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IL-7 promotes integrated glucose and amino acid sensing during homeostatic CD4+ T cell proliferation

ABSTRACT: Homeostatic proliferation, driven by cytokines including IL-7, maintains stable T cell populations over time and expands these during lymphopenia, for example following stem cell transplantation. Yet, impaired T cell expansion in this context is associated with diminished immune protection, whilst excessive proliferation contributes to graft versus host disease. This highlights the need to understand molecular mechanisms regulating this process. Here, we studied the metabolic basis for IL-7-driven CD4+ T cell proliferation. We observed that IL-7 promotes glucose uptake and metabolism, including usage for nucleotide synthesis and oxidation in the tricarboxylic acid (TCA) cycle. Of note, contrary to other TCA metabolites, glucose-derived citrate does not accumulate in IL-7 treated cells, indicating diversion into other processes. In agreement, IL-7 promotes glucose-dependent histone acetylation and chromatin accessibility during proliferation. This is particularly notable at gene loci of the amino acid-sensing Ragulator complex. Consistently, expression of its subunit LAMTOR5 is promoted by IL-7 in a glucose-dependent manner. Functionally, glucose availability determined amino acid-dependent mTOR activation in CD4+ T cells, confirming integrated sensing of these nutrients. LAMTOR5 deletion impaired IL-7-mediated CD4+ T cell expansion, establishing that glycolysis in absence of Ragulator activation was insufficient to initiate this process. Clinically, CD4+ T cells isolated from patients following myeloablative autologous stem cell transplantation demonstrate coordinated upregulation of genes encoding glycolytic and TCA cycle enzymes, as well as amino acid sensing machinery and mTOR targets. Our findings uncover integrated sensing of glucose and amino acid metabolism and demonstrate its relevance during homeostatic T cell proliferation.

INSTRUMENT(S): Exactive

ORGANISM(S): Human

SUBMITTER: Sarah Dimeloe

PROVIDER: MSV000096546 | MassIVE | Wed Nov 27 05:39:00 GMT 2024

REPOSITORIES: MassIVE

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Project description:Malic enzymes decarboxylate the tricarboxylic acid (TCA) cycle intermediate malate to the glycolytic end-product pyruvate and are well positioned to regulate metabolic flux in central carbon metabolism. The bacterium Sinorhizobium meliloti has a NAD(P)-malic enzyme (DME) and a NADP-malic enzyme (TME) and DME is required for symbiotic N2-fixation. To help understand the role of these enzymes, we examined growth, metabolic and transcriptional consequences resulting from the deletion of these enzymes. Few effects were observed upon growth with glucose, whereas growth with the gluconeogenic substrate, succinate, resulted in transcriptional and metabolic effects particularly in the dme mutant strains. When grown with succinate, DME mutant cells accumulated hexose sugar phosphates and trehalose, while TME mutants accumulated putrescine. Succinate-grown DME mutant cells also showed increased transcription of genes for gluconeogenesis and for pathways such as amino acid and fatty acid synthesis that divert metabolites away from the TCA cycle. These data suggested that, DME is required to regulate the levels of TCA cycle intermediates and that the activity of TME is insufficient to prevent the accumulation of TCA cycle intermediates in cells utilizing succinate as carbon source. Consistent with this, in short-1-3 hour incubations with succinate, dme mutant cells excreted large amounts of malate whereas little malate was excreted from tme or wild-type cells. These results support the suggestion that DME is required for N2-fixation in alfalfa because it is required for synthesis of pyruvate and acetyl-CoA and the rapid metabolism of C4-dicarboxylates supplied by the plant. RNA expression was measured for S. meliloti in exponential phase grown in MOPS (morpholinpropanesulfonic acid) buffered minimal media under 2 growth conditions: 1) 15 mM succinate, 2) 15 mM glucose; using wild type cells as well as dme and tme mutant strains (6 experiments, 2 replicates: total 12 samples)

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IL-7 promotes integrated glucose and amino acid sensing during homeostatic CD4+ T cell proliferation

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