Selective activation of Ca(2+)-activated PKCs in Aplysia neurons by 5-HT.
Ca(2+)-activated and Ca(2+)-independent protein kinase Cs (PKCs) are present in the nervous system of the marine mollusk Aplysia californica (Kruger et al., 1991). Sensitizing stimuli or application of the facilitatory transmitter 5-HT to intact isolated ganglia produces the presynaptic facilitation of sensory-to-motor neuron synapses that underlies behavioral sensitization, which is a simple form of learning. Activation of PKC can also produce this presynaptic facilitation (Braha et al., 1990). To determine which type of PKC is activated, we developed a sensitive and selective assay to measure both Ca(2+)-activated and Ca(2+)-independent PKC activities in crude supernatant and membrane fractions of nervous tissue. This assay is based on the specific binding of the Ca(2+)-activated PKCs to phosphatidylserine vesicles in the presence of Ca2+ and makes use of a novel synthetic peptide with sequences conforming to phylogenetically conserved pseudosubstrate regions of the Ca(2+)-independent kinases. We provide evidence that the presynaptic facilitation is produced by a Ca(2+)-activated isoform: application of 5-HT increases the amount of the Ca(2+)-activated PKC activity associated with the membrane. Under these conditions, no increase in Ca(2+)-independent kinase activity is seen.
Sossin
W S
WS
Center for Neurobiology and Behavior, Columbia University, College of Physicians and Surgeons, New York, New York.
Schwartz
J H
JH
D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia; D002118:Calcium / Q000494:pharmacology*; D004789:Enzyme Activation; D008969:Molecular Sequence Data; D009474:Neurons / Q000201:enzymology*; D009479:Neuropeptides / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*
D009479:Neuropeptides; D012701:Serotonin; D011493:Protein Kinase C; D002118:Calcium