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物的积累。虽然这个话题已经得到了高度的研究，但关于这些淀粉样包涵体是导致疾病还是代表细胞保护机制的表现的问题，仍然存在重大争议。因此，为了了解蛋白质聚集性疾病的防御机制，有必要定义淀粉样聚集性发生的途径以及这一过程是如何调控的。亨廷顿病(HD)中的疾病相关蛋白Huntingtin(Htt)将用于研究一种细胞途径，以保护细胞免受易于聚集的细胞毒蛋白的攻击。这项研究将利用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，因为该疾病的关键特征，如Htt包涵体和多聚Q长度依赖的毒性已被概括。此外，从酵母到哺乳动物，大量的细胞过程都是保守的，因此它是一个合适的有机体，可以在其中识别途径的组成部分。我们实验室筛选新的Htt毒性抑制物的初步数据表明，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Hsp70/Hsp90共伴侣各自抑制与酵母中延长的多Q Htt片段(Htt103Q)相关的毒性。这种毒性抑制与耐十二烷基硫酸酯的Htt103Q数量的增加有关。这项研究的具体目标是(1)确定聚集和富含Q蛋白的Htt毒性抑制之间的联系；(2)确定保护性促进聚集发生的细胞途径。这些目标将通过上位性实验中对酵母聚集和遗传操作的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应用于HD的一些神经元模型，包括诱导表达突变Htt片段的PC12细胞系。总之，这些研究将确定通过聚集抑制淀粉样变性疾病蛋白毒性的基本原则。这些信息将揭示一条有组织地促进蛋白质毒素物种组装的途径，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.