Signal Termination by PHLPP, PH domain Leucine-rich repeat Protein Phosphatase

描述(申请人提供)：本提案的长期目标是了解我们发现的新型磷酸酶PHLPP(PH域富含亮氨酸重复蛋白磷酸酶，发音为flip)介导的信号终止的分子、细胞和生理机制。PHLPP通过特异性地去磷酸化一个关键的调节残基--疏水基序来终止两种致癌蛋白激酶Akt和蛋白激酶C的信号传递。PHLPP在多种人类癌症中经常缺失，它在小鼠中的缺失会促进前列腺癌的发生。因此，推动这一提议的中心假设是PHLPP终止生长信号通路，并且放松调控导致病理生理状态，特别是癌症。提出了三个目标：1.PHLPP的分子机制。我们的目标是在AIMS 2和AIMS 3中确定PHLPP的小分子抑制物或激活剂，作为细胞研究的工具。此外，我们还将测试PHLPP中与癌症相关的突变正在失活并因此赋予肿瘤细胞生存优势的假设。2.PHLPP的细胞机制。本部分的目的是了解在细胞中控制PHLPP功能的机制。首先，我们将使用创新的活细胞成像技术来测试这一假设，即PDZ支架NHERF上的空间协调增加了PHLPP控制Akt信号的幅度和持续时间的能力。其次，我们将阐述PHLPP抑制细胞内生长因子受体水平的机制。3.病理生理学中的PHLPP。这一目标解决了PHLPP在癌症中的作用。具体地说，我们将检验这一假设，即E3连接酶2-TrCP对PHLPP的放松调控有助于胶质母细胞瘤的发生。此外，我们将使用小鼠模型研究PHLPP1和PHLPP2在前列腺癌中的作用，并使用3D培养模型研究PHLPP2在乳腺细胞生长中的作用。

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to understand the molecular, cellular and physiological mechanisms of signal termination mediated by the novel phosphatase PHLPP (PH domain Leucine- rich repeat Protein Phosphatase; pronounced 'flip') that we discovered. PHLPP terminates signaling by two oncogenic kinases, Akt and protein kinase C, by specifically dephosphorylating a key regulatory residue, the hydrophobic motif, which we originally identified on protein kinase C. PHLPP is frequently deleted in diverse human cancers and its deletion in mice promotes prostate tumors. Thus, the central hypothesis driving this proposal is that PHLPP terminates growth signaling pathways and that deregulation leads to pathophysiological states, notably cancer. Three Aims are proposed: 1. Molecular Mechanisms of PHLPP. The goals are to identify small molecule inhibitors or activators of PHLPP to use as tools in cellular studies in Aims 2 and 3. In addition, we will test the hypothesis that cancer-associated mutations in PHLPP are inactivating and thus confer a survival advantage to tumor cells. 2. Cellular Mechanisms of PHLPP. The goal of this section is to understand the mechanisms that control the function of PHLPP in cells. First, we will use innovative live cell imaging technologies to test the hypothesis that spatial coordination on the PDZ scaffold NHERF increases the ability of PHLPP to control the amplitude and duration of Akt signaling. Second, we will address the mechanism by which PHLPP suppresses the levels of growth factor receptors in cells. 3. PHLPP in pathophysiology. This Aim addresses the role of PHLPP in cancer. Specifically, we will test that hypothesis that deregulation of PHLPP by the E3 ligase 2-TrCP contributes to glioblastoma. In addition, we will address the roles of PHLPP1 and PHLPP2 in prostate cancer using a mouse model and in breast cell growth using a 3D culture model.