Host nucleic acid receptors can recognize the viral DNA or RNA upon virus infection, which further triggers multiple signal pathways to promote the translocation of the interferon regulatory factor 3 (IRF3) into nucleus and produce type I interferon (IFN), leading to the host antiviral response. Here, we report a novel negative regulator Annexin A2 (ANXA2) that regulates type I IFN production through multiple mechanisms. Ectopic expression of ANXA2 inhibited the production of type I IFN induced by DNA- and RNA viruses and enhanced virus replication, while knockout of ANXA2 expression enhanced the production of type I IFN and inhibited virus replication. Mechanistically, ANXA2 not only disrupted MDA5 recruiting MAVS, but also inhibited the interaction between MAVS and TRAF3 upon RNA virus infection. In addition, ANXA2 impacted the translocation of STING from endoplasmic reticulum to Golgi apparatus upon DNA virus infection. Interestingly, ANXA2 also inhibited IRF3 phosphorylation and nuclear translocation through competing with TANK-binds kinase 1 (TBK1) and inhibitor-κB kinase ε (IKKε) for binding to IRF3. Anxa2 deficiency in vivo increased the production of type I IFN, which resulted in suppression of encephalomyocarditis virus (EMCV) replication. Our findings reveal that ANXA2, as a negative regulator of type I IFN production, plays an important role in regulating the host antiviral responses.
Annexin is a family of evolutionarily conserved multi-gene proteins, which are widely distributed in various tissues and cells of plants and animals. These proteins can reversibly bind to phospholipid membranes and to calcium ions (Ca 2+ ). To date, several studies have confirmed that some members of the Annexin family regulate the antiviral innate immune response. Until now, regulation of the production of type I IFN by ANXA2 is not reported. In this study, ANXA2 were found to strongly inhibit the production of type I IFN, leading to increased virus replication while knockout of ANXA2 expression inhibited virus replication by increasing the amount of IFN. Compared with wild-type littermates, ANXA2 deficiency mice produced more type I IFN to inhibit virus replication. Our results provide methanistic insights into the novel role of ANXA2 in the antiviral innate immune responses.