Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan.
Genes Cells. 2013 Feb;18(2):90-109. doi: 10.1111/gtc.12021. Epub 2012 Dec 12.
Nonmuscle myosin II forms a folded conformation (10S form) in the inactivated state; however, the physiological importance of the 10S form is still unclear. To investigate the role of 10S form, we generated a chimeric mutant of nonmuscle myosin IIB (IIB-SK1·2), in which S1462-R1490 and L1551-E1577 were replaced with the corresponding portions of skeletal muscle myosin heavy chain. The IIB-SK1·2 mutant did not fold into a 10S form under physiological condition in vitro. IIB-SK1·2 was less dynamic by stabilizing the filamentous form and accumulated in the posterior region of migrating cells. IIB-SK1·2 functioned properly in cytokinesis but altered migratory properties; the rate and directional persistence were increased by IIB-SK1·2 expression. Surprisingly, endogenous nonmuscle myosin IIA was excluded from the posterior region of migrating cells expressing IIB-SK1·2, which may underlie the change of the cellular migratory properties. These results suggest that the 10S form is necessary for maintaining nonmuscle myosin II in an unassembled state and for recruitment of nonmuscle myosin II to a specific region of the cell.
非肌肉肌球蛋白 II 在失活状态下形成折叠构象（10S 形式）；然而，10S 形式的生理重要性仍不清楚。为了研究 10S 形式的作用，我们生成了非肌肉肌球蛋白 IIB（IIB-SK1·2）的嵌合突变体，其中 S1462-R1490 和 L1551-E1577 被骨骼肌肌球蛋白重链的相应部分取代。在体外生理条件下，IIB-SK1·2 突变体不会折叠成 10S 形式。IIB-SK1·2 通过稳定丝状形式而变得不那么动态，并在迁移细胞的后区域积累。IIB-SK1·2 在胞质分裂中正常发挥作用，但改变了迁移特性；通过表达 IIB-SK1·2，速率和方向持续性增加。令人惊讶的是，表达 IIB-SK1·2 的迁移细胞的后区域排除了内源性非肌肉肌球蛋白 IIA，这可能是细胞迁移特性变化的基础。这些结果表明，10S 形式对于将非肌肉肌球蛋白 II 保持在未组装状态以及将非肌肉肌球蛋白 II 募集到细胞的特定区域是必要的。
