MAPK3 and infection: Thus, EIEC induced an increase of 50% of ERK1/2 phosphorylation at 0.5 h and lower than 20% at 1 and 2 h but 75% at 4 h of infection, while co-stimulation with EGF after infection, only caused an increase in about 50% at 0.5 and 1 h, and 60 and 70% at 2 h and 4 h, respectively (Figure 5E).