bims-camemi 2019-11-17 papers

bims-camemi

Biomed News

on Mitochondrial metabolism in cancer

Issue of 2019‒11‒17
forty papers selected by
Christian Frezza,

Nutrient regulation of mTORC1 at a glance.
A Compendium of Genetic Modifiers of Mitochondrial Dysfunction Reveals Intra-organelle Buffering.
A split-GFP tool reveals differences in the sub-mitochondrial distribution of wt and mutant alpha-synuclein.
NIX-Mediated Mitophagy Promotes Effector Memory Formation in Antigen-Specific CD8+ T Cells.
3-Methylglutaric acid in energy metabolism.
MITRAC15/COA1 promotes mitochondrial translation in a ND2 ribosome-nascent chain complex.
Context-dependent activation of SIRT3 is necessary for anchorage-independent survival and metastasis of ovarian cancer cells.
Biochemical thresholds for pathological presentation of ATP synthase deficiencies.
mTORC2 links growth factor signaling with epigenetic regulation of iron metabolism in glioblastoma.
Overexpression of pink1 or parkin in indirect flight muscles promotes mitochondrial proteostasis and extends lifespan in Drosophila melanogaster.
Pivotal Role of Mitochondria in Macrophage Response to Bacterial Pathogens.
Polycystin-1 Regulates Actomyosin Contraction and the Cellular Response to Extracellular Stiffness.
Hematopoietic Stem Cell Transplantation in Inborn Errors of Metabolism.
Stress signaling and cellular proliferation reverse the effects of mitochondrial mistranslation.
Longevity in response to lowered insulin signaling requires glycine N-methyltransferase-dependent spermidine production.
Mitochondrial oxidative phosphorylation complex regulates NLRP3 inflammasome activation and predicts patient survival in nasopharyngeal carcinoma.
Lactate Buildup at the Site of Chronic Inflammation Promotes Disease by Inducing CD4+ T Cell Metabolic Rewiring.
Intrinsic and Extrinsic Determinants of T Cell Metabolism in Health and Disease.
Corrupted ER-mitochondrial calcium homeostasis promotes the collapse of proteostasis.
Metabolic Remodeling Promotes Cardiac Hypertrophy by Directing Glucose to Aspartate Biosynthesis.
eIF4A supports an oncogenic translation program in pancreatic ductal adenocarcinoma.
Mitochondrial DNA heteroplasmy rises in substantial nigra of aged PINK1 KO mice.
Visualizing Mitochondrial Form and Function within the Cell.
Metabolic vulnerability in tumours illuminated.
Misregulation of Drosophila Myc Disrupts Circadian Behavior and Metabolism.
Knockdown of Pyruvate Kinase M2 Inhibits Cell Proliferation, Metabolism, and Migration in Renal Cell Carcinoma.
Microbial Metabolite Signaling Is Required for Systemic Iron Homeostasis.
Metabolic pathway analyses identify proline biosynthesis pathway as a promoter of liver tumorigenesis.
Mitochondrial Dysfunction in Aging and Cancer.
Mutant p53 antagonizes p63/p73-mediated tumor suppression via Notch1.
Succinate accumulation induces mitochondrial reactive oxygen species generation and promotes status epilepticus in the kainic acid rat model.
Combined mTORC1/mTORC2 inhibition blocks growth and induces catastrophic macropinocytosis in cancer cells.
A Brief History of Mitochondrial Pathologies.
Prolyl hydroxylase substrate adenylosuccinate lyase is an oncogenic driver in triple negative breast cancer.
Integrated Analyses of Microbiome and Longitudinal Metabolome Data Reveal Microbial-Host Interactions on Sulfur Metabolism in Parkinson's Disease.
At a Glance: A History of Autophagy and Cancer.
Metabolomic Changes of Human Proximal Tubular Cell Line in High Glucose Environment.
Marine Proteobacteria metabolize glycolate via the β-hydroxyaspartate cycle.
Xanthine oxidase inhibitor ameliorates postischemic renal injury in mice by promoting resynthesis of adenine nucleotides.
The Acidic Tumor Microenvironment as a Driver of Cancer.

J Cell Sci. 2019 Nov 13. pii: jcs222570. [Epub ahead of print]132(21):

Nutrient regulation of mTORC1 at a glance.

Kendall J Condon, David M Sabatini.

  The mechanistic target of rapamycin (mTOR) signaling pathway coordinates environmental and intracellular cues to control eukaryotic cell growth. As a pivot point between anabolic and catabolic processes, mTOR complex 1 (mTORC1) signaling has established roles in regulating metabolism, translation and autophagy. Hyperactivity of the mTOR pathway is associated with numerous human diseases, including diabetes, cancer and epilepsy. Pharmacological inhibition of the mTOR pathway can extend lifespan in a variety of model organisms. Given its broad control of essential cellular processes and clear relevance to human health, there is extensive interest in elucidating how upstream inputs regulate mTORC1 activation. In this Cell Science at a Glance article and accompanying poster, we summarize our understanding of how extracellular and intracellular signals feed into the mTOR pathway, how the lysosome acts as an mTOR signaling hub, and how downstream signaling controls autophagy and lysosome biogenesis.

Keywords:  Amino acids; Autophagy; Cell growth; Glucose; Lysosome; Nutrients; Signaling; mTORC1

DOI:  https://doi.org/10.1242/jcs.222570
Cell. 2019 Nov 14. pii: S0092-8674(19)31182-1. [Epub ahead of print]179(5): 1222-1238.e17

A Compendium of Genetic Modifiers of Mitochondrial Dysfunction Reveals Intra-organelle Buffering.

Tsz-Leung To, Alejandro M Cuadros, Hardik Shah, Wendy H W Hung, Yang Li, Sharon H Kim, Daniel H F Rubin, Ryan H Boe, Sneha Rath, John K Eaton, Federica Piccioni, Amy Goodale, Zohra Kalani, John G Doench, David E Root, Stuart L Schreiber, Scott B Vafai, Vamsi K Mootha.

  Mitochondrial dysfunction is associated with a spectrum of human conditions, ranging from rare, inborn errors of metabolism to the aging process. To identify pathways that modify mitochondrial dysfunction, we performed genome-wide CRISPR screens in the presence of small-molecule mitochondrial inhibitors. We report a compendium of chemical-genetic interactions involving 191 distinct genetic modifiers, including 38 that are synthetic sick/lethal and 63 that are suppressors. Genes involved in glycolysis (PFKP), pentose phosphate pathway (G6PD), and defense against lipid peroxidation (GPX4) scored high as synthetic sick/lethal. A surprisingly large fraction of suppressors are pathway intrinsic and encode mitochondrial proteins. A striking example of such "intra-organelle" buffering is the alleviation of a chemical defect in complex V by simultaneous inhibition of complex I, which benefits cells by rebalancing redox cofactors, increasing reductive carboxylation, and promoting glycolysis. Perhaps paradoxically, certain forms of mitochondrial dysfunction may best be buffered with "second site" inhibitors to the organelle.

Keywords:  CRISPR screening; G6PD; GPX4; LARP1; complex I; genetic modifier; metformin; mitochondria; redox cofactors; reductive carboxylation

DOI:  https://doi.org/10.1016/j.cell.2019.10.032
Cell Death Dis. 2019 Nov 12. 10(11): 857

A split-GFP tool reveals differences in the sub-mitochondrial distribution of wt and mutant alpha-synuclein.

Mattia Vicario, Domenico Cieri, Francesca Vallese, Cristina Catoni, Lucia Barazzuol, Paola Berto, Alessandro Grinzato, Laura Barbieri, Marisa Brini, Tito Calì.

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by dopaminergic neuronal loss that initiates in the substantia nigra pars compacta and by the formation of intracellular inclusions mainly constituted by aberrant α-synuclein (α-syn) deposits known as Lewy bodies. Most cases of PD are sporadic, but about 10% are familial, among them those caused by mutations in SNCA gene have an autosomal dominant transmission. SNCA encodes α-syn, a small 140-amino acids protein that, under physiological conditions, is mainly localized at the presynaptic terminals. It is prevalently cytosolic, but its presence has been reported in the nucleus, in the mitochondria and, more recently, in the mitochondria-associated ER membranes (MAMs). Whether different cellular localizations may reflect specific α-syn activities is presently unclear and its action at mitochondrial level is still a matter of debate. Mounting evidence supports a role for α-syn in several mitochondria-derived activities, among which maintenance of mitochondrial morphology and modulation of complex I and ATP synthase activity. α-syn has been proposed to localize at the outer membrane (OMM), in the intermembrane space (IMS), at the inner membrane (IMM) and in the mitochondrial matrix, but a clear and comparative analysis of the sub-mitochondrial localization of WT and mutant α-syn is missing. Furthermore, the reasons for this spread sub-mitochondrial localization under physiological and pathological circumstances remain elusive. In this context, we decided to selectively monitor the sub-mitochondrial distribution of the WT and PD-related α-syn mutants A53T and A30P by taking advantage from a bimolecular fluorescence complementation (BiFC) approach. We also investigated whether cell stress could trigger α-syn translocation within the different mitochondrial sub-compartments and whether PD-related mutations could impinge on it. Interestingly, the artificial targeting of α-syn WT (but not of the mutants) to the mitochondrial matrix impacts on ATP production, suggesting a potential role within this compartment.

DOI: https://doi.org/10.1038/s41419-019-2092-1
Cell Rep. 2019 Nov 12. pii: S2211-1247(19)31332-4. [Epub ahead of print]29(7): 1862-1877.e7

NIX-Mediated Mitophagy Promotes Effector Memory Formation in Antigen-Specific CD8+ T Cells.

Shubhranshu S Gupta, Robert Sharp, Colby Hofferek, Le Kuai, Gerald W Dorn, Jin Wang, Min Chen.

  Autophagy plays a critical role in the maintenance of immunological memory. However, the molecular mechanisms involved in autophagy-regulated effector memory formation in CD8+ T cells remain unclear. Here we show that deficiency in NIX-dependent mitophagy leads to metabolic defects in effector memory T cells. Deletion of NIX caused HIF1α accumulation and altered cellular metabolism from long-chain fatty acid to short/branched-chain fatty acid oxidation, thereby compromising ATP synthesis during effector memory formation. Preventing HIF1α accumulation restored long-chain fatty acid metabolism and effector memory formation in antigen-specific CD8+ T cells. Our study suggests that NIX-mediated mitophagy is critical for effector memory formation in T cells.

Keywords:  CD8(+) T cells; HIF1α; NIX; autophagy; effector memory cells; fatty acid metabolism; long-chain fatty acid oxidation; mitochondrial superoxide; mitophagy; short/branched-chain fatty acid oxidation

DOI:  https://doi.org/10.1016/j.celrep.2019.10.032
Clin Chim Acta. 2019 Nov 12. pii: S0009-8981(19)32121-7. [Epub ahead of print]

3-Methylglutaric acid in energy metabolism.

Dylan E Jones, Leanne Perez, Robert O Ryan.

  3-methylglutaric (3MG) acid is a conspicuous C6 dicarboxylic organic acid classically associated with two distinct leucine pathway enzyme deficiencies. 3MG acid is excreted in urine of individuals harboring deficiencies in 3-hydroxy-3-methylglutaryl (HMG) CoA lyase (HMGCL) or 3-methylglutaconyl CoA hydratase (AUH). Whereas 3MG CoA is not part of the leucine catabolic pathway, it is likely formed via a side reaction involving reduction of the α-ß trans double bond in the leucine pathway intermediate, 3-methylglutaconyl CoA. While the metabolic basis for the accumulation of 3MG acid in subjects with deficiencies in HMGCL or AUH is apparent, the occurrence of 3MG aciduria in a host of unrelated inborn errors of metabolism associated with compromised mitochondrial energy metabolism is less clear. Herein, a novel mitochondrial biosynthetic pathway termed "the acetyl CoA diversion pathway", provides an explanation. The pathway is initiated by defective electron transport chain function which, ultimately, inhibits acetyl CoA entry into the TCA cycle. When this occurs, 3MG acid is synthesized in five steps from acetyl CoA via a novel reaction sequence, providing a metabolic rationale for the connection between 3MG aciduria and compromised mitochondrial energy metabolism.

Keywords:  3-methylglutaconic acid; Organic aciduria; acetyl CoA diversion pathway; inborn error of metabolism; leucine; mitochondria

DOI:  https://doi.org/10.1016/j.cca.2019.11.006
EMBO Rep. 2019 Nov 13. e48833

MITRAC15/COA1 promotes mitochondrial translation in a ND2 ribosome-nascent chain complex.

Cong Wang, Ricarda Richter-Dennerlein, David Pacheu-Grau, Fan Liu, Ying Zhu, Sven Dennerlein, Peter Rehling.

  The mitochondrial genome encodes for thirteen core subunits of the oxidative phosphorylation system. These proteins assemble with imported proteins in a modular manner into stoichiometric enzyme complexes. Assembly factors assist in these biogenesis processes by providing co-factors or stabilizing transient assembly stages. However, how expression of the mitochondrial-encoded subunits is regulated to match the availability of nuclear-encoded subunits is still unresolved. Here, we address the function of MITRAC15/COA1, a protein that participates in complex I biogenesis and complex IV biogenesis. Our analyses of a MITRAC15 knockout mutant reveal that MITRAC15 is required for translation of the mitochondrial-encoded complex I subunit ND2. We find that MITRAC15 is a constituent of a ribosome-nascent chain complex during ND2 translation. Chemical crosslinking analyses demonstrate that binding of the ND2-specific assembly factor ACAD9 to the ND2 polypeptide occurs at the C-terminus and thus downstream of MITRAC15. Our analyses demonstrate that expression of the founder subunit ND2 of complex I undergoes regulation. Moreover, a ribosome-nascent chain complex with MITRAC15 is at the heart of this process.

Keywords:  complex I; mitochondria; nascent chain; translation

DOI:  https://doi.org/10.15252/embr.201948833
Oncogene. 2019 Nov 13.

Context-dependent activation of SIRT3 is necessary for anchorage-independent survival and metastasis of ovarian cancer cells.

Yeon Soo Kim, Piyushi Gupta Vallur, Victoria M Jones, Beth L Worley, Sara Shimko, Dong-Hui Shin, LaTaijah C Crawford, Chi-Wei Chen, Katherine M Aird, Thomas Abraham, Trevor G Shepherd, Joshua I Warrick, Nam Y Lee, Rebecca Phaeton, Karthikeyan Mythreye, Nadine Hempel.

Tumor cells must alter their antioxidant capacity for maximal metastatic potential. Yet the antioxidant adaptations required for ovarian cancer transcoelomic metastasis, which is the passive dissemination of cells in the peritoneal cavity, remain largely unexplored. Somewhat contradicting the need for oxidant scavenging are previous observations that expression of SIRT3, a nutrient stress sensor and regulator of mitochondrial antioxidant defenses, is often suppressed in many primary tumors. We have discovered that this mitochondrial deacetylase is specifically upregulated in a context-dependent manner in cancer cells. SIRT3 activity and expression transiently increased following ovarian cancer cell detachment and in tumor cells derived from malignant ascites of high-grade serous adenocarcinoma patients. Mechanistically, SIRT3 prevents mitochondrial superoxide surges in detached cells by regulating the manganese superoxide dismutase (SOD2). This mitochondrial stress response is under dual regulation by SIRT3. SIRT3 rapidly increases SOD2 activity as an early adaptation to cellular detachment, which is followed by SIRT3-dependent increases in SOD2 mRNA during sustained anchorage-independence. In addition, SIRT3 inhibits glycolytic capacity in anchorage-independent cells thereby contributing to metabolic changes in response to detachment. While manipulation of SIRT3 expression has few deleterious effects on cancer cells in attached conditions, SIRT3 upregulation and SIRT3-mediated oxidant scavenging are required for anoikis resistance in vitro following matrix detachment, and both SIRT3 and SOD2 are necessary for colonization of the peritoneal cavity in vivo. Our results highlight the novel context-specific, pro-metastatic role of SIRT3 in ovarian cancer.

DOI: https://doi.org/10.1038/s41388-019-1097-7
Biochem Biophys Res Commun. 2019 Nov 12. pii: S0006-291X(19)32153-9. [Epub ahead of print]

Biochemical thresholds for pathological presentation of ATP synthase deficiencies.

Hana Nuskova, Jana Mikesova, Iuliia Efimova, Alena Pecinova, Petr Pecina, Zdenek Drahota, Josef Houstek, Tomas Mracek.

  Mitochondrial ATP synthase is responsible for production of the majority of cellular ATP. Disorders of ATP synthase in humans can be caused by numerous mutations in both structural subunits and specific assembly factors. They are associated with variable pathogenicity and clinical phenotypes ranging from mild to the most severe mitochondrial diseases. To shed light on primary/pivotal functional consequences of ATP synthase deficiency, we explored human HEK 293 cells with a varying content of fully assembled ATP synthase, selectively downregulated to 15-80% of controls by the knockdown of F1 subunits γ, δ and ε. Examination of cellular respiration and glycolytic flux revealed that enhanced glycolysis compensates for insufficient mitochondrial ATP production while reduced dissipation of mitochondrial membrane potential leads to elevated ROS production. Both insufficient energy provision and increased oxidative stress contribute to the resulting pathological phenotype. The threshold for manifestation of the ATP synthase defect and subsequent metabolic remodelling equals to 10-30% of residual ATP synthase activity. The metabolic adaptations are not able to sustain proliferation in a galactose medium, although sufficient under glucose-rich conditions. As metabolic alterations occur when the content of ATP synthase drops below 30%, some milder ATP synthase defects may not necessarily manifest with a mitochondrial disease phenotype, as long as the threshold level is not exceeded.

Keywords:  ATP synthase; Deficiency; Oxidative phosphorylation; Reactive oxygen species; Threshold effect

DOI:  https://doi.org/10.1016/j.bbrc.2019.11.033
J Biol Chem. 2019 Nov 11. pii: jbc.RA119.011519. [Epub ahead of print]

mTORC2 links growth factor signaling with epigenetic regulation of iron metabolism in glioblastoma.

Kenta Masui, Mio Harachi, Shiro Ikegami, Huijun Yang, Hiromi Onizuka, William H Yong, Timothy F Cloughesy, Yoshihiro Muragaki, Takakazu Kawamata, Nobutaka Arai, Takashi Komori, Webster K Cavenee, Paul S Mischel, Noriyuki Shibata.

  In cancer, aberrant growth factor receptor signaling reprograms cellular metabolism and global gene transcription to drive aggressive growth, but the underlying mechanisms are not well understood. Here we show that in the highly lethal brain tumor glioblastoma (GBM), mechanistic target of rapamycin complex 2 (mTORC2), a critical core component of the growth factor signaling system, couples acetyl-CoA production with nuclear translocation of histone-modifying enzymes including pyruvate dehydrogenase (PDH) and class IIa histone deacetylases (HDACs) to globally alter histone acetylation. Integrated analyses in orthotopic mouse models and in clinical GBM samples reveal that mTORC2 controls iron metabolisms via histone H3 acetylation of the iron-related gene promoter, promoting tumor cell survival. These results nominate mTORC2 as a critical epigenetic regulator of iron metabolism in cancer.

Keywords:  acetyl coenzyme A (acetyl-CoA); glioblastoma; glucose metabolism; histone acetylation; iron metabolism; mammalian target of rapamycin (mTOR)

DOI:  https://doi.org/10.1074/jbc.RA119.011519
PLoS One. 2019 ;14(11): e0225214

Overexpression of pink1 or parkin in indirect flight muscles promotes mitochondrial proteostasis and extends lifespan in Drosophila melanogaster.

Hongbin Si, Peng Ma, Qiying Liang, Youjie Yin, Ping Wang, Qi Zhang, Saifei Wang, Hansong Deng.

Dysfunctional mitochondria have been implicated in aging and age-related disorders such as Parkinson's diseases (PD). We previously showed that pink1 and parkin, two familial PD genes, function in a linear pathway to maintain mitochondrial integrity and function. Studies of mammalian cell lines also suggest that these genes regulate mitochondrial autophagy(mitophagy). Overexpressing Parkin promotes proteostasis and function of aged muscles both in fruit flies and mice, and recent studies also indicated that mitochondrial ubiquitination are accumulated in aged muscles. However, the underlying mechanisms for pink1 and parkin mediated mitophagy on longevity is not fully understood. Here, we found that mitochondrial ubiquitination increased in indirect flight muscles (IFMs) in an age-dependent manner. Overexpression of pink1 or parkin in IFMs can abolish mitochondrial ubiquitination, restore ATP level and extend lifespan, while blocking autophagy via ATG1 knock-down suppress these effects in aged IFMs. Taken together, these results show that pink1/parkin promotes mitophagy of mitochondrial ubiquitination in aged muscles and extend lifespan in an Atg1-dependent manner. Our study provides physiological evidence that mitophagy of mitochondrial ubiquitination mediated by PINK1/ Parkin is crucial for muscle function and highlights the role of mitophagy in the pathogenesis of chronic diseases like PD.

DOI: https://doi.org/10.1371/journal.pone.0225214
Front Immunol. 2019 ;10 2461

Pivotal Role of Mitochondria in Macrophage Response to Bacterial Pathogens.

Elodie Ramond, Anne Jamet, Mathieu Coureuil, Alain Charbit.

  Mitochondria are essential organelles that act as metabolic hubs and signaling platforms within the cell. Numerous mitochondrial functions, including energy metabolism, lipid synthesis, and autophagy regulation, are intimately linked to mitochondrial dynamics, which is shaped by ongoing fusion and fission events. Recently, several intracellular bacterial pathogens have been shown to modulate mitochondrial functions to maintain their replicative niche. Through selected examples of human bacterial pathogens, we will discuss how infection induces mitochondrial changes in infected macrophages, triggering modifications of the host metabolism that lead to important immunological reprogramming.

Keywords:  bacterial infection; cell polarization; immunometabolism; macrophage; mitochondria

DOI:  https://doi.org/10.3389/fimmu.2019.02461
Sci Rep. 2019 Nov 12. 9(1): 16640

Polycystin-1 Regulates Actomyosin Contraction and the Cellular Response to Extracellular Stiffness.

Elisa Agnese Nigro, Gianfranco Distefano, Marco Chiaravalli, Vittoria Matafora, Maddalena Castelli, Angela Pesenti Gritti, Angela Bachi, Alessandra Boletta.

Polycystin-1 (PC-1) and 2 (PC-2) are the products of the PKD1 and PKD2 genes, which are mutated in Autosomal Dominant Polycystic Kidney Disease (ADPKD). They form a receptor/channel complex that has been suggested to function as a mechanosensor, possibly activated by ciliary bending in the renal tubule, and resulting in calcium influx. This model has recently been challenged, leaving the question as to which mechanical stimuli activate the polycystins still open. Here, we used a SILAC/Mass-Spec approach to identify intracellular binding partners of tagged-endogenous PC-1 whereby we detected a class of interactors mediating regulation of cellular actomyosin contraction. Accordingly, using gain and loss-of-function cellular systems we found that PC-1 negatively regulates cellular contraction and YAP activation in response to extracellular stiffness. Thus, PC-1 enables cells to sense the rigidity of the extracellular milieu and to respond appropriately. Of note, in an orthologous murine model of PKD we found evidence of increased actomyosin contraction, leading to enhanced YAP nuclear translocation and transcriptional activity. Finally, we show that inhibition of ROCK-dependent actomyosin contraction by Fasudil reversed YAP activation and significantly improved disease progression, in line with recent studies. Our data suggest a possible direct role of PC-1 as a mechanosensor of extracellular stiffness.

DOI: https://doi.org/10.1038/s41598-019-53061-0
Front Pediatr. 2019 ;7 433

Hematopoietic Stem Cell Transplantation in Inborn Errors of Metabolism.

Emily Y Tan, Jaap Jan Boelens, Simon A Jones, Robert F Wynn.

  Hematopoietic stem cell transplantation (HSCT) has been established as an effective therapy for selected inborn errors of metabolism. The success of HSCT in metabolic disease is best exemplified through the treatment of Hurler's syndrome, a lysosomal storage disease. Through the collaborative effort of several international centers, factors that predict successful patient and transplant outcomes have been identified. In this review, we discuss the principles that underlie the use of HSCT in metabolic diseases. We consider the clinical indications, conditioning regimens, and disease-specific follow-up for HSCT in different metabolic diseases. We highlight persisting challenges in HSCT to delay progression of certain organ systems that remain refractory to HSCT and the relatively high rates of aplastic graft failure. Finally, we evaluate the variable applicability of these principles to other inherited metabolic disorders including peroxisomal, mitochondrial, and other lysosomal storage diseases.

Keywords:  bone marrow transplant; hematopoietic stem cell transplantation; inborn errors of metabolism; lysosomal storage disease; mitochondrial disease; peroxisomal disease

DOI:  https://doi.org/10.3389/fped.2019.00433
EMBO J. 2019 Nov 13. e102155

Stress signaling and cellular proliferation reverse the effects of mitochondrial mistranslation.

Nicola Ferreira, Kara L Perks, Giulia Rossetti, Danielle L Rudler, Laetitia A Hughes, Judith A Ermer, Louis H Scott, Irina Kuznetsova, Tara R Richman, Vinod K Narayana, Laila N Abudulai, Anne-Marie J Shearwood, Henrietta Cserne Szappanos, Dedreia Tull, George C Yeoh, Livia C Hool, Aleksandra Filipovska, Oliver Rackham.

  Translation fidelity is crucial for prokaryotes and eukaryotic nuclear-encoded proteins; however, little is known about the role of mistranslation in mitochondria and its potential effects on metabolism. We generated yeast and mouse models with error-prone and hyper-accurate mitochondrial translation, and found that translation rate is more important than translational accuracy for cell function in mammals. Specifically, we found that mitochondrial mistranslation causes reduced overall mitochondrial translation and respiratory complex assembly rates. In mammals, this effect is compensated for by increased mitochondrial protein stability and upregulation of the citric acid cycle. Moreover, this induced mitochondrial stress signaling, which enables the recovery of mitochondrial translation via mitochondrial biogenesis, telomerase expression, and cell proliferation, and thereby normalizes metabolism. Conversely, we show that increased fidelity of mitochondrial translation reduces the rate of protein synthesis without eliciting a mitochondrial stress response. Consequently, the rate of translation cannot be recovered and this leads to dilated cardiomyopathy in mice. In summary, our findings reveal mammalian-specific signaling pathways that respond to changes in the fidelity of mitochondrial protein synthesis and affect metabolism.

Keywords:  metabolism; mitochondria; mitochondrial ribosome; protein synthesis; stress response

DOI:  https://doi.org/10.15252/embj.2019102155
Aging Cell. 2019 Nov 13. e13043

Longevity in response to lowered insulin signaling requires glycine N-methyltransferase-dependent spermidine production.

Luke S Tain, Chirag Jain, Tobias Nespital, Jenny Froehlich, Yvonne Hinze, Sebastian Grönke, Linda Partridge.

  Reduced insulin/IGF signaling (IIS) extends lifespan in multiple organisms. Different processes in different tissues mediate this lifespan extension, with a set of interplays that remain unclear. We here show that, in Drosophila, reduced IIS activity modulates methionine metabolism, through tissue-specific regulation of glycine N-methyltransferase (Gnmt), and that this regulation is required for full IIS-mediated longevity. Furthermore, fat body-specific expression of Gnmt was sufficient to extend lifespan. Targeted metabolomics showed that reducing IIS activity led to a Gnmt-dependent increase in spermidine levels. We also show that both spermidine treatment and reduced IIS activity are sufficient to extend the lifespan of Drosophila, but only in the presence of Gnmt. This extension of lifespan was associated with increased levels of autophagy. Finally, we found that increased expression of Gnmt occurs in the liver of liver-specific IRS1 KO mice and is thus an evolutionarily conserved response to reduced IIS. The discovery of Gnmt and spermidine as tissue-specific modulators of IIS-mediated longevity may aid in developing future therapeutic treatments to ameliorate aging and prevent disease.

Keywords:  IGF; aging; autophagy; insulin; lifespan; metabolism; polyamine

DOI:  https://doi.org/10.1111/acel.13043
Mol Cell Proteomics. 2019 Nov 13. pii: mcp.RA119.001808. [Epub ahead of print]

Mitochondrial oxidative phosphorylation complex regulates NLRP3 inflammasome activation and predicts patient survival in nasopharyngeal carcinoma.

I-Che Chung, Lih-Chyang Chen, Ngan-Ming Tsang, Wen-Yu Chuang, Tzu-Chieh Liao, Sheng-Ning Yuan, Chun-Nan OuYang, David M Ojcius, Chih-Ching Wu, Yu-Sun Chang.

  We previously reported that tumor inflammasomes play a key role in tumor control and act as favorable prognostic markers in nasopharyngeal carcinoma (NPC). Activated inflammasomes frequently form distinguishable specks and govern the cellular secretion of IL-1β. However, we know little about the biological and biochemical differences between cells with and without apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) speck formation. In this study, we used proteomic iTRAQ analysis to analyze the proteomes of NPC cells that differ in their ASC speck formation upon cisplatin treatment. We identified proteins that were differentially over-expressed in cells with specks, and found that they fell into two Gene ontology (GO) pathways: mitochondrial oxidative phosphorylation (OxPhos) and ubiquinone metabolism. We observed up-regulation of various components of the OxPhos machinery (including NDUFB3, NDUFB8 and ATP5B), and subsequently found that these changes lead to mitochondrial ROS (mtROS) production, which promotes the formation and activation of NLRP3 inflammasomes and subsequent pyroptosis. In NPC patients, better local recurrence-free survival was significantly associated with high-level expression of NDUFB8 (P=0.037) and ATP5B (P=0.029), as examined using immunohistochemistry. However, there were no significant associations between the expression of NDUFB8 and ATP5B with overall survival of NPC patients. Together, our results demonstrate that upregulated mitochondrial OxPhos components are strongly associated with NLRP3 inflammasome activation in NPC. Our findings further suggest that high-level expression of OxPhos components could be markers for local recurrence and/or promising therapeutic targets in patients with NPC.

Keywords:  Cancer Biology*; Inflammatory response; Mitochondria function or biology; Oxidative stress; iTRAQ; nasopharyngeal carcinoma

DOI:  https://doi.org/10.1074/mcp.RA119.001808
Cell Metab. 2019 Oct 29. pii: S1550-4131(19)30559-5. [Epub ahead of print]

Lactate Buildup at the Site of Chronic Inflammation Promotes Disease by Inducing CD4+ T Cell Metabolic Rewiring.

Valentina Pucino, Michelangelo Certo, Vinay Bulusu, Danilo Cucchi, Katriona Goldmann, Elena Pontarini, Robert Haas, Joanne Smith, Sarah E Headland, Kevin Blighe, Massimiliano Ruscica, Frances Humby, Myles J Lewis, Jurre J Kamphorst, Michele Bombardieri, Costantino Pitzalis, Claudio Mauro.

  Accumulation of lactate in the tissue microenvironment is a feature of both inflammatory disease and cancer. Here, we assess the response of immune cells to lactate in the context of chronic inflammation. We report that lactate accumulation in the inflamed tissue contributes to the upregulation of the lactate transporter SLC5A12 by human CD4+ T cells. SLC5A12-mediated lactate uptake into CD4+ T cells induces a reshaping of their effector phenotype, resulting in increased IL17 production via nuclear PKM2/STAT3 and enhanced fatty acid synthesis. It also leads to CD4+ T cell retention in the inflamed tissue as a consequence of reduced glycolysis and enhanced fatty acid synthesis. Furthermore, antibody-mediated blockade of SLC5A12 ameliorates the disease severity in a murine model of arthritis. Finally, we propose that lactate/SLC5A12-induced metabolic reprogramming is a distinctive feature of lymphoid synovitis in rheumatoid arthritis patients and a potential therapeutic target in chronic inflammatory disorders.

Keywords:  T cell; cytokines; immunometabolism; inflammation; lactate; lactate transporter; metabolic crosstalk; signaling; translational research

DOI:  https://doi.org/10.1016/j.cmet.2019.10.004
Front Mol Biosci. 2019 ;6 118

Intrinsic and Extrinsic Determinants of T Cell Metabolism in Health and Disease.

Haydn Munford, Sarah Dimeloe.

  T lymphocytes are a critical component of the adaptive immune system, with key roles in the immune response to infection and cancer. Their activity is fundamentally underpinned by dynamic, regulated changes in their metabolism. This ensures adequate availability of energy and biosynthetic precursors for clonal expansion and effector function, and also directly regulates cell signaling, gene transcription, and protein translation. In health, distinct T cells subtypes demonstrate differences in intrinsic metabolic capacity which correlate with their specialized immune functions. In disease, T cells with impaired immune function appear to be likewise metabolically impaired. Furthermore, diseased tissue environments-through inadequate provision of nutrients and oxygen, or accumulation of metabolic intermediates, end-products, and cytokines- can impose metabolic insufficiency upon these cells, and further compound intrinsic impairments. These intrinsic and extrinsic determinants of T cell metabolism and their potential compound effects, together with the mechanisms involved form the subject of this review. We will also discuss how dysfunctional metabolic pathways may be therapeutically targeted to restore normal T cell function in disease.

Keywords:  T cell; adaptive immune cells; cancer; glycolysis; hypoxia; immunology; metabolism; mitochondria

DOI:  https://doi.org/10.3389/fmolb.2019.00118
Aging Cell. 2019 Nov 12. e13065

Corrupted ER-mitochondrial calcium homeostasis promotes the collapse of proteostasis.

Zahra Ashkavand, Shaarika Sarasija, Kerry C Ryan, Jocelyn T Laboy, Kenneth R Norman.

  Aging and age-related diseases are associated with a decline of protein homeostasis (proteostasis), but the mechanisms underlying this decline are not clear. In particular, decreased proteostasis is a widespread molecular feature of neurodegenerative diseases, such as Alzheimer's disease (AD). Familial AD is largely caused by mutations in the presenilin encoding genes; however, their role in AD is not understood. In this study, we investigate the role of presenilins in proteostasis using the model system Caenorhabditis elegans. Previously, we found that mutations in C. elegans presenilin cause elevated ER to mitochondria calcium signaling, which leads to an increase in mitochondrial generated oxidative stress. This, in turn, promotes neurodegeneration. To understand the cellular mechanisms driving neurodegeneration, using several molecular readouts of protein stability in C. elegans, we find that presenilin mutants have widespread defects in proteostasis. Markedly, we demonstrate that these defects are independent of the protease activity of presenilin and that reduction in ER to mitochondrial calcium signaling can significantly prevent the proteostasis defects observed in presenilin mutants. Furthermore, we show that supplementing presenilin mutants with antioxidants suppresses the proteostasis defects. Our findings indicate that defective ER to mitochondria calcium signaling promotes proteostatic collapse in presenilin mutants by increasing oxidative stress.

Keywords:   Caenorhabditis elegans ; Alzheimer's disease; calcium homeostasis; mitochondria; oxidative stress

DOI:  https://doi.org/10.1111/acel.13065
Circ Res. 2019 Nov 11.

Metabolic Remodeling Promotes Cardiac Hypertrophy by Directing Glucose to Aspartate Biosynthesis.

Julia Ritterhoff, Sara Young, Outi Villet, Dan Shao, Fausto Carnevale Neto, Lisa F Bettcher, Yun-Wei A Hsu, Stephen C Kolwicz, Daniel Raftery, Rong Tian.

  Rationale: Hypertrophied hearts switch from mainly using fatty acids (FA) to an increased reliance on glucose for energy production. It has been shown that preserving fatty acid oxidation (FAO) prevents the pathological shift of substrate preference, preserves cardiac function and energetics, and reduces cardiomyocyte (CM) hypertrophy during cardiac stresses. However, it remains elusive if substrate metabolism regulates CM hypertrophy directly or via a secondary effect of improving cardiac energetics. Objective: The goal of this study was to determine the mechanisms of how preservation of FAO prevents the hypertrophic growth of cardiomyocytes. Methods and Results: We cultured adult rat CMs in a medium containing glucose and mixed chain fatty acids and induced pathological hypertrophy by phenylephrine (PE). PE-induced hypertrophy was associated with increased glucose consumption and higher intracellular aspartate levels, resulting in increased synthesis of nucleotides, RNA and proteins. These changes could be prevented by increasing FAO via deletion of acetyl-CoA-carboxylase 2 (ACC2) in PE stimulated CMs and in pressure overload induced cardiac hypertrophy in vivo. Furthermore, aspartate supplementation was sufficient to reverse the anti-hypertrophic effect of ACC2 deletion demonstrating a causal role of elevated aspartate level in CM hypertrophy. 15N and 13C stable isotope tracing revealed that glucose but not glutamine contributed to increased biosynthesis of aspartate which supplied nitrogen for nucleotide synthesis during CM hypertrophy. Conclusions: Our data show that increased glucose consumption is required to support aspartate synthesis that drives the increase of biomass during cardiac hypertrophy. Preservation of FAO prevents the shift of metabolic flux into the anabolic pathway and maintains catabolic metabolism for energy production, thus preventing cardiac hypertrophy and improving myocardial energetics.

Keywords:  aspartate; fatty acid oxidation; nucleotide synthesis; pathological hypertrophy; substrate metabolism

DOI:  https://doi.org/10.1161/CIRCRESAHA.119.315483
Nat Commun. 2019 Nov 13. 10(1): 5151

eIF4A supports an oncogenic translation program in pancreatic ductal adenocarcinoma.

Karina Chan, Francis Robert, Christian Oertlin, Dana Kapeller-Libermann, Daina Avizonis, Johana Gutierrez, Abram Handly-Santana, Mikhail Doubrovin, Julia Park, Christina Schoepfer, Brandon Da Silva, Melissa Yao, Faith Gorton, Junwei Shi, Craig J Thomas, Lauren E Brown, John A Porco, Michael Pollak, Ola Larsson, Jerry Pelletier, Iok In Christine Chio.

Pancreatic ductal adenocarcinoma (PDA) is a lethal malignancy with limited treatment options. Although metabolic reprogramming is a hallmark of many cancers, including PDA, previous attempts to target metabolic changes therapeutically have been stymied by drug toxicity and tumour cell plasticity. Here, we show that PDA cells engage an eIF4F-dependent translation program that supports redox and central carbon metabolism. Inhibition of the eIF4F subunit, eIF4A, using the synthetic rocaglate CR-1-31-B (CR-31) reduced the viability of PDA organoids relative to their normal counterparts. In vivo, CR-31 suppresses tumour growth and extends survival of genetically-engineered murine models of PDA. Surprisingly, inhibition of eIF4A also induces glutamine reductive carboxylation. As a consequence, combined targeting of eIF4A and glutaminase activity more effectively inhibits PDA cell growth both in vitro and in vivo. Overall, our work demonstrates the importance of eIF4A in translational control of pancreatic tumour metabolism and as a therapeutic target against PDA.

DOI: https://doi.org/10.1038/s41467-019-13086-5
Biochem Biophys Res Commun. 2019 Nov 11. pii: S0006-291X(19)32014-5. [Epub ahead of print]

Mitochondrial DNA heteroplasmy rises in substantial nigra of aged PINK1 KO mice.

Jie Li, Chunyan Xue, Qingtao Gao, Jieqiong Tan, Zhengqing Wan.

  Mutations in PINK1 and Parkin result in early-onset autosomal recessive Parkinson's disease (PD). PINK1/Parkin pathway maintain mitochondrial function by mediating the clearance of damaged mitochondria. However, the role of PINK1/Parkin in maintaining the balance of mtDNA heteroplasmy is still unknown. Here, we isolated mitochondrial DNA (mtDNA) from cortex, striatum and substantia nigra of wildtype (WT), PINK1 knockout (PINK1 KO) and Parkin knockout (Parkin KO) mice to analyze mtDNA heteroplasmy induced by PINK1/Parkin deficiency or aging. Our results showed that the Single Nucleotide Variants (SNVs) of late-onset somatic variants mainly increased with aging. Conversely, the early-onset somatic variants exhibited significant increase in the cortex and substantia nigra of PINK1 KO mice than WT mice of the same age. Increased average variant allele frequency was observed in aged PINK1 KO mice and in substantial nigra of aged Parkin KO mice than in WT mice. Cumulative variant allele frequency in the substantia nigra of PINK1 KO mice was significantly higher than that in WT mice, further supporting the pivotal role of PINK1 in mtDNA maintenance. This study presented a new evidence for PINK1 and Parkin in participating in mitochondrial quality control and provided clues for further revealing the role of PINK1 and Parkin in the pathogenesis of PD.

Keywords:  PINK1; Parkin; Parkinson’s disease; mtDNA heteroplasmy

DOI:  https://doi.org/10.1016/j.bbrc.2019.10.112
Trends Mol Med. 2019 Nov 06. pii: S1471-4914(19)30263-1. [Epub ahead of print]

Visualizing Mitochondrial Form and Function within the Cell.

Brian Glancy.

  The specific cellular role of mitochondria is influenced by the surrounding environment because effective mitochondrial function requires the delivery of inputs (e.g., oxygen) and export of products (e.g., signaling molecules) to and from other cellular components, respectively. Recent technological developments in mitochondrial imaging have led to a more precise and comprehensive understanding of the spatial relationships governing the function of this complex organelle, opening a new era of mitochondrial research. Here, I highlight current imaging approaches for visualizing mitochondrial form and function within complex cellular environments. Increasing clarity of mitochondrial behavior within cells will continue to lend mechanistic insights into the role of mitochondria under normal and pathological conditions and point to spatially regulated processes that can be targeted to improve cellular function.

Keywords:  3D electron microscopy; Energy metabolism; super-resolution microscopy; systems-level imaging

DOI:  https://doi.org/10.1016/j.molmed.2019.09.009
Nature. 2019 Nov;575(7782): 296-297

Metabolic vulnerability in tumours illuminated.

Aparna D Rao, Ralph J DeBerardinis.



Keywords:  Cancer; Medical research

DOI:  https://doi.org/10.1038/d41586-019-03239-3
Cell Rep. 2019 Nov 12. pii: S2211-1247(19)31322-1. [Epub ahead of print]29(7): 1778-1788.e4

Misregulation of Drosophila Myc Disrupts Circadian Behavior and Metabolism.

Annie L Hsieh, Xiangzhong Zheng, Zhifeng Yue, Zachary E Stine, Anthony Mancuso, Seth D Rhoades, Rebekah Brooks, Aalim M Weljie, Robert N Eisenman, Amita Sehgal, Chi V Dang.

Drosophila Myc (dMyc) is highly conserved and functions as a transcription factor similar to mammalian Myc. We previously found that oncogenic Myc disrupts the molecular clock in cancer cells. Here, we demonstrate that misregulation of dMyc expression affects Drosophila circadian behavior. dMyc overexpression results in a high percentage of arrhythmic flies, concomitant with increases in the expression of clock genes cyc, tim, cry, and cwo. Conversely, flies with hypomorphic mutations in dMyc exhibit considerable arrhythmia, which can be rescued by loss of dMnt, a suppressor of dMyc activity. Metabolic profiling of fly heads revealed that loss of dMyc and its overexpression alter steady-state metabolite levels and have opposing effects on histidine, the histamine precursor, which is rescued in dMyc mutants by ablation of dMnt and could contribute to effects of dMyc on locomotor behavior. Our results demonstrate a role of dMyc in modulating Drosophila circadian clock, behavior, and metabolism.

DOI: https://doi.org/10.1016/j.celrep.2019.10.022
Int J Mol Sci. 2019 Nov 10. pii: E5622. [Epub ahead of print]20(22):

Knockdown of Pyruvate Kinase M2 Inhibits Cell Proliferation, Metabolism, and Migration in Renal Cell Carcinoma.

Prasanta Dey, Ji Yeon Son, Amit Kundu, Kyeong Seok Kim, Yura Lee, Kyungsil Yoon, Sungpil Yoon, Byung Mu Lee, Ki Taek Nam, Hyung Sik Kim.

  Emerging evidence indicates that the activity of pyruvate kinase M2 (PKM2) isoform is crucial for the survival of tumor cells. However, the molecular mechanism underlying the function of PKM2 in renal cancer is undetermined. Here, we reveal the overexpression of PKM2 in the proximal tubule of renal tumor tissues from 70 cases of patients with renal carcinoma. The functional role of PKM2 in human renal cancer cells following small-interfering RNA-mediated PKM2 knockdown, which retarded 786-O cell growth was examined. Targeting PKM2 affected the protein kinase B (AKT)/mechanistic target of the rapamycin 1 (mTOR) pathway, and downregulated the expression of glycolytic enzymes, including lactate dehydrogenase A and glucose transporter-1, and other downstream signaling key proteins. PKM2 knockdown changed glycolytic metabolism, mitochondrial function, adenosine triphosphate (ATP) level, and intracellular metabolite formation and significantly reduced 786-O cell migration and invasion. Acridine orange and monodansylcadaverine staining, immunocytochemistry, and immunoblotting analyses revealed the induction of autophagy in renal cancer cells following PKM2 knockdown. This is the first study to indicate PKM2/AKT/mTOR as an important regulatory axis mediating the changes in the metabolism of renal cancer cells.

Keywords:  autophagy; invasion; metabolism; migration; pyruvate kinase M2

DOI:  https://doi.org/10.3390/ijms20225622
Cell Metab. 2019 Nov 01. pii: S1550-4131(19)30560-1. [Epub ahead of print]

Microbial Metabolite Signaling Is Required for Systemic Iron Homeostasis.

Nupur K Das, Andrew J Schwartz, Gabrielle Barthel, Naohiro Inohara, Qing Liu, Amanda Sankar, David R Hill, Xiaoya Ma, Olivia Lamberg, Matthew K Schnizlein, Juan L Arqués, Jason R Spence, Gabriel Nunez, Andrew D Patterson, Duxin Sun, Vincent B Young, Yatrik M Shah.

  Iron is a central micronutrient needed by all living organisms. Competition for iron in the intestinal tract is essential for the maintenance of indigenous microbial populations and for host health. How symbiotic relationships between hosts and native microbes persist during times of iron limitation is unclear. Here, we demonstrate that indigenous bacteria possess an iron-dependent mechanism that inhibits host iron transport and storage. Using a high-throughput screen of microbial metabolites, we found that gut microbiota produce metabolites that suppress hypoxia-inducible factor 2α (HIF-2α) a master transcription factor of intestinal iron absorption and increase the iron-storage protein ferritin, resulting in decreased intestinal iron absorption by the host. We identified 1,3-diaminopropane (DAP) and reuterin as inhibitors of HIF-2α via inhibition of heterodimerization. DAP and reuterin effectively ameliorated systemic iron overload. This work provides evidence of intestine-microbiota metabolic crosstalk that is essential for systemic iron homeostasis.

Keywords:  EPAS1; HIF; HIF-2a; anemia; ferritin; hemochromatosis; hypoxia; hypoxia-inducible factor; iron; metabolites; microbiota

DOI:  https://doi.org/10.1016/j.cmet.2019.10.005
J Hepatol. 2019 Nov 11. pii: S0168-8278(19)30667-1. [Epub ahead of print]

Metabolic pathway analyses identify proline biosynthesis pathway as a promoter of liver tumorigenesis.

Zhaobing Ding, Russell E Ericksen, Nathalie Escande-Beillard, Qian Yi Lee, Abigail Loh, Simon Denil, Michael Steckel, Andrea Haegebarth, Timothy Shen Wai Ho, Pierce Chow, Han Chong Toh, Bruno Reversade, Sylvia Gruenewald, Weiping Han.

  BACKGROUND AIM: Under the regulation of various oncogenic pathways, cancer cells undergo adaptive metabolic programming to maintain specific metabolic states that support their uncontrolled proliferation. As it has been difficult to directly and effectively inhibit oncogenic signaling cascades with pharmaceutical compounds, focusing on the downstream metabolic pathways that enable indefinite growth may provide therapeutic opportunities. Thus, we sought to characterize metabolic changes in hepatocellular carcinoma (HCC) development and identify metabolic targets required for tumorigenesis.METHODS: We compared gene expression profiles of Morris Hepatoma (MH3924a) and DEN (Diethylnitrosamine)-induced HCC models to those of liver tissues from normal and rapidly regenerating liver models, and performed gain- and loss-of-function studies of the identified gene targets for their roles in cancer cell proliferation in vitro and in vivo.
RESULTS: The proline biosynthetic PYCR1 (Pyrroline-5-Carboxylate Reductase 1) was identified as a top up-regulated gene in the HCC models. Knockdown (KD) of PYCR1 potently reduced cell proliferation of multiple HCC cell lines in vitro and tumor growth in vivo. Conversely, overexpression of PYCR1 enhanced the proliferation of the HCC cell lines. Importantly, PYCR1 expression was not elevated in the regenerating liver, and KD or overexpression of PYCR1 had no effect on proliferation of non-cancerous cells. Besides PYCR1, we found that additional proline biosynthetic enzymes, such as ALDH18A1, were upregulated in HCC models and also regulated HCC cell proliferation. Clinical data demonstrated that PYCR1 expression was increased in HCC, correlated with tumor grade, and was an independent predictor of clinical outcome.
CONCLUSION: Enhanced expression of proline biosynthetic enzymes promotes HCC cell proliferation. Inhibition of PYCR1 or ALDH18A1 may be a novel therapeutic strategy to target HCC.

Keywords:  cancer; drug discovery; enzyme; hepatocellular carcinoma; metabolism; oncology; therapy

DOI:  https://doi.org/10.1016/j.jhep.2019.10.026
J Clin Med. 2019 Nov 15. pii: E1983. [Epub ahead of print]8(11):

Mitochondrial Dysfunction in Aging and Cancer.

Loredana Moro.

  Aging is a major risk factor for developing cancer, suggesting that these two events may represent two sides of the same coin. It is becoming clear that some mechanisms involved in the aging process are shared with tumorigenesis, through convergent or divergent pathways. Increasing evidence supports a role for mitochondrial dysfunction in promoting aging and in supporting tumorigenesis and cancer progression to a metastatic phenotype. Here, a summary of the current knowledge of three aspects of mitochondrial biology that link mitochondria to aging and cancer is presented. In particular, the focus is on mutations and changes in content of the mitochondrial genome, activation of mitochondria-to-nucleus signaling and the newly discovered mitochondria-telomere communication.

Keywords:  aging; cancer; mitochondria-to-nucleus signaling; mitochondrial DNA

DOI:  https://doi.org/10.3390/jcm8111983
Proc Natl Acad Sci U S A. 2019 Nov 11. pii: 201913919. [Epub ahead of print]

Mutant p53 antagonizes p63/p73-mediated tumor suppression via Notch1.

Jin Zhang, Wenqiang Sun, Xiangmudong Kong, Yanhong Zhang, Hee Jung Yang, Cong Ren, Yuqian Jiang, Mingyi Chen, Xinbin Chen.

  p53 is the most frequently mutated gene in human cancers and mutant p53 has a gain of function (GOF) that promotes tumor progression and therapeutic resistance. One of the major GOF activities of mutant p53 is to suppress 2 other p53 family proteins, p63 and p73. However, the molecular basis is not fully understood. Here, we examined whether mutant p53 antagonizes p63/p73-mediated tumor suppression in vivo by using mutant p53-R270H knockin and TAp63/p73-deficient mouse models. We found that knockin mutant p53-R270H shortened the life span of p73 +/- mice and subjected TAp63 +/- or p73 +/- mice to T lymphoblastic lymphomas (TLBLs). To unravel the underlying mechanism, we showed that mutant p53 formed a complex with Notch1 intracellular domain (NICD) and antagonized p63/p73-mediated repression of HES1 and ECM1. As a result, HES1 and ECM1 were overexpressed in TAp63 +/- ;p53 R270H/- and p73 +/- ;p53 R270H/- TLBLs, suggesting that normal function of HES1 and ECM1 in T cell activation is hyperactivated, leading to lymphomagenesis. Together, our data reveal a previously unappreciated mechanism by which GOF mutant p53 hijacks the p63/p73-regulated transcriptional program via the Notch1 pathway.

Keywords:  GOF; Notch1; T-ALL; mutant p53; p63/p73

DOI:  https://doi.org/10.1073/pnas.1913919116
Redox Biol. 2019 Oct 31. pii: S2213-2317(19)31142-5. [Epub ahead of print]28 101365

Succinate accumulation induces mitochondrial reactive oxygen species generation and promotes status epilepticus in the kainic acid rat model.

Yurong Zhang, Mengdi Zhang, Wei Zhu, Jie Yu, Qiaoyun Wang, Jinjin Zhang, Yaru Cui, Xiaohong Pan, Xue Gao, Hongliu Sun.

  Though succinate accumulation is associated with reactive oxygen species (ROS) production and neuronal injury, which play critical roles in epilepsy, it is unclear whether succinate accumulation contributes to the onset of epilepsy or seizures. We sought to investigate changes in succinate, oxidative stress, and mito-SOX levels, as well as mitophagy and neuronal change, in different status epilepticus (SE) rat models. Our results demonstrate that KA-induced SE was accompanied by increased levels of succinate, oxidative stress, and mito-SOX, as well as mitophagy and neuronal degeneration. The similarly increased levels of succinate, oxidative stress, and mito-SOX were also found in pilocarpine-induced SE. Moreover, the reduction of succinate accumulation by the inhibition of succinate dehydrogenase (SDH), malate/aspartate shuttle (MAS), or purine nucleotide cycle (PNC) served to reduce succinate, oxidative stress, and mito-SOX levels, thereby preventing oxidative stress-related neuronal damage and lessening seizure severity. Interestingly, simulating succinate accumulation with succinic acid dimethyl ester may induce succinate accumulation and increased oxidative stress and mito-SOX levels, as well as behavior and seizures in electroencephalograms similar to those observed in rats exposed to KA. Our results indicate that succinate accumulation may contribute to the increased oxidative stress/mitochondrial ROS levels, neuronal degeneration, and SE induced by KA administration. Furthermore, we found that succinate accumulation was mainly due to the inverse catalysis of SDH from fumarate, which was supplemented by the MAS and PNC pathways. These results reveal new insights into the mechanisms underlying SE and that reducing succinate accumulation may be a clinically useful therapeutic target in SE.

Keywords:  Mitophagy; Neurodegeneration; Reactive oxygen species; Status epilepticus; Succinate

DOI:  https://doi.org/10.1016/j.redox.2019.101365
Proc Natl Acad Sci U S A. 2019 Nov 15. pii: 201911393. [Epub ahead of print]

Combined mTORC1/mTORC2 inhibition blocks growth and induces catastrophic macropinocytosis in cancer cells.

Ritesh K Srivastava, Changzhao Li, Jasim Khan, Nilam Sanjib Banerjee, Louise T Chow, Mohammad Athar.

  The mammalian target of rapamycin (mTOR) pathway, which plays a critical role in regulating cellular growth and metabolism, is aberrantly regulated in the pathogenesis of a variety of neoplasms. Here we demonstrate that dual mTORC1/mTORC2 inhibitors OSI-027 and PP242 cause catastrophic macropinocytosis in rhabdomyosarcoma (RMS) cells and cancers of the skin, breast, lung, and cervix, whereas the effects are much less pronounced in immortalized human keratinocytes. Using RMS as a model, we characterize in detail the mechanism of macropinocytosis induction. Macropinosomes are distinct from endocytic vesicles and autophagosomes in that they are single-membrane bound vacuoles formed by projection, ruffling, and contraction of plasma membranes. They are positive for EEA-1 and LAMP-1 and contain watery fluid but not organelles. The vacuoles then merge and rupture, killing the cells. We confirmed the inhibition of mTORC1/mTORC2 as the underpinning mechanism for macropinocytosis. Exposure to rapamycin, an mTORC1 inhibitor, or mTORC2 knockdown alone had little or reduced effect relative to the combination. We further demonstrate that macropinocytosis depends on MKK4 activated by elevated reactive oxygen species. In a murine xenograft model, OSI-027 reduced RMS tumor growth. Molecular characterization of the residual tumors was consistent with the induction of macropinocytosis. Furthermore, relative to the control xenograft tumors, the residual tumors manifested reduced expression of cell proliferation markers and proteins that drive the epithelial mesenchymal transition. These data indicate a role of mTORC2 in regulating tumor growth by macropinocytosis and suggest that dual inhibitors could help block refractory or recurrent RMS and perhaps other neoplasms and other cancer as well.

Keywords:  EMT; RMS xenografts; mTORC1/2 inhibitors; macropinocytosis; rhabdomyosarcoma cell lines

DOI:  https://doi.org/10.1073/pnas.1911393116
Int J Mol Sci. 2019 Nov 12. pii: E5643. [Epub ahead of print]20(22):

A Brief History of Mitochondrial Pathologies.

Salvatore DiMauro.

  The history of "mitochondrial pathologies", namely genetic pathologies affecting mitochondrial metabolism because of mutations in nuclear DNA-encoded genes for proteins active inside mitochondria or mutations in mitochondrial DNA-encoded genes, began in 1988. In that year, two different groups of researchers discovered, respectively, large-scale single deletions of mitochondrial DNA (mtDNA) in muscle biopsies from patients with "mitochondrial myopathies" and a point mutation in the mtDNA gene for subunit 4 of NADH dehydrogenase (MTND4), associated with maternally inherited Leber's hereditary optic neuropathy (LHON). Henceforth, a novel conceptual "mitochondrial genetics", separate from mendelian genetics, arose, based on three features of mtDNA: (1) polyplasmy; (2) maternal inheritance; and (3) mitotic segregation. Diagnosis of mtDNA-related diseases became possible through genetic analysis and experimental approaches involving histochemical staining of muscle or brain sections, single-fiber polymerase chain reaction (PCR) of mtDNA, and the creation of patient-derived "cybrid" (cytoplasmic hybrid) immortal fibroblast cell lines. The availability of the above-mentioned techniques along with the novel sensitivity of clinicians to such disorders led to the characterization of a constantly growing number of pathologies. Here is traced a brief historical perspective on the discovery of autonomous pathogenic mtDNA mutations and on the related mendelian pathology altering mtDNA integrity.

Keywords:  mendelian and maternal inheritance; mitochondrial pathologies; mtDNA mutations

DOI:  https://doi.org/10.3390/ijms20225643
Nat Commun. 2019 Nov 15. 10(1): 5177

Prolyl hydroxylase substrate adenylosuccinate lyase is an oncogenic driver in triple negative breast cancer.

Giada Zurlo, Xijuan Liu, Mamoru Takada, Cheng Fan, Jeremy M Simon, Travis S Ptacek, Javier Rodriguez, Alex von Kriegsheim, Juan Liu, Jason W Locasale, Adam Robinson, Jing Zhang, Jessica M Holler, Baek Kim, Marie Zikánová, Jörgen Bierau, Ling Xie, Xian Chen, Mingjie Li, Charles M Perou, Qing Zhang.

Protein hydroxylation affects protein stability, activity, and interactome, therefore contributing to various diseases including cancers. However, the transiency of the hydroxylation reaction hinders the identification of hydroxylase substrates. By developing an enzyme-substrate trapping strategy coupled with TAP-TAG or orthogonal GST- purification followed by mass spectrometry, we identify adenylosuccinate lyase (ADSL) as an EglN2 hydroxylase substrate in triple negative breast cancer (TNBC). ADSL expression is higher in TNBC than other breast cancer subtypes or normal breast tissues. ADSL knockout impairs TNBC cell proliferation and invasiveness in vitro and in vivo. An integrated transcriptomics and metabolomics analysis reveals that ADSL activates the oncogenic cMYC pathway by regulating cMYC protein level via a mechanism requiring ADSL proline 24 hydroxylation. Hydroxylation-proficient ADSL, by affecting adenosine levels, represses the expression of the long non-coding RNA MIR22HG, thus upregulating cMYC protein level. Our findings highlight the role of ADSL hydroxylation in controlling cMYC and TNBC tumorigenesis.

DOI: https://doi.org/10.1038/s41467-019-13168-4
Cell Rep. 2019 Nov 12. pii: S2211-1247(19)31335-X. [Epub ahead of print]29(7): 1767-1777.e8

Integrated Analyses of Microbiome and Longitudinal Metabolome Data Reveal Microbial-Host Interactions on Sulfur Metabolism in Parkinson's Disease.

Johannes Hertel, Amy C Harms, Almut Heinken, Federico Baldini, Cyrille C Thinnes, Enrico Glaab, Daniel A Vasco, Maik Pietzner, Isobel D Stewart, Nicholas J Wareham, Claudia Langenberg, Claudia Trenkwalder, Rejko Krüger, Thomas Hankemeier, Ronan M T Fleming, Brit Mollenhauer, Ines Thiele.

  Parkinson's disease (PD) exhibits systemic effects on the human metabolism, with emerging roles for the gut microbiome. Here, we integrate longitudinal metabolome data from 30 drug-naive, de novo PD patients and 30 matched controls with constraint-based modeling of gut microbial communities derived from an independent, drug-naive PD cohort, and prospective data from the general population. Our key results are (1) longitudinal trajectory of metabolites associated with the interconversion of methionine and cysteine via cystathionine differed between PD patients and controls; (2) dopaminergic medication showed strong lipidomic signatures; (3) taurine-conjugated bile acids correlated with the severity of motor symptoms, while low levels of sulfated taurolithocholate were associated with PD incidence in the general population; and (4) computational modeling predicted changes in sulfur metabolism, driven by A. muciniphila and B. wadsworthia, which is consistent with the changed metabolome. The multi-omics integration reveals PD-specific patterns in microbial-host sulfur co-metabolism that may contribute to PD severity.

Keywords:  Parkinson's disease; bile acid metabolism; metabolic modeling; metabolism; metabolomics; metagenomics; microbiome; neurodegenerative disease; taurine metabolism; transsulfuration pathway

DOI:  https://doi.org/10.1016/j.celrep.2019.10.035
Semin Cancer Biol. 2019 Nov 07. pii: S1044-579X(19)30167-1. [Epub ahead of print]

At a Glance: A History of Autophagy and Cancer.

Xin Wen, Daniel J Klionsky.

  Since the first discovery of the lysosome and the definition of autophagy by Christian de Duve more than 60 years ago, research on autophagy, a process targeting cytoplasmic materials for lysosomal degradation and recycling, has expanded dramatically. This research has extended our understanding of the basic mechanism of autophagy as well as its role in pathophysiology. Autophagy deficiency has been reported to be involved in numerous diseases, among which cancer has been extensively studied, in part because autophagy appears to play a dual role, depending on the stage of tumorigenesis. In this review, we will briefly revisit the intriguing history of autophagy and cancer, underscoring the importance of harnessing this pathway for the benefit of human health.

Keywords:  ATG; autophagy; cancer; lysosome; stress; tumor

DOI:  https://doi.org/10.1016/j.semcancer.2019.11.005
Sci Rep. 2019 Nov 12. 9(1): 16617

Metabolomic Changes of Human Proximal Tubular Cell Line in High Glucose Environment.

Pascal Zhongping Wei, Winston Wing-Shing Fung, Jack Kit-Chung Ng, Ka-Bik Lai, Cathy Choi-Wan Luk, Kai Ming Chow, Philip Kam-Tao Li, Cheuk Chun Szeto.

Hyperglycemia causes mitochondrial damage renal tubular cells, which contribute to the progression of diabetic kidney disease. However, the metabolic aberration of renal tubular cells in an hyperglycemic milieu has not been fully elucidated. In this study, human proximal renal tubular cell line (HK-2 cell) are incubated in glucose and mannitol at 5 mM or 25 mM. Cellular metabolome was determined by capillary electrophoresis time of flight mass spectrometer (CE-TOF/MS) and capillary electrophoresis-triple quadrupole mass spectrometry (CE-QqQMS). A total of 116 metabolites were quantified. Principal component analysis (PCA) revealed excellent clustering of metabolomic changes for different treatment conditions, and exposure to glucose at 5 and 25 mM lead to distinct metabolomic profiles as compared to samples treated with serum-free medium or mannitol as osmotic control. Hierarchical clustering analysis showed a number of characteristic changes in metabolic profile following exposure to 5 mM or 25 mM glucose. Notably, lactate-to-pyruvate ratio was significantly increased, while cellular levels of citric acid, α-ketoglutaric acid (i.e. 2-oxoglutaric acid), and fumaric acid were significantly reduced after exposure to glucose at 25 mM but not 5 mM. Moreover, cellular levels of reduced glutathione and total glutathione were significantly decreased, and S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH) ratio was significantly increased after exposure to glucose 25 mM but not 5 mM. We conclude that in response to high glucose, HK-2 cells characteristic metabolomic changes, including increase in lactate-to-pyruvate ratio, reduction in Krebs cycle metabolites, reduction in glutathione antioxidant activity, and increase in cellular methylation potential. Our results may shed light on the pathogenesis of diabetic kidney disease, but the expression of glucose metabolism-related protein and enzyme activity in HK-2 cells after hyperglycemia condition need to be confirmed by further studies.

DOI: https://doi.org/10.1038/s41598-019-53214-1
Nature. 2019 Nov 13.

Marine Proteobacteria metabolize glycolate via the β-hydroxyaspartate cycle.

Lennart Schada von Borzyskowski, Francesca Severi, Karen Krüger, Lucas Hermann, Alexandre Gilardet, Felix Sippel, Bianca Pommerenke, Peter Claus, Niña Socorro Cortina, Timo Glatter, Stefan Zauner, Jan Zarzycki, Bernhard M Fuchs, Erhard Bremer, Uwe G Maier, Rudolf I Amann, Tobias J Erb.

One of the most abundant sources of organic carbon in the ocean is glycolate, the secretion of which by marine phytoplankton results in an estimated annual flux of one petagram of glycolate in marine environments1. Although it is generally accepted that glycolate is oxidized to glyoxylate by marine bacteria2-4, the further fate of this C2 metabolite is not well understood. Here we show that ubiquitous marine Proteobacteria are able to assimilate glyoxylate via the β-hydroxyaspartate cycle (BHAC) that was originally proposed 56 years ago5. We elucidate the biochemistry of the BHAC and describe the structure of its key enzymes, including a previously unknown primary imine reductase. Overall, the BHAC enables the direct production of oxaloacetate from glyoxylate through only four enzymatic steps, representing-to our knowledge-the most efficient glyoxylate assimilation route described to date. Analysis of marine metagenomes shows that the BHAC is globally distributed and on average 20-fold more abundant than the glycerate pathway, the only other known pathway for net glyoxylate assimilation. In a field study of a phytoplankton bloom, we show that glycolate is present in high nanomolar concentrations and taken up by prokaryotes at rates that allow a full turnover of the glycolate pool within one week. During the bloom, genes that encode BHAC key enzymes are present in up to 1.5% of the bacterial community and actively transcribed, supporting the role of the BHAC in glycolate assimilation and suggesting a previously undescribed trophic interaction between autotrophic phytoplankton and heterotrophic bacterioplankton.

DOI: https://doi.org/10.1038/s41586-019-1748-4
JCI Insight. 2019 Nov 14. pii: 124816. [Epub ahead of print]4(22):

Xanthine oxidase inhibitor ameliorates postischemic renal injury in mice by promoting resynthesis of adenine nucleotides.

Kentaro Fujii, Akiko Kubo, Kazutoshi Miyashita, Masaaki Sato, Aika Hagiwara, Hiroyuki Inoue, Masaki Ryuzaki, Masanori Tamaki, Takako Hishiki, Noriyo Hayakawa, Yasuaki Kabe, Hiroshi Itoh, Makoto Suematsu.

  Although oxidative stress plays central roles in postischemic renal injury, region-specific alterations in energy and redox metabolism caused by short-duration ischemia remain unknown. Imaging mass spectrometry enabled us to reveal spatial heterogeneity of energy and redox metabolites in the postischemic murine kidney. After 10-minute ischemia and 24-hour reperfusion (10mIR), in the cortex and outer stripes of the outer medulla, ATP substantially decreased, but not in the inner stripes of the outer medulla and inner medulla. 10mIR caused renal injury with elevation of fractional excretion of sodium, although histological damage by oxidative stress was limited. Ischemia-induced NADH elevation in the cortex indicated prolonged production of reactive oxygen species by xanthine oxidase (XOD). However, consumption of reduced glutathione after reperfusion suggested the amelioration of oxidative stress. An XOD inhibitor, febuxostat, which blocks the degradation pathway of adenine nucleotides, promoted ATP recovery and exerted renoprotective effects in the postischemic kidney. Because effects of febuxostat were canceled by silencing of the hypoxanthine phosphoribosyl transferase 1 gene in cultured tubular cells, mechanisms for the renoprotective effects appear to involve the purine salvage pathway, which uses hypoxanthine to resynthesize adenine nucleotides, including ATP. These findings suggest a novel therapeutic approach for acute ischemia/reperfusion renal injury with febuxostat through salvaging high-energy adenine nucleotides.

Keywords:  Drug therapy; Nephrology; Therapeutics

DOI:  https://doi.org/10.1172/jci.insight.124816
Annu Rev Physiol. 2019 Nov 15.

The Acidic Tumor Microenvironment as a Driver of Cancer.

Ebbe Boedtkjer, Stine F Pedersen.

Acidic metabolic waste products accumulate in the tumor microenvironment because of high metabolic activity and insufficient perfusion. In tumors, the acidity of the interstitial space and the relatively well-maintained intracellular pH influence cancer and stromal cell function, their mutual interplay, and their interactions with the extracellular matrix. Tumor pH is spatially and temporally heterogeneous, and the fitness advantage of cancer cells adapted to extracellular acidity is likely particularly evident when they encounter less acidic tumor regions, for instance, during invasion. Through complex effects on genetic stability, epigenetics, cellular metabolism, proliferation, and survival, the compartmentalized pH microenvironment favors cancer development. Cellular selection exacerbates the malignant phenotype, which is further enhanced by acid-induced cell motility, extracellular matrix degradation, attenuated immune responses, and modified cellular and intercellular signaling. In this review, we discuss how the acidity of the tumor microenvironment influences each stage in cancer development, from dysplasia to full-blown metastatic disease. Expected final online publication date for the Annual Review of Physiology, Volume 82 is February 10, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

DOI: https://doi.org/10.1146/annurev-physiol-021119-034627