Inhibition of protein kinase C function by injection of intracellular receptors for the enzyme.

We tested the hypothesis that the translocation and function of protein kinase C (PKC) requires the binding of PKC to its intracellular receptors (RACKs), using insulin-induced maturation of Xenopus oocytes. We show that after exposure of oocytes to insulin, PKC translocated from the cytosol to the particulate fraction. PKC is also required for insulin-induced oocyte maturation: microinjection of a PKC inhibitory peptide delayed maturation. To determine whether translocation of PKC was a result of the binding of PKC to the RACKs in the particulate fraction, we microinjected purified rat brain RACKs into oocytes before insulin exposure. Microinjection of RACKs, but not inactive phosphorylated RACKS, inhibited PKC translocation and delayed oocyte maturation. These results suggest an in vivo role for RACKs in a function mediated by PKC.