Molecular Mechanisms of Neuroprotection in Polyglutamine-Dependent Degeneration

重新提交的竞争性续订R01申请的主要前提是了解 脊髓小脑性共济失调3型(SCA3)，全世界最常见的显性共济失调。SCA3是 由ATXN3基因中CAG三联体的异常重复扩增引起的，这转化为一个长的 脱泛素酶ataxin-3中的多聚谷氨酰胺(PolyQ)区域。SCA3是如何发生的仍未解决；这种疾病 对病人来说都是致命的。SCA3属于多Q病家族，包括另外八种 精神错乱。在每种疾病中，神经元毒性的主要罪魁祸首是原发灶内的谷氨酰胺重复 其致病蛋白的序列。超过正常范围的多聚Q扩张会导致蛋白质错误折叠， 神经元功能障碍和死亡。有明确的证据表明，多酚毒性呈现的方式- 中枢神经系统受影响的区域和细胞过程被扰乱-由多聚Q外部的多肽区域调节 区域，即通常所说的蛋白质上下文。多Q退化的这个基本方面是 虽然每种疾病都是由相似的突变引起的，但出现的症状和 受影响的神经系统区域各不相同。为了了解多Q疾病的生物学，我们需要 为了了解每个多聚Q区域周围的蛋白质区域如何控制和调节 扩展重复。我们在这项竞争性续订申请中的重点是系统地了解 SCA3中的蛋白质背景。我们的总体假设是，阿塔克辛-3的致病性是由 异常的多聚Q链扩张是由该蛋白的非多聚Q结构域上的特定结合伙伴控制的。 我们在这个R01奖的前一个周期中的工作提供了关于蛋白质背景在SCA3中的作用的关键线索。 我们发现，它的两个非多Q区域对由 体内的Aaxin-3。一个区域控制ataxin-3与蛋白酶体相关蛋白RAD23的相互作用； 另一种是由SCA3蛋白直接与AAA ATPase VCP/p97结合。每个交互组件都有一个 对致病因子ataxin-3的毒性有明确而特异的影响。在这个周期中，我们寻求扩展我们的发现 并通过新的模式和方法推动我们的工作。我们提出了一种系统的、跨学科的 一系列研究以确定非多Q结构域对聚集性、毒性和细胞特性的作用 体内致病的ataxin-3，同时也更广泛地研究细胞对这种有毒蛋白的反应。我们 我们相信，我们的工作将为SCA3中蛋白质上下文的作用增加亟需的视角 互补并逐步拓宽角度，建立研究这种疾病的新工具，并提供新的 概念上的进展可能会为生物学提供其他蛋白毒性疾病的信息。

The central premise of this resubmitted, competitive renewal R01 application is to understand the biology of disease in Spinocerebellar Ataxia Type 3 (SCA3), the most common dominant ataxia worldwide. SCA3 is caused by abnormal CAG triplet repeat expansion in the gene ATXN3, which translates into a long polyglutamine (polyQ) tract in the deubiquitinase ataxin-3. How SCA3 occurs remains unresolved; this disease is uniformly fatal in patients. SCA3 belongs to the family of polyQ diseases, which includes another eight disorders. In each disease, the primary culprit of neuronal toxicity is the glutamine repeat within the primary sequence of its causative protein. PolyQ expansion beyond normal ranges leads to protein misfolding, neuronal dysfunction and death. There is clear evidence that the manner in which polyQ toxicity presents— CNS areas impacted and cellular processes perturbed—is regulated by peptide regions outside of the polyQ tract, what is commonly referred to as protein context. This fundamental aspect of polyQ degeneration is underscored by the fact that although a similar mutation causes each disease, the symptoms presented and the nervous system areas impacted differ among them. To understand the biology of polyQ diseases, we need to comprehend how the protein areas around each polyQ region control and modulate the toxicity of the expanded repeat. Our focus in this competitive renewal application is to systematically understand the role of protein context in SCA3. Our over-arching hypothesis is that pathogenicity conferred onto ataxin-3 by abnormal polyQ tract expansion is controlled by specific binding partners at this protein's non-polyQ domains. Our work during the prior cycle of this R01 award provided key clues about the role of protein context in SCA3. We found that two of its non-polyQ regions exert significant modulatory effect on degeneration caused by ataxin-3 in vivo. One region controls the interaction of ataxin-3 with the proteasome-associated protein Rad23; the other is used by the SCA3 protein to directly bind to the AAA ATPase VCP/p97. Each interaction has a specific and clear effect on the toxicity of pathogenic ataxin-3. In this cycle, we seek to expand on our findings and to propel our work through novel models and approaches. We propose a systematic and interdisciplinary set of studies to define the role of non-polyQ domains on the aggregation, toxicity and cellular properties of pathogenic ataxin-3 in vivo, while also investigating more broadly the cellular response to this toxic protein. We are confident that our work will add much needed perspective to the role of protein context in SCA3 from complementary and progressively wider angles, establish novel tools to study this disease, and provide new conceptual advances that will likely inform the biology of other proteotoxic disorders.