CD97 negatively regulates the innate immune response against RNA viruses by promoting RNF125-mediated RIG-I degradation.

The G protein-coupled receptor ADGRE5 (CD97) binds to various metabolites that play crucial regulatory roles in metabolism. However, its function in the antiviral innate immune response remains to be determined. In this study, we report that CD97 inhibits virus-induced type-I interferon (IFN-I) release and enhances RNA virus replication in cells and mice. CD97 was identified as a new negative regulator of the innate immune receptor RIG-I, and RIG-1 degradation led to the suppression of the IFN-I signaling pathway. Furthermore, overexpression of CD97 promoted the ubiquitination of RIG-I, resulting in its degradation, but did not impact its mRNA expression. Mechanistically, CD97 upregulates RNF125 expression to induce RNF125-mediated RIG-I degradation via K48-linked ubiquitination at Lys181 after RNA virus infection. Most importantly, CD97-deficient mice are more resistant than wild-type mice to RNA virus infection. We also found that sanguinarine-mediated inhibition of CD97 effectively blocks VSV and SARS-CoV-2 replication. These findings elucidate a previously unknown mechanism through which CD97 negatively regulates RIG-I in the antiviral innate immune response and provide a molecular basis for the development of new therapeutic strategies and the design of targeted antiviral agents.

DLG1 promotes the antiviral innate immune response by inhibiting p62-mediated autophagic degradation of IKKε.

IMPORTANCE: The type-I interferon (IFN-I) signaling pathway is the first line of antiviral innate immunity. It must be precisely regulated against virus-induced damage. The tightly regulated mechanisms of action of host genes in the antiviral innate immune signaling pathway are still worth studying. Here, we report a novel role of DLG1 in positively regulating the IκB kinase epsilon (IKKε)-mediated IFN-I signaling response against negative-stranded RNA virus replication, whereas the RNA virus inhibits the expression of DLG1 for immune escape. Importantly, the E3 ligase March2 interacts with and promotes K27-linked polyubiquitination of IKKε, and p62 is a cargo receptor that recognizes ubiquitinated IKKε for eventual autophagic degradation. Together, the current findings elucidate the role of DLG1 in the antiviral IFN-I signaling pathway and viral infection repression.