Targeting glutamine metabolism mitigates Foxp3-deficiency mediated disease

Abstract Regulatory T (Treg) cells play a key role in enforcing peripheral immunological tolerance to self-antigens. Foxp3 has been widely described as a master regulator for Treg differentiation and maintenance of their suppressive functions. Upon Foxp3 loss of function mutations, Foxp3-deficient Tregs (ΔTreg) develop in the thymus, however, these cells present impaired suppressive capacity and an effector T cell (Teff)-like phenotype. Among the Teff-like characteristics is the shift in their metabolism towards glycolysis and enhanced mitochondrial respiration. Metabolomic analysis revealed an increase in glutamine consumption. Here, we used 6-diazo-5-oxo-norleucine (DON), a broad inhibitor of glutamine-utilizing enzymes to treat Foxp3 deficient mice (Foxp3 ΔeGFPiCre), and observed a significant decrease in Teff cell activation, and IFNγ production from both ΔTreg and Teff cells together with a significant increase in survival. This effect was enhanced when we combined DON treatment with a ΔTreg specific Rictor depletion (Foxp3 ΔeGFPiCreRictor Δ/Δ). Given that glutamine is a key amino acid for T cell activation, we evaluated if this was a pan-T cell effect by inducing Treg depletion in Foxp3 DTRmice with concomitant DON treatment. Surprisingly, in the absence of Tregs, DON was not able to prevent autoimmune disease. These results suggest that DON mitigates Foxp3-deficiency mediated disease in a ΔTreg dependent manner, by improving their suppressive capacities. We are currently performing metabolomic studies to better understand the role of glutamine usage in ΔTreg, more specifically if glutamine is directed to glutaminolysis, nucleotide or glutathione synthesis and how this contributes to Treg cell loss of function. NIH grant 1R01AI153174