The noncanonical inflammasome in health and disease

Innate immune signaling plays a significant role in the rapid cellular responses against foreign entities. An inflammasome is a large cytosolic polymer of a pattern recognition receptor with/without an adaptor protein, formed in response to these entities. Canonically, an inflammasome can recruit and lead to auto-activation of caspase-1, subsequent maturation and secretion of inflammatory cytokines, and pyroptosis. One particular inflammasome, the noncanonical inflammasome, is formed by caspase-4 or -5 (mouse caspase-11) upon binding of lipopolysaccharide and is essential for controlling gram-negative bacterial infection. However, prolonged hyper-activation of the non-canonical inflammasome has been implicated in the pathogenesis of inflammatory diseases and endotoxemia sepsis. This review will summarize the recent advances on the noncanonical inflammasome, its mechanism of activation, key cellular regulators and role in health and disease.