Seneca Valley virus 2B and 3 C proteins attenuate the cGAS-STING signaling pathway by targeting STING for degradation

Seneca Valley virus (SVV), an emerging porcine picornavirus, has attracted significant attention recently as it presents a substantial threat to the global pork industry. Stimulator of interferon genes (STING) is an endoplasmic reticulum (ER)-associated adaptor protein that plays a crucial role in the type I interferon (IFN-I) signaling pathway, which triggers IFN-stimulated gene (ISG) production to elicit antiviral innate immunity. SVV has evolved numerous strategies to counteract the IFN-I signaling pathway and evade innate immunity. However, the mechanism underlying immune evasion in SVV infection remains unclear. In this study, we observed that SVV 2B and 3 C protease (3 C^pro) proteins promoted STING degradation to antagonize IFN-I activation through autophagy and caspase pathways, respectively. Mechanistically, 2B bound to STING, recruiting toll-interacting protein (Tollip) and neighbor of BRCA1 gene 1 (NBR1) to promote STING for autophagy degradation, and 2B prevented the STING-TBK1 interaction. Furthermore, SVV 3 C^pro antagonized host IFN-I signaling by cleaving interferon-stimulated gene 60 (ISG60) at Gln-406. The cleaved ISG60 products failed to inhibit SVV infection. Collectively, our study uncovered that SVV subverts the IFN-I response by targeting STING and ISG60, providing deeper insights into a novel mechanism utilized by SVV to antagonize the host's innate immune response.