Figure 1.

FGF2-mediated uPA upregulation in FGFR1-transfected L6 cells requires ERK₂ activation. (A) Parental (▪) and wt-FGFR1-transfected cells (•) were stimulated with different amounts of FGF2. Cell-associated uPA activity was evaluated after 24 h. For both cell lines, uPA activity measured in nonstimulated cells (ranging from 0.1 to 0.2 OD at 405 nm) was subtracted from all the values. (B) Northern blot analysis was performed using a murine uPA probe on total RNA extracted from parallel cultures incubated overnight with 10 ng/ml FGF2. Uniform loading of samples was judged by methylene blue staining of the filter. (C) wt-FGFR1-transfected cells were preincubated for 30 min at 37°C with no addition (1, 2) or with 100 μM PD 098059 (3) or 10 μM SB 210313 (4) before addition of 100 ng/ml FGF2 (2–4). After 24 h, cell-associated uPA activity was measured. uPA activity in control nontransfected L6 cells incubated under the same experimental conditions was subtracted from all the values. (D) Parallel cultures were lysed 20 min after FGF2 addition, and cell lysates were probed with anti-ERK₂ antibody in a Western blot. *Erk-2 indicates the phosphorylated protein.