversal potential is near +40 mV. In honeybees, GABA does not activate any ionic membrane currents in muscle fibres from the tibia, but L-glutamate, an excitatory neurotransmitter at the neuromuscular synapse induces fast activation of an inward current when the membrane potential is voltage clamped close to its resting value. Instead of undergoing desensitization as is the case in many other preparations, a component of this glutamate-activated current has a sustained component, the reversal potential of which is close to 0 mV, as demonstrated with voltage ramps. Future investigations will allow extensive pharmacological characterization of membrane ionic currents and excitation–contraction coupling in skeletal muscle from honeybee, a useful insect that became a model to study many physiological phenomena and which plays a major role in plant pollination and in stability of environmental vegetal biodiversity.
Collapse
Affiliation(s)
- Claude Collet
- Ecologie des invertébrés, INRA, Institut National de la Recherche Agronomique, UMR406, Domaine St Paul, Site Agroparc, F-84914 Avignon cedex 9, France.
| | | |
Collapse
|
28
|
Hopf FW, Turner PR, Steinhardt RA. Calcium misregulation and the pathogenesis of muscular dystrophy. Subcell Biochem 2007; 45:429-464. [PMID: 18193647 DOI: 10.1007/978-1-4020-6191-2_16] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Although the exact nature of the relationship between calcium and the pathogenesis of Duchenne muscular dystrophy (DMD) is not fully understood, this is an important issue which has been addressed in several recent reviews (Alderton and Steinhardt, 2000a, Gailly, 2002, Allen et al., 2005). A key question when trying to understand the cellular basis of DMD is how the absence or low level of expression of dystrophin, a cytoskeletal protein, results in the slow but progressive necrosis of muscle fibres. Although loss of cytoskeletal and sarcolemmal integrity which results from the absence of dystrophin clearly plays a key role in the pathogenesis associated with DMD, a number of lines of evidence also establish a role for misregulation of calcium ions in the DMD pathology, particularly in the cytoplasmic space just under the sarcolemma. A number of calcium-permeable channels have been identified which can exhibit greater activity in dystrophic muscle cells, and exIsting evidence suggests that these may represent different variants of the same channel type (perhaps the transient receptor potential channel, TRPC). In addition, a prominent role for calcium-activated proteases in the DMD pathology has been established, as well as modulation of other intracellular regulatory proteins and signaling pathways. Whether dystrophin and its associated proteins have a direct role in the regulation of calcium ions, calcium channels or intracellular calcium stores, or indirectly alters calcium regulation through enhancement of membrane tearing, remains unclear. Here we focus on areas of consensus or divergence amongst the existing literature, and propose areas where future research would be especially valuable.
Collapse
Affiliation(s)
- F W Hopf
- Ernest Gallo Clinic and Research Center, University of California, San Francisco, 5858 Horton St., Suite 200, Emeryville, CA 94608, USA.
| | | | | |
Collapse
|
29
|
Pathophysiology of duchenne muscular dystrophy: current hypotheses. Pediatr Neurol 2007; 36:1-7. [PMID: 17162189 DOI: 10.1016/j.pediatrneurol.2006.09.016] [Citation(s) in RCA: 300] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2006] [Revised: 07/11/2006] [Accepted: 09/20/2006] [Indexed: 11/15/2022]
Abstract
Duchenne muscular dystrophy is a devastating inherited neuromuscular disorder that affects one in 3300 live male births. Although the responsible gene and its product, dystrophin, have been characterized for more than 15 years, and a mouse model (mdx) has been developed, comprehensive understanding of the mechanism leading from the absence of dystrophin to the muscular degeneration is still debated. First, dystrophin is considered a key structural element in the muscle fiber, and the primary function of the dystrophin-associated protein complex is to stabilize plasma membrane, although a role of signaling is still possible. Mechanically induced damage through eccentric contractions puts a high stress on fragile membranes and provokes micro-lesions that could eventually lead to loss of calcium homeostasis, and cell death. Altered regeneration, inflammation, impaired vascular adaptation, and fibrosis are probably downstream events that take part in the muscular dystrophy and that probably vary a lot along species (i.e., mdx mice), probands within families, stressing the importance of epigenic factors. Because no etiologic therapy is available for Duchenne muscular dystrophy, a better understanding of the primary and downstream mechanisms could prove useful for producing new adjuvant treatments. All pathophysiologic mechanisms are reviewed together with perspectives on management.
Collapse
|
30
|
Boittin FX, Petermann O, Hirn C, Mittaud P, Dorchies OM, Roulet E, Ruegg UT. Ca2+-independent phospholipase A2 enhances store-operated Ca2+ entry in dystrophic skeletal muscle fibers. J Cell Sci 2006; 119:3733-42. [PMID: 16926189 DOI: 10.1242/jcs.03184] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Duchenne muscular dystrophy is caused by deficiency of dystrophin and leads to progressive weakness. It has been proposed that the muscle degeneration occurring in this disease is caused by increased Ca2+ influx due to enhanced activity of cationic channels that are activated either by stretch of the plasma membrane (stretch-activated channels) or by Ca2+-store depletion (store-operated channels). Using both cytosolic Ca2+ measurements with Fura-2 and the manganese quench method, we show here that store-operated Ca2+ entry is greatly enhanced in dystrophic skeletal flexor digitorum brevis fibers isolated from mdx5cv mice, a mouse model of Duchenne muscular dystrophy. Moreover, we show for the first time that store-operated Ca2+ entry in these fibers is under the control of the Ca2+-independent phospholipase A2 and that the exaggerated Ca2+ influx can be completely attenuated by inhibitors of this enzyme. Enhanced store-operated Ca2+ entry in dystrophic fibers is likely to be due to a near twofold overexpression of Ca2+-independent phospholipase A2. The Ca2+-independent phospholipase A2 pathway therefore appears as an attractive target to reduce excessive Ca2+ influx and subsequent degeneration occurring in dystrophic fibers.
Collapse
Affiliation(s)
- François-Xavier Boittin
- Laboratory of Pharmacology, Geneva-Lausanne School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 1211 Geneva 4, Switzerland
| | | | | | | | | | | | | |
Collapse
|
31
|
Allard B, Couchoux H, Pouvreau S, Jacquemond V. Sarcoplasmic reticulum Ca2+ release and depletion fail to affect sarcolemmal ion channel activity in mouse skeletal muscle. J Physiol 2006; 575:69-81. [PMID: 16777939 PMCID: PMC1819412 DOI: 10.1113/jphysiol.2006.112367] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 04/27/2006] [Accepted: 06/15/2006] [Indexed: 11/08/2022] Open
Abstract
In skeletal muscle, sarcoplasmic reticulum (SR) Ca2+ depletion is suspected to trigger a calcium entry across the plasma membrane and recent studies also suggest that the opening of channels spontaneously active at rest and possibly involved in Duchenne dystrophy may be regulated by SR Ca2+ depletion. Here we simultaneously used the cell-attached and whole-cell voltage-clamp techniques as well as intracellular Ca2+ measurements on single isolated mouse skeletal muscle fibres to unravel any possible change in membrane conductance that would depend upon SR Ca2+ release and/or SR Ca2+ depletion. Delayed rectifier K+ single channel activity was routinely detected during whole-cell depolarizing pulses. In addition the activity of channels carrying unitary inward currents of approximately 1.5 pA at -80 mV was detected in 17 out of 127 and in 21 out of 59 patches in control and mdx dystrophic fibres, respectively. In both populations of fibres, large whole-cell depolarizing pulses did not reproducibly increase this channel activity. This was also true when, repeated application of the whole-cell pulses led to exhaustion of the Ca2+ transient. SR Ca2+ depletion produced by the SR Ca2+ pump inhibitor cyclopiazonic acid (CPA) also failed to induce any increase in the resting whole-cell conductance and in the inward single channel activity. Overall results indicate that voltage-activated SR Ca2+ release and/or SR Ca2+ depletion are not sufficient to activate the opening of channels carrying inward currents at negative voltages and challenge the physiological relevance of a store-operated membrane conductance in adult skeletal muscle.
Collapse
Affiliation(s)
- Bruno Allard
- Physiologie Intégrative, Cellulaire et Moléculaire, UMR CNRS 5123, Université C. Bernard Lyon I, 43 bd du 11 Novembre 1918, 69622 Villeurbanne cedex, France
| | | | | | | |
Collapse
|
32
|
Constantin B, Sebille S, Cognard C. New insights in the regulation of calcium transfers by muscle dystrophin-based cytoskeleton: implications in DMD. J Muscle Res Cell Motil 2006; 27:375-86. [PMID: 16897576 DOI: 10.1007/s10974-006-9085-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 06/28/2006] [Indexed: 01/18/2023]
Abstract
Calcium mishandling in Duchenne muscular dystrophy (DMD) suggested that dystrophin, a membrane-associated cytoskeleton protein, may regulate calcium-signalling cascades such as calcium entries. Calcium overload in human DMD myotubes is dependent on their contractile activity suggesting the involvement of channels being activated during contraction and/or calcium release. Forced expression of mini-dystrophin in dystrophin-deficient myotubes, reactivates appropriate sarcolemmal expression of dystrophin-associated proteins and restores normal calcium handling in the cytosol. Furthermore, the recombinant mini-dystrophin reduced the store-operated calcium influx across the sarcolemma, and the mitochondrial calcium uptake during this influx. A slow component of calcium release dependent on IP3R, as well as the production of IP3, were also reduced to normal levels by expression of mini-dystrophin. Our studies provide a new model for the convergent regulation of transmembrane calcium influx and IP3-dependent calcium release by the dystrophin-based cytoskeleton (DBC). We also suggest molecular association of such channels with DBC which may provide the scaffold for assembling a multiprotein-signalling complex that modulates the channel activity. This suggests that the loss of this molecular association could participate in the alteration of calcium homeostasis observed in DMD muscle cells.
Collapse
Affiliation(s)
- Bruno Constantin
- Institut de Physiologie et Biologie Cellulaires, CNRS, UMR-6187, University of Poitiers, 86022, Poitiers, France.
| | | | | |
Collapse
|
33
|
Lafoux A, Divet A, Gervier P, Huchet-Cadiou C. Greater susceptibility of the sarcoplasmic reticulum to H2O2 injuries in diaphragm muscle from mdx mice. J Pharmacol Exp Ther 2006; 318:1359-67. [PMID: 16801456 DOI: 10.1124/jpet.106.103291] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of the present study was to investigate the direct effects of a reactive oxygen species, H(2)O(2), on the contractile function and sarcoplasmic reticulum properties of dystrophin-deficient diaphragm using chemically skinned fibers and sarcoplasmic reticulum vesicle preparations. The results obtained using Triton X-100-skinned fibers demonstrate that exposure to 1 mM H(2)O(2) had similar effects on the maximal Ca(2+)-activated tension and on the Ca(2+) sensitivity of the contractile apparatus of diaphragm fibers in Bl10 and mdx mice. The effects of H(2)O(2) were also assessed on sarcoplasmic reticulum function using saponin-skinned fibers and sarcoplasmic reticulum vesicle preparations. We found that H(2)O(2) induced changes in sarcoplasmic reticulum properties, particularly in the Ca(2+) pump function. The most important finding was that diaphragm muscle from mdx mice displayed increased sensitivity to the oxidant. Furthermore, in isolated superfused diaphragm muscle from mdx mice, the data demonstrate that the amount of superoxide anion produced under fatiguing conditions was increased. Our study shows that the sarcoplasmic reticulum, and the Ca(2+) pump in particular, in dystrophin-deficient muscles display increased susceptibility to H(2)O(2) injuries. This suggests that free radicals might, therefore, be involved in the pathophysiological pathway and dysregulation of Ca(2+) homeostasis of muscular dystrophy.
Collapse
Affiliation(s)
- Aude Lafoux
- Université de Nantes, Centre National de la Recherche Scientifique, Unité Mixte Recherche 6204, Biotechnologie, Biocatalyse et Biorégulation, Faculté des Sciences et des Techniques, F-44322 Nantes, Cedex 03, France
| | | | | | | |
Collapse
|
34
|
Pouvreau S, Csernoch L, Allard B, Sabatier JM, De Waard M, Ronjat M, Jacquemond V. Transient loss of voltage control of Ca2+ release in the presence of maurocalcine in skeletal muscle. Biophys J 2006; 91:2206-15. [PMID: 16782801 PMCID: PMC1557560 DOI: 10.1529/biophysj.105.078089] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In skeletal muscle, sarcoplasmic reticulum (SR) calcium release is controlled by the plasma membrane voltage through interactions between the voltage-sensing dihydropyridine receptor (DHPr) and the ryanodine receptor (RYr) calcium release channel. Maurocalcine (MCa), a scorpion toxin peptide presenting some homology with a segment of a cytoplasmic loop of the DHPr, has been previously shown to strongly affect the activity of the isolated RYr. We injected MCa into mouse skeletal muscle fibers and measured intracellular calcium under voltage-clamp conditions. Voltage-activated calcium transients exhibited similar properties in control and in MCa-injected fibers during the depolarizing pulses, and the voltage dependence of calcium release was similar under the two conditions. However, MCa was responsible for a pronounced sustained phase of Ca(2+) elevation that proceeded for seconds following membrane repolarization, with no concurrent alteration of the membrane current. The magnitude of the underlying uncontrolled extra phase of Ca(2+) release correlated well with the peak calcium release during the pulse. Results suggest that MCa binds to RYr that open on membrane depolarization and that this interaction specifically alters the process of repolarization-induced closure of the channels.
Collapse
Affiliation(s)
- Sandrine Pouvreau
- Physiologie Intégrative Cellulaire et Moléculaire, Université Claude Bernard Lyon 1, UMR CNRS 5123, Bâtiment Raphael Dubois, 43 boulevard du 11 novembre 1918, F 69622 Villeurbanne Cedex, France
| | | | | | | | | | | | | |
Collapse
|
35
|
Han R, Grounds MD, Bakker AJ. Measurement of sub-membrane [Ca2+] in adult myofibers and cytosolic [Ca2+] in myotubes from normal and mdx mice using the Ca2+ indicator FFP-18. Cell Calcium 2006; 40:299-307. [PMID: 16765438 DOI: 10.1016/j.ceca.2006.04.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 04/04/2006] [Accepted: 04/12/2006] [Indexed: 10/24/2022]
Abstract
The hypothesis that intracellular Ca(2+) is elevated in dystrophic (mdx) skeletal muscle due to increased Ca(2+) influx is controversial. As the sub-sarcolemmal Ca(2+) ([Ca(2+)](mem)) should be even higher than the global cytosolic Ca(2+) in the presence of increased Ca(2+) influx, we investigated [Ca(2+)](mem) levels in collagenase-isolated adult flexor digitorum brevis (FDB) myofibres and myotubes of mdx and normal mice with the near-membrane Ca(2+) indicator FFP-18. Confocal imaging showed strong localization of FFP-18 to the sarcolemma only. No significant difference in [Ca(2+)](mem) was found in FDB myofibres of normal (77.3+/-3.8 nM, n=68) and mdx (79.3+/-5.6 nM, n=21, p=0.89) mice using FFP-18. Increasing external Ca(2+) to 18 mM did not significantly affect [Ca(2+)](mem) in either the normal or mdx myofibres. In the myotubes, the FFP-18 was non-selectively incorporated, distributing throughout the cytoplasm, and FFP-18-derived [Ca(2+)] values were similar to values obtained with Fura-2. Nevertheless, in the mdx myotubes, the [Ca(2+)] measured with FFP-18 increased linearly to a level approximately 2.75 times that of controls as the time of culture was prolonged. In older mdx myotubes (>or=8 days in culture), 18 mM extracellular Ca(2+) increased the steady state cytosolic [Ca(2+)] to approximately 22 times greater level than controls. This study suggests that the sub-sarcolemmal Ca(2+) homeostasis is well maintained in isolated adult mdx myofibers and also further supports the hypothesis that cytosolic Ca(2+) handling is compromised in mdx myotubes.
Collapse
Affiliation(s)
- Renzhi Han
- School of Biomedical and Chemical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
| | | | | |
Collapse
|
36
|
Batchelor CL, Winder SJ. Sparks, signals and shock absorbers: how dystrophin loss causes muscular dystrophy. Trends Cell Biol 2006; 16:198-205. [PMID: 16515861 DOI: 10.1016/j.tcb.2006.02.001] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2005] [Revised: 01/17/2006] [Accepted: 02/16/2006] [Indexed: 11/20/2022]
Abstract
The dystrophin-glycoprotein complex (DGC) can be considered as a specialized adhesion complex, linking the extracellular matrix to the actin cytoskeleton, primarily in muscle cells. Mutations in several components of the DGC lead to its partial or total loss, resulting in various forms of muscular dystrophy. These typically manifest as progressive wasting diseases with loss of muscle integrity. Debate is ongoing about the precise function of the DGC: initially a strictly mechanical role was proposed but it has been suggested that there is aberrant calcium handling in muscular dystrophy and, more recently, changes in MAP kinase and GTPase signalling have been implicated in the aetiology of the disease. Here, we discuss new and interesting developments in these aspects of DGC function and attempt to rationalize the mechanical, calcium and signalling hypotheses to provide a unifying hypothesis of the underlying process of muscular dystrophy.
Collapse
Affiliation(s)
- Clare L Batchelor
- Centre for Developmental and Biomedical Genetics, Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield, UK, S10 2TN
| | | |
Collapse
|
37
|
Woods CE, Novo D, DiFranco M, Capote J, Vergara JL. Propagation in the transverse tubular system and voltage dependence of calcium release in normal and mdx mouse muscle fibres. J Physiol 2005; 568:867-80. [PMID: 16123111 PMCID: PMC1464167 DOI: 10.1113/jphysiol.2005.089318] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Using a two-microelectrode voltage clamp technique, we investigated possible mechanisms underlying the impaired excitation-contraction coupling in skeletal muscle fibres of the mdx mouse, a model of the human disease Duchenne muscular dystrophy. We evaluated the role of the transverse tubular system (T-system) by using the potentiometric indicator di-8 ANEPPS, and that of the sarcoplasmic reticulum (SR) Ca2+ release by measuring Ca2+ transients with a low affinity indicator in the presence of high EGTA concentrations under voltage clamp conditions. We observed minimal differences in the T-system structure and the T-system electrical propagation was not different between normal and mdx mice. Whereas the maximum Ca2+ release elicited by voltage pulses was reduced by approximately 67% in mdx fibres, in agreement with previous results obtained using AP stimulation, the voltage dependence of SR Ca2+ release was identical to that seen in normal fibres. Taken together, our data suggest that the intrinsic ability of the sarcoplasmic reticulum to release Ca2+ may be altered in the mdx mouse.
Collapse
Affiliation(s)
- Christopher E Woods
- Department of Physiology, UCLA School of Medicine, Los Angeles, CA 90095, USA
| | | | | | | | | |
Collapse
|
38
|
Pouvreau S, Jacquemond V. Nitric oxide synthase inhibition affects sarcoplasmic reticulum Ca2+ release in skeletal muscle fibres from mouse. J Physiol 2005; 567:815-28. [PMID: 15994183 PMCID: PMC1474226 DOI: 10.1113/jphysiol.2005.089599] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Nitric oxide (NO) generated by skeletal muscle is believed to regulate force production but how this is achieved remains poorly understood. In the present work we tested the effects of NO synthase (NOs) inhibitors on membrane current and intracellular calcium in isolated skeletal muscle fibres from mouse, under voltage-clamp conditions. Resting [Ca(2+)] and [Ca(2+)] transients evoked by large depolarizations exhibited similar properties in control fibres and in fibres loaded with tenth millimolar levels of the NOs inhibitor N-nitro-L-arginine (L-NNA). Yet the voltage dependence of calcium release was found to be shifted by approximately 15 mV towards negative values in the presence of L-NNA. This effect could be reproduced by the other NOs inhibitor S-methyl-L-thiocitrulline (L-SMT). Separate experiments showed that the voltage dependence of charge movement and of the slow calcium current were unaffected by the presence of L-NNA, ruling out an effect on the voltage sensor. A negative shift in the voltage dependence of calcium release with no concurrent alteration in the properties of charge movement was also observed in fibres exposed to the oxidant H(2)O(2) (1 mM). Conversely the reducing agent dithiothreitol (10 mM) had no obvious effect on Ca(2+) release. Overall, the results indicate that physiological levels of NO exert a tonic inhibitory control on the activation of the calcium release channels. Changes in the voltage dependence of Ca(2+) release activation may be a ubiquitous physiological consequence of redox-related modifications of the ryanodine receptor.
Collapse
Affiliation(s)
- Sandrine Pouvreau
- Physiologie Intégrative Cellulaire et Moléculaire, Université Claude Bernard - Lyon 1, UMR CNRS 5123, Villeurbanne, France
| | | |
Collapse
|
39
|
Ursu D, Schuhmeier RP, Melzer W. Voltage-controlled Ca2+ release and entry flux in isolated adult muscle fibres of the mouse. J Physiol 2004; 562:347-65. [PMID: 15528246 PMCID: PMC1665514 DOI: 10.1113/jphysiol.2004.073882] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The voltage-activated fluxes of Ca(2+) from the sarcoplasmic reticulum (SR) and from the extracellular space were studied in skeletal muscle fibres of adult mice. Single fibres of the interosseus muscle were enzymatically isolated and voltage clamped using a two-electrode technique. The fibres were perfused from the current-passing micropipette with a solution containing 15 mm EGTA and 0.2 mm of either fura-2 or the faster, lower affinity indicator fura-FF. Electrical recordings in parallel with the fluorescence measurements allowed the estimation of intramembrane gating charge movements and transmembrane Ca(2+) inward current exhibiting half-maximal activation at -7.60 +/- 1.29 and 3.0 +/- 1.44 mV, respectively. The rate of Ca(2+) release from the SR was calculated after fitting the relaxation phases of fluorescence ratio signals with a kinetic model to quantify overall Ca(2+) removal. Results obtained with the two indicators were similar. Ca(2+) release was 2-3 orders of magnitude larger than the flux carried by the L-type Ca(2+) current. At maximal depolarization (+50 mV), release flux peaked at about 3 ms after the onset of the voltage pulse and then decayed in two distinct phases. The slower phase, most likely resulting from SR depletion, indicated a decrease in lumenal Ca(2+) content by about 80% within 100 ms. Unlike in frog fibres, the kinetics of the rapid phase of decay showed no dependence on the filling state of the SR and the results provide little evidence for a substantial increase of SR permeability on depletion. The approach described here promises insight into excitation-contraction coupling in future studies of genetically altered mice.
Collapse
Affiliation(s)
- D Ursu
- University of Ulm, Department of Applied Physiology, Albert-Einstein-Allee 11, D-89069 Ulm, Germany
| | | | | |
Collapse
|
40
|
Pouvreau S, Allard B, Berthier C, Jacquemond V. Control of intracellular calcium in the presence of nitric oxide donors in isolated skeletal muscle fibres from mouse. J Physiol 2004; 560:779-94. [PMID: 15375195 PMCID: PMC1665293 DOI: 10.1113/jphysiol.2004.072397] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Accepted: 09/14/2004] [Indexed: 12/26/2022] Open
Abstract
In skeletal muscle, nitric oxide (NO) is commonly referred to as a modulator of the activity of the ryanodine receptor (RyR) calcium release channel. However the reported effects of NO on isolated sarcoplasmic reticulum (SR) preparations and single ryanodine receptor (RyR) activity are diverse, and how NO affects SR calcium release and intracellular calcium homeostasis under physiological conditions remains poorly documented and hardly predictable. Here, we studied the effects of NO donors on membrane current and intracellular [Ca(2+)] in single skeletal muscle fibres from mouse, under voltage-clamp conditions. When fibres were chronically exposed to millimolar levels of sodium nitroprusside (SNP) and challenged by short membrane depolarizations, there was a progressive increase in the resting [Ca(2+)] level. This effect was use-dependent with the slope of rise in resting [Ca(2+)] being increased two-fold when the depolarizing pulse level was raised from -20 to +10 mV. Analysis of the decay of the [Ca(2+)] transients suggested that cytoplasmic Ca(2+) removal processes were largely unaffected by the presence of SNP. Also the functional properties of the dihydropyridine receptor were very similar under control conditions and in the presence of SNP. The resting [Ca(2+)] elevation due to SNP was accompanied by a depression of the peak calcium release elicited by pulses to +10 mV. The effects of SNP could be reproduced by the chemically distinct NO donor NOC-12. They could be reversed upon exposure of the fibres to the thiol reducing agent dithiothreitol. Results suggest that large levels of NO produce a redox-sensitive continuous leak of Ca(2+) from the SR, through a limited number of release channels that do not close once they are activated by membrane depolarization. This SR Ca(2+) leak and the resulting increase in resting [Ca(2+)] may be important in mediating the effects of excess NO on voltage-activated calcium release.
Collapse
Affiliation(s)
- Sandrine Pouvreau
- Physiologie Intégrative Cellulaire et Moléculaire, Université Claude Bernard - Lyon 1, UMR CNRS 5123, Bât. Raphael Dubois, 43 boulevard du 11 novembre 1918, F 69622 Villeurbanne Cedex, France
| | | | | | | |
Collapse
|
41
|
Marchand E, Constantin B, Balghi H, Claudepierre MC, Cantereau A, Magaud C, Mouzou A, Raymond G, Braun S, Cognard C. Improvement of calcium handling and changes in calcium-release properties after mini- or full-length dystrophin forced expression in cultured skeletal myotubes. Exp Cell Res 2004; 297:363-79. [PMID: 15212940 DOI: 10.1016/j.yexcr.2004.02.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2003] [Revised: 01/30/2004] [Indexed: 10/26/2022]
Abstract
Dystrophin is a cytoskeletal protein normally expressed underneath the sarcolemma of muscle fibers. The lack of dystrophin in Duchenne muscular Dystrophy (DMD) muscles results in fiber necrosis, which was proposed to be mediated by chronic calcium mishandling. The extensive comparison of dystrophic cells from human or mdx mice with normal muscles have suggested that the lack of dystrophin may alter the resting calcium permeability and steady-state levels of calcium, but this latter observation remains controversial. It is also not clear, whether calcium mishandling is resulting from the dystrophic process or if dystrophin can directly regulate calcium handling in muscle cells. This prompted us to determine if transfection of full-length dystrophin or Becker Muscular Dystrophy (BMD) minidystrophin, a candidate for viral-mediated gene therapy, could change calcium handling properties. We took advantage of specific properties of Sol8 cell line showing the absence of dystrophin expression together with a drastic calcium mishandling. Here, we show that full-length dystrophin allowed the recovery of a low resting intracellular-free calcium concentration together with lower calcium transients. We also show for the first time that stable expression of minidystrophin was able to restore normal calcium handling in Sol8 myotubes through a better control of steady-state levels, calcium transients, and subcellular calcium events. It suggests that dystrophin could play a regulatory role on calcium homeostasis apparatus and that functional links exist between calcium signaling and cytoskeleton.
Collapse
MESH Headings
- Animals
- Calcium/metabolism
- Carbocyanines
- Cells, Cultured
- Dystrophin/genetics
- Dystrophin/metabolism
- Fluorescent Dyes
- Green Fluorescent Proteins
- Homeostasis
- Immunohistochemistry
- Luminescent Proteins
- Mice
- Mice, Inbred C3H
- Microinjections
- Microscopy, Confocal
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle, Skeletal/cytology
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscular Dystrophy, Duchenne/pathology
- Plasmids
- Retroviridae/genetics
Collapse
Affiliation(s)
- Eric Marchand
- Institut de Physiologie et Biologie Cellulaire, UMR CNRS/Université de Poitiers 6187, Pôle Biologie Santé, 86022 Poitiers cedex, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Morel JL, Rakotoarisoa L, Jeyakumar LH, Fleischer S, Mironneau C, Mironneau J. Decreased expression of ryanodine receptors alters calcium-induced calcium release mechanism in mdx duodenal myocytes. J Biol Chem 2004; 279:21287-93. [PMID: 14985349 DOI: 10.1074/jbc.m311124200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It is generally believed that alterations of calcium homeostasis play a key role in skeletal muscle atrophy and degeneration observed in Duchenne's muscular dystrophy and mdx mice. Mechanical activity is also impaired in gastrointestinal muscles, but the cellular and molecular mechanisms of this pathological state have not yet been investigated. We showed, in mdx duodenal myocytes, that both caffeine- and depolarization-induced calcium responses were inhibited, whereas acetylcholine- and thapsigargin-induced calcium responses were not significantly affected compared with control mice. Calcium-induced calcium release efficiency was impaired in mdx duodenal myocytes depending only on inhibition of ryanodine receptor expression. Duodenal myocytes expressed both type 2 and type 3 ryanodine receptors and were unable to produce calcium sparks. In control and mdx duodenal myocytes, both caffeine- and depolarization-induced calcium responses were dose-dependently and specifically inhibited with the anti-type 2 ryanodine receptor antibody. A strong inhibition of type 2 ryanodine receptor in mdx duodenal myocytes was observed on the mRNA as well as on the protein level. Taken together, our results suggest that inhibition of type 2 ryanodine receptor expression in mdx duodenal myocytes may account for the decreased calcium release from the sarcoplasmic reticulum and reduced mechanical activity.
Collapse
Affiliation(s)
- Jean-Luc Morel
- Laboratoire de Signalisation et Interactions Cellulaires, CNRS UMR 5017, Université de Bordeaux II, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France
| | | | | | | | | | | |
Collapse
|
43
|
Plant DR, Lynch GS. Depolarization-induced contraction and SR function in mechanically skinned muscle fibers from dystrophic mdx mice. Am J Physiol Cell Physiol 2003; 285:C522-8. [PMID: 12724137 DOI: 10.1152/ajpcell.00369.2002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Dystrophin is absent in muscle fibers of patients with Duchenne muscular dystrophy (DMD) and in muscle fibers from the mdx mouse, an animal model of DMD. Disrupted excitation-contraction (E-C) coupling has been postulated to be a functional consequence of the lack of dystrophin, although the evidence for this is not entirely clear. We used mechanically skinned fibers (with a sealed transverse tubular system) prepared from fast extensor digitorum longus muscles of wild-type control and dystrophic mdx mice to test the hypothesis that dystrophin deficiency would affect the depolarization-induced contractile response (DICR) and sarcoplasmic reticulum (SR) function. DICR was similar in muscle fibers from mdx and control mice, indicating normal voltage regulation of Ca2+ release. Nevertheless, rundown of DICR (<50% of initial) was reached more rapidly in fibers from mdx than control mice [control: 32 +/- 5 depolarizations (n = 14 fibers) vs. mdx: 18 +/- 1 depolarizations (n = 7) before rundown, P < 0.05]. The repriming rate for DICRs was decreased in fibers from mdx mice, with lower submaximal DICR observed after 5, 10, and 20 s of repriming compared with fibers from control mice (P < 0.05). SR Ca2+ reloading was not different in fibers from control and mdx mice, and no difference was observed in SR Ca2+ leak. Caffeine (2-7 mM)-induced contraction was diminished in fibers from mdx mice compared with control (P < 0.05), indicating depressed SR Ca2+ release channel activity. Our findings indicate that fast fibers from mdx mice exhibit some impairment in the events mediating E-C coupling and SR Ca2+ release channel activity.
Collapse
Affiliation(s)
- David R Plant
- Department of Physiology, The University of Melbourne, Victoria 3010, Australia
| | | |
Collapse
|
44
|
Raymackers JM, Debaix H, Colson-Van Schoor M, De Backer F, Tajeddine N, Schwaller B, Gailly P, Gillis JM. Consequence of parvalbumin deficiency in the mdx mouse: histological, biochemical and mechanical phenotype of a new double mutant. Neuromuscul Disord 2003; 13:376-87. [PMID: 12798793 DOI: 10.1016/s0960-8966(03)00031-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We tested the hypothesis whether the mild dystrophy in mdx mice could result from the contribution of the cytosolic calcium buffer parvalbumin in maintaining a normal cytosolic [Ca2+]i, in spite of an increased passive Ca2+ influx. By crossing mdx mice with parvalbumin-deficient mice, double mutant mice, lacking both dystrophin and parvalbumin, were obtained. Though resting cytosolic [Ca2+]i and total calcium content were similar to that of mdx muscles, this new animal model presented a slightly more severe phenotype than the mdx mouse. Muscle pseudo-hypertrophy, the density of myotubes and of centronucleated fibres as well as the loss of IIB fibres were all increased in parvalbumin-deficient mdx mice. Many of these deficits were overcome in late adulthood, albeit fibrosis was clearly more pronounced than in mdx muscles. At 90 days, parvalbumin-deficient mdx mice showed higher levels of creatine phosphokinase and lower muscle strength, in vivo, than mdx mice. Isometric tension of isolated muscle was reduced, but the susceptibility to eccentric contraction was not increased. The slight aggravation of muscle dystrophy observed in mdx mice deprived of parvalbumin cannot explain the severity of the affection observed in xmd dogs and Duchenne dystrophy patients where parvalbumin is constitutively not expressed.
Collapse
Affiliation(s)
- J M Raymackers
- Department of Physiology and Pharmacology, Catholic University of Louvain, B-1200 Brussels, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
45
|
Collet C, Csernoch L, Jacquemond V. Intramembrane charge movement and L-type calcium current in skeletal muscle fibers isolated from control and mdx mice. Biophys J 2003; 84:251-65. [PMID: 12524279 PMCID: PMC1302607 DOI: 10.1016/s0006-3495(03)74846-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Dystrophin-deficient muscle fibers from mdx mice are believed to suffer from increased calcium entry and elevated submembranous calcium level, the actual source and functional consequences of which remain obscure. Here we compare the properties of the dihydropyridine receptor as voltage sensor and calcium channel in control and mdx muscle fibers, using the silicone-voltage clamp technique. In control fibers charge movement followed a two-state Boltzmann distribution with values for maximal charge, midpoint voltage, and steepness of 23 +/- 2 nC/ micro F, -37 +/- 3 mV, and 13 +/- 1 mV (n = 7). Essentially identical values were obtained in mdx fibers and the time course of charge recovery from inactivation was also similar in the two populations (tau approximately 6 s). In control fibers the voltage dependence of the slow calcium current elicited by 100-ms-long pulses gave values for maximal conductance, apparent reversal potential, half-activation potential, and steepness factor of 156 +/- 15 S/F, 65.5 +/- 2.9 mV, -0.76 +/- 1.2 mV, and 6.2 +/- 0.5 mV (n = 17). In mdx fibers, the half-activation potential of the calcium current was slightly more negative (-6.2 +/- 1.2 mV, n = 16). Also, when using longer pulses, the time constant of calcium current decay was found to be significantly larger (by a factor of 1.5-2) in mdx than in control fibers. These changes in calcium current properties are unlikely to be primarily responsible for a dramatic alteration of intracellular calcium homeostasis. They may be speculated to result, at least in part, from remodeling of the submembranous cytoskeleton network due to the absence of dystrophin.
Collapse
Affiliation(s)
- C Collet
- Laboratoire de Physiologie des Eléments Excitables, Université Claude Bernard, F69622 Villeurbanne, France
| | | | | |
Collapse
|
46
|
Gillis JM. Multivariate evaluation of the functional recovery obtained by the overexpression of utrophin in skeletal muscles of the mdx mouse. Neuromuscul Disord 2002; 12 Suppl 1:S90-4. [PMID: 12206802 DOI: 10.1016/s0960-8966(02)00088-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This paper summarizes the various aspects of functional recovery obtained in dystrophin-deficient muscles of the mdx mice where utrophin was overexpressed. This includes preliminary results on tetracycline-controlled expression of utrophin. It is shown that overexpression of utrophin leads to major functional improvements and that full-length utrophin is more efficient than truncated utrophin, missing a part of the central rod-segment. A generalized way of presenting improvements obtained by any treatment in the form of a 'recovery score' is emphasized. The quantitative aspect of the replacement of dystrophin by utrophin is discussed.
Collapse
Affiliation(s)
- Jean-Marie Gillis
- Département de Physiologie, Université Catholique de Louvain, UCL 5540, Avenue Hippocrate 55, 1200 Brussels, Belgium.
| |
Collapse
|
47
|
Vandebrouck C, Martin D, Colson-Van Schoor M, Debaix H, Gailly P. Involvement of TRPC in the abnormal calcium influx observed in dystrophic (mdx) mouse skeletal muscle fibers. J Cell Biol 2002; 158:1089-96. [PMID: 12235126 PMCID: PMC2173225 DOI: 10.1083/jcb.200203091] [Citation(s) in RCA: 277] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Duchenne muscular dystrophy results from the lack of dystrophin, a cytoskeletal protein associated with the inner surface membrane, in skeletal muscle. The absence of dystrophin induces an abnormal increase of sarcolemmal calcium influx through cationic channels in adult skeletal muscle fibers from dystrophic (mdx) mice. We observed that the activity of these channels was increased after depletion of the stores of calcium with thapsigargin or caffeine. By analogy with the situation observed in nonexcitable cells, we therefore hypothesized that these store-operated channels could belong to the transient receptor potential channel (TRPC) family. We measured the expression of TRPC isoforms in normal and mdx adult skeletal muscles fibers, and among the seven known isoforms, five were detected (TRPC1, 2, 3, 4, and 6) by RT-PCR. Western blot analysis and immunocytochemistry of normal and mdx muscle fibers demonstrated the localization of TRPC1, 4, and 6 proteins at the plasma membrane. Therefore, an antisense strategy was used to repress these TRPC isoforms. In parallel with the repression of the TRPCs, we observed that the occurrence of calcium leak channels was decreased to one tenth of its control value (patch-clamp technique), showing the involvement of TRPC in the abnormal calcium influx observed in dystrophic fibers.
Collapse
Affiliation(s)
- Clarisse Vandebrouck
- Département de Physiologie, Université Catholique de Louvain (UCL 5540), Avenue Hippocrate 55, 1200 Brussels, Belgium
| | | | | | | | | |
Collapse
|
48
|
De Backer F, Vandebrouck C, Gailly P, Gillis JM. Long-term study of Ca(2+) homeostasis and of survival in collagenase-isolated muscle fibres from normal and mdx mice. J Physiol 2002; 542:855-65. [PMID: 12154184 PMCID: PMC2290435 DOI: 10.1113/jphysiol.2002.020487] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Skeletal muscles of the mdx mouse lack dystrophin offering the possibility to study the role of intracellular Ca(2+) ions in fibre degeneration. Flexor digitorum brevis muscles of 3-month-old mdx and normal mice were dissociated with collagenase; fibres were maintained in culture for 6 days (d0 to d5) and their survival was assessed. Cytosolic [Ca(2+)], passive Mn(2+) influx (indicative of Ca(2+) influx) and activity of mechanosensitive/voltage-independent Ca(2+) channels were studied over the same period. Survival of normal fibres declined steadily from d0 to d3, but an acceleration of fibre death occurred in mdx fibres from d1 to d2. This could be greatly reduced but not abolished by lowering external [Ca(2+)] 10-fold. In the d0-d5 period, both mdx and normal fibres showed transient increases of Mn(2+) influx and activity of the Ca(2+) channels; these peaked at d1 and disappeared by d3-d4. Increases were always significantly larger in mdx fibres. Altogether, over the 6 days, 130 paired measurements of [Ca(2+)](i) and Mn(2+) influx were made on 68 fibres from mdx and 62 fibres from normal mice. In 90 % of the fibres, [Ca(2+)](i) remained within the 25-85 nM limits while Mn(2+) influx varied more than 10-fold. The median for Mn(2+) influx was 45 % greater in fibres from mdx mice than in fibres from control C57 mice. However, there was no significant difference between [Ca(2+)](i) medians in fibres from normal and mdx mice. Addition of 25-75 nM of a Ca(2+) ionophore (4-bromo-A23187) to the medium did not affect the level of cytosolic [Ca(2+)] in both types of fibres, while markedly increasing the rate of Mn(2+) influx, as expected. Thus, Ca(2+) homeostasis was equally robust in mdx and normal fibres. The remaining 10 % of the fibres showed, at d1, high levels of Mn(2+) influx and/or elevated [Ca(2+)](i) above 100 nM. This did not affect survival of normal fibres but was probably responsible of the increased death rate in mdx fibres.
Collapse
Affiliation(s)
- F De Backer
- Département de Physiologie, Université Catholique de Louvain, 1200 Bruxelles, Belgium
| | | | | | | |
Collapse
|
49
|
Blake DJ, Weir A, Newey SE, Davies KE. Function and genetics of dystrophin and dystrophin-related proteins in muscle. Physiol Rev 2002; 82:291-329. [PMID: 11917091 DOI: 10.1152/physrev.00028.2001] [Citation(s) in RCA: 813] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The X-linked muscle-wasting disease Duchenne muscular dystrophy is caused by mutations in the gene encoding dystrophin. There is currently no effective treatment for the disease; however, the complex molecular pathology of this disorder is now being unravelled. Dystrophin is located at the muscle sarcolemma in a membrane-spanning protein complex that connects the cytoskeleton to the basal lamina. Mutations in many components of the dystrophin protein complex cause other forms of autosomally inherited muscular dystrophy, indicating the importance of this complex in normal muscle function. Although the precise function of dystrophin is unknown, the lack of protein causes membrane destabilization and the activation of multiple pathophysiological processes, many of which converge on alterations in intracellular calcium handling. Dystrophin is also the prototype of a family of dystrophin-related proteins, many of which are found in muscle. This family includes utrophin and alpha-dystrobrevin, which are involved in the maintenance of the neuromuscular junction architecture and in muscle homeostasis. New insights into the pathophysiology of dystrophic muscle, the identification of compensating proteins, and the discovery of new binding partners are paving the way for novel therapeutic strategies to treat this fatal muscle disease. This review discusses the role of the dystrophin complex and protein family in muscle and describes the physiological processes that are affected in Duchenne muscular dystrophy.
Collapse
Affiliation(s)
- Derek J Blake
- Medical Research Council, Functional Genetics Unit, Department of Human Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | | | | | | |
Collapse
|
50
|
Collet C, Jacquemond V. Sustained release of calcium elicited by membrane depolarization in ryanodine-injected mouse skeletal muscle fibers. Biophys J 2002; 82:1509-23. [PMID: 11867465 PMCID: PMC1301951 DOI: 10.1016/s0006-3495(02)75504-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The effect of micromolar intracellular levels of ryanodine was tested on the myoplasmic free calcium concentration ([Ca(2+)](i)) measured from a portion of isolated mouse skeletal muscle fibers voltage-clamped at -80 mV. When ryanodine-injected fibers were transiently depolarized to 0 mV, the early decay phase of [Ca(2+)](i) upon membrane repolarization was followed by a steady elevated [Ca(2+)](i) level. This effect could be qualitatively well simulated, assuming that ryanodine binds to release channels that open during depolarization and that ryanodine-bound channels do not close upon repolarization. The amplitude of the postpulse [Ca(2+)](i) elevation depended on the duration of the depolarization, being hardly detectable for pulses shorter than 100 ms, and very prominent for duration pulses of seconds. Within a series of consecutive pulses of the same duration, the effect of ryanodine produced a staircase increase in resting [Ca(2+)](i), the slope of which was approximately twice larger for depolarizations to 0 or +10 mV than to -30 or -20 mV. Overall results are consistent with the "open-locked" state because of ryanodine binding to calcium release channels that open during depolarization. Within the voltage-sensitive range of calcium release, increasing either the amplitude or the duration of the depolarization seems to enhance the fraction of release channels accessible to ryanodine.
Collapse
Affiliation(s)
- Claude Collet
- Laboratoire de Physiologie des Eléments Excitables, Université Claude Bernard Lyon 1, F69622 Villeurbanne, France
| | | |
Collapse
|