Ethanol-induced translocation of cAMP-dependent protein kinase to the nucleus - Mechanism and functional consequences

Ethanol induces translocation of the catalytic subunit (C alpha) of cAMP-dependent protein kinase (PKA) from the Golgi area to the nucleus in NG108-15 cells. Ethanol also induces translocation of the RII beta regulatory subunit of PKA to the nucleus; RI and C beta are not translocated. Nuclear PKA activity in ethanol-treated cells is no longer regulated by cAMP. Gel filtration and immunoprecipitation analysis confirm that ethanol blocks the dissociation of C alpha with RII but does not induce dissociation of these subunits. Ethanol also reduces inhibition of C alpha by the PKA inhibitor PKI. Pre-incubation of C alpha with ethanol decreases phosphorylation of Leu-Arg-Arg-Ala-Ser-Leu-Gly (Kemptide) and casein but has no effect on the phosphorylation of highly charged molecules such as histone H1 or protamine. cAMP-response element-binding protein (CREB) phosphorylation by C alpha is also increased in ethanol-treated cells. This increase in CREB phosphorylation is inhibited by the PKA antagonist (R-p)-cAMPS and by an adenosine receptor antagonist. These results suggest that ethanol affects a cascade of events allowing for sustained nuclear localization of C alpha and prolonged CREB phosphorylation. These events may account for ethanol-induced changes in cAMP-dependent gene expression.