Structural polymorphism in the misfolding and aggregation of expanded polyglutamine proteins

描述（由申请人提供）：许多毁灭性的神经退行性疾病是由蛋白质错误折叠导致斑块或内含错误折叠蛋白质的包涵体引起的。尽管人们认识到蛋白质错误折叠的核心作用，但我们通常缺乏对致病分子事件的了解，部分原因是阿尔茨海默病（AD）等疾病的复杂病因。亨廷顿氏病（HD）和至少8种其他神经退行性疾病已经被追溯到不同基因之间发生的一个显著的明确的突变：预先存在的CAG密码子重复序列的扩展。在HD中，这导致亨廷顿蛋白内的聚谷氨酰胺（polyQ）通道扩张，扩张超过~35 Gln的“阈值”，导致毁灭性的神经退行性疾病，发病年龄取决于扩张程度。仅HD一项就使20多万美国人面临患病风险，目前尚无有效的治疗或预防方法。我们对错误折叠途径的认识的显著提高，对于设计能够改善错误折叠、疾病发作和毒性的治疗方法至关重要。为了满足这一需求，我们将部署最先进的魔角旋转（MAS）核磁共振波谱。这种方法以前允许我们用位点特异性和原子分辨率表征各种蛋白质聚集体，最近包括一系列聚谷氨酰胺相关聚集体。我们在这一努力中过去和未来的成功得益于深入的核磁共振专业知识、精致的核磁共振硬件和高效的合作，这使得我们能够深入了解HD的错误折叠过程和致病毒性。根据我们现有的核磁共振数据和机制研究，我们假设分子内坍缩成可能常见的ß-发夹构象具有关键作用。至关重要的是，这种构象变化促进了错误折叠的多聚体自组装成低聚体和纤维聚集体，这些聚集体可能包含崩塌初始结构的标志性结构基序特征。因此，通过研究错误折叠态，我们探索

DESCRIPTION (provided by applicant): Many devastating neurodegenerative diseases result from protein misfolding that leads to plaques or inclusions containing the misfolded protein. Despite a recognized central role of protein misfolding, we generally lack insight into the causative molecular events, in part due to the complex etiology of diseases like Alzheimer's Disease (AD). Huntington's Disease (HD) and at least eight other neurodegenerative disorders have been traced to a remarkable well-defined mutation occurring across different genes: the expansion of a pre-existing CAG codon repeat. In HD, this leads to expansion of a polyglutamine (polyQ) tract within the huntingtin protein, with expansion beyond a "threshold" of ~35 Gln leading to a devastating neurodegenerative disease, with the age of onset dependent on the degree of expansion. HD alone places more than 200,000 Americans at risk of disease, with currently no effective curative or preventative treatments. A dramatic improvement in our knowledge of the misfolding pathway is essential to enable the design of treatments that can ameliorate misfolding, disease onset and toxicity. To address this need, we will deploy state-of-the-art magic-angle-spinning (MAS) NMR spectroscopy. This approach has previously allowed us to characterize various protein aggregates with site-specific and atomic resolution, most recently including an array of polyglutamine-related aggregates. Our past and future success in this endeavor is enabled by an in-depth NMR expertise, exquisite NMR hardware, and highly effective collaborations, which have allowed for key insights into the misfolding process and disease-causing toxicity in HD. Informed by our existing NMR data and mechanistic studies, we hypothesize that there is a critical role for intramolecular collapse into a likely common ß-hairpin conformation. Crucially, this conformational change facilitates self-assembly of the misfolded polyQ into oligomeric and fibrillar aggregates that likely contain a signature structural motif characteristic of the collapsed initial structure. Thus, by studying the misfolded states, we probe the molecular underpinnings of the misfolding by expanded polyglutamine. Using MAS ssNMR we will both characterize and leverage an unusual spectroscopic signature that we hypothesize to reflect a unique internal polymorphism that is characteristic of misfolded polyQ domains. Applying these methods to different disease-related proteins, we test our hypothesis that a common structural mechanism is at work across the polyglutamine disease family. We will examine diseases where previous work suggests qualitative differences in the misfolded structure (and thus misfolding mechanism), and in HD will examine polymorphic aggregates that reportedly have differing toxicities. This work will provide the much needed systematic and detailed characterization of this family of disorders that will not only benefit their treatment, bt will also impact our understanding of structure and toxicity as applied to amyloid-related diseases with more complex etiologies, ranging from AD to various systemic amyloidoses.