Assembly and structures of polyglutamine aggregates

描述（由申请人提供）： 包括亨廷顿病在内的九种人类遗传性神经变性疾病是由不同蛋白质编码区中CAG重复序列的扩增引起的。这些蛋白质在大小、结构、亚细胞定位以及已知的功能上不同。由于它们唯一的共同特征是由CAG重复序列编码的聚谷氨酰胺（polyGIn）序列，并且由于除了1种蛋白质之外，所有这些蛋白质的疾病风险的重复长度阈值都在相同的30-40长度范围内，因此几乎可以肯定神经毒性是由扩展的polyGIn序列的某些特性触发的。该提案建立在并继续了以前的授权的线程，通过更详细地调查扩展polyGIn序列的生物物理特性，特别是淀粉样蛋白聚集体的形成。在最近的工作中，我们表明，聚GIn聚集的成核涉及单体聚GIn内的一个非常不利的折叠反应;本提案的第一个目的是更详细地调查的聚集反应的伸长和成核阶段，以及它们对溶液条件变化的响应。在最近的工作中，我们表明，成核反应，因此，聚集的整体侵略性，是由环境中的良性重复长度polyGIn肽的影响很大;该提案的第二个目的是调查如何在polyGIn序列中的局部序列上下文和突变断裂，发现在人类基因组中的富含Gin的序列，影响聚集能力。在最近的其他工作中，我们表明，分子伴侣Hdj 2，以前显示，以保护生物体免受polyGIn毒性，抑制polyGIn聚集过程在体外;新建议的第三个目的是确定结构Hdj 2如何识别和中和聚集倾向polyGIn序列。这些研究将继续我们的长期目标，即确定polyGIn序列如何形成毒性聚集体，以及序列和细胞环境如何调节其内在聚集倾向，从而最终确定疾病风险。

DESCRIPTION (provided by applicant): Nine (9) human genetic neurodegenerative diseases, including Huntington's disease, are caused by the expansion of CAG repeat sequences in the coding regions of different proteins. These proteins differ in size, structure, sub-cellular localization, and, where known, function. Since their only common feature is the polyglutamine (polyGIn) sequence encoded by the CAG repeat, and since for all but 1 of these proteins the repeat length threshold for disease risk is in the same 30-40 length range, neurotoxicity is almost certainly triggered by some property of the expanded polyGIn sequence. This proposal builds on and continues the threads of the previous grant by investigating in more detail the biophysical properties of expanded polyGIn sequences, focusing in particular on the formation of amyloid-like aggregates. In recent work we showed that nucleation of polyGIn aggregation involves a highly unfavorable folding reaction within monomeric polyGIn; The first aim of this proposal is to investigate in greater detail the elongation and nucleation phases of the aggregation reaction, and their responses to changes in solution conditions. In very recent work we showed that the nucleation reaction, and hence the overall aggressiveness of aggregation, is greatly influenced by benign-repeat length polyGIn peptides in the environment; The second aim of this proposal is to investigate how local sequence context and mutational breaks in the polyGIn sequence, as found in Gin-rich sequences in the human genome, impact aggregation ability. In other recent work we showed that the molecular chaperone Hdj2, previously shown to protect organisms against polyGIn toxicity, inhibits the polyGIn aggregation process in vitro; The third aim of the new proposal is to determine structurally how Hdj2 recognizes and neutralizes aggregation-prone polyGIn sequences. These studies will continue our long-term goal of determining how polyGIn sequences form toxic aggregates, and how both sequence and cellular contexts modulate their intrinsic aggregation propensity, thus ultimately determining disease risk.