The role of ubiquitination in regulating GABA(A) receptor functional expression

描述(申请人提供)：-氨基丁酸(GABAA)受体是大脑中突触抑制的关键部位，也是治疗药物的关键药物靶点，包括苯二氮卓类药物、巴比妥酸盐、全身麻醉药和神经类固醇。此外，GABAA受体功能受损是许多CMS病理的核心，包括癫痫、焦虑、睡眠障碍、成瘾、自闭症、精神发育迟滞、抑郁症和精神分裂症。赖氨酸残基的泛素化是调节蛋白质半衰期和胞内命运的一种常用的细胞机制。这一公认的范式加上我们的初步研究，使我们形成了一个中心假说，推动了这一提议中描述的实验：GABAA受体受到赖氨酸残基与单个受体亚单位的胞内域的直接泛素化，这一过程受到神经元活动的动态调节。依赖于泛素化的亚基，这种共价修饰可以减少分泌途径中的受体半衰期或增强溶菌体靶向性，从而调节GABAA受体细胞表面的稳定性和突触抑制的效果。我们的努力将集中在四个互补但不同的实验目标上：1.检验GABAA受体3亚单位泛素化通过调节质膜插入来调节受体细胞表面稳定性的假说2.检验GABAA受体2亚单位泛素化通过调节溶菌体靶向调节受体细胞表面稳定性的假说3.检验泛素化调节GABAA受体介导的突触抑制效应的假说4.检验神经元活动通过共同调节受体泛素化来调节GABAA受体细胞表面稳定性的假说，我们的方法将为更深入地理解调控GABAA受体在突触部位聚集的主要决定因素提供更深入的了解。这些研究的结果将有可能对开发新的治疗策略做出重大贡献，这些疾病包括癫痫、焦虑、睡眠障碍、成瘾、自闭症、精神发育迟滞、抑郁症和精神分裂症。

DESCRIPTION (provided by applicant): ?-aminobutyric acid (GABAA) receptors are key sites of synaptic inhibition in the brain and are critical drug targets for therapeutic agents including benzodiazepines, barbiturates, general anesthetics and neurosteroids. Moreover compromised GABAA receptor function is central to a number of CMS pathologies including epilepsy, anxiety, sleep disorders, addiction, autism, mental retardation, depression and schizophrenia. Ubiquitination of lysine residues is a commonly used cellular mechanism to regulate both protein half-life and the endocytic fate. This accepted paradigm together with our preliminary studies has led us to formulate a central hypothesis driving the experiments described in this proposal: GABAA receptors are subject to direct ubiquitination of lysine residues with the intracellular domains of individual receptor subunits, a process that is subject to dynamic modulation by neuronal activity. Depending on the subunit ubiquitinated this covalent modification acts to decrease receptor half-life within the secretory pathway or enhances lysozomal targeting, thereby modulating GABAA receptor cell surface stability and the efficacy of synaptic inhibition. Our efforts will center on four complementary but distinct experimental goals: 1. To test the hypothesis that GABAA receptor ¿3 subunit ubiquitination regulates receptor cell surface stability by modulating insertion at the plasma membrane 2. To test the hypothesis that GABAA receptor ?2 subunit ubiquitination regulates receptor cell surface stability by modulating lysozomal targeting 3. To test the hypothesis that ubiquitination modulates the efficacy of synaptic inhibition mediated by GABAA receptors 4. To test the hypothesis that neuronal activity regulates GABAA receptor cell surface stability by modulating receptor ubiquitination Together, our approaches will provide a more thorough understanding of the primary determinants that regulate accumulation of GABAA receptors at synaptic sites. The results of these studies will have the potential to make significant contributions to the development of novel therapeutic strategies for such debilitating disorders as epilepsy, anxiety, sleep disorders, addiction, autism, mental retardation, depression and schizophrenia.