Cytosolic DNA-induced CGAS-STING1-dependent autophagy promotes SFTSV and EV-71 replication

The CGAS-STING1 pathway is an innate immune system that can detect double-stranded DNA in the cytoplasm and trigger antiviral immune responses. Increasing evidence indicates that CGAS-STING1 signaling can induce autophagy; however, the activation and potential role of the CGAS-STING1-dependent autophagy during RNA virus infection remain unclear. Here, we initially observed that cytosolic DNA acts as a potent inducer of CGAS-STING1-dependent autophagy. Unexpectedly, pre-activation of this pathway via DNA-CGAS-STING1 (1-340) transfection significantly promoted the replication of RNA viruses tested including SFTSV and enterovirus 71 (EV-71). Using SFTSV as a model to investigate the physiological trigger during infection, we demonstrated that SFTSV induces mitochondrial damage, leading to the leakage of mitochondrial DNA (mtDNA) into the cytoplasm. This endogenous mtDNA activates CGAS-STING1-dependent autophagy, which SFTSV then exploits for its replication. Indeed, depletion of mtDNA abolishes SFTSV-induced autophagy and impairs viral replication. Mechanistically, the SFTSV nucleoprotein directly interacts with STING1, hijacking STING1-derived membranes from the endoplasmic reticulum-Golgi intermediate compartment (ERGIC) and Golgi apparatus to form its replication platform. Our study reveals a new host anti-RNA virus strategy, namely activating CGAS-STING1-dependent autophagy through cytosolic DNA, as well as the mechanism by which SFTSV hijacks CGAS-STING1-dependent autophagy for viral replication.Abbreviations: CGAS: cyclic GMP-AMP synthase; ER: endoplasmic reticulum; ERGIC: endoplasmic reticulum-Golgi intermediate compartment; EV-71: enterovirus 71; EtBr: ethidium bromide; Gn: glycoproteins N; IFN-I: type I interferon; KO: knockout; MOIs: multiplicities of infection; NP: nucleoprotein; NSs: non-structural proteins; ROS: reactive oxygen species; SFTSV: Severe fever with thrombocytopenia syndrome virus; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1; VDAC1: voltage dependent anion channel 1; WT: wild-type; gDNA: genomic DNA; mtDNA: mitochondrial DNA.