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首页> 外文期刊>American Journal of Physiology >Dynamics of myosin replacement in skeletal muscle cells
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Dynamics of myosin replacement in skeletal muscle cells

机译：骨髓肌细胞肌素替代的动态

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Highly organized thick filaments in skeletal muscle cells are formed from ~300 myosin molecules. Each thick-filament-associated myosin molecule is thought to be constantly exchanged. However, the mechanism of myosin replacement remains unclear, as does the source of myosin for substitution. Here, we investigated the dynamics of myosin exchange in the myofibrils of cultured myotubes by fluorescent recovery after photo-bleaching and found that myofibrillar myosin is actively replaced with an exchange half-life of ~3 h. Myosin replacement was not disrupted by the absence of the microtubule system or by actomyosin interactions, suggesting that known cytoskeletal systems are dispensable for myosin substitution. Intriguingly, myosin replacement was independent of myosin binding protein C, which links myosin molecules together to form thick filaments. This implies that an individual myosin molecule rather than a thick filament functions as an exchange unit. Furthermore, the myosin substitution rate was decreased by the inhibition of protein synthesis, suggesting that newly synthesized myosin, as well as preexisting cytosolic myosin, contributes to myosin replacement in myofibrils. Notably, incorporation and release of myosin occurred simultaneously in myofibrils, but rapid myosin release from myofibrils was observed without protein synthesis. Collectively, our results indicate that myosin shuttles between myofibrils and the nonmyofibriliar cytosol to maintain a dynamic equilibrium in skeletal muscle cells.
机译：骨骼肌细胞中高度有组织的厚细丝由〜300毫肌蛋白分子形成。认为每个厚细丝相关的肌蛋白分子被认为是不断交换的。然而，肌球蛋白替代的机制仍然尚不清楚，肌球蛋白的来源是替代的。在这里，我们调查了光漂白后荧光恢复在培养的肌纤维中肌原纤维在培养的肌纤维中的动态，发现Myofibrar肌蛋白被主动替换为〜3小时的交换半衰期。肌球蛋白替代未被微管系统或肌动素相互作用破坏，表明已知的细胞骨骼系统可用于肌菌素替代。有趣的是，Myosin替代物独立于肌球蛋白结合蛋白C，其将肌蛋白分子连接在一起以形成厚的长丝。这意味着单个肌球蛋白分子而不是厚的灯丝用作交换单元。此外，通过抑制蛋白质合成来降低肌素替代率，表明新合成的肌球蛋白以及预先存在的胞质肌蛋白，有助于肌纤维中的肌蛋白替代。值得注意的是，在肌原纤维中同时发生肌蛋白的掺入和释放，但观察到从肌纤维纤维纤维的快速肌霉菌释放而没有蛋白质合成。集体，我们的结果表明肌纤维和非纤维纤维素之间的肌球蛋白梭在骨骼肌细胞中保持动态平衡。

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