PABPC1 Restricts Bat-Origin Swine Acute Diarrhea Syndrome Coronavirus Infection via TOLLIP-Mediated Degradation of Viral Nucleocapsid Protein.

The emergence of swine acute diarrhea syndrome coronavirus (SADS-CoV), an alpha-coronavirus that causes fatal enteric disease in neonatal piglets with mortality rates up to 90%, demonstrates that bat-origin coronavirus has expanded its host range to pigs. Although SADS-CoV exhibits significant pandemic potential and capacity for cross-species transmission, the replication mechanisms of SADS-CoV remain largely unexplored. Identifying host factors responsible for SADS-CoV replication and elucidating its underlying mechanisms is essential for advancing fundamental knowledge of coronavirus biology and developing antiviral therapies. Here, we identified PABPC1 as a novel interactor of the SADS-CoV nucleocapsid (N) protein. Overexpression of PABPC1 restricted SADS-CoV infection, whereas knockdown of PABPC1 enhanced viral replication. Further study indicated PABPC1 as a host restriction factor of SADS-CoV in a manner dependent on its PABC domain. Mechanistically, PABPC1 enhances the ubiquitination of the N protein, therefore facilitating its recognition by the cargo receptor TOLLIP for selective autophagic degradation. This study systematically analyzes the interaction of host factors and the SADS-CoV N protein and identifies PABPC1 as a host restriction factor that limits viral replication via TOLLIP-mediated selective autophagy degradation of the N protein. These findings expand our knowledge of the SADS-CoV replication mechanism and provide additional antiviral strategies for controlling SADS-CoV.