Investigating the Activation Mechanism of SARM1 during Axon Degeneration

项目摘要 损伤后，轴突开始通过以轴突断裂和解体为特征的过程死亡 髓磷脂鞘。这个过程通常被称为沃勒变性后，奥古斯都沃勒。类沃勒 在形态学上类似于沃勒变性的变性，与早期阶段的 许多神经退行性疾病，包括阿尔茨海默病、亨廷顿病和帕金森病。Wallerian 长期以来，退化被认为是被动发生的，但发现了积极预防或促进退化的蛋白质， 退化否定了这个想法。其中一种蛋白质是SARM 1。SARM 1是NAD+水解酶，其切割NAD+以 烟酰胺、ADPR和环状ADPR;这些产物的产生最终导致轴突变性。 此外，SARM 1基因敲除可延迟Wallerian样疾病动物模型的退化，包括 创伤性脑损伤和周围神经病变。鉴于SARM 1在沃勒氏病样疾病中的关键作用， 该建议的中心假设是SARM 1抑制将防止轴突的病理生理学 与神经变性疾病相关的变性。然而，SARM 1抑制剂的开发受到限制 缺乏对这种酶的调节、结构和机制的了解。因此，目标 这项建议的目的是了解SARM 1在沃勒变性背景下的调节，这一目标将 通过追求以下具体目标来实现。目的1：鉴定调节SARM 1的蛋白质 活动邻近依赖性标记也将用于鉴定与SARM 1相互作用的蛋白质。的影响 SARM 1相互作用蛋白对NAD+水解酶活性和SARM 1介导的轴突变性的影响也将被研究。 评估。这些实验将确定轴突变性过程中调节SARM 1的分子间事件。 目的二是了解TIR-1的结构和功能，C. SARM 1的elegans直系同源物。在这里， 我们将解析TIR-1的结构，并对该酶的酶学机制进行研究。这些研究将 补充最近的结构和动力学研究的SARM 1，并将产生见解的分子内 SARM 1/TIR-1的特征有助于其退化能力。调查对 在神经退行性疾病的背景下，SARM 1在分子间和分子内都是一个快速发展的领域。 因此，这项工作的完成将大大提高我们对基本分子的理解， 控制轴突退化的机制这些研究将有助于深入了解SARM 1在轴突中的作用。 这将对神经退行性疾病的治疗方法的发展产生广泛的影响。 疾病

PROJECT SUMMARY After injury, axons begin to die via a process that is characterized by axonal fragmentation and disintegration of myelin sheath. This process is often termed Wallerian degeneration after Augustus Waller. Wallerian-like degeneration, which is morphologically similar to Wallerian degeneration, is associated with the early stages of many neurodegenerative diseases, including as Alzheimer’s, Huntington’s, and Parkinson’s Diseases. Wallerian degeneration was long thought to occur passively, but the discovery of proteins that actively prevent or promote degeneration negated this idea. One such protein is SARM1. SARM1 is a NAD+ hydrolase that cleaves NAD+ to nicotinamide, ADPR, and cyclic ADPR; generation of these products ultimately leads to axonal degeneration. Moreover, SARM1 knockout delays degeneration in animal models of Wallerian-like diseases, including traumatic brain injury and peripheral neuropathy. Given the critical role of SARM1 in Wallerian-like diseases, the central hypothesis of this proposal is that SARM1 inhibition would prevent the pathophysiology of axon degeneration associated with neurodegenerative diseases. However, development of SARM1 inhibitors is limited by the lack of knowledge surrounding the regulation, structure, and mechanism of this enzyme. As such, the goal of this proposal is to understand SARM1 regulation in the context of Wallerian degeneration, and this goal will be achieved by pursing the following Specific Aims. Aim 1 focuses on identifying proteins that regulate SARM1 activity. Proximity dependent labeling will also be used to identify proteins that interact with SARM1. The impact of SARM1 interacting proteins on NAD+ hydrolase activity and SARM1-mediated axon degeneration will also be assessed. These experiments will identify intermolecular events that regulate SARM1 during axon degeneration. Aim 2 will focus on understanding the structure and function of TIR-1, the C. elegans ortholog of SARM1. Here, we will solve the TIR-1 structure and characterize the enzymatic mechanism of this enzyme. These studies will complement recent structural and kinetic studies of SARM1 and will yield insights into the intramolecular characteristics of SARM1/TIR-1 that contribute to its degenerative capacity. Investigation into the regulation of SARM1, both inter- and intramolecularly, is a rapidly growing field in the context of neurodegenerative diseases. As such, completion of this work will significantly enhance our understanding of the fundamental molecular mechanisms that control axonal degeneration. These studies will yield insights into the role of SARM1 in axon degeneration, which will have broad implications in the development of therapeutics for neurodegenerative diseases.