Mutation V618G shows increased membrane abundance. (A) Representative western blot of NMDAR protein abundance in HEK293T cells non-transfected (NT) or transfected with GluN1-GluN2B^WT (WT), GluN1-GluN2B^V15M (V15M), or GluN1-GluN2B^V618G (V618G). Input (I): total lysate; surface (S): biotinylated fractions corresponding to membrane proteins. Middle panel: Na⁺/K⁺ ATPase α1 subunit (ATP1A1). Lower panel: tubulin. All sections of the image correspond to the same experiment. Some lanes have been omitted since they are not relevant for this study. Arrows indicate migration of molecular mass markers (MW; values in KDa). (B) Protein abundance for the indicated GluN2B subunit variants calculated as the ratio GluN2B/tubulin levels, then normalized to WT values. N = 4; *, P < 0.05 (one-way ANOVA/Dunnett’s test). (C) Total GluN2B membrane abundance calculated as the ratio GluN2B/ATP1A1 membrane fractions (S), normalized to WT membrane values. All graphs: data points represent mean ± SEM. Source data are available for this figure: SourceData F5.