Structure and Genesis of tau Filaments

描述（由申请人提供）：神经原纤维病变是单发神经退行性疾病如阿尔茨海默病的标志性病理。病变主要由tau组成，这是一种微管相关蛋白，通常起促进微管蛋白组装、微管稳定性和细胞骨架完整性的作用。在疾病病变中积累的tau蛋白不同于微管相关蛋白的聚集状态和翻译后修饰。尽管在描述宏观聚集途径方面取得了进展，但对于病变形成如何与分子水平上的事件或神经变性的细胞机制联系在一起，尚未达成共识。为了解决这些关键问题，该实验室开发了强大的方法来定量体外tau纤维化，一阶动力学模型合理化组装行为，以及紧密结合配体，可用于检测和抑制tau聚集。基于这些发现，我们假设在接近生理条件下，tau纤维在成核-延伸机制中通过部分折叠的中间体形成，并且该反应途径产生了可用于选择性结合小分子配体的新型药物载体。进一步假设翻译后修饰、突变和外源效应通过选择性地与组装种相互作用触发或增强聚集。目前的提议有三个具体目标来检验这些假设。首先，确定tau纤圆的动力学途径，最后进行反应的数学模拟。其次，将利用定量分析和构效关系建立新型纤维化抑制剂的作用机制，从而确定靶点并阐明该过程中药物干预的潜力。最后，将确定翻译后修饰和致病突变作用的分子机制。总之，这些数据将阐明伴随成纤维的分子事件，以及在体内拮抗甚至逆转早期tau纤维形成的可行性。

DESCRIPTION (provided by applicant): Neurofibrillary lesions are a hallmark pathology of tauopathic neurodegenerative disorders such as Alzheimer's disease. The lesions are composed primarily of tau, a microtubule-associated protein that normally functions to promote tubulin assembly, microtubule stability, and cytoskeletal integrity. The tau that accumulates in disease lesions differs from microtubule-associated protein in its state of aggregation and posttranslational modification. Despite progress in describing the macroscopic aggregation pathway, a consensus has not emerged on how lesion formation links to events on the molecular level or to the cellular mechanisms of neurodegeneration. To address these crucial questions, this laboratory developed powerful methods for quantifying tau fibrillization in vitro, a first-order kinetic model rationalizing assembly behavior, and tight-binding ligands potentially useful for detecting and inhibiting tau aggregation. On the basis of these findings, it is hypothesized that under near physiological conditions tau fibrillizes via a partially folded intermediate in a nucleation-elongation mechanism, and that the reaction pathway creates novel pharmacophores available for selective binding of small-molecule ligands. It is further postulated that posttranslational modifications, mutations, and exogenous effectors trigger or enhance aggregation by selectively interacting with assembly species. The present proposal has three Specific Aims that test these hypotheses. First, the kinetic pathway through which tau fibrillizes will be determined, culminating in a mathematical simulation of the reaction. Second, the mechanism of action of novel fibrillization inhibitors will be established using quantitative assays and structure-activity relationships, leading to target identification and clarification of the potential for pharmacological intervention in the process. Finally, the molecular mechanisms underlying the effects of posttranslational modifications and disease causing mutations will be determined. Together, these data will clarify the molecular events accompanying fibrillization, and feasibility of antagonizing and even reversing early stage tau filament formation in vivo.