Regulation of phosphorylation at Ser1303 of GluN2B receptor in the postsynaptic density

Abstract Neuronal N -methyl-D-aspartate subtype of ionotropic glutamate receptor (NMDAR) that plays essential roles in excitatory synaptic transmission is regulated by phosphorylation. However, the kinases and phosphatases involved in this regulation are not completely known. We show that the GluN2B subunit of NMDAR is phosphorylated at Ser 1303 by protein kinase C (PKC) and is dephosphorylated by protein phosphatase 1 (PP1), but not protein phosphatase 2A (PP2A) in isolated postsynaptic density (PSD). Although PSD is known to harbor PKC, PP1 and PP2A, their ability to regulate phosphorylation of GluN2B-Ser 1303 would depend on the accessibility of GluN2B-Ser 1303 to these proteins. Since PSD preparation is likely to maintain the organization of its component proteins as inside neurons, accessibility of kinases and phosphatases to GluN2B-Ser 1303 in vivo would be addressed by experiments using this system. Using an antibody specific for the phosphorylated state of GluN2B-Ser 1303 we demonstrate that PP1 is the major phosphatase in rat brain PSD that can dephosphorylate the GluN2B-Ser 1303 endogenous to PSD. We also show that PKC present in PSD can phosphorylate GluN2B-Ser 1303 . The events reported here might be important in regulating GluN2B-Ser 1303 phosphorylation in vivo .