Ataxin-2 as a genetic risk factor for ALS: New insights into neurodegeneration

描述（由申请人提供）：肌萎缩侧索硬化症（ALS）是一种破坏性神经退行性疾病，对运动神经元造成严重破坏。最近，RNA结合蛋白和RNA代谢途径的核心作用已经出现。TDP-43是一种RNA结合蛋白，已被鉴定为大多数ALS患者神经元中病理性包涵体的组分。此外，编码TDP-43（TARDBP）的基因中的致病性突变与家族性和散发性ALS病例相关。这些数据表明TDP-43的病理活性对ALS至关重要。然而，尽管TDP-43具有核心重要性，但人们对它如何引起疾病和导致ALS的蛋白质相互作用伴侣知之甚少。 这项Co-PI研究提案汇集了两位酵母和苍蝇遗传学专家，他们使用这些简单但强大的系统对帕金森病和ALS等毁灭性人类年龄相关疾病的机制进行了根本性的发现。重要的是，在酵母中的发现可以转化为果蝇疾病模型，并从酵母和苍蝇到人类患者。使用这些系统，我们发现共济失调蛋白-2，一种多聚谷氨酰胺（polyQ）蛋白，其polyQ重复扩增导致脊髓小脑共济失调2型（SCA 2），是酵母和苍蝇中TDP-43毒性的有效修饰剂。从这一发现出发，我们测试并发现人类共济失调蛋白-2基因ATXN 2中27- 33个Qs的polyQ扩增与ALS显著相关。这些数据表明，ATXN 2是一种新的和相对常见的ALS易感性疾病基因，TDP-43/Atx 2相互作用是ALS和可能与TDP-43病理学相关的其他疾病的关键靶标。为了揭示这种相互作用的机制，我们提出了三个具体目标。在目标1中，我们将使用哺乳动物细胞培养物和果蝇来定义TDP-43和共济失调蛋白-2蛋白的结构域，这对变性和功能的协同相互作用至关重要。这些研究将深入了解蛋白质的活性和病理情况下受影响的过程。在目标2中，我们将利用果蝇遗传学的力量来定义对TDP-43和共济失调蛋白-2之间的协同作用至关重要的其他基因。这将揭示对扰动过程的理解和治疗靶向的新途径。最后，在目标3中，我们将讨论共济失调蛋白-2在神经退行性变中的更大作用。ALS与额颞叶变性（FTLD）共享疾病谱，并且TDP- 43病理学表征其他神经变性疾病。我们将评估其他疾病中共济失调蛋白-2的polyQ重复长度，以评估相关疾病中是否发生扩增。总之，这些发现将揭示TDP-43/共济失调蛋白-2相互作用的关键方面，共济失调蛋白-2在神经退行性疾病中的更广泛作用，以及新的治疗见解的基础。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that wreaks havoc on motor neurons. Recently, a central role for RNA binding proteins and RNA metabolism pathways has emerged. TDP-43 is an RNA binding protein that has been identified as a component of pathological inclusions in neurons of most ALS patients. Further, pathogenic mutations in the gene encoding TDP-43 (TARDBP) are associated with familial and sporadic ALS cases. These data argue that pathological activities of TDP-43 are critical to ALS. Despite the central importance of TDP-43, however, little is understood about how it causes disease and protein interaction partners that lead to ALS. This Co-PI research proposal brings together two experts in yeast and fly genetics who have made fundamental discoveries into mechanisms of devastating human age-related diseases such as Parkinson's disease and ALS using these simple but powerful systems. Importantly, discoveries made in yeast are translatable to Drosophila disease models, and from yeast and flies to human patients. Using these systems, we have found that ataxin-2, a polyglutamine (polyQ) protein, whose polyQ repeat expansions cause spinocerebellar ataxia type 2 (SCA2), is a potent modifier of TDP-43 toxicity in yeast and fly. Launching from this finding, we tested and found that polyQ expansions of 27-33Qs in the human ataxin-2 gene, ATXN2, are significantly associated with ALS. These data argue that ATXN2 is a new and relatively common ALS susceptibility disease gene, and that the TDP-43/Atx2 interaction is a critical target in ALS and perhaps other diseases associated with TDP-43 pathology. With the goal to reveal mechanistic insight into this interaction, we propose three Specific Aims. In Aim 1, we will use mammalian cell culture and Drosophila to define the domains of the TDP-43 and ataxin-2 proteins that are critical for the synergistic interaction in degeneration and function. These studies will provide insight into the activity of the proteins and processes affected in the pathological situation. In Aim 2, we will use the power of fly genetics to define additional genes critical for the synergy between TDP-43 and ataxin-2. This will reveal understanding of the processes perturbed and new pathways for therapeutic targeting. Finally, in Aim 3, we will address the greater role of ataxin-2 in neurodegeneration. ALS shares a disease spectrum with frontotemporal lobar degeneration (FTLD) and TDP- 43 pathology characterizes other neurodegenerative diseases. We will assess polyQ repeat lengths of ataxin-2 in other diseases to assess whether expansions occur in related disorders. Taken together, these findings will reveal key aspects of the TDP-43/ataxin-2 interaction central to ALS, the broader role of ataxin-2 in neurodegenerative disease, and the foundation for novel therapeutic insights.