N-methyl-D-aspartate glutamate receptors (NMDARs) play a pivotal role in neural development and synaptic plasticity, as well as in neurological disease. Since NMDARs exert their function at the cell surface, their density in the plasma membrane is finely tuned by a plethora of molecules that regulate their production, trafficking, docking and internalization in response to external stimuli. In addition to transcriptional regulation, the density of NMDARs is also influenced by post-translational mechanisms like phosphorylation, a modification that also affects their biophysical properties. We previously described the increased surface expression of GluN1/GluN2A receptors in transgenic mice overexpressing the Dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A), suggesting that DYRK1A regulates NMDARs. Here we have further investigated whether the density and activity of NMDARs were modulated by DYRK1A phosphorylation. Accordingly, we show that endogenous DYRK1A is recruited to GluN2A-containing NMDARs in the adult mouse brain, and we identify a DYRK1A phosphorylation site at Ser1048 of GluN2A, within its intracellular C-terminal domain. Mechanistically, the DYRK1A-dependent phosphorylation of GluN2A at Ser1048 hinders the internalization of GluN1/GluN2A, causing an increase of surface GluN1/GluN2A in heterologous systems, as well as in primary cortical neurons. Furthermore, GluN2A phosphorylation at Ser1048 increases the current density and potentiates the gating of GluN1/GluN2A receptors. We conclude that DYRK1A is a direct regulator of NMDA receptors and we propose a novel mechanism for the control of NMDAR activity in neurons.

This work was supported by grants from the Spanish Ministry of Health (PS10/00548,PS13/00135 to Xavier Altafaj), the Jérôme Le jeune Foundation (to Xavier Altafaj), the Red HERACLES (RD12/0042/0014 to José M. Fernández-Fernández), the Spanish Ministry o fEconomy and Competitiveness (SAF2012-31089 to José M. Fernández-Fernándezand BFU2010-15347 to Susana de la Luna), FEDER Funds and the Generalitat de Catalunya (SGR14-297 to Xavier Altafaj and Carlos Sindreu, and SGR14-674 toSusana de la Luna). Xavier Altafaj and Cristina Grauare financed by a contract from the Instituto de Salud Carlos III (MS10/00548 andPS10/00548)