bims-camemi Biomed News
on Mitochondrial metabolism in cancer
Issue of 2019‒06‒09
fifty-four papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit


  1. Semin Cell Dev Biol. 2019 May 30. pii: S1084-9521(18)30169-1. [Epub ahead of print]
    Ferro F, Servais S, Besson P, Roger S, Dumas JF, Brisson L.
      Metabolic reprogramming in tumours is now recognized as a hallmark of cancer, participating both in tumour growth and cancer progression. Cancer cells develop global metabolic adaptations allowing them to survive in the low oxygen and nutrient tumour microenvironment. Among these metabolic adaptations, cancer cells use glycolysis but also mitochondrial oxidations to produce ATP and building blocks needed for their high proliferation rate. Another particular adaptation of cancer cell metabolism is the use of autophagy and specific forms of autophagy like mitophagy to recycle intracellular components in condition of metabolic stress or during anticancer treatments. The plasticity of cancer cell metabolism is a major limitation of anticancer treatments and could participate to therapy resistances. The aim of this review is to report recent advances in the understanding of the relationship between tumour metabolism and autophagy/mitophagy in order to propose new therapeutic strategies.
    Keywords:  Cancer metabolism; ROS; autophagy; ion channel; mitochondria; mitophagy
    DOI:  https://doi.org/10.1016/j.semcdb.2019.05.029
  2. Methods Enzymol. 2019 ;pii: S0076-6879(19)30056-4. [Epub ahead of print]622 431-448
    Briney CA, Najera S, Meier JL.
      Dysregulated cellular metabolism is an emerging hallmark of cancer. Improved methods to profile aberrant metabolic activity thus have substantial applications as tools for diagnosis and understanding the biology of malignant tumors. Here we describe the utilization of a bioorthogonal ligation to fluorescently detect the TCA cycle oncometabolite fumarate. This method enables the facile measurement of fumarate hydratase activity in cell and tissue samples, and can be used to detect disruptions in metabolism that underlie the genetic cancer syndrome hereditary leiomyomatosis and renal cell cancer (HLRCC). The current method has substantial utility for sensitive fumarate hydratase activity profiling, and also provides a foundation for future applications in diagnostic detection and imaging of cancer metabolism.
    Keywords:  Bioorthogonal; Bioorthogonal oncometabolite ligation: HLRCC; Click chemistry; Cycloaddition; Fluorogenic; Fumarate; Fumarate hydratase; Hereditary cancer; Profiling; Sensor; Tetrazole
    DOI:  https://doi.org/10.1016/bs.mie.2019.02.037
  3. Cancer Metab. 2019 ;7 6
    Røsland GV, Dyrstad SE, Tusubira D, Helwa R, Tan TZ, Lotsberg ML, Pettersen IKN, Berg A, Kindt C, Hoel F, Jacobsen K, Arason AJ, Engelsen AST, Ditzel HJ, Lønning PE, Krakstad C, Thiery JP, Lorens JB, Knappskog S, Tronstad KJ.
      Background: Epithelial to mesenchymal transition (EMT) is a well-characterized process of cell plasticity that may involve metabolic rewiring. In cancer, EMT is associated with malignant progression, tumor heterogeneity, and therapy resistance. In this study, we investigated the role of succinate dehydrogenase (SDH) as a potential key regulator of EMT.Methods: Associations between SDH subunits and EMT were explored in gene expression data from breast cancer patient cohorts, followed by in-depth studies of SDH suppression as a potential mediator of EMT in cultured cells.
    Results: We found an overall inverse association between EMT and the SDH subunit C (SDHC) when analyzing gene expression in breast tumors. This was particularly evident in carcinomas of basal-like molecular subtype compared to non-basal-like tumors, and a low SDHC expression level tended to have a prognostic impact in those patients. Studies in cultured cells revealed that EMT was induced by SDH inhibition through SDHC CRISPR/Cas9 knockdown or by the enzymatic inhibitor malonate. Conversely, overexpression of EMT-promoting transcription factors TWIST and SNAI2 caused decreased levels of SDHB and C and reduced rates of SDH-linked mitochondrial respiration. Cells overexpressing TWIST had reduced mitochondrial mass, and the organelles were thinner and more fragmented compared to controls.
    Conclusions: Our findings suggest that downregulation of SDHC promotes EMT and that this is accompanied by structural remodeling of the mitochondrial organelles. This may confer survival benefits upon exposure to hostile microenvironment including oxidative stress and hypoxia during cancer progression.
    Keywords:  Breast cancer; Cell metabolism; Cell plasticity; Mitochondria; SDH
    DOI:  https://doi.org/10.1186/s40170-019-0197-8
  4. J Biol Chem. 2019 Jun 03. pii: jbc.RA119.008775. [Epub ahead of print]
    Guo L, Carraro M, Carrer A, Minervini G, Urbani A, Masgras I, Tosatto SCE, Szabò I, Bernardi P, Lippe G.
      The mitochondrial F-ATP synthase is a complex molecular motor arranged in V-shaped dimers that is responsible for most cellular ATP synthesis in aerobic conditions. In the yeast F-ATP synthase, subunits e and g of the FO sector constitute a lateral domain, which is required for dimer stability and cristae formation. Here, by using site-directed mutagenesis we identified Arg-8 of subunit e as a critical residue in mediating interactions between subunits e and g, most likely through an interaction with Glu-83 of subunit g. Consistent with this hypothesis (i) substitution of Arg-8 in subunit e (eArg-8) with Ala or Glu or of Glu-83 in subunit g (gGlu-83) with Ala or Lys destabilized the digitonin-extracted F-ATP synthase, resulting in decreased dimer formation, as revealed by blue-native electrophoresis; and (ii) simultaneous substitution of eArg-8 with Glu and of gGlu-83 with Lys rescued digitonin-stable F-ATP synthase dimers. When tested in lipid bilayers for generation of Ca2+-dependent channels, wild-type dimers displayed the high-conductance channel activity expected for the mitochondrial megachannel/permeability transition pore, whereas dimers obtained at low digitonin concentrations from the Arg-8 variants displayed currents of strikingly small conductance. Remarkably, double replacement of eArg-8 with Glu and of gGlu-83 with Lys restored high-conductance channels indistinguishable from those seen in wild-type enzymes. These findings suggest that the interaction of subunit e with subunit g is important for generation of the full-conductance megachannel from F-ATP synthase.
    Keywords:  ATP synthase; dimerization; high-conductance channel; megachannel; mitochondria; mitochondrial permeability transition (MPT); molecular motor; yeast
    DOI:  https://doi.org/10.1074/jbc.RA119.008775
  5. PLoS Genet. 2019 Jun;15(6): e1008085
    Silva Ramos E, Motori E, Brüser C, Kühl I, Yeroslaviz A, Ruzzenente B, Kauppila JHK, Busch JD, Hultenby K, Habermann BH, Jakobs S, Larsson NG, Mourier A.
      Mitochondrial dynamics is an essential physiological process controlling mitochondrial content mixing and mobility to ensure proper function and localization of mitochondria at intracellular sites of high-energy demand. Intriguingly, for yet unknown reasons, severe impairment of mitochondrial fusion drastically affects mtDNA copy number. To decipher the link between mitochondrial dynamics and mtDNA maintenance, we studied mouse embryonic fibroblasts (MEFs) and mouse cardiomyocytes with disruption of mitochondrial fusion. Super-resolution microscopy revealed that loss of outer mitochondrial membrane (OMM) fusion, but not inner mitochondrial membrane (IMM) fusion, leads to nucleoid clustering. Remarkably, fluorescence in situ hybridization (FISH), bromouridine labeling in MEFs and assessment of mitochondrial transcription in tissue homogenates revealed that abolished OMM fusion does not affect transcription. Furthermore, the profound mtDNA depletion in mouse hearts lacking OMM fusion is not caused by defective integrity or increased mutagenesis of mtDNA, but instead we show that mitochondrial fusion is necessary to maintain the stoichiometry of the protein components of the mtDNA replisome. OMM fusion is necessary for proliferating MEFs to recover from mtDNA depletion and for the marked increase of mtDNA copy number during postnatal heart development. Our findings thus link OMM fusion to replication and distribution of mtDNA.
    DOI:  https://doi.org/10.1371/journal.pgen.1008085
  6. Front Physiol. 2019 ;10 517
    Escobar-Henriques M, Joaquim M.
      Mitochondria are dynamic organelles engaged in quality control and aging processes. They constantly undergo fusion, fission, transport, and anchoring events, which empower mitochondria with a very interactive behavior. The membrane remodeling processes needed for fusion require conserved proteins named mitofusins, MFN1 and MFN2 in mammals and Fzo1 in yeast. They are the first determinants deciding on whether communication and content exchange between different mitochondrial populations should occur. Importantly, each cell possesses hundreds of mitochondria, with a different severity of mitochondrial mutations or dysfunctional proteins, which potentially spread damage to the entire network. Therefore, the degree of their merging capacity critically influences cellular fitness. In turn, the mitochondrial network rapidly and dramatically changes in response to metabolic and environmental cues. Notably, cancer or obesity conditions, and stress experienced by neurons and cardiomyocytes, for example, triggers the downregulation of mitofusins and thus fragmentation of mitochondria. This places mitofusins upfront in sensing and transmitting stress. In fact, mitofusins are almost entirely exposed to the cytoplasm, a topology suitable for a critical relay point in information exchange between mitochondria and their cellular environment. Consistent with their topology, mitofusins are either activated or repressed by cytosolic post-translational modifiers, mainly by ubiquitin. Ubiquitin is a ubiquitous small protein orchestrating multiple quality control pathways, which is covalently attached to lysine residues in its substrates, or in ubiquitin itself. Importantly, from a chain of events also mediated by E1 and E2 enzymes, E3 ligases perform the ultimate and determinant step in substrate choice. Here, we review the ubiquitin E3 ligases that modify mitofusins. Two mitochondrial E3 enzymes-March5 and MUL1-one ligase located to the ER-Gp78-and finally three cytosolic enzymes-MGRN1, HUWE1, and Parkin-were shown to ubiquitylate mitofusins, in response to a variety of cellular inputs. The respective outcomes on mitochondrial morphology, on contact sites to the endoplasmic reticulum and on destructive processes, like mitophagy or apoptosis, are presented. Ultimately, understanding the mechanisms by which E3 ligases and mitofusins sense and bi-directionally signal mitochondria-cytosolic dysfunctions could pave the way for therapeutic approaches in neurodegenerative, cardiovascular, and obesity-linked diseases.
    Keywords:  E3 ligases; ER; MFN1/MFN2; mitochondria; mitofusins; mitophagy; quality control; ubiquitin
    DOI:  https://doi.org/10.3389/fphys.2019.00517
  7. Semin Cell Dev Biol. 2019 May 30. pii: S1084-9521(18)30187-3. [Epub ahead of print]
    Abate M, Festa A, Falco M, Lombardi A, Luce A, Grimaldi A, Zappavigna S, Sperlongano P, Irace C, Caraglia M, Misso G.
      Mitochondria are the key energy-producing organelles and cellular source of reactive species. They are responsible for managing cell life and death by a balanced homeostasis passing through a network of structures, regulated principally via fission and fusion. Herein we discuss about the most advanced findings considering mitochondria as dynamic biophysical systems playing compelling roles in the regulation of energy metabolism in both physiologic and pathologic processes controlling cell death and survival. Precisely, we focus on the mitochondrial commitment to the onset, maintenance and counteraction of apoptosis, autophagy and senescence in the bioenergetic reprogramming of cancer cells. In this context, looking for a pharmacological manipulation of cell death processes as a successful route for future targeted therapies, there is major biotechnological challenge in underlining the location, function and molecular mechanism of mitochondrial proteins. Based on the critical role of mitochondrial functions for cellular health, a better knowledge of the main molecular players in mitochondria disfunction could be decisive for the therapeutical control of degenerative diseases, including cancer.
    Keywords:  apoptosis; autophagy; cancer; metabolism; mitochondrion; senescence
    DOI:  https://doi.org/10.1016/j.semcdb.2019.05.022
  8. Trends Cell Biol. 2019 May 31. pii: S0962-8924(19)30084-4. [Epub ahead of print]
    Bose S, Ramesh V, Locasale JW.
      Acetate and the related metabolism of acetyl-coenzyme A (acetyl-CoA) confer numerous metabolic functions, including energy production, lipid synthesis, and protein acetylation. Despite its importance as a nutrient for cellular metabolism, its source has been unclear. Recent studies have provided evidence to support the existence of a de novo pathway for acetate production derived from pyruvate, the end product of glycolysis. This mechanism of pyruvate-derived acetate generation could have far-reaching implications for the regulation of central carbon metabolism. In this Opinion, we discuss our current understanding of acetate metabolism in the context of cell-autonomous metabolic regulation, cell-cell interactions, and systemic physiology. Applications relevant to health and disease, particularly cancer, are emphasized.
    Keywords:  acetate metabolism; alcoholism; cancer; lipogenesis; nutrition
    DOI:  https://doi.org/10.1016/j.tcb.2019.05.005
  9. J Biol Chem. 2019 Jun 06. pii: jbc.RA118.007152. [Epub ahead of print]
    Pestoni JC, Klingeman Plati S, Valdivia Camacho OD, Fuse MA, Onatunde M, Sparrow NA, Karajannis MA, Fernández-Valle C, Franco MC.
      Neurofibromatosis type 2 (NF2) is an autosomal-dominant disorder characterized by the development of bilateral vestibular schwannomas. The NF2 gene encodes the tumor suppressor merlin, and loss of merlin activity promotes tumorigenesis and causes NF2. Cellular redox signaling has been implicated in different stages of tumor development. Among reactive nitrogen species, peroxynitrite is the most powerful oxidant produced by cells. We recently showed that peroxynitrite-mediated tyrosine nitration down-regulates mitochondrial metabolism in tumor cells. However, whether peroxynitrite supports a metabolic shift that could be exploited for therapeutic development is unknown. Here, we show that vestibular schwannomas from NF2 patients and human, merlin-deficient (MD) Schwann cells have high levels of endogenous tyrosine nitration, indicating production of peroxynitrite. Further, scavenging or inhibiting peroxynitrite formation significantly and selectively decreased survival of human and mouse MD-Schwann cells. Using multiple complementary methods, we also found that merlin deficiency leads to a reprogramming of energy metabolism characterized by a peroxynitrite-dependent decrease of oxidative phosphorylation and increased glycolysis and glutaminolysis. In MD Schwann cells, scavenging of peroxynitrite increased mitochondrial oxygen consumption and membrane potential, mediated by the up-regulation of the levels and activity of mitochondrial complex IV. This increase in mitochondrial activity correlated with a decrease in the glycolytic rate and glutamine dependency. This is the first demonstration of a peroxynitrite-dependent reprogramming of energy metabolism in tumor cells. Oxidized proteins constitute a novel target for therapeutic development not only for the treatment of NF2 schwannomas but also other tumors in which peroxynitrite plays a regulatory role.
    Keywords:  Schwann cells; bioenergetics; energy metabolism; merlin; neurofibromatosis; nitration; peroxynitrite; redox signaling; schwannoma; tumor metabolism
    DOI:  https://doi.org/10.1074/jbc.RA118.007152
  10. Nat Cell Biol. 2019 Jun;21(6): 710-720
    Sênos Demarco R, Uyemura BS, D'Alterio C, Jones DL.
      The capacity of stem cells to self-renew or differentiate has been attributed to distinct metabolic states. A genetic screen targeting regulators of mitochondrial dynamics revealed that mitochondrial fusion is required for the maintenance of male germline stem cells (GSCs) in Drosophila melanogaster. Depletion of Mitofusin (dMfn) or Opa1 led to dysfunctional mitochondria, activation of Target of rapamycin (TOR) and a marked accumulation of lipid droplets. Enhancement of lipid utilization by the mitochondria attenuated TOR activation and rescued the loss of GSCs that was caused by inhibition of mitochondrial fusion. Moreover, constitutive activation of the TOR-pathway target and lipogenesis factor Sterol regulatory element binding protein (SREBP) also resulted in GSC loss, whereas inhibition of SREBP rescued GSC loss triggered by depletion of dMfn. Our findings highlight a critical role for mitochondrial fusion and lipid homeostasis in GSC maintenance, providing insight into the potential impact of mitochondrial and metabolic diseases on the function of stem and/or germ cells.
    DOI:  https://doi.org/10.1038/s41556-019-0332-3
  11. Microb Cell. 2019 May 20. 6(6): 286-294
    Corcoles-Saez I, Ferat JL, Costanzo M, Boone CM, Cha RS.
      Ribonucleotide reductase (RNR) is an essential holoenzyme required for de novo synthesis of dNTPs. The Saccharomyces cerevisiae genome encodes for two catalytic subunits, Rnr1 and Rnr3. While Rnr1 is required for DNA replication and DNA damage repair, the function(s) of Rnr3 is unknown. Here, we show that carbon source, an essential nutrient, impacts Rnr1 and Rnr3 abundance: Non-fermentable carbon sources or limiting concentrations of glucose down regulate Rnr1 and induce Rnr3 expression. Oppositely, abundant glucose induces Rnr1 expression and down regulates Rnr3. The carbon source dependent regulation of Rnr3 is mediated by Mec1, the budding yeast ATM/ATR checkpoint response kinase. Unexpectedly, this regulation is independent of all currently known components of the Mec1 DNA damage response network, including Rad53, Dun1, and Tel1, implicating a novel Mec1 signalling axis. rnr3Δ leads to growth defects under respiratory conditions and rescues temperature sensitivity conferred by the absence of Tom6, a component of the mitochondrial TOM (translocase of outer membrane) complex responsible for mitochondrial protein import. Together, these results unveil involvement of Rnr3 in mitochondrial functions and Mec1 in mediating the carbon source dependent regulation of Rnr3.
    Keywords:  Mec1; Rnr1; Rnr3; carbon source; dNTP; mitochondria; respiration
    DOI:  https://doi.org/10.15698/mic2019.06.680
  12. Cell Metab. 2019 May 17. pii: S1550-4131(19)30245-1. [Epub ahead of print]
    Wang W, Ishibashi J, Trefely S, Shao M, Cowan AJ, Sakers A, Lim HW, O'Connor S, Doan MT, Cohen P, Baur JA, King MT, Veech RL, Won KJ, Rabinowitz JD, Snyder NW, Gupta RK, Seale P.
      The precursor cells for metabolically beneficial beige adipocytes can alternatively become fibrogenic and contribute to adipose fibrosis. We found that cold exposure or β3-adrenergic agonist treatment of mice decreased the fibrogenic profile of precursor cells and stimulated beige adipocyte differentiation. This fibrogenic-to-adipogenic transition was impaired in aged animals, correlating with reduced adipocyte expression of the transcription factor PRDM16. Genetic loss of Prdm16 mimicked the effect of aging in promoting fibrosis, whereas increasing PRDM16 in aged mice decreased fibrosis and restored beige adipose development. PRDM16-expressing adipose cells secreted the metabolite β-hydroxybutyrate (BHB), which blocked precursor fibrogenesis and facilitated beige adipogenesis. BHB catabolism in precursor cells, mediated by BDH1, was required for beige fat differentiation in vivo. Finally, dietary BHB supplementation in aged animals reduced adipose fibrosis and promoted beige fat formation. Together, our results demonstrate that adipocytes secrete a metabolite signal that controls beige fat remodeling.
    Keywords:  BDH1; PRDM16; UCP1; adipose fibrosis; beige fat; beta hydroxybutyrate; brown fat; fibro-adipogenic progenitor
    DOI:  https://doi.org/10.1016/j.cmet.2019.05.005
  13. Nat Commun. 2019 Jun 06. 10(1): 2474
    Haythorne E, Rohm M, van de Bunt M, Brereton MF, Tarasov AI, Blacker TS, Sachse G, Silva Dos Santos M, Terron Exposito R, Davis S, Baba O, Fischer R, Duchen MR, Rorsman P, MacRae JI, Ashcroft FM.
      Diabetes is a global health problem caused primarily by the inability of pancreatic β-cells to secrete adequate levels of insulin. The molecular mechanisms underlying the progressive failure of β-cells to respond to glucose in type-2 diabetes remain unresolved. Using a combination of transcriptomics and proteomics, we find significant dysregulation of major metabolic pathways in islets of diabetic βV59M mice, a non-obese, eulipidaemic diabetes model. Multiple genes/proteins involved in glycolysis/gluconeogenesis are upregulated, whereas those involved in oxidative phosphorylation are downregulated. In isolated islets, glucose-induced increases in NADH and ATP are impaired and both oxidative and glycolytic glucose metabolism are reduced. INS-1 β-cells cultured chronically at high glucose show similar changes in protein expression and reduced glucose-stimulated oxygen consumption: targeted metabolomics reveals impaired metabolism. These data indicate hyperglycaemia induces metabolic changes in β-cells that markedly reduce mitochondrial metabolism and ATP synthesis. We propose this underlies the progressive failure of β-cells in diabetes.
    DOI:  https://doi.org/10.1038/s41467-019-10189-x
  14. Cell Signal. 2019 May 29. pii: S0898-6568(19)30120-2. [Epub ahead of print]
    Mendelski MN, Keshet A, Hoffschröer N, Strieder T, Winter SA, Paul RJ.
      Signalling pathways provide a fine-tuned control network for catabolic and anabolic cellular processes under changing environmental conditions (e.g. changes in oxygen partial pressure, Po2). These pathways frequently activate or deactivate transcription factors (TFs) in the cytoplasm, with the subsequent nuclear translocation of activated TFs constituting a prerequisite for gene control and expression. This study introduces a newly developed fluorometric method for the quantification of relationships between environmental factors and the subcellular localization of reporter-coupled TFs in Caenorhabditis elegans (and possibly other transparent organisms). We applied this method to determine and analyse the relationship between Po2 and the subcellular localization of the GFP-coupled transcription factor DAF-16 (FoxO) of the DAF-2 (insulin/IGF-1) signalling pathway via the DAF-16::GFP fluorescence intensity of whole worms (Po2 characteristic). The Po2 characteristic resembled the Po2-specific metabolic rate of C. elegans, with a critical Po2 (Pco2) of 3.6 kPa separating two Po2 ranges, where either anaerobic metabolism and DAF-16::GFP nuclear occupancy strongly increased (i.e. decreasing DAF-16::GFP fluorescence intensity) (Po2 < Pco2) or aerobic metabolism and DAF-16::GFP cytoplasmic localization prevailed (Po2 > Pco2). These results and other data, which included the Po2-specific mitochondrial oxidation-reduction state of whole worms (as determined using the endogenous NADH fluorescence) and the effects of higher levels of reactive oxygen species (ROS) or RNAi-mediated knockdowns of catabolic or anabolic control genes (aak-2 or let-363) on the Po2 characteristic, suggest that ROS play a decisive role for DAF-16 nuclear translocation due to tissue hypoxia or higher anabolic activity induced by aak-2(RNAi). As DAF-16 and its target genes are of central importance for the cellular stress resistance, ROS-mediated relationships between metabolism and DAF-16 subcellular (i.e. nuclear) localization provide protection of the cell machinery against elevated ROS formation under challenging metabolic conditions.
    Keywords:  AAK-2/AMPK; DAF-16/FoxO; Hypoxia; LET-363/TOR; Redox
    DOI:  https://doi.org/10.1016/j.cellsig.2019.05.015
  15. Cancers (Basel). 2019 Jun 04. pii: E770. [Epub ahead of print]11(6):
    Bott AJ, Maimouni S, Zong WX.
      Metabolic programs are known to be altered in cancers arising from various tissues. Malignant transformation can alter signaling pathways related to metabolism and increase the demand for both energy and biomass for the proliferating cancerous cells. This scenario is further complexed by the crosstalk between transformed cells and the microenvironment. One of the most common metabolic alterations, which occurs in many tissues and in the context of multiple oncogenic drivers, is the increased demand for the amino acid glutamine. Many studies have attributed this increased demand for glutamine to the carbon backbone and its role in the tricarboxylic acid (TCA) cycle anaplerosis. However, an increasing number of studies are now emphasizing the importance of glutamine functioning as a proteogenic building block, a nitrogen donor and carrier, an exchanger for import of other amino acids, and a signaling molecule. Herein, we highlight the recent literature on glutamine's versatile role in cancer, with a focus on nitrogen metabolism, and therapeutic implications of glutamine metabolism in cancer.
    Keywords:  cancer; glutamate; glutamate ammonia ligase (GLUL); glutaminase (GLS); glutamine; glutamine synthetase (GS); glutaminolysis; metabolism
    DOI:  https://doi.org/10.3390/cancers11060770
  16. Bioessays. 2019 Jun 03. e1800265
    Walton ZE, Brooks RC, Dang CV.
      Acidity, generated in hypoxia or hypermetabolic states, perturbs homeostasis and is a feature of solid tumors. That acid peripherally disperses lysosomes is a three-decade-old observation, yet one little understood or appreciated. However, recent work has recognized the inhibitory impact this spatial redistribution has on mechanistic target of rapamycin complex 1 (mTORC1), a key regulator of metabolism. This finding argues for a paradigm shift in localization of mTORC1 activator Ras homolog enriched in brain (RHEB), a conclusion several others have now independently reached. Thus, mTORC1, known to sense amino acids, mitogens, and energy to restrict biosynthesis to times of adequate resources, also senses pH and, via dampened mTOR-governed synthesis of clock proteins, regulates the circadian clock to achieve concerted responses to metabolic stress. While this may allow cancer to endure metabolic deprivation, immune cell mTOR signaling likewise exhibits pH sensitivity, suggesting that suppression of antitumor immune function by solid tumor acidity may additionally fuel cancers, an obstacle potentially reversible through therapeutic pH manipulation.
    Keywords:  Ras homolog enriched in brain (RHEB); acidity; cancer immunity; circadian clock; lysosome trafficking; mechanistic target of rapamycin (mTOR); pH
    DOI:  https://doi.org/10.1002/bies.201800265
  17. Urol Oncol. 2019 May 30. pii: S1078-1439(19)30161-9. [Epub ahead of print]
    DiNatale RG, Sanchez A, Hakimi AA, Reznik E.
      The last 30 years of research in renal cell carcinoma (RCC) has revealed that the vast majority of RCC histologies share a recurrent pattern of mutations to metabolic genes, including VHL, MTOR, ELOC, TSC1/2, FH, SDH, and mitochondrial DNA. This has prompted intense study of the consequences of these mutations on cellular metabolism and physiology in vivo by leveraging high-throughput technologies to measure small-molecule metabolites (i.e., metabolomics). The purpose of this review is to give a broad and integrated view on the discoveries made in RCC with metabolomics, and to give a basic understanding of the experimental design of metabolomic studies. Our discussion is organized around five concepts which synthesize discoveries from genomics and metabolomics into the molecular basis of RCC and transcend the different RCC histologies: (1) metabolic phenotypes unique to certain genotypes, (2) mitochondrial dysfunction, (3) the oxidative stress response, (4) epigenetics, and (5) therapy targeted to metabolism. We conclude by proposing several promising lines of investigation that intersect metabolism with emerging ideas in RCC biology.
    Keywords:  Carcinogenesis; Metabolism; Metabolomics; Neoplasms; Renal cell carcinoma
    DOI:  https://doi.org/10.1016/j.urolonc.2019.04.028
  18. Trends Endocrinol Metab. 2019 May 30. pii: S1043-2760(19)30086-4. [Epub ahead of print]
    Verlande A, Masri S.
      The circadian clock is a biological mechanism that dictates an array of rhythmic physiological processes. Virtually all cells contain a functional clock whose disruption results in altered timekeeping and detrimental systemic effects, including cancer. Recent advances have connected genetic disruption of the clock with multiple transcriptional and signaling networks controlling tumor initiation and progression. An additional feature of this circadian control relies on cellular metabolism, both within the tumor microenvironment and the organism systemically. A discussion of major advances related to cancer metabolism and the circadian clock will be outlined, including new efforts related to metabolic flux of transformed cells, metabolic heterogeneity of tumors, and the implications of circadian control of these pathways.
    Keywords:  circadian clock cancer; epigenetics; metabolism; oncogenes; tumor suppressors
    DOI:  https://doi.org/10.1016/j.tem.2019.05.001
  19. J Neurosci Res. 2019 Jun 06.
    Jakobsen E, Lange SC, Bak LK.
      Mitochondria produce the bulk of the ATP in most cells, including brain cells. Regulating this complex machinery to match the energetic needs of the cell is a complicated process that we have yet to understand in its entirety. In this context, 3',5'-cyclic AMP (cAMP) has been suggested to play a seminal role in signaling-metabolism coupling and regulation of mitochondrial ATP production. In cells, cAMP signals may affect mitochondria from the cytosolic side but more recently, a cAMP signal produced within the matrix of mitochondria by soluble adenylyl cyclase (sAC) has been suggested to regulate respiration and thus ATP production. However, little is known about these processes in brain mitochondria, and the effectors of the cAMP signal generated within the matrix are not completely clear since both protein kinase A (PKA) and exchange protein activated by cAMP 1 (EPAC1) have been suggested to be involved. Here, we review the current knowledge and relate it to brain mitochondria. Further, based on measurements of respiration, membrane potential, and ATP production in isolated mouse brain cortical mitochondria we show that inhibitors of sAC, PKA, or EPAC affect mitochondrial function in distinct ways. In conclusion, we suggest that brain mitochondria do regulate their function via sAC-mediated cAMP signals and that both PKA and EPAC could be involved downstream of sAC. Finally, due to the role of faulty mitochondrial function in a range of neurological diseases, we expect that the function of sAC-cAMP-PKA/EPAC signaling in brain mitochondria will likely attract further attention.
    Keywords:  EPAC; OXPHOS; PKA; RRID:SCR_002798; RRID:SCR_014526; cAMP; mitochondria; soluble adenylyl cyclase
    DOI:  https://doi.org/10.1002/jnr.24477
  20. Semin Cell Dev Biol. 2019 May 30. pii: S1084-9521(18)30191-5. [Epub ahead of print]
    Bader V, Winklhofer KF.
      Mitochondria are essential organelles for the maintenance of neuronal integrity, based on their manifold functions in regulating cellular metabolism and coordinating cell death and viability pathways. Accordingly, mitochondrial damage, dysfunction, or ineffective mitochondrial quality control is associated with neurological disorders and can occur as a cause or consequence of neurodegenerative diseases. Recent research revealed that mitochondria play a central role in orchestrating both innate and adaptive immune responses, thereby providing a link between neurodegenerative and neuroinflammatory processes. Here we summarize new insights into the complex interplay between mitochondria, innate immunity and neurodegeneration.
    Keywords:  cGAS/STING; inflammasome; innate immunity; mitochondria; neurodegeneration; neuroinflammation
    DOI:  https://doi.org/10.1016/j.semcdb.2019.05.028
  21. Cell. 2019 May 29. pii: S0092-8674(19)30508-2. [Epub ahead of print]
    van Heesch S, Witte F, Schneider-Lunitz V, Schulz JF, Adami E, Faber AB, Kirchner M, Maatz H, Blachut S, Sandmann CL, Kanda M, Worth CL, Schafer S, Calviello L, Merriott R, Patone G, Hummel O, Wyler E, Obermayer B, Mücke MB, Lindberg EL, Trnka F, Memczak S, Schilling M, Felkin LE, Barton PJR, Quaife NM, Vanezis K, Diecke S, Mukai M, Mah N, Oh SJ, Kurtz A, Schramm C, Schwinge D, Sebode M, Harakalova M, Asselbergs FW, Vink A, de Weger RA, Viswanathan S, Widjaja AA, Gärtner-Rommel A, Milting H, Dos Remedios C, Knosalla C, Mertins P, Landthaler M, Vingron M, Linke WA, Seidman JG, Seidman CE, Rajewsky N, Ohler U, Cook SA, Hubner N.
      Gene expression in human tissue has primarily been studied on the transcriptional level, largely neglecting translational regulation. Here, we analyze the translatomes of 80 human hearts to identify new translation events and quantify the effect of translational regulation. We show extensive translational control of cardiac gene expression, which is orchestrated in a process-specific manner. Translation downstream of predicted disease-causing protein-truncating variants appears to be frequent, suggesting inefficient translation termination. We identify hundreds of previously undetected microproteins, expressed from lncRNAs and circRNAs, for which we validate the protein products in vivo. The translation of microproteins is not restricted to the heart and prominent in the translatomes of human kidney and liver. We associate these microproteins with diverse cellular processes and compartments and find that many locate to the mitochondria. Importantly, dozens of microproteins are translated from lncRNAs with well-characterized noncoding functions, indicating previously unrecognized biology.
    Keywords:  ORF detection; circRNAs; dilated cardiomyopathy; heart failure; human heart; lncRNAs; microproteins; protein-truncating variants; ribosome profiling; short ORFs; titin; translational regulation; translatome
    DOI:  https://doi.org/10.1016/j.cell.2019.05.010
  22. Autophagy. 2019 Jun 06.
    Carleton G, Lum JJ.
      Macroautophagy/autophagy is a critical regulator of adaptive T cell immunity and homeostasis. However, the role of T cell autophagy in regulating antitumor immune responses is less clear. In a recent study, we showed that deletion of the essential autophagy genes Atg5, Atg14, or Atg16l1 in host tissues dramatically impairs growth of autophagy-competent syngeneic tumors. We further demonstrated that CD8+ T cells lacking Atg5 acquire an effector memory phenotype and produce more IFNG/IFN-γ (interferon gamma) and TNF/TNF-α (tumor necrosis factor). These phenotypic changes are accompanied by enhanced glucose metabolism that results in alterations in histone methylation, and upregulation of glycolytic and immune response genes. In accordance with this, we observed control of tumor growth in autophagy-competent mice after adoptive transfer with a sub-therapeutic dose of atg5-/- T cells. Collectively, we discovered a unique, cell-autonomous role for T cell autophagy in the metabolic control of antitumor immunity.
    Keywords:  Antitumor immunity; CD8 T cells; SAM; autophagy; glycolysis; lactate; methylation
    DOI:  https://doi.org/10.1080/15548627.2019.1628545
  23. Liver Res. 2018 Sep;2(3): 125-132
    Lemasters JJ, Zhong Z.
      Mitophagy (mitochondrial autophagy) in hepatocytes is an essential quality control mechanism that removes for lysosomal digestion damaged, effete and superfluous mitochondria. Mitophagy has distinct variants. In type 1 mitophagy, typical of nutrient deprivation, cup-shaped sequestration membranes (phagophores) grow, surround and sequester individual mitochondria into mitophagosomes, often in coordination with mitochondrial fission. After sequestration, the outer compartment of the mitophagosome acidifies and the entrapped mitochondrion depolarizes, followed by fusion with lysosomes. By contrast, mitochondrial depolarization stimulates type 2 mitophagy, which is characterized by coalescence of autophagic microtubule-associated protein 1A/1B-light chain 3 (LC3)-containing structures on mitochondrial surfaces without the formation of a phagophore or mitochondrial fission. Oppositely to type 1 mitophagy, the inhibition of phosphoinositide-3-kinase (PI3K) does not block type 2 mitophagy. In type 3 mitophagy, or micromitophagy, mitochondria-derived vesicles (MDVs) enriched in oxidized proteins bud off from mitochondrial inner and outer membranes and incorporate into multivesicular bodies by vesicle scission into the lumen. In response to ethanol feeding, widespread ethanol-induced hepatocellular mitochondrial depolarization occurs to facilitate hepatic ethanol metabolism. As a consequence, type 2 mitophagy develops in response to the mitochondrial depolarization. After chronic high ethanol feeding, processing of depolarized mitochondria by mitophagy becomes compromised, leading to release of mitochondrial damage-associated molecular patterns (mtDAMPs) that promote inflammatory and profibrogenic responses. We propose that the persistence of mitochondrial responses for acute ethanol metabolism links initial adaptive ethanol metabolism to mitophagy and then to chronic maladaptive changes initiating onset and the progression of alcoholic liver disease (ALD).
    Keywords:  Alcoholic liver disease (ALD); Ethanol; Green fluorescent protein-light chain 3 (GFP-LC3); Hepatocytes; Mitochondrial damage-associated molecular patterns (mtDAMPs); Mitophagy
    DOI:  https://doi.org/10.1016/j.livres.2018.09.005
  24. Neuromolecular Med. 2019 Jun 06.
    Sperling JA, Sakamuri SSVP, Albuck AL, Sure VN, Evans WR, Peterson NR, Rutkai I, Mostany R, Satou R, Katakam PVG.
      Measuring mitochondrial respiration in brain tissue is very critical in understanding the physiology and pathology of the central nervous system. Particularly, measurement of respiration in isolated mitochondria provides the advantage over the whole cells or tissues as the changes in respiratory function are intrinsic to mitochondrial structures rather than the cellular signaling that regulates mitochondria. Moreover, a high-throughput technique for measuring mitochondrial respiration minimizes the experimental time and the sample-to-sample variation. Here, we provide a detailed protocol for measuring respiration in isolated brain non-synaptosomal mitochondria using Agilent Seahorse XFe24 Analyzer. We optimized the protocol for the amount of mitochondria and concentrations of ADP, oligomycin, and trifluoromethoxy carbonylcyanide phenylhydrazone (FCCP) for measuring respiratory parameters for complex I-mediated respiration. In addition, we measured complex II-mediated respiratory parameters. We observed that 10 µg of mitochondrial protein per well, ADP concentrations ranging between 2.5 and 10 mmol/L along with 5 µmol/L of oligomycin, and 5 µmol/L of FCCP are ideal for measuring the complex I-mediated respiration in isolated mouse brain mitochondria. Furthermore, we determined that 2.5 µg of mitochondrial protein per well is ideal for measuring complex II-mediated respiration. Notably, we provide a discussion of logical analysis of data and how the assay could be utilized to design mechanistic studies for experimental stroke. In conclusion, we provide detailed experimental design for measurement of various respiratory parameters in isolated brain mitochondria utilizing a novel high-throughput technique along with interpretation and analysis of data.
    Keywords:  Isolated mitochondria; Mitochondrial respiration; Non-synaptosomal mitochondria; Oxygen consumption rate
    DOI:  https://doi.org/10.1007/s12017-019-08552-8
  25. Mitochondrion. 2019 Jun 03. pii: S1567-7249(18)30221-6. [Epub ahead of print]
    Santos-Alves E, Rizo-Roca D, Marques-AleixoI , Coxito P, Martins S, Guimarães JT, Oliveira PJ, Torrella JR, Magalhães J, Ascensão A.
      Doxorubicin (DOX), a widely used and efficient antineoplastic agent, is mainly limited by cardiotoxicity, although other tissues including liver are also affected. The effects of exercise to cope with DOX side-effects has already been studied in the heart and brain, demonstrating successful results. However, the benefits of this non-pharmacological strategy have not been so extensively checked in the liver. We here aimed to ascertain whether exercise could mitigate DOX-induced liver harmful effects using mitochondria as a model for evaluating toxicity. Twenty-four male rats were divided into four groups: SED + SAL (sedentary with saline administration), SED + DOX (sedentary with DOX administration), ET + DOX (endurance-trained with DOX administration) and VPA + DOX (voluntary physical activity with DOX administration). Isolated liver mitochondria were obtained for evaluation of their respiratory activity and transmembrane electrical potential endpoints. Molecular markers of oxidative damage (carbonyls, MDA, aconitase, MnSOD), mitochondrial dynamics (PGC-1α, TFAM, OPA1, DRP1, MFN1) and auto(mito)phagy signaling (p62, LC3, Beclin1, Bcl-2, PINK, Parkin) were measured. Transmission electron microscopy evaluation was used to analyze mitochondrial morphological alterations. When compared to SED + SAL, respiratory function of SED + DOX was compromised. Decreased SOD and aconitase activities and increased MDA content, decreases in PGC-1α, TFAM, OPA1 and MFN1 expressions, and increases in DRP1 and LC3II/LC3I ratio were also observed after DOX administration. However, these alterations were reverted or mitigated in the ET + DOX group. Semi-quantitative and qualitative analyses from microphotographs showed that liver mitochondria of SED + DOX animals were more circular and had lower density, whereas the animals with exercise showed a tendency to revert this phenotype and increase the mitochondrial density. Taken together, our results suggest that physical exercise, particularly ET, positively reversed the deleterious effects caused by DOX administration, such as oxidative damage, mitochondrial dysfunction, and altered mitochondrial dynamics toward fission, thus contributing to increase liver resistance against DOX administration.
    Keywords:  Doxorubicin; Exercise; Hepatotoxicity; Mitochondrial dysfunction
    DOI:  https://doi.org/10.1016/j.mito.2019.05.008
  26. Redox Biol. 2019 May 21. pii: S2213-2317(19)30131-4. [Epub ahead of print]24 101227
    Vajrychova M, Salovska B, Pimkova K, Fabrik I, Tambor V, Kondelova A, Bartek J, Hodny Z.
      Under normal conditions, the cellular redox status is maintained in a steady state by reduction and oxidation processes. These redox alterations in the cell are mainly sensed by protein thiol residues of cysteines thus regulating protein function. The imbalance in redox homeostasis may therefore regulate protein turnover either directly by redox modulating of transcription factors or indirectly by the degradation of damaged proteins due to oxidation. A new analytical method capable of simultaneously assessing cellular protein expression and cysteine oxidation would provide a valuable tool for the field of cysteine-targeted biology. Here, we show a workflow based on protein quantification using metabolic labeling and determination of cysteine oxidation using reporter ion quantification. We applied this approach to determine protein and redox changes in cells after 5-min, 60-min and 32-h exposure to H2O2, respectively. Based on the functional analysis of our data, we confirmed a biological relevance of this approach and its applicability for parallel mapping of cellular proteomes and redoxomes under diverse conditions. In addition, we revealed a specific pattern of redox changes in peroxiredoxins in a short time-interval cell exposure to H2O2. Overall, our present study offers an innovative, versatile experimental approach to the multifaceted assessment of cellular proteome and its redox status, with broad implications for biomedical research towards a better understanding of organismal physiology and diverse disease conditions.
    Keywords:  Cysteine; Liquid chromatography/mass spectrometry; Peroxiredoxin; Proteome; Redoxome; SILAC-iodoTMT labeling
    DOI:  https://doi.org/10.1016/j.redox.2019.101227
  27. Cell Mol Life Sci. 2019 Jun 06.
    Jayarajan V, Appukuttan A, Aslam M, Reusch P, Regitz-Zagrosek V, Ladilov Y.
      The downregulation of AMP-activated protein kinase (AMPK) activity contributes to numerous pathologies. Recent reports suggest that the elevation of cellular cAMP promotes AMPK activity. However, the source of the cAMP pool that controls AMPK activity remains unknown. Mammalian cells possess two cAMP sources: membrane-bound adenylyl cyclase (tmAC) and intracellularly localized, type 10 soluble adenylyl cyclase (sAC). Due to the localization of sAC and AMPK in similar intracellular compartments, we hypothesized that sAC may control AMPK activity. In this study, sAC expression and activity were manipulated in H9C2 cells, adult rat cardiomyocytes or endothelial cells. sAC knockdown depleted the cellular cAMP content and decreased AMPK activity in an EPAC-dependent manner. Functionally, sAC knockdown reduced cellular ATP content, increased mitochondrial ROS formation and led to mitochondrial depolarization. Furthermore, sAC downregulation led to EPAC-dependent mitophagy disturbance, indicated by an increased mitochondrial mass and unaffected mitochondrial biogenesis. Consistently, sAC overexpression or stimulation with bicarbonate significantly increased AMPK activity and cellular ATP content. In contrast, tmAC inhibition or stimulation produced no effect on AMPK activity. Therefore, the sAC-EPAC axis may regulate basal and induced AMPK activity and support mitophagy, cellular energy and redox homeostasis. The study argues for sAC as a potential target in treating pathologies associated with AMPK downregulation.
    Keywords:  ADCY10; AMPK; ATP; Mitophagy; ROS; cAMP
    DOI:  https://doi.org/10.1007/s00018-019-03152-y
  28. Genes Dev. 2019 Jun 01. 33(11-12): 610-619
    Poillet-Perez L, White E.
      Macroautophagy (referred to here as autophagy) degrades and recycles cytoplasmic constituents to sustain cellular and mammalian metabolism and survival during starvation. Deregulation of autophagy is involved in numerous diseases, such as cancer. Cancers up-regulate autophagy and depend on it for survival, growth, and malignancy in a tumor cell-autonomous fashion. Recently, it has become apparent that autophagy in host tissues as well as the tumor cells themselves contribute to tumor growth. Understanding how autophagy regulates metabolism and tumor growth has revealed new essential tumor nutrients, where they come from, and how they are supplied and used, which can now be targeted for cancer therapy.
    Keywords:  autophagy; cancer; metabolism
    DOI:  https://doi.org/10.1101/gad.325514.119
  29. Crit Rev Biochem Mol Biol. 2019 Jun 04. 1-15
    Sullivan MR, Vander Heiden MG.
      Proliferation requires that cells accumulate sufficient biomass to grow and divide. Cancer cells within tumors must acquire a variety of nutrients, and tumor growth slows or stops if necessary metabolites are not obtained in sufficient quantities. Importantly, the metabolic demands of cancer cells can be different from those of untransformed cells, and nutrient accessibility in tumors is different than in many normal tissues. Thus, cancer cell survival and proliferation may be limited by different metabolic factors than those that are necessary to maintain noncancerous cells. Understanding the variables that dictate which nutrients are critical to sustain tumor growth may identify vulnerabilities that could be used to treat cancer. This review examines the various cell-autonomous, local, and systemic factors that determine which nutrients are limiting for tumor growth.
    Keywords:  Cancer; collateral lethality; metabolism; nutrient limitation; tumor microenvironment
    DOI:  https://doi.org/10.1080/10409238.2019.1611733
  30. Cell. 2019 May 20. pii: S0092-8674(19)30501-X. [Epub ahead of print]
    Zhang W, Wang G, Xu ZG, Tu H, Hu F, Dai J, Chang Y, Chen Y, Lu Y, Zeng H, Cai Z, Han F, Xu C, Jin G, Sun L, Pan BS, Lai SW, Hsu CC, Xu J, Chen ZZ, Li HY, Seth P, Hu J, Zhang X, Li H, Lin HK.
      RLR-mediated type I IFN production plays a pivotal role in elevating host immunity for viral clearance and cancer immune surveillance. Here, we report that glycolysis, which is inactivated during RLR activation, serves as a barrier to impede type I IFN production upon RLR activation. RLR-triggered MAVS-RIG-I recognition hijacks hexokinase binding to MAVS, leading to the impairment of hexokinase mitochondria localization and activation. Lactate serves as a key metabolite responsible for glycolysis-mediated RLR signaling inhibition by directly binding to MAVS transmembrane (TM) domain and preventing MAVS aggregation. Notably, lactate restoration reverses increased IFN production caused by lactate deficiency. Using pharmacological and genetic approaches, we show that lactate reduction by lactate dehydrogenase A (LDHA) inactivation heightens type I IFN production to protect mice from viral infection. Our study establishes a critical role of glycolysis-derived lactate in limiting RLR signaling and identifies MAVS as a direct sensor of lactate, which functions to connect energy metabolism and innate immunity.
    Keywords:  MAVS; RLR signaling; glucose metabolism; interferon; lactate
    DOI:  https://doi.org/10.1016/j.cell.2019.05.003
  31. Nat Protoc. 2019 Jun 05.
    Llufrio EM, Cho K, Patti GJ.
      Identification of previously unreported metabolites (so-called 'unknowns') in untargeted metabolomic data has become an increasingly active area of research. Considerably less attention, however, has been dedicated to identifying unknown metabolic pathways. Yet, for each unknown metabolite structure, there is potentially a yet-to-be-discovered chemical transformation. Elucidating these biochemical connections is essential to advancing our knowledge of cellular metabolism and can be achieved by tracking an isotopically labeled precursor to an unexpected product. In addition to their role in mapping metabolic fates, isotopic labels also provide critical insight into pathway dynamics (i.e., metabolic fluxes) that cannot be obtained from conventional label-free metabolomic analyses. When labeling is compared quantitatively between conditions, for example, isotopic tracers can enable relative pathway activities to be inferred. To discover unexpected chemical transformations or unanticipated differences in metabolic pathway activities, we have developed X13CMS, a platform for analyzing liquid chromatography/mass spectrometry (LC/MS) data at the systems level. After providing cells, animals, or patients with an isotopically enriched metabolite (e.g., 13C, 15N, or 2H), X13CMS identifies compounds that have incorporated the isotopic tracer and reports the extent of labeling for each. The analysis can be performed with a single condition, or isotopic fates can be compared between multiple conditions. The choice of which metabolite to enrich and which isotopic label to use is highly context dependent, but 13C-glucose and 13C-glutamine are often applied because they feed a large number of metabolic pathways. X13CMS is freely available.
    DOI:  https://doi.org/10.1038/s41596-019-0167-1
  32. Cell Rep. 2019 Jun 04. pii: S2211-1247(19)30630-8. [Epub ahead of print]27(10): 3034-3048.e5
    Cai Y, Xue F, Qin H, Chen X, Liu N, Fleming C, Hu X, Zhang HG, Chen F, Zheng J, Yan J.
      Dermal γδT cells play critical roles in skin homeostasis and inflammation. However, the underlying molecular mechanisms by which these cells are activated have not been fully understood. Here, we show that the mechanistic or mammalian target of rapamycin (mTOR) and STAT3 pathways are activated in dermal γδT cells in response to innate stimuli such as interleukin-1β (IL-1β) and IL-23. Although both mTOR complex 1 (mTORC1) and mTORC2 are essential for dermal γδT cell proliferation, mTORC2 deficiency leads to decreased dermal γδT17 cells. It appears that mitochondria-mediated oxidative phosphorylation is critical in this process. Notably, although the STAT3 pathway is critical for dermal Vγ4T17 effector function, it is not required for Vγ6T17 cells. Transcription factor IRF-4 activation promotes dermal γδT cell IL-17 production by linking IL-1β and IL-23 signaling. The absence of mTORC2 in dermal γδT cells, but not STAT3, ameliorates skin inflammation. Taken together, our results demonstrate that the mTOR-STAT3 signaling differentially regulates dermal γδT cell effector function in skin inflammation.
    Keywords:  IL-1 signaling; IL-17; IL-23 signaling; STAT3; Vgamma4; Vgamma6; gammadelta T cells; mTOR; psoriasis; skin inflammation
    DOI:  https://doi.org/10.1016/j.celrep.2019.05.019
  33. Cancer Discov. 2019 Jun;9(6): 699-701
    Horton S, Huntly BJP.
      Mutations in isoforms of isocitrate dehydrogenase (IDH) enzymes are described in multiple cancers and both mutant and wild-type IDH are important for the generation and maintenance of tumors, but how their activity is regulated is poorly understood. An article in this issue of Cancer Discovery identifies a novel posttranslational mechanism of IDH1 regulation involving phosphorylation of specific tyrosine residues by a network of kinases that alter the specificity of substrate and cofactor binding, dimer formation, and ultimately enzyme activity.See related article by Chen et al., p. 756.
    DOI:  https://doi.org/10.1158/2159-8290.CD-19-0373
  34. Cell Metab. 2019 May 14. pii: S1550-4131(19)30246-3. [Epub ahead of print]
    Aguayo-Mazzucato C, Andle J, Lee TB, Midha A, Talemal L, Chipashvili V, Hollister-Lock J, van Deursen J, Weir G, Bonner-Weir S.
      Type 2 diabetes (T2D) is an age-related disease. Although changes in function and proliferation of aged β cells resemble those preceding the development of diabetes, the contribution of β cell aging and senescence remains unclear. We generated a β cell senescence signature and found that insulin resistance accelerates β cell senescence leading to loss of function and cellular identity and worsening metabolic profile. Senolysis (removal of senescent cells), using either a transgenic INK-ATTAC model or oral ABT263, improved glucose metabolism and β cell function while decreasing expression of markers of aging, senescence, and senescence-associated secretory profile (SASP). Beneficial effects of senolysis were observed in an aging model as well as with insulin resistance induced both pharmacologically (S961) and physiologically (high-fat diet). Human senescent β cells also responded to senolysis, establishing the foundation for translation. These novel findings lay the framework to pursue senolysis of β cells as a preventive and alleviating strategy for T2D.
    Keywords:  SASP; beta cells; glucose metabolism; insulin resistance; insulin secretion; senescence; senescence signature; senescence-associated secretory profile; senolytic therapies; type 2 diabetes
    DOI:  https://doi.org/10.1016/j.cmet.2019.05.006
  35. Nat Immunol. 2019 Jun 03.
    Hu Q, Ye Y, Chan LC, Li Y, Liang K, Lin A, Egranov SD, Zhang Y, Xia W, Gong J, Pan Y, Chatterjee SS, Yao J, Evans KW, Nguyen TK, Park PK, Liu J, Coarfa C, Donepudi SR, Putluri V, Putluri N, Sreekumar A, Ambati CR, Hawke DH, Marks JR, Gunaratne PH, Caudle AS, Sahin AA, Hortobagyi GN, Meric-Bernstam F, Chen L, Yu D, Hung MC, Curran MA, Han L, Lin C, Yang L.
      How tumor cells genetically lose antigenicity and evade immune checkpoints remains largely elusive. We report that tissue-specific expression of the human long noncoding RNA LINK-A in mouse mammary glands initiates metastatic mammary gland tumors, which phenotypically resemble human triple-negative breast cancer (TNBC). LINK-A expression facilitated crosstalk between phosphatidylinositol-(3,4,5)-trisphosphate and inhibitory G-protein-coupled receptor (GPCR) pathways, attenuating protein kinase A-mediated phosphorylation of the E3 ubiquitin ligase TRIM71. Consequently, LINK-A expression enhanced K48-polyubiquitination-mediated degradation of the antigen peptide-loading complex (PLC) and intrinsic tumor suppressors Rb and p53. Treatment with LINK-A locked nucleic acids or GPCR antagonists stabilized the PLC components, Rb and p53, and sensitized mammary gland tumors to immune checkpoint blockers. Patients with programmed ccll death protein-1(PD-1) blockade-resistant TNBC exhibited elevated LINK-A levels and downregulated PLC components. Hence we demonstrate lncRNA-dependent downregulation of antigenicity and intrinsic tumor suppression, which provides the basis for developing combinational immunotherapy treatment regimens and early TNBC prevention.
    DOI:  https://doi.org/10.1038/s41590-019-0400-7
  36. Toxicol Appl Pharmacol. 2019 May 29. pii: S0041-008X(19)30203-0. [Epub ahead of print] 114601
    Qi Z, Shi W, Zhao Y, Ji X, Liu KJ.
      High concentration of zinc has been reported to act as a critical mediator of neuronal death in the ischemic brain. Our previous studies showed that labile zinc accumulates in cerebromicrovessels and contributes to blood-brain barrier (BBB) permeability increase after cerebral ischemia. However, the role of mitochondrial zinc in ischemia-induced BBB permeability alteration is still unclear. In this study, we showed that ischemia/reperfusion induced free zinc accumulation in endothelial cells (ECs), resulting in increased generation of reactive oxygen species (ROS) in both cultured ECs and in microvessels isolated from the brain of ischemic rats. Furthermore, we found that zinc was highly accumulated in mitochondria, leading to mitochondrial ROS generation under the ischemic condition. Moreover, zinc overload in mitochondria resulted in the collapse of the network of mitochondria, which was mediated through Dynamin-related protein-1 (Drp-1) dependent mitochondrial fission pathway. Finally, the zinc overload in mitochondria activated matrix metalloproteinase-2 and led to ischemia-induced BBB permeability increase. This study demonstrated that zinc-ROS pathway in mitochondria contributes to the ischemia-induced BBB disruption via Drp-1 dependent mitochondrial fission pathway.
    Keywords:  Blood–Brain Barrier (BBB); Fission; Ischemia/reperfusion; Mitochondria; Reactive Oxygen Species (ROS); Zinc
    DOI:  https://doi.org/10.1016/j.taap.2019.114601
  37. Cell Metab. 2019 Jun 04. pii: S1550-4131(19)30253-0. [Epub ahead of print]29(6): 1236-1238
    Hughey CC, Crawford PA.
      Pyruvate carboxylase-mediated anaplerosis is a well-known regulator of gluconeogenesis. In this issue of Cell Metabolism, Cappel et al. (2019) show that pyruvate carboxylase action has far-reaching roles in metabolic homeostasis as it integrates glucose metabolism with tricarboxylic acid cycle flux, ureagenesis, redox potential, and defense against oxidative stress.
    DOI:  https://doi.org/10.1016/j.cmet.2019.05.013
  38. Nat Commun. 2019 Jun 04. 10(1): 2450
    Racioppi L, Nelson ER, Huang W, Mukherjee D, Lawrence SA, Lento W, Masci AM, Jiao Y, Park S, York B, Liu Y, Baek AE, Drewry DH, Zuercher WJ, Bertani FR, Businaro L, Geradts J, Hall A, Means AR, Chao N, Chang CY, McDonnell DP.
      Tumor-associated myeloid cells regulate tumor growth and metastasis, and their accumulation is a negative prognostic factor for breast cancer. Here we find calcium/calmodulin-dependent kinase kinase (CaMKK2) to be highly expressed within intratumoral myeloid cells in mouse models of breast cancer, and demonstrate that its inhibition within myeloid cells suppresses tumor growth by increasing intratumoral accumulation of effector CD8+ T cells and immune-stimulatory myeloid subsets. Tumor-associated macrophages (TAMs) isolated from Camkk2-/- mice expressed higher levels of chemokines involved in the recruitment of effector T cells compared to WT. Similarly, in vitro generated Camkk2-/- macrophages recruit more T cells, and have a reduced capability to suppress T cell proliferation, compared to WT. Treatment with CaMKK2 inhibitors blocks tumor growth in a CD8+ T cell-dependent manner, and facilitates a favorable reprogramming of the immune cell microenvironment. These data, credential CaMKK2 as a myeloid-selective checkpoint, the inhibition of which may have utility in the immunotherapy of breast cancer.
    DOI:  https://doi.org/10.1038/s41467-019-10424-5
  39. Cells. 2019 Jun 04. pii: E539. [Epub ahead of print]8(6):
    Feichtinger RG, Neureiter D, Kemmerling R, Mayr JA, Kiesslich T, Kofler B.
      Abstract: Cancer cells frequently exhibit dysfunctional oxidative phosphorylation (OXPHOS) and a concomitant increase in glycolytic flux. We investigated the expression of OXPHOS complex subunits and mitochondrial mass in 34 human cholangiocellular carcinomas (CCCs) and adjacent normal tissue by using tissue microarrays. In the tumor periphery, all OXPHOS complexes were reduced except complex I. In addition, significantly lower levels of complex IV were found at the tumor center (p < 0.0001). Mitochondrial mass, as indicated by VDAC1 expression, was significantly increased in CCCs compared to corresponding normal tissue (p < 0.0001). VDAC1 levels were inversely correlated with UICC (Union Internationale Contre le Cancer) cancer stage classification (p = 0.0065). Furthermore, significantly lower VDAC1 was present in patients with lymph node involvement (p = 0.02). Consistent with this, patients whose carcinomas expressed VDAC1 at low to moderate levels had significantly reduced survival compared to high expressors (p < 0.05). Therefore, low mitochondrial mass is associated with more aggressive CCC. These metabolic features are indicative of a Warburg phenotype in CCCs. This metabolic signature has potential therapeutic implications because tumors with low mitochondrial function may be targeted by metabolic therapies such as a high-fat, low-carbohydrate ketogenic diet.
    Keywords:  cholangiocellular carcinoma; energy metabolism; mitochondria; oxidative phosphorylation
    DOI:  https://doi.org/10.3390/cells8060539
  40. Sci Rep. 2019 Jun 03. 9(1): 8176
    Waters LR, Ahsan FM, Ten Hoeve J, Hong JS, Kim DNH, Minasyan A, Braas D, Graeber TG, Zangle TA, Teitell MA.
      Ampk is an energy gatekeeper that responds to decreases in ATP by inhibiting energy-consuming anabolic processes and promoting energy-generating catabolic processes. Recently, we showed that Lkb1, an understudied kinase in B lymphocytes and a major upstream kinase for Ampk, had critical and unexpected roles in activating naïve B cells and in germinal center formation. Therefore, we examined whether Lkb1 activities during B cell activation depend on Ampk and report surprising Ampk activation with in vitro B cell stimulation in the absence of energy stress, coupled to rapid biomass accumulation. Despite Ampk activation and a controlling role for Lkb1 in B cell activation, Ampk knockout did not significantly affect B cell activation, differentiation, nutrient dynamics, gene expression, or humoral immune responses. Instead, Ampk loss specifically repressed the transcriptional expression of IgD and its regulator, Zfp318. Results also reveal that early activation of Ampk by phenformin treatment impairs germinal center formation but does not significantly alter antibody responses. Combined, the data show an unexpectedly specific role for Ampk in the regulation of IgD expression during B cell activation.
    DOI:  https://doi.org/10.1038/s41598-019-43985-y
  41. Methods Enzymol. 2019 ;pii: S0076-6879(19)30036-9. [Epub ahead of print]622 293-307
    Darabedian N, Pratt MR.
      O-GlcNAcylation is a widespread posttranslational modification of intracellular proteins. Phenotypic and genetic experiments have established key roles for O-GlcNAc in development, mammalian cell survival, and several human diseases. However, the underlying mechanisms by which this modification alters biological pathways are still being discovered. An important part of this discovery process is the discovery of O-GlcNAcylated proteins, where chemical approaches have been particularly powerful. Here we describe how to combine one of these approaches, metabolic chemical reporters (MCRs), with bioorthogonal chemistry and Western blotting to identify potentially O-GlcNAcylated proteins.
    Keywords:  Bioorthogonal; Biotin enrichment; Click chemistry; Metabolic chemical reporter; O-GlcNAc
    DOI:  https://doi.org/10.1016/bs.mie.2019.02.017
  42. Integr Comp Biol. 2019 Jun 05. pii: icz097. [Epub ahead of print]
    Hood WR, Williams AS, Hill GE.
      Longevity plays a key role in the fitness of organisms, so understanding the processes that underlie variance in senescence has long been a focus of ecologists and evolutionary biologists. For decades, the performance and ultimate decline of mitochondria have been implicated in the demise of somatic tissue, but exactly why mitochondrial function declines as individuals age has remained elusive. A possible source of decline that has been of intense debate is mutations to the mitochondrial DNA. There are two primary sources of such mutations: oxidative damage, which is widely discussed by ecologists interested in aging, and mitochondrial replication error, which is less familiar to most ecologists. The goal of this review is to introduce ecologists and evolutionary biologists to the concept of mitochondrial replication error and to review the current status of research on the relative importance of replication error in senescence. We conclude by detailing some of the gaps in our knowledge that currently make it difficult to deduce the relative importance of replication error in wild populations and encourage organismal biologists to consider this variable both when interpreting their results and as viable measure to include in their studies.
    DOI:  https://doi.org/10.1093/icb/icz097
  43. Clin Cancer Res. 2019 Jun 04. pii: clincanres.4140.2018. [Epub ahead of print]
    Chalishazar MD, Wait SJ, Huang F, Ireland AS, Mukhopadhyay A, Lee Y, Schuman S, Guthrie MR, Berrett K, Vahrenkamp J, Hu Z, Kudla M, Modzelewska K, Wang G, Ingolia NT, Gertz J, Lum DH, Cosulich SC, Bomalaski JS, DeBerardinis RJ, Oliver TG.
      PURPOSE: Small cell lung cancer (SCLC) has been treated clinically as a homogeneous disease, but recent discoveries suggest that SCLC is heterogeneous. Whether metabolic differences exist among SCLC subtypes is largely unexplored. In this study, we aimed to determine whether metabolic vulnerabilities exist between SCLC subtypes that can be therapeutically exploited.EXPERIMENTAL DESIGN: We performed steady state metabolomics on tumors isolated from distinct GEMMs representing the MYC and MYCL-driven subtypes of SCLC. Using genetic and pharmacological approaches, we validated our findings in chemo-naive and resistant human SCLC cell lines, multiple GEMMs, four human cell line xenografts, and four newly-derived PDX models.
    RESULTS: We discover that SCLC subtypes driven by different MYC family members have distinct metabolic profiles. MYC-driven SCLC preferentially depends on arginine-regulated pathways including polyamine biosynthesis and mTOR pathway activation. Chemo-resistant SCLC cells exhibit increased MYC expression and similar metabolic liabilities as chemo-naive MYC-driven cells. Arginine depletion with pegylated arginine deiminase (ADI-PEG 20) dramatically suppresses tumor growth and promotes survival of mice specifically with MYC-driven tumors, including in GEMMs, human cell line xenografts, and a PDX from a relapsed patient. Finally, ADI-PEG 20 is significantly more effective than the standard of care chemotherapy.
    CONCLUSIONS: These data identify metabolic heterogeneity within SCLC and suggest arginine deprivation as a subtype-specific therapeutic vulnerability for MYC-driven SCLC.
    DOI:  https://doi.org/10.1158/1078-0432.CCR-18-4140
  44. J Cell Physiol. 2019 Jun 07.
    Wang Q, Xu J, Li X, Liu Z, Han Y, Xu X, Li X, Tang Y, Liu Y, Yu T, Li X.
      Mitochondrial fusion is linked to heart and liver ischemia-reperfusion (IR) insult. Unfortunately, there is no report to elucidate the detailed influence of mitochondrial fusion in renal IR injury. This study principally investigated the mechanism by which mitochondrial fusion protected kidney against IR injury. Our results indicated that sirtuin 3 (Sirt3) was inhibited after renal IR injury in vivo and in vitro. Overexpression of Sirt3 improved kidney function, modulated oxidative injury, repressed inflammatory damage, and reduced tubular epithelial cell apoptosis. The molecular investigation found that Sirt3 overexpression attenuated IR-induced mitochondrial damage in renal tubular epithelial cells, as evidenced by decreased reactive oxygen species production, increased antioxidants sustained mitochondrial membrane potential, and inactivated mitochondria-initiated death signaling. In addition, our information also illuminated that Sirt3 maintained mitochondrial homeostasis against IR injury by enhancing optic atrophy 1 (OPA1)-triggered fusion of mitochondrion. Inhibition of OPA1-induced fusion repressed Sirt3 overexpression-induced kidney protection, leading to mitochondrial dysfunction. Further, our study illustrated that OPA1-induced fusion could be affected through ERK; inhibition of ERK abolished the regulatory impacts of Sirt3 on OPA1 expression and mitochondrial fusion, leading to mitochondrial damage and tubular epithelial cell apoptosis. Altogether, our results suggest that renal IR injury is closely associated with Sirt3 downregulation and mitochondrial fusion inhibition. Regaining Sirt3 and/or activating mitochondrial fission by modifying the ERK-OPA1 cascade may represent new therapeutic modalities for renal IR injury.
    Keywords:  ERK-OPA1 signaling pathway; Sirt3; mitochondrial fusion; renal IR injury
    DOI:  https://doi.org/10.1002/jcp.28918
  45. Cell Cycle. 2019 Jun 03. 1-19
    Ghashghaeinia M, Köberle M, Mrowietz U, Bernhardt I.
      Mature human erythrocytes are dependent on anerobic glycolysis, i.e. catabolism (oxidation) of one glucose molecule to produce two ATP and two lactate molecules. Proliferating tumor cells mimick mature human erythrocytes to glycolytically generate two ATP molecules. They deliberately avoid or switch off their respiration, i.e. tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) machinery and consequently dispense with the production of additional 36 ATP molecules from one glucose molecule. This phenomenon is named aerobic glycolysis or Warburg effect. The present review deals with the fate of a glucose molecule after entering a mature human erythrocyte or a proliferating tumor cell and describes why it is useful for a proliferating tumor cell to imitate a mature erythrocyte. Blood consisting of plasma and cellular components (99% of the cells are erythrocytes) may be regarded as a mobile organ, constantly exercising a direct interaction with other organs. Therefore, the use of drugs, which influences the biological activity of erythrocytes, has an immediate effect on the entire organism. Abbreviations: TCA: tricarboxylic acid cycle; OXPHOS: oxidative phosphorylation; GSH: reduced state of glutathione; NFκB: Nuclear factor of kappa B; PKB (Akt): protein kinase B; NOS: nitric oxide synthase; IgG: immune globulin G; H2S: hydrogen sulfide; slanDCs: Human 6-sulfo LacNAc-expressing dendritic cells; IL-8: interleukin-8; LPS: lipopolysaccharide; ROS: reactive oxygen species; PPP: pentose phosphate pathway; NADPH: nicotinamide adenine dinucleotide phosphate hydrogen; R5P: ribose-5-phophate; NAD: nicotinamide adenine dinucleotide; FAD: flavin adenine dinucleotide; O2●-: superoxide anion; G6P: glucose 6-phosphate; HbO2: Oxyhemoglobin; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GAP: glyceraldehyde-3-phosphate; 1,3-BPG: 1,3-bis-phosphoglycerate; 2,3-BPG: 2,3-bisphosphoglycerte; PGAM1: phosphoglycerate mutase 1; 3-PG: 3-phosphoglycerate; 2-PG: 2-phosphoglycerate; MIPP1: Multiple inositol polyphosphate phosphatase; mTORC1: mammalian target of rapamycin complex 1; Ru5P: ribulose 5-phosphate; ox-PPP: oxidative branch of pentose phosphate pathway; PGK: phosphoglycerate kinase; IFN-γ: interferon-γ; LDH: lactate dehydrogenase; STAT3: signal transducer and activator of transcription 3; Rheb: Ras homolog enriched in Brain; H2O2: hydrogen peroxide; ROOH: lipid peroxide; SOD: superoxide dismutase; MRC: mitochondrial respiratory chain; MbFe2+-O2: methmyoglobin; RNR: ribonucleotide reductase; PRPP: phosphoribosylpyrophosphate; PPi: pyrophosphate; GSSG: oxidized state of glutathione; non-ox-PPP: non-oxidative branch of pentose phosphate pathway; RPI: ribose-5-phosphate isomerase; RPE: ribulose 5-phosphate 3-epimerase; X5P: xylulose 5-phosphate; TK: transketolase; TA: transaldolase; F6P: fructose-6-phosphate; AR2: aldose reductase 2; SD: sorbitol dehydrogenase; HK: hexokinase; MG: mehtylglyoxal; DHAP: dihydroxyacetone phosphate; TILs: tumor-infiltrating lymphocytes; MCTs: monocarboxylate transporters; pHi: intracellular pH; Hif-1α: hypoxia-induced factor 1; NHE1: sodium/H+ (Na+/H+) antiporter 1; V-ATPase: vacuolar-type proton ATPase; CAIX: carbonic anhydrase; CO2: carbon dioxide; HCO3-: bicarbonate; NBC: sodium/bicarbonate (Na+/HCO3-) symporter; pHe: extracellular pH; GLUT-1: glucose transporter 1; PGK-1: phosphoglycerate kinase 1.
    Keywords:  Proliferating tumor cells; erythrocytes; glycolysis; ion channels; pentose phosphate pathway; tumor acidic microenvironment
    DOI:  https://doi.org/10.1080/15384101.2019.1618125
  46. PLoS One. 2019 ;14(6): e0218003
    Bueno M, Zank D, Buendia-Roldán I, Fiedler K, Mays BG, Alvarez D, Sembrat J, Kimball B, Bullock JK, Martin JL, Nouraie M, Kaufman BA, Rojas M, Pardo A, Selman M, Mora AL.
      We have previously shown that endoplasmic reticulum stress (ER stress) represses the PTEN inducible kinase 1 (PINK1) in lung type II alveolar epithelial cells (AECII) reducing mitophagy and increasing the susceptibility to lung fibrosis. Although increased circulating mitochondrial DNA (mtDNA) has been reported in chronic lung diseases, the contribution of mitophagy in the modulation of mitochondrial DAMP release and activation of profibrotic responses is unknown. In this study, we show that ER stress and PINK1 deficiency in AECII led to mitochondrial stress with significant oxidation and damage of mtDNA and subsequent extracellular release. Extracellular mtDNA was recognized by TLR9 in AECII by an endocytic-dependent pathway. PINK1 deficiency-dependent mtDNA release promoted activation of TLR9 and triggered secretion of the profibrotic factor TGF-β which was rescued by PINK1 overexpression. Enhanced mtDNA oxidation and damage were found in aging and IPF human lungs and, in concordance, levels of circulating mtDNA were significantly elevated in plasma and bronchoalveolar lavage (BAL) from patients with IPF. Free mtDNA was found elevated in other ILDs with low expression of PINK1 including hypersensitivity pneumonitis and autoimmune interstitial lung diseases. These results support a role for PINK1 mediated mitophagy in the attenuation of mitochondrial damage associated molecular patterns (DAMP) release and control of TGF-β mediated profibrotic responses.
    DOI:  https://doi.org/10.1371/journal.pone.0218003
  47. Sci Rep. 2019 Jun 03. 9(1): 8184
    Monshupanee T, Chairattanawat C, Incharoensakdi A.
      The photoautotrophic cyanobacterium Synechocystis sp. PCC 6803 assimilates carbon dioxide as the sole carbon source, and a major portion of the assimilated carbon is metabolically consumed by the tricarboxylic acid (TCA) cycle. Effects of partial interference of TCA cycle metabolic activity on other carbon metabolism have yet to be examined. Here, the γ-aminobutyric acid (GABA) shunt, one of the metabolic pathways for completing TCA cycle in Synechocystis, was disrupted via inactivating the glutamate decarboxylase gene (gdc). Under normal photoautotrophic condition, cell growth and the level of the TCA cycle metabolites succinate, malate and citrate were decreased by 25%, 35%, 19% and 28%, respectively, in Δgdc mutant relative to those in the wild type (WT). The cellular levels of glycogen and total lipids of the Δgdc mutant were comparable to those of the WT, but the intracellular levels of pyruvate and bioplastic poly(3-hydroxybutyrate) (PHB) were 1.23- and 2.50-fold higher, respectively, in Δgdc mutant. Thus, disruption of the GABA shunt pathway reduced the TCA cycle metabolites levels, but positively enhanced the bioaccumulation of pyruvate and PHB. The PHB production rate in Δgdc mutant was 2.0-fold higher than in the WT under normal photoautotrophy.
    DOI:  https://doi.org/10.1038/s41598-019-44729-8
  48. Cell Metab. 2019 May 27. pii: S1550-4131(19)30249-9. [Epub ahead of print]
    Li Q, Wang Y, Wu S, Zhou Z, Ding X, Shi R, Thorne RF, Zhang XD, Hu W, Wu M.
      We report that circACC1, a circular RNA derived from human ACC1, plays a critical role in cellular responses to metabolic stress. CircACC1 is preferentially produced over ACC1 in response to serum deprivation by the transcription factor c-Jun. It functions to stabilize and promote the enzymatic activity of the AMPK holoenzyme by forming a ternary complex with the regulatory β and γ subunits. The cellular levels of circACC1 modulate both fatty acid β-oxidation and glycolysis, resulting in profound changes in cellular lipid storage. In a tumor xenograft model, silencing or enforced expression of circACC1 resulted in growth inhibition and enhancement, respectively. Moreover, increased AMPK activation in colorectal cancer tissues was frequently associated with elevated circACC1 expression. We conclude that circACC1 serves as an economic means to elicit AMPK activation and moreover propose that cancer cells exploit circACC1 during metabolic reprogramming.
    Keywords:  AMPK; c-Jun; circACC1; circular RNA; fatty acid β oxidation; glycolysis; lipid metabolism; metabolic reprogramming; non-coding RNA; serum deprivation
    DOI:  https://doi.org/10.1016/j.cmet.2019.05.009
  49. Proc Natl Acad Sci U S A. 2019 Jun 03. pii: 201822067. [Epub ahead of print]
    Hwang I, Jo K, Shin KC, Kim JI, Ji Y, Park YJ, Park J, Jeon YG, Ka S, Suk S, Noh HL, Choe SS, Alfadda AA, Kim JK, Kim S, Kim JB.
      Accumulating evidence suggests that subcutaneous and visceral adipose tissues are differentially associated with metabolic disorders. In obesity, subcutaneous adipose tissue is beneficial for metabolic homeostasis because of repressed inflammation. However, the underlying mechanism remains unclear. Here, we demonstrate that γ-aminobutyric acid (GABA) sensitivity is crucial in determining fat depot-selective adipose tissue macrophage (ATM) infiltration in obesity. In diet-induced obesity, GABA reduced monocyte migration in subcutaneous inguinal adipose tissue (IAT), but not in visceral epididymal adipose tissue (EAT). Pharmacological modulation of the GABAB receptor affected the levels of ATM infiltration and adipose tissue inflammation in IAT, but not in EAT, and GABA administration ameliorated systemic insulin resistance and enhanced insulin-dependent glucose uptake in IAT, accompanied by lower inflammatory responses. Intriguingly, compared with adipose-derived stem cells (ADSCs) from EAT, IAT-ADSCs played key roles in mediating GABA responses that repressed ATM infiltration in high-fat diet-fed mice. These data suggest that selective GABA responses in IAT contribute to fat depot-selective suppression of inflammatory responses and protection from insulin resistance in obesity.
    Keywords:  adipose tissue macrophage (ATM); adipose-derived stem cell (ADSC); epididymal adipose tissue (EAT); gamma (γ)-aminobutyric acid (GABA); inguinal adipose tissue (IAT)
    DOI:  https://doi.org/10.1073/pnas.1822067116
  50. Cell Metab. 2019 Jun 04. pii: S1550-4131(19)30252-9. [Epub ahead of print]29(6): 1240-1242
    Domínguez-Andrés J, Netea MG.
      In this issue of Cell Metabolism, Du et al. (2019) describe how insulin-like growth factor 2 (IGF-2), a protein with structural similarity to insulin, induces an anti-inflammatory phenotype in maturing macrophages through reprogramming of their mitochondrial metabolism. These anti-inflammatory properties are maintained upon secondary stimulation and alleviate experimental autoimmune encephalomyelitis (EAE) in vivo.
    DOI:  https://doi.org/10.1016/j.cmet.2019.05.012
  51. Biochim Biophys Acta Rev Cancer. 2019 May 29. pii: S0304-419X(19)30015-0. [Epub ahead of print]
    Grasmann G, Smolle E, Olschewski H, Leithner K.
      Cancer cells constantly face a fluctuating nutrient supply and interference with adaptive responses might be an effective therapeutic approach. It has been discovered that in the absence of glucose, cancer cells can synthesize crucial metabolites by expressing phosphoenolpyruvate carboxykinase (PEPCK, PCK1 or PCK2) using abbreviated forms of gluconeogenesis. Gluconeogenesis, which in essence is the reverse pathway of glycolysis, uses lactate or amino acids to feed biosynthetic pathways branching from glycolysis. PCK1 and PCK2 have been shown to be critical for the growth of certain cancers. In contrast, fructose-1,6-bisphosphatase 1 (FBP1), a downstream gluconeogenesis enzyme, inhibits glycolysis and tumor growth, partly by non-enzymatic mechanisms. This review sheds light on current knowledge of cancer cell gluconeogenesis and its role in metabolic reprogramming, cancer cell plasticity, and tumor growth.
    Keywords:  Adaptation; Gluconeogenesis; Metabolic plasticity; Starvation; Tumor
    DOI:  https://doi.org/10.1016/j.bbcan.2019.05.006
  52. Cancers (Basel). 2019 May 31. pii: E761. [Epub ahead of print]11(6):
    Peruzzo R, Szabo I.
      Mitochondrial ion channels are emerging oncological targets, as modulation of these ion-transporting proteins may impact on mitochondrial membrane potential, efficiency of oxidative phosphorylation and reactive oxygen production. In turn, these factors affect the release of cytochrome c, which is the point of no return during mitochondrial apoptosis. Many of the currently used chemotherapeutics induce programmed cell death causing damage to DNA and subsequent activation of p53-dependent pathways that finally leads to cytochrome c release from the mitochondrial inter-membrane space. The view is emerging, as summarized in the present review, that ion channels located in this organelle may account in several cases for the resistance that cancer cells can develop against classical chemotherapeutics, by preventing drug-induced apoptosis. Thus, pharmacological modulation of these channel activities might be beneficial to fight chemo-resistance of different types of cancer cells.
    Keywords:  mitochondrial ion channels; permeabilization and cytochrome c release; resistance to apoptosis
    DOI:  https://doi.org/10.3390/cancers11060761
  53. Mitochondrion. 2019 Jun 03. pii: S1567-7249(19)30055-8. [Epub ahead of print]
    Wang T, Xie X, Liu H, Chen F, Du J, Wang X, Jiang X, Yu F, Fan H.
      Pyridine Nucleotide-Disulphide Oxidoreductase Domain 2 (PYROXD2), a Hepatitis B virus X protein (HBx)-interacting protein, is significantly down-regulated in hepatocellular carcinoma (HCC), however its exact biological function remains unclear. The aim of this study is to investigate the subcellular localization and biological function of PYROXD2 in hepatic cells. The results showed that PYROXD2 was imported to the mitochondrial inner membrane/matrix by Tom40 and Tim23, but not Mia40. PYROXD2 151-230aa might be the mitochondrial targeting sequence. PYROXD2 interacted with complex IV subunit COX5B. Knockout of PYROXD2 decreased MMP, intracellular ROS, complex IV activity, cell proliferation, ATP content and mtDNA copy number, but increased mtROS levels and the number of immature mitochondria. In summary, our data illustrated that PYROXD2 localizes to the mitochondrial inner membrane/matrix, and it plays important roles in regulating mitochondrial function.
    Keywords:  COX5B; Complex IV; Mitochondria; PYROXD2
    DOI:  https://doi.org/10.1016/j.mito.2019.05.007
  54. Arch Pathol Lab Med. 2019 Jun 06.
    Ibrahim A, Chopra S.
      Succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumor (GIST) is a subset of wild-type GIST that constitutes approximately 10% of gastric GISTs. SDH-mutated GISTs lack mutations in the proto-oncogene receptor tyrosine kinase (also known as KIT, c-KIT, or CD117) or platelet-derived growth factor receptor α (PDGFR-α). These tumors have female predilection, affect children and young adults, and have a spectrum of behavior from indolent to progressive. These tumors have characteristic morphologic features including multinodular architecture, multiple tumors, lymphovascular involvement, and occasional lymph node metastasis. They can be seen in patients with Carney triad or Carney-Stratakis syndrome. Although a mutation in any one of the SDH subunits can be pathogenic, deficiency of a single subunit leads to loss of detectable SDH subunit B by immunohistochemistry, enabling a convenient, tissue-based screening method. The prognosis and the clinical course of these tumors is different from that of KIT- or PDGFR-α-mutated GISTs. Surgical management is considered the main line of treatment. SDH-mutated GISTs do not respond well to the common targeted therapy, with no objective tumor response to imatinib. The role of the pathologist in diagnosing these cases is imperative in management and subsequent follow-up.
    DOI:  https://doi.org/10.5858/arpa.2018-0370-RS