Charras Guillaume T, Hu Chi-Kuo, Coughlin Margaret, Mitchison Timothy J
Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
J Cell Biol. 2006 Nov 6;175(3):477-90. doi: 10.1083/jcb.200602085.
Contractile actin cortex is involved in cell morphogenesis, movement, and cytokinesis, but its organization and assembly are poorly understood. During blebbing, the membrane detaches from the cortex and inflates. As expansion ceases, contractile cortex re-assembles under the membrane and drives bleb retraction. This cycle enabled us to measure the temporal sequence of protein recruitment to the membrane during cortex reassembly and to explore dependency relationships. Expanding blebs were devoid of actin, but proteins of the erythrocytic submembranous cytoskeleton were present. When expansion ceased, ezrin was recruited to the membrane first, followed by actin, actin-bundling proteins, and, finally, contractile proteins. Complete assembly of the contractile cortex, which was organized into a cagelike mesh of filaments, took approximately 30 s. Cytochalasin D blocked recruitment of actin and alpha-actinin, but had no effect on membrane association of ankyrin B and ezrin. Ezrin played no role in actin nucleation, but was essential for tethering the membrane to the cortex. The Rho pathway was important for cortex assembly in blebs.
收缩性肌动蛋白皮层参与细胞形态发生、运动和胞质分裂，但其组织和组装过程仍知之甚少。在形成泡状凸起时，细胞膜与皮层分离并膨胀。当膨胀停止时，收缩性皮层在膜下重新组装并驱动泡状凸起回缩。这个循环使我们能够测量皮层重新组装过程中蛋白质募集到膜上的时间顺序，并探索依赖性关系。正在膨胀的泡状凸起不含肌动蛋白，但存在红细胞膜下细胞骨架的蛋白质。当膨胀停止时，埃兹蛋白首先被募集到膜上，随后是肌动蛋白、肌动蛋白束蛋白，最后是收缩蛋白。收缩性皮层完全组装成丝状的笼状网格大约需要30秒。细胞松弛素D阻断了肌动蛋白和α - 辅肌动蛋白的募集，但对锚蛋白B和埃兹蛋白与膜的结合没有影响。埃兹蛋白在肌动蛋白成核过程中不起作用，但对于将膜与皮层连接至关重要。Rho信号通路对泡状凸起中皮层的组装很重要。
