Fig. 5. Colocalization of endocytosed EGF, transferrin and FGF1 after 2 hours. (A) HeLa cells were transiently transfected with FGFR1, 2, 3 or 4 and incubated for 2 hours at 37°C with Cy3-FGF1 and Alexa 488-EGF in the presence of 50 U/ml heparin and 0.3 mM leupeptin. Alexa 647-transferrin (Tf) was added after 90 minutes. The cells were fixed and examined by confocal microscopy. Insets show selected areas of the images enlarged (3x). Bar, 5 µm. (B) The percentage of FGF1-positive structures within transfected cells that colocalized with EGF, Tf, neither EGF nor Tf, or both EGF and Tf was quantitated as described in Materials and Methods. Error bars denote the s.d.; n=15.