Molecular genetical analysis on structure and function of GABA_A and GABA_B receptors

对脑GABA_A和GABA_B受体进行了分子遗传学和分子药理学研究，结果表明：1）人脑GABA_A受体α_1亚基由456个氨基酸残基组成，其序列与牛脑相似; 2)GABA_A受体α ^<>1亚基在人脑中表达单一mRNA（4.6Kb）。3)人脑GABA_A受体α_1亚基具有外显子-内含子结构。4)人脑GABA_A受体α_1亚单位由4个跨膜区组成。5)人脑GABA_A受体α_1亚单位mRNA的显微注射诱导功能相关的GABA_A受体的表达。6)小鼠和大鼠脑中GABA_A受体α_1亚基由两个mRNA（4.1和-4.6K）通过选择性剪接表达。7)GABA_（B）受体的纯化倍数达13，000倍。8)GABA_（B）受体通过Gi或Go蛋白与腺苷酸环化酶、磷酸肌醇周转酶和钙通道负性偶联，这种偶联可被受体的增溶所消除。9)GABA_B受体是一种分子量为80 Kda的糖蛋白。10)GABA_A受体激动剂可使GABA_A受体表达下调，这种下调是通过抑制mRNA表达而引起的。11)纯化的GABA_A和GABA_B受体均可在磷脂囊泡上功能性重构。12)GABA_A和GABA_B受体的单克隆抗体（GA-1：Ige，GB-1：IgM）通过将各自的受体蛋白注射到BalB/C小鼠中并通过随后筛选特异性克隆而获得。13)利用纯化和重组的GABA_A和GABA_B受体蛋白可分析各种药物对这两种受体的直接作用。

Molecular genetical and molecular pharmacological studies on cerebral GABA_A and GABA_B receptors have been employed and the following results were obtained.1) The alpha_1-subunits of human brain GABA_A receptor consists of 456 amino acid residues and its sequence is similar to that of bovine brain. 2) The single mRNA (4.6Kb) for GABA_A receptor alpha^<>1-subunit is expressed in human brain. 3) The alpha_1-subunit of GABA_A receptor in the human brain possesses exon-intron organization. 4) The alpha_1-subunit of GABA_A receptor in the human brain consists of four transmembrane domains. 5) The microinjection of mRNA for GABA_A receptor alpha_1-subunit from the human brain induces the expression of functionally relevant GABA_A receptor. 6) The GABA_A receptor alpha_1-subunit in the mouse and rat brains is expressed from two mRNAs (4.1 and-4.6K) by an alternative splicing. 7) The 13, 000 fold purification of GABA_B receptor is achieved by baclofen-affinity column chromatography. 8) The GABA_B receptor is negatively coupled with adenylate cyclas, inositol phosphate turnover and calcium channel via Gi or Go protein and these couplings can be eliminated by solubilization of the receptor. 9) The GABA_B receptor is a glycoprotein having the molecular weight of 80 Kda. 10) The GABA_A receptor can be down-regulated by a prolonged exposure to its agonist and this downregulation is caused by the suppression of the expression of mRNA. 11) Both purified GABA_A and GABA_B receptors can be functionally reconstituted on phospholipid vesicles. 12) Monoclonal antibodies for GABA_A and GABA_B receptors (GA-I : Ige, GB-I : IgM) are obtained by the injection of respective receptor protein to Balb/C mouse and by the subsequent screening of specific clones. 13) The derect actions of various drugs on GABA_A and GABA_B receptors can be analyzed using purified and reconstituted each receptor protein.