title: Restricting Glutamine or Glutamine-Dependent Purine and Pyrimidine Syntheses Promotes Human T Cells with High FOXP3 Expression and Regulatory Properties.
abstract: T cell subsets differ in their metabolic requirements, and further insight into such differences might be harnessed to selectively promote regulatory T cells (Tregs) for therapies in autoimmunity and transplantation. We found that Gln restriction during human T cell activation favored CD4 T cells with high expression of the Treg transcription factor FOXP3. This resulted from shrinking numbers and reduced proliferation of activated FOXP3(lo/-)CD4 T cells while FOXP3(hi)CD4 T cell numbers increased. This gain was abolished by blocking Gln synthetase, an enzyme that responds to Gln and purine/pyrimidine deficiencies. The shift toward FOXP3(hi)CD4 T cells under Gln restriction was recapitulated with inhibitors of Gln-dependent pyrimidine and purine syntheses that together closely mimicked declining cell numbers and cell cycles, and by small interfering RNA knockdown of the respective rate-limiting Gln-consuming enzymes CAD and PPAT. FOXP3(hi)-enriched CD25(hi)CD4 T cells from these cultures inhibited proliferation, but they also produced effector cytokines, including IL-17A. The latter was largely confined to CTLA-4(hi)-expressing FOXP3(hi)-enriched CD25(hi)CD4 T cells that suppressed proliferation more weakly than did CTLA-4(lo/-)CD25(hi)FOXP3(hi)-enriched T cells. A causal link between high IL-17A production and impaired suppression of proliferation could not be demonstrated, however. Collectively, these results reveal a Gln synthetase-dependent increase and resilience of FOXP3(hi) cells under Gln restriction, and they demonstrate that impaired Gln-dependent nucleotide synthesis promotes FOXP3(hi) cells with regulator properties. It remains to be investigated to what extent the concomitant retention of IL-17A-producing CD4 T cells may limit the therapeutic potential of Tregs enriched through targeting these pathways in vivo.
authors.affiliation: Department of Autoimmunity, Transplantation and Inflammation Research, Novartis Institutes for BioMedical Research, 4002 Basel, Switzerland bmetzler022@gmail.com.
authors.forename: Barbara
authors.initials: B
authors.lastname: Metzler
authors.affiliation: Department of Autoimmunity, Transplantation and Inflammation Research, Novartis Institutes for BioMedical Research, 4002 Basel, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Gfeller
authors.affiliation: Department of Autoimmunity, Transplantation and Inflammation Research, Novartis Institutes for BioMedical Research, 4002 Basel, Switzerland.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Guinet
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000502:physiology; D049109:Cell Proliferation; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D051858:Forkhead Transcription Factors / Q000235:genetics*; D005786:Gene Expression Regulation; D005974:Glutamate-Ammonia Ligase / Q000037:antagonists & inhibitors / Q000378:metabolism; D005973:Glutamine / Q000096:biosynthesis / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D020381:Interleukin-17 / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008213:Lymphocyte Activation; D011687:Purines / Q000096:biosynthesis*; D011743:Pyrimidines / Q000096:biosynthesis*
chemical_list: D016207:Cytokines; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; C508717:IL17A protein, human; D020381:Interleukin-17; D011687:Purines; D011743:Pyrimidines; D005973:Glutamine; D005974:Glutamate-Ammonia Ligase