The ability of protein kinase C (PKC) to regulate the responsiveness of adenylyl cyclase to different activators was assessed. Membranes prepared from Sf9 cells infected with recombinant baculoviruses encoding either type II or IV adenylyl cyclase were incubated with recombinant PKCα (purified from Sf9 cells), and the effects on adenylyl cyclase activity were measured after reconstitution with G(sα), Gβγ, or forskolin. PKCα treatment of type II adenylyl cyclase leads to increases in basal, forskolin-stimulated, and βγ-stimulated activities and greater sensitivity to stimulation by G(sα). Paradoxically, most of the βγ potentiation of G(sα)-stimulated activity is eliminated by pretreatment with PKCα. By contrast, treatment of type IV adenylyl cyclase with PKCα has little effect on the basal, forskolin-stimulated, or βγ-stimulated activities but markedly reduces the G(sα)stimulated and βγ-potentiated activity of this isoform. These studies demonstrate that protein kinases can alter both the activity of adenylyl cyclase isoforms and their responsiveness to G protein regulation, thereby altering the ability of adenylyl cyclases to integrate signals derived from multiple hormonal inputs.
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