bims-camemi Biomed news
on Mitochondrial metabolism in cancer
Issue of 2018‒09‒02
sixteen papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit


  1. Transl Res. 2018 Jul 31. pii: S1931-5244(18)30114-2. [Epub ahead of print]
    Pustylnikov S, Costabile F, Beghi S, Faccibene A.
      An essential advantage during eukaryotic cell evolution was the acquisition of a network of mitochondria as a source of energy for cell metabolism and contrary to conventional wisdom, functional mitochondria are essential for the cancer cell. Multiple aspects of mitochondrial biology beyond bioenergetics support transformation including mitochondrial biogenesis, fission and fusion dynamics, cell death susceptibility, oxidative stress regulation, metabolism, and signaling. In cancer, the metabolism of cells is reprogrammed for energy generation from oxidative phosphorylation to aerobic glycolysis and impacts cancer mitochondrial function. Furthermore cancer cells can also modulate energy metabolism within the cancer microenvironment including immune cells and induce "metabolic anergy" of antitumor immune response. Classical approaches targeting the mitochondria of cancer cells usually aim at inducing changing energy metabolism or directly affecting functions of mitochondrial antiapoptotic proteins but most of such approaches miss the required specificity of action and carry important side effects. Several types of cancers harbor somatic mitochondrial DNA mutations and specific immune response to mutated mitochondrial proteins has been observed. An attractive alternative way to target the mitochondria in cancer cells is the induction of an adaptive immune response against mutated mitochondrial proteins. Here, we review the cancer cell-intrinsic and cell-extrinsic mechanisms through which mitochondria influence all steps of oncogenesis, with a focus on the therapeutic potential of targeting mitochondrial DNA mutations or Tumor Associated Mitochondria Antigens using the immune system.
    DOI:  https://doi.org/10.1016/j.trsl.2018.07.013
  2. Int J Cardiol. 2018 Aug 23. pii: S0167-5273(17)37943-3. [Epub ahead of print]
    Li F, Fan X, Zhang Y, Zhang Y, Ma X, Kou J, Yu B.
      BACKGROUND: Mitochondrial fission is the essential mechanisms of myocardial ischemia/reperfusion (MI/R)-induced cardiomyocytes apoptosis. Myosin II plays a key role in fission due to the recruitment and actomyosin constriction at the fission site in U2OS cells. However, the role of myosin IIA-actin interaction in regulating MI/R-induced cardiomyocytes mitochondrial fission and apoptosis remains to be fully elucidated.METHODS AND RESULTS: When cardiomyocytes are exposed to simulated I/R injury, the myosin IIA protein translocated from the juxtamembrane to the cytoplasm, interacted with actin filaments, formed stress fibers and generated contractile forces. Treatment with the myosin II inhibitor blebbistatin attenuated the myosin IIA-actin complex induced actomyosin contractility and prevented cardiomyocytes apoptosis as reflected by inhibition of cleaved caspase-3 expression, normalization of Bcl-2/Bax levels and decreased apoptotic cells. Meanwhile, blebbistatin inhibited the activation of PINK1/Parkin pathway and ameliorated mitochondrial fission as evidenced by improvement of mitochondrial morphology, inhibition of Drp1 phosphorylation at Ser616 and translocation. Furthermore, CRISPR/Cas9 knockout of myosin IIA blocked I/R-induced apoptosis, suppressed PINK1/Parkin pathway and reduced mitochondrial fission. Importantly, blebbistatin attenuated myocardial apoptosis, inhibited myosin IIA-actin interaction and PINK1/Parkin pathway, suppressed myocardial ultrastructure abnormalities and mitochondrial fission in a mouse MI/R injury model.
    CONCLUSIONS: Inhibition of actomyosin contractility induced by myosin IIA-actin interaction could impede myocardial apoptosis and MI/R injury via PINK1/Parkin pathway and mitochondrial fission modulation both in vitro and in vivo, which may be applicable for the development of therapies for cardiovascular diseases.
    Keywords:  Cardiomyocyte apoptosis; Mitochondrial fission; Myocardial ischemia/reperfusion injury; Myosin IIA–actin interaction; PINK1/Parkin pathway
    DOI:  https://doi.org/10.1016/j.ijcard.2018.04.079
  3. Adv Clin Chem. 2018 ;pii: S0065-2423(18)30032-5. [Epub ahead of print]86 127-155
    Ilie IR.
      Polycystic ovary syndrome (PCOS) is a common female endocrine disorder, which still remains largely unsolved in terms of etiology and pathogenesis despite important advances in our understanding of its genetic, epigenetic, or environmental factor implications. It is a heterogeneous disease, frequently associated with insulin resistance, chronic inflammation, and oxidative stress and probably accompanied with subclinical cardiovascular disease (CVD) and some malignant lesions as well, such as endometrial cancer. Discrepancies in the clinical phenotype and progression of PCOS exist between different population groups, which nuclear genetic studies have so far failed to explain. Over the last years, mitochondrial dysfunction has been increasingly recognized as an important contributor to an array of diseases. Because mitochondria are under the dual genetic control of both the mitochondrial and nuclear genomes, mutations within either DNA molecule may result in deficiency in respiratory chain function that leads to a reduced ability to produce cellular adenosine-5'-triphosphate and to an excessive production of reactive oxygen species. However, the association between variants in mitochondrial genome, mitochondrial dysfunction, and PCOS has been investigated to a lesser extent. May mutations in mitochondrial DNA (mtDNA) become an additional target of investigations on the missing PCOS heritability? Are mutations in mtDNA implicated in the initiation and progression of PCOS complications, e.g., CVDs, diabetes mellitus, cancers?
    Keywords:  Mitochondrial; Mitochondrial dysfunction; Oxidative stress; Polycystic ovary syndrome; mtDNA mutations
    DOI:  https://doi.org/10.1016/bs.acc.2018.05.003
  4. Pharmacol Res. 2018 Aug 23. pii: S1043-6618(18)30467-5. [Epub ahead of print]
    Joshi AU, Mochly-Rosen D.
      Mitochondria are best known for their role in ATP generation. However, studies over the past two decades have shown that mitochondria do much more than that. Mitochondria regulate both necrotic and apoptotic cell death pathways, they store and therefore coordinate cellular Ca2+ signaling, they generate and metabolize important building blocks, by-products and signaling molecules, and they also generate and are targets of free radical species that modulate many aspects of cell physiology and pathology. Most estimates suggest that although the brain makes up only 2 percent of body weight, utilizes about 20 percent of the body's total ATP. Thus, mitochondrial dysfunction greatly impacts brain functions and is indeed associated with numerous neurodegenerative diseases. Furthermore, a number of abnormal disease-associated proteins have been shown to interact directly with mitochondria, leading to mitochondrial dysfunction and subsequent neuronal cell death. Here, we discuss the role of mitochondrial dynamics impairment in the pathological processes associated with neurodegeneration and suggest that a therapy targeting mitochondrialdysfunction holds a great promise.
    Keywords:  Drp1; Mitochondrial dynamics; Neurodegeneration; Neuroinflammation; P110; Protein–Protein interactions
    DOI:  https://doi.org/10.1016/j.phrs.2018.08.010
  5. Autophagy. 2018 Aug 27.
    Nnah IC, Wang B, Saqcena C, Weber GF, Bonder EM, Bagley D, De Cegli R, Napolitano G, Medina DL, Ballabio A, Dobrowolski R.
      The mechanistic target of rapamycin kinase complex 1 (MTORC1) is a central cellular kinase that integrates major signaling pathways, allowing for regulation of anabolic and catabolic processes including macroautophagy/autophagy and lysosomal biogenesis. Essential to these processes is the regulatory activity of TFEB (transcription factor EB). In a regulatory feedback loop modulating transcriptional levels of RRAG/Rag GTPases, TFEB controls MTORC1 tethering to membranes and induction of anabolic processes upon nutrient replenishment. We now show that TFEB promotes expression of endocytic genes and increases rates of cellular endocytosis during homeostatic baseline and starvation conditions. TFEB-mediated endocytosis drives assembly of the MTORC1-containing nutrient sensing complex through the formation of endosomes that carry the associated proteins RRAGD, the amino acid transporter SLC38A9, and activate AKT/protein kinase B (AKT p-T308). TFEB-induced signaling endosomes en route to lysosomes are induced by amino acid starvation and are required to dissociate TSC2, re-tether and activate MTORC1 on endolysosomal membranes. This study characterizes TFEB-mediated endocytosis as a critical process leading to activation of MTORC1 and autophagic function, thus identifying the importance of the dynamic endolysosomal system in cellular clearance.
    Keywords:  TOR signaling; autophagic mechanisms; cell biology; endosome; lysosome
    DOI:  https://doi.org/10.1080/15548627.2018.1511504
  6. Life Sci. 2018 Aug 22. pii: S0024-3205(18)30493-4. [Epub ahead of print]
    Jang Y, Kwon I, Song W, Cosio-Lima LM, Taylor S, Lee Y.
      AIM: Endurance exercise (EE) has been reported to confer neuroprotection against Parkinson's disease (PD); however, underlying molecular mechanisms of the protection remain still unclear. Since mitochondrial impairment is commonly observed in the brain of PD patients and animals, this study investigated whether EE-induced neuroprotection is associated with mitochondrial phenotypes, using a mouse model of PD induced by intraperitoneal administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).MAIN METHODS: SH-SY5Y cells were cultured with a neurotoxin MPP+ known to cause PD-like symptoms to examine if modifications of mitochondrial morphology are linked to etiology of PD. For in vivo experiments, C57BL/6 male mice were randomly assigned to four groups: control (CON, n = 12), endurance exercise (EXE, n = 12), MPTP (MPTP, n = 12) and MPTP plus endurance exercise (MPTP + EXE, n = 12). Mice assigned to endurance exercise performed treadmill running at 12 m/min for 60 min/day, 5 days/week for 6 weeks.
    KEY FINDINGS: SH-SY5Y cells exposed to a neurotoxin MPP+ exhibited mitochondrial fragmentation and diminished mitochondrial proteins, and cell death. Similarly, animals administered with MPTP displayed comparable impairments in the substantia nigra pars compacta (SNpc). In contrast, EE intervention restored motor function to control levels and reduced apoptosis. These propitious effects of EE were associated with mitochondrial phenotypic changes such as upregulated anti-apoptotic proteins (e.g., MCL-1 and BLC-2), reduced a pro-apoptotic protein (e.g., AIF), and improved mitochondrial biogenesis and fusion.
    SIGNIFICANCE: Our finding that EE-induced mitochondrial phenotypic changes that resist mitochondrial impairment and cell death against PD introduce potential insight into mitochondria as a new therapeutic target for PD.
    Keywords:  Apoptosis; Endurance exercise; Mitochondria biogenesis; Mitochondria dynamics; Parkinson's disease; Substantia Nigra par compacta
    DOI:  https://doi.org/10.1016/j.lfs.2018.08.045
  7. Gastroenterology. 2018 Aug 22. pii: S0016-5085(18)34893-5. [Epub ahead of print]
    Edderkaoui M, Chheda C, Soufi B, Zayou F, Hu R, Ramanujan VK, Pan X, Boros LG, Tajbakhsh J, Madhav A, Bhowmick N, Wang Q, Lewis M, Tuli R, Habtezion A, Murali R, Pandol SJ.
      BACKGROUND & AIMS: Growth, progression, and drug resistance of pancreatic ductal adenocarcinomas (PDACs) have been associated with increased levels and activity of glycogen synthase kinase 3 beta (GSK3B) and histone deacetylases (HCACs). We designed and synthesized molecules that simultaneously inhibit the activities of both enzymes. We tested the effects of one of these molecules, metavert, in pancreatic cancer cells and mice with pancreatic tumors.METHODS: We tested the ability of metavert to bind GSK3B and HDACs using surface plasmon resonance. MIA PaCa-2, Bx-PC3, HPAF-II, and HPDE6 cell lines were incubated with different concentrations of metavert, with or without paclitaxel or gemcitabine, or with other inhibitors of GSK3B and HDACs; cells were analyzed for apoptosis and migration and by immunoblotting, immunofluorescence, and real-time PCR. Krasþ/LSLG12D;Trp53þ/LSLR172H;Pdx-1-Cre (KPC) mice (2 months old) were given injections of metavert (5 mg/Kg, 3 times/week) or vehicle (control). B6.129J mice with tumors grown from UN-KPC961-Luc cells were given injections of metavert or vehicle. Tumors and metastases were counted and pancreata were analyzed by immunohistochemistry. Glucose metabolism was measured using 13C-glucose tracer and mass spectroscopy and flow cytometry. Cytokine levels in blood samples were measured using multiplexing ELISA.
    RESULTS: Metavert significantly reduced survival of PDAC cells but not non-transformed cells; the agent reduced markers of the epithelial to mesenchymal transition and stem cells in PDAC cell lines. Cells incubated with metavert in combination with irradiation and paclitaxel or gemcitabine had reduced survival compared to cells incubated with either agent alone; metavert increased killing of drug-resistant PDAC cells by paclitaxel and gemcitabine. PDAC cells incubated with metavert acquired normalized glucose metabolism. Administration of metavert (alone or in combination with gemcitibine) to KPC mice or mice with syngeneic tumors significantly increased their survival times, slowed tumor growth, prevented tumor metastasis, decreased tumor infiltration by tumor-associated macrophages, and decreased blood levels of cytokines.
    CONCLUSIONS: In studies of PDAC cells and 2 mouse models of PDAC, we found a dual inhibitor of GSK3B and HDACS (metavert) to induce cancer cell apoptosis, reduce migration and expression of stem cell markers, and slow growth of tumors and metastases. Metavert had synergistic effects with gemcitabine.
    Keywords:  EMT; Pancreas; chemotherapeutic agent; neoplasm
    DOI:  https://doi.org/10.1053/j.gastro.2018.08.028
  8. Autophagy. 2018 Aug 27.
    Kang R, Zhu S, Zeh HJ, Klionsky DJ, Tang D.
      Ferroptosis is a form of regulated cell death caused by iron accumulation and oxidative injury. BECN1 is a key regulator of macroautophagy/autophagy, a catabolic process of degradation induced by starvation or other stressors. Our recent findings reveal a novel alternative mechanism by which BECN1 can promote ferroptosis through the regulation of activity of the cysteine and glutamate antiporter system xc- in cancer cells. BECN1-dependent autophagy requires the formation of the BECN1-containing class III phosphatidylinositol 3-kinase (PtdIns3K) complex, whereas BECN1-dependent ferroptosis requires the formation of a BECN1-SLC7A11 complex. Furthermore, AMP-activated protein kinase (AMPK) is required for BECN1 phosphorylation to trigger formation of the BECN1-SLC7A11 complex in the process of inhibiting system xc- activity and inducing lipid peroxidation. These findings suggest that the autophagy-dependent and -independent functions of BECN1 play distinct roles in regulated cell death.
    Keywords:  AMPK; BECN1; SLC7A11; autophagy; cancer; chemotherapy; ferroptosis; phosphorylation; redox
    DOI:  https://doi.org/10.1080/15548627.2018.1513758
  9. Toxicol In Vitro. 2018 Aug 22. pii: S0887-2333(18)30471-5. [Epub ahead of print]
    Nair A, Preetha Rani MR, Shyni GL, Raghu KG.
      Several mechanisms have been proposed for the heart dysfunction during hyperglycemia. The aim of the present in vitro study is to elucidate the role of alteration in redox homeostasis in the induction of apoptosis during hyperglycemia in H9c2 cells via dysfunction in mitochondria and polyol pathway and evaluation of the beneficial effect of cinnamic acid against the same. The H9c2 cells were incubated with 33 mM glucose for 48 h to simulate the diabetic condition. Cell injury was confirmed with a significant increase of atrial natriuretic peptide and lactate dehydrogenase release. Alterations in innate antioxidant system, polyol pathway, mitochondrial integrity, dynamics and apoptosis were investigated. Hyperglycemic insult has significantly affected redox homeostasis via depletion of superoxide dismutase, glutathione and enhanced reactive oxygen species generation. It also caused dysregulation in mitochondrial dynamics (fusion, fission proteins), dissipation of mitochondrial transmembrane potential and increased sorbitol accumulation. Finally, apoptosis was observed with up regulation of Bax, activation of caspase-3 and downregulation of Bcl-2. Cinnamic acid cotreatment increased the innate antioxidant status, improved mitochondrial function and prevented apoptosis in H9c2 cardiomyoblasts. Moreover this in vitro model is found to be ideal for elucidation of mechanisms at the cellular and molecular level of any physiological, pharmacological and toxicological incidents in H9c2 cells.
    Keywords:  Calcium; Cinnamic acid; H9c2 cells; Hyperglycemia; Mitochondria
    DOI:  https://doi.org/10.1016/j.tiv.2018.08.010
  10. Pharmacol Res. 2018 Aug 23. pii: S1043-6618(18)30831-4. [Epub ahead of print]
    Kuske M, Westphal D, Wehner R, Schmitz M, Beissert S, Praetorius C, Meier F.
      Targeted therapy with BRAF inhibitors (BRAFi) and MEK inhibitors (MEKi) provides rapid disease control with high response rates in patients with BRAF-mutant metastatic melanoma. However, the majority of patients develop resistance to therapy during the course of therapy. Immune checkpoint inhibitors show a slower onset of action with lower response rates, with responders showing sustained response. The combination of BRAFi/MEKi and immune checkpoint inhibitors combines the hope for a fast, reliable and lasting response to therapy. Preclinical data supports this hypothesis. With the help of the PubMed database, a comprehensive search and analysis of preclinical and clinical studies on the combination of BRAFi/MEKi with immune checkpoint inhibitors was performed and yielded the following results: 1) In vivo, BRAFi and MEKi have no negative effects on immune cells; BRAFi and MEKi generate 2) an immune stimulating tumor microenvironment, 3) an increased infiltration of immune cells into the tumors, 4.) a better recognition of melanoma cells by immune effector cells, and 5) a better functionality of the immune effector cells. In addition, in vivo experiments 6) demonstrated a superiority of the combination treatment compared to the individual strategies in both BRAF-mutant and BRAF wild-type melanomas. In summary, available data show that both BRAFi and MEKi have beneficial effects on the antitumor immunity and the tumor microenvironment as a whole, which is mediated by different mechanisms. Currently, clinical studies are underway to investigate combinations of BRAFi and MEKi with immune checkpoint inhibitors. The results of these studies are eagerly awaited.
    Keywords:  BRAF; Binimetinib (PubChem CID: 10288191); Cobimetinib (PubChem CID: 16222096); Dabrafenib (PubChem CID: 44462760); Encorafenib (PubChem CID: 50922675); Immunological effects; MEK; Trametinib (PubChem CID: 11707110); Vemurafenib (PubChem CID: 42611257); immunotherapy; melanoma; targeted therapy
    DOI:  https://doi.org/10.1016/j.phrs.2018.08.019
  11. Psychiatry Res. 2018 Aug 18. pii: S0165-1781(18)30593-6. [Epub ahead of print]269 115-117
    Yamaki N, Otsuka I, Numata S, Yanagi M, Mouri K, Okazaki S, Boku S, Horai T, Ohmori T, Shirakawa O, Sora I, Hishimoto A.
      Numerous evidence indicated mitochondrial abnormalities in the pathophysiology of bipolar disorder (BD); however, it remains unclear whether aberrant mitochondrial DNA (mtDNA) copy number (cn) occur in BD due to the conflicting results in previous studies. Here, peripheral blood mtDNAcn in 69 BD patients and 54 controls were analysed via qPCR. BD patients had significantly lower mtDNAcn compared to controls (regardless of their BD type [BD I or II]). Meta-analysis for all previous BD-mtDNAcn studies combining our results with previously published studies failed to identify any significant association. Meanwhile, Asian-specific meta-analysis remarkably revealed lower mtDNAcn in BD patients.
    Keywords:  Bipolar disorder (BD); Meta-analysis; Mitochondria
    DOI:  https://doi.org/10.1016/j.psychres.2018.08.014
  12. Transl Res. 2018 Aug 04. pii: S1931-5244(18)30116-6. [Epub ahead of print]
    Widlansky ME, Hill RB.
      Diabetes-related vascular complication rates remain unacceptably high despite guideline-based medical therapies that are significantly more effective in individuals without diabetes. This critical gap represents an opportunity for researchers and clinicians to collaborate on targeting mechanisms and pathways that specifically contribute to vascular pathology in patients with diabetes mellitus. Dysfunctional mitochondria producing excessive mitochondrial reactive oxygen species (mtROS) play a proximal cell-signaling role in the development of vascular endothelial dysfunction in the setting of diabetes. Targeting the mechanisms of production of mtROS or mtROS themselves represents an attractive method to reduce the prevalence and severity of diabetic vascular disease. This review focuses on the role of mitochondria in the development of diabetic vascular disease and current developments in methods to improve mitochondrial health to improve vascular outcomes in patients with DM.
    Keywords:  Abbreviations: CuZn SODq; DM; Drp1; ETC; FFA; HUVECs; Mdivi-1; Mfn1/2; MnSOD; NMN; NO; NR; OPA-1; SIRT1; SS; Szeto-Schiller; UCP2; copper-zinc superoxide dismutase; diabetes mellitus; dynamin-related protein 1; electron transport chain; free fatty acids; human umbilical vein endothelial cells; mPTP; manganese superoxide dismutase; mitochondrial division inhibitor 1; mitochondrial membrane potential; mitochondrial permeability transition pore; mitochondrial reactive oxygen species; mitofusin 1/2; mtROS; nicotinamide mononucleotide; nicotinamide riboside; nitric oxide; optic atrophy protein 1; sirtuin-1; uncoupling protein 2; Δψ(m)
    DOI:  https://doi.org/10.1016/j.trsl.2018.07.015
  13. Toxicol In Vitro. 2018 Aug 23. pii: S0887-2333(18)30470-3. [Epub ahead of print]53 148-159
    Sun DZ, Song CQ, Xu YM, Wang R, Liu W, Liu Z, Dong XS.
      Paraquat (PQ) is one of the most popular herbicides and has been widely used all over the world over the past several decades. However, PQ exposure can cause multiple organ failure, especially acute lung injury in humans as well as in rodent animals. Mitochondrial dysfunction plays a crucial role in PQ-induced lung cell damage. Mitophagy, defined as the selective autophagic elimination process of mitochondria, is a significant mechanism controlling mitochondrial quality. In this study, we investigated PINK1/Parkin-mediated mitophagy activated in the process of the PQ-induced cell apoptosis by using human lung epithelial-like A549 cells. We showed that PQ inhibited cell viability and induced mitochondrial damage as well as cell apoptosis in A549 cells. During this process, PQ induced PINK1/Parkin-mediated mitophagy. Knocking down the expression of Parkin gene by the transient transfection of Parkin small interfering RNA mitigated PQ-induced mitophagy and worsened A549 cell apoptosis. On the contrary, overexpression of Parkin attenuated PQ-induced cell injury by promoting mitophagy. These results indicated PINK1/Parkin-mediated mitophagy played a protective role in PQ-induced A549 cell damage and provided a potential therapeutic strategy for enhancing mitophagy against PQ poisoning.
    Keywords:  A549 cell; Apoptosis; Mitophagy; PINK1/Parkin; Paraquat
    DOI:  https://doi.org/10.1016/j.tiv.2018.08.009
  14. J Am Chem Soc. 2018 Aug 27.
    Kathiresan M, English AM.
      LC-MS/MS profiling reveals that the proteoforms of cytochrome c peroxidase (Ccp1) isolated from respiring yeast mitochondria are oxidized at numerous Met, Trp and Tyr residues. In vitro oxidation of recombinant Ccp1 by H2O2 in the absence of its reducing substrate, ferrocytochrome c, gives rise to similar proteoforms, indicating uncoupling of Ccp1 oxidation and reduction in mitochondria. The oxidative modifications found in the Ccp1 proteoforms are consistent with radical transfer (hole hopping) from the heme along several chains of redox-active residues (Trp, Met, Tyr). These modifications delineate likely hole-hopping pathways to novel substrate-binding sites. Moreover, a decrease in recombinant Ccp1 oxidation by H2O2 in vitro in the presence of glutathione supports a protective role for hole hopping to this antioxidant. Isolation and characterization of extramitochondrial Ccp1 proteoforms reveals that hole hopping from the heme in these proteoforms results in selective oxidation of the proximal heme ligand (H175) and heme labilization. Previously, we demonstrated that this labilized heme is recruited for catalase maturation (Kathiresan M, Martins D, English AM. Respiration triggers heme transfer from cytochrome c peroxidase to catalase in yeast mitochondria. Proc Natl Acad Sci USA, 2014, 111, 17468-17473). Following heme release, apoCcp1 exits mitochondria, yielding the extramitochondrial proteoforms that we characterize here. The targeting of Ccp1 for selective H175 oxidation may be linked to the phosphorylation status of Y153 close to the heme since pY153 is abundant in certain proteoforms. In sum, when insufficient electrons from ferrocytochrome c are available to Ccp1 in mitochondria, hole hopping from its heme expands its physiological functions. Specifically, we observe an unprecedented hole-hopping sequence for heme labilization and identify hole-hopping pathways from the heme to novel substrates and to glutathione at Ccp1's surface. Furthermore, our results underscore the power of proteoform profiling by LC-MS/MS in exploring the cellular roles of oxidoreductases.
    DOI:  https://doi.org/10.1021/jacs.8b05966
  15. Biochem Pharmacol. 2018 Aug 22. pii: S0006-2952(18)30358-7. [Epub ahead of print]
    Peyton KJ, Liu XM, Yu Y, Yates B, Behnammanesh G, Durante W.
      Glutaminase-1 (GLS1) is a mitochondrial enzyme found in endothelial cells (ECs) that metabolizes glutamine to glutamate and ammonia. Although glutaminolysis modulates the function of human umbilical vein ECs, it is not known whether these findings extend to human ECs beyond the fetal circulation. Furthermore, the molecular mechanism by which GLS1 regulates EC function is not defined. In this study, we show that the absence of glutamine in the culture media or the inhibition of GLS1 activity or expression blocked the proliferation and migration of ECs derived from the human umbilical vein, the human aorta, and the human microvasculature. GLS1 inhibition arrested ECs in the G0/G1 phase of the cell cycle and this was associated with a significant decline in cyclin A expression. Restoration of cyclin A expression via adenoviral-mediated gene transfer improved the proliferative, but not the migratory, response of GLS1-inhibited ECs. Glutamine deprivation or GLS1 inhibition also stimulated the production of reactive oxygen species and this was associated with a marked decline in heme oxygenase-1 (HO-1) expression. GLS1 inhibition also sensitized ECs to the cytotoxic effect of hydrogen peroxide and this was prevented by the overexpression of HO-1. In conclusion, the metabolism of glutamine by GLS1 promotes human EC proliferation, migration, and survival irrespective of the vascular source. While cyclin A contributes to the proliferative action of GLS1, HO-1 mediates its pro-survival effect. These results identify GLS1 as a promising therapeutic target in treating diseases associated with aberrant EC proliferation, migration, and viability.
    Keywords:  6-Diazo-5-oxo-L-norleucine (DON, PubChem CID: 5359375); CB-839 (PubChem CID: 71577426); Endothelial cells; Glutaminase; Migration; Proliferation; bis-2-(5-Phenylacetomido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES, PubChem CID: 3372016)
    DOI:  https://doi.org/10.1016/j.bcp.2018.08.032
  16. Autophagy. 2018 Aug 27.
    Furukawa K, Kanki T.
      Macroautophagy/autophagy (bulk autophagy) is a catabolic process that nonselectively degrades cytoplasmic proteins and organelles. In contrast to bulk autophagy, selective types of autophagy target specific cellular components as cargos, whereas their specific receptor proteins play central roles in cargo selection. In the yeast Saccharomyces cerevisiae, receptor proteins for the cytoplasm-to-vacuole targeting pathway, mitophagy, and pexophagy are phosphoregulated by kinases. This phosphorylation facilitates interaction with the scaffold/adaptor protein Atg11, subsequently recruiting core autophagy proteins to initiate autophagosome formation. However, the molecular mechanism inhibiting this phosphorylation to prevent unrequired selective autophagy remains unknown. Our recent study revealed that the protein phosphatase 2A-like protein phosphatase Ppg1 and its associated Far complex cooperatively inhibit mitophagy by counteracting casein kinase 2-mediated phosphorylation of the mitophagy receptor Atg32. Herein, we summarize our findings regarding Ppg1 and pose unanswered questions.
    Keywords:  Atg32; Far complex; Ppg1; autophagy; casein kinase 2; mitochondria; mitophagy; yeast
    DOI:  https://doi.org/10.1080/15548627.2018.1511505