INTERACTION OF RAS AND RHO SIGNAL TRANSDUCTION PATHWAYS

Ras和Rho GTP酶介导与正常 细胞生长控制和肿瘤发生。虽然这两个群体 的GTP酶与不同的效应靶相互作用，现在很明显 它们的协调活动负责它们的生物功能 在细胞增殖和形态方面。RAS和RHO的作用机制 然而，有丝分裂原促进的通路偶联目前尚不清楚。 在RAS特异性和RHO特异性之间形成的细胞复合体 GTP酶激活蛋白(GAP)建立了直接的物理连接 在RAS和RHO信号之间。这个复合体的作用，RasGAPpl9O 复杂的，在RAS和Rho介导的细胞信号正在被研究。 在这个实验室之前的研究中，几种生化特性 包括它与RasGAP的关联，它的 RhoGAP的活性及其GTP酶的活性。此外，使用 在小鼠的基因敲除策略中，pl9O的一个特定的生物学作用是 在发育中的神经系统中确定，在那里需要蛋白质 在中线寻找轴突路径。此外，这些研究已经 发现p190是细胞内唯一主要的酪氨酸磷酸化蛋白。 大脑，这表明它在大脑中执行一般的信号功能 神经系统。在新提出的研究中，有三个具体问题 将解决：L。p190在启动的信号通路中的位置 通过细胞外有丝分裂原？2.鉴定的生化特性是如何 P190及其蛋白的相互作用解释了其可能的功能 RAS和RHO介导的信号通路的协调者？3.什么是 RasGAP-PL90复合体在已定义的生物系统中的作用，即， 轴突引导？为了解决pl9O的信号转导作用，该信号通路 导致pl9O磷酸化的基因将被鉴定出来，而细胞 将研究破坏RasGAP-p190复合体的后果。 蛋白质与PL90的相互作用将通过表征进行研究 在酵母双杂交中鉴定的几个候选的pl90型相互作用子 屏幕上。P190在轴突通路中的明显作用表明，pl9O 可能介导细胞外轴突引导信号的下游信号。 这将直接在两个记录在案的相关信号系统中进行测试 在轴突引导下。PL90基因敲除小鼠将被用来确认 这类观测的生物学相关性。这些研究应该有助于 建立pl9O在RAS和Rho介导中的作用之间的联系 信号转导和一种特定的生物功能可能 需要RAS和RHO GTP酶的协调活动。

The Ras and Rho GTPases mediate signaling pathways associated with normal cellular growth control as well as oncogenesis. Although these two groups of GTPases interact with different effector targets, it is now clear that their coordinated activity is responsible for their biological functions in cell proliferation and morphology. The mechanism by which Ras and Rho pathways are coupled is presently unknown, however, a mitogen-promoted cellular complex that forms between a Ras-specific and a Rho-specific GTPase activating protein (GAP) establishes a direct physical connection between Ras and Rho signals. The role of this complex, the RasGAPpl9O complex, in Ras- and Rho-mediated cellular signaling is being investigated. In previous studies from this laboratory, several biochemical properties of p190 have been established, including its association with RasGAP, its activity as a RhoGAP, and its GTPase activity. In addition, using a knockout strategy in mice, a specific biological role for pl9O has been identified in the developing nervous system, where the protein is required for axonal pathfinding at the midline. Moreover, these studies have identified p190 as the single major tyrosine-phosphorylated protein in the brain, suggesting that it performs a general signaling function in the nervous system. In the newly proposed studies, three specific questions will be addressed: l. Where does p190 fit into signaling pathways initiated by extracellular mitogens? 2. How do the identified biochemical properties of p190 and its protein interactions account for its putative function as a coordinator of Ras- and Rho-mediated signaling pathways? 3. What is the role of the RasGAP-pl90 complex in a defined biological system, namely, axon guidance? To address the signaling role of pl9O, the kinase pathways that lead to pl9O phosphorylation will be identified, and the cellular consequences of disrupting the RasGAP-p190 complex will be examined. Protein interactions with pl90 will be investigated by the characterization of several candidate pl9O-interactors identified in a yeast two-hybrid screen. The apparent role of p190 in axonal pathfinding suggests that pl9O might mediate the downstream signals of extracellular axon guidance cues. This will be tested directly in two documented signaling systems associated with axon guidance. The pl90 knockout mice will be used to confirm the biological relevance of such observations. These studies should help to establish a connection between the role of pl9O in Ras- and Rho-mediated signal transduction and a specific biological function that is likely to require the coordinated activities of both Ras and Rho GTPases.