EEF2-inactivating toxins engage the NLRP1 inflammasome and promote epithelial barrier disruption upon Pseudomonas infection

The intracellular inflammasome complex have been implicated in the maladaptive tissue damage and inflammation observed in chronic Pseudomonas aeruginosa infection. Human airway and corneal epithelial cells, which are critically altered during chronic infections mediated by P. aeruginosa , specifically express the inflammasome sensor NLRP1. Here, together with a companion study, we report that the NLRP1 inflammasome detects Exotoxin A (EXOA), a ribotoxin released by P. aeruginosa Type 2 Secretion System (T2SS) during chronic infection. Mechanistically, EXOA-driven Eukaryotic Elongation Factor 2 (EEF2) ribosylation and covalent inactivation promotes ribotoxic stress and subsequent NLRP1 inflammasome activation, a process shared with other EEF2-inactivating toxins, Diphtheria Toxin and Cholix Toxin. Biochemically, irreversible EEF2 inactivation triggers ribosome stress-associated kinases ZAKα- and P38-dependent NLRP1 phosphorylation and subsequent proteasome-driven functional degradation. Finally, Cystic Fibrosis cells from patients exhibit exacerbated P38 activity and hypersensitivity to EXOA-induced ribotoxic stress-dependent NLRP1 inflammasome activation, a process inhibited by the use of ZAKα inhibitors. Altogether, our results show the importance of P. aeruginosa virulence factor EXOA at promoting NLRP1-dependent epithelial damage and identify ZAKα as a critical sensor of virulence-inactivated EEF2. KEY POINTS P. aeruginosa induces NLRP1-dependent pyroptosis in human corneal and nasal epithelial cells P. aeruginosa Exotoxin A (EXOA) and other EEF2-inactivating bacterial exotoxins activate the human NLRP1 inflammasome EEF2 inactivation promotes ribotoxic stress response and ZAKα kinase-dependent NLRP1 inflammasome activation. Bronchial epithelial cells from Cystic Fibrosis patients show extreme sensitivity to ribotoxic stress-dependent NLRP1 inflammasome activation in response to Exotoxin A P38 and ZAKα inhibition protects Cystic Fibrosis epithelial cell from EXOA-induced pyroptosis