Grass Carp Parkin Degrades Tbk1 via the Autophagic Degradation to Suppress the Ifn Response

Interferon (IFN) serves as a critical antiviral effector molecule in innate immunity, however, its excessive or inappropriate expression can lead to chronic inflammation and autoimmune diseases, necessitating precise regulation. This study reveals that Parkin, an E3 ubiquitin protein ligase encoded by the grass carp parkin gene, negatively regulates IFN expression. Following infection with grass carp reovirus (GCRV), Parkin expression is significantly upregulated at both cellular and tissue levels. Functional experiments demonstrated that overexpression of Parkin markedly suppressed IFN expression induced by GCRV or its analog poly I﹕C, whereas knockdown of parkin enhanced IFN production. Mechanistically, Parkin bound to and promoted the degradation of TANK-binding kinase 1 (TBK1) via the autophagy-lysosomal pathway, thereby blocking the TBK1-mediated IFN response. Furthermore, overexpression of Parkin promotedGCRV proliferation, while parkin knockdown inhibited viral replication. In summary, grass carp Parkin plays an important role in antiviral immunity by negatively regulating the IFN response through targeted degradation of TBK1.