bims-mibica 2022-08-21 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2022‒08‒21
37 papers selected by
Kelsey Fisher-Wellman, East Carolina University

O-GlcNAcylation suppresses TRAP1 activity and promotes mitochondrial respiration.
Noncanonical PDK4 action alters mitochondrial dynamics to affect the cellular respiratory status.
Mitochondrial hyperfusion via metabolic sensing of regulatory amino acids.
Melatonin drives apoptosis in head and neck cancer by increasing mitochondrial ROS generated via reverse electron transport.
Apparent "mild depolarization of the inner mitochondrial membrane" as a result of a possible generation of the outer membrane potential.
Genetic impairment of succinate metabolism disrupts bioenergetic sensing in adrenal neuroendocrine cancer.
PINK1-dependent and Parkin-independent mitophagy is involved in reprogramming of glycometabolism in pancreatic cancer cells.
Saturation of the mitochondrial NADH shuttles drives aerobic glycolysis in proliferating cells.
FKBP4 regulates 5-fluorouracil sensitivity in colon cancer by controlling mitochondrial respiration.
Proteasome granule formation is regulated through mitochondrial respiration and kinase signaling.
Mitochondrial microproteins link metabolic cues to respiratory chain biogenesis.
Carbon source availability drives nutrient utilization in CD8+ T cells.
Glucose feeds the tricarboxylic acid cycle via excreted ethanol in fermenting yeast.
De novo pyrimidine synthesis is a targetable vulnerability in IDH mutant glioma.
Tissue-specific reductions in mitochondrial efficiency and increased ROS release rates during ageing in zebra finches, Taeniopygia guttata.
SHMT2-mediated mitochondrial serine metabolism drives 5-FU resistance by fueling nucleotide biosynthesis.
Dietary methionine starvation impairs acute myeloid leukemia progression.
Metabolic analyses reveal dysregulated NAD+ metabolism and altered mitochondrial state in ulcerative colitis.
Mitochondrial mRNA localization is governed by translation kinetics and spatial transport.
The mitochondrial calcium uniporter engages UCP1 to form a thermoporter that promotes thermogenesis.
The A'-helix of CYP11A1 remodels mitochondrial cristae.
Transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor-resistant pancreatic ductal adenocarcinoma.
Regulation of nuclear DNA damage response by mitochondrial morphofunctional pathway.
A druggable addiction to de novo pyrimidine biosynthesis in diffuse midline glioma.
MTP18 inhibition triggers mitochondrial hyperfusion to induce apoptosis through ROS-mediated lysosomal membrane permeabilization-dependent pathway in oral cancer.
Inhibition of mutant IDH1 promotes cycling of acute myeloid leukemia stem cells.
m6A RNA methylation-mediated NDUFA4 promotes cell proliferation and metabolism in gastric cancer.
Targeting Mitophagy to Promote Apoptosis is a Potential Therapeutic Strategy for Cancer.
Development of artesunate intelligent prodrug liposomes based on mitochondrial targeting strategy.
A practical guide for the analysis, standardization and interpretation of oxygen consumption measurements.
Succinate uptake by T cells suppresses their effector function via inhibition of mitochondrial glucose oxidation.
Identification and characterization of in vitro expanded hematopoietic stem cells.
Longitudinal single-cell transcriptomics reveals distinct patterns of recurrence in acute myeloid leukemia.
Mitochondria-targeted alginate/triphenylphosphonium-grafted-chitosan for treatment of hepatocellular carcinoma.
Intestinal tissue-resident T cell activation depends on metabolite availability.
A new gene set identifies senescent cells and predicts senescence-associated pathways across tissues.
Mitochondrial miRNAs (MitomiRs): Their potential roles in breast and other cancers.

Cell Stress Chaperones. 2022 Aug 17.

O-GlcNAcylation suppresses TRAP1 activity and promotes mitochondrial respiration.

Seungchan Kim, Sarah J Backe, Laura A Wengert, Anna E Johnson, Roman V Isakov, Michael S Bratslavsky, Mark R Woodford.

  The molecular chaperone TNF-receptor-associated protein-1 (TRAP1) controls mitochondrial respiration through regulation of Krebs cycle and electron transport chain activity. Post-translational modification (PTM) of TRAP1 regulates its activity, thereby controlling global metabolic flux. O-GlcNAcylation is one PTM that is known to impact mitochondrial metabolism, however the major effectors of this regulatory PTM remain inadequately resolved. Here we demonstrate that TRAP1-O-GlcNAcylation decreases TRAP1 ATPase activity, leading to increased mitochondrial metabolism. O-GlcNAcylation of TRAP1 occurs following mitochondrial import and provides critical regulatory feedback, as the impact of O-GlcNAcylation on mitochondrial metabolism shows TRAP1-dependence. Mechanistically, loss of TRAP1-O-GlcNAcylation decreased TRAP1 binding to ATP, and interaction with its client protein succinate dehydrogenase (SDHB). Taken together, TRAP1-O-GlcNAcylation serves to regulate mitochondrial metabolism by the reversible attenuation of TRAP1 chaperone activity.

Keywords:  GlcNAcylation; Metabolism; Molecular chaperone; Post-translational modification; TRAP1

DOI:  https://doi.org/10.1007/s12192-022-01293-x
Proc Natl Acad Sci U S A. 2022 Aug 23. 119(34): e2120157119

Noncanonical PDK4 action alters mitochondrial dynamics to affect the cellular respiratory status.

Themis Thoudam, Dipanjan Chanda, Ibotombi Singh Sinam, Byung-Gyu Kim, Mi-Jin Kim, Chang Joo Oh, Jung Yi Lee, Min-Ji Kim, Soo Yeun Park, Shin Yup Lee, Min-Kyo Jung, Ji Young Mun, Robert A Harris, Naotada Ishihara, Jae-Han Jeon, In-Kyu Lee.

  Dynamic regulation of mitochondrial morphology provides cells with the flexibility required to adapt and respond to electron transport chain (ETC) toxins and mitochondrial DNA-linked disease mutations, yet the mechanisms underpinning the regulation of mitochondrial dynamics machinery by these stimuli is poorly understood. Here, we show that pyruvate dehydrogenase kinase 4 (PDK4) is genetically required for cells to undergo rapid mitochondrial fragmentation when challenged with ETC toxins. Moreover, PDK4 overexpression was sufficient to promote mitochondrial fission even in the absence of mitochondrial stress. Importantly, we observed that the PDK4-mediated regulation of mitochondrial fission was independent of its canonical function, i.e., inhibitory phosphorylation of the pyruvate dehydrogenase complex (PDC). Phosphoproteomic screen for PDK4 substrates, followed by nonphosphorylatable and phosphomimetic mutations of the PDK4 site revealed cytoplasmic GTPase, Septin 2 (SEPT2), as the key effector molecule that acts as a receptor for DRP1 in the outer mitochondrial membrane to promote mitochondrial fission. Conversely, inhibition of the PDK4-SEPT2 axis could restore the balance in mitochondrial dynamics and reinvigorates cellular respiration in mitochondrial fusion factor, mitofusin 2-deficient cells. Furthermore, PDK4-mediated mitochondrial reshaping limits mitochondrial bioenergetics and supports cancer cell growth. Our results identify the PDK4-SEPT2-DRP1 axis as a regulator of mitochondrial function at the interface between cellular bioenergetics and mitochondrial dynamics.

Keywords:  OCR; dynamin-related protein 1; mitochondrial fission; pyruvate dehydrogenase kinase 4; septin 2

DOI:  https://doi.org/10.1073/pnas.2120157119
Cell Rep. 2022 Aug 16. pii: S2211-1247(22)01015-4. [Epub ahead of print]40(7): 111198

Mitochondrial hyperfusion via metabolic sensing of regulatory amino acids.

Mahmud O Abdullah, Run X Zeng, Chelsea L Margerum, David Papadopoli, Cian Monnin, Kaylee B Punter, Charles Chu, Mohammad Al-Rofaidi, Naser F Al-Tannak, Domenica Berardi, Zahra Rattray, Nicholas J W Rattray, Sheela A Abraham, Eeva-Liisa Eskelinen, David G Watson, Daina Avizonis, Ivan Topisirovic, Edmond Y W Chan.

  The relationship between nutrient starvation and mitochondrial dynamics is poorly understood. We find that cells facing amino acid starvation display clear mitochondrial fusion as a means to evade mitophagy. Surprisingly, further supplementation of glutamine (Q), leucine (L), and arginine (R) did not reverse, but produced stronger mitochondrial hyperfusion. Interestingly, the hyperfusion response to Q + L + R was dependent upon mitochondrial fusion proteins Mfn1 and Opa1 but was independent of MTORC1. Metabolite profiling indicates that Q + L + R addback replenishes amino acid and nucleotide pools. Inhibition of fumarate hydratase, glutaminolysis, or inosine monophosphate dehydrogenase all block Q + L + R-dependent mitochondrial hyperfusion, which suggests critical roles for the tricarboxylic acid (TCA) cycle and purine biosynthesis in this response. Metabolic tracer analyses further support the idea that supplemented Q promotes purine biosynthesis by serving as a donor of amine groups. We thus describe a metabolic mechanism for direct sensing of cellular amino acids to control mitochondrial fusion and cell fate.

Keywords:  CP: Cell biology; CP: Metabolism; Drp1; Mfn1; Mfn2; Opa1; amino acid sensing; arginine; dynamics; fusion; glutamine; hyperfusion; leucine; mitochondria; stable isotope tracer

DOI:  https://doi.org/10.1016/j.celrep.2022.111198
J Pineal Res. 2022 Aug 19.

Melatonin drives apoptosis in head and neck cancer by increasing mitochondrial ROS generated via reverse electron transport.

Javier Florido, Laura Martinez-Ruiz, César Rodriguez-Santana, Alba López-Rodríguez, Agustín Hidalgo-Gutiérrez, Cécile Cottet-Rousselle, Frédéric Lamarche, Uwe Schlattner, Ana Guerra-Librero, Paula Aranda-Martínez, Darío Acuña-Castroviejo, Luis C López, Germaine Escames.

  The oncostatic effects of melatonin correlate with increased reactive oxygen species (ROS) levels, but how melatonin induces this ROS generation is unknown. In the present study, we aimed to elucidate the two seemingly opposing actions of melatonin regarding its relationship with free radicals. We analyzed the effects of melatonin on head and neck squamous cell carcinoma cell lines (Cal-27 and SCC-9), which were treated with 0.5 or 1 mM melatonin. We further examined the potential effects of melatonin to induce ROS and apoptosis in Cal-27 xenograft mice. Here we report that melatonin mediates apoptosis in head and neck cancer by driving mitochondrial reverse electron transport (RET) to induce ROS production. Melatonin-induced changes in tumoral metabolism led to increased mitochondrial activity that in turn induced ROS-dependent mitochondrial uncoupling. Interestingly, mitochondrial complex inhibitors, including rotenone, abolished the ROS elevation indicating that melatonin increased ROS generation via RET. Melatonin also increased membrane potential and CoQ10 H2 /CoQ10 ratio to elevate mitochondrial ROS production, which are essential conditions for RET. We found that genetic manipulation of cancer cells with alternative oxidase (AOX), which transfers electrons from QH2 to oxygen, inhibited melatonin-induced ROS generation and apoptosis. RET restored the melatonin-induced oncostatic effect, highlighting the importance of RET as the site of ROS production. These results illustrate that RET and ROS production are crucial factors in melatonin's effects in cancer cells and establish the dual effect of melatonin in protecting normal cells and inducing apoptosis in cancer cells. This article is protected by copyright. All rights reserved.

Keywords:  Melatonin; apoptosis; head and neck cancer cells; mitochondria; oxidative damage; reactive oxygen species; reverse electron transport

DOI:  https://doi.org/10.1111/jpi.12824
Biochim Biophys Acta Biomembr. 2022 Aug 16. pii: S0005-2736(22)00170-5. [Epub ahead of print]1864(11): 184032

Apparent "mild depolarization of the inner mitochondrial membrane" as a result of a possible generation of the outer membrane potential.

Victor V Lemeshko.

  Recently reported kinase-linked mild depolarization of mitochondria, which prevents the generation of the reactive oxygen species (ROS) and disappears in various organs of the old mice, has been assumed to represent a crucial component of the mitochondrial anti-aging program. To measure mitochondrial inner membrane potential (IMP), the authors used fluorescent probe safranin O+. It is widely accepted that the accumulation of such cationic probes in the mitochondrial matrix depends exclusively on IMP, thus completely ignoring the possibility of the outer membrane potential (OMP) generation. However, computational analysis performed in the presented work suggests that the kinase-linked generation of the positive OMP might take place under the described conditions, because the measured potential includes the algebraic sum of both IMP and OMP. Alternatively to the suggested mild depolarization of mitochondria, the reported experimental data might reflect mainly a change of the positive OMP generated by the VDAC-kinase complexes. We also demonstrate that the reported in the literature mitochondrial hyperpolarization induced by erastin (known to prevent VDAC-tubulin interactions) and the depolarization caused by the mitochondrial VDAC knockdowns in the cancer cells might actually represent a decrease or increase, respectively, of the magnitude of the kinase-linked positive OMP. This is consistent with our hypothesis that VDAC voltage gating by the kinase-linked metabolically-dependent OMP plays a very important physiological role in regulating the cell energy metabolism under normal and pathological conditions, in the maintenance of the cell death resistance and even in the genetic aging program.

Keywords:  Mitochondria; Mitochondrial outer membrane; Outer membrane potential; VDAC; VDAC-hexokinase complexes

DOI:  https://doi.org/10.1016/j.bbamem.2022.184032
Cell Rep. 2022 Aug 16. pii: S2211-1247(22)01035-X. [Epub ahead of print]40(7): 111218

Genetic impairment of succinate metabolism disrupts bioenergetic sensing in adrenal neuroendocrine cancer.

Priyanka Gupta, Keehn Strange, Rahul Telange, Ailan Guo, Heather Hatch, Amin Sobh, Jonathan Elie, Angela M Carter, John Totenhagen, Chunfeng Tan, Yogesh A Sonawane, Jiri Neuzil, Amarnath Natarajan, Ashley J Ovens, Jonathan S Oakhill, Thorsten Wiederhold, Karel Pacak, Hans K Ghayee, Laurent Meijer, Sushanth Reddy, James A Bibb.

  Metabolic dysfunction mutations can impair energy sensing and cause cancer. Loss of function of the mitochondrial tricarboxylic acid (TCA) cycle enzyme subunit succinate dehydrogenase B (SDHB) results in various forms of cancer typified by pheochromocytoma (PC). Here we delineate a signaling cascade where the loss of SDHB induces the Warburg effect, triggers dysregulation of [Ca2+]i, and aberrantly activates calpain and protein kinase Cdk5, through conversion of its cofactor from p35 to p25. Consequently, aberrant Cdk5 initiates a phospho-signaling cascade where GSK3 inhibition inactivates energy sensing by AMP kinase through dephosphorylation of the AMP kinase γ subunit, PRKAG2. Overexpression of p25-GFP in mouse adrenal chromaffin cells also elicits this phosphorylation signaling and causes PC. A potent Cdk5 inhibitor, MRT3-007, reverses this phospho-cascade, invoking a senescence-like phenotype. This therapeutic approach halted tumor progression in vivo. Thus, we reveal an important mechanistic feature of metabolic sensing and demonstrate that its dysregulation underlies tumor progression in PC and likely other cancers.

Keywords:  AMPK; CP: Cancer; CP: Metabolism; Cdk5; PRKAG2; SDHB; Warburg effect; cancer bioenergetics; neuroendocrine tumor; p53; pheochromocytoma; senescence

DOI:  https://doi.org/10.1016/j.celrep.2022.111218
Biochem Biophys Res Commun. 2022 Aug 05. pii: S0006-291X(22)01109-3. [Epub ahead of print]625 167-173

PINK1-dependent and Parkin-independent mitophagy is involved in reprogramming of glycometabolism in pancreatic cancer cells.

Natsumi Miyazaki, Reika Shiratori, Taichi Oshima, Zhiheng Zhang, Robert Valencia, Joshua Kranrod, Liye Fang, John M Seubert, Kousei Ito, Shigeki Aoki.

  Cancer cells rely on glycolysis to generate ATP for survival. However, inhibiting glycolysis is insufficient for the eradication of cancer cells because glycolysis-suppressed cells undergo metabolic reprogramming toward mitochondrial oxidative phosphorylation. We previously described that upon glycolytic suppression in pancreatic cancer cells, intracellular glycometabolism is shifted toward mitochondrial oxidative phosphorylation in an autophagy-dependent manner for cellular survival. Here, we hypothesized that mitophagy, which selectively degrades mitochondria via autophagy, is involved in mitochondrial activation under metabolic reprogramming. We revealed that glycolytic suppression notably increased mitochondrial membrane potential and mitophagy in a pancreatic cancer cell model (PANC-1). PTEN-induced kinase 1 (PINK1), a ubiquitin kinase that regulates mitophagy in healthy cells, regulated mitochondrial activation through mitophagy by glycolytic suppression. However, Parkin, a ubiquitin ligase regulated by PINK1 in healthy cells to induce mitophagy, was not involved in the PINK1-dependent mitophagy of the cancer glycometabolism. These results imply that cancer cells and healthy cells have different regulatory pieces of machinery for mitophagy, and inhibition of cancer-specific mechanisms may be a potential strategy for cancer therapy targeting metabolic reprogramming.

Keywords:  Glycometabolism; Mitophagy; PINK1; Pancreatic cancer; Parkin

DOI:  https://doi.org/10.1016/j.bbrc.2022.08.004
Mol Cell. 2022 Aug 12. pii: S1097-2765(22)00703-1. [Epub ahead of print]

Saturation of the mitochondrial NADH shuttles drives aerobic glycolysis in proliferating cells.

Yahui Wang, Ethan Stancliffe, Ronald Fowle-Grider, Rencheng Wang, Cheng Wang, Michaela Schwaiger-Haber, Leah P Shriver, Gary J Patti.

  Proliferating cells exhibit a metabolic phenotype known as "aerobic glycolysis," which is characterized by an elevated rate of glucose fermentation to lactate irrespective of oxygen availability. Although several theories have been proposed, a rationalization for why proliferating cells seemingly waste glucose carbon by excreting it as lactate remains elusive. Using the NCI-60 cell lines, we determined that lactate excretion is strongly correlated with the activity of mitochondrial NADH shuttles, but not proliferation. Quantifying the fluxes of the malate-aspartate shuttle (MAS), the glycerol 3-phosphate shuttle (G3PS), and lactate dehydrogenase under various conditions demonstrated that proliferating cells primarily transform glucose to lactate when glycolysis outpaces the mitochondrial NADH shuttles. Increasing mitochondrial NADH shuttle fluxes decreased glucose fermentation but did not reduce the proliferation rate. Our results reveal that glucose fermentation, a hallmark of cancer, is a secondary consequence of MAS and G3PS saturation rather than a unique metabolic driver of cellular proliferation.

Keywords:  NADH shuttles; aerobic glycolysis; cancer metabolism; glycerol 3-phosphate shuttle; isotope-tracer analysis; malate-aspartate shuttle; metabolic flux; metabolomics; the Warburg effect

DOI:  https://doi.org/10.1016/j.molcel.2022.07.007
Life Sci Alliance. 2022 Nov;pii: e202201413. [Epub ahead of print]5(11):

FKBP4 regulates 5-fluorouracil sensitivity in colon cancer by controlling mitochondrial respiration.

Zhenyu Zhu, Qingsheng Hou, Bishi Wang, Changhao Li, Luguang Liu, Weipeng Gong, Jie Chai, Hongliang Guo, Yanhan Jia.

Mitochondrial respiration and metabolism play a key role in the pathogenesis and progression of colon adenocarcinoma (COAD). Here, we report a functional pool of FKBP4, a co-chaperone protein, in the mitochondrial intermembrane space (IMS) of colon cancer cells. We found that IMS-localized FKBP4 is essential for the maintenance of mitochondrial respiration, thus contributing to the sensitivity of COAD cells to 5-fluorouracil (5-FU). Mechanistically, FKBP4 interacts with COA6 and controls the assembly of the mitochondrial COA6/SCO1/SCO2 complex, thereby governing COA6-regulated biogenesis and activity of mitochondrial cytochrome c oxidase (complex IV). Thus, our data reveal IMS-localized FKBP4 as a novel regulator of 5-FU sensitivity in COAD, linking mitochondrial respiration to 5-FU sensitivity in COAD.

DOI: https://doi.org/10.26508/lsa.202201413
J Cell Sci. 2022 Aug 17. pii: jcs.259778. [Epub ahead of print]

Proteasome granule formation is regulated through mitochondrial respiration and kinase signaling.

Kenrick A Waite, Jeroen Roelofs.

  In yeast, proteasomes are enriched in cell nuclei where they execute important cellular functions. Nutrient-stress can change this localization indicating proteasomes respond to the cell's metabolic state. However, the signals that connect these processes remain poorly understood. Carbon starvation triggers a reversible translocation of proteasomes to cytosolic condensates known as proteasome storage granules (PSGs). Surprisingly, we observed strongly reduced levels of proteasome granules when cells had active cellular respiration prior to starvation. This suggests the mitochondrial activity of cells is a determining factor in the response of proteasomes to carbon starvation. Consistent with this, upon inhibition of mitochondrial function we observed proteasomes relocalize to granules. These links between proteasomes and metabolism involve specific signaling pathways, as we identified a MAP kinase cascade that is critical to the formation of proteasome granules after respiratory growth but not following glycolytic growth. Furthermore, the yeast homolog of AMP kinase, Snf1, is important for proteasome granule formation induced by mitochondrial inhibitors, while dispensable for granule formation following carbon starvation. We propose a model where mitochondrial activity promotes proteasome nuclear localization.

Keywords:  MAP kinases; Mitochondrial inhibition; Mitochondrial respiration; Proteaphagy; Proteasome; Proteasome storage granules (PSG)

DOI:  https://doi.org/10.1242/jcs.259778
Cell Rep. 2022 Aug 16. pii: S2211-1247(22)01021-X. [Epub ahead of print]40(7): 111204

Mitochondrial microproteins link metabolic cues to respiratory chain biogenesis.

Chao Liang, Shan Zhang, David Robinson, Matthew Vander Ploeg, Rebecca Wilson, Jiemin Nah, Dale Taylor, Sheryl Beh, Radiance Lim, Lei Sun, Deborah M Muoio, David A Stroud, Lena Ho.

  Electron transport chain (ETC) biogenesis is tightly coupled to energy levels and availability of ETC subunits. Complex III (CIII), controlling ubiquinol:ubiquinone ratio in ETC, is an attractive node for modulating ETC levels during metabolic stress. Here, we report the discovery of mammalian Co-ordinator of mitochondrial CYTB (COM) complexes that regulate the stepwise CIII biogenesis in response to nutrient and nuclear-encoded ETC subunit availability. The COMA complex, consisting of UQCC1/2 and membrane anchor C16ORF91, facilitates translation of CIII enzymatic core subunit CYTB. Subsequently, microproteins SMIM4 and BRAWNIN together with COMA subunits form the COMB complex to stabilize nascent CYTB. Finally, UQCC3-containing COMC facilitates CYTB hemylation and association with downstream CIII subunits. Furthermore, when nuclear CIII subunits are limiting, COMB is required to chaperone nascent CYTB to prevent OXPHOS collapse. Our studies highlight CYTB synthesis as a key regulatory node of ETC biogenesis and uncover the roles of microproteins in maintaining mitochondrial homeostasis.

Keywords:  CP: Metabolism; CYTB; SEPs; SMIM4; UQCC1; UQCC2; complex III; electron transport chain; microproteins; nuclear-mitochondrial coordination; smORFs

DOI:  https://doi.org/10.1016/j.celrep.2022.111204
Cell Metab. 2022 Aug 11. pii: S1550-4131(22)00311-4. [Epub ahead of print]

Carbon source availability drives nutrient utilization in CD8+ T cells.

Irem Kaymak, Katarzyna M Luda, Lauren R Duimstra, Eric H Ma, Joseph Longo, Michael S Dahabieh, Brandon Faubert, Brandon M Oswald, McLane J Watson, Susan M Kitchen-Goosen, Lisa M DeCamp, Shelby E Compton, Zhen Fu, Ralph J DeBerardinis, Kelsey S Williams, Ryan D Sheldon, Russell G Jones.

  How environmental nutrient availability impacts T cell metabolism and function remains poorly understood. Here, we report that the presence of physiologic carbon sources (PCSs) in cell culture medium broadly impacts glucose utilization by CD8+ T cells, independent of transcriptional changes in metabolic reprogramming. The presence of PCSs reduced glucose contribution to the TCA cycle and increased effector function of CD8+ T cells, with lactate directly fueling the TCA cycle. In fact, CD8+ T cells responding to Listeria infection preferentially consumed lactate over glucose as a TCA cycle substrate in vitro, with lactate enhancing T cell bioenergetic and biosynthetic capacity. Inhibiting lactate-dependent metabolism in CD8+ T cells by silencing lactate dehydrogenase A (Ldha) impaired both T cell metabolic homeostasis and proliferative expansion in vivo. Together, our data indicate that carbon source availability shapes T cell glucose metabolism and identifies lactate as a bioenergetic and biosynthetic fuel for CD8+ effector T cells.

Keywords:  (13)C tracing; T cells; TCA cycle; immunometabolism; lactate; metabolic programming; metabolomics

DOI:  https://doi.org/10.1016/j.cmet.2022.07.012
Nat Chem Biol. 2022 Aug 15.

Glucose feeds the tricarboxylic acid cycle via excreted ethanol in fermenting yeast.

Tianxia Xiao, Artem Khan, Yihui Shen, Li Chen, Joshua D Rabinowitz.

Ethanol and lactate are typical waste products of glucose fermentation. In mammals, glucose is catabolized by glycolysis into circulating lactate, which is broadly used throughout the body as a carbohydrate fuel. Individual cells can both uptake and excrete lactate, uncoupling glycolysis from glucose oxidation. Here we show that similar uncoupling occurs in budding yeast batch cultures of Saccharomyces cerevisiae and Issatchenkia orientalis. Even in fermenting S. cerevisiae that is net releasing ethanol, media 13C-ethanol rapidly enters and is oxidized to acetaldehyde and acetyl-CoA. This is evident in exogenous ethanol being a major source of both cytosolic and mitochondrial acetyl units. 2H-tracing reveals that ethanol is also a major source of both NADH and NADPH high-energy electrons, and this role is augmented under oxidative stress conditions. Thus, uncoupling of glycolysis from the oxidation of glucose-derived carbon via rapidly reversible reactions is a conserved feature of eukaryotic metabolism.

DOI: https://doi.org/10.1038/s41589-022-01091-7
Cancer Cell. 2022 Aug 12. pii: S1535-6108(22)00324-5. [Epub ahead of print]

De novo pyrimidine synthesis is a targetable vulnerability in IDH mutant glioma.

Diana D Shi, Milan R Savani, Michael M Levitt, Adam C Wang, Jennifer E Endress, Cylaina E Bird, Joseph Buehler, Sylwia A Stopka, Michael S Regan, Yu-Fen Lin, Vinesh T Puliyappadamba, Wenhua Gao, Januka Khanal, Laura Evans, Joyce H Lee, Lei Guo, Yi Xiao, Min Xu, Bofu Huang, Rebecca B Jennings, Dennis M Bonal, Misty S Martin-Sandoval, Tammie Dang, Lauren C Gattie, Amy B Cameron, Sungwoo Lee, John M Asara, Harley I Kornblum, Tak W Mak, Ryan E Looper, Quang-De Nguyen, Sabina Signoretti, Stefan Gradl, Andreas Sutter, Michael Jeffers, Andreas Janzer, Mark A Lehrman, Lauren G Zacharias, Thomas P Mathews, Julie-Aurore Losman, Timothy E Richardson, Daniel P Cahill, Ralph J DeBerardinis, Keith L Ligon, Lin Xu, Peter Ly, Nathalie Y R Agar, Kalil G Abdullah, Isaac S Harris, William G Kaelin, Samuel K McBrayer.

  Mutations affecting isocitrate dehydrogenase (IDH) enzymes are prevalent in glioma, leukemia, and other cancers. Although mutant IDH inhibitors are effective against leukemia, they seem to be less active in aggressive glioma, underscoring the need for alternative treatment strategies. Through a chemical synthetic lethality screen, we discovered that IDH1-mutant glioma cells are hypersensitive to drugs targeting enzymes in the de novo pyrimidine nucleotide synthesis pathway, including dihydroorotate dehydrogenase (DHODH). We developed a genetically engineered mouse model of mutant IDH1-driven astrocytoma and used it and multiple patient-derived models to show that the brain-penetrant DHODH inhibitor BAY 2402234 displays monotherapy efficacy against IDH-mutant gliomas. Mechanistically, this reflects an obligate dependence of glioma cells on the de novo pyrimidine synthesis pathway and mutant IDH's ability to sensitize to DNA damage upon nucleotide pool imbalance. Our work outlines a tumor-selective, biomarker-guided therapeutic strategy that is poised for clinical translation.

Keywords:  DHODH; IDH; cancer metabolism; genetically engineered mouse model; glioma; isocitrate dehydrogenase; pyrimidine nucleotides

DOI:  https://doi.org/10.1016/j.ccell.2022.07.011
Geroscience. 2022 Aug 19.

Tissue-specific reductions in mitochondrial efficiency and increased ROS release rates during ageing in zebra finches, Taeniopygia guttata.

Pablo Salmón, Caroline Millet, Colin Selman, Pat Monaghan, Neal J Dawson.

  Mitochondrial dysfunction and oxidative damage have long been suggested as critically important mechanisms underlying the ageing process in animals. However, conflicting data exist on whether this involves increased production of mitochondrial reactive oxygen species (ROS) during ageing. We employed high-resolution respirometry and fluorometry on flight muscle (pectoralis major) and liver mitochondria to simultaneously examine mitochondrial function and ROS (H2O2) release rates in young (3 months) and old (4 years) zebra finches (Taeniopygia guttata). Respiratory capacities for oxidative phosphorylation did not differ between the two age groups in either tissue. Respiratory control ratios (RCR) of liver mitochondria also did not differ between the age classes. However, RCR in muscle mitochondria was 55% lower in old relative to young birds, suggesting that muscle mitochondria in older individuals are less efficient. Interestingly, this observed reduction in muscle RCR was driven almost entirely by higher mitochondrial LEAK-state respiration. Maximum mitochondrial ROS release rates were found to be greater in both flight muscle (1.3-fold) and the liver (1.9-fold) of old birds. However, while maximum ROS (H2O2) release rates from mitochondria increased with age across both liver and muscle tissues, the liver demonstrated a proportionally greater age-related increase in ROS release than muscle. This difference in age-related increases in ROS release rates between muscle and liver tissues may be due to increased mitochondrial leakiness in the muscle, but not the liver, of older birds. This suggests that age-related changes in cellular function seem to occur in a tissue-specific manner in zebra finches, with flight muscle exhibiting signs of minimising age-related increase in ROS release, potentially to reduce damage to this crucial tissue in older individuals.

Keywords:  Ageing; Birds; Mitochondrial physiology; Proton leak; Reactive oxygen species; Senescence

DOI:  https://doi.org/10.1007/s11357-022-00624-1
Cell Rep. 2022 Aug 16. pii: S2211-1247(22)01050-6. [Epub ahead of print]40(7): 111233

SHMT2-mediated mitochondrial serine metabolism drives 5-FU resistance by fueling nucleotide biosynthesis.

Erica Pranzini, Elisa Pardella, Livio Muccillo, Angela Leo, Ilaria Nesi, Alice Santi, Matteo Parri, Tong Zhang, Alejandro Huerta Uribe, Tiziano Lottini, Lina Sabatino, Anna Caselli, Annarosa Arcangeli, Giovanni Raugei, Vittorio Colantuoni, Paolo Cirri, Paola Chiarugi, Oliver D K Maddocks, Paolo Paoli, Maria Letizia Taddei.

  5-Fluorouracil (5-FU) is a key component of chemotherapy for colorectal cancer (CRC). 5-FU efficacy is established by intracellular levels of folate cofactors and DNA damage repair strategies. However, drug resistance still represents a major challenge. Here, we report that alterations in serine metabolism affect 5-FU sensitivity in in vitro and in vivo CRC models. In particular, 5-FU-resistant CRC cells display a strong serine dependency achieved either by upregulating endogenous serine synthesis or increasing exogenous serine uptake. Importantly, regardless of the serine feeder strategy, serine hydroxymethyltransferase-2 (SHMT2)-driven compartmentalization of one-carbon metabolism inside the mitochondria represents a specific adaptation of resistant cells to support purine biosynthesis and potentiate DNA damage response. Interfering with serine availability or affecting its mitochondrial metabolism revert 5-FU resistance. These data disclose a relevant mechanism of mitochondrial serine use supporting 5-FU resistance in CRC and provide perspectives for therapeutic approaches.

Keywords:  5-FU resistance; CP: Cancer; DNA damage response; Serine metabolism; colorectal cancer; mitochondrial metabolism; nucleotide metabolism; one-carbon metabolism (OCM)

DOI:  https://doi.org/10.1016/j.celrep.2022.111233
Blood. 2022 Aug 19. pii: blood.2022017575. [Epub ahead of print]

Dietary methionine starvation impairs acute myeloid leukemia progression.

Alan Cunningham, Ayşegül Erdem, Islam Alshamleh, Marjan Geugien, Maurien Pruis, Diego A Pereira-Martins, Fiona van den Heuvel, Albertus Wierenga, Hilde Anna Ten Berge, Robin Dennebos, Vincent van den Boom, Shanna M Hogeling, Isabel Weinhäuser, Ruth Knops, Pim de Blaauw, M Rebecca Heiner-Fokkema, Carolien Woolthuis, Ulrich Günther, Eduardo M Rego, Joost Martens, Joop H Jansen, Harald Schwalbe, Gerwin Huls, Jan Jacob Schuringa.

Targeting altered tumor cell metabolism might provide an attractive opportunity for patients with acute myeloid leukemia (AML). An amino acid dropout screen on primary leukemic stem cells and progenitor populations revealed a number of amino acid dependencies, of which methionine was one of the strongest. By using various metabolite rescue experiments, NMR-based metabolite quantifications and 13C-tracing, polysomal profiling, and ChIP-seq, we identified that methionine is used predominantly for protein translation and to provide methyl groups to histones via S-adenosylmethionine for epigenetic marking. H3K36me3 was consistently the most heavily impacted mark following loss of methionine. Methionine depletion also reduced total RNA levels, enhanced apoptosis and induced a cell cycle block. ROS levels were not increased following methionine depletion and replacement of methionine with glutathione or N-acetylcysteine could not rescue phenotypes, excluding a role for methionine in controlling redox balance control in AML. Although considered to be an essential amino acid, methionine can be recycled from homocysteine. We uncovered that this is primarily performed by the enzyme methionine synthase and only when methionine availability becomes limiting. In vivo, dietary methionine starvation was not only tolerated by mice, but also significantly delayed both cell line and patient-derived AML progression. Finally, we show that inhibition of the H3K36-specific methyltransferase SETD2 phenocopies much of the cytotoxic effects of methionine depletion, providing a more targeted therapeutic approach. In conclusion, we show that methionine depletion is a vulnerability in AML that can be exploited therapeutically, and we provide mechanistic insight into how cells metabolize and recycle methionine.

DOI: https://doi.org/10.1182/blood.2022017575
PLoS One. 2022 ;17(8): e0273080

Metabolic analyses reveal dysregulated NAD+ metabolism and altered mitochondrial state in ulcerative colitis.

Yu Hui Kang, Sarah A Tucker, Silvia F Quevedo, Aslihan Inal, Joshua R Korzenik, Marcia C Haigis.

Ulcerative colitis (UC) is a complex, multifactorial disease driven by a dysregulated immune response against host commensal microbes. Despite rapid advances in our understanding of host genomics and transcriptomics, the metabolic changes in UC remain poorly understood. We thus sought to investigate distinguishing metabolic features of the UC colon (14 controls and 19 patients). Metabolomics analyses revealed inflammation state as the primary driver of metabolic variation rather than diagnosis, with multiple metabolites differentially regulated between inflamed and uninflamed tissues. Specifically, inflamed tissues were characterized by reduced levels of nicotinamide adenine dinucleotide (NAD+) and enhanced levels of nicotinamide (NAM) and adenosine diphosphate ribose (ADPr). The NAD+/NAM ratio, which was reduced in inflamed patients, served as an effective classifier for inflammation in UC. Mitochondria were also structurally altered in UC, with UC patient colonocytes displaying reduced mitochondrial density and number. Together, these findings suggest a link between mitochondrial dysfunction, inflammation, and NAD+ metabolism in UC.

DOI: https://doi.org/10.1371/journal.pone.0273080
PLoS Comput Biol. 2022 Aug 19. 18(8): e1010413

Mitochondrial mRNA localization is governed by translation kinetics and spatial transport.

Ximena G Arceo, Elena F Koslover, Brian M Zid, Aidan I Brown.

For many nuclear-encoded mitochondrial genes, mRNA localizes to the mitochondrial surface co-translationally, aided by the association of a mitochondrial targeting sequence (MTS) on the nascent peptide with the mitochondrial import complex. For a subset of these co-translationally localized mRNAs, their localization is dependent on the metabolic state of the cell, while others are constitutively localized. To explore the differences between these two mRNA types we developed a stochastic, quantitative model for MTS-mediated mRNA localization to mitochondria in yeast cells. This model includes translation, applying gene-specific kinetics derived from experimental data; and diffusion in the cytosol. Even though both mRNA types are co-translationally localized we found that the steady state number, or density, of ribosomes along an mRNA was insufficient to differentiate the two mRNA types. Instead, conditionally-localized mRNAs have faster translation kinetics which modulate localization in combination with changes to diffusive search kinetics across metabolic states. Our model also suggests that the MTS requires a maturation time to become competent to bind mitochondria. Our work indicates that yeast cells can regulate mRNA localization to mitochondria by controlling mitochondrial volume fraction (influencing diffusive search times) and gene translation kinetics (adjusting mRNA binding competence) without the need for mRNA-specific binding proteins. These results shed light on both global and gene-specific mechanisms that enable cells to alter mRNA localization in response to changing metabolic conditions.

DOI: https://doi.org/10.1371/journal.pcbi.1010413
Cell Metab. 2022 Aug 11. pii: S1550-4131(22)00310-2. [Epub ahead of print]

The mitochondrial calcium uniporter engages UCP1 to form a thermoporter that promotes thermogenesis.

Kaili Xue, Dongmei Wu, Yushuang Wang, Yiheng Zhao, Hongyu Shen, Jingfei Yao, Xun Huang, Xinmeng Li, Zhao Zhou, Zihao Wang, Yifu Qiu.

  Uncoupling protein 1 (UCP1)-mediated adaptive thermogenesis protects mammals against hypothermia and metabolic dysregulation. Whether and how mitochondrial calcium regulates this process remains unclear. Here, we show that mitochondrial calcium uniporter (MCU) recruits UCP1 through essential MCU regulator (EMRE) to form an MCU-EMRE-UCP1 complex upon adrenergic stimulation. This complex formation increases mitochondrial calcium uptake to accelerate the tricarboxylic acid cycle and supply more protons that promote uncoupled respiration, functioning as a thermogenic uniporter. Mitochondrial calcium uptake 1 (MICU1) negatively regulates thermogenesis probably through inhibiting thermogenic uniporter formation. Accordingly, the deletion of Mcu or Emre in brown adipocytes markedly impairs thermogenesis and exacerbates obesity and metabolic dysfunction. Remarkably, the enhanced assembly of the thermogenic uniporter via Micu1 knockout or expressing linked EMRE-UCP1 results in opposite phenotypes. Thus, we have uncovered a "thermoporter" that provides a driving force for the UCP1 operation in thermogenesis, which could be leveraged to combat obesity and associated metabolic disorders.

Keywords:  UCP1; brown adipose tissue; metabolic dysfunction; mitochondrial calcium uniporter; obesity; thermogenesis

DOI:  https://doi.org/10.1016/j.cmet.2022.07.011
J Biomed Sci. 2022 Aug 18. 29(1): 61

The A'-helix of CYP11A1 remodels mitochondrial cristae.

Karen G Rosal, Wei-Yi Chen, Bon-Chu Chung.

  BACKGROUND: CYP11A1 is a protein located in the inner membrane of mitochondria catalyzing the first step of steroid synthesis. As a marker gene for steroid-producing cells, the abundance of CYP11A1 characterizes the extent of steroidogenic cell differentiation. Besides, the mitochondria of fully differentiated steroidogenic cells are specialized with tubulovesicular cristae. The participation of CYP11A1 in the change of mitochondrial structure and the differentiation of steroid-producing cells, however, has not been investigated.METHODS: We engineered nonsteroidogenic monkey kidney COS1 cells to express CYP11A1 upon doxycycline induction and examined the mitochondrial structure of these cells. We also mapped the CYP11A1 domains that confer structural changes of mitochondria. We searched for CYP11A1-interacting proteins and investigated the role of this interacting protein in shaping mitochondrial structure. Finally, we examined the effect of CYP11A1 overexpression on the amount of mitochondrial contact site and cristae organizing system.
RESULTS: We found that CYP11A1 overexpression led to the formation of tubulovesicular cristae in mitochondria. We also identified the A'-helix located at amino acid #57-68 to be sufficient for membrane insertion and crista remodeling. We identified heat shock protein 60 (Hsp60) as the CYP11A1-interacting protein and showed that Hsp60 is required for CYP11A1 accumulation and crista remodeling. Finally, we found that the small MIC10 subcomplex of the mitochondrial contact site and cristae organizing system was reduced when CYP11A1 was overexpressed.
CONCLUSIONS: CYP11A1 participates in the formation of tubulovesicular cristae in the mitochondria of steroidogenic cells. Its A'-helix is sufficient for the formation of tubulovesicular cristae and for protein integration into the membrane. CYP11A1 interacts with Hsp60, which is required for CYP11A1 accumulation. The accumulation of CYP11A1 leads to the reduction of MIC10 complex and changes mitochondrial structure.

Keywords:  Cristae remodeling; Hsp60; MIC10; Membrane; Mitochondrial structure; P450scc; Pregnenolone; Steroidogenesis

DOI:  https://doi.org/10.1186/s12929-022-00846-7
Front Oncol. 2022 ;12 926437

Transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor-resistant pancreatic ductal adenocarcinoma.

Parmanand Malvi, Vipin Rawat, Romi Gupta, Narendra Wajapeyee.

  Metabolic reprogramming, due in part to the overexpression of metabolic enzymes, is a key hallmark of cancer cells. Lactate dehydrogenase (LDHA), a metabolic enzyme that catalyzes the interconversion of lactate and pyruvate, is overexpressed in a wide variety of cancer types, including pancreatic ductal adenocarcinoma (PDAC). Furthermore, the genetic or pharmacological inhibition of LDHA suppresses cancer growth, demonstrating a cancer-promoting role for this enzyme. Therefore, several pharmacological LDHA inhibitors are being developed and tested as potential anti-cancer therapeutic agents. Because cancer cells are known to rapidly adapt and become resistant to anti-cancer therapies, in this study, we modeled the adaptation of cancer cells to LDHA inhibition. Using PDAC as a model system, we studied the molecular aspects of cells resistant to the competitive LDHA inhibitor sodium oxamate. We performed unbiased RNA-sequencing (RNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), and metabolomics analyses of parental and oxamate-resistant PDAC cells treated with and without oxamate to identify the transcriptional, chromatin, and metabolic landscapes of these cells. We found that oxamate-resistant PDAC cells were significantly different from parental cells at the levels of mRNA expression, chromatin accessibility, and metabolites. Additionally, an integrative analysis combining the RNA-seq and ATAC-seq datasets identified a subset of differentially expressed mRNAs that directly correlated with changes in chromatin accessibility. Finally, functional analysis of differentially expressed metabolic genes in parental and oxamate-resistant PDAC cells treated with and without oxamate, together with an integrative analysis of RNA-seq and metabolomics data, revealed changes in metabolic enzymes that might explain the changes in metabolite levels observed in these cells. Collectively, these studies identify the transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor resistance in PDAC cells. Future functional studies related to these changes remain necessary to reveal the direct roles played by these changes in the development of LDHA inhibitor resistance and uncover approaches for more effective use of LDHA inhibitors in cancer therapy.

Keywords:  LDHA; cancer metabolism; chromatin accessibility; metabolomics; transcriptomics

DOI:  https://doi.org/10.3389/fonc.2022.926437
Nucleic Acids Res. 2022 Aug 18. pii: gkac690. [Epub ahead of print]

Regulation of nuclear DNA damage response by mitochondrial morphofunctional pathway.

Nguyen Thi Kim Oanh, Ho-Soo Lee, Yong-Hyun Kim, Sunwoo Min, Yeon-Ji Park, June Heo, Yong-Yea Park, Won-Chung Lim, Hyeseong Cho.

Cells are constantly challenged by genotoxic stresses that can lead to genome instability. The integrity of the nuclear genome is preserved by the DNA damage response (DDR) and repair. Additionally, these stresses can induce mitochondria to transiently hyperfuse; however, it remains unclear whether canonical DDR is linked to these mitochondrial morphological changes. Here, we report that the abolition of mitochondrial fusion causes a substantial defect in the ATM-mediated DDR signaling. This deficiency is overcome by the restoration of mitochondria fusion. In cells with fragmented mitochondria, genotoxic stress-induced activation of JNK and its translocation to DNA lesion are lost. Importantly, the mitochondrial fusion machinery of MFN1/MFN2 associates with Sab (SH3BP5) and JNK, and these interactions are indispensable for the Sab-mediated activation of JNK and the ATM-mediated DDR signaling. Accordingly, the formation of BRCA1 and 53BP1 foci, as well as homology and end-joining repair are impaired in cells with fragmented mitochondria. Together, these data show that mitochondrial fusion-dependent JNK signaling is essential for the DDR, providing vital insight into the integration of nuclear and cytoplasmic stress signals.

DOI: https://doi.org/10.1093/nar/gkac690
Cancer Cell. 2022 Aug 15. pii: S1535-6108(22)00325-7. [Epub ahead of print]

A druggable addiction to de novo pyrimidine biosynthesis in diffuse midline glioma.

Sharmistha Pal, Jakub P Kaplan, Huy Nguyen, Sylwia A Stopka, Milan R Savani, Michael S Regan, Quang-De Nguyen, Kristen L Jones, Lisa A Moreau, Jingyu Peng, Marina G Dipiazza, Andrew J Perciaccante, Xiaoting Zhu, Bradley R Hunsel, Kevin X Liu, Sanda Alexandrescu, Rachid Drissi, Mariella G Filbin, Samuel K McBrayer, Nathalie Y R Agar, Dipanjan Chowdhury, Daphne A Haas-Kogan.

  Diffuse midline glioma (DMG) is a uniformly fatal pediatric cancer driven by oncohistones that do not readily lend themselves to drug development. To identify druggable targets for DMG, we conducted a genome-wide CRISPR screen that reveals a DMG selective dependency on the de novo pathway for pyrimidine biosynthesis. This metabolic vulnerability reflects an elevated rate of uridine/uracil degradation that depletes DMG cells of substrates for the alternate salvage pyrimidine biosynthesis pathway. A clinical stage inhibitor of DHODH (rate-limiting enzyme in the de novo pathway) diminishes uridine-5'-phosphate (UMP) pools, generates DNA damage, and induces apoptosis through suppression of replication forks-an "on-target" effect, as shown by uridine rescue. Matrix-assisted laser desorption/ionization (MALDI) mass spectroscopy imaging demonstrates that this DHODH inhibitor (BAY2402234) accumulates in the brain at therapeutically relevant concentrations, suppresses de novo pyrimidine biosynthesis in vivo, and prolongs survival of mice bearing intracranial DMG xenografts, highlighting BAY2402234 as a promising therapy against DMGs.

Keywords:  ATR; BAY2402234; DHODH; DPYD; de novo pyrimidine synthesis; diffuse intrinsic pontine glioma; diffuse midline glioma; elimusertib; pyrimidine degradation; replication stress

DOI:  https://doi.org/10.1016/j.ccell.2022.07.012
Free Radic Biol Med. 2022 Aug 16. pii: S0891-5849(22)00547-0. [Epub ahead of print]

MTP18 inhibition triggers mitochondrial hyperfusion to induce apoptosis through ROS-mediated lysosomal membrane permeabilization-dependent pathway in oral cancer.

Debasna Pritimanjari Panigrahi, Srimanta Patra, Bishnu Prasad Behera, Pradyota Kumar Behera, Shankargouda Patil, Birija Sankar Patro, Laxmidhar Rout, Itisam Sarangi, Sujit Kumar Bhutia.

  Although stress-induced mitochondrial hyperfusion (SIMH) exerts a protective role in aiding cell survival, in the absence of mitochondrial fission, SIMH drives oxidative stress-related induction of apoptosis. In this study, our data showed that MTP18, a mitochondrial fission-promoting protein expression, was increased in oral cancer. We have screened and identified S28, a novel inhibitor of MTP18, which was found to induce SIMH and subsequently trigger apoptosis. Interestingly, it inhibited MTP18-mediated mitochondrial fission, as shown by a decrease in p-Drp1 along with increased Mfn1 expression in oral cancer cells. Moreover, S28 induced autophagy but not mitophagy due to the trouble in engulfment of hypoperfused mitochondria. Interestingly, S28-mediated SIMH resulted in the loss of mitochondrial membrane potential, leading to the consequent generation of mitochondrial superoxide to induce intrinsic apoptosis. Mechanistically, S28-induced mitochondrial superoxide caused lysosomal membrane permeabilization (LMP), resulting in decreased lysosomal pH, which impaired autophagosome-lysosome fusion. In this setting, it showed that overexpression of MTP18 resulted in mitochondrial fission leading to mitophagy and inhibition of ROS-mediated LMP and apoptosis. Further, S28, in combination with FDA-approved anticancer drugs, exhibited higher apoptotic activity and decreased cell viability, suggesting the MTP18 inhibition combined with the anticancer drug could have greater efficacy against cancer.

Keywords:  Apoptosis; Hyperfused mitochondria; Lysosomal membrane permeabilization; MTP18; Mitochondrial superoxide

DOI:  https://doi.org/10.1016/j.freeradbiomed.2022.08.019
Cell Rep. 2022 Aug 16. pii: S2211-1247(22)00995-0. [Epub ahead of print]40(7): 111182

Inhibition of mutant IDH1 promotes cycling of acute myeloid leukemia stem cells.

Emily Gruber, Joan So, Alexander C Lewis, Rheana Franich, Rachel Cole, Luciano G Martelotto, Amy J Rogers, Eva Vidacs, Peter Fraser, Kym Stanley, Lisa Jones, Anna Trigos, Niko Thio, Jason Li, Brandon Nicolay, Scott Daigle, Adriana E Tron, Marc L Hyer, Jake Shortt, Ricky W Johnstone, Lev M Kats.

  Approximately 20% of acute myeloid leukemia (AML) patients carry mutations in IDH1 or IDH2 that result in over-production of the oncometabolite D-2-hydroxyglutarate (2-HG). Small molecule inhibitors that block 2-HG synthesis can induce complete morphological remission; however, almost all patients eventually acquire drug resistance and relapse. Using a multi-allelic mouse model of IDH1-mutant AML, we demonstrate that the clinical IDH1 inhibitor AG-120 (ivosidenib) exerts cell-type-dependent effects on leukemic cells, promoting delayed disease regression. Although single-agent AG-120 treatment does not fully eradicate the disease, it increases cycling of rare leukemia stem cells and triggers transcriptional upregulation of the pyrimidine salvage pathway. Accordingly, AG-120 sensitizes IDH1-mutant AML to azacitidine, with the combination of AG-120 and azacitidine showing vastly improved efficacy in vivo. Our data highlight the impact of non-genetic heterogeneity on treatment response and provide a mechanistic rationale for the observed combinatorial effect of AG-120 and azacitidine in patients.

Keywords:  2-HG; CP: cancer; IDH1; ivosidenib; leukemia stem cells; non-genetic heterogeneity; pyrimidine salvage

DOI:  https://doi.org/10.1016/j.celrep.2022.111182
Cell Death Dis. 2022 Aug 17. 13(8): 715

m6A RNA methylation-mediated NDUFA4 promotes cell proliferation and metabolism in gastric cancer.

Weihong Xu, Yanan Lai, Yunqi Pan, Meiyu Tan, Yanyun Ma, Huiming Sheng, Jiucun Wang.

Gastric cancer (GC) is a malignancy with poor prognosis. NDUFA4 is reported to correlate with the progression of GC. However, its underlying mechanism in GC is unknown. Our study was to reveal the pathogenic mechanism of NDUFA4 in GC. NDUFA4 expression was explored in single-cell and bulk RNA-seq data as well as GC tissue microarray. Mitochondrial respiration and glycolysis were estimated by oxygen consumption rate and extracellular acidification rate, respectively. The interaction between NDUFA4 and METTL3 was validated by RNA immunoprecipitation. Flow cytometry was used to estimate cell cycle, apoptosis and mitochondrial activities. NDUFA4 was highly expressed in GC and its high expression indicated a poor prognosis. The knockdown of NDUFA4 could reduce cell proliferation and inhibit tumor growth. Meanwhile, NDUFA4 could promote glycolytic and oxidative metabolism in GC cells, whereas the inhibition of glycolysis suppressed the proliferation and tumor growth of GC. Besides, NDUFA4 inhibited ROS level and promoted MMP level in GC cells, whereas the inhibition of mitochondrial fission could reverse NDUFA4-induced glycolytic and oxidative metabolism and tumor growth of GC. Additionally, METTL3 could increase the m6A level of NDUFA4 mRNA via the m6A reader IGF2BP1 to promote NDUFA4 expression in GC cells. Our study revealed that NDUFA4 was increased by m6A methylation and could promote GC development via enhancing cell glycolysis and mitochondrial fission. NDUFA4 was a potential target for GC treatment.

DOI: https://doi.org/10.1038/s41419-022-05132-w
Autophagy. 2022 Aug 13.

Targeting Mitophagy to Promote Apoptosis is a Potential Therapeutic Strategy for Cancer.

Yancheng Tang, Liming Wang, Jiangjiang Qin, Ying-Ying Lu, Han-Ming Shen, Hu-Biao Chen.

Many anticancer agents exert cytotoxicity and trigger apoptosis through the induction of mitochondrial dysfunction. Mitophagy, as the key mitochondrial quality control mechanism, can remove damaged mitochondria in an effective and timely manner, which may result in drug resistance. Although the implication of mitophagy in neurodegenerative diseases has been extensively studied, the role and mechanism of mitophagy in tumorigenesis and cancer therapy are largely unknown. In a recent study, we found that the inhibition of PINK1-PRKN-mediated mitophagy can significantly enhance the anticancer efficacy of magnolol, a natural product with potential anticancer properties. On the one hand, magnolol can induce severe mitochondrial dysfunction, including mitochondrial depolarization, excessive mitochondrial fragmentation and the generation of mitochondrial ROS, leading to apoptosis. On the other hand, magnolol induces PINK1-PRKN-dependent mitophagy via activation of two rounds of feedforward amplification loops. The blockage of mitophagy through genetic or pharmacological approaches promotes rather than attenuates magnolol-induced cell death. Furthermore, inhibition of mitophagy by using distinct inhibitors targeting different mitophagic stages effectively enhances magnolol's anticancer efficacy in vivo. Taken together, our findings strongly indicate that manipulation of mitophagy in cancer treatment will be a promising therapeutic strategy for overcoming cancer drug resistance and improving the therapeutic efficacy of anticancer agents.

DOI: https://doi.org/10.1080/15548627.2022.2112830
J Nanobiotechnology. 2022 Aug 13. 20(1): 376

Development of artesunate intelligent prodrug liposomes based on mitochondrial targeting strategy.

Liwei Gu, Jiaxing Zhang, Dandan Liu, Jiayun Chen, Shuzhi Liu, Qing Peng, Ya Tian, Maobo Du, Junzhe Zhang, Wei Xiao, Shuo Shen, Jigang Wang.

  Breast cancer is the leading cause of cancer-related deaths in women and remains a formidable therapeutic challenge. Mitochondria participate in a myriad of essential cellular processes, such as metabolism, and are becoming an ideal target for cancer therapy. Artemisinin and its derivatives have demonstrated multiple activities in the context of various cancers. Mitochondrial autophagy(mitophagy) is one of the important anti-tumor mechanisms of artemisinin drugs. However, the lack of specific tumor targeting ability limits the anti-tumor efficacy of artemisinin drugs. In this study, a GSH-sensitive artesunate smart conjugate (TPP-SS-ATS) was synthesized and liposomes (TPP-SS-ATS-LS) that target tumor cells and mitochondria were further prepared. The advantages of TPP-SS-ATS-LS targeting to the breast tumor were verified by in vivo and in vitro evaluations. In our study, the cytotoxicity was obviously enhanced in vitro and tumor growth inhibition rate was increased from 37.7% to 56.4% at equivalent artesunate dosage in breast cancer orthotopic implanted mice. Meanwhile, mitochondrial dysfunction, suppression of ATP production and respiratory capacity were detected in breast cancer cells. We further discovered that TPP-SS-ATS-LS inhibited tumor cells proliferation through mitophagy by regulating PHB2 and PINK1 expression. These results provide new research strategies for the development of new artemisinin-based anti-tumor drugs.

Keywords:  Anti-tumor; Artesunate smart conjugate; Liposomes; Mitochondrial targeting; Mitophagy

DOI:  https://doi.org/10.1186/s12951-022-01569-5
Nat Metab. 2022 Aug 15.

A practical guide for the analysis, standardization and interpretation of oxygen consumption measurements.

Ajit S Divakaruni, Martin Jastroch.

Measurement of oxygen consumption is a powerful and uniquely informative experimental technique. It can help identify mitochondrial mechanisms of action following pharmacologic and genetic interventions, and characterize energy metabolism in physiology and disease. The conceptual and practical benefits of respirometry have made it a frontline technique to understand how mitochondrial function can interface with-and in some cases control-cell physiology. Nonetheless, an appreciation of the complexity and challenges involved with such measurements is required to avoid common experimental and analytical pitfalls. Here we provide a practical guide to oxygen consumption measurements covering the selection of experimental models and instrumentation, as well as recommendations for the collection, interpretation and normalization of data. These guidelines are provided with the intention of aiding experimental design and enhancing the overall reputability, transparency and reliability of oxygen consumption measurements.

DOI: https://doi.org/10.1038/s42255-022-00619-4
Cell Rep. 2022 Aug 16. pii: S2211-1247(22)01010-5. [Epub ahead of print]40(7): 111193

Succinate uptake by T cells suppresses their effector function via inhibition of mitochondrial glucose oxidation.

Nancy Gudgeon, Haydn Munford, Emma L Bishop, James Hill, Taylor Fulton-Ward, David Bending, Jennie Roberts, Daniel A Tennant, Sarah Dimeloe.

  Succinate dehydrogenase (SDH) loss-of-function mutations drive succinate accumulation in tumor microenvironments, for example in the neuroendocrine tumors pheochromocytoma (PC) and paraganglioma (PG). Control of innate immune cell activity by succinate is described, but effects on T cells have not been interrogated. Here we report that exposure of human CD4+ and CD8+ T cells to tumor-associated succinate concentrations suppresses degranulation and cytokine secretion, including of the key anti-tumor cytokine interferon-γ (IFN-γ). Mechanistically, this is associated with succinate uptake-partly via the monocarboxylate transporter 1 (MCT1)-inhibition of succinyl coenzyme A synthetase activity and impaired glucose flux through the tricarboxylic acid cycle. Consistently, pharmacological and genetic interventions restoring glucose oxidation rescue T cell function. Tumor RNA-sequencing data from patients with PC and PG reveal profound suppression of IFN-γ-induced genes in SDH-deficient tumors compared with those with other mutations, supporting a role for succinate in modulating the anti-tumor immune response in vivo.

Keywords:  CP: immunology; CP: metabolism; T cell; metabolism; metabolite; succinate; tumor microenvironment

DOI:  https://doi.org/10.1016/j.celrep.2022.111193
EMBO Rep. 2022 Aug 16. e55502

Identification and characterization of in vitro expanded hematopoietic stem cells.

James L C Che, Daniel Bode, Iwo Kucinski, Alyssa H Cull, Fiona Bain, Hans J Becker, Maria Jassinskaja, Melania Barile, Grace Boyd, Miriam Belmonte, Andy G X Zeng, Kyomi J Igarashi, Juan Rubio-Lara, Mairi S Shepherd, Anna Clay, John E Dick, Adam C Wilkinson, Hiromitsu Nakauchi, Satoshi Yamazaki, Berthold Göttgens, David G Kent.

  Hematopoietic stem cells (HSCs) cultured outside the body are the fundamental component of a wide range of cellular and gene therapies. Recent efforts have achieved > 200-fold expansion of functional HSCs, but their molecular characterization has not been possible since the majority of cells are non-HSCs and single cell-initiated cultures have substantial clone-to-clone variability. Using the Fgd5 reporter mouse in combination with the EPCR surface marker, we report exclusive identification of HSCs from non-HSCs in expansion cultures. By directly linking single-clone functional transplantation data with single-clone gene expression profiling, we show that the molecular profile of expanded HSCs is similar to proliferating fetal HSCs and reveals a gene expression signature, including Esam, Prdm16, Fstl1, and Palld, that can identify functional HSCs from multiple cellular states. This "repopulation signature" (RepopSig) also enriches for HSCs in human datasets. Together, these findings demonstrate the power of integrating functional and molecular datasets to better derive meaningful gene signatures and opens the opportunity for a wide range of functional screening and molecular experiments previously not possible due to limited HSC numbers.

Keywords:  HSC expansion; hematopoiesis; hematopoietic stem cells; self-renewal gene signature; single cell biology

DOI:  https://doi.org/10.15252/embr.202255502
Mol Cancer. 2022 Aug 19. 21(1): 166

Longitudinal single-cell transcriptomics reveals distinct patterns of recurrence in acute myeloid leukemia.

Yanan Zhai, Prashant Singh, Anna Dolnik, Peter Brazda, Nader Atlasy, Nunzio Del Gaudio, Konstanze Döhner, Hartmut Döhner, Saverio Minucci, Joost Martens, Lucia Altucci, Wout Megchelenbrink, Lars Bullinger, Hendrik G Stunnenberg.

  BACKGROUND: Acute myeloid leukemia (AML) is a heterogeneous and aggressive blood cancer that results from diverse genetic aberrations in the hematopoietic stem or progenitor cells (HSPCs) leading to the expansion of blasts in the hematopoietic system. The heterogeneity and evolution of cancer blasts can render therapeutic interventions ineffective in a yet poorly understood patient-specific manner. In this study, we investigated the clonal heterogeneity of diagnosis (Dx) and relapse (Re) pairs at genetic and transcriptional levels, and unveiled the underlying pathways and genes contributing to recurrence.METHODS: Whole-exome sequencing was used to detect somatic mutations and large copy number variations (CNVs). Single cell RNA-seq was performed to investigate the clonal heterogeneity between Dx-Re pairs and amongst patients.
RESULTS: scRNA-seq analysis revealed extensive expression differences between patients and Dx-Re pairs, even for those with the same -presumed- initiating events. Transcriptional differences between and within patients are associated with clonal composition and evolution, with the most striking differences in patients that gained large-scale copy number variations at relapse. These differences appear to have significant molecular implications, exemplified by a DNMT3A/FLT3-ITD patient where the leukemia switched from an AP-1 regulated clone at Dx to a mTOR signaling driven clone at Re. The two distinct AML1-ETO pairs share genes related to hematopoietic stem cell maintenance and cell migration suggesting that the Re leukemic stem cell-like (LSC-like) cells evolved from the Dx cells.
CONCLUSIONS: In summary, the single cell RNA data underpinned the tumor heterogeneity not only amongst patient blasts with similar initiating mutations but also between each Dx-Re pair. Our results suggest alternatively and currently unappreciated and unexplored mechanisms leading to therapeutic resistance and AML recurrence.

Keywords:  Acute myeloid Leukemia; Genome analysis; Leukemic stem cells; Recurrence; Single-cell RNA sequencing

DOI:  https://doi.org/10.1186/s12943-022-01635-4
RSC Adv. 2022 Aug 04. 12(34): 21690-21703

Mitochondria-targeted alginate/triphenylphosphonium-grafted-chitosan for treatment of hepatocellular carcinoma.

Kholoud K Arafa, Mohamed A Hamzawy, Shaker A Mousa, Ibrahim M El-Sherbiny.

Mitochondrial targeting of anticancer drugs can effectively eradicate chemotherapy-refractory cells through different mechanisms. This work presents the rational designing of mitochondria-targeted core-shell polymeric nanoparticles (NPs) for efficient delivery of doxorubicin (DOX) to the hepatic carcinoma mitochondria. DOX was electrostatically nano-complexed with sodium alginate (SAL) then coated with mitotropic triphenylphosphonium-grafted chitosan (TPP+-g-CS) nanoshell. Polyvinyl alcohol (PVA) was co-solubilized into the TPP+-g-CS solution to enhance the stability of the developed NPs. The optimum NPs formula is composed of TPP+-g-CS (0.05% w/v) coating a DOX-SAL core complex (0.05% w/v), with 0.2% PVA relative to CS (w/w). The optimum NPs attained an entrapment efficiency of 63.33 ± 10.18%; exhibited a spherical shape with particle size of 70-110 nm and a positive surface charge which enhances mitochondrial uptake. FTIR and DSC studies results were indicative of an efficacious poly-complexation. In vitro biological experiments proved that the developed mitotropic NPs exhibited a significantly lower IC50, effectively induced apoptotic cell death and cell cycle arrest. Moreover, the in vivo studies demonstrated an enhanced antitumor bioactivity for the mitotropic NPs along with a reduced biological toxicity profile. In conclusion, this study proposes a promising nanocarrier system for the efficient targeting of DOX to the mitochondria of hepatic tumors.

DOI: https://doi.org/10.1039/d2ra03240f
Proc Natl Acad Sci U S A. 2022 Aug 23. 119(34): e2202144119

Intestinal tissue-resident T cell activation depends on metabolite availability.

Špela Konjar, Cristina Ferreira, Filipa Sofia Carvalho, Patrícia Figueiredo-Campos, Júlia Fanczal, Sofia Ribeiro, Vanessa Alexandra Morais, Marc Veldhoen.

  The metabolic capacity of many cells is tightly regulated and can adapt to changes in metabolic resources according to environmental changes. Tissue-resident memory (TRM) CD8+ T cells are one of the most abundant T cell populations and offer rapid protection against invading pathogens, especially at the epithelia. TRM cells metabolically adapt to their tissue niche, such as the intestinal epithelial barrier. In the small intestine, the types of TRM cells are intraepithelial lymphocytes (IELs), which contain high levels of cytotoxic molecules and express activation markers, suggesting a heightened state of activation. We hypothesize that the tissue environment may determine IEL activity. We show that IEL activation, in line with its semiactive status, is metabolically faster than circulating CD8+ T cells. IEL glycolysis and oxidative phosphorylation (OXPHOS) are interdependently regulated and are dependent on rapid access to metabolites from the environment. IELs are restrained by local availability of metabolites, but, especially, glucose levels determine their activity. Importantly, this enables functional control of intestinal TRM cells by metabolic means within the fragile environment of the intestinal epithelial barrier.

Keywords:  IELs; T cells; glucose; metabolism; tissue-resident memory T cells

DOI:  https://doi.org/10.1073/pnas.2202144119
Nat Commun. 2022 Aug 16. 13(1): 4827

A new gene set identifies senescent cells and predicts senescence-associated pathways across tissues.

Dominik Saul, Robyn Laura Kosinsky, Elizabeth J Atkinson, Madison L Doolittle, Xu Zhang, Nathan K LeBrasseur, Robert J Pignolo, Paul D Robbins, Laura J Niedernhofer, Yuji Ikeno, Diana Jurk, João F Passos, LaTonya J Hickson, Ailing Xue, David G Monroe, Tamara Tchkonia, James L Kirkland, Joshua N Farr, Sundeep Khosla.

Although cellular senescence drives multiple age-related co-morbidities through the senescence-associated secretory phenotype, in vivo senescent cell identification remains challenging. Here, we generate a gene set (SenMayo) and validate its enrichment in bone biopsies from two aged human cohorts. We further demonstrate reductions in SenMayo in bone following genetic clearance of senescent cells in mice and in adipose tissue from humans following pharmacological senescent cell clearance. We next use SenMayo to identify senescent hematopoietic or mesenchymal cells at the single cell level from human and murine bone marrow/bone scRNA-seq data. Thus, SenMayo identifies senescent cells across tissues and species with high fidelity. Using this senescence panel, we are able to characterize senescent cells at the single cell level and identify key intercellular signaling pathways. SenMayo also represents a potentially clinically applicable panel for monitoring senescent cell burden with aging and other conditions as well as in studies of senolytic drugs.

DOI: https://doi.org/10.1038/s41467-022-32552-1
Mitochondrion. 2022 Aug 10. pii: S1567-7249(22)00071-X. [Epub ahead of print]66 74-81

Mitochondrial miRNAs (MitomiRs): Their potential roles in breast and other cancers.

Elif Erturk, Omer Enes Onur, Oguzhan Akgun, Gonca Tuna, Yaren Yildiz, Ferda Ari.

  Breast cancer is the most common cancer in women worldwide. MicroRNAs (miRNAs) are non-coding RNAs that are involved in the post-transcriptional regulation of gene expression. Although miRNAs mainly act in the cytoplasm, they can be found in the mitochondrial compartment of the cell. These miRNAs called "MitomiR", they can change mitochondrial functions by regulating proteins at the mitochondrial level and cause cancer. In this review, we have aimed to explain miRNA biogenesis, transport pathways to mitochondria, and summarize mitomiRs that have been shown to play an important role in mitochondrial function, especially in the initiation and progression of breast cancer.

Keywords:  Breast Cancer; Mitochondria; MitomiRs; miRNAs

DOI:  https://doi.org/10.1016/j.mito.2022.08.002