Figure 5.

Coendocytosis of E-cadherin is required for nuclear translocation of FGFR1. (A) Immunofluorescence labeling of MCF-7 cells by using antibodies to E-cadherin (red) and FGFR1 (green), either without (top) or with (bottom) prior incubation with FGF-1 for 24 h at 37°C. FGF induces changes in the morphology and staining in regions of the monolayer. Outline separates cells with (outside dotted outline) and without (inside dotted outline) nuclear FGFR1 labeling. (B) MCF-7 cells were transiently transfected with E-cadherin-GFP, incubated with FGF-1 for 4 h at 37°C, fixed, and stained for immunofluorescence by using an anti-FGFR1 antibody. Arrow depicts particularly strong cell surface labeling. (C) MCF-7 cells stably overexpressing E-cadherin-GFP were incubated with FGF-1 for 2 h, fixed, and stained for endogenous FGFR1. (D) Quantification of cells expressing nuclear FGFR1 labeling after transfection with E-cadherin-GFP in either serum-grown control cells or in cells stimulated with FGF-1 or FGF-2 for 4 h. Control cells represent untransfected cells from the same experiment. (E) Extracts of wild-type MCF-7 cells (wt-MCF-7) and MCF-7 cells stably overexpressing E-cadherin-GFP (hE-GFP-MCF-7) in serum, or with FGF-1 for 2 h, and immunoblotted for E-cadherin, FGFR1 and tubulin.