bims-camemi Biomed News
on Mitochondrial metabolism in cancer
Issue of 2020‒11‒01
forty-two papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit


  1. Nat Metab. 2020 Oct 26.
    Zhang Y, Taufalele PV, Cochran JD, Robillard-Frayne I, Marx JM, Soto J, Rauckhorst AJ, Tayyari F, Pewa AD, Gray LR, Teesch LM, Puchalska P, Funari TR, McGlauflin R, Zimmerman K, Kutschke WJ, Cassier T, Hitchcock S, Lin K, Kato KM, Stueve JL, Haff L, Weiss RM, Cox JE, Rutter J, Taylor EB, Crawford PA, Lewandowski ED, Des Rosiers C, Abel ED.
      In addition to fatty acids, glucose and lactate are important myocardial substrates under physiologic and stress conditions. They are metabolized to pyruvate, which enters mitochondria via the mitochondrial pyruvate carrier (MPC) for citric acid cycle metabolism. In the present study, we show that MPC-mediated mitochondrial pyruvate utilization is essential for the partitioning of glucose-derived cytosolic metabolic intermediates, which modulate myocardial stress adaptation. Mice with cardiomyocyte-restricted deletion of subunit 1 of MPC (cMPC1-/-) developed age-dependent pathologic cardiac hypertrophy, transitioning to a dilated cardiomyopathy and premature death. Hypertrophied hearts accumulated lactate, pyruvate and glycogen, and displayed increased protein O-linked N-acetylglucosamine, which was prevented by increasing availability of non-glucose substrates in vivo by a ketogenic diet (KD) or a high-fat diet, which reversed the structural, metabolic and functional remodelling of non-stressed cMPC1-/- hearts. Although concurrent short-term KDs did not rescue cMPC1-/- hearts from rapid decompensation and early mortality after pressure overload, 3 weeks of a KD before transverse aortic constriction was sufficient to rescue this phenotype. Together, our results highlight the centrality of pyruvate metabolism to myocardial metabolism and function.
    DOI:  https://doi.org/10.1038/s42255-020-00288-1
  2. Cancer Res. 2020 Oct 28. pii: canres.1998.2020. [Epub ahead of print]
    Xiao Y, Rabien A, Buschow R, Amstislavskiy V, Busch J, Kilic E, Villegas SL, Timmermann B, Schütte M, Mielke T, Yaspo ML, Jung K, Meierhofer D.
      Chromophobe renal cell carcinoma (chRCC) accounts for approximately 5% of all renal cancers and around 30% of chRCC cases have mutations in TP53. ChRCC is poorly supported by microvessels and has markably lower glucose uptake than clear cell RCC (ccRCC) and papillary RCC (pRCC). Currently, the metabolic status and mechanisms by which this tumor adapts to nutrient-poor microenvironments remain to be investigated. In this study, we performed proteome and metabolome profiling of chRCC tumors and adjacent kidney tissues and identified major metabolic alterations in chRCC tumors, including the classical Warburg effect, the downregulation of gluconeogenesis and amino acid metabolism, and the upregulation of protein degradation and endocytosis. ChRCC cells depended on extracellular macromolecules as an amino acid source by activating endocytosis to sustain cell proliferation and survival. Inhibition of the PLCG2/IP3/Ca2+/PKC pathway significantly impaired the activation of endocytosis for amino acids uptakes into chRCC cells. In chRCC, whole-exome sequencing revealed that TP53 mutations were not related to expression of PLCG2 and activation of endocytosis. Our study provides novel perspectives on metabolic rewiring in chRCC and identifies the PLCG2/IP3/Ca2+/PKC axis as a potential therapeutic target in chRCC patients.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-1998
  3. Front Physiol. 2020 ;11 554904
    Gherardi G, Monticelli H, Rizzuto R, Mammucari C.
      Recently, the role of mitochondrial activity in high-energy demand organs and in the orchestration of whole-body metabolism has received renewed attention. In mitochondria, pyruvate oxidation, ensured by efficient mitochondrial pyruvate entry and matrix dehydrogenases activity, generates acetyl CoA that enters the TCA cycle. TCA cycle activity, in turn, provides reducing equivalents and electrons that feed the electron transport chain eventually producing ATP. Mitochondrial Ca2+ uptake plays an essential role in the control of aerobic metabolism. Mitochondrial Ca2+ accumulation stimulates aerobic metabolism by inducing the activity of three TCA cycle dehydrogenases. In detail, matrix Ca2+ indirectly modulates pyruvate dehydrogenase via pyruvate dehydrogenase phosphatase 1, and directly activates isocitrate and α-ketoglutarate dehydrogenases. Here, we will discuss the contribution of mitochondrial Ca2+ uptake to the metabolic homeostasis of organs involved in systemic metabolism, including liver, skeletal muscle, and adipose tissue. We will also tackle the role of mitochondrial Ca2+ uptake in the heart, a high-energy consuming organ whose function strictly depends on appropriate Ca2+ signaling.
    Keywords:  aerobic metabolism; mitochondria; mitochondrial calcium uniporter (MCU); mitochondrial calcium uptake; systemic metabolism
    DOI:  https://doi.org/10.3389/fphys.2020.554904
  4. J Biol Chem. 2020 Oct 30. pii: jbc.REV120.011202. [Epub ahead of print]
    Basu U, Bostwick AM, Das K, Dittenhafer-Reed KE, Patel SS.
      Mitochondria are specialized compartments that produce requisite ATP to fuel cellular functions and serve as centers of metabolite processing, cellular signaling, and apoptosis. To accomplish these roles, mitochondria rely on the genetic information in their small genome (mitochondrial DNA) and the nucleus. A growing appreciation for mitochondria's role in a myriad of human diseases, including inherited genetic disorders, degenerative diseases, inflammation, and cancer, has fueled the study of biochemical mechanisms that control mitochondrial function. The mitochondrial transcriptional machinery is different from nuclear machinery. The in vitro reconstituted transcriptional complexes of Saccharomyces cerevisiae (yeast) and humans, aided with high-resolution structures and biochemical characterizations, have provided a deeper understanding of the mechanism and regulation of mitochondrial DNA transcription. In this review, we will discuss recent advances in the structure and mechanism of mitochondrial transcription initiation. We will follow up with recent discoveries and formative findings regarding the regulatory events that control mitochondrial DNA transcription, focusing on those involved in crosstalk between the mitochondria and nucleus.
    Keywords:  DNA transcription; RNA polymerase; enzyme structure; human mitochondrial RNA polymerase; mitochondrial DNA (mtDNA); mitochondrial DNA transcription; mitochondrial gene regulation; transcription regulation; yeast mitochondrial RNA polymerase
    DOI:  https://doi.org/10.1074/jbc.REV120.011202
  5. Cell Physiol Biochem. 2020 Oct 30. 54(6): 1101-1114
    Rodríguez-Graciani KM, Chapa-Dubocq XR, MacMillan-Crow LA, Javadov S.
      BACKGROUND/AIMS: Structural and functional alterations in mitochondria, particularly, the inner mitochondrial membrane (IMM) plays a critical role in mitochondria-mediated cell death in response to cardiac ischemia-reperfusion (IR) injury. The integrity of IMM can be affected by two potential intra-mitochondrial factors: i) mitochondrial matrix swelling, and ii) proteolytic cleavage of the long optic atrophy type 1 (L-OPA1), an IMM-localized dynamin-like GTPase engaged in the regulation of structural organization and integrity of the mitochondrial cristae. However, the relationship between these two factors in response to oxidative stress remains unclear. Here, we elucidated the effects of cardiac IR injury on L-OPA1 cleavage and OMA1 activity.METHODS: Langendorff-mode perfused isolated rat hearts were subjected to 25-min of global ischemia followed by 90-min reperfusion in the presence or absence of XJB-5-131 (XJB, a mitochondria-targeting ROS scavenger) and sanglifehrin A (SfA, a permeability transition pore inhibitor).
    RESULTS: XJB in combination with SfA increased post-ischemic recovery of cardiac function and reduced mitochondrial ROS production at 30- and 60-min reperfusion and affected mitochondrial swelling. L-OPA1 levels were reduced in IR hearts; however, neither XJB, SfA, and their combination prevented IR-induced reduction of L-OPA1 cleavage. Likewise, IR increased the OMA1 enzymatic activity, which remained unchanged in the presence of XJB and/or SfA.
    CONCLUSION: IR-induced cardiac and mitochondrial dysfunctions are associated with OMA1 activation and L-OPA1 cleavage. However, XJB, SfA, and their combination do not prevent these changes despite improved heart and mitochondria function, thus, suggesting that different mechanisms can be implicated in L-OPA1 processing in response to cardiac IR injury.
    Keywords:  Cardiac ischemia-reperfusion; Mitochondria; Optic atrophy type 1 protein; Reactive oxygen species; Mitochondrial swelling; Permeability transition pores
    DOI:  https://doi.org/10.33594/000000303
  6. Nature. 2020 Oct 28.
    Shang M, Cappellesso F, Amorim R, Serneels J, Virga F, Eelen G, Carobbio S, Rincon MY, Maechler P, De Bock K, Ho PC, Sandri M, Ghesquière B, Carmeliet P, Di Matteo M, Berardi E, Mazzone M.
      Muscle regeneration is sustained by infiltrating macrophages and the consequent activation of satellite cells1-4. Macrophages and satellite cells communicate in different ways1-5, but their metabolic interplay has not been investigated. Here we show, in a mouse model, that muscle injuries and ageing are characterized by intra-tissue restrictions of glutamine. Low levels of glutamine endow macrophages with the metabolic ability to secrete glutamine via enhanced glutamine synthetase (GS) activity, at the expense of glutamine oxidation mediated by glutamate dehydrogenase 1 (GLUD1). Glud1-knockout macrophages display constitutively high GS activity, which prevents glutamine shortages. The uptake of macrophage-derived glutamine by satellite cells through the glutamine transporter SLC1A5 activates mTOR and promotes the proliferation and differentiation of satellite cells. Consequently, macrophage-specific deletion or pharmacological inhibition of GLUD1 improves muscle regeneration and functional recovery in response to acute injury, ischaemia or ageing. Conversely, SLC1A5 blockade in satellite cells or GS inactivation in macrophages negatively affects satellite cell functions and muscle regeneration. These results highlight the metabolic crosstalk between satellite cells and macrophages, in which macrophage-derived glutamine sustains the functions of satellite cells. Thus, the targeting of GLUD1 may offer therapeutic opportunities for the regeneration of injured or aged muscles.
    DOI:  https://doi.org/10.1038/s41586-020-2857-9
  7. iScience. 2020 Oct 23. 23(10): 101638
    Knatko EV, Tatham MH, Zhang Y, Castro C, Higgins M, Dayalan Naidu S, Leonardi C, de la Vega L, Honda T, Griffin JL, Hay RT, Dinkova-Kostova AT.
      Transcription factor nuclear factor erythroid 2 p45-related factor 2 (Nrf2) and its main negative regulator, Kelch-like ECH-associated protein 1 (Keap1), are at the interface between redox and intermediary metabolism, allowing adaptation and survival under conditions of oxidative, inflammatory, and metabolic stress. Nrf2 is the principal determinant of redox homeostasis, and contributes to mitochondrial function and integrity and cellular bioenergetics. Using proteomics and lipidomics, we show that genetic downregulation of Keap1 in mice, and the consequent Nrf2 activation to pharmacologically relevant levels, leads to upregulation of carboxylesterase 1 (Ces1) and acyl-CoA oxidase 2 (Acox2), decreases triglyceride levels, and alters the lipidome. This is accompanied by downregulation of hepatic ATP-citrate lyase (Acly) and decreased levels of acetyl-CoA, a trigger for autophagy. These findings suggest that downregulation of Keap1 confers features of a fasted metabolic state, which is an important consideration in the drug development of Keap1-targeting pharmacologic Nrf2 activators.
    Keywords:  Human Metabolism; Molecular Biology; Omics
    DOI:  https://doi.org/10.1016/j.isci.2020.101638
  8. J Inherit Metab Dis. 2020 Oct 25.
    Stewart JB.
      Mitochondrial disorders make up a large class of heritable diseases that cause a broad array of different human pathologies. They can affect many different organ systems, or display very specific tissue presentation, and can lead to illness either in childhood or later in life. While the over 1200 genes encoded in the nuclear DNA play an important role in human mitochondrial disease, it has been known for over 30 years that mutations of the mitochondria's own small, multicopy DNA chromosome (mtDNA) can lead to heritable human diseases. Unfortunately, animal mtDNA has resisted transgenic and directed genome editing technologies until quite recently. As such, animal models to aid in our understanding of these diseases, and to explore pre-clinical therapeutic research have been quite rare. This review will discuss the unusual properties of animal mitochondria that have hindered the generation of animal models. It will also discuss the existing mammalian models of human mtDNA disease, describe the methods employed in their generation, and will discuss recent advances in the targeting of DNA-manipulating enzymes to the mitochondria and how these may be employed to generate new models. This article is protected by copyright. All rights reserved.
    Keywords:  Animal models; heteroplasmy; homoplasmy; mitochondrial DNA; mitochondrial disease
    DOI:  https://doi.org/10.1002/jimd.12324
  9. FEBS Lett. 2020 Oct 30.
    Valpadashi A, Callegari S, Linden A, Neumann P, Ficner R, Urlaub H, Deckers M, Rehling P.
      The majority of mitochondrial proteins are nuclear encoded and imported into mitochondria as precursor proteins via dedicated translocases. The Translocase of the Inner Membrane 22 (TIM22) is a multisubunit molecular machine specialised for the translocation of hydrophobic, multi-transmembrane-spanning proteins with internal targeting signals into the inner mitochondrial membrane. Here, we undertook a crosslinking-mass spectrometry (XL-MS) approach to determine the molecular arrangement of subunits of the human TIM22 complex. Crosslinking of the isolated TIM22 complex using the BS3 crosslinker resulted in the broad generation of crosslinks across the majority of TIM22 components, including the small TIM chaperone complex. The crosslinking data uncovered several unexpected features, opening new avenues for a deeper investigation into the steps required for TIM22-mediated translocation in humans.
    Keywords:  Carrier translocase; TIM22; crosslinking-mass spectrometry; mitochondria; protein translocation
    DOI:  https://doi.org/10.1002/1873-3468.13978
  10. BMC Biol. 2020 Oct 29. 18(1): 156
    Kreimendahl S, Schwichtenberg J, Günnewig K, Brandherm L, Rassow J.
      BACKGROUND: The uptake of newly synthesized nuclear-encoded mitochondrial proteins from the cytosol is mediated by a complex of mitochondrial outer membrane proteins comprising a central pore-forming component and associated receptor proteins. Distinct fractions of proteins initially bind to the receptor proteins and are subsequently transferred to the pore-forming component for import. The aim of this study was the identification of the decisive elements of this machinery that determine the specific selection of the proteins that should be imported.RESULTS: We identified the essential internal targeting signal of the members of the mitochondrial metabolite carrier proteins, the largest protein family of the mitochondria, and we investigated the specific recognition of this signal by the protein import machinery at the mitochondrial outer surface. We found that the outer membrane import receptors facilitated the uptake of these proteins, and we identified the corresponding binding site, marked by cysteine C141 in the receptor protein Tom70. However, in tests both in vivo and in vitro, the import receptors were neither necessary nor sufficient for specific recognition of the targeting signals. Although these signals are unrelated to the amino-terminal presequences that mediate the targeting of other mitochondrial preproteins, they were found to resemble presequences in their strict dependence on a content of positively charged residues as a prerequisite of interactions with the import pore.
    CONCLUSIONS: The general import pore of the mitochondrial outer membrane appears to represent not only the central channel of protein translocation but also to form the decisive general selectivity filter in the uptake of the newly synthesized mitochondrial proteins.
    Keywords:  Chaperones; Ion channel; Mitochondria; Protein targeting; Selectivity filter; TOM complex; Tom40; Tom70
    DOI:  https://doi.org/10.1186/s12915-020-00888-z
  11. Curr Opin Physiol. 2020 Oct;17 197-206
    Carvalho EJ, Stathopulos PB, Madesh M.
      Mitochondrial calcium (mCa2+) homeostasis also plays a key role in the buffering of cytosolic calcium (cCa2+) and calcium transported into the mitochondrial matrix regulates cellular metabolism, migration and cell fate decisions. Recent work has highlighted the importance of mCa2+ homeostasis in regulating cellular function. The discovery of the mCa2+ uptake complex has shed new light on the role of mCa2+ dynamics in cytoskeletal remodeling, mitochondrial shape and motility in cellular dynamics. Here we attempt to decipher the vast landscape of calcium regulatory effects of the mitochondria, the underlying mechanisms and the dynamics that control cellular function.
    DOI:  https://doi.org/10.1016/j.cophys.2020.08.010
  12. Int J Mol Sci. 2020 Oct 26. pii: E7941. [Epub ahead of print]21(21):
    Dong L, Gopalan V, Holland O, Neuzil J.
      Mitochondria are essential cellular organelles, controlling multiple signalling pathways critical for cell survival and cell death. Increasing evidence suggests that mitochondrial metabolism and functions are indispensable in tumorigenesis and cancer progression, rendering mitochondria and mitochondrial functions as plausible targets for anti-cancer therapeutics. In this review, we summarised the major strategies of selective targeting of mitochondria and their functions to combat cancer, including targeting mitochondrial metabolism, the electron transport chain and tricarboxylic acid cycle, mitochondrial redox signalling pathways, and ROS homeostasis. We highlight that delivering anti-cancer drugs into mitochondria exhibits enormous potential for future cancer therapeutic strategies, with a great advantage of potentially overcoming drug resistance. Mitocans, exemplified by mitochondrially targeted vitamin E succinate and tamoxifen (MitoTam), selectively target cancer cell mitochondria and efficiently kill multiple types of cancer cells by disrupting mitochondrial function, with MitoTam currently undergoing a clinical trial.
    Keywords:  anti-cancer strategy; drug delivery; mitocans; mitochondrial targeting
    DOI:  https://doi.org/10.3390/ijms21217941
  13. Int J Mol Sci. 2020 Oct 27. pii: E7994. [Epub ahead of print]21(21):
    Juszczak F, Caron N, Mathew AV, Declèves AE.
      Chronic kidney disease (CKD) is prevalent in 9.1% of the global population and is a significant public health problem associated with increased morbidity and mortality. CKD is associated with highly prevalent physiological and metabolic disturbances such as hypertension, obesity, insulin resistance, cardiovascular disease, and aging, which are also risk factors for CKD pathogenesis and progression. Podocytes and proximal tubular cells of the kidney strongly express AMP-activated protein kinase (AMPK). AMPK plays essential roles in glucose and lipid metabolism, cell survival, growth, and inflammation. Thus, metabolic disease-induced renal diseases like obesity-related and diabetic chronic kidney disease demonstrate dysregulated AMPK in the kidney. Activating AMPK ameliorates the pathological and phenotypical features of both diseases. As a metabolic sensor, AMPK regulates active tubular transport and helps renal cells to survive low energy states. AMPK also exerts a key role in mitochondrial homeostasis and is known to regulate autophagy in mammalian cells. While the nutrient-sensing role of AMPK is critical in determining the fate of renal cells, the role of AMPK in kidney autophagy and mitochondrial quality control leading to pathology in metabolic disease-related CKD is not very clear and needs further investigation. This review highlights the crucial role of AMPK in renal cell dysfunction associated with metabolic diseases and aims to expand therapeutic strategies by understanding the molecular and cellular processes underlying CKD.
    Keywords:  AMPK; autophagy; chronic kidney disease; diabetes; lipid metabolism; lipotoxicity; mitochondrial homeostasis; obesity; proximal tubule
    DOI:  https://doi.org/10.3390/ijms21217994
  14. Cell Rep. 2020 Oct 27. pii: S2211-1247(20)31310-3. [Epub ahead of print]33(4): 108321
    Ingaramo MC, Sánchez JA, Perrimon N, Dekanty A.
      The tumor suppressor p53 regulates multiple metabolic pathways at the cellular level. However, its role in the context of a whole animal response to metabolic stress is poorly understood. Using Drosophila, we show that AMP-activated protein kinase (AMPK)-dependent Dmp53 activation is critical for sensing nutrient stress, maintaining metabolic homeostasis, and extending organismal survival. Under both nutrient deprivation and high-sugar diet, Dmp53 activation in the fat body represses expression of the Drosophila Leptin analog, Unpaired-2 (Upd2), which remotely controls Dilp2 secretion in insulin-producing cells. In starved Dmp53-depleted animals, elevated Upd2 expression in adipose cells and activation of Upd2 receptor Domeless in the brain result in sustained Dilp2 circulating levels and impaired autophagy induction at a systemic level, thereby reducing nutrient stress survival. These findings demonstrate an essential role for the AMPK-Dmp53 axis in nutrient stress responses and expand the concept that adipose tissue acts as a sensing organ that orchestrates systemic adaptation to nutrient status.
    Keywords:  AMPK; Drosophila; Leptin; Upd2; fat body; insulin-producing cells; inter-organ communication; metabolism; p53; starvation
    DOI:  https://doi.org/10.1016/j.celrep.2020.108321
  15. Cardiovasc Res. 2020 Oct 29. pii: cvaa310. [Epub ahead of print]
    Gierhardt M, Pak O, Sydykov A, Kraut S, Schäffer J, Garcia C, Veith C, Zeidan EM, Brosien M, Quanz K, Esfandiary A, Saraji A, Hadzic S, Kojonazarov B, Wilhelm J, Ghofrani HA, Schermuly RT, Seeger W, Grimminger F, Herden C, Schulz R, Weissmann N, Heger J, Sommer N.
      AIMS: The pulmonary vascular tone and hypoxia-induced alterations of the pulmonary vasculature may be regulated by the mitochondrial membrane permeability transition pore (mPTP) that controls mitochondrial calcium load and apoptosis. We thus investigated, if the mitochondrial proteins p66shc and cyclophilin D (CypD) that regulate mPTP opening affect the pulmonary vascular tone.METHODS AND RESULTS: Mice deficient for p66shc (p66shc-/-), CypD (CypD-/-), or both proteins (p66shc/CypD-/-) exhibited decreased pulmonary vascular resistance (PVR) compared to wild-type mice determined in isolated lungs and in vivo. In contrast, systemic arterial pressure was only lower in CypD-/- mice. As cardiac function and pulmonary vascular remodelling did not differ between genotypes, we determined alterations of vascular contractility in isolated lungs and calcium handling in pulmonary arterial smooth muscle cells (PASMC) as underlying reason for decreased PVR. Potassium chloride (KCl)-induced pulmonary vasoconstriction and KCl-induced cytosolic calcium increase determined by Fura-2 were attenuated in all gene-deficient mice. In contrast, KCl-induced mitochondrial calcium increase determined by the genetically encoded Mito-Car-GECO and calcium retention capacity were increased only in CypD-/- and p66shc/CypD-/- mitochondria indicating that decreased mPTP opening affected KCl-induced intracellular calcium peaks in these cells. All mouse strains showed a similar pulmonary vascular response to chronic hypoxia, while acute hypoxic pulmonary vasoconstriction was decreased in gene-deficient mice indicating that CypD and p66shc regulates vascular contractility but not remodelling.
    CONCLUSIONS: We conclude that p66shc specifically regulates the pulmonary vascular tone, while CypD also affects systemic pressure. However, only CypD acts via regulation of mPTP opening and mitochondrial calcium regulation.
    TRANSLATIONAL PERSPECTIVE: Pulmonary hypertension is a progressive disease of the pulmonary vasculature ultimately resulting in right heart failure. Thus, therapeutic options targeting specifically the pulmonary vasculature are urgently needed.Our study describes for the first time the role of the proteins p66shc and CypD in the regulation of the pulmonary vascular tone. As the effect of p66shc-/- was specific for the pulmonary vasculature, it is an interesting target for future research on therapies for pulmonary vascular diseases like pulmonary hypertension.
    DOI:  https://doi.org/10.1093/cvr/cvaa310
  16. Endocr Relat Cancer. 2020 Sep 01. pii: ERC-20-0346.R1. [Epub ahead of print]
    Moog S, Lussey-Lepoutre C, Favier J.
      Pheochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumors arising from the adrenal medulla or extra-adrenal paraganglia. Around 40% of all cases are caused by a germline mutation in a susceptibility gene, half of which being found in an SDHx gene (SDHA, SDHB, SDHC, SDHD or SDHAF2). They encode the four subunits and assembly factor of succinate dehydrogenase (SDH), a mitochondrial enzyme involved both in the tricarboxylic acid cycle and in the electron transport chain. SDHx mutations lead to the accumulation of succinate, which acts as an oncometabolite by inhibiting iron(II) and alpha-ketoglutarate dependent dioxygenases thereby regulating the cell's hypoxic response and epigenetic processes. Moreover, SDHx mutations induce cell metabolic reprogramming and redox imbalance. Major discoveries in PPGL pathophysiology have been made since the initial discovery of SDHD gene mutations in 2000, improving the understanding of their biology, and patient management. It indeed provides new opportunities for diagnostic tools and innovative therapeutic targets in order to improve the prognosis of patients affected by these rare tumors, in particular in the context of metastatic diseases associated with SDHB mutations. This review first describes an overview of the pathophysiology and then focuses on clinical implications of the epigenetic and metabolic reprogramming of SDH-deficient PPGL.
    DOI:  https://doi.org/10.1530/ERC-20-0346
  17. Nat Metab. 2020 Oct 26.
    McCommis KS, Kovacs A, Weinheimer CJ, Shew TM, Koves TR, Ilkayeva OR, Kamm DR, Pyles KD, King MT, Veech RL, DeBosch BJ, Muoio DM, Gross RW, Finck BN.
      The myocardium is metabolically flexible; however, impaired flexibility is associated with cardiac dysfunction in conditions including diabetes and heart failure. The mitochondrial pyruvate carrier (MPC) complex, composed of MPC1 and MPC2, is required for pyruvate import into the mitochondria. Here we show that MPC1 and MPC2 expression is downregulated in failing human and mouse hearts. Mice with cardiac-specific deletion of Mpc2 (CS-MPC2-/-) exhibited normal cardiac size and function at 6 weeks old, but progressively developed cardiac dilation and contractile dysfunction, which was completely reversed by a high-fat, low-carbohydrate ketogenic diet. Diets with higher fat content, but enough carbohydrate to limit ketosis, also improved heart failure, while direct ketone body provisioning provided only minor improvements in cardiac remodelling in CS-MPC2-/- mice. An acute fast also improved cardiac remodelling. Together, our results reveal a critical role for mitochondrial pyruvate use in cardiac function, and highlight the potential of dietary interventions to enhance cardiac fat metabolism to prevent or reverse cardiac dysfunction and remodelling in the setting of MPC deficiency.
    DOI:  https://doi.org/10.1038/s42255-020-00296-1
  18. Cancer Cell. 2020 Sep 23. pii: S1535-6108(20)30478-5. [Epub ahead of print]
    Kaymak I, Williams KS, Cantor JR, Jones RG.
      Immune cells' metabolism influences their differentiation and function. Given that a complex interplay of environmental factors within the tumor microenvironment (TME) can have a profound impact on the metabolic activities of immune, stromal, and tumor cell types, there is emerging interest to advance understanding of these diverse metabolic phenotypes in the TME. Here, we discuss cell-extrinsic contributions to the metabolic activities of immune cells. Then, considering recent technical advances in experimental systems and metabolic profiling technologies, we propose future directions to better understand how immune cells meet their metabolic demands in the TME, which can be leveraged for therapeutic benefit.
    Keywords:  immunology; immunometabolism; in vitro modeling; metabolism; metabolomics; physiologic media; stable isotope tracing; tumor microenvironment
    DOI:  https://doi.org/10.1016/j.ccell.2020.09.004
  19. Front Oncol. 2020 ;10 575854
    Sünderhauf A, Raschdorf A, Hicken M, Schlichting H, Fetzer F, Brethack AK, Perner S, Kemper C, Ghebrehiwet B, Sina C, Derer S.
      Self-sustained cell proliferation constitutes one hallmark of cancer enabled by aerobic glycolysis which is characterized by imbalanced glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) activity, named the Warburg effect. The C1q binding protein (C1QBP; gC1qR) is pivotal for mitochondrial protein translation and thus OXPHOS activity. Due to its fundamental role in balancing OXPHOS and glycolysis, c1qbp -/- mice display embryonic lethality, while gC1qR is excessively up-regulated in cancer. Although gC1qR encompasses an N-terminal mitochondrial leader it is also located in other cellular compartments. Hence, we aimed to investigate mechanisms regulating gC1qR cellular localization and its impact on tumor cell metabolism. We identified two caspase-1 cleavage sites in human gC1qR. GC1qR cleavage by active caspase-1 was unraveled as a cellular mechanism that prevents mitochondrial gC1qR import, thereby enabling aerobic glycolysis and enhanced cell proliferation. Ex vivo, tumor grading correlated with non-mitochondrial-located gC1qR as well as with caspase-1 activation in colorectal carcinoma patients. Together, active caspase-1 cleaves gC1qR and boosts aerobic glycolysis in tumor cells.
    Keywords:  C1qbp; OXPHOS; aerobic glycolysis; caspase-1; gC1qR; inflammasome; mitochondria; p32/HABP1
    DOI:  https://doi.org/10.3389/fonc.2020.575854
  20. Front Immunol. 2020 ;11 550145
    Wolff SEC, Wang XL, Jiao H, Sun J, Kalsbeek A, Yi CX, Gao Y.
      Microglia are the immune cells of the brain. Hyperactivation of microglia contributes to the pathology of metabolic and neuroinflammatory diseases. Evidence has emerged that links the circadian clock, cellular metabolism, and immune activity in microglia. Rev-erb nuclear receptors are known for their regulatory role in both the molecular clock and cell metabolism, and have recently been found to play an important role in neuroinflammation. The Rev-erbα agonist SR9011 disrupts circadian rhythm by altering intracellular clock machinery. However, the exact role of Rev-erbα in microglial immunometabolism remains to be elucidated. In the current study, we explored whether SR9011 also had such a detrimental impact on microglial immunometabolic functions. Primary microglia were isolated from 1-3 days old Sprague-Dawley rat pups. The expression of clock genes, cytokines and metabolic genes was evaluated using RT-PCR and rhythmic expression was analyzed. Phagocytic activity was determined by the uptake capacity of fluorescent microspheres. Mitochondria function was evaluated by measuring oxygen consumption rate and extracellular acidification rate. We found that key cytokines and metabolic genes are rhythmically expressed in microglia. SR9011 disturbed rhythmic expression of clock genes in microglia. Pro-inflammatory cytokine expression was attenuated by SR9011 during an immune challenge by TNFα, while expression of the anti-inflammatory cytokine Il10 was stimulated. Moreover, SR9011 decreased phagocytic activity, mitochondrial respiration, ATP production, and metabolic gene expression. Our study highlights the link between the intrinsic clock and immunometabolism of microglia. We show that Rev-erbα is implicated in both metabolic homeostasis and the inflammatory responses in microglia, which has important implications for the treatment of metabolic and neuroinflammatory diseases.
    Keywords:  Innate immunity; clock genes; cytokines; immunometabolism; microglia; neuroinflammation; phagocytosis
    DOI:  https://doi.org/10.3389/fimmu.2020.550145
  21. Sci Transl Med. 2020 Oct 28. pii: eabb8969. [Epub ahead of print]12(567):
    Uhl FM, Chen S, O'Sullivan D, Edwards-Hicks J, Richter G, Haring E, Andrieux G, Halbach S, Apostolova P, Büscher J, Duquesne S, Melchinger W, Sauer B, Shoumariyeh K, Schmitt-Graeff A, Kreutz M, Lübbert M, Duyster J, Brummer T, Boerries M, Madl T, Blazar BR, Groß O, Pearce EL, Zeiser R.
      Acute myeloid leukemia (AML) relapse after allogeneic hematopoietic cell transplantation (allo-HCT) has a dismal prognosis. We found that T cells of patients relapsing with AML after allo-HCT exhibited reduced glycolysis and interferon-γ production. Functional studies in multiple mouse models of leukemia showed that leukemia-derived lactic acid (LA) interfered with T cell glycolysis and proliferation. Mechanistically, LA reduced intracellular pH in T cells, led to lower transcription of glycolysis-related enzymes, and decreased activity of essential metabolic pathways. Metabolic reprogramming by sodium bicarbonate (NaBi) reversed the LA-induced low intracellular pH, restored metabolite concentrations, led to incorporation of LA into the tricarboxylic acid cycle as an additional energy source, and enhanced graft-versus-leukemia activity of murine and human T cells. NaBi treatment of post-allo-HCT patients with relapsed AML improved metabolic fitness and interferon-γ production in T cells. Overall, we show that metabolic reprogramming of donor T cells is a pharmacological strategy for patients with relapsed AML after allo-HCT.
    DOI:  https://doi.org/10.1126/scitranslmed.abb8969
  22. Curr Opin Physiol. 2020 Oct;17 207-223
    Wang Y, Tao A, Vaeth M, Feske S.
      T cells are an essential component of the immune system that provide antigen-specific acute and long lasting immune responses to infections and tumors, ascertain the maintenance of immunological tolerance and, on the flipside, mediate autoimmunity in a variety of diseases. The activation of T cells through antigen recognition by the T cell receptor (TCR) results in transient and sustained Ca2+ signals that are shaped by the opening of Ca2+ channels in the plasma membrane and cellular organelles. The dynamic regulation of intracellular Ca2+ concentrations controls a variety of T cell functions on the timescale of seconds to days after signal initiation. Among the more recently identified roles of Ca2+ signaling in T cells is the regulation of metabolic pathways that control the function of many T cell subsets. In this review, we discuss how Ca2+ regulates several metabolic programs in T cells such as the activation of AMPK and the PI3K-AKT-mTORC1 pathway, aerobic glycolysis, mitochondrial metabolism including tricarboxylic acid (TCA) cycle function and oxidative phosphorylation (OXPHOS), as well as lipid metabolism.
    DOI:  https://doi.org/10.1016/j.cophys.2020.07.016
  23. STAR Protoc. 2020 Sep 18. 1(2): 100048
    Rauter T, Depaoli MR, Bischof H, Graier WF, Malli R.
      The metabolic activity of cells is interrelated with cell signaling, functions, and fate. Uncontrolled cancer cell proliferation requires metabolic adaptations. Research focusing on understanding the characteristics of cell metabolism is crucial for the development of novel diagnostic and therapeutic strategies. Here, we describe protocols for the ATP profiling of single cancer cells by fluorescence live-cell imaging. In response to distinct metabolic inhibitions, we record individual mitochondrial ATP dynamics using established Förster resonance energy transfer-based genetically encoded fluorescent ATP probes. For complete details on the use and execution of this protocol, please refer to Depaoli et al. (2018).
    DOI:  https://doi.org/10.1016/j.xpro.2020.100048
  24. J Biol Chem. 2020 Oct 27. pii: jbc.RA120.015238. [Epub ahead of print]
    Shao W, Hwang J, Liu C, Mukhopadhyay D, Zhao S, Shen MC, Alpergin ESS, Wolfgang MJ, Farber SA, Espenshade PJ.
      Oxygen regulates hypoxia-inducible factor (HIF) transcription factors to control cell metabolism, erythrogenesis, and angiogenesis. While much has been elucidated about how oxygen regulates HIF, whether lipids affect HIF activity is unknown. Here, using cultured cells and two animal models, we demonstrate that lipoprotein-derived fatty acids are an independent regulator of HIF. Decreasing extracellular lipid supply inhibited HIF prolyl hydroxylation, leading to accumulation of the HIFα subunit of these heterodimeric transcription factors comparable to hypoxia with activation of downstream target genes. Addition of fatty acids to culture media suppressed this signal, which required an intact mitochondrial respiratory chain. Mechanistically, fatty acids and oxygen are distinct signals integrated to control HIF activity. Finally, we observed lipid signaling to HIF and changes in target gene expression in developing zebrafish and adult fluorescent reporter mice, and this pathway operates in cancer cells from a range of tissues. This study identifies fatty acids as a physiological modulator of HIF, defining a mechanism for lipoprotein regulation that functions in parallel to oxygen.
    Keywords:  fatty acid; hypoxia-inducible factor (HIF); lipoprotein; low-density lipoprotein (LDL); lysosomal acid lipase; mitochondria
    DOI:  https://doi.org/10.1074/jbc.RA120.015238
  25. FEBS Lett. 2020 Oct 28.
    Goncalves RLS, Schlame M, Bartelt A, Brand MD, Hotamışlıgil GS.
      Barth Syndrome (BTHS) is a rare X-linked genetic disorder caused by mutations in the gene encoding the transacylase tafazzin and characterized by loss of cardiolipin and severe cardiomyopathy. Mitochondrial oxidants have been implicated in the cardiomyopathy in BTHS. Eleven mitochondrial sites produce superoxide/H2 O2 at significant rates. Which of these sites generate oxidants at excessive rates in BTHS is unknown. Here, we measured the maximum capacity of superoxide/H2 O2 production from each site and the ex vivo rate of superoxide/H2 O2 production in the heart and skeletal muscle mitochondria of the tafazzin knockdown mice (tazkd) from 3 to 12 months of age. Despite reduced oxidative capacity, superoxide/H2 O2 production is indistinguishable between tazkd mice and wildtype littermates. These observations raise questions about the involvement of mitochondrial oxidants in BTHS pathology.
    Keywords:  Barth syndrome; cardiomyopathy; mitochondria; mitochondrial reactive oxygen species (ROS); superoxide/H2O2; tafazzin; tazkd mice; “ex vivo” rate of superoxide/H2O2 production
    DOI:  https://doi.org/10.1002/1873-3468.13973
  26. PLoS Pathog. 2020 Oct 26. 16(10): e1008957
    Rezinciuc S, Bezavada L, Bahadoran A, Duan S, Wang R, Lopez-Ferrer D, Finkelstein D, McGargill MA, Green DR, Pasa-Tolic L, Smallwood HS.
      Infection with the influenza virus triggers an innate immune response that initiates the adaptive response to halt viral replication and spread. However, the metabolic response fueling the molecular mechanisms underlying changes in innate immune cell homeostasis remain undefined. Although influenza increases parasitized cell metabolism, it does not productively replicate in dendritic cells. To dissect these mechanisms, we compared the metabolism of dendritic cells to that of those infected with active and inactive influenza A virus and those treated with toll-like receptor agonists. Using quantitative mass spectrometry, pulse chase substrate utilization assays and metabolic flux measurements, we found global metabolic changes in dendritic cells 17 hours post infection, including significant changes in carbon commitment via glycolysis and glutaminolysis, as well as mitochondrial respiration. Influenza infection of dendritic cells led to a metabolic phenotype distinct from that induced by TLR agonists, with significant resilience in terms of metabolic plasticity. We identified c-Myc as one transcription factor modulating this response. Restriction of c-Myc activity or mitochondrial substrates significantly changed the immune functions of dendritic cells, such as reducing motility and T cell activation. Transcriptome analysis of inflammatory dendritic cells isolated following influenza infection showed similar metabolic reprogramming occurs in vivo. Thus, early in the infection process, dendritic cells respond with global metabolic restructuring, that is present in inflammatory lung dendritic cells after infection, and this is important for effector function. These findings suggest metabolic switching in dendritic cells plays a vital role in initiating the immune response to influenza infection.
    DOI:  https://doi.org/10.1371/journal.ppat.1008957
  27. Front Immunol. 2020 ;11 559576
    Highton AJ, Diercks BP, Möckl F, Martrus G, Sauter J, Schmidt AH, Bunders MJ, Körner C, Guse AH, Altfeld M.
      Natural killer (NK) cells are an important component of the innate immune system for the control of intracellular pathogens and cancer cells. NK cells demonstrate heterogeneous expression of inhibitory surface receptors. Signaling through these various receptors during NK cell development promotes functionality, referred to as NK cell education. Here we investigated the impact of education on NK cell metabolism through functional assessment of critical metabolic pathways and calcium signaling. Educated NK cells had an increased uptake of the metabolic substrates 2-NBDG, a fluorescent glucose analog, and BODIPY FL C16, a fluorescent palmitate, compared to uneducated NK cells. Comparison of NK cells educated via KIRs or NKG2A showed that NKG2A-educated NK cells were the main contributor to these differences in uptake of metabolites, and that NKG2A-educated NK cells were functionally more resilient in response to metabolic blockade of oxidative phosphorylation. Furthermore, NKG2A-educated NK cells exhibited higher peak calcium concentration following stimulation, indicating stronger signaling events taking place in these educated NK cells. These results demonstrate that cellular metabolism plays an important role in the functional differences observed between educated and uneducated NK cells, and show that NKG2A-educated NK cells remain more functionally competent than KIR-educated NK cells when oxidative phosphorylation is restricted. Understanding metabolic programming during NK cell education may unveil future targets to manipulate NK cell function for use in clinical settings, such as cancer therapies.
    Keywords:  KIR; NK cell education; NKG2A; glycolysis; immunometabolism; oxidative phoshorylation
    DOI:  https://doi.org/10.3389/fimmu.2020.559576
  28. Cancer Metab. 2020 ;8 23
    Ruiz-Rodado V, Lita A, Dowdy T, Celiku O, Saldana AC, Wang H, Yang CZ, Chari R, Li A, Zhang W, Song H, Zhang M, Ahn S, Davis D, Chen X, Zhuang Z, Herold-Mende C, Walters KJ, Gilbert MR, Larion M.
      Background: Targeting glutamine metabolism in cancer has become an increasingly vibrant area of research. Mutant IDH1 (IDH1 mut ) gliomas are considered good candidates for targeting this pathway because of the contribution of glutamine to their newly acquired function: synthesis of 2-hydroxyglutarate (2HG).Methods: We have employed a combination of 13C tracers including glutamine and glucose for investigating the metabolism of patient-derived IDH1 mut glioma cell lines through NMR and LC/MS. Additionally, genetic loss-of-function (in vitro and in vivo) approaches were performed to unravel the adaptability of these cell lines to the inhibition of glutaminase activity.
    Results: We report the adaptability of IDH1 mut cells' metabolism to the inhibition of glutamine/glutamate pathway. The glutaminase inhibitor CB839 generated a decrease in the production of the downstream metabolites of glutamate, including those involved in the TCA cycle and 2HG. However, this effect on metabolism was not extended to viability; rather, our patient-derived IDH1 mut cell lines display a metabolic plasticity that allows them to overcome glutaminase inhibition.
    Conclusions: Major metabolic adaptations involved pathways that can generate glutamate by using alternative substrates from glutamine, such as alanine or aspartate. Indeed, asparagine synthetase was upregulated both in vivo and in vitro revealing a new potential therapeutic target for a combinatory approach with CB839 against IDH1 mut gliomas.
    Keywords:  13C tracing; AGI5198; CB839; Gliomas; Glutaminase; IDH1-mutant
    DOI:  https://doi.org/10.1186/s40170-020-00229-2
  29. J Cell Mol Med. 2020 Oct 26.
    Yelek C, Mignion L, Joudiou N, Terrasi R, Gourgue F, Van Hul M, Delzenne N, Gallez B, Corbet C, Muccioli GG, Feron O, Cani PD, Jordan BF.
      Acetate is reported as a regulator of fat mass but also as lipogenic source for cancer cells. Breast cancer is surrounded by adipose tissue and has been associated with obesity. However, whether acetate contributes to cancer cell metabolism as lipogenic substrate and/or by changing fat storage and eventually obesity-induced breast cancer progression remains unknown. Therefore, we studied the contribution of acetate to breast cancer metabolism and progression. In vitro, we found that acetate is not a bioenergetic substrate under normoxia and did not result in a significant change of growth. However, by using lipidomic approaches, we discovered that acetate changes the lipid profiles of the cells under hypoxia. Moreover, while mice fed a high-fat diet (HFD) developed bigger tumours than their lean counterparts, exogenous acetate supplementation leads to a complete abolishment of fat mass gain without reverting the HFD-induced obesity-driven tumour progression. In conclusion, although acetate protects against diet-induced obesity, our data suggest that it is not affecting HFD-driven tumour progression.
    Keywords:  acetate; high-fat diet; hypoxia; metabolism; obesity; tumour growth
    DOI:  https://doi.org/10.1111/jcmm.16034
  30. Front Oncol. 2020 ;10 578418
    Chavez-Dominguez R, Perez-Medina M, Lopez-Gonzalez JS, Galicia-Velasco M, Aguilar-Cazares D.
      During tumorigenesis, cancer cells are exposed to a wide variety of intrinsic and extrinsic stresses that challenge homeostasis and growth. Cancer cells display activation of distinct mechanisms for adaptation and growth even in the presence of stress. Autophagy is a catabolic mechanism that aides in the degradation of damaged intracellular material and metabolite recycling. This activity helps meet metabolic needs during nutrient deprivation, genotoxic stress, growth factor withdrawal and hypoxia. However, autophagy plays a paradoxical role in tumorigenesis, depending on the stage of tumor development. Early in tumorigenesis, autophagy is a tumor suppressor via degradation of potentially oncogenic molecules. However, in advanced stages, autophagy promotes the survival of tumor cells by ameliorating stress in the microenvironment. These roles of autophagy are intricate due to their interconnection with other distinct cellular pathways. In this review, we present a broad view of the participation of autophagy in distinct phases of tumor development. Moreover, autophagy participation in important cellular processes such as cell death, metabolic reprogramming, metastasis, immune evasion and treatment resistance that all contribute to tumor development, is reviewed. Finally, the contribution of the hypoxic and nutrient deficient tumor microenvironment in regulation of autophagy and these hallmarks for the development of more aggressive tumors is discussed.
    Keywords:  autophagy; carcinogenesis; cell death; chemotherapy and targeted therapy resistance; immune evasion; metabolic reprograming; metastasis; tumor microenvironment
    DOI:  https://doi.org/10.3389/fonc.2020.578418
  31. J Biol Chem. 2020 Oct 29. pii: jbc.RA120.014248. [Epub ahead of print]
    Walvekar AS, Kadamur G, Sreedharan S, Gupta R, Srinivasan R, Laxman S.
      Methionine, through S-adenosylmethionine, activates a multifaceted growth program in which ribosome biogenesis, carbon metabolism, amino acid and nucleotide biosynthesis are induced. This growth program requires the activity of the Gcn4 transcription factor (called ATF4 in mammals), which facilitates the supply of metabolic precursors that are essential for anabolism. However, how Gcn4 itself is regulated in the presence of methionine is unknown. Here, we discover that Gcn4 protein levels are increased by methionine, despite conditions of high cell growth and translation (where the roles of Gcn4 are not well studied). We demonstrate that this mechanism of Gcn4 induction is independent of transcription, as well as the conventional Gcn2/eIF2α-mediated increased translation of Gcn4. Instead, when methionine is abundant, Gcn4 phosphorylation is decreased, which reduces its ubiquitination and therefore degradation. Gcn4 is dephosphorylated by the protein phosphatase PP2A; our data show that when methionine is abundant, the conserved methyltransferase Ppm1 methylates and alters the activity of the catalytic subunit of PP2A, shifting the balance of Gcn4 towards a dephosphorylated, stable state. The absence of Ppm1 or the loss of the PP2A methylation destabilizes Gcn4 even when methionine is abundant, leading to collapse of the Gcn4-dependent anabolic program. These findings reveal a novel, methionine-dependent signaling and regulatory axis. Here methionine directs a conserved methyltransferase Ppm1, via its target phosphatase PP2A, to selectively stabilize Gcn4. Through this, cells conditionally modify a major phosphatase to stabilize a metabolic master-regulator and drive anabolism.
    Keywords:  Gcn4; S-adenosylmethionine (SAM); Saccharomyces cerevisiae; amino acid; methionine; methyltransferase; nucleotide; protein methylation; protein phosphatase 2 (PP2A)
    DOI:  https://doi.org/10.1074/jbc.RA120.014248
  32. Cell Cycle. 2020 Oct 28. 1-3
    Ma Y, Han F, Min J, Lin W.
      Ferroptosis is a newly identified form of cell death that is regulated by many metabolic pathways, including iron, lipid and amino acids. Recent two studies reveal that the mitochondria and energy stress could also mediate ferroptosis. Gao et al. report that mitochondria play an essential role in ferroptosis induced by cysteine deprivation. In addition, Lee et al. show that energy stress depressed ferroptosis partly through activation of AMP-activated protein kinase. These findings provide potential therapeutic strategies for treating ferroptosis-related diseases, such as cancer, tissue injury and neurodegenerative diseases.
    Keywords:  Ferroptosis; energy stress; mitochondria
    DOI:  https://doi.org/10.1080/15384101.2020.1838781
  33. Nat Metab. 2020 Oct 26.
    Fernandez-Caggiano M, Kamynina A, Francois AA, Prysyazhna O, Eykyn TR, Krasemann S, Crespo-Leiro MG, Vieites MG, Bianchi K, Morales V, Domenech N, Eaton P.
      Cardiomyocytes rely on metabolic substrates, not only to fuel cardiac output, but also for growth and remodelling during stress. Here we show that mitochondrial pyruvate carrier (MPC) abundance mediates pathological cardiac hypertrophy. MPC abundance was reduced in failing hypertrophic human hearts, as well as in the myocardium of mice induced to fail by angiotensin II or through transverse aortic constriction. Constitutive knockout of cardiomyocyte MPC1/2 in mice resulted in cardiac hypertrophy and reduced survival, while tamoxifen-induced cardiomyocyte-specific reduction of MPC1/2 to the attenuated levels observed during pressure overload was sufficient to induce hypertrophy with impaired cardiac function. Failing hearts from cardiomyocyte-restricted knockout mice displayed increased abundance of anabolic metabolites, including amino acids and pentose phosphate pathway intermediates and reducing cofactors. These hearts showed a concomitant decrease in carbon flux into mitochondrial tricarboxylic acid cycle intermediates, as corroborated by complementary 1,2-[13C2]glucose tracer studies. In contrast, inducible cardiomyocyte overexpression of MPC1/2 resulted in increased tricarboxylic acid cycle intermediates, and sustained carrier expression during transverse aortic constriction protected against cardiac hypertrophy and failure. Collectively, our findings demonstrate that loss of the MPC1/2 causally mediates adverse cardiac remodelling.
    DOI:  https://doi.org/10.1038/s42255-020-00276-5
  34. Front Pharmacol. 2020 ;11 581114
    Patergnani S, Vitto VAM, Pinton P, Rimessi A.
      Cystic fibrosis (CF) is a genetic disease associated to mutations in the cystic fibrosis transmembrane conductance regulator gene, which results in the alteration of biological fluid and electrolyte homeostasis. The characteristic pathological manifestation is represented by exaggerated proinflammatory response in lung of CF patients, driven by recurrent infections and worsen by hypersecretion of proinflammatory mediators and progressive tissue destruction. Treating inflammation remains a priority in CF. However, current anti-inflammatory treatments, including non-steroidal agents, are poorly effective and present dramatic side effects in CF patients. Different studies suggest an intimate relationship between mitochondria and CF lung disease, supporting the hypothesis that a decline in mitochondrial function endorses the development of the hyperinflammatory phenotype observed in CF lung. This allowed the implementation of a new concept: the "mito-inflammation," a compartmentalization of inflammatory process, related to the role of mitochondria in engage and sustain the inflammatory responses, resulting a druggable target to counteract the amplification of inflammatory signals in CF. Here, we will offer an overview of the contribution of mitochondria in the pathogenesis of CF lung disease, delving into mitochondrial quality control responses, which concur significantly to exacerbation of CF lung inflammatory responses. Finally, we will discuss the new therapeutic avenues that aim to target the mito-inflammation, an alternative therapeutic advantage for mitochondrial quality control that improves CF patient's inflammatory state.
    Keywords:  cystic fibrosis; inflammation; lung; mitochondria; mitochondrial stress response
    DOI:  https://doi.org/10.3389/fphar.2020.581114
  35. Proc Natl Acad Sci U S A. 2020 Oct 29. pii: 202011645. [Epub ahead of print]
    Holmes DL, Vogt DT, Lagunoff M.
      Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). The main proliferating component of KS tumors is a cell of endothelial origin termed the spindle cell. Spindle cells are predominantly latently infected with only a small percentage of cells undergoing viral replication. As there is no direct treatment for latent KSHV, identification of host vulnerabilities in latently infected endothelial cells could be exploited to inhibit KSHV-associated tumor cells. Using a pooled CRISPR-Cas9 lentivirus library, we identified host factors that are essential for the survival or proliferation of latently infected endothelial cells in culture, but not their uninfected counterparts. Among the many host genes identified, there was an enrichment in genes localizing to the mitochondria, including genes involved in mitochondrial translation. Antibiotics that inhibit bacterial and mitochondrial translation specifically inhibited the expansion of latently infected endothelial cells and led to increased cell death in patient-derived PEL cell lines. Direct inhibition of mitochondrial respiration or ablation of mitochondrial genomes leads to increased death in latently infected cells. KSHV latent infection decreases mitochondrial numbers, but there are increases in mitochondrial size, genome copy number, and transcript levels. We found that multiple gene products of the latent locus localize to the mitochondria. During latent infection, KSHV significantly alters mitochondrial biology, leading to enhanced sensitivity to inhibition of mitochondrial respiration, which provides a potential therapeutic avenue for KSHV-associated cancers.
    Keywords:  Crispr/Cas9; HHV-8; KSHV; Kaposi’s sarcoma; mitochondria
    DOI:  https://doi.org/10.1073/pnas.2011645117
  36. Nat Commun. 2020 10 28. 11(1): 5444
    Crameri F, Shephard GE, Heron PJ.
      The accurate representation of data is essential in science communication. However, colour maps that visually distort data through uneven colour gradients or are unreadable to those with colour-vision deficiency remain prevalent in science. These include, but are not limited to, rainbow-like and red-green colour maps. Here, we present a simple guide for the scientific use of colour. We show how scientifically derived colour maps report true data variations, reduce complexity, and are accessible for people with colour-vision deficiencies. We highlight ways for the scientific community to identify and prevent the misuse of colour in science, and call for a proactive step away from colour misuse among the community, publishers, and the press.
    DOI:  https://doi.org/10.1038/s41467-020-19160-7
  37. Nat Genet. 2020 Nov;52(11): 1208-1218
    Kinker GS, Greenwald AC, Tal R, Orlova Z, Cuoco MS, McFarland JM, Warren A, Rodman C, Roth JA, Bender SA, Kumar B, Rocco JW, Fernandes PACM, Mader CC, Keren-Shaul H, Plotnikov A, Barr H, Tsherniak A, Rozenblatt-Rosen O, Krizhanovsky V, Puram SV, Regev A, Tirosh I.
      Cultured cell lines are the workhorse of cancer research, but the extent to which they recapitulate the heterogeneity observed among malignant cells in tumors is unclear. Here we used multiplexed single-cell RNA-seq to profile 198 cancer cell lines from 22 cancer types. We identified 12 expression programs that are recurrently heterogeneous within multiple cancer cell lines. These programs are associated with diverse biological processes, including cell cycle, senescence, stress and interferon responses, epithelial-mesenchymal transition and protein metabolism. Most of these programs recapitulate those recently identified as heterogeneous within human tumors. We prioritized specific cell lines as models of cellular heterogeneity and used them to study subpopulations of senescence-related cells, demonstrating their dynamics, regulation and unique drug sensitivities, which were predictive of clinical response. Our work describes the landscape of heterogeneity within diverse cancer cell lines and identifies recurrent patterns of heterogeneity that are shared between tumors and specific cell lines.
    DOI:  https://doi.org/10.1038/s41588-020-00726-6
  38. Nat Ecol Evol. 2020 Oct 26.
    Vosseberg J, van Hooff JJE, Marcet-Houben M, van Vlimmeren A, van Wijk LM, Gabaldón T, Snel B.
      Eukaryogenesis is one of the most enigmatic evolutionary transitions, during which simple prokaryotic cells gave rise to complex eukaryotic cells. While evolutionary intermediates are lacking, gene duplications provide information on the order of events by which eukaryotes originated. Here we use a phylogenomics approach to reconstruct successive steps during eukaryogenesis. We find that gene duplications roughly doubled the proto-eukaryotic gene repertoire, with families inherited from the Asgard archaea-related host being duplicated most. By relatively timing events using phylogenetic distances, we inferred that duplications in cytoskeletal and membrane-trafficking families were among the earliest events, whereas most other families expanded predominantly after mitochondrial endosymbiosis. Altogether, we infer that the host that engulfed the proto-mitochondrion had some eukaryote-like complexity, which drastically increased upon mitochondrial acquisition. This scenario bridges the signs of complexity observed in Asgard archaeal genomes to the proposed role of mitochondria in triggering eukaryogenesis.
    DOI:  https://doi.org/10.1038/s41559-020-01320-z
  39. Cancer Res. 2020 Oct 28. pii: canres.1287.2020. [Epub ahead of print]
    Liu Y, Guo B, Aguilera-Jimenez E, Chu VS, Zhou J, Wu Z, Francis JM, Yang X, Choi PS, Bailey SD, Zhang X.
      Activation of transcription factors is a key driver event in cancer. We and others have recently reported that the Krüppel-like transcription factor KLF5 is activated in multiple epithelial cancer types including squamous cancer and gastrointestinal adenocarcinoma, yet the functional consequences and the underlying mechanisms of this activation remain largely unknown. Here we demonstrate that activation of KLF5 results in strongly selective KLF5 dependency for these cancer types. KLF5 bound lineage-specific regulatory elements and activated gene expression programs essential to cancer cells. HiChIP analysis revealed that multiple distal KLF5 binding events cluster and synergize to activate individual target genes. Immunoprecipitation-mass spectrometry assays showed that KLF5 interacts with other transcription factors such as TP63 and YAP1, as well as the CBP/EP300 acetyltransferase complex. Furthermore, KLF5 guided the CBP/EP300 complex to increase acetylation of H3K27, which in turn enhanced recruitment of the bromodomain protein BRD4 to chromatin. The 3D chromatin architecture aggregated KLF5-dependent BRD4 binding to activate Polymerase II (POL2) elongation at KLF5-target genes, which conferred a transcriptional vulnerability to proteolysis-targeting chimera (PROTAC)-induced degradation of BRD4. Our study demonstrates that KLF5 plays an essential role in multiple epithelial cancers by activating cancer-related genes through 3D chromatin loops, providing an evidence-based rationale for targeting the KLF5 pathway.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-1287
  40. EMBO J. 2020 Oct 30. e105753
    Flores-Romero H, Ros U, Garcia-Saez AJ.
      The discovery of alternative signaling pathways that regulate cell death has revealed multiple strategies for promoting cell death with diverse consequences at the tissue and organism level. Despite the divergence in the molecular components involved, membrane permeabilization is a common theme in the execution of regulated cell death. In apoptosis, the permeabilization of the outer mitochondrial membrane by BAX and BAK releases apoptotic factors that initiate the caspase cascade and is considered the point of no return in cell death commitment. Pyroptosis and necroptosis also require the perforation of the plasma membrane at the execution step, which involves Gasdermins in pyroptosis, and MLKL in the case of necroptosis. Although BAX/BAK, Gasdermins and MLKL share certain molecular features like oligomerization, they form pores in different cellular membranes via distinct mechanisms. Here, we compare and contrast how BAX/BAK, Gasdermins, and MLKL alter membrane permeability from a structural and biophysical perspective and discuss the general principles of membrane permeabilization in the execution of regulated cell death.
    Keywords:  apoptosis; cell death; membrane pores; necroptosis; pyroptosis
    DOI:  https://doi.org/10.15252/embj.2020105753
  41. Nat Commun. 2020 10 28. 11(1): 5455
    Wang L, Wang S, Shi Y, Li R, Günther S, Ong YT, Potente M, Yuan Z, Liu E, Offermanns S.
      The expansion of the white adipose tissue (WAT) in obesity goes along with increased mechanical, metabolic and inflammatory stress. How adipocytes resist this stress is still poorly understood. Both in human and mouse adipocytes, the transcriptional co-activators YAP/TAZ and YAP/TAZ target genes become activated during obesity. When fed a high-fat diet (HFD), mice lacking YAP/TAZ in white adipocytes develop severe lipodystrophy with adipocyte cell death. The pro-apoptotic factor BIM, which is downregulated in adipocytes of obese mice and humans, is strongly upregulated in YAP/TAZ-deficient adipocytes under HFD, and suppression of BIM expression reduces adipocyte apoptosis. In differentiated adipocytes, TNFα and IL-1β promote YAP/TAZ nuclear translocation via activation of RhoA-mediated actomyosin contractility and increase YAP/TAZ-mediated transcriptional regulation by activation of c-Jun N-terminal kinase (JNK) and AP-1. Our data indicate that the YAP/TAZ signaling pathway may be a target to control adipocyte cell death and compensatory adipogenesis during obesity.
    DOI:  https://doi.org/10.1038/s41467-020-19229-3
  42. Mol Metab. 2020 Oct 23. pii: S2212-8778(20)30180-0. [Epub ahead of print] 101106
    Gheller BJ, Blum JE, Lim EW, Handzlik MK, Hannah Fong EH, Ko A, Khanna S, Gheller ME, Bender EL, Alexander MS, Stover PJ, Field MS, Cosgrove BD, Metallo CM, Thalacker-Mercer AE.
      OBJECTIVE: Skeletal muscle regeneration relies on muscle-specific, adult stem cells (MuSCs), MuSC progeny, muscle progenitor cells (MPCs), and a coordinated myogenic program that is influenced by the extracellular environment. Following injury, MPCs undergo a transient and rapid period of population expansion, which is necessary to repair damaged myofibers and restore muscle homeostasis. Certain pathologies (e.g., metabolic disease and muscle dystrophies) and advanced age are associated with dysregulated muscle regeneration. The availability of serine and glycine, two nutritionally, non-essential amino acids, is altered in humans with these pathologies and these amino acids have been shown to influence the proliferative state of non-muscle cells. Our objective was to determine the role of serine/glycine on MuSC/MPC function.METHODS: For in vitro experiments, primary, human MPCs (hMPCs) were used and for in vivo experiments young (4-6 mo) and old (>20 mo) mice were used. Serine/glycine availability was manipulated using specially formulated media in vitro or dietary restriction in vivo followed by downstream metabolic and cell proliferation analyses.
    RESULTS: We identified that serine/glycine are essential for hMPC proliferation. Dietary restriction of serine/glycine, in a mouse model of skeletal muscle regeneration, lowered the abundance of MuSCs 3 days post injury. Stable-isotope tracing studies showed that hMPCs rely on extracellular serine/glycine for population expansion because they exhibit a limited capacity for de novo serine/glycine biosynthesis. Restriction of serine/glycine to hMPCs resulted in cell cycle arrest in G0/G1. Extracellular serine/glycine were necessary to support glutathione and global protein synthesis in hMPCs. Finally, using an aged mouse model we find that reduced serine/glycine availability augmented intermyocellular adipocytes 28 days post injury.
    CONCLUSIONS: These studies demonstrate that despite an absolute requirement of serine/glycine for MuSC/MPC proliferation, de novo synthesis is inadequate to support these demands making extracellular serine and glycine conditionally essential for efficient skeletal muscle regeneration.
    Keywords:  Muscle; glycine metabolism; muscle metabolism; muscle progenitor cell; muscle regeneration; muscle stem cell; proliferation; protein synthesis; serine metabolism
    DOI:  https://doi.org/10.1016/j.molmet.2020.101106