Elucidating factors involved in formation and propagation of yeast prion strains

描述（由申请人提供）：朊病毒是一种自我繁殖聚集或淀粉样结构的蛋白质，其将蛋白质从其天然状态转化为这种聚集构象。导致蛋白质错误折叠紊乱的蛋白质，如阿尔茨海默病中的淀粉样蛋白-2，现在被认为以朊病毒样方式错误折叠和聚集。当哺乳动物朊病毒蛋白PrP采用其朊病毒构象（PrPSc）时，它会形成一种感染性淀粉样蛋白，导致致命的神经退行性疾病，称为传染性海绵状脑病。PrPSc的不同构象，称为朊病毒株，可能是“物种屏障”以及朊病毒疾病中所见的疾病潜伏期和病理学变化的根本原因。病理变化也见于其他神经退行性疾病，表明不同的蛋白质构象也可能参与这些疾病。然而，仍然不清楚如何不同的自繁殖结构可以来自一个多肽。朊病毒株是如何从头产生的，以及单个朊病毒蛋白如何获得和繁殖不同的构象，这些都是完全未知的。对酵母酿酒酵母内源性朊病毒的研究提供了许多关于哺乳动物朊病毒株（称为酵母变种）之间可能存在的结构差异的信息。酵母翻译终止因子Sup 35 p聚集形成[PSI+]朊病毒。[PSI+]是一种表观遗传因子，具有许多表型后果，因为它全面影响翻译，并可能参与调节细胞如何响应波动的环境。有趣的是，[PSI+]的自发转化需要存在另一种朊病毒[RNQ+]，由Rnq 1 p形成。这两种朊病毒形成不同的变体，可以很容易地在酵母细胞中进行监测。这使我们能够研究哪些因素在决定蛋白质如何采用不同的自传播构象方面发挥作用。以下具体目标将使用整合的分子、遗传和生物化学方法来研究不同的蛋白质构象如何有助于年龄相关疾病的形成和表型变异：1）确定[RNQ+]变体如何促进[PSI+]的形成; 2）（A）阐明调节[RNQ+]变体形成和繁殖的基因内和基因外机制;（B）阐明定义朊病毒变体的关键生化特性。总的来说，这一建议将提高我们对朊病毒变异体的物理和分子基础的理解，并深入了解替代蛋白质构象如何影响物种之间的遗传性，并导致神经退行性疾病疾病进展的变化。

DESCRIPTION (provided by applicant): Prions are proteins that self-propagate an aggregated or amyloid-like structure that converts protein from its native state to this aggregated conformation. Proteins that contribute to protein misfolding disorders, like amyloid-2 in Alzheimer's disease, are now thought to misfold and aggregate in a prion-like fashion. When the mammalian prion protein, PrP, adopts its prion conformation (PrPSc), it forms an infectious amyloid that causes fatal neurodegenerative disorders called transmissible spongiform encephalopathies. Different conformations of PrPSc, referred to as prion strains, may be the underlying cause of both the "species barrier" as well as much of the variation in disease latency and pathology seen in prion diseases. Pathologic variation is also seen in other neurodegenerative disorders, suggesting distinct protein conformations may be involved in these diseases as well. Yet, it is still unclear how different self-propagating structures can originate from one polypeptide. Precisely how prion strains arise de novo and how a single prion protein can acquire and propagate different conformations is entirely unknown. The investigation of prions endogenous to the yeast Saccharomyces cerevisiae has provided much information about the structural differences possible among mammalian prion strains (called variants in yeast). The yeast translation termination factor Sup35p aggregates to form the [PSI+] prion. [PSI+] is an epigenetic factor that has many phenotypic consequences as it globally impacts translation and may be involved in regulating how a cell responds to fluctuating environments. Interestingly, the spontaneous conversion of [PSI+] requires the presence of another prion, [RNQ+], formed by Rnq1p. Both of these prions form different variants that can easily be monitored in the yeast cell. This allows us to examine what factors play a role in dictating how a protein can adopt distinct self-propagating conformations. The following specific aims will use an integrated molecular, genetic, and biochemical approach to investigate how different protein conformations could contribute to both the formation and phenotypic variation of age-related diseases: 1) Determine how [RNQ+] variants facilitate the formation of [PSI+]; 2) (A) Elucidate intragenic and extragenic mechanisms that regulate the formation and propagation of [RNQ+] variants; (B) Elucidate the key biochemical properties that define prion variants. Overall, this proposal will enhance our understanding of the physical and molecular basis of prion variants and provide insight into how alternative protein conformations can impact transmissibility between species and cause variation in disease progression of neurodegenerative disorders.