MAPK3 and infection: To test if VopQ induces EGR1 and FOS expression by activating the ERK1/2 MAPK pathway early during infection, we starved MEFs to remove basal ERK1/2 phosphorylation, infected them with V. parahaemolyticus T3SS1+ or V. parahaemolyticus T3SS1− for 45, 60, 75, and 90 min, and probed for phospho-ERK1/2 as well as for the presence of downstream Egr1 by Western blotting.