bims-camemi 2020-03-01 papers

bims-camemi

Biomed News

on Mitochondrial metabolism in cancer

Issue of 2020‒03‒01
33 papers selected by
Christian Frezza,

Macropinocytosis Renders a Subset of Pancreatic Tumor Cells Resistant to mTOR Inhibition.
MYC Regulation of D2HGDH and L2HGDH Influences the Epigenome and Epitranscriptome.
Regulation of branched-chain amino acid metabolism by hypoxia-inducible factor in glioblastoma.
AMP-activated protein kinase (AMPK) regulates astrocyte oxidative metabolism by balancing TCA cycle dynamics.
Cytosolic, but not matrix, calcium is essential for adjustment of mitochondrial pyruvate supply.
Metabolic features of cancer cells in NRF2 addiction status.
A Quantitative Tissue-Specific Landscape of Protein Redox Regulation during Aging.
ATP Synthase Subunit a Supports Permeability Transition in Yeast Lacking Dimerization Subunits and Modulates yPTP Conductance.
Increased mitochondrial and lipid metabolism is a conserved effect of Insulin/PI3K pathway downregulation in adipose tissue.
Light Microscopy of Mitochondria at the Nanoscale.
Regulation of mitochondrial plasticity by the i-AAA protease YME1L.
Spatial modeling of prostate cancer metabolic gene expression reveals extensive heterogeneity and selective vulnerabilities.
Betaine restores epigenetic control and supports neuronal mitochondria in the cuprizone mouse model of multiple sclerosis.
Advances into understanding metabolites as signaling molecules in cancer progression.
Wounding triggers MIRO-1 dependent mitochondrial fragmentation that accelerates epidermal wound closure through oxidative signaling.
Lipid availability determines fate of skeletal progenitor cells via SOX9.
S-nitrosylation affects TRAP1 structure and ATPase activity and modulates cell response to apoptotic stimuli.
Mutant p53-Associated Molecular Mechanisms of ROS Regulation in Cancer Cells.
The epigenetic regulators and metabolic changes in ferroptosis-associated cancer progression.
MUC1 oncoprotein mitigates ER stress via CDA-mediated reprogramming of pyrimidine metabolism.
Haploid genetic screens identify SPRING/C12ORF49 as a determinant of SREBP signaling and cholesterol metabolism.
Knockdown of HMGB1 Suppresses Hypoxia-Induced Mitochondrial Biogenesis in Pancreatic Cancer Cells.
Crosstalk with lung epithelial cells regulates Sfrp2-mediated latency in breast cancer dissemination.
Tumour heterogeneity and the evolutionary trade-offs of cancer.
NAD- and NADPH-Contributing Enzymes as Therapeutic Targets in Cancer: An Overview.
Reign in the membrane: How common lipids govern mitochondrial function.
AMPK-dependent activation of the Cyclin Y/CDK16 complex controls autophagy.
Tension in tumour cells keeps metabolism high.
Suppression of iron mobilization from lysosomes to mitochondria attenuates liver injury after acetaminophen overdose in vivo in mice: Protection by minocycline.
Metabolic flux analysis of secondary metabolism in plants.
Regulatory CD8 T cells that recognize Qa-1 expressed by CD4 T-helper cells inhibit rejection of heart allografts.
Tumour metabolism and its unique properties in prostate adenocarcinoma.
Chemical Biology Framework to Illuminate Proteostasis.

Cell Rep. 2020 Feb 25. pii: S2211-1247(20)30105-4. [Epub ahead of print]30(8): 2729-2742.e4

Macropinocytosis Renders a Subset of Pancreatic Tumor Cells Resistant to mTOR Inhibition.

Evdokia Michalopoulou, Francesca R Auciello, Vinay Bulusu, David Strachan, Andrew D Campbell, Jacqueline Tait-Mulder, Saadia A Karim, Jennifer P Morton, Owen J Sansom, Jurre J Kamphorst.

  Pancreatic ductal adenocarcinoma (PDAC) features a near-universal mutation in KRAS. Additionally, the tumor suppressor PTEN is lost in ∼10% of patients, and in mouse models, this dramatically accelerates tumor progression. While oncogenic KRAS and phosphatidylinositol 3-kinase (PI3K) cause divergent metabolic phenotypes individually, how they synergize to promote tumor metabolic alterations and dependencies remains unknown. We show that in KRAS-driven murine PDAC cells, loss of Pten strongly enhances both mTOR signaling and macropinocytosis. Protein scavenging alleviates sensitivity to mTOR inhibition by rescuing AKT phosphorylation at serine 473 and consequently cell proliferation. Combined inhibition of mTOR and lysosomal processing of internalized protein eliminates the macropinocytosis-mediated resistance. Our results indicate that mTORC2, rather than mTORC1, is an important regulator of protein scavenging and that protein-mediated resistance could explain the lack of effectiveness of mTOR inhibitors in certain genetic backgrounds. Concurrent inhibition of mTOR and protein scavenging might be a valuable therapeutic approach.

Keywords:  AKT; cancer metabolism; mTORC2; macropinocytosis; metabolic scavenging; pancreatic ductal adenocarcinoma

DOI:  https://doi.org/10.1016/j.celrep.2020.01.080
Cell Chem Biol. 2020 Feb 24. pii: S2451-9456(20)30040-4. [Epub ahead of print]

MYC Regulation of D2HGDH and L2HGDH Influences the Epigenome and Epitranscriptome.

ZhiJun Qiu, An-Ping Lin, Shoulei Jiang, Sara M Elkashef, Jamie Myers, Subramanya Srikantan, Binu Sasi, John Z Cao, Lucy A Godley, Dinesh Rakheja, Yingli Lyu, Siyuan Zheng, Muniswamy Madesh, Yuzuru Shiio, Patricia L M Dahia, Ricardo C T Aguiar.

  Mitochondrial D2HGDH and L2HGDH catalyze the oxidation of D-2-HG and L-2-HG, respectively, into αKG. This contributes to cellular homeostasis in part by modulating the activity of αKG-dependent dioxygenases. Signals that control the expression/activity of D2HGDH/L2HGDH are presumed to broadly influence physiology and pathology. Using cell and mouse models, we discovered that MYC directly induces D2HGDH and L2HGDH transcription. Furthermore, in a manner suggestive of D2HGDH, L2HGDH, and αKG dependency, MYC activates TET enzymes and RNA demethylases, and promotes their nuclear localization. Consistent with these observations, in primary B cell lymphomas MYC expression positively correlated with enhancer hypomethylation and overexpression of lymphomagenic genes. Together, these data provide additional evidence for the role of mitochondria metabolism in influencing the epigenome and epitranscriptome, and imply that in specific contexts wild-type TET enzymes could demethylate and activate oncogenic enhancers.

Keywords:  2-hydroxyglutarate; DNA methylation; MYC; RNA methylation; alpha-ketoglutarate; dioxygenases; enhancer; lymphoma; metabolites; super-enhancer

DOI:  https://doi.org/10.1016/j.chembiol.2020.02.002
Cell Mol Life Sci. 2020 Feb 22.

Regulation of branched-chain amino acid metabolism by hypoxia-inducible factor in glioblastoma.

Bo Zhang, Yan Chen, Xiaolei Shi, Mi Zhou, Lei Bao, Kimmo J Hatanpaa, Toral Patel, Ralph J DeBerardinis, Yingfei Wang, Weibo Luo.

  Hypoxia-inducible factors (HIFs) mediate metabolic reprogramming in response to hypoxia. However, the role of HIFs in branched-chain amino acid (BCAA) metabolism remains unknown. Here we show that hypoxia upregulates mRNA and protein levels of the BCAA transporter LAT1 and the BCAA metabolic enzyme BCAT1, but not their paralogs LAT2-4 and BCAT2, in human glioblastoma (GBM) cell lines as well as primary GBM cells. Hypoxia-induced LAT1 protein upregulation is mediated by both HIF-1 and HIF-2 in GBM cells. Although both HIF-1α and HIF-2α directly bind to the hypoxia response element at the first intron of the human BCAT1 gene, HIF-1α is exclusively responsible for hypoxia-induced BCAT1 expression in GBM cells. Knockout of HIF-1α and HIF-2α significantly reduces glutamate labeling from BCAAs in GBM cells under hypoxia, which provides functional evidence for HIF-mediated reprogramming of BCAA metabolism. Genetic or pharmacological inhibition of BCAT1 inhibits GBM cell growth under hypoxia. Together, these findings uncover a previously unrecognized HIF-dependent metabolic pathway that increases GBM cell growth under conditions of hypoxic stress.

Keywords:  Branched-chain amino acid; Gene regulation; Glioblastoma; Hypoxia; Hypoxia-inducible factor; Metabolism

DOI:  https://doi.org/10.1007/s00018-020-03483-1
Glia. 2020 Feb 24.

AMP-activated protein kinase (AMPK) regulates astrocyte oxidative metabolism by balancing TCA cycle dynamics.

Caroline M Voss, Jens V Andersen, Emil Jakobsen, Olga Siamka, Melis Karaca, Pierre Maechler, Helle S Waagepetersen.

  AMP-activated protein kinase (AMPK) is an important energy sensor located in cells throughout the human body. From the periphery, AMPK is known to be a metabolic master switch controlling the use of energy fuels. The energy sensor is activated when the energy status of the cell is low, initiating energy-producing pathways and deactivating energy-consuming pathways. All brain cells are crucially dependent on energy production for survival, and the availability of energy substrates must be closely regulated. Intriguingly, the role of AMPK in the regulation of brain cell metabolism has been sparsely investigated, particularly in astrocytes. By investigating metabolism of 13 C-labeled energy substrates in acutely isolated hippocampal slices and cultured astrocytes, with subsequent mass spectrometry analysis, we here show that activation of AMPK increases glycolysis as well as the capacity of the TCA cycle, that is, anaplerosis, through the activity of pyruvate carboxylase (PC) in astrocytes. In addition, we demonstrate that AMPK activation leads to augmented astrocytic glutamate oxidation via pyruvate recycling (i.e., cataplerosis). This regulatory mechanism induced by AMPK activation is mediated via glutamate dehydrogenase (GDH) shown in a CNS-specific GDH knockout mouse. Collectively, these findings demonstrate that AMPK regulates TCA cycle dynamics in astrocytes via PC and GDH activity. AMPK functionality has been shown to be hampered in Alzheimer's and Parkinson's disease and our findings may therefore add to the toolbox for discovery of new metabolic drug targets.

Keywords:   13C; AICAR; anaplerosis; brain slices; cataplerosis; glycolysis; mitochondria; seahorse

DOI:  https://doi.org/10.1002/glia.23808
J Biol Chem. 2020 Feb 24. pii: jbc.RA119.011902. [Epub ahead of print]

Cytosolic, but not matrix, calcium is essential for adjustment of mitochondrial pyruvate supply.

Marten Szibor, Zemfira Gizatullina, Timur Gainutdinov, Thomas Endres, Grazyna Debska-Vielhaber, Matthias Kunz, Niki Karavasili, Kerstin Hallmann, Frank Schreiber, Alexandra Bamberger, Michael Schwarzer, Torsten Doenst, Hans-Jochen Heinze, Volkmar Leßmann, Stephan Vielhaber, Wolfram S Kunz, Frank N Gellerich.

  Mitochondrial oxidative phosphorylation (OXPHOS) and cellular workload are tightly balanced by the key cellular regulator, calcium (Ca2+). Current models assume that cytosolic Ca2+ regulates workload and that mitochondrial Ca2+ uptake precedes activation of matrix dehydrogenases, thereby matching OXPHOS substrate supply to ATP demand. Surprisingly, knock-out (KO) of the mitochondrial Ca2+ uniporter (MCU) in mice results in only minimal phenotypic changes and does not alter OXPHOS. This implies that adaptive activation of mitochondrial dehydrogenases by intramitochondrial Ca2+ cannot be the exclusive mechanism for OXPHOS control. We hypothesized that cytosolic Ca2+, but not mitochondrial matrix Ca2+, may adapt OXPHOS to workload by adjusting the rate of pyruvate supply from the cytosol to the mitochondria. Here, we studied the role of malate aspartate shuttle (MAS)-dependent substrate supply on OXPHOS responses to changing Ca2+ concentrations in isolated brain and heart mitochondria, synaptosomes, fibroblasts, and thymocytes from wild-type (WT) and MCU KO mice, and the isolated working rat heart. Our results indicate that extramitochondrial Ca2+ controls up to 85% of maximal pyruvate-driven OXPHOS rates, mediated by the activity of the complete MAS, and that intramitochondrial Ca2+ accounts for the remaining 15%. Of note, the complete MAS as applied here, included besides its classical NADH oxidation reaction the generation of cytosolic pyruvate. Part of this largely neglected mechanism has previously been described as the "mitochondrial gas pedal". Its implementation into OXPHOS control models integrates seemingly contradictory results and warrants a critical reappraisal of metabolic control mechanisms in health and disease.

Keywords:  bioenergetics; calcium; malate-aspartate shuttle; mitochondria; mitochondrial calcium uniporter; mouse; respiratory chain

DOI:  https://doi.org/10.1074/jbc.RA119.011902
Biophys Rev. 2020 Feb 28.

Metabolic features of cancer cells in NRF2 addiction status.

Keito Okazaki, Thales Papagiannakopoulos, Hozumi Motohashi.

  The KEAP1-NRF2 system is a sulfur-employing defense mechanism against oxidative and electrophilic stress. NRF2 is a potent transcription activator for genes mediating sulfur-involving redox reactions, and KEAP1 controls the NRF2 activity in response to the stimuli by utilizing reactivity of sulfur atoms. In many human cancer cells, the KEAP1-mediated regulation of NRF2 activity is abrogated, resulting in the persistent activation of NRF2. Persistently activated NRF2 drives malignant progression of cancers by increasing therapeutic resistance and promoting aggressive tumorigenesis, a state termed as NRF2 addiction. In NRF2-addicted cancer cell, NRF2 contributes to metabolic reprogramming in cooperation with other oncogenic pathways. In particular, NRF2 strongly activates cystine uptake coupled with glutamate excretion and glutathione synthesis, which increases consumption of intracellular glutamate. Decreased availability of glutamate limits anaplerosis of the TCA cycle, resulting in low mitochondrial respiration, and nitrogen source, resulting in the high dependency on exogenous non-essential amino acids. The highly enhanced glutathione synthesis is also likely to alter sulfur metabolism, which can contribute to the maintenance of the mitochondrial membrane potential in normal cells. The potent antioxidant and detoxification capacity supported by abundant production of glutathione is achieved at the expense of central carbon metabolism and requires skewed metabolic flow of sulfur. These metabolic features of NRF2 addiction status provide clues for novel therapeutic strategies to target NRF2-addicted cancer cells.

Keywords:  Cysteine; Glutamate; Glutathione synthesis; KEAP1/NRF2; Metabolic liabilities; Non-essential amino acids; Sulfur metabolism

DOI:  https://doi.org/10.1007/s12551-020-00659-8
Cell. 2020 Feb 25. pii: S0092-8674(20)30156-2. [Epub ahead of print]

A Quantitative Tissue-Specific Landscape of Protein Redox Regulation during Aging.

Haopeng Xiao, Mark P Jedrychowski, Devin K Schweppe, Edward L Huttlin, Qing Yu, David E Heppner, Jiaming Li, Jiani Long, Evanna L Mills, John Szpyt, Zhixiang He, Guangyan Du, Ryan Garrity, Anita Reddy, Laura Pontano Vaites, Joao A Paulo, Tinghu Zhang, Nathanael S Gray, Steven P Gygi, Edward T Chouchani.

  Mammalian tissues engage in specialized physiology that is regulated through reversible modification of protein cysteine residues by reactive oxygen species (ROS). ROS regulate a myriad of biological processes, but the protein targets of ROS modification that drive tissue-specific physiology in vivo are largely unknown. Here, we develop Oximouse, a comprehensive and quantitative mapping of the mouse cysteine redox proteome in vivo. We use Oximouse to establish several paradigms of physiological redox signaling. We define and validate cysteine redox networks within each tissue that are tissue selective and underlie tissue-specific biology. We describe a common mechanism for encoding cysteine redox sensitivity by electrostatic gating. Moreover, we comprehensively identify redox-modified disease networks that remodel in aged mice, establishing a systemic molecular basis for the long-standing proposed links between redox dysregulation and tissue aging. We provide the Oximouse compendium as a framework for understanding mechanisms of redox regulation in physiology and aging.

Keywords:  ROS; aging; cysteine; proteomics; reactive oxygen species

DOI:  https://doi.org/10.1016/j.cell.2020.02.012
Cell Physiol Biochem. 2020 Feb 27. 54(2): 211-229

ATP Synthase Subunit a Supports Permeability Transition in Yeast Lacking Dimerization Subunits and Modulates yPTP Conductance.

Katarzyna Niedzwiecka, Emilia Baranowska, Chiranjit Panja, Roza Kucharczyk.

  BACKGROUND/AIMS: Mitochondrial ATP synthase, in addition to being involved in ATP synthesis, is involved in permeability transition pore (PTP) formation, which precedes apoptosis in mammalian cells and programmed cell death in yeast. Mutations in genes encoding ATP synthase subunits cause neuromuscular disorders and have been identified in cancer samples. PTP is also involved in pathology. We previously found that in Saccharomyces cerevisiae, two mutations in ATP synthase subunit a (atp6-P163S and atp6-K90E, equivalent to those detected in prostate and thyroid cancer samples, respectively) in the OM45-GFP background affected ROS and calcium homeostasis and delayed yeast PTP (yPTP) induction upon calcium treatment by modulating the dynamics of ATP synthase dimer/oligomer formation. The Om45 protein is a component of the porin complex, which is equivalent to mammalian VDAC. We aimed to investigate yPTP function in atp6-P163S and atp6-K90E mutants lacking the e and g dimerization subunits of ATP synthase.METHODS: Triple mutants with the atp6-P163S or atp6-K90E mutation, the OM45-GFP gene and deletion of the TIM11 gene encoding subunit e were constructed by crossing and tetrad dissection. In spores capable of growing, the original atp6 mutations reverted to wild type, and two compensatory mutations, namely, atp6-C33S-T215C, were selected. The effects of these mutations on cellular physiology, mitochondrial morphology, bioenergetics and permeability transition (PT) were analyzed by fluorescence and electron microscopy, mitochondrial respiration, ATP synthase activity, calcium retention capacity and swelling assays.
RESULTS: The atp6-C33S-T215C mutations in the OM45-GFP background led to delayed growth at elevated temperature on both fermentative and respiratory media and increased sensitivity to high calcium ions concentration or hydrogen peroxide in the medium. The ATP synthase activity was reduced by approximately 50% and mitochondrial network was hyperfused in these cells grown at elevated temperature. The atp6-C33S-T215C stabilized ATP synthase dimers and restored the yPTP properties in Tim11∆ cells. In OM45-GFP cells, in which Tim11 is present, these mutations increased the fraction of swollen mitochondria by up to 85% vs 60% in the wild type, although the time required for calcium release doubled.
CONCLUSION: ATP synthase subunit e is essential in the S. cerevisiae atp6-P163S and atp6-K90E mutants. In addition to subunits e and g, subunit a is critical for yPTP induction and conduction. The increased yPTP conduction decrease the S. cerevisiae cell fitness.

Keywords:  Mitochondria; Permeability transition pore; ATP synthase; ATP6; Subunit a; S. cerevisiae

DOI:  https://doi.org/10.33594/000000215
Sci Rep. 2020 Feb 25. 10(1): 3418

Increased mitochondrial and lipid metabolism is a conserved effect of Insulin/PI3K pathway downregulation in adipose tissue.

Lucia Bettedi, Anqi Yan, Eugene Schuster, Nazif Alic, Lazaros C Foukas.

The Insulin/IGF-1 signalling (IIS) pathway plays an essential role in the regulation of glucose and lipid homeostasis. At the same time, a reduction in the IIS pathway activity can extend lifespan and healthspan in various model organisms. Amongst a number of body organs that sense and respond to insulin/IGF-1, the adipose tissue has a central role in both the metabolic and lifespan effects of IIS at the organismal level. Genetic inactivation of IIS components specifically in the adipose tissue has been shown before to improve metabolic profile and extend lifespan in various model organisms. We sought to identify conserved molecular mechanisms that may underlie the beneficial effects of IIS inhibition in the adipose tissue, specifically at the level of phosphoinositide 3-kinase (PI3K), a key IIS effector molecule. To this end, we inactivated PI3K by genetic means in the fly fat body and by pharmacological inhibition in mammalian adipocytes. Gene expression studies revealed changes to metabolism and upregulation of mitochondrial activity in mouse adipocytes and fly fat bodies with downregulated PI3K, which were confirmed by biochemical assays in mammalian adipocytes. These data suggest that PI3K inactivation has a conserved effect of upregulating mitochondrial metabolism in both fly and mammalian adipose tissue, which likely contributes to the health- and life-span extending effect of IIS pathway downregulation.

DOI: https://doi.org/10.1038/s41598-020-60210-3
Annu Rev Biophys. 2020 Feb 24.

Light Microscopy of Mitochondria at the Nanoscale.

Stefan Jakobs, Till Stephan, Peter Ilgen, Christian Brüser.

Mitochondria are essential for eukaryotic life. These double-membrane organelles often form highly dynamic tubular networks interacting with many cellular structures. Their highly convoluted contiguous inner membrane compartmentalizes the organelle, which is crucial for mitochondrial function. Since the diameter of the mitochondrial tubules is generally close to the diffraction limit of light microcopy, it is often challenging, if not impossible, to visualize submitochondrial structures or protein distributions using conventional light microscopy. This renders super-resolution microscopy particularly valuable, and attractive, for studying mitochondria. Super-resolution microscopy encompasses a diverse set of approaches that extend resolution, as well as nanoscopy techniques that can even overcome the diffraction limit. In this review, we provide an overview of recent studies using super-resolution microscopy to investigate mitochondria, discuss the strengths and opportunities of the various methods in addressing specific questions in mitochondrial biology, and highlight potential future developments. Expected final online publication date for the Annual Review of Biophysics, Volume 49 is May 6, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

DOI: https://doi.org/10.1146/annurev-biophys-121219-081550
Biol Chem. 2020 Feb 01. pii: /j/bchm.just-accepted/hsz-2020-0120/hsz-2020-0120.xml. [Epub ahead of print]

Regulation of mitochondrial plasticity by the i-AAA protease YME1L.

Yohsuke Ohba, Thomas MacVicar, Thomas Langer.

  Mitochondria are multifaceted metabolic organelles and adapt dynamically to various developmental transitions and environmental challenges. The metabolic flexibility of mitochondria is provided by alterations in the mitochondrial proteome and is tightly coupled to changes in the shape of mitochondria. Mitochondrial proteases are emerging as important post-translational regulators of mitochondrial plasticity. The i-AAA protease YME1L, an ATP-dependent proteolytic complex in the mitochondrial inner membrane, coordinates mitochondrial biogenesis and dynamics with the metabolic output of mitochondria. mTORC1 dependent lipid signalling drives proteolytic rewiring of mitochondria by YME1L. While the tissue-specific loss of YME1L in mice is associated with heart failure, disturbed eye development and axonal degeneration in the spinal cord, YME1L activity supports growth of pancreatic ductal adenocarcinoma cells. YME1L thus represents a key regulatory protease determining mitochondrial plasticity and metabolic reprogramming and is emerging as a promising therapeutic target.

Keywords:  Lipin1; YME1L; cancer; i-AAA protease; mTORC1; mitochondria; mitochondrial plasticity; mitochondrial proteases

DOI:  https://doi.org/10.1515/hsz-2020-0120
Sci Rep. 2020 Feb 26. 10(1): 3490

Spatial modeling of prostate cancer metabolic gene expression reveals extensive heterogeneity and selective vulnerabilities.

Yuliang Wang, Shuyi Ma, Walter L Ruzzo.

Spatial heterogeneity is a fundamental feature of the tumor microenvironment (TME), and tackling spatial heterogeneity in neoplastic metabolic aberrations is critical for tumor treatment. Genome-scale metabolic network models have been used successfully to simulate cancer metabolic networks. However, most models use bulk gene expression data of entire tumor biopsies, ignoring spatial heterogeneity in the TME. To account for spatial heterogeneity, we performed spatially-resolved metabolic network modeling of the prostate cancer microenvironment. We discovered novel malignant-cell-specific metabolic vulnerabilities targetable by small molecule compounds. We predicted that inhibiting the fatty acid desaturase SCD1 may selectively kill cancer cells based on our discovery of spatial separation of fatty acid synthesis and desaturation. We also uncovered higher prostaglandin metabolic gene expression in the tumor, relative to the surrounding tissue. Therefore, we predicted that inhibiting the prostaglandin transporter SLCO2A1 may selectively kill cancer cells. Importantly, SCD1 and SLCO2A1 have been previously shown to be potently and selectively inhibited by compounds such as CAY10566 and suramin, respectively. We also uncovered cancer-selective metabolic liabilities in central carbon, amino acid, and lipid metabolism. Our novel cancer-specific predictions provide new opportunities to develop selective drug targets for prostate cancer and other cancers where spatial transcriptomics datasets are available.

DOI: https://doi.org/10.1038/s41598-020-60384-w
Epigenetics. 2020 Feb 25.

Betaine restores epigenetic control and supports neuronal mitochondria in the cuprizone mouse model of multiple sclerosis.

Naveen K Singhal, Sarah Sternbach, Sheila Fleming, Kholoud Alkhayer, John Shelestak, Daniela Popescu, Alyx Weaver, Robert Clements, Brandi Wasek, Teodoro Bottiglieri, Ernest J Freeman, Jennifer McDonough.

Methionine metabolism is dysregulated in multiple sclerosis (MS). The methyl donor betaine is depleted in the MS brain where it is linked to changes in levels of histone H3 trimethylated on lysine 4 (H3K4me3) and mitochondrial impairment. We investigated the effects of replacing this depleted betaine in the cuprizone mouse model of MS. Supplementation with betaine restored epigenetic control and alleviated neurological disability in cuprizone mice. Betaine increased the methylation potential (SAM/SAH ratio), levels of H3K4me3, enhanced neuronal respiration, and prevented axonal damage. We show that the methyl donor betaine and the betaine homocysteine methyltransferase (BHMT) enzyme can act in the nucleus to repair epigenetic control and activate neuroprotective transcriptional programs. ChIP-seq data suggest that BHMT acts on chromatin to increase the SAM/SAH ratio and histone methyltransferase activity locally to increase H3K4me3 and activate transcriptional programs that support neuronal energetics. These data suggest that the methyl donor betaine may provide neuroprotection in MS where mitochondrial impairment damages axons and causes disability.

DOI: https://doi.org/10.1080/15592294.2020.1735075
Curr Opin Cell Biol. 2020 Feb 22. pii: S0955-0674(20)30020-X. [Epub ahead of print]63 144-153

Advances into understanding metabolites as signaling molecules in cancer progression.

Joyce Y Liu, Kathryn E Wellen.

  Recent years have seen a great expansion in our knowledge of the roles that metabolites play in cellular signaling. Structural data have provided crucial insights into mechanisms through which amino acids are sensed. New nutrient-coupled protein and RNA modifications have been identified and characterized. A growing list of functions has been ascribed to metabolic regulation of modifications such as acetylation, methylation, and glycosylation. A current challenge lies in developing an integrated understanding of the roles that metabolic signaling mechanisms play in physiology and disease, which will inform the design of strategies to target such mechanisms. In this brief article, we review recent advances in metabolic signaling through post-translational modification during cancer progression, to provide a framework for understanding signaling roles of metabolites in the context of cancer biology and illuminate areas for future investigation.

Keywords:  Cancer; Metabolic signaling; Metabolism

DOI:  https://doi.org/10.1016/j.ceb.2020.01.013
Nat Commun. 2020 Feb 26. 11(1): 1050

Wounding triggers MIRO-1 dependent mitochondrial fragmentation that accelerates epidermal wound closure through oxidative signaling.

Hongying Fu, Hengda Zhou, Xinghai Yu, Jingxiu Xu, Jinghua Zhou, Xinan Meng, Jianzhi Zhao, Yu Zhou, Andrew D Chisholm, Suhong Xu.

Organisms respond to tissue damage through the upregulation of protective responses which restore tissue structure and metabolic function. Mitochondria are key sources of intracellular oxidative metabolic signals that maintain cellular homeostasis. Here we report that tissue and cellular wounding triggers rapid and reversible mitochondrial fragmentation. Elevated mitochondrial fragmentation either in fzo-1 fusion-defective mutants or after acute drug treatment accelerates actin-based wound closure. Wounding triggered mitochondrial fragmentation is independent of the GTPase DRP-1 but acts via the mitochondrial Rho GTPase MIRO-1 and cytosolic Ca2+. The fragmented mitochondria and accelerated wound closure of fzo-1 mutants are dependent on MIRO-1 function. Genetic and transcriptomic analyzes show that enhanced mitochondrial fragmentation accelerates wound closure via the upregulation of mtROS and Cytochrome P450. Our results reveal how mitochondrial dynamics respond to cellular and tissue injury and promote tissue repair.

DOI: https://doi.org/10.1038/s41467-020-14885-x
Nature. 2020 Feb 26.

Lipid availability determines fate of skeletal progenitor cells via SOX9.

Nick van Gastel, Steve Stegen, Guy Eelen, Sandra Schoors, Aurélie Carlier, Veerle W Daniëls, Ninib Baryawno, Dariusz Przybylski, Maarten Depypere, Pieter-Jan Stiers, Dennis Lambrechts, Riet Van Looveren, Sophie Torrekens, Azeem Sharda, Patrizia Agostinis, Diether Lambrechts, Frederik Maes, Johan V Swinnen, Liesbet Geris, Hans Van Oosterwyck, Bernard Thienpont, Peter Carmeliet, David T Scadden, Geert Carmeliet.

The avascular nature of cartilage makes it a unique tissue1-4, but whether and how the absence of nutrient supply regulates chondrogenesis remain unknown. Here we show that obstruction of vascular invasion during bone healing favours chondrogenic over osteogenic differentiation of skeletal progenitor cells. Unexpectedly, this process is driven by a decreased availability of extracellular lipids. When lipids are scarce, skeletal progenitors activate forkhead box O (FOXO) transcription factors, which bind to the Sox9 promoter and increase its expression. Besides initiating chondrogenesis, SOX9 acts as a regulator of cellular metabolism by suppressing oxidation of fatty acids, and thus adapts the cells to an avascular life. Our results define lipid scarcity as an important determinant of chondrogenic commitment, reveal a role for FOXO transcription factors during lipid starvation, and identify SOX9 as a critical metabolic mediator. These data highlight the importance of the nutritional microenvironment in the specification of skeletal cell fate.

DOI: https://doi.org/10.1038/s41586-020-2050-1
Biochem Pharmacol. 2020 Feb 20. pii: S0006-2952(20)30097-6. [Epub ahead of print] 113869

S-nitrosylation affects TRAP1 structure and ATPase activity and modulates cell response to apoptotic stimuli.

Fiorella Faienza, Matteo Lambrughi, Salvatore Rizza, Chiara Pecorari, Paola Giglio, Juan Salamanca Viloria, Maria Francesca Allega, Giovanni Chiappetta, Joëlle Vinh, Francesca Pacello, Andrea Battistoni, Andrea Rasola, Elena Papaleo, Giuseppe Filomeni.

The mitochondrial chaperone TRAP1 has been involved in several mitochondrial functions, and modulation of its expression/activity has been suggested to play a role in the metabolic reprogramming distinctive of cancer cells. TRAP1 posttranslational modifications, i.e. phosphorylation, can modify its capability to bind to different client proteins and modulate its oncogenic activity. Recently, it has been also demonstrated that TRAP1 is S-nitrosylated at Cys501, a redox modification associated with its degradation via the proteasome. Here we report molecular dynamics simulations of TRAP1, together with analysis of long-range structural communication, providing a model according to which Cys501 S-nitrosylation induces conformational changes to distal sites in the structure of the protein. The modification is also predicted to alter open and closing motions for the chaperone function. By means of colorimetric assays and site directed mutagenesis aimed at generating C501S variant, we also experimentally confirmed that selective S-nitrosylation of Cys501 decreases ATPase activity of recombinant TRAP1. Coherently, C501S mutant was more active and conferred protection to cell death induced by staurosporine. Overall, our results provide the first in silico, in vitro and cellular evidence of the relevance of Cys501 S-nitrosylation in TRAP1 biology.

DOI: https://doi.org/10.1016/j.bcp.2020.113869
Biomolecules. 2020 Feb 26. pii: E361. [Epub ahead of print]10(3):

Mutant p53-Associated Molecular Mechanisms of ROS Regulation in Cancer Cells.

Marco Cordani, Giovanna Butera, Raffaella Pacchiana, Francesca Masetto, Nidula Mullappilly, Chiara Riganti, Massimo Donadelli.

  The TP53 tumor suppressor gene is the most frequently altered gene in tumors and an increasing number of studies highlight that mutant p53 proteins can acquire oncogenic properties, referred to as gain-of-function (GOF). Reactive oxygen species (ROS) play critical roles as intracellular messengers, regulating numerous signaling pathways linked to metabolism and cell growth. Tumor cells frequently display higher ROS levels compared to healthy cells as a result of their increased metabolism as well as serving as an oncogenic agent because of its damaging and mutational properties. Several studies reported that in contrast with the wild type protein, mutant p53 isoforms fail to exert antioxidant activities and rather increase intracellular ROS, driving a pro-tumorigenic survival. These pro-oxidant oncogenic abilities of GOF mutant p53 include signaling and metabolic rewiring, as well as the modulation of critical ROS-related transcription factors and antioxidant systems, which lead ROS unbalance linked to tumor progression. The studies summarized here highlight that GOF mutant p53 isoforms might constitute major targets for selective therapeutic intervention against several types of tumors and that ROS enhancement driven by mutant p53 might represent an "Achilles heel" of cancer cells, suggesting pro-oxidant drugs as a therapeutic approach for cancer patients bearing the mutant TP53 gene.

Keywords:  Gain-of-function; ROS; cancer; mutant p53; oxidative stress

DOI:  https://doi.org/10.3390/biom10030361
Mol Cancer. 2020 Feb 27. 19(1): 39

The epigenetic regulators and metabolic changes in ferroptosis-associated cancer progression.

Yuqing Wu, Siwei Zhang, Xiaoxiao Gong, Samantha Tam, Desheng Xiao, Shuang Liu, Yongguang Tao.

  Ferroptosis, a novel form of regulated cell death, is different from other types of cell death in morphology, genetics and biochemistry. Increasing evidence indicates that ferroptosis has significant implications on cell death linked to cardiomyopathy, tumorigenesis, and cerebral hemorrhage to name a few. Here we summarize current literature on ferroptosis, including organelle dysfunction, signaling transduction pathways, metabolic reprogramming and epigenetic regulators in cancer progression. With regard to organelles, mitochondria-induced cysteine starvation, endoplasmic reticulum-related oxidative stress, lysosome dysfunction and golgi stress-related lipid peroxidation all contribute to induction of ferroptosis. Understanding the underlying mechanism in ferroptosis could provide insight into the treatment of various intractable diseases including cancers.

Keywords:  Cancer; Chromatin remodeling factor; Endoplasmic reticulum; Epigenetics; Ferroptosis; Golgi; Immunotherapy; Iron; Lipid peroxidation; Lysosome; Metabolism; Mitochondria; Organelles; lncRNA

DOI:  https://doi.org/10.1186/s12943-020-01157-x
Oncogene. 2020 Feb 26.

MUC1 oncoprotein mitigates ER stress via CDA-mediated reprogramming of pyrimidine metabolism.

Appolinaire A Olou, Ryan J King, Fang Yu, Pankaj K Singh.

The Mucin 1 (MUC1) protein is overexpressed in various cancers and mediates chemotherapy resistance. However, the mechanism is not fully understood. Given that most chemotherapeutic drugs disrupt ER homeostasis as part of their toxicity, and MUC1 expression is regulated by proteins involved in ER homeostasis, we investigated the link between MUC1 and ER homeostasis. MUC1 knockdown in pancreatic cancer cells enhanced unfolded protein response (UPR) signaling and cell death upon ER stress induction. Transcriptomic analysis revealed alterations in the pyrimidine metabolic pathway and cytidine deaminase (CDA). ChIP and CDA activity assays showed that MUC1 occupied CDA gene promoter upon ER stress induction correlating with increased CDA expression and activity in MUC1-expressing cells as compared with MUC1 knockdown cells. Inhibition of either the CDA or pyrimidine metabolic pathway diminished survival in MUC1-expressing cancer cells upon ER stress induction. Metabolomic analysis demonstrated that MUC1-mediated CDA activity corresponded to deoxycytidine to deoxyuridine metabolic reprogramming upon ER stress induction. The resulting increase in deoxyuridine mitigated ER stress-induced cytotoxicity. In addition, given (1) the established roles of MUC1 in protecting cells against reactive oxygen species (ROS) insults, (2) ER stress-generated ROS further promote ER stress and (3) the emerging anti-oxidant property of deoxyuridine, we further investigated if MUC1 regulated ER stress by a deoxyuridine-mediated modulation of ROS levels. We observed that deoxyuridine could abrogate ROS-induced ER stress to promote cancer cell survival. Taken together, our findings demonstrate a novel MUC1-CDA axis of the adaptive UPR that provides survival advantage upon ER stress induction.

DOI: https://doi.org/10.1038/s41388-020-1225-4
Nat Commun. 2020 Feb 28. 11(1): 1128

Haploid genetic screens identify SPRING/C12ORF49 as a determinant of SREBP signaling and cholesterol metabolism.

Anke Loregger, Matthijs Raaben, Joppe Nieuwenhuis, Josephine M E Tan, Lucas T Jae, Lisa G van den Hengel, Sebastian Hendrix, Marlene van den Berg, Saskia Scheij, Ji-Ying Song, Ivo J Huijbers, Lona J Kroese, Roelof Ottenhoff, Michel van Weeghel, Bart van de Sluis, Thijn Brummelkamp, Noam Zelcer.

The sterol-regulatory element binding proteins (SREBP) are central transcriptional regulators of lipid metabolism. Using haploid genetic screens we identify the SREBP Regulating Gene (SPRING/C12ORF49) as a determinant of the SREBP pathway. SPRING is a glycosylated Golgi-resident membrane protein and its ablation in Hap1 cells, Hepa1-6 hepatoma cells, and primary murine hepatocytes reduces SREBP signaling. In mice, Spring deletion is embryonic lethal yet silencing of hepatic Spring expression also attenuates the SREBP response. Mechanistically, attenuated SREBP signaling in SPRINGKO cells results from reduced SREBP cleavage-activating protein (SCAP) and its mislocalization to the Golgi irrespective of the cellular sterol status. Consistent with limited functional SCAP in SPRINGKO cells, reintroducing SCAP restores SREBP-dependent signaling and function. Moreover, in line with the role of SREBP in tumor growth, a wide range of tumor cell lines display dependency on SPRING expression. In conclusion, we identify SPRING as a previously unrecognized modulator of SREBP signaling.

DOI: https://doi.org/10.1038/s41467-020-14811-1
Onco Targets Ther. 2020 ;13 1187-1198

Knockdown of HMGB1 Suppresses Hypoxia-Induced Mitochondrial Biogenesis in Pancreatic Cancer Cells.

Liangchun Yang, Fanghua Ye, Li Zeng, Yanling Li, Wenwen Chai.

  Purpose: To explore the regulatory effect of HMGB1 upon hypoxia-induced mitochondrial biogenesis in pancreatic cancer PANC1/CFPAC1 cells.Methods: After a down-regulation of HMGB1 expression by lentivirus-mediated RNAi, the effect of knocking down HMGB1 on hypoxia-induced mitochondrial biogenesis was examined. NRF-1/TFAM expression, mtDNA copy number, ATP content and mitochondrial number/morphology in hypoxia-treated pancreatic cancer cells were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), Western blot, mtDNA and ATP assay kits and electron microscopy, respectively. Cell proliferation was measured by MTS assay. And protein and acetylation levels of PGC-1α and SIRT1 activity were detected by Western blot, immunoprecipitation (IP) and SIRT1 activity kit.
Results: Hypoxia enhanced the expressions of NRF-1/TFAM, boosted mtDNA copy number and ATP content and increased the number of mitochondria in pancreatic cancer cells while induction was suppressed by a knockdown of HMGB1. Knocking down HMGB1 expression lowered hypoxia-induced PGC-1α/SIRT1 expression and activity, phosphorylation of AMPK. PGC-1α over-expression by a plasmid transfection failed to boost mtDNA copy number or ATP content in HMGB1-knockdown cells. A knockdown of HMGB1 attenuated hypoxia with AICAR (an AMPK activator)-induced expression of NRF-1, TFAM, PGC-1α, SIRT1 and the proteins of complexes Ⅰ& Ⅲ and reduced the acetylation level of PGC-1α/SIRT1 activity. Additionally, SRT1720 (a SIRT1 activator)-induced elevation in SIRT1 activity boosted hypoxia-induced PGC-1α deacetylation, except in HMGB1-knockdown cells.
Conclusion: As a novel regulator of mitochondrial biogenesis via AMPK/SIRT1 pathway under hypoxia, HMGB1 may become a potential drug target for therapeutic interventions in pancreatic cancer.

Keywords:  AMPK/SIRT1 pathway; HMGB1; PGC-1α; mitochondrial biogenesis; pancreatic cancer

DOI:  https://doi.org/10.2147/OTT.S234530
Nat Cell Biol. 2020 Feb 24.

Crosstalk with lung epithelial cells regulates Sfrp2-mediated latency in breast cancer dissemination.

Marco Montagner, Rahul Bhome, Steven Hooper, Probir Chakravarty, Xiao Qin, Jahangir Sufi, Ajay Bhargava, Colin D H Ratcliffe, Yutaka Naito, Arianna Pocaterra, Christopher J Tape, Erik Sahai.

The process of metastasis is complex1. In breast cancer, there are frequently long time intervals between cells leaving the primary tumour and growth of overt metastases2,3. Reasons for disease indolence and subsequent transition back to aggressive growth include interactions with myeloid and fibroblastic cells in the tumour microenvironment and ongoing immune surveillance4-6. However, the signals that cause actively growing cells to enter an indolent state, thereby enabling them to survive for extended periods of time, are not well understood. Here we reveal how the behaviour of indolent breast cancer cells in the lung is determined by their interactions with alveolar epithelial cells, in particular alveolar type 1 cells. This promotes the formation of fibronectin fibrils by indolent cells that drive integrin-dependent pro-survival signals. Combined in vivo RNA sequencing and drop-out screening identified secreted frizzled-related protein 2 (SFRP2) as a key mediator of this interaction. Sfrp2 is induced in breast cancer cells by signals from lung epithelial cells and promotes fibronectin fibril formation and survival, whereas blockade of Sfrp2 expression reduces the burden of indolent disease.

DOI: https://doi.org/10.1038/s41556-020-0474-3
Nat Rev Cancer. 2020 Feb 24.

Tumour heterogeneity and the evolutionary trade-offs of cancer.

Jean Hausser, Uri Alon.

Tumours vary in gene expression programmes and genetic alterations. Understanding this diversity and its biological meaning requires a theoretical framework, which could in turn guide the development of more accurate prognosis and therapy. Here, we review the theory of multi-task evolution of cancer, which is based upon the premise that tumours evolve in the host and face selection trade-offs between multiple biological functions. This theory can help identify the major biological tasks that cancer cells perform and the trade-offs between these tasks. It introduces the concept of specialist tumours, which focus on one task, and generalist tumours, which perform several tasks. Specialist tumours are suggested to be sensitive to therapy targeting their main task. Driver mutations tune gene expression towards specific tasks in a tissue-dependent manner and thus help to determine whether a tumour is specialist or generalist. We discuss potential applications of the theory of multi-task evolution to interpret the spatial organization of tumours and intratumour heterogeneity.

DOI: https://doi.org/10.1038/s41568-020-0241-6
Biomolecules. 2020 Feb 26. pii: E358. [Epub ahead of print]10(3):

NAD- and NADPH-Contributing Enzymes as Therapeutic Targets in Cancer: An Overview.

Alvinsyah Adhityo Pramono, Gulam M Rather, Herry Herman, Keri Lestari, Joseph R Bertino.

  Actively proliferating cancer cells require sufficient amount of NADH and NADPH for biogenesis and to protect cells from the detrimental effect of reactive oxygen species. As both normal and cancer cells share the same NAD biosynthetic and metabolic pathways, selectively lowering levels of NAD(H) and NADPH would be a promising strategy for cancer treatment. Targeting nicotinamide phosphoribosyltransferase (NAMPT), a rate limiting enzyme of the NAD salvage pathway, affects the NAD and NADPH pool. Similarly, lowering NADPH by mutant isocitrate dehydrogenase 1/2 (IDH1/2) which produces D-2-hydroxyglutarate (D-2HG), an oncometabolite that downregulates nicotinate phosphoribosyltransferase (NAPRT) via hypermethylation on the promoter region, results in epigenetic regulation. NADPH is used to generate D-2HG, and is also needed to protect dihydrofolate reductase, the target for methotrexate, from degradation. NAD and NADPH pools in various cancer types are regulated by several metabolic enzymes, including methylenetetrahydrofolate dehydrogenase, serine hydroxymethyltransferase, and aldehyde dehydrogenase. Thus, targeting NAD and NADPH synthesis under special circumstances is a novel approach to treat some cancers. This article provides the rationale for targeting the key enzymes that maintain the NAD/NADPH pool, and reviews preclinical studies of targeting these enzymes in cancers.

Keywords:  IDH mutation; NAD/NADPH pool; NADK inhibitor; NAMPT inhibitor; dihydrofolate reductase

DOI:  https://doi.org/10.3390/biom10030358
Curr Opin Cell Biol. 2020 Feb 24. pii: S0955-0674(20)30007-7. [Epub ahead of print]63 162-173

Reign in the membrane: How common lipids govern mitochondrial function.

Katsuhiko Funai, Scott A Summers, Jared Rutter.

The lipids that make up biological membranes tend to be the forgotten molecules of cell biology. The paucity of data on these important entities likely reflects the difficulties of studying and understanding their biological roles, rather than revealing a lack of importance. Indeed, the lipid composition of biological membranes has a profound impact on a diverse array of cellular processes. The focus of this review is on the effects of different lipid classes on the function of mitochondria, particularly bioenergetics, in health and disease.

DOI: https://doi.org/10.1016/j.ceb.2020.01.006
Nat Commun. 2020 Feb 25. 11(1): 1032

AMPK-dependent activation of the Cyclin Y/CDK16 complex controls autophagy.

Marc Dohmen, Sarah Krieg, Georgios Agalaridis, Xiaoqing Zhu, Saifeldin N Shehata, Elisabeth Pfeiffenberger, Jan Amelang, Mareike Bütepage, Elena Buerova, Carolina M Pfaff, Dipanjan Chanda, Stephan Geley, Christian Preisinger, Kei Sakamoto, Bernhard Lüscher, Dietbert Neumann, Jörg Vervoorts.

The AMP-activated protein kinase (AMPK) is a master sensor of the cellular energy status that is crucial for the adaptive response to limited energy availability. AMPK is implicated in the regulation of many cellular processes, including autophagy. However, the precise mechanisms by which AMPK controls these processes and the identities of relevant substrates are not fully understood. Using protein microarrays, we identify Cyclin Y as an AMPK substrate that is phosphorylated at Serine 326 (S326) both in vitro and in cells. Phosphorylation of Cyclin Y at S326 promotes its interaction with the Cyclin-dependent kinase 16 (CDK16), thereby stimulating its catalytic activity. When expressed in cells, Cyclin Y/CDK16 is sufficient to promote autophagy. Moreover, Cyclin Y/CDK16 is necessary for efficient AMPK-dependent activation of autophagy. This functional interaction is mediated by AMPK phosphorylating S326 of Cyclin Y. Collectively, we define Cyclin Y/CDK16 as downstream effector of AMPK for inducing autophagy.

DOI: https://doi.org/10.1038/s41467-020-14812-0
Nature. 2020 Feb;578(7796): 517-518

Tension in tumour cells keeps metabolism high.

Nadia M E Ayad, Valerie M Weaver.



Keywords:  Cancer; Cell biology; Metabolism

DOI:  https://doi.org/10.1038/d41586-020-00314-y
Toxicol Appl Pharmacol. 2020 Feb 25. pii: S0041-008X(20)30054-5. [Epub ahead of print] 114930

Suppression of iron mobilization from lysosomes to mitochondria attenuates liver injury after acetaminophen overdose in vivo in mice: Protection by minocycline.

Jiangting Hu, John J Lemasters.

  Acetaminophen (APAP) overdose causes hepatotoxicity involving mitochondrial dysfunction. Previous studies showed that translocation of Fe2+ from lysosomes into mitochondria by the mitochondrial Ca2+ uniporter (MCU) promotes the mitochondrial permeability transition (MPT) after APAP. Here, our Aim was to assess protection by iron chelation and MCU inhibition against APAP hepatotoxicity in mice. C57BL/6 mice and hepatocytes were administered toxic doses of APAP with and without starch-desferal (an iron chelator), minocycline (MCU inhibitor), or N-acetylcysteine (NAC). In mice, starch-desferal and minocycline pretreatment decreased ALT and liver necrosis after APAP by >60%. At 24 h after APAP, loss of fluorescence of mitochondrial rhodamine 123 occurred in pericentral hepatocytes often accompanied by propidium iodide labeling, indicating mitochondrial depolarization and cell death. Starch-desferal and minocycline pretreatment decreased mitochondrial depolarization and cell death by more than half. In cultured hepatocytes, cell killing at 10 h after APAP decreased from 83% to 49%, 35% and 27%, respectively, by 1 h posttreatment with minocycline, NAC, and minocycline plus NAC. With 4 h posttreatment in vivo, minocycline and minocycline plus NAC decreased ALT and necrosis by ~20% and ~50%, respectively, but NAC alone was not effective. In conclusion, minocycline and starch-desferal decrease mitochondrial dysfunction and severe liver injury after APAP overdose, suggesting that the MPT is likely triggered by iron uptake into mitochondria through MCU. In vivo, minocycline and minocycline plus NAC posttreatment after APAP protect at later time points than NAC alone, indicating that minocycline has a longer window of efficacy than NAC.

Keywords:  Acetaminophen; Calcium uniporter; Iron; Liver; Minocycline; Mitochondria

DOI:  https://doi.org/10.1016/j.taap.2020.114930
Metab Eng Commun. 2020 Jun;10 e00123

Metabolic flux analysis of secondary metabolism in plants.

Meng-Ling Shih, John A Morgan.

  Numerous secondary metabolites from plants are important for their medicinal, nutraceutical or sensory properties. Recently, significant progress has been made in the identification of the genes and enzymes of plant secondary metabolic pathways. Hence, there is interest in using synthetic biology to enhance the production of targeted valuable metabolites in plants. In this article, we examine the contribution that metabolic flux analysis will have on informing the rational selection of metabolic engineering targets as well as analysis of carbon and energy efficiency. Compared to microbes, plants have more complex tissue, cellular and subcellular organization, making precise metabolite concentration measurements more challenging. We review different techniques involved in quantifying flux and provide examples illustrating the application of the techniques. For linear and branched pathways that lead to end products with low turnover, flux quantification is straightforward and doesn't require isotopic labeling. However, for metabolites synthesized via parallel pathways, there is a requirement for isotopic labeling experiments. If the fed isotopically labeled carbons don't scramble, one needs to apply transient label balancing methods. In the transient case, it is also necessary to measure metabolite concentrations. While flux analysis is not able to directly identify mechanisms of regulation, it is a powerful tool to examine flux distribution at key metabolic nodes in intermediary metabolism, detect flux to wasteful side pathways, and show how parallel pathways handle flux in wild-type and engineered plants under a variety of physiological conditions.

Keywords:  13C MFA, Steady state isotopically labeled metabolic flux analysis; BA, Benzoic acid; DMAPP, Dimethylallyl diphosphate; GC, Gas chromatography; INST-MFA, Isotopically non-steady state metabolic flux analysis; IP, Isopentenyl phosphate; IPP, Isopentenyl diphosphate; LC, Liquid chromatography; MEP, Methylerythritol 4-phosphate; MFA, Metabolic flux analysis; MS, Mass spectrometry; MVA, Mevalonic acid; MVAP, Mevalonate 5-phosphate; MVAPP, Mevalonate 5-diphosphate; Metabolic channeling; Metabolic flux analysis; NMR, Nuclear magnetic resonance; Phe, Phenylalanine; Plant secondary metabolites; Stable isotopic labeling; Subcellular compartmentation

DOI:  https://doi.org/10.1016/j.mec.2020.e00123
Proc Natl Acad Sci U S A. 2020 Feb 28. pii: 201918950. [Epub ahead of print]

Regulatory CD8 T cells that recognize Qa-1 expressed by CD4 T-helper cells inhibit rejection of heart allografts.

John Y Choi, Siawosh K Eskandari, Songjie Cai, Ina Sulkaj, Jean Pierre Assaker, Hazim Allos, Juliano AlHaddad, Saif A Muhsin, Eman Alhussain, Amr Mansouri, Melissa Y Yeung, Marc A J Seelen, Hye-Jung Kim, Harvey Cantor, Jamil R Azzi.

  Induction of longstanding immunologic tolerance is essential for survival of transplanted organs and tissues. Despite recent advances in immunosuppression protocols, allograft damage inflicted by antibody specific for donor organs continues to represent a major obstacle to graft survival. Here we report that activation of regulatory CD8 T cells (CD8 Treg) that recognize the Qa-1 class Ib major histocompatibility complex (MHC), a mouse homolog of human leukocyte antigen-E (HLA-E), inhibits antibody-mediated immune rejection of heart allografts. We analyzed this response using a mouse model that harbors a point mutation in the class Ib MHC molecule Qa-1, which disrupts Qa-1 binding to the T cell receptor (TCR)-CD8 complex and impairs the CD8 Treg response. Despite administration of cytotoxic T lymphocyte antigen 4 (CTLA-4) immunoglobulin (Ig), Qa-1 mutant mice developed robust donor-specific antibody responses and accelerated heart graft rejection. We show that these allo-antibody responses reflect diminished Qa-1-restricted CD8 Treg-mediated suppression of host follicular helper T cell-dependent antibody production. These findings underscore the critical contribution of this Qa-1/HLA-E-dependent regulatory pathway to maintenance of transplanted organs and suggest therapeutic approaches to ameliorate allograft rejection.

Keywords:  Ab-mediated rejection; CD8 Treg; HLA-E; Qa-1; follicular helper T cell

DOI:  https://doi.org/10.1073/pnas.1918950117
Nat Rev Urol. 2020 Feb 28.

Tumour metabolism and its unique properties in prostate adenocarcinoma.

David A Bader, Sean E McGuire.

Anabolic metabolism mediated by aberrant growth factor signalling fuels tumour growth and progression. The first biochemical descriptions of the altered metabolic nature of solid tumours were reported by Otto Warburg almost a century ago. Now, the study of tumour metabolism is being redefined by the development of new molecular tools, tumour modelling systems and precise instrumentation together with important advances in genetics, cell biology and spectroscopy. In contrast to Warburg's original hypothesis, accumulating evidence demonstrates a critical role for mitochondrial metabolism and substantial variation in the way in which different tumours metabolize nutrients to generate biomass. Furthermore, computational and experimental approaches suggest a dominant influence of the tissue-of-origin in shaping the metabolic reprogramming that enables tumour growth. For example, the unique metabolic properties of prostate adenocarcinoma are likely to stem from the distinct metabolism of the prostatic epithelium from which it emerges. Normal prostatic epithelium employs comparatively glycolytic metabolism to sustain physiological citrate secretion, whereas prostate adenocarcinoma consumes citrate to power oxidative phosphorylation and fuel lipogenesis, enabling tumour progression through metabolic reprogramming. Current data suggest that the distinct metabolic aberrations in prostate adenocarcinoma are driven by the androgen receptor, providing opportunities for functional metabolic imaging and novel therapeutic interventions that will be complementary to existing diagnostic and treatment options.

DOI: https://doi.org/10.1038/s41585-020-0288-x
Annu Rev Biochem. 2020 Feb 25.

Chemical Biology Framework to Illuminate Proteostasis.

Rebecca M Sebastian, Matthew D Shoulders.

Protein folding in the cell is mediated by an extensive network of >1,000 chaperones, quality control factors, and trafficking mechanisms collectively termed the proteostasis network. While the components and organization of this network are generally well established, our understanding of how protein-folding problems are identified, how the network components integrate to successfully address challenges, and what types of biophysical issues each proteostasis network component is capable of addressing remains immature. We describe a chemical biology-informed framework for studying cellular proteostasis that relies on selection of interesting protein-folding problems and precise researcher control of proteostasis network composition and activities. By combining these methods with multifaceted strategies to monitor protein folding, degradation, trafficking, and aggregation in cells, researchers continue to rapidly generate new insights into cellular proteostasis. Expected final online publication date for the Annual Review of Biochemistry, Volume 89 is June 22, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

DOI: https://doi.org/10.1146/annurev-biochem-013118-111552