Molecular Mechanisms of Neuroprotection in Polyglutamine-Dependent Degeneration

这种重新提交的竞争性更新R 01申请的中心前提是了解 脊髓小脑性共济失调3型（SCA 3）是世界上最常见的显性共济失调。SCA 3是 由基因ATXN 3中异常的CAG三联体重复扩增引起，其翻译成长的 去泛素化共济失调蛋白-3中的多聚谷氨酰胺（polyQ）区。SCA 3是如何发生的仍然没有解决;这种疾病 对病人来说都是致命的SCA 3属于polyQ疾病家族，其中包括另外八种 紊乱在每种疾病中，神经元毒性的罪魁祸首是原发性神经元内的谷氨酰胺重复。 其致病蛋白的序列。PolyQ扩增超出正常范围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polyQ毒性的表现方式- 中枢神经系统区域受到影响，细胞过程受到干扰-由polyQ外的肽区域调节 道，通常被称为蛋白质上下文。polyQ退化的基本方面是 强调的事实是，虽然类似的突变导致每种疾病，症状， 受影响的神经系统区域各不相同。为了了解polyQ疾病的生物学，我们需要 为了理解每个polyQ区域周围的蛋白区域如何控制和调节药物的毒性， 扩大重复。我们在此竞争性续约申请中的重点是系统地了解以下方面的作用： SCA 3中的蛋白质背景。我们的过度假设是， 异常的polyQ束扩展由该蛋白质的非polyQ结构域处的特异性结合配偶体控制。 我们在R 01奖项的前一个周期的工作提供了关于蛋白质背景在SCA 3中的作用的关键线索。 我们发现，它的两个非polyQ区域对由细胞凋亡引起的退化具有显著的调节作用。 体内共济失调蛋白-3。一个区域控制共济失调蛋白-3与蛋白酶体相关蛋白Rad 23的相互作用; 另一个被SCA 3蛋白用于直接结合AAA ATP酶VCP/p97。每个交互都有一个 对致病性共济失调蛋白-3的毒性具有特异性和明确的作用。在这一周期中，我们寻求扩大我们的发现， 并通过新的模式和方法来推动我们的工作。我们提出了一个系统的和跨学科的 一组研究，以确定非polyQ结构域对聚合物的聚集、毒性和细胞特性的作用。 致病性共济失调蛋白-3在体内，同时也研究更广泛的细胞反应，这种有毒蛋白。我们 我们相信，我们的工作将为SCA 3中蛋白质背景的作用增加急需的视角， 互补和逐步扩大的角度，建立新的工具来研究这种疾病，并提供新的 概念上的进步，可能会告知其他蛋白毒性疾病的生物学。

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.