The inflammasome is a macromolecular protein complex that mediates proteolytic cleavage of pro-IL-1β and -IL-18 and induces cell death in the form of pyroptosis. Certain nucleotide-binding oligomerization domain-like receptors (NLRs), absent in melanoma 2 (AIM2)-like receptors (ALRs), or tripartite motif (TRIM) family receptors trigger the assembly of an inflammasome in response to pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs). Recent studies have revealed a multitude of host components and signals that are essential for controlling canonical and noncanonical inflammasome activation and pyroptosis. These include pore-forming gasdermin proteins, the never in mitosis A-related kinase 7 (NEK7), IFN-inducible proteins (IFIs), reactive oxygen species (ROS), autophagy, potassium efflux, mitochondrial perturbations, and microbial metabolites. Here, we provide a comprehensive overview of the molecular and signaling mechanisms that provide stringent regulation over the activation and effector functions of the inflammasome.

Infection is a dynamic biological process underpinned by a complex interplay between the pathogen and the host. Microbes from all domains of life, including bacteria, viruses, fungi, and protozoan parasites, have the capacity to cause infection. Infection is sensed by the host, which often leads to activation of the inflammasome, a cytosolic macromolecular signaling platform that mediates the release of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 and cleavage of the pore-forming protein gasdermin D, leading to pyroptosis. Host-mediated sensing of the infection occurs when pathogens inject or carry pathogen-associated molecular patterns (PAMPs) into the cytoplasm or induce damage that causes cytosolic liberation of danger-associated molecular patterns (DAMPs) in the host cell. Recognition of PAMPs and DAMPs by inflammasome sensors, including NLRP1, NLRP3, NLRC4, NAIP, AIM2, and Pyrin, initiates a cascade of events that culminate in inflammation and cell death. However, pathogens can deploy virulence factors capable of minimizing or evading host detection. This review presents a comprehensive overview of the mechanisms of microbe-induced activation of the inflammasome and the functional consequences of inflammasome activation in infectious diseases. We also explore the microbial strategies used in the evasion of inflammasome sensing at the host-microbe interaction interface.

Host recognition of microbial components is essential in mediating an effective immune response. Cytosolic bacteria must secure entry into the host cytoplasm to facilitate replication, and in doing so, liberating microbial ligands which activate cytosolic innate immune sensors and the inflammasome. Here, we identified a multi-component enterotoxin hemolysin BL (HBL) which

Inflammasomes are important for host defence against pathogens and homeostasis with commensal microbes. Here, we show non-haemolytic enterotoxin (NHE) from the neglected human foodborne pathogen Bacillus cereus is an activator of the NLRP3 inflammasome and pyroptosis. NHE is a non-redundant toxin to haemolysin BL (HBL) despite having a similar mechanism of action. Via a putative transmembrane region, subunit C of NHE initiates binding to the plasma membrane, leading to the recruitment of subunit B and subunit A, thus forming a tripartite lytic pore that is permissive to efflux of potassium. NHE mediates killing of cells from multiple lineages and hosts, highlighting a versatile functional repertoire in different host species. These data indicate that NHE and HBL operate synergistically to induce inflammation and show that multiple virulence factors from the same pathogen with conserved function and mechanism of action can be exploited for sensing by a single inflammasome.

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