TBK1 recruitment to STING activates both IRF3 and NF-κB that mediate immune defense against tumors and viral infections

Abstract

Significance The cGAS-STING pathway is important for immune defense against infection and cancer. STING activation triggers multiple signaling cascades leading to activation of IRF3, NF-κB, and autophagy. By generating mice harboring mutations of STING that specifically inactivate different signaling cascades, we found that ablation of IRF3 activation, which is essential for the induction of type I interferons, was not sufficient to abolish the immune defense against virus infection and cancer in mouse models. Rather, impairing the ability of STING to recruit TBK1, which is important for activating both IRF3 and NF-κB, abolished the immune defense functions of STING. These results demonstrate that the recruitment of TBK1 to STING has functions that are broader than activating IRF3 and inducing type I interferons. The induction of type I interferons through the transcription factor interferon regulatory factor 3 (IRF3) is considered a major outcome of stimulator of interferon genes (STING) activation that drives immune responses against DNA viruses and tumors. However, STING activation can also trigger other downstream pathways such as nuclear factor κB (NF-κB) signaling and autophagy, and the roles of interferon (IFN)-independent functions of STING in infectious diseases or cancer are not well understood. Here, we generated a STING mouse strain with a mutation (S365A) that disrupts IRF3 binding and therefore type I interferon induction but not NF-κB activation or autophagy induction. We also generated STING mice with mutations that disrupt the recruitment of TANK-binding kinase 1 (TBK1), which is important for both IRF3 and NF-κB activation but not autophagy induction (L373A or ∆CTT, which lacks the C-terminal tail). The STING-S365A mutant mice, but not L373A or ∆CTT mice, were still resistant to herpes simplex virus 1 (HSV-1) infections and mounted an antitumor response after cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) treatment despite the absence of STING-induced interferons. These results demonstrate that STING can function independently of type I interferons and autophagy, and that TBK1 recruitment to STING is essential for antiviral and antitumor immunity.