Characterization of protein kinase C activities in postsynaptic density fractions prepared from cerebral cortex, hippocampus, and cerebellum

Abstract

Protein kinase C (PKC) activities, especially, substrates and PKC isozymes, associated with postsynaptic density (PSD) fractions isolated from rat cerebral cortex, hippocampus, or cerebellum were investigated. The 17k M r major substrate for PKC was associated with PSD fractions prepared from cerebral cortex and hippocampus, and several substrates including 18k M r, protein were associated with PSD fraction isolated from cerebellum. The content of 17k M r, substrate was extremely low in the PSD fraction prepared from cerebellum. PKCs-β and λ were associated with PSD fractions and PKC-α was virtually absent in the fraction prepared from the three different regions of the brain. All of PKCs-α, β, and λ were associated with synaptosome fractions. The 36k M r bands immunoreactive with anti-PKC-β antibody, probably degradation products of native PKC-β, were detected in both the PSD and synaptosome fractions from the three regions, and the ratio of the degradation fragments to native PKC molecule was higher in PSD fractions than in synaptosome fractions. The results suggest postsynaptic roles of PKCs-β and λ and involvement of proteolytic activation of PKC-β in the postsynaptic signal processing.