Publications by authors named "Marie-Clotilde Alves-Guerra"

26 Publications

  • Page 1 of 1

Mitochondrial Aurora kinase A induces mitophagy by interacting with MAP1LC3 and Prohibitin 2.

Life Sci Alliance 2021 06 5;4(6). Epub 2021 Apr 5.

University of Rennes, Centre National de la Recherche Scientifique (CNRS), (IGDR) Genetics and Development Institute of Rennes, Unité Mixte de Recherche (UMR) 6290, Rennes, France.

Epithelial and haematologic tumours often show the overexpression of the serine/threonine kinase AURKA. Recently, AURKA was shown to localise at mitochondria, where it regulates mitochondrial dynamics and ATP production. Here we define the molecular mechanisms of AURKA in regulating mitochondrial turnover by mitophagy. AURKA triggers the degradation of Inner Mitochondrial Membrane/matrix proteins by interacting with core components of the autophagy pathway. On the inner mitochondrial membrane, the kinase forms a tripartite complex with MAP1LC3 and the mitophagy receptor PHB2, which triggers mitophagy in a PARK2/Parkin-independent manner. The formation of the tripartite complex is induced by the phosphorylation of PHB2 on Ser39, which is required for MAP1LC3 to interact with PHB2. Last, treatment with the PHB2 ligand xanthohumol blocks AURKA-induced mitophagy by destabilising the tripartite complex and restores normal ATP production levels. Altogether, these data provide evidence for a role of AURKA in promoting mitophagy through the interaction with PHB2 and MAP1LC3. This work paves the way to the use of function-specific pharmacological inhibitors to counteract the effects of the overexpression of AURKA in cancer.
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http://dx.doi.org/10.26508/lsa.202000806DOI Listing
June 2021

The role of uncoupling protein 2 in macrophages and its impact on obesity-induced adipose tissue inflammation and insulin resistance.

J Biol Chem 2020 12;295(51):17535-17548

Nutrition, Metabolism, and Genomics Group, Division of Human Nutrition and Health, Wageningen University, Wageningen, The Netherlands; Department of Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. Electronic address:

The development of a chronic, low-grade inflammation originating from adipose tissue in obese subjects is widely recognized to induce insulin resistance, leading to the development of type 2 diabetes. The adipose tissue microenvironment drives specific metabolic reprogramming of adipose tissue macrophages, contributing to the induction of tissue inflammation. Uncoupling protein 2 (UCP2), a mitochondrial anion carrier, is thought to separately modulate inflammatory and metabolic processes in macrophages and is up-regulated in macrophages in the context of obesity and diabetes. Here, we investigate the role of UCP2 in macrophage activation in the context of obesity-induced adipose tissue inflammation and insulin resistance. Using a myeloid-specific knockout of UCP2 (Ucp2), we found that UCP2 deficiency significantly increases glycolysis and oxidative respiration, both unstimulated and after inflammatory conditions. Strikingly, fatty acid loading abolished the metabolic differences between Ucp2 macrophages and their floxed controls. Furthermore, Ucp2 macrophages show attenuated pro-inflammatory responses toward Toll-like receptor-2 and -4 stimulation. To test the relevance of macrophage-specific Ucp2 deletion in vivo, Ucp2 and Ucp2 mice were rendered obese and insulin resistant through high-fat feeding. Although no differences in adipose tissue inflammation or insulin resistance was found between the two genotypes, adipose tissue macrophages isolated from diet-induced obese Ucp2 mice showed decreased TNFα secretion after ex vivo lipopolysaccharide stimulation compared with their Ucp2 littermates. Together, these results demonstrate that although UCP2 regulates both metabolism and the inflammatory response of macrophages, its activity is not crucial in shaping macrophage activation in the adipose tissue during obesity-induced insulin resistance.
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http://dx.doi.org/10.1074/jbc.RA120.014868DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7762953PMC
December 2020

UCP2 Deficiency Increases Colon Tumorigenesis by Promoting Lipid Synthesis and Depleting NADPH for Antioxidant Defenses.

Cell Rep 2019 08;28(9):2306-2316.e5

INSERM U1016, Institut Cochin, 75014 Paris, France; CNRS UMR 8104, 75014 Paris, France; Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France. Electronic address:

Colorectal cancer (CRC) is associated with metabolic and redox perturbation. The mitochondrial transporter uncoupling protein 2 (UCP2) controls cell proliferation in vitro through the modulation of cellular metabolism, but the underlying mechanism in tumors in vivo remains unexplored. Using murine intestinal cancer models and CRC patient samples, we find higher UCP2 protein levels in tumors compared to their non-tumoral counterparts. We reveal the tumor-suppressive role of UCP2 as its deletion enhances colon and small intestinal tumorigenesis in AOM/DSS-treated and Apc mice, respectively, and correlates with poor survival in the latter model. Mechanistically, UCP2 loss increases levels of oxidized glutathione and proteins in tumors. UCP2 deficiency alters glycolytic pathways while promoting phospholipid synthesis, thereby limiting the availability of NADPH for buffering oxidative stress. We show that UCP2 loss renders colon cells more prone to malignant transformation through metabolic reprogramming and perturbation of redox homeostasis and could favor worse outcomes in CRC.
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http://dx.doi.org/10.1016/j.celrep.2019.07.097DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6718829PMC
August 2019

Glioblastoma Stem- Cells, Metabolic Strategy to Kill a Challenging Target.

Front Oncol 2019 6;9:118. Epub 2019 Mar 6.

CRCINA, INSERM CNRS, Université de Nantes, Nantes, France.

Over the years, substantial evidence has definitively confirmed the existence of cancer stem- cells within tumors such as Glioblastoma (GBM). The importance of Glioblastoma stem- cells (GSCs) in tumor progression and relapse clearly highlights that cancer eradication requires killing of GSCs that are intrinsically resistant to conventional therapies as well as eradication of the non-GSCs cells since GSCs emergence relies on a dynamic process. The past decade of research highlights that metabolism is a significant player in tumor progression and actually might orchestrate it. The growing interest in cancer metabolism reprogrammation can lead to innovative approaches exploiting metabolic vulnerabilities of cancer cells. These approaches are challenging since they require overcoming the compensatory and adaptive responses of GSCs. In this review, we will summarize the current knowledge on GSCs with a particular focus on their metabolic complexity. We will also discuss potential approaches targeting GSCs metabolism to potentially improve clinical care.
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http://dx.doi.org/10.3389/fonc.2019.00118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6415584PMC
March 2019

Aurora kinase A localises to mitochondria to control organelle dynamics and energy production.

Elife 2018 08 2;7. Epub 2018 Aug 2.

CNRS, UMR 6290, Rennes, France.

Many epithelial cancers show cell cycle dysfunction tightly correlated with the overexpression of the serine/threonine kinase Aurora A (AURKA). Its role in mitotic progression has been extensively characterised, and evidence for new AURKA functions emerges. Here, we reveal that AURKA is located and imported in mitochondria in several human cancer cell lines. Mitochondrial AURKA impacts on two organelle functions: mitochondrial dynamics and energy production. When AURKA is expressed at endogenous levels during interphase, it induces mitochondrial fragmentation independently from RALA. Conversely, AURKA enhances mitochondrial fusion and ATP production when it is over-expressed. We demonstrate that AURKA directly regulates mitochondrial functions and that AURKA over-expression promotes metabolic reprogramming by increasing mitochondrial interconnectivity. Our work paves the way to anti-cancer therapeutics based on the simultaneous targeting of mitochondrial functions and AURKA inhibition.
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http://dx.doi.org/10.7554/eLife.38111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140714PMC
August 2018

The histone demethylase Phf2 acts as a molecular checkpoint to prevent NAFLD progression during obesity.

Nat Commun 2018 05 29;9(1):2092. Epub 2018 May 29.

INSERM, U1016, Institut Cochin, Paris, France.

Aberrant histone methylation profile is reported to correlate with the development and progression of NAFLD during obesity. However, the identification of specific epigenetic modifiers involved in this process remains poorly understood. Here, we identify the histone demethylase Plant Homeodomain Finger 2 (Phf2) as a new transcriptional co-activator of the transcription factor Carbohydrate Responsive Element Binding Protein (ChREBP). By specifically erasing H3K9me2 methyl-marks on the promoter of ChREBP-regulated genes, Phf2 facilitates incorporation of metabolic precursors into mono-unsaturated fatty acids, leading to hepatosteatosis development in the absence of inflammation and insulin resistance. Moreover, the Phf2-mediated activation of the transcription factor NF-E2-related factor 2 (Nrf2) further reroutes glucose fluxes toward the pentose phosphate pathway and glutathione biosynthesis, protecting the liver from oxidative stress and fibrogenesis in response to diet-induced obesity. Overall, our findings establish a downstream epigenetic checkpoint, whereby Phf2, through facilitating H3K9me2 demethylation at specific gene promoters, protects liver from the pathogenesis progression of NAFLD.
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http://dx.doi.org/10.1038/s41467-018-04361-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5974278PMC
May 2018

β-catenin-activated hepatocellular carcinomas are addicted to fatty acids.

Gut 2019 02 12;68(2):322-334. Epub 2018 Apr 12.

INSERM, U1016, Institut Cochin, Paris, France.

Objectives: -mutated hepatocellular carcinomas (HCCs) constitute a major part of human HCC and are largely inaccessible to target therapy. Yet, little is known about the metabolic reprogramming induced by β-catenin oncogenic activation in the liver. We aimed to decipher such reprogramming and assess whether it may represent a new avenue for targeted therapy of -mutated HCC.

Design: We used mice with hepatocyte-specific oncogenic activation of β-catenin to evaluate metabolic reprogramming using metabolic fluxes on tumourous explants and primary hepatocytes. We assess the role of in knock-out mice and analysed the consequences of fatty acid oxidation (FAO) using etomoxir. We explored the expression of the FAO pathway in an annotated human HCC dataset.

Results: β-catenin-activated HCC were not glycolytic but intensively oxidised fatty acids. We found that is a β-catenin target involved in FAO metabolic reprograming. Deletion of was sufficient to block the initiation and progression of β-catenin-dependent HCC development. FAO was also enriched in human -mutated HCC, under the control of the transcription factor PPARα.

Conclusions: FAO induced by β-catenin oncogenic activation in the liver is the driving force of the β-catenin-induced HCC. Inhibiting FAO by genetic and pharmacological approaches blocks HCC development, showing that inhibition of FAO is a suitable therapeutic approach for -mutated HCC.
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http://dx.doi.org/10.1136/gutjnl-2017-315448DOI Listing
February 2019

The mitochondrial uncoupling protein 2 gene is causal for the spontaneous polycystic liver diseases in mice.

Mitochondrion 2018 09 14;42:50-53. Epub 2017 Nov 14.

Lübeck Institute of Experimental Dermatology, University of Lübeck, Germany; College of Medicine, Sharjah Institute for Medical Research, University of Sharjah, AE-27272, United Arab Emirates. Electronic address:

Polycystic liver diseases (PCLDs) are autosomal dominant disorders. To date, 3 genes are known to be associated with the disease, SEC63 and PRKCSH and LRP5. Here, we report that mice deficient in the mitochondrial uncoupling protein 2 gene (Ucp2) spontaneously developed PCLDs when they were over 12months old. Macroscopical observation, blood chemistry as well as histopathological analysis demonstrated the PCLDs found in Ucp2 mice were very similar to the findings in human PCLDs. This is the first report describing the gene encoding mitochondrial protein is causative for PCLDs. UCP2 may be a biomarker of the PCLDs in humans.
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http://dx.doi.org/10.1016/j.mito.2017.10.011DOI Listing
September 2018

Mitochondrial Protein UCP2 Controls Pancreas Development.

Diabetes 2018 01 27;67(1):78-84. Epub 2017 Oct 27.

INSERM, U1016, Institut Cochin, Paris, France

The mitochondrial carrier uncoupling protein (UCP) 2 belongs to the family of the UCPs. Despite its name, it is now accepted that UCP2 is rather a metabolite transporter than a UCP. UCP2 can regulate oxidative stress and/or energetic metabolism. In rodents, UCP2 is involved in the control of α- and β-cell mass as well as insulin and glucagon secretion. Our aim was to determine whether the effects of UCP2 observed on β-cell mass have an embryonic origin. Thus, we used knockout mice. We found an increased size of the pancreas in fetuses at embryonic day 16.5, associated with a higher number of α- and β-cells. This phenotype was caused by an increase of PDX1 progenitor cells. Perinatally, an increase in the proliferation of endocrine cells also participates in their expansion. Next, we analyzed the oxidative stress in the pancreata. We quantified an increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2) in the mutant, suggesting an increased production of reactive oxygen species (ROS). Phosphorylation of AKT, an ROS target, was also activated in the pancreata. Finally, administration of the antioxidant -acetyl-l-cysteine to pregnant mice alleviated the effect of knocking out UCP2 on pancreas development. Together, these data demonstrate that UCP2 controls pancreas development through the ROS-AKT signaling pathway.
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http://dx.doi.org/10.2337/db17-0118DOI Listing
January 2018

Efficient Mitochondrial Glutamine Targeting Prevails Over Glioblastoma Metabolic Plasticity.

Clin Cancer Res 2017 Oct 18;23(20):6292-6304. Epub 2017 Jul 18.

CRCINA, INSERM, Université de Nantes, France.

Glioblastoma (GBM) is the most common and malignant form of primary human brain tumor in adults, with an average survival at diagnosis of 18 months. Metabolism is a new attractive therapeutic target in cancer; however, little is known about metabolic heterogeneity and plasticity within GBM tumors. We therefore aimed to investigate metabolic phenotyping of primary cultures in the context of molecular tumor heterogeneity to provide a proof of concept for personalized metabolic targeting of GBM. We have analyzed extensively several primary GBM cultures using transcriptomics, metabolic phenotyping assays, and mitochondrial respirometry. We found that metabolic phenotyping clearly identifies 2 clusters, GLN and GLN, mainly based on metabolic plasticity and glutamine (GLN) utilization. Inhibition of glutamine metabolism slows the and growth of GLN GBM cultures despite metabolic adaptation to nutrient availability, in particular by increasing pyruvate shuttling into mitochondria. Furthermore, phenotypic and molecular analyses show that highly proliferative GLN cultures are CD133 and display a mesenchymal signature in contrast to CD133 GLN GBM cells. Our results show that metabolic phenotyping identified an essential metabolic pathway in a GBM cell subtype, and provide a proof of concept for theranostic metabolic targeting. .
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http://dx.doi.org/10.1158/1078-0432.CCR-16-3102DOI Listing
October 2017

Ionizing radiation induces long-term senescence in endothelial cells through mitochondrial respiratory complex II dysfunction and superoxide generation.

Free Radic Biol Med 2017 07 19;108:750-759. Epub 2017 Apr 19.

CRCINA, INSERM, CNRS, Université de Nantes, Nantes, France; Institut de Cancérologie de l'Ouest, Saint-Herblain F-44800, France. Electronic address:

Ionizing radiation causes oxidative stress, leading to acute and late cellular responses. We previously demonstrated that irradiation of non-proliferating endothelial cells, as observed in normal tissues, induces early apoptosis, which can be inhibited by pretreatment with Sphingosine-1-Phosphate. We now propose to better characterize the long-term radiation response of endothelial cells by studying the molecular pathways associated with senescence and its link with acute apoptosis. First, senescence was validated in irradiated quiescent microvascular HMVEC-L in a dose- and time-dependent manner by SA β-galactosidase staining, p16 and p21 expression, pro-inflammatory IL-8 secretion and DNA damage response activation. This premature aging was induced independently of Sphingosine 1-Phosphate treatment, supporting its non-connection with acute IR-induced apoptosis. Then, senescence under these conditions showed persistent activation of p53 pathway and mitochondrial dysfunctions, characterized by O2·- generation, inhibition of respiratory complex II activity and over-expression of SOD2 and GPX1 detoxification enzymes. Senescence was significantly inhibited by treatment with pifithrin-α, a p53 inhibitor, or by MnTBAP, a superoxide dismutase mimetic, validating those molecular actors in IR-induced endothelial cell aging. However, MnTBAP, but not pifithrin-α, was able to limit superoxide generation and to rescue the respiratory complex II activity. Furthermore, MnTBAP was not modulating p53 up-regulation, suggesting that IR-induced senescence in quiescent endothelial cells is provided by at least 2 different pathways dependent of the mitochondrial oxidative stress response and the p53 activation. Further characterization of the actors involved in the respiratory complex II dysfunction will open new pharmacological strategies to modulate late radiation toxicity.
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http://dx.doi.org/10.1016/j.freeradbiomed.2017.04.019DOI Listing
July 2017

Muscle expression of a malonyl-CoA-insensitive carnitine palmitoyltransferase-1 protects mice against high-fat/high-sucrose diet-induced insulin resistance.

Am J Physiol Endocrinol Metab 2016 09 9;311(3):E649-60. Epub 2016 Aug 9.

Institut National de la Santé et de la Recherche Médicale, U1016, Institut Cochin, Paris, France; Centre National de la Recherche Scientifique, UMR8104, Paris, France; Université Paris Descartes, Sorbonne Paris Cité, Paris, France;

Impaired skeletal muscle mitochondrial fatty acid oxidation (mFAO) has been implicated in the etiology of insulin resistance. Carnitine palmitoyltransferase-1 (CPT1) is a key regulatory enzyme of mFAO whose activity is inhibited by malonyl-CoA, a lipogenic intermediate. Whereas increasing CPT1 activity in vitro has been shown to exert a protective effect against lipid-induced insulin resistance in skeletal muscle cells, only a few studies have addressed this issue in vivo. We thus examined whether a direct modulation of muscle CPT1/malonyl-CoA partnership is detrimental or beneficial for insulin sensitivity in the context of diet-induced obesity. By using a Cre-LoxP recombination approach, we generated mice with skeletal muscle-specific and inducible expression of a mutated CPT1 form (CPT1mt) that is active but insensitive to malonyl-CoA inhibition. When fed control chow, homozygous CPT1mt transgenic (dbTg) mice exhibited decreased CPT1 sensitivity to malonyl-CoA inhibition in isolated muscle mitochondria, which was sufficient to substantially increase ex vivo muscle mFAO capacity and whole body fatty acid utilization in vivo. Moreover, dbTg mice were less prone to high-fat/high-sucrose (HFHS) diet-induced insulin resistance and muscle lipotoxicity despite similar body weight gain, adiposity, and muscle malonyl-CoA content. Interestingly, these CPT1mt-protective effects in dbTg-HFHS mice were associated with preserved muscle insulin signaling, increased muscle glycogen content, and upregulation of key genes involved in muscle glucose metabolism. These beneficial effects of muscle CPT1mt expression suggest that a direct modulation of the malonyl-CoA/CPT1 partnership in skeletal muscle could represent a potential strategy to prevent obesity-induced insulin resistance.
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http://dx.doi.org/10.1152/ajpendo.00020.2016DOI Listing
September 2016

UCPs, at the interface between bioenergetics and metabolism.

Biochim Biophys Acta 2016 10 16;1863(10):2443-56. Epub 2016 Apr 16.

Inserm U1016, Institut Cochin, 75014 Paris Cedex, France; CNRS UMR 8104, 75014 Paris Cedex, France; Université Paris Descartes UMRS1016, 75014 Paris Cedex, France; Hôpital Necker-Enfants Malades AP-HP, Paris, France.

The first member of the uncoupling protein (UCP) family, brown adipose tissue uncoupling protein 1 (UCP1), was identified in 1976. Twenty years later, two closely related proteins, UCP2 and UCP3, were described in mammals. Homologs of these proteins exist in other organisms, including plants. Uncoupling refers to a deterioration of energy conservation between substrate oxidation and ADP phosphorylation. Complete energy conservation loss would be fatal but fine-tuning can be beneficial for processes such as thermogenesis, redox control, and prevention of mitochondrial ROS release. The coupled/uncoupled state of mitochondria is related to the permeability of the inner membrane and the proton transport mediated by activated UCPs underlies the uncoupling activity of these proteins. Proton transport by UCP1 is activated by fatty acids and this ensures thermogenesis. In vivo in absence of this activation UCP1 remains inhibited with no transport activity. A similar situation now seems unlikely for UCP2 and UCP3 and while activation of their proton transport has been described its physiological relevance remains uncertain and their influence can be envisaged as a result of another transport pathway that takes place in the absence of activation. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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http://dx.doi.org/10.1016/j.bbamcr.2016.04.013DOI Listing
October 2016

UCP2 induces metabolic reprogramming to inhibit proliferation of cancer cells.

Mol Cell Oncol 2015 Jan-Mar;2(1):e975024. Epub 2014 Dec 1.

Inserm, U1016; Institut Cochin; Paris, 75014, France; CNRS; UMR 8104; Paris, France; Université Paris Descartes; Sorbonne Paris Cité; Paris, France.

Invalidation of uncoupling protein 2 (Ucp2) increases glucose utilization and proliferation in normal cells. We recently reported that cancer cells that overexpress UCP2 become less tumorigenic while switching their metabolism from glycolysis to oxidative phosphorylation. UCP2 appears to be a key regulator of cellular metabolism with a relevant function against tumorigenesis.
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http://dx.doi.org/10.4161/23723556.2014.975024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4905249PMC
June 2016

NACK is an integral component of the Notch transcriptional activation complex and is critical for development and tumorigenesis.

Cancer Res 2014 Sep 18;74(17):4741-51. Epub 2014 Jul 18.

Molecular Oncology Program, Division of Surgical Oncology, Dewitt Daughtry Family Department of Surgery, and Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, Florida.

The Notch signaling pathway governs many distinct cellular processes by regulating transcriptional programs. The transcriptional response initiated by Notch is highly cell context dependent, indicating that multiple factors influence Notch target gene selection and activity. However, the mechanism by which Notch drives target gene transcription is not well understood. Herein, we identify and characterize a novel Notch-interacting protein, Notch activation complex kinase (NACK), which acts as a Notch transcriptional coactivator. We show that NACK associates with the Notch transcriptional activation complex on DNA, mediates Notch transcriptional activity, and is required for Notch-mediated tumorigenesis. We demonstrate that Notch1 and NACK are coexpressed during mouse development and that homozygous loss of NACK is embryonic lethal. Finally, we show that NACK is also a Notch target gene, establishing a feed-forward loop. Thus, our data indicate that NACK is a key component of the Notch transcriptional complex and is an essential regulator of Notch-mediated tumorigenesis and development.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-1547DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4154994PMC
September 2014

Mitochondrial retrograde signaling mediated by UCP2 inhibits cancer cell proliferation and tumorigenesis.

Cancer Res 2014 Jul 22;74(14):3971-82. Epub 2014 May 22.

Authors' Affiliations: Inserm, U1016, Institut Cochin; CNRS, UMR 8104; Université Paris Descartes, Sorbonne Paris Cité, Paris;

Cancer cells tilt their energy production away from oxidative phosphorylation (OXPHOS) toward glycolysis during malignant progression, even when aerobic metabolism is available. Reversing this phenomenon, known as the Warburg effect, may offer a generalized anticancer strategy. In this study, we show that overexpression of the mitochondrial membrane transport protein UCP2 in cancer cells is sufficient to restore a balance toward oxidative phosphorylation and to repress malignant phenotypes. Altered expression of glycolytic and oxidative enzymes mediated the effects of this metabolic shift. Notably, UCP2 overexpression increased signaling from the master energy-regulating kinase, adenosine monophosphate-activated protein kinase, while downregulating expression of hypoxia-induced factor. In support of recent new evidence about UCP2 function, we found that UCP2 did not function in this setting as a membrane potential uncoupling protein, but instead acted to control routing of mitochondria substrates. Taken together, our results define a strategy to reorient mitochondrial function in cancer cells toward OXPHOS that restricts their malignant phenotype.
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http://dx.doi.org/10.1158/0008-5472.CAN-13-3383DOI Listing
July 2014

Analysis of uncoupling protein 2-deficient mice upon anaesthesia and sedation revealed a role for UCP2 in locomotion.

PLoS One 2012 10;7(8):e41846. Epub 2012 Aug 10.

INSERM U1016, CNRS UMR8104, Institut Cochin, Paris, France.

General anaesthesia is associated with hypothermia, oxidative stress, and immune depression. Uncoupling Protein (UCP2) is a member of the mitochondrial carrier family present in many organs including the spleen, the lung and the brain. A role of UCP2 in the activation of the inflammatory/immune cells, in the secretion of hormones, and in the excitability of neurons by regulating the production of reactive oxygen species has been discussed. Because of the side effects of anaesthesia listed above, we aimed to question the expression and the function of UCP2 during anaesthesia. Induction of anaesthesia with ketamine (20 mg/kg) or isoflurane (3.6%) and induction of sedation with the α2 adrenergic receptor agonist medetomidine (0.2 mg/kg) stimulated infiltration of immune cells in the lung and increased UCP2 protein content in the lung, in both immune and non-immune cells. UCP2 content in the lung inversely correlated with body temperature decrease induced by medetomidine treatment. Challenge of the Ucp2(-/-) mice with isoflurane and medetomidine revealed an earlier behavioral recovery phenotype. Transponder analysis of body temperature and activity showed no difference between Ucp2(-/-) and control mice in basal conditions. However, upon an acute decrease of body temperature induced by medetomidine, Ucp2(-/-) mice exhibited increased locomotion activity. Together, these results show that UCP2 is rapidly mobilized during anaesthesia and sedation in immune cells, and suggest a role of UCP2 in locomotion.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0041846PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3416814PMC
March 2013

Deletion of UCP2 in iNOS deficient mice reduces the severity of the disease during experimental autoimmune encephalomyelitis.

PLoS One 2011 8;6(8):e22841. Epub 2011 Aug 8.

Institut Cochin INSERM U1016, CNRS UMR8104, Faculté Paris Descartes, Paris, France.

Uncoupling protein 2 is a member of the mitochondrial anion carrier family that is widely expressed in neurons and the immune cells of humans. Deletion of Ucp2 gene in mice pre-activates the immune system leading to higher resistance toward infection and to an increased susceptibility to develop chronic inflammatory diseases as previously exemplified with the Experimental Autoimmune Encephalomyelitis (EAE), a mouse model for multiple sclerosis. Given that oxidative stress is enhanced in Ucp2-/- mice and that nitric oxide (NO) also plays a critical function in redox balance and in chronic inflammation, we generated mice deficient for both Ucp2 and iNos genes and submitted them to EAE. Mice lacking iNos gene exhibited the highest clinical score (3.4+/-0.5 p<0.05). Surprisingly, mice deficient for both genes developed milder disease with reduced immune cell infiltration, cytokines and ROS production as compared to iNos-/- mice.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0022841PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3152556PMC
February 2012

Assembly of a Notch transcriptional activation complex requires multimerization.

Mol Cell Biol 2011 Apr 18;31(7):1396-408. Epub 2011 Jan 18.

Molecular Oncology Program, Division of Surgical Oncology, Dewitt Daughtry Family of Surgery and Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, 1600 NW 10th Avenue, Miami, FL 33136, USA.

Notch transmembrane receptors direct essential cellular processes, such as proliferation and differentiation, through direct cell-to-cell interactions. Inappropriate release of the intracellular domain of Notch (N(ICD)) from the plasma membrane results in the accumulation of deregulated nuclear N(ICD) that has been linked to human cancers, notably T-cell acute lymphoblastic leukemia (T-ALL). Nuclear N(ICD) forms a transcriptional activation complex by interacting with the coactivator protein Mastermind-like 1 and the DNA binding protein CSL (for CBF-1/Suppressor of Hairless/Lag-1) to regulate target gene expression. Although it is well understood that N(ICD) forms a transcriptional activation complex, little is known about how the complex is assembled. In this study, we demonstrate that N(ICD) multimerizes and that these multimers function as precursors for the stepwise assembly of the Notch activation complex. Importantly, we demonstrate that the assembly is mediated by N(ICD) multimers interacting with Skip and Mastermind. These interactions form a preactivation complex that is then resolved by CSL to form the Notch transcriptional activation complex on DNA.
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http://dx.doi.org/10.1128/MCB.00360-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3135300PMC
April 2011

Mastermind-like 1 Is a specific coactivator of beta-catenin transcription activation and is essential for colon carcinoma cell survival.

Cancer Res 2007 Sep;67(18):8690-8

Molecular and Cellular Oncogenesis, The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.

Misregulation of the Wnt signaling pathway has been linked to many human cancers including colon carcinoma and melanoma. The primary mediator of the oncogenic effects of the Wnt signaling pathway is beta-catenin. Accumulation of nuclear beta-catenin and transcription activation of lymphoid enhancer factor 1 (LEF1)/T-cell factor (TCF) target genes underlie the oncogenic activity. However, the mechanism of beta-catenin-mediated transcriptional activation remains poorly understood. In this study, we identified Mastermind-like 1 (Maml1), which is thought to be a specific coactivator for the Notch pathway, as a coactivator for beta-catenin. We found that Maml1 participates in the Wnt signaling by modulating the beta-catenin/TCF activity. We show in vivo that Maml1 is recruited by beta-catenin on the cyclin D1 and c-Myc promoters. Importantly, we show that Maml1 functions in the Wnt/beta-catenin pathway independently of Notch signaling. Finally, we show that the knockdown of Mastermind-like family proteins in colonic carcinoma cells results in cell death by affecting beta-catenin-induced expression of cyclin D1 and c-Myc. This is the first demonstration of a role for the Mastermind-like family in another signaling pathway and that the knockdown of Mastermind-like family function leads to tumor cell death.
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http://dx.doi.org/10.1158/0008-5472.CAN-07-1720DOI Listing
September 2007

Resistance to cerebral ischemic injury in UCP2 knockout mice: evidence for a role of UCP2 as a regulator of mitochondrial glutathione levels.

J Neurochem 2004 Jun;89(5):1283-92

Department of Psychiatry, University Hospitals Geneva, Geneva, Switzerland.

Uncoupling protein 2 (UCP2) is suggested to be a regulator of reactive oxygen species production in mitochondria. We performed a detailed study of brain injury, including regional and cellular distribution of UCP2 mRNA, as well as measures of oxidative stress markers following permanent middle cerebral artery occlusion in UCP2 knockout (KO) and wild-type (WT) mice. Three days post ischemia, there was a massive induction of UCP2 mRNA confined to microglia in the peri-infarct area of WT mice. KO mice were less sensitive to ischemia as assessed by reduced brain infarct size, decreased densities of deoxyuridine triphosphate nick end-labelling (TUNEL)-labelled cells in the peri-infact area and lower levels of lipid peroxidation compared with WT mice. This resistance may be related to the substantial increase of basal manganese superoxide dismutase levels in neurons of KO mice. Importantly, we found a specific decrease of mitochondrial glutathione (GSH) levels in UCP2 expressing microglia of WT, but not in KO mice after ischemia. This specific association between UCP2 and mitochondrial GSH levels regulation was further confirmed using lipopolysaccharide models of peripheral inflammation, and in purified peritoneal macrophages. Moreover, our data imply that UCP2 is not directly involved in the regulation of ROS production but acts by regulating mitochondrial GSH levels in microglia.
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http://dx.doi.org/10.1111/j.1471-4159.2004.02432.xDOI Listing
June 2004

The biology of mitochondrial uncoupling proteins.

Diabetes 2004 Feb;53 Suppl 1:S130-5

Centre National de la Recherche Scientifique, Unité Propre de Recherche 9078, Faculté de Médecine and Institut de Recherches Necker-Enfants Malades (IRNEM), Paris, France.

Uncoupling proteins (UCPs) are mitochondrial transporters present in the inner membrane of mitochondria. They are found in all mammals and in plants. They belong to the family of anion mitochondrial carriers including adenine nucleotide transporters. The term "uncoupling protein" was originally used for UCP1, which is uniquely present in mitochondria of brown adipocytes, the thermogenic cells that maintain body temperature in small rodents. In these cells, UCP1 acts as a proton carrier activated by free fatty acids and creates a shunt between complexes of the respiratory chain and ATP synthase. Activation of UCP1 enhances respiration, and the uncoupling process results in a futile cycle and dissipation of oxidation energy as heat. UCP2 is ubiquitous and highly expressed in the lymphoid system, macrophages, and pancreatic islets. UCP3 is mainly expressed in skeletal muscles. In comparison to the established uncoupling and thermogenic activities of UCP1, UCP2 and UCP3 appear to be involved in the limitation of free radical levels in cells rather than in physiological uncoupling and thermogenesis. Moreover, UCP2 is a regulator of insulin secretion and UCP3 is involved in fatty acid metabolism.
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http://dx.doi.org/10.2337/diabetes.53.2007.s130DOI Listing
February 2004

Uncoupling protein 2, but not uncoupling protein 1, is expressed in the female mouse reproductive tract.

J Biol Chem 2003 Nov 26;278(46):45843-7. Epub 2003 Aug 26.

CNRS, Unité Propre de Recherche 9078, Faculté de Médecine Necker-Enfants malades, 156 rue de Vaugirard, 75730 Paris Cedex 15, France.

Uncoupling proteins (UCPs) are transporters of the inner mitochondrial membrane. Whereas UCP1 is uniquely present in brown adipose tissue where it uncouples respiration from ATP synthesis and activates respiration and heat production, UCP2 is present in numerous tissues, and its exact function remains to be clarified. Two sets of data provided the rationale for this study: (i) the intriguing report that UCP1 is present in uterus of mice (Nibbelink, M., Moulin, K., Arnaud, E., Duval, C., Penicaud, L., and Casteilla, L. (2001) J. Biol. Chem. 276, 47291-47295); and (ii) an observation that Ucp2(-/-) female mice (homozygous matings) have smaller litters compared with Ucp2(+/+) animals (S. Rousset and A.-M. Cassard-Doulcier, unpublished observations). These data prompted us to examine the expression of UCP1 and UCP2 in the reproductive tract of female mice. Using wild type, Ucp1(-/-) mice, and Ucp2(-/-) mice, we were unable to detect UCP1 in uterus of mice with appropriate antibodies, and we conclude that the signal assigned to UCP1 by others was neither UCP1 nor UCP2. Using a polyclonal antibody against UCP2 and tissues from Ucp2(-/-) mice as controls, UCP2 was detected in ovary, oviduct, and uterus. Expression of Ucp2 mRNA was also observed in ovary and uterus using in situ hybridization analysis. Bone marrow transplantation experiments revealed that the UCP2 signal of the ovary was restricted to ovarian cells. UCP2 level in ovary decreased during follicular growth and increased during the pre-ovulatory period, during which aspects of an inflammatory process are known to exist. Because UCP2 down-regulates reactive oxygen species, a role in the regulation of inflammatory events linked to the preparation of ovulation is suggested.
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http://dx.doi.org/10.1074/jbc.M306980200DOI Listing
November 2003

Bone marrow transplantation reveals the in vivo expression of the mitochondrial uncoupling protein 2 in immune and nonimmune cells during inflammation.

J Biol Chem 2003 Oct 7;278(43):42307-12. Epub 2003 Aug 7.

CNRS UPR 9078, Faculté de Médecine Necker-Enfants Malades, 156 rue de Vaugirard, 75730 Paris Cedex 15, France.

The mitochondrial uncoupling protein 2 (UCP2) is expressed in spleen, lung, intestine, white adipose tissue, and immune cells. Bone marrow transplantation in mice was used to assess the contribution of immune cells to the expression of UCP2 in basal condition and during inflammation. Immune cells accounted for the total amount of UCP2 expression in the spleen, one-third of its expression in the lung, and did not participate in its expression in the intestine. LPS injection stimulated UCP2 expression in lung, spleen, and intestine in both immune and non-immune cells. Successive injections of LPS and dexamethasone or N-acetyl-cysteine prevented the induction of UCP2 in all three tissues, suggesting that oxygen free radical generation plays a role in UCP2 regulation. Finally, both previous studies and our data show that there is down-regulation of UCP2 in immune cells during their activation in the early stages of the LPS response followed by an up-regulation in UCP2 during the later stages to protect all cells against oxidative stress.
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http://dx.doi.org/10.1074/jbc.M306951200DOI Listing
October 2003

Pancreatic beta-cell lipotoxicity induced by overexpression of hormone-sensitive lipase.

Diabetes 2003 Aug;52(8):2057-65

Department of Cell and Molecular Biology, Lund University, Lund, Sweden.

Lipid perturbations associated with triglyceride overstorage in beta-cells impair insulin secretion, a process termed lipotoxicity. To assess the role of hormone-sensitive lipase, which is expressed and enzymatically active in beta-cells, in the development of lipotoxicity, we generated transgenic mice overexpressing hormone-sensitive lipase specifically in beta-cells. Transgenic mice developed glucose intolerance and severely blunted glucose-stimulated insulin secretion when challenged with a high-fat diet. As expected, both lipase activity and forskolin-stimulated lipolysis was increased in transgenic compared with wild-type islets. This was reflected in significantly lower triglycerides levels in transgenic compared with wild-type islets in mice receiving the high-fat diet, whereas no difference in islet triglycerides was found between the two genotypes under low-fat diet conditions. Our results highlight the importance of mobilization of the islet triglyceride pool in the development of beta-cell lipotoxicity. We propose that hormone-sensitive lipase is involved in mediating beta-cell lipotoxicity by providing ligands for peroxisome proliferator-activated receptors and other lipid-activated transcription factors, which in turn alter the expression of critical genes. One such gene might be uncoupling protein-2, which was found to be upregulated in transgenic islets, a change that was accompanied by decreased ATP levels.
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http://dx.doi.org/10.2337/diabetes.52.8.2057DOI Listing
August 2003

No evidence for a basal, retinoic, or superoxide-induced uncoupling activity of the uncoupling protein 2 present in spleen or lung mitochondria.

J Biol Chem 2002 Jul 14;277(29):26268-75. Epub 2002 May 14.

Ceremod CNRS UPR9078, 9 rue Jules Hetzel, Meudon 92190, France.

The phenotypes observed in mice whose uncoupling protein (Ucp2) gene had been invalidated by homologous recombination (Ucp2(-/-) mice) are consistent with an increase in mitochondrial membrane potential in macrophages and pancreatic beta cells. This could support an uncoupling (proton transport) activity of UCP2 in the inner mitochondrial membrane in vivo. We used mitochondria from lung or spleen, the two organs expressing the highest level of UCP2, to compare the proton leak of the mitochondrial inner membrane of wild-type and Ucp2(-/-) mice. No difference was observed under basal conditions. Previous reports have concluded that retinoic acid and superoxide activate proton transport by UCP2. Spleen mitochondria showed a higher sensitivity to retinoic acid than liver mitochondria, but this was not caused by UCP2. In contrast with a previous report, superoxide failed to increase the proton leak rate in kidney mitochondria, where no UCP2 expression was detected, and also in spleen mitochondria, which does not support stimulation of UCP2 uncoupling activity by superoxide. Finally, no increase in the ATP/ADP ratio was observed in spleen or lung of Ucp2(-/-) mice. Therefore, no evidence could be gathered for the uncoupling activity of the UCP2 present in spleen or lung mitochondria. Although this may be explained by difficulties with isolated mitochondria, it may also indicate that UCP2 has another physiological significance in spleen and lung.
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http://dx.doi.org/10.1074/jbc.M202535200DOI Listing
July 2002