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Pedersen KK, Cheng AJ, Westerblad H, Olesen JH, Overgaard K. Moderately elevated extracellular [K+] potentiates submaximal force and power in skeletal muscle via increased [Ca2+]i during contractions. Am J Physiol Cell Physiol 2019; 317:C900-C909. [DOI: 10.1152/ajpcell.00104.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The extracellular K+ concentration ([K+]o) increases during physical exercise. We here studied whether moderately elevated [K+]o may increase force and power output during contractions at in vivo-like subtetanic frequencies and whether such potentiation was associated with increased cytosolic free Ca2+ concentration ([Ca2+]i) during contractions. Isolated whole soleus and extensor digitorum longus (EDL) rat muscles were incubated at different levels of [K+]o, and isometric and dynamic contractility were tested at various stimulation frequencies. Furthermore, [Ca2+]i at rest and during contraction was measured along with isometric force in single mouse flexor digitorum brevis (FDB) fibers exposed to elevated [K+]o. Elevating [K+]o from 4 mM up to 8 mM (soleus) and 11 mM (EDL) increased isometric force at subtetanic frequencies, 2–15 Hz in soleus and up to 50 Hz in EDL, while inhibition was seen at tetanic frequency in both muscle types. Elevating [K+]o also increased peak power of dynamic subtetanic contractions, with potentiation being more pronounced in EDL than in soleus muscles. The force-potentiating effect of elevated [K+]o was transient in FDB single fibers, reaching peak after ~4 and 2.5 min in 9 and 11 mM [K+]o, respectively. At the time of peak potentiation, force and [Ca2+]i during 15-Hz contractions were significantly increased, whereas force was slightly decreased and [Ca2+]i unchanged during 50-Hz contractions. Moderate elevation of [K+]o can transiently potentiate force and power during contractions at subtetanic frequencies, which can be explained by a higher [Ca2+]i during contractions.
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Affiliation(s)
- Katja K. Pedersen
- Department of Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark
| | - Arthur J. Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Jonas H. Olesen
- Department of Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark
| | - Kristian Overgaard
- Department of Public Health, Section of Sport Science, Aarhus University, Aarhus, Denmark
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2
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Neyroud D, Cheng AJ, Donnelly C, Bourdillon N, Gassner AL, Geiser L, Rudaz S, Kayser B, Westerblad H, Place N. Toxic doses of caffeine are needed to increase skeletal muscle contractility. Am J Physiol Cell Physiol 2018; 316:C246-C251. [PMID: 30566390 DOI: 10.1152/ajpcell.00269.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Discrepant results have been reported regarding an intramuscular mechanism underlying the ergogenic effect of caffeine on neuromuscular function in humans. Here, we reevaluated the effect of caffeine on muscular force production in humans and combined this with measurements of the caffeine dose-response relationship on force and cytosolic free [Ca2+] ([Ca2+]i) in isolated mouse muscle fibers. Twenty-one healthy and physically active men (29 ± 9 yr, 178 ± 6 cm, 73 ± 10 kg, mean ± SD) took part in the present study. Nine participants were involved in two experimental sessions during which supramaximal single and paired electrical stimulations (at 10 and 100 Hz) were applied to the femoral nerve to record evoked forces. Evoked forces were recorded before and 1 h after ingestion of 1) 6 mg caffeine/kg body mass or 2) placebo. Caffeine plasma concentration was measured in 12 participants. In addition, submaximal tetanic force and [Ca2+]i were measured in single mouse flexor digitorum brevis (FDB) muscle fibers exposed to 100 nM up to 5 mM caffeine. Six milligrams of caffeine per kilogram body mass (plasma concentration ~40 µM) did not increase electrically evoked forces in humans. In superfused FDB single fibers, millimolar caffeine concentrations (i.e., 15- to 35-fold above usual concentrations observed in humans) were required to increase tetanic force and [Ca2+]i. Our results suggest that toxic doses of caffeine are required to increase muscle contractility, questioning the purported intramuscular ergogenic effect of caffeine in humans.
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Affiliation(s)
- Daria Neyroud
- Institute of Sport Sciences, University of Lausanne , Lausanne , Switzerland
| | - Arthur J Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet , Stockholm , Sweden
| | - Chris Donnelly
- Institute of Sport Sciences, University of Lausanne , Lausanne , Switzerland
| | - Nicolas Bourdillon
- Institute of Sport Sciences, University of Lausanne , Lausanne , Switzerland
| | - Anne-Laure Gassner
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Lausanne, Switzerland
| | - Laurent Geiser
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Lausanne, Switzerland
| | - Serge Rudaz
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Lausanne, Switzerland
| | - Bengt Kayser
- Institute of Sport Sciences, University of Lausanne , Lausanne , Switzerland
| | - Håkan Westerblad
- Department of Physiology and Pharmacology, Karolinska Institutet , Stockholm , Sweden
| | - Nicolas Place
- Institute of Sport Sciences, University of Lausanne , Lausanne , Switzerland
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3
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Glass LD, Cheng AJ, MacIntosh BR. Role of Ca 2+ in changing active force during intermittent submaximal stimulation in intact, single mouse muscle fibers. Pflugers Arch 2018; 470:1243-1254. [PMID: 29671103 PMCID: PMC6060763 DOI: 10.1007/s00424-018-2143-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/02/2018] [Accepted: 04/04/2018] [Indexed: 12/27/2022]
Abstract
Fatigue of single mouse fibers during repeated high-frequency stimulation results initially from decreased Ca2+ sensitivity while free myoplasmic calcium concentration ([Ca2+]m) increases, followed by decreasing [Ca2+]m. Recovery of active force with low-frequency stimulation is slow and persistent fatigue results from low [Ca2+]m. However, the consequences of intermittent submaximal contractions are not known. The aim of the present study was to investigate the changes in [Ca2+]m and active force during intermittent submaximal contractions and subsequent recovery. Single fibers of mouse flexor digitorum brevis muscles at 32 °C were stimulated with 40 or 50 Hz, for 350 ms every 2 s for 2 min and then every 1 s until < 40% of initial force. Values obtained during the intermittent stimulation were compared with a control force-[Ca2+]m relationship. A "P"-shaped pattern in the force-[Ca2+]m relationship was observed during intermittent stimulation. Early in the intermittent stimulation, [Ca2+]m increased while active force decreased. Subsequent force potentiation was accompanied by increased Ca2+ sensitivity. Later, as active force declined, [Ca2+]m decreased significantly (p < 0.001). This was followed, in the final phase, by a significant decrease in Ca2+ sensitivity determined by [Ca2+]m at half-maximal force (Ca50) (p = 0.001). Low-frequency fatigue persisted during recovery while Ca50 was not significantly different from prefatigue (p > 0.5). In conclusion, the main mechanism of fatigue is due to decreases in both [Ca2+]m and Ca2+ sensitivity following the initial force potentiation. The intermittent submaximal contractions resulted in persistent low-frequency fatigue seen during recovery, which was explained by depressed [Ca2+]m with no change in Ca2+ sensitivity.
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Affiliation(s)
- Lisa D. Glass
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta T2N 1N4 Canada
| | - Arthur J. Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Brian R. MacIntosh
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta T2N 1N4 Canada
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4
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Eremeeva EV, Vysotski ES. Exploring Bioluminescence Function of the Ca2+
-regulated Photoproteins with Site-directed Mutagenesis. Photochem Photobiol 2018; 95:8-23. [DOI: 10.1111/php.12945] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 05/25/2018] [Indexed: 11/29/2022]
Affiliation(s)
- Elena V. Eremeeva
- Photobiology Laboratory; Institute of Biophysics SB RAS; Federal Research Center “Krasnoyarsk Science Center SB RAS”; Krasnoyarsk Russia
| | - Eugene S. Vysotski
- Photobiology Laboratory; Institute of Biophysics SB RAS; Federal Research Center “Krasnoyarsk Science Center SB RAS”; Krasnoyarsk Russia
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5
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Pratt SJP, Hernández-Ochoa EO, Lee RM, Ory EC, Lyons JS, Joca HC, Johnson A, Thompson K, Bailey P, Lee CJ, Mathias T, Vitolo MI, Trudeau M, Stains JP, Ward CW, Schneider MF, Martin SS. Real-time scratch assay reveals mechanisms of early calcium signaling in breast cancer cells in response to wounding. Oncotarget 2018; 9:25008-25024. [PMID: 29861849 PMCID: PMC5982755 DOI: 10.18632/oncotarget.25186] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 04/03/2018] [Indexed: 01/11/2023] Open
Abstract
Aggressive cellular phenotypes such as uncontrolled proliferation and increased migration capacity engender cellular transformation, malignancy and metastasis. While genetic mutations are undisputed drivers of cancer initiation and progression, it is increasingly accepted that external factors are also playing a major role. Two recently studied modulators of breast cancer are changes in the cellular mechanical microenvironment and alterations in calcium homeostasis. While many studies investigate these factors separately in breast cancer cells, very few do so in combination. This current work sets a foundation to explore mechano-calcium relationships driving malignant progression in breast cancer. Utilizing real-time imaging of an in vitro scratch assay, we were able to resolve mechanically-sensitive calcium signaling in human breast cancer cells. We observed rapid initiation of intracellular calcium elevations within seconds in cells at the immediate wound edge, followed by a time-dependent increase in calcium in cells at distances up to 500μm from the scratch wound. Calcium signaling to neighboring cells away from the wound edge returned to baseline within seconds. Calcium elevations at the wound edge however, persisted for up to 50 minutes. Rigorous quantification showed that extracellular calcium was necessary for persistent calcium elevation at the wound edge, but intercellular signal propagation was dependent on internal calcium stores. In addition, intercellular signaling required extracellular ATP and activation of P2Y2 receptors. Through comparison of scratch-induced signaling from multiple cell lines, we report drastic reductions in response from aggressively tumorigenic and metastatic cells. The real-time scratch assay established here provides quantitative data on the molecular mechanisms that support rapid scratch-induced calcium signaling in breast cancer cells. These mechanisms now provide a clear framework for investigating which short-term calcium signals promote long-term changes in cancer cell biology.
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Affiliation(s)
- Stephen J P Pratt
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Rachel M Lee
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Eleanor C Ory
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - James S Lyons
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Humberto C Joca
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Ashley Johnson
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Keyata Thompson
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Patrick Bailey
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Cornell J Lee
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Trevor Mathias
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Michele I Vitolo
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Matt Trudeau
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Joseph P Stains
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Christopher W Ward
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, USA.,School of Nursing, University of Maryland, Baltimore, MD, USA
| | - Martin F Schneider
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Stuart S Martin
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.,Marlene and Stewart Greenebaum NCI Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA
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6
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Bioluminescent and biochemical properties of Cys-free Ca 2+ -regulated photoproteins obelin and aequorin. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2017; 174:97-105. [DOI: 10.1016/j.jphotobiol.2017.07.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 11/18/2022]
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Mechanical isolation, and measurement of force and myoplasmic free [Ca 2+] in fully intact single skeletal muscle fibers. Nat Protoc 2017; 12:1763-1776. [PMID: 28771237 DOI: 10.1038/nprot.2017.056] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Mechanical dissection of single intact mammalian skeletal muscle fibers permits real-time measurement of intracellular properties and contractile function of living fibers. A major advantage of mechanical over enzymatic fiber dissociation is that single fibers can be isolated with their tendons remaining attached, which allows contractile forces (in the normal expected range of 300-450 kN/m2) to be measured during electrical stimulation. Furthermore, the sarcolemma of single fibers remains fully intact after mechanical dissection, and hence the living fibers can be studied with intact intracellular milieu and normal function and metabolic properties, as well as ionic control. Given that Ca2+ is the principal regulator of the contractile force, measurements of myoplasmic free [Ca2+] ([Ca2+]i) can be used to further delineate the intrinsic mechanisms underlying changes in skeletal muscle function. [Ca2+]i measurements are most commonly performed in intact single fibers using ratiometric fluorescent indicators such as indo-1 or fura-2. These Ca2+ indicators are introduced into the fiber by pressure injection or by using the membrane-permeable indo-1 AM, and [Ca2+]i is measured by calculating a ratio of the fluorescence at specific wavelengths emitted for the Ca2+-free and Ca2+-bound forms of the dye. We describe here the procedures for mechanical dissection, and for force and [Ca2+]i measurement in intact single fibers from mouse flexor digitorum brevis (FDB) muscle, which is the most commonly used muscle in studies using intact single fibers. This technique can also be used to isolate intact single fibers from various muscles and from various species. As an alternative to Ca2+ indicators, single fibers can also be loaded with fluorescent indicators to measure, for instance, reactive oxygen species, pH, and [Mg2+], or they can be injected with proteins to change functional properties. The entire protocol, from dissection to the start of an experiment on a single fiber, takes ∼3 h.
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8
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Ma Q, Ye L, Liu H, Shi Y, Zhou N. An overview of Ca 2+ mobilization assays in GPCR drug discovery. Expert Opin Drug Discov 2017; 12:511-523. [PMID: 28277837 DOI: 10.1080/17460441.2017.1303473] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION Calcium ions (Ca2+) serve as a second messenger or universal signal transducer implicated in the regulation of a wide range of physiological processes. A change in the concentration of intracellular Ca2+ is an important step in intracellular signal transduction. G protein-coupled receptors (GPCRs), the largest and most versatile group of cell surface receptors, transduce extracellular signals into intracellular responses via their coupling to heterotrimeric G proteins. Since Ca2+ plays a crucial role in GPCR-induced signaling, measurement of intracellular Ca2+ has attracted more and more attention in GPCR-targeted drug discovery. Areas covered: This review focuses on the most popular functional assays measuring GPCRs-induced intracellular Ca2+ signaling. These include photoprotein-based, synthetic fluorescent indicator-based and genetically encoded calcium indicator (GECI)-based Ca2+ mobilization assays. A brief discussion of the design strategy of fluorescent probes in GPCR studies is also presented. Expert opinion: GPCR-mediated intracellular signaling is multidimensional. There is an urgent need for the development of multiple-readout screening assays capable of simultaneous detection of biased signaling and screening of both agonists and antagonists in the same assay. It is also necessary to develop GECIs offering low cost and consistent assays suitable for investigating GPCR activation in vivo.
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Affiliation(s)
- Qiang Ma
- a College of Life Sciences, Zijingang Campus , Zhejiang University, Institute of Biochemistry and Molecular Biology , Hangzhou , Zhejiang , China
| | - Lingyan Ye
- a College of Life Sciences, Zijingang Campus , Zhejiang University, Institute of Biochemistry and Molecular Biology , Hangzhou , Zhejiang , China
| | - Hongxia Liu
- b Department of Internal Medicine , Edong Healthcare Group , Huangshi , Hubei , China
| | - Ying Shi
- a College of Life Sciences, Zijingang Campus , Zhejiang University, Institute of Biochemistry and Molecular Biology , Hangzhou , Zhejiang , China
| | - Naiming Zhou
- a College of Life Sciences, Zijingang Campus , Zhejiang University, Institute of Biochemistry and Molecular Biology , Hangzhou , Zhejiang , China
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9
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Eremeeva EV, Bartsev SI, van Berkel WJH, Vysotski ES. Unanimous Model for Describing the Fast Bioluminescence Kinetics of Ca2+-regulated Photoproteins of Different Organisms. Photochem Photobiol 2016; 93:495-502. [DOI: 10.1111/php.12664] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 09/29/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Elena V. Eremeeva
- Photobiology Laboratory; Institute of Biophysics SB RAS; Federal Research Center “Krasnoyarsk Science Center SB RAS”; Krasnoyarsk Russia
| | - Sergey I. Bartsev
- Theoretical Biophysics Laboratory; Institute of Biophysics SB RAS; Federal Research Center “Krasnoyarsk Science Center SB RAS”; Krasnoyarsk Russia
| | | | - Eugene S. Vysotski
- Photobiology Laboratory; Institute of Biophysics SB RAS; Federal Research Center “Krasnoyarsk Science Center SB RAS”; Krasnoyarsk Russia
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10
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Schneidereit D, Vass H, Reischl B, Allen RJ, Friedrich O. Calcium Sensitive Fluorescent Dyes Fluo-4 and Fura Red under Pressure: Behaviour of Fluorescence and Buffer Properties under Hydrostatic Pressures up to 200 MPa. PLoS One 2016; 11:e0164509. [PMID: 27764134 PMCID: PMC5072694 DOI: 10.1371/journal.pone.0164509] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 09/26/2016] [Indexed: 11/18/2022] Open
Abstract
The fluorescent Ca2+ sensitive dyes Fura Red (ratiometric) and Fluo-4 (non-ratiometric) are widely utilized for the optical assessment of Ca2+ fluctuations in vitro as well as in situ. The fluorescent behavior of these dyes is strongly depends on temperature, pH, ionic strength and pressure. It is crucial to understand the response of these dyes to pressure when applying calcium imaging technologies in the field of high pressure bioscience. Therefore, we use an optically accessible pressure vessel to pressurize physiological Ca2+-buffered solutions at different fixed concentrations of free Ca2+ (1 nM to 25.6 μM) and a specified dye concentration (12 μM) to pressures of 200 MPa, and record dye fluorescence intensity. Our results show that Fluo-4 fluorescence intensity is reduced by 31% per 100 MPa, the intensity of Fura Red is reduced by 10% per 100 MPa. The mean reaction volume for the dissociation of calcium from the dye molecules [Formula: see text] is determined to -17.8 ml mol-1 for Fluo-4 and -21.3 ml mol-1 for Fura Red. Additionally, a model is presented that is used to correct for pressure-dependent changes in pH and binding affinity of Ca2+ to EGTA, as well as to determine the influence of these changes on dye fluorescence.
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Affiliation(s)
- D. Schneidereit
- Institute of Medical Biotechnology, Friedrich-Alexander-University Erlangen-Nuernberg, 91052 Erlangen, Bavaria, Germany
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University Erlangen-Nuernberg, 91052 Erlangen, Bavaria, Germany
- * E-mail:
| | - H. Vass
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, Scotland, United Kingdom
| | - B. Reischl
- Institute of Medical Biotechnology, Friedrich-Alexander-University Erlangen-Nuernberg, 91052 Erlangen, Bavaria, Germany
| | - R. J. Allen
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, Scotland, United Kingdom
| | - O. Friedrich
- Institute of Medical Biotechnology, Friedrich-Alexander-University Erlangen-Nuernberg, 91052 Erlangen, Bavaria, Germany
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University Erlangen-Nuernberg, 91052 Erlangen, Bavaria, Germany
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11
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Malikova NP, Borgdorff AJ, Vysotski ES. Semisynthetic photoprotein reporters for tracking fast Ca(2+) transients. Photochem Photobiol Sci 2016; 14:2213-24. [PMID: 26508209 DOI: 10.1039/c5pp00328h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Changes in the intracellular concentration of free ionized calcium ([Ca(2+)]i) control a host of cellular processes as varied as vision, muscle contraction, neuronal signal transmission, proliferation, apoptosis etc. The disturbance in Ca(2+)-signaling causes many severe diseases. To understand the mechanisms underlying the control by calcium and how disorder of this regulation relates to pathological conditions, it is necessary to measure [Ca(2+)]i. The Ca(2+)-regulated photoproteins which are responsible for bioluminescence of marine coelenterates have been successfully used for this purpose over the years. Here we report the results on comparative characterization of bioluminescence properties of aequorin from Aequorea victoria, obelin from Obelia longissima, and clytin from Clytia gregaria charged by native coelenterazine and coelenterazine analogues f, i, and hcp. The comparison of specific bioluminescence activity, stability, emission spectra, stopped-flow kinetics, sensitivity to calcium, and effect of physiological concentrations of Mg(2+) establishes obelin-hcp as an excellent semisynthetic photoprotein to keep track of fast intracellular Ca(2+) transients. The rate of rise of its light signal on a sudden change of [Ca(2+)] is almost 3- and 11-fold higher than those of obelin and aequorin with native coelenterazine, respectively, and 20 times higher than that of the corresponding aequorin-hcp. In addition, obelin-hcp preserves a high specific bioluminescence activity and displays higher Ca(2+)-sensitivity as compared to obelin charged by native coelenterazine and sensitivity to Ca(2+) comparable with those of aequorin-f and aequorin-hcp.
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Affiliation(s)
- Natalia P Malikova
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia
| | - Aren J Borgdorff
- Institut des Neurosciences Alfred Fessard, UPR 3294, Centre National de la Recherche Scientifique, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France.
| | - Eugene S Vysotski
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia
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12
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Llano-Diez M, Cheng AJ, Jonsson W, Ivarsson N, Westerblad H, Sun V, Cacciani N, Larsson L, Bruton J. Impaired Ca(2+) release contributes to muscle weakness in a rat model of critical illness myopathy. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2016; 20:254. [PMID: 27510990 PMCID: PMC5050561 DOI: 10.1186/s13054-016-1417-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 07/20/2016] [Indexed: 01/01/2023]
Abstract
BACKGROUND Critical illness myopathy is an acquired skeletal muscle disorder with severe myosin loss and muscle weakness frequently seen in intensive care unit (ICU) patients. It is unknown if impaired excitation-contraction coupling contributes to the muscle weakness. METHODS We used a unique ICU model where rats were deeply sedated, post-synaptically pharmacologically paralyzed, mechanically ventilated and closely monitored for up to ten days. Single intact fibers from the flexor digitorum brevis muscle were isolated and used to measure force and free myoplasmic [Ca(2+)] ([Ca(2+)]i) during tetanic contractions. RESULTS Fibers from ICU rats had 80 % lower tetanic [Ca(2+)]i and produced only 15 % of the force seen in fibers from sham-operated (SHAM) rats. In the presence of 5 mM caffeine, tetanic [Ca(2+)]i was similar in fibers from ICU and SHAM rats but force was 50 % lower in fibers from ICU rats than SHAM rats. Confocal imaging showed disrupted tetanic [Ca(2+)]i transients in fibers from ICU rats compared to SHAM rats. Western blots showed similar levels of Na(+) channel and dihydropyridine receptor (DHPR) protein expression, whereas ryanodine receptor (RyR) and sarco-endoplasmic reticulum Ca(2+) ATPase 1 (SERCA1) expression was markedly lower in muscle of ICU rats than in SHAM rats. Immunohistochemical analysis showed that distribution of Na(+) channel and DHPR protein on the sarcolemma was disrupted in fibers from ICU rats compared with SHAM rats. CONCLUSIONS These results suggest that impaired SR Ca(2+) release contributes to the muscle weakness seen in patients in ICU.
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Affiliation(s)
- Monica Llano-Diez
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - Arthur J Cheng
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - William Jonsson
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - Niklas Ivarsson
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - Håkan Westerblad
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - Vic Sun
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - Nicola Cacciani
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - Lars Larsson
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden
| | - Joseph Bruton
- Department of Physiology & Pharmacology, Karolinska Institutet, von Eulers väg, 8, 2 floor, Stockholm, 171 77, Sweden.
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Burakova LP, Natashin PV, Markova SV, Eremeeva EV, Malikova NP, Cheng C, Liu ZJ, Vysotski ES. Mitrocomin from the jellyfish Mitrocoma cellularia with deleted C-terminal tyrosine reveals a higher bioluminescence activity compared to wild type photoprotein. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2016; 162:286-297. [PMID: 27395792 DOI: 10.1016/j.jphotobiol.2016.06.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/30/2016] [Accepted: 06/30/2016] [Indexed: 10/21/2022]
Abstract
The full-length cDNA genes encoding five new isoforms of Ca(2+)-regulated photoprotein mitrocomin from a small tissue sample of the outer bell margin containing photocytes of only one specimen of the luminous jellyfish Mitrocoma cellularia were cloned, sequenced, and characterized after their expression in Escherichia coli and subsequent purification. The analysis of cDNA nucleotide sequences encoding mitrocomin isoforms allowed suggestion that two isoforms might be the products of two allelic genes differing in one amino acid residue (64R/Q) whereas other isotypes appear as a result of transcriptional mutations. In addition, the crystal structure of mitrocomin was determined at 1.30Å resolution which expectedly revealed a high similarity with the structures of other hydromedusan photoproteins. Although mitrocomin isoforms reveal a high degree of identity of amino acid sequences, they vary in specific bioluminescence activities. At that, all isotypes displayed the identical bioluminescence spectra (473-474nm with no shoulder at 400nm). Fluorescence spectra of Ca(2+)-discharged mitrocomins were almost identical to their light emission spectra similar to the case of Ca(2+)-discharged aequorin, but different from Ca(2+)-discharged obelins and clytin which fluorescence is red-shifted by 25-30nm from bioluminescence spectra. The main distinction of mitrocomin from other hydromedusan photoproteins is an additional Tyr at the C-terminus. Using site-directed mutagenesis, we showed that this Tyr is not important for bioluminescence because its deletion even increases specific activity and efficiency of apo-mitrocomin conversion into active photoprotein, in contrast to C-terminal Pro of other photoproteins. Since genes in a population generally exist as different isoforms, it makes us anticipate the cloning of even more isoforms of mitrocomin and other hydromedusan photoproteins with different bioluminescence properties.
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Affiliation(s)
- Ludmila P Burakova
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia
| | - Pavel V Natashin
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Svetlana V Markova
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia
| | - Elena V Eremeeva
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia
| | - Natalia P Malikova
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia
| | - Chongyun Cheng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhi-Jie Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Institute of Molecular and Clinical Medicine, Kunming Medical University, Kunming 650500, China; iHuman Institute, ShanghaiTech University, Shanghai 201210, China.
| | - Eugene S Vysotski
- Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia.
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Yeste M, Jones C, Amdani SN, Patel S, Coward K. Oocyte activation deficiency: a role for an oocyte contribution? Hum Reprod Update 2015; 22:23-47. [DOI: 10.1093/humupd/dmv040] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 08/13/2015] [Indexed: 12/11/2022] Open
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Ollivier H, Marchant J, Le Bayon N, Servili A, Claireaux G. Calcium response of KCl-excited populations of ventricular myocytes from the European sea bass (Dicentrarchus labrax): a promising approach to integrate cell-to-cell heterogeneity in studying the cellular basis of fish cardiac performance. J Comp Physiol B 2015. [PMID: 26205950 DOI: 10.1007/s00360-015-0924-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Climate change challenges the capacity of fishes to thrive in their habitat. However, through phenotypic diversity, they demonstrate remarkable resilience to deteriorating conditions. In fish populations, inter-individual variation in a number of fitness-determining physiological traits, including cardiac performance, is classically observed. Information about the cellular bases of inter-individual variability in cardiac performance is scarce including the possible contribution of excitation-contraction (EC) coupling. This study aimed at providing insight into EC coupling-related Ca(2+) response and thermal plasticity in the European sea bass (Dicentrarchus labrax). A cell population approach was used to lay the methodological basis for identifying the cellular determinants of cardiac performance. Fish were acclimated at 12 and 22 °C and changes in intracellular calcium concentration ([Ca(2+)]i) following KCl stimulation were measured using Fura-2, at 12 or 22 °C-test. The increase in [Ca(2+)]i resulted primarily from extracellular Ca(2+) entry but sarcoplasmic reticulum stores were also shown to be involved. As previously reported in sea bass, a modest effect of adrenaline was observed. Moreover, although the response appeared relatively insensitive to an acute temperature change, a difference in Ca(2+) response was observed between 12- and 22 °C-acclimated fish. In particular, a greater increase in [Ca(2+)]i at a high level of adrenaline was observed in 22 °C-acclimated fish that may be related to an improved efficiency of adrenaline under these conditions. In conclusion, this method allows a rapid screening of cellular characteristics. It represents a promising tool to identify the cellular determinants of inter-individual variability in fishes' capacity for environmental adaptation.
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Affiliation(s)
| | - James Marchant
- Unité PFOM-ARN, LEMAR, Centre Ifremer de Brest, Plouzané, France
| | - Nicolas Le Bayon
- Unité PFOM-ARN, LEMAR, Centre Ifremer de Brest, Plouzané, France
| | - Arianna Servili
- Unité PFOM-ARN, LEMAR, Centre Ifremer de Brest, Plouzané, France
| | - Guy Claireaux
- Unité PFOM-ARN, LEMAR, Centre Ifremer de Brest, Plouzané, France
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16
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Cheng AJ, Bruton JD, Lanner JT, Westerblad H. Antioxidant treatments do not improve force recovery after fatiguing stimulation of mouse skeletal muscle fibres. J Physiol 2014; 593:457-72. [PMID: 25630265 DOI: 10.1113/jphysiol.2014.279398] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 10/30/2014] [Indexed: 12/20/2022] Open
Abstract
The contractile performance of skeletal muscle declines during intense activities, i.e. fatigue develops. Fatigued muscle can enter a state of prolonged low-frequency force depression (PLFFD). PLFFD can be due to decreased tetanic free cytosolic [Ca(2+) ] ([Ca(2+) ]i ) and/or decreased myofibrillar Ca(2+) sensitivity. Increases in reactive oxygen and nitrogen species (ROS/RNS) may contribute to fatigue-induced force reductions. We studied whether pharmacological ROS/RNS inhibition delays fatigue and/or counteracts the development of PLFFD. Mechanically isolated mouse fast-twitch fibres were fatigued by sixty 150 ms, 70 Hz tetani given every 1 s. Experiments were performed in standard Tyrode solution (control) or in the presence of: NADPH oxidase (NOX) 2 inhibitor (gp91ds-tat); NOX4 inhibitor (GKT137831); mitochondria-targeted antioxidant (SS-31); nitric oxide synthase (NOS) inhibitor (l-NAME); the general antioxidant N-acetylcysteine (NAC); a cocktail of SS-31, l-NAME and NAC. Spatially and temporally averaged [Ca(2+) ]i and peak force were reduced by ∼20% and ∼70% at the end of fatiguing stimulation, respectively, with no marked differences between groups. PLFFD was similar in all groups, with 30 Hz force being decreased by ∼60% at 30 min of recovery. PLFFD was mostly due to decreased tetanic [Ca(2+) ]i in control fibres and in the presence of NOX2 or NOX4 inhibitors. Conversely, in fibres exposed to SS-31 or the anti ROS/RNS cocktail, tetanic [Ca(2+) ]i was not decreased during recovery so PLFFD was only caused by decreased myofibrillar Ca(2+) sensitivity. The cocktail also increased resting [Ca(2+) ]i and ultimately caused cell death. In conclusion, ROS/RNS-neutralizing compounds did not counteract the force decline during or after induction of fatigue.
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Affiliation(s)
- Arthur J Cheng
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden
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17
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Characterization of hydromedusan Ca2+-regulated photoproteins as a tool for measurement of Ca2+concentration. Anal Bioanal Chem 2014; 406:5715-26. [DOI: 10.1007/s00216-014-7986-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Revised: 05/30/2014] [Accepted: 06/18/2014] [Indexed: 10/25/2022]
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18
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Nielsen J, Cheng AJ, Ørtenblad N, Westerblad H. Subcellular distribution of glycogen and decreased tetanic Ca2+ in fatigued single intact mouse muscle fibres. J Physiol 2014; 592:2003-12. [PMID: 24591577 DOI: 10.1113/jphysiol.2014.271528] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In skeletal muscle fibres, glycogen has been shown to be stored at different subcellular locations: (i) between the myofibrils (intermyofibrillar); (ii) within the myofibrils (intramyofibrillar); and (iii) subsarcolemmal. Of these, intramyofibrillar glycogen has been implied as a critical regulator of sarcoplasmic reticulum Ca(2+) release. The aim of the present study was to test directly how the decrease in cytoplasmic free Ca(2+) ([Ca(2+)]i) during repeated tetanic contractions relates to the subcellular glycogen distribution. Single fibres of mouse flexor digitorum brevis muscles were fatigued with 70 Hz, 350 ms tetani given at 2 s (high-intensity fatigue, HIF) or 10 s (low-intensity fatigue, LIF) intervals, while force and [Ca(2+)]i were measured. Stimulation continued until force decreased to 30% of its initial value. Fibres were then prepared for analyses of subcellular glycogen distribution by transmission electron microscopy. At fatigue, tetanic [Ca(2+)]i was reduced to 70 ± 4% and 54 ± 4% of the initial in HIF (P < 0.01, n = 9) and LIF (P < 0.01, n = 5) fibres, respectively. At fatigue, the mean inter- and intramyofibrillar glycogen content was 60-75% lower than in rested control fibres (P < 0.05), whereas subsarcolemmal glycogen was similar to control. Individual fibres showed a good correlation between the fatigue-induced decrease in tetanic [Ca(2+)]i and the reduction in intermyofibrillar (P = 0.051) and intramyofibrillar (P = 0.0008) glycogen. In conclusion, the fatigue-induced decrease in tetanic [Ca(2+)]i, and hence force, is accompanied by major reductions in inter- and intramyofibrillar glycogen. The stronger correlation between decreased tetanic [Ca(2+)]i and reduced intramyofibrillar glycogen implies that sarcoplasmic reticulum Ca(2+) release critically depends on energy supply from the intramyofibrillar glycogen pool.
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Calderón JC, Bolaños P, Caputo C. The excitation-contraction coupling mechanism in skeletal muscle. Biophys Rev 2014; 6:133-160. [PMID: 28509964 PMCID: PMC5425715 DOI: 10.1007/s12551-013-0135-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 12/06/2013] [Indexed: 12/27/2022] Open
Abstract
First coined by Alexander Sandow in 1952, the term excitation-contraction coupling (ECC) describes the rapid communication between electrical events occurring in the plasma membrane of skeletal muscle fibres and Ca2+ release from the SR, which leads to contraction. The sequence of events in twitch skeletal muscle involves: (1) initiation and propagation of an action potential along the plasma membrane, (2) spread of the potential throughout the transverse tubule system (T-tubule system), (3) dihydropyridine receptors (DHPR)-mediated detection of changes in membrane potential, (4) allosteric interaction between DHPR and sarcoplasmic reticulum (SR) ryanodine receptors (RyR), (5) release of Ca2+ from the SR and transient increase of Ca2+ concentration in the myoplasm, (6) activation of the myoplasmic Ca2+ buffering system and the contractile apparatus, followed by (7) Ca2+ disappearance from the myoplasm mediated mainly by its reuptake by the SR through the SR Ca2+ adenosine triphosphatase (SERCA), and under several conditions movement to the mitochondria and extrusion by the Na+/Ca2+ exchanger (NCX). In this text, we review the basics of ECC in skeletal muscle and the techniques used to study it. Moreover, we highlight some recent advances and point out gaps in knowledge on particular issues related to ECC such as (1) DHPR-RyR molecular interaction, (2) differences regarding fibre types, (3) its alteration during muscle fatigue, (4) the role of mitochondria and store-operated Ca2+ entry in the general ECC sequence, (5) contractile potentiators, and (6) Ca2+ sparks.
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Affiliation(s)
- Juan C Calderón
- Physiology and Biochemistry Research Group-Physis, Department of Physiology and Biochemistry, Faculty of Medicine, University of Antioquia UdeA, Calle 70 No 52-21, Medellín, Colombia.
- Laboratory of Cellular Physiology, Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela.
- Departamento de Fisiología y Bioquímica, Grupo de Investigación en Fisiología y Bioquímica-Physis, Facultad de Medicina, Universidad de Antioquia, Calle 70 No 52-21, Medellín, Colombia.
| | - Pura Bolaños
- Laboratory of Cellular Physiology, Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
| | - Carlo Caputo
- Laboratory of Cellular Physiology, Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
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Shkryl VM, Blatter LA. Ca(2+) release events in cardiac myocytes up close: insights from fast confocal imaging. PLoS One 2013; 8:e61525. [PMID: 23637847 PMCID: PMC3630194 DOI: 10.1371/journal.pone.0061525] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 03/11/2013] [Indexed: 02/02/2023] Open
Abstract
The spatio-temporal properties of Ca2+ transients during excitation-contraction coupling and elementary Ca2+ release events (Ca2+ sparks) were studied in atrial and ventricular myocytes with ultra-fast confocal microscopy using a Zeiss LSM 5 LIVE system that allows sampling rates of up to 60 kHz. Ca2+ sparks which originated from subsarcolemmal junctional sarcoplasmic reticulum (j-SR) release sites in atrial myocytes were anisotropic and elongated in the longitudinal direction of the cell. Ca2+ sparks in atrial cells originating from non-junctional SR and in ventricular myocytes were symmetrical. Ca2+ spark recording in line scan mode at 40,000 lines/s uncovered step-like increases of [Ca2+]i. 2-D imaging of Ca2+ transients revealed an asynchronous activation of release sites and allowed the sequential recording of Ca2+ entry through surface membrane Ca2+ channels and subsequent activation of Ca2+-induced Ca2+ release. With a latency of 2.5 ms after application of an electrical stimulus, Ca2+ entry could be detected that was followed by SR Ca2+ release after an additional 3 ms delay. Maximum Ca2+ release was observed 4 ms after the beginning of release. The timing of Ca2+ entry and release was confirmed by simultaneous [Ca2+]i and membrane current measurements using the whole cell voltage-clamp technique. In atrial cells activation of discrete individual release sites of the j-SR led to spatially restricted Ca2+ release events that fused into a peripheral ring of elevated [Ca2+]i that subsequently propagated in a wave-like fashion towards the center of the cell. In ventricular myocytes asynchronous Ca2+ release signals from discrete sites with no preferential subcellular location preceded the whole-cell Ca2+ transient. In summary, ultra-fast confocal imaging allows investigation of Ca2+ signals with a time resolution similar to patch clamp technique, however in a less invasive fashion.
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Affiliation(s)
- Vyacheslav M. Shkryl
- Deptartment of General Physiology of the Nervous System, A. A. Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - Lothar A. Blatter
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, United States of America
- * E-mail:
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Zong M, Bruton JD, Grundtman C, Yang H, Li JH, Alexanderson H, Palmblad K, Andersson U, Harris HE, Lundberg IE, Westerblad H. TLR4 as receptor for HMGB1 induced muscle dysfunction in myositis. Ann Rheum Dis 2012; 72:1390-9. [DOI: 10.1136/annrheumdis-2012-202207] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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