Structure and Function of GABA-A Receptors

GABA-A受体是中枢神经中含量最丰富的抑制性神经递质受体 该系统是无数治疗化合物和药物滥用的目标。神经系统的功能 受兴奋性和抑制性信号的平衡控制；GABA-A受体功能障碍导致 焦虑症和兴奋性毒性障碍，包括癫痫。这种五聚体配体的主要异构体-门控 氯通道存在于脑内的突触后膜上。氨基丁酸(γ-氨基丁酸)是 内源性神经递质和该受体的激动剂。苯二氮类药物，如安定(安定)和 咪达唑仑(VERED)是一种正变构调节剂，美国5%的人服用它来治疗焦虑和失眠。 巴比妥类药物如戊巴比妥，麻醉剂如异氟醚和异丙酚，神经类固醇和乙醇都是 正向调节因子通过非重叠位点起作用。这种丰富的药理作用源于络合物 突触GABA-A受体的亚单位组装。主要的突触亚型由两个α1组成 亚基、两个β2亚基和一个γ2亚基。在这里，我们建议解决缺乏结构性信息的问题 使用直接方法的生理性GABA-A受体。在三个具体目标中，我们建议澄清 苯二氮卓增强这些受体的结构机制，执行互补 对重组受体进行电生理实验，并对其结构进行平行表征 巴比妥酸盐、麻醉药和神经类固醇调节的基本原理。这两个结构性目标是 独立的，并将产生基本新的和不同的结构信息的主要GABA-A 中枢神经系统中的受体类型，与细胞外和跨膜部位的配体形成复合体。这个 功能目标补充了确定苯二氮卓类药物结合、疗效的决定因素的结构工作 和变构信号。结构和功能的总和将阐明定义异构体的原理 组装和配体识别，并将阐明药物结合如何改变分子行为，具有广泛的 Cys-loop受体超家族的相关性。

The GABA-A receptor is the most abundant inhibitory neurotransmitter receptor in the central nervous system and is the target of myriad therapeutic compounds and drugs of abuse. Function of the nervous system is governed by a balance of excitatory and inhibitory signaling; GABA-A receptor dysfunction results in disorders of anxiety and excitotoxicity including epilepsy. The principal isoform of this pentameric ligand-gated chloride channel is found on post-synaptic membranes in the brain. GABA (γ-aminobutyric acid) is the endogenous neurotransmitter and agonist of this receptor. Benzodiazepines, like diazepam (Valium) and midazolam (Versed), are positive allosteric modulators taken by 5% of the US for anxiety and insomnia. Barbiturates like pentobarbital, anesthetics like isoflurane and propofol, neurosteroids, and ethanol are all positive modulators acting through non-overlapping sites. This rich pharmacology derives from the complex subunit assembly of the synaptic GABA-A receptor. The predominant synaptic isoform consists of two α1 subunits, two β2 subunits and one γ2 subunit. Here we propose to address a lack of structural information on physiological GABA-A receptors using a direct approach. In three Specific Aims, we propose to elucidate the structural mechanism of benzodiazepine potentiation of these receptors, perform complementary electrophysiological experiments on the recombinant receptor, and in parallel characterize the structural principles underlying modulation by barbiturates, anesthetics and neurosteroids. The two structural Aims are independent and will yield fundamentally new and distinct structural information for the principal GABA-A receptor type in the central nervous system in complex with extracellular and transmembrane-site ligands. The functional Aim complements the structural work to define determinants for benzodiazepine binding, efficacy and allosteric signaling. The sum of structures and function will illuminate principles defining heteromer assembly and ligand recognition and will elucidate how drug binding changes molecular behavior, with broad relevance across the Cys-loop receptor superfamily.