Roles of Cdc42 and its signaling partners in cell growth and differentiation

描述（由申请人提供）：Ras相关的GTdR Cdc 42在广泛的细胞过程中发挥重要作用，包括细胞极性的建立和细胞生长和迁移的控制。Cdc 42偶联信号活性的适当调节对于其细胞功能至关重要，如由致癌鸟嘌呤核苷酸交换因子（GEF）或突变引起的Cdc 42的超活化所证明的，所述突变引起GDP加速交换为GTP，导致裸鼠中的细胞转化和肿瘤形成。在过去的资助期间，我们确定了Cdc 42及其调节蛋白Cool-1（用于克隆库），其功能既作为GEF又作为Cdc 42的靶点/效应器，通过帮助维持适当的EGF受体（EGFR）稳态来调节细胞生长。我们还发现，Cool-1的磷酸化-去磷酸化循环影响细胞迁移，提出了一种有趣的可能性，即Cdc 42及其信号伙伴可能协调细胞生长控制与细胞运动的调节。此外，我们对不同细胞和遗传模型系统的研究突出了Cdc 42在细胞分化和细胞命运决定中的作用。在未来的资助期内，我们将继续将联合收割机生物化学和结构生物学研究与遗传学方法相结合，以扩展这些发现，并更好地确定Cdc 42及其调节蛋白如何影响三个基本重要的细胞过程，即细胞生长，迁移和分化。这些研究将构成3个特定的调查领域。1)确定Cdc 42及其信号伙伴如何共同维持适当的EGFR稳态。在这些研究中，我们将特别感兴趣的是确定的调节线索，设置Cdc 42介导的信号，建立EGFR偶联的促有丝分裂信号与受体下调和降解之间的适当平衡的时间。2.）研究Cool-1及其结合伴侣如何调节细胞迁移。在这里，我们将跟踪最近的线索表明，酷-1的磷酸化刺激其从猫（酷相关的酪氨酸激酶底物）的解离，并有助于触发焦点复合物的解体。我们还想看看Cool-1的Cdc 42-GEF活性是否由其磷酸化引发，对细胞迁移具有重要的调节作用。3.）第三章研究Cdc 42及其信号伙伴在细胞分化中的作用。我们将探讨Cdc 42可能参与确保神经元分化所需的信号活动的适当寿命。此外，我们将建立在我们最近在小鼠胚胎（P19）细胞中的研究，表明Cdc 42和我们最近发现的双重功能Cdc 42- GEF/靶效应器，在神经发生中发挥重要作用。我们期望这些研究将产生新的见解，了解Cdc 42如何能够介导正常生物学结果所必需的多种细胞反应，并且当失调时，会引起各种疾病状态，包括癌症和神经退行性疾病。

DESCRIPTION (provided by applicant): The Ras-related GTPase Cdc42 plays important roles in a wide range of cellular processes including the establishment of cell polarity and the control of cell growth and migration. The proper regulation of Cdc42- coupled signaling activities is crucial for its cellular functions, as evidenced by the hyper-activation of Cdc42 by oncogenic guanine nucleotide exchange factors (GEFs), or mutations that give rise to an accelerated exchange of GDP for GTP, resulting in cellular transformation and tumor formation in nude mice. During the past funding period, we established how Cdc42 and its regulatory protein Cool-1 (for Cloned-out of library), which functions both as a GEF and a target/effector for Cdc42, regulate cell growth by helping to maintain proper EGF receptor (EGFR) homeostasis. We also discovered that the phosphorylation-dephosphorylation cycle of Cool-1 influences cell migration, raising the interesting possibility that Cdc42 and its signaling partners may coordinate cell growth control with the regulation of cell motility. Moreover, our studies with different cell and genetic model systems have highlighted a role for Cdc42 in cellular differentiation and cell fate determination. In the coming funding period, we will continue to combine biochemical and structural biology-based studies with genetic approaches to extend these findings and better establish how Cdc42 and its regulatory proteins impact three fundamentally important cellular processes, namely cell growth, migration, and differentiation. These studies will constitute 3 specific lines of investigation. 1) Determine how Cdc42 and its signaling partners work together to maintain proper EGFR homeostasis. In these studies, we will be particularly interested in determining the regulatory cues that set the timing for the Cdc42- mediated signals that establish the proper balance between EGFR-coupled mitogenic signaling versus receptor down-regulation and degradation. 2.) Examine how Cool-1 and its binding partners regulate cell migration. Here, we will follow-up recent clues suggesting that the phosphorylation of Cool-1 stimulates its dissociation from Cat (for Cool-associated tyrosine kinase substrate) and helps trigger the disassembly of focal complexes. We also will want to see whether the Cdc42-GEF activity of Cool-1, which is triggered by its phosphorylation, confers important regulatory effects on cell migration. 3.) Examine the roles of Cdc42 and its signaling partners in cellular differentiation. We will explore the possible involvement of Cdc42 in ensuring the proper lifetime for signaling activities necessary for neuronal differentiation. In addition, we will build on our recent studies in mouse embryonic (P19) cells that suggest Cdc42 and a dual function Cdc42- GEF/target-effector that we recently discovered, play important roles in neurogenesis. We expect that these studies will yield new insights into how Cdc42 is able to mediate a diversity of cellular responses that are necessary for normal biological outcomes and, when de-regulated, gives rise to a variety of disease states including cancer and neurodegenerative disorders.