bims-camemi Biomed news
on Mitochondrial metabolism in cancer
Issue of 2018‒11‒18
sixty-six papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit

  1. JCI Insight. 2018 Nov 15. pii: 121689. [Epub ahead of print]3(22):
    Kwong JQ, Huo J, Bround MJ, Boyer JG, Schwanekamp JA, Ghazal N, Maxwell JT, Jang YC, Khuchua Z, Shi K, Bers DM, Davis J, Molkentin JD.
      The mitochondrial Ca2+ uniporter (MCU) complex mediates acute mitochondrial Ca2+ influx. In skeletal muscle, MCU links Ca2+ signaling to energy production by directly enhancing the activity of key metabolic enzymes in the mitochondria. Here, we examined the role of MCU in skeletal muscle development and metabolic function by generating mouse models for the targeted deletion of Mcu in embryonic, postnatal, and adult skeletal muscle. Loss of Mcu did not affect muscle growth and maturation or otherwise cause pathology. Skeletal muscle-specific deletion of Mcu in mice also did not affect myofiber intracellular Ca2+ handling, but it did inhibit acute mitochondrial Ca2+ influx and mitochondrial respiration stimulated by Ca2+, resulting in reduced acute exercise performance in mice. However, loss of Mcu also resulted in enhanced muscle performance under conditions of fatigue, with a preferential shift toward fatty acid metabolism, resulting in reduced body fat with aging. Together, these results demonstrate that MCU-mediated mitochondrial Ca2+ regulation underlies skeletal muscle fuel selection at baseline and under enhanced physiological demands, which affects total homeostatic metabolism.
    Keywords:  Calcium; Cardiology; Mitochondria; Muscle Biology
  2. Cell Mol Life Sci. 2018 Nov 14.
    de Almeida Chuffa LG, Seiva FRF, Cucielo MS, Silveira HS, Reiter RJ, Lupi LA.
      Cancers of the reproductive organs have a strong association with mitochondrial defects, and a deeper understanding of the role of this organelle in preneoplastic-neoplastic changes is important to determine the appropriate therapeutic intervention. Mitochondria are involved in events during cancer development, including metabolic and oxidative status, acquisition of metastatic potential, resistance to chemotherapy, apoptosis, and others. Because of their origin from melatonin-producing bacteria, mitochondria are speculated to produce melatonin and its derivatives at high levels; in addition, exogenously administered melatonin accumulates in the mitochondria against a concentration gradient. Melatonin is transported into tumor cell by GLUT/SLC2A and/or by the PEPT1/2 transporters, and plays beneficial roles in mitochondrial homeostasis, such as influencing oxidative phosphorylation and electron flux, ATP synthesis, bioenergetics, calcium influx, and mitochondrial permeability transition pore. Moreover, melatonin promotes mitochondrial homeostasis by regulating nuclear DNA and mtDNA transcriptional activities. This review focuses on the main functions of melatonin on mitochondrial processes, and reviews from a mechanistic standpoint, how mitochondrial crosstalk evolved in ovarian, endometrial, cervical, breast, and prostate cancers relative to melatonin's known actions. We put emphasis on signaling pathways whereby melatonin interferes within cancer-cell mitochondria after its administration. Depending on subtype and intratumor metabolic heterogeneity, melatonin seems to be helpful in promoting apoptosis, anti-proliferation, pro-oxidation, metabolic shifting, inhibiting neovasculogenesis and controlling inflammation, and restoration of chemosensitivity. This results in attenuation of development, progression, and metastatic potential of reproductive cancers, in addition to lowering the risk of recurrence and improving the life quality of patients.
    Keywords:  Breast cancer; Cervical cancer; Endometrial cancer; Melatonin; Mitochondrial function; Ovarian cancer; Prostate cancer
  3. Cell Rep. 2018 Nov 13. pii: S2211-1247(18)31646-2. [Epub ahead of print]25(7): 1800-1815.e4
    Gotoh K, Morisaki T, Setoyama D, Sasaki K, Yagi M, Igami K, Mizuguchi S, Uchiumi T, Fukui Y, Kang D.
      Dendritic cell (DC) maturation induced by Toll-like receptor agonists requires activation of downstream signal transduction and metabolic changes. The endogenous metabolite citrate has recently emerged as a modulator of DC activation. However, the metabolic requirements that support citrate production remain poorly defined. Here, we demonstrate that p32/C1qbp, which functions as a multifunctional chaperone protein in mitochondria, supports mitochondrial metabolism and DC maturation. Metabolic analysis revealed that the citrate increase induced by lipopolysaccharide (LPS) is impaired in p32-deficient DCs. We also found that p32 interacts with dihydrolipoamide S-acetyltransferase (E2 component of pyruvate dehydrogenase [PDH] complex) and positively regulates PDH activity in DCs. Therefore, we suggest that DC maturation is regulated by citrate production via p32-dependent PDH activity. p32-null mice administered a PDH inhibitor show decreased DC maturation and ovalbumin-specific IgG production in vivo, suggesting that p32 may serve as a therapeutic target for DC-related autoimmune diseases.
    Keywords:  citrate; dendritic cell; mitochondria; p32/C1qbp; pyruvate dehydrogenase
  4. J Cell Physiol. 2018 Nov 11.
    Tahrir FG, Langford D, Amini S, Mohseni Ahooyi T, Khalili K.
      Mitochondria play an important role in maintaining cardiac homeostasis by supplying the major energy required for cardiac excitation-contraction coupling as well as controlling the key intracellular survival and death pathways. Healthy mitochondria generate ATP molecules through an aerobic process known as oxidative phosphorylation (OXPHOS). Mitochondrial injury during myocardial infarction (MI) impairs OXPHOS and results in the excessive production of reactive oxygen species (ROS), bioenergetic insufficiency, and contributes to the development of cardiovascular diseases. Therefore, mitochondrial biogenesis along with proper mitochondrial quality control machinery, which removes unhealthy mitochondria is pivotal for mitochondrial homeostasis and cardiac health. Upon damage to the mitochondrial network, mitochondrial quality control components are recruited to segregate the unhealthy mitochondria and target aberrant mitochondrial proteins for degradation and elimination. Impairment of mitochondrial quality control and accumulation of abnormal mitochondria have been reported in the pathogenesis of various cardiac disorders and heart failure. Here, we provide an overview of the recent studies describing various mechanistic pathways underlying mitochondrial homeostasis with the main focus on cardiac cells. In addition, this review demonstrates the potential effects of mitochondrial quality control dysregulation in the development of cardiovascular disease.
    Keywords:  bcl-2-associated athanogene 3 (BAG3); cardiomyopathy; fission; fusion; ischemia/reperfusion (IR) injury; mitochondrial quality control; mitophagy; proteasome
  5. J Cell Physiol. 2018 Nov 11.
    Dahlmans D, Houzelle A, Andreux P, Wang X, Jörgensen JA, Moullan N, Daemen S, Kersten S, Auwerx J, Hoeks J.
      Proper mitochondrial function plays a central role in cellular metabolism. Various diseases as well as aging are associated with diminished mitochondrial function. Previously, we identified 19 miRNAs putatively involved in the regulation of mitochondrial metabolism in skeletal muscle, a highly metabolically active tissue. In the current study, these 19 miRNAs were individually silenced in C2C12 myotubes using antisense oligonucleotides, followed by measurement of the expression of 27 genes known to play a major role in regulating mitochondrial metabolism. Based on the outcomes, we then focused on miR-382-5p and identified pathways affected by its silencing using microarrays, investigated protein expression, and studied cellular respiration. Silencing of miRNA-382-5p significantly increased the expression of several genes involved in mitochondrial dynamics and biogenesis. Conventional microarray analysis in C2C12 myotubes silenced for miRNA-382-5p revealed a collective downregulation of mitochondrial ribosomal proteins and respiratory chain proteins. This effect was accompanied by an imbalance between mitochondrial proteins encoded by the nuclear and mitochondrial DNA (1.35-fold, p < 0.01) and an induction of HSP60 protein (1.31-fold, p < 0.05), indicating activation of the mitochondrial unfolded protein response (mtUPR). Furthermore, silencing of miR-382-5p reduced basal oxygen consumption rate by 14% ( p < 0.05) without affecting mitochondrial content, pointing towards a more efficient mitochondrial function as a result of improved mitochondrial quality control. Taken together, silencing of miR-382-5p induces a mitonuclear protein imbalance and activates the mtUPR in skeletal muscle, a phenomenon that was previously associated with improved longevity.
    Keywords:  microRNA; mitochondria; protein stress; skeletal muscle
  6. World Neurosurg. 2018 Nov 12. pii: S1878-8750(18)32543-9. [Epub ahead of print]
    Niu F, Dong J, Xu X, Zhang B, Liu B.
      BACKGROUND: Growing evidences have implicated dysfunctional mitochondria in the pathophysiology of neurodegenerative disorders. Selective degradation of dysfunctional mitochondria is termed mitophagy and constitutes a pivotal component of mitochondrial quality control to maintain cellular homeostasis. Mitochondrial fission plays prominent roles in controlling mitochondrial shape and function. However, it is unclear whether mitochondrial fission in the context of eliminating damaged mitochondria is involved in traumatic brain injury (TBI). The objective of this study was to examine the role of mitochondrial division inhibitor 1 (Mdivi1), a small-molecule inhibitor of dynamin-related protein (Drp1), in general autophagy and mitophagy after controlled cortical impact (CCI).METHODS: Mitophagy and the role of Drp1 in this process after CCI were examined using western blotting, electron microscopy, double immunofluorescence staining, neurological severity scores (NSS), and hematoxylin and eosin (HE) staining. Statistical analysis was performed using one-way ANOVA followed by the least significant difference (LSD) test or the Games-Howell test.
    RESULTS: Animals exposed to CCI exhibited induction of mitophagy and fragmentation of mitochondria. When fission was blocked with Mdivi1, the mitochondria became excessively long and interconnected. Inhibition of Drp1 blocked the induction of mitophagy specifically, which aggravated neurological manifestations and neuronal apoptosis. Mdivi1 activated caspase-3 and caspase-9, implying that selective degradation of damaged mitochondria by autophagy markedly decreased cell apoptosis induced by TBI and thus promoted cell survival.
    CONCLUSIONS: This study supports the hypothesis that Drp1-dependent mitochondrial fission contributes to mitophagy in TBI, and further understanding the regulatory mechanisms of Drp1 will provide opportunities to develop novel strategies against TBI.
    Keywords:  Drp1; TBI; mitochondrial fission; mitophagy
  7. Mol Cell. 2018 Nov 15. pii: S1097-2765(18)30883-9. [Epub ahead of print]72(4): 610-624
    Ringel AE, Tucker SA, Haigis MC.
      Growing appreciation of the diversity of post-translational modifications (PTMs) in the mitochondria necessitates reevaluation of the roles these modifications play in both health and disease. Compared to the cytosol and nucleus, the mitochondrial proteome is highly acylated, and remodeling of the mitochondrial "acylome" is a key adaptive mechanism that regulates fundamental aspects of mitochondrial biology. It is clear that we need to understand the underlying chemistry that regulates mitochondrial acylation, as well as how chemical properties of the acyl chain impact biological functions. Here, we dissect the sources of PTMs in the mitochondria, review major mitochondrial pathways that control levels of PTMs, and highlight how sirtuin enzymes respond to the bioenergetic state of the cell via NAD+ availability to regulate mitochondrial biology. By providing a framework connecting the chemistry of these modifications, their biochemical consequences, and the pathways that regulate the levels of acyl PTMs, we will gain a deeper understanding of the physiological significance of mitochondrial acylation and its role in mitochondrial adaptation.
  8. Biochim Biophys Acta Mol Basis Dis. 2018 Nov 09. pii: S0925-4439(18)30450-2. [Epub ahead of print]
    Sandra Chocron E, Munkácsy E, Pickering AM.
      The mitochondrial genome (mtDNA) represents a tiny fraction of the whole genome, comprising just 16.6 kilobases encoding 37 genes involved in oxidative phosphorylation and the mitochondrial translation machinery. Despite its small size, much interest has developed in recent years regarding the role of mtDNA as a determinant of both aging and age-associated diseases. A number of studies have presented compelling evidence for key roles of mtDNA in age-related pathology, although many are correlative rather than demonstrating cause. In this review we will evaluate the evidence supporting and opposing a role for mtDNA in age-associated functional declines and diseases. We provide an overview of mtDNA biology, damage and repair as well as the influence of mitochondrial haplogroups, epigenetics and maternal inheritance in aging and longevity.
    Keywords:  Aging; Lifespan; Mitochondria; mtDNA
  9. Biochim Biophys Acta Mol Cell Res. 2018 Nov 09. pii: S0167-4889(18)30335-5. [Epub ahead of print]
    Braymer JJ, Stümpfig M, Thelen S, Mühlenhoff U, Lill R.
      Iron‑sulfur (Fe/S) clusters are versatile inorganic cofactors that play central roles in essential cellular functions, from respiration to genome stability. >30 proteins involved in Fe/S protein biogenesis in eukaryotes are known, many of which bind clusters via cysteine residues. This opens up the possibility that the thiol-reducing glutaredoxin and thioredoxin systems are required at both the Fe/S biogenesis and target protein level to counteract thiol oxidation. To address the possible interplay of thiol redox chemistry and Fe/S protein biogenesis, we have characterized the status of the mitochondrial (ISC) and cytosolic (CIA) Fe/S protein assembly machineries in Saccharomyces cerevisiae mutants in which the three partially redundant glutathione (Glr1) and thioredoxin (Trr1 and Trr2) oxidoreductases have been inactivated in either mitochondria, cytosol, or both compartments. Cells devoid of mitochondrial oxidoreductases maintained a functional mitochondrial ISC machinery and showed no altered iron homeostasis despite a non-functional complex II of the respiratory chain due to redox-specific defects. In cells that lack either cytosolic or total cellular thiol reducing capacity, both the ISC system and iron homeostasis were normal, yet cytosolic and nuclear Fe/S target proteins were not matured. This dysfunction could be attributed to a failure in the assembly of [4Fe‑4S] clusters in the CIA factor Nar1, even though Nar1 maintained robust protein levels and stable interactions with later-acting CIA components. Overall, our analysis has uncovered a hitherto unknown thiol-dependence of the CIA machinery and has demonstrated the surprisingly varying sensitivity of Fe/S proteins to thiol oxidation.
    Keywords:  Glutathione oxidoreductase; Iron homeostasis; Iron‑sulfur clusters; Saccharomyces cerevisiae; Thiol redox chemistry; Thioredoxin oxidoreductase
  10. J Gerontol A Biol Sci Med Sci. 2018 Nov 13.
    Valentine JM, Li ME, Shoelson SE, Zhang N, Reddick RL, Musi N.
      NFB is a transcription factor that controls immune and inflammatory signaling pathways. In skeletal muscle, NFB has been implicated in the regulation of metabolic processes and tissue mass; yet, its affects on mitochondrial function in this tissue are unclear. To investigate the role of NFB on mitochondrial function and its relationship with muscle mass across the lifespan, we study a mouse model with muscle-specific NFB suppression (MISR mice). In wild type mice there was a natural decline in muscle mass with aging that was accompanied by decreased mitochondrial function and mRNA expression of electron transport chain subunits. NFB inactivation downregulated expression of PPARGC1A, while upregulating TFEB and PPARGC1B, as well as decreased gastrocnemius (but not soleus) muscle mass in early life (1-6 months old). Lower oxygen consumption rates occurred in gastrocnemius and soleus muscles from young MISR mice, whereas soleus (but not gastrocnemius) muscles from old MISR mice displayed increased oxygen consumption compared to age-matched controls. We conclude that the NFB pathway plays an important role in muscle development and growth. The extent to which NFB suppression alters mitochondrial function is age-dependent and muscle-specific. Lastly, mitochondrial function and muscle mass are tightly associated in both genotypes and across the lifespan.
  11. Front Endocrinol (Lausanne). 2018 ;9 637
    Ježek J, Plecitá-Hlavatá L, Ježek P.
      Human hepatocellular carcinoma HepG2 cells are forced to oxidative phosphorylation (OXPHOS), when cultured in aglycemic conditions at galactose and glutamine. These Oxphos cells represent a prototype of cancer cell bioenergetics with mixed aerobic glycolysis and OXPHOS. We aimed to determine fractions of (i) glutaminolytic pathway involving aminotransferase reaction supplying 2-oxoglutarate (2OG) to the Krebs cycle vs. (ii) active segment of the Krebs cycle with aconitase and isocitrate dehydrogenase-3 (ACO-IDH3), which is typically inactive in cancer cells due to the citrate export from mitochondria. At normoxia, Oxphos cell respiration was decreased down to ~15 and ~10% by the aminotransferase inhibitor aminooxyacetate (AOA) or with AOA plus the glutamate-dehydrogenase inhibitor bithionol, respectively. Phosphorylating to non-phosphorylating respiration ratios dropped from >6.5 to 1.9 with AOA and to zero with AOA plus bithionol. Thus, normoxic Oxphos HepG2 cells rely predominantly on glutaminolysis. Addition of membrane-permeant dimethyl-2-oxoglutarate (dm2OG) to inhibited cells instantly partially restored respiration, evidencing the lack of 2OG-dehydrogenase substrate upon aminotransferase inhibition. Surprisingly, after 72 hr of 5% O2 hypoxia, the AOA (bithionol) inhibition ceased and respiration was completely restored. Thus in aglycemic HepG2 cells, the hypoxia-induced factor (HIF) upregulation of glycolytic enzymes enabled acceleration of glycolysis pathway, preceded by galactolysis (Leloir pathway), redirecting pyruvate via still incompletely blocked pyruvate dehydrogenase toward the ACO-IDH3. Glycolytic flux upregulation at hypoxia was evidently matched by a higher activity of the Leloir pathway in Oxphos cells. Hypoxic Oxphos cells increased 2-fold the NADPH oxidase activity, whereas hypoxic glycolytic cells decreased it. Oxphos cells and glycolytic cells at 5 mM glucose decreased their reduced glutathione fraction. In contrast to aglycemic cells, glycolytic HepG2 cells decreased their respiration at hypoxia despite the dm2OG presence, i.e., even at unlimited respiratory substrate availability for 72 hr at 5% O2, exhibiting the canonical HIF-mediated adaptation. Nevertheless, their ATP content was much higher with dm2OG as compared to its absence during hypoxic adaptation. Thus, the metabolic plasticity of cancer cells is illustrated under conditions frequently established for solid tumors in vivo, such as aglycemia plus hypoxia. Consequently, a wide acceptance of the irreversible and exclusive Warburg phenotype in cancer cells is incorrect.
    Keywords:  HepG2 cells; Warburg phenotype; aminotransferase inhibiton; cancer mitochondria; glutaminolysis; hypoxia
  12. Cell Mol Neurobiol. 2018 Nov 12.
    Nagakannan P, Islam MI, Karimi-Abdolrezaee S, Eftekharpour E.
      The involvement of glutamate in neuronal cell death in neurodegenerative diseases and neurotrauma is mediated through excitotoxicity or oxytosis. The latter process induces oxidative stress via glutamate-mediated inhibition of cysteine transporter xCT, leading to depletion of the cellular glutathione pool. Mitochondrial damage, loss of mitochondrial membrane potential (MMP), and depletion of energy metabolites have been shown in this process. The Voltage-Dependent Anion Channel-1 (VDAC1) is one of the main components of the mitochondrial outer membrane and plays a gatekeeping role in mitochondria-cytoplasm transport of metabolites. In this study, we explored the possible participation of VDAC-1 in the pathophysiology of oxytosis. Administration of glutamate in HT22 cells that lack the glutamate ionotropic receptors induced an upregulation and oligomerization of VDAC1. This was associated with an increase in ROS and loss of cell survival. Glutamate-mediated oxytosis in this model also decreased MMP and promoted ATP depletion, resulting in translocation of cytochrome c (cyt C) and apoptosis inducing factor (AIF) from mitochondria into the cytosol. This was also accompanied by cleavage of AIF to form truncated AIF. Inhibition of VDAC1 oligomerization using 4,4'-Diisothiocyanatostilbene-2,2'-disulfonate (DIDS), significantly improved the cell survival, decreased the ROS levels, improved mitochondrial functions, and decreased the mitochondrial damage. Notably, DIDS also inhibited the mitochondrial fragmentation caused by glutamate, indicating the active role of VDAC1 oligomerization in the process of mitochondrial fragmentation in oxytosis. These results suggest a critical role for VDAC1 in mitochondrial fragmentation and its potential therapeutic value against glutamate-mediated oxidative neurotoxicity.
    Keywords:  AIF; Caspase-independent apoptosis; DIDS; Ferroptosis; Glutamate toxicity; Oxidative stress
  13. Curr Opin Toxicol. 2018 Apr;8 102-110
    Garza-Lombó C, Schroder A, Reyes-Reyes EM, Franco R.
      The mechanistic (or mammalian) target of rapamycin (mTOR) and the adenosine monophosphate-activated protein kinase (AMPK) regulate cell survival and metabolism in response to diverse stimuli such as variations in amino acid content, changes in cellular bioenergetics, oxygen levels, neurotrophic factors and xenobiotics. This Opinion paper aims to discuss the current state of knowledge regarding how mTOR and AMPK regulate the metabolism and survival of brain cells and the close interrelationship between both signaling cascades. It is now clear that both mTOR and AMPK pathways regulate cellular homeostasis at multiple levels. Studies so far demonstrate that dysregulation in these two pathways is associated with neuronal injury, degeneration and neurotoxicity, but the mechanisms involved remain unclear. Most of the work so far has been focused on their antagonistic regulation of autophagy, but recent findings highlight that changes in protein synthesis, metabolism and mitochondrial function are likely to play a role in the regulatory effects of both mTOR and AMPK on neuronal health. Understanding the role and relationship between these two master regulators of cell metabolism is crucial for future therapeutic approaches to counteract alterations in cell metabolism and survival in brain injury and disease.
    Keywords:  adenosine monophosphate-activated protein kinase; autophagy; cell death; energy failure; glycolysis; mammalian target of rapamycin; mitochondria; nutrient deprivation
  14. iScience. 2018 May 25. pii: S2589-0042(18)30053-1. [Epub ahead of print]3 226-237
    Xie X, Venit T, Drou N, Percipalle P.
      In eukaryotic cells, actin regulates both cytoplasmic and nuclear functions. However, whether actin-based structures are present in the mitochondria and are involved in mitochondrial functions has not been investigated. Here, using wild-type ?-actin +/+ and knockout (KO) ?-actin ?/? mouse embryonic fibroblasts we show evidence for the defect in maintaining mitochondrial membrane potential (MMP) in ?-actin-null cells. MMP defects were associated with impaired mitochondrial DNA (mtDNA) transcription and nuclear oxidative phosphorylation (OXPHOS) gene expression. Using super-resolution microscopy we provided direct evidence on the presence of ?-actin-containing structures inside mitochondria. Large aggregates of TFAM-stained nucleoids were observed in bulb-shaped mitochondria in KO cells, suggesting defects in mitochondrial nucleoid segregation without ?-actin. The observation that mitochondria-targeted ?-actin rescued mtDNA transcription and MMP suggests an indispensable functional role of a mitochondrial ?-actin pool necessary for mitochondrial quality control.
    Keywords:  Cell Biology; Functional Aspects of Cell Biology; Molecular Biology
  15. Cell Physiol Biochem. 2018 ;50(5): 1840-1855
    Carraro M, Checchetto V, Sartori G, Kucharczyk R, di Rago JP, Minervini G, Franchin C, Arrigoni G, Giorgio V, Petronilli V, Tosatto SCE, Lippe G, Szabó I, Bernardi P.
      BACKGROUND/AIMS: The permeability transition pore (PTP) is an unselective, Ca2+-dependent high conductance channel of the inner mitochondrial membrane whose molecular identity has long remained a mystery. The most recent hypothesis is that pore formation involves the F-ATP synthase, which consistently generates Ca2+-activated channels. Available structures do not display obvious features that can accommodate a channel; thus, how the pore can form and whether its activity can be entirely assigned to F-ATP synthase is the matter of debate. In this study, we investigated the role of F-ATP synthase subunits e, g and b in PTP formation.METHODS: Yeast null mutants for e, g and the first transmembrane (TM) α-helix of subunit b were generated and evaluated for mitochondrial morphology (electron microscopy), membrane potential (Rhodamine123 fluorescence) and respiration (Clark electrode). Homoplasmic C23S mutant of subunit a was generated by in vitro mutagenesis followed by biolistic transformation. F-ATP synthase assembly was evaluated by BN-PAGE analysis. Cu2+ treatment was used to induce the formation of F-ATP synthase dimers in the absence of e and g subunits. The electrophysiological properties of F-ATP synthase were assessed in planar lipid bilayers.
    RESULTS: Null mutants for the subunits e and g display dimer formation upon Cu2+ treatment and show PTP-dependent mitochondrial Ca2+ release but not swelling. Cu2+ treatment causes formation of disulfide bridges between Cys23 of subunits a that stabilize dimers in absence of e and g subunits and favors the open state of wild-type F-ATP synthase channels. Absence of e and g subunits decreases conductance of the F-ATP synthase channel about tenfold. Ablation of the first TM of subunit b, which creates a distinct lateral domain with e and g, further affected channel activity.
    CONCLUSION: F-ATP synthase e, g and b subunits create a domain within the membrane that is critical for the generation of the high-conductance channel, thus is a prime candidate for PTP formation. Subunits e and g are only present in eukaryotes and may have evolved to confer this novel function to F-ATP synthase.
    Keywords:  Calcium; F-ATP synthase; Mitochondrial megachannel; Permeability transition; Yeast mitochondria
  16. Science. 2018 Nov 16. pii: eaat9528. [Epub ahead of print]362(6416):
    Kory N, Wyant GA, Prakash G, Uit de Bos J, Bottanelli F, Pacold ME, Chan SH, Lewis CA, Wang T, Keys HR, Guo YE, Sabatini DM.
      One-carbon metabolism generates the one-carbon units required to synthesize many critical metabolites, including nucleotides. The pathway has cytosolic and mitochondrial branches, and a key step is the entry, through an unknown mechanism, of serine into mitochondria, where it is converted into glycine and formate. In a CRISPR-based genetic screen in human cells for genes of the mitochondrial pathway, we found sideroflexin 1 (SFXN1), a multipass inner mitochondrial membrane protein of unclear function. Like cells missing mitochondrial components of one-carbon metabolism, those null for SFXN1 are defective in glycine and purine synthesis. Cells lacking SFXN1 and one of its four homologs, SFXN3, have more severe defects, including being auxotrophic for glycine. Purified SFXN1 transports serine in vitro. Thus, SFXN1 functions as a mitochondrial serine transporter in one-carbon metabolism.
  17. J Mol Cell Biol. 2018 Nov 14.
    Song S, Wen Y, Tong H, Loro E, Gong Y, Liu J, Hong S, Li L, Khurana TS, Chu M, Sun Z.
      Histone deacetylase 3 (HDAC3) is a major HDAC, whose enzymatic activity is targeted by small molecule inhibitors for treating a variety of conditions. However, its enzymatic activity is largely dispensable for its function in embryonic development and hepatic lipid metabolism. HDAC3 plays a pivotal role in regulating muscle fuel metabolism and contractile function. Here, we address whether these muscular functions of HDAC3 require its enzymatic activity. By mutating the NCoR/SMRT corepressors in a knock-in mouse model named NS-DADm, we ablated the enzymatic activity of HDAC3 without affecting its protein levels. Compared to the control mice, skeletal muscles from NS-DADm mice showed lower force generation, enhanced fatigue resistance, enhanced fatty acid oxidation, reduced glucose uptake during exercise, upregulated expression of metabolic genes involved in branched-chain amino acids (BCAAs) catabolism, and reduced muscle mass during aging, without changes in the muscle fiber type composition or mitochondrial protein content. These muscular phenotypes are similar to those observed in the HDAC3-depleted skeletal muscles, which demonstrates that, unlike that in the liver or embryonic development, the metabolic function of HDAC3 in skeletal muscles requires its enzymatic activity. These results suggest that drugs specifically targeting HDAC3 enzyme activity could be developed and tested to modulate muscle energy metabolism and exercise performance.
  18. Cell Rep. 2018 Nov 13. pii: S2211-1247(18)31648-6. [Epub ahead of print]25(7): 1772-1785.e6
    Nakamura-Ishizu A, Matsumura T, Stumpf PS, Umemoto T, Takizawa H, Takihara Y, O'Neil A, Majeed ABBA, MacArthur BD, Suda T.
      During acute myelosuppression or thrombocytopenia, bone marrow (BM) hematopoietic cells respond rapidly to replenish peripheral blood platelets. While the cytokine thrombopoietin (Thpo) both regulates platelet production and maintains HSC potential, whether Thpo controls megakaryocyte (Mk)-lineage differentiation of HSCs is unclear. Here, we show that Thpo rapidly upregulates mitochondrial activity in HSCs, an activity accompanied by differentiation to an Mk lineage. Moreover, in unperturbed hematopoiesis, HSCs with high mitochondrial activity exhibit Mk-lineage differentiation in vitro and myeloid lineage-biased reconstitution in vivo. Furthermore, Thpo skewed HSCs to express the tetraspanin CD9, a pattern correlated with mitochondrial activity. Mitochondria-active HSCs are resistant to apoptosis and oxidative stress upon Thpo stimulation. Thpo-regulated mitochondrial activity associated with mitochondrial translocation of STAT3 phosphorylated at serine 727. Overall, we report an important role for Thpo in regulating rapid Mk-lineage commitment. Thpo-dependent changes in mitochondrial metabolism prime HSCs to undergo direct differentiation to an Mk lineage.
    Keywords:  hematopoietic stem cell; lineage differentiation; megakaryocyte; mitochondria; thrombopoietin
  19. Sci Signal. 2018 Nov 13. pii: eaat5185. [Epub ahead of print]11(556):
    Nishimura A, Shimauchi T, Tanaka T, Shimoda K, Toyama T, Kitajima N, Ishikawa T, Shindo N, Numaga-Tomita T, Yasuda S, Sato Y, Kuwahara K, Kumagai Y, Akaike T, Ide T, Ojida A, Mori Y, Nishida M.
      Defective mitochondrial dynamics through aberrant interactions between mitochondria and actin cytoskeleton is increasingly recognized as a key determinant of cardiac fragility after myocardial infarction (MI). Dynamin-related protein 1 (Drp1), a mitochondrial fission-accelerating factor, is activated locally at the fission site through interactions with actin. Here, we report that the actin-binding protein filamin A acted as a guanine nucleotide exchange factor for Drp1 and mediated mitochondrial fission-associated myocardial senescence in mice after MI. In peri-infarct regions characterized by mitochondrial hyperfission and associated with myocardial senescence, filamin A colocalized with Drp1 around mitochondria. Hypoxic stress induced the interaction of filamin A with the GTPase domain of Drp1 and increased Drp1 activity in an actin-binding-dependent manner in rat cardiomyocytes. Expression of the A1545T filamin mutant, which potentiates actin aggregation, promoted mitochondrial hyperfission under normoxia. Furthermore, pharmacological perturbation of the Drp1-filamin A interaction by cilnidipine suppressed mitochondrial hyperfission-associated myocardial senescence and heart failure after MI. Together, these data demonstrate that Drp1 association with filamin and the actin cytoskeleton contributes to cardiac fragility after MI and suggests a potential repurposing of cilnidipine, as well as provides a starting point for innovative Drp1 inhibitor development.
  20. Onco Targets Ther. 2018 ;11 7213-7227
    Lu C, Chen X, Wang Q, Xu X, Xu B.
      Background and objective: The present study was designed to explore the roles of mitochondrial fission and MAPK-ERK-YAP signaling pathways and to determine their mutual relationship in TNFα-mediated glioblastoma mitochondrial apoptosis.Materials and methods: Cellular viability was measured via TUNEL staining, MTT assays, and Western blot. Immunofluorescence was performed to observe mitochondrial fission. YAP overexpression assays were conducted to observe the regulatory mechanisms of MAPK-ERK-YAP signaling pathways in mitochondrial fission and glioblastoma mitochondrial apoptosis.
    Results: The results in our present study indicated that TNFα treatment dose dependently increased the apoptotic rate of glioblastoma cells. Functional studies confirmed that TNFα-induced glioblastoma apoptosis was attributable to increased mitochondrial fission. Excessive mitochondrial fission promoted mitochondrial dysfunction, as evidenced by decreased mitochondrial potential, repressed ATP metabolism, elevated ROS synthesis, and downregulated antioxidant factors. In addition, the fragmented mitochondria liberated cyt-c into the cytoplasm/nucleus where it activated a caspase-9-involved mitochondrial apoptosis pathway. Furthermore, our data identified MAPK-ERK-YAP signaling pathways as the primary molecular mechanisms by which TNFα modulated mitochondrial fission and glioblastoma apoptosis. Reactivation of MAPK-ERK-YAP signaling pathways via overexpression of YAP neutralized the cytotoxicity of TNFα, attenuated mitochondrial fission, and favored glioblastoma cell survival.
    Conclusion: Overall, our data highlight that TNFα-mediated glioblastoma apoptosis stems from increased mitochondrial fission and inactive MAPK-ERK-YAP signaling pathways, which provide potential targets for new therapies against glioblastoma.
    Keywords:  MAPK-ERK-YAP signaling pathways; TNFα; apoptosis; glioblastoma; mitochondrial fission; mitochondrion
  21. Biochim Biophys Acta Bioenerg. 2018 Nov 08. pii: S0005-2728(18)30170-1. [Epub ahead of print]
    Ježek P, Jabůrek M, Porter RK.
      Brown adipose tissue (BAT) and brown in white (brite) adipose tissue, termed also beige, are major sites of mammalian nonshivering thermogenesis. Mitochondrial uncoupling protein 1 (UCP1), specific for these tissues, is the key factor for heat production. Recent molecular aspects of UCP1 structure provide irrefutable support for the fatty acid cycling model of coupling, i.e. when UCP1 expels fatty acid anions in a uniport mode from the matrix, while uncoupling. Protonophoretic function is ensured by return of the protonated fatty acid to the matrix independent of UCP1. This mechanism is advantageous for mitochondrial uncoupling and compatible with heat production in a pro-thermogenic environment, such as BAT. It must still be verified whether posttranslational modification of UCP1, such as sulfenylation of Cys253, linked to redox activity, promotes UCP1 activity. BAT biogenesis and UCP1 expression, has also been linked to the pro-oxidant state of mitochondria, further endorsing a redox signalling link promoting an establishment of pro-thermogenic state. We discuss circumstances under which promotion of superoxide formation exceeds its attenuation by uncoupling in mitochondria and throughout point out areas of future research into UCP1 function.
    Keywords:  Brown adipose tissue; Fatty acid cycling; Mitochondrial uncoupling protein1; Redox regulation; UCP1
  22. Redox Biol. 2018 Nov 02. pii: S2213-2317(18)30558-5. [Epub ahead of print]20 414-426
    Xu T, Ding W, Ao X, Chu X, Wan Q, Wang Y, Xiao D, Yu W, Li M, Yu F, Wang J.
      Necrosis is a key factor in myocardial injury during cardiac pathological processes, such as myocardial infarction (MI), ischemia/reperfusion (I/R) injury and heart failure. Increasing evidence suggests that several aspects of necrosis are programmed and tightly regulated, so targeting the necrosis process has become a new trend for myocardial protection. Multiple cellular signaling pathways have been implicated in necrotic cell death, such as the death receptor-mediated extrinsic and mitochondrial intrinsic pathways. However, the precise mechanisms underlying myocardial necrosis remain unclear. In this study, we showed that apoptosis repressor with caspase recruitment domain (ARC) participated in the mitochondrial intrinsic pathway and inhibited myocardial necrosis by preventing the opening of the mitochondrial permeability transition pore (mPTP). ARC attenuated necrotic cell death triggered by exposure to 500 μM hydrogen peroxide (H2O2) in the cardiomyocyte cell line H9c2. In mice, ARC ameliorated myocardial necrosis, reduced the myocardial infarct size and improved long-term heart function during I/R injury. Mechanistically, it has been shown that the inhibition of necrosis by ARC was dependent on its mitochondrial localization and that ARC prevented the opening of mPTP by targeting CypD, the main regulator of mPTP. In addition, ARC expression was negatively regulated by the transcription factor p53 at the transcriptional level during the necrosis process. These findings identified the novel role of ARC in myocardial necrosis and delineated the p53-ARC-CypD/mPTP necrosis pathway during ischemia- and oxidative stress-induced myocardial damage, which can provide a new strategy for cardiac protection.
    Keywords:  ARC; CypD; Myocardial necrosis; mPTP
  23. Redox Biol. 2018 Nov 03. pii: S2213-2317(18)30738-9. [Epub ahead of print]20 451-457
    Tai Y, Cao F, Li M, Li P, Xu T, Wang X, Yu Y, Gu B, Yu X, Cai X, Ao F, Ge P, Xiang L, Yang B, Jiang Y, Li Y.
      Metabolic reprogramming is a feature of cancer cells and crucial for tumor growth and metastasis. Interferon-γ (IFNγ) is a cytokine that plays a pivotal role in host antitumor immunity. However, little is known about the roles of metabolic reprogramming in immune responses. Here, we show that colon cancer cells reprogram metabolism to coordinate proper cellular responses to IFNγ by downregulating mitochondrial pyruvate carrier (MPC)1 and 2 via STAT3 signaling. Forced overexpression of MPC promote the production of reactive oxygen species and enhance the apoptosis induced by IFNγ in colon cancer cells. Moreover, inhibiting STAT3 sensitize the antitumor efficacy of IFN-γ against colon cancer cells. Our findings present a previously unrecognized mechanism that colon cancer manipulate to resist IFNγ mediated antitumor immunity that have implications for targeting a unique aspect of this disease.
    Keywords:  Colon cancer; Glycolysis; Interferon-γ; Mitochondrial pyruvate carriers; Redox
  24. Int J Mol Sci. 2018 Nov 10. pii: E3550. [Epub ahead of print]19(11):
    Mungo E, Bergandi L, Salaroglio IC, Doublier S.
      Emerging evidence supports the idea that a dysfunction in cell metabolism could sustain a resistant phenotype in cancer cells. As the success of chemotherapeutic agents is often questioned by the occurrence of multidrug resistance (MDR), a multiple cross-resistance towards different anti-cancer drugs represent a major obstacle to cancer treatment. The present study has clarified the involvement of the carbon metabolites in a more aggressive tumor colon adenocarcinoma phenotype and in a chemoresistant mesothelioma, and the role of pyruvate treatment in the reversion of the potentially related resistance. For the first time, we have shown that human colon adenocarcinoma cells (HT29) and its chemoresistant counterpart (HT29-dx) displayed different carbon metabolism: HT29-dx cells had a higher glucose consumption compared to HT29 cells, whereas human malignant mesothelioma (HMM) cells showed a lower glucose consumption compared to HT29 cells, accompanied by a lower pyruvate production and, consequently, a higher production of lactate. When treated with pyruvate, both HT29-dx and HMM cells exhibited a re-established accumulation of doxorubicin and a lower survival ability, a decreased activity of multidrug resistance protein 1 (MRP1) and a restored mitochondrial respiratory chain function, improving the effectiveness of the chemotherapeutic agents in these resistant cancer cells.
    Keywords:  carbon metabolism; chemoresistance; human colon adenocarcinoma cells; human pleural mesothelioma cells; mitochondria respiratory chain; pyruvate
  25. Free Radic Biol Med. 2018 Nov 12. pii: S0891-5849(18)31244-9. [Epub ahead of print]
    Aparicio-Trejo OE, Reyes-Fermín LM, Briones-Herrera A, Tapia E, León-Contreras C, Hernández-Pando R, Sánchez-Lozada LG, Pedraza-Chaverri J.
      Folic acid (FA)-induced acute kidney injury (AKI) is a widely used model for studies of the renal damage and its progression to chronic state. However, the molecular mechanisms by which FA induces AKI remain poorly understood. Since renal function depends on mitochondrial homeostasis, it has been suggested that mitochondrial alterations contribute to AKI development. Additionally, N-acetyl-cysteine (NAC) can be a protective agent to prevent mitochondrial and renal dysfunction in this model, given its ability to increase mitochondrial glutathione (GSH) and to control the S-glutathionylation levels, a reversible post-translational modification that has emerged as a mechanism able to link mitochondrial energy metabolism and redox homeostasis. However, this hypothesis has not been explored. The present study demonstrates for the first time that at 24h, FA induced mitochondrial bioenergetics, redox state, dynamics and mitophagy alterations, which are involved in the mechanisms responsible for the AKI development. On the other hand, NAC preadministration was able to prevent mitochondrial bioenergetics, redox state and dynamics alterations as well as renal damage. The protective effects of NAC on mitochondria and renal function could be related to its observed capacity to preserve the S-glutathionylation process and GSH levels in mitochondria. Taken together, our results support the idea that these mitochondrial processes can be targets for the prevention of the renal damage and its progression in FA-induced AKI model.
    Keywords:  Acute kidney damage; N-acetyl-cysteine; folic acid; mitochondrial bioenergetics; mitochondrial dynamics and S-glutathionylation
  26. J Neurotrauma. 2018 Nov 12.
    Hubbard WB, Joseph B, Spry M, Vekaria H, Saatman KE, Sulllivan PG.
      Mild traumatic brain injuries (mTBI), accounting for over 80% of TBIs, can cause cognitive and behavioral impairments, the severity and duration of which increase after additional mTBIs. While mTBI does not cause widespread neuronal death, the mechanisms underlying increased cellular susceptibility to subsequent head impacts remain unknown. To investigate the hypothesis that altered mitochondrial bioenergetics underlie cellular vulnerability to repeated insults, we employed a mouse model of mild closed head injury (CHI) to examine mitochondrial function and oxidative stress, as these mechanisms are often intertwined. Mitochondrial respiration was assayed (Seahorse XFe24 Flux Analyzer) from cortex and hippocampus collected at 6h, 24h, 48h, and 96h post-injury. State III (ADP-mediated) respiration was significantly decreased in the hippocampal mitochondria of the CHI group compared to sham at 48h post-injury. Furthermore, cortex-derived mitochondria exhibited a decrease in State III respiration at 24h and 48h post-injury. No significant differences were observed at 6h or 96h post-injury in either region of interest. A second CHI repeated either 48h or 96h after the first did not worsen State III respiration at 48h after the final injury compared to a single CHI, but CHI repeated at a 48h interval prolonged cortical mitochondrial dysfunction to 96h after the final injury. Markers of oxidative stress were significantly elevated after two CHI delivered 48h apart, but not after single CHI or two CHI delivered 96h apart. This study establishes that mTBI results in early mitochondrial dysfunction, which may be a determinant for cellular vulnerability to repeated head impacts. Thus, therapies targeting mitochondrial impairment could improve outcomes after repeated mTBI.
  27. J Pineal Res. 2018 Nov 11. e12538
    Jou MJ, Peng TI, Reiter RJ.
      Cyclic 3-hydroxymelatonin (C3-OHM) and N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) are two major cascade metabolites of melatonin. We previously showed melatonin provides multiple levels of mitochondria-targeted protection beyond as a mitochondrial antioxidant during ionomycin-induced mitochondrial Ca2+ (mCa2+ ) stress in RBA1 astrocytes. Using non-invasive laser scanning fluorescence coupled time-lapse digital imaging microscopy, this study investigated whether C3-OHM and AFMK also provide mitochondrial levels of protection during ionomycin-induced mCa2+ stress in RBA1 astrocytes. Interestingly, precise temporal and spatial dynamic live mitochondrial images revealed that C3-OHM and AFMK prevented specifically mCa2+ -mediated mitochondrial reactive oxygen species (mROS) formation and hence mROS-mediated depolarization of mitochondrial membrane potential (△Ψm ) and permanent lethal opening of the MPT (p-MPT). The antioxidative effects of AFMK, however, was less potent than that of C3-OHM. Whether C3-OHM and AFMK targeted directly the MPT was investigated under a condition of "oxidation free-Ca2+ stress" using a classic antioxidant vitamin E to removed mCa2+ -mediated mROS stress and the potential antioxidative effects of C3-OHM and AFMK. Intriguingly, two compounds still effectively postponed "oxidation free-Ca2+ stress"-mediated depolarization of △Ψm and p-MPT. Measurements using a MPT pore specific indicator Calcein further identified that C3-OHM and AFMK, rather than inhibiting, stabilized the MPT in its transient protective opening mode (t-MPT), a critical mechanism to reduce overloaded mROS and mCa2+ . These multiple layers of mitochondrial protection provided by C3-OHM and AFMK thus crucially allow melatonin to extend its metabolic cascades of mitochondrial protection during mROS- and mCa2+ -mediated MPT-associated apoptotic stresses and may provide therapeutic benefits against astrocyte-mediated neurodegeneration in the CNS. This article is protected by copyright. All rights reserved.
    Keywords:   AFMK ; mROS ; C3-OHM; mCa2+; melatonin; mitochondria-targeted antioxidant; mitochondrial permeability transition
  28. J Mol Biol. 2018 Nov 08. pii: S0022-2836(18)30933-1. [Epub ahead of print]
    Martins VM, Fernandes TR, Afonso CB, Lopes D, Domingues MRM, Côrte-Real M, Sousa MJ.
      Endoplasmic reticulum-mitochondria contact sites (ER-MCS) have been a subject of increasing scientific interest since the discovery that these structures are disrupted in several pathologies. Due to the emerging data that correlates ER-MCS function to known events of the apoptotic program, we aimed to dissect this interplay using our well-established model of acetic acid-induced apoptosis in Saccharomyces cerevisiae. Until recently, the only known tethering complex between ER and mitochondria in this organism was the ER-mitochondria encounter structure (ERMES). Following our results from a screening designed to identify genes whose deletion rendered cells with an altered sensitivity to acetic acid, we hypothesized that the ERMES complex could be involved in cell death mediated by this stressor. Herein we demonstrate that single ablation of the ERMES components Mdm10p, Mdm12p and Mdm34p increases the resistance of S. cerevisiae to acetic acid-induced apoptosis, which is associated with a prominent delay in the appearance of several apoptotic markers. Moreover, abrogation of Mdm10p or Mdm34p abolished cytochrome c release from mitochondria. Since these two proteins are embedded in the mitochondrial outer membrane, we propose that the ERMES complex plays a part in cytochrome c release, a key event of the apoptotic cascade. In all, these findings will aid in targeted therapies for diseases where apoptosis is disrupted, as well as assist in the development of acetic acid-resistant strains for industrial processes.
    Keywords:  Membrane contact sites; Mitochondrial outer membrane permeabilization; Weak acid; Yeast cell death
  29. Cell Mol Life Sci. 2018 Nov 10.
    Altieri DC.
      Changes in cellular metabolism are now a recognized hallmark of cancer. Although this process is ripe with therapeutic potential in the clinic, its complexity and extraordinary plasticity have systematically defied dogmas and oversimplifications. Perhaps, best exemplifying this intricacy is the role of mitochondria in cancer, which in just a few years has gone from largely unnoticed to pivotal disease driver. The underlying mechanisms are only beginning to emerge. However, there is now clear evidence linking the dynamic nature of mitochondria to the machinery of tumor cell motility and metastatic spreading. These studies may open fresh therapeutic options for patients with disseminated cancer, currently an incurable and mostly lethal condition.
    Keywords:  Cancer; Dynamics; Metastasis; Mitochondria; Trafficking; Tumor cell invasion
  30. J Pathol. 2018 Nov 14.
    Qin N, Cai T, Ke Q, Yuan Q, Luo J, Mao X, Jiang L, Cao H, Wen P, Zen K, Zhou Y, Yang J.
      Acute kidney injury (AKI) is a public health concern with high morbidity and mortality rates in hospitalized patients and because survivors have increased risk of progression to chronic kidney disease. Mitochondrial damage is the critical driver of AKI-associated dysfunction and loss of tubular epithelial cells; however, the pathways that mediate these events are poorly defined. Here, in murine ischemia/reperfusion-induced (I/R-induced) AKI, we determined that mitochondrial damage is associated with the level of renal uncoupling protein 2 (UCP2). In hypoxia-damaged proximal tubular cells (PTCs), a disruption of mitochondrial dynamics demonstrated by mitochondrial fragmentation and disturbance between fusion and fission was clearly indicated. Ucp2-deficient mice (knockout mice) with I/R injury experienced more severe AKI and mitochondrial fragmentation than wild-type (WT) mice. Moreover, genetic or pharmacologic treatment increased UCP2 expression, improved renal function, reduced tubular injury and limited mitochondrial fission. In cultured proximal tubular epithelial cells, hypoxia-induced mitochondrial fission was exacerbated in cells with UCP2 deletion, while an increase of UCP2 ameliorated the hypoxia-induced disturbance of the balance between mitochondrial fusion and fission. Furthermore, results following modulation of UCP2 suggested it has a role in preserving mitochondrial integrity by preventing loss of membrane potential and reducing subsequent mitophagy. Taken together, our results indicate that UCP2 is protective against AKI and suggest that enhancing UCP2 to improve mitochondrial dynamics has potential as a strategy for improving outcomes of renal injury. This article is protected by copyright. All rights reserved.
    Keywords:  Acute kidney injury; fission; fusion; hypoxia; mitochondrial membrane potential; mitophagy
  31. Trends Endocrinol Metab. 2018 Nov 12. pii: S1043-2760(18)30189-9. [Epub ahead of print]
    Mills CA, Trub AG, Hirschey MD.
      Fatty acid synthesis (FAS) in mitochondria produces a key metabolite called lipoic acid. However, a new study by Van Vranken et al.[1] (Mol. Cell 2018;71:567-580) shows that mitochondrial FAS regulates the assembly of oxidative phosphorylation complexes, thereby functioning as a nutrient sensor for mitochondrial respiration.
    Keywords:  acetyl-coA; acyl-carrier protein (ACP); fatty acid synthesis; mitochondria; nutrient sensing
  32. EMBO J. 2018 Nov 12. pii: e99576. [Epub ahead of print]
    Rashid T, Nemazanyy I, Paolini C, Tatsuta T, Crespin P, de Villeneuve D, Brodesser S, Benit P, Rustin P, Baraibar MA, Agbulut O, Olivier A, Protasi F, Langer T, Chrast R, de Lonlay P, de Foucauld H, Blaauw B, Pende M.
      As a consequence of impaired glucose or fatty acid metabolism, bioenergetic stress in skeletal muscles may trigger myopathy and rhabdomyolysis. Genetic mutations causing loss of function of the LPIN1 gene frequently lead to severe rhabdomyolysis bouts in children, though the metabolic alterations and possible therapeutic interventions remain elusive. Here, we show that lipin1 deficiency in mouse skeletal muscles is sufficient to trigger myopathy. Strikingly, muscle fibers display strong accumulation of both neutral and phospholipids. The metabolic lipid imbalance can be traced to an altered fatty acid synthesis and fatty acid oxidation, accompanied by a defect in acyl chain elongation and desaturation. As an underlying cause, we reveal a severe sarcoplasmic reticulum (SR) stress, leading to the activation of the lipogenic SREBP1c/SREBP2 factors, the accumulation of the Fgf21 cytokine, and alterations of SR-mitochondria morphology. Importantly, pharmacological treatments with the chaperone TUDCA and the fatty acid oxidation activator bezafibrate improve muscle histology and strength of lipin1 mutants. Our data reveal that SR stress and alterations in SR-mitochondria contacts are contributing factors and potential intervention targets of the myopathy associated with lipin1 deficiency.
    Keywords:  endoplasmic reticulum stress; genetic disease; metabolism; myopathy
  33. Arch Biochem Biophys. 2018 Nov 12. pii: S0003-9861(18)30675-1. [Epub ahead of print]
    Triolo M, Hood DA.
      Skeletal muscle mitochondria are essential in providing the energy required for locomotion. In response to contractile activity, the production of mitochondria is upregulated to meet the energy demands placed upon muscle cells. In a coordinated fashion, exercise also promotes the breakdown of dysfunctional mitochondria via mitophagy. Mitophagy is characterized by the selection of poorly functioning organelles, engulfment in an autophagosome and transport to lysosomes for degradation. In addition to the activation of mitophagy, exercise also elevates lysosome biogenesis. This coordinated increase in mitophagy targeting and lysosomal biogenesis serves to enhance the capacity for autophagosomal degradation, thereby aiding in the maintenance of mitochondrial quality. Lysosome dysfunction, as observed in lysosomal storage disorders (LSDs), negatively impacts mitochondrial function likely through the suppression of mitophagy. Since exercise is capable of activating mitophagy and lysosome biogenesis, researchers have begun to investigate physical activity as an effective therapy for LSDs. This review summarizes the current understanding of how mitophagy and lysosomal biogenesis are regulated in exercising skeletal, with potential therapeutic implications.
    Keywords:  Exercise; Lysosomal storage disorders; Lysosomes; Mitochondria; Mitophagy; Skeletal muscle
  34. Oncotarget. 2018 Oct 12. 9(80): 35028-35040
    Coluccia R, Raffa S, Ranieri D, Micaloni A, Valente S, Salerno G, Scrofani C, Testa M, Gallo G, Pagannone E, Torrisi MR, Volpe M, Rubattu S.
      Oxidative stress is currently viewed as a key factor in the genesis and progression of Heart Failure (HF). The aim of this study was to characterize the mitochondrial changes linked to oxidative stress generation in circulating peripheral blood mononuclear cells isolated from chronic HF patients (HF_PBMCs) in order to highlight the involvement of mitochondrial dysfunction in the pathophysiology of HF. To assess the production of reactive oxygen species (ROS), mitochondrial function and ultrastructure and the mitophagic flux in circulating PBMCs we enrolled 15 patients with HF and a control group of ten healthy subjects. The HF_PBMCs showed a mitochondrial population consisting of damaged and less functional organelles responsible of higher superoxide anion production both at baseline and under in vitro stress conditions, with evidence of cellular apoptosis. Although the mitophagic flux at baseline was enhanced in HF_PBMCs at level similar to those that could be achieved in control PBMCs only under inflammatory stress conditions, the activation of mitophagy was unable to preserve a proper mitochondrial dynamics upon stress stimuli in HF. In summary, circulating HF_PBMCs show structural and functional derangements of mitochondria with overproduction of reactive oxidant species. This mitochondrial failure sustains a leucocyte dysfunctional status in the blood that may contribute to development and persistence of stress conditions within the cardiovascular system in HF.
    Keywords:  Pathology; heart failure; mitochondrial dysfunction; mitophagy; oxidative stress; peripheral blood mononuclear cells
  35. Neurochem Int. 2018 Nov 10. pii: S0197-0186(18)30385-1. [Epub ahead of print]
    Borst K, Schwabenland M, Prinz M.
      In the last decade tremendous progress has been made in understanding how the immune system reacts to insults. During this progress it became obvious that those immune responses are tightly regulated and cross-linked with distinct metabolic changes in immune cells. Extensive research has been conducted mainly on subtypes of T cells, which use different metabolic pathways during differentiation processes and activation states. In addition, it has also been established later, that the innate immune cell lineage of myeloid cells includes a variety of different subsets of bone marrow-derived as well as tissue-specific macrophages, which elicit much more functions than simply killing bacteria. To execute this high variety of functions, also macrophages use different metabolic pathways and are tightly regulated by key metabolic regulators, such as the mechanistic target of rapamycin (mTOR). Upon activation, metabolic changes within the cell occur to meet the requirements of the phenotypic switch. In addition, metabolic changes correlate with the ability of innate immune cells to show hallmarks of adaptive immune responses. Little is known about specific metabolic changes of myeloid cells and specifically microglia in vivo. Microglia are key players in neurodegenerative and neuroinflammatory diseases and have become a major target of medical research. Here, we review the existing data on microglia metabolism and the connection of microglia phenotypes with neuroinflammatory and neurodegenerative diseases. Lastly, we will discuss how our knowledge about the cellular metabolism might be used to develop new treatment options for neurological diseases.
    Keywords:  Immunometabolism; Microglia; Neurodegeneration; Neuroinflammation
  36. Viruses. 2018 Nov 13. pii: E629. [Epub ahead of print]10(11):
    Albert M, Bécares M, Falqui M, Fernández-Lozano C, Guerra S.
      Viruses are responsible for the majority of infectious diseases, from the common cold to HIV/AIDS or hemorrhagic fevers, the latter with devastating effects on the human population. Accordingly, the development of efficient antiviral therapies is a major goal and a challenge for the scientific community, as we are still far from understanding the molecular mechanisms that operate after virus infection. Interferon-stimulated gene 15 (ISG15) plays an important antiviral role during viral infection. ISG15 catalyzes a ubiquitin-like post-translational modification termed ISGylation, involving the conjugation of ISG15 molecules to de novo synthesized viral or cellular proteins, which regulates their stability and function. Numerous biomedically relevant viruses are targets of ISG15, as well as proteins involved in antiviral immunity. Beyond their role as cellular powerhouses, mitochondria are multifunctional organelles that act as signaling hubs in antiviral responses. In this review, we give an overview of the biological consequences of ISGylation for virus infection and host defense. We also compare several published proteomic studies to identify and classify potential mitochondrial ISGylation targets. Finally, based on our recent observations, we discuss the essential functions of mitochondria in the antiviral response and examine the role of ISG15 in the regulation of mitochondrial processes, specifically OXPHOS and mitophagy.
    Keywords:  OXPHOS; interferon; mitochondria; mitophagy; ubiquitin-like modification
  37. Brain Res Bull. 2018 Nov 08. pii: S0361-9230(18)30564-1. [Epub ahead of print]
    Wen D, Cui C, Duan W, Wang W, Wang Y, Liu Y, Li Z, Li C.
      Amyotrophic lateral sclerosis (ALS) is a common neurodegenerative disorder, but little is known about the exact causes and pathophysiology of this disease. In transgenic mouse models of ALS, mitochondrial abnormalities develop during the disease and might contribute to the progression of ALS. Gene therapy was recently shown to induce beneficial effects. For example, the delivery of human insulin-like growth factor-1 (hIGF-1) by self-complementary adeno-associated virus (AAV) vectors has been shown to prolong the lifespan of ALS transgenic mice. However, the function of IGF-1 in mitochondria has not been systematically studied in ALS models. In this study, scAAV9-hIGF-1 was intramuscularly injected into transgenic SOD1G93A mice and administered to cell lines expressing the ~25-kDa C-terminal fragment of transactive response DNA-binding protein (TDP-25). The mitochondrial electrical transmembrane potential was hyperpolarized, and electron microscopy findings revealed that the abnormal mitochondria were transformed. Moreover, the intrinsic mitochondrial apoptotic process was modified through the upregulation of anti-apoptotic proteins (B-cell lymphoma-extra large (Bcl-xl) and B-cell lymphoma-2 (Bcl-2)), the downregulation of pro-apoptotic proteins (Bcl-2-associated x protein (Bax) and Bcl-2 homologous antagonist killer (Bak)) and a reduction in mitochondrial cytochrome c release. Mitophagy was also increased after scAAV9-hIGF-1 treatment, as evidenced by a decrease in the p62 level and an increase in the LC3-II level. Furthermore, the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system was used to delete the IGF-1 gene in SOD1G93A model mice via an intrathecal injection of scAAV9-sgRNA-IGF1-Cas9 to confirm these findings. The protective effect of IGF-1 on the mitochondria decreased after genetic deletion. These novel findings demonstrate that IGF-1 strongly protects mitochondria from apoptosis and upregulates mitophagy in mouse and cell models of ALS. Therefore, therapies that specifically protect mitochondrial function might be promising strategies for treating ALS.
    Keywords:  TDP-25; amyotrophic lateral sclerosis; insulin-like growth factor 1; intrinsic apoptosis pathway; mitochondria; mitophagy; transgenic SOD1(G93A) mice
  38. Hum Mol Genet. 2018 Nov 14.
    Munro B, Horvath R, Müller JS.
      Deoxyguanosine kinase (dGK) is an essential rate limiting component of the mitochondrial purine nucleotide salvage pathway, encoded by the nuclear gene DGUOK. Mutations in DGUOK lead to mitochondrial DNA (mtDNA) depletion typically in the liver and brain, causing a hepatocerebral phenotype. Previous work has shown thatin cultured DGUOK patient cellsit is possible to rescue mtDNA depletion by increasing substrate amounts for dGK. In this study we developed a mutant dguok zebrafish (Danio rerio) line using CRISPR/Cas9 mediated mutagenesis; dguok-/-fish have significantly reduced mtDNA levels compared to wild-type fish. When supplemented with only one purine nucleoside (dGuo), mtDNA copy number in both mutant and wild-type juvenile animals was significantly reduced,contrasting with previous cell culture studies, possibly due to nucleotide pool imbalance. However,in adult dguok-/-fish we detected a significant increase in liver mtDNA copy number when supplemented with both purine nucleosides. This study further supports the idea that nucleoside supplementation has a potential therapeutic benefit in mtDNA depletion syndromes by substrate enhancement of the purine nucleoside salvage pathway and might improve the liver pathology in patients.
  39. J Biol Chem. 2018 Nov 14. pii: jbc.RA118.003061. [Epub ahead of print]
    Yoon MK, Kim BY, Lee JY, Ha JH, Kim SA, Lee DH, Lee MS, Lee MK, Choi JS, Cho JH, Kim JH, Kim S, Song J, Park SG, Park BC, Bae KH, Choi SU, Chi SW.
      In response to genotoxic stress, the tumor suppressor protein p73 induces apoptosis and cell cycle arrest. Despite extensive studies on p73-mediated apoptosis, little is known about the cytoplasmic apoptotic function of p73. Here, using H1299 lung cancer cells and diverse biochemical approaches, including colony formation, DNA fragmentation, GST pull-down, and apoptosis assays along with NMR spectroscopy, we show that p73 induces transcription-independent apoptosis via its transactivation domain (TAD) through a mitochondrial pathway and that this apoptosis is mediated by the interaction between p73-TAD and the anti-apoptotic protein B-cell lymphoma-extra large (Bcl-XL or BCL2L1). This binding disrupted an interaction between Bcl-XL and the pro-apoptotic protein BH3-interacting domain death agonist (BID). In particular, we found that a 16-mer p73-TAD peptide motif (p73-TAD16) mediates transcription-independent apoptosis, accompanied by cytochrome c release from the mitochondria, by interacting with Bcl-XL Interestingly, the structure of the Bcl-XL-p73-TAD16 peptide complex revealed a novel mechanism of Bcl-XL recognition by p73-TAD. We observed that the α-helical p73-TAD16 peptide binds to a non-canonical site in Bcl-XL, comprising the BH1, BH2, and BH3 domains in an orientation opposite to those of pro-apoptotic BH3 peptides. Taken together, our results indicate that the cytoplasmic apoptotic function of p73 is mediated through a non-canonical mode of Bcl-XL recognition. This finding sheds light on a critical transcription-independent, p73-mediated mechanism for apoptosis induction, which has potential implications for anticancer therapy.
    Keywords:  BCL2L1; BH3-interacting domain death agonist; Bcl-XL; apoptosis; cancer; p73; protein structure; protein-protein interaction; transactivation domain; tumor suppressor gene
  40. EBioMedicine. 2018 Nov 09. pii: S2352-3964(18)30493-6. [Epub ahead of print]
    Lyu Z, Mao Z, Li Q, Xia Y, Liu Y, He Q, Wang Y, Zhao H, Lu Z, Zhou Q.
      BACKGROUND: The renal tubules, which have distant metabolic features and functions in different segments, reabsorb >99% of approximately 180 l of water and 25,000 mmol of Na + daily. Defective metabolism in renal tubules is involved in the pathobiology of kidney diseases. However, the mechanisms underlying the metabolic regulation in renal tubules remain to be defined.METHODS: We quantitatively compared the proteomes of the isolated proximal tubules (PT) and distal tubules (DT) from C57BL/6 mouse using tandem mass tag (TMT) labeling-based quantitative mass spectrometry. Bioinformatics analysis of the differentially expressed proteins revealed the significant differences between PT and DT in metabolism pathway. We also performed in vitro and in vivo assays to investigate the molecular mechanism underlying the distant metabolic features in PT and DT.
    FINDINGS: We demonstrate that the renal proximal tubule (PT) has high expression of lipid metabolism enzymes, which is transcriptionally upregulated by abundantly expressed PPARα/γ. In contrast, the renal distal tubule (DT) has elevated glycolytic enzyme expression, which is mediated by highly expressed c-Myc. Importantly, PPARγ transcriptionally enhances the protease iRhom2 expression in PT, which suppresses EGF expression and secretion and subsequent EGFR-dependent glycolytic gene expression and glycolysis. PPARγ inhibition reduces iRhom2 expression and increases EGF and GLUT1 expression in PT in mice, resulting in renal tubule hypertrophy, tubulointerstitial fibrosis and damaged kidney functions, which are rescued by 2-deoxy-d-glucose treatment.
    INTERPRETATION: These findings delineate instrumental mechanisms underlying the active lipid metabolism and suppressed glycolysis in PT and active glycolysis in DT and reveal critical roles for PPARs and c-Myc in maintaining renal metabolic homeostasis. FUND: This work was supported by the National Natural Science Foundation of China (grants 81572076 and 81873932; to Q.Z.), the Applied Development Program of the Science and Technology Committee of Chongqing (cstc2014yykfB10003; Q.Z.), the Program of Populace Creativities Workshops of the Science and Technology Committee of Chongqing (Q.Z.), the special demonstration programs for innovation and application of techniques (cstc2018jscx-mszdX0022) from the Science and Technology Committee of Chongqing (Q.Z.).
    Keywords:  C-Myc; Glycolysis; Kidney; Lipid metabolism; Nrf2; PPARα; PPARγ; Renal distal tubules; Renal proximal tubules
  41. EMBO Rep. 2018 Nov 12. pii: e46377. [Epub ahead of print]
    Yan WW, Liang YL, Zhang QX, Wang D, Lei MZ, Qu J, He XH, Lei QY, Wang YP.
      Sirtuins (SIRTs) are a class of lysine deacylases that regulate cellular metabolism and energy homeostasis. Although sirtuins have been proposed to function in nutrient sensing and signaling, the underlying mechanism remains elusive. SIRT7, a histone H3K18-specific deacetylase, epigenetically controls mitochondria biogenesis, ribosomal biosynthesis, and DNA repair. Here, we report that SIRT7 is methylated at arginine 388 (R388), which inhibits its H3K18 deacetylase activity. Protein arginine methyltransferase 6 (PRMT6) directly interacts with and methylates SIRT7 at R388 in vitro and in vivo R388 methylation suppresses the H3K18 deacetylase activity of SIRT7 without modulating its subcellular localization. PRMT6-induced H3K18 hyperacetylation at SIRT7-target gene promoter epigenetically promotes mitochondria biogenesis and maintains mitochondria respiration. Moreover, high glucose enhances R388 methylation in mouse fibroblasts and liver tissue. PRMT6 signals glucose availability to SIRT7 in an AMPK-dependent manner. AMPK induces R388 hypomethylation by disrupting the association between PRMT6 and SIRT7. Together, PRMT6-induced arginine methylation of SIRT7 coordinates glucose availability with mitochondria biogenesis to maintain energy homeostasis. Our study uncovers the regulatory role of SIRT7 arginine methylation in glucose sensing and mitochondria biogenesis.
    Keywords:  PRMT6; SIRT7; arginine methylation; glucose sensing; mitochondria biogenesis
  42. Front Endocrinol (Lausanne). 2018 ;9 642
    Ducheix S, Magré J, Cariou B, Prieur X.
      Type 2 diabetes (T2D) is a major risk factor for heart failure. Diabetic cardiomyopathy (DC) is characterized by diastolic dysfunction and left ventricular hypertrophy. Epidemiological data suggest that hyperglycaemia contributes to the development of DC. Several cellular pathways have been implicated in the deleterious effects of high glucose concentrations in the heart: oxidative stress, accumulation of advanced glycation end products (AGE), and chronic hexosamine biosynthetic pathway (HBP) activation. In the present review, we focus on the effect of chronic activation of the HBP on diabetic heart function. The HBP supplies N-acetylglucosamine moiety (O-GlcNAc) that is O-linked by O-GlcNAc transferase (OGT) to proteins on serine or threonine residues. This post-translational protein modification modulates the activity of the targeted proteins. In the heart, acute activation of the HBP in response to ischaemia-reperfusion injury appears to be protective. Conversely, chronic activation of the HBP in the diabetic heart affects Ca2+ handling, contractile properties, and mitochondrial function and promotes stress signaling, such as left ventricular hypertrophy and endoplasmic reticulum stress. Many studies have shown that O-GlcNAc impairs the function of key protein targets involved in these pathways, such as phospholamban, calmodulin kinase II, troponin I, and FOXO1. The data show that excessive O-GlcNAcylation is a major trigger of the glucotoxic events that affect heart function under chronic hyperglycaemia. Supporting this finding, pharmacological or genetic inhibition of the HBP in the diabetic heart improves heart function. In addition, the SGLT2 inhibitor dapagliflozin, a glucose lowering agent, has recently been shown to lower cardiac HBP in a lipodystophic T2D mice model and to concomitantly improve the diastolic dysfunction of these mice. Therefore, targeting cardiac-excessive O-GlcNAcylation or specific target proteins represents a potential therapeutic option to treat glucotoxicity in the diabetic heart.
    Keywords:  O-GlcNAcylation; cardiomyopathy; diabetes; glucotoxicity; metabolism
  43. Cell Death Dis. 2018 Nov 14. 9(11): 1135
    Iannetti EF, Smeitink JAM, Willems PHGM, Beyrath J, Koopman WJH.
      Cell models of mitochondrial complex I (CI) deficiency display activation of glycolysis to compensate for the loss in mitochondrial ATP production. This adaptation can mask other relevant deficiency-induced aberrations in cell physiology. Here we investigated the viability, mitochondrial morphofunction, ROS levels and ATP homeostasis of primary skin fibroblasts from Leigh Syndrome (LS) patients with isolated CI deficiency. These cell lines harbored mutations in nuclear DNA (nDNA)-encoded CI genes (NDUFS7, NDUFS8, NDUFV1) and, to prevent glycolysis upregulation, were cultured in a pyruvate-free medium in which glucose was replaced by galactose. Following optimization of the cell culture protocol, LS fibroblasts died in the galactose medium, whereas control cells did not. LS cell death was dose-dependently inhibited by pyruvate, malate, oxaloacetate, α-ketoglutarate, aspartate, and exogenous NAD+ (eNAD), but not by lactate, succinate, α-ketobutyrate, and uridine. Pyruvate and eNAD increased the cellular NAD+ content in galactose-treated LS cells to a different extent and co-incubation studies revealed that pyruvate-induced rescue was not primarily mediated by NAD+. Functionally, in LS cells glucose-by-galactose replacement increased mitochondrial fragmentation and mass, depolarized the mitochondrial membrane potential (Δψ), increased H2DCFDA-oxidizing ROS levels, increased mitochondrial ATP generation, and reduced the total cellular ATP content. These aberrations were differentially rescued by pyruvate and eNAD, supporting the conclusion that these compounds rescue galactose-induced LS cell death via different mechanisms. These findings establish a cell-based strategy for intervention testing and enhance our understanding of CI deficiency pathophysiology.
  44. Hum Mol Genet. 2018 Nov 16.
    Seminotti B, Leipnitz G, Karunanidhi A, Kochersperger C, Roginskaya VY, Basu S, Wang Y, Wipf P, Van Houten B, Mohsen AW, Vockley J.
      Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is the most common defect of mitochondrial long-chain fatty acid β-oxidation (FAO). Patients present with heterogeneous clinical phenotypes affecting heart, liver, and skeletal muscle predominantly. The full pathophysiology of the disease is unclear and patient response to current therapeutic regimens is incomplete. To identify additional cellular alterations and explore more effective therapies, mitochondrial bioenergetics and redox homeostasis were assessed in VLCAD deficient fibroblasts, and several protective compounds were evaluated. The results revealed cellular and tissue changes, including decreased respiratory chain function, increased reactive oxygen species (ROS) production, and altered mitochondrial function and signaling pathways in a variety of VLCAD deficient fibroblasts. The mitochondrially enriched electron and free radical scavengers JP4-039 and XJB-5-131 improved respiratory chain function and decreased ROS production significantly, suggesting that they are viable candidate compounds to further develop to treat VLCAD deficient patients.
  45. Biochemistry. 2018 Nov 14.
    Grankvist N, Lehmann K, Jain M, Nilsson R.
      Metabolism of branched-chain amino acids (BCAA) and has recently been implicated in growth of several cancer cell types. Gabapentin, a synthetic amino acid, is commonly used in high concentrations in this context to inhibit the cytosolic branched-chain amino acid transferase (BCAT1) enzyme. Here, we report that 10 mM gabapentin reduces growth of HCT116 cells, which have an active branched-chain amino acid transferase but express very low levels of BCAT1, and presumably rely on the mitochondrial BCAT2 enzyme. Gabapentin did not affect transamination of BCAA to branched-chain keto acids (BCKA) in HCT116 cells, nor the reverse formation of BCAA from BCKA, indicating that the branched-chain amino acid transaminase is not inhibited. Moreover, the growth-inhibitory effect of gabapentin could not be rescued by supplementation with BCKA, and this was not due to lack of uptake of BCKA, indicating that other effects of gabapentin are important. An untargeted LC-MS analysis of gabapentin-treated cells revealed a marked depletion of branched-chain carnitines. These results demonstrate that gabapentin at high concentrations can inhibit cell proliferation without affecting BCAT1, and may affect mitochondrial BCKA catabolism.
  46. Nat Immunol. 2018 Dec;19(12): 1330-1340
    Michelet X, Dyck L, Hogan A, Loftus RM, Duquette D, Wei K, Beyaz S, Tavakkoli A, Foley C, Donnelly R, O'Farrelly C, Raverdeau M, Vernon A, Pettee W, O'Shea D, Nikolajczyk BS, Mills KHG, Brenner MB, Finlay D, Lynch L.
      Up to 49% of certain types of cancer are attributed to obesity, and potential mechanisms include overproduction of hormones, adipokines, and insulin. Cytotoxic immune cells, including natural killer (NK) cells and CD8+ T cells, are important in tumor surveillance, but little is known about the impact of obesity on immunosurveillance. Here, we show that obesity induces robust peroxisome proliferator-activated receptor (PPAR)-driven lipid accumulation in NK cells, causing complete 'paralysis' of their cellular metabolism and trafficking. Fatty acid administration, and PPARα and PPARδ (PPARα/δ) agonists, mimicked obesity and inhibited mechanistic target of rapamycin (mTOR)-mediated glycolysis. This prevented trafficking of the cytotoxic machinery to the NK cell-tumor synapse. Inhibiting PPARα/δ or blocking the transport of lipids into mitochondria reversed NK cell metabolic paralysis and restored cytotoxicity. In vivo, NK cells had blunted antitumor responses and failed to reduce tumor growth in obesity. Our results demonstrate that the lipotoxic obese environment impairs immunosurveillance and suggest that metabolic reprogramming of NK cells may improve cancer outcomes in obesity.
  47. Br J Pharmacol. 2018 Nov 15.
    Leanza L, Checchetto V, Biasutto L, Rossa A, Costa R, Bachmann M, Zoratti M, Szabo I.
      The field of mitochondrial ion channels has undergone a rapid development during the last three decades, due to the molecular identification of some of the channels residing in the outer and inner membranes. Relevant information about the function of these channels in physiological and pathological settings was gained thanks to genetic models for a few, mitochondria-specific channels. However, many ion channels have multiple localization within the cell hampering a clear-cut determination of their function by pharmacological means. The present review summarizes our current knowledge about the ins and outs of mitochondrial ion channels with special focus on the channels that have received much attention in recent years, namely the voltage-dependent anion channels, the permeability transition pore (also called mitochondrial megachannel), the mitochondrial calcium uniporter and some of the inner membrane-located potassium channels. In addition, possible strategies to overcome difficulties of specifically targeting mitochondrial channels versus their counterparts active in other membranes are discussed, as well as the possibilities of modulating channel function by small peptides that compete for binding with protein interaction partners. Altogether, these promising tools along with large-scale chemical screenings set up to identify new, specific channel modulators will hopefully allow to pinpoint the actual function of most mitochondrial ion channels in the near future and to pharmacologically affect important pathologies in which they are involved, such as neurodegeneration, ischemic damage and cancer.
  48. iScience. 2018 May 25. pii: S2589-0042(18)30045-2. [Epub ahead of print]3 192-207
    Pan J, Lee Y, Cheng G, Zielonka J, Zhang Q, Bajzikova M, Xiong D, Tsaih SW, Hardy M, Flister M, Olsen CM, Wang Y, Vang O, Neuzil J, Myers CR, Kalyanaraman B, You M.
      We synthesized a mitochondria-targeted honokiol (Mito-HNK) that facilitates its mitochondrial accumulation; this dramatically increases its potency and efficacy against highly metastatic lung cancer lines in vitro, and in orthotopic lung tumor xenografts and brain metastases in vivo. Mito-HNK is >100-fold more potent than HNK in inhibiting cell proliferation, inhibiting mitochondrial complex ?, stimulating reactive oxygen species generation, oxidizing mitochondrial peroxiredoxin-3, and suppressing the phosphorylation of mitoSTAT3. Within lung cancer brain metastases in mice, Mito-HNK induced the mediators of cell death and decreased the pathways that support invasion and proliferation. In contrast, in the non-malignant stroma, Mito-HNK suppressed pathways that support metastatic lesions, including those involved in inflammation and angiogenesis. Mito-HNK showed no toxicity and targets the metabolic vulnerabilities of primary and metastatic lung cancers. Its pronounced anti-invasive and anti-metastatic effects in the brain are particularly intriguing given the paucity of treatment options for such patients either alone or in combination with standard chemotherapeutics.
    Keywords:  Immunology; Medicinal and Aromatic Plants; Natural Product Chemistry
  49. Sci Signal. 2018 Nov 13. pii: eaav3267. [Epub ahead of print]11(556):
    Boyer MJ, Eguchi S.
      The interplay between the actin cytoskeleton and mitochondria has been implicated in cell and tissue homeostasis and physiological function. In this issue of Science Signaling, Nishimura et al. demonstrate that inhibiting the interaction of filamin A, an actin cytoskeleton regulator, with Drp1, a modulator of mitochondrial dynamics, attenuates mitochondrial hyperfission and cardiomyocyte senescence after myocardial infarction.
  50. Cell Rep. 2018 Nov 13. pii: S2211-1247(18)31645-0. [Epub ahead of print]25(7): 1841-1855.e5
    Miller DSJ, Bloxham RD, Jiang M, Gori I, Saunders RE, Das D, Chakravarty P, Howell M, Hill CS.
      Signal transduction pathways stimulated by secreted growth factors are tightly regulated at multiple levels between the cell surface and the nucleus. The trafficking of cell surface receptors is emerging as a key step for regulating appropriate cellular responses, with perturbations in this process contributing to human diseases, including cancer. For receptors recognizing ligands of the transforming growth factor β (TGF-β) family, little is known about how trafficking is regulated or how this shapes signaling dynamics. Here, using whole genome small interfering RNA (siRNA) screens, we have identified the ESCRT (endosomal sorting complex required for transport) machinery as a crucial determinant of signal duration. Downregulation of ESCRT components increases the outputs of TGF-β signaling and sensitizes cells to low doses of ligand in their microenvironment. This sensitization drives an epithelial-to-mesenchymal transition (EMT) in response to low doses of ligand, and we demonstrate a link between downregulation of the ESCRT machinery and cancer survival.
    Keywords:  ESCRT machinery; SMAD2; TGF-β; epithelial-to-mesenchymal transition; receptor trafficking; signaling dynamics
  51. Biochim Biophys Acta Bioenerg. 2018 Nov 08. pii: S0005-2728(18)30674-1. [Epub ahead of print]
    Rocha M, Springett R.
      The proton pumps of the mitochondrial electron transport chain (ETC) convert redox energy into the proton motive force (ΔP), which is subsequently used by the ATP synthase to regenerate ATP. The limited available redox free energy requires the proton pumps to operate close to equilibrium in order to maintain a high ΔP, which in turn is need to maintain a high phosphorylation potential. Current biochemical assays measure complex activities far from equilibrium and so shed little light on their function under physiological conditions. Here we combine absorption spectroscopy of the ETC hemes, NADH fluorescence spectroscopy and oxygen consumption to simultaneously measure the redox potential of the intermediate redox pools, the components of ΔP and the electron flux in RAW 264.7 mouse macrophages. We confirm that complex I and III operate near equilibrium and quantify the linear relationship between flux and disequilibrium as a metric of their function under physiological conditions. In addition, we quantify the dependence of complex IV turnover on ΔP and the redox potential of cytochrome c to determine the complex IV driving force and find that the turnover is proportional to this driving force. This form of quantification is a more relevant metric of ETC function than standard biochemical assays and can be used to study the effect of mutations in either mitochondrial or nuclear genome affecting mitochondrial function, post-translation changes, different subunit isoforms, as well as the effect of pharmaceuticals on ETC function.
    Keywords:  ATP; Electron transport chain; Equilibrium; Free energy; Proton pumping; Turnover
  52. Cell Rep. 2018 Nov 13. pii: S2211-1247(18)31629-2. [Epub ahead of print]25(7): 1708-1717.e5
    Cai J, Pires KM, Ferhat M, Chaurasia B, Buffolo MA, Smalling R, Sargsyan A, Atkinson DL, Summers SA, Graham TE, Boudina S.
      Autophagy is a homeostatic cellular process involved in the degradation of long-lived or damaged cellular components. The role of autophagy in adipogenesis is well recognized, but its role in mature adipocyte function is largely unknown. We show that the autophagy proteins Atg3 and Atg16L1 are required for proper mitochondrial function in mature adipocytes. In contrast to previous studies, we found that post-developmental ablation of autophagy causes peripheral insulin resistance independently of diet or adiposity. Finally, lack of adipocyte autophagy reveals cross talk between fat and liver, mediated by lipid peroxide-induced Nrf2 signaling. Our data reveal a role for autophagy in preventing lipid peroxide formation and its transfer in insulin-sensitive peripheral tissues.
    Keywords:  adipocytes; adiponectin; adipose tissue; autophagy; inflammation; insulin resistance; lipid peroxide; mitochondria
  53. PLoS One. 2018 ;13(11): e0206897
    Guha M, Srinivasan S, Johnson FB, Ruthel G, Guja K, Garcia-Diaz M, Kaufman BA, Glineburg MR, Fang J, Nakagawa H, Basha J, Kundu T, Avadhani NG.
      Telomeres protect against chromosomal damage. Accelerated telomere loss has been associated with premature aging syndromes such as Werner's syndrome and Dyskeratosis Congenita, while, progressive telomere loss activates a DNA damage response leading to chromosomal instability, typically observed in cancer cells and senescent cells. Therefore, identifying mechanisms of telomere length maintenance is critical for understanding human pathologies. In this paper we demonstrate that mitochondrial dysfunction plays a causal role in telomere shortening. Furthermore, hnRNPA2, a mitochondrial stress responsive lysine acetyltransferase (KAT) acetylates telomere histone H4at lysine 8 of (H4K8) and this acetylation is associated with telomere attrition. Cells containing dysfunctional mitochondria have higher telomere H4K8 acetylation and shorter telomeres independent of cell proliferation rates. Ectopic expression of KAT mutant hnRNPA2 rescued telomere length possibly due to impaired H4K8 acetylation coupled with inability to activate telomerase expression. The phenotypic outcome of telomere shortening in immortalized cells included chromosomal instability (end-fusions) and telomerase activation, typical of an oncogenic transformation; while in non-telomerase expressing fibroblasts, mitochondrial dysfunction induced-telomere attrition resulted in senescence. Our findings provide a mechanistic association between dysfunctional mitochondria and telomere loss and therefore describe a novel epigenetic signal for telomere length maintenance.
  54. Nature. 2018 Nov 14.
    Poillet-Perez L, Xie X, Zhan L, Yang Y, Sharp DW, Hu ZS, Su X, Maganti A, Jiang C, Lu W, Zheng H, Bosenberg MW, Mehnert JM, Guo JY, Lattime E, Rabinowitz JD, White E.
      Autophagy captures intracellular components and delivers them to lysosomes, where they are degraded and recycled to sustain metabolism and to enable survival during starvation1-5. Acute, whole-body deletion of the essential autophagy gene Atg7 in adult mice causes a systemic metabolic defect that manifests as starvation intolerance and gradual loss of white adipose tissue, liver glycogen and muscle mass1. Cancer cells also benefit from autophagy. Deletion of essential autophagy genes impairs the metabolism, proliferation, survival and malignancy of spontaneous tumours in models of autochthonous cancer6,7. Acute, systemic deletion of Atg7 or acute, systemic expression of a dominant-negative ATG4b in mice induces greater regression of KRAS-driven cancers than does tumour-specific autophagy deletion, which suggests that host autophagy promotes tumour growth1,8. Here we show that host-specific deletion of Atg7 impairs the growth of multiple allografted tumours, although not all tumour lines were sensitive to host autophagy status. Loss of autophagy in the host was associated with a reduction in circulating arginine, and the sensitive tumour cell lines were arginine auxotrophs owing to the lack of expression of the enzyme argininosuccinate synthase 1. Serum proteomic analysis identified the arginine-degrading enzyme arginase I (ARG1) in the circulation of Atg7-deficient hosts, and in vivo arginine metabolic tracing demonstrated that serum arginine was degraded to ornithine. ARG1 is predominantly expressed in the liver and can be released from hepatocytes into the circulation. Liver-specific deletion of Atg7 produced circulating ARG1, and reduced both serum arginine and tumour growth. Deletion of Atg5 in the host similarly released circulating arginine and suppressed tumorigenesis, which demonstrates that this phenotype is specific to autophagy function rather than to deletion of Atg7. Dietary supplementation of Atg7-deficient hosts with arginine partially restored levels of circulating arginine and tumour growth. Thus, defective autophagy in the host leads to the release of ARG1 from the liver and the degradation of circulating arginine, which is essential for tumour growth; this identifies a metabolic vulnerability of cancer.
  55. Pharmacol Ther. 2018 Nov 12. pii: S0163-7258(18)30201-8. [Epub ahead of print]
    Ramapriyan R, da Silva Caetano M, Barsoumian HB, Mafra ACP, Zambalde EP, Menon H, Tsouko E, Welsh JW, Cortez MA.
      Many metabolic alterations, including the Warburg effect, occur in cancer cells that influence the tumor microenvironment, including switching to glycolysis from oxidative phosphorylation, using opportunistic modes of nutrient acquisition, and increasing lipid biosynthesis. The altered metabolic landscape of the tumor microenvironment can suppress the infiltration of immune cells and other functions of antitumor immunity through the production of immune-suppressive metabolites. Metabolic dysregulation in cancer cells further affects the expression of cell surface markers, which interferes with immune surveillance. Immune checkpoint therapies have revolutionized the standard of care for some patients with cancer, but disease in many others is resistant to immunotherapy. Specific metabolic pathways involved in immunotherapy resistance include PI3K-Akt-mTOR, hypoxia-inducible factor (HIF), adenosine, JAK/STAT, and Wnt/Beta-catenin. Depletion of essential amino acids such as glutamine and tryptophan and production of metabolites like kynurenine in the tumor microenvironment also blunt immune cell function. Targeted therapies against metabolic checkpoints could work in synergy with immune checkpoint therapy. This combined strategy could be refined by profiling patients' mutation status before treatment and identifying the optimal sequencing of therapies. This personalized combinatorial approach, which has yet to be explored, may well pave the way for overcoming resistance to immunotherapy.
    Keywords:  Cancer metabolism; Immune checkpoints; Immunotherapy resistance; Tumor microenvironment; Warburg effect
  56. Signal Transduct Target Ther. 2018 ;3 30
    Wang YP, Lei QY.
      Metabolite sensing is one of the most fundamental biological processes. During evolution, multilayered mechanisms developed to sense fluctuations in a wide spectrum of metabolites, including nutrients, to coordinate cellular metabolism and biological networks. To date, AMPK and mTOR signaling are among the best-understood metabolite-sensing and signaling pathways. Here, we propose a sensor-transducer-effector model to describe known mechanisms of metabolite sensing and signaling. We define a metabolite sensor by its specificity, dynamicity, and functionality. We group the actions of metabolite sensing into three different modes: metabolite sensor-mediated signaling, metabolite-sensing module, and sensing by conjugating. With these modes of action, we provide a systematic view of how cells sense sugars, lipids, amino acids, and metabolic intermediates. In the future perspective, we suggest a systematic screen of metabolite-sensing macromolecules, high-throughput discovery of biomacromolecule-metabolite interactomes, and functional metabolomics to advance our knowledge of metabolite sensing and signaling. Most importantly, targeting metabolite sensing holds great promise in therapeutic intervention of metabolic diseases and in improving healthy aging.
  57. Nat Cell Biol. 2018 Nov 12.
    Lafont E, Draber P, Rieser E, Reichert M, Kupka S, de Miguel D, Draberova H, von Mässenhausen A, Bhamra A, Henderson S, Wojdyla K, Chalk A, Surinova S, Linkermann A, Walczak H.
      The linear-ubiquitin chain assembly complex (LUBAC) modulates signalling via various immune receptors. In tumour necrosis factor (TNF) signalling, linear (also known as M1) ubiquitin enables full gene activation and prevents cell death. However, the mechanisms underlying cell death prevention remain ill-defined. Here, we show that LUBAC activity enables TBK1 and IKKε recruitment to and activation at the TNF receptor 1 signalling complex (TNFR1-SC). While exerting only limited effects on TNF-induced gene activation, TBK1 and IKKε are essential to prevent TNF-induced cell death. Mechanistically, TBK1 and IKKε phosphorylate the kinase RIPK1 in the TNFR1-SC, thereby preventing RIPK1-dependent cell death. This activity is essential in vivo, as it prevents TNF-induced lethal shock. Strikingly, NEMO (also known as IKKγ), which mostly, but not exclusively, binds the TNFR1-SC via M1 ubiquitin, mediates the recruitment of the adaptors TANK and NAP1 (also known as AZI2). TANK is constitutively associated with both TBK1 and IKKε, while NAP1 is associated with TBK1. We discovered a previously unrecognized cell death checkpoint that is mediated by TBK1 and IKKε, and uncovered an essential survival function for NEMO, whereby it enables the recruitment and activation of these non-canonical IKKs to prevent TNF-induced cell death.
  58. Cell Metab. 2018 Nov 05. pii: S1550-4131(18)30637-5. [Epub ahead of print]
    Eichner LJ, Brun SN, Herzig S, Young NP, Curtis SD, Shackelford DB, Shokhirev MN, Leblanc M, Vera LI, Hutchins A, Ross DS, Shaw RJ, Svensson RU.
      AMPK, a conserved sensor of low cellular energy, can either repress or promote tumor growth depending on the context. However, no studies have examined AMPK function in autochthonous genetic mouse models of epithelial cancer. Here, we examine the role of AMPK in murine KrasG12D-mediated non-small-cell lung cancer (NSCLC), a cancer type in humans that harbors frequent inactivating mutations in the LKB1 tumor suppressor-the predominant upstream activating kinase of AMPK and 12 related kinases. Unlike LKB1 deletion, AMPK deletion in KrasG12D lung tumors did not accelerate lung tumor growth. Moreover, deletion of AMPK in KrasG12D p53f/f tumors reduced lung tumor burden. We identified a critical role for AMPK in regulating lysosomal gene expression through the Tfe3 transcription factor, which was required to support NSCLC growth. Thus, AMPK supports the growth of KrasG12D-dependent lung cancer through the induction of lysosomes, highlighting an unrecognized liability of NSCLC.
    Keywords:  AMPK; Kras; LKB1; Tfe3; Tfeb; cancer; lung; lysosomes; metabolism; tumor
  59. Genes Cells. 2018 Nov 12.
    Kawata K, Yugi K, Hatano A, Kokaji T, Tomizawa Y, Fujii M, Uda S, Kubota H, Matsumoto M, Nakayama KI, Kuroda S.
      Cellular signaling regulates various cellular functions via protein phosphorylation. Phosphoproteomic data potentially includes information for a global regulatory network from signaling to cellular functions, but a procedure to reconstruct this network using such data has yet to be established. In this paper we provide a procedure to reconstruct a global regulatory network from signaling to cellular functions from phosphoproteomic data by integrating prior knowledge of cellular functions and inference of the kinase-substrate relationships (KSRs). We used phosphoproteomic data from insulin-stimulated Fao hepatoma cells, and identified protein phosphorylation regulated by insulin specifically over-represented in cellular functions in the KEGG database. We inferred kinases for protein phosphorylation by KSRs, and connected the kinases in the insulin-signaling layer to the phosphorylated proteins in the cellular functions, revealing that the insulin signal is selectively transmitted via the Pi3k-Akt and Erk signaling pathways to cellular adhesions and RNA maturation, respectively. Thus, we provide a method to reconstruct global regulatory network from signaling to cellular functions based on phosphoproteomic data. This article is protected by copyright. All rights reserved.
    Keywords:  Trans-omics; cellular functions; insulin signaling; network integration; phosphoproteomic data; phosphorylation; systems biology
  60. J Cardiovasc Pharmacol. 2018 Nov 08.
    Ma S, Dong Z.
      The role of OPA1-related mitochondrial fusion in cardiac reperfusion stress has remained elusive. The aim of our study is to explore whether melatonin alleviates cardiac IR injury by modulating OPA1-related mitochondrial fusion. We found that melatonin reduced infarct area, sustained myocardial function and suppressed cardiomyocyte death during cardiac reperfusion stress. Biological studies have revealed that IR-inhibited mitochondrial fusion was largely reversed by melatonin via upregulated OPA1 expression. Knocking down OPA1 abrogated the protective effects of melatonin on mitochondrial energy metabolism and mitochondrial apoptosis. In addition, we also found that melatonin modified OPA1 expression via the Yap-Hippo pathway; blockade of the Yap-Hippo pathway induced cardiomyocyte death and mitochondrial damage despite treatment with melatonin. Altogether, our data demonstrated that cardiac IR injury is closely associated with defective OPA1-related mitochondrial fusion. Melatonin supplementation enhances OPA1-related mitochondrial fusion by activating the Yap-Hippo pathway, ultimately reducing cardiac reperfusion stress.
  61. Acta Pharmacol Sin. 2018 Nov 16.
    Cheng ZJ, Miao DL, Su QY, Tang XL, Wang XL, Deng LB, Shi HD, Xin HB.
      Cancer cells always require more nutrients, energy, and biosynthetic activity to sustain their rapid proliferation than normal cells. Previous studies have shown the impact of THZ1, a covalent inhibitor of cyclin-dependent kinase 7 (CDK7), on transcription regulation and cell-cycle arrest in numerous cancers, but its effects on cellular metabolism in cancer cells remain unknown. In this study we elucidated the anticancer mechanism of THZ1 in human non-small-cell lung cancer (NSCLC) cells. We showed that treatment with THZ1 (10-1000 nM) dose-dependently suppressed the proliferation of human NSCLC cell lines H1299, A549, H292, and H23, and markedly inhibited the migration of these NSCLC cells. Furthermore, treatment with THZ1 (50 nM) arrested cell cycle at G2/M phase and induced apoptosis in these NSCLC cell lines. More importantly, we revealed that treatment with THZ1 (50 nM) blocked the glycolysis pathway but had no effect on glutamine metabolism. We further demonstrated that THZ1 treatment altered the expression pattern of glutaminase 1 (GLS1) isoforms through promoting the ubiquitination and degradation of NUDT21. Combined treatment of THZ1 with a glutaminase inhibitor CB-839 (500 nM) exerted a more potent anti-proliferative effect in these NSCLC cell lines than treatment with THZ1 or CB-839 alone. Our results demonstrate that the inhibitory effect of THZ1 on the growth of human NSCLC cells is partially attributed to interfering with cancer metabolism. Thus, we provide a new potential therapeutic strategy for NSCLC treatment by combining THZ1 with the inhibitors of glutamine metabolism.
    Keywords:  CB-839; CDK7 inhibitor; THZ1; anti-proliferative effect; cell apoptosis; cell-cycle arrest; glutamine metabolism; glycolysis pathway; non-small-cell lung cancer
  62. Front Physiol. 2018 ;9 1543
    Bernardi P.
    Keywords:  ATP synthase; calcium; channels; mitochondria; permeability transition pore
  63. J Appl Physiol (1985). 2018 Nov 15.
    Wilson RJ, Drake JC, Cui D, Ritger ML, Guan Y, Call JA, Zhang M, Leitner LM, Gödecke A, Yan Z.
      Ischemia-reperfusion (IR) due to temporary restriction of blood flow causes tissue/organ damages under various disease conditions, including stroke, myocardial infarction, trauma and orthopedic surgery. In the limbs, IR injury to motor nerves and muscle fibers causes reduced mobility and quality of life. Endurance exercise training has been shown to increase tissue resistance to numerous pathological insults. To elucidate the impact of endurance exercise training on IR injury in skeletal muscle, sedentary and exercise-trained mice (5 weeks of voluntary running) were subjected to ischemia by unilateral application of a rubber band tourniquet above the femur for 1 hour followed by reperfusion. IR caused significant muscle injury and denervation at neuromuscular junction (NMJ) as early as 3 hours after tourniquet release as well as depressed muscle strength and neuromuscular transmission in sedentary mice. Despite similar degree of muscle atrophy and oxidative stress, exercise-trained mice had significantly reduced muscle injury and denervation at NMJ with improved regeneration and functional recovery following IR. Together, these data suggest that endurance exercise training preserves motor nerve and myofiber structure and function from IR injury and promote functional regeneration.
    Keywords:  endurance exercise training; ischemia-reperfusion; mitochondria; neuromuscular junction; oxidative stress
  64. Curr Biol. 2018 Nov 05. pii: S0960-9822(18)31203-X. [Epub ahead of print]28(21): 3393-3407.e5
    Kaurov I, Vancová M, Schimanski B, Cadena LR, Heller J, Bílý T, Potěšil D, Eichenberger C, Bruce H, Oeljeklaus S, Warscheid B, Zdráhal Z, Schneider A, Lukeš J, Hashimi H.
      The mitochondrial contact site and cristae organization system (MICOS) is a multiprotein complex responsible for cristae formation. Even though cristae are found in all mitochondria capable of oxidative phosphorylation, only Mic10 and Mic60 appear to be conserved throughout eukaryotes. The remaining 4 or 5 known MICOS subunits are specific to the supergroup Opisthokonta, which includes yeast and mammals that are the only organisms in which this complex has been analyzed experimentally. We have isolated the MICOS from Trypanosoma brucei, a member of the supergroup Excavata that is profoundly diverged from opisthokonts. We show that it is required for the maintenance of the unique discoidal cristae that typify excavates, such as euglenids and kinetoplastids, the latter of which include trypanosomes. The trypanosome MICOS consists of 9 subunits, most of which are essential for normal growth. Unlike in opisthokonts, it contains two distinct Mic10 orthologs and an unconventional putative Mic60 that lacks a mitofilin domain. Interestingly, one of the essential trypanosomatid-specific MICOS subunits called TbMic20 is a thioredoxin-like protein that appears to be involved in import of intermembrane space proteins, including respiratory chain complex assembly factors. This result points to trypanosome MICOS coordinating cristae shaping and population of its membrane with proteins involved in respiration, the latter via the catalytic activity of TbMic20. Thus, trypanosome MICOS allows us to define which of its features are conserved in all eukaryotes and decipher those that represent lineage-specific adaptations.
    Keywords:  MICOS; Trypanosoma brucei; cristae; intermembrane space; mitochondria; protein import
  65. Immunol Cell Biol. 2018 Nov 14.
    Yu XH, Zhang DW, Zheng XL, Tang CK.
      Macrophages play a central role in innate immunity as the first line of defense against pathogen infection. Upon exposure to inflammatory stimuli, macrophages rapidly respond and subsequently undergo metabolic reprogramming to substantially produce cellular metabolites, such as itaconate. As a derivate of the tricarboxylic acid cycle, itaconate is derived from the decarboxylation of cis-aconitate mediated by immunoresponsive gene 1 in the mitochondrial matrix. It is well known that itaconate has a direct anti-microbial effect by inhibiting isocitrate lyase. Strikingly, two recent studies published in Nature showed that itaconate markedly decreases the production of pro-inflammatory mediators in lipopolysaccharide-treated macrophages and ameliorates sepsis and psoriasis in animal models, revealing a novel biological action of itaconate beyond its regular roles in anti-microbial defense. The mechanism for this anti-inflammatory effect has been proposed to involve the inhibition of succinate dehydrogenase, blockade of IκBζ translation, and activation of Nrf2. These intriguing discoveries provide a new explanation for how macrophages are switched from a pro- to an anti-inflammatory state to limit the damage and facilitate tissue repair under pro-inflammatory conditions. Thus, the emerging effect of itaconate as a crucial determinant of macrophage inflammation has important implications in further understanding cellular immunometabolism and developing future therapeutics for the treatment of inflammatory diseases. In this review, we focus on the roles of itaconate in controlling the inflammatory response during macrophage activation, providing a rationale for future investigation and therapeutic intervention. This article is protected by copyright. All rights reserved.
    Keywords:   SDH ; IRG1; IκBζ; Nrf2; inflammation; itaconate
  66. FEBS Lett. 2018 Nov 11.
    Sahoo S, Ranjith Kumar R, Nicolay B, Mohite O, Sivaraman K, Khetan V, Rishi P, Ganesan S, Subramanian K, Raman K, Miles W, Elchuri SV.
      Retinoblastoma (RB) is a childhood eye cancer. Currently chemotherapy, local therapy and enucleation are the main ways in which these tumors are managed. The present work is the first study that uses constraint-based reconstruction and analysis approaches to identify and explain RB-specific survival strategies, which are RB tumor-specific. Importantly, our model-specific secretion profile is also found in RB1-depleted human retinal cells in vitro and suggest that novel biomarkers involved in lipid metabolism may be important. Finally, RB-specific synthetic lethals have been predicted as lipid and nucleoside transport proteins that can aid in novel drug target development. This article is protected by copyright. All rights reserved.
    Keywords:  Retinoblastoma; cancer metabolism; constraint-based reconstruction and modeling; synthetic lethal; systems biology