Fig. 5. Transferrin localization and dynamics in the presence of Grb2-YFP or NSH3m-YFP. (A) Transferrin uptake by COS-7 cells co-expressing EGFR-CFP with either wild-type Grb2-YFP (top) or NSH3m-YFP (bottom) was monitored by confocal time-lapse imaging. Images were collected 20 min after EGF stimulation following 40-min incubation with transferrin-TRITC. (B) Uptake and sequestration of biotinylated Tfn (B-Tfn) in COS-7 cells was measured by avidin inaccessibility (See Materials and Methods). Assays were performed in the absence (open symbols) or presence of EGF (closed symbols). Data shown are representative of three independent experiments.