Turnover of regulatory subunit of cyclic AMP-dependent protein kinase in S49 mouse lymphoma cells. Regulation by catalytic subunit and analogs of cyclic AMP.

Turnover of regulatory subunit (R) of type I cAMP-dependent protein kinase in intact S49 mouse lymphoma cells was studied using two-dimensional gel electrophoresis to analyze [35S]methionine label in R during label-chase experiments. R decays exponentially with a half-life of about 8.4 h in drug-free, wild type cells. In mutant cells lacking functional kinase catalytic subunit, R is about 10 times more labile than in wild type cells. 8-bromo-cAMP, isoproterenol, and cholera toxin destabilize R in wild type cells to an extent comparable to the "kinase-negative" mutation. In contrast, dibutyryl-cAMP stabilizes R in both wild type and kinase-negative cells. Sodium butyrate has no significant effect on R stability. These results are discussed in terms of R structure and the regulation of R expression.