Inflammasomes: Intracellular detection of extracellular bacteria

Abstract

The non-canonical inflammasome triggers host cell death and inflammation upon recognition of cytosolic LPS. A recent report in Cell now shows that Outer Membrane Vesicles (OMVs) of extracellular Gram-negative bacteria can deliver LPS into the host cell cytosol.

Figure 1

Gram-negative bacteria release LPS-containing Outer Membrane vesicles (OMVs), which can be internalized by host cells through endocytosis. OMVs escape the early endosomes before these mature into late endosomes/lysosomes and translocate to the cytosol. Here, the LPS found in OMVs is sensed by the non-canonical inflammasome, resulting in the activation of caspase-11 in mouse cells or caspase-4 or caspase-5 in human cells. These caspases initiate pyroptotic host cell death and activate the non-canonical NLRP3 pathway, which drives caspase-1-dependent cytokine maturation.