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Physical interaction of junctophilin and the CaV1.1 C terminus is crucial for skeletal muscle contraction.

ABSTRACT: Close physical association of CaV1.1 L-type calcium channels (LTCCs) at the sarcolemmal junctional membrane (JM) with ryanodine receptors (RyRs) of the sarcoplasmic reticulum (SR) is crucial for excitation-contraction coupling (ECC) in skeletal muscle. However, the molecular mechanism underlying the JM targeting of LTCCs is unexplored. Junctophilin 1 (JP1) and JP2 stabilize the JM by bridging the sarcolemmal and SR membranes. Here, we examined the roles of JPs in localization and function of LTCCs. Knockdown of JP1 or JP2 in cultured myotubes inhibited LTCC clustering at the JM and suppressed evoked Ca2+ transients without disrupting JM structure. Coimmunoprecipitation and GST pull-down assays demonstrated that JPs physically interacted with 12-aa residues in the proximal C terminus of the CaV1.1. A JP1 mutant lacking the C terminus including the transmembrane domain (JP1?CT) interacted with the sarcolemmal/T-tubule membrane but not the SR membrane. Expression of this mutant in adult mouse muscles in vivo exerted a dominant-negative effect on endogenous JPs, impairing LTCC-RyR coupling at triads without disrupting JM morphology, and substantially reducing Ca2+ transients without affecting SR Ca2+ content. Moreover, the contractile force of the JP1?CT-expressed muscle was dramatically reduced compared with the control. Taken together, JPs recruit LTCCs to the JM through physical interaction and ensure robust ECC at triads in skeletal muscle.

SUBMITTER: Nakada T

PROVIDER: S-EPMC5924888 | biostudies-other | 2018 Apr

REPOSITORIES: biostudies-other

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Physical interaction of junctophilin and the Ca<sub>V</sub>1.1 C terminus is crucial for skeletal muscle contraction.

Nakada Tsutomu T Kashihara Toshihide T Komatsu Masatoshi M Kojima Katsuhiko K Takeshita Toshikazu T Yamada Mitsuhiko M

Proceedings of the National Academy of Sciences of the United States of America 20180409 17

Close physical association of Ca<sub>V</sub>1.1 L-type calcium channels (LTCCs) at the sarcolemmal junctional membrane (JM) with ryanodine receptors (RyRs) of the sarcoplasmic reticulum (SR) is crucial for excitation-contraction coupling (ECC) in skeletal muscle. However, the molecular mechanism underlying the JM targeting of LTCCs is unexplored. Junctophilin 1 (JP1) and JP2 stabilize the JM by bridging the sarcolemmal and SR membranes. Here, we examined the roles of JPs in localization and func ...[more]

PMID: 29632175

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Dataset Information

Physical interaction of junctophilin and the CaV1.1 C terminus is crucial for skeletal muscle contraction.

Publications

Physical interaction of junctophilin and the Ca<sub>V</sub>1.1 C terminus is crucial for skeletal muscle contraction.

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