Non-haemolytic enterotoxin induces pore-formation and activation of the inflammasome and pyroptosis

Abstract

Abstract Inflammasomes are central to innate immunity mediating host defence against pathogens and maintaining homeostasis with commensal microbes. The sensing of pathogens, danger, or homeostasis-altering signals by inflammasome sensor proteins is the molecular basis driving assembly of the inflammasome complex. Here, we identify non-haemolytic enterotoxin (NHE) as an activator of the NLRP3 inflammasome. We show that NHE, found in the neglected human foodborne pathogen Bacillus cereus, is a non-redundant toxin to haemolysin BL (HBL) despite exhibiting a similar mechanism of action. NHE-induced activation of NLRP3 has a delayed kinetic to that induced by HBL. Subunit C of NHE, via its putative transmembrane region, initiates binding to the plasma membrane, leading to the recruitment of subunit B and subunit A, forming a tripartite lytic pore permissive to efflux of potassium. NHE mediates killing of cells from multiple lineages and hosts, highlighting its versatile functional repertoire in different host species. Moreover, our data suggest that both NHE and HBL operate synergistically to induce inflammation in the host. Overall, our results highlight that multiple virulence factors from the same pathogen exhibiting conserved function and mechanism of action can be exploited for sensing by a single inflammasome, ultimately leading to increased capacity of the host to detect and defend against naturally-occurring genetic variants.