HEF1 Functions in Cell Division-Related Signaling

描述(申请人提供)：很早就知道，细胞形状调节正常(未转化)细胞的生长控制和贴壁依赖性，转化的细胞表现出改变的形态和基质附着特性。细胞的形状主要由其内部肌动蛋白的细胞骨架结构决定，并受细胞外基质(ECM)、整合素受体系统和内部信号网络之间的局部粘连的影响。HEF1及其相关蛋白pl30Cas和EFS/Sin定义了Cas(Crk相关底物)信号蛋白家族。这个家族的所有成员都居住在间期细胞的焦点粘连处，部分功能是作为支架组装蛋白质复合体，这些复合体通过整合素传递信号。对这些蛋白质的初步研究主要集中在确定它们在细胞黏附和细胞迁移过程中的作用，从而确定该家族成员是这些过程中整合素信号的重要转导分子。然而，我们在这项资助的最后阶段的工作中发现了一些HEF1特异的功能，这些功能表明该蛋白具有独特的活性，可以作为细胞黏附状态在细胞凋亡中的哨兵。此外，最近的工作有力地表明，HEF1在有丝分裂时的切割和重新定位对于胞质分裂的适当进展是重要的，并且HEF1的这一功能涉及调节RhoA GTP酶的激活周期。基于这些和本文讨论的其他结果，我们认为HEF1通过有丝分裂和胞质分裂作为细胞周期进程的调节因子具有独特的功能，并且这种作用与其在依恋相关的生存信号中的作用是分开的。为了研究这一想法，我们提出了三个目标。我们将检验HEF1直接与RhoA-Global蛋白ECT2/Pebble相互作用在有丝分裂中激活RhoA的假设。我们将评估HEF1在中心体的作用，验证一个补充假设，即HEF1通过调节中心体相关的M期进程调节器来控制有丝分裂进程。最后，我们将确定HEF1解除调控对癌症基因组不稳定的长期后果。

DESCRIPTION (provided by applicant): It has long been known that cell shape regulates growth control and anchorage dependence in normal (untransformed) cells, and that transformed cells exhibit altered morphology and matrix attachment properties. The shape of a cell is determined primarily by its internal actin cytoskeletal architecture and influenced by focal adhesions, which constitute points of linkage between the extracellular matrix (ECM), the integrin receptor system land internal signaling networks. HEF1, and the related proteins pl30Cas and Efs/Sin, define the Cas (Crk-associated substrate) family of signaling proteins. All members of this family reside at focal adhesions in interphase cells, and function in part as scaffolds to assemble complexes of proteins that transmit signals originating through integrins. Initial studies of these proteins focused in large part on defining their roles in the processes of cell adhesion and cell migration, leading to the determination that members of this family are important transducers of integrin signaling in these processes. However, our work in the last period of this grant has identified a number of HEF1-specific functions that suggest unique activities for this protein as a sentinel of cell adhesion status in apoptosis. Further, recent work has strongly suggested that the cleavage and relocalization of HEF1 at mitosis is important for appropriate progression through cytokinesis, and that this function of HEF1 involves regulation of the activation cycle of the RhoA GTPase. Based on these and other results discussed herein, we propose that HEF1 has a unique function as a regulator of cell cycle progression through mitosis and cytokinesis, and that this effect is separable from its roles in attachment-related survival signaling. To investigate this idea, we propose three aims. We will test the hypothesis that HEF1 directly interacts with the RhoA-GEF protein ECT2/Pebble to activate RhoA in mitosis. We will evaluate the action of HEF1 at centrosomes, testing a complementary hypothesis that HEF1 controls mitotic progression by regulating centrosomally-associated regulators of M-phase progression. Finally, we will determine the long-term consequences of HEF1 deregulation for genomic instability in cancer.