HEF1 Functions in Cell Division-Related Signaling

描述（由申请人提供）：长期以来已知细胞形状调节正常（未转化）细胞的生长控制和锚定依赖性，并且转化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细胞骨架结构决定，并受到粘着斑的影响，粘着斑构成细胞外基质（ECM）、整合素受体系统和内部信号网络之间的连接点。 HEF 1和相关蛋白p130 Cas和Efs/Sin定义了Cas（Crk相关底物）信号传导蛋白家族。 该家族的所有成员都位于间期细胞中的粘着斑处，并部分地作为支架来组装蛋白质复合物，所述蛋白质复合物传递源自整合素的信号。 这些蛋白质的初步研究集中在很大程度上定义其在细胞粘附和细胞迁移过程中的作用，从而确定该家族的成员是这些过程中整合素信号传导的重要换能器。 然而，我们在该资助的最后一段时间的工作已经确定了一些HEF 1特异性功能，表明这种蛋白质作为细胞凋亡中细胞粘附状态的哨兵的独特活性。此外，最近的工作强烈表明，在有丝分裂的切割和重新定位的HEF 1是重要的适当的进展，通过胞质分裂，这一功能的HEF 1涉及调节的RhoA GT3的激活周期。 基于本文讨论的这些和其他结果，我们提出HEF 1具有通过有丝分裂和胞质分裂作为细胞周期进展的调节剂的独特功能，并且这种作用与其在附着相关的存活信号传导中的作用是分离的。 为了研究这个想法，我们提出了三个目标。我们将测试HEF 1直接与RhoA-GEF蛋白ECT 2/Pebble相互作用以在有丝分裂中激活RhoA的假设。我们将评估HEF 1在中心体的作用，检验HEF 1通过调节M期进程的中心体相关调节因子来控制有丝分裂进程的互补假设。 最后，我们将确定HEF 1失调对癌症基因组不稳定性的长期影响。

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.