O-GlcNAc regulates CD4+ T cell differentiation

Abstract Chronic inflammation is a feature of diabetes and obesity and enhances the risk of atherosclerosis and cancer. Specifically, proinflammatory Th1 and Th17 CD4+ T cells are increased in metabolic diseases. However, a clear molecular mechanism linking metabolic changes with proinflammatory T cells is lacking. We hypothesize that elevated levels of O-linked β-N-acetylglucosamine (O-GlcNAc), a post-translational modification of nuclear and cytoplasmic proteins, promotes proinflammatory CD4+ T cell differentiation. Since production of O-GlcNAc involves input from carbohydrate, amino acid, fatty acid, and nucleic acid metabolism, the modification acts as a general sensor of a cell’s nutritional status. To investigate O-GlcNAc’s role, we cultured mouse splenic CD4+ T cells with Thiamet-G (TMG), a selective inhibitor of the enzyme that removes O-GlcNAc (O-GlcNAcase, OGA), before activating with anti-CD3 and anti-CD28 under permissive Th0 conditions. We find a significant two-fold increase in protein and transcript levels of IL-17A, the eponymous Th17 cytokine. Intracellular cytokine staining shows two-fold increases in IFNγ+ cells, IL-17+ cells, and IFNγ+IL-17+ cells. Phosphorylation of STAT3 and STAT4, the transcriptionally active form of STATs which define the Th17 and Th1 lineage programs respectively, is increased in TMG-treated cells within 10 minutes of T cell receptor activation. Collectively, our data suggest that elevated O-GlcNAc levels prime Th17, Th1, and Th1-like Th17 CD4+ T cell differentiation by increasing activated STAT3 and STAT4. Further study into the molecular mechanism of how O-GlcNAcylation promotes proinflammatory T cells may provide insight into how nutritional excess exacerbates inflammation.