Senju Yosuke, Miyata Hidetake
Department of Physics, Graduate School of Science, Tohoku University, Sendai, Miyagi 980-8578, Japan.
J Biochem. 2009 Feb;145(2):137-50. doi: 10.1093/jb/mvn151. Epub 2008 Nov 13.
We studied the process of formation of stress fibres and involvement of phosphorylation of myosin-II during spreading of Swiss 3T3 fibroblasts. In cells that were allowed to spread for 1 h on a glass surface, circular bundles of actin and myosin-II filament were present. At 2-3 h after the plating, cells showed a polygonal and polarized shape. The proportion of the cells having circular bundles was decreased, whereas that of the cells with straight bundles of actin filaments was increased. At 4 h after the plating, cells were completely polarized and stress fibres were present at the periphery and the dorsal and ventral surfaces of the cells. Thus, spreading cells possessed different forms of actomyosin bundles corresponding to the cell shape. In circular bundles and stress fibres, myosin regulatory light chains were diphosphorylated. Formation of circular bundles and stress fibres was suppressed after the treatment of the cells with Y-27632, a Rho-kinase inhibitor, or blebbistatin, a myosin-II inhibitor. In digitonin-extracted cells, circular bundles as well as stress fibres contracted following the addition of Mg-ATP. These results suggest that circular bundles are contractile structures containing actin and phosphorylated myosin-II filaments, and the formation of circular bundles is regulated by Rho-kinase.
我们研究了瑞士3T3成纤维细胞铺展过程中应力纤维的形成过程以及肌球蛋白-II磷酸化的参与情况。在允许在玻璃表面铺展1小时的细胞中，存在肌动蛋白和肌球蛋白-II丝的圆形束。接种后2 - 3小时，细胞呈现多边形且极化的形状。具有圆形束的细胞比例降低，而具有直的肌动蛋白丝束的细胞比例增加。接种后4小时，细胞完全极化，应力纤维出现在细胞的周边以及背侧和腹侧表面。因此，铺展的细胞具有与细胞形状相对应的不同形式的肌动球蛋白束。在圆形束和应力纤维中，肌球蛋白调节轻链被双磷酸化。用Rho激酶抑制剂Y - 27632或肌球蛋白-II抑制剂blebbistatin处理细胞后，圆形束和应力纤维的形成受到抑制。在洋地黄皂苷提取的细胞中，加入Mg - ATP后，圆形束以及应力纤维会收缩。这些结果表明，圆形束是包含肌动蛋白和磷酸化肌球蛋白-II丝的收缩结构，并且圆形束的形成受Rho激酶调节。
