The PAK4 kinase in cell growth and transformation

描述（由申请人提供）：拟议实验的目的是确定丝氨酸/苏氨酸激酶Pak4在调节细胞生长和转化中的作用。Pak4是Rho gtpase Cdc42和Rac的效应物，最初被鉴定为在细胞骨架组织中起作用的蛋白质。最近，Pak4也被证明在控制细胞生长和存活方面具有重要作用。Pak4在癌细胞系中过表达，Pak4在已建立的永生化细胞系中高度转化。相比之下，在原代细胞中，Pak4具有完全不同的功能，引发过早衰老而不是促进生长。在这两方面，Pak4与强癌基因（如致癌基因Ras）相似，后者在永生化细胞中高度转化，但在原代细胞中抑制生长。研究Pak4在细胞生长中的作用对于了解Pak4和Rho gtpase如何与癌性转化相关非常重要。本课题的实验将利用我们实验室已经生成的Pak4 null成纤维细胞，研究Pak4在永生化细胞中调控细胞生长转化和原代细胞过早衰老中的作用。将讨论以下目标：目标1.1。Pak4在致癌转化中起什么作用？永生化Pak4缺失和对照成纤维细胞将用于验证Pak4对于Rho GTPases及其激活物的转化至关重要的假设。我们还将研究Pak4介导的转化所涉及的信号通路。目标1.2。Pak4在控制细胞增殖中起什么作用？细胞增殖和转化的控制是密切相关的。在这里，我们将使用永生化的Pak4缺失成纤维细胞来验证Pak4是应答Rho GTPases的细胞周期进入和增殖所必需的假设。我们还将确定在细胞周期进程中，细胞周期调节蛋白是否在Pak4的下游发挥作用。目标2。哪些信号通路介导Pak4诱导原代细胞过早衰老？我们将首先验证Pak4诱导原代细胞衰老是由ERK MAP激酶介导的，导致细胞周期调节蛋白的诱导和随后细胞生长的抑制。我们还将验证细胞骨架调节蛋白在Pak4诱导的衰老中发挥重要作用的假设。最后，我们还将确定Pak4是否在癌基因诱导的衰老中是必需的。

DESCRIPTION (provided by applicant): The goal of the proposed experiments is to determine how the serine/threonine kinase Pak4 functions in the regulation of cell growth and transformation. Pak4 is an effector of the Rho GTPases Cdc42 and Rac, and was originally identified as a protein that functions in cytoskeletal organization. More recently, Pak4 was also shown to have important roles in controlling cell growth and survival. Pak4 is overexpressed in cancer cell lines, and Pak4 is highly transforming in established immortalized cell lines. In contrast, in primary cells Pak4 has a completely different function and triggers premature senescence rather than increased growth. In both respects Pak4 is similar to strong oncogenes such as oncogenic Ras, which are highly transforming in immortalized cells but inhibit growth in primary cells. Studying the role for Pak4 in cell growth is very important for understanding how Pak4 and Rho GTPases are associated with oncogenic transformation. The experiments in this proposal will take advantage of Pak4 null fibroblasts that have been generated in our lab, in order to study Pak4's role in the regulation of cell growth and transformation in immortalized cells, and premature senescence in primary cells. The following aims will be addressed: Aim 1.1. What role does Pak4 have in oncogenic transformation? Immortalized Pak4 null and control fibroblasts will be used to test the hypothesis that Pak4 is essential for transformation by Rho GTPases and their activators. We will also study the signaling pathways involved in Pak4 mediated transformation. Aim 1.2. What role does Pak4 have in the control of cell proliferation? The control of cell proliferation and transformation are closely associated. Here we will use the immortalized Pak4 null fibroblasts to test the hypothesis that Pak4 is required for cell cycle entry and proliferation in response to Rho GTPases. We will also determine whether cell cycle regulatory proteins function downstream to Pak4 during cell cycle progression. Aim 2. What signaling pathways mediate Pak4 induced premature senescence in primary cells? We will first test the hypothesis that Pak4 induced senescence in primary ceils is mediated by the ERK MAP Kinase, leading to induction of cell cycle regulatory proteins and subsequent inhibition of cell growth. We will also test the hypothesis that cytoskeletal regulatory proteins play an important role in Pak4 induced senescence. Finally, we will also determine whether Pak4 is required for oncogene induced senescence.