The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Ophry Pines - One of the best experts on this subject based on the ideXlab platform.
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Fumarase from the tca cycle to dna damage response and tumor suppression
Frontiers in Molecular Biosciences, 2018Co-Authors: Michael Leshets, Yardena B H Silas, Norbert Lehming, Ophry PinesAbstract:: Fumarase is an enzyme of the tricarboxylic acid (TCA) cycle in mitochondria, but in recent years, it has emerged as a participant in the response to DNA double strand breaks (DSBs) in the nucleus. In fact, this enzyme is dual-targeted and can be also readily detected in the mitochondrial and cytosolic/nuclear compartments of all the eukaryotic organisms examined. Intriguingly, this evolutionary conserved cytosolic population of Fumarase, its enzymatic activity and the associated metabolite fumarate, are required for the cellular DNA damage response (DDR) to double-strand breaks. Here we review findings from yeast and human cells regarding how Fumarase and fumarate may precisely participate in the DNA damage response. In yeast, cytosolic Fumarase is involved in the homologous recombination (HR) repair pathway, through its function in the DSB resection process. One target of this regulation is the resection enzyme Sae2. In human cells, Fumarase is involved in the non-homologous end joining (NHEJ) repair pathway. Fumarase is phosphorylated by the DNA-dependent protein kinase (DNA-PK) complex, which induces the recruitment of Fumarase to the DSB and local generation of fumarate. Fumarate inhibits the lysine demethylase 2B (KDM2B), thereby facilitating the dimethylation of histone H3, which leads to the repair of the break by the NHEJ pathway. Finally, we discuss the question how Fumarase may function as a tumor suppressor via its metabolite substrate fumarate. We offer a number of models which can explain an apparent contradiction regarding how fumarate absence/accumulation, as a function of subcellular location and stage can determine tumorigenesis. Fumarate, on the one hand, a positive regulator of genome stability (its absence supports genome instability and tumorigenesis) and, on the other hand, its accumulation drives angiogenesis and proliferation (thereby supporting tumor establishment).
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Fumarase is involved in dna double strand break resection through a functional interaction with sae2
Current Genetics, 2018Co-Authors: Michael Leshets, Norbert Lehming, Ophry Pines, Dharanidharan Ramamurthy, Michael LisbyAbstract:One of the most severe forms of DNA damage is the double-strand break (DSB). Failure to properly repair the damage can cause mutation, gross chromosomal rearrangements and lead to the development of cancer. In eukaryotes, homologous recombination (HR) and non-homologous end joining (NHEJ) are the main DSB repair pathways. Fumarase is a mitochondrial enzyme which functions in the tricarboxylic acid cycle. Intriguingly, the enzyme can be readily detected in the cytosolic compartment of all organisms examined, and we have shown that cytosolic Fumarase participates in the DNA damage response towards DSBs. In human cells, Fumarase was shown to be involved in NHEJ, but it is still unclear whether Fumarase is also important for the HR pathway. Here we show that the depletion of cytosolic Fumarase in yeast prolongs the presence of Mre11 at the DSBs, and decreases the kinetics of repair by the HR pathway. Overexpression of Sae2 endonuclease reduced the DSB sensitivity of the cytosolic Fumarase depleted yeast, suggesting that Sae2 and Fumarase functionally interact. Our results also suggest that Sae2 and cytosolic Fumarase physically interact in vivo. Sae2 has been shown to be important for the DSB resection process, which is essential for the repair of DSBs by the HR pathway. Depletion of cytosolic Fumarase inhibited DSB resection, while the overexpression of cytosolic Fumarase or Sae2 restored resection. Together with our finding that cytosolic Fumarase depletion reduces Sae2 cellular amounts, our results suggest that cytosolic Fumarase is important for the DSB resection process by regulating Sae2 levels.
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Fumarase a mitochondrial metabolic enzyme and a cytosolic nuclear component of the dna damage response
PLOS Biology, 2010Co-Authors: Esti Singer, Ohad Yogev, Eitan Shaulian, Michal Goldberg, Ophry PinesAbstract:In eukaryotes, Fumarase (FH in human) is a well-known tricarboxylic-acid-cycle enzyme in the mitochondrial matrix. However, conserved from yeast to humans is a cytosolic isoenzyme of Fumarase whose function in this compartment remains obscure. A few years ago, FH was surprisingly shown to underlie a tumor susceptibility syndrome, Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC). A biallelic inactivation of FH has been detected in almost all HLRCC tumors, and therefore FH was suggested to function as a tumor suppressor. Recently it was suggested that FH inhibition leads to elevated intracellular fumarate, which in turn acts as a competitive inhibitor of HPH (HIF prolyl hydroxylase), thereby causing stabilization of HIF (Hypoxia-inducible factor) by preventing proteasomal degradation. The transcription factor HIF increases the expression of angiogenesis regulated genes, such as VEGF, which can lead to high microvessel density and tumorigenesis. Yet this mechanism does not fully explain the large cytosolic population of Fumarase molecules. We constructed a yeast strain in which Fumarase is localized exclusively to mitochondria. This led to the discovery that the yeast cytosolic Fumarase plays a key role in the protection of cells from DNA damage, particularly from DNA double-strand breaks. We show that the cytosolic Fumarase is a member of the DNA damage response that is recruited from the cytosol to the nucleus upon DNA damage induction. This function of Fumarase depends on its enzymatic activity, and its absence in cells can be complemented by high concentrations of fumaric acid. Our findings suggest that Fumarase and fumaric acid are critical elements of the DNA damage response, which underlies the tumor suppressor role of Fumarase in human cells and which is most probably HIF independent. This study shows an exciting crosstalk between primary metabolism and the DNA damage response, thereby providing a scenario for metabolic control of tumor propagation.
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the presequence of Fumarase is exposed to the cytosol during import into mitochondria
Journal of Molecular Biology, 2006Co-Authors: Sharon Karniely, Neta Regevrudzki, Ophry PinesAbstract:The majority of mitochondrial proteins can be imported into mitochondria following termination of their translation in the cytosol. Import of Fumarase and several other proteins into mitochondria does not appear to occur post-translationally according to standard in vivo and in vitro assays. However, the nature of interaction between the translation and translocation apparatuses during import of these proteins is unknown. Therefore, a major question is whether the nascent chains of these proteins are exposed to the cytosol during import into mitochondria. We asked directly if the presequence of Fumarase can be cleaved by externally added mitochondrial processing peptidase (MPP) during import, using an in vitro translation–translocation coupled reaction. The presequence of Fumarase was cleaved by externally added MPP during import, indicating a lack of, or a loose physical connection between, the translation and translocation of this protein. Exchanging the authentic presequence of Fumarase for that of the more efficient Su9-ATPase presequence reduced the exposure of Fumarase precursors to externally added MPP en route to mitochondria. Therefore, exposure to cytosolic MPP is dependent on the presequence and not on the mature part of Fumarase. On the other hand, following translation in the absence of mitochondria, the authentic Fumarase presequence and that of Su9-ATPase become inaccessible to added MPP when attached to mature Fumarase. Thus, folding of the mature portion of Fumarase, which conceals the presequence, is the reason for its inability to be imported in classical post-translational assays. Another unique feature of Fumarase is its distribution between the mitochondria and the cytosol. We show that in vivo the switch of the authentic presequence with that of Su9-ATPase caused more Fumarase molecules to be localized to the mitochondria. A possible mechanism by which the cytosolic exposure, the targeting efficiency, and the subcellular distribution of Fumarase are dictated by the presequence is discussed.
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folding of Fumarase during mitochondrial import determines its dual targeting in yeast
Journal of Biological Chemistry, 2003Co-Authors: Ehud Sass, Sharon Karniely, Ophry PinesAbstract:Abstract We have previously proposed that a single translation product of the FUM1 gene encoding Fumarase is distributed between the cytosol and mitochondria of Saccharomyces cerevisiae and that all Fumarase translation products are targeted and processed in mitochondria before distribution. Thus, Fumarase processed in mitochondria returns to the cytosol. In the current work, we (i) generated mutations throughout the coding sequence which resulted in Fumarases with altered conformations that are targeted to mitochondria but have lost their ability to be distributed; (ii) showed by mass spectrometry that mature cytosolic and mitochondrial Fumarase isoenzymes are identical; and (iii) showed that hsp70 chaperones in the cytosol (Ssa) and mitochondria (Ssc1) can affect Fumarase distribution. The results are discussed in light of our model of targeting and distribution, which suggests that rapid folding of Fumarase into an import-incompetent state provides the driving force for retrograde movement of the processed protein back to the cytosol through the translocation pore.
Maria Flavia Di Renzo - One of the best experts on this subject based on the ideXlab platform.
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cells lacking the Fumarase tumor suppressor are protected from apoptosis through a hypoxia inducible factor independent ampk dependent mechanism
Molecular and Cellular Biology, 2012Co-Authors: Chiara Bardella, Pierre Rustin, Martina Olivero, Annalisa Lorenzato, Massimo Geuna, Julie Adam, Linda Oflaherty, Ian Tomlinson, Patrick J Pollard, Maria Flavia Di RenzoAbstract:Loss-of-function mutations of the tumor suppressor gene encoding Fumarase (FH) occur in individuals with hereditary leiomyomatosis and renal cell cancer syndrome (HLRCC). We found that loss of FH activity conferred protection from apoptosis in normal human renal cells and fibroblasts. In FH-defective cells, both hypoxia-inducible factor 1α (HIF-1α) and HIF-2α accumulated, but they were not required for apoptosis protection. Conversely, AMP-activated protein kinase (AMPK) was activated and required, as evidenced by the finding that FH inactivation failed to protect AMPK-null mouse embryo fibroblasts (MEFs) and AMPK-depleted human renal cells. Activated AMPK was detected in renal cysts, which occur in mice with kidney-targeted deletion of Fh1 and in kidney cancers of HLRCC patients. In Fh1-null MEFs, AMPK activation was sustained by fumarate accumulation and not by defective energy metabolism. Addition of fumarate and succinate to kidney cells led to extracellular signal-regulated kinase 1/2 (ERK1/2) and AMPK activation, probably through a receptor-mediated mechanism. These findings reveal a new mechanism of tumorigenesis due to FH loss and an unexpected pro-oncogenic role for AMPK that is important in considering AMPK reactivation as a therapeutic strategy against cancer.
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Fumarase tumor suppressor gene and met oncogene cooperate in upholding transformation and tumorigenesis
The FASEB Journal, 2010Co-Authors: Barbara Costa, Chiara Bardella, Martina Olivero, Annalisa Lorenzato, Daniela Dettori, Nadia Coltella, Cosimo Martino, Cristina Cammarata, Peter Carmeliet, Maria Flavia Di RenzoAbstract:Loss of the fumarate hydratase (FH) tumor suppressor gene results in the development of benign tumors that rarely, but regrettably, progress to very aggressive cancers. Using mouse embryo fibroblasts (MEFs) to model transformation, we found that fh knockdown results in increased expression of the met oncogene-encoded tyrosine kinase receptor through hypoxia-inducible factor (hif) stabilization. MET-increased expression was alone able to stabilize hif, thus establishing a feed forward loop that might enforce tumor progression. The fh-defective MEFs showed increased motility and protection from apoptosis. Motility, but not survival, relied on hif-1α and was greatly enhanced by MET ligand hepatocyte growth factor. Met cooperated with a weakly oncogenic ras in making MEFs transformed and tumorigenic, as shown by in vitro and in vivo assays. Loss of fh was not equally effective by itself but enhanced the transformed and tumorigenic phenotype induced by ras and MET. Consistently, the rescue of Fumarase expressi...
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a cancer predisposing hot spot mutation of the Fumarase gene creates a dominant negative protein
International Journal of Cancer, 2008Co-Authors: Annalisa Lorenzato, Pierre Rustin, Martina Olivero, Mario Perro, Jean Briere, Maria Flavia Di RenzoAbstract:The Fumarase (Fumarate Hydratase, FH) is a tumor suppressor gene whose germline heterozygous mutations predispose to hereditary leiomyomatosis and renal cell cancer (HLRCC). The FH gene encodes an enzyme of the Krebs cycle, functioning as a homotetramer and catalyzing the hydration of fumarate to malate. Among the numerous FH mutations reported so far, the R190H missense mutation is the most frequent in HLRCC patients. Here we show the functional analyses of the R190H, in comparison to the better characterized E319Q mutation. We first expressed wild-type and mutated proteins in FH deficient human skin fibroblasts, using lentiviral vectors. The wild-type transgene was able to restore the FH enzymatic activity in cells, while the R190H- and E319Q-FH were not. More interestingly, when the same transgenes were expressed in normal, FH-proficient cells, only the R190H-FH reduced the endogenous FH enzymatic activity. By enforcing the expression of equal amount of wild-type and R190H-FH in the same cell, we showed that the mutated FH protein directly inhibited enzymatic activity by nearly abrogating the FH homotetramer formation. These data demonstrate the dominant negative effect of the R190H missense mutation in the FH gene and suggest that the FH tumor-suppressing activity might be impaired in cells carrying a heterozygous mutation. © 2007 Wiley-Liss, Inc.
Zhongmin Tian - One of the best experts on this subject based on the ideXlab platform.
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insufficient Fumarase contributes to hypertension by an imbalance of redox metabolism in dahl salt sensitive rats
Hypertension Research, 2019Co-Authors: Xuewei Zheng, Meng Chen, Xiaoxue Li, Pengfei Yang, Xinrui Zhao, Yanan Ouyang, Zhe Yang, Mingyu Liang, Zhongmin TianAbstract:Fumarase insufficiencies can increase reactive oxygen species (ROS). This study will further dissect the imbalance of redox metabolism and the mechanism of ROS production using proteomic technology in Fumarase knockdown HK-2 cells. The contribution of Fumarase was further confirmed by supplementation of fumarate and malate in Dahl salt-sensitive rats. Proteomic analysis indicated that Fumarase knockdown in HK-2 cells changed the expression or activity of NADPH oxidase (NOX), mitochondrial respiratory chain Complex I and III, ATP synthase subunits, and α-oxoglutarate dehydrogenase (OGDH). Meanwhile, the activities of key antioxidant enzymes, including glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione reductase, glutathione peroxidase, and glutathione S-transferase, increased significantly. The apparent activation of antioxidant defense appeared insufficient as the glutathione and GSH/GSSG ratio were decreased significantly. Dahl salt-sensitive rats exhibited changes in redox metabolism similar to HK-2 cells with Fumarase knockdown. Supplementation with fumarate and malate increased and decreased, respectively, blood pressure and H2O2 and malondialdehyde in salt-sensitive rats. These results indicated that insufficient Fumarase activity increased ROS by regulating NOX, Complex I and III, ATPase alpha, and OGDH and the imbalance of glutathione metabolism, which may be one of the main reasons for salt-sensitive hypertension. Malate may be a potentially effective drug for the prevention and treatment of salt-sensitive hypertension.
Mingyu Liang - One of the best experts on this subject based on the ideXlab platform.
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insufficient Fumarase contributes to hypertension by an imbalance of redox metabolism in dahl salt sensitive rats
Hypertension Research, 2019Co-Authors: Xuewei Zheng, Meng Chen, Xiaoxue Li, Pengfei Yang, Xinrui Zhao, Yanan Ouyang, Zhe Yang, Mingyu Liang, Zhongmin TianAbstract:Fumarase insufficiencies can increase reactive oxygen species (ROS). This study will further dissect the imbalance of redox metabolism and the mechanism of ROS production using proteomic technology in Fumarase knockdown HK-2 cells. The contribution of Fumarase was further confirmed by supplementation of fumarate and malate in Dahl salt-sensitive rats. Proteomic analysis indicated that Fumarase knockdown in HK-2 cells changed the expression or activity of NADPH oxidase (NOX), mitochondrial respiratory chain Complex I and III, ATP synthase subunits, and α-oxoglutarate dehydrogenase (OGDH). Meanwhile, the activities of key antioxidant enzymes, including glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione reductase, glutathione peroxidase, and glutathione S-transferase, increased significantly. The apparent activation of antioxidant defense appeared insufficient as the glutathione and GSH/GSSG ratio were decreased significantly. Dahl salt-sensitive rats exhibited changes in redox metabolism similar to HK-2 cells with Fumarase knockdown. Supplementation with fumarate and malate increased and decreased, respectively, blood pressure and H2O2 and malondialdehyde in salt-sensitive rats. These results indicated that insufficient Fumarase activity increased ROS by regulating NOX, Complex I and III, ATPase alpha, and OGDH and the imbalance of glutathione metabolism, which may be one of the main reasons for salt-sensitive hypertension. Malate may be a potentially effective drug for the prevention and treatment of salt-sensitive hypertension.
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insufficient Fumarase contributes to generating reactive oxygen species in dahl salt sensitive rats
bioRxiv, 2018Co-Authors: Xuewei Zheng, Meng Chen, Xiaoxue Li, Mingyu Liang, Zai Yang, Zhiqi TianAbstract:Dahl SS rats exhibit greater levels of renal medullary oxidative stress and lower levels of Fumarase activities. Fumarase insufficiencies can increase reactive oxygen species (ROS), the mechanism of which, however, is not clear. A proteomic analysis indicated Fumarase knockdown in HK-2 cells resulted in changes in the expression or activity of NADPH oxidase, mitochondrial respiratory chain complex I and III, ATP synthase subunits, and α-oxoglutarate dehydrogenase, all of which are sites of ROS formation. Meantime, the activities of key antioxidant enzymes such as G6PD, 6PGD, GR, GPx and GST increased significantly too. The apparent activation of antioxidant defense appeared insufficient as glutathione precursors, glutathione and GSH/GSSG ratio were decreased. SS rats exhibited changes in redox metabolism similar to HK-2 cells with Fumarase knockdown. Supplementation with fumarate and malate, the substrate and product of Fumarase, increased and decreased, respectively, blood pressure and the levels of H2O2 and MDA in kidney tissues of SS rats. These results indicate Fumarase insufficiencies cause a wide range of changes at several sites of ROS production and antioxidant mechanisms.
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Abstract 497: H2O2 in Fumarase Insufficiencies in Dahl Salt-Sensitive Rats.
Hypertension, 2012Co-Authors: Mingyu LiangAbstract:We have shown previously that renal insufficiencies of Fumarase, an enzyme in the tricarboxylic acid cycle, appear to contribute to salt-induced hypertension in Dahl salt-sensitive (SS) rats. The present study examined the molecular mechanism underlying Fumarase insufficiencies in SS rats. Protein abundance and enzymatic activity of Fumarase was significantly lower in the renal medulla of SS rats compared to salt-insensitive Sprague-Dawley rats. We screened several factors including TGFβ1, TNFα, and H2O2 for their effects on Fumarase expression. These factors were selected for screening because they had been reported to be elevated in the kidneys of the SS rat and they represent a pro-fibrotic, pro-inflammatory, and oxidative milieu present in the kidneys of the SS rat. Cultured human renal epithelial cells were treated with TGFβ1 (3 ng/ml), TNFα (25 ng/ml), or H2O2 (500 μM) for 24 hours. H2O2 substantially reduced Fumarase mRNA levels (normalized by 18S rRNA) to less than 10% of control. TNFα tended to suppress Fumarase expression, but the effect did not reach statistical significance. TGFβ1 did not have significant effects on Fumarase mRNA levels. The greater than 90% loss of Fumarase following the H2O2 treatment was accompanied by significant cell death. To determine if the down-regulation of Fumarase was simply a consequence of the cytotoxicity of H2O2, we treated HRE cells with 100 μM of H2O2 for 48 hours. The lower dose of H2O2 did not cause significant cell death. Yet, Fumarase mRNA was still down-regulated to 79.6% ± 4.7% of control (n=4, P
Xuewei Zheng - One of the best experts on this subject based on the ideXlab platform.
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insufficient Fumarase contributes to hypertension by an imbalance of redox metabolism in dahl salt sensitive rats
Hypertension Research, 2019Co-Authors: Xuewei Zheng, Meng Chen, Xiaoxue Li, Pengfei Yang, Xinrui Zhao, Yanan Ouyang, Zhe Yang, Mingyu Liang, Zhongmin TianAbstract:Fumarase insufficiencies can increase reactive oxygen species (ROS). This study will further dissect the imbalance of redox metabolism and the mechanism of ROS production using proteomic technology in Fumarase knockdown HK-2 cells. The contribution of Fumarase was further confirmed by supplementation of fumarate and malate in Dahl salt-sensitive rats. Proteomic analysis indicated that Fumarase knockdown in HK-2 cells changed the expression or activity of NADPH oxidase (NOX), mitochondrial respiratory chain Complex I and III, ATP synthase subunits, and α-oxoglutarate dehydrogenase (OGDH). Meanwhile, the activities of key antioxidant enzymes, including glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione reductase, glutathione peroxidase, and glutathione S-transferase, increased significantly. The apparent activation of antioxidant defense appeared insufficient as the glutathione and GSH/GSSG ratio were decreased significantly. Dahl salt-sensitive rats exhibited changes in redox metabolism similar to HK-2 cells with Fumarase knockdown. Supplementation with fumarate and malate increased and decreased, respectively, blood pressure and H2O2 and malondialdehyde in salt-sensitive rats. These results indicated that insufficient Fumarase activity increased ROS by regulating NOX, Complex I and III, ATPase alpha, and OGDH and the imbalance of glutathione metabolism, which may be one of the main reasons for salt-sensitive hypertension. Malate may be a potentially effective drug for the prevention and treatment of salt-sensitive hypertension.
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insufficient Fumarase contributes to generating reactive oxygen species in dahl salt sensitive rats
bioRxiv, 2018Co-Authors: Xuewei Zheng, Meng Chen, Xiaoxue Li, Mingyu Liang, Zai Yang, Zhiqi TianAbstract:Dahl SS rats exhibit greater levels of renal medullary oxidative stress and lower levels of Fumarase activities. Fumarase insufficiencies can increase reactive oxygen species (ROS), the mechanism of which, however, is not clear. A proteomic analysis indicated Fumarase knockdown in HK-2 cells resulted in changes in the expression or activity of NADPH oxidase, mitochondrial respiratory chain complex I and III, ATP synthase subunits, and α-oxoglutarate dehydrogenase, all of which are sites of ROS formation. Meantime, the activities of key antioxidant enzymes such as G6PD, 6PGD, GR, GPx and GST increased significantly too. The apparent activation of antioxidant defense appeared insufficient as glutathione precursors, glutathione and GSH/GSSG ratio were decreased. SS rats exhibited changes in redox metabolism similar to HK-2 cells with Fumarase knockdown. Supplementation with fumarate and malate, the substrate and product of Fumarase, increased and decreased, respectively, blood pressure and the levels of H2O2 and MDA in kidney tissues of SS rats. These results indicate Fumarase insufficiencies cause a wide range of changes at several sites of ROS production and antioxidant mechanisms.
