The activation of N-Methyl D-Aspartate Receptor (NMDAR) by glutamate is crucial in the nervous system function, particularly in memory and learning. NMDAR is composed by two GluN1 and two GluN2 subunits. GluN2B has been reported to participate in the prevalent NMDAR subtype at synapses, the GluN1/2A/2B. Here we studied the regulation of GluN2B expression in cortical neurons finding that glutamate up-regulates GluN2B translation through the action of nitric oxide (NO), which induces the phosphorylation of the eukaryotic translation initiation factor 2 α (eIF2α). It is a process mediated by the NO-heme-regulated eIF2α kinase (HRI), as the effect was avoided when a specific HRI inhibitor or a HRI small interfering RNA (siHRI) were used. We found that the expressed GluN2B co-localizes with PSD-95 at the postsynaptic ending, which strengthen the physiological relevance of the proposed mechanism. Moreover the receptors bearing GluN2B subunits upon NO stimulation are functional as high Ca2+ entry was measured and increases the co-localization between GluN2B and GluN1 subunits. In addition, the injection of the specific HRI inhibitor in mice produces a decrease in memory retrieval as tested by the Novel Object Recognition performance. Summarizing our data suggests that glutamatergic stimulation induces HRI activation by NO to trigger GluN2B expression and this process would be relevant to maintain postsynaptic activity in cortical neurons.

This work was supported by the Plan Estatal de I+D+I 2013-2016 and the ISCIII-Subdirección/nGeneral de Evaluación y Fomento de la Investigación (Grants PI13/00408; PI13/00135; Red HERACLES RD12/0042/0014) and FEDER Funds; the Spanish Ministry of Economy and Competitiveness (SAF2014-52228-R; SAF2015-69762-R; BFU2015-68568-P); MINECO (PCIN-2014-105); Fundació la Marató de TV3 (20134030 and 20140210); FONDECYT 3140355 (ERF),/n1120512 (AAR) and 3120015 (LVR)