Ca2+/diacylglycerol-activated, phospholipid-dependent protein kinase in the Hermissenda CNS.
In mammalian systems, Ca2+/diacylglycerol-activated phospholipid-dependent protein kinase (C-kinase) appears to play an important role in regulating physiological responses that outlast the transient rise in cytosolic Ca2+. Electrophysiological experiments in neurons of the nudibranch mollusc, Hermissenda crassicornis, have suggested a role for C-kinase in the long-lasting reductions in early and late K+ currents that have been observed following associative learning. Accordingly, we have investigated the catalytic properties of C-kinase in Hermissenda CNS. Following homogenization in Ca2+-free buffer, C-kinase can be separated from Ca2+/calmodulin-dependent protein kinase by centrifugation; C-kinase activity is found in the supernatant whereas essentially all of the Ca2+/calmodulin-dependent protein kinase is found in the membrane fraction. Addition of Ca2+, phosphatidylserine, and diacylglycerol to the cytosol results in phosphorylation of at least eight endogenous proteins. The Hermissenda CNS C-kinase can also phosphorylate lysine-rich histone, a substrate for mammalian C-kinase. The molluscan enzyme exhibits phospholipid specificity in that phosphatidylserine is much more effective than phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, and phosphatidic acid. Addition of diacylglycerol, in the presence of Ca2+ and phosphatidylserine, increases the activity of the C-kinase. The percentage of activation by diacylglycerol is larger at lower Ca2+ concentrations. Enzyme activity is inhibited by trifluoperazine and polymixin B sulfate. These studies indicate that the Hermissenda C-kinase is catalytically similar to mammalian C-kinase.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004594:Electrophysiology; D004789:Enzyme Activation; D007527:Isoenzymes / Q000378:metabolism; D008970:Molecular Weight; D008974:Mollusca / Q000201:enzymology*; D009474:Neurons / Q000201:enzymology; D010743:Phospholipids / Q000378:metabolism; D010766:Phosphorylation; D011112:Polymyxin B / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology
D007527:Isoenzymes; D010743:Phospholipids; D014268:Trifluoperazine; D011493:Protein Kinase C; D011112:Polymyxin B; D002118:Calcium