AN AUTONOMOUS KINASE GENERATED DURING LONG-TERM FACILITATION IN APLYSIA IS RELATED TO THE CA2-KINASE-C APL-II( INDEPENDENT PROTEIN)

Prolonged treatment with serotonin leads to long-term facilitation of sensory-to-motor neuron synapses in Aplysia. We have shown previously that there is a protein synthesis-dependent increase in an autonomous kinase activity that phosphorylates a protein kinase C substrate durin g an intermediate phase of this facilitation. Here, I report that the increase in autonomous activity was independent of RNA synthesis, sugg esting it may play a role in the maintenance phase of synaptic facilit ation. Immunoprecipitation experiments using an antibody specific to t he Ca2+-independent protein kinase C, Ap1 II, demonstrated that the au tonomous kinase activity increased by serotonin emanated from Ap1 II. Chelerythrine, an inhibitor targeted, to the substrate binding site of protein kinase C, also blocked the autonomous kinase activity increas ed by serotonin. Using immunoblotting experiments and calphostin-C, an inhibitor targeted to the regulatory domain of protein kinase C, the autonomous activity is shown not to be a catalytic fragment of Ap1 II. Furthermore, a higher concentration of calphostin-C was required to i nhibit autonomous kinase activity than regulated kinase activity, sugg esting that calphostin-C's binding site in the regulatory domain of Ap 1 II is modified in the autonomous kinase. These data suggest that an autonomous kinase derived from Ap1 II may play a role in synaptic faci litation in Aplysia.