O-GlcNAcylation of irf3 by a novel Zebrafish O-GlcNAc transferase isoform Ogtb_tv3 facilitates its sufficient activation and innate antiviral response

Metabolic pathways are crucial for regulating immune responses, yet the specific mechanisms influencing innate immunity in fish during viral infections remain poorly understood. This study aims to bridge this gap by elucidating the role of the hexosamine biosynthesis pathway (HBP)–associated O-linked β-N-acetylglucosamine (O-GlcNAc) signaling in enhancing antiviral innate immunity in zebrafish. We discovered that infection with spring viremia of carp virus (SVCV) significantly activates the HBP, leading to enhanced protein O-GlcNAcylation in zebrafish. We identified a novel O-GlcNAc transferase isoform, Ogtb_tv3, essential for the O-GlcNAcylation of the transcription factor IRF3. This modification is crucial for the full activation of IRF3 and the subsequent initiation of antiviral gene expression. Pharmacological enhancement of the HBP - O-GlcNAc pathway further potentiated these antiviral responses, directly linking metabolic activity to immune efficacy. Our findings demonstrate that O-GlcNAcylation mediated by Ogtb_tv3 within the HBP is critical for activating IRF3 during SVCV infection, thus enhancing the immune response in zebrafish. This study highlights the significant role of glucose metabolism in antiviral innate immunity and suggests targeting metabolic pathways as a novel therapeutic strategy against viral infections.