O-GlcNAcylation licenses RNF166 to degrade the M protein of porcine coronaviruses.

Uridine diphosphate N‑acetylglucosamine (UDP‑GlcNAc) has often been overlooked because its source pathway contributes little to glucose flux. However, through O‑GlcNAcylation, even small fluctuations in UDP‑GlcNAc levels can be amplified to shape immune responses. In this study, we utilized porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus with zoonotic potential, as a model to investigate the role of UDP-GlcNAc in viral infection. Our findings demonstrate that upon PDCoV infection, host cells increase the synthesis of UDP-GlcNAc, which inhibits viral replication by remodeling metabolic pathways. Mechanistically, O-linked N-acetylglucosamine transferase (OGT) transfers an O-GlcNAc moiety from UDP-GlcNAc to RNF166 at T157, resulting in O-GlcNAcylation. This modification enables RNF166 to ubiquitinate the PDCoV membrane (M) protein at K207, thereby promoting its degradation via the ubiquitin-proteasome pathway. Notably, these effects are common in the host response to porcine coronavirus infections, highlighting the intricate interplay among metabolism, glycosylation, and ubiquitination in immune responses.