Crystallographic analysis of protein phosphatase 2A

描述（由申请人提供）：可逆蛋白丝氨酸/苏氨酸磷酸化是细胞调控的基本机制。虽然在人类基因组中已经鉴定出400多种丝氨酸/苏氨酸激酶，但只有少数丝氨酸/苏氨酸磷酸酶的催化亚基。与之前认为磷酸酶具有组成性活性的假设相反，最近的研究表明，许多磷酸酶受到高度调控，主要是通过形成具有不同调控或靶向亚基的蛋白质复合物。本研究的重点是蛋白磷酸酶2A (PP2A)，这是一种调节细胞活性几乎所有方面的核心人类磷酸酶，是一种关键的肿瘤抑制因子。PP2A的失调与乳腺癌、肺癌和结直肠癌以及阿尔茨海默病以及对病毒和寄生虫感染的易感性有关。典型的PP2A全酶包含支架A亚基，催化C亚基和许多调节B亚基中的一个，它们分为B， B'和B"家族。尽管具有重要的功能，但PP2A如何形成功能复合体以及复合体的组装如何受到调控，在很大程度上仍然是未知的。在本课题中，我们旨在通过x射线晶体学和相关生化分析的结构测定，为了解PP2A异三聚体配合物的组装和调控提供结构基础。我们的研究不仅对理解蛋白质丝氨酸/苏氨酸去磷酸化的调控具有重要意义，而且对设计PP2A激活剂稳定PP2A的功能组装或破坏PP2A抑制蛋白相互作用也具有重要意义。这些化合物对癌症治疗很有用。

DESCRIPTION (provided by applicant): Reversible protein Ser/Thr phosphorylation is a fundamental mechanism for cell regulation. While more than 400 Ser/Thr kinases have been identified in the human genome, there are only a few catalytic subunits for Ser/Thr phosphatases. In contrast to the previous assumption that phosphatases are constitutively active, recent work has shown that many phosphatases are highly regulated, largely through the formation of protein complexes with different regulatory or targeting subunits. This proposal focuses on the protein phosphatase 2A (PP2A), a central human phosphatase that regulates almost all aspects of cellular activity and is a critical tumor suppressor. Deregulation of PP2A is associated with breast, lung, and colorectal cancers as well as Alzheimer's Disease and susceptibility to viral and parasitic infection. A typical PP2A holoenzyme contains a scaffold A subunit, a catalytic C subunit and one of many regulatory B subunits, which are divided into B, B' and B" families. Despite the functional importance, it is still largely unknown how PP2A forms a functional complex and how the complex assembly is regulated. In this proposal, we aim to provide the structural basis for understanding the assembly and regulation of PP2A heterotrimeric complexes, through structural determination by X-ray crystallography and related biochemical analysis. Our study will be important not only for understanding the regulation of protein Ser/Thr dephosphorylation, but also for designing PP2A activators that either stabilize functional PP2A assembly or disrupt PP2A-inhibitory protein interactions. Such compounds can be useful for cancer treatment.