bims-camemi Biomed news
on Mitochondrial metabolism in cancer
Issue of 2019‒04‒14
thirty papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit

  1. Clin Genet. 2019 Apr 12.
    Eijkelenkamp K, Osinga TE, Links TP, van der Horst-Schrivers ANA.
      Succinate dehydrogenase (SDH) mutations lead to the accumulation of succinate, which acts as an oncometabolite. Germline SDHx mutations predispose to paraganglioma (PGL) and pheochromocytoma (PCC), as well as to renal cell carcinoma and gastro-intestinal stromal tumors. The SDHx genes were the first tumor suppressor genes discovered which encode for a mitochondrial enzyme, thereby supporting Otto Warburg's hypothesis in 1926 that a direct link existed between mitochondrial dysfunction and cancer. Accumulation of succinate is the hallmark of tumorigenesis in PGL and PCC. Succinate accumulation inhibits several α-ketoglutarate dioxygenases, thereby inducing the pseudohypoxia pathway and causing epigenetic changes. Moreover, SDH loss as a consequence of SDHx mutations can lead to reprogramming of cell metabolism. Metabolomics can be used as a diagnostic tool, as succinate and other metabolites can be measured in tumor tissue, plasma and urine with different techniques. Furthermore, these pathophysiological characteristics provide insight into therapeutic targets for metastatic disease. This review provides an overview of the pathophysiology and clinical implications of oncometabolite succinate in SDHx mutations.
    Keywords:  SDH mutation; oncometabolites; paraganglioma; pheochromocytoma; succinate
  2. Philos Trans R Soc Lond B Biol Sci. 2019 Feb 04. 374(1765): 20180285
    Palm W.
      Macropinocytosis is an evolutionarily conserved form of endocytosis that mediates non-selective uptake of extracellular fluid and the solutes contained therein. In mammalian cells, macropinocytosis is initiated by growth factor-mediated activation of the Ras and PI3-kinase signalling pathways. In malignant cells, oncogenic activation of growth factor signalling sustains macropinocytosis cell autonomously. Recent studies of cancer metabolism, discussed here, have begun to define a role for macropinocytosis as a nutrient uptake route. Macropinocytic cancer cells ingest macromolecules in bulk and break them down in the lysosome to support metabolism and macromolecular synthesis. Thereby, macropinocytosis allows cells to tap into the copious nutrient stores of extracellular macromolecules when canonical nutrients are scarce. These findings demonstrate that macropinocytosis promotes metabolic flexibility and resilience, which enables cancer cells to survive and grow in nutrient-poor environments. Implications for physiological roles of growth factor-stimulated macropinocytosis in cell metabolism and its relationship with other nutrient uptake pathways are considered. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
    Keywords:  cancer metabolism; growth factors; lysosome; mTORC1; macropinocytosis; nutrients
  3. Nat Rev Mol Cell Biol. 2019 Apr 11.
    Zhu J, Thompson CB.
      Cellular metabolism is at the foundation of all biological activities. The catabolic processes that support cellular bioenergetics and survival have been well studied. By contrast, how cells alter their metabolism to support anabolic biomass accumulation is less well understood. During the commitment to cell proliferation, extensive metabolic rewiring must occur in order for cells to acquire sufficient nutrients such as glucose, amino acids, lipids and nucleotides, which are necessary to support cell growth and to deal with the redox challenges that arise from the increased metabolic activity associated with anabolic processes. Defining the mechanisms of this metabolic adaptation for cell growth and proliferation is now a major focus of research. Understanding the principles that guide anabolic metabolism may ultimately enhance ways to treat diseases that involve deregulated cell growth and proliferation, such as cancer.
  4. Diabetes Metab J. 2019 Mar 27.
    Woo CY, Jang JE, Lee SE, Koh EH, Lee KU.
      Adipose tissue inflammation is considered a major contributing factor in the development of obesity-associated insulin resistance and cardiovascular diseases. However, the cause of adipose tissue inflammation is presently unclear. The role of mitochondria in white adipocytes has long been neglected because of their low abundance. However, recent evidence suggests that mitochondria are essential for maintaining metabolic homeostasis in white adipocytes. In a series of recent studies, we found that mitochondrial function in white adipocytes is essential to the synthesis of adiponectin, which is the most abundant adipokine synthesized from adipocytes, with many favorable effects on metabolism, including improvement of insulin sensitivity and reduction of atherosclerotic processes and systemic inflammation. From these results, we propose a new hypothesis that mitochondrial dysfunction in adipocytes is a primary cause of adipose tissue inflammation and compared this hypothesis with a prevailing concept that "adipose tissue hypoxia" may underlie adipose tissue dysfunction in obesity. Recent studies have emphasized the role of the mitochondrial quality control mechanism in maintaining mitochondrial function. Future studies are warranted to test whether an inadequate mitochondrial quality control mechanism is responsible for mitochondrial dysfunction in adipocytes and adipose tissue inflammation.
    Keywords:  11-Beta-hydroxysteroid dehydrogenases; Adipocytes; Adiponectin; Hypoxia; Inflammation; Mitochondria; Mitochondrial quality control; Nitric oxide; Obesity
  5. EMBO J. 2019 Apr 12. pii: e100785. [Epub ahead of print]
    Tavoulari S, Thangaratnarajah C, Mavridou V, Harbour ME, Martinou JC, Kunji ER.
      The mitochondrial pyruvate carrier (MPC) is critical for cellular homeostasis, as it is required in central metabolism for transporting pyruvate from the cytosol into the mitochondrial matrix. MPC has been implicated in many diseases and is being investigated as a drug target. A few years ago, small membrane proteins, called MPC1 and MPC2 in mammals and Mpc1, Mpc2 and Mpc3 in yeast, were proposed to form large protein complexes responsible for this function. However, the MPC complexes have never been isolated and their composition, oligomeric state and functional properties have not been defined. Here, we identify the functional unit of MPC from Saccharomyces cerevisiae In contrast to earlier hypotheses, we demonstrate that MPC is a hetero-dimer, not a multimeric complex. When not engaged in hetero-dimers, the yeast Mpc proteins can also form homo-dimers that are, however, inactive. We show that the earlier described substrate transport properties and inhibitor profiles are embodied by the hetero-dimer. This work provides a foundation for elucidating the structure of the functional complex and the mechanism of substrate transport and inhibition.
    Keywords:  mitochondria; oligomeric state; protein complex; pyruvate; transport proteins
  6. Elife. 2019 Apr 08. pii: e40260. [Epub ahead of print]8
    Zdraljevic S, Fox BW, Strand C, Panda O, Tenjo FJ, Brady SC, Crombie TA, Doench JG, Schroeder FC, Andersen EC.
      We find that variation in the dbt-1 gene underlies natural differences in Caenorhabditis elegans responses to the toxin arsenic. This gene encodes the E2 subunit of the branched-chain α-keto acid dehydrogenase (BCKDH) complex, a core component of branched-chain amino acid (BCAA) metabolism. We causally linked a non-synonymous variant in the conserved lipoyl domain of DBT-1 to differential arsenic responses. Using targeted metabolomics and chemical supplementation, we demonstrate that differences in responses to arsenic are caused by variation in iso-branched chain fatty acids. Additionally, we show that levels of branched chain fatty acids in human cells are perturbed by arsenic treatment. This finding has broad implications for arsenic toxicity and for arsenic-focused chemotherapeutics across human populations. Our study implicates the BCKDH complex and BCAA metabolism in arsenic responses, demonstrating the power of C. elegans natural genetic diversity to identify novel mechanisms by which environmental toxins affect organismal physiology.Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
    Keywords:  C. elegans; environmental toxin; evolutionary biology; genetics; genomics; human cell lines; natural variation
  7. Sci Rep. 2019 Apr 08. 9(1): 5752
    McMillan RP, Stewart S, Budnick JA, Caswell CC, Hulver MW, Mukherjee K, Srivastava S.
      Mitochondrial DNA (mtDNA) 3243A > G tRNALeu(UUR) heteroplasmic mutation (m.3243A > G) exhibits clinically heterogeneous phenotypes. While the high mtDNA heteroplasmy exceeding a critical threshold causes mitochondrial encephalomyopathy, lactic acidosis with stroke-like episodes (MELAS) syndrome, the low mtDNA heteroplasmy causes maternally inherited diabetes with or without deafness (MIDD) syndrome. How quantitative differences in mtDNA heteroplasmy produces distinct pathological states has remained elusive. Here we show that despite striking similarities in the energy metabolic gene expression signature, the mitochondrial bioenergetics, biogenesis and fuel catabolic functions are distinct in cells harboring low or high levels of the m.3243 A > G mutation compared to wild type cells. We further demonstrate that the low heteroplasmic mutant cells exhibit a coordinate induction of transcriptional regulators of the mitochondrial biogenesis, glucose and fatty acid metabolism pathways that lack in near homoplasmic mutant cells compared to wild type cells. Altogether, these results shed new biological insights on the potential mechanisms by which low mtDNA heteroplasmy may progressively cause diabetes mellitus.
  8. Cell Rep. 2019 Apr 09. pii: S2211-1247(19)30349-3. [Epub ahead of print]27(2): 525-536.e4
    Márquez S, Fernández JJ, Mancebo C, Herrero-Sánchez C, Alonso S, Sandoval TA, Rodríguez Prados M, Cubillos-Ruiz JR, Montero O, Fernández N, Sánchez Crespo M.
      Increased glycolysis parallels immune cell activation, but the role of pyruvate remains largely unexplored. We found that stimulation of dendritic cells with the fungal surrogate zymosan causes decreases of pyruvate, citrate, itaconate, and α-ketoglutarate, while increasing oxaloacetate, succinate, lactate, oxygen consumption, and pyruvate dehydrogenase activity. Expression of IL10 and IL23A (the gene encoding the p19 chain of IL-23) depended on pyruvate dehydrogenase activity. Mechanistically, pyruvate reinforced histone H3 acetylation, and acetate rescued the effect of mitochondrial pyruvate carrier inhibition, most likely because it is a substrate of the acetyl-CoA producing enzyme ACSS2. Mice lacking the receptor of the lipid mediator platelet-activating factor (PAF; 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine) showed reduced production of IL-10 and IL-23 that is explained by the requirement of acetyl-CoA for PAF biosynthesis and its ensuing autocrine function. Acetyl-CoA therefore intertwines fatty acid remodeling of glycerophospholipids and energetic metabolism during cytokine induction.
    Keywords:  Lands’ cycle; Warburg effect; acetyl-CoA; arachidonic acid; cytokines; fungi; glycolysis; immunometabolism; platelet-activating factor; tricarboxylic acid cycle
  9. Cell Rep. 2019 Apr 09. pii: S2211-1247(19)30353-5. [Epub ahead of print]27(2): 502-513.e5
    DeVorkin L, Pavey N, Carleton G, Comber A, Ho C, Lim J, McNamara E, Huang H, Kim P, Zacharias LG, Mizushima N, Saitoh T, Akira S, Beckham W, Lorzadeh A, Moksa M, Cao Q, Murthy A, Hirst M, DeBerardinis RJ, Lum JJ.
      Autophagy is a cell survival process essential for the regulation of immune responses to infections. However, the role of T cell autophagy in anti-tumor immunity is less clear. Here, we demonstrate a cell-autonomous role for autophagy in the regulation of CD8+ T-cell-mediated control of tumors. Mice deficient for the essential autophagy genes Atg5, Atg14, or Atg16L1 display a dramatic impairment in the growth of syngeneic tumors. Moreover, T cells lacking Atg5 have a profound shift to an effector memory phenotype and produce greater amounts of interferon-γ (IFN-γ) and tumor necrosis factor α (TNF-α). Mechanistically, Atg5-/- CD8+ T cells exhibit enhanced glucose metabolism that results in alterations in histone methylation, increases in H3K4me3 density, and transcriptional upregulation of both metabolic and effector target genes. Nonetheless, glucose restriction is sufficient to suppress Atg5-dependent increases in effector function. Thus, autophagy-dependent changes in CD8+ T cell metabolism directly regulate anti-tumor immunity.
    Keywords:  CD8(+) T cells; SAM; anti-tumor immunity; autophagy; glycolysis; lactate; methylation
  10. EMBO Mol Med. 2019 Apr 12. pii: e8734. [Epub ahead of print]
    Indrieri A, Carrella S, Romano A, Spaziano A, Marrocco E, Fernandez-Vizarra E, Barbato S, Pizzo M, Ezhova Y, Golia FM, Ciampi L, Tammaro R, Henao-Mejia J, Williams A, Flavell RA, De Leonibus E, Zeviani M, Surace EM, Banfi S, Franco B.
      Mitochondrial diseases (MDs) are a heterogeneous group of devastating and often fatal disorders due to defective oxidative phosphorylation. Despite the recent advances in mitochondrial medicine, effective therapies are still not available for these conditions. Here, we demonstrate that the microRNAs miR-181a and miR-181b (miR-181a/b) regulate key genes involved in mitochondrial biogenesis and function and that downregulation of these miRNAs enhances mitochondrial turnover in the retina through the coordinated activation of mitochondrial biogenesis and mitophagy. We thus tested the effect of miR-181a/b inactivation in different animal models of MDs, such as microphthalmia with linear skin lesions and Leber's hereditary optic neuropathy. We found that miR-181a/b downregulation strongly protects retinal neurons from cell death and significantly ameliorates the disease phenotype in all tested models. Altogether, our results demonstrate that miR-181a/b regulate mitochondrial homeostasis and that these miRNAs may be effective gene-independent therapeutic targets for MDs characterized by neuronal degeneration.
    Keywords:  LHON; miR‐181; microRNA; mitochondrial disease; neurodegeneration
  11. Stem Cells. 2019 Apr 12.
    Li X, Wu L, Zopp M, Kopelov S, Du W.
      Emerging evidence have shown that resting quiescent hematopoietic stem cells (HSCs) prefer to utilize anaerobic glycolysis rather than mitochondrial respiration for energy production. Compelling evidence has also revealed that altered metabolic energetics in HSC underlies the onset of certain blood diseases. However, the mechanisms responsible for energetic reprogramming remain elusive. We recently found that Fanconi anemia (FA) HSCs are more dependent on mitochondrial respiration relative to glycolysis in their resting state for energy metabolism. Here we have investigated the role of deficient glycolysis in FA HSC maintenance. We observed significantly reduced glucose consumption, lactate production and ATP production in HSCs but not less primitive multipotent progenitors or restricted hematopoietic progenitors of Fanca-/- and Fancc-/- mice compared to those of wild-type mice, which was associated with an over-activated p53-TIGAR metabolic axis. We have utilized Fanca-/- HSCs deficient for p53 to show that the p53-TIGAR axis suppressed glycolysis in FA HSCs, leading to enhanced pentose phosphate pathway and cellular antioxidant function, and consequently reduced DNA damage and attenuated HSC exhaustion. Furthermore, by using Fanca-/- HSCs carrying the separation-of-function mutant p53R172P transgene that selectively impairs the p53 function in apoptosis but not cell-cycle control, we demonstrated that the cell-cycle function of p53 was not required for glycolytic suppression in FA HSCs. Finally, ectopic expression of the glycolytic rate-limiting enzyme PFKFB3 specifically antagonized p53-TIGAR-mediated metabolic reprogramming in FA HSCs. Together, our results suggest that p53-TIGAR metabolic axis-mediated glycolytic suppression may play a compensatory role in attenuating DNA damage and proliferative exhaustion in FA HSCs. SIGNIFICANCE STATEMENT: We show that Fanconi anemia (FA) hematopoietic stem cells (HSCs) but not less primitive multipotent progenitors, exhibit significantly lower glycolysis than that in wild-type HSCs, which is associated with an over-activated p53-TIGAR metabolic axis. Further, the p53-TIGAR axis suppresses glycolysis in FA HSCs, leading to enhanced pentose phosphate pathway and cellular antioxidant function, and consequently reduced DNA damage and HSC exhaustion. Ectopic expression of PFKFB3 specifically antagonizes p53-TIGAR-mediated metabolic reprogramming in FA HSCs. These results identify a compensatory role for the p53-TIGAR metabolic axis-mediated glycolytic suppression in attenuating DNA damage and genomic instability in FA HSCs. © AlphaMed Press 2019.
    Keywords:  Fanconi anemia; Hematopoietic stem cells (HSCs); TP53-inducible glycolysis and apoptosis regulator (TIGAR); glycolysis; p53
  12. Int J Mol Sci. 2019 Apr 05. pii: E1700. [Epub ahead of print]20(7):
    Armstrong JA, Cash NJ, Morton JC, Tepikin AV, Sutton R, Criddle DN.
      Mitochondrial dysfunction is a core feature of acute pancreatitis, a severe disease in which oxidative stress is elevated. Mitochondrial targeting of antioxidants is a potential therapeutic strategy for this and other diseases, although thus far mixed results have been reported. We investigated the effects of mitochondrial targeting with the antioxidant MitoQ on pancreatic acinar cell bioenergetics, adenosine triphosphate (ATP) production and cell fate, in comparison with the non-antioxidant control decyltriphenylphosphonium bromide (DecylTPP) and general antioxidant N-acetylcysteine (NAC). MitoQ (µM range) and NAC (mM range) caused sustained elevations of basal respiration and the inhibition of spare respiratory capacity, which was attributable to an antioxidant action since these effects were minimal with DecylTPP. Although MitoQ but not DecylTPP decreased cellular NADH levels, mitochondrial ATP turnover capacity and cellular ATP concentrations were markedly reduced by both MitoQ and DecylTPP, indicating a non-specific effect of mitochondrial targeting. All three compounds were associated with a compensatory elevation of glycolysis and concentration-dependent increases in acinar cell apoptosis and necrosis. These data suggest that reactive oxygen species (ROS) contribute a significant negative feedback control of basal cellular metabolism. Mitochondrial targeting using positively charged molecules that insert into the inner mitochondrial member appears to be deleterious in pancreatic acinar cells, as does an antioxidant strategy for the treatment of acute pancreatitis.
    Keywords:  DecylTPP; MitoQ; Seahorse; antioxidants; mitochondrial dysfunction; mitochondrial targeting; oxidative stress; pancreatic acinar cell
  13. J Biol Chem. 2019 Apr 11. pii: jbc.RA118.003505. [Epub ahead of print]
    Svoboda P, Krizova E, Sestakova S, Vapenkova K, Knejzlik Z, Rimpelova S, Rayova D, Volfova N, Křížová I, Rumlová M, Sykora D, Kizek R, Haluzik M, Zidek V, Zidkova J, Skop V.
      Nicotinamide phosphoribosyltransferase (NAMPT) is located in both the nucleus and cytoplasm and has multiple biological functions including catalyzing the rate-limiting step in NAD synthesis. Moreover, up-regulated NAMPT expression has been observed in many cancers. However, the determinants and regulation of NAMPT's nuclear transport are not known. Here, we constructed a GFP-NAMPT fusion protein to study NAMPT's subcellular trafficking. We observed that in unsynchronized 3T3-L1 preadipocytes, 25% of cells have higher GFP-NAMPT fluorescence in the cytoplasm and 62% in the nucleus. In HepG2 hepatocytes, 6% of cells had higher GFP-NAMPT fluorescence in the cytoplasm and 84% in the nucleus. In both 3T3-L1 and HepG2 cells, GFP-NAMPT was excluded from the nucleus immediately after mitosis and migrated back into it as the cell cycle progressed. In HepG2 cells, endogenous, untagged NAMPT displayed similar changes with the cell cycle, and in non-mitotic cells, GFP-NAMPT accumulated in the nucleus. Similarly, genotoxic, oxidative, or dicarbonyl stress also caused nuclear NAMPT localization. These interventions also increased poly(ADP-ribosyl) polymerases (PARP) and sirtuins (SIRT) activity, suggesting an increased cellular demand for NAD. We identified a nuclear localization signal in NAMPT and amino acid substitution in this sequence (424RSKK to ASGA), which does not affect its enzymatic activity, blocked nuclear NAMPT transport, slowed cell growth, and increased histone H3 acetylation. These results suggest that NAMPT is transported into the nucleus where it presumably increases NAD synthesis, required for cell proliferation. We conclude that specific inhibition of NAMPT transport into the nucleus might be a potential avenue for managing cancer.
    Keywords:  GFP fusion; NAMPT; Nuclear localization; Pre-B cell colony enhancing factor (PBEF).; Visfatin; cancer; epigenetics; nicotinamide adenine dinucleotide (NAD); sirtuin
  14. Nat Commun. 2019 04 08. 10(1): 1617
    Zou Y, Palte MJ, Deik AA, Li H, Eaton JK, Wang W, Tseng YY, Deasy R, Kost-Alimova M, Dančík V, Leshchiner ES, Viswanathan VS, Signoretti S, Choueiri TK, Boehm JS, Wagner BK, Doench JG, Clish CB, Clemons PA, Schreiber SL.
      Clear-cell carcinomas (CCCs) are a histological group of highly aggressive malignancies commonly originating in the kidney and ovary. CCCs are distinguished by aberrant lipid and glycogen accumulation and are refractory to a broad range of anti-cancer therapies. Here we identify an intrinsic vulnerability to ferroptosis associated with the unique metabolic state in CCCs. This vulnerability transcends lineage and genetic landscape, and can be exploited by inhibiting glutathione peroxidase 4 (GPX4) with small-molecules. Using CRISPR screening and lipidomic profiling, we identify the hypoxia-inducible factor (HIF) pathway as a driver of this vulnerability. In renal CCCs, HIF-2α selectively enriches polyunsaturated lipids, the rate-limiting substrates for lipid peroxidation, by activating the expression of hypoxia-inducible, lipid droplet-associated protein (HILPDA). Our study suggests targeting GPX4 as a therapeutic opportunity in CCCs, and highlights that therapeutic approaches can be identified on the basis of cell states manifested by morphological and metabolic features in hard-to-treat cancers.
  15. Metabolism. 2019 Apr 08. pii: S0026-0495(19)30072-1. [Epub ahead of print]
    Lettieri-Barbato D, Ioannilli L, Aquilano K, Ciccarone F, Rosina M, Ciriolo MR.
      OBJECTIVE: Mitochondria play pivotal roles in orchestrating signaling pathways in order to guarantee metabolic homeostasis under different stimuli. It has been demonstrated that the mito-nuclear communication is fundamental for facing physiological and/or stress-mediated cellular response through the activation of nuclear transcription factors. Here, we focused on the Forkhead box protein O1 (FoxO1) transcription factor that belongs to the FoxOs family proteins and is considered a "nutrients sensor" modulating the expression of nutrient-stress response genes.METHODS: In vitro and in vivo experimental systems, including 3 T3-L1 white, X-9 beige and T37i brown adipocytes and different fat depots from C57BL/6 mice were used. The mitochondrial localization of FoxO1 was demonstrated by western blot analysis, confocal microscopy and chromatin immunoprecipitation assay, after sub-cellular compartment isolation. RT-qPCR analysis was used to evaluate the expression of antioxidant and mitochondrial genes after modulation of FoxO1 activity/localization. Treatment with diverse reactive oxygen species (ROS) species/sources were performed and assessed by cytofluorimetric analysis.
    RESULTS: We demonstrated that FoxO1 not exclusively localizes to cytosol and nucleus of adipocytes but also to mitochondria where it binds to mitochondrial DNA. We also proved that mitochondrial FoxO1 is phosphorylated upon normal feeding condition. Mitochondrial FoxO1 responds to starvation leaving mitochondrial compartment by ROS-mediated activation of the mitochondrial phosphatase PTPMT1. Indeed, FoxO1 de-phosphorylation and mito-to-nucleus shuttling was observed under starvation. Moreover, we provided evidence that ROS species/sources are able to differently modulate the mitochondrial localization of FoxO1.
    CONCLUSION: The ability to localize at different cell compartments, including mitochondria, highlights a different layer of regulation of FoxO1 necessary for assuring a fast and efficient nutrient-stress response in white/beige adipose tissue. FoxO1 could be thus endorsed in the list of transcription factors involved in the mito-nuclear communication where ROS can act as upstream signals.
    Keywords:  Mitochondrial retrograde signaling; Nutrient restriction; PTPMT1; ROS
  16. Biol Rev Camb Philos Soc. 2019 Apr 10.
    Dando I, Pozza ED, Ambrosini G, Torrens-Mas M, Butera G, Mullappilly N, Pacchiana R, Palmieri M, Donadelli M.
      Tumour repopulation is recognized as a crucial event in tumour relapse where therapy-sensitive dying cancer cells influence the tumour microenvironment to sustain therapy-resistant cancer cell growth. Recent studies highlight the role of the oncometabolites succinate, fumarate, and 2-hydroxyglutarate in the aggressiveness of cancer cells and in the worsening of the patient's clinical outcome. These oncometabolites can be produced and secreted by cancer and/or surrounding cells, modifying the tumour microenvironment and sustaining an invasive neoplastic phenotype. In this review, we report recent findings concerning the role in cancer development of succinate, fumarate, and 2-hydroxyglutarate and the regulation of their related enzymes succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase. We propose that oncometabolites are crucially involved in tumour repopulation. The study of the mechanisms underlying the relationship between oncometabolites and tumour repopulation is fundamental for identifying efficient anti-cancer therapeutic strategies and novel serum biomarkers in order to overcome cancer relapse.
    Keywords:  2-hydroxyglutarate; cancer; fumarate; metabolism; oncometabolites; succinate
  17. Nat Commun. 2019 04 11. 10(1): 1689
    Rogers C, Erkes DA, Nardone A, Aplin AE, Fernandes-Alnemri T, Alnemri ES.
      Gasdermin E (GSDME/DFNA5) cleavage by caspase-3 liberates the GSDME-N domain, which mediates pyroptosis by forming pores in the plasma membrane. Here we show that GSDME-N also permeabilizes the mitochondrial membrane, releasing cytochrome c and activating the apoptosome. Cytochrome c release and caspase-3 activation in response to intrinsic and extrinsic apoptotic stimuli are significantly reduced in GSDME-deficient cells comparing with wild type cells. GSDME deficiency also accelerates cell growth in culture and in a mouse model of melanoma. Phosphomimetic mutation of the highly conserved phosphorylatable Thr6 residue of GSDME, inhibits its pore-forming activity, thus uncovering a potential mechanism by which GSDME might be regulated. Like GSDME-N, inflammasome-generated gasdermin D-N (GSDMD-N), can also permeabilize the mitochondria linking inflammasome activation to downstream activation of the apoptosome. Collectively, our results point to a role of gasdermin proteins in targeting the mitochondria to promote cytochrome c release to augment the mitochondrial apoptotic pathway.
  18. Cell Death Differ. 2019 Apr 11.
    Schulman JJ, Szczesniak LM, Bunker EN, Nelson HA, Roe MW, Wagner LE, Yule DI, Wojcikiewicz RJH.
      Bok (Bcl-2-related ovarian killer) is a member of the Bcl-2 protein family that governs the intrinsic apoptosis pathway, but the cellular role that Bok plays is controversial. Remarkably, endogenous Bok is constitutively bound to inositol 1,4,5-trisphosphate receptors (IP3Rs) and is stabilized by this interaction. Here we report that despite the strong association with IP3Rs, deletion of Bok expression by CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 nuclease)-mediated gene editing does not alter calcium mobilization via IP3Rs or calcium influx into the mitochondria. Rather, Bok deletion significantly reduces mitochondrial fusion rate, resulting in mitochondrial fragmentation. This phenotype is reversed by exogenous wild-type Bok and by an IP3R binding-deficient Bok mutant, and may result from a decrease in mitochondrial motility. Bok deletion also enhances mitochondrial spare respiratory capacity and membrane potential. Finally, Bok does not play a major role in apoptotic signaling, since Bok deletion does not alter responsiveness to various apoptotic stimuli. Overall, despite binding to IP3Rs, Bok does not alter IP3R-mediated Ca2+ signaling, but is required to maintain normal mitochondrial fusion, morphology, and bioenergetics.
  19. Cell Rep. 2019 Apr 09. pii: S2211-1247(19)30356-0. [Epub ahead of print]27(2): 359-373.e6
    Dengler MA, Robin AY, Gibson L, Li MX, Sandow JJ, Iyer S, Webb AI, Westphal D, Dewson G, Adams JM.
      To elicit apoptosis, BAX metamorphoses from an inert cytosolic monomer into homo-oligomers that permeabilize the mitochondrial outer membrane (MOM). A long-standing puzzle is that BH3 domains apparently activate BAX by not only its canonical groove but also a proposed site involving helices α1 and α6. Our mutagenesis studies reveal that late steps like oligomerization require activation through the groove but probably not earlier steps like MOM association. Conversely, α1 or α6 obstruction and alanine mutagenesis scanning implicate these helices early in BAX activation. The α1 and α6 mutations lowered BH3 binding, altered the BAX conformation, and reduced its MOM translocation and integration; their exposure of the BAX α1-α2 loop allosterically sequestered its α9 membrane anchor in the groove. The crystal structure of an α6 mutant revealed additional allosteric effects. The results suggest that the α1 and α6 region drives MOM association and integration, whereas groove binding favors subsequent steps toward oligomerization.
    Keywords:  BAX activation; BCL-2 family; allosteric changes; apoptosis; crystal structure; membrane association; oligomerization; protein conformation; protein-protein association
  20. Cell Rep. 2019 Apr 09. pii: S2211-1247(19)30352-3. [Epub ahead of print]27(2): 491-501.e6
    Nguyen T, Kirsch BJ, Asaka R, Nabi K, Quinones A, Tan J, Antonio MJ, Camelo F, Li T, Nguyen S, Hoang G, Nguyen K, Udupa S, Sazeides C, Shen YA, Elgogary A, Reyes J, Zhao L, Kleensang A, Chaichana KL, Hartung T, Betenbaugh MJ, Marie SK, Jung JG, Wang TL, Gabrielson E, Le A.
      N-acetyl-aspartyl-glutamate (NAAG) is a peptide-based neurotransmitter that has been extensively studied in many neurological diseases. In this study, we show a specific role of NAAG in cancer. We found that NAAG is more abundant in higher grade cancers and is a source of glutamate in cancers expressing glutamate carboxypeptidase II (GCPII), the enzyme that hydrolyzes NAAG to glutamate and N-acetyl-aspartate (NAA). Knocking down GCPII expression through genetic alteration or pharmacological inhibition of GCPII results in a reduction of both glutamate concentrations and cancer growth. Moreover, targeting GCPII in combination with glutaminase inhibition accentuates these effects. These findings suggest that NAAG serves as an important reservoir to provide glutamate to cancer cells through GCPII when glutamate production from other sources is limited. Thus, GCPII is a viable target for cancer therapy, either alone or in combination with glutaminase inhibition.
    Keywords:  GCPII; N-acetyl-aspartyl-glutamate; NAAG; glutamate carboxypeptidase II; glutamate deprivation; glutamate reservoir; glutaminase inhibitor; metabolomics; stable isotope resolved
  21. J Cell Biol. 2019 Apr 12. pii: jcb.201804101. [Epub ahead of print]
    Zheng Y, Zhang X, Wu X, Jiang L, Ahsan A, Ma S, Xiao Z, Han F, Qin ZH, Hu W, Chen Z.
      Mitophagy protects against ischemic neuronal injury by eliminating damaged mitochondria, but it is unclear how mitochondria in distal axons are cleared. We find that oxygen and glucose deprivation-reperfusion reduces mitochondrial content in both cell bodies and axons. Axonal mitochondria elimination was not abolished in Atg7 fl/fl ;nes-Cre neurons, suggesting the absence of direct mitophagy in axons. Instead, axonal mitochondria were enwrapped by autophagosomes in soma and axon-derived mitochondria prioritized for elimination by autophagy. Intriguingly, axonal mitochondria showed prompt loss of anterograde motility but increased retrograde movement upon reperfusion. Anchoring of axonal mitochondria by syntaphilin blocked neuronal mitophagy and aggravated injury. Conversely, induced binding of mitochondria to dynein reinforced retrograde transport and enhanced mitophagy to prevent mitochondrial dysfunction and attenuate neuronal injury. Therefore, we reveal somatic autophagy of axonal mitochondria in ischemic neurons and establish a direct link of retrograde mitochondrial movement with mitophagy. Our findings may provide a new concept for reducing ischemic neuronal injury by correcting mitochondrial motility.
  22. Philos Trans R Soc Lond B Biol Sci. 2019 Feb 04. 374(1765): 20180153
    Commisso C.
      In tumour cells, macropinocytosis functions as an amino acid supply route and supports cancer cell survival and proliferation. Initially demonstrated in oncogenic KRAS-driven models of pancreatic cancer, macropinocytosis triggers the internalization of extracellular proteins via discrete endocytic vesicles called macropinosomes. The incoming protein cargo is targeted for lysosome-dependent degradation, causing the intracellular release of amino acids. These protein-derived amino acids support metabolic fitness by contributing to the intracellular amino acid pools, as well as to the biosynthesis of central carbon metabolites. In this way, macropinocytosis represents a novel amino acid supply route that tumour cells use to survive the nutrient-poor conditions of the tumour microenvironment. Macropinocytosis has also emerged as an entry mechanism for a variety of nanomedicines, suggesting that macropinocytosis regulation in the tumour setting can be harnessed for the delivery of anti-cancer therapeutics. A slew of recent studies point to the possibility that macropinocytosis is a pervasive feature of many different tumour types. In this review, we focus on the role of this important uptake mechanism in a variety of cancers and highlight the main molecular drivers of macropinocytosis in these malignancies. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
    Keywords:  RAS; cancer; macropinocytosis; metabolism; tumour
  23. Philos Trans R Soc Lond B Biol Sci. 2019 Feb 04. 374(1765): 20180157
    Swanson JA, Yoshida S.
      Macropinosome formation occurs as a localized sequence of biochemical activities and associated morphological changes, which may be considered a form of signal transduction leading to the construction of an organelle. Macropinocytosis may also convey information about the availability of extracellular nutrients to intracellular regulators of metabolism. Consistent with this idea, activation of the metabolic regulator mechanistic target of rapamycin complex-1 (mTORC1) in response to acute stimulation by growth factors and extracellular amino acids requires internalization of amino acids by macropinocytosis. This suggests that macropinocytosis is necessary for mTORC1-dependent growth of metazoan cells, both as a route for delivery of amino acids to sensors associated with lysosomes and as a platform for growth factor-dependent signalling to mTORC1 via phosphatidylinositol 3-kinase (PI3K) and the Akt pathway. Because the biochemical signals required for the construction of macropinosomes are also required for cell growth, and inhibition of macropinocytosis inhibits growth factor signalling to mTORC1, we propose that signalling by growth factor receptors is organized into stochastic, structure-dependent cascades of chemical reactions that both build a macropinosome and stimulate mTORC1. More generally, as discrete units of signal transduction, macropinosomes may be subject to feedback regulation by metabolism and cell dimensions. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
    Keywords:  actin; growth factors; phosphatidylinositol 3-kinase
  24. J Cell Physiol. 2019 Apr 10.
    Li Y, Jia A, Wang Y, Dong L, Wang Y, He Y, Wang S, Cao Y, Yang H, Bi Y, Liu G.
      The metabolism of immune cells reprograms inflammatory responses to protect against infection by pathogenic microorganisms, but the immune effects of glycolysis and the oxidative phosphorylation (OXPHOS) metabolic pathway remain unclear. Herein, the effects of glycolysis or OXPHOS on the neutrophils and T cells were investigated using a pharmacological approach in mice. 2-Deoxy-d-glucose (2-DG), which blocks the key enzyme hexokinase of glycolysis, and dimethyl malonate (DMM), which blocks the key element succinate of OXPHOS, both efficiently expanded the population of neutrophils, but significantly inhibited tumor necrosis factor a secretion and reactive oxygen species (ROS) production. These compounds also effectively inhibited the differentiation of type 1 T helper cells (Th1) but had no effects on the differentiation of type 2 T helper cells (Th2) and regulatory T cells. A study of the underlying mechanism showed that hypoxia-inducible factor 1-alpha (HIF1α) was an upstream signal in the regulation of glycolysis, but not OXPHOS. In thioglycolate broth-induced neutrophil peritonitis, blockade of glycolysis or OXPHOS efficiently expanded the population of neutrophils, but diminished their abilities to secrete proinflammatory factors, produce ROS, and phagocytose bacteria. In Listeria monocytogenes bacteria-infected mice, 2-DG or DMM treatment consistently inhibited antibacterial activity and Th1 function. Thus, our results provide a basis for comprehensively understanding the role of glycolysis and OXPHOS in anti-infectious immunity.
    Keywords:  bacterial infection; glucose metabolism; glycolysis; immune cells; infectious diseases; oxidative phosphorylation
  25. Nat Cell Biol. 2019 Apr 08.
    Chu B, Kon N, Chen D, Li T, Liu T, Jiang L, Song S, Tavana O, Gu W.
      It is well established that ferroptosis is primarily controlled by glutathione peroxidase 4 (GPX4). Surprisingly, we observed that p53 activation modulates ferroptotic responses without apparent effects on GPX4 function. Instead, ALOX12 inactivation diminishes p53-mediated ferroptosis induced by reactive oxygen species stress and abrogates p53-dependent inhibition of tumour growth in xenograft models, suggesting that ALOX12 is critical for p53-mediated ferroptosis. The ALOX12 gene resides on human chromosome 17p13.1, a hotspot of monoallelic deletion in human cancers. Loss of one Alox12 allele is sufficient to accelerate tumorigenesis in Eμ-Myc lymphoma models. Moreover, ALOX12 missense mutations from human cancers abrogate its ability to oxygenate polyunsaturated fatty acids and to induce p53-mediated ferroptosis. Notably, ALOX12 is dispensable for ferroptosis induced by erastin or GPX4 inhibitors; conversely, ACSL4 is required for ferroptosis upon GPX4 inhibition but dispensable for p53-mediated ferroptosis. Thus, our study identifies an ALOX12-mediated, ACSL4-independent ferroptosis pathway that is critical for p53-dependent tumour suppression.
  26. J Cell Physiol. 2019 Apr 08.
    Ferrada L, Salazar K, Nualart F.
      For a long time, the effect of vitamin C on cancer cells has been a controversial concept. From Linus Pauling's studies in 1976, it was proposed that ascorbic acid (AA) could selectively kill tumor cells. However, further research suggested that vitamin C has no effect on tumor survival. In the last decade, new and emerging functions for vitamin C have been discovered using the reduced form, AA, and the oxidized form, dehydroascorbic acid (DHA), independently. In this review, we summarized the latest findings related to the effects of DHA on the survival and metabolism of tumor cells. At the same time, we put special emphasis on the bystander effect and the recycling capacity of vitamin C in various cellular models, and how these concepts can affect the experimentation with vitamin C and its therapeutic application in the treatment against cancer.
    Keywords:  Linus Pauling; cancer cells; cell death; dehydroascorbic acid; metabolism; vitamin C
  27. Sci Rep. 2019 Apr 11. 9(1): 5937
    Nguyen TV, Alfaro AC, Young T, Green S, Zarate E, Merien F.
      The antimicrobial role of itaconic acid (ITA) has been recently discovered in mammalian cells. In our previous studies, we discovered that marine molluscs biosynthesise substantial quantities of ITA when exposed to marine pathogens, but its antimicrobial function to Vibrio bacteria is currently unknown. Thus, in this study, we used an untargeted gas chromatography-mass spectrometry (GC-MS) platform to identify metabolic changes of Vibrio sp. DO1 (V. corallyliticus/neptunius-like isolate) caused by ITA exposure. Vibrio sp. DO1 was cultured in Luria-Bertani broth supplemented with 3 mM sodium acetate and with different concentrations of ITA (0, 3 and 6 mM) for 24 h. The results showed that ITA completely inhibited Vibrio sp. growth at 6 mM and partially inhibited the bacterial growth at 3 mM. A principal component analysis (PCA) revealed a clear separation between metabolite profiles of Vibrio sp. DO1 in the 3 mM ITA treatment and the control, which were different in 25 metabolites. Among the altered metabolites, the accumulation of glyoxylic acid and other metabolites in glyoxylate cycle (cis-aconitic acid, isocitric acid and fumaric acid) together with the increase of isocitrate lyase (ICL) activity in the 3 mM ITA treatment compared to the control suggest that ITA inhibited Vibrio sp. growth via disruption of central carbon metabolism.
  28. Sci Rep. 2019 Apr 10. 9(1): 5873
    Roh TH, Yim H, Roh J, Lee KB, Park SH, Jeong SY, Kim SH, Kim JH.
      Succinate dehydrogenase (SDH) is a mitochondrial enzyme that plays an important role in both the Krebs cycle and the electron transport chain. SDH inactivation is associated with tumorigenesis in certain types of tumor. SDH consists of subunits A, B, C and D (SDHA, SDHB, SDHC, and SDHD, respectively). Immunohistochemistry for SDHB is a reliable method for detecting the inactivation of SDH by mutations in SDHA, SDHB, SDHC, SDHD and SDH complex assembly factor 2 (SDHAF2) genes with high sensitivity and specificity. SDHB immunohistochemistry has been used to examine the inactivation of SDH in various types of tumors. However, data on central nervous system (CNS) tumors are very limited. In the present study, we investigated the loss of SDHB immunoexpression in 90 cases of CNS tumors. Among the 90 cases of CNS tumors, only three cases of hemangioblastoma showed loss of SDHB immunoexpression. We further investigated SDHB immunoexpression in 35 cases of hemangioblastoma and found that 28 (80%) showed either negative or weak-diffuse pattern of SDHB immunoexpression, which suggests the inactivation of SDH. Our results suggest that SDH inactivation may represent an alternative pathway in the tumorigenesis of hemangioblastoma.
  29. Philos Trans R Soc Lond B Biol Sci. 2019 Feb 04. 374(1765): 20180154
    Florey O, Overholtzer M.
      Adaptive strategies used by cells to scavenge and recycle essential nutrients are important for survival in nutrient-depleted environments such as cancer tissues. Autophagy and macropinocytosis are two major mechanisms that promote nutrient recycling and scavenging, which share considerable, yet poorly understood, cross-regulation. Here we review recent findings that connect these starvation response mechanisms and discuss the implications of their crosstalk. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
    Keywords:  autophagy; entosis, phagocytosis; macropinocytosis
  30. Semin Cell Dev Biol. 2019 Apr 09. pii: S1084-9521(18)30091-0. [Epub ahead of print]
    Paolicelli RC, Angiari S.
      Since the observation that obesity-associated low-grade chronic inflammation is a crucial driver for the onset of systemic metabolic disorders such as type 2 diabetes, a number of studies have highlighted the role of both the innate and the adaptive immune system in such pathologies. Moreover, researchers have recently demonstrated that immune cells can modulate their intracellular metabolic profile to control their activation and effector functions. These discoveries represent the foundations of a research area known as "immunometabolism", an emerging field of investigation that may lead to the development of new-generation therapies for the treatment of inflammatory and metabolic diseases. Most of the studies in the field have focused their attention on both circulating white blood cells and leukocytes residing within metabolic tissues such as adipose tissue, liver and pancreas. However, immunometabolism of immune cells in non-metabolic tissues, including central nervous system microglia, have long been neglected. In this review, we highlight the most recent findings suggesting that microglial cells play a central role in metabolic disorders and that interfering with the metabolic profile of microglia can modulate their functionality and pathogenicity in neurological diseases.
    Keywords:  Immunometabolism; Inflammation; Metabolic diseases; Metabolism; Microglia