Studies on the structure of gamma-aminobutyric acid type A receptor subtypes

A型γ-氨基丁酸受体（GABAAR）是一种亲氯配体门控离子通道 介导成人大脑中的快速阶段性突触抑制，并且是巴比妥类药物的药物靶点， 苯二氮卓类、静脉麻醉剂和神经类固醇。与其在调节 神经元兴奋性、GABAAR活性的改变导致焦虑、自闭症、抑郁、癫痫， 药物滥用和精神分裂症。受体是可以由α（1-6）组装的杂五聚体， β（1-3）、γ（1-3）、δ、ε、θ和π亚基。令人惊讶的是，到目前为止，我们对天然药物分子结构的理解 GABAARs亚型以及这些蛋白质如何靶向抑制性突触尚不清楚。但这些 考虑到GABAAR在决定神经元兴奋性中的关键作用， 神经精神疾病和药物靶点。 为了解决这些问题，我们将确定组装的主要GABAAR亚型的结构 α1和α2亚基的合成然后，我们将评估哪些蛋白质与这些受体亚型共纯化。 最丰富的“受体相关蛋白”在不同GABAAR的突触靶向中发挥的作用 然后将检查亚型。我们的研究将通过我们在2010年开发的新型小鼠品系来促进。 其中α1和α2亚基的N-末端已经用不同的荧光报告基因修饰; pHlourin/9E10-α2（pHα2）和mKate/FLAG-α1（mKα1）。这些增加的功能是无声的，但允许 单个GABAAR亚型的连续亲和纯化，并使用蓝色-天然 聚丙烯酰胺凝胶电泳（BN-PAGE），然后进行液相色谱-质谱联用 （LC-MS/MS）。使用这些新工具的初步实验使我们能够制定一个中心假设 α2和α1亚基组装成两种不同的GABAAR亚型; 'α2/α1' 含有等摩尔量的两种α亚基（α2α1βγ2）和不含α 2 α 1 β γ 2的“α1/α1”。 亚基（α1βγ2）。这些亚型通过血影蛋白靶向不同的突触子集， 与这些GABAAR亚型密切相关。我们的实验将集中在以下具体的 目的： 目标1.为了验证神经元组装GABAAR亚型的假设， α1βγ2亚基。目标2.为了验证α2/α1和α1/α1 GABAAR亚型与GABAAR的表达相关的假设， 不同的幽灵。目标3.为了验证血影蛋白促进突触特异性 以伽马-氨基丁酸为目标。 总的来说，我们的研究将为天然GABAAR的结构和过程提供新的见解。 调节它们在抑制性突触处的积累，这些信息可能会导致对 以及癫痫和其他神经精神疾病的治疗。

Type A γ-aminobutyric receptors (GABAAR) are Cl--preferring ligand gated ion channels that mediate fast phasic synaptic inhibition in the adult brain and are are drug targets for barbiturates, benzodiazepines, intravenous anesthetics, and neurosteroids. Consistent with their essential role in regulating neuronal excitability, modification in GABAAR activity contribute to anxiety, autism, depression, epilepsy, substance abuse and schizophrenia. The receptors are heteropentamers that can be assembled from α(1-6), β(1-3), γ(1-3), δ, ε, θ and π subunits. Surprisingly, to date our comprehension of the molecular structure of native GABAARs subtypes, and how these proteins are targeted to inhibitory synapses is rudimentary. However, these issues are of fundamental importance given the critical role GABAARs play in determining neuronal excitability, in neuropsychiatric diseases and as drug targets. To address these issues, we will determine the structure of the principal GABAAR subtypes assembled from α1 and α2 subunits in the brain. We will then assess which proteins co-purify with these receptor subtypes. The roles that the most abundant “receptor-associated proteins” play in the synaptic targeting of distinct GABAAR subtypes will then be examined. Our studies will be facilitated by the novel mouse lines we have developed in which the N-terminus of the α1 and α2 subunits have been modified with distinct fluorescent reporters; pHlourin/9E10-α2 (pHα2) and mKate/FLAG-α1 (mKα1). These additions are functionally silent but allow sequential affinity purification of individual GABAAR subtypes, and analysis of their structure using blue-native polyacrylamide gel electrophoresis (BN-PAGE) followed by liquid chromatography coupled mass spectroscopy (LC-MS/MS). Preliminary experiments using these new tools have allowed us to formulate a central hypothesis that will be tested here; α2- and α1-subunits are assembled into two distinct GABAAR subtypes; ‘α2/α1’ containing equimolar amounts of both α subunits (α2α1βγ2), and ‘α1/α1’ which does not contain an α2 subunit (α1βγ2). These subtypes are targeted to distinct subsets of synapses by spectrins, which are intimately associated with these GABAAR subtypes. Our experiments will focus on the following specific aims: Aim 1. To test the hypothesis that neurons assemble GABAAR subtypes containing α2α1βγ2 and α1βγ2 subunits. Aim 2. To test the hypothesis that the α2/α1 and α1/α1 GABAAR subtypes are associated with distinct spectrins. Aim 3. To test the hypothesis that spectrins facilitate the synapse-specific targeting of GABAARs. Collectively, our study will provide novel insights into the structure of native GABAARs and the processes that regulate their accumulation at inhibitory synapses, information that may lead to improved understanding of, and treatments for epilepsy and other neuropsychiatric disorders.