bims-camemi Biomed News
on Mitochondrial metabolism in cancer
Issue of 2020‒01‒26
twenty-nine papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit


  1. Nat Commun. 2020 Jan 24. 11(1): 498
    Lee P, Malik D, Perkons N, Huangyang P, Khare S, Rhoades S, Gong YY, Burrows M, Finan JM, Nissim I, Gade TPF, Weljie AM, Simon MC.
      Tumour cells frequently utilize glutamine to meet bioenergetic and biosynthetic demands of rapid cell growth. However, glutamine dependence can be highly variable between in vitro and in vivo settings, based on surrounding microenvironments and complex adaptive responses to glutamine deprivation. Soft tissue sarcomas (STSs) are mesenchymal tumours where cytotoxic chemotherapy remains the primary approach for metastatic or unresectable disease. Therefore, it is critical to identify alternate therapies to improve patient outcomes. Using autochthonous STS murine models and unbiased metabolomics, we demonstrate that glutamine metabolism supports sarcomagenesis. STS subtypes expressing elevated glutaminase (GLS) levels are highly sensitive to glutamine starvation. In contrast to previous studies, treatment of autochthonous tumour-bearing animals with Telaglenastat (CB-839), an orally bioavailable GLS inhibitor, successfully inhibits undifferentiated pleomorphic sarcoma (UPS) tumour growth. We reveal glutamine metabolism as critical for sarcomagenesis, with CB-839 exhibiting potent therapeutic potential.
    DOI:  https://doi.org/10.1038/s41467-020-14374-1
  2. Antioxid Redox Signal. 2020 Jan 22.
    Liu L, Liao X, Wu H, Li Y, Zhu Y, Chen Q.
      Mitochondria are the cellular powerhouses for ATP synthesis through oxidative phosphorylation (OXPHOS), and the centers for fatty acid β-oxidation, metabolite synthesis, ROS production, innate immunity and apoptosis. To fulfill these critical functions, mitochondrial quality and homeostasis must be well maintained to avoid potential damage to the cell. Abnormal mitochondrial quality contributes to aging and age-related disorders, such as metabolic syndrome, cancers and neurodegenerative diseases. Mitophagy is a cellular process that selectively removes damaged or superfluous mitochondria by autolysosomal degradation and is regarded as one of the major mechanisms responsible for mitochondrial quality control. To date, distinct mitophagy pathways have been discovered, including receptor-mediated mitophagy and ubiquitin-dependent mitophagy, of which the PINK1/Parkin-dependent mechanism is the best characterized to date. Emerging knowledge of these pathways shows that they play important roles in sensing mitochondrial stress and signaling for metabolic adaptations. Here, we provide a review on the molecular mechanisms for mitophagy and its interplay with cellular metabolism, with a particular focus on its role in metabolic and aging related disorders.
    DOI:  https://doi.org/10.1089/ars.2019.8013
  3. Cell Death Dis. 2020 Jan 20. 11(1): 38
    Lee DE, Yoo JE, Kim J, Kim S, Kim S, Lee H, Cheong H.
      In mammals, autophagosome formation is initiated by ULK1 via the posttranslational modification of this protein. However, the precise role of ULK1 ubiquitination in modulating autophagy is unknown. Here, we show that NEDD4L, an E3 ubiquitin ligase, binds ULK1 in pancreatic cancer cells. ULK1 expression was stabilized in NEDD4L knockdown cells compared to that in control cells, suggesting that NEDD4L is involved in ULK1 ubiquitination and its subsequent degradation. Autophagy activity was enhanced in NEDD4L knockdown cells compared to control cells. NEDD4L-depleted cells exhibited an increase in the cellular oxygen consumption rate (OCR) and mitochondrial membrane potential, and maintained mitochondrial fusion status in response to metabolic stress. Enhanced OCR and mitochondrial fusion morphology in NEDD4L knockdown cells were repressed by siRNA targeting ULK1. In addition to ULK1, ASCT2, a glutamine transporter, was accumulated in NEDD4L-depleted cells; this is important for maintaining autophagy activation and mitochondrial metabolic function. Finally, the cellular growth and survival rate increased in NEDD4L knockdown cells compared to control cells. However, the genetic or pharmacological blockade of either ULK1 or ASCT2 in NEDD4L-depleted cells sensitized pancreatic cancer cells, particularly in response to nutrient deprivation. In a mouse xenograft model of pancreatic cancer, the use of autophagy inhibitors suppressed tumor growth more in NEDD4L-depleted cells than in tumors from control cells. NEDD4L and ULK1 levels were inversely correlated in two different pancreatic cancer mouse models-xenograft mouse and KPC mouse models. These results suggest that NEDD4L suppressed autophagy and mitochondrial metabolism by reducing cellular ULK1 or ASCT2 levels, and thus could repress the growth and survival of pancreatic cancer cells. Therefore, ubiquitin ligase-mediated autophagy plays a critical role in regulating mitochondrial metabolism, thereby contributing to the growth and survival of certain cancers with low NEDD4L levels.
    DOI:  https://doi.org/10.1038/s41419-020-2242-5
  4. Cancers (Basel). 2020 Jan 17. pii: E237. [Epub ahead of print]12(1):
    Conroy LR, Dougherty S, Kruer T, Metcalf S, Lorkiewicz P, He L, Yin X, Zhang X, Arumugam S, Young LEA, Sun RC, Clem BF.
      Dysregulated metabolism is a hallmark of cancer cells and is driven in part by specific genetic alterations in various oncogenes or tumor suppressors. The retinoblastoma protein (pRb) is a tumor suppressor that canonically regulates cell cycle progression; however, recent studies have highlighted a functional role for pRb in controlling cellular metabolism. Here, we report that loss of the gene encoding pRb (Rb1) in a transgenic mutant Kras-driven model of lung cancer results in metabolic reprogramming. Our tracer studies using bolus dosing of [U-13C]-glucose revealed an increase in glucose carbon incorporation into select glycolytic intermediates. Consistent with this result, Rb1-depleted tumors exhibited increased expression of key glycolytic enzymes. Interestingly, loss of Rb1 did not alter mitochondrial pyruvate oxidation compared to lung tumors with intact Rb1. Additional tracer studies using [U-13C,15N]-glutamine and [U-13C]-lactate demonstrated that loss of Rb1 did not alter glutaminolysis or utilization of circulating lactate within the tricarboxylic acid cycle (TCA) in vivo. Taken together, these data suggest that the loss of Rb1 promotes a glycolytic phenotype, while not altering pyruvate oxidative metabolism or glutamine anaplerosis in Kras-driven lung tumors.
    Keywords:  Rb1; TCA anaplerosis; glycolysis; lung cancer; metabolomics
    DOI:  https://doi.org/10.3390/cancers12010237
  5. Exp Gerontol. 2020 Jan 16. pii: S0531-5565(19)30765-X. [Epub ahead of print] 110841
    Castro-Portuguez R, Sutphin GL.
      Aging is characterized by a progressive decline in the normal physiological functions of an organism, ultimately leading to mortality. Nicotinamide adenine dinucleotide (NAD+) is an essential cofactor that plays a critical role in mitochondrial energy production as well as many enzymatic redox reactions. Age-associated decline in NAD+ is implicated as a driving factor in several categories of age-associated disease, including metabolic and neurodegenerative disease, as well as deficiency in the mechanisms of cellular defense against oxidative stress. The kynurenine metabolic pathway is the sole de novo NAD+ biosynthetic pathway, generating NAD+ from ingested tryptophan. Altered kynurenine pathway activity is associated with both aging and a variety of age-associated diseases. Kynurenine pathway interventions can extend lifespan in both fruit flies and nematodes, and altered NAD+ metabolism represents one potential mediating mechanism. Recent studies demonstrate that supplementation with NAD+ or NAD+-precursors increase longevity and promote healthy aging in fruit flies, nematodes, and mice. NAD+ levels and the intrinsic relationship to mitochondrial function have been widely studied in the context of aging. Mitochondrial function and dynamics have both been are implicated in longevity determination in a range of organisms from yeast to humans, at least in part due to their intimate link to regulating an organism's cellular energy economy and capacity to resist oxidative stress. Recent findings support the idea that complex communication between the mitochondria and the nucleus orchestrates a series of events and stress responses involving mitophagy, mitochondrial number, mitochondrial unfolded protein response (UPRmt), and mitochondria fission and fusion events. In this review, we discuss how mitochondrial morphological changes and dynamics operate during aging, and how altered metabolism of tryptophan to NAD+ through the kynurenine pathway interacts with these processes.
    Keywords:  Kynurenine pathway; Mitochondria; NAD; Oxidative stress; Tryptophan
    DOI:  https://doi.org/10.1016/j.exger.2020.110841
  6. J Biol Chem. 2020 Jan 24. pii: jbc.RA119.011526. [Epub ahead of print]
    Dumbrepatil AB, Zegalia KA, Sajja K, Kennedy RT, Marsh ENG.
      Understanding the mechanisms by which viruses evade host-cell immune defenses is important for developing improved antiviral therapies. In an unusual twist, human cytomegalovirus (HCMV) co-opts the antiviral radical SAM enzyme, viperin (Virus inhibitory protein, endoplasmic reticulum-associated, interferon-inducible), to enhance viral infectivity. This process involves translocation of viperin to the mitochondrion where it binds the β-subunit (HADHB) of the mitochondrial trifunctional enzyme complex that catalyzes the thiolysis of β-ketoacyl-CoA esters as part of fatty acid β-oxidation. Here, we investigated how the interaction between these two enzymes alters their activities and affects cellular ATP levels. Experiments with purified enzymes indicated that viperin inhibits the thiolase activity of HADHB, but, unexpectedly, HADHB activates viperin leading to the synthesis of the antiviral nucleotide 3'-deoxy-3',4'-didehydro-CTP. Measurements of enzyme activities in lysates prepared from transfected HEK 293T cells expressing these enzymes mirrored the findings obtained with purified enzymes. Thus, localizing viperin to the mitochondria decreased thiolase activity and co-expression of HADHB significantly increased viperin activity. Furthermore, targeting viperin to mitochondria also increased the rate at which HADHB is retro-translocated out of mitochondria and degraded, providing an additional mechanism by which viperin reduces HADHB activity. Targeting viperin to the mitochondria decreased cellular ATP levels by > 50 %, consistent with the enzyme disrupting fatty acid catabolism. These results provide biochemical insight into the mechanism by which HCMV subverts viperin; they also provide a biochemical rationale for viperin's recently discovered role in regulating thermogenesis in adipose tissues.
    Keywords:  HADHB thiolase; cytomegalovirus; enzyme degradation; enzyme inhibitor; fatty acid oxidation; innate immunity; metabolic regulation; metalloenzyme; mitochondria; mitochondrial trifunctional protein; radical SAM enzyme; viperin
    DOI:  https://doi.org/10.1074/jbc.RA119.011526
  7. Mitochondrion. 2020 Jan 20. pii: S1567-7249(19)30230-2. [Epub ahead of print]
    Garza-Lombó C, Pappa A, Panayiotidis MI, Franco R.
      Autophagy is a ubiquitous homeostatic mechanism for the degradation or turnover of cellular components. Degradation of mitochondria via autophagy (mitophagy) is involved in a number of physiological processes including cellular homeostasis, differentiation and aging. Upon stress or injury, mitophagy prevents the accumulation of damaged mitochondria and the increased steady state levels of reactive oxygen species leading to oxidative stress and cell death. A number of human diseases, particularly neurodegenerative disorders, have been linked to the dysregulation of mitophagy. In this mini-review, we aimed to review the molecular mechanisms involved in the regulation of mitophagy and their relationship with redox signaling and oxidative stress.
    Keywords:  autophagy; fission; fusion; mitochondrial dynamics
    DOI:  https://doi.org/10.1016/j.mito.2020.01.002
  8. Trends Biochem Sci. 2020 Jan 16. pii: S0968-0004(19)30263-4. [Epub ahead of print]
    Fernández-García J, Altea-Manzano P, Pranzini E, Fendt SM.
      Metabolism is at the cornerstone of all cellular functions and mounting evidence of its deregulation in different diseases emphasizes the importance of a comprehensive understanding of metabolic regulation at the whole-organism level. Stable-isotope measurements are a powerful tool for probing cellular metabolism and, as a result, are increasingly used to study metabolism in in vivo settings. The additional complexity of in vivo metabolic measurements requires paying special attention to experimental design and data interpretation. Here, we review recent work where in vivo stable-isotope measurements have been used to address relevant biological questions within an in vivo context, summarize different experimental and data interpretation approaches and their limitations, and discuss future opportunities in the field.
    Keywords:  in vivo metabolism; metabolic models; stable-isotope tracers; tracer analysis
    DOI:  https://doi.org/10.1016/j.tibs.2019.12.002
  9. Cell. 2020 Jan 23. pii: S0092-8674(19)31397-2. [Epub ahead of print]180(2): 296-310.e18
    Hughes CE, Coody TK, Jeong MY, Berg JA, Winge DR, Hughes AL.
      Mitochondria and lysosomes are functionally linked, and their interdependent decline is a hallmark of aging and disease. Despite the long-standing connection between these organelles, the function(s) of lysosomes required to sustain mitochondrial health remains unclear. Here, working in yeast, we show that the lysosome-like vacuole maintains mitochondrial respiration by spatially compartmentalizing amino acids. Defects in vacuole function result in a breakdown in intracellular amino acid homeostasis, which drives age-related mitochondrial decline. Among amino acids, we find that cysteine is most toxic for mitochondria and show that elevated non-vacuolar cysteine impairs mitochondrial respiration by limiting intracellular iron availability through an oxidant-based mechanism. Cysteine depletion or iron supplementation restores mitochondrial health in vacuole-impaired cells and prevents mitochondrial decline during aging. These results demonstrate that cysteine toxicity is a major driver of age-related mitochondrial deterioration and identify vacuolar amino acid compartmentation as a cellular strategy to minimize amino acid toxicity.
    Keywords:  V-ATPase; aging; amino acid; cysteine; iron; lysosome; mitochondria; vacuole; yeast
    DOI:  https://doi.org/10.1016/j.cell.2019.12.035
  10. Sci Rep. 2020 Jan 23. 10(1): 1021
    Salehi R, Mazier HL, Nivet AL, Reunov AA, Lima P, Wang Q, Fiocco A, Isidoro C, Tsang BK.
      In this study, we investigated in an androgenized rat model the involvement of autophagy and mitochondrial dynamics in granulosa cells in the pathogenesis of polycystic ovarian syndrome (PCOS) and its modulation by exogenous gonadotropin (eCG). We found 5α-dihydrotestosterone (DHT) treatment reduces ovarian length and weight with predominantly late antral and/or preovulatory stage follicles and no corpora lutea. DHT increased the population of large lysosomes (>50 micron) and macroautophagy, an event associated with granulosa cell apoptosis. Increased granulosa cell Dynamin Related Protein 1 (Drp1) content in the DHT group was accompanied by increased circular and constricted, but reduced rod-shaped, mitochondria. eCG eliminated all atypical follicles and increased the number of late antral and preovulatory follicles with less granulosa cell apoptosis. eCG-treated rats had a higher proportion of connected mitochondria, and in combination with DHT had a lower proportion of circular and constricted mitochondria than rats treated with DHT alone, suggesting that eCG induces mitochondrial fusion and attenuates fission in granulosa cells. In summary, we observed that DHT-induced up-regulation of Drp1 is associated with excessive mitochondrial fission, macroautophagy and apoptosis in granulosa cells at the antral stage of development in an androgenized rat model for PCOS, a response partially attenuated by exogenous gonadotropin.
    DOI:  https://doi.org/10.1038/s41598-020-57672-w
  11. Plants (Basel). 2020 Jan 17. pii: E117. [Epub ahead of print]9(1):
    Toleco MR, Naake T, Zhang Y, Heazlewood JL, R Fernie A.
      The evolution of membrane-bound organelles among eukaryotes led to a highly compartmentalized metabolism. As a compartment of the central carbon metabolism, mitochondria must be connected to the cytosol by molecular gates that facilitate a myriad of cellular processes. Members of the mitochondrial carrier family function to mediate the transport of metabolites across the impermeable inner mitochondrial membrane and, thus, are potentially crucial for metabolic control and regulation. Here, we focus on members of this family that might impact intracellular central plant carbon metabolism. We summarize and review what is currently known about these transporters from in vitro transport assays and in planta physiological functions, whenever available. From the biochemical and molecular data, we hypothesize how these relevant transporters might play a role in the shuttling of organic acids in the various flux modes of the TCA cycle. Furthermore, we also review relevant mitochondrial carriers that may be vital in mitochondrial oxidative phosphorylation. Lastly, we survey novel experimental approaches that could possibly extend and/or complement the widely accepted proteoliposome reconstitution approach.
    Keywords:  MCF; TCA cycle; mitochondrial carriers; oxidative phosphorylation; transporters
    DOI:  https://doi.org/10.3390/plants9010117
  12. Nat Commun. 2020 Jan 23. 11(1): 454
    Corbet C, Bastien E, Santiago de Jesus JP, Dierge E, Martherus R, Vander Linden C, Doix B, Degavre C, Guilbaud C, Petit L, Michiels C, Dessy C, Larondelle Y, Feron O.
      Acidosis, a common characteristic of the tumor microenvironment, is associated with alterations in metabolic preferences of cancer cells and progression of the disease. Here we identify the TGF-β2 isoform at the interface between these observations. We document that acidic pH promotes autocrine TGF-β2 signaling, which in turn favors the formation of lipid droplets (LD) that represent energy stores readily available to support anoikis resistance and cancer cell invasiveness. We find that, in cancer cells of various origins, acidosis-induced TGF-β2 activation promotes both partial epithelial-to-mesenchymal transition (EMT) and fatty acid metabolism, the latter supporting Smad2 acetylation. We show that upon TGF-β2 stimulation, PKC-zeta-mediated translocation of CD36 facilitates the uptake of fatty acids that are either stored as triglycerides in LD through DGAT1 or oxidized to generate ATP to fulfill immediate cellular needs. We also address how, by preventing fatty acid mobilization from LD, distant metastatic spreading may be inhibited.
    DOI:  https://doi.org/10.1038/s41467-019-14262-3
  13. Cell Death Dis. 2020 Jan 23. 11(1): 51
    Turchi R, Tortolici F, Guidobaldi G, Iacovelli F, Falconi M, Rufini S, Faraonio R, Casagrande V, Federici M, De Angelis L, Carotti S, Francesconi M, Zingariello M, Morini S, Bernardini R, Mattei M, Rosa P, Piemonte F, Lettieri-Barbato D, Aquilano K.
      Decreased expression of mitochondrial frataxin (FXN) causes Friedreich's ataxia (FRDA), a neurodegenerative disease with type 2 diabetes (T2D) as severe comorbidity. Brown adipose tissue (BAT) is a mitochondria-enriched and anti-diabetic tissue that turns excess energy into heat to maintain metabolic homeostasis. Here we report that the FXN knock-in/knock-out (KIKO) mouse shows hyperlipidemia, reduced energy expenditure and insulin sensitivity, and elevated plasma leptin, recapitulating T2D-like signatures. FXN deficiency leads to disrupted mitochondrial ultrastructure and oxygen consumption as well as lipid accumulation in BAT. Transcriptomic data highlights cold intolerance in association with iron-mediated cell death (ferroptosis). Impaired PKA-mediated lipolysis and expression of genes controlling mitochondrial metabolism, lipid catabolism and adipogenesis were observed in BAT of KIKO mice as well as in FXN-deficient T37i brown and primary adipocytes. Significant susceptibility to ferroptosis was observed in adipocyte precursors that showed increased lipid peroxidation and decreased glutathione peroxidase 4. Collectively our data point to BAT dysfunction in FRDA and suggest BAT as promising therapeutic target to overcome T2D in FRDA.
    DOI:  https://doi.org/10.1038/s41419-020-2253-2
  14. Exp Mol Med. 2020 Jan 24.
    Lieu EL, Nguyen T, Rhyne S, Kim J.
      Over 90 years ago, Otto Warburg's seminal discovery of aerobic glycolysis established metabolic reprogramming as one of the first distinguishing characteristics of cancer1. The field of cancer metabolism subsequently revealed additional metabolic alterations in cancer by focusing on central carbon metabolism, including the citric acid cycle and pentose phosphate pathway. Recent reports have, however, uncovered substantial non-carbon metabolism contributions to cancer cell viability and growth. Amino acids, nutrients vital to the survival of all cell types, experience reprogrammed metabolism in cancer. This review outlines the diverse roles of amino acids within the tumor and in the tumor microenvironment. Beyond their role in biosynthesis, they serve as energy sources and help maintain redox balance. In addition, amino acid derivatives contribute to epigenetic regulation and immune responses linked to tumorigenesis and metastasis. Furthermore, in discussing the transporters and transaminases that mediate amino acid uptake and synthesis, we identify potential metabolic liabilities as targets for therapeutic intervention.
    DOI:  https://doi.org/10.1038/s12276-020-0375-3
  15. Cell Rep. 2020 Jan 21. pii: S2211-1247(19)31708-5. [Epub ahead of print]30(3): 725-738.e4
    Zhang W, Gong J, Yang H, Wan L, Peng Y, Wang X, Sun J, Li F, Geng Y, Li D, Liu N, Mei G, Cao Y, Yan Q, Li H, Zhang Y, He X, Zhang Q, Zhang R, Wu F, Zhong H, Wei C.
      Recent reports have shown the critical role of the mitochondrial antiviral signaling (MAVS) protein in virus-induced apoptosis, but the involvement of MAVS in tumorigenesis is still poorly understood. Herein, we report that MAVS is a key regulator of p53 activation and is critical for protecting against tumorigenesis. We find that MAVS promotes p53-dependent cell death in response to DNA damage. MAVS interacts with p53 and mediates p53 mitochondrial recruitment under genotoxic stress. Mechanistically, MAVS inhibits p53 ubiquitination by blocking the formation of the p53-murine double-minute 2 (MDM2) complex, leading to the stabilization of p53. Notably, compared with their wild-type littermates, MAVS knockout mice display decreased resistance to azoxymethane (AOM) or AOM/dextran sulfate sodium salt (DSS)-induced colon cancer. MAVS expression is significantly downregulated in human colon cancer tissues. These results unveil roles for MAVS in DNA damage response and tumor suppression.
    Keywords:  MAVS; p53; tumor suppression; ubiquitination
    DOI:  https://doi.org/10.1016/j.celrep.2019.12.051
  16. FASEB J. 2020 Jan 19.
    Al Amir Dache Z, Otandault A, Tanos R, Pastor B, Meddeb R, Sanchez C, Arena G, Lasorsa L, Bennett A, Grange T, El Messaoudi S, Mazard T, Prevostel C, Thierry AR.
      Mitochondria are considered as the power-generating units of the cell due to their key role in energy metabolism and cell signaling. However, mitochondrial components could be found in the extracellular space, as fragments or encapsulated in vesicles. In addition, this intact organelle has been recently reported to be released by platelets exclusively in specific conditions. Here, we demonstrate for the first time, that blood preparation with resting platelets, contains whole functional mitochondria in normal physiological state. Likewise, we show, that normal and tumor cultured cells are able to secrete their mitochondria. Using serial centrifugation or filtration followed by polymerase chain reaction-based methods, and Whole Genome Sequencing, we detect extracellular full-length mitochondrial DNA in particles over 0.22 µm holding specific mitochondrial membrane proteins. We identify these particles as intact cell-free mitochondria using fluorescence-activated cell sorting analysis, fluorescence microscopy, and transmission electron microscopy. Oxygen consumption analysis revealed that these mitochondria are respiratory competent. In view of previously described mitochondrial potential in intercellular transfer, this discovery could greatly widen the scope of cell-cell communication biology. Further steps should be developed to investigate the potential role of mitochondria as a signaling organelle outside the cell and to determine whether these circulating units could be relevant for early detection and prognosis of various diseases.
    Keywords:  blood; circulating DNA; mitochondria; mitochondrial genome; respiratory competent
    DOI:  https://doi.org/10.1096/fj.201901917RR
  17. J Inherit Metab Dis. 2020 Jan 18.
    Bleeker JC, Visser G, Clarke K, Ferdinandusse S, de Haan FH, Houtkooper RH, IJlst L, Kok IL, Langeveld M, van der Pol WL, de Sain-van der Velden MGM, Sibeijn-Kuiper A, Takken T, Wanders RJA, van Weeghel M, Wijburg FA, van der Woude LH, Wüst RCI, Cox PJ, Jeneson JAL.
      BACKGROUND: A maladaptive shift from fat to carbohydrate (CHO) oxidation during exercise is thought to underlie myopathy and exercise-induced rhabdomyolysis in patients with fatty acid oxidation (FAO) disorders. We hypothesized that ingestion of a ketone ester (KE) drink prior to exercise could serve as an alternative oxidative substrate supply to boost muscular ATP homeostasis. To establish a rational basis for therapeutic use of KE supplementation in FAO, we tested this hypothesis in patients deficient in Very Long-Chain acyl-CoA Dehydrogenase (VLCAD).METHODS: Five patients (range 17-45 y; 4M/1F) patients were included in an investigator-initiated, randomized, blinded, placebo-controlled, 2-way cross-over study. Patients drank either a KE+CHO mix or an isocaloric CHO equivalent and performed 35 min upright cycling followed by 10 minutes supine cycling inside a Magnetic Resonance scanner at individual maximal FAO work rate (fatmax; ~40% VO2 max). The protocol was repeated after a one-week interval with the alternate drink. Primary outcome measures were quadriceps phosphocreatine (PCr), Pi and pH dynamics during exercise and recovery assayed by in vivo 31 P-MR spectroscopy. Secondary outcomes included plasma and muscle metabolites and respiratory gas exchange recordings.
    RESULTS: Ingestion of KE rapidly induced mild ketosis and increased muscle BHB content. During exercise at FATMAX, VLCADD-specific plasma acylcarnitine levels, quadriceps glycolytic intermediate levels and in vivo Pi/PCr ratio were all lower in KE+CHO than CHO.
    CONCLUSION: These results provide a rational basis for future clinical trials of synthetic ketone ester supplementation therapy in patients with FAO disorders. This article is protected by copyright. All rights reserved.
    Keywords:  VLCADD; fatty acid oxidation; in vivo 31P MRS; ketone ester; mitochondrial energy transduction; muscle; nutritional ketosis; very long-chain acyl-CoA dehydrogenase
    DOI:  https://doi.org/10.1002/jimd.12217
  18. Proc Natl Acad Sci U S A. 2020 Jan 21. pii: 201917968. [Epub ahead of print]
    Toth A, Meyrat A, Stoldt S, Santiago R, Wenzel D, Jakobs S, von Ballmoos C, Ott M.
      Mitochondria have a characteristic ultrastructure with invaginations of the inner membrane called cristae that contain the protein complexes of the oxidative phosphorylation system. How this particular morphology of the respiratory membrane impacts energy conversion is currently unknown. One proposed role of cristae formation is to facilitate the establishment of local proton gradients to fuel ATP synthesis. Here, we determined the local pH values at defined sublocations within mitochondria of respiring yeast cells by fusing a pH-sensitive GFP to proteins residing in different mitochondrial subcompartments. Only a small proton gradient was detected over the inner membrane in wild type or cristae-lacking cells. Conversely, the obtained pH values did barely permit ATP synthesis in a reconstituted system containing purified yeast F1F0 ATP synthase, although, thermodynamically, a sufficiently high driving force was applied. At higher driving forces, where robust ATP synthesis was observed, a P-side pH value of 6 increased the ATP synthesis rate 3-fold compared to pH 7. In contrast, when ATP synthase was coreconstituted with an active proton-translocating cytochrome oxidase, ATP synthesis readily occurred at the measured, physiological pH values. Our study thus reveals that the morphology of the inner membrane does not influence the subcompartmental pH values and is not necessary for robust oxidative phosphorylation in mitochondria. Instead, it is likely that the dense packing of the oxidative phosphorylation complexes in the cristae membranes assists kinetic coupling between proton pumping and ATP synthesis.
    Keywords:  ATP synthesis; cristae; energy conversion; kinetic coupling; mitochondria
    DOI:  https://doi.org/10.1073/pnas.1917968117
  19. Nat Commun. 2020 Jan 21. 11(1): 409
    Eisenberg-Lerner A, Benyair R, Hizkiahou N, Nudel N, Maor R, Kramer MP, Shmueli MD, Zigdon I, Cherniavsky Lev M, Ulman A, Sagiv JY, Dayan M, Dassa B, Rosenwald M, Shachar I, Li J, Wang Y, Dezorella N, Khan S, Porat Z, Shimoni E, Avinoam O, Merbl Y.
      The Golgi is a dynamic organelle whose correct assembly is crucial for cellular homeostasis. Perturbations in Golgi structure are associated with numerous disorders from neurodegeneration to cancer. However, whether and how dispersal of the Golgi apparatus is actively regulated under stress, and the consequences of Golgi dispersal, remain unknown. Here we demonstrate that 26S proteasomes are associated with the cytosolic surface of Golgi membranes to facilitate Golgi Apparatus-Related Degradation (GARD) and degradation of GM130 in response to Golgi stress. The degradation of GM130 is dependent on p97/VCP and 26S proteasomes, and required for Golgi dispersal. Finally, we show that perturbation of Golgi homeostasis induces cell death of multiple myeloma in vitro and in vivo, offering a therapeutic strategy for this malignancy. Taken together, this work reveals a mechanism of Golgi-localized proteasomal degradation, providing a functional link between proteostasis control and Golgi architecture, which may be critical in various secretion-related pathologies.
    DOI:  https://doi.org/10.1038/s41467-019-14038-9
  20. Cancers (Basel). 2020 Jan 23. pii: E280. [Epub ahead of print]12(2):
    Liu Y, Pang Y, Caisova V, Ding J, Yu D, Zhou Y, Huynh TT, Ghayee H, Pacak K, Yang C.
      Succinate dehydrogenase subunit B (SDHB) deficiency frequently occurs in cluster I pheochromocytomas and paragangliomas (PCPGs). SDHB-mutated PCPGs are characterized by alterations in the electron transport chain, metabolic reprogramming of the tricarboxylic cycle, and elevated levels of reactive oxygen species (ROS). We discovered that SDHB-deficient PCPG cells exhibit increased oxidative stress burden, which leads to elevated demands for glutathione metabolism. Mechanistically, nuclear factor erythroid 2-related factor 2 (NRF2)-guided glutathione de novo synthesis plays a key role in supporting cellular survival and the proliferation of SDHB-knockdown (SDHBKD) cells. NRF2 blockade not only disrupted ROS homeostasis in SDHB-deficient cells but also caused severe cytotoxicity by the accumulation of DNA oxidative damage. Brusatol, a potent NRF2 inhibitor, showed a promising effect in suppressing SDHBKD metastatic lesions in vivo, with prolonged overall survival in mice bearing PCPG allografts. Our findings highlight a novel therapeutic strategy of targeting the NRF2-driven glutathione metabolic pathway against SDHB-mutated PCPG.
    Keywords:  NRF2; SDHB mutation; glutathione metabolism; paraganglioma; pheochromocytoma
    DOI:  https://doi.org/10.3390/cancers12020280
  21. Cell. 2020 Jan 23. pii: S0092-8674(19)31379-0. [Epub ahead of print]180(2): 278-295.e23
    Cader MZ, de Almeida Rodrigues RP, West JA, Sewell GW, Md-Ibrahim MN, Reikine S, Sirago G, Unger LW, Inglesias-Romero AB, Ramshorn K, Haag LM, Saveljeva S, Ebel JF, Rosenstiel P, Kaneider NC, Lee JC, Lawley TD, Bradley A, Dougan G, Modis Y, Griffin JL, Kaser A.
      Mutations in FAMIN cause arthritis and inflammatory bowel disease in early childhood, and a common genetic variant increases the risk for Crohn's disease and leprosy. We developed an unbiased liquid chromatography-mass spectrometry screen for enzymatic activity of this orphan protein. We report that FAMIN phosphorolytically cleaves adenosine into adenine and ribose-1-phosphate. Such activity was considered absent from eukaryotic metabolism. FAMIN and its prokaryotic orthologs additionally have adenosine deaminase, purine nucleoside phosphorylase, and S-methyl-5'-thioadenosine phosphorylase activity, hence, combine activities of the namesake enzymes of central purine metabolism. FAMIN enables in macrophages a purine nucleotide cycle (PNC) between adenosine and inosine monophosphate and adenylosuccinate, which consumes aspartate and releases fumarate in a manner involving fatty acid oxidation and ATP-citrate lyase activity. This macrophage PNC synchronizes mitochondrial activity with glycolysis by balancing electron transfer to mitochondria, thereby supporting glycolytic activity and promoting oxidative phosphorylation and mitochondrial H+ and phosphate recycling.
    Keywords:  C13orf31; Crohn's disease; FAMIN; LACC1; Still's disease; immunometabolism; pH homeostasis; purine metabolism; purine nucleotide cycle; redox homeostasis
    DOI:  https://doi.org/10.1016/j.cell.2019.12.017
  22. Curr Opin Biotechnol. 2020 Jan 15. pii: S0958-1669(19)30146-6. [Epub ahead of print]63 111-117
    Britt EC, John SV, Locasale JW, Fan J.
      Immune cells are capable of sensing various signals in the microenvironment and turning on specific immune functions in response. The appropriate transition of immune cells into diverse functional states, which is crucial for immunity, involves complex and well-regulated changes in transcriptional program. Accumulating evidence shows that epigenetic remodeling plays a central role in mediating the transcriptional program for immune cell activation and immunological memory. Concurrently, immune cells undergo significant metabolic reprogramming during immune response. Here we review recent studies that demonstrate shifts in metabolic state can orchestrate immune cell functions through its impact on epigenetic remodeling, and the microenvironment can exert its influence on immune cells through the metabolic regulation of epigenetics. We also discuss the systems biology approaches that enabled these discoveries.
    DOI:  https://doi.org/10.1016/j.copbio.2019.12.008
  23. Leukemia. 2020 Jan 23.
    Gerner RR, Macheiner S, Reider S, Siegmund K, Grabherr F, Mayr L, Texler B, Moser P, Effenberger M, Schwaighofer H, Moschen AR, Kircher B, Oberacher H, Zeiser R, Tilg H, Nachbaur D.
      Acute graft-versus-host disease (aGVHD) and tumor relapse remain major complications after allogeneic hematopoietic stem cell transplantation. Alloreactive T cells and cancer cells share a similar metabolic phenotype to meet the bioenergetic demands necessary for cellular proliferation and effector functions. Nicotinamide adenine dinucleotide (NAD) is an essential co-factor in energy metabolism and is constantly replenished by nicotinamide phosphoribosyl-transferase (Nampt), the rate-limiting enzyme in the NAD salvage pathway. Here we show, that Nampt blockage strongly ameliorates aGVHD and limits leukemic expansion. Nampt was highly elevated in serum of patients with gastrointestinal GVHD and was particularly abundant in human and mouse intestinal T cells. Therapeutic application of the Nampt small-molecule inhibitor, Fk866, strongly attenuated experimental GVHD and caused NAD depletion in T-cell subsets, which displayed differential susceptibility to NAD shortage. Fk866 robustly inhibited expansion of alloreactive but not memory T cells and promoted FoxP3-mediated lineage stability in regulatory T cells. Furthermore, Fk866 strongly reduced the tumor burden in mouse leukemia and graft-versus-leukemia models. Ex vivo studies using lymphocytes from GVHD patients demonstrated potent antiproliferative properties of Fk866, suggesting potential clinical utility. Thus, targeting NAD immunometabolism represents a novel approach to selectively inhibit alloreactive T cells during aGVHD with additional antileukemic efficacy.
    DOI:  https://doi.org/10.1038/s41375-020-0709-0
  24. Proc Natl Acad Sci U S A. 2020 Jan 21. pii: 201913841. [Epub ahead of print]
    Gallagher FA, Woitek R, McLean MA, Gill AB, Manzano Garcia R, Provenzano E, Riemer F, Kaggie J, Chhabra A, Ursprung S, Grist JT, Daniels CJ, Zaccagna F, Laurent MC, Locke M, Hilborne S, Frary A, Torheim T, Boursnell C, Schiller A, Patterson I, Slough R, Carmo B, Kane J, Biggs H, Harrison E, Deen SS, Patterson A, Lanz T, Kingsbury Z, Ross M, Basu B, Baird R, Lomas DJ, Sala E, Wason J, Rueda OM, Chin SF, Wilkinson IB, Graves MJ, Abraham JE, Gilbert FJ, Caldas C, Brindle KM.
      Our purpose is to investigate the feasibility of imaging tumor metabolism in breast cancer patients using 13C magnetic resonance spectroscopic imaging (MRSI) of hyperpolarized 13C label exchange between injected [1-13C]pyruvate and the endogenous tumor lactate pool. Treatment-naïve breast cancer patients were recruited: four triple-negative grade 3 cancers; two invasive ductal carcinomas that were estrogen and progesterone receptor-positive (ER/PR+) and HER2/neu-negative (HER2-), one grade 2 and one grade 3; and one grade 2 ER/PR+ HER2- invasive lobular carcinoma (ILC). Dynamic 13C MRSI was performed following injection of hyperpolarized [1-13C]pyruvate. Expression of lactate dehydrogenase A (LDHA), which catalyzes 13C label exchange between pyruvate and lactate, hypoxia-inducible factor-1 (HIF1α), and the monocarboxylate transporters MCT1 and MCT4 were quantified using immunohistochemistry and RNA sequencing. We have demonstrated the feasibility and safety of hyperpolarized 13C MRI in early breast cancer. Both intertumoral and intratumoral heterogeneity of the hyperpolarized pyruvate and lactate signals were observed. The lactate-to-pyruvate signal ratio (LAC/PYR) ranged from 0.021 to 0.473 across the tumor subtypes (mean ± SD: 0.145 ± 0.164), and a lactate signal was observed in all of the grade 3 tumors. The LAC/PYR was significantly correlated with tumor volume (R = 0.903, P = 0.005) and MCT 1 (R = 0.85, P = 0.032) and HIF1α expression (R = 0.83, P = 0.043). Imaging of hyperpolarized [1-13C]pyruvate metabolism in breast cancer is feasible and demonstrated significant intertumoral and intratumoral metabolic heterogeneity, where lactate labeling correlated with MCT1 expression and hypoxia.
    Keywords:  breast cancer; cancer metabolism; magnetic resonance imaging; metabolic imaging
    DOI:  https://doi.org/10.1073/pnas.1913841117
  25. Cell. 2020 Jan 23. pii: S0092-8674(19)31385-6. [Epub ahead of print]180(2): 387-402.e16
    Nusinow DP, Szpyt J, Ghandi M, Rose CM, McDonald ER, Kalocsay M, Jané-Valbuena J, Gelfand E, Schweppe DK, Jedrychowski M, Golji J, Porter DA, Rejtar T, Wang YK, Kryukov GV, Stegmeier F, Erickson BK, Garraway LA, Sellers WR, Gygi SP.
      Proteins are essential agents of biological processes. To date, large-scale profiling of cell line collections including the Cancer Cell Line Encyclopedia (CCLE) has focused primarily on genetic information whereas deep interrogation of the proteome has remained out of reach. Here, we expand the CCLE through quantitative profiling of thousands of proteins by mass spectrometry across 375 cell lines from diverse lineages to reveal information undiscovered by DNA and RNA methods. We observe unexpected correlations within and between pathways that are largely absent from RNA. An analysis of microsatellite instable (MSI) cell lines reveals the dysregulation of specific protein complexes associated with surveillance of mutation and translation. These and other protein complexes were associated with sensitivity to knockdown of several different genes. These data in conjunction with the wider CCLE are a broad resource to explore cellular behavior and facilitate cancer research.
    Keywords:  CCLE; MSI; RNA/Protein correlation; TMT; cancer cell lines; microsatellite instability; protein expression; quantitative proteomics; systems biology
    DOI:  https://doi.org/10.1016/j.cell.2019.12.023
  26. Methods Appl Fluoresc. 2020 Jan 23.
    Cao R, Wallrabe H, Siller K, Periasamy A.
      Increasingly, the auto-fluorescent coenzymes NAD(P)H and FAD are being tracked by multi-photon fluorescence lifetime microscopy (FLIM) and used as versatile markers for changes in mammalian metabolism. The cellular redox state of different cell model systems, organoids and tissue sections is investigated in a range of pathologies where the metabolism is disrupted or reprogrammed; the latter is particularly relevant in cancer biology. Yet, the actual optimized process of acquiring images by FLIM, execute a correct lifetime fitting procedure and subsequent processing and analysis can be challenging for new users. Questions remain of how to optimize FLIM experiments, whether any potential photo-bleaching affects FLIM results and whether fixed specimens can be used in experiments. We have broken down the multi-step sequence into best-practice application of FLIM for NAD(P)H and FAD imaging, with images generated by a time-correlated-single-photon-counting (TCSPC) system, fitted with Becker & Hickl software and further processed with open-source ImageJ/Fiji and Python software.
    Keywords:  FAD; FLIM; Metabolic Imaging; Multiphoton; NAD(P)H
    DOI:  https://doi.org/10.1088/2050-6120/ab6f25
  27. Nat Commun. 2020 Jan 22. 11(1): 431
    Brunner JS, Vulliard L, Hofmann M, Kieler M, Lercher A, Vogel A, Russier M, Brüggenthies JB, Kerndl M, Saferding V, Niederreiter B, Junza A, Frauenstein A, Scholtysek C, Mikami Y, Klavins K, Krönke G, Bergthaler A, O'Shea JJ, Weichhart T, Meissner F, Smolen JS, Cheng P, Yanes O, Menche J, Murray PJ, Sharif O, Blüml S, Schabbauer G.
      Multinucleated giant cells (MGCs) are implicated in many diseases including schistosomiasis, sarcoidosis and arthritis. MGC generation is energy intensive to enforce membrane fusion and cytoplasmic expansion. Using receptor activator of nuclear factor kappa-Β ligand (RANKL) induced osteoclastogenesis to model MGC formation, here we report RANKL cellular programming requires extracellular arginine. Systemic arginine restriction improves outcome in multiple murine arthritis models and its removal induces preosteoclast metabolic quiescence, associated with impaired tricarboxylic acid (TCA) cycle function and metabolite induction. Effects of arginine deprivation on osteoclastogenesis are independent of mTORC1 activity or global transcriptional and translational inhibition. Arginine scarcity also dampens generation of IL-4 induced MGCs. Strikingly, in extracellular arginine absence, both cell types display flexibility as their formation can be restored with select arginine precursors. These data establish how environmental amino acids control the metabolic fate of polykaryons and suggest metabolic ways to manipulate MGC-associated pathologies and bone remodelling.
    DOI:  https://doi.org/10.1038/s41467-020-14285-1
  28. Nat Biotechnol. 2020 Jan 20.
    Hijazi M, Smith R, Rajeeve V, Bessant C, Cutillas PR.
      Understanding how oncogenic mutations rewire regulatory-protein networks is important for rationalizing the mechanisms of oncogenesis and for individualizing anticancer treatments. We report a chemical phosphoproteomics method to elucidate the topology of kinase-signaling networks in mammalian cells. We identified >6,000 protein phosphorylation sites that can be used to infer >1,500 kinase-kinase interactions and devised algorithms that can reconstruct kinase network topologies from these phosphoproteomics data. Application of our methods to primary acute myeloid leukemia and breast cancer tumors quantified the relationship between kinase expression and activity, and enabled the identification of hitherto unknown kinase network topologies associated with drug-resistant phenotypes or specific genetic mutations. Using orthogonal methods we validated that PIK3CA wild-type cells adopt MAPK-dependent circuitries in breast cancer cells and that the kinase TTK is important in acute myeloid leukemia. Our phosphoproteomic signatures of network circuitry can identify kinase topologies associated with both phenotypes and genotypes of cancer cells.
    DOI:  https://doi.org/10.1038/s41587-019-0391-9