Analysis of the role of the mitogen-activated protein kinase in mediating cyclic-adenosine 3',5'-monophosphate effects on prolactin promoter activity.
The mechanisms mediating cAMP effects to stimulate transcription of the PRL gene have been examined. Treatments that elevate intracellular cAMP concentrations were found to stimulate the mitogen-activated protein kinase (MAPK) in GH(3) cells. Elevated cAMP was also found to stimulate activation of the GTP-binding protein, Rap1. Rap1GAP1 reduced cAMP-induced phosphorylation of MAPK, offering evidence that Rap1 may play a role in mediating activation of MAPK. Treatment of GH(3) cells with PD98059, an inhibitor of the MAPK pathway, reduced the ability of forskolin to activate a PRL reporter gene, providing evidence that MAPK contributes to cAMP-mediated effects on the PRL promoter. As previous studies have implicated Ets factor binding sites within the PRL promoter in mediating responses to MAPK, we expected that the Ets sites would also play a role in cAMP responsiveness. Surprisingly, mutation of all of the consensus Ets factor binding sites in the proximal PRL promoter greatly reduced responsiveness to epidermal growth factor (EGF) and TRH but did not reduce cAMP responsiveness. Experiments using an expression vector for adenovirus 12S E1a provided evidence that the coactivators, CREB binding protein and/or p300, probably play a role in cAMP responsiveness of the PRL promoter. Interestingly, the ability of a GAL4-p300 fusion protein to enhance reporter gene activity was stimulated by cAMP in a MAPK-dependent manner. These findings provide evidence for a model for cAMP-induced PRL transcription involving Rap1-induced MAPK activity leading to stimulation of the transcriptional coactivators, CBP and p300.
Kievit
P
P
Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, Oregon 97201, USA.
Lauten
J D
JD
Maurer
R A
RA
D000818:Animals; D001665:Binding Sites; D050882:CREB-Binding Protein; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins; D050881:E1A-Associated p300 Protein; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010911:Pituitary Neoplasms; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011388:Prolactin / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D051381:Rats; D013449:Sulfonamides; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D050807:ets-Domain Protein Elk-1; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
D004268:DNA-Binding Proteins; C494114:Elk1 protein, rat; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007546:Isoquinolines; D009687:Nuclear Proteins; D015221:Potassium Channels; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D013449:Sulfonamides; D015534:Trans-Activators; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D005576:Colforsin; D013973:Thyrotropin-Releasing Hormone; D004815:Epidermal Growth Factor; D011388:Prolactin; D000242:Cyclic AMP; D050882:CREB-Binding Protein; C494365:Crebbp protein, rat; D050881:E1A-Associated p300 Protein; C494362:Ep300 protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020827:rap1 GTP-Binding Proteins; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one