Effect of FGFR on the collapse response of EphB2 cells. EphB2 or EphB2+iFGFR cells were incubated at 4°C with Cy3-labeled anti-EphB2 antibody to label cell surface EphB2. (a and b) The cells were incubated with culture medium at 37°C containing 1 μg/ml ephrinB1-Fc, and time-lapse images were collected. (a) More than 90% of EphB2 cells undergo rapid collapse with concurrent endocytosis of cell surface EphB2. (b) More than 95% of EphB2+iFGFR cells do not collapse, whereas endocytosis of EphB2 occurs with similar kinetics as for EphB2 cells. (c) EphB2 cells incubated with anti-EphB2 antibody in the absence of ephrinB1-Fc do not collapse.