Innate sensing of picornavirus infection involves cGAS-STING-mediated antiviral responses triggered by mitochondrial DNA release

Abstract

Cyclic GMP-AMP synthase (cGAS) plays a key role in the innate immune responses to both DNA and RNA virus infection. Here, we found that enterovirus 71 (EV-A71), Seneca Valley virus (SVV), and foot-and-mouth disease virus (FMDV) infection triggered mitochondria damage and mitochondrial DNA (mtDNA) release in vitro and vivo. These responses were mediated by picornavirus 2B proteins which induced mtDNA release during viral replication. SVV infection caused the opening of mitochondrial permeability transition pore (mPTP) and led to voltage-dependent anion channel 1 (VDAC1)- and BCL2 antagonist/killer 1 (Bak) and Bak/BCL2-associated X (Bax)-dependent mtDNA leakage into the cytoplasm, while EV-A71 and FMDV infection induced mPTP opening and resulted in VDAC1-dependent mtDNA release. The released mtDNA bound to cGAS and activated cGAS-mediated antiviral immune response. cGAS was essential for inhibiting EV-A71, SVV, and FMDV replication by regulation of IFN-β production. cGAS deficiency contributed to higher mortality of EV-A71- or FMDV-infected mice. In addition, we found that SVV 2C protein was responsible for decreasing cGAS expression through the autophagy pathway. The 9th and 153rd amino acid sites in 2C were critical for induction of cGAS degradation. Furthermore, we also show that EV-A71, CA16, and EMCV 2C antagonize the cGAS-stimulator of interferon genes (STING) pathway through interaction with STING, and highly conserved amino acids Y155 and S156 were critical for this inhibitory effect. In conclusion, these data reveal novel mechanisms of picornaviruses to block the antiviral effect mediated by the cGAS-STING signaling pathway, which will provide insights for developing antiviral strategies against picornaviruses.

The antiviral response triggered by the cGAS/STING pathway is subverted by the foot-and-mouth disease virus proteases

“…As a whole, the enhancing effect on FMDV infection observed for the two different compounds tested, known to interfere with the cGAS/STING pathway at different steps, highlights the relevance of this DNA-sensing antiviral route against FMDV infection. This is in agreement with a recent work showing that over-expression of cGAS in porcine kidney cells (PK15) reduced FMDV replication [ 31 ]. We further confirmed the key role of the cGAS enzymatic activity for restraining FMDV infection using recombinant po cGAS-eGFP proteins that were overexpressed either in the wild-type version or as the E200A/D202A inactive form in swine IBRS2 and WSL cells that were subsequently infected with FMDV at different MOI (Supplementary Fig.…”

“…1b). Although it has been recently reported that FMDV infection induced the decrease of STING but did not affect the expression of cGAS in swine PK15 cells [ 31 ], our data suggest that cGAS could be specifically targeted for degradation during FMDV infection. To test that hypothesis, we first studied the effect of co-expression in HEK293 cells of N-terminal FLAG-tagged porcine cGAS (3xFLAG- po cGAS) together with the FMDV-encoded proteases Lbpro and 3Cpro either in their catalytically active wild-type forms or their inactive counterparts Lb(C51A) [ 33 ] and 3C(H46Y) [ 34 ] carrying mutations in their corresponding active sites.…”

“…Also, a recent work showed that the 3C protease encoded by the Seneca valley virus (SVV) can cleave porcine cGAS overexpressed in human cells [ 30 ]. Moreover, triggering of IFN-I responses has been associated to mitochondrial damage and DNA release during picornaviral infection and overexpression of the FMDV non-structural 2B protein induced mtDNA release to the cytosol in swine PK-15 cells [ 31 ]. Here, we show that endogenous cGAS is degraded during FMDV infection in swine cells and describe the double cleavage of cGAS exerted by the two FMDV-encoded Leader and 3C proteases.…”

The regulation of cGAS-STING signaling by RNA virus-derived components

“…It is worth noting that the cGAS-STING signaling can also be regulated by other RNA virus components, such as influenza virus (IAV), encephalomyocarditis virus (EMCV), and lymphocytic choriomeningitis virus (LCMV) [ 73 , 77 – 79 ]. In IAV infection, researchers have demonstrated that STING-dependent IFN-β gene expression was indispensable for limiting viral replication.…”

Porcine deltacoronavirus nonstructural protein 2 inhibits type I and III IFN production by targeting STING for degradation

“…RNA-stimulated signaling is mainly dependent on the adaptor protein mitochondrial antiviral-signaling (MAVS), whereas the signaling triggered by DNA mainly relies on the adaptor protein stimulator of interferon genes (STING) during viral infection [11]. Due to the cross-talk mechanisms between RNA and DNA sensing pathways, the activation of cGAS-STING signaling by RNA viruses has been gradually discovered [12,13]. SARS-CoV-2 infection was reported to activate cGAS-STING through DNA damage, chromatin damage and mitochondrial DNA release [14][15][16].…”