bims-mibica 2023-05-21 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2023–05–21
thirty-one papers selected by
Kelsey Fisher-Wellman, East Carolina University

The cyclic lipopeptide micafungin induces rupture of isolated mitochondria by reprograming the mitochondrial inner membrane anion channel.
Role of creatine shuttle in colorectal cancer cells.
Mechanism of rotenone binding to respiratory complex I depends on ligand flexibility.
Inflamed macrophages sans mitochondrial pyruvate carrier?
VDAC as a voltage-dependent mitochondrial gatekeeper under physiological conditions.
GPAM mediated lysophosphatidic acid synthesis regulates mitochondrial dynamics in acute myeloid leukemia.
Systematic identification of anticancer drug targets reveals a nucleus-to-mitochondria ROS-sensing pathway.
Metabolic Adaptation to Tyrosine Kinase Inhibition in Leukemia Stem Cells.
Generating Mitochondrial-Nuclear Exchange (MNX) Mice to Identify Mitochondrial Determinants of Cancer Metastasis.
Uridine-derived ribose fuels glucose-restricted pancreatic cancer.
The mitochondrial intermembrane space protein mitofissin drives mitochondrial fission required for mitophagy.
Role of UCP2 in the Energy Metabolism of the Cancer Cell Line A549.
Weight loss increases skeletal muscle mitochondrial energy efficiency in obese mice.
Impact of acute stress on murine metabolomics and metabolic flux.
Conserved cardiolipin-mitochondrial ADP/ATP carrier interactions assume distinct structural and functional roles that are clinically relevant.
Dichloroacetic acid and rapamycin synergistically inhibit tumor progression.
Bioactive Compounds from Curcuma amada and Their Effect on Acute Myeloid Leukemia.
Metformin reprograms tryptophan metabolism to stimulate CD8+ T cell function in colorectal cancer.
Ferroptosis: the vulnerability within a cancer monster.
Mitochondrial pyruvate carrier-mediated metabolism is dispensable for the classical activation of macrophages.
Using mass spectrometry imaging to map fluxes quantitatively in the tumor ecosystem.
Salvage of ribose from uridine or RNA supports glycolysis in nutrient-limited conditions.
Mitochondrial DNA Changes in Respiratory Complex I Genes in Brain Gliomas.
Cancer-cell-derived fumarate suppresses the anti-tumor capacity of CD8+ T cells in the tumor microenvironment.
Excess dietary sugar alters colonocyte metabolism and impairs the proliferative response to damage.
PD-L1 stimulation can promote proliferation and survival of leukemic cells by influencing glucose and fatty acid metabolism in acute myeloid leukemia.
Targeting NRF2 uncovered an intrinsic susceptibility of acute myeloid leukemia cells to ferroptosis.
Emerging roles of nucleotide metabolism in cancer.
A small protein coded within the mitochondrial canonical gene nd4 regulates mitochondrial bioenergetics.
Mechanism of ADP-Inhibited ATP Hydrolysis in Single Proton-Pumping FoF1-ATP Synthase Trapped in Solution.
Venetoclax with decitabine or azacitidine in the first-line treatment of acute myeloid leukemia.

Mitochondrion. 2023 May 16. pii: S1567-7249(23)00037-5. [Epub ahead of print]

The cyclic lipopeptide micafungin induces rupture of isolated mitochondria by reprograming the mitochondrial inner membrane anion channel.

Jonathan Hosler, Ngoc Hoang, Kristin Shirey Edwards.

  The antifungal activity of the drug micafungin, a cyclic lipopeptide that interacts with membrane proteins, may involve inhibition of fungal mitochondria. In humans, mitochondria are spared by the inability of micafungin to cross the cytoplasmic membrane. Using isolated mitochondria, we find that micafungin initiates the uptake of salts, causing rapid swelling and rupture of mitochondria with release of cytochrome c. The inner membrane anion channel (IMAC) is altered by micafungin to transfer both cations and anions. We propose that binding of anionic micafungin to IMAC attracts cations into the ion pore for the rapid transfer of ion pairs.

Keywords:  Anion transport; Cyclic lipopeptides; Inner mitochondrial anion channel; Ion channel; Micafungin; Mitochondrial respiratory chain complex; Mitochondrial transport

DOI:  https://doi.org/10.1016/j.mito.2023.05.004
Oncotarget. 2023 May 19. 14 485-501

Role of creatine shuttle in colorectal cancer cells.

Mayu Kita, Rina Fujiwara-Tani, Shingo Kishi, Shiori Mori, Hitoshi Ohmori, Chie Nakashima, Kei Goto, Takamitsu Sasaki, Kiyomu Fujii, Isao Kawahara, Ujjal Kumar Bhawal, Yi Luo, Hiroki Kuniyasu.

  The creatine shuttle translocates the energy generated by oxidative phosphorylation to the cytoplasm via mitochondrial creatine kinase (MTCK) and creatine kinase B (CKB) in the cytoplasm. It is not apparent how the creatine shuttle is related to cancer. Here, we analyzed the expression and function of CKB and MTCK in colorectal cancer (CRC) and investigated the role of the creatine shuttle in CRC. Compared with normal mucosa, 184 CRC tissues had higher levels of CKB and MTCK, and these levels were associated with histological grade, tumor invasion, and distant metastasis. CK inhibitor dinitrofluorobenzene (DNFB) on CRC cell lines HT29 and CT26 inhibited cell proliferation and stemness to less than 2/3 and 1/20 of their control levels, respectively. In this treatment, the production of reactive oxygen species increased, mitochondrial respiration decreased, and mitochondrial volume and membrane potential decreased. In a syngeneic BALB/c mouse model using CT26 cells pretreated with DNFB, peritoneal metastasis was suppressed to 70%. Phosphorylation of EGFR, AKT, and ERK1/2 was inhibited in DNFB-treated tumors. High ATP concentrations prevented EGFR phosphorylation in HT29 cells following DNFB treatment, CKB or MTCK knockdown, and cyclocreatine administration. Despite not being immunoprecipitated, CKB and EGFR were brought closer together by EGF stimulation. These findings imply that blocking the creatine shuttle decreases the energy supply, suppresses oxidative phosphorylation, and blocks ATP delivery to phosphorylation signals, preventing signal transduction. These findings highlight the critical role of the creatine shuttle in cancer cells and suggest a potential new cancer treatment target.

Keywords:  ATP metabolism; creatine kinase B; mitochondrial creatine kinase; phosphorylation signal; stemness

DOI:  https://doi.org/10.18632/oncotarget.28436
Sci Rep. 2023 Apr 25. 13(1): 6738

Mechanism of rotenone binding to respiratory complex I depends on ligand flexibility.

Caroline S Pereira, Murilo H Teixeira, David A Russell, Judy Hirst, Guilherme M Arantes.

Respiratory complex I is a major cellular energy transducer located in the inner mitochondrial membrane. Its inhibition by rotenone, a natural isoflavonoid, has been used for centuries by indigenous peoples to aid in fishing and, more recently, as a broad-spectrum pesticide or even a possible anticancer therapeutic. Unraveling the molecular mechanism of rotenone action will help to design tuned derivatives and to understand the still mysterious catalytic mechanism of complex I. Although composed of five fused rings, rotenone is a flexible molecule and populates two conformers, bent and straight. Here, a rotenone derivative locked in the straight form was synthesized and found to inhibit complex I with 600-fold less potency than natural rotenone. Large-scale molecular dynamics and free energy simulations of the pathway for ligand binding to complex I show that rotenone is more stable in the bent conformer, either free in the membrane or bound to the redox active site in the substrate-binding Q-channel. However, the straight conformer is necessary for passage from the membrane through the narrow entrance of the channel. The less potent inhibition of the synthesized derivative is therefore due to its lack of internal flexibility, and interconversion between bent and straight forms is required to enable efficient kinetics and high stability for rotenone binding. The ligand also induces reconfiguration of protein loops and side-chains inside the Q-channel similar to structural changes that occur in the open to closed conformational transition of complex I. Detailed understanding of ligand flexibility and interactions that determine rotenone binding may now be exploited to tune the properties of synthetic derivatives for specific applications.

DOI: https://doi.org/10.1038/s41598-023-33333-6
Nat Metab. 2023 May 15.

Inflamed macrophages sans mitochondrial pyruvate carrier?

Laurent Yvan-Charvet, Edward Benjamin Thorp.

DOI: https://doi.org/10.1038/s42255-023-00789-9
Biochim Biophys Acta Biomembr. 2023 May 16. pii: S0005-2736(23)00057-3. [Epub ahead of print] 184175

VDAC as a voltage-dependent mitochondrial gatekeeper under physiological conditions.

Victor V Lemeshko.

  Mitochondria, composed of two membranes, play a key role in energy production in eukaryotic cells. The main function of the inner membrane is oxidative phosphorylation, while the mitochondrial outer membrane (MOM) seems to control the energy flux and exchange of various charged metabolites between mitochondria and the cytosol. Metabolites cross MOM via the various isoforms of voltage-dependent anion channel (VDAC). In turn, VDACs interact with some enzymes, other proteins and molecules, including drugs. This work aimed to analyze various literature experimental data related to targeting mitochondrial VDACs and VDAC-kinase complexes on the basis of the hypothesis of generation of the outer membrane potential (OMP) and OMP-dependent reprogramming of cell energy metabolism. Our previous model of the VDAC-hexokinase-linked generation of OMP was further complemented in this study with an additional regulation of the MOM permeability by the OMP-dependent docking of cytosolic proteins like tubulin to VDACs. Computational analysis of the model suggests that OMP changes might be involved in the mechanisms of apoptosis promotion through the so-called transient hyperpolarization of mitochondria. The high concordance of the performed computational estimations with many published experimental data allows concluding that OMP generation under physiological conditions is highly probable and VDAC might function as an OMP-dependent gatekeeper of mitochondria, controlling cell life and death. The proposed model of OMP generation allows understanding in more detail the mechanisms of cancer death resistance and anticancer action of various drugs and treatments influencing VDAC voltage-gating properties, VDAC content, mitochondrial hexokinase activity and VDAC-kinase interactions in MOM.

Keywords:  Diseases; Membrane potential; Mitochondria; Mitochondrial outer membrane; VDAC

DOI:  https://doi.org/10.1016/j.bbamem.2023.184175
Cancer Sci. 2023 May 17.

GPAM mediated lysophosphatidic acid synthesis regulates mitochondrial dynamics in acute myeloid leukemia.

Hidetoshi Irifune, Yu Kochi, Toshihiro Miyamoto, Teppei Sakoda, Koji Kato, Yuya Kunisaki, Koichi Akashi, Yoshikane Kikushige.

  Metabolic alterations, especially in the mitochondria, play important roles in several kinds of cancers, including acute myeloid leukemia (AML). However, AML-specific molecular mechanisms that regulate mitochondrial dynamics remain elusive. Through the metabolite screening comparing CD34+ AML cells and healthy hematopoietic stem/progenitor cells, we identified enhanced lysophosphatidic acid (LPA) synthesis activity in AML. LPA is synthesized from glycerol-3-phosphate by glycerol-3-phosphate acyltransferases (GPATs), rate-limiting enzymes of the LPA synthesis pathway. Among the four isozymes of GPATs, glycerol-3-phosphate acyltransferases, mitochondrial (GPAM) was highly expressed in AML cells, and the inhibition of LPA synthesis by silencing GPAM or FSG67 (a GPAM-inhibitor) significantly impaired AML propagation through the induction of mitochondrial fission, resulting in the suppression of oxidative phosphorylation and the elevation of reactive oxygen species. Notably, inhibition of this metabolic synthesis pathway by FSG67 administration did not affect normal human hematopoiesis in vivo. Therefore, the GPAM-mediated LPA synthesis pathway from G3P represents a critical metabolic mechanism that specifically regulates mitochondrial dynamics in human AML, and GPAM is a promising potential therapeutic target.

Keywords:  GPAM; acute myeloid leukemia; lysophosphatidic acid; mitochondrial dynamics; oxidative phosphorylation

DOI:  https://doi.org/10.1111/cas.15835
Cell. 2023 May 11. pii: S0092-8674(23)00422-1. [Epub ahead of print]

Systematic identification of anticancer drug targets reveals a nucleus-to-mitochondria ROS-sensing pathway.

Junbing Zhang, Claire M Simpson, Jacqueline Berner, Harrison B Chong, Jiafeng Fang, Zehra Ordulu, Tommy Weiss-Sadan, Anthony P Possemato, Stefan Harry, Mariko Takahashi, Tzu-Yi Yang, Marianne Richter, Himani Patel, Abby E Smith, Alexander D Carlin, Adriaan F Hubertus de Groot, Konstantin Wolf, Lei Shi, Ting-Yu Wei, Benedikt R Dürr, Nicholas J Chen, Tristan Vornbäumen, Nina O Wichmann, Mohammed S Mahamdeh, Venkatesh Pooladanda, Yusuke Matoba, Shaan Kumar, Eugene Kim, Sara Bouberhan, Esther Oliva, Bo R Rueda, Roy J Soberman, Nabeel Bardeesy, Brian B Liau, Michael Lawrence, Matt P Stokes, Sean A Beausoleil, Liron Bar-Peled.

  Multiple anticancer drugs have been proposed to cause cell death, in part, by increasing the steady-state levels of cellular reactive oxygen species (ROS). However, for most of these drugs, exactly how the resultant ROS function and are sensed is poorly understood. It remains unclear which proteins the ROS modify and their roles in drug sensitivity/resistance. To answer these questions, we examined 11 anticancer drugs with an integrated proteogenomic approach identifying not only many unique targets but also shared ones-including ribosomal components, suggesting common mechanisms by which drugs regulate translation. We focus on CHK1 that we find is a nuclear H2O2 sensor that launches a cellular program to dampen ROS. CHK1 phosphorylates the mitochondrial DNA-binding protein SSBP1 to prevent its mitochondrial localization, which in turn decreases nuclear H2O2. Our results reveal a druggable nucleus-to-mitochondria ROS-sensing pathway-required to resolve nuclear H2O2 accumulation and mediate resistance to platinum-based agents in ovarian cancers.

Keywords:  CHK1; chemical proteomics; chemoresistance; mitochondrial translation; nuclear ROS; nucleus-to-mitochondria signaling

DOI:  https://doi.org/10.1016/j.cell.2023.04.026
Blood. 2023 May 16. pii: blood.2022018196. [Epub ahead of print]

Metabolic Adaptation to Tyrosine Kinase Inhibition in Leukemia Stem Cells.

Shaowei Qiu, Vipul S Sheth, Chengcheng Yan, Juan Liu, Balu K Chacko, Hui Li, David K Crossman, Seth D Fortmann, Sajesan Aryal, Ashley Rennhack, Maria B Grant, Robert S Welner, Andrew J Paterson, Adam R Wende, Victor M Darley-Usmar, Rui Lu, Jason W Locasale, Ravi Bhatia.

Tyrosine kinase inhibitors (TKI) are very effective in treating chronic myelogenous leukemia (CML), but primitive, quiescent leukemia stem cells persist as a barrier to cure. We performed a comprehensive evaluation of metabolic adaptation to TKI treatment and its role in CML hematopoietic stem and progenitor cell persistence. Using a CML mouse model, we found that glycolysis, glutaminolysis, TCA cycle and oxidative phosphorylation (OXPHOS) were initially inhibited by TKI treatment in CML committed progenitors but were restored with continued treatment, reflecting both selection and metabolic reprogramming of specific subpopulations. TKI treatment selectively enriched primitive CML stem cells with reduced metabolic gene expression. Persistent CML stem cells also showed metabolic adaptation to TKI treatment through altered substrate utilization and maintenance of mitochondrial respiration. Evaluation of transcription factors underlying these changes identified increased HIF-1 protein levels and activity in TKI-treated stem cells. Treatment with a HIF-1 inhibitor depleted murine and human CML stem cells in combination with TKI treatment. HIF-1 inhibition increased mitochondrial activity and ROS levels, and reduced quiescence, increased cycling, and reduced self-renewal and regenerating potential of dormant CML stem cells. We therefore identify HIF-1-mediated inhibition of OXPHOS and ROS and maintenance of CML stem cell dormancy and repopulating potential as a key mechanism of CML stem cell adaptation to TKI treatment. Our results identify a key metabolic dependency in CML stem cells persisting after TKI treatment that can be targeted to enhance their elimination.

DOI: https://doi.org/10.1182/blood.2022018196
Methods Mol Biol. 2023 ;2660 43-59

Generating Mitochondrial-Nuclear Exchange (MNX) Mice to Identify Mitochondrial Determinants of Cancer Metastasis.

Danny R Welch, Melissa A Larson, Carolyn J Vivian, Jay L Vivian.

  Understanding the contributions of mitochondrial genetics to disease pathogenesis is facilitated by a new and unique model-the mitochondrial-nuclear exchange mouse. Here we report the rationale for their development, the methods used to create them, and a brief summary of how MNX mice have been used to understand the contributions of mitochondrial DNA in multiple diseases, focusing on cancer metastasis. Polymorphisms in mtDNA which distinguish mouse strains exert intrinsic and extrinsic effects on metastasis efficiency by altering epigenetic marks in the nuclear genome, changing production of reactive oxygen species, altering the microbiota, and influencing immune responses to cancer cells. Although the focus of this report is cancer metastasis, MNX mice have proven to be valuable in studying mitochondrial contributions to other diseases as well.

Keywords:  Animal model; Genetics; Mitochondria; Mitochondria-nuclear exchange mice

DOI:  https://doi.org/10.1007/978-1-0716-3163-8_4
Nature. 2023 May 17.

Uridine-derived ribose fuels glucose-restricted pancreatic cancer.

Zeribe C Nwosu, Matthew H Ward, Peter Sajjakulnukit, Pawan Poudel, Chanthirika Ragulan, Steven Kasperek, Megan Radyk, Damien Sutton, Rosa E Menjivar, Anthony Andren, Juan J Apiz-Saab, Zachary Tolstyka, Kristee Brown, Ho-Joon Lee, Lindsey N Dzierozynski, Xi He, Hari Ps, Julia Ugras, Gift Nyamundanda, Li Zhang, Christopher J Halbrook, Eileen S Carpenter, Jiaqi Shi, Leah P Shriver, Gary J Patti, Alexander Muir, Marina Pasca di Magliano, Anguraj Sadanandam, Costas A Lyssiotis.

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease notoriously resistant to therapy1,2. This is mediated in part by a complex tumour microenvironment3, low vascularity4, and metabolic aberrations5,6. Although altered metabolism drives tumour progression, the spectrum of metabolites used as nutrients by PDA remains largely unknown. Here we identified uridine as a fuel for PDA in glucose-deprived conditions by assessing how more than 175 metabolites impacted metabolic activity in 21 pancreatic cell lines under nutrient restriction. Uridine utilization strongly correlated with the expression of uridine phosphorylase 1 (UPP1), which we demonstrate liberates uridine-derived ribose to fuel central carbon metabolism and thereby support redox balance, survival and proliferation in glucose-restricted PDA cells. In PDA, UPP1 is regulated by KRAS-MAPK signalling and is augmented by nutrient restriction. Consistently, tumours expressed high UPP1 compared with non-tumoural tissues, and UPP1 expression correlated with poor survival in cohorts of patients with PDA. Uridine is available in the tumour microenvironment, and we demonstrated that uridine-derived ribose is actively catabolized in tumours. Finally, UPP1 deletion restricted the ability of PDA cells to use uridine and blunted tumour growth in immunocompetent mouse models. Our data identify uridine utilization as an important compensatory metabolic process in nutrient-deprived PDA cells, suggesting a novel metabolic axis for PDA therapy.

DOI: https://doi.org/10.1038/s41586-023-06073-w
Mol Cell. 2023 May 06. pii: S1097-2765(23)00316-7. [Epub ahead of print]

The mitochondrial intermembrane space protein mitofissin drives mitochondrial fission required for mitophagy.

Tomoyuki Fukuda, Kentaro Furukawa, Tatsuro Maruyama, Shun-Ichi Yamashita, Daisuke Noshiro, Chihong Song, Yuta Ogasawara, Kentaro Okuyama, Jahangir Md Alam, Manabu Hayatsu, Tetsu Saigusa, Keiichi Inoue, Kazuho Ikeda, Akira Takai, Lin Chen, Vikramjit Lahiri, Yasushi Okada, Shinsuke Shibata, Kazuyoshi Murata, Daniel J Klionsky, Nobuo N Noda, Tomotake Kanki.

  Mitophagy plays an important role in mitochondrial homeostasis by selective degradation of mitochondria. During mitophagy, mitochondria should be fragmented to allow engulfment within autophagosomes, whose capacity is exceeded by the typical mitochondria mass. However, the known mitochondrial fission factors, dynamin-related proteins Dnm1 in yeasts and DNM1L/Drp1 in mammals, are dispensable for mitophagy. Here, we identify Atg44 as a mitochondrial fission factor that is essential for mitophagy in yeasts, and we therefore term Atg44 and its orthologous proteins mitofissin. In mitofissin-deficient cells, a part of the mitochondria is recognized by the mitophagy machinery as cargo but cannot be enwrapped by the autophagosome precursor, the phagophore, due to a lack of mitochondrial fission. Furthermore, we show that mitofissin directly binds to lipid membranes and brings about lipid membrane fragility to facilitate membrane fission. Taken together, we propose that mitofissin acts directly on lipid membranes to drive mitochondrial fission required for mitophagy.

Keywords:  Atg44; autophagy; crystal structure analysis; dynamin-related protein; high-speed atomic force microscopy; mitochondria; mitochondrial fission; mitofissin; mitophagy; yeast

DOI:  https://doi.org/10.1016/j.molcel.2023.04.022
Int J Mol Sci. 2023 May 01. pii: 8123. [Epub ahead of print]24(9):

Role of UCP2 in the Energy Metabolism of the Cancer Cell Line A549.

Jessica Segalés, Carlos Sánchez-Martín, Aleida Pujol-Morcillo, Marta Martín-Ruiz, Patricia de Los Santos, Daniel Lobato-Alonso, Eduardo Oliver, Eduardo Rial.

  The uncoupling protein UCP2 is a mitochondrial carrier for which transport activity remains controversial. The physiological contexts in which UCP2 is expressed have led to the assumption that, like UCP1, it uncouples oxidative phosphorylation and thereby reduces the generation of reactive oxygen species. Other reports have involved UCP2 in the Warburg effect, and results showing that UCP2 catalyzes the export of matrix C4 metabolites to facilitate glutamine utilization suggest that the carrier could be involved in the metabolic adaptations required for cell proliferation. We have examined the role of UCP2 in the energy metabolism of the lung adenocarcinoma cell line A549 and show that UCP2 silencing decreased the basal rate of respiration, although this inhibition was not compensated by an increase in glycolysis. Silencing did not lead to either changes in proton leakage, as determined by the rate of respiration in the absence of ATP synthesis, or changes in the rate of formation of reactive oxygen species. The decrease in energy metabolism did not alter the cellular energy charge. The decreased cell proliferation observed in UCP2-silenced cells would explain the reduced cellular ATP demand. We conclude that UCP2 does not operate as an uncoupling protein, whereas our results are consistent with its activity as a C4-metabolite carrier involved in the metabolic adaptations of proliferating cells.

Keywords:  UCP2; Warburg; cancer; proliferation; reactive oxygen species; uncoupling

DOI:  https://doi.org/10.3390/ijms24098123
Life Metab. 2023 Apr;pii: load014. [Epub ahead of print]2(2):

Weight loss increases skeletal muscle mitochondrial energy efficiency in obese mice.

Patrick J Ferrara, Marisa J Lang, Jordan M Johnson, Shinya Watanabe, Kelsey L McLaughlin, J Alan Maschek, Anthony R P Verkerke, Piyarat Siripoksup, Amandine Chaix, James E Cox, Kelsey H Fisher-Wellman, Katsuhiko Funai.

  Weight loss from an overweight state is associated with a disproportionate decrease in whole-body energy expenditure that may contribute to the heightened risk for weight regain. Evidence suggests that this energetic mismatch originates from lean tissue. Although this phenomenon is well documented, the mechanisms have remained elusive. We hypothesized that increased mitochondrial energy efficiency in skeletal muscle is associated with reduced expenditure under weight loss. Wildtype (WT) male C57BL6/N mice were fed with high fat diet for 10 weeks, followed by a subset of mice that were maintained on the obesogenic diet (OB) or switched to standard chow to promote weight loss (WL) for additional 6 weeks. Mitochondrial energy efficiency was evaluated using high-resolution respirometry and fluorometry. Mass spectrometric analyses were employed to describe the mitochondrial proteome and lipidome. Weight loss promoted ~50% increase in the efficiency of oxidative phosphorylation (ATP produced per O2 consumed, or P/O) in skeletal muscle. However, weight loss did not appear to induce significant changes in mitochondrial proteome, nor any changes in respiratory supercomplex formation. Instead, it accelerated the remodeling of mitochondrial cardiolipin (CL) acyl-chains to increase tetralinoleoyl CL (TLCL) content, a species of lipids thought to be functionally critical for the respiratory enzymes. We further show that lowering TLCL by deleting the CL transacylase tafazzin was sufficient to reduce skeletal muscle P/O and protect mice from diet-induced weight gain. These findings implicate skeletal muscle mitochondrial efficiency as a novel mechanism by which weight loss reduces energy expenditure in obesity.

Keywords:  energy efficiency; energy expenditure; mitochondria; oxidative phosphorylation; phospholipids; weight loss

DOI:  https://doi.org/10.1093/lifemeta/load014
Proc Natl Acad Sci U S A. 2023 05 23. 120(21): e2301215120

Impact of acute stress on murine metabolomics and metabolic flux.

Won Dong Lee, Lingfan Liang, Jenna AbuSalim, Connor S R Jankowski, Laith Z Samarah, Michael D Neinast, Joshua D Rabinowitz.

  Plasma metabolite concentrations and labeling enrichments are common measures of organismal metabolism. In mice, blood is often collected by tail snip sampling. Here, we systematically examined the effect of such sampling, relative to gold-standard sampling from an in-dwelling arterial catheter, on plasma metabolomics and stable isotope tracing. We find marked differences between the arterial and tail circulating metabolome, which arise from two major factors: handling stress and sampling site, whose effects were deconvoluted by taking a second arterial sample immediately after tail snip. Pyruvate and lactate were the most stress-sensitive plasma metabolites, rising ~14 and ~5-fold. Both acute handling stress and adrenergic agonists induce extensive, immediate production of lactate, and modest production of many other circulating metabolites, and we provide a reference set of mouse circulatory turnover fluxes with noninvasive arterial sampling to avoid such artifacts. Even in the absence of stress, lactate remains the highest flux circulating metabolite on a molar basis, and most glucose flux into the TCA cycle in fasted mice flows through circulating lactate. Thus, lactate is both a central player in unstressed mammalian metabolism and strongly produced in response to acute stress.

Keywords:  catecholamine; in vivo; isotope tracing; metabolomics; stress

DOI:  https://doi.org/10.1073/pnas.2301215120
bioRxiv. 2023 May 06. pii: 2023.05.05.539595. [Epub ahead of print]

Conserved cardiolipin-mitochondrial ADP/ATP carrier interactions assume distinct structural and functional roles that are clinically relevant.

Nanami Senoo, Dinesh K Chinthapalli, Matthew G Baile, Vinaya K Golla, Bodhisattwa Saha, Oluwaseun B Ogunbona, James A Saba, Teona Munteanu, Yllka Valdez, Kevin Whited, Dror Chorev, Nathan N Alder, Eric R May, Carol V Robinson, Steven M Claypool.

The mitochondrial phospholipid cardiolipin (CL) promotes bioenergetics via oxidative phosphorylation (OXPHOS). Three tightly bound CLs are evolutionarily conserved in the ADP/ATP carrier (AAC in yeast; adenine nucleotide translocator, ANT in mammals) which resides in the inner mitochondrial membrane and exchanges ADP and ATP to enable OXPHOS. Here, we investigated the role of these buried CLs in the carrier using yeast Aac2 as a model. We introduced negatively charged mutations into each CL-binding site of Aac2 to disrupt the CL interactions via electrostatic repulsion. While all mutations disturbing the CL-protein interaction destabilized Aac2 monomeric structure, transport activity was impaired in a pocket-specific manner. Finally, we determined that a disease-associated missense mutation in one CL-binding site in ANT1 compromised its structure and transport activity, resulting in OXPHOS defects. Our findings highlight the conserved significance of CL in AAC/ANT structure and function, directly tied to specific lipid-protein interactions.

DOI: https://doi.org/10.1101/2023.05.05.539595
J Zhejiang Univ Sci B. 2023 May 15. pii: 1673-1581(2023)05-0397-09. [Epub ahead of print]24(5): 397-405

Dichloroacetic acid and rapamycin synergistically inhibit tumor progression.

Huan Chen, Kunming Liang, Cong Hou, Hai-Long Piao.

  Mammalian target of rapamycin (mTOR) controls cellular anabolism, and mTOR signaling is hyperactive in most cancer cells. As a result, inhibition of mTOR signaling benefits cancer patients. Rapamycin is a US Food and Drug Administration (FDA)-approved drug, a specific mTOR complex 1 (mTORC1) inhibitor, for the treatment of several different types of cancer. However, rapamycin is reported to inhibit cancer growth rather than induce apoptosis. Pyruvate dehydrogenase complex (PDHc) is the gatekeeper for mitochondrial pyruvate oxidation. PDHc inactivation has been observed in a number of cancer cells, and this alteration protects cancer cells from senescence and nicotinamide adenine dinucleotide (NAD+‍) exhaustion. In this paper, we describe our finding that rapamycin treatment promotes pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1) phosphorylation and leads to PDHc inactivation dependent on mTOR signaling inhibition in cells. This inactivation reduces the sensitivity of cancer cells' response to rapamycin. As a result, rebooting PDHc activity with dichloroacetic acid (DCA), a pyruvate dehydrogenase kinase (PDK) inhibitor, promotes cancer cells' susceptibility to rapamycin treatment in vitro and in vivo.

Keywords:  Dichloroacetic acid (DCA); Mammalian target of rapamycin (mTOR); Pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1); Rapamycin

DOI:  https://doi.org/10.1631/jzus.B2200356
Crit Rev Oncog. 2022 ;27(3): 23-31

Bioactive Compounds from Curcuma amada and Their Effect on Acute Myeloid Leukemia.

Ajila Chandran, Varsha Jayasankar, Paul Spagnuolo, Jayasankar Subramanian.

Acute myeloid leukemia (AML) is an aggressive blood cancer with limited chemotherapy options and negative patient outcomes. Investigations with bioactive compounds from dietary sources against cancer have increased in the recent years, which highlight the need for novel therapeutic approaches and new anti-leukemic agents possessing higher efficacy and selectivity for AML cells and fewer negative side effects. Bioactive compounds demonstrated the ability to induce cell cycle blockage and apoptosis or autophagy in cancer cells, as well as inhibition of proliferation/migration and tumor progression, etc. Bioactive compounds isolated from dietary sources such as mango ginger show promise for AML treatment. Curcuma amada roots have been used in traditional medicine and showed antioxidant, antimicrobial and anticancer properties. Bioactive molecules isolated from C. amada showed effects on the mitochondrial metabolism and reduced the viability of multiple leukemic cell lines.

DOI: https://doi.org/10.1615/CritRevOncog.2023047542
Cancer Res. 2023 May 17. pii: CAN-22-3042. [Epub ahead of print]

Metformin reprograms tryptophan metabolism to stimulate CD8+ T cell function in colorectal cancer.

Xiaowen Huang, Tiantian Sun, Jilin Wang, Xialu Hong, Huimin Chen, Tingting Yan, Chengbei Zhou, Danfeng Sun, Chen Yang, TaChung Yu, Wenyu Su, Wan Du, Hua Xiong.

Colorectal carcinogenesis coincides with immune cell dysfunction. Metformin has been reported to play a role in stimulating anti-tumor immunity, suggesting it could be used to overcome immunosuppression in colorectal cancer (CRC). Herein, using single-cell RNA sequencing, we showed that metformin remodels the immune landscape of CRC. In particular, metformin treatment expanded the proportion of CD8+ T cells and potentiated their function. Analysis of the metabolic activities of cells in the CRC tumor microenvironment (TME) at a single-cell resolution demonstrated that metformin reprogrammed tryptophan metabolism, which was reduced in CRC cells and increased in CD8+ T cells. Untreated CRC cells outcompeted CD8+ T cells for tryptophan, leading to impaired CD8+ T cell function. Metformin in turn reduced tryptophan uptake by CRC cells, thereby restoring tryptophan availability for CD8+ T cells and increasing their cytotoxicity. Metformin inhibited tryptophan uptake in CRC cells by downregulating MYC, which led to a reduction in the tryptophan transporter SLC7A5. This work highlights metformin as an essential regulator of T-cell antitumor immunity by reprogramming tryptophan metabolism, suggesting it could be a potential immunotherapeutic strategy for treating CRC.

DOI: https://doi.org/10.1158/0008-5472.CAN-22-3042
J Clin Invest. 2023 May 15. pii: e170027. [Epub ahead of print]133(10):

Ferroptosis: the vulnerability within a cancer monster.

Wanqing Xie, Shivani Agarwal, Jindan Yu.

Treatment-resistant cancer, such as neuroendocrine prostate cancer (NEPC), is a lethal disease with limited therapeutic options. RB1 is a tumor suppressor gene that is lost in a majority of NEPC tumors. In this issue of the JCI, Wang and colleagues examined how RB1 loss may sensitize cancer cells to ferroptosis inducers through elevation of ACSL4, a key enzyme that promotes lipid peroxidation and triggers ferroptosis. We discuss a high potential of RB1-deficient cells to undergo ferroptosis due to the elevation of ACSL4. This is normally kept in check by abundant expression of GPX4, an antioxidant enzyme, in cancer cells. This balance, however, is tilted by GPX4 inhibitors, leading to massive ferroptosis. We highlight possible therapeutic strategies that exploit this inherent vulnerability for targeting RB1-deficient, treatment-resistant cancer.

DOI: https://doi.org/10.1172/JCI170027
Nat Metab. 2023 May 15.

Mitochondrial pyruvate carrier-mediated metabolism is dispensable for the classical activation of macrophages.

Linyu Ran, Song Zhang, Guosheng Wang, Pei Zhao, Jiaxing Sun, Jiaqi Zhou, Haiyun Gan, Ryounghoon Jeon, Qiang Li, Joerg Herrmann, Feilong Wang.

Glycolysis is essential for the classical activation of macrophages (M1), but how glycolytic pathway metabolites engage in this process remains to be elucidated. Glycolysis leads to production of pyruvate, which can be transported into the mitochondria by the mitochondrial pyruvate carrier (MPC) followed by utilization in the tricarboxylic acid cycle. Based on studies that used the MPC inhibitor UK5099, the mitochondrial route has been considered to be of significance for M1 activation. Using genetic approaches, here we show that the MPC is dispensable for metabolic reprogramming and activation of M1 macrophages. In addition, MPC depletion in myeloid cells has no impact on inflammatory responses and macrophage polarization toward the M1 phenotype in a mouse model of endotoxemia. While UK5099 reaches maximal MPC inhibitory capacity at approximately 2-5 μM, higher concentrations are required to inhibit inflammatory cytokine production in M1 and this is independent of MPC expression. Taken together, MPC-mediated metabolism is dispensable for the classical activation of macrophages and UK5099 inhibits inflammatory responses in M1 macrophages due to effects other than MPC inhibition.

DOI: https://doi.org/10.1038/s42255-023-00800-3
Nat Commun. 2023 May 19. 14(1): 2876

Using mass spectrometry imaging to map fluxes quantitatively in the tumor ecosystem.

Michaela Schwaiger-Haber, Ethan Stancliffe, Dhanalakshmi S Anbukumar, Blake Sells, Jia Yi, Kevin Cho, Kayla Adkins-Travis, Milan G Chheda, Leah P Shriver, Gary J Patti.

Tumors are comprised of a multitude of cell types spanning different microenvironments. Mass spectrometry imaging (MSI) has the potential to identify metabolic patterns within the tumor ecosystem and surrounding tissues, but conventional workflows have not yet fully integrated the breadth of experimental techniques in metabolomics. Here, we combine MSI, stable isotope labeling, and a spatial variant of Isotopologue Spectral Analysis to map distributions of metabolite abundances, nutrient contributions, and metabolic turnover fluxes across the brains of mice harboring GL261 glioma, a widely used model for glioblastoma. When integrated with MSI, the combination of ion mobility, desorption electrospray ionization, and matrix assisted laser desorption ionization reveals alterations in multiple anabolic pathways. De novo fatty acid synthesis flux is increased by approximately 3-fold in glioma relative to surrounding healthy tissue. Fatty acid elongation flux is elevated even higher at 8-fold relative to surrounding healthy tissue and highlights the importance of elongase activity in glioma.

DOI: https://doi.org/10.1038/s41467-023-38403-x
Nat Metab. 2023 May 17.

Salvage of ribose from uridine or RNA supports glycolysis in nutrient-limited conditions.

Owen S Skinner, Joan Blanco-Fernández, Russell P Goodman, Akinori Kawakami, Hongying Shen, Lajos V Kemény, Lena Joesch-Cohen, Matthew G Rees, Jennifer A Roth, David E Fisher, Vamsi K Mootha, Alexis A Jourdain.

Glucose is vital for life, serving as both a source of energy and carbon building block for growth. When glucose is limiting, alternative nutrients must be harnessed. To identify mechanisms by which cells can tolerate complete loss of glucose, we performed nutrient-sensitized genome-wide genetic screens and a PRISM growth assay across 482 cancer cell lines. We report that catabolism of uridine from the medium enables the growth of cells in the complete absence of glucose. While previous studies have shown that uridine can be salvaged to support pyrimidine synthesis in the setting of mitochondrial oxidative phosphorylation deficiency1, our work demonstrates that the ribose moiety of uridine or RNA can be salvaged to fulfil energy requirements via a pathway based on: (1) the phosphorylytic cleavage of uridine by uridine phosphorylase UPP1/UPP2 into uracil and ribose-1-phosphate (R1P), (2) the conversion of uridine-derived R1P into fructose-6-P and glyceraldehyde-3-P by the non-oxidative branch of the pentose phosphate pathway and (3) their glycolytic utilization to fuel ATP production, biosynthesis and gluconeogenesis. Capacity for glycolysis from uridine-derived ribose appears widespread, and we confirm its activity in cancer lineages, primary macrophages and mice in vivo. An interesting property of this pathway is that R1P enters downstream of the initial, highly regulated steps of glucose transport and upper glycolysis. We anticipate that 'uridine bypass' of upper glycolysis could be important in the context of disease and even exploited for therapeutic purposes.

DOI: https://doi.org/10.1038/s42255-023-00774-2
Biomedicines. 2023 Apr 15. pii: 1183. [Epub ahead of print]11(4):

Mitochondrial DNA Changes in Respiratory Complex I Genes in Brain Gliomas.

Paulina Kozakiewicz, Ludmiła Grzybowska-Szatkowska, Marzanna Ciesielka, Paulina Całka, Jacek Osuchowski, Paweł Szmygin, Bożena Jarosz, Marta Ostrowska-Leśko, Jarosław Dudka, Angelika Tkaczyk-Wlizło, Brygida Ślaska.

  Mitochondria are organelles necessary for oxidative phosphorylation. The interest in the role of mitochondria in the process of carcinogenesis results from the fact that a respiratory deficit is found in dividing cells, especially in cells with accelerated proliferation. The study included tumor and blood material from 30 patients diagnosed with glioma grade II, III and IV according to WHO (World Health Organization). DNA was isolated from the collected material and next-generation sequencing was performed on the MiSeqFGx apparatus (Illumina). The study searched for a possible relationship between the occurrence of specific mitochondrial DNA polymorphisms in the respiratory complex I genes and brain gliomas of grade II, III and IV. The impact of missense changes on the biochemical properties, structure and functioning of the encoded protein, as well as their potential harmfulness, were assessed in silico along with their belonging to a given mitochondrial subgroup. The A3505G, C3992T, A4024G, T4216C, G5046A, G7444A, T11253C, G12406A and G13604C polymorphisms were assessed as deleterious changes in silico, indicating their association with carcinogenesis.

Keywords:  ND1; brain tumor; mitochondria; mtDNA polymorphisms

DOI:  https://doi.org/10.3390/biomedicines11041183
Cell Metab. 2023 May 05. pii: S1550-4131(23)00171-7. [Epub ahead of print]

Cancer-cell-derived fumarate suppresses the anti-tumor capacity of CD8+ T cells in the tumor microenvironment.

Jie Cheng, Jinxin Yan, Ying Liu, Jiangzhou Shi, Haoyu Wang, Hanyang Zhou, Yinglin Zhou, Tongcun Zhang, Lina Zhao, Xianbin Meng, Haipeng Gong, Xinxiang Zhang, Haichuan Zhu, Peng Jiang.

  Metabolic alterations in the microenvironment significantly modulate tumor immunosensitivity, but the underlying mechanisms remain obscure. Here, we report that tumors depleted of fumarate hydratase (FH) exhibit inhibition of functional CD8+ T cell activation, expansion, and efficacy, with enhanced malignant proliferative capacity. Mechanistically, FH depletion in tumor cells accumulates fumarate in the tumor interstitial fluid, and increased fumarate can directly succinate ZAP70 at C96 and C102 and abrogate its activity in infiltrating CD8+ T cells, resulting in suppressed CD8+ T cell activation and anti-tumor immune responses in vitro and in vivo. Additionally, fumarate depletion by increasing FH expression strongly enhances the anti-tumor efficacy of anti-CD19 CAR T cells. Thus, these findings demonstrate a role for fumarate in controlling TCR signaling and suggest that fumarate accumulation in the tumor microenvironment (TME) is a metabolic barrier to CD8+ T cell anti-tumor function. And potentially, fumarate depletion could be an important strategy for tumor immunotherapy.

Keywords:  CD8(+) T cell activation; FH; ZAP70; anti-tumor immune response; fumarate; fumarate hydrolase; succination; tumor microenvironment

DOI:  https://doi.org/10.1016/j.cmet.2023.04.017
Cell Mol Gastroenterol Hepatol. 2023 May 10. pii: S2352-345X(23)00063-2. [Epub ahead of print]

Excess dietary sugar alters colonocyte metabolism and impairs the proliferative response to damage.

Ansen H P Burr, Junyi Ji, Kadir Ozler, Heather L Mentrup, Onur Eskiocak, Brian Yueh, Rachel Cumberland, Ashley V Menk, Natalie Rittenhouse, Chris W Marshall, Pailin Chiaranunt, Xiaoyi Zhang, Lauren Mullinax, Abigail Overacre-Delgoffe, Vaughn S Cooper, Amanda C Poholek, Greg M Delgoffe, Kevin P Mollen, Semir Beyaz, Timothy W Hand.

   BACKGROUND: The colonic epithelium requires continuous renewal by crypt resident intestinal stem cells (ISCs) and transit amplifying (TA) cells to maintain barrier integrity, especially after inflammatory damage. The diet of high-income countries contains increasing amounts of sugar, such as sucrose. ISCs and TA cells are sensitive to dietary metabolites, but whether excess sugar affects their function directly is unknown.
METHODS: Here we use a combination of 3-dimensional colonoids and a mouse model of colon damage/repair (DSS colitis) to demonstrate the direct effect of sugar on the transcriptional, metabolic, and regenerative functions of crypt ISCs and TA cells.
RESULTS: We demonstrate that high sugar conditions directly limit murine and human colonoid development, which is associated with a reduction in the expression of proliferative genes, ATP levels and the accumulation of pyruvate. Treatment of colonoids with DCA, which forces pyruvate into the TCA cycle, restored their growth. In concert, DSS treatment of mice fed a high sugar diet led to massive irreparable damage that was independent of the colonic microbiota and its metabolites. Analyses on crypt cells from high-sucrose-fed mice revealed a reduction in the expression of ISC genes, impeded proliferative potential and increased glycolytic potential without a commensurate increase in aerobic respiration.
CONCLUSION: Taken together, our results indicate that short-term, excess dietary sucrose can directly modulate intestinal crypt cell metabolism and inhibit ISC/TA cell regenerative proliferation. This knowledge may inform diets that better support the treatment of acute intestinal injury.

Keywords:  DCA; colitis; mitochondria; renewal; stemness

DOI:  https://doi.org/10.1016/j.jcmgh.2023.05.001
BMC Cancer. 2023 May 16. 23(1): 447

PD-L1 stimulation can promote proliferation and survival of leukemic cells by influencing glucose and fatty acid metabolism in acute myeloid leukemia.

Mojdeh Soltani, Mustafa Ghanadian, Behrooz Ghezelbash, Abolfazl Shokouhi, Andrey A Zamyatnin, Alexandr V Bazhin, Mazdak Ganjalikhani-Hakemi.

   BACKGROUND: Leukemic cell metabolism plays significant roles in their proliferation and survival. These metabolic adaptations are under regulation by different factors. Programmed Death Ligand -1 (CD-274) is one of the immune checkpoint ligands that do not only cause the immune escape of cancer cells, but also have some intracellular effects in these cells. PD-L1 is overexpressed on leukemic stem cells and relates with poor prognosis of AML. In this study, we investigated effects of PD-L1 stimulation on critical metabolic pathways of glucose and fatty acid metabolisms that have important roles in proliferation and survival of leukemic cells.
METHODS: After confirmation of PD-L1 expression by flow cytometry assay, we used recombinant protein PD-1 for stimulation of the PD-L1 on two AML cell lines, HL-60 and THP-1. Then we examined the effect of PD-L1 stimulation on glucose and fatty acid metabolism in cells at the genomic and metabolomic levels in a time dependent manner. We investigated expression changes of rate limiting enzymes of theses metabolic pathways (G6PD, HK-2, CPT1A, ATGL1 and ACC1) by qRT-PCR and also the relative abundance changes of free fatty acids of medium by GC.
RESULTS: We identified a correlation between PD-L1 stimulation and both fatty acid and glucose metabolism. The PD-L1 stimulated cells showed an influence in the pentose phosphate pathway and glycolysis by increasing expression of G6PD and HK-2 (P value = 0.0001). Furthermore, PD-L1 promoted fatty acid β-oxidation by increasing expression of CPT1A (P value = 0.0001), however, their fatty acid synthesis was decreased by reduction of ACC1 expression (P value = 0.0001).
CONCLUSION: We found that PD-L1 can promote proliferation and survival of AML stem cells probably through some metabolic changes in leukemic cells. Pentose phosphate pathway that has a critical role in cell proliferation and fatty acids β-oxidation that promote cell survival, both are increased by PD-L1 stimulation on AML cells.

Keywords:  AML; Acute myeloid leukemia; Fatty acid oxidation; Immunometabolism; PD-1; Pentose phosphate pathway; Programmed death ligand-1

DOI:  https://doi.org/10.1186/s12885-023-10947-7
Exp Hematol Oncol. 2023 May 17. 12(1): 47

Targeting NRF2 uncovered an intrinsic susceptibility of acute myeloid leukemia cells to ferroptosis.

Xin Liu, Shuxin Zhong, Kangjie Qiu, Xi Chen, Weiyue Wu, Jiamian Zheng, Yanwen Liu, Haolong Wu, Shiyun Fan, Dingrui Nie, Xianfeng Wang, Zhi Yu, Ziwei Liao, Mengjun Zhong, Yangqiu Li, Chengwu Zeng.

  Drug resistance and poor treatment response are major obstacles to the effective treatment of acute myeloid leukemia (AML). A deeper understanding of the mechanisms regulating drug resistance and response genes in AML is therefore urgently needed. Our previous research has highlighted the important role of nuclear factor E2-related factor 2 (NRF2) in AML, where it plays a critical role in detoxifying reactive oxygen species and influencing sensitivity to chemotherapy. In this study, we identify a core set of direct NRF2 targets that are involved in ferroptosis, a novel form of cell death. Of particular interest, we find that glutathione peroxidase 4 (GPX4) is a key ferroptosis gene that is consistently upregulated in AML, and high expression of GPX4 is associated with poor prognosis for AML patients. Importantly, simultaneous inhibition of NRF2 with ML385 and GPX4 with FIN56 or RSL3 synergistically targets AML cells, triggering ferroptosis. Treatment with ML385 + FIN56/RSL3 resulted in a marked reduction in NRF2 and GPX4 expression. Furthermore, NRF2 knockdown enhanced the sensitivity of AML cells to the ferroptosis inducers. Taken together, our results suggest that combination therapy targeting both NRF2 and GPX4 may represent a promising approach for the treatment of AML.

Keywords:  Acute myeloid leukemia; Ferroptosis; GPX4; NRF2

DOI:  https://doi.org/10.1186/s40164-023-00411-4
Trends Cancer. 2023 May 10. pii: S2405-8033(23)00064-X. [Epub ahead of print]

Emerging roles of nucleotide metabolism in cancer.

Diana D Shi, Milan R Savani, Kalil G Abdullah, Samuel K McBrayer.

  Nucleotides are substrates for multiple anabolic pathways, most notably DNA and RNA synthesis. Since nucleotide synthesis inhibitors began to be used for cancer therapy in the 1950s, our understanding of how nucleotides function in tumor cells has evolved, prompting a resurgence of interest in targeting nucleotide metabolism for cancer therapy. In this review, we discuss recent advances that challenge the idea that nucleotides are mere building blocks for the genome and transcriptome and highlight ways that these metabolites support oncogenic signaling, stress resistance, and energy homeostasis in tumor cells. These findings point to a rich network of processes sustained by aberrant nucleotide metabolism in cancer and reveal new therapeutic opportunities.

Keywords:  metabolism; nucleotides; purines; pyrimidines

DOI:  https://doi.org/10.1016/j.trecan.2023.04.008
BMC Biol. 2023 May 18. 21(1): 111

A small protein coded within the mitochondrial canonical gene nd4 regulates mitochondrial bioenergetics.

Laura Kienzle, Stefano Bettinazzi, Thierry Choquette, Marie Brunet, Hajar Hosseini Khorami, Jean-François Jacques, Mathilde Moreau, Xavier Roucou, Christian R Landry, Annie Angers, Sophie Breton.

   BACKGROUND: Mitochondria have a central role in cellular functions, aging, and in certain diseases. They possess their own genome, a vestige of their bacterial ancestor. Over the course of evolution, most of the genes of the ancestor have been lost or transferred to the nucleus. In humans, the mtDNA is a very small circular molecule with a functional repertoire limited to only 37 genes. Its extremely compact nature with genes arranged one after the other and separated by short non-coding regions suggests that there is little room for evolutionary novelties. This is radically different from bacterial genomes, which are also circular but much larger, and in which we can find genes inside other genes. These sequences, different from the reference coding sequences, are called alternatives open reading frames or altORFs, and they are involved in key biological functions. However, whether altORFs exist in mitochondrial protein-coding genes or elsewhere in the human mitogenome has not been fully addressed.
RESULTS: We found a downstream alternative ATG initiation codon in the + 3 reading frame of the human mitochondrial nd4 gene. This newly characterized altORF encodes a 99-amino-acid-long polypeptide, MTALTND4, which is conserved in primates. Our custom antibody, but not the pre-immune serum, was able to immunoprecipitate MTALTND4 from HeLa cell lysates, confirming the existence of an endogenous MTALTND4 peptide. The protein is localized in mitochondria and cytoplasm and is also found in the plasma, and it impacts cell and mitochondrial physiology.
CONCLUSIONS: Many human mitochondrial translated ORFs might have so far gone unnoticed. By ignoring mtaltORFs, we have underestimated the coding potential of the mitogenome. Alternative mitochondrial peptides such as MTALTND4 may offer a new framework for the investigation of mitochondrial functions and diseases.

Keywords:  Alternative open reading frame; Homo sapiens; Mitochondria; Mitochondrial bioenergetics; Mitochondrial proteome; Mitogenome; Protein coding potential; nd4

DOI:  https://doi.org/10.1186/s12915-023-01609-y
Int J Mol Sci. 2023 May 08. pii: 8442. [Epub ahead of print]24(9):

Mechanism of ADP-Inhibited ATP Hydrolysis in Single Proton-Pumping FoF1-ATP Synthase Trapped in Solution.

Iván Pérez, Thomas Heitkamp, Michael Börsch.

  FoF1-ATP synthases in mitochondria, in chloroplasts, and in most bacteria are proton-driven membrane enzymes that supply the cells with ATP made from ADP and phosphate. Different control mechanisms exist to monitor and prevent the enzymes' reverse chemical reaction of fast wasteful ATP hydrolysis, including mechanical or redox-based blockade of catalysis and ADP inhibition. In general, product inhibition is expected to slow down the mean catalytic turnover. Biochemical assays are ensemble measurements and cannot discriminate between a mechanism affecting all enzymes equally or individually. For example, all enzymes could work more slowly at a decreasing substrate/product ratio, or an increasing number of individual enzymes could be completely blocked. Here, we examined the effect of increasing amounts of ADP on ATP hydrolysis of single Escherichia coli FoF1-ATP synthases in liposomes. We observed the individual catalytic turnover of the enzymes one after another by monitoring the internal subunit rotation using single-molecule Förster resonance energy transfer (smFRET). Observation times of single FRET-labeled FoF1-ATP synthases in solution were extended up to several seconds using a confocal anti-Brownian electrokinetic trap (ABEL trap). By counting active versus inhibited enzymes, we revealed that ADP inhibition did not decrease the catalytic turnover of all FoF1-ATP synthases equally. Instead, increasing ADP in the ADP/ATP mixture reduced the number of remaining active enzymes that operated at similar catalytic rates for varying substrate/product ratios.

Keywords:  ABEL trap; ADP inhibition; ATP hydrolysis; FoF1-ATP synthase; catalytic mechanism; single-molecule FRET; subunit rotation

DOI:  https://doi.org/10.3390/ijms24098442
EJHaem. 2023 May;4(2): 381-392

Venetoclax with decitabine or azacitidine in the first-line treatment of acute myeloid leukemia.

Ian M Bouligny, Graeme Murray, Michael Doyel, Tilak Patel, Josh Boron, Valerie Tran, Juhi Gor, Yiwei Hang, Yanal Alnimer, Kyle Zacholski, Chad Venn, Nolan A Wages, Steven Grant, Keri R Maher.

  Treatment paradigms for acute myeloid leukemia (AML) have evolved at a rapid pace in recent years. The combination of venetoclax with a hypomethylating agent prolonged survival in clinical trials when compared to hypomethylating agent monotherapy. However, little is known about the performance of venetoclax-based regimens outside of clinical trials, given conflicting safety and efficacy data. Even less is known about the impact of the hypomethylating agent backbone. In this study, we demonstrate that decitabine-venetoclax is associated with a significantly higher rate of grade three or higher thrombocytopenia, but lower rates of lymphocytopenia compared to azacitidine-venetoclax. There was no difference in response or survival across ELN 2017 cytogenetic risk categories in the overall cohort. Significantly more patients succumb to relapsed or refractory disease than death from any other cause. We demonstrated that a Charlson comorbidity index score threshold of seven identifies exceptionally high-risk patients, providing evidence for clinical use to reduce the risk of early treatment-related mortality. Lastly, we provide evidence that measurable residual disease negativity and an IDH mutation predict a significant survival benefit outside clinical trials. Taken together, these data illuminate the real-world performance of venetoclax and decitabine or azacitidine in the treatment of AML.

Keywords:  AML; BCL2; acute leukemia; chemotherapy; clinical research; malignant hematology

DOI:  https://doi.org/10.1002/jha2.663