bims-camemi Biomed News
on Mitochondrial metabolism in cancer
Issue of 2019‒12‒22
twenty-nine papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit


  1. Nature. 2019 Dec 18.
    Tasdogan A, Faubert B, Ramesh V, Ubellacker JM, Shen B, Solmonson A, Murphy MM, Gu Z, Gu W, Martin M, Kasitinon SY, Vandergriff T, Mathews TP, Zhao Z, Schadendorf D, DeBerardinis RJ, Morrison SJ.
      Metastasis requires cancer cells to undergo metabolic changes that are poorly understood1-3. Here we show that metabolic differences among melanoma cells confer differences in metastatic potential as a result of differences in the function of the MCT1 transporter. In vivo isotope tracing analysis in patient-derived xenografts revealed differences in nutrient handling between efficiently and inefficiently metastasizing melanomas, with circulating lactate being a more prominent source of tumour lactate in efficient metastasizers. Efficient metastasizers had higher levels of MCT1, and inhibition of MCT1 reduced lactate uptake. MCT1 inhibition had little effect on the growth of primary subcutaneous tumours, but resulted in depletion of circulating melanoma cells and reduced the metastatic disease burden in patient-derived xenografts and in mouse melanomas. In addition, inhibition of MCT1 suppressed the oxidative pentose phosphate pathway and increased levels of reactive oxygen species. Antioxidants blocked the effects of MCT1 inhibition on metastasis. MCT1high and MCT1-/low cells from the same melanomas had similar capacities to form subcutaneous tumours, but MCT1high cells formed more metastases after intravenous injection. Metabolic differences among cancer cells thus confer differences in metastatic potential as metastasizing cells depend on MCT1 to manage oxidative stress.
    DOI:  https://doi.org/10.1038/s41586-019-1847-2
  2. Proc Natl Acad Sci U S A. 2019 Dec 16. pii: 201911954. [Epub ahead of print]
    Greene KS, Lukey MJ, Wang X, Blank B, Druso JE, Lin MJ, Stalnecker CA, Zhang C, Negrón Abril Y, Erickson JW, Wilson KF, Lin H, Weiss RS, Cerione RA.
      The mitochondrial enzyme glutaminase (GLS) is frequently up-regulated during tumorigenesis and is being evaluated as a target for cancer therapy. GLS catalyzes the hydrolysis of glutamine to glutamate, which then supplies diverse metabolic pathways with carbon and/or nitrogen. Here, we report that SIRT5, a mitochondrial NAD+-dependent lysine deacylase, plays a key role in stabilizing GLS. In transformed cells, SIRT5 regulates glutamine metabolism by desuccinylating GLS and thereby protecting it from ubiquitin-mediated degradation. Moreover, we show that SIRT5 is up-regulated during cellular transformation and supports proliferation and tumorigenesis. Elevated SIRT5 expression in human breast tumors correlates with poor patient prognosis. These findings reveal a mechanism for increasing GLS expression in cancer cells and establish a role for SIRT5 in metabolic reprogramming and mammary tumorigenesis.
    Keywords:  SIRT5; cancer; glutaminase; metabolism; sirtuin
    DOI:  https://doi.org/10.1073/pnas.1911954116
  3. Mech Ageing Dev. 2019 Dec 13. pii: S0047-6374(19)30201-5. [Epub ahead of print] 111196
    Montava-Garriga L, Singh F, Ball G, Ganley IG.
      Mitophagy is a natural phenomenon and entails the lysosomal degradation of mitochondria by the autophagy pathway. In recent years, the development of fluorescent pH-sensitive mitochondrial reporters has greatly facilitated the monitoring of mitophagy by distinguishing between cytosolic mitochondria or those delivered to acidic lysosomes. We recently published the mito-QC reporter, which consists of a mitochondrial outer membrane-localised tandem mCherry-GFP tag. This allows the quantification of mitophagy via the increase in red-only mCherry signal that arises when the GFP signal is quenched upon mitochondrial delivery to lysosomes. Here we develop a macro for FIJI, the mito-QC Counter, and describe its use to allow reliable and consistent semi-automated quantification of mitophagy. In this methods article we describe step-by-step how to detect and quantify mitophagy and show that mitophagy levels can be reliably calculated in different cell lines and under distinct stimuli. Finally, we show that the mito-QC Counter can be used to quantify mitophagy in tissues of mito-QC transgenic mice. We demonstrate that mitophagy levels in skeletal muscle correlates with glycolytic activity. Our present data show that the mito-QC Counter macro for FIJI enables the robust quantification of mitophagy both in vitro and in vivo.
    Keywords:  FIJI; autophagy; mito-QC; mitochondria; mitolysosome; mitophagy
    DOI:  https://doi.org/10.1016/j.mad.2019.111196
  4. Allergy. 2019 Dec 19.
    Jones N, Vincent EE, Felix LC, Cronin JG, Scott LM, Hole PS, Lacy P, Thornton CA.
      INTRODUCTION: Eosinophils have been long implicated in anti-parasite immunity and allergic diseases and, more recently, in regulating adipose tissue homeostasis. The metabolic processes that govern eosinophils, particularly upon activation, are unknown.METHODS: Peripheral blood eosinophils were isolated for analysis of metabolic processes using extracellular flux analysis and individual metabolites by stable isotope tracer analysis coupled to gas chromatography-mass spectrometry following treatment with IL-3, IL-5 or granulocyte-macrophage colony-stimulating factor (GM-CSF). Eosinophil metabolism was elucidated using pharmacological inhibitors.
    RESULTS: Human eosinophils engage a largely glycolytic metabolism but also employ mitochondrial metabolism. Cytokine stimulation generates citric acid cycle (TCA) intermediates from both glucose and glutamine revealing this previously unknown role for mitochondria upon eosinophil activation. We further show that the metabolic program driven by IL-5 is dependent on the STAT5/PI3K/Akt signalling axis and that nicotinamide adenine dinucleotide phosphate oxidase (NOX)-dependent ROS production might be a driver of mitochondrial metabolism upon eosinophil activation.
    CONCLUSION: We demonstrate for the first time that eosinophils are capable of metabolic plasticity, evidenced by increased glucose-derived lactate production upon ROS inhibition. Collectively this study reveals a role for both glycolysis and mitochondrial metabolism in cytokine-stimulated eosinophils. Selective targeting of eosinophil metabolism may be of therapeutic benefit in eosinophil-mediated diseases and regulation of tissue homeostasis.
    Keywords:  IL-5; TCA cycle; eosinophils; glycolysis; metabolism
    DOI:  https://doi.org/10.1111/all.14158
  5. Cancer Lett. 2019 Dec 12. pii: S0304-3835(19)30623-8. [Epub ahead of print]471 72-87
    Lee YG, Nam Y, Shin KJ, Yoon S, Park WS, Joung JY, Seo JK, Jang J, Lee S, Nam D, Caino MC, Suh PG, Chan Chae Y.
      Androgen receptor (AR) signaling plays a central role in metabolic reprogramming for prostate cancer (PCa) growth and progression. Mitochondria are metabolic powerhouses of the cell and support several hallmarks of cancer. However, the molecular links between AR signaling and the mitochondria that support the metabolic demands of PCa cells are poorly understood. Here, we demonstrate increased levels of dynamin-related protein 1 (DRP1), a mitochondrial fission mediator, in androgen-sensitive and castration-resistant AR-driven PCa. AR signaling upregulates DRP1 to form the VDAC-MPC2 complex, increases pyruvate transport into mitochondria, and supports mitochondrial metabolism, including oxidative phosphorylation and lipogenesis. DRP1 inhibition activates the cellular metabolic stress response, which involves AMPK phosphorylation, induction of autophagy, and the ER unfolded protein response, and attenuates androgen-induced proliferation. Additionally, DRP1 expression facilitates PCa cell survival under diverse metabolic stress conditions, including hypoxia and oxidative stress. Moreover, we found that increased DRP1 expression was indicative of poor prognosis in patients with castration-resistant PCa. Collectively, our findings link androgen signaling-mediated mitochondrial dynamics to metabolic reprogramming; moreover, they have important implications for understanding PCa progression.
    Keywords:  Cancer metabolism; Cancer therapy; Hormone receptor; Mitochondrial fission
    DOI:  https://doi.org/10.1016/j.canlet.2019.12.017
  6. Antioxid Redox Signal. 2019 Dec 18.
    Jezek P.
      SIGNIFICANCE: Cancer cells are stabilized in an undifferentiated state similar to stem cells. This leads to profound modifications of their metabolism, which further modifies their genetics and epigenetics as malignancy progresses. Specific metabolites and enzymes may serve as clinical markers of cancer progression. Recent Advances: Both 2-hydroxyglutarate (2HG) enantiomers are associated with reprogrammed metabolism, in grade III/IV glioma, glioblastoma and acute myeloid leukemia (AML) cells, and numerous other cancer types, while acting also in the crosstalk of tumors with immune cells. 2HG contributes to specific alternations in cancer metabolism and developed oxidative stress, while also inducing decisions on the differentiation of naïve T lymphocytes, and serves as a signal messenger in immune cells. Moreover, 2HG inhibits chromatin-modifying enzymes, namely 2-oxoglutarate-dependent dioxygenases, interferes with hypoxia-induced factor (HIF) transcriptome reprogramming and mTOR pathway, thus dysregulating gene expression and further promoting cancerogenesis.CRITICAL ISSUES: Typically heterozygous mutations within the active sites of isocitrate dehydrogenase IDH1R132H and mitochondrial IDH2R140Q provide cells with millimolar R-2HG concentrations, while side-activities of lactate and malate dehydrogenase form submillimolar S-2HG. However, even wild-type IDH1 and IDH2, notably under shifts toward reductive carboxylation glutaminolysis or changes in other enzymes, lead to "intermediate" 0.01-0.1 mM 2HG levels, e.g. in breast carcinoma, compared to 10-8 M in non-cancer cells.
    FUTURE DIRECTIONS: Uncovering further molecular metabolism details specific for given cancer cell types and sequence-specific epigenetic alternations will lead to the design of diagnostic approaches, not only predicting patients' prognosis or uncovering metastases and tumor remissions, but also for early diagnostics.
    DOI:  https://doi.org/10.1089/ars.2019.7902
  7. Antioxid Redox Signal. 2019 Dec 16.
    Ngoi NYL, Eu JQ, Hirpara J, Wang L, Lim JSJ, Lee SC, Lim YC, Pervaiz S, Goh BC, Wong ALA.
      Significance: Cancer cells exhibit altered metabolic pathways to keep up with biosynthetic and reduction-oxidation needs during tumor proliferation and metastasis. The common induction of metabolic pathways during cancer progression, regardless of cancer histio- or genotype, makes cancer metabolism an attractive target for therapeutic exploitation. Recent Advances: Emerging data suggest that these altered pathways may even result in resistance to anticancer therapies. Identifying specific metabolic dependencies that are unique to cancer cells has proved challenging in this field, limiting the therapeutic window for many candidate drug approaches. Critical Issues: Cancer cells display significant metabolic flexibility in nutrient-limited environments, hampering the longevity of suppressing cancer metabolism through any singular approach. Combinatorial "synthetic lethal" approaches may have a better chance for success and promising strategies are reviewed here. The dynamism of the immune system adds a level of complexity, as various immune populations in the tumor microenvironment often share metabolic pathways with cancer, with successive alterations during immune activation and quiescence. Decoding the reprogramming of metabolic pathways within cancer cells and stem cells, as well as examining metabolic symbiosis between components of the tumor microenvironment, would be essential to further meaningful drug development within the tumor's metabolic ecosystem. Future Directions: In this article, we examine evidence for the therapeutic potential of targeting metabolic alterations in cancer, and we discuss the drawbacks and successes that have stimulated this field. Antioxid. Redox Signal. 00, 000-000.
    Keywords:  cancer therapy; cell metabolism; metabolic vulnerability
    DOI:  https://doi.org/10.1089/ars.2019.7947
  8. Cancer Res. 2019 Dec 17. pii: canres.2481.2019. [Epub ahead of print]
    Brinker AE, Vivian CJ, Beadnell TC, Koestler DC, Teoh ST, Lunt SY, Welch DR.
      Mitochondria contribute to tumor growth through multiple metabolic pathways, regulation of extracellular pH, calcium signaling, and apoptosis. Using the Mitochondrial Nuclear Exchange (MNX) mouse models, which pair nuclear genomes with different mitochondrial genomes, we previously showed that mitochondrial single nucleotide polymorphisms (SNPs) regulate mammary carcinoma tumorigenicity and metastatic potential in genetic crosses. Here we tested the hypothesis that polymorphisms in stroma significantly affect tumorigenicity and experimental lung metastasis. Using syngeneic cancer cells (EO771 mammary carcinoma and B16-F10 melanoma cells) injected into wild-type and MNX mice [i.e., same nuclear DNA but different mitochondrial DNA (mtDNA], we showed mt-SNP-dependent increase (C3H/HeN) or decrease (C57BL/6J) in experimental metastasis. Superoxide scavenging reduced experimental metastasis. In addition, expression of lung nuclear-encoded genes changed specifically with mt-SNP. Thus, mitochondrial-nuclear cross-talk alters nuclear-encoded signaling pathways which mediate metastasis via both intrinsic and extrinsic mechanisms.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-19-2481
  9. Cell Rep. 2019 Dec 17. pii: S2211-1247(19)31558-X. [Epub ahead of print]29(12): 4127-4143.e8
    Naiman S, Huynh FK, Gil R, Glick Y, Shahar Y, Touitou N, Nahum L, Avivi MY, Roichman A, Kanfi Y, Gertler AA, Doniger T, Ilkayeva OR, Abramovich I, Yaron O, Lerrer B, Gottlieb E, Harris RA, Gerber D, Hirschey MD, Cohen HY.
      The pro-longevity enzyme SIRT6 regulates various metabolic pathways. Gene expression analyses in SIRT6 heterozygotic mice identify significant decreases in PPARα signaling, known to regulate multiple metabolic pathways. SIRT6 binds PPARα and its response element within promoter regions and activates gene transcription. Sirt6+/- results in significantly reduced PPARα-induced β-oxidation and its metabolites and reduced alanine and lactate levels, while inducing pyruvate oxidation. Reciprocally, starved SIRT6 transgenic mice show increased pyruvate, acetylcarnitine, and glycerol levels and significantly induce β-oxidation genes in a PPARα-dependent manner. Furthermore, SIRT6 mediates PPARα inhibition of SREBP-dependent cholesterol and triglyceride synthesis. Mechanistically, SIRT6 binds PPARα coactivator NCOA2 and decreases liver NCOA2 K780 acetylation, which stimulates its activation of PPARα in a SIRT6-dependent manner. These coordinated SIRT6 activities lead to regulation of whole-body respiratory exchange ratio and liver fat content, revealing the interactions whereby SIRT6 synchronizes various metabolic pathways, and suggest a mechanism by which SIRT6 maintains healthy liver.
    Keywords:  PPARα; SIRT6; beta-oxidation; deacetylase; fasting; liver
    DOI:  https://doi.org/10.1016/j.celrep.2019.11.067
  10. Nature. 2019 Dec 18.
    Wan L, Chong S, Xuan F, Liang A, Cui X, Gates L, Carroll TS, Li Y, Feng L, Chen G, Wang SP, Ortiz MV, Daley SK, Wang X, Xuan H, Kentsis A, Muir TW, Roeder RG, Li H, Li W, Tjian R, Wen H, Allis CD.
      Modifications of histone proteins have essential roles in normal development and human disease. Recognition of modified histones by 'reader' proteins is a key mechanism that mediates the function of histone modifications, but how the dysregulation of these readers might contribute to disease remains poorly understood. We previously identified the ENL protein as a reader of histone acetylation via its YEATS domain, linking it to the expression of cancer-driving genes in acute leukaemia1. Recurrent hotspot mutations have been found in the ENL YEATS domain in Wilms tumour2,3, the most common type of paediatric kidney cancer. Here we show, using human and mouse cells, that these mutations impair cell-fate regulation by conferring gain-of-function in chromatin recruitment and transcriptional control. ENL mutants induce gene-expression changes that favour a premalignant cell fate, and, in an assay for nephrogenesis using murine cells, result in undifferentiated structures resembling those observed in human Wilms tumour. Mechanistically, although bound to largely similar genomic loci as the wild-type protein, ENL mutants exhibit increased occupancy at a subset of targets, leading to a marked increase in the recruitment and activity of transcription elongation machinery that enforces active transcription from target loci. Furthermore, ectopically expressed ENL mutants exhibit greater self-association and form discrete and dynamic nuclear puncta that are characteristic of biomolecular hubs consisting of local high concentrations of regulatory factors. Such mutation-driven ENL self-association is functionally linked to enhanced chromatin occupancy and gene activation. Collectively, our findings show that hotspot mutations in a chromatin-reader domain drive self-reinforced recruitment, derailing normal cell-fate control during development and leading to an oncogenic outcome.
    DOI:  https://doi.org/10.1038/s41586-019-1842-7
  11. Antioxid Redox Signal. 2019 Dec 17.
    Scagliola A, Mainini F, Cardaci S.
      SIGNIFICANCE: the tricarboxylic acid (TCA) cycle is a housekeeping metabolic pathway essential for generation of energy and biosynthetic intermediates. Alterations of the TCA cycle play a pivotal role in oncogenesis and inflammation. As such, some metabolic vulnerabilities, imposed by TCA cycle dysfunction in cancer, have been identified. Similarly, the TCA cycle appeared as an actionable pathway in immunopathologies. Recent Advances: metabolic changes accompanying cell transformation have been usually considered as adaptive mechanisms to malignant transformation. The identification of oncogenic mutations in some TCA cycle enzymes changed this view, indicating altered mitochondrial metabolism as an instrumental mechanism for cancer initiation. Similarly, the observation that TCA cycle-derived metabolites have multiple signaling roles in immune cells, supports the idea of this pathway as a metabolic rheostat of immune responses.CRITICAL ISSUES: this review summarizes the crucial role of TCA cycle in pathophysiology describing the post-translational and epigenetic impact of oncometabolites accumulation in cancer and immune cells.
    FUTURE DIRECTIONS: additional studies will be necessary to further explore the role of oncometabolites in paracrine signaling and to identify genuine metabolic and nutritional liabilities imposed by TCA cycle dysfunction in cancer, hardly to be escaped by resistance mechanisms.
    DOI:  https://doi.org/10.1089/ars.2019.7974
  12. Cell Metab. 2019 Dec 06. pii: S1550-4131(19)30621-7. [Epub ahead of print]
    Mazumdar C, Driggers EM, Turka LA.
      Here, we explore the manipulation of immune cell metabolism as a strategy in target discovery and drug development for immune-mediated diseases. Comparing exploitation of metabolic pathways to kill tumor cells for cancer treatment with the reprogramming of immune cells to treat autoimmune diseases highlights differences that confer several advantages to the latter (including a more favorable therapeutic index and greater target stability). We discuss technological capabilities and gaps, including the challenge of relating in vitro observations to in vivo biology. Finally, we conclude by identifying future opportunities that will move the field forward and accelerate drug discovery.
    DOI:  https://doi.org/10.1016/j.cmet.2019.11.014
  13. ACS Sens. 2019 Dec 17.
    Yoshida T, Nakajima H, Takahashi S, Kakizuka A, Imamura H.
      Branched-chain amino acids (BCAAs) are essential amino acids, controlling cellular metabolic processes as signaling molecules; therefore, utilization of intracellular BCAAs may be regulated by the availability of nutrients in the environment. However, spatial and temporal regulation of intracellular BCAA concentration in response to environmental conditions has been unclear due to the lack of suitable methods for measuring BCAA concentrations inside single living cells. Here, we developed a Förster resonance energy transfer (FRET)-based genetically encoded biosensor for BCAAs, termed optical biosensor for leucine-isoleucine-valine (OLIVe). The biosensor showed approximately 2-fold changes in FRET values corresponding to BCAA concentrations. Importantly, FRET signals from HeLa cells expressing OLIVe in the cytoplasm and nucleus correlated with bulk intracellular BCAA concentrations determined from populations of cells by a biochemical method, and were decreased by knockdown of L-type amino acid transporter 1 (LAT1), a transporter for BCAAs, indicating that OLIVe can reliably report intracellular BCAA concentrations inside single living cells. We also succeeded in imaging BCAA concentrations in the mitochondria using mitochondria-targeted OLIVe. Using the BCAA imaging technique, we found apparently correlated concentrations between the cytoplasm and the mitochondria. We also found that extracellular non-BCAA amino acids affected intracellular BCAA concentrations. Of these amino acids, extracellular glutamine markedly increased intracellular BCAA concentrations in a LAT1-dependent manner. Unexpectedly, extracellular pyruvate was also found to have significant positive effects on maintaining intracellular BCAA concentrations, suggesting that the cells have pyruvate-dependent systems to import BCAAs and/or to regulate BCAA metabolism.
    Keywords:  BCAA; FRET; biosensor; isoleucine; leucine; live imaging; single cell; valine
    DOI:  https://doi.org/10.1021/acssensors.9b02067
  14. Nat Commun. 2019 Dec 20. 10(1): 5823
    Mnatsakanyan N, Llaguno MC, Yang Y, Yan Y, Weber J, Sigworth FJ, Jonas EA.
      Purified mitochondrial ATP synthase has been shown to form Ca2+-activated, large conductance channel activity similar to that of mitochondrial megachannel (MMC) or mitochondrial permeability transition pore (mPTP) but the oligomeric state required for channel formation is being debated. We reconstitute purified monomeric ATP synthase from porcine heart mitochondria into small unilamellar vesicles (SUVs) with the lipid composition of mitochondrial inner membrane and analyze its oligomeric state by electron cryomicroscopy. The cryo-EM density map reveals the presence of a single ATP synthase monomer with no density seen for a second molecule tilted at an 86o angle relative to the first. We show that this preparation of SUV-reconstituted ATP synthase monomers, when fused into giant unilamellar vesicles (GUVs), forms voltage-gated and Ca2+-activated channels with the key features of mPTP. Based on our findings we conclude that the ATP synthase monomer is sufficient, and dimer formation is not required, for mPTP activity.
    DOI:  https://doi.org/10.1038/s41467-019-13766-2
  15. Cell Physiol Biochem. 2019 ;53(S1): 52-62
    Checchetto V, Prosdocimi E, Leanza L.
      Kv1.3 is a voltage gated potassium channel located in the plasma membrane, as well as at intracellular levels, such as mitochondria (mitoKv1.3), nucleus and Golgi apparatus. The plasma membrane channel has been shown to be important for cell proliferation, while the mitochondrial counterpart has been related to modulation of cell death. Moreover, altered expression of Kv1.3 was observed in various tumors and Kv1.3 seems to be involved in development and progression of various cancerous forms. Recent experimental evidences have proved that pharmacological inhibition of the mitoKv1.3 succeeded in reducing up to 90% of tumor volume in vivo in orthotopic mouse model. Furthermore, mitoKv1.3 modulation could impact on cell proliferation as well as on regulation of intracellular signaling pathways. Indeed, the treatment with sub-lethal doses of mitoKv1.3 inhibitors can downregulate Wnt-β catenin signaling by reducing mitochondrial ATP production and triggering ER-stress. In this review, we describe the role of the mitoKv1.3 in cell death, cancer and intracellular signaling. We will discuss how pharmacological modulation of mitochondrial potassium fluxes impact on mitochondrial membrane potential, reactive oxygen species production and ATP synthesis. All these changes in mitochondrial fitness are related to cell proliferation as well as to cell death and finally on cancer development and progression, so Kv1.3 (and mitoKv1.3) could be now considered a new oncological target.
    Keywords:  Potassium channel; Mitochondria; Kv1.3; Cancer; Signaling
    DOI:  https://doi.org/10.33594/000000195
  16. Cell Stem Cell. 2019 Dec 09. pii: S1934-5909(19)30466-7. [Epub ahead of print]
    Alvarez-Dominguez JR, Donaghey J, Rasouli N, Kenty JHR, Helman A, Charlton J, Straubhaar JR, Meissner A, Melton DA.
      Stem-cell-derived tissues could transform disease research and therapy, yet most methods generate functionally immature products. We investigate how human pluripotent stem cells (hPSCs) differentiate into pancreatic islets in vitro by profiling DNA methylation, chromatin accessibility, and histone modification changes. We find that enhancer potential is reset upon lineage commitment and show how pervasive epigenetic priming steers endocrine cell fates. Modeling islet differentiation and maturation regulatory circuits reveals genes critical for generating endocrine cells and identifies circadian control as limiting for in vitro islet function. Entrainment to circadian feeding/fasting cycles triggers islet metabolic maturation by inducing cyclic synthesis of energy metabolism and insulin secretion effectors, including antiphasic insulin and glucagon pulses. Following entrainment, hPSC-derived islets gain persistent chromatin changes and rhythmic insulin responses with a raised glucose threshold, a hallmark of functional maturity, and function within days of transplantation. Thus, hPSC-derived tissues are amenable to functional improvement by circadian modulation.
    Keywords:  circadian clock; enhancers; epigenome; hESCs; in vitro differentiation; islets of Langerhans; pancreas; pioneer factors; tissue maturation; β cells
    DOI:  https://doi.org/10.1016/j.stem.2019.11.011
  17. Cell Rep. 2019 Dec 17. pii: S2211-1247(19)31537-2. [Epub ahead of print]29(12): 3825-3834.e4
    Murgia M, Tan J, Geyer PE, Doll S, Mann M, Klopstock T.
      The mosaic distribution of cytochrome c oxidase+ (COX+) and COX- muscle fibers in mitochondrial disorders allows the sampling of fibers with compensated and decompensated mitochondrial function from the same individual. We apply laser capture microdissection to excise individual COX+ and COX- fibers from the biopsies of mitochondrial myopathy patients. Using mass spectrometry-based proteomics, we quantify >4,000 proteins per patient. While COX+ fibers show a higher expression of respiratory chain components, COX- fibers display protean adaptive responses, including upregulation of mitochondrial ribosomes, translation proteins, and chaperones. Upregulated proteins include C1QBP, required for mitoribosome formation and protein synthesis, and STOML2, which organizes cardiolipin-enriched microdomains and the assembly of respiratory supercomplexes. Factoring in fast/slow fiber type, COX- slow fibers show a compensatory upregulation of beta-oxidation, the AAA+ protease AFG3L1, and the OPA1-dependent cristae remodeling program. These findings reveal compensatory mechanisms in muscle fibers struggling with energy shortage and metabolic stress.
    Keywords:  COX; CPEO; chronic progressive external ophthalmoplegia; cytochrome c oxidase; laser microdissection; mass spectrometry; mitochondrial myopathy; proteomics; single muscle fibers
    DOI:  https://doi.org/10.1016/j.celrep.2019.11.055
  18. Cell Physiol Biochem. 2019 ;53(S1): 63-78
    Bachmann M, Pontarin G, Szabo I.
      Mitochondria play a central role in cancer development, by contributing to most of the classical hallmarks of cancer, including sustained proliferation, metabolic re-programming, apoptosis resistance, invasion and induction of angiogenesis [1]. In addition, mitochondria affect also the function of anti- and pro-tumoral immune cells in the tumor microenvironment. Mitochondria harbor a plethora of regulated ion channels whose function is related to ion/ metabolite transport and to fine-tuning of mitochondrial membrane potential as well as of reactive oxygen species release. As a consequence, growing evidence link ion channels located both in the outer and inner mitochondrial membranes to several cancer hallmarks. The present review summarizes our recent knowledge about the participation and role of mitochondrial channels leading to acquisition of cancer hallmarks and thus to cancer progression.
    Keywords:  Cancer hallmarks; Mitochondrial ion channels; Modulation of mitochondrial function; Modulation of hallmark capabilities by ion channel modulators
    DOI:  https://doi.org/10.33594/000000198
  19. Immunity. 2019 Dec 17. pii: S1074-7613(19)30489-3. [Epub ahead of print]51(6): 980-981
    Notarangelo G, Haigis MC.
      In a recent issue of Nature, Zhang et al. (2019) describe an additional histone post-translational modification, named histone lactylation. Following increased lactate production as a consequence of M1 polarization, histone lactylation regulates the induction of an M2-like phenotype in late stages of M1 macrophage activation to promote wound healing.
    DOI:  https://doi.org/10.1016/j.immuni.2019.11.008
  20. Front Cell Dev Biol. 2019 ;7 301
    Plummer JD, Johnson JE.
      Methionine restriction (MR) is one of only a few dietary manipulations known to robustly extend healthspan in mammals. For example, rodents fed a methionine-restricted diet are up to 45% longer-lived than control-fed animals. Tantalizingly, ongoing studies suggest that humans could enjoy similar benefits from this intervention. While the benefits of MR are likely due, at least in part, to improved cellular stress tolerance, it remains to be determined exactly how MR extends organismal healthspan. In previous work, we made use of the yeast chronological lifespan (CLS) assay to model the extension of cellular lifespan conferred by MR and explore the genetic requirements for this extension. In these studies, we demonstrated that both dietary MR (D-MR) and genetic MR (G-MR) (i.e., impairment of the cell's methionine biosynthetic machinery) significantly extend the CLS of yeast. This extension was found to require the mitochondria-to-nucleus retrograde (RTG) stress signaling pathway, and was associated with a multitude of gene expression changes, a significant proportion of which was also dependent on RTG signaling. Here, we show work aimed at understanding how a subset of the observed expression changes are causally related to MR-dependent CLS extension. Specifically, we find that multiple autophagy-related genes are upregulated by MR, likely resulting in an increased autophagic capacity. Consistent with activated autophagy being important for the benefits of MR, we also find that loss of any of several core autophagy factors abrogates the extended CLS observed for methionine-restricted cells. In addition, epistasis analyses provide further evidence that autophagy activation underlies the benefits of MR to yeast. Strikingly, of the many types of selective autophagy known, our data clearly demonstrate that MR-mediated CLS extension requires only the autophagic recycling of mitochondria (i.e., mitophagy). Indeed, we find that functional mitochondria are required for the full benefit of MR to CLS. Finally, we observe substantial alterations in carbon metabolism for cells undergoing MR, and provide evidence that such changes are directly responsible for the extended lifespan of methionine-restricted yeast. In total, our data indicate that MR produces changes in carbon metabolism that, together with the oxidative metabolism of mitochondria, result in extended cellular lifespan.
    Keywords:  ageing; aging; autophagy; healthspan; longevity; methioninase; mitochondria; yeast
    DOI:  https://doi.org/10.3389/fcell.2019.00301
  21. JCI Insight. 2019 Dec 19. pii: 129756. [Epub ahead of print]4(24):
    Lowe MM, Boothby I, Clancy S, Ahn RS, Liao W, Nguyen DN, Schumann K, Marson A, Mahuron KM, Kingsbury GA, Liu Z, Munoz Sandoval P, Rodriguez RS, Pauli ML, Taravati K, Arron ST, Neuhaus IM, Harris HW, Kim EA, Shin US, Krummel MF, Daud A, Scharschmidt TC, Rosenblum MD.
      Distinct subsets of Tregs reside in nonlymphoid tissues where they mediate unique functions. To interrogate the biology of tissue Tregs in human health and disease, we phenotypically and functionally compared healthy skin Tregs with those in peripheral blood, inflamed psoriatic skin, and metastatic melanoma. The mitochondrial enzyme, arginase 2 (ARG2), was preferentially expressed in Tregs in healthy skin, increased in Tregs in metastatic melanoma, and reduced in Tregs from psoriatic skin. ARG2 enhanced Treg suppressive capacity in vitro and conferred a selective advantage for accumulation in inflamed tissues in vivo. CRISPR-mediated deletion of this gene in primary human Tregs was sufficient to skew away from a tissue Treg transcriptional signature. Notably, the inhibition of ARG2 increased mTOR signaling, whereas the overexpression of this enzyme suppressed it. Taken together, our results suggest that Tregs express ARG2 in human tissues to both regulate inflammation and enhance their metabolic fitness.
    Keywords:  Adaptive immunity; Immunology; Metabolism
    DOI:  https://doi.org/10.1172/jci.insight.129756
  22. Science. 2019 12 20. 366(6472): 1531-1536
    Kim J, Gupta R, Blanco LP, Yang S, Shteinfer-Kuzmine A, Wang K, Zhu J, Yoon HE, Wang X, Kerkhofs M, Kang H, Brown AL, Park SJ, Xu X, Zandee van Rilland E, Kim MK, Cohen JI, Kaplan MJ, Shoshan-Barmatz V, Chung JH.
      Mitochondrial stress releases mitochondrial DNA (mtDNA) into the cytosol, thereby triggering the type Ι interferon (IFN) response. Mitochondrial outer membrane permeabilization, which is required for mtDNA release, has been extensively studied in apoptotic cells, but little is known about its role in live cells. We found that oxidatively stressed mitochondria release short mtDNA fragments via pores formed by the voltage-dependent anion channel (VDAC) oligomers in the mitochondrial outer membrane. Furthermore, the positively charged residues in the N-terminal domain of VDAC1 interact with mtDNA, promoting VDAC1 oligomerization. The VDAC oligomerization inhibitor VBIT-4 decreases mtDNA release, IFN signaling, neutrophil extracellular traps, and disease severity in a mouse model of systemic lupus erythematosus. Thus, inhibiting VDAC oligomerization is a potential therapeutic approach for diseases associated with mtDNA release.
    DOI:  https://doi.org/10.1126/science.aav4011
  23. Autophagy. 2019 Dec 19. 1-3
    Holdgaard SG, Cianfanelli V, Cecconi F.
      The selective clearance of cellular components by macroautophagy (hereafter autophagy) is critical for maintaining cellular homeostasis. In this punctum, we summarize and discuss our recent findings regarding a novel type of selective autophagy that targets centriolar satellites (CS) for degradation, a process we termed doryphagy from the Greek word "doryphoros", standing for "satellite". CS are microtubule-associated protein complexes that regulate centrosome composition. We show that CS degradation is mediated through a direct interaction between GABARAPs and an LC3-interacting region (LIR) motif in the CS protein PCM1. Autophagy-deficient systems accumulate large abnormal CS and consequently display centrosome reorganization and abnormal mitoses. Our findings provide a mechanistic link between macroautophagy deficiency and centrosome abnormalities and exemplify how mammalian Atg8-family proteins (mATG8s) can regulate substrate specificity.
    Keywords:  Centriolar satellites; PCM1; centrosome; doryphagy; mitosis; selective autophagy
    DOI:  https://doi.org/10.1080/15548627.2019.1703356
  24. Cancer Discov. 2019 Dec 20.
      KRAS4A, but not KRAS4B, directly interacts with hexokinase 1 (HK1) on outer mitochondrial membranes.
    DOI:  https://doi.org/10.1158/2159-8290.CD-RW2019-189
  25. Nat Commun. 2019 Dec 20. 10(1): 5800
    Cai W, Su L, Liao L, Liu ZZ, Langbein L, Dulaimi E, Testa JR, Uzzo RG, Zhong Z, Jiang W, Yan Q, Zhang Q, Yang H.
      p53 acetylation is indispensable for its transcriptional activity and tumor suppressive function. However, the identity of reader protein(s) for p53 acetylation remains elusive. PBRM1, the second most highly mutated tumor suppressor gene in kidney cancer, encodes PBRM1. Here, we identify PBRM1 as a reader for p53 acetylation on lysine 382 (K382Ac) through its bromodomain 4 (BD4). Notably, mutations on key residues of BD4 disrupt recognition of p53 K382Ac. The mutation in BD4 also reduces p53 binding to promoters of target genes such as CDKN1A (p21). Consequently, the PBRM1 BD4 mutant fails to fully support p53 transcriptional activity and is defective as a tumor suppressor. We also find that expressions of PBRM1 and p21 correlate with each other in human kidney cancer samples. Our findings uncover a tumor suppressive mechanism of PBRM1 in kidney cancer and provide a mechanistic insight into the crosstalk between p53 and SWI/SNF complexes.
    DOI:  https://doi.org/10.1038/s41467-019-13608-1
  26. Elife. 2019 Dec 16. pii: e52135. [Epub ahead of print]8
    Yamaguchi N, Weinberg EM, Nguyen A, Liberti MV, Goodarzi H, Janjigian YY, Paty PB, Saltz LB, Kingham TP, Loo JM, Stanchina E, Tavazoie S.
      Colorectal cancer (CRC) is a major cause of human death. Mortality is primarily due to metastatic organ colonization, with the liver being the primary organ affected. We modeled metastatic CRC (mCRC) liver colonization using patient-derived primary and metastatic tumor xenografts (PDX). Such PDX modeling predicted patient survival outcomes. In vivo selection of multiple PDXs for enhanced metastatic colonization capacity upregulated the gluconeogenic enzyme PCK1, which enhanced liver metastatic hypoxic growth by driving pyrimidine nucleotide biosynthesis under hypoxia. Consistently, highly metastatic tumors upregulated multiple pyrimidine biosynthesis intermediary metabolites. Therapeutic inhibition of the pyrimidine biosynthetic enzyme DHODH with leflunomide substantially impaired CRC liver metastatic colonization and hypoxic growth. Our findings provide a potential mechanistic basis for the epidemiologic association of anti-gluconeogenic drugs with improved CRC metastasis outcomes, reveal the exploitation of a gluconeogenesis enzyme for pyrimidine biosynthesis under hypoxia, and implicate DHODH and PCK1 as metabolic therapeutic targets in colorectal cancer metastatic progression.
    Keywords:  cancer biology; human; human biology; medicine
    DOI:  https://doi.org/10.7554/eLife.52135
  27. Curr Biol. 2019 Dec 16. pii: S0960-9822(19)31463-0. [Epub ahead of print]29(24): R1316-R1318
    Gitschlag BL, Patel MR.
      Resource limitation underlies competition in the living world, even between intracellular populations of mitochondria. A new study shows that reducing the availability of an essential cellular resource, namely the enzyme that replicates mitochondrial DNA (mtDNA), can alter the selective advantage of one mtDNA type over another.
    DOI:  https://doi.org/10.1016/j.cub.2019.11.024
  28. Front Endocrinol (Lausanne). 2019 ;10 773
    Bhattacharya D, Scimè A.
      The last few decades have witnessed an outstanding advancement in our understanding of the hallmarks of endocrine cancers. This includes the epithelial to mesenchymal transition (EMT), a process that alters the morphology and functional characteristics of carcinoma cells. The mesenchymal stem cell like phenotype produced by EMT allows the dislocation of cancer cells from the primary tumor site with inheritance of motility, metastatic and invasive properties. A fundamental driver thought to initiate and propagate EMT is metabolic reprogramming that occur during these transitions. Though there remains a paucity of data regarding the alterations that occur during EMT in endocrine cancers, the contribution of deregulated metabolism is a prominent feature. This mini review focuses on metabolic reprogramming events that occur in cancer cells and in particular those of endocrine origin. It highlights the main metabolic reprogramming outcomes of EMT, encompassing glycolysis, mitochondria oxidative phosphorylation and function, glutamine and lipid metabolism. Comprehending the metabolic changes that occur during EMT will help formulate potential bioenergetic targets as therapies for endocrine cancer metastasis.
    Keywords:  endocrine cancers; epithelial-mesenchymal transition; metabolism; metastasis; mitochondria
    DOI:  https://doi.org/10.3389/fendo.2019.00773
  29. Angew Chem Int Ed Engl. 2019 Dec 21.
    Yamashita Y, Vinogradova E, Zhang X, Suciu R, Cravatt B.
      Target engagement assays are crucial for establishing the mechanism-of-action of small molecules in living systems. Integral membrane transporters, due to their specialized biophysical properties and activity assays, can present a challenging protein class for assessing cellular engagement by small molecules. Here, we describe the chemical proteomic discovery of alpha-chloroacetamide (aCA) compounds that covalently modify cysteine-54 (C54) of the MPC2 subunit of the mitochondrial pyruvate carrier (MPC) complex. We leverage this finding to create an alkyne-modified aCA, YY4-yne, that serves as a versatile cellular target engagement probe for MPC2 in click chemistry-enabled western blotting or global mass spectrometry-based proteomic experiments. Using YY4-yne, we demonstrate that UK-5099, an alpha-cyanocinnamate inhibitor of the MPC complex, first discovered more than 30 years ago, but still with a poorly defined mechanism-of-action, engages MPC2 with remarkable selectivity in human cells. These findings support a model where UK-5099 inhibits the MPC complex by binding to C54 of MPC2 in a covalent reversible manner that can be quantified in cells using the YY4-yne probe.
    Keywords:  chemical proteomics, covalent probe, inhibitor, membrane transporter, target engagement
    DOI:  https://doi.org/10.1002/anie.201914391