Structural and Cellular Choreography for Decommissioning and Recycling of PP2A Holoenzymes

项目总结 蛋白磷酸酶2A(PP2A)是一种普遍存在的、最重要的丝氨酸/苏氨酸磷酸酶，它调节 参与多种生物途径的大量细胞蛋白的磷酸化状态。 PP2A的去聚合与许多人类癌症、阿尔茨海默病和易感性有关 病原体。PP2A核心酶是一种高度保守的支架和催化亚基的异源二聚体，它 通过结合一个可变的和高度多样化的调节亚单位来形成异三聚体全酶，该亚单位决定了 底物选择性。建立在严密控制PP2A全酶的结构编排研究进展的基础上 生物发生，特别是PP2Ac的潜伏期和激活所需的构象开关，我们进一步 对从全酶中回收PP2Ac进行了引人注目的观察。我们还观察到了一种新的功能 PP2A全酶去甲基化及其相互作用的PME-1 之前被认为是专门作用于核心酶的。这里提出的研究将扩展我们的 对PP2A络合物进行了初步的电子显微镜分析，并利用结构、生化、生物物理和 用细胞生物学方法阐明控制PME-1新功能和机制的机制 全酶调节(特异性目标1)，从PP2A全酶中回收PP2Ac(特异性目标2)，以及新的 PP2A全酶的生物发生和循环以及PME-1在细胞中的多方面作用 发信号。这些研究将建立一个新的PP2A全酶生物发生和循环的调控回路 在不同的细胞和生理过程中精确和动态地控制PP2A全酶，并提供 理解正常和转化中PP2A功能调节机制的新框架 人类细胞。

PROJECT SUMMARY Protein phosphatase 2A (PP2A) is a ubiquitous and the most prominant Ser/Thr phosphatase that regulates the phosphorylation status of a large number of cellular proteins involved in diverse biological pathways. Derulagulation of PP2A is associated with many human cancers, Alzheimer's Disease and susceptibility to pathogens. The PP2A core enzyme is a heterodimer of highly conserved scaffold and catalytic subunits, which forms the heterotrimeric holoenzyme by binding a variable and highly diverse regulatory subunit that determines substrate selectivity. Built on recent advance on structural choreography of tight control of PP2A holoenzyme biogenesis, in particular, the conformational switches of PP2Ac required for its latency and activation, we further made a striking observation on recycling of PP2Ac from holoenzymes. We also observed a novel function of PME-1 (PP2A-specific methylesterase 1) in demethylation of and interaction with PP2A holoenzymes; PME-1 was previously thought to specifically act on the core enzyme. The research proposed here will extend our preliminary electron microscopic analyses of PP2A complexes, and use structural, biochemical, biophysical and cell biological approaches to elucidate mechanisms that control novel function and mechanism of PME-1 in holoenzyme regulation (Specific Aim 1), recycling of PP2Ac from PP2A holoenzymes (Specific Aim 2), and novel insights into PP2A holoenzyme biogenesis and recycling and the multi-faceted roles of PME-1 in cellular signaling. These studies will establish a novel regulation loop of PP2A holoenzyme biogenesis and recycling for precise and dynamic control of PP2A holoenzymes in diverse cellular and physiological processes, and provides a novel framework for understanding the mechanisms that regulate PP2A functions in normal and transformed human cells.