Kanzaki Keita, Watanabe Daiki, Kuratani Mai, Yamada Takashi, Matsunaga Satoshi, Wada Masanobu
Faculty of Health and Welfare Science, Okayama Prefectural University, Okayama, Japan.
Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan.
J Appl Physiol (1985). 2017 Feb 1;122(2):396-405. doi: 10.1152/japplphysiol.00270.2016. Epub 2016 Dec 15.
The aim of this study was to examine the in vivo effects of eccentric contraction (ECC) on calpain-dependent proteolysis of Ca-regulatory proteins and force production in fast-twitch skeletal muscles. Rat extensor digitorum longus muscles were exposed to 200 repeated ECC in situ and excised immediately [recovery 0 (REC0)] or 3 days [recovery 3 (REC3)] after cessation of ECC. Calpain inhibitor (CI)-treated rats were intraperitoneally injected with MDL-28170 before ECC and during REC3. Tetanic force was markedly reduced at REC0 and remained reduced at REC3. CI treatment ameliorated the ECC-induced force decline but only at REC3. No evidence was found for proteolysis of dihydropyridine receptor (DHPR), junctophilin (JP)1, JP2, ryanodine receptor (RyR), sarcoplasmic reticulum Ca-ATPase (SERCA)1a, or junctional face protein-45 at REC0. At REC3, ECC resulted in decreases in DHPR, JP1, JP2, RyR, and SERCA1a. CI treatment prevented the decreases in DHPR, JP1, and JP2, whereas it had little effect on RyR and SERCA1a. These findings suggest that DHPR, JP1, and JP2, but not RyR and SERCA1a, undergo calpain-dependent proteolysis in in vivo muscles subjected to ECC and that impaired function of DHPR and/or JP might cause prolonged force deficits with ECC. Calpain-dependent proteolysis is one of the contributing factors to muscle damage that occurs with eccentric contraction (ECC). It is unclear, however, whether calpains account for proteolysis of Ca-regulatory proteins in in vivo muscles subjected to ECC. Here, we provide evidence that dihydropyridine receptor and junctophilin, but not ryanodine receptor and sarcoplasmic reticulum Ca-ATPase, undergo calpain-dependent proteolysis.
本研究的目的是检测离心收缩（ECC）对快速收缩骨骼肌中钙蛋白酶依赖性钙调节蛋白水解及力量产生的体内效应。将大鼠趾长伸肌原位进行200次重复ECC，在ECC停止后立即切除[恢复0（REC0）]或3天后切除[恢复3（REC3）]。在ECC前及REC3期间，对用钙蛋白酶抑制剂（CI）处理的大鼠腹腔注射MDL - 28170。强直收缩力在REC0时显著降低，并在REC3时仍保持降低。CI处理改善了ECC诱导的力量下降，但仅在REC3时。在REC0时未发现二氢吡啶受体（DHPR）、连接素（JP）1、JP2、兰尼碱受体（RyR）、肌浆网钙ATP酶（SERCA）1a或连接面蛋白45发生蛋白水解的证据。在REC3时，ECC导致DHPR、JP1、JP2、RyR和SERCA1a减少。CI处理可防止DHPR、JP1和JP2的减少，而对RyR和SERCA1a影响不大。这些发现表明，在接受ECC的体内肌肉中，DHPR、JP1和JP2而非RyR和SERCA1a会发生钙蛋白酶依赖性蛋白水解，并且DHPR和/或JP功能受损可能导致ECC后力量持续不足。钙蛋白酶依赖性蛋白水解是离心收缩（ECC）时发生的肌肉损伤的促成因素之一。然而，尚不清楚钙蛋白酶是否参与了接受ECC的体内肌肉中钙调节蛋白的蛋白水解。在此，我们提供证据表明二氢吡啶受体和连接素会发生钙蛋白酶依赖性蛋白水解，而兰尼碱受体和肌浆网钙ATP酶则不会。
