Role of Vav family proteins in cell signaling and cancer

描述（由申请人提供）：Vav家族是一组癌蛋白，在脊椎动物中有三个代表（Vav， Vav2和Vav3），在无脊椎动物中有单个成员。这些蛋白催化Rho/Rac家族gtp结合蛋白上的核苷酸交换，从而促进这些gtp酶从无活性（与gdp结合）状态转变为活性（与gtp结合）状态。Vav蛋白的酶活性在信号转导过程中受到酪氨酸直接磷酸化的严格调控。因此，它们只有在被上游具有内在或相关酪氨酸激酶活性的受体磷酸化时才会被激活。一些证据表明，Vav蛋白的功能对发育和有丝分裂过程都至关重要。因此，通过同源重组缺失vav和vav2基因导致淋巴细胞系成熟缺陷和缺乏适当的抗原反应。此外，Vav和Vav2的功能获得突变体的异位表达在啮齿动物成纤维细胞中诱导了高水平的细胞转化。最后，最近的研究结果表明Vav通路在人类淋巴细胞性病毒（如HIV、HTLV和γ -疱疹病毒）的致病周期中起作用。我们实验室的长期目标是在生化、结构、细胞和有机体水平上实现该蛋白质家族的全面表征。为了实现这一目标，将进行以下研究。在目标1中，结构生物学和生化技术将用于可视化这些蛋白质在与上游调节剂和GTPase底物结合时所经历的构象变化。在Aim 2中，蛋白质组学和表达克隆方法将用于揭示基于翻译后修饰和与其他细胞内分子相互作用的Vav蛋白的调控机制。在Aim 3中，信号技术将被用来剖析在Vav通路中运行的新的串扰和反馈机制。在Aim 4中，三个vav家族基因的敲除小鼠将被用于研究vav蛋白在细胞信号传导和生理过程中的作用，当不受控制时，这些生理过程会导致人类疾病。综上所述，这些研究应该为Vav蛋白在信号转导过程中的运作方式提供一个统一的视角，同时，为设计药理学工具提供有价值的信息，这些工具可以帮助在未来操纵Vav家族依赖的生物过程。

DESCRIPTION (provided by applicant): The Vav family is a group of oncoproteins with three representatives in vertebrates (Vav, Vav2, and Vav3) and single members in invertebrates. These proteins catalyze the exchange of nucleotides on GTP-binding proteins of the Rho/Rac family, thereby facilitating the transition of these GTPases from their inactive (GDP-bound) to their active (GTP-bound) state. The enzyme activity of Vav proteins is tightly regulated during signal transduction by direct tyrosine phosphorylation. As a consequence, they only become activated when phosphorylated by upstream receptors with intrinsic or associated tyrosine kinase activity. Several lines of evidence demonstrate that the function of Vav proteins is crucial for both developmental and mitogenic processes. Thus, the deletion of vav and vav2 genes by homologous recombination results in defective maturation of lymphocyte lineages and lack of proper antigenic responses. Furthermore, the ectopic expression of gain-of-function mutants of Vav and Vav2 induces high levels of cellular transformation in rodent fibroblasts. Finally, recent results have implicated the Vav pathway in the pathogenic cycle of human lymphotropic viruses such as HIV, HTLV, and gamma-herpesviruses. The long-term objective of our laboratory is to achieve a comprehensive characterization of this protein family at the biochemical, structural, cellular, and organism level. To achieve this objective, the following studies will be carried out. In Aim 1, structural biology and biochemical techniques will be used to visualize the conformational changes underwent by these proteins upon binding to upstream regulators and GTPase substrates. In Aim 2, proteomic and expression cloning approaches will be used to reveal regulatory mechanisms of Vav proteins based on both posttranslational modifications and interactions with other intracellular molecules. In Aim 3, signaling techniques will be utilized to dissect new crosstalk and feedback mechanisms operating in the Vav pathway. In Aim 4, available knockout mice for the three vav family genes will be used to study the role of Vav proteins in cell signaling and physiological processes that, when deregulated, contribute to human disease. Taken together, these studies should provide a unified vision of the modus operandi of Vav proteins during signal transduction and, at the same time, supply valuable information for the design of pharmacological tools that could aid in the manipulation of Vav family-dependent biological processes in the future.