Protein kinase C phosphorylates a 47 Mr protein (F1) directly related to synaptic plasticity.

Ca2+-phospholipid-dependent protein kinase C, and activators of protein kinase C (phosphatidylserine, phorbol esters) stimulate the in vitro phosphorylation of a 47 kdalton phosphoprotein (protein F1) previously shown (Routtenberg, Lovinger and Steward, Behav. neural Biol., 43 (1985) 3-11) to be directly related to the plasticity of long-term potentiation. These data indicate that protein F1 serves as a protein kinase C substrate, and suggest the hypothesis that protein kinase C is involved in processes of long-term potentiation.