Yam Patricia T, Wilson Cyrus A, Ji Lin, Hebert Benedict, Barnhart Erin L, Dye Natalie A, Wiseman Paul W, Danuser Gaudenz, Theriot Julie A
Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
J Cell Biol. 2007 Sep 24;178(7):1207-21. doi: 10.1083/jcb.200706012.
We have analyzed the spontaneous symmetry breaking and initiation of actin-based motility in keratocytes (fish epithelial cells). In stationary keratocytes, the actin network flow was inwards and radially symmetric. Immediately before motility initiation, the actin network flow increased at the prospective cell rear and reoriented in the perinuclear region, aligning with the prospective axis of movement. Changes in actin network flow at the cell front were detectable only after cell polarization. Inhibition of myosin II or Rho kinase disrupted actin network organization and flow in the perinuclear region and decreased the motility initiation frequency, whereas increasing myosin II activity with calyculin A increased the motility initiation frequency. Local stimulation of myosin activity in stationary cells by the local application of calyculin A induced directed motility initiation away from the site of stimulation. Together, these results indicate that large-scale actin-myosin network reorganization and contractility at the cell rear initiate spontaneous symmetry breaking and polarized motility of keratocytes.
我们分析了角膜细胞（鱼类上皮细胞）中基于肌动蛋白的运动的自发对称性破缺和起始过程。在静止的角膜细胞中，肌动蛋白网络流是向内且呈径向对称的。就在运动起始之前，肌动蛋白网络流在预期的细胞后端增加，并在核周区域重新定向，与预期的运动轴对齐。只有在细胞极化后才能检测到细胞前端肌动蛋白网络流的变化。抑制肌球蛋白II或Rho激酶会破坏核周区域的肌动蛋白网络组织和流动，并降低运动起始频率，而用花萼海绵诱癌素A增加肌球蛋白II活性则会增加运动起始频率。通过局部应用花萼海绵诱癌素A对静止细胞中的肌球蛋白活性进行局部刺激，可诱导远离刺激部位的定向运动起始。总之，这些结果表明，细胞后端大规模的肌动蛋白-肌球蛋白网络重组和收缩性引发了角膜细胞的自发对称性破缺和极化运动。
