bims-mibica Biomed News
on Mitochondrial bioenergetics in cancer
Issue of 2021‒08‒01
37 papers selected by
Kelsey Fisher-Wellman
East Carolina University

  1. J Biol Chem. 2021 Jul 24. pii: S0021-9258(21)00807-3. [Epub ahead of print] 101005
      Barth syndrome (BTHS) is an X-linked disorder of mitochondrial phospholipid metabolism caused by pathogenic variants in the gene TAFFAZIN (TAZ), which results in abnormal cardiolipin (CL) content in the inner mitochondrial membrane. To identify unappreciated pathways of mitochondrial dysfunction in BTHS, we utilized an unbiased proteomics strategy and identified that complex I of the mitochondrial respiratory chain and the mitochondrial quality control protease PARL are altered in a new HEK293-based TAZ-deficiency model. Follow-up studies confirmed decreased steady state levels of specific complex I subunits and an assembly factor in the absence of TAZ; this decrease is in part based on decreased transcription, and results in reduced complex I assembly and function. PARL, a rhomboid protease associated with the inner mitochondrial membrane with a role in the mitochondrial response to stress such as mitochondrial membrane depolarization, is increased in TAZ-deficient cells. The increased abundance of PARL correlates with augmented processing of a downstream target, PGAM5, both at baseline and in response to mitochondrial depolarization. To clarify the relationship between abnormal CL content, complex I levels, and increased PARL expression that occurs when TAZ is missing, we used blue-native page and gene expression analysis to determine that these defects are remediated by SS-31 and bromoenol lactone, pharmacologic agents that bind CL or inhibit CL deacylation, respectively. These findings have the potential to enhance our understanding of the cardiac pathology of BTHS, where defective mitochondrial quality control and complex I dysfunction have well-recognized roles in the pathology of diverse forms of cardiac dysfunction.
    Keywords:  Barth Syndrome; Cardiolipin; Mitochondrial metabolism
  2. Am J Physiol Cell Physiol. 2021 07 28.
      Mitochondria are recognized as signaling organelles because, under stress, mitochondria can trigger various signaling pathways to coordinate the cell's response. The specific pathway(s) engaged by mitochondria in response to mitochondrial energy defects in vivo and in high-energy tissues like the heart are not fully understood. Here, we investigated cardiac pathways activated in response to mitochondrial energy dysfunction by studying mice with cardiomyocyte-specific loss of the mitochondrial phosphate carrier (SLC25A3), an established model that develops cardiomyopathy as a result of defective mitochondrial ATP synthesis. Mitochondrial energy dysfunction induced a striking pattern of acylome remodeling, with significantly increased post-translational acetylation and malonylation. Mass spectrometry-based proteomics further revealed that energy dysfunction-induced remodeling of the acetylome and malonylome preferentially impacts mitochondrial proteins. Acetylation and malonylation modified a highly interconnected interactome of mitochondrial proteins, and both modifications were present on the enzyme isocitrate dehydrogenase 2 (IDH2). Intriguingly, IDH2 activity was enhanced in SLC25A3-deleted mitochondria, and further study of IDH2 sites targeted by both acetylation and malonylation revealed that these modifications can have site-specific and distinct functional effects. Finally, we uncovered a novel crosstalk between the two modifications, whereby mitochondrial energy dysfunction-induced acetylation of sirtuin 5 (SIRT5), inhibited its function. Because SIRT5 is a mitochondrial deacylase with demalonylase activity, this finding suggests that acetylation can modulate the malonylome. Together, our results position acylations as an arm of the mitochondrial response to energy dysfunction and suggest a mechanism by which focal disruption to the energy production machinery can have an expanded impact on global mitochondrial function.
    Keywords:  acetylation; acylations; energy; heart; mitochondria
  3. Dev Cell. 2021 Jul 26. pii: S1534-5807(21)00529-3. [Epub ahead of print]56(14): 2010-2012
      Cancers are dependent on mitochondria, the powerhouse of the cell, and autophagy, the mechanism to preserve mitochondrial quality and function. In this issue of Developmental Cell, Towers et al. identify mitochondria-derived vesicles (MDVs) as a new adaptive mechanism enabling cancer cells to compensate for autophagy loss and to maintain mitochondrial function.
  4. Toxicol Lett. 2021 Jul 24. pii: S0378-4274(21)00195-8. [Epub ahead of print]350 143-151
      Remdesivir (RDV) is a novel antiviral drug whose mitochondrial effects are not well known. In vitro effects of RDV on the mitochondrial respiration, individual respiratory complexes, and the activity of monoamine oxidase (MAO-A and MAO-B) were measured in isolated mitochondria. At micromolar RDV concentrations, minimal or no inhibitory effects on the studied mitochondrial enzymes were found. At very high concentrations of RDV, there was partial inhibition of complex I- (IC50 675 μmol/L, residual activity 39.4 %) and complex II-linked (IC50 81.8 μmol/L, residual activity 40.7 %) respiration, without inhibition of complex IV-linked respiration, and partial inhibition both of MAO-A (IC50 26.6 μmol/L, residual activity 35.2 %) and MAO-B (IC50 89.8 μmol/L, residual activity 34.0 %) activity. Individual respiratory complexes (I, II + III, and IV) were partially inhibited at a high drug concentration. The active metabolite of RDV (GS-443902) had very little effect on mitochondrial oxygen consumption rate with residual activity of 87.0 % for complex I-linked respiration, 90.3 % for complex II-linked respiration, and with no inhibition of complex IV-linked respiration. In conclusion, measurement of the effect of RDV and its active metabolite on isolated mitochondria shows that there is very little direct effect on mitochondrial respiration occurs at therapeutic drug concentration.
    Keywords:  Isolated mitochondria; Mitochondrial respiratory rate; Monoamine oxidase; Remdesivir; Respiratory complex
  5. J Cell Sci. 2021 07 01. pii: jcs252197. [Epub ahead of print]134(13):
      The mitochondrial inner membrane is a protein-rich environment containing large multimeric complexes, including complexes of the mitochondrial electron transport chain, mitochondrial translocases and quality control machineries. Although the inner membrane is highly proteinaceous, with 40-60% of all mitochondrial proteins localised to this compartment, little is known about the spatial distribution and organisation of complexes in this environment. We set out to survey the arrangement of inner membrane complexes using stochastic optical reconstruction microscopy (STORM). We reveal that subunits of the TIM23 complex, TIM23 and TIM44 (also known as TIMM23 and TIMM44, respectively), and the complex IV subunit COXIV, form organised clusters and show properties distinct from the outer membrane protein TOM20 (also known as TOMM20). Density based cluster analysis indicated a bimodal distribution of TIM44 that is distinct from TIM23, suggesting distinct TIM23 subcomplexes. COXIV is arranged in larger clusters that are disrupted upon disruption of complex IV assembly. Thus, STORM super-resolution microscopy is a powerful tool for examining the nanoscale distribution of mitochondrial inner membrane complexes, providing a 'visual' approach for obtaining pivotal information on how mitochondrial complexes exist in a cellular context.
    Keywords:  COXIV; Mitochondria; Mitochondrial complexes; Nanoscopy; Protein import; STORM; TIM23
  6. Elife. 2021 Jul 26. pii: e68710. [Epub ahead of print]10
      Respiratory complex I is a multi-subunit membrane protein complex that reversibly couples NADH oxidation and ubiquinone reduction with proton translocation against trans-membrane potential. Complex I from Escherichia coli is among the best functionally characterized complexes, but its structure remains unknown, hindering further mechanistic studies to understand the enzyme coupling mechanism. Here we describe the single particle cryo-electron microscopy (cryo-EM) structure of the entire catalytically active E. coli complex I reconstituted into lipid nanodiscs. The structure of this mesophilic bacterial complex I displays highly dynamic connection between the peripheral and membrane domains. The peripheral domain assembly is stabilized by unique terminal extensions and an insertion loop. The membrane domain structure reveals novel dynamic features. Unusual conformation of the conserved interface between the peripheral and membrane domains suggests an uncoupled conformation of the complex. Considering constraints imposed by the structural data we suggest a new simple hypothetical coupling mechanism for the molecular machine.
    Keywords:  E. coli; molecular biophysics; structural biology
  7. Oxid Med Cell Longev. 2021 ;2021 5595652
      Autophagy plays a double-edged sword for cancer; particularly, mitophagy plays important roles in the selective degradation of damaged mitochondria. However, whether mitophagy is involved in killing effects of tumor cells by ionizing radiation (IR) and its underlying mechanism remain elusive. The purpose is to evaluate the effects of mitochondrial ROS (mROS) on autophagy after IR; furthermore, we hypothesized that KillerRed (KR) targeting mitochondria could induce mROS generation, subsequent mitochondrial depolarization, accumulation of Pink1, and recruitment of PARK2 to promote the mitophagy. Thereby, we would achieve a new strategy to enhance mROS accumulation and clarify the roles and mechanisms of radiosensitization by KR and IR. Our data demonstrated that IR might cause autophagy of both MCF-7 and HeLa cells, which is related to mitochondria and mROS, and the ROS scavenger N-acetylcysteine (NAC) could reduce the effects. Based on the theory, mitochondrial targeting vector sterile α- and HEAT/armadillo motif-containing protein 1- (Sarm1-) mtKR has been successfully constructed, and we found that ROS levels have significantly increased after light exposure. Furthermore, mitochondrial depolarization of HeLa cells was triggered, such as the decrease of Na+K+ ATPase, Ca2+Mg2+ ATPase, and mitochondrial respiratory complex I and III activities, and mitochondrial membrane potential (MMP) has significantly decreased, and voltage-dependent anion channel 1 (VDAC1) protein has significantly increased in the mitochondria. Additionally, HeLa cell proliferation was obviously inhibited, and the cell autophagic rates dramatically increased, which referred to the regulation of the Pink1/PARK2 pathway. These results indicated that mitophagy induced by mROS can initiate the sensitization of cancer cells to IR and might be regulated by the Pink1/PARK2 pathway.
  8. Dev Cell. 2021 Jul 26. pii: S1534-5807(21)00546-3. [Epub ahead of print]56(14): 2014-2015
      Mechanisms by which cells remove damaged mitochondria extracellularly are unclear. Recent work by Jiao and colleagues in Cell shows that migrating cells expel dysfunctional mitochondria in membrane-bound structures called migrasomes to maintain mitochondrial homeostasis.
  9. Dis Model Mech. 2021 Jul 27. pii: dmm.048995. [Epub ahead of print]
      Mitochondrial dysfunction in different cell types is associated to several pathological processes and potentially contributes to chronic inflammatory and ageing-related diseases. Mitochondrial Transcription Factor A (TFAM) plays a critical role in maintaining mtDNA integrity and function. Taking advantage of the Tfamfl/fl UBC-Cre/ERT2+/+ mice, we sought to develop a cellular in vitro system to investigate the role of mitochondrial dysfunction in the stromal cell component. We describe an inducible model of mitochondrial dysfunction by stable depletion of TFAM in primary mouse skin fibroblast (SK-FB) after 4-hydroxytamoxifen (4-OHT) administration. Tfam gene deletion caused a sustained reduction of Tfam and mtDNA-encoded mRNA expression in Cre(+) cultured for low (LP) and high passages (HP). Ultimately, Tfam knockout translated into a loss of TFAM protein. TFAM depletion led to a substantial reduction of the mitochondrial respiratory chain (MRC) complexes that was exacerbated in HP SK-FB cultures. The assembly pattern showed that the respiratory complexes fail to reach the respirasome in 4-OHT Cre(+) SK-FB. Functionally, we determined the mitochondrial function and the glycolytic activity by mito-stress and glycolysis-stress test respectively. These analysis showed that mitochondrial dysfunction was developed after long-term 4-OHT treatment in HP Cre(+) SK-FB and was compensated by an increase in the glycolytic capacity. Finally, expression analysis revealed that 4-OHT-treated HP Cre(+) SK-FB showed a senescent and pro-inflammatory phenotype. In conclusion, we have generated and validated the first ex vivo model of fibroblast mitochondrial dysfunction that results in a pro-inflammatory phenotype applicable to explore this process in other cell types in a variety of pathological conditions.
    Keywords:  Cellular senescence; Fibroblasts; Inflammation; Mitochondrial dysfunction; TFAM
  10. FEBS J. 2021 Jul 26.
      Mitochondria form a branched tubular network in many types of cells, depending on a balance between mitochondrial fusion and fission. How mitochondrial fusion and fission are involved in regulating mitochondrial function and cell proliferation is not well understood. Here, we dissected the roles of mitochondrial fusion and fission in mitochondrial function and cell proliferation in fission yeast. We examined mitochondrial membrane potential by staining cells with DiOC6 and assessed mitochondrial respiration by directly measuring oxygen consumption of cells with a dissolved oxygen respirometer. We found that defects in mitochondrial fission or fusion reduce mitochondrial membrane potential and compromise mitochondrial respiration while the absence of both mitochondrial fusion and fission restores wild-type-like respiration, normal membrane potential, and tubular networks of mitochondria. Moreover, we found that the absence of either mitochondrial fission or fusion prolongs the cell cycle and that the absence of both mitochondrial fusion and fission significantly delays cell cycle progression after nitrogen replenishment. The prolonged/delayed cell cycle is likely due to the deregulation of Cdc2 activation. Hence, our work not only establishes an intimate link between mitochondrial morphology and function but also underscores the importance of mitochondrial dynamics in regulating the cell cycle.
    Keywords:  Cell cycle; Dnm1; Fzo1; Mitochondria; Mitochondrial dynamics
  11. FASEB J. 2021 08;35(8): e21765
      The bioactive lipid intermediate palmitoyl CoA (PCoA) can inhibit mitochondrial ADP/ATP transport, though the physiological relevance of this regulation remains unclear. We questioned whether myocardial ischemia provides a pathological setting in which PCoA regulation of ADP/ATP transport would be beneficial, and secondly, whether the chronically elevated lipid content within the diabetic heart could make mitochondria less sensitive to the effects of PCoA. PCoA acutely decreased ADP-stimulated state 3 respiration and increased the apparent Km for ADP twofold. The half maximal inhibitory concentration (IC50 ) of PCoA in control mitochondria was 22 µM. This inhibitory effect of PCoA on respiration was blunted in diabetic mitochondria, with no significant difference in the Km for ADP in the presence of PCoA, and an increase in the IC50 to 32 µM PCoA. The competitive inhibition by PCoA was localised to the phosphorylation apparatus, particularly the ADP/ATP carrier (AAC). During ischemia, the AAC imports ATP into the mitochondria, where it is hydrolysed by reversal of the ATP synthase, regenerating the membrane potential. Addition of PCoA dose-dependently prevented this wasteful ATP hydrolysis for membrane repolarisation during ischemia, however, this beneficial effect was blunted in diabetic mitochondria. Finally, using 31 P-magnetic resonance spectroscopy we demonstrated that diabetic hearts lose ATP more rapidly during ischemia, with a threefold higher ATP decay rate compared with control hearts. In conclusion, PCoA plays a role in protecting mitochondrial energetics during ischemia, by preventing wasteful ATP hydrolysis. However, this beneficial effect is blunted in diabetes, contributing to the impaired energy metabolism seen during myocardial ischemia in the diabetic heart.
    Keywords:  diabetes; energetics; fatty acids; heart; ischemia; mitochondria
  12. Front Oncol. 2021 ;11 652008
      Abnormal metabolism serves a critical role in glioblastoma (GBM). Biochanin A (BCA), a flavonoid phenolic compound found in edible and herbal plants, has antioxidative and antitumor activities. However, it remains unclear whether BCA has an effect on energy metabolism. The aim of the present study was to evaluate the anticancer effects and molecular mechanism of the effect of BCA on energy metabolism. We observed that BCA inhibited the growth of U251 cells by the mitochondria-mediated intrinsic apoptotic pathway. BCA treatment reduced metabolic function, repressed mitochondrial membrane potential, and increased the production of reactive oxygen species (ROS) in GBM. In addition, we found that BCA decreased aerobic glycolysis by inactivation of the AKT/mTOR pathway. Taken together, the results demonstrate that treatment with BCA inhibited the proliferation of GBM by regulating metabolic reprogramming.
    Keywords:  biochanin A; energy metabolism; glioblastoma; proliferation; reactive oxygen species
  13. Asian Pac J Cancer Prev. 2021 Jul 01. pii: 89699. [Epub ahead of print]22(7): 2295-2302
      BACKGROUND: Glioblastoma is the most common primary malignant tumor of the central nervous system that occurs in the spinal cord or brain. Pseudosynanceia Melanostigma is a venomous stonefish in the Persian Gulf, which our knowledge about is little. This study's goal is to investigate the toxicity of stonefish crude venom on mitochondria isolated from U87 cells.METHODS: In the first stage, we extracted venom stonefish and then isolated mitochondria have exposed to different concentrations of venom. Finally, mitochondrial toxicity parameters (Succinate dehydrogenase (SDH) activity, Reactive oxygen species (ROS), cytochrome c release, Mitochondrial Membrane Potential (MMP), and mitochondrial swelling) have evaluated.
    RESULTS: To determine mitochondrial parameters, we used 115, 230, and 460 µg/ml concentrations. The results of our study show that the venom of stonefish selectively increases upstream parameters of apoptosis such as mitochondrial swelling, cytochrome c release, MMP collapse and ROS.
    CONCLUSION: This study suggests that Pseudosynanceia Melanostigma crude venom has selectively caused toxicity by increasing active mitochondrial oxygen radicals. This venom could potentially be a candidate for the treatment of glioblastoma.<br />.
    Keywords:  Anticancer; Glioblastoma; Pseudosynanceia Melanostigma; Stone fish venom; mitochondria
  14. Cell Death Dis. 2021 Jul 29. 12(8): 751
      POLRMT (RNA polymerase mitochondrial) is responsible for the transcription of mitochondrial genome encoding key components of oxidative phosphorylation. This process is important for cancer cell growth. The current study tested expression and potential functions of POLRMT in non-small cell lung cancer (NSCLC). TCGA cohorts and the results from the local lung cancer tissues showed that POLRMT is overexpressed in human lung cancer tissues. In both primary human NSCLC cells and A549 cells, POLRMT silencing (by targeted lentiviral shRNAs) or knockout (through CRSIPR/Cas9 gene editing method) potently inhibited cell viability, proliferation, migration, and invasion, and induced apoptosis activation. On the contrast, ectopic overexpression of POLRMT using a lentiviral construct accelerated cell proliferation and migration in NSCLC cells. The mtDNA contents, mRNA levels of mitochondrial transcripts, and subunits of respiratory chain complexes, as well as S6 phosphorylation, were decreased in POLRMT-silenced or -knockout NSCLC cells, but increased after ectopic POLRMT overexpression. In vivo, intratumoral injection of POLRMT shRNA adeno-associated virus (AAV) potently inhibited NSCLC xenograft growth in severe combined immune deficiency mice. The mtDNA contents, mRNA levels of mitochondria respiratory chain complex subunits, and S6 phosphorylation were decreased in POLRMT shRNA AAV-injected NSCLC xenograft tissues. These results show that POLRMT is a novel and important oncogene required for NSCLC cell growth in vitro and in vivo.
  15. Cell Rep. 2021 Jul 27. pii: S2211-1247(21)00882-2. [Epub ahead of print]36(4): 109459
      Active brown adipose tissue (BAT) consumes copious amounts of glucose, yet how glucose metabolism supports thermogenesis is unclear. By combining transcriptomics, metabolomics, and stable isotope tracing in vivo, we systematically analyze BAT glucose utilization in mice during acute and chronic cold exposure. Metabolite profiling reveals extensive temperature-dependent changes in the BAT metabolome and transcriptome upon cold adaptation, discovering unexpected metabolite markers of thermogenesis, including increased N-acetyl-amino acid production. Time-course stable isotope tracing further reveals rapid incorporation of glucose carbons into glycolysis and TCA cycle, as well as several auxiliary pathways, including NADPH, nucleotide, and phospholipid synthesis pathways. Gene expression differences inconsistently predict glucose fluxes, indicating that posttranscriptional mechanisms also govern glucose utilization. Surprisingly, BAT swiftly generates fatty acids and acyl-carnitines from glucose, suggesting that lipids are rapidly synthesized and immediately oxidized. These data reveal versatility in BAT glucose utilization, highlighting the value of an integrative-omics approach to understanding organ metabolism.
    Keywords:  BAT; brown adipocyte; brown adipose tissue; brown fat; glucose metabolism; lipid metabolism; metabolomics; stable isotope tracing; temperature acclimation; thermogenesis
  16. FASEB J. 2021 Aug;35(8): e21796
      Polycystin-1 (PC1) is a transmembrane protein found in different cell types, including cardiomyocytes. Alterations in PC1 expression have been linked to mitochondrial damage in renal tubule cells and in patients with autosomal dominant polycystic kidney disease. However, to date, the regulatory role of PC1 in cardiomyocyte mitochondria is not well understood. The analysis of mitochondrial morphology from cardiomyocytes of heterozygous PC1 mice (PDK1+/- ) using transmission electron microscopy showed that cardiomyocyte mitochondria were smaller with increased mitochondria density and circularity. These parameters were consistent with mitochondrial fission. We knocked-down PC1 in cultured rat cardiomyocytes and human-induced pluripotent stem cells (iPSC)-derived cardiomyocytes to evaluate mitochondrial function and morphology. The results showed that downregulation of PC1 expression results in reduced protein levels of sub-units of the OXPHOS complexes and less functional mitochondria (reduction of mitochondrial membrane potential, mitochondrial respiration, and ATP production). This mitochondrial dysfunction activates the elimination of defective mitochondria by mitophagy, assessed by an increase of autophagosome adapter protein LC3B and the recruitment of the Parkin protein to the mitochondria. siRNA-mediated PC1 knockdown leads to a loss of the connectivity of the mitochondrial network and a greater number of mitochondria per cell, but of smaller sizes, which characterizes mitochondrial fission. PC1 silencing also deregulates the AKT-FoxO1 signaling pathway, which is involved in the regulation of mitochondrial metabolism, mitochondrial morphology, and processes that are part of cell quality control, such as mitophagy. Together, these data provide new insights about the controls that PC1 exerts on mitochondrial morphology and function in cultured cardiomyocytes dependent on the AKT-FoxO1 signaling pathway.
    Keywords:  FoxO1; cardiomyocyte; mitochondrial dynamics; mitochondrial metabolism; mitophagy; polycystin-1
  17. Nat Commun. 2021 Jul 30. 12(1): 4626
      Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer that has remained clinically challenging to manage. Here we employ an RNAi-based in vivo functional genomics platform to determine epigenetic vulnerabilities across a panel of patient-derived PDAC models. Through this, we identify protein arginine methyltransferase 1 (PRMT1) as a critical dependency required for PDAC maintenance. Genetic and pharmacological studies validate the role of PRMT1 in maintaining PDAC growth. Mechanistically, using proteomic and transcriptomic analyses, we demonstrate that global inhibition of asymmetric arginine methylation impairs RNA metabolism, which includes RNA splicing, alternative polyadenylation, and transcription termination. This triggers a robust downregulation of multiple pathways involved in the DNA damage response, thereby promoting genomic instability and inhibiting tumor growth. Taken together, our data support PRMT1 as a compelling target in PDAC and informs a mechanism-based translational strategy for future therapeutic development.Statement of significancePDAC is a highly lethal cancer with limited therapeutic options. This study identified and characterized PRMT1-dependent regulation of RNA metabolism and coordination of key cellular processes required for PDAC tumor growth, defining a mechanism-based translational hypothesis for PRMT1 inhibitors.
  18. Chin J Cancer Res. 2021 Jun 30. 33(3): 308-322
      Objective: α-ketoglutarate (α-KG) is the substrate to hydroxylate collagen and hypoxia-inducible factor-1α (HIF-1α), which are important for cancer metastasis. Previous studies have shown that the upregulation of collagen prolyl 4-hydroxylase in breast cancer cells stabilizes the expression of HIF-1α by depleting α-KG levels. We hypothesized that mitochondrial malic enzyme 2 (ME2) might also affect HIF-1α expression via modulating α-KG levels in breast cancer cells.Methods: We evaluated ME2 protein expression in 100 breast cancer patients using immunohistochemistry and correlated with clinicopathological indicators. The effect of ME2 knockout on cancer metastasis was evaluated using an orthotopic breast cancer model. The effect of ME2 knockout or knockdown on the levels of α-KG and HIF-1α proteins in breast cancer cell lines was determined both in vitro and in vivo.
    Results: ME2 was found to be upregulated in the human breast cancerous tissues compared with the matched precancerous tissues (P<0.001). The elevated expression of ME2 was associated with a poor prognosis (P=0.019). ME2 upregulation was also related to lymph node metastasis (P=0.016), pathological staging (P=0.033), and vascular cancer embolus (P=0.014). Also, ME2 knockout significantly inhibited lung metastasisin vivo. In the tumors formed by ME2 knockout cells, the levels of α-KG were significantly increased and collagen hydroxylation level did not change significantly but HIF-1α protein expression was significantly decreased, compared to the control samples. In cell culture, cells with ME2 knockout or knockdown demonstrated significantly higher α-KG levels but significantly lower HIF-1α protein expression than control cells under hypoxia. Exogenous malate and α-KG exerted similar effect on HIF-1α in breast cancer cells to ME2 knockout or knockdown. Additionally, treatment with malate significantly decreased 4T1 breast cancer lung metastasis. ME2 expression was associated with HIF-1α levels in human breast cancer samples (P=0.008).
    Conclusions: Our results provide evidence that upregulation of ME2 is associated with a poor prognosis of breast cancer patients and propose a mechanistic understanding of a link between ME2 and breast cancer metastasis.
    Keywords:  Malic enzyme 2; breast cancer; hypoxia-inducible factor-1α; malate; metastasis; α-ketoglutarate
  19. Front Med (Lausanne). 2021 ;8 674986
      The mitochondrial calcium uniporter is an intensively investigated calcium channel, and its molecular components, structural features, and encoded genes have long been explored. Further studies have shown that the mitochondrial calcium unidirectional transporter (MCU) is a macromolecular complex related to intracellular and extracellular calcium regulation. Based on the current understanding, the MCU is crucial for maintaining cytosolic Ca2+ (cCa2+) homeostasis by modulating mitochondrial Ca2+ (mCa2+) uptake. The elevation of MCU-induced calcium levels is confirmed to be the main cause of mitochondrial reactive oxygen species (mROS) generation, which leads to disordered cellular metabolic patterns and cell death. In particular, in an I/R injury model, cancer cells, and adipocytes, MCU expression is maintained at high levels. As is well accepted, the AMPK/PGC-1α/SIRT3 pathway is believed to have an affinity for mROS formation and energy consumption. Therefore, we identified a link between MCU-related mROS formation and the AMPK/PGC-1α/SIRT3 signaling pathway in controlling cell metabolism and cell death, which may provide a new possibility of targeting the MCU to reverse relevant diseases.
    Keywords:  AMPK/PGC-1α/SIRT3; cell death; metabolism; mitochondrial calcium uniporter; mitochondrial reactive oxygen species
  20. mBio. 2021 Jul 27. e0124721
      Monocytes play an important role in the host defense against Plasmodium vivax as the main source of inflammatory cytokines and mitochondrial reactive oxygen species (mROS). Here, we show that monocyte metabolism is altered during human P. vivax malaria, with mitochondria playing a major function in this switch. The process involves a reprograming in which the cells increase glucose uptake and produce ATP via glycolysis instead of oxidative phosphorylation. P. vivax infection results in dysregulated mitochondrial gene expression and in altered membrane potential leading to mROS increase rather than ATP production. When monocytes were incubated with P. vivax-infected reticulocytes, mitochondria colocalized with phagolysosomes containing parasites representing an important source mROS. Importantly, the mitochondrial enzyme superoxide dismutase 2 (SOD2) is simultaneously induced in monocytes from malaria patients. Taken together, the monocyte metabolic reprograming with an increased mROS production may contribute to protective responses against P. vivax while triggering immunomodulatory mechanisms to circumvent tissue damage. IMPORTANCE Plasmodium vivax is the most widely distributed causative agent of human malaria. To achieve parasite control, the human immune system develops a substantial inflammatory response that is also responsible for the symptoms of the disease. Among the cells involved in this response, monocytes play an important role. Here, we show that monocyte metabolism is altered during malaria, with its mitochondria playing a major function in this switch. This change involves a reprograming process in which the cells increase glucose uptake and produce ATP via glycolysis instead of oxidative phosphorylation. The resulting altered mitochondrial membrane potential leads to an increase in mitochondrial reactive oxygen species rather than ATP. These data suggest that agents that change metabolism should be investigated and used with caution during malaria.
    Keywords:  P. vivax; malaria; metabolism; mitochondria; mitochondrial metabolism; monocytes; reactive oxygen species
  21. Sci Rep. 2021 Jul 29. 11(1): 15471
      Oxidative stress and reactive oxygen species (ROS) are central to many physiological and pathophysiological processes. However, due to multiple technical challenges, it is hard to capture a comprehensive readout of the cell, involving both biochemical and functional status. We addressed this problem by developing a fully parallelized workflow for metabolomics (providing absolute quantities for > 100 metabolites including TCA cycle, pentose phosphate pathway, purine metabolism, glutathione metabolism, cysteine and methionine metabolism, glycolysis and gluconeogenesis) and live cell imaging microscopy. The correlative imaging strategy was applied to study morphological and metabolic adaptation of cancer cells upon short-term hydrogen peroxide (H2O2) exposure in vitro. The combination provided rich metabolic information at the endpoint of exposure together with imaging of mitochondrial effects. As a response, superoxide concentrations were elevated with a strong mitochondrial localization, and multi-parametric image analysis revealed a shift towards fragmentation. In line with this, metabolism reflected both the impaired mitochondrial function and shifts to support the first-line cellular defense and compensate for energy loss. The presented workflow combining high-end technologies demonstrates the applicability for the study of short-term oxidative stress, but it can be suitable for the in-depth study of various short-term oxidative and other cellular stress-related phenomena.
  22. EMBO J. 2021 Jul 26. e107336
      During tumor growth-when nutrient and anabolic demands are high-autophagy supports tumor metabolism and growth through lysosomal organelle turnover and nutrient recycling. Ras-driven tumors additionally invoke non-autonomous autophagy in the microenvironment to support tumor growth, in part through transfer of amino acids. Here we uncover a third critical role of autophagy in mediating systemic organ wasting and nutrient mobilization for tumor growth using a well-characterized malignant tumor model in Drosophila melanogaster. Micro-computed X-ray tomography and metabolic profiling reveal that RasV12 ; scrib-/- tumors grow 10-fold in volume, while systemic organ wasting unfolds with progressive muscle atrophy, loss of body mass, -motility, -feeding, and eventually death. Tissue wasting is found to be mediated by autophagy and results in host mobilization of amino acids and sugars into circulation. Natural abundance Carbon 13 tracing demonstrates that tumor biomass is increasingly derived from host tissues as a nutrient source as wasting progresses. We conclude that host autophagy mediates organ wasting and nutrient mobilization that is utilized for tumor growth.
    Keywords:   Drosophila ; autophagy; cancer cachexia; muscle; tumor; wasting
  23. Aging Cell. 2021 Jul 27. e13444
      The nuclear factor-erythroid 2-related factor-2 (Nrf2), a major antioxidant transcription factor, is decreased in several age-related diseases including age-related macular degeneration (AMD), the most common cause of blindness among the elderly in western society. Since Nrf2's mito-protective response is understudied, we investigated its antioxidant response on mitochondria. Control and Nrf2-deficient retinal pigmented epithelial (RPE) cells were compared after treating with cigarette smoke extract (CSE). Mitochondrial antioxidant abundance and reactive oxygen species (ROS) were quantified. Mitochondrial function was assessed by TMRM assay, NADPH, electron transport chain activity, and Seahorse. Results were corroborated in Nrf2-/- mice and relevance to AMD was provided by immunohistochemistry of human globes. CSE induced mitochondrial ROS to impair mitochondrial function. H2 O2 increase in particular, was magnified by Nrf2 deficiency, and corresponded with exaggerated mitochondrial dysfunction. While Nrf2 did not affect mitochondrial antioxidant abundance, oxidized PRX3 was magnified by Nrf2 deficiency due to decreased NADPH from decreased expression of IDH2 and pentose phosphate pathway (PPP) genes. With severe CSE stress, intrinsic apoptosis was activated to increase cell death. PPP component TALDO1 immunolabeling was decreased in dysmorphic RPE of human AMD globes. Despite limited regulation of mitochondrial antioxidant expression, Nrf2 influences PPP and IDH shuttle activity that indirectly supplies NADPH for the TRX2 system. These results provide insight into how Nrf2 deficiency impacts the mitochondrial antioxidant response, and its role in AMD pathobiology.
    Keywords:  aging; mitochondria; oxidative stress; reactive oxygen species
  24. Mol Cancer Res. 2021 Jul 26. pii: molcanres.MCR-21-0098-E.2021. [Epub ahead of print]
      MicroRNA-200c (miR-200c) is a tumor suppressor microRNA that plays a critical role in regulating epithelial phenotype and cancer stemness. p53 deficiency downregulates the expression of miR-200c and leads to epithelial-mesenchymal transition (EMT) and stemness phenotype, which contributes to the progression of breast cancers. In this study, we demonstrated that CRISPR-mediated knockout of miR-200c induces metabolic features similar to the metabolic rewiring caused by p53 hot-spot mutations, and that impairing this metabolic reprogramming interferes with miR-200c deficiency-induced stemness and transformation. Moreover, restoring miR-200c expression compromised EMT, stem cell properties, and the Warburg effect caused by p53 mutations, suggesting that mutant p53 induces EMT-associated phenotypes and metabolic reprogramming by downregulating miR-200c. Mechanistically, decreased expression of PCK2 was observed in miR-200c- and p53-deficient mammary epithelial cells, and forced expression of miR-200c restored PCK2 in p53 mutant-expressing cells. Reduced PCK2 expression not only led to attenuated oxidative phosphorylation (OXPHOS) and increased stemness in normal mammary epithelial cells but also compromised the enhanced OXPHOS and suppression of cancer stemness exerted by miR-200c in p53 mutation-bearing basal-like breast cancer (BLBC) cells. Clinically, PCK2 expression is negatively associated with EMT markers and is downregulated in basal-like subtype and cases with low miR-200c expression or p53 mutation. Notably, low expression of PCK2 is associated with poor overall survival in breast cancer patient. Implications: Together, our results suggest that p53 and miR-200c regulate OXPHOS and stem/cancer stemness through PCK2, and loss of the p53-miR-200c-PCK2 axis might provide metabolic advantages that facilitate cancer stemness, leading to the progression of BLBCs.
  25. Sci Rep. 2021 Jul 30. 11(1): 15510
      Ischemia is a major cause of kidney damage. Proximal tubular epithelial cells (PTECs) are highly susceptible to ischemic insults that frequently cause acute kidney injury (AKI), a potentially life-threatening condition with high mortality. Accumulating evidence has identified altered mitochondrial function as a central pathologic feature of AKI. The mitochondrial NAD+-dependent enzyme sirtuin 5 (SIRT5) is a key regulator of mitochondrial form and function, but its role in ischemic renal injury (IRI) is unknown. SIRT5 expression was increased in murine PTECs after IRI in vivo and in human PTECs (hPTECs) exposed to an oxygen/nutrient deprivation (OND) model of IRI in vitro. SIRT5-depletion impaired ATP production, reduced mitochondrial membrane potential, and provoked mitochondrial fragmentation in hPTECs. Moreover, SIRT5 RNAi exacerbated OND-induced mitochondrial bioenergetic dysfunction and swelling, and increased degradation by mitophagy. These findings suggest SIRT5 is required for normal mitochondrial function in hPTECs and indicate a potentially important role for the enzyme in the regulation of mitochondrial biology in ischemia.
  26. ACS Appl Mater Interfaces. 2021 Jul 26.
      Targeted therapies of melanoma are of urgent need considering the resistance of this aggressive type of cancer to chemotherapeutics. The voltage-dependent anion channel 1 (VDAC1)-hexokinase-II (HK-II) complex is an emerging target for novel anticancer therapies based on induced mitochondria-mediated apoptosis. The low cell membrane permeability of the anticancer 12-mer peptide N-Ter (RDVFTKGYGFGL) derived from the N-terminal fragment of the VDAC1 protein impedes the intracellular targeting. Here, novel multiblock VDAC1-derived cationic amphiphilic peptides (referred to as Pal-N-Ter-TAT, pFL-N-Ter-TAT, and Pal-pFL-N-Ter-TAT) are designed with a self-assembly propensity and cell-penetrating properties. The created multiblock amphiphilic peptides of partial α-helical conformations form nanoparticles of ellipsoid-like shapes and are characterized by enhanced cellular uptake. The amphiphilic peptides can target mitochondria and dissociate the VDAC1-HK-II complex at the outer mitochondrial membrane, which result in mitochondria-mediated apoptosis. The latter is associated with decrease of the mitochondrial membrane potential, cytochrome c release, and changes of the expression levels of the apoptotic proteins in A375 melanoma cells. Importantly, the mitochondrial VDAC1-derived amphiphilic peptides have a comparable IC50 value for melanoma cells to a small-molecule drug, sorafenib, which has been previously used in clinical trials for melanoma. These results demonstrate the potential of the designed peptide constructs for efficient melanoma inhibition.
    Keywords:  VDAC1-derived amphiphilic peptides; cell-penetrating peptides (CPP); human melanoma cells; mitochondria-mediated apoptosis; protein−protein interaction inhibition; self-assembly; targeting VDAC1−HK-II complex
  27. Mol Carcinog. 2021 Jul 29.
      Rohitukine, a chromone alkaloid extracted from Dysoxylum binectariferum, has a propitious anticancer activity. Our previous study shows that a new Rohitukine derivative IIIM-290 restricts the growth of pancreatic cancer in vivo and in vitro. In the present findings, we report the mechanism of cell death induced by IIIM-290 in MOLT-4 cells (acute lymphoblastic leukemia) and its anticancer potential against various murine leukemic tumor models in vivo. We found that IIIM-290 induced apoptosis through upregulation of different apoptotic proteins like PUMA, BAX, cytochrome c, cleaved (active) caspase-3, and cleaved PARP in MOLT-4 cells. Moreover, IIIM-290 abated mitochondrial membrane potential, elevated calcium levels, reactive oxygen species, and arrested growth of MOLT-4 cells in the synthesis (S) phase of the cell cycle. Interestingly, the elevation in proapoptotic markers was p53 dependent-the silencing of p53 abrogated apoptosis (programmed cell death) triggered by IIIM-290 in MOLT-4 cells. Furthermore, IIIM-290 significantly enhanced the survival of animals with P388 and L1210 leukemia. Thus, our results put IIIM-290 as a potential candidate for the anticancer lead.
    Keywords:  CDK-9; L1210; MOLT-4; P388; apoptosis
  28. Cell Death Dis. 2021 Jul 27. 12(8): 741
      Conventional chemotherapy is still of great utility in oncology and rationally constructing combinations with it remains a top priority. Drug-induced mitochondrial apoptotic priming, measured by dynamic BH3 profiling (DBP), has been shown in multiple cancers to identify drugs that promote apoptosis in vivo. We therefore hypothesized that we could use DBP to identify drugs that would render cancers more sensitive to conventional chemotherapy. We found that targeted agents that increased priming of non-small cell lung cancer (NSCLC) tumor cells resulted in increased sensitivity to chemotherapy in vitro. To assess whether targeted agents that increase priming might enhance the efficacy of cytotoxic agents in vivo as well, we carried out an efficacy study in a PC9 xenograft mouse model. The BH3 mimetic navitoclax, which antagonizes BCL-xL, BCL-w, and BCL-2, consistently primed NSCLC tumors in vitro and in vivo. The BH3 mimetic venetoclax, which electively antagonizes BCL-2, did not. Combining navitoclax with etoposide significantly reduced tumor burden compared to either single agent, while adding venetoclax to etoposide had no effect on tumor burden. Next, we assessed priming of primary patient NSCLC tumor cells on drugs from a clinically relevant oncology combination screen (CROCS). Results confirmed for the first time the utility of BCL-xL inhibition by navitoclax in priming primary NSCLC tumor cells and identified combinations that primed further. This is a demonstration of the principle that DBP can be used as a functional precision medicine tool to rationally construct combination drug regimens that include BH3 mimetics in solid tumors like NSCLC.
  29. Mitochondrion. 2021 Jul 21. pii: S1567-7249(21)00097-0. [Epub ahead of print]
      We investigated the concordance of mitochondrial DNA heteroplasmic mutations (heteroplasmies) in 6,745 maternal pairs of European (EA, n=4,718 pairs) and African (AA, n=2,027 pairs) Americans in whole blood. Mother-offspring pairs displayed the highest concordance rate, followed by sibling-sibling and more distantly-related maternal pairs. The allele fractions of concordant heteroplasmies exhibited high correlation (R2=0.8) between paired individuals. Discordant heteroplasmies were more likely to be in coding regions, be nonsynonymous or nonsynonymous-deleterious (p<0.001). The number of deleterious heteroplasmies was significantly correlated with advancing age (20-44, 45-64, and ≥65 years, p-trend=0.01). One standard deviation increase in heteroplasmic burden (i.e., the number of heteroplasmies carried by an individual) was associated with 0.17 to 0.26 (p<1e-23) standard deviation decrease in mtDNA copy number, independent of age. White blood cell count and differential count jointly explained 0.5% to 1.3% (p≤0.001) variance in heteroplasmic burden. A genome-wide association and meta-analysis identified a region at 11p11.12 (top signal rs779031139, p=2.0e-18, minor allele frequency=0.38) associated with the heteroplasmic burden. However, the 11p11.12 region is adjacent to a nuclear mitochondrial DNA (NUMT) corresponding to a 542 bp area of the D-loop. This region was no longer significant after removing heteroplasmic mutations within the 542 bp from the heteroplasmic burden. The discovery that blood mtDNA heteroplasmic mutations were both inherited and somatic origins and that an increase in heteroplasmic burden was strongly associated with a decrease in average number of mtDNA copy number in blood are important findings to be considered in association studies of mtDNA with disease traits.
  30. BMC Cancer. 2021 Jul 28. 21(1): 863
      BACKGROUND: Cell-to-cell fusion is emerging as a key element of the metastatic process in various cancer types. We recently showed that hybrids made from the spontaneous merging of pre-malignant (IMR90 E6E7, i.e. E6E7) and malignant (IMR90 E6E7 RST, i.e. RST) mesenchymal cells recapitulate the main features of human undifferentiated pleomorphic sarcoma (UPS), with a highly rearranged genome and increased spreading capacities. To better characterize the intrinsic properties of these hybrids, we investigated here their metabolic energy profile compared to their parents.RESULTS: Our results unveiled that hybrids harbored a Warburg-like metabolism, like their RST counterparts. However, hybrids displayed a much greater metabolic activity, enhancing glycolysis to proliferate. Interestingly, modifying the metabolic environmental conditions through the use of 5-aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR), an activator of the 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK), specifically reduced the growth of hybrids, and also abrogated the invasive capacity of hybrids displaying enhanced glycolysis. Furthermore, AICAR efficiently blocked the tumoral features related to the aggressiveness of human UPS cell lines.
    CONCLUSION: Altogether, our findings strongly suggest that hybrids rely on higher energy flux to proliferate and that a drug altering this metabolic equilibrium could impair their survival and be potentially considered as a novel therapeutic strategy.
    Keywords:  AICAR; AMPK; Cell fusion; Energy metabolism; Invasion
  31. Nat Commun. 2021 Jul 30. 12(1): 4651
      The integrated stress response (ISR) is an essential stress-support pathway increasingly recognized as a determinant of tumorigenesis. Here we demonstrate that ISR is pivotal in lung adenocarcinoma (LUAD) development, the most common histological type of lung cancer and a leading cause of cancer death worldwide. Increased phosphorylation of the translation initiation factor eIF2 (p-eIF2α), the focal point of ISR, is related to invasiveness, increased growth, and poor outcome in 928 LUAD patients. Dissection of ISR mechanisms in KRAS-driven lung tumorigenesis in mice demonstrated that p-eIF2α causes the translational repression of dual specificity phosphatase 6 (DUSP6), resulting in increased phosphorylation of the extracellular signal-regulated kinase (p-ERK). Treatments with ISR inhibitors, including a memory-enhancing drug with limited toxicity, provides a suitable therapeutic option for KRAS-driven lung cancer insofar as they substantially reduce tumor growth and prolong mouse survival. Our data provide a rationale for the implementation of ISR-based regimens in LUAD treatment.
  32. Biomed Pharmacother. 2020 Oct;pii: S0753-3322(20)30708-3. [Epub ahead of print]130 110515
      PURPOSE: This paper concerns the cytotoxicity of 9-chloro-1-nitroacridine (1a) and 9-chloro-4-methyl-1-nitroacridine (1b) against two biologically different melanoma forms: melanotic and amelanotic. Melanomas are tumors characterized by high heterogeneity and poor susceptibility to chemotherapies. Among new analogs synthesized by us, compound 1b exhibited the highest anticancer potency. Because of that, in this study, we analyzed the mechanism of action for 1a and its 4-methylated derivative, 1b, against a pair of biological melanoma forms, with regard to proliferation, cell death mechanism and energetic state.METHODS: Cytotoxicity was evaluated by XTT assay. Cell death was estimated by plasma membrane structure changes (phosphatidylserine externalization), caspase activation, and ROS presence. The energetic state of cells was estimated based on NAD and ATP levels, and the activity of tricarboxylic acid cycle enzymes (pyruvate dehydrogenase complex, aconitase, isocitrate dehydrogenase).
    RESULTS: The chloroacridines affect biological forms of melanoma in different ways. Amelanotic (Ab) melanoma (with inhibited melanogenesis and higher malignancy) was particularly sensitive to the action of the chloroacridines. The Ab melanoma cells died through apoptosis and through death without caspase activation. Diminished activity of TAC enzymes was noticed among Ab melanoma cells together with ATP/NAD depletion, especially in the case of 1b.
    CONCLUSION: Our data show that the biological forms of the tumors responded to 1a and its 4-methylated analog in different ways. 1a and 1b could be inducers of regulated melanoma cell death, especially the amelanotic form. Although the mechanism of the cell death is not fully understood, 1b may act by interfering with the TAC enzymes and blocking specific pathways leading to tumor growth. This could encourage further investigation of its anticancer activity, especially against the amelanotic form of melanoma.
    Keywords:  Amelanotic melanoma; Apoptosis; Cell death; Chloroacridine; Melanotic melanoma; Tricarboxylic acid cycle enzymes
  33. Dis Markers. 2021 ;2021 7675269
      Cancer is a heterogeneous group of diseases, the progression of which demands an accumulation of genetic mutations and epigenetic alterations of the human nuclear genome or possibly in the mitochondrial genome as well. Despite modern diagnostic and therapeutic approaches to battle cancer, there are still serious concerns about the increase in death from cancer globally. Recently, a growing number of researchers have extensively focused on the burgeoning area of biomarkers development research, especially in noninvasive early cancer detection. Intergenomic cross talk has triggered researchers to expand their studies from nuclear genome-based cancer researches, shifting into the mitochondria-mediated associations with carcinogenesis. Thus, it leads to the discoveries of established and potential mitochondrial biomarkers with high specificity and sensitivity. The research field of mitochondrial DNA (mtDNA) biomarkers has the great potential to confer vast benefits for cancer therapeutics and patients in the future. This review seeks to summarize the comprehensive insights of nuclear genome cancer biomarkers and their usage in clinical practices, the intergenomic cross talk researches that linked mitochondrial dysfunction to carcinogenesis, and the current progress of mitochondrial cancer biomarker studies and development.
  34. Cancer Lett. 2021 Jul 22. pii: S0304-3835(21)00352-9. [Epub ahead of print]518 230-242
      Fascin is a pro-metastatic actin-bundling protein that is upregulated in all metastatic carcinomas. Fascin promotes cancer cell migration and invasion by facilitating membrane protrusions, such as filopodia and invadopodia. Aerobic glycolysis is a key feature of cancer metabolism and provides critical intermediate metabolites for tumor growth. Here, we report that fascin increases glycolysis in lung cancer to promote tumor growth and metastasis. Fascin promotes glycolytic flux by increasing the expression and activities of phosphofructose-kinases 1 and 2 (PFK1 and 2). Fascin mediates glycolytic functions via activation of yes-associated protein 1 (YAP1) through its canonical actin-bundling activity by promoting the binding of YAP1 to a TEAD1/4 binding motif located 30 bp upstream of the PFKFB3 transcription start site to activate its transcription. Examination of the TCGA database suggests that the fascin-YAP1-PFKFB3 axis is likely conserved across different types of cancers. Importantly, pharmacological inhibitors of fascin suppressed YAP1-PFKFB3 signaling and glycolysis in cancer cell lines, organoid cultures, and xenograft metastasis models. Taken together, our data reveal that the glycolytic function of fascin is essential for the promotion of lung cancer growth and metabolism, and suggest that pharmacological inhibitors of fascin may be used to reprogram cancer metabolism in lung and potentially other cancers with fascin upregulation.
    Keywords:  Fascin inhibitor; Metabolism; YAP1
  35. Nat Commun. 2021 07 28. 12(1): 4583
      Voltage dependent anion channel 2 (VDAC2) is an outer mitochondrial membrane porin known to play a significant role in apoptosis and calcium signaling. Abnormalities in calcium homeostasis often leads to electrical and contractile dysfunction and can cause dilated cardiomyopathy and heart failure. However, the specific role of VDAC2 in intracellular calcium dynamics and cardiac function is not well understood. To elucidate the role of VDAC2 in calcium homeostasis, we generated a cardiac ventricular myocyte-specific developmental deletion of Vdac2 in mice. Our results indicate that loss of VDAC2 in the myocardium causes severe impairment in excitation-contraction coupling by altering both intracellular and mitochondrial calcium signaling. We also observed adverse cardiac remodeling which progressed to severe cardiomyopathy and death. Reintroduction of VDAC2 in 6-week-old knock-out mice partially rescued the cardiomyopathy phenotype. Activation of VDAC2 by efsevin increased cardiac contractile force in a mouse model of pressure-overload induced heart failure. In conclusion, our findings demonstrate that VDAC2 plays a crucial role in cardiac function by influencing cellular calcium signaling. Through this unique role in cellular calcium dynamics and excitation-contraction coupling VDAC2 emerges as a plausible therapeutic target for heart failure.
  36. MedComm (Beijing). 2020 Dec;1(3): 328-337
      Bcl-xL, an antiapoptotic protein, is frequently overexpressed in cancer to promote survival of tumor cells. However, we have previously shown that Bcl-xL promotes migration, invasion, and metastasis independent of its antiapoptotic function in mitochondria. The pro-metastatic function of Bcl-xL may require its translocation into the nucleus. Besides overexpression, patient-associated mutations of Bcl-xL have been identified in large-scale cancer genomics projects. Understanding the functions of these mutations will guide the development of precision medicine. Here, we selected four patient-associated Bcl-xL mutations, R132W, N136K, R165W, and A201T, to investigate their impacts on antiapoptosis, migration, and nuclear translocation. We found that all four mutation proteins could be detected in both the nucleus and cytosol. Although all four mutations disrupted the antiapoptosis function, one of these mutants, N136K, significantly improved the ability to promote cell migration. These data suggest the importance of developing novel Bcl-xL inhibitors to ablate both antiapoptotic and pro-metastatic functions of Bcl-xL in cancer.
    Keywords:  Bcl-xL; antiapoptosis; migration; mutations; nucleus
  37. Nat Commun. 2021 07 28. 12(1): 4579
      There is evidence that diet and nutrition are modifiable risk factors for several cancers, but associations may be flawed due to inherent biases. Nutritional epidemiology studies have largely relied on a single assessment of diet using food frequency questionnaires. We conduct an umbrella review of meta-analyses of observational studies to evaluate the strength and validity of the evidence for the association between food/nutrient intake and risk of developing or dying from 11 primary cancers. It is estimated that only few single food/nutrient and cancer associations are supported by strong or highly suggestive meta-analytic evidence, and future similar research is unlikely to change this evidence. Alcohol consumption is positively associated with risk of postmenopausal breast, colorectal, esophageal, head & neck and liver cancer. Consumption of dairy products, milk, calcium and wholegrains are inversely associated with colorectal cancer risk. Coffee consumption is inversely associated with risk of liver cancer and skin basal cell carcinoma.