Fig. 2. Relative surface labeling of 5-HT_1AR and related mutants in transfected COS-7 cells, LLC-PK1 cells and hippocampal neurons. Transfection of COS-7 cells (A) and hippocampal neurons (B) with Flag-5-HT_1A (wild-type), Flag-I414/415A-5-HT_1A or Flag-C417/420S-5-HT_1A. Surface staining with mouse monoclonal anti-Flag M2 antibody and intracellular labeling with rabbit anti-Flag after plasma membrane permeabilization are shown. Bars, 10 µm. (C) Quantification of the percentage of surface labeling of each construct in transfected COS-7 cells, LLC-PK1 cells and neurons. Data are expressed as mean relative surface labeling ± s.e.m. of 10-15 transfected cells per construct. ***P<0.001, when compared with levels in the wild type.