EGFR-GFP is ER-retained in cells treated with BFA (5 μg/ml) and PAO (2.5 μM), whereas in wortmannin (10 μM) treated cells, retention occurs in the ER and Golgi apparatus. (A) Attached RBL cells transiently expressing EGFR-GFP were processed as described for Figure 1, except that inhibitors were added at hour 3. At hour 8 cells were fixed, permeabilized, and incubated with an anti-PDI antibody followed by Alexa 555-anti-mouse IgG to label the ER lumen. (B) The same cells shown in A were incubated with an anti-GM130 antibody followed by Alexa 647-anti-mouse IgG to label the Golgi apparatus. Scale bars show 5 μm.