Regulation of lipid metabolism is a primordial function of STING

The stimulator of interferon genes (STING) is a pivotal regulator of type I interferon (IFN) responses. Although the IFN system is confined to vertebrates, STING is present across metazoans and in some unicellular eukaryotes, suggesting involvement in distinct functions prior to vertebrate divergence. We here explored the conservation of STING-mediated regulation of polyunsaturated fatty acid (PUFA) metabolism. We found that tested STING homologs from vertebrates, invertebrates, and unicellular eukaryotes interacted with the fatty acid desaturase 2 (FADS2) rate-limiting enzyme in PUFA metabolism and subsequent functional outputs. The ability to regulate lipid metabolism did not correlate with antiviral activity, suggesting that the cooptation of this metabolic pathway by the IFN-based immune system is independent of STING-associated immune responses. Thus, STING-mediated metabolic regulation is an evolutionarily conserved feature and a primordial STING function.