Tamada Masako, Perez Tomas D, Nelson W James, Sheetz Michael P
Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
J Cell Biol. 2007 Jan 1;176(1):27-33. doi: 10.1083/jcb.200609116.
Actomyosin contraction powers the sealing of epithelial sheets during embryogenesis and wound closure; however, the mechanisms are poorly understood. After laser ablation wounding of Madin-Darby canine kidney cell monolayers, we observed distinct steps in wound closure from time-lapse images of myosin distribution during resealing. Immediately upon wounding, actin and myosin II regulatory light chain accumulated at two locations: (1) in a ring adjacent to the tight junction that circumscribed the wound and (2) in fibers at the base of the cell in membranes extending over the wound site. Rho-kinase activity was required for assembly of the myosin ring, and myosin II activity was required for contraction but not for basal membrane extension. As it contracted, the myosin ring moved toward the basal membrane with ZO-1 and Rho-kinase. Thus, we suggest that tight junctions serve as attachment points for the actomyosin ring during wound closure and that Rho-kinase is required for localization and activation of the contractile ring.
在胚胎发育和伤口愈合过程中，肌动球蛋白收缩为上皮细胞层的封闭提供动力；然而，其机制尚不清楚。在用激光烧蚀法损伤麦迪逊-达比犬肾细胞单层后，我们从重新封闭过程中肌球蛋白分布的延时图像观察到伤口愈合的不同步骤。受伤后立即观察到，肌动蛋白和肌球蛋白II调节轻链在两个位置积累：（1）在与围绕伤口的紧密连接相邻的环中，以及（2）在延伸到伤口部位的细胞膜中细胞基部的纤维中。肌球蛋白环的组装需要Rho激酶活性，收缩需要肌球蛋白II活性，但基底膜延伸不需要。随着收缩，肌球蛋白环与紧密连接蛋白1和Rho激酶一起向基底膜移动。因此，我们认为紧密连接在伤口愈合过程中作为肌动球蛋白环的附着点，并且Rho激酶是收缩环定位和激活所必需的。
