REGULATION OF GABA-A RECEPTOR SUBUNIT EXPRESSION

GABA/A受体是一种异源寡聚整合膜蛋白， 通过打开门控的固有C1通道使膜超极化 神经递质GABA的作用。 受体包含不同的类 的变构位点，通过调节GABA的作用， 这些位点与相应的效应分子的相互作用， 如苯二氮卓类、神经类固醇和内源性肽。 基因 GABA/A受体的编码亚基构成复合物， 调节多基因家族 至少有14种不同的结构相关的 已经从成年大鼠脑中克隆了cDNA，每个cDNA编码一个 在神经元和神经胶质细胞群中发现的受体亚单位。 虽然 形成受体复合物所需的亚基的化学计量不是 已知，很明显， GABA（A）受体由以下物质的组合和化学计量定义： 这些子单位，有理由相信，大量的 受体亚型存在于哺乳动物脑中。 我们已经开发了一种聚合酶链反应衍生的检测方法， 定量每个GABA/A受体亚基mRNA的绝对量 其cDNA序列是可用的。 我们将使用该分析来 分析受体亚基mRNA的表达谱 发育（体内）和小脑颗粒细胞分化， 体外（目标1）。 这些信息将与可比较的 在体内发育过程中进行原位杂交分析（目的2）。 我们将 测试细胞类型特异性表达模式的假设， 受体亚基mRNA受异源（Aim 3）和 同源（Aim 4）受体刺激。 在Aim 5的比赛中，我们将 研究跨突触调节的机制， GABA/A受体亚基mRNA可能是介导的。 其意义 这项工作源于这样一种假设，即GABA/A受体亚型存在于 在离散的神经元群体中， 通过传入突触信号传导施加于突触后神经元。 此外，我们假设这些受体亚型的表达 是通过正常的大脑活动进行生理调整的， 失败，功能变得异常。 理解这一功能 监管可能为新的治疗方法提供可能性， 纠正某些脑功能异常

The GABA/A receptor is a hetero-oligomeric integral membrane protein that hyperpolarizes membranes by opening an intrinsic C1-channel that is gated by the neurotransmitter GABA. The receptor contains different classes of allosteric sites which modulate the action of GABA through the interaction of these sites with corresponding effector molecules, such as benzodiazepines, neurosteroids and endogenous peptides. Genes encoding subunits of the GABA/A receptor constitute a complex and tightly regulated multigene family. At least 14 different, structurally related cDNAs have been cloned from adult rat brain, each of which encodes a receptor subunit found in neuronal and glial populations. Although the stoichiometry of subunits needed to form the receptor complex is not known, it is clear that the physiologic and pharmacologic properties of GABA(A) receptors are defined by the combinations and stoichiometry of these subunits and there are reasons to believe that a vast number of receptor subtypes exists in mammalian brain. We have developed a polymerase chain reaction derived assay for quantitating the absolute amounts of each GABA/A receptor subunit mRNA for which a cDNA sequence is available. We will use this assay to analyze the profiles of expression of the receptor subunit mRNAs during development (in vivo) and as cerebellar granule cells differentiate in vitro (Aim 1). This information will be correlated with a comparable in situ hybridization analysis during development in vivo (Aim 2). We will test the hypothesis that cell type specific patterns of expression of the receptor subunit mRNAs are influenced by both heterologous (Aim 3) and homologous (Aim 4) receptor stimulation. In the contest of Aim 5 we will investigate mechanisms through which the trans-synaptic regulation of GABA/A receptor subunit mRNAs may be mediated. The significance of this work derives from the hypothesis that GABA/A receptor subtypes present in discrete neuronal populations specify the level of response that can be imposed on a post-synaptic neuron by afferent synaptic signaling. Moreover, we hypothesize that the expression of these receptor subtypes is physiologically adjusted by normal brain activity and when this tuning fails, function becomes abnormal. An understanding of this functional regulation may offer the possibility for new therapeutic approaches to rectify certain brain function abnormalities.