bims-camemi Biomed News
on Mitochondrial metabolism in cancer
Issue of 2023‒03‒05
fifty-four papers selected by
Christian Frezza
University Hospital Cologne

  1. Sci Adv. 2023 Mar;9(9): eadd5220
      Cellular metabolism is important for adult neural stem/progenitor cell (NSPC) behavior. However, its role in the transition from quiescence to proliferation is not fully understood. We here show that the mitochondrial pyruvate carrier (MPC) plays a crucial and unexpected part in this process. MPC transports pyruvate into mitochondria, linking cytosolic glycolysis to mitochondrial tricarboxylic acid cycle and oxidative phosphorylation. Despite its metabolic key function, the role of MPC in NSPCs has not been addressed. We show that quiescent NSPCs have an active mitochondrial metabolism and express high levels of MPC. Pharmacological MPC inhibition increases aspartate and triggers NSPC activation. Furthermore, genetic Mpc1 ablation in vitro and in vivo also activates NSPCs, which differentiate into mature neurons, leading to overall increased hippocampal neurogenesis in adult and aged mice. These findings highlight the importance of metabolism for NSPC regulation and identify an important pathway through which mitochondrial pyruvate import controls NSPC quiescence and activation.
  2. Cell. 2023 Feb 22. pii: S0092-8674(23)00097-1. [Epub ahead of print]
      The uptake and metabolism of nutrients support fundamental cellular process from bioenergetics to biomass production and cell fate regulation. While many studies of cell metabolism focus on cancer cells, the principles of metabolism elucidated in cancer cells apply to a wide range of mammalian cells. The goal of this review is to discuss how the field of cancer metabolism provides a framework for revealing principles of cell metabolism and for dissecting the metabolic networks that allow cells to meet their specific demands. Understanding context-specific metabolic preferences and liabilities will unlock new approaches to target cancer cells to improve patient care.
  3. Cancer Res. 2023 Mar 02. pii: CAN-22-3000. [Epub ahead of print]
      Cysteine plays critical roles in cellular biosynthesis, enzyme catalysis, and redox metabolism. The intracellular cysteine pool can be sustained by cystine uptake or de novo synthesis from serine and homocysteine. Demand for cysteine is increased during tumorigenesis for generating glutathione to deal with oxidative stress. While cultured cells have been shown to be highly dependent on exogenous cystine for proliferation and survival, how diverse tissues obtain and use cysteine in vivo has not been characterized. We comprehensively interrogated cysteine metabolism in normal murine tissues and cancers that arise from them using stable isotope 13C1-serine and 13C6-cystine tracing. De novo cysteine synthesis was highest in normal liver and pancreas and absent in lung tissue, while cysteine synthesis was either inactive or downregulated during tumorigenesis. By contrast, cystine uptake and metabolism to downstream metabolites was a universal feature of normal tissues and tumors. However, differences in glutathione labeling from cysteine were evident across tumor types. Thus, cystine is a major contributor to the cysteine pool in tumors, and glutathione metabolism is differentially active across tumor types.
  4. Cell Metab. 2023 Feb 22. pii: S1550-4131(23)00012-8. [Epub ahead of print]
      Multiple cancers regulate oxidative stress by activating the transcription factor NRF2 through mutation of its negative regulator, KEAP1. NRF2 has been studied extensively in KEAP1-mutant cancers; however, the role of this pathway in cancers with wild-type KEAP1 remains poorly understood. To answer this question, we induced NRF2 via pharmacological inactivation of KEAP1 in a panel of 50+ non-small cell lung cancer cell lines. Unexpectedly, marked decreases in viability were observed in >13% of the cell lines-an effect that was rescued by NRF2 ablation. Genome-wide and targeted CRISPR screens revealed that NRF2 induces NADH-reductive stress, through the upregulation of the NAD+-consuming enzyme ALDH3A1. Leveraging these findings, we show that cells treated with KEAP1 inhibitors or those with endogenous KEAP1 mutations are selectively vulnerable to Complex I inhibition, which impairs NADH oxidation capacity and potentiates reductive stress. Thus, we identify reductive stress as a metabolic vulnerability in NRF2-activated lung cancers.
    Keywords:  NADH/NAD(+); NRF2-KEAP1 pathway; functional genomic; non-small cell lung cancer; oxidative phosphorylation; reductive stress
  5. Mitochondrion. 2023 Feb 28. pii: S1567-7249(23)00016-8. [Epub ahead of print]
      Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.
    Keywords:  Aerobic glycolysis; Aging; Cancer; Diabetes; Embryogenesis; Inflammation; Neurodegeneration; Oxidative phosphorylation; Pyruvate dehydrogenase complex; Sepsis
  6. J Clin Invest. 2023 Mar 02. pii: e167133. [Epub ahead of print]
      Circadian rhythmicity in renal function suggests rhythmic adaptations in renal metabolism. Todecipher the role of the circadian clock in renal metabolism, we studied diurnal changes in renal metabolic pathways using integrated transcriptomic, proteomic, and metabolomic analysisperformed on control mice and mice with inducible deletion of the circadian clock regulator Bmal1 in the renal tubule (cKOt). With this unique resource, we demonstrated that ~30% RNAs, ~20% proteins and ~20% metabolites are rhythmic in kidneys of control mice. Several key metabolic pathways including NAD+ biosynthesis, fatty acid transport, carnitine shuttle,and b-oxidation displayed impairments in kidneys of cKOt, resulting in a perturbedmitochondrial activity. Carnitine reabsorption from the primary urine was one of the mostimpacted processes with a ~50% reduction in plasma carnitine levels and a parallel systemicdecrease in tissues carnitine content. This suggests that the circadian clock in the renal tubule controls both kidney and systemic physiology.
    Keywords:  Bioenergetics; Bioinformatics; Fatty acid oxidation; Nephrology
  7. Cell Rep. 2023 Feb 26. pii: S2211-1247(23)00164-X. [Epub ahead of print]42(3): 112153
      Pyruvate dehydrogenase (PDH) is the central enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle. The importance of PDH function in T helper 17 (Th17) cells still remains to be studied. Here, we show that PDH is essential for the generation of a glucose-derived citrate pool needed for Th17 cell proliferation, survival, and effector function. In vivo, mice harboring a T cell-specific deletion of PDH are less susceptible to developing experimental autoimmune encephalomyelitis. Mechanistically, the absence of PDH in Th17 cells increases glutaminolysis, glycolysis, and lipid uptake in a mammalian target of rapamycin (mTOR)-dependent manner. However, cellular citrate remains critically low in mutant Th17 cells, which interferes with oxidative phosphorylation (OXPHOS), lipid synthesis, and histone acetylation, crucial for transcription of Th17 signature genes. Increasing cellular citrate in PDH-deficient Th17 cells restores their metabolism and function, identifying a metabolic feedback loop within the central carbon metabolism that may offer possibilities for therapeutically targeting Th17 cell-driven autoimmunity.
    Keywords:  CP: Immunology; CP: Metabolism; IL-17; T cells; Th17 cells; acetyl-CoA; citrate; epigenetics; experimental autoimmune encephalomyelitis; glucose metabolism; histone acetylation; pyruvate dehydrogenase
  8. Cell Res. 2023 Mar 02.
      A well-established role of cyclic GMP-AMP synthase (cGAS) is the recognition of cytosolic DNA, which is linked to the activation of host defense programs against pathogens via stimulator of interferon genes (STING)-dependent innate immune response. Recent advance has also revealed that cGAS may be involved in several noninfectious contexts by localizing to subcellular compartments other than the cytosol. However, the subcellular localization and function of cGAS in different biological conditions is unclear; in particular, its role in cancer progression remains poorly understood. Here we show that cGAS is localized to mitochondria and protects hepatocellular carcinoma cells from ferroptosis in vitro and in vivo. cGAS anchors to the outer mitochondrial membrane where it associates with dynamin-related protein 1 (DRP1) to facilitate its oligomerization. In the absence of cGAS or DRP1 oligomerization, mitochondrial ROS accumulation and ferroptosis increase, inhibiting tumor growth. Collectively, this previously unrecognized role for cGAS in orchestrating mitochondrial function and cancer progression suggests that cGAS interactions in mitochondria can serve as potential targets for new cancer interventions.
  9. Nat Commun. 2023 Mar 01. 14(1): 1172
      The hypoxic ventilatory response (HVR) is a life-saving reflex, triggered by the activation of chemoreceptor glomus cells in the carotid body (CB) connected with the brainstem respiratory center. The molecular mechanisms underlying glomus cell acute oxygen (O2) sensing are unclear. Genetic disruption of mitochondrial complex I (MCI) selectively abolishes the HVR and glomus cell responsiveness to hypoxia. However, it is unknown what functions of MCI (metabolic, proton transport, or signaling) are essential for O2 sensing. Here we show that transgenic mitochondrial expression of NDI1, a single-molecule yeast NADH/quinone oxidoreductase that does not directly contribute to proton pumping, fully recovers the HVR and glomus cell sensitivity to hypoxia in MCI-deficient mice. Therefore, maintenance of mitochondrial NADH dehydrogenase activity and the electron transport chain are absolutely necessary for O2-dependent regulation of breathing. NDI1 expression also rescues other systemic defects caused by MCI deficiency. These data explain the role of MCI in acute O2 sensing by arterial chemoreceptors and demonstrate the optimal recovery of complex organismal functions by gene therapy.
  10. bioRxiv. 2023 Feb 22. pii: 2023.02.21.528863. [Epub ahead of print]
      Mitochondrial reactive oxygen species (mROS) are central to physiology. While excess mROS production has been associated with several disease states, its precise sources, regulation, and mechanism of generation in vivo remain unknown, limiting translational efforts. Here we show that in obesity, hepatic ubiquinone (Q) synthesis is impaired, which raises the QH 2 /Q ratio, driving excessive mROS production via reverse electron transport (RET) from site I Q in complex I. Using multiple complementary genetic and pharmacological models in vivo we demonstrated that RET is critical for metabolic health. In patients with steatosis, the hepatic Q biosynthetic program is also suppressed, and the QH 2 /Q ratio positively correlates with disease severity. Our data identify a highly selective mechanism for pathological mROS production in obesity, which can be targeted to protect metabolic homeostasis.
  11. Arch Biochem Biophys. 2023 Feb 28. pii: S0003-9861(23)00055-3. [Epub ahead of print]737 109556
      To cope with the requirements of energy and building blocks for rapid proliferation, cancer cells reprogram their metabolic pathways profoundly, especially in oxygen- and nutrients-deficient tumor microenvironments. However, functional mitochondria and mitochondria-dependent oxidative phosphorylation are still necessary for the tumorigenesis and metastasis of cancer cells. We show here that mitochondrial elongation factor 4 (mtEF4) is commonly upregulated in breast tumors compared to adjacent non-cancerous tissues, and is relevant to tumor progression and poor prognosis. Down regulation of mtEF4 in breast cancer cells impairs the assembly of mitochondrial respiration complexes, decreases mitochondrial respiration, reduces ATP production, attenuates the formation of lamellipodia, and suppresses cell motility in vitro and cancer metastasis in vivo. On the contrary, upregulation of mtEF4 elevates the mitochondrial oxidative phosphorylation, which contributes to the migratory capacities of breast cancer cells. mtEF4 also increases the potential of glycolysis, probably via an AMPK-related mechanism. In summary, we provide direct evidences that the aberrantly upregulated mtEF4 contributes to the metastasis of breast cancer by coordinating metabolic pathways.
    Keywords:  Breast cancer; Glycolysis; Metastasis; Mitochondrial elongation factor 4; Oxidative phosphorylation; Tumorigenesis
  12. Trends Biochem Sci. 2023 Feb 28. pii: S0968-0004(23)00034-8. [Epub ahead of print]
      Isotope-assisted metabolic flux analysis (iMFA) is a powerful method to mathematically determine the metabolic fluxome from experimental isotope labeling data and a metabolic network model. While iMFA was originally developed for industrial biotechnological applications, it is increasingly used to analyze eukaryotic cell metabolism in physiological and pathological states. In this review, we explain how iMFA estimates the intracellular fluxome, including data and network model (inputs), the optimization-based data fitting (process), and the flux map (output). We then describe how iMFA enables analysis of metabolic complexities and discovery of metabolic pathways. Our goal is to expand the use of iMFA in metabolism research, which is essential to maximizing the impact of metabolic experiments and continuing to advance iMFA and biocomputational techniques.
    Keywords:  fluxomics; mass spectrometry; metabolic modeling isotope labeling
  13. Redox Biol. 2023 Feb 09. pii: S2213-2317(23)00028-9. [Epub ahead of print]61 102627
      Metabolic reprogramming and metabolic plasticity allow cancer cells to fine-tune their metabolism and adapt to the ever-changing environments of the metastatic cascade, for which lipid metabolism and oxidative stress are of particular importance. NADPH is a central co-factor for both lipid and redox homeostasis, suggesting that cancer cells may require larger pools of NADPH to efficiently metastasize. NADPH is recycled through reduction of NADP+ by several enzymatic systems in cells; however, de novo NADP+ is synthesized only through one known enzymatic reaction, catalyzed by NAD+ kinase (NADK). Here, we show that NADK is upregulated in metastatic breast cancer cells enabling de novo production of NADP(H) and the expansion of the NADP(H) pools thereby increasing the ability of these cells to adapt to the challenges of the metastatic cascade and efficiently metastasize. Mechanistically, we found that metastatic signals lead to a histone H3.3 variant-mediated epigenetic regulation of the NADK promoter, resulting in increased NADK levels in cells with metastatic ability. Together, our work presents a previously uncharacterized role for NADK and de novo NADP(H) production as a contributor to breast cancer progression and suggests that NADK constitutes an important and much needed therapeutic target for metastatic breast cancers.
    Keywords:  Breast cancer; Metastasis; NADK; NADPH; Redox
  14. iScience. 2023 Feb 17. 26(2): 106040
      Dietary nutrient availability and gene expression, together, influence tissue metabolic activity. Here, we explore whether altering dietary nutrient composition in the context of mouse liver cancer suffices to overcome chronic gene expression changes that arise from tumorigenesis and western-style diet (WD). We construct a mouse genome-scale metabolic model and estimate metabolic fluxes in liver tumors and non-tumoral tissue after computationally varying the composition of input diet. This approach, called Systematic Diet Composition Swap (SyDiCoS), revealed that, compared to a control diet, WD increases production of glycerol and succinate irrespective of specific tissue gene expression patterns. Conversely, differences in fatty acid utilization pathways between tumor and non-tumor liver are amplified with WD by both dietary carbohydrates and lipids together. Our data suggest that combined dietary component modifications may be required to normalize the distinctive metabolic patterns that underlie selective targeting of tumor metabolism.
    Keywords:  Biological sciences; Cancer; Cellular physiology; Physiology
  15. Nat Commun. 2023 Feb 27. 14(1): 1121
      Liver tumour-initiating cells (TICs) contribute to tumour initiation, metastasis, progression and drug resistance. Metabolic reprogramming is a cancer hallmark and plays vital roles in liver tumorigenesis. However, the role of metabolic reprogramming in TICs remains poorly explored. Here, we identify a mitochondria-encoded circular RNA, termed mcPGK1 (mitochondrial circRNA for translocating phosphoglycerate kinase 1), which is highly expressed in liver TICs. mcPGK1 knockdown impairs liver TIC self-renewal, whereas its overexpression drives liver TIC self-renewal. Mechanistically, mcPGK1 regulates metabolic reprogramming by inhibiting mitochondrial oxidative phosphorylation (OXPHOS) and promoting glycolysis. This alters the intracellular levels of α-ketoglutarate and lactate, which are modulators in Wnt/β-catenin activation and liver TIC self-renewal. In addition, mcPGK1 promotes PGK1 mitochondrial import via TOM40 interactions, reprogramming metabolism from oxidative phosphorylation to glycolysis through PGK1-PDK1-PDH axis. Our work suggests that mitochondria-encoded circRNAs represent an additional regulatory layer controlling mitochondrial function, metabolic reprogramming and liver TIC self-renewal.
  16. Nat Metab. 2023 Feb;5(2): 294-313
      Many cell biological and biochemical mechanisms controlling the fundamental process of eukaryotic cell division have been identified; however, the temporal dynamics of biosynthetic processes during the cell division cycle are still elusive. Here, we show that key biosynthetic processes are temporally segregated along the cell cycle. Using budding yeast as a model and single-cell methods to dynamically measure metabolic activity, we observe two peaks in protein synthesis, in the G1 and S/G2/M phase, whereas lipid and polysaccharide synthesis peaks only once, during the S/G2/M phase. Integrating the inferred biosynthetic rates into a thermodynamic-stoichiometric metabolic model, we find that this temporal segregation in biosynthetic processes causes flux changes in primary metabolism, with an acceleration of glucose-uptake flux in G1 and phase-shifted oscillations of oxygen and carbon dioxide exchanges. Through experimental validation of the model predictions, we demonstrate that primary metabolism oscillates with cell-cycle periodicity to satisfy the changing demands of biosynthetic processes exhibiting unexpected dynamics during the cell cycle.
  17. Nat Commun. 2023 Mar 02. 14(1): 1187
      Ferroptosis is mediated by lipid peroxidation of phospholipids containing polyunsaturated fatty acyl moieties. Glutathione, the key cellular antioxidant capable of inhibiting lipid peroxidation via the activity of the enzyme glutathione peroxidase 4 (GPX-4), is generated directly from the sulfur-containing amino acid cysteine, and indirectly from methionine via the transsulfuration pathway. Herein we show that cysteine and methionine deprivation (CMD) can synergize with the GPX4 inhibitor RSL3 to increase ferroptotic cell death and lipid peroxidation in both murine and human glioma cell lines and in ex vivo organotypic slice cultures. We also show that a cysteine-depleted, methionine-restricted diet can improve therapeutic response to RSL3 and prolong survival in a syngeneic orthotopic murine glioma model. Finally, this CMD diet leads to profound in vivo metabolomic, proteomic and lipidomic alterations, highlighting the potential for improving the efficacy of ferroptotic therapies in glioma treatment with a non-invasive dietary modification.
  18. Nature. 2023 Feb 28.
    Keywords:  Cancer; Medical research; Metabolism
  19. Cancer Discov. 2023 Feb 27. pii: CD-22-0825. [Epub ahead of print]
      Oncogenic mutations in isocitrate dehydrogenase (IDH)-1 and -2 occur in a wide range of cancers, including acute myeloid leukemia (AML) and glioma. Mutant IDH enzymes convert 2-oxoglutarate (2OG) to (R)-2-hydroxyglutarate ((R)-2HG)), an oncometabolite that is hypothesized to promote cellular transformation by dysregulating 2OG-dependent enzymes. The only (R)-2HG target that has been convincingly shown to contribute to transformation by mutant IDH is the myeloid tumor suppressor TET2. However, there is ample evidence to suggest that (R)-2HG has other functionally relevant targets in IDH-mutant cancers. Here, we show that (R)-2HG inhibits KDM5 histone lysine demethylases and that this inhibition contributes to cellular transformation in IDH-mutant AML and IDH-mutant glioma. These studies provide the first evidence of a functional link between dysregulation of histone lysine methylation and transformation in IDH-mutant cancers.
  20. Commun Biol. 2023 Mar 01. 6(1): 231
      Alleles within the chr19p13.1 locus are associated with increased risk of both ovarian and breast cancer and increased expression of the ANKLE1 gene. ANKLE1 is molecularly characterized as an endonuclease that efficiently cuts branched DNA and shuttles between the nucleus and cytoplasm. However, the role of ANKLE1 in mammalian development and homeostasis remains unknown. In normal development ANKLE1 expression is limited to the erythroblast lineage and we found that ANKLE1's role is to cleave the mitochondrial genome during erythropoiesis. We show that ectopic expression of ANKLE1 in breast epithelial-derived cells leads to genome instability and mitochondrial DNA (mtDNA) cleavage. mtDNA degradation then leads to mitophagy and causes a shift from oxidative phosphorylation to glycolysis (Warburg effect). Moreover, mtDNA degradation activates STAT1 and expression of epithelial-mesenchymal transition (EMT) genes. Reduction in mitochondrial content contributes to apoptosis resistance, which may allow precancerous cells to avoid apoptotic checkpoints and proliferate. These findings provide evidence that ANKLE1 is the causal cancer susceptibility gene in the chr19p13.1 locus and describe mechanisms by which higher ANKLE1 expression promotes cancer risk.
  21. Front Physiol. 2023 ;14 1106662
      A physiological increase in cardiac workload results in adaptive cardiac remodeling, characterized by increased oxidative metabolism and improvements in cardiac performance. Insulin-like growth factor-1 (IGF-1) has been identified as a critical regulator of physiological cardiac growth, but its precise role in cardiometabolic adaptations to physiological stress remains unresolved. Mitochondrial calcium (Ca2+) handling has been proposed to be required for sustaining key mitochondrial dehydrogenase activity and energy production during increased workload conditions, thus ensuring the adaptive cardiac response. We hypothesized that IGF-1 enhances mitochondrial energy production through a Ca2+-dependent mechanism to ensure adaptive cardiomyocyte growth. We found that stimulation with IGF-1 resulted in increased mitochondrial Ca2+ uptake in neonatal rat ventricular myocytes and human embryonic stem cell-derived cardiomyocytes, estimated by fluorescence microscopy and indirectly by a reduction in the pyruvate dehydrogenase phosphorylation. We showed that IGF-1 modulated the expression of mitochondrial Ca2+ uniporter (MCU) complex subunits and increased the mitochondrial membrane potential; consistent with higher MCU-mediated Ca2+ transport. Finally, we showed that IGF-1 improved mitochondrial respiration through a mechanism dependent on MCU-mediated Ca2+ transport. In conclusion, IGF-1-induced mitochondrial Ca2+ uptake is required to boost oxidative metabolism during cardiomyocyte adaptive growth.
    Keywords:  MCU complex; human embryonic stem cell derived-cardiomyocytes (hES-CMs); insulin-like growth factor 1 (IGF-1); mitochondrial calcium handling; neonatal rat ventricular myocytes (NRVMs); physiological cardiac hypertrophy
  22. EMBO J. 2023 Feb 27. e111148
      Osteoclasts are bone-resorbing polykaryons responsible for skeletal remodeling during health and disease. Coincident with their differentiation from myeloid precursors, osteoclasts undergo extensive transcriptional and metabolic reprogramming in order to acquire the cellular machinery necessary to demineralize bone and digest its interwoven extracellular matrix. While attempting to identify new regulatory molecules critical to bone resorption, we discovered that murine and human osteoclast differentiation is accompanied by the expression of Zeb1, a zinc-finger transcriptional repressor whose role in normal development is most frequently linked to the control of epithelial-mesenchymal programs. However, following targeting, we find that Zeb1 serves as an unexpected regulator of osteoclast energy metabolism. In vivo, Zeb1-null osteoclasts assume a hyperactivated state, markedly decreasing bone density due to excessive resorptive activity. Mechanistically, Zeb1 acts in a rheostat-like fashion to modulate murine and human osteoclast activity by transcriptionally repressing an ATP-buffering enzyme, mitochondrial creatine kinase 1 (MtCK1), thereby controlling the phosphocreatine energy shuttle and mitochondrial respiration. Together, these studies identify a novel Zeb1/MtCK1 axis that exerts metabolic control over bone resorption in vitro and in vivo.
    Keywords:  Zeb1; bone resorption; mitochondrial creatine kinase; osteoclast; skeletal remodeling
  23. Antioxid Redox Signal. 2023 Feb 27.
      AIMS: Targeting tumor metabolism may improve the outcomes for patients with glioblastoma (GBM). To further preclinical efforts targeting metabolism in GBM, we tested the hypothesis that brain tumors can be stratified into distinct metabolic groups with different patient outcomes. Therefore, to determine if tumor metabolites relate to patient survival, we profiled the metabolomes of human gliomas and correlated metabolic information with clinical data.RESULTS: We found that isocitrate dehydrogenase-wildtype (IDHwt) GBMs are metabolically distinguishable from IDH mutated (IDHmut) astrocytomas and oligodendrogliomas. Survival of patients with IDHmut gliomas was expectedly more favorable than those with IDHwt GBM, and metabolic signatures can stratify IDHwt GBMs subtypes with varying prognoses. Patients whose GBMs were enriched in amino acids had improved survival while those whose tumors were enriched for nucleotides, redox molecules and lipid metabolites fared more poorly. These findings were recapitulated in validation cohorts using both metabolomic and transcriptomic data.
    INNOVATION: Our results suggest the existence of metabolic subtypes of GBM with differing prognoses and further support the concept that metabolism may drive the aggressiveness of human gliomas.
    CONCLUSIONS: Our data show that metabolic signatures of human gliomas can inform patient survival. These findings may be used clinically to tailor novel metabolically targeted agents for GBM patients with different metabolic phenotypes.
  24. bioRxiv. 2023 Feb 23. pii: 2023.02.22.529581. [Epub ahead of print]
      Glioma cells hijack developmental transcriptional programs to control cell state. During neural development, lineage trajectories rely on specialized metabolic pathways. However, the link between tumor cell state and metabolic programs is poorly understood in glioma. Here we uncover a glioma cell state-specific metabolic liability that can be leveraged therapeutically. To model cell state diversity, we generated genetically engineered murine gliomas, induced by deletion of p53 alone (p53) or with constitutively active Notch signaling (N1IC), a pathway critical in controlling cellular fate. N1IC tumors harbored quiescent astrocyte-like transformed cell states while p53 tumors were predominantly comprised of proliferating progenitor-like cell states. N1IC cells exhibit distinct metabolic alterations, with mitochondrial uncoupling and increased ROS production rendering them more sensitive to inhibition of the lipid hydroperoxidase GPX4 and induction of ferroptosis. Importantly, treating patient-derived organotypic slices with a GPX4 inhibitor induced selective depletion of quiescent astrocyte-like glioma cell populations with similar metabolic profiles.
  25. Nat Metab. 2023 Feb;5(2): 185
  26. Nat Commun. 2023 Feb 25. 14(1): 1097
      Brown adipose tissue (BAT) plays a pivotal role in maintaining body temperature and energy homeostasis. BAT dysfunction is associated with impaired metabolic health. Here, we show that Ssu72 phosphatase is essential for mRNA translation of genes required for thermogenesis in BAT. Ssu72 is found to be highly expressed in BAT among adipose tissue depots, and the expression level of Ssu72 is increased upon acute cold exposure. Mice lacking adipocyte Ssu72 exhibit cold intolerance during acute cold exposure. Mechanistically, Ssu72 deficiency alters cytosolic mRNA translation program through hyperphosphorylation of eIF2α and reduces translation of mitochondrial oxidative phosphorylation (OXPHOS) subunits, resulting in mitochondrial dysfunction and defective thermogenesis in BAT. In addition, metabolic dysfunction in Ssu72-deficient BAT returns to almost normal after restoring Ssu72 expression. In summary, our findings demonstrate that cold-responsive Ssu72 phosphatase is involved in cytosolic translation of key thermogenic effectors via dephosphorylation of eIF2α in brown adipocytes, providing insights into metabolic benefits of Ssu72.
  27. Cell Rep. 2023 Mar 03. pii: S2211-1247(23)00197-3. [Epub ahead of print]42(3): 112186
      Branched-chain amino acids (BCAAs) provide nutrient signals for cell survival and growth. How BCAAs affect CD8+ T cell functions remains unexplored. Herein, we report that accumulation of BCAAs in CD8+ T cells due to the impairment of BCAA degradation in 2C-type serine/threonine protein phosphatase (PP2Cm)-deficient mice leads to hyper-activity of CD8+ T cells and enhanced anti-tumor immunity. CD8+ T cells from PP2Cm-/- mice upregulate glucose transporter Glut1 expression in a FoxO1-dependent manner with more glucose uptake, as well as increased glycolysis and oxidative phosphorylation. Moreover, BCAA supplementation recapitulates CD8+ T cell hyper-functions and synergizes with anti-PD-1, in line with a better prognosis in NSCLC patients containing high BCAAs when receiving anti-PD-1 therapy. Our finding thus reveals that accumulation of BCAAs promotes effector function and anti-tumor immunity of CD8+ T cells through reprogramming glucose metabolism, making BCAAs alternative supplementary components to increase the clinical efficacy of anti-PD-1 immunotherapy against tumors.
    Keywords:  CD8(+) T cells; CP: Immunology; anti-tumor immunity; branched-chain amino acid accumulation; effector function; glucose metabolism; synergy with anti-PD-1 treatment
  28. bioRxiv. 2023 Feb 21. pii: 2023.02.20.529259. [Epub ahead of print]
      Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by two orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.
  29. Nat Metab. 2023 Mar 02.
      Whereas cholesterol is vital for cell growth, proliferation, and remodeling, dysregulation of cholesterol metabolism is associated with multiple age-related pathologies. Here we show that senescent cells accumulate cholesterol in lysosomes to maintain the senescence-associated secretory phenotype (SASP). We find that induction of cellular senescence by diverse triggers enhances cellular cholesterol metabolism. Senescence is associated with the upregulation of the cholesterol exporter ABCA1, which is rerouted to the lysosome, where it moonlights as a cholesterol importer. Lysosomal cholesterol accumulation results in the formation of cholesterol-rich microdomains on the lysosomal limiting membrane enriched with the mammalian target of rapamycin complex 1 (mTORC1) scaffolding complex, thereby sustaining mTORC1 activity to support the SASP. We further show that pharmacological modulation of lysosomal cholesterol partitioning alters senescence-associated inflammation and in vivo senescence during osteoarthritis progression in male mice. Our study reveals a potential unifying theme for the role of cholesterol in the aging process through the regulation of senescence-associated inflammation.
  30. Cancer Res. 2023 Feb 27. pii: CAN-22-3551. [Epub ahead of print]
      Alpha-fetoprotein (AFP) is expressed by stem-like and poor outcome hepatocellular cancer tumors and is a clinical tumor biomarker. AFP has been demonstrated to inhibit dendritic cell differentiation and maturation and to block oxidative phosphorylation. To identify the critical metabolic pathways leading to human dendritic cell functional suppression, here we utilized two recently described single cell profiling methods, scMEP (single-cell metabolic profiling) and SCENITH (single-cell energetic metabolism by profiling translation inhibition). Glycolytic capacity and glucose dependence of dendritic cells was significantly increased by tumor-derived, but not normal cord blood-derived, AFP, leading to increased glucose uptake and lactate secretion. Key molecules in the electron transport chain in particular were regulated by tumor-derived AFP. These metabolic changes occurred at mRNA and protein levels, with negative impact on dendritic cell stimulatory capacity. Tumor-derived AFP bound significantly more polyunsaturated fatty acids than cord blood-derived AFP. Polyunsaturated fatty acids bound to AFP increased metabolic skewing and promoted dendritic cell functional suppression. Polyunsaturated fatty acids inhibited dendritic cell differentiation in vitro, and ω-6 polyunsaturated fatty acids conferred potent immunoregulation when bound to tumor-derived AFP. Together, these findings provide mechanistic insights into how AFP antagonizes the innate immune response to limit anti-tumor immunity.
  31. bioRxiv. 2023 Feb 24. pii: 2023.02.23.529575. [Epub ahead of print]
      While the poor prognosis of glioblastoma arises from the invasion of a subset of tumor cells, little is known of the metabolic alterations within these cells that fuel invasion. We integrated spatially addressable hydrogel biomaterial platforms, patient site-directed biopsies, and multi-omics analyses to define metabolic drivers of invasive glioblastoma cells. Metabolomics and lipidomics revealed elevations in the redox buffers cystathionine, hexosylceramides, and glucosyl ceramides in the invasive front of both hydrogel-cultured tumors and patient site-directed biopsies, with immunofluorescence indicating elevated reactive oxygen species (ROS) markers in invasive cells. Transcriptomics confirmed upregulation of ROS-producing and response genes at the invasive front in both hydrogel models and patient tumors. Amongst oncologic ROS, hydrogen peroxide specifically promoted glioblastoma invasion in 3D hydrogel spheroid cultures. A CRISPR metabolic gene screen revealed cystathionine gamma lyase (CTH), which converts cystathionine to the non-essential amino acid cysteine in the transsulfuration pathway, to be essential for glioblastoma invasion. Correspondingly, supplementing CTH knockdown cells with exogenous cysteine rescued invasion. Pharmacologic CTH inhibition suppressed glioblastoma invasion, while CTH knockdown slowed glioblastoma invasion in vivo . Our studies highlight the importance of ROS metabolism in invasive glioblastoma cells and support further exploration of the transsulfuration pathway as a mechanistic and therapeutic target.
  32. Cell Metab. 2023 Feb 18. pii: S1550-4131(23)00037-2. [Epub ahead of print]
      With age, skeletal muscle stem cells (MuSCs) activate out of quiescence more slowly and with increased death, leading to defective muscle repair. To explore the molecular underpinnings of these defects, we combined multiomics, single-cell measurements, and functional testing of MuSCs from young and old mice. The multiomics approach allowed us to assess which changes are causal, which are compensatory, and which are simply correlative. We identified glutathione (GSH) metabolism as perturbed in old MuSCs, with both causal and compensatory components. Contrary to young MuSCs, old MuSCs exhibit a population dichotomy composed of GSHhigh cells (comparable with young MuSCs) and GSHlow cells with impaired functionality. Mechanistically, we show that antagonism between NRF2 and NF-κB maintains this bimodality. Experimental manipulation of GSH levels altered the functional dichotomy of aged MuSCs. These findings identify a novel mechanism of stem cell aging and highlight glutathione metabolism as an accessible target for reversing MuSC aging.
    Keywords:  GSH; MuSC; NAC; aging; bimodality; multiomics; satellite cells; stem cells
  33. bioRxiv. 2023 Feb 22. pii: 2023.02.22.529457. [Epub ahead of print]
      DNA damage resistance is a major barrier to effective DNA-damaging therapy in multiple myeloma (MM). To discover novel mechanisms through which MM cells overcome DNA damage, we investigated how MM cells become resistant to antisense oligonucleotide (ASO) therapy targeting ILF2, a DNA damage regulator that is overexpressed in 70% of MM patients whose disease has progressed after standard therapies have failed. Here, we show that MM cells undergo an adaptive metabolic rewiring and rely on oxidative phosphorylation to restore energy balance and promote survival in response to DNA damage activation. Using a CRISPR/Cas9 screening strategy, we identified the mitochondrial DNA repair protein DNA2, whose loss of function suppresses MM cells' ability to overcome ILF2 ASO-induced DNA damage, as being essential to counteracting oxidative DNA damage and maintaining mitochondrial respiration. Our study revealed a novel vulnerability of MM cells that have an increased demand for mitochondrial metabolism upon DNA damage activation.STATEMENT OF SIGNIFICANCE: Metabolic reprogramming is a mechanism through which cancer cells maintain survival and become resistant to DNA-damaging therapy. Here, we show that targeting DNA2 is synthetically lethal in myeloma cells that undergo metabolic adaptation and rely on oxidative phosphorylation to maintain survival after DNA damage activation.
  34. iScience. 2023 Mar 17. 26(3): 106118
      Different evolutionary processes push cancers to increasingly aggressive behaviors, energetically sustained by metabolic reprogramming. The collective signature emerging from this transition is macroscopically displayed by positron emission tomography (PET). In fact, the most readily PET measure, the maximum standardized uptake value (SUVmax), has been found to have prognostic value in different cancers. However, few works have linked the properties of this metabolic hotspot to cancer evolutionary dynamics. Here, by analyzing diagnostic PET images from 512 patients with cancer, we found that SUVmax scales superlinearly with the mean metabolic activity (SUVmean), reflecting a dynamic preferential accumulation of activity on the hotspot. Additionally, SUVmax increased with metabolic tumor volume (MTV) following a power law. The behavior from the patients data was accurately captured by a mechanistic evolutionary dynamics model of tumor growth accounting for phenotypic transitions. This suggests that non-genetic changes may suffice to fuel the observed sustained increases in tumor metabolic activity.
    Keywords:  Cancer; Cancer systems biology; Human metabolism; Mathematical biosciences
  35. Brief Bioinform. 2023 Mar 01. pii: bbad064. [Epub ahead of print]
      The use of stable isotope tracers and mass spectrometry (MS) is the gold standard method for the analysis of fatty acid (FA) metabolism. Yet, current state-of-the-art tools provide limited and difficult-to-interpret information about FA biosynthetic routes. Here we present FAMetA, an R package and a web-based application ( that uses 13C mass isotopologue profiles to estimate FA import, de novo lipogenesis, elongation and desaturation in a user-friendly platform. The FAMetA workflow covers the required functionalities needed for MS data analyses. To illustrate its utility, different in vitro and in vivo experimental settings are used in which FA metabolism is modified. Thanks to the comprehensive characterization of FA biosynthesis and the easy-to-interpret graphical representations compared to previous tools, FAMetA discloses unnoticed insights into how cells reprogram their FA metabolism and, when combined with FASN, SCD1 and FADS2 inhibitors, it enables the identification of new FAs by the metabolic reconstruction of their synthesis route.
    Keywords:  fatty acids; inhibitors; lipid metabolism; mass spectrometry; stable isotopes
  36. Nature. 2023 Mar 01.
      Most human cells require anchorage for survival. Cell-substrate adhesion activates diverse signalling pathways, without which cells undergo anoikis-a form of programmed cell death1. Acquisition of anoikis resistance is a pivotal step in cancer disease progression, as metastasizing cells often lose firm attachment to surrounding tissue2,3. In these poorly attached states, cells adopt rounded morphologies and form small hemispherical plasma membrane protrusions called blebs4-11. Bleb function has been thoroughly investigated in the context of amoeboid migration, but it has been examined far less in other scenarios12. Here we show by three-dimensional imaging and manipulation of cell morphological states that blebbing triggers the formation of plasma membrane-proximal signalling hubs that confer anoikis resistance. Specifically, in melanoma cells, blebbing generates plasma membrane contours that recruit curvature-sensing septin proteins as scaffolds for constitutively active mutant NRAS and effectors. These signalling hubs activate ERK and PI3K-well-established promoters of pro-survival pathways. Inhibition of blebs or septins has little effect on the survival of well-adhered cells, but in detached cells it causes NRAS mislocalization, reduced MAPK and PI3K activity, and ultimately, death. This unveils a morphological requirement for mutant NRAS to operate as an effective oncoprotein. Furthermore, whereas some BRAF-mutated melanoma cells do not rely on this survival pathway in a basal state, inhibition of BRAF and MEK strongly sensitizes them to both bleb and septin inhibition. Moreover, fibroblasts engineered to sustain blebbing acquire the same anoikis resistance as cancer cells even without harbouring oncogenic mutations. Thus, blebs are potent signalling organelles capable of integrating myriad cellular information flows into concerted cellular responses, in this case granting robust anoikis resistance.
  37. bioRxiv. 2023 Feb 22. pii: 2023.02.22.529577. [Epub ahead of print]
      Mutations in CHCHD10, a mitochondrial protein with still undefined function, are associated with dominant multi-system mitochondrial diseases. CHCHD10 knock-in mice harboring a heterozygous S55L mutation (equivalent to the human pathogenic S59L mutation) develop a fatal mitochondrial cardiomyopathy. The heart of S55L knock-in mice shows extensive metabolic rewiring triggered by proteotoxic mitochondrial integrated stress response (mtISR). In the mutant heart, mtISR initiates well before the onset of mild bioenergetic impairments and is associated with a shift from fatty acid oxidation to glycolytic metabolism and widespread metabolic imbalance. We tested therapeutic interventions to counteract the metabolic rewiring and ameliorate the metabolic imbalance. Heterozygous S55L mice were subjected to chronic high fat diet (HFD) to decrease insulin sensitivity and glucose uptake and enhance fatty acid utilization in the heart. Metabolomics and gene expression profiles demonstrated that HFD achieved an increase of fatty acid utilization in the heart accompanied by a decrease in cardiomyopathy markers. Surprisingly, HFD also decreased the accumulation of aggregated CHCHD10 in the S55L heart. Importantly, HFD increased the survival of mutant female mice exposed to acceleration of the mitochondrial cardiomyopathy associated with pregnancy. Our findings indicate that metabolic alterations can be effectively targeted for therapeutic intervention in mitochondrial cardiomyopathies associated with proteotoxic stress.
  38. Proc Natl Acad Sci U S A. 2023 Mar 07. 120(10): e2211937120
      The vast majority of human pancreatic ductal adenocarcinomas (PDACs) harbor TP53 mutations, underscoring p53's critical role in PDAC suppression. PDAC can arise when pancreatic acinar cells undergo acinar-to-ductal metaplasia (ADM), giving rise to premalignant pancreatic intraepithelial neoplasias (PanINs), which finally progress to PDAC. The occurrence of TP53 mutations in late-stage PanINs has led to the idea that p53 acts to suppress malignant transformation of PanINs to PDAC. However, the cellular basis for p53 action during PDAC development has not been explored in detail. Here, we leverage a hyperactive p53 variant-p5353,54-which we previously showed is a more robust PDAC suppressor than wild-type p53, to elucidate how p53 acts at the cellular level to dampen PDAC development. Using both inflammation-induced and KRASG12D-driven PDAC models, we find that p5353,54 both limits ADM accumulation and suppresses PanIN cell proliferation and does so more effectively than wild-type p53. Moreover, p5353,54 suppresses KRAS signaling in PanINs and limits effects on the extracellular matrix (ECM) remodeling. While p5353,54 has highlighted these functions, we find that pancreata in wild-type p53 mice similarly show less ADM, as well as reduced PanIN cell proliferation, KRAS signaling, and ECM remodeling relative to Trp53-null mice. We find further that p53 enhances chromatin accessibility at sites controlled by acinar cell identity transcription factors. These findings reveal that p53 acts at multiple stages to suppress PDAC, both by limiting metaplastic transformation of acini and by dampening KRAS signaling in PanINs, thus providing key new understanding of p53 function in PDAC.
    Keywords:  ADM; PanIN; p53; pancreatic cancer; pancreatitis
  39. Nat Commun. 2023 Mar 03. 14(1): 1214
      Identifying the mechanisms underlying the regulation of immune checkpoint molecules and the therapeutic impact of targeting them in cancer is critical. Here we show that high expression of the immune checkpoint B7-H3 (CD276) and high mTORC1 activity correlate with immunosuppressive phenotypes and worse clinical outcomes in 11,060 TCGA human tumors. We find that mTORC1 upregulates B7-H3 expression via direct phosphorylation of the transcription factor YY2 by p70 S6 kinase. Inhibition of B7-H3 suppresses mTORC1-hyperactive tumor growth via an immune-mediated mechanism involving increased T-cell activity and IFN-γ responses coupled with increased tumor cell expression of MHC-II. CITE-seq reveals strikingly increased cytotoxic CD38+CD39+CD4+ T cells in B7-H3-deficient tumors. In pan-human cancers, a high cytotoxic CD38+CD39+CD4+ T-cell gene signature correlates with better clinical prognosis. These results show that mTORC1-hyperactivity, present in many human tumors including tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM), drives B7-H3 expression leading to suppression of cytotoxic CD4+ T cells.
  40. Antioxid Redox Signal. 2023 Feb 27.
      SIGNIFICANCE: Metabolic end products and intermediates can exert signaling functions as chemical sources for histone post-translational modifications, which remodel chromatin and affect gene expression. Among them, lactic acid is responsible for histone lactylation, a recently discovered histone mark that occurs in high lactate conditions, such as those resulting from the Warburg effect in cancer cells.RECENT ADVANCES: Late-breaking studies have advanced the knowledge on the mechanisms involved in histone lactylation, requiring independent non-enzyme-dependent and enzyme-dependent reactions, which is emerging as an important hallmark of cancer cells linking metabolic changes to gene expression reprogramming.
    CRITICAL ISSUES: Here, we give an overview about this new epigenetic modification, focusing on its mechanism of action in tumors and tumor microenvironment.
    FUTURE DIRECTIONS: Further investigation on the competition mechanism between lactylation and acetylation, as well as on the mechanisms by which lactate fluctuation can control a specific gene set in a given tissue are needed in the coming years to exploit new anti-cancer therapeutic approaches.
  41. Cell Rep. 2023 Feb 28. pii: S2211-1247(23)00216-4. [Epub ahead of print]42(3): 112205
      Aerobic glycolysis, a metabolic pathway essential for effector T cell survival and proliferation, regulates differentiation of autoimmune T helper (Th) 17 cells, but the mechanism underlying this regulation is largely unknown. Here, we identify a glycolytic intermediate metabolite, phosphoenolpyruvate (PEP), as a negative regulator of Th17 differentiation. PEP supplementation or inhibition of downstream glycolytic enzymes in differentiating Th17 cells increases intracellular PEP levels and inhibits interleukin (IL)-17A expression. PEP supplementation inhibits expression of signature molecules for Th17 and Th2 cells but does not significantly affect glycolysis, cell proliferation, or survival of T helper cells. Mechanistically, PEP binds to JunB and inhibits DNA binding of the JunB/basic leucine zipper transcription factor ATF-like (BATF)/interferon regulatory factor 4 (IRF4) complex, thereby modulating the Th17 transcriptional program. Furthermore, daily administration of PEP to mice inhibits generation of Th17 cells and ameliorates Th17-dependent autoimmune encephalomyelitis. These data demonstrate that PEP links aerobic glycolysis to the Th17 transcriptional program, suggesting the therapeutic potential of PEP for autoimmune diseases.
    Keywords:  AP-1; CP: Immunology; Th17; autoimmune disease; cellular metabolism; glycolysis; phosphoenolpyruvate; transcriptional program
  42. Redox Biol. 2023 Feb 24. pii: S2213-2317(23)00044-7. [Epub ahead of print]61 102643
      Cholesterol is a crucial component of membrane bilayers by regulating their structural and functional properties. Cholesterol traffics to different cellular compartments including mitochondria, whose cholesterol content is low compared to other cell membranes. Despite the limited availability of cholesterol in the inner mitochondrial membrane (IMM), the metabolism of cholesterol in the IMM plays important physiological roles, acting as the precursor for the synthesis of steroid hormones and neurosteroids in steroidogenic tissues and specific neurons, respectively, or the synthesis of bile acids through an alternative pathway in the liver. Accumulation of cholesterol in mitochondria above physiological levels has a negative impact on mitochondrial function through several mechanisms, including the limitation of crucial antioxidant defenses, such as the glutathione redox cycle, increased generation of reactive oxygen species and consequent oxidative modification of cardiolipin, and defective assembly of respiratory supercomplexes. These adverse consequences of increased mitochondrial cholesterol trafficking trigger the onset of oxidative stress and cell death, and, ultimately, contribute to the development of diverse diseases, including metabolic liver diseases (i.e. fatty liver disease and liver cancer), as well as lysosomal disorders (i.e. Niemann-Pick type C disease) and neurodegenerative diseases (i.e. Alzheimer's disease). In this review, we summarize the metabolism and regulation of mitochondrial cholesterol and its potential impact on liver and neurodegenerative diseases.
    Keywords:  Cholesterol; Liver disease; Metabolism; Mitochondria; Neurodegeneration; ROS
  43. Biochem J. 2022 Mar 02. pii: BCJ20220611. [Epub ahead of print]
      Superoxide/hydrogen peroxide production by site IQ in complex I of the electron transport chain is conventionally assayed during reverse electron transport from ubiquinol to NAD. However, S1QELs (specific suppressors of superoxide/hydrogen peroxide production by site IQ) have potent effects in cells and in vivo during presumed forward electron transport. Therefore, we tested whether site IQ generates S1QEL-sensitive superoxide/hydrogen peroxide during forward electron transport (site IQf), or alternatively, whether reverse electron transport and associated S1QEL-sensitive superoxide/hydrogen peroxide production (site IQr) occurs in cells under normal conditions. We introduce an assay to determine if electron flow through complex I is thermodynamically forward or reverse: on blocking electron flow through complex I, the endogenous matrix NAD pool will become more reduced if flow before the challenge was forward, but more oxidised if flow was reverse. Using this assay we show in the model system of isolated rat skeletal muscle mitochondria that superoxide/hydrogen peroxide production by site IQ can be equally great whether reverse electron transport or forward electron transport is running. We show that sites IQr and IQf are equally sensitive to S1QELs, and to rotenone and piericidin A, inhibitors that block the Q-site of complex I. We exclude the possibility that some sub-fraction of the mitochondrial population running site IQr during forward electron transport is responsible for S1QEL-sensitive superoxide/hydrogen peroxide production by site IQ. Finally, we show that superoxide/hydrogen peroxide production by site IQ in cells occurs during forward electron transport, and is S1QEL-sensitive.
    Keywords:  Reverse electron transport; S1QEL; complex I; electron transport chain; mitochondria; reactive oxygen species
  44. Semin Cell Dev Biol. 2023 Feb 27. pii: S1084-9521(23)00037-X. [Epub ahead of print]
      Maintaining proper metabolite levels in a complex metabolic network is crucial for maintaining a high flux through the network. In this paper, we discuss major regulatory mechanisms over the Calvin Benson Cycle (CBC) with regard to their roles in conferring homeostasis of metabolite levels in CBC. These include: 1) Redox regulation of enzymes in the CBC on one hand ensures that metabolite levels stay above certain lower bounds under low light while on the other hand increases the flux through the CBC under high light. 2) Metabolite regulations, especially allosteric regulations of major regulatory enzymes, ensure the rapid up-regulation of fluxes to ensure sufficient amount of triose phosphate is available for end product synthesis and concurrently avoid phosphate limitation. 3) A balanced activities of enzymes in the CBC help maintain balanced flux through CBC; some innate product feedback mechanisms, in particular the ADP feedback regulation of GAPDH and F6P feedback regulation of FBPase, exist in CBC to achieve such a balanced enzyme activities and hence flux distribution in the CBC for greater photosynthetic efficiency. Transcriptional regulation and natural variations of enzymes controlling CBC metabolite homeostasis should be further explored to maximize the potential of engineering CBC for greater efficiency.
    Keywords:  Allosteric regulation; Balanced investment; Calvin Benson Cycle; Efficiency; Feedback inhibition; Metabolic homeostasis
  45. Nat Immunol. 2023 Feb 27.
      Antigen-specific CD8+ T cell accumulation in tumors is a prerequisite for effective immunotherapy, and yet the mechanisms of lymphocyte transit are not well defined. Here we show that tumor-associated lymphatic vessels control T cell exit from tumors via the chemokine CXCL12, and intratumoral antigen encounter tunes CXCR4 expression by effector CD8+ T cells. Only high-affinity antigen downregulates CXCR4 and upregulates the CXCL12 decoy receptor, ACKR3, thereby reducing CXCL12 sensitivity and promoting T cell retention. A diverse repertoire of functional tumor-specific CD8+ T cells, therefore, exit the tumor, which limits the pool of CD8+ T cells available to exert tumor control. CXCR4 inhibition or loss of lymphatic-specific CXCL12 boosts T cell retention and enhances tumor control. These data indicate that strategies to limit T cell egress might be an approach to boost the quantity and quality of intratumoral T cells and thereby response to immunotherapy.
  46. bioRxiv. 2023 Feb 23. pii: 2023.02.23.529704. [Epub ahead of print]
      As one of the most successful human pathogens, Mycobacterium tuberculosis ( Mtb ) has evolved a diverse array of determinants to subvert host immunity and alter host metabolic patterns. However, the mechanisms of pathogen interference with host metabolism remain poorly understood. Here we show that a novel glutamine metabolism antagonist, JHU083, inhibits Mtb proliferation in vitro and in vivo. JHU083-treated mice exhibit weight gain, improved survival, a 2.5 log lower lung bacillary burden at 35 days post-infection, and reduced lung pathology. JHU083 treatment also initiates earlier T-cell recruitment, increased proinflammatory myeloid cell infiltration, and a reduced frequency of immunosuppressive myeloid cells when compared to uninfected and rifampin-treated controls. Metabolomics analysis of lungs from JHU083-treated Mtb -infected mice revealed reduced glutamine levels, citrulline accumulation suggesting elevated NOS activity, and lowered levels of quinolinic acid which is derived from the immunosuppressive metabolite kynurenine. When tested in an immunocompromised mouse model of Mtb infection, JHU083 lost its therapeutic efficacy suggesting the drug’s host-directed effects are likely to be predominant. Collectively, these data reveal that JHU083-mediated glutamine metabolism inhibition results in dual antibacterial and host-directed activity against tuberculosis.
  47. Nat Rev Mol Cell Biol. 2023 Mar 02.
      Maintenance of protein homeostasis and organelle integrity and function is critical for cellular homeostasis and cell viability. Autophagy is the principal mechanism that mediates the delivery of various cellular cargoes to lysosomes for degradation and recycling. A myriad of studies demonstrate important protective roles for autophagy against disease. However, in cancer, seemingly opposing roles of autophagy are observed in the prevention of early tumour development versus the maintenance and metabolic adaptation of established and metastasizing tumours. Recent studies have addressed not only the tumour cell intrinsic functions of autophagy, but also the roles of autophagy in the tumour microenvironment and associated immune cells. In addition, various autophagy-related pathways have been described, which are distinct from classical autophagy, that utilize parts of the autophagic machinery and can potentially contribute to malignant disease. Growing evidence on how autophagy and related processes affect cancer development and progression has helped guide efforts to design anticancer treatments based on inhibition or promotion of autophagy. In this Review, we discuss and dissect these different functions of autophagy and autophagy-related processes during tumour development, maintenance and progression. We outline recent findings regarding the role of these processes in both the tumour cells and the tumour microenvironment and describe advances in therapy aimed at autophagy processes in cancer.
  48. Cell Rep. 2023 Feb 28. pii: S2211-1247(23)00156-0. [Epub ahead of print]42(3): 112145
      The Krebs cycle-derived metabolite itaconate, whose production is catalyzed by immune response gene 1 (IRG1), has potential to link immunity and metabolism in activated macrophages through alkylation or competitive inhibition of target proteins. In support of this, our previous study demonstrated that the stimulator of interferon genes (STING) signaling platform functions as a hub in macrophage immunity and has a profound impact on the prognosis of sepsis. Interestingly, we find that itaconate, an endogenous immunomodulator, can significantly inhibit the activation of STING signaling. Moreover, 4-octyl itaconate (4-OI), which is a permeable itaconate derivative, can alkylate cysteine sites 65, 71, 88, and 147 of STING, thereby inhibiting its phosphorylation. Furthermore, itaconate and 4-OI inhibit the production of inflammatory factors in sepsis models. Our results broaden the knowledge on the role of the IRG1-itaconate axis in immunomodulation and highlight itaconate and its derivatives as potential therapeutic agents in sepsis.
    Keywords:  4-OI; CLP; CP: Immunology; IRG1; Itaconate; STING; inflammation; metabolite
  49. Nat Commun. 2023 Feb 27. 14(1): 984
      Dysregulation of Th17 and Treg cells contributes to the pathophysiology of many autoimmune diseases. Herein, we show that itaconate, an immunomodulatory metabolite, inhibits Th17 cell differentiation and promotes Treg cell differentiation by orchestrating metabolic and epigenetic reprogramming. Mechanistically, itaconate suppresses glycolysis and oxidative phosphorylation in Th17- and Treg-polarizing T cells. Following treatment with itaconate, the S-adenosyl-L-methionine/S-adenosylhomocysteine ratio and 2-hydroxyglutarate levels are decreased by inhibiting the synthetic enzyme activities in Th17 and Treg cells, respectively. Consequently, these metabolic changes are associated with altered chromatin accessibility of essential transcription factors and key gene expression in Th17 and Treg cell differentiation, including decreased RORγt binding at the Il17a promoter. The adoptive transfer of itaconate-treated Th17-polarizing T cells ameliorates experimental autoimmune encephalomyelitis. These results indicate that itaconate is a crucial metabolic regulator for Th17/Treg cell balance and could be a potential therapeutic agent for autoimmune diseases.