Suppression of polyQ proteotoxicity by glutamine rich proteins

许多神经退行性疾病的一个关键特征是淀粉样聚集体的积累。虽然这一主题已经得到了深入的研究，主要的争议仍然围绕着这些淀粉样蛋白夹杂物是否导致疾病或代表一种细胞保护机制的表现的问题。因此，为了了解蛋白质聚集疾病的防御机制，有必要确定淀粉样蛋白聚集发生的途径以及如何调节该过程。亨廷顿蛋白（Htt）是亨廷顿病（HD）中的疾病相关蛋白，将用于研究针对聚集倾向细胞毒性蛋白的细胞途径。本研究将利用HD的酿酒酵母模型进行。酵母是研究HD的可靠和有用的模型，因为疾病的关键特征如Htt包涵体和polyQ长度依赖性毒性被概括。此外，从酵母到哺乳动物，大量的细胞过程是保守的，因此使其成为鉴定途径组分的合适生物体。我们实验室筛选Htt毒性新抑制剂的初步数据表明聚集在抑制毒性中起着至关重要的作用。几种富含Q的蛋白质以及Hsp 70/Hsp 90共分子伴侣各自抑制与酵母中的延伸polyQ Htt片段（Htt 103 Q）相关的毒性。这种毒性抑制与SDS抗性Htt 103 Q的量的增加相关。拟议研究的具体目标是（1）确定聚集和富Q蛋白介导的Htt毒性抑制之间的联系，以及（2）定义保护性促进聚集发生的细胞途径。这些目标将通过在上位性实验中对酵母的聚集和遗传操作进行视觉和生化监测等手段来实现。在这些研究中获得的数据将被应用到一些神经元模型的HD，包括PC 12细胞系诱导表达突变体Htt片段。总之，这些研究将确定通过聚集抑制淀粉样蛋白病蛋白质毒性的基本原则。这些信息将揭示有组织的蛋白毒性物质的促进组装的途径，以及某些细胞因子，如富含Q的蛋白质和分子伴侣，如何调节组装。

A key characteristic in numerous neurodegenerative diseases is the accumulation of amyloid- like aggregates. Although this topic has been highly studied, major controversy still surrounds the question of whether these amyloid inclusions cause the disease or represent a manifestation of a cytoprotective mechanism. Thus to gain an understanding of defense mechanisms against protein aggregation diseases, it is necessary to define the pathway by which amyloid-like aggregation occurs and how this process is regulated. Huntingtin (Htt), the disease associated protein in Huntington's disease (HD), will be used in order to study a cellular pathway for protection against aggregation prone cytotoxic proteins. This study will be carried out utilizing a Saccharomyces cerevisiae model of HD. Yeast is a reliable and useful model to study HD because key characteristics of the disease such as Htt inclusions and polyQ length dependent toxicity are recapitulated. Furthermore, a vast number of cellular processes are conserved from yeast to mammals thus making it a suitable organism in which to identify components of a pathway. Preliminary data in our lab from a screen for novel suppressors of Htt toxicity suggest a vital role for aggregation in the inhibition of toxicity. Several Q-rich proteins as well as an Hsp70/Hsp90 co-chaperone each suppress toxicity associated with an extended polyQ Htt fragment (Htt103Q) in yeast. This toxicity suppression correlates with an increase in the amount of SDS-resistant Htt103Q. The specific goals of the proposed research are (1) to determine the link between aggregation and Q-rich protein mediated suppression of Htt toxicity and (2) to define the cellular pathway by which protective facilitated aggregation occurs. These goals will be achieved by means such as visual and biochemical monitoring of aggregation and genetic manipulation of yeast in epistatic experiments. Data obtained during these studies will be applied to some neuronal models for HD including a PC12 cell line which inducibly expresses a mutant Htt fragment. Altogether, these studies will define basic principles for suppression of proteotoxicity of an amyloidogenic disease protein via aggregation. This information will uncover a pathway for organized facilitated assembly of proteotoxic species and how certain cellular factors, such as Q-rich proteins and molecular chaperones, modulate assembly.