Functional Analysis of O-GlcNAc using Synthetic Protein Chemistry

修改项目摘要/摘要(摘要)：O-GlcNAc修饰是一种动态的蛋白质修饰，是哺乳动物胚胎发育所必需的，在糖尿病、神经退行性疾病和癌症等疾病中调节不当。虽然大约有1,000种蛋白质被O-GlcNAc修饰，但绝大多数修饰对蛋白质功能的影响是完全未知的。我们研究计划的长期目标是通过确定O-GlcNAc对人类疾病关键蛋白质的生化后果来填补这些缺失的空白。为了实现这一目标，我们使用碳水化合物和合成蛋白质化学的组合来构建O-GlcNAc修饰蛋白质，用于后续的生物实验。这种化学方法是独一无二的，因为它是目前产生均一和位点特异的O-GlcNAc修饰蛋白质的唯一方法。我们已经非常成功地使用合成蛋白质来确定O-GlcNAc在防止神经退行性疾病中蛋白质的淀粉样蛋白聚集方面具有多方面的作用。具体地说，我们发现O-GlcNAc既直接抑制淀粉样蛋白形成蛋白的聚集，又激活某些小分子伴侣的活性。在这项提议中，我们将继续以这些发现为基础。在目标1中，我们将确定O-GlcNAc如何抑制α-突触核蛋白淀粉样蛋白形成的早期阶段。在目标2中，我们将测试O-GlcNAc是否改变α-突触核蛋白淀粉样蛋白的结构/毒性关系。在目标3中，我们研究了O-GlcNAc如何改变小的热休克蛋白相互作用组。最后，在目标4中，我们将确定O-GlcNAc是否可以挽救导致Charcot-Marie-Tooth病的突变伴侣的活性。随着这些独立目标的完成，我们将进一步揭示O-GlcNAc抑制蛋白质聚集的机制，并提供关键数据支持正在进行的针对O-GlcNAc的治疗努力。

Modified Project Summary/Abstract (The abstract contained no specific references to the in vivo mouse experiments and therefore is unchanged): O-GlcNAc modification is a dynamic protein-modification that is absolutely required for embryonic development in mammals, and is misregulated in diseases, including diabetes, neurodegeneration and cancer. Although approximately 1,000 proteins are modified by O-GlcNAc, the effects of the vast majority of these modifications on protein function are completely unknown. The long-term goal of our research program is to fill in these missing gaps by determining the biochemical consequences of O-GlcNAc on proteins that are key to human disease. To accomplish this goal, we use a combination of carbohydrate and synthetic protein chemistries to build O-GlcNAc modified proteins for subsequent biological experiments. This chemical approach is uniquely enabling, as it is currently the only way to generate homogeneous and site-specifically O-GlcNAc modified proteins. We have been very successful and have used synthetic proteins to determine that O-GlcNAc has a multifaceted role in preventing the amyloid aggregation of proteins in neurodegenerative diseases. Specifically, we have found that O-GlcNAc both directly inhibits the aggregation of amyloid forming proteins and activates the activity of certain small chaperones. In this proposal we will continue to build on these discoveries. In Aim 1, we will determine how O-GlcNAc inhibits the early stages of α-synuclein amyloid formation. In Aim 2, we will test whether O-GlcNAc alters the structure/toxicity relationships of α-synuclein amyloids. In Aim 3, we examine how O-GlcNAc alters the small heat shock protein interactome. Finally, in Aim 4, we will determine if O-GlcNAc can rescue the activity of mutant chaperones that cause Charcot-Marie-Tooth disease. At the conclusion of these independent aims, we will have further unravelled the mechanisms by which O-GlcNAc inhibits protein aggregation and provided critical data to support the ongoing efforts to target O-GlcNAc therapeutically.