Stomatin-Like Protein 2 Binds Cardiolipin and Regulates Mitochondrial Biogenesis and Function▿

PubMed Central

Christie, Darah A.; Lemke, Caitlin D.; Elias, Isaac M.; Chau, Luan A.; Kirchhof, Mark G.; Li, Bo; Ball, Eric H.; Dunn, Stanley D.; Hatch, Grant M.; Madrenas, Joaquín

2011-01-01

Stomatin-like protein 2 (SLP-2) is a widely expressed mitochondrial inner membrane protein of unknown function. Here we show that human SLP-2 interacts with prohibitin-1 and -2 and binds to the mitochondrial membrane phospholipid cardiolipin. Upregulation of SLP-2 expression increases cardiolipin content and the formation of metabolically active mitochondrial membranes and induces mitochondrial biogenesis. In human T lymphocytes, these events correlate with increased complex I and II activities, increased intracellular ATP stores, and increased resistance to apoptosis through the intrinsic pathway, ultimately enhancing cellular responses. We propose that the function of SLP-2 is to recruit prohibitins to cardiolipin to form cardiolipin-enriched microdomains in which electron transport complexes are optimally assembled. Likely through the prohibitin functional interactome, SLP-2 then regulates mitochondrial biogenesis and function. PMID:21746876

Strenuous exercise induces mitochondrial damage in skeletal muscle of old mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Sangho; Kim, Minjung; Lim, Wonchung

Strenuous exercise is known to cause excessive ROS generation and inflammation. However, the mechanisms responsible for the regulation of mitochondrial integrity in the senescent muscle during high-intensity exercise (HE) are not well studied. Here, we show that HE suppresses up-regulation of mitochondrial function despite increase in mitochondrial copy number, following excessive ROS production, proinflammatory cytokines and NFκB activation. Moreover, HE in the old group resulted in the decreasing of both fusion (Mfn2) and fission (Drp1) proteins that may contribute to alteration of mitochondrial morphology. This study suggests that strenuous exercise does not reverse age-related mitochondrial damage and dysfunction by themore » increased ROS and inflammation. - Highlights: • Effect of exercise on mitochondrial function of aged skeletal muscles was studied. • Strenuous exercise triggered excessive ROS production and inflammatory cytokines. • Strenuous exercise suppressed mitochondrial function in senescent muscle.« less

Mitochondrial O-GlcNAc Transferase (mOGT) Regulates Mitochondrial Structure, Function, and Survival in HeLa Cells*

PubMed Central

Sacoman, Juliana L.; Dagda, Raul Y.; Burnham-Marusich, Amanda R.; Dagda, Ruben K.; Berninsone, Patricia M.

2017-01-01

O-Linked N-acetylglucosamine transferase (OGT) catalyzes O-GlcNAcylation of target proteins and regulates numerous biological processes. OGT is encoded by a single gene that yields nucleocytosolic and mitochondrial isoforms. To date, the role of the mitochondrial isoform of OGT (mOGT) remains largely unknown. Using high throughput proteomics, we identified 84 candidate mitochondrial glycoproteins, of which 44 are novel. Notably, two of the candidate glycoproteins identified (cytochrome oxidase 2 (COX2) and NADH:ubiquinone oxidoreductase core subunit 4 (MT-ND4)) are encoded by mitochondrial DNA. Using siRNA in HeLa cells, we found that reducing endogenous mOGT expression leads to alterations in mitochondrial structure and function, including Drp1-dependent mitochondrial fragmentation, reduction in mitochondrial membrane potential, and a significant loss of mitochondrial content in the absence of mitochondrial ROS. These defects are associated with a compensatory increase in oxidative phosphorylation per mitochondrion. mOGT is also critical for cell survival; siRNA-mediated knockdown of endogenous mOGT protected cells against toxicity mediated by rotenone, a complex I inhibitor. Conversely, reduced expression of both nucleocytoplasmic (ncOGT) and mitochondrial (mOGT) OGT isoforms is associated with increased mitochondrial respiration and elevated glycolysis, suggesting that ncOGT is a negative regulator of cellular bioenergetics. Last, we determined that mOGT is probably involved in the glycosylation of a restricted set of mitochondrial targets. We identified four proteins implicated in mitochondrial biogenesis and metabolism regulation as candidate substrates of mOGT, including leucine-rich PPR-containing protein and mitochondrial aconitate hydratase. Our findings suggest that mOGT is catalytically active in vivo and supports mitochondrial structure, health, and survival, whereas ncOGT predominantly regulates cellular bioenergetics. PMID:28100784

The dynamic regulation of NAD metabolism in mitochondria

PubMed Central

Stein, Liana Roberts; Imai, Shin-ichiro

2012-01-01

Mitochondria are intracellular powerhouses that produce ATP and carry out diverse functions for cellular energy metabolism. While the maintenance of an optimal NAD/NADH ratio is essential for mitochondrial function, it has recently become apparent that the maintenance of the mitochondrial NAD pool also has critical importance. The biosynthesis, transport, and catabolism of NAD and its key intermediates play an important role in the regulation of NAD-consuming mediators, such as sirtuins, poly-ADP-ribose polymerases, and CD38/157 ectoenzymes, in intra- and extracellular compartments. Mitochondrial NAD biosynthesis is also modulated in response to nutritional and environmental stimuli. In this article, we discuss this dynamic regulation of NAD metabolism in mitochondria to shed light on the intimate connection between NAD and mitochondrial function. PMID:22819213

Mitochondrial dynamics regulate melanogenesis through proteasomal degradation of MITF via ROS-ERK activation.

PubMed

Kim, Eun Sung; Park, So Jung; Goh, Myeong-Jin; Na, Yong-Joo; Jo, Doo Sin; Jo, Yoon Kyung; Shin, Ji Hyun; Choi, Eun Sun; Lee, Hae-Kwang; Kim, Ju-Yeon; Jeon, Hong Bae; Kim, Jin Cheon; Cho, Dong-Hyung

2014-11-01

Mitochondrial dynamics control mitochondrial functions as well as their morphology. However, the role of mitochondrial dynamics in melanogenesis is largely unknown. Here, we show that mitochondrial dynamics regulate melanogenesis by modulating the ROS-ERK signaling pathway. Genetic and chemical inhibition of Drp1, a mitochondrial fission protein, increased melanin production and mitochondrial elongation in melanocytes and melanoma cells. In contrast, down-regulation of OPA1, a mitochondria fusion regulator, suppressed melanogensis but induced massive mitochondrial fragmentation in hyperpigmented cells. Consistently, treatment with CCCP, a mitochondrial fission chemical inducer, also efficiently repressed melanogenesis. Furthermore, we found that ROS production and ERK phosphorylation were increased in cells with fragmented mitochondria. And inhibition of ROS or ERK suppressed the antimelanogenic effect of mitochondrial fission in α-MSH-treated cells. In addition, the activation of ROS-ERK pathway by mitochondrial fission induced phosphorylation of serine73 on MITF accelerating its proteasomal degradation. In conclusion, mitochondrial dynamics may regulate melanogenesis by modulating ROS-ERK signaling pathway. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Mitochondrial Ca2+ and membrane potential, an alternative pathway for Interleukin 6 to regulate CD4 cell effector function

PubMed Central

Yang, Rui; Lirussi, Dario; Thornton, Tina M; Jelley-Gibbs, Dawn M; Diehl, Sean A; Case, Laure K; Madesh, Muniswamy; Taatjes, Douglas J; Teuscher, Cory; Haynes, Laura; Rincón, Mercedes

2015-01-01

IL-6 plays an important role in determining the fate of effector CD4 cells and the cytokines that these cells produce. Here we identify a novel molecular mechanism by which IL-6 regulates CD4 cell effector function. We show that IL-6-dependent signal facilitates the formation of mitochondrial respiratory chain supercomplexes to sustain high mitochondrial membrane potential late during activation of CD4 cells. Mitochondrial hyperpolarization caused by IL-6 is uncoupled from the production of ATP by oxidative phosphorylation. However, it is a mechanism to raise the levels of mitochondrial Ca2+ late during activation of CD4 cells. Increased levels of mitochondrial Ca2+ in the presence of IL-6 are used to prolong Il4 and Il21 expression in effector CD4 cells. Thus, the effect of IL-6 on mitochondrial membrane potential and mitochondrial Ca2+ is an alternative pathway by which IL-6 regulates effector function of CD4 cells and it could contribute to the pathogenesis of inflammatory diseases. DOI: http://dx.doi.org/10.7554/eLife.06376.001 PMID:25974216

Analysis of functional domains of rat mitochondrial Fis1, the mitochondrial fission-stimulating protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jofuku, Akihiro; Ishihara, Naotada; Mihara, Katsuyoshi

2005-07-29

In yeast, mitochondrial-fission is regulated by the cytosolic dynamin-like GTPase (Dnm1p) in conjunction with a peripheral protein, Mdv1p, and a C-tail-anchored outer membrane protein, Fis1p. In mammals, a dynamin-related protein (Drp1) and Fis1 are involved in the mitochondrial-fission reaction as Dnm1 and Fis1 orthologues, respectively. The involvement of other component(s), such as the Mdv1 homologue, and the mechanisms regulating mitochondrial-fission remain unclear. Here, we identified rat Fis1 (rFis1) and analyzed its structure-function relationship. Blue-native-polyacrylamide gel electrophoresis revealed that rFis1 formed a {approx}200-kDa complex in the outer mitochondrial membrane. Its expression in HeLa cells promoted extensive mitochondrial fragmentation, and gene knock-downmore » by RNAi induced extension of the mitochondrial networks. Taking advantage of these properties, we analyzed functional domains of rFis1. These experiments revealed that the N-terminal and C-terminal segments are both essential for oligomeric rFis1 interaction, and the middle TPR-like domains regulate proper oligomer assembly. Any mutations that disturb the proper oligomeric assembly compromise mitochondrial division-stimulating activity of rFis1.« less

Lipoic acid metabolism and mitochondrial redox regulation.

PubMed

Solmonson, Ashley D; DeBerardinis, Ralph J

2017-11-30

Lipoic acid is an essential cofactor for mitochondrial metabolism and is synthesized de novo using intermediates from mitochondrial fatty acid synthesis type II, S-adenosylmethionine and iron-sulfur clusters. This cofactor is required for catalysis by multiple mitochondrial 2-ketoacid dehydrogenase complexes, including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase. Lipoic acid also plays a critical role in stabilizing and regulating these multi-enzyme complexes.  Many of these dehydrogenases are regulated by reactive oxygen species, mediated through the disulfide bond of the prosthetic lipoyl moiety.  Collectively, its functions explain why lipoic acid is required for cell growth, mitochondrial activity and coordination of fuel metabolism. Lipoic acid is an essential cofactor for mitochondrial metabolism and is synthesized de novo using intermediates from mitochondrial fatty acid synthesis type II, S-adenosylmethionine and iron-sulfur clusters. This cofactor is required for catalysis by multiple mitochondrial 2-ketoacid dehydrogenase complexes, including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase. Lipoic acid also plays a critical role in stabilizing and regulating these multi-enzyme complexes.  Many of these dehydrogenases are regulated by reactive oxygen species, mediated through the disulfide bond of the prosthetic lipoyl moiety.  Collectively, its functions explain why lipoic acid is required for cell growth, mitochondrial activity and coordination of fuel metabolism. Copyright © 2017, The American Society for Biochemistry and Molecular Biology.

Mitochondrial Ion Channels/Transporters as Sensors and Regulators of Cellular Redox Signaling

PubMed Central

Ryu, Shin-Young; Jhun, Bong Sook; Hurst, Stephen

2014-01-01

Abstract Significance: Mitochondrial ion channels/transporters and the electron transport chain (ETC) serve as key sensors and regulators for cellular redox signaling, the production of reactive oxygen species (ROS) and nitrogen species (RNS) in mitochondria, and balancing cell survival and death. Although the functional and pharmacological characteristics of mitochondrial ion transport mechanisms have been extensively studied for several decades, the majority of the molecular identities that are responsible for these channels/transporters have remained a mystery until very recently. Recent Advances: Recent breakthrough studies uncovered the molecular identities of the diverse array of major mitochondrial ion channels/transporters, including the mitochondrial Ca2+ uniporter pore, mitochondrial permeability transition pore, and mitochondrial ATP-sensitive K+ channel. This new information enables us to form detailed molecular and functional characterizations of mitochondrial ion channels/transporters and their roles in mitochondrial redox signaling. Critical Issues: Redox-mediated post-translational modifications of mitochondrial ion channels/transporters and ETC serve as key mechanisms for the spatiotemporal control of mitochondrial ROS/RNS generation. Future Directions: Identification of detailed molecular mechanisms for redox-mediated regulation of mitochondrial ion channels will enable us to find novel therapeutic targets for many diseases that are associated with cellular redox signaling and mitochondrial ion channels/transporters. Antioxid. Redox Signal. 21, 987–1006. PMID:24180309

cAMP/PKA signaling balances respiratory activity with mitochondria dependent apoptosis via transcriptional regulation

PubMed Central

2010-01-01

Background Appropriate control of mitochondrial function, morphology and biogenesis are crucial determinants of the general health of eukaryotic cells. It is therefore imperative that we understand the mechanisms that co-ordinate mitochondrial function with environmental signaling systems. The regulation of yeast mitochondrial function in response to nutritional change can be modulated by PKA activity. Unregulated PKA activity can lead to the production of mitochondria that are prone to the production of ROS, and an apoptotic form of cell death. Results We present evidence that mitochondria are sensitive to the level of cAMP/PKA signaling and can respond by modulating levels of respiratory activity or committing to self execution. The inappropriate activation of one of the yeast PKA catalytic subunits, Tpk3p, is sufficient to commit cells to an apoptotic death through transcriptional changes that promote the production of dysfunctional, ROS producing mitochondria. Our data implies that cAMP/PKA regulation of mitochondrial function that promotes apoptosis engages the function of multiple transcription factors, including HAP4, SOK2 and SCO1. Conclusions We propose that in yeast, as is the case in mammalian cells, mitochondrial function and biogenesis are controlled in response to environmental change by the concerted regulation of multiple transcription factors. The visualization of cAMP/TPK3 induced cell death within yeast colonies supports a model that PKA regulation plays a physiological role in coordinating respiratory function and cell death with nutritional status in budding yeast. PMID:21108829

The cyclophilin D/Drp1 axis regulates mitochondrial fission contributing to oxidative stress-induced mitochondrial dysfunctions in SH-SY5Y cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Anqi; Gan, Xueqi; Chen, Ruiqi

Oxidative stress plays a central role in the pathogenesis of various neurodegenerative diseases. Increasing evidences have demonstrated that structural abnormalities in mitochondria are involved in oxidative stress related nerve cell damage. And Drp1 plays a critical role in mitochondrial dynamic imbalance insulted by oxidative stress-derived mitochondria. However, the status of mitochondrial fusion and fission pathway and its relationship with mitochondrial properties such as mitochondrial membrane permeability transition pore (mPTP) have not been fully elucidated. Here, we demonstrated for the first time the role of Cyclophilin D (CypD), a crucial component for mPTP formation, in the regulation of mitochondrial dynamics inmore » oxidative stress treated nerve cell. We observed that CypD-mediated phosphorylation of Drp1 and subsequently augmented Drp1 recruitment to mitochondria and shifts mitochondrial dynamics toward excessive fission, which contributes to the mitochondrial structural and functional dysfunctions in oxidative stress-treated nerve cells. CypD depletion or over expression accompanies mitochondrial dynamics/functions recovery or aggravation separately. We also demonstrated first time the link between the CypD to mitochondrial dynamics. Our data offer new insights into the mechanism of mitochondrial dynamics which contribute to the mitochondrial dysfunctions, specifically the role of CypD in Drp1-mediated mitochondrial fission. The protective effect of CsA, or other molecules affecting the function of CypD hold promise as a potential novel therapeutic strategy for governing oxidative stress pathology via mitochondrial pathways. - Highlights: • Demonstrated first time the link between the mPTP to mitochondrial dynamics. • The role of Cyclophilin D in the regulation of Drp1-mediated mitochondrial fission. • CsA as a potential target for governing oxidative stress related neuropathology.« less

Brain mitochondrial bioenergetics change with rapid and prolonged shifts in aggression in the honey bee, Apis mellifera.

PubMed

Rittschof, Clare C; Vekaria, Hemendra J; Palmer, Joseph H; Sullivan, Patrick G

2018-04-25

Neuronal function demands high-level energy production, and as such, a decline in mitochondrial respiration characterizes brain injury and disease. A growing number of studies, however, link brain mitochondrial function to behavioral modulation in non-diseased contexts. In the honey bee, we show for the first time that an acute social interaction, which invokes an aggressive response, may also cause a rapid decline in brain mitochondrial bioenergetics. The degree and speed of this decline has only been previously observed in the context of brain injury. Furthermore, in the honey bee, age-related increases in aggressive tendency are associated with increased baseline brain mitochondrial respiration, as well as increased plasticity in response to metabolic fuel type in vitro Similarly, diet restriction and ketone body feeding, which commonly enhance mammalian brain mitochondrial function in vivo , cause increased aggression. Thus, even in normal behavioral contexts, brain mitochondria show a surprising degree of variation in function over both rapid and prolonged time scales, with age predicting both baseline function and plasticity in function. These results suggest that mitochondrial function is integral to modulating aggression-related neuronal signaling. We hypothesize that variation in function reflects mitochondrial calcium buffering activity, and that shifts in mitochondrial function signal to the neuronal soma to regulate gene expression and neural energetic state. Modulating brain energetic state is emerging as a critical component of the regulation of behavior in non-diseased contexts. © 2018. Published by The Company of Biologists Ltd.

Response of mitochondrial function to hypothyroidism in normal and regenerated rat skeletal muscle.

PubMed

Zoll, J; Ventura-Clapier, R; Serrurier, B; Bigard, A X

2001-01-01

Although thyroid hormones induce a well known decrease in muscle oxidative capacity, nothing is known concerning their effects on mitochondrial function and regulation in situ. Similarly, the influence of regeneration process is not completely understood. We investigated the effects of hypothyroidism on mitochondrial function in fast gastrocnemius (GS) and slow soleus (SOL) muscles either intact or having undergone a cycle of degeneration/regeneration (Rg SOL) following a local injection of myotoxin. Thyroid hormone deficiency was induced by thyroidectomy and propylthiouracyl via drinking water. Respiration was measured in muscle fibres permeabilised by saponin in order to assess the oxidative capacity of the muscles and the regulation of mitochondria in situ. Oxidative capacities were 8.9 in SOL, 8.5 in Rg SOL and 5.9 micromol O2/min/g dry weight in GS and decreased by 52, 42 and 39% respectively (P < 0.001) in hypothyroid rats. Moreover, the Km of mitochondrial respiration for the phosphate acceptor ADP exhibited a two-fold decrease in Rg SOL and intact SOL by hypothyroidism (P < 0.01), while mitochondrial creatine kinase activity and sensitivity of mitochondrial respiration to creatine were not altered. The results of this study demonstrate that hypothyroidism markedly altered the sensitivity of mitochondrial respiration to ADP but not to creatine in SOL muscles, suggesting that mitochondrial regulation could be partially controlled by thyroid hormones. On the other hand, mitochondrial function completely recovered following regeneration/degeneration, suggesting that thyroid hormones are not involved in the regeneration process per se.

Hypoxia-induced decrease of UCP3 gene expression in rat heart parallels metabolic gene switching but fails to affect mitochondrial respiratory coupling.

PubMed

Essop, M Faadiel; Razeghi, Peter; McLeod, Chris; Young, Martin E; Taegtmeyer, Heinrich; Sack, Michael N

2004-02-06

Mitochondrial uncoupling proteins 2 and 3 (UCP2 and UCP3) are postulated to contribute to antioxidant defense, nutrient partitioning, and energy efficiency in the heart. To distinguish isotype function in response to metabolic stress we measured cardiac mitochondrial function and cardiac UCP gene expression following chronic hypobaric hypoxia. Isolated mitochondrial O(2) consumption and ATP synthesis rate were reduced but respiratory coupling was unchanged compared to normoxic groups. Concurrently, left ventricular UCP3 mRNA levels were significantly decreased with hypoxia (p<0.05) while UCP2 levels remained unchanged versus controls. Diminished UCP3 expression was associated with coordinate regulation of counter-regulatory metabolic genes. From these data, we propose a role for UCP3 in the regulation of fatty acid oxidation in the heart as opposed to uncoupling of mitochondria. Moreover, the divergent hypoxia-induced regulation of UCP2 and UCP3 supports distinct mitochondrial regulatory functions of these inner mitochondrial membrane proteins in the heart in response to metabolic stress.

Mangiferin protects mitochondrial function by preserving mitochondrial hexokinase-II in vessel endothelial cells.

PubMed

Song, Junna; Li, Yi; Song, Junmei; Hou, Fangjie; Liu, Baolin; Li, Aiying

2017-07-01

Hexokinase-II (HK-II) confers protection against cell death and this study was designed to investigate the effect of mangiferin on the regulation of mitochondrial HK-II. In vessel endothelial cells, saturated fatty acid palmitate (PA) stimulation induced HK-II detachment from mitochondria due to cellular acidification. Mangiferin reduced lactate accumulation by improving pyruvate dehydrogenase activity, promoted Akt translocation to HK-II and prevented HK-II detachment from mitochondria. Knockdown of Akt2 diminished the protective effect of mangiferin on mitochondrial HK-II, confirming the role of Akt in the regulation of HK-II. Mangiferin prevented mitochondrial permeability transition pore opening, restored mitochondrial membrane potential and thereby protected cell from apoptosis. In high-fat diet fed mice, oral administration of mangiferin induced Akt phosphorylation, increased HK-II binding to mitochondria and resultantly protected vessel endothelial function, demonstrating its protective effect on endothelial integrity in vivo. This finding provided a novel strategy for the protection of mitochondrial function in the endothelium. Copyright © 2017 Elsevier B.V. All rights reserved.

Regulation of ROS Production and Vascular Function by Carbon Monoxide

PubMed Central

Choi, Yoon Kyung; Por, Elaine D.; Kwon, Young-Guen; Kim, Young-Myeong

2012-01-01

Carbon monoxide (CO) is a gaseous molecule produced from heme by heme oxygenase (HO). CO interacts with reduced iron of heme-containing proteins, leading to its involvement in various cellular events via its production of mitochondrial reactive oxygen species (ROS). CO-mediated ROS production initiates intracellular signal events, which regulate the expression of adaptive genes implicated in oxidative stress and functions as signaling molecule for promoting vascular functions, including angiogenesis and mitochondrial biogenesis. Therefore, CO generated either by exogenous delivery or by HO activity can be fundamentally involved in regulating mitochondria-mediated redox cascades for adaptive gene expression and improving blood circulation (i.e., O2 delivery) via neovascularization, leading to the regulation of mitochondrial energy metabolism. This paper will highlight the biological effects of CO on ROS generation and cellular redox changes involved in mitochondrial metabolism and angiogenesis. Moreover, cellular mechanisms by which CO is exploited for disease prevention and therapeutic applications will also be discussed. PMID:22928087

Mitochondrial Ubiquitin Ligase in Cardiovascular Disorders.

PubMed

Yu, Tao; Zhang, Yinfeng; Li, Pei-Feng

2017-01-01

Mitochondrial dynamics play a critical role in cellular responses and physiological process. However, their dysregulation leads to a functional degradation, which results in a diverse array of common disorders, including cardiovascular disease. In this background, the mitochondrial ubiquitin ligase has been attracting substantial research interest in recent years. Mitochondrial ubiquitin ligase is localized in the mitochondrial outer membrane, where it plays an essential role in the regulation of mitochondrial dynamics and apoptosis. In this chapter, we provide a comprehensive overview of the functions of mitochondrial ubiquitin ligases identified hitherto, with a special focus on cardiovascular disorders.

O-GlcNAcomic Profiling Identifies Widespread O-Linked β-N-Acetylglucosamine Modification (O-GlcNAcylation) in Oxidative Phosphorylation System Regulating Cardiac Mitochondrial Function*♦

PubMed Central

Ma, Junfeng; Liu, Ting; Wei, An-Chi; Banerjee, Partha; O'Rourke, Brian; Hart, Gerald W.

2015-01-01

Dynamic cycling of O-linked β-N-acetylglucosamine (O-GlcNAc) on nucleocytoplasmic proteins serves as a nutrient sensor to regulate numerous biological processes. However, mitochondrial protein O-GlcNAcylation and its effects on function are largely unexplored. In this study, we performed a comparative analysis of the proteome and O-GlcNAcome of cardiac mitochondria from rats acutely (12 h) treated without or with thiamet-G (TMG), a potent and specific inhibitor of O-GlcNAcase. We then determined the functional consequences in mitochondria isolated from the two groups. O-GlcNAcomic profiling finds that over 88 mitochondrial proteins are O-GlcNAcylated, with the oxidative phosphorylation system as a major target. Moreover, in comparison with controls, cardiac mitochondria from TMG-treated rats did not exhibit altered protein abundance but showed overall elevated O-GlcNAcylation of many proteins. However, O-GlcNAc was unexpectedly down-regulated at certain sites of specific proteins. Concomitantly, TMG treatment resulted in significantly increased mitochondrial oxygen consumption rates, ATP production rates, and enhanced threshold for permeability transition pore opening by Ca2+. Our data reveal widespread and dynamic mitochondrial protein O-GlcNAcylation, serving as a regulator to their function. PMID:26446791

Pyruvate dehydrogenase has a major role in mast cell function, and its activity is regulated by mitochondrial microphthalmia transcription factor.

PubMed

Sharkia, Israa; Hadad Erlich, Tal; Landolina, Nadine; Assayag, Miri; Motzik, Alex; Rachmin, Inbal; Kay, Gillian; Porat, Ziv; Tshori, Sagi; Berkman, Neville; Levi-Schaffer, Francesca; Razin, Ehud

2017-07-01

We have recently observed that oxidative phosphorylation-mediated ATP production is essential for mast cell function. Pyruvate dehydrogenase (PDH) is the main regulator of the Krebs cycle and is located upstream of the electron transport chain. However, the role of PDH in mast cell function has not been described. Microphthalmia transcription factor (MITF) regulates the development, number, and function of mast cells. Localization of MITF to the mitochondria and its interaction with mitochondrial proteins has not been explored. We sought to explore the role played by PDH in mast cell exocytosis and to determine whether MITF is localized in the mitochondria and involved in regulation of PDH activity. Experiments were performed in vitro by using human and mouse mast cells, as well as rat basophil leukemia cells, and in vivo in mice. The effect of PDH inhibition on mast cell function was examined. PDH interaction with MITF was measured before and after immunologic activation. Furthermore, mitochondrial localization of MITF and its effect on PDH activity were determined. PDH is essential for immunologically mediated degranulation of mast cells. After activation, PDH is serine dephosphorylated. In addition, for the first time, we show that MITF is partially located in the mitochondria and interacts with PDH. This interaction is dependent on the phosphorylation state of PDH. Furthermore, mitochondrial MITF regulates PDH activity. The association of mitochondrial MITF with PDH emerges as an important regulator of mast cell function. Our findings indicate that PDH could arise as a new target for the manipulation of allergic diseases. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Developmentally regulated GTP-binding protein 2 depletion leads to mitochondrial dysfunction through downregulation of dynamin-related protein 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vo, Mai-Tram; Ko, Myoung Seok; Lee, Unn Hwa

Mitochondrial dynamics, including constant fusion and fission, play critical roles in maintaining mitochondrial morphology and function. Here, we report that developmentally regulated GTP-binding protein 2 (DRG2) regulates mitochondrial morphology by modulating the expression of the mitochondrial fission gene dynamin-related protein 1 (Drp1). shRNA-mediated silencing of DRG2 induced mitochondrial swelling, whereas expression of an shRNA-resistant version of DRG2 decreased mitochondrial swelling in DRG2-depleted cells. Analysis of the expression levels of genes involved in mitochondrial fusion and fission revealed that DRG2 depletion significantly decreased the level of Drp1. Overexpression of Drp1 rescued the defect in mitochondrial morphology induced by DRG2 depletion. DRG2more » depletion reduced the mitochondrial membrane potential, oxygen consumption rate (OCR), and amount of mitochondrial DNA (mtDNA), whereas it increased reactive oxygen species (ROS) production and apoptosis. Taken together, our data demonstrate that DRG2 acts as a regulator of mitochondrial fission by controlling the expression of Drp1. - Highlights: • DRG2 depletion increased mitochondrial swelling. • DRG2 depletion inhibited the expression of Drp1. • Overexpression of DRG2 or Drp1 rescued mitochondrial shape in DRG2 depleted cells. • DRG2 depletion induced mitochondrial dysfunction.« less

Mitochondrial fission proteins regulate programmed cell death in yeast.

PubMed

Fannjiang, Yihru; Cheng, Wen-Chih; Lee, Sarah J; Qi, Bing; Pevsner, Jonathan; McCaffery, J Michael; Hill, R Blake; Basañez, Gorka; Hardwick, J Marie

2004-11-15

The possibility that single-cell organisms undergo programmed cell death has been questioned in part because they lack several key components of the mammalian cell death machinery. However, yeast encode a homolog of human Drp1, a mitochondrial fission protein that was shown previously to promote mammalian cell death and the excessive mitochondrial fragmentation characteristic of apoptotic mammalian cells. In support of a primordial origin of programmed cell death involving mitochondria, we found that the Saccharomyces cerevisiae homolog of human Drp1, Dnm1, promotes mitochondrial fragmentation/degradation and cell death following treatment with several death stimuli. Two Dnm1-interacting factors also regulate yeast cell death. The WD40 repeat protein Mdv1/Net2 promotes cell death, consistent with its role in mitochondrial fission. In contrast to its fission function in healthy cells, Fis1 unexpectedly inhibits Dnm1-mediated mitochondrial fission and cysteine protease-dependent cell death in yeast. Furthermore, the ability of yeast Fis1 to inhibit mitochondrial fission and cell death can be functionally replaced by human Bcl-2 and Bcl-xL. Together, these findings indicate that yeast and mammalian cells have a conserved programmed death pathway regulated by a common molecular component, Drp1/Dnm1, that is inhibited by a Bcl-2-like function.

Calcineurin Regulates Myocardial Function during Acute Endotoxemia

PubMed Central

Joshi, Mandar S.; Julian, Mark W.; Huff, Jennifer E.; Bauer, John A.; Xia, Yong; Crouser, Elliott D.

2006-01-01

Rationale: Cyclosporin A (CsA) is known to preserve cardiac contractile function during endotoxemia, but the mechanism is unclear. Increased nitric oxide (NO) production and altered mitochondrial function are implicated as mechanisms contributing to sepsis-induced cardiac dysfunction, and CsA has the capacity to reduce NO production and inhibit mitochondrial dysfunction relating to the mitochondrial permeability transition (MPT). Objectives: We hypothesized that CsA would protect against endotoxin-mediated cardiac contractile dysfunction by attenuating NO production and preserving mitochondrial function. Methods: Left ventricular function was measured continuously over 4 h in cats assigned as follows: control animals (n = 7); LPS alone (3 mg/kg, n = 8); and CsA (6 mg/kg, n = 7), a calcineurin inhibitor that blocks the MPT, or tacrolimus (FK506, 0.1 mg/kg, n = 7), a calcineurin inhibitor lacking MPT activity, followed in 30 min by LPS. Myocardial tissue was then analyzed for NO synthase-2 expression, tissue nitration, protein carbonylation, and mitochondrial morphology and function. Measurements and Main Results: LPS treatment resulted in impaired left ventricular contractility, altered mitochondrial morphology and function, and increased protein nitration. As hypothesized, CsA pretreatment normalized cardiac performance and mitochondrial respiration and reduced myocardial protein nitration. Unexpectedly, FK506 pretreatment had similar effects, normalizing both cardiac and mitochondrial parameters. However, CsA and FK506 pretreatments markedly increased protein carbonylation in the myocardium despite elevated manganese superoxide dismutase activity during endotoxemia. Conclusions: Our data indicate that calcineurin is a critical regulator of mitochondrial respiration, tissue nitration, protein carbonylation, and contractile function in the heart during acute endotoxemia. PMID:16424445

Regulation of mitochondrial function and endoplasmic reticulum stress by nitric oxide in pluripotent stem cells

PubMed Central

Caballano-Infantes, Estefania; Terron-Bautista, José; Beltrán-Povea, Amparo; Cahuana, Gladys M; Soria, Bernat; Nabil, Hajji; Bedoya, Francisco J; Tejedo, Juan R

2017-01-01

Mitochondrial dysfunction and endoplasmic reticulum stress (ERS) are global processes that are interrelated and regulated by several stress factors. Nitric oxide (NO) is a multifunctional biomolecule with many varieties of physiological and pathological functions, such as the regulation of cytochrome c inhibition and activation of the immune response, ERS and DNA damage; these actions are dose-dependent. It has been reported that in embryonic stem cells, NO has a dual role, controlling differentiation, survival and pluripotency, but the molecular mechanisms by which it modulates these functions are not yet known. Low levels of NO maintain pluripotency and induce mitochondrial biogenesis. It is well established that NO disrupts the mitochondrial respiratory chain and causes changes in mitochondrial Ca2+ flux that induce ERS. Thus, at high concentrations, NO becomes a potential differentiation agent due to the relationship between ERS and the unfolded protein response in many differentiated cell lines. Nevertheless, many studies have demonstrated the need for physiological levels of NO for a proper ERS response. In this review, we stress the importance of the relationships between NO levels, ERS and mitochondrial dysfunction that control stem cell fate as a new approach to possible cell therapy strategies. PMID:28289506

Regulation of mitochondrial function and endoplasmic reticulum stress by nitric oxide in pluripotent stem cells.

PubMed

Caballano-Infantes, Estefania; Terron-Bautista, José; Beltrán-Povea, Amparo; Cahuana, Gladys M; Soria, Bernat; Nabil, Hajji; Bedoya, Francisco J; Tejedo, Juan R

2017-02-26

Mitochondrial dysfunction and endoplasmic reticulum stress (ERS) are global processes that are interrelated and regulated by several stress factors. Nitric oxide (NO) is a multifunctional biomolecule with many varieties of physiological and pathological functions, such as the regulation of cytochrome c inhibition and activation of the immune response, ERS and DNA damage; these actions are dose-dependent. It has been reported that in embryonic stem cells, NO has a dual role, controlling differentiation, survival and pluripotency, but the molecular mechanisms by which it modulates these functions are not yet known. Low levels of NO maintain pluripotency and induce mitochondrial biogenesis. It is well established that NO disrupts the mitochondrial respiratory chain and causes changes in mitochondrial Ca 2+ flux that induce ERS. Thus, at high concentrations, NO becomes a potential differentiation agent due to the relationship between ERS and the unfolded protein response in many differentiated cell lines. Nevertheless, many studies have demonstrated the need for physiological levels of NO for a proper ERS response. In this review, we stress the importance of the relationships between NO levels, ERS and mitochondrial dysfunction that control stem cell fate as a new approach to possible cell therapy strategies.

Redox regulation of mitochondrial proteins and proteomes by cysteine thiol switches.

PubMed

Nietzel, Thomas; Mostertz, Jörg; Hochgräfe, Falko; Schwarzländer, Markus

2017-03-01

Mitochondria are hotspots of cellular redox biochemistry. Respiration as a defining mitochondrial function is made up of a series of electron transfers that are ultimately coupled to maintaining the proton motive force, ATP production and cellular energy supply. The individual reaction steps involved require tight control and flexible regulation to maintain energy and redox balance in the cell under fluctuating demands. Redox regulation by thiol switching has been a long-standing candidate mechanism to support rapid adjustment of mitochondrial protein function at the posttranslational level. Here we review recent advances in our understanding of cysteine thiol switches in the mitochondrial proteome with a focus on their operation in vivo. We assess the conceptual basis for thiol switching in mitochondria and discuss to what extent insights gained from in vitro studies may be valid in vivo, considering thermodynamic, kinetic and structural constraints. We compare functional proteomic approaches that have been used to assess mitochondrial protein thiol switches, including thioredoxin trapping, redox difference gel electrophoresis (redoxDIGE), isotope-coded affinity tag (OxICAT) and iodoacetyl tandem mass tag (iodoTMT) labelling strategies. We discuss conditions that may favour active thiol switching in mitochondrial proteomes in vivo, and appraise recent advances in dissecting their impact using combinations of in vivo redox sensing and quantitative redox proteomics. Finally we focus on four central facets of mitochondrial biology, aging, carbon metabolism, energy coupling and electron transport, exemplifying the current emergence of a mechanistic understanding of mitochondrial regulation by thiol switching in living plants and animals. Copyright © 2016 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

NITRIC OXIDE, MITOCHONDRIAL HYPERPOLARIZATION AND T-CELL ACTIVATION

PubMed Central

Nagy, Gyorgy; Koncz, Agnes; Fernandez, David; Perl, Andras

2007-01-01

T lymphocyte activation is associated with nitric oxide (NO) production that plays an essential role in multiple T cell functions. NO acts as a messenger, activating soluble guanyl cyclase and participating in the transduction signaling pathways involving cyclic GMP. NO modulates mitochondrial events that are involved in apoptosis and regulates mitochondrial membrane potential and mitochondrial biogenesis in many cell types, including lymphocytes. Mitochondrial hyperpolarization (MHP), an early and reversible event during both T lymphocyte activation and apoptosis, is regulated by NO. Here, we discuss recent evidence that NO-induced MHP represents a molecular switch in multiple T cell signaling pathways. Overproduction of NO in systemic lupus erythematosus (SLE) induces mitochondrial biogenesis and alters Ca2+ signaling. Thus, while NO plays a physiological role in lymphocyte cell signaling, its overproduction may disturb normal T cell function, contributing to the pathogenesis of autoimmunity. PMID:17462531

Redox Regulation of Mitochondrial Function

PubMed Central

Handy, Diane E.

2012-01-01

Abstract Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function. Antioxid. Redox Signal. 16, 1323–1367. PMID:22146081

Glucose Modulates Respiratory Complex I Activity in Response to Acute Mitochondrial Dysfunction

PubMed Central

Cannino, Giuseppe; El-Khoury, Riyad; Pirinen, Marja; Hutz, Bettina; Rustin, Pierre; Jacobs, Howard T.; Dufour, Eric

2012-01-01

Proper coordination between glycolysis and respiration is essential, yet the regulatory mechanisms involved in sensing respiratory chain defects and modifying mitochondrial functions accordingly are unclear. To investigate the nature of this regulation, we introduced respiratory bypass enzymes into cultured human (HEK293T) cells and studied mitochondrial responses to respiratory chain inhibition. In the absence of respiratory chain inhibitors, the expression of alternative respiratory enzymes did not detectably alter cell physiology or mitochondrial function. However, in permeabilized cells NDI1 (alternative NADH dehydrogenase) bypassed complex I inhibition, whereas alternative oxidase (AOX) bypassed complex III or IV inhibition. In contrast, in intact cells the effects of the AOX bypass were suppressed by growth on glucose, whereas those produced by NDI1 were unaffected. Moreover, NDI1 abolished the glucose suppression of AOX-driven respiration, implicating complex I as the target of this regulation. Rapid Complex I down-regulation was partly released upon prolonged respiratory inhibition, suggesting that it provides an “emergency shutdown” system to regulate metabolism in response to dysfunctions of the oxidative phosphorylation. This system was independent of HIF1, mitochondrial superoxide, or ATP synthase regulation. Our findings reveal a novel pathway for adaptation to mitochondrial dysfunction and could provide new opportunities for combatting diseases. PMID:23007390

Receptor Tyrosine Kinase ErbB2 Translocates into Mitochondria and Regulates Cellular Metabolism

PubMed Central

Ding, Yan; Liu, Zixing; Desai, Shruti; Zhao, Yuhua; Liu, Hao; Pannell, Lewis K; Yi, Hong; Wright, Elizabeth R; Owen, Laurie B; Dean-Colomb, Windy; Fodstad, Oystein; Lu, Jianrong; LeDoux, Susan P; Wilson, Glenn L; Tan, Ming

2012-01-01

It is well known that ErbB2, a receptor tyrosine kinase, localizes on the plasma membrane. Here we describe a novel observation that ErbB2 also localizes in mitochondria of cancer cells and patient samples. We found that ErbB2 translocates into mitochondria through the association with mtHSP70. Additionally, mitochondrial ErbB2 (mtErbB2) negatively regulates mitochondrial respiratory functions. Oxygen consumption and activities of complexes of the mitochondrial electron transport chain were decreased in mtErbB2-overexpressing cells. Mitochondrial membrane potential and the cellular ATP level also were decreased. In contrast, mtErbB2 enhanced cellular glycolysis. The translocation of ErbB2 and its impact on mitochondrial function are kinase dependent. Interestingly, cancer cells with higher levels of mtErbB2 were more resistant to ErbB2 targeting antibody trastuzumab. Our study provides a novel perspective on the metabolic regulatory function of ErbB2 and reveals that mtErbB2 plays an important role in the regulation of cellular metabolism and cancer cell resistance to therapeutics. PMID:23232401

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jeehye; Lee, Gina; Chung, Jongkyeong

The two Parkinson's disease (PD) genes, PTEN-induced kinase 1 (PINK1) and parkin, are linked in a common pathway which affects mitochondrial integrity and function. However, it is still not known what this pathway does in the mitochondria. Therefore, we investigated its physiological function in Drosophila. Because Drosophila PINK1 and parkin mutants show changes in mitochondrial morphology in both indirect flight muscles and dopaminergic neurons, we here investigated whether the PINK1-Parkin pathway genetically interacts with the regulators of mitochondrial fusion and fission such as Drp1, which promotes mitochondrial fission, and Opa1 or Marf, which induces mitochondrial fusion. Surprisingly, DrosophilaPINK1 and parkinmore » mutant phenotypes were markedly suppressed by overexpression of Drp1 or downregulation of Opa1 or Marf, indicating that the PINK1-Parkin pathway regulates mitochondrial remodeling process in the direction of promoting mitochondrial fission. Therefore, we strongly suggest that mitochondrial fusion and fission process could be a prominent therapeutic target for the treatment of PD.« less

Powering Up Mitichondrial Functions to Treat Mitochondrial Disease

DTIC Science & Technology

2017-10-01

derived hormone whose serum level correlates positively with the severity of mitochondrial cardiomyopathy (recently published with DOD grant support...derived hormone that regulates body growth. Circulating GDF15 level correlates positively with the severity of mitochondrial cardiomyopathy and can...Pei lab recently discovered that GDF15 is a heart-derived hormone that regulates body growth. Circulating GDF15 level correlates positively with the

Permeabilization of brain tissue in situ enables multiregion analysis of mitochondrial function in a single mouse brain.

PubMed

Herbst, Eric A F; Holloway, Graham P

2015-02-15

Mitochondrial function in the brain is traditionally assessed through analysing respiration in isolated mitochondria, a technique that possesses significant tissue and time requirements while also disrupting the cooperative mitochondrial reticulum. We permeabilized brain tissue in situ to permit analysis of mitochondrial respiration with the native mitochondrial morphology intact, removing the need for isolation time and minimizing tissue requirements to ∼2 mg wet weight. The permeabilized brain technique was validated against the traditional method of isolated mitochondria and was then further applied to assess regional variation in the mouse brain with ischaemia-reperfusion injuries. A transgenic mouse model overexpressing catalase within mitochondria was applied to show the contribution of mitochondrial reactive oxygen species to ischaemia-reperfusion injuries in different brain regions. This technique enhances the accessibility of addressing physiological questions in small brain regions and in applying transgenic mouse models to assess mechanisms regulating mitochondrial function in health and disease. Mitochondria function as the core energy providers in the brain and symptoms of neurodegenerative diseases are often attributed to their dysregulation. Assessing mitochondrial function is classically performed in isolated mitochondria; however, this process requires significant isolation time, demand for abundant tissue and disruption of the cooperative mitochondrial reticulum, all of which reduce reliability when attempting to assess in vivo mitochondrial bioenergetics. Here we introduce a method that advances the assessment of mitochondrial respiration in the brain by permeabilizing existing brain tissue to grant direct access to the mitochondrial reticulum in situ. The permeabilized brain preparation allows for instant analysis of mitochondrial function with unaltered mitochondrial morphology using significantly small sample sizes (∼2 mg), which permits the analysis of mitochondrial function in multiple subregions within a single mouse brain. Here this technique was applied to assess regional variation in brain mitochondrial function with acute ischaemia-reperfusion injuries and to determine the role of reactive oxygen species in exacerbating dysfunction through the application of a transgenic mouse model overexpressing catalase within mitochondria. Through creating accessibility to small regions for the investigation of mitochondrial function, the permeabilized brain preparation enhances the capacity for examining regional differences in mitochondrial regulation within the brain, as the majority of genetic models used for unique approaches exist in the mouse model. © 2014 The Authors. The Journal of Physiology © 2014 The Physiological Society.

A novel mitochondrial matrix serine/threonine protein phosphatase regulates the mitochondria permeability transition pore and is essential for cellular survival and development

PubMed Central

Lu, Gang; Ren, Shuxun; Korge, Paavo; Choi, Jayoung; Dong, Yuan; Weiss, James; Koehler, Carla; Chen, Jau-nian; Wang, Yibin

2007-01-01

Mitochondria play a central role in the regulation of programmed cell death signaling. Here, we report the finding of a mitochondrial matrix-targeted protein phosphatase 2C family member (PP2Cm) that regulates mitochondrial membrane permeability transition pore (MPTP) opening and is essential for cell survival, embryonic development, and cardiac function. PP2Cm is highly conserved among vertebrates, with the highest expression levels detected in the heart and brain. Small hairpin RNA (shRNA)-mediated knockdown of PP2Cm resulted in cell death associated with loss of mitochondrial membrane potential in cultured cardiac mycoytes and an induction of hepatocyte apoptosis in vivo. PP2Cm-deficient mitochondria showed elevated susceptibility to calcium-induced MPTP opening, whereas mitochondrial oxidative phosphorylation activities were not affected. Finally, inactivation of PP2Cm in developing zebrafish embryos caused abnormal cardiac and neural development as well as heart failure associated with induced apoptosis. These data suggest that PP2Cm is a novel mitochondrial protein phosphatase that has a critical function in cell death and survival, and may play a role in regulating the MPTP opening. PMID:17374715

MIDAS/GPP34, a nuclear gene product, regulates total mitochondrial mass in response to mitochondrial dysfunction.

PubMed

Nakashima-Kamimura, Naomi; Asoh, Sadamitsu; Ishibashi, Yoshitomo; Mukai, Yuri; Shidara, Yujiro; Oda, Hideaki; Munakata, Kae; Goto, Yu-Ichi; Ohta, Shigeo

2005-11-15

To investigate the regulatory system in mitochondrial biogenesis involving crosstalk between the mitochondria and nucleus, we found a factor named MIDAS (mitochondrial DNA absence sensitive factor) whose expression was enhanced by the absence of mitochondrial DNA (mtDNA). In patients with mitochondrial diseases, MIDAS expression was increased only in dysfunctional muscle fibers. A majority of MIDAS localized to mitochondria with a small fraction in the Golgi apparatus in HeLa cells. To investigate the function of MIDAS, we stably transfected HeLa cells with an expression vector carrying MIDAS cDNA or siRNA. Cells expressing the MIDAS protein and the siRNA constitutively showed an increase and decrease in the total mass of mitochondria, respectively, accompanying the regulation of a mitochondria-specific phospholipid, cardiolipin. In contrast, amounts of the mitochondrial DNA, RNA and proteins did not depend upon MIDAS. Thus, MIDAS is involved in the regulation of mitochondrial lipids, leading to increases of total mitochondrial mass in response to mitochondrial dysfunction.

Mitochondrial proteome disruption in the diabetic heart through targeted epigenetic regulation at the mitochondrial heat shock protein 70 (mtHsp70) nuclear locus.

PubMed

Shepherd, Danielle L; Hathaway, Quincy A; Nichols, Cody E; Durr, Andrya J; Pinti, Mark V; Hughes, Kristen M; Kunovac, Amina; Stine, Seth M; Hollander, John M

2018-06-01

>99% of the mitochondrial proteome is nuclear-encoded. The mitochondrion relies on a coordinated multi-complex process for nuclear genome-encoded mitochondrial protein import. Mitochondrial heat shock protein 70 (mtHsp70) is a key component of this process and a central constituent of the protein import motor. Type 2 diabetes mellitus (T2DM) disrupts mitochondrial proteomic signature which is associated with decreased protein import efficiency. The goal of this study was to manipulate the mitochondrial protein import process through targeted restoration of mtHsp70, in an effort to restore proteomic signature and mitochondrial function in the T2DM heart. A novel line of cardiac-specific mtHsp70 transgenic mice on the db/db background were generated and cardiac mitochondrial subpopulations were isolated with proteomic evaluation and mitochondrial function assessed. MicroRNA and epigenetic regulation of the mtHsp70 gene during T2DM were also evaluated. MtHsp70 overexpression restored cardiac function and nuclear-encoded mitochondrial protein import, contributing to a beneficial impact on proteome signature and enhanced mitochondrial function during T2DM. Further, transcriptional repression at the mtHsp70 genomic locus through increased localization of H3K27me3 during T2DM insult was observed. Our results suggest that restoration of a key protein import constituent, mtHsp70, provides therapeutic benefit through attenuation of mitochondrial and contractile dysfunction in T2DM. Copyright © 2018 Elsevier Ltd. All rights reserved.

Acidosis overrides oxygen deprivation to maintain mitochondrial function and cell survival

PubMed Central

Khacho, Mireille; Tarabay, Michelle; Patten, David; Khacho, Pamela; MacLaurin, Jason G.; Guadagno, Jennifer; Bergeron, Richard; Cregan, Sean P.; Harper, Mary-Ellen; Park, David S.; Slack, Ruth S.

2014-01-01

Sustained cellular function and viability of high-energy demanding post-mitotic cells rely on the continuous supply of ATP. The utilization of mitochondrial oxidative phosphorylation for efficient ATP generation is a function of oxygen levels. As such, oxygen deprivation, in physiological or pathological settings, has profound effects on cell metabolism and survival. Here we show that mild extracellular acidosis, a physiological consequence of anaerobic metabolism, can reprogramme the mitochondrial metabolic pathway to preserve efficient ATP production regardless of oxygen levels. Acidosis initiates a rapid and reversible homeostatic programme that restructures mitochondria, by regulating mitochondrial dynamics and cristae architecture, to reconfigure mitochondrial efficiency, maintain mitochondrial function and cell survival. Preventing mitochondrial remodelling results in mitochondrial dysfunction, fragmentation and cell death. Our findings challenge the notion that oxygen availability is a key limiting factor in oxidative metabolism and brings forth the concept that mitochondrial morphology can dictate the bioenergetic status of post-mitotic cells. PMID:24686499

FOXO3a regulates BNIP3 and modulates mitochondrial calcium, dynamics, and function in cardiac stress

PubMed Central

Kohlbrenner, Erik; Gamb, Scott I.; Guenzel, Adam J.; Klaus, Katherine; Fayyaz, Ahmed U.; Nair, K. Sreekumaran; Hajjar, Roger J.

2016-01-01

The forkhead box O3a (FOXO3a) transcription factor has been shown to regulate glucose metabolism, muscle atrophy, and cell death in postmitotic cells. Its role in regulation of mitochondrial and myocardial function is not well studied. Based on previous work, we hypothesized that FOXO3a, through BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 (BNIP3), modulates mitochondrial morphology and function in heart failure (HF). We modulated the FOXO3a-BNIP3 pathway in normal and phenylephrine (PE)-stressed adult cardiomyocytes (ACM) in vitro and developed a cardiotropic adeno-associated virus serotype 9 encoding dominant-negative FOXO3a (AAV9.dn-FX3a) for gene delivery in a rat model of HF with preserved ejection fraction (HFpEF). We found that FOXO3a upregulates BNIP3 expression in normal and PE-stressed ACM, with subsequent increases in mitochondrial Ca2+, leading to decreased mitochondrial membrane potential, mitochondrial fragmentation, and apoptosis. Whereas dn-FX3a attenuated the increase in BNIP3 expression and its consequences in PE-stressed ACM, AAV9.dn-FX3a delivery in an experimental model of HFpEF decreased BNIP3 expression, reversed adverse left ventricular remodeling, and improved left ventricular systolic and, particularly, diastolic function, with improvements in mitochondrial structure and function. Moreover, AAV9.dn-FX3a restored phospholamban phosphorylation at S16 and enhanced dynamin-related protein 1 phosphorylation at S637. Furthermore, FOXO3a upregulates maladaptive genes involved in mitochondrial apoptosis, autophagy, and cardiac atrophy. We conclude that FOXO3a activation in cardiac stress is maladaptive, in that it modulates Ca2+ cycling, Ca2+ homeostasis, and mitochondrial dynamics and function. Our results suggest an important role of FOXO3a in HF, making it an attractive potential therapeutic target. Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/role-of-foxo3a-in-heart-failure/. PMID:27694219

Endonuclease G is a novel determinant of cardiac hypertrophy and mitochondrial function

PubMed Central

McDermott-Roe, Chris; Ye, Junmei; Ahmed, Rizwan; Sun, Xi-Ming; Serafín, Anna; Ware, James; Bottolo, Leonardo; Muckett, Phil; Cañas, Xavier; Zhang, Jisheng; Rowe, Glenn C.; Buchan, Rachel; Lu, Han; Braithwaite, Adam; Mancini, Massimiliano; Hauton, David; Martí, Ramon; García-Arumí, Elena; Hubner, Norbert; Jacob, Howard; Serikawa, Tadao; Zidek, Vaclav; Papousek, Frantisek; Kolar, Frantisek; Cardona, Maria; Ruiz-Meana, Marisol; García-Dorado, David; Comella, Joan X; Felkin, Leanne E; Barton, Paul JR; Arany, Zoltan; Pravenec, Michal; Petretto, Enrico; Sanchis, Daniel; Cook, Stuart A.

2011-01-01

Left ventricular mass (LVM) is a highly heritable trait1 and an independent risk factor for all-cause mortality2. To date, genome-wide association studies (GWASs) have not identified the genetic factors underlying LVM variation3 and the regulatory mechanisms for blood pressure (BP)-independent cardiac hypertrophy remain poorly understood4,5. Unbiased systems-genetics approaches in the rat6,7 now provide a powerful complementary tool to GWAS and we applied integrative genomics to dissect a highly replicated, BP-independent LVM locus on rat chromosome 3p. We identified endonuclease G (Endog), previously implicated in apoptosis8 but not hypertrophy, as the gene at the locus and demonstrated loss-of-function mutation in Endog associated with increased LVM and impaired cardiac function. Inhibition of Endog in cultured cardiomyocytes resulted in an increase in cell size and hypertrophic biomarkers in the absence of pro-hypertrophic stimulation. Genome-wide network analysis unexpectedly inferred ENDOG in fundamental mitochondrial processes unrelated to apoptosis. We showed direct regulation of ENDOG by ERRα and PGC1α, master regulators of mitochondrial and cardiac function9,10,11, interaction of ENDOG with the mitochondrial genome and ENDOG-mediated regulation of mitochondrial mass. At baseline, Endog deleted mouse heart had depleted mitochondria, mitochondrial dysfunction and elevated reactive oxygen species (ROS), which was associated with enlarged and steatotic cardiomyocytes. Our studies establish further the link between mitochondrial dysfunction, ROS and heart disease and demonstrate a new role for Endog in maladaptive cardiac hypertrophy. PMID:21979051

Mutations in nuclear genes alter post-transcriptional regulation of mitochondrial genes.

USDA-ARS?s Scientific Manuscript database

Nuclear gene products are required for the expression of mitochondrial genes and elaboration of functional mitochondrial protein complexes. To better understand the roles of these nuclear genes, we exploited the mitochondrial encoded S-type of cytoplasmic male sterility (CMS-S) and developed a nove...

Yap-Hippo pathway regulates cerebral hypoxia-reoxygenation injury in neuroblastoma N2a cells via inhibiting ROCK1/F-actin/mitochondrial fission pathways.

PubMed

Geng, Chizi; Wei, Jianchao; Wu, Chengsi

2018-05-23

Yes-associated protein (Yap), a regulator of cellular apoptosis, has been demonstrated to be involved in cerebral ischemia-reperfusion (IR) injury through poorly defined mechanisms. The present study aimed to explore the role of Yap in regulating cerebral IR injury in vitro, with a focus on mitochondrial fission and ROCK1/F-actin pathways. Our data demonstrated that Yap was actually downregulated in N2a cells after cerebral hypoxia-reoxygenation (HR) injury, and that lower expression of Yap was closely associated with increased cell death. However, the reintroduction of Yap was able to suppress the HR-mediated N2a cells death via blocking the mitochondria-related apoptotic signal. At the molecular levels, Yap overexpression sustained mitochondrial potential, normalized the mitochondrial respiratory function, reduced ROS overproduction, limited HtrA2/Omi release from mitochondria into the nucleus, and suppressed pro-apoptotic proteins activation. Subsequently, functional studies have further illustrated that HR-mediated mitochondrial apoptosis was highly regulated by mitochondrial fission, whereas Yap overexpression was able to attenuate HR-mediated mitochondrial fission and, thus, promote N2a cell survival in the context of HR injury. At last, we demonstrated that Yap handled mitochondrial fission via closing ROCK1/F-actin signaling pathways. Activation of ROCK1/F-actin pathways abrogated the protective role of Yap overexpression on mitochondrial homeostasis and N2a cell survival in the setting of HR injury. Altogether, our data identified Yap as the endogenous defender to relieve HR-mediated nerve damage via antagonizing ROCK1/F-actin/mitochondrial fission pathways.

The mitochondrial elongation factors MIEF1 and MIEF2 exert partially distinct functions in mitochondrial dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Tong; Yu, Rong; Jin, Shao-Bo

2013-11-01

Mitochondria are dynamic organelles whose morphology is regulated by a complex balance of fission and fusion processes, and we still know relatively little about how mitochondrial dynamics is regulated. MIEF1 (also called MiD51) has recently been characterized as a key regulator of mitochondrial dynamics and in this report we explore the functions of its paralog MIEF2 (also called MiD49), to learn to what extent MIEF2 is functionally distinct from MIEF1. We show that MIEF1 and MIEF2 have many functions in common. Both are anchored in the mitochondrial outer membrane, recruit Drp1 from the cytoplasm to the mitochondrial surface and causemore » mitochondrial fusion, and MIEF2, like MIEF1, can interact with Drp1 and hFis1. MIEF1 and MIEF2, however, also differ in certain aspects. MIEF1 and MIEF2 are differentially expressed in human tissues during development. When overexpressed, MIEF2 exerts a stronger fusion-promoting effect than MIEF1, and in line with this, hFis1 and Mff can only partially revert the MIEF2-induced fusion phenotype, whereas MIEF1-induced fusion is reverted to a larger extent by hFis1 and Mff. MIEF2 forms high molecular weight oligomers, while MIEF1 is largely present as a dimer. Furthermore, MIEF1 and MIEF2 use distinct domains for oligomerization: in MIEF1, the region from amino acid residues 109–154 is required, whereas oligomerization of MIEF2 depends on amino acid residues 1 to 49, i.e. the N-terminal end. We also show that oligomerization of MIEF1 is not required for its mitochondrial localization and interaction with Drp1. In conclusion, our data suggest that the mitochondrial regulators MIEF1 and MIEF2 exert partially distinct functions in mitochondrial dynamics. - Highlights: • MIEF1 and MIEF2 recruit Drp1 to mitochondria and cause mitochondrial fusion. • MIEF2, like MIEF1, can interact with Drp1 and hFis1. • MIEF1 and MIEF2 are differentially expressed in human tissues during development. • MIEF2 exerts a stronger fusion-promoting effect than MIEF1. • MIEF2 can form oligomers, while MIEF1 is largely present as a dimer.« less

Protective role of Parkin in skeletal muscle contractile and mitochondrial function.

PubMed

Gouspillou, Gilles; Godin, Richard; Piquereau, Jérome; Picard, Martin; Mofarrahi, Mahroo; Mathew, Jasmin; Purves-Smith, Fennigje M; Sgarioto, Nicolas; Hepple, Russell T; Burelle, Yan; Hussain, Sabah N A

2018-04-22

Parkin, an E3 ubiquitin ligase encoded by the Park2 gene, has been implicated in the regulation of mitophagy, a quality control process in which defective mitochondria are degraded. The exact physiological significance of Parkin in regulating mitochondrial function and contractility in skeletal muscle remains largely unexplored. Using Park2 -/- mice, we show that Parkin ablation causes a decrease in muscle specific force, a severe decrease in mitochondrial respiration, mitochondrial uncoupling and an increased susceptibility to opening of the permeability transition pore. These results demonstrate that Parkin plays a protective role in the maintenance of normal mitochondrial and contractile functions in skeletal muscles. Parkin is an E3 ubiquitin ligase encoded by the Park2 gene. Parkin has been implicated in the regulation of mitophagy, a quality control process in which defective mitochondria are sequestered in autophagosomes and delivered to lysosomes for degradation. Although Parkin has been mainly studied for its implication in neuronal degeneration in Parkinson disease, its role in other tissues remains largely unknown. In the present study, we investigated the skeletal muscles of Park2 knockout (Park2 -/- ) mice to test the hypothesis that Parkin plays a physiological role in mitochondrial quality control in normal skeletal muscle, a tissue highly reliant on mitochondrial content and function. We first show that the tibialis anterior (TA) of Park2 -/- mice display a slight but significant decrease in its specific force. Park2 -/ - muscles also show a trend for type IIB fibre hypertrophy without alteration in muscle fibre type proportion. Compared to Park2 +/+ muscles, the mitochondrial function of Park2 -/- skeletal muscles was significantly impaired, as indicated by the significant decrease in ADP-stimulated mitochondrial respiratory rates, uncoupling, reduced activities of respiratory chain complexes containing mitochondrial DNA (mtDNA)-encoded subunits and increased susceptibility to opening of the permeability transition pore. Muscles of Park2 -/- mice also displayed a decrease in the content of the mitochondrial pro-fusion protein Mfn2 and an increase in the pro-fission protein Drp1 suggesting an increase in mitochondrial fragmentation. Finally, Park2 ablation resulted in an increase in basal autophagic flux in skeletal muscles. Overall, the results of the present study demonstrate that Parkin plays a protective role in the maintenance of normal mitochondrial and contractile functions in normal skeletal muscles. © 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.

Mitochondrial uncoupling proteins regulate angiotensin-converting enzyme expression: crosstalk between cellular and endocrine metabolic regulators suggested by RNA interference and genetic studies.

PubMed

Dhamrait, Sukhbir S; Maubaret, Cecilia; Pedersen-Bjergaard, Ulrik; Brull, David J; Gohlke, Peter; Payne, John R; World, Michael; Thorsteinsson, Birger; Humphries, Steve E; Montgomery, Hugh E

2016-07-01

Uncoupling proteins (UCPs) regulate mitochondrial function, and thus cellular metabolism. Angiotensin-converting enzyme (ACE) is the central component of endocrine and local tissue renin-angiotensin systems (RAS), which also regulate diverse aspects of whole-body metabolism and mitochondrial function (partly through altering mitochondrial UCP expression). We show that ACE expression also appears to be regulated by mitochondrial UCPs. In genetic analysis of two unrelated populations (healthy young UK men and Scandinavian diabetic patients) serum ACE (sACE) activity was significantly higher amongst UCP3-55C (rather than T) and UCP2 I (rather than D) allele carriers. RNA interference against UCP2 in human umbilical vein endothelial cells reduced UCP2 mRNA sixfold (P < 0·01) whilst increasing ACE expression within a physiological range (<1·8-fold at 48 h; P < 0·01). Our findings suggest novel hypotheses. Firstly, cellular feedback regulation may occur between UCPs and ACE. Secondly, cellular UCP regulation of sACE suggests a novel means of crosstalk between (and mutual regulation of) cellular and endocrine metabolism. This might partly explain the reduced risk of developing diabetes and metabolic syndrome with RAS antagonists and offer insight into the origins of cardiovascular disease in which UCPs and ACE both play a role. © 2016 The Authors. BioEssays published by WILEY Periodicals, Inc.

Mitochondrial uncoupling proteins regulate angiotensin‐converting enzyme expression: crosstalk between cellular and endocrine metabolic regulators suggested by RNA interference and genetic studies

PubMed Central

Maubaret, Cecilia; Pedersen‐Bjergaard, Ulrik; Brull, David J.; Gohlke, Peter; Payne, John R.; World, Michael; Thorsteinsson, Birger; Humphries, Steve E.; Montgomery, Hugh E.

2015-01-01

Uncoupling proteins (UCPs) regulate mitochondrial function, and thus cellular metabolism. Angiotensin‐converting enzyme (ACE) is the central component of endocrine and local tissue renin–angiotensin systems (RAS), which also regulate diverse aspects of whole‐body metabolism and mitochondrial function (partly through altering mitochondrial UCP expression). We show that ACE expression also appears to be regulated by mitochondrial UCPs. In genetic analysis of two unrelated populations (healthy young UK men and Scandinavian diabetic patients) serum ACE (sACE) activity was significantly higher amongst UCP3‐55C (rather than T) and UCP2 I (rather than D) allele carriers. RNA interference against UCP2 in human umbilical vein endothelial cells reduced UCP2 mRNA sixfold (P < 0·01) whilst increasing ACE expression within a physiological range (<1·8‐fold at 48 h; P < 0·01). Our findings suggest novel hypotheses. Firstly, cellular feedback regulation may occur between UCPs and ACE. Secondly, cellular UCP regulation of sACE suggests a novel means of crosstalk between (and mutual regulation of) cellular and endocrine metabolism. This might partly explain the reduced risk of developing diabetes and metabolic syndrome with RAS antagonists and offer insight into the origins of cardiovascular disease in which UCPs and ACE both play a role. PMID:27347560

Mitochondrial uncoupling proteins regulate angiotensin-converting enzyme expression: crosstalk between cellular and endocrine metabolic regulators suggested by RNA interference and genetic studies.

PubMed

Dhamrait, Sukhbir S; Maubaret, Cecilia; Pedersen-Bjergaard, Ulrik; Brull, David J; Gohlke, Peter; Payne, John R; World, Michael; Thorsteinsson, Birger; Humphries, Steve E; Montgomery, Hugh E

2016-01-01

Uncoupling proteins (UCPs) regulate mitochondrial function, and thus cellular metabolism. Angiotensin-converting enzyme (ACE) is the central component of endocrine and local tissue renin-angiotensin systems (RAS), which also regulate diverse aspects of whole-body metabolism and mitochondrial function (partly through altering mitochondrial UCP expression). We show that ACE expression also appears to be regulated by mitochondrial UCPs. In genetic analysis of two unrelated populations ( healthy young UK men and Scandinavian diabetic patients ) serum ACE (sACE) activity was significantly higher amongst UCP3-55C (rather than T) and UCP2 I (rather than D) allele carriers. RNA interference against UCP2 in human umbilical vein endothelial cells reduced UCP2 mRNA sixfold ( P  < 0·01) whilst increasing ACE expression within a physiological range (<1·8-fold at 48 h; P  < 0·01). Our findings suggest novel hypotheses. Firstly, cellular feedback regulation may occur between UCPs and ACE. Secondly, cellular UCP regulation of sACE suggests a novel means of crosstalk between (and mutual regulation of) cellular and endocrine metabolism. This might partly explain the reduced risk of developing diabetes and metabolic syndrome with RAS antagonists and offer insight into the origins of cardiovascular disease in which UCPs and ACE both play a role.

Regulation of mitochondrial bioenergetics by the non-canonical roles of mitochondrial dynamics proteins in the heart.

PubMed

Wang, Wang; Fernandez-Sanz, Celia; Sheu, Shey-Shing

2018-05-01

Recent advancement in mitochondrial research has significantly extended our knowledge on the role and regulation of mitochondria in health and disease. One important breakthrough is the delineation of how mitochondrial morphological changes, termed mitochondrial dynamics, are coupled to the bioenergetics and signaling functions of mitochondria. In general, it is believed that fusion leads to an increased mitochondrial respiration efficiency and resistance to stress-induced dysfunction while fission does the contrary. This concept seems not applicable to adult cardiomyocytes. The mitochondria in adult cardiomyocytes exhibit fragmented morphology (tilted towards fission) and show less networking and movement as compared to other cell types. However, being the most energy-demanding cells, cardiomyocytes in the adult heart possess vast number of mitochondria, high level of energy flow, and abundant mitochondrial dynamics proteins. This apparent discrepancy could be explained by recently identified new functions of the mitochondrial dynamics proteins. These "non-canonical" roles of mitochondrial dynamics proteins range from controlling inter-organelle communication to regulating cell viability and survival under metabolic stresses. Here, we summarize the newly identified non-canonical roles of mitochondrial dynamics proteins. We focus on how these fission and fusion independent roles of dynamics proteins regulate mitochondrial bioenergetics. We also discuss potential molecular mechanisms, unique intracellular location, and the cardiovascular disease relevance of these non-canonical roles of the dynamics proteins. We propose that future studies are warranted to differentiate the canonical and non-canonical roles of dynamics proteins and to identify new approaches for the treatment of heart diseases. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers. Copyright © 2017 Elsevier B.V. All rights reserved.

p53 improves aerobic exercise capacity and augments skeletal muscle mitochondrial DNA content.

PubMed

Park, Joon-Young; Wang, Ping-Yuan; Matsumoto, Takumi; Sung, Ho Joong; Ma, Wenzhe; Choi, Jeong W; Anderson, Stasia A; Leary, Scot C; Balaban, Robert S; Kang, Ju-Gyeong; Hwang, Paul M

2009-09-25

Exercise capacity is a physiological characteristic associated with protection from both cardiovascular and all-cause mortality. p53 regulates mitochondrial function and its deletion markedly diminishes exercise capacity, but the underlying genetic mechanism orchestrating this is unclear. Understanding the biology of how p53 improves exercise capacity may provide useful insights for improving both cardiovascular as well as general health. The purpose of this study was to understand the genetic mechanism by which p53 regulates aerobic exercise capacity. Using a variety of physiological, metabolic, and molecular techniques, we further characterized maximum exercise capacity and the effects of training, measured various nonmitochondrial and mitochondrial determinants of exercise capacity, and examined putative regulators of mitochondrial biogenesis. As p53 did not affect baseline cardiac function or inotropic reserve, we focused on the involvement of skeletal muscle and now report a wider role for p53 in modulating skeletal muscle mitochondrial function. p53 interacts with Mitochondrial Transcription Factor A (TFAM), a nuclear-encoded gene important for mitochondrial DNA (mtDNA) transcription and maintenance, and regulates mtDNA content. The increased mtDNA in p53(+/+) compared to p53(-/-) mice was more marked in aerobic versus glycolytic skeletal muscle groups with no significant changes in cardiac tissue. These in vivo observations were further supported by in vitro studies showing overexpression of p53 in mouse myoblasts increases both TFAM and mtDNA levels whereas depletion of TFAM by shRNA decreases mtDNA content. Our current findings indicate that p53 promotes aerobic metabolism and exercise capacity by using different mitochondrial genes and mechanisms in a tissue-specific manner.

The cyclophilin D/Drp1 axis regulates mitochondrial fission contributing to oxidative stress-induced mitochondrial dysfunctions in SH-SY5Y cells.

PubMed

Xiao, Anqi; Gan, Xueqi; Chen, Ruiqi; Ren, Yanming; Yu, Haiyang; You, Chao

2017-01-29

Oxidative stress plays a central role in the pathogenesis of various neurodegenerative diseases. Increasing evidences have demonstrated that structural abnormalities in mitochondria are involved in oxidative stress related nerve cell damage. And Drp1 plays a critical role in mitochondrial dynamic imbalance insulted by oxidative stress-derived mitochondria. However, the status of mitochondrial fusion and fission pathway and its relationship with mitochondrial properties such as mitochondrial membrane permeability transition pore (mPTP) have not been fully elucidated. Here, we demonstrated for the first time the role of Cyclophilin D (CypD), a crucial component for mPTP formation, in the regulation of mitochondrial dynamics in oxidative stress treated nerve cell. We observed that CypD-mediated phosphorylation of Drp1 and subsequently augmented Drp1 recruitment to mitochondria and shifts mitochondrial dynamics toward excessive fission, which contributes to the mitochondrial structural and functional dysfunctions in oxidative stress-treated nerve cells. CypD depletion or over expression accompanies mitochondrial dynamics/functions recovery or aggravation separately. We also demonstrated first time the link between the CypD to mitochondrial dynamics. Our data offer new insights into the mechanism of mitochondrial dynamics which contribute to the mitochondrial dysfunctions, specifically the role of CypD in Drp1-mediated mitochondrial fission. The protective effect of CsA, or other molecules affecting the function of CypD hold promise as a potential novel therapeutic strategy for governing oxidative stress pathology via mitochondrial pathways. Copyright © 2016 Elsevier Inc. All rights reserved.

ROS regulation of axonal mitochondrial transport is mediated by Ca2+ and JNK in Drosophila

PubMed Central

Liao, Pin-Chao; Tandarich, Lauren C.

2017-01-01

Mitochondria perform critical functions including aerobic ATP production and calcium (Ca2+) homeostasis, but are also a major source of reactive oxygen species (ROS) production. To maintain cellular function and survival in neurons, mitochondria are transported along axons, and accumulate in regions with high demand for their functions. Oxidative stress and abnormal mitochondrial axonal transport are associated with neurodegenerative disorders. However, we know little about the connection between these two. Using the Drosophila third instar larval nervous system as the in vivo model, we found that ROS inhibited mitochondrial axonal transport more specifically, primarily due to reduced flux and velocity, but did not affect transport of other organelles. To understand the mechanisms underlying these effects, we examined Ca2+ levels and the JNK (c-Jun N-terminal Kinase) pathway, which have been shown to regulate mitochondrial transport and general fast axonal transport, respectively. We found that elevated ROS increased Ca2+ levels, and that experimental reduction of Ca2+ to physiological levels rescued ROS-induced defects in mitochondrial transport in primary neuron cell cultures. In addition, in vivo activation of the JNK pathway reduced mitochondrial flux and velocities, while JNK knockdown partially rescued ROS-induced defects in the anterograde direction. We conclude that ROS have the capacity to regulate mitochondrial traffic, and that Ca2+ and JNK signaling play roles in mediating these effects. In addition to transport defects, ROS produces imbalances in mitochondrial fission-fusion and metabolic state, indicating that mitochondrial transport, fission-fusion steady state, and metabolic state are closely interrelated in the response to ROS. PMID:28542430

Phosphatidic acid (PA)-preferring phospholipase A1 regulates mitochondrial dynamics.

PubMed

Baba, Takashi; Kashiwagi, Yuriko; Arimitsu, Nagisa; Kogure, Takeshi; Edo, Ayumi; Maruyama, Tomohiro; Nakao, Kazuki; Nakanishi, Hiroki; Kinoshita, Makoto; Frohman, Michael A; Yamamoto, Akitsugu; Tani, Katsuko

2014-04-18

Recent studies have suggested that phosphatidic acid (PA), a cone-shaped phospholipid that can generate negative curvature of lipid membranes, participates in mitochondrial fusion. However, precise mechanisms underling the production and consumption of PA on the mitochondrial surface are not fully understood. Phosphatidic acid-preferring phospholipase A1 (PA-PLA1)/DDHD1 is the first identified intracellular phospholipase A1 and preferentially hydrolyzes PA in vitro. Its cellular and physiological functions have not been elucidated. In this study, we show that PA-PLA1 regulates mitochondrial dynamics. PA-PLA1, when ectopically expressed in HeLa cells, induced mitochondrial fragmentation, whereas its depletion caused mitochondrial elongation. The effects of PA-PLA1 on mitochondrial morphology appear to counteract those of MitoPLD, a mitochondrion-localized phospholipase D that produces PA from cardiolipin. Consistent with high levels of expression of PA-PLA1 in testis, PA-PLA1 knock-out mice have a defect in sperm formation. In PA-PLA1-deficient sperm, the mitochondrial structure is disorganized, and an abnormal gap structure exists between the middle and principal pieces. A flagellum is bent at that position, leading to a loss of motility. Our results suggest a possible mechanism of PA regulation of the mitochondrial membrane and demonstrate an in vivo function of PA-PLA1 in the organization of mitochondria during spermiogenesis.

Neuronal CRTC-1 governs systemic mitochondrial metabolism and lifespan via a catecholamine signal.

PubMed

Burkewitz, Kristopher; Morantte, Ianessa; Weir, Heather J M; Yeo, Robin; Zhang, Yue; Huynh, Frank K; Ilkayeva, Olga R; Hirschey, Matthew D; Grant, Ana R; Mair, William B

2015-02-26

Low energy states delay aging in multiple species, yet mechanisms coordinating energetics and longevity across tissues remain poorly defined. The conserved energy sensor AMP-activated protein kinase (AMPK) and its corresponding phosphatase calcineurin modulate longevity via the CREB regulated transcriptional coactivator (CRTC)-1 in C. elegans. We show that CRTC-1 specifically uncouples AMPK/calcineurin-mediated effects on lifespan from pleiotropic side effects by reprogramming mitochondrial and metabolic function. This pro-longevity metabolic state is regulated cell nonautonomously by CRTC-1 in the nervous system. Neuronal CRTC-1/CREB regulates peripheral metabolism antagonistically with the functional PPARα ortholog, NHR-49, drives mitochondrial fragmentation in distal tissues, and suppresses the effects of AMPK on systemic mitochondrial metabolism and longevity via a cell-nonautonomous catecholamine signal. These results demonstrate that while both local and distal mechanisms combine to modulate aging, distal regulation overrides local contribution. Targeting central perception of energetic state is therefore a potential strategy to promote healthy aging. Copyright © 2015 Elsevier Inc. All rights reserved.

Neuronal CRTC-1 governs systemic mitochondrial metabolism and lifespan via a catecholamine signal

PubMed Central

Burkewitz, Kristopher; Morantte, Ianessa; Weir, Heather J.M.; Yeo, Robin; Zhang, Yue; Huynh, Frank K.; Ilkayeva, Olga R.; Hirschey, Matthew D.; Grant, Ana R.; Mair, William B.

2015-01-01

SUMMARY Low energy states delay aging in multiple species, yet mechanisms coordinating energetics and longevity across tissues remain poorly defined. The conserved energy sensor AMP-activated protein kinase (AMPK) and its corresponding phosphatase calcineurin modulate longevity via the CREB regulated transcriptional coactivator (CRTC)-1 in C. elegans. We show that CRTC-1 specifically uncouples AMPK/calcineurin-mediated effects on lifespan from pleiotropic side effects by reprogramming mitochondrial and metabolic function. This pro-longevity metabolic state is regulated cell-nonautonomously by CRTC-1 in the nervous system. Neuronal CRTC-1/CREB regulates peripheral metabolism antagonistically with the functional PPARα ortholog, NHR-49, drives mitochondrial fragmentation in distal tissues, and suppresses the effects of AMPK on systemic mitochondrial metabolism and longevity via a cell-nonautonomous catecholamine signal. These results demonstrate that while both local and distal mechanisms combine to modulate aging, distal regulation overrides local contribution. Targeting central perception of energetic state is therefore a potential strategy to promote healthy aging. PMID:25723162

Mitochondria-associated endoplasmic reticulum membranes allow adaptation of mitochondrial metabolism to glucose availability in the liver.

PubMed

Theurey, Pierre; Tubbs, Emily; Vial, Guillaume; Jacquemetton, Julien; Bendridi, Nadia; Chauvin, Marie-Agnès; Alam, Muhammad Rizwan; Le Romancer, Muriel; Vidal, Hubert; Rieusset, Jennifer

2016-04-01

Mitochondria-associated endoplasmic reticulum membranes (MAM) play a key role in mitochondrial dynamics and function and in hepatic insulin action. Whereas mitochondria are important regulators of energy metabolism, the nutritional regulation of MAM in the liver and its role in the adaptation of mitochondria physiology to nutrient availability are unknown. In this study, we found that the fasted to postprandial transition reduced the number of endoplasmic reticulum-mitochondria contact points in mouse liver. Screening of potential hormonal/metabolic signals revealed glucose as the main nutritional regulator of hepatic MAM integrity both in vitro and in vivo Glucose reduced organelle interactions through the pentose phosphate-protein phosphatase 2A (PP-PP2A) pathway, induced mitochondria fission, and impaired respiration. Blocking MAM reduction counteracted glucose-induced mitochondrial alterations. Furthermore, disruption of MAM integrity mimicked effects of glucose on mitochondria dynamics and function. This glucose-sensing system is deficient in the liver of insulin-resistant ob/ob and cyclophilin D-KO mice, both characterized by chronic disruption of MAM integrity, mitochondrial fission, and altered mitochondrial respiration. These data indicate that MAM contribute to the hepatic glucose-sensing system, allowing regulation of mitochondria dynamics and function during nutritional transition. Chronic disruption of MAM may participate in hepatic mitochondrial dysfunction associated with insulin resistance. © The Author (2016). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.

Genomic integration of ERRγ-HNF1β regulates renal bioenergetics and prevents chronic kidney disease.

PubMed

Zhao, Juanjuan; Lupino, Katherine; Wilkins, Benjamin J; Qiu, Chengxiang; Liu, Jian; Omura, Yasuhiro; Allred, Amanda L; McDonald, Caitlin; Susztak, Katalin; Barish, Grant D; Pei, Liming

2018-05-22

Mitochondrial dysfunction is increasingly recognized as a critical determinant of both hereditary and acquired kidney diseases. However, it remains poorly understood how mitochondrial metabolism is regulated to support normal kidney function and how its dysregulation contributes to kidney disease. Here, we show that the nuclear receptor estrogen-related receptor gamma (ERRγ) and hepatocyte nuclear factor 1 beta (HNF1β) link renal mitochondrial and reabsorptive functions through coordinated epigenomic programs. ERRγ directly regulates mitochondrial metabolism but cooperatively controls renal reabsorption via convergent binding with HNF1β. Deletion of ERRγ in renal epithelial cells (RECs), in which it is highly and specifically expressed, results in severe renal energetic and reabsorptive dysfunction and progressive renal failure that recapitulates phenotypes of animals and patients with HNF1β loss-of-function gene mutations. Moreover, ERRγ expression positively correlates with renal function and is decreased in patients with chronic kidney disease (CKD). REC-ERRγ KO mice share highly overlapping renal transcriptional signatures with human patients with CKD. Together these findings reveal a role for ERRγ in directing independent and HNF1β-integrated programs for energy production and use essential for normal renal function and the prevention of kidney disease.

Mitochondrial Dynamics: Coupling Mitochondrial Fitness with Healthy Aging.

PubMed

Sebastián, David; Palacín, Manuel; Zorzano, Antonio

2017-03-01

Aging is associated with a decline in mitochondrial function and the accumulation of abnormal mitochondria. However, the precise mechanisms by which aging promotes these mitochondrial alterations and the role of the latter in aging are still not fully understood. Mitochondrial dynamics is a key process regulating mitochondrial function and quality. Altered expression of some mitochondrial dynamics proteins has been recently associated with aging and with age-related alterations in yeast, Caenorhabditis elegans, mice, and humans. Here, we review the link between alterations in mitochondrial dynamics, aging, and age-related impairment. We propose that the dysregulation of mitochondrial dynamics leads to age-induced accumulation of unhealthy mitochondria and contributes to alterations linked to aging, such as diabetes and neurodegeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impaired Insulin Signaling is Associated with Hepatic Mitochondrial Dysfunction in IR+/−-IRS-1+/− Double Heterozygous (IR-IRS1dh) Mice

PubMed Central

Franko, Andras; Kunze, Alexander; Böse, Marlen; von Kleist-Retzow, Jürgen-Christoph; Paulsson, Mats; Hartmann, Ursula; Wiesner, Rudolf J.

2017-01-01

Mitochondria play a pivotal role in energy metabolism, but whether insulin signaling per se could regulate mitochondrial function has not been identified yet. To investigate whether mitochondrial function is regulated by insulin signaling, we analyzed muscle and liver of insulin receptor (IR)+/−-insulin receptor substrate-1 (IRS-1)+/− double heterozygous (IR-IRS1dh) mice, a well described model for insulin resistance. IR-IRS1dh mice were studied at the age of 6 and 12 months and glucose metabolism was determined by glucose and insulin tolerance tests. Mitochondrial enzyme activities, oxygen consumption, and membrane potential were assessed using spectrophotometric, respirometric, and proton motive force analysis, respectively. IR-IRS1dh mice showed elevated serum insulin levels. Hepatic mitochondrial oxygen consumption was reduced in IR-IRS1dh animals at 12 months of age. Furthermore, 6-month-old IR-IRS1dh mice demonstrated enhanced mitochondrial respiration in skeletal muscle, but a tendency of impaired glucose tolerance. On the other hand, 12-month-old IR-IRS1dh mice showed improved glucose tolerance, but normal muscle mitochondrial function. Our data revealed that deficiency in IR/IRS-1 resulted in normal or even elevated skeletal muscle, but impaired hepatic mitochondrial function, suggesting a direct cross-talk between insulin signaling and mitochondria in the liver. PMID:28556799

Impaired Insulin Signaling is Associated with Hepatic Mitochondrial Dysfunction in IR+/--IRS-1+/- Double Heterozygous (IR-IRS1dh) Mice.

PubMed

Franko, Andras; Kunze, Alexander; Böse, Marlen; von Kleist-Retzow, Jürgen-Christoph; Paulsson, Mats; Hartmann, Ursula; Wiesner, Rudolf J

2017-05-30

Mitochondria play a pivotal role in energy metabolism, but whether insulin signaling per se could regulate mitochondrial function has not been identified yet. To investigate whether mitochondrial function is regulated by insulin signaling, we analyzed muscle and liver of insulin receptor (IR) +/- -insulin receptor substrate-1 (IRS-1) +/- double heterozygous (IR-IRS1dh) mice, a well described model for insulin resistance. IR-IRS1dh mice were studied at the age of 6 and 12 months and glucose metabolism was determined by glucose and insulin tolerance tests. Mitochondrial enzyme activities, oxygen consumption, and membrane potential were assessed using spectrophotometric, respirometric, and proton motive force analysis, respectively. IR-IRS1dh mice showed elevated serum insulin levels. Hepatic mitochondrial oxygen consumption was reduced in IR-IRS1dh animals at 12 months of age. Furthermore, 6-month-old IR-IRS1dh mice demonstrated enhanced mitochondrial respiration in skeletal muscle, but a tendency of impaired glucose tolerance. On the other hand, 12-month-old IR-IRS1dh mice showed improved glucose tolerance, but normal muscle mitochondrial function. Our data revealed that deficiency in IR/IRS-1 resulted in normal or even elevated skeletal muscle, but impaired hepatic mitochondrial function, suggesting a direct cross-talk between insulin signaling and mitochondria in the liver.

Cdc48 regulates a deubiquitylase cascade critical for mitochondrial fusion

PubMed Central

den Brave, Fabian

2018-01-01

Cdc48/p97, a ubiquitin-selective chaperone, orchestrates the function of E3 ligases and deubiquitylases (DUBs). Here, we identify a new function of Cdc48 in ubiquitin-dependent regulation of mitochondrial dynamics. The DUBs Ubp12 and Ubp2 exert opposing effects on mitochondrial fusion and cleave different ubiquitin chains on the mitofusin Fzo1. We demonstrate that Cdc48 integrates the activities of these two DUBs, which are themselves ubiquitylated. First, Cdc48 promotes proteolysis of Ubp12, stabilizing pro-fusion ubiquitylation on Fzo1. Second, loss of Ubp12 stabilizes Ubp2 and thereby facilitates removal of ubiquitin chains on Fzo1 inhibiting fusion. Thus, Cdc48 synergistically regulates the ubiquitylation status of Fzo1, allowing to control the balance between activation or repression of mitochondrial fusion. In conclusion, we unravel a new cascade of ubiquitylation events, comprising Cdc48 and two DUBs, fine-tuning the fusogenic activity of Fzo1. PMID:29309037

Redox regulation of mitochondrial function with emphasis on cysteine oxidation reactions☆

PubMed Central

Mailloux, Ryan J.; Jin, Xiaolei; Willmore, William G.

2013-01-01

Mitochondria have a myriad of essential functions including metabolism and apoptosis. These chief functions are reliant on electron transfer reactions and the production of ATP and reactive oxygen species (ROS). The production of ATP and ROS are intimately linked to the electron transport chain (ETC). Electrons from nutrients are passed through the ETC via a series of acceptor and donor molecules to the terminal electron acceptor molecular oxygen (O2) which ultimately drives the synthesis of ATP. Electron transfer through the respiratory chain and nutrient oxidation also produces ROS. At high enough concentrations ROS can activate mitochondrial apoptotic machinery which ultimately leads to cell death. However, if maintained at low enough concentrations ROS can serve as important signaling molecules. Various regulatory mechanisms converge upon mitochondria to modulate ATP synthesis and ROS production. Given that mitochondrial function depends on redox reactions, it is important to consider how redox signals modulate mitochondrial processes. Here, we provide the first comprehensive review on how redox signals mediated through cysteine oxidation, namely S-oxidation (sulfenylation, sulfinylation), S-glutathionylation, and S-nitrosylation, regulate key mitochondrial functions including nutrient oxidation, oxidative phosphorylation, ROS production, mitochondrial permeability transition (MPT), apoptosis, and mitochondrial fission and fusion. We also consider the chemistry behind these reactions and how they are modulated in mitochondria. In addition, we also discuss emerging knowledge on disorders and disease states that are associated with deregulated redox signaling in mitochondria and how mitochondria-targeted medicines can be utilized to restore mitochondrial redox signaling. PMID:24455476

Redox regulation of mitochondrial function with emphasis on cysteine oxidation reactions.

PubMed

Mailloux, Ryan J; Jin, Xiaolei; Willmore, William G

2014-01-01

Mitochondria have a myriad of essential functions including metabolism and apoptosis. These chief functions are reliant on electron transfer reactions and the production of ATP and reactive oxygen species (ROS). The production of ATP and ROS are intimately linked to the electron transport chain (ETC). Electrons from nutrients are passed through the ETC via a series of acceptor and donor molecules to the terminal electron acceptor molecular oxygen (O2) which ultimately drives the synthesis of ATP. Electron transfer through the respiratory chain and nutrient oxidation also produces ROS. At high enough concentrations ROS can activate mitochondrial apoptotic machinery which ultimately leads to cell death. However, if maintained at low enough concentrations ROS can serve as important signaling molecules. Various regulatory mechanisms converge upon mitochondria to modulate ATP synthesis and ROS production. Given that mitochondrial function depends on redox reactions, it is important to consider how redox signals modulate mitochondrial processes. Here, we provide the first comprehensive review on how redox signals mediated through cysteine oxidation, namely S-oxidation (sulfenylation, sulfinylation), S-glutathionylation, and S-nitrosylation, regulate key mitochondrial functions including nutrient oxidation, oxidative phosphorylation, ROS production, mitochondrial permeability transition (MPT), apoptosis, and mitochondrial fission and fusion. We also consider the chemistry behind these reactions and how they are modulated in mitochondria. In addition, we also discuss emerging knowledge on disorders and disease states that are associated with deregulated redox signaling in mitochondria and how mitochondria-targeted medicines can be utilized to restore mitochondrial redox signaling.

The Kunitz-protease inhibitor domain in amyloid precursor protein reduces cellular mitochondrial enzymes expression and function.

PubMed

Chua, Li-Min; Lim, Mei-Li; Wong, Boon-Seng

2013-08-09

Mitochondrial dysfunction is a prominent feature of Alzheimer's disease (AD) and this can be contributed by aberrant metabolic enzyme function. But, the mechanism causing this enzymatic impairment is unclear. Amyloid precursor protein (APP) is known to be alternatively spliced to produce three major isoforms in the brain (APP695, APP751, APP770). Both APP770 and APP751 contain the Kunitz Protease Inhibitory (KPI) domain, but the former also contain an extra OX-2 domain. APP695 on the other hand, lacks both domains. In AD, up-regulation of the KPI-containing APP isoforms has been reported. But the functional contribution of this elevation is unclear. In the present study, we have expressed and compared the effect of the non-KPI containing APP695 and the KPI-containing APP751 on mitochondrial function. We found that the KPI-containing APP751 significantly decreased the expression of three major mitochondrial metabolic enzymes; citrate synthase, succinate dehydrogenase and cytochrome c oxidase (COX IV). This reduction lowers the NAD(+)/NADH ratio, COX IV activity and mitochondrial membrane potential. Overall, this study demonstrated that up-regulation of the KPI-containing APP isoforms is likely to contribute to the impairment of metabolic enzymes and mitochondrial function in AD. Copyright © 2013 Elsevier Inc. All rights reserved.

Mitochondrial dysfunction as a central actor in intellectual disability-related diseases: an overview of Down syndrome, autism, Fragile X and Rett syndrome.

PubMed

Valenti, Daniela; de Bari, Lidia; De Filippis, Bianca; Henrion-Caude, Alexandra; Vacca, Rosa Anna

2014-10-01

Clinical manifestations typical of mitochondrial diseases are often present in various genetic syndromes associated with intellectual disability, a condition leading to deficit in cognitive functions and adaptive behaviors. Until now, the causative mechanism leading to intellectual disability is unknown and the progression of the condition is poorly understood. We first report latest advances on genetic and environmental regulation of mitochondrial function and its role in brain development. Starting from the structure, function and regulation of the oxidative phosphorylation apparatus, we review how mitochondrial biogenesis and dynamics play a central role in neurogenesis and neuroplasticity. We then discuss how dysfunctional mitochondria and alterations in reactive oxygen species homeostasis are potentially involved in the pathogenesis of various neurodevelopmental syndromes with a special focus on Down, Rett, Fragile X syndromes and autism spectrum disorders. Finally, we review and suggest novel therapeutic approaches aimed at improving intellectual disability by activating mitochondrial function and reducing oxidative stress to amiliorate the quality of life in the subjects affected. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dynamic survey of mitochondria by ubiquitin

PubMed Central

Escobar-Henriques, Mafalda; Langer, Thomas

2014-01-01

Ubiquitin is a post-translational modifier with proteolytic and non-proteolytic roles in many biological processes. At mitochondria, it performs regulatory homeostatic functions and contributes to mitochondrial quality control. Ubiquitin is essential for mitochondrial fusion, regulates mitochondria-ER contacts, and participates in maternal mtDNA inheritance. Under stress, mitochondrial dysfunction induces ubiquitin-dependent responses that involve mitochondrial proteome remodeling and culminate in organelle removal by mitophagy. In addition, many ubiquitin-dependent mechanisms have been shown to regulate innate immune responses and xenophagy. Here, we review the emerging roles of ubiquitin at mitochondria. PMID:24569520

Mitochondrial Quality Control via the PGC1α-TFEB Signaling Pathway Is Compromised by Parkin Q311X Mutation But Independently Restored by Rapamycin.

PubMed

Siddiqui, Almas; Bhaumik, Dipa; Chinta, Shankar J; Rane, Anand; Rajagopalan, Subramanian; Lieu, Christopher A; Lithgow, Gordon J; Andersen, Julie K

2015-09-16

Following its activation by PINK1, parkin is recruited to depolarized mitochondria where it ubiquitinates outer mitochondrial membrane proteins, initiating lysosomal-mediated degradation of these organelles. Mutations in the gene encoding parkin, PARK2, result in both familial and sporadic forms of Parkinson's disease (PD) in conjunction with reductions in removal of damaged mitochondria. In contrast to what has been reported for other PARK2 mutations, expression of the Q311X mutation in vivo in mice appears to involve a downstream step in the autophagic pathway at the level of lysosomal function. This coincides with increased PARIS expression and reduced expression of a reciprocal signaling pathway involving the master mitochondrial regulator peroxisome proliferator-activated receptor-gamma coactivator (PGC1α) and the lysosomal regulator transcription factor EB (TFEB). Treatment with rapamycin was found to independently restore PGC1α-TFEB signaling in a manner not requiring parkin activity and to abrogate impairment of mitochondrial quality control and neurodegenerative features associated with this in vivo model. Losses in PGC1α-TFEB signaling in cultured rat DAergic cells expressing the Q311X mutation associated with reduced mitochondrial function and cell viability were found to be PARIS-dependent and to be independently restored by rapamycin in a manner requiring TFEB. Studies in human iPSC-derived neurons demonstrate that TFEB induction can restore mitochondrial function and cell viability in a mitochondrially compromised human cell model. Based on these data, we propose that the parkin Q311X mutation impacts on mitochondrial quality control via PARIS-mediated regulation of PGC1α-TFEB signaling and that this can be independently restored via upregulation of TFEB function. Mutations in PARK2 are generally associated with loss in ability to interact with PINK1, impacting on autophagic initiation. Our data suggest that, in the case of at least one parkin mutation, Q311X, detrimental effects are due to inhibition at the level of downstream lysosomal function. Mechanistically, this involves elevations in PARIS protein levels and subsequent effects on PGC1α-TFEB signaling that normally regulates mitochondrial quality control. Treatment with rapamycin independently restores PGC1α-TFEB signaling in a manner not requiring parkin activity and abrogates subsequent mitochondrial impairment and neuronal cell loss. Taken in total, our data suggest that the parkin Q311X mutation impacts on mitochondrial quality control via PARIS-mediated regulation of PGC1α-TFEB signaling and that this can be independently restored via rapamycin. Copyright © 2015 the authors 0270-6474/15/3512833-12$15.00/0.

Interaction between hormonal and mitochondrial signalling during growth, development and in plant defence responses.

PubMed

Berkowitz, Oliver; De Clercq, Inge; Van Breusegem, Frank; Whelan, James

2016-05-01

Mitochondria play a central role in plant metabolism as they are a major source of ATP through synthesis by the oxidative phosphorylation pathway and harbour key metabolic reactions such as the TCA cycle. The energy and building blocks produced by mitochondria are essential to drive plant growth and development as well as to provide fuel for responses to abiotic and biotic stresses. The majority of mitochondrial proteins are encoded in the nuclear genome and have to be imported into the organelle. For the regulation of the corresponding genes intricate signalling pathways exist to adjust their expression. Signals directly regulate nuclear gene expression (anterograde signalling) to adjust the protein composition of the mitochondria to the needs of the cell. In parallel, mitochondria communicate back their functional status to the nucleus (retrograde signalling) to prompt transcriptional regulation of responsive genes via largely unknown signalling mechanisms. Plant hormones are the major signalling components regulating all layers of plant development and cellular functions. Increasing evidence is now becoming available that plant hormones are also part of signalling networks controlling mitochondrial function and their biogenesis. This review summarizes recent advances in understanding the interaction of mitochondrial and hormonal signalling pathways. © 2016 John Wiley & Sons Ltd.

p21{sup WAF1/CIP1} deficiency induces mitochondrial dysfunction in HCT116 colon cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Ae Jeong; Jee, Hye Jin; Song, Naree

2013-01-11

Highlights: Black-Right-Pointing-Pointer p21{sup -/-} HCT116 cells exhibited an increase in mitochondrial mass. Black-Right-Pointing-Pointer The expression levels of PGC-1{alpha} and AMPK were upregulated in p21{sup -/-} HCT116 cells. Black-Right-Pointing-Pointer The proliferation of p21{sup -/-} HCT116 cells in galactose medium was significantly impaired. Black-Right-Pointing-Pointer p21 may play a role in maintaining proper mitochondrial mass and respiratory function. -- Abstract: p21{sup WAF1/CIP1} is a critical regulator of cell cycle progression. However, the role of p21 in mitochondrial function remains poorly understood. In this study, we examined the effect of p21 deficiency on mitochondrial function in HCT116 human colon cancer cells. We found thatmore » there was a significant increase in the mitochondrial mass of p21{sup -/-} HCT116 cells, as measured by 10-N-nonyl-acridine orange staining, as well as an increase in the mitochondrial DNA content. In contrast, p53{sup -/-} cells had a mitochondrial mass comparable to that of wild-type HCT116 cells. In addition, the expression levels of the mitochondrial biogenesis regulators PGC-1{alpha} and TFAM and AMPK activity were also elevated in p21{sup -/-} cells, indicating that p21 deficiency induces the rate of mitochondrial biogenesis through the AMPK-PGC-1{alpha} axis. However, the increase in mitochondrial biogenesis in p21{sup -/-} cells did not accompany an increase in the cellular steady-state level of ATP. Furthermore, p21{sup -/-} cells exhibited significant proliferation impairment in galactose medium, suggesting that p21 deficiency induces a defect in the mitochondrial respiratory chain in HCT116 cells. Taken together, our results suggest that the loss of p21 results in an aberrant increase in the mitochondrial mass and in mitochondrial dysfunction in HCT116 cells, indicating that p21 is required to maintain proper mitochondrial mass and respiratory function.« less

Cyclin D1 Determines Mitochondrial Function In Vivo†

PubMed Central

Sakamaki, Toshiyuki; Casimiro, Mathew C.; Ju, Xiaoming; Quong, Andrew A.; Katiyar, Sanjay; Liu, Manran; Jiao, Xuanmao; Li, Anping; Zhang, Xueping; Lu, Yinan; Wang, Chenguang; Byers, Stephen; Nicholson, Robert; Link, Todd; Shemluck, Melvin; Yang, Jianguo; Fricke, Stanley T.; Novikoff, Phyllis M.; Papanikolaou, Alexandros; Arnold, Andrew; Albanese, Christopher; Pestell, Richard

2006-01-01

The cyclin D1 gene encodes a regulatory subunit of the holoenzyme that phosphorylates and inactivates the pRb tumor suppressor to promote nuclear DNA synthesis. cyclin D1 is overexpressed in human breast cancers and is sufficient for the development of murine mammary tumors. Herein, cyclin D1 is shown to perform a novel function, inhibiting mitochondrial function and size. Mitochondrial activity was enhanced by genetic deletion or antisense or small interfering RNA to cyclin D1. Global gene expression profiling and functional analysis of mammary epithelial cell-targeted cyclin D1 antisense transgenics demonstrated that cyclin D1 inhibits mitochondrial activity and aerobic glycolysis in vivo. Reciprocal regulation of these genes was observed in cyclin D1-induced mammary tumors. Cyclin D1 thus integrates nuclear DNA synthesis and mitochondrial function. PMID:16809779

Constriction of the mitochondrial inner compartment is a priming event for mitochondrial division

PubMed Central

Cho, Bongki; Cho, Hyo Min; Jo, Youhwa; Kim, Hee Dae; Song, Myungjae; Moon, Cheil; Kim, Hyongbum; Kim, Kyungjin; Sesaki, Hiromi; Rhyu, Im Joo; Kim, Hyun; Sun, Woong

2017-01-01

Mitochondrial division is critical for the maintenance and regulation of mitochondrial function, quality and distribution. This process is controlled by cytosolic actin-based constriction machinery and dynamin-related protein 1 (Drp1) on mitochondrial outer membrane (OMM). Although mitochondrial physiology, including oxidative phosphorylation, is also important for efficient mitochondrial division, morphological alterations of the mitochondrial inner-membrane (IMM) have not been clearly elucidated. Here we report spontaneous and repetitive constriction of mitochondrial inner compartment (CoMIC) associated with subsequent division in neurons. Although CoMIC is potentiated by inhibition of Drp1 and occurs at the potential division spots contacting the endoplasmic reticulum, it appears on IMM independently of OMM. Intra-mitochondrial influx of Ca2+ induces and potentiates CoMIC, and leads to K+-mediated mitochondrial bulging and depolarization. Synergistically, optic atrophy 1 (Opa1) also regulates CoMIC via controlling Mic60-mediated OMM–IMM tethering. Therefore, we propose that CoMIC is a priming event for efficient mitochondrial division. PMID:28598422

Mitochondrial Redox Signaling and Tumor Progression.

PubMed

Chen, Yuxin; Zhang, Haiqing; Zhou, Huanjiao Jenny; Ji, Weidong; Min, Wang

2016-03-25

Cancer cell can reprogram their energy production by switching mitochondrial oxidative phosphorylation to glycolysis. However, mitochondria play multiple roles in cancer cells, including redox regulation, reactive oxygen species (ROS) generation, and apoptotic signaling. Moreover, these mitochondrial roles are integrated via multiple interconnected metabolic and redox sensitive pathways. Interestingly, mitochondrial redox proteins biphasically regulate tumor progression depending on cellular ROS levels. Low level of ROS functions as signaling messengers promoting cancer cell proliferation and cancer invasion. However, anti-cancer drug-initiated stress signaling could induce excessive ROS, which is detrimental to cancer cells. Mitochondrial redox proteins could scavenger basal ROS and function as "tumor suppressors" or prevent excessive ROS to act as "tumor promoter". Paradoxically, excessive ROS often also induce DNA mutations and/or promotes tumor metastasis at various stages of cancer progression. Targeting redox-sensitive pathways and transcriptional factors in the appropriate context offers great promise for cancer prevention and therapy. However, the therapeutics should be cancer-type and stage-dependent.

SIRT1 Activation by Resveratrol Alleviates Cardiac Dysfunction via Mitochondrial Regulation in Diabetic Cardiomyopathy Mice.

PubMed

Ma, Sai; Feng, Jing; Zhang, Ran; Chen, Jiangwei; Han, Dong; Li, Xiang; Yang, Bo; Li, Xiujuan; Fan, Miaomiao; Li, Congye; Tian, Zuhong; Wang, Yabin; Cao, Feng

2017-01-01

Diabetic cardiomyopathy (DCM) is a major threat for diabetic patients. Silent information regulator 1 (SIRT1) has a regulatory effect on mitochondrial dynamics, which is associated with DCM pathological changes. Our study aims to investigate whether resveratrol, a SRIT1 activator, could exert a protective effect against DCM. Cardiac-specific SIRT1 knockout (SIRT1 KO ) mice were generated using Cre-loxP system. SIRT1 KO mice displayed symptoms of DCM, including cardiac hypertrophy and dysfunction, insulin resistance, and abnormal glucose metabolism. DCM and SIRT1 KO hearts showed impaired mitochondrial biogenesis and function, while SIRT1 activation by resveratrol reversed this in DCM mice. High glucose caused increased apoptosis, impaired mitochondrial biogenesis, and function in cardiomyocytes, which was alleviated by resveratrol. SIRT1 deletion by both SIRT1 KO and shRNA abolished the beneficial effects of resveratrol. Furthermore, the function of SIRT1 is mediated via the deacetylation effect on peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), thus inducing increased expression of nuclear respiratory factor 1 (NRF-1), NRF-2, estrogen-related receptor-α (ERR-α), and mitochondrial transcription factor A (TFAM). Cardiac deletion of SIRT1 caused phenotypes resembling DCM. Activation of SIRT1 by resveratrol ameliorated cardiac injuries in DCM through PGC-1α-mediated mitochondrial regulation. Collectively, SIRT1 may serve as a potential therapeutic target for DCM.

Regulation of mitochondria-dynactin interaction and mitochondrial retrograde transport in axons.

PubMed

Drerup, Catherine M; Herbert, Amy L; Monk, Kelly R; Nechiporuk, Alex V

2017-04-17

Mitochondrial transport in axons is critical for neural circuit health and function. While several proteins have been found that modulate bidirectional mitochondrial motility, factors that regulate unidirectional mitochondrial transport have been harder to identify. In a genetic screen, we found a zebrafish strain in which mitochondria fail to attach to the dynein retrograde motor. This strain carries a loss-of-function mutation in actr10 , a member of the dynein-associated complex dynactin. The abnormal axon morphology and mitochondrial retrograde transport defects observed in actr10 mutants are distinct from dynein and dynactin mutant axonal phenotypes. In addition, Actr10 lacking the dynactin binding domain maintains its ability to bind mitochondria, arguing for a role for Actr10 in dynactin-mitochondria interaction. Finally, genetic interaction studies implicated Drp1 as a partner in Actr10-dependent mitochondrial retrograde transport. Together, this work identifies Actr10 as a factor necessary for dynactin-mitochondria interaction, enhancing our understanding of how mitochondria properly localize in axons.

Protein kinase C epsilon regulates mitochondrial pools of Nampt and NAD following resveratrol and ischemic preconditioning in the rat cortex

PubMed Central

Morris-Blanco, Kahlilia C; Cohan, Charles H; Neumann, Jake T; Sick, Thomas J; Perez-Pinzon, Miguel A

2014-01-01

Preserving mitochondrial pools of nicotinamide adenine dinucleotide (NAD) or nicotinamide phosphoribosyltransferase (Nampt), an enzyme involved in NAD production, maintains mitochondrial function and confers neuroprotection after ischemic stress. However, the mechanisms involved in regulating mitochondrial-localized Nampt or NAD have not been defined. In this study, we investigated the roles of protein kinase C epsilon (PKCɛ) and AMP-activated protein kinase (AMPK) in regulating mitochondrial pools of Nampt and NAD after resveratrol or ischemic preconditioning (IPC) in the cortex and in primary neuronal-glial cortical cultures. Using the specific PKCɛ agonist ψɛRACK, we found that PKCɛ induced robust activation of AMPK in vitro and in vivo and that AMPK was required for PKCɛ-mediated ischemic neuroprotection. In purified mitochondrial fractions, PKCɛ enhanced Nampt levels in an AMPK-dependent manner and was required for increased mitochondrial Nampt after IPC or resveratrol treatment. Analysis of intrinsic NAD autofluorescence using two-photon microscopy revealed that PKCɛ modulated NAD in the mitochondrial fraction. Further assessments of mitochondrial NAD concentrations showed that PKCɛ has a key role in regulating the mitochondrial NAD+/nicotinamide adenine dinucleotide reduced (NADH) ratio after IPC and resveratrol treatment in an AMPK- and Nampt-dependent manner. These findings indicate that PKCɛ is critical to increase or maintain mitochondrial Nampt and NAD after pathways of ischemic neuroprotection in the brain. PMID:24667915

Metformin improves cardiac function in mice with heart failure after myocardial infarction by regulating mitochondrial energy metabolism.

PubMed

Sun, Dan; Yang, Fei

2017-04-29

To investigate whether metformin can improve the cardiac function through improving the mitochondrial function in model of heart failure after myocardial infarction. Male C57/BL6 mice aged about 8 weeks were selected and the anterior descending branch was ligatured to establish the heart failure model after myocardial infarction. The cardiac function was evaluated via ultrasound after 3 days to determine the modeling was successful, and the mice were randomly divided into two groups. Saline group (Saline) received the intragastric administration of normal saline for 4 weeks, and metformin group (Met) received the intragastric administration of metformin for 4 weeks. At the same time, Shame group (Sham) was set up. Changes in cardiac function in mice were detected at 4 weeks after operation. Hearts were taken from mice after 4 weeks, and cell apoptosis in myocardial tissue was detected using TUNEL method; fresh mitochondria were taken and changes in oxygen consumption rate (OCR) and respiratory control rate (RCR) of mitochondria in each group were detected using bio-energy metabolism tester, and change in mitochondrial membrane potential (MMP) of myocardial tissue was detected via JC-1 staining; the expressions and changes in Bcl-2, Bax, Sirt3, PGC-1α and acetylated PGC-1α in myocardial tissue were detected by Western blot. RT-PCR was used to detect mRNA levels in Sirt3 in myocardial tissues. Metformin improved the systolic function of heart failure model rats after myocardial infarction and reduced the apoptosis of myocardial cells after myocardial infarction. Myocardial mitochondrial respiratory function and membrane potential were decreased after myocardial infarction, and metformin treatment significantly improved the mitochondrial respiratory function and mitochondrial membrane potential; Metformin up-regulated the expression of Sirt3 and the activity of PGC-1α in myocardial tissue of heart failure after myocardial infarction. Metformin decreases the acetylation level of PGC-1α through up-regulating Sirt3, mitigates the damage to mitochondrial membrane potential of model of heart failure after myocardial infarction and improves the respiratory function of mitochondria, thus improving the cardiac function of mice. Copyright © 2017. Published by Elsevier Inc.

Dual functions of a small regulatory subunit in the mitochondrial calcium uniporter complex.

PubMed

Tsai, Ming-Feng; Phillips, Charles B; Ranaghan, Matthew; Tsai, Chen-Wei; Wu, Yujiao; Willliams, Carole; Miller, Christopher

2016-04-21

Mitochondrial Ca(2+) uptake, a process crucial for bioenergetics and Ca(2+) signaling, is catalyzed by the mitochondrial calcium uniporter. The uniporter is a multi-subunit Ca(2+)-activated Ca(2+) channel, with the Ca(2+) pore formed by the MCU protein and Ca(2+)-dependent activation mediated by MICU subunits. Recently, a mitochondrial inner membrane protein EMRE was identified as a uniporter subunit absolutely required for Ca(2+) permeation. However, the molecular mechanism and regulatory purpose of EMRE remain largely unexplored. Here, we determine the transmembrane orientation of EMRE, and show that its known MCU-activating function is mediated by the interaction of transmembrane helices from both proteins. We also reveal a second function of EMRE: to maintain tight MICU regulation of the MCU pore, a role that requires EMRE to bind MICU1 using its conserved C-terminal polyaspartate tail. This dual functionality of EMRE ensures that all transport-competent uniporters are tightly regulated, responding appropriately to a dynamic intracellular Ca(2+) landscape.

Fumarate hydratase is a critical metabolic regulator of hematopoietic stem cell functions.

PubMed

Guitart, Amelie V; Panagopoulou, Theano I; Villacreces, Arnaud; Vukovic, Milica; Sepulveda, Catarina; Allen, Lewis; Carter, Roderick N; van de Lagemaat, Louie N; Morgan, Marcos; Giles, Peter; Sas, Zuzanna; Gonzalez, Marta Vila; Lawson, Hannah; Paris, Jasmin; Edwards-Hicks, Joy; Schaak, Katrin; Subramani, Chithra; Gezer, Deniz; Armesilla-Diaz, Alejandro; Wills, Jimi; Easterbrook, Aaron; Coman, David; So, Chi Wai Eric; O'Carroll, Donal; Vernimmen, Douglas; Rodrigues, Neil P; Pollard, Patrick J; Morton, Nicholas M; Finch, Andrew; Kranc, Kamil R

2017-03-06

Strict regulation of stem cell metabolism is essential for tissue functions and tumor suppression. In this study, we investigated the role of fumarate hydratase (Fh1), a key component of the mitochondrial tricarboxylic acid (TCA) cycle and cytosolic fumarate metabolism, in normal and leukemic hematopoiesis. Hematopoiesis-specific Fh1 deletion (resulting in endogenous fumarate accumulation and a genetic TCA cycle block reflected by decreased maximal mitochondrial respiration) caused lethal fetal liver hematopoietic defects and hematopoietic stem cell (HSC) failure. Reexpression of extramitochondrial Fh1 (which normalized fumarate levels but not maximal mitochondrial respiration) rescued these phenotypes, indicating the causal role of cellular fumarate accumulation. However, HSCs lacking mitochondrial Fh1 (which had normal fumarate levels but defective maximal mitochondrial respiration) failed to self-renew and displayed lymphoid differentiation defects. In contrast, leukemia-initiating cells lacking mitochondrial Fh1 efficiently propagated Meis1 / Hoxa9 -driven leukemia. Thus, we identify novel roles for fumarate metabolism in HSC maintenance and hematopoietic differentiation and reveal a differential requirement for mitochondrial Fh1 in normal hematopoiesis and leukemia propagation. © 2017 Guitart et al.

Atypical mitochondrial fission upon bacterial infection

PubMed Central

Stavru, Fabrizia; Palmer, Amy E.; Wang, Chunxin; Youle, Richard J.; Cossart, Pascale

2013-01-01

We recently showed that infection by Listeria monocytogenes causes mitochondrial network fragmentation through the secreted pore-forming toxin listeriolysin O (LLO). Here, we examine factors involved in canonical fusion and fission. Strikingly, LLO-induced mitochondrial fragmentation does not require the traditional fission machinery, as Drp1 oligomers are absent from fragmented mitochondria following Listeria infection or LLO treatment, as the dynamin-like protein 1 (Drp1) receptor Mff is rapidly degraded, and as fragmentation proceeds efficiently in cells with impaired Drp1 function. LLO does not cause processing of the fusion protein optic atrophy protein 1 (Opa1), despite inducing a decrease in the mitochondrial membrane potential, suggesting a unique Drp1- and Opa1-independent fission mechanism distinct from that triggered by uncouplers or the apoptosis inducer staurosporine. We show that the ER marks LLO-induced mitochondrial fragmentation sites even in the absence of functional Drp1, demonstrating that the ER activity in regulating mitochondrial fission can be induced by exogenous agents and that the ER appears to regulate fission by a mechanism independent of the canonical mitochondrial fission machinery. PMID:24043775

Connecting mitochondrial dynamics and life-or-death events via Bcl-2 family proteins.

PubMed

Aouacheria, Abdel; Baghdiguian, Stephen; Lamb, Heather M; Huska, Jason D; Pineda, Fernando J; Hardwick, J Marie

2017-10-01

The morphology of a population of mitochondria is the result of several interacting dynamical phenomena, including fission, fusion, movement, elimination and biogenesis. Each of these phenomena is controlled by underlying molecular machinery, and when defective can cause disease. New understanding of the relationships between form and function of mitochondria in health and disease is beginning to be unraveled on several fronts. Studies in mammals and model organisms have revealed that mitochondrial morphology, dynamics and function appear to be subject to regulation by the same proteins that regulate apoptotic cell death. One protein family that influences mitochondrial dynamics in both healthy and dying cells is the Bcl-2 protein family. Connecting mitochondrial dynamics with life-death pathway forks may arise from the intersection of Bcl-2 family proteins with the proteins and lipids that determine mitochondrial shape and function. Bcl-2 family proteins also have multifaceted influences on cells and mitochondria, including calcium handling, autophagy and energetics, as well as the subcellular localization of mitochondrial organelles to neuronal synapses. The remarkable range of physical or functional interactions by Bcl-2 family proteins is challenging to assimilate into a cohesive understanding. Most of their effects may be distinct from their direct roles in apoptotic cell death and are particularly apparent in the nervous system. Dual roles in mitochondrial dynamics and cell death extend beyond BCL-2 family proteins. In this review, we discuss many processes that govern mitochondrial structure and function in health and disease, and how Bcl-2 family proteins integrate into some of these processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mitochondria: more than just a powerhouse.

PubMed

McBride, Heidi M; Neuspiel, Margaret; Wasiak, Sylwia

2006-07-25

Pioneering biochemical studies have long forged the concept that the mitochondria are the 'energy powerhouse of the cell'. These studies, combined with the unique evolutionary origin of the mitochondria, led the way to decades of research focusing on the organelle as an essential, yet independent, functional component of the cell. Recently, however, our conceptual view of this isolated organelle has been profoundly altered with the discovery that mitochondria function within an integrated reticulum that is continually remodeled by both fusion and fission events. The identification of a number of proteins that regulate these activities is beginning to provide mechanistic details of mitochondrial membrane remodeling. However, the broader question remains regarding the underlying purpose of mitochondrial dynamics and the translation of these morphological transitions into altered functional output. One hypothesis has been that mitochondrial respiration and metabolism may be spatially and temporally regulated by the architecture and positioning of the organelle. Recent evidence supports and expands this idea by demonstrating that mitochondria are an integral part of multiple cell signaling cascades. Interestingly, proteins such as GTPases, kinases and phosphatases are involved in bi-directional communication between the mitochondrial reticulum and the rest of the cell. These proteins link mitochondrial function and dynamics to the regulation of metabolism, cell-cycle control, development, antiviral responses and cell death. In this review we will highlight the emerging evidence that provides molecular definition to mitochondria as a central platform in the execution of diverse cellular events.

RIP140/PGC-1α axis involved in vitamin A-induced neural differentiation by increasing mitochondrial function.

PubMed

Mu, Qing; Yu, Weidong; Zheng, Shuying; Shi, Hongxia; Li, Mei; Sun, Jie; Wang, Di; Hou, Xiaoli; Liu, Ling; Wang, Xinjuan; Zhao, Zhuran; Liang, Rong; Zhang, Xue; Dong, Wei; Zeng, Chaomei; Guo, Jingzhu

2018-03-07

Vitamin A deficiency and mitochondrial dysfunction are both associated with neural differentiation-related disorders, such as Alzheimer's disease (AD) and Down syndrome (DS). The mechanism of vitamin A-induced neural differentiation and the notion that vitamin A can regulate the morphology and function of mitochondria in its induction of neural differentiation through the RIP140/PGC-1α axis are unclear. The aim of this study was to investigate the roles and underlying mechanisms of RIP140/PGC-1α axis in vitamin A-induced neural differentiation. Human neuroblastoma cells (SH-SY5Y) were used as a model of neural stem cells, which were incubated with DMSO, 9-cis-retinoic acid (9-cis-RA), 13-cis-retinoic acid (13-cis-RA) and all-trans-retinoic acid (at-RA). Neural differentiation of SH-SY5Y was evaluated by Sandquist calculation, combined with immunofluorescence and real-time polymerase chain reaction (PCR) of neural markers. Mitochondrial function was estimated by ultrastructure assay using transmission electron microscopy (TEM) combined with the expression of PGC-1α and NEMGs using real-time PCR. The participation of the RA signaling pathway was demonstrated by adding RA receptor antagonists. Vitamin A derivatives are able to regulate mitochondrial morphology and function, and furthermore to induce neural differentiation through the RA signaling pathway. The RIP140/PGC-1α axis is involved in the regulation of mitochondrial function in vitamin A derivative-induced neural differentiation.

Mitochondrial quality control and communications with the nucleus are important in maintaining mitochondrial function and cell health☆☆☆

PubMed Central

Kotiadis, Vassilios N.; Duchen, Michael R.; Osellame, Laura D.

2014-01-01

Background The maintenance of cell metabolism and homeostasis is a fundamental characteristic of living organisms. In eukaryotes, mitochondria are the cornerstone of these life supporting processes, playing leading roles in a host of core cellular functions, including energy transduction, metabolic and calcium signalling, and supporting roles in a number of biosynthetic pathways. The possession of a discrete mitochondrial genome dictates that the maintenance of mitochondrial ‘fitness’ requires quality control mechanisms which involve close communication with the nucleus. Scope of review This review explores the synergistic mechanisms that control mitochondrial quality and function and ensure cellular bioenergetic homeostasis. These include antioxidant defence mechanisms that protect against oxidative damage caused by reactive oxygen species, while regulating signals transduced through such free radicals. Protein homeostasis controls import, folding, and degradation of proteins underpinned by mechanisms that regulate bioenergetic capacity through the mitochondrial unfolded protein response. Autophagic machinery is recruited for mitochondrial turnover through the process of mitophagy. Mitochondria also communicate with the nucleus to exact specific transcriptional responses through retrograde signalling pathways. Major conclusions The outcome of mitochondrial quality control is not only reliant on the efficient operation of the core homeostatic mechanisms but also in the effective interaction of mitochondria with other cellular components, namely the nucleus. General significance Understanding mitochondrial quality control and the interactions between the organelle and the nucleus will be crucial in developing therapies for the plethora of diseases in which the pathophysiology is determined by mitochondrial dysfunction. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research. PMID:24211250

Mitochondria, calcium, and tumor suppressor Fus1: At the crossroad of cancer, inflammation, and autoimmunity

PubMed Central

Uzhachenko, Roman; Shanker, Anil; Yarbrough, Wendell G.; Ivanova, Alla V.

2015-01-01

Mitochondria present a unique set of key intracellular functions such as ATP synthesis, production of reactive oxygen species (ROS) and Ca2+ buffering. Mitochondria both encode and decode Ca2+ signals and these interrelated functions have a direct impact on cell signaling and metabolism. High proliferative potential is a key energy-demanding feature shared by cancer cells and activated T lymphocytes. Switch of a metabolic state mediated by alterations in mitochondrial homeostasis plays a fundamental role in maintenance of the proliferative state. Recent studies show that tumor suppressors have the ability to affect mitochondrial homeostasis controlling both cancer and autoimmunity. Herein, we discuss established and putative mechanisms of calcium–dependent regulation of both T cell and tumor cell activities. We use the mitochondrial protein Fus1 as a case of tumor suppressor that controls immune response and tumor growth via maintenance of mitochondrial homeostasis. We focus on the regulation of mitochondrial Ca2+ handling as a key function of Fus1 and highlight the mechanisms of a crosstalk between Ca2+ accumulation and mitochondrial homeostasis. Given the important role of Ca2+ signaling, mitochondrial Ca2+ transport and ROS production in the activation of NFAT and NF-κB transcription factors, we outline the importance of Fus1 activities in this context. PMID:26246474

An in silico argument for mitochondrial microRNA as a determinant of primary non function in liver transplantation.

PubMed

Khorsandi, Shirin Elizabeth; Salehi, Siamak; Cortes, Miriam; Vilca-Melendez, Hector; Menon, Krishna; Srinivasan, Parthi; Prachalias, Andreas; Jassem, Wayel; Heaton, Nigel

2018-02-15

Mitochondria have their own genomic, transcriptomic and proteomic machinery but are unable to be autonomous, needing both nuclear and mitochondrial genomes. The aim of this work was to use computational biology to explore the involvement of Mitochondrial microRNAs (MitomiRs) and their interactions with the mitochondrial proteome in a clinical model of primary non function (PNF) of the donor after cardiac death (DCD) liver. Archival array data on the differential expression of miRNA in DCD PNF was re-analyzed using a number of publically available computational algorithms. 10 MitomiRs were identified of importance in DCD PNF, 7 with predicted interaction of their seed sequence with the mitochondrial transcriptome that included both coding, and non coding areas of the hypervariability region 1 (HVR1) and control region. Considering miRNA regulation of the nuclear encoded mitochondrial proteome, 7 hypothetical small proteins were identified with homolog function that ranged from co-factor for formation of ATP Synthase, REDOX balance and an importin/exportin protein. In silico, unconventional seed interactions, both non canonical and alternative seed sites, appear to be of greater importance in MitomiR regulation of the mitochondrial genome. Additionally, a number of novel small proteins of relevance in transplantation have been identified which need further characterization.

Skeletal muscle mitochondria: a major player in exercise, health and disease.

PubMed

Russell, Aaron P; Foletta, Victoria C; Snow, Rod J; Wadley, Glenn D

2014-04-01

Maintaining skeletal muscle mitochondrial content and function is important for sustained health throughout the lifespan. Exercise stimulates important key stress signals that control skeletal mitochondrial biogenesis and function. Perturbations in mitochondrial content and function can directly or indirectly impact skeletal muscle function and consequently whole-body health and wellbeing. This review will describe the exercise-stimulated stress signals and molecular mechanisms positively regulating mitochondrial biogenesis and function. It will then discuss the major myopathies, neuromuscular diseases and conditions such as diabetes and ageing that have dysregulated mitochondrial function. Finally, the impact of exercise and potential pharmacological approaches to improve mitochondrial function in diseased populations will be discussed. Exercise activates key stress signals that positively impact major transcriptional pathways that transcribe genes involved in skeletal muscle mitochondrial biogenesis, fusion and metabolism. The positive impact of exercise is not limited to younger healthy adults but also benefits skeletal muscle from diseased populations and the elderly. Impaired mitochondrial function can directly influence skeletal muscle atrophy and contribute to the risk or severity of disease conditions. Pharmacological manipulation of exercise-induced pathways that increase skeletal muscle mitochondrial biogenesis and function in critically ill patients, where exercise may not be possible, may assist in the treatment of chronic disease. This review highlights our understanding of how exercise positively impacts skeletal muscle mitochondrial biogenesis and function. Exercise not only improves skeletal muscle mitochondrial health but also enables us to identify molecular mechanisms that may be attractive targets for therapeutic manipulation. This article is part of a Special Issue entitled Frontiers of mitochondrial research. Copyright © 2013 Elsevier B.V. All rights reserved.

Fas cell surface death receptor controls hepatic lipid metabolism by regulating mitochondrial function.

PubMed

Item, Flurin; Wueest, Stephan; Lemos, Vera; Stein, Sokrates; Lucchini, Fabrizio C; Denzler, Rémy; Fisser, Muriel C; Challa, Tenagne D; Pirinen, Eija; Kim, Youngsoo; Hemmi, Silvio; Gulbins, Erich; Gross, Atan; O'Reilly, Lorraine A; Stoffel, Markus; Auwerx, Johan; Konrad, Daniel

2017-09-07

Nonalcoholic fatty liver disease is one of the most prevalent metabolic disorders and it tightly associates with obesity, type 2 diabetes, and cardiovascular disease. Reduced mitochondrial lipid oxidation contributes to hepatic fatty acid accumulation. Here, we show that the Fas cell surface death receptor (Fas/CD95/Apo-1) regulates hepatic mitochondrial metabolism. Hepatic Fas overexpression in chow-fed mice compromises fatty acid oxidation, mitochondrial respiration, and the abundance of mitochondrial respiratory complexes promoting hepatic lipid accumulation and insulin resistance. In line, hepatocyte-specific ablation of Fas improves mitochondrial function and ameliorates high-fat-diet-induced hepatic steatosis, glucose tolerance, and insulin resistance. Mechanistically, Fas impairs fatty acid oxidation via the BH3 interacting-domain death agonist (BID). Mice with genetic or pharmacological inhibition of BID are protected from Fas-mediated impairment of mitochondrial oxidation and hepatic steatosis. We suggest Fas as a potential novel therapeutic target to treat obesity-associated fatty liver and insulin resistance.Hepatic steatosis is a common disease closely associated with metabolic syndrome and insulin resistance. Here Item et al. show that Fas, a member of the TNF receptor superfamily, contributes to mitochondrial dysfunction, steatosis development, and insulin resistance under high fat diet.

Mitochondrial fragmentation in excitotoxicity requires ROCK activation.

PubMed

Martorell-Riera, Alejandro; Segarra-Mondejar, Marc; Reina, Manuel; Martínez-Estrada, Ofelia M; Soriano, Francesc X

2015-01-01

Mitochondria morphology constantly changes through fission and fusion processes that regulate mitochondrial function, and it therefore plays a prominent role in cellular homeostasis. Cell death progression is associated with mitochondrial fission. Fission is mediated by the mainly cytoplasmic Drp1, which is activated by different post-translational modifications and recruited to mitochondria to perform its function. Our research and other studies have shown that in the early moments of excitotoxic insult Drp1 must be nitrosylated to mediate mitochondrial fragmentation in neurons. Nonetheless, mitochondrial fission is a multistep process in which filamentous actin assembly/disassembly and myosin-mediated mitochondrial constriction play prominent roles. Here we establish that in addition to nitric oxide production, excitotoxicity-induced mitochondrial fragmentation also requires activation of the actomyosin regulator ROCK. Although ROCK1 has been shown to phosphorylate and activate Drp1, experiments using phosphor-mutant forms of Drp1 in primary cortical neurons indicate that in excitotoxic conditions, ROCK does not act directly on Drp1 to mediate fission, but may act on the actomyosin complex. Thus, these data indicate that a wider range of signaling pathways than those that target Drp1 are amenable to be inhibited to prevent mitochondrial fragmentation as therapeutic option.

Mitochondrial health, the epigenome and healthspan

PubMed Central

Aon, Miguel A.; Cortassa, Sonia; Juhaszova, Magdalena; Sollott, Steven J.

2016-01-01

Food nutrients and metabolic supply-demand dynamics constitute environmental factors that interact with our genome influencing health and disease states. These gene–environment interactions converge at the metabolic-epigenome-genome axis to regulate gene expression and phenotypic outcomes. Mounting evidence indicates that nutrients and lifestyle strongly influence genome-metabolic functional interactions determining disease via altered epigenetic regulation. The mitochondrial network is a central player of the metabolic-epigenome-genome axis, regulating the level of key metabolites (NAD+, AcCoA, ATP) acting as substrates/cofactors for acetyl transferases, kinases (e.g., protein kinase A), deacetylases (e.g., sirtuins). The chromatin, an assembly of DNA and nucleoproteins, regulates the transcriptional process, acting at the epigenomic interface between metabolism and the genome. Within this framework, we review existing evidence showing that preservation of mitochondrial network function is directly involved in decreasing the rate of damage accumulation thus slowing aging and improving healthspan. PMID:27358026

Hydrogen peroxide production regulates the mitochondrial function in insulin resistant muscle cells: effect of catalase overexpression.

PubMed

Barbosa, Marina R; Sampaio, Igor H; Teodoro, Bruno G; Sousa, Thais A; Zoppi, Claudio C; Queiroz, André L; Passos, Madla A; Alberici, Luciane C; Teixeira, Felipe R; Manfiolli, Adriana O; Batista, Thiago M; Cappelli, Ana Paula Gameiro; Reis, Rosana I; Frasson, Danúbia; Kettelhut, Isis C; Parreiras-e-Silva, Lucas T; Costa-Neto, Claudio M; Carneiro, Everardo M; Curi, Rui; Silveira, Leonardo R

2013-10-01

The mitochondrial redox state plays a central role in the link between mitochondrial overloading and insulin resistance. However, the mechanism by which the ROS induce insulin resistance in skeletal muscle cells is not completely understood. We examined the association between mitochondrial function and H2O2 production in insulin resistant cells. Our hypothesis is that the low mitochondrial oxygen consumption leads to elevated ROS production by a mechanism associated with reduced PGC1α transcription and low content of phosphorylated CREB. The cells were transfected with either the encoded sequence for catalase overexpression or the specific siRNA for catalase inhibition. After transfection, myotubes were incubated with palmitic acid (500μM) and the insulin response, as well as mitochondrial function and fatty acid metabolism, was determined. The low mitochondrial oxygen consumption led to elevated ROS production by a mechanism associated with β-oxidation of fatty acids. Rotenone was observed to reduce the ratio of ROS production. The elevated H2O2 production markedly decreased the PGC1α transcription, an effect that was accompanied by a reduced phosphorylation of Akt and CREB. The catalase transfection prevented the reduction in the phosphorylated level of Akt and upregulated the levels of phosphorylated CREB. The mitochondrial function was elevated and H2O2 production reduced, thus increasing the insulin sensitivity. The catalase overexpression improved mitochondrial respiration protecting the cells from fatty acid-induced, insulin resistance. This effect indicates that control of hydrogen peroxide production regulates the mitochondrial respiration preventing the insulin resistance in skeletal muscle cells by a mechanism associated with CREB phosphorylation and β-oxidation of fatty acids. Copyright © 2013 Elsevier B.V. All rights reserved.

Mitochondrial Respiratory Function Induces Endogenous Hypoxia

PubMed Central

Prior, Sara; Kim, Ara; Yoshihara, Toshitada; Tobita, Seiji; Takeuchi, Toshiyuki; Higuchi, Masahiro

2014-01-01

Hypoxia influences many key biological functions. In cancer, it is generally believed that hypoxic condition is generated deep inside the tumor because of the lack of oxygen supply. However, consumption of oxygen by cancer should be one of the key means of regulating oxygen concentration to induce hypoxia but has not been well studied. Here, we provide direct evidence of the mitochondrial role in the induction of intracellular hypoxia. We used Acetylacetonatobis [2-(2′-benzothienyl) pyridinato-kN, kC3’] iridium (III) (BTP), a novel oxygen sensor, to detect intracellular hypoxia in living cells via microscopy. The well-differentiated cancer cell lines, LNCaP and MCF-7, showed intracellular hypoxia without exogenous hypoxia in an open environment. This may be caused by high oxygen consumption, low oxygen diffusion in water, and low oxygen incorporation to the cells. In contrast, the poorly-differentiated cancer cell lines: PC-3 and MDAMB231 exhibited intracellular normoxia by low oxygen consumption. The specific complex I inhibitor, rotenone, and the reduction of mitochondrial DNA (mtDNA) content reduced intracellular hypoxia, indicating that intracellular oxygen concentration is regulated by the consumption of oxygen by mitochondria. HIF-1α was activated in endogenously hypoxic LNCaP and the activation was dependent on mitochondrial respiratory function. Intracellular hypoxic status is regulated by glucose by parabolic dose response. The low concentration of glucose (0.045 mg/ml) induced strongest intracellular hypoxia possibly because of the Crabtree effect. Addition of FCS to the media induced intracellular hypoxia in LNCaP, and this effect was partially mimicked by an androgen analog, R1881, and inhibited by the anti-androgen, flutamide. These results indicate that mitochondrial respiratory function determines intracellular hypoxic status and may regulate oxygen-dependent biological functions. PMID:24586439

Mitochondrial DNA 3243A>G heteroplasmy is associated with changes in cytoskeletal protein expression and cell mechanics.

PubMed

Kandel, Judith; Picard, Martin; Wallace, Douglas C; Eckmann, David M

2017-06-01

Mitochondrial and mechanical alterations in cells have both been shown to be hallmarks of human disease. However, little research has endeavoured to establish connections between these two essential features of cells in both functional and dysfunctional situations. In this work, we hypothesized that a specific genetic alteration in mitochondrial function known to cause human disease would trigger changes in cell mechanics. Using a previously characterized set of mitochondrial cybrid cell lines, we examined the relationship between heteroplasmy for the mitochondrial DNA (mtDNA) 3243A>G mutation, the cell cytoskeleton, and resulting cellular mechanical properties. We found that cells with increasing mitochondrial dysfunction markedly differed from one another in gene expression and protein production of various co-regulated cytoskeletal elements. The intracellular positioning and organization of actin also differed across cell lines. To explore the relationship between these changes and cell mechanics, we then measured cellular mechanical properties using atomic force microscopy and found that cell stiffness correlated with gene expression data for known determinants of cell mechanics, γ-actin, α-actinin and filamin A. This work points towards a mechanism linking mitochondrial genetics to single-cell mechanical properties. The transcriptional and structural regulation of cytoskeletal components by mitochondrial function may explain why energetic and mechanical alterations often coexist in clinical conditions. © 2017 The Author(s).

Critical contribution of RIPK1 mediated mitochondrial dysfunction and oxidative stress to compression-induced rat nucleus pulposus cells necroptosis and apoptosis.

PubMed

Chen, Songfeng; Lv, Xiao; Hu, Binwu; Zhao, Lei; Li, Shuai; Li, Zhiliang; Qing, Xiangcheng; Liu, Hongjian; Xu, Jianzhong; Shao, Zengwu

2018-04-28

The aim of this study was to investigate whether RIPK1 mediated mitochondrial dysfunction and oxidative stress contributed to compression-induced nucleus pulposus (NP) cells necroptosis and apoptosis, together with the interplay relationship between necroptosis and apoptosis in vitro. Rat NP cells underwent various periods of 1.0 MPa compression. To determine whether compression affected mitochondrial function, we evaluated the mitochondrial membrane potential, mitochondrial permeability transition pore (mPTP), mitochondrial ultrastructure and ATP content. Oxidative stress-related indicators reactive oxygen species, superoxide dismutase and malondialdehyde were also assessed. To verify the relevance between oxidative stress and necroptosis together with apoptosis, RIPK1 inhibitor necrostatin-1(Nec-1), mPTP inhibitor cyclosporine A (CsA), antioxidants and small interfering RNA technology were utilized. The results established that compression elicited a time-dependent mitochondrial dysfunction and elevated oxidative stress. Nec-1 and CsA restored mitochondrial function and reduced oxidative stress, which corresponded to decreased necroptosis and apoptosis. CsA down-regulated mitochondrial cyclophilin D expression, but had little effects on RIPK1 expression and pRIPK1 activation. Additionally, we found that Nec-1 largely blocked apoptosis; whereas, the apoptosis inhibitor Z-VAD-FMK increased RIPK1 expression and pRIPK1 activation, and coordinated regulation of necroptosis and apoptosis enabled NP cells survival more efficiently. In contrast to Nec-1, SiRIPK1 exacerbated mitochondrial dysfunction and oxidative stress. In summary, RIPK1-mediated mitochondrial dysfunction and oxidative stress play a crucial role in NP cells necroptosis and apoptosis during compression injury. The synergistic regulation of necroptosis and apoptosis may exert more beneficial effects on NP cells survival, and ultimately delaying or even retarding intervertebral disc degeneration.

CED-9 and mitochondrial homeostasis in C. elegans muscle

PubMed Central

Tan, Frederick J.; Husain, Michelle; Manlandro, Cara Marie; Koppenol, Marijke; Fire, Andrew Z.; Hill, R. Blake

2009-01-01

Summary Mitochondrial homeostasis reflects a dynamic balance between membrane fission and fusion events thought essential for mitochondrial function. We report here that altered expression of the C. elegans BCL2 homolog CED-9 affects both mitochondrial fission and fusion. Although striated muscle cells lacking CED-9 have no alteration in mitochondrial size or ultrastructure, these cells appear more sensitive to mitochondrial fragmentation. By contrast, increased CED-9 expression in these cells produces highly interconnected mitochondria. This mitochondrial phenotype is partially suppressed by increased expression of the dynamin-related GTPase DRP-1, with suppression dependent on the BH3 binding pocket of CED-9. This suppression suggests that CED-9 directly regulates DRP-1, a model supported by our finding that CED-9 activates the GTPase activity of human DRP1. Thus, CED-9 is capable of regulating the mitochondrial fission-fusion cycle but is not essential for either fission or fusion. PMID:18827010

Loss of BIM increases mitochondrial oxygen consumption and lipid oxidation, reduces adiposity and improves insulin sensitivity in mice.

PubMed

Wali, Jibran A; Galic, Sandra; Tan, Christina Yr; Gurzov, Esteban N; Frazier, Ann E; Connor, Timothy; Ge, Jingjing; Pappas, Evan G; Stroud, David; Varanasi, L Chitra; Selck, Claudia; Ryan, Michael T; Thorburn, David R; Kemp, Bruce E; Krishnamurthy, Balasubramanian; Kay, Thomas Wh; McGee, Sean L; Thomas, Helen E

2018-01-01

BCL-2 proteins are known to engage each other to determine the fate of a cell after a death stimulus. However, their evolutionary conservation and the many other reported binding partners suggest an additional function not directly linked to apoptosis regulation. To identify such a function, we studied mice lacking the BH3-only protein BIM. BIM -/- cells had a higher mitochondrial oxygen consumption rate that was associated with higher mitochondrial complex IV activity. The consequences of increased oxygen consumption in BIM -/- mice were significantly lower body weights, reduced adiposity and lower hepatic lipid content. Consistent with reduced adiposity, BIM -/- mice had lower fasting blood glucose, improved insulin sensitivity and hepatic insulin signalling. Lipid oxidation was increased in BIM -/- mice, suggesting a mechanism for their metabolic phenotype. Our data suggest a role for BIM in regulating mitochondrial bioenergetics and metabolism and support the idea that regulation of metabolism and cell death are connected.

Impact of Aging and Exercise on Mitochondrial Quality Control in Skeletal Muscle

PubMed Central

Kim, Yuho; Triolo, Matthew

2017-01-01

Mitochondria are characterized by its pivotal roles in managing energy production, reactive oxygen species, and calcium, whose aging-related structural and functional deteriorations are observed in aging muscle. Although it is still unclear how aging alters mitochondrial quality and quantity in skeletal muscle, dysregulation of mitochondrial biogenesis and dynamic controls has been suggested as key players for that. In this paper, we summarize current understandings on how aging regulates muscle mitochondrial biogenesis, while focusing on transcriptional regulations including PGC-1α, AMPK, p53, mtDNA, and Tfam. Further, we review current findings on the muscle mitochondrial dynamic systems in aging muscle: fusion/fission, autophagy/mitophagy, and protein import. Next, we also discuss how endurance and resistance exercises impact on the mitochondrial quality controls in aging muscle, suggesting possible effective exercise strategies to improve/maintain mitochondrial health. PMID:28656072

The destiny of Ca(2+) released by mitochondria.

PubMed

Takeuchi, Ayako; Kim, Bongju; Matsuoka, Satoshi

2015-01-01

Mitochondrial Ca(2+) is known to regulate diverse cellular functions, for example energy production and cell death, by modulating mitochondrial dehydrogenases, inducing production of reactive oxygen species, and opening mitochondrial permeability transition pores. In addition to the action of Ca(2+) within mitochondria, Ca(2+) released from mitochondria is also important in a variety of cellular functions. In the last 5 years, the molecules responsible for mitochondrial Ca(2+) dynamics have been identified: a mitochondrial Ca(2+) uniporter (MCU), a mitochondrial Na(+)-Ca(2+) exchanger (NCLX), and a candidate for a mitochondrial H(+)-Ca(2+) exchanger (Letm1). In this review, we focus on the mitochondrial Ca(2+) release system, and discuss its physiological and pathophysiological significance. Accumulating evidence suggests that the mitochondrial Ca(2+) release system is not only crucial in maintaining mitochondrial Ca(2+) homeostasis but also participates in the Ca(2+) crosstalk between mitochondria and the plasma membrane and between mitochondria and the endoplasmic/sarcoplasmic reticulum.

Phosphatase and Tensin Homolog Deleted on Chromosome 10 (PTEN) Signaling Regulates Mitochondrial Biogenesis and Respiration via Estrogen-related Receptor α (ERRα)*

PubMed Central

Li, Yang; He, Lina; Zeng, Ni; Sahu, Divya; Cadenas, Enrique; Shearn, Colin; Li, Wei; Stiles, Bangyan L.

2013-01-01

Mitochondrial abnormalities are associated with cancer development, yet how oncogenic signals affect mitochondrial functions has not been fully understood. In this study, we investigate the relationship between mitochondrial alterations and PI3K/protein kinase B (AKT) signaling activation using hepatocytes and liver tissues as our experimental models. We show here that liver-specific deletion of Pten, which leads to activation of PI3K/AKT, is associated with elevated oxidative stress, increased mitochondrial mass, and augmented respiration accompanied by enhanced glycolysis. Consistent with these observations, estrogen-related receptor α (ERRα), an orphan nuclear receptor known for its role in mitochondrial biogenesis, is up-regulated in the absence of phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Our pharmacological and genetic studies show that PI3K/AKT activity regulates the expression of ERRα and mitochondrial biogenesis/respiration. Furthermore, cAMP-response element-binding protein, as a downstream target of AKT, plays a role in the regulation of ERRα, independent of PKA signaling. ERRα regulates reactive oxygen species production, and ERRα knockdown attenuates proliferation and colony-forming potential in Pten-null hepatocytes. Finally, analysis of clinical datasets from liver tissues showed a negative correlation between expressions of ERRα and PTEN in patients with liver cancer. Therefore, this study has established a previously unrecognized link between a growth signal and mitochondrial metabolism. PMID:23836899

Mitochondrial Energy and Redox Signaling in Plants

PubMed Central

Schwarzländer, Markus

2013-01-01

Abstract Significance: For a plant to grow and develop, energy and appropriate building blocks are a fundamental requirement. Mitochondrial respiration is a vital source for both. The delicate redox processes that make up respiration are affected by the plant's changing environment. Therefore, mitochondrial regulation is critically important to maintain cellular homeostasis. This involves sensing signals from changes in mitochondrial physiology, transducing this information, and mounting tailored responses, by either adjusting mitochondrial and cellular functions directly or reprogramming gene expression. Recent Advances: Retrograde (RTG) signaling, by which mitochondrial signals control nuclear gene expression, has been a field of very active research in recent years. Nevertheless, no mitochondrial RTG-signaling pathway is yet understood in plants. This review summarizes recent advances toward elucidating redox processes and other bioenergetic factors as a part of RTG signaling of plant mitochondria. Critical Issues: Novel insights into mitochondrial physiology and redox-regulation provide a framework of upstream signaling. On the other end, downstream responses to modified mitochondrial function have become available, including transcriptomic data and mitochondrial phenotypes, revealing processes in the plant that are under mitochondrial control. Future Directions: Drawing parallels to chloroplast signaling and mitochondrial signaling in animal systems allows to bridge gaps in the current understanding and to deduce promising directions for future research. It is proposed that targeted usage of new technical approaches, such as quantitative in vivo imaging, will provide novel leverage to the dissection of plant mitochondrial signaling. Antioxid. Redox Signal. 18, 2122–2144. PMID:23234467

Adrenergic Signaling Regulates Mitochondrial Ca2+ Uptake Through Pyk2-Dependent Tyrosine Phosphorylation of the Mitochondrial Ca2+ Uniporter

PubMed Central

Jhun, Bong Sook; Xu, Shangcheng; Hurst, Stephen; Raffaello, Anna; Liu, Xiaoyun; Yi, Bing; Zhang, Huiliang; Gross, Polina; Mishra, Jyotsna; Ainbinder, Alina; Kettlewell, Sarah; Smith, Godfrey L.; Dirksen, Robert T.; Wang, Wang; Rizzuto, Rosario

2014-01-01

Abstract Aims: Mitochondrial Ca2+ homeostasis is crucial for balancing cell survival and death. The recent discovery of the molecular identity of the mitochondrial Ca2+ uniporter pore (MCU) opens new possibilities for applying genetic approaches to study mitochondrial Ca2+ regulation in various cell types, including cardiac myocytes. Basal tyrosine phosphorylation of MCU was reported from mass spectroscopy of human and mouse tissues, but the signaling pathways that regulate mitochondrial Ca2+ entry through posttranslational modifications of MCU are completely unknown. Therefore, we investigated α1-adrenergic-mediated signal transduction of MCU posttranslational modification and function in cardiac cells. Results: α1-adrenoceptor (α1-AR) signaling translocated activated proline-rich tyrosine kinase 2 (Pyk2) from the cytosol to mitochondrial matrix and accelerates mitochondrial Ca2+ uptake via Pyk2-dependent MCU phosphorylation and tetrametric MCU channel pore formation. Moreover, we found that α1-AR stimulation increases reactive oxygen species production at mitochondria, mitochondrial permeability transition pore activity, and initiates apoptotic signaling via Pyk2-dependent MCU activation and mitochondrial Ca2+ overload. Innovation: Our data indicate that inhibition of α1-AR-Pyk2-MCU signaling represents a potential novel therapeutic target to limit or prevent mitochondrial Ca2+ overload, oxidative stress, mitochondrial injury, and myocardial death during pathophysiological conditions, where chronic adrenergic stimulation is present. Conclusion: The α1-AR-Pyk2-dependent tyrosine phosphorylation of the MCU regulates mitochondrial Ca2+ entry and apoptosis in cardiac cells. Antioxid. Redox Signal. 21, 863–879. PMID:24800979

Protosappanin B protects PC12 cells against oxygen-glucose deprivation-induced neuronal death by maintaining mitochondrial homeostasis via induction of ubiquitin-dependent p53 protein degradation.

PubMed

Zeng, Ke-Wu; Liao, Li-Xi; Zhao, Ming-Bo; Song, Fang-Jiao; Yu, Qian; Jiang, Yong; Tu, Peng-Fei

2015-03-15

Protosappanin B (PTB) is a bioactive dibenzoxocin derivative isolated from Caesalpinia sappan L. Here, we investigated the neuroprotective effects and the potential mechanisms of PTB on oxygen-glucose deprivation (OGD)-injured PC12 cells. Results showed that PTB significantly increased cell viability, inhibited cell apoptosis and up-regulated the expression of growth-associated protein 43 (a marker of neural outgrowth). Moreover, our study revealed that PTB effectively maintained mitochondrial homeostasis by up-regulation of mitochondrial membrane potential (MMP), inhibition of cytochrome c release from mitochondria and inactivation of mitochondrial caspase-9/3 apoptosis pathway. Further study showed that PTB significantly promoted cytoplasmic component degradation of p53 protein, a key negative regulator for mitochondrial function, resulting in a release of Bcl-2 from p53-Bcl-2 complex and an enhancing translocation of Bcl-2 to mitochondrial outer membrane. Finally, we found the degradation of p53 protein was induced by PTB via activation of a MDM2-dependent ubiquitination process. Taken together, our findings provided a new viewpoint of neuronal protection strategy for anoxia and ischemic injury with natural small molecular dibenzoxocin derivative by activating ubiquitin-dependent p53 protein degradation as well as increasing mitochondrial function. Copyright © 2015 Elsevier B.V. All rights reserved.

Gamma rays induce a p53-independent mitochondrial biogenesis that is counter-regulated by HIF1α

PubMed Central

Bartoletti-Stella, A; Mariani, E; Kurelac, I; Maresca, A; Caratozzolo, M F; Iommarini, L; Carelli, V; Eusebi, L H; Guido, A; Cenacchi, G; Fuccio, L; Rugolo, M; Tullo, A; Porcelli, A M; Gasparre, G

2013-01-01

Mitochondrial biogenesis is an orchestrated process that presides to the regulation of the organelles homeostasis within a cell. We show that γ-rays, at doses commonly used in the radiation therapy for cancer treatment, induce an increase in mitochondrial mass and function, in response to a genotoxic stress that pushes cells into senescence, in the presence of a functional p53. Although the main effector of the response to γ-rays is the p53-p21 axis, we demonstrated that mitochondrial biogenesis is only indirectly regulated by p53, whose activation triggers a murine double minute 2 (MDM2)-mediated hypoxia-inducible factor 1α (HIF1α) degradation, leading to the release of peroxisome-proliferator activated receptor gamma co-activator 1β inhibition by HIF1α, thus promoting mitochondrial biogenesis. Mimicking hypoxia by HIF1α stabilization, in fact, blunts the mitochondrial response to γ-rays as well as the induction of p21-mediated cell senescence, indicating prevalence of the hypoxic over the genotoxic response. Finally, we also show in vivo that post-radiotherapy mitochondrial DNA copy number increase well correlates with lack of HIF1α increase in the tissue, concluding this may be a useful molecular tool to infer the trigger of a hypoxic response during radiotherapy, which may lead to failure of activation of cell senescence. PMID:23764844

A Functional Antagonistic Relationship between Auxin and Mitochondrial Retrograde Signaling Regulates Alternative Oxidase1a Expression in Arabidopsis1[W][OPEN

PubMed Central

Ivanova, Aneta; Law, Simon R.; Narsai, Reena; Duncan, Owen; Lee, Jae-Hoon; Zhang, Botao; Van Aken, Olivier; Radomiljac, Jordan D.; van der Merwe, Margaretha; Yi, KeKe; Whelan, James

2014-01-01

The perception and integration of stress stimuli with that of mitochondrion function are important during periods of perturbed cellular homeostasis. In a continuous effort to delineate these mitochondrial/stress-interacting networks, forward genetic screens using the mitochondrial stress response marker alternative oxidase 1a (AOX1a) provide a useful molecular tool to identify and characterize regulators of mitochondrial stress signaling (referred to as regulators of alternative oxidase 1a [RAOs] components). In this study, we reveal that mutations in genes coding for proteins associated with auxin transport and distribution resulted in a greater induction of AOX1a in terms of magnitude and longevity. Three independent mutants for polarized auxin transport, rao3/big, rao4/pin-formed1, and rao5/multidrug-resistance1/abcb19, as well as the Myb transcription factor rao6/asymmetric leaves1 (that displays altered auxin patterns) were identified and resulted in an acute sensitivity toward mitochondrial dysfunction. Induction of the AOX1a reporter system could be inhibited by the application of auxin analogs or reciprocally potentiated by blocking auxin transport. Promoter activation studies with AOX1a::GUS and DR5::GUS lines further confirmed a clear antagonistic relationship between the spatial distribution of mitochondrial stress and auxin response kinetics, respectively. Genome-wide transcriptome analyses revealed that mitochondrial stress stimuli, such as antimycin A, caused a transient suppression of auxin signaling and conversely, that auxin treatment repressed a part of the response to antimycin A treatment, including AOX1a induction. We conclude that mitochondrial stress signaling and auxin signaling are reciprocally regulated, balancing growth and stress response(s). PMID:24820025

Obesity-induced down-regulation of the mitochondrial translocator protein (TSPO) impairs placental steroid production.

PubMed

Lassance, Luciana; Haghiac, Maricela; Minium, Judi; Catalano, Patrick; Hauguel-de Mouzon, Sylvie

2015-01-01

Low concentrations of estradiol and progesterone are hallmarks of adverse pregnancy outcomes as is maternal obesity. During pregnancy, placental cholesterol is the sole source of sex steroids. Cholesterol trafficking is the limiting step in sex steroid biosynthesis and is mainly mediated by the translocator protein (TSPO), present in the mitochondrial outer membrane. The objective of the study was to investigate the effects of maternal obesity in placental sex steroid biosynthesis and TSPO regulation. One hundred forty-four obese (body mass index 30-35 kg/m(2)) and 90 lean (body mass index 19-25 kg/m(2)) pregnant women (OP and LP, respectively) recruited at scheduled term cesarean delivery. Placenta and maternal blood were collected. This study was conducted at MetroHealth Medical Center (Cleveland, Ohio). Maternal metabolic components (fasting glucose, insulin, leptin, estradiol, progesterone, and total cholesterol) and placental weight were measured. Placenta (mitochondria and membranes separated) and cord blood cholesterol values were verified. The expression and regulation of TSPO and mitochondrial function were analyzed. Plasma estradiol and progesterone concentrations were significantly lower (P < .04) in OP as compared with LP women. Maternal and cord plasma cholesterol were not different between groups. Placental citrate synthase activity and mitochondrial DNA, markers of mitochondrial density, were unchanged, but the mitochondrial cholesterol concentrations were 40% lower in the placenta of OP. TSPO gene and protein expressions were decreased 2-fold in the placenta of OP. In vitro trophoblast activation of the innate immune pathways with lipopolysaccharide and long-chain saturated fatty acids reduced TSPO expression by 2- to 3-fold (P < .05). These data indicate that obesity in pregnancy impairs mitochondrial steroidogenic function through the negative regulation of mitochondrial TSPO.

Mitochondria-targeted molecules MitoQ and SS31 reduce mutant huntingtin-induced mitochondrial toxicity and synaptic damage in Huntington's disease

PubMed Central

Yin, Xiangling; Manczak, Maria; Reddy, P. Hemachandra

2016-01-01

The objective of this study was to determine the protective effects of the mitochondria-targeted molecules MitoQ and SS31 in striatal neurons that stably express mutant huntingtin (Htt) (STHDhQ111/Q111) in Huntington's disease (HD). We studied mitochondrial and synaptic activities by measuring mRNA and the protein levels of mitochondrial and synaptic genes, mitochondrial function, and ultra-structural changes in MitoQ- and SS31-treated mutant Htt neurons relative to untreated mutant Htt neurons. We used gene expression analysis, biochemical methods, transmission electron microscopy (TEM) and confocal microscopy methods. In the MitoQ- and SS31-treated mutant Htt neurons, fission genes Drp1 and Fis1 were down-regulated, and fusion genes Mfn1, Mfn2 and Opa1 were up-regulated relative to untreated neurons, suggesting that mitochondria-targeted molecules reduce fission activity. Interestingly, the mitochondrial biogenesis genes PGC1α, PGC1β, Nrf1, Nrf2 and TFAM were up-regulated in MitoQ- and SS31-treated mutant Htt neurons. The synaptic genes synaptophysin and PSD95 were up-regulated, and mitochondrial function was normal in the MitoQ- and SS31-treated mutant Htt neurons. Immunoblotting findings of mitochondrial and synaptic proteins agreed with the mRNA findings. TEM studies revealed decreased numbers of structurally intact mitochondria in MitoQ- and SS31-treated mutant Htt neurons. These findings suggest that mitochondria-targeted molecules MitoQ and SS31 are protective against mutant Htt-induced mitochondrial and synaptic damage in HD neurons, and these mitochondria-targeted molecules are potential therapeutic molecules for the treatment of HD neurons. PMID:26908605

Mitochondria-targeted molecules MitoQ and SS31 reduce mutant huntingtin-induced mitochondrial toxicity and synaptic damage in Huntington's disease.

PubMed

Yin, Xiangling; Manczak, Maria; Reddy, P Hemachandra

2016-05-01

The objective of this study was to determine the protective effects of the mitochondria-targeted molecules MitoQ and SS31 in striatal neurons that stably express mutant huntingtin (Htt) (STHDhQ111/Q111) in Huntington's disease (HD). We studied mitochondrial and synaptic activities by measuring mRNA and the protein levels of mitochondrial and synaptic genes, mitochondrial function, and ultra-structural changes in MitoQ- and SS31-treated mutant Htt neurons relative to untreated mutant Htt neurons. We used gene expression analysis, biochemical methods, transmission electron microscopy (TEM) and confocal microscopy methods. In the MitoQ- and SS31-treated mutant Htt neurons, fission genes Drp1 and Fis1 were down-regulated, and fusion genes Mfn1, Mfn2 and Opa1 were up-regulated relative to untreated neurons, suggesting that mitochondria-targeted molecules reduce fission activity. Interestingly, the mitochondrial biogenesis genes PGC1α, PGC1β, Nrf1, Nrf2 and TFAM were up-regulated in MitoQ- and SS31-treated mutant Htt neurons. The synaptic genes synaptophysin and PSD95 were up-regulated, and mitochondrial function was normal in the MitoQ- and SS31-treated mutant Htt neurons. Immunoblotting findings of mitochondrial and synaptic proteins agreed with the mRNA findings. TEM studies revealed decreased numbers of structurally intact mitochondria in MitoQ- and SS31-treated mutant Htt neurons. These findings suggest that mitochondria-targeted molecules MitoQ and SS31 are protective against mutant Htt-induced mitochondrial and synaptic damage in HD neurons, and these mitochondria-targeted molecules are potential therapeutic molecules for the treatment of HD neurons. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

SIRT1 activation by curcumin pretreatment attenuates mitochondrial oxidative damage induced by myocardial ischemia reperfusion injury.

PubMed

Yang, Yang; Duan, Weixun; Lin, Yan; Yi, Wei; Liang, Zhenxing; Yan, Juanjuan; Wang, Ning; Deng, Chao; Zhang, Song; Li, Yue; Chen, Wensheng; Yu, Shiqiang; Yi, Dinghua; Jin, Zhenxiao

2013-12-01

Ischemia reperfusion (IR) injury (IRI) is harmful to the cardiovascular system and causes mitochondrial oxidative stress. Silent information regulator 1 (SIRT1), a type of histone deacetylase, contributes to IRI. Curcumin (Cur) is a strong natural antioxidant and is the active component in Curcuma longa; Cur has protective effects against IRI and may regulate the activity of SIRT1. This study was designed to investigate the protective effect of Cur pretreatment on myocardial IRI and to elucidate this potential mechanism. Isolated and in vivo rat hearts and cultured neonatal rat cardiomyocytes were subjected to IR. Prior to this procedure, the hearts or cardiomyocytes were exposed to Cur in the absence or presence of the SIRT1 inhibitor sirtinol or SIRT1 siRNA. Cur conferred a cardioprotective effect, as shown by improved postischemic cardiac function, decreased myocardial infarct size, decreased myocardial apoptotic index, and several biochemical parameters, including the up-regulation of the antiapoptotic protein Bcl2 and the down-regulation of the proapoptotic protein Bax. Sirtinol and SIRT1 siRNA each blocked the Cur-mediated cardioprotection by inhibiting SIRT1 signaling. Cur also resulted in a well-preserved mitochondrial redox potential, significantly elevated mitochondrial superoxide dismutase activity, and decreased formation of mitochondrial hydrogen peroxide and malondialdehyde. These observations indicated that the IR-induced mitochondrial oxidative damage was remarkably attenuated. However, this Cur-elevated mitochondrial function was reversed by sirtinol or SIRT1 siRNA treatment. In summary, our results demonstrate that Cur pretreatment attenuates IRI by reducing IR-induced mitochondrial oxidative damage through the activation of SIRT1 signaling. © 2013 Elsevier Inc. All rights reserved.

Tools for assessing mitochondrial dynamics in mouse tissues and neurodegenerative models

NASA Astrophysics Data System (ADS)

Pham, Anh H.

Mitochondria are dynamic organelles that undergo membrane fusion and fission and transport. The dynamic properties of mitochondria are important for regulating mitochondrial function. Defects in mitochondrial dynamics are linked neurodegenerative diseases and affect the development of many tissues. To investigate the role of mitochondrial dynamics in diseases, versatile tools are needed to explore the physiology of these dynamic organelles in multiple tissues. Current tools for monitoring mitochondrial dynamics have been limited to studies in cell culture, which may be inadequate model systems for exploring the network of tissues. Here, we have generated mouse models for monitoring mitochondrial dynamics in a broad spectrum of tissues and cell types. The Photo-Activatable Mitochondrial (PhAM floxed) line enables Cre-inducible expression of a mitochondrial targeted photoconvertible protein, Dendra2 (mito-Dendra2). In the PhAMexcised line, mito-Dendra2 is ubiquitously expressed to facilitate broad analysis of mitochondria at various developmental processes. We have utilized these models to study mitochondrial dynamics in the nigrostriatal circuit of Parkinson's disease (PD) and in the development of skeletal muscles. Increasing evidences implicate aberrant regulation of mitochondrial fusion and fission in models of PD. To assess the function of mitochondrial dynamics in the nigrostriatal circuit, we utilized transgenic techniques to abrogate mitochondrial fusion. We show that deletion of the Mfn2 leads to the degeneration of dopaminergic neurons and Parkinson's-like features in mice. To elucidate the dynamic properties of mitochondria during muscle development, we established a platform for examining mitochondrial compartmentalization in skeletal muscles. This model system may yield clues to the role of mitochondrial dynamics in mitochondrial myopathies.

SIRT1 Activation by Resveratrol Alleviates Cardiac Dysfunction via Mitochondrial Regulation in Diabetic Cardiomyopathy Mice

PubMed Central

Zhang, Ran; Chen, Jiangwei; Li, Xiang; Yang, Bo; Li, Xiujuan; Fan, Miaomiao; Li, Congye; Tian, Zuhong

2017-01-01

Background Diabetic cardiomyopathy (DCM) is a major threat for diabetic patients. Silent information regulator 1 (SIRT1) has a regulatory effect on mitochondrial dynamics, which is associated with DCM pathological changes. Our study aims to investigate whether resveratrol, a SRIT1 activator, could exert a protective effect against DCM. Methods and Results Cardiac-specific SIRT1 knockout (SIRT1KO) mice were generated using Cre-loxP system. SIRT1KO mice displayed symptoms of DCM, including cardiac hypertrophy and dysfunction, insulin resistance, and abnormal glucose metabolism. DCM and SIRT1KO hearts showed impaired mitochondrial biogenesis and function, while SIRT1 activation by resveratrol reversed this in DCM mice. High glucose caused increased apoptosis, impaired mitochondrial biogenesis, and function in cardiomyocytes, which was alleviated by resveratrol. SIRT1 deletion by both SIRT1KO and shRNA abolished the beneficial effects of resveratrol. Furthermore, the function of SIRT1 is mediated via the deacetylation effect on peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), thus inducing increased expression of nuclear respiratory factor 1 (NRF-1), NRF-2, estrogen-related receptor-α (ERR-α), and mitochondrial transcription factor A (TFAM). Conclusions Cardiac deletion of SIRT1 caused phenotypes resembling DCM. Activation of SIRT1 by resveratrol ameliorated cardiac injuries in DCM through PGC-1α-mediated mitochondrial regulation. Collectively, SIRT1 may serve as a potential therapeutic target for DCM. PMID:28883902

Myopathy caused by mammalian target of rapamycin complex 1 (mTORC1) inactivation is not reversed by restoring mitochondrial function

PubMed Central

Romanino, Klaas; Mazelin, Laetitia; Albert, Verena; Conjard-Duplany, Agnès; Lin, Shuo; Bentzinger, C. Florian; Handschin, Christoph; Puigserver, Pere; Zorzato, Francesco; Schaeffer, Laurent; Gangloff, Yann-Gaël; Rüegg, Markus A.

2011-01-01

Mammalian target of rapamycin complex 1 (mTORC1) is central to the control of cell, organ, and body size. Skeletal muscle-specific inactivation of mTORC1 in mice results in smaller muscle fibers, fewer mitochondria, increased glycogen stores, and a progressive myopathy that causes premature death. In mTORC1-deficient muscles, peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α), which regulates mitochondrial biogenesis and glucose homeostasis, is strongly down-regulated. Here we tested whether induction of mitochondrial biogenesis pharmacologically or by the overexpression of PGC-1α is sufficient to reverse the phenotype of mice deficient for mTORC1. We show that both approaches normalize mitochondrial function, such as oxidative capacity and expression of mitochondrial genes. However, they do not prevent or delay the progressive myopathy. In addition, we find that mTORC1 has a much stronger effect than PGC-1α on the glycogen content in muscle. This effect is based on the strong activation of PKB/Akt in mTORC1-deficient mice. We also show that activation of PKB/Akt not only affects glycogen synthesis but also diminishes glycogen degradation. Thus, our work provides strong functional evidence that mitochondrial dysfunction in mice with inactivated mTORC1 signaling is caused by the down-regulation of PGC-1α. However, our data also show that the impairment of mitochondria does not lead directly to the lethal myopathy. PMID:22143799

Powering Up Mitochondrial Functions to Treat Mitochondrial Disease

DTIC Science & Technology

2017-10-01

derived hormone whose serum level correlates positively with the severity of mitochondrial cardiomyopathy (recently published with DOD grant support...o Pei lab has recently discovered that GDF15 is a heart-derived hormone that regulates body growth. Circulating GDF15 level correlates positively...Circulating GDF15 level correlates positively with the severity of mitochondrial cardiomyopathy and can be used as a serum biomarker for our 5

Exercise improves mitochondrial and redox-regulated stress responses in the elderly: better late than never!

PubMed

Cobley, James N; Moult, Peter R; Burniston, Jatin G; Morton, James P; Close, Graeme L

2015-04-01

Ageing is associated with several physiological declines to both the cardiovascular (e.g. reduced aerobic capacity) and musculoskeletal system (muscle function and mass). Ageing may also impair the adaptive response of skeletal muscle mitochondria and redox-regulated stress responses to an acute exercise bout, at least in mice and rodents. This is a functionally important phenomenon, since (1) aberrant mitochondrial and redox homeostasis are implicated in the pathophysiology of musculoskeletal ageing and (2) the response to repeated exercise bouts promotes exercise adaptations and some of these adaptations (e.g. improved aerobic capacity and exercise-induced mitochondrial remodelling) offset age-related physiological decline. Exercise-induced mitochondrial remodelling is mediated by upstream signalling events that converge on downstream transcriptional co-factors and factors that orchestrate a co-ordinated nuclear and mitochondrial transcriptional response associated with mitochondrial remodelling. Recent translational human investigations have demonstrated similar exercise-induced mitochondrial signalling responses in older compared with younger skeletal muscle, regardless of training status. This is consistent with data indicating normative mitochondrial remodelling responses to long-term exercise training in the elderly. Thus, human ageing is not accompanied by diminished mitochondrial plasticity to acute and chronic exercise stimuli, at least for the signalling pathways measured to date. Exercise-induced increases in reactive oxygen and nitrogen species promote an acute redox-regulated stress response that manifests as increased heat shock protein and antioxidant enzyme content. In accordance with previous reports in rodents and mice, it appears that sedentary ageing is associated with a severely attenuated exercise-induced redox stress response that might be related to an absent redox signal. In this regard, regular exercise training affords some protection but does not completely override age-related defects. Despite some failed redox-regulated stress responses, it seems mitochondrial responses to exercise training are intact in skeletal muscle with age and this might underpin the protective effect of exercise training on age-related musculoskeletal decline. Whilst further investigation is required, recent data suggest that it is never too late to begin exercise training and that lifelong training provides protection against several age-related declines at both the molecular (e.g. reduced mitochondrial function) and whole-body level (e.g. aerobic capacity).

Cold ischemia contributes to the development of chronic rejection and mitochondrial injury after cardiac transplantation.

PubMed

Schneeberger, Stefan; Amberger, Albert; Mandl, Julia; Hautz, Theresa; Renz, Oliver; Obrist, Peter; Meusburger, Hugo; Brandacher, Gerald; Mark, Walter; Strobl, Daniela; Troppmair, Jakob; Pratschke, Johann; Margreiter, Raimund; Kuznetsov, Andrey V

2010-12-01

Chronic rejection (CR) remains an unsolved hurdle for long-term heart transplant survival. The effect of cold ischemia (CI) on progression of CR and the mechanisms resulting in functional deficit were investigated by studying gene expression, mitochondrial function, and enzymatic activity. Allogeneic (Lew→F344) and syngeneic (Lew→Lew) heart transplantations were performed with or without 10 h of CI. After evaluation of myocardial contraction, hearts were excised at 2, 10, 40, and 60 days for investigation of vasculopathy, gene expression, enzymatic activities, and mitochondrial respiration. Gene expression studies identified a gene cluster coding for subunits of the mitochondrial electron transport chain regulated in response to CI and CR. Myocardial performance, mitochondrial function, and mitochondrial marker enzyme activities declined in all allografts with time after transplantation. These declines were more rapid and severe in CI allografts (CR-CI) and correlated well with progression of vasculopathy and fibrosis. Mitochondria related gene expression and mitochondrial function are substantially compromised with the progression of CR and show that CI impacts on progression, gene profile, and mitochondrial function of CR. Monitoring mitochondrial function and enzyme activity might allow for earlier detection of CR and cardiac allograft dysfunction. © 2010 The Authors. Journal compilation © 2010 European Society for Organ Transplantation.

Cardiolipin Fatty Acid Remodeling Regulates Mitochondrial Function by Modifying the Electron Entry Point in the Respiratory Chain

PubMed Central

Vergeade, Aurelia; Bertram, Clinton C.; Bikineyeva, Alfiya T.; Zackert, William E.; Zinkel, Sandra S.; May, James M.; Dikalov, Sergey I.; Roberts, L. Jackson; Boutaud, Olivier

2016-01-01

Modifications of cardiolipin (CL) levels or compositions are associated with changes in mitochondrial function in a wide range of pathologies. We have made the discovery that acetaminophen remodels CL fatty acids composition from tetralinoleoyl to linoleoyltrioleoyl-CL, a remodeling that is associated with decreased mitochondrial respiration. Our data show that CL remodeling causes a shift in electron entry from complex II to the β-oxidation electron transfer flavoprotein quinone oxidoreductase (ETF/QOR) pathway. These data demonstrate that electron entry in the respiratory chain is regulated by CL fatty acid composition and provide proof-of-concept that pharmacological intervention can be used to modify CL composition. PMID:27085476

Plasmatic concentration of organochlorine lindane acts as metabolic disruptors in HepG2 liver cell line by inducing mitochondrial disorder

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benarbia, Mohammed el Amine; Inserm 1063, Angers; Macherel, David

Lindane (LD) is a persistent environmental pollutant that has been the subject of several toxicological studies. However, concentrations used in most of the reported studies were relatively higher than those found in the blood of the contaminated area residents and effects of low concentrations remain poorly investigated. Moreover, effects on cell metabolism and mitochondrial function of exposure to LD have received little attention. This study was designed to explore the effects of low concentrations of LD on cellular metabolism and mitochondrial function, using the hepatocarcinoma cell line HepG2. Cells were exposed to LD for 24, 48 and 72 h andmore » different parameters linked with mitochondrial regulation and energy metabolism were analyzed. Despite having any impact on cellular viability, exposure to LD at plasmatic concentrations led to an increase of maximal respiratory capacity, complex I activity, intracellular ATP and NO release but decreased uncoupled respiration to ATP synthesis and medium lactate levels. In addition, LD exposure resulted in the upregulation of mitochondrial biogenesis genes. We suggest that, at plasmatic concentrations, LD acts as a metabolic disruptor through impaired mitochondrial function and regulation with an impact on cellular energetic metabolism. In addition, we propose that a cellular assay based on the analysis of mitochondria function, such as described here for LD, may be applicable for larger studies on the effects of low concentrations of xenobiotics, because of the exquisite sensitivity of this organelle. - Highlights: Our data clearly demonstrated in HepG2 cells that exposure at plasmatic low concentrations of LD were able to: • Impair mitochondrial function • Caused alteration on nucleo-mitochondrial cross-talk • Increase nitric oxide release and protein nitration • Impair cellular energetic metabolism and lipid accumulation.« less

ISC1-dependent metabolic adaptation reveals an indispensable role for mitochondria in induction of nuclear genes during the diauxic shift in Saccharomyces cerevisiae.

PubMed

Kitagaki, Hiroshi; Cowart, L Ashley; Matmati, Nabil; Montefusco, David; Gandy, Jason; de Avalos, Silvia Vaena; Novgorodov, Sergei A; Zheng, Jim; Obeid, Lina M; Hannun, Yusuf A

2009-04-17

Growth of Saccharomyces cerevisiae following glucose depletion (the diauxic shift) depends on a profound metabolic adaptation accompanied by a global reprogramming of gene expression. In this study, we provide evidence for a heretofore unsuspected role for Isc1p in mediating this reprogramming. Initial studies revealed that yeast cells deleted in ISC1, the gene encoding inositol sphingolipid phospholipase C, which resides in mitochondria in the post-diauxic phase, showed defective aerobic respiration in the post-diauxic phase but retained normal intrinsic mitochondrial functions, including intact mitochondrial DNA, normal oxygen consumption, and normal mitochondrial polarization. Microarray analysis revealed that the Deltaisc1 strain failed to up-regulate genes required for nonfermentable carbon source metabolism during the diauxic shift, thus suggesting a mechanism for the defective supply of respiratory substrates into mitochondria in the post-diauxic phase. This defect in regulating nuclear gene induction in response to a defect in a mitochondrial enzyme raised the possibility that mitochondria may initiate diauxic shift-associated regulation of nucleus-encoded genes. This was established by demonstrating that in respiratory-deficient petite cells these genes failed to be up-regulated across the diauxic shift in a manner similar to the Deltaisc1 strain. Isc1p- and mitochondrial function-dependent genes significantly overlapped with Adr1p-, Snf1p-, and Cat8p-dependent genes, suggesting some functional link among these factors. However, the retrograde response was not activated in Deltaisc1, suggesting that the response of Deltaisc1 cannot be simply attributed to mitochondrial dysfunction. These results suggest a novel role for Isc1p in allowing the reprogramming of gene expression during the transition from anaerobic to aerobic metabolism.

Functional Properties of the Mitochondrial Carrier System.

PubMed

Taylor, Eric B

2017-09-01

The mitochondrial carrier system (MCS) transports small molecules between mitochondria and the cytoplasm. It is integral to the core mitochondrial function to regulate cellular chemistry by metabolism. The mammalian MCS comprises the transporters of the 53-member canonical SLC25A family and a lesser number of identified noncanonical transporters. The recent discovery and investigations of the mitochondrial pyruvate carrier (MPC) illustrate the diverse effects a single mitochondrial carrier may exert on cellular function. However, the transport selectivities of many carriers remain unknown, and most have not been functionally investigated in mammalian cells. The mechanisms coordinating their function as a unified system remain undefined. Increased accessibility to molecular genetic and metabolomic technologies now greatly enables investigation of the MCS. Continued investigation of the MCS may reveal how mitochondria encode complex regulatory information within chemical thermodynamic gradients. This understanding may enable precision modulation of cellular chemistry to counteract the dysmetabolism inherent in disease. Copyright © 2017 Elsevier Ltd. All rights reserved.

Functional TASK-3-Like Channels in Mitochondria of Aldosterone-Producing Zona Glomerulosa Cells.

PubMed

Yao, Junlan; McHedlishvili, David; McIntire, William E; Guagliardo, Nick A; Erisir, Alev; Coburn, Craig A; Santarelli, Vincent P; Bayliss, Douglas A; Barrett, Paula Q

2017-08-01

Ca 2+ drives aldosterone synthesis in the cytosolic and mitochondrial compartments of the adrenal zona glomerulosa cell. Membrane potential across each of these compartments regulates the amplitude of the Ca 2+ signal; yet, only plasma membrane ion channels and their role in regulating cell membrane potential have garnered investigative attention as pathological causes of human hyperaldosteronism. Previously, we reported that genetic deletion of TASK-3 channels (tandem pore domain acid-sensitive K + channels) from mice produces aldosterone excess in the absence of a change in the cell membrane potential of zona glomerulosa cells. Here, we report using yeast 2-hybrid, immunoprecipitation, and electron microscopic analyses that TASK-3 channels are resident in mitochondria, where they regulate mitochondrial morphology, mitochondrial membrane potential, and aldosterone production. This study provides proof of principle that mitochondrial K + channels, by modulating inner mitochondrial membrane morphology and mitochondrial membrane potential, have the ability to play a pathological role in aldosterone dysregulation in steroidogenic cells. © 2017 American Heart Association, Inc.

Temporal manipulation of mitochondrial function by virulent Francisella tularensis to limit inflammation and control cell death.

PubMed

Jessop, Forrest; Schwarz, Benjamin; Heitmann, Emily; Buntyn, Robert; Wehrly, Tara; Bosio, Catharine M

2018-05-14

Francisella tularensis ssp tularensis (Ftt) is a highly pathogenic intracellular bacterium that suppresses host inflammation by impairing the metabolic shift from oxidative phosphorylation to glycolysis. Decreased mitochondrial metabolism is central to initiating a metabolic shift to glycolysis and regulating inflammation, but Ftt manipulation of host mitochondrial function has not been explored. We demonstrate using extracellular flux analysis that Ftt infection initially improves host macrophage mitochondrial bioenergetics in a capsule dependent manner. Enhancement of mitochondrial function by Ftt allowed for modest replication and inhibition of apoptosis early after infection. However, using live cell imaging we found that Ftt facilitated the loss of mitochondrial function at later time points during infection in a capsule independent fashion. This loss of function was paired with oncosis and rapid bacterial replication. Inhibition of oncosis reduced intracellular bacteria numbers, underscoring the requirement for this process during Ftt infection. These findings establish that temporal mitochondrial manipulation by Ftt is critical for maintenance of a non-inflammatory environment and subsequently aids in optimal replication and dissemination of this pathogenic organism. Copyright © 2018 American Society for Microbiology.

New Model of Action for Mood Stabilizers: Phosphoproteome from Rat Pre-Frontal Cortex Synaptoneurosomal Preparations

PubMed Central

Corena-McLeod, Maria; Walss-Bass, Consuelo; Oliveros, Alfredo; Gordillo Villegas, Andres; Ceballos, Carolina; Charlesworth, Cristine M.; Madden, Benjamin; Linser, Paul J.; Van Ekeris, Leslie; Smith, Kristin; Richelson, Elliott

2013-01-01

Background Mitochondrial short and long-range movements are necessary to generate the energy needed for synaptic signaling and plasticity. Therefore, an effective mechanism to transport and anchor mitochondria to pre- and post-synaptic terminals is as important as functional mitochondria in neuronal firing. Mitochondrial movement range is regulated by phosphorylation of cytoskeletal and motor proteins in addition to changes in mitochondrial membrane potential. Movement direction is regulated by serotonin and dopamine levels. However, data on mitochondrial movement defects and their involvement in defective signaling and neuroplasticity in relationship with mood disorders is scarce. We have previously reported the effects of lithium, valproate and a new antipsychotic, paliperidone on protein expression levels at the synaptic level. Hypothesis Mitochondrial function defects have recently been implicated in schizophrenia and bipolar disorder. We postulate that mood stabilizer treatment has a profound effect on mitochondrial function, synaptic plasticity, mitochondrial migration and direction of movement. Methods Synaptoneurosomal preparations from rat pre-frontal cortex were obtained after 28 daily intraperitoneal injections of lithium, valproate and paliperidone. Phosphorylated proteins were identified using 2D-DIGE and nano LC-ESI tandem mass spectrometry. Results Lithium, valproate and paliperidone had a substantial and common effect on the phosphorylation state of specific actin, tubulin and myosin isoforms as well as other proteins associated with neurofilaments. Furthermore, different subunits from complex III and V of the electron transfer chain were heavily phosphorylated by treatment with these drugs indicating selective phosphorylation. Conclusions Mood stabilizers have an effect on mitochondrial function, mitochondrial movement and the direction of this movement. The implications of these findings will contribute to novel insights regarding clinical treatment and the mode of action of these drugs. PMID:23690912

An MRM-based workflow for quantifying cardiac mitochondrial protein phosphorylation in murine and human tissue.

PubMed

Lam, Maggie P Y; Scruggs, Sarah B; Kim, Tae-Young; Zong, Chenggong; Lau, Edward; Wang, Ding; Ryan, Christopher M; Faull, Kym F; Ping, Peipei

2012-08-03

The regulation of mitochondrial function is essential for cardiomyocyte adaptation to cellular stress. While it has long been understood that phosphorylation regulates flux through metabolic pathways, novel phosphorylation sites are continually being discovered in all functionally distinct areas of the mitochondrial proteome. Extracting biologically meaningful information from these phosphorylation sites requires an adaptable, sensitive, specific and robust method for their quantification. Here we report a multiple reaction monitoring-based mass spectrometric workflow for quantifying site-specific phosphorylation of mitochondrial proteins. Specifically, chromatographic and mass spectrometric conditions for 68 transitions derived from 23 murine and human phosphopeptides, and their corresponding unmodified peptides, were optimized. These methods enabled the quantification of endogenous phosphopeptides from the outer mitochondrial membrane protein VDAC, and the inner membrane proteins ANT and ETC complexes I, III and V. The development of this quantitative workflow is a pivotal step for advancing our knowledge and understanding of the regulatory effects of mitochondrial protein phosphorylation in cardiac physiology and pathophysiology. This article is part of a Special Issue entitled: Translational Proteomics. Copyright © 2012 Elsevier B.V. All rights reserved.

Mitochondrial functionality in reproduction: from gonads and gametes to embryos and embryonic stem cells.

PubMed

Ramalho-Santos, João; Varum, Sandra; Amaral, Sandra; Mota, Paula C; Sousa, Ana Paula; Amaral, Alexandra

2009-01-01

Mitochondria are multitasking organelles involved in ATP synthesis, reactive oxygen species (ROS) production, calcium signalling and apoptosis; and mitochondrial defects are known to cause physiological dysfunction, including infertility. The goal of this review was to identify and discuss common themes in mitochondrial function related to mammalian reproduction. The scientific literature was searched for studies reporting on the several aspects of mitochondrial activity in mammalian testis, sperm, oocytes, early embryos and embryonic stem cells. ATP synthesis and ROS production are the most discussed aspects of mitochondrial function. Metabolic shifts from mitochondria-produced ATP to glycolysis occur at several stages, notably during gametogenesis and early embryo development, either reflecting developmental switches or substrate availability. The exact role of sperm mitochondria is especially controversial. Mitochondria-generated ROS function in signalling but are mostly described when produced under pathological conditions. Mitochondria-based calcium signalling is primarily important in embryo activation and embryonic stem cell differentiation. Besides pathologically triggered apoptosis, mitochondria participate in apoptotic events related to the regulation of spermatogonial cell number, as well as gamete, embryo and embryonic stem cell quality. Interestingly, data from knock-out (KO) mice is not always straightforward in terms of expected phenotypes. Finally, recent data suggests that mitochondrial activity can modulate embryonic stem cell pluripotency as well as differentiation into distinct cellular fates. Mitochondria-based events regulate different aspects of reproductive function, but these are not uniform throughout the several systems reviewed. Low mitochondrial activity seems a feature of 'stemness', being described in spermatogonia, early embryo, inner cell mass cells and embryonic stem cells.

Prolonged Fasting Identifies Heat Shock Protein 10 as a Sirtuin 3 Substrate

PubMed Central

Lu, Zhongping; Chen, Yong; Aponte, Angel M.; Battaglia, Valentina; Gucek, Marjan; Sack, Michael N.

2015-01-01

Although Sirtuin 3 (SIRT3), a mitochondrially enriched deacetylase and activator of fat oxidation, is down-regulated in response to high fat feeding, the rate of fatty acid oxidation and mitochondrial protein acetylation are invariably enhanced in this dietary milieu. These paradoxical data implicate that additional acetylation modification-dependent levels of regulation may be operational under nutrient excess conditions. Because the heat shock protein (Hsp) Hsp10-Hsp60 chaperone complex mediates folding of the fatty acid oxidation enzyme medium-chain acyl-CoA dehydrogenase, we tested whether acetylation-dependent mitochondrial protein folding contributes to this regulatory discrepancy. We demonstrate that Hsp10 is a functional SIRT3 substrate and that, in response to prolonged fasting, SIRT3 levels modulate mitochondrial protein folding. Acetyl mutagenesis of Hsp10 lysine 56 alters Hsp10-Hsp60 binding, conformation, and protein folding. Consistent with Hsp10-Hsp60 regulation of fatty acid oxidation enzyme integrity, medium-chain acyl-CoA dehydrogenase activity and fat oxidation are elevated by Hsp10 acetylation. These data identify acetyl modification of Hsp10 as a nutrient-sensing regulatory node controlling mitochondrial protein folding and metabolic function. PMID:25505263

Cofilin1-dependent actin dynamics control DRP1-mediated mitochondrial fission

PubMed Central

Rehklau, Katharina; Hoffmann, Lena; Gurniak, Christine B; Ott, Martin; Witke, Walter; Scorrano, Luca; Culmsee, Carsten; Rust, Marco B

2017-01-01

Mitochondria form highly dynamic networks in which organelles constantly fuse and divide. The relevance of mitochondrial dynamics is evident from its implication in various human pathologies, including cancer or neurodegenerative, endocrine and cardiovascular diseases. Dynamin-related protein 1 (DRP1) is a key regulator of mitochondrial fission that oligomerizes at the mitochondrial outer membrane and hydrolyzes GTP to drive mitochondrial fragmentation. Previous studies demonstrated that DRP1 recruitment and mitochondrial fission is promoted by actin polymerization at the mitochondrial surface, controlled by the actin regulatory proteins inverted formin 2 (INF2) and Spire1C. These studies suggested the requirement of additional actin regulatory activities to control DRP1-mediated mitochondrial fission. Here we show that the actin-depolymerizing protein cofilin1, but not its close homolog actin-depolymerizing factor (ADF), is required to maintain mitochondrial morphology. Deletion of cofilin1 caused mitochondrial DRP1 accumulation and fragmentation, without altering mitochondrial function or other organelles’ morphology. Mitochondrial morphology in cofilin1-deficient cells was restored upon (i) re-expression of wild-type cofilin1 or a constitutively active mutant, but not of an actin-binding-deficient mutant, (ii) pharmacological destabilization of actin filaments and (iii) genetic depletion of DRP1. Our work unraveled a novel function for cofilin1-dependent actin dynamics in mitochondrial fission, and identified cofilin1 as a negative regulator of mitochondrial DRP1 activity. We conclude that cofilin1 is required for local actin dynamics at mitochondria, where it may balance INF2/Spire1C-induced actin polymerization. PMID:28981113

Arterial Smooth Muscle Mitochondria Amplify Hydrogen Peroxide Microdomains Functionally Coupled to L-Type Calcium Channels

PubMed Central

Chaplin, Nathan L.; Nieves-Cintrón, Madeline; Fresquez, Adriana M.; Navedo, Manuel F.; Amberg, Gregory C.

2015-01-01

Rationale Mitochondria are key integrators of convergent intracellular signaling pathways. Two important second messengers modulated by mitochondria are calcium and reactive oxygen species. To date, coherent mechanisms describing mitochondrial integration of calcium and oxidative signaling in arterial smooth muscle are incomplete. Objective To address and add clarity to this issue we tested the hypothesis that mitochondria regulate subplasmalemmal calcium and hydrogen peroxide microdomain signaling in cerebral arterial smooth muscle. Methods and Results Using an image-based approach we investigated the impact of mitochondrial regulation of L-type calcium channels on subcellular calcium and ROS signaling microdomains in isolated arterial smooth muscle cells. Our single cell observations were then related experimentally to intact arterial segments and to living animals. We found that subplasmalemmal mitochondrial amplification of hydrogen peroxide microdomain signaling stimulates L-type calcium channels and that this mechanism strongly impacts the functional capacity of the vasoconstrictor angiotensin II. Importantly, we also found that disrupting this mitochondrial amplification mechanism in vivo normalized arterial function and attenuated the hypertensive response to systemic endothelial dysfunction. Conclusions From these observations we conclude that mitochondrial amplification of subplasmalemmal calcium and hydrogen peroxide microdomain signaling is a fundamental mechanism regulating arterial smooth muscle function. As the principle components involved are fairly ubiquitous and positioning of mitochondria near the plasma membrane is not restricted to arterial smooth muscle, this mechanism could occur in many cell types and contribute to pathological elevations of intracellular calcium and increased oxidative stress associated with many diseases. PMID:26390880

Erythropoietin activates SIRT1 to protect human cardiomyocytes against doxorubicin-induced mitochondrial dysfunction and toxicity.

PubMed

Cui, Lan; Guo, Jiabin; Zhang, Qiang; Yin, Jian; Li, Jin; Zhou, Wei; Zhang, Tingfen; Yuan, Haitao; Zhao, Jun; Zhang, Li; Carmichael, Paul L; Peng, Shuangqing

2017-06-05

The hormone erythropoietin (EPO) has been demonstrated to protect against chemotherapy drug doxorubicin (DOX)-induced cardiotoxicity, but the underlying mechanism remains obscure. We hypothesized that silent mating type information regulation 2 homolog 1 (SIRT1), an NAD + -dependent protein deacetylase that activates peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), plays a crucial role in regulating mitochondrial function and mediating the beneficial effect of EPO. Our study in human cardiomyocyte AC16 cells showed that DOX-induced cytotoxicity and mitochondrial dysfunction, as manifested by decreased mitochondrial DNA (mtDNA) copy number, mitochondrial membrane potential, and increased mitochondrial superoxide accumulation, can be mitigated by EPO pretreatment. EPO was found to upregulate SIRT1 activity and protein expression to reverse DOX-induced acetylation of PGC-1α and suppression of a suite of PGC-1α-activated genes involved in mitochondrial function and biogenesis, such as nuclear respiratory factor-1 (NRF1), mitochondrial transcription factor A (TFAM), citrate synthase (CS), superoxide dismutase 2 (SOD2), cytochrome c oxidase IV (COXIV), and voltage-dependent anion channel (VDAC). Silencing of SIRT1 via small RNA interference sensitized AC16 cells to DOX-induced cytotoxicity and reduction in mtDNA copy number. Although with SIRT1 silenced, EPO could reverse to some extent DOX-induced mitochondrial superoxide accumulation, loss of mitochondrial membrane potential and ATP depletion, it failed to normalize protein expression of PGC-1α and its downstream genes. Taken together, our results indicated that EPO may activate SIRT1 to enhance mitochondrial function and protect against DOX-induced cardiotoxicity. Copyright © 2017 Elsevier B.V. All rights reserved.

Weight loss by Ppc-1, a novel small molecule mitochondrial uncoupler derived from slime mold.

PubMed

Suzuki, Toshiyuki; Kikuchi, Haruhisa; Ogura, Masato; Homma, Miwako K; Oshima, Yoshiteru; Homma, Yoshimi

2015-01-01

Mitochondria play a key role in diverse processes including ATP synthesis and apoptosis. Mitochondrial function can be studied using inhibitors of respiration, and new agents are valuable for discovering novel mechanisms involved in mitochondrial regulation. Here, we screened small molecules derived from slime molds and other microorganisms for their effects on mitochondrial oxygen consumption. We identified Ppc-1 as a novel molecule which stimulates oxygen consumption without adverse effects on ATP production. The kinetic behavior of Ppc-1 suggests its function as a mitochondrial uncoupler. Serial administration of Ppc-1 into mice suppressed weight gain with no abnormal effects on liver or kidney tissues, and no evidence of tumor formation. Serum fatty acid levels were significantly elevated in mice treated with Ppc-1, while body fat content remained low. After a single administration, Ppc-1 distributes into various tissues of individual animals at low levels. Ppc-1 stimulates adipocytes in culture to release fatty acids, which might explain the elevated serum fatty acids in Ppc-1-treated mice. The results suggest that Ppc-1 is a unique mitochondrial regulator which will be a valuable tool for mitochondrial research as well as the development of new drugs to treat obesity.

Berberine Regulated Lipid Metabolism in the Presence of C75, Compound C, and TOFA in Breast Cancer Cell Line MCF-7.

PubMed

Tan, Wen; Zhong, Zhangfeng; Wang, Shengpeng; Suo, Zhanwei; Yang, Xian; Hu, Xiaodong; Wang, Yitao

2015-01-01

Berberine interfering with cancer reprogramming metabolism was confirmed in our previous study. Lipid metabolism and mitochondrial function were also the core parts in reprogramming metabolism. In the presence of some energy-related inhibitors, including C75, compound C, and TOFA, the discrete roles of berberine in lipid metabolism and mitochondrial function were elucidated. An altered lipid metabolism induced by berberine was observed under the inhibition of FASN, AMPK, and ACC in breast cancer cell MCF-7. And the reversion of berberine-induced lipid suppression indicated that ACC inhibition might be involved in that process instead of FASN inhibition. A robust apoptosis induced by berberine even under the inhibition of AMPK and lipid synthesis was also indicated. Finally, mitochondrial function regulation under the inhibition of AMPK and ACC might be in an ACL-independent manner. Undoubtedly, the detailed mechanisms of berberine interfering with lipid metabolism and mitochondrial function combined with energy-related inhibitors need further investigation, including the potential compensatory mechanisms for ATP production and the upregulation of ACL.

Berberine Regulated Lipid Metabolism in the Presence of C75, Compound C, and TOFA in Breast Cancer Cell Line MCF-7

PubMed Central

Tan, Wen; Zhong, Zhangfeng; Suo, Zhanwei; Yang, Xian; Hu, Xiaodong; Wang, Yitao

2015-01-01

Berberine interfering with cancer reprogramming metabolism was confirmed in our previous study. Lipid metabolism and mitochondrial function were also the core parts in reprogramming metabolism. In the presence of some energy-related inhibitors, including C75, compound C, and TOFA, the discrete roles of berberine in lipid metabolism and mitochondrial function were elucidated. An altered lipid metabolism induced by berberine was observed under the inhibition of FASN, AMPK, and ACC in breast cancer cell MCF-7. And the reversion of berberine-induced lipid suppression indicated that ACC inhibition might be involved in that process instead of FASN inhibition. A robust apoptosis induced by berberine even under the inhibition of AMPK and lipid synthesis was also indicated. Finally, mitochondrial function regulation under the inhibition of AMPK and ACC might be in an ACL-independent manner. Undoubtedly, the detailed mechanisms of berberine interfering with lipid metabolism and mitochondrial function combined with energy-related inhibitors need further investigation, including the potential compensatory mechanisms for ATP production and the upregulation of ACL. PMID:26351511

Mitochondrial and Chloroplast Stress Responses Are Modulated in Distinct Touch and Chemical Inhibition Phases1[OPEN

PubMed Central

Ivanova, Aneta; Millar, A. Harvey; Whelan, James

2016-01-01

Previous studies have identified a range of transcription factors that modulate retrograde regulation of mitochondrial and chloroplast functions in Arabidopsis (Arabidopsis thaliana). However, the relative importance of these regulators and whether they act downstream of separate or overlapping signaling cascades is still unclear. Here, we demonstrate that multiple stress-related signaling pathways, with distinct kinetic signatures, converge on overlapping gene sets involved in energy organelle function. The transcription factor ANAC017 is almost solely responsible for transcript induction of marker genes around 3 to 6 h after chemical inhibition of organelle function and is a key regulator of mitochondrial and specific types of chloroplast retrograde signaling. However, an independent and highly transient gene expression phase, initiated within 10 to 30 min after treatment, also targets energy organelle functions, and is related to touch and wounding responses. Metabolite analysis demonstrates that this early response is concurrent with rapid changes in tricarboxylic acid cycle intermediates and large changes in transcript abundance of genes encoding mitochondrial dicarboxylate carrier proteins. It was further demonstrated that transcription factors AtWRKY15 and AtWRKY40 have repressive regulatory roles in this touch-responsive gene expression. Together, our results show that several regulatory systems can independently affect energy organelle function in response to stress, providing different means to exert operational control. PMID:27208304

Mitochondrial DNA Unwinding Enzyme Required for Liver Regeneration | Center for Cancer Research

Cancer.gov

The liver has an exceptional capacity to proliferate. This ability allows the liver to regenerate its mass after partial surgical removal or injury and is the key to successful partial liver transplants. Liver cells, called hepatocytes, are packed with mitochondria, and regulating mitochondrial DNA (mtDNA) copy number is crucial to mitochondrial function, including energy production, during proliferation. Yves Pommier, M.D., Ph.D., of CCR’s Developmental Therapeutics Branch, and his colleagues recently showed that the vertebrate mitochondrial topoisomerase, Top1mt, was critical in maintaining mitochondrial function in the heart after doxorubicin-induced damage. The group wondered whether Top1mt might play a similar role in liver regeneration.

Altered Cytoskeleton as a Mitochondrial Decay Signature in the Retinal Pigment Epithelium

PubMed Central

Sripathi, Srinivasa R.; He, Weilue; Sylvester, O’Donnell; Neksumi, Musa; Um, Ji-Yeon; Dluya, Thagriki; Bernstein, Paul S.; Jahng, Wan Jin

2016-01-01

Mitochondria mediate energy metabolism, apoptosis, and aging, while mitochondrial disruption leads to age-related diseases that include age-related macular degeneration (AMD). Descriptions of mitochondrial morphology have been non-systematic and qualitative, due to lack of knowledge on the molecular mechanism of mitochondrial dynamics. The current study analyzed mitochondrial size, shape, and position quantitatively in retinal pigment epithelial cells (RPE) using a systematic computational model to suggest mitochondrial trafficking under oxidative environment. Our previous proteomic study suggested that prohibitin is a mitochondrial decay biomarker in the RPE. The current study examined the prohibitin interactome map using immunoprecipitation data to determine the indirect signaling on cytoskeletal changes and transcriptional regulation by prohibitin. Immunocytochemistry and immunoprecipitation demonstrated that there is a positive correlation between mitochondrial changes and altered filaments as well as prohibitin interactions with kinesin and unknown proteins in the RPE. Specific cytoskeletal and nuclear protein-binding mechanisms may exist to regulate prohibitin-mediated reactions as key elements, including vimentin and p53, to control apoptosis in mitochondria and the nucleus. Prohibitin may regulate mitochondrial trafficking through unknown proteins that include 110 kDa protein with myosin head domain and 88 kDa protein with cadherin repeat domain. Altered cytoskeleton may represent a mitochondrial decay signature in the RPE. The current study suggests that mitochondrial dynamics and cytoskeletal changes are critical for controlling mitochondrial distribution and function. Further, imbalance of retrograde vs. anterograde mitochondrial trafficking may initiate the pathogenic reaction in adult-onset neurodegenerative diseases. PMID:27029380

Altered Cytoskeleton as a Mitochondrial Decay Signature in the Retinal Pigment Epithelium.

PubMed

Sripathi, Srinivas R; He, Weilue; Sylvester, O'Donnell; Neksumi, Musa; Um, Ji-Yeon; Dluya, Thagriki; Bernstein, Paul S; Jahng, Wan Jin

2016-06-01

Mitochondria mediate energy metabolism, apoptosis, and aging, while mitochondrial disruption leads to age-related diseases that include age-related macular degeneration. Descriptions of mitochondrial morphology have been non-systematic and qualitative, due to lack of knowledge on the molecular mechanism of mitochondrial dynamics. The current study analyzed mitochondrial size, shape, and position quantitatively in retinal pigment epithelial cells (RPE) using a systematic computational model to suggest mitochondrial trafficking under oxidative environment. Our previous proteomic study suggested that prohibitin is a mitochondrial decay biomarker in the RPE. The current study examined the prohibitin interactome map using immunoprecipitation data to determine the indirect signaling on cytoskeletal changes and transcriptional regulation by prohibitin. Immunocytochemistry and immunoprecipitation demonstrated that there is a positive correlation between mitochondrial changes and altered filaments as well as prohibitin interactions with kinesin and unknown proteins in the RPE. Specific cytoskeletal and nuclear protein-binding mechanisms may exist to regulate prohibitin-mediated reactions as key elements, including vimentin and p53, to control apoptosis in mitochondria and the nucleus. Prohibitin may regulate mitochondrial trafficking through unknown proteins that include 110 kDa protein with myosin head domain and 88 kDa protein with cadherin repeat domain. Altered cytoskeleton may represent a mitochondrial decay signature in the RPE. The current study suggests that mitochondrial dynamics and cytoskeletal changes are critical for controlling mitochondrial distribution and function. Further, imbalance of retrograde versus anterograde mitochondrial trafficking may initiate the pathogenic reaction in adult-onset neurodegenerative diseases.

Mitochondrial DNA Unwinding Enzyme Required for Liver Regeneration | Center for Cancer Research

Cancer.gov

The liver has an exceptional capacity to proliferate. This ability allows the liver to regenerate its mass after partial surgical removal or injury and is the key to successful partial liver transplants. Liver cells, called hepatocytes, are packed with mitochondria, and regulating mitochondrial DNA (mtDNA) copy number is crucial to mitochondrial function, including energy

The Membrane-Bound NAC Transcription Factor ANAC013 Functions in Mitochondrial Retrograde Regulation of the Oxidative Stress Response in Arabidopsis[C][W

PubMed Central

De Clercq, Inge; Vermeirssen, Vanessa; Van Aken, Olivier; Vandepoele, Klaas; Murcha, Monika W.; Law, Simon R.; Inzé, Annelies; Ng, Sophia; Ivanova, Aneta; Rombaut, Debbie; van de Cotte, Brigitte; Jaspers, Pinja; Van de Peer, Yves; Kangasjärvi, Jaakko; Whelan, James; Van Breusegem, Frank

2013-01-01

Upon disturbance of their function by stress, mitochondria can signal to the nucleus to steer the expression of responsive genes. This mitochondria-to-nucleus communication is often referred to as mitochondrial retrograde regulation (MRR). Although reactive oxygen species and calcium are likely candidate signaling molecules for MRR, the protein signaling components in plants remain largely unknown. Through meta-analysis of transcriptome data, we detected a set of genes that are common and robust targets of MRR and used them as a bait to identify its transcriptional regulators. In the upstream regions of these mitochondrial dysfunction stimulon (MDS) genes, we found a cis-regulatory element, the mitochondrial dysfunction motif (MDM), which is necessary and sufficient for gene expression under various mitochondrial perturbation conditions. Yeast one-hybrid analysis and electrophoretic mobility shift assays revealed that the transmembrane domain–containing NO APICAL MERISTEM/ARABIDOPSIS TRANSCRIPTION ACTIVATION FACTOR/CUP-SHAPED COTYLEDON transcription factors (ANAC013, ANAC016, ANAC017, ANAC053, and ANAC078) bound to the MDM cis-regulatory element. We demonstrate that ANAC013 mediates MRR-induced expression of the MDS genes by direct interaction with the MDM cis-regulatory element and triggers increased oxidative stress tolerance. In conclusion, we characterized ANAC013 as a regulator of MRR upon stress in Arabidopsis thaliana. PMID:24045019

Eicosapentaenoic acid and arachidonic acid differentially regulate adipogenesis, acquisition of a brite phenotype and mitochondrial function in primary human adipocytes.

PubMed

Fleckenstein-Elsen, Manuela; Dinnies, Daniela; Jelenik, Tomas; Roden, Michael; Romacho, Tania; Eckel, Jürgen

2016-09-01

n-3 and n-6 PUFAs have several opposing biological effects and influence white adipose tissue (WAT) function. The recent discovery of thermogenic UCP1-expressing brite adipocytes within WAT raised the question whether n-3 and n-6 PUFAs exert differential effects on brite adipocyte formation and mitochondrial function. Primary human preadipocytes were treated with n-3 PUFAs (eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) or n-6 PUFA (arachidonic acid, ARA) during differentiation, and adipogenesis, white and brite gene expression markers, mitochondrial content and function were analyzed at day 12 of differentiation. Adipogenesis was equally increased by n-3 and n-6 PUFAs. The n-6 PUFA ARA increased lipid droplet size and expression of the white-specific marker TCF21 while decreased mitochondrial protein expression and respiratory function. In contrast, EPA increased expression of the brown adipocyte-related genes UCP1 and CPT1B, and improved mitochondrial function of adipocytes. The opposing effects of EPA and ARA on gene expression and mitochondrial function were also observed in cells treated from day 8 to 12 of adipocyte differentiation. EPA promotes brite adipogenesis and improves parameters of mitochondrial function, such as increased expression of CPTB1, citrate synthase activity and higher maximal respiratory capacity, while ARA reduced mitochondrial spare respiratory capacity in vitro. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ginsenoside Rg3 attenuates sepsis-induced injury and mitochondrial dysfunction in liver via AMPK-mediated autophagy flux.

PubMed

Xing, Wei; Yang, Lei; Peng, Yue; Wang, Qianlu; Gao, Min; Yang, Mingshi; Xiao, Xianzhong

2017-08-31

Sepsis-led mitochondrial dysfunction has become a critical pathophysiological procedure in sepsis. Since ginsenosides have been applied in the treatment of mitochondrial dysfunction, ginsenoside Rg3 was employed to study its effects on the mitochondrial dysfunction induced by sepsis. The apoptosis rate, oxygen consumption rate (OCR), reactive oxygen species (ROS), antioxidant glutathione (GSH) pools, and mitochondrial transmembrane potential (MTP) were determined in LPS-induced sepsis hepatocytes treated with different concentrations of Rg3. Then, the protein expression levels of mitochondrial biogenesis related transcription factors, autophagy-related proteins, and AMP-activated protein kinase (AMPK) signal pathway related proteins were determined by Western blotting in both in vitro and in vivo sepsis models. Rg3 shows functions of promotion of OCR, attenuation of ROS, and maintenance of GSH pools, and its conjugating activity in the in vitro sepsis models. Rg3-treated cells were observed to have a higher MTP value compared with the LPS only induced cells. Moreover, Rg3 treatment can inhibit mitochondrial dysfunction via increasing the protein expression levels of mitochondrial biogenesis related transcription factors. Rg3 treatment has the function of inhibitor of apoptosis of human primary hepatocytes, and Rg3 can up-regulate the autophagy-related proteins and activate AMPK signal pathway in sepsis models. Meanwhile, the mitochondrial protective function exerted by Rg3 decreased after the autophagy inhibitors or AMPK inhibitor treatment in LPS-induced human primary hepatocytes. Rg3 can improve mitochondrial dysfunction by regulating autophagy in mitochondria via activating the AMPK signal pathway, thus protecting cell and organ injuries caused by sepsis. © 2017 The Author(s).

PGC-1α Regulation of Mitochondrial Degeneration in Experimental Diabetic Neuropathy

PubMed Central

Choi, Joungil; Chandrasekaran, Krish; Inoue, Tatsuya; Muragundla, Anjaneyulu; Russell, James W.

2014-01-01

Mitochondrial degeneration is considered to play an important role in the development of diabetic peripheral neuropathy in humans. Mitochondrial degeneration and the corresponding protein regulation associated with the degeneration were studied in an animal model of diabetic neuropathy. PGC-1α and its-regulated transcription factors including TFAM and NRF1, which are master regulators of mitochondrial biogenesis, are significantly downregulated in streptozotocin diabetic dorsal root ganglion (DRG) neurons. Diabetic mice develop peripheral neuropathy, loss of mitochondria, decreased mitochondrial DNA content and increased protein oxidation. Importantly, this phenotype is exacerbated in PGC-1α (−/−) diabetic mice, which develop a more severe neuropathy with reduced mitochondrial DNA and a further increase in protein oxidation. PGC-1α (−/−) diabetic mice develop an increase in total cholesterol and triglycerides, and a decrease in TFAM and NRF1 protein levels. Loss of PGC-1α causes severe mitochondrial degeneration with vacuolization in DRG neurons, coupled with reduced state 3 and 4 respiration, reduced expression of oxidative stress response genes and an increase in protein oxidation. In contrast, overexpression of PGC-1α in cultured adult mouse neurons prevents oxidative stress associated with increased glucose levels. The study provides new insights into the role of PGC-1α in mitochondrial regeneration in peripheral neurons and suggests that therapeutic modulation of PGC-1α function may be an attractive approach for treatment of diabetic neuropathy. PMID:24423644

The axonal transport of mitochondria

PubMed Central

Saxton, William M.; Hollenbeck, Peter J.

2012-01-01

Vigorous transport of cytoplasmic components along axons over substantial distances is crucial for the maintenance of neuron structure and function. The transport of mitochondria, which serves to distribute mitochondrial functions in a dynamic and non-uniform fashion, has attracted special interest in recent years following the discovery of functional connections among microtubules, motor proteins and mitochondria, and their influences on neurodegenerative diseases. Although the motor proteins that drive mitochondrial movement are now well characterized, the mechanisms by which anterograde and retrograde movement are coordinated with one another and with stationary axonal mitochondria are not yet understood. In this Commentary, we review why mitochondria move and how they move, focusing particularly on recent studies of transport regulation, which implicate control of motor activity by specific cell-signaling pathways, regulation of motor access to transport tracks and static microtubule–mitochondrion linkers. A detailed mechanism for modulating anterograde mitochondrial transport has been identified that involves Miro, a mitochondrial Ca2+-binding GTPase, which with associated proteins, can bind and control kinesin-1. Elements of the Miro complex also have important roles in mitochondrial fission–fusion dynamics, highlighting questions about the interdependence of biogenesis, transport, dynamics, maintenance and degradation. PMID:22619228

Global Identification of New Substrates for the Yeast Endoribonuclease, RNase Mitochondrial RNA Processing (MRP)*

PubMed Central

Aulds, Jason; Wierzbicki, Sara; McNairn, Adrian; Schmitt, Mark E.

2012-01-01

RNase mitochondrial RNA processing (MRP) is an essential, evolutionarily conserved endoribonuclease composed of 10 different protein subunits and a single RNA. RNase MRP has established roles in multiple pathways including ribosome biogenesis, cell cycle regulation, and mitochondrial DNA replication. Although each of these functions is important to cell growth, additional functions may exist given the essential nature of the complex. To identify novel RNase MRP substrates, we utilized RNA immunoprecipitation and microarray chip analysis to identify RNA that physically associates with RNase MRP. We identified several new potential substrates for RNase MRP including a cell cycle-regulated transcript, CTS1; the yeast homolog of the mammalian p27Kip1, SIC1; and the U2 RNA component of the spliceosome. In addition, we found RNase MRP to be involved in the regulation of the Ty1 transposon RNA. These results reinforce and broaden the role of RNase MRP in cell cycle regulation and help to identify new roles of this endoribonuclease. PMID:22977255

Global identification of new substrates for the yeast endoribonuclease, RNase mitochondrial RNA processing (MRP).

PubMed

Aulds, Jason; Wierzbicki, Sara; McNairn, Adrian; Schmitt, Mark E

2012-10-26

RNase mitochondrial RNA processing (MRP) is an essential, evolutionarily conserved endoribonuclease composed of 10 different protein subunits and a single RNA. RNase MRP has established roles in multiple pathways including ribosome biogenesis, cell cycle regulation, and mitochondrial DNA replication. Although each of these functions is important to cell growth, additional functions may exist given the essential nature of the complex. To identify novel RNase MRP substrates, we utilized RNA immunoprecipitation and microarray chip analysis to identify RNA that physically associates with RNase MRP. We identified several new potential substrates for RNase MRP including a cell cycle-regulated transcript, CTS1; the yeast homolog of the mammalian p27(Kip1), SIC1; and the U2 RNA component of the spliceosome. In addition, we found RNase MRP to be involved in the regulation of the Ty1 transposon RNA. These results reinforce and broaden the role of RNase MRP in cell cycle regulation and help to identify new roles of this endoribonuclease.

Copper deficiency alters cell bioenergetics and induces mitochondrial fusion through up-regulation of MFN2 and OPA1 in erythropoietic cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bustos, Rodrigo I.; Jensen, Erik L.; Ruiz, Lina M.

2013-08-02

Highlights: •In copper deficiency, cell proliferation is not affected. In turn, cell differentiation is impaired. •Enlarged mitochondria are due to up-regulation of MNF2 and OPA1. •Mitochondria turn off respiratory chain and ROS production. •Energy metabolism switch from mitochondria to glycolysis. -- Abstract: Copper is essential in cell physiology, participating in numerous enzyme reactions. In mitochondria, copper is a cofactor for respiratory complex IV, the cytochrome c oxidase. Low copper content is associated with anemia and the appearance of enlarged mitochondria in erythropoietic cells. These findings suggest a connection between copper metabolism and bioenergetics, mitochondrial dynamics and erythropoiesis, which has notmore » been explored so far. Here, we describe that bathocuproine disulfonate-induced copper deficiency does not alter erythropoietic cell proliferation nor induce apoptosis. However it does impair erythroid differentiation, which is associated with a metabolic switch between the two main energy-generating pathways. That is, from mitochondrial function to glycolysis. Switching off mitochondria implies a reduction in oxygen consumption and ROS generation along with an increase in mitochondrial membrane potential. Mitochondrial fusion proteins MFN2 and OPA1 were up-regulated along with the ability of mitochondria to fuse. Morphometric analysis of mitochondria did not show changes in total mitochondrial biomass but rather bigger mitochondria because of increased fusion. Similar results were also obtained with human CD34+, which were induced to differentiate into red blood cells. In all, we have shown that adequate copper levels are important for maintaining proper mitochondrial function and for erythroid differentiation where the energy metabolic switch plus the up-regulation of fusion proteins define an adaptive response to copper deprivation to keep cells alive.« less

Role of FAST Kinase Domains 3 (FASTKD3) in Post-transcriptional Regulation of Mitochondrial Gene Expression*

PubMed Central

Boehm, Erik; Zornoza, María; Jourdain, Alexis A.; Delmiro Magdalena, Aitor; García-Consuegra, Inés; Torres Merino, Rebeca; Orduña, Antonio; Martín, Miguel A.; Martinou, Jean-Claude; De la Fuente, Miguel A.; Simarro, María

2016-01-01

The Fas-activated serine/threonine kinase (FASTK) family of proteins has recently emerged as a central regulator of mitochondrial gene expression through the function of an unusual RNA-binding domain named RAP (for RNA-binding domain abundant in Apicomplexans), shared by all six members of the family. Here we describe the role of one of the less characterized members, FASTKD3, in mitochondrial RNA metabolism. First, we show that, in contrast to FASTK, FASTKD2, and FASTKD5, FASTKD3 does not localize in mitochondrial RNA granules, which are sites of processing and maturation of mtRNAs and ribosome biogenesis. Second, we generated FASTKD3 homozygous knock-out cell lines by homologous recombination and observed that the absence of FASTKD3 resulted in increased steady-state levels and half-lives of a subset of mature mitochondrial mRNAs: ND2, ND3, CYTB, COX2, and ATP8/6. No aberrant processing of RNA precursors was observed. Rescue experiments demonstrated that RAP domain is required for FASTKD3 function in mRNA stability. Besides, we describe that FASTKD3 is required for efficient COX1 mRNA translation without altering mRNA levels, which results in a decrease in the steady-state levels of COX1 protein. This finding is associated with reduced mitochondrial complex IV assembly and activity. Our observations suggest that the function of this family of proteins goes beyond RNA processing and ribosome assembly and includes RNA stability and translation regulation within mitochondria. PMID:27789713

miR-504 mediated down-regulation of nuclear respiratory factor 1 leads to radio-resistance in nasopharyngeal carcinoma

PubMed Central

Zhao, Luqing; Tang, Min; Hu, Zheyu; Yan, Bin; Pi, Weiwei; Li, Zhi; Zhang, Jing; Zhang, Liqin; Jiang, Wuzhong; Li, Guo; Qiu, Yuanzheng; Hu, Fang; Liu, Feng; Lu, Jingchen; Chen, Xue; Xiao, Lanbo; Xu, Zhijie; Tao, Yongguang; Yang, Lifang; Bode, Ann M.; Dong, Zigang; Zhou, Jian; Fan, Jia; Sun, Lunquan; Cao, Ya

2015-01-01

microRNAs (miRNAs) are involved in the various processes of DNA damage repair and play crucial roles in regulating response of tumors to radiation therapy. Here, we used nasopharyngeal carcinoma (NPC) radio-resistant cell lines as models and found that the expression of miR-504 was significantly up-regulated. In contrast, the expression of nuclear respiratory factor 1 (NRF1) and other mitochondrial metabolism factors, including mitochondrial transcription factor A (TFAM) and oxidative phosphorylation (OXPHOS) complex III were down-regulated in these cell lines. At the same time, the Seahorse cell mitochondrial stress test results indicated that the mitochondrial respiratory capacity was impaired in NPC radio-resistant cell lines and in a miR-504 over-expressing cell line. We also conducted dual luciferase reporter assays and verified that miR-504 could directly target NRF1. Additionally, miR-504 could down-regulate the expression of TFAM and OXPHOS complexes I, III, and IV and impaired the mitochondrial respiratory function of NPC cells. Furthermore, serum from NPC patients showed that miR-504 was up-regulated during different weeks of radiotherapy and correlated with tumor, lymph nodes and metastasis (TNM) stages and total tumor volume. The radio-therapeutic effect at three months after radiotherapy was evaluated. Results indicated that patients with high expression of miR-504 exhibited a relatively lower therapeutic effect ratio of complete response (CR), but a higher ratio of partial response (PR), compared to patients with low expression of miR-504. Taken together, these results demonstrated that miR-504 affected the radio-resistance of NPC by down-regulating the expression of NRF1 and disturbing mitochondrial respiratory function. Thus, miR-504 might become a promising biomarker of NPC radio-resistance and targeting miR-504 might improve tumor radiation response. PMID:26201446

Bcl-2 is a novel interacting partner for the 2-oxoglutarate carrier and a key regulator of mitochondrial glutathione

PubMed Central

Wilkins, Heather M.; Marquardt, Kristin; Lash, Lawrence H.; Linseman, Daniel A.

2011-01-01

Despite making up only a minor fraction of the total cellular glutathione, recent studies indicate that the mitochondrial glutathione pool is essential for cell survival. Selective depletion of mitochondrial glutathione is sufficient to sensitize cells to mitochondrial oxidative stress (MOS)1 and intrinsic apoptosis. Glutathione is synthesized exclusively in the cytoplasm and must be actively transported into mitochondria. Therefore, regulation of mitochondrial glutathione transport is a key factor in maintaining the antioxidant status of mitochondria. Bcl-2 is resident in the outer mitochondrial membrane where it acts as a central regulator of the intrinsic apoptotic cascade. In addition, Bcl-2 displays an antioxidant-like function that has been linked experimentally to the regulation of cellular glutathione content. We have previously demonstrated a novel interaction between recombinant Bcl-2 and reduced glutathione (GSH) which was antagonized by either Bcl-2 homology-3 domain (BH3) mimetics or a BH3-only protein, recombinant Bim. These previous findings prompted us to investigate if this novel Bcl-2/GSH interaction might play a role in regulating mitochondrial glutathione transport. Incubation of primary cultures of cerebellar granule neurons (CGNs) with the BH3 mimetic, HA14-1, induced MOS and caused specific depletion of the mitochondrial glutathione pool. Bcl-2 was co-immunoprecipitated with GSH following chemical cross-linking in CGNs and this Bcl-2/GSH interaction was antagonized by pre-incubation with HA14-1. Moreover, both HA14-1 and recombinant Bim inhibited GSH transport into isolated rat brain mitochondria. To further investigate a possible link between Bcl-2 function and mitochondrial glutathione transport, we next examined if Bcl-2 associated with the 2-oxoglutarate carrier (OGC), an inner mitochondrial membrane protein known to transport glutathione in liver and kidney. Following co-transfection of CHO cells, Bcl-2 was co-immunoprecipitated with OGC and this novel interaction was significantly enhanced by glutathione monoethylester (GSH-MEE). Similarly, recombinant Bcl-2 interacted with recombinant OGC in the presence of GSH. Bcl-2 and OGC co-transfection in CHO cells significantly increased the mitochondrial glutathione pool. Finally, the ability of Bcl-2 to protect CHO cells from apoptosis induced by hydrogen peroxide was significantly attenuated by the OGC inhibitor phenylsuccinate. These data suggest that GSH binding by Bcl-2 enhances its affinity for the OGC. Bcl-2 and OGC appear to act in a coordinated manner to increase the mitochondrial glutathione pool and enhance resistance of cells to oxidative stress. We conclude that regulation of mitochondrial glutathione transport is a principal mechanism by which Bcl-2 suppresses MOS. PMID:22115789

Exercise training protects against aging-induced mitochondrial fragmentation in mouse skeletal muscle in a PGC-1α dependent manner.

PubMed

Halling, Jens Frey; Ringholm, Stine; Olesen, Jesper; Prats, Clara; Pilegaard, Henriette

2017-10-01

Aging is associated with impaired mitochondrial function, whereas exercise training enhances mitochondrial content and function in part through activation of PGC-1α. Mitochondria form dynamic networks regulated by fission and fusion with profound effects on mitochondrial functions, yet the effects of aging and exercise training on mitochondrial network structure remain unclear. This study examined the effects of aging and exercise training on mitochondrial network structure using confocal microscopy on mitochondria-specific stains in single muscle fibers from PGC-1α KO and WT mice. Hyperfragmentation of mitochondrial networks was observed in aged relative to young animals while exercise training normalized mitochondrial network structure in WT, but not in PGC-1α KO. Mitochondrial fission protein content (FIS1 and DRP1) relative to mitochondrial content was increased with aging in both WT and PGC-1α KO mice, while exercise training lowered mitochondrial fission protein content relative to mitochondrial content only in WT. Mitochondrial fusion protein content (MFN1/2 and OPA1) was unaffected by aging and lifelong exercise training in both PGC-1α KO and WT mice. The present results provide evidence that exercise training rescues aging-induced mitochondrial fragmentation in skeletal muscle by suppressing mitochondrial fission protein expression in a PGC-1α dependent manner. Copyright © 2017 Elsevier Inc. All rights reserved.

Mitochondria in mesenchymal stem cell biology and cell therapy: From cellular differentiation to mitochondrial transfer.

PubMed

Hsu, Yi-Chao; Wu, Yu-Ting; Yu, Ting-Hsien; Wei, Yau-Huei

2016-04-01

Mesenchymal stem cells (MSCs) are characterized to have the capacity of self-renewal and the potential to differentiate into mesoderm, ectoderm-like and endoderm-like cells. MSCs hold great promise for cell therapies due to their multipotency in vitro and therapeutic advantage of hypo-immunogenicity and lower tumorigenicity. Moreover, it has been shown that MSCs can serve as a vehicle to transfer mitochondria into cells after cell transplantation. Mitochondria produce most of the energy through oxidative phosphorylation in differentiated cells. It has been increasingly clear that the switch of energy supply from glycolysis to aerobic metabolism is essential for successful differentiation of MSCs. Post-translational modifications of proteins have been established to regulate mitochondrial function and metabolic shift during MSCs differentiation. In this article, we review and provide an integrated view on the roles of different protein kinases and sirtuins in the maintenance and differentiation of MSCs. Importantly, we provide evidence to suggest that alteration in the expression of Sirt3 and Sirt5 and relative changes in the acylation levels of mitochondrial proteins might be involved in the activation of mitochondrial function and adipogenic differentiation of adipose-derived MSCs. We summarize their roles in the regulation of mitochondrial biogenesis and metabolism, oxidative responses and differentiation of MSCs. On the other hand, we discuss recent advances in the study of mitochondrial dynamics and mitochondrial transfer as well as their roles in the differentiation and therapeutic application of MSCs to improve cell function in vitro and in animal models. Accumulating evidence has substantiated that the therapeutic potential of MSCs is conferred not only by cell replacement and paracrine effects but also by transferring mitochondria into injured tissues or cells to modulate the cellular metabolism in situ. Therefore, elucidation of the underlying mechanisms in the regulation of mitochondrial metabolism of MSCs may ultimately improve therapeutic outcomes of stem cell therapy in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

Estrogen receptor α protects pancreatic β-cells from apoptosis by preserving mitochondrial function and suppressing endoplasmic reticulum stress.

PubMed

Zhou, Zhenqi; Ribas, Vicent; Rajbhandari, Prashant; Drew, Brian G; Moore, Timothy M; Fluitt, Amy H; Reddish, Britany R; Whitney, Kate A; Georgia, Senta; Vergnes, Laurent; Reue, Karen; Liesa, Marc; Shirihai, Orian; van der Bliek, Alexander M; Chi, Nai-Wen; Mahata, Sushil K; Tiano, Joseph P; Hewitt, Sylvia C; Tontonoz, Peter; Korach, Kenneth S; Mauvais-Jarvis, Franck; Hevener, Andrea L

2018-03-30

Estrogen receptor α (ERα) action plays an important role in pancreatic β-cell function and survival; thus, it is considered a potential therapeutic target for the treatment of type 2 diabetes in women. However, the mechanisms underlying the protective effects of ERα remain unclear. Because ERα regulates mitochondrial metabolism in other cell types, we hypothesized that ERα may act to preserve insulin secretion and promote β-cell survival by regulating mitochondrial-endoplasmic reticulum (EndoRetic) function. We tested this hypothesis using pancreatic islet-specific ERα knockout (PERαKO) mice and Min6 β-cells in culture with Esr1 knockdown (KD). We found that Esr1-KD promoted reactive oxygen species production that associated with reduced fission/fusion dynamics and impaired mitophagy. Electron microscopy showed mitochondrial enlargement and a pro-fusion phenotype. Mitochondrial cristae and endoplasmic reticulum were dilated in Esr1-KD compared with ERα replete Min6 β-cells. Increased expression of Oma1 and Chop was paralleled by increased oxygen consumption and apoptosis susceptibility in ERα-KD cells. In contrast, ERα overexpression and ligand activation reduced both Chop and Oma1 expression, likely by ERα binding to consensus estrogen-response element sites in the Oma1 and Chop promoters. Together, our findings suggest that ERα promotes β-cell survival and insulin secretion through maintenance of mitochondrial fission/fusion-mitophagy dynamics and EndoRetic function, in part by Oma1 and Chop repression.

Weight Loss by Ppc-1, a Novel Small Molecule Mitochondrial Uncoupler Derived from Slime Mold

PubMed Central

Suzuki, Toshiyuki; Kikuchi, Haruhisa; Ogura, Masato; Homma, Miwako K.; Oshima, Yoshiteru; Homma, Yoshimi

2015-01-01

Mitochondria play a key role in diverse processes including ATP synthesis and apoptosis. Mitochondrial function can be studied using inhibitors of respiration, and new agents are valuable for discovering novel mechanisms involved in mitochondrial regulation. Here, we screened small molecules derived from slime molds and other microorganisms for their effects on mitochondrial oxygen consumption. We identified Ppc-1 as a novel molecule which stimulates oxygen consumption without adverse effects on ATP production. The kinetic behavior of Ppc-1 suggests its function as a mitochondrial uncoupler. Serial administration of Ppc-1 into mice suppressed weight gain with no abnormal effects on liver or kidney tissues, and no evidence of tumor formation. Serum fatty acid levels were significantly elevated in mice treated with Ppc-1, while body fat content remained low. After a single administration, Ppc-1 distributes into various tissues of individual animals at low levels. Ppc-1 stimulates adipocytes in culture to release fatty acids, which might explain the elevated serum fatty acids in Ppc-1-treated mice. The results suggest that Ppc-1 is a unique mitochondrial regulator which will be a valuable tool for mitochondrial research as well as the development of new drugs to treat obesity. PMID:25668511

Distinct intracellular sAC-cAMP domains regulate ER Ca2+ signaling and OXPHOS function.

PubMed

Valsecchi, Federica; Konrad, Csaba; D'Aurelio, Marilena; Ramos-Espiritu, Lavoisier S; Stepanova, Anna; Burstein, Suzanne R; Galkin, Alexander; Magranè, Jordi; Starkov, Anatoly; Buck, Jochen; Levin, Lonny R; Manfredi, Giovanni

2017-11-01

cAMP regulates a wide variety of physiological functions in mammals. This single second messenger can regulate multiple, seemingly disparate functions within independently regulated cell compartments. We have previously identified one such compartment inside the matrix of the mitochondria, where soluble adenylyl cyclase (sAC) regulates oxidative phosphorylation (OXPHOS). We now show that sAC knockout fibroblasts have a defect in OXPHOS activity and attempt to compensate for this defect by increasing OXPHOS proteins. Importantly, sAC knockout cells also exhibit decreased probability of endoplasmic reticulum (ER) Ca 2+ release associated with diminished phosphorylation of the inositol 3-phosphate receptor. Restoring sAC expression exclusively in the mitochondrial matrix rescues OXPHOS activity and reduces mitochondrial biogenesis, indicating that these phenotypes are regulated by intramitochondrial sAC. In contrast, Ca 2+ release from the ER is only rescued when sAC expression is restored throughout the cell. Thus, we show that functionally distinct, sAC-defined, intracellular cAMP signaling domains regulate metabolism and Ca 2+ signaling. © 2017. Published by The Company of Biologists Ltd.

MacroH2A1.1 regulates mitochondrial respiration by limiting nuclear NAD+ consumption.

PubMed

Posavec Marjanović, Melanija; Hurtado-Bagès, Sarah; Lassi, Maximilian; Valero, Vanesa; Malinverni, Roberto; Delage, Hélène; Navarro, Miriam; Corujo, David; Guberovic, Iva; Douet, Julien; Gama-Perez, Pau; Garcia-Roves, Pablo M; Ahel, Ivan; Ladurner, Andreas G; Yanes, Oscar; Bouvet, Philippe; Suelves, Mònica; Teperino, Raffaele; Pospisilik, J Andrew; Buschbeck, Marcus

2017-11-01

Histone variants are structural components of eukaryotic chromatin that can replace replication-coupled histones in the nucleosome. The histone variant macroH2A1.1 contains a macrodomain capable of binding NAD + -derived metabolites. Here we report that macroH2A1.1 is rapidly induced during myogenic differentiation through a switch in alternative splicing, and that myotubes that lack macroH2A1.1 have a defect in mitochondrial respiratory capacity. We found that the metabolite-binding macrodomain was essential for sustained optimal mitochondrial function but dispensable for gene regulation. Through direct binding, macroH2A1.1 inhibits basal poly-ADP ribose polymerase 1 (PARP-1) activity and thus reduces nuclear NAD + consumption. The resultant accumulation of the NAD + precursor NMN allows for maintenance of mitochondrial NAD + pools that are critical for respiration. Our data indicate that macroH2A1.1-containing chromatin regulates mitochondrial respiration by limiting nuclear NAD + consumption and establishing a buffer of NAD + precursors in differentiated cells.

Increased mitochondrial functions in human glioblastoma cells persistently infected with measles virus.

PubMed

Takahashi, Megumi; Wolf, Alexander M; Watari, Eiji; Norose, Yoshihiko; Ohta, Shigeo; Takahashi, Hidemi

2013-09-01

Measles virus (MV) is known for its ability to cause an acute infection with a potential of development of persistent infection. However, knowledge of how viral genes and cellular factors interact to cause or maintain the persistent infection has remained unclear. We have previously reported the possible involvement of mitochondrial short chain enoyl-CoA hydratase (ECHS), which is localized at mitochondria, in the regulation of MV replication. In this study we found increased functions of mitochondria in MV-persistently infected cells compared with uninfected or acutely infected cells. Furthermore, impairment of mitochondrial functions by treatment with mitochondrial inhibitors such as ethidium bromide (EtBr) or carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) induced the cytopathic effects of extensive syncytial formation in persistently infected cells. These findings suggest that mitochondria are one of the subcellular organelles contributing to regulate persistent infection of MV. Recent studies showed mitochondria provide an integral platform for retinoic acid-inducible protein (RIG-I)-like cytosolic receptors (RLRs) signaling and participate in cellular innate antiviral immunity. Our findings not only reveal a role of mitochondria in RLR mediated antiviral signaling but also suggest that mitochondria contribute to the regulation of persistent viral infection. Copyright © 2013 Elsevier B.V. All rights reserved.

APR3 modulates oxidative stress and mitochondrial function in ARPE-19 cells.

PubMed

Li, Yuan; Zou, Xuan; Gao, Jing; Cao, Ke; Feng, Zhihui; Liu, Jiankang

2018-05-24

Impairment of retinal pigment epithelial (RPE) cells is considered a key contributor to the development of age-related macular degeneration. Apoptosis-related protein 3 (APR3) was recently discovered after treatment with all- trans retinoic acid, a pivotal molecule in RPE cells. However, the function of APR3 remains poorly understood. In the present study, we found that APR3 could interact with nuclear factor (erythroid-derived 2)-like 2, which is a regulator of phase II enzymes, and that knockdown of APR3 promoted nuclear factor (erythroid-derived 2)-like 2 nuclear translocation and activated expression of phase II enzymes, which was accompanied by improved redox status and mitochondrial activity. Overexpression of APR3 revealed its mitochondrial localization and induced a robust production of reactive oxygen species that was accompanied by impaired mitochondrial oxygen consumption, complex activity, and lower ATP content, resulting in significant changes in mitochondrial structure, which may contribute to cell apoptosis. High doses of all- trans retinoic acid treatment were found to significantly induce APR3 expression, increase reactive oxygen species levels, and decrease ATP content, which were abolished by knockdown of APR3. These results indicate that APR3 plays a vital role in regulating redox status and mitochondrial activity and thus suggest APR3 might be a potential novel target for study of treatment of age-related macular degeneration.-Li, Y., Zou, X., Gao, J., Cao, K., Feng, Z., Liu, J. APR3 modulates oxidative stress and mitochondrial function in ARPE-19 cells.

Design of 3-D adipospheres for quantitative metabolic study

PubMed Central

Akama, Takeshi; Leung, Brendan M.; Labuz, Joseph M.; Takayama, Shuichi; Chun, Tae-Hwa

2017-01-01

Quantitative assessment of adipose mitochondrial activity is critical for better understanding of adipose tissue function in obesity and diabetes. While the two-dimensional (2-D) tissue culture method has been sufficient to discover key molecules that regulate adipocyte differentiation and function, the method is insufficient to determine the role of extracellular matrix (ECM) molecules and their modifiers, such as matrix metalloproteinases (MMPs), in regulating adipocyte function in three-dimensional (3-D) in vivo-like microenvironments. By using a 3-D hanging drop tissue culture system, we are able to produce scalable 3-D adipospheres that are suitable for quantitative mitochondrial study in 3-D microenvironment. PMID:28244051

Gem1 and ERMES Do Not Directly Affect Phosphatidylserine Transport from ER to Mitochondria or Mitochondrial Inheritance

PubMed Central

Nguyen, Tammy T; Lewandowska, Agnieszka; Choi, Jae-Yeon; Markgraf, Daniel F; Junker, Mirco; Bilgin, Mesut; Ejsing, Christer S; Voelker, Dennis R; Rapoport, Tom A; Shaw, Janet M

2012-01-01

In yeast, a protein complex termed the ER-Mitochondria Encounter Structure (ERMES) tethers mitochondria to the endoplasmic reticulum. ERMES proteins are implicated in a variety of cellular functions including phospholipid synthesis, mitochondrial protein import, mitochondrial attachment to actin, polarized mitochondrial movement into daughter cells during division, and maintenance of mitochondrial DNA (mtDNA). The mitochondrial-anchored Gem1 GTPase has been proposed to regulate ERMES functions. Here, we show that ERMES and Gem1 have no direct role in the transport of phosphatidylserine (PS) from the ER to mitochondria during the synthesis of phosphatidylethanolamine (PE), as PS to PE conversion is not affected in ERMES or gem1 mutants. In addition, we report that mitochondrial inheritance defects in ERMES mutants are a secondary consequence of mitochondrial morphology defects, arguing against a primary role for ERMES in mitochondrial association with actin and mitochondrial movement. Finally, we show that ERMES complexes are long-lived, and do not depend on the presence of Gem1. Our findings suggest that the ERMES complex may have primarily a structural role in maintaining mitochondrial morphology. PMID:22409400

The transcriptional repressor Sum1p counteracts Sir2p in regulation of the actin cytoskeleton, mitochondrial quality control and replicative lifespan in Saccharomyces cerevisiae.

PubMed

Higuchi-Sanabria, Ryo; Vevea, Jason D; Charalel, Joseph K; Sapar, Maria L; Pon, Liza A

2016-01-18

Increasing the stability or dynamics of the actin cytoskeleton can extend lifespan in C. elegans and S. cerevisiae . Actin cables of budding yeast, bundles of actin filaments that mediate cargo transport, affect lifespan control through effects on mitochondrial quality control. Sir2p, the founding member of the Sirtuin family of lifespan regulators, also affects actin cable dynamics, assembly, and function in mitochondrial quality control. Here, we obtained evidence for novel interactions between Sir2p and Sum1p, a transcriptional repressor that was originally identified through mutations that genetically suppress sir2 ∆ phenotypes unrelated to lifespan. We find that deletion of SUM1 in wild-type cells results in increased mitochondrial function and actin cable abundance. Furthermore, deletion of SUM1 suppresses defects in actin cables and mitochondria of sir2 ∆ yeast, and extends the replicative lifespan and cellular health span of sir2 ∆ cells. Thus, Sum1p suppresses Sir2p function in control of specific aging determinants and lifespan in budding yeast.

Elongator-dependent modification of cytoplasmic tRNALysUUU is required for mitochondrial function under stress conditions

PubMed Central

Tigano, Marco; Ruotolo, Roberta; Dallabona, Cristina; Fontanesi, Flavia; Barrientos, Antoni; Donnini, Claudia; Ottonello, Simone

2015-01-01

To gain a wider view of the pathways that regulate mitochondrial function, we combined the effect of heat stress on respiratory capacity with the discovery potential of a genome-wide screen in Saccharomyces cerevisiae. We identified 105 new genes whose deletion impairs respiratory growth at 37°C by interfering with processes such as transcriptional regulation, ubiquitination and cytosolic tRNA wobble uridine modification via 5-methoxycarbonylmethyl-2-thiouridine formation. The latter process, specifically required for efficient decoding of AA-ending codons under stress conditions, was covered by multiple genes belonging to the Elongator (e.g. ELP3) and urmylation (e.g., NCS6) pathways. ELP3 or NCS6 deletants had impaired mitochondrial protein synthesis. Their respiratory deficiency was selectively rescued by overexpression of tRNALysUUU as well by overexpression of genes (BCK1 and HFM1) with a strong bias for the AAA codon read by this tRNA. These data extend the mitochondrial regulome, demonstrate that heat stress can impair respiration by disturbing cytoplasmic translation of proteins critically involved in mitochondrial function and document, for the first time, the involvement in such process of the Elongator and urmylation pathways. Given the conservation of these pathways, the present findings may pave the way to a better understanding of the human mitochondrial regulome in health and disease. PMID:26240381

A novel fission-independent role of dynamin-related protein 1 in cardiac mitochondrial respiration

PubMed Central

Zhang, Huiliang; Wang, Pei; Bisetto, Sara; Yoon, Yisang; Chen, Quan; Sheu, Shey-Shing; Wang, Wang

2017-01-01

Aims Mitochondria in adult cardiomyocytes exhibit static morphology and infrequent dynamic changes, despite the high abundance of fission and fusion regulatory proteins in the heart. Previous reports have indicated that fusion proteins may bear functions beyond morphology regulation. Here, we investigated the role of fission protein, dynamin-related protein 1 (DRP1), on mitochondrial respiration regulation in adult cardiomyocytes. Methods and results By using genetic or pharmacological approaches, we manipulated the activity or protein level of fission and fusion proteins and found they mildly influenced mitochondrial morphology in adult rodent cardiomyocytes, which is in contrast to their significant effect in H9C2 cardiac myoblasts. Intriguingly, inhibiting endogenous DRP1 by dominant-negative DRP1 mutation (K38A), shRNA, or Mdivi-1 suppressed maximal respiration and respiratory control ratio in isolated mitochondria from adult mouse heart or in adult cardiomyocytes from rat. Meanwhile, basal respiration was increased due to increased proton leak. Facilitating mitofusin-mediated fusion by S3 compound, however, failed to inhibit mitochondrial respiration in adult cardiomyocytes. Mechanistically, DRP1 inhibition did not affect the maximal activity of individual respiratory chain complexes or the assembly of supercomplexes. Knocking out cyclophilin D, a regulator of mitochondrial permeability transition pore (mPTP), abolished the effect of DRP1 inhibition on respiration. Finally, DRP1 inhibition decreased transient mPTP-mediated mitochondrial flashes, delayed laser-induced mPTP opening and suppressed mitochondrial reactive oxygen species (ROS). Conclusion These results uncover a novel non-canonical function of the fission protein, DRP1 in maintaining or positively stimulating mitochondrial respiration, bioenergetics and ROS signalling in adult cardiomyocyte, which is likely independent of morphological changes. PMID:27794519

A novel fission-independent role of dynamin-related protein 1 in cardiac mitochondrial respiration.

PubMed

Zhang, Huiliang; Wang, Pei; Bisetto, Sara; Yoon, Yisang; Chen, Quan; Sheu, Shey-Shing; Wang, Wang

2017-02-01

Mitochondria in adult cardiomyocytes exhibit static morphology and infrequent dynamic changes, despite the high abundance of fission and fusion regulatory proteins in the heart. Previous reports have indicated that fusion proteins may bear functions beyond morphology regulation. Here, we investigated the role of fission protein, dynamin-related protein 1 (DRP1), on mitochondrial respiration regulation in adult cardiomyocytes. By using genetic or pharmacological approaches, we manipulated the activity or protein level of fission and fusion proteins and found they mildly influenced mitochondrial morphology in adult rodent cardiomyocytes, which is in contrast to their significant effect in H9C2 cardiac myoblasts. Intriguingly, inhibiting endogenous DRP1 by dominant-negative DRP1 mutation (K38A), shRNA, or Mdivi-1 suppressed maximal respiration and respiratory control ratio in isolated mitochondria from adult mouse heart or in adult cardiomyocytes from rat. Meanwhile, basal respiration was increased due to increased proton leak. Facilitating mitofusin-mediated fusion by S3 compound, however, failed to inhibit mitochondrial respiration in adult cardiomyocytes. Mechanistically, DRP1 inhibition did not affect the maximal activity of individual respiratory chain complexes or the assembly of supercomplexes. Knocking out cyclophilin D, a regulator of mitochondrial permeability transition pore (mPTP), abolished the effect of DRP1 inhibition on respiration. Finally, DRP1 inhibition decreased transient mPTP-mediated mitochondrial flashes, delayed laser-induced mPTP opening and suppressed mitochondrial reactive oxygen species (ROS). These results uncover a novel non-canonical function of the fission protein, DRP1 in maintaining or positively stimulating mitochondrial respiration, bioenergetics and ROS signalling in adult cardiomyocyte, which is likely independent of morphological changes. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For Permissions, please email: journals.permissions@oup.com.

Nitric Oxide and Mitochondrial Function in Neurological Diseases.

PubMed

Ghasemi, Mehdi; Mayasi, Yunis; Hannoun, Anas; Eslami, Seyed Majid; Carandang, Raphael

2018-04-15

Mitochondria are key cellular organelles that play crucial roles in the energy production and regulation of cellular metabolism. Accumulating evidence suggests that mitochondrial activity can be modulated by nitric oxide (NO). As a key neurotransmitter in biologic systems, NO mediates the majority of its function through activation of the cyclic guanylyl cyclase (cGC) signaling pathway and S-nitrosylation of a variety of proteins involved in cellular functioning including those involved in mitochondrial biology. Moreover, excess NO or the formation of reactive NO species (RNS), e.g., peroxynitrite (ONOO - ), impairs mitochondrial functioning and this, in conjunction with nuclear events, eventually affects neuronal cell metabolism and survival, contributing to the pathogenesis of several neurodegenerative diseases. In this review we highlight the possible mechanisms underlying the noxious effects of excess NO and RNS on mitochondrial function including (i) negative effects on electron transport chain (ETC); (ii) ONOO - -mediated alteration in mitochondrial permeability transition; (iii) enhanced mitochondrial fragmentation and autophagy through S-nitrosylation of key proteins involved in this process such as dynamin-related protein 1 (DRP-1) and Parkin/PINK1 (protein phosphatase and tensin homolog-induced kinase 1) complex; (iv) alterations in the mitochondrial metabolic pathways including Krebs cycle, glycolysis, fatty acid metabolism, and urea cycle; and finally (v) mitochondrial ONOO - -induced nuclear toxicity and subsequent release of apoptosis-inducing factor (AIF) from mitochondria, causing neuronal cell death. These proposed mechanisms highlight the multidimensional nature of NO and its signaling in the mitochondrial function. Understanding the mechanisms by which NO mediates mitochondrial (dys)function can provide new insights into the treatment of neurodegenerative diseases. Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

Developmentally regulated HEART STOPPER, a mitochondrially targeted L18 ribosomal protein gene, is required for cell division, differentiation, and seed development in Arabidopsis

PubMed Central

Zhang, Hongyu; Luo, Ming; Day, Robert C.; Talbot, Mark J.; Ivanova, Aneta; Ashton, Anthony R.; Chaudhury, Abed M.; Macknight, Richard C.; Hrmova, Maria; Koltunow, Anna M.

2015-01-01

Evidence is presented for the role of a mitochondrial ribosomal (mitoribosomal) L18 protein in cell division, differentiation, and seed development after the characterization of a recessive mutant, heart stopper (hes). The hes mutant produced uncellularized endosperm and embryos arrested at the late globular stage. The mutant embryos differentiated partially on rescue medium with some forming callus. HES (At1g08845) encodes a mitochondrially targeted member of a highly diverged L18 ribosomal protein family. The substitution of a conserved amino residue in the hes mutant potentially perturbs mitoribosomal function via altered binding of 5S rRNA and/or influences the stability of the 50S ribosomal subunit, affecting mRNA binding and translation. Consistent with this, marker genes for mitochondrial dysfunction were up-regulated in the mutant. The slow growth of the endosperm and embryo indicates a defect in cell cycle progression, which is evidenced by the down-regulation of cell cycle genes. The down-regulation of other genes such as EMBRYO DEFECTIVE genes links the mitochondria to the regulation of many aspects of seed development. HES expression is developmentally regulated, being preferentially expressed in tissues with active cell division and differentiation, including developing embryos and the root tips. The divergence of the L18 family, the tissue type restricted expression of HES, and the failure of other L18 members to complement the hes phenotype suggest that the L18 proteins are involved in modulating development. This is likely via heterogeneous mitoribosomes containing different L18 members, which may result in differential mitochondrial functions in response to different physiological situations during development. PMID:26105995

A cannabinoid link between mitochondria and memory.

PubMed

Hebert-Chatelain, Etienne; Desprez, Tifany; Serrat, Román; Bellocchio, Luigi; Soria-Gomez, Edgar; Busquets-Garcia, Arnau; Pagano Zottola, Antonio Christian; Delamarre, Anna; Cannich, Astrid; Vincent, Peggy; Varilh, Marjorie; Robin, Laurie M; Terral, Geoffrey; García-Fernández, M Dolores; Colavita, Michelangelo; Mazier, Wilfrid; Drago, Filippo; Puente, Nagore; Reguero, Leire; Elezgarai, Izaskun; Dupuy, Jean-William; Cota, Daniela; Lopez-Rodriguez, Maria-Luz; Barreda-Gómez, Gabriel; Massa, Federico; Grandes, Pedro; Bénard, Giovanni; Marsicano, Giovanni

2016-11-24

Cellular activity in the brain depends on the high energetic support provided by mitochondria, the cell organelles which use energy sources to generate ATP. Acute cannabinoid intoxication induces amnesia in humans and animals, and the activation of type-1 cannabinoid receptors present at brain mitochondria membranes (mtCB 1 ) can directly alter mitochondrial energetic activity. Although the pathological impact of chronic mitochondrial dysfunctions in the brain is well established, the involvement of acute modulation of mitochondrial activity in high brain functions, including learning and memory, is unknown. Here, we show that acute cannabinoid-induced memory impairment in mice requires activation of hippocampal mtCB 1 receptors. Genetic exclusion of CB 1 receptors from hippocampal mitochondria prevents cannabinoid-induced reduction of mitochondrial mobility, synaptic transmission and memory formation. mtCB 1 receptors signal through intra-mitochondrial Gα i protein activation and consequent inhibition of soluble-adenylyl cyclase (sAC). The resulting inhibition of protein kinase A (PKA)-dependent phosphorylation of specific subunits of the mitochondrial electron transport system eventually leads to decreased cellular respiration. Hippocampal inhibition of sAC activity or manipulation of intra-mitochondrial PKA signalling or phosphorylation of the Complex I subunit NDUFS2 inhibit bioenergetic and amnesic effects of cannabinoids. Thus, the G protein-coupled mtCB 1 receptors regulate memory processes via modulation of mitochondrial energy metabolism. By directly linking mitochondrial activity to memory formation, these data reveal that bioenergetic processes are primary acute regulators of cognitive functions.

MOF Acetyl Transferase Regulates Transcription and Respiration in Mitochondria.

PubMed

Chatterjee, Aindrila; Seyfferth, Janine; Lucci, Jacopo; Gilsbach, Ralf; Preissl, Sebastian; Böttinger, Lena; Mårtensson, Christoph U; Panhale, Amol; Stehle, Thomas; Kretz, Oliver; Sahyoun, Abdullah H; Avilov, Sergiy; Eimer, Stefan; Hein, Lutz; Pfanner, Nikolaus; Becker, Thomas; Akhtar, Asifa

2016-10-20

A functional crosstalk between epigenetic regulators and metabolic control could provide a mechanism to adapt cellular responses to environmental cues. We report that the well-known nuclear MYST family acetyl transferase MOF and a subset of its non-specific lethal complex partners reside in mitochondria. MOF regulates oxidative phosphorylation by controlling expression of respiratory genes from both nuclear and mtDNA in aerobically respiring cells. MOF binds mtDNA, and this binding is dependent on KANSL3. The mitochondrial pool of MOF, but not a catalytically deficient mutant, rescues respiratory and mtDNA transcriptional defects triggered by the absence of MOF. Mof conditional knockout has catastrophic consequences for tissues with high-energy consumption, triggering hypertrophic cardiomyopathy and cardiac failure in murine hearts; cardiomyocytes show severe mitochondrial degeneration and deregulation of mitochondrial nutrient metabolism and oxidative phosphorylation pathways. Thus, MOF is a dual-transcriptional regulator of nuclear and mitochondrial genomes connecting epigenetics and metabolism. Copyright © 2016 Elsevier Inc. All rights reserved.

The Role of PGC-1α in Vascular Regulation: Implications for Atherosclerosis

PubMed Central

Kadlec, Andrew O.; Chabowski, Dawid S.; Ait-Aissa, Karima; Gutterman, David D.

2016-01-01

Mitochondrial dysfunction results in high levels of oxidative stress and mitochondrial damage, leading to disruption of endothelial homeostasis. Recent discoveries have clarified several pathways whereby mitochondrial dysregulation contributes to endothelial dysfunction and vascular disease burden. One such pathway centers around PGC-1α, a transcriptional coactivator linked to mitochondrial biogenesis and antioxidant defense, among other functions. Although primarily investigated for its therapeutic potential in obesity and skeletal muscle differentiation, the ability of PGC-1α to alter a multitude of cellular functions has sparked interest in its role in the vasculature. Within this context, recent studies demonstrate that PGC-1α plays a key role in endothelial cell and smooth muscle cell regulation through effects on oxidative stress, apoptosis, inflammation, and cell proliferation. The ability of PGC-1α to impact these parameters is relevant to vascular disease progression, particularly in relation to atherosclerosis. Upregulation of PGC-1α can prevent the development of, and even encourage regression of, atherosclerotic lesions. Therefore, PGC-1α is poised to serve as a promising target in vascular disease. This review details recent findings related to PGC-1α in vascular regulation, regulation of PGC-1α itself, the role of PGC-1α in atherosclerosis, and therapies that target this key protein. PMID:27312223

Mitochondrial Glutathione: Regulation and Functions.

PubMed

Calabrese, Gaetano; Morgan, Bruce; Riemer, Jan

2017-11-20

Mitochondrial glutathione fulfills crucial roles in a number of processes, including iron-sulfur cluster biosynthesis and peroxide detoxification. Recent Advances: Genetically encoded fluorescent probes for the glutathione redox potential (E GSH ) have permitted extensive new insights into the regulation of mitochondrial glutathione redox homeostasis. These probes have revealed that the glutathione pools of the mitochondrial matrix and intermembrane space (IMS) are highly reduced, similar to the cytosolic glutathione pool. The glutathione pool of the IMS is in equilibrium with the cytosolic glutathione pool due to the presence of porins that allow free passage of reduced glutathione (GSH) and oxidized glutathione (GSSG) across the outer mitochondrial membrane. In contrast, limited transport of glutathione across the inner mitochondrial membrane ensures that the matrix glutathione pool is kinetically isolated from the cytosol and IMS. In contrast to the situation in the cytosol, there appears to be extensive crosstalk between the mitochondrial glutathione and thioredoxin systems. Further, both systems appear to be intimately involved in the removal of reactive oxygen species, particularly hydrogen peroxide (H 2 O 2 ), produced in mitochondria. However, a detailed understanding of these interactions remains elusive. We postulate that the application of genetically encoded sensors for glutathione in combination with novel H 2 O 2 probes and conventional biochemical redox state assays will lead to fundamental new insights into mitochondrial redox regulation and reinvigorate research into the physiological relevance of mitochondrial redox changes. Antioxid. Redox Signal. 27, 1162-1177.

Mitochondria localize to injured axons to support regeneration

PubMed Central

Han, Sung Min; Baig, Huma S.; Hammarlund, Marc

2016-01-01

SUMMARY Axon regeneration is essential to restore the nervous system after axon injury. However, the neuronal cell biology that underlies axon regeneration is incompletely understood. Here we use in vivo single-neuron analysis to investigate the relationship between nerve injury, mitochondrial localization, and axon regeneration. Mitochondria translocate into injured axons, so that average mitochondria density increases after injury. Moreover, single-neuron analysis reveals that axons that fail to increase mitochondria have poor regeneration. Experimental alterations to axonal mitochondrial distribution or mitochondrial respiratory chain function result in corresponding changes to regeneration outcomes. Axonal mitochondria are specifically required for growth cone migration, identifying a key energy challenge for injured neurons. Finally, mitochondrial localization to the axon after injury is regulated in part by dual-leucine zipper kinase-1 (DLK-1), a conserved regulator of axon regeneration. These data identify regulation of axonal mitochondria as a new cell biological mechanism that helps determine the regenerative response of injured neurons. PMID:28009276

Telomeres and Mitochondria in the Aging Heart

PubMed Central

Moslehi, Javid; DePinho, Ronald A.; Sahin, Ergün

2013-01-01

Studies in humans and in mice have highlighted the importance of short telomeres and impaired mitochondrial function in driving age-related functional decline in the heart. Although telomere and mitochondrial dysfunction have been viewed mainly in isolation, recent studies in telomerase-deficient mice have provided evidence for an intimate link between these two processes. Telomere dysfunction induces a profound p53-dependent repression of the master regulators of mitochondrial biogenesis and function, peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α and PGC-1β in the heart, which leads to bioenergetic compromise due to impaired oxidative phosphorylation and ATP generation. This telomere-p53-PGC mitochondrial/metabolic axis integrates many factors linked to heart aging including increased DNA damage, p53 activation, mitochondrial, and metabolic dysfunction and provides a molecular basis of how dysfunctional telomeres can compromise cardiomyocytes and stem cell compartments in the heart to precipitate cardiac aging. PMID:22539756

Mitochondria in the nervous system: From health to disease, Part I.

PubMed

Polster, Brian M; Carrì, Maria Teresa; Beart, Philip M

2017-10-01

In Part I of this Special Issue on "Mitochondria in the Nervous System: From Health to Disease", the editors bring together contributions from experts in brain mitochondrial research to provide an up-to-date overview of mitochondrial functioning in physiology and pathology. The issue provides cutting edge reviews on classical areas of mitochondrial biology that include energy substrate utilization, calcium handling, mitochondria-endoplasmic reticulum communication, and cell death regulation. Additional reviews and original research articles touch upon key mitochondrial defects seen across multiple neurodegenerative conditions, including fragmentation, loss of respiratory capacity, calcium overload, elevated reactive oxygen species generation, perturbed NAD + metabolism, altered protein acetylation, and compromised mitophagy. Emerging links between the genetics of neurodegenerative disorders and disruption in mitochondrial function are discussed, and a new mouse model of Complex I deficiency is described. Finally, novel ways to rescue mitochondrial structure and function in acute and chronic brain injury are explored. Copyright © 2017. Published by Elsevier Ltd.

Multifunctional Mitochondrial AAA Proteases

PubMed Central

Glynn, Steven E.

2017-01-01

Mitochondria perform numerous functions necessary for the survival of eukaryotic cells. These activities are coordinated by a diverse complement of proteins encoded in both the nuclear and mitochondrial genomes that must be properly organized and maintained. Misregulation of mitochondrial proteostasis impairs organellar function and can result in the development of severe human diseases. ATP-driven AAA+ proteins play crucial roles in preserving mitochondrial activity by removing and remodeling protein molecules in accordance with the needs of the cell. Two mitochondrial AAA proteases, i-AAA and m-AAA, are anchored to either face of the mitochondrial inner membrane, where they engage and process an array of substrates to impact protein biogenesis, quality control, and the regulation of key metabolic pathways. The functionality of these proteases is extended through multiple substrate-dependent modes of action, including complete degradation, partial processing, or dislocation from the membrane without proteolysis. This review discusses recent advances made toward elucidating the mechanisms of substrate recognition, handling, and degradation that allow these versatile proteases to control diverse activities in this multifunctional organelle. PMID:28589125

Multifunctional Mitochondrial AAA Proteases.

PubMed

Glynn, Steven E

2017-01-01

Mitochondria perform numerous functions necessary for the survival of eukaryotic cells. These activities are coordinated by a diverse complement of proteins encoded in both the nuclear and mitochondrial genomes that must be properly organized and maintained. Misregulation of mitochondrial proteostasis impairs organellar function and can result in the development of severe human diseases. ATP-driven AAA+ proteins play crucial roles in preserving mitochondrial activity by removing and remodeling protein molecules in accordance with the needs of the cell. Two mitochondrial AAA proteases, i-AAA and m-AAA, are anchored to either face of the mitochondrial inner membrane, where they engage and process an array of substrates to impact protein biogenesis, quality control, and the regulation of key metabolic pathways. The functionality of these proteases is extended through multiple substrate-dependent modes of action, including complete degradation, partial processing, or dislocation from the membrane without proteolysis. This review discusses recent advances made toward elucidating the mechanisms of substrate recognition, handling, and degradation that allow these versatile proteases to control diverse activities in this multifunctional organelle.

Mitochondrial Effects of PGC-1alpha Silencing in MPP+ Treated Human SH-SY5Y Neuroblastoma Cells

PubMed Central

Ye, Qinyong; Chen, Chun; Si, Erwang; Cai, Yousheng; Wang, Juhua; Huang, Wanling; Li, Dongzhu; Wang, Yingqing; Chen, Xiaochun

2017-01-01

The dopaminergic neuron degeneration and loss that occurs in Parkinson’s disease (PD) has been tightly linked to mitochondrial dysfunction. Although the aged-related cause of the mitochondrial defect observed in PD patients remains unclear, nuclear genes are of potential importance to mitochondrial function. Human peroxisome proliferator-activated receptor γ coactivator-1alpha (PGC-1α) is a multi-functional transcription factor that tightly regulates mitochondrial biogenesis and oxidative capacity. The goal of the present study was to explore the potential pathogenic effects of interference by the PGC-1α gene on N-methyl-4-phenylpyridinium ion (MPP+)-induced SH-SY5Y cells. We utilized RNA interference (RNAi) technology to probe the pathogenic consequences of inhibiting PGC-1α in the SH-SY5Y cell line. Remarkably, a reduction in PGC-1α resulted in the reduction of mitochondrial membrane potential, intracellular ATP content and intracellular H2O2 generation, leading to the translocation of cytochrome c (cyt c) to the cytoplasm in the MPP+-induced PD cell model. The expression of related proteins in the signaling pathway (e.g., estrogen-related receptor α (ERRα), nuclear respiratory factor 1 (NRF-1), NRF-2 and Peroxisome proliferator-activated receptor γ (PPARγ)) also decreased. Our finding indicates that small interfering RNA (siRNA) interference targeting the PGC-1α gene could inhibit the function of mitochondria in several capacities and that the PGC-1α gene may modulate mitochondrial function by regulating the expression of ERRα, NRF-1, NRF-2 and PPARγ. Thus, PGC-1α can be considered a potential therapeutic target for PD. PMID:28611589

Intrauterine Growth Retardation Increases the Susceptibility of Pigs to High-Fat Diet-Induced Mitochondrial Dysfunction in Skeletal Muscle

PubMed Central

Liu, Jingbo; Chen, Daiwen; Yao, Ying; Yu, Bing; Mao, Xiangbing; He, Jun; Huang, Zhiqing; Zheng, Ping

2012-01-01

It has been recognized that there is a relationship between prenatal growth restriction and the development of metabolic-related diseases in later life, a process involved in mitochondrial dysfunction. In addition, intrauterine growth retardation (IUGR) increases the susceptibility of offspring to high-fat (HF) diet-induced metabolic syndrome. Recent findings suggested that HF feeding decreased mitochondrial oxidative capacity and impaired mitochondrial function in skeletal muscle. Therefore, we hypothesized that the long-term consequences of IUGR on mitochondrial biogenesis and function make the offspring more susceptible to HF diet-induced mitochondrial dysfunction. Normal birth weight (NBW), and IUGR pigs were allotted to control or HF diet in a completely randomized design, individually. After 4 weeks of feeding, growth performance and molecular pathways related to mitochondrial function were determined. The results showed that IUGR decreased growth performance and plasma insulin concentrations. In offspring fed a HF diet, IUGR was associated with enhanced plasma leptin levels, increased concentrations of triglyceride and malondialdehyde (MDA), and reduced glycogen and ATP contents in skeletal muscle. High fat diet-fed IUGR offspring exhibited decreased activities of lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G6PD). These alterations in metabolic traits of IUGR pigs were accompanied by impaired mitochondrial respiration function, reduced mitochondrial DNA (mtDNA) contents, and down-regulated mRNA expression levels of genes responsible for mitochondrial biogenesis and function. In conclusion, our results suggest that IUGR make the offspring more susceptible to HF diet-induced mitochondrial dysfunction. PMID:22523560

Targeted siRNA Screens Identify ER-to-Mitochondrial Calcium Exchange in Autophagy and Mitophagy Responses in RPE1 Cells

PubMed Central

MacVicar, Thomas D. B.; Mannack, Lilith V. J. C.; Lees, Robert M.; Lane, Jon D.

2015-01-01

Autophagy is an important stress response pathway responsible for the removal and recycling of damaged or redundant cytosolic constituents. Mitochondrial damage triggers selective mitochondrial autophagy (mitophagy), mediated by a variety of response factors including the Pink1/Parkin system. Using human retinal pigment epithelial cells stably expressing autophagy and mitophagy reporters, we have conducted parallel screens of regulators of endoplasmic reticulum (ER) and mitochondrial morphology and function contributing to starvation-induced autophagy and damage-induced mitophagy. These screens identified the ER chaperone and Ca2+ flux modulator, sigma non-opioid intracellular receptor 1 (SIGMAR1), as a regulator of autophagosome expansion during starvation. Screens also identified phosphatidyl ethanolamine methyl transferase (PEMT) and the IP3-receptors (IP3Rs) as mediators of Parkin-induced mitophagy. Further experiments suggested that IP3R-mediated transfer of Ca2+ from the ER lumen to the mitochondrial matrix via the mitochondrial Ca2+ uniporter (MCU) primes mitochondria for mitophagy. Importantly, recruitment of Parkin to damaged mitochondria did not require IP3R-mediated ER-to-mitochondrial Ca2+ transfer, but mitochondrial clustering downstream of Parkin recruitment was impaired, suggesting involvement of regulators of mitochondrial dynamics and/or transport. Our data suggest that Ca2+ flux between ER and mitochondria at presumed ER/mitochondrial contact sites is needed both for starvation-induced autophagy and for Parkin-mediated mitophagy, further highlighting the importance of inter-organellar communication for effective cellular homeostasis. PMID:26110381

Chemoprevention of obesity by dietary natural compounds targeting mitochondrial regulation.

PubMed

Lai, Ching-Shu; Wu, Jia-Ching; Ho, Chi-Tang; Pan, Min-Hsiung

2017-06-01

Mitochondria are at the center stage in the control of energy homeostasis in many organs and tissues including adipose tissue. Recently, abundant evidence from experimental studies has clearly supported the strong correlation between mitochondrial dysfunction in adipocytes and obesity. Various physiological conditions such as excessive nutrition, genetic factors, hypoxia, and toxins disrupt mitochondrial function by impairing mitochondrial biogenesis, dynamics, and oxidative capacity. Mitochondrial dysfunction in adipocytes could have an impact on differentiation, adipogenesis, insulin sensitivity, and the significant alteration in their metabolic function, which ultimately results in obesity and type 2 diabetes. Numerous dietary natural compounds are the subject of research for the prevention and treatment of obesity through reprogramming multiple metabolic pathways. Some of them have the potential against obesity by modulating insulin signaling, decreasing oxidative damage, downregulating adipokines secretion, and increasing mitochondrial DNA that improves mitochondrial function and thus maintain metabolic homeostasis. Here, we focus on and summarize and briefly discuss the currently known targets and the mitochondria-targeting effects of dietary natural compounds in the intervention of obesity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Essential Role for COPI in mRNA Localization to Mitochondria and Mitochondrial Function.

PubMed

Zabezhinsky, Dmitry; Slobodin, Boris; Rapaport, Doron; Gerst, Jeffrey E

2016-04-19

Nuclear-encoded mRNAs encoding mitochondrial proteins (mMPs) can localize directly to the mitochondrial surface, yet how mMPs target mitochondria and whether RNA targeting contributes to protein import into mitochondria and cellular metabolism are unknown. Here, we show that the COPI vesicle coat complex is necessary for mMP localization to mitochondria and mitochondrial function. COPI inactivation leads to reduced mMP binding to COPI itself, resulting in the dissociation of mMPs from mitochondria, a reduction in mitochondrial membrane potential, a decrease in protein import in vivo and in vitro, and severe deficiencies in mitochondrial respiration. Using a model mMP (OXA1), we observed that COPI inactivation (or mutation of the potential COPI-interaction site) led to altered mRNA localization and impaired cellular respiration. Overall, COPI-mediated mMP targeting is critical for mitochondrial protein import and function, and transcript delivery to the mitochondria or endoplasmic reticulum is regulated by cis-acting RNA sequences and trans-acting proteins. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Mitochondrial Aspects of Synaptic Dysfunction in Alzheimer’s Disease

PubMed Central

Cai, Qian; Tammineni, Prasad

2016-01-01

Alzheimer’s disease (AD) is characterized by brain deposition of amyloid plaques and tau neurofibrillary tangles along with steady cognitive decline. Synaptic damage, an early pathological event, correlates strongly with cognitive deficits and memory loss. Mitochondria are essential organelles for synaptic function. Neurons utilize specialized mechanisms to drive mitochondrial trafficking to synapses in which mitochondria buffer Ca2+ and serve as local energy sources by supplying ATP to sustain neurotransmitter release. Mitochondrial abnormalities are one of the earliest and prominent features in AD patient brains. Amyloid-β (Aβ) and tau both trigger mitochondrial alterations. Accumulating evidence suggests that mitochondrial perturbation acts as a key factor that is involved in synaptic failure and degeneration in AD. The importance of mitochondria in supporting synaptic function has made them a promising target of new therapeutic strategy for AD. Here, we review the molecular mechanisms regulating mitochondrial function at synapses, highlight recent findings on the disturbance of mitochondrial dynamics and transport in AD, and discuss how these alterations impact synaptic vesicle release and thus contribute to synaptic pathology associated with AD. PMID:27767992

Novel roles of folic acid as redox regulator: Modulation of reactive oxygen species sinker protein expression and maintenance of mitochondrial redox homeostasis on hepatocellular carcinoma.

PubMed

Lai, Kun-Goung; Chen, Chi-Fen; Ho, Chun-Te; Liu, Jun-Jen; Liu, Tsan-Zon; Chern, Chi-Liang

2017-06-01

We provide herein several lines of evidence to substantiate that folic acid (or folate) is a micronutrient capable of functioning as a novel redox regulator on hepatocellular carcinoma. First, we uncovered that folate deficiency could profoundly downregulate two prominent anti-apoptotic effectors including survivin and glucose-regulated protein-78. Silencing of either survivin or glucose-regulated protein-78 via small interfering RNA interfering technique established that both effectors could serve as reactive oxygen species sinker proteins. Second, folate deficiency-triggered oxidative-nitrosative stress could strongly induce endoplasmic reticulum stress that in turn could provoke cellular glutathione depletion through the modulation of the following two crucial events: (1) folate deficiency could strongly inhibit Bcl-2 expression leading to severe suppression of the mitochondrial glutathione pool and (2) folate deficiency could also profoundly inhibit two key enzymes that governing cellular glutathione redox regulation including γ-glutamylcysteinyl synthetase heavy chain, a catalytic enzyme for glutathione biosynthesis, and mitochondrial isocitrate dehydrogenase 2, an enzyme responsible for providing nicotinamide adenine dinucleotide phosphate necessary for regenerating oxidized glutathione disulfide back to glutathione via mitochondrial glutathione reductase. Collectively, we add to the literature new data to strengthen the notion that folate is an essential micronutrient that confers a novel role to combat reactive oxygen species insults and thus serves as a redox regulator via upregulating reactive oxygen species sinker proteins and averting mitochondrial glutathione depletion through proper maintenance of redox homeostasis via positively regulating glutathione biosynthesis, glutathione transporting system, and mitochondrial glutathione recycling process.

Neuron-specific specificity protein 4 bigenomically regulates the transcription of all mitochondria- and nucleus-encoded cytochrome c oxidase subunit genes in neurons.

PubMed

Johar, Kaid; Priya, Anusha; Dhar, Shilpa; Liu, Qiuli; Wong-Riley, Margaret T T

2013-11-01

Neurons are highly dependent on oxidative metabolism for their energy supply, and cytochrome c oxidase (COX) is a key energy-generating enzyme in the mitochondria. A unique feature of COX is that it is one of only four proteins in mammalian cells that are bigenomically regulated. Of its thirteen subunits, three are encoded in the mitochondrial genome and ten are nuclear-encoded on nine different chromosomes. The mechanism of regulating this multisubunit, bigenomic enzyme poses a distinct challenge. In recent years, we found that nuclear respiratory factors 1 and 2 (NRF-1 and NRF-2) mediate such bigenomic coordination. The latest candidate is the specificity factor (Sp) family of proteins. In N2a cells, we found that Sp1 regulates all 13 COX subunits. However, we discovered recently that in primary neurons, it is Sp4 and not Sp1 that regulates some of the key glutamatergic receptor subunit genes. The question naturally arises as to the role of Sp4 in regulating COX in primary neurons. The present study utilized multiple approaches, including chromatin immunoprecipitation, promoter mutational analysis, knockdown and over-expression of Sp4, as well as functional assays to document that Sp4 indeed functionally regulate all 13 subunits of COX as well as mitochondrial transcription factors A and B. The present study discovered that among the specificity family of transcription factors, it is the less known neuron-specific Sp4 that regulates the expression of all 13 subunits of mitochondrial cytochrome c oxidase (COX) enzyme in primary neurons. Sp4 also regulates the three mitochondrial transcription factors (TFAM, TFB1M, and TFB2M) and a COX assembly protein SURF-1 in primary neurons. © 2013 International Society for Neurochemistry.

Kinesin-1 and mitochondrial motility control by discrimination of structurally equivalent but distinct subdomains in Ran-GTP-binding domains of Ran-binding protein 2.

PubMed

Patil, Hemangi; Cho, Kyoung-in; Lee, James; Yang, Yi; Orry, Andrew; Ferreira, Paulo A

2013-03-27

The pleckstrin homology (PH) domain is a versatile fold that mediates a variety of protein-protein and protein-phosphatidylinositol lipid interactions. The Ran-binding protein 2 (RanBP2) contains four interspersed Ran GTPase-binding domains (RBD(n = 1-4)) with close structural homology to the PH domain of Bruton's tyrosine kinase. The RBD2, kinesin-binding domain (KBD) and RBD3 comprise a tripartite domain (R2KR3) of RanBP2 that causes the unfolding, microtubule binding and biphasic activation of kinesin-1, a crucial anterograde motor of mitochondrial motility. However, the interplay between Ran GTPase and R2KR3 of RanBP2 in kinesin-1 activation and mitochondrial motility is elusive. We use structure-function, biochemical, kinetic and cell-based assays with time-lapse live-cell microscopy of over 260,000 mitochondrial-motility-related events to find mutually exclusive subdomains in RBD2 and RBD3 towards Ran GTPase binding, kinesin-1 activation and mitochondrial motility regulation. The RBD2 and RBD3 exhibit Ran-GTP-independent, subdomain and stereochemical-dependent discrimination on the biphasic kinetics of kinesin-1 activation or regulation of mitochondrial motility. Further, KBD alone and R2KR3 stimulate and suppress, respectively, multiple biophysical parameters of mitochondrial motility. The regulation of the bidirectional transport of mitochondria by either KBD or R2KR3 is highly coordinated, because their kinetic effects are accompanied always by changes in mitochondrial motile events of either transport polarity. These studies uncover novel roles in Ran GTPase-independent subdomains of RBD2 and RBD3, and KBD of RanBP2, that confer antagonizing and multi-modal mechanisms of kinesin-1 activation and regulation of mitochondrial motility. These findings open new venues towards the pharmacological harnessing of cooperative and competitive mechanisms regulating kinesins, RanBP2 or mitochondrial motility in disparate human disorders.

Mitochondria and FOXO3: breath or die.

PubMed

Hagenbuchner, Judith; Ausserlechner, Michael J

2013-01-01

Forkhead box O (FOXO) transcription factors are regulators of cell-type specific apoptosis and cell cycle arrest but also control longevity and reactive oxygen species (ROS). ROS-control by FOXO is mediated by transcriptional activation of detoxifying enzymes such as Superoxide dismutase 2 (SOD2), Catalase or Sestrins or by the repression of mitochondrial respiratory chain proteins resulting in reduced mitochondrial activity. FOXO3 also regulates the adaptation to hypoxia by reducing mitochondrial mass and oxygen consumption during HIF-1α activation. In neuronal tumor cells, FOXO3 triggers ROS-accumulation as a consequence of transient mitochondrial outer membrane permeabilization, which is essential for FOXO3-induced apoptosis in these cells. Cellular ROS levels are affected by the FOXO-targets Bim, BclxL, and Survivin. All three proteins localize to mitochondria and affect mitochondrial membrane potential, respiration and cellular ROS levels. Bim-activation by FOXO3 causes mitochondrial depolarization resulting in a transitory decrease of respiration and ROS production. Survivin, on the other hand, actively changes mitochondrial architecture, respiration-efficacy and energy metabolism. This ability distinguishes Survivin from other anti-apoptotic proteins such as BclxL, which inhibits ROS by inactivating Bim but does not alter mitochondrial function. Importantly, FOXO3 simultaneously also activates ROS-detoxification via induction of SESN3. In this paper we discuss the hypothesis that the delicate balance between ROS-accumulation by Bim-triggered mitochondrial damage, mitochondrial architecture and ROS-detoxifying proteins determines cell fate. We provide evidence for a FOXO self-reactivating loop and for novel functions of FOXO3 in controlling mitochondrial respiration of neuronal cells, which further supports the current view that FOXO transcription factors are information-integrating sentinels of cellular stress and critical modulators of cell homeostasis.

A functional interplay between the small GTPase Rab11a and mitochondria-shaping proteins regulates mitochondrial positioning and polarization of the actin cytoskeleton downstream of Src family kinases.

PubMed

Landry, Marie-Claude; Champagne, Claudia; Boulanger, Marie-Chloé; Jetté, Alexandra; Fuchs, Margit; Dziengelewski, Claire; Lavoie, Josée N

2014-01-24

It is believed that mitochondrial dynamics is coordinated with endosomal traffic rates during cytoskeletal remodeling, but the mechanisms involved are largely unknown. The adenovirus early region 4 ORF4 protein (E4orf4) subverts signaling by Src family kinases (SFK) to perturb cellular morphology, membrane traffic, and organellar dynamics and to trigger cell death. Using E4orf4 as a model, we uncovered a functional connection between mitochondria-shaping proteins and the small GTPase Rab11a, a key regulator of polarized transport via recycling endosomes. We found that E4orf4 induced dramatic changes in the morphology of mitochondria along with their mobilization at the vicinity of a polarized actin network typifying E4orf4 action, in a manner controlled by SFK and Rab11a. Mitochondrial remodeling was associated with increased proximity between Rab11a and mitochondrial membranes, changes in fusion-fission dynamics, and mitochondrial relocalization of the fission factor dynamin-related protein 1 (Drp1), which was regulated by the Rab11a effector protein FIP1/RCP. Knockdown of FIP1/RCP or inhibition of Drp1 markedly impaired mitochondrial remodeling and actin assembly, involving Rab11a-mediated mitochondrial dynamics in E4orf4-induced signaling. A similar mobilization of mitochondria near actin-rich structures was mediated by Rab11 and Drp1 in viral Src-transformed cells and contributed to the biogenesis of podosome rosettes. These findings suggest a role for Rab11a in the trafficking of Drp1 to mitochondria upon SFK activation and unravel a novel functional interplay between Rab11a and mitochondria during reshaping of the cell cytoskeleton, which would facilitate mitochondria redistribution near energy-requiring actin-rich structures.

The polycystins are modulated by cellular oxygen-sensing pathways and regulate mitochondrial function

PubMed Central

Padovano, Valeria; Kuo, Ivana Y.; Stavola, Lindsey K.; Aerni, Hans R.; Flaherty, Benjamin J.; Chapin, Hannah C.; Ma, Ming; Somlo, Stefan; Boletta, Alessandra; Ehrlich, Barbara E.; Rinehart, Jesse; Caplan, Michael J.

2017-01-01

Autosomal dominant polycystic kidney disease is caused by mutations in the genes encoding polycystin-1 (PC1) and polycystin-2 (PC2), which form an ion channel complex that may mediate ciliary sensory processes and regulate endoplasmic reticulum (ER) Ca2+ release. Loss of PC1 expression profoundly alters cellular energy metabolism. The mechanisms that control the trafficking of PC1 and PC2, as well as their broader physiological roles, are poorly understood. We found that O2 levels regulate the subcellular localization and channel activity of the polycystin complex through its interaction with the O2-sensing prolyl hydroxylase domain containing protein EGLN3 (or PHD3), which hydroxylates PC1. Moreover, cells lacking PC1 expression use less O2 and show less mitochondrial Ca2+ uptake in response to bradykinin-induced ER Ca2+ release, indicating that PC1 can modulate mitochondrial function. These data suggest a novel role for the polycystins in sensing and responding to cellular O2 levels. PMID:27881662

Barth Syndrome: From Mitochondrial Dysfunctions Associated with Aberrant Production of Reactive Oxygen Species to Pluripotent Stem Cell Studies

PubMed Central

Saric, Ana; Andreau, Karine; Armand, Anne-Sophie; Møller, Ian M.; Petit, Patrice X.

2016-01-01

Mutations in the gene encoding the enzyme tafazzin, TAZ, cause Barth syndrome (BTHS). Individuals with this X-linked multisystem disorder present cardiomyopathy (CM) (often dilated), skeletal muscle weakness, neutropenia, growth retardation, and 3-methylglutaconic aciduria. Biopsies of the heart, liver and skeletal muscle of patients have revealed mitochondrial malformations and dysfunctions. It is the purpose of this review to summarize recent results of studies on various animal or cell models of Barth syndrome, which have characterized biochemically the strong cellular defects associated with TAZ mutations. Tafazzin is a mitochondrial phospholipidlysophospholipid transacylase that shuttles acyl groups between phospholipids and regulates the remodeling of cardiolipin (CL), a unique inner mitochondrial membrane phospholipid dimer consisting of two phosphatidyl residues linked by a glycerol bridge. After their biosynthesis, the acyl chains of CLs may be modified in remodeling processes involving up to three different enzymes. Their characteristic acyl chain composition depends on the function of tafazzin, although the enzyme itself surprisingly lacks acyl specificity. CLs are crucial for correct mitochondrial structure and function. In addition to their function in the basic mitochondrial function of ATP production, CLs play essential roles in cardiac function, apoptosis, autophagy, cell cycle regulation and Fe-S cluster biosynthesis. Recent developments in tafazzin research have provided strong insights into the link between mitochondrial dysfunction and the production of reactive oxygen species (ROS). An important tool has been the generation of BTHS-specific induced pluripotent stem cells (iPSCs) from BTHS patients. In a complementary approach, disease-specific mutations have been introduced into wild-type iPSC lines enabling direct comparison with isogenic controls. iPSC-derived cardiomyocytes were then characterized using biochemical and classical bioenergetic approaches. The cells are tested in a “heart-on-chip” assay to model the pathophysiology in vitro, to characterize the underlying mechanism of BTHS deriving from TAZ mutations, mitochondrial deficiencies and ROS production and leading to tissue defects, and to evaluate potential therapies with the use of mitochondrially targeted antioxidants. PMID:26834781

Mitochondrial-Nuclear Communication by Prohibitin Shuttling Under Oxidative Stress

PubMed Central

Sripathi, Srinivas; He, Weilue; Atkinson, Cameron; Smith, Joey; Liu, Zhicong; Elledge, Beth; Jahng, Wan Jin

2017-01-01

Mitochondrial-nuclear communication is critical to maintain mitochondrial activity under stress conditions. Adaptation of the mitochondria-nucleus network to changes in the intracellular oxidation and reduction milieu is critical for the survival of retinal and retinal pigment epithelial (RPE) cells, in relation to their high oxygen demand and rapid metabolism. However, the generation and transmittal of mitochondrial signal to the nucleus remains elusive. Previously, our in vivo study revealed that prohibitin is up-regulated in the retina but is down-regulated in RPE in the aging and diabetic model. In this study, the functional role of prohibitin in the retina and the RPE was studied using biochemical methods, including lipid binding assay, 2D gel electrophoresis, immunocytochemistry, Western blot, and knockdown approach. Protein depletion by siRNA characterized prohibitin as an anti-apoptotic molecule in mitochondria, while lipid binding assay demonstrated subcellular communications between mitochondria and the nucleus under oxidative stress. The changes of the expressions and localization of mitochondrial prohibitin triggered by reactive oxygen species are crucial for mitochondrial integrity. We propose that prohibitin shuttles between mitochondria and the nucleus as an anti-apoptotic molecule and a transcriptional regulator under stress environment in the retina and RPE. PMID:21879722

Etomoxir-induced increase in UCP3 supports a role of uncoupling protein 3 as a mitochondrial fatty acid anion exporter.

PubMed

Schrauwen, Patrick; Hinderling, Vera; Hesselink, Matthijs K C; Schaart, Gert; Kornips, Esther; Saris, Wim H M; Westerterp-Plantenga, Margriet; Langhans, Wolfgang

2002-10-01

The physiological function of human uncoupling protein-3 is still unknown. Uncoupling protein-3 is increased during fasting and high-fat feeding. In these situations the availability of fatty acids to the mitochondria exceeds the capacity to metabolize fatty acids, suggesting a role for uncoupling protein-3 in handling of non-metabolizable fatty acids. To test the hypothesis that uncoupling protein-3 acts as a mitochondrial exporter of non-metabolizable fatty acids from the mitochondrial matrix, we gave human subjects Etomoxir (which blocks mitochondrial entry of fatty acids) or placebo in a cross-over design during a 36-h stay in a respiration chamber. Etomoxir inhibited 24-h fat oxidation and fat oxidation during exercise by approximately 14-19%. Surprisingly, uncoupling protein-3 content in human vastus lateralis muscle was markedly up-regulated within 36 h of Etomoxir administration. Up-regulation of uncoupling protein-3 was accompanied by lowered fasting blood glucose and increased translocation of glucose transporter-4. These data support the hypothesis that the physiological function of uncoupling protein-3 is to facilitate the outward transport of non-metabolizable fatty acids from the mitochondrial matrix and thus prevents mitochondria from the potential deleterious effects of high fatty acid levels. In addition our data show that up-regulation of uncoupling protein-3 can be beneficial in the treatment of type 2 diabetes.

DNA Precursor Metabolism and Mitochondrial Genome Stability

DTIC Science & Technology

2003-04-01

mitochondrial DNA replication , to learn how the pool sizes are regulated, and to understand how perturbations of normal dNTP metabolism within the...mitochondria raises the possibility, however unlikely, that it is serving a function in addition to its role in DNA replication . The literature on non-DNA...is below since many authors do not follow the 200 word limit 14. SUBJECT TERMS Mitochondria, Genome stability, DNA precursors, Mitochondrial DNA

Altering the Mitochondrial Fatty Acid Synthesis (mtFASII) Pathway Modulates Cellular Metabolic States and Bioactive Lipid Profiles as Revealed by Metabolomic Profiling

PubMed Central

Clay, Hayley B.; Parl, Angelika K.; Mitchell, Sabrina L.; Singh, Larry; Bell, Lauren N.; Murdock, Deborah G.

2016-01-01

Despite the presence of a cytosolic fatty acid synthesis pathway, mitochondria have retained their own means of creating fatty acids via the mitochondrial fatty acid synthesis (mtFASII) pathway. The reason for its conservation has not yet been elucidated. Therefore, to better understand the role of mtFASII in the cell, we used thin layer chromatography to characterize the contribution of the mtFASII pathway to the fatty acid composition of selected mitochondrial lipids. Next, we performed metabolomic analysis on HeLa cells in which the mtFASII pathway was either hypofunctional (through knockdown of mitochondrial acyl carrier protein, ACP) or hyperfunctional (through overexpression of mitochondrial enoyl-CoA reductase, MECR). Our results indicate that the mtFASII pathway contributes little to the fatty acid composition of mitochondrial lipid species examined. Additionally, loss of mtFASII function results in changes in biochemical pathways suggesting alterations in glucose utilization and redox state. Interestingly, levels of bioactive lipids, including lysophospholipids and sphingolipids, directly correlate with mtFASII function, indicating that mtFASII may be involved in the regulation of bioactive lipid levels. Regulation of bioactive lipid levels by mtFASII implicates the pathway as a mediator of intracellular signaling. PMID:26963735

Mechanisms Behind Pyrroloquinoline Quinone Supplementation on Skeletal Muscle Mitochondrial Biogenesis: Possible Synergistic Effects with Exercise.

PubMed

Hwang, Paul; Willoughby, Darryn S

2018-05-01

There is clear evidence that endurance exercise training elicits intramuscular adaptations that can lead to elevations in mitochondrial biogenesis, oxidative capacity, mitochondrial density, and mitochondrial function. Mitochondrial biogenesis is regulated by the activation of the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1-alpha. This master regulator of mitochondrial biogenesis activates nuclear respiratory factors (NRF-1, NRF-2) and mitochondrial transcription factor A, which enables the expansion of mitochondrial size and transcription of mitochondrial DNA. Pyrroloquinoline quinone (PQQ) has been identified as a novel supplement that is involved in various physiological processes such as redox modulation, cellular energy metabolism, and mitochondrial biogenesis and is a potent antioxidant. Since both exercise and supplemental PQQ have mechanisms associated with mitochondrial biogenesis, it is plausible that a differential additive ergogenic benefit with PQQ can ensue. However, there is a major paucity of research exploring the role of PQQ in conjunction with exercise. In this respect, the purpose of the critical literature review will be to present a comprehensive overview of PQQ and the proposed mechanisms underlying mitochondrial biogenesis. Because exercise can instigate the molecular responses indicative of mitochondrial biogenesis, it is plausible that PQQ and exercise may instigate a synergistic response. Key teaching points • Endurance exercise training enables skeletal muscle adaptations that can induce increases in mitochondrial biogenesis, improve oxidative capacity, mitochondrial density, and mitochondrial function. • Pyrroloquinoline quinone (PQQ) has been identified as a novel supplement that is involved in physiological processes including redox modulation, cellular energy metabolism, mitochondrial biogenesis, and antioxidant potential. • There is emerging evidence to support that PQQ supplementation can upregulate the molecular signaling responses indicative of mitochondrial biogenesis within skeletal muscle. • If both endurance exercise and PQQ supplementation can elicit increases in the molecular responses indicative of mitochondrial biogenesis, it is possible that both PQQ and exercise may instigate a synergistic ergogenic response. • There is a scarcity of research exploring the possible role of PQQ supplementation with concomitant endurance exercise. Therefore, future research is necessary to investigate the ergogenic potential behind PQQ supplementation in conjunction with endurance exercise.

NDE1 and GSK3β Associate with TRAK1 and Regulate Axonal Mitochondrial Motility: Identification of Cyclic AMP as a Novel Modulator of Axonal Mitochondrial Trafficking.

PubMed

Ogawa, Fumiaki; Murphy, Laura C; Malavasi, Elise L V; O'Sullivan, Shane T; Torrance, Helen S; Porteous, David J; Millar, J Kirsty

2016-05-18

Mitochondria are essential for neuronal function, providing the energy required to power neurotransmission, and fulfilling many important additional roles. In neurons, mitochondria must be efficiently transported to sites, including synapses, where their functions are required. Neurons, with their highly elongated morphology, are consequently extremely sensitive to defective mitochondrial trafficking which can lead to neuronal ill-health/death. We recently demonstrated that DISC1 associates with mitochondrial trafficking complexes where it associates with the core kinesin and dynein adaptor molecule TRAK1. We now show that the DISC1 interactors NDE1 and GSK3β also associate robustly with TRAK1 and demonstrate that NDE1 promotes retrograde axonal mitochondrial movement. GSK3β is known to modulate axonal mitochondrial motility, although reports of its actual effect are conflicting. We show that, in our system, GSK3β promotes anterograde mitochondrial transport. Finally, we investigated the influence of cAMP elevation upon mitochondrial motility, and found a striking increase in mitochondrial motility and retrograde movement. DISC1, NDE1, and GSK3β are implicated as risk factors for major mental illness. Our demonstration that they function together within mitochondrial trafficking complexes suggests that defective mitochondrial transport may be a contributory disease mechanism in some cases of psychiatric disorder.

The Mitochondrial Calcium Uniporter: Mice can live and die without it

PubMed Central

Harrington, Josephine L; Murphy, Elizabeth

2014-01-01

Calcium is of critical importance to mitochondrial and cell function, and calcium signaling is highly localized in the cell. When stimulated, mitochondria are capable of rapidly taking up calcium, affecting both matrix energetics within mitochondria and shaping the amplitude and frequency of cytosolic calcium “waves”. During pathological conditions a large increase in mitochondrial calcium levels is thought to activate the mitochondrial permeability transition pore, resulting in cell death. The protein responsible for mitochondrial calcium uptake, the mitochondrial calcium uniporter (MCU), was identified in 2011 and its molecular elucidation has stimulated and invigorated research in this area. MCU knockout mice have been created, a variety of other regulators have been identified, and a disease phenotype in humans has been attributed to the loss of a uniporter regulator. In the three years since its molecular elucidation, further research into the MCU has revealed a complex uniporter, and raised many questions about its physiologic and pathologic cell roles. PMID:25451167

Multi-Parametric Analysis and Modeling of Relationships between Mitochondrial Morphology and Apoptosis

PubMed Central

Reis, Yara; Wolf, Thomas; Brors, Benedikt; Hamacher-Brady, Anne; Eils, Roland; Brady, Nathan R.

2012-01-01

Mitochondria exist as a network of interconnected organelles undergoing constant fission and fusion. Current approaches to study mitochondrial morphology are limited by low data sampling coupled with manual identification and classification of complex morphological phenotypes. Here we propose an integrated mechanistic and data-driven modeling approach to analyze heterogeneous, quantified datasets and infer relations between mitochondrial morphology and apoptotic events. We initially performed high-content, multi-parametric measurements of mitochondrial morphological, apoptotic, and energetic states by high-resolution imaging of human breast carcinoma MCF-7 cells. Subsequently, decision tree-based analysis was used to automatically classify networked, fragmented, and swollen mitochondrial subpopulations, at the single-cell level and within cell populations. Our results revealed subtle but significant differences in morphology class distributions in response to various apoptotic stimuli. Furthermore, key mitochondrial functional parameters including mitochondrial membrane potential and Bax activation, were measured under matched conditions. Data-driven fuzzy logic modeling was used to explore the non-linear relationships between mitochondrial morphology and apoptotic signaling, combining morphological and functional data as a single model. Modeling results are in accordance with previous studies, where Bax regulates mitochondrial fragmentation, and mitochondrial morphology influences mitochondrial membrane potential. In summary, we established and validated a platform for mitochondrial morphological and functional analysis that can be readily extended with additional datasets. We further discuss the benefits of a flexible systematic approach for elucidating specific and general relationships between mitochondrial morphology and apoptosis. PMID:22272225

Aconitase couples metabolic regulation to mitochondrial DNA maintenance.

PubMed

Chen, Xin Jie; Wang, Xiaowen; Kaufman, Brett A; Butow, Ronald A

2005-02-04

Mitochondrial DNA (mtDNA) is essential for cells to maintain respiratory competency and is inherited as a protein-DNA complex called the nucleoid. We have identified 22 mtDNA-associated proteins in yeast, among which is mitochondrial aconitase (Aco1p). We show that this Krebs-cycle enzyme is essential for mtDNA maintenance independent of its catalytic activity. Regulation of ACO1 expression by the HAP and retrograde metabolic signaling pathways directly affects mtDNA maintenance. When constitutively expressed, Aco1p can replace the mtDNA packaging function of the high-mobility-group protein Abf2p. Thus, Aco1p may integrate metabolic signals and mtDNA maintenance.

Elongator-dependent modification of cytoplasmic tRNALysUUU is required for mitochondrial function under stress conditions.

PubMed

Tigano, Marco; Ruotolo, Roberta; Dallabona, Cristina; Fontanesi, Flavia; Barrientos, Antoni; Donnini, Claudia; Ottonello, Simone

2015-09-30

To gain a wider view of the pathways that regulate mitochondrial function, we combined the effect of heat stress on respiratory capacity with the discovery potential of a genome-wide screen in Saccharomyces cerevisiae. We identified 105 new genes whose deletion impairs respiratory growth at 37°C by interfering with processes such as transcriptional regulation, ubiquitination and cytosolic tRNA wobble uridine modification via 5-methoxycarbonylmethyl-2-thiouridine formation. The latter process, specifically required for efficient decoding of AA-ending codons under stress conditions, was covered by multiple genes belonging to the Elongator (e.g. ELP3) and urmylation (e.g., NCS6) pathways. ELP3 or NCS6 deletants had impaired mitochondrial protein synthesis. Their respiratory deficiency was selectively rescued by overexpression of tRNA(Lys) UUU as well by overexpression of genes (BCK1 and HFM1) with a strong bias for the AAA codon read by this tRNA. These data extend the mitochondrial regulome, demonstrate that heat stress can impair respiration by disturbing cytoplasmic translation of proteins critically involved in mitochondrial function and document, for the first time, the involvement in such process of the Elongator and urmylation pathways. Given the conservation of these pathways, the present findings may pave the way to a better understanding of the human mitochondrial regulome in health and disease. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

Ebselen protects mitochondrial function and oxidative stress while inhibiting the mitochondrial apoptosis pathway after acute spinal cord injury.

PubMed

Jia, Zhi-Qiang; Li, San-Qiang; Qiao, Wei-Qiang; Xu, Wen-Zhong; Xing, Jian-Wu; Liu, Jian-Tao; Song, Hui; Gao, Zhong-Yang; Xing, Bing-Wen; He, Xi-Jing

2018-05-04

Ebselen is a fat-soluble small molecule and organic selenium compound that regulates the activity of glutathione peroxidase to alleviate mitochondrial oxidative stress and improve mitochondrial function. In the present study, we aimed to investigate the effects of ebselen on mitochondrial oxidative stress response, mitochondrial apotosis, and motor behaviors after spinal cord injury (SCI). We found that ebselen significantly increased the BBB score in motor behavior, thus suggesting a rescue effect of ebselen on motor function after SCI in rats. Meanwhile, we revealed that ebselen can increase glutathione (GSH) content as well as superoxide dismutase (SOD) and catalase (CAT) activities after SCI-this suggests ebselen has an antioxidant effect. Furthermore, the ATP content and Na + -K + -ATPase activity in mitochondria were increased by ebselen after SCI, while the mitochondrial membrane potential (MMP) was decreased by ebselen. The Cytochrome C and Smac release from mitochondria were reduced by ebselen after SCI, thus indicating improved membrane permeability by ebselen. Moreover, the alterations in caspase-3, Bax and Bcl-2 protein expression, as well as the proportion of cell apoptosis were improved by ebselen treatment, which together suggested that ebselen has an inhibitory effect on mitochondrial apotosis pathways after SCI. Taken together, our results suggest that ebselen can inhibit secondary damage caused by spinal cord injury. Indeed it plays a neuroprotective role in spinal cord injury perhaps by improving mitochondrial function and inhibiting the mitochondrial apoptosis pathway. Copyright © 2018 Elsevier B.V. All rights reserved.

Advances in the quantification of mitochondrial function in primary human immune cells through extracellular flux analysis.

PubMed

Nicholas, Dequina; Proctor, Elizabeth A; Raval, Forum M; Ip, Blanche C; Habib, Chloe; Ritou, Eleni; Grammatopoulos, Tom N; Steenkamp, Devin; Dooms, Hans; Apovian, Caroline M; Lauffenburger, Douglas A; Nikolajczyk, Barbara S

2017-01-01

Numerous studies show that mitochondrial energy generation determines the effectiveness of immune responses. Furthermore, changes in mitochondrial function may regulate lymphocyte function in inflammatory diseases like type 2 diabetes. Analysis of lymphocyte mitochondrial function has been facilitated by introduction of 96-well format extracellular flux (XF96) analyzers, but the technology remains imperfect for analysis of human lymphocytes. Limitations in XF technology include the lack of practical protocols for analysis of archived human cells, and inadequate data analysis tools that require manual quality checks. Current analysis tools for XF outcomes are also unable to automatically assess data quality and delete untenable data from the relatively high number of biological replicates needed to power complex human cell studies. The objectives of work presented herein are to test the impact of common cellular manipulations on XF outcomes, and to develop and validate a new automated tool that objectively analyzes a virtually unlimited number of samples to quantitate mitochondrial function in immune cells. We present significant improvements on previous XF analyses of primary human cells that will be absolutely essential to test the prediction that changes in immune cell mitochondrial function and fuel sources support immune dysfunction in chronic inflammatory diseases like type 2 diabetes.

Plant uncoupling mitochondrial proteins.

PubMed

Vercesi, Aníbal Eugênio; Borecký, Jiri; Maia, Ivan de Godoy; Arruda, Paulo; Cuccovia, Iolanda Midea; Chaimovich, Hernan

2006-01-01

Uncoupling proteins (UCPs) are membrane proteins that mediate purine nucleotide-sensitive free fatty acid-activated H(+) flux through the inner mitochondrial membrane. After the discovery of UCP in higher plants in 1995, it was acknowledged that these proteins are widely distributed in eukaryotic organisms. The widespread presence of UCPs in eukaryotes implies that these proteins may have functions other than thermogenesis. In this review, we describe the current knowledge of plant UCPs, including their discovery, biochemical properties, distribution, gene family, gene expression profiles, regulation of gene expression, and evolutionary aspects. Expression analyses and functional studies on the plant UCPs under normal and stressful conditions suggest that UCPs regulate energy metabolism in the cellular responses to stress through regulation of the electrochemical proton potential (Deltamu(H)+) and production of reactive oxygen species.

Molecular identity of cardiac mitochondrial chloride intracellular channel proteins.

PubMed

Ponnalagu, Devasena; Gururaja Rao, Shubha; Farber, Jason; Xin, Wenyu; Hussain, Ahmed Tafsirul; Shah, Kajol; Tanda, Soichi; Berryman, Mark; Edwards, John C; Singh, Harpreet

2016-03-01

Emerging evidences demonstrate significance of chloride channels in cardiac function and cardioprotection from ischemia-reperfusion (IR) injury. Unlike mitochondrial potassium channels sensitive to calcium (BKCa) and ATP (KATP), molecular identity of majority of cardiac mitochondrial chloride channels located at the inner membrane is not known. In this study, we report the presence of unique dimorphic chloride intracellular channel (CLIC) proteins namely CLIC1, CLIC4 and CLIC5 as abundant CLICs in the rodent heart. Further, CLIC4, CLIC5, and an ortholog present in Drosophila (DmCLIC) localize to adult cardiac mitochondria. We found that CLIC4 is enriched in the outer mitochondrial membrane, whereas CLIC5 is present in the inner mitochondrial membrane. Also, CLIC5 plays a direct role in regulating mitochondrial reactive oxygen species (ROS) generation. Our study highlights that CLIC5 is localized to the cardiac mitochondria and directly modulates mitochondrial function. Copyright © 2016 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

MicroRNA as biomarkers of mitochondrial toxicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baumgart, Bethany R., E-mail: bethany.baumgart@bms

Mitochondrial toxicity can be difficult to detect as most cells can tolerate reduced activity as long as minimal capacity for function is maintained. However, once minimal capacity is lost, apoptosis or necrosis occurs quickly. Identification of more sensitive, early markers of mitochondrial toxicity was the objective of this work. Rotenone, a mitochondrial complex I inhibitor, and 3-nitropropionic acid (3-NP), a mitochondrial complex II inhibitor, were administered daily to male Sprague–Dawley rats at subcutaneous doses of 0.1 or 0.3 mg/kg/day and intraperitoneal doses of 5 or 10 mg/kg/day, respectively, for 1 week. Samples of kidney, skeletal muscle (quadriceps femoris), and serummore » were collected for analysis of mitochondrial DNA (mtDNA) copy number and microRNA (miRNA) expression patterns. MtDNA was significantly decreased with administration of rotenone at 0.3 mg/kg/day and 3-NP at 5 and 10 mg/kg/day in the quadriceps femoris and with 3-NP at 10 mg/kg/day in the kidney. Additionally, rotenone and 3-NP treatment produced changes to miRNA expression that were similar in direction (i.e. upregulation, downregulation) to those previously linked to mitochondrial functions, such as mitochondrial damage and biogenesis (miR-122, miR-202-3p); regulation of ATP synthesis, abolished oxidative phosphorylation, and loss of membrane potential due to increased reactive oxygen species (ROS) production (miR-338-5p, miR-546, miR-34c); and mitochondrial DNA damage and depletion (miR-546). These results suggest that miRNAs may be sensitive biomarkers for early detection of mitochondrial toxicity. - Highlights: • MtDNA decreased after treatment with respiratory chain inhibitors rotenone and 3-NP. • Decrease in mtDNA is generally dose-related and indicative of mitochondrial toxicity. • Altered miRNA has reported roles in regulating mitochondrial function. • Induction of miR-338-5p in kidney and serum suggests potential as renal biomarker. • Induction of miR-122 implies that expression may not adhere to liver-specific pattern.« less

11β-HSD1 Modulates the Set Point of Brown Adipose Tissue Response to Glucocorticoids in Male Mice

PubMed Central

Doig, Craig L.; Fletcher, Rachel S.; Morgan, Stuart A.; McCabe, Emma L.; Larner, Dean P.; Tomlinson, Jeremy W.; Stewart, Paul M.; Philp, Andrew

2017-01-01

Glucocorticoids (GCs) are potent regulators of energy metabolism. Chronic GC exposure suppresses brown adipose tissue (BAT) thermogenic capacity in mice, with evidence for a similar effect in humans. Intracellular GC levels are regulated by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity, which can amplify circulating GC concentrations. Therefore, 11β-HSD1 could modulate the impact of GCs on BAT function. This study investigated how 11β-HSD1 regulates the molecular architecture of BAT in the context of GC excess and aging. Circulating GC excess was induced in 11β-HSD1 knockout (KO) and wild-type mice by supplementing drinking water with 100 μg/mL corticosterone, and the effects on molecular markers of BAT function and mitochondrial activity were assessed. Brown adipocyte primary cultures were used to examine cell autonomous consequences of 11β-HSD1 deficiency. Molecular markers of BAT function were also examined in aged 11β-HSD1 KO mice to model lifetime GC exposure. BAT 11β-HSD1 expression and activity were elevated in response to GC excess and with aging. 11β-HSD1 KO BAT resisted the suppression of uncoupling protein 1 (UCP1) and mitochondrial respiratory chain subunit proteins normally imposed by GC excess. Furthermore, brown adipocytes from 11β-HSD1 KO mice had elevated basal mitochondrial function and were able to resist GC-mediated repression of activity. BAT from aged 11β-HSD1 KO mice showed elevated UCP1 protein and mitochondrial content, and a favorable profile of BAT function. These data reveal a novel mechanism in which increased 11β-HSD1 expression, in the context of GC excess and aging, impairs the molecular and metabolic function of BAT. PMID:28368470

The mitochondrial outer membrane protein hFis1 regulates mitochondrial morphology and fission through self-interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serasinghe, Madhavika N.; Mitochondrial Research and Innovation Group, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642; Yoon, Yisang

2008-11-15

Mitochondrial fission in mammals is mediated by at least two proteins, DLP1/Drp1 and hFis1. DLP1 mediates the scission of mitochondrial membranes through GTP hydrolysis, and hFis1 is a putative DLP1 receptor anchored at the mitochondrial outer membrane by a C-terminal single transmembrane domain. The cytosolic domain of hFis1 contains six {alpha}-helices ({alpha}1-{alpha}6) out of which {alpha}2-{alpha}5 form two tetratricopeptide repeat (TPR) folds. In this study, by using chimeric constructs, we demonstrated that the cytosolic domain contains the necessary information for hFis1 function during mitochondrial fission. By using transient expression of different mutant forms of the hFis1 protein, we found thatmore » hFis1 self-interaction plays an important role in mitochondrial fission. Our results show that deletion of the {alpha}1 helix greatly increased the formation of dimeric and oligomeric forms of hFis1, indicating that {alpha}1 helix functions as a negative regulator of the hFis1 self-interaction. Further mutational approaches revealed that a tyrosine residue in the {alpha}5 helix and the linker between {alpha}3 and {alpha}4 helices participate in hFis1 oligomerization. Mutations causing oligomerization defect greatly reduced the ability to induce not only mitochondrial fragmentation by full-length hFis1 but also the formation of swollen ball-shaped mitochondria caused by {alpha}1-deleted hFis1. Our data suggest that oligomerization of hFis1 in the mitochondrial outer membrane plays a role in mitochondrial fission, potentially through participating in fission factor recruitment.« less

Muscle FBPase binds to cardiomyocyte mitochondria under glycogen synthase kinase-3 inhibition or elevation of cellular Ca2+ level.

PubMed

Gizak, Agnieszka; Pirog, Michal; Rakus, Dariusz

2012-01-02

A growing body of research suggests that fructose 1,6-bisphosphatase (FBPase) might be involved in regulation of cell mortality/survival. However, the precise role of FBPase in the process remains unknown. Here, we show for the first time that in HL-1 cardiomyocytes, inhibition of glycogen synthase kinase-3 results in translocation of FBPase to mitochondria. In vitro experiments demonstrate that FBPase reduces the rate of calcium-induced mitochondrial swelling, affects ATP synthesis and interacts with mitochondrial proteins involved in regulation of volume and energy homeostasis. We suggest that FBPase might be engaged in a regulation of cell survival by influencing mitochondrial function. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

OPTICAL AND PHARMACOLOGICAL TOOLS TO INVESTIGATE THE ROLE OF MITOCHONDRIA DURING OXIDATIVE STRESS AND NEURODEGENERATION

PubMed Central

Foster, Kelley A.; Galeffi, Francesca; Gerich, Florian J.; Turner, Dennis A.; Müller, Michael

2007-01-01

Mitochondria are critical for cellular ATP production; however, recent studies suggest that these organelles fulfill a much broader range of tasks. For example, they are involved in the regulation of cytosolic Ca2+ levels, intracellular pH and apoptosis, and are the major source of reactive oxygen species (ROS). Various reactive molecules that originate from mitochondria, such as ROS, are critical in pathological events, such as ischemia, as well as in physiological events such as long-term potentiation, neuronal-vascular coupling and neuronal-glial interactions. Due to their key roles in the regulation of several cellular functions, the dysfunction of mitochondria may be critical in various brain disorders. There has been increasing interest in the development of tools that modulate mitochondrial function, and the refinement of techniques that allow for real time monitoring of mitochondria, particularly within their intact cellular environment. Innovative imaging techniques are especially powerful since they allow for mitochondrial visualization at high resolution, tracking of mitochondrial structures and optical real time monitoring of parameters of mitochondrial function. Among the techniques discussed are the uses of classic imaging techniques such as rhodamine-123, the highly advanced semi-conductor nanoparticles (quantum dots), and wide field microscopy as well as high-resolution multi-photon imaging. We have highlighted the use of these techniques to study mitochondrial function in brain tissue and have included studies from our laboratories in which these techniques have been successfully applied. PMID:16920246

The Permeability Transition Pore Controls Cardiac Mitochondrial Maturation and Myocyte Differentiation

PubMed Central

Hom, Jennifer R.; Quintanilla, Rodrigo A.; Hoffman, David L.; Karen L., de Mesy Bentley; Molkentin, Jeffery D.; Sheu, Shey-Shing; Porter, George A.

2011-01-01

SUMMARY Although mature myocytes rely on mitochondria as the primary source of energy, the role of mitochondria in the developing heart is not well known. Here, we find closure of the mitochondrial permeability transition pore (mPTP) drives maturation of mitochondrial structure and function and myocyte differentiation. Cardiomyocytes at embryonic day (E) 9.5, when compared to E13.5, displayed fragmented mitochondria with few cristae, a less polarized mitochondrial membrane potential, higher reactive oxygen species (ROS) levels, and an open mPTP. Pharmacologic and genetic closing of the mPTP yielded maturation of mitochondrial structure and function, lowered ROS, and increased myocyte differentiation (measured by counting Z-bands). Furthermore, myocyte differentiation was inhibited and enhanced with oxidant and antioxidant treatment, respectively, suggesting that redox signaling pathways lie downstream of mitochondria to regulate cardiac myocyte differentiation. PMID:21920313

Akt phosphorylates the TR3 orphan receptor and blocks its targeting to the mitochondria.

PubMed

Chen, Hang-Zi; Zhao, Bi-Xing; Zhao, Wen-Xiu; Li, Li; Zhang, Bing; Wu, Qiao

2008-11-01

Acutely transforming retrovirus AKT8 in rodent T cell lymphoma (Akt) phosphorylates and regulates the function of many cellular proteins involved in processes such as metabolism, apoptosis and proliferation. However, the precise mechanisms by which Akt promotes cell survival and inhibits apoptosis have been characterized in part only. TR3, an orphan receptor, functions as a transcription factor that can both positively or negatively regulate gene expression. We have reported previously that the translocation of TR3 from the nucleus to the mitochondria can elicit a proapoptotic effect in gastric cancer cells. In our present study, we demonstrate that Akt phosphorylates cytoplasmic TR3 through its physical interaction with the N-terminus of TR3. When coexpressed with Akt, TR3 mitochondrial targeting was blocked and this protein adopted a diffuse expression pattern in the cytoplasm. Moreover, Akt displayed an ability to disrupt the interaction of TR3 with Bcl-2, which is thought to be a critical requirement for mitochondrial TR3 to elicit apoptosis. Consistently, insulin was also found to induce the phosphorylation of TR3 and abolish 12-O-tetradecanoylphorbol-13-acetate-induced mitochondrial localization, which was dependent upon the activation of the phophatidylinositol-3-OH-kinase-Akt signaling pathway. Taken together, our current data demonstrate a unique role for Akt in inhibiting TR3 functions that are not related to transcriptional activity but that correlate with the regulation of its mitochondrial association. This may represent a novel signal pathway by which Akt exerts its antiapoptotic effects in gastric cancer cells, i.e. by regulating the phosphorylation and redistribution of orphan receptors.

Drp1-dependent mitophagy protects against cisplatin-induced apoptosis of renal tubular epithelial cells by improving mitochondrial function

PubMed Central

Qi, Jia; Duan, Suyan; Huang, Zhimin; Zhang, Chengning; Wu, Lin; Zeng, Ming; Zhang, Bo; Wang, Ningning; Mao, Huijuan; Zhang, Aihua; Xing, Changying; Yuan, Yanggang

2017-01-01

Cisplatin chemotherapy often causes acute kidney injury (AKI) in cancer patients. There is increasing evidence that mitochondrial dysfunction plays an important role in cisplatin-induced nephrotoxicity. Degradation of damaged mitochondria is carried out by mitophagy. Although mitophagy is considered of particular importance in protecting against AKI, little is known of the precise role of mitophagy and its molecular mechanisms during cisplatin-induced nephrotoxicity. Also, evidence that activation of mitophagy improved mitochondrial function is lacking. Furthermore, several evidences have shown that mitochondrial fission coordinates with mitophagy. The aim of this study was to investigate whether activation of mitophagy protects against mitochondrial dysfunction and renal proximal tubular cells injury during cisplatin treatment. The effect of mitochondrial fission on mitophagy was also investigated. In cultured human renal proximal tubular cells, we observed that 3-methyladenine, a pharmacological inhibitor of autophagy, blocked mitophagy and exacerbated cisplatin-induced mitochondrial dysfunction and cells injury. In contrast, autophagy activator rapamycin enhanced mitophagy and protected against the harmful effects of cisplatin on mitochondrial function and cells viability. Suppression of mitochondrial fission by knockdown of its main regulator dynamin-related protein-1 (Drp1) decreased cisplatin-induced mitophagy. Meanwhile, Drp1 suppression protected against cisplatin-induced cells injury by inhibiting mitochondrial dysfunction. Our results provide evidence that Drp1-depedent mitophagy has potential as renoprotective targets for the treatment of cisplatin-induced AKI. PMID:28423497

Genetics of Mitochondrial Disease.

PubMed

Saneto, Russell P

2017-01-01

Mitochondria are intracellular organelles responsible for adenosine triphosphate production. The strict control of intracellular energy needs require proper mitochondrial functioning. The mitochondria are under dual controls of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). Mitochondrial dysfunction can arise from changes in either mtDNA or nDNA genes regulating function. There are an estimated ∼1500 proteins in the mitoproteome, whereas the mtDNA genome has 37 proteins. There are, to date, ∼275 genes shown to give rise to disease. The unique physiology of mitochondrial functioning contributes to diverse gene expression. The onset and range of phenotypic expression of disease is diverse, with onset from neonatal to seventh decade of life. The range of dysfunction is heterogeneous, ranging from single organ to multisystem involvement. The complexity of disease expression has severely limited gene discovery. Combining phenotypes with improvements in gene sequencing strategies are improving the diagnosis process. This chapter focuses on the interplay of the unique physiology and gene discovery in the current knowledge of genetically derived mitochondrial disease. Copyright © 2017 Elsevier Inc. All rights reserved.

Mitochondrial poly(ADP-ribose) polymerase: The Wizard of Oz at work.

PubMed

Brunyanszki, Attila; Szczesny, Bartosz; Virág, László; Szabo, Csaba

2016-11-01

Among multiple members of the poly(ADP-ribose) polymerase (PARP) family, PARP1 accounts for the majority of PARP activity in mammalian cells. Although PARP1 is predominantly localized to the nucleus, and its nuclear regulatory roles are most commonly studied and are the best characterized, several lines of data demonstrate that PARP1 is also present in the mitochondria, and suggest that mitochondrial PARP (mtPARP) plays an important role in the regulation of various cellular functions in health and disease. The goal of the current article is to review the experimental evidence for the mitochondrial localization of PARP1 and its intra-mitochondrial functions, with focus on cellular bioenergetics, mitochondrial DNA repair and mitochondrial dysfunction. In addition, we also propose a working model for the interaction of mitochondrial and nuclear PARP during oxidant-induced cell death. MtPARP is similar to the Wizard of Oz in the sense that it is enigmatic, it has been elusive for a long time and it remains difficult to be interrogated. mtPARP - at least in some cell types - works incessantly "behind the curtains" as an orchestrator of many important cellular functions. Copyright © 2016 Elsevier Inc. All rights reserved.

Mitochondria and Iron: Current Questions

PubMed Central

Paul, Bibbin T.; Manz, David H.; Torti, Frank M.; Torti, Suzy V.

2017-01-01

Introduction Mitochondria are cellular organelles that perform numerous bioenergetic, biosynthetic, and regulatory functions and play a central role in iron metabolism. Extracellular iron is taken up by cells and transported to the mitochondria, where it is utilized for synthesis of cofactors essential to the function of enzymes involved in oxidation-reduction reactions, DNA synthesis and repair, and a variety of other cellular processes. Areas Covered This article reviews the trafficking of iron to the mitochondria and normal mitochondrial iron metabolism, including heme synthesis and iron-sulfur cluster biogenesis. Much of our understanding of mitochondrial iron metabolism has been revealed by pathologies that disrupt normal iron metabolism. These conditions affect not only iron metabolism but mitochondrial function and systemic health. Therefore, this article also discusses these pathologies, including conditions of systemic and mitochondrial iron dysregulation as well as cancer. Literature covering these areas was identified via PubMed searches using keywords: Iron, mitochondria, Heme Synthesis, Iron-sulfur Cluster, and Cancer. References cited by publications retrieved using this search strategy were also consulted. Expert Commentary While much has been learned about mitochondrial iron, key questions remain. Developing a better understanding of mitochondrial iron regulation will be paramount in developing therapies for syndromes that affect mitochondrial iron. PMID:27911100

Mitochondrial Dysfunctions in Bipolar Disorder: Effect of the Disease and Pharmacotherapy.

PubMed

Cikankova, Tereza; Sigitova, Ekaterina; Zverova, Martina; Fisar, Zdenek; Raboch, Jiri; Hroudova, Jana

2017-01-01

Exact pathophysiological mechanisms of bipolar disorder have not been sufficiently clarified. We review the evidence of mitochondrial dysfunctions on the relation between both disease and pharmacotherapy. Mitochondria produce the most of energy-rich molecules of adenosine triphosphate (ATP), apart from energy production they are involved in other functions: regulation of free radicals, antioxidant defenses, lipid peroxidation, calcium metabolism and participate in the intrinsic pathway of apoptosis. According to increasing evidence dysfunctions of mitochondria are associated with affective disorders, a hypothesis of impaired mitochondrial functions has been proposed in bipolar disorder pathogenesis. Mitochondrial DNA mutations and/or polymorphisms, impaired phospholipid metabolism and glycolytic shift, decrease in ATP production, increased oxidative stress and changes of intracellular calcium are concerned in mood disorders and effects of mood stabilizers. Recent studies have also provided data about the positive effects of chronic treatment by mood stabilizers on mitochondrial functions. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Mitochondria: Targeting mitochondrial reactive oxygen species with mitochondriotropic polyphenolic-based antioxidants.

PubMed

Teixeira, José; Deus, Cláudia M; Borges, Fernanda; Oliveira, Paulo J

2018-04-01

Mitochondrial function and regulation of redox balance is fundamental in controlling cellular life and death pathways. Antioxidants have been used to counteract disruption of redox networks, normally associated with progressive loss of cell homeostasis and disease pathophysiology, although therapeutic success is limited mainly due to pharmacokinetic drawbacks. Attempts to improve mitochondrial function in a range of diseases spurred active drug discovery efforts. Currently, the most effective strategy to deliver drugs to mitochondria is the covalent link of lipophilic cations to the bioactive compound. Although targeting mitochondrial oxidative stress with antioxidants has been demonstrated, clinical use has been hampered by several challenges, with no FDA-approved drug so far. Development of new mitochondriotropic antioxidant agents based on dietary polyphenols has recently gained momentum. Due to their nature, mitochondria-targeted multi-functional antioxidants can trigger stress responses and contribute to tissue protection through hormesis mechanisms, inhibiting excessive mitochondrial ROS production and associated diseases. Copyright © 2018 Elsevier Ltd. All rights reserved.

MicroRNA-210 regulates mitochondrial free radical response to hypoxia and krebs cycle in cancer cells by targeting iron sulfur cluster protein ISCU.

PubMed

Favaro, Elena; Ramachandran, Anassuya; McCormick, Robert; Gee, Harriet; Blancher, Christine; Crosby, Meredith; Devlin, Cecilia; Blick, Christopher; Buffa, Francesca; Li, Ji-Liang; Vojnovic, Borivoj; Pires das Neves, Ricardo; Glazer, Peter; Iborra, Francisco; Ivan, Mircea; Ragoussis, Jiannis; Harris, Adrian L

2010-04-26

Hypoxia in cancers results in the upregulation of hypoxia inducible factor 1 (HIF-1) and a microRNA, hsa-miR-210 (miR-210) which is associated with a poor prognosis. In human cancer cell lines and tumours, we found that miR-210 targets the mitochondrial iron sulfur scaffold protein ISCU, required for assembly of iron-sulfur clusters, cofactors for key enzymes involved in the Krebs cycle, electron transport, and iron metabolism. Down regulation of ISCU was the major cause of induction of reactive oxygen species (ROS) in hypoxia. ISCU suppression reduced mitochondrial complex 1 activity and aconitase activity, caused a shift to glycolysis in normoxia and enhanced cell survival. Cancers with low ISCU had a worse prognosis. Induction of these major hallmarks of cancer show that a single microRNA, miR-210, mediates a new mechanism of adaptation to hypoxia, by regulating mitochondrial function via iron-sulfur cluster metabolism and free radical generation.

Mitochondrial function, ornamentation, and immunocompetence.

PubMed

Koch, Rebecca E; Josefson, Chloe C; Hill, Geoffrey E

2017-08-01

Understanding the mechanisms that link ornamental displays and individual condition is key to understanding the evolution and function of ornaments. Immune function is an aspect of individual quality that is often associated with the expression of ornamentation, but a general explanation for why the expression of some ornaments seems to be consistently linked to immunocompetence remains elusive. We propose that condition-dependent ornaments may be linked to key aspects of immunocompetence through co-dependence on mitochondrial function. Mitochondrial involvement in immune function is rarely considered outside of the biomedical literature, but the role of mitochondria as the primary energy producers of the cell and the centres of biosynthesis, the oxidative stress response, and cellular signalling place them at the hub of a variety of immune pathways. A promising new mechanistic explanation for correlations between a wide range of ornamental traits and the properties of individual quality is that mitochondrial function may be the 'shared pathway' responsible for links between ornament production and individual condition. Herein, we first review the role of mitochondria as both signal transducers and metabolic regulators of immune function. We then describe connections between hormonal pathways and mitochondria, with implications for both immune function and the expression of ornamentation. Finally, we explore the possibility that ornament expression may link directly to mitochondrial function. Considering condition-dependent traits within the framework of mitochondrial function has the potential to unify central tenets within the study of sexual selection, eco-immunology, oxidative stress ecology, stress and reproductive hormone biology, and animal physiology. © 2016 Cambridge Philosophical Society.

Integrated genomic analysis of mitochondrial RNA processing in human cancers.

PubMed

Idaghdour, Youssef; Hodgkinson, Alan

2017-04-18

The mitochondrial genome is transcribed as continuous polycistrons of RNA containing multiple genes. As a consequence, post-transcriptional events are critical for the regulation of gene expression and therefore all aspects of mitochondrial function. One particularly important process is the m 1 A/m 1 G RNA methylation of the ninth position of different mitochondrial tRNAs, which allows efficient processing of mitochondrial mRNAs and protein translation, and de-regulation of genes involved in these processes has been associated with altered mitochondrial function. Although mitochondria play a key role in cancer, the status of mitochondrial RNA processing in tumorigenesis is unknown. We measure and assess mitochondrial RNA processing using integrated genomic analysis of RNA sequencing and genotyping data from 1226 samples across 12 different cancer types. We focus on the levels of m 1 A and m 1 G RNA methylation in mitochondrial tRNAs in normal and tumor samples and use supervised and unsupervised statistical analysis to compare the levels of these modifications to patient whole genome genotypes, nuclear gene expression, and survival outcomes. We find significant changes to m 1 A and m 1 G RNA methylation levels in mitochondrial tRNAs in tumor tissues across all cancers. Pathways of RNA processing are strongly associated with methylation levels in normal tissues (P = 3.27 × 10 -31 ), yet these associations are lost in tumors. Furthermore, we report 18 gene-by-disease-state interactions where altered RNA methylation levels occur under cancer status conditional on genotype, implicating genes associated with mitochondrial function or cancer (e.g., CACNA2D2, LMO2, and FLT3) and suggesting that nuclear genetic variation can potentially modulate an individual's ability to maintain unaltered rates of mitochondrial RNA processing under cancer status. Finally, we report a significant association between the magnitude of methylation level changes in tumors and patient survival outcomes. We report widespread variation of mitochondrial RNA processing between normal and tumor tissues across all cancer types investigated and show that these alterations are likely modulated by patient genotype and may impact patient survival outcomes. These results highlight the potential clinical relevance of altered mitochondrial RNA processing and provide broad new insights into the importance and complexity of these events in cancer.

Diabetes and mitochondrial function: Role of hyperglycemia and oxidative stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rolo, Anabela P.; Palmeira, Carlos M.

2006-04-15

Hyperglycemia resulting from uncontrolled glucose regulation is widely recognized as the causal link between diabetes and diabetic complications. Four major molecular mechanisms have been implicated in hyperglycemia-induced tissue damage: activation of protein kinase C (PKC) isoforms via de novo synthesis of the lipid second messenger diacylglycerol (DAG), increased hexosamine pathway flux, increased advanced glycation end product (AGE) formation, and increased polyol pathway flux. Hyperglycemia-induced overproduction of superoxide is the causal link between high glucose and the pathways responsible for hyperglycemic damage. In fact, diabetes is typically accompanied by increased production of free radicals and/or impaired antioxidant defense capabilities, indicating amore » central contribution for reactive oxygen species (ROS) in the onset, progression, and pathological consequences of diabetes. Besides oxidative stress, a growing body of evidence has demonstrated a link between various disturbances in mitochondrial functioning and type 2 diabetes. Mutations in mitochondrial DNA (mtDNA) and decreases in mtDNA copy number have been linked to the pathogenesis of type 2 diabetes. The study of the relationship of mtDNA to type 2 diabetes has revealed the influence of the mitochondria on nuclear-encoded glucose transporters, glucose-stimulated insulin secretion, and nuclear-encoded uncoupling proteins (UCPs) in {beta}-cell glucose toxicity. This review focuses on a range of mitochondrial factors important in the pathogenesis of diabetes. We review the published literature regarding the direct effects of hyperglycemia on mitochondrial function and suggest the possibility of regulation of mitochondrial function at a transcriptional level in response to hyperglycemia. The main goal of this review is to include a fresh consideration of pathways involved in hyperglycemia-induced diabetic complications.« less

Thyrotropin-releasing hormone controls mitochondrial biology in human epidermis.

PubMed

Knuever, Jana; Poeggeler, Burkhard; Gáspár, Erzsébet; Klinger, Matthias; Hellwig-Burgel, Thomas; Hardenbicker, Celine; Tóth, Balázs I; Bíró, Tamás; Paus, Ralf

2012-03-01

Mitochondrial capacity and metabolic potential are under the control of hormones, such as thyroid hormones. The most proximal regulator of the hypothalamic-pituitary-thyroid (HPT) axis, TRH, is the key hypothalamic integrator of energy metabolism via its impact on thyroid hormone secretion. Here, we asked whether TRH directly modulates mitochondrial functions in normal, TRH-receptor-positive human epidermis. Organ-cultured human skin was treated with TRH (5-100 ng/ml) for 12-48 h. TRH significantly increased epidermal immunoreactivity for the mitochondria-selective subunit I of respiratory chain complex IV (MTCO1). This resulted from an increased MTCO1 transcription and protein synthesis and a stimulation of mitochondrial biogenesis as demonstrated by transmission electron microscopy and TRH-enhanced mitochondrial DNA synthesis. TRH also significantly stimulated the transcription of several other mitochondrial key genes (TFAM, HSP60, and BMAL1), including the master regulator of mitochondrial biogenesis (PGC-1α). TRH significantly enhanced mitochondrial complex I and IV enzyme activity and enhanced the oxygen consumption of human skin samples, which shows that the stimulated mitochondria are fully vital because the main source for cellular oxygen consumption is mitochondrial endoxidation. These findings identify TRH as a potent, novel neuroendocrine stimulator of mitochondrial activity and biogenesis in human epidermal keratinocytes in situ. Thus, human epidermis offers an excellent model for dissecting neuroendocrine controls of human mitochondrial biology under physiologically relevant conditions and for exploring corresponding clinical applications.

Monomeric cocoa catechins enhance β-cell function by increasing mitochondrial respiration.

PubMed

Rowley, Thomas J; Bitner, Benjamin F; Ray, Jason D; Lathen, Daniel R; Smithson, Andrew T; Dallon, Blake W; Plowman, Chase J; Bikman, Benjamin T; Hansen, Jason M; Dorenkott, Melanie R; Goodrich, Katheryn M; Ye, Liyun; O'Keefe, Sean F; Neilson, Andrew P; Tessem, Jeffery S

2017-11-01

A hallmark of type 2 diabetes (T2D) is β-cell dysfunction and the eventual loss of functional β-cell mass. Therefore, mechanisms that improve or preserve β-cell function could be used to improve the quality of life of individuals with T2D. Studies have shown that monomeric, oligomeric and polymeric cocoa flavanols have different effects on obesity, insulin resistance and glucose tolerance. We hypothesized that these cocoa flavanols may have beneficial effects on β-cell function. INS-1 832/13-derived β-cells and primary rat islets cultured with a monomeric catechin-rich cocoa flavanol fraction demonstrated enhanced glucose-stimulated insulin secretion, while cells cultured with total cocoa extract and with oligomeric or polymeric procyanidin-rich fraction demonstrated no improvement. The increased glucose-stimulated insulin secretion in the presence of the monomeric catechin-rich fraction corresponded with enhanced mitochondrial respiration, suggesting improvements in β-cell fuel utilization. Mitochondrial complex III, IV and V components are up-regulated after culture with the monomer-rich fraction, corresponding with increased cellular ATP production. The monomer-rich fraction improved cellular redox state and increased glutathione concentration, which corresponds with nuclear factor, erythroid 2 like 2 (Nrf2) nuclear localization and expression of Nrf2 target genes including nuclear respiratory factor 1 (Nrf1) and GA binding protein transcription factor alpha subunit (GABPA), essential genes for increasing mitochondrial function. We propose a model by which monomeric cocoa catechins improve the cellular redox state, resulting in Nrf2 nuclear migration and up-regulation of genes critical for mitochondrial respiration, glucose-stimulated insulin secretion and ultimately improved β-cell function. These results suggest a mechanism by which monomeric cocoa catechins exert their effects as an effective complementary strategy to benefit T2D patients. Copyright © 2017 Elsevier Inc. All rights reserved.

Insulin acutely improves mitochondrial function of rat and human skeletal muscle by increasing coupling efficiency of oxidative phosphorylation.

PubMed

Nisr, Raid B; Affourtit, Charles

2014-02-01

Insulin is essential for the regulation of fuel metabolism and triggers the uptake of glucose by skeletal muscle. The imported glucose is either stored or broken down, as insulin stimulates glycogenesis and ATP synthesis. The mechanism by which ATP production is increased is incompletely understood at present and, generally, relatively little functional information is available on the effect of insulin on mitochondrial function. In this paper we have exploited extracellular flux technology to investigate insulin effects on the bioenergetics of rat (L6) and human skeletal muscle myoblasts and myotubes. We demonstrate that a 20-min insulin exposure significantly increases (i) the cell respiratory control ratio, (ii) the coupling efficiency of oxidative phosphorylation, and (iii) the glucose sensitivity of anaerobic glycolysis. The improvement of mitochondrial function is explained by an insulin-induced immediate decrease of mitochondrial proton leak. Palmitate exposure annuls the beneficial mitochondrial effects of insulin. Our data improve the mechanistic understanding of insulin-stimulated ATP synthesis, and reveal a hitherto undisclosed insulin sensitivity of cellular bioenergetics that suggests a novel way of detecting insulin responsiveness of cells. © 2013.

Insulin acutely improves mitochondrial function of rat and human skeletal muscle by increasing coupling efficiency of oxidative phosphorylation☆

PubMed Central

Nisr, Raid B.; Affourtit, Charles

2014-01-01

Insulin is essential for the regulation of fuel metabolism and triggers the uptake of glucose by skeletal muscle. The imported glucose is either stored or broken down, as insulin stimulates glycogenesis and ATP synthesis. The mechanism by which ATP production is increased is incompletely understood at present and, generally, relatively little functional information is available on the effect of insulin on mitochondrial function. In this paper we have exploited extracellular flux technology to investigate insulin effects on the bioenergetics of rat (L6) and human skeletal muscle myoblasts and myotubes. We demonstrate that a 20-min insulin exposure significantly increases (i) the cell respiratory control ratio, (ii) the coupling efficiency of oxidative phosphorylation, and (iii) the glucose sensitivity of anaerobic glycolysis. The improvement of mitochondrial function is explained by an insulin-induced immediate decrease of mitochondrial proton leak. Palmitate exposure annuls the beneficial mitochondrial effects of insulin. Our data improve the mechanistic understanding of insulin-stimulated ATP synthesis, and reveal a hitherto undisclosed insulin sensitivity of cellular bioenergetics that suggests a novel way of detecting insulin responsiveness of cells. PMID:24212054

Pink1 and Parkin regulate Drosophila intestinal stem cell proliferation during stress and aging.

PubMed

Koehler, Christopher L; Perkins, Guy A; Ellisman, Mark H; Jones, D Leanne

2017-08-07

Intestinal stem cells (ISCs) maintain the midgut epithelium in Drosophila melanogaster Proper cellular turnover and tissue function rely on tightly regulated rates of ISC division and appropriate differentiation of daughter cells. However, aging and epithelial injury cause elevated ISC proliferation and decreased capacity for terminal differentiation of daughter enteroblasts (EBs). The mechanisms causing functional decline of stem cells with age remain elusive; however, recent findings suggest that stem cell metabolism plays an important role in the regulation of stem cell activity. Here, we investigate how alterations in mitochondrial homeostasis modulate stem cell behavior in vivo via RNA interference-mediated knockdown of factors involved in mitochondrial dynamics. ISC/EB-specific knockdown of the mitophagy-related genes Pink1 or Parkin suppresses the age-related loss of tissue homeostasis, despite dramatic changes in mitochondrial ultrastructure and mitochondrial damage in ISCs/EBs. Maintenance of tissue homeostasis upon reduction of Pink1 or Parkin appears to result from reduction of age- and stress-induced ISC proliferation, in part, through induction of ISC senescence. Our results indicate an uncoupling of cellular, tissue, and organismal aging through inhibition of ISC proliferation and provide insight into strategies used by stem cells to maintain tissue homeostasis despite severe damage to organelles. © 2017 Koehler et al.

Molecular chaperone TRAP1 regulates a metabolic switch between mitochondrial respiration and aerobic glycolysis

PubMed Central

Yoshida, Soichiro; Tsutsumi, Shinji; Muhlebach, Guillaume; Sourbier, Carole; Lee, Min-Jung; Lee, Sunmin; Vartholomaiou, Evangelia; Tatokoro, Manabu; Beebe, Kristin; Miyajima, Naoto; Mohney, Robert P.; Chen, Yang; Hasumi, Hisashi; Xu, Wanping; Fukushima, Hiroshi; Nakamura, Ken; Koga, Fumitaka; Kihara, Kazunori; Trepel, Jane; Picard, Didier; Neckers, Leonard

2013-01-01

TRAP1 (TNF receptor-associated protein), a member of the HSP90 chaperone family, is found predominantly in mitochondria. TRAP1 is broadly considered to be an anticancer molecular target. However, current inhibitors cannot distinguish between HSP90 and TRAP1, making their utility as probes of TRAP1-specific function questionable. Some cancers express less TRAP1 than do their normal tissue counterparts, suggesting that TRAP1 function in mitochondria of normal and transformed cells is more complex than previously appreciated. We have used TRAP1-null cells and transient TRAP1 silencing/overexpression to show that TRAP1 regulates a metabolic switch between oxidative phosphorylation and aerobic glycolysis in immortalized mouse fibroblasts and in human tumor cells. TRAP1-deficiency promotes an increase in mitochondrial respiration and fatty acid oxidation, and in cellular accumulation of tricarboxylic acid cycle intermediates, ATP and reactive oxygen species. At the same time, glucose metabolism is suppressed. TRAP1-deficient cells also display strikingly enhanced invasiveness. TRAP1 interaction with and regulation of mitochondrial c-Src provide a mechanistic basis for these phenotypes. Taken together with the observation that TRAP1 expression is inversely correlated with tumor grade in several cancers, these data suggest that, in some settings, this mitochondrial molecular chaperone may act as a tumor suppressor. PMID:23564345

Magnesium and calcium-enriched deep-sea water promotes mitochondrial biogenesis by AMPK-activated signals pathway in 3T3-L1 preadipocytes.

PubMed

Ha, Byung Geun; Moon, Deok-Soo; Kim, Hyeon Ju; Shon, Yun Hee

2016-10-01

Recent studies showed that deficiencies of essential minerals including Mg, Ca, and K, and trace minerals including Se, Zn, and V, have implications for the development, prevention, and treatment of several chronic diseases including obesity and type 2 diabetes. Our previous studies revealed that balanced deep-sea water (BDSW), which is composed of desalinated water enriched with Mg and Ca, has potential as a treatment for diabetes and obesity. In this study, to determine whether BDSW regulates mitochondrial biogenesis and function, we investigated its effects on mitochondrial DNA (mtDNA) content, mitochondrial enzyme activity, expression of key transcription factors and mitochondria-specific genes, phosphorylation of signaling molecules associated with mitochondrial biogenesis, and mitochondrial function in 3T3-L1 preadipocytes. BDSW increased mitochondrial biogenesis in a dose-dependent manner. Quantitative real-time PCR revealed that BDSW enhances expression of PGC1-α, NRF1, and TFAM genes. Upregulation of these genes was supported by increased mitochondria staining, CytC oxidase activity, and AMPK phosphorylation. The stimulatory effect of BDSW on mitochondrial biogenesis and function suggests a novel mechanism for BDSW-induced anti-diabetic and anti-obesity action. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Mitochondrial CHCHD-Containing Proteins: Physiologic Functions and Link with Neurodegenerative Diseases.

PubMed

Zhou, Zhi-Dong; Saw, Wuan-Ting; Tan, Eng-King

2017-09-01

The coiled-coil-helix-coiled-coil-helix domain (CHCHD)-containing proteins are evolutionarily conserved nucleus-encoded small mitochondrial proteins with important functions. So far, nine members have been identified in this protein family. All CHCHD proteins have at least one functional coiled-coil-helix-coiled-coil-helix (CHCH) domain, which is stabilized by two pairs of disulfide bonds between two helices. CHCHD proteins have various important pathophysiological roles in mitochondria and other key cellular processes. Mutations of CHCHD proteins have been associated with various human neurodegenerative diseases. Mutations of CHCHD10 are associated with amyotrophic lateral sclerosis (ALS) and/or frontotemporal lobe dementia (FTD), motor neuron disease, and late-onset spinal muscular atrophy and autosomal dominant mitochondrial myopathy. CHCHD10 stabilizes mitochondrial crista ultrastructure and maintains its integrity. In patients with CHCHD10 mutations, there are abnormal mitochondrial crista structure, deficiencies of respiratory chain complexes, impaired mitochondrial respiration, and multiple mitochondrial DNA (mtDNA) deletions. Recently, CHCHD2 mutations are linked with autosomal dominant and sporadic Parkinson's disease (PD). The CHCHD2 is a multifunctional protein and plays roles in regulation of mitochondrial metabolism, synthesis of respiratory chain components, and modulation of cell apoptosis. With a better understanding of the pathophysiologic roles of CHCHD proteins, they may be potential novel therapeutic targets for human neurodegenerative diseases.

Mitochondrial iron chelation ameliorates cigarette-smoke induced bronchitis and emphysema in mice

PubMed Central

Cloonan, Suzanne M.; Glass, Kimberly; Laucho-Contreras, Maria E.; Bhashyam, Abhiram R.; Cervo, Morgan; Pabón, Maria A.; Konrad, Csaba; Polverino, Francesca; Siempos, Ilias I.; Perez, Elizabeth; Mizumura, Kenji; Ghosh, Manik C.; Parameswaran, Harikrishnan; Williams, Niamh C.; Rooney, Kristen T.; Chen, Zhi-Hua; Goldklang, Monica P.; Yuan, Guo-Cheng; Moore, Stephen C.; Demeo, Dawn L.; Rouault, Tracey A.; D’Armiento, Jeanine M.; Schon, Eric A.; Manfredi, Giovanni; Quackenbush, John; Mahmood, Ashfaq; Silverman, Edwin K.; Owen, Caroline A.; Choi, Augustine M.K.

2015-01-01

Chronic obstructive pulmonary disease (COPD) is linked to both cigarette smoking and genetic determinants. We have previously identified iron-responsive element binding protein 2 (IRP2) as an important COPD susceptibility gene, with IRP2 protein increased in the lungs of individuals with COPD. Here we demonstrate that mice deficient in Irp2 were protected from cigarette smoke (CS)-induced experimental COPD. By integrating RIP-Seq, RNA-Seq, gene expression and functional enrichment clustering analysis, we identified IRP2 as a regulator of mitochondrial function in the lung. IRP2 increased mitochondrial iron loading and cytochrome c oxidase (COX), which led to mitochondrial dysfunction and subsequent experimental COPD. Frataxin-deficient mice with higher mitochondrial iron loading had impaired airway mucociliary clearance (MCC) and higher pulmonary inflammation at baseline, whereas synthesis of cytochrome c oxidase (Sco2)-deficient mice with reduced COX were protected from CS-induced pulmonary inflammation and impairment of MCC. Mice treated with a mitochondrial iron chelator or mice fed a low-iron diet were protected from CS-induced COPD. Mitochondrial iron chelation also alleviated CS-impairment of MCC, CS-induced pulmonary inflammation and CS-associated lung injury in mice with established COPD, suggesting a critical functional role and potential therapeutic intervention for the mitochondrial-iron axis in COPD. PMID:26752519

Mitochondrial Flash: Integrative Reactive Oxygen Species and pH Signals in Cell and Organelle Biology

PubMed Central

Gong, Guohua; Wang, Xianhua; Wei-LaPierre, Lan; Cheng, Heping; Dirksen, Robert

2016-01-01

Abstract Significance: Recent breakthroughs in mitochondrial research have advanced, reshaped, and revolutionized our view of the role of mitochondria in health and disease. These discoveries include the development of novel tools to probe mitochondrial biology, the molecular identification of mitochondrial functional proteins, and the emergence of new concepts and mechanisms in mitochondrial function regulation. The discovery of “mitochondrial flash” activity has provided unique insights not only into real-time visualization of individual mitochondrial redox and pH dynamics in live cells but has also advanced understanding of the excitability, autonomy, and integration of mitochondrial function in vivo. Recent Advances: The mitochondrial flash is a transient and stochastic event confined within an individual mitochondrion and is observed in a wide range of organisms from plants to Caenorhabditis elegans to mammals. As flash events involve multiple transient concurrent changes within the mitochondrion (e.g., superoxide, pH, and membrane potential), a number of different mitochondrial targeted fluorescent indicators can detect flash activity. Accumulating evidence indicates that flash events reflect integrated snapshots of an intermittent mitochondrial process arising from mitochondrial respiration chain activity associated with the transient opening of the mitochondrial permeability transition pore. Critical Issues: We review the history of flash discovery, summarize current understanding of flash biology, highlight controversies regarding the relative roles of superoxide and pH signals during a flash event, and bring forth the integration of both signals in flash genesis. Future Directions: Investigations using flash as a biomarker and establishing its role in cell signaling pathway will move the field forward. Antioxid. Redox Signal. 25, 534–549. PMID:27245241

Miro-Working beyond Mitochondria and Microtubules.

PubMed

Tang, Bor Luen

2018-03-04

The small GTPase Miro is best known for its regulation of mitochondrial movement by engaging with the microtubule-based motor proteins kinesin and dynein. Very recent findings have now showed that Miro also targets peroxisomes and regulates microtubule-dependent peroxisome motility. Moreover, Miro recruits and stabilizes the myosin motor Myo19 at the mitochondria to enable actin-based mitochondria movement, which is important for mitochondrial segregation during mitosis. Miro thus has much broader functions that previously known, and these new findings may have important implications on disease pathology.

PINK1/Parkin-Dependent Mitochondrial Surveillance: From Pleiotropy to Parkinson's Disease

PubMed Central

Mouton-Liger, Francois; Jacoupy, Maxime; Corvol, Jean-Christophe; Corti, Olga

2017-01-01

Parkinson's disease (PD) is one of the most frequent neurodegenerative disease caused by the preferential, progressive degeneration of the dopaminergic (DA) neurons of the substantia nigra (SN) pars compacta. PD is characterized by a multifaceted pathological process involving protein misfolding, mitochondrial dysfunction, neuroinflammation and metabolism deregulation. The molecular mechanisms governing the complex interplay between the different facets of this process are still unknown. PARK2/Parkin and PARK6/PINK1, two genes responsible for familial forms of PD, act as a ubiquitous core signaling pathway, coupling mitochondrial stress to mitochondrial surveillance, by regulating mitochondrial dynamics, the removal of damaged mitochondrial components by mitochondria-derived vesicles, mitophagy, and mitochondrial biogenesis. Over the last decade, PINK1/Parkin-dependent mitochondrial quality control emerged as a pleiotropic regulatory pathway. Loss of its function impinges on a number of physiological processes suspected to contribute to PD pathogenesis. Its role in the regulation of innate immunity and inflammatory processes stands out, providing compelling support to the contribution of non-cell-autonomous immune mechanisms in PD. In this review, we illustrate the central role of this multifunctional pathway at the crossroads between mitochondrial stress, neuroinflammation and metabolism. We discuss how its dysfunction may contribute to PD pathogenesis and pinpoint major unresolved questions in the field. PMID:28507507

MicroRNA-138 and MicroRNA-25 Down-regulate Mitochondrial Calcium Uniporter, Causing the Pulmonary Arterial Hypertension Cancer Phenotype

PubMed Central

Hong, Zhigang; Chen, Kuang-Hueih; DasGupta, Asish; Potus, Francois; Dunham-Snary, Kimberly; Bonnet, Sebastien; Tian, Lian; Fu, Jennifer; Breuils-Bonnet, Sandra; Provencher, Steeve; Wu, Danchen; Mewburn, Jeffrey; Ormiston, Mark L.

2017-01-01

Rationale: Pulmonary arterial hypertension (PAH) is an obstructive vasculopathy characterized by excessive pulmonary artery smooth muscle cell (PASMC) proliferation, migration, and apoptosis resistance. This cancer-like phenotype is promoted by increased cytosolic calcium ([Ca2+]cyto), aerobic glycolysis, and mitochondrial fission. Objectives: To determine how changes in mitochondrial calcium uniporter (MCU) complex (MCUC) function influence mitochondrial dynamics and contribute to PAH’s cancer-like phenotype. Methods: PASMCs were isolated from patients with PAH and healthy control subjects and assessed for expression of MCUC subunits. Manipulation of the pore-forming subunit, MCU, in PASMCs was achieved through small interfering RNA knockdown or MCU plasmid-mediated up-regulation, as well as through modulation of the upstream microRNAs (miRs) miR-138 and miR-25. In vivo, nebulized anti-miRs were administered to rats with monocrotaline-induced PAH. Measurements and Main Results: Impaired MCUC function, resulting from down-regulation of MCU and up-regulation of an inhibitory subunit, mitochondrial calcium uptake protein 1, is central to PAH’s pathogenesis. MCUC dysfunction decreases intramitochondrial calcium ([Ca2+]mito), inhibiting pyruvate dehydrogenase activity and glucose oxidation, while increasing [Ca2+]cyto, promoting proliferation, migration, and fission. In PAH PASMCs, increasing MCU decreases cell migration, proliferation, and apoptosis resistance by lowering [Ca2+]cyto, raising [Ca2+]mito, and inhibiting fission. In normal PASMCs, MCUC inhibition recapitulates the PAH phenotype. In PAH, elevated miRs (notably miR-138) down-regulate MCU directly and also by decreasing MCU’s transcriptional regulator cAMP response element–binding protein 1. Nebulized anti-miRs against miR-25 and miR-138 restore MCU expression, reduce cell proliferation, and regress established PAH in the monocrotaline model. Conclusions: These results highlight miR-mediated MCUC dysfunction as a unifying mechanism in PAH that can be therapeutically targeted. PMID:27648837

Melatonin, mitochondria and hypertension.

PubMed

Baltatu, Ovidiu C; Amaral, Fernanda G; Campos, Luciana A; Cipolla-Neto, Jose

2017-11-01

Melatonin, due to its multiple means and mechanisms of action, plays a fundamental role in the regulation of the organismal physiology by fine tunning several functions. The cardiovascular system is an important site of action as melatonin regulates blood pressure both by central and peripheral interventions, in addition to its relation with the renin-angiotensin system. Besides, the systemic management of several processes, melatonin acts on mitochondria regulation to maintain a healthy cardiovascular system. Hypertension affects target organs in different ways and cellular energy metabolism is frequently involved due to mitochondrial alterations that include a rise in reactive oxygen species production and an ATP synthesis decrease. The discussion that follows shows the role played by melatonin in the regulation of mitochondrial physiology in several levels of the cardiovascular system, including brain, heart, kidney, blood vessels and, particularly, regulating the renin-angiotensin system. This discussion shows the putative importance of using melatonin as a therapeutic tool involving its antioxidant potential and its action on mitochondrial physiology in the cardiovascular system.

Differential regulation of mitochondrial pyruvate carrier genes modulates respiratory capacity and stress tolerance in yeast.

PubMed

Timón-Gómez, Alba; Proft, Markus; Pascual-Ahuir, Amparo

2013-01-01

Mpc proteins are highly conserved from yeast to humans and are necessary for the uptake of pyruvate at the inner mitochondrial membrane, which is used for leucine and valine biosynthesis and as a fuel for respiration. Our analysis of the yeast MPC gene family suggests that amino acid biosynthesis, respiration rate and oxidative stress tolerance are regulated by changes in the Mpc protein composition of the mitochondria. Mpc2 and Mpc3 are highly similar but functionally different: Mpc2 is most abundant under fermentative non stress conditions and important for amino acid biosynthesis, while Mpc3 is the most abundant family member upon salt stress or when high respiration rates are required. Accordingly, expression of the MPC3 gene is highly activated upon NaCl stress or during the transition from fermentation to respiration, both types of regulation depend on the Hog1 MAP kinase. Overexpression experiments show that gain of Mpc2 function leads to a severe respiration defect and ROS accumulation, while Mpc3 stimulates respiration and enhances tolerance to oxidative stress. Our results identify the regulated mitochondrial pyruvate uptake as an important determinant of respiration rate and stress resistance.

Decreased mitochondrial respiration in aneurysmal aortas of Fibulin-4 mutant mice is linked to PGC1A regulation.

PubMed

van der Pluijm, I; Burger, J; van Heijningen, P M; IJpma, A; van Vliet, N; Milanese, C; Schoonderwoerd, K; Sluiter, W; Ringuette, L J; Dekkers, D H W; Que, I; Kaijzel, E L; Te Riet, L; MacFarlane, E; Das, D; van der Linden, R; Vermeij, M; Demmers, J A; Mastroberardino, P G; Davis, E C; Yanagisawa, H; Dietz, H; Kanaar, R; Essers, J

2018-06-21

Thoracic aortic aneurysms are a life-threatening condition often diagnosed too late. To discover novel robust biomarkers, we aimed to better understand the molecular mechanisms underlying aneurysm formation. In Fibulin-4R/R mice, the extracellular matrix protein Fibulin-4 is 4-fold reduced, resulting in progressive ascending aneurysm formation and early death around 3 months of age. We performed proteomics and genomics studies on Fibulin-4R/R mouse aortas. Intriguingly, we observed alterations in mitochondrial protein composition in Fibulin-4R/R aortas. Consistently, functional studies in Fibulin-4R/R vascular smooth muscle cells (VSMCs) revealed lower oxygen consumption rates, but increased acidification rates. Yet, mitochondria in Fibulin-4R/R VSMCs showed no aberrant cytoplasmic localization. We found similar reduced mitochondrial respiration in Tgfbr-1M318R/+ VSMCs, a mouse model for Loeys-Dietz syndrome. Interestingly, also human fibroblasts from Marfan (FBN1) and Loeys-Dietz syndrome (TGFBR2 and SMAD3) patients showed lower oxygen consumption. While individual mitochondrial complex I-V activities were unaltered in Fibulin-4R/R heart and muscle, these tissues showed similar decreased oxygen consumption. Furthermore, aortas of aneurysmal Fibulin-4R/R mice displayed increased ROS levels. Consistent with these findings, gene expression analyses revealed dysregulation of metabolic pathways. Accordingly, blood ketone levels of Fibulin-4R/R mice were reduced and liver fatty acids were decreased, while liver glycogen was increased, indicating dysregulated metabolism at the organismal level. As predicted by gene expression analysis, the activity of PGC1α, a key regulator between mitochondrial function and organismal metabolism, was downregulated in Fibulin-4R/R VSMCs. Increased TGFβ reduced PGC1α levels, indicating involvement of TGFβ signalling in PGC1α regulation. Activation of PGC1α restored the decreased oxygen consumption in Fibulin-4R/R VSMCs and improved their reduced growth potential, emphasizing the importance of this key regulator. Our data indicate altered mitochondrial function and metabolic dysregulation, leading to increased ROS levels and altered energy production, as a novel mechanism, which may contribute to thoracic aortic aneurysm formation.

The Mitochondrial Cardiolipin Remodeling Enzyme Lysocardiolipin Acyltransferase Is a Novel Target in Pulmonary Fibrosis

PubMed Central

Huang, Long Shuang; Mathew, Biji; Zhao, Yutong; Noth, Imre; Reddy, Sekhar P.; Harijith, Anantha; Usatyuk, Peter V.; Berdyshev, Evgeny V.; Kaminski, Naftali; Zhou, Tong; Zhang, Wei; Zhang, Yanmin; Rehman, Jalees; Kotha, Sainath R.; Gurney, Travis O.; Parinandi, Narasimham L.; Lussier, Yves A.; Garcia, Joe G. N.

2014-01-01

Rationale: Lysocardiolipin acyltransferase (LYCAT), a cardiolipin-remodeling enzyme regulating the 18:2 linoleic acid pattern of mammalian mitochondrial cardiolipin, is necessary for maintaining normal mitochondrial function and vascular development. We hypothesized that modulation of LYCAT expression in lung epithelium regulates development of pulmonary fibrosis. Objectives: To define a role for LYCAT in human and murine models of pulmonary fibrosis. Methods: We analyzed the correlation of LYCAT expression in peripheral blood mononuclear cells (PBMCs) with the outcomes of pulmonary functions and overall survival, and used the murine models to establish the role of LYCAT in fibrogenesis. We studied the LYCAT action on cardiolipin remodeling, mitochondrial reactive oxygen species generation, and apoptosis of alveolar epithelial cells under bleomycin challenge. Measurements and Main Results: LYCAT expression was significantly altered in PBMCs and lung tissues from patients with idiopathic pulmonary fibrosis (IPF), which was confirmed in two preclinical murine models of IPF, bleomycin- and radiation-induced pulmonary fibrosis. LYCAT mRNA expression in PBMCs directly and significantly correlated with carbon monoxide diffusion capacity, pulmonary function outcomes, and overall survival. In both bleomycin- and radiation-induced pulmonary fibrosis murine models, hLYCAT overexpression reduced several indices of lung fibrosis, whereas down-regulation of native LYCAT expression by siRNA accentuated fibrogenesis. In vitro studies demonstrated that LYCAT modulated bleomycin-induced cardiolipin remodeling, mitochondrial membrane potential, reactive oxygen species generation, and apoptosis of alveolar epithelial cells, potential mechanisms of LYCAT-mediated lung protection. Conclusions: This study is the first to identify modulation of LYCAT expression in fibrotic lungs and offers a novel therapeutic approach for ameliorating lung inflammation and pulmonary fibrosis. PMID:24779708

Proteomic Dissection of the Mitochondrial DNA Metabolism Apparatus in Arabidopsis

DOE Office of Scientific and Technical Information (OSTI.GOV)

SAlly A. Mackenzie

2004-01-06

This study involves the investigation of nuclear genetic components that regulate mitochondrial genome behavior in higher plants. The approach utilizes the advanced plant model system of Arabidopsis thaliana to identify and functionally characterize multiple components of the mitochondrial DNA replication, recombination and mismatch repair system and their interaction partners. The rationale for the research stems from the central importance of mitochondria to overall cellular metabolism and the essential nature of the mitochondrial genome to mitochondrial function. Relatively little is understood about mitochondrial DNA maintenance and transmission in higher eukaryotes, and the higher plant mitochondrial genome displays unique properties and behavior.more » This investigation has revealed at least three important properties of plant mitochondrial DNA metabolism components. (1) Many are dual targeted to mitochondrial and chloroplasts by novel mechanisms, suggesting that the mitochondria a nd chloroplast share their genome maintenance apparatus. (2)The MSH1 gene, originating as a component of mismatch repair, has evolved uniquely in plants to participate in differential replication of the mitochondrial genome. (3) This mitochondrial differential replication process, termed substoichiometric shifting and also involving a RecA-related gene, appears to represent an adaptive mechanism to expand plant reproductive capacity and is likely present throughout the plant kingdom.« less

Cord blood-derived CD34+ hematopoietic cells with low mitochondrial mass are enriched in hematopoietic repopulating stem cell function.

PubMed

Romero-Moya, Damia; Bueno, Clara; Montes, Rosa; Navarro-Montero, Oscar; Iborra, Francisco J; López, Luis Carlos; Martin, Miguel; Menendez, Pablo

2013-07-01

The homeostasis of the hematopoietic stem/progenitor cell pool relies on a fine-tuned balance between self-renewal, differentiation and proliferation. Recent studies have proposed that mitochondria regulate these processes. Although recent work has contributed to understanding the role of mitochondria during stem cell differentiation, it remains unclear whether the mitochondrial content/function affects human hematopoietic stem versus progenitor function. We found that mitochondrial mass correlates strongly with mitochondrial membrane potential in CD34(+) hematopoietic stem/progenitor cells. We, therefore, sorted cord blood CD34(+) cells on the basis of their mitochondrial mass and analyzed the in vitro homeostasis and clonogenic potential as well as the in vivo repopulating potential of CD34(+) cells with high (CD34(+) Mito(High)) versus low (CD34(+) Mito(Low)) mitochondrial mass. The CD34(+) Mito(Low) fraction contained 6-fold more CD34(+)CD38(-) primitive cells and was enriched in hematopoietic stem cell function, as demonstrated by its significantly greater hematopoietic reconstitution potential in immuno-deficient mice. In contrast, the CD34(+) Mito(High) fraction was more enriched in hematopoietic progenitor function with higher in vitro clonogenic capacity. In vitro differentiation of CD34(+) Mito(Low) cells was significantly delayed as compared to that of CD34(+) Mito(High) cells. The eventual complete differentiation of CD34(+) Mito(Low) cells, which coincided with a robust expansion of the CD34(-) differentiated progeny, was accompanied by mitochondrial adaptation, as shown by significant increases in ATP production and expression of the mitochondrial genes ND1 and COX2. In conclusion, cord blood CD34(+) cells with low levels of mitochondrial mass are enriched in hematopoietic repopulating stem cell function whereas high levels of mitochondrial mass identify hematopoietic progenitors. A mitochondrial response underlies hematopoietic stem/progenitor cell differentiation and proliferation of lineage-committed CD34(-) cells.

Mitochondrial fission is required for cardiomyocyte hypertrophy mediated by a Ca2+-calcineurin signaling pathway.

PubMed

Pennanen, Christian; Parra, Valentina; López-Crisosto, Camila; Morales, Pablo E; Del Campo, Andrea; Gutierrez, Tomás; Rivera-Mejías, Pablo; Kuzmicic, Jovan; Chiong, Mario; Zorzano, Antonio; Rothermel, Beverly A; Lavandero, Sergio

2014-06-15

Cardiomyocyte hypertrophy has been associated with diminished mitochondrial metabolism. Mitochondria are crucial organelles for the production of ATP, and their morphology and function are regulated by the dynamic processes of fusion and fission. The relationship between mitochondrial dynamics and cardiomyocyte hypertrophy is still poorly understood. Here, we show that treatment of cultured neonatal rat cardiomyocytes with the hypertrophic agonist norepinephrine promotes mitochondrial fission (characterized by a decrease in mitochondrial mean volume and an increase in the relative number of mitochondria per cell) and a decrease in mitochondrial function. We demonstrate that norepinephrine acts through α1-adrenergic receptors to increase cytoplasmic Ca(2+), activating calcineurin and promoting migration of the fission protein Drp1 (encoded by Dnml1) to mitochondria. Dominant-negative Drp1 (K38A) not only prevented mitochondrial fission, it also blocked hypertrophic growth of cardiomyocytes in response to norepinephrine. Remarkably, an antisense adenovirus against the fusion protein Mfn2 (AsMfn2) was sufficient to increase mitochondrial fission and stimulate a hypertrophic response without agonist treatment. Collectively, these results demonstrate the importance of mitochondrial dynamics in the development of cardiomyocyte hypertrophy and metabolic remodeling. © 2014. Published by The Company of Biologists Ltd.

Mitochondrial functions mediate cellulase gene expression in Trichoderma reesei.

PubMed

Abrahão-Neto, J; Rossini, C H; el-Gogary, S; Henrique-Silva, F; Crivellaro, O; el-Dorry, H

1995-08-22

We examined the effects of inhibition of mitochondrial functions on the expression of two nuclear genes encoding the extracellular cellobiohydrolase I (cbh1) and endoglucanase I (egl1) of the cellulase system of the filamentous fungus Trichoderma reesei. The cbh1 and egl1 transcripts are repressed at a low oxygen tension, and by glucose at a concentration known to repress mitochondrial respiration. The transcripts are also down-regulated by chemical agents known to dissipate the proton electrochemical gradient of the inner mitochondrial membrane and blocking of the electron-transport chain, such as DNP and KCN, respectively. These results suggest that expression of those transcripts is influenced by the physiological state of the mitochondria. In addition, heterologous gene fusion shows that the sensitivity of the expression of those transcripts to the functional state of the mitochondria is transcriptionally controlled through the 5'-flanking DNA sequence of those genes.

Mitochondrial dysfunction as a trigger of innate immune responses and inflammation.

PubMed

West, A Phillip

2017-11-01

A growing literature indicates that mitochondria are key participants in innate immune pathways, functioning as both signaling platforms and contributing to effector responses. In addition to regulating antiviral signaling and antibacterial immunity, mitochondria are also important drivers of inflammation caused by sterile injury. Much research on mitochondrial control of immunity now centers on understanding how mitochondrial constituents released during cellular damage simulate the innate immune system. When mitochondrial integrity is compromised, mitochondrial damage-associated molecular patterns engage pattern recognition receptors, trigger inflammation, and promote pathology in an expanding list of diseases. Here, I review the emerging knowledge of mitochondrial dysfunction in innate immune responses and discuss how environmental exposures may induce mitochondrial damage to potentiate inflammation and human disease. Copyright © 2017 Elsevier B.V. All rights reserved.

The E3 ligase Mule protects the heart against oxidative stress and mitochondrial dysfunction through Myc-dependent inactivation of Pgc-1α and Pink1.

PubMed

Dadson, Keith; Hauck, Ludger; Hao, Zhenyue; Grothe, Daniela; Rao, Vivek; Mak, Tak W; Billia, Filio

2017-02-02

Cardiac homeostasis requires proper control of protein turnover. Protein degradation is principally controlled by the Ubiquitin-Proteasome System. Mule is an E3 ubiquitin ligase that regulates cellular growth, DNA repair and apoptosis to maintain normal tissue architecture. However, Mule's function in the heart has yet to be described. In a screen, we found reduced Mule expression in left ventricular samples from end-stage heart failure patients. Consequently, we generated conditional cardiac-specific Mule knockout (Mule  fl/fl(y) ;mcm) mice. Mule ablation in adult Mule  fl/fl(y) ;mcm mice prevented myocardial c-Myc polyubiquitination, leading to c-Myc accumulation and subsequent reduced expression of Pgc-1α, Pink1, and mitochondrial complex proteins. Furthermore, these mice developed spontaneous cardiac hypertrophy, left ventricular dysfunction, and early mortality. Co-deletion of Mule and c-Myc rescued this phenotype. Our data supports an indispensable role for Mule in cardiac homeostasis through the regulation of mitochondrial function via maintenance of Pgc-1α and Pink1 expression and persistent negative regulation of c-Myc.

SIRT3 mediates multi-tissue coupling for metabolic fuel switching.

PubMed

Dittenhafer-Reed, Kristin E; Richards, Alicia L; Fan, Jing; Smallegan, Michael J; Fotuhi Siahpirani, Alireza; Kemmerer, Zachary A; Prolla, Tomas A; Roy, Sushmita; Coon, Joshua J; Denu, John M

2015-04-07

SIRT3 is a member of the Sirtuin family of NAD(+)-dependent deacylases and plays a critical role in metabolic regulation. Organism-wide SIRT3 loss manifests in metabolic alterations; however, the coordinating role of SIRT3 among metabolically distinct tissues is unknown. Using multi-tissue quantitative proteomics comparing fasted wild-type mice to mice lacking SIRT3, innovative bioinformatic analysis, and biochemical validation, we provide a comprehensive view of mitochondrial acetylation and SIRT3 function. We find SIRT3 regulates the acetyl-proteome in core mitochondrial processes common to brain, heart, kidney, liver, and skeletal muscle, but differentially regulates metabolic pathways in fuel-producing and fuel-utilizing tissues. We propose an additional maintenance function for SIRT3 in liver and kidney where SIRT3 expression is elevated to reduce the acetate load on mitochondrial proteins. We provide evidence that SIRT3 impacts ketone body utilization in the brain and reveal a pivotal role for SIRT3 in the coordination between tissues required for metabolic homeostasis. Copyright © 2015 Elsevier Inc. All rights reserved.

Desnutrin/ATGL Activates PPARδ to Promote Mitochondrial Function for Insulin Secretion in Islet β cells

PubMed Central

Tang, Tianyi; Abbott, Marcia J.; Ahmadian, Maryam; Lopes, Andressa B.; Wang, Yuhui; Sul, Hei Sook

2013-01-01

Excessive caloric intake leading to obesity is associated with insulin resistance and dysfuntion of islet β cells. High fat feeding decreases desnutrin (also called ATGL/PNPLA2) levels in islets. Here we show that desnutrin ablation via RIP-Cre (βKO) or RIP-CreER results in hyperglycemia with impaired glucose-stimulated insulin secretion (GSIS). Due to decreased lipolysis, islets have higher TAG content but lower free FA levels. βKO islets exhibit impaired mitochondrial respiration and lower production of ATP required for GSIS, along with decreased expression of PPARδ target genes involved in mitochondrial oxidation. Furthermore, synthetic PPARδ, but not PPARα, agonist restores GSIS and expression of mitochondrial oxidative genes in βKO mice, revealing desnutrin-catalyzed lipolysis generates PPARδ ligands. Finally, adenoviral expression of desnutrin in βKO islets restores all defects of βKO islet phenotype and function including GSIS and mitochondrial defects, demonstrating the critical role of the desnutrin-PPARδ-mitochondrial oxidation axis in regulating islet β cell GSIS. PMID:24268737

Mitochondrial AAA proteases--towards a molecular understanding of membrane-bound proteolytic machines.

PubMed

Gerdes, Florian; Tatsuta, Takashi; Langer, Thomas

2012-01-01

Mitochondrial AAA proteases play an important role in the maintenance of mitochondrial proteostasis. They regulate and promote biogenesis of mitochondrial proteins by acting as processing enzymes and ensuring the selective turnover of misfolded proteins. Impairment of AAA proteases causes pleiotropic defects in various organisms including neurodegeneration in humans. AAA proteases comprise ring-like hexameric complexes in the mitochondrial inner membrane and are functionally conserved from yeast to man, but variations are evident in the subunit composition of orthologous enzymes. Recent structural and biochemical studies revealed how AAA proteases degrade their substrates in an ATP dependent manner. Intersubunit coordination of the ATP hydrolysis leads to an ordered ATP hydrolysis within the AAA ring, which ensures efficient substrate dislocation from the membrane and translocation to the proteolytic chamber. In this review, we summarize recent findings on the molecular mechanisms underlying the versatile functions of mitochondrial AAA proteases and their relevance to those of the other AAA+ machines. Copyright © 2011 Elsevier B.V. All rights reserved.

Uncoupling Protein 2 and Metabolic Diseases

PubMed Central

Sreedhar, Annapoorna; Zhao, Yunfeng

2017-01-01

Mitochondria are fascinating organelles involved in various cellular-metabolic activities that are integral for mammalian development. Although they perform diverse, yet interconnected functions, mitochondria are remarkably regulated by complex signaling networks. Therefore, it is not surprising that mitochondrial dysfunction is involved in plethora of diseases, including neurodegenerative and metabolic disorders. One of the many factors that lead to mitochondrial-associated metabolic diseases is the uncoupling protein-2, a family of mitochondrial anion proteins present in the inner mitochondrial membrane. Since their discovery, uncoupling proteins have attracted considerable attention due to their involvement in mitochondrial-mediated oxidative stress and energy metabolism. This review attempts to provide a summary of recent developments in the field of uncoupling protein 2 relating to mitochondrial associated metabolic diseases. PMID:28351676

Mitochondrial Dynamics in Diabetes

PubMed Central

Galloway, Chad A.; Jhun, Bong Sook; Yu, Tianzheng

2011-01-01

Abstract Mitochondria are at the center of cellular energy metabolism and regulate cell life and death. The cell biological aspect of mitochondria, especially mitochondrial dynamics, has drawn much attention through implications in human pathology, including neurological disorders and metabolic diseases. Mitochondrial fission and fusion are the main processes governing the morphological plasticity and are controlled by multiple factors, including mechanochemical enzymes and accessory proteins. Emerging evidence suggests that mitochondrial dynamics plays an important role in metabolism–secretion coupling in pancreatic β-cells as well as complications of diabetes. This review describes an overview of mechanistic and functional aspects of mitochondrial fission and fusion, and comments on the recent advances connecting mitochondrial dynamics with diabetes and diabetic complications. Antioxid. Redox Signal. 14, 439–457. PMID:20518704

Negative regulation of STAT3 protein-mediated cellular respiration by SIRT1 protein.

PubMed

Bernier, Michel; Paul, Rajib K; Martin-Montalvo, Alejandro; Scheibye-Knudsen, Morten; Song, Shaoming; He, Hua-Jun; Armour, Sean M; Hubbard, Basil P; Bohr, Vilhelm A; Wang, Lili; Zong, Yaping; Sinclair, David A; de Cabo, Rafael

2011-06-03

In mammals, the transcriptional activity of signal transducer and activator of transcription 3 (STAT3) is regulated by the deacetylase SIRT1. However, whether the newly described nongenomic actions of STAT3 toward mitochondrial oxidative phosphorylation are dependent on SIRT1 is unclear. In this study, Sirt1 gene knock-out murine embryonic fibroblast (MEF) cells were used to delineate the role of SIRT1 in the regulation of STAT3 mitochondrial function. Here, we show that STAT3 mRNA and protein levels and the accumulation of serine-phosphorylated STAT3 in mitochondria were increased significantly in Sirt1-KO cells as compared with wild-type MEFs. Various mitochondrial bioenergetic parameters, such as the oxygen consumption rate in cell cultures, enzyme activities of the electron transport chain complexes in isolated mitochondria, and production of ATP and lactate, indicated that Sirt1-KO cells exhibited higher mitochondrial respiration as compared with wild-type MEFs. Two independent approaches, including ectopic expression of SIRT1 and siRNA-mediated knockdown of STAT3, led to reduction in intracellular ATP levels and increased lactate production in Sirt1-KO cells that were approaching those of wild-type controls. Comparison of profiles of phospho-antibody array data indicated that the deletion of SirT1 was accompanied by constitutive activation of the pro-inflammatory NF-κB pathway, which is key for STAT3 induction and increased cellular respiration in Sirt1-KO cells. Thus, SIRT1 appears to be a functional regulator of NF-κB-dependent STAT3 expression that induces mitochondrial biogenesis. These results have implications for understanding the interplay between STAT3 and SIRT1 in pro-inflammatory conditions.

Negative Regulation of STAT3 Protein-mediated Cellular Respiration by SIRT1 Protein*

PubMed Central

Bernier, Michel; Paul, Rajib K.; Martin-Montalvo, Alejandro; Scheibye-Knudsen, Morten; Song, Shaoming; He, Hua-Jun; Armour, Sean M.; Hubbard, Basil P.; Bohr, Vilhelm A.; Wang, Lili; Zong, Yaping; Sinclair, David A.; de Cabo, Rafael

2011-01-01

In mammals, the transcriptional activity of signal transducer and activator of transcription 3 (STAT3) is regulated by the deacetylase SIRT1. However, whether the newly described nongenomic actions of STAT3 toward mitochondrial oxidative phosphorylation are dependent on SIRT1 is unclear. In this study, Sirt1 gene knock-out murine embryonic fibroblast (MEF) cells were used to delineate the role of SIRT1 in the regulation of STAT3 mitochondrial function. Here, we show that STAT3 mRNA and protein levels and the accumulation of serine-phosphorylated STAT3 in mitochondria were increased significantly in Sirt1-KO cells as compared with wild-type MEFs. Various mitochondrial bioenergetic parameters, such as the oxygen consumption rate in cell cultures, enzyme activities of the electron transport chain complexes in isolated mitochondria, and production of ATP and lactate, indicated that Sirt1-KO cells exhibited higher mitochondrial respiration as compared with wild-type MEFs. Two independent approaches, including ectopic expression of SIRT1 and siRNA-mediated knockdown of STAT3, led to reduction in intracellular ATP levels and increased lactate production in Sirt1-KO cells that were approaching those of wild-type controls. Comparison of profiles of phospho-antibody array data indicated that the deletion of SirT1 was accompanied by constitutive activation of the pro-inflammatory NF-κB pathway, which is key for STAT3 induction and increased cellular respiration in Sirt1-KO cells. Thus, SIRT1 appears to be a functional regulator of NF-κB-dependent STAT3 expression that induces mitochondrial biogenesis. These results have implications for understanding the interplay between STAT3 and SIRT1 in pro-inflammatory conditions. PMID:21467030

MitomiRs in human inflamm-aging: a hypothesis involving miR-181a, miR-34a and miR-146a.

PubMed

Rippo, Maria Rita; Olivieri, Fabiola; Monsurrò, Vladia; Prattichizzo, Francesco; Albertini, Maria Cristina; Procopio, Antonio Domenico

2014-08-01

Mitochondria are intimately involved in the aging process. The decline of autophagic clearance during aging affects the equilibrium between mitochondrial fusion and fission, leading to a build-up of dysfunctional mitochondria, oxidative stress, chronic low-grade inflammation, and increased apoptosis rates, the main hallmarks of aging. Current research suggests that a large number of microRNAs (miRs or miRNAs) are differentially expressed during cell aging. Other lines of evidence indicate that several miRs likely share in "inflamm-aging", an aging-related state characterized by systemic chronic inflammation that in turn provides a biological background favoring susceptibility to age-related diseases and disabilities. Interestingly, miRs can modulate mitochondrial activity, and a discrete miR set has recently been identified in mitochondria of different species and cell types (mitomiRs). Here we show that some mitomiRs (let7b, mir-146a, -133b, -106a, -19b, -20a, -34a, -181a and -221) are also among the miRs primarily involved in cell aging and in inflamm-aging. Of note, Ingenuity Pathway Analysis (IPA) of aging-related mitomiR targets has disclosed a number of resident mitochondrial proteins playing large roles in energy metabolism, mitochondrial transport and apoptosis. Among these, Bcl-2 family members--which are critically involved in maintaining mitochondrial integrity--may play a role in controlling mitochondrial function and dysfunction during cellular aging, also considering that Bcl-2, the master member of the family, is an anti-oxidant and anti-apoptotic factor and regulates mitochondrial fission/fusion and autophagy. This intriguing hypothesis is supported by several observations: i) in endothelial cells undergoing replicative senescence (HUVECs), a well-established model of cell senescence, miR-146a, miR-34a, and miR-181a are over-expressed whereas their target Bcl-2 is down-regulated; ii) IPA of the miR-146a, miR-34a and miR-181a network shows that they are closely linked to each other, to Bcl-2 and to mitochondria; and iii) miR-146a, miR-34a, and miR-181a are involved in important cell functions (growth, proliferation, death, survival, maintenance) and age-related diseases (cancer, skeletal and muscle disorders, neurological, cardiovascular and metabolic diseases). In conclusion several aging-related mitomiRs may play a direct role in controlling mitochondrial function by regulating mitochondrial protein expression. Their modulation could thus mediate the loss of mitochondrial integrity and function in aging cells, inducing or contributing to the inflammatory response and to age-related diseases. Copyright © 2014 Elsevier Inc. All rights reserved.

Regulation of thermogenesis in plants: the interaction of alternative oxidase and plant uncoupling mitochondrial protein.

PubMed

Zhu, Yan; Lu, Jianfei; Wang, Jing; Chen, Fu; Leng, Feifan; Li, Hongyu

2011-01-01

Thermogenesis is a process of heat production in living organisms. It is rare in plants, but it does occur in some species of angiosperm. The heat is generated via plant mitochondrial respiration. As possible involvement in thermogenesis of mitochondrial factors, alternative oxidases (AOXs) and plant uncoupling mitochondrial proteins (PUMPs) have been well studied. AOXs and PUMPs are ubiquitously present in the inner membrane of plant mitochondria. They serve as two major energy dissipation systems that balance mitochondrial respiration and uncoupled phosphorylation by dissipating the H+ redox energy and proton electrochemical gradient (ΔμH+) as heat, respectively. AOXs and PUMPs exert similar physiological functions during homeothermic heat production in thermogenic plants. AOXs have five isoforms, while PUMPs have six. Both AOXs and PUMPs are encoded by small nuclear multigene families. Multiple isoforms are expressed in different tissues or organs. Extensive studies have been done in the area of thermogenesis in higher plants. In this review, we focus on the involvement and regulation of AOXs and PUMPs in thermogenesis.

The Impact of Reproductive Technologies on Stallion Mitochondrial Function.

PubMed

Peña, F J; Plaza Davila, M; Ball, B A; Squires, E L; Martin Muñoz, P; Ortega Ferrusola, C; Balao da Silva, C

2015-08-01

The traditional assessment of stallion sperm comprises evaluation of sperm motility and membrane integrity and identification of abnormal morphology of the spermatozoa. More recently, the progressive introduction of flow cytometry is increasing the number of tests available. However, compared with other sperm structures and functions, the evaluation of mitochondria has received less attention in stallion andrology. Recent research indicates that sperm mitochondria are key structures in sperm function suffering major changes during biotechnological procedures such as cryopreservation. In this paper, mitochondrial structure and function will be reviewed in the stallion, when possible specific stallion studies will be discussed, and general findings on mammalian mitochondrial function will be argued when relevant. Especial emphasis will be put on their role as source of reactive oxygen species and in their role regulating sperm lifespan, a possible target to investigate with the aim to improve the quality of frozen-thawed stallion sperm. Later on, the impact of current sperm technologies, principally cryopreservation, on mitochondrial function will be discussed pointing out novel areas of research interest with high potential to improve current sperm technologies. © 2015 Blackwell Verlag GmbH.

Mechanisms by Which Dietary Fatty Acids Regulate Mitochondrial Structure-Function in Health and Disease.

PubMed

Sullivan, E Madison; Pennington, Edward Ross; Green, William D; Beck, Melinda A; Brown, David A; Shaikh, Saame Raza

2018-05-01

Mitochondria are the energy-producing organelles within a cell. Furthermore, mitochondria have a role in maintaining cellular homeostasis and proper calcium concentrations, building critical components of hormones and other signaling molecules, and controlling apoptosis. Structurally, mitochondria are unique because they have 2 membranes that allow for compartmentalization. The composition and molecular organization of these membranes are crucial to the maintenance and function of mitochondria. In this review, we first present a general overview of mitochondrial membrane biochemistry and biophysics followed by the role of different dietary saturated and unsaturated fatty acids in modulating mitochondrial membrane structure-function. We focus extensively on long-chain n-3 (ω-3) polyunsaturated fatty acids and their underlying mechanisms of action. Finally, we discuss implications of understanding molecular mechanisms by which dietary n-3 fatty acids target mitochondrial structure-function in metabolic diseases such as obesity, cardiac-ischemia reperfusion injury, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and select cancers.

Mitochondrial Proteome Studies in Seeds during Germination

PubMed Central

Czarna, Malgorzata; Kolodziejczak, Marta; Janska, Hanna

2016-01-01

Seed germination is considered to be one of the most critical phases in the plant life cycle, establishing the next generation of a plant species. It is an energy-demanding process that requires functioning mitochondria. One of the earliest events of seed germination is progressive development of structurally simple and metabolically quiescent promitochondria into fully active and cristae-containing mitochondria, known as mitochondrial biogenesis. This is a complex and tightly regulated process, which is accompanied by sequential and dynamic gene expression, protein synthesis, and post-translational modifications. The aim of this review is to give a comprehensive summary of seed mitochondrial proteome studies during germination of various plant model organisms. We describe different gel-based and gel-free proteomic approaches used to characterize mitochondrial proteomes of germinating seeds as well as challenges and limitations of these proteomic studies. Furthermore, the dynamic changes in the abundance of the mitochondrial proteomes of germinating seeds are illustrated, highlighting numerous mitochondrial proteins involved in respiration, tricarboxycylic acid (TCA) cycle, metabolism, import, and stress response as potentially important for seed germination. We then review seed mitochondrial protein carbonylation, phosphorylation, and S-nitrosylation as well as discuss the possible link between these post-translational modifications (PTMs) and the regulation of seed germination. PMID:28248229

Mitochondrial Dynamics in Diabetic Cardiomyopathy

PubMed Central

Galloway, Chad A.

2015-01-01

Abstract Significance: Cardiac function is energetically demanding, reliant on efficient well-coupled mitochondria to generate adenosine triphosphate and fulfill the cardiac demand. Predictably then, mitochondrial dysfunction is associated with cardiac pathologies, often related to metabolic disease, most commonly diabetes. Diabetic cardiomyopathy (DCM), characterized by decreased left ventricular function, arises independently of coronary artery disease and atherosclerosis. Dysregulation of Ca2+ handling, metabolic changes, and oxidative stress are observed in DCM, abnormalities reflected in alterations in mitochondrial energetics. Cardiac tissue from DCM patients also presents with altered mitochondrial morphology, suggesting a possible role of mitochondrial dynamics in its pathological progression. Recent Advances: Abnormal mitochondrial morphology is associated with pathologies across diverse tissues, suggesting that this highly regulated process is essential for proper cell maintenance and physiological homeostasis. Highly structured cardiac myofibers were hypothesized to limit alterations in mitochondrial morphology; however, recent work has identified morphological changes in cardiac tissue, specifically in DCM. Critical Issues: Mitochondrial dysfunction has been reported independently from observations of altered mitochondrial morphology in DCM. The temporal relationship and causative nature between functional and morphological changes of mitochondria in the establishment/progression of DCM is unclear. Future Directions: Altered mitochondrial energetics and morphology are not only causal for but also consequential to reactive oxygen species production, hence exacerbating oxidative damage through reciprocal amplification, which is integral to the progression of DCM. Therefore, targeting mitochondria for DCM will require better mechanistic characterization of morphological distortion and bioenergetic dysfunction. Antioxid. Redox Signal. 22, 1545–1562. PMID:25738230

Mitochondrial genome and epigenome: two sides of the same coin.

PubMed

D'Aquila, Patrizia; Montesanto, Alberto; Guarasci, Francesco; Passarino, Giuseppe; Bellizzi, Dina

2017-01-01

The involvement of mitochondrial content, structure and function as well as of the mitochondrial genome (mtDNA) in cell biology, by participating in the main processes occurring in the cells, has been a topic of intense interest for many years. More specifically, the progressive accumulation of variations in mtDNA of post-mitotic tissues represents a major contributing factor to both physiological and pathological phenotypes. Recently, an epigenetic overlay on mtDNA genetics is emerging, as demonstrated by the implication of the mitochondrial genome in the regulation of the intracellular epigenetic landscape being itself object of epigenetic modifications. Indeed, in vitro and population studies strongly suggest that, similarly to nuclear DNA, also mtDNA is subject to methylation and hydroxymethylation. It follows that the mitochondrial-nucleus cross talk and mitochondrial retrograde signaling in cellular properties require a concerted functional cooperation between genetic and epigenetic changes. The present paper aims to review the current advances in mitochondrial epigenetics studies and the increasing indication of mtDNA methylation status as an attractive biomarker for peculiar pathological phenotypes and environmental exposure.

Melatonin and human mitochondrial diseases

PubMed Central

Sharafati-Chaleshtori, Reza; Shirzad, Hedayatollah; Rafieian-Kopaei, Mahmoud; Soltani, Amin

2017-01-01

Mitochondrial dysfunction is one of the main causative factors in a wide variety of complications such as neurodegenerative disorders, ischemia/reperfusion, aging process, and septic shock. Decrease in respiratory complex activity, increase in free radical production, increase in mitochondrial synthase activity, increase in nitric oxide production, and impair in electron transport system and/or mitochondrial permeability are considered as the main factors responsible for mitochondrial dysfunction. Melatonin, the pineal gland hormone, is selectively taken up by mitochondria and acts as a powerful antioxidant, regulating the mitochondrial bioenergetic function. Melatonin increases the permeability of membranes and is the stimulator of antioxidant enzymes including superoxide dismutase, glutathione peroxidase, glutathione reductase, and catalase. It also acts as an inhibitor of lipoxygenase. Melatonin can cause resistance to oxidation damage by fixing the microsomal membranes. Melatonin has been shown to retard aging and inhibit neurodegenerative disorders, ischemia/reperfusion, septic shock, diabetes, cancer, and other complications related to oxidative stress. The purpose of the current study, other than introducing melatonin, was to present the recent findings on clinical effects in diseases related to mitochondrial dysfunction including diabetes, cancer, gastrointestinal diseases, and diseases related to brain function. PMID:28400824

Methane rescues retinal ganglion cells and limits retinal mitochondrial dysfunction following optic nerve crush.

PubMed

Wang, Ruobing; Sun, Qinglei; Xia, Fangzhou; Chen, Zeli; Wu, Jiangchun; Zhang, Yuelu; Xu, Jiajun; Liu, Lin

2017-06-01

Secondary degeneration is a common event in traumatic central nervous system disorders, which involves neuronal apoptosis and mitochondrial dysfunction. Exogenous methane exerts the therapeutic effects in many organ injury. Our study aims to investigate the potential neuroprotection of methane in a rat model of optic nerve crush (ONC). Adult male Sprague-Dawley rats were subjected to ONC and administrated intraperitoneally with methane-saturated or normal saline (10 ml/kg) once per day for one week after ONC. The retinal ganglion cells (RGCs) density was assessed by hematoxylin and eosin staining and Fluoro-Gold retrogradely labeling. Visual function was evaluated by flash visual evoked potentials (FVEP). The retinal apoptosis was measured by terminal-deoxy-transferase-mediated dUTP nick end labeling (TUNEL) assay and the expression of apoptosis-related factors, such as phosphorylated Bcl-2-associated death promoter (pBAD), phosphorylated glycogen synthase kinase-3β (pGSK-3β), Bcl-2 associated X protein (Bax) and Bcl-2 extra large (Bcl-xL). Retinal mitochondrial function was assessed by the mRNA expressions of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM), the mitochondrial DNA (mtDNA) copy number, citrate synthase activity and ATP content. Methane treatment significantly improved the RGC loss and visual dysfunction following ONC. As expected, methane also remarkably inhibited the retinal neural apoptosis, such as the fewer TUNEL-positive cells in ganglion cell layer, accompanied by the up-regulations of anti-apoptotic factors (pGSK-3β, pBAD, Bcl-xL) and the down-regulation of pro-apoptotic factor (Bax). Furthermore, methane treatment suppressed up-regulations of critical mitochondrial components (PGC-1α, NRF1 and TFAM) mRNA and mtDNA copy number, as well as improved the reduction of functional mitochondria markers, including citrate synthase activity and ATP content, in retinas with ONC. Taken together, methane treatment promotes RGC survival and limits retinal mitochondrial dysfunction against ONC insult. Methane can be a potential neuroprotective agent for traumatic and glaucomatous neurodegeneration. Copyright © 2017. Published by Elsevier Ltd.

A Drosophila mutant of LETM1, a candidate gene for seizures in Wolf-Hirschhorn syndrome.

PubMed

McQuibban, Angus G; Joza, Nicholas; Megighian, Aram; Scorzeto, Michele; Zanini, Damiano; Reipert, Siegfried; Richter, Constance; Schweyen, Rudolf J; Nowikovsky, Karin

2010-03-15

Human Wolf-Hirschhorn syndrome (WHS) is a multigenic disorder resulting from a hemizygous deletion on chromosome 4. LETM1 is the best candidate gene for seizures, the strongest haploinsufficiency phenotype of WHS patients. Here, we identify the Drosophila gene CG4589 as the ortholog of LETM1 and name the gene DmLETM1. Using RNA interference approaches in both Drosophila melanogaster cultured cells and the adult fly, we have assayed the effects of down-regulating the LETM1 gene on mitochondrial function. We also show that DmLETM1 complements growth and mitochondrial K(+)/H(+) exchange (KHE) activity in yeast deficient for LETM1. Genetic studies allowing the conditional inactivation of LETM1 function in specific tissues demonstrate that the depletion of DmLETM1 results in roughening of the adult eye, mitochondrial swelling and developmental lethality in third-instar larvae, possibly the result of deregulated mitophagy. Neuronal specific down-regulation of DmLETM1 results in impairment of locomotor behavior in the fly and reduced synaptic neurotransmitter release. Taken together our results demonstrate the function of DmLETM1 as a mitochondrial osmoregulator through its KHE activity and uncover a pathophysiological WHS phenotype in the model organism D. melanogaster.

Voluntary exercise promotes beneficial anti-aging mechanisms in SAMP8 female brain.

PubMed

Bayod, Sergi; Guzmán-Brambila, Carolina; Sanchez-Roige, Sandra; Lalanza, Jaume F; Kaliman, Perla; Ortuño-Sahagun, Daniel; Escorihuela, Rosa M; Pallàs, Mercè

2015-02-01

Regular physical exercise mediates health and longevity promotion involving Sirtuin 1 (SIRT1)-regulated pathways. The anti-aging activity of SIRT1 is achieved, at least in part, by means of fine-tuning the adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway by preventing the transition of an originally pro-survival program into a pro-aging mechanism. Additionally, SIRT1 promotes mitochondrial function and reduces the production of reactive oxygen species (ROS) through regulating peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), the master controller of mitochondrial biogenesis. Here, by using senescence-accelerated mice prone 8 (SAMP8) as a model for aging, we determined the effect of wheel-running as a paradigm for long-term voluntary exercise on SIRT1-AMPK pathway and mitochondrial functionality measured by oxidative phosphorylation (OXPHOS) complex content in the hippocampus and cortex. We found differential activation of SIRT1 in both tissues and hippocampal-specific activation of AMPK. These findings correlated well with significant changes in OXPHOS in the hippocampal, but not in the cerebral cortex, area. Collectively, the results revealed greater benefits of the exercise in the wheel-running intervention in a murine model of senescence, which was directly related with mitochondrial function and which was mediated through the modulation of SIRT1 and AMPK pathways.

Protective Effect of Bendavia (SS-31) Against Oxygen/Glucose-Deprivation Stress-Induced Mitochondrial Damage in Human Brain Microvascular Endothelial Cells.

PubMed

Imai, Takahiko; Mishiro, Keisuke; Takagi, Toshinori; Isono, Aoi; Nagasawa, Hideko; Tsuruma, Kazuhiro; Shimazawa, Masamitsu; Hara, Hideaki

2017-01-01

Mitochondria play a key role in cell survival by perfoming functions such as adenosine tri-phosphate (ATP) synthesis, regulation of apoptotic cell death, calcium storage. Hypoxic conditions induce mitochondrial dysfunction, which leads to endothelial injury in cerebral ischemia. Functional disorders include the following: collapse of mitochondrial membrane potential, reduction of ATP synthesis, and generation of reactive oxygen species (ROS). Bendavia, a novel tetra-peptide, has been reported to restrict the uncoupling of the mitochondrial membrane chain, protect the synthesis of ATP, and inhibit ROS generation. In the present study, we investigated whether bendavia protects mitochondria under hypoxic and starved conditions by using human brain microvascular endothelial cells (HBMVECs). After pre-treatment with bendavia, we exposed HBMVECs to oxygen glucose deprivation (OGD) for 6 h. We then assessed cell viability, the level of caspase-3/7 activity, ROS generation, mitochondrial membrane potential, ATP contents, and the number of mitochondria. Bendavia recovered cell viability and reduced the caspase-3/7 activity induced by OGDinduced damage. Bendavia also recovered mitochondrial functions. These results suggest that bendavia protects mitochondrial function against OGD-induced injury and inhibits apoptosis in HBMVECs. Consequently, our findings indicate that bendavia might become the new therapeutic drug of choice to target mitochondria in case of cerebral ischemia. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Prenatal iron deficiency causes sex-dependent mitochondrial dysfunction and oxidative stress in fetal rat kidneys and liver.

PubMed

Woodman, Andrew G; Mah, Richard; Keddie, Danae; Noble, Ronan M N; Panahi, Sareh; Gragasin, Ferrante S; Lemieux, Hélène; Bourque, Stephane L

2018-06-01

Prenatal iron deficiency alters fetal developmental trajectories, which results in persistent changes in organ function. Here, we studied the effects of prenatal iron deficiency on fetal kidney and liver mitochondrial function. Pregnant Sprague-Dawley rats were fed partially or fully iron-restricted diets to induce a state of moderate or severe iron deficiency alongside iron-replete control rats. We assessed mitochondrial function via high-resolution respirometry and reactive oxygen species generation via fluorescence microscopy on gestational d 21. Hemoglobin levels were reduced in dams in the moderate (-31%) and severe groups (-54%) compared with controls, which was accompanied by 55% reductions in fetal hemoglobin levels in both moderate and severe groups versus controls. Male iron-deficient kidneys exhibited globally reduced mitochondrial content and respiration, as well as increased cytosolic superoxide and decreased NO. Female iron-deficient kidneys exhibited complex II down-regulation and increased mitochondrial oxidative stress. Male iron-deficient livers exhibited reduced complex IV respiration and increased cytosolic superoxide, whereas female liver tissues exhibited no alteration in oxidant levels or mitochondrial function. These findings indicate that prenatal iron deficiency causes changes in mitochondrial content and function as well as oxidant status in a sex- and organ-dependent manner, which may be an important mechanism that underlies the programming of cardiovascular disease.-Woodman, A. G., Mah, R., Keddie, D., Noble, R. M. N., Panahi, S., Gragasin, F. S., Lemieux, H., Bourque, S. L. Prenatal iron deficiency causes sex-dependent mitochondrial dysfunction and oxidative stress in fetal rat kidneys and liver.

Overexpression of DJ-1/PARK7, the Parkinson's disease-related protein, improves mitochondrial function via Akt phosphorylation on threonine 308 in dopaminergic neuron-like cells.

PubMed

Zhang, Yi; Gong, Xiao-Gang; Wang, Zhen-Zhen; Sun, Hong-Mei; Guo, Zhen-Yu; Hu, Jing-Hong; Ma, Ling; Li, Ping; Chen, Nai-Hong

2016-05-01

DJ-1/PARK7, the Parkinson's disease-related protein, plays an important role in mitochondrial function. However, the mechanisms by which DJ-1 affects mitochondrial function are not fully understood. Akt is a promoter of neuron survival and is partly involved in the neurodegenerative process. This research aimed at investigating a possible relationship between DJ-1 and Akt signalling in regulating mitochondrial function in the dopaminergic neuron-like cells SH-SY5Y and PC-12. Overexpression of DJ-1 was firstly validated at both the transcriptional and translational levels after transit transfection with plasmid pcDNA3-Flag-DJ-1. Confocal fluorescence microscopy demonstrated that overexpression of DJ-1 increased the mitochondrial mass, but did not disrupt the mitochondrial morphology. In addition, mitochondrial complex I activity was raised in DJ-1-overexpressing cells, and this rise occurred with an increase in cellular adenosine 5'-triphosphate content. Moreover, immunoblotting demonstrated that the levels of phosphoinositide 3-kinase and the total Akt were not altered in DJ-1-overexpressing cells, and nor was the Akt phosphorylation on serine 473 changed. By contrast, Akt phosphorylation on threonine 308 was significantly augmented by overexpression of DJ-1, and the expression of glycogen synthase kinase-3beta, a downstream effector of Akt, was suppressed. In summary, these results suggest that overexpression of DJ-1 improves the mitochondrial function, at least in part, through a mechanism involving Akt phosphorylation on threonine 308. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Mitochondrial-Nuclear Epistasis: Implications for Human Aging and Longevity

PubMed Central

Tranah, Gregory

2010-01-01

There is substantial evidence that mitochondria are involved in the aging process. Mitochondrial function requires the coordinated expression of hundreds of nuclear genes and a few dozen mitochondrial genes, many of which have been associated with either extended or shortened life span. Impaired mitochondrial function resulting from mtDNA and nuclear DNA variation is likely to contribute to an imbalance in cellular energy homeostasis, increased vulnerability to oxidative stress, and an increased rate of cellular senescence and aging. The complex genetic architecture of mitochondria suggests that there may be an equally complex set of gene interactions (epistases) involving genetic variation in the nuclear and mitochondrial genomes. Results from Drosophila suggest that the effects of mtDNA haplotypes on longevity vary among different nuclear allelic backgrounds, which could account for the inconsistent associations that have been observed between mitochondrial DNA (mtDNA) haplogroups and survival in humans. A diversity of pathways may influence the way mitochondria and nuclear – mitochondrial interactions modulate longevity, including: oxidative phosphorylation; mitochondrial uncoupling; antioxidant defenses; mitochondrial fission and fusion; and sirtuin regulation of mitochondrial genes. We hypothesize that aging and longevity, as complex traits having a significant genetic component, are likely to be controlled by nuclear gene variants interacting with both inherited and somatic mtDNA variability. PMID:20601194

Mitochondrial transport in neurons: impact on synaptic homeostasis and neurodegeneration

PubMed Central

Sheng, Zu-Hang; Cai, Qian

2016-01-01

Mitochondria have a number of essential roles in neuronal function. Their complex mobility patterns within neurons are characterized by frequent changes in direction. Mobile mitochondria can become stationary or pause in regions that have a high metabolic demand and can move again rapidly in response to physiological changes. Defects in mitochondrial transport are implicated in the pathogenesis of several major neurological disorders. Research into the mechanisms that regulate mitochondrial transport is thus an important emerging frontier. PMID:22218207

[Recent progress of mitochondrial quality control in ischemic heart disease and its role in cardio-protection of vagal nerve].

PubMed

Xue, Run-Qing; Xu, Man; Yu, Xiao-Jiang; Liu, Long-Zhu; Zang, Wei-Jin

2017-10-25

Ischemic heart disease (IHD) is the life-threatening cardiovascular disease. Mitochondria have emerged as key participants and regulators of cellular energy demands and signal transduction. Mitochondrial quality is controlled by a number of coordinated mechanisms including mitochondrial fission, fusion and mitophagy, which plays an important role in maintaining healthy mitochondria and cardiac function. Recently, dysfunction of each process in mitochondrial quality control has been observed in the ischemic hearts. This review describes the mechanism of mitochondrial dynamics and mitophagy as well as its performance linked to myocardial ischemia. Moreover, in combination with our study, we will discuss the effect of vagal nerve on mitochondria in cardio-protection.

Cross-Talk Between Mitochondrial Fusion and the Hippo Pathway in Controlling Cell Proliferation During Drosophila Development.

PubMed

Deng, Qiannan; Guo, Ting; Zhou, Xiu; Xi, Yongmei; Yang, Xiaohang; Ge, Wanzhong

2016-08-01

Cell proliferation and tissue growth depend on the coordinated regulation of multiple signaling molecules and pathways during animal development. Previous studies have linked mitochondrial function and the Hippo signaling pathway in growth control. However, the underlying molecular mechanisms are not fully understood. Here we identify a Drosophila mitochondrial inner membrane protein ChChd3 as a novel regulator for tissue growth. Loss of ChChd3 leads to tissue undergrowth and cell proliferation defects. ChChd3 is required for mitochondrial fusion and removal of ChChd3 increases mitochondrial fragmentation. ChChd3 is another mitochondrial target of the Hippo pathway, although it is only partially required for Hippo pathway-mediated overgrowth. Interestingly, lack of ChChd3 leads to inactivation of Hippo activity under normal development, which is also dependent on the transcriptional coactivator Yorkie (Yki). Furthermore, loss of ChChd3 induces oxidative stress and activates the JNK pathway. In addition, depletion of other mitochondrial fusion components, Opa1 or Marf, inactivates the Hippo pathway as well. Taken together, we propose that there is a cross-talk between mitochondrial fusion and the Hippo pathway, which is essential in controlling cell proliferation and tissue homeostasis in Drosophila. Copyright © 2016 by the Genetics Society of America.

The expression pattern and potential functions of PHB in the spermiogenesis of Phascolosoma esculenta.

PubMed

Hou, Cong-Cong; Gao, Xin-Ming; Ni, Jie; Mu, Dan-Li; Yang, Hai-Yan; Liu, Cheng; Zhu, Jun-Quan

2018-04-30

Prohibitin (PHB) is a ubiquitous, evolutionarily conserved protein that is mainly localized in the inner mitochondrial membrane and exerts various mitochondrial functions. Here, we first cloned the phb gene from P. esculenta. The Pe-PHB protein has high homology and a similar protein structure to that of other animals, and it can be divided into the N-terminal hydrophobic/transmembrane domain, SPFH domain, and C-terminal coiled-coil domain. The Pe-phb gene is widely expressed, and the gene expression of phb is highest in coelomic fluid where spermiogenesis occurs, indicating a specific function in the coelom. We further observed continuous expression of the phb gene and localization of PHB proteins in mitochondria during spermiogenesis, indicating that PHB, as a mitochondrial component, may play a role during this process via its mitochondrial function. In addition, ubiquitination of mitochondria was detected, and the PHB signal was co-localized with the poly-ubiquitin signal during spermiogenesis. Mature sperm also showed ubiquitination of mitochondria and PHB. Therefore, PHB may be a substrate of poly-ubiquitin to regulate the ubiquitination of mitochondria and even subsequent elimination during P. esculenta spermiogenesis, and it has a potential role in guaranteeing the maternal inheritance of mitochondria. Taken together, these results support the hypothesis that PHB participates in the spermiogenesis of P. esculenta by maintaining the normal function of mitochondria and regulating the degradation of mitochondria. Copyright © 2018. Published by Elsevier B.V.

Adolescent Binge Alcohol Exposure Affects the Brain Function Through Mitochondrial Impairment.

PubMed

Tapia-Rojas, Cheril; Carvajal, Francisco J; Mira, Rodrigo G; Arce, Camila; Lerma-Cabrera, José Manuel; Orellana, Juan A; Cerpa, Waldo; Quintanilla, Rodrigo A

2018-05-01

In the young population, binge drinking is a pattern of problematic alcohol consumption, characterized by a short period of heavy drinking followed by abstinence which is frequently repeated over time. This drinking pattern is associated with mental problems, use of other drugs, and an increased risk of excessive alcohol intake during adulthood. However, little is known about the effects of binge drinking on brain function in adolescents and its neurobiological impact during the adulthood. In the present study, we evaluated the effects of alcohol on hippocampal memory, synaptic plasticity, and mitochondrial function in adolescent rats after a binge drinking episode in vivo. These effects were analyzed at 1, 3, or 7 weeks post alcohol exposure. Our results showed that binge-like ethanol pre-treated (BEP) rats exhibited early alterations in learning and memory tests accompanied by an impairment of synaptic plasticity that was total and partially compensated, respectively. These changes could be attributed to a rapid increase in oxidative damage and a late inflammatory response induced by post ethanol exposure. Additionally, BEP alters the regulation of mitochondrial dynamics and modifies the expression of mitochondrial permeability transition pore (mPTP) components, such as cyclophilin D (Cyp-D) and the voltage-dependent anion channel (VDAC). These mitochondrial structural changes result in the impairment of mitochondrial bioenergetics, decreasing ATP production progressively until adulthood. These results strongly suggest that teenage alcohol binge drinking impairs the function of the adult hippocampus including memory and synaptic plasticity as a consequence of the mitochondrial damage induced by alcohol and that the recovery of hippocampal function could implicate the activation of alternative pathways that fail to reestablish mitochondrial function.

Parkin and PINK1 function in a vesicular trafficking pathway regulating mitochondrial quality control

PubMed Central

McLelland, Gian-Luca; Soubannier, Vincent; Chen, Carol X; McBride, Heidi M; Fon, Edward A

2014-01-01

Mitochondrial dysfunction has long been associated with Parkinson's disease (PD). Parkin and PINK1, two genes associated with familial PD, have been implicated in the degradation of depolarized mitochondria via autophagy (mitophagy). Here, we describe the involvement of parkin and PINK1 in a vesicular pathway regulating mitochondrial quality control. This pathway is distinct from canonical mitophagy and is triggered by the generation of oxidative stress from within mitochondria. Wild-type but not PD-linked mutant parkin supports the biogenesis of a population of mitochondria-derived vesicles (MDVs), which bud off mitochondria and contain a specific repertoire of cargo proteins. These MDVs require PINK1 expression and ultimately target to lysosomes for degradation. We hypothesize that loss of this parkin- and PINK1-dependent trafficking mechanism impairs the ability of mitochondria to selectively degrade oxidized and damaged proteins leading, over time, to the mitochondrial dysfunction noted in PD. PMID:24446486

Deletion of PRKAA triggers mitochondrial fission by inhibiting the autophagy-dependent degradation of DNM1L.

PubMed

Wang, Qilong; Wu, Shengnan; Zhu, Huaiping; Ding, Ye; Dai, Xiaoyan; Ouyang, Changhan; Han, Young-Min; Xie, Zhonglin; Zou, Ming-Hui

2017-02-01

PRKAA (protein kinase, AMP-activated, α catalytic subunit) regulates mitochondrial biogenesis, function, and turnover. However, the molecular mechanisms by which PRKAA regulates mitochondrial dynamics remain poorly characterized. Here, we report that PRKAA regulated mitochondrial fission via the autophagy-dependent degradation of DNM1L (dynamin 1-like). Deletion of Prkaa1/AMPKα1 or Prkaa2/AMPKα2 resulted in defective autophagy, DNM1L accumulation, and aberrant mitochondrial fragmentation in the mouse aortic endothelium. Furthermore, autophagy inhibition by chloroquine treatment or ATG7 small interfering RNA (siRNA) transfection, upregulated DNM1L expression and triggered DNM1L-mediated mitochondrial fragmentation. In contrast, autophagy activation by overexpression of ATG7 or chronic administration of rapamycin, the MTOR inhibitor, promoted DNM1L degradation and attenuated mitochondrial fragmentation in Prkaa2-deficient (prkaa2 -/- ) mice, suggesting that defective autophagy contributes to enhanced DNM1L expression and mitochondrial fragmentation. Additionally, the autophagic receptor protein SQSTM1/p62, which bound to DNM1L and led to its translocation into the autophagosome, was involved in DNM1L degradation by the autophagy-lysosome pathway. Gene silencing of SQSTM1 markedly reduced the association between SQSTM1 and DNM1L, impaired the degradation of DNM1L, and enhanced mitochondrial fragmentation in PRKAA-deficient endothelial cells. Finally, the genetic (DNM1L siRNA) or pharmacological (mdivi-1) inhibition of DNMA1L ablated mitochondrial fragmentation in the mouse aortic endothelium and prevented the acetylcholine-induced relaxation of isolated mouse aortas. This suggests that aberrant DNM1L is responsible for enhanced mitochondrial fragmentation and endothelial dysfunction in prkaa knockout mice. Overall, our results show that PRKAA deletion promoted mitochondrial fragmentation in vascular endothelial cells by inhibiting the autophagy-dependent degradation of DNM1L.

Resveratrol and the mitochondria: From triggering the intrinsic apoptotic pathway to inducing mitochondrial biogenesis, a mechanistic view.

PubMed

de Oliveira, Marcos Roberto; Nabavi, Seyed Fazel; Manayi, Azadeh; Daglia, Maria; Hajheydari, Zohreh; Nabavi, Seyed Mohammad

2016-04-01

Mitochondria, the power plants of the cell, are known as a cross-road of different cellular signaling pathways. These cytoplasmic double-membraned organelles play a pivotal role in energy metabolism and regulate calcium flux in the cells. It is well known that mitochondrial dysfunction is associated with different diseases such as neurodegeneration and cancer. A growing body of literature has shown that polyphenolic compounds exert direct effects on mitochondrial ultra-structure and function. Resveratrol is known as one of the most common bioactive constituents of red wine, which improves mitochondrial functions under in vitro and in vivo conditions. This paper aims to review the molecular pathways underlying the beneficial effects of resveratrol on mitochondrial structure and functions. In addition, we discuss the chemistry and main sources of resveratrol. Resveratrol represents the promising effects on mitochondria in different experimental models. However, there are several reports on the detrimental effects elicited by resveratrol on mitochondria. An understanding of the chemistry and source of resveratrol, its bioavailability and the promising effects on mitochondria brings a new hope to therapy of mitochondrial dysfunction-related diseases. Copyright © 2016 Elsevier B.V. All rights reserved.

Synergistic interaction of fatty acids and oxysterols impairs mitochondrial function and limits liver adaptation during nafld progression.

PubMed

Bellanti, Francesco; Villani, Rosanna; Tamborra, Rosanna; Blonda, Maria; Iannelli, Giuseppina; di Bello, Giorgia; Facciorusso, Antonio; Poli, Giuseppe; Iuliano, Luigi; Avolio, Carlo; Vendemiale, Gianluigi; Serviddio, Gaetano

2018-05-01

The complete mechanism accounting for the progression from simple steatosis to steatohepatitis in nonalcoholic fatty liver disease (NAFLD) has not been elucidated. Lipotoxicity refers to cellular injury caused by hepatic free fatty acids (FFAs) and cholesterol accumulation. Excess cholesterol autoxidizes to oxysterols during oxidative stress conditions. We hypothesize that interaction of FAs and cholesterol derivatives may primarily impair mitochondrial function and affect biogenesis adaptation during NAFLD progression. We demonstrated that the accumulation of specific non-enzymatic oxysterols in the liver of animals fed high-fat+high-cholesterol diet induces mitochondrial damage and depletion of proteins of the respiratory chain complexes. When tested in vitro, 5α-cholestane-3β,5,6β-triol (triol) combined to FFAs was able to reduce respiration in isolated liver mitochondria, induced apoptosis in primary hepatocytes, and down-regulated transcription factors involved in mitochondrial biogenesis. Finally, a lower protein content in the mitochondrial respiratory chain complexes was observed in human non-alcoholic steatohepatitis. In conclusion, hepatic accumulation of FFAs and non-enzymatic oxysterols synergistically facilitates development and progression of NAFLD by impairing mitochondrial function, energy balance and biogenesis adaptation to chronic injury. Copyright © 2017. Published by Elsevier B.V.

Dual Functions of α-Ketoglutarate Dehydrogenase E2 in the Krebs Cycle and Mitochondrial DNA Inheritance in Trypanosoma brucei

PubMed Central

Sykes, Steven E.

2013-01-01

The dihydrolipoyl succinyltransferase (E2) of the multisubunit α-ketoglutarate dehydrogenase complex (α-KD) is an essential Krebs cycle enzyme commonly found in the matrices of mitochondria. African trypanosomes developmentally regulate mitochondrial carbohydrate metabolism and lack a functional Krebs cycle in the bloodstream of mammals. We found that despite the absence of a functional α-KD, bloodstream form (BF) trypanosomes express α-KDE2, which localized to the mitochondrial matrix and inner membrane. Furthermore, α-KDE2 fractionated with the mitochondrial genome, the kinetoplast DNA (kDNA), in a complex with the flagellum. A role for α-KDE2 in kDNA maintenance was revealed in α-KDE2 RNA interference (RNAi) knockdowns. Following RNAi induction, bloodstream trypanosomes showed pronounced growth reduction and often failed to equally distribute kDNA to daughter cells, resulting in accumulation of cells devoid of kDNA (dyskinetoplastic) or containing two kinetoplasts. Dyskinetoplastic trypanosomes lacked mitochondrial membrane potential and contained mitochondria of substantially reduced volume. These results indicate that α-KDE2 is bifunctional, both as a metabolic enzyme and as a mitochondrial inheritance factor necessary for the distribution of kDNA networks to daughter cells at cytokinesis. PMID:23125353

Dual functions of α-ketoglutarate dehydrogenase E2 in the Krebs cycle and mitochondrial DNA inheritance in Trypanosoma brucei.

PubMed

Sykes, Steven E; Hajduk, Stephen L

2013-01-01

The dihydrolipoyl succinyltransferase (E2) of the multisubunit α-ketoglutarate dehydrogenase complex (α-KD) is an essential Krebs cycle enzyme commonly found in the matrices of mitochondria. African trypanosomes developmentally regulate mitochondrial carbohydrate metabolism and lack a functional Krebs cycle in the bloodstream of mammals. We found that despite the absence of a functional α-KD, bloodstream form (BF) trypanosomes express α-KDE2, which localized to the mitochondrial matrix and inner membrane. Furthermore, α-KDE2 fractionated with the mitochondrial genome, the kinetoplast DNA (kDNA), in a complex with the flagellum. A role for α-KDE2 in kDNA maintenance was revealed in α-KDE2 RNA interference (RNAi) knockdowns. Following RNAi induction, bloodstream trypanosomes showed pronounced growth reduction and often failed to equally distribute kDNA to daughter cells, resulting in accumulation of cells devoid of kDNA (dyskinetoplastic) or containing two kinetoplasts. Dyskinetoplastic trypanosomes lacked mitochondrial membrane potential and contained mitochondria of substantially reduced volume. These results indicate that α-KDE2 is bifunctional, both as a metabolic enzyme and as a mitochondrial inheritance factor necessary for the distribution of kDNA networks to daughter cells at cytokinesis.

Principal Aspects Regarding the Maintenance of Mammalian Mitochondrial Genome Integrity.

PubMed

Vasileiou, Panagiotis V S; Mourouzis, Iordanis; Pantos, Constantinos

2017-08-22

Mitochondria have emerged as key players regarding cellular homeostasis not only due to their contribution regarding energy production through oxidative phosphorylation, but also due to their involvement in signaling, ion regulation, and programmed cell death. Indeed, current knowledge supports the notion that mitochondrial dysfunction is a hallmark in the pathogenesis of various diseases. Mitochondrial biogenesis and function require the coordinated action of two genomes: nuclear and mitochondrial. Unfortunately, both intrinsic and environmental genotoxic insults constantly threaten the integrity of nuclear as well as mitochondrial DNA. Despite the extensive research that has been made regarding nuclear genome instability, the importance of mitochondrial genome integrity has only recently begun to be elucidated. The specific architecture and repair mechanisms of mitochondrial DNA, as well as the dynamic behavior that mitochondria exert regarding fusion, fission, and autophagy participate in mitochondrial genome stability, and therefore, cell homeostasis.

Principal Aspects Regarding the Maintenance of Mammalian Mitochondrial Genome Integrity

PubMed Central

Vasileiou, Panagiotis V. S.; Mourouzis, Iordanis; Pantos, Constantinos

2017-01-01

Mitochondria have emerged as key players regarding cellular homeostasis not only due to their contribution regarding energy production through oxidative phosphorylation, but also due to their involvement in signaling, ion regulation, and programmed cell death. Indeed, current knowledge supports the notion that mitochondrial dysfunction is a hallmark in the pathogenesis of various diseases. Mitochondrial biogenesis and function require the coordinated action of two genomes: nuclear and mitochondrial. Unfortunately, both intrinsic and environmental genotoxic insults constantly threaten the integrity of nuclear as well as mitochondrial DNA. Despite the extensive research that has been made regarding nuclear genome instability, the importance of mitochondrial genome integrity has only recently begun to be elucidated. The specific architecture and repair mechanisms of mitochondrial DNA, as well as the dynamic behavior that mitochondria exert regarding fusion, fission, and autophagy participate in mitochondrial genome stability, and therefore, cell homeostasis. PMID:28829360

Thioredoxin-2 Inhibits Mitochondrial ROS Generation and ASK1 Activity to Maintain Cardiac Function

PubMed Central

Huang, Qunhua; Zhou, Huanjiao Jenny; Zhang, Haifeng; Huang, Yan; Hinojosa-Kirschenbaum, Ford; Fan, Peidong; Yao, Lina; Belardinelli, Luiz; Tellides, George; Giordano, Frank J.; Budas, Grant R.; Min, Wang

2015-01-01

Background Thioredoxin 2 (Trx2) is a key mitochondrial protein which regulates cellular redox and survival by suppressing mitochondrial ROS generation and by inhibiting apoptosis stress kinase-1 (ASK1)-dependent apoptotic signaling. To date, the role of the mitochondrial Trx2 system in heart failure pathogenesis has not been investigated. Methods and Results Western blot and histological analysis revealed that Trx2 protein expression levels were reduced in hearts from patients with dilated cardiomyopathy (DCM), with a concomitant increase in increased ASK1 phosphorylation/activity. Cardiac-specific Trx2 knockout mice (Trx2-cKO). Trx2-cKO mice develop spontaneous DCM at 1 month of age with increased heart size, reduced ventricular wall thickness, and a progressive decline in left ventricular (LV) contractile function, resulting in mortality due to heart failure by ~4 months of age. The progressive decline in cardiac function observed in Trx2-cKO mice was accompanied by disruption of mitochondrial ultrastructure, mitochondrial membrane depolarization, increased mitochondrial ROS generation and reduced ATP production, correlating with increased ASK1 signaling and increased cardiomyocyte apoptosis. Chronic administration of a highly selective ASK1 inhibitor improved cardiac phenotype and reduced maladaptive LV remodeling with significant reductions in oxidative stress, apoptosis, fibrosis and cardiac failure. Cellular data from Trx2-deficient cardiomyocytes demonstrated that ASK1 inhibition reduced apoptosis and reduced mitochondrial ROS generation. Conclusions Our data support an essential role for mitochondrial Trx2 in preserving cardiac function by suppressing mitochondrial ROS production and ASK1-dependent apoptosis. Inhibition of ASK1 represents a promising therapeutic strategy for the treatment of dilated cardiomyopathy and heart failure. PMID:25628390

CypD-mPTP axis regulates mitochondrial functions contributing to osteogenic dysfunction of MC3T3-E1 cells in inflammation.

PubMed

Gan, Xueqi; Zhang, Ling; Liu, Beilei; Zhu, Zhuoli; He, Yuting; Chen, Junsheng; Zhu, Junfei; Yu, Haiyang

2018-04-20

Bone is a dynamic organ, the bone-forming osteoblasts and bone-resorbing osteoclasts form the physiological basis of bone remodeling process. During pathological process of numerous inflammatory diseases, these two aspects are uncoupled and the balance is usually tipped in favor of bone destruction. Evidence suggests that the inflammatory destruction of bone is mainly attributed to oxidative stress and is closely related to mitochondrial dysfunction. The mechanisms underlying osteogenic dysfunction in inflammation still need further investigation. Reactive oxygen species (ROS) is associated with mitochondrial dysfunction and cellular damage. Here, we reported an unexplored role of cyclophilin D (CypD), the major modulator of mitochondrial permeability transition pore (mPTP), and the CypD-mPTP axis in inflammation-induced mitochondrial dysfunction and bone damage. And the protective effects of knocking down CypD by siRNA interference or the addition of cyclosporin A (CsA), an inhibitor of CypD, were evidenced by rescued mitochondrial function and osteogenic function of osteoblast under tumor necrosis factor-α (TNF-α) treatment. These findings provide new insights into the role of CypD-mPTP-dependent mitochondrial pathway in the inflammatory bone injury. The protective effect of CsA or other moleculars affecting the mPTP formation may hold promise as a potential novel therapeutic strategy for inflammation-induced bone damage via mitochondrial pathways.

The effects of mitochondrial genotype on hypoxic survival and gene expression in a hybrid population of the killifish, Fundulus heteroclitus

PubMed Central

Flight, Patrick A.; Nacci, Diane; Champlin, Denise; Whitehead, Andrew; Rand, David M.

2012-01-01

The physiological link between oxygen availability and mitochondrial function is well established. However, whether or not fitness variation is associated with mitochondrial genotypes in the field remains a contested topic in evolutionary biology. In this study we draw on a population of the teleost fish, Fundulus heteroclitus, where functionally distinct subspecies hybridize, likely as a result of past glacial events. We had two specific aims: 1) to determine the effect of mtDNA genotype on survivorship of male and female fish under hypoxic stress; 2) to determine the effect of hypoxic stress, sex and mtDNA genotype on gene expression. We found an unexpected and highly significant effect of sex on survivorship under hypoxic conditions, but no significant effect of mtDNA genotype. Gene expression analyses revealed hundreds of transcripts differentially regulated by sex and hypoxia. Mitochondrial transcripts and other predicted pathways were among those influenced by hypoxic stress, and a transcript corresponding to the mtDNA control region was the most highly suppressed transcript under conditions of hypoxia. An RT-PCR experiment on the control region was consistent with microarray results. Effects of mtDNA sequence variation on genome expression were limited, however a potentially important epistasis between mtDNA sequence and expression of a nuclear-encoded mitochondrial translation protein was discovered. Overall, these results confirm that mitochondrial regulation is a major component of hypoxia tolerance and further suggest that purifying selection has been the predominant selective force on mitochondrial genomes in these two subspecies. PMID:21980951

PDGF-AA-induced filamentous mitochondria benefit dermal papilla cells in cellular migration.

PubMed

Mifude, C; Kaseda, K

2015-06-01

Human dermal papilla cells (HDPCs) play essential roles in hair follicular morphogenesis and postnatal hair growth cycles. Previous reports demonstrated that platelet-derived growth factor-AA (PDGF-AA) enhanced the formation of dermal condensates in hair follicular development. Additionally, PDGF-AA induces/maintains the anagen phase of the hair cycle. It is likely that mitochondrial morphology and functions are tightly coupled with maintenance of these energy-demanding activities. However, little is known about the mitochondrial regulation in HDPCs. Thus, we investigated the PDGF-involved mitochondrial regulation in HDPCs. The mitochondrial morphologies of HDPCs were examined in the presence or absence of PDGF-AA under a fluorescent microscope. ATP production and cellular motility were investigated. The relationship between mitochondrial morphology and the cellular functions was discussed. We observed that primary HDPCs contained mitochondria with filamentous and/or rounded morphologies. Both types of mitochondria showed similar membrane potentials. Interestingly, in the presence of PDGF-AA, but not PDGF-BB, the balance between the two morphologies shifted towards the filamentous form. Concomitantly, both mitochondrial enzymatic activity and total cellular ATP level were augmented by PDGF-AA. These two parameters were closely correlated, suggesting the mitochondrial involvement in the PDGF-augmented ATP production. Moreover, PDGF-AA accelerated the migration of HDPCs in a gap-filling assay, but did not change the rate of cellular proliferation. Notably, filamentous mitochondria dominated migrating HDPCs. PDGF-AA benefits HDPCs in the process of migration, by increasing the number of filamentous mitochondria. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Genistein modulates oxidative stress in breast cancer cell lines according to ERα/ERβ ratio: effects on mitochondrial functionality, sirtuins, uncoupling protein 2 and antioxidant enzymes.

PubMed

Nadal-Serrano, Mercedes; Pons, Daniel Gabriel; Sastre-Serra, Jorge; Blanquer-Rosselló, M del Mar; Roca, Pilar; Oliver, Jordi

2013-09-01

Genistein is a biologically active isoflavone with estrogenic activity and can be found in a variety of soy products. This natural compound displays a wide array of biological activities, but it is best known for its ability to inhibit cancer progression, especially for hormone-related ones such as breast cancer. Genistein has been shown to bind both the estrogen receptor alpha (ERα) and the estrogen receptor beta (ERβ), although it has a higher affinity for the ERβ. The ERα/ERβ ratio is a prognostic marker for breast tumors, and ERβ expression could indicate the presence of tumors more benign in state, whereas ERα indicates malignant tumors. The objective of the present study was to investigate the effects of genistein on oxidative stress and mitochondrial functionality through its interaction with the estrogen receptor in breast cancer cell lines with different ERα/ERβ ratios. The lower ERα/ERβ ratio T47D cell line showed lower oxidative stress and greater mitochondrial functionality, along with an up-regulation of uncoupling protein 2 and sirtuins. On the other hand, genistein-treated MCF-7 cell line, with the highest ERα/ERβ ratio, reported no changes for the control situation. On the whole, our results show different genistein effects depending on ERα/ERβ ratio for oxidative stress regulation, mitochondrial functionality, and modulation of UCPs, antioxidant enzymes and sirtuins in breast cancer cell lines. Effects of genistein on oxidative stress and mitochondria could be due at least in part, to a higher ERβ presence, but could also be due to up-regulation of ERβ caused by the genistein treatment. Copyright © 2013 Elsevier Ltd. All rights reserved.

Regulation of Mitochondrial Structure and Dynamics by the Cytoskeleton and Mechanical Factors.

PubMed

Bartolák-Suki, Erzsébet; Imsirovic, Jasmin; Nishibori, Yuichiro; Krishnan, Ramaswamy; Suki, Béla

2017-08-21

Mitochondria supply cells with energy in the form of ATP, guide apoptosis, and contribute to calcium buffering and reactive oxygen species production. To support these diverse functions, mitochondria form an extensive network with smaller clusters that are able to move along microtubules aided by motor proteins. Mitochondria are also associated with the actin network, which is involved in cellular responses to various mechanical factors. In this review, we discuss mitochondrial structure and function in relation to the cytoskeleton and various mechanical factors influencing cell functions. We first summarize the morphological features of mitochondria with an emphasis on fission and fusion as well as how network properties govern function. We then review the relationship between the mitochondria and the cytoskeletal structures, including mechanical interactions. We also discuss how stretch and its dynamic pattern affect mitochondrial structure and function. Finally, we present preliminary data on how extracellular matrix stiffness influences mitochondrial morphology and ATP generation. We conclude by discussing the more general role that mitochondria may play in mechanobiology and how the mechanosensitivity of mitochondria may contribute to the development of several diseases and aging.

Regulation of Mitochondrial Structure and Dynamics by the Cytoskeleton and Mechanical Factors

PubMed Central

Bartolák-Suki, Erzsébet; Imsirovic, Jasmin; Nishibori, Yuichiro; Krishnan, Ramaswamy; Suki, Béla

2017-01-01

Mitochondria supply cells with energy in the form of ATP, guide apoptosis, and contribute to calcium buffering and reactive oxygen species production. To support these diverse functions, mitochondria form an extensive network with smaller clusters that are able to move along microtubules aided by motor proteins. Mitochondria are also associated with the actin network, which is involved in cellular responses to various mechanical factors. In this review, we discuss mitochondrial structure and function in relation to the cytoskeleton and various mechanical factors influencing cell functions. We first summarize the morphological features of mitochondria with an emphasis on fission and fusion as well as how network properties govern function. We then review the relationship between the mitochondria and the cytoskeletal structures, including mechanical interactions. We also discuss how stretch and its dynamic pattern affect mitochondrial structure and function. Finally, we present preliminary data on how extracellular matrix stiffness influences mitochondrial morphology and ATP generation. We conclude by discussing the more general role that mitochondria may play in mechanobiology and how the mechanosensitivity of mitochondria may contribute to the development of several diseases and aging. PMID:28825689

Specific Sirt1 Activator-mediated Improvement in Glucose Homeostasis Requires Sirt1-Independent Activation of AMPK.

PubMed

Park, Sung-Jun; Ahmad, Faiyaz; Um, Jee-Hyun; Brown, Alexandra L; Xu, Xihui; Kang, Hyeog; Ke, Hengming; Feng, Xuesong; Ryall, James; Philp, Andrew; Schenk, Simon; Kim, Myung K; Sartorelli, Vittorio; Chung, Jay H

2017-04-01

The specific Sirt1 activator SRT1720 increases mitochondrial function in skeletal muscle, presumably by activating Sirt1. However, Sirt1 gain of function does not increase mitochondrial function, which raises a question about the central role of Sirt1 in SRT1720 action. Moreover, it is believed that the metabolic effects of SRT1720 occur independently of AMP-activated protein kinase (AMPK), an important metabolic regulator that increases mitochondrial function. Here, we show that SRT1720 activates AMPK in a Sirt1-independent manner and SRT1720 activates AMPK by inhibiting a cAMP degrading phosphodiesterase (PDE) in a competitive manner. Inhibiting the cAMP effector protein Epac prevents SRT1720 from activating AMPK or Sirt1 in myotubes. Moreover, SRT1720 does not increase mitochondrial function or improve glucose tolerance in AMPKα2 knockout mice. Interestingly, weight loss induced by SRT1720 is not sufficient to improve glucose tolerance. Therefore, contrary to current belief, the metabolic effects produced by SRT1720 require AMPK, which can be activated independently of Sirt1. Published by Elsevier B.V.

Metformin Reduces Hepatic Expression of SIRT3, the Mitochondrial Deacetylase Controlling Energy Metabolism

PubMed Central

Buler, Marcin; Aatsinki, Sanna-Mari; Izzi, Valerio; Hakkola, Jukka

2012-01-01

Metformin inhibits ATP production in mitochondria and this may be involved in the anti-hyperglycemic effects of the drug. Sirtuin 3 (SIRT3) is a mitochondrial protein deacetylase that regulates the function of the electron transport chain and maintains basal ATP yield. We hypothesized that metformin treatment could diminish mitochondrial ATP production through downregulation of SIRT3 expression. Glucagon and cAMP induced SIRT3 mRNA in mouse primary hepatocytes. Metformin prevented SIRT3 induction by glucagon. Moreover, metformin downregulated constitutive expression of SIRT3 in primary hepatocytes and in the liver in vivo. Estrogen related receptor alpha (ERRα) mediates regulation of Sirt3 gene by peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). ERRα mRNA expression was regulated in a similar manner as SIRT3 mRNA by glucagon, cAMP and metformin. However, a higher metformin concentration was required for downregulation of ERRα than SIRT3. ERRα siRNA attenuated PGC-1α mediated induction of SIRT3, but did not affect constitutive expression. Overexpression of the constitutively active form of AMP-activated protein kinase (AMPK) induced SIRT3 mRNA, indicating that the SIRT3 downregulation by metformin is not mediated by AMPK. Metformin reduced the hepatocyte ATP level. This effect was partially counteracted by SIRT3 overexpression. Furthermore, metformin decreased mitochondrial SIRT3 protein levels and this was associated with enhanced acetylation of several mitochondrial proteins. However, metformin increased mitochondrial mass in hepatocytes. Altogether, our results indicate that metformin attenuates mitochondrial expression of SIRT3 and suggest that this mechanism is involved in regulation of energy metabolism by metformin in the liver and may contribute to the therapeutic action of metformin. PMID:23166782

Human mesenchymal stromal cells transplanted into mice stimulate renal tubular cells and enhance mitochondrial function.

PubMed

Perico, Luca; Morigi, Marina; Rota, Cinzia; Breno, Matteo; Mele, Caterina; Noris, Marina; Introna, Martino; Capelli, Chiara; Longaretti, Lorena; Rottoli, Daniela; Conti, Sara; Corna, Daniela; Remuzzi, Giuseppe; Benigni, Ariela

2017-10-17

Mesenchymal stromal cells (MSCs) are renoprotective and drive regeneration following injury, although cellular targets of such an effect are still ill-defined. Here, we show that human umbilical cord (UC)-MSCs transplanted into mice stimulate tubular cells to regain mitochondrial mass and function, associated with enhanced microtubule-rich projections that appear to mediate mitochondrial trafficking to create a reparative dialogue among adjacent tubular cells. Treatment with UC-MSCs in mice with cisplatin-induced acute kidney injury (AKI) regulates mitochondrial biogenesis in proximal tubuli by enhancing PGC1α expression, NAD + biosynthesis and Sirtuin 3 (SIRT3) activity, thus fostering antioxidant defenses and ATP production. The functional role of SIRT3 in tubular recovery is highlighted by data that in SIRT3-deficient mice with AKI, UC-MSC treatment fails to induce renoprotection. These data document a previously unrecognized mechanism through which UC-MSCs facilitate renal repair, so as to induce global metabolic reprogramming of damaged tubular cells to sustain energy supply.Mesenchymal stromal cells drive renal regeneration following injury. Here, the authors show that human mesenchymal stromal cells, when transplanted into mice with acute kidney injury, stimulate renal tubular cell growth and enhance mitochondrial function via SIRT3.

Mitochondrial shaping cuts.

PubMed

Escobar-Henriques, Mafalda; Langer, Thomas

2006-01-01

A broad range of cellular processes are regulated by proteolytic events. Proteolysis has now also been established to control mitochondrial morphology which results from the balanced action of fusion and fission. Two out of three known core components of the mitochondrial fusion machinery are under proteolytic control. The GTPase Fzo1 in the outer membrane of mitochondria is degraded along two independent proteolytic pathways. One controls mitochondrial fusion in vegetatively growing cells, the other one acts upon mating factor-induced cell cycle arrest. Fusion also depends on proteolytic processing of the GTPase Mgm1 by the rhomboid protease Pcp1 in the inner membrane of mitochondria. Functional links of AAA proteases or other proteolytic components to mitochondrial dynamics are just emerging. This review summarises the current understanding of regulatory roles of proteolytic processes for mitochondrial plasticity.

O-GlcNAcase deficiency suppresses skeletal myogenesis and insulin sensitivity in mice through the modulation of mitochondrial homeostasis.

PubMed

Wang, Xun; Feng, Zhihui; Wang, Xueqiang; Yang, Liang; Han, Shujun; Cao, Ke; Xu, Jie; Zhao, Lin; Zhang, Yong; Liu, Jiankang

2016-06-01

O-GlcNAcylation is implicated in modulating mitochondrial function, which is closely involved in regulating muscle metabolism. The presence of O-GlcNAcase (OGA), the enzyme involved in the removal of O-GlcNAc, in mitochondria was recently confirmed in rats. In the present study, we investigated the regulation of myogenesis and muscle insulin sensitivity to OGA in mice, with a focus on mitochondria. C57BL/6J mice fed a high-fat diet for 4 months were used to observe mitochondrial density, activity and O-GlcNAcylation in muscle. Small interfering RNA and overexpression vectors were used to modulate protein content in vitro. High-fat feeding decreased the OGA level and largely increased mitochondrial O-GlcNAcylation in mouse skeletal muscle that was accompanied by decreased levels of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), decreased mitochondrial density and disrupted mitochondrial complex activities. Knockdown of OGA in C2C12 myoblasts promoted PGC-1α degradation, resulting in the suppression of mitochondrial biogenesis and myogenesis, whereas neither knockdown of O-GlcNAc transferase nor overexpression of OGA had significant effects on myogenesis. Mitochondrial dysfunction as evidenced by decreased ATP content and increased reactive oxygen species production, and increased lipid and protein oxidation was observed in both myoblasts and myotubes after OGA knockdown. Meanwhile, elevated O-GlcNAcylation through either OGA knockdown or treatment with the OGA inhibitor PUGNAc and the O-GlcNAc transferase substrate D-GlcNAc suppressed myotube insulin signalling transduction and glucose uptake. OGA overexpression had no significant effect on insulin sensitivity but sufficiently improved the insulin resistance induced by D-GlcNAc treatment. These data suggest that OGA can modulate mitochondrial density via PGC-1α and mitochondrial function via protein O-GlcNAcylation. In this manner, OGA appears to play a key role in myogenesis and the development of muscle insulin resistance.

Acute Mitochondrial Inhibition by Mitogen-activated Protein Kinase/Extracellular Signal-regulated Kinase Kinase (MEK) 1/2 Inhibitors Regulates Proliferation*

PubMed Central

Ripple, Maureen O.; Kim, Namjoon; Springett, Roger

2013-01-01

The Ras-MEK1/2-ERK1/2 kinase signaling pathway regulates proliferation, survival, and differentiation and, because it is often aberrant in tumors, is a popular target for small molecule inhibition. A novel metabolic analysis that measures the real-time oxidation state of NAD(H) and the hemes of the electron transport chain and oxygen consumption within intact, living cells found that structurally distinct MEK1/2 inhibitors had an immediate, dose-dependent effect on mitochondrial metabolism. The inhibitors U0126, MIIC and PD98059 caused NAD(H) reduction, heme oxidation, and decreased oxygen consumption, characteristic of complex I inhibition. PD198306, an orally active MEK1/2 inhibitor, acted as an uncoupler. Each MEK1/2 inhibitor depleted phosphorylated ERK1/2 and inhibited proliferation, but the most robust antiproliferative effects always correlated with the metabolic failure which followed mitochondrial inhibition rather than inhibition of MEK1/2. This warrants rethinking the role of ERK1/2 in proliferation and emphasizes the importance of mitochondrial function in this process. PMID:23235157

Azilsartan, an angiotensin II type 1 receptor blocker, attenuates tert-butyl hydroperoxide-induced endothelial cell injury through inhibition of mitochondrial dysfunction and anti-inflammatory activity.

PubMed

Liu, Hao; Mao, Ping; Wang, Jia; Wang, Tuo; Xie, Chang-Hou

2016-03-01

Angiotensin II type 1 receptor (AT1-R) blockers protect against brain ischemia by mechanisms dependent on and independent of arterial blood pressure. However, the effects of AT1-R blockers on brain endothelial cell injury and detailed mechanisms remain unclear. The goal of this study is to investigate whether azilsartan, an AT1-R blocker, could attenuate oxidative injury in endothelial cells via regulating mitochondrial function and inflammatory responses. We found that treatment with azilsartan suppressed tert-butyl hydroperoxide (t-BHP)-induced oxidative damage in murine brain endothelial cells (mBECs) by increasing cell viability, decreasing lactate dehydrogenase (LDH) release and inhibiting cell apoptosis. Azilsartan significantly inhibited reactive oxygen species (ROS) generation and lipid peroxidation, but had no effect on antioxidant system. We also detected preserved mitochondrial function after azilsartan treatment, as evidenced by increased mitochondrial membrane potential (MMP), reduced cytochrome c release, preserved ATP synthesis and inhibited mitochondrial swelling. In addition, azilsartan differently regulated expression of inflammatory cytokines and increased the activation of endothelial nitric oxide synthase (eNOS). Pretreatment with eNOS inhibitor L-NIO partially prevented the azilsartan-induced regulation of cytokines and protection. Furthermore, azilsartan-induced protection in our in vitro model was shown to be associated with protein stability of peroxisome proliferator-activated receptor-γ (PPAR-γ). Overall, our data suggest that the AT1-R blocker azilsartan may have therapeutic values in treating endothelial dysfunction associated neurological disorders through anti-oxidative and anti-inflammatory properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stomatin-Like Protein 2 Is Required for In Vivo Mitochondrial Respiratory Chain Supercomplex Formation and Optimal Cell Function

PubMed Central

Mitsopoulos, Panagiotis; Chang, Yu-Han; Wai, Timothy; König, Tim; Dunn, Stanley D.; Langer, Thomas

2015-01-01

Stomatin-like protein 2 (SLP-2) is a mainly mitochondrial protein that is widely expressed and is highly conserved across evolution. We have previously shown that SLP-2 binds the mitochondrial lipid cardiolipin and interacts with prohibitin-1 and -2 to form specialized membrane microdomains in the mitochondrial inner membrane, which are associated with optimal mitochondrial respiration. To determine how SLP-2 functions, we performed bioenergetic analysis of primary T cells from T cell-selective Slp-2 knockout mice under conditions that forced energy production to come almost exclusively from oxidative phosphorylation. These cells had a phenotype characterized by increased uncoupled mitochondrial respiration and decreased mitochondrial membrane potential. Since formation of mitochondrial respiratory chain supercomplexes (RCS) may correlate with more efficient electron transfer during oxidative phosphorylation, we hypothesized that the defect in mitochondrial respiration in SLP-2-deficient T cells was due to deficient RCS formation. We found that in the absence of SLP-2, T cells had decreased levels and activities of complex I-III2 and I-III2-IV1-3 RCS but no defects in assembly of individual respiratory complexes. Impaired RCS formation in SLP-2-deficient T cells correlated with significantly delayed T cell proliferation in response to activation under conditions of limiting glycolysis. Altogether, our findings identify SLP-2 as a key regulator of the formation of RCS in vivo and show that these supercomplexes are required for optimal cell function. PMID:25776552

Mitochondrial Approaches to Protect Against Cardiac Ischemia and Reperfusion Injury

PubMed Central

Camara, Amadou K. S.; Bienengraeber, Martin; Stowe, David F.

2011-01-01

The mitochondrion is a vital component in cellular energy metabolism and intracellular signaling processes. Mitochondria are involved in a myriad of complex signaling cascades regulating cell death vs. survival. Importantly, mitochondrial dysfunction and the resulting oxidative and nitrosative stress are central in the pathogenesis of numerous human maladies including cardiovascular diseases, neurodegenerative diseases, diabetes, and retinal diseases, many of which are related. This review will examine the emerging understanding of the role of mitochondria in the etiology and progression of cardiovascular diseases and will explore potential therapeutic benefits of targeting the organelle in attenuating the disease process. Indeed, recent advances in mitochondrial biology have led to selective targeting of drugs designed to modulate or manipulate mitochondrial function, to the use of light therapy directed to the mitochondrial function, and to modification of the mitochondrial genome for potential therapeutic benefit. The approach to rationally treat mitochondrial dysfunction could lead to more effective interventions in cardiovascular diseases that to date have remained elusive. The central premise of this review is that if mitochondrial abnormalities contribute to the etiology of cardiovascular diseases (e.g., ischemic heart disease), alleviating the mitochondrial dysfunction will contribute to mitigating the severity or progression of the disease. To this end, this review will provide an overview of our current understanding of mitochondria function in cardiovascular diseases as well as the potential role for targeting mitochondria with potential drugs or other interventions that lead to protection against cell injury. PMID:21559063

VALSARTAN REGULATES MYOCARDIAL AUTOPHAGY AND MITOCHONDRIAL TURNOVER IN EXPERIMENTAL HYPERTENSION

PubMed Central

Zhang, Xin; Li, Zi-Lun; Crane, John A.; Jordan, Kyra L.; Pawar, Aditya S.; Textor, Stephen C.; Lerman, Amir; Lerman, Lilach O.

2014-01-01

Renovascular hypertension alters cardiac structure and function. Autophagy is activated during left ventricular hypertrophy and linked to adverse cardiac function. The Angiotensin II receptor blocker Valsartan lowers blood pressure and is cardioprotective, but whether it modulates autophagy in the myocardium is unclear. We hypothesized that Valsartan would alleviate autophagy and improve left ventricular myocardial mitochondrial turnover in swine renovascular hypertension. Domestic pigs were randomized to control, unilateral renovascular hypertension, and renovascular hypertension treated with Valsartan (320 mg/day) or conventional triple therapy (Reserpine+hydralazine+hydrochlorothiazide) for 4 weeks post 6-weeks of renovascular hypertension (n=7 each group). Left ventricular remodeling, function and myocardial oxygenation and microcirculation were assessed by multi-detector computer tomography, blood-oxygen-level-dependent magnetic resonance imaging and microcomputer tomography. Myocardial autophagy, markers for mitochondrial degradation and biogenesis, and mitochondrial respiratory-chain proteins were examined ex vivo. Renovascular hypertension induced left ventricular hypertrophy and myocardial hypoxia, enhanced cellular autophagy and mitochondrial degradation, and suppressed mitochondrial biogenesis. Valsartan and triple therapy similarly decreased blood pressure, but Valsartan solely alleviated left ventricular hypertrophy, ameliorated myocardial autophagy and mitophagy, and increased mitochondrial biogenesis. In contrast, triple therapy only slightly attenuated autophagy and preserved mitochondrial proteins, but elicited no improvement in mitophagy. These data suggest a novel potential role of Valsartan in modulating myocardial autophagy and mitochondrial turnover in renovascular hypertension-induced hypertensive heart disease, which may possibly bolster cardiac repair via a blood pressure-independent manner. PMID:24752430

Unchanged mitochondrial organization and compartmentation of high-energy phosphates in creatine-deficient GAMT−/− mouse hearts

PubMed Central

Branovets, Jelena; Sepp, Mervi; Kotlyarova, Svetlana; Jepihhina, Natalja; Sokolova, Niina; Aksentijevic, Dunja; Lygate, Craig A.; Neubauer, Stefan; Birkedal, Rikke

2013-01-01

Disruption of the creatine kinase (CK) system in hearts of CK-deficient mice leads to changes in the ultrastructure and regulation of mitochondrial respiration. We expected to see similar changes in creatine-deficient mice, which lack the enzyme guanidinoacetate methyltransferase (GAMT) to produce creatine. The aim of this study was to characterize the changes in cardiomyocyte mitochondrial organization, regulation of respiration, and intracellular compartmentation associated with GAMT deficiency. Three-dimensional mitochondrial organization was assessed by confocal microscopy. On populations of permeabilized cardiomyocytes, we recorded ADP and ATP kinetics of respiration, competition between mitochondria and pyruvate kinase for ADP produced by ATPases, ADP kinetics of endogenous pyruvate kinase, and ATP kinetics of ATPases. These data were analyzed by mathematical models to estimate intracellular compartmentation. Quantitative analysis of morphological and kinetic data as well as derived model fits showed no difference between GAMT-deficient and wild-type mice. We conclude that inactivation of the CK system by GAMT deficiency does not alter mitochondrial organization and intracellular compartmentation in relaxed cardiomyocytes. Thus, our results suggest that the healthy heart is able to preserve cardiac function at a basal level in the absence of CK-facilitated energy transfer without compromising intracellular organization and the regulation of mitochondrial energy homeostasis. This raises questions on the importance of the CK system as a spatial energy buffer in unstressed cardiomyocytes. PMID:23792673

Mitochondrial Regulation of Cell Cycle and Proliferation

PubMed Central

Antico Arciuch, Valeria Gabriela; Elguero, María Eugenia; Poderoso, Juan José

2012-01-01

Abstract Eukaryotic mitochondria resulted from symbiotic incorporation of α-proteobacteria into ancient archaea species. During evolution, mitochondria lost most of the prokaryotic bacterial genes and only conserved a small fraction including those encoding 13 proteins of the respiratory chain. In this process, many functions were transferred to the host cells, but mitochondria gained a central role in the regulation of cell proliferation and apoptosis, and in the modulation of metabolism; accordingly, defective organelles contribute to cell transformation and cancer, diabetes, and neurodegenerative diseases. Most cell and transcriptional effects of mitochondria depend on the modulation of respiratory rate and on the production of hydrogen peroxide released into the cytosol. The mitochondrial oxidative rate has to remain depressed for cell proliferation; even in the presence of O2, energy is preferentially obtained from increased glycolysis (Warburg effect). In response to stress signals, traffic of pro- and antiapoptotic mitochondrial proteins in the intermembrane space (B-cell lymphoma-extra large, Bcl-2-associated death promoter, Bcl-2 associated X-protein and cytochrome c) is modulated by the redox condition determined by mitochondrial O2 utilization and mitochondrial nitric oxide metabolism. In this article, we highlight the traffic of the different canonical signaling pathways to mitochondria and the contributions of organelles to redox regulation of kinases. Finally, we analyze the dynamics of the mitochondrial population in cell cycle and apoptosis. Antioxid. Redox Signal. 16, 1150–1180. PMID:21967640

Effects of exercise on obesity-induced mitochondrial dysfunction in skeletal muscle

PubMed Central

Heo, Jun-Won; No, Mi-Hyun; Park, Dong-Ho; Kang, Ju-Hee; Seo, Dae Yun; Han, Jin; Neufer, P. Darrell

2017-01-01

Obesity is known to induce inhibition of glucose uptake, reduction of lipid metabolism, and progressive loss of skeletal muscle function, which are all associated with mitochondrial dysfunction in skeletal muscle. Mitochondria are dynamic organelles that regulate cellular metabolism and bioenergetics, including ATP production via oxidative phosphorylation. Due to these critical roles of mitochondria, mitochondrial dysfunction results in various diseases such as obesity and type 2 diabetes. Obesity is associated with impairment of mitochondrial function (e.g., decrease in O2 respiration and increase in oxidative stress) in skeletal muscle. The balance between mitochondrial fusion and fission is critical to maintain mitochondrial homeostasis in skeletal muscle. Obesity impairs mitochondrial dynamics, leading to an unbalance between fusion and fission by favorably shifting fission or reducing fusion proteins. Mitophagy is the catabolic process of damaged or unnecessary mitochondria. Obesity reduces mitochondrial biogenesis in skeletal muscle and increases accumulation of dysfunctional cellular organelles, suggesting that mitophagy does not work properly in obesity. Mitochondrial dysfunction and oxidative stress are reported to trigger apoptosis, and mitochondrial apoptosis is induced by obesity in skeletal muscle. It is well known that exercise is the most effective intervention to protect against obesity. Although the cellular and molecular mechanisms by which exercise protects against obesity-induced mitochondrial dysfunction in skeletal muscle are not clearly elucidated, exercise training attenuates mitochondrial dysfunction, allows mitochondria to maintain the balance between mitochondrial dynamics and mitophagy, and reduces apoptotic signaling in obese skeletal muscle. PMID:29200899

Hyperoxia activates ATM independent from mitochondrial ROS and dysfunction.

PubMed

Resseguie, Emily A; Staversky, Rhonda J; Brookes, Paul S; O'Reilly, Michael A

2015-08-01

High levels of oxygen (hyperoxia) are often used to treat individuals with respiratory distress, yet prolonged hyperoxia causes mitochondrial dysfunction and excessive reactive oxygen species (ROS) that can damage molecules such as DNA. Ataxia telangiectasia mutated (ATM) kinase is activated by nuclear DNA double strand breaks and delays hyperoxia-induced cell death through downstream targets p53 and p21. Evidence for its role in regulating mitochondrial function is emerging, yet it has not been determined if mitochondrial dysfunction or ROS activates ATM. Because ATM maintains mitochondrial homeostasis, we hypothesized that hyperoxia induces both mitochondrial dysfunction and ROS that activate ATM. In A549 lung epithelial cells, hyperoxia decreased mitochondrial respiratory reserve capacity at 12h and basal respiration by 48 h. ROS were significantly increased at 24h, yet mitochondrial DNA double strand breaks were not detected. ATM was not required for activating p53 when mitochondrial respiration was inhibited by chronic exposure to antimycin A. Also, ATM was not further activated by mitochondrial ROS, which were enhanced by depleting manganese superoxide dismutase (SOD2). In contrast, ATM dampened the accumulation of mitochondrial ROS during exposure to hyperoxia. Our findings suggest that hyperoxia-induced mitochondrial dysfunction and ROS do not activate ATM. ATM more likely carries out its canonical response to nuclear DNA damage and may function to attenuate mitochondrial ROS that contribute to oxygen toxicity. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Mitochondrial Ceramide-Rich Macrodomains Functionalize Bax upon Irradiation

PubMed Central

Lee, Hyunmi; Rotolo, Jimmy A.; Mesicek, Judith; Penate-Medina, Tuula; Rimner, Andreas; Liao, Wen-Chieh; Yin, Xianglei; Ragupathi, Govind; Ehleiter, Desiree; Gulbins, Erich; Zhai, Dayong; Reed, John C.; Haimovitz-Friedman, Adriana; Fuks, Zvi; Kolesnick, Richard

2011-01-01

Background Evidence indicates that Bax functions as a “lipidic” pore to regulate mitochondrial outer membrane permeabilization (MOMP), the apoptosis commitment step, through unknown membrane elements. Here we show mitochondrial ceramide elevation facilitates MOMP-mediated cytochrome c release in HeLa cells by generating a previously-unrecognized mitochondrial ceramide-rich macrodomain (MCRM), which we visualize and isolate, into which Bax integrates. Methodology/Principal Findings MCRMs, virtually non-existent in resting cells, form upon irradiation coupled to ceramide synthase-mediated ceramide elevation, optimizing Bax insertion/oligomerization and MOMP. MCRMs are detected by confocal microscopy in intact HeLa cells and isolated biophysically as a light membrane fraction from HeLa cell lysates. Inhibiting ceramide generation using a well-defined natural ceramide synthase inhibitor, Fumonisin B1, prevented radiation-induced Bax insertion, oligomerization and MOMP. MCRM deconstruction using purified mouse hepatic mitochondria revealed ceramide alone is non-apoptogenic. Rather Bax integrates into MCRMs, oligomerizing therein, conferring 1–2 log enhanced cytochrome c release. Consistent with this mechanism, MCRM Bax isolates as high molecular weight “pore-forming” oligomers, while non-MCRM membrane contains exclusively MOMP-incompatible monomeric Bax. Conclusions/Significance Our recent studies in the C. elegans germline indicate that mitochondrial ceramide generation is obligate for radiation-induced apoptosis, although a mechanism for ceramide action was not delineated. Here we demonstrate that ceramide, generated in the mitochondrial outer membrane of mammalian cells upon irradiation, forms a platform into which Bax inserts, oligomerizes and functionalizes as a pore. We posit conceptualization of ceramide as a membrane-based stress calibrator, driving membrane macrodomain organization, which in mitochondria regulates intensity of Bax-induced MOMP, and is pharmacologically tractable in vitro and in vivo. PMID:21695182

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagland, Hanne R.; Nilsson, Linn I.H.; Burri, Lena

Highlights: Black-Right-Pointing-Pointer We investigated mechanisms of mitochondrial regulation in rat hepatocytes. Black-Right-Pointing-Pointer Tetradecylthioacetic acid (TTA) was employed to activate mitochondrial oxidation. Black-Right-Pointing-Pointer Mitochondrial biogenesis and respiration were induced. Black-Right-Pointing-Pointer It was confirmed that PPAR target genes were induced. Black-Right-Pointing-Pointer The mechanism involved activation mTOR. -- Abstract: The hypolipidemic effect of peroxisome proliferator-activated receptor (PPAR) activators has been explained by increasing mitochondrial fatty acid oxidation, as observed in livers of rats treated with the pan-PPAR activator tetradecylthioacetic acid (TTA). PPAR-activation does, however, not fully explain the metabolic adaptations observed in hepatocytes after treatment with TTA. We therefore characterized the mitochondrial effects,more » and linked this to signalling by the metabolic sensor, the mammalian target of rapamycin (mTOR). In hepatocytes isolated from TTA-treated rats, the changes in cellular content and morphology were consistent with hypertrophy. This was associated with induction of multiple mitochondrial biomarkers, including mitochondrial DNA, citrate synthase and mRNAs of mitochondrial proteins. Transcription analysis further confirmed activation of PPAR{alpha}-associated genes, in addition to genes related to mitochondrial biogenesis and function. Analysis of mitochondrial respiration revealed that the capacity of both electron transport and oxidative phosphorylation were increased. These effects coincided with activation of the stress related factor, ERK1/2, and mTOR. The protein level and phosphorylation of the downstream mTOR actors eIF4G and 4E-BP1 were induced. In summary, TTA increases mitochondrial respiration by inducing hypertrophy and mitochondrial biogenesis in rat hepatocytes, via adaptive regulation of PPARs as well as mTOR.« less

Mitochondrial targeting of HIF-1α inhibits hypoxia-induced apoptosis independently of its transcriptional activity.

PubMed

Li, Hong-Sheng; Zhou, Yan-Ni; Li, Lu; Li, Sheng-Fu; Long, Dan; Chen, Xue-Lu; Zhang, Jia-Bi; Li, You-Ping; Feng, Li

2018-04-25

The transcription factor hypoxia inducible factor-1α (HIF-1α) mediates adaptive responses to hypoxia by nuclear translocation and regulation of gene expression. Mitochondrial changes are critical for the adaptive response to hypoxia. However, the transcriptional and non-transcriptional mechanisms by which HIF-1α regulates mitochondria under hypoxia are poorly understood. Here, we examined the subcellular localization of HIF-1α in human cells and identified a small fraction of HIF-1α that translocated to the mitochondria after exposure to hypoxia or hypoxia-mimicking pharmacological agents. To probe the function of this HIF-1α population, we ectopically expressed a mitochondrial-targeted form of HIF-1α (mito-HIF-1α). Expression of mito-HIF-1α was sufficient to attenuate apoptosis induced by exposure to hypoxia or H 2 O 2 -induced oxidative stress. Moreover, mito-HIF-1α expression reduced the production of reactive oxygen species, the collapse of mitochondrial membrane potential, and the expression of mitochondrial DNA-encoded mRNA in response to hypoxia. However, these functions of mito-HIF-1α were independent of its conventional transcriptional activity. Finally, the livers of mice with CCl 4 -induced fibrosis showed a progressive increase in HIF-1α association with the mitochondria, indicating the clinical relevance of this finding. These data suggested that mitochondrial HIF-1α protects against apoptosis independently of its well-known role as a transcription factor. Copyright © 2018. Published by Elsevier Inc.

Azoxystrobin, a mitochondrial complex III Qo site inhibitor, exerts beneficial metabolic effects in vivo and in vitro.

PubMed

Gao, An-Hui; Fu, Yan-Yun; Zhang, Kun-Zhi; Zhang, Mei; Jiang, Hao-Wen; Fan, Li-Xia; Nan, Fa-Jun; Yuan, Chong-Gang; Li, Jia; Zhou, Yu-Bo; Li, Jing-Ya

2014-07-01

Several anti-diabetes drugs exert beneficial effects against metabolic syndrome by inhibiting mitochondrial function. Although much progress has been made toward understanding the role of mitochondrial function inhibitors in treating metabolic diseases, the potential effects of these inhibitors on mitochondrial respiratory chain complex III remain unclear. We investigated the metabolic effects of azoxystrobin (AZOX), a Qo inhibitor of complex III, in a high-fat diet-fed mouse model with insulin resistance in order to elucidate the mechanism by which AZOX improves glucose and lipid metabolism at the metabolic cellular level. Acute administration of AZOX in mice increased the respiratory exchange ratio. Chronic treatment with AZOX reduced body weight and significantly improved glucose tolerance and insulin sensitivity in high-fat diet-fed mice. AZOX treatment resulted in decreased triacylglycerol accumulation and down-regulated the expression of genes involved in liver lipogenesis. AZOX increased glucose uptake in L6 myotubes and 3T3-L1 adipocytes and inhibited de novo lipogenesis in HepG2 cells. The findings indicate that AZOX-mediated alterations to lipid and glucose metabolism may depend on AMP-activated protein kinase (AMPK) signaling. AZOX, a Qo inhibitor of mitochondrial respiratory complex III, exerts whole-body beneficial effects on the regulation of glucose and lipid homeostasis in high-fat diet-fed mice. These findings provide evidence that a Qo inhibitor of mitochondrial respiratory complex III could represent a novel approach for the treatment of obesity. Copyright © 2014 Elsevier B.V. All rights reserved.

Application of the principles of systems biology and Wiener's cybernetics for analysis of regulation of energy fluxes in muscle cells in vivo.

PubMed

Guzun, Rita; Saks, Valdur

2010-03-08

The mechanisms of regulation of respiration and energy fluxes in the cells are analyzed based on the concepts of systems biology, non-equilibrium steady state kinetics and applications of Wiener's cybernetic principles of feedback regulation. Under physiological conditions cardiac function is governed by the Frank-Starling law and the main metabolic characteristic of cardiac muscle cells is metabolic homeostasis, when both workload and respiration rate can be changed manifold at constant intracellular level of phosphocreatine and ATP in the cells. This is not observed in skeletal muscles. Controversies in theoretical explanations of these observations are analyzed. Experimental studies of permeabilized fibers from human skeletal muscle vastus lateralis and adult rat cardiomyocytes showed that the respiration rate is always an apparent hyperbolic but not a sigmoid function of ADP concentration. It is our conclusion that realistic explanations of regulation of energy fluxes in muscle cells require systemic approaches including application of the feedback theory of Wiener's cybernetics in combination with detailed experimental research. Such an analysis reveals the importance of limited permeability of mitochondrial outer membrane for ADP due to interactions of mitochondria with cytoskeleton resulting in quasi-linear dependence of respiration rate on amplitude of cyclic changes in cytoplasmic ADP concentrations. The system of compartmentalized creatine kinase (CK) isoenzymes functionally coupled to ANT and ATPases, and mitochondrial-cytoskeletal interactions separate energy fluxes (mass and energy transfer) from signalling (information transfer) within dissipative metabolic structures - intracellular energetic units (ICEU). Due to the non-equilibrium state of CK reactions, intracellular ATP utilization and mitochondrial ATP regeneration are interconnected by the PCr flux from mitochondria. The feedback regulation of respiration occurring via cyclic fluctuations of cytosolic ADP, Pi and Cr/PCr ensures metabolic stability necessary for normal function of cardiac cells.

The L‐type Ca2+ channel facilitates abnormal metabolic activity in the cTnI‐G203S mouse model of hypertrophic cardiomyopathy

PubMed Central

Viola, Helena; Johnstone, Victoria; Cserne Szappanos, Henrietta; Richman, Tara; Tsoutsman, Tatiana; Filipovska, Aleksandra; Semsarian, Christopher

2016-01-01

Key points Genetic mutations in cardiac troponin I (cTnI) are associated with development of hypertrophic cardiomyopathy characterized by myocyte remodelling, disorganization of cytoskeletal proteins and altered energy metabolism.The L‐type Ca2+ channel is the main route for calcium influx and is crucial to cardiac excitation and contraction. The channel also regulates mitochondrial function in the heart by a functional communication between the channel and mitochondria via the cytoskeletal network.We find that L‐type Ca2+ channel kinetics are altered in cTnI‐G203S cardiac myocytes and that activation of the channel causes a significantly greater increase in mitochondrial membrane potential and metabolic activity in cTnI‐G203S cardiac myocytes.These responses occur as a result of impaired communication between the L‐type Ca2+ channel and cytoskeletal protein F‐actin, involving decreased movement of actin–myosin and block of the mitochondrial voltage‐dependent anion channel, resulting in a ‘hypermetabolic’ mitochondrial state.We propose that L‐type Ca2+ channel antagonists, such as diltiazem, might be effective in reducing the cardiomyopathy by normalizing mitochondrial metabolic activity. Abstract Genetic mutations in cardiac troponin I (cTnI) account for 5% of families with hypertrophic cardiomyopathy. Hypertrophic cardiomyopathy is associated with disorganization of cytoskeletal proteins and altered energy metabolism. The L‐type Ca2+ channel (ICa‐L) plays an important role in regulating mitochondrial function. This involves a functional communication between the channel and mitochondria via the cytoskeletal network. We investigate the role of ICa‐L in regulating mitochondrial function in 25‐ to 30‐week‐old cardiomyopathic mice expressing the human disease‐causing mutation Gly203Ser in cTnI (cTnI‐G203S). The inactivation rate of ICa‐L is significantly faster in cTnI‐G203S myocytes [cTnI‐G203S: τ1 = 40.68 ± 3.22, n = 10 vs. wild‐type (wt): τ1 = 59.05 ± 6.40, n = 6, P < 0.05]. Activation of ICa‐L caused a greater increase in mitochondrial membrane potential (Ψm, 29.19 ± 1.85%, n = 15 vs. wt: 18.84 ± 2.01%, n = 10, P < 0.05) and metabolic activity (24.40 ± 6.46%, n = 8 vs. wt: 9.98 ± 1.57%, n = 9, P < 0.05). The responses occurred because of impaired communication between ICa‐L and F‐actin, involving lack of dynamic movement of actin–myosin and block of the mitochondrial voltage‐dependent anion channel. Similar responses were observed in precardiomyopathic mice. ICa‐L antagonists nisoldipine and diltiazem decreased Ψm to basal levels. We conclude that the Gly203Ser mutation leads to impaired functional communication between ICa‐L and mitochondria, resulting in a ‘hypermetabolic’ state. This might contribute to development of cTnI‐G203S cardiomyopathy because the response is present in young precardiomyopathic mice. ICa‐L antagonists might be effective in reducing the cardiomyopathy by altering mitochondrial function. PMID:27062056

Metabolic Plasticity in Cancer Cells: Reconnecting Mitochondrial Function to Cancer Control

PubMed Central

Ramanujan, V. Krishnan

2015-01-01

Anomalous increase in glycolytic activity defines one of the key metabolic alterations in cancer cells. A realization of this feature has led to critical advancements in cancer detection techniques such as positron emission tomography (PET) as well as a number of therapeutic avenues targeting the key glycolytic steps within a cancer cell. A normal healthy cell’s survival relies on a sensitive balance between the primordial glycolysis and a more regulated mitochondrial bioenergetics. The salient difference between these two bioenergetics pathways is that oxygen availability is an obligatory requirement for mitochondrial pathway while glycolysis can function without oxygen. Early observations that some cancer cells up-regulate glycolytic activity even in the presence of oxygen (aerobic glycolysis) led to a hypothesis that such an altered cancer cell metabolism stems from inherent mitochondrial dysfunction. While a general validity of this hypothesis is still being debated, a number of recent research efforts have yielded clarity on the physiological origins of this aerobic glycolysis phenotype in cancer cells. Building on these recent studies, we present a generalized scheme of cancer cell metabolism and propose a novel hypothesis that might rationalize new avenues of cancer intervention. PMID:26457230

14,15-EET promotes mitochondrial biogenesis and protects cortical neurons against oxygen/glucose deprivation-induced apoptosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lai; Chen, Man; Yuan, Lin

2014-07-18

Highlights: • 14,15-EET inhibits OGD-induced apoptosis in cortical neurons. • Mitochondrial biogenesis of cortical neurons is promoted by 14,15-EET. • 14,15-EET preserves mitochondrial function of cortical neurons under OGD. • CREB mediates effect of 14,15-EET on mitochondrial biogenesis and function. - Abstract: 14,15-Epoxyeicosatrienoic acid (14,15-EET), a metabolite of arachidonic acid, is enriched in the brain cortex and exerts protective effect against neuronal apoptosis induced by ischemia/reperfusion. Although apoptosis has been well recognized to be closely associated with mitochondrial biogenesis and function, it is still unclear whether the neuroprotective effect of 14,15-EET is mediated by promotion of mitochondrial biogenesis and functionmore » in cortical neurons under the condition of oxygen–glucose deprivation (OGD). In this study, we found that 14,15-EET improved cell viability and inhibited apoptosis of cortical neurons. 14,15-EET significantly increased the mitochondrial mass and the ratio of mitochondrial DNA to nuclear DNA. Key makers of mitochondrial biogenesis, peroxisome proliferator activator receptor gamma-coactivator 1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (TFAM), were elevated at both mRNA and protein levels in the cortical neurons treated with 14,15-EET. Moreover, 14,15-EET markedly attenuated the decline of mitochondrial membrane potential, reduced ROS, while increased ATP synthesis. Knockdown of cAMP-response element binding protein (CREB) by siRNA blunted the up-regulation of PGC-1α and NRF-1 stimulated by 14,15-EET, and consequently abolished the neuroprotective effect of 14,15-EET. Our results indicate that 14,15-EET protects neurons from OGD-induced apoptosis by promoting mitochondrial biogenesis and function through CREB mediated activation of PGC-1α and NRF-1.« less

Mitochondrial Chaperones in the Brain: Safeguarding Brain Health and Metabolism?

PubMed

Castro, José Pedro; Wardelmann, Kristina; Grune, Tilman; Kleinridders, André

2018-01-01

The brain orchestrates organ function and regulates whole body metabolism by the concerted action of neurons and glia cells in the central nervous system. To do so, the brain has tremendously high energy consumption and relies mainly on glucose utilization and mitochondrial function in order to exert its function. As a consequence of high rate metabolism, mitochondria in the brain accumulate errors over time, such as mitochondrial DNA (mtDNA) mutations, reactive oxygen species, and misfolded and aggregated proteins. Thus, mitochondria need to employ specific mechanisms to avoid or ameliorate the rise of damaged proteins that contribute to aberrant mitochondrial function and oxidative stress. To maintain mitochondria homeostasis (mitostasis), cells evolved molecular chaperones that shuttle, refold, or in coordination with proteolytic systems, help to maintain a low steady-state level of misfolded/aggregated proteins. Their importance is exemplified by the occurrence of various brain diseases which exhibit reduced action of chaperones. Chaperone loss (expression and/or function) has been observed during aging, metabolic diseases such as type 2 diabetes and in neurodegenerative diseases such as Alzheimer's (AD), Parkinson's (PD) or even Huntington's (HD) diseases, where the accumulation of damage proteins is evidenced. Within this perspective, we propose that proper brain function is maintained by the joint action of mitochondrial chaperones to ensure and maintain mitostasis contributing to brain health, and that upon failure, alter brain function which can cause metabolic diseases.

Mechanisms of iron sensing and regulation in the yeast Saccharomyces cerevisiae.

PubMed

Martínez-Pastor, María Teresa; Perea-García, Ana; Puig, Sergi

2017-04-01

Iron is a redox active element that functions as an essential cofactor in multiple metabolic pathways, including respiration, DNA synthesis and translation. While indispensable for eukaryotic life, excess iron can lead to oxidative damage of macromolecules. Therefore, living organisms have developed sophisticated strategies to optimally regulate iron acquisition, storage and utilization in response to fluctuations in environmental iron bioavailability. In the yeast Saccharomyces cerevisiae, transcription factors Aft1/Aft2 and Yap5 regulate iron metabolism in response to low and high iron levels, respectively. In addition to producing and assembling iron cofactors, mitochondrial iron-sulfur (Fe/S) cluster biogenesis has emerged as a central player in iron sensing. A mitochondrial signal derived from Fe/S synthesis is exported and converted into an Fe/S cluster that interacts directly with Aft1/Aft2 and Yap5 proteins to regulate their transcriptional function. Various conserved proteins, such as ABC mitochondrial transporter Atm1 and, for Aft1/Aft2, monothiol glutaredoxins Grx3 and Grx4 are implicated in this iron-signaling pathway. The analysis of a wide range of S. cerevisiae strains of different geographical origins and sources has shown that yeast strains adapted to high iron display growth defects under iron-deficient conditions, and highlighted connections that exist in the response to both opposite conditions. Changes in iron accumulation and gene expression profiles suggest differences in the regulation of iron homeostasis genes.

Rejuvenating cellular respiration for optimizing respiratory function: targeting mitochondria.

PubMed

Agrawal, Anurag; Mabalirajan, Ulaganathan

2016-01-15

Altered bioenergetics with increased mitochondrial reactive oxygen species production and degradation of epithelial function are key aspects of pathogenesis in asthma and chronic obstructive pulmonary disease (COPD). This motif is not unique to obstructive airway disease, reported in related airway diseases such as bronchopulmonary dysplasia and parenchymal diseases such as pulmonary fibrosis. Similarly, mitochondrial dysfunction in vascular endothelium or skeletal muscles contributes to the development of pulmonary hypertension and systemic manifestations of lung disease. In experimental models of COPD or asthma, the use of mitochondria-targeted antioxidants, such as MitoQ, has substantially improved mitochondrial health and restored respiratory function. Modulation of noncoding RNA or protein regulators of mitochondrial biogenesis, dynamics, or degradation has been found to be effective in models of fibrosis, emphysema, asthma, and pulmonary hypertension. Transfer of healthy mitochondria to epithelial cells has been associated with remarkable therapeutic efficacy in models of acute lung injury and asthma. Together, these form a 3R model--repair, reprogramming, and replacement--for mitochondria-targeted therapies in lung disease. This review highlights the key role of mitochondrial function in lung health and disease, with a focus on asthma and COPD, and provides an overview of mitochondria-targeted strategies for rejuvenating cellular respiration and optimizing respiratory function in lung diseases. Copyright © 2016 the American Physiological Society.

Control of mitochondrial physiology and cell death by the Bcl-2 family proteins Bax and Bok.

PubMed

D'Orsi, Beatrice; Mateyka, Julia; Prehn, Jochen H M

2017-10-01

Neuronal cell death is often triggered by events that involve intracellular increases in Ca 2+ . Under resting conditions, the intracellular Ca 2+ concentration is tightly controlled by a number of extrusion and sequestering mechanisms involving the plasma membrane, mitochondria, and ER. These mechanisms act to prevent a disruption of neuronal ion homeostasis. As these processes require ATP, excessive Ca 2+ overloading may cause energy depletion, mitochondrial dysfunction, and may eventually lead to Ca 2+ -dependent cell death. Excessive Ca 2+ entry though glutamate receptors (excitotoxicity) has been implicated in several neurologic and chronic neurodegenerative diseases, including ischemic stroke, epilepsy, and Alzheimer's disease. Recent evidence has revealed that excitotoxic cell death is regulated by the B-cell lymphoma-2 (Bcl-2) family of proteins. Bcl-2 proteins, comprising of both pro-apoptotic and anti-apoptotic members, have been shown to not only mediate the intrinsic apoptosis pathway by controlling mitochondrial outer membrane (MOM) integrity, but to also control neuronal Ca 2+ homeostasis and energetics. In this review, the role of Bcl-2 family proteins in the regulation of apoptosis, their expression in the central nervous system and how they control Ca 2+ -dependent neuronal injury are summarized. We review the current knowledge on Bcl-2 family proteins in the regulation of mitochondrial function and bioenergetics, including the fusion and fission machinery, and their role in Ca 2+ homeostasis regulation at the mitochondria and ER. Specifically, we discuss how the 'pro-apoptotic' Bcl-2 family proteins, Bax and Bok, physiologically expressed in the nervous system, regulate such 'non-apoptotic/daytime' functions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Assessment of Mitochondrial Dysfunction Arising from Treatment with Hepatotoxicants

PubMed Central

King, Adrienne L.; Bailey, Shannon M.

2010-01-01

Studies demonstrate that mitochondrial dysfunction is a key causative factor in liver disease. Indeed, defects in mitochondrial energy metabolism, disrupted calcium handling, and increased reactive oxygen/nitrogen species production are observed in many metabolic disorders and diseases induced by toxicants. Mitochondria have emerged as a main research focus through work defining new functions of this key organelle in normal cellular physiology and pathophysiology. Specifically, studies show a critical role of mitochondrial reactive oxygen/nitrogen species production in regulating cellular signaling pathways involved in cell survival and death. Given this, along with advances made in proteomics technologies, mitochondria are recognized as top candidates for proteomics analysis. However, assessment of mitochondrial function and it’s proteome following toxicant exposure are not trivial undertakings. In this chapter a technique used to isolate mitochondria from liver tissue is presented along with methods needed to assess mitochondria functionality. The methods described include measurement of mitochondrial respiration, calcium accumulation, and reactive oxygen species production. A presentation of proteomics approaches is also included to allow researchers the basic tools needed to identify alterations in the mitochondrial proteome that contribute to toxicant-mediated diseases. Specifically, methods are presented that demonstrate how thiol labeling reagents in combination with electrophoresis and western blotting can be used to detect oxidant-mediated alterations in mitochondrial protein thiols. A few select pieces data are presented highlighting the power of proteomics to identify mitochondrial targets that contribute to mitochondrial dysfunction and hepatotoxicity in response to specific toxicant exposures and metabolic stressors such as alcohol and environmental tobacco smoke. PMID:23045017

Sirtuin 1 Agonist Minimizes Injury and Improves the Immune Response Following Traumatic Shock.

PubMed

Luciano, Jason A; Kautza, Benjamin; Darwiche, Sophie; Martinez, Silvia; Stratimirovic, Sladjana; Waltz, Paul; Sperry, Jason; Rosengart, Matthew; Shiva, Sruti; Zuckerbraun, Brian S

2015-08-01

Survival from traumatic injury requires a coordinated and controlled inflammatory and immune response. Mitochondrial and metabolic responses to stress have been shown to play a role in these inflammatory and immune responses. We hypothesized that increases in mitochondrial biogenesis via a sirtuin 1 agonist would decrease tissue injury and partially ameliorate the immunosuppression seen following trauma. C57Bl/6 mice were subjected to a multiple trauma model. Mice were pretreated with either 100 mg/kg per day of the sirtuin 1 agonist, Srt1720, via oral gavage for 2 days prior to trauma and extended until the day the animals were killed, or they were pretreated with peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) siRNA via hydrodynamic tail vein injection 48 h prior to trauma. Markers for mitochondrial function and biogenesis were measured in addition to splenocyte proliferative capacity and bacterial clearance. Srt1720 was noted to improve mitochondrial biogenesis, mitochondrial function, and complex IV activity following traumatic injury (P < 0.05), whereas knockdown of PGC1α resulted in exacerbation of mitochondrial dysfunction (P < 0.05). These changes in mitochondrial function were associated with altered severity of hepatic injury with significant reductions in serum alanine aminotransferase levels seen in mice treated with srt1720. Splenocyte proliferative capacity and intraperitoneal bacterial clearance were evaluated as markers for overall immune function following trauma-hemorrhage. Treatment with Srt1720 minimized the trauma-induced decreases in splenocyte proliferation (P < 0.05), whereas treatment with PGC1α siRNA led to diminished bacterial clearance. The PGC1α signaling pathway is an important regulator of mitochondrial function and biogenesis, which can potentially be harnessed to protect against hepatic injury and minimize the immunosuppression that is seen following trauma-hemorrhage.

Carbohydrate Metabolism Is Perturbed in Peroxisome-deficient Hepatocytes Due to Mitochondrial Dysfunction, AMP-activated Protein Kinase (AMPK) Activation, and Peroxisome Proliferator-activated Receptor γ Coactivator 1α (PGC-1α) Suppression*

PubMed Central

Peeters, Annelies; Fraisl, Peter; van den Berg, Sjoerd; Ver Loren van Themaat, Emiel; Van Kampen, Antoine; Rider, Mark H.; Takemori, Hiroshi; van Dijk, Ko Willems; Van Veldhoven, Paul P.; Carmeliet, Peter; Baes, Myriam

2011-01-01

Hepatic peroxisomes are essential for lipid conversions that include the formation of mature conjugated bile acids, the degradation of branched chain fatty acids, and the synthesis of docosahexaenoic acid. Through unresolved mechanisms, deletion of functional peroxisomes from mouse hepatocytes (L-Pex5−/− mice) causes severe structural and functional abnormalities at the inner mitochondrial membrane. We now demonstrate that the peroxisomal and mitochondrial anomalies trigger energy deficits, as shown by increased AMP/ATP and decreased NAD+/NADH ratios. This causes suppression of gluconeogenesis and glycogen synthesis and up-regulation of glycolysis. As a consequence, L-Pex5−/− mice combust more carbohydrates resulting in lower body weights despite increased food intake. The perturbation of carbohydrate metabolism does not require a long term adaptation to the absence of functional peroxisomes as similar metabolic changes were also rapidly induced by acute elimination of Pex5 via adenoviral administration of Cre. Despite its marked activation, peroxisome proliferator-activated receptor α (PPARα) was not causally involved in these metabolic perturbations, because all abnormalities still manifested when peroxisomes were eliminated in a peroxisome proliferator-activated receptor α null background. Instead, AMP-activated kinase activation was responsible for the down-regulation of glycogen synthesis and induction of glycolysis. Remarkably, PGC-1α was suppressed despite AMP-activated kinase activation, a paradigm not previously reported, and they jointly contributed to impaired gluconeogenesis. In conclusion, lack of functional peroxisomes from hepatocytes results in marked disturbances of carbohydrate homeostasis, which are consistent with adaptations to an energy deficit. Because this is primarily due to impaired mitochondrial ATP production, these L-Pex5-deficient livers can also be considered as a model for secondary mitochondrial hepatopathies. PMID:22002056

c-Myc and AMPK Control Cellular Energy Levels by Cooperatively Regulating Mitochondrial Structure and Function

PubMed Central

Edmunds, Lia R.; Sharma, Lokendra; Wang, Huabo; Kang, Audry; d’Souza, Sonia; Lu, Jie; McLaughlin, Michael; Dolezal, James M.; Gao, Xiaoli; Weintraub, Susan T.; Ding, Ying; Zeng, Xuemei; Yates, Nathan; Prochownik, Edward V.

2015-01-01

The c-Myc (Myc) oncoprotein and AMP-activated protein kinase (AMPK) regulate glycolysis and oxidative phosphorylation (Oxphos) although often for different purposes. Because Myc over-expression depletes ATP with the resultant activation of AMPK, we explored the potential co-dependency of and cross-talk between these proteins by comparing the consequences of acute Myc induction in ampk+/+ (WT) and ampk-/- (KO) murine embryo fibroblasts (MEFs). KO MEFs showed a higher basal rate of glycolysis than WT MEFs and an appropriate increase in response to activation of a Myc-estrogen receptor (MycER) fusion protein. However, KO MEFs had a diminished ability to increase Oxphos, mitochondrial mass and reactive oxygen species in response to MycER activation. Other differences between WT and KO MEFs, either in the basal state or following MycER induction, included abnormalities in electron transport chain function, levels of TCA cycle-related oxidoreductases and cytoplasmic and mitochondrial redox states. Transcriptional profiling of pathways pertinent to glycolysis, Oxphos and mitochondrial structure and function also uncovered significant differences between WT and KO MEFs and their response to MycER activation. Finally, an unbiased mass-spectrometry (MS)-based survey capable of quantifying ~40% of all mitochondrial proteins, showed about 15% of them to be AMPK- and/or Myc-dependent in their steady state. Significant differences in the activities of the rate-limiting enzymes pyruvate kinase and pyruvate dehydrogenase, which dictate pyruvate and acetyl coenzyme A abundance, were also differentially responsive to Myc and AMPK and could account for some of the differences in basal metabolite levels that were also detected by MS. Thus, Myc and AMPK are highly co-dependent and appear to engage in significant cross-talk across numerous pathways which support metabolic and ATP-generating functions. PMID:26230505

miR-27 regulates mitochondrial networks by directly targeting the mitochondrial fission factor.

PubMed

Tak, Hyosun; Kim, Jihye; Jayabalan, Aravinth Kumar; Lee, Heejin; Kang, Hoin; Cho, Dong-Hyung; Ohn, Takbum; Nam, Suk Woo; Kim, Wook; Lee, Eun Kyung

2014-11-28

Mitochondrial morphology is dynamically regulated by forming small, fragmented units or interconnected networks, and this is a pivotal process that is used to maintain mitochondrial homeostasis. Although dysregulation of mitochondrial dynamics is related to the pathogenesis of several human diseases, its molecular mechanism is not fully elucidated. In this study, we demonstrate the potential role of miR-27 in the regulation of mitochondrial dynamics. Mitochondrial fission factor (MFF) mRNA is a direct target of miR-27, whose ectopic expression decreases MFF expression through binding to its 3'-untranslated region. Expression of miR-27 results in the elongation of mitochondria as well as an increased mitochondrial membrane potential and mitochondrial ATP level. Our results suggest that miR-27 is a novel regulator affecting morphological mitochondrial changes by targeting MFF.

miR-27 regulates mitochondrial networks by directly targeting the mitochondrial fission factor

PubMed Central

Tak, Hyosun; Kim, Jihye; Jayabalan, Aravinth Kumar; Lee, Heejin; Kang, Hoin; Cho, Dong-Hyung; Ohn, Takbum; Nam, Suk Woo; Kim, Wook; Lee, Eun Kyung

2014-01-01

Mitochondrial morphology is dynamically regulated by forming small, fragmented units or interconnected networks, and this is a pivotal process that is used to maintain mitochondrial homeostasis. Although dysregulation of mitochondrial dynamics is related to the pathogenesis of several human diseases, its molecular mechanism is not fully elucidated. In this study, we demonstrate the potential role of miR-27 in the regulation of mitochondrial dynamics. Mitochondrial fission factor (MFF) mRNA is a direct target of miR-27, whose ectopic expression decreases MFF expression through binding to its 3′-untranslated region. Expression of miR-27 results in the elongation of mitochondria as well as an increased mitochondrial membrane potential and mitochondrial ATP level. Our results suggest that miR-27 is a novel regulator affecting morphological mitochondrial changes by targeting MFF. PMID:25431021

Impaired mitochondria and intracellular calcium transients in the salivary glands of obese rats.

PubMed

Ittichaicharoen, Jitjiroj; Apaijai, Nattayaporn; Tanajak, Pongpan; Sa-Nguanmoo, Piangkwan; Chattipakorn, Nipon; Chattipakorn, Siriporn C

2017-04-01

Long-term consumption of a high-fat diet (HFD) causes not only obese-insulin resistance, but is also associated with mitochondrial dysfunction in several organs. However, the effect of obese-insulin resistance on salivary glands has not been investigated. We hypothesized that obese-insulin resistance induced by HFD impaired salivary gland function by reducing salivation, increasing inflammation, and fibrosis, as well as impairing mitochondrial function and calcium transient signaling. Male Wistar rats (200-220 g) were fed either a ND or an HFD (n = 8/group) for 16 weeks. At the end of week 16, salivary flow rates, metabolic parameters, and plasma oxidative stress were determined. Rats were then sacrificed and submandibular glands were removed to determine inflammation, fibrosis, apoptosis, mitochondrial function and dynamics, and intracellular calcium transient signaling. Long-term consumption of an HFD caused obese-insulin resistance and increased oxidative stress, fibrosis, inflammation, and apoptosis in the salivary glands. In addition, impaired mitochondrial function, as indicated by increased mitochondrial reactive oxygen species, mitochondrial membrane depolarization, and mitochondrial swelling in salivary glands and impaired intracellular calcium regulation, as indicated by a reduced intracellular calcium transient rising rate, decay rates, and amplitude of salivary acinar cells, were observed in HFD-fed rats. However, salivary flow rate and level of aquaporin 5 protein were not different between both groups. Although HFD consumption did not affect salivation, it caused obese-insulin resistance, leading to pathophysiological alteration of salivary glands, including impaired intracellular calcium transients, increased oxidative stress and inflammation, and salivary mitochondrial dysfunction.

Lipids of mitochondria.

PubMed

Horvath, Susanne E; Daum, Günther

2013-10-01

A unique organelle for studying membrane biochemistry is the mitochondrion whose functionality depends on a coordinated supply of proteins and lipids. Mitochondria are capable of synthesizing several lipids autonomously such as phosphatidylglycerol, cardiolipin and in part phosphatidylethanolamine, phosphatidic acid and CDP-diacylglycerol. Other mitochondrial membrane lipids such as phosphatidylcholine, phosphatidylserine, phosphatidylinositol, sterols and sphingolipids have to be imported. The mitochondrial lipid composition, the biosynthesis and the import of mitochondrial lipids as well as the regulation of these processes will be main issues of this review article. Furthermore, interactions of lipids and mitochondrial proteins which are highly important for various mitochondrial processes will be discussed. Malfunction or loss of enzymes involved in mitochondrial phospholipid biosynthesis lead to dysfunction of cell respiration, affect the assembly and stability of the mitochondrial protein import machinery and cause abnormal mitochondrial morphology or even lethality. Molecular aspects of these processes as well as diseases related to defects in the formation of mitochondrial membranes will be described. Copyright © 2013 Elsevier Ltd. All rights reserved.

Melatonin: A Mitochondrial Targeting Molecule Involving Mitochondrial Protection and Dynamics

PubMed Central

Tan, Dun-Xian; Manchester, Lucien C.; Qin, Lilan; Reiter, Russel J.

2016-01-01

Melatonin has been speculated to be mainly synthesized by mitochondria. This speculation is supported by the recent discovery that aralkylamine N-acetyltransferase/serotonin N-acetyltransferase (AANAT/SNAT) is localized in mitochondria of oocytes and the isolated mitochondria generate melatonin. We have also speculated that melatonin is a mitochondria-targeted antioxidant. It accumulates in mitochondria with high concentration against a concentration gradient. This is probably achieved by an active transportation via mitochondrial melatonin transporter(s). Melatonin protects mitochondria by scavenging reactive oxygen species (ROS), inhibiting the mitochondrial permeability transition pore (MPTP), and activating uncoupling proteins (UCPs). Thus, melatonin maintains the optimal mitochondrial membrane potential and preserves mitochondrial functions. In addition, mitochondrial biogenesis and dynamics is also regulated by melatonin. In most cases, melatonin reduces mitochondrial fission and elevates their fusion. Mitochondrial dynamics exhibit an oscillatory pattern which matches the melatonin circadian secretory rhythm in pinealeocytes and probably in other cells. Recently, melatonin has been found to promote mitophagy and improve homeostasis of mitochondria. PMID:27999288

Control mechanisms in mitochondrial oxidative phosphorylation☆

PubMed Central

Hroudová, Jana; Fišar, Zdeněk

2013-01-01

Distribution and activity of mitochondria are key factors in neuronal development, synaptic plasticity and axogenesis. The majority of energy sources, necessary for cellular functions, originate from oxidative phosphorylation located in the inner mitochondrial membrane. The adenosine-5’- triphosphate production is regulated by many control mechanism–firstly by oxygen, substrate level, adenosine-5’-diphosphate level, mitochondrial membrane potential, and rate of coupling and proton leak. Recently, these mechanisms have been implemented by “second control mechanisms,” such as reversible phosphorylation of the tricarboxylic acid cycle enzymes and electron transport chain complexes, allosteric inhibition of cytochrome c oxidase, thyroid hormones, effects of fatty acids and uncoupling proteins. Impaired function of mitochondria is implicated in many diseases ranging from mitochondrial myopathies to bipolar disorder and schizophrenia. Mitochondrial dysfunctions are usually related to the ability of mitochondria to generate adenosine-5’-triphosphate in response to energy demands. Large amounts of reactive oxygen species are released by defective mitochondria, similarly, decline of antioxidative enzyme activities (e.g. in the elderly) enhances reactive oxygen species production. We reviewed data concerning neuroplasticity, physiology, and control of mitochondrial oxidative phosphorylation and reactive oxygen species production. PMID:25206677

Control mechanisms in mitochondrial oxidative phosphorylation.

PubMed

Hroudová, Jana; Fišar, Zdeněk

2013-02-05

Distribution and activity of mitochondria are key factors in neuronal development, synaptic plasticity and axogenesis. The majority of energy sources, necessary for cellular functions, originate from oxidative phosphorylation located in the inner mitochondrial membrane. The adenosine-5'- triphosphate production is regulated by many control mechanism-firstly by oxygen, substrate level, adenosine-5'-diphosphate level, mitochondrial membrane potential, and rate of coupling and proton leak. Recently, these mechanisms have been implemented by "second control mechanisms," such as reversible phosphorylation of the tricarboxylic acid cycle enzymes and electron transport chain complexes, allosteric inhibition of cytochrome c oxidase, thyroid hormones, effects of fatty acids and uncoupling proteins. Impaired function of mitochondria is implicated in many diseases ranging from mitochondrial myopathies to bipolar disorder and schizophrenia. Mitochondrial dysfunctions are usually related to the ability of mitochondria to generate adenosine-5'-triphosphate in response to energy demands. Large amounts of reactive oxygen species are released by defective mitochondria, similarly, decline of antioxidative enzyme activities (e.g. in the elderly) enhances reactive oxygen species production. We reviewed data concerning neuroplasticity, physiology, and control of mitochondrial oxidative phosphorylation and reactive oxygen species production.

Desnutrin/ATGL activates PPARδ to promote mitochondrial function for insulin secretion in islet β cells.

PubMed

Tang, Tianyi; Abbott, Marcia J; Ahmadian, Maryam; Lopes, Andressa B; Wang, Yuhui; Sul, Hei Sook

2013-12-03

Excessive caloric intake leading to obesity is associated with insulin resistance and dysfunction of islet β cells. High-fat feeding decreases desnutrin (also called ATGL/PNPLA2) levels in islets. Here we show that desnutrin ablation via RIP-Cre (βKO) or RIP-CreER results in hyperglycemia with impaired glucose-stimulated insulin secretion (GSIS). Due to decreased lipolysis, islets have higher TAG content but lower free FA levels. βKO islets exhibit impaired mitochondrial respiration and lower production of ATP required for GSIS, along with decreased expression of PPARδ target genes involved in mitochondrial oxidation. Furthermore, synthetic PPARδ, but not PPARα, agonist restores GSIS and expression of mitochondrial oxidative genes in βKO mice, revealing that desnutrin-catalyzed lipolysis generates PPARδ ligands. Finally, adenoviral expression of desnutrin in βKO islets restores all defects of βKO islet phenotype and function, including GSIS and mitochondrial defects, demonstrating the critical role of the desnutrin-PPARδ-mitochondrial oxidation axis in regulating islet β cell GSIS. Copyright © 2013 Elsevier Inc. All rights reserved.

Distinct Mechanisms of Pathogenic DJ-1 Mutations in Mitochondrial Quality Control

PubMed Central

Strobbe, Daniela; Robinson, Alexis A.; Harvey, Kirsten; Rossi, Lara; Ferraina, Caterina; de Biase, Valerio; Rodolfo, Carlo; Harvey, Robert J.; Campanella, Michelangelo

2018-01-01

The deglycase and chaperone protein DJ-1 is pivotal for cellular oxidative stress responses and mitochondrial quality control. Mutations in PARK7, encoding DJ-1, are associated with early-onset familial Parkinson’s disease and lead to pathological oxidative stress and/or disrupted protein degradation by the proteasome. The aim of this study was to gain insights into the pathogenic mechanisms of selected DJ-1 missense mutations, by characterizing protein–protein interactions, core parameters of mitochondrial function, quality control regulation via autophagy, and cellular death following dopamine accumulation. We report that the DJ-1M26I mutant influences DJ-1 interactions with SUMO-1, in turn enhancing removal of mitochondria and conferring increased cellular susceptibility to dopamine toxicity. By contrast, the DJ-1D149A mutant does not influence mitophagy, but instead impairs Ca2+ dynamics and free radical homeostasis by disrupting DJ-1 interactions with a mitochondrial accessory protein known as DJ-1-binding protein (DJBP/EFCAB6). Thus, individual DJ-1 mutations have different effects on mitochondrial function and quality control, implying mutation-specific pathomechanisms converging on impaired mitochondrial homeostasis. PMID:29599708

Mitofusin-2 protects against cold stress-induced cell injury in HEK293 cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wenbin; Chen, Yaomin; Yang, Qun

2010-06-25

Mitochondrial impairment is hypothesized to contribute to cell injury during cold stress. Mitochondria fission and fusion are closely related in the function of the mitochondria, but the precise mechanisms whereby these processes regulate cell injury during cold stress remain to be determined. HEK293 cells were cultured in a cold environment (4.0 {+-} 0.1 {sup o}C) for 2, 4, 8, or 12 h. Western blot analyses showed that these cells expressed decreased fission-related protein Drp1 and increased fusion-related protein Mfn2 at 4 h; meanwhile, electron microscopy analysis revealed large and long mitochondrial morphology within these cells, indicating increased mitochondrial fusion. Withmore » silencing of Mfn2 but not of Mfn1 by siRNA promoted cold-stress-induced cell death with decreased ATP production in HEK293 cells. Our results show that increased expression of Mfn2 and mitochondrial fusion are important for mitochondrial function as well as cell survival during cold stress. These findings have important implications for understanding the mechanisms of mitochondrial fusion and fission in cold-stress-induced cell injury.« less

Mitochondrial respiratory chain complexes as sources and targets of thiol-based redox-regulation.

PubMed

Dröse, Stefan; Brandt, Ulrich; Wittig, Ilka

2014-08-01

The respiratory chain of the inner mitochondrial membrane is a unique assembly of protein complexes that transfers the electrons of reducing equivalents extracted from foodstuff to molecular oxygen to generate a proton-motive force as the primary energy source for cellular ATP-synthesis. Recent evidence indicates that redox reactions are also involved in regulating mitochondrial function via redox-modification of specific cysteine-thiol groups in subunits of respiratory chain complexes. Vice versa the generation of reactive oxygen species (ROS) by respiratory chain complexes may have an impact on the mitochondrial redox balance through reversible and irreversible thiol-modification of specific target proteins involved in redox signaling, but also pathophysiological processes. Recent evidence indicates that thiol-based redox regulation of the respiratory chain activity and especially S-nitrosylation of complex I could be a strategy to prevent elevated ROS production, oxidative damage and tissue necrosis during ischemia-reperfusion injury. This review focuses on the thiol-based redox processes involving the respiratory chain as a source as well as a target, including a general overview on mitochondria as highly compartmentalized redox organelles and on methods to investigate the redox state of mitochondrial proteins. This article is part of a Special Issue entitled: Thiol-Based Redox Processes. Copyright © 2014 Elsevier B.V. All rights reserved.

Interaction between AIF and CHCHD4 Regulates Respiratory Chain Biogenesis.

PubMed

Hangen, Emilie; Féraud, Olivier; Lachkar, Sylvie; Mou, Haiwei; Doti, Nunzianna; Fimia, Gian Maria; Lam, Ngoc-Vy; Zhu, Changlian; Godin, Isabelle; Muller, Kevin; Chatzi, Afroditi; Nuebel, Esther; Ciccosanti, Fabiola; Flamant, Stéphane; Bénit, Paule; Perfettini, Jean-Luc; Sauvat, Allan; Bennaceur-Griscelli, Annelise; Ser-Le Roux, Karine; Gonin, Patrick; Tokatlidis, Kostas; Rustin, Pierre; Piacentini, Mauro; Ruvo, Menotti; Blomgren, Klas; Kroemer, Guido; Modjtahedi, Nazanine

2015-06-18

Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein that, beyond its apoptotic function, is required for the normal expression of major respiratory chain complexes. Here we identified an AIF-interacting protein, CHCHD4, which is the central component of a redox-sensitive mitochondrial intermembrane space import machinery. Depletion or hypomorphic mutation of AIF caused a downregulation of CHCHD4 protein by diminishing its mitochondrial import. CHCHD4 depletion sufficed to induce a respiratory defect that mimicked that observed in AIF-deficient cells. CHCHD4 levels could be restored in AIF-deficient cells by enforcing its AIF-independent mitochondrial localization. This modified CHCHD4 protein reestablished respiratory function in AIF-deficient cells and enabled AIF-deficient embryoid bodies to undergo cavitation, a process of programmed cell death required for embryonic morphogenesis. These findings explain how AIF contributes to the biogenesis of respiratory chain complexes, and they establish an unexpected link between the vital function of AIF and the propensity of cells to undergo apoptosis. Copyright © 2015 Elsevier Inc. All rights reserved.

The modulation of the biological activities of mitochondrial histone Abf2p by yeast PKA and its possible role in the regulation of mitochondrial DNA content during glucose repression.

PubMed

Cho, J H; Lee, Y K; Chae, C B

2001-12-30

The mitochondrial histone, Abf2p, of Saccharomyces cerevisiae is essential for the maintenance of mitochondrial DNA (mtDNA) and appears to play an important role in the recombination and copy number determination of mtDNA. Abf2p, encoded by a nuclear gene, is a member of HMG1 DNA-binding protein family and has two HMG1-Box domains, HMG1-Box A and B. To investigate the role of Abf2p in the control of mtDNA copy number, we asked if the in vivo functions of Abf2p are regulated by the possible modification such as phosphorylation. We found that the N-terminal extended segment (KRPT(21)S(22)) of HMG1-Box A is rapidly and specifically phosphorylated by cAMP-dependent protein kinase (PKA) in vitro. The phosphorylation in this region inhibits the binding of Abf2p to all kinds of DNA including four-way junction DNA and the supercoiling activity of Abf2p itself. The abf2 mutant cells with an abf2(T21A/S22A) allele defective in the phosphorylation site have a severe defect in the regulation of mtDNA content during glucose repression in vivo. These observations suggest that the phosphorylation via PKA, that is activated during glucose repression, may regulate the in vivo functions of Abf2p for the control of mtDNA content during shift from gluconeogenic to fermentative growth.

Estrogen amelioration of Aβ-induced defects in mitochondria is mediated by mitochondrial signaling pathway involving ERβ, AKAP and Drp1.

PubMed

Sarkar, Saumyendra; Jun, Sujung; Simpkins, James W

2015-08-07

Perturbations in dynamic properties of mitochondria including fission, fusion, and movement lead to disruption of energy supply to synapses contributing to neuropathology and cognitive dysfunction in Alzheimer׳s disease (AD). The molecular mechanisms underlying these defects are still unclear. Previously, we have shown that ERβ is localized in the mitochondria and ERβ knock down disrupts mitochondrial functions. Because a selective ERβ modulator (DPN) can activate PKA, and localized PKA signaling in the mitochondrial membrane regulates mitochondrial structure and functions, we reasoned that ERβ signaling in the mitochondrial membrane rescues many of the mitochondrial defects caused by soluble Aβ oligomer. We now report that DPN treatment in primary hippocampal neurons attenuates soluble Aβ-oligomer induced dendritic mitochondrial fission and reduced mobility. Additionally, Aβ treatment reduced the respiratory reserve capacity of hippocampal neuron and inhibited phosphorylation of Drp1 at its PKA site, which induces excessive mitochondrial fission, and DPN treatment ameliorates these inhibitions. Finally, we discovered a direct interaction of ERβ with a mitochondrial resident protein AKAP1, which induces the PKA-mediated local signaling pathway involved in increased oxidative phosphorylation and inhibition of mitochondrial fission. Taken together, our findings highlight the possibility that ERβ signaling pathway may be a useful mitochondria-directed therapeutic target for AD. Copyright © 2015 Elsevier B.V. All rights reserved.

Enhanced Mitochondrial Transient Receptor Potential Channel, Canonical Type 3-Mediated Calcium Handling in the Vasculature From Hypertensive Rats.

PubMed

Wang, Bin; Xiong, Shiqiang; Lin, Shaoyang; Xia, Weijie; Li, Qiang; Zhao, Zhigang; Wei, Xing; Lu, Zongshi; Wei, Xiao; Gao, Peng; Liu, Daoyan; Zhu, Zhiming

2017-07-15

Mitochondrial Ca 2+ homeostasis is fundamental to the regulation of mitochondrial reactive oxygen species (ROS) generation and adenosine triphosphate production. Recently, transient receptor potential channel, canonical type 3 (TRPC3), has been shown to localize to the mitochondria and to play a role in maintaining mitochondrial calcium homeostasis. Inhibition of TRPC3 attenuates vascular calcium influx in spontaneously hypertensive rats (SHRs). However, it remains elusive whether mitochondrial TRPC3 participates in hypertension by increasing mitochondrial calcium handling and ROS production. In this study we demonstrated increased TRPC3 expression in purified mitochondria in the vasculature from SHRs, which facilitates enhanced mitochondrial calcium uptake and ROS generation compared with Wistar-Kyoto rats. Furthermore, inhibition of TRPC3 by its specific inhibitor, Pyr3, significantly decreased the vascular mitochondrial ROS production and H 2 O 2 synthesis and increased adenosine triphosphate content. Administration of telmisartan can improve these abnormalities. This beneficial effect was associated with improvement of the mitochondrial respiratory function through recovering the activity of pyruvate dehydrogenase in the vasculature of SHRs. In vivo, chronic administration of telmisartan suppressed TRPC3-mediated excessive mitochondrial ROS generation and vasoconstriction in the vasculature of SHRs. More importantly, TRPC3 knockout mice exhibited significantly ameliorated hypertension through reduction of angiotensin II-induced mitochondrial ROS generation. Together, we give experimental evidence for a potential mechanism by which enhanced TRPC3 activity at the cytoplasmic and mitochondrial levels contributes to redox signaling and calcium dysregulation in the vasculature from SHRs. Angiotensin II or telmisartan can regulate [Ca 2+ ] mito , ROS production, and mitochondrial energy metabolism through targeting TRPC3. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

Role of the mitochondrial DNA replication machinery in mitochondrial DNA mutagenesis, aging and age-related diseases

PubMed Central

DeBalsi, Karen L.; Hoff, Kirsten E.; Copeland, William C.

2016-01-01

As regulators of bioenergetics in the cell and the primary source of endogenous reactive oxygen species (ROS), dysfunctional mitochondria have been implicated for decades in the process of aging and age-related diseases. Mitochondrial DNA (mtDNA) is replicated and repaired by nuclear-encoded mtDNA polymerase γ (Pol γ) and several other associated proteins, which compose the mtDNA replication machinery. Here, we review evidence that errors caused by this replication machinery and failure to repair these mtDNA errors results in mtDNA mutations. Clonal expansion of mtDNA mutations results in mitochondrial dysfunction, such as decreased electron transport chain (ETC) enzyme activity and impaired cellular respiration. We address the literature that mitochondrial dysfunction, in conjunction with altered mitochondrial dynamics, is a major driving force behind aging and age-related diseases. Additionally, interventions to improve mitochondrial function and attenuate the symptoms of aging are examined. PMID:27143693

Mitophagy in hematopoietic stem cells

PubMed Central

Joshi, Aashish; Kundu, Mondira

2013-01-01

Hematopoietic stem cells (HSCs) are inherently quiescent and self-renewing, yet can differentiate and commit to multiple blood cell types. Intracellular mitochondrial content is dynamic, and there is an increase in mitochondrial content during differentiation and lineage commitment in HSCs. HSCs reside in a hypoxic niche within the bone marrow and rely heavily on glycolysis, while differentiated and committed progenitors rely on oxidative phosphorylation. Increased oxidative phosphorylation during differentiation and commitment is not only due to increased mitochondrial content but also due to changes in mitochondrial cytosolic distribution and efficiency. These changes in the intracellular mitochondrial landscape contribute signals toward regulating differentiation and commitment. Thus, a functional relationship exists between the mitochondria in HSCs and the state of the HSCs (i.e., stemness vs. differentiated). This review focuses on how autophagy-mediated mitochondrial clearance (i.e., mitophagy) may affect HSC mitochondrial content, thereby influencing the fate of HSCs and maintenance of hematopoietic homeostasis. PMID:24135495

No evidence for a local renin-angiotensin system in liver mitochondria

PubMed Central

Astin, Ronan; Bentham, Robert; Djafarzadeh, Siamak; Horscroft, James A.; Kuc, Rhoda E.; Leung, Po Sing; Skipworth, James R. A.; Vicencio, Jose M.; Davenport, Anthony P.; Murray, Andrew J.; Takala, Jukka; Jakob, Stephan M.; Montgomery, Hugh; Szabadkai, Gyorgy

2013-01-01

The circulating, endocrine renin-angiotensin system (RAS) is important to circulatory homeostasis, while ubiquitous tissue and cellular RAS play diverse roles, including metabolic regulation. Indeed, inhibition of RAS is associated with improved cellular oxidative capacity. Recently it has been suggested that an intra-mitochondrial RAS directly impacts on metabolism. Here we sought to rigorously explore this hypothesis. Radiolabelled ligand-binding and unbiased proteomic approaches were applied to purified mitochondrial sub-fractions from rat liver, and the impact of AngII on mitochondrial function assessed. Whilst high-affinity AngII binding sites were found in the mitochondria-associated membrane (MAM) fraction, no RAS components could be detected in purified mitochondria. Moreover, AngII had no effect on the function of isolated mitochondria at physiologically relevant concentrations. We thus found no evidence of endogenous mitochondrial AngII production, and conclude that the effects of AngII on cellular energy metabolism are not mediated through its direct binding to mitochondrial targets. PMID:23959064

Identification of Genes Potentially Regulated by Human Polynucleotide Phosphorylase (hPNPaseold-35) Using Melanoma as a Model

PubMed Central

Sokhi, Upneet K.; Bacolod, Manny D.; Dasgupta, Santanu; Emdad, Luni; Das, Swadesh K.; Dumur, Catherine I.; Miles, Michael F.; Sarkar, Devanand; Fisher, Paul B.

2013-01-01

Human Polynucleotide Phosphorylase (hPNPaseold-35 or PNPT1) is an evolutionarily conserved 3′→5′ exoribonuclease implicated in the regulation of numerous physiological processes including maintenance of mitochondrial homeostasis, mtRNA import and aging-associated inflammation. From an RNase perspective, little is known about the RNA or miRNA species it targets for degradation or whose expression it regulates; except for c-myc and miR-221. To further elucidate the functional implications of hPNPaseold-35 in cellular physiology, we knocked-down and overexpressed hPNPaseold-35 in human melanoma cells and performed gene expression analyses to identify differentially expressed transcripts. Ingenuity Pathway Analysis indicated that knockdown of hPNPaseold-35 resulted in significant gene expression changes associated with mitochondrial dysfunction and cholesterol biosynthesis; whereas overexpression of hPNPaseold-35 caused global changes in cell-cycle related functions. Additionally, comparative gene expression analyses between our hPNPaseold-35 knockdown and overexpression datasets allowed us to identify 77 potential “direct” and 61 potential “indirect” targets of hPNPaseold-35 which formed correlated networks enriched for cell-cycle and wound healing functional association, respectively. These results provide a comprehensive database of genes responsive to hPNPaseold-35 expression levels; along with the identification new potential candidate genes offering fresh insight into cellular pathways regulated by PNPT1 and which may be used in the future for possible therapeutic intervention in mitochondrial- or inflammation-associated disease phenotypes. PMID:24143183

Live-Cell Imaging of Mitochondria and the Actin Cytoskeleton in Budding Yeast.

PubMed

Higuchi-Sanabria, Ryo; Swayne, Theresa C; Boldogh, Istvan R; Pon, Liza A

2016-01-01

Maintenance and regulation of proper mitochondrial dynamics and functions are necessary for cellular homeostasis. Numerous diseases, including neurodegeneration and muscle myopathies, and overall cellular aging are marked by declining mitochondrial function and subsequent loss of multiple other cellular functions. For these reasons, optimized protocols are needed for visualization and quantification of mitochondria and their function and fitness. In budding yeast, mitochondria are intimately associated with the actin cytoskeleton and utilize actin for their movement and inheritance. This chapter describes optimal approaches for labeling mitochondria and the actin cytoskeleton in living budding yeast cells, for imaging the labeled cells, and for analyzing the resulting images.

Overexpression of PGC-1α increases peroxisomal activity and mitochondrial fatty acid oxidation in human primary myotubes.

PubMed

Huang, Tai-Yu; Zheng, Donghai; Houmard, Joseph A; Brault, Jeffrey J; Hickner, Robert C; Cortright, Ronald N

2017-04-01

Peroxisomes are indispensable organelles for lipid metabolism in humans, and their biogenesis has been assumed to be under regulation by peroxisome proliferator-activated receptors (PPARs). However, recent studies in hepatocytes suggest that the mitochondrial proliferator PGC-1α (peroxisome proliferator-activated receptor gamma coactivator-1α) also acts as an upstream transcriptional regulator for enhancing peroxisomal abundance and associated activity. It is unknown whether the regulatory mechanism(s) for enhancing peroxisomal function is through the same node as mitochondrial biogenesis in human skeletal muscle (HSkM) and whether fatty acid oxidation (FAO) is affected. Primary myotubes from vastus lateralis biopsies from lean donors (BMI = 24.0 ± 0.6 kg/m 2 ; n = 6) were exposed to adenovirus encoding human PGC-1α or GFP control. Peroxisomal biogenesis proteins (peroxins) and genes ( PEXs ) responsible for proliferation and functions were assessed by Western blotting and real-time qRT-PCR, respectively. [1- 14 C]palmitic acid and [1- 14 C]lignoceric acid (exclusive peroxisomal-specific substrate) were used to assess mitochondrial oxidation of peroxisomal-derived metabolites. After overexpression of PGC-1α, 1 ) peroxisomal membrane protein 70 kDa (PMP70), PEX19, and mitochondrial citrate synthetase protein content were significantly elevated ( P < 0.05), 2 ) PGC-1α , PMP70 , key PEXs , and peroxisomal β-oxidation mRNA expression levels were significantly upregulated ( P < 0.05), and 3 ) a concomitant increase in lignoceric acid oxidation by both peroxisomal and mitochondrial activity was observed ( P < 0.05). These novel findings demonstrate that, in addition to the proliferative effect on mitochondria, PGC-1α can induce peroxisomal activity and accompanying elevations in long-chain and very-long-chain fatty acid oxidation by a peroxisomal-mitochondrial functional cooperation, as observed in HSkM cells. Copyright © 2017 the American Physiological Society.

Pifithrin-α provides neuroprotective effects at the level of mitochondria independently of p53 inhibition.

PubMed

Neitemeier, Sandra; Ganjam, Goutham K; Diemert, Sebastian; Culmsee, Carsten

2014-12-01

Impaired mitochondrial integrity and function are key features of intrinsic death pathways in neuronal cells. Therefore, key regulators of intrinsic death pathways acting upstream of mitochondria are potential targets for therapeutic approaches of neuroprotection. The tumor suppressor p53 is a well-established regulator of cellular responses towards different kinds of lethal stress, including oxidative stress. Recent reports suggested that p53 may affect mitochondrial integrity and function through both, transcriptional activation of mitochondria-targeted pro-death proteins and direct effects at the mitochondrial membrane. In the present study, we compared the effects of pharmacological inhibition of p53 by pifithrin-α with those of selective p53 gene silencing by RNA interference. Using MTT assay and real-time cell impedance measurements we confirmed the protective effect of both strategies against glutamate-induced oxidative stress in immortalized mouse hippocampal HT-22 neurons. Further, we observed full restoration of mitochondrial membrane potential and inhibition of glutamate-induced mitochondrial fragmentation by pifithrin-α which was, in contrast, not achieved by p53 gene silencing. Downregulation of p53 by siRNA decreased p53 transcriptional activity and reduced expression levels of p21 mRNA, while pifithrin-α did not affect these endpoints. These results suggest a neuroprotective effect of pifithrin-α which occurred at the level of mitochondria and independently of p53 inhibition.

An Essential Role for ECSIT in Mitochondrial Complex I Assembly and Mitophagy in Macrophages.

PubMed

Carneiro, Flávia R G; Lepelley, Alice; Seeley, John J; Hayden, Matthew S; Ghosh, Sankar

2018-03-06

ECSIT is a mitochondrial complex I (CI)-associated protein that has been shown to regulate the production of mitochondrial reactive oxygen species (mROS) following engagement of Toll-like receptors (TLRs). We have generated an Ecsit conditional knockout (CKO) mouse strain to study the in vivo role of ECSIT. ECSIT deletion results in profound alteration of macrophage metabolism, leading to a striking shift to reliance on glycolysis, complete disruption of CI activity, and loss of the CI holoenzyme and multiple subassemblies. An increase in constitutive mROS production in ECSIT-deleted macrophages prevents further TLR-induced mROS production. Surprisingly, ECSIT-deleted cells accumulate damaged mitochondria because of defective mitophagy. ECSIT associates with the mitophagy regulator PINK1 and exhibits Parkin-dependent ubiquitination. However, upon ECSIT deletion, we observed increased mitochondrial Parkin without the expected increase in mitophagy. Taken together, these results demonstrate a key role of ECSIT in CI function, mROS production, and mitophagy-dependent mitochondrial quality control. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Maintenance and expression of the S. cerevisiae mitochondrial genome--from genetics to evolution and systems biology.

PubMed

Lipinski, Kamil A; Kaniak-Golik, Aneta; Golik, Pawel

2010-01-01

As a legacy of their endosymbiotic eubacterial origin, mitochondria possess a residual genome, encoding only a few proteins and dependent on a variety of factors encoded by the nuclear genome for its maintenance and expression. As a facultative anaerobe with well understood genetics and molecular biology, Saccharomyces cerevisiae is the model system of choice for studying nucleo-mitochondrial genetic interactions. Maintenance of the mitochondrial genome is controlled by a set of nuclear-coded factors forming intricately interconnected circuits responsible for replication, recombination, repair and transmission to buds. Expression of the yeast mitochondrial genome is regulated mostly at the post-transcriptional level, and involves many general and gene-specific factors regulating splicing, RNA processing and stability and translation. A very interesting aspect of the yeast mitochondrial system is the relationship between genome maintenance and gene expression. Deletions of genes involved in many different aspects of mitochondrial gene expression, notably translation, result in an irreversible loss of functional mtDNA. The mitochondrial genetic system viewed from the systems biology perspective is therefore very fragile and lacks robustness compared to the remaining systems of the cell. This lack of robustness could be a legacy of the reductive evolution of the mitochondrial genome, but explanations involving selective advantages of increased evolvability have also been postulated. Copyright © 2009 Elsevier B.V. All rights reserved.

Nix restores mitophagy and mitochondrial function to protect against PINK1/Parkin-related Parkinson's disease.

PubMed

Koentjoro, Brianada; Park, Jin-Sung; Sue, Carolyn M

2017-03-10

Therapeutic targets are needed to develop neuroprotective treatments for Parkinson's disease (PD). Mitophagy, the selective autophagic elimination of dysfunctional mitochondria, is essential for the maintenance of mitochondrial integrity and is predominantly regulated by the PINK1/Parkin-mediated pathway. Loss of function mutations in Parkin and PINK1 cause an accumulation of dysfunctional mitochondria, leading to nigral neurodegeneration and early-onset PD with a high penetrance rate. We previously identified an asymptomatic homozygous Parkin mutation carrier who had not developed PD by her eighth decade despite the loss of functional Parkin. Here we discover a putative mechanism that protects her against PD. In contrast to Parkin-related PD patient-derived cells, the asymptomatic carrier cells show preserved mitochondrial function and mitophagy which is mediated by mitochondrial receptor Nip3-like protein X (Nix). Nix-mediated mitophagy was not affected by PINK1 knockdown. Both genetic and pharmacological induction of Nix restores mitophagy in PINK1- and Parkin-related PD patient cell lines, confirming its ability to induce mitophagy in the absence of PINK1/Parkin-mediated pathway. Moreover, Nix over-expression improves mitochondrial ATP production in these patient cells. Our results demonstrate that Nix can serve as an alternative mediator of mitophagy to maintain mitochondrial turnover, identifying Nix as a promising target for neuroprotective treatment in PINK1/Parkin-related PD.

Induction of autophagy by ARHI (DIRAS3) alters fundamental metabolic pathways in ovarian cancer models.

PubMed

Ornelas, Argentina; McCullough, Christopher R; Lu, Zhen; Zacharias, Niki M; Kelderhouse, Lindsay E; Gray, Joshua; Yang, Hailing; Engel, Brian J; Wang, Yan; Mao, Weiqun; Sutton, Margie N; Bhattacharya, Pratip K; Bast, Robert C; Millward, Steven W

2016-10-26

Autophagy is a bulk catabolic process that modulates tumorigenesis, therapeutic resistance, and dormancy. The tumor suppressor ARHI (DIRAS3) is a potent inducer of autophagy and its expression results in necroptotic cell death in vitro and tumor dormancy in vivo. ARHI is down-regulated or lost in over 60 % of primary ovarian tumors yet is dramatically up-regulated in metastatic disease. The metabolic changes that occur during ARHI induction and their role in modulating death and dormancy are unknown. We employed Nuclear Magnetic Resonance (NMR)-based metabolomic strategies to characterize changes in key metabolic pathways in both cell culture and xenograft models of ARHI expression and autophagy. These pathways were further interrogated by cell-based immunofluorescence imaging, tracer uptake studies, targeted metabolic inhibition, and in vivo PET/CT imaging. Induction of ARHI in cell culture models resulted in an autophagy-dependent increase in lactate production along with increased glucose uptake and enhanced sensitivity to glycolytic inhibitors. Increased uptake of glutamine was also dependent on autophagy and dramatically sensitized cultured ARHI-expressing ovarian cancer cell lines to glutaminase inhibition. Induction of ARHI resulted in a reduction in mitochondrial respiration, decreased mitochondrial membrane potential, and decreased Tom20 staining suggesting an ARHI-dependent loss of mitochondrial function. ARHI induction in mouse xenograft models resulted in an increase in free amino acids, a transient increase in [ 18 F]-FDG uptake, and significantly altered choline metabolism. ARHI expression has previously been shown to trigger autophagy-associated necroptosis in cell culture. In this study, we have demonstrated that ARHI expression results in decreased cellular ATP/ADP, increased oxidative stress, and decreased mitochondrial function. While this bioenergetic shock is consistent with programmed necrosis, our data indicates that the accompanying up-regulation of glycolysis and glutaminolysis is autophagy-dependent and serves to support cell viability rather than facilitate necroptotic cell death. While the mechanistic basis for metabolic up-regulation following ARHI induction is unknown, our preliminary data suggest that decreased mitochondrial function and increased metabolic demand may play a role. These alterations in fundamental metabolic pathways during autophagy-associated necroptosis may provide the basis for new therapeutic strategies for the treatment of dormant ovarian tumors.

FAD-dependent lysine-specific demethylase-1 regulates cellular energy expenditure

PubMed Central

Hino, Shinjiro; Sakamoto, Akihisa; Nagaoka, Katsuya; Anan, Kotaro; Wang, Yuqing; Mimasu, Shinya; Umehara, Takashi; Yokoyama, Shigeyuki; Kosai, Ken-ichiro; Nakao, Mitsuyoshi

2012-01-01

Environmental factors such as nutritional state may act on the epigenome that consequently contributes to the metabolic adaptation of cells and the organisms. The lysine-specific demethylase-1 (LSD1) is a unique nuclear protein that utilizes flavin adenosine dinucleotide (FAD) as a cofactor. Here we show that LSD1 epigenetically regulates energy-expenditure genes in adipocytes depending on the cellular FAD availability. We find that the loss of LSD1 function, either by short interfering RNA or by selective inhibitors in adipocytes, induces a number of regulators of energy expenditure and mitochondrial metabolism such as PPARγ coactivator-1α resulting in the activation of mitochondrial respiration. In the adipose tissues from mice on a high-fat diet, expression of LSD1-target genes is reduced, compared with that in tissues from mice on a normal diet, which can be reverted by suppressing LSD1 function. Our data suggest a novel mechanism where LSD1 regulates cellular energy balance through coupling with cellular FAD biosynthesis. PMID:22453831

FAD-dependent lysine-specific demethylase-1 regulates cellular energy expenditure.

PubMed

Hino, Shinjiro; Sakamoto, Akihisa; Nagaoka, Katsuya; Anan, Kotaro; Wang, Yuqing; Mimasu, Shinya; Umehara, Takashi; Yokoyama, Shigeyuki; Kosai, Ken-Ichiro; Nakao, Mitsuyoshi

2012-03-27

Environmental factors such as nutritional state may act on the epigenome that consequently contributes to the metabolic adaptation of cells and the organisms. The lysine-specific demethylase-1 (LSD1) is a unique nuclear protein that utilizes flavin adenosine dinucleotide (FAD) as a cofactor. Here we show that LSD1 epigenetically regulates energy-expenditure genes in adipocytes depending on the cellular FAD availability. We find that the loss of LSD1 function, either by short interfering RNA or by selective inhibitors in adipocytes, induces a number of regulators of energy expenditure and mitochondrial metabolism such as PPARγ coactivator-1α resulting in the activation of mitochondrial respiration. In the adipose tissues from mice on a high-fat diet, expression of LSD1-target genes is reduced, compared with that in tissues from mice on a normal diet, which can be reverted by suppressing LSD1 function. Our data suggest a novel mechanism where LSD1 regulates cellular energy balance through coupling with cellular FAD biosynthesis.

Cyclophilin D is required for mitochondrial removal by autophagy in cardiac cells

PubMed Central

Carreira, Raquel S.; Lee, Youngil; Ghochani, Mariam; Gustafsson, Åsa B.; Gottlieb, Roberta A.

2013-01-01

Autophagy is a highly regulated intracellular degradation process by which cells remove cytosolic long-lived proteins and damaged organelles. The mitochondrial permeability transition (MPT) results in mitochondrial depolarization and increased reactive oxygen species production, which can trigger autophagy. Therefore, we hypothesized that the MPT may have a role in signaling autophagy in cardiac cells. Mitochondrial membrane potential was lower in HL-1 cells subjected to starvation compared to cells maintained in full medium. Mitochondrial membrane potential was preserved in starved cells treated with cyclosporin A (CsA), suggesting the MPT pore is associated with starvation-induced depolarization. Starvation-induced autophagy in HL-1 cells, neonatal rat cardiomyocytes and adult mouse cardiomyocytes was inhibited by CsA. Starvation failed to induce autophagy in CypD-deficient murine cardiomyocytes, whereas in myocytes from mice overexpressing CypD the levels of autophagy were enhanced even under fed conditions. Collectively, these results demonstrate a role for CypD and the MPT in the initiation of autophagy. We also analyzed the role of the MPT in the degradation of mitochondria by biochemical analysis and electron microscopy. HL-1 cells subjected to starvation in the presence of CsA had higher levels of mitochondrial proteins (by Western blot), more mitochondria and less autophagosomes (by electron microscopy) then cells starved in the absence of CsA. Our results suggest a physiologic function for CypD and the MPT in the regulation of starvation-induced autophagy. Starvation-induced autophagy regulated by CypD and the MPT may represent a homeostatic mechanism for cellular and mitochondrial quality control. PMID:20364102

Differential expression of the nuclear-encoded mitochondrial transcriptome in pediatric septic shock.

PubMed

Weiss, Scott L; Cvijanovich, Natalie Z; Allen, Geoffrey L; Thomas, Neal J; Freishtat, Robert J; Anas, Nick; Meyer, Keith; Checchia, Paul A; Shanley, Thomas P; Bigham, Michael T; Fitzgerald, Julie; Banschbach, Sharon; Beckman, Eileen; Howard, Kelli; Frank, Erin; Harmon, Kelli; Wong, Hector R

2014-11-19

Increasing evidence supports a role for mitochondrial dysfunction in organ injury and immune dysregulation in sepsis. Although differential expression of mitochondrial genes in blood cells has been reported for several diseases in which bioenergetic failure is a postulated mechanism, there are no data about the blood cell mitochondrial transcriptome in pediatric sepsis. We conducted a focused analysis using a multicenter genome-wide expression database of 180 children ≤ 10 years of age with septic shock and 53 healthy controls. Using total RNA isolated from whole blood within 24 hours of PICU admission for septic shock, we evaluated 296 nuclear-encoded mitochondrial genes using a false discovery rate of 1%. A series of bioinformatic approaches were applied to compare differentially expressed genes across previously validated gene expression-based subclasses (groups A, B, and C) of pediatric septic shock. In total, 118 genes were differentially regulated in subjects with septic shock compared to healthy controls, including 48 genes that were upregulated and 70 that were downregulated. The top scoring canonical pathway was oxidative phosphorylation, with general downregulation of the 51 genes corresponding to the electron transport system (ETS). The top two gene networks were composed primarily of mitochondrial ribosomal proteins highly connected to ETS complex I, and genes encoding for ETS complexes I, II, and IV that were highly connected to the peroxisome proliferator activated receptor (PPAR) family. There were 162 mitochondrial genes differentially regulated between groups A, B, and C. Group A, which had the highest maximum number of organ failures and mortality, exhibited a greater downregulation of mitochondrial genes compared to groups B and C. Based on a focused analysis of a pediatric septic shock transcriptomic database, nuclear-encoded mitochondrial genes were differentially regulated early in pediatric septic shock compared to healthy controls, as well as across genotypic and phenotypic distinct pediatric septic shock subclasses. The nuclear genome may be an important mechanism contributing to alterations in mitochondrial bioenergetic function and outcomes in pediatric sepsis.

Ursolic acid improves domoic acid-induced cognitive deficits in mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Dong-mei; Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Xuzhou Normal University, Xuzhou 221116, Jiangsu Province; Lu, Jun, E-mail: lu-jun75@163.com

Our previous findings suggest that mitochondrial dysfunction is the mechanism underlying cognitive deficits induced by domoic acid (DA). Ursolic acid (UA), a natural triterpenoid compound, possesses many important biological functions. Evidence shows that UA can activate PI3K/Akt signaling and suppress Forkhead box protein O1 (FoxO1) activity. FoxO1 is an important regulator of mitochondrial function. Here we investigate whether FoxO1 is involved in the oxidative stress-induced mitochondrial dysfunction in DA-treated mice and whether UA inhibits DA-induced mitochondrial dysfunction and cognitive deficits through regulating the PI3K/Akt and FoxO1 signaling pathways. Our results showed that FoxO1 knockdown reversed the mitochondrial abnormalities and cognitivemore » deficits induced by DA in mice through decreasing HO-1 expression. Mechanistically, FoxO1 activation was associated with oxidative stress-induced JNK activation and decrease of Akt phosphorylation. Moreover, UA attenuated the mitochondrial dysfunction and cognitive deficits through promoting Akt phosphorylation and FoxO1 nuclear exclusion in the hippocampus of DA-treated mice. LY294002, an inhibitor of PI3K/Akt signaling, significantly decreased Akt phosphorylation in the hippocampus of DA/UA mice, which weakened UA actions. These results suggest that UA could be recommended as a possible candidate for the prevention and therapy of cognitive deficits in excitotoxic brain disorders. - Highlights: • Ursolic acid (UA) is a naturally triterpenoid compound. • UA attenuated the mitochondrial dysfunction and cognitive deficits. • Mechanistically, UA activates PI3K/Akt signaling and suppresses FoxO1 activity. • UA could be recommended as a possible candidate for anti-excitotoxic brain disorders.« less

Minnelide/Triptolide Impairs Mitochondrial Function by Regulating SIRT3 in P53-Dependent Manner in Non-Small Cell Lung Cancer.

PubMed

Kumar, Ajay; Corey, Catherine; Scott, Iain; Shiva, Sruti; D'Cunha, Jonathan

2016-01-01

Minnelide/Triptolide (TL) has recently emerged as a potent anticancer drug in non-small cell lung cancer (NSCLC). However, the precise mechanism of its action remains ambiguous. In this study, we elucidated the molecular basis for TL-induced cell death in context to p53 status. Cell death was attributed to dysfunction of mitochondrial bioenergetics in p53-deficient cells, which was characterized by decreased mitochondrial respiration, steady-state ATP level and membrane potential, but augmented reactive oxygen species (ROS). Increased ROS production resulted in oxidative stress in TL-treated cells. This was exhibited by elevated nuclear levels of a redox-sensitive transcriptional factor, NF-E2-related factor-2 (NRF2), along with diminished cellular glutathione (GSH) content. We further demonstrated that in the absence of p53, TL blunted the expression of mitochondrial SIRT3 triggering increased acetylation of NDUAF9 and succinate dehydrogenase, components of complexes I and II of the electron transport chain (ETC). TL-mediated hyperacetylation of complexes I and II proteins and these complexes displayed decreased enzymatic activities. We also provide the evidence that P53 regulate steady-state level of SIRT3 through Proteasome-Pathway. Finally, forced overexpression of Sirt3, but not deacetylase-deficient mutant of Sirt3 (H243Y), restored the deleterious effect of TL on p53-deficient cells by rescuing mitochondrial bioenergetics. On contrary, Sirt3 deficiency in the background of wild-type p53 triggered TL-induced mitochondrial impairment that echoed TL effect in p53-deficeint cells. These findings illustrate a novel mechanism by which TL exerts its potent effects on mitochondrial function and ultimately the viability of NSCLC tumor.

BID links ferroptosis to mitochondrial cell death pathways.

PubMed

Neitemeier, Sandra; Jelinek, Anja; Laino, Vincenzo; Hoffmann, Lena; Eisenbach, Ina; Eying, Roman; Ganjam, Goutham K; Dolga, Amalia M; Oppermann, Sina; Culmsee, Carsten

2017-08-01

Ferroptosis has been defined as an oxidative and iron-dependent pathway of regulated cell death that is distinct from caspase-dependent apoptosis and established pathways of death receptor-mediated regulated necrosis. While emerging evidence linked features of ferroptosis induced e.g. by erastin-mediated inhibition of the X c - system or inhibition of glutathione peroxidase 4 (Gpx4) to an increasing number of oxidative cell death paradigms in cancer cells, neurons or kidney cells, the biochemical pathways of oxidative cell death remained largely unclear. In particular, the role of mitochondrial damage in paradigms of ferroptosis needs further investigation. In the present study, we find that erastin-induced ferroptosis in neuronal cells was accompanied by BID transactivation to mitochondria, loss of mitochondrial membrane potential, enhanced mitochondrial fragmentation and reduced ATP levels. These hallmarks of mitochondrial demise are also established features of oxytosis, a paradigm of cell death induced by X c - inhibition by millimolar concentrations of glutamate. Bid knockout using CRISPR/Cas9 approaches preserved mitochondrial integrity and function, and mediated neuroprotective effects against both, ferroptosis and oxytosis. Furthermore, the BID-inhibitor BI-6c9 inhibited erastin-induced ferroptosis, and, in turn, the ferroptosis inhibitors ferrostatin-1 and liproxstatin-1 prevented mitochondrial dysfunction and cell death in the paradigm of oxytosis. These findings show that mitochondrial transactivation of BID links ferroptosis to mitochondrial damage as the final execution step in this paradigm of oxidative cell death. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Brain region- and sex-specific modulation of mitochondrial glucocorticoid receptor phosphorylation in fluoxetine treated stressed rats: effects on energy metabolism.

PubMed

Adzic, Miroslav; Lukic, Iva; Mitic, Milos; Djordjevic, Jelena; Elaković, Ivana; Djordjevic, Ana; Krstic-Demonacos, Marija; Matić, Gordana; Radojcic, Marija

2013-12-01

Antidepressants affect glucocorticoid receptor (GR) functioning partly through modulation of its phosphorylation but their effects on mitochondrial GR have remained undefined. We investigated the ability of chronic fluoxetine treatment to affect chronic stress-induced changes of mitochondrial GR and its phosphoisoforms (pGRs) in the prefrontal cortex and hippocampus of female and male rats. Since mitochondrial GR regulates oxidative phosphorylation, expression of mitochondrial-encoded subunits of cytochrome (cyt) c oxidase and its activity were also investigated. Chronic stress caused accumulation of the GR in mitochondria of female prefrontal cortex, while the changes in the hippocampus were sex-specific at the levels of pGRs. Expression of mitochondrial COXs genes corresponded to chronic stress-modulated mitochondrial GR in both tissues of both genders and to cyt c oxidase activity in females. Moreover, the metabolic parameters in stressed animals were affected by fluoxetine therapy only in the hippocampus. Namely, fluoxetine effects on mitochondrial COXs and cyt c oxidase activity in the hippocampus seem to be conveyed through pGR232 in females, while in males this likely occurs through other mechanisms. In summary, sex-specific regulation of cyt c oxidase by the stress and antidepressant treatment and its differential convergence with mitochondrial GR signaling in the prefrontal cortex and hippocampus could contribute to clarification of sex-dependent vulnerability to stress-related disorders and sex-specific clinical impact of antidepressants. Copyright © 2013 Elsevier Ltd. All rights reserved.

Phytochemicals prevent mitochondrial membrane permeabilization and protect SH-SY5Y cells against apoptosis induced by PK11195, a ligand for outer membrane translocator protein.

PubMed

Wu, Yuqiu; Shamoto-Nagai, Masayo; Maruyama, Wakako; Osawa, Toshihiko; Naoi, Makoto

2017-01-01

Epidemiological studies present the beneficial effects of dietary habits on prevention of aging-associated decline of brain function. Phytochemicals, the second metabolites of food, protect neuronal cells from cell death in cellular models of neurodegenerative disorders, and the neuroprotective activity has been ascribed to the anti-oxidant and anti-inflammatory functions. In this paper, the cellular mechanism of neuroprotection by phytochemicals was investigated, using the cellular model of mitochondrial apoptosis induced by PK11195, a ligand of outer membrane translocator protein, in SH-SY5Y cells. PK11195 induced mitochondrial membrane permeabilization with rapid transit production of superoxide (superoxide flashes) and calcium release from mitochondria, and activated apoptosis signal pathway. Study on the structure-activity relationship of astaxanthin, ferulic acid derivatives, and sesame lignans revealed that these phytochemicals inhibited mitochondrial membrane permeabilization and protected cells from apoptosis. Ferulic acid derivatives and sesame lignans inhibited or enhanced the mitochondrial pore formation and cell death by PK11195 according to their amphiphilic properties, not directly depending on the antioxidant activity. Regulation of pore formation at mitochondrial membrane is discussed as a novel mechanism behind neuroprotective activity of phytochemicals in aging and age-associated neurodegenerative disorders, and also behind dual functions of phytochemicals in neuronal and cancer cells.

An Arabidopsis mitochondria-localized RRL protein mediates abscisic acid signal transduction through mitochondrial retrograde regulation involving ABI4.

PubMed

Yao, Xuan; Li, Juanjuan; Liu, Jianping; Liu, Kede

2015-10-01

The molecular mechanisms of abscisic acid (ABA) signalling have been studied for many years; however, how mitochondria-localized proteins play roles in ABA signalling remains unclear. Here an Arabidopsis mitochondria-localized protein RRL (RETARDED ROOT GROWTH-LIKE) was shown to function in ABA signalling. A previous study had revealed that the Arabidopsis mitochondria-localized protein RRG (RETARDED ROOT GROWTH) is required for cell division in the root meristem. RRL shares 54% and 57% identity at the nucleotide and amino acid sequences, respectively, with RRG; nevertheless, RRL shows a different function in Arabidopsis. In this study, disruption of RRL decreased ABA sensitivity whereas overexpression of RRL increased ABA sensitivity during seed germination and seedling growth. High expression levels of RRL were found in germinating seeds and developing seedlings, as revealed by β-glucuronidase (GUS) staining of ProRRL-GUS transgenic lines. The analyses of the structure and function of mitochondria in the knockout rrl mutant showed that the disruption of RRL causes extensively internally vacuolated mitochondria and reduced ABA-stimulated reactive oxygen species (ROS) production. Previous studies have revealed that the expression of alternative oxidase (AOX) in the alternative respiratory pathway is increased by mitochondrial retrograde regulation to regain ROS levels when the mitochondrial electron transport chain is impaired. The APETALA2 (AP2)-type transcription factor ABI4 is a regulator of ALTERNATIVE OXIDASE1a (AOX1a) in mitochondrial retrograde signalling. This study showed that ABA-induced AOX1a and ABI4 expression was inhibited in the rrl mutant, suggesting that RRL is probably involved in ABI4-mediated mitochondrial retrograde signalling. Furthermore, the results revealed that ABI4 is a downstream regulatory factor in RRL-mediated ABA signalling in seed germination and seedling growth. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

The conserved regulation of mitochondrial uncoupling proteins: From unicellular eukaryotes to mammals.

PubMed

Woyda-Ploszczyca, Andrzej M; Jarmuszkiewicz, Wieslawa

2017-01-01

Uncoupling proteins (UCPs) belong to the mitochondrial anion carrier protein family and mediate regulated proton leak across the inner mitochondrial membrane. Free fatty acids, aldehydes such as hydroxynonenal, and retinoids activate UCPs. However, there are some controversies about the effective action of retinoids and aldehydes alone; thus, only free fatty acids are commonly accepted positive effectors of UCPs. Purine nucleotides such as GTP inhibit UCP-mediated mitochondrial proton leak. In turn, membranous coenzyme Q may play a role as a redox state-dependent metabolic sensor that modulates the complete activation/inhibition of UCPs. Such regulation has been observed for UCPs in microorganisms, plant and animal UCP1 homologues, and UCP1 in mammalian brown adipose tissue. The origin of UCPs is still under debate, but UCP homologues have been identified in all systematic groups of eukaryotes. Despite the differing levels of amino acid/DNA sequence similarities, functional studies in unicellular and multicellular organisms, from amoebae to mammals, suggest that the mechanistic regulation of UCP activity is evolutionarily well conserved. This review focuses on the regulatory feedback loops of UCPs involving free fatty acids, aldehydes, retinoids, purine nucleotides, and coenzyme Q (particularly its reduction level), which may derive from the early stages of evolution as UCP first emerged. Copyright © 2016 Elsevier B.V. All rights reserved.

The role of nNOS and PGC-1α in skeletal muscle cells.

PubMed

Baldelli, Sara; Lettieri Barbato, Daniele; Tatulli, Giuseppe; Aquilano, Katia; Ciriolo, Maria Rosa

2014-11-15

Neuronal nitric oxide synthase (nNOS) and peroxisome proliferator activated receptor γ co-activator 1α (PGC-1α) are two fundamental factors involved in the regulation of skeletal muscle cell metabolism. nNOS exists as several alternatively spliced variants, each having a specific pattern of subcellular localisation. Nitric oxide (NO) functions as a second messenger in signal transduction pathways that lead to the expression of metabolic genes involved in oxidative metabolism, vasodilatation and skeletal muscle contraction. PGC-1α is a transcriptional coactivator and represents a master regulator of mitochondrial biogenesis by promoting the transcription of mitochondrial genes. PGC-1α can be induced during physical exercise, and it plays a key role in coordinating the oxidation of intracellular fatty acids with mitochondrial remodelling. Several lines of evidence demonstrate that NO could act as a key regulator of PGC-1α expression; however, the link between nNOS and PGC-1α in skeletal muscle remains only poorly understood. In this Commentary, we review important metabolic pathways that are governed by nNOS and PGC-1α, and aim to highlight how they might intersect and cooperatively regulate skeletal muscle mitochondrial and lipid energetic metabolism and contraction. © 2014. Published by The Company of Biologists Ltd.

Mitofusins and the mitochondrial permeability transition: the potential downside of mitochondrial fusion

PubMed Central

Papanicolaou, Kyriakos N.; Phillippo, Matthew M.

2012-01-01

Mitofusins (Mfn-1 and Mfn-2) are transmembrane proteins that bind and hydrolyze guanosine 5′-triphosphate to bring about the merging of adjacent mitochondrial membranes. This event is necessary for mitochondrial fusion, a biological process that is critical for organelle function. The broad effects of mitochondrial fusion on cell bioenergetics have been extensively studied, whereas the local effects of mitofusin activity on the structure and integrity of the fusing mitochondrial membranes have received relatively little attention. From the study of fusogenic proteins, theoretical models, and simulations, it has been noted that the fusion of biological membranes is associated with local perturbations on the integrity of the membrane that present in the form of lipidic holes which open on the opposing bilayers. These lipidic holes represent obligate intermediates that make the fusion process thermodynamically more favorable and at the same time induce leakage to the fusing membranes. In this perspectives article we present the relevant evidence selected from a spectrum of membrane fusion/leakage models and attempt to couple this information with observations conducted with cardiac myocytes or mitochondria deficient in Mfn-1 and Mfn-2. More specifically, we argue in favor of a situation whereby mitochondrial fusion in cardiac myocytes is coupled with outer mitochondrial membrane destabilization that is opportunistically employed during the process of mitochondrial permeability transition. We hope that these insights will initiate research on this new hypothesis of mitochondrial permeability transition regulation, a poorly understood mitochondrial function with significant consequences on myocyte survival. PMID:22636681

Validation of the use of an artificial mitochondrial reporter DNA vector containing a Cytomegalovirus promoter for mitochondrial transgene expression.

PubMed

Yamada, Yuma; Ishikawa, Takuya; Harashima, Hideyoshi

2017-08-01

Mitochondria have their own gene expression system that is independent of the nuclear system, and control cellular functions in cooperation with the nucleus. While a number of useful technologies for achieving nuclear transgene expression have been reported, only a few have focused on mitochondria. In this study, we validated the utility of an artificial mitochondrial DNA vector with a virus promoter on mitochondrial transgene expression. We designed and constructed pCMV-mtLuc (CGG) that contains a CMV promotor derived from Cytomegalovirus and an artificial mitochondrial genome with a NanoLuc (Nluc) luciferase gene that records adjustments to the mitochondrial codon system. Nluc luciferase activity measurements showed that the pCMV-mtLuc (CGG) efficiently produced the Nluc luciferase protein in human HeLa cells. Moreover, we optimized the mitochondrial transfection of pCMV-mtLuc (CGG) using a MITO-Porter system, a liposome-based carrier for mitochondrial delivery via membrane fusion. As a result, we found that transfection of pCMV-mtLuc (CGG) by MITO-Porter modified with the KALA peptide (cationic amphipathic cell-penetrating peptide) showed a high mitochondrial transgene expression. The developed mitochondrial transgene expression system represents a potentially useful tool for the fields of nanoscience and nanotechnology for controlling the intracellular microenvironment via the regulation of mitochondrial function and promises to open additional innovative research fields of study. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nuclear Transcription Factors in the Mitochondria: A New Paradigm in Fine-Tuning Mitochondrial Metabolism.

PubMed

Sepuri, Naresh Babu V; Tammineni, Prasad; Mohammed, Fareed; Paripati, Arunkumar

2017-01-01

Noncanonical functions of several nuclear transcription factors in the mitochondria have been gaining exceptional traction over the years. These transcription factors include nuclear hormone receptors like estrogen, glucocorticoid, and thyroid hormone receptors: p53, IRF3, STAT3, STAT5, CREB, NF-kB, and MEF-2D. Mitochondria-localized nuclear transcription factors regulate mitochondrial processes like apoptosis, respiration and mitochondrial transcription albeit being nuclear in origin and having nuclear functions. Hence, the cell permits these multi-stationed transcription factors to orchestrate and fine-tune cellular metabolism at various levels of operation. Despite their ubiquitous distribution in different subcompartments of mitochondria, their targeting mechanism is poorly understood. Here, we review the current status of mitochondria-localized transcription factors and discuss the possible targeting mechanism besides the functional interplay between these factors.

Mitochondrial-targeted DNA delivery using a DF-MITO-Porter, an innovative nano carrier with cytoplasmic and mitochondrial fusogenic envelopes

NASA Astrophysics Data System (ADS)

Yamada, Yuma; Kawamura, Eriko; Harashima, Hideyoshi

2012-08-01

Mitochondrial gene therapy has the potential for curing a variety of diseases that are associated with mitochondrial DNA mutations and/or defects. To achieve this, it will be necessary to deliver therapeutic agents into the mitochondria in diseased cells. A number of mitochondrial drug delivery systems have been reported to date. However, reports of mitochondrial-targeted DNA delivery are limited. To achieve this, the therapeutic agent must be taken up by the cell (1), after which, the multi-processes associated with intracellular trafficking must be sophisticatedly regulated so as to release the agent from the endosome and deliver it to the cytosol (2) and to pass through the mitochondrial membrane (3). We report herein on the mitochondrial delivery of oligo DNA as a model therapeutic using a Dual Function (DF)-MITO-Porter, an innovative nano carrier designed for mitochondrial delivery. The critical structural elements of the DF-MITO-Porter include mitochondria-fusogenic inner envelopes and endosome-fusogenic outer envelopes, modified with octaarginine which greatly assists in cellular uptake. Inside the cell, the carrier passes through the endosomal and mitochondrial membranes via step-wise membrane fusion. When the oligo DNA was packaged in the DF-MITO-Porter, cellular uptake efficiency was strongly enhanced. Intracellular observation using confocal laser scanning microscopy showed that the DF-MITO-Porter was effectively released from endosomes. Moreover, the findings confirmed that the mitochondrial targeting activity of the DF-MITO-Porter was significantly higher than that of a carrier without outer endosome-fusogenic envelopes. These results support the conclusion that mitochondrial-targeted DNA delivery using a DF-MITO-Porter can be achieved when intracellular trafficking is optimally regulated.

Compartmentalized Regulation of Parkin-Mediated Mitochondrial Quality Control in the Drosophila Nervous System In Vivo.

PubMed

Sung, Hyun; Tandarich, Lauren C; Nguyen, Kenny; Hollenbeck, Peter J

2016-07-13

In neurons, the normal distribution and selective removal of mitochondria are considered essential for maintaining the functions of the large asymmetric cell and its diverse compartments. Parkin, a E3 ubiquitin ligase associated with familial Parkinson's disease, has been implicated in mitochondrial dynamics and removal in cells including neurons. However, it is not clear how Parkin functions in mitochondrial turnover in vivo, or whether Parkin-dependent events of the mitochondrial life cycle occur in all neuronal compartments. Here, using the live Drosophila nervous system, we investigated the involvement of Parkin in mitochondrial dynamics, distribution, morphology, and removal. Contrary to our expectations, we found that Parkin-deficient animals do not accumulate senescent mitochondria in their motor axons or neuromuscular junctions; instead, they contain far fewer axonal mitochondria, and these displayed normal motility behavior, morphology, and metabolic state. However, the loss of Parkin did produce abnormal tubular and reticular mitochondria restricted to the motor cell bodies. In addition, in contrast to drug-treated, immortalized cells in vitro, mature motor neurons rarely displayed Parkin-dependent mitophagy. These data indicate that the cell body is the focus of Parkin-dependent mitochondrial quality control in neurons, and argue that a selection process allows only healthy mitochondria to pass from cell bodies to axons, perhaps to limit the impact of mitochondrial dysfunction. Parkin has been proposed to police mitochondrial fidelity by binding to dysfunctional mitochondria via PTEN (phosphatase and tensin homolog)-induced putative kinase 1 (PINK1) and targeting them for autophagic degradation. However, it is unknown whether and how the PINK1/Parkin pathway regulates the mitochondrial life cycle in neurons in vivo Using Drosophila motor neurons, we show that parkin disruption generates an abnormal mitochondrial network in cell bodies in vivo and reduces the number of axonal mitochondria without producing any defects in their axonal transport, morphology, or metabolic state. Furthermore, while cultured neurons display Parkin-dependent axonal mitophagy, we find this is vanishingly rare in vivo under normal physiological conditions. Thus, both the spatial distribution and mechanism of mitochondrial quality control in vivo differ substantially from those observed in vitro. Copyright © 2016 the authors 0270-6474/16/367375-17$15.00/0.

Compartmentalized Regulation of Parkin-Mediated Mitochondrial Quality Control in the Drosophila Nervous System In Vivo

PubMed Central

Sung, Hyun; Tandarich, Lauren C.; Nguyen, Kenny

2016-01-01

In neurons, the normal distribution and selective removal of mitochondria are considered essential for maintaining the functions of the large asymmetric cell and its diverse compartments. Parkin, a E3 ubiquitin ligase associated with familial Parkinson's disease, has been implicated in mitochondrial dynamics and removal in cells including neurons. However, it is not clear how Parkin functions in mitochondrial turnover in vivo, or whether Parkin-dependent events of the mitochondrial life cycle occur in all neuronal compartments. Here, using the live Drosophila nervous system, we investigated the involvement of Parkin in mitochondrial dynamics, distribution, morphology, and removal. Contrary to our expectations, we found that Parkin-deficient animals do not accumulate senescent mitochondria in their motor axons or neuromuscular junctions; instead, they contain far fewer axonal mitochondria, and these displayed normal motility behavior, morphology, and metabolic state. However, the loss of Parkin did produce abnormal tubular and reticular mitochondria restricted to the motor cell bodies. In addition, in contrast to drug-treated, immortalized cells in vitro, mature motor neurons rarely displayed Parkin-dependent mitophagy. These data indicate that the cell body is the focus of Parkin-dependent mitochondrial quality control in neurons, and argue that a selection process allows only healthy mitochondria to pass from cell bodies to axons, perhaps to limit the impact of mitochondrial dysfunction. SIGNIFICANCE STATEMENT Parkin has been proposed to police mitochondrial fidelity by binding to dysfunctional mitochondria via PTEN (phosphatase and tensin homolog)-induced putative kinase 1 (PINK1) and targeting them for autophagic degradation. However, it is unknown whether and how the PINK1/Parkin pathway regulates the mitochondrial life cycle in neurons in vivo. Using Drosophila motor neurons, we show that parkin disruption generates an abnormal mitochondrial network in cell bodies in vivo and reduces the number of axonal mitochondria without producing any defects in their axonal transport, morphology, or metabolic state. Furthermore, while cultured neurons display Parkin-dependent axonal mitophagy, we find this is vanishingly rare in vivo under normal physiological conditions. Thus, both the spatial distribution and mechanism of mitochondrial quality control in vivo differ substantially from those observed in vitro. PMID:27413149

G2019S leucine-rich repeat kinase 2 causes uncoupling protein-mediated mitochondrial depolarization

PubMed Central

Papkovskaia, Tatiana D.; Chau, Kai-Yin; Inesta-Vaquera, Francisco; Papkovsky, Dmitri B.; Healy, Daniel G.; Nishio, Koji; Staddon, James; Duchen, Michael R.; Hardy, John; Schapira, Anthony H.V.; Cooper, J. Mark

2012-01-01

The G2019S leucine rich repeat kinase 2 (LRRK2) mutation is the most common genetic cause of Parkinson's disease (PD), clinically and pathologically indistinguishable from idiopathic PD. Mitochondrial abnormalities are a common feature in PD pathogenesis and we have investigated the impact of G2019S mutant LRRK2 expression on mitochondrial bioenergetics. LRRK2 protein expression was detected in fibroblasts and lymphoblasts at levels higher than those observed in the mouse brain. The presence of G2019S LRRK2 mutation did not influence LRRK2 expression in fibroblasts. However, the expression of the G2019S LRRK2 mutation in both fibroblast and neuroblastoma cells was associated with mitochondrial uncoupling. This was characterized by decreased mitochondrial membrane potential and increased oxygen utilization under basal and oligomycin-inhibited conditions. This resulted in a decrease in cellular ATP levels consistent with compromised cellular function. This uncoupling of mitochondrial oxidative phosphorylation was associated with a cell-specific increase in uncoupling protein (UCP) 2 and 4 expression. Restoration of mitochondrial membrane potential by the UCP inhibitor genipin confirmed the role of UCPs in this mechanism. The G2019S LRRK2-induced mitochondrial uncoupling and UCP4 mRNA up-regulation were LRRK2 kinase-dependent, whereas endogenous LRRK2 levels were required for constitutive UCP expression. We propose that normal mitochondrial function was deregulated by the expression of G2019S LRRK2 in a kinase-dependent mechanism that is a modification of the normal LRRK2 function, and this leads to the vulnerability of selected neuronal populations in PD. PMID:22736029

14,15-EET promotes mitochondrial biogenesis and protects cortical neurons against oxygen/glucose deprivation-induced apoptosis.

PubMed

Wang, Lai; Chen, Man; Yuan, Lin; Xiang, Yuting; Zheng, Ruimao; Zhu, Shigong

2014-07-18

14,15-Epoxyeicosatrienoic acid (14,15-EET), a metabolite of arachidonic acid, is enriched in the brain cortex and exerts protective effect against neuronal apoptosis induced by ischemia/reperfusion. Although apoptosis has been well recognized to be closely associated with mitochondrial biogenesis and function, it is still unclear whether the neuroprotective effect of 14,15-EET is mediated by promotion of mitochondrial biogenesis and function in cortical neurons under the condition of oxygen-glucose deprivation (OGD). In this study, we found that 14,15-EET improved cell viability and inhibited apoptosis of cortical neurons. 14,15-EET significantly increased the mitochondrial mass and the ratio of mitochondrial DNA to nuclear DNA. Key makers of mitochondrial biogenesis, peroxisome proliferator activator receptor gamma-coactivator 1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (TFAM), were elevated at both mRNA and protein levels in the cortical neurons treated with 14,15-EET. Moreover, 14,15-EET markedly attenuated the decline of mitochondrial membrane potential, reduced ROS, while increased ATP synthesis. Knockdown of cAMP-response element binding protein (CREB) by siRNA blunted the up-regulation of PGC-1α and NRF-1 stimulated by 14,15-EET, and consequently abolished the neuroprotective effect of 14,15-EET. Our results indicate that 14,15-EET protects neurons from OGD-induced apoptosis by promoting mitochondrial biogenesis and function through CREB mediated activation of PGC-1α and NRF-1. Copyright © 2014 Elsevier Inc. All rights reserved.

Translating the basic knowledge of mitochondrial functions to metabolic therapy: role of L-carnitine.

PubMed

Marcovina, Santica M; Sirtori, Cesare; Peracino, Andrea; Gheorghiade, Mihai; Borum, Peggy; Remuzzi, Giuseppe; Ardehali, Hossein

2013-02-01

Mitochondria play important roles in human physiological processes, and therefore, their dysfunction can lead to a constellation of metabolic and nonmetabolic abnormalities such as a defect in mitochondrial gene expression, imbalance in fuel and energy homeostasis, impairment in oxidative phosphorylation, enhancement of insulin resistance, and abnormalities in fatty acid metabolism. As a consequence, mitochondrial dysfunction contributes to the pathophysiology of insulin resistance, obesity, diabetes, vascular disease, and chronic heart failure. The increased knowledge on mitochondria and their role in cellular metabolism is providing new evidence that these disorders may benefit from mitochondrial-targeted therapies. We review the current knowledge of the contribution of mitochondrial dysfunction to chronic diseases, the outcomes of experimental studies on mitochondrial-targeted therapies, and explore the potential of metabolic modulators in the treatment of selected chronic conditions. As an example of such modulators, we evaluate the efficacy of the administration of L-carnitine and its analogues acetyl and propionyl L-carnitine in several chronic diseases. L-carnitine is intrinsically involved in mitochondrial metabolism and function as it plays a key role in fatty acid oxidation and energy metabolism. In addition to the transportation of free fatty acids across the inner mitochondrial membrane, L-carnitine modulates their oxidation rate and is involved in the regulation of vital cellular functions such as apoptosis. Thus, L-carnitine and its derivatives show promise in the treatment of chronic conditions and diseases associated with mitochondrial dysfunction but further translational studies are needed to fully explore their potential. Copyright © 2013 Mosby, Inc. All rights reserved.

Evidence of a bigenomic regulation of mitochondrial gene expression by thyroid hormone during rat brain development.

PubMed

Sinha, Rohit Anthony; Pathak, Amrita; Mohan, Vishwa; Babu, Satish; Pal, Amit; Khare, Drirh; Godbole, Madan M

2010-07-02

Hypothyroidism during early mammalian brain development is associated with decreased expression of various mitochondrial encoded genes along with evidence for mitochondrial dysfunction. However, in-spite of the similarities between neurological disorders caused by perinatal hypothyroidism and those caused by various genetic mitochondrial defects we still do not know as to how thyroid hormone (TH) regulates mitochondrial transcription during development and whether this regulation by TH is nuclear mediated or through mitochondrial TH receptors? We here in rat cerebellum show that hypothyroidism causes reduction in expression of nuclear encoded genes controlling mitochondrial biogenesis like PGC-1alpha, NRF-1alpha and Tfam. Also, we for the first time demonstrate a mitochondrial localization of thyroid hormone receptor (mTR) isoform in developing brain capable of binding a TH response element (DR2) present in D-loop region of mitochondrial DNA. These results thus indicate an integrated nuclear-mitochondrial cross talk in regulation of mitochondrial transcription by TH during brain development. Copyright 2010 Elsevier Inc. All rights reserved.

Evidence of a bigenomic regulation of mitochondrial gene expression by thyroid hormone during rat brain development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinha, Rohit Anthony; Pathak, Amrita; Mohan, Vishwa

Hypothyroidism during early mammalian brain development is associated with decreased expression of various mitochondrial encoded genes along with evidence for mitochondrial dysfunction. However, in-spite of the similarities between neurological disorders caused by perinatal hypothyroidism and those caused by various genetic mitochondrial defects we still do not know as to how thyroid hormone (TH) regulates mitochondrial transcription during development and whether this regulation by TH is nuclear mediated or through mitochondrial TH receptors? We here in rat cerebellum show that hypothyroidism causes reduction in expression of nuclear encoded genes controlling mitochondrial biogenesis like PGC-1{alpha}, NRF-1{alpha} and Tfam. Also, we for themore » first time demonstrate a mitochondrial localization of thyroid hormone receptor (mTR) isoform in developing brain capable of binding a TH response element (DR2) present in D-loop region of mitochondrial DNA. These results thus indicate an integrated nuclear-mitochondrial cross talk in regulation of mitochondrial transcription by TH during brain development.« less

GLP-1 promotes mitochondrial metabolism in vascular smooth muscle cells by enhancing endoplasmic reticulum-mitochondria coupling.

PubMed

Morales, Pablo E; Torres, Gloria; Sotomayor-Flores, Cristian; Peña-Oyarzún, Daniel; Rivera-Mejías, Pablo; Paredes, Felipe; Chiong, Mario

2014-03-28

Incretin GLP-1 has important metabolic effects on several tissues, mainly through the regulation of glucose uptake and usage. One mechanism for increasing cell metabolism is modulating endoplasmic reticulum (ER)-mitochondria communication, as it allows for a more efficient transfer of Ca(2+) into the mitochondria, thereby increasing activity. Control of glucose metabolism is essential for proper vascular smooth muscle cell (VSMC) function. GLP-1 has been shown to produce varied metabolic actions, but whether it regulates glucose metabolism in VSMC remains unknown. In this report, we show that GLP-1 increases mitochondrial activity in the aortic cell line A7r5 by increasing ER-mitochondria coupling. GLP-1 increases intracellular glucose and diminishes glucose uptake without altering glycogen content. ATP, mitochondrial potential and oxygen consumption increase at 3h of GLP-1 treatment, paralleled by increased Ca(2+) transfer from the ER to the mitochondria. Furthermore, GLP-1 increases levels of Mitofusin-2 (Mfn2), an ER-mitochondria tethering protein, via a PKA-dependent mechanism. Accordingly, PKA inhibition and Mfn2 down-regulation prevented mitochondrial Ca(2+) increases in GLP-1 treated cells. Inhibiting both Ca(2+) release from the ER and Ca(2+) entry into mitochondria as well as diminishing Mfn2 levels blunted the increase in mitochondrial activity in response to GLP-1. Altogether, these results strongly suggest that GLP-1 increases ER-mitochondria communication in VSMC, resulting in higher mitochondrial activity. Copyright © 2014 Elsevier Inc. All rights reserved.

Dietary Fat and Hepatic Lipogenesis: Mitochondrial Citrate Carrier as a Sensor of Metabolic Changes1

PubMed Central

Ferramosca, Alessandra; Zara, Vincenzo

2014-01-01

Citrate carrier (CIC) is an integral protein of the inner mitochondrial membrane that has a fundamental role in hepatic intermediary metabolism. Its primary function is to catalyze the transport of citrate from mitochondria, where this molecule is formed, to cytosol, where this molecule is used for fatty acid (FA) and cholesterol synthesis. Therefore, mitochondrial CIC acts upstream of cytosolic lipogenic reactions, and its regulation is particularly important in view of the modulation of hepatic lipogenesis. Although a great deal of data are currently available on the dietary modulation of cytosolic lipogenic enzymes, little is known about the nutritional regulation of CIC transport activity. In this review, we describe the differential effects of distinct FAs present in the diet on the activity of mitochondrial CIC. In particular, polyunsaturated FAs were powerful modulators of the activity of mitochondrial CIC by influencing its expression through transcriptional and posttranscriptional mechanisms. On the contrary, saturated and monounsaturated FAs did not influence mitochondrial CIC activity. Moreover, variations in CIC activity were connected to similar alterations in the metabolic pathways to which the transported citrate is channeled. Therefore, CIC may be considered as a sensor for changes occurring inside the hepatocyte and may represent an important target for the regulation of hepatic lipogenesis. The crucial role of this protein is reinforced by the recent discovery of its involvement in other cellular processes, such as glucose-stimulated insulin secretion, inflammation, tumorigenesis, genome stability, and sperm metabolism. PMID:24829468

Dietary fat and hepatic lipogenesis: mitochondrial citrate carrier as a sensor of metabolic changes.

PubMed

Ferramosca, Alessandra; Zara, Vincenzo

2014-05-01

Citrate carrier (CIC) is an integral protein of the inner mitochondrial membrane that has a fundamental role in hepatic intermediary metabolism. Its primary function is to catalyze the transport of citrate from mitochondria, where this molecule is formed, to cytosol, where this molecule is used for fatty acid (FA) and cholesterol synthesis. Therefore, mitochondrial CIC acts upstream of cytosolic lipogenic reactions, and its regulation is particularly important in view of the modulation of hepatic lipogenesis. Although a great deal of data are currently available on the dietary modulation of cytosolic lipogenic enzymes, little is known about the nutritional regulation of CIC transport activity. In this review, we describe the differential effects of distinct FAs present in the diet on the activity of mitochondrial CIC. In particular, polyunsaturated FAs were powerful modulators of the activity of mitochondrial CIC by influencing its expression through transcriptional and posttranscriptional mechanisms. On the contrary, saturated and monounsaturated FAs did not influence mitochondrial CIC activity. Moreover, variations in CIC activity were connected to similar alterations in the metabolic pathways to which the transported citrate is channeled. Therefore, CIC may be considered as a sensor for changes occurring inside the hepatocyte and may represent an important target for the regulation of hepatic lipogenesis. The crucial role of this protein is reinforced by the recent discovery of its involvement in other cellular processes, such as glucose-stimulated insulin secretion, inflammation, tumorigenesis, genome stability, and sperm metabolism. © 2014 American Society for Nutrition.

DDX3 DEAD-box RNA helicase plays a central role in mitochondrial protein quality control in Leishmania

PubMed Central

Padmanabhan, Prasad Kottayil; Zghidi-Abouzid, Ouafa; Samant, Mukesh; Dumas, Carole; Aguiar, Bruno Guedes; Estaquier, Jerome; Papadopoulou, Barbara

2016-01-01

DDX3 is a highly conserved member of ATP-dependent DEAD-box RNA helicases with multiple functions in RNA metabolism and cellular signaling. Here, we describe a novel function for DDX3 in regulating the mitochondrial stress response in the parasitic protozoan Leishmania. We show that genetic inactivation of DDX3 leads to the accumulation of mitochondrial reactive oxygen species (ROS) associated with a defect in hydrogen peroxide detoxification. Upon stress, ROS production is greatly enhanced, causing mitochondrial membrane potential loss, mitochondrial fragmentation, and cell death. Importantly, this phenotype is exacerbated upon oxidative stress in parasites forced to use the mitochondrial oxidative respiratory machinery. Furthermore, we show that in the absence of DDX3, levels of major components of the unfolded protein response as well as of polyubiquitinated proteins increase in the parasite, particularly in the mitochondrion, as an indicator of mitochondrial protein damage. Consistent with these findings, immunoprecipitation and mass-spectrometry studies revealed potential interactions of DDX3 with key components of the cellular stress response, particularly the antioxidant response, the unfolded protein response, and the AAA-ATPase p97/VCP/Cdc48, which is essential in mitochondrial protein quality control by driving proteosomal degradation of polyubiquitinated proteins. Complementation studies using DDX3 deletion mutants lacking conserved motifs within the helicase core support that binding of DDX3 to ATP is essential for DDX3's function in mitochondrial proteostasis. As a result of the inability of DDX3-depleted Leishmania to recover from ROS damage and to survive various stresses in the host macrophage, parasite intracellular development was impaired. Collectively, these observations support a central role for the Leishmania DDX3 homolog in preventing ROS-mediated damage and in maintaining mitochondrial protein quality control. PMID:27735940

Fndc5 knockdown induced suppression of mitochondrial integrity and significantly decreased cardiac differentiation of mouse embryonic stem cells.

PubMed

Nazem, Shima; Rabiee, Farzaneh; Ghaedi, Kamran; Babashah, Sadegh; Sadeghizadeh, Majid; Nasr-Esfahani, Mohammad Hossein

2018-06-01

Fibronectin type III domain-containing 5 protein (Fndc5) is a glycosylated protein with elevated expression in high energy demanded tissues as heart, brain, and muscle. It has been shown that upregulation of Fndc5 is regulated by peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1α), which is known as a master regulator of mitochondrial function and biogenesis. Also, our group indicated that Fndc5 expression increases gradually during cardiac differentiation of mouse embryonic stem cells (mESCs). In this paper, to clarify the importance of Fndc5 in cardiac differentiation, we south to knock down Fndc5 expression by generation a stably transduced mESC line that derives the expression of a short hairpin RNA (shRNA) against Fndc5 gene following doxycycline (Dox) induction. Knock-down of Fndc5 demonstrated a considerable decrease in expression of cardiac progenitor and cardiomyocyte markers. Considering the fact that mitochondria play a crucial role in cardiac differentiation of ESCs, we investigated the role of Fndc5, as a downstream target of PGC1-α, on mitochondrial indices. Results showed that expression of nuclear encoded mitochondrial genes including PGC1-α, Atp5b, Ndufb5, and SOD2 significantly decreased. Moreover, mitochondrial membrane potential (ΔΨm) and relative ATP content of cardiomyocytes decreased markedly with relative ROS level increase. Together, our results suggest that Fndc5 attenuates process of cardiac differentiation of mESCs which is associated with modulation of mitochondrial function and gene expression. © 2017 Wiley Periodicals, Inc.

Mitochondrial-epigenetic crosstalk in environmental toxicology.

PubMed

Weinhouse, Caren

2017-11-01

Crosstalk between the nuclear epigenome and mitochondria, both in normal physiological function and in responses to environmental toxicant exposures, is a developing sub-field of interest in environmental and molecular toxicology. The majority (∼99%) of mitochondrial proteins are encoded in the nuclear genome, so programmed communication among nuclear, cytoplasmic, and mitochondrial compartments is essential for maintaining cellular health. In this review, we will focus on correlative and mechanistic evidence for direct impacts of each system on the other, discuss demonstrated or potential crosstalk in the context of chemical insult, and highlight biological research questions for future study. We will first review the two main signaling systems: nuclear signaling to the mitochondria [anterograde signaling], best described in regulation of oxidative phosphorylation (OXPHOS) and mitochondrial biogenesis in response to environmental signals received by the nucleus, and mitochondrial signals to the nucleus [retrograde signaling]. Both signaling systems can communicate intracellular energy needs or a need to compensate for dysfunction to maintain homeostasis, but both can also relay inappropriate signals in the presence of dysfunction in either system and contribute to adverse health outcomes. We will first review these two signaling systems and highlight known or biologically feasible epigenetic contributions to both, then briefly discuss the emerging field of epigenetic regulation of the mitochondrial genome, and finally discuss putative "crosstalk phenotypes", including biological phenomena, such as caloric restriction, maintenance of stemness, and circadian rhythm, and states of disease or loss of function, such as cancer and aging, in which both the nuclear epigenome and mitochondria are strongly implicated. Copyright © 2017 Elsevier B.V. All rights reserved.

PINK1-Mediated Phosphorylation of Parkin Boosts Parkin Activity in Drosophila

PubMed Central

Shiba-Fukushima, Kahori; Inoshita, Tsuyoshi; Hattori, Nobutaka; Imai, Yuzuru

2014-01-01

Two genes linked to early onset Parkinson's disease, PINK1 and Parkin, encode a protein kinase and a ubiquitin-ligase, respectively. Both enzymes have been suggested to support mitochondrial quality control. We have reported that Parkin is phosphorylated at Ser65 within the ubiquitin-like domain by PINK1 in mammalian cultured cells. However, it remains unclear whether Parkin phosphorylation is involved in mitochondrial maintenance and activity of dopaminergic neurons in vivo. Here, we examined the effects of Parkin phosphorylation in Drosophila, in which the phosphorylation residue is conserved at Ser94. Morphological changes of mitochondria caused by the ectopic expression of wild-type Parkin in muscle tissue and brain dopaminergic neurons disappeared in the absence of PINK1. In contrast, phosphomimetic Parkin accelerated mitochondrial fragmentation or aggregation and the degradation of mitochondrial proteins regardless of PINK1 activity, suggesting that the phosphorylation of Parkin boosts its ubiquitin-ligase activity. A non-phosphorylated form of Parkin fully rescued the muscular mitochondrial degeneration due to the loss of PINK1 activity, whereas the introduction of the non-phosphorylated Parkin mutant in Parkin-null flies led to the emergence of abnormally fused mitochondria in the muscle tissue. Manipulating the Parkin phosphorylation status affected spontaneous dopamine release in the nerve terminals of dopaminergic neurons, the survivability of dopaminergic neurons and flight activity. Our data reveal that Parkin phosphorylation regulates not only mitochondrial function but also the neuronal activity of dopaminergic neurons in vivo, suggesting that the appropriate regulation of Parkin phosphorylation is important for muscular and dopaminergic functions. PMID:24901221

Fasting and refeeding differentially regulate NLRP3 inflammasome activation in human subjects.

PubMed

Traba, Javier; Kwarteng-Siaw, Miriam; Okoli, Tracy C; Li, Jessica; Huffstutler, Rebecca D; Bray, Amanda; Waclawiw, Myron A; Han, Kim; Pelletier, Martin; Sauve, Anthony A; Siegel, Richard M; Sack, Michael N

2015-11-03

Activation of the NLRP3 inflammasome is associated with metabolic dysfunction, and intermittent fasting has been shown to improve clinical presentation of NLRP3 inflammasome-linked diseases. As mitochondrial perturbations, which function as a damage-associated molecular pattern, exacerbate NLRP3 inflammasome activation, we investigated whether fasting blunts inflammasome activation via sirtuin-mediated augmentation of mitochondrial integrity. We performed a clinical study of 19 healthy volunteers. Each subject underwent a 24-hour fast and then was fed a fixed-calorie meal. Blood was drawn during the fasted and fed states and analyzed for NRLP3 inflammasome activation. We enrolled an additional group of 8 healthy volunteers to assess the effects of the sirtuin activator, nicotinamide riboside, on NLRP3 inflammasome activation. In the fasting/refeeding study, individuals showed less NLRP3 inflammasome activation in the fasted state compared with that in refed conditions. In a human macrophage line, depletion of the mitochondrial-enriched sirtuin deacetylase SIRT3 increased NLRP3 inflammasome activation in association with excessive mitochondrial ROS production. Furthermore, genetic and pharmacologic SIRT3 activation blunted NLRP3 activity in parallel with enhanced mitochondrial function in cultured cells and in leukocytes extracted from healthy volunteers and from refed individuals but not in those collected during fasting. Together, our data indicate that nutrient levels regulate the NLRP3 inflammasome, in part through SIRT3-mediated mitochondrial homeostatic control. Moreover, these results suggest that deacetylase-dependent inflammasome attenuation may be amenable to targeting in human disease. ClinicalTrials.gov NCT02122575 and NCT00442195. Division of Intramural Research, NHLBI of the NIH.

MOXI Is a Mitochondrial Micropeptide That Enhances Fatty Acid β-Oxidation.

PubMed

Makarewich, Catherine A; Baskin, Kedryn K; Munir, Amir Z; Bezprozvannaya, Svetlana; Sharma, Gaurav; Khemtong, Chalermchai; Shah, Akansha M; McAnally, John R; Malloy, Craig R; Szweda, Luke I; Bassel-Duby, Rhonda; Olson, Eric N

2018-06-26

Micropeptide regulator of β-oxidation (MOXI) is a conserved muscle-enriched protein encoded by an RNA transcript misannotated as non-coding. MOXI localizes to the inner mitochondrial membrane where it associates with the mitochondrial trifunctional protein, an enzyme complex that plays a critical role in fatty acid β-oxidation. Isolated heart and skeletal muscle mitochondria from MOXI knockout mice exhibit a diminished ability to metabolize fatty acids, while transgenic MOXI overexpression leads to enhanced β-oxidation. Additionally, hearts from MOXI knockout mice preferentially oxidize carbohydrates over fatty acids in an isolated perfused heart system compared to wild-type (WT) animals. MOXI knockout mice also exhibit a profound reduction in exercise capacity, highlighting the role of MOXI in metabolic control. The functional characterization of MOXI provides insight into the regulation of mitochondrial metabolism and energy homeostasis and underscores the regulatory potential of additional micropeptides that have yet to be identified. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Overexpression of Mitochondrial Phosphate Transporter 3 Severely Hampers Plant Development through Regulating Mitochondrial Function in Arabidopsis.

PubMed

Jia, Fengjuan; Wan, Xiaomin; Zhu, Wei; Sun, Dan; Zheng, Chengchao; Liu, Pei; Huang, Jinguang

2015-01-01

Mitochondria are abundant and important organelles present in nearly all eukaryotic cells, which maintain metabolic communication with the cytosol through mitochondrial carriers. The mitochondrial membrane localized phosphate transporter (MPT) plays vital roles in diverse development and signaling processes, especially the ATP biosynthesis. Among the three MPT genes in Arabidopsis genome, AtMPT3 was proven to be a major member, and its overexpression gave rise to multiple developmental defects including curly leaves with deep color, dwarfed stature, and reduced fertility. Transcript profiles revealed that genes involved in plant metabolism, cellular redox homeostasis, alternative respiration pathway, and leaf and flower development were obviously altered in AtMPT3 overexpression (OEMPT3) plants. Moreover, OEMPT3 plants also accumulated higher ATP content, faster respiration rate and more reactive oxygen species (ROS) than wild type plants. Overall, our studies showed that AtMPT3 was indispensable for Arabidopsis normal growth and development, and provided new sights to investigate its possible regulation mechanisms.

Overexpression of Mitochondrial Phosphate Transporter 3 Severely Hampers Plant Development through Regulating Mitochondrial Function in Arabidopsis

PubMed Central

Jia, Fengjuan; Wan, Xiaomin; Zhu, Wei; Sun, Dan; Zheng, Chengchao; Liu, Pei; Huang, Jinguang

2015-01-01

Mitochondria are abundant and important organelles present in nearly all eukaryotic cells, which maintain metabolic communication with the cytosol through mitochondrial carriers. The mitochondrial membrane localized phosphate transporter (MPT) plays vital roles in diverse development and signaling processes, especially the ATP biosynthesis. Among the three MPT genes in Arabidopsis genome, AtMPT3 was proven to be a major member, and its overexpression gave rise to multiple developmental defects including curly leaves with deep color, dwarfed stature, and reduced fertility. Transcript profiles revealed that genes involved in plant metabolism, cellular redox homeostasis, alternative respiration pathway, and leaf and flower development were obviously altered in AtMPT3 overexpression (OEMPT3) plants. Moreover, OEMPT3 plants also accumulated higher ATP content, faster respiration rate and more reactive oxygen species (ROS) than wild type plants. Overall, our studies showed that AtMPT3 was indispensable for Arabidopsis normal growth and development, and provided new sights to investigate its possible regulation mechanisms. PMID:26076137

Up-regulation of avian uncoupling protein in cold-acclimated and hyperthyroid ducklings prevents reactive oxygen species production by skeletal muscle mitochondria.

PubMed

Rey, Benjamin; Roussel, Damien; Romestaing, Caroline; Belouze, Maud; Rouanet, Jean-Louis; Desplanches, Dominique; Sibille, Brigitte; Servais, Stéphane; Duchamp, Claude

2010-04-28

Although identified in several bird species, the biological role of the avian homolog of mammalian uncoupling proteins (avUCP) remains extensively debated. In the present study, the functional properties of isolated mitochondria were examined in physiological or pharmacological situations that induce large changes in avUCP expression in duckling skeletal muscle. The abundance of avUCP mRNA, as detected by RT-PCR in gastrocnemius muscle but not in the liver, was markedly increased by cold acclimation (CA) or pharmacological hyperthyroidism but was down-regulated by hypothyroidism. Activators of UCPs, such as superoxide with low doses of fatty acids, stimulated a GDP-sensitive proton conductance across the inner membrane of muscle mitochondria from CA or hyperthyroid ducklings. The stimulation was much weaker in controls and not observed in hypothyroid ducklings or in any liver mitochondrial preparations. The production of endogenous mitochondrial reactive oxygen species (ROS) was much lower in muscle mitochondria from CA and hyperthyroid ducklings than in the control or hypothyroid groups. The addition of GDP markedly increased the mitochondrial ROS production of CA or hyperthyroid birds up to, or above, the level of control or hypothyroid ducklings. Differences in ROS production among groups could not be attributed to changes in antioxidant enzyme activities (superoxide dismutase or glutathione peroxidase). This work provides the first functional in vitro evidence that avian UCP regulates mitochondrial ROS production in situations of enhanced metabolic activity.

Up-regulation of avian uncoupling protein in cold-acclimated and hyperthyroid ducklings prevents reactive oxygen species production by skeletal muscle mitochondria

PubMed Central

2010-01-01

Background Although identified in several bird species, the biological role of the avian homolog of mammalian uncoupling proteins (avUCP) remains extensively debated. In the present study, the functional properties of isolated mitochondria were examined in physiological or pharmacological situations that induce large changes in avUCP expression in duckling skeletal muscle. Results The abundance of avUCP mRNA, as detected by RT-PCR in gastrocnemius muscle but not in the liver, was markedly increased by cold acclimation (CA) or pharmacological hyperthyroidism but was down-regulated by hypothyroidism. Activators of UCPs, such as superoxide with low doses of fatty acids, stimulated a GDP-sensitive proton conductance across the inner membrane of muscle mitochondria from CA or hyperthyroid ducklings. The stimulation was much weaker in controls and not observed in hypothyroid ducklings or in any liver mitochondrial preparations. The production of endogenous mitochondrial reactive oxygen species (ROS) was much lower in muscle mitochondria from CA and hyperthyroid ducklings than in the control or hypothyroid groups. The addition of GDP markedly increased the mitochondrial ROS production of CA or hyperthyroid birds up to, or above, the level of control or hypothyroid ducklings. Differences in ROS production among groups could not be attributed to changes in antioxidant enzyme activities (superoxide dismutase or glutathione peroxidase). Conclusion This work provides the first functional in vitro evidence that avian UCP regulates mitochondrial ROS production in situations of enhanced metabolic activity. PMID:20426850

Quercetin attenuates mitochondrial dysfunction and biogenesis via upregulated AMPK/SIRT1 signaling pathway in OA rats.

PubMed

Qiu, Linan; Luo, Yuju; Chen, Xiaojuan

2018-07-01

Despite the severity of osteoarthritis (OA), current medical therapy strategies for OA aim at symptom control and pain reduction, as there is no ideal drug for effective OA treatment. OA rat model was used to explore the therapeutic function of quercetin on remission of OA, by determining the reactive oxygen species (ROS) levels, mitochondrial function and extracellular matrix integrity. Quercetin could attenuate ROS generation and augment the glutathione (GSH) and glutathione peroxidase (GPx) expression levels in OA rat. Quercetin not only enhanced mitochondrial membrane potential, oxygen consumption, adenosine triphosphate (ATP) levels in mitochondria, but also increased the mitochondrial copy number. Furthermore, the interlukin (IL)-1β-induced accumulation of nitric oxide (NO), matrixmetalloproteinase (MMP)-3) and MMP-13 could be suppressed by quercetin. Finally, we confirmed that the therapeutic properties of quercetin on OA might function through the adenosine monophosphate-activated protein kinase/sirtuin 1 (AMPK/SIRT1) signaling pathway. In summary, quercetin could alleviate OA through attenuating the ROS levels, reversing the mitochondrial dysfunction and keeping the integrality of extracellular matrix of joint cartilage. The underlying mechanism might involve the regulation of AMPK/SIRT1 signaling pathway. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Modulation of mitochondrial metabolism as a biochemical trait in blood feeding organisms: the redox vampire hypothesis redux.

PubMed

Ferreira, Caroline M; Oliveira, Matheus P; Paes, Marcia C; Oliveira, Marcus F

2018-06-01

Hematophagous organisms undergo remarkable metabolic changes during the blood digestion process, increasing fermentative glucose metabolism, and reducing respiratory rates, both consequence of functional mitochondrial remodeling. Here, we review the pathways involved in energy metabolism and mitochondrial functionality in a comparative framework across different hematophagous species, and consider how these processes regulate redox homeostasis during blood digestion. The trend across distinct species indicate that a switch in energy metabolism might represent an important defensive mechanism to avoid the potential harmful interaction of oxidants generated from aerobic energy metabolism with products derived from blood digestion. Indeed, in insect vectors, blood feeding transiently reduces respiratory rates and oxidant production, irrespective of tissue and insect model. On the other hand, a different scenario is observed in several unrelated parasite species when exposed to blood digestion products, as respiratory rates reduce and mitochondrial oxidant production increase. The emerging picture indicates that re-wiring of energy metabolism, through reduced mitochondrial function, culminates in improved tolerance to redox insults and seems to represent a key step for hematophagous organisms to cope with the overwhelming and potentially toxic blood meal. © 2018 International Federation for Cell Biology.

SR/ER-mitochondrial local communication: Calcium and ROS

PubMed Central

Csordás, György; Hajnóczky, György

2009-01-01

Mitochondria form junctions with the sarco/endoplasmic reticulum (SR/ER), which support signal transduction and biosynthetic pathways and affect organellar distribution. Recently, these junctions have received attention because of their pivotal role in mediating calcium signal propagation to the mitochondria, which is important for both ATP production and mitochondrial cell death. Many of the SR/ER-mitochondrial calcium transporters and signaling proteins are sensitive to redox regulation and are directly exposed to the reactive oxygen species (ROS) produced in the mitochondria and SR/ER. Although ROS has been emerging as a novel signaling entity, the redox signaling of the SR/ER-mitochondrial interface is yet to be elucidated. We describe here possible mechanisms of the mutual interaction between local Ca2+ and ROS signaling in the control of SR/ER-mitochondrial function. PMID:19527680

Myostatin induces mitochondrial metabolic alteration and typical apoptosis in cancer cells

PubMed Central

Liu, Y; Cheng, H; Zhou, Y; Zhu, Y; Bian, R; Chen, Y; Li, C; Ma, Q; Zheng, Q; Zhang, Y; Jin, H; Wang, X; Chen, Q; Zhu, D

2013-01-01

Myostatin, a member of the transforming growth factor-β superfamily, regulates the glucose metabolism of muscle cells, while dysregulated myostatin activity is associated with a number of metabolic disorders, including muscle cachexia, obesity and type II diabetes. We observed that myostatin induced significant mitochondrial metabolic alterations and prolonged exposure of myostatin induced mitochondria-dependent apoptosis in cancer cells addicted to glycolysis. To address the underlying mechanism, we found that the protein levels of Hexokinase II (HKII) and voltage-dependent anion channel 1 (VDAC1), two key regulators of glucose metabolisms as well as metabolic stress-induced apoptosis, were negatively correlated. In particular, VDAC1 was dramatically upregulated in cells that are sensitive to myostatin treatment whereas HKII was downregulated and dissociated from mitochondria. Myostatin promoted the translocation of Bax from cytosol to mitochondria, and knockdown of VDAC1 inhibited myostatin-induced Bax translocation and apoptosis. These apoptotic changes can be partially rescued by repletion of ATP, or by ectopic expression of HKII, suggesting that perturbation of mitochondrial metabolism is causally linked with subsequent apoptosis. Our findings reveal novel function of myostatin in regulating mitochondrial metabolism and apoptosis in cancer cells. PMID:23412387

Sirtuin signaling controls mitochondrial function in glycogen storage disease type Ia.

PubMed

Cho, Jun-Ho; Kim, Goo-Young; Mansfield, Brian C; Chou, Janice Y

2018-05-08

Glycogen storage disease type Ia (GSD-Ia) deficient in glucose-6-phosphatase-α (G6Pase-α) is a metabolic disorder characterized by impaired glucose homeostasis and a long-term complication of hepatocellular adenoma/carcinoma (HCA/HCC). Mitochondrial dysfunction has been implicated in GSD-Ia but the underlying mechanism and its contribution to HCA/HCC development remain unclear. We have shown that hepatic G6Pase-α deficiency leads to downregulation of sirtuin 1 (SIRT1) signaling that underlies defective hepatic autophagy in GSD-Ia. SIRT1 is a NAD + -dependent deacetylase that can deacetylate and activate peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), a master regulator of mitochondrial integrity, biogenesis, and function. We hypothesized that downregulation of hepatic SIRT1 signaling in G6Pase-α-deficient livers impairs PGC-1α activity, leading to mitochondrial dysfunction. Here we show that the G6Pase-α-deficient livers display defective PGC-1α signaling, reduced numbers of functional mitochondria, and impaired oxidative phosphorylation. Overexpression of hepatic SIRT1 restores PGC-1α activity, normalizes the expression of electron transport chain components, and increases mitochondrial complex IV activity. We have previously shown that restoration of hepatic G6Pase-α expression normalized SIRT1 signaling. We now show that restoration of hepatic G6Pase-α expression also restores PGC-1α activity and mitochondrial function. Finally, we show that HCA/HCC lesions found in G6Pase-α-deficient livers contain marked mitochondrial and oxidative DNA damage. Taken together, our study shows that downregulation of hepatic SIRT1/PGC-1α signaling underlies mitochondrial dysfunction and that oxidative DNA damage incurred by damaged mitochondria may contribute to HCA/HCC development in GSD-Ia.

Mitochondrial Protein Interaction Mapping Identifies Regulators of Respiratory Chain Function.

PubMed

Floyd, Brendan J; Wilkerson, Emily M; Veling, Mike T; Minogue, Catie E; Xia, Chuanwu; Beebe, Emily T; Wrobel, Russell L; Cho, Holly; Kremer, Laura S; Alston, Charlotte L; Gromek, Katarzyna A; Dolan, Brendan K; Ulbrich, Arne; Stefely, Jonathan A; Bohl, Sarah L; Werner, Kelly M; Jochem, Adam; Westphall, Michael S; Rensvold, Jarred W; Taylor, Robert W; Prokisch, Holger; Kim, Jung-Ja P; Coon, Joshua J; Pagliarini, David J

2016-08-18

Mitochondria are essential for numerous cellular processes, yet hundreds of their proteins lack robust functional annotation. To reveal functions for these proteins (termed MXPs), we assessed condition-specific protein-protein interactions for 50 select MXPs using affinity enrichment mass spectrometry. Our data connect MXPs to diverse mitochondrial processes, including multiple aspects of respiratory chain function. Building upon these observations, we validated C17orf89 as a complex I (CI) assembly factor. Disruption of C17orf89 markedly reduced CI activity, and its depletion is found in an unresolved case of CI deficiency. We likewise discovered that LYRM5 interacts with and deflavinates the electron-transferring flavoprotein that shuttles electrons to coenzyme Q (CoQ). Finally, we identified a dynamic human CoQ biosynthetic complex involving multiple MXPs whose topology we map using purified components. Collectively, our data lend mechanistic insight into respiratory chain-related activities and prioritize hundreds of additional interactions for further exploration of mitochondrial protein function. Copyright © 2016 Elsevier Inc. All rights reserved.

The Arabidopsis Mitochondrial Protease FtSH4 Is Involved in Leaf Senescence via Regulation of WRKY-Dependent Salicylic Acid Accumulation and Signaling.

PubMed

Zhang, Shengchun; Li, Cui; Wang, Rui; Chen, Yaxue; Shu, Si; Huang, Ruihua; Zhang, Daowei; Li, Jian; Xiao, Shi; Yao, Nan; Yang, Chengwei

2017-04-01

Mitochondria and autophagy play important roles in the networks that regulate plant leaf senescence and cell death. However, the molecular mechanisms underlying the interactions between mitochondrial signaling and autophagy are currently not well understood. This study characterized the function of the Arabidopsis ( Arabidopsis thaliana ) mitochondrial AAA-protease gene FtSH4 in regulating autophagy and senescence, finding that FtSH4 mediates WRKY-dependent salicylic acid (SA) accumulation and signaling. Knockout of FtSH4 in the ftsh4-4 mutant resulted in severe leaf senescence, cell death, and high autophagy levels. The level of SA increased dramatically in the ftsh4-4 mutant. Expression of nahG in the ftsh4-4 mutant led to decreased SA levels and suppressed the leaf senescence and cell death phenotypes. The transcript levels of several SA synthesis and signaling genes, including SALICYLIC ACID INDUCTION DEFICIENT2 ( SID2 ), NON-RACE-SPECIFIC DISEASE RESISTANCE1 ( NDR1 ), and NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEINS1 ( NPR1 ), increased significantly in the ftsh4-4 mutants compared with the wild type. Loss of function of SID2 , NDR1 , or NPR1 in the ftsh4-4 mutant reversed the ftsh4-4 senescence and autophagy phenotypes. Furthermore, ftsh4-4 mutants had elevated levels of transcripts of several WRKY genes, including WRKY40 , WRKY46 , WRKY51 , WRKY60 , WRKY63 , and WRKY75 ; all of these WRKY proteins can bind to the promoter of SID2 Loss of function of WRKY75 in the ftsh4-4 mutants decreased the levels of SA and reversed the senescence phenotype. Taken together, these results suggest that the mitochondrial ATP-dependent protease FtSH4 may regulate the expression of WRKY genes by modifying the level of reactive oxygen species and the WRKY transcription factors that control SA synthesis and signaling in autophagy and senescence. © 2017 American Society of Plant Biologists. All Rights Reserved.

Chronic AMPK activation via loss of FLCN induces functional beige adipose tissue through PGC-1α/ERRα

PubMed Central

Yan, Ming; Audet-Walsh, Étienne; Manteghi, Sanaz; Dufour, Catherine Rosa; Walker, Benjamin; Baba, Masaya; St-Pierre, Julie; Giguère, Vincent; Pause, Arnim

2016-01-01

The tumor suppressor folliculin (FLCN) forms a repressor complex with AMP-activated protein kinase (AMPK). Given that AMPK is a master regulator of cellular energy homeostasis, we generated an adipose-specific Flcn (Adipoq-FLCN) knockout mouse model to investigate the role of FLCN in energy metabolism. We show that loss of FLCN results in a complete metabolic reprogramming of adipose tissues, resulting in enhanced oxidative metabolism. Adipoq-FLCN knockout mice exhibit increased energy expenditure and are protected from high-fat diet (HFD)-induced obesity. Importantly, FLCN ablation leads to chronic hyperactivation of AMPK, which in turns induces and activates two key transcriptional regulators of cellular metabolism, proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α) and estrogen-related receptor α (ERRα). Together, the AMPK/PGC-1α/ERRα molecular axis positively modulates the expression of metabolic genes to promote mitochondrial biogenesis and activity. In addition, mitochondrial uncoupling proteins as well as other markers of brown fat are up-regulated in both white and brown FLCN-null adipose tissues, underlying the increased resistance of Adipoq-FLCN knockout mice to cold exposure. These findings identify a key role of FLCN as a negative regulator of mitochondrial function and identify a novel molecular pathway involved in the browning of white adipocytes and the activity of brown fat. PMID:27151976

Structural Modification of (-)-Epigallocatechin Gallate (EGCG) Shows Significant Enhancement in Mitochondrial Biogenesis.

PubMed

Ha, Taewoong; Kim, Mi Kyoung; Park, Kwang-Su; Jung, Woong; Choo, Hyunah; Chong, Youhoon

2018-04-18

(-)-Epigallocatechin-3-gallate (EGCG) is known as a mitochondria-targeted molecule that can prevent mitochondrial deterioration and induce mitochondrial biogenesis by modulating key regulators of mitochondrial metabolism. In this study, we tackled whether derivatization of EGCG could result in enhancement of its effects on mitochondrial biogenesis. EGCG, EGCG peracetate (AcEGCG), and its 4″- O-alkyl substituted congeners prepared by previously reported procedures were biologically evaluated. Interestingly, EGCG and AcEGCG were only marginally effective in inducing mitochondrial biogenesis, while AcEGCG congeners with an alkyl group at the 4″- O position showed significantly increased biological activity compared to their parent compound. Among these series, 3f with a methyl-branched carbonate chain at the 4″- O position of the AcEGCG scaffold showed the most enhancement in inducing mitochondrial biogenesis. Hepa1-6 cells treated with 3f exhibited increases in both mitochondrial mass (1.5 times) and relative mtDNA content to nDNA (1.5 times). As a mitochondrial biogenesis enhancer, 3f also increased expression levels of regulators for mitochondrial function, including PGC-1α (4.0 fold), p-AMPK (2.5 fold), SIRT1 (4.2 fold), ERRα (1.8 fold), NRF-1 (1.6 fold), NRF-2 (1.7 fold), and mtTFA (1.6 folds). Investigation of oxidative phosphorylation by mitochondria in the presence of 3f revealed that 3f increased the NAD + /NADH ratio, the amount of cytochrome c, ATP synthesis, and oxygen consumption in Hepa1-6 cells by 2.2, 1.4, 1.5, and 2.1 fold, respectively. Taken together, these results warrant an extensive structure-activity relationship study for EGCG derivatives to develop novel mitochondrial biogenesis enhancers.

Metabolic Dysfunction Consistent with Premature Aging Results from Deletion of Pim Kinases

PubMed Central

Din, Shabana; Konstandin, Mathias H; Johnson, Bevan; Emathinger, Jacqueline; Völkers, Mirko; Toko, Haruhiro; Collins, Brett; Ormachea, Lucy; Samse, Kaitlen; Kubli, Dieter A; De La Torre, Andrea; Kraft, Andrew S; Gustafsson, Asa B; Kelly, Daniel P; Sussman, Mark A

2014-01-01

Rationale The senescent cardiac phenotype is accompanied by changes in mitochondrial function and biogenesis causing impairment in energy provision. The relationship between myocardial senescence and Pim kinases deserves attention since Pim-1 kinase is cardioprotective, in part, by preservation of mitochondrial integrity. Study of the pathological effects resulting from genetic deletion of all Pim kinase family members could provide important insight regarding cardiac mitochondrial biology and the aging phenotype. Objective Demonstrate myocardial senescence is promoted by loss of Pim leading to premature aging and aberrant mitochondrial function. Methods and Results Cardiac myocyte senescence was evident at three months of age in Pim Triple KnockOut (PTKO) mice, where all three isoforms of Pim kinase family members are genetically deleted. Cellular hypertrophic remodeling and fetal gene program activation was followed by heart failure at six months in PTKO mice. Metabolic dysfunction is an underlying cause of cardiac senescence and instigates a decline in cardiac function. Altered mitochondrial morphology is evident consequential to Pim deletion together with decreased ATP levels and increased phosphorylated AMPK, exposing an energy deficiency in PTKO mice. Expression of the genes encoding master regulators of mitochondrial biogenesis, PPARγ coactivator-1 (PGC-1) α and β were diminished in PTKO hearts, as were downstream targets included in mitochondrial energy transduction, including fatty acid oxidation. Reversal of the dysregulated metabolic phenotype was observed by overexpressing c-Myc, a downstream target of Pim kinases. Conclusion Pim kinases prevent premature cardiac aging and maintain a healthy pool of functional mitochondria leading to efficient cellular energetics. PMID:24916111

Sonic hedgehog pathway activation increases mitochondrial abundance and activity in hippocampal neurons

PubMed Central

Yao, Pamela J.; Manor, Uri; Petralia, Ronald S.; Brose, Rebecca D.; Wu, Ryan T. Y.; Ott, Carolyn; Wang, Ya-Xian; Charnoff, Ari; Lippincott-Schwartz, Jennifer; Mattson, Mark P.

2017-01-01

Mitochondria are essential organelles whose biogenesis, structure, and function are regulated by many signaling pathways. We present evidence that, in hippocampal neurons, activation of the Sonic hedgehog (Shh) signaling pathway affects multiple aspects of mitochondria. Mitochondrial mass was increased significantly in neurons treated with Shh. Using biochemical and fluorescence imaging analyses, we show that Shh signaling activity reduces mitochondrial fission and promotes mitochondrial elongation, at least in part, via suppression of the mitochondrial fission protein dynamin-like GTPase Drp1. Mitochondria from Shh-treated neurons were more electron-dense, as revealed by electron microscopy, and had higher membrane potential and respiratory activity. We further show that Shh protects neurons against a variety of stresses, including the mitochondrial poison rotenone, amyloid β-peptide, hydrogen peroxide, and high levels of glutamate. Collectively our data suggest a link between Shh pathway activity and the physiological properties of mitochondria in hippocampal neurons. PMID:27932496

Regulation of mitochondrial energy production in cardiac cells of rainbow trout (Oncorhynchus mykiss).

PubMed

Birkedal, R; Gesser, H

2004-04-01

In skinned rat cardiac fibres, mitochondrial affinity for endogenous ADP generated by creatine kinase and Ca2+-activated ATPases is higher than for exogenous ADP added to the surrounding medium, suggesting that mitochondria are functionally coupled to creatine kinase and ATPases. Such a coupling may be weaker or absent in ectothermic vertebrate cardiac cells, because they typically have less elaborate intracellular membrane structures, higher glycolytic capacity and lower working temperature. Therefore, we examined skinned cardiac fibres from rainbow trout at 10 degrees C. The apparent mitochondrial affinity for endogenous ADP was obtained by stimulation with ATP and recording of the release of ADP into the surrounding medium. The apparent affinity for endogenous ADP was much higher than for exogenous ADP suggesting a functional coupling between mitochondria and ATPases. The apparent affinity for exogenous ADP and ATP was increased by creatine or an increase in Ca2+-activity, which should increase intrafibrillar turnover of ATP to ADP. In conclusion, ADP seems to be channelled from creatine kinase and ATPases to mitochondria without being released to the surrounding medium. Thus, despite difference in structure, temperature and metabolic capacity, trout myocardium resembles that of rat with regard to the regulation of mitochondrial respiration. Copyright 2004 Springer-Verlag

Disrupted Skeletal Muscle Mitochondrial Dynamics, Mitophagy, and Biogenesis during Cancer Cachexia: A Role for Inflammation

PubMed Central

VanderVeen, Brandon N.; Fix, Dennis K.

2017-01-01

Chronic inflammation is a hallmark of cancer cachexia in both patients and preclinical models. Cachexia is prevalent in roughly 80% of cancer patients and accounts for up to 20% of all cancer-related deaths. Proinflammatory cytokines IL-6, TNF-α, and TGF-β have been widely examined for their regulation of cancer cachexia. An established characteristic of cachectic skeletal muscle is a disrupted capacity for oxidative metabolism, which is thought to contribute to cancer patient fatigue, diminished metabolic function, and muscle mass loss. This review's primary objective is to highlight emerging evidence linking cancer-induced inflammation to the dysfunctional regulation of mitochondrial dynamics, mitophagy, and biogenesis in cachectic muscle. The potential for either muscle inactivity or exercise to alter mitochondrial dysfunction during cancer cachexia will also be discussed. PMID:28785374

Proteomic and Metabolic Analyses of S49 Lymphoma Cells Reveal Novel Regulation of Mitochondria by cAMP and Protein Kinase A*

PubMed Central

Wilderman, Andrea; Guo, Yurong; Divakaruni, Ajit S.; Perkins, Guy; Zhang, Lingzhi; Murphy, Anne N.; Taylor, Susan S.; Insel, Paul A.

2015-01-01

Cyclic AMP (cAMP), acting via protein kinase A (PKA), regulates many cellular responses, but the role of mitochondria in such responses is poorly understood. To define such roles, we used quantitative proteomic analysis of mitochondria-enriched fractions and performed functional and morphologic studies of wild-type (WT) and kin− (PKA-null) murine S49 lymphoma cells. Basally, 75 proteins significantly differed in abundance between WT and kin− S49 cells. WT, but not kin−, S49 cells incubated with the cAMP analog 8-(4-chlorophenylthio)adenosine cAMP (CPT-cAMP) for 16 h have (a) increased expression of mitochondria-related genes and proteins, including ones in pathways of branched-chain amino acid and fatty acid metabolism and (b) increased maximal capacity of respiration on branched-chain keto acids and fatty acids. CPT-cAMP also regulates the cellular rate of ATP-utilization, as the rates of both ATP-linked respiration and proton efflux are decreased in WT but not kin− cells. CPT-cAMP protected WT S49 cells from glucose or glutamine deprivation, In contrast, CPT-cAMP did not protect kin− cells or WT cells treated with the PKA inhibitor H89 from glutamine deprivation. Under basal conditions, the mitochondrial structure of WT and kin− S49 cells is similar. Treatment with CPT-cAMP produced apoptotic changes (i.e. decreased mitochondrial density and size and loss of cristae) in WT, but not kin− cells. Together, these findings show that cAMP acts via PKA to regulate multiple aspects of mitochondrial function and structure. Mitochondrial perturbation thus likely contributes to cAMP/PKA-mediated cellular responses. PMID:26203188

Tauroursodeoxycholic acid increases neural stem cell pool and neuronal conversion by regulating mitochondria-cell cycle retrograde signaling

PubMed Central

Xavier, Joana M; Morgado, Ana L; Rodrigues, Cecília MP; Solá, Susana

2014-01-01

The low survival and differentiation rates of stem cells after either transplantation or neural injury have been a major concern of stem cell-based therapy. Thus, further understanding long-term survival and differentiation of stem cells may uncover new targets for discovery and development of novel therapeutic approaches. We have previously described the impact of mitochondrial apoptosis-related events in modulating neural stem cell (NSC) fate. In addition, the endogenous bile acid, tauroursodeoxycholic acid (TUDCA) was shown to be neuroprotective in several animal models of neurodegenerative disorders by acting as an anti-apoptotic and anti-oxidant molecule at the mitochondrial level. Here, we hypothesize that TUDCA might also play a role on NSC fate decision. We found that TUDCA prevents mitochondrial apoptotic events typical of early-stage mouse NSC differentiation, preserves mitochondrial integrity and function, while enhancing self-renewal potential and accelerating cell cycle exit of NSCs. Interestingly, TUDCA prevention of mitochondrial alterations interfered with NSC differentiation potential by favoring neuronal rather than astroglial conversion. Finally, inhibition of mitochondrial reactive oxygen species (mtROS) scavenger and adenosine triphosphate (ATP) synthase revealed that the effect of TUDCA is dependent on mtROS and ATP regulation levels. Collectively, these data underline the importance of mitochondrial stress control of NSC fate decision and support a new role for TUDCA in this process. PMID:25483094

Mitochondrial Biogenesis in Diverse Cauliflower Cultivars under Mild and Severe Drought. Impaired Coordination of Selected Transcript and Proteomic Responses, and Regulation of Various Multifunctional Proteins

PubMed Central

Rurek, Michał; Czołpińska, Magdalena; Staszak, Aleksandra Maria; Nowak, Witold; Krzesiński, Włodzimierz; Spiżewski, Tomasz

2018-01-01

Mitochondrial responses under drought within Brassica genus are poorly understood. The main goal of this study was to investigate mitochondrial biogenesis of three cauliflower (Brassica oleracea var. botrytis) cultivars with varying drought tolerance. Diverse quantitative changes (decreases in abundance mostly) in the mitochondrial proteome were assessed by two-dimensional gel electrophoresis (2D PAGE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Respiratory (e.g., complex II, IV (CII, CIV) and ATP synthase subunits), transporter (including diverse porin isoforms) and matrix multifunctional proteins (e.g., components of RNA editing machinery) were diversely affected in their abundance under two drought levels. Western immunoassays showed additional cultivar-specific responses of selected mitochondrial proteins. Dehydrin-related tryptic peptides (found in several 2D spots) immunopositive with dehydrin-specific antisera highlighted the relevance of mitochondrial dehydrin-like proteins for the drought response. The abundance of selected mRNAs participating in drought response was also determined. We conclude that mitochondrial biogenesis was strongly, but diversely affected in various cauliflower cultivars, and associated with drought tolerance at the proteomic and functional levels. However, discussed alternative oxidase (AOX) regulation at the RNA and protein level were largely uncoordinated due to the altered availability of transcripts for translation, mRNA/ribosome interactions, and/or miRNA impact on transcript abundance and translation. PMID:29642585

Deficiency of PHB complex impairs respiratory supercomplex formation and activates mitochondrial flashes.

PubMed

Jian, Chongshu; Xu, Fengli; Hou, Tingting; Sun, Tao; Li, Jinghang; Cheng, Heping; Wang, Xianhua

2017-08-01

Prohibitins (PHBs; prohibitin 1, PHB1 or PHB, and prohibitin 2, PHB2) are evolutionarily conserved and ubiquitously expressed mitochondrial proteins. PHBs form multimeric ring complexes acting as scaffolds in the inner mitochondrial membrane. Mitochondrial flashes (mitoflashes) are newly discovered mitochondrial signaling events that reflect electrical and chemical excitations of the organelle. Here, we investigate the possible roles of PHBs in the regulation of mitoflash signaling. Downregulation of PHBs increases mitoflash frequency by up to 5.4-fold due to elevated basal reactive oxygen species (ROS) production in the mitochondria. Mechanistically, PHB deficiency impairs the formation of mitochondrial respiratory supercomplexes (RSCs) without altering the abundance of individual respiratory complex subunits. These impairments induced by PHB deficiency are effectively rescued by co-expression of PHB1 and PHB2, indicating that the multimeric PHB complex acts as the functional unit. Furthermore, downregulating other RSC assembly factors, including SCAFI (also known as COX7A2L), RCF1a (HIGD1A), RCF1b (HIGD2A), UQCC3 and SLP2 (STOML2), all activate mitoflashes through elevating mitochondrial ROS production. Our findings identify the PHB complex as a new regulator of RSC formation and mitoflash signaling, and delineate a general relationship among RSC formation, basal ROS production and mitoflash biogenesis. © 2017. Published by The Company of Biologists Ltd.

Effect of Overproduction of Mitochondrial Uncoupling Protein 2 on Cos7 Cells: Induction of Senescent-like Morphology and Oncotic Cell Death.

PubMed

Nishio, Koji; Ma, Qian

2016-01-01

The maintenance of mitochondrial membrane potential is essential for cell growth and survival. Mitochondrial uncoupling protein 2 plays the most important roles in uncoupling oxidative phosphorylation and decreasing mitochondrial O2- production by regulating the mitochondrial membrane potential. We propose that mouse UCP2 has two glycine-rich motifs, motif 1: EGIRGLWKG (170-178) and a known Walker A-like motif 2: EGPRAFYKG (264-272). These motifs seem to be important for the function of UCP2. We investigated the biological effects of overproduced-UCP2 and its physiological consequence in Cos7 cells. We introduced several amino acid changes in the motif 1. The expression vectors of the green fluorescent protein (GFP)-fused UCP2 and mutant UCP2 were constructed and expressed in Cos7 cells. The UCP2-GFP-expressed cells significantly down-regulated the mitochondrial membrane potentials and induced the enlarged cell shapes. Next we generated the stably UCP2-GFP-expressed Cos7 cells by selection with the antibiotic Genecitin (G418). Within the first few weeks following G418-selection, the stably UCP2-GFP-expressed cells could not divide well and gradually manifested the irregular and enlarged senescent-like cell morphology. The UCP2/K177E- or UCP2/G174L-expressed cells did not induce the enlarged cell shapes. Hence, UCP2/K177E and UCP2/G174L produced the functional incompetence of the glycine-rich motif 1. The senescent-like cells significantly decreased the mitochondrial membrane potentials and finally died nearly one month. Overproduction of UCP2 irreversibly reduces the mitochondrial membrane potentials and induces the senescent-like morphology and finally oncotic cell death in Cos7 cells. These changes seem to occur from the irreversible metabolic changes following total loss of cellular ATP.

Mitochondrial activity and dynamics changes regarding metabolism in ageing and obesity.

PubMed

López-Lluch, Guillermo

2017-03-01

Mitochondria play an essential role in ageing and longevity. During ageing, a general deregulation of metabolism occurs, affecting molecular, cellular and physiological activities in the organism. Dysfunction of mitochondria has been associated with ageing and age-related diseases indicating their importance in the maintenance of cell homeostasis. Three major nutritional sensors, mTOR, AMPK and Sirtuins are involved in the control of mitochondrial physiology. These nutritional sensors control mitochondrial biogenesis, dynamics by regulating fusion and fission processes, and turnover through mito- and autophagy. Apart of the known factors involved in fusion, OPA1 and mitofusins, and fission, DRP1 and FIS1, emerging factors such as prohibitins and sestrins can play important functions in mitochondrial dynamics regulation. Mitochondria is also affected by sexual hormones that suffer drastic changes during ageing. The recent literature demonstrates the complex interaction between nutritional sensors and mitochondrial homeostasis in the physiology of adipose tissue and in the accumulation of fat in other organs such as muscle and liver. In this article, the role of mitochondrial homeostasis in ageing and age-dependent fat accumulation is revised. This review highlights the importance of mitochondria in the accumulation of fat during ageing and related diseases such as obesity, metabolic syndrome or type 2 diabetes mellitus. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Interleukin-15 Modulates Adipose Tissue by Altering Mitochondrial Mass and Activity

PubMed Central

Barra, Nicole G.; Palanivel, Rengasamy; Denou, Emmanuel; Chew, Marianne V.; Gillgrass, Amy; Walker, Tina D.; Kong, Josh; Richards, Carl D.; Jordana, Manel; Collins, Stephen M.; Trigatti, Bernardo L.; Holloway, Alison C.; Raha, Sandeep; Steinberg, Gregory R.; Ashkar, Ali A.

2014-01-01

Interleukin-15 (IL-15) is an immunomodulatory cytokine that affects body mass regulation independent of lymphocytes; however, the underlying mechanism(s) involved remains unknown. In an effort to investigate these mechanisms, we performed metabolic cage studies, assessed intestinal bacterial diversity and macronutrient absorption, and examined adipose mitochondrial activity in cultured adipocytes and in lean IL-15 transgenic (IL-15tg), overweight IL-15 deficient (IL-15−/−), and control C57Bl/6 (B6) mice. Here we show that differences in body weight are not the result of differential activity level, food intake, or respiratory exchange ratio. Although intestinal microbiota differences between obese and lean individuals are known to impact macronutrient absorption, differing gut bacteria profiles in these murine strains does not translate to differences in body weight in colonized germ free animals and macronutrient absorption. Due to its contribution to body weight variation, we examined mitochondrial factors and found that IL-15 treatment in cultured adipocytes resulted in increased mitochondrial membrane potential and decreased lipid deposition. Lastly, IL-15tg mice have significantly elevated mitochondrial activity and mass in adipose tissue compared to B6 and IL-15−/− mice. Altogether, these results suggest that IL-15 is involved in adipose tissue regulation and linked to altered mitochondrial function. PMID:25517731

Resveratrol induces mitochondrial biogenesis in endothelial cells.

PubMed

Csiszar, Anna; Labinskyy, Nazar; Pinto, John T; Ballabh, Praveen; Zhang, Hanrui; Losonczy, Gyorgy; Pearson, Kevin; de Cabo, Rafael; Pacher, Pal; Zhang, Cuihua; Ungvari, Zoltan

2009-07-01

Pathways that regulate mitochondrial biogenesis are potential therapeutic targets for the amelioration of endothelial dysfunction and vascular disease. Resveratrol was shown to impact mitochondrial function in skeletal muscle and the liver, but its role in mitochondrial biogenesis in endothelial cells remains poorly defined. The present study determined whether resveratrol induces mitochondrial biogenesis in cultured human coronary arterial endothelial cells (CAECs). In CAECs resveratrol increased mitochondrial mass and mitochondrial DNA content, upregulated protein expression of electron transport chain constituents, and induced mitochondrial biogenesis factors (proliferator-activated receptor-coactivator-1alpha, nuclear respiratory factor-1, mitochondrial transcription factor A). Sirtuin 1 (SIRT1) was induced, and endothelial nitric oxide (NO) synthase (eNOS) was upregulated in a SIRT1-dependent manner. Knockdown of SIRT1 (small interfering RNA) or inhibition of NO synthesis prevented resveratrol-induced mitochondrial biogenesis. In aortas of type 2 diabetic (db/db) mice impaired mitochondrial biogenesis was normalized by chronic resveratrol treatment, showing the in vivo relevance of our findings. Resveratrol increases mitochondrial content in endothelial cells via activating SIRT1. We propose that SIRT1, via a pathway that involves the upregulation of eNOS, induces mitochondrial biogenesis. Resveratrol induced mitochondrial biogenesis in the aortas of type 2 diabetic mice, suggesting the potential for new treatment approaches targeting endothelial mitochondria in metabolic diseases.

Resveratrol induces mitochondrial biogenesis in endothelial cells

PubMed Central

Csiszar, Anna; Labinskyy, Nazar; Pinto, John T.; Ballabh, Praveen; Zhang, Hanrui; Losonczy, Gyorgy; Pearson, Kevin; de Cabo, Rafael; Pacher, Pal; Zhang, Cuihua; Ungvari, Zoltan

2009-01-01

Pathways that regulate mitochondrial biogenesis are potential therapeutic targets for the amelioration of endothelial dysfunction and vascular disease. Resveratrol was shown to impact mitochondrial function in skeletal muscle and the liver, but its role in mitochondrial biogenesis in endothelial cells remains poorly defined. The present study determined whether resveratrol induces mitochondrial biogenesis in cultured human coronary arterial endothelial cells (CAECs). In CAECs resveratrol increased mitochondrial mass and mitochondrial DNA content, upregulated protein expression of electron transport chain constituents, and induced mitochondrial biogenesis factors (proliferator-activated receptor-coactivator-1α, nuclear respiratory factor-1, mitochondrial transcription factor A). Sirtuin 1 (SIRT1) was induced, and endothelial nitric oxide (NO) synthase (eNOS) was upregulated in a SIRT1-dependent manner. Knockdown of SIRT1 (small interfering RNA) or inhibition of NO synthesis prevented resveratrol-induced mitochondrial biogenesis. In aortas of type 2 diabetic (db/db) mice impaired mitochondrial biogenesis was normalized by chronic resveratrol treatment, showing the in vivo relevance of our findings. Resveratrol increases mitochondrial content in endothelial cells via activating SIRT1. We propose that SIRT1, via a pathway that involves the upregulation of eNOS, induces mitochondrial biogenesis. Resveratrol induced mitochondrial biogenesis in the aortas of type 2 diabetic mice, suggesting the potential for new treatment approaches targeting endothelial mitochondria in metabolic diseases. PMID:19429820

Implications of mitochondrial uncoupling in skeletal muscle in the development and treatment of obesity.

PubMed

Thrush, A Brianne; Dent, Robert; McPherson, Ruth; Harper, Mary-Ellen

2013-10-01

Understanding the metabolic factors that contribute to obesity development and weight loss success are critical for combating obesity and obesity-related disorders. This review provides an overview of energy metabolism with a particular focus on mitochondrial function in health and in obesity. Mitochondrial proton leak contributes significantly to whole body energy expenditure and the potential role of energy uncoupling in weight loss success is discussed. We provide evidence to support the hypothesis that differences in energy efficiency are important regulators of body weight and weight loss success. © 2013 FEBS.

Stathmin Mediates Hepatocyte Resistance to Death from Oxidative Stress by down Regulating JNK

PubMed Central

Zhao, Enpeng; Amir, Muhammad; Lin, Yu; Czaja, Mark J.

2014-01-01

Stathmin 1 performs a critical function in cell proliferation by regulating microtubule polymerization. This proliferative function is thought to explain the frequent overexpression of stathmin in human cancer and its correlation with a bad prognosis. Whether stathmin also functions in cell death pathways is unclear. Stathmin regulates microtubules in part by binding free tubulin, a process inhibited by stathmin phosphorylation from kinases including c-Jun N-terminal kinase (JNK). The involvement of JNK activation both in stathmin phosphorylation, and in hepatocellular resistance to oxidative stress, led to an examination of the role of stathmin/JNK crosstalk in oxidant-induced hepatocyte death. Oxidative stress from menadione-generated superoxide induced JNK-dependent stathmin phosphorylation at Ser-16, Ser-25 and Ser-38 in hepatocytes. A stathmin knockdown sensitized hepatocytes to both apoptotic and necrotic cell death from menadione without altering levels of oxidant generation. The absence of stathmin during oxidative stress led to JNK overactivation that was the mechanism of cell death as a concomitant knockdown of JNK1 or JNK2 blocked death. Hepatocyte death from JNK overactivation was mediated by the effects of JNK on mitochondria. Mitochondrial outer membrane permeabilization occurred in stathmin knockdown cells at low concentrations of menadione that triggered apoptosis, whereas mitochondrial β-oxidation and ATP homeostasis were compromised at higher, necrotic menadione concentrations. Stathmin therefore mediates hepatocyte resistance to death from oxidative stress by down regulating JNK and maintaining mitochondrial integrity. These findings demonstrate a new mechanism by which stathmin promotes cell survival and potentially tumor growth. PMID:25285524

Dietary fat overcomes the protective activity of thrombospondin-1 signaling in the Apc(Min/+) model of colon cancer.

PubMed

Soto-Pantoja, D R; Sipes, J M; Martin-Manso, G; Westwood, B; Morris, N L; Ghosh, A; Emenaker, N J; Roberts, D D

2016-05-30

Thrombospondin 1 is a glycoprotein that regulates cellular phenotype through interactions with its cellular receptors and extracellular matrix-binding partners. Thrombospondin 1 locally regulates angiogenesis and inflammatory responses that contribute to colorectal carcinogenesis in Apc(Min/+) mice. The ability of thrombospondin 1 to regulate responses of cells and tissues to a variety of stresses suggested that loss of thrombospondin 1 may also have broader systemic effects on metabolism to modulate carcinogenesis. Apc(Min/+):Thbs1(-/-) mice exhibited decreased survival and higher tumor multiplicities in the small and large intestine relative to Apc(Min/+) mice when fed a low (5%) fat western diet. However, the protective effect of endogenous thrombospondin 1 was lost when the mice were fed a western diet containing 21% fat. Biochemical profiles of liver tissue identified systemic metabolic changes accompanying the effects of thrombospondin 1 and dietary lipid intake on tumorigenesis. A high-fat western diet differentially regulated elements of amino acid, energy and lipid metabolism in Apc(Min/+):Thbs1(-/-) mice relative to Apc(Min/+):Thbs1(+/+)mice. Metabolic changes in ketone body and tricarboxylic acid cycle intermediates indicate functional interactions between Apc and thrombospondin 1 signaling that control mitochondrial function. The cumulative diet-dependent differential changes observed in Apc(Min/+):Thbs1(-/-) versus Apc(Min/+) mice include altered amino acid and lipid metabolism, mitochondrial dysfunction, eicosanoids and ketone body formation. This metabolic profile suggests that the protective role of thrombospondin 1 to decrease adenoma formation in Apc(Min/+) mice results in part from improved mitochondrial function.

The protective effect of lipid emulsion in preventing bupivacaine-induced mitochondrial injury and apoptosis of H9C2 cardiomyocytes.

PubMed

Chen, Zhe; Jin, Zhousheng; Xia, Yun; Zhao, Shishi; Xu, Xuzhong; Papadimos, Thomas J; Wang, Quanguang

2017-11-01

Lipid emulsion (LE) has been shown to be effective in the resuscitation of bupivacaine-induced cardiac arrest, but the precise mechanism of this action has not been fully elucidated. Pursuant to this lack of information on the mechanism in which LE protects the myocardium during bupivacaine-induced toxicity, we explored mitochondrial function and cell apoptosis. H9C2 cardiomyocytes were used in study. Cells were randomly divided in different groups and were cultivated 6 h, 12 h, and 24 h. The mitochondria were extracted and mitochondrial ATP content was measured, as was mitochondrial membrane potential, the concentration of calcium ion (Ca2+), and the activity of Ca2+-ATP enzyme (Ca2+-ATPase). Cells from groups Bup1000, LE group, and Bup1000LE were collected to determine cell viability, cell apoptosis, and electron microscopy scanning of mitochondrial ultrastructure (after 24 h). We found that LE can reverse the inhibition of the mitochondrial function induced by bupivacaine, regulate the concentration of calcium ion in mitochondria, resulting in the protection of myocardial cells from toxicity induced by bupivacaine.

Drp1 loss-of-function reduces cardiomyocyte oxygen dependence protecting the heart from ischemia-reperfusion injury.

PubMed

Zepeda, Ramiro; Kuzmicic, Jovan; Parra, Valentina; Troncoso, Rodrigo; Pennanen, Christian; Riquelme, Jaime A; Pedrozo, Zully; Chiong, Mario; Sánchez, Gina; Lavandero, Sergio

2014-06-01

Mitochondria are key organelles for ATP production in cardiomyocytes, which is regulated by processes of fission and fusion. We hypothesized that the mitochondria fusion protein dynamin-related protein 1 (Drp1) inhibition, attenuates ischemia-reperfusion (I/R) injury through modifications in mitochondrial metabolism. Rats were subjected to I/R through coronary artery ligation, and isolated cardiomyocytes were treated with an ischemia-mimicking solution. In vivo, cardiac function, myocardial infarction area, and mitochondrial morphology were determined, whereas in vitro, viability, mitochondrial membrane potential, intracellular ATP levels, and oxygen consumption rate (OCR) were assessed. In both models, an adenovirus expressing Drp1 dominant-negative K38A (Drp1K38A) was used to induce Drp1 loss-of-function. Our results showed that I/R stimulated mitochondrial fission. Myocardial infarction size and cell death induced by I/R were significantly reduced, whereas cardiac function after I/R was improved in Drp1K38A-treated rats compared with controls. Drp1K38A-transduced cardiomyocytes showed lower OCR with no decrease in intracellular ATP levels, and on I/R, a larger decrease in OCR with a smaller reduction in intracellular ATP level was observed. However, proton leak-associated oxygen consumption was comparatively higher in Drp1K38A-treated cardiomyocytes, suggesting a protective mitochondrial uncoupling effect against I/R. Collectively, our results show that Drp1 inhibition triggers cardioprotection by reducing mitochondrial metabolism during I/R.

Mitochondrial structure and dynamics as critical factors in honey bee (Apis mellifera L.) caste development.

PubMed

Santos, Douglas Elias; Alberici, Luciane Carla; Hartfelder, Klaus

2016-06-01

The relationship between nutrition and phenotype is an especially challenging question in cases of facultative polyphenism, like the castes of social insects. In the honey bee, Apis mellifera, unexpected modifications in conserved signaling pathways revealed the hypoxia response as a possible mechanism underlying the regulation of body size and organ growth. Hence, the current study was designed to investigate possible causes of why the three hypoxia core genes are overexpressed in worker larvae. Parting from the hypothesis that this has an endogenous cause and is not due to differences in external oxygen levels we investigated mitochondrial numbers and distribution, as well as mitochondrial oxygen consumption rates in fat body cells of queen and worker larvae during the caste fate-critical larval stages. By immunofluorescence and electron microscopy we found higher densities of mitochondria in queen larval fat body, a finding further confirmed by a citrate synthase assay quantifying mitochondrial functional units. Oxygen consumption measurements by high-resolution respirometry revealed that queen larvae have higher maximum capacities of ATP production at lower physiological demand. Finally, the expression analysis of mitogenesis-related factors showed that the honey bee TFB1 and TFB2 homologs, and a nutritional regulator, ERR, are overexpressed in queen larvae. These results are strong evidence that the differential nutrition of queen and worker larvae by nurse bees affects mitochondrial dynamics and functionality in the fat body of these larvae, hence explaining their differential hypoxia response. Copyright © 2016 Elsevier Ltd. All rights reserved.

PINK1 deficiency enhances autophagy and mitophagy induction.

PubMed

Gómez-Sánchez, Rubén; Yakhine-Diop, Sokhna M S; Bravo-San Pedro, José M; Pizarro-Estrella, Elisa; Rodríguez-Arribas, Mario; Climent, Vicente; Martin-Cano, Francisco E; González-Soltero, María E; Tandon, Anurag; Fuentes, José M; González-Polo, Rosa A

2016-03-01

Parkinson's disease (PD) is a neurodegenerative disorder with poorly understood etiology. Increasing evidence suggests that age-dependent compromise of the maintenance of mitochondrial function is a key risk factor. Several proteins encoded by PD-related genes are associated with mitochondria including PTEN-induced putative kinase 1 (PINK1), which was first identified as a gene that is upregulated by PTEN. Loss-of-function PINK1 mutations induce mitochondrial dysfunction and, ultimately, neuronal cell death. To mitigate the negative effects of altered cellular functions cells possess a degradation mechanism called autophagy for recycling damaged components; selective elimination of dysfunctional mitochondria by autophagy is termed mitophagy. Our study indicates that autophagy and mitophagy are upregulated in PINK1-deficient cells, and is the first report to demonstrate efficient fluxes by one-step analysis. We propose that autophagy is induced to maintain cellular homeostasis under conditions of non-regulated mitochondrial quality control.

PINK1 deficiency enhances autophagy and mitophagy induction

PubMed Central

Gómez-Sánchez, Rubén; Yakhine-Diop, Sokhna M S; Bravo-San Pedro, José M; Pizarro-Estrella, Elisa; Rodríguez-Arribas, Mario; Climent, Vicente; Martin-Cano, Francisco E; González-Soltero, María E; Tandon, Anurag; Fuentes, José M; González-Polo, Rosa A

2016-01-01

Parkinson's disease (PD) is a neurodegenerative disorder with poorly understood etiology. Increasing evidence suggests that age-dependent compromise of the maintenance of mitochondrial function is a key risk factor. Several proteins encoded by PD-related genes are associated with mitochondria including PTEN-induced putative kinase 1 (PINK1), which was first identified as a gene that is upregulated by PTEN. Loss-of-function PINK1 mutations induce mitochondrial dysfunction and, ultimately, neuronal cell death. To mitigate the negative effects of altered cellular functions cells possess a degradation mechanism called autophagy for recycling damaged components; selective elimination of dysfunctional mitochondria by autophagy is termed mitophagy. Our study indicates that autophagy and mitophagy are upregulated in PINK1-deficient cells, and is the first report to demonstrate efficient fluxes by one-step analysis. We propose that autophagy is induced to maintain cellular homeostasis under conditions of non-regulated mitochondrial quality control. PMID:27308585

Thermal sensitivity of mitochondrial respiration efficiency and protein phosphorylation in the clam Mercenaria mercenaria.

PubMed

Ulrich, P N; Marsh, A G

2009-01-01

The mitochondria of intertidal invertebrates continue to function when organisms are exposed to rapid substantial shifts in temperature. To test if mitochondrial physiology of the clam Mercenaria mercenaria is compromised under elevated temperatures, we measured mitochondrial respiration efficiency at 15 degrees C, 18 degrees C, and 21 degrees C using a novel, high-throughput, microplate respirometry methodology developed for this study. Though phosphorylating (state 3) and resting (state 4) respiration rates were unaffected over this temperature range, respiratory control ratios (RCRs: ratio of state 3 to state 4 respiration rates) decreased significantly above 18 degrees C (p < 0.05). The drop in RCR was not associated with reduction of phosphorylation efficiency, suggesting that, while aerobic scope of mitochondrial respiration is limited at elevated temperatures, mitochondria continue to efficiently produce adenosine triphosphate. We further investigated the response of clam mitochondria to elevated temperatures by monitoring phosphorylation of mitochondrial protein. Three proteins clearly demonstrated significant time- and temperature-specific phosphorylation patterns. The protein-specific patterns of phosphorylation may suggest that a suite of protein kinases and phosphatases regulate mitochondrial physiology in response to temperature. Thus, while aerobic scope of clam mitochondrial respiration is reduced at moderate temperatures, specific protein phosphorylation responses reflect large shifts in function that are initiated within the organelle at higher temperatures.

The Rise of Mitochondria in Medicine

PubMed Central

Picard, Martin; Wallace, Douglas C; Burelle, Yan

2016-01-01

Once considered exclusively the cell's powerhouse, mitochondria are now recognized to perform multiple essential cellular functions beyond energy production, impacting most areas of cell biology and medicine. Since the emergence of molecular biology and the discovery of pathogenic mitochondrial DNA defects in the 1980's, research advances have revealed a number of common human diseases which share an underlying pathogenesis involving mitochondrial dysfunction. Mitochondria undergo function-defining dynamic shape changes, communicate with each other, regulate gene expression within the nucleus, modulate synaptic transmission within the brain, release molecules that contribute to oncogenic transformation and trigger inflammatory responses systemically, and influence the regulation of complex physiological systems. Novel “mitopathogenic” mechanisms are thus being uncovered across a number of medical disciplines including genetics, oncology, neurology, immunology, and critical care medicine. Increasing knowledge of the bioenergetic aspects of human disease has provided new opportunities for diagnosis, therapy, prevention, and in connecting various domains of medicine. In this article, we overview specific aspects of mitochondrial biology that have contributed to – and likely will continue to enhance the progress of modern medicine. PMID:27423788

Superresolution imaging of viral protein trafficking

PubMed Central

Salka, Kyle; Bhuvanendran, Shivaprasad; Yang, David

2015-01-01

The endoplasmic reticulum (ER) membrane is closely apposed to the outer mitochondrial membrane (OMM), which facilitates communication between these organelles. These contacts, known as mitochondria-associated membranes (MAM), facilitate calcium signaling, lipid transfer, as well as antiviral and stress responses. How cellular proteins traffic to the MAM, are distributed therein, and interact with ER and mitochondrial proteins are subject of great interest. The human cytomegalovirus UL37 exon 1 protein or viral mitochondria-localized inhibitor of apoptosis (vMIA) is crucial for viral growth. Upon synthesis at the ER, vMIA traffics to the MAM and OMM, where it reprograms the organization and function of these compartments. vMIA significantly changes the abundance of cellular proteins at the MAM and OMM, including proteins that regulate calcium homeostasis and cell death. Through the use of superresolution imaging, we have shown that vMIA is distributed at the OMM in nanometer scale clusters. This is similar to the clusters reported for the mitochondrial calcium channel, VDAC, as well as electron transport chain, translocase of the OMM complex, and mitochondrial inner membrane organizing system components. Thus, aside from addressing how vMIA targets the MAM and regulates survival of infected cells, biochemical studies and superresolution imaging of vMIA offer insights into the formation, organization, and functioning of MAM. Here, we discuss these insights into trafficking, function, and organization of vMIA at the MAM and OMM and discuss how the use of superresolution imaging is contributing to the study of the formation and trafficking of viruses. PMID:25724304

Antimetastatic effects of cordycepin mediated by the inhibition of mitochondrial activity and estrogen-related receptor α in human ovarian carcinoma cells

PubMed Central

Wang, Chia-Woei; Hsu, Wei-Hsuan; Tai, Chen-Jei

2017-01-01

Cordycepin (3′-deoxyadenosine) is a compound for antitumor, which has been found to exert antiangiogenic, antimetastatic, and antiproliferative effects, as well as inducing apoptosis. However, the association between cancer metastasis and mitochondrial activity in cordycepin-treated ovarian carcinoma cells remains unclear. The 50 and 100 μM of cordycepin inhibits mitochondrial fusion and induces mitochondrial fission, respectively. These suggested that cordycepin showed the down-regulation of mitochondrial function and limitation of energy production. Because of activation of mitochondria and generation of energy are needed in cancer cell migration/invasion. After 24 h treatment, cordycepin suppresses epithelial–mesenchymal transition and migration in ovarian carcinoma cells through inhibiting estrogen-related receptor (ERR)-α. The ERRα is a co-transcription factor for gene expressions associated with mitochondrial fusion. Our results indicate that cordycepin suppresses metastasis and migration of ovarian carcinoma cells via inhibiting mitochondrial activity in non-toxic concentrations, and cordycepin has potential benefits in ovarian cancer therapy. PMID:27966445

Estrogen-related receptor {alpha} is essential for the expression of antioxidant protection genes and mitochondrial function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rangwala, Shamina M.; Li, Xiaoyan; Lindsley, Loren

2007-05-25

Estrogen-related receptor {alpha} (ERR{alpha}) is an important mediator of mitochondrial biogenesis and function. To investigate the transcriptional network controlling these phenomena, we investigated mitochondrial gene expression in embryonic fibroblasts isolated from ERR{alpha} null mice. Peroxisome proliferator-activated receptor {gamma} coactivator-1{alpha} (PGC-1{alpha}) stimulated mitochondrial gene expression program in control cells, but not in the ERR{alpha} null cells. Interestingly, the induction of levels of mitochondrial oxidative stress protection genes in response to increased PGC-1{alpha} levels was dependent on ERR{alpha}. Furthermore, we found that the PGC-1{alpha}-mediated induction of estrogen-related receptor {gamma} and nuclear respiratory factor 2 (NRF-2), was dependent on the presence of ERR{alpha}.more » Basal levels of NRF-2 were decreased in the absence of ERR{alpha}. The absence of ERR{alpha} resulted in a decrease in citrate synthase enzyme activity in response to PGC-1{alpha} overexpression. Our results indicate an essential role for ERR{alpha} as a key regulator of oxidative metabolism.« less

Mitochondrial Optic Atrophy (OPA) 1 Processing Is Altered in Response to Neonatal Hypoxic-Ischemic Brain Injury

PubMed Central

Baburamani, Ana A.; Hurling, Chloe; Stolp, Helen; Sobotka, Kristina; Gressens, Pierre; Hagberg, Henrik; Thornton, Claire

2015-01-01

Perturbation of mitochondrial function and subsequent induction of cell death pathways are key hallmarks in neonatal hypoxic-ischemic (HI) injury, both in animal models and in term infants. Mitoprotective therapies therefore offer a new avenue for intervention for the babies who suffer life-long disabilities as a result of birth asphyxia. Here we show that after oxygen-glucose deprivation in primary neurons or in a mouse model of HI, mitochondrial protein homeostasis is altered, manifesting as a change in mitochondrial morphology and functional impairment. Furthermore we find that the mitochondrial fusion and cristae regulatory protein, OPA1, is aberrantly cleaved to shorter forms. OPA1 cleavage is normally regulated by a balanced action of the proteases Yme1L and Oma1. However, in primary neurons or after HI in vivo, protein expression of YmelL is also reduced, whereas no change is observed in Oma1 expression. Our data strongly suggest that alterations in mitochondria-shaping proteins are an early event in the pathogenesis of neonatal HI injury. PMID:26393574

Mitochondrial Energy Metabolism and Redox Signaling in Brain Aging and Neurodegeneration

PubMed Central

Yin, Fei; Boveris, Alberto

2014-01-01

Abstract Significance: The mitochondrial energy-transducing capacity is essential for the maintenance of neuronal function, and the impairment of energy metabolism and redox homeostasis is a hallmark of brain aging, which is particularly accentuated in the early stages of neurodegenerative diseases. Recent Advances: The communications between mitochondria and the rest of the cell by energy- and redox-sensitive signaling establish a master regulatory device that controls cellular energy levels and the redox environment. Impairment of this regulatory devise is critical for aging and the early stages of neurodegenerative diseases. Critical Issues: This review focuses on a coordinated metabolic network—cytosolic signaling, transcriptional regulation, and mitochondrial function—that controls the cellular energy levels and redox status as well as factors which impair this metabolic network during brain aging and neurodegeneration. Future Directions: Characterization of mitochondrial function and mitochondria-cytosol communications will provide pivotal opportunities for identifying targets and developing new strategies aimed at restoring the mitochondrial energy-redox axis that is compromised in brain aging and neurodegeneration. Antioxid. Redox Signal. 20, 353–371. PMID:22793257

The plant i-AAA protease controls the turnover of an essential mitochondrial protein import component.

PubMed

Opalińska, Magdalena; Parys, Katarzyna; Murcha, Monika W; Jańska, Hanna

2018-01-29

Mitochondria are multifunctional organelles that play a central role in energy metabolism. Owing to the life-essential functions of these organelles, mitochondrial content, quality and dynamics are tightly controlled. Across the species, highly conserved ATP-dependent proteases prevent malfunction of mitochondria through versatile activities. This study focuses on a molecular function of the plant mitochondrial inner membrane-embedded AAA protease (denoted i -AAA) FTSH4, providing its first bona fide substrate. Here, we report that the abundance of the Tim17-2 protein, an essential component of the TIM17:23 translocase (Tim17-2 together with Tim50 and Tim23), is directly controlled by the proteolytic activity of FTSH4. Plants that are lacking functional FTSH4 protease are characterized by significantly enhanced capacity of preprotein import through the TIM17:23-dependent pathway. Taken together, with the observation that FTSH4 prevents accumulation of Tim17-2, our data point towards the role of this i -AAA protease in the regulation of mitochondrial biogenesis in plants. © 2018. Published by The Company of Biologists Ltd.

The use of high-throughput screening techniques to evaluate mitochondrial toxicity.

PubMed

Wills, Lauren P

2017-11-01

Toxicologists and chemical regulators depend on accurate and effective methods to evaluate and predict the toxicity of thousands of current and future compounds. Robust high-throughput screening (HTS) experiments have the potential to efficiently test large numbers of chemical compounds for effects on biological pathways. HTS assays can be utilized to examine chemical toxicity across multiple mechanisms of action, experimental models, concentrations, and lengths of exposure. Many agricultural, industrial, and pharmaceutical chemicals classified as harmful to human and environmental health exert their effects through the mechanism of mitochondrial toxicity. Mitochondrial toxicants are compounds that cause a decrease in the number of mitochondria within a cell, and/or decrease the ability of mitochondria to perform normal functions including producing adenosine triphosphate (ATP) and maintaining cellular homeostasis. Mitochondrial dysfunction can lead to apoptosis, necrosis, altered metabolism, muscle weakness, neurodegeneration, decreased organ function, and eventually disease or death of the whole organism. The development of HTS techniques to identify mitochondrial toxicants will provide extensive databases with essential connections between mechanistic mitochondrial toxicity and chemical structure. Computational and bioinformatics approaches can be used to evaluate compound databases for specific chemical structures associated with toxicity, with the goal of developing quantitative structure-activity relationship (QSAR) models and mitochondrial toxicophores. Ultimately these predictive models will facilitate the identification of mitochondrial liabilities in consumer products, industrial compounds, pharmaceuticals and environmental hazards. Copyright © 2017 Elsevier B.V. All rights reserved.

Metabolic reprogramming during neuronal differentiation.

PubMed

Agostini, M; Romeo, F; Inoue, S; Niklison-Chirou, M V; Elia, A J; Dinsdale, D; Morone, N; Knight, R A; Mak, T W; Melino, G

2016-09-01

Newly generated neurons pass through a series of well-defined developmental stages, which allow them to integrate into existing neuronal circuits. After exit from the cell cycle, postmitotic neurons undergo neuronal migration, axonal elongation, axon pruning, dendrite morphogenesis and synaptic maturation and plasticity. Lack of a global metabolic analysis during early cortical neuronal development led us to explore the role of cellular metabolism and mitochondrial biology during ex vivo differentiation of primary cortical neurons. Unexpectedly, we observed a huge increase in mitochondrial biogenesis. Changes in mitochondrial mass, morphology and function were correlated with the upregulation of the master regulators of mitochondrial biogenesis, TFAM and PGC-1α. Concomitant with mitochondrial biogenesis, we observed an increase in glucose metabolism during neuronal differentiation, which was linked to an increase in glucose uptake and enhanced GLUT3 mRNA expression and platelet isoform of phosphofructokinase 1 (PFKp) protein expression. In addition, glutamate-glutamine metabolism was also increased during the differentiation of cortical neurons. We identified PI3K-Akt-mTOR signalling as a critical regulator role of energy metabolism in neurons. Selective pharmacological inhibition of these metabolic pathways indicate existence of metabolic checkpoint that need to be satisfied in order to allow neuronal differentiation.

Metabolic reprogramming during neuronal differentiation

PubMed Central

Agostini, M; Romeo, F; Inoue, S; Niklison-Chirou, M V; Elia, A J; Dinsdale, D; Morone, N; Knight, R A; Mak, T W; Melino, G

2016-01-01

Newly generated neurons pass through a series of well-defined developmental stages, which allow them to integrate into existing neuronal circuits. After exit from the cell cycle, postmitotic neurons undergo neuronal migration, axonal elongation, axon pruning, dendrite morphogenesis and synaptic maturation and plasticity. Lack of a global metabolic analysis during early cortical neuronal development led us to explore the role of cellular metabolism and mitochondrial biology during ex vivo differentiation of primary cortical neurons. Unexpectedly, we observed a huge increase in mitochondrial biogenesis. Changes in mitochondrial mass, morphology and function were correlated with the upregulation of the master regulators of mitochondrial biogenesis, TFAM and PGC-1α. Concomitant with mitochondrial biogenesis, we observed an increase in glucose metabolism during neuronal differentiation, which was linked to an increase in glucose uptake and enhanced GLUT3 mRNA expression and platelet isoform of phosphofructokinase 1 (PFKp) protein expression. In addition, glutamate–glutamine metabolism was also increased during the differentiation of cortical neurons. We identified PI3K–Akt–mTOR signalling as a critical regulator role of energy metabolism in neurons. Selective pharmacological inhibition of these metabolic pathways indicate existence of metabolic checkpoint that need to be satisfied in order to allow neuronal differentiation. PMID:27058317

Fluid Mechanical Forces and Endothelial Mitochondria: A Bioengineering Perspective.

PubMed

Scheitlin, Christopher G; Nair, Devi M; Crestanello, Juan A; Zweier, Jay L; Alevriadou, B Rita

2014-12-01

Endothelial cell dysfunction is the hallmark of every cardiovascular disease/condition, including atherosclerosis and ischemia/reperfusion injury. Fluid shear stress acting on the vascular endothelium is known to regulate cell homeostasis. Altered hemodynamics is thought to play a causative role in endothelial dysfunction. The dysfunction is associated with/preceded by mitochondrial oxidative stress. Studies by our group and others have shown that the form and/or function of the mitochondrial network are affected when endothelial cells are exposed to shear stress in the absence or presence of additional physicochemical stimuli. The present review will summarize the current knowledge on the interconnections among intracellular Ca 2+ - nitric oxide - mitochondrial reactive oxygen species, mitochondrial fusion/fission, autophagy/mitophagy, and cell apoptosis vs. survival. More specifically, it will list the evidence on potential regulation of the above intracellular species and processes by the fluid shear stress acting on the endothelium under either physiological flow conditions or during reperfusion (following a period of ischemia). Understanding how the local hemodynamics affects mitochondrial physiology and the cell redox state may lead to development of novel therapeutic strategies for prevention or treatment of the endothelial dysfunction and, hence, of cardiovascular disease.

Acute high-altitude hypoxic brain injury: Identification of ten differential proteins

PubMed Central

Li, Jianyu; Qi, Yuting; Liu, Hui; Cui, Ying; Zhang, Li; Gong, Haiying; Li, Yaxiao; Li, Lingzhi; Zhang, Yongliang

2013-01-01

Hypobaric hypoxia can cause severe brain damage and mitochondrial dysfunction, and is involved in hypoxic brain injury. However, little is currently known about the mechanisms responsible for mitochondrial dysfunction in hypobaric hypoxic brain damage. In this study, a rat model of hypobaric hypoxic brain injury was established to investigate the molecular mechanisms associated with mitochondrial dysfunction. As revealed by two-dimensional electrophoresis analysis, 16, 21, and 36 differential protein spots in cerebral mitochondria were observed at 6, 12, and 24 hours post-hypobaric hypoxia, respectively. Furthermore, ten protein spots selected from each hypobaric hypoxia subgroup were similarly regulated and were identified by mass spectrometry. These detected proteins included dihydropyrimidinase-related protein 2, creatine kinase B-type, isovaleryl-CoA dehydrogenase, elongation factor Ts, ATP synthase beta-subunit, 3-mercaptopyruvate sulfurtransferase, electron transfer flavoprotein alpha-subunit, Chain A of 2-enoyl-CoA hydratase, NADH dehydrogenase iron-sulfur protein 8 and tropomyosin beta chain. These ten proteins are all involved in the electron transport chain and the function of ATP synthase. Our findings indicate that hypobaric hypoxia can induce the differential expression of several cerebral mitochondrial proteins, which are involved in the regulation of mitochondrial energy production. PMID:25206614

Integration of Posttranscriptional Gene Networks into Metabolic Adaptation and Biofilm Maturation in Candida albicans

PubMed Central

Harrison, Paul F.; Lo, Tricia L.; Quenault, Tara; Dagley, Michael J.; Bellousoff, Matthew; Powell, David R.; Beilharz, Traude H.; Traven, Ana

2015-01-01

The yeast Candida albicans is a human commensal and opportunistic pathogen. Although both commensalism and pathogenesis depend on metabolic adaptation, the regulatory pathways that mediate metabolic processes in C. albicans are incompletely defined. For example, metabolic change is a major feature that distinguishes community growth of C. albicans in biofilms compared to suspension cultures, but how metabolic adaptation is functionally interfaced with the structural and gene regulatory changes that drive biofilm maturation remains to be fully understood. We show here that the RNA binding protein Puf3 regulates a posttranscriptional mRNA network in C. albicans that impacts on mitochondrial biogenesis, and provide the first functional data suggesting evolutionary rewiring of posttranscriptional gene regulation between the model yeast Saccharomyces cerevisiae and C. albicans. A proportion of the Puf3 mRNA network is differentially expressed in biofilms, and by using a mutant in the mRNA deadenylase CCR4 (the enzyme recruited to mRNAs by Puf3 to control transcript stability) we show that posttranscriptional regulation is important for mitochondrial regulation in biofilms. Inactivation of CCR4 or dis-regulation of mitochondrial activity led to altered biofilm structure and over-production of extracellular matrix material. The extracellular matrix is critical for antifungal resistance and immune evasion, and yet of all biofilm maturation pathways extracellular matrix biogenesis is the least understood. We propose a model in which the hypoxic biofilm environment is sensed by regulators such as Ccr4 to orchestrate metabolic adaptation, as well as the regulation of extracellular matrix production by impacting on the expression of matrix-related cell wall genes. Therefore metabolic changes in biofilms might be intimately linked to a key biofilm maturation mechanism that ultimately results in untreatable fungal disease. PMID:26474309

Control of mitochondrial biogenesis and function by the ubiquitin-proteasome system.

PubMed

Bragoszewski, Piotr; Turek, Michal; Chacinska, Agnieszka

2017-04-01

Mitochondria are pivotal organelles in eukaryotic cells. The complex proteome of mitochondria comprises proteins that are encoded by nuclear and mitochondrial genomes. The biogenesis of mitochondrial proteins requires their transport in an unfolded state with a high risk of misfolding. The mislocalization of mitochondrial proteins is deleterious to the cell. The electron transport chain in mitochondria is a source of reactive oxygen species that damage proteins. Mitochondrial dysfunction is linked to many pathological conditions and, together with the loss of cellular protein homeostasis (proteostasis), are hallmarks of ageing and ageing-related degeneration diseases. The pathogenesis of neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, has been associated with mitochondrial and proteostasis failure. Thus, mitochondrial proteins require sophisticated surveillance mechanisms. Although mitochondria form a proteasome-exclusive compartment, multiple lines of evidence indicate a crucial role for the cytosolic ubiquitin-proteasome system (UPS) in the quality control of mitochondrial proteins. The proteasome affects mitochondrial proteins at stages of their biogenesis and maturity. The effects of the UPS go beyond the removal of damaged proteins and include the adjustment of mitochondrial proteome composition, the regulation of organelle dynamics and the protection of cellular homeostasis against mitochondrial failure. In turn, mitochondrial activity and mitochondrial dysfunction adjust the activity of the UPS, with implications at the cellular level. © 2017 The Authors.

Control of mitochondrial biogenesis and function by the ubiquitin–proteasome system

PubMed Central

Bragoszewski, Piotr; Turek, Michal

2017-01-01

Mitochondria are pivotal organelles in eukaryotic cells. The complex proteome of mitochondria comprises proteins that are encoded by nuclear and mitochondrial genomes. The biogenesis of mitochondrial proteins requires their transport in an unfolded state with a high risk of misfolding. The mislocalization of mitochondrial proteins is deleterious to the cell. The electron transport chain in mitochondria is a source of reactive oxygen species that damage proteins. Mitochondrial dysfunction is linked to many pathological conditions and, together with the loss of cellular protein homeostasis (proteostasis), are hallmarks of ageing and ageing-related degeneration diseases. The pathogenesis of neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, has been associated with mitochondrial and proteostasis failure. Thus, mitochondrial proteins require sophisticated surveillance mechanisms. Although mitochondria form a proteasome-exclusive compartment, multiple lines of evidence indicate a crucial role for the cytosolic ubiquitin–proteasome system (UPS) in the quality control of mitochondrial proteins. The proteasome affects mitochondrial proteins at stages of their biogenesis and maturity. The effects of the UPS go beyond the removal of damaged proteins and include the adjustment of mitochondrial proteome composition, the regulation of organelle dynamics and the protection of cellular homeostasis against mitochondrial failure. In turn, mitochondrial activity and mitochondrial dysfunction adjust the activity of the UPS, with implications at the cellular level. PMID:28446709

Modulation of ROS levels in fibroblasts by altering mitochondria regulates the process of wound healing.

PubMed

Janda, Jaroslav; Nfonsam, Valentine; Calienes, Fernanda; Sligh, James E; Jandova, Jana

2016-05-01

Mitochondria are the major source of reactive oxygen species (ROS) in fibroblasts which are thought to be crucial regulators of wound healing with a potential to affect the expression of nuclear genes involved in this process. ROS generated by mitochondria are involved in all stages of tissue repair process but the regulation of ROS-generating system in fibroblasts still remains poorly understood. The purpose of this study was to better understand molecular mechanisms of how the regulation of ROS levels generated by mitochondria may influence the process of wound repair. Cybrid model system of mtDNA variations was used to study the functional consequences of altered ROS levels on wound healing responses in a uniform nuclear background of cultured ρ(0) fibroblasts. Mitochondrial ROS in cybrids were modulated by antioxidants that quench ROS to examine their ability to close the wound. Real-time PCR arrays were used to investigate whether ROS generated by specific mtDNA variants have the ability to alter expression of some key nuclear-encoded genes central to the wound healing response and oxidative stress. Our data suggest levels of mitochondrial ROS affect expression of some nuclear encoded genes central to wound healing response and oxidative stress and modulation of mitochondrial ROS by antioxidants positively affects in vitro process of wound closure. Thus, regulation of mitochondrial ROS-generating system in fibroblasts can be used as effective natural redox-based strategy to help treat non-healing wounds.

Central roles of iron in the regulation of oxidative stress in the yeast Saccharomyces cerevisiae.

PubMed

Matsuo, Ryo; Mizobuchi, Shogo; Nakashima, Maya; Miki, Kensuke; Ayusawa, Dai; Fujii, Michihiko

2017-10-01

Oxygen is essential for aerobic organisms but causes cytotoxicity probably through the generation of reactive oxygen species (ROS). In this study, we screened for the genes that regulate oxidative stress in the yeast Saccharomyces cerevisiae, and found that expression of CTH2/TIS11 caused an increased resistance to ROS. CTH2 is up-regulated upon iron starvation and functions to remodel metabolism to adapt to iron starvation. We showed here that increased resistance to ROS by CTH2 would likely be caused by the decreased ROS production due to the decreased activity of mitochondrial respiration, which observation is consistent with the fact that CTH2 down-regulates the mitochondrial respiratory proteins. We also found that expression of CTH1, a paralog of CTH2, also caused an increased resistance to ROS. This finding supported the above view, because mitochondrial respiratory proteins are the common targets of CTH1 and CTH2. We further showed that supplementation of iron in medium augmented the growth of S. cerevisiae under oxidative stress, and expression of CTH2 and supplementation of iron collectively enhanced its growth under oxidative stress. Since CTH2 is regulated by iron, these findings suggested that iron played crucial roles in the regulation of oxidative stress in S. cerevisiae.

tRNA travels from the cytoplasm to organelles

PubMed Central

Rubio, Mary Anne T.; Hopper, Anita K.

2011-01-01

Transfer RNAs (tRNAs) encoded by the nuclear genome are surprisingly dynamic. Although tRNAs function in protein synthesis occurring on cytoplasmic ribosomes, tRNAs can transit from the cytoplasm to the nucleus and then again return to the cytoplasm by a process known as the tRNA retrograde process. Subsets of the cytoplasmic tRNAs are also imported into mitochondria and function in mitochondrial protein synthesis. The numbers of tRNA species that are imported into mitchondria differ among organisms, ranging from just a few to the entire set needed to decode mitochondrially encoded mRNAs. For some tRNAs, import is dependent on the mitochondrial protein import machinery, whereas the majority of tRNA mitochondrial import is independent of this machinery. Although cytoplasmic proteins and proteins located on the mitochondrial surface participating in the tRNA import process have been described for several organisms, the identity of these proteins differ among organisms. Likewise, the tRNA determinants required for mitochondrial import differ among tRNA species and organisms. Here, we present an overview and discuss the current state of knowledge regarding the mechanisms involved in the tRNA retrograde process and continue with an overview of tRNA import into mitochondria. Finally, we highlight areas of future research to understand the function and regulation of movement of tRNAs between the cytoplasm and organelles. PMID:21976284

Mitochondrial multifaceted dysfunction in schizophrenia; complex I as a possible pathological target.

PubMed

Ben-Shachar, Dorit

2017-09-01

Mitochondria are key players in various essential cellular processes beyond being the main energy supplier of the cell. Accordingly, they are involved in neuronal synaptic transmission, neuronal growth and sprouting and consequently neuronal plasticity and connectivity. In addition, mitochondria participate in the modulation of gene transcription and inflammation as well in physiological responses in health and disease. Schizophrenia is currently regarded as a neurodevelopmental disorder associated with impaired immune system, aberrant neuronal differentiation and abnormalities in various neurotransmitter systems mainly the dopaminergic, glutaminergic and GABAergic. Ample evidence has been accumulated over the last decade indicating a multifaceted dysfunction of mitochondria in schizophrenia. Indeed, mitochondrial deficit can be of relevance for the majority of the pathologies observed in this disease. In the present article, we overview specific deficits of the mitochondria in schizophrenia, with a focus on the first complex (complex I) of the mitochondrial electron transport chain (ETC). We argue that complex I, being a major factor in the regulation of mitochondrial ETC, is a possible key modulator of various functions of the mitochondria. We review biochemical, molecular, cellular and functional evidence for mitochondrial impairments and their possible convergence to impact in-vitro neuronal differentiation efficiency in schizophrenia. Mitochondrial function in schizophrenia may advance our knowledge of the disease pathophysiology and open the road for new treatment targets for the benefit of the patients. Copyright © 2016 Elsevier B.V. All rights reserved.

Calcium and mitochondrial metabolism in ceramide-induced cardiomyocyte death.

PubMed

Parra, Valentina; Moraga, Francisco; Kuzmicic, Jovan; López-Crisosto, Camila; Troncoso, Rodrigo; Torrealba, Natalia; Criollo, Alfredo; Díaz-Elizondo, Jessica; Rothermel, Beverly A; Quest, Andrew F G; Lavandero, Sergio

2013-08-01

Ceramides are important intermediates in the biosynthesis and degradation of sphingolipids that regulate numerous cellular processes, including cell cycle progression, cell growth, differentiation and death. In cardiomyocytes, ceramides induce apoptosis by decreasing mitochondrial membrane potential and promoting cytochrome-c release. Ca(2+) overload is a common feature of all types of cell death. The aim of this study was to determine the effect of ceramides on cytoplasmic Ca(2+) levels, mitochondrial function and cardiomyocyte death. Our data show that C2-ceramide induces apoptosis and necrosis in cultured cardiomyocytes by a mechanism involving increased Ca(2+) influx, mitochondrial network fragmentation and loss of the mitochondrial Ca(2+) buffer capacity. These biochemical events increase cytosolic Ca(2+) levels and trigger cardiomyocyte death via the activation of calpains. Copyright © 2013 Elsevier B.V. All rights reserved.

Application of the Principles of Systems Biology and Wiener’s Cybernetics for Analysis of Regulation of Energy Fluxes in Muscle Cells in Vivo

PubMed Central

Guzun, Rita; Saks, Valdur

2010-01-01

The mechanisms of regulation of respiration and energy fluxes in the cells are analyzed based on the concepts of systems biology, non-equilibrium steady state kinetics and applications of Wiener’s cybernetic principles of feedback regulation. Under physiological conditions cardiac function is governed by the Frank-Starling law and the main metabolic characteristic of cardiac muscle cells is metabolic homeostasis, when both workload and respiration rate can be changed manifold at constant intracellular level of phosphocreatine and ATP in the cells. This is not observed in skeletal muscles. Controversies in theoretical explanations of these observations are analyzed. Experimental studies of permeabilized fibers from human skeletal muscle vastus lateralis and adult rat cardiomyocytes showed that the respiration rate is always an apparent hyperbolic but not a sigmoid function of ADP concentration. It is our conclusion that realistic explanations of regulation of energy fluxes in muscle cells require systemic approaches including application of the feedback theory of Wiener’s cybernetics in combination with detailed experimental research. Such an analysis reveals the importance of limited permeability of mitochondrial outer membrane for ADP due to interactions of mitochondria with cytoskeleton resulting in quasi-linear dependence of respiration rate on amplitude of cyclic changes in cytoplasmic ADP concentrations. The system of compartmentalized creatine kinase (CK) isoenzymes functionally coupled to ANT and ATPases, and mitochondrial-cytoskeletal interactions separate energy fluxes (mass and energy transfer) from signalling (information transfer) within dissipative metabolic structures – intracellular energetic units (ICEU). Due to the non-equilibrium state of CK reactions, intracellular ATP utilization and mitochondrial ATP regeneration are interconnected by the PCr flux from mitochondria. The feedback regulation of respiration occurring via cyclic fluctuations of cytosolic ADP, Pi and Cr/PCr ensures metabolic stability necessary for normal function of cardiac cells. PMID:20479996

Oncostatin M (OSM) protects against cardiac ischaemia/reperfusion injury in diabetic mice by regulating apoptosis, mitochondrial biogenesis and insulin sensitivity.

PubMed

Sun, Dongdong; Li, Shuang; Wu, Hao; Zhang, Mingming; Zhang, Xiaotian; Wei, Liping; Qin, Xing; Gao, Erhe

2015-06-01

Oncostatin M (OSM) exhibits many unique biological activities by activating Oβ receptor. However, its role in myocardial I/R injury in diabetic mice remains unknown. The involvement of OSM was assessed in diabetic mice which underwent myocardial I/R injury by OSM treatment or genetic deficiency of OSM receptor Oβ. Its mechanism on cardiomyocyte apoptosis, mitochondrial biogenesis and insulin sensitivity were further studied. OSM alleviated cardiac I/R injury by inhibiting cardiomyocyte apoptosis through inhibition of inositol pyrophosphate 7 (IP7) production, thus activating PI3K/Akt/BAD pathway, decreasing Bax expression while up-regulating Bcl-2 expression and decreasing the ratio of Bax to Bcl-2 in db/db mice. OSM enhanced mitochondrial biogenesis and mitochondrial function in db/db mice subjected to cardiac I/R injury. On the contrary, OSM receptor Oβ knockout exacerbated cardiac I/R injury, increased IP7 production, enhanced cardiomyocyte apoptosis, impaired mitochondrial biogenesis, glucose homoeostasis and insulin sensitivity in cardiac I/R injured diabetic mice. Inhibition of IP7 production by TNP (IP6K inhibitor) exerted similar effects of OSM. The mechanism of OSM on cardiac I/R injury in diabetic mice is partly associated with IP7/Akt and adenine mononucleotide protein kinase/PGC-1α pathway. OSM protects against cardiac I/R Injury by regulating apoptosis, insulin sensitivity and mitochondrial biogenesis in diabetic mice through inhibition of IP7 production. © 2015 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Analysis of barosensitive mechanisms in yeast for Pressure Regulated Fermentation

NASA Astrophysics Data System (ADS)

Nomura, Kazuki; Iwahashi, Hitoshi; Iguchi, Akinori; Shigematsu, Toru

2013-06-01

Introduction: We are intending to develop a novel food processing technology, Pressure Regulated Fermentation (PReF), using pressure sensitive (barosensitive) fermentation microorganisms. Objectives of our study are to clarify barosensitive mechanisms for application to PReF technology. We isolated Saccharomyces cerevisiae barosensitive mutant a924E1 that was derived from the parent KA31a. Methods: Gene expression levels were analyzed by DNA microarray. The altered genes of expression levels were classified according to the gene function. Mutated genes were estimated by mating and producing diploid strains and confirmed by PCR of mitochondrial DNA (mtDNA). Results and Discussion: Gene expression profiles showed that genes of `Energy' function and that of encoding protein localized in ``Mitochondria'' were significantly down regulated in the mutant. These results suggest the respiratory deficiency and relationship between barosensitivity and respiratory deficiency. Since the respiratory functions of diploids showed non Mendelian inheritance, the respiratory deficiency was indicated to be due to mtDNA mutation. PCR analysis showed that the region of COX1 locus was deleted. COX1 gene encodes the subunit 1 of cytochrome c oxidase. For this reason, barosensitivity is strongly correlated with mitochondrial functions.

Contributions of Bcl-xL to acute and long term changes in bioenergetics during neuronal plasticity.

PubMed

Jonas, Elizabeth A

2014-08-01

Mitochondria manufacture and release metabolites and manage calcium during neuronal activity and synaptic transmission, but whether long term alterations in mitochondrial function contribute to the neuronal plasticity underlying changes in organism behavior patterns is still poorly understood. Although normal neuronal plasticity may determine learning, in contrast a persistent decline in synaptic strength or neuronal excitability may portend neurite retraction and eventual somatic death. Anti-death proteins such as Bcl-xL not only provide neuroprotection at the neuronal soma during cell death stimuli, but also appear to enhance neurotransmitter release and synaptic growth and development. It is proposed that Bcl-xL performs these functions through its ability to regulate mitochondrial release of bioenergetic metabolites and calcium, and through its ability to rapidly alter mitochondrial positioning and morphology. Bcl-xL also interacts with proteins that directly alter synaptic vesicle recycling. Bcl-xL translocates acutely to sub-cellular membranes during neuronal activity to achieve changes in synaptic efficacy. After stressful stimuli, pro-apoptotic cleaved delta N Bcl-xL (ΔN Bcl-xL) induces mitochondrial ion channel activity leading to synaptic depression and this is regulated by caspase activation. During physiological states of decreased synaptic stimulation, loss of mitochondrial Bcl-xL and low level caspase activation occur prior to the onset of long term decline in synaptic efficacy. The degree to which Bcl-xL changes mitochondrial membrane permeability may control the direction of change in synaptic strength. The small molecule Bcl-xL inhibitor ABT-737 has been useful in defining the role of Bcl-xL in synaptic processes. Bcl-xL is crucial to the normal health of neurons and synapses and its malfunction may contribute to neurodegenerative disease. Copyright © 2013. Published by Elsevier B.V.

Fasting and refeeding differentially regulate NLRP3 inflammasome activation in human subjects

PubMed Central

Traba, Javier; Kwarteng-Siaw, Miriam; Okoli, Tracy C.; Li, Jessica; Huffstutler, Rebecca D.; Bray, Amanda; Waclawiw, Myron A.; Han, Kim; Pelletier, Martin; Sauve, Anthony A.; Siegel, Richard M.; Sack, Michael N.

2015-01-01

BACKGROUND. Activation of the NLRP3 inflammasome is associated with metabolic dysfunction, and intermittent fasting has been shown to improve clinical presentation of NLRP3 inflammasome–linked diseases. As mitochondrial perturbations, which function as a damage-associated molecular pattern, exacerbate NLRP3 inflammasome activation, we investigated whether fasting blunts inflammasome activation via sirtuin-mediated augmentation of mitochondrial integrity. METHODS. We performed a clinical study of 19 healthy volunteers. Each subject underwent a 24-hour fast and then was fed a fixed-calorie meal. Blood was drawn during the fasted and fed states and analyzed for NRLP3 inflammasome activation. We enrolled an additional group of 8 healthy volunteers to assess the effects of the sirtuin activator, nicotinamide riboside, on NLRP3 inflammasome activation. RESULTS. In the fasting/refeeding study, individuals showed less NLRP3 inflammasome activation in the fasted state compared with that in refed conditions. In a human macrophage line, depletion of the mitochondrial-enriched sirtuin deacetylase SIRT3 increased NLRP3 inflammasome activation in association with excessive mitochondrial ROS production. Furthermore, genetic and pharmacologic SIRT3 activation blunted NLRP3 activity in parallel with enhanced mitochondrial function in cultured cells and in leukocytes extracted from healthy volunteers and from refed individuals but not in those collected during fasting. CONCLUSIONS. Together, our data indicate that nutrient levels regulate the NLRP3 inflammasome, in part through SIRT3-mediated mitochondrial homeostatic control. Moreover, these results suggest that deacetylase-dependent inflammasome attenuation may be amenable to targeting in human disease. TRIAL REGISTRATION. ClinicalTrials.gov NCT02122575 and NCT00442195. FUNDING. Division of Intramural Research, NHLBI of the NIH. PMID:26529255

Complex IV Deficient Surf1−/− Mice Initiate Mitochondrial Stress Responses

PubMed Central

Pulliam, Daniel A.; Deepa, Sathyaseelan S.; Liu, Yuhong; Hill, Shauna; Lin, Ai-Ling; Bhattacharya, Arunabh; Shi, Yun; Sloane, Lauren; Viscomi, Carlo; Zeviani, Massimo; Van Remmen, Holly

2014-01-01

Summary Mutations in SURF1 cytochrome c oxidase (COX) assembly protein are associated with Leigh’s syndrome, a human mitochondrial disorder that manifests as severe mitochondrial phenotypes and early lethality. In contrast, mice lacking the Surf1 protein (Surf1−/−) are viable and were previously shown to have enhanced longevity and a greater than 50% reduction in COX activity. We measured mitochondrial function in heart and skeletal muscle, and despite the significant reduction in COX activity, we found little or no difference in reactive oxygen species (ROS) generation, membrane potential, ATP production or respiration in isolated mitochondria from Surf1−/− mice compared to wild-type. However, blood lactate levels are elevated and Surf1−/− mice have reduced running endurance, suggesting compromised mitochondrial energy metabolism in vivo. Decreased COX activity in Surf1−/− mice is associated with increased markers of mitochondrial biogenesis (PGC-1α and VDAC) in both heart and skeletal muscle. While mitochondrial biogenesis is a common response in the two tissues, skeletal muscle have an up-regulation of the mitochondrial unfolded protein response (UPRMT) and heart exhibits induction of the Nrf2 antioxidant response pathway. These data are the first to report induction of the UPRMT in a mammalian model of diminished COX activity. In addition our results suggest that impaired mitochondrial function can lead to induction of mitochondrial stress pathways to confer protective effects on cellular homeostasis. Loss of complex IV assembly factor Surf1 in mice results in compensatory responses including mitochondrial biogenesis, the nrf2 pathway and the mitochondrial unfolded protein response. This compensatory response may contribute to the lack of deleterious phenotypes under basal conditions. PMID:24911525

Mice Lacking TR4 Nuclear Receptor Develop Mitochondrial Myopathy with Deficiency in Complex I

PubMed Central

Liu, Su; Lee, Yi-Fen; Chou, Samuel; Uno, Hideo; Li, Gonghui; Brookes, Paul; Massett, Michael P.; Wu, Qiao; Chen, Lu-Min

2011-01-01

The estimated incidence of mitochondrial diseases in humans is approximately 1:5000 to 1:10,000, whereas the molecular mechanisms for more than 50% of human mitochondrial disease cases still remain unclear. Here we report that mice lacking testicular nuclear receptor 4 (TR4−/−) suffered mitochondrial myopathy, and histological examination of TR4−/− soleus muscle revealed abnormal mitochondrial accumulation. In addition, increased serum lactate levels, decreased mitochondrial ATP production, and decreased electron transport chain complex I activity were found in TR4−/− mice. Restoration of TR4 into TR4−/− myoblasts rescued mitochondrial ATP generation capacity and complex I activity. Further real-time PCR quantification and promoter studies found TR4 could modulate complex I activity via transcriptionally regulating the complex I assembly factor NDUFAF1, and restoration of NDUFAF1 level in TR4−/− myoblasts increased mitochondrial ATP generation capacity and complex I activity. Together, these results suggest that TR4 plays vital roles in mitochondrial function, which may help us to better understand the pathogenesis of mitochondrial myopathy, and targeting TR4 via its ligands/activators may allow us to develop better therapeutic approaches. PMID:21622535

Gene expression profiling in equine polysaccharide storage myopathy revealed inflammation, glycogenesis inhibition, hypoxia and mitochondrial dysfunctions.

PubMed

Barrey, Eric; Mucher, Elodie; Jeansoule, Nicolas; Larcher, Thibaut; Guigand, Lydie; Herszberg, Bérénice; Chaffaux, Stéphane; Guérin, Gérard; Mata, Xavier; Benech, Philippe; Canale, Marielle; Alibert, Olivier; Maltere, Péguy; Gidrol, Xavier

2009-08-07

Several cases of myopathies have been observed in the horse Norman Cob breed. Muscle histology examinations revealed that some families suffer from a polysaccharide storage myopathy (PSSM). It is assumed that a gene expression signature related to PSSM should be observed at the transcriptional level because the glycogen storage disease could also be linked to other dysfunctions in gene regulation. Thus, the functional genomic approach could be conducted in order to provide new knowledge about the metabolic disorders related to PSSM. We propose exploring the PSSM muscle fiber metabolic disorders by measuring gene expression in relationship with the histological phenotype. Genotypying analysis of GYS1 mutation revealed 2 homozygous (AA) and 5 heterozygous (GA) PSSM horses. In the PSSM muscles, histological data revealed PAS positive amylase resistant abnormal polysaccharides, inflammation, necrosis, and lipomatosis and active regeneration of fibers. Ultrastructural evaluation revealed a decrease of mitochondrial number and structural disorders. Extensive accumulation of an abnormal polysaccharide displaced and partially replaced mitochondria and myofibrils. The severity of the disease was higher in the two homozygous PSSM horses.Gene expression analysis revealed 129 genes significantly modulated (p < 0.05). The following genes were up-regulated over 2 fold: IL18, CTSS, LUM, CD44, FN1, GST01. The most down-regulated genes were the following: mitochondrial tRNA, SLC2A2, PRKCalpha, VEGFalpha. Data mining analysis showed that protein synthesis, apoptosis, cellular movement, growth and proliferation were the main cellular functions significantly associated with the modulated genes (p < 0.05). Several up-regulated genes, especially IL18, revealed a severe muscular inflammation in PSSM muscles. The up-regulation of glycogen synthase kinase-3 (GSK3beta) under its active form could be responsible for glycogen synthase (GYS1) inhibition and hypoxia-inducible factor (HIF1alpha) destabilization. The main disorders observed in PSSM muscles could be related to mitochondrial dysfunctions, glycogenesis inhibition and the chronic hypoxia of the PSSM muscles.

Toward a new STATe: The role of STATs in mitochondrial function

PubMed Central

Meier, Jeremy A.; Larner, Andrew C.

2014-01-01

Signal Transducers and Activators of Transcription (STATs) have been studied extensively and have been associated with virtually every biochemical pathway. Until recently, however, they were thought to exert these effects solely as a nuclear transcription factor. The finding that STAT3 localizes to the mitochondria and modulates respiration has opened up a new avenue through which STATs may regulate the cell. Recently, other members of the STAT family (STAT1, STAT2, STAT5, and STAT6) have also been shown to be present in the mitochondria. Coordinate regulation at the nucleus and mitochondria by these proteins places them in a unique position to drive cellular processes to achieve a specific response. This review summarizes recent findings that have led to our current understanding of how STATs influence mitochondrial function in health and disease. PMID:24434063

PPAR-γ Regulates Carnitine Homeostasis and Mitochondrial Function in a Lamb Model of Increased Pulmonary Blood Flow

PubMed Central

Rafikov, Ruslan; Kumar, Sanjiv; Hou, Yali; Oishi, Peter E.; Datar, Sanjeev A.; Raff, Gary; Fineman, Jeffrey R.; Black, Stephen M.

2012-01-01

Objective Carnitine homeostasis is disrupted in lambs with endothelial dysfunction secondary to increased pulmonary blood flow (Shunt). Our recent studies have also indicated that the disruption in carnitine homeostasis correlates with a decrease in PPAR-γ expression in Shunt lambs. Thus, this study was carried out to determine if there is a causal link between loss of PPAR-γ signaling and carnitine dysfunction, and whether the PPAR-γ agonist, rosiglitazone preserves carnitine homeostasis in Shunt lambs. Methods and Results siRNA-mediated PPAR-γ knockdown significantly reduced carnitine palmitoyltransferases 1 and 2 (CPT1 and 2) and carnitine acetyltransferase (CrAT) protein levels. This decrease in carnitine regulatory proteins resulted in a disruption in carnitine homeostasis and induced mitochondrial dysfunction, as determined by a reduction in cellular ATP levels. In turn, the decrease in cellular ATP attenuated NO signaling through a reduction in eNOS/Hsp90 interactions and enhanced eNOS uncoupling. In vivo, rosiglitazone treatment preserved carnitine homeostasis and attenuated the development of mitochondrial dysfunction in Shunt lambs maintaining ATP levels. This in turn preserved eNOS/Hsp90 interactions and NO signaling. Conclusion Our study indicates that PPAR-γ signaling plays an important role in maintaining mitochondrial function through the regulation of carnitine homeostasis both in vitro and in vivo. Further, it identifies a new mechanism by which PPAR-γ regulates NO signaling through Hsp90. Thus, PPAR-γ agonists may have therapeutic potential in preventing the endothelial dysfunction in children with increased pulmonary blood flow. PMID:22962578

Receptor-mediated Drp1 oligomerization on endoplasmic reticulum

PubMed Central

Ji, Wei-Ke; Fan, Xintao; Strack, Stefan

2017-01-01

Drp1 is a dynamin guanosine triphosphatase important for mitochondrial and peroxisomal division. Drp1 oligomerization and mitochondrial recruitment are regulated by multiple factors, including interaction with mitochondrial receptors such as Mff, MiD49, MiD51, and Fis. In addition, both endoplasmic reticulum (ER) and actin filaments play positive roles in mitochondrial division, but mechanisms for their roles are poorly defined. Here, we find that a population of Drp1 oligomers is associated with ER in mammalian cells and is distinct from mitochondrial or peroxisomal Drp1 populations. Subpopulations of Mff and Fis1, which are tail-anchored proteins, also localize to ER. Drp1 oligomers assemble on ER, from which they can transfer to mitochondria. Suppression of Mff or inhibition of actin polymerization through the formin INF2 significantly reduces all Drp1 oligomer populations (mitochondrial, peroxisomal, and ER bound) and mitochondrial division, whereas Mff targeting to ER has a stimulatory effect on division. Our results suggest that ER can function as a platform for Drp1 oligomerization, and that ER-associated Drp1 contributes to mitochondrial division. PMID:29158231

Functional proteomics of nonalcoholic steatohepatitis: Mitochondrial proteins as targets of S-adenosylmethionine

PubMed Central

Santamaría, Enrique; Avila, Matías A.; Latasa, M. Ujue; Rubio, Angel; Martín-Duce, Antonio; Lu, Shelly C.; Mato, José M.; Corrales, Fernando J.

2003-01-01

Recent work shows that S-adenosylmethionine (AdoMet) helps maintain normal liver function as chronic hepatic deficiency results in spontaneous development of steatohepatitis and hepatocellular carcinoma. The mechanisms by which these nontraditional functions of AdoMet occur are unknown. Here, we use knockout mice deficient in hepatic AdoMet synthesis (MAT1A−/−) to study the proteome of the liver during the development of steatohepatitis. One hundred and seventeen protein spots, differentially expressed during the development of steatohepatitis, were selected and identified by peptide mass fingerprinting. Among them, 12 proteins were found to be affected from birth, when MAT1A−/− expression is switched on in WT mouse liver, to the rise of histological lesions, which occurs at ≈8 months. Of the 12 proteins, 4 [prohibitin 1 (PHB1), cytochrome c oxidase I and II, and ATPase β-subunit] have known roles in mitochondrial function. We show that the alteration in expression of PHB1 correlates with a loss of mitochondrial function. Experiments in isolated rat hepatocytes indicate that AdoMet regulates PHB1 content, thus suggesting ways by which steatohepatitis may be induced. Importantly, we found the expression of these mitochondrial proteins was abnormal in ob/ob mice and obese patients who are at risk for nonalcoholic steatohepatitis. PMID:12631701

Monoamine Oxidase B Prompts Mitochondrial and Cardiac Dysfunction in Pressure Overloaded Hearts

PubMed Central

Kaludercic, Nina; Carpi, Andrea; Nagayama, Takahiro; Sivakumaran, Vidhya; Zhu, Guangshuo; Lai, Edwin W.; Bedja, Djahida; De Mario, Agnese; Chen, Kevin; Gabrielson, Kathleen L.; Lindsey, Merry L.; Pacak, Karel; Takimoto, Eiki; Shih, Jean C.; Kass, David A.; Di Lisa, Fabio

2014-01-01

Abstract Aims: Monoamine oxidases (MAOs) are mitochondrial flavoenzymes responsible for neurotransmitter and biogenic amines catabolism. MAO-A contributes to heart failure progression via enhanced norepinephrine catabolism and oxidative stress. The potential pathogenetic role of the isoenzyme MAO-B in cardiac diseases is currently unknown. Moreover, it is has not been determined yet whether MAO activation can directly affect mitochondrial function. Results: In wild type mice, pressure overload induced by transverse aortic constriction (TAC) resulted in enhanced dopamine catabolism, left ventricular (LV) remodeling, and dysfunction. Conversely, mice lacking MAO-B (MAO-B−/−) subjected to TAC maintained concentric hypertrophy accompanied by extracellular signal regulated kinase (ERK)1/2 activation, and preserved LV function, both at early (3 weeks) and late stages (9 weeks). Enhanced MAO activation triggered oxidative stress, and dropped mitochondrial membrane potential in the presence of ATP synthase inhibitor oligomycin both in neonatal and adult cardiomyocytes. The MAO-B inhibitor pargyline completely offset this change, suggesting that MAO activation induces a latent mitochondrial dysfunction, causing these organelles to hydrolyze ATP. Moreover, MAO-dependent aldehyde formation due to inhibition of aldehyde dehydrogenase 2 activity also contributed to alter mitochondrial bioenergetics. Innovation: Our study unravels a novel role for MAO-B in the pathogenesis of heart failure, showing that both MAO-driven reactive oxygen species production and impaired aldehyde metabolism affect mitochondrial function. Conclusion: Under conditions of chronic hemodynamic stress, enhanced MAO-B activity is a major determinant of cardiac structural and functional disarrangement. Both increased oxidative stress and the accumulation of aldehyde intermediates are likely liable for these adverse morphological and mechanical changes by directly targeting mitochondria. Antioxid. Redox Signal. 20, 267–280. PMID:23581564

Reduction in Autophagy by (-)-Epigallocatechin-3-Gallate (EGCG): a Potential Mechanism of Prevention of Mitochondrial Dysfunction After Subarachnoid Hemorrhage.

PubMed

Chen, Ying; Huang, Liyong; Zhang, Huiyong; Diao, Xiling; Zhao, Shuyang; Zhou, Wenke

2017-01-01

Mitochondrial dysfunction and subsequent autophagy, which are common features in central nervous system (CNS) disorders, were found to contribute to neuronal cell injury after subarachnoid hemorrhage (SAH). (-)-Epigallocatechin-3-gallate (EGCG), the main biological active of tea catechin, is well known for its beneficial effects in the treatment of CNS diseases. Here, the ability of EGCG to rescue cellular injury and mitochondrial function following the improvement of autophagic flux after SAH was investigated. As expected, EGCG-protected mitochondrial function depended on the inhibition of cytosolic Ca 2+ concentration ([Ca 2+ ] i ) influx via voltage-gated calcium channels (VGCCs) and, consequently, mitochondrial Ca 2+ concentration ([Ca 2+ ] m ) overload via mitochondrial Ca 2+ uniporter (MCU). The attenuated [Ca 2+ ] i and [Ca 2+ ] m levels observed in the EGCG-treated group likely lessened oxyhemoglobin (OxyHb)-induced mitochondrial dysfunction, including mitochondrial membrane potential depolarization, mitochondrial membrane permeability transition pore (mPTP) opening, reactive oxygen species (ROS), and cytochrosome c (cyt c) releasing. Subsequently, EGCG can restore the disrupted autophagy flux after SAH both at the initiation and formation stages by regulating Atg5, LC3B, and Becn-1 (Beclin-1) mRNA expressions. Thus, precondition EGCG resulted in autophagosomes and more autolysosomes compared with SAH group. As a result, EGCG pre-treatment increased the neurological score and decreased cell death. This study suggested that the mitochondrial dysfunction and abnormal autophagy flux synergistically contribute to SAH pathogenesis. Thus, EGCG can be regarded as a new pharmacological agent that targets both mitochondria and altered autophagy in SAH therapy.

Moderate intensity exercise prevents diabetic cardiomyopathy associated contractile dysfunction through restoration of mitochondrial function and connexin 43 levels in db/db mice.

PubMed

Veeranki, Sudhakar; Givvimani, Srikanth; Kundu, Sourav; Metreveli, Naira; Pushpakumar, Sathnur; Tyagi, Suresh C

2016-03-01

Although the cardiovascular benefits of exercise are well known, exercise induced effects and mechanisms in prevention of cardiomyopathy are less clear during obesity associated type-2 diabetes. The current study assessed the impact of moderate intensity exercise on diabetic cardiomyopathy by examining cardiac function and structure and mitochondrial function. Obese-diabetic (db/db), and lean control (db/+) mice, were subjected to a 5 week, 300 m run on a tread-mill for 5 days/week at the speeds of 10-11 m/min. Various physiological parameters were recorded and the heart function was evaluated with M-mode echocardiography. Contraction parameters and calcium transits were examined on isolated cardiomyocytes. At the molecular level: connexin 43 and 37 (Cx43 and 37) levels, mitochondrial biogenesis regulators: Mfn2 and Drp-1 levels, mitochondrial trans-membrane potential and cytochrome c leakage were assessed through western blotting immunohistochemistry and flow cytometry. Ability of exercise to reverse oxygen consumption rate (OCR), tissue ATP levels, and cardiac fibrosis were also determined. The exercise regimen was able to prevent diabetic cardiac functional deficiencies: ejection fraction (EF) and fractional shortening (FS). Improvements in contraction velocity and contraction maximum were noted with the isolated cardiomyocytes. Restoration of interstitial and micro-vessels associated Cx43 levels and improved gap junction intercellular communication (GJIC) were observed. The decline in the Mfn2/Drp-1 ratio in the db/db mice hearts was prevented after exercise. The exercise regimen further attenuated transmembrane potential decline and cytochrome c leakage. These corrections further led to improvements in OCR and tissue ATP levels and reduction in cardiac fibrosis. Moderate intensity exercise produced significant cardiovascular benefits by improving mitochondrial function through restoration of Cx43 networks and mitochondrial trans-membrane potential and prevention of excessive mitochondrial fission. Copyright © 2016 Elsevier Ltd. All rights reserved.

Improvement of liver injury and survival by JNK2 and iNOS deficiency in liver transplants from cardiac death mice.

PubMed

Liu, Qinlong; Rehman, Hasibur; Krishnasamy, Yasodha; Schnellmann, Rick G; Lemasters, John J; Zhong, Zhi

2015-07-01

Inclusion of liver grafts from cardiac death donors (CDD) would increase the availability of donor livers but is hampered by a higher risk of primary non-function. Here, we seek to determine mechanisms that contribute to primary non-function of liver grafts from CDD with the goal to develop strategies for improved function and outcome, focusing on c-Jun-N-terminal kinase (JNK) activation and mitochondrial depolarization, two known mediators of graft failure. Livers explanted from wild-type, inducible nitric oxide synthase knockout (iNOS(-/-)), JNK1(-/-) or JNK2(-/-) mice after 45-min aorta clamping were implanted into wild-type recipients. Mitochondrial depolarization was detected by intravital confocal microscopy in living recipients. After transplantation of wild-type CDD livers, graft iNOS expression and 3-nitrotyrosine adducts increased, but hepatic endothelial NOS expression was unchanged. Graft injury and dysfunction were substantially higher in CDD grafts than in non-CDD grafts. iNOS deficiency and inhibition attenuated injury and improved function and survival of CDD grafts. JNK1/2 and apoptosis signal-regulating kinase-1 activation increased markedly in wild-type CDD grafts, which was blunted by iNOS deficiency. JNK inhibition and JNK2 deficiency, but not JNK1 deficiency, decreased injury and improved function and survival of CDD grafts. Mitochondrial depolarization and binding of phospho-JNK2 to Sab, a mitochondrial protein linked to the mitochondrial permeability transition, were higher in CDD than in non-CDD grafts. iNOS deficiency, JNK inhibition and JNK2 deficiency all decreased mitochondrial depolarization and blunted ATP depletion in CDD grafts. JNK inhibition and deficiency did not decrease 3-nitrotyrosine adducts in CDD grafts. The iNOS-JNK2-Sab pathway promotes CDD graft failure via increased mitochondrial depolarization, and is an attractive target to improve liver function and survival in CDD liver transplantation recipients. Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Photobiomodulation reduces photoreceptor death and regulates cytoprotection in early states of P23H retinal dystrophy

NASA Astrophysics Data System (ADS)

Kirk, Diana K.; Gopalakrishnan, Sandeep; Schmitt, Heather; Abroe, Betsy; Stoehr, Michele; Dubis, Adam; Carroll, Joseph; Stone, Jonathan; Valter, Krisztina; Eells, Janis

2013-03-01

Irradiation by light in the far-red to near-infrared (NIR) region of the spectrum (photobiomodulation, PBM) has been demonstrated to attenuate the severity of neurodegenerative disease in experimental and clinical studies. The purpose of this study was to test the hypothesis that 670 nm PBM would protect against the loss of retinal function and improve photoreceptor survival in a rodent model of retinitis pigmentosa, the P23H transgenic rat. P23H rat pups were treated once per day with a 670 nm LED array (180 sec treatments at 50 mW/cm2; fluence 9 joules/cm2) (Quantum Devices Inc., Barneveld WI) from postnatal day (p) 16-20 or from p10-20. Sham-treated rats were restrained, but not exposed to NIR light. The status of the retina was determined at p22 by assessment of mitochondrial function, oxidative stress and cell death. In a second series of studies, retinal status was assessed at p30 by measuring photoreceptor function by ERG and retinal morphology by Spectral Domain Optical Coherence Tomography (SD-OCT). 670 nm PBM increased retinal mitochondrial cytochrome oxidase activity and upregulated the retina's production of the key mitochondrial antioxidant enzyme, MnSOD. PBM also attenuated photoreceptor cell loss and improved photoreceptor function. PBM protects photoreceptors in the developing P23H retina, by augmenting mitochondrial function and stimulating antioxidant protective pathways. Photobiomodulation may have therapeutic potential, where mitochondrial damage is a step in the death of photoreceptors.

14-3-3 protein is a regulator of the mitochondrial and chloroplast ATP synthase.

PubMed

Bunney, T D; van Walraven, H S; de Boer, A H

2001-03-27

Mitochondrial and chloroplast ATP synthases are key enzymes in plant metabolism, providing cells with ATP, the universal energy currency. ATP synthases use a transmembrane electrochemical proton gradient to drive synthesis of ATP. The enzyme complexes function as miniature rotary engines, ensuring energy coupling with very high efficiency. Although our understanding of the structure and functioning of the synthase has made enormous progress in recent years, our understanding of regulatory mechanisms is still rather preliminary. Here we report a role for 14-3-3 proteins in the regulation of ATP synthases. These 14-3-3 proteins are highly conserved phosphoserine/phosphothreonine-binding proteins that regulate a wide range of enzymes in plants, animals, and yeast. Recently, the presence of 14-3-3 proteins in chloroplasts was illustrated, and we show here that plant mitochondria harbor 14-3-3s within the inner mitochondrial-membrane compartment. There, the 14-3-3 proteins were found to be associated with the ATP synthases, in a phosphorylation-dependent manner, through direct interaction with the F(1) beta-subunit. The activity of the ATP synthases in both organelles is drastically reduced by recombinant 14-3-3. The rapid reduction in chloroplast ATPase activity during dark adaptation was prevented by a phosphopeptide containing the 14-3-3 interaction motif, demonstrating a role for endogenous 14-3-3 in the down-regulation of the CF(o)F(1) activity. We conclude that regulation of the ATP synthases by 14-3-3 represents a mechanism for plant adaptation to environmental changes such as light/dark transitions, anoxia in roots, and fluctuations in nutrient supply.

The oncogenic tyrosine kinase Lyn impairs the pro-apoptotic function of Bim.

PubMed

Aira, Lazaro E; Villa, Elodie; Colosetti, Pascal; Gamas, Parvati; Signetti, Laurie; Obba, Sandrine; Proics, Emma; Gautier, Fabien; Bailly-Maitre, Béatrice; Jacquel, Arnaud; Robert, Guillaume; Luciano, Frédéric; Juin, Philippe P; Ricci, Jean-Ehrland; Auberger, Patrick; Marchetti, Sandrine

2018-04-01

Phosphorylation of Ser/Thr residues is a well-established modulating mechanism of the pro-apoptotic function of the BH3-only protein Bim. However, nothing is known about the putative tyrosine phosphorylation of this Bcl-2 family member and its potential impact on Bim function and subsequent Bax/Bak-mediated cytochrome c release and apoptosis. As we have previously shown that the tyrosine kinase Lyn could behave as an anti-apoptotic molecule, we investigated whether this Src family member could directly regulate the pro-apoptotic function of Bim. In the present study, we show that Bim is phosphorylated onto tyrosine residues 92 and 161 by Lyn, which results in an inhibition of its pro-apoptotic function. Mechanistically, we show that Lyn-dependent tyrosine phosphorylation of Bim increases its interaction with anti-apoptotic members such as Bcl-xL, therefore limiting mitochondrial outer membrane permeabilization and subsequent apoptosis. Collectively, our data uncover one molecular mechanism through which the oncogenic tyrosine kinase Lyn negatively regulates the mitochondrial apoptotic pathway, which may contribute to the transformation and/or the chemotherapeutic resistance of cancer cells.

Kv3.4 is modulated by HIF-1α to protect SH-SY5Y cells against oxidative stress-induced neural cell death.

PubMed

Song, Min Seok; Ryu, Pan Dong; Lee, So Yeong

2017-05-18

The Kv3.4 channel is characterized by fast inactivation and sensitivity to oxidation. However, the physiological role of Kv3.4 as an oxidation-sensitive channel has yet to be investigated. Here, we demonstrate that Kv3.4 plays a pivotal role in oxidative stress-related neural cell damage as an oxidation-sensitive channel and that HIF-1α down-regulates Kv3.4 function, providing neuroprotection. MPP + and CoCl 2 are reactive oxygen species (ROS)-generating reagents that induce oxidative stress. However, only CoCl 2 decreases the expression and function of Kv3.4. HIF-1α, which accumulates in response to CoCl 2 treatment, is a key factor in Kv3.4 regulation. In particular, mitochondrial Kv3.4 was more sensitive to CoCl 2 . Blocking Kv3.4 function using BDS-II, a Kv3.4-specific inhibitor, protected SH-SY5Y cells against MPP + -induced neural cell death. Kv3.4 inhibition blocked MPP + -induced cytochrome c release from the mitochondrial intermembrane space to the cytosol and mitochondrial membrane potential depolarization, which are characteristic features of apoptosis. Our results highlight Kv3.4 as a possible new therapeutic paradigm for oxidative stress-related diseases, including Parkinson's disease.

Cardioprotection by modulation of mitochondrial respiration during ischemia–reperfusion: Role of apoptosis-inducing factor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Aijun; Department of Anesthesiology, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030; Szczepanek, Karol

Highlights: •Blockade of electron transport prevents the loss of AIF from mitochondria during IR. •Blockade of electron transport decreases caspase-independent cell death during IR. •Mitochondrial AIF content is down-regulated in Harlequin mice. •Blockade of electron transport protects Harlequin mouse hearts during IR. •Amobarbital protection is partially dependent on mitochondrial AIF content. -- Abstract: The transient, reversible blockade of electron transport (BET) during ischemia or at the onset of reperfusion protects mitochondria and decreases cardiac injury. Apoptosis inducing factor (AIF) is located within the mitochondrial intermembrane space. A release of AIF from mitochondria into cytosol and nucleus triggers caspase-independent cell death.more » We asked if BET prevents the loss of AIF from mitochondria as a mechanism of protection in the buffer perfused heart. BET during ischemia with amobarbital, a rapidly reversible inhibitor of mitochondrial complex I, attenuated a release of AIF from mitochondria into cytosol, in turn decreasing the formation of cleaved and activated PARP-1. These results suggest that BET-mediated protection may occur through prevention of the loss of AIF from mitochondria during ischemia–reperfusion. In order to further clarify the role of mitochondrial AIF in BET-mediated protection, Harlequin (Hq) mice, a genetic model with mitochondrial AIF deficiency, were used to test whether BET could still decrease cell injury in Hq mouse hearts during reperfusion. BET during ischemia protected Hq mouse hearts against ischemia–reperfusion injury and improved mitochondrial function in these hearts during reperfusion. Thus, cardiac injury can still be decreased in the presence of down-regulated mitochondrial AIF content. Taken together, BET during ischemia protects both hearts with normal mitochondrial AIF content and hearts with mitochondrial AIF deficiency. Although preservation of mitochondrial AIF content plays a key role in reducing cell injury during reperfusion, the protection derived from the BET is not fully dependent on AIF-driven mechanisms.« less

Transcriptome response signatures associated with the overexpression of a mitochondrial uncoupling protein (AtUCP1) in tobacco.

PubMed

Laitz, Alessandra Vasconcellos Nunes; Acencio, Marcio Luis; Budzinski, Ilara G F; Labate, Mônica T V; Lemke, Ney; Ribolla, Paulo Eduardo Martins; Maia, Ivan G

2015-01-01

Mitochondrial inner membrane uncoupling proteins (UCP) dissipate the proton electrochemical gradient established by the respiratory chain, thus affecting the yield of ATP synthesis. UCP overexpression in plants has been correlated with oxidative stress tolerance, improved photosynthetic efficiency and increased mitochondrial biogenesis. This study reports the main transcriptomic responses associated with the overexpression of an UCP (AtUCP1) in tobacco seedlings. Compared to wild-type (WT), AtUCP1 transgenic seedlings showed unaltered ATP levels and higher accumulation of serine. By using RNA-sequencing, a total of 816 differentially expressed genes between the investigated overexpressor lines and the untransformed WT control were identified. Among them, 239 were up-regulated and 577 were down-regulated. As a general response to AtUCP1 overexpression, noticeable changes in the expression of genes involved in energy metabolism and redox homeostasis were detected. A substantial set of differentially expressed genes code for products targeted to the chloroplast and mainly involved in photosynthesis. The overall results demonstrate that the alterations in mitochondrial function provoked by AtUCP1 overexpression require important transcriptomic adjustments to maintain cell homeostasis. Moreover, the occurrence of an important cross-talk between chloroplast and mitochondria, which culminates in the transcriptional regulation of several genes involved in different pathways, was evidenced.

Laccase-13 Regulates Seed Setting Rate by Affecting Hydrogen Peroxide Dynamics and Mitochondrial Integrity in Rice.

PubMed

Yu, Yang; Li, Quan-Feng; Zhang, Jin-Ping; Zhang, Fan; Zhou, Yan-Fei; Feng, Yan-Zhao; Chen, Yue-Qin; Zhang, Yu-Chan

2017-01-01

Seed setting rate is one of the most important components of rice grain yield. To date, only several genes regulating setting rate have been identified in plant. In this study, we showed that laccase-13 ( OsLAC13 ), a member of laccase family genes which are known for their roles in modulating phenylpropanoid pathway and secondary lignification in cell wall, exerts a regulatory function in rice seed setting rate. OsLAC13 expressed in anthers and promotes hydrogen peroxide production both in vitro and in the filaments and anther connectives. Knock-out of OsLAC13 showed significantly increased seed setting rate, while overexpression of this gene exhibited induced mitochondrial damage and suppressed sugar transportation in anthers, which in turn affected seed setting rate. OsLAC13 also induced H 2 O 2 production and mitochondrial damage in the root tip cells which caused the lethal phenotype. We also showed that high abundant of OsmiR397, the suppressor of OsLAC13 mRNA, increased the seed setting rate of rice plants, and restrains H 2 O 2 accumulation in roots during oxidative stress. Our results suggested a novel regulatory role of OsLAC13 gene in regulating seed setting rate by affecting H 2 O 2 dynamics and mitochondrial integrity in rice.

Changes of TSPO-mediated mitophagy signaling pathway in learned helplessness mice.

PubMed

Li, Dongmei; Zheng, Ji; Wang, Mingyang; Feng, Lu; Ren, Zhili; Liu, Yanyong; Yang, Nan; Zuo, Pingping

2016-11-30

Low response rate was witnessed with the present monoaminergic based antidepressants, urging a need for new therapeutic target identification. Accumulated evidences strongly suggest that mitochondrial deficit is implicated in major depression and 18kDa translocator protein (TSPO) plays an important role in regulating mitochondrial function. However the changes of TSPO and TSPO mediated mitophagy pathway in the depressive brain is unclear. In present study, a well validated animal model of depression, learned helplessness (LH), was employed to investigate the relevant changes. Significant behavioral changes were observed in the LH mice. Results showed that TSPO and other mitophagy related proteins, such as VDAC1, Pink1 and Beclin1 were significantly decreased by LH challenge. Moreover, KIFC2, relevant to the mitochondrial transport and Snap25, relevant to neurotransmitter vesicle release, were also obviously down-regulated in the LH mice, which further rendered supportive evidence for the existing mitochondrial dysfunction in LH mice. Present results demonstrated that LH induced depressive symptoms and affected TSPO-mediated mitophagy pathway, indicating a potential target candidate for depression treatment. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Activation of Akt is essential for the propagation of mitochondrial respiratory stress signaling and activation of the transcriptional coactivator heterogeneous ribonucleoprotein A2.

PubMed

Guha, Manti; Fang, Ji-Kang; Monks, Robert; Birnbaum, Morris J; Avadhani, Narayan G

2010-10-15

Mitochondrial respiratory stress (also called mitochondrial retrograde signaling) activates a Ca(2+)/calcineurin-mediated signal that culminates in transcription activation/repression of a large number of nuclear genes. This signal is propagated through activation of the regulatory proteins NFκB c-Rel/p50, C/EBPδ, CREB, and NFAT. Additionally, the heterogeneous ribonucleoprotein A2 (hnRNPA2) functions as a coactivator in up-regulating the transcription of Cathepsin L, RyR1, and Glut-4, the target genes of stress signaling. Activation of IGF1R, which causes a metabolic switch to glycolysis, cell invasiveness, and resistance to apoptosis, is a phenotypic hallmark of C2C12 myoblasts subjected to mitochondrial stress. In this study, we report that mitochondrial stress leads to increased expression, activation, and nuclear localization of Akt1. Mitochondrial respiratory stress also activates Akt1-gene expression, which involves hnRNPA2 as a coactivator, indicating a complex interdependency of these two factors. Using Akt1(-/-) mouse embryonic fibroblasts and Akt1 mRNA-silenced C2C12 cells, we show that Akt1-mediated phosphorylation is crucial for the activation and recruitment of hnRNPA2 to the enhanceosome complex. Akt1 mRNA silencing in mtDNA-depleted cells resulted in reversal of the invasive phenotype, accompanied by sensitivity to apoptotic stimuli. These results show that Akt1 is an important regulator of the nuclear transcriptional response to mitochondrial stress.

Pathways and Subcellular Compartmentation of NAD Biosynthesis in Human Cells

PubMed Central

Nikiforov, Andrey; Dölle, Christian; Niere, Marc; Ziegler, Mathias

2011-01-01

NAD is a vital redox carrier, and its degradation is a key element of important regulatory pathways. NAD-mediated functions are compartmentalized and have to be fueled by specific biosynthetic routes. However, little is known about the different pathways, their subcellular distribution, and regulation in human cells. In particular, the route(s) to generate mitochondrial NAD, the largest subcellular pool, is still unknown. To visualize organellar NAD changes in cells, we targeted poly(ADP-ribose) polymerase activity into the mitochondrial matrix. This activity synthesized immunodetectable poly(ADP-ribose) depending on mitochondrial NAD availability. Based on this novel detector system, detailed subcellular enzyme localizations, and pharmacological inhibitors, we identified extracellular NAD precursors, their cytosolic conversions, and the pathway of mitochondrial NAD generation. Our results demonstrate that, besides nicotinamide and nicotinic acid, only the corresponding nucleosides readily enter the cells. Nucleotides (e.g. NAD and NMN) undergo extracellular degradation resulting in the formation of permeable precursors. These precursors can all be converted to cytosolic and mitochondrial NAD. For mitochondrial NAD synthesis, precursors are converted to NMN in the cytosol. When taken up into the organelles, NMN (together with ATP) serves as substrate of NMNAT3 to form NAD. NMNAT3 was conclusively localized to the mitochondrial matrix and is the only known enzyme of NAD synthesis residing within these organelles. We thus present a comprehensive dissection of mammalian NAD biosynthesis, the groundwork to understand regulation of NAD-mediated processes, and the organismal homeostasis of this fundamental molecule. PMID:21504897

Mitochondrial p53 mediates a transcription-independent regulation of cell respiration and interacts with the mitochondrial F₁F₀-ATP synthase

PubMed Central

Bergeaud, Marie; Mathieu, Lise; Guillaume, Arnaud; Moll, Ute M; Mignotte, Bernard; Le Floch, Nathalie; Vayssière, Jean-Luc; Rincheval, Vincent

2013-01-01

We and others previously reported that endogenous p53 can be located at mitochondria in the absence of stress, suggesting that p53 has a role in the normal physiology of this organelle. The aim of this study was to characterize in unstressed cells the intramitochondrial localization of p53 and identify new partners and functions of p53 in mitochondria. We find that the intramitochondrial pool of p53 is located in the intermembrane space and the matrix. Of note, unstressed HCT116 p53+/+ cells simultaneously show increased O₂ consumption and decreased mitochondrial superoxide production compared with their p53-null counterpart. This data was confirmed by stable H1299 cell lines expressing low levels of p53 specifically targeted to the matrix. Using immunoprecipitation and mass spectrometry, we identified the oligomycin sensitivity-conferring protein (OSCP), a subunit of the F₁F₀-ATP synthase complex, as a new partner of endogenous p53, specifically interacting with p53 localized in the matrix. Interestingly, this interaction seems implicated in mitochondrial p53 localization. Moreover, p53 localized in the matrix promotes the assembly of F₁F₀-ATP synthase. Taking into account that deregulations of mitochondrial respiration and reactive oxygen species production are tightly linked to cancer development, we suggest that mitochondrial p53 may be an important regulator of normal mitochondrial and cellular physiology, potentially exerting tumor suppression activity inside mitochondria. PMID:23966169

Mitochondrial p53 mediates a transcription-independent regulation of cell respiration and interacts with the mitochondrial F₁F0-ATP synthase.

PubMed

Bergeaud, Marie; Mathieu, Lise; Guillaume, Arnaud; Moll, Ute M; Mignotte, Bernard; Le Floch, Nathalie; Vayssière, Jean-Luc; Rincheval, Vincent

2013-09-01

We and others previously reported that endogenous p53 can be located at mitochondria in the absence of stress, suggesting that p53 has a role in the normal physiology of this organelle. The aim of this study was to characterize in unstressed cells the intramitochondrial localization of p53 and identify new partners and functions of p53 in mitochondria. We find that the intramitochondrial pool of p53 is located in the intermembrane space and the matrix. Of note, unstressed HCT116 p53(+/+) cells simultaneously show increased O₂ consumption and decreased mitochondrial superoxide production compared with their p53-null counterpart. This data was confirmed by stable H1299 cell lines expressing low levels of p53 specifically targeted to the matrix. Using immunoprecipitation and mass spectrometry, we identified the oligomycin sensitivity-conferring protein (OSCP), a subunit of the F₁F₀-ATP synthase complex, as a new partner of endogenous p53, specifically interacting with p53 localized in the matrix. Interestingly, this interaction seems implicated in mitochondrial p53 localization. Moreover, p53 localized in the matrix promotes the assembly of F₁F₀-ATP synthase. Taking into account that deregulations of mitochondrial respiration and reactive oxygen species production are tightly linked to cancer development, we suggest that mitochondrial p53 may be an important regulator of normal mitochondrial and cellular physiology, potentially exerting tumor suppression activity inside mitochondria.

Parkin and PINK1 functions in oxidative stress and neurodegeneration.

PubMed

Barodia, Sandeep K; Creed, Rose B; Goldberg, Matthew S

2017-07-01

Loss-of-function mutations in the genes encoding Parkin and PINK1 are causally linked to autosomal recessive Parkinson's disease (PD). Parkin, an E3 ubiquitin ligase, and PINK1, a mitochondrial-targeted kinase, function together in a common pathway to remove dysfunctional mitochondria by autophagy. Presumably, deficiency for Parkin or PINK1 impairs mitochondrial autophagy and thereby increases oxidative stress due to the accumulation of dysfunctional mitochondria that release reactive oxygen species. Parkin and PINK1 likely have additional functions that may be relevant to the mechanisms by which mutations in these genes cause neurodegeneration, such as regulating inflammation, apoptosis, or dendritic morphogenesis. Here we briefly review what is known about functions of Parkin and PINK1 related to oxidative stress and neurodegeneration. Copyright © 2016 Elsevier Inc. All rights reserved.

Inhibition of mitochondrial fission prevents hypoxia-induced metabolic shift and cellular proliferation of pulmonary arterial smooth muscle cells.

PubMed

Parra, Valentina; Bravo-Sagua, Roberto; Norambuena-Soto, Ignacio; Hernández-Fuentes, Carolina P; Gómez-Contreras, Andrés G; Verdejo, Hugo E; Mellado, Rosemarie; Chiong, Mario; Lavandero, Sergio; Castro, Pablo F

2017-11-01

Chronic hypoxia exacerbates proliferation of pulmonary arterial smooth muscle cells (PASMC), thereby reducing the lumen of pulmonary arteries. This leads to poor blood oxygenation and cardiac work overload, which are the basis of diseases such as pulmonary artery hypertension (PAH). Recent studies revealed an emerging role of mitochondria in PAH pathogenesis, as key regulators of cell survival and metabolism. In this work, we assessed whether hypoxia-induced mitochondrial fragmentation contributes to the alterations of both PASMC death and proliferation. In previous work in cardiac myocytes, we showed that trimetazidine (TMZ), a partial inhibitor of lipid oxidation, stimulates mitochondrial fusion and preserves mitochondrial function. Thus, here we evaluated whether TMZ-induced mitochondrial fusion can prevent human PASMC proliferation in an in vitro hypoxic model. Using confocal fluorescence microscopy, we showed that prolonged hypoxia (48h) induces mitochondrial fragmentation along with higher levels of the mitochondrial fission protein DRP1. Concomitantly, both mitochondrial potential and respiratory rates decreased, indicative of mitochondrial dysfunction. In accordance with a metabolic shift towards non-mitochondrial ATP generation, mRNA levels of glycolytic markers HK2, PFKFB2 and GLUT1 increased during hypoxia. Incubation of PASMC with TMZ, prior to hypoxia, prevented all these changes and precluded the increase in PASMC proliferation. These findings were also observed using Mdivi-1 (a pharmacological DRP1 inhibitor) or a dominant negative DRP1 K38A as pre-treatments. Altogether, our data indicate that TMZ exerts a protective role against hypoxia-induced PASMC proliferation, by preserving mitochondrial function, thus highlighting DRP1-dependent morphology as a novel therapeutic approach for diseases such as PAH. Copyright © 2017 Elsevier B.V. All rights reserved.

A role for peroxisome proliferator-activated receptor γ coactivator-1 in the control of mitochondrial dynamics during postnatal cardiac growth.

PubMed

Martin, Ola J; Lai, Ling; Soundarapandian, Mangala M; Leone, Teresa C; Zorzano, Antonio; Keller, Mark P; Attie, Alan D; Muoio, Deborah M; Kelly, Daniel P

2014-02-14

Increasing evidence has shown that proper control of mitochondrial dynamics (fusion and fission) is required for high-capacity ATP production in the heart. Transcriptional coactivators, peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1) α and PGC-1β, have been shown to regulate mitochondrial biogenesis in the heart at the time of birth. The function of PGC-1 coactivators in the heart after birth has been incompletely understood. Our aim was to assess the role of PGC-1 coactivators during postnatal cardiac development and in adult hearts in mice. Conditional gene targeting was used in mice to explore the role of PGC-1 coactivators during postnatal cardiac development and in adult hearts. Marked mitochondrial structural derangements were observed in hearts of PGC-1α/β-deficient mice during postnatal growth, including fragmentation and elongation, associated with the development of a lethal cardiomyopathy. The expression of genes involved in mitochondrial fusion (Mfn1, Opa1) and fission (Drp1, Fis1) was altered in the hearts of PGC-1α/β-deficient mice. PGC-lα was shown to directly regulate Mfn1 gene transcription by coactivating the estrogen-related receptor α on a conserved DNA element. Surprisingly, PGC-1α/β deficiency in the adult heart did not result in evidence of abnormal mitochondrial dynamics or heart failure. However, transcriptional profiling demonstrated that PGC-1 coactivators are required for high-level expression of nuclear- and mitochondrial-encoded genes involved in mitochondrial dynamics and energy transduction in the adult heart. These results reveal distinct developmental stage-specific programs involved in cardiac mitochondrial dynamics.

Characterization of Bombyx mori mitochondrial transcription factor A, a conserved regulator of mitochondrial DNA.

PubMed

Sumitani, Megumi; Kondo, Mari; Kasashima, Katsumi; Endo, Hitoshi; Nakamura, Kaoru; Misawa, Toshihiko; Tanaka, Hiromitsu; Sezutsu, Hideki

2017-04-15

In the present study, we initially cloned and characterized a mitochondrial transcription factor A (Tfam) homologue in the silkworm, Bombyx mori. Bombyx mori TFAM (BmTFAM) localized to mitochondria in cultured silkworm and human cells, and co-localized with mtDNA nucleoids in human HeLa cells. In an immunoprecipitation analysis, BmTFAM was found to associate with human mtDNA in mitochondria, indicating its feature as a non-specific DNA-binding protein. In spite of the low identity between BmTFAM and human TFAM (26.5%), the expression of BmTFAM rescued mtDNA copy number reductions and enlarged mtDNA nucleoids in HeLa cells, which were induced by human Tfam knockdown. Thus, BmTFAM compensates for the function of human TFAM in HeLa cells, demonstrating that the mitochondrial function of TFAM is highly conserved between silkworms and humans. BmTfam mRNA was strongly expressed in early embryos. Through double-stranded RNA (dsRNA)-based RNA interference (RNAi) in silkworm embryos, we found that the knockdown of BmTFAM reduced the amount of mtDNA and induced growth retardation at the larval stage. Collectively, these results demonstrate that BmTFAM is a highly conserved mtDNA regulator and may be a good candidate for investigating and modulating mtDNA metabolism in this model organism. Copyright © 2017 Elsevier B.V. All rights reserved.

S-nitrosylation drives cell senescence and aging in mammals by controlling mitochondrial dynamics and mitophagy.

PubMed

Rizza, Salvatore; Cardaci, Simone; Montagna, Costanza; Di Giacomo, Giuseppina; De Zio, Daniela; Bordi, Matteo; Maiani, Emiliano; Campello, Silvia; Borreca, Antonella; Puca, Annibale A; Stamler, Jonathan S; Cecconi, Francesco; Filomeni, Giuseppe

2018-04-10

S -nitrosylation, a prototypic redox-based posttranslational modification, is frequently dysregulated in disease. S -nitrosoglutathione reductase (GSNOR) regulates protein S -nitrosylation by functioning as a protein denitrosylase. Deficiency of GSNOR results in tumorigenesis and disrupts cellular homeostasis broadly, including metabolic, cardiovascular, and immune function. Here, we demonstrate that GSNOR expression decreases in primary cells undergoing senescence, as well as in mice and humans during their life span. In stark contrast, exceptionally long-lived individuals maintain GSNOR levels. We also show that GSNOR deficiency promotes mitochondrial nitrosative stress, including excessive S -nitrosylation of Drp1 and Parkin, thereby impairing mitochondrial dynamics and mitophagy. Our findings implicate GSNOR in mammalian longevity, suggest a molecular link between protein S -nitrosylation and mitochondria quality control in aging, and provide a redox-based perspective on aging with direct therapeutic implications.

Mitochondrial dynamics in the regulation of neurogenesis: From development to the adult brain.

PubMed

Khacho, Mireille; Slack, Ruth S

2018-01-01

Mitochondria are classically known to be the cellular energy producers, but a renewed appreciation for these organelles has developed with the accumulating discoveries of additional functions. The importance of mitochondria within the brain has been long known, particularly given the high-energy demanding nature of neurons. The energy demands imposed by neurons require the well-orchestrated morphological adaptation and distribution of mitochondria. Recent studies now reveal the importance of mitochondrial dynamics not only in mature neurons but also during neural development, particularly during the process of neurogenesis and neural stem cell fate decisions. In this review, we will highlight the recent findings that illustrate the importance of mitochondrial dynamics in neurodevelopment and neural stem cell function. Developmental Dynamics 247:47-53, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Mitochondrial protein acetylation mediates nutrient sensing of mitochondrial protein synthesis and mitonuclear protein balance.

PubMed

Di Domenico, Antonella; Hofer, Annette; Tundo, Federica; Wenz, Tina

2014-11-01

Changes in nutrient supply require global metabolic reprogramming to optimize the utilization of the nutrients. Mitochondria as a central component of the cellular metabolism play a key role in this adaptive process. Since mitochondria harbor their own genome, which encodes essential enzymes, mitochondrial protein synthesis is a determinant of metabolic adaptation. While regulation of cytoplasmic protein synthesis in response to metabolic challenges has been studied in great detail, mechanisms which adapt mitochondrial translation in response to metabolic challenges remain elusive. Our results suggest that the mitochondrial acetylation status controlled by Sirt3 and its proposed opponent GCN5L1 is an important regulator of the metabolic adaptation of mitochondrial translation. Moreover, both proteins modulate regulators of cytoplasmic protein synthesis as well as the mitonuclear protein balance making Sirt3 and GCN5L1 key players in synchronizing mitochondrial and cytoplasmic translation. Our results thereby highlight regulation of mitochondrial translation as a novel component in the cellular nutrient sensing scheme and identify mitochondrial acetylation as a new regulatory principle for the metabolic competence of mitochondrial protein synthesis. © 2014 International Union of Biochemistry and Molecular Biology.

Chronic fluoxetine treatment directs energy metabolism towards the citric acid cycle and oxidative phosphorylation in rat hippocampal nonsynaptic mitochondria.

PubMed

Filipović, Dragana; Costina, Victor; Perić, Ivana; Stanisavljević, Andrijana; Findeisen, Peter

2017-03-15

Fluoxetine (Flx) is the principal treatment for depression; however, the precise mechanisms of its actions remain elusive. Our aim was to identify protein expression changes within rat hippocampus regulated by chronic Flx treatment versus vehicle-controls using proteomics. Fluoxetine-hydrohloride (15mg/kg) was administered daily to adult male Wistar rats for 3weeks, and cytosolic and nonsynaptic mitochondrial hippocampal proteomes were analyzed. All differentially expressed proteins were functionally annotated according to biological process and molecular function using Uniprot and Blast2GO. Our comparative study revealed that in cytosolic and nonsynaptic mitochondrial fractions, 60 and 3 proteins respectively, were down-regulated, and 23 and 60 proteins, respectively, were up-regulated. Proteins differentially regulated in cytosolic and nonsynaptic mitochondrial fractions were primarily related to cellular and metabolic processes. Of the identified proteins, the expressions of calretinin and parvalbumine were confirmed. The predominant molecular functions of differentially expressed proteins in both cell hippocampal fractions were binding and catalytic activity. Most differentially expressed proteins in nonsynaptic mitochondria were catalytic enzymes involved in the pyruvate metabolism, citric acid cycle, oxidative phosphorylation, ATP synthesis, ATP transduction and glutamate metabolism. Results indicate that chronic Flx treatment may influence proteins involved in calcium signaling, cytoskeletal structure, chaperone system and stimulates energy metabolism via the upregulation of GAPDH expression in cytoplasm, as well as directing energy metabolism toward the citric acid cycle and oxidative phosphorylation in nonsynaptic mitochondria. This approach provides new insight into the chronic effects of Flx treatment on protein expression in a key brain region associated with stress response and memory. Copyright © 2017 Elsevier B.V. All rights reserved.

Differential Effects of Sepsis and Chronic Inflammation on Diaphragm Muscle Fiber Type, Thyroid Hormone Metabolism, and Mitochondrial Function.

PubMed

Bloise, Flavia F; van der Spek, Anne H; Surovtseva, Olga V; Ortiga-Carvalho, Tania Maria; Fliers, Eric; Boelen, Anita

2016-04-01

The diaphragm is the main respiratory muscle, and its function is compromised during severe illness. Altered local thyroid hormone (TH) metabolism may be a determinant of impaired muscle function during illness. This study investigates the effects of bacterial sepsis and chronic inflammation on muscle fiber type, local TH metabolism, and mitochondrial function in the diaphragm. Two mouse models were used: sepsis induced by S. pneumoniae infection or chronic inflammation induced by subcutaneous turpentine injection. In vitro, the effect of bacterial endotoxin (LPS) on mitochondrial function in C2C12 myotubes was studied. Sepsis induced a transient increase in the fiber type I profile and increased Dio3 expression while decreasing Dio2, Thra1, and Slc16a2 expression. Triiodothyronine positively regulated genes Tnni2 and Myog were decreased, indicating reduced TH signaling in the diaphragm. In contrast, chronic inflammation increased the fiber type II profile in the diaphragm as well as Thra1, Thrb1, and Myog expression while decreasing Dio3 expression, suggesting increased TH responsiveness during chronic inflammation. LPS-stimulated C2C12 myotubes showed decreased Dio2 expression and reduced basal oxygen consumption as well as non-mitochondrial respiration. The same respiratory profile was induced by Dio2 knockdown in myotubes. The in vivo results show differential effects of sepsis and chronic inflammation on diaphragm muscle fiber type, TH metabolism, and mitochondrial function, while the in vitro results point to a causal role for altered TH metabolism in functional muscle impairment. These findings may be relevant for the pathogenesis of impaired respiratory function in critical illness.

Alpha Lipoamide Ameliorates Motor Deficits and Mitochondrial Dynamics in the Parkinson's Disease Model Induced by 6-Hydroxydopamine.

PubMed

Zhou, Bo; Wen, Min; Lin, Xin; Chen, Yun-Hua; Gou, Yun; Li, Yong; Zhang, Yi; Li, Hong-Wei; Tang, Lei

2018-05-01

The precise mechanisms underlying neuronal injury in Parkinson's disease (PD) are not yet fully elucidated; however, evidence from the in vitro and in vivo PD models suggest that mitochondrial dysfunction may play a major role in PD pathogenesis. Alpha lipoamide, a neutral amide derivative of the lipoic acid, is a better cofactor for mitochondrial dehydrogenase with a stronger protective effect on mitochondria than lipoic acid. Identification of these protective effects of alpha lipoamide on mitochondria, together with the evidence that mitochondrial dysfunction plays a critical role in PD, we speculate that alpha lipoamide may exert a protective effect in PD by regulating the mitochondrial function. The present study investigated the neuroprotective effects of alpha lipoamide in an animal model of PD induced by 6-hydroxydopamine (6-OHDA). The results demonstrated that alpha lipoamide could significantly antagonize the 6-OHDA-induced behavioral damages; restore ATP levels in the midbrain; and also improve the fragmentation, vacuolization, and morphology of the mitochondria. The results of Western blot indicated that alpha lipoamide significantly restored the number of dopaminergic neurons in midbrain and substantially recovered the balance between mitochondrial fission, fusion, and transport. In conclusion, the results demonstrated that alpha lipoamide might exert a significant neuroprotective effect in the animal model of PD by regulation of the dynamic properties of mitochondria.

Transcriptional requirements of the distal heavy-strand promoter of mtDNA

PubMed Central

Zollo, Ornella; Tiranti, Valeria; Sondheimer, Neal

2012-01-01

The heavy strand of mtDNA contains two promoters with nonoverlapping functions. The role of the minor heavy-strand promoter (HSP2) is controversial, because the promoter has been difficult to activate in an in vitro system. We have isolated HSP2 by excluding its interaction with the more powerful HSP1 promoter, and we find that it is transcribed efficiently by recombinant mtRNA polymerase and mitochondrial transcription factor B2. The mitochondrial transcription factor A is not required for initiation, but it has the ability to alternatively activate and repress the HSP2 transcriptional unit depending on the ratio between mitochondrial transcription factor A and other transcription factors. The positioning of transcriptional initiation agrees with our current understanding of HSP2 activity in vivo. Serial deletion of HSP2 shows that only proximal sequences are required. Several mutations, including the disruption of a polycytosine track upstream of the HSP2 initiation site, influence transcriptional activity. Transcription from HSP2 is also observed when HeLa cell mitochondrial extract is used as the source of mitochondrial polymerase, and this transcription is maintained when HSP2 is provided in proper spacing and context to the HSP1 promoter. Studies of the linked heavy-strand promoters show that they are differentially regulated by ATP dosage. We conclude that HSP2 is transcribed and has features that allow it to regulate mitochondrial mRNA synthesis. PMID:22454497

SLP-2 negatively modulates mitochondrial sodium-calcium exchange.

PubMed

Da Cruz, Sandrine; De Marchi, Umberto; Frieden, Maud; Parone, Philippe A; Martinou, Jean-Claude; Demaurex, Nicolas

2010-01-01

Mitochondria play a major role in cellular calcium homeostasis. Despite decades of studies, the molecules that mediate and regulate the transport of calcium ions in and out of the mitochondrial matrix remain unknown. Here, we investigate whether SLP-2, an inner membrane mitochondrial protein of unknown function, modulates the activity of mitochondrial Ca(2+) transporters. In HeLa cells depleted of SLP-2, the amplitude and duration of mitochondrial Ca(2+) elevations evoked by agonists were decreased compared to control cells. SLP-2 depletion increased the rates of calcium extrusion from mitochondria. This effect disappeared upon Na(+) removal or addition of CGP-37157, an inhibitor of the mitochondrial Na(+)/Ca(2+) exchanger, and persisted in permeabilized cells exposed to a fixed cytosolic Na(+) and Ca(2+) concentration. The rates of mitochondrial Ca(2+) extrusion were prolonged in SLP-2 over-expressing cells, independently of the amplitude of mitochondrial Ca(2+) elevations. The amplitude of cytosolic Ca(2+) elevations was increased by SLP-2 depletion and decreased by SLP-2 over-expression. These data show that SLP-2 modulates mitochondrial calcium extrusion, thereby altering the ability of mitochondria to buffer Ca(2+) and to shape cytosolic Ca(2+) signals. 2009 Elsevier Ltd. All rights reserved.

Mitochondrial Bioenergetics Is Altered in Fibroblasts from Patients with Sporadic Alzheimer's Disease.

PubMed

Pérez, María J; Ponce, Daniela P; Osorio-Fuentealba, Cesar; Behrens, Maria I; Quintanilla, Rodrigo A

2017-01-01

The identification of an early biomarker to diagnose Alzheimer's disease (AD) remains a challenge. Neuropathological studies in animal and AD patients have shown that mitochondrial dysfunction is a hallmark of the development of the disease. Current studies suggest the use of peripheral tissues, like skin fibroblasts as a possibility to detect the early pathological alterations present in the AD brain. In this context, we studied mitochondrial function properties (bioenergetics and morphology) in cultured fibroblasts obtained from AD, aged-match and young healthy patients. We observed that AD fibroblasts presented a significant reduction in mitochondrial length with important changes in the expression of proteins that control mitochondrial fusion. Moreover, AD fibroblasts showed a distinct alteration in proteolytic processing of OPA1, a master regulator of mitochondrial fusion, compared to control fibroblasts. Complementary to these changes AD fibroblasts showed a dysfunctional mitochondrial bioenergetics profile that differentiates these cells from aged-matched and young patient fibroblasts. Our findings suggest that the human skin fibroblasts obtained from AD patients could replicate mitochondrial impairment observed in the AD brain. These promising observations suggest that the analysis of mitochondrial bioenergetics could represent a promising strategy to develop new diagnostic methods in peripheral tissues of AD patients.

Mitochondrial Bioenergetics Is Altered in Fibroblasts from Patients with Sporadic Alzheimer's Disease

PubMed Central

Pérez, María J.; Ponce, Daniela P.; Osorio-Fuentealba, Cesar; Behrens, Maria I.; Quintanilla, Rodrigo A.

2017-01-01

The identification of an early biomarker to diagnose Alzheimer's disease (AD) remains a challenge. Neuropathological studies in animal and AD patients have shown that mitochondrial dysfunction is a hallmark of the development of the disease. Current studies suggest the use of peripheral tissues, like skin fibroblasts as a possibility to detect the early pathological alterations present in the AD brain. In this context, we studied mitochondrial function properties (bioenergetics and morphology) in cultured fibroblasts obtained from AD, aged-match and young healthy patients. We observed that AD fibroblasts presented a significant reduction in mitochondrial length with important changes in the expression of proteins that control mitochondrial fusion. Moreover, AD fibroblasts showed a distinct alteration in proteolytic processing of OPA1, a master regulator of mitochondrial fusion, compared to control fibroblasts. Complementary to these changes AD fibroblasts showed a dysfunctional mitochondrial bioenergetics profile that differentiates these cells from aged-matched and young patient fibroblasts. Our findings suggest that the human skin fibroblasts obtained from AD patients could replicate mitochondrial impairment observed in the AD brain. These promising observations suggest that the analysis of mitochondrial bioenergetics could represent a promising strategy to develop new diagnostic methods in peripheral tissues of AD patients. PMID:29056898

Drosophila mitochondrial transcription factor B1 modulates mitochondrial translation but not transcription or DNA copy number in Schneider cells.

PubMed

Matsushima, Yuichi; Adán, Cristina; Garesse, Rafael; Kaguni, Laurie S

2005-04-29

We report the cloning and molecular analysis of Drosophila mitochondrial transcription factor (d-mtTF) B1. An RNA interference (RNAi) construct was designed that reduces expression of d-mtTFB1 to 5% of its normal level in Schneider cells. In striking contrast with our previous study on d-mtTFB2, we found that RNAi knock-down of d-mtTFB1 does not change the abundance of specific mitochondrial RNA transcripts, nor does it affect the copy number of mitochondrial DNA. In a corollary manner, overexpression of d-mtTFB1 did not increase either the abundance of mitochondrial RNA transcripts or mitochondrial DNA copy number. Our data suggest that, unlike d-mtTFB2, d-mtTFB1 does not have a critical role in either transcription or regulation of the copy number of mitochondrial DNA. Instead, because we found that RNAi knockdown of d-mtTFB1 reduces mitochondrial protein synthesis, we propose that it serves its primary role in modulating translation. Our work represents the first study to document the role of mtTFB1 in vivo and establishes clearly functional differences between mtTFB1 and mtTFB2.

Cancer: Mitochondrial Origins.

PubMed

Stefano, George B; Kream, Richard M

2015-12-01

The primacy of glucose derived from photosynthesis as an existential source of chemical energy across plant and animal phyla is universally accepted as a core principle in the biological sciences. In mammalian cells, initial processing of glucose to triose phosphate intermediates takes place within the cytosolic glycolytic pathway and terminates with temporal transport of reducing equivalents derived from pyruvate metabolism by membrane-associated respiratory complexes in the mitochondrial matrix. The intra-mitochondrial availability of molecular oxygen as the ultimate electron acceptor drives the evolutionary fashioned chemiosmotic production of ATP as a high-efficiency biological process. The mechanistic bases of carcinogenesis have demonstrated profound alteration of normative mitochondrial function, notably dysregulated respiratory processes. Accordingly, the classic Warburg effect functionally links aerobic glycolysis, aberrant production and release of lactate, and metabolic down-regulation of mitochondrial oxidative processes with the carcinogenetic phenotype. We surmise, however, that aerobic fermentation by cancer cells may also represent a developmental re-emergence of an evolutionarily conserved early phenotype, which was "sidelined" with the emergence of mitochondrial oxidative phosphorylation as a primary mechanism for ATP production in normal cells. Regardless of state-dependent physiological status in mixed populations of cancer cells, it has been established that mitochondria are functionally linked to the initiation of cancer and its progression. Biochemical, molecular, and physiological differences in cancer cell mitochondria, notably mtDNA heteroplasmy and allele-specific expression of selected nuclear genes, may represent major focal points for novel targeting and elimination of cancer cells in metastatic disease afflicting human populations. To date, and despite considerable research efforts, the practical realization of advanced mitochondrial targeted therapies has not been forthcoming.

Bioenergetic adaptation in response to autophagy regulators during rotenone exposure

PubMed Central

Giordano, Samantha; Dodson, Matthew; Ravi, Saranya; Redmann, Matthew; Ouyang, Xiaosen; Usmar, Victor M Darley; Zhang, Jianhua

2015-01-01

Parkinson’s disease (PD) is the second most common neurodegenerative disorder with both mitochondrial dysfunction and insufficient autophagy playing a key role in its pathogenesis. Among the risk factors, exposure to the environmental neurotoxin rotenone increases the probability of developing PD. We previously reported that in differentiated SH-SY5Y cells, rotenone-induced cell death is directly related to inhibition of mitochondrial function. How rotenone at nM concentrations inhibits mitochondrial function, and whether it can engage the autophagy pathway necessary to remove damaged proteins and organelles, is unknown. We tested the hypothesis that autophagy plays a protective role against rotenone toxicity in primary neurons. We found that rotenone (10–100 nM) immediately inhibited cellular bioenergetics. Concentrations that decreased mitochondrial function at 2 hr, caused cell death at 24 hr with an LD50 of 10 nM. Overall autophagic flux was decreased by 10 nM rotenone at both 2 and 24 hr, but surprisingly mitophagy, or autophagy of the mitochondria, was increased at 24 hr, suggesting that a mitochondrial-specific lysosomal degradation pathway may be activated. Upregulation of autophagy by rapamycin protected against cell death while inhibition of autophagy by 3-methyladenine (3-MA) exacerbated cell death. Interestingly, while 3-MA exacerbated the rotenone-dependent effects on bioenergetics, rapamycin did not prevent rotenone-induced mitochondrial dysfunction, but caused reprogramming of mitochondrial substrate usage associated with both complex I and complex II activities. Taken together, these data demonstrate that autophagy can play a protective role in primary neuron survival in response to rotenone; moreover, surviving neurons exhibit bioenergetic adaptations to this metabolic stressor. PMID:25081478

The Emerging Role of Skeletal Muscle Metabolism as a Biological Target and Cellular Regulator of Cancer-Induced Muscle Wasting

PubMed Central

Carson, James A.; Hardee, Justin P.; VanderVeen, Brandon N.

2015-01-01

While skeletal muscle mass is an established primary outcome related to understanding cancer cachexia mechanisms, considerable gaps exist in our understanding of muscle biochemical and functional properties that have recognized roles in systemic health. Skeletal muscle quality is a classification beyond mass, and is aligned with muscle’s metabolic capacity and substrate utilization flexibility. This supplies an additional role for the mitochondria in cancer-induced muscle wasting. While the historical assessment of mitochondria content and function during cancer-induced muscle loss was closely aligned with energy flux and wasting susceptibility, this understanding has expanded to link mitochondria dysfunction to cellular processes regulating myofiber wasting. The primary objective of this article is to highlight muscle mitochondria and oxidative metabolism as a biological target of cancer cachexia and also as a cellular regulator of cancer-induced muscle wasting. Initially, we examine the role of muscle metabolic phenotype and mitochondria content in cancer-induced wasting susceptibility. We then assess the evidence for cancer-induced regulation of skeletal muscle mitochondrial biogenesis, dynamics, mitophagy, and oxidative stress. In addition, we discuss environments associated with cancer cachexia that can impact the regulation of skeletal muscle oxidative metabolism. The article also examines the role of cytokine-mediated regulation of mitochondria function regulation, followed by the potential role of cancer-induced hypogonadism. Lastly, a role for decreased muscle use in cancer-induced mitochondrial dysfunction is reviewed. PMID:26593326

Blockade of Drp1 rescues oxidative stress-induced osteoblast dysfunction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gan, Xueqi; Huang, Shengbin; Yu, Qing

Osteoblast dysfunction, induced by oxidative stress, plays a critical role in the pathophysiology of osteoporosis. However, the underlying mechanisms remain unclarified. Imbalance of mitochondrial dynamics has been closely linked to oxidative stress. Here, we reveal an unexplored role of dynamic related protein 1(Drp1), the major regulator in mitochondrial fission, in the oxidative stress-induced osteoblast injury model. We demonstrate that levels of phosphorylation and expression of Drp1 significantly increased under oxidative stress. Blockade of Drp1, through pharmaceutical inhibitor or gene knockdown, significantly protected against H{sub 2}O{sub 2}-induced osteoblast dysfunction, as shown by increased cell viability, improved cellular alkaline phosphatase (ALP) activitymore » and mineralization and restored mitochondrial function. The protective effects of blocking Drp1 in H{sub 2}O{sub 2}-induced osteoblast dysfunction were evidenced by increased mitochondrial function and suppressed production of reactive oxygen species (ROS). These findings provide new insights into the role of the Drp1-dependent mitochondrial pathway in the pathology of osteoporosis, indicating that the Drp1 pathway may be targetable for the development of new therapeutic approaches in the prevention and the treatment of osteoporosis. - Highlights: • Oxidative stress is an early pathological event in osteoporosis. • Imbalance of mitochondrial dynamics are linked to oxidative stress in osteoporosis. • The role of the Drp1-dependent mitochondrial pathway in osteoporosis.« less

The N-terminus of survivin is a mitochondrial-targeting sequence and Src regulator

PubMed Central

Dunajová, Lucia; Cash, Emily; Markus, Robert; Rochette, Sophie; Townley, Amelia R.

2016-01-01

ABSTRACT Survivin (also known as BIRC5) is a cancer-associated protein that exists in several locations in the cell. Its cytoplasmic residence in interphase cells is governed by CRM1 (also known as XPO1)-mediated nuclear exportation, and its localisation during mitosis to the centromeres and midzone microtubules is that of a canonical chromosomal passenger protein. In addition to these well-established locations, survivin is also a mitochondrial protein, but how it gets there and its function therein is presently unclear. Here, we show that the first ten amino acids at the N-terminus of survivin are sufficient to target GFP to the mitochondria in vivo, and ectopic expression of this decapeptide decreases cell adhesion and accelerates proliferation. The data support a signalling mechanism in which this decapeptide regulates the tyrosine kinase Src, leading to reduced focal adhesion plaques and disruption of F-actin organisation. This strongly suggests that the N-terminus of survivin is a mitochondrial-targeting sequence that regulates Src, and that survivin acts in concert with Src to promote tumorigenesis. PMID:27246243

The Mitochondrial Protein NLRX1 Controls the Balance between Extrinsic and Intrinsic Apoptosis*

PubMed Central

Soares, Fraser; Tattoli, Ivan; Rahman, Muhammed A.; Robertson, Susan J.; Belcheva, Antoaneta; Liu, Daniel; Streutker, Catherine; Winer, Shawn; Winer, Daniel A.; Martin, Alberto; Philpott, Dana J.; Arnoult, Damien; Girardin, Stephen E.

2014-01-01

NLRX1 is a mitochondrial Nod-like receptor (NLR) protein whose function remains enigmatic. Here, we observed that NLRX1 expression was glucose-regulated and blunted by SV40 transformation. In transformed but not primary murine embryonic fibroblasts, NLRX1 expression mediated resistance to an extrinsic apoptotic signal, whereas conferring susceptibility to intrinsic apoptotic signals, such as glycolysis inhibition, increased cytosolic calcium and endoplasmic reticulum stress. In a murine model of colorectal cancer induced by azoxymethane, NLRX1−/− mice developed fewer tumors than wild type mice. In contrast, in a colitis-associated cancer model combining azoxymethane and dextran sulfate sodium, NLRX1−/− mice developed a more severe pathology likely due to the increased sensitivity to dextran sulfate sodium colitis. Together, these results identify NLRX1 as a critical mitochondrial protein implicated in the regulation of apoptosis in cancer cells. The unique capacity of NLRX1 to regulate the cellular sensitivity toward intrinsic versus extrinsic apoptotic signals suggests a critical role for this protein in numerous physiological processes and pathological conditions. PMID:24867956

Bcl-2 prevents loss of mitochondria in CCCP-induced apoptosis.

PubMed

de Graaf, Aniek O; van den Heuvel, Lambert P; Dijkman, Henry B P M; de Abreu, Ronney A; Birkenkamp, Kim U; de Witte, Theo; van der Reijden, Bert A; Smeitink, Jan A M; Jansen, Joop H

2004-10-01

Bcl-2 family proteins regulate apoptosis at the level of mitochondria. To examine the mechanism of Bcl-2 function, we investigated the effects of the protonophore carbonyl cyanide m-chlorophenyl hydrazone (CCCP) on two hematopoietic cell lines and Bcl-2 overexpressing transfectants. CCCP directly interferes with mitochondrial function and induces apoptosis. We show that Bcl-2 inhibits apoptosis and that the antiapoptotic effect of Bcl-2 takes place upstream of caspase activation and nuclear changes associated with apoptosis, since these were markedly inhibited in cells overexpressing Bcl-2. Bcl-2 does not prevent the decrease in mitochondrial membrane potential nor the alterations in cellular ATP content induced by CCCP in FL5.12 and Jurkat cells. A higher number of mitochondria was observed in untreated Bcl-2 transfected cells compared to parental cells, as shown by electron microscopy. Exposure to CCCP induced a dramatic decrease in the number of mitochondria and severely disrupted mitochondrial ultrastructure, with apparent swelling and loss of cristae in parental cells. Bcl-2 clearly diminished the disruption of mitochondrial structure and preserved a higher number of mitochondria. These data suggest that CCCP induces apoptosis by structural disruption of mitochondria and that Bcl-2 prevents apoptosis and mitochondrial degeneration by preserving mitochondrial integrity.

The Role of Mitochondrial DNA in Mediating Alveolar Epithelial Cell Apoptosis and Pulmonary Fibrosis

PubMed Central

Kim, Seok-Jo; Cheresh, Paul; Jablonski, Renea P.; Williams, David B.; Kamp, David W.

2015-01-01

Convincing evidence has emerged demonstrating that impairment of mitochondrial function is critically important in regulating alveolar epithelial cell (AEC) programmed cell death (apoptosis) that may contribute to aging-related lung diseases, such as idiopathic pulmonary fibrosis (IPF) and asbestosis (pulmonary fibrosis following asbestos exposure). The mammalian mitochondrial DNA (mtDNA) encodes for 13 proteins, including several essential for oxidative phosphorylation. We review the evidence implicating that oxidative stress-induced mtDNA damage promotes AEC apoptosis and pulmonary fibrosis. We focus on the emerging role for AEC mtDNA damage repair by 8-oxoguanine DNA glycosylase (OGG1) and mitochondrial aconitase (ACO-2) in maintaining mtDNA integrity which is important in preventing AEC apoptosis and asbestos-induced pulmonary fibrosis in a murine model. We then review recent studies linking the sirtuin (SIRT) family members, especially SIRT3, to mitochondrial integrity and mtDNA damage repair and aging. We present a conceptual model of how SIRTs modulate reactive oxygen species (ROS)-driven mitochondrial metabolism that may be important for their tumor suppressor function. The emerging insights into the pathobiology underlying AEC mtDNA damage and apoptosis is suggesting novel therapeutic targets that may prove useful for the management of age-related diseases, including pulmonary fibrosis and lung cancer. PMID:26370974

A specific role of the yeast mitochondrial carriers MRS3/4p in mitochondrial iron acquisition under iron-limiting conditions.

PubMed

Mühlenhoff, Ulrich; Stadler, Jochen A; Richhardt, Nadine; Seubert, Andreas; Eickhorst, Thomas; Schweyen, Rudolf J; Lill, Roland; Wiesenberger, Gerlinde

2003-10-17

The yeast genes MRS3 and MRS4 encode two members of the mitochondrial carrier family with high sequence similarity. To elucidate their function we utilized genome-wide expression profiling and found that both deletion and overexpression of MRS3/4 lead to up-regulation of several genes of the "iron regulon." We therefore analyzed the two major iron-utilizing processes, heme formation and Fe/S protein biosynthesis in vivo, in organello (intact mitochondria), and in vitro (mitochondrial extracts). Radiolabeling of yeast cells with 55Fe revealed a clear correlation between MRS3/4 expression levels and the efficiency of these biosynthetic reactions indicating a role of the carriers in utilization and/or transport of iron in vivo. Similar effects on both heme formation and Fe/S protein biosynthesis were seen in organello using mitochondria isolated from cells grown under iron-limiting conditions. The correlation between MRS3/4 expression levels and the efficiency of the two iron-utilizing processes was lost upon detergent lysis of mitochondria. As no significant changes in the mitochondrial membrane potential were observed upon overexpression or deletion of MRS3/4, our results suggest that Mrs3/4p carriers are directly involved in mitochondrial iron uptake. Mrs3/4p function in mitochondrial iron transport becomes evident under iron-limiting conditions only, indicating that the two carriers do not represent the sole system for mitochondrial iron acquisition.

Atorvastatin inhibits the apoptosis of human umbilical vein endothelial cells induced by angiotensin II via the lysosomal-mitochondrial axis.

PubMed

Chang, Ye; Li, Yuan; Ye, Ning; Guo, Xiaofan; Li, Zhao; Sun, Guozhe; Sun, Yingxian

2016-09-01

This study was aimed to evaluate lysosomes-mitochondria cross-signaling in angiotensin II (Ang II)-induced apoptosis of human umbilical vein endothelial cells (HUVECs) and whether atorvastatin played a protective role via lysosomal-mitochondrial axis. Apoptosis was detected by flow cytometry, Hoechst 33342 and AO/EB assay. The temporal relationship of lysosomal and mitochondrial permeabilization was established. Activity of Cathepsin D (CTSD) was suppressed by pharmacological and genetic approaches. Proteins production were measured by western blotting. Our study showed that Ang II could induce the apoptosis of HUVECs in a dose-depended and time-depended manner. Exposure to 1 μM Ang II for 24 h resulted in mitochondrial depolarization, cytochrome c release, and increased ROS production. Lysosomal permeabilization and CTSD redistribution into the cytoplasm occurred several hours prior to mitochondrial dysfunction. These effects were all suppressed by atorvastatin. Either pharmacological or genetic inhibition of CTSD preserved mitochondrial function and decreased apoptosis in HUVECs. Most importantly, we found that the protective effect of atorvastatin was significantly greater than pharmacological or genetic inhibition of CTSD. Finally, overexpression of CTSD without exposure to Ang II had no effect on mitochondrial function and apoptosis. Our data strongly suggested that Ang II induced apoptosis through the lysosomal-mitochondrial axis in HUVECs. Furthermore, atorvastatin played an important role in the regulation of lysosomes and mitochondria stability, resulting in an antagonistic role against Ang II on HUVECs.

Down-regulated energy metabolism genes associated with mitochondria oxidative phosphorylation and fatty acid metabolism in viral cardiomyopathy mouse heart.

PubMed

Xu, Jing; Nie, Hong-gang; Zhang, Xiao-dong; Tian, Ye; Yu, Bo

2011-08-01

The majority of experimental and clinical studies indicates that the hypertrophied and failing myocardium are characterized by changes in energy and substrate metabolism that attributed to failing heart changes at the genomic level, in fact, heart failure is caused by various diseases, their energy metabolism and substrate are in different genetic variations, then the potential significance of the molecular mechanisms for the aetiology of heart failure is necessary to be evaluated. Persistent viral infection (especially coxsackievirus group B3) of the myocardium in viral myocarditis and viral dilated cardiomyopathy has never been neglected by experts. This study aimed to explore the role and regulatory mechanism of the altered gene expression for energy metabolism involved in mitochondrial oxidative phosphorylation, fatty acid metabolism in viral dilated cardiomyopathy. cDNA Microarray technology was used to evaluate the expression of >35,852 genes in a mice model of viral dilated cardiomyopathy. In total 1385 highly different genes expression, we analyzed 33 altered genes expression for energy metabolism involved in mitochondrial oxidative phosphorylation, fatty acid metabolism and further selected real-time-PCR for quantity one of regulatory mechanisms for energy including fatty acid metabolism-the UCP2 and assayed cytochrome C oxidase activity by Spectrophotometer to explore mitochondrial oxidative phosphorylation function. We found obviously different expression of 33 energy metabolism genes associated with mitochondria oxidative phosphorylation, fatty acid metabolism in cardiomyopathy mouse heart, the regulatory gene for energy metabolism: UCP2 was down-regulated and cytochrome C oxidase activity was decreased. Genes involved in both fatty acid metabolism and mitochondrial oxidative phosphorylation were down-regulated, mitochondrial uncoupling proteins (UCP2) expression did not increase but decrease which might be a kind of adaptive protection response to regulate energy metabolism for ATP produce.

Potassium channels in brain mitochondria.

PubMed

Bednarczyk, Piotr

2009-01-01

Potassium channels are the most widely distributed class of ion channels. These channels are transmembrane proteins known to play important roles in both normal and pathophysiological functions in all cell types. Various potassium channels are recognised as potential therapeutic targets in the treatment of Parkinson's disease, Alzheimer's disease, brain/spinal cord ischaemia and sepsis. In addition to their importance as therapeutic targets, certain potassium channels are known for their beneficial roles in anaesthesia, cardioprotection and neuroprotection. Some types of potassium channels present in the plasma membrane of various cells have been found in the inner mitochondrial membrane as well. Potassium channels have been proposed to regulate mitochondrial membrane potential, respiration, matrix volume and Ca(+) ion homeostasis. It has been proposed that mitochondrial potassium channels mediate ischaemic preconditioning in various tissues. However, the specificity of a pharmacological agents and the mechanisms underlying their effects on ischaemic preconditioning remain controversial. The following potassium channels from various tissues have been identified in the inner mitochondrial membrane: ATP-regulated (mitoK(ATP)) channel, large conductance Ca(2+)-regulated (mitoBK(Ca)) channel, intermediate conductance Ca(2+)-regulated (mitoIK(Ca)) channel, voltage-gated (mitoKv1.3 type) channel, and twin-pore domain (mitoTASK-3) channel. It has been shown that increased potassium flux into brain mitochondria induced by either the mitoK(ATP) channel or mitoBK(Ca) channel affects the beneficial effects on neuronal cell survival under pathological conditions. Recently, differential distribution of mitoBK(Ca) channels has been observed in neuronal mitochondria. These findings may suggest a neuroprotective role for the mitoBK(Ca) channel in specific brain structures. This minireview summarises current data on brain mitochondrial potassium channels and the efforts to identify their molecular correlates.

Dietary fatty acid composition and the homeostatic regulation of mitochondrial phospholipid classes in red muscle of rainbow trout (Oncorhynchus mykiss).

PubMed

Martin, Nicolas; Kraffe, Edouard; Le Grand, Fabienne; Marty, Yanic; Bureau, Dominique P; Guderley, Helga

2015-01-01

Although dietary lipid quality markedly affects fatty acid (FA) composition of mitochondrial membranes from rainbow trout red muscle (Oncorhynchus mykiss), mitochondrial processes are relatively unchanged. As certain classes of phospholipids interact more intimately with membrane proteins than others, we examined whether specific phospholipid classes from these muscle mitochondria were more affected by dietary FA composition than others. To test this hypothesis, we fed trout with two diets differing only in their FA composition: Diet 1 had higher levels of 18:1n-9 and 18:2n-6 than Diet 2, while 22:6n-3 and 22:5n-6 were virtually absent from Diet 1 and high in Diet 2. After 5 months, trout fed Diet 2 had higher proportions of phosphatidylcholine (PC) and less phosphatidylethanolamine (PE) in mitochondrial membranes than those fed Diet 1. The FA composition of PC, PE and cardiolipin (CL) showed clear evidence of regulated incorporation of dietary FA. For trout fed Diet 2, 22:6n-3 was the most abundant FA in PC, PE and CL. The n-6 FA were consistently higher in all phospholipid classes of trout fed Diet 1, with shorter n-6 FA being favoured in CL than in PC and PE. Despite these marked changes in individual FA levels with diet, general characteristics such as total polyunsaturated FA, total monounsaturated FA and total saturated FA were conserved in PE and CL, confirming differential regulation of the FA composition of PC, PE and CL. The regulated changes of phospholipid classes presumably maintain critical membrane characteristics despite varying nutritional quality. We postulate that these changes aim to protect mitochondrial function. © 2014 Wiley Periodicals, Inc.

N-acetylcysteine inhibits the up-regulation of mitochondrial biogenesis genes in livers from rats fed ethanol chronically

USDA-ARS?s Scientific Manuscript database

Background: Chronic ethanol (EtOH) administration to experimental animals induces hepatic oxidative stress and up-regulates mitochondrial biogenesis. The mechanisms by which chronic EtOH up-regulates mitochondrial biogenesis have not been fully explored. In this work, we hypothesized that oxidative ...

Carbon monoxide stimulates astrocytic mitochondrial biogenesis via L-type Ca{sup 2+} channel-mediated PGC-1α/ERRα activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Yoon Kyung; Park, Joon Ha; Baek, Yi-Yong

Carbon monoxide (CO), derived by the enzymatic reaction of heme oxygenase (HO), is a cellular regulator of energy metabolism and cytoprotection; however, its underlying mechanism has not been clearly elucidated. Astrocytes pre-exposed to the CO-releasing compound CORM-2 increased mitochondrial biogenesis, mitochondrial electron transport components (cytochrome c, Cyt c; cytochrome c oxidase subunit 2, COX2), and ATP synthesis. The increased mitochondrial function was correlated with activation of AMP-activated protein kinase α and upregulation of HO-1, peroxisome proliferators-activated receptor γ-coactivator-1α (PGC-1α), and estrogen-related receptor α (ERRα). These events elicited by CORM-2 were suppressed by Ca{sup 2+} chelators, a HO inhibitor, and anmore » L-type Ca{sup 2+} channel blocker, but not other Ca{sup 2+} channel inhibitors. Among the HO byproducts, combined CORM-2 and bilirubin treatment effectively increased PGC-1α, Cyt c and COX2 expression, mitochondrial biogenesis, and ATP synthesis, and these increases were blocked by Ca{sup 2+} chelators. Moreover, cerebral ischemia significantly increased HO-1, PGC-1α, and ERRα levels, subsequently increasing Cyt c and COX2 expression, in wild-type mice, compared with HO-1{sup +/−} mice. These results suggest that HO-1-derived CO enhances mitochondrial biogenesis in astrocytes by activating L-type Ca{sup 2+} channel-mediated PGC-1α/ERRα axis, leading to maintenance of astrocyte function and neuroprotection/recovery against damage of brain function. - Highlights: • CORM-pretreated astrocytes induces mitochondrial biogenesis by activating L-type Ca{sup 2+} channel-mediated PGC-1α stabilization. • Cerebral ischemia increased electron transport chain proteins (e.g. Cyt c and COX2), in WT mice, compared with HO-1{sup +/−} mice. • CO/HO-1 pathway increases astrocytic mitochondrial functions via a PGC-1α/ERRα axis.« less

MicroRNA-761 regulates mitochondrial biogenesis in mouse skeletal muscle in response to exercise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Yanli; Zhao, Chaoxian; Sun, Xuewen

MicroRNAs (miRNAs) have been suggested to play critical roles in skeletal muscle in response to exercise. Previous study has shown that miR-761 was involved in a novel model regulating the mitochondrial network. However, its role in mitochondrial biogenesis remains poorly understood. Therefore, the current study was aimed to examine the effect of miR-761 on mitochondrial biogenesis in skeletal muscle. Real-time quantitative PCR analysis demonstrated that aberrantly expressed miR-761 is involved in exercise activity and miR-761 is decreased by exercise training compared with the sedentary control mice. miR-761 suppresses mitochondrial biogenesis of C{sub 2}C{sub 12} myocytes by targeting the 3′-UTR ofmore » peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1 (PGC-1α). Overexpression of miR-761 was capable of inhibiting the protein expression levels of PGC-1α. Moreover, miR-761 overexpression suppressed the p38 MAPK signaling pathway and down-regulated the expression of phosphorylated MAPK-activated protein kinase-2 (P-MK2), a downstream kinase of p38 MAPK. The phosphorylation of activating transcription factors 2 (ATF2) that plays a functional role in linking the activation of the p38 MAPK pathway to enhanced transcription of the PGC-1α was also inhibited by the overexpression of miR-761. These findings revealed a novel regulation mechanism for miR-761 in skeletal myocytes, and contributed to a better understanding of the modulation of skeletal muscle in response to exercise. - Highlights: • Endurance exercise decreases miR-761 expression in skeletal muscle. • MiR-761 suppresses mitochondrial biogenesis in C{sub 2}C{sub 12} myocytes. • MiR-761 directly targeted PGC-1α expression. • MiR-761 suppresses p38 MAPK signaling pathways in C{sub 2}C{sub 12} myocytes. • A novel mechanism for miR-761 in skeletal myocytes is demonstrated.« less

Intact mitochondrial Ca2+ uniport is essential for agonist-induced activation of endothelial nitric oxide synthase (eNOS).

PubMed

Charoensin, Suphachai; Eroglu, Emrah; Opelt, Marissa; Bischof, Helmut; Madreiter-Sokolowski, Corina T; Kirsch, Andrijana; Depaoli, Maria R; Frank, Saša; Schrammel, Astrid; Mayer, Bernd; Waldeck-Weiermair, Markus; Graier, Wolfgang F; Malli, Roland

2017-01-01

Mitochondrial Ca 2+ uptake regulates diverse endothelial cell functions and has also been related to nitric oxide (NO • ) production. However, it is not entirely clear if the organelles support or counteract NO • biosynthesis by taking up Ca 2+ . The objective of this study was to verify whether or not mitochondrial Ca 2+ uptake influences Ca 2+ -triggered NO • generation by endothelial NO • synthase (eNOS) in an immortalized endothelial cell line (EA.hy926), respective primary human umbilical vein endothelial cells (HUVECs) and eNOS-RFP (red fluorescent protein) expressing human embryonic kidney (HEK293) cells. We used novel genetically encoded fluorescent NO • probes, the geNOps, and Ca 2+ sensors to monitor single cell NO • and Ca 2+ dynamics upon cell treatment with ATP, an inositol 1,4,5-trisphosphate (IP 3 )-generating agonist. Mitochondrial Ca 2+ uptake was specifically manipulated by siRNA-mediated knock-down of recently identified key components of the mitochondrial Ca 2+ uniporter machinery. In endothelial cells and the eNOS-RFP expressing HEK293 cells we show that reduced mitochondrial Ca 2+ uptake upon the knock-down of the mitochondrial calcium uniporter (MCU) protein and the essential MCU regulator (EMRE) yield considerable attenuation of the Ca 2+ -triggered NO • increase independently of global cytosolic Ca 2+ signals. The knock-down of mitochondrial calcium uptake 1 (MICU1), a gatekeeper of the MCU, increased both mitochondrial Ca 2+ sequestration and Ca 2+ -induced NO • signals. The positive correlation between mitochondrial Ca 2+ elevation and NO • production was independent of eNOS phosphorylation at serine 1177 . Our findings emphasize that manipulating mitochondrial Ca 2+ uptake may represent a novel strategy to control eNOS-mediated NO • production. Copyright © 2016. Published by Elsevier Inc.

NDUFA4L2 protects against ischaemia/reperfusion-induced cardiomyocyte apoptosis and mitochondrial dysfunction by inhibiting complex I.

PubMed

Li, Jianhua; Bai, Caiyan; Guo, Junxia; Liang, Wanqian; Long, Jingning

2017-07-01

Myocardial ischaemia/reperfusion (I/R) injury may cause the apoptosis of cardiomyocytes as well as mitochondrial dysfunction. The aims of the present study were to investigate whether NADH dehydrogenase 1 alpha subcomplex subunit 4-like 2 (NDUFA4L2) on myocardial ischaemia-reperfusion (I/R) injury and the underlying molecular mechanism. The hypoxia-reperfusion (H/R) model was established in vitro using H9c2 cells to simulate I/R injury. NDUFA4L2 and complex I expression levels were detected using RT-PCR and western blot. The apoptosis of H9c2 cells was evaluated by flow cytometry and the expression of Bax and Bcl-2 was detected by western blot. The mitochondrial function was assessed by ATP concentration, mPTP opening and cytochrome c (cyto C) expression. Our data indicated that NDUFA4L2 expression was significantly down-regulated in myocardial H/R injury. Overexpression of NDUFA4L2 led to a dramatic prevention of H/R-induced apoptosis accompanied by a decrease in the expression of Bax and an increase in the expression of Bcl-2. Meanwhile, augmentation of NDUFA4L2 dramatically prevented mitochondrial dysfunction caused by H/R as reflecting in the increased ATP concentration, delayed mPTP opening, as well as down-regulated cyto C expression. Moreover, complex I activation was heightened and negatively regulated by NDUFA4L2. Silencing complex I conspicuously attenuated cell apoptosis and mitochondrial dysfunction. Taken together, our findings demonstrated that NDUFA4L2 protects against H/R injury by preventing myocardium apoptosis and mitochondrial dysfunction via the complex I, and may be a potential therapeutic approach for attenuating myocardial I/R injury. © 2017 John Wiley & Sons Australia, Ltd.