Molecular mechanism of protein kinase C enhancement of N-methyl-D-aspartate receptor calcium-dependent inactivation

Glutamate is the major excitatory neurotransmitter in the central nervous system. N-Methyl-D-aspartame receptors (NMDAR) belong to the family of ionotropic glutamate receptors, implicated in synaptic plasticity, synaptogenesis, excitotoxicity, and the induction of long term potentiation. The NMDA receptor subunit, NR1, has a large intracellular C-terminal tail that has been shown to bind both Calmodulin (CaM) and alpha-actinin, and has been shown to be a target of PKC and PKA phosphorylation. We proposed that PKC phosphorylation of certain serine residues on the NR1 subunit can enhance calcium-dependent inactivation of the NMDAR through the rearrangement of Calmodulin and alpha-actinin binding. Through the use of whole-cell recording of recombinant receptors expressed in HEK293 cells, site-directed mutagenesis of the NR1 subunit, and immuno-precipitation combined with Western blotting techniques, we conclude that the NR1 C-terminus is not involved in the PKC enhancement of calcium dependent inactivation in HEK293 cells expressing NR1-1a/NR2A subunits.