An Epilepsy-Associated GRIN2A Rare Variant Disrupts CaMKIIα Phosphorylation of GluN2A and NMDA Receptor Trafficking

• Published in: Cell reports (Cambridge) Vol. 32; no. 9; p. 108104
• Main Authors: Mota Vieira, Marta, Nguyen, Thien A., Wu, Kunwei, Badger, John D., Collins, Brett M., Anggono, Victor, Lu, Wei, Roche, Katherine W.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2020
• Subjects: Animals; Calcium-Calmodulin-Dependent Protein Kinase Type 1 - genetics; Calcium-Calmodulin-Dependent Protein Kinase Type 1 - metabolism; CaMKIIα; endocytic sorting; epilepsy; Epilepsy - genetics; Epilepsy - metabolism; Female; GRIN2A rare variants; HEK293 Cells; HeLa Cells; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; NMDA receptors; Phosphorylation; protein trafficking; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate - genetics; Receptors, N-Methyl-D-Aspartate - metabolism; epilepsy; GRIN2A rare variants; CaMKIIα; protein trafficking; endocytic sorting; NMDA receptors
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2020.108104

Rare variants in GRIN genes, which encode NMDAR subunits, are strongly associated with neurodevelopmental disorders. Among these, GRIN2A, which encodes the GluN2A subunit of NMDARs, is widely accepted as an epilepsy-causative gene. Here, we functionally characterize the de novo GluN2A-S1459G mutation identified in an epilepsy patient. We show that S1459 is a CaMKIIα phosphorylation site, and that endogenous phosphorylation is regulated during development and in response to synaptic activity in a dark rearing model. GluN2A-S1459 phosphorylation results in preferential binding of NMDARs to SNX27 and a corresponding decrease in PSD-95 binding, which consequently regulates NMDAR trafficking. Furthermore, the epilepsy-associated GluN2A-S1459G variant displays defects in interactions with both SNX27 and PSD-95, resulting in trafficking deficits, reduced spine density, and decreased excitatory synaptic transmission. These data demonstrate a role for CaMKIIα phosphorylation of GluN2A in receptor targeting and implicate NMDAR trafficking defects as a link to epilepsy. [Display omitted] •The epilepsy-associated variant GluN2A-S1459G causes NMDAR trafficking defects•GluN2A-S1459G disrupts NMDAR interactions and leads to reduced mEPSC frequency•GluN2A is phosphorylated by CaMKII at S1459, which is regulated by neuronal activity•GluN2A-S1459 phosphorylation dictates binding to PDZ domain-containing proteins Mota Vieira et al. identify CaMKII phosphorylation of the GluN2A subunit on S1459 as a mechanism regulating NMDAR trafficking. An epilepsy-associated rare variant at this same residue, GluN2A-S1459G, results in altered protein interactions, decreased NMDAR surface expression, and reduced synaptic function, providing potential insight into an epilepsy phenotype.