bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2020‒10‒18
33 papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. Nat Commun. 2020 Oct 16. 11(1): 5265
      Pancreatic ductal adenocarcinoma (PDAC), the fourth leading cause of cancer death, has a 5-year survival rate of approximately 7-9%. The ineffectiveness of anti-PDAC therapies is believed to be due to the existence of a subpopulation of tumor cells known as cancer stem cells (CSCs), which are functionally plastic, and have exclusive tumorigenic, chemoresistant and metastatic capacities. Herein, we describe a 2D in vitro system for long-term enrichment of pancreatic CSCs that is amenable to biological and CSC-specific studies. By changing the carbon source from glucose to galactose in vitro, we force PDAC cells to utilize OXPHOS, resulting in enrichment of CSCs defined by increased CSC biomarker and pluripotency gene expression, greater tumorigenic potential, induced but reversible quiescence, increased OXPHOS activity, enhanced invasiveness, and upregulated immune evasion properties. This CSC enrichment method can facilitate the discovery of new CSC-specific hallmarks for future development into targets for PDAC-based therapies.
  2. Redox Biol. 2020 Sep 30. pii: S2213-2317(20)30945-9. [Epub ahead of print]37 101740
      Electrophilic aldehyde (4-hydroxynonenal; 4-HNE), formed after lipid peroxidation, is a mediator of mitochondrial dysfunction and implicated in both the pathogenesis and the progression of cardiovascular disease. Manganese superoxide dismutase (MnSOD), a nuclear-encoded antioxidant enzyme, catalyzes the dismutation of superoxide radicals (O2•-) in mitochondria. To study the role of MnSOD in the myocardium, we generated a cardiomyocyte-specific SOD2 (SOD2Δ) deficient mouse strain. Unlike global SOD2 knockout mice, SOD2Δ mice reached adolescence; however, they die at ~4 months of age due to heart failure. Ultrastructural analysis of SOD2Δ hearts revealed altered mitochondrial architecture, with prominent disruption of the cristae and vacuole formation. Noninvasive echocardiographic measurements in SOD2Δ mice showed dilated cardiomyopathic features such as decreased ejection fraction and fractional shortening along with increased left ventricular internal diameter. An increased incidence of ventricular tachycardia was observed during electrophysiological studies of the heart in SOD2Δ mice. Oxidative phosphorylation (OXPHOS) measurement using a Seahorse XF analyzer in SOD2Δ neonatal cardiomyocytes and adult cardiac mitochondria displayed reduced O2 consumption, particularly during basal conditions and after the addition of FCCP (H+ ionophore/uncoupler), compared to that in SOD2fl hearts. Measurement of extracellular acidification (ECAR) to examine glycolysis in these cells showed a pattern precisely opposite that of the oxygen consumption rate (OCR) among SOD2Δ mice compared to their SOD2fl littermates. Analysis of the activity of the electron transport chain complex identified a reduction in Complex I and Complex V activity in SOD2Δ compared to SOD2fl mice. We demonstrated that a deficiency of SOD2 increases reactive oxygen species (ROS), leading to subsequent overproduction of 4-HNE inside mitochondria. Mechanistically, proteins in the mitochondrial respiratory chain complex and TCA cycle (NDUFS2, SDHA, ATP5B, and DLD) were the target of 4-HNE adduction in SOD2Δ hearts. Our findings suggest that the SOD2 mediated 4-HNE signaling nexus may play an important role in cardiomyopathy.
    Keywords:  Heart failure; Manganese superoxide dismutase; Superoxide radicals
  3. Nat Commun. 2020 Oct 16. 11(1): 5261
      Respiratory complex I (NADH:ubiquinone oxidoreductase) captures the free energy from oxidising NADH and reducing ubiquinone to drive protons across the mitochondrial inner membrane and power oxidative phosphorylation. Recent cryo-EM analyses have produced near-complete models of the mammalian complex, but leave the molecular principles of its long-range energy coupling mechanism open to debate. Here, we describe the 3.0-Å resolution cryo-EM structure of complex I from mouse heart mitochondria with a substrate-like inhibitor, piericidin A, bound in the ubiquinone-binding active site. We combine our structural analyses with both functional and computational studies to demonstrate competitive inhibitor binding poses and provide evidence that two inhibitor molecules bind end-to-end in the long substrate binding channel. Our findings reveal information about the mechanisms of inhibition and substrate reduction that are central for understanding the principles of energy transduction in mammalian complex I.
  4. Aging Cell. 2020 Oct 13. e13166
      Mitochondrial dysfunction is frequently associated with impairment in metabolic homeostasis and insulin action, and is thought to underlie cellular aging. However, it is unclear whether mitochondrial dysfunction is a cause or consequence of insulin resistance in humans. To determine the impact of intrinsic mitochondrial dysfunction on metabolism and insulin action, we performed comprehensive metabolic phenotyping of the polymerase gamma (PolG) D257A "mutator" mouse, a model known to accumulate supraphysiological mitochondrial DNA (mtDNA) point mutations. We utilized the heterozygous PolG mutator mouse (PolG+/mut ) because it accumulates mtDNA point mutations ~ 500-fold > wild-type mice (WT), but fails to develop an overt progeria phenotype, unlike PolGmut/mut animals. To determine whether mtDNA point mutations induce metabolic dysfunction, we examined male PolG+/mut mice at 6 and 12 months of age during normal chow feeding, after 24-hr starvation, and following high-fat diet (HFD) feeding. No marked differences were observed in glucose homeostasis, adiposity, protein/gene markers of metabolism, or oxygen consumption in muscle between WT and PolG+/mut mice during any of the conditions or ages studied. However, proteomic analyses performed on isolated mitochondria from 12-month-old PolG+/mut mouse muscle revealed alterations in the expression of mitochondrial ribosomal proteins, electron transport chain components, and oxidative stress-related factors compared with WT. These findings suggest that mtDNA point mutations at levels observed in mammalian aging are insufficient to disrupt metabolic homeostasis and insulin action in male mice.
    Keywords:  POLG; aging; insulin resistance; metabolism; mitochondria; mitochondrial DNA; obesity
  5. Antioxid Redox Signal. 2020 Oct 16.
      Catecholamine metabolism via monoamine oxidase (MAO) contributes to cardiac injury in models of ischemia and diabetes, but the pathogenic mechanisms involved are unclear. MAO deaminates norepinephrine (NE) and dopamine (DA) to produce H2O2 and highly reactive 'catecholaldehydes,' which may be toxic to mitochondria due to the localization of MAO to the outer mitochondrial membrane. Here, we performed a comprehensive analysis of catecholamine metabolism and its impact on mitochondrial energetics in atrial myocardium obtained from patients with and without type 2 diabetes. Metabolomics analysis of atrial tissue from these patients showed decreased catecholamine levels in the myocardium, supporting an increased flux through MAOs. Content and maximal activity of MAO-A and -B were higher in myocardium of diabetes patients and associated with BMI. Catecholaldehyde-modified protein adducts were more abundant in myocardial tissue extracts from diabetes patients and confirmed to be MAO-dependent. Moreover, NE treatment suppressed mitochondrial ATP production in permeabilized myofibers from diabetes patients in a MAO-dependent manner. Aldehyde dehydrogenase (ALDH) activity was substantially decreased in atrial myocardium from these patients, and metabolomics confirmed lower levels of ALDH-catalyzed catecholamine metabolites. Proteomic analysis of catechol-modified proteins in isolated cardiac mitochondria from these patients identified >300 mitochondrial proteins to be potential targets of these unique carbonyls. These findings illustrate a unique form of carbonyl toxicity driven by MAO-mediated metabolism of catecholamines, and reveal new pathogenic factors underlying cardiometabolic disease. Most importantly, they suggest that pharmacotherapies targeting aldehyde stress and catecholamine metabolism in heart may be beneficial in patients with diabetes and cardiac disease.
  6. Transl Res. 2020 Oct 09. pii: S1931-5244(20)30239-5. [Epub ahead of print]
      Metformin is the first-line medication for treatment of type 2 diabetes and has been shown to reduce heart damage and death. However, mechanisms by which metformin protects human heart remain debated. The aim of the study was to evaluate the cardioprotective effect of metformin on cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) and mitochondria isolated from human cardiac tissue. At concentrations ≤ 2.5 mM, metformin significantly increased oxygen consumption rate (OCR) in the hiPSC-CMs by activating AMPK-dependent signaling and enhancing mitochondrial biogenesis. This effect was abrogated by compound C, an inhibitor of AMPK. At concentrations > 5 mM, metformin inhibited the cellular OCR and triggered metabolic reprogramming by enhancing glycolysis and glutaminolysis in the cardiomyocytes. In isolated cardiac mitochondria, metformin did not increase the OCR at any concentrations but inhibited the OCR starting at 1 mM through direct inhibition of electron-transport chain (ETC) complex I. This was associated with reduction of superoxide production and attenuation of Ca2+-induced mitochondrial permeability transition pore (mPTP) opening in the mitochondria. Thus, in human heart, metformin might improve cardioprotection due to its biphasic effect on mitochondria: at low concentrations, it activates mitochondrial biogenesis via AMPK signaling and increases the OCR; at high concentrations, it inhibits the respiration by directly affecting the activity of complex I, reduces oxidative stress and delays mPTP formation. Moreover, metformin at high concentrations causes metabolic reprogramming by enhancing glycolysis and glutaminolysis. These effects can be a beneficial adjunct to patients with impaired endogenous cardioprotective responses.
    Keywords:  Cardiac mitochondria; metabolic reprogramming; metformin; mitochondrial permeability transition pore; oxidative stress
  7. PLoS Genet. 2020 Oct 16. 16(10): e1009046
      The Ccr4-Not complex functions as an effector of multiple signaling pathways that control gene transcription and mRNA turnover. Consequently, Ccr4-Not contributes to a diverse array of processes, which includes a significant role in cell metabolism. Yet a mechanistic understanding of how it contributes to metabolism is lacking. Herein, we provide evidence that Ccr4-Not activates nutrient signaling through the essential target of rapamycin complex 1 (TORC1) pathway. Ccr4-Not disruption reduces global TORC1 signaling, and it also upregulates expression of the cell wall integrity (CWI) pathway terminal kinase Mpk1. Although CWI signaling represses TORC1 signaling, we find that Ccr4-Not loss inhibits TORC1 independently of CWI activation. Instead, we demonstrate that Ccr4-Not promotes the function of the vacuole V-ATPase, which interacts with the Gtr1 GTPase-containing EGO complex to stimulate TORC1 in response to nutrient sufficiency. Bypassing the V-ATPase requirement in TORC1 activation using a constitutively active Gtr1 mutant fully restores TORC1 signaling in Ccr4-Not deficient cells. Transcriptome analysis and functional studies revealed that loss of the Ccr4 subunit activates the TORC1 repressed retrograde signaling pathway to upregulate mitochondrial activity. Blocking this mitochondrial upregulation in Ccr4-Not deficient cells further represses TORC1 signaling, and it causes synergistic deficiencies in mitochondrial-dependent metabolism. These data support a model whereby Ccr4-Not loss impairs V-ATPase dependent TORC1 activation that forces cells to enhance mitochondrial metabolism to sustain a minimal level of TORC1 signaling necessary for cell growth and proliferation. Therefore, Ccr4-Not plays an integral role in nutrient signaling and cell metabolism by promoting V-ATPase dependent TORC1 activation.
  8. PLoS Genet. 2020 Oct 15. 16(10): e1009140
      Precise regulation of stem cell activity is crucial for tissue homeostasis. In Drosophila, intestinal stem cells (ISCs) maintain the midgut epithelium and respond to oxidative challenges. However, the connection between intestinal homeostasis and redox signaling remains obscure. Here we find that Caliban (Clbn) functions as a regulator of mitochondrial dynamics in enterocytes (ECs) and is required for intestinal homeostasis. The clbn knock-out flies have a shortened lifespan and lose the intestinal homeostasis. Clbn is highly expressed and localizes to the outer membrane of mitochondria in ECs. Mechanically, Clbn mediates mitochondrial dynamics in ECs and removal of clbn leads to mitochondrial fragmentation, accumulation of reactive oxygen species, ECs damage, activation of JNK and JAK-STAT signaling pathways. Moreover, multiple mitochondria-related genes are differentially expressed between wild-type and clbn mutated flies by a whole-genome transcriptional profiling. Furthermore, loss of clbn promotes tumor growth in gut generated by activated Ras in intestinal progenitor cells. Our findings reveal an EC-specific function of Clbn in regulating mitochondrial dynamics, and provide new insight into the functional link among mitochondrial redox modulation, tissue homeostasis and longevity.
  9. J Biol Chem. 2020 10 15. pii: jbc.REV120.015101. [Epub ahead of print]
      Mitochondrial DNA (mtDNA) encodes proteins and RNAs that support the functions of mitochondria and thereby numerous physiological processes. Mutations of mtDNA can cause mitochondrial diseases and are implicated in ageing. The mtDNA within cells is organized into nucleoids within the mitochondrial matrix, but how mtDNA nucleoids are formed and regulated within cells remains incompletely resolved. Visualization of mtDNA within cells is a powerful means by which mechanistic insight can be gained. Manipulation of the amount, and sequence of, mtDNA within cells is important experimentally and for developing therapeutic interventions to treat mitochondrial disease. This review details recent developments and opportunities for improvements in the experimental tools and techniques that can be used to visualize, quantify and manipulate the properties of mtDNA within cells.
    Keywords:  aging; gene editing; microscopy; mitochondria; mitochondrial DNA (mtDNA); mitochondrial disease; mitophagy
  10. Sci Rep. 2020 Oct 15. 10(1): 17339
      Mucosal and skin cancers are associated with infections by human papillomaviruses (HPV). The manner how viral oncoproteins hijack the host cell metabolism to meet their own energy demands and how this may contribute to tumorigenesis is poorly understood. We now show that the HPV oncoprotein E7 of HPV8, HPV11 and HPV16 directly interact with the beta subunit of the mitochondrial ATP-synthase (ATP5B), which may therefore represent a conserved feature across different HPV genera. By measuring both glycolytic and mitochondrial activity we observed that the association of E7 with ATP5B was accompanied by reduction of glycolytic activity. Interestingly, there was a drastic increase in spare mitochondrial respiratory capacity in HPV8-E7 and an even more profound increase in HPV16-E7 expressing cells. In addition, we could show that ATP5B levels were unchanged in betaHPV positive skin cancers. However, comparing HPV-positive and HPV-negative oropharyngeal squamous cell carcinomas (OPSCC) we noticed that, while ATP5B expression levels did not correlate with patient overall survival in HPV-negative OPSCC, there was a strong correlation within the HPV16-positive OPSCC patient group. These novel findings provide evidence that HPV targets the host cell energy metabolism important for viral life cycle and HPV-mediated tumorigenesis.
  11. Life Sci. 2020 Oct 13. pii: S0024-3205(20)31339-4. [Epub ahead of print] 118586
      AIMS: Mitochondrial dysfunction is receiving considerable attention due to irreplaceable biological function of mitochondria. Ionizing radiation and tigecycline (TIG) alone can cause mitochondrial dysfunction, playing important role in tumor therapy. However, prior studies fail to investigate combined mechanism of carbon ion irradiation (IR) and TIG on tumor proliferation inhibition. The study aimed to explore the combined effects of both on autophagy and apoptosis.MATERIALS AND METHODS: NSCLC cells A549 and H1299 were treated with carbon ion, TIG, or both. Cell survival rate, autophagy, apoptosis, expression of mitochondrial signaling proteins were determined by clone formation assay, immunofluorescence of LC3B, flow cytometry and western blotting, respectively; ATP content, mitochondrial membrane potential (MMP) and Ca2+ level in mitochondria were used to assessed mitochondrial function.
    KEY FINDINGS: Results showed IR combined TIG inhibited cells proliferation by increasing apoptosis in both cells and enhancing autophagy in H1299 cells. Additionally, combination treatment induced the most severe mitochondrial dysfunction by sharply reducing ATP, MMP and increasing Ca2+ level of mitochondria. Up-regulation and down-regulation of mitochondrial translation proteins (EF-Tu, GFM1 and MRPS12) expression affected apoptosis and autophagy, while the level of p-mTOR was consistent with their expression in both cell types. In A549 cells, p-AMPK level decreased while p-Akt and p-mTOR increased after combination treatment.
    SIGNIFICANCE: Overall, our results showed that p-Akt and p-AMPK antagonistically targeted p-mTOR to regulate mitochondrial translation proteins to affect autophagy and apoptosis. Furthermore, this study suggests that combination of carbon ion and TIG is a potential therapeutic option against tumors.
    Keywords:  Akt/AMPK/mTOR pathway; Carbon ion radiation; Mitochondrial dysfunction; Mitochondrial translation; Tigecycline
  12. Sci Rep. 2020 Oct 12. 10(1): 17012
      Statins are prescribed to treat hypercholesterolemia and to reduce the risk of cardiovascular disease. However, statin users frequently report myalgia, which can discourage physical activity or cause patients to discontinue statin use, negating the potential benefit of the treatment. Although a proposed mechanism responsible for Statin-Associated Myopathy (SAM) suggests a correlation with impairment of mitochondrial function, the relationship is still poorly understood. Here, we provide evidence that long-term treatment of hypercholesterolemic patients with Simvastatin at a therapeutic dose significantly display increased mitochondrial respiration in peripheral blood mononuclear cells (PBMCs), and platelets compared to untreated controls. Furthermore, the amount of superoxide is higher in mitochondria in PBMCs, and platelets from Simvastatin-treated patients than in untreated controls, and the abundance of mitochondrial superoxide, but not mitochondrial respiration trends with patient-reported myalgia. Ubiquinone (also known as coenzyme Q10) has been suggested as a potential treatment for SAM; however, an 8-week course of oral ubiquinone had no impact on mitochondrial functions or the abundance of superoxide in mitochondria from PBMCs, and platelets. These results demonstrate that long-term treatment with Simvastatin increases respiration and the production of superoxide in mitochondria of PBMCs and platelets.
  13. Surg Oncol. 2020 Oct 08. pii: S0960-7404(20)30406-0. [Epub ahead of print]35 453-459
      BACKGROUND: To investigate the impact of type 2 diabetes mellitus (T2DM) and metformin treatment on the prognosis of oral squamous cell carcinoma (OSCC) patients received radical surgical treatment.METHODS: Eight hundred and fifty-two patients with OSCC between January 2011 and January 2015 were included in the cohort study. Propensity score analysis was used to balance the characteristics of patients with or without T2DM and those of patients with T2DM treated with or without metformin. Five-year OSCC-free survival (OFS) was used to evaluate the prognosis of OSCC patients.
    RESULTS: Two hundred and sixty-nine patients without T2DM and 138 patients with T2DM were selected after the propensity score matching. The 5-year OFS of patients with T2DM was significantly lower than that of those without T2DM, both before (P = 0.019) and after (P = 0.014) the propensity score matching. Forty-four metformin users of OSCC patients with T2DM and 44 patients never users were further compared after the propensity score matching. The 5-year OFS of metformin users was significantly higher than that of metformin never users both before (P = 0.005) and after (P = 0.002) the propensity score matching.
    CONCLUSIONS: T2DM is associated with a higher risk of OSCC recurrence that can be reduced by metformin treatment.
    Keywords:  Cohort study with propensity score analysis; Oral squamous cell carcinoma; Type 2 diabetes mellitus
  14. J Cell Biol. 2020 Nov 02. pii: e202003024. [Epub ahead of print]219(11):
      MICOS is a conserved multisubunit complex that localizes to mitochondrial cristae junctions and organizes cristae positioning within the organelle. MICOS is organized into two independent subcomplexes; however, the mechanisms that dictate the assembly and spatial positioning of each MICOS subcomplex are poorly understood. Here, we determine that MICOS subcomplexes target independently of one another to sites on the inner mitochondrial membrane that are in proximity to contact sites between mitochondria and the ER. One subcomplex, composed of Mic27/Mic26/Mic10/Mic12, requires ERMES complex function for its assembly. In contrast, the principal MICOS component, Mic60, self-assembles and localizes in close proximity to the ER through an independent mechanism. We also find that Mic60 can uniquely redistribute adjacent to forced mitochondria-vacuole contact sites. Our data suggest that nonoverlapping properties of interorganelle contact sites provide spatial cues that enable MICOS assembly and ultimately lead to proper physical and functional organization of mitochondria.
  15. Int J Mol Sci. 2020 Oct 10. pii: E7461. [Epub ahead of print]21(20):
      Long-chain acylcarnitines (LCAC) are implicated in ischemia-reperfusion (I/R)-induced myocardial injury and mitochondrial dysfunction. Yet, molecular mechanisms underlying involvement of LCAC in cardiac injury are not sufficiently studied. It is known that in cardiomyocytes, palmitoylcarnitine (PC) can induce cytosolic Ca2+ accumulation, implicating L-type calcium channels, Na+/Ca2+ exchanger, and Ca2+-release from sarcoplasmic reticulum (SR). Alternatively, PC can evoke dissipation of mitochondrial potential (ΔΨm) and mitochondrial permeability transition pore (mPTP). Here, to dissect the complex nature of PC action on Ca2+ homeostasis and oxidative phosphorylation (OXPHOS) in cardiomyocytes and mitochondria, the methods of fluorescent microscopy, perforated path-clamp, and mitochondrial assays were used. We found that LCAC in dose-dependent manner can evoke Ca2+-sparks and oscillations, long-living Ca2+ enriched microdomains, and, finally, Ca2+ overload leading to hypercontracture and cardiomyocyte death. Collectively, PC-driven cardiotoxicity involves: (I) redistribution of Ca2+ from SR to mitochondria with minimal contribution of external calcium influx; (II) irreversible inhibition of Krebs cycle and OXPHOS underlying limited mitochondrial Ca2+ buffering; (III) induction of mPTP reinforced by PC-calcium interplay; (IV) activation of Ca2+-dependent phospholipases cPLA2 and PLC. Based on the inhibitory analysis we may suggest that simultaneous inhibition of both phospholipases could be an effective strategy for protection against PC-mediated toxicity in cardiomyocytes.
    Keywords:  Ca2+ overload; Krebs cycle; L-type calcium channels; cardiomyocytes; mitochondrial permeability transition pore; palmitoylcarnitine toxicity; phospholipases
  16. EMBO Rep. 2020 Oct 12. e50085
      The cultured brown adipocytes can oxidize glucose in vitro, but it is still not fully clear whether brown adipose tissue (BAT) could completely oxidize glucose in vivo. Although positron emission tomography (PET) with 18 F-fluorodeoxyglucose (18 F-FDG) showed a high level of glucose uptake in the activated BAT, the non-metabolizable 18 F-FDG cannot fully demonstrate intracellular glucose metabolism. Through in vivo [U-13 C]glucose tracing, here we show that chronic cold exposure dramatically activates glucose oxidation in BAT and the browning/beiging subcutaneous white adipose tissue (sWAT). Specifically, chronic cold exposure enhances glucose flux into the mitochondrial TCA cycle. Metabolic flux analysis models that β3-adrenergic receptor (β3-AR) agonist significantly enhances the flux of mitochondrial pyruvate uptake through mitochondrial pyruvate carrier (MPC) in the differentiated primary brown adipocytes. Furthermore, in vivo MPC inhibition blocks cold-induced glucose oxidation and impairs body temperature maintenance in mice. Together, mitochondrial pyruvate uptake and oxidation serve an important energy source in the chronic cold exposure activated BAT and beige adipose tissue, which supports a role for glucose oxidation in brown fat thermogenesis.
    Keywords:  BAT; in vivo glucose tracing; metabolic flux analysis; mitochondrial pyruvate carrier
  17. Bioengineering (Basel). 2020 Oct 12. pii: E126. [Epub ahead of print]7(4):
      Our research objective was to develop novel drug delivery vehicles consisting of TiO2 and Al2O3 nanoparticles encapsulated by a bilayer shell that allows the reversible embedment of hydrophobic drugs. The first shell is formed by covalent binding of hydrophobic phosphonic acid at the metal oxide surface. The second shell composed of amphiphilic sodium dodecylbenzenesulfonate emerges by self-aggregation driven by hydrophobic interactions between the dodecylbenzene moiety and the hydrophobic first shell. The resulting double layer provides hydrophobic pockets suited for the intake of hydrophobic drugs. The nanoparticles were loaded with the anticancer drugs quercetin and 7-amino-4-methylcoumarin. Irradiation with X-rays was observed to release the potential anticancer drugs into the cytoplasm. In Michigan Cancer Foundation (MCF)-10 A cells, quercetin and 7-amino-4-methylcoumarin acted as antioxidants by protecting the non-tumorigenic cells from harmful radiation effects. In contrast, these agents increased the reactive oxygen species (ROS) formation in cancerous MCF-7 cells. Quercetin and 7-amino-4-methylcoumarin were shown to induce apoptosis via the mitochondrial pathway in cancer cells by determining an increase in TUNEL-positive cells and a decrease in mitochondrial membrane potential after irradiation. After X-ray irradiation, the survival fraction of MCF-7 cells with drug-loaded nanoparticles considerably decreased, which demonstrates the excellent performance of the double-layer stabilized nanoparticles as drug delivery vehicles.
    Keywords:  Al2O3 nanoparticles; TiO2 nanoparticles; chemotherapy; drug delivery; quercetin; radiotherapy; shell-by-shell nanoparticles
  18. Biochemistry (Mosc). 2020 Jul;85(7): 820-832
      The concept of "electric cables" involved in bioenergetic processes in a living cell was proposed half a century ago [Skulachev, V. P. (1971) Curr. Top. Bioenerg., Elsevier, pp. 127-190]. Membrane structures of a cell were considered as probable pathways for transferring transmembrane electrochemical potential. Further studies have shown that coupling membranes (inner mitochondrial membrane or bacterial cell membrane), i.e., those involved in the generation of membrane potential, can also serve for its transfer. A wide range of organisms from almost all major taxa have been discovered to employ the energy-transmitting function of coupling membranes. Macroscopic (millimeter or even centimeter in length) cable-like structures have been found, the most striking examples of which are giant mitochondria of some unicellular organisms (algae, fungi, protozoa) and animal tissues, filamentous mitochondria, mitochondrial reticulum in animal muscle tissue, and trichomes of cyanobacteria. The importance of such "electric cables" in cells or multicellular structures is determined by their ability to provide rapid energy exchange between metabolic counterparts, energy producers and energy consumers, as the diffusive transport of soluble macroergic molecules (ATP, etc.) requires much longer time. However, in the last 10-15 years, a new type of bacterial "electric cables" of presumably proteinaceous nature has been discovered, which serve a quite different purpose in cell bioenergetics. The molecular structure and functions of these cables will be discussed in the second part of the review ("Electric cables of living cells. II. Bacterial electron conductors").
  19. Cancers (Basel). 2020 Oct 12. pii: E2939. [Epub ahead of print]12(10):
      Colorectal cancer is a common malignancy worldwide. Physical activity and a healthy diet contribute to energy balance and have been recommended for the prevention of colorectal cancer. We suggest that the individual differences in energy balance can be explained by genetic polymorphisms involved in mitochondria, which play a central role in energy metabolism at the cellular level. This study aimed to evaluate the association between genetic variants of the mitochondrial citric acid cycle and colorectal cancer. Study participants comprised 3523 colorectal cancer cases and 10,522 matched controls from the UK Biobank study. Odds ratios (ORs) and 95% confidence intervals (CIs) for colorectal cancer were estimated using a conditional logistic regression model. We found a significant association between the SUCLG2 gene rs35494829 and colon cancer (ORs [95% CIs] per increment of the minor allele, 0.82 [0.74-0.92]). Statistical significance was observed in the interactions of the citric acid cycle variants with obesity, energy intake, and vigorous physical activity in colorectal cancer. We also identified significant SNP-SNP interactions among citric acid cycle SNPs in colorectal cancer. The results of this study may provide evidence for bioenergetics in the development of colorectal cancer and for establishing a precise prevention strategy.
    Keywords:  citric acid cycle; colorectal neoplasms; diet; obesity; physical activity; single nucleotide polymorphism
  20. Neural Regen Res. 2021 Apr;16(4): 659-665
      Metabolic rewiring and deregulation of the cell cycle are hallmarks shared by many cancers. Concerted mutations in key tumor suppressor genes, such as PTEN, and oncogenes predispose cancer cells for marked utilization of resources to fuel accelerated cell proliferation and chemotherapeutic resistance. Mounting research has demonstrated that PTEN-induced putative kinase 1 (PINK1) acts as a pivotal regulator of mitochondrial homeostasis in several cancer types, a function that also extends to the regulation of tumor cell proliferative capacity. In addition, involvement of PINK1 in modulating inflammatory responses has been highlighted by recent studies, further expounding PINK1's multifunctional nature. This review discusses the oncogenic roles of PINK1 in multiple tumor cell types, with an emphasis on maintenance of mitochondrial homeostasis, while also evaluating literature suggesting a dual oncolytic mechanism based on PINK1's modulation of the Warburg effect. From a clinical standpoint, its expression may also dictate the response to genotoxic stressors commonly used to treat multiple malignancies. By detailing the evidence suggesting that PINK1 possesses distinct prognostic value in the clinical setting and reviewing the duality of PINK1 function in a context-dependent manner, we present avenues for future studies of this dynamic protein.
    Keywords:  PINK1; Warburg effect; apoptosis; cancer; cell cycle; inflammation; metabolic stress; mitochondral quality control; mitophagy; tumor
  21. Chemistry. 2020 Oct 13.
      Chemoresistance is one of the major challenges for cancer treatment, more recently ascribed to defective mitochondrial outer membrane permeabilization (MOMP), significantly diminishing chemotherapeutic agent-induced apoptosis. A boron-dipyrromethene (BODIPY) chromophore-based triarylsulfonium photoacid generator (BD-PAG) was used to target mitochondria with the aim to regulate mitochondrial pH and further depolarize the mitochondrial membrane. Cell viability assays demonstrated the relative biocompatibility of BD-PAG in the dark while live cell imaging suggested high accumulation in mitochondria. Specific assays indicated that BD-PAG is capable of regulating mitochondrial pH with significant effects on mitochondrial membrane depolarization. Therapeutic tests using chlorambucil in combination with BD-PAG revealed a new strategy in chemoresistance suppression.
    Keywords:  cancer; chemoresistance; mitochondria; photo-trigger
  22. Front Cell Infect Microbiol. 2020 ;10 493
      Almost 140 years after its discovery, tuberculosis remains the leading infectious cause of death globally. For half a century, patients with drug-sensitive and drug-resistant tuberculosis have undergone long, arduous, and complex treatment processes with several antimicrobials that primarily function through direct bactericidal activity. Long-term utilization of these antimicrobials has been well-characterized and associated with numerous toxic side-effects. With the prevalence of drug-resistant strains on the rise and new therapies for tuberculosis urgently required, a more thorough understanding of these antimicrobials is a necessity. In order to progress from the "one size fits all" treatment approach, understanding how these antimicrobials affect mitochondrial function and bioenergetics may provide further insight into how these drugs affect the overall functions of host immune cells during tuberculosis infection. Such insights may help to inform future studies, instigate discussion, and help toward establishing personalized approaches to using such antimicrobials which could help to pave the way for more tailored treatment regimens. While recent research has highlighted the important role mitochondria and bioenergetics play in infected host cells, only a small number of studies have examined how these antimicrobials affect mitochondrial function and immunometabolic processes within these immune cells. This short review highlights how these antimicrobials affect key elements of mitochondrial function, leading to further discussion on how they affect bioenergetic processes, such as glycolysis and oxidative phosphorylation, and how antimicrobial-induced alterations in these processes can be linked to downstream changes in inflammation, autophagy, and altered bactericidal activity.
    Keywords:  antimicrobials; bioenergetics; cellular metabolism; glycolysis; mitochondrial function; oxidative phosphorylation; tuberculosis
  23. Biochim Biophys Acta Bioenerg. 2020 Oct 13. pii: S0005-2728(20)30172-9. [Epub ahead of print] 148322
    Keywords:  ATPase; F(1)F(O) ATP Synthase; IF1; IF1-H49K; OXPHOS; Opa1; Tracking And Localization Microscopy (TALM); inhibitory factor 1; mitochondria; mitochondrial ultrastructure; spatiotemporal organization; superresolution microscopy
  24. Pharmacol Res. 2020 Oct 13. pii: S1043-6618(20)31556-5. [Epub ahead of print] 105248
      The ubiquitin-proteasome system constitutes a major pathway for protein degradation in the cell. Therefore the crosstalk of this pathway with mitochondria is a major topic with direct relevance to many mitochondrial diseases. Proteasome dysfunction triggers not only protein toxicity, but also mitochondrial dysfunction. The involvement of proteasomes in the regulation of protein transport into mitochondria contributes to an increase in mitochondrial function defects. On the other hand, mitochondrial impairment stimulates reactive oxygen species production, which increases protein damage, and protein misfolding and aggregation leading to proteasome overload. Concurrently, mitochondrial dysfunction compromises cellular ATP production leading to reduced protein ubiquitination and proteasome activity. In this review we discuss the complex relationship and interdependence of the ubiquitin-proteasome system and mitochondria. Furthermore, we describe pharmacological inhibition of proteasome activity as a novel strategy to treat a group of mitochondrial diseases.
    Keywords:  mitochondria; mitochondrial diseases; mitochondrial toxicity; proteasome; proteasome inhibitors; protein homeostasis
  25. Cancers (Basel). 2020 Oct 14. pii: E2978. [Epub ahead of print]12(10):
      Resistance to chemotherapy often results from dysfunctional apoptosis, however multiple proteins with overlapping functions regulate this pathway. We sought to determine whether an extensively validated, deterministic apoptosis systems model, 'DR_MOMP', could be used as a stratification tool for the apoptosis sensitiser and BCL-2 antagonist, ABT-199 in patient-derived xenograft (PDX) models of colorectal cancer (CRC). Through quantitative profiling of BCL-2 family proteins, we identified two PDX models which were predicted by DR_MOMP to be sufficiently sensitive to 5-fluorouracil (5-FU)-based chemotherapy (CRC0344), or less responsive to chemotherapy but sensitised by ABT-199 (CRC0076). Treatment with ABT-199 significantly improved responses of CRC0076 PDXs to 5-FU-based chemotherapy, but showed no sensitisation in CRC0344 PDXs, as predicted from systems modelling. 18F-Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) scans were performed to investigate possible early biomarkers of response. In CRC0076, a significant post-treatment decrease in mean standard uptake value was indeed evident only in the combination treatment group. Radiomic CT feature analysis of pre-treatment images in CRC0076 and CRC0344 PDXs identified features which could phenotypically discriminate between models, but were not predictive of treatment responses. Collectively our data indicate that systems modelling may identify metastatic (m)CRC patients benefitting from ABT-199, and that 18F-FDG-PET could independently support such predictions.
    Keywords:  ABT-199; BCL-2; FOLFOX; PDX; Venetoclax; colorectal cancer; deterministic modelling; preclinical imaging; radiomics; systems biology
  26. Cell Death Dis. 2020 Oct 16. 11(10): 872
      Apoptotic priming controls the commitment of cells to apoptosis by determining how close they lie to mitochondrial permeabilisation. Variations in priming are important for how both healthy and cancer cells respond to chemotherapeutic agents, but how it is dynamically coordinated by Bcl-2 proteins remains unclear. The Bcl-2 family protein Bid is phosphorylated when cells enter mitosis, increasing apoptotic priming and sensitivity to antimitotic drugs. Here, we report an unbiased proximity biotinylation (BioID) screen to identify regulators of apoptotic priming in mitosis, using Bid as bait. The screen primarily identified proteins outside of the canonical Bid interactome. Specifically, we found that voltage-dependent anion-selective channel protein 2 (VDAC2) was required for Bid phosphorylation-dependent changes in apoptotic priming during mitosis. These results highlight the importance of the wider Bcl-2 family interactome in regulating the temporal control of apoptotic priming.
  27. Cancer Lett. 2020 Oct 07. pii: S0304-3835(20)30508-5. [Epub ahead of print]496 57-71
      Despite the growing recognition of metabolic reprogramming as an important hallmark of cancer in the past few years, the molecular mechanisms underlying metabolic alterations during tumorigenesis remain unclear. In this study, we identified a critical role of Her4 in rewiring cancer metabolism toward tumor-promoting metabolic processes, including increased glycolysis, glutaminolysis, mitochondrial biogenesis, and oxidative phosphorylation, which may in part cooperate to promote tumorigenesis. We found that overexpression of Her4 promoted the stabilization of c-Myc through a CIP2A-mediated increase in c-MycS62 phosphorylation and GSK3β-mediated decrease in c-MycT58 phosphorylation, both of which decreased c-Myc degradation. Furthermore, Her4 was found to increase glucose uptake and tumor growth in an osteosarcoma xenograft model. Overall, these findings provide a better understanding of the involvement of Her4 in tumorigenesis and document its potential role in metabolic reprogramming for the first time. We believe that our study might lead to promising opportunities for targeted metabolic therapy for cancer.
    Keywords:  Glutaminolysis; Glycolysis; Her4; Oxidative phosphorylation; c-Myc
  28. Biochem Pharmacol. 2020 Oct 12. pii: S0006-2952(20)30518-9. [Epub ahead of print] 114282
      In the past mitochondria were considered as the "powerhouse" of cell, since they generate more than 90% of ATP in aerobic conditions through the oxidative phosphorylation. However, based on the current knowledge, mitochondria play several other cellular functions, including participation in calcium homeostasis, generation of free radicals and oxidative species, triggering/regulation of apoptosis, among others. Additionally, previous discoveries recognized mitochondria as highly dynamic structures, which undergo morphological alterations resulting in long or short fragments inside the living cells. This highly regulated process was referred as mitochondrial dynamics and involves mitochondrial fusion and fission. Thus, the number of mitochondria and the morphology of mitochondrial networks depend on the mitochondrial dynamics, biogenesis, and mitophagy. In each cell, there is a delicate balance between fusion and fission to allow the maintenance of appropriate mitochondrial functions. It has been proposed that the fusion and fission dynamics process controls cell cycle, metabolism, and survival, being implicated in a wide range of physiological and pathological conditions. Mitochondrial fusion is mediated by dynamin-like proteins, including mitofusin 1 (MFN1), mitofusin 2 (MFN2), and optic atrophy 1 protein (OPA1). Conversely, mitochondrial fission results in a large number of small fragments, which is mediated mainly by dynamin-related protein 1 (DRP1). Interestingly, there is growing evidence proposing that tumor cells modify the mitochondrial dynamics rheostat in order to gain proliferative and survival advantages. Increased mitochondrial fission has been reported in several types of human cancer cells (melanoma, ovarian, breast, lung, thyroid, glioblastoma, and others) and some studies have reported a possible direct correlation between increased mitochondrial fusion and chemoresistance of tumor cells. Here, the current knowledge about alterations of mitochondrial dynamics in cancer will be reviewed and its potential as a target for adjuvant cancer chemotherapy will be discussed.
    Keywords:  Bioenergetics; Cancer; Cell death; Chemotherapy; Mitochondrial dynamics
  29. Nat Metab. 2020 Oct 12.
      Cellular metabolism has emerged as a major biological node governing cellular behaviour. Metabolic pathways fuel cellular energy needs, providing basic chemical molecules to sustain cellular homeostasis, proliferation and function. Changes in nutrient consumption or availability therefore can result in complete reprogramming of cellular metabolism towards stabilizing core metabolite pools, such as ATP, S-adenosyl methionine, acetyl-CoA, NAD/NADP and α-ketoglutarate. Because these metabolites underlie a variety of essential metabolic reactions, metabolism has evolved to operate in separate subcellular compartments through diversification of metabolic enzyme complexes, oscillating metabolic activity and physical separation of metabolite pools. Given that these same core metabolites are also consumed by chromatin modifiers in the establishment of epigenetic signatures, metabolite consumption on and release from chromatin directly influence cellular metabolism and gene expression. In this Review, we highlight recent studies describing the mechanisms determining nuclear metabolism and governing the redistribution of metabolites between the nuclear and non-nuclear compartments.
  30. Nature. 2020 Oct 14.
    Alexander G Bick, Joshua S Weinstock, Satish K Nandakumar, Charles P Fulco, Erik L Bao, Seyedeh M Zekavat, Mindy D Szeto, Xiaotian Liao, Matthew J Leventhal, Joseph Nasser, Kyle Chang, Cecelia Laurie, Bala Bharathi Burugula, Christopher J Gibson, Amy E Lin, Margaret A Taub, Francois Aguet, Kristin Ardlie, Braxton D Mitchell, Kathleen C Barnes, Arden Moscati, Myriam Fornage, Susan Redline, Bruce M Psaty, Edwin K Silverman, Scott T Weiss, Nicholette D Palmer, Ramachandran S Vasan, Esteban G Burchard, Sharon L R Kardia, Jiang He, Robert C Kaplan, Nicholas L Smith, Donna K Arnett, David A Schwartz, Adolfo Correa, Mariza de Andrade, Xiuqing Guo, Barbara A Konkle, Brian Custer, Juan M Peralta, Hongsheng Gui, Deborah A Meyers, Stephen T McGarvey, Ida Yii-Der Chen, M Benjamin Shoemaker, Patricia A Peyser, Jai G Broome, Stephanie M Gogarten, Fei Fei Wang, Quenna Wong, May E Montasser, Michelle Daya, Eimear E Kenny, Kari E North, Lenore J Launer, Brian E Cade, Joshua C Bis, Michael H Cho, Jessica Lasky-Su, Donald W Bowden, L Adrienne Cupples, Angel C Y Mak, Lewis C Becker, Jennifer A Smith, Tanika N Kelly, Stella Aslibekyan, Susan R Heckbert, Hemant K Tiwari, Ivana V Yang, John A Heit, Steven A Lubitz, Jill M Johnsen, Joanne E Curran, Sally E Wenzel, Daniel E Weeks, Dabeeru C Rao, Dawood Darbar, Jee-Young Moon, Russell P Tracy, Erin J Buth, Nicholas Rafaels, Ruth J F Loos, Peter Durda, Yongmei Liu, Lifang Hou, Jiwon Lee, Priyadarshini Kachroo, Barry I Freedman, Daniel Levy, Lawrence F Bielak, James E Hixson, James S Floyd, Eric A Whitsel, Patrick T Ellinor, Marguerite R Irvin, Tasha E Fingerlin, Laura M Raffield, Sebastian M Armasu, Marsha M Wheeler, Ester C Sabino, John Blangero, L Keoki Williams, Bruce D Levy, Wayne Huey-Herng Sheu, Dan M Roden, Eric Boerwinkle, JoAnn E Manson, Rasika A Mathias, Pinkal Desai, Kent D Taylor, Andrew D Johnson, , Paul L Auer, Charles Kooperberg, Cathy C Laurie, Thomas W Blackwell, Albert V Smith, Hongyu Zhao, Ethan Lange, Leslie Lange, Stephen S Rich, Jerome I Rotter, James G Wilson, Paul Scheet, Jacob O Kitzman, Eric S Lander, Jesse M Engreitz, Benjamin L Ebert, Alexander P Reiner, Siddhartha Jaiswal, Gonçalo Abecasis, Vijay G Sankaran, Sekar Kathiresan, Pradeep Natarajan.
      Age is the dominant risk factor for most chronic human diseases, but the mechanisms through which ageing confers this risk are largely unknown1. The age-related acquisition of somatic mutations that lead to clonal expansion in regenerating haematopoietic stem cell populations has recently been associated with both haematological cancer2-4 and coronary heart disease5-this phenomenon is termed clonal haematopoiesis of indeterminate potential (CHIP)6. Simultaneous analyses of germline and somatic whole-genome sequences provide the opportunity to identify root causes of CHIP. Here we analyse high-coverage whole-genome sequences from 97,691 participants of diverse ancestries in the National Heart, Lung, and Blood Institute Trans-omics for Precision Medicine (TOPMed) programme, and identify 4,229 individuals with CHIP. We identify associations with blood cell, lipid and inflammatory traits that are specific to different CHIP driver genes. Association of a genome-wide set of germline genetic variants enabled the identification of three genetic loci associated with CHIP status, including one locus at TET2 that was specific to individuals of African ancestry. In silico-informed in vitro evaluation of the TET2 germline locus enabled the identification of a causal variant that disrupts a TET2 distal enhancer, resulting in increased self-renewal of haematopoietic stem cells. Overall, we observe that germline genetic variation shapes haematopoietic stem cell function, leading to CHIP through mechanisms that are specific to clonal haematopoiesis as well as shared mechanisms that lead to somatic mutations across tissues.
  31. Biochim Biophys Acta Bioenerg. 2020 Oct 09. pii: S0005-2728(20)30176-6. [Epub ahead of print] 148326
      The structure of the entire respiratory complex I is now known at reasonably high resolution for many species - bacteria, yeast, and several mammals, including human. The structure reveals an almost 30 angstrom tunnel-like chamber for ubiquinone binding in the core part of the enzyme, at the joint between the membrane and hydrophilic arms of the enzyme. Here we characterize the geometric bottleneck forming the entrance of the quinone reaction chamber. Computer simulations of quinone/quinol passage through the bottleneck suggest that in all structures available, from bacterial to human, this bottleneck is too narrow for the quinone or quinol to pass and that a conformational change is required to open the channel. Moreover, the bottleneck is too narrow even for isoprenoid tail free passage. We conclude that the closed structure is an artifact of the crystallization packing forces, low temperature, or other unnatural conditions occurring in the structural data acquisition procedure that affect this flexible part of the enzyme. Two of the helices forming the bottleneck are in direct contact with the subunit (ND3) that was recently demonstrated to be involved in conformational changes during the redox proton pumping cycle, which indicates flexibility of that part of the enzyme. We conclude that the published structures are all locked in the unfunctional states and do not represent correctly the functional enzyme; we discuss possible ways to open the structure in the context of possible mechanisms of the enzyme.
    Keywords:  Complex I; electron transport chain; ubiquinone
  32. Blood. 2020 Oct 16. pii: blood.2020008017. [Epub ahead of print]
      Cancer and normal cells utilize multiple anti-apoptotic BCL2 proteins to prevent cell death. Therapeutic targeting of multiple BCL2 family proteins enhances tumor killing, but is also associated with increased systemic toxicity. Here, we demonstrate that the dual targeting of MCL1 and BCL2 proteins, using the small molecules S63845 and venetoclax, induces durable remissions in mice harboring human DLBCL tumors but is accompanied by hematological toxicity and weight loss. To mitigate these toxicities, we encapsulated S63845 or venetoclax into nanoparticles targeting P-selectin that is enriched in tumor endothelial cells. In vivo and ex vivo imaging demonstrated preferential targeting of the nanoparticles to lymphoma tumors over vital organs. Mass-spectrometry analyses after nanoparticle drug administration confirmed tumor enrichment of the drug while reducing plasma levels. Furthermore, nanoparticle encapsulation allowed 3.5 to 6.5-fold reduction in drug dose, induced sustained remissions and minimized toxicity. Our results support the development of nanoparticles to deliver BH3 mimetic combinations in lymphoma and in general for toxic drugs in cancer therapy.
  33. PLoS One. 2020 ;15(10): e0240517
      Mitochondrial diseases are a clinically heterogenous group of disorders caused by respiratory chain dysfunction and associated with progressive, multi-systemic phenotype. There is no effective treatment or cure, and no FDA-approved drug for treating mitochondrial disease. To identify and characterize potential therapeutic compounds, we developed an in vitro screening assay and identified a group of direct AMP-activated protein kinase (AMPK) activators originally developed for the treatment of diabetes and metabolic syndrome. Unlike previously investigated AMPK agonists such as AICAR, these compounds allosterically activate AMPK in an AMP-independent manner, thereby increasing specificity and decreasing pleiotropic effects. The direct AMPK activator PT1 significantly improved mitochondrial function in assays of cellular respiration, energy status, and cellular redox. PT1 also protected against retinal degeneration in a mouse model of photoreceptor degeneration associated with mitochondrial dysfunction and oxidative stress, further supporting the therapeutic potential of AMP-independent AMPK agonists in the treatment of mitochondrial disease.