The PAK4 kinase in cell growth and transformation

描述（由申请人提供）：所提出的实验的目的是确定丝氨酸/苏氨酸激酶Pak 4在细胞生长和转化的调节中如何起作用。Pak 4是Rho GTP酶Cdc 42和Rac的效应子，并且最初被鉴定为在细胞骨架组织中起作用的蛋白质。最近，Pak 4也被证明在控制细胞生长和存活方面具有重要作用。Pak 4在癌细胞系中过表达，并且Pak 4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，Pak 4具有完全不同的功能，并引发过早衰老而不是增加生长。在这两个方面，Pak 4类似于强致癌基因，如致癌Ras，其在永生化细胞中高度转化，但抑制原代细胞的生长。研究Pak 4在细胞生长中的作用对于理解Pak 4和Rho GTP酶如何与致癌转化相关非常重要。本实验将利用本实验室已产生的Pak 4空成纤维细胞，以研究Pak 4在永生化细胞的细胞生长和转化以及原代细胞的早衰中的调节作用。将处理以下目标：目标1.1。Pak 4在致癌转化中起什么作用？永生化的Pak 4无效和对照成纤维细胞将用于检验Pak 4对于Rho GTP酶及其激活剂的转化是必需的这一假设。我们还将研究参与Pak 4介导的转化的信号通路。目标1.2。Pak 4在控制细胞增殖中起什么作用？细胞增殖和转化的控制密切相关。在这里，我们将使用永生化的Pak 4空成纤维细胞来测试Pak 4是响应于Rho GTP酶的细胞周期进入和增殖所需的假设。我们还将确定细胞周期调控蛋白在细胞周期进程中是否在Pak 4下游发挥作用。目标2.什么样的信号通路介导Pak 4诱导的原代细胞早衰？我们将首先检验Pak 4诱导的原代细胞衰老是由ERK MAP激酶介导的，导致细胞周期调节蛋白的诱导和随后的细胞生长抑制的假设。我们还将测试的假设，即细胞骨架调节蛋白在Pak 4诱导衰老中发挥重要作用。最后，我们还将确定Pak 4是否是癌基因诱导衰老所必需的。

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.