Beta-adrenergic stimulation of cFOS via protein kinase A is mediated by cAMP regulatory element binding protein (CREB)-dependent and tissue-specific CREB-independent mechanisms in corticotrope cells.
Catecholamines stimulate proopiomelanocortin (POMC) gene expression in corticotrope cells, but the molecular mechanisms of these effects are not known. While beta-adrenergic receptors stimulate the protein kinase A (PKA) system, the POMC promoter does not have classical cAMP-response elements (CREs). Therefore, we investigated the induction of the c-fos protooncogen, previously shown to increase POMC transcription in AtT20 cells. In this corticotrope-derived cell line, we show that activation of beta-receptors with isoprenaline (Iso) induces a transient rise in c-fos mRNA levels. Gel mobility shift assays with a labeled AP1 consensus sequence (TGACTCA) showed induction of specific binding activity after Iso treatment. Cotransfection experiments with dominant inhibitory PKA mutants and reporter genes containing c-fos promoter sequences showed that c-fos induction by Iso is entirely dependent on a functional PKA activity. Furthermore, we show that beta-receptor induction of c-fos in corticotrophs is mediated by at least two distinct cAMP-responsive sequences. cAMP regulatory element binding (CREB)-dependent induction is observed on the CRE located at -60 bp on the c-fos promoter. A region located in the vicinity of the dyad symetry element (-290) is also found to mediate tissue-specific cAMP induction. Transcriptional activation by this site, although sensitive to PKA antagonism, is not blocked by CREB mutants.
Boutillier
A L
AL
Institut de Physiologie et de Chimie Biologique, Strasbourg, France.
Barthel
F
F
Roberts
J L
JL
Loeffler
J P
JP
D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D016762:Genes, fos; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D008668:Metallothionein / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010911:Pituitary Neoplasms; D011333:Pro-Opiomelanocortin / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D017384:Sequence Deletion; D014162:Transfection; D014407:Tumor Cells, Cultured
D017362:Cyclic AMP Response Element-Binding Protein; D009838:Oligodeoxyribonucleotides; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D011333:Pro-Opiomelanocortin; D008668:Metallothionein; D000242:Cyclic AMP; D015500:Chloramphenicol O-Acetyltransferase; D011494:Protein Kinases; D007545:Isoproterenol