Annexin A2 (ANXA2) is known to promote the replication of diverse RNA viruses, often through interactions with specific viral proteins. However, whether it also employs a broad-spectrum, virus-independent strategy to facilitate viral replication remains unclear. Here, we identify ANXA2 as a novel negative regulator of the host antiviral response by targeting the RIG-I-like receptor (RLR) signaling pathway. We demonstrate that overexpression of ANXA2 suppresses type I interferon (IFN) production induced by RNA viruses or poly(I:C), whereas ANXA2 deficiency enhances IFN production and restricts viral replication both in vitro and in vivo. Mechanistically, ANXA2 functions as a scaffold protein that concurrently disrupts two critical steps in RLR signaling: it impedes the recruitment of MAVS by MDA5 through interacting with the CARD domain of MDA5, and it inhibits the MAVS-TRAF3 interaction by binding to the linker region of MAVS. Consequently, ANXA2 deficiency leads to enhanced type I IFN production in mice, which effectively restrains replication of encephalomyocarditis virus and vesicular stomatitis virus. Collectively, our study uncovers a novel and broad-spectrum immunomodulatory function of ANXA2, wherein it dampens antiviral innate immunity by sabotaging key protein-protein interactions (MDA5-MAVS or MAVS-TRAF3) within the RLR pathway, thereby presenting a potential target for developing antiviral strategies.

Importance: Subsequent to RNA viral infection, a series of complex cascade reactions are initiated, leading to the production of type I interferons and, consequently, the resistance of the organism to viral infection. This study elucidates the function of Annexin A2 (ANXA2) as a novel key negative regulator in the host antiviral immune response. Mechanistically, ANXA2 achieves its inhibitory effect by disrupting critical signaling steps in the RLR pathway, specifically interfering with key interactions between MDA5 and MAVS, as well as between MAVS and TRAF3. These findings are significant in that they reveal an unknown mechanism by which viruses exploit host proteins to evade immunity, and they position ANXA2 as a potential therapeutic target for developing novel antiviral strategies. The validation of these findings in an ANXA2-deficient mouse model, which exhibits enhanced interferon production and restricted viral replication, serves to further reinforce the physiological relevance of these observations.

Keywords: Annexin A2; MDA5; type I IFN.