The E3 ubiquitin ligase tripartite motif 33 is essential for cytosolic RNA-induced NLRP3 inflammasome activation.

NLRP3 is a key component of caspase-activating macromolecular protein complexes called inflammasomes. It has been found that DHX33 is a cytosolic dsRNA sensor for the NLRP3 inflammasome, which induces caspase-1-dependent production of IL-1β and IL-18 upon activation. However, how the cytosolic dsRNAs induce the interaction between DHX33 and the NLRP3 inflammasome remains unknown. In this study, we report that TRIM33, a member of the tripartite motif (TRIM) family, can bind DHX33 directly and induce DHX33 ubiquitination via the lysine 218 upon dsRNA stimulation. Knocking down of TRIM33 abolished the dsRNA-induced NLRP3 inflammasome activation in both THP-1-derived macrophages and human monocyte-derived macrophages. The ubiquitination of DHX33 by TRIM33 is lysine 63 specific and is required for the formation of the DHX33-NLRP3 inflammasome complex.