Retinoylation of the type II cAMP-binding regulatory subunit of cAMP-dependent protein kinase is increased in psoriatic human fibroblasts

Abstract

Previously, we have reported a defect in the cAMP-dependent protein kinases (cAMP-PK) in psoriatic cells (i.e., a decrease in 8-azido-[32P]cAMP binding to the regulatory subunits and a decrease in phosphotransferase activity) which is rapidly reversed with retinoic acid (RA) treatment of these cells. This led us to examine a possible direct interaction between retinoids and the RI and RII regulatory subunits through retinoylation. Retinoylation of RI and RII present in normal and psoriatic human fibroblasts was analysed by [3H]RA treatment of these cells, followed either by chromatographic separation of the regulatory subunits or by their specific immunoprecipitation. These studies indicated that RI and RII can be retinoylated. [3H]RA labeling of the RII subunit was significantly (P < 0.005) greater in psoriatic fibroblasts (nine subjects; mean 7.47 relative units +/- 1.37 SEM) compared to normal fibroblasts (eight subjects; mean 2.46 relative +/- 0.49 SEM). [3H]RA labeling of and the increase in 8-azido-[32P]-binding to the RI and RII subunit in psoriatic fibroblasts showed a similar time course. This suggests that the rapid effect of retinoic acid treatment to enhance 8-azido-[32P]-cAMP binding to the RI and RII in psoriatic fibroblasts may be due, in part, to covalent modification of the regulatory subunits by retinoylation.