Palmitic Acid Promotes Antiviral Innate Immunity via ZDHHC20‐Mediated CMPK2 Palmitoylation

ABSTRACT While immunometabolic crosstalk is critical for antiviral defence, the regulation of this process, particularly through post‐translational modifications, remains incompletely understood. How specific metabolites and associated modifications orchestrate antiviral immunity remains unclear. By screening a metabolic chemical library, we identify palmitic acid (PA) as an activator of antiviral immunity in macrophages. PA induces UMP‐CMP kinase 2 (CMPK2) palmitoylation, maintaining its mitochondrial localization. CMPK2 is vital for the production of 3'‐deoxy‐3',4',‐didehydrocytidine triphosphate (ddhCTP) and the stabilization of mitochondrial antiviral signaling protein (MAVS), both of which are crucial for defence against RNA viruses. Cmpk2 deficiency impairs IFN‐I production and increases viral replication. Furthermore, the palmitoyl transferase ZDHHC20 catalyzes CMPK2 palmitoylation at cysteines 137 and 153, which are depalmitoylated by the thioesterase PPT1. PPT1 deficiency restores CMPK2 palmitoylation and antiviral immunity. Both a palm oil‐rich diet and the in vivo administration of the PPT1 inhibitor DC661 increase IFN‐I production. Therefore, the PA‐ZDHHC20‐CMPK2‐PPT1 axis enhances the antiviral response, indicating that targeting PPT1 has the potential to treat RNA virus infections.