GABA(A) RECEPTOR SUBTYPES - LIGAND-BINDING HETEROGENEITY DEMONSTRATED BY PHOTOAFFINITY-LABELING AND AUTORADIOGRAPHY
GABA(A) RECEPTOR SUBTYPES - LIGAND-BINDING HETEROGENEITY DEMONSTRATED BY PHOTOAFFINITY-LABELING AND AUTORADIOGRAPHY
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DOI：
10.1111/j.1471-4159.1993.tb13643.x
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发表时间：
1993-10-01
影响因子：
4.7
通讯作者：
OLSEN, RW
中科院分区：
文献类型：
--
作者：
BUREAU, MH;OLSEN, RW
在大鼠中枢神经系统中，在GABA和苯二氮卓类识别位点，观察到γ-氨基丁酸A型（GABA（A））受体与多种配体的结合亲和力的异质性。[H-3]氟硝西泮和[H-3]蝇蕈醇对亲和柱纯化的受体蛋白的光亲和标记通过十二烷基硫酸钠中的凝胶电泳进行检查。麻醉剂巴比妥酸盐（戊巴比妥）和类固醇（阿法沙酮）都有差异地刺激[H-3]氟硝西泮掺入51-kDa α 1亚基比掺入53-kDa α 2多肽更多，[H-3]蝇蕈醇掺入55-kDa β 2亚基比掺入58-kDa β 3多肽更多。与这些多肽的结合也受到其他变构调节剂和竞争性抑制剂的不同影响，包括苯二氮卓类“1型”选择性配体CL 218，872。这种药物对单个51-kDa α 1多肽的异源亲和力强烈表明I型受体与II型受体一样是异质性的。在脑切片中，[H-3]蝇蕈醇结合的增强程度表现出显着的区域变化，类似的类固醇和巴比妥类药物，GABA类似物THIP和牛磺酸抑制蝇蕈醇结合的区域变化的亲和力，几乎是彼此相反。调节[H-3]氟硝西泮结合类固醇，巴比妥类药物，和THIP显着不同的地区。两者合计，配体结合异质性表现出的光亲和标记和放射自显影证明存在多种药理学结合亚型的多个多肽基因产物组合成几个寡聚异源受体。结合亚型的区域分布与不同亚基基因产物的区域分布的比较允许关于存在于脑中的天然药理学受体亚型的可能亚基组成的以下结论：苯二氮卓类药物的寡聚体受体亚型的性质依赖于α和α以外的亚基，GABA-苯二氮卓类偶联依赖于α亚基的性质，GABA位点药理学取决于β亚基的性质，包括α和β在内的几种亚基有助于对类固醇和巴比妥类药物的敏感程度。最后，离散亚基的存在可能是必要的，但不足以假定一个定义的药理学性质。
Heterogeneity of binding affinities for a variety of ligands was observed for gamma-aminobutyric acid type A (GABA(A)) receptors in the rat CNS, at both GABA and benzodiazepine recognition sites. Photoaffinity labeling by [H-3]flunitrazepam and [H-3]muscimol to affinity column-purified receptor proteins was examined by gel electrophoresis in sodium dodecyl sulfate. Anesthetic barbiturates (pentobarbital) and steroids (alphaxalone) both differentially stimulated the incorporation of [H-3]flunitrazepam more so into the 51-kDa alpha1 subunit than into the 53-kDa alpha2 polypeptide, and incorporation of [H-3]muscimol into the 55-kDa beta2 subunit more so than the 58-kDa beta3 polypeptide. Binding to these polypeptides was also affected differentially by other allosteric modulators and competitive inhibitors, including the benzodiazepine ''type 1 '' selective ligand CL218,872. Heterogeneity in affinity of this drug for the single 51-kDa alpha1 polypeptide strongly suggests that type I receptors, like type II, are heterogeneous. In brain sections, the extent of enhancement of [H-3]muscimol binding showed significant regional variation, similar for both steroids and barbiturates, and the GABA analogues THIP and taurine inhibited muscimol binding with regional variations in affinity that were almost opposites of each other. Modulation of [H-3]flunitrazepam binding by steroids, barbiturates, and THIP significantly varied with regions. Taken together, ligand binding heterogeneity exhibited by photoaffinity labeling and autoradiography demonstrate the existence of multiple pharmacological-binding subtypes resulting from the combination of multiple polypeptide gene products into several oligomeric isoreceptors. Comparison of the regional distribution of binding subtypes with that of different subunit gene products allows the following conclusions about possible subunit compositions of native pharmacological receptor subtypes present in the brain: Benzodiazepine pharmacology of the oligomeric receptor isoforms is dependent on the nature of a and subunits other than alpha, GABA-benzodiazepine coupling is dependent on the nature of the alpha subunits, GABA site pharmacology is dependent on the nature of the beta subunits, and several subunits including alpha and beta contribute to the degree of sensitivity to steroids and barbiturates. Finally, the presence of discrete subunits may be necessary but is not sufficient to postulate a defined pharmacological property.