Phosphoethanolamine Cytidylyltransferase 2 Integrates DAG Metabolism and TBK1 Activation to Regulate Antiviral Innate Immunity

However, its specific role in antiviral innate immunity remains poorly understood. Here, we demonstrate that inhibition of phosphoethanolamine cytidylyltransferase 2 (PCYT2), a key enzyme in PE biosynthesis, promotes TBK1 activation to enhance antiviral immune response.

Mechanistically, PCYT2 deficiency leads to the accumulation of diacylglycerol (DAG), which activates protein kinase C δ (PKCδ). We identify PKCδ as a direct kinase for TBK1, and demonstrate that it binds to and phosphorylates TBK1 at Ser716. This Ser716 phosphorylation facilitates subsequent canonical phosphorylation at Ser172, resulting in hyperactivation of the TBK1–IRF3 axis.