The Effect of Protein Kinase C Activation on G_z-Mediated Regulation of Type 2 and 6 Adenylyl Cyclases

Three serine-to-alanine mutants of the α subunit of the heterotrimeric G protein G_z (α_z) were examined for their signaling properties in the presence of phorbol ester treatment. All three α_z mutants resembled wild-type α_z in their abilities to inhibit α_s-stimulated type 6 adenylyl cyclase (AC6) and phorbol ester treatment reduced their magnitudes of inhibition. Depending on the permissive condition, the βγ-mediated stimulation of type 2 adenylyl cyclase (AC2) was differentially regulated by α_z and the three mutants. Mutation of Ser²⁷ but not Ser¹⁶ of α_z affected the efficient release of βγ subunits upon receptor activation and abolished the stimulation of phosphorylated but not α_s-stimulated AC2.