Expression and co-localization of GFP-CaMKII mutants and GluN2B in heterologous cells after stimulation. A, in HEK cells stimulated with ionomycin (10 μm, 5 min), GFP-CaMKII wild type, and T286A, but not K42M, co-localized with co-expressed GluN2B, detected by immunocytochemistry after fixation. B, quantification of co-localization experiments as shown in panel A (n = 22–23). GFP-CaMKII wild type and T28A showed similar co-localization with GluN2B, while K42M co-localized significantly less (**, p < 0.001 in Neuman-Keuls multiple comparison test, after one-way ANOVA). C, quantification of GFP-CaMKII and GluN2B-immunodetection fluorescence intensity showed that both GFP-CaMKII wild type and T286A expressed to a similar level as the K42M mutant; the level of co-expressed GluN2B was similar for CaMKII wild type and K42M, but slightly higher for T286A (*, p < 0.01; all in Neuman-Keuls multiple comparison test, after one-way ANOVA). Error bars show S.E. in all panels.