MAPK3 and infection: We found that EDL993 Δtir mutant strain was not able to suppress ERK1/2 signaling in HT-29 cells upon infection; neither was EDL993 WT able to suppress ERK1/2 signaling in HT-29 cells treated with PKA inhibitor, showing that the abrogated ERK1/2 activation was associated with E. coli O157:H7 Tir-induced PKA activation and autophagy inhibition.