Dbl-like Regulators of Small GTP-binding Proteins

描述（由申请人提供）：该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，并研究GEF异常与人类疾病的关系。与Dbl相关的gef代表了一个大的细胞生长调节分子家族，有70多个哺乳动物成员。它们的细胞功能密切依赖于它们相互作用和激活特定Rho gtpase的能力，从而导致各种生理反应，包括细胞分裂、细胞运动、细胞增殖和存活。Dbl家族成员在羧基端与Pleckstrin-homology （PH）结构域串联具有Dbl-homology （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 GTPase识别和GEF活性，而PH结构域与其他调控基序一起参与细胞内靶向和/或DH结构域功能的调节。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GEF的致癌激活是否可能与癌症发展有关，并利用其机制特征设计干扰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Rho GEF （LARG）在生理和病理相关的原发性造血干细胞/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找Clg和MLL-LARG融合活化与白血病发生的功能关联。在第三个目标中，我们将基于结构-功能知识设计GEF-Rho GTPase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为Dbl家族GEFs的生理/病理作用提供有价值的信息，并在Rho GTPase激活剂与人类病理状况（如癌症）之间建立密切联系。该结果也可能为干预gef介导的信号传导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.