Pregnenolone sulfate block of GABAA receptors:: mechanism and involvement of a residue in the M2 region of the α subunit
Pregnenolone sulfate block of GABAA receptors:: mechanism and involvement of a residue in the M2 region of the α subunit
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DOI：
10.1111/j.1469-7793.2001.0673e.x
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发表时间：
2001-05-01
影响因子：
5.5
通讯作者：
Steinbach, JH
中科院分区：
文献类型：
--
作者：
Akk, G;Bracamontes, J;Steinbach, JH
1.神经甾体在脑中产生，并可对神经元的膜通道具有快速作用。硫酸孕烯醇酮（PS）是一种硫酸化神经类固醇，其降低γ-氨基丁酸A（GABA（A））受体的反应。我们分析了PX对由α 1、β 2和γ 2L亚基形成的重组GABA（A）受体的单通道电流的作用.电流是由一定浓度的GABA引起的，该浓度引起半最大响应（50 μ M）和饱和浓度（1 mM）。PS减少了单通道活动的集群在任何浓度的GABA的持续时间。3. PS对快速过程没有明显影响：对通道开放和关闭没有明显影响，对GABA亲和力也没有明显影响，并且快速恢复的脱敏状态不受影响。相反，PS产生了一种缓慢发展的阻滞，其发生率与具有开放或封闭通道以及具有一个或两个结合GABA分子的受体相似。阻断率与膜电位无关，这意味着带电荷的硫酸根部分不会穿过膜场。α 1亚基通道衬里部分的细胞内末端附近的特定残基的变化对阻滞速率有重大影响。残基α 1 V256 S的突变使阻断率降低了30倍。β 2亚基同源位置的突变（β 2 A252 S）没有影响，γ 2L亚基的互补突变（γ 2LS 266 A）也没有影响。这似乎是可能的，这个残基是参与了一个构象变化的基础块PS，而不是明的一部分结合位点的PS。
1. Neurosteroids are produced in the brain, and can have rapid actions on membrane channels of neurons. Pregnenolone sulfate (PS) is a sulfated neurosteroid which reduces the responses of the gamma -aminobutyric acid A (GABA(A)) receptor. We analysed the actions of PX on single-channel currents from recombinant GABA(A) receptors formed from alpha1, beta2 and gamma 2L subunits.2. Currents were elicited by a concentration of GABA eliciting a half-maximal response (50 muM) and a saturating coneentration (1 mM). PS reduced the duration of clusters of single-channel activity at either concentration of GABA.3. PS had no discernable effect on rapid processes: no effects were apparent on channel opening and closing, nor on GABA affinity, and a rapidly recovering desensitised state was not affected. Instead, PS produced a slowly developing block which occurred at a similar rate for receptors with open or closed channels and with one or two bound GABA molecules.4. The rate of block was independent of membrane potential, implying that the charged sulfate moiety does not move through the membrane field.5. Change in a specific residue near the intracellular end of the channel lining portion of the alpha1 subunit had a major effect on the rate of block. Mutation of the residue alpha1 V256S reduced the rate of block by 30-fold. A mutation at the homologous position of the beta2 subunit (beta2 A252S) had no effect, nor did a complementary mutation in the gamma 2L subunit (gamma 2LS266A). It seems likely that this residue is involved in a conformational change underlying block by PS, instead of for ming part of the binding site for PS.