Effect of thiol group modification on ion flux and ligand binding properties of the GABAA-benzodiazepine receptor chloride channel complex.
Effect of thiol group modification on ion flux and ligand binding properties of the GABAA-benzodiazepine receptor chloride channel complex.
复制标题
硫醇基团修饰对 GABAA-苯二氮卓受体氯离子通道复合物的离子通量和配体结合特性的影响。
DOI：
10.1002/syn.890100405
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Baier,LD
中科院分区：
文献类型：
--
作者：
Allan,AM;Baier,LD
修饰硫醇基团的试剂已显示改变在多种受体位点处的配体结合。此外，巯基的烷基化已显示出阻断离子通道电导。我们研究了巯基试剂对γ-氨基丁酸（GABA）激活的氯离子通量（36 Cl −）和[3 H]-地西泮在小鼠脑膜制备物（微囊）中结合的影响。在氯化汞（HgC 12）、对氯汞苯磺酸（pCMBS）、苯甲酸羟汞（HMB）、N-乙基马来酰亚胺（NEM）或碘乙酸（IAA）存在下孵育微囊可减弱GABA刺激的Cl−摄取。巯基试剂降低了GABA诱导Cl−摄取的最大刺激和效力。巯基试剂处理降低了高亲和力[3 H]-蝇蕈醇平衡结合的亲和力。在不存在GABA激动剂的情况下，从用pCMBS处理的微囊制备的上清液刺激未暴露于硫醇试剂的微囊中的Cl−摄取。取自pCMBS处理的微囊的上清液也刺激[3 H]-地西泮结合。这种作用被GABA受体拮抗剂荷包牡丹碱阻断。来自pCMBS处理的微囊的上清液中的内源性GABA的浓度是来自对照微囊的上清液中的内源性GABA的浓度的六倍。巯基试剂导致内源性GABA水平增加是由于GABA释放增加和高亲和力GABA摄取减少。
Agents that modify thiol groups have been shown to alter ligand binding at a variety of receptor sites. In addition, alkylation of sulfhydryls has been shown to block ion channel conductance. We studied the effects of thiol reagents on γ‐aminobutyric acid (GABA)‐activated chloride flux (36Cl−) and [3H]‐diazepam binding in mouse brain membrane preparation (microsacs). Incubation of microsacs in the presence of: mercuric chloride (HgC12), p‐chloromercuriphenylsulfonic acid (pCMBS), hydroxymercuribenzoate (HMB), n‐ethylmaleimide (NEM), or iodoacetic acid (IAA) attenuated GABA‐stimulated Cl−uptake. The thiol reagents reduced both maximal stimulation and the potency of GABA to induce Cl−uptake. Thiol reagent treatment decreased the affinity of high‐affinity [3H]‐muscimol equilibrium binding. Supernatant prepared from microsacs treated with pCMBS stimulated Cl−uptake in the absence of GABA agonist in microsacs unexposed to thiol reagents. The supernatant taken from pCMBS‐treated microsacs also stimulated [3H]‐diazepam binding. This effect was blocked by the addition of the GABA receptor antagonist bicuculline. The concentration of endogenous GABA in supernatant from pCMBS‐treated microsacs was sixfold greater than that in supernatant from control microsacs. This increase in levels of endogenous GABA by thiol reagents was due to both an increase in GABA release and a decrease in high‐affinity GABA uptake.