Type II regulatory subunit of protein kinase restores cAMP-dependent transcription in a cAMP-unresponsive cell line.

cAMP-dependent protein kinase appears to play a role in cAMP-induced gene expression in mammalian cells. There exist two major types of cAMP-dependent protein kinase, type I and type II, which are distinguished by their regulatory subunits, RI and RII, respectively. We investigated the role of type I and type II protein kinase in the cAMP-induced gene expression by either stable or co-transfection of RI alpha, RII alpha, or RII beta gene in an expression vector together with somatostatin-chloramphenicol acetyltransferase (SS-CAT) fusion gene using a cAMP-unresponsive mutant pheochromocytoma cell line (A126-1B2). Introduction of the RII beta gene restored the capability of these cells to induce the SS-CAT gene expression in response to forskolin stimulus and induced a changed morphology which resembled that of wild type. The RII alpha gene also induced SS-CAT gene expression but to a lesser degree than that achieved by the RII beta gene, whereas the RI alpha gene had no effect. The induction of SS-CAT gene expression by the RII beta gene was specifically blocked by the 21-mer RII beta antisense oligodeoxynucleotide. These results show for the first time that type II but not type I regulatory subunit of cAMP-dependent protein kinase is essential for a cAMP-induced gene transcription.