Sterile- or pathogen-induced endolysosomal damage activate the NLRP6 inflammasome in human intestinal epithelial cells

Abstract

NLRP6 controls host defense against bacteria and viruses in the gastrointestinal tract by a poorly understood mechanism. Here, we report that NLRP6 forms an inflammasome upon endolysosomal damage caused by sterile triggers or bacterial pathogens such as Listeria monocytogenes in human intestinal epithelial cells (IECs). NLRP6 activation required Listeriolysin O-dependent cytosolic invasion of L. monocytogenes and drove IEC pyroptosis via ASC/Caspase-1-mediated GSDMD cleavage. NLRP6 inflammasome formation was independent of bacterial PAMPs, such as lipoteichoic acid or dsRNA, which were previously reported to activate NLRP6. L. monocytogenes mutants deficient in cell-to-cell spread or escape from secondary vacuoles induced less cell death, linking bacteria-induced endolysosomal damage to NLRP6 activation. Finally, sterile endolysosomal damage recapitulated pathogen-induced NLRP6 activation and drove IEC pyroptosis. In summary, our study reveals that NLRP6 allows IECs to detect endolysosomal damage, thereby not only making it responsive to pathogens but more generally to wide-ranging sources of pathological endolysosomal damage.