cAMP-dependent protein kinase type I regulates ethanol-induced cAMP response element-mediated gene expression via activation of CREB-binding protein and inhibition of MAPK.
We have shown that the two types of cAMP-dependent protein kinase (PKA) in NG108-15 cells differentially mediate forskolin- and ethanol-induced cAMP response element (CRE)-binding protein (CREB) phosphorylation and CRE-mediated gene transcription. Activated type II PKA is translocated into the nucleus where it phosphorylates CREB. By contrast, activated type I PKA does not translocate to the nucleus but is required for CRE-mediated gene transcription by inducing the activation of other transcription cofactors such as CREB-binding protein (CBP). We show here that CBP is required for forskolin- and ethanol-induced CRE-mediated gene expression. Forskolin- and ethanol-induced CBP phosphorylation, demonstrable at 10 min, persists up to 24 h. CBP phosphorylation requires type I PKA but not type II PKA. In NG108-15 cells, ethanol and forskolin activation of type I PKA also inhibits several components of the MAPK pathway including B-Raf kinase, ERK1/2, and p90RSK phosphorylation. As a result, unphosphorylated p90RSK no longer binds to nor inhibits CBP. Moreover, MEK inhibition by PD98059 induces a significant increase of CRE-mediated gene activation. Taken together, our findings suggest that inhibition of the MAPK pathway enhances cAMP-dependent gene activation during exposure of NG108-15 cells to ethanol. This mechanism appears to involve type I PKA-dependent phosphorylation of CBP and inhibition of MEK-dependent phosphorylation of p90RSK. Under these conditions p90RSK is no longer bound to CBP, thereby promoting CBP-dependent CREB-mediated gene expression.
Ernest Gallo Clinic and Research Center, Department of Neurology, University of California, San Francisco, Emeryville, CA 94608, USA. anconst@itsa.ucsf.edu
Anastasia
A
Constantinescu
Meiye
M
Wu
Orna
O
Asher
Ivan
I
Diamond
D015153:Blotting, Western; D050882:CREB-Binding Protein; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D015533:Transcriptional Activation
D004791:Enzyme Inhibitors; D005419:Flavonoids; D009687:Nuclear Proteins; D015534:Trans-Activators; D005576:Colforsin; D000431:Ethanol; D000242:Cyclic AMP; D008156:Luciferases; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D048493:Proto-Oncogene Proteins B-raf; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one