RIOK2 kinase regulates the translocation of the FADD-RIPK1-Caspase-8 complex to the ER and the cleavage of Gasdermin D to drive pyroptosis.

Macrophage infection by the pathogenic bacteria Yersinia or mimic stimulation of lipopolysaccharide (LPS) and transforming growth factor-β-activated kinase 1 (TAK1) inhibitor or tumor necrosis factor (TNF) and TAK1 inhibitor induces caspase-8-mediated gasdermin D (GSDMD) cleavage and pyroptosis. However, the upstream regulator of caspase-8-dependent cleavage of GSDMD remains elusive. Here we show that Serine/threonine-protein kinase RIO2 (RIOK2) interacts with the Fas-associated protein with death domain (FADD) and is essential for caspase-8-driven GSDMD cleavage. RIOK2's kinase activity drives the transport of lysosome to ER through activating myosin II and thereby translocate FADD-RIPK1-caspase-8 complex from lysosome to ER. Importantly, RIOK2's ATPase activity enhances its binding to this complex and directly triggers caspase-8 and gasdermin D cleavage both at ER and in vitro. Furthermore, RIOK2-mediated pyroptosis enhances host defense against Yersinia infection. Thus, our findings define an upstream regulator of caspase-8-dependent pyroptosis, implying a role of organelle crosstalk in spatial cleavage of gasdermins.