Benke D, Fritschy J M, Trzeciak A, Bannwarth W, Mohler H
Institute of Pharmacology, ETH and University of Zurich, Switzerland.
J Biol Chem. 1994 Oct 28;269(43):27100-7.
Native gamma-aminobutyric acid type A (GABAA) receptors containing different beta-subunit variants were identified immunobiochemically with antisera recognizing selectively the beta 1-, beta 2-, or beta 3-subunit. As determined by immunoprecipitation, the beta 2-subunit was present in 55-60% of GABAA receptors, while only minor receptor populations contained the beta 1-subunit (16-18%) or the beta 3-subunit (19-25%). Since the sum of these values amounts to about 100%, it is concluded that GABAA receptors largely contain only a single type of beta-subunit. Pharmacologically, receptors containing the beta 2-subunit differed from those containing the beta 1- or beta 3-subunit by their differential affinities for benzodiazepine receptor ligands. The subunit composition was analyzed biochemically in receptors immunoprecipitated by the beta 2-subunit antiserum. The beta 2-subunit was preferentially associated with the alpha 1-subunit (rarely with the alpha 2-subunit) and with the gamma 2-subunit; negligible or no immunoreactivity was detected for the alpha 3-, alpha 5-, or beta 1-subunit. A stringent co-expression of alpha 1- and beta 2-subunits was confirmed by double immunofluorescence staining on the cellular level. Neurons expressing the beta 3-subunit immunoreactivity were largely double labeled by the alpha 2-subunit antiserum. Thus, the subunit combinations alpha 1 beta 2 gamma 2 and alpha 2 beta 3 gamma 2 represent two main GABAA receptor subtypes, which together amount to 75-85% of the diazepam-sensitive GABAA receptors.
用选择性识别β1、β2或β3亚基的抗血清通过免疫生物化学方法鉴定了含有不同β亚基变体的天然γ-氨基丁酸A型（GABAA）受体。通过免疫沉淀测定，β2亚基存在于55%-60%的GABAA受体中，而只有少量受体群体含有β1亚基（16%-18%）或β3亚基（19%-25%）。由于这些值的总和约为100%，因此得出结论，GABAA受体在很大程度上仅包含单一类型的β亚基。在药理学上，含有β2亚基的受体与含有β1或β3亚基的受体在对苯二氮䓬受体配体的亲和力上存在差异。通过β2亚基抗血清免疫沉淀的受体对其亚基组成进行了生化分析。β2亚基优先与α1亚基（很少与α2亚基）和γ2亚基结合；未检测到α3、α5或β1亚基的免疫反应性或免疫反应性可忽略不计。通过细胞水平的双重免疫荧光染色证实了α1和β2亚基的严格共表达。表达β3亚基免疫反应性的神经元在很大程度上被α2亚基抗血清双重标记。因此，亚基组合α1β2γ2和α2β3γ2代表两种主要的GABAA受体亚型，它们总共占地西泮敏感GABAA受体的75%-85%。
