FTO O-GlcNAcylation downregulates NLRP3 inflammasome and pyroptosis in macrophages

The fat mass and obesity-associated protein (FTO), a key RNA N6-methyladenosine (m6A) demethylase, has recently emerged as a significant regulator of inflammatory response. However, the specific role and underlying mechanisms of FTO, especially FTO O-GlcNAcylation, in inflammation remain elusive. Here we report a mechanism that O-GlcNAcylation modification controls the biological functions of the FTO protein in macrophage inflammatory response. For the first time, we demonstrate that FTO undergoes O-GlcNAcylation specifically at the Ser95 site. The bacterial endotoxin (lipopolysaccharide, LPS) stimulation enhances FTO O-GlcNAcylation in macrophages through the FOXO1-GFAT2 axis. LPS-enhanced O-GlcNAcylation of FTO promotes TRIM21-mediated FTO ubiquitination degradation and suppresses NLRP3-ASC-Casp1 inflammasome activation and gasdermin D pyroptosis in murine macrophages. FTO O-GlcNAcylation deficiency aggravates S. Typhimurium or LPS-induced sepsis and dextran sulfate sodium (DSS)-induced inflammatory bowel diseases (IBD), while FTO O-GlcNAcylation suppresses the hyperinflammatory phenotype in mice. These findings reveal a novel mechanism that FTO O-GlcNAcylation promotes its degradation and downregulates FTO-mediated inflammatory response. Regulation of FTO O-GlcNAcylation may offer a potential therapeutic strategy for combating endotoxin-induced inflammatory disease and other FTO abnormal expression-associated diseases.