What factors determine the number of nonmuscle myosin II in the sarcomeric unit of stress fibers?
What factors determine the number of nonmuscle myosin II in the sarcomeric unit of stress fibers?
复制标题
哪些因素决定应力纤维肌节单位中非肌肉肌球蛋白 II 的数量？
DOI：
10.1007/s10237-020-01375-8
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发表时间：
2021
影响因子：
3.5
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Saito;T.;Huang;W.;Matsui;T.S.;Kuragano;M.;Takahashi;M.;Deguchi;S.
肌动蛋白应激纤维（SFs）是非肌肉细胞中的一种可收缩器官，具有明显类似于肌肉中肌原纤维肌节的可收缩单元。因此，SFs的功能通常是基于肌肉的良好特征来解决的。然而，与肌原纤维中固定数量的肌球蛋白分子不同，SFs中可收缩肌体单元内的非肌球蛋白II （NMII）的数量相当低，并且由于某种原因而变化。在这里，我们讨论了哪些因素可能决定SFs中NMII的具体数量。我们用一个理论模型提出，这个数字正好介于SFs在静态条件下承受细胞张力和在细胞被迫缩短时迅速分解的功能之间。我们在表达肌球蛋白调节轻链突变体的人骨肉瘤U2OS细胞中监测了缩短诱导的SFs解体，该突变体实际上调节了NMII与肌动蛋白丝的相互作用，观察到的行为确实与理论结果一致。SFs的这种情况特异性可能允许非肌肉细胞对机械应力做出适应性反应，以避免如前所述的促炎信号的激活，即与基本上专门表现收缩活动的肌肉不同的行为。
Actin stress fibers (SFs), a contractile apparatus in nonmuscle cells, possess a contractile unit that is apparently similar to the sarcomere of myofibrils in muscles. The function of SFs has thus often been addressed based on well-characterized properties of muscles. However, unlike the fixed number of myosin molecules in myofibrils, the number of nonmuscle myosin II (NMII) within the contractile sarcomeric unit in SFs is quite low and variable for some reason. Here we address what factors may determine the specific number of NMII in SFs. We suggest with a theoretical model that the number lies just in between the function of SFs for bearing cellular tension under static conditions and for promptly disintegrating upon forced cell shortening. We monitored shortening-induced disintegration of SFs in human osteosarcoma U2OS cells expressing mutants of myosin regulatory light chain that virtually regulates the interaction of NMII with actin filaments, and the behaviors observed were indeed consistent with the theoretical consequences. This situation-specific nature of SFs may allow nonmuscle cells to respond adaptively to mechanical stress to circumvent activation of pro-inflammatory signals as previously indicated, i.e., a behavior distinct from that of muscles that are basically specialized for exhibiting contractile activity.