Cellular Targets of Polyomavirus Transforming Proteins

描述（由申请人提供）：研究细胞蛋白， 乳多空病毒肿瘤抗原的靶向作用越来越多地被证明 对我们理解人类癌症很重要， 进入在癌症中起作用的信号转导途径。我们有 确定了多瘤病毒中型（MT）和小型（ST）肿瘤的靶点之一 蛋白磷酸酶2A（PP 2A）是一种高度保守的酶， 参与细胞增殖和凋亡的控制。这种酶 对于多瘤病毒诱导的肿瘤发生很重要， 与人类癌症有关，既作为突变或失调的靶点， 作为抗癌治疗的潜在靶点。一个长期的目标， 拟议的项目是帮助描绘调节的分子机制， PP 2A在细胞周期、细胞凋亡和肿瘤中的作用。这项研究将导致 新的细胞药物靶点的鉴定，这将使我们能够更多地 特异性调节PP 2A在细胞凋亡和癌症相关途径中功能。 在这些靶点水平发挥作用的药物可能毒性较小， 因此更适用于抗癌治疗。因此，这笔赠款将侧重于 1）了解MT和ST信号如何阻断细胞凋亡，2）了解 MT和ST如何改变PP 2A的功能，3）识别PP 2A被 针对特定底物，以及4）阐明PP 2A的正常机制 调控在目标I中，我们将使用野生型和突变型ST和MT， 环氧合酶-2抑制剂，以确定MT和ST是否调节PI 通过PP 2A结合的3-激酶/Akt/Bad/Bcl-2抗凋亡途径和/或 环氧合酶-2诱导。我们还将研究Akt和Bcl-2是否在 通过使用免疫共沉淀被已知的PP 2A调节亚基靶向 接近。在目标II中，我们将测试哪些PP 2A调节亚基是 在体内通过表达MT和ST取代PP 2A。此外， 研究一个新家族正常和MT/ST调节的磷酸化， PP 2A靶向亚基。最后，在目标III中，我们将研究该机制 在甲基转移酶水平调节PP 2A甲基化， 通过测试这些酶是否受 区室化或磷酸化。

DESCRIPTION (provided by applicant): The study of cellular proteins that are targeted by the tumor antigens of papovaviruses is proving increasingly important to our understanding of human cancer, yielding important insights into signal transduction pathways that play a role in cancer. We have identified one of the targets of polyomavirus middle (MT) and small (ST) tumor antigens as protein phosphatase 2A (PP2A), a highly conserved enzyme known to be involved in the control of cell proliferation and apoptosis. This enzyme is important for polyomavirus-induced tumorigenesis and has also has been implicated in human cancer, both as a target of mutation or misregulation and as a potential target for anti-cancer therapies. A long-term goal of the proposed project is to help delineate the molecular mechanisms that regulate PP2A, especially in cell cycle, apoptosis, and cancer. This research will lead to the identification of new cellular drug targets that will allow us to more specifically modulate PP2A function in apoptosis- and cancer-relevant pathways. Drugs that function at the level of these targets would likely be less toxic, and therefore more useful for anti-cancer therapy. Thus, this grant will focus on 1) understanding how MT and ST signal to block apoptosis, 2) understanding how MT and ST alter PP2A function, 3) identifying mechanisms by which PP2A is targeted to specific substrates, and 4) elucidating normal mechanisms of PP2A regulation. In Aim I, we will use wt and mutant STs and MTs and cyclooxygenase-2 inhibitors to determine if MT and ST modulate the PI 3-kinase/Akt/Bad/Bcl-2 anti-apoptotic pathway by PP2A binding and/or cyclooxygenase-2 induction. We will also investigate whether Akt and Bcl-2 are targeted by known PP2A regulatory subunits by using coimmunoprecipitation approaches. In Aim II, we will test which PP2A regulatory subunits are displaced from PP2A in vivo by expression of MT and ST. Moreover, we will investigate normal and MT/ST modulated phosphorylation of a novel family of PP2A targeting subunits. Finally, in Aim III we will investigate the mechanism of regulation of PP2A methylation at the level of the methyltransferase and methylesterase enzymes by testing whether these enzymes are regulated by compartmentalization or phosphorylation.