Differential expression of type I and type II cyclic AMP-dependent protein kinases during cell cycle and cyclic AMP-induced growth arrest

The activation state of cyclic AMP-dependent protein kinase(s) (ATP:protein phosphotransferase, EC 2.7.1.37) is transiently increased 2-fold as a function of G₁ progression in mitotically synchronized Chinese hamster ovary cells. The cellular content of type I kinase increases concomitantly with the increase in general protein, whereas the activity of type II kinase increases as a function of time in G₁ to a maximum at the G₁/S border. In contrast, in the presence of dibutyryl-cyclic AMP, there is a decrease of type II kinase and a several-fold increase of type I kinase. In proliferating cells, the ratio of type I to type II was 0.37, while in the dibutyryl-cyclic AMP growth-arrested cells it was 3.96. The increase in type II kinase during G₁ transition and the increase in type I kinase during dibutyryl-cyclic AMP treatment were dependent on protein synthesis. A similar pattern of type I and type II kinase expression during cell cycle progression occurred in RAT-1 fibroblasts and Rat-1 cells transformed by Rous sarcoma virus. The inclusion of dibutyryl-cyclic AMP in the growth media promoted a marked increase in type I holoenzyme, which was inhibited by cycloheximide, and a decrease in type II kinase. Neither AMP nor sodium butyrate had any effect on cellular kinase levels, whereas 8-bromo-cyclic AMP mimicked the action of dibutyryl-cyclic AMP. Estimation of half-lives for the kinase types showed that there was little turnover of either type during normal G₁ progression, rapid turnover of both types as cells exited from mitosis, and selective turnover of type II upon addition of dibutyryl-cyclic AMP.