TYPE-SPECIFIC STIMULATION OF ADENYLYLCYCLASE BY PROTEIN-KINASE-C

Ca2+-stimulable (type I), Ca2+-insensitive (type II), and Ca2+-inhibitable adenylylcyclase (type VI) were transiently expressed in the human embryonic kidney 293 cell line. Phorbol 12,13-dibutyrate (PDBu) increased cAMP synthesis by the Ca2+-insensitive type II adenylylcyclase more than 9-fold within 10 min, while the treatment had no effect on the other two types of adenylylcyclases. This stimulatory effect of PDBu on type II activity was dose-dependent and synergistic with the effect of forskolin. Another phorbol ester, phorbol 12-myristate 13-acetate (PMA), had a similar stimulatory effect on type II activity, while its inactive isomer, 4alpha-phorbol 12-myristate 13-acetate (4alpha-PMA), had no effect. Staurosporine, a potent protein kinase C (PKC) inhibitor, markedly attenuated the action of PDBu on cAMP synthesis by type II adenylylcyclase. These results are particularly significant in that they indicate that a species of adenylylcyclase that is insensitive to regulation by one arm of the phosphatidylinositide pathway, i.e. Ca2+, nevertheless can be regulated by the other arm, i.e. PKC.