Non-oxidative pentose phosphate pathway controls regulatory T cell function by integrating metabolism and epigenetics

Regulatory T cells (Tregs) are critical for maintaining immune homeostasis and preventing autoimmunity. Here, we show that the non-oxidative pentose phosphate pathway (PPP) regulates Treg function to prevent autoimmunity. Deletion of transketolase (TKT), an indispensable enzyme of non-oxidative PPP, in Tregs causes a fatal autoimmune disease in mice, with impaired Treg suppressive capability despite regular Treg numbers and normal Foxp3 expression levels. Mechanistically, reduced glycolysis and enhanced oxidative stress induced by TKT deficiency triggers excessive fatty acid and amino acid catabolism, resulting in uncontrolled oxidative phosphorylation and impaired mitochondrial fitness. Reduced ?-KG levels as a result of reductive TCA cycle activity leads to DNA hypermethylation, thereby limiting functional gene expression and suppressive activity of TKT-deficient Tregs. We also find that TKT levels are frequently downregulated in Tregs of patients with autoimmune disorders. Our study identifies the non-oxidative PPP as an integrator of metabolic and epigenetic processes that control Treg function. Overall design: CD4+CD25+YFP+ Tregs were isolated from 7-week-old WT and cKO mice which were added DMaKG or vehicle in drinking (n=3 per group). Total RNA was isolated from Tregs and used for RNA sequencing analysis by the Illumina HiSeq X Ten platform. In detail, mRNA was first randomly interrupted using divalent cations in NEB Fragmentation Buffer, then used to prepare libraries with the NEBNext Ultra RNA Library Prep Kit (New England Biolabs, Ipswich, MA), and finally sequenced using the Illumina HiSeq X Ten platform.