RNF115-Tollip coordination mediates selective autophagic degradation of N protein during PEDV infection.

Porcine epidemic diarrhea virus (PEDV) is a highly lethal swine coronavirus that poses a persistent threat to animal health due to its adaptability and frequent mutations. Despite available vaccines, control remains challenging because of immune evasion and complex host responses. Understanding virus-host interactions, particularly selective degradation pathways, is crucial for improving control strategies. This study systematically reveals the role of E3 ubiquitin ligase RNF115 (also known as BCA2 or Rabring7) during PEDV infection, identifying it as a key regulator of selective autophagy. PEDV infection significantly suppresses RNF115 expression, while exogenous overexpression of RNF115 inhibits viral replication in a time- and dose-dependent manner. In contrast, knockdown of RNF115 promotes viral proliferation, highlighting its critical antiviral function. Notably, RNF115 not only enhances autophagic flux or maintains cellular homeostasis but also selectively targets and degrades the viral N protein. This process involves RNF115-mediated formation of K63-linked polyubiquitin chains, with key ubiquitination sites on N protein identified as K271, K276, K302, K359, and K375. Furthermore, the C25 and C38 residues of RNF115 are critical for its ability to ubiquitinate N protein. In addition, we identified Tollip as a key adaptor that forms a stable complex with RNF115 and the N protein, facilitating substrate recognition. Knockdown of Tollip significantly impaired N protein ubiquitination and degradation, underscoring its bridging role in RNF115-mediated selective autophagy. This study elucidates that RNF115 mediates selective autophagy during PEDV infection and also provides potential therapeutic targets at the site of PEDV nuclear coat protein degradation.