Spines of neurons co-transfected with Norbin-GFP and either PSD-95-mCherry, LifeAct-mCherry, mGluR5-mCherry or Homer1C-DsRed imaged with 3D-SIM. A) Norbin clusters close to, but do not colocalize with, PSD-95 (arrow), B) Norbin and actin show a high degree of colocalization and cluster at proximal sites, frequently towards the base of the spine head (full arrow). C) Norbin and PSD-95 do not immunoprecipitate. D) Norbin and actin do immunoprecipitate. E) Western blots of brain homogenate (Hom.) and PSD fractions (PSD-F) show that Norbin is absent in the PSD fraction. F) Norbin and mGluR5 colocalize in spines. G) Norbin and Homer1C colocalize in spines. H) Median PCC is significantly lower for Norbin-PSD-95 (PCC = 0.49, n = 27) than for Norbin-Actin (PCC = 0.83, n = 27, ***p < 0.00001), Norbin-Homer1C (PCC = 0.73, n = 25, **p < 0.001) and Norbin-mGluR5 (PCC = 0.65, n = 21, *p < 0.05), Kruskal-Wallis test. Scale bars = 400 nm. n = number of analyzed spines.