Macrophages infected with Gram-negative bacteria expressing Type III secretion system (T3SS) activate the NLRC4 inflammasome, resulting in Gasdermin D (GSDMD)-mediated IL-1β secretion and pyroptosis. Here we examined inflammasome signaling in neutrophils infected withPseudomonas aeruginosastrain PAO1 that expresses the T3SS effectors ExoS and ExoT. IL-1β secretion by neutrophils required the T3SS needle and translocon proteins and GSDMD. In macrophages, PAO1 and mutants lacking ExoS and ExoT (ΔexoST) stimulated NLRC4 for IL-1β secretion. While IL-1β release fromΔexoSTinfected neutrophils was also NLRC4-dependent, this was redirected to NLRP3-dependence by PAO1 infection via the ADP ribosyl transferase activity of ExoS. Genetic and pharmacologic approaches revealed that NLRP3, but not NLRC4, was essential for bacterial killing and limiting disease severity in a murine model ofP. aeruginosacorneal infection. This reveals a novel role for ExoS ADPRT in regulating inflammasome subtype usage by neutrophils versus macrophages and an unexpected role for NLRP3 inP. aeruginosakeratitis.
