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Catacuzzeno L, Conti F, Franciolini F. Fifty years of gating currents and channel gating. J Gen Physiol 2023; 155:e202313380. [PMID: 37410612 PMCID: PMC10324510 DOI: 10.1085/jgp.202313380] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/12/2023] [Accepted: 06/02/2023] [Indexed: 07/08/2023] Open
Abstract
We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This retrospective tries to illustrate the context knowledge on channel gating and the impact gating-current recording had then, and how it continued to clarify concepts, elaborate new ideas, and steer the scientific debate in these 50 years. The notion of gating particles and gating currents was first put forward by Hodgkin and Huxley in 1952 as a necessary assumption for interpreting the voltage dependence of the Na and K conductances of the action potential. 20 years later, gating currents were actually recorded, and over the following decades have represented the most direct means of tracing the movement of the gating charges and gaining insights into the mechanisms of channel gating. Most work in the early years was focused on the gating currents from the Na and K channels as found in the squid giant axon. With channel cloning and expression on heterologous systems, other channels as well as voltage-dependent enzymes were investigated. Other approaches were also introduced (cysteine mutagenesis and labeling, site-directed fluorometry, cryo-EM crystallography, and molecular dynamics [MD] modeling) to provide an integrated and coherent view of voltage-dependent gating in biological macromolecules. The layout of this retrospective reflects the past 50 years of investigations on gating currents, first addressing studies done on Na and K channels and then on other voltage-gated channels and non-channel structures. The review closes with a brief overview of how the gating-charge/voltage-sensor movements are translated into pore opening and the pathologies associated with mutations targeting the structures involved with the gating currents.
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Affiliation(s)
- Luigi Catacuzzeno
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Franco Conti
- Department of Physics, University of Genova, Genova, Italy
| | - Fabio Franciolini
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
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2
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Bibollet H, Nguyen EL, Miranda DR, Ward CW, Voss AA, Schneider MF, Hernández‐Ochoa EO. Voltage sensor current, SR Ca 2+ release, and Ca 2+ channel current during trains of action potential-like depolarizations of skeletal muscle fibers. Physiol Rep 2023; 11:e15675. [PMID: 37147904 PMCID: PMC10163276 DOI: 10.14814/phy2.15675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/30/2023] [Accepted: 03/31/2023] [Indexed: 05/07/2023] Open
Abstract
In skeletal muscle, CaV 1.1 serves as the voltage sensor for both excitation-contraction coupling (ECC) and L-type Ca2+ channel activation. We have recently adapted the technique of action potential (AP) voltage clamp (APVC) to monitor the current generated by the movement of intramembrane voltage sensors (IQ ) during single imposed transverse tubular AP-like depolarization waveforms (IQAP ). We now extend this procedure to monitoring IQAP , and Ca2+ currents during trains of tubular AP-like waveforms in adult murine skeletal muscle fibers, and compare them with the trajectories of APs and AP-induced Ca2+ release measured in other fibers using field stimulation and optical probes. The AP waveform remains relatively constant during brief trains (<1 sec) for propagating APs in non-V clamped fibers. Trains of 10 AP-like depolarizations at 10 Hz (900 ms), 50 Hz (180 ms), or 100 Hz (90 ms) did not alter IQAP amplitude or kinetics, consistent with previous findings in isolated muscle fibers where negligible charge immobilization occurred during 100 ms step depolarizations. Using field stimulation, Ca2+ release did exhibit a considerable decline from pulse to pulse during the train, also consistent with previous findings, indicating that the decline of Ca2+ release during a short train of APs is not correlated to modification of charge movement. Ca2+ currents during single or 10 Hz trains of AP-like depolarizations were hardly detectable, were minimal during 50 Hz trains, and became more evident during 100 Hz trains in some fibers. Our results verify predictions on the behavior of the ECC machinery in response to AP-like depolarizations and provide a direct demonstration that Ca2+ currents elicited by single AP-like waveforms are negligible, but can become more prominent in some fibers during short high-frequency train stimulation that elicits maximal isometric force.
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Affiliation(s)
- Hugo Bibollet
- Department of Biochemistry and Molecular BiologyUniversity of Maryland School of MedicineBaltimoreMarylandUSA
| | - Elton L. Nguyen
- Department of Biological SciencesWright State UniversityDaytonOhioUSA
| | - Daniel R. Miranda
- Department of Biological SciencesWright State UniversityDaytonOhioUSA
| | - Christopher W. Ward
- Department of OrthopedicsUniversity of Maryland School of MedicineBaltimoreMarylandUSA
| | - Andrew A. Voss
- Department of Biological SciencesWright State UniversityDaytonOhioUSA
| | - Martin F. Schneider
- Department of Biochemistry and Molecular BiologyUniversity of Maryland School of MedicineBaltimoreMarylandUSA
| | - Erick O. Hernández‐Ochoa
- Department of Biochemistry and Molecular BiologyUniversity of Maryland School of MedicineBaltimoreMarylandUSA
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3
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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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5
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Cairns SP, Leader JP, Higgins A, Renaud JM. The peak force - resting membrane potential relationships of mouse fast- and slow-twitch muscle. Am J Physiol Cell Physiol 2022; 322:C1151-C1165. [PMID: 35385328 DOI: 10.1152/ajpcell.00401.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We endeavored to understand the factors determining the peak force‑resting membrane potential (EM) relationships of isolated slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles from mice (25oC), especially in relation to fatigue. Inter-relationships between intracellular K+‑activity (aK+i), extracellular K+‑concentration ([K+]o), resting EM, action potentials and force were studied. The large resting EM variation was mainly due to the variability of aK+i. Action potential overshoot‑resting EM relationships determined at 4 and 8-10mM[K+]o following short (<5min) and prolonged (>50min) depolarization periods revealed a constant overshoot from ‑90 to ‑70mV providing a safety margin. Overshoot decline with depolarization beyond ‑70mV was less following short than prolonged depolarization. Inexcitable fibers occurred only with prolonged depolarization. The overshoot decline during action potential trains (2‑s) exceeded that during short depolarizations. Concomitant lower extracellular [Na+] and raised [K+]o depressed the overshoot in an additive manner and peak force in a synergistic manner. Raised [K+]o-induced force loss was exacerbated with transverse wire versus parallel plate stimulation in soleus, implicating action potential propagation failure in the surface membrane. Increasing stimulus pulse parameters restored tetanic force at 9‑10mM[K+]o in soleus, but not EDL, indicative of action potential failure within trains. The peak tetanic force‑resting EM relationships (determined using resting EM from deeper rather than surface fibers) were dynamic and show pronounced force depression over ‑69 to ‑60mV in both muscle-types, implicating that such depolarization contributes to fatigue. The K+-Na+-interaction shifted this relationship towards less depolarized potentials suggesting that the combined ionic effect is physiologically important during fatigue.
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Affiliation(s)
- Simeon P Cairns
- SPRINZ, School of Sport and Recreation, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, New Zealand.,Health and Rehabilitation Research Institute, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, New Zealand.,Department of Physiology, School of Medicine, University of Auckland, Auckland, New Zealand
| | - John P Leader
- Department of Physiology, University of Otago, Dunedin, New Zealand.,Department of Medicine, University of Otago, Dunedin, New Zealand
| | - Amanda Higgins
- Department of Cellular and Molecular Medicine, Neuromuscular Research Center, University of Ottawa, Ottawa, Canada
| | - Jean-Marc Renaud
- Department of Cellular and Molecular Medicine, Neuromuscular Research Center, University of Ottawa, Ottawa, Canada
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Wang X, Nawaz M, DuPont C, Myers JH, Burke SR, Bannister RA, Foy BD, Voss AA, Rich MM. The role of action potential changes in depolarization-induced failure of excitation contraction coupling in mouse skeletal muscle. eLife 2022; 11:71588. [PMID: 34985413 PMCID: PMC8730720 DOI: 10.7554/elife.71588] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 12/24/2021] [Indexed: 12/24/2022] Open
Abstract
Excitation-contraction coupling (ECC) is the process by which electrical excitation of muscle is converted into force generation. Depolarization of skeletal muscle resting potential contributes to failure of ECC in diseases such as periodic paralysis, intensive care unit acquired weakness and possibly fatigue of muscle during vigorous exercise. When extracellular K+ is raised to depolarize the resting potential, failure of ECC occurs suddenly, over a narrow range of resting potentials. Simultaneous imaging of Ca2+ transients and recording of action potentials (APs) demonstrated failure to generate Ca2+ transients when APs peaked at potentials more negative than -30mV. An AP property that closely correlated with failure of the Ca2+ transient was the integral of AP voltage with respect to time. Simultaneous recording of Ca2+ transients and APs with electrodes separated by 1.6mm revealed AP conduction fails when APs peak below -21mV. We hypothesize propagation of APs and generation of Ca2+ transients are governed by distinct AP properties: AP conduction is governed by AP peak, whereas Ca2+ release from the sarcoplasmic reticulum is governed by AP integral. The reason distinct AP properties may govern distinct steps of ECC is the kinetics of the ion channels involved. Na channels, which govern propagation, have rapid kinetics and are insensitive to AP width (and thus AP integral) whereas Ca2+ release is governed by gating charge movement of Cav1.1 channels, which have slower kinetics such that Ca2+ release is sensitive to AP integral. The quantitative relationships established between resting potential, AP properties, AP conduction and Ca2+ transients provide the foundation for future studies of failure of ECC induced by depolarization of the resting potential.
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Affiliation(s)
- Xueyong Wang
- Wright State University, Department of Neuroscience, Cell Biology, and Physiology, Dayton, United States
| | - Murad Nawaz
- Wright State University, Department of Neuroscience, Cell Biology, and Physiology, Dayton, United States
| | - Chris DuPont
- Wright State University, Department of Neuroscience, Cell Biology, and Physiology, Dayton, United States
| | - Jessica H Myers
- Wright State University, Department of Neuroscience, Cell Biology, and Physiology, Dayton, United States
| | - Steve Ra Burke
- Wright State University, Department of Biological Sciences, Dayton, United States
| | - Roger A Bannister
- University of Maryland School of Medicine, Departments of Pathology/Biochemistry & Molecular Biology, Baltimore, United States
| | - Brent D Foy
- Wright State University, Department of Physics, Dayton, United States
| | - Andrew A Voss
- Wright State University, Department of Biological Sciences, Dayton, United States
| | - Mark M Rich
- Wright State University, Department of Neuroscience, Cell Biology, and Physiology, Dayton, United States
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7
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Uwera F, Ammar T, McRae C, Hayward LJ, Renaud JM. Lower Ca2+ enhances the K+-induced force depression in normal and HyperKPP mouse muscles. J Gen Physiol 2021; 152:151656. [PMID: 32291438 PMCID: PMC7335014 DOI: 10.1085/jgp.201912511] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 02/18/2020] [Accepted: 03/21/2020] [Indexed: 12/20/2022] Open
Abstract
Hyperkalemic periodic paralysis (HyperKPP) manifests as stiffness or subclinical myotonic discharges before or during periods of episodic muscle weakness or paralysis. Ingestion of Ca2+ alleviates HyperKPP symptoms, but the mechanism is unknown because lowering extracellular [Ca2+] ([Ca2+]e) has no effect on force development in normal muscles under normal conditions. Lowering [Ca2+]e, however, is known to increase the inactivation of voltage-gated cation channels, especially when the membrane is depolarized. Two hypotheses were tested: (1) lowering [Ca2+]e depresses force in normal muscles under conditions that depolarize the cell membrane; and (2) HyperKPP muscles have a greater sensitivity to low Ca2+-induced force depression because many fibers are depolarized, even at a normal [K+]e. In wild type muscles, lowering [Ca2+]e from 2.4 to 0.3 mM had little effect on tetanic force and membrane excitability at a normal K+ concentration of 4.7 mM, whereas it significantly enhanced K+-induced depression of force and membrane excitability. In HyperKPP muscles, lowering [Ca2+]e enhanced the K+-induced loss of force and membrane excitability not only at elevated [K+]e but also at 4.7 mM K+. Lowering [Ca2+]e increased the incidence of generating fast and transient contractures and gave rise to a slower increase in unstimulated force, especially in HyperKPP muscles. Lowering [Ca2+]e reduced the efficacy of salbutamol, a β2 adrenergic receptor agonist and a treatment for HyperKPP, to increase force at elevated [K+]e. Replacing Ca2+ by an equivalent concentration of Mg2+ neither fully nor consistently reverses the effects of lowering [Ca2+]e. These results suggest that the greater Ca2+ sensitivity of HyperKPP muscles primarily relates to (1) a greater effect of Ca2+ in depolarized fibers and (2) an increased proportion of depolarized HyperKPP muscle fibers compared with control muscle fibers, even at normal [K+]e.
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Affiliation(s)
- Francine Uwera
- University of Ottawa, Department of Cellular and Molecular Medicine, Ottawa, Ontario, Canada
| | - Tarek Ammar
- University of Ottawa, Department of Cellular and Molecular Medicine, Ottawa, Ontario, Canada
| | - Callum McRae
- University of Ottawa, Department of Cellular and Molecular Medicine, Ottawa, Ontario, Canada
| | - Lawrence J Hayward
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA
| | - Jean-Marc Renaud
- University of Ottawa, Department of Cellular and Molecular Medicine, Ottawa, Ontario, Canada
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Hostrup M, Cairns SP, Bangsbo J. Muscle Ionic Shifts During Exercise: Implications for Fatigue and Exercise Performance. Compr Physiol 2021; 11:1895-1959. [PMID: 34190344 DOI: 10.1002/cphy.c190024] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Exercise causes major shifts in multiple ions (e.g., K+ , Na+ , H+ , lactate- , Ca2+ , and Cl- ) during muscle activity that contributes to development of muscle fatigue. Sarcolemmal processes can be impaired by the trans-sarcolemmal rundown of ion gradients for K+ , Na+ , and Ca2+ during fatiguing exercise, while changes in gradients for Cl- and Cl- conductance may exert either protective or detrimental effects on fatigue. Myocellular H+ accumulation may also contribute to fatigue development by lowering glycolytic rate and has been shown to act synergistically with inorganic phosphate (Pi) to compromise cross-bridge function. In addition, sarcoplasmic reticulum Ca2+ release function is severely affected by fatiguing exercise. Skeletal muscle has a multitude of ion transport systems that counter exercise-related ionic shifts of which the Na+ /K+ -ATPase is of major importance. Metabolic perturbations occurring during exercise can exacerbate trans-sarcolemmal ionic shifts, in particular for K+ and Cl- , respectively via metabolic regulation of the ATP-sensitive K+ channel (KATP ) and the chloride channel isoform 1 (ClC-1). Ion transport systems are highly adaptable to exercise training resulting in an enhanced ability to counter ionic disturbances to delay fatigue and improve exercise performance. In this article, we discuss (i) the ionic shifts occurring during exercise, (ii) the role of ion transport systems in skeletal muscle for ionic regulation, (iii) how ionic disturbances affect sarcolemmal processes and muscle fatigue, (iv) how metabolic perturbations exacerbate ionic shifts during exercise, and (v) how pharmacological manipulation and exercise training regulate ion transport systems to influence exercise performance in humans. © 2021 American Physiological Society. Compr Physiol 11:1895-1959, 2021.
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Affiliation(s)
- Morten Hostrup
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Simeon Peter Cairns
- SPRINZ, School of Sport and Recreation, Auckland University of Technology, Auckland, New Zealand.,Health and Rehabilitation Research Institute, Auckland University of Technology, Auckland, New Zealand
| | - Jens Bangsbo
- Section of Integrative Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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9
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Lindinger MI, Cairns SP. Regulation of muscle potassium: exercise performance, fatigue and health implications. Eur J Appl Physiol 2021; 121:721-748. [PMID: 33392745 DOI: 10.1007/s00421-020-04546-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 10/29/2020] [Indexed: 12/30/2022]
Abstract
This review integrates from the single muscle fibre to exercising human the current understanding of the role of skeletal muscle for whole-body potassium (K+) regulation, and specifically the regulation of skeletal muscle [K+]. We describe the K+ transport proteins in skeletal muscle and how they contribute to, or modulate, K+ disturbances during exercise. Muscle and plasma K+ balance are markedly altered during and after high-intensity dynamic exercise (including sports), static contractions and ischaemia, which have implications for skeletal and cardiac muscle contractile performance. Moderate elevations of plasma and interstitial [K+] during exercise have beneficial effects on multiple physiological systems. Severe reductions of the trans-sarcolemmal K+ gradient likely contributes to muscle and whole-body fatigue, i.e. impaired exercise performance. Chronic or acute changes of arterial plasma [K+] (hyperkalaemia or hypokalaemia) have dangerous health implications for cardiac function. The current mechanisms to explain how raised extracellular [K+] impairs cardiac and skeletal muscle function are discussed, along with the latest cell physiology research explaining how calcium, β-adrenergic agonists, insulin or glucose act as clinical treatments for hyperkalaemia to protect the heart and skeletal muscle in vivo. Finally, whether these agents can also modulate K+-induced muscle fatigue are evaluated.
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Affiliation(s)
- Michael I Lindinger
- Research and Development, The Nutraceutical Alliance, Burlington, ON, L7N 2Z9, Canada
| | - Simeon P Cairns
- SPRINZ, School of Sport and Recreation, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, 1020, New Zealand.
- Health and Rehabilitation Research Institute, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, 1020, New Zealand.
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10
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Melzer W. ECC meets CEU-New focus on the backdoor for calcium ions in skeletal muscle cells. J Gen Physiol 2020; 152:152046. [PMID: 32851409 PMCID: PMC7537343 DOI: 10.1085/jgp.202012679] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In this issue, Michelucci et al. report the existence of specific sites acting as Ca2+ entry units (CEUs) in fast skeletal muscle of mice lacking calsequestrin (CASQ1), the major Ca2+ binding protein of the SR. The CEU provides constitutive and store-operated Ca2+ entry (SOCE) and resistance to force decline resulting from SR Ca2+ depletion during repetitive muscle activity.
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Affiliation(s)
- Werner Melzer
- Institute of Applied Physiology, Ulm University, Ulm, Germany
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11
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Ferreira JJ, Pequera G, Launikonis BS, Ríos E, Brum G. A chloride channel blocker prevents the suppression by inorganic phosphate of the cytosolic calcium signals that control muscle contraction. J Physiol 2020; 599:157-170. [PMID: 32991741 DOI: 10.1113/jp279917] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 09/25/2020] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Accumulation of inorganic phosphate (Pi ) may contribute to muscle fatigue by precipitating calcium salts inside the sarcoplasmic reticulum (SR). Neither direct demonstration of this process nor definition of the entry pathway of Pi into SR are fully established. We showed that Pi promoted Ca2+ release at concentrations below 10 mm and decreased it at higher concentrations. This decrease correlated well with that of [Ca2+ ]SR . Pre-treatment of permeabilized myofibres with 2 mm Cl- channel blocker 9-anthracenecarboxylic acid (9AC) inhibited both effects of Pi . The biphasic dependence of Ca2+ release on [Pi ] is explained by a direct effect of Pi acting on the SR Ca2+ release channel, combined with the intra-SR precipitation of Ca2+ salts. The effects of 9AC demonstrate that Pi enters the SR via a Cl- pathway of an as-yet-undefined molecular nature. ABSTRACT Fatiguing exercise causes hydrolysis of phosphocreatine, increasing the intracellular concentration of inorganic phosphate (Pi ). Pi diffuses into the sarcoplasmic reticulum (SR) where it is believed to form insoluble Ca2+ salts, thus contributing to the impairment of Ca2+ release. Information on the Pi entrance pathway is still lacking. In amphibian muscles endowed with isoform 3 of the RyR channel, Ca2+ spark frequency is correlated with the Ca2+ load of the SR and can be used to monitor this variable. We studied the effects of Pi on Ca2+ sparks in permeabilized fibres of the frog. Relative event frequency (f/fref ) rose with increasing [Pi ], reaching 2.54 ± 1.6 at 5 mm, and then decreased monotonically, reaching 0.09 ± 0.03 at [Pi ] = 80 mm. Measurement of [Ca2+ ]SR confirmed a decrease correlated with spark frequency at high [Pi ]. A large [Ca2+ ]SR surge was observed upon Pi removal. Anion channels are a putative path for Pi into the SR. We tested the effect of the chloride channel blocker 9-anthracenecarboxylic acid (9AC) on Pi entrance. 9AC (400 µm) applied to the cytoplasm produced a non-significant increase in spark frequency and reduced the Pi effects on this parameter. Fibre treatment with 2 mm 9AC in the presence of high cytoplasmic Mg2+ suppressed the effects of Pi on [Ca2+ ]SR and spark frequency up to 55 mm [Pi ]. These results suggest that chloride channels (or transporters) provide the main pathway of inorganic phosphate into the SR and confirm that Pi impairs Ca2+ release by accumulating and precipitating with Ca2+ inside the SR, thus contributing to myogenic fatigue.
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Affiliation(s)
- Juan J Ferreira
- Laboratorio de Biofísica del Músculo, Departamento de Biofísica, Facultad de Medicina, Montevideo, Uruguay
| | - Germán Pequera
- Laboratorio de Biofísica del Músculo, Departamento de Biofísica, Facultad de Medicina, Montevideo, Uruguay
| | - Bradley S Launikonis
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Eduardo Ríos
- Section of Cellular Signaling, Department of Physiology and Biophysics, Rush University, Chicago, IL, USA
| | - Gustavo Brum
- Laboratorio de Biofísica del Músculo, Departamento de Biofísica, Facultad de Medicina, Montevideo, Uruguay
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