Post-translational abnormality of the type II cyclic AMP-dependent protein kinase in psoriasis: Modulation by retinoic acid

Previously, we have reported a decrease in the binding of a cAMP analog to the regulatory subunits of cAMP-dependent protein kinase (cAMP-PK), as well as a decrease in cAMP-PK activities, in psoriatic cells. Retinoic acid (RA) treatment of these cells can induce an increase in cAMP-PK toward normal levels. To better define the effect of retinoic acid on the cAMP-PK system in psoriatic fibroblasts, Western blot analysis using an RIIα specific antibody and in vivo phosphorylation experiments were carried out to determine possible changes in the RII regulatory subunit. Our results indicate a decrease in the binding of the cAMP analog 8-azido-[³²P]-cAMP with no change in the level of RII protein in psoriatic fibroblasts. In addition, by two-dimensional gel electrophoresis we observed the presence of a phosphorylated form of RII unique to psoriatic cells which is suppressed by RA treatment. This study suggests an altered posttranslational modification of the cAMP-PKII in psoriatic fibrobiasts which can be reversed by exposure of these cells to RA.