DUSP6 mediates T cell receptor-engaged glycolysis and restrains TFH cell differentiation

Activated T cells undergo metabolic reprogramming and effectorcell differentiation but the factors involved are unclear. Utilizing mice lacking DUSP6 (DUSP6−/−), we show that this phosphatase regulates T cell receptor (TCR) signaling to influence follicular helper T (TFH) cell differentiation and T cell metabolism. In vitro, DUSP6−/− CD4⁺ TFH cells produced elevated IL-21. In vivo, TFH cells were increased in DUSP6−/− mice and in transgenic OTII-DUSP6−/− mice at steady state. After immunization, DUSP6−/− and OTII-DUSP6−/− mice generated more TFH cells and produced more antigen-specific IgG2 than controls. Activated DUSP6−/− T cells showed enhanced JNK and p38 phosphorylation but impaired glycolysis. JNK or p38 inhibitors significantly reduced IL-21 production but did not restore glycolysis. TCR-stimulated DUSP6−/− T cells could not induce phosphofructokinase activity and relied on glucose-independent fueling of mitochondrial respiration. Upon CD28 costimulation, activated DUSP6−/− T cells did not undergo the metabolic commitment to glycolysis pathway to maintain viability. Unexpectedly, inhibition of fatty acid oxidation drastically lowered IL-21 production in DUSP6−/− TFH cells. Our findings suggest that DUSP6 connects TCR signaling to activation-induced metabolic commitment toward glycolysis and restrains TFH cell differentiation via inhibiting IL-21 production.