RNF187 inhibits porcine reproductive and respiratory syndrome virus replication by recruiting the autophagy receptor NDP52 to degrade nsp12

Porcine reproductive and respiratory syndrome is one of the most devastating diseases affecting global swine production. Viral nonstructural protein 12 (nsp12) is a key factor in viral replication during viral subgenomic RNA synthesis. We identified the host E3 ubiquitin ligase RING finger protein 187 (RNF187) as a novel anti-porcine reproductive and respiratory syndrome virus (PRRSV) host-restriction factor. RNF187 directly interacts with nsp12, and the overexpression of RNF187 significantly inhibits the expression of the viral nucleocapsid (N) protein and the titer of viruses, whereas the knockdown of RNF187 promotes viral replication. Mechanistic studies showed that RNF187 mediates the degradation of nsp12 in a dose-dependent manner. This degradation process can be blocked by the autophagy inhibitor, 3-methyladenine (3-MA). These results indicate that RNF187 degrades nsp12 via the autophagy pathway rather than the proteasome pathway. Mechanistically, RNF187 acts as a scaffold protein to recruit the autophagic cargo receptor NDP52 and promotes the K63-linked polyubiquitination at lysine 130 (K130) of nsp12, thereby targeting nsp12 for autophagy-lysosomal degradation. This study revealed a novel host defense mechanism mediated by the RNF187-NDP52 axis, which restricts PRRSV infection by targeting nsp12, thereby providing a potential target for the development of antiviral strategies.