To demonstrate the functional importance of the MEK signaling pathway on PGE2 biosynthesis during this Gram-negative infection, we used a chemical inhibitor of MEK signaling during YopJC172A Y. pseudotuberculosis or ΔyopBY. enterocolitica infection of macrophages, which indeed downregulated PGE2 biosynthesis compared to vehicle-treated infected cells (Fig. 4). The gene discussed is MAP2K7; the disease is infection.