Stimulatory Effects of Protein Kinase C and Calmodulin Kinase II on N-Methyl-d-Aspartate Receptor/Channels in the Postsynaptic Density of Rat Brain

Abstract: To clarify the regulatory mechanism of the N -methyl- d -aspartate (NMDA) receptor/channel by several protein kinases, we examined the effects of purified type II of protein kinase C (PKC-II), endogenous Ca²⁺/calmodulin-dependent protein kinase II (CaMK-II), and purified cyclic AMP-dependent protein kinase on NMDA receptor/ channel activity in the postsynaptic density (PSD) of rat brain. Purified PKC-II and endogenous CaMK-II catalyzed the phosphorylation of 80–200-kDa proteins in the PSD and l -glutamate-(or NMDA)-induced increase of (+)-5-³H]methyl-10, 11-dihydro-5 H -dibenzoa, d]cyclohepten-5, 10-imine maleate (³H]MK-801; open channel blocker for NMDA receptor/channel) binding activity was significantly enhanced. However, the pretreatment of PKC-II-and CaMK-II-catalyzed phosphorylation did not change the binding activity of l -³H]glutamate, cis -4-³H](phospho-nomethyl)piperidine-2-carboxylate (³H]CGS-19755; competitive NMDA receptor antagonist), ³H]glycine, α-³H]-amino-3-hydroxy-5-methyl-isoxazole-4-propionate, or ³H]-kainate in the PSD. Pretreatment with PKC-II-and CaMK-II-catalyzed phosphorylation enhanced l -glutamate-induced increase of ³H]MK-801 binding additionally, although purified cyclic AMP-dependent protein kinase did not change l -glutamate-induced ³H]MK-801 binding. From these results, it is suggested that PKC-II and/or CaMK-II appears to induce the phosphorylation of the channel domain of the NMDA receptor/channel in the PSD and then cause an enhancement of Ca²⁺ influx through the channel.