Spinophilin regulates phosphorylation and interactions of the GluN2B subunit of the N‐methyl‐d‐aspartate receptor. Issue 2 (2nd August 2019)

• Record Type: Journal Article
• Authors: Salek, Asma B.; Edler, Michael C.; McBride, Jonathon P.; Baucum, Anthony J.
• Is Part Of: Journal of neurochemistry. Volume 151:Issue 2(2019)
• Page Start: 185
• Page End: 203
• Publication Date: 2019-08-02
• Subjects: postsynaptic -- protein phosphatase 1 -- protein phosphorylation -- protein‐protein interactions -- proteomics -- signaling; Neurochemistry -- Periodicals; 616.8042
• DOI: 10.1111/jnc.14831
• Languages: English
• ISSNs: 0022-3042

Abstract

Abstract: N ‐methyl‐d ‐Aspartate receptors (NMDARs) are abundant postsynaptic proteins that are critical for normal synaptic communication. NMDAR channel function is regulated by multiple properties, including phosphorylation. Inhibition of protein phosphatase 1 (PP1) in hippocampal neurons increases NMDAR activity, an effect abrogated by loss of spinophilin, the major PP1‐targeting protein in the postsynaptic density. However, how spinophilin regulates PP1‐dependent NMDAR function is unclear. We hypothesize that spinophilin regulates PP1 binding to the NMDAR to alter NMDAR phosphorylation. Our data demonstrate that spinophilin interacts with the GluN2B subunit of the NMDAR. In human embryonic kidney 293 FT cells, activation and/or overexpression of protein kinase A increased the association between spinophilin and the GluN2B subunit of the NMDAR. Functionally, we found that spinophilin overexpression decreased PP1 binding to the GluN2B subunit of the NMDAR and attenuated the PP1‐dependent dephosphorylation of GluN2B at Ser‐1284. Moreover, in P28 hippocampal lysates isolated from spinophilin KO compared to WT mice, there was increased binding of GluN2B to PP1, decreased phosphorylation of GluN2B at Ser‐1284, and altered GluN2B protein interactions with postsynaptic density‐enriched proteins. Together, our data demonstrate that spinophilin decreases PP1 binding to GluN2B and concomitantly enhances the phosphorylation of GluN2B at Ser‐1284. The putative consequences of these spinophilin‐dependent alterations in GluN2B phosphorylation and interactions on synaptic GluN2B localization and function are discussed. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/ Abstract : Appropriate function of the GluN2B subunit of the N ‐methyl‐d ‐aspartate receptor (NMDAR) requires proper phosphorylation of the receptor. Here, we report that protein phosphatase 1 (PP1) dephosphorylates GluN2B at Ser‐1284, an effect attenuated by overexpression of the synaptic PP1 targeting protein, spinophilin. Conversely, spinophilin knockout mice had increased PP1 binding to GluN2B, decreased Ser‐1284 phosphorylation, and altered GluN2B interactions with multiple synaptic proteins. These data implicate spinophilin in normal PP1 and synaptic protein targeting to GluN2B as well as appropriate Ser‐1284 phosphorylation. GluN2B phosphorylation at Ser‐1284 is altered in ischemia, suggesting a putative role for spinophilin in NMDAR physiology and pathology.