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Gain-of-function mutations in isocitrate dehydrogenase (IDH) in human cancers result in the production of d -2-hydroxyglutarate ( d -2HG), an oncometabolite that promotes tumorigenesis through epigenetic alterations. The cancer cell–intrinsic effects of d -2HG are well understood, but its tumor cell–nonautonomous roles remain poorly explored. We compared the oncometabolite d -2HG with its enantiomer, l -2HG, and found that tumor-derived d -2HG was taken up by CD8 + T cells and altered their metabolism and antitumor functions in an acute and reversible fashion. We identified the glycolytic enzyme lactate dehydrogenase (LDH) as a molecular target of d -2HG. d -2HG and inhibition of LDH drive a metabolic program and immune CD8 + T cell signature marked by decreased cytotoxicity and impaired interferon-γ signaling that was recapitulated in clinical samples from human patients with IDH1 mutant gliomas.

X-linked immunodeficiency with magnesium defect, EBV infection, and neoplasia (XMEN) disease are caused by deficiency of the magnesium transporter 1 (MAGT1) gene. We studied 23 patients with XMEN, 8 of whom were EBV naive. We observed lymphadenopathy (LAD), cytopenias, liver disease, cavum septum pellucidum (CSP), and increased CD4-CD8-B220-TCRαβ+ T cells (αβDNTs), in addition to the previously described features of an inverted CD4/CD8 ratio, CD4+ T lymphocytopenia, increased B cells, dysgammaglobulinemia, and decreased expression of the natural killer group 2, member D (NKG2D) receptor. EBV-associated B cell malignancies occurred frequently in EBV-infected patients. We studied patients with XMEN and patients with autoimmune lymphoproliferative syndrome (ALPS) by deep immunophenotyping (32 immune markers) using time-of-flight mass cytometry (CyTOF). Our analysis revealed that the abundance of 2 populations of naive B cells (CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4++CD10+CD38+ and CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4+CD10-CD38-) could differentially classify XMEN, ALPS, and healthy individuals. We also performed glycoproteomics analysis on T lymphocytes and show that XMEN disease is a congenital disorder of glycosylation that affects a restricted subset of glycoproteins. Transfection of MAGT1 mRNA enabled us to rescue proteins with defective glycosylation. Together, these data provide new clinical and pathophysiological foundations with important ramifications for the diagnosis and treatment of XMEN disease.

Summary: T cell stimulation is metabolically demanding. To exit quiescence, T cells rely on environmental nutrients, including glucose and the amino acids glutamine, leucine, serine, and arginine. The expression of transporters for these nutrients is tightly regulated and required for T cell activation. In contrast to these amino acids, which are essential or require multi-step biosynthesis, alanine can be made from pyruvate by a single transamination. Here, we show that extracellular alanine is nevertheless required for efficient exit from quiescence during naive T cell activation and memory T cell restimulation. Alanine deprivation leads to metabolic and functional impairments. Mechanistically, this vulnerability reflects the low expression of alanine aminotransferase, the enzyme required for interconverting pyruvate and alanine, whereas activated T cells instead induce alanine transporters. Stable isotope tracing reveals that alanine is not catabolized but instead supports protein synthesis. Thus, T cells depend on exogenous alanine for protein synthesis and normal activation. : In health, T lymphocytes are in a resting state. However, stimulation with their cognate antigen induces massive growth and proliferation. Ron-Harel et al. demonstrate that T cells rely on extracellular alanine for activation. Consumed alanine is used primarily for protein synthesis, and alanine deprivation inhibits T cell metabolism and effector functions. Keywords: T cells, T cell activation, protein synthesis, metabolism, alanine

Summary: Upon nutrient stimulation, pre-adipocytes undergo differentiation to transform into mature adipocytes capable of storing nutrients as fat. We profiled cellular metabolite consumption to identify early metabolic drivers of adipocyte differentiation. We find that adipocyte differentiation raises the uptake and consumption of numerous amino acids. In particular, branched-chain amino acid (BCAA) catabolism precedes and promotes peroxisome proliferator-activated receptor gamma (PPARγ), a key regulator of adipogenesis. In early adipogenesis, the mitochondrial sirtuin SIRT4 elevates BCAA catabolism through the activation of methylcrotonyl-coenzyme A (CoA) carboxylase (MCCC). MCCC supports leucine oxidation by catalyzing the carboxylation of 3-methylcrotonyl-CoA to 3-methylglutaconyl-CoA. Sirtuin 4 (SIRT4) expression is decreased in adipose tissue of numerous diabetic mouse models, and its expression is most correlated with BCAA enzymes, suggesting a potential role for SIRT4 in adipose pathology through the alteration of BCAA metabolism. In summary, this work provides a temporal analysis of adipocyte differentiation and uncovers early metabolic events that stimulate transcriptional reprogramming.

The tumor microenvironment (TME) is a unique metabolic niche that can inhibit T cell metabolism and cytotoxicity. To dissect the metabolic interplay between tumors and T cells, we establish an in vitro system that recapitulates the metabolic niche of the TME and allows us to define cell-specific metabolism. We identify tumor-derived lactate as an inhibitor of CD8

The tumor microenvironment (TME) is a unique metabolic niche that can inhibit CD8+ T cell metabolism and cytotoxic activity. It has been a challenge to dissect the metabolic interplay between tumors and T cells. Consequently, the mechanisms whereby the TME regulates CD8+ T cell function are not completely understood. Here we establish an in vitro system that recapitulates the metabolic niche of the TME and allows us to define cell-specific metabolism. We identify tumor-derived lactate as a direct inhibitor of CD8+ T cell cytotoxicity, revealing an unexpected metabolic shunt in the tricarboxylic acid (TCA) cycle in CD8+ T cells. Metabolically fit cytotoxic T cells shunt succinate out of the TCA cycle to promote autocrine signaling via the succinate receptor (SUCNR1), a G-protein coupled cell surface receptor. This leaves CD8+ T cells reliant on pyruvate carboxylase (PC) to replenish TCA cycle intermediates (anaplerosis). In contrast, lactate reduces PC-mediated anaplerosis, thus depleting the TCA cycle and reducing SUCNR1 signaling. Notably, inhibition of pyruvate dehydrogenase (PDH) is sufficient to override lactate-mediated reprogramming, and to restore PC activity, succinate secretion, and autocrine activation of SUCNR1 both in vitro and in vivo using syngeneic tumor models. Thus, dissecting the CD8+ T cell-specific metabolic adaptation to the TME unexpectedly revealed that a TCA cycle succinate shunt and plasticity in pyruvate flux is a crucial determinant of CD8+ T cell anti-tumor activity. Furthermore, we identify PDH as a potential drug target to allow CD8+ T cells to retain cytotoxicity and overcome a lactate-rich TME. These studies demonstrate that the TME remodels CD8+ T cell pyruvate metabolism, leading to a reduction in CD8+ T cell cytotoxicity and anti-tumor immunity.

Significance T cell-mediated immune responses are compromised in aged individuals, leading to increased morbidity and reduced response to vaccination. Finding new ways to boost T cell immunity in the elderly is key for enhancing their immune competence. In this work, we performed a systematic analysis of proteins and metabolites in young versus aged T cells. Metabolic rewiring occurs in young T cells following stimulation but is dampened in aged T cells. Moreover, we show that aged T cell functions can be enhanced by metabolite addition., T cell-mediated immune responses are compromised in aged individuals, leading to increased morbidity and reduced response to vaccination. While cellular metabolism tightly regulates T cell activation and function, metabolic reprogramming in aged T cells has not been thoroughly studied. Here, we report a systematic analysis of metabolism during young versus aged naïve T cell activation. We observed a decrease in the number and activation of naïve T cells isolated from aged mice. While young T cells demonstrated robust mitochondrial biogenesis and respiration upon activation, aged T cells generated smaller mitochondria with lower respiratory capacity. Using quantitative proteomics, we defined the aged T cell proteome and discovered a specific deficit in the induction of enzymes of one-carbon metabolism. The activation of aged naïve T cells was enhanced by addition of products of one-carbon metabolism (formate and glycine). These studies define mechanisms of skewed metabolic remodeling in aged T cells and provide evidence that modulation of metabolism has the potential to promote immune function in aged individuals.

Magnesium transporter 1 (MAGT1) critically mediates magnesium homeostasis in eukaryotes and is highly-conserved across different evolutionary branches. In humans, loss–of–function mutations in the MAGT1 gene cause X-linked magnesium deficiency with Epstein-Barr virus (EBV) infection and neoplasia (XMEN), a disease that has a broad range of clinical and immunological consequences. We have previously shown that EBV susceptibility in XMEN is associated with defective expression of the antiviral natural-killer group 2 member D (NKG2D) protein and abnormal Mg(2+) transport. New evidence suggests that MAGT1 is the human homolog of the yeast OST3/OST6 proteins that form an integral part of the N-linked glycosylation complex, although the exact contributions of these perturbations in the glycosylation pathway to disease pathogenesis are still unknown. Using MS-based glycoproteomics, along with CRISPR/Cas9-KO cell lines, natural killer cell-killing assays, and RNA-Seq experiments, we now demonstrate that humans lacking functional MAGT1 have a selective deficiency in both immune and nonimmune glycoproteins, and we identified several critical glycosylation defects in important immune-response proteins and in the expression of genes involved in immunity, particularly CD28. We show that MAGT1 function is partly interchangeable with that of the paralog protein tumor-suppressor candidate 3 (TUSC3) but that each protein has a different tissue distribution in humans. We observed that MAGT1-dependent glycosylation is sensitive to Mg(2+) levels and that reduced Mg(2+) impairs immune-cell function via the loss of specific glycoproteins. Our findings reveal that defects in protein glycosylation and gene expression underlie immune defects in an inherited disease due to MAGT1 deficiency.

In a recent issue of Nature, Zhang et al. (2019) describe an additional histone post-translational modification, named histone lactylation. Following increased lactate production as a consequence of M1 polarization, histone lactylation regulates the induction of an M2-like phenotype in late stages of M1 macrophage activation to promote wound healing.

The FDA-approval of potent targeted therapies has led to great changes in the therapeutic landscape of chronic lymphocytic leukemia (CLL). As a key example, venetoclax, a first-in-class BCL-2 inhibitor, leads to response in about 80% of patients with relapsed/refractory (R/R) CLL. Disease progression on venetoclax, however, has been increasingly observed, and better biologic understanding of resistance mechanisms to this agent is needed. To systematically discover the potential mechanisms of resistance to venetoclax, we performed both genome-scale loss- (LOF) and gain-of-function (GOF) genetic modifier screens in the BCL-2-driven OCI-Ly1 lymphoma cell line using CRISPR-Cas9 sgRNA and ORF libraries, respectively. Significant hits from both screens included the BCL-2 family: the LOF screen with pro-apoptotic genes (PMAIP1, BAX, BAK1, BCL-2L11) and the GOF screen with anti-apoptotic genes (BCL2L1, BCL2L2, BCL2, MCL1). In addition, the LOF screen uncovered genes in pathways relevant to lymphoid biology (i.e, NFKBIA) and lymphoid transcription factors and modulators (IKZF5, ID3, EP300, NFIA). The GOF screen also uncovered components of the energy-stress sensor PKA/AMPK signaling pathways (ADIPOQ, PRKAR2B, PRKAA2) and regulators of mitochondrial metabolism. In parallel, we performed an integrated transcriptome, whole proteome and functional characterization of an OCI-Ly1 cell line rendered resistant to venetoclax (OCI-Ly1-R) from the parental cell line (OCI-Ly1-S). RNA-seq and spectrometry-based proteomics revealed coordinated dysregulation of transcripts and proteins in the resistant line originating from genes critical to cellular metabolism, cell cycle, B-cell biology and autophagy. Of the transcripts and proteins significantly associated with the resistant cell line, only MCL-1 overlapped with the gene hits from the genome-scale screens. Treatment of the OCI-Ly-R cells with the MCL-1 inhibitor S63845 synergized with venetoclax. Given the dysregulation of proteins critical to metabolism in both the GOF screen and in OCI-Ly1-R cells, we also evaluated the role of metabolic reprogramming in venetoclax resistance. We first assessed mitochondrial respiration by measuring the oxygen consumption rate. Compared to OCI-Ly-S cells, OCI-Ly1-R cells demonstrated markedly higher respiration levels, suggesting a state of higher oxidative phosphorylation (OXPHOS). More directly, we measured oxygen consumption following venetoclax exposure. Consistent with impairment of OXPHOS by venetoclax, we observed both an immediate decrease in oxygen consumption and an immediate burst of glycolysis following venetoclax in the OCI-Ly1-S cells, but not in the OCI-Ly1-R cells. In line with these findings, the AMPK inhibitor dorsomorphin and mitochondrial electron transport chain (mETC) inhibitors synergized with venetoclax in OCI-Ly1-S cells. Transcriptome related to ID3 (identified as one of the LOF screen targets) was characterized in isogenic ID3-knockout OCI-Ly1 lines. It revealed PRKAR2B overexpression as a key effect, suggesting a role for ID3, and perhaps of other lymphoid transcription factors in regulating metabolic reprogramming associated with resistance. Indeed, exposure of ID3 knockout lines to mETC inhibitors overcame resistance to venetoclax. To determine if there is a genetic basis for the drug resistance seen in OCI-Ly1-R cells, we compared whole-exome sequencing (WES) results of DNA isolated from the OCI-Ly1-R and OCI-Ly1-S cell lines. A clear region was amplified on chromosome 1q23, which includes MCL1 and PRKAB2 (the regulatory subunit of AMPK). Similarly, a WES-based analysis of paired CLL DNA samples isolated from 6 R/R CLL patients just prior to venetoclax initiation and at time of progression on venetoclax was performed. We did not identify any non-silent somatic single nucleotide in BCL2 or its family members at baseline or at progression, despite marked clonal shifts in all patients. We confirmed the presence of the amp(1q23) as acquired at relapse after venetoclax in 3 out of 6 patients. Our study reveals that venetoclax resistance implicates changes not only for outer mitochondrial membrane (MCL-1 expression) but also for inner membrane (oxydative metabolism). Such mitochondrial reprogramming represents a new vulnerability that can potentially be exploited through combinatorial therapy with metabolic modulators to overcome resistance. Disclosures Guieze: abbvie: Honoraria; janssen: Honoraria; gilead: Honoraria. Thompson:Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Research Funding; Adaptive Biotechnologies: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees. Davids:Merck: Consultancy; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; MEI Pharma: Consultancy, Research Funding; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Surface Oncology: Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Brown:Sun Pharmaceutical Industries: Research Funding; Abbvie: Consultancy; Acerta / Astra-Zeneca: Membership on an entity's Board of Directors or advisory committees; Morphosys: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy; Janssen: Consultancy; Sunesis: Consultancy; Roche/Genentech: Consultancy; Verastem: Consultancy, Research Funding; Boehringer: Consultancy; Loxo: Consultancy; Beigene: Membership on an entity's Board of Directors or advisory committees; Invectys: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; Gilead: Consultancy, Research Funding; Pharmacyclics: Consultancy; Genentech: Consultancy. Wierda:AbbVie, Inc: Research Funding; Genentech: Research Funding. Letai:AstraZeneca: Consultancy, Other: Lab research report; Novartis: Consultancy, Other: Lab research report; AbbVie: Consultancy, Other: Lab research report; Flash Therapeutics: Equity Ownership; Vivid Biosciences: Equity Ownership. Wu:Neon Therapeutics: Equity Ownership.