Figure 3.

Kinetics of HGF- and EGF-induced phosphorylation, c-Met receptor, and its downstream signaling proteins. A549 and H1838 cells were starved overnight in media containing 0.5% BSA for 18 h and were stimulated with 40 ng/ml HGF or 5 ng/ml of EGF or both for various intervals of time. Cell lysates were prepared and western blotting performed as described in materials and methods section (A). In A549 cells, synergistic phosphorylation of c-Met (Tyr 1003) and downstream signaling protein Akt (Serine 473) was observed at 2.5 min after stimulation with a combination of EGF and HGF (B). In H1838 cells, HGF and EGF together induced synergistic phosphorylation of phospho c-Met (Tyr 1003) and phospho c-Met (Tyr 1230/1234/1235). (C) Synergistic phosphorylation of Akt (Serine 473) and ERK1+ERK2 (Thr202/Tyr204), which are downstream signaling intermediates