Molecular Analysis of Drosophila GABA Transporters

γ -氨基丁酸（GABA）是脊椎动物和无脊椎动物神经系统中主要的抑制性神经递质。GABA转运体通过选择性地从突触间隙中再摄取GABA，在很大程度上介导GABA刺激的抑制反应的终止。在这种生理背景下，高效的GABA转运机制确保了神经传递的保真度。此外，哺乳动物GABA转运体异构体的多样性被认为调节GABA能神经传递的不同方面；初步研究表明果蝇也是如此。我们从果蝇头部文库中克隆了几个部分GABA转运体同源cdna，显示出与哺乳动物GABA转运体广泛的序列同源性。果蝇体内实验可获得的GABA转运体（DGATs）的存在，有助于采用分子遗传学方法更好地理解GABA对行为的神经化学作用。我们假设，gaba介导的神经传递通过干扰DGAT功能将导致异常行为的改变。我们还假设DGAT家族的不同成员调节gaba介导的行为的不同方面。为了验证这些假设，我们将解决三个具体目标：1)我们将分析由GABA转运蛋白功能和GABA介导的神经传递扰动引起的成虫药物诱导行为。2)我们将鉴定果蝇GABA转运蛋白家族（DGATs）的不同成员，并通过在昆虫细胞中的表达对其进行功能表征。3)我们将分析GABA转运体表达异常的果蝇突变株的行为表型。提出的工作将扩展我们对gaba介导的神经传递的基本调节机制的认识。

Gamma-aminobutryic acid (GABA) is the principal inhibitory neurotransmitter in both vertebrate and invertebrate nervous systems. GABA transporters largely mediate termination of GABA-stimulated inhibitory responses by the selective reuptake of GABA from the synaptic cleft. In this physiological context, efficient GABA transport mechanisms ensure the fidelity of neurotransmission. In addition, diversity in the mammalian GABA transporter isoforms is believed to regulate different aspects of GABAergic neurotransmission; preliminary work suggests the same is true for Drosophila. We cloned several partial GABA transporter-homologous cDNAs from a Drosophila head library that displayed extensive sequence homology with mammalian GABA transporters. The existence of experimentally accessible GABA transporters in Drosophila (DGATs) facilitates undertaking a molecular- genetic approach to better understand the neurochemical actions of GABA on behaviors. We hypothesize that alterations in GABA-mediated neurotransmission via perturbations in DGAT function will result in aberrant behaviors. We also hypothesize that different members of the DGAT family regulate different aspects of GABA-mediated behaviors. To verify these hypotheses, we will address three specific aims: 1) We will analyze pharmacologically induced behaviors In the adult fly that result from perturbations in GABA transporter function and GABA- mediated neurotransmission. 2) We will identify distinct members of the Drosophila GABA transporter family (DGATs) and functionally characterize the proteins by expressing them in Insect cells. 3) We will analyze the behavioral phenotypes of mutant strains of flies with abnormal GABA transporter expression. The proposed work will extend our knowledge of basic regulatory mechanisms governing GABA-mediated neurotransmission.