RIPK3-MLKL necroptotic signalling amplifies STING pathway and exacerbates lethal sepsis

Abstract

Backgrounds: The stimulator of interferon genes (STING) is an important driver in various inflammatory diseases.

Methods and results: Here, we have demonstrated that inhibition of RIPK3 and MLKL dampens STING signaling, indicating that necroptosis may be involved in sustaining STING signaling. Furthermore, RIPK3 knockout in HT-29 cells significantly suppressed STING signaling. Mechanistically, RIPK3 inhibits autophagic flux during STING activation. RIPK3 knockout inhibits STING signaling by intensifying STING autophagy. In contrast, MLKL regulates the STING pathway bidirectionally. MLKL deficiency enhances STING signaling, whereas suppression of MLKL-mediated pore formation restricts STING signaling. Mechanistically, upon abrogating the pro-necroptotic activity of MLKL, MLKL bound to activated STING is secreted to the extracellular space, where it restricts TBK1 and IRF3 recruitment. Targeting necroptotic signaling ameliorates STING activation during DMXAA-induced intestinal injury and sepsis.

Conclusions: These findings elucidate molecular mechanisms linking necroptosis to the STING pathway, and suggest a potential benefit of therapeutic targeting of necroptosis in STING-driven inflammatory diseases.

Keywords: MLKL; RIPK3; STING; inflammation; sepsis.