Figure 4. Stat proteins and PLCγ1 cannot be activated by low EGF concentrations in A431 cells.

Serum-starved A431 cells were treated with either 1 nM or 32 nM EGF. Phosphorylation of EGFR and downstream signaling proteins was monitored over the course of 30 minutes by quantitative immunoblotting. PLCγ1 and the Stat proteins were only activated at the high concentration of EGF (32 nM). All other signaling proteins were activated at both high (32 nM) and low (1 nM) concentrations of EGF. Phosphorylation levels were scaled relative to the maximum signal observed for each antibody. Error bars indicate the range of two biological replicates.