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Szentesi P, Dienes B, Kutchukian C, Czirjak T, Buj-Bello A, Jacquemond V, Csernoch L. Disrupted T-tubular network accounts for asynchronous calcium release in MTM1-deficient skeletal muscle. J Physiol 2023; 601:99-121. [PMID: 36408764 PMCID: PMC10107287 DOI: 10.1113/jp283650] [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: 07/26/2022] [Accepted: 11/14/2022] [Indexed: 11/22/2022] Open
Abstract
In mammalian skeletal muscle, the propagation of surface membrane depolarization into the interior of the muscle fibre along the transverse (T) tubular network is essential for the synchronized release of calcium from the sarcoplasmic reticulum (SR) via ryanodine receptors (RyRs) in response to the conformational change in the voltage-sensor dihydropyridine receptors. Deficiency in 3-phosphoinositide phosphatase myotubularin (MTM1) has been reported to disrupt T-tubules, resulting in impaired SR calcium release. Here confocal calcium transients recorded in muscle fibres of MTM1-deficient mice were compared with the results from a model where propagation of the depolarization along the T-tubules was modelled mathematically with disruptions in the network assumed to modify the access and transmembrane resistance as well as the capacitance. If, in simulations, T-tubules were assumed to be partially or completely inaccessible to the depolarization and RyRs at these points to be prime for calcium-induced calcium release, all the features of measured SR calcium release could be reproduced. We conclude that the inappropriate propagation of the depolarization into the fibre interior is the initial critical cause of severely impaired SR calcium release in MTM1 deficiency, while the Ca2+ -triggered opening of RyRs provides an alleviating support to the diseased process. KEY POINTS: Myotubular myopathy is a fatal disease due to genetic deficiency in the phosphoinositide phosphatase MTM1. Although the causes are known and corresponding gene therapy strategies are being developed, there is no mechanistic understanding of the disease-associated muscle function failure. Resolving this issue is of primary interest not only for a fundamental understanding of how MTM1 is critical for healthy muscle function, but also for establishing the related cellular mechanisms most primarily or stringently affected by the disease, which are thus of potential interest as therapy targets. The mathematical modelling approach used in the present work proves that the disease-associated alteration of the plasma membrane invagination network is sufficient to explain the dysfunctions of excitation-contraction coupling, providing the first integrated quantitative framework that explains the associated contraction failure.
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Affiliation(s)
- Peter Szentesi
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Beatrix Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Candice Kutchukian
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5261, INSERM U-1315, Institut NeuroMyoGène, Lyon, France
| | - Tamas Czirjak
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Ana Buj-Bello
- Genethon, Evry, France.,Université Paris-Saclay, Evry, France
| | - Vincent Jacquemond
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5261, INSERM U-1315, Institut NeuroMyoGène, Lyon, France
| | - László Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,ELRN-UD Cell Physiology Research Group, Debrecen, Hungary
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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: 4] [Impact Index Per Article: 2.0] [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.
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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:
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Jaque-Fernández F, Jorquera G, Troc-Gajardo J, Pietri-Rouxel F, Gentil C, Buvinic S, Allard B, Jaimovich E, Jacquemond V, Casas M. Pannexin-1 and CaV1.1 show reciprocal interaction during excitation-contraction and excitation-transcription coupling in skeletal muscle. J Gen Physiol 2021; 153:212695. [PMID: 34636893 PMCID: PMC8515650 DOI: 10.1085/jgp.202012635] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/24/2021] [Accepted: 09/15/2021] [Indexed: 01/18/2023] Open
Abstract
One of the most important functions of skeletal muscle is to respond to nerve stimuli by contracting. This function ensures body movement but also participates in other important physiological roles, like regulation of glucose homeostasis. Muscle activity is closely regulated to adapt to different demands and shows a plasticity that relies on both transcriptional activity and nerve stimuli. These two processes, both dependent on depolarization of the plasma membrane, have so far been regarded as separated and independent processes due to a lack of evidence of common protein partners or molecular mechanisms. In this study, we reveal intimate functional interactions between the process of excitation-induced contraction and the process of excitation-induced transcriptional activity in skeletal muscle. We show that the plasma membrane voltage-sensing protein CaV1.1 and the ATP-releasing channel Pannexin-1 (Panx1) regulate each other in a reciprocal manner, playing roles in both processes. Specifically, knockdown of CaV1.1 produces chronically elevated extracellular ATP concentrations at rest, consistent with disruption of the normal control of Panx1 activity. Conversely, knockdown of Panx1 affects not only activation of transcription but also CaV1.1 function on the control of muscle fiber contraction. Altogether, our results establish the presence of bidirectional functional regulations between the molecular machineries involved in the control of contraction and transcription induced by membrane depolarization of adult muscle fibers. Our results are important for an integrative understanding of skeletal muscle function and may impact our understanding of several neuromuscular diseases.
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Affiliation(s)
- Francisco Jaque-Fernández
- Programa de Fisiología y Biofísica, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile
| | - Gonzalo Jorquera
- Programa de Fisiología y Biofísica, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile.,Centro de Neurobiología y Fisiopatología Integrativa, Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jennifer Troc-Gajardo
- Programa de Fisiología y Biofísica, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile
| | - France Pietri-Rouxel
- Université Pierre et Marie Curie, Université Paris 06, Institut National de la Santé et de la Recherche Médicale/Centre National de la Recherche Scientifique/Institut de Myologie/Centre de Recherche en Myologie, Groupement hospitalier universitaire Pitié Salpêtrière, Paris, France
| | - Christel Gentil
- Université Pierre et Marie Curie, Université Paris 06, Institut National de la Santé et de la Recherche Médicale/Centre National de la Recherche Scientifique/Institut de Myologie/Centre de Recherche en Myologie, Groupement hospitalier universitaire Pitié Salpêtrière, Paris, France
| | - Sonja Buvinic
- Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile, Santiago, Chile
| | - Bruno Allard
- Université Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR-5310, Institut National de la Santé et de la Recherche Médicale U-1217, Institut NeuroMyoGène, Lyon, France
| | - Enrique Jaimovich
- Programa de Fisiología y Biofísica, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile.,Center for Exercise, Metabolism and Cancer, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile
| | - Vincent Jacquemond
- Université Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique UMR-5310, Institut National de la Santé et de la Recherche Médicale U-1217, Institut NeuroMyoGène, Lyon, France
| | - Mariana Casas
- Programa de Fisiología y Biofísica, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile.,Center for Exercise, Metabolism and Cancer, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile
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Jaque-Fernandez F, Beaulant A, Berthier C, Monteiro L, Allard B, Casas M, Rieusset J, Jacquemond V. Preserved Ca 2+ handling and excitation-contraction coupling in muscle fibres from diet-induced obese mice. Diabetologia 2020; 63:2471-2481. [PMID: 32840676 DOI: 10.1007/s00125-020-05256-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/06/2020] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS Disrupted intracellular Ca2+ handling is known to play a role in diabetic cardiomyopathy but it has also been postulated to contribute to obesity- and type 2 diabetes-associated skeletal muscle dysfunction. Still, there is so far very limited functional insight into whether, and if so to what extent, muscular Ca2+ homeostasis is affected in this situation, so as to potentially determine or contribute to muscle weakness. In differentiated muscle, force production is under the control of the excitation-contraction coupling process: upon plasma membrane electrical activity, the CaV1.1 voltage sensor/Ca2+ channel in the plasma membrane triggers opening of the ryanodine receptor Ca2+ release channel in the sarcoplasmic reticulum (SR) membrane. Opening of the ryanodine receptor triggers the rise in cytosolic Ca2+, which activates contraction while Ca2+ uptake by the SR ATPase Ca2+-pump promotes relaxation. These are the core mechanisms underlying the tight control of muscle force by neuronal electrical activity. This study aimed at characterising their inherent physiological function in a diet-induced mouse model of obesity and type 2 diabetes. METHODS Intact muscle fibres were isolated from mice fed either with a standard chow diet or with a high-fat, high-sucrose diet generating obesity, insulin resistance and glucose intolerance. Properties of muscle fibres were investigated with a combination of whole-cell voltage-clamp electrophysiology and confocal fluorescence imaging. The integrity and density of the plasma membrane network (transverse tubules) that carries the membrane excitation throughout the muscle fibres was assessed with the dye Di-8-ANEPPS. CaV1.1 Ca2+ channel activity was studied by measuring the changes in current across the plasma membrane elicited by voltage-clamp depolarising pulses of increasing amplitude. SR Ca2+ release through ryanodine receptors was simultaneously detected with the Ca2+-sensitive dye Rhod-2 in the cytosol. CaV1.1 voltage-sensing activity was separately characterised from the properties of intra-plasma-membrane charge movement produced by short voltage-clamp depolarising pulses. Spontaneous Ca2+ release at rest was assessed with the Ca2+-sensitive dye Fluo-4. The rate of SR Ca2+ uptake was assessed from the time course of cytosolic Ca2+ recovery after the end of voltage excitation using the Ca2+-sensitive dye Fluo-4FF. The response to a fatigue-stimulation protocol was determined from the time course of decline of the peak Fluo-4FF Ca2+ transients elicited by 30 trains of 5-ms-long depolarising pulses delivered at 100 Hz. RESULTS The transverse tubule network architecture and density were well preserved in the fibres from the obese mice. The CaV1.1 Ca2+ current and voltage-sensing properties were also largely unaffected with mean values for maximum conductance and maximum amount of charge of 234 ± 12 S/F and 30.7 ± 1.6 nC/μF compared with 196 ± 13 S/F and 32.9 ± 2.0 nC/μF in fibres from mice fed with the standard diet, respectively. Voltage-activated SR Ca2+ release through ryanodine receptors also exhibited very similar properties in the two groups with mean values for maximum rate of Ca2+ release of 76.0 ± 6.5 and 78.1 ± 4.4 μmol l-1 ms-1, in fibres from control and obese mice, respectively. The response to a fatigue protocol was also largely unaffected in fibres from the obese mice, and so were the rate of cytosolic Ca2+ removal and the spontaneous Ca2+ release activity at rest. CONCLUSIONS/INTERPRETATION The functional properties of the main mechanisms involved in the control of muscle Ca2+ homeostasis are well preserved in muscle fibres from obese mice, at the level of both the plasma membrane and of the SR. We conclude that intracellular Ca2+ handling and excitation-contraction coupling in skeletal muscle fibres are not primary targets of obesity and type 2 diabetes. Graphical abstract.
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Affiliation(s)
- Francisco Jaque-Fernandez
- Institut NeuroMyoGène, UMR CNRS 5310 - Inserm U1217 - Université Claude Bernard Lyon 1 - Univ Lyon, Faculté de Médecine et de Pharmacie, Lyon, France
| | - Agathe Beaulant
- CarMeN Laboratory, Inserm, INRA, INSA Lyon, Université Claude Bernard Lyon 1 - Univ Lyon, Pierre-Bénite, France
| | - Christine Berthier
- Institut NeuroMyoGène, UMR CNRS 5310 - Inserm U1217 - Université Claude Bernard Lyon 1 - Univ Lyon, Faculté de Médecine et de Pharmacie, Lyon, France
| | - Laloé Monteiro
- Institut NeuroMyoGène, UMR CNRS 5310 - Inserm U1217 - Université Claude Bernard Lyon 1 - Univ Lyon, Faculté de Médecine et de Pharmacie, Lyon, France
| | - Bruno Allard
- Institut NeuroMyoGène, UMR CNRS 5310 - Inserm U1217 - Université Claude Bernard Lyon 1 - Univ Lyon, Faculté de Médecine et de Pharmacie, Lyon, France
| | - Mariana Casas
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Jennifer Rieusset
- CarMeN Laboratory, Inserm, INRA, INSA Lyon, Université Claude Bernard Lyon 1 - Univ Lyon, Pierre-Bénite, France
| | - Vincent Jacquemond
- Institut NeuroMyoGène, UMR CNRS 5310 - Inserm U1217 - Université Claude Bernard Lyon 1 - Univ Lyon, Faculté de Médecine et de Pharmacie, Lyon, France.
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Divalent cations permeation in a Ca 2+ non-conducting skeletal muscle dihydropyridine receptor mouse model. Cell Calcium 2020; 91:102256. [PMID: 32866694 DOI: 10.1016/j.ceca.2020.102256] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/16/2020] [Accepted: 07/19/2020] [Indexed: 11/22/2022]
Abstract
In response to excitation of skeletal muscle fibers, trains of action potentials induce changes in the configuration of the dihydropyridine receptor (DHPR) anchored in the tubular membrane which opens the Ca2+ release channel in the sarcoplasmic reticulum membrane. The DHPR also functions as a voltage-gated Ca2+ channel that conducts L-type Ca2+ currents routinely recorded in mammalian muscle fibers, which role was debated for more than four decades. Recently, to allow a closer look into the role of DHPR Ca2+ influx in mammalian muscle, a knock-in (ki) mouse model (ncDHPR) carrying mutation N617D (adjacent to domain II selectivity filter E) in the DHPRα1S subunit abolishing Ca2+ permeation through the channel was generated [Dayal et al., 2017]. In the present study, the Mn2+ quenching technique was initially intended to be used on voltage-clamped muscle fibers from this mouse to determine whether Ca2+ influx through a pathway distinct from DHPR may occur to compensate for the absence of DHPR Ca2+ influx. Surprisingly, while N617D DHPR muscle fibers of the ki mouse do not conduct Ca2+, Mn2+ entry and subsequent quenching did occur because Mn2+ was able to permeate and produce L-type currents through N617D DHPR. N617D DHPR was also found to conduct Ba2+ and Ba2+ currents were strongly blocked by external Ca2+. Ba2+ permeation was smaller, current kinetics slower and Ca2+ block more potent than in wild-type DHPR. These results indicate that residue N617 when replaced by the negatively charged residue D is suitably located at entrance of the pore to trap external Ca2+ impeding in this way permeation. Because Ba2+ binds with lower affinity to D, Ba2+ currents occur, but with reduced amplitudes as compared to Ba2+ currents through wild-type channels. We conclude that mutations located outside the selectivity filter influence channel permeation and possibly channel gating in a fully differentiated skeletal muscle environment.
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Allard B. Evaluation of mutant muscle Ca 2+ channel properties using two different expression systems. J Gen Physiol 2018; 150:897-899. [PMID: 29848491 PMCID: PMC6028501 DOI: 10.1085/jgp.201812095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Allard appraises recent studies investigating the pathological mechanism of hypokalemic periodic paralysis mutations.
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Affiliation(s)
- Bruno Allard
- Institut NeuroMyoGène, Université Lyon 1, Lyon, France
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Allard B. From excitation to intracellular Ca 2+ movements in skeletal muscle: Basic aspects and related clinical disorders. Neuromuscul Disord 2018; 28:394-401. [DOI: 10.1016/j.nmd.2018.03.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 02/19/2018] [Accepted: 03/05/2018] [Indexed: 01/18/2023]
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Allard B, Fuster C. When muscle Ca 2+ channels carry monovalent cations through gating pores: insights into the pathophysiology of type 1 hypokalaemic periodic paralysis. J Physiol 2018; 596:2019-2027. [PMID: 29572832 DOI: 10.1113/jp274955] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 03/12/2018] [Indexed: 12/22/2022] Open
Abstract
Patients suffering from type 1 hypokalaemic periodic paralysis (HypoPP1) experience attacks of muscle paralysis associated with hypokalaemia. The disease arises from missense mutations in the gene encoding the α1 subunit of the dihydropyridine receptor (DHPR), a protein complex anchored in the tubular membrane of skeletal muscle fibres which controls the release of Ca2+ from sarcoplasmic reticulum and also functions as a Ca2+ channel. The vast majority of mutations consist of the replacement of one of the outer arginines in S4 segments of the α1 subunit by neutral residues. Early studies have shown that muscle fibres from HypoPP1 patients are abnormally depolarized at rest in low K+ to the point of inducing muscle inexcitability. The relationship between HypoPP1 mutations and depolarization has long remained unknown. More recent investigations conducted in the closely structurally related voltage-gated Na+ and K+ channels have shown that comparable S4 arginine substitutions gave rise to elevated inward currents at negative potentials called gating pore currents. Experiments performed in muscle fibres from different models revealed such an inward resting current through HypoPP1 mutated Ca2+ channels. In mouse fibres transfected with HypoPP1 mutated channels, the elevated resting current was found to carry H+ for the R1239H arginine-to-histidine mutation in a S4 segment and Na+ for the V876E HypoPP1 mutation, which has the peculiarity of not being located in S4 segments. Muscle paralysis probably results from the presence of a gating pore current associated with hypokalaemia for both mutations, possibly aggravated by external acidosis for the R1239H mutation.
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Affiliation(s)
- Bruno Allard
- Institut NeuroMyoGene, Université de Lyon, Université Lyon 1, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622 Villeurbanne, France
| | - Clarisse Fuster
- Institut NeuroMyoGene, Université de Lyon, Université Lyon 1, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622 Villeurbanne, France
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Fuster C, Perrot J, Berthier C, Jacquemond V, Charnet P, Allard B. Na leak with gating pore properties in hypokalemic periodic paralysis V876E mutant muscle Ca channel. J Gen Physiol 2017; 149:1139-1148. [PMID: 29114033 PMCID: PMC5715907 DOI: 10.1085/jgp.201711834] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 09/18/2017] [Accepted: 10/12/2017] [Indexed: 12/26/2022] Open
Abstract
Type 1 hypokalemic periodic paralysis (HypoPP1) is a poorly understood genetic neuromuscular disease characterized by episodic attacks of paralysis associated with low blood K+ The vast majority of HypoPP1 mutations involve the replacement of an arginine by a neutral residue in one of the S4 segments of the α1 subunit of the skeletal muscle voltage-gated Ca2+ channel, which is thought to generate a pathogenic gating pore current. The V876E HypoPP1 mutation has the peculiarity of being located in the S3 segment of domain III, rather than an S4 segment, raising the question of whether such a mutation induces a gating pore current. Here we successfully transfer cDNAs encoding GFP-tagged human wild-type (WT) and V876E HypoPP1 mutant α1 subunits into mouse muscles by electroporation. The expression profile of these WT and V876E channels shows a regular striated pattern, indicative of their localization in the t-tubule membrane. In addition, L-type Ca2+ current properties are the same in V876E and WT fibers. However, in the presence of an external solution containing low-Cl- and lacking Na+ and K+, V876E fibers display an elevated leak current at negative voltages that is increased by external acidification to a higher extent in V876E fibers, suggesting that the leak current is carried by H+ ions. However, in the presence of Tyrode's solution, the rate of change in intracellular pH produced by external acidification was not significantly different in V876E and WT fibers. Simultaneous measurement of intracellular Na+ and current in response to Na+ readmission in the external solution reveals a rate of Na+ influx associated with an inward current, which are both significantly larger in V876E fibers. These data suggest that the V876E mutation generates a gating pore current that carries strong resting Na+ inward currents in physiological conditions that are likely responsible for the severe HypoPP1 symptoms associated with this mutation.
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Affiliation(s)
- Clarisse Fuster
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR Centre National de la Recherche Scientifique 5310, Institut National de la Santé et de la Recherche Médicale U1217, Villeurbanne, France
| | - Jimmy Perrot
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR Centre National de la Recherche Scientifique 5310, Institut National de la Santé et de la Recherche Médicale U1217, Villeurbanne, France
| | - Christine Berthier
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR Centre National de la Recherche Scientifique 5310, Institut National de la Santé et de la Recherche Médicale U1217, Villeurbanne, France
| | - Vincent Jacquemond
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR Centre National de la Recherche Scientifique 5310, Institut National de la Santé et de la Recherche Médicale U1217, Villeurbanne, France
| | - Pierre Charnet
- Institut des Biomolécules Max Mousseron, Université Montpellier 1 et 2, UMR Centre National de la Recherche Scientifique 5247, Montpellier, France
| | - Bruno Allard
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR Centre National de la Recherche Scientifique 5310, Institut National de la Santé et de la Recherche Médicale U1217, Villeurbanne, France
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Ferreira Gregorio J, Pequera G, Manno C, Ríos E, Brum G. The voltage sensor of excitation-contraction coupling in mammals: Inactivation and interaction with Ca 2. J Gen Physiol 2017; 149:1041-1058. [PMID: 29021148 PMCID: PMC5677103 DOI: 10.1085/jgp.201611725] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 01/03/2017] [Accepted: 09/07/2017] [Indexed: 12/14/2022] Open
Abstract
In excitation–contraction coupling, voltage-sensing modules (VSMs) of CaV1.1 Ca2+ channels simultaneously gate the associated pore and Ca2+ release channels in the sarcoplasmic reticulum. Ferreira Gregorio et al. find that VSMs adopt two inactivated states, and the degree of inactivation is dependent on external Ca2+ and the mouse strain used. In skeletal muscle, the four-helix voltage-sensing modules (VSMs) of CaV1.1 calcium channels simultaneously gate two Ca2+ pathways: the CaV1.1 pore itself and the RyR1 calcium release channel in the sarcoplasmic reticulum. Here, to gain insight into the mechanism by which VSMs gate RyR1, we quantify intramembrane charge movement associated with VSM activation (sensing current) and gated Ca2+ release flux in single muscle cells of mice and rats. As found for most four-helix VSMs, upon sustained depolarization, rodent VSMs lose the ability to activate Ca2+ release channels opening; their properties change from a functionally capable mode, in which the mobile sensor charge is called charge 1, to an inactivated mode, charge 2, with a voltage dependence shifted toward more negative voltages. We find that charge 2 is promoted and Ca2+ release inactivated when resting, well-polarized muscle cells are exposed to low extracellular [Ca2+] and that the opposite occurs in high [Ca2+]. It follows that murine VSMs are partly inactivated at rest, which establishes the reduced availability of voltage sensing as a pathogenic mechanism in disorders of calcemia. We additionally find that the degree of resting inactivation is significantly different in two mouse strains, which underscores the variability of voltage sensor properties and their vulnerability to environmental conditions. Our studies reveal that the resting and activated states of VSMs are equally favored by extracellular Ca2+. Promotion by an extracellular species of two states of the VSM that differ in the conformation of the activation gate requires the existence of a second gate, inactivation, topologically extracellular and therefore accessible from outside regardless of the activation state.
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Affiliation(s)
| | - Germán Pequera
- Departamento de Biofísica, Facultad de Medicina, Montevideo, Uruguay
| | - Carlo Manno
- Section of Cellular Signaling, Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL
| | - Eduardo Ríos
- Section of Cellular Signaling, Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL
| | - Gustavo Brum
- Departamento de Biofísica, Facultad de Medicina, Montevideo, Uruguay
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Flucher BE, Tuluc P. How and why are calcium currents curtailed in the skeletal muscle voltage-gated calcium channels? J Physiol 2017; 595:1451-1463. [PMID: 27896815 PMCID: PMC5330888 DOI: 10.1113/jp273423] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 11/24/2016] [Indexed: 01/09/2023] Open
Abstract
Voltage‐gated calcium channels represent the sole mechanism converting electrical signals of excitable cells into cellular functions such as contraction, secretion and gene regulation. Specific voltage‐sensing domains detect changes in membrane potential and control channel gating. Calcium ions entering through the channel function as second messengers regulating cell functions, with the exception of skeletal muscle, where CaV1.1 essentially does not function as a channel but activates calcium release from intracellular stores. It has long been known that calcium currents are dispensable for skeletal muscle contraction. However, the questions as to how and why the channel function of CaV1.1 is curtailed remained obscure until the recent discovery of a developmental CaV1.1 splice variant with normal channel functions. This discovery provided new means to study the molecular mechanisms regulating the channel gating and led to the understanding that in skeletal muscle, calcium currents need to be restricted to allow proper regulation of fibre type specification and to prevent mitochondrial damage.
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Affiliation(s)
- Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Austria
| | - Petronel Tuluc
- Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Austria
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Arias-Calderón M, Almarza G, Díaz-Vegas A, Contreras-Ferrat A, Valladares D, Casas M, Toledo H, Jaimovich E, Buvinic S. Characterization of a multiprotein complex involved in excitation-transcription coupling of skeletal muscle. Skelet Muscle 2016; 6:15. [PMID: 27069569 PMCID: PMC4827232 DOI: 10.1186/s13395-016-0087-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 03/19/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Electrical activity regulates the expression of skeletal muscle genes by a process known as "excitation-transcription" (E-T) coupling. We have demonstrated that release of adenosine 5'-triphosphate (ATP) during depolarization activates membrane P2X/P2Y receptors, being the fundamental mediators between electrical stimulation, slow intracellular calcium transients, and gene expression. We propose that this signaling pathway would require the proper coordination between the voltage sensor (dihydropyridine receptor, DHPR), pannexin 1 channels (Panx1, ATP release conduit), nucleotide receptors, and other signaling molecules. The goal of this study was to assess protein-protein interactions within the E-T machinery and to look for novel constituents in order to characterize the signaling complex. METHODS Newborn derived myotubes, adult fibers, or triad fractions from rat or mouse skeletal muscles were used. Co-immunoprecipitation, 2D blue native SDS/PAGE, confocal microscopy z-axis reconstruction, and proximity ligation assays were combined to assess the physical proximity of the putative complex interactors. An L6 cell line overexpressing Panx1 (L6-Panx1) was developed to study the influence of some of the complex interactors in modulation of gene expression. RESULTS Panx1, DHPR, P2Y2 receptor (P2Y2R), and dystrophin co-immunoprecipitated in the different preparations assessed. 2D blue native SDS/PAGE showed that DHPR, Panx1, P2Y2R and caveolin-3 (Cav3) belong to the same multiprotein complex. We observed co-localization and protein-protein proximity between DHPR, Panx1, P2Y2R, and Cav3 in adult fibers and in the L6-Panx1 cell line. We found a very restricted location of Panx1 and Cav3 in a putative T-tubule zone near the sarcolemma, while DHPR was highly expressed all along the transverse (T)-tubule. By Panx1 overexpression, extracellular ATP levels were increased both at rest and after electrical stimulation. Basal mRNA levels of the early gene cfos and the oxidative metabolism markers citrate synthase and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) were significantly increased by Panx1 overexpression. Interleukin 6 expression evoked by 20-Hz electrical stimulation (270 pulses, 0.3 ms each) was also significantly upregulated in L6-Panx1 cells. CONCLUSIONS We propose the existence of a relevant multiprotein complex that coordinates events involved in E-T coupling. Unveiling the molecular actors involved in the regulation of gene expression will contribute to the understanding and treatment of skeletal muscle disorders due to wrong-expressed proteins, as well as to improve skeletal muscle performance.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Animals
- Animals, Newborn
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Caveolin 3/genetics
- Caveolin 3/metabolism
- Cell Line
- Connexins/genetics
- Connexins/metabolism
- Dystrophin/genetics
- Dystrophin/metabolism
- Electric Stimulation
- Gene Expression Regulation
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Multiprotein Complexes
- Muscle Contraction
- Muscle Fibers, Skeletal/metabolism
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Protein Binding
- Rats, Wistar
- Receptors, Purinergic P2Y2/genetics
- Receptors, Purinergic P2Y2/metabolism
- Transcription, Genetic
- Transcriptional Activation
- Transfection
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Affiliation(s)
- Manuel Arias-Calderón
- />Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
- />Instituto de Investigación en Ciencias Odontológicas, Facultad de Odontología, Universidad de Chile, Sergio Livingstone Pohlhammer 943, 8380492 Santiago, Chile
| | - Gonzalo Almarza
- />Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
| | - Alexis Díaz-Vegas
- />Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
| | - Ariel Contreras-Ferrat
- />Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
| | - Denisse Valladares
- />Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
| | - Mariana Casas
- />Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
| | - Héctor Toledo
- />Programa de Biología Molecular y Celular, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
| | - Enrique Jaimovich
- />Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
- />Programa de Biología Molecular y Celular, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, 8380453 Chile
| | - Sonja Buvinic
- />Instituto de Investigación en Ciencias Odontológicas, Facultad de Odontología, Universidad de Chile, Sergio Livingstone Pohlhammer 943, 8380492 Santiago, Chile
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13
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Robin G, Allard B. Voltage-gated Ca(2+) influx through L-type channels contributes to sarcoplasmic reticulum Ca(2+) loading in skeletal muscle. J Physiol 2015; 593:4781-97. [PMID: 26383921 DOI: 10.1113/jp270252] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 09/08/2015] [Indexed: 12/15/2022] Open
Abstract
Muscle contraction is triggered by Ca(2+) ions released from the sarcoplasmic reticulum (SR) in response to depolarization of skeletal muscle fibres. Muscle activation is also associated with a voltage-activated trans-sarcolemmal Ca(2+) influx early identified as a current flowing through L-type Ca(2+) channels. Because removal of external Ca(2+) does not impede fibres from contracting, a negligible role was given to this voltage-activated Ca(2+) entry, although the decline of Ca(2+) release is more pronounced in the absence of Ca(2+) during long-lasting activation. Furthermore, it is not clearly established whether Ca(2+) exclusively flows through L-type channels or in addition through a parallel voltage-activated pathway distinct from L-type channels. Here, by monitoring the quenching of fura-2 fluorescence resulting from Mn(2+) influx in voltage-controlled mouse and zebrafish isolated muscle fibres, we show that the L-type current is the only contributor to Ca(2+) influx during long-lasting depolarizations in skeletal muscle. Calibration of the Mn(2+) quenching signal allowed us to estimate a mean Mn(2+) current of 0.31 ± 0.06 A F(-1) flowing through L-type channels during a train of action potentials. Measurements of SR Ca(2+) changes with fluo-5N in response to depolarization revealed that an elevated voltage-activated Ca(2+) current potentiated SR Ca(2+) loading and addition of external Mn(2+) produced quenching of fluo-5N in the SR, indicating that voltage-activated Ca(2+) /Mn(2+) influx contributes to SR Ca(2+) /Mn(2+) loading.
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Affiliation(s)
- Gaëlle Robin
- Université de Lyon, Université Lyon 1, CNRS UMR 5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Villeurbanne, France
| | - Bruno Allard
- Université de Lyon, Université Lyon 1, CNRS UMR 5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Villeurbanne, France
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14
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Berthier C, Kutchukian C, Bouvard C, Okamura Y, Jacquemond V. Depression of voltage-activated Ca2+ release in skeletal muscle by activation of a voltage-sensing phosphatase. J Gen Physiol 2015; 145:315-30. [PMID: 25825170 PMCID: PMC4380211 DOI: 10.1085/jgp.201411309] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 03/05/2015] [Indexed: 12/30/2022] Open
Abstract
Phosphoinositides act as signaling molecules in numerous cellular transduction processes, and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) regulates the function of several types of plasma membrane ion channels. We investigated the potential role of PtdIns(4,5)P2 in Ca(2+) homeostasis and excitation-contraction (E-C) coupling of mouse muscle fibers using in vivo expression of the voltage-sensing phosphatases (VSPs) Ciona intestinalis VSP (Ci-VSP) or Danio rerio VSP (Dr-VSP). Confocal images of enhanced green fluorescent protein-tagged Dr-VSP revealed a banded pattern consistent with VSP localization within the transverse tubule membrane. Rhod-2 Ca(2+) transients generated by 0.5-s-long voltage-clamp depolarizing pulses sufficient to elicit Ca(2+) release from the sarcoplasmic reticulum (SR) but below the range at which VSPs are activated were unaffected by the presence of the VSPs. However, in Ci-VSP-expressing fibers challenged by 5-s-long depolarizing pulses, the Ca(2+) level late in the pulse (3 s after initiation) was significantly lower at 120 mV than at 20 mV. Furthermore, Ci-VSP-expressing fibers showed a reversible depression of Ca(2+) release during trains, with the peak Ca(2+) transient being reduced by ∼30% after the application of 10 200-ms-long pulses to 100 mV. A similar depression was observed in Dr-VSP-expressing fibers. Cav1.1 Ca(2+) channel-mediated current was unaffected by Ci-VSP activation. In fibers expressing Ci-VSP and a pleckstrin homology domain fused with monomeric red fluorescent protein (PLCδ1PH-mRFP), depolarizing pulses elicited transient changes in mRFP fluorescence consistent with release of transverse tubule-bound PLCδ1PH domain into the cytosol; the voltage sensitivity of these changes was consistent with that of Ci-VSP activation, and recovery occurred with a time constant in the 10-s range. Our results indicate that the PtdIns(4,5)P2 level is tightly maintained in the transverse tubule membrane of the muscle fibers, and that VSP-induced depletion of PtdIns(4,5)P2 impairs voltage-activated Ca(2+) release from the SR. Because Ca(2+) release is thought to be independent from InsP3 signaling, the effect likely results from an interaction between PtdIns(4,5)P2 and a protein partner of the E-C coupling machinery.
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Affiliation(s)
- Christine Berthier
- Centre National de la Recherche Scientifique UMR 5534, Université Lyon 1, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, 69100 Villeurbanne, France
| | - Candice Kutchukian
- Centre National de la Recherche Scientifique UMR 5534, Université Lyon 1, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, 69100 Villeurbanne, France
| | - Clément Bouvard
- Centre National de la Recherche Scientifique UMR 5534, Université Lyon 1, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, 69100 Villeurbanne, France
| | - Yasushi Okamura
- Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Vincent Jacquemond
- Centre National de la Recherche Scientifique UMR 5534, Université Lyon 1, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, 69100 Villeurbanne, France
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15
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Rodríguez EG, Lefebvre R, Bodnár D, Legrand C, Szentesi P, Vincze J, Poulard K, Bertrand-Michel J, Csernoch L, Buj-Bello A, Jacquemond V. Phosphoinositide substrates of myotubularin affect voltage-activated Ca²⁺ release in skeletal muscle. Pflugers Arch 2014; 466:973-85. [PMID: 24022704 DOI: 10.1007/s00424-013-1346-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 08/29/2013] [Accepted: 08/29/2013] [Indexed: 12/19/2022]
Abstract
Skeletal muscle excitation–contraction (E–C) coupling is altered in several models of phosphatidylinositol phosphate (PtdInsP) phosphatase deficiency and ryanodine receptor activity measured in vitro was reported to be affected by certain PtdInsPs, thus prompting investigation of the physiological role of PtdInsPs in E–C coupling. We measured intracellular Ca2+ transients in voltage-clamped mouse muscle fibres microinjected with a solution containing a PtdInsP substrate (PtdIns(3,5)P2 or PtdIns(3)P) or product (PtdIns(5)P or PtdIns) of the myotubularin phosphatase MTM1. No significant change was observed in the presence of either PtdIns(5)P or PtdIns but peak SR Ca2+ release was depressed by ~30% and 50% in fibres injected with PtdIns(3,5)P2 and PtdIns(3)P, respectively, with no concurrent alteration in the membrane current signals associated with the DHPR function as well as in the voltage dependence of Ca2+ release inactivation. In permeabilized muscle fibres, the frequency of spontaneous Ca2+ release events was depressed in the presence of the three tested phosphorylated forms of PtdInsP with PtdIns(3,5)P2 being the most effective, leading to an almost complete disappearance of Ca2+ release events. Results support the possibility that pathological accumulation of MTM1 substrates may acutely depress ryanodine receptor-mediated Ca2+ release. Overexpression of a mCherry-tagged form of MTM1 in muscle fibres revealed a striated pattern consistent with the triadic area. Ca2+ release remained although unaffected by MTM1 overexpression and was also unaffected by the PtdIns-3-kinase inhibitor LY2940002, suggesting that the 3-phosphorylated PtdIns lipids active on voltage-activated Ca2+ release are inherently maintained at a low level, inefficient on Ca2+ release in normal conditions.
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16
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Casas M, Buvinic S, Jaimovich E. ATP signaling in skeletal muscle: from fiber plasticity to regulation of metabolism. Exerc Sport Sci Rev 2014; 42:110-6. [PMID: 24949845 DOI: 10.1249/jes.0000000000000017] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Tetanic electrical stimulation releases adenosine triphosphate (ATP) from muscle fibers through pannexin-1 channels in a frequency-dependent manner; extracellular ATP activates signals that ultimately regulate gene expression and is able to increase glucose transport through activation of P2Y receptors, phosphatidylinositol 3-kinase, Akt, and AS160. We hypothesize that this mechanism is an important link between exercise and the regulation of muscle fiber plasticity and metabolism.
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Affiliation(s)
- Mariana Casas
- 1Center for Molecular Studies of the Cell, Biomedical Sciences Institute, Faculty of Medicine, Universidad de Chile; and 2Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile, Santiago, Chile
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17
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Altamirano F, Valladares D, Henríquez-Olguín C, Casas M, López JR, Allen PD, Jaimovich E. Nifedipine treatment reduces resting calcium concentration, oxidative and apoptotic gene expression, and improves muscle function in dystrophic mdx mice. PLoS One 2013; 8:e81222. [PMID: 24349043 PMCID: PMC3857175 DOI: 10.1371/journal.pone.0081222] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 10/09/2013] [Indexed: 11/18/2022] Open
Abstract
Duchenne Muscular Dystrophy (DMD) is a recessive X-linked genetic disease, caused by mutations in the gene encoding dystrophin. DMD is characterized in humans and in mdx mice by a severe and progressive destruction of muscle fibers, inflammation, oxidative/nitrosative stress, and cell death. In mdx muscle fibers, we have shown that basal ATP release is increased and that extracellular ATP stimulation is pro-apoptotic. In normal fibers, depolarization-induced ATP release is blocked by nifedipine, leading us to study the potential therapeutic effect of nifedipine in mdx muscles and its relation with extracellular ATP signaling. Acute exposure to nifedipine (10 µM) decreased [Ca(2+)]r, NF-κB activity and iNOS expression in mdx myotubes. In addition, 6-week-old mdx mice were treated with daily intraperitoneal injections of nifedipine, 1 mg/Kg for 1 week. This treatment lowered the [Ca(2+)]r measured in vivo in the mdx vastus lateralis. We demonstrated that extracellular ATP levels were higher in adult mdx flexor digitorum brevis (FDB) fibers and can be significantly reduced after 1 week of treatment with nifedipine. Interestingly, acute treatment of mdx FDB fibers with apyrase, an enzyme that completely degrades extracellular ATP to AMP, reduced [Ca(2+)]r to a similar extent as was seen in FDB fibers after 1-week of nifedipine treatment. Moreover, we demonstrated that nifedipine treatment reduced mRNA levels of pro-oxidative/nitrosative (iNOS and gp91(phox)/p47(phox) NOX2 subunits) and pro-apoptotic (Bax) genes in mdx diaphragm muscles and lowered serum creatine kinase (CK) levels. In addition, nifedipine treatment increased muscle strength assessed by the inverted grip-hanging test and exercise tolerance measured with forced swimming test in mdx mice. We hypothesize that nifedipine reduces basal ATP release, thereby decreasing purinergic receptor activation, which in turn reduces [Ca(2+)]r in mdx skeletal muscle cells. The results in this work open new perspectives towards possible targets for pharmacological approaches to treat DMD.
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Affiliation(s)
- Francisco Altamirano
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | - Denisse Valladares
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Carlos Henríquez-Olguín
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Mariana Casas
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Jose R. López
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
- Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Paul D. Allen
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
- Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Enrique Jaimovich
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- * E-mail:
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Valladares D, Almarza G, Contreras A, Pavez M, Buvinic S, Jaimovich E, Casas M. Electrical stimuli are anti-apoptotic in skeletal muscle via extracellular ATP. Alteration of this signal in Mdx mice is a likely cause of dystrophy. PLoS One 2013; 8:e75340. [PMID: 24282497 PMCID: PMC3839923 DOI: 10.1371/journal.pone.0075340] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 08/11/2013] [Indexed: 12/20/2022] Open
Abstract
ATP signaling has been shown to regulate gene expression in skeletal muscle and to be altered in models of muscular dystrophy. We have previously shown that in normal muscle fibers, ATP released through Pannexin1 (Panx1) channels after electrical stimulation plays a role in activating some signaling pathways related to gene expression. We searched for a possible role of ATP signaling in the dystrophy phenotype. We used muscle fibers from flexor digitorum brevis isolated from normal and mdx mice. We demonstrated that low frequency electrical stimulation has an anti-apoptotic effect in normal muscle fibers repressing the expression of Bax, Bim and PUMA. Addition of exogenous ATP to the medium has a similar effect. In dystrophic fibers, the basal levels of extracellular ATP were higher compared to normal fibers, but unlike control fibers, they do not present any ATP release after low frequency electrical stimulation, suggesting an uncoupling between electrical stimulation and ATP release in this condition. Elevated levels of Panx1 and decreased levels of Cav1.1 (dihydropyridine receptors) were found in triads fractions prepared from mdx muscles. Moreover, decreased immunoprecipitation of Cav1.1 and Panx1, suggest uncoupling of the signaling machinery. Importantly, in dystrophic fibers, exogenous ATP was pro-apoptotic, inducing the transcription of Bax, Bim and PUMA and increasing the levels of activated Bax and cytosolic cytochrome c. These evidence points to an involvement of the ATP pathway in the activation of mechanisms related with cell death in muscular dystrophy, opening new perspectives towards possible targets for pharmacological therapies.
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Affiliation(s)
- Denisse Valladares
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Gonzalo Almarza
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Ariel Contreras
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Mario Pavez
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Sonja Buvinic
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Departamento de Ciencias Básicas y Comunitarias, Facultad de Odontología, Universidad de Chile, Santiago, Chile
| | - Enrique Jaimovich
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Mariana Casas
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- * E-mail:
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Johnson EK, Li B, Yoon JH, Flanigan KM, Martin PT, Ervasti J, Montanaro F. Identification of new dystroglycan complexes in skeletal muscle. PLoS One 2013; 8:e73224. [PMID: 23951345 PMCID: PMC3738564 DOI: 10.1371/journal.pone.0073224] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/18/2013] [Indexed: 01/16/2023] Open
Abstract
The dystroglycan complex contains the transmembrane protein β-dystroglycan and its interacting extracellular mucin-like protein α-dystroglycan. In skeletal muscle fibers, the dystroglycan complex plays an important structural role by linking the cytoskeletal protein dystrophin to laminin in the extracellular matrix. Mutations that affect any of the proteins involved in this structural axis lead to myofiber degeneration and are associated with muscular dystrophies and congenital myopathies. Because loss of dystrophin in Duchenne muscular dystrophy (DMD) leads to an almost complete loss of dystroglycan complexes at the myofiber membrane, it is generally assumed that the vast majority of dystroglycan complexes within skeletal muscle fibers interact with dystrophin. The residual dystroglycan present in dystrophin-deficient muscle is thought to be preserved by utrophin, a structural homolog of dystrophin that is up-regulated in dystrophic muscles. However, we found that dystroglycan complexes are still present at the myofiber membrane in the absence of both dystrophin and utrophin. Our data show that only a minority of dystroglycan complexes associate with dystrophin in wild type muscle. Furthermore, we provide evidence for at least three separate pools of dystroglycan complexes within myofibers that differ in composition and are differentially affected by loss of dystrophin. Our findings indicate a more complex role of dystroglycan in muscle than currently recognized and may help explain differences in disease pathology and severity among myopathies linked to mutations in DAPC members.
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Affiliation(s)
- Eric K. Johnson
- Center for Gene Therapy, the Research Institute at Nationwide Children’s Hospital, and The Ohio State University Biochemistry Program, Columbus, Ohio, United States of America
- Ohio State Biochemistry Program, the Ohio State University, Columbus, Ohio, United States of America
| | - Bin Li
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Jung Hae Yoon
- Center for Gene Therapy, the Research Institute at Nationwide Children’s Hospital, and The Ohio State University Biochemistry Program, Columbus, Ohio, United States of America
| | - Kevin M. Flanigan
- Center for Gene Therapy, the Research Institute at Nationwide Children’s Hospital, and The Ohio State University Biochemistry Program, Columbus, Ohio, United States of America
- Department of Pediatrics, the Ohio State University College of Medicine, Columbus, Ohio, United States of America
| | - Paul T. Martin
- Center for Gene Therapy, the Research Institute at Nationwide Children’s Hospital, and The Ohio State University Biochemistry Program, Columbus, Ohio, United States of America
- Department of Pediatrics, the Ohio State University College of Medicine, Columbus, Ohio, United States of America
| | - James Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Federica Montanaro
- Center for Gene Therapy, the Research Institute at Nationwide Children’s Hospital, and The Ohio State University Biochemistry Program, Columbus, Ohio, United States of America
- Ohio State Biochemistry Program, the Ohio State University, Columbus, Ohio, United States of America
- Department of Pediatrics, the Ohio State University College of Medicine, Columbus, Ohio, United States of America
- * E-mail:
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Tjondrokoesoemo A, Li N, Lin PH, Pan Z, Ferrante CJ, Shirokova N, Brotto M, Weisleder N, Ma J. Type 1 inositol (1,4,5)-trisphosphate receptor activates ryanodine receptor 1 to mediate calcium spark signaling in adult mammalian skeletal muscle. J Biol Chem 2012; 288:2103-9. [PMID: 23223241 DOI: 10.1074/jbc.m112.425975] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Functional coupling between inositol (1,4,5)-trisphosphate receptor (IP(3)R) and ryanodine receptor (RyR) represents a critical component of intracellular Ca(2+) signaling in many excitable cells; however, the role of this mechanism in skeletal muscle remains elusive. In skeletal muscle, RyR-mediated Ca(2+) sparks are suppressed in resting conditions, whereas application of transient osmotic stress can trigger activation of Ca(2+) sparks that are restricted to the periphery of the fiber. Here we show that onset of these spatially confined Ca(2+) sparks involves interaction between activation of IP(3)R and RyR near the sarcolemmal membrane. Pharmacological prevention of IP(3) production or inhibition of IP(3)R channel activity abolishes stress-induced Ca(2+) sparks in skeletal muscle. Although genetic ablation of the type 2 IP(3)R does not appear to affect Ca(2+) sparks in skeletal muscle, specific silencing of the type 1 IP(3)R leads to ablation of stress-induced Ca(2+) sparks. Our data indicate that membrane-delimited signaling involving cross-talk between IP(3)R1 and RyR1 contributes to Ca(2+) spark activation in skeletal muscle.
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Affiliation(s)
- Andoria Tjondrokoesoemo
- Department of Physiology and Biophysics, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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21
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Khairallah RJ, Shi G, Sbrana F, Prosser BL, Borroto C, Mazaitis MJ, Hoffman EP, Mahurkar A, Sachs F, Sun Y, Chen YW, Raiteri R, Lederer WJ, Dorsey SG, Ward CW. Microtubules underlie dysfunction in duchenne muscular dystrophy. Sci Signal 2012; 5:ra56. [PMID: 22871609 DOI: 10.1126/scisignal.2002829] [Citation(s) in RCA: 191] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Duchenne muscular dystrophy (DMD) is a fatal X-linked degenerative muscle disease caused by the absence of the microtubule-associated protein dystrophin, which results in a disorganized and denser microtubule cytoskeleton. In addition, mechanotransduction-dependent activation of calcium (Ca(2+)) and reactive oxygen species (ROS) signaling underpins muscle degeneration in DMD. We show that in muscle from adult mdx mice, a model of DMD, a brief physiologic stretch elicited microtubule-dependent activation of NADPH (reduced-form nicotinamide adenine dinucleotide phosphate) oxidase-dependent production of ROS, termed X-ROS. Further, X-ROS amplified Ca(2+) influx through stretch-activated channels in mdx muscle. Consistent with the importance of the microtubules to the dysfunction in mdx muscle, muscle cells with dense microtubule structure, such as those from adult mdx mice or from young wild-type mice treated with Taxol, showed increased X-ROS production and Ca(2+) influx, whereas cells with a less dense microtubule network, such as young mdx or adult mdx muscle treated with colchicine or nocodazole, showed little ROS production or Ca(2+) influx. In vivo treatments that disrupted the microtubule network or inhibited NADPH oxidase 2 reduced contraction-induced injury in adult mdx mice. Furthermore, transcriptome analysis identified increased expression of X-ROS-related genes in human DMD skeletal muscle. Together, these data show that microtubules are the proximate element responsible for the dysfunction in Ca(2+) and ROS signaling in DMD and could be effective therapeutic targets for intervention.
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Affiliation(s)
- Ramzi J Khairallah
- Center for Biomedical Engineering and Technology and Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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22
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Tuckwell HC. Quantitative aspects of L-type Ca2+ currents. Prog Neurobiol 2012; 96:1-31. [DOI: 10.1016/j.pneurobio.2011.09.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 09/16/2011] [Accepted: 09/23/2011] [Indexed: 12/24/2022]
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23
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Golini L, Chouabe C, Berthier C, Cusimano V, Fornaro M, Bonvallet R, Formoso L, Giacomello E, Jacquemond V, Sorrentino V. Junctophilin 1 and 2 proteins interact with the L-type Ca2+ channel dihydropyridine receptors (DHPRs) in skeletal muscle. J Biol Chem 2011; 286:43717-43725. [PMID: 22020936 DOI: 10.1074/jbc.m111.292755] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Junctophilins (JPs) anchor the endo/sarcoplasmic reticulum to the plasma membrane, thus contributing to the assembly of junctional membrane complexes in striated muscles and neurons. Recent studies have shown that JPs may be also involved in regulating Ca2+ homeostasis. Here, we report that in skeletal muscle, JP1 and JP2 are part of a complex that, in addition to ryanodine receptor 1 (RyR1), includes caveolin 3 and the dihydropyridine receptor (DHPR). The interaction between JPs and DHPR was mediated by a region encompassing amino acids 230-369 and amino acids 216-399 in JP1 and JP2, respectively. Immunofluorescence studies revealed that the pattern of DHPR and RyR signals in C2C12 cells knocked down for JP1 and JP2 was rather diffused and characterized by smaller puncta in contrast to that observed in control cells. Functional experiments revealed that down-regulation of JPs in differentiated C2C12 cells resulted in a reduction of intramembrane charge movement and the L-type Ca2+ current accompanied by a reduced number of DHPRs at the plasma membrane, whereas there was no substantial alteration in Ca2+ release from the sterol regulatory element-binding protein. Altogether, these results suggest that JP1 and JP2 can facilitate the assembly of DHPR with other proteins of the excitation-contraction coupling machinery.
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Affiliation(s)
- Lucia Golini
- Molecular Medicine Section, Department of Neuroscience, and Interuniversity Institute of Myology, University of Siena, 53100 Siena, Italy
| | - Christophe Chouabe
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Université Lyon 1, UMR CNRS 5534, 69622 Villeurbanne cedex, France
| | - Christine Berthier
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Université Lyon 1, UMR CNRS 5534, 69622 Villeurbanne cedex, France
| | - Vincenza Cusimano
- Molecular Medicine Section, Department of Neuroscience, and Interuniversity Institute of Myology, University of Siena, 53100 Siena, Italy
| | - Mara Fornaro
- Molecular Medicine Section, Department of Neuroscience, and Interuniversity Institute of Myology, University of Siena, 53100 Siena, Italy
| | - Robert Bonvallet
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Université Lyon 1, UMR CNRS 5534, 69622 Villeurbanne cedex, France
| | - Luca Formoso
- Molecular Medicine Section, Department of Neuroscience, and Interuniversity Institute of Myology, University of Siena, 53100 Siena, Italy
| | - Emiliana Giacomello
- Molecular Medicine Section, Department of Neuroscience, and Interuniversity Institute of Myology, University of Siena, 53100 Siena, Italy
| | - Vincent Jacquemond
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Université Lyon 1, UMR CNRS 5534, 69622 Villeurbanne cedex, France
| | - Vincenzo Sorrentino
- Molecular Medicine Section, Department of Neuroscience, and Interuniversity Institute of Myology, University of Siena, 53100 Siena, Italy.
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24
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Disrupted membrane structure and intracellular Ca²⁺ signaling in adult skeletal muscle with acute knockdown of Bin1. PLoS One 2011; 6:e25740. [PMID: 21984944 PMCID: PMC3184157 DOI: 10.1371/journal.pone.0025740] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 09/11/2011] [Indexed: 11/19/2022] Open
Abstract
Efficient intracellular Ca2+ ([Ca2+]i) homeostasis in skeletal muscle requires intact triad junctional complexes comprised of t-tubule invaginations of plasma membrane and terminal cisternae of sarcoplasmic reticulum. Bin1 consists of a specialized BAR domain that is associated with t-tubule development in skeletal muscle and involved in tethering the dihydropyridine receptors (DHPR) to the t-tubule. Here, we show that Bin1 is important for Ca2+ homeostasis in adult skeletal muscle. Since systemic ablation of Bin1 in mice results in postnatal lethality, in vivo electroporation mediated transfection method was used to deliver RFP-tagged plasmid that produced short –hairpin (sh)RNA targeting Bin1 (shRNA-Bin1) to study the effect of Bin1 knockdown in adult mouse FDB skeletal muscle. Upon confirming the reduction of endogenous Bin1 expression, we showed that shRNA-Bin1 muscle displayed swollen t-tubule structures, indicating that Bin1 is required for the maintenance of intact membrane structure in adult skeletal muscle. Reduced Bin1 expression led to disruption of t-tubule structure that was linked with alterations to intracellular Ca2+ release. Voltage-induced Ca2+ released in isolated single muscle fibers of shRNA-Bin1 showed that both the mean amplitude of Ca2+ current and SR Ca2+ transient were reduced when compared to the shRNA-control, indicating compromised coupling between DHPR and ryanodine receptor 1. The mean frequency of osmotic stress induced Ca2+ sparks was reduced in shRNA-Bin1, indicating compromised DHPR activation. ShRNA-Bin1 fibers also displayed reduced Ca2+ sparks' amplitude that was attributed to decreased total Ca2+ stores in the shRNA-Bin1 fibers. Human mutation of Bin1 is associated with centronuclear myopathy and SH3 domain of Bin1 is important for sarcomeric protein organization in skeletal muscle. Our study showing the importance of Bin1 in the maintenance of intact t-tubule structure and ([Ca2+]i) homeostasis in adult skeletal muscle could provide mechanistic insight on the potential role of Bin1 in skeletal muscle contractility and pathology of myopathy.
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25
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DiFranco M, Tran P, Quiñonez M, Vergara JL. Functional expression of transgenic 1sDHPR channels in adult mammalian skeletal muscle fibres. J Physiol 2011; 589:1421-42. [PMID: 21262876 DOI: 10.1113/jphysiol.2010.202804] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We investigated the effects of the overexpression of two enhanced green fluorescent protein (EGFP)-tagged α1sDHPR variants on Ca2+ currents (ICa), charge movements (Q) and SR Ca2+ release of muscle fibres isolated from adult mice. Flexor digitorum brevis (FDB)muscles were transfected by in vivo electroporation with plasmids encoding for EGFP-α1sDHPR-wt and EGFP-α1sDHPR-T935Y (an isradipine-insensitive mutant). Two-photon laser scanning microscopy (TPLSM) was used to study the subcellular localization of transgenic proteins, while ICa, Q and Ca2+ release were studied electrophysiologically and optically under voltage-clamp conditions. TPLSM images demonstrated that most of the transgenic α1sDHPR was correctly targeted to the transverse tubular system (TTS). Immunoblotting analysis of crude extracts of transfected fibres demonstrated the synthesis of bona fide transgenic EGFP-α1sDHPR-wt in quantities comparable to that of native α1sDHPR. Though expression of both transgenic variants of the alpha subunit of the dihydropyridine receptor (α1sDHPR) resulted in ∼50% increase in Q, they surprisingly had no effect on the maximal Ca2+ conductance (gCa) nor the SR Ca2+ release. Nonetheless, fibres expressing EGFP-α1sDHPR-T935Y exhibited up to 70% isradipine-insensitive ICa (ICa-ins) with a right-shifted voltage dependence compared to that in control fibres. Interestingly, Qand SRCa2+ release also displayed right-shifted voltage dependence in fibres expressing EGFP-α1sDHPR-T935Y. In contrast, the midpoints of the voltage dependence of gCa, Q and Ca2+ release were not different from those in control fibres and in fibres expressing EGFP-α1sDHPR-wt. Overall, our results suggest that transgenic α1sDHPRs are correctly trafficked and inserted in the TTS membrane, and that a substantial fraction of the mworks as conductive Ca2+ channels capable of physiologically controlling the release of Ca2+ from the SR. A plausible corollary of this work is that the expression of transgenic variants of the α1sDHPR leads to the replacement of native channels interacting with the ryanodine receptor 1 (RyR1), thus demonstrating the feasibility of molecular remodelling of the triads in adult skeletal muscle fibres.
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Affiliation(s)
- Marino DiFranco
- Department of Physiology, David Geffen School of Medicine, UCLA, 10833 Le Conte Avenue, Los Angeles, CA 90095-1751, USA
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26
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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.
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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.
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27
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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: 144] [Impact Index Per Article: 9.6] [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.
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28
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Berbey C, Allard B. Electrically silent divalent cation entries in resting and active voltage-controlled muscle fibers. Biophys J 2009; 96:2648-57. [PMID: 19348748 DOI: 10.1016/j.bpj.2009.01.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 01/05/2009] [Accepted: 01/06/2009] [Indexed: 02/06/2023] Open
Abstract
Ca2+ is known to enter skeletal muscle at rest and during activity. Except for the well-characterized Ca2+ entry through L-type channels, pathways involved in these Ca2+ entries remain elusive in adult muscle. This study investigates Ca2+ influx at rest and during activity using the method of Mn2+ quenching of fura-2 fluorescence on voltage-controlled adult skeletal muscle cells. Resting rate of Mn2+ influx depended on external [Mn2+] and membrane potential. At -80 mV, replacement of Mg2+ by Mn2+ gave rise to an outward current associated with an increase in cell input resistance. Calibration of fura-2 response indicated that Mn2+ influx was too small to be resolved as a macroscopic current. Partial depletion of the sarcoplasmic reticulum induced by a train of action potentials in the presence of cyclopiazonic acid led to a slight increase in resting Mn2+ influx but no change in cell input resistance and membrane potential. Trains of action potentials considerably increased Mn2+ entry through an electrically silent pathway independent of L-type channels, which provided 24% of the global Mn2+ influx at +30 mV under voltage-clamp conditions. Within this context, the nature and the physiological role of the Ca2+ pathways involved during muscle excitation still remain open questions.
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Affiliation(s)
- Céline Berbey
- Physiologie Intégrative Cellulaire et Moléculaire, Université Lyon 1, Centre National de la Recherche Scientifique Unité Mixte de Recherche, 5123 Villeurbanne, France
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29
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Launikonis BS, Stephenson DG, Friedrich O. Rapid Ca2+ flux through the transverse tubular membrane, activated by individual action potentials in mammalian skeletal muscle. J Physiol 2009; 587:2299-312. [PMID: 19332499 DOI: 10.1113/jphysiol.2009.168682] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Periods of low frequency stimulation are known to increase the net Ca(2+) uptake in skeletal muscle but the mechanism responsible for this Ca(2+) entry is not known. In this study a novel high-resolution fluorescence microscopy approach allowed the detection of an action potential-induced Ca(2+) flux across the tubular (t-) system of rat extensor digitorum longus muscle fibres that appears to be responsible for the net uptake of Ca(2+) in working muscle. Action potentials were triggered in the t-system of mechanically skinned fibres from rat by brief field stimulation and t-system [Ca(2+)] ([Ca(2+)](t-sys)) and cytoplasmic [Ca(2+)] ([Ca(2+)](cyto)) were simultaneously resolved on a confocal microscope. When initial [Ca(2+)](t-sys) was > or = 0.2 mM a Ca(2+) flux from t-system to the cytoplasm was observed following a single action potential. The action potential-induced Ca(2+) flux and associated t-system Ca(2+) permeability decayed exponentially and displayed inactivation characteristics such that further Ca(2+) entry across the t-system could not be observed after 2-3 action potentials at 10 Hz stimulation rate. When [Ca(2+)](t-sys) was closer to 0.1 mM, a transient rise in [Ca(2+)](t-sys) was observed almost concurrently with the increase in [Ca(2+)](cyto) following the action potential. The change in direction of Ca(2+) flux was consistent with changes in the direction of the driving force for Ca(2+). This is the first demonstration of a rapid t-system Ca(2+) flux associated with a single action potential in mammalian skeletal muscle. The properties of this channel are inconsistent with a flux through the L-type Ca(2+) channel suggesting that an as yet unidentified t-system protein is conducting this current. This action potential-activated Ca(2+) flux provides an explanation for the previously described Ca(2+) entry and accumulation observed with prolonged, intermittent muscle activity.
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Affiliation(s)
- Bradley S Launikonis
- School of Biomedical Sciences, University of Queensland, Brisbane, Qld 4072, Australia.
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30
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Collet C. Excitation-contraction coupling in skeletal muscle fibers from adult domestic honeybee. Pflugers Arch 2009; 458:601-12. [DOI: 10.1007/s00424-009-0642-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 01/09/2009] [Accepted: 01/22/2009] [Indexed: 10/21/2022]
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31
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Teichmann MDH, Wegner FV, Fink RHA, Chamberlain JS, Launikonis BS, Martinac B, Friedrich O. Inhibitory control over Ca(2+) sparks via mechanosensitive channels is disrupted in dystrophin deficient muscle but restored by mini-dystrophin expression. PLoS One 2008; 3:e3644. [PMID: 18982068 PMCID: PMC2575405 DOI: 10.1371/journal.pone.0003644] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 10/17/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In dystrophic skeletal muscle, osmotic stimuli somehow relieve inhibitory control of dihydropyridine receptors (DHPR) on spontaneous sarcoplasmic reticulum elementary Ca(2+) release events (ECRE) in high Ca(2+) external environments. Such 'uncontrolled' Ca(2+) sparks were suggested to act as dystrophic signals. They may be related to mechanosensitive pathways but the mechanisms are elusive. Also, it is not known whether truncated dystrophins can correct the dystrophic disinhibition. METHODOLOGY/PRINCIPAL FINDINGS We recorded ECRE activity in single intact fibers from adult wt, mdx and mini-dystrophin expressing mice (MinD) under resting isotonic conditions and following hyper-/hypo-osmolar external shock using confocal microscopy and imaging techniques. Isotonic ECRE frequencies were small in wt and MinD fibers, but were markedly increased in mdx fibers. Osmotic challenge dramatically increased ECRE activity in mdx fibers. Sustained osmotic challenge induced marked exponential ECRE activity adaptation that was three times faster in mdx compared to wt and MinD fibers. Rising external Ca(2+) concentrations amplified osmotic ECRE responses. The eliminated ECRE suppression in intact osmotically stressed mdx fibers was completely and reversibly resuscitated by streptomycine (200 microM), spider peptide GsMTx-4 (5 microM) and Gd(3+) (20 microM) that block unspecific, specific cationic and Ca(2+) selective mechanosensitive channels (MsC), respectively. ECRE morphology was not substantially altered by membrane stress. During hyperosmotic challenge, membrane potentials were polarised and a putative depolarisation through aberrant MsC negligible excluding direct activation of ECRE through tubular depolarisation. CONCLUSIONS/SIGNIFICANCE Dystrophin suppresses spontaneous ECRE activity by control of mechanosensitive pathways which are suggested to interact with the inhibitory DHPR loop to the ryanodine receptor. MsC-related disinhibition prevails in dystrophic muscle and can be resuscitated by transgenic mini-dystrophin expression. Our results have important implications for the pathophysiology of DMD where abnormal MsC in dystrophic muscle confer disruption of microdomain Ca(2+) homeostasis. MsC blockers should have considerable therapeutic potential if more muscle specific compounds can be found.
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MESH Headings
- Adult
- Animals
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/physiology
- Dystrophin/genetics
- Dystrophin/metabolism
- Humans
- Ion Channels/metabolism
- Mechanotransduction, Cellular/physiology
- Membrane Potentials/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Mice, Transgenic
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/physiology
- Muscle, Skeletal/cytology
- Muscle, Skeletal/physiology
- Muscle, Skeletal/physiopathology
- Muscular Dystrophy, Duchenne/physiopathology
- Osmotic Pressure
- Ryanodine Receptor Calcium Release Channel/metabolism
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Affiliation(s)
- Martin D. H. Teichmann
- Medical Biophysics, Department of Systems Physiology, Institute of Physiology and Pathophysiology, Ruprecht-Karls-University, Heidelberg, Germany
| | - Frederic v. Wegner
- Medical Biophysics, Department of Systems Physiology, Institute of Physiology and Pathophysiology, Ruprecht-Karls-University, Heidelberg, Germany
| | - Rainer H. A. Fink
- Medical Biophysics, Department of Systems Physiology, Institute of Physiology and Pathophysiology, Ruprecht-Karls-University, Heidelberg, Germany
| | - Jeffrey S. Chamberlain
- Department of Neurology, University of Washington, Seattle, Washington, United States of America
| | - Bradley S. Launikonis
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Boris Martinac
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Oliver Friedrich
- Medical Biophysics, Department of Systems Physiology, Institute of Physiology and Pathophysiology, Ruprecht-Karls-University, Heidelberg, Germany
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
- * E-mail:
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32
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Royer L, Pouvreau S, Ríos E. Evolution and modulation of intracellular calcium release during long-lasting, depleting depolarization in mouse muscle. J Physiol 2008; 586:4609-29. [PMID: 18687715 PMCID: PMC2614033 DOI: 10.1113/jphysiol.2008.157990] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Accepted: 08/06/2008] [Indexed: 01/21/2023] Open
Abstract
Intracellular calcium signals regulate multiple cellular functions. They depend on release of Ca(2+) from cellular stores into the cytosol, a process that in many types of cells appears to be tightly controlled by changes in [Ca(2+)] within the store. In contrast with cardiac muscle, where depletion of Ca(2+) in the sarcoplasmic reticulum is a crucial determinant of termination of Ca(2+) release, in skeletal muscle there is no agreement regarding the sign, or even the existence of an effect of SR Ca(2+) level on Ca(2+) release. To address this issue we measured Ca(2+) transients in mouse flexor digitorum brevis (FDB) skeletal muscle fibres under voltage clamp, using confocal microscopy and the Ca(2+) monitor rhod-2. The evolution of Ca(2+) release flux was quantified during long-lasting depolarizations that reduced severely the Ca(2+) content of the SR. As in all previous determinations in mammals and non-mammals, release flux consisted of an early peak, relaxing to a lower level from which it continued to decay more slowly. Decay of flux in this second stage, which has been attributed largely to depletion of SR Ca(2+), was studied in detail. A simple depletion mechanism without change in release permeability predicts an exponential decay with time. In contrast, flux decreased non-exponentially, to a finite, measurable level that could be maintained for the longest pulses applied (1.8 s). An algorithm on the flux record allowed us to define a quantitative index, the normalized flux rate of change (NFRC), which was shown to be proportional to the ratio of release permeability P and inversely proportional to Ca(2+) buffering power B of the SR, thus quantifying the 'evacuability' or ability of the SR to empty its content. When P and B were constant, flux then decayed exponentially, and NFRC was equal to the exponential rate constant. Instead, in most cases NFRC increased during the pulse, from a minimum reached immediately after the early peak in flux, to a time between 200 and 250 ms, when the index was no longer defined. NFRC increased by 111% on average (in 27 images from 18 cells), reaching 300% in some cases. The increase may reflect an increase in P, a decrease in B, or both. On experimental and theoretical grounds, both changes are to be expected upon SR depletion. A variable evacuability helps maintain a constant Ca(2+) output under conditions of diminishing store Ca(2+) load.
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Affiliation(s)
- Leandro Royer
- Department of Molecular Biophysics & Physiology, Section of Cellular Signalling, Rush University School of Medicine, Chicago, IL 60612, USA
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33
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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.
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Affiliation(s)
- Stephen Hollingworth
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA
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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.
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Affiliation(s)
- Norbert Weiss
- Physiologie Intégrative Cellulaire et Moléculaire, Université Claude Bernard-Lyon 1,Villeurbanne Cedex, France
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L-type Ca2+ channel function is linked to dystrophin expression in mammalian muscle. PLoS One 2008; 3:e1762. [PMID: 18516256 PMCID: PMC2408559 DOI: 10.1371/journal.pone.0001762] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 02/08/2008] [Indexed: 11/19/2022] Open
Abstract
Background In dystrophic mdx skeletal muscle, aberrant Ca2+ homeostasis and fibre degeneration are found. The absence of dystrophin in models of Duchenne muscular dystrophy (DMD) has been connected to altered ion channel properties e.g. impaired L-type Ca2+ currents. In regenerating mdx muscle, ‘revertant’ fibres restore dystrophin expression. Their functionality involving DHPR-Ca2+-channels is elusive. Methods and Results We developed a novel ‘in-situ’ confocal immuno-fluorescence and imaging technique that allows, for the first time, quantitative subcellular dystrophin-DHPR colocalization in individual, non-fixed, muscle fibres. Tubular DHPR signals alternated with second harmonic generation signals originating from myosin. Dystrophin-DHPR colocalization was substantial in wt fibres, but diminished in most mdx fibres. Mini-dystrophin (MinD) expressing fibres successfully restored colocalization. Interestingly, in some aged mdx fibres, colocalization was similar to wt fibres. Most mdx fibres showed very weak membrane dystrophin staining and were classified ‘mdx-like’. Some mdx fibres, however, had strong ‘wt-like’ dystrophin signals and were identified as ‘revertants’. Split mdx fibres were mostly ‘mdx-like’ and are not generally ‘revertants’. Correlations between membrane dystrophin and DHPR colocalization suggest a restored putative link in ‘revertants’. Using the two-micro-electrode-voltage clamp technique, Ca2+-current amplitudes (imax) showed very similar behaviours: reduced amplitudes in most aged mdx fibres (as seen exclusively in young mdx mice) and a few mdx fibres, most likely ‘revertants’, with amplitudes similar to wt or MinD fibres. Ca2+ current activation curves were similar in ‘wt-like’ and ‘mdx-like’ aged mdx fibres and are not the cause for the differences in current amplitudes. imax amplitudes were fully restored in MinD fibres. Conclusions We present evidence for a direct/indirect DHPR-dystrophin interaction present in wt, MinD and ‘revertant’ mdx fibres but absent in remaining mdx fibres. Our imaging technique reliably detects single isolated ‘revertant’ fibres that could be used for subsequent physiological experiments to study mechanisms and therapy concepts in DMD.
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DiFranco M, Capote J, Quiñonez M, Vergara JL. Voltage-dependent dynamic FRET signals from the transverse tubules in mammalian skeletal muscle fibers. ACTA ACUST UNITED AC 2008; 130:581-600. [PMID: 18040060 PMCID: PMC2151662 DOI: 10.1085/jgp.200709831] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two hybrid voltage-sensing systems based on fluorescence resonance energy transfer (FRET) were used to record membrane potential changes in the transverse tubular system (TTS) and surface membranes of adult mice skeletal muscle fibers. Farnesylated EGFP or ECFP (EGFP-F and ECFP-F) were used as immobile FRET donors, and either non-fluorescent (dipicrylamine [DPA]) or fluorescent (oxonol dye DiBAC(4)(5)) lipophilic anions were used as mobile energy acceptors. Flexor digitorum brevis (FDB) muscles were transfected by in vivo electroporation with pEGFP-F and pECFP-F. Farnesylated fluorescent proteins were efficiently expressed in the TTS and surface membranes. Voltage-dependent optical signals resulting from resonance energy transfer from fluorescent proteins to DPA were named QRET transients, to distinguish them from FRET transients recorded using DiBAC(4)(5). The peak DeltaF/F of QRET transients elicited by action potential stimulation is twice larger in fibers expressing ECFP-F as those with EGFP-F (7.1% vs. 3.6%). These data provide a unique experimental demonstration of the importance of the spectral overlap in FRET. The voltage sensitivity of QRET and FRET signals was demonstrated to correspond to the voltage-dependent translocation of the charged acceptors, which manifest as nonlinear components in current records. For DPA, both electrical and QRET data were predicted by radial cable model simulations in which the maximal time constant of charge translocation was 0.6 ms. FRET signals recorded in response to action potentials in fibers stained with DiBAC(4)(5) exhibit DeltaF/F amplitudes as large as 28%, but their rising phase was slower than those of QRET signals. Model simulations require a time constant for charge translocation of 1.6 ms in order to predict current and FRET data. Our results provide the basis for the potential use of lipophilic ions as tools to test for fast voltage-dependent conformational changes of membrane proteins in the TTS.
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Affiliation(s)
- Marino DiFranco
- Department of Physiology, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA 90095, USA
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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.
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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
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Allard B. Sarcolemmal ion channels in dystrophin-deficient skeletal muscle fibres. J Muscle Res Cell Motil 2006; 27:367-73. [PMID: 16874448 DOI: 10.1007/s10974-006-9083-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 06/26/2006] [Indexed: 11/29/2022]
Abstract
Duchenne muscular dystrophy (DMD) is a genetic disease caused by mutations in the dystrophin gene and characterized by progressive skeletal muscle degeneration. A current hypothesis suggests that degeneration of dystrophin-deficient skeletal muscle results from a chronic intracellular Ca2+ overload. Ca2+ handling in skeletal muscle is tightly controlled by the membrane potential which is set by sarcolemmal ion channels activity. Also, with regard to the subsarcolemmal localization of dystrophin, it is reasonable to enquire if the distribution and function of ion channels might be affected by the absence of dystrophin. This paper briefly summarizes the current knowledge of the properties of sarcolemmal ion channels in fully differentiated dystrophin-deficient skeletal muscle fibres.
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Affiliation(s)
- Bruno Allard
- Physiologie Intégrative, Cellulaire et Moléculaire, UMR CNRS 5123, Université C. Bernard Lyon 1, 43 bd du 11 Novembre 1918, 69622, Villeurbanne cedex, France.
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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.
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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
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Yoshida M, Yonetani A, Shirasaki T, Wada K. Dietary NaCl supplementation prevents muscle necrosis in a mouse model of Duchenne muscular dystrophy. Am J Physiol Regul Integr Comp Physiol 2006; 290:R449-55. [PMID: 16179484 DOI: 10.1152/ajpregu.00684.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The mdx mouse is an animal model for Duchenne muscular dystrophy. Mdx mice fed a 12% NaCl diet from birth up to 20 days of age (mdx-Na mice) had an ∼50% reduction in serum creatine kinase (CK) activity compared with mdx mice fed a standard diet. Most notably, necrotic fibers in tibialis anterior (TA) muscle of mdx-Na mice were reduced by 99% and were similar in control mice. These mdx mice displayed significantly elevated blood Ca2+ and Na+ levels, while the total calcium content of their TA muscle was reduced to the level of control mice. In addition, mdx-Na mice had elevated zinc and magnesium contents in their TA muscle. These results suggest that elevated serum Na+ leads to Ca2+ extrusion from muscle via the Na+/Ca2+ exchanger causing a decrease in intracellular Ca2+ levels and an increase in blood Ca2+ levels. Extracellular Ca2+ and, in addition, Zn2+ and Mg2+ might also contribute to the stabilization of the cell membrane. Other possibilities explaining the surprisingly efficacious beneficial effect of dietary sodium exist and are discussed.
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Affiliation(s)
- Mizuko Yoshida
- Department of Degenerative Neurological Disease, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo 187-8052, Japan.
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Zaldivar D, García MC, Sánchez JA. Ciliary neurotrophic factor promotes inactivation of muscle Ca2+ channels via PKC. Biochem Biophys Res Commun 2005; 338:1572-7. [PMID: 16274672 DOI: 10.1016/j.bbrc.2005.10.125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Accepted: 10/21/2005] [Indexed: 01/15/2023]
Abstract
The actions of the ciliary neurotrophic factor (CNTF) were assessed on adult mouse skeletal muscle L-type Ca2+ currents and on Ca2+ release from sarcoplasmic reticulum. Currents were measured with the whole cell patch clamp technique. Ca2+ signals in response to single action potentials were recorded with Fluo3-AM. CNTF (20 ng/ml) reversibly reduced the amplitude of Ca2+ channel currents by 50% within 15 min. In addition, CNTF greatly increased the rate of inactivation during depolarizing pulses and shifted the steady state inactivation curve by -12 mV. The effects of CNTF were mimicked by the PKC activator PMA and prevented by the PKC-inhibitor chelerythrine. In contrast to the effects on the Ca2+ conductance, charge movement and Ca2+ signals remained unaffected by CNTF. These results suggest that CNTF can rapidly decrease muscle Ca2+ channel currents by promoting inactivation, probably through an intracellular PKC-dependent mechanism.
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Affiliation(s)
- Daniel Zaldivar
- Departmento de Farmacología, Centro de Investigación y de Estudios Avanzados del I.P.N., México, DF 07360, Mexico
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Abstract
The heart is a rhythmic electromechanical pump, the functioning of which depends on action potential generation and propagation, followed by relaxation and a period of refractoriness until the next impulse is generated. Myocardial action potentials reflect the sequential activation and inactivation of inward (Na(+) and Ca(2+)) and outward (K(+)) current carrying ion channels. In different regions of the heart, action potential waveforms are distinct, owing to differences in Na(+), Ca(2+), and K(+) channel expression, and these differences contribute to the normal, unidirectional propagation of activity and to the generation of normal cardiac rhythms. Changes in channel functioning, resulting from inherited or acquired disease, affect action potential repolarization and can lead to the generation of life-threatening arrhythmias. There is, therefore, considerable interest in understanding the mechanisms that control cardiac repolarization and rhythm generation. Electrophysiological studies have detailed the properties of the Na(+), Ca(2+), and K(+) currents that generate cardiac action potentials, and molecular cloning has revealed a large number of pore forming (alpha) and accessory (beta, delta, and gamma) subunits thought to contribute to the formation of these channels. Considerable progress has been made in defining the functional roles of the various channels and in identifying the alpha-subunits encoding these channels. Much less is known, however, about the functioning of channel accessory subunits and/or posttranslational processing of the channel proteins. It has also become clear that cardiac ion channels function as components of macromolecular complexes, comprising the alpha-subunits, one or more accessory subunit, and a variety of other regulatory proteins. In addition, these macromolecular channel protein complexes appear to interact with the actin cytoskeleton and/or the extracellular matrix, suggesting important functional links between channel complexes, as well as between cardiac structure and electrical functioning. Important areas of future research will be the identification of (all of) the molecular components of functional cardiac ion channels and delineation of the molecular mechanisms involved in regulating the expression and the functioning of these channels in the normal and the diseased myocardium.
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Affiliation(s)
- Jeanne M Nerbonne
- Dept. of Molecular Biology and Pharmacology, Washington University Medical School, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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García MC, Carrillo E, Galindo JM, Hernández A, Copello JA, Fill M, Sánchez JA. Short-term regulation of excitation-contraction coupling by the beta1a subunit in adult mouse skeletal muscle. Biophys J 2005; 89:3976-84. [PMID: 16183888 PMCID: PMC1366963 DOI: 10.1529/biophysj.105.067116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The beta1a subunit of the skeletal muscle voltage-gated Ca2+ channel plays a fundamental role in the targeting of the channel to the tubular system as well as in channel function. To determine whether this cytosolic auxiliary subunit is also a regulatory protein of Ca2+ release from the sarcoplasmic reticulum in vivo, we pressure-injected the beta1a subunit into intact adult mouse muscle fibers and recorded, with Fluo-3 AM, the intracellular Ca2+ signal induced by the action potential. We found that the beta1a subunit significantly increased, within minutes, the amplitude of Ca2+ release without major changes in its time course. beta1a subunits with the carboxy-terminus region deleted did not show an effect on Ca2+ release. The possibility that potentiation of Ca2+ release is due to a direct interaction between the beta1a subunit and the ryanodine receptor was ruled out by bilayer experiments of RyR1 single-channel currents and also by Ca2+ flux experiments. Our data suggest that the beta1a subunit is capable of regulating E-C coupling in the short term and that the integrity of the carboxy-terminus region is essential for its modulatory effect.
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Affiliation(s)
- María C García
- Departmento de Farmacología, Centro de Investigación y de Estudios Avanzados del I.P.N., Mexico, D.F. 07360, Mexico
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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.
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Affiliation(s)
- Sandrine Pouvreau
- Physiologie Intégrative Cellulaire et Moléculaire, Université Claude Bernard - Lyon 1, UMR CNRS 5123, Villeurbanne, France
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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.
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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
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Fraysse B, Liantonio A, Cetrone M, Burdi R, Pierno S, Frigeri A, Pisoni M, Camerino C, De Luca A. The alteration of calcium homeostasis in adult dystrophic mdx muscle fibers is worsened by a chronic exercise in vivo. Neurobiol Dis 2004; 17:144-54. [PMID: 15474352 DOI: 10.1016/j.nbd.2004.06.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Revised: 05/14/2004] [Accepted: 06/03/2004] [Indexed: 11/24/2022] Open
Abstract
Chronic exercise in vivo aggravates dystrophy in mdx mice. Calcium homeostasis was evaluated ex vivo by micro-spectrofluorometry on tendon-to-tendon dissected extensor digitorum longus (EDL) muscle fibers. Resting cytosolic calcium ([Ca2+]i) and sarcolemmal permeability through Gd3+ -sensitive mechanosensitive calcium (MsCa) channel were significantly higher in mdx vs. wild-type fibers. The exercise further enhanced [Ca2+]i in mdx fibers and increased sarcolemmal permeability by activating nifedipine-sensitive leak calcium channels. The two genotypes did not differ in caffeine sensitivity and in the excitation-calcium release (ECaR) coupling mechanism by K+ depolarization. The exercise produced a similar adaptation of activation curve of ECaR and of sensitivity to caffeine. However, the inactivation of ECaR of mdx fibers did not adapt to exercise. No fiber phenotype transition occurred in exercised muscle. We provide the first evidence that an in vivo exercise worsens the impaired calcium homeostasis of dystrophic fibers, supporting the role of enhanced calcium entrance in dystrophic progression.
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Affiliation(s)
- Bodvael Fraysse
- Unit of Pharmacology, Department of Pharmacobiology, Faculty of Pharmacy, University of Bari, Bari, Italy
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Dowling P, Doran P, Ohlendieck K. Drastic reduction of sarcalumenin in Dp427 (dystrophin of 427 kDa)-deficient fibres indicates that abnormal calcium handling plays a key role in muscular dystrophy. Biochem J 2004; 379:479-88. [PMID: 14678011 PMCID: PMC1224066 DOI: 10.1042/bj20031311] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2003] [Revised: 12/10/2003] [Accepted: 12/16/2003] [Indexed: 11/17/2022]
Abstract
Although the primary abnormality in dystrophin is the underlying cause for mdx (X-chromosome-linked muscular dystrophy), abnormal Ca2+ handling after sarcolemmal microrupturing appears to be the pathophysiological mechanism leading to muscle weakness. To develop novel pharmacological strategies for eliminating Ca2+-dependent proteolysis, it is crucial to determine the fate of Ca2+-handling proteins in dystrophin-deficient fibres. In the present study, we show that a key luminal Ca2+-binding protein SAR (sarcalumenin) is affected in mdx skeletal-muscle fibres. One- and two-dimensional immunoblot analyses revealed the relative expression of the 160 kDa SR (sarcoplasmic reticulum) protein to be approx. 70% lower in mdx fibres when compared with normal skeletal muscles. This drastic reduction in SAR was confirmed by immunofluorescence microscopy. Patchy internal labelling of SAR in dystrophic fibres suggests an abnormal formation of SAR domains. Differential co-immunoprecipitation experiments and chemical cross-linking demonstrated a tight linkage between SAR and the SERCA1 (sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase 1) isoform of the SR Ca2+-ATPase. However, the relative expression of the fast Ca2+ pump was not decreased in dystrophic membrane preparations. This implies that the reduction in SAR and calsequestrin-like proteins plays a central role in the previously reported impairment of Ca2+ buffering in the dystrophic SR [Culligan, Banville, Dowling and Ohlendieck (2002) J. Appl. Physiol. 92, 435-445]. Impaired Ca2+ shuttling between the Ca2+-uptake SERCA units and calsequestrin clusters via SAR, as well as an overall decreased luminal ion-binding capacity, might indirectly amplify the Ca2+-leak-channel-induced increase in cytosolic Ca2+ levels. This confirms the idea that abnormal Ca2+ cycling is involved in Ca2+-induced myonecrosis. Hence, manipulating disturbed Ca2+ handling might represent new modes of abolishing proteolytic degradation in muscular dystrophy.
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Affiliation(s)
- Paul Dowling
- Department of Biology, National University of Ireland, Maynooth, County Kildare, Ireland
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48
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Friedrich O, Both M, Gillis JM, Chamberlain JS, Fink RHA. Mini-dystrophin restores L-type calcium currents in skeletal muscle of transgenic mdx mice. J Physiol 2004; 555:251-65. [PMID: 14594987 PMCID: PMC1664821 DOI: 10.1113/jphysiol.2003.054213] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 09/01/2003] [Accepted: 10/27/2003] [Indexed: 11/08/2022] Open
Abstract
L-type calcium currents (iCa) were recorded using the two-microelectrode voltage-clamp technique in single short toe muscle fibres of three different mouse strains: (i) C57/SV129 wild-type mice (wt); (ii) mdx mice (an animal model for Duchenne muscular dystrophy; and (iii) transgenically engineered mini-dystrophin (MinD)-expressing mdx mice. The activation and inactivation properties of iCa were examined in 2- to 18-month-old animals. Ca2+ current densities at 0 mV in mdx fibres increased with age, but were always significantly smaller compared to age-matched wild-type fibres. Time-to-peak (TTP) of iCa was prolonged in mdx fibres compared to wt fibres. MinD fibres always showed similar TTP and current amplitudes compared to age-matched wt fibres. In all three genotypes, the voltage-dependent inactivation and deactivation of iCa were similar. Intracellular resting calcium concentration ([Ca2+]i) and the distribution of dihydropyridine binding sites were also not different in young animals of all three genotypes, whereas iCa was markedly reduced in mdx fibres. We conclude, that dystrophin influences L-type Ca2+ channels via a direct or indirect linkage which may be disrupted in mdx mice and may be crucial for proper excitation-contraction coupling initiating Ca2+ release from the sarcoplasmic reticulum. This linkage seems to be fully restored in the presence of mini-dystrophin.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium/pharmacology
- Calcium Channels, L-Type/biosynthesis
- Calcium Channels, L-Type/genetics
- Dose-Response Relationship, Drug
- Dystrophin/biosynthesis
- Dystrophin/genetics
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Mice, Transgenic
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Muscular Dystrophies/genetics
- Muscular Dystrophies/metabolism
- Protein Binding/drug effects
- Protein Binding/physiology
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Affiliation(s)
- O Friedrich
- Medical Biophysics, Institute of Physiology and Pathophysiology, INF 326, Ruprecht-Karls-University, 69120 Heidelberg, Germany
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49
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Ahern CA, Sheridan DC, Cheng W, Mortenson L, Nataraj P, Allen P, De Waard M, Coronado R. Ca2+ current and charge movements in skeletal myotubes promoted by the beta-subunit of the dihydropyridine receptor in the absence of ryanodine receptor type 1. Biophys J 2003; 84:942-59. [PMID: 12547776 PMCID: PMC1302672 DOI: 10.1016/s0006-3495(03)74911-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The beta-subunit of the dihydropyridine receptor (DHPR) enhances the Ca(2+) channel and voltage-sensing functions of the DHPR. In skeletal myotubes, there is additional modulation of DHPR functions imposed by the presence of ryanodine receptor type-1 (RyR1). Here, we examined the participation of the beta-subunit in the expression of L-type Ca(2+) current and charge movements in RyR1 knock-out (KO), beta1 KO, and double beta1/RyR1 KO myotubes generated by mating heterozygous beta1 KO and RyR1 KO mice. Primary myotube cultures of each genotype were transfected with various beta-isoforms and then whole-cell voltage-clamped for measurements of Ca(2+) and gating currents. Overexpression of the endogenous skeletal beta1a isoform resulted in a low-density Ca(2+) current either in RyR1 KO (36 +/- 9 pS/pF) or in beta1/RyR1 KO (34 +/- 7 pS/pF) myotubes. However, the heterologous beta2a variant with a double cysteine motif in the N-terminus (C3, C4), recovered a Ca(2+) current that was entirely wild-type in density in RyR1 KO (195 +/- 16 pS/pF) and was significantly enhanced in double beta1/RyR1 KO (115 +/- 18 pS/pF) myotubes. Other variants tested from the four beta gene families (beta1a, beta1b, beta1c, beta3, and beta4) were unable to enhance Ca(2+) current expression in RyR1 KO myotubes. In contrast, intramembrane charge movements in beta2a-expressing beta1a/RyR1 KO myotubes were significantly lower than in beta1a-expressing beta1a/RyR1 KO myotubes, and the same tendency was observed in the RyR1 KO myotube. Thus, beta2a had a preferential ability to recover Ca(2+) current, whereas beta1a had a preferential ability to rescue charge movements. Elimination of the double cysteine motif (beta2a C3,4S) eliminated the RyR1-independent Ca(2+) current expression. Furthermore, Ca(2+) current enhancement was observed with a beta2a variant lacking the double cysteine motif and fused to the surface membrane glycoprotein CD8. Thus, tethering the beta2a variant to the myotube surface activated the DHPR Ca(2+) current and bypassed the requirement for RyR1. The data suggest that the Ca(2+) current expressed by the native skeletal DHPR complex has an inherently low density due to inhibitory interactions within the DHPR and that the beta1a-subunit is critically involved in process.
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Affiliation(s)
- Chris A Ahern
- Department of Physiology, University of Wisconsin School of Medicine, Madison, Wisconsin 53706, USA
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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.
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Affiliation(s)
- C Collet
- Laboratoire de Physiologie des Eléments Excitables, Université Claude Bernard, F69622 Villeurbanne, France
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