Amyloid aggregation and prion formation in bacteria

 描述(由申请人提供)：Prion是具有感染性的、自我繁殖的蛋白质聚集体，最初是在一组致命的神经退行性疾病的背景下被描述的，这种疾病被称为传染性海绵状脑病(TSE)，困扰着人类和其他哺乳动物。在β的情况下，蛋白质的罪魁祸首是一种名为PrP的内源蛋白质，它具有固有的经历戏剧性构象转换的能力，导致形成独特的跨TSE聚集体(称为淀粉样蛋白)，这种聚集体既是自我模板的，也是具有传染性的。在萌芽中的酵母和其他真菌中也发现了普鲁恩，它们作为基于蛋白质的遗传元件，为含有它们的细胞赋予了新的表型。和PrP一样，真菌中的Prion蛋白要么以天然的、可溶的形式存在，要么以具有感染性的自我延续的淀粉样蛋白形式(Prion形式)存在。真菌普恩蛋白参与多种细胞过程，在特定的应激条件下，其普恩形式可以提高细胞的存活率。尽管Pron蛋白广泛分布于整个真菌王国，但目前尚不清楚它们是否存在于生命的细菌领域。这项拟议研究的基础是我们最近的证明，即大肠杆菌细胞可以以一种依赖于保守的细胞伴侣组件的活性的方式来繁殖模型酵母Pron，该组件也是Pron在酵母中繁殖所必需的。这些发现表明，在生命的细菌领域中，基于蛋白质的遗传的基本要求得到了满足，这表明类似Pron的现象可能早于细菌和酵母之间的进化分裂。这项拟议的研究将通过开发工具和方法来揭示细菌中的普恩样蛋白，同时研究决定蛋白质淀粉样变性的决定因素，从而解决这一假说。在目标1中，我们将系统地研究Pron在大肠杆菌中繁殖的伴侣要求。在目标2中，我们将筛选细菌编码的多肽的淀粉样变性，作为一种手段来识别候选的普恩样蛋白，并产生一个无偏见的实验数据集，用于评估蛋白质淀粉样变性的空间拉链模型。在目标3中，我们将开发和实施一套互补的方法来检测细菌中的普里恩现象。总之，拟议的实验将使我们能够更深入地了解Pron形成和繁殖的细胞需求，将有助于阐明蛋白质淀粉样变性的内在决定因素，并将有助于发现新的基于蛋白质的表观遗传学来源，即生命细菌领域的表型多样性。

 DESCRIPTION (provided by applicant): Prions are infectious, self-propagating protein aggregates that were first described in the context of a group of fatal neurodegenerative diseases known as the transmissible spongiform encephalopathies (TSEs), which afflict humans and other mammals. The protein culprit in the case of the TSEs is an endogenous protein called PrP that has an inherent ability to undergo a dramatic conformational conversion, leading to the formation of distinctive cross-β aggregates (termed amyloid) that are both self-templating and infectious. Prions have also been uncovered in budding yeast and other fungi, where they act as protein-based genetic elements that confer new phenotypes on those cells that harbor them. Like PrP, fungal prion proteins exist in either a native, soluble form or a self-perpetuating, amyloid form (the prion form) that is infectious. Involved in diverse cellular processes, fungal prion proteins can, in their prion forms, enhance cell survival under specific stress conditions. Although prion proteins are widely distributed throughout the fungal kingdom, it is not yet known if they exist in the bacterial domain of life. The foundation for the proposed research is our recent demonstration that E. coli cells can propagate a model yeast prion in a manner that depends on the activity of a conserved cellular chaperone assembly that is also required for prion propagation in yeast. These findings indicate that the basic requirements for protein-based heredity are satisfied in the bacterial domain of life, suggesting that prion-like phenomena may predate the evolutionary split between bacteria and yeast. The proposed research will address this hypothesis through the development of tools and approaches for uncovering prion-like proteins in bacteria, while at the same time investigating the determinants that dictate protein amyloidogenicity. In aim 1, we will systematically investigate the chaperone requirements for prion propagation in E. coli. In aim 2, we will screen bacterially encoded polypeptides for amyloidogenicity, as a means to identify candidate prion-like proteins and also to generate an unbiased experimental data set for evaluating the steric zipper model for protein amyloidogenicity. In aim 3, we will develop and implement a complementary set of approaches to detect prion-like phenomena in bacteria. Together, the proposed experiments will enable a deeper understanding of the cellular requirements for prion formation and propagation, will help elucidate the intrinsic determinants of protein amyloidogenicity and will facilitate the discovery f new protein-based epigenetic sources of phenotypic diversity in the bacterial domain of life.