Defining TMEM184b-Controlled Pathways in Nerve Terminal Maintenance and Axon Degeneration

我们工作的总体目标是了解神经末梢和轴突在整个过程中是如何维持的。 生命以及它们对伤害的反应。在外周神经系统(PNS)，长的初级运动和感觉 轴突及其终末容易受到包括新陈代谢应激在内的各种促退行性损伤。 在糖尿病期间，化疗药物的神经毒性、创伤和遗传性疾病包括 肌萎缩侧索硬化症(ALS)。在这些疾病中，终末和轴突通常 最先受影响的结构，它们的退化先于细胞体死亡。通过绘制细胞图， 神经末梢和轴突变性早期事件的遗传和生化格局，我们可能 找出延缓或防止神经退行性疾病变性的方法。 我们重点研究了TMEM184b的轴突和突触功能，TMEM184b是一种新发现的7-通道 三叉神经节中的跨膜蛋白。小鼠TMEM184b基因缺失导致进行性双侧运动营养不良 和感觉神经末梢，还会导致感觉运动障碍。除了这些神经末梢 表型，果蝇或小鼠体内TMEM184b的减少会导致损伤后轴突的完整性延长， 提示TMEM184b在轴突退行性变的级联反应中起活跃作用。自噬小体的积累和 溶酶体是负责蛋白质和细胞器降解的隔室，在突变组织中可见。基座 根据这些数据，我们假设TMEM184b调控自噬的一个步骤。因为自噬是已知的 促进轴突变性并改变突触结构，这一假说可以解释轴突和 TMEM184b突变小鼠的突触表型。 使用小鼠和果蝇系统，我们将用分子和 遗传分析、电生理学、细胞生物学和行为学。在目标1中，我们将查明 通过研究神经肌肉突触发现缺乏TMEM184b的果蝇和小鼠的感觉运动缺陷 传递和感觉转导，终末期营养不良的分子特征和评估 周围神经轴突运输。在目标2中，我们将探索由以下因素控制的细胞和分子通路 TMEM184b在培养的神经元和移植组织中的作用，特别关注连接TMEM184b生物 控制自噬的活性。在目标3中，我们将确定TMEM184b如何有助于促进退行性变 我们将询问TMEM184b在损伤神经中的作用 轴突变性在中枢神经系统中是保守的。 综上所述，我们的研究将描述一种新的神经元自噬控制机制，这可能是 神经退行性疾病的早期阶段。这项工作将有助于发现新的拦截策略 神经退行性疾病中的神经末梢和轴突变性。

The overall objective of our work is to understand how nerve terminals and axons are maintained throughout life and how they respond to injury. In the peripheral nervous system (PNS), long primary motor and sensory axons and their terminals are susceptible to a wide variety of pro-degenerative insults, including metabolic stress during diabetes, neurotoxicities of chemotherapy drugs, traumatic injuries, and genetic disorders including Charcot-Marie-Tooth and Amyotrophic Lateral Sclerosis (ALS). In these disorders, terminals and axons are often the first affected structures, and their degeneration precedes cell body death. By mapping out the cellular, genetic, and biochemical landscape of the early events of nerve terminal and axon degeneration, we might identify ways to delay or prevent this degeneration in neurodegenerative disorders. We are focused on the axonal and synaptic functions of TMEM184b, a newly discovered 7-pass transmembrane protein, in the PNS. Loss of TMEM184b in mice causes progressive dystrophies in both motor and sensory nerve terminals, and also causes sensorimotor deficits. In addition to these nerve terminal phenotypes, reduction of TMEM184b in Drosophila or in mice leads to prolonged axon integrity after injury, suggesting TMEM184b is active in the axon degeneration cascade. Accumulations of autophagosomes and lysosomes, compartments responsible for protein and organelle degradation, are seen in mutant tissues. Based on these data, we hypothesize that TMEM184b regulates a step in autophagy. Because autophagy is known to promote axon degeneration and also alter synapse structure, this hypothesis would explain both the axon and synapse phenotypes of TMEM184b mutant mice. Using both mouse and Drosophila systems, we will test our hypothesis with a combination of molecular and genetic analysis, electrophysiology, cell biology, and behavior. In Aim 1, we will ascertain the root causes of the sensorimotor deficits seen in both flies and mice lacking TMEM184b by investigating neuromuscular synaptic transmission and sensory transduction, molecularly characterizing terminal dystrophies, and evaluating peripheral nerve axon transport. In Aim 2, we will probe the cellular and molecular pathways controlled by TMEM184b in cultured neurons and explanted tissues, with a particular focus on linking TMEM184b biological activity to the control of autophagy. In Aim 3, we will identify how TMEM184b contributes to pro-degenerative pathways in injured nerves using genetic epistasis and biochemistry, and we will ask whether TMEM184b's role in axon degeneration is conserved in the central nervous system. In summary, our research will describe a new mechanism of autophagy control in neurons that may underlie early stages of neurodegenerative diseases. This work will contribute to the discovery of new strategies to block nerve terminal and axon degeneration in neurodegenerative disorders.