Retinoid induced changes in cAMP-dependent protein kinase activity detected by a new minigel assay

A new method for the resolution of protein kinases in nondenaturing minigels was used to analyze the type of PKA induced by retinyl acetate in transformed mouse 10T1/2 cells. Protein kinases in 0.5 microliters aliquots of cell extracts were resolved on nondenaturing gradient Phastgels and assayed for PKA activity in situ using a specific peptide substrate and [32P]ATP. Retinyl acetate caused a decrease in type I and an increase in type II PKA isoforms after about 36 h in culture. The system provides a quick and sensitive means for analyzing the activity of PKA isoforms from small numbers of cells.