Structural polymorphism in the misfolding and aggregation of expanded polyglutamine proteins

描述（由申请人提供）：许多破坏性神经退行性疾病是由蛋白质错误折叠引起的，导致含有错误折叠蛋白质的斑块或包涵体。尽管蛋白质错误折叠的核心作用是公认的，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。亨廷顿病（HD）和至少八种其他神经退行性疾病已被追溯到一个显着的明确定义的突变发生在不同的基因：一个预先存在的CAG密码子重复的扩展。在HD中，这导致亨廷顿蛋白内的多聚谷氨酰胺（polyQ）束的扩展，扩展超过约35 Gln的“阈值”，导致破坏性神经退行性疾病，发病年龄取决于扩展程度。仅HD就有超过20万美国人处于疾病风险中，目前没有有效的治疗或预防治疗。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是至关重要的。 为了满足这一需求，我们将部署最先进的魔角旋转（MAS）NMR光谱。这种方法以前使我们能够表征具有位点特异性和原子分辨率的各种蛋白质聚集体，最近包括一系列聚谷氨酰胺相关聚集体。我们过去和未来在这奋进的成功得益于深入的NMR专业知识，精致的NMR硬件和高效的合作，这使得我们能够深入了解HD中的错误折叠过程和致病毒性。根据我们现有的NMR数据和机理研究，我们假设分子内塌缩成可能的常见β-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polyQ自组装成低聚物和纤维状聚集体，这些聚集体可能含有塌陷的初始结构的特征性结构基序。因此，通过研究错误折叠态，我们探索 分子基础的错误折叠由扩大聚谷氨酰胺。使用MAS ssNMR，我们将同时表征和利用一个不寻常的光谱特征，我们假设，以反映一个独特的内部多态性是错误折叠的polyQ结构域的特征。将这些方法应用于不同的疾病相关蛋白质，我们测试了我们的假设，即一个共同的结构机制是在整个多聚谷氨酰胺疾病家族的工作。我们将检查疾病，以前的工作表明在错误折叠的结构（从而错误折叠机制）的定性差异，并在HD将检查多态性聚集体，据报道有不同的毒性。这项工作将提供这一疾病家族急需的系统和详细的表征，这不仅有利于他们的治疗，也将影响我们对结构和毒性的理解，适用于具有更复杂病因的淀粉样蛋白相关疾病，从AD到各种系统性淀粉样蛋白病。

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 β-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.