The Upregulation of NR2A-Containing N-Methyl-d-Aspartate Receptor Function by Tyrosine Phosphorylation of Postsynaptic Density 95 Via Facilitating Src/Proline-Rich Tyrosine Kinase 2 Activation

Abstract

The activation of postsynaptic N-methyl-D-aspartate (NMDA) receptors is required for long-term potentiation (LTP) of synaptic transmission. Postsynaptic density 95 (PSD-95) serves as a scaffold protein that tethers NMDA receptor subunits, kinases, and signal molecules. Our previous study proves that PSD-95 is a substrate of Src/Fyn and identifies Y523 on PSD-95 as a principal phosphorylation site. In this paper, we try to define an involvement and molecular consequences of PSD-95 phosphorylation by Src in NMDA receptor regulation. We found that either NMDA or chemical LTP induction leads to rapid phosphorylation of PSD-95 by Src in cultured cortical neurons. The phosphorylation of Y523 on PSD-95 potentiates NR2A-containing NMDA receptor current amplitude, implying an important role of Src-mediated PSD-95 phosphorylation in NMDA receptor activation. Comparing to wild-type PSD-95, overexpression of nonphosphorylatable mutant PSD-95Y523F attenuated the NMDA-stimulated NR2A tyrosine phosphorylation that enhances electrophysiological responses of NMDA receptor channels, while did not affect the membrane localization of NR2A subunits. PSD-95Y523D, a phosphomimetic mutant of PSD-95, induced NR2A tyrosine phosphorylation even if there was no NMDA treatment. In addition, the deficiency of Y523 phosphorylation on PSD-95 impaired the facilitatory effect of PSD-95 on the activation of Src and proline-rich tyrosine kinase 2 (Pyk2) and decreased the binding of Pyk2 with PSD-95. These results indicate that PSD-95 phosphorylation by Src facilitates the integration of Pyk2 to PSD-95 signal complex, the activation of Pyk2/Src, as well as the subsequent tyrosine phosphorylation of NR2A, which ultimately results in the upregulation of NMDA receptor function and synaptic transmission.

Up-regulation of GluN2A-containing NMDA receptor protects cultured cortical neuron cells from oxidative stress

“…1 C and D). Consistent with other in vivo studies [17] , these data showed distinct expression pattern of the GluN2A- and GluN2B- containing NMDA receptor after depolarization. However in this study, we are interested in the impact of this dynamic expression of GluN2A-containing NMDA receptor on excitotoxicity induced by depolarization thus we inhibited the increase of GluN2A with a formerly developed peptide, while the NMDA receptor non-selective antagonist APV was used as a comparing manipulation other than control treatment.…”

“…However the contribution of different subtypes of the NMDA receptor in oxidative stress was not clearly investigated. More importantly, Zhao et al, recently found that the depolarization of neurons during ischemia stroke would specifically up-regulate the GluN2A-containing NMDA receptors [17] , but whether this selective and dynamic regulation of the GluN2A-containing subtype potentiates neuronal protection or neuronal death is still not clear.…”

Anxiolytic effects of polydatin through the blockade of neuroinflammation in a chronic pain mouse model

“…Each type of GluN2, including GluN2A and GluN2B, exerts its function largely by associating with the postsynaptic density protein PSD-95. 44 Moreover, synaptophysin, a major resident of the synaptic vesicle membrane, relates closely with the packaging and storage of synaptic vesicles and release of neurotransmitters. 15,45 In the present study, the upregulation of NMDARs and AMPARs in the amygdala after CFA injection increased the excitatory transmission, which contributed to anxiety-like behaviors in mice.…”

Pyk2 modulates hippocampal excitatory synapses and contributes to cognitive deficits in a Huntington’s disease model

“…Therefore, the functional deficit is likely to result from its combination with dysregulation of NMDA receptors and possibly other proteins. PSD-95 is phosphorylated by c-Abl and SFKs on several tyrosine residues, which can favour PSD-95 aggregation and GluN2A activation2845. Thus, there appears to be a reciprocal interaction between Pyk2 and PSD-95, each enhancing the function of the other, thereby directly and indirectly regulating NMDA receptors and PSD organization.…”