Protein Aggregation and Inclusion Body Formation

描述（由申请人提供）：蛋白聚集体和泛素（Ub）在细胞质包涵体（IB）中的积累是神经退行性疾病唯一最明确的诊断神经病理学标志物。尽管具有普遍的诊断意义，但IB形成的细胞生物学机制，以及这些结构的形成是否反映了致病或保护过程，仍然是一个未解之谜。该研究项目的长期目标是阐明IB形成和Ub沉积的分子机制，并对哺乳动物细胞如何对致病性易聚集蛋白的慢性表达作出反应进行综合理解。该项目在之前的资助期内支持的研究利用亨廷顿病（HD）细胞模型的单细胞分析表明，尽管成熟的IB同时含有聚集的亨廷顿蛋白（htt）和Ub，但这两种蛋白以截然不同的动力学被募集到IB。这些观察结果，加上来自神经退行性疾病遗传模型的新数据，表明了一种模型，在这种模型中，像htt这样的折叠缺陷聚集倾向蛋白的慢性表达，负担了细胞的蛋白质平衡能力（即细胞维持蛋白质折叠和降解之间正确动态平衡的能力），导致正常蛋白从生产折叠逐渐转向泛素蛋白酶体系统。最终压倒细胞降解蛋白质的能力。本提案中的研究旨在使用最先进的蛋白质组学和生物成像技术严格测试和完善这一新兴模型。这些研究将提供对蛋白质聚集和蛋白质静止之间动态相互作用的全面理解，并将阐明神经退行性疾病生物学中长期存在的争议之一。

DESCRIPTION (provided by applicant): Accumulation of protein aggregates and ubiquitin (Ub) into cytoplasmic inclusion bodies (IB) is the single most definitive diagnostic neuropathological marker of neurodegenerative disease. Despite this universal diagnostic significance, the cell biological mechanisms underlying IB formation and, indeed, whether formation of these structures reflects a pathogenic or protective process, remains an unresolved mystery. The long-term objective of this research project is to elucidate the molecular mechanisms that underlie IB formation and Ub deposition and to develop an integrated understanding of how mammalian cells respond to the chronic expression of pathogenic, aggregation-prone proteins. The research supported by this project during the previous funding period exploited single-cell analysis of a cellular model of Huntington's disease (HD) to show that, although mature IB contain both aggregated huntingtin (htt) and Ub, the two proteins are recruited to IB with vastly different kinetics. These observations, together with emerging data from genetic models of neurodegenerative disease, suggest a model in which chronic expression of a folding-defective aggregation-prone protein like htt, burdens the cell's proteostasis capacity (ie, the cell's ability to maintain the correct dynamic equilibrium between protein folding and degradation) leading to a progressive diversion of normal proteins from productive folding to the ubiquitin proteasome system, ultimately overwhelming the cell's capacity to degrade proteins. The research in this proposal aims to rigorously testand refine this emerging model using state-of-the-art proteomic and bioimaging technologies. These studies will provide a comprehensive understanding of the dynamic interaction between protein aggregation and proteostasis and will illuminate one of the longest-standing controversies in neurodegenerative disease biology.