Nhamburo P T, Hoffman P L, Tabakoff B
Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, Rockville, MD 20852.
Adv Alcohol Subst Abuse. 1988;7(3-4):103-5. doi: 10.1300/J251v07n03_16.
The acute in vitro effects of ethanol on cerebral cortical adenylate cyclase activity and beta-adrenergic receptor characteristics suggested a site of action of ethanol at Gs, the stimulatory guanine nucleotide binding protein. After chronic ethanol ingestion, the beta-adrenergic receptor appeared to be uncoupled (i.e., the form of the receptor with high affinity for agonist was undetectable), and stimulation of adenylate cyclase activity by isoproterenol or guanine nucleotides was reduced, suggesting an alteration in the properties of Gs. To further characterize this change, cholera and pertussis toxin-mediated 32P-ADP-ribosylation of mouse cortical membranes was assessed in mice that had chronically ingested ethanol in a liquid diet. 32P-labeled proteins were separated by SDS-PAGE and quantitated by autoradiography. There was a selective 30-50% decrease in cholera toxin-induced labeling of 46 kDa protein band in membranes of ethanol-fed mice, with no apparent change in pertussis toxin-induced labeling. The 46 kDa protein has a molecular weight similar to that of the alpha subunit of Gs, suggesting a reduced amount of this protein or a change in its characteristics as a substrate for cholera toxin-induced ADP-ribosylation in cortical membranes of ethanol-fed mice.
乙醇对大脑皮质腺苷酸环化酶活性和β-肾上腺素能受体特性的急性体外效应表明，乙醇的作用位点在Gs，即刺激性鸟嘌呤核苷酸结合蛋白。长期摄入乙醇后，β-肾上腺素能受体似乎发生了解偶联（即对激动剂具有高亲和力的受体形式无法检测到），异丙肾上腺素或鸟嘌呤核苷酸对腺苷酸环化酶活性的刺激作用降低，这表明Gs的特性发生了改变。为了进一步表征这种变化，对长期以液体饮食摄入乙醇的小鼠的小鼠皮质膜进行了霍乱毒素和百日咳毒素介导的32P-ADP-核糖基化评估。通过SDS-PAGE分离32P标记的蛋白质，并通过放射自显影进行定量。在喂食乙醇的小鼠的膜中，霍乱毒素诱导的46 kDa蛋白带标记选择性降低了30-50%，而百日咳毒素诱导的标记没有明显变化。46 kDa蛋白的分子量与Gs的α亚基相似，这表明在喂食乙醇的小鼠的皮质膜中，这种蛋白的量减少或其作为霍乱毒素诱导的ADP-核糖基化底物的特性发生了变化。
