NPRL2 restricts porcine reproductive and respiratory syndrome virus replication by targeting viral Nsp1α for autophagic degradation

Host factors that directly target viral immune antagonists are crucial for antiviral defense. In this study, we identify NPRL2 as a novel host restriction factor that directly interacts with the porcine reproductive and respiratory syndrome virus (PRRSV) protein Nsp1α, a key viral virulence factor. This interaction is mediated by the C-terminal domain of NPRL2 and the PCPα domain of Nsp1α. Functional studies demonstrated that NPRL2 overexpression inhibits PRRSV replication, while its knockdown enhanced viral propagation. Mechanistically, NPRL2 acts as a bridge, mediating K63-linked ubiquitination of Nsp1α at lysine 150 and subsequently recruiting the autophagic machinery for its degradation. This process was confirmed by monitoring LC3-II conversion and autophagic flux. Our findings reveal a precise mechanism by which NPRL2 antagonizes PRRSV by targeting a critical viral protein for autophagic degradation, highlighting the therapeutic potential of harnessing the host's ubiquitin-autophagy pathway to combat viral infections.