bims-camemi Biomed News
on Mitochondrial metabolism in cancer
Issue of 2020‒01‒19
thirty-five papers selected by
Christian Frezza
University of Cambridge, MRC Cancer Unit


  1. Mol Metab. 2019 Dec 19. pii: S2212-8778(19)30953-6. [Epub ahead of print]
    Bayram S, Fürst S, Forbes M, Kempa S.
      BACKGROUND: Cancer cell metabolism can be characterised by adaptive metabolic alterations, which support abnormal proliferative cell growth with high energetic demand. De novo nucleotide biosynthesis is essential for providing nucleotides for RNA and DNA synthesis, and drugs targeting this biosynthetic pathway have proven to be effective anticancer therapeutics. Nevertheless, cancers are often able to circumvent chemotherapeutic interventions and become therapy resistant. Our understanding of the changing metabolic profile of the cancer cell and the mode of action of therapeutics is dependent on technological advances in biochemical analysis.SCOPE OF REVIEW: This review begins with information about carbon- and nitrogen-donating pathways to build purine and pyrimidine moieties in the course of nucleotide biosynthesis. We discuss the application of stable isotope resolved metabolomics to investigate the dynamics of cancer cell metabolism and outline the benefits of high-resolution accurate mass spectrometry, which enables multiple tracer studies.
    CONCLUSION: With the technological advances in mass spectrometry that allow for the analysis of the metabolome in high resolution, the application of stable isotope resolved metabolomics has become an important technique in the investigation of biological processes. The literature in the area of isotope labelling is dominated by 13C tracer studies. Metabolic pathways have to be considered as complex interconnected networks and should be investigated as such. Moving forward to simultaneous tracing of different stable isotopes will help elucidate the interplay between carbon and nitrogen flow and the dynamics of de novo nucleotide biosynthesis within the cell.
    Keywords:  Cancer metabolism; Flux analysis; Isotope resolved metabolomics
    DOI:  https://doi.org/10.1016/j.molmet.2019.12.002
  2. Mol Metab. 2019 Nov 23. pii: S2212-8778(19)30943-3. [Epub ahead of print]
    Garcia-Bermudez J, Williams RT, Guarecuco R, Birsoy K.
      BACKGROUND: Cancer cells rewire their metabolism to meet the energetic and biosynthetic demands of their high proliferation rates and environment. Metabolic reprogramming of cancer cells may result in strong dependencies on nutrients that could be exploited for therapy. While these dependencies may be in part due to the nutrient environment of tumors, mutations or expression changes in metabolic genes also reprogram metabolic pathways and create addictions to extracellular nutrients.SCOPE OF REVIEW: This review summarizes the major nutrient dependencies of cancer cells focusing on their discovery and potential mechanisms by which metabolites become limiting for tumor growth. We further detail available therapeutic interventions based on these metabolic features and highlight opportunities for restricting nutrient availability as an anti-cancer strategy.
    MAJOR CONCLUSIONS: Strategies to limit nutrients required for tumor growth using dietary interventions or nutrient degrading enzymes have previously been suggested for cancer therapy. The best clinical example of exploiting cancer nutrient dependencies is the treatment of leukemia with l-asparaginase, a first-line chemotherapeutic that depletes serum asparagine. Despite the success of nutrient starvation in blood cancers, it remains unclear whether this approach could be extended to other solid tumors. Systematic studies to identify nutrient dependencies unique to individual tumor types have the potential to discover targets for therapy.
    Keywords:  Amino acids; Asparaginase; Cancer metabolism; Diet; Metabolic therapy; Nutrient dependencies
    DOI:  https://doi.org/10.1016/j.molmet.2019.11.011
  3. Redox Biol. 2020 Jan 07. pii: S2213-2317(19)31435-1. [Epub ahead of print]30 101418
    Shin D, Lee J, You JH, Kim D, Roh JL.
      Ferroptosis is a new form of regulated cell death driven by iron-dependent lipid peroxidation. Glutaminolysis and tricarboxylic acid cycle are involved in ferroptosis, but the underlying metabolic process remains unclear. We examined the role of dihydrolipoamide dehydrogenase (DLD) in ferroptosis induction in head and neck cancer (HNC). The effects of cystine deprivation or sulfasalazine treatment and of DLD gene silencing/overexpression were tested on HNC cell lines and mouse tumor xenograft models. These effects were analyzed with regard to cell death, lipid reactive oxygen species (ROS) and mitochondrial iron production, mitochondrial membrane potential, mRNA/protein expression, and α-ketoglutarate dehydrogenase (KGDH)/succinate/aconitase activities. Cystine deprivation induced ferroptosis via glutaminolysis. Cystine deprivation or import inhibition using sulfasalazine induced cancer cell death and increased lipid ROS and mitochondrial iron levels, which had been significantly decreased by short-interfering RNA (siRNA) or short hairpin RNA (shRNA) targeting DLD (P < 0.01) but not by dihydrolipoyl succinyltransferase. The same results were noted in an in vivo mouse model transplanted with vector or shDLD-transduced HN9 cells. After cystine deprivation or sulfasalazine treatment, mitochondrial membrane potential, mitochondrial free iron level, KGDH activity, and succinate content significantly increased (P < 0.001), which had been blocked by DLD siRNA or shRNA and were consequently rescued by resistant DLD cDNA. Cystine deprivation caused iron starvation response and mitochondrial iron accumulation for Fenton reaction and ferroptosis. Our data suggest a close association of DLD with cystine deprivation- or import inhibition-induced ferroptosis.
    Keywords:  Cystine deprivation; Dihydrolipoamide dehydrogenase; Ferroptosis; Iron; Mitochondria
    DOI:  https://doi.org/10.1016/j.redox.2019.101418
  4. Annu Rev Biophys. 2020 Jan 13.
    Ruan L, Wang Y, Zhang X, Tomaszewski A, McNamara JT, Li R.
      Mitochondria are essential organelles in eukaryotes. Most mitochondrial proteins are encoded by the nuclear genome and translated in the cytosol. Nuclear-encoded mitochondrial proteins need to be imported, processed, folded, and assembled into their functional states. To maintain protein homeostasis (proteostasis), mitochondria are equipped with a distinct set of quality control machineries. Deficiencies in such systems lead to mitochondrial dysfunction, which is a hallmark of aging and many human diseases, such as neurodegenerative diseases, cardiovascular diseases, and cancer. In this review, we discuss the unique challenges and solutions of proteostasis in mitochondria. The import machinery coordinates with mitochondrial proteases and chaperones to maintain the mitochondrial proteome. Moreover, mitochondrial proteostasis depends on cytosolic protein quality control mechanisms during crises. In turn, mitochondria facilitate cytosolic proteostasis. Increasing evidence suggests that enhancing mitochondrial proteostasis may hold therapeutic potential to protect against protein aggregation-associated cellular defects. Expected final online publication date for the Annual Review of Biophysics, Volume 49 is May 6, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
    DOI:  https://doi.org/10.1146/annurev-biophys-121219-081604
  5. Nat Metab. 2019 Oct;1(10): 975-984
    Wescott AP, Kao JPY, Lederer WJ, Boyman L.
      Regulation of ATP production by mitochondria, critical to multicellular life, is poorly understood. Here we investigate the molecular controls of this process in heart and provide a framework for its Ca2+-dependent regulation. We find that the entry of Ca2+ into the matrix through the mitochondrial calcium uniporter (MCU) in heart has neither an apparent cytosolic Ca2+ threshold nor gating function and guides ATP production by its influence on the inner mitochondrial membrane (IMM) potential, ΔΨm. This regulation occurs by matrix Ca2+-dependent modulation of pyruvate and glutamate dehydrogenase activity and not through any effect of Ca2+ on ATP Synthase or on Electron Transport Chain Complexes II, III or IV. Examining the ΔΨm dependence of ATP production over the range of -60 mV to -170 mV in detail reveals that cardiac ATP synthase has a voltage dependence that distinguishes it fundamentally from the previous standard, the bacterial ATP synthase. Cardiac ATP synthase operates with a different ΔΨm threshold for ATP production than bacterial ATP synthase and reveals a concave-upwards shape without saturation. Skeletal muscle MCU Ca2+ flux, while also having no apparent cytosolic Ca2+ threshold, is substantially different from the cardiac MCU, yet the ATP synthase voltage dependence in skeletal muscle is identical to that in the heart. These results suggest that while the conduction of cytosolic Ca2+ signals through the MCU appears to be tissue-dependent, as shown by earlier work1, the control of ATP synthase by ΔΨm appears to be broadly consistent among tissues but is clearly different from bacteria.
    DOI:  https://doi.org/10.1038/s42255-019-0126-8
  6. Methods Mol Biol. 2020 ;2111 257-265
    Chen X, Sherman JW, Wang R.
      T lymphocytes are the major components of the adaptive immune system. It's been known that T cells are able to engage a diverse range of metabolic programs to meet the metabolic demands during their life cycle from early development, activation to functional differentiation. Central carbon metabolic pathways provide energy, reducing power, and biosynthetic precursors to support T cell homeostasis, proliferation, and immune functions. As such, quantitative or semiquantitative analysis of central carbon metabolic flux activities offers mechanistic details, as well as insights into the regulation of metabolic pathways and the impact of changing metabolic programs on T cell life cycle. Global profiling of cellular metabolites by mass spectrometry-based metabolomics and metabolic flux analysis (MFA) using radioactive and nonradioactive/stable isotope approaches are powerful tools for determination of central carbon metabolic pathway activity. Here, we describe in detail the procedure for the radioisotope-based approach of analyzing central carbon metabolic fluxes in T cells.
    Keywords:  Central carbon metabolism; Radioactive isotope; T lymphocytes
    DOI:  https://doi.org/10.1007/978-1-0716-0266-9_20
  7. Nat Commun. 2020 Jan 13. 11(1): 229
    Hämälistö S, Stahl JL, Favaro E, Yang Q, Liu B, Christoffersen L, Loos B, Guasch Boldú C, Joyce JA, Reinheckel T, Barisic M, Jäättelä M.
      Lysosomes are membrane-surrounded cytoplasmic organelles filled with a powerful cocktail of hydrolases. Besides degrading cellular constituents inside the lysosomal lumen, lysosomal hydrolases promote tissue remodeling when delivered to the extracellular space and cell death when released to the cytosol. Here, we show that spatially and temporally controlled lysosomal leakage contributes to the accurate chromosome segregation in normal mammalian cell division. One or more chromatin-proximal lysosomes leak in the majority of prometaphases, after which active cathepsin B (CTSB) localizes to the metaphase chromatin and cleaves a small subset of histone H3. Stabilization of lysosomal membranes or inhibition of CTSB activity during mitotic entry results in a significant increase in telomere-related chromosome segregation defects, whereas cells and tissues lacking CTSB and cells expressing CTSB-resistant histone H3 accumulate micronuclei and other nuclear defects. These data suggest that lysosomal leakage and chromatin-associated CTSB contribute to proper chromosome segregation and maintenance of genomic integrity.
    DOI:  https://doi.org/10.1038/s41467-019-14009-0
  8. Proc Natl Acad Sci U S A. 2020 Jan 17. pii: 201914553. [Epub ahead of print]
    Liu K, Lin L, Li Q, Xue Y, Zheng F, Wang G, Zheng C, Du L, Hu M, Huang Y, Shao C, Kong X, Melino G, Shi Y, Wang Y.
      Preadipocytes can give rise to either white adipocytes or beige adipocytes. Owing to their distinct abilities in nutrient storage and energy expenditure, strategies that specifically promote "beiging" of adipocytes hold great promise for counterbalancing obesity and metabolic diseases. Yet, factors dictating the differentiation fate of adipocyte progenitors remain to be elucidated. We found that stearoyl-coenzyme A desaturase 1 (Scd1)-deficient mice, which resist metabolic stress, possess augmentation in beige adipocytes under basal conditions. Deletion of Scd1 in mature adipocytes expressing Fabp4 or Ucp1 did not affect thermogenesis in mice. Rather, Scd1 deficiency shifted the differentiation fate of preadipocytes from white adipogenesis to beige adipogenesis. Such effects are dependent on succinate accumulation in adipocyte progenitors, which fuels mitochondrial complex II activity. Suppression of mitochondrial complex II by Atpenin A5 or oxaloacetic acid reverted the differentiation potential of Scd1-deficient preadipocytes to white adipocytes. Furthermore, supplementation of succinate was found to increase beige adipocyte differentiation both in vitro and in vivo. Our data reveal an unappreciated role of Scd1 in determining the cell fate of adipocyte progenitors through succinate-dependent regulation of mitochondrial complex II.
    Keywords:  beige fat biogenesis; mitochondrial complex II; preadipocytes; stearoyl-coenzyme A desaturase 1 (Scd1); succinate
    DOI:  https://doi.org/10.1073/pnas.1914553117
  9. Cancer Cell. 2020 Jan 13. pii: S1535-6108(19)30572-0. [Epub ahead of print]37(1): 71-84.e7
    Chen CC, Li B, Millman SE, Chen C, Li X, Morris JP, Mayle A, Ho YJ, Loizou E, Liu H, Qin W, Shah H, Violante S, Cross JR, Lowe SW, Zhang L.
      Cancer cells rely on altered metabolism to support abnormal proliferation. We performed a CRISPR/Cas9 functional genomic screen targeting metabolic enzymes and identified PDXK-an enzyme that produces pyridoxal phosphate (PLP) from vitamin B6-as an acute myeloid leukemia (AML)-selective dependency. PDXK kinase activity is required for PLP production and AML cell proliferation, and pharmacological blockade of the vitamin B6 pathway at both PDXK and PLP levels recapitulated PDXK disruption effects. PDXK disruption reduced intracellular concentrations of key metabolites needed for cell division. Furthermore, disruption of PLP-dependent enzymes ODC1 or GOT2 selectively inhibited AML cell proliferation and their downstream products partially rescued PDXK disruption induced proliferation blockage. Our work identifies the vitamin B6 pathway as a pharmacologically actionable dependency in AML.
    Keywords:  ABT-199/venetoclax; B cell lymphoma-2; CRISPR/Cas9 functional genomics; PLP-dependent enzyme; acute myeloid leukemia; pyridoxal kinase; pyridoxal phosphate; selective metabolic dependency; therapeutic target; vitamin B6
    DOI:  https://doi.org/10.1016/j.ccell.2019.12.002
  10. J Biol Chem. 2020 Jan 17. pii: jbc.RA119.011727. [Epub ahead of print]
    Xu R, Ritz BK, Wang Y, Huang J, Zhao C, Gong K, Liu X, Du J.
      Defects in energy metabolism in either the retina or the immediately adjacent retinal pigment epithelium (RPE) underlie retinal degeneration but the metabolic dependency between retina and RPE remain unclear. Nitrogen-containing metabolites such as amino acids are essential for energy metabolism. Here, we found that 15N-labeled ammonium is predominantly assimilated into glutamine in both the retina and RPE/choroid ex vivo. 15N-ammonium tracing in vivo show that, like the brain, the retina can synthesize asparagine from ammonium, but RPE/choroid and the liver cannot. However, unless present at toxic concentrations, ammonium cannot be recycled into glutamate in the retina and RPE/choroid. Tracing with 15N-labeled amino acids show that the retina predominantly uses aspartate transaminase for de novo synthesis of glutamate, glutamine and aspartate, whereas RPE uses multiple transaminases to utilize and synthesize amino acids. Retina consumes more leucine than RPE but little leucine is catabolized. The synthesis of serine and glycine is active in RPE but limited in the retina. RPE, but not the retina, uses alanine as mitochondrial substrates through mitochondrial pyruvate carrier (MPC). However, when the MPC is inhibited, alanine may directly enter the retinal mitochondria but not those of RPE. In conclusion, our results demonstrate that the retina and RPE differ in nitrogen metabolism and highlight that the RPE supports retinal metabolism through active amino acid metabolism.
    Keywords:  amino acid; metabolism; mitochondrial metabolism; nitrogen metabolism; retinal metabolism
    DOI:  https://doi.org/10.1074/jbc.RA119.011727
  11. Cell Rep. 2020 Jan 14. pii: S2211-1247(19)31678-X. [Epub ahead of print]30(2): 481-496.e6
    Blagih J, Zani F, Chakravarty P, Hennequart M, Pilley S, Hobor S, Hock AK, Walton JB, Morton JP, Gronroos E, Mason S, Yang M, McNeish I, Swanton C, Blyth K, Vousden KH.
      Loss of p53 function contributes to the development of many cancers. While cell-autonomous consequences of p53 mutation have been studied extensively, the role of p53 in regulating the anti-tumor immune response is still poorly understood. Here, we show that loss of p53 in cancer cells modulates the tumor-immune landscape to circumvent immune destruction. Deletion of p53 promotes the recruitment and instruction of suppressive myeloid CD11b+ cells, in part through increased expression of CXCR3/CCR2-associated chemokines and macrophage colony-stimulating factor (M-CSF), and attenuates the CD4+ T helper 1 (Th1) and CD8+ T cell responses in vivo. p53-null tumors also show an accumulation of suppressive regulatory T (Treg) cells. Finally, we show that two key drivers of tumorigenesis, activation of KRAS and deletion of p53, cooperate to promote immune tolerance.
    Keywords:  Kras; T cell response; myeloid cells; p53; tumor
    DOI:  https://doi.org/10.1016/j.celrep.2019.12.028
  12. Circ Res. 2020 Jan 17. 126(2): 280-293
    Bauer TM, Murphy E.
      Adult cardiomyocytes are postmitotic cells that undergo very limited cell division. Thus, cardiomyocyte death as occurs during myocardial infarction has very detrimental consequences for the heart. Mitochondria have emerged as an important regulator of cardiovascular health and disease. Mitochondria are well established as bioenergetic hubs for generating ATP but have also been shown to regulate cell death pathways. Indeed many of the same signals used to regulate metabolism and ATP production, such as calcium and reactive oxygen species, are also key regulators of mitochondrial cell death pathways. It is widely hypothesized that an increase in calcium and reactive oxygen species activate a large conductance channel in the inner mitochondrial membrane known as the PTP (permeability transition pore) and that opening of this pore leads to necroptosis, a regulated form of necrotic cell death. Strategies to reduce PTP opening either by inhibition of PTP or inhibiting the rise in mitochondrial calcium or reactive oxygen species that activate PTP have been proposed. A major limitation of inhibiting the PTP is the lack of knowledge about the identity of the protein(s) that form the PTP and how they are activated by calcium and reactive oxygen species. This review will critically evaluate the candidates for the pore-forming unit of the PTP and discuss recent data suggesting that assumption that the PTP is formed by a single molecular identity may need to be reconsidered.
    Keywords:  calcium; cell death; mitochondria; permeability; reactive oxygen species
    DOI:  https://doi.org/10.1161/CIRCRESAHA.119.316306
  13. Autophagy. 2020 Jan 16. 1-16
    Matsuda J, Takahashi A, Takabatake Y, Sakai S, Minami S, Yamamoto T, Fujimura R, Namba-Hamano T, Yonishi H, Nakamura J, Kimura T, Kaimori JY, Matsui I, Takahashi M, Nakao M, Izumi Y, Bamba T, Matsusaka T, Niimura F, Yanagita M, Yoshimori T, Isaka Y.
      Macroautophagy/autophagy is a lysosomal degradation system which plays a protective role against kidney injury. RUBCN/Rubicon (RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein) inhibits the fusion of autophagosomes and lysosomes. However, its physiological role in kidney proximal tubular epithelial cells (PTECs) remains uncertain. In the current study, we analyzed the phenotype of newly generated PTEC-specific rubcn-deficient (KO) mice. Additionally, we investigated the role of RUBCN in lipid metabolism using isolated rubcn-deficient PTECs. Although KO mice exhibited sustained high autophagic flux in PTECs, they were not protected from acute ischemic kidney injury. Unexpectedly, KO mice exhibited hallmark features of metabolic syndrome accompanied by expanded lysosomes containing multi-layered phospholipids in PTECs. RUBCN deficiency in cultured PTECs promoted the mobilization of phospholipids from cellular membranes to lysosomes via enhanced autophagy. Treatment of KO PTECs with oleic acid accelerated fatty acids transfer to mitochondria. Furthermore, KO PTECs promoted massive triglyceride accumulation in hepatocytes (BNL-CL2 cells) co-cultured in transwell, suggesting accelerated fatty acids efflux from the PTECs contributes to the metabolic syndrome in KO mice. This study shows that sustained high autophagic flux by RUBCN deficiency in PTECs leads to metabolic syndrome concomitantly with an accelerated mobilization of phospholipids from cellular membranes to lysosomes.Abbreviations: ABC: ATP binding cassette; ACADM: acyl-CoA dehydrogenase medium chain; ACTB: actin, beta; ATG: autophagy related; AUC: area under the curve; Baf: bafilomycin A1; BAT: brown adipose tissue; BODIPY: boron-dipyrromethene; BSA: bovine serum albumin; BW: body weight; CAT: chloramphenicol acetyltransferase; CM: complete medium; CPT1A: carnitine palmitoyltransferase 1a, liver; CQ: chloroquine; CTRL: control; EGFP: enhanced green fluorescent protein; CTSD: cathepsin D; EAT: epididymal adipose tissue; EGFR: epidermal growth factor receptor; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; FA: fatty acid; FBS: fetal bovine serum; GTT: glucose tolerance test; HE: hematoxylin and eosin; HFD: high-fat diet; I/R: ischemia-reperfusion; ITT: insulin tolerance test; KAP: kidney androgen regulated protein; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LD: lipid droplet; LRP2: low density lipoprotein receptor related protein 2; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MAT: mesenteric adipose tissue; MS: mass spectrometry; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NDRG1: N-myc downstream regulated 1; NDUFB5: NADH:ubiquinone oxidoreductase subunit B5; NEFA: non-esterified fatty acid; OA: oleic acid; OCT: optimal cutting temperature; ORO: Oil Red O; PAS: Periodic-acid Schiff; PFA: paraformaldehyde; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PPARA: peroxisome proliferator activated receptor alpha; PPARGC1A: PPARG coactivator 1 alpha; PTEC: proximal tubular epithelial cell; RAB7A: RAB7A, member RAS oncogene family; RPS6: ribosomal protein S6; RPS6KB1: ribosomal protein S6 kinase B1; RT: reverse transcription; RUBCN: rubicon autophagy regulator; SAT: subcutaneous adipose tissue; SFC: supercritical fluid chromatography; SQSTM1: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1; SV-40: simian virus-40; TFEB: transcription factor EB; TG: triglyceride; TS: tissue specific; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; UN: urea nitrogen; UQCRB: ubiquinol-cytochrome c reductase binding protein; UVRAG: UV radiation resistance associated; VPS: vacuolar protein sorting; WAT: white adipose tissue.
    Keywords:  Autophagic flux; RUBCN/Rubicon; autophagy; lipid efflux; lysosome; metabolic syndrome
    DOI:  https://doi.org/10.1080/15548627.2020.1712107
  14. Cell Metab. 2020 Jan 07. pii: S1550-4131(19)30672-2. [Epub ahead of print]31(1): 13-15
    Santoro MM.
      Although confirmed as the primary lipophilic antioxidant molecule endogenously produced by cells, the non-mitochondrial pool of CoQ10's functional role is still well debated. Recently, both Bersuker et al. (2019) and Doll et al. (2019) have identified FSP1 as a novel CoQ10 plasma membrane oxidoreductase, protecting cells from glutathione-independent ferroptosis.
    DOI:  https://doi.org/10.1016/j.cmet.2019.12.007
  15. RNA Biol. 2020 Jan 17. 1-12
    Powell CA, Minczuk M.
      RNA species play host to a plethora of post-transcriptional modifications which together make up the epitranscriptome. 5-methyluridine (m5U) is one of the most common modifications made to cellular RNA, where it is found almost ubiquitously in bacterial and eukaryotic cytosolic tRNAs at position 54. Here, we demonstrate that m5U54 in human mitochondrial tRNAs is catalysed by the nuclear-encoded enzyme TRMT2B, and that its repertoire of substrates is expanded to ribosomal RNAs, catalysing m5U429 in 12S rRNA. We show that TRMT2B is not essential for viability in human cells and that knocking-out the gene shows no obvious phenotype with regards to RNA stability, mitochondrial translation, or cellular growth.
    Keywords:  5-methyluridine; Mitochondria; post-transcriptional modifications; rRNA; tRNA
    DOI:  https://doi.org/10.1080/15476286.2020.1712544
  16. Mol Cancer Res. 2020 Jan 15. pii: molcanres.0606.2019. [Epub ahead of print]
    Li AM, Ducker GS, Li Y, Seoane JA, Xiao Y, Melemenidis S, Zhou Y, Liu L, Vanharanta S, Graves EE, Rankin EB, Curtis C, Massague J, Rabinowitz JD, Thompson CB, Ye J.
      Breast cancer is the most common cancer among American women and a major cause of mortality. To identify metabolic pathways as potential targets to treat metastatic breast cancer, we performed metabolomics profiling on breast cancer cell line MDA-MB-231 and its tissue-tropic metastatic subclones. Here, we report that these subclones with increased metastatic potential display an altered metabolic profile compared to the parental population. In particular, the mitochondrial serine and one-carbon (1C) unit pathway is upregulated in metastatic subclones. Mechanistically, the mitochondrial serine and 1C unit pathway drives the faster proliferation of subclones through enhanced de novo purine biosynthesis. Inhibition of the first rate-limiting enzyme of the mitochondrial serine and 1C unit pathway, serine hydroxymethyltransferase (SHMT2), potently suppresses proliferation of metastatic subclones in culture and impairs growth of lung metastatic subclones at both primary and metastatic sites in mice. Some human breast cancers exhibit a significant association between the expression of genes in the mitochondrial serine and 1C unit pathway with disease outcome and higher expression of SHMT2 in metastatic tumor tissue compared to primary tumors. In addition to breast cancer, a few other cancer types, such as adrenocortical carcinoma (ACC) and kidney chromophobe cell carcinoma (KICH), also display increased SHMT2 expression during disease progression. Together, these results suggest that mitochondrial serine and 1C unit plays an important role in promoting cancer progression, particularly in late stage cancer. Implications: This study identifies mitochondrial serine and 1C unit metabolism as an important pathway during the progression of a subset of human breast cancers.
    DOI:  https://doi.org/10.1158/1541-7786.MCR-19-0606
  17. Int J Mol Sci. 2020 Jan 05. pii: E355. [Epub ahead of print]21(1):
    Di Rita A, Maiorino T, Bruqi K, Volpicelli F, Bellenchi GC, Strappazzon F.
      The selective elimination of dysfunctional mitochondria through mitophagy is crucial for preserving mitochondrial quality and cellular homeostasis. The most described mitophagy pathway is regulated by a positive ubiquitylation feedback loop in which the PINK1 (PTEN induced kinase 1) kinase phosphorylates both ubiquitin and the E3 ubiquitin ligase PRKN (Parkin RBR E3 ubiquitin ligase), also known as PARKIN. This event recruits PRKN to the mitochondria, thus amplifying ubiquitylation signal. Here we report that miR-218 targets PRKN and negatively regulates PINK1/PRKN-mediated mitophagy. Overexpression of miR-218 reduces PRKN mRNA levels, thus also reducing protein content and deregulating the E3 ubiquitin ligase action. In fact, following miR-218 overexpression, mitochondria result less ubiquitylated and the autophagy machinery fails to proceed with correct mitochondrial clearance. Since mitophagy defects are associated with various human diseases, these results qualify miR-218 as a promising therapeutic target for human diseases.
    Keywords:  PARKIN/PRKN; miR-218; microRNA; mitochondria; mitophagy
    DOI:  https://doi.org/10.3390/ijms21010355
  18. Int J Biochem Cell Biol. 2020 Jan 10. pii: S1357-2725(20)30011-X. [Epub ahead of print] 105694
    Busch KB.
      Mitochondria are known as dynamic organelles that fuse and divide under the control of certain proteins. These dynamics are important to shape mitochondria, maintain a healthy mitochondrial population, and enable physiological adaptations, to name just a few key processes. We are less aware that mitochondrial membrane lipids and proteins also exhibit dynamics in terms of lateral mobility and translocation. This single molecule dynamics is equally important for the above processes as it enables interaction with other proteins and complexes. Here we discuss some mitochondrial proteins and the role of their specific dynamic spatiotemporal organization for function and adaptation. For example, respiratory proteins are preferentially localized in cristae sheets, ATP synthase at the edges of cristae and compounds of the MICOS complex at cristae junctions. Trajectory patterns show how and whether molecules are restricted in their mobility and how this determines their distribution. The formation of supercomplexes has an influence on this. Recent studies have also shown that the distribution of proteins is not absolutely static. For example, the metabolic state of the cell obviously determines the activity of the mitochondria and finally the organization of the bioenergetic and structure-determining proteins inside. The ATP synthase has both classifications and additionally shows functional interactions with other cristae shaping proteins at cristae cunctions. To understand the dynamics of mitochondria we have to consider all scales: from the dynamics of the molecular structure of the proteins to the dynamics of the molecules with respect to their localization and lateral mobility to the dynamics of the organelle structure.
    Keywords:  ATP synthase; MICOS; OXPHOS supercomplexes; Single molecule tracking; membrane protein diffusion; spatio-temporal organization; superresolution
    DOI:  https://doi.org/10.1016/j.biocel.2020.105694
  19. Methods Mol Biol. 2020 ;2108 197-207
    Kaur P, Nagar S, Bhagwat M, Uddin MM, Zhu Y, Vancura A.
      Interferon-γ (IFNγ) is a pleiotropic cytokine that signals to many different cell types. IFNγ has both antitumor functions and pro-tumorigenic effects and regulates different aspects of cell physiology, including metabolism. Cancer cells undergo a complex rearrangement of metabolic pathways that allows them to satisfy the needs of increased proliferation, and many cancer cells redirect glucose metabolism from oxidative phosphorylation to aerobic glycolysis. In this chapter, we describe a protocol that utilizes the Agilent Seahorse XFp Analyzer to assess mitochondrial respiration and glycolysis in ovarian cancer cells treated with IFNγ.
    Keywords:  Extracellular acidification; Glycolysis; Interferon-γ; Mitochondrial respiration; Ovarian cancer; Oxygen consumption rate
    DOI:  https://doi.org/10.1007/978-1-0716-0247-8_17
  20. Annu Rev Biochem. 2020 Jan 14.
    Lill R, Freibert SA.
      Mitochondria are essential in most eukaryotes and are involved in numerous biological functions including ATP production, cofactor biosyntheses, apoptosis, lipid synthesis, and steroid metabolism. Work over the past two decades has uncovered the biogenesis of cellular iron-sulfur (Fe/S) proteins as the essential and minimal function of mitochondria. This process is catalyzed by the bacteria-derived iron-sulfur cluster assembly (ISC) machinery and has been dissected into three major steps: de novo synthesis of a [2Fe-2S] cluster on a scaffold protein; Hsp70 chaperone-mediated trafficking of the cluster and insertion into [2Fe-2S] target apoproteins; and catalytic conversion of the [2Fe-2S] into a [4Fe-4S] cluster and subsequent insertion into recipient apoproteins. ISC components of the first two steps are also required for biogenesis of numerous essential cytosolic and nuclear Fe/S proteins, explaining the essentiality of mitochondria. This review summarizes the molecular mechanisms underlying the ISC protein-mediated maturation of mitochondrial Fe/S proteins and the importance for human disease. Expected final online publication date for the Annual Review of Biochemistry, Volume 89 is June 22, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
    DOI:  https://doi.org/10.1146/annurev-biochem-013118-111540
  21. J Clin Invest. 2020 Jan 13. pii: 130038. [Epub ahead of print]
    Luo C, Balsa E, Perry EA, Liang J, Tavares CD, Vazquez F, Widlund HR, Puigserver P.
      Oncogene-targeted and immune checkpoint therapies have revolutionized the clinical management of malignant melanoma and now offer hope to patients with advanced disease. Intimately connected to patients' overall clinical risk is whether the initial primary melanoma lesion will metastasize and cause advanced disease, but underlying mechanisms are not entirely understood. A subset of melanomas display heightened peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α) expression that maintains cell survival cues by promoting mitochondrial function, but also suppresses metastatic spread. Here, we show that PGC1α expression in melanoma cells was silenced by chromatin modifications that involve promoter H3K27 trimethylation. Pharmacological EZH2 inhibition diminished H3K27me3 histone markers, increased PGC1α expression, and functionally suppressed invasion within PGC1α-silenced melanoma cells. Mechanistically, PGC1α silencing activated transcription factor 12 (TCF12), to increase expression of WNT5A, which in turn stabilized YAP protein levels to promote melanoma migration and metastasis. Accordingly, inhibition of components of this transcription-signaling axis, including TCF12, WNT5A, or YAP, blocked melanoma migration in vitro and metastasis in vivo. These results indicate that epigenetic control of melanoma metastasis involved altered expression of PGC1α and an association with the inherent metabolic state of the tumor.
    Keywords:  Cancer; Cell Biology; Cell migration/adhesion; Melanoma; Oncology
    DOI:  https://doi.org/10.1172/JCI130038
  22. J Biol Chem. 2020 Jan 14. pii: jbc.RA119.010315. [Epub ahead of print]
    Mader J, Huber J, Bonn F, Doetsch V, Rogov VV, Bremm A.
      Deubiquitinases (DUBs) are vital for the regulation of ubiquitin signals, and both catalytic activity of and target recruitment by DUBs need to be tightly controlled. Here, we identify asparagine hydroxylation as a novel posttranslational modification involved in the regulation of Cezanne (also known as OTU domain-containing protein 7B (OTUD7B)), a DUB that controls key cellular functions and signaling pathways. We demonstrate that Cezanne is a substrate for factor inhibiting HIF1 (FIH1)- and oxygen-dependent asparagine hydroxylation. We found that FIH1 modifies Asn35 within the uncharacterized N-terminal ubiquitin-associated (UBA)-like domain of Cezanne (UBACez), which lacks conserved UBA domain properties. We show that UBACez binds Lys11-, Lys48-, Lys63- and Met1-linked ubiquitin chains in vitro, establishing UBACez as a functional ubiquitin-binding domain. Our findings also reveal that the interaction of UBACez with ubiquitin is mediated via a non-canonical surface, and that hydroxylation of Asn35 inhibits ubiquitin binding. Recently, it has been suggested that Cezanne recruitment to specific target proteins depends on UBACez Our results indicate that UBACez can indeed fulfil this role as regulatory domain by binding various ubiquitin chain types. They also uncover that this interaction with ubiquitin, and thus with modified substrates, can be modulated by oxygen-dependent asparagine hydroxylation, suggesting that Cezanne is regulated by oxygen levels.
    Keywords:  Cezanne; FIH1; UBA domain; deubiquitylation (deubiquitination); hydroxylation; nuclear magnetic resonance (NMR); post-translational modification (PTM); protein-protein interaction; ubiquitin
    DOI:  https://doi.org/10.1074/jbc.RA119.010315
  23. Nat Commun. 2020 Jan 16. 11(1): 139
    von Loga K, Woolston A, Punta M, Barber LJ, Griffiths B, Semiannikova M, Spain G, Challoner B, Fenwick K, Simon R, Marx A, Sauter G, Lise S, Matthews N, Gerlinger M.
      Mismatch repair deficient (dMMR) gastro-oesophageal adenocarcinomas (GOAs) show better outcomes than their MMR-proficient counterparts and high immunotherapy sensitivity. The hypermutator-phenotype of dMMR tumours theoretically enables high evolvability but their evolution has not been investigated. Here we apply multi-region exome sequencing (MSeq) to four treatment-naive dMMR GOAs. This reveals extreme intratumour heterogeneity (ITH), exceeding ITH in other cancer types >20-fold, but also long phylogenetic trunks which may explain the exquisite immunotherapy sensitivity of dMMR tumours. Subclonal driver mutations are common and parallel evolution occurs in RAS, PIK3CA, SWI/SNF-complex genes and in immune evasion regulators. MSeq data and evolution analysis of single region-data from 64 MSI GOAs show that chromosome 8 gains are early genetic events and that the hypermutator-phenotype remains active during progression. MSeq may be necessary for biomarker development in these heterogeneous cancers. Comparison with other MSeq-analysed tumour types reveals mutation rates and their timing to determine phylogenetic tree morphologies.
    DOI:  https://doi.org/10.1038/s41467-019-13915-7
  24. Cell Death Dis. 2020 Jan 13. 11(1): 26
    Ke Q, Yuan Q, Qin N, Shi C, Luo J, Fang Y, Xu L, Sun Q, Zen K, Jiang L, Zhou Y, Yang J.
      Mitochondrial dysfunction leads to loss of renal function and structure; however, the precise mechanisms by which mitochondrial function can regulate renal fibrosis remain unclear. Proximal tubular cells (PTCs) prefer fatty acid oxidation as their energy source and dysregulation of lipid metabolism has been linked to tubulointerstitial fibrosis (TIF). Here, we demonstrated that mitochondrial uncoupling protein 2 (UCP2) regulates TIF through the stimulation of lipid deposition and extracellular matrix (ECM) accumulation. We show that UCP2 expression was increased in human biopsy sample and mouse kidney tissues with TIF. Moreover, UCP2-deficient mice displayed mitigated renal fibrosis in I/R-induced mouse model of TIF. Consistent with these results, UCP2 deficiency displayed reduced lipid deposition and ECM accumulation in vivo and in vitro. In UCP2-deficient PTCs, inhibition of TIF resulted from downregulation of hypoxia-inducible factor-1α (HIF-1α), a key regulator of lipid metabolism and ECM accumulation. Furthermore, we describe a molecular mechanism by which UCP2 regulates HIF-1α stabilization through regulation of mitochondrial respiration and tissue hypoxia during TIF. HIF-1α inhibition by siRNA suppressed lipid and ECM accumulation by restoration of PPARα and CPT1α, as well as suppression of fibronectin and collagen I expression in PTCs. In conclusion, our results suggest that UCP2 regulates TIF by inducing the HIF-1α stabilization pathway in tubular cells. These results identify UCP2 as a potential therapeutic target in treating chronic renal fibrosis.
    DOI:  https://doi.org/10.1038/s41419-019-2219-4
  25. Biomolecules. 2020 Jan 14. pii: E135. [Epub ahead of print]10(1):
    Avolio R, Matassa DS, Criscuolo D, Landriscina M, Esposito F.
      Metabolic reprogramming, carried out by cancer cells to rapidly adapt to stress such as hypoxia and limited nutrient conditions, is an emerging concepts in tumor biology, and is now recognized as one of the hallmarks of cancer. In contrast with conventional views, based on the classical Warburg effect, these metabolic alterations require fully functional mitochondria and finely-tuned regulations of their activity. In turn, the reciprocal regulation of the metabolic adaptations of cancer cells and the microenvironment critically influence disease progression and response to therapy. This is also realized through the function of specific stress-adaptive proteins, which are able to relieve oxidative stress, inhibit apoptosis, and facilitate the switch between metabolic pathways. Among these, the molecular chaperone tumor necrosis factor receptor associated protein 1 (TRAP1), the most abundant heat shock protein 90 (HSP90) family member in mitochondria, is particularly relevant because of its role as an oncogene or a tumor suppressor, depending on the metabolic features of the specific tumor. This review highlights the interplay between metabolic reprogramming and cancer progression, and the role of mitochondrial activity and oxidative stress in this setting, examining the possibility of targeting pathways of energy metabolism as a therapeutic strategy to overcome drug resistance, with particular emphasis on natural compounds and inhibitors of mitochondrial HSP90s.
    Keywords:  cancer metabolic reprogramming; drug resistance; heat shock protein 90 (HSP90); oxidative stress; targeting metabolism for cancer therapy; tumor necrosis factor receptor associated protein 1 (TRAP1)
    DOI:  https://doi.org/10.3390/biom10010135
  26. Nat Rev Rheumatol. 2020 Jan 16.
    Sharabi A, Tsokos GC.
      T cell subsets are critically involved in the development of systemic autoimmunity and organ inflammation in systemic lupus erythematosus (SLE). Each T cell subset function (such as effector, helper, memory or regulatory function) is dictated by distinct metabolic pathways requiring the availability of specific nutrients and intracellular enzymes. The activity of these enzymes or nutrient transporters influences the differentiation and function of T cells in autoimmune responses. Data are increasingly emerging on how metabolic processes control the function of various T cell subsets and how these metabolic processes are altered in SLE. Specifically, aberrant glycolysis, glutaminolysis, fatty acid and glycosphingolipid metabolism, mitochondrial hyperpolarization, oxidative stress and mTOR signalling underwrite the known function of T cell subsets in patients with SLE. A number of medications that are used in the care of patients with SLE affect cell metabolism, and the development of novel therapeutic approaches to control the activity of metabolic enzymes in T cell subsets represents a promising endeavour in the search for effective treatment of systemic autoimmune diseases.
    DOI:  https://doi.org/10.1038/s41584-019-0356-x
  27. Nat Commun. 2020 Jan 14. 11(1): 259
    Lohard S, Bourgeois N, Maillet L, Gautier F, Fétiveau A, Lasla H, Nguyen F, Vuillier C, Dumont A, Moreau-Aubry A, Frapin M, David L, Loussouarn D, Kerdraon O, Campone M, Jézéquel P, Juin PP, Barillé-Nion S.
      A fascinating but uncharacterized action of antimitotic chemotherapy is to collectively prime cancer cells to apoptotic mitochondrial outer membrane permeabilization (MOMP), while impacting only on cycling cell subsets. Here, we show that a proapoptotic secretory phenotype is induced by activation of cGAS/STING in cancer cells that are hit by antimitotic treatment, accumulate micronuclei and maintain mitochondrial integrity despite intrinsic apoptotic pressure. Organotypic cultures of primary human breast tumors and patient-derived xenografts sensitive to paclitaxel exhibit gene expression signatures typical of type I IFN and TNFα exposure. These cytokines induced by cGAS/STING activation trigger NOXA expression in neighboring cells and render them acutely sensitive to BCL-xL inhibition. cGAS/STING-dependent apoptotic effects are required for paclitaxel response in vivo, and they are amplified by sequential, but not synchronous, administration of BH3 mimetics. Thus anti-mitotic agents propagate apoptotic priming across heterogeneously sensitive cancer cells through cytosolic DNA sensing pathway-dependent extracellular signals, exploitable by delayed MOMP targeting.
    DOI:  https://doi.org/10.1038/s41467-019-13689-y
  28. Br J Cancer. 2020 Jan 16.
    Casciano JC, Perry C, Cohen-Nowak AJ, Miller KD, Vande Voorde J, Zhang Q, Chalmers S, Sandison ME, Liu Q, Hedley A, McBryan T, Tang HY, Gorman N, Beer T, Speicher DW, Adams PD, Liu X, Schlegel R, McCarron JG, Wakelam MJO, Gottlieb E, Kossenkov AV, Schug ZT.
      BACKGROUND: Recent studies have suggested that fatty acid oxidation (FAO) is a key metabolic pathway for the growth of triple negative breast cancers (TNBCs), particularly those that have high expression of MYC. However, the underlying mechanism by which MYC promotes FAO remains poorly understood.METHODS: We used a combination of metabolomics, transcriptomics, bioinformatics, and microscopy to elucidate a potential mechanism by which MYC regulates FAO in TNBC.
    RESULTS: We propose that MYC induces a multigenic program that involves changes in intracellular calcium signalling and fatty acid metabolism. We determined key roles for fatty acid transporters (CD36), lipases (LPL), and kinases (PDGFRB, CAMKK2, and AMPK) that each contribute to promoting FAO in human mammary epithelial cells that express oncogenic levels of MYC. Bioinformatic analysis further showed that this multigenic program is highly expressed and predicts poor survival in the claudin-low molecular subtype of TNBC, but not other subtypes of TNBCs, suggesting that efforts to target FAO in the clinic may best serve claudin-low TNBC patients.
    CONCLUSION: We identified critical pieces of the FAO machinery that have the potential to be targeted for improved treatment of patients with TNBC, especially the claudin-low molecular subtype.
    DOI:  https://doi.org/10.1038/s41416-019-0711-3
  29. Antioxid Redox Signal. 2020 Jan 13.
    Montagna C, Cirotti C, Rizza S, Filomeni G.
      SIGNIFICANCE: Cysteines have an essential role in redox signaling, transforming an oxidant signal into a biological response. Among reversible cysteine post-translational modifications, S-nitrosylation acts as a redox-switch in several patho-physiological events, such as ischemia-reperfusion, synaptic transmission, cancer, and muscular dysfunctions. Recent Advances: Growing pieces of in vitro and in vivo evidence argue for S-nitrosylation being deeply involved in development and aging, and playing a role in the onset of different pathological states. New findings suggest it being an enzymatically regulated cellular process, with deep impact on mitochondrial structure and function, and in cellular metabolism. In light of this, the recent discovery of the new denitrosylase S-nitrosoCoA reductase takes on even greater importance and opens new perspectives on S-nitrosylation as general mechanism of cellular homeostasis.CRITICAL ISSUES: Based on these recent findings, we aim at summarizing and elaborating on the established and emerging crucial roles of S-nitrosylation in mitochondrial metabolism and mitophagy, and provide an overview of the patho-physiological effects induced by its deregulation.
    FUTURE DIRECTIONS: The identification of new S-nitrosylation targets, and the comprehension of the mechanisms through which S-nitrosylation modulates specific classes of proteins, i.e. those impinging on diverse mitochondrial functions, may help better understand the pathophysiology of aging, and propose lines of intervention to slow down or extend the onset of aging-related diseases.
    DOI:  https://doi.org/10.1089/ars.2019.7872
  30. Nat Rev Cancer. 2020 Jan 13.
    Vishwakarma M, Piddini E.
      The tumour microenvironment plays a critical role in determining tumour fate. Within that environment, and indeed throughout epithelial tissues, cells experience competition with their neighbours, with those less fit being eliminated by fitter adjacent cells. Herein we discuss evidence suggesting that mutations in cancer cells may be selected for their ability to exploit cell competition to kill neighbouring host cells, thereby facilitating tumour expansion. In some instances, cell competition may help host tissues to defend against cancer, by removing neoplastic and aneuploid cells. Cancer risk factors, such as high-sugar or high-fat diet and inflammation, impact cell competition-based host defences, suggesting that their effect on tumour risk may in part be accounted for by their influence on cell competition. We propose that interventions aimed at modifying the strength and direction of cell competition could induce cancer cell killing and form the basis for novel anticancer therapies.
    DOI:  https://doi.org/10.1038/s41568-019-0231-8
  31. Nat Rev Mol Cell Biol. 2020 Jan 14.
    Liu GY, Sabatini DM.
      The mTOR pathway integrates a diverse set of environmental cues, such as growth factor signals and nutritional status, to direct eukaryotic cell growth. Over the past two and a half decades, mapping of the mTOR signalling landscape has revealed that mTOR controls biomass accumulation and metabolism by modulating key cellular processes, including protein synthesis and autophagy. Given the pathway's central role in maintaining cellular and physiological homeostasis, dysregulation of mTOR signalling has been implicated in metabolic disorders, neurodegeneration, cancer and ageing. In this Review, we highlight recent advances in our understanding of the complex regulation of the mTOR pathway and discuss its function in the context of physiology, human disease and pharmacological intervention.
    DOI:  https://doi.org/10.1038/s41580-019-0199-y
  32. Sci Rep. 2020 Jan 17. 10(1): 546
    Uribe-Lewis S, Carroll T, Menon S, Nicholson A, Manasterski PJ, Winton DJ, Buczacki SJA, Murrell A.
      Cytosine hydroxymethylation (5hmC) in mammalian DNA is the product of oxidation of methylated cytosines (5mC) by Ten-Eleven-Translocation (TET) enzymes. While it has been shown that the TETs influence 5mC metabolism, pluripotency and differentiation during early embryonic development, the functional relationship between gene expression and 5hmC in adult (somatic) stem cell differentiation is still unknown. Here we report that 5hmC levels undergo highly dynamic changes during adult stem cell differentiation from intestinal progenitors to differentiated intestinal epithelium. We profiled 5hmC and gene activity in purified mouse intestinal progenitors and differentiated progeny to identify 43425 differentially hydroxymethylated regions and 5325 differentially expressed genes. These differentially marked regions showed both losses and gains of 5hmC after differentiation, despite lower global levels of 5hmC in progenitor cells. In progenitors, 5hmC did not correlate with gene transcript levels, however, upon differentiation the global increase in 5hmC content showed an overall positive correlation with gene expression level as well as prominent associations with histone modifications that typify active genes and enhancer elements. Our data support a gene regulatory role for 5hmC that is predominant over its role in controlling DNA methylation states.
    DOI:  https://doi.org/10.1038/s41598-019-57214-z
  33. Nat Biotechnol. 2020 Jan 13.
    Patgiri A, Skinner OS, Miyazaki Y, Schleifer G, Marutani E, Shah H, Sharma R, Goodman RP, To TL, Robert Bao X, Ichinose F, Zapol WM, Mootha VK.
      An elevated intracellular NADH:NAD+ ratio, or 'reductive stress', has been associated with multiple diseases, including disorders of the mitochondrial electron transport chain. As the intracellular NADH:NAD+ ratio can be in near equilibrium with the circulating lactate:pyruvate ratio, we hypothesized that reductive stress could be alleviated by oxidizing extracellular lactate to pyruvate. We engineered LOXCAT, a fusion of bacterial lactate oxidase (LOX) and catalase (CAT), which irreversibly converts lactate and oxygen to pyruvate and water. Addition of purified LOXCAT to the medium of cultured human cells with a defective electron transport chain decreased the extracellular lactate:pyruvate ratio, normalized the intracellular NADH:NAD+ ratio, upregulated glycolytic ATP production and restored cellular proliferation. In mice, tail-vein-injected LOXCAT lowered the circulating lactate:pyruvate ratio, blunted a metformin-induced rise in blood lactate:pyruvate ratio and improved NADH:NAD+ balance in the heart and brain. Our study lays the groundwork for a class of injectable therapeutic enzymes that alleviates intracellular redox imbalances by directly targeting circulating redox-coupled metabolites.
    DOI:  https://doi.org/10.1038/s41587-019-0377-7
  34. Nat Commun. 2020 Jan 13. 11(1): 190
    Kim M, Sujkowski A, Namkoong S, Gu B, Cobb T, Kim B, Kowalsky AH, Cho CS, Semple I, Ro SH, Davis C, Brooks SV, Karin M, Wessells RJ, Lee JH.
      Exercise is among the most effective interventions for age-associated mobility decline and metabolic dysregulation. Although long-term endurance exercise promotes insulin sensitivity and expands respiratory capacity, genetic components and pathways mediating the metabolic benefits of exercise have remained elusive. Here, we show that Sestrins, a family of evolutionarily conserved exercise-inducible proteins, are critical mediators of exercise benefits. In both fly and mouse models, genetic ablation of Sestrins prevents organisms from acquiring metabolic benefits of exercise and improving their endurance through training. Conversely, Sestrin upregulation mimics both molecular and physiological effects of exercise, suggesting that it could be a major effector of exercise metabolism. Among the various targets modulated by Sestrin in response to exercise, AKT and PGC1α are critical for the Sestrin effects in extending endurance. These results indicate that Sestrin is a key integrating factor that drives the benefits of chronic exercise to metabolism and physical endurance.
    DOI:  https://doi.org/10.1038/s41467-019-13442-5
  35. Cancer Discov. 2020 Jan 15. pii: CD-19-0435. [Epub ahead of print]
    Sodir NM, Kortlever RM, Barthet VJA, Campos T, Pellegrinet L, Kupczak S, Anastasiou P, Brown Swigart L, Soucek L, Arends MJ, Littlewood TD, Evan GI.
      The signature features of pancreatic ductal adenocarcinoma (PDAC) are its fibroinflammatory stroma, poor immune activity and dismal prognosis. We show that acute activation of Myc in indolent PanIN epithelial cells in vivo is, alone, sufficient to trigger immediate release of instructive signals that together coordinate changes in multiple stromal and immune cell types and trigger transition to pancreatic adenocarcinomas that share all the characteristic stromal features of their spontaneous human counterpart. We also demonstrate that this Myc-driven PDAC switch is completely and immediately reversible: Myc deactivation/inhibition triggers meticulous disassembly of advanced PDAC tumor and stroma and concomitant death of tumor cells. Hence, both the formation and deconstruction of the complex PDAC phenotype are continuously dependent on a single, reversible Myc switch.
    DOI:  https://doi.org/10.1158/2159-8290.CD-19-0435