REGULATION OF GABA-A RECEPTOR SUBUNIT EXPRESSION

GABA/A受体是一种异源寡聚体完整膜蛋白， 通过打开被选通的固有的c1通道使膜超极化 通过神经递质GABA。受体包含不同的类别 通过调节GABA的作用的变构位点 这些部位与相应的效应器分子的相互作用，如 如苯二氮类药物、神经类固醇和内源性多肽。基因 编码GABA/A受体的亚基构成了一个复杂而紧密的 受调控的多基因家族。至少14种不同的、结构相关的 已从成年大鼠的脑中克隆出cDNA，每个cDNA编码一个 在神经元和神经胶质细胞中发现的受体亚单位。尽管 形成受体复合体所需亚基的化学计量比不是 已知，很明显，它的生理和药理特性 GABA(A)受体由以下各项的组合和化学计量来定义 这些亚基，有理由相信，大量的 哺乳动物大脑中存在受体亚型。 我们已经建立了一种聚合酶链式反应衍生的分析方法 定量测定各GABA/A受体亚单位mRNA的绝对量 它的cdna序列是可用的。我们将利用这一化验方法 分析受体亚单位mRNAs的表达谱 发育(体内)和小脑颗粒细胞分化 体外实验(目标1)。这一信息将与可比的 体内发育过程中的原位杂交分析(目标2)。我们会 测试细胞类型特定的表达模式的假设 受体亚单位mRNAs同时受异源(目标3)和 同源(目标4)受体刺激。在目标5的较量中，我们将 探讨脑内跨突触调节的机制 GABA/A受体亚单位mRNAs可能参与了这一过程。这件事的意义 这项工作源于GABA/A受体亚型存在的假设 在离散的神经元群体中指定反应的水平， 通过传入突触信号施加于突触后神经元。 此外，我们假设这些受体亚型的表达 是由正常的大脑活动进行生理调节的，当这种调节 出现故障，则功能变得异常。对此功能的理解 监管可能为新的治疗方法提供可能性 纠正某些大脑功能异常。

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.