Regulation of Amyloid Fibril Assembly by Hsp40 Molecular Chaperones

描述（由申请人提供）：蛋白质聚集和淀粉样蛋白沉积表征了多种神经退行性疾病，包括阿尔茨海默病和亨廷顿病。天然蛋白质转化为成熟淀粉样原纤维是一个复杂的，知之甚少的过程。细胞内淀粉样蛋白组装的调节与几种神经退行性疾病具有显著相关性，并且进一步理解该过程背后的机制将提供实质性的治疗见解。芽殖酵母具有几种称为朊病毒的内源性蛋白质，它们组装成细胞内的淀粉样原纤维。朊病毒[RNQ+]在蛋白质Rnq 1过表达时对酵母菌有毒。因此，酵母朊病毒[RNQ+]作为一个易于处理的，但功能强大的模型系统，研究原纤维组装和分子伴侣如何调节这一途径，以防止细胞毒性物质的积累。具体地说，我们发现，1型热休克蛋白40 Ydj 1相互作用的Gln/Asn丰富的朊病毒结构域从Rnq 1和调节该片段的聚集和毒性。将解决两个具体问题：1）酵母朊病毒[RNQ+]中的哪些特征调节组装成有毒或良性聚集体？2)热休克蛋白40 Ydj 1如何维持Rnq 1朊病毒结构域处于良性构象？具体目标1将研究如何全长Rnq 1和谷氨酰胺/天冬酰胺丰富的朊病毒结构域组装成生物化学不同的蛋白质聚集体。我们预测朊病毒装配的效率将决定当这些蛋白质表达时，是否有毒性的中间物种积累。具体目标2将解决Ydj 1如何与Rnq 1朊病毒结构域相互作用，并缓冲SDS不溶性朊病毒的积累。Ydj 1具有几个特征，不同于其他热休克蛋白40，但共享与其人类同源物Hdj-2，可能有助于特异性识别的亲水性，聚集倾向的基板。总之，这些研究将产生额外的机制，了解分子伴侣如何调节淀粉样蛋白组装，以防止有毒蛋白聚集体的异常积累。公共卫生相关性：许多神经退行性疾病是由细胞内错误折叠蛋白质的积累引起的。这项研究将研究细胞如何调节蛋白质聚集体组装成有毒或良性形式。

DESCRIPTION (provided by applicant): Protein aggregation and amyloid deposition characterize a variety of neurodegenerative disorders including Alzheimer's Disease and Huntingtin's disease. The conversion of a native protein into mature amyloid fibril is a complex, poorly understood process. The regulation of amyloid assembly within the cell has significant relevance to several neurodegenerative disorders and further understanding of the mechanisms behind this process will provide substantial therapeutic insight. Budding yeast possess several endogenous proteins called prions that assemble into intracellular, amyloid-like fibrils. The prion [RNQ+] is toxic to yeast when the protein Rnq1 is overexpressed. Thus, the yeast prion [RNQ+] serves as a tractable, yet powerful model system to study fibril assembly and how molecular chaperones regulate this pathway to prevent the accumulation of cytotoxic species. Specifically, we find that the Type 1 Hsp40 Ydj1 interacts with the Gln/Asn rich prion domain from Rnq1 and modulates the aggregation and toxicity of this fragment. Two specific questions will be addressed: 1) What features in the yeast prion [RNQ+] regulate assembly into toxic or benign aggregates? 2) How does the Hsp40 Ydj1 maintain the Rnq1 prion domain in a benign conformation? Specific Aim 1 will investigate how full-length Rnq1 and the Gln/Asn-rich prion domain assemble into biochemically-distinct protein aggregates. We predict the efficiency of prion assembly will determine whether toxic, intermediate species accumulate when these proteins are expressed. Specific Aim 2 will address how Ydj1 interacts with the Rnq1 prion domain and buffers the accumulation of SDS-insoluble prion. Ydj1 possesses several features distinct from other Hsp40s yet shared with its human homolog Hdj-2 that may contribute to specific recognition of hydrophilic, aggregate-prone substrates. Altogether, these studies will yield additional mechanistic understanding of how molecular chaperones modulate amyloid assembly to prevent, the aberrant accumulation of toxic protein aggregates. PUBLIC HEALTH RELEVANCE: Numerous neurodegenerative disorders are caused by the accumulation of misfolded proteins within the cell. This research will examine how cells regulate the assembly of protein aggregates into toxic or benign forms.