Functions and regulation of Dbl-family guanine nucleotide exchange factors

描述（由申请人提供）：Rho GTPases作为二进制开关，从gtp结合的“关闭”状态循环到gtp结合的“打开”状态，能够参与无数效应物来协调通常需要改变细胞骨架的大量细胞反应。例如，需要Rho gtpase的细胞反应包括：趋化性、分化和分裂、伤口愈合、吞噬、轴突寻路和极化分泌。与Rho gtpase结合的鸟嘌呤核苷酸的循环在几个点上受到严格控制。特别是鸟嘌呤核苷酸交换因子（gef）直接结合Rho GTPases，加速结合的GDP的排出和GTP的装载。在人类中大约有70个成员，db -家族的蛋白质代表了Rho GTPases最大的gef群。所有Dbl家族成员都具有Dbl同源性（DH）结构域，这是参与Rho GTPases和催化交换所必需的。在绝大多数DH结构域的c端发现了一个pleckstrin同源（PH）结构域。这些相关的PH结构域的性质尚不完全清楚，但一般来说，这种串联连接有助于协调Rho GTPase的激活，使特定的磷酸肌苷与dh相关的PH结构域结合。考虑到dbl家族gef在调控Rho gtpase激活中的重要性，以及这些gtpase在细胞生物学的许多方面的核心作用，我们在理解这些交换因子的调控及其在控制生物学事件中的相关作用方面投入了大量资金。因此，此应用程序有三个具体目标：明确调节dbl家族gef自身抑制的保守机制。2. 确定dbl家族gef在癌症和神经元发育中的作用。3. 定义DH/PH磁带协同功能的一般机制。

DESCRIPTION (provided by applicant): Rho GTPases function as binary switches, cycling from GDP-bound "off" states to GTP-bound "on" states capable of engaging myriad effectors to coordinate a plethora of cellular responses that typically require changes in the cytoskeleton. For example, cellular responses that require Rho GTPases include: chemotaxis, differentiation and division, wound-healing, phagocytosis, axonal pathfinding, and polarized secretion. The cycling of guanine nucleotides bound to Rho GTPases is tightly controlled at several points. In particular, guanine nucleotide exchange factors (GEFs) directly bind Rho GTPases to accelerate the ejection of bound GDP and the loading of GTP. With approximately seventy members in humans, the Dbl-family of proteins represents the largest groups of GEFs for Rho GTPases. All Dbl-family members possess a characteristic Dbl homology (DH) domain necessary to engage Rho GTPases and catalyze exchange. A pleckstrin homology (PH) domain is found immediately C-terminal to the vast majority of DH domains. The nature of these associated PH domains is not fully understood, but in general, this tandem linkage serves to coordinate Rho GTPase activation with the binding of specific phosphoinositides to the DH-associated PH domains. Given the importance of Dbl-family GEFs in regulating the activation of Rho GTPases and the central role of these GTPases to numerous facets of cell biology, we are heavily invested in understanding the regulation of these exchange factors and their associated roles in controlling biological events. Accordingly, this application has three specific aims: 1. To define conserved mechanisms regulating the auto-inhibition of Dbl-family GEFs. 2. To define roles for a subset of Dbl-family GEFs in cancer and neuronal development. 3. To define general mechanisms underlying the cooperative functioning of DH/PH cassettes. Public Health Relevance: The dysregulated activation of Rho GTPases, often mediated by Dbl-family guanine nucleotide exchange factors (GEFs), is associated with numerous developmental, immunological, and proliferative diseases, including cancer. The proposed work is designed to illuminate conserved mechanisms regulating the activation of Rho GTPases by Dbl-family GEFs and to place this regulation within the context of models of cancer progression and neuronal development.