bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2021‒10‒31
thirty-five papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. Leuk Lymphoma. 2021 Oct 27. 1-8
      Cancer cells reprogram their metabolism to maintain sustained proliferation, which creates unique metabolic dependencies between malignant and healthy cells that can be exploited for therapy. In acute myeloid leukemia (AML), mitochondrial inhibitors that block tricarboxylic acid cycle enzymes or electron transport chain complexes have recently shown clinical promise. The isocitrate dehydrogenase 1 inhibitor ivosidenib, the isocitrate dehydrogenase 2 inhibitor enasidenib, and the BH3 mimetic venetoclax received FDA approval for treatment of AML in the last few years. Other mitochondrial inhibitors including CPI-613, CB-839, dihydroorotate dehydrogenase inhibitors, IACS-010759, and mubritinib, have shown encouraging preclinical efficacy and are currently being evaluated in clinical trials. In this review, we summarize recent metabolism-based therapies and their ability to target altered cancer metabolism in AML.
    Keywords:  Targeted therapy; acute myeloid leukemia; mitochondrial metabolism
  2. Cell Chem Biol. 2021 Oct 22. pii: S2451-9456(21)00441-4. [Epub ahead of print]
      Efforts to target glucose metabolism in cancer have been limited by the poor potency and specificity of existing anti-glycolytic agents and a poor understanding of the glucose dependence of cancer subtypes in vivo. Here, we present an extensively characterized series of potent, orally bioavailable inhibitors of the class I glucose transporters (GLUTs). The representative compound KL-11743 specifically blocks glucose metabolism, triggering an acute collapse in NADH pools and a striking accumulation of aspartate, indicating a dramatic shift toward oxidative phosphorylation in the mitochondria. Disrupting mitochondrial metabolism via chemical inhibition of electron transport, deletion of the malate-aspartate shuttle component GOT1, or endogenous mutations in tricarboxylic acid cycle enzymes, causes synthetic lethality with KL-11743. Patient-derived xenograft models of succinate dehydrogenase A (SDHA)-deficient cancers are specifically sensitive to KL-11743, providing direct evidence that TCA cycle-mutant tumors are vulnerable to GLUT inhibitors in vivo.
    Keywords:  GLUT inhibitor; PDX models; electron transport chain inhibitors; glycolysis; imaging; malate-aspartate shuttle; mitochondrial inhibitors; pharmacology; redox biology; toxicology
  3. Mol Med Rep. 2021 Dec;pii: 873. [Epub ahead of print]24(6):
      Ginsenoside Rh2 (G‑Rh2) is a monomeric compound that extracted from ginseng and possesses anti‑cancer activities both in vitro and in vivo. Previously, we reported that G‑Rh2 induces apoptosis in HeLa cervical cancer cells and that the process was related to reactive oxygen species (ROS) accumulation and mitochondrial dysfunction. However, the upstream mechanisms of G‑Rh2, along with its cellular targets, remain to be elucidated. In the present study, the Cell Counting Kit‑8 assay, flow cytometry and Hoechst staining revealed that G‑Rh2 significantly inhibited cell viability and induced apoptosis of cervical cancer cells. However, G‑Rh2 was demonstrated to be non‑toxic to End1/e6e7 cells. JC‑1, rhodamine 123 staining, oxidative phosphorylation and glycolysis capacity assays demonstrated that G‑Rh2 exposure caused an immediate decrease in mitochondrial transmembrane potential due to its inhibition of mitochondrial oxidative phosphorylation, as well as glycolysis, both of which reduced cellular ATP production. Western blotting and electron transport chain (ETC) activity assays revealed that G‑Rh2 significantly inhibited the activity of ETC complexes I, III and V. Overexpression of ETC complex III partially significantly restored mitochondrial ROS and inhibited the apoptosis of cervical cancer cells induced by G‑Rh2. The predicted results of binding energy in molecular docking, confirmed that G‑Rh2 was highly likely to induce mitochondrial ROS production and promote cell apoptosis by targeting the ETC complex, especially for ETC complex III. Taken together, the present results revealed the potential anti‑cervical cancer activity of G‑Rh2 and provide direct evidence for the contribution of impaired ETC complex activity to cervical cancer cell death.
    Keywords:  ginsenoside Rh2; mitochondria; mitochondrial electron transfer chain complexes; oxidative phosphorylation; reactive oxygen species
  4. Mol Cell Biochem. 2021 Oct 30.
      The relative contribution of mitochondrial respiration and subsequent energy production in malignant cells has remained controversial to date. Enhanced aerobic glycolysis and impaired mitochondrial respiration have gained more attention in the metabolic study of cancer. In contrast to the popular concept, mitochondria of cancer cells oxidize a diverse array of metabolic fuels to generate a majority of the cellular energy by respiration. Several mitochondrial respiratory chain (MRC) subunits' expressions are critical for the growth, metastasis, and cancer cell invasion. Also, the assembly factors, which regulate the integration of individual MRC complexes into native super-complexes, are upregulated in cancer. Moreover, a series of anti-cancer drugs function by inhibiting respiration and ATP production. In this review, we have specified the roles of mitochondrial fuels, MRC subunits, and super-complex assembly factors that promote active respiration across different cancer types and discussed the potential roles of MRC inhibitor drugs in controlling cancer.
    Keywords:  Cancer; Drugs; Metabolic fuels; Mitochondria; Respiratory chain subunits; Super-complex
  5. Cell Metab. 2021 Oct 25. pii: S1550-4131(21)00482-4. [Epub ahead of print]
      Wound healing is a coordinated process that initially relies on pro-inflammatory macrophages, followed by a pro-resolution function of these cells. Changes in cellular metabolism likely dictate these distinct activities, but the nature of these changes has been unclear. Here, we profiled early- versus late-stage skin wound macrophages in mice at both the transcriptional and functional levels. We found that glycolytic metabolism in the early phase is not sufficient to ensure productive repair. Instead, by combining conditional disruption of the electron transport chain with deletion of tgcqmitochondrial aspartyl-tRNA synthetase, followed by single-cell sequencing analysis, we found that a subpopulation of early-stage wound macrophages are marked by mitochondrial ROS (mtROS) production and HIF1α stabilization, which ultimately drives a pro-angiogenic program essential for timely healing. In contrast, late-phase, pro-resolving wound macrophages are marked by IL-4Rα-mediated mitochondrial respiration and mitohormesis. Collectively, we identify changes in mitochondrial metabolism as a critical control mechanism for macrophage effector functions during wound healing.
    Keywords:  metabolism; mitochondria; mitochondrial repurposing; mitohormesis; monocyte/macrophage; tissue repair; type 2 immunity; wound healing
  6. Mol Metab. 2021 Oct 22. pii: S2212-8778(21)00206-4. [Epub ahead of print] 101359
      OBJECTIVE: Liver mitochondria adapt to high calorie intake. We investigated how exercise alters the early compensatory response of mitochondria and thus prevents fatty liver disease as a long-term consequence of overnutrition.METHODS: We compared the effects of a steatogenic high-energy diet (HED, for 6 weeks) on mitochondrial metabolism of sedentary and treadmill-trained C57BL/6N mice. We applied multi-OMICs analyses to study the alterations in the proteome, transcriptome and lipids in isolated mitochondria of liver and skeletal muscle as well as in whole tissue and examined the functional consequences by high resolution respirometry.
    RESULTS: HED increased the respiratory capacity of isolated liver mitochondria, both in sedentary and in trained mice. However, proteomics analysis of the mitochondria and transcriptomics indicated that training modified the adaptation of the hepatic metabolism to HED on the level of respiratory complex I, glucose oxidation, pyruvate and acetyl-CoA metabolism and lipogenesis. Training also counteracted the HED-induced increase in fasting insulin, glucose tolerance, and liver fat. This was accompanied by lower diacylglycerol species and JNK phosphorylation in the livers of trained HED-fed mice, two mechanisms that can reverse hepatic insulin resistance. In skeletal muscle, the combination of HED and training improved the oxidative capacity to a greater extent than training alone by increasing respiration of isolated mitochondria and total mitochondrial protein content.
    CONCLUSION: We provide a comprehensive insight into the early adaptations of mitochondria in liver and skeletal muscle to HED and endurance training. Our results suggest that exercise disconnects the HED-induced increase in mitochondrial substrate oxidation from pyruvate and acetyl-CoA-driven lipid synthesis. This could contribute to the prevention of deleterious long-term effects of high fat and sugar intake on hepatic mitochondrial function and insulin sensitivity.
    Keywords:  MAFLD; acetyl-CoA; exercise; lipidomics; mitochondrial supercomplexes; proteomics
  7. J Pathol. 2021 Oct 26.
      Cancer cells have an altered metabolic state that supports their growth; for example, aerobic glycolysis, known as the Warburg effect. Colorectal cancer cells have been reported to exhibit the Warburg effect and mainly rely on glycolysis for progression and have dysfunctional mitochondria. So far, how mitochondrial function influences the properties of colorectal cancer cells is unclear. Here, we demonstrated that mitochondria maintain histone acetylation, in particular H3K27ac, a surrogate epigenomic marker of active super-enhancers, in colorectal cancer cells. Immunohistochemistry was used on human colorectal adenocarcinoma specimens and showed that mitochondrial mass and H3K27ac marks were increased in adenocarcinoma lesions compared to adjacent non-neoplastic mucosa. Immunoblotting after using inhibitors of the mitochondrial respiratory complex or mitochondrial DNA-depleted human colorectal cancer cells revealed that mitochondria maintained pan-histone acetylation and H3K27ac marks. Notably, anchorage-independent growth, a feature of cancer, increased mitochondrial mass and H3K27ac marks in human colorectal cancer cells. These findings indicate that mitochondria in human colorectal cancer cells are not dysfunctional, as formerly believed, but function as inducers of histone acetylation. This article is protected by copyright. All rights reserved.
    Keywords:  Anchorage-independent growth; Colorectal cancer; H3K27ac; Histone acetylation; Mitochondria
  8. Dev Cell. 2021 Oct 22. pii: S1534-5807(21)00809-1. [Epub ahead of print]
      In order to combat molecular damage, most cellular proteins undergo rapid turnover. We have previously identified large nuclear protein assemblies that can persist for years in post-mitotic tissues and are subject to age-related decline. Here, we report that mitochondria can be long lived in the mouse brain and reveal that specific mitochondrial proteins have half-lives longer than the average proteome. These mitochondrial long-lived proteins (mitoLLPs) are core components of the electron transport chain (ETC) and display increased longevity in respiratory supercomplexes. We find that COX7C, a mitoLLP that forms a stable contact site between complexes I and IV, is required for complex IV and supercomplex assembly. Remarkably, even upon depletion of COX7C transcripts, ETC function is maintained for days, effectively uncoupling mitochondrial function from ongoing transcription of its mitoLLPs. Our results suggest that modulating protein longevity within the ETC is critical for mitochondrial proteome maintenance and the robustness of mitochondrial function.
    Keywords:  age mosaicism; aging; electron transport chain; heterogeneity; long-lived proteins; mitochondria; muscle; neurons; protein homeostasis; supercomplexes
  9. Nature. 2021 Oct 27.
      Glutathione (GSH) is a small-molecule thiol that is abundant in all eukaryotes and has key roles in oxidative metabolism1. Mitochondria, as the major site of oxidative reactions, must maintain sufficient levels of GSH to perform protective and biosynthetic functions2. GSH is synthesized exclusively in the cytosol, yet the molecular machinery involved in mitochondrial GSH import remains unknown. Here, using organellar proteomics and metabolomics approaches, we identify SLC25A39, a mitochondrial membrane carrier of unknown function, as a regulator of GSH transport into mitochondria. Loss of SLC25A39 reduces mitochondrial GSH import and abundance without affecting cellular GSH levels. Cells lacking both SLC25A39 and its paralogue SLC25A40 exhibit defects in the activity and stability of proteins containing iron-sulfur clusters. We find that mitochondrial GSH import is necessary for cell proliferation in vitro and red blood cell development in mice. Heterologous expression of an engineered bifunctional bacterial GSH biosynthetic enzyme (GshF) in mitochondria enables mitochondrial GSH production and ameliorates the metabolic and proliferative defects caused by its depletion. Finally, GSH availability negatively regulates SLC25A39 protein abundance, coupling redox homeostasis to mitochondrial GSH import in mammalian cells. Our work identifies SLC25A39 as an essential and regulated component of the mitochondrial GSH-import machinery.
  10. Front Oncol. 2021 ;11 745924
      The cancer metabolic alteration is considered a hallmark and fast becoming a road for therapeutic intervention. Mitochondria have been regarded as essential cell elements that fuel the metabolic needs of most cancer cell types. Leukemia stem cells (LSCs) are a heterogeneous, highly self-renewing, and pluripotent cell population within leukemic cells. The most important source of ATP and metabolites to fulfill the bioenergetics and biosynthetic needs of most cancer stem cells is the mitochondria. In addition, mitochondria have a core role in autophagy and cell death and are the main source of reactive oxygen species (ROS) generation. Overall, growing evidence now shows that mitochondrial activities and pathways have changed to adapt with different types of leukemia, thus mitochondrial metabolism could be targeted for blood malignancy therapy. This review focuses on the function of mitochondria in LSC of the different leukemia types.
    Keywords:  leukemia; leukemia stem cell; metabolism; mitochondria; mitophagy
  11. Sci Rep. 2021 Oct 27. 11(1): 21234
      Membrane bound nicotinamide nucleotide transhydrogenase (TH) catalyses the hydride transfer from NADH to NADP+. Under physiological conditions, this reaction is endergonic and must be energized by the pmf, coupled to transmembrane proton transport. Recent structures of transhydrogenase holoenzymes suggest new mechanistic details, how the long-distance coupling between hydride transfer in the peripheral nucleotide binding sites and the membrane-localized proton transfer occurs that now must be tested experimentally. Here, we provide protocols for the efficient expression and purification of the Escherichia coli transhydrogenase and its reconstitution into liposomes, alone or together with the Escherichia coli F1F0 ATP synthase. We show that E. coli transhydrogenase is a reversible enzyme that can also work as a NADPH-driven proton pump. In liposomes containing both enzymes, NADPH driven H+-transport by TH is sufficient to instantly fuel ATP synthesis, which adds TH to the pool of pmf generating enzymes. If the same liposomes are energized with ATP, NADPH production by TH is stimulated > sixfold both by a pH gradient or a membrane potential. The presented protocols and results reinforce the tight coupling between hydride transfer in the peripheral nucleotide binding sites and transmembrane proton transport and provide powerful tools to investigate their coupling mechanism.
  12. Sci Rep. 2021 Oct 26. 11(1): 21048
      Viruses need cells for their replication and, therefore, ways to hijack cellular functions. Mitochondria play fundamental roles within the cell in metabolism, immunity and regulation of homeostasis due to which some viruses aim to alter mitochondrial functions. Herein we show that the nucleoprotein (NP) of arenaviruses enters the mitochondria of infected cells, affecting the mitochondrial morphology. Reptarenaviruses cause boid inclusion body disease (BIBD) that is characterized, especially in boas, by the formation of cytoplasmic inclusion bodies (IBs) comprising reptarenavirus NP within the infected cells. We initiated this study after observing electron-dense material reminiscent of IBs within the mitochondria of reptarenavirus infected boid cell cultures in an ultrastructural study. We employed immuno-electron microscopy to confirm that the mitochondrial inclusions indeed contain reptarenavirus NP. Mutations to a putative N-terminal mitochondrial targeting signal (MTS), identified via software predictions in both mamm- and reptarenavirus NPs, did not affect the mitochondrial localization of NP, suggesting that it occurs independently of MTS. In support of MTS-independent translocation, we did not detect cleavage of the putative MTSs of arenavirus NPs in reptilian or mammalian cells. Furthermore, in vitro translated NPs could not enter isolated mitochondria, suggesting that the translocation requires cellular factors or conditions. Our findings suggest that MTS-independent mitochondrial translocation of NP is a shared feature among arenaviruses. We speculate that by targeting the mitochondria arenaviruses aim to alter mitochondrial metabolism and homeostasis or affect the cellular defense.
  13. Antioxid Redox Signal. 2021 Oct 29.
      AIMS: Lung cancer is the leading cause of cancer death worldwide, and tobacco smoking is a recognized major risk factor for lung tumor development. We analyzed the effect of tobacco-specific nitrosamines (TSNAs) on human lung adenocarcinoma metabolic reprogramming, an emergent hallmark of carcinogenesis.RESULTS: A series of in vitro and in vivo bioenergetic, proteomic, metabolomic and tumor biology studies were performed to analyze changes in lung cancer cell metabolism and the consequences for hallmarks of cancer, including tumor growth, cancer cell invasion and redox signaling. The findings revealed that nitrosamine ketone (NNK) stimulates mitochondrial function and promotes lung tumor growth in vivo. These malignant properties were acquired from the induction of mitochondrial biogenesis induced by the upregulation and activation of the beta-adrenergic receptor (β2-AR)-nicotinic acetylcholine receptor subunit alpha-7 (CHRNAα7)-dependent nitrosamine canonical signaling pathway. The observed NNK metabolic effects were mediated by TFAM overexpression and revealed a key role for mitochondrial reactive oxygen species (mtROS) and Annexin A1 in tumor growth promotion. Conversely, ectopic expression of the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) rescued the reprogramming and malignant metabolic effects of exposure to NNK and overexpression of TFAM, underlining the link between NNK and mitochondrial redox signaling in lung cancer.
    INNOVATION: Our findings describe the metabolic changes caused by NNK in a mechanistic framework for understanding how cigarette smoking causes lung cancer.
    CONCLUSION: Mitochondria play a role in the promotion of lung cancer induced by tobacco-specific nitrosamines.
  14. Mol Ther Oncolytics. 2021 Dec 17. 23 82-95
      Reprogramming of cellular metabolism is a hallmark of cancer. Mitochondrial ATP synthase (MAS) produces most of the ATP that drives the cell. High expression of the MAS-composing proteins is found during cancer and is linked to a poor prognosis in glioblastoma, ovarian cancer, prostate cancer, breast cancer, and clear cell renal cell carcinoma. Cell surface-expressed ATP synthase, translocated from mitochondrion to cell membrane, involves the angiogenesis, tumorigenesis, and metastasis of cancer. ATP synthase has therefore been considered a therapeutic target. We review recent various ATP synthase inhibitors that suppress tumor growth and are being tested for the clinic.
    Keywords:  ATP synthase inhibitor; cancer metabolism; chemotherapy; mitochondrial ATP synthase; mitochondrial metabolism
  15. Cell Rep. 2021 Oct 26. pii: S2211-1247(21)01350-4. [Epub ahead of print]37(4): 109880
      Targeting mitochondrial metabolism has emerged as a treatment option for cancer patients. The ABL tyrosine kinases promote metastasis, and enhanced ABL signaling is associated with a poor prognosis in lung adenocarcinoma patients. Here we show that ABL kinase allosteric inhibitors impair mitochondrial integrity and decrease oxidative phosphorylation. To identify metabolic vulnerabilities that enhance this phenotype, we utilized a CRISPR/Cas9 loss-of-function screen and identified HMG-CoA reductase, the rate-limiting enzyme of the mevalonate pathway and target of statin therapies, as a top-scoring sensitizer to ABL inhibition. Combination treatment with ABL allosteric inhibitors and statins decreases metastatic lung cancer cell survival in vitro in a synergistic manner. Notably, combination therapy in mouse models of lung cancer brain metastasis and therapy resistance impairs metastatic colonization with a concomitant increase in animal survival. Thus, metabolic combination therapy might be effective to decrease metastatic outgrowth, leading to increased survival for lung cancer patients with advanced disease.
    Keywords:  ABL kinases; HMGCR; brain metastasis; lung adenocarcinoma; statins; therapy resistance
  16. Nat Metab. 2021 Oct 25.
      We have previously suggested a central role for mitochondria in the observed sex differences in metabolic traits. However, the mechanisms by which sex differences affect adipose mitochondrial function and metabolic syndrome are unclear. Here we show that in both mice and humans, adipose mitochondrial functions are elevated in females and are strongly associated with adiposity, insulin resistance and plasma lipids. Using a panel of diverse inbred strains of mice, we identify a genetic locus on mouse chromosome 17 that controls mitochondrial mass and function in adipose tissue in a sex- and tissue-specific manner. This locus contains Ndufv2 and regulates the expression of at least 89 mitochondrial genes in females, including oxidative phosphorylation genes and those related to mitochondrial DNA content. Overexpression studies indicate that Ndufv2 mediates these effects by regulating supercomplex assembly and elevating mitochondrial reactive oxygen species production, which generates a signal that increases mitochondrial biogenesis.
  17. Mol Cell. 2021 Oct 15. pii: S1097-2765(21)00800-5. [Epub ahead of print]
      Cell state changes are associated with proteome remodeling to serve newly emergent cell functions. Here, we show that NGN2-driven conversion of human embryonic stem cells to induced neurons (iNeurons) is associated with increased PINK1-independent mitophagic flux that is temporally correlated with metabolic reprogramming to support oxidative phosphorylation. Global multiplex proteomics during neurogenesis revealed large-scale remodeling of functional modules linked with pluripotency, mitochondrial metabolism, and proteostasis. Differentiation-dependent mitophagic flux required BNIP3L and its LC3-interacting region (LIR) motif, and BNIP3L also promoted mitophagy in dopaminergic neurons. Proteomic analysis of ATG12-/- iNeurons revealed accumulation of endoplasmic reticulum, Golgi, and mitochondria during differentiation, indicative of widespread organelle remodeling during neurogenesis. This work reveals broad organelle remodeling of membrane-bound organelles during NGN2-driven neurogenesis via autophagy, identifies BNIP3L's central role in programmed mitophagic flux, and provides a proteomic resource for elucidating how organelle remodeling and autophagy alter the proteome during changes in cell state.
    Keywords:  autophagy; iNeurons; mitophagy; proteomics
  18. Nat Struct Mol Biol. 2021 Oct 28.
      Mitochondria, the only semiautonomous organelles in mammalian cells, possess a circular, double-stranded genome termed mitochondrial DNA (mtDNA). While nuclear genomic DNA compaction, chromatin compartmentalization and transcription are known to be regulated by phase separation, how the mitochondrial nucleoid, a highly compacted spherical suborganelle, is assembled and functions is unknown. Here we assembled mitochondrial nucleoids in vitro and show that mitochondrial transcription factor A (TFAM) undergoes phase separation with mtDNA to drive nucleoid self-assembly. Moreover, nucleoid droplet formation promotes recruitment of the transcription machinery via a special, co-phase separation that concentrates transcription initiation, elongation and termination factors, and retains substrates to facilitate mtDNA transcription. We propose a model of mitochondrial nucleoid self-assembly driven by phase separation, and a pattern of co-phase separation involved in mitochondrial transcriptional regulation, which orchestrates the roles of TFAM in both mitochondrial nucleoid organization and transcription.
  19. Elife. 2021 Oct 26. pii: e70899. [Epub ahead of print]10
      Using a high-throughput mitochondrial phenotyping platform to quantify multiple mitochondrial features among molecularly-defined immune cell subtypes, we quantify the natural variation in citrate synthase, mitochondrial DNA copy number (mtDNAcn), and respiratory chain enzymatic activities in human neutrophils, monocytes, B cells, and naïve and memory T lymphocyte subtypes. In mixed peripheral blood mononuclear cells (PBMCs) from the same individuals, we show to what extent mitochondrial measures are confounded by both cell type distributions and contaminating platelets. Cell subtype-specific measures among women and men spanning 4 decades of life indicate potential age- and sex-related differences, including an age-related elevation in mtDNAcn, which are masked or blunted in mixed PBMCs. Finally, a proof-of-concept, repeated-measures study in a single individual validates cell type differences and also reveals week-to-week changes in mitochondrial activities. Larger studies are required to validate and mechanistically extend these findings. These mitochondrial phenotyping data build upon established immunometabolic differences among leukocyte sub-populations, and provide foundational quantitative knowledge to develop interpretable blood-based assays of mitochondrial health.
    Keywords:  cell biology; human; immunology; inflammation
  20. Nucleic Acid Ther. 2021 Oct 25.
      Mitochondria are highly dynamic organelles that produce ATP and maintain metabolic, catabolic, and redox homeostasis. Mitochondria owe this dynamic nature to their constant fission and fusion-processes that are regulated, in part, by fusion factors (MFN1 and MFN2) and fission factors (DRP1, FIS1, MFF, MIEF1, MIEF2) located on the outer mitochondrial membrane. While mitochondrial fusion and fission are known to influence mitochondrial morphology and function, a key question is whether rebalancing mitochondrial morphology can ameliorate mitochondrial dysfunction in the context of mitochondrial pathology. In this study, we used antisense oligonucleotides (ASOs) to systematically evaluate the effects of fusion and fission factors in vitro. Free uptake by cells of fusion or fission factor ASOs caused robust decreases in target gene expression and altered a variety of mitochondrial parameters, including mitochondrial size and respiration, which were dose dependent. In Mfn1 knockout mouse embryonic fibroblasts (MEFs) and MFN2-R94Q (Charcot-Marie-Tooth Type 2 Disease-associated mutation) MEFs, two cellular models of mitochondrial dysfunction, we found that ASO-mediated silencing of only Drp1 restored mitochondrial morphology and enhanced mitochondrial respiration. Together, these data demonstrate in vitro proof-of-concept for rebalancing mitochondrial morphology to rescue function using ASOs and suggest that ASO-mediated modulation of mitochondrial dynamics may be a viable therapeutic approach to restore mitochondrial homeostasis in diseases driven by mitochondrial dysfunction.
    Keywords:  antisense; mitochondria; mitochondrial dynamics; oligonucleotides
  21. Am J Physiol Cell Physiol. 2021 Oct 27.
      Mitochondria are considered to be the powerhouse of the cell. Normal functioning of the mitochondria is not only essential for cellular energy production but also for several immunomodulatory processes. Macrophages operate in metabolic niches and rely on rapid adaptation to specific metabolic conditions such as hypoxia, nutrient limitations or reactive oxygen species to neutralize pathogens. In this regard, the fast reprogramming of mitochondrial metabolism is indispensable to provide the cells with the necessary energy and intermediates to efficiently mount the inflammatory response. Moreover, mitochondria act as a physical scaffold for several proteins involved in immune signaling cascades and their dysfunction is immediately associated with a dampened immune response. In this review, we put special focus on mitochondrial function in macrophages and highlight how mitochondrial metabolism is involved in macrophage activation.
    Keywords:  Itaconic acid; Macrophages; Metabolism; Mitochondira
  22. Mol Biol Cell. 2021 Oct 27. mbcE21060286
      Drp1 is a key regulator of mitochondrial fission, a large cytoplasmic GTPase recruited to the mitochondrial surface via transmembrane adaptors to initiate scission. While Brownian motion likely accounts for the local interactions between Drp1 and the mitochondrial adaptors, how this essential enzyme is targeted from more distal regions like the cell periphery remains unknown. Based on proteomic interactome screening and cell-based studies, we report that GIPC mediates the actin-based retrograde transport of Drp1 towards the perinuclear mitochondria to enhance fission. Drp1 interacts with GIPC through its atypical C-terminal PDZ-binding motif. Loss of this interaction abrogates Drp1 retrograde transport resulting in cytoplasmic mislocalization and reduced fission despite retaining normal intrinsic GTPase activity. Functionally, we demonstrate that GIPC potentiates the Drp1-driven proliferative and migratory capacity in cancer cells. Together, these findings establish a direct molecular link between altered GIPC expression and Drp1 function in cancer progression and metabolic disorders.
  23. J Biol Chem. 2021 Oct 26. pii: S0021-9258(21)01155-8. [Epub ahead of print] 101349
      Mitochondrial protein translocation is an intricately regulated process that requires dedicated translocases at the outer and inner membranes. The presequence translocase complex, TIM23, facilitates most of the import of preproteins containing presequences into the mitochondria, and its primary structural organization is highly conserved. As part of the translocase motor, two J-proteins DnaJC15 and DnaJC19, are recruited to form two independent translocation machineries (Translocase A and Translocase B, respectively). On the other hand, the J-like protein subunit of TIM23, Magmas (orthologous to the yeast subunit Pam16), can regulate human import motor activity by forming a heterodimer with DnaJC19 and DnaJC15. However, the precise coordinated regulation of two human import motors by a single Magmas protein is poorly understood. Here we report two additional Magmas variants (Magmas-1 and Magmas-2) constitutively expressed in the mammalian system. Both Magmas variants are functional orthologs of Pam16 with an evolutionarily conserved J-like domain critical for cell survival. Moreover, Magmas variants are peripherally associated with the inner membrane as part of the human import motor for translocation. Our results demonstrate that Magmas-1 is predominantly recruited to translocase B, while Magmas-2 is majorly associated with translocase A. Strikingly, both variants exhibit differential J-protein inhibitory activity in modulating import motor, thereby regulating overall translocase function. Based on our findings, we hypothesize that additional Magmas variants are of evolutionary significance in humans to maximize protein import in familial-linked pathological conditions.
    Keywords:  Magmas; Mitochondria; Mitochondrial translocase of inner membrane; Protein import; Protein translocation
  24. Br J Cancer. 2021 Oct 23.
      BACKGROUND: The mechanisms underlying metastasis of colorectal cancer (CRC) remain unclear. C14orf159 is a mitochondrial matrix protein converting D-glutamate to 5-oxo-D-proline. Other metabolic functions of C14orf159, especially on mitochondrial metabolism, and its contribution to CRC metastasis, are not elucidated.METHODS: Metabolome analysis by gas chromatography-mass spectrometry, RNA-sequencing analysis, flow cytometry, migration and invasion assay, sphere-formation assay using C14orf159-knockout and -stable expressing cells, immunohistochemistry of C14orf159 in human CRC specimens, and xenograft experiments using Balb/c nude mice were conducted.
    RESULTS: C14orf159 maintained the mitochondrial membrane potential of human CRC cells, and its involvement in amino acid and glutathione metabolism was demonstrated. In human CRC specimens, a decrease in C14orf159 expression at the invasive front of the tumour and in metastasis was determined. C14orf159 was also shown to attenuate the migration, invasion, and spheroid growth of CRC cells in vitro and colorectal tumour growth and metastasis in vivo. Mechanistically, C14orf159 reduced the expression of genes involved in CRC metastasis, including members of the Wnt and MMP family, by maintaining the mitochondrial membrane potential.
    CONCLUSIONS: Our findings link mitochondrial membrane potential to Wnt/β-catenin signalling and reveal a previously unrecognised function of the mitochondrial matrix protein C14orf159 as a suppressor of CRC metastasis.
  25. Nat Commun. 2021 Oct 26. 12(1): 6176
      Serine is a non-essential amino acid that is critical for tumour proliferation and depletion of circulating serine results in reduced tumour growth and increased survival in various cancer models. While many cancer cells cultured in a standard tissue culture medium depend on exogenous serine for optimal growth, here we report that these cells are less sensitive to serine/glycine depletion in medium containing physiological levels of metabolites. The lower requirement for exogenous serine under these culture conditions reflects both increased de novo serine synthesis and the use of hypoxanthine (not present in the standard medium) to support purine synthesis. Limiting serine availability leads to increased uptake of extracellular hypoxanthine, sparing available serine for other pathways such as glutathione synthesis. Taken together these results improve our understanding of serine metabolism in physiologically relevant nutrient conditions and allow us to predict interventions that may enhance the therapeutic response to dietary serine/glycine limitation.
  26. Urol Case Rep. 2022 Jan;40 101885
      Succinate dehydrogenase (SDH) deficient renal cell carcinoma (RCC) are uncommon renal tumors that typically present in relatively younger patients. SDH mutations are known to cause cancer, but often presents with hereditary paragangliomas, pheochromocytomas, and gastrointestinal stromal tumors. This report details a case of SDH deficient RCC in a patient with no know contributing family history. Patient presented with recurrent urinary tract infections and groin pain. Computerized tomography (CT) revealed a 4 cm mass in the right kidney. Partial nephrectomy was performed, and the patient had an uneventful recovery. Immunohistochemical staining revealed the tumor was SDH negative.
    Keywords:  Partial nephrectomy; Renal cancer; Renal cell carcinoma; Succinate dehydrogenase
  27. Autophagy. 2021 Oct 25. 1-18
      Mitochondrial remodeling is dysregulated in metabolic diseases but the underlying mechanism is not fully understood. We report here that BDNF (brain derived neurotrophic factor) provokes mitochondrial fission and clearance in skeletal muscle via the PRKAA/AMPK-PINK1-PRKN/Parkin and PRKAA-DNM1L/DRP1-MFF pathways. Depleting Bdnf expression in myotubes reduced fatty acid-induced mitofission and mitophagy, which was associated with mitochondrial elongation and impaired lipid handling. Muscle-specific bdnf knockout (MBKO) mice displayed defective mitofission and mitophagy, and accumulation of dysfunctional mitochondria in the muscle when they were fed with a high-fat diet (HFD). These animals also have exacerbated body weight gain, increased intramyocellular lipid deposition, reduced energy expenditure, poor metabolic flexibility, and more insulin resistance. In contrast, consuming a BDNF mimetic (7,8-dihydroxyflavone) increased mitochondrial content, and enhanced mitofission and mitophagy in the skeletal muscles. Hence, BDNF is an essential myokine to maintain mitochondrial quality and function, and its repression in obesity might contribute to impaired metabolism.Abbreviation: 7,8-DHF: 7,8-dihydroxyflavone; ACACA/ACC: acetyl Coenzyme A carboxylase alpha; ACAD: acyl-Coenzyme A dehydrogenase family; ACADVL: acyl-Coenzyme A dehydrogenase, very long chain; ACOT: acyl-CoA thioesterase; CAMKK2: calcium/calmodulin-dependent protein kinase kinase 2, beta; BDNF: brain derived neurotrophic factor; BNIP3: BCL2/adenovirus E1B interacting protein 3; BNIP3L/NIX: BCL2/adenovirus E1B interacting protein 3-like; CCL2/MCP-1: chemokine (C-C motif) ligand 2; CCL5: chemokine (C-C motif) ligand 5; CNS: central nervous system; CPT1B: carnitine palmitoyltransferase 1b, muscle; Cpt2: carnitine palmitoyltransferase 2; CREB: cAMP responsive element binding protein; DNM1L/DRP1: dynamin 1-like; E2: estrogen; EHHADH: enoyl-CoenzymeA hydratase/3-hydroxyacyl CoenzymeA dehydrogenase; ESR1/ER-alpha: estrogen receptor 1 (alpha); FA: fatty acid; FAO: fatty acid oxidation; FCCP: carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone; FFA: free fatty acids; FGF21: fibroblast growth factor 21; FUNDC1: FUN14 domain containing 1; HADHA: hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha; HFD: high-fat diet; iWAT: inguinal white adipose tissues; MAP1LC3A/LC3A: microtubule-associated protein 1 light chain 3 alpha; MBKO; muscle-specific bdnf knockout; IL6/IL-6: interleukin 6; MCEE: methylmalonyl CoA epimerase; MFF: mitochondrial fission factor; NTRK2/TRKB: neurotrophic tyrosine kinase, receptor, type 2; OPTN: optineurin; PA: palmitic acid; PARL: presenilin associated, rhomboid-like; PDH: pyruvate dehydrogenase; PINK1: PTEN induced putative kinase 1; PPARGC1A/PGC-1α: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; PRKAA/AMPK: protein kinase, AMP-activated, alpha 2 catalytic subunit; ROS: reactive oxygen species; TBK1: TANK-binding kinase 1; TG: triacylglycerides; TNF/TNFα: tumor necrosis factor; TOMM20: translocase of outer mitochondrial membrane 20; ULK1: unc-51 like kinase 1.
    Keywords:  BDNF; mitochondria; mitophagy; muscle; obesity
  28. Exp Cell Res. 2021 Oct 21. pii: S0014-4827(21)00446-8. [Epub ahead of print]409(1): 112892
      Carnitine palmitoyltransferase 2 (CPT2) has been demonstrated to act as a tumor promotor or suppressor in different types of cancers. However, little is known about the effect of CPT2 on colorectal cancer (CRC). In the present study, we analyzed CPT2 expression in CRC tissues and cells. CPT2 was overexpressed in CRC cell lines (SW480 and RKO), and its effects and molecular mechanism on the proliferation, glycolysis, stemness, and oxaliplatin sensitivity were investigated. The xenograft experiment was used to confirm the influence of CPT2 on CRC tumorigenesis in vivo. We found that CPT2 expression was significantly downregulated in CRC patients, and its lower expression was associated with the poor prognosis, large tumor size, advanced TNM stage, and poor histological grade differentiation of patients. Upregulation of CPT2 significantly inhibited the proliferation, glycolytic metabolism, cancer stem cell properties, and oxaliplatin resistance in CRC cells. Also, the increase of CPT2 inhibited tumorigenesis, stemness and glycolysis, while enhanced oxaliplatin sensitivity in mouse models. Mechanistically, CPT2 functioned via suppressing the activation of Wnt/β-catenin pathway through repressing ROS production. In conclusion, our results demonstrated that CPT2 was decreased in CRC, and CPT2 downregulation could trigger stemness and oxaliplatin resistance in CRC via activating the ROS/Wnt/β-catenin-induced glycolytic metabolism. This study indicates that CPT2 is a potential therapeutic target for CRC.
    Keywords:  CPT2; Colorectal cancer; Oxaliplatin resistance; Stemness; Wnt/β-catenin
  29. J Biol Chem. 2021 Oct 21. pii: S0021-9258(21)01145-5. [Epub ahead of print] 101339
      Mitochondria are important organelles in eukaryotes. Turnover and quality control of mitochondria are regulated at the transcriptional and post-translational level by several cellular mechanisms. Removal of defective mitochondrial proteins is mediated by mitochondria resident proteases or by proteasomal degradation of individual proteins. Clearance of bulk mitochondria occurs via a selective form of autophagy termed mitophagy. In yeast and some developing metazoan cells (e.g. oocytes and reticulocytes), mitochondria are largely removed by ubiquitin-independent mechanisms. In such cases the regulation of mitophagy is mediated via phosphorylation of mitochondria-anchored autophagy receptors. On the other hand, ubiquitin-dependent recruitment of cytosolic autophagy receptors occurs in situations of cellular stress or disease, where dysfunctional mitochondria would cause oxidative damage. In mammalian cells, a well-studied ubiquitin-dependent mitophagy pathway induced by mitochondrial depolarization is regulated by the mitochondrial protein kinase PINK1 that upon activation recruits the ubiquitin ligase parkin. Here we review mechanisms of mitophagy with an emphasis on post-translational modifications that regulate various mitophagy pathways. We describe the autophagy components involved with particular emphasis on post-translational modifications. We detail the phosphorylations mediated by PINK1 and parkin-mediated ubiquitylations of mitochondrial proteins that can be modulated by deubiquitylating enzymes. We also discuss the role of accessory factors regulating mitochondrial fission/fusion and the interplay with pro- and anti-apoptotic Bcl-2 family members. Comprehensive knowledge of the processes of mitophagy is essential for the understanding of vital mitochondrial turnover in health and disease.
    Keywords:  autophagy; mitochondria; phosphorylation; protein kinase PINK1; ubiquitin ligase parkin; ubiquitylation
  30. Nat Commun. 2021 Oct 27. 12(1): 6201
      Cancer incidence increases with age and is a leading cause of death. Caloric restriction (CR) confers benefits on health and survival and delays cancer. However, due to CR's stringency, dietary alternatives offering the same cancer protection have become increasingly attractive. Short cycles of a plant-based diet designed to mimic fasting (FMD) are protective against tumorigenesis without the chronic restriction of calories. Yet, it is unclear whether the fasting time, level of dietary restriction, or nutrient composition is the primary driver behind cancer protection. Using a breast cancer model in mice, we compare the potency of daily CR to that of periodic caloric cycling on FMD or an isocaloric standard laboratory chow against primary tumor growth and metastatic burden. Here, we report that daily CR provides greater protection against tumor growth and metastasis to the lung, which may be in part due to the unique immune signature observed with daily CR.
  31. Yeast. 2021 Oct 24.
      The antioxidant phenotype caused by resveratrol has been recognized as a key piece in the health benefits exerted by this phytochemical in diseases related to aging. It has recently been proposed that a mitochondrial pro-oxidant mechanism could be the cause of resveratrol antioxidant properties. In this regard, the hypothesis that resveratrol impedes electron transport to complex III of the electron transport chain as its main target suggests that resveratrol could increase reactive oxygen species (ROS) generation through reverse electron transport or by the semiquinones formation. This idea also explains that cells respond to resveratrol oxidative damage, inducing their antioxidant systems. Moreover, resveratrol pro-oxidant properties could accelerate the aging process, according to the free radical theory of aging, which postulates that organisms age due to the accumulation of the harmful effects of ROS in cells. Nonetheless, there is no evidence linking the chronological lifespan (CLS) shorten occasioned by resveratrol with a pro-oxidant mechanism. Hence, this study aimed to evaluate whether resveratrol shortens the CLS of Saccharomyces cerevisiae due to a pro-oxidant activity. Herein, we provide evidence that supplementation with 100 μM of resveratrol at 5% glucose: 1) shorted the CLS of ctt1∆ and yap1∆ strains; 2) decreased ROS levels and increased the catalase activity in WT strain; 3) maintained unaffected the ROS levels and did not change the catalase activity in ctt1∆ strain; 4) lessened the exponential growth of ctt1∆ strain, which was restored with the adding of reduced glutathione. These results indicate that resveratrol decreases CLS by a pro-oxidant mechanism.
    Keywords:  Oxidative stress; Saccharomyces cerevisiae; aging; antioxidant systems; catalase; resveratrol
  32. Cell Metab. 2021 Oct 22. pii: S1550-4131(21)00481-2. [Epub ahead of print]
      Individual hosts within populations often show inter-individual variation in their susceptibility to bacterial pathogen-related diseases. Utilizing Drosophila, we highlight that phenotypic variation in host-pathogen susceptibility within populations is driven by energetic trade-offs, facilitated by infection-mediated changes in glutamate metabolism. Furthermore, host-pathogen susceptibility is conditioned by life history, which adjusts immunometabolic sensing in muscles to direct vitamin-dependent reallocation of host energy substrates from the adipose tissue (i.e., a muscle-adipose tissue axis). Life history conditions inter-individual variation in the activation strength of intra-muscular NF-κB signaling. Limited intra-muscular NF-κB signaling activity allows for enhanced infection-mediated mitochondrial biogenesis and function, which stimulates glutamate dehydrogenase-dependent synthesis of glutamate. Muscle-derived glutamate acts as a systemic metabolite to promote lipid mobilization through modulating vitamin B enzymatic cofactor transport and function in the adipose tissue. This energy substrate reallocation improves pathogen clearance and boosts host survival. Finally, life history events that adjust energetic trade-offs can shape inter-individual variation in host-pathogen susceptibility after infection.
    Keywords:  Smvt; glutamate; glutamate dehydrogenase; immunometabolism; innate immunity; life history; lipid metabolism; mitochondria; muscle; vitamin
  33. Nat Methods. 2021 Oct 28.
      Liquid chromatography-high-resolution mass spectrometry (LC-MS)-based metabolomics aims to identify and quantify all metabolites, but most LC-MS peaks remain unidentified. Here we present a global network optimization approach, NetID, to annotate untargeted LC-MS metabolomics data. The approach aims to generate, for all experimentally observed ion peaks, annotations that match the measured masses, retention times and (when available) tandem mass spectrometry fragmentation patterns. Peaks are connected based on mass differences reflecting adduction, fragmentation, isotopes, or feasible biochemical transformations. Global optimization generates a single network linking most observed ion peaks, enhances peak assignment accuracy, and produces chemically informative peak-peak relationships, including for peaks lacking tandem mass spectrometry spectra. Applying this approach to yeast and mouse data, we identified five previously unrecognized metabolites (thiamine derivatives and N-glucosyl-taurine). Isotope tracer studies indicate active flux through these metabolites. Thus, NetID applies existing metabolomic knowledge and global optimization to substantially improve annotation coverage and accuracy in untargeted metabolomics datasets, facilitating metabolite discovery.
  34. BMC Cancer. 2021 Oct 28. 21(1): 1153
      BACKGROUND: Disease relapse remains common following treatment of acute myeloid leukemia (AML) and is due to chemoresistance of leukemia cells with disease repopulating potential. To date, attempts to define the characteristics of in vivo resistant blasts have focused on comparisons between leukemic cells at presentation and relapse. However, further treatment responses are often seen following relapse, suggesting that most blasts remain chemosensitive. We sought to characterise in vivo chemoresistant blasts by studying the transcriptional and genetic features of blasts from before and shortly after induction chemotherapy using paired samples from six patients with primary refractory AML.METHODS: Leukemic blasts were isolated by fluorescence-activated cell sorting. Fluorescence in situ hybridization (FISH), targeted genetic sequencing and detailed immunophenotypic analysis were used to confirm that sorted cells were leukemic. Sorted blasts were subjected to RNA sequencing. Lentiviral vectors expressing short hairpin RNAs were used to assess the effect of FOXM1 knockdown on colony forming capacity, proliferative capacity and apoptosis in cell lines, primary AML cells and CD34+ cells from healthy donors.
    RESULTS: Molecular genetic analysis revealed early clonal selection occurring after induction chemotherapy. Immunophenotypic characterisation found leukemia-associated immunophenotypes in all cases that persisted following treatment. Despite the genetic heterogeneity of the leukemias studied, transcriptional analysis found concerted changes in gene expression in resistant blasts. Remarkably, the gene expression signature suggested that post-chemotherapy blasts were more proliferative than those at presentation. Resistant blasts also appeared less differentiated and expressed leukemia stem cell (LSC) maintenance genes. However, the proportion of immunophenotypically defined LSCs appeared to decrease following treatment, with implications for the targeting of these cells on the basis of cell surface antigen expression. The refractory gene signature was highly enriched with targets of the transcription factor FOXM1. shRNA knockdown experiments demonstrated that the viability of primary AML cells, but not normal CD34+ cells, depended on FOXM1 expression.
    CONCLUSIONS: We found that chemorefractory blasts from leukemias with varied genetic backgrounds expressed a common transcriptional program. In contrast to the notion that LSC quiescence confers resistance to chemotherapy we find that refractory blasts are both actively proliferating and enriched with LSC maintenance genes. Using primary patient material from a relevant clinical context we also provide further support for the role of FOXM1 in chemotherapy resistance, proliferation and stem cell function in AML.
    Keywords:  Acute myeloid leukemia; Drug resistance; FOXM1; Leukemia stem cell; Quiescence; Transcriptome
  35. Redox Biol. 2021 Oct 15. pii: S2213-2317(21)00329-3. [Epub ahead of print]47 102169
      Mitochondrial dysfunction is related to common age-related disorders, including neurodegenerative diseases, metabolic syndrome, and carcinogenesis. Therefore, maintaining the functionality and integrity of mitochondria is important for human health. Herein, we found that sulfide:quinone oxidoreductase (Sqr), which oxidizes hydrogen sulfide to reactive sulfur species (RSS), was indispensable to mitochondria health in the eukaryotic model microorganism Schizosaccharomyces pombe. Sqr knock-out led to morphological changes and functional deficiencies of mitochondria and apoptosis in S. pombe. The Sqr knock-out strain displayed the same phenotypes as the cysteine-synthesis-deficient strain, and cysteine addition complemented the effects caused by Sqr knock-out. In S. pombe, Sqr was the main RSS producer in mitochondria, and RSS instead of H2S was used by cysteine synthase to synthesize cysteine. This finding rewrites the cysteine biosynthesis route in S. pombe and may also in other eukaryotes and prokaryotes, and highlights the importance of cysteine and RSS in maintaining mitochondrial health.
    Keywords:  Cysteine biosynthesis; Hydrogen sulfide; Mitochondria health; Reactive sulfur species; Schizosaccharomyces pombe; Sqr