AMPA Receptor Ubiquitination and Pathological Synaptic Hyperexcitability

美国有300万人患有癫痫。尽管目前抗癫痫药物的发展 药物提高癫痫发作阈值，三分之一的癫痫患者要么对药物反应差，要么继续用药- 抵抗力强。我们的研究旨在促进对癫痫患者神经元兴奋性异常的认识。 改善治疗结果的意图。我们专注于α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic 酸性受体(AMPA Receptor；AMPAR)是神经系统中含量最丰富的受体，也是最重要的受体之一。 研究兴奋性突触蛋白。在癫痫患者中观察到AMPAR水平升高， 药物抑制AMPAR已用于临床缓解癫痫。尽管如此， 事实是，AMPAR的动态平衡如何调节大脑兴奋性以及如何失调仍不清楚。 Ampar会导致癫痫。我们最近发现了一种新的泛素E3连接酶，它是GluA1亚单位的 神经前体细胞AMPAR表达发育下调基因4-样(Nedd4-2)。NedD4-2是 由癫痫相关基因编码，已在患者中发现三个错义突变 患有癫痫。我们最近发表的文章表明，Nedd4-2介导了神经元和大脑的兴奋性。 Ampar依赖的方式(朱等人，PLOS Genetics，2017)。然而，目前仍不清楚(1)是否和 Nedd4-2如何调节AMPAR以影响兴奋性突触传递；以及(2)如何与癫痫相关 突变会影响Nedd4-2在这方面的功能。目标1和目标2旨在回答这些问题。 Nedd4-2是肿瘤抑制基因P53转录抑制的靶基因。我们的工作表明 P53的抑制以Nedd4-2依赖的方式降低了小鼠的急性癫痫敏感性。这一发现， 结合我们以前的工作，我们认为P53-Ned4-2是维持大脑兴奋性的一个新的信号轴 大概是通过限制AMPAR。目的3研究P53-Nedd4-2信号转导和AMPAR的调控 利用小鼠颞叶癫痫临床前模型泛素化，并确定P53-Nedd4- 2在此模型中癫痫发生的信号转导。成功完成这一项目将提高 认识癫痫患者离子通道调节障碍，促进未来治疗方法的发展 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.