Cell Transformation by Dbl-like onco-proteins

描述（由申请方提供）：Dbl癌基因产物最初被鉴定为来自人弥漫性B细胞淋巴瘤的转化基因。现在很明显，Dbl只是一个不断增长的细胞蛋白家族的一员，该家族包含一个独特的结构“签名”：普列克底物蛋白同源性（PH）和Dbl同源性（DH）结构域的串联排列。大多数DbI样基因的突变形式被鉴定为引起多种人类恶性和侵袭性病理，表明这些分子在调节正常细胞生长中的关键作用。迄今为止，只有一种生物化学活性与Db1相关蛋白有关，即作为Rho亚家族的低分子量GTP结合蛋白（如Rho、Cdc42和Rac）的激活剂（引起GTP结合）.通常假设Dbl分子表现出的致癌能力的基础是其引起GT3活化的能力的结果。根据这一假设，Cdc42、Rac和Rho蛋白的激活等位基因被证明具有生长调节特性。拟议的研究旨在更好地了解Dbl诱导哺乳动物细胞转化的分子机制。将采取两种具体的调查途径，这两种途径构成本建议的具体目标。这些目的是：1）了解原Dbl的活性在正常（非转化）细胞中是如何调节的。我们建议解决的作用，相互作用的蛋白质，细胞内定位和磷酸化事件在调节生长促进信号来源于原Dbl。2)了解Dbl激活Cdc42后导致其致癌转化的下游信号通路。我们建议确定Cdc42的一个新的目标，这是一个可能的候选人介导的Dbl转化信号和表征的信号传导途径，源于Dbl，并导致通过激活PDK1和Akt的生存途径的刺激。

DESCRIPTION (provided by applicant): The Dbl oncogene product was originally identified as the transforming gene from human diffuse B- cell lymphoma. It is now evident that Dbl is only one member of a growing family of cellular proteins that contain a unique structural 'signature': the tandem arrangement of pleckstrin homology (PH) and Dbl homology (DH) domains. Mutated versions of most DbI- like genes were identified as causing a variety of human malignant and invasive pathologies, suggesting a key role for these molecules in regulation of normal cell growth. To date, only one biochemical activity has been associated with Dbl- related proteins, namely to serve activators of (cause GTP binding to) low Mw GTP- binding proteins from the Rho- subfamily, such as Rho, Cdc42 and Rac. It is generally hypothesized that the basis for the oncogenic capability exhibited by Dbl molecules is an outcome of their ability to cause GTPase activation. In accordance with this hypothesis, activated alleles of Cdc42, Rac and Rho proteins were demonstrated to possess growth- regulatory properties. The proposed research aims at gaining a better understanding of the molecular mechanisms that underlie Dbl- induced transformation of mammalian cells. Two specific avenues of investigation will be pursued that constitute the specific aims of this proposal. These aims are: 1) To understand how the activity of proto- Dbl is regulated in normal (non-transformed) cells. We propose to address the roles of interacting proteins, intra-cellular localization and phosphorylation events in regulating the growth- promoting signals originating from proto- Dbl. 2) To understand the down-stream signaling pathway that leads from activation of Cdc42 by Dbl to oncogenic transformation. We propose to identify a novel target of Cdc42 that is a likely candidate for mediating Dbl- transformation signals and to characterize the signaling pathway that originates from Dbl and leads to stimulation of survival pathways via activation of PDK1 and Akt.