Avian TRIM13 attenuates antiviral innate immunity by targeting MAVS for autophagic degradation.

MAVS (mitochondrial antiviral signaling protein) is a crucial adaptor in antiviral innate immunity that must be tightly regulated to maintain immune homeostasis. In this study, we identified the duck Anas platyrhynchos domesticus TRIM13 (ApdTRIM13) as a novel negative regulator of duck MAVS (ApdMAVS) that mediates the antiviral innate immune response. Upon infection with RNA viruses, ApdTRIM13 expression increased, and it specifically binds to ApdMAVS through its TM domain, facilitating the degradation of ApdMAVS in a manner independent of E3 ligase activity. Furthermore, ApdTRIM13 recruits the autophagic cargo receptor duck SQSTM1 (ApdSQSTM1), which facilitates its interaction with ApdMAVS independent of ubiquitin signaling, and subsequently delivers ApdMAVS to phagophores for degradation. Depletion of ApdSQSTM1 reduces ApdTRIM13-mediated autophagic degradation of ApdMAVS, thereby enhancing the antiviral immune response. Collectively, our findings reveal a novel mechanism by which ApdTRIM13 regulates type I interferon production by targeting ApdMAVS for selective autophagic degradation mediated by ApdSQSTM1, providing insights into the crosstalk between selective autophagy and innate immune responses in avian species.