Regulation of NMDA receptor trafficking and gating by activity-dependent CaMKIIα phosphorylation of the GluN2A subunit

SUMMARY NMDA receptor (NMDAR)-dependent Ca2+ influx underpins multiple forms of synaptic plasticity. Most synaptic NMDAR currents in the adult forebrain are mediated by GluN2A-containing receptors, which are rapidly inserted into synapses during long-term potentiation (LTP); however, the underlying molecular mechanisms remain poorly understood. In this study, we show that GluN2A is phosphorylated at Ser-1459 by Ca2+/calmodulin-dependent kinase IIα (CaMKIIα) in response to glycine stimulation that mimics LTP in primary neurons. Phosphorylation of Ser-1459 promotes GluN2A interaction with the sorting nexin 27 (SNX27)-retromer complex, thereby enhancing the endosomal recycling of NMDARs. Loss of SNX27 or CaMKIIα function blocks the glycine-induced increase in GluN2A-NMDARs on the neuronal membrane. Interestingly, mutations of Ser-1459, including the rare S1459G human epilepsy variant, prolong the decay times of NMDAR-mediated synaptic currents in heterosynapses by increasing the duration of channel opening. These findings not only identify a critical role of Ser-1459 phosphorylation in regulating the function of NMDARs, but they also explain how the S1459G variant dysregulates NMDAR function.
Graphical Abstract
In brief Yong et al. identify that activity-dependent phosphorylation of Ser-1459 in the GluN2A C-terminal domain by CaMKIIα promotes its interaction with the SNX27-retromer complex, thereby enhancing the surface expression of NMDARs during synaptic potentiation. Mutations of Ser-1459 prolong the decay times of NMDAR-mediated synaptic currents by increasing the duration of channel opening.