Pathway of Protein Misfolding Intiation in vivo

描述（由申请人提供）：神经退行性疾病，包括阿尔茨海默氏病、亨廷顿氏病和帕金森病以及传染性海棉状脑病（朊病毒疾病），与一种不寻常的疾病机制有关，在这种疾病机制中，细胞编码蛋白质的替代构象出现，随后将同一蛋白质的正常构象错误折叠成类似状态。这些疾病的自发出现已被证明随着年龄的增长而增加，这表明存在细胞机制来阻止致病性错误折叠途径的启动。尽管这些蛋白质的构象自我复制机制已经得到了很好的研究，但我们对这种状态启动的机制理解还远远落后。了解可溶性功能蛋白在初始错误折叠过程中所采取的途径可以为预防和治疗这些疾病提供新的治疗靶点。我们研究的长期目标是了解细胞环境如何调节蛋白质折叠途径，以创造正常的生理和疾病状态。本提案的目的是确定蛋白质错误折叠的途径是如何在体内启动的。在这些研究中，我们将利用酿酒酵母的Sup35/[PSI+]朊病毒系统。虽然Sup35折叠从正常（[psi-]）途径切换到错误折叠（[psi +]）途径的机制尚不清楚，但这一过程依赖于另一种朊病毒蛋白Rnq1的错误折叠形式的存在，或者依赖于具有非天然C端延伸的Sup35变体。我们假设这些因素绕过了错误折叠Sup35积累的限速步骤，导致了[PSI+]的出现。为了验证这一假设，我们将操纵Sup35错误折叠途径中关键参与者和Sup35序列的表达水平，并将[PSI+]出现频率的变化与体内Sup35蛋白的生物发生变化联系起来。通过了解蛋白质折叠途径是如何被细胞环境调节的，我们将开始揭示这些过程对正常细胞生理学和疾病的出现和传播的分子贡献。

DESCRIPTION (provided by applicant): Neurodegenerative diseases, including Alzheimer's, Huntington's and Parkinson's Diseases and the Transmissible Spongiform Encephalopathies (prion diseases), have been linked to an unusual disease mechanism, in which alternative conformations of cellularly encoded proteins arise and subsequently direct the misfolding of normal conformers of the same protein to a like state. The spontaneous appearance of these disorders has been shown to increase with age, suggesting that cellular mechanisms exist to prevent the pathogenic misfolding pathways from initiating. Although the mechanism of conformational self-replication for these proteins has been well-studied, our mechanistic understanding of the initiation of this state lags far behind. Understanding the pathway that soluble, functional proteins take during this initial misfolding event can provide new therapeutic targets for the prevention and treatment of these diseases. The long-term goal of our research is to understand how the cellular environment regulates protein folding pathways to create both normal physiological and disease states. The objective of this proposal is to determine how a pathway of protein misfolding is initiated in vivo. For these studies, we will exploit the Sup35/[PSI+] prion system of Saccharomyces cerevisiae. While the mechanism by which Sup35 folding switches from the normal ([psi-]) to the misfolded ([PSI+]) pathway is still unknown, this process is dependent on presence of the misfolded form of another prion protein, Rnq1, or on a Sup35 variant with a non-native C- terminal extension. We hypothesize that these factors bypass the rate-limiting step for accumulation of misfolded Sup35, leading to [PSI+] appearance. To test this hypothesis, we will manipulate both the expressing levels of key players in the Sup35 misfolding pathway and the Sup35 sequence and link changes in the frequency of [PSI+] appearance to changes in the biogenesis of the Sup35 protein in vivo. By developing an understanding of how protein folding pathways can be modulated by their cellular environment, we will begin to reveal the molecular contributions of these processes to both normal cellular physiology and to the appearance and spread of diseases. PUBLIC HEALTH RELEVANCE: Severe neurodegenerative diseases, including Alzheimer's, Huntington's and Parkinson's Diseases as well as the Transmissible Spongiform Encephalopathies (prion diseases) have been linked to an unusual disease mechanism, in which alternative conformations of normal cellularly encoded proteins arise and subsequently direct the misfolding of normal conformers of the same protein to a like state. Understanding the pathway that soluble, functional proteins take during the initial misfolding event can provide new therapeutic targets for the prevention and treatment of these diseases.