期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1987
卷号：84
期号：8
页码：2246-2250
DOI：10.1073/pnas.84.8.2246
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We proposed that a rapidly turning over protein, induced in response to catecholamine stimulation of C6-2B rat astrocytoma cells, inhibits subsequent hormonal activation of adenylate cyclase. Studies upon which our hypothesis is based and confirmatory work in a variety of other cell lines and in vivo have utilized actinomycin D and cycloheximide to inhibit RNA and protein synthesis, respectively. These inhibitors, however, are not specific and have been reported also to interfere with other cellular processes. Diphtheria toxin is a specific protein synthesis inhibitor that acts only by ADP-ribosylating elongation factor 2, thus preventing peptide chain elongation. We thus tested whether diphtheria toxin could prevent catecholamine-induced desensitization in A431 human epidermoid carcinoma cells. The toxin inhibited protein synthesis and altered the time course of isoproterenol-stimulated cAMP accumulation as did the less-specific protein synthesis inhibitor cycloheximide. Cellular cAMP content after a 30-min exposure to isoproterenol was similar in control and in toxin-treated cells. However, after 4 hr of treatment with isoproterenol, toxin-treated cells accumulated up to six times more cAMP than controls. When cells or cell-free adenylate cyclase preparations were rechallenged with agonists, toxin-mediated inhibition of protein synthesis prevented desensitization. These results show that diphtheria toxin, a specific inhibitor of protein synthesis, can interfere with the normal physiological regulation of cAMP metabolism in eukaryotic cells and provide compelling evidence that catecholamine stimulation of adenylate cyclase promotes the synthesis of a protein(s) that, in some way, inhibits hormone-stimulated adenylate cyclase.
