Metabolic control of TH17 and induced Treg cell balance by an epigenetic mechanism

Abstract

Metabolism has been shown to integrate with epigenetics and transcription to modulate cell fate and function. Beyond meeting the bioenergetic and biosynthetic demands of T-cell differentiation, whether metabolism might control T-cell fate by an epigenetic mechanism is unclear. Here, through the discovery and mechanistic characterization of a small molecule, (aminooxy)acetic acid, that reprograms the differentiation of T helper 17 (T17) cells towards induced regulatory T (iT) cells, we show that increased transamination, mainly catalysed by GOT1, leads to increased levels of 2-hydroxyglutarate in differentiating T17 cells. The accumulation of 2-hydroxyglutarate resulted in hypermethylation of the Foxp3 gene locus and inhibited Foxp3 transcription, which is essential for fate determination towards T17 cells. Inhibition of the conversion of glutamate to α-ketoglutaric acid prevented the production of 2-hydroxyglutarate, reduced methylation of the Foxp3 gene locus, and increased Foxp3 expression. This consequently blocked the differentiation of T17 cells by antagonizing the function of transcription factor RORγt and promoted polarization into iT cells. Selective inhibition of GOT1 with (aminooxy)acetic acid ameliorated experimental autoimmune encephalomyelitis in a therapeutic mouse model by regulating the balance between T17 and iT cells. Targeting a glutamate-dependent metabolic pathway thus represents a new strategy for developing therapeutic agents against T17-mediated autoimmune diseases.

Distinct Regulation of Th17 and Th1 Cell Differentiation by Glutaminase-Dependent Metabolism

“…Although GLS fl/fl CD4-Cre + T cells efficiently deleted Gls compared to control GLS fl/fl T cells (Figure 3A), lymphocyte frequencies and numbers were unaltered (Figure 3B). Treg cells have been previously shown to be increased by ASCT2 or GOT1 deficiency (Nakaya et al, 2014; Xu et al, 2017) but were unchanged with GLS deficiency. Resting GLS fl/fl CD4-Cre + CD4 T cells also had normal cell size and phenotype (Figure 3C).…”

“…Deficient GLS activity may alter differentiation through production of cofactors, including α-KG and 2-hydroxyglutarate (2-HG), for epigenetic marks and changes in chromatin status (Reid et al, 2017; Xu et al, 2017). Intracellular levels of α-KG were reduced in CB839-treated Th1 but not Th17 cells, while 2-HG increased in both Th1 and Th17 (Figures S5A and S5B).…”

“…Changes in α-KG and 2-HG may alter histone methylation and chromatin accessibility that influence T cell differentiation (Xu et al, 2017). Histone trimethylation was globally assessed by flow cytometry.…”

“…Deficiency of the glutamine transporter ASCT2 suppressed proliferation, impaired both Th1 and Th17 T cell specification, and enhanced Treg generation (Nakaya et al, 2014). Suppression of GOT1, which converts aspartate and α-KG to glutamate and oxaloacetate, impaired Th17 with increased Treg differentiation (Xu et al, 2017). GLS deficiency differs to selectively promote Th1 and impair Th17 differentiation while not affecting Treg.…”

“…Glutamine deprivation or deletion of ASCT2 was shown to promote Foxp3 expression, the transcription factor of regulatory T cells (Treg) (Klysz et al, 2015; Nakaya et al, 2014). Inhibition or silencing of the glutamic-oxaloacetate transaminase 1 (GOT1) enzyme that mediates conversion of glutamate to α-KG led to a shift in differentiation of Th17 to Treg via methylation of the Foxp3 locus (Xu et al, 2017). Further, direct treatment of T cells with α-KG altered gene expression and chromatin methylation, in part through the CCCTC-binding factor (CTCF) (Chisolm et al, 2017).…”