Evidence for a role of calmodulin in the regulation of prolactin gene expression.
Epidermal growth factor (EGF) stimulates prolactin (PRL) gene expression in GH3 cells in a Ca2+-dependent manner (White, B. A., and Bancroft, F. C. (1983) J. Biol. Chem. 258, 4618-4622). The present report shows that the phenothiazine, calmidazolium (compound R 24571), blocks the ability of EGF plus Ca2+ to increase levels of PRL mRNA. Calmidazolium inhibition of this response is dose dependent in the range of 0.05-1.00 microM. Total inhibition of the response was consistently obtained at a level of calmidazolium (0.5 microM) that had no effect on total cytoplasmic RNA synthesis, total cytoplasmic protein synthesis, cell viability, or extent of EGF plus Ca2+-induced cell aggregation. The drug inhibited the increase in PRL mRNA when given immediately before or 48 h after treatment with EGF plus Ca2+. Another calmodulin inhibitor, W13, similarly blocked the ability of EGF plus Ca2+ to stimulate PRL mRNA, whereas the less active analog, W12, had little effect. These results implicate Ca2+-binding proteins such as calmodulin in the mechanism of action of EGF in GH3 cells, and, therefore, provide further evidence for a role of intracellular Ca2+ in the regulation of the expression of a specific eukaryotic gene, the PRL gene.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000502:physiology*; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D010911:Pituitary Neoplasms / Q000378:metabolism; D011388:Prolactin / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D013449:Sulfonamides / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D002147:Calmodulin; D007093:Imidazoles; D012333:RNA, Messenger; D013449:Sulfonamides; C031938:calmidazolium; D013973:Thyrotropin-Releasing Hormone; D004815:Epidermal Growth Factor; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; D011388:Prolactin; D002118:Calcium