多聚谷氨酰胺蛋白募集正常蛋白质的细胞效应及分子机制

Misfolding of proteins may cause their amyloidogenic aggregation and inclusion formation, which strongly associates with the pathogenesis of some neurodegenerative diseases. Polyglutamine (PolyQ) sequences are originated by expansion of the CAG tri-nucleotide repeat in particular genes, while PolyQ-expanded proteins readily undergo misfolding and thus form inclusions. In this project, we will take two PolyQ proteins, Ataxin-3 and Ataxin-7, as model proteins to investigate the cellular effects and molecular mechanism underlying the sequestration of normal cellular proteins by PolyQ-expanded protein aggregates and inclusions. We will focus on the PolyQ proteins that sequester some cellular key proteins including ubiquitin chains, P97/VCP, USP22, and so on. By using molecular and cellular approaches, we will clarify some controversial viewpoints or hypotheses: whether PolyQ expansion affects the structures of local sequences and interactions with other proteins; whether a PolyQ protein sequesters cellular proteins through specific interactions; and whether the cytotoxicity of PolyQ inclusions is resulted from sequestration of the cellular key proteins. The research will provide fundamental information for deciphering pathologies of the neurodegenerative diseases and discovering pharmaceutical therapy.

蛋白质的错误折叠会引起淀粉样积聚和包涵体的形成，与神经退行性疾病的发生密切相关。多聚谷氨酰胺（PolyQ）序列是由特定基因的CAG三核苷酸重复延伸所引起的; PolyQ延伸蛋白易发生积聚并在细胞内形成包涵体。本申请项目以两个PolyQ蛋白Ataxin-3和Ataxin-7 为对象和模型，研究PolyQ蛋白募集正常蛋白质的细胞效应及分子机制。我们将重点研究PolyQ蛋白的积聚包涵体对与之特异相互作用的关键蛋白质的募集作用，这些蛋白质包括泛素链、P97/VCP、USP22等。通过分子和细胞水平的研究，将澄清一些基本观点或假设：如PolyQ延伸是否影响其周围序列的结构和蛋白质相互作用；PolyQ包涵体募集其它蛋白质是否通过特异的相互作用；PolyQ包涵体的细胞毒性是否由于募集其它关键蛋白质所产生的。该项目的研究成果将为神经退行性疾病发病机理和预防治疗提供理论依据。

多聚谷氨酰胺 (PolyQ) 的延伸容易引起蛋白质发生积聚并在细胞内形成具有细胞毒性的包涵体。本项目应用生物化学和细胞生物学的技术方法研究了两个PolyQ 蛋白Ataxin-3 (Atx3)和Ataxin-7(Atx7)的积聚和募集作用的细胞效应及分子机制。研究发现Atx7积聚募集USP22并导致其去泛素化功能的损伤；积聚的Atx3通过泛素化作用募集细胞中的泛素接头蛋白(UBQLN2，hHR23B)而使其功能受损。我们还提出了“挟持模型”论述蛋白质积聚的募集作用导致细胞毒性或神经退行性。通过该项目的实施，研究成果为进一步理解蛋白质积聚的细胞效应和相关的神经退行性疾病的发病机理提供依据。