Fig. 3. EGF receptor is predominantly retained in CD63+ endosomes in FTI treated cells. HeLa cells were serum starved overnight in the presence or absence of FTI and then incubated with 100 ng/ml EGF for 2 hours. Cells were fixed and stained for endogenous EGF receptor (green), nuclei (blue) and endosomal markers (red). EEA1 was used as a marker for early endosomes, CD63 for late endosomes and LAMP-1 for late endosomes/lysosomes. FTI-treatment led to retention of EGF receptor+ vesicles (compare top and bottom panels). In FTI-treated cells EGF receptor did not colocalise with EEA1 (d), almost completely colocalised with CD63 (e) and partially colocalised with LAMP-1 (f). The merged image in panel (e) is split in panels (g,h) to allow clearer visualisation of the EGF receptor (g) and CD63 (h) signals in FTI treated cells; colocalising vesicles (green arrowheads), non-overlapping signals (red arrowheads). Scale bar, 10 µm.