Dbl-like Regulators of Small GTP-binding Proteins

描述（由申请人提供）：本项目的长期目标是了解Dbl家族鸟嘌呤核苷酸交换因子（GEF）的信号传导机制，并检查GEF异常与人类疾病的关系。Dbl相关的GEF代表了具有超过70个哺乳动物成员的细胞生长调节分子的大家族。它们的细胞功能密切依赖于它们相互作用和激活特异性Rho GTP酶的能力，从而导致各种生理反应，包括胞质分裂、细胞运动、细胞增殖和存活。Dbl家族成员共享在羧基末端与Pleckstrin同源性（PH）结构域串联的Dbl同源性（DH）结构域的结构模块。先前的研究已经确定DH结构域负责Rho GT3识别和GEF活性，而PH结构域与另外的调节基序一起参与DH结构域功能的细胞内靶向和/或调节。为了继续我们上一个资助期的研究路线，我们计划追求三个具体目标，以检查GEFs的致癌激活是否可能与癌症发展相关，并利用机制特征来设计干扰Dbl家族GEF信号传导的方法。在第一个目标中，我们将研究Dbl家族的两个成员，共同位点淋巴瘤/白血病GEF（Clg）和白血病相关的Rho GEF（LARG）在生理和病理相关的初级造血干/祖细胞中的信号传导机制。在第二个目标中，我们将在小鼠移植模型中寻求Clg和融合MLL-LARG激活与白血病发生的功能关联。在第三个目标中，我们将根据结构-功能知识设计GEF-Rho GTdR相互作用的肽和小分子抑制剂。总之，这些机制和功能研究将提供有关Dbl家族GEF的生理/病理作用的有价值的信息，并在Rho GT3激活剂与人类病理状况如癌症之间建立密切联系。这些结果也可能为GEF介导的信号转导的干预提供有价值的药理学试剂。

DESCRIPTION (provided by applicant): The long-term objectives of this project are to understand the signaling mechanisms of the Dbl family guanine nucleotide exchange factors (GEFs) and to examine the involvement of the GEF abnormalities in human diseases. The Dbl related GEFs represent a large family of cell growth regulatory molecules with over 70 mammalian members. Their cellular functions intimately depend on their ability to interact and activate specific Rho GTPases, leading to various physiological responses including cytokinesis, cell movement, cell proliferation and survival. The Dbl family members share the structural module of a Dbl-homology (DH) domain in tandem at the carboxyl terminus with a Pleckstrin-homology (PH) domain. Previous studies have established that the DH domain is responsible for Rho GTPase recognition and the GEF activity, whereas the PH domain, together with additional regulatory motifs, is involved in intracellular targeting and/or modulation of the DH domain function. To continue the lines of studies of our last funding period, we plan to pursue three specific aims to examine whether oncogenic activation of the GEFs might be associated with cancer development and to utilize the mechanistic features to devise ways to interfere with the Dbl family GEF signaling. In the first aim we will examine the signaling mechanisms of two members of the Dbl family, Common Site lymphoma/leukemia GEF (Clg) and Leukemia associated Rho GEF (LARG), in the physiologically and pathologically relevant primary hematopoietic stem/progenitor cells. In the second aim we will seek a functional association of Clg and the fusion MLL-LARG activation with leukemogenesis in a mouse transplant model. In the third aim we will devise peptide and small molecule inhibitors of the GEF-Rho GTPase interaction based on the structure-function knowledge. Together, these mechanistic and functional studies will provide valuable information on the physiological/pathological roles of Dbl family GEFs and draw a close connection between the Rho GTPase activators and human pathological conditions such as cancer. The results may also provide valuable pharmacological reagents for the intervention of the GEF-mediated signaling.