bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2020‒05‒24
37 papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. Elife. 2020 May 20. pii: e55845. [Epub ahead of print]9
    Stephenson ZA, Harvey RF, Pryde KR, Mistry S, Hardy RE, Serreli R, Chung I, Allen TE, Stoneley M, MacFarlane M, Fischer PM, Hirst J, Kellam B, Willis AE.
      Disruption of mitochondrial function selectively targets tumour cells that are dependent on oxidative phosphorylation. However, due to their high energy demands, cardiac cells are disproportionately targeted by mitochondrial toxins resulting in a loss of cardiac function. An analysis of the effects of mubritinib on cardiac cells showed that this drug did not inhibit HER2 as reported, but directly inhibits mitochondrial respiratory complex I, reducing cardiac-cell beat rate, with prolonged exposure resulting in cell death. We used a library of chemical variants of mubritinib and showed that modifying the 1H-1,2,3-triazole altered complex I inhibition, identifying the heterocyclic 1,3-nitrogen motif as the toxicophore. The same toxicophore is present in a second anti-cancer therapeutic carboxyamidotriazole (CAI) and we demonstrate that CAI also functions through complex I inhibition, mediated by the toxicophore. Complex I inhibition is directly linked to anti-cancer cell activity, with toxicophore modification ablating the desired effects of these compounds on cancer cell proliferation and apoptosis.
    Keywords:  biochemistry; cancer biology; chemical biology; human
  2. BMC Biol. 2020 May 20. 18(1): 54
    Wright JJ, Fedor JG, Hirst J, Roessler MM.
      BACKGROUND: For decades, semiquinone intermediates have been suggested to play an essential role in catalysis by one of the most enigmatic proton-pumping enzymes, respiratory complex I, and different mechanisms have been proposed on their basis. However, the difficulty in investigating complex I semiquinones, due to the many different enzymes embedded in the inner mitochondrial membrane, has resulted in an ambiguous picture and no consensus.RESULTS: In this paper, we re-examine the highly debated origin of semiquinone species in mitochondrial membranes using a novel approach. Our combination of a semi-artificial chimeric respiratory chain with pulse EPR spectroscopy (HYSCORE) has enabled us to conclude, unambiguously and for the first time, that the majority of the semiquinones observed in mitochondrial membranes originate from complex III. We also identify a minor contribution from complex II.
    CONCLUSIONS: We are unable to attribute any semiquinone signals unambiguously to complex I and, reconciling our observations with much of the previous literature, conclude that they are likely to have been misattributed to it. We note that, for this earlier work, the tools we have relied on here to deconvolute overlapping EPR signals were not available. Proposals for the mechanism of complex I based on the EPR signals of semiquinone species observed in mitochondrial membranes should thus be treated with caution until future work has succeeded in isolating any complex I semiquinone EPR spectroscopic signatures present.
    Keywords:  Electron paramagnetic resonance; NADH:ubiquinone oxidoreductase; Respiratory complex I; Semiquinones
  3. Cell Stem Cell. 2020 May 12. pii: S1934-5909(20)30149-1. [Epub ahead of print]
    Singh RP, Jeyaraju DV, Voisin V, Hurren R, Xu C, Hawley JR, Barghout SH, Khan DH, Gronda M, Wang X, Jitkova Y, Sharon D, Liyanagae S, MacLean N, Seneviratene AK, Mirali S, Borenstein A, Thomas GE, Soriano J, Orouji E, Minden MD, Arruda A, Chan SM, Bader GD, Lupien M, Schimmer AD.
      Leukemic stem cells (LSCs) rely on oxidative metabolism and are differentially sensitive to targeting mitochondrial pathways, which spares normal hematopoietic cells. A subset of mitochondrial proteins is folded in the intermembrane space via the mitochondrial intermembrane assembly (MIA) pathway. We found increased mRNA expression of MIA pathway substrates in acute myeloid leukemia (AML) stem cells. Therefore, we evaluated the effects of inhibiting this pathway in AML. Genetic and chemical inhibition of ALR reduces AML growth and viability, disrupts LSC self-renewal, and induces their differentiation. ALR inhibition preferentially decreases its substrate COX17, a mitochondrial copper chaperone, and knockdown of COX17 phenocopies ALR loss. Inhibiting ALR and COX17 increases mitochondrial copper levels which in turn inhibit S-adenosylhomocysteine hydrolase (SAHH) and lower levels of S-adenosylmethionine (SAM), DNA methylation, and chromatin accessibility to lower LSC viability. These results provide insight into mechanisms through which mitochondrial copper controls epigenetic status and viability of LSCs.
    Keywords:  ALR; AML; COX17; LSCs; copper
  4. Cancer Lett. 2020 May 14. pii: S0304-3835(20)30227-5. [Epub ahead of print]
    Yang YF, Wang YY, Hsiao M, Lo S, Chang YC, Jan YH, Lai TC, Lee YC, Hsieh YC, Yuan SF.
      The tumor microenvironment (TME) and metabolic reprogramming have been implicated in cancer development and progression. However, the link between TME, metabolism, and cancer progression in lung cancer is unclear. In the present study, we identified IMPAD1 from the conditioned medium of highly invasive CL1-5. High expression of IMPAD1 was associated with a poorer clinical phenotype in lung cancer patients, with reduced survival and increased lymph node metastasis. Knockdown of IMPAD1 significantly inhibited migration/invasion abilities and metastasis in vitro and in vivo. Upregulation of IMPAD1 and subsequent accumulation of AMP in cells increased the pAMPK, leading to Notch1 and HEY1 upregulation. As AMP is an ADORA1 agonist, treatment with ADORA1 inhibitor reduced the expression of pAMPK and HEY1 expression in IMPAD1-overexpressing cells. IMPAD1 caused mitochondria dysfunction by inhibiting mitochondrial Complex I activity, which reduced mitochondrial ROS levels and activated the AMPK-HEY1 pathway. Collectively this study supports the multipotent role of IMPAD1 in promotion of lung cancer metastasis by simultaneously increasing AMP levels, inhibition of Complex I activity to decrease ROS levels, thereby activating AMPK-Notch1-HEY1 signaling, and providing an alternative metabolic pathway in energy stress conditions.
    Keywords:  ADORA1; AMP; IMPAD1; Lung cancer; Metabolism; Tumor microenvironment
  5. J Mol Cell Cardiol. 2020 May 19. pii: S0022-2828(20)30191-7. [Epub ahead of print]
    Roman B, Kaur P, Ashok D, Kohr M, Biswas R, O'Rourke B, Steenbergen C, Das S.
      AIMS: In cardiomyocytes, there is microRNA (miR) in the mitochondria that originates from the nuclear genome and matures in the cytoplasm before translocating into the mitochondria. Overexpression of one such miR, miR-181c, can lead to heart failure by stimulating reactive oxygen species (ROS) production and increasing mitochondrial calcium level ([Ca2+]m). Mitochondrial calcium uptake 1 protein (MICU1), a regulatory protein in the mitochondrial calcium uniporter complex, plays an important role in regulating [Ca2+]m. Obesity results in miR-181c overexpression and a decrease in MICU1. We hypothesize that lowering miR-181c would protect against obesity-induced cardiac dysfunction.METHODS AND RESULTS: We used an in vivo mouse model of high-fat diet (HFD) for 18 weeks and induced high lipid load in H9c2 cells with oleate-conjugated bovine serum albumin in vitro. We tested the cardioprotective role of lowering miR-181c by using miR-181c/d-/- mice (in vivo) and AntagomiR against miR-181c (in vitro). HFD significantly upregulated heart levels of miR-181c and led to cardiac hypertrophy in wild-type mice, but not in miR-181c/d-/- mice. HFD also increased in ROS production and pyruvate dehydrogenase activity (a surrogate for [Ca2+]m), but the increases were alleviated in miR-181c/d-/- mice. Moreover, miR-181c/d-/- mice fed a HFD had higher levels of MICU1 than did wild-type mice fed a HFD, attenuating the rise in [Ca2+]m. Overexpression of miR-181c in neonatal ventricular cardiomyocytes (NMVM) caused increased ROS production, which oxidized transcription factor Sp1 and led to a loss of Sp1, thereby slowing MICU1 transcription. Hence, miR-181c increases [Ca2+]m through Sp1 oxidation and downregulation of MICU1, suggesting that the cardioprotective effect of miR-181c/d-/- results from inhibition of Sp1 oxidation.
    CONCLUSION: This study has identified a unique nuclear-mitochondrial communication mechanism in the heart orchestrated by miR-181c. Obesity-induced overexpression of miR-181c increases [Ca2+]m via downregulation of MICU1 and leads to cardiac injury. A strategy to inhibit miR-181c in cardiomyocytes can preserve cardiac function during obesity by improving mitochondrial function. Altering miR-181c expression may provide a pharmacologic approach to improve cardiomyopathy in individuals with obesity/type 2 diabetes.
    Keywords:  MICU1; Mitochondria; Mitochondrial calcium; Obesity; miR-181c; microRNA
  6. J Mol Cell Cardiol. 2020 May 11. pii: S0022-2828(20)30124-3. [Epub ahead of print]144 24-34
    Cole LK, Mejia EM, Sparagna GC, Vandel M, Xiang B, Han X, Dedousis N, Kaufman BA, Dolinsky VW, Hatch GM.
      Cardiolipin (CL) is a unique tetra-acyl phospholipid localized to the inner mitochondrial membrane and essential for normal respiratory function. It has been previously reported that the failing human heart and several rodent models of cardiac pathology have a selective loss of CL. A rare genetic disease, Barth syndrome (BTHS), is similarly characterized by a cardiomyopathy due to reduced levels of cardiolipin. A mouse model of cardiolipin deficiency was recently developed by knocking-down the cardiolipin biosynthetic enzyme tafazzin (TAZ KD). These mice develop an age-dependent cardiomyopathy due to mitochondrial dysfunction. Since reduced mitochondrial capacity in the heart may promote the accumulation of lipids, we examined whether cardiolipin deficiency in the TAZ KD mice promotes the development of a lipotoxic cardiomyopathy. In addition, we investigated whether treatment with resveratrol, a small cardioprotective nutraceutical, attenuated the aberrant lipid accumulation and associated cardiomyopathy. Mice deficient in tafazzin and the wildtype littermate controls were fed a low-fat diet, or a high-fat diet with or without resveratrol for 16 weeks. In the absence of obesity, TAZ KD mice developed a hypertrophic cardiomyopathy characterized by reduced left-ventricle (LV) volume (~36%) and 30-50% increases in isovolumetric contraction (IVCT) and relaxation times (IVRT). The progression of cardiac hypertrophy with tafazzin-deficiency was associated with several underlying pathological processes including altered mitochondrial complex I mediated respiration, elevated oxidative damage (~50% increase in reactive oxygen species, ROS), the accumulation of triglyceride (~250%) as well as lipids associated with lipotoxicity (diacylglyceride ~70%, free-cholesterol ~44%, ceramide N:16-35%) compared to the low-fat fed controls. Treatment of TAZ KD mice with resveratrol maintained normal LV volumes and preserved systolic function of the heart. The beneficial effect of resveratrol on cardiac function was accompanied by a significant improvement in mitochondrial respiration, ROS production and oxidative damage to the myocardium. Resveratrol treatment also attenuated the development of cardiac steatosis in tafazzin-deficient mice through reduced de novo fatty acid synthesis. These results indicate for the first time that cardiolipin deficiency promotes the development of a hypertrophic lipotoxic cardiomyopathy. Furthermore, we determined that dietary resveratrol attenuates the cardiomyopathy by reducing ROS, cardiac steatosis and maintaining mitochondrial function.
    Keywords:  Hypertrophy; Lipotoxicity; Mitochondria; Oxidative stress; Resveratrol
  7. Antioxid Redox Signal. 2020 May 22.
    Sanchez-Martin C, Menon D, Moroni E, Ferraro M, Masgras I, Elsey J, Arbiser JL, Colombo G, Rasola A.
      INTRODUCTION: TRAP1, the mitochondrial paralog of the Hsp90 family of molecular chaperones, is required for neoplastic growth in several tumor cell models, where it inhibits succinate dehydrogenase (SDH) activity, thus favoring bioenergetic rewiring, maintenance of redox homeostasis and orchestration of a HIF1α-mediated pseudohypoxic program. Development of selective TRAP1 inhibitors is instrumental for targeted development of anti-neoplastic drugs, but was hampered up to now by the high degree of homology among catalytic pockets of Hsp90 family members. The vegetal derivative honokiol and its lipophilic bis-dichloroacetate ester, honokiol DCA (HDCA), are small molecule compounds with antineoplastic activity. HDCA leads to oxidative stress and apoptosis in in vivo tumor models and displays an action that is functionally opposed to that of TRAP1, as it induces both SDH and the mitochondrial deacetylase SIRT3, which further enhances SDH activity.AIMS: We investigated whether HDCA could interact with TRAP1 inhibiting its chaperone function, and the effects of HDCA on tumor cells harboring TRAP1.
    RESULTS: An allosteric binding site in TRAP1 is able to host HDCA, which inhibits TRAP1 but not Hsp90 ATPase activity. In neoplastic cells, HDCA reverts TRAP1-dependent downregulation of SDH, decreases proliferation rate, increases mitochondrial superoxide levels and abolishes tumorigenic growth.
    INNOVATION: HDCA is a potential lead compound for the generation of anti-neoplastic approaches based on the allosteric inhibition of TRAP1 chaperone activity.
    CONCLUSIONS: We have identified a selective TRAP1 inhibitor that can be used to better dissect TRAP1 biochemical functions and to tailor novel tumor-targeting strategies.
  8. Cell Physiol Biochem. 2020 May 20. 54(4): 517-537
    Guedouari H, Savoie MC, Jean S, Djeungoue-Petga MA, Pichaud N, Hebert-Chatelain E.
      BACKGROUND/AIMS: Src kinase family members, including c-Src, are involved in numerous signaling pathways and have been observed inside different cellular compartments. Notably, c-Src modulates carbohydrate and fatty acid metabolism and is involved in the metabolic rewiring of cancer cells. This kinase is found within mitochondria where it targets different proteins to impact on the organelle functions and overall metabolism. Surprisingly, no global metabolic characterization of Src has been performed although c-Src knock-out mice have been available for 30 years. Considering that c-Src is sensitive to various metabolites, c-Src might represent a crucial player in metabolic adjustments induced by nutrient stress. The aim of this work was to characterize the impact of c-Src on mitochondrial activity and overall metabolism using multi-omic characterization.METHODS: Src+/+ and Src-/- mice were fed ad libitum or fasted during 24h and were then analyzed using multi-omics.
    RESULTS: We observed that deletion of c-Src is linked to lower phosphorylation of Y412-NDUFA8, inhibition of oxygen consumption and accumulation of metabolites involved in glycolysis, TCA cycle and amino acid metabolism in mice fed ad libitum. Finally, metabolomics and (phosphotyrosine) proteomics are differently impacted by Src according to nutrient availability.
    CONCLUSION: The findings presented here highlight that c-Src reduces mitochondrial metabolism and impacts the metabolic adjustment induced by nutrient stress.
    Keywords:  Mitochondria; c-Src kinase; Metabolism; NDUFA8; Nutrient availability; Phosphoproteomics
  9. Biomed Pharmacother. 2020 May 15. pii: S0753-3322(20)30399-1. [Epub ahead of print]127 110207
    Pal S, Porwal K, Rajak S, Sinha RA, Chattopadhyay N.
      Anabolic therapies for osteoporosis including dietary polyphenols promote osteoblast function by influencing its energy metabolism. Among the dietary polyphenols, the beneficial skeletal effects of genistein (an isoflavone), kaempferol (a flavone), resveratrol (RES, a stilbenoid) and epigallocatechin gallate (EGCG, a catechin) have been reported in preclinical studies. We studied the action mechanism of these nutraceuticals on osteoblast bioenergetics. All stimulated differentiation of human fetal osteoblasts (hFOB). However, only EGCG and RES stimulated mitochondrial parameters including basal and maximum respiration, spare respiratory capacity and ATP production (a measure of the activity of electron transport chain/ETC). Increases in these parameters were due to increased mitochondrial biogenesis and consequent upregulation of several mitochondrial proteins including those involved in ETC. Rotenone blocked the osteogenic effect of EGCG and RES suggesting the mediatory action of mitochondria. Both compounds rapidly activated AMPK, and dorsomorphin (an AMPK inhibitor) abolished ATP production stimulated by these compounds. Moreover, EGCG and RES upregulated the mitochondrial biogenesis factor, PGC-1α which is downstream of AMPK activation, and silencing PGC-1α blocked their stimulatory effects on ATP production and hFOB differentiation. Adiponectin receptor 1 (AdipoR1) is an upstream regulator of PGC-1α, and both compounds increased the expression of AdipoR1 but not AdipoR2. Silencing AdipoR1 blocked the upregulation of EGCG/RES-induced PGC-1α and hFOB differentiation. In rat calvarium, both compounds increased AdipoR1, PGC-1α, and RunX2 (the osteoblast transcription factor) with a concomitant increase in mitochondrial copy number and ATP levels. We conclude that EGCG and RES display osteogenic effects by reprogramming osteoblastic bioenergetics by acting as the AdipoR1 agonists.
    Keywords:  Adiponectin receptor; EGCG; Human osteoblast; Mitochondrial biogenesis; Resveretrol
  10. Nat Commun. 2020 May 21. 11(1): 2549
    Yu B, Ma J, Li J, Wang D, Wang Z, Wang S.
      Mitochondria undergo dynamic fusion/fission, biogenesis and mitophagy in response to stimuli or stresses. Disruption of mitochondrial homeostasis could lead to cell senescence, although the underlying mechanism remains unclear. We show that deletion of mitochondrial phosphatase PGAM5 leads to accelerated retinal pigment epithelial (RPE) senescence in vitro and in vivo. Mechanistically, PGAM5 is required for mitochondrial fission through dephosphorylating DRP1. PGAM5 deletion leads to increased mitochondrial fusion and decreased mitochondrial turnover. As results, cellular ATP and reactive oxygen species (ROS) levels are elevated, mTOR and IRF/IFN-β signaling pathways are enhanced, leading to cellular senescence. Overexpression of Drp1 K38A or S637A mutant phenocopies or rescues mTOR activation and senescence in PGAM5-/- cells, respectively. Young but not aging Pgam5-/- mice are resistant to sodium iodate-induced RPE cell death. Our studies establish a link between defective mitochondrial fission, cellular senescence and age-dependent oxidative stress response, which have implications in age-related diseases.
  11. EMBO J. 2020 May 20. e104073
    Acin-Perez R, Benador IY, Petcherski A, Veliova M, Benavides GA, Lagarrigue S, Caudal A, Vergnes L, Murphy AM, Karamanlidis G, Tian R, Reue K, Wanagat J, Sacks H, Amati F, Darley-Usmar VM, Liesa M, Divakaruni AS, Stiles L, Shirihai OS.
      Respirometry is the gold standard measurement of mitochondrial oxidative function, as it reflects the activity of the electron transport chain complexes working together. However, the requirement for freshly isolated mitochondria hinders the feasibility of respirometry in multi-site clinical studies and retrospective studies. Here, we describe a novel respirometry approach suited for frozen samples by restoring electron transfer components lost during freeze/thaw and correcting for variable permeabilization of mitochondrial membranes. This approach preserves 90-95% of the maximal respiratory capacity in frozen samples and can be applied to isolated mitochondria, permeabilized cells, and tissue homogenates with high sensitivity. We find that primary changes in mitochondrial function, detected in fresh tissue, are preserved in frozen samples years after collection. This approach will enable analysis of the integrated function of mitochondrial Complexes I to IV in one measurement, collected at remote sites or retrospectively in samples residing in tissue biobanks.
    Keywords:  frozen tissue; methodology; mitochondrial content; mitochondrial uncoupled respiration; oxygen consumption
  12. Nat Metab. 2020 May;2(5): 397-412
    Tran KV, Brown EL, DeSouza T, Jespersen NZ, Nandrup-Bus C, Yang Q, Yang Z, Desai A, Min SY, Rojas-Rodriguez R, Lundh M, Feizi A, Willenbrock H, Larsen TJ, Severinsen MCK, Malka K, Mozzicato AM, Deshmukh AS, Emanuelli B, Pedersen BK, Fitzgibbons T, Scheele C, Corvera S, Nielsen S.
      Human thermogenic adipose tissue mitigates metabolic disease, raising much interest in understanding its development and function. Here, we show that human thermogenic adipocytes specifically express a primate-specific long non-coding RNA, LINC00473 which is highly correlated with UCP1 expression and decreased in obesity and type-2 diabetes. LINC00473 is detected in progenitor cells, and increases upon differentiation and in response to cAMP. In contrast to other known adipocyte LincRNAs, LINC00473 shuttles out of the nucleus, colocalizes and can be crosslinked to mitochondrial and lipid droplet proteins. Up- or down- regulation of LINC00473 results in reciprocal alterations in lipolysis, respiration and transcription of genes associated with mitochondrial oxidative metabolism. Depletion of PLIN1 results in impaired cAMP-responsive LINC00473 expression and lipolysis, indicating bidirectional interactions between PLIN1, LINC00473 and mitochondrial oxidative functions. Thus, we suggest that LINC00473 is a key regulator of human thermogenic adipocyte function, and reveals a role for a LincRNA in inter-organelle communication and human energy metabolism.
    Keywords:  PLIN1; adipocyte; beige; brite; brown; fat; forskolin; lipid droplet; lipolysis; mitochondria; non-coding RNA; norepinephrine; respiration
  13. Sci Rep. 2020 May 18. 10(1): 8182
    Schömel N, Gruber L, Alexopoulos SJ, Trautmann S, Olzomer EM, Byrne FL, Hoehn KL, Gurke R, Thomas D, Ferreirós N, Geisslinger G, Wegner MS.
      The only enzyme in the glycosphingolipid (GSL) metabolic pathway, which produces glucosylceramide (GlcCer) de novo is UDP-glucose ceramide glucosyltransferase (UGCG). UGCG is linked to pro-cancerous processes such as multidrug resistance development and increased proliferation in several cancer types. Previously, we showed an UGCG-dependent glutamine metabolism adaption to nutrient-poor environment of breast cancer cells. This adaption includes reinforced oxidative stress response and fueling the tricarboxylic acid (TCA) cycle by increased glutamine oxidation. In the current study, we investigated glycolytic and oxidative metabolic phenotypes following UGCG overexpression (OE). UGCG overexpressing MCF-7 cells underwent a metabolic shift from quiescent/aerobic to energetic metabolism by increasing both glycolysis and oxidative glucose metabolism. The energetic metabolic phenotype was not associated with increased mitochondrial mass, however, markers of mitochondrial turnover were increased. UGCG OE altered sphingolipid composition of the endoplasmic reticulum (ER)/mitochondria fractions that may contribute to increased mitochondrial turnover and increased cell metabolism. Our data indicate that GSL are closely connected to cell energy metabolism and this finding might contribute to development of novel therapeutic strategies for cancer treatment.
  14. Toxicol Appl Pharmacol. 2020 May 16. pii: S0041-008X(20)30179-4. [Epub ahead of print] 115055
    van der Mark VA, Adam AAA, Chang JC, Oude Elferink RP, Chamuleau RAFM, Hoekstra R.
      The liver cell line HepaRG is one of the preferred sources of human hepatocytes for in vitro applications. However, mitochondrial energy metabolism is relatively low, which affects hepatic functionality and sensitivity to hepatotoxins. Culturing in a bioartificial liver (BAL) system with high oxygen, medium perfusion, low substrate stiffness, and 3D conformation increases HepaRG functionality and mitochondrial activity compared to conventional monolayer culturing. In addition, drug metabolism has been improved by overexpression of the constitutive androstane receptor (CAR), a regulator of drug and energy metabolism in the new HepaRG-CAR line. Here, we investigated the effect of BAL culturing on the HepaRG-CAR line by applying a simple and downscaled BAL culture procedure based on shaking 3D cultures, named Bal-in-a-dish (BALIAD). We compared monolayer and BALIAD cultures of HepaRG and HepaRG-CAR cells. CAR overexpression and BALIAD culturing synergistically or additively increased transcript levels of CAR and three of the seven tested CAR target genes in biotransformation. Additionally, Cytochrome P450 3A4 activity was 35-fold increased. The mitochondrial energy metabolism was enhanced; lactate production and glucose consumption switched into lactate elimination and glucose production. BALIAD culturing alone reduced glycogen content and increased oxygen consumption and mitochondrial content. Both CAR overexpression and BALIAD culturing decreased mitochondrial superoxide levels. HepaRG-CAR BALIADs were most sensitive to mitochondrial toxicity induced by the hepatotoxin amiodarone, as indicated by oxygen consumption and mitochondrial superoxide accumulation. These data show that BALIAD culturing of HepaRG-CAR cells induces high mitochondrial energy metabolism and xenobiotic metabolism, increasing its potential for drug toxicity studies.
    Keywords:  Amiodarone; Energy metabolism; Hepatocyte; Mitochondria
  15. Antioxidants (Basel). 2020 May 15. pii: E431. [Epub ahead of print]9(5):
    Meza-Torres C, Hernández-Camacho JD, Cortés-Rodríguez AB, Fang L, Bui Thanh T, Rodríguez-Bies E, Navas P, López-Lluch G.
      Resveratrol (RSV) is a bioactive natural molecule that induces antioxidant activity and increases protection against oxidative damage. RSV could be used to mitigate damages associated to metabolic diseases and aging. Particularly, RSV regulates different aspects of mitochondrial metabolism. However, no information is available about the effects of RSV on Coenzyme Q (CoQ), a central component in the mitochondrial electron transport chain. Here, we report for the first time that RSV modulates COQ genes and parameters associated to metabolic syndrome in mice. Mice fed with high fat diet (HFD) presented a higher weight gain, triglycerides (TGs) and cholesterol levels while RSV reverted TGs to control level but not weight or cholesterol. HFD induced a decrease of COQs gene mRNA level, whereas RSV reversed this decrease in most of the COQs genes. However, RSV did not show effect on CoQ9, CoQ10 and total CoQ levels, neither in CoQ-dependent antioxidant enzymes. HFD influenced mitochondrial dynamics and mitophagy markers. RSV modulated the levels of PINK1 and PARKIN and their ratio, indicating modulation of mitophagy. In summary, we report that RSV influences some of the metabolic adaptations of HFD affecting mitochondrial physiology while also regulates COQs gene expression levels in a process that can be associated with mitochondrial dynamics and turnover.
    Keywords:  antioxidant; coenzyme Q; high-fat diet; liver; mitochondria; resveratrol
  16. Biochem Biophys Res Commun. 2020 May 15. pii: S0006-291X(20)30873-1. [Epub ahead of print]
    Qin X, Xu Y, Peng S, Qian S, Zhang X, Shen S, Yang J, Ye J.
      Induction of apoptosis is a strategy in the treatment of glioma, a malignant tumor with the highest prevalence in the brain. Sodium butyrate (NaB) induces apoptosis in glioma cells at pharmacological dosages (>2.5 mM), but the mechanism remains largely unknown beyond the mitochondrial potential drop. In this study, NaB was found to open the mitochondrial permeability transient pore (MPTP) to induce a proton leak in the mechanism of apoptosis. The MPTP opening led to collapse of mitochondrial potential and suppression of ATP production in the NaB-treated cells. Proton leak was increased in the mitochondria under the coupling and uncoupling conditions from the MPTP opening. The proton leak was associated with an elevation in the protein abundance of adenine nucleotide translocator 2 (ANT2) and was blocked by an ANT-specific inhibitor of bongkrekic acid (BA). These data suggest that the proton leak is induced by NaB for the mitochondrial potential drop in the induction of apoptosis. The mechanism may be related to activation of ANT2 in the MPTP complex.
    Keywords:  ANT; ATP; Apoptosis; Glioma; MPTP
  17. Sci Adv. 2020 Apr;6(16): eaba0694
    Sommer N, Alebrahimdehkordi N, Pak O, Knoepp F, Strielkov I, Scheibe S, Dufour E, Andjelković A, Sydykov A, Saraji A, Petrovic A, Quanz K, Hecker M, Kumar M, Wahl J, Kraut S, Seeger W, Schermuly RT, Ghofrani HA, Ramser K, Braun T, Jacobs HT, Weissmann N, Szibor M.
      Mitochondria play an important role in sensing both acute and chronic hypoxia in the pulmonary vasculature, but their primary oxygen-sensing mechanism and contribution to stabilization of the hypoxia-inducible factor (HIF) remains elusive. Alteration of the mitochondrial electron flux and increased superoxide release from complex III has been proposed as an essential trigger for hypoxic pulmonary vasoconstriction (HPV). We used mice expressing a tunicate alternative oxidase, AOX, which maintains electron flux when respiratory complexes III and/or IV are inhibited. Respiratory restoration by AOX prevented acute HPV and hypoxic responses of pulmonary arterial smooth muscle cells (PASMC), acute hypoxia-induced redox changes of NADH and cytochrome c, and superoxide production. In contrast, AOX did not affect the development of chronic hypoxia-induced pulmonary hypertension and HIF-1α stabilization. These results indicate that distal inhibition of the mitochondrial electron transport chain in PASMC is an essential initial step for acute but not chronic oxygen sensing.
  18. Biosci Rep. 2020 May 21. pii: BSR20200665. [Epub ahead of print]
    Qiang S, Ma L, Peng S, Xu Y, Wu K, Shen S, Zhang X, Sun Y, Ye J.
      MECR (mitochondrial 2-enoyl-acyl-carrier protein reductase) is an enzyme in the mitochondrial fatty acid synthase (mtFAS) pathway. MECR activity remains unknown in the mechanism of insulin resistance in the pathogenesis of type 2 diabetes. In this study, MECR activity was investigated in diet-induced obese (DIO) mice. Mecr mRNA was induced by insulin in cell culture, and was elevated in the liver of DIO mice in the presence hyperinsulinemia. However, MECR protein was decreased in the liver of DIO mice, and the reduction was blocked by treatment of the DIO mice with berberine (BBR). The mechanism of MECR protein regulation was investigated with a focus on ATP. The protein was decreased in the cell lysate and DIO liver by an increase in ATP levels. The ATP protein reduction was blocked in the liver of BBR-treated mice by suppression of ATP elevation. The MERC protein reduction was associated with insulin resistance and the protein restoration was associated with improvement of insulin sensitivity by BBR in the DIO mice. The data suggests that MECR protein is regulated in hepatocytes by ATP in association with insulin resistance. The study provides evidence for a relationship of MECR protein and insulin resistance.
    Keywords:  ATP; Berberine; MECR; hepatic physiology; insulin resistance; mitochondrial dysfunction
  19. Cell Metab. 2020 May 15. pii: S1550-4131(20)30240-0. [Epub ahead of print]
    Timper K, Del Río-Martín A, Cremer AL, Bremser S, Alber J, Giavalisco P, Varela L, Heilinger C, Nolte H, Trifunovic A, Horvath TL, Kloppenburg P, Backes H, Brüning JC.
      Astrocytes represent central regulators of brain glucose metabolism and neuronal function. They have recently been shown to adapt their function in response to alterations in nutritional state through responding to the energy state-sensing hormones leptin and insulin. Here, we demonstrate that glucagon-like peptide (GLP)-1 inhibits glucose uptake and promotes β-oxidation in cultured astrocytes. Conversely, postnatal GLP-1 receptor (GLP-1R) deletion in glial fibrillary acidic protein (GFAP)-expressing astrocytes impairs astrocyte mitochondrial integrity and activates an integrated stress response with enhanced fibroblast growth factor (FGF)21 production and increased brain glucose uptake. Accordingly, central neutralization of FGF21 or astrocyte-specific FGF21 inactivation abrogates the improvements in glucose tolerance and learning in mice lacking GLP-1R expression in astrocytes. Collectively, these experiments reveal a role for astrocyte GLP-1R signaling in maintaining mitochondrial integrity, and lack of GLP-1R signaling mounts an adaptive stress response resulting in an improvement of systemic glucose homeostasis and memory formation.
    Keywords:  FGF-21; GLP-1; astrocytes; energy homeostasis; glucose metabolism; hepatic glucose production; mitochondria; obesity; stress response; ß-oxidation
  20. Cell Rep. 2020 May 19. pii: S2211-1247(20)30612-4. [Epub ahead of print]31(7): 107659
    Sorge S, Theelke J, Yildirim K, Hertenstein H, McMullen E, Müller S, Altbürger C, Schirmeier S, Lohmann I.
      The mitochondrial electron transport chain (ETC) enables essential metabolic reactions; nonetheless, the cellular responses to defects in mitochondria and the modulation of signaling pathway outputs are not understood. We show that Notch signaling and ETC attenuation via knockdown of COX7a induces massive over-proliferation. The tumor-like growth is caused by a transcriptional response through the eIF2α-kinase PERK and ATF4, which activates the expression of metabolic enzymes, nutrient transporters, and mitochondrial chaperones. We find this stress adaptation to be beneficial for progenitor cell fitness, as it renders cells sensitive to proliferation induced by the Notch signaling pathway. Intriguingly, over-proliferation is not caused by transcriptional cooperation of Notch and ATF4, but it is mediated in part by pH changes resulting from the Warburg metabolism induced by ETC attenuation. Our results suggest that ETC function is monitored by the PERK-ATF4 pathway, which can be hijacked by growth-promoting signaling pathways, leading to oncogenic pathway activity.
    Keywords:  ATF4; Drosophila; ETC; ETC impairment; ISR; LDH; Notch pathway; PERK; UPR; lactate; mitochondrial electron transport chain; pH; proliferation
  21. Nat Commun. 2020 May 22. 11(1): 2592
    Chen PL, Huang KT, Cheng CY, Li JC, Chan HY, Lin TY, Su MP, Yang WY, Chang HC, Wang HD, Chen CH.
      Mitochondrial aging, which results in mitochondrial dysfunction, is strongly linked to many age-related diseases. Aging is associated with mitochondrial enlargement and transport of cytosolic proteins into mitochondria. The underlying homeostatic mechanisms that regulate mitochondrial morphology and function, and their breakdown during aging, remain unclear. Here, we identify a mitochondrial protein trafficking pathway in Drosophila melanogaster involving the mitochondria-associated protein Dosmit. Dosmit induces mitochondrial enlargement and the formation of double-membraned vesicles containing cytosolic protein within mitochondria. The rate of vesicle formation increases with age. Vesicles originate from the outer mitochondrial membrane as observed by tracking Tom20 localization, and the process is mediated by the mitochondria-associated Rab32 protein. Dosmit expression level is closely linked to the rate of ubiquitinated protein aggregation, which are themselves associated with age-related diseases. The mitochondrial protein trafficking route mediated by Dosmit offers a promising target for future age-related mitochondrial disease therapies.
  22. Signal Transduct Target Ther. 2020 May 20. 5(1): 56
    Xie L, Shi F, Li Y, Li W, Yu X, Zhao L, Zhou M, Hu J, Luo X, Tang M, Fan J, Zhou J, Gao Q, Wu W, Zhang X, Liao W, Bode AM, Cao Y.
      Latent membrane protein 1 (LMP1) is a major Epstein-Barr virus (EBV)-encoded oncoprotein involved in latency infection that regulates mitochondrial functions to facilitate cell survival. Recently, mitochondrial fission has been demonstrated as a crucial mechanism in oncovirus-mediated carcinogenesis. Mitochondrial dynamin-related protein 1 (Drp1)-mediated mitochondrial fission has an impact on the chemoresistance of cancers. However, the mechanism by which oncogenic stress promotes mitochondrial fission, potentially contributing to tumorigenesis, is not entirely understood. The role of Drp1 in the oncogenesis and prognosis of EBV-LMP1-positive nasopharyngeal carcinoma (NPC) was determined in our study. We show that EBV-LMP1 exhibits a new function in remodeling mitochondrial morphology by activating Drp1. A high level of p-Drp1 (Ser616) or a low level of p-Drp1 (Ser637) correlates with poor overall survival and disease-free survival. Furthermore, the protein level of p-Drp1 (Ser616) is related to the clinical stage (TNM stage) of NPC. Targeting Drp1 impairs mitochondrial function and induces cell death in LMP1-positive NPC cells. In addition, EBV-LMP1 regulates Drp1 through two oncogenic signaling axes, AMPK and cyclin B1/Cdk1, which promote cell survival and cisplatin resistance in NPC. Our findings provide novel insight into the role of EBV-LMP1-driven mitochondrial fission in regulating Drp1 phosphorylation at serine 616 and serine 637. Disruption of Drp1 could be a promising therapeutic strategy for LMP1-positive NPC.
  23. Front Pharmacol. 2020 ;11 545
    Maciel L, de Oliveira DF, Monnerat G, Campos de Carvalho AC, Nascimento JHM.
      Humoral factors released during ischemic preconditioning (IPC) protect the myocardium against ischemia/reperfusion (I/R) injury. We have recently identified 10 kDa-heat shock protein (HSP10) and a fraction of small 5-10 kDa peptides (5-10-sP) in the coronary effluent of IPC-treated hearts and demonstrated their cardioprotective potential. We here used our isolated mitochondria model to characterize the impact of exogenous HSP10 and 5-10-sP on mitochondria function from myocardium subjected to I/R injury. Isolated perfused rat hearts were submitted to 30-min global ischemia and 10-min reperfusion. Before ischemia, isolated hearts were infused with saline or 5-10-sP, with or without a mitochondrial ATP-sensitive-K+-channel blocker (5HD 10 μmol·L-1) or PKC inhibitor (chelerythrine 10 μmol·L-1), before I/R. HSP10 (1 µmol·L-1) was infused into isolated hearts before I/R without blockers. At 10-min reperfusion, the mitochondria were isolated and mitochondrial function was assessed. In a subset of experiments, freshly isolated mitochondria were directly incubated with HSP10 or 5-10-sP with or without 5HD or chelerythrine before in vitro hypoxia/reoxygenation. Infusion of 5-10-sP (n = 5) and HSP10 (n = 5) into isolated hearts before I/R improved mitochondrial ADP-stimulated respiration, ATP production and prevented mitochondrial ROS formation compared to the I/R group (n = 5); this effect was abrogated by 5HD and chelerythrine. In freshly isolated mitochondria with in vitro hypoxia/reoxygenation, HSP10 (n = 16) and 5-10-sP (n = 16) incubation prevented reductions of mitochondrial ADP-stimulated respiration (91.5 ± 5.1 nmol O2/min/mg PTN), ATP production (250.1 ± 9.3 μmol ATP/200μg PTN), and prevented mitochondrial ROS production (219.7 ± 9.0 nmol H2O2/200μg PTN) induced by hypoxia/reoxygenation (n = 12, 51.5 ± 5.0 nmol O2/min/mg PTN; 187 ± 21.7 μmol ATP/200 μg PTN; 339.0 ± 14.3 nmol H2O2/200 μg PTN, p < 0.001, respectively). 5HD reduced the ADP-stimulated respiration in the HSP10 group (65.84 ± 3.3 nmol O2/min/mg PTN), ATP production (193.7 ± 12.1 μmol ATP/200μg PTN) and increased ROS in the 5-10-sP group (274.4 ± 21.7 nmol H2O2/200 μg PTN). Mitochondria are a target of the cardioprotection induced by 5-10-sP and HSP10. This protection is dependent of PKC and mKATP activation. HSP10 can act directly on mitochondria and protects against hypoxia/reoxygenation injury by mKATP activation.
    Keywords:  HSP10; cardioprotection; humoral factors; ischemic preconditioning; mitochondria
  24. Transl Oncol. 2020 May 13. pii: S1936-5233(20)30021-8. [Epub ahead of print]13(8): 100785
    Lippmann J, Petri K, Fulda S, Liese J.
      Ferroptosis, a newly discovered form of cell death mediated by reactive oxygen species (ROS) and lipid peroxidation, has recently been shown to have an impact on various cancer types; however, so far there are only few studies about its role in hepatocellular carcinoma (HCC). The delicate equilibrium of ROS in cancer cells has found to be crucial for cell survival, thus increased levels may trigger ferroptosis in HCC. In our study, we investigated the effect of different ROS modulators and ferroptosis inducers on a human HCC cell line and a human hepatoblastoma cell line. We identified a novel synergistic cell death induction by the combination of Auranofin and buthionine sulfoxime (BSO) or by Erastin and BSO at subtoxic concentrations. We found a caspase-independent, redox-regulated cell death, which could be rescued by different inhibitors of ferroptosis. Both cotreatments stimulated lipid peroxidation. All these findings indicated ferroptotic cell death. Both cotreatments affected the canonical ferroptosis pathway through GPX4 downregulation. We also found an accumulation of Nrf2 and HO-1, indicating an additional effect on the non-canonical pathway. Our results implicate that targeting these two main ferroptotic pathways simultaneously can overcome chemotherapy resistance in HCC.
  25. Cancer Lett. 2020 Aug 01. pii: S0304-3835(20)30233-0. [Epub ahead of print]484 50-64
    Galland S, Martin P, Fregni G, Letovanec I, Stamenkovic I.
      Solid tumor growth triggers a dynamic host response, which recapitulates wound healing and defines the tumor microenvironment (TME). In addition to the action of the tumor cells themselves, the TME is maintained by a myriad of immune and stromal cell-derived soluble mediators and extracellular matrix components whose combined action supports tumor progression. However, therapeutic targeting of the TME has proven challenging because of incomplete understanding of the tumor-host crosstalk at the molecular level. Here, we investigated the crosstalk between mesenchymal stromal cells (MSCs) and primary cancer cells (PCCs) from human squamous cell lung carcinoma (SCC). We discovered that PCCs secrete CCL3 and stimulate IL-6, CCL2, ICAM-1 and VCAM-1 expression in MSCs and that the MSC-PCC crosstalk can be disrupted by the lipid-lowering drug simvastatin, which displays pleiotropic effects on cell metabolism and suppresses IL-6 and CCL2 production by MSCs and CCL3 secretion by PCCs. In addition, simvastatin inhibited spheroid formation by PCCs and negatively affected PCC survival. Our observations demonstrate that commonly used statins may be repurposed to target the TME in lung carcinoma.
    Keywords:  CCL2; CCL3; Interleukin-6; Lung cancer; Mesenchymal stromal cells; Simvastatin
  26. J Biol Chem. 2020 May 19. pii: jbc.RA120.013867. [Epub ahead of print]
    Holbert CE, Dunworth M, Foley JR, Dunston TT, Murray Stewart T, Casero RA.
      Polyamines are small polycationic alkylamines involved in many fundamental cellular processes, including proliferation, nucleic acid synthesis, apoptosis, and protection from oxidative damage. It has been proposed that in addition to these functions, elevated levels of polyamines promote longevity in various biological systems, including yeast, drosophila, and murine models. A series of in vitro mechanistic studies by multiple investigators has led to the conclusion that addition of exogenous spermidine promotes longevity through autophagy induction; however, these experiments were confounded by the use of mammalian cell culture systems supplemented with fetal bovine serum (FBS). Using cell viability assays, LC3B immunoblots, and live-cell fluorescence microscopy, we report here that in the presence of ruminant serum, exogenously added polyamines are quickly oxidized by the copper-containing bovine serum amine oxidase (BSAO). This polyamine oxidation resulted in the production of harmful byproducts including hydrogen peroxide, ammonia, and reactive aldehydes. Our data demonstrate that it is critically important to prevent confounding BSAO-induced cytotoxicity in mechanistic studies of the roles of polyamines in autophagy.
    Keywords:  amine oxidase; autophagy; beta-oxidation; bovine serum amine oxidase; cytotoxicity; hydrogen peroxide; oxidative stress; polyamine; spermidine; spermine
  27. Biotechnol Bioeng. 2020 May 21.
    Bulté DB, Palomares LA, Parra CG, Martínez JA, Contreras MA, Noriega LG, Ramírez OT.
      CHO cells are characterized by a low glucose catabolic efficiency, resulting in undesirable lactate production. Here, it is hypothesized that such low efficiency is determined by the transport of pyruvate into the mitochondria. The Mitochondrial Pyruvate Carrier (MPC), responsible for introducing pyruvate into the mitochondria, is formed by two subunits, MPC1 and MPC2. Stable CHO cell lines, overexpressing the genes of both subunits, were constructed to facilitate the entry of pyruvate into the mitochondria and its incorporation into oxidative pathways. Significant overexpression of both genes, compared to the basal level of the control cells, was verified, and subcellular localization of both subunits in the mitochondria was confirmed. Kinetic evaluation of the best MPC overexpressing CHO cells showed a reduction of up to 50% in the overall yield of lactate production with respect to the control. An increase in specific growth rate and maximum viable cell concentration, as well as an increase of up to 40% on the maximum concentration of two recombinant model proteins transiently expressed (alkaline phosphatase or a monoclonal antibody), was also observed. Hybrid cybernetic modelling, that considered 89 reactions, 25 extracellular metabolites, and a network of 62 intracellular metabolites, explained that the best MPC overexpression case resulted in an increased metabolic flux across the mitochondrial membrane, activated a more balanced growth, and reduced the Warburg effect without compromising glucose consumption rate and maximum cell concentration. Overall, this work showed that transport of pyruvate into the mitochondria limits the efficiency of glucose oxidation, which can be overcome by a cell engineering approach. This article is protected by copyright. All rights reserved.
    Keywords:  CHO cells; Warburg effect; glucose metabolism; mitochondrial pyruvate carrier; recombinant protein production
  28. Open Biol. 2020 May;10(5): 200061
    Lawless C, Greaves L, Reeve AK, Turnbull DM, Vincent AE.
      How mitochondrial DNA mutations clonally expand in an individual cell is a question that has perplexed mitochondrial biologists for decades. A growing body of literature indicates that mitochondrial DNA mutations play a major role in ageing, metabolic diseases, neurodegenerative diseases, neuromuscular disorders and cancers. Importantly, this process of clonal expansion occurs for both inherited and somatic mitochondrial DNA mutations. To complicate matters further there are fundamental differences between mitochondrial DNA point mutations and deletions, and between mitotic and post-mitotic cells, that impact this pathogenic process. These differences, along with the challenges of investigating a longitudinal process occurring over decades in humans, have so far hindered progress towards understanding clonal expansion. Here we summarize our current understanding of the clonal expansion of mitochondrial DNA mutations in different tissues and highlight key unanswered questions. We then discuss the various existing biological models, along with their advantages and disadvantages. Finally, we explore what has been achieved with mathematical modelling so far and suggest future work to advance this important area of research.
    Keywords:  ageing; clonal expansion; disease; heteroplasmy; mtDNA; mutation
  29. J Am Chem Soc. 2020 May 22.
    Shen FF, Dai SY, Wong NK, Deng S, Wong AS, Yang D.
      Molecules that are capable of disrupting cellular ion homeostasis offer unique opportunities to treat cancer. However, previously reported synthetic ion transporters showed limited value as promiscuous ionic disruption caused toxicity to both healthy cells and cancer cells indiscriminately. Here we report a simple yet efficient synthetic K+ transporter that takes advantage of the endogenous subcellular pH gradient and membrane potential to site-selectively mediate K+/H+ transport on the mitochondrial and lysosomal membranes in living cells. Consequent mitochondrial and lysosomal damages enhanced cytotoxicity to chemo-resistant ovarian cancer stem cells (CSCs) via apoptosis induction and autophagy suppression with remarkable selectivity (up to 47-fold). The eradication of CSCs blunted tumor formation in mice. We believe this strategy can be exploited in the structural design and applications of next-generation synthetic cation transporters for the treatment of cancer and other diseases related to dysfunctional K+ channels.
  30. Science. 2020 May 21. pii: eaax0860. [Epub ahead of print]
    Desdín-Micó G, Soto-Heredero G, Aranda JF, Oller J, Carrasco E, Gabandé-Rodríguez E, Blanco EM, Alfranca A, Cussó L, Desco M, Ibañez B, Gortazar AR, Fernández-Marcos P, Navarro MN, Hernaez B, Alcamí A, Baixauli F, Mittelbrunn M.
      The impact of immunometabolism on age-associated diseases remains uncertain. Here, we show that T cells with dysfunctional mitochondria due to mitochondrial transcription factor A (TFAM) deficiency act as accelerators of senescence. In mice, these cells instigate multiple aging-related features, including metabolic, cognitive, physical, and cardiovascular alterations, which together result in premature death. T cell metabolic failure induces the accumulation of circulating cytokines, which resembles chronic inflammation characteristic of aging ("inflammaging"). This cytokine storm itself acts as a systemic inducer of senescence. Blocking TNF-α signaling or preventing senescence with NAD+ precursors partially rescues premature aging in mice with Tfam-deficient T cells. Thus, T cells can regulate organismal fitness and lifespan, highlighting the importance of tight immunometabolic control in both aging and the onset of age-associated diseases.
  31. Nat Commun. 2020 May 22. 11(1): 2578
    Li Z, Peng Y, Li J, Chen Z, Chen F, Tu J, Lin S, Wang H.
      Studies on biological functions of N6-methyladenosine (m6A) modification in mRNA have sprung up in recent years. We find m6A can positively regulate the glycolysis of cancer cells. Specifically, m6A-sequencing and functional studies confirm that pyruvate dehydrogenase kinase 4 (PDK4) is involved in m6A regulated glycolysis and ATP generation. The m6A modified 5'UTR of PDK4 positively regulates its translation elongation and mRNA stability via binding with YTHDF1/eEF-2 complex and IGF2BP3, respectively. Targeted specific demethylation of PDK4 m6A by dm6ACRISPR system can significantly decrease the expression of PDK4 and glycolysis of cancer cells. Further, TATA-binding protein (TBP) can transcriptionally increase the expression of Mettl3 in cervical cancer cells via binding to its promoter. In vivo and clinical data confirm the positive roles of m6A/PDK4 in tumor growth and progression of cervical and liver cancer. Our study reveals that m6A regulates glycolysis of cancer cells through PDK4.
  32. Sci Rep. 2020 May 19. 10(1): 8219
    Passamonti M, Calderone M, Delpero M, Plazzi F.
      Gene expression involves multiple processes, from transcription to translation to the mature, functional peptide, and it is regulated at multiple levels. Small RNA molecules are known to bind RNA messengers affecting their fate in the cytoplasm (a process generically termed 'RNA interference'). Such small regulatory RNAs are well-known to be originated from the nuclear genome, while the role of mitochondrial genome in RNA interference was largely overlooked. However, evidence is growing that mitochondrial DNA does provide the cell a source of interfering RNAs. Small mitochondrial highly transcribed RNAs (smithRNAs) have been proposed to be transcribed from the mitochondrion and predicted to regulate nuclear genes. Here, for the first time, we show in vivo clues of the activity of two smithRNAs in the Manila clam, Ruditapes philippinarum. Moreover, we show that smithRNAs are present and can be annotated in representatives of the three main bilaterian lineages; in some cases, they were already described and assigned to a small RNA category (e.g., piRNAs) given their biogenesis, while in other cases their biogenesis remains unclear. If mitochondria may affect nuclear gene expression through RNA interference, this opens a plethora of new possibilities for them to interact with the nucleus and makes metazoan mitochondrial DNA a much more complex genome than previously thought.
  33. iScience. 2020 Apr 29. pii: S2589-0042(20)30301-1. [Epub ahead of print]23(5): 101116
    Gansemer ER, McCommis KS, Martino M, King-McAlpin AQ, Potthoff MJ, Finck BN, Taylor EB, Rutkowski DT.
      Many metabolic diseases disrupt endoplasmic reticulum (ER) homeostasis, but little is known about how metabolic activity is communicated to the ER. Here, we show in hepatocytes and other metabolically active cells that decreasing the availability of substrate for the tricarboxylic acid (TCA) cycle diminished NADPH production, elevated glutathione oxidation, led to altered oxidative maturation of ER client proteins, and attenuated ER stress. This attenuation was prevented when glutathione oxidation was disfavored. ER stress was also alleviated by inhibiting either TCA-dependent NADPH production or Glutathione Reductase. Conversely, stimulating TCA activity increased NADPH production, glutathione reduction, and ER stress. Validating these findings, deletion of the Mitochondrial Pyruvate Carrier-which is known to decrease TCA cycle activity and protect the liver from steatohepatitis-also diminished NADPH, elevated glutathione oxidation, and alleviated ER stress. Together, our results demonstrate a novel pathway by which mitochondrial metabolic activity is communicated to the ER through the relay of redox metabolites.
    Keywords:  biological sciences; cell biology; functional aspects of cell biology
  34. Signal Transduct Target Ther. 2020 ;5 56
    Xie L, Shi F, Li Y, Li W, Yu X, Zhao L, Zhou M, Hu J, Luo X, Tang M, Fan J, Zhou J, Gao Q, Wu W, Zhang X, Liao W, Bode AM, Cao Y.
      Latent membrane protein 1 (LMP1) is a major Epstein-Barr virus (EBV)-encoded oncoprotein involved in latency infection that regulates mitochondrial functions to facilitate cell survival. Recently, mitochondrial fission has been demonstrated as a crucial mechanism in oncovirus-mediated carcinogenesis. Mitochondrial dynamin-related protein 1 (Drp1)-mediated mitochondrial fission has an impact on the chemoresistance of cancers. However, the mechanism by which oncogenic stress promotes mitochondrial fission, potentially contributing to tumorigenesis, is not entirely understood. The role of Drp1 in the oncogenesis and prognosis of EBV-LMP1-positive nasopharyngeal carcinoma (NPC) was determined in our study. We show that EBV-LMP1 exhibits a new function in remodeling mitochondrial morphology by activating Drp1. A high level of p-Drp1 (Ser616) or a low level of p-Drp1 (Ser637) correlates with poor overall survival and disease-free survival. Furthermore, the protein level of p-Drp1 (Ser616) is related to the clinical stage (TNM stage) of NPC. Targeting Drp1 impairs mitochondrial function and induces cell death in LMP1-positive NPC cells. In addition, EBV-LMP1 regulates Drp1 through two oncogenic signaling axes, AMPK and cyclin B1/Cdk1, which promote cell survival and cisplatin resistance in NPC. Our findings provide novel insight into the role of EBV-LMP1-driven mitochondrial fission in regulating Drp1 phosphorylation at serine 616 and serine 637. Disruption of Drp1 could be a promising therapeutic strategy for LMP1-positive NPC.
    Keywords:  Cancer microenvironment; Drug development; Head and neck cancer
  35. Mol Ther Nucleic Acids. 2020 May 01. pii: S2162-2531(20)30125-6. [Epub ahead of print]20 801-811
    Wu Z, Sun H, Wang C, Liu W, Liu M, Zhu Y, Xu W, Jin H, Li J.
      Circular RNAs (circRNAs), a novel family of non-coding RNAs, play crucial roles in cancer progression. While the existing research focuses on nuclear genome-derived (nu)-circRNAs, the biological and clinical characteristics of mitochondrial genome-derived (mt)-circRNAs remain largely unknown, especially in chronic lymphocytic leukemia (CLL). In this study, we attempted to identify the novel characteristics of mc-COX2 (mitochondrial genome-derived circRNAs [mc]), one of the mt-circRNAs that can be involved in CLL progression. mt-circRNAs were found to be highly expressed in the plasma exosomes of CLL patients. The endogenous reduction of mc-COX2 can affect mitochondrial functions, suppress cell proliferation, and induce cell apoptosis. The upregulation of mc-COX2 was positively associated with leukemogenesis and worsening survival of CLL patients. Notably, functional analysis revealed that mc-COX2, as differing from conventional nu-circRNAs, was less stable and may function through novel mechanisms other than acting as the competing endogenous RNA. We also screened and tested several chemical compounds and small-molecule inhibitors that can decrease the generation of mc-COX2. It was found that the silencing of mc-COX2 in CLL cells strengthened the anti-tumor effects of drugs used in coordination. Our findings prove that mc-COX2, a critical mt-circRNA highly expressed in plasma, derived from CLL cells and delivered by exosomes, is associated with the progression and prognosis of CLL.
    Keywords:  chronic lymphocytic leukemia; circular RNA; exosome; mitochondria; small-molecule inhibitors
  36. Diabetes. 2020 May 21. pii: db191074. [Epub ahead of print]
    Lantier L, Williams AS, Williams IM, Guerin A, Bracy DP, Goelzer M, Foretz M, Viollet B, Hughey CC, Wasserman DH.
      Insulin resistance due to overnutrition places a burden on energy-producing pathways in skeletal muscle (SkM). Nevertheless, energy state is not compromised. The hypothesis that the energy sensor AMP-activated protein kinase (AMPK) is necessary to offset the metabolic burden of overnutrition was tested using chow-fed and high fat (HF)-fed SkM-specific AMPKα1α2 knockout (mdKO) mice and AMPKα1α2lox/lox littermates (WT). Lean mdKO and WT mice were phenotypically similar. HF-fed mice were equally obese and maintained lean mass regardless of genotype. Results did not support the hypothesis that AMPK is protective during overnutrition. Paradoxically, mdKO mice were more insulin sensitive. Insulin-stimulated SkM glucose uptake was ∼two-fold greater in mdKO mice in vivo. Furthermore, insulin signaling, SkM GLUT4 translocation, hexokinase activity, and glycolysis were increased. AMPK and insulin signaling intersect at mTOR, a critical node for cell proliferation and survival. Basal mTOR activation was reduced by 50% in HF-fed mdKO mice, but was normalized by insulin-stimulation. Mitochondrial function was impaired in mdKO mice, but energy charge was preserved by AMP deamination. Results show a surprising reciprocity between SkM AMPK signaling and insulin action that manifests with diet-induced obesity, as insulin action is preserved to protect fundamental energetic processes in the muscle.
  37. Int J Mol Sci. 2020 May 14. pii: E3466. [Epub ahead of print]21(10):
    Ludvigsen M, Thorlacius-Ussing L, Vorum H, Moyer MP, Stender MT, Thorlacius-Ussing O, Honoré B.
      In the western world, colorectal cancer (CRC) is the third most common cause of cancer-related deaths. Survival is closely related to the stage of cancer at diagnosis striking the clinical need for biomarkers capable of early detection. To search for possible biological parameters for early diagnosis of CRC we evaluated protein expression for three CREC (acronym: Cab45, reticulocalbin, ERC-55, calumenin) proteins: reticulocalbin, calumenin, and ERC-55 in a cellular model consisting of a normal derived colon mucosa cell line, NCM460, and a primary adenocarcinoma cell line of the colon, SW480. Furthermore, this cellular model was analyzed by a top-down proteomic approach, 2-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for novel putative diagnostic markers by identification of differentially expressed proteins between the two cell lines. A different colorectal carcinoma cell line, HCT 116, was used in a bottom-up proteomic approach with label-free quantification (LFQ) LC-MS/MS. The two cellular models gave sets of putative diagnostic CRC biomarkers. Various of these novel putative markers were verified with increased expression in CRC patient neoplastic tissue compared to the expression in a non-involved part of the colon, including reticulocalbin, calumenin, S100A6 and protein SET. Characterization of these novel identified biological features for CRC patients may have diagnostic potential and therapeutic relevance in this malignancy characterized by a still unmet clinical need.
    Keywords:  biomarkers; cellular model system; colorectal adenocarcinoma; colorectal cancer; protein expression; proteomics