FGF-R1/PDGF-Rα interaction examined by FRET in single-plane confocal images of PAE cells transfected with human PDGF-Rα. (A) Cells grown in culture medium without growth factors. Donor-fluorophore signal, corresponding to the FGF-R1 (section 1) and acceptor-fluorophore signal corresponding to PDGF-Rα (section 2) are shown; no FRET between these receptors was detected (section 3). (B-C) Cells treated with FGF-2/PDGF-BB mixture (20 ng/mL each). Donor-fluorophore signal, corresponding to the FGF-R1 (section 1) and the acceptor-fluorophore signal corresponding to PDGF-Rα (section 2), are shown; ligand-induced FRET is evident in section 3. Graphs reported below each panel show the signal quantification measured along the arrow. Original magnification, 100 ×; objective lens used was 40×/1.0 numeric aperture. Slides were marked with an aqueous medium with antifading agents (Biomedia, Foster City, CA). Images were processed using Adobe Photoshop version 5 (Adobe Systems, San Jose, CA).