title: Synergistic activation of cAMP and calcium on cAMP-response-element-mediated gene expression in GH3 pituitary tumor cells.
abstract: Signals responsible for expression of the vasoactive intestinal peptide (VIP)-stimulated prolactin gene in GH3 pituitary tumor cells were examined. Transfection with a deoxyribonucleic acid (DNA) construct containing the chloramphenicol acetyltransferase (CAT) gene fused to the 2.5-kb prolactin 5'-upstream regulatory sequence indicated that VIP stimulated CAT expression. However, this effect could not be mimicked by 8-bromo-cyclic adenosine monophosphate (8-Br-cAMP), and was inhibited by the L-type Ca(2+)-channel blocker verapamil. While KCl had little effect on CAT activity, combined treatment with KCl and 8-Br-cAMP synergistically activated CAT expression. Potentiation between KCl and 8-Br-c-AMP was also seen with c-fos messenger ribonucleic acid (mRNA) expression. In addition, KCl and 8-Br-cAMP synergistically activated cAMP response element (CRE)-mediated CAT expression, and the synergism was abolished by verapamil. In the presence of okadaic acid, cAMP had no significant activation on CRE-driven CAT expression, whereas KCl-stimulated CAT expression was greatly potentiated. These results indicate that cAMP and Ca2+ synergistically activated CRE-driven gene expression through non-overlapping phosphorylation events in GH3 cells.
authors.affiliation: Institute of Biochemistry, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors.forename: J H
authors.initials: JH
authors.lastname: Lin
authors.forename: Y C
authors.initials: YC
authors.lastname: Jang
authors.forename: D C
authors.initials: DC
authors.lastname: Wen
authors.forename: F F
authors.initials: FF
authors.lastname: Wang
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics* / Q000378:metabolism; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D016762:Genes, fos / Q000187:drug effects; D010766:Phosphorylation; D010911:Pituitary Neoplasms; D011189:Potassium Chloride / Q000494:pharmacology; D011388:Prolactin / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000235:genetics*; D014407:Tumor Cells, Cultured / Q000201:enzymology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D017362:Cyclic AMP Response Element-Binding Protein; D012333:RNA, Messenger; D015124:8-Bromo Cyclic Adenosine Monophosphate; D014660:Vasoactive Intestinal Peptide; D011189:Potassium Chloride; D011388:Prolactin; D000242:Cyclic AMP; D002118:Calcium