Role of Molecular Chaperones in Stress Response and Disease

许多生物体经常遇到快速反应、高度蛋白质毒性的应激条件，包括暴露在 生理性抗菌剂次氯酸(HOCl)、温度高度升高或酸胁迫。为了生存 在这些应激条件下，他们雇佣了一类不依赖于ATP的应激特异性伴侣，其 翻译后激活是针对需要其伴侣功能的应激条件而定制的。我们的 Lab研究了其中四个应激特异性伴侣蛋白：Hsp33，它由氧化二硫键激活 形成以保护细菌和真核寄生虫免受HOCl2的侵袭，HOCl2通常由 天然的宿主防御；Get3，一种氧化还原调节的Hsp33类似物，保护酵母菌和可能的其他 真核生物抵抗氧化蛋白损伤；HdeA，通过酸诱导的解离而迅速激活 保护肠道细菌免受哺乳动物胃中的酸胁迫；以及线粒体 来自婴儿利什曼原虫的Prdx2，它是一种温度调节的伴侣蛋白，可以保护寄生虫免受 当它们从昆虫转移到温血哺乳动物时，温度突然发生变化。所有这四种蛋白质 在非应激条件下，伴侣蛋白不活跃并稳定折叠，但在非常迅速的情况下被激活， 应激诱导的构象重排，将它们转化为具有广泛固有区域的蛋白质 无序。我们现在将结合突变、生化和高分辨率结构工具来阐明 这些蛋白质的精确工作机制，验证了应激诱导的去折叠有助于 产生新的、高度灵活的蛋白质-蛋白质相互作用位点。这些研究有可能开辟一种 在伴侣研究、蛋白质折叠和应激反应途径方面的全新视角。在一个 在单独的研究中，我们发现聚磷酸盐(Polyp)，这是一种普遍保守的，非常 聚合物含量丰富，分布广泛，是一种高效的蛋白质稳定支架。这 表明蛋白质伴侣并不是处理蛋白毒性应激的唯一细胞解决方案 条件。我们发现，息肉通过将蛋白质稳定在 以β-Sheet构象为主。这一发现有助于解释息肉如何增强对压力的抵抗力。 导致蛋白质展开的条件。同时，它也解释了息肉是如何加速 细菌生物膜的形成等过程，依赖于淀粉样蛋白在 形成纤维的交叉β片状构象。我们最近意识到息肉同样可以加速纤维的形成。 疾病相关的淀粉样蛋白。这种活动似乎减少了有毒低聚物的数量，而且大多数 重要的是，保护神经元免受淀粉样蛋白的毒性。我们现在将进一步调查这一令人振奋的建议 息肉是淀粉样变过程中一种重要的生理细胞保护性修饰物，可能在 在帕金森病和其他潜在的与淀粉样蛋白相关的神经退行性疾病中的作用 队形。

Many organisms regularly encounter fast-acting, highly proteotoxic stress conditions, including exposure to the physiological antimicrobial hypochlorous acid (HOCl), highly elevated temperatures or acid stress. To survive these stress conditions, they employ a class of ATP-independent, stress specific chaperones, whose posttranslational activation is tailored towards the stress conditions that require their chaperone functions. Our lab investigates four of these stress-specific chaperones; Hsp33, which is activated by oxidative disulfide bond formation to protect bacteria and eukaryotic parasites against HOCl, which is commonly produced by cells of the innate host defense; Get3, a redox-regulated Hsp33 analogue that protects yeast and likely other eukaryotes against oxidative protein damage; HdeA, which is rapidly activated by acid-induced dissociation and protects enteric bacteria against acid-stress encountered in the mammalian stomach; and mitochondrial Prdx2 from Leishmania infantum, which is a temperature-regulated chaperone that protects parasites against the sudden temperature shift as they transit from insects to warm-blooded mammals. All four of these proteins are chaperone-inactive and stably folded under non-stress conditions but are activated following very rapid, stress-induced conformational rearrangements, converting them into proteins with extensive regions of intrinsic disorder. We will now combine mutational, biochemical and high-resolution structural tools to elucidate the precise working mechanism of these proteins, testing the hypothesis that stress-induced unfolding serves to generate novel, highly flexible protein-protein interaction sites. These studies have the potential to open up a completely new perspective in chaperone research, protein folding and stress response pathways. In a separate line of research, we discovered that polyphosphate (polyP), which is a universally conserved, very abundant and ubiquitously distributed polymer, works as a highly effective protein-stabilizing scaffold. This demonstrates that protein chaperones are not the only cellular solution to deal with proteotoxic stress conditions. We found that polyP increases the thermostability of proteins by stabilizing them in a predominantly β-sheet conformation. This finding helps to explain how polyP confers resistance to stress conditions that cause protein unfolding. At the same time, it also explains how polyP acts to accelerate processes such as bacterial biofilm formation, which depend on the stabilization of amyloid-like proteins in a fibril-forming cross-β-sheet conformation. We recently realized that polyP equally accelerates fibril formation of disease-associated amyloids. This activity appears to reduce the amount of toxic oligomers and, most importantly, protects neurons against amyloid toxicity. We will now further investigate this exciting suggestion that polyP is a physiologically important cytoprotective modifier of amyloidogenic processes, and might play a role in Parkinson's disease and potentially other neurodegenerative diseases associated with amyloid formation.