NLRP11 is required for canonical NLRP3 and non-canonical inflammasome activation during human macrophage infection with mycobacteria.

Abstract

The NLRP11 protein is only expressed in primates and participates in the activation of the canonical NLRP3 and non-canonical NLRP3 inflammasome activation after infection with gram-negative bacteria. Here, we generated a series of defined NLRP11 deletion mutants to further analyze the role of NLRP11 in NLRP3 inflammasome activation. Like the complete NLRP11 deletion mutant (NLRP11 ^-/- ), the NLRP11 mutant lacking the NACHT and LRR domains (NLRP11 ^ΔN_LRR ) showed reduced activation of the canonical NLRP3 inflammasome, whereas a pyrin domain mutant (NLRP11 ^ΔPYD ) had no effect on NLRP3 activation. The NLRP11 ^-/- and NLRP11 ^ΔN_LRR mutants but not the NLRP11 ^ΔPYD mutant also displayed reduced activation of caspase-4 during infection with the intracytosolic, gram-negative pathogen Shigella flexneri. We found that the human adapted, acid-fast pathogen Mycobacterium tuberculosis and the opportunistic pathogen M. kansasii both activate the non-canonical NLRP11 inflammasome in a caspase-4/5-dependent pathway. In conclusion, we show that NLRP11 functions in the non-canonical caspase-4/5 inflammasome activation pathway and the canonical NRLP3 inflammasome pathway, and that NLRP11 is required for full recognition of mycobacteria by each of these pathways. Our work extends the spectrum of bacterial pathogen recognition by the non-canonical NLRP11-caspase4/5 pathway beyond gram-negative bacteria.