Structural and Cellular Choreography for Decommissioning and Recycling of PP2A Holoenzymes

项目摘要 蛋白磷酸酶2A（PP 2A）是一种广泛存在的丝氨酸/苏氨酸磷酸酶， 磷酸化状态的大量细胞蛋白质参与不同的生物途径。 PP 2A的去活化与许多人类癌症、阿尔茨海默病和对阿尔茨海默病的易感性有关。 病原体PP 2A核心酶是高度保守的支架和催化亚基的异二聚体， 通过结合一个可变的和高度多样化的调节亚基形成异源三聚体全酶， 底物选择性基于PP 2A全酶紧密控制的结构编排的最新进展 生物起源，特别是PP 2Ac的潜伏期和激活所需的构象开关，我们进一步 对全酶中PP 2Ac的回收进行了惊人的观察。我们还观察到一种新的功能， PME-1（PP 2A特异性甲酯酶1）在PP 2A全酶的去甲基化和与PP 2A全酶的相互作用中的作用; PME-1 以前被认为是专门作用于核心酶。这里提出的研究将扩展我们的 PP 2A复合物的初步电子显微镜分析，并使用结构，生物化学，生物物理和 细胞生物学方法来阐明控制PME-1的新功能和机制的机制， 全酶调节（特异性目标1）、从PP 2A全酶中回收PP 2Ac（特异性目标2），以及新的 深入了解PP 2A全酶的生物发生和再循环以及PME-1在细胞内的多方面作用 发信号。这些研究将建立一个新的PP 2A全酶生物合成和循环的调控回路， 在不同的细胞和生理过程中精确和动态控制PP 2A全酶，并提供 一个新的框架，了解机制，调节PP 2A的功能，在正常和转化 人体细胞

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.