Fig. 3. Comparison of endogenous and transfected levels of Homer1b and mGluR5. A–D, Immunocytochemical staining of endogenous Homer proteins revealed with a pan-Homer antibody (red) in cultured hippocampal neurons (A) and Ptk2 cells (C) transfected or not with Homer1b-GFP (green, arrow) and phase contrast pictures of the same cells (B, D). Homer1b is endogenously expressed in some cultured hippocampal neurons (red, arrowhead) but not in other neurons or nontransfected Ptk2 cells (asterisk).E, Western blots revealed by anti-Homer1b (left blot) and anti-mGluR5 (middle, right blots). Each line contained, from left toright, extracts of control Ptk2 cells, Ptk2 cells transfected with Homer1b-GFP plus mGluR5-myc, cultured hippocampal neurons, and dissected hippocampi. Arrows on theleft indicate the molecular weights of 45 and 71 kDa, corresponding, respectively, to Homer1b and Homer1b-GFP.Arrows on the right indicate the molecular weights of 150 and 300 kDa, corresponding, respectively, to monomeric and dimeric mGluR5. Control Ptk2 cells express no Homer1b or mGluR5, whereas cultured neurons express Homer1b and low levels of mGluR5, as revealed on the right-most line, which is the same as that for the middle blot but exposed for a longer time.