Functions and regulation of Dbl-family guanine nucleotide exchange factors

说明书(申请人提供)：Rho GTP酶起到二元开关的作用，从GDP结合的“关”状态循环到GTP结合的“开”状态，能够吸引无数的效应器来协调过多的细胞反应，这通常需要细胞骨架的变化。例如，需要Rho GTP酶的细胞反应包括：趋化、分化和分裂、伤口愈合、吞噬、轴突寻路和极化分泌。与Rho GTP酶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)直接与Rho GTP酶结合，加速结合的GDP的排出和GTP的负载。DBL蛋白家族在人类中大约有70个成员，是Rho GTP酶最大的GEF组。所有的DBL家族成员都具有与Rho GTP酶结合和催化交换所必需的DBL同源结构域。在绝大多数的水解区的C末端立即发现一个Pleckstrin同源(PH)区。这些相关PH结构域的性质尚不完全清楚，但通常情况下，这种串联连接用于协调Rho GTP酶的激活与特定磷脂酰肌醇与DH相关PH结构域的结合。鉴于DBL家族GEF在调节Rho GTP酶的激活中的重要性，以及这些GTP酶在细胞生物学的许多方面的中心作用，我们在了解这些交换因子的调节及其在控制生物事件中的相关作用方面投入了大量的精力。因此，该应用有三个特定的目的：1.确定调节DBL家族GEF自身抑制的保守机制。2.确定DBL家族GEF的子集在癌症和神经元发育中的作用。3.确定DH/PH盒协同作用的一般机制。 公共卫生相关性：Rho GTP酶的异常激活，通常由DBL家族的鸟核苷酸交换因子(GEF)介导，与包括癌症在内的许多发育、免疫和增殖性疾病有关。这项拟议的工作旨在阐明DBL家族GEF激活Rho GTP酶的保守机制，并将这一调控置于癌症进展和神经元发育模型的背景下。

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.