alpha1-adrenergic receptor activation of c-fos expression in transfected rat-1 fibroblasts: role of Ca2+.
alpha1-Adrenergic receptors mediate mitogenic responses and increase intracellular free Ca2+ ([Ca2+]i) in vascular smooth muscle cells. Induction of c-fos is a critical early event in cell growth; expression of this gene is regulated by a number of signaling pathways including Ca2+. We wondered whether Ca2+ signaling plays a critical role in the induction of c-fos gene by alpha1-adrenergic receptors. Using stably transfected rat-1 fibroblasts, we confirmed that PE induced c-fos mRNA expression in a time- and dose-dependent manner, and also increased [Ca2+]i (measured with Fura-2 AM). These responses were blocked by the alpha1-adrenergic receptor antagonist doxazosin. Both intracellular Ca2+ chelation (using BAPTA/AM) and extracellular Ca2+ depletion (using EGTA) significantly inhibited PE-induced c-fos expression by alpha1A and alpha1B receptors. Brief (1-min) stimulation of alpha1A and alpha1B receptors with PE did not maximally induce c-fos expression, suggesting that a sustained increase in [Ca2+]i due to Ca2+ influx is required. The calmodulin (CaM) antagonists, R24571, W7, and trifluoperazine, but not the CaM-dependent protein kinases inhibitor KN-62, significantly inhibited c-fos induction by alpha1A and alpha1B receptors. Neither inhibition of protein kinase C nor inhibition of adenylyl cyclase modified c-fos induction by PE. These results suggest that alpha1-adrenergic receptor-induced c-fos expression in rat-1 cells is dependent on a Ca2+/CaM-associated pathway.
Chen
J
J
Veterans Affairs Palo Alto Health Care System, Geriatrics Research, Education and Clinical Center, Palo Alto, California, USA.
Lin
R
R
Hu
Z W
ZW
Hoffman
B B
BB
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D058668:Adrenergic alpha-1 Receptor Antagonists; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D017292:Doxazosin / Q000494:pharmacology*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D016762:Genes, fos / Q000187:drug effects*; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D047428:Protein Kinase Inhibitors; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014268:Trifluoperazine / Q000494:pharmacology
C547715:Adra1a protein, rat; C547718:Adra1b protein, rat; C547721:Adra1d protein, rat; D058668:Adrenergic alpha-1 Receptor Antagonists; D002147:Calmodulin; D004791:Enzyme Inhibitors; D007093:Imidazoles; D047428:Protein Kinase Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D018340:Receptors, Adrenergic, alpha-1; D011994:Recombinant Proteins; D013449:Sulfonamides; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D014268:Trifluoperazine; C031938:calmidazolium; D004533:Egtazic Acid; C063302:KN 62; C017967:W 7; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017292:Doxazosin; D002118:Calcium