Cell Transformation by Dbl-like onco-proteins

描述（由申请人提供）：Dbl癌基因产物最初被确定为来自人弥漫性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成员之一，该家族含有独特的结构“特征”：pleckstrin同源（PH）和Dbl同源（DH）结构域的串联排列。大多数DbI样基因的突变版本被确定为引起各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起关键作用。迄今为止，只有一种生化活性与Dbl-相关蛋白相关，即作为Rho-亚家族的低分子量GTP结合蛋白的激活剂（导致GTP结合），如Rho， Cdc42和Rac。一般假设，Dbl分子表现出的致癌能力的基础是它们引起GTPase激活的能力的结果。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。提出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，构成这项建议的具体目标。这些目标是：1)了解如何在正常（未转化）细胞中调节原Dbl的活性。我们建议研究相互作用蛋白、细胞内定位和磷酸化事件在调节原Dbl产生的促生长信号中的作用。2)了解Dbl激活Cdc42到致癌转化的下游信号通路。我们建议鉴定Cdc42的一个新靶点，它可能是介导Dbl-转化信号的候选靶点，并表征起源于Dbl的信号通路，并通过激活PDK1和Akt来刺激生存途径。

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.