Regulation of phosphorylation of protein kinace C in neurons

In Aplysia, persistent increases in synaptic strength are mediated by persistent activation of protein kinase C. In particular, the novel PKC Apl II is persistently active between 90 minutes and 2 hours after training. Although unknown, the most likely mechanism of persistent activation is phosphorylation. We characterized phosphorylation of PKC Apl II at a conserved hydrophobic site, serine 729, with a phosphospecific antibody. Phosphorylation of S729 increased and persisted 2 hours after serotonin treatment, but did not change after phorbol ester activation. Furthermore, a serine 729 to alanine mutation reduced the activity and stability of ApI II. We studied upstream regulation of S729 phosphorylation, and showed that it is affected by both PDK-1 and atypical PKC Apl III in SF9 cells but not by FRAP or PtdIns3K in neurons. Finally we characterized atypical PKC Apl III using immunoblotting, and used kinase assays to identify isoform specific inhibitors for future studies