Inhibition of Cbl-mediated FGFR1 degradation results in FGF-2–induced cell migration. (A, left) Lysates from HeLa cells stably transfected with Cbl or dn-Cbl were immunoblotted for Cbl using tubulin as loading control. (right) Transfected cells were stimulated with FGF-2 or FGL in the presence of cycloheximide for the indicated time intervals followed by lysis and immunoblotting for FGFR1 using tubulin as loading control. NT, not transfected. (B) HeLa cells stably expressing either wild-type Cbl or dn-Cbl were transfected with HA-FGFR1. Cells were incubated with anti-HA antibody and stimulated with either FGF-2 or FGL. Cells were processed as for Fig. 3 A. Asterisks mark cells where HA-FGFR1 recycled back to the cell surface. Bar, 10 µm. (C) Hela cells stably transfected with either wild-type Cbl (gray bars) or dn-Cbl (black bars) and nontransfected cells (white bars) were stimulated with FGF-2 or FGL before migration assay in modified Boyden chambers. (D) HeLa cells transfected with an empty vector (open symbols) or with GFP-tagged dn-Rab11 (closed symbols) were serum starved and stimulated with FGF-2 or FGL for the indicated time intervals. Cell proliferation was determined as described in Materials and methods. *, P < 0.005 relative to untreated cells. Data represent the mean ± SEM from three independent experiments.