Signaling by p21-activated protein kinases

描述(由申请人提供)：p21激活的蛋白激酶(PAK)将是CDC42和rac1的关键效应者；两个Rho家族GTP酶调节各种基本的生物学过程，包括细胞增殖、形状控制、迁移和应激反应。这些过程中的异常是许多重要的人类疾病的基础，包括大多数恶性肿瘤。最近，我们和其他人发现，PAK参与了与肿瘤发生密切相关的两个特定过程：基因组稳定性(通过调节中心体功能)和细胞增殖(通过影响ERK信号转导级联中的元件)。这些发现表明，PAK在肿瘤发生中发挥核心作用，这些酶可能是抗肿瘤治疗的合适靶点。在这里，我们试图揭示PAK调节乳腺上皮细胞中这些重要过程的机制，以及这些机制是否也适用于活的生物体。在第一个目标中，我们将使用功能获得和功能丧失的方法来研究Pak在基因组稳定性中的作用，特别是它对中心体和有丝分裂纺锤体的影响。在第二个目标中，我们将使用生化和遗传手段来研究A组PAK如何调控三维生长的乳腺上皮细胞中的ERK信号通路。一种特定的PAK抑制剂的使用，以及来自我们最近构建的pak1和pak2基因敲除小鼠的细胞，为我们提供了实现这些目标的独特试剂。在第三个目标中，我们将使用与我们的Pak基因敲除小鼠杂交的Neu转基因小鼠，以及在乳腺组织中表达特定Pak抑制物的转基因小鼠，来测试乳腺癌模型中是否需要Pak功能。实现这项提案中提出的目标将有助于阐明PAK调节与人类肿瘤发生密切相关的两个基本生物特性的机制：基因组稳定性和细胞增殖。出于这些原因，了解Pak的功能不仅具有内在的科学意义，而且可能与为未来的癌症治疗寻找有用的新靶点有关。建议的工作直接关系到我们对乳腺癌的理解和治疗。如果我们确定p21激活的激酶(PAK)是Neu2癌基因(人类乳腺癌中最常见的突变基因之一)导致小鼠乳腺癌所必需的，那么阻断Pak功能的药物可能被用作治疗人类这种疾病的一种新的和特异的方法。

DESCRIPTION (provided by applicant): The p21-activated protein kinases (Paks) are to be key effectors for Cdc42 and Rac1; two Rho-family GTPases that regulate a variety of fundamental biological processes, including cell proliferation, shape control, migration, and stress response. Abnormalities in these processes underlie many important human diseases, including most malignancies. Recently, we, and others, have implicated Paks in two specific processes that are germane to tumorigenesis: genomic stability (via regulation of centrosome function) and cell proliferation (via effects on elements in the ERK signal transduction cascade). These findings suggest that Paks play a central role in tumorigenesis and that these enzymes might be suitable targets for anti- neoplastic therapy. Here, we seek to uncover the mechanisms by which Paks regulate these vital processes in breast epithelial cells and if these mechanisms also apply in living organisms. In the first aim, we will use both gain-of-function and loss-of-function methods to study the role of Pak in genomic stability, with particular emphasis on its effects on the centrosome and mitotic spindle. In the second aim, we will use both biochemical and genetic means to examine how group A Paks regulate the ERK signaling pathway in mammary epithelial cells grown in a three-dimensional format. The use of a specific Pak inhibitor, as well as cells derived from our recently constructed Pak1 and Pak2 knock-out mice, give us unique reagents with which to accomplish these goals. In the third aim, we will test if Pak function is required for tumorigenesis in a breast cancer model, using Neu-transgenic mice crossed with our Pak knock-out mice and also with a transgenic mouse that expresses a specific Pak inhibitor in mammary tissues. Achieving the aims set forth in this proposal will shed light on the mechanisms by which Paks regulate two fundamental biologic properties that are germane to human tumorigenesis: genomic stability and cell proliferation. For these reasons, understanding Pak function is not only of intrinsic scientific interest but is also likely to be relevant to identifying useful new targets for future cancer therapy. The proposed work is directly relevant to our understanding and treatment of breast cancer. If we establish that p21-activated kinases (Paks) are required for the Neu2 oncogene (one of the most commonly mutated genes in human breast cancer) to cause breast cancer in mice, then drugs that block Pak function might be used as a new and specific means to treat this disease in humans.