Biphasic modulation of GABAA receptor binding by steroids suggests functional correlates
Biphasic modulation of GABAA receptor binding by steroids suggests functional correlates
复制标题
DOI：
10.1023/a:1022524421464
复制
发表时间：
1999-11-01
影响因子：
4.4
通讯作者：
Olsen, RW
中科院分区：
文献类型：
--
作者：
Srinivasan, S;Sapp, DW;Olsen, RW
神经活性类固醇和GABA受体的其他阳性调节剂在调节[S-35]TBPS与大鼠脑膜匀浆结合的有效性和效价方面显示出区域差异，具有双相浓度依赖性。在结合试验中存在的GABA防止类固醇浓度依赖性曲线的增强相，而拮抗剂荷包牡丹碱和RU 5135防止抑制相。使用重组GABAA受体（使用杆状病毒在昆虫细胞系Sf 9中表达），类固醇对[S-35]TBPS结合的增强对γ 2亚基的存在和α亚基的性质敏感（α 1 β 2 γ 2S > α 1 β 2、α 6 β 2、α 6 β 2 γ 2S和α 6 β 2 δ）。在小脑中，RU 5135的加入减少了抑制期，并揭示了神经活性类固醇对TBPS结合的小幅增强。类固醇和GABA位点配体的亚基依赖性相互作用与三态模型一致，其中由GABA或类固醇单配体化的受体对TBPS具有不同于静息状态的亲和力，并且由GABA、类固醇或两者双配体化的受体对TBPS几乎没有亲和力。
Neuroactive steroids and other positive modulators of GABA, receptors showed regional variation in both the efficacy and potency for modulation of [S-35]TBPS binding to rat brain membrane homogenates, with biphasic concentration-dependence. GABA present in the binding assays prevented the enhancement phase of the steroid concentration-dependence plot while the antagonists bicuculline and RU5135 prevented the inhibition phase. Using recombinant GABAA receptors, expressed in insect cell line Sf9 using baculovirus, enhancement by steroids of [S-35]TBPS binding was sensitive to the presence of the gamma 2 subunit and the nature of the a subunit (alpha 1 beta 2 gamma 2S > alpha 1 beta 2, alpha 6 beta 2, alpha 6 beta 2 gamma 2S, and alpha 6 beta 2 delta). As in cerebellum, addition of RU5135 reduced the inhibitory phase and revealed a small enhancement of TBPS binding by neuroactive steroids. The subunit-dependent interactions of steroid and GABA site ligands are consistent with a three-state model in which the receptor mono-liganded by GABA or steroid has a different affinity for TBPS than the resting state, and the receptor biliganded by GABA, steroid, or both has little affinity for TBPS.