1
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Guffens L, Derua R, Janssens V. PME-1 sensitizes glioblastoma cells to oxidative stress-induced cell death by attenuating PP2A-B55α-mediated inactivation of MAPKAPK2-RIPK1 signaling. Cell Death Discov 2023; 9:265. [PMID: 37500619 PMCID: PMC10374899 DOI: 10.1038/s41420-023-01572-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 07/13/2023] [Accepted: 07/20/2023] [Indexed: 07/29/2023] Open
Abstract
Glioblastoma (GBM) is the most common primary brain tumor in adults. Current standard therapy is surgery followed by radiotherapy, with concurrent and adjuvant temozolomide chemotherapy. GBM is characterized by almost uniformly fatal outcomes, highlighting the unmet clinical need for more efficient, biomarker-guided treatments. Protein phosphatase methylesterase-1 (PME-1), a regulator of the tumor suppressive phosphatase PP2A, promotes PP2A demethylation and inactivation, and is overexpressed in 44% of GBM, associated with increased tumor grade and cellular proliferation. Here, we aimed to investigate how reactive oxygen species (ROS), a frequent by-product of radiotherapy and temozolomide chemotherapy, regulate PP2A function via its methylesterase PME-1, and how PME-1 overexpression impacts the response of GBM cells to oxidative stress. We found that in two glioblastoma cell lines, U87MG and U251MG, expression of PME-1 is positively correlated with the sensitivity of the cells to H2O2 or t-BHP-induced oxidative stress. Experiments using the irreversible pharmacologic PME-1 inhibitor, AMZ30, and different PME-1 mutants, revealed that the methylesterase function, the PP2A binding capacity, and the nuclear localization of PME-1 are all important for the sensitizing effect of PME-1 expression. Furthermore, we identified increased nuclear localization of the PP2A-B55α subunit, increased binding of PP2A-B55α to PME-1, and increased B55α-bound PP2A-C demethylation upon oxidative stress. Lastly, we uncovered increased stress-induced phosphorylation and activity of MAPKAPK2 and RIPK1 in PME-1 overexpressing U87MG cells, which caused the observed sensitization to t-BHP treatment. Our data reveal a novel role for PME-1 in oxidative stress-induced GBM cell death, regulating nuclear PP2A-B55α activity and MAPKAPK2-RIPK1 signaling. Patients with GBM tumors overexpressing PME-1, although having a worse prognosis due to increased cellular proliferation of the tumor, could actually be more responsive to oxidative stress-inducing therapies.
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Affiliation(s)
- Liesbeth Guffens
- Laboratory of Protein Phosphorylation & Proteomics, Dept. Cellular & Molecular Medicine, KU Leuven, B-3000, Leuven, Belgium
- KU Leuven Cancer Institute (LKI), B-3000, Leuven, Belgium
| | - Rita Derua
- Laboratory of Protein Phosphorylation & Proteomics, Dept. Cellular & Molecular Medicine, KU Leuven, B-3000, Leuven, Belgium
- SyBioMa, KU Leuven, B-3000, Leuven, Belgium
| | - Veerle Janssens
- Laboratory of Protein Phosphorylation & Proteomics, Dept. Cellular & Molecular Medicine, KU Leuven, B-3000, Leuven, Belgium.
- KU Leuven Cancer Institute (LKI), B-3000, Leuven, Belgium.
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2
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Patil NK, Bohannon JK, Vachharajani V, McCall CE. Editorial: The Roles of Mitochondria in Immunity. Front Immunol 2022; 13:914639. [PMID: 35651600 PMCID: PMC9149419 DOI: 10.3389/fimmu.2022.914639] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 04/28/2022] [Indexed: 02/01/2023] Open
Affiliation(s)
- Naeem K. Patil
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Julia K. Bohannon
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, United States,Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Vidula Vachharajani
- Departments of Critical Care Medicine and Inflammation and Immunity, Cleveland, Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States
| | - Charles E. McCall
- Department of Internal Medicine, Wake Forest School of Medicine, Winston Salem, NC, United States,*Correspondence: Charles E. McCall,
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3
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Idelfonso-García OG, Alarcón-Sánchez BR, Vásquez-Garzón VR, Baltiérrez-Hoyos R, Villa-Treviño S, Muriel P, Serrano H, Pérez-Carreón JI, Arellanes-Robledo J. Is Nucleoredoxin a Master Regulator of Cellular Redox Homeostasis? Its Implication in Different Pathologies. Antioxidants (Basel) 2022; 11:antiox11040670. [PMID: 35453355 PMCID: PMC9030443 DOI: 10.3390/antiox11040670] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/26/2022] [Accepted: 03/28/2022] [Indexed: 01/27/2023] Open
Abstract
Nucleoredoxin (NXN), an oxidoreductase enzyme, contributes to cellular redox homeostasis by regulating different signaling pathways in a redox-dependent manner. By interacting with seven proteins so far, namely disheveled (DVL), protein phosphatase 2A (PP2A), phosphofructokinase-1 (PFK1), translocation protein SEC63 homolog (SEC63), myeloid differentiation primary response gene-88 (MYD88), flightless-I (FLII), and calcium/calmodulin-dependent protein kinase II type alpha (CAMK2A), NXN is involved in the regulation of several key cellular processes, including proliferation, organogenesis, cell cycle progression, glycolysis, innate immunity and inflammation, motility, contraction, protein transport into the endoplasmic reticulum, neuronal plasticity, among others; as a result, NXN has been implicated in different pathologies, such as cancer, alcoholic and polycystic liver disease, liver fibrogenesis, obesity, Robinow syndrome, diabetes mellitus, Alzheimer’s disease, and retinitis pigmentosa. Together, this evidence places NXN as a strong candidate to be a master redox regulator of cell physiology and as the hub of different redox-sensitive signaling pathways and associated pathologies. This review summarizes and discusses the current insights on NXN-dependent redox regulation and its implication in different pathologies.
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Affiliation(s)
- Osiris Germán Idelfonso-García
- Laboratory of Liver Diseases, National Institute of Genomic Medicine–INMEGEN, Mexico City 14610, Mexico; (O.G.I.-G.); (B.R.A.-S.); (J.I.P.-C.)
- Department of Health Sciences, Metropolitan Autonomous University-Iztapalapa Campus, Mexico City 09340, Mexico;
| | - Brisa Rodope Alarcón-Sánchez
- Laboratory of Liver Diseases, National Institute of Genomic Medicine–INMEGEN, Mexico City 14610, Mexico; (O.G.I.-G.); (B.R.A.-S.); (J.I.P.-C.)
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute–CINVESTAV-IPN, Mexico City 07360, Mexico;
| | - Verónica Rocío Vásquez-Garzón
- Laboratory of Fibrosis and Cancer, Faculty of Medicine and Surgery, ‘Benito Juárez’ Autonomous University of Oaxaca–UABJO, Oaxaca 68020, Mexico; (V.R.V.-G.); (R.B.-H.)
- Directorate of Cátedras, National Council of Science and Technology–CONACYT, Mexico City 03940, Mexico
| | - Rafael Baltiérrez-Hoyos
- Laboratory of Fibrosis and Cancer, Faculty of Medicine and Surgery, ‘Benito Juárez’ Autonomous University of Oaxaca–UABJO, Oaxaca 68020, Mexico; (V.R.V.-G.); (R.B.-H.)
- Directorate of Cátedras, National Council of Science and Technology–CONACYT, Mexico City 03940, Mexico
| | - Saúl Villa-Treviño
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute–CINVESTAV-IPN, Mexico City 07360, Mexico;
| | - Pablo Muriel
- Laboratory of Experimental Hepatology, Department of Pharmacology, Center for Research and Advanced Studies of the National Polytechnic Institute–CINVESTAV-IPN, Mexico City 07360, Mexico;
| | - Héctor Serrano
- Department of Health Sciences, Metropolitan Autonomous University-Iztapalapa Campus, Mexico City 09340, Mexico;
| | - Julio Isael Pérez-Carreón
- Laboratory of Liver Diseases, National Institute of Genomic Medicine–INMEGEN, Mexico City 14610, Mexico; (O.G.I.-G.); (B.R.A.-S.); (J.I.P.-C.)
| | - Jaime Arellanes-Robledo
- Laboratory of Liver Diseases, National Institute of Genomic Medicine–INMEGEN, Mexico City 14610, Mexico; (O.G.I.-G.); (B.R.A.-S.); (J.I.P.-C.)
- Directorate of Cátedras, National Council of Science and Technology–CONACYT, Mexico City 03940, Mexico
- Correspondence: ; Tel.: +52-55-5350-1900 (ext. 1218)
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4
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Regulation of Cardiac PKA Signaling by cAMP and Oxidants. Antioxidants (Basel) 2021; 10:antiox10050663. [PMID: 33923287 PMCID: PMC8146537 DOI: 10.3390/antiox10050663] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/16/2021] [Accepted: 04/20/2021] [Indexed: 12/31/2022] Open
Abstract
Pathologies, such as cancer, inflammatory and cardiac diseases are commonly associated with long-term increased production and release of reactive oxygen species referred to as oxidative stress. Thereby, protein oxidation conveys protein dysfunction and contributes to disease progression. Importantly, trials to scavenge oxidants by systemic antioxidant therapy failed. This observation supports the notion that oxidants are indispensable physiological signaling molecules that induce oxidative post-translational modifications in target proteins. In cardiac myocytes, the main driver of cardiac contractility is the activation of the β-adrenoceptor-signaling cascade leading to increased cellular cAMP production and activation of its main effector, the cAMP-dependent protein kinase (PKA). PKA-mediated phosphorylation of substrate proteins that are involved in excitation-contraction coupling are responsible for the observed positive inotropic and lusitropic effects. PKA-actions are counteracted by cellular protein phosphatases (PP) that dephosphorylate substrate proteins and thus allow the termination of PKA-signaling. Both, kinase and phosphatase are redox-sensitive and susceptible to oxidation on critical cysteine residues. Thereby, oxidation of the regulatory PKA and PP subunits is considered to regulate subcellular kinase and phosphatase localization, while intradisulfide formation of the catalytic subunits negatively impacts on catalytic activity with direct consequences on substrate (de)phosphorylation and cardiac contractile function. This review article attempts to incorporate the current perception of the functionally relevant regulation of cardiac contractility by classical cAMP-dependent signaling with the contribution of oxidant modification.
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5
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Meng L, Lu C, Wu B, Lan C, Mo L, Chen C, Wang X, Zhang N, Lan L, Wang Q, Zeng X, Li X, Tang S. Taurine Antagonizes Macrophages M1 Polarization by Mitophagy-Glycolysis Switch Blockage via Dragging SAM-PP2Ac Transmethylation. Front Immunol 2021; 12:648913. [PMID: 33912173 PMCID: PMC8071881 DOI: 10.3389/fimmu.2021.648913] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Accepted: 03/22/2021] [Indexed: 12/11/2022] Open
Abstract
The excessive M1 polarization of macrophages drives the occurrence and development of inflammatory diseases. The reprogramming of macrophages from M1 to M2 can be achieved by targeting metabolic events. Taurine promotes for the balance of energy metabolism and the repair of inflammatory injury, preventing chronic diseases and complications. However, little is known about the mechanisms underlying the action of taurine modulating the macrophage polarization phenotype. In this study, we constructed a low-dose LPS/IFN-γ-induced M1 polarization model to simulate a low-grade pro-inflammatory process. Our results indicate that the taurine transporter TauT/SlC6A6 is upregulated at the transcriptional level during M1 macrophage polarization. The nutrient uptake signal on the membrane supports the high abundance of taurine in macrophages after taurine supplementation, which weakens the status of methionine metabolism, resulting in insufficient S-adenosylmethionine (SAM). The low availability of SAM is directly sensed by LCMT-1 and PME-1, hindering PP2Ac methylation. PP2Ac methylation was found to be necessary for M1 polarization, including the positive regulation of VDAC1 and PINK1. Furthermore, its activation was found to promote the elimination of mitochondria by macrophages via the mitophagy pathway for metabolic adaptation. Mechanistically, taurine inhibits SAM-dependent PP2Ac methylation to block PINK1-mediated mitophagy flux, thereby maintaining a high mitochondrial density, which ultimately hinders the conversion of energy metabolism to glycolysis required for M1. Our findings reveal a novel mechanism of taurine-coupled M1 macrophage energy metabolism, providing novel insights into the occurrence and prevention of low-grade inflammation, and propose that the sensing of taurine and SAM availability may allow communication to inflammatory response in macrophages.
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Affiliation(s)
- Ling Meng
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
| | - Cailing Lu
- School of Public Health, Guangxi Medical University, Nanning, China
| | - Bin Wu
- School of Public Health, Guangxi Medical University, Nanning, China
| | - Chunhua Lan
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
| | - Laiming Mo
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,School of Public Health, Guangxi Medical University, Nanning, China
| | - Chengying Chen
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
| | - Xinhang Wang
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
| | - Ning Zhang
- School of Public Health, Guangxi Medical University, Nanning, China
| | - Li Lan
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
| | - Qihui Wang
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
| | - Xia Zeng
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
| | - Xiyi Li
- School of Public Health, Guangxi Medical University, Nanning, China
| | - Shen Tang
- School of Basic Medical Sciences, Guangxi Medical University, Nanning, China.,Guangxi Colleges and Universities Key Laboratory of Preclinical Medicine, Guangxi Medical University, Nanning, China
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6
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Lee SY, Lee YY, Choi JS, Kim KS, Min DS, Park SY, Han JS. Nitration of protein phosphatase 2A increases via Epac1/PLCε/CaMKII/HDAC5/iNOS cascade in human endometrial stromal cell decidualization. FASEB J 2020; 34:14407-14423. [PMID: 33000885 DOI: 10.1096/fj.202001212r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/31/2020] [Accepted: 08/13/2020] [Indexed: 12/11/2022]
Abstract
Decidualization of the endometrial stroma is an essential differentiation process for embryo implantation and maintenance of pregnancy. We previously reported that protein phosphatase 2A (PP2A) acts as a key mediator during cAMP-induced decidualization of human endometrial stromal cells (hESCs). However, the mechanism underlying its activation has remained obscure in hESCs. In the present study, we aimed to reveal the mechanism that induces the nitration of PP2A catalytic subunit (PP2Ac) during cAMP-induced decidualization of hESCs. First, cAMP-induced PP2Ac nitration was significantly repressed using L-NAME, an inhibitor of nitric oxide synthase (NOS). Among several NOS isoforms, only inducible NOS (iNOS) was highly expressed in hESCs, indicating that iNOS directly induces the nitration of PP2Ac. Second, cAMP-induced iNOS expression and PP2Ac nitration were decreased by treatment with TSA, an inhibitor of histone deacetylase 5 (HDAC5). cAMP-induced phosphorylation of CaMKII and HDAC5 was suppressed by treatment with U73122 (an inhibitor of phospholipase C) or transfection of PLCε siRNA. Finally, small G protein Rap1 and its guanine nucleotide exchange factor Epac1 were found to be involved in cAMP-induced PP2A activation. Taken together, our results suggest that PP2Ac nitration during cAMP-induced decidualization of hESCs is induced through the Epac1-Rap1-PLCε-CaMKII-HDAC5-iNOS signaling pathway.
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Affiliation(s)
- So Young Lee
- Department of Biomedical Sciences, Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul, Republic of Korea
| | - Yun Young Lee
- Department of Biomedical Sciences, Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul, Republic of Korea.,Biomedical Research Institute and Department of Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul, Republic of Korea
| | - Joong-Sub Choi
- Department of Obstetrics and Gynecology, College of Medicine, Hanyang University, Seoul, Republic of Korea
| | - Kyeong Soo Kim
- Department of Pharmaceutical Engineering, Gyeongnam National University of Science and Technology, Jinju, Republic of Korea
| | - Do Sik Min
- Department of Pharmacy, College of Pharmacy, Yonsei University, Incheon, Republic of Korea
| | - Shin-Young Park
- Biomedical Research Institute and Department of Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul, Republic of Korea
| | - Joong-Soo Han
- Department of Biomedical Sciences, Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul, Republic of Korea.,Biomedical Research Institute and Department of Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul, Republic of Korea
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7
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Elgenaidi IS, Spiers JP. Regulation of the phosphoprotein phosphatase 2A system and its modulation during oxidative stress: A potential therapeutic target? Pharmacol Ther 2019; 198:68-89. [PMID: 30797822 DOI: 10.1016/j.pharmthera.2019.02.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 02/15/2019] [Indexed: 02/06/2023]
Abstract
Phosphoprotein phosphatases are of growing interest in the pathophysiology of many diseases and are often the neglected partner of protein kinases. One family member, PP2A, accounts for dephosphorylation of ~55-70% of all serine/threonine phosphosites. Interestingly, dysregulation of kinase signalling is a hallmark of many diseases in which an increase in oxidative stress is also noted. With this in mind, we assess the evidence to support oxidative stress-mediated regulation of the PP2A system In this article, we first present an overview of the PP2A system before providing an analysis of the regulation of PP2A by endogenous inhibitors, post translational modification, and miRNA. Next, a detailed critique of data implicating reactive oxygen species, ischaemia, ischaemia-reperfusion, and hypoxia in regulating the PP2A holoenzyme and associated regulators is presented. Finally, the pharmacological targeting of PP2A, its endogenous inhibitors, and enzymes responsible for its post-translational modification are covered. There is extensive evidence that oxidative stress modulates multiple components of the PP2A system, however, most of the data pertains to the catalytic subunit of PP2A. Irrespective of the underlying aetiology, free radical-mediated attenuation of PP2A activity is an emerging theme. However, in many instances, a dichotomy exists, which requires clarification and mechanistic insight. Nevertheless, this raises the possibility that pharmacological activation of PP2A, either through small molecule activators of PP2A or CIP2A/SET antagonists may be beneficial in modulating the cellular response to oxidative stress. A better understanding of which, will have wide ranging implications for cancer, heart disease and inflammatory conditions.
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Affiliation(s)
- I S Elgenaidi
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland
| | - J P Spiers
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland.
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8
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Raman D, Pervaiz S. Redox inhibition of protein phosphatase PP2A: Potential implications in oncogenesis and its progression. Redox Biol 2019; 27:101105. [PMID: 30686777 PMCID: PMC6859563 DOI: 10.1016/j.redox.2019.101105] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 01/04/2019] [Accepted: 01/09/2019] [Indexed: 01/17/2023] Open
Abstract
Cellular processes are dictated by the active signaling of proteins relaying messages to regulate cell proliferation, apoptosis, signal transduction and cell communications. An intricate web of protein kinases and phosphatases are critical to the proper transmission of signals across such cascades. By governing 30–50% of all protein dephosphorylation in the cell, with prominent substrate proteins being key regulators of signaling cascades, the phosphatase PP2A has emerged as a celebrated player in various developmental and tumorigenic pathways, thereby posing as an attractive target for therapeutic intervention in various pathologies wherein its activity is deregulated. This review is mainly focused on refreshing our understanding of the structural and functional complexity that cocoons the PP2A phosphatase, and its expression in cancers. Additionally, we focus on its physiological regulation as well as into recent advents and strategies that have shown promise in countering the deregulation of the phosphatase through its targeted reactivation. Finally, we dwell upon one of the key regulators of PP2A in cancer cells-cellular redox status-its multifarious nature, and its integration into the reactome of PP2A, highlighting some of the significant impacts that ROS can inflict on the structural modifications and functional aspect of PP2A.
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Affiliation(s)
- Deepika Raman
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Shazib Pervaiz
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Medical Science Cluster Cancer Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; National University Cancer Institute, National University Health System, Singapore, Singapore; NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore.
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9
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Liu L, Huang Z, Chen J, Wang J, Wang S. Protein phosphatase 2A mediates JS-K-induced apoptosis by affecting Bcl-2 family proteins in human hepatocellular carcinoma HepG2 cells. J Cell Biochem 2018; 119:6633-6643. [PMID: 29693750 DOI: 10.1002/jcb.26845] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 03/09/2018] [Indexed: 12/18/2022]
Abstract
Protein phosphatase 2A (PP2A) is an important enzyme within various signal transduction pathways. The present study was investigated PP2A mediates JS-K-induced apoptosis by affecting Bcl-2 family protein. JS-K showed diverse inhibitory effects in five HCC cell lines, especially HepG2 cells. JS-K caused a dose- and time-dependent reduction in cell viability and increased in levels of LDH release. Meanwhile, JS-K- induced apoptosis was characterized by mitochondrial membrane potential reduction, Hoechst 33342+ /PI+ dual staining, release of cytochrome c (Cyt c), and activation of cleaved caspase-9/3. Moreover, JS-K-treatment could lead to the activation of protein phosphatase 2A-C (PP2A-C), decrease of anti-apoptotic Bcl-2 family-protein expression including p-Bcl-2 (Ser70), Bcl-2, Bcl-xL, and Mcl-1 as well as the increase of pro-apoptosis Bcl-2 family-protein including Bim, Bad, Bax, and Bak. Furthermore, JS-K caused a marked increase of intracellular NO levels while pre-treatment with Carboxy-PTIO (a NO scavenger) reduced the cytotoxicity effects and the apoptosis rate. Meanwhile, pre-treatment with Carboxy-PTIO attenuated the JS-K-induced up-regulation of PP2A, Cyt c, and cleaved-caspase-9/3 activation. The silencing PP2A-C by siRNA could abolish the activation of PP2A-C, down-regulation of anti-apoptotic Bcl-2 family-protein (p-Bcl-2, Bcl-2, Bcl-xL, and Mcl-1), increase of pro-apoptosis Bcl-2 family-protein (Bim, Bad, Bax, and Bak) and apoptotic-related protein (Cyt c, cleaved caspase-9/3) that were caused by JS-K in HepG2 cells. In addition, pre-treatment with OA (a PP2A inhibitor) also attenuated the above effects induced by JS-K. In summary, NO release from JS-K induces apoptosis through PP2A activation, which contributed to the regulation of Bcl-2 family proteins.
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Affiliation(s)
- Ling Liu
- Department of Pharmacy, Medical College, Henan University of Science and Technology, Luoyang, China
| | - Zile Huang
- Department of Pharmacy, Medical College, Henan University of Science and Technology, Luoyang, China
| | - Jingjing Chen
- Department of Pharmacy, Medical College, Henan University of Science and Technology, Luoyang, China
| | - Jiangang Wang
- Department of Pharmacy, Medical College, Henan University of Science and Technology, Luoyang, China
| | - Shuying Wang
- Department of Pharmacy, Medical College, Henan University of Science and Technology, Luoyang, China
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10
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Netrin-1 suppresses the MEK/ERK pathway and ITGB4 in pancreatic cancer. Oncotarget 2017; 7:24719-33. [PMID: 27034160 PMCID: PMC5029736 DOI: 10.18632/oncotarget.8348] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 02/05/2016] [Indexed: 12/21/2022] Open
Abstract
The axon guidance factor netrin-1 promotes tumorigenesis in multiple types of cancers, particularly at their advanced stages. Here, we investigate whether netrin-1 is involved in the in vivo growth of pancreatic adenocarcinoma. We show that netrin-1 is significantly under-expressed in stage-I/II pancreatic ductal adenocarcinoma (PDAC). Netrin-1 over-expression effectively arrests the growth of xenografted PDAC cells without decreasing cell proliferation or increasing apoptosis in two-dimensional cultures in vitro. Integrin-beta4 (ITGB4) expression is significantly reduced, and ITGB4-knockdown mimics the tumor-suppressive effect of netrin-1, implying that ITGB4 is a main target of netrin-1 in constraining PDAC. We further show that netrin-1 signals to UNC5B/FAK to stimulate nitric oxide production, which promotes PP2A-mediated inhibition of the MEK/ERK pathway and decreases phosphorylated-c-Jun recruitment to the ITGB4 promoter. Our findings suggest that netrin-1 can suppress the growth of PDAC and provide a mechanistic insight into this suppression.
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11
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Kake S, Tsuji S, Enjoji S, Hanasaki S, Hayase H, Yabe R, Tanaka Y, Nakagawa T, Liu HP, Chang SC, Usui T, Ohama T, Sato K. The role of SET/I2PP2A in canine mammary tumors. Sci Rep 2017; 7:4279. [PMID: 28655918 PMCID: PMC5487328 DOI: 10.1038/s41598-017-04291-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 05/12/2017] [Indexed: 01/27/2023] Open
Abstract
Canine mammary tumor is the most common neoplasm in female dogs, and it has generated considerable attention as a translational model for human breast cancer. Ser/Thr protein phosphatase 2A (PP2A) plays a critical role as a tumor suppressor, and SET/I2PP2A, the endogenous inhibitory protein of PP2A, binds directly to PP2A and suppresses its phosphatase activity. Here, we investigated the role of SET in the tumorigenic growth in canine mammary tumor as well as in the sensitivity of tumors to existing therapeutics. Elevated protein levels of SET were observed in advanced-stage of canine mammary tumor tissues of dogs compared with paired normal tissues. Knockdown of SET expression in a canine mammary tumor cell line CIP-m led to increased PP2A activity and decreased cell proliferation, colony formation, and in vivo tumor growth. We observed suppression of mTOR, β-catenin, and NFκB signaling by SET knockdown. The sensitivity of CIP-m cells to doxorubicin was decreased by SET knockdown, while SET knockdown in CIP-m cells did not affect sensitivity to 4-OH-tamoxifen, carboplatin, bortezomib, and X-ray radiation. These data suggest that SET plays important roles in the tumor progression of a subset of canine mammary tumor by suppressing PP2A activity and enhancing mTOR, β-catenin, and NFκB signaling.
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Affiliation(s)
- Satoru Kake
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
- Department of Comparative Animal Science, College of Life Science, Kurashiki University of Science and The Arts, Okayama, Japan
| | - Shunya Tsuji
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Shuhei Enjoji
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Sayaka Hanasaki
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Hiroshi Hayase
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Ryotaro Yabe
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Yuiko Tanaka
- The Laboratory of Veterinary Surgery and the Veterinary Medical Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Takayuki Nakagawa
- The Laboratory of Veterinary Surgery and the Veterinary Medical Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Hao-Ping Liu
- Department of Veterinary Medicine, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan
| | - Shih-Chieh Chang
- Department of Veterinary Medicine, Veterinary Medical Teaching Hospital, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan
| | - Tatsuya Usui
- Laboratory of Veterinary Toxicology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Takashi Ohama
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan.
| | - Koichi Sato
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
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12
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Wilson A, Yakovlev VA. Cells redox environment modulates BRCA1 expression and DNA homologous recombination repair. Free Radic Biol Med 2016; 101:190-201. [PMID: 27771433 DOI: 10.1016/j.freeradbiomed.2016.10.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 10/18/2016] [Accepted: 10/18/2016] [Indexed: 12/12/2022]
Abstract
Cancer development and progression have been linked to oxidative stress, a condition characterized by unbalanced increase in ROS and RNS production. The main endogenous initiators of the redox imbalance in cancer cells are defective mitochondria, elevated NOX activity, and uncoupled NOS3. Traditionally, most attention has been paid to direct oxidative damage to DNA by certain ROS. However, increase in oxidative DNA lesions does not always lead to malignancy. Hence, additional ROS-dependent, pro-carcinogenic mechanisms must be important. Our recent study demonstrated that Tyr nitration of PP2A stimulates its activity and leads to downregulation of BRCA1 expression. This provides a mechanism for chromosomal instability essential for tumor progression. In the present work, we demonstrated that inhibition of ROS production by generating mitochondrial-electron-transport-deficient cell lines (ρ0 cells) or by inhibition of NOX activity with a selective peptide inhibitor significantly reduced PP2A Tyr nitration and its activity in different cancer cell lines. As a result of the decreased PP2A activity, BRCA1 expression was restored along with a significantly enhanced level of DNA HRR. We used TCGA database to analyze the correlation between expressions of the NOX regulatory subunits, NOS isoforms, and BRCA1 in the 3 cancer research studies: breast invasive carcinoma, ovarian cystadenocarcinoma, and lung adenocarcinoma. TCGA database analysis demonstrated that the high expression levels of most of the NOX regulatory subunits responsible for stimulation of NOX1-NOX4 were associated with significant downregulation of BRCA1 expression.
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MESH Headings
- A549 Cells
- Adenocarcinoma/genetics
- Adenocarcinoma/metabolism
- Adenocarcinoma/pathology
- Adenocarcinoma of Lung
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Breast Neoplasms/pathology
- Carcinoma, Ductal, Breast/genetics
- Carcinoma, Ductal, Breast/metabolism
- Carcinoma, Ductal, Breast/pathology
- Chromosomal Instability
- Cystadenocarcinoma, Serous/genetics
- Cystadenocarcinoma, Serous/metabolism
- Cystadenocarcinoma, Serous/pathology
- Databases, Genetic
- Electron Transport
- Female
- Gene Expression Regulation, Neoplastic
- Humans
- Isoenzymes/genetics
- Isoenzymes/metabolism
- Lung Neoplasms/genetics
- Lung Neoplasms/metabolism
- Lung Neoplasms/pathology
- MCF-7 Cells
- Mitochondria/metabolism
- Mitochondria/pathology
- NADPH Oxidase 1/genetics
- NADPH Oxidase 1/metabolism
- Nitric Oxide Synthase Type III/genetics
- Nitric Oxide Synthase Type III/metabolism
- Ovarian Neoplasms/genetics
- Ovarian Neoplasms/metabolism
- Ovarian Neoplasms/pathology
- Oxidation-Reduction
- Oxidative Stress
- Phosphoprotein Phosphatases/genetics
- Phosphoprotein Phosphatases/metabolism
- Reactive Oxygen Species/metabolism
- Recombinational DNA Repair
- Signal Transduction
- Ubiquitin-Protein Ligases/genetics
- Ubiquitin-Protein Ligases/metabolism
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Affiliation(s)
- Aaron Wilson
- Department of Radiation Oncology, Massey Cancer Center, Virginia Commonwealth University, 401 College Street, Richmond, VA 23298, United States
| | - Vasily A Yakovlev
- Department of Radiation Oncology, Massey Cancer Center, Virginia Commonwealth University, 401 College Street, Richmond, VA 23298, United States.
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13
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Peroxynitrite: From interception to signaling. Arch Biochem Biophys 2016; 595:153-60. [PMID: 27095233 DOI: 10.1016/j.abb.2015.06.022] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 06/12/2015] [Indexed: 12/18/2022]
Abstract
Peroxynitrite is a strong oxidant and nitrating species that mediates certain biological effects of superoxide and nitrogen monoxide. These biological effects include oxidative damage to proteins as well as the formation of 3-nitrotyrosyl moieties in proteins. As a consequence, such proteins may lose their activity, gain altered function, or become prone to proteolytic degradation - resulting in modulation of cellular protein turnover and in the modulation of signaling cascades. In analogy to hydrogen peroxide, peroxynitrite may be scavenged by selenoproteins like glutathione peroxidase-1 (GPx-1) or by selenocompounds with a GPx-like activity, such as ebselen; in further analogy to H2O2, peroxiredoxins have also been established as contributors to peroxynitrite reduction. This review covers three aspects of peroxynitrite biochemistry, (i) the interaction of selenocompounds/-proteins with peroxynitrite, (ii) peroxynitrite-induced modulation of cellular proteolysis, and (iii) peroxynitrite-induced modulation of cellular signaling.
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14
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Abstract
SIGNIFICANCE Breast cancer is a unique disease characterized by heterogeneous cell populations causing roadblocks in therapeutic medicine, owing to its complex etiology and primeval understanding of the biology behind its genesis, progression, and sustenance. Globocan statistics indicate over 1.7 million new breast cancer diagnoses in 2012, accounting for 25% of all cancer morbidities. RECENT ADVANCES Despite these dismal statistics, the introduction of molecular gene signature platforms, progressive therapeutic approaches in diagnosis, and management of breast cancer has led to more effective treatment strategies and control measures concurrent with an equally reassuring decline in the mortality rate. CRITICAL ISSUES However, an enormous body of research in this area is requisite as high mortality associated with metastatic and/or drug refractory tumors continues to present a therapeutic challenge. Despite advances in systemic chemotherapy, the median survival of patients harboring metastatic breast cancers continues to be below 2 years. FUTURE DIRECTIONS Hence, a massive effort to scrutinize and evaluate chemotherapeutics on the basis of the molecular classification of these cancers is undertaken with the objective to devise more attractive and feasible approaches to treat breast cancers and improve patients' quality of life. This review aims to summarize the current understanding of the biology of breast cancer as well as challenges faced in combating breast cancer, with special emphasis on the current battery of treatment strategies. We will also try and gain perspective from recent encounters on novel findings responsible for the progression and metastatic transformation of breast cancer cells in an endeavor to develop more targeted treatment options. Antioxid. Redox Signal. 25, 337-370.
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Affiliation(s)
- Deepika Raman
- 1 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore , Singapore, Singapore
| | - Chuan Han Jonathan Foo
- 2 NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , Singapore, Singapore
| | - Marie-Veronique Clement
- 2 NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , Singapore, Singapore .,3 Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore , Singapore, Singapore
| | - Shazib Pervaiz
- 1 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore , Singapore, Singapore .,2 NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , Singapore, Singapore .,4 National University Cancer Institute , NUHS, Singapore, Singapore .,5 School of Biomedical Sciences, Curtin University , Perth, Australia
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15
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Zhang X, Damacharla D, Ma D, Qi Y, Tagett R, Draghici S, Kowluru A, Yi Z. Quantitative proteomics reveals novel protein interaction partners of PP2A catalytic subunit in pancreatic β-cells. Mol Cell Endocrinol 2016; 424:1-11. [PMID: 26780722 PMCID: PMC4779412 DOI: 10.1016/j.mce.2016.01.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 12/15/2015] [Accepted: 01/07/2016] [Indexed: 12/19/2022]
Abstract
Protein phosphatase 2A (PP2A) is one of the major serine/threonine phosphatases. We hypothesize that PP2A regulates signaling cascades in pancreatic β-cells in the context of glucose-stimulated insulin secretion (GSIS). Using co-immunoprecipitation (co-IP) and tandem mass spectrometry, we globally identified the protein interaction partners of the PP2A catalytic subunit (PP2Ac) in insulin-secreting pancreatic β-cells. Among the 514 identified PP2Ac interaction partners, 476 were novel. This represents the first global view of PP2Ac protein-protein interactions caused by hyperglycemic conditions. Additionally, numerous PP2Ac partners were found involved in a variety of signaling pathways in the β-cell function, such as insulin secretion. Our data suggest that PP2A interacts with various signaling proteins necessary for physiological insulin secretion as well as signaling proteins known to regulate cell dysfunction and apoptosis in the pancreatic β-cells.
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Affiliation(s)
- Xiangmin Zhang
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, 48201, USA
| | - Divyasri Damacharla
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, 48201, USA
| | - Danjun Ma
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, 48201, USA
| | - Yue Qi
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, 48201, USA
| | - Rebecca Tagett
- Department of Computer Science, College of Engineering, Wayne State University, Detroit, MI, USA
| | - Sorin Draghici
- Department of Computer Science, College of Engineering, Wayne State University, Detroit, MI, USA
| | - Anjaneyulu Kowluru
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, 48201, USA; β-Cell Biochemistry Laboratory, John D. Dingell VA Medical Center, Detroit, MI, 48201, USA
| | - Zhengping Yi
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, 48201, USA.
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16
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Deng Y, Guo Y, Liu P, Zeng R, Ning Y, Pei G, Li Y, Chen M, Guo S, Li X, Han M, Xu G. Blocking protein phosphatase 2A signaling prevents endothelial-to-mesenchymal transition and renal fibrosis: a peptide-based drug therapy. Sci Rep 2016; 6:19821. [PMID: 26805394 PMCID: PMC4726189 DOI: 10.1038/srep19821] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 12/18/2015] [Indexed: 02/04/2023] Open
Abstract
Endothelial-to-mesenchymal transition (EndMT) contributes to the emergence of fibroblasts and plays a significant role in renal interstitial fibrosis. Protein phosphatase 2A (PP2A) is a major serine/threonine protein phosphatase in eukaryotic cells and regulates many signaling pathways. However, the significance of PP2A in EndMT is poorly understood. In present study, the role of PP2A in EndMT was evaluated. We demonstrated that PP2A activated in endothelial cells (EC) during their EndMT phenotype acquisition and in the mouse model of obstructive nephropathy (i.e., UUO). Inhibition of PP2A activity by its specific inhibitor prevented EC undergoing EndMT. Importantly, PP2A activation was dependent on tyrosine nitration at 127 in the catalytic subunit of PP2A (PP2Ac). Our renal-protective strategy was to block tyrosine127 nitration to inhibit PP2A activation by using a mimic peptide derived from PP2Ac conjugating a cell penetrating peptide (CPP: TAT), termed TAT-Y127WT. Pretreatment withTAT-Y127WT was able to prevent TGF-β1-induced EndMT. Administration of the peptide to UUO mice significantly ameliorated renal EndMT level, with preserved density of peritubular capillaries and reduction in extracellular matrix deposition. Taken together, these results suggest that inhibiting PP2Ac nitration using a mimic peptide is a potential preventive strategy for EndMT in renal fibrosis.
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Affiliation(s)
- Yuanjun Deng
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Yanyan Guo
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Ping Liu
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Rui Zeng
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Yong Ning
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Guangchang Pei
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Yueqiang Li
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Meixue Chen
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Shuiming Guo
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Xiaoqing Li
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Min Han
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Gang Xu
- Division of Nephrology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
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17
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Yabe R, Miura A, Usui T, Mudrak I, Ogris E, Ohama T, Sato K. Protein Phosphatase Methyl-Esterase PME-1 Protects Protein Phosphatase 2A from Ubiquitin/Proteasome Degradation. PLoS One 2015; 10:e0145226. [PMID: 26678046 PMCID: PMC4683032 DOI: 10.1371/journal.pone.0145226] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 12/01/2015] [Indexed: 11/30/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a conserved essential enzyme that is implicated as a tumor suppressor based on its central role in phosphorylation-dependent signaling pathways. Protein phosphatase methyl esterase (PME-1) catalyzes specifically the demethylation of the C-terminal Leu309 residue of PP2A catalytic subunit (PP2Ac). It has been shown that PME-1 affects the activity of PP2A by demethylating PP2Ac, but also by directly binding to the phosphatase active site, suggesting loss of PME-1 in cells would enhance PP2A activity. However, here we show that PME-1 knockout mouse embryonic fibroblasts (MEFs) exhibit lower PP2A activity than wild type MEFs. Loss of PME-1 enhanced poly-ubiquitination of PP2Ac and shortened the half-life of PP2Ac protein resulting in reduced PP2Ac levels. Chemical inhibition of PME-1 and rescue experiments with wild type and mutated PME-1 revealed methyl-esterase activity was necessary to maintain PP2Ac protein levels. Our data demonstrate that PME-1 methyl-esterase activity protects PP2Ac from ubiquitin/proteasome degradation.
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Affiliation(s)
- Ryotaro Yabe
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
| | - Akane Miura
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
| | - Tatsuya Usui
- Laboratory of Veterinary Toxicology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
| | - Ingrid Mudrak
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, 1030, Austria
| | - Egon Ogris
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, 1030, Austria
| | - Takashi Ohama
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
- * E-mail:
| | - Koichi Sato
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, 753–8515, Japan
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18
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Zhan X, Wang X, Desiderio DM. Mass spectrometry analysis of nitrotyrosine-containing proteins. MASS SPECTROMETRY REVIEWS 2015; 34:423-448. [PMID: 24318073 DOI: 10.1002/mas.21413] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 09/03/2013] [Accepted: 09/03/2013] [Indexed: 06/02/2023]
Abstract
Oxidative stress plays important roles in a wide range of diseases such as cancer, inflammatory disease, neurodegenerative disorders, etc. Tyrosine nitration in a protein is a chemically stable oxidative modification, and a marker of oxidative injuries. Mass spectrometry (MS) is a key technique to identify nitrotyrosine-containing proteins and nitrotyrosine sites in endogenous and synthetic nitroproteins and nitropeptides. However, in vivo nitrotyrosine-containing proteins occur with extreme low-abundance to severely challenge the use of MS to identify in vivo nitroproteins and nitrotyrosine sites. A preferential enrichment of nitroproteins and/or nitropeptides is necessary before MS analysis. Current enrichment methods include immuno-affinity techniques, chemical derivation of the nitro group plus target isolations, followed with tandem mass spectrometry analysis. This article reviews the MS techniques and pertinent before-MS enrichment techniques for the identification of nitrotyrosine-containing proteins. This article reviews future trends in the field of nitroproteomics, including quantitative nitroproteomics, systems biological networks of nitroproteins, and structural biology study of tyrosine nitration to completely clarify the biological functions of tyrosine nitration.
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Affiliation(s)
- Xianquan Zhan
- Key Laboratory of Cancer Proteomics of Chinese Ministry of Health, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan, 410008, P.R. China
- Hunan Engineering Laboratory for Structural Biology and Drug Design, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan, 410008, P.R. China
- State Local Joint Engineering Laboratory for Anticancer Drugs, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan, 410008, P.R. China
- The State Key Laboratory of Medical Genetics, Central South University, 88 Xiangya Road, Changsha, Hunan, 410008, P.R. China
| | - Xiaowei Wang
- Key Laboratory of Cancer Proteomics of Chinese Ministry of Health, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan, 410008, P.R. China
- Hunan Engineering Laboratory for Structural Biology and Drug Design, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan, 410008, P.R. China
- State Local Joint Engineering Laboratory for Anticancer Drugs, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan, 410008, P.R. China
| | - Dominic M Desiderio
- The Charles B. Stout Neuroscience Mass Spectrometry Laboratory, Department of Neurology, College of Medicine, University of Tennessee Health Science Center, 847 Monroe Avenue, Memphis, Tennessee, 38163
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19
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Ohama T. [Targeting PP2A inhibitors as a novel anti-cancer strategy
]. Nihon Yakurigaku Zasshi 2015; 145:293-8. [PMID: 26063151 DOI: 10.1254/fpj.145.293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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20
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Enjoji S, Yabe R, Fujiwara N, Tsuji S, Vitek MP, Mizuno T, Nakagawa T, Usui T, Ohama T, Sato K. The therapeutic effects of SET/I2PP2A inhibitors on canine melanoma. J Vet Med Sci 2015; 77:1451-6. [PMID: 26062569 PMCID: PMC4667663 DOI: 10.1292/jvms.15-0193] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Canine melanoma is one of the most important diseases in small animal medicine.
Protein phosphatase 2A (PP2A), a well conserved serine/threonine phosphatase, plays a
critical role as a tumor suppressor. SET/I2PP2A is an endogenous inhibitor for PP2A, which
directly binds to PP2A and suppresses its phosphatase activity. Elevated SET protein
levels have been reported to exacerbate human tumor progression. The role of SET in canine
melanoma, however, has not been understood. Here, we investigated the potential
therapeutic role for SET inhibitors in canine melanoma. The expression of SET protein was
observed in 6 canine melanoma cell lines. We used CMeC-1 cells (primary origin) and CMeC-2
cells (metastatic origin) to generate cell lines stably expressing SET-targeting shRNAs.
Knockdown of SET expression in CMeC-2, but not in CMeC-1, leads to decreased cell
proliferation, invasion and colony formation. Phosphorylation level of p70 S6 kinase was
decreased by SET knockdown in CMeC-2, suggesting the involvement of mTOR (mammalian target
of rapamycin)/p70 S6 kinase signaling. The SET inhibitors, OP449 and FTY720, more
effectively killed CMeC-2 than CMeC-1. We observed PP2A activation in CMeC-2 treated with
OP449 and FTY720. These results demonstrated the potential therapeutic application of SET
inhibitors for canine melanoma.
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Affiliation(s)
- Shuhei Enjoji
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan
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21
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Ser70 phosphorylation of Bcl-2 by selective tyrosine nitration of PP2A-B56δ stabilizes its antiapoptotic activity. Blood 2014; 124:2223-34. [DOI: 10.1182/blood-2014-03-563296] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Key Points
O2− modifies B56δ at Y289 to block the PP2A holoenzyme assembly. This results in S70 Bcl-2 phosphorylation and promotes tumor chemoresistance. Primary lymphomas with low SOD1 have high B56δ tyrosine nitration and S70pBcl-2.
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22
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Yabe R, Fujiwara N, Mizuno T, Usui T, Ohama T, Sato K. Characterization of SET/I2PP2A isoforms in dogs. J Vet Med Sci 2014; 76:1235-40. [PMID: 24897959 DOI: 10.1292/jvms.14-0209] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
SET is an endogenous protein phosphatase 2A (PP2A) inhibitor and is associated with a poor prognosis in human leukemia. Previously, we reported increased SET protein levels in canine lymphoma cell lines and the potential therapeutic application of SET antagonists in canine lymphoma. Here, we found that canine cells express several isoforms of the SET protein. We cloned 4 isoforms of SET, named SETα, β, γ and δ. Genomic BLAST showed that the SET genes are located on chromosomes X, 7, 1 and 8, respectively. An immunofluorescent study showed nuclear localization of SETα and β, and nuclear and cytosolic localization of SETγ and δ. We confirmed that SETα and β possess the ability to associate with PP2A. Our data reveal the existence of unique SET isoforms that should be taken into account in SET-targeting drug development studies in dogs.
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Affiliation(s)
- Ryotaro Yabe
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi 753-8515, Japan
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Abstract
SIGNIFICANCE Evidence is emerging that parenteral administration of high-dose vitamin C may warrant development as an adjuvant therapy for patients with sepsis. RECENT ADVANCES Sepsis increases risk of death and disability, but its treatment consists only of supportive therapies because no specific therapy is available. The characteristics of severe sepsis include ascorbate (reduced vitamin C) depletion, excessive protein nitration in microvascular endothelial cells, and microvascular dysfunction composed of refractive vasodilation, endothelial barrier dysfunction, and disseminated intravascular coagulation. Parenteral administration of ascorbate prevents or even reverses these pathological changes and thereby decreases hypotension, edema, multiorgan failure, and death in animal models of sepsis. CRITICAL ISSUES Dehydroascorbic acid appears to be as effective as ascorbate for protection against microvascular dysfunction, organ failure, and death when injected in sepsis models, but information about pharmacodynamics and safety in human subjects is only available for ascorbate. Although the plasma ascorbate concentration in critically ill and septic patients is normalized by repletion protocols that use high doses of parenteral ascorbate, and such doses are tolerated well by most healthy subjects, whether such large amounts of the vitamin trigger adverse effects in patients is uncertain. FUTURE DIRECTIONS Further study of sepsis models may determine if high concentrations of ascorbate in interstitial fluid have pro-oxidant and bacteriostatic actions that also modify disease progression. However, the ascorbate depletion observed in septic patients receiving standard care and the therapeutic mechanisms established in models are sufficient evidence to support clinical trials of parenteral ascorbate as an adjuvant therapy for sepsis.
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Affiliation(s)
- John X Wilson
- Department of Exercise and Nutrition Sciences, University at Buffalo , Buffalo, New York
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24
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The NO/ONOO-cycle as the central cause of heart failure. Int J Mol Sci 2013; 14:22274-330. [PMID: 24232452 PMCID: PMC3856065 DOI: 10.3390/ijms141122274] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 10/23/2013] [Accepted: 10/24/2013] [Indexed: 01/08/2023] Open
Abstract
The NO/ONOO-cycle is a primarily local, biochemical vicious cycle mechanism, centered on elevated peroxynitrite and oxidative stress, but also involving 10 additional elements: NF-κB, inflammatory cytokines, iNOS, nitric oxide (NO), superoxide, mitochondrial dysfunction (lowered energy charge, ATP), NMDA activity, intracellular Ca(2+), TRP receptors and tetrahydrobiopterin depletion. All 12 of these elements have causal roles in heart failure (HF) and each is linked through a total of 87 studies to specific correlates of HF. Two apparent causal factors of HF, RhoA and endothelin-1, each act as tissue-limited cycle elements. Nineteen stressors that initiate cases of HF, each act to raise multiple cycle elements, potentially initiating the cycle in this way. Different types of HF, left vs. right ventricular HF, with or without arrhythmia, etc., may differ from one another in the regions of the myocardium most impacted by the cycle. None of the elements of the cycle or the mechanisms linking them are original, but they collectively produce the robust nature of the NO/ONOO-cycle which creates a major challenge for treatment of HF or other proposed NO/ONOO-cycle diseases. Elevated peroxynitrite/NO ratio and consequent oxidative stress are essential to both HF and the NO/ONOO-cycle.
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FUJIWARA N, KAWASAKI H, YABE R, CHRISTENSEN DJ, VITEK MP, MIZUNO T, SATO K, OHAMA T. A Potential Therapeutic Application of SET/I2PP2A Inhibitor OP449 for Canine T-cell Lymphoma. J Vet Med Sci 2013; 75:349-54. [DOI: 10.1292/jvms.12-0366] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Nobuyuki FUJIWARA
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Japan
| | - Hideyoshi KAWASAKI
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Japan
| | - Ryotaro YABE
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Japan
| | - Dale J. CHRISTENSEN
- Department of Medicine (Hematology), Duke University, Durham, NC, U.S.A
- Oncotide Pharmaceuticals, Inc., Research Triangle Park, NC, U.S.A
| | - Michael P. VITEK
- Departments of Medicine (Neurology) and Neurobiology, Duke University, Durham, NC, U.S.A
| | - Takuya MIZUNO
- Laboratory of Veterinary Internal Medicine, Joint Faculty of Veterinary Medicine, Yamaguchi University, Japan
| | - Koichi SATO
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Japan
| | - Takashi OHAMA
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Japan
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26
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Bachi A, Dalle-Donne I, Scaloni A. Redox Proteomics: Chemical Principles, Methodological Approaches and Biological/Biomedical Promises. Chem Rev 2012. [DOI: 10.1021/cr300073p] [Citation(s) in RCA: 189] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Angela Bachi
- Biological Mass Spectrometry Unit, San Raffaele Scientific Institute, 20132 Milan, Italy
| | | | - Andrea Scaloni
- Proteomics & Mass Spectrometry Laboratory, ISPAAM, National Research Council, 80147 Naples, Italy
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Yakovlev VA. Nitric oxide-dependent downregulation of BRCA1 expression promotes genetic instability. Cancer Res 2012; 73:706-15. [PMID: 23108140 DOI: 10.1158/0008-5472.can-12-3270] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Elevated levels of nitric oxide (NO) and reactive nitrogen species (RNS) may link inflammation to the initiation, promotion, and progression of cancer. Traditionally, this link has been thought to be mediated by the effects of NO/RNS in generating DNA damage. However, this damage also stimulates DNA repair responses with subsequent blocks to cell proliferation and apoptosis, thereby preventing accumulation of NO/RNS-generated mutations. In addressing this conundrum, I describe here an alternative mechanism for understanding mutagenesis by NO/RNS. Moderate NO/RNS concentrations stimulated mutagenesis not directly by generating DNA damage but indirectly by modifying the activities of DNA repair and genome stability factors without affecting cell proliferation. NO/RNS at concentrations physiologically relevant to inflammation stimulated PP2A activity, leading to dephosphorylation of RBL2, its accumulation in the nucleus, and formation of RBL2/E2F4 complexes. RBL2/E2F4 formation in turn led to a shift in BRCA1 promoter occupancy from complexes containing activator E2F1 to complexes containing repressor E2F4, downregulating BRCA1 expression. By inhibiting BRCA1 expression, NO/RNS thereby reduces the ability of cells to repair DNA double-strand breaks through homologous recombination repair, increasing the involvement of error-prone nonhomologous end joining (NHEJ). In summary, NO/RNS stimulates genetic instability by inhibiting BRCA1 expression and shifting DNA repair from high fidelity to error-prone mechanisms.
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Affiliation(s)
- Vasily A Yakovlev
- Department of Radiation Oncology, Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
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28
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Homer CR, Kabi A, Marina-García N, Sreekumar A, Nesvizhskii AI, Nickerson KP, Chinnaiyan AM, Nuñez G, McDonald C. A dual role for receptor-interacting protein kinase 2 (RIP2) kinase activity in nucleotide-binding oligomerization domain 2 (NOD2)-dependent autophagy. J Biol Chem 2012; 287:25565-76. [PMID: 22665475 DOI: 10.1074/jbc.m111.326835] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Autophagy is triggered by the intracellular bacterial sensor NOD2 (nucleotide-binding, oligomerization domain 2) as an anti-bacterial response. Defects in autophagy have been implicated in Crohn's disease susceptibility. The molecular mechanisms of activation and regulation of this process by NOD2 are not well understood, with recent studies reporting conflicting requirements for RIP2 (receptor-interacting protein kinase 2) in autophagy induction. We examined the requirement of NOD2 signaling mediated by RIP2 for anti-bacterial autophagy induction and clearance of Salmonella typhimurium in the intestinal epithelial cell line HCT116. Our data demonstrate that NOD2 stimulates autophagy in a process dependent on RIP2 tyrosine kinase activity. Autophagy induction requires the activity of the mitogen-activated protein kinases MEKK4 and p38 but is independent of NFκB signaling. Activation of autophagy was inhibited by a PP2A phosphatase complex, which interacts with both NOD2 and RIP2. PP2A phosphatase activity inhibited NOD2-dependent autophagy but not activation of NFκB or p38. Upon stimulation of NOD2, the phosphatase activity of the PP2A complex is inhibited through tyrosine phosphorylation of the catalytic subunit in a process dependent on RIP2 activity. These findings demonstrate that RIP2 tyrosine kinase activity is not only required for NOD2-dependent autophagy but plays a dual role in this process. RIP2 both sends a positive autophagy signal through activation of p38 MAPK and relieves repression of autophagy mediated by the phosphatase PP2A.
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Affiliation(s)
- Craig R Homer
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
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29
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Zhou G, Kamenos G, Pendem S, Wilson JX, Wu F. Ascorbate protects against vascular leakage in cecal ligation and puncture-induced septic peritonitis. Am J Physiol Regul Integr Comp Physiol 2011; 302:R409-16. [PMID: 22116513 DOI: 10.1152/ajpregu.00153.2011] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Vascular leakage in multiple organs is a characteristic pathological change in sepsis. Our recent study revealed that ascorbate protects endothelial barrier function in microvascular endothelial cell monolayers through inhibiting serine/threonine protein phosphatase 2A (PP2A) activation (Han M, Pendem S, Teh SL, Sukumaran DK, Wu F, Wilson JX. Free Radic Biol Med 48: 128-135, 2010). The present study addressed the mechanism of protection by ascorbate against vascular leakage in cecal ligation and puncture (CLP)-induced septic peritonitis in mice. CLP caused NADPH oxidase activation and endothelial nitric oxide synthase (eNOS) uncoupling to produce superoxide, increased NO production by inducible NOS (iNOS) and neuronal NOS (nNOS) activity, and elevated 3-nitrotyrosine (a product of peroxynitrite) formation and PP2A activity in the hindlimb skeletal muscles at 12 h after CLP. The increase in PP2A activity was associated with decreased levels of phosphorylated serine and threonine in occludin, which was immunoprecipitated from freshly harvested endothelial cells of the septic skeletal muscles. Moreover, CLP increased the vascular permeability to fluorescent dextran and Evans blue dye in skeletal muscles. An intravenous bolus injection of ascorbate (200 mg/kg body wt), given 30 min prior to CLP, prevented eNOS uncoupling, attenuated the increases in iNOS and nNOS activity, decreased 3-nitrotyrosine formation and PP2A activity, preserved the phosphorylation state of occludin, and completely inhibited the vascular leakage of dextran and Evans blue. A delayed ascorbate injection, given 3 h after CLP, also prevented the vascular permeability increase. We conclude that ascorbate injection protects against vascular leakage in sepsis by sequentially inhibiting excessive production of NO and superoxide, formation of peroxynitrite, PP2A activation, and occludin dephosphorylation. Our study provides a scientific basis for injection of ascorbate as an adjunct treatment for vascular leakage in sepsis.
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Affiliation(s)
- Gang Zhou
- Dept. of Exercise and Nutrition Sciences, Univ. at Buffalo, Buffalo, NY 14214-8028, USA
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30
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Yakovlev VA, Mikkelsen RB. Protein tyrosine nitration in cellular signal transduction pathways. J Recept Signal Transduct Res 2010; 30:420-9. [PMID: 20843272 DOI: 10.3109/10799893.2010.513991] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
How specificity and reversibility in tyrosine nitration are defined biologically in cellular systems is poorly understood. As more investigations identify proteins involved in cell regulatory pathways in which only a small fraction of that protein pool is modified by nitration to affect cell function, the mechanisms of biological specificity and reversal should come into focus. In this review experimental evidence has been summarized to suggest that tyrosine nitration is a highly selective modification and under certain physiological conditions fulfills the criteria of a physiologically relevant signal. It can be specific, reversible, occurs on a physiological time scale, and, depending on a target, can result in either activation or inhibition.
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Affiliation(s)
- Vasily A Yakovlev
- Department of Radiation Oncology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, USA
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31
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Kilili GK, Kyriakis JM. Mammalian Ste20-like kinase (Mst2) indirectly supports Raf-1/ERK pathway activity via maintenance of protein phosphatase-2A catalytic subunit levels and consequent suppression of inhibitory Raf-1 phosphorylation. J Biol Chem 2010; 285:15076-15087. [PMID: 20212043 DOI: 10.1074/jbc.m109.078915] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many tumor suppressor proteins act to blunt the effects of mitogenic signaling pathways. Loss of function mutations in the merlin tumor suppressor underlie neurofibromatosis type 2 (NF2), a familial autosomal dominant cancer syndrome. Studies of Drosophila suggest that Hippo (hpo) is required for inhibition of cell proliferation mediated by dMer, the orthologue of human merlin. Mammalian sterile 20-like kinase-2 (Mst2) is a mammalian Hpo orthologue, and numerous studies implicate Mst2 as a tumor suppressor. Mst2 is negatively regulated by the proto-oncoprotein Raf-1 in a manner independent of the kinase activity of Raf-1. We sought to determine whether, in mammalian cells, merlin could positively regulate Mst2. We also sought to determine whether Mst2, in addition to being negatively regulated by Raf-1, might itself reciprocally regulate Raf-1. In contrast to findings from Drosophila, we find no evidence that mammalian merlin positively regulates mammalian Mst2. Instead, surprisingly, RNA interference silencing of Mst2 leads to elevated inhibitory phosphorylation of Raf-1 at Ser-259 and impaired Raf-1 kinase activity. Consequent to this, ERK pathway activation and cell proliferation are attenuated. Phosphatase-2A (PP2A) dephosphorylates Raf-1 Ser-259 in response to mitogens. Interestingly RNA interference silencing of Mst2 triggers a striking proteasome-dependent decrease in the levels of the catalytic subunit of PP2A (PP2A-C). A similar effect is achieved upon silencing of large tumor suppressor (LATS)-1 and LATS2, direct substrates of Mst2. Our studies reveal a more complex role for Mst2 than previously thought. The Mst2 --> LATS1/2 pathway, by maintaining PP2A-C levels, may, in some situations, positively affect mitogenic signaling.
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Affiliation(s)
- Geoffrey K Kilili
- Molecular Cardiology Research Institute, Tufts Medical Center, and the Department of Biochemistry, Tufts University Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts 02111
| | - John M Kyriakis
- Molecular Cardiology Research Institute, Tufts Medical Center, and the Department of Biochemistry, Tufts University Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts 02111.
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