A possible role of the junctional face protein JP‐45 in modulating Ca<sup>2+</sup> release in skeletal muscle

Gouadon, Elodie; Schuhmeier, Ralph Peter; Ursu, Daniel; Anderson, Ayuk A.; Treves, Susan; Zorzato, Francesco; Lehmann‐Horn, Frank; Melzer, Werner

doi:10.1113/jphysiol.2005.104406

Cited by 19 publications

(14 citation statements)

References 40 publications

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“…This difference was not statistically significant. The maximum value of L‐type current amplitude found here is smaller than that previously reported for C2C12 cells using the same extracellular calcium concentration of 10 m m (Schuhmeier & Melzer, 2004; Gouadon et al 2006). This discrepancy can be explained by the use of cells at different stages of development.…”

Section: Resultscontrasting

confidence: 86%

The calcium channel α2/δ1 subunit is involved in extracellular signalling

García

Nabhani

Garcı́a

2008

The Journal of Physiology

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The α2/δ1 subunit forms part of the dihydropyridine receptor, an essential protein complex for excitation-contraction (EC) coupling in skeletal muscle. Because of the lack of a viable knock-out animal, little is known regarding the role of the α2/δ1 subunit in EC coupling or in other cell functions. Interestingly, the α2/δ1 appears before the α1 subunit in development and contains extracellular conserved domains known to be important in cell signalling and inter-protein interactions. These facts raise the possibility that the α2/δ1 subunit performs vital functions not associated with EC coupling. Here, we tested the hypothesis that the α2/δ1 subunit is important for interactions of muscle cells with their environment. Using confocal microscopy, we followed the immunolocalization of α2/δ1 and α1 subunits with age. We found that in 2-day-old myotubes, the α2/δ1 subunit concentrated towards the ends of the cells, while the α1 subunit clustered near the centre. As myotubes aged (6-12 days), the α2/δ1 became evenly distributed along the myotubes and co-localized with α1. When the expression of α2/δ1 was blocked with siRNA, migration, attachment and spreading of myoblasts were impaired while the L-type calcium current remained unaffected. The results suggest a previously unidentified role of the α2/δ1 subunit in skeletal muscle and support the involvement of this protein in extracellular signalling. This new role of the α2/δ1 subunit may be crucial for muscle development, muscle repair and at times in which myoblast attachment and migration are fundamental.

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Section: Resultscontrasting

confidence: 86%

The calcium channel α2/δ1 subunit is involved in extracellular signalling

García

Nabhani

Garcı́a

2008

The Journal of Physiology

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“…4D) without significantly affecting charge movement half-activation potential (Table 2). These results together with previous studies on JP45 overexpression (30,34) indicate that the stoichiometry of JP45-Ca v 1.1 subunit exhibited by mature skeletal muscle is crucial for maintaining the molecular and functional expression of the Ca v 1.1 subunit (31). Because the Ca v 1.1 charge movement is the activating signal for RyR1-mediated calcium release from the SR, we performed experiments to evaluate whether depolarization-induced calcium release from the SR of JP45 KO mice is also affected.…”

Section: Electrophysiological Properties Of Skeletal Muscle Fibers Frmentioning

confidence: 58%

Loss of skeletal muscle strength by ablation of the sarcoplasmic reticulum protein JP45

Delbono

Xia²,

Treves³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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Skeletal muscle constitutes Ϸ40% of the human body mass, and alterations in muscle mass and strength may result in physical disability. Therefore, the elucidation of the factors responsible for muscle force development is of paramount importance. Excitationcontraction coupling (ECC) is a process during which the skeletal muscle surface membrane is depolarized, causing a transient release of calcium from the sarcoplasmic reticulum that activates the contractile proteins. The ECC machinery is complex, and the functional role of many of its protein components remains elusive. This study demonstrates that deletion of the gene encoding the sarcoplasmic reticulum protein JP45 results in decreased muscle strength in young mice. Specifically, this loss of muscle strength in JP45 knockout mice is caused by decreased functional expression of the voltage-dependent Ca 2؉ channel Cav1.1, which is the molecule that couples membrane depolarization and calcium release from the sarcoplasmic reticulum. These results point to JP45 as one of the molecules involved in the development or maintenance of skeletal muscle strength.calcium release ͉ excitation-contraction coupling

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“…These include calsequestrin, a Ca 2+ ‐binding protein that facilitates the concentration of Ca 2+ close to the RyR1 channels (9), triadin and junctin, two integral SR membrane proteins known to bind both calsequestrin and RyR1 (10–12). Additional triadic proteins have been recently identified, including the junctional SR protein JP‐45 and junctate; yet, their functions still need to be better defined (12–14).…”

Section: The Junctional Sr: Where the Sr Meets The T‐tubule/plasma Mementioning

confidence: 99%

The Sarcoplasmic Reticulum: An Organized Patchwork of Specialized Domains

Rossi

Barone

Giacomello

et al. 2008

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The sarcoplasmic reticulum (SR) of skeletal muscle cells is a convoluted structure composed of a variety of tubules and cisternae, which share a continuous lumen delimited by a single continuous membrane, branching to form a network that surrounds each myofibril. In this network, some specific domains basically represented by the longitudinal SR and the junctional SR can be distinguished. These domains are mainly dedicated to Ca 21 homeostasis in relation to regulation of muscle contraction, with the longitudinal SR representing the sites of Ca 21 uptake and storage and the junctional SR representing the sites of Ca 21 release. To perform its functions, the SR takes contact with other cellular elements, the sarcolemma, the contractile apparatus and the mitochondria, giving rise to a number of interactions, most of which are still to be defined at the molecular level. This review will describe some of the most recent advancements in understanding the organization of this complex network and its specific domains. Furthermore, we shall address initial evidence on how SR proteins are retained at distinct SR domains.

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A possible role of the junctional face protein JP‐45 in modulating Ca²⁺ release in skeletal muscle

Cited by 19 publications

References 40 publications

The calcium channel α2/δ1 subunit is involved in extracellular signalling

The calcium channel α2/δ1 subunit is involved in extracellular signalling

Loss of skeletal muscle strength by ablation of the sarcoplasmic reticulum protein JP45

The Sarcoplasmic Reticulum: An Organized Patchwork of Specialized Domains

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A possible role of the junctional face protein JP‐45 in modulating Ca2+ release in skeletal muscle

Cited by 19 publications

References 40 publications

The calcium channel α2/δ1 subunit is involved in extracellular signalling

The calcium channel α2/δ1 subunit is involved in extracellular signalling

Loss of skeletal muscle strength by ablation of the sarcoplasmic reticulum protein JP45

The Sarcoplasmic Reticulum: An Organized Patchwork of Specialized Domains

Contact Info

Product

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A possible role of the junctional face protein JP‐45 in modulating Ca²⁺ release in skeletal muscle