TGFβ limits Myc-dependent TCR-induced metabolic reprogramming in CD8+ T cells

Abstract

T cell activation is dependent upon the integration of antigenic, costimulatory and cytokine-derived signals and the availability and acquisition of nutrients from the environment. Furthermore, T cell activation is accompanied by reprogramming of cellular metabolism to provide the energy and building blocks for proliferation, differentiation and effector function. Transforming growth factor {beta} (TGF{beta}) has pleiotropic effects on T cell populations, having both an essential role in the maintenance of immune tolerance but also context-dependent pro-inflammatory functions. We set out to define the mechanisms underpinning the suppressive effects of TGF{beta} on mouse CD8+ T cell activation. RNA-sequencing analysis of TCR-stimulated T cells determined that Myc-regulated genes were highly enriched within gene sets downregulated by TGF{beta}. Functional analysis demonstrated that TGF{beta} impeded TCR-induced upregulation of amino acid transporter expression, amino acid uptake and protein synthesis. Furthermore, TCR-induced upregulation of Myc-dependent glycolytic metabolism was substantially inhibited by TGF{beta} treatment with minimal effects on mitochondrial respiration or mTOR activation. Thus, our data suggest that inhibition of Myc-dependent metabolic reprogramming represents a major mechanism underpinning the suppressive effects of TGF{beta} on CD8+ T cell activation.