Control of amino-acid transport by antigen receptors coordinates the metabolic reprogramming essential for T cell differentiation

The role of branched-chain amino acids in cardio-oncology: A review

Cancer and cardiovascular diseases (CVDs) are global health challenges. In cancer patients, CVD is the second leading cause of death following disease progression. There are few specialized services for cardio-oncology patients worldwide currently. Branched-chain amino acids (BCAAs) are essential amino acids that promote protein synthesis and energy homeostasis. The disruption of BCAAs metabolism facilitates the development of cancer and CVDs while the benefit of BCAA supplement is full of controversy. In this review, we summarized BCAA-related studies in cardiometabolism, cancer and chemotherapy-induced cardiotoxicity, and provided our perspectives on the roles of BCAAs in cardio-oncology. We find that supplementation of BCAAs presents protective effects in cardiometabolic diseases, while the influence on cancer is intricate and varies across different types of cancers. Large-scale clinical studies are needed to understand the long-term effects of BCAA intake and its impact on different stages of the disease. BCAAs have potential to mitigate chemotherapy-induced cardiotoxicity. Continued research is still essential to understand the precise mechanisms, determine optimal dosage and timing, and assess the effectiveness of BCAA supplement in cardio-oncology, in particular clinical research.

Post-translational modifications and the reprogramming of tumor metabolism

Metabolic reprogramming occurs alongside tumor development. As cancers advance from precancerous lesions to locally invasive tumors and then to metastatic tumors, metabolic patterns exhibit distinct changes, including mutations in metabolic enzymes and modifications in the activity of metabolic regulatory proteins. Alterations in metabolic patterns can influence tumor evolution, either establishing or alleviating metabolic burdens and facilitating cancer growth. To fully understand how metabolic reprogramming helps tumors grow and find the metabolic activities that are most useful for treating tumors, we need to have a deeper understanding of how metabolic patterns are controlled as tumors grow. Post-translational modifications (PTMs), a critical mechanism in the regulation of protein function, can influence protein activity, stability, and interactions in several ways. In tumor cells, PTMs-mediated metabolic reprogramming is a crucial mechanism for adapting to the challenging microenvironment and sustaining fast growth. This article will deeply explore the intricate regulatory mechanism of PTMs on metabolic reprogramming and its role in tumor progression, with the expectation of providing new theoretical basis and potential targets for tumor treatment.

Tumor-stromal metabolic crosstalk in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a dire prognosis. Standard-of-care chemotherapy regimens offer marginal survival benefit and carry risk of severe toxicity, while immunotherapy approaches have uniformly failed in clinical trials. Extensive desmoplasia in the PDAC tumor microenvironment (TME) disrupts blood flow to and from the tumor, thereby creating a nutrient-depleted, hypoxic, and acidic milieu that suppresses the function of antitumor immune cells and imparts chemotherapy resistance. Additionally, recent seminal studies have demonstrated crucial roles for metabolic crosstalk - the exchange of metabolites between PDAC cells and stromal cell populations in the TME - in establishing and maintaining core malignant behaviors of PDAC: tumor growth, metastasis, immune evasion, and therapy resistance. In this review, we provide a conceptual overview of metabolic crosstalk and how it evolves under various selection pressures in the TME, analyze the landscape of proposed tumorigenic metabolic crosstalk pathways, and highlight potentially druggable nodes.

Restricting SLC7A5-mediated Leucine uptake in T cells prevents acute GVHD and maintains GVT response

The L-Leu amino acid transporter SLC7A5 has become an important target in inflammation and cancer. However, its role in acute graft-versus-host disease (aGVHD) and graft versus tumor (GVT) remains unexplored. We demonstrate that SLC7A5 deletion affected T cell activation, expansion and survival, and reduced IFNγ and granzyme B expression, thus controlling aGVHD, but without effect on tumor growth. On the other hand, dietary restriction of L-Leu reduced aGVHD by controlling T cell expansion, inducing apoptosis, and affecting granzyme B secretion. However, CD8 T cells did not fail to activate and express IFNγ in the absence of L-Leu, and showed an increased proportion of central memory T cells, which contributed to the GVT response. Deletion of SLC7A5 in T cells compromises mTORC1, glycolysis and mitochondrial oxidation. On the contrary, L-Leu removal reduced mTORC1 and completely blocked glycolysis but preserved mitochondrial function, favoring the generation of central memory responses and expression of stemness marker TCF1. In addition, our metabolomics data underscores the L-Leu-derived metabolite β-hydroxybutyrate as an important marker for SLC7A5-dependent allogenic T cell expansion in aGVHD.

Genomic and Transcriptomic Profiling of Amino Acid Compositions in Common Carp Fillets

Fish are rich sources of amino acids (AAs), particularly human essential amino acids (HEAAs). Exploring the regulatory mechanisms behind the changes in the combined AA content in the fillet and enhancing the content of AAs, especially HEAAs, in fillets of farmed fish is crucial for meeting human nutritional needs. After hot acidic hydrolysis of 304 common carp fillets, we quantified the contents of 17 single AAs and 5 AA groups and observed significant variations among them. Except for Pro, 16 single AAs and all AA groups showed medium-to-high heritabilities over 0.2. Through a genome-wide association study (GWAS), we identified 1974 SNPs and candidate genes associated with at least one AA content. Using transcriptome data from groups with the highest and lowest contents for each AA, 7089 candidate genes were related to the concentrations of at least two AAs. For the total HEAA content, 121 SNPs and their associated genes preferred ATPase-coupled transmembrane transporter activity, and 4727 differentially expressed genes were enriched in cytokine activity, chemokine activity, oxidoreductase activity, and ion binding. With the optimal genomic selection programs and associated SNPs, the correlation between the actual AA contents and estimated breeding values was high and positive, ranging from 0.76 to 0.90. These findings revealed the major-effect processes and regulatory mechanisms modulating the differences in fillet AA contents. The genomic selection programs will guide the future selection of common carp with high AA contents.

CD27 costimulation supports metabolic fitness of CD4+ T cells by enhancing de novo nucleotide and protein synthesis

T cells undergo many metabolic changes throughout the different phases of their response in lymphoid and nonlymphoid tissues. Cell metabolism meets demands for energy and biosynthesis, particularly during cell division and effector differentiation. As costimulatory receptors, CD28 and various TNF receptor (TNFR) family members shape T-cell clonal expansion, survival and effector functions and are important clinical targets. While CD28 is acknowledged as a metabolic regulator, little is known about how TNFRs shape T-cell metabolism. We here identify TNFR family member CD27 as a metabolic regulator in activated human CD4+ T cells. In the context of CD3 signaling and CD28 costimulation, CD27 proved to regulate specific metabolic functions, as determined by metabolomics and metabolic tracer experiments. CD27 costimulation supported upregulation of glycolysis, the pentose phosphate pathway and the TCA cycle, increasing the use of glucose-derived carbon and glutamine-derived nitrogen as building blocks for de novo nucleotide synthesis. It also promoted uptake of amino acids (AAs) and modulated pathways of AA metabolism. Accordingly, CD27 costimulation boosted protein translation in CD3- and CD3/CD28-activated CD4+ T cells, which proceeded via enhanced mTOR pathway activation. Remarkably, CD27, OX40 and 4-1BB all enhanced CD3-induced mTOR signaling, but only CD27 could overrule inhibitory PD-1 signaling. CD27 costimulation increased IL-2, IFNγ and TNFα production by CD3-activated CD4+ T cells, also in presence of PD-1 signaling. Next to previously defined beneficial effects of CD27 on activated T-cell survival and CTL differentiation and Th1 effector differentiation, these data support its essential contribution to T-cell metabolism and its relevance as a therapeutic target.

Unravelling the modified T cell receptor through Gen-Next CAR T cell therapy in Glioblastoma: Current status and future challenges

PURPOSE

Despite current technological advancements in the treatment of glioma, immediate alleviation of symptoms can be catered by therapeutic modalities, including surgery, chemotherapy, and combinatorial radiotherapy that exploit aberrations of glioma. Additionally, a small number of target antigens, their heterogeneity, and immune evasion are the potential reasons for developing targeted therapies. This oncologic milestone has catalyzed interest in developing immunotherapies against Glioblastoma to improve overall survival and cure patients with high-grade glioma. The next-gen CAR-T Cell therapy is one of the effective immunotherapeutic strategies in which autologous T cells have been modified to express receptors against GBM and it modulates cytotoxicity.

METHODS

In this review article, we examine preclinical and clinical outcomes, and limitations as well as present cutting-edge techniques to improve the function of CAR-T cell therapy and explore the possibility of combination therapy.

FINDINGS

To date, several CAR T-cell therapies are being evaluated in clinical trials for GBM and other brain malignancies and multiple preclinical studies have demonstrated encouraging outcomes.

IMPLICATIONS

CAR-T cell therapy represents a promising therapeutic paradigm in the treatment of solid tumors but a few limitations include, the blood-brain barrier (BBB), antigen escape, tumor microenvironment (TME), tumor heterogeneity, and its plasticity that suppresses immune responses weakens the ability of this therapy. Additional investigation is required that can accurately identify the targets and reflect the similar architecture of glioblastoma, thus optimizing the efficiency of CAR-T cell therapy; allowing for the selection of patients most likely to benefit from immuno-based treatments.

Integrating transcriptomic and metabolomic analyses to characterize the potential function of SLC1A5 in thyroid cancer

BACKGROUND

Alanine Serine Cysteine transporter 2 (ASCT2/SLC1A5) is a key glutamine transporter in cancer cells and has been shown in a variety of cancers to promote tumor growth by reprogramming glutamine metabolism and altering the tumor microenvironment. However, the role in thyroid cancer remains unknown.

METHODS

To investigate the expression and prognostic value of SLC1A5 in thyroid cancer using publically available databases, and to define the relationship with clinical characteristics. SLC1A5 expression in TPC-1 and B-CPAP was knocked down using SLC1A5 siRNA to investigate its effects on cell growth and apoptosis. Transcriptome sequencing and metabolite analysis were carried out in the SLC1A5 siRNA group to identify major transcriptomic or metabolite changes that could lead to apoptosis. In addition, we explored for the connection of SLC1A5 with the tumor microenvironment using algorithms like ESTIMATE and CIBERSORT.

RESULTS

High SLC1A5 expression in THCA is related with a poor prognosis and advanced clinical stage. In vitro findings showed that SLC1A5 knockdown reduced THCA cell activity and accelerated apoptosis, and the results were consistent with the effect of SLC1A5 inhibitor GPNA. While RNA sequencing analysis revealed that NF-κb signaling was enhanced and oxidative phosphorylation levels were lowered. Metabolomics findings indicated that Glutathione and purine metabolism were dramatically affected in the SLC1A5 siRNA group. Furthermore, immune microenvironment study revealed that SLC1A5 had a positive correlation with the amount of CD4 + T memory-activated cells and T cell follicular helper cells.

CONCLUSION

SLC1A5 may be a possible target in THCA. Our findings indicate that DEGs and differential metabolites are mostly linked to numerous signaling pathways and immunological modulation, which may play an important role in SLC1A5 regulation of THCA development.

Cholesterol homeostasis and lipid raft dynamics at the basis of tumor-induced immune dysfunction in chronic lymphocytic leukemia

Autologous T-cell therapies show limited efficacy in chronic lymphocytic leukemia (CLL), where acquired immune dysfunction prevails. In CLL, disturbed mitochondrial metabolism has been linked to defective T-cell activation and proliferation. Recent research suggests that lipid metabolism regulates mitochondrial function and differentiation in T cells, yet its role in CLL remains unexplored. This comprehensive study compares T-cell lipid metabolism in CLL patients and healthy donors, revealing critical dependence on exogenous cholesterol for human T-cell expansion following TCR-mediated activation. Using multi-omics and functional assays, we found that T cells present in viably frozen samples of patients with CLL (CLL T cells) showed impaired adaptation to cholesterol deprivation and inadequate upregulation of key lipid metabolism transcription factors. CLL T cells exhibited altered lipid storage, with increased triacylglycerols and decreased cholesterol, and inefficient fatty acid oxidation (FAO). Functional consequences of reduced FAO in T cells were studied using samples from patients with inherent FAO disorders. Reduced FAO was associated with lower T-cell activation but did not affect proliferation. This implicates low cholesterol levels as a primary factor limiting T-cell proliferation in CLL. CLL T cells displayed fewer and less clustered lipid rafts, potentially explaining the impaired immune synapse formation observed in these patients. Our findings highlight significant disruptions in lipid metabolism as drivers of functional deficiencies in CLL T cells, underscoring the pivotal role of cholesterol in T-cell proliferation. This study suggests that modulating cholesterol metabolism could enhance T-cell function in CLL, presenting novel immunotherapeutic approaches to improve outcome in this challenging disease.

ICI-induced cardiovascular toxicity: mechanisms and immune reprogramming therapeutic strategies

The advent of immune checkpoint inhibitors (ICIs) has revolutionized cancer treatment, offering life-saving benefits to tumor patients. However, the utilize of ICI agents is often accompanied by immune-related adverse events (irAEs), among which cardiovascular toxicities have attracted more and more attention. ICI induced cardiovascular toxicities predominantly present as acute myocarditis and chronic atherosclerosis, both of which are driven by excessive immune activation. Reprogramming of T cells and macrophages has been demonstrated as a pivotal factor in the pathogenesis of these complications. Therapeutic strategies targeting glycolysis, fatty acid oxidation, reactive oxygen species (ROS) production and some other key signaling have shown promise in mitigating immune hyperactivation and inflammation. In this review, we explored the intricate mechanisms underlying ICI-induced cardiovascular toxicities and highlighted the protective potential of immune reprogramming. We emphasize the roles of T cell and macrophage reprogramming in the heart and vasculature, showcasing their contributions to both short-term and long-term regulation of cardiovascular health. Ultimately, a deeper understanding of these processes will not only enhance the safety of ICIs but also pave the way for innovative strategies to manage immune-related toxicities in cancers therapy.

Mitochondrial protein OPA1 is required for the expansion of effector CD8 T cells

Short-lived effector cells are characterized metabolically by a highly glycolytic state, driving energy and biomass acquisition, whereas memory-fated T cells have historically been described as meeting these requirements through mitochondrial metabolism. Here, we show that the mitochondrial protein optic atrophy 1 (OPA1) is critical for rapidly dividing CD8 T cells in vivo, the requirement for which is most pronounced in effector CD8 T cells. More specifically, OPA1 supports proper cell cycle initiation and progression and the viability and survival of CD8 T cells during clonal expansion. Use of mice deficient in the mitochondrial membrane fusion proteins Mitofusin 1 and 2 (MFN1/2) in both in vivo proliferation/differentiation assays and ex vivo metabolic analysis indicates that the requirement for OPA1 during cell division supersedes its role in mitochondrial fusion. We conclude that OPA1 is critical for the generation and accumulation of short-lived effector cells that arise during the response to infection.

Distinct CD8+ T cell dynamics associate with response to neoadjuvant cancer immunotherapies

We leverage a clinical trial (NCT04080804) that compared neoadjuvant anti-PD-1, anti-PD-1+CTLA-4, and anti-PD-1+LAG-3 therapies in head and neck squamous cell carcinoma patients. Combination therapies promote higher pathologic response rates versus monotherapy, and major pathologic response is associated with better survival. To address whether successful immune checkpoint inhibitor (ICI) regimens act through similar or distinct pathways, we robustly and longitudinally characterize transcriptional and proteomic dynamics of CD8+ tumor-infiltrating lymphocytes (TILs) in a clonal manner. Anti-PD-1+LAG-3 reprograms CD8+ TIL with type-I interferon response and exhaustion gene programs into effector memory and resident memory (TEM/TRM). In contrast, anti-PD-1+CTLA-4 activates and expands pre-existing TEM/TRM CD8+ TIL, but does not rejuvenate exhausted phenotypes into T effector cells. Anti-PD-1+LAG-3, but not anti-PD-1+CTLA-4, induces widespread TCR sharing among the different transcriptional states, as well as increased TCR diversity in responding patients. Our data suggest doublet regimen-specific transcriptional and clonal dynamics of tumor-reactive CD8+ T cells.

Early transcriptional effects of inflammatory cytokines reveal highly redundant cytokine networks

Inflammatory cytokines are fundamental mediators of the organismal response to injury, infection, or other harmful stimuli. To elucidate the early and mostly direct transcriptional signatures of inflammatory cytokines, we profiled all immunologic cell types by RNAseq after systemic exposure to IL1β, IL6, and TNFα. Our results revealed a significant overlap in the responses, with broad divergence between myeloid and lymphoid cells, but with very few cell-type-specific responses. Pathway and motif analysis identified several main controllers (NF-κB, IRF8, and PU.1), but the largest portion of the response appears to be mediated by MYC, which was also implicated in the response to γc cytokines. Indeed, inflammatory and γc cytokines elicited surprisingly similar responses (∼50% overlap in NK cells). Significant overlap with interferon-induced responses was observed, paradoxically in lymphoid but not myeloid cell types. These results point to a highly redundant cytokine network, with intertwined effects between disparate cytokines and cell types.

Valine and isoleucine deficiency in necrotic enteritis challenge impact growth performance, intestinal health, and muscle growth in broilers

Necrotic enteritis (NE), an enteric disease caused by Clostridium perfringens, and antagonistic effects due to dietary branched-chain amino acid (BCAA) imbalance are key factors that negatively affect chicken growth. The current study was conducted to investigate the effects of valine and isoleucine deficiency in NE challenged broilers. A total of 336 seven-d-old male Cobb 500 were allotted to four treatments with six replicates. The four treatments were as follows: (1) non-challenged control (NC; leucine:lysine = 1.31, valine:lysine = 0.73, and isoleucine:lysine = 0.63), (2) NE-challenged group (NE), (3) NE-challenged with 85 % valine deficiency group (NE-VAL; valine:lysine = 0.62), and (4) NE-challenged with 85 % isoleucine deficiency group (NE-ILE; isoleucine:lysine = 0.54). E. maxima and C. perfringens were administered on d 14 and 18, respectively, and the experiment lasted until d 21. The NE-VAL group had the lowest growth performance measurements compared to the other groups (P < 0.001). All NE-challenged groups had significantly reduced overall growth performance measurements compared to the NC group (P < 0.001). The NE-ILE group showed no difference in any of the measurements compared to the NE group. On d 21, the NE group had significantly increased intestinal permeability, jejunal lesion scores, C. perfringens colony counts, and jejunal chemokine and cytokine gene expression levels, along with decreased intestinal morphology compared to the NC group (P < 0.05). The NE-VAL group had significantly decreased breast muscle yield, reduced lean and total tissue weight, and increased expression levels of mechanistic target of rapamycin pathway and BCAA catabolism-related genes compared to the NE group (P < 0.05). This may explain why the NE-VAL group had the lowest growth performance, as the two negative effects of NE infection and valine deficiency are separated. In conclusion, the negative effects of NE challenge and valine deficiency were independent; valine deficiency showed a similar response to that exhibited by high leucine levels, despite reduced feed intake caused by NE challenge.

Metabolic Dialogue Shapes Immune Response in the Tumor Microenvironment

The fate of immune cells is fundamentally linked to their metabolic program, which is also influenced by the metabolic landscape of their environment. The tumor microenvironment represents a unique system for intercellular metabolic interactions, where tumor-derived metabolites suppress effector CD8+ T cells and promote tumor-promoting macrophages, reinforcing an immune-suppressive niche. This review will discuss recent advancements in metabolism research, exploring the interplay between various metabolites and their effects on immune cells within the tumor microenvironment.

Targeting PD-1 and CD85j can restore intratumoral CD4+ GzmB+ T-cell functions to combat MHC-II-expressing tumors

BACKGROUND

A subset of CD4+ T cells with cytotoxic activity has been identified, and these cells exert their effects by expressing perforin and granzymes. Despite the progress made in characterizing cytotoxic CD4+ T cells in various diseases, the status of cytotoxic CD4+ T cells in non-small cell lung cancer (NSCLC) and the underlying mechanisms involved in promoting intratumoral cytotoxic CD4+ T-cell activation remain unclear.

METHODS

We used flow cytometry to examine the phenotypic and functional properties of CD4+GzmB+ T cells in the peripheral blood and tumor tissues of patients with NSCLC. Loss-of-function analyses and RNA sequencing were used to identify the underlying mechanisms involved in the effects of interleukin (IL)-15 on the restoration of CD4+GzmB+ T-cell function in vitro. A patient-derived lung cancer explant model and an animal model were used to verify the effects of immune checkpoint inhibitors on CD4+GzmB+ T-cell activation.

RESULTS

In patients with NSCLC, impaired cytolytic function of tumor-infiltrated granzyme B (GzmB)-expressing CD4+ T cells was restored by IL-15 through activation of the AKT-FOXO1-T-bet axis. Moreover, IL-15 stimulation increased solute carrier family 7 member 5 (SLC7A5) expression in CD4+GzmB+ T cells in an Protein Kinase B (AKT)-dependent manner, and inhibition of SLC7A5 abrogated the effect of IL-15 on CD4+GzmB+ T cells. Additionally, we showed that the immune checkpoint molecules programmed cell death-1 (PD-1) and CD85j were mutually exclusively expressed in CD4+GzmB+ T cells and that dual targeting of PD-1 and CD85j enhanced the effector function of CD4+GzmB+ T cells by activating the AKT pathway. Notably, tumor cells expressing major histocompatibility complex (MHC)-II and IL-15 determine the effectiveness of CD4+GzmB+ T-cell-mediated antitumor immunity in response to immunotherapy.

CONCLUSIONS

Our study demonstrated that tumor-infiltrating CD4+GzmB+ T cells fail to eliminate tumors. Dual blockade of PD-1 and CD85j alongside IL-15 restores the effector function of CD4+GzmB+ T cells and drives CD4+GzmB+ T-cell transformation in the tumor microenvironment to combat MHC-II-expressing tumors.

Protein Synthesis and Metabolism in T Cells

T lymphocytes are essential for immune responses to pathogens and tumors. Their ability to rapidly clonally expand and differentiate to effector cells following infection, and then to curb effector function following infection clearance, is fundamental for adaptive immunity. Proteome remodeling in response to immune activation is a fundamental mechanism that allows T cells to swiftly reprogram for acquisition of effector function and is possible only because antigen receptor- and cytokine-driven signal transduction pathways can trigger massive increases in protein synthesis. Equally, the ability to repress protein synthesis supports a return to quiescence once pathogens are cleared to avoid autoimmunity and to generate memory T cell populations. This review discusses what is known about T cell proteomes and the regulatory mechanisms that control protein synthesis in T cells. The focus is on how this fundamental process is dynamically controlled to ensure immune homeostasis.

SIRT7 regulates T-cell antitumor immunity through modulation BCAA and fatty acid metabolism

SIRT7, one of the least studied members of the Sirtuins family, is an NAD+-dependent lysine deacetylase and desuccinylase. While previous studies using affinity enrichment and quantitative proteomics identified numerous lysine-deacetylated substrates of SIRT7, its lysine-desuccinylated substrates remain underexplored, limiting our understanding of its role in cellular homeostasis. Here, we demonstrated that SIRT7 is predominantly expressed in immune tissues, especially in adaptive immune cells, including T cells. Through proteomics, lysine succinylome, and acetylome analysis of spleen from wild-type (WT) and Sirt7-/- mice, we identified significant succinylation of proteins involved in the branched-chain amino acid (BCAA) catabolism pathway in Sirt7-/- mice. We further found that SIRT7 partially localizes to mitochondria, interacting with key enzymes of the BCAA catabolism pathway and promoting their desuccinylation. Sirt7 deficiency leads to enhanced BCAA catabolism, accumulation of acyl-CoA, and increased fatty acid (FA) synthesis. As T cells rely heavily on amino acid metabolism for activation, differentiation, and function, we investigated the impact of SIRT7 using a T cell-specific Sirt7 knockout mouse model (Sirt7fl/flCd4-Cre). Our results show that SIRT7 is crucial for T cell proliferation, activation, and antitumor function. Sirt7 deficiency in T cells results in the accumulation of BCAA metabolites and FAs, reduced cytotoxic cytokines secretion such as IFN-γ, and T cell exhaustion. Reducing BCAA levels with BT2, a BCKDK inhibitor, or BCAA-free treatment alleviated these effects, while FA treatment exacerbates them. Overall, our findings identify SIRT7 as a critical regulator linking BCAA and FA metabolism to T cell antitumor immunity, providing new insights into its potential as a therapeutic target.

Autophagy repression by antigen and cytokines shapes mitochondrial, migration and effector machinery in CD8 T cells

Autophagy shapes CD8 T cell fate; yet the timing, triggers and targets of this process are poorly defined. Herein, we show that naive CD8 T cells have high autophagic flux, and we identify an autophagy checkpoint whereby antigen receptor engagement and inflammatory cytokines acutely repress autophagy by regulating amino acid transporter expression and intracellular amino acid delivery. Activated T cells with high levels of amino acid transporters have low autophagic flux in amino-acid-replete conditions but rapidly reinduce autophagy when amino acids are restricted. A census of proteins degraded and fueled by autophagy shows how autophagy shapes CD8 T cell proteomes. In cytotoxic T cells, dominant autophagy substrates include cytolytic effector molecules, and amino acid and glucose transporters. In naive T cells, mitophagy dominates and selective mitochondrial pruning supports the expression of molecules that coordinate T cell migration and survival. Autophagy thus differentially prunes naive and effector T cell proteomes and is dynamically repressed by antigen receptors and inflammatory cytokines to shape T cell differentiation.

Lysosomes in the immunometabolic reprogramming of immune cells in atherosclerosis

Lysosomes have a central role in the disposal of extracellular and intracellular cargo and also function as metabolic sensors and signalling platforms in the immunometabolic reprogramming of macrophages and other immune cells in atherosclerosis. Lysosomes can rapidly sense the presence of nutrients within immune cells, thereby switching from catabolism of extracellular material to the recycling of intracellular cargo. Such a fine-tuned degradative response supports the generation of metabolic building blocks through effectors such as mTORC1 or TFEB. By coupling nutrients to downstream signalling and metabolism, lysosomes serve as a crucial hub for cellular function in innate and adaptive immune cells. Lysosomal dysfunction is now recognized to be a hallmark of atherogenesis. Perturbations in nutrient-sensing and signalling have profound effects on the capacity of immune cells to handle cholesterol, perform phagocytosis and efferocytosis, and limit the activation of the inflammasome and other inflammatory pathways. Strategies to improve lysosomal function hold promise as novel modulators of the immunoinflammatory response associated with atherosclerosis. In this Review, we describe the crosstalk between lysosomal biology and immune cell function and polarization, with a particular focus on cellular immunometabolic reprogramming in the context of atherosclerosis.

Amino Acid Metabolism and Immune Dysfunction in Urea Cycle Disorders: T and B Cell Perspectives

Urea cycle disorders (UCDs) are a group of genetic metabolic conditions characterized by enzyme deficiencies responsible for detoxifying ammonia. Hyperammonemia, the accumulation of intermediate metabolites, and a deficiency of essential amino acids-due to a protein-restrictive diet and the use of ammonia scavengers-can increase the risk of infections, particularly during metabolic crises. While the underlying mechanisms of immune suppression are still being fully elucidated, hyperammonemia may impair the function of immune cells, particularly T cells and macrophages, inhibiting the proliferation of T cells and cytokine production. Arginine, which is essential for T-cell activation and function, may also be limited in these patients, and its depletion can increase their vulnerability to infections. Twenty-four UCD patients and 31 healthy donors were recruited for the study. Peripheral lymphocyte subset analysis, intracellular protein and cytokine staining, and proliferation assays were performed by flow cytometry. Amino acid levels were measured using the HPLC method. The UCD patients exhibited low lymphocyte-proliferation capacity in both proximal and distal defects in response to phytohaemagglutinin (PHA) and anti-CD2, anti-CD3, and anti-CD28 (CD-mix), which was lower than healthy controls. Proximal-UCD patients exhibited a significantly higher response for IFN-γ compared to both distal-UCD patients and healthy controls. The different amino acids in the culture medium were changed significantly in the groups. This study highlights significant immune dysfunctions in UCD patients, particularly impaired T-cell proliferation and altered amino acid metabolism. Proximal UCD patients exhibited a higher IFN-γ response, indicating a potential for hyperinflammation. Despite this, infection rates did not significantly differ between proximal UCD and distal UCD patients, although distal UCD patients had higher hospitalization rates. Amino acid analysis revealed distinct metabolic disruptions, emphasizing the complex interplay between metabolism and immune function. These findings suggest that UCDs cause profound immune alterations, necessitating further research to develop targeted therapeutic strategies.

Targeting metabolic dysfunction of CD8 T cells and natural killer cells in cancer

The importance of metabolic pathways in regulating immune responses is now well established, and a mapping of the bioenergetic metabolism of different immune cell types is under way. CD8 T cells and natural killer (NK) cells contribute to cancer immunosurveillance through their cytotoxic functions and secretion of cytokines and chemokines, complementing each other in target recognition mechanisms. Several immunotherapies leverage these cell types by either stimulating their activity or redirecting their specificity against tumour cells. However, the anticancer activity of CD8 T cells and NK cells is rapidly diminished in the tumour microenvironment, closely linked to a decline in their metabolic capacities. Various strategies have been developed to restore cancer immunosurveillance, including targeting bioenergetic metabolism or genetic engineering. This Review provides an overview of metabolic dysfunction in CD8 T cells and NK cells within the tumour microenvironment, highlighting current therapies aiming to overcome these issues.

Regulatory T cells in the tumor microenvironment display a unique chromatin accessibility profile

Regulatory T cells (Tregs) are a suppressive CD4+ T cell population that limit the antitumor immune response. In this study, we analyzed the chromatin accessibility of Tregs in the murine tumor microenvironment (TME) to identify tumor-specific accessible peaks and if these are altered over time in the tumor microenvironment, with or without anti-PD-1 immunotherapy. We found that despite little change in chromatin accessibility of Tregs in the tumor over time, Tregs have a distinct chromatin accessibility signature in the TME compared with Tregs in the periphery. This distinct tumor Treg chromatin accessibility profile highlights reduced accessibility at loci important for an CD4+ conventional T cell (CD4+ Foxp3-) effector phenotype. Analysis of chromatin accessibility in Tregs from B16 and MC38 tumor models indicated that Tregs from skin-resident tumors are most similar to naïve skin resident Tregs but still bear key differences attributable to the TME. We also found that Tregs do not alter their transcriptome or chromatin accessibility following immunotherapy. We conclude that although chromatin accessibility in Tregs is somewhat similar to their tissue residency, the TME may drive a unique chromatin accessibility profile. Treg chromatin accessibility in the tumor appears remarkably stable and unaltered by tumor type, over time, or following immunotherapy.

Nutrient-driven histone code determines exhausted CD8+ T cell fates

Exhausted T cells (TEX) in cancer and chronic viral infections undergo metabolic and epigenetic remodeling, impairing their protective capabilities. However, the impact of nutrient metabolism on epigenetic modifications that control TEX differentiation remains unclear. We showed that TEX cells shifted from acetate to citrate metabolism by down-regulating acetyl-CoA synthetase 2 (ACSS2) while maintaining ATP-citrate lyase (ACLY) activity. This metabolic switch increased citrate-dependent histone acetylation, mediated by histone acetyltransferase KAT2A-ACLY interactions, at TEX signature genes while reducing acetate-dependent histone acetylation, dependent on p300-ACSS2 complexes, at effector and memory T cell genes. Nuclear ACSS2 overexpression or ACLY inhibition prevented TEX differentiation and enhanced tumor-specific T cell responses. These findings unveiled a nutrient-instructed histone code governing CD8+ T cell differentiation, with implications for metabolic- and epigenetic-based T cell therapies.

Microenvironmental β-TrCP negates amino acid transport to trigger CD8+ T cell exhaustion in human non-small cell lung cancer

CD8+ T cell exhaustion (Tex) has been widely acknowledged in human cancer, while the underlying mechanisms remain unclear. Here, we demonstrate that reduced amino acid (aa) metabolism and mTOR inactivation are accountable for Tex in human non-small cell lung cancer (NSCLC). NSCLC cells impede the T cell-intrinsic transcription of SLC7A5 and SLC38A1, disrupting aa transport and consequently leading to mTOR inactivation. Further, the ubiquitination of YAP1 protein is the basis for NSCLC-mediated transcriptional inhibition of aa transporters. Mechanistically, NSCLC cells transfer β-TrCP-containing exosomes into T cells, inducing YAP1 ubiquitination and Tex. Consequently, inhibiting cancer-associated β-TrCP effectively restores the anti-tumor immune response of CD8+ T cells and curtails tumor growth in NSCLC patient-derived organoids. Together, our findings highlight a β-TrCP-dependent mechanism in steering intrinsic metabolic adaptation and CD8+ Tex, emphasizing microenvironmental β-TrCP as an immune checkpoint for therapeutic exploration against human NSCLC.

Global Trends in Research of Amino Acid Metabolism in T Lymphocytes in Recent 15 Years: A Bibliometric Analysis

Amino acid metabolism in T cells determines the therapeutic efficacy of T-cell-targeting drugs. To assess the direction of amino acid metabolism in T cells and construct related knowledge structure, we performed a bibliometric analysis aiming at amino acid metabolism in T cells utilizing studies publicized in recent 15 years. Three hundred thirty-seven related studies were downloaded from the Web of Science Core Collection (WoSCC), and the information on countries, institutes, and authors was collected and analyzed. In addition, the present research status and future trends were explored according to the results yielded from the analysis of cited references and keywords. This study revealed that publications regarding amino acid metabolism in T cells gradually increased each year. The USA is the top producer and most influential country in this field. Recent research has focused on the correlation between the metabolism of several amino acids and regulatory T cells (Tregs) and CD8+ T cells. Overall, this research offers a comprehensive exhibition on the field of amino acid metabolism in T cells, which will help researchers to study this domain more effectively and intuitively.

Immunometabolism of Tregs: mechanisms, adaptability, and therapeutic implications in diseases

Immunometabolism is an emerging field that explores the intricate interplay between immune cells and metabolism. Regulatory T cells (Tregs), which maintain immune homeostasis in immunometabolism, play crucial regulatory roles. The activation, differentiation, and function of Tregs are influenced by various metabolic pathways, such as the Mammalian targets of rapamycin (mTOR) pathway and glycolysis. Correspondingly, activated Tregs can reciprocally impact these metabolic pathways. Tregs also possess robust adaptive capabilities, thus enabling them to adapt to various microenvironments, including the tumor microenvironment (TME). The complex mechanisms of Tregs in metabolic diseases are intriguing, particularly in conditions like MASLD, where Tregs are significantly upregulated and contribute to fibrosis, while in diabetes, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA), they show downregulation and reduced anti-inflammatory capacity. These phenomena suggest that the differentiation and function of Tregs are influenced by the metabolic environment, and imbalances in either can lead to the development of metabolic diseases. Thus, moderate differentiation and inhibitory capacity of Tregs are critical for maintaining immune system balance. Given the unique immunoregulatory abilities of Tregs, the development of targeted therapeutic drugs may position them as novel targets in immunotherapy. This could contribute to restoring immune system balance, resolving metabolic dysregulation, and fostering innovation and progress in immunotherapy.

Immunoprotective effect of chitosan nanoparticles with different particle sizes against H9N2 avian influenza infection

H9N2 is the most common avian influenza virus (AIV), which causes significant losses in chickens. Safe and effective vaccines are crucial for the prevention of H9N2 AIVs. Chitosan nanoparticles, as novel adjuvants, enhance vaccine immunity and biocompatibility; however, the impact of particle size on the immunological effects remains underexplored. To solve these problems and to prepare an efficient novel H9N2 vaccine, we constructed four N-2-HACC/CMCS NPs (NHC NPs) of different particle sizes (165.6 ± 12.0 nm, 272.5 ± 7.0 nm, 343.2 ± 8.0 nm, and 443.5 ± 15.0 nm). Subsequent in vivo immunogenicity screening revealed that H9N2 with the 272.5 ± 7.0 nm NHC NPs vaccine group induced higher levels of neutralizing antibodies in the early stage of the immune response, while the 343.2 ± 8.0 nm NHC NPs vaccine group induced higher levels of neutralizing antibodies in the late stages of the immune response. Subsequently, the results of the optimal particle size combination screening revealed that more neutralizing antibodies were induced when the NHC NPs particle size combination of 272.5 ± 7.0 nm:343.2 ± 8.0 nm ratio was 1.5:1. This optimal particle size combination for NP vaccines promoted lymphocyte proliferation, induced higher IgG2a/IgG1 ratios, and promoted the production of cytokines (i.e., IL-2, IL-4, and IFN-γ). Moreover, a mechanistic analysis revealed that the optimal NHC NPs combination triggered the activation of antigen presenting cells via TLR4 and participated in immune responses through the production of NO and TNF-α. Taken together, our study revealed that the optimal combination of NHC NPs may be a promising strategy against influenza viruses.

Transmembrane Amino Acid Transporters in Shaping the Metabolic Profile of Breast Cancer Cell Lines: The Focus on Molecular Biological Subtype

Amino acid metabolism in breast cancer cells is unique for each molecular biological subtype of breast cancer. In this review, the features of breast cancer cell metabolism are considered in terms of changes in the amino acid composition due to the activity of transmembrane amino acid transporters. In addition to the main signaling pathway PI3K/Akt/mTOR, the activity of the oncogene c-Myc, HIF, p53, GATA2, NF-kB and MAT2A have a direct effect on the amino acid metabolism of cancer cells, their growth and proliferation, as well as the maintenance of homeostatic equilibrium. A distinctive feature of luminal subtypes of breast cancer from TNBC is the ability to perform gluconeogenesis. Breast cancers with a positive expression of the HER2 receptor, in contrast to TNBC and luminal A subtype, have a distinctive active synthesis and consumption of fatty acids. It is interesting to note that amino acid transporters exhibit their activity depending on the pH level inside the cell. In the most aggressive forms of breast cancer or with the gradual progression of the disease, pH will also change, which will directly affect the metabolism of amino acids. Using the cell lines presented in this review, we can trace the characteristic features inherent in each of the molecular biological subtypes of breast cancer and develop the most optimal therapeutic targets.

Engineering bacteria for cancer immunotherapy by inhibiting IDO activity and reprogramming CD8+ T cell response

Inhibiting indoleamine 2,3 dioxygenase (IDO) for anticancer therapy has garnered significant attention in recent years. However, current IDO inhibitors face significant challenges which limit their clinical application. Here, we genetically engineered a high tryptophan-expressing Clostridium butyricum (L-Trp CB) strain that can colonize tumors strictly following systemic administration. We revealed that butyrate produced by L-Trp CB can inhibit IDO activity, preventing tryptophan catabolism and kynurenine accumulation in tumors. In addition, the large released tryptophan by L-Trp CB can provide discrete signals that support CD8+ T cell activation and energy metabolism within the tumor microenvironment. We observed that L-Trp CB significantly restored the proportion and function of CD8+ T cells, leading to significantly delayed tumor growth in both mouse and rabbit multiple tumor models with limited side effects. We here provide a synthetic biology treatment strategy for enhanced tumor immunotherapy by inhibiting IDO activity and reprogramming CD8+ T cell response in tumors.

Metabolic immunoengineering approaches to enhance CD8+ T cell-based cancer immunotherapy

Many cancer immunotherapies rely on robust CD8+ T cells capable of eliminating cancer cells and establishing long-term tumor control. Recent insights into immunometabolism highlight the importance of nutrients and metabolites in T cell activation and differentiation. Within the tumor microenvironment (TME), CD8+ tumor-infiltrating lymphocytes (TILs) undergo metabolic adaptations to survive but compromise their effector function and differentiation. Targeting metabolism holds promise for enhancing CD8+ T cell-mediated antitumor immunity. Here, we overview the metabolic features of CD8+ TILs and their impact on T cell effector function and differentiation. We also highlight immunoengineering strategies by leveraging the Yin-Yang of metabolic modulation for improving cancer immunotherapy.

Asparagine availability controls germinal center B cell homeostasis

The rapid proliferation of germinal center (GC) B cells requires metabolic reprogramming to meet energy demands, yet these metabolic processes are poorly understood. By integrating metabolomic and transcriptomic profiling of GC B cells, we identified that asparagine (Asn) metabolism was highly up-regulated and essential for B cell function. Asparagine synthetase (ASNS) was up-regulated after B cell activation through the integrated stress response sensor GCN2. Conditional deletion of Asns in B cells impaired survival and proliferation in low Asn conditions. Removal of environmental Asn by asparaginase or dietary restriction compromised the GC reaction, impairing affinity maturation and the humoral response to influenza infection. Furthermore, metabolic adaptation to the absence of Asn required ASNS, and oxidative phosphorylation, mitochondrial homeostasis, and synthesis of nucleotides were particularly sensitive to Asn deprivation. These findings demonstrate that Asn metabolism acts as a key regulator of B cell function and GC homeostasis.

Immune imbalance in Lupus Nephritis: The intersection of T-Cell and ferroptosis

Ferroptosis is a novel form of cell death characterized by unlimited accumulation of iron-dependent lipid peroxides. It is often accompanied by disease, and the relationship between ferroptosis of immune cells and immune regulation has been attracting increasing attention. Initially, it was found in cancer research that the inhibition of regulatory T cell (Treg) ferroptosis and the promotion of CD8+ T cell ferroptosis jointly promoted the formation of an immune-tolerant environment in tumors. T-cell ferroptosis has subsequently been found to have immunoregulatory effects in other diseases. As an autoimmune disease characterized by immune imbalance, T-cell ferroptosis has attracted attention for its potential in regulating immune balance in lupus nephritis. This article reviews the metabolic processes within different T-cell subsets in lupus nephritis (LN), including T follicular helper (TFH) cells, T helper (Th)17 cells, Th1 cells, Th2 cells, and Treg cells, and reveals that these cellular metabolisms not only facilitate the formation of a T-cell immune imbalance but are also closely associated with the occurrence of ferroptosis. Consequently, we hypothesize that targeting the metabolic pathways of ferroptosis could become a novel research direction for effectively treating the immune imbalance in lupus nephritis by altering T-cell differentiation and the incidence of ferroptosis.

The role of mitochondria in tumor metastasis and advances in mitochondria-targeted cancer therapy

Mitochondria are central actors in diverse physiological phenomena ranging from energy metabolism to stress signaling and immune modulation. Accumulating scientific evidence points to the critical involvement of specific mitochondrial-associated events, including mitochondrial quality control, intercellular mitochondrial transfer, and mitochondrial genetics, in potentiating the metastatic cascade of neoplastic cells. Furthermore, numerous recent studies have consistently emphasized the highly significant role mitochondria play in coordinating the regulation of tumor-infiltrating immune cells and immunotherapeutic interventions. This review provides a comprehensive and rigorous scholarly investigation of this subject matter, exploring the intricate mechanisms by which mitochondria contribute to tumor metastasis and examining the progress of mitochondria-targeted cancer therapies.

Metabolic drives affecting Th17/Treg gene expression changes and differentiation: impact on immune-microenvironment regulation

The CD4+ T-cell population plays a vital role in the adaptive immune system by coordinating the immune response against different pathogens. A significant transformation occurs in CD4+ cells during an immune response, as they shift from a dormant state to an active state. This transformation leads to extensive proliferation, differentiation, and cytokine production, which contribute to regulating and coordinating the immune response. Th17 and Treg cells are among the most intriguing CD4+ T-cell subpopulations in terms of genetics and metabolism. Gene expression modulation processes rely on and are linked to metabolic changes in cells. Lactylation is a new model that combines metabolism and gene modulation to drive Th17/Treg differentiation and functional processes. The focus of this review is on the metabolic pathways that impact lymphocyte gene modulation in a functionally relevant manner.

Widespread genomic de novo DNA methylation occurs following CD8+ T cell activation and proliferation

This research investigates the intricate dynamics of DNA methylation in the hours following CD8+ T cell activation, during a critical yet understudied temporal window. DNA methylation is an epigenetic modification central to regulation of gene expression and directing immune responses. Our investigation spanned 96-h post-activation and unveils a nuanced tapestry of global and site-specific methylation changes. We identified 15,626 significant differentially methylated CpGs spread across the genome, with the most significant changes occurring within the genes ADAM10, ICA1, and LAPTM5. While many changes had modest effect sizes, approximately 120 CpGs exhibited a log2FC above 1.5, with cell activation and proliferation pathways the most affected. Relatively few of the differentially methylated CpGs occurred along adjacent gene regions. The exceptions were seven differentially methylated gene regions, with the Human T cell Receptor Alpha Joining Genes demonstrating consistent methylation change over a 3kb window. We also investigated whether an inflammatory environment could alter DNA methylation during activation, with proliferating cells exposed to the oxidant glycine chloramine. No substantial differential methylation was observed in this context. The temporal perspective of early activation adds depth to the evolving field of epigenetic immunology, offering insights with implications for therapeutic innovation and expanding our understanding of epigenetic modulation in immune function.

Tragedy of the commons: the resource struggle during Plasmodium infection

Plasmodium spp. have an ancient history with humans, having been described in ancient texts dating back 3500 years ago, which has led to an evolutionary arms race between Plasmodium and humans with Plasmodium successfully subverting durable, sterilizing host immunity. Mechanisms of immune evasion include polymorphism and antigenic variation, as well as dysregulated immune responses, each facilitating transmission and Plasmodium parasite persistence. Notably, metabolite signaling cues in the host and parasite have more recently been appreciated as key drivers for disease progression. Here, we highlight the metabolic interplay between the host and Plasmodium parasites during malaria. We discuss how immunometabolism studies may be leveraged to elucidate this complex relationship and offer opportunities to augment either vaccine- or infection-induced protective immunity.

Fueling the fight against cancer: Exploring the impact of branched-chain amino acid catalyzation on cancer and cancer immune microenvironment

Metabolism of Branched-chain amino acids (BCAAs) is essential for the nutrient necessities in mammals. Catalytic enzymes serve to direct the whole-body BCAAs oxidation which involve in the development of various metabolic disorders. The reprogrammed metabolic elements are also responsible for malignant oncogenic processes, and favor the formation of distinctive immunosuppressive microenvironment surrounding different cancers. The impotent immune surveillance related to BCAAs dysfunction is a novel topic to investigate. Here we focus on the BCAA catalysts that contribute to metabolic changes and dysregulated immune reactions in cancer progression. We summarize the current knowledge of BCAA catalyzation, highlighting the interesting roles of BCAA metabolism in the treatment of cancers.

Metabolic footprint and logic through the T cell life cycle

A simple definition of life is a system that can self-replicate (proliferation) and self-sustain (metabolism). At the cellular level, metabolism has evolved to drive proliferation, which requires energy and building blocks to duplicate cellular biomass before division. T lymphocytes (or T cells) are required for adaptive immune responses, protecting us against invading and malignant agents capable of hyper-replication. To gain a competitive advantage over these agents, activated T cells can duplicate their biomass and divide into two daughter cells in as short as 2-6 hours, considered the fastest cell division among all cell types in vertebrates. Thus, the primary task of cellular metabolism has evolved to commit available resources to drive T cell hyperproliferation. Beyond that, the T cell life cycle involves an ordered series of fate-determining events that drive cells to transition between discrete cell states. At the life stages not involved in hyperproliferation, T cells engage metabolic programs that are more flexible to sustain viability and maintenance and sometimes are fine-tuned to support specific cellular activities. Here, we focus on the central carbon metabolism, which is most relevant to cell proliferation. We provide examples of how the changes in the central carbon metabolism may or may not change the fate of T cells and further explore a few conceptual frameworks, such as metabolic flexibility, the Goldilocks Principle, overflow metabolism, and effector-signaling metabolites, in the context of T cell fate transitions.

Chronic inflammation degrades CD4 T cell immunity to prior vaccines in treated HIV infection

To date, our understanding of how HIV infection impacts vaccine-induced cellular immunity is limited. Here, we investigate inflammation, immune activation and antigen-specific T cell responses in HIV-uninfected and antiretroviral-treated HIV-infected people. Our findings highlight lower recall responses of antigen-specific CD4 T cells that correlate with high plasma cytokines levels, T cell hyperactivation and an altered composition of the T subsets enriched with more differentiated cells in the HIV-infected group. Transcriptomic analysis reveals that antigen-specific CD4 T cells of the HIV-infected group have a reduced expression of gene sets previously reported to correlate with vaccine-induced pathogen-specific protective immunity and further identifies a consistent impairment of the IFNα and IFNγ response pathways as mechanism for the functional loss of recall CD4 T cell responses in antiretroviral-treated people. Lastly, in vitro treatment with drugs that reduce inflammation results in higher memory CD4 T cell IFNγ responses. Together, our findings suggest that vaccine-induced cellular immunity may benefit from strategies to counteract inflammation in HIV infection.

Neurotrophic factor Neuritin modulates T cell electrical and metabolic state for the balance of tolerance and immunity

The adaptive T cell response is accompanied by continuous rewiring of the T cell's electric and metabolic state. Ion channels and nutrient transporters integrate bioelectric and biochemical signals from the environment, setting cellular electric and metabolic states. Divergent electric and metabolic states contribute to T cell immunity or tolerance. Here, we report in mice that neuritin (Nrn1) contributes to tolerance development by modulating regulatory and effector T cell function. Nrn1 expression in regulatory T cells promotes its expansion and suppression function, while expression in the T effector cell dampens its inflammatory response. Nrn1 deficiency in mice causes dysregulation of ion channel and nutrient transporter expression in Treg and effector T cells, resulting in divergent metabolic outcomes and impacting autoimmune disease progression and recovery. These findings identify a novel immune function of the neurotrophic factor Nrn1 in regulating the T cell metabolic state in a cell context-dependent manner and modulating the outcome of an immune response.

Amino acid metabolic reprogramming in the tumor microenvironment and its implication for cancer therapy

Amino acids are essential building blocks for proteins, crucial energy sources for cell survival, and key signaling molecules supporting the resistant growth of tumor cells. In tumor cells, amino acid metabolic reprogramming is characterized by the enhanced uptake of amino acids as well as their aberrant synthesis, breakdown, and transport, leading to immune evasion and malignant progression of tumor cells. This article reviews the altered amino acid metabolism in tumor cells and its impact on tumor microenvironment, and also provides an overview of the current clinical applications of amino acid metabolism. Innovative drugs targeting amino acid metabolism hold great promise for precision and personalized cancer therapy.

Reciprocal regulation of mTORC1 signaling and ribosomal biosynthesis determines cell cycle progression in activated T cells

Ribosomal biosynthesis in nucleoli is an energy-demanding process driven by all RNA polymerases and hundreds of auxiliary proteins. We investigated how this process is regulated in activated T lymphocytes by T cell receptor (TCR) signals and the multiprotein complexes mTORC1 and mTORC2, both of which contain the kinase mTOR. Deficiency in mTORC1 slowed the proliferation of T cells, with further delays in each consecutive division, an effect not seen with deficiency in mTORC2. mTORC1 signaling was stimulated by components of conventional TCR signaling, and, reciprocally, TCR sensitivity was decreased by mTORC1 inhibition. The substantial increase in the amount of RNA per cell induced by TCR activation was reduced by 50% by deficiency in mTORC1, but not in mTORC2 or in S6 kinases 1 and 2, which are activated downstream of mTORC1. RNA-seq data showed that mTORC1 deficiency reduced the abundance of all RNA biotypes, although rRNA processing was largely intact in activated T cells. Imaging cytometry with FISH probes for nascent pre-rRNA revealed that deletion of mTORC1, but not that of mTORC2, reduced the number and expansion of nucleolar sites of active transcription. Protein translation was consequently decreased by 50% in the absence of mTORC1. Inhibiting RNA polymerase I blocked not only proliferation but also mTORC1 signaling. Our data show that TCR signaling, mTORC1 activity, and ribosomal biosynthesis in the nucleolus regulate each other during biomass production in clonally expanding T cells.

GLUT1 overexpression in CAR-T cells induces metabolic reprogramming and enhances potency

The intensive nutrient requirements needed to sustain T cell activation and proliferation, combined with competition for nutrients within the tumor microenvironment, raise the prospect that glucose availability may limit CAR-T cell function. Here, we seek to test the hypothesis that stable overexpression (OE) of the glucose transporter GLUT1 in primary human CAR-T cells would improve their function and antitumor potency. We observe that GLUT1OE in CAR-T cells increases glucose consumption, glycolysis, glycolytic reserve, and oxidative phosphorylation, and these effects are associated with decreased T cell exhaustion and increased Th17 differentiation. GLUT1OE also induces broad metabolic reprogramming associated with increased glutathione-mediated resistance to reactive oxygen species, and increased inosine accumulation. When challenged with tumors, GLUT1OE CAR-T cells secrete more proinflammatory cytokines and show enhanced cytotoxicity in vitro, and demonstrate superior tumor control and persistence in mouse models. Our collective findings support a paradigm wherein glucose availability is rate limiting for effector CAR-T cell function and demonstrate that enhancing glucose availability via GLUT1OE could augment antitumor immune function.

Focusing on CD8+ T-cell phenotypes: improving solid tumor therapy

Vigorous CD8+ T cells play a crucial role in recognizing tumor cells and combating solid tumors. How T cells efficiently recognize and target tumor antigens, and how they maintain the activity in the "rejection" of solid tumor microenvironment, are major concerns. Recent advances in understanding of the immunological trajectory and lifespan of CD8+ T cells have provided guidance for the design of more optimal anti-tumor immunotherapy regimens. Here, we review the newly discovered methods to enhance the function of CD8+ T cells against solid tumors, focusing on optimizing T cell receptor (TCR) expression, improving antigen recognition by engineered T cells, enhancing signal transduction of the TCR-CD3 complex, inducing the homing of polyclonal functional T cells to tumors, reversing T cell exhaustion under chronic antigen stimulation, and reprogramming the energy and metabolic pathways of T cells. We also discuss how to participate in the epigenetic changes of CD8+ T cells to regulate two key indicators of anti-tumor responses, namely effectiveness and persistence.

Identification of amino acids metabolomic profiling in human plasma distinguishes lupus nephritis from systemic lupus erythematosus

Lupus nephritis (LN) is an immunoinflammatory glomerulonephritis associated with renal involvement in systemic lupus erythematosus (SLE). Given the close relationship between plasma amino acids (AAs) and renal function, this study aimed to elucidate the plasma AA profiles in LN patients and identify key AAs and diagnostic patterns that distinguish LN patients from those with SLE and healthy controls. Participants were categorized into three groups: normal controls (NC), SLE, and LN. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was employed to quantify AA levels in human plasma. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were utilized to identify key AAs. The diagnostic capacity of the models was assessed using receiver operating characteristic (ROC) curve analysis and area under the ROC curve (AUC) values. Significant alterations in plasma AA profiles were observed in LN patients compared to the SLE and NC groups. The OPLS-DA model effectively separated LN patients from the SLE and NC groups. A joint model using histidine (His), lysine (Lys), and tryptophan (Trp) demonstrated exceptional diagnostic performance, achieving an AUC of 1.0 with 100% sensitivity, specificity, and accuracy in predicting LN. Another joint model comprising arginine (Arg), valine (Val), and Trp also exhibited robust predictive performance, with an AUC of 0.998, sensitivity of 93.80%, specificity of 100%, and accuracy of 95.78% in distinguishing between SLE and LN. The joint forecasting models showed excellent predictive capabilities in identifying LN and categorizing lupus disease status. This approach provides a novel perspective for the early identification, prevention, treatment, and management of LN based on variations in plasma AA levels.

BCKDK modification enhances the anticancer efficacy of CAR-T cells by reprogramming branched chain amino acid metabolism

Altered branched chain amino acids (BCAAs), including leucine, isoleucine, and valine, are frequently observed in patients with advanced cancer. We evaluated the efficacy of chimeric antigen receptor (CAR) T cell-mediated cancer cell lysis potential in the immune microenvironment of BCAA supplementation and deletion. BCAA supplementation increased cancer cell killing percentage, while accelerating BCAA catabolism and decreasing BCAA transporter decreased cancer cell lysis efficacy. We thus designed BCKDK engineering CAR T cells for the reprogramming of BCAA metabolism in the tumor microenvironment based on the genotype and phenotype modification. BCKDK overexpression (OE) in CAR-T cells significantly improved cancer cell lysis, while BCKDK knockout (KO) resulted in inferior lysis potential. In an in vivo experiment, BCKDK-OE CAR-T cell treatment significantly prolonged the survival of mice bearing NALM6-GL cancer cells, with the differentiation of central memory cells and an increasing proportion of CAR-T cells in the peripheral circulation. BCKDK-KO CAR-T cell treatment resulted in shorter survival and a decreasing percentage of CAR-T cells in the peripheral circulation. In conclusion, BCKDK-engineered CAR-T cells exert a distinct phenotype for superior anticancer efficiency.

The tRNA Gm18 methyltransferase TARBP1 promotes hepatocellular carcinoma progression via metabolic reprogramming of glutamine

Cancer cells rely on metabolic reprogramming to sustain the prodigious energetic requirements for rapid growth and proliferation. Glutamine metabolism is frequently dysregulated in cancers and is being exploited as a potential therapeutic target. Using CRISPR/Cas9 interference (CRISPRi) screening, we identified TARBP1 (TAR (HIV-1) RNA Binding Protein 1) as a critical regulator involved in glutamine reliance of cancer cell. Consistent with this discovery, TARBP1 amplification and overexpression are frequently observed in various cancers. Knockout of TARBP1 significantly suppresses cell proliferation, colony formation and xenograft tumor growth. Mechanistically, TARBP1 selectively methylates and stabilizes a small subset of tRNAs, which promotes efficient protein synthesis of glutamine transporter-ASCT2 (also known as SLC1A5) and glutamine import to fuel the growth of cancer cell. Moreover, we found that the gene expression of TARBP1 and ASCT2 are upregulated in combination in clinical cohorts and their upregulation is associated with unfavorable prognosis of HCC (hepatocellular carcinoma). Taken together, this study reveals the unexpected role of TARBP1 in coordinating the tRNA availability and glutamine uptake during HCC progression and provides a potential target for tumor therapy.

Oleic acid enhances proliferation and calcium mobilization of CD3/CD28 activated CD4+ T cells through incorporation into membrane lipids

Unsaturated fatty acids (UFA) are crucial for T-cell effector functions, as they can affect the growth, differentiation, survival, and function of T cells. Nonetheless, the mechanisms by which UFA affects T-cell behavior are ill-defined. Therefore, we analyzed the processing of oleic acid, a prominent UFA abundantly present in blood, adipocytes, and the fat pads surrounding lymph nodes, in CD4+ T cells. We found that exogenous oleic acid increases proliferation and enhances the calcium flux response upon CD3/CD28 activation. By using a variety of techniques, we found that the incorporation of oleic acid into membrane lipids, rather than regulation of cellular metabolism or TCR expression, is essential for its effects on CD4+ T cells. These results provide novel insights into the mechanism through which exogenous oleic acid enhances CD4+ T-cell function.