Abstract 477: The Regulatory Role Of TIFA In The Noncanonical Inflammasome

Noncanonical inflammasome is a novel form of inflammasome, in which caspase-4/5 are both the effectors and the receptors. The activation of the noncanonical inflammasome induces pyroptosis and NLRP3 inflammasome activation. Although intracellular lipopolysaccharide (LPS) is a well-known inducer of noncanonical inflammasome, the role of noncanonical inflammasome in various infectious and noninfectious diseases is still unknown. TIFA [TRAF-interacting protein with a forkhead-associated (FHA) domain] is an immune regulator that activates the NF-κB pathway and the NLRP3 inflammasome and is upregulated in the granulocytes of MIS-C patients. TIFA self-oligomerizes via the interaction between the FHA domain and phosphorylated Thr9 on adjacent TIFA molecules. Phosphorylated TIFA oligomerizes TRAF6 or caspase-1 which ultimately activates NF-κB and the NLRP3 inflammasome. We found that several inflammatory conditions induced the noncanonical inflammasome, the release of IL-1β, and pyroptosis. Mechanistically, TIFA oligomerized caspase-4 and activated caspase-4 via TIFA Thr9 phosphorylation. By analyzing COVID-19 single-cell RNA sequencing dataset, we found that the TIFA/caspase-4 pathway is upregulated in COVID-19-specific neutrophils subset. Leukocytes isolated from COVID-19 patients exhibited activated TIFA and caspase-4 p30, suggesting that the TIFA/caspase-4 pathway played a role during the onset of COVID-19. Together, our results reveal a novel mechanism of the noncanonical inflammasome and its involvement in non-bacterial infectious and sterile inflammatory diseases.