Genetic analysis of mitochondria-dependent cellular toxicity of alpha-synuclein

蛋白质包涵体是阿尔茨海默病和退行性痴呆的共同病理特征。路易体是路易体痴呆的主要蛋白质病理改变，它含有难溶的错折叠α-突触核蛋白。在尸检的患者脑组织中，路易体和路易体相关的病理经常与神经原纤维Tau缠结和A斑块同时出现，这是阿尔茨海默病的两个病理特征。退行性痴呆患者中蛋白质病理的过度并存表明，蛋白质错误折叠、堆积和进行性沉积是常见的神经机制。线粒体损伤和功能障碍被认为是这种常见机制之一。这一提议采用了一种新的细胞模型，该模型能够在迫使细胞经历线粒体依赖的呼吸的同时表达聚集倾向蛋白。与线粒体在驱动蛋白质病理中的作用一致，随着细胞被迫呼吸，α-突触核蛋白和其他一些与神经退行性疾病相关的蛋白质变得极其有毒。毒性与细胞质蛋白包涵体的形成增加和明显的线粒体损伤相吻合。系统的遗传筛查发现了保护细胞免受几种易于聚集的蛋白质毒性的人类基因，包括α-突触核蛋白和TdP-43，后者与额颞部痴呆有关。基因筛查还发现了增强毒性的人类基因，其中很大一部分增强基因具有已知的线粒体相关功能。这些发现导致了线粒体作为调节蛋白质错误折叠和毒性的驱动力的提议的前提。概述了两个特定的目标，以表征已识别的人类基因抑制子和增强子的调控效果，特别是对线粒体功能和功能障碍的关注。拟议工作的完成将揭示线粒体在调节易于聚集的蛋白质毒性方面的新作用，并确定推动阿尔茨海默病和退行性痴呆常见蛋白质病理的细胞靶点。

Proteinaceous inclusions are common pathological features of Alzheimer’s disease and degenerative dementias. Lewy body, containing insoluble misfolded α-synuclein, is the predominant protein pathology of Lewy body dementia. In autopsied brain tissues from patients, Lewy body and Lewy-related pathology frequently co-occur with neurofibrillary Tau tangles and A plaques, two pathological hallmarks of Alzheimer’s disease. The excessive co-occurrence of protein pathology in patients with degenerative dementia is indicative of common neurological mechanisms underlying aberrant protein misfolding, accumulation and progressive deposition. Mitochondrial damage and dysfunction are thought to be one of such common mechanisms. This proposal employs a novel cellular model that enables the expression of aggregation prone proteins while forcing cells to undergo mitochondria-dependent respiration. Consistent with a role of mitochondria in driving protein pathology, α-synuclein and a few other neurodegenerative disease-associated proteins become exceedingly more toxic as cells are forced to respire. Toxicity coincides with elevated formation of cytoplasmic protein inclusions and pronounced mitochondrial damages. Systematic genetic screens identified human genes that protect cells from the toxicity of several aggregation prone proteins, including α-synuclein and TDP-43, which is associated with Frontotemporal dementia. Genetic screens also identified human genes that enhance the toxicity with a significant fraction of those enhancer genes having known mitochondrial related functions. These findings lead to the premise of the proposal that mitochondria act as a driving force to regulate protein misfolding and toxicity. Two specific aims are outlined to characterize the regulatory effects of the identified human-gene suppressors and enhancers with a particular focus on mitochondrial function and dysfunction. Completion of the proposed work will reveal new roles of mitochondria in modulating the toxicity of aggregation prone proteins and identify cellular targets that drive common protein pathology in Alzheimer’s disease and degenerative dementia.