AMPA Receptor Ubiquitination and Pathological Synaptic Hyperexcitability

癫痫影响着美国300万人。尽管目前抗癫痫药物的发展 药物，以提高癫痫发作阈值，三分之一的癫痫患者要么反应不佳的药物或保持药物， 抵抗我们的研究旨在促进对癫痫患者神经元兴奋性失调的理解， 改善治疗效果的意图。重点介绍了α-氨基-3-羟基-5-甲基-4-异恶唑丙酸 酸受体（AMPA受体; AMPAR），神经系统中最丰富的受体，也是一种良好的 研究兴奋性突触蛋白。在癫痫患者中观察到AMPAR水平升高， 在临床实践中，抑制AMPAR的药物已被用于缓解癫痫。尽管所有这些 事实上，目前尚不清楚AMPAR的稳态如何介导大脑兴奋性以及如何失调 AMPAR导致癫痫。我们最近发现了一种新的泛素E3连接酶，其作用于GluA 1亚基， AMPAR，神经前体细胞表达发育下调基因4样（Nedd 4 -2）。Nedd 4 -2是 由癫痫相关基因编码，其中三个错义突变已在患者中发现， 患有癫痫我们最近的出版物表明，Nedd 4 -2介导的神经元和大脑兴奋性，在一个神经元， AMPAR依赖性方式（Zhu等人，PLOS Genetics，2017）。然而，目前尚不清楚（1）是否和 Nedd 4 -2如何调节AMPAR以影响兴奋性突触传递;以及（2）癫痫相关的 突变影响Nedd 4 -2在这方面的功能。目标1和目标2旨在回答这些问题。 Nedd 4 -2是肿瘤抑制因子p53的靶基因，并受其转录抑制。我们的工作表明 抑制p53以Nedd 4 -2依赖的方式降低小鼠急性癫痫发作的易感性。这一发现， 结合我们以前的工作，提示p53-Nedd 4 -2是维持大脑兴奋性的一个新的信号转导轴 通过限制AMPAR。目的3研究p53-Nedd 4 -2信号通路与AMPAR的调控 泛素化的小鼠颞叶癫痫的临床前模型，并确定p53-Nedd 4- 2信号在癫痫发生中的作用。成功完成该项目将提高 了解癫痫的离子通道失调，促进治疗癫痫的未来发展 癫痫

Epilepsy affects 3 million people in the United States. Despite the development of current antiepileptic drugs to raise seizure threshold, one-third of epilepsy patients either respond poorly to the drugs or remain drug- resistant. Our research aims to facilitate the understanding neuronal excitability dysregulation in epilepsy with the intention to improve therapeutic outcome. We focus on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA receptor; AMPAR), the most abundant receptor in the nervous system and one of the well- studied excitatory synaptic proteins. Elevated levels of AMPAR have been observed in epilepsy patients, and pharmacologically inhibiting AMPAR has been used in clinical practice for alleviating epilepsy. Despite all these facts, it remains unclear how the homeostasis of AMPAR mediates brain excitability and how dysregulated AMPAR contributes to epilepsy. We recently identified a novel ubiquitin E3 ligase for the GluA1 subunit of AMPAR, neural precursor cell expressed developmentally downregulated gene 4-like (Nedd4-2). Nedd4-2 is encoded by an epilepsy-associated gene, in which three missense mutations have been identified in patients with epilepsy. Our recent publication demonstrated that Nedd4-2 mediates neuronal and brain excitability in an AMPAR-dependent manner (Zhu et al., PLOS Genetics, 2017). However, it remains unknown (1) whether and how Nedd4-2 modulates AMPAR to affect excitatory synaptic transmission; and (2) how epilepsy-associated mutations affect the functions of Nedd4-2 in this regard. Aim 1 and Aim 2 are designed to answer these questions. Nedd4-2 is a target gene of, and transcriptionally repressed by, the tumor suppressor p53. Our work showed that inhibition of p53 reduces acute seizure susceptibility in mice in a Nedd4-2-dependent manner. This finding, together with our previous work, suggests p53-Nedd4-2 as a novel signaling axis to maintain brain excitability presumably through limiting AMPAR. Aim 3 will study the regulation of p53-Nedd4-2 signaling and AMPAR ubiquitination using a preclinical model of temporal lobe epilepsy in mice, and determine the roles of p53-Nedd4- 2 signaling in epileptogenesis in this model. Successfully accomplishing this project will improve the understanding of ion channel dysregulation in epilepsy and foster future development of therapies in treating epilepsy.