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Flucher BE, Campiglio M. STAC proteins: The missing link in skeletal muscle EC coupling and new regulators of calcium channel function. Biochim Biophys Acta Mol Cell Res 2019; 1866:1101-1110. [PMID: 30543836 DOI: 10.1016/j.bbamcr.2018.12.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 12/04/2018] [Accepted: 12/05/2018] [Indexed: 01/19/2023]
Abstract
Excitation-contraction coupling is the signaling process by which action potentials control calcium release and consequently the force of muscle contraction. Until recently, three triad proteins were known to be essential for skeletal muscle EC coupling: the voltage-gated calcium channel CaV1.1 acting as voltage sensor, the SR calcium release channel RyR1 representing the only relevant calcium source, and the auxiliary CaV β1a subunit. Whether CaV1.1 and RyR1 are directly coupled or whether their interaction is mediated by another triad protein is still unknown. The recent identification of the adaptor protein STAC3 as fourth essential component of skeletal muscle EC coupling prompted vigorous research to reveal its role in this signaling process. Accumulating evidence supports its possible involvement in linking CaV1.1 and RyR1 in skeletal muscle EC coupling, but also indicates a second, much broader role of STAC proteins in the regulation of calcium/calmodulin-dependent feedback regulation of L-type calcium channels.
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Affiliation(s)
- Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Schöpfstraße 41, A6020 Innsbruck, Austria.
| | - Marta Campiglio
- Department of Physiology and Medical Physics, Medical University Innsbruck, Schöpfstraße 41, A6020 Innsbruck, Austria
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Sultana N, Dienes B, Benedetti A, Tuluc P, Szentesi P, Sztretye M, Rainer J, Hess MW, Schwarzer C, Obermair GJ, Csernoch L, Flucher BE. Restricting calcium currents is required for correct fiber type specification in skeletal muscle. Development 2016; 143:1547-59. [PMID: 26965373 PMCID: PMC4909858 DOI: 10.1242/dev.129676] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 02/29/2016] [Indexed: 11/20/2022]
Abstract
Skeletal muscle excitation-contraction (EC) coupling is independent of calcium influx. In fact, alternative splicing of the voltage-gated calcium channel CaV1.1 actively suppresses calcium currents in mature muscle. Whether this is necessary for normal development and function of muscle is not known. However, splicing defects that cause aberrant expression of the calcium-conducting developmental CaV1.1e splice variant correlate with muscle weakness in myotonic dystrophy. Here, we deleted CaV1.1 (Cacna1s) exon 29 in mice. These mice displayed normal overall motor performance, although grip force and voluntary running were reduced. Continued expression of the developmental CaV1.1e splice variant in adult mice caused increased calcium influx during EC coupling, altered calcium homeostasis, and spontaneous calcium sparklets in isolated muscle fibers. Contractile force was reduced and endurance enhanced. Key regulators of fiber type specification were dysregulated and the fiber type composition was shifted toward slower fibers. However, oxidative enzyme activity and mitochondrial content declined. These findings indicate that limiting calcium influx during skeletal muscle EC coupling is important for the secondary function of the calcium signal in the activity-dependent regulation of fiber type composition and to prevent muscle disease.
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Affiliation(s)
- Nasreen Sultana
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Beatrix Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen 4032, Hungary
| | - Ariane Benedetti
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Petronel Tuluc
- Department of Pharmacology, University of Innsbruck, Innsbruck 6020, Austria
| | - Peter Szentesi
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen 4032, Hungary
| | - Monika Sztretye
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen 4032, Hungary
| | - Johannes Rainer
- Division of Molecular Pathophysiology, Biocenter, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Michael W Hess
- Division of Histology and Embryology, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Christoph Schwarzer
- Department of Pharmacology, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Gerald J Obermair
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck 6020, Austria
| | - Laszlo Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen 4032, Hungary
| | - Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck 6020, Austria
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