A bioactive mammalian disaccharide associated with autoimmunity activates a STING-TBK1-dependent immune response

DNase III, also known as TREX1, is a 314 amino acid endoplasmic reticulum (ER) tail-anchored 3' exonuclease where the N-terminal region contains the DNase domain and the C-terminal end controls TREX1 localization to the surface of the ER. Disease mutations in the C-terminal region alters TREX1 ability to interact with the oligosaccharyltransferase (OST) subunits Ribophorin 1 (RPN1) and DDOST leading to rapid hydrolysis of lipid-linked oligosaccharides (LLOs) into bioactive free oligosaccharides (fOS) in a switch-like manner. Bioassay-guided fractionation of the fOS pool revealed that the structure responsible for the bioactivity is a mannose (Man) b1-4 N-acetylglucosamine (GlcNAc) disaccharide. The bioactive disaccharide is produced from OST's hydrolyzed LLOs in the cytoplasm and activates a STING-TBK1 dependent immune signal that leads to the upregulation of interferon-stimulated genes (ISGs) and chemokine genes. Overall design: Examine the trancriptome of RAW 264.7 cells when treated with 10uM of Trex1-/- fOS or the ManGn disaccharide for 24 hours.