皮层肌动蛋白结合蛋白cortactin在细胞胞质断裂和小鼠受精卵发育中的作用

Cytokinesis is the last step in mitosis. During cytokinesis, the contraction of the contractile ring and the fusion of membrane vesicles to the cleavage furrow lead to the formation of two daughter cells. The blockade of cytokinesis induces the formation of binucleated or multi-nucleated cells. In mammalian cells, the contraction of the contractile ring and the fusion of the membrane vesicles are two synchronized steps. Either the disruption of the contractile ring or the blockade of membrane vesicle fusion will lead to the inhibition of cytokinesis. Cortactin is a F-actin associated protein and the substrate of Src kinase. It colocalizes with F-actin in the cortical structures of adherent cells and associates with the F-actin cytoskeleton through the F-actin binding tandem cortactin repeats and the N-terminal acidic domain that interacts with the actin-related protein 2/3 complex (ARP2/3) for dendritic actin nucleation. Thus, cortactin can provide the cross-linking between actin filaments. In addition, cortactin can associate with trans-golgi vesicles and regulate post-golgi membrane vesicle transportation. The homozygote of cortactin knockout mouse is lethal at the division of the fertilized egg, indicating the failur of the first cell division. In cultured mammalian cells, the suppression of cortactin expression by RNA interference leads to the increase of the binucleated or multinucleated cells. These observation indicates that cortactin is involved in the regulation of cytokinesis. Since cortactin can interact with F-actin as well as trans-golgi membrane vesicles, cortactin can act like a bridge molecule between contractile ring and the membrane vesicles. In this proposal, we would like to test this hypothesis and to elucidate the function of cortactin in cytokinesis and murine zygotic development.

胞质断裂（cytokinesis）是细胞有丝分裂的最后步骤，由微丝收缩环收缩和细胞膜融合使得细胞分裂成为两个子细胞。抑制胞质断裂导致双核乃至多核细胞的形成。哺乳动物细胞的胞质断裂过程主要是由微丝收缩环不断收缩，并伴随细胞膜囊泡在收缩凹陷（cleavage furrow）处融合形成细胞膜间隔来实现的。因此，正常的胞质断裂需要收缩环的收缩与细胞膜囊泡融合的协同作用。皮层肌动蛋白结合蛋白cortactin是一个微丝结合蛋白质，介导微丝间相互作用形成微丝网络；cortactin也能结合高尔基小泡等细胞膜囊泡。敲除cortactin基因的纯合子小鼠卵裂期致死，显示cortactin在受精卵分裂过程中有着重要作用。在培养细胞中抑制cortactin表达，双核和多核细胞的比例增加。Cortactin的这些特性提示它参与了胞质断裂过程的调控。本项目的研究主要是探索cortactin调控胞质断裂的分子机制。