Oligopeptide Repeats and Prion Propagation

描述(由申请人提供)：错误折叠正常的细胞编码蛋白质及其随后的聚集已成为哺乳动物几种神经退行性疾病的常见机制，包括亨廷顿氏症和可传播的海绵状脑病(Pron病)。在这个过程中的一个关键事件是错误折叠形式的有效放大，当现有的聚集体引导正常蛋白质转换到类似状态时就会发生错误折叠形式。这种自动催化的错误折叠受到相关蛋白质中的序列元素的影响，例如调节错误折叠形式的外观和持久性的重复元素。尽管它们很重要，但这些序列元件影响自催化错误折叠途径的机制(S)目前尚不清楚。这项提议的目标是解决知识方面的这一重大差距。在这项工作中，我们将在酿酒酵母中使用Sup35/[PSI+]Prion系统。Sup35蛋白含有一个寡肽重复序列的五个半不完整拷贝。一个或多个完整重复序列的缺失完全取消了Sup35的自动催化错误折叠，而重复区域的扩展增加了细胞采用和传播这种形式的倾向。我们假设，寡肽的重复通过影响Sup35物理相互作用的性质来改变Sup35错误折叠途径中离散步骤的效率，从而改变Prion相关表型的稳定性。为了验证这一假说，我们将确定Sup35自身催化错误折叠途径中的步骤(S)，该步骤会因重复次数的变化以及这些变化对Sup35与自身和其他细胞因素相互作用的影响而改变。通过了解特定的序列元件如何调节体内的蛋白质折叠环境，我们将开始了解它们如何对正常细胞状态和相应的疾病状态做出贡献。了解这些序列元件如何在细胞环境中调节蛋白质折叠途径，将有助于深入了解蛋白质错误折叠疾病是如何启动和维持的。

DESCRIPTION (provided by applicant): The misfolding normal, cellular encoded proteins and their subsequent aggregation has emerged as a common mechanism underlying several neurodegenerative diseases in mammals, including Huntington's and the Transmissible Spongiform Encephalopathies (prion diseases). A key event in this process is the efficient amplification of misfolded form, which occurs when existing aggregates direct the conversion of normal protein to a like state. This autocatalytic misfolding in influenced by sequence elements within the implicated proteins, such as repeated elements that modulate both the appearance and persistence of the misfolded form. Despite their importance, the mechanism(s) by which these sequence elements influence the autocatalytic misfolding pathway is currently unknown. The goal of this proposal is to address this significant gap in knowledge. For this work, we will use the Sup35/[PSI+] prion system in the yeast S. cerevisiae. The Sup35 protein contains five and a half imperfect copies of an oligopeptide repeat. Deletion of one or more full repeats completely abolishes the autocatalytic misfolding of Sup35, while expansion of the repeat region increases the propensity of cells to adopt and propagate this form. We hypothesize that the oligopeptide repeats alter the efficiency of discrete steps in the Sup35 misfolding pathway and thereby the stability of the prion-associated phenotype by impacting the nature of Sup35 physical interactions. To test this hypothesis, we will identify the step(s) in the Sup35 autocatalytic misfolding pathway that are altered by variation in the number of repeats and impact of these variations on Sup35 interactions with itself and other cellular factors. By understanding how specific sequence elements modulate the protein folding environment in vivo, we will begin to understand how they contribute to both the normal cellular state and the corresponding disease state. Understanding how these sequence elements can modulate protein folding pathways within the context of the cellular environment will provide insight into how protein misfolding diseases are initiated and maintained.