1
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Wuerger LTD, Sprenger H, Krasikova K, Templin M, Stahl A, Herfurth UM, Sieg H, Braeuning A. A multi-omics approach to elucidate okadaic acid-induced changes in human HepaRG hepatocarcinoma cells. Arch Toxicol 2024:10.1007/s00204-024-03796-1. [PMID: 38832940 DOI: 10.1007/s00204-024-03796-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Accepted: 05/23/2024] [Indexed: 06/06/2024]
Abstract
Okadaic acid (OA), a prevalent marine biotoxin found in shellfish, is known for causing acute gastrointestinal symptoms. Despite its potential to reach the bloodstream and the liver, the hepatic effects of OA are not well understood, highlighting a significant research gap. This study aims to comprehensively elucidate the impact of OA on the liver by examining the transcriptome, proteome, and phosphoproteome alterations in human HepaRG liver cells exposed to non-cytotoxic OA concentrations. We employed an integrative multi-omics approach, encompassing RNA sequencing, shotgun proteomics, phosphoproteomics, and targeted DigiWest analysis. This enabled a detailed exploration of gene and protein expression changes, alongside phosphorylation patterns under OA treatment. The study reveals concentration- and time-dependent deregulation in gene and protein expression, with a significant down-regulation of xenobiotic and lipid metabolism pathways. Up-regulated pathways include actin crosslink formation and a deregulation of apoptotic pathways. Notably, our results revealed that OA, as a potent phosphatase inhibitor, induces alterations in actin filament organization. Phosphoproteomics data highlighted the importance of phosphorylation in enzyme activity regulation, particularly affecting proteins involved in the regulation of the cytoskeleton. OA's inhibition of PP2A further leads to various downstream effects, including alterations in protein translation and energy metabolism. This research expands the understanding of OA's systemic impact, emphasizing its role in modulating the phosphorylation landscape, which influences crucial cellular processes. The results underscore OA's multifaceted effects on the liver, particularly through PP2A inhibition, impacting xenobiotic metabolism, cytoskeletal dynamics, and energy homeostasis. These insights enhance our comprehension of OA's biological significance and potential health risks.
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Affiliation(s)
- Leonie T D Wuerger
- Department of Food Safety, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Heike Sprenger
- Department of Food Safety, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Ksenia Krasikova
- Department of Food Safety, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Markus Templin
- NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany
| | - Aaron Stahl
- NMI Natural and Medical Sciences Institute at the University Tübingen, Reutlingen, Germany
| | - Uta M Herfurth
- Department of Food Safety, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Holger Sieg
- Department of Food Safety, German Federal Institute for Risk Assessment, Berlin, Germany.
| | - Albert Braeuning
- Department of Food Safety, German Federal Institute for Risk Assessment, Berlin, Germany
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2
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Wuerger LT, Birkholz G, Oberemm A, Sieg H, Braeuning A. Proteomic analysis of hepatic effects of okadaic acid in HepaRG human liver cells. EXCLI JOURNAL 2023; 22:1135-1145. [PMID: 38054204 PMCID: PMC10694344 DOI: 10.17179/excli2023-6458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 10/18/2023] [Indexed: 12/07/2023]
Abstract
The marine biotoxin okadaic acid (OA) is produced by dinoflagellates and enters the human food chain by accumulating in the fatty tissue of filter-feeding shellfish. Consumption of highly contaminated shellfish can lead to diarrheic shellfish poisoning. However, apart from the acute effects in the intestine, OA can also provoke toxic effects in the liver, as it is able to pass the intestinal barrier into the blood stream. However, molecular details of OA-induced hepatotoxicity are still insufficiently characterized, and especially at the proteomic level data are scarce. In this study, we used human HepaRG liver cells and exposed them to non-cytotoxic OA concentrations for 24 hours. Global changes in protein expression were analyzed using 2-dimensional gel electrophoresis in combination with mass-spectrometric protein identification. The results constitute the first proteomic analysis of OA effects in human liver cells and indicate, amongst others, that OA affects the energy homeostasis, induces oxidative stress, and induces cytoskeletal changes.
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Affiliation(s)
- Leonie T.D. Wuerger
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Greta Birkholz
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Axel Oberemm
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Holger Sieg
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Albert Braeuning
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
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3
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Park SY, Kang JH, Jung HJ, Hwang JH, Chun HS, Yoon YS, Oh SH. Okadaic Acid Is at Least as Toxic as Dinophysistoxin-1 after Repeated Administration to Mice by Gavage. Toxins (Basel) 2023; 15:587. [PMID: 37888618 PMCID: PMC10611360 DOI: 10.3390/toxins15100587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/07/2023] [Accepted: 09/21/2023] [Indexed: 10/28/2023] Open
Abstract
Okadaic acid (OA) and its analogues cause diarrhetic shellfish poisoning (DSP) in humans, and risk assessments of these toxins require toxicity equivalency factors (TEFs), which represent the relative toxicities of analogues. However, no human death by DSP toxin has been reported, and its current TEF value is based on acute lethality. To properly reflect the symptoms of DSP, such as diarrhea without death, the chronic toxicity of DSP toxins at sublethal doses should be considered. In this study, we obtained acute oral LD50 values for OA and dinophysistoxin-1 (DTX-1) (1069 and 897 μg/kg, respectively) to set sublethal doses. Mice were treated with sublethal doses of OA and DTX-1 for 7 days. The mice lost body weight, and the disease activity index and intestinal crypt depths increased. Furthermore, these changes were more severe in OA-treated mice than in the DTX-1-treated mice. Strikingly, ascites was observed, and its severity was greater in mice treated with OA. Our findings suggest that OA is at least as toxic as DTX-1 after repeated oral administration at a low dose. This is the first study to compare repeated oral dosing of DSP toxins. Further sub-chronic and chronic studies are warranted to determine appropriate TEF values for DSP toxins.
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Affiliation(s)
- Se Yong Park
- Department of Anatomy and Cell Biology, College of Veterinary Medicine, Seoul National University, Seoul 08826, Republic of Korea;
| | - Ju-Hee Kang
- College of Pharmacy, Gachon University, Incheon 21963, Republic of Korea; (J.-H.K.); (H.J.J.); (J.H.H.)
| | - Hyun Jin Jung
- College of Pharmacy, Gachon University, Incheon 21963, Republic of Korea; (J.-H.K.); (H.J.J.); (J.H.H.)
| | - Jung Ho Hwang
- College of Pharmacy, Gachon University, Incheon 21963, Republic of Korea; (J.-H.K.); (H.J.J.); (J.H.H.)
| | - Hyang Sook Chun
- Food Toxicology Laboratory, School of Food Science and Technology, Chung-Ang University, Anseong 17546, Republic of Korea;
| | - Yeo Sung Yoon
- Department of Anatomy and Cell Biology, College of Veterinary Medicine, Seoul National University, Seoul 08826, Republic of Korea;
| | - Seung Hyun Oh
- College of Pharmacy, Gachon University, Incheon 21963, Republic of Korea; (J.-H.K.); (H.J.J.); (J.H.H.)
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4
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Wuerger LTD, Kudiabor F, Alarcan J, Templin M, Poetz O, Sieg H, Braeuning A. Okadaic Acid Activates JAK/STAT Signaling to Affect Xenobiotic Metabolism in HepaRG Cells. Cells 2023; 12:770. [PMID: 36899906 PMCID: PMC10000888 DOI: 10.3390/cells12050770] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 02/23/2023] [Accepted: 02/24/2023] [Indexed: 03/06/2023] Open
Abstract
Okadaic acid (OA) is a marine biotoxin that is produced by algae and accumulates in filter-feeding shellfish, through which it enters the human food chain, leading to diarrheic shellfish poisoning (DSP) after ingestion. Furthermore, additional effects of OA have been observed, such as cytotoxicity. Additionally, a strong downregulation of the expression of xenobiotic-metabolizing enzymes in the liver can be observed. The underlying mechanisms of this, however, remain to be examined. In this study, we investigated a possible underlying mechanism of the downregulation of cytochrome P450 (CYP) enzymes and the nuclear receptors pregnane X receptor (PXR) and retinoid-X-receptor alpha (RXRα) by OA through NF-κB and subsequent JAK/STAT activation in human HepaRG hepatocarcinoma cells. Our data suggest an activation of NF-κB signaling and subsequent expression and release of interleukins, which then activate JAK-dependent signaling and thus STAT3. Moreover, using the NF-κB inhibitors JSH-23 and Methysticin and the JAK inhibitors Decernotinib and Tofacitinib, we were also able to demonstrate a connection between OA-induced NF-κB and JAK signaling and the downregulation of CYP enzymes. Overall, we provide clear evidence that the effect of OA on the expression of CYP enzymes in HepaRG cells is regulated through NF-κB and subsequent JAK signaling.
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Affiliation(s)
- Leonie T. D. Wuerger
- Department of Food Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Felicia Kudiabor
- Department of Food Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Jimmy Alarcan
- Department of Food Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Markus Templin
- NMI Natural and Medical Sciences Institute, Markwiesenstraße 55, 72770 Reutlingen, Germany
| | - Oliver Poetz
- NMI Natural and Medical Sciences Institute, Markwiesenstraße 55, 72770 Reutlingen, Germany
- SIGNATOPE GmbH, Markwiesenstraße 55, 72770 Reutlingen, Germany
| | - Holger Sieg
- Department of Food Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Albert Braeuning
- Department of Food Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
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Wuerger LT, Hammer HS, Hofmann U, Kudiabor F, Sieg H, Braeuning A. Okadaic acid influences xenobiotic metabolism in HepaRG cells. EXCLI JOURNAL 2022; 21:1053-1065. [PMID: 36172076 PMCID: PMC9489895 DOI: 10.17179/excli2022-5033] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 07/28/2022] [Indexed: 11/10/2022]
Abstract
Okadaic acid (OA) is an algae-produced lipophilic marine biotoxin that accumulates in the fatty tissue of filter-feeding shellfish. Ingestion of contaminated shellfish leads to the diarrheic shellfish poisoning syndrome. Furthermore, several other effects of OA like genotoxicity, liver toxicity and tumor-promoting properties have been observed, probably linked to the phosphatase-inhibiting properties of the toxin. It has been shown that at high doses OA can disrupt the physical barrier of the intestinal epithelium. As the intestine and the liver do not only constitute a physical, but also a metabolic barrier against xenobiotic exposure, we here investigated the impact of OA on the expression of cytochrome P450 (CYP) enzymes and transporter proteins in human HepaRG cells liver cells in vitro at non-cytotoxic concentrations. The interplay of OA with known CYP inducers was also studied. Data show that the expression of various xenobiotic-metabolizing CYPs was downregulated after exposure to OA. Moreover, OA was able to counteract the activation of CYPs by their inducers. A number of transporters were also mainly downregulated. Overall, we demonstrate that OA has a significant effect on xenobiotic metabolism barrier in liver cells, highlighting the possibility for interactions of OA exposure with the metabolism of drugs and xenobiotics.
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Affiliation(s)
- Leonie T.D. Wuerger
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Helen S. Hammer
- SIGNATOPE GmbH, Markwiesenstraße 55, 72770 Reutlingen, Germany
| | - Ute Hofmann
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Auerbachstr. 112, 70376 Stuttgart, and University of Tübingen, 72074 Tübingen, Germany
| | - Felicia Kudiabor
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Holger Sieg
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany,*To whom correspondence should be addressed: Holger Sieg, German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany, E-mail:
| | - Albert Braeuning
- German Federal Institute for Risk Assessment, Department of Food Safety, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
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Dörner MF, Boknik P, Köpp F, Buchwalow IB, Neumann J, Gergs U. Mechanisms of Systolic Cardiac Dysfunction in PP2A, PP5 and PP2AxPP5 Double Transgenic Mice. Int J Mol Sci 2021; 22:ijms22179448. [PMID: 34502355 PMCID: PMC8431312 DOI: 10.3390/ijms22179448] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 08/26/2021] [Accepted: 08/26/2021] [Indexed: 12/15/2022] Open
Abstract
As part of our ongoing studies on the potential pathophysiological role of serine/threonine phosphatases (PP) in the mammalian heart, we have generated transgenic mice with cardiac muscle cell-specific overexpression of PP2Acα (PP2A) and PP5 (PP5). For further studies we crossbred PP2A and PP5 mice to obtain PP2AxPP5 double transgenic mice (PP2AxPP5, DT) and compared them with littermate wild-type mice (WT) serving as a control. The mortality of DT mice was greatly enhanced vs. other genotypes. Cardiac fibrosis was noted histologically and mRNA levels of collagen 1α, collagen 3α and fibronectin 1 were augmented in DT. DT and PP2A mice exhibited an increase in relative heart weight. The ejection fraction (EF) was reduced in PP2A and DT but while the EF of PP2A was nearly normalized after β-adrenergic stimulation by isoproterenol, it was almost unchanged in DT. Moreover, left atrial preparations from DT were less sensitive to isoproterenol treatment both under normoxic conditions and after hypoxia. In addition, levels of the hypertrophy markers atrial natriuretic peptide and B-type natriuretic peptide as well as the inflammation markers interleukin 6 and nuclear factor kappa B were increased in DT. PP2A enzyme activity was enhanced in PP2A vs. WT but similar to DT. This was accompanied by a reduced phosphorylation state of phospholamban at serine-16. Fittingly, the relaxation times in left atria from DT were prolonged. In summary, cardiac co-overexpression of PP2A and PP5 were detrimental to animal survival and cardiac function, and the mechanism may involve dephosphorylation of important regulatory proteins but also fibrosis and inflammation.
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Affiliation(s)
- Mara-Francine Dörner
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle, Germany; (M.-F.D.); (F.K.); (J.N.)
- Mibe GmbH Arzneimittel, D-06796 Brehna, Germany
| | - Peter Boknik
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Westfälische Wilhelms-Universität, D-48149 Münster, Germany;
| | - Friedrich Köpp
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle, Germany; (M.-F.D.); (F.K.); (J.N.)
| | - Igor B. Buchwalow
- Institute for Hematopathology, Fangdieckstr. 75a, D-22547 Hamburg, Germany;
| | - Joachim Neumann
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle, Germany; (M.-F.D.); (F.K.); (J.N.)
| | - Ulrich Gergs
- Institut für Pharmakologie und Toxikologie, Medizinische Fakultät, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle, Germany; (M.-F.D.); (F.K.); (J.N.)
- Correspondence: ; Tel.: +49-345-557-4093
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7
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Rivero-Rodríguez F, Díaz-Quintana A, Velázquez-Cruz A, González-Arzola K, Gavilan MP, Velázquez-Campoy A, Ríos RM, De la Rosa MA, Díaz-Moreno I. Inhibition of the PP2A activity by the histone chaperone ANP32B is long-range allosterically regulated by respiratory cytochrome c. Redox Biol 2021; 43:101967. [PMID: 33882408 PMCID: PMC8082267 DOI: 10.1016/j.redox.2021.101967] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/03/2021] [Accepted: 04/03/2021] [Indexed: 12/26/2022] Open
Abstract
Repair of injured DNA relies on nucleosome dismantling by histone chaperones and de-phosphorylation events carried out by Protein Phosphatase 2A (PP2A). Typical histone chaperones are the Acidic leucine-rich Nuclear Phosphoprotein 32 family (ANP32) members, e.g. ANP32A, which is also a well-known PP2A inhibitor (a.k.a. I1PP2A). Here we report the novel interaction between the endogenous family member B—so-called ANP32B—and endogenous cytochrome c in cells undergoing camptothecin-induced DNA damage. Soon after DNA lesions but prior to caspase cascade activation, the hemeprotein translocates to the nucleus to target the Low Complexity Acidic Region (LCAR) of ANP32B; in a similar way, our group recently reported that the hemeprotein targets the acidic domain of SET/Template Activating Factor-Iβ (SET/TAF-Iβ), which is another histone chaperone and PP2A inhibitor (a.k.a. I2PP2A). The nucleosome assembly activity of ANP32B is indeed unaffected by cytochrome c binding. Like ANP32A, ANP32B inhibits PP2A activity and is thus herein referred to as I3PP2A. Our data demonstrates that ANP32B-dependent inhibition of PP2A is regulated by respiratory cytochrome c, which induces long-distance allosteric changes in the structured N-terminal domain of ANP32B upon binding to the C-terminal LCAR. In agreement with the reported role of PP2A in the DNA damage response, we propose a model wherein cytochrome c is translocated from the mitochondria into the nucleus upon DNA damage to modulate PP2A activity via its interaction with ANP32B. Respiratory cytochrome c interacts with ANP32B under DNA damage in the nucleus. Cytochrome c binding to ANP32B LCAR restores ANP32B-mediated PP2A inhibition. Cytochrome c emerges as a DNA Damage Response regulator.
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Affiliation(s)
- Francisco Rivero-Rodríguez
- Institute for Chemical Research (IIQ), Scientific Research Centre "Isla de La Cartuja" (cicCartuja), University of Seville, CSIC, Avda. Américo Vespucio 49, Seville, 41092, Spain
| | - Antonio Díaz-Quintana
- Institute for Chemical Research (IIQ), Scientific Research Centre "Isla de La Cartuja" (cicCartuja), University of Seville, CSIC, Avda. Américo Vespucio 49, Seville, 41092, Spain
| | - Alejandro Velázquez-Cruz
- Institute for Chemical Research (IIQ), Scientific Research Centre "Isla de La Cartuja" (cicCartuja), University of Seville, CSIC, Avda. Américo Vespucio 49, Seville, 41092, Spain
| | - Katiuska González-Arzola
- Institute for Chemical Research (IIQ), Scientific Research Centre "Isla de La Cartuja" (cicCartuja), University of Seville, CSIC, Avda. Américo Vespucio 49, Seville, 41092, Spain
| | - Maria P Gavilan
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, University of Seville, CSIC, University Pablo de Olavide, Avda. Américo Vespucio 24, Seville, 41092, Spain
| | - Adrián Velázquez-Campoy
- Institute for Biocomputation and Physics of Complex Systems (BIFI), Joint Units IQFR-CSICBIFI,and GBsC-CSIC-BIFI, Universidad de Zaragoza, 50018, Zaragoza, Spain; Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009, Zaragoza, Spain; Instituto de Investigación Sanitaria de Aragón (IIS Aragon), Zaragoza, Spain; Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (CIBERehd), 28029, Madrid, Spain; Fundación ARAID, Gobierno de Aragón, 50018, Zaragoza, Spain
| | - Rosa M Ríos
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, University of Seville, CSIC, University Pablo de Olavide, Avda. Américo Vespucio 24, Seville, 41092, Spain
| | - Miguel A De la Rosa
- Institute for Chemical Research (IIQ), Scientific Research Centre "Isla de La Cartuja" (cicCartuja), University of Seville, CSIC, Avda. Américo Vespucio 49, Seville, 41092, Spain
| | - Irene Díaz-Moreno
- Institute for Chemical Research (IIQ), Scientific Research Centre "Isla de La Cartuja" (cicCartuja), University of Seville, CSIC, Avda. Américo Vespucio 49, Seville, 41092, Spain.
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8
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Wang J, Shen T, Zhu W, Dou L, Gu H, Zhang L, Yang Z, Chen H, Zhou Q, Sánchez ER, Field LJ, Mayo LD, Xie Z, Xiao D, Lin X, Shou W, Yong W. Protein phosphatase 5 and the tumor suppressor p53 down-regulate each other's activities in mice. J Biol Chem 2018; 293:18218-18229. [PMID: 30262665 DOI: 10.1074/jbc.ra118.004256] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 09/17/2018] [Indexed: 12/20/2022] Open
Abstract
Protein phosphatase 5 (PP5), a serine/threonine phosphatase, has a wide range of biological functions and exhibits elevated expression in tumor cells. We previously reported that pp5-deficient mice have altered ataxia-telangiectasia mutated (ATM)-mediated signaling and function. However, this regulation was likely indirect, as ATM is not a known PP5 substrate. In the current study, we found that pp5-deficient mice are hypersensitive to genotoxic stress. This hypersensitivity was associated with the marked up-regulation of the tumor suppressor tumor protein p53 and its downstream targets cyclin-dependent kinase inhibitor 1A (p21), MDM2 proto-oncogene (MDM2), and phosphatase and tensin homolog (PTEN) in pp5-deficient tissues and cells. These observations suggested that PP5 plays a role in regulating p53 stability and function. Experiments conducted with p53 +/- pp5 +/- or p53 +/- pp5 -/- mice revealed that complete loss of PP5 reduces tumorigenesis in the p53 +/- mice. Biochemical analyses further revealed that PP5 directly interacts with and dephosphorylates p53 at multiple serine/threonine residues, resulting in inhibition of p53-mediated transcriptional activity. Interestingly, PP5 expression was significantly up-regulated in p53-deficient cells, and further analysis of pp5 promoter activity revealed that p53 strongly represses PP5 transcription. Our results suggest a reciprocal regulatory interplay between PP5 and p53, providing an important feedback mechanism for the cellular response to genotoxic stress.
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Affiliation(s)
- Jun Wang
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China,; School of Life Sciences, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Tao Shen
- DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas 77030
| | - Wuqiang Zhu
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Longyu Dou
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China
| | - Hao Gu
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China
| | - Lingling Zhang
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China
| | - Zhenyun Yang
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Hanying Chen
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Qi Zhou
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Edwin R Sánchez
- Department of Physiology and Pharmacology, College of Medicine, University of Toledo, Toledo, Ohio 43614, and
| | - Loren J Field
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Lindsey D Mayo
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Zhongwen Xie
- School of Life Sciences, Anhui Agricultural University, Hefei, Anhui 230036, China
| | - Deyong Xiao
- Fountain Valley Institute of Life Sciences and Fountain Valley Biomedical Technology Company, Dalian Hi-Tech Industrial Zone, Dalian 116023, China
| | - Xia Lin
- DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas 77030
| | - Weinian Shou
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202,.
| | - Weidong Yong
- From the Comparative Medical Center, Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing 100021, China,; Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202,.
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9
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Wu M, Yu G, Yan T, Ke D, Wang Q, Liu R, Wang JZ, Zhang B, Chen D, Wang X. Phosphorylation of SET mediates apoptosis via P53 hyperactivation and NM23-H1 nuclear import. Neurobiol Aging 2018; 69:38-47. [PMID: 29852409 DOI: 10.1016/j.neurobiolaging.2018.04.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Revised: 04/12/2018] [Accepted: 04/27/2018] [Indexed: 01/22/2023]
Abstract
Apoptosis plays an important role in neuron loss in Alzheimer's disease (AD). SET, an endogenous inhibitor of protein phosphatase-2A, is phosphorylated in AD brains and positively correlates with cell apoptosis. However, the mechanism underlying phosphorylated SET association with apoptosis remains unknown. Here, we show that mimetic phosphorylation of SET (S9E) induced apoptosis of primary cultured neurons. To investigate its mechanism, we overexpressed SET (S9E) in HEK293/tau cells and observed apoptosis accompanied with a marked increase of cleaved caspase-3 and cytoplasmic SET (S9E) retention with enhanced protein phosphatase-2A inhibition, which subsequently caused p53 hyperphosphorylation and activation. In addition, it caused the release of nucleoside diphosphate kinase A isoform a, a positive regulator of p53 with a DNase activity from SET/nucleoside diphosphate kinase A isoform a complex, and migration into the nucleus, resulting in DNA damage. Besides, it reduced nuclear tau accumulation leading to DNA protection deficiency. These findings suggest that SET phosphorylation is involved in the neuronal apoptotic pathway in AD and provide a new insight into the mechanism of this pathology.
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Affiliation(s)
- Mengjuan Wu
- Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Guang Yu
- Experimental Medicine Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Tonghai Yan
- Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Dan Ke
- Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qun Wang
- Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Rong Liu
- Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jian-Zhi Wang
- Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Bin Zhang
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Dan Chen
- School of Public Health, Wuhan University of Science and Technology, Wuhan, China
| | - Xiaochuan Wang
- Department of Pathophysiology, School of Basic Medicine, Key Laboratory of Education Ministry of China for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China.
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10
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Microcystin-LR induces anoikis resistance to the hepatocyte uptake transporter OATP1B3-expressing cell lines. Toxicology 2014; 326:53-61. [DOI: 10.1016/j.tox.2014.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 10/05/2014] [Accepted: 10/06/2014] [Indexed: 11/22/2022]
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11
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Fan YL, Chen L, Wang J, Yao Q, Wan JQ. Over expression of PPP2R2C inhibits human glioma cells growth through the suppression of mTOR pathway. FEBS Lett 2013; 587:3892-7. [PMID: 24126060 DOI: 10.1016/j.febslet.2013.09.029] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 08/28/2013] [Accepted: 09/17/2013] [Indexed: 11/29/2022]
Abstract
PPP2R2C encodes a gamma isoform of the subunit B55 subfamily, which is a regulatory subunit of Protein phosphatase type 2A (PP2A). Our study shows that PPP2R2C is downregulated in glioma cells and human brain cancer patient samples. Overexpression of PPP2R2C inhibited cancer cell proliferation both in vitro and in vivo through the suppression of the activity of S6K in the mTOR pathway. Moreover, exogenous expression of PPP2R2C promoted the formation of a complex with the PP2A-C subunit to further enhance the binding of PP2A-C with S6K. Our results suggest that PPP2R2C is a potential tumor suppressor gene in human brain cancers. This study will provide novel insight into the development of therapeutic strategies in the treatment of human brain tumors.
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Affiliation(s)
- Yi-Ling Fan
- Department of Neurosurgery, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai 200127, China
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12
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Martin L, Latypova X, Wilson CM, Magnaudeix A, Perrin ML, Terro F. Tau protein phosphatases in Alzheimer's disease: the leading role of PP2A. Ageing Res Rev 2013; 12:39-49. [PMID: 22771380 DOI: 10.1016/j.arr.2012.06.008] [Citation(s) in RCA: 160] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 06/28/2012] [Indexed: 12/21/2022]
Abstract
Tau phosphorylation is regulated by a balance between tau kinase and phosphatase activities. Disruption of this equilibrium was suggested to be at the origin of abnormal tau phosphorylation and thereby that might contributes to tau aggregation. Thus, understanding the regulation modes of tau dephosphorylation is of high interest in determining the possible causes at the origin of the formation of tau aggregates and to elaborate protection strategies to cope with these lesions in AD. Among the possible and relatively specific interventions that reverse tau phosphorylation is the stimulation of certain tau phosphatases. Here, we reviewed tau protein phosphatases, their physiological roles and regulation, their involvement in tau phosphorylation and the relevance to AD. We also reviewed the most common compounds acting on each tau phosphatase including PP2A.
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Affiliation(s)
- Ludovic Martin
- Groupe de Neurobiologie Cellulaire, Homéostasie cellulaire et pathologies, Faculté de Médecine, Limoges, France.
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13
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Guo L, Liew HP, Camus S, Goh AM, Chee LL, Lunny DP, Lane EB, Lane DP. Ionizing radiation induces a dramatic persistence of p53 protein accumulation and DNA damage signaling in mutant p53 zebrafish. Oncogene 2012; 32:4009-16. [PMID: 23069659 DOI: 10.1038/onc.2012.409] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 06/28/2012] [Accepted: 07/23/2012] [Indexed: 12/14/2022]
Abstract
Mutant p53 proteins accumulate to high levels in human tumors and in preneoplastic lesions in the skin and fallopian tube. However examination of tissues from mice and fish that are homozygous for mutant p53 surprisingly showed that the protein was present only at low levels except in the tumors that arose in these animals. The mutant protein did accumulate, however, following treatment with ionizing radiation in the same tissues in which the wild-type protein is induced. Here we study in detail the accumulation of mutant and wild-type p53 proteins following ionizing radiation in zebrafish embryos. We found that the mutant protein was induced by lower levels of radiation and reached higher levels than the wild-type protein. Morpholino knockdown of the zebrafish homologs of Mdm2 and Mdm4 caused dramatic accumulation of mutant p53 protein. The most remarkable results were observed by examining p53 protein levels over an extended time course. Mutant p53 protein increased and persisted for days after irradiation and this was accompanied by persistent elevation of phosphorylated H2AX (γH2AX), implying that the resolution of DNA damage signaling in these embryos is severely compromised by mutations in p53. Thus mutation in p53 results in an exaggerated and persistent damage response, which could in turn drive the process of cancer development as high levels of mutant p53 can act as an oncoprotein to drive invasion and metastasis.
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Affiliation(s)
- L Guo
- p53 Laboratory, Biomedical Science Institutes, Singapore
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14
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Freeman AK, Monteiro AN. Phosphatases in the cellular response to DNA damage. Cell Commun Signal 2010; 8:27. [PMID: 20860841 PMCID: PMC2954851 DOI: 10.1186/1478-811x-8-27] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 09/22/2010] [Indexed: 12/11/2022] Open
Abstract
In the last fifteen years, rapid progress has been made in delineating the cellular response to DNA damage. The DNA damage response network is composed of a large number of proteins with different functions that detect and signal the presence of DNA damage in order to coordinate DNA repair with a variety of cellular processes, notably cell cycle progression. This signal, which radiates from the chromatin template, is driven primarily by phosphorylation events, mainly on serine and threonine residues. While we have accumulated detailed information about kinases and their substrates our understanding of the role of phosphatases in the DNA damage response is still preliminary. Identifying the phosphatases and their regulation will be instrumental to obtain a complete picture of the dynamics of the DNA damage response. Here we give an overview of the DNA damage response in mammalian cells and then review the data on the role of different phosphatases and discuss their biological relevance.
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Affiliation(s)
- Alyson K Freeman
- Risk Assessment, Detection, and Intervention Program, H, Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, 33612, USA.
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15
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Takumi S, Komatsu M, Furukawa T, Ikeda R, Sumizawa T, Akenaga H, Maeda Y, Aoyama K, Arizono K, Ando S, Takeuchi T. p53 Plays an important role in cell fate determination after exposure to microcystin-LR. ENVIRONMENTAL HEALTH PERSPECTIVES 2010; 118:1292-8. [PMID: 20421190 PMCID: PMC2944092 DOI: 10.1289/ehp.1001899] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Accepted: 04/26/2010] [Indexed: 05/03/2023]
Abstract
BACKGROUND Microcystin-LR, a cyclic heptapeptide, possesses the ability to inhibit the serine/threonine protein phosphatases PP1 and PP2A and, consequently, exhibits acute hepatocytotoxicity. Moreover, microcystin-LR induces cellular proliferation, resulting in tumor-promoting activity in hepatocytes. However, mechanisms that regulate the balance between cell death and proliferation after microcystin-LR treatment remain unclear. OBJECTIVE We examined the contribution of the transcription factor p53, as well as that of the hepatic uptake transporter for microcystin-LR, organic anion transporting polypeptide 1B3 (OATP1B3), to the cellular response to microcystin-LR exposure. METHODS We analyzed intracellular signaling responses to microcystin-LR by immunoblotting and real-time reverse-transcriptase polymerase chain reaction techniques using HEK293 human embryonic kidney cells stably transfected with SLCO1B3 (HEK293-OATP1B3). In addition, we analyzed the effect of attenuation of p53 function, via the p53 inhibitor pifithrin-alpha, and knockdown of p53 mRNA on the cytotoxicity of microcystin-LR using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS Microcystin-LR induced the phosphorylation and accumulation of p53 in HEK293-OATP1B3 cells, which resulted in up-regulation of the expression of p53 transcript targets, including p21 and seven in absentia homolog 1 (siah-1). In addition, microcystin-LR activated Akt signaling through the phosphorylation of Akt and glycogen synthase kinase 3beta. Although Akt signaling was activated, the accumulation of p53 led cells to apoptosis after treatment with 50 nM microcystin-LR for 24 hr. Both pharmacological inhibition of transcription factor activity of p53 by pifithrin-alpha and knockdown of p53 with small hairpin RNA attenuated the susceptibility of HEK293-OATP1B3 cells to microcystin-LR. CONCLUSIONS This study demonstrates the importance of p53 in the regulation of cell fate after exposure to microcystin-LR. Our results suggest that, under conditions of p53 inactivation (including p53 mutation), chronic exposure to low doses of microcystin-LR may lead to cell proliferation through activation of Akt signaling. Results of this study may contribute to the development of chemoprevention and chemotherapeutic approaches to microcystin-LR poisoning.
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Affiliation(s)
- Shota Takumi
- Department of Environmental Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
- Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan
| | - Masaharu Komatsu
- Department of Environmental Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
- Department of Food and Chemical Biology, Faculty of Fisheries, Kagoshima University, Kagoshima, Japan
- Address correspondence to M. Komatsu, Department of Food and Chemical Biology, Faculty of Fisheries, Kagoshima University, 890-0056 Kagoshima, Japan. Telephone: 81-99-286-4200. Fax: 81-99-286-4200. E-mail:
| | | | - Ryuji Ikeda
- Department of Clinical Pharmacy and Pharmacology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Tomoyuki Sumizawa
- Department of Environmental Toxicology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Hitomi Akenaga
- Department of Food and Chemical Biology, Faculty of Fisheries, Kagoshima University, Kagoshima, Japan
| | - Yuta Maeda
- Department of Food and Chemical Biology, Faculty of Fisheries, Kagoshima University, Kagoshima, Japan
| | - Kohji Aoyama
- Department of Environmental Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Koji Arizono
- Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan
| | - Seiichi Ando
- Department of Food and Chemical Biology, Faculty of Fisheries, Kagoshima University, Kagoshima, Japan
| | - Toru Takeuchi
- Department of Environmental Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
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16
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Ham BM, Jayachandran H, Yang F, Jaitly N, Polpitiya AD, Monroe ME, Wang L, Zhao R, Purvine SO, Livesay EA, Camp DG, Rossie S, Smith RD. Novel Ser/Thr protein phosphatase 5 (PP5) regulated targets during DNA damage identified by proteomics analysis. J Proteome Res 2010; 9:945-53. [PMID: 20039704 DOI: 10.1021/pr9008207] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The DNA damage response likely includes a global phosphorylation signaling cascade process for sensing the damaged DNA condition and coordinating responses to cope with and repair the perturbed cellular state. We utilized a label-free liquid chromatography-mass spectrometry approach to evaluate changes in protein phosphorylation associated with PP5 activity during the DNA damage response. Biological replicate analyses of bleomycin-treated HeLa cells expressing either WT-PP5 or mutant inactive PP5 lead to the identification of six potential target proteins of PP5 action. Four of these putative targets have been previously reported to be involved in DNA damage responses. Using phospho-site specific antibodies, we confirmed that phosphorylation of one target, ribosomal protein S6, was selectively decreased in cells overexpressing catalytically inactive PP5. Our findings also suggest that PP5 may play a role in controlling translation and in regulating substrates for proline-directed kinases, such as MAP kinases and cyclin-dependent protein kinases that are involved in response to DNA damage.
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Affiliation(s)
- Bryan M Ham
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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17
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Comparison of gene expression profiles in BALB/c 3T3 transformed foci exposed to tumor promoting agents. Toxicol In Vitro 2010; 24:430-8. [DOI: 10.1016/j.tiv.2009.10.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Revised: 09/17/2009] [Accepted: 10/12/2009] [Indexed: 11/18/2022]
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18
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Chatterjee A, Wang L, Armstrong DL, Rossie S. Activated Rac1 GTPase translocates protein phosphatase 5 to the cell membrane and stimulates phosphatase activity in vitro. J Biol Chem 2009; 285:3872-3882. [PMID: 19948726 DOI: 10.1074/jbc.m109.088427] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Physiological studies of ion channel regulation have implicated the Ser/Thr protein phosphatase 5 (PP5) as an effector of Rac1 GTPase signaling, but direct biochemical evidence for PP5 regulation by Rac1 is lacking. In this study we used immunoprecipitation, in vitro binding, cellular fractionation, and immunofluorescence techniques to show that the tetratricopeptide repeat domain of PP5 interacts specifically and directly with active Rac1. Consequently, activation of Rac1 promoted PP5 translocation to the plasma membrane in intact cells and stimulated PP5 phosphatase activity in vitro. In contrast, neither constitutively active RhoA-V14 nor dominant negative Rac1N17, which preferentially binds GDP and retains an inactive conformation, bound PP5 or stimulated its activity. In addition, Rac1N17 and Rac1(PBRM), a mutant lacking the C-terminal polybasic region required for Rac1 association with the membrane, both failed to cause membrane translocation of PP5. Mutation of predicted contact residues in the PP5 tetratricopeptide repeat domain or within Rac1 also disrupted co-immunoprecipitation of Rac1-PP5 complexes and membrane translocation of PP5. Specific binding of PP5 to activated Rac1 provides a direct mechanism by which PP5 can be stimulated and recruited to participate in Rac1-mediated signaling pathways.
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Affiliation(s)
- Anindya Chatterjee
- From the Department of Biochemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907 and
| | - Ling Wang
- From the Department of Biochemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907 and
| | - David L Armstrong
- the Environmental Biology Program, NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709
| | - Sandra Rossie
- From the Department of Biochemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907 and.
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19
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Beghin A, Belin S, Sleiman RH, Brunet Manquat S, Goddard S, Tabone E, Jordheim LP, Treilleux I, Poupon MF, Diaz JJ, Dumontet C. ADP ribosylation factor like 2 (Arl2) regulates breast tumor aggressivity in immunodeficient mice. PLoS One 2009; 4:e7478. [PMID: 19829707 PMCID: PMC2759505 DOI: 10.1371/journal.pone.0007478] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 09/02/2009] [Indexed: 11/19/2022] Open
Abstract
We have previously reported that ADP ribosylation factor like 2 (Arl2), a small GTPase, content influences microtubule dynamics and cell cycle distribution in breast tumor cells, as well as the degree and distribution of phosphorylated P53. Here we show, in two different human breast adenocarcinoma models, that Arl2 content has a major impact on breast tumor cell aggressivity both in vitro and in vivo. Cells with reduced content of Arl2 displayed reduced contact inhibition, increased clonogenic or cluster formation as well as a proliferative advantage over control cells in an in vitro competition assay. These cells also caused larger tumors in SCID mice, a phenotype which was mimicked by the in vivo administration of siRNA directed against Arl2. Cells with increased Arl2 content displayed reduced aggressivity, both in vitro and in vivo, with enhanced necrosis and were also found to contain increased PP2A phosphatase activity. A rt-PCR analysis of fresh human tumor breast samples suggested that low Arl2 expression was associated with larger tumor size and greater risk of lymph node involvement at diagnosis. These data underline the role of Arl2, a small GTPase, as an important regulator of breast tumor cell aggressivity, both in vitro and in vivo.
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Affiliation(s)
- Anne Beghin
- Inserm, U590, Lyon, France
- Université Lyon 1, ISPB, Lyon, France
| | - Stéphane Belin
- CNRS, Centre de Génétique Moléculaire et Cellulaire, UMR 5534, Villeurbanne, France
| | | | | | - Sophie Goddard
- Centre Léon Bérard, Service Anatomie-Cytologie Pathologiques, Lyon, France
| | - Eric Tabone
- Centre Léon Bérard, Service Anatomie-Cytologie Pathologiques, Lyon, France
| | | | - Isabelle Treilleux
- Centre Léon Bérard, Service Anatomie-Cytologie Pathologiques, Lyon, France
| | | | - Jean-Jacques Diaz
- CNRS, Centre de Génétique Moléculaire et Cellulaire, UMR 5534, Villeurbanne, France
| | - Charles Dumontet
- Inserm, U590, Lyon, France
- Université Lyon 1, ISPB, Lyon, France
- * E-mail:
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20
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Sanchez-Ortiz E, Hahm BK, Armstrong DL, Rossie S. Protein phosphatase 5 protects neurons against amyloid-beta toxicity. J Neurochem 2009; 111:391-402. [PMID: 19686245 DOI: 10.1111/j.1471-4159.2009.06337.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amyloid-beta (Abeta) is thought to promote neuronal cell loss in Alzheimer's disease, in part through the generation of reactive oxygen species (ROS) and subsequent activation of mitogen-activated protein kinase (MAPK) pathways. Protein phosphatase 5 (PP5) is a ubiquitously expressed serine/threonine phosphatase which has been implicated in several cell stress response pathways and shown to inactivate MAPK pathways through key dephosphorylation events. Therefore, we examined whether PP5 protects dissociated embryonic rat cortical neurons in vitro from cell death evoked by Abeta. As predicted, neurons in which PP5 expression was decreased by small-interfering RNA treatment were more susceptible to Abeta toxicity. In contrast, over-expression of PP5, but not the inactive mutant, PP5(H304Q), prevented MAPK phosphorylation and neurotoxicity induced by Abeta. PP5 also prevented cell death caused by direct treatment with H(2)O(2), but did not prevent Abeta-induced production of ROS. Thus, the neuroprotective effect of PP5 requires its phosphatase activity and lies downstream of Abeta-induced generation of ROS. In summary, our data indicate that PP5 plays a pivotal neuroprotective role against cell death induced by Abeta and oxidative stress. Consequently, PP5 might be an effective therapeutic target in Alzheimer's disease and other neurodegenerative disorders in which oxidative stress is implicated.
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Affiliation(s)
- Efrain Sanchez-Ortiz
- Department of Biochemistry and Purdue Cancer Center, Purdue University, West Lafayette, Indiana 47907, USA
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21
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Abstract
BACKGROUND/AIMS Iron overload can cause liver toxicity and increase the risk of liver failure or hepatocellular carcinoma in humans. Curcumin (diferuloylmethane), a component of the food spice turmeric, has antioxidant, iron binding and hepatoprotective properties. The aim of this study was to quantify its effects on iron overload and the resulting downstream toxic effects in cultured T51B rat liver epithelial cells. METHODS T51B cells were loaded with ferric ammonium citrate (FAC) with or without the iron delivery agent 8-hydroxyquinoline. Cytotoxicity was measured by methylthiazolyldiphenyl-tetrazolium bromide assay. Iron uptake and iron bioavailability were documented by chemical assay, quench of calcein fluorescence and ferritin induction. Reactive oxygen species (ROS) were measured by a fluorescence assay using 2',7'-dichlorodihydrofluorescein diacetate. Oxidative stress signalling to jnk, c-jun and p38 was measured by a Western blot with phospho-specific antibodies. RESULTS Curcumin bound iron, but did not block iron uptake or bioavailability in T51B cells given FAC. However, it reduced cytotoxicity, blocked the generation of ROS and eliminated signalling to cellular stress pathways caused by iron. Inhibition was observed over a wide range of FAC concentrations (50-500 microM), with an apparent IC(50) in all cases between 5 and 10 microM curcumin. In contrast, desferoxamine blocked both iron uptake and toxic effects of iron at concentrations that depended on the FAC concentration. The effects of curcumin also differed from those of alpha-tocopherol, which did not bind iron and was less effective at blocking iron-stimulated ROS generation. CONCLUSIONS Curcumin reduced iron-dependent oxidative stress and iron toxicity in T51B cells without blocking iron uptake.
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Affiliation(s)
- Donald J. Messner
- Bastyr University, Kenmore WA, Benaroya Research Institute and Virginia Mason Medical Center, Seattle WA,Correspondence to Donald J. Messner, Address Bastyr University, 14500 Juanita Drive NE, Kenmore WA 98028, Phone (425) 602-3423, Fax (425) 602-3079, Email
| | | | - Kris V. Kowdley
- Benaroya Research Institute and Virginia Mason Medical Center, Seattle WA
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22
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Messner DJ, Kowdley KV. Neoplastic transformation of rat liver epithelial cells is enhanced by non-transferrin-bound iron. BMC Gastroenterol 2008; 8:2. [PMID: 18254965 PMCID: PMC2275280 DOI: 10.1186/1471-230x-8-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2007] [Accepted: 02/06/2008] [Indexed: 12/26/2022] Open
Abstract
Background Iron overload is associated with liver toxicity, cirrhosis, and hepatocellular carcinoma in humans. While most iron circulates in blood as transferrin-bound iron, non-transferrin-bound iron (NTBI) also becomes elevated and contributes to toxicity in the setting of iron overload. The mechanism for iron-related carcinogenesis is not well understood, in part due to a shortage of suitable experimental models. The primary aim of this study was to investigate NTBI-related hepatic carcinogenesis using T51B rat liver epithelial cells, a non-neoplastic cell line previously developed for carcinogenicity and tumor promotion studies. Methods T51B cells were loaded with iron by repeated addition of ferric ammonium citrate (FAC) to the culture medium. Iron internalization was documented by chemical assay, ferritin induction, and loss of calcein fluorescence. Proliferative effects were determined by cell count, toxicity was determined by MTT assay, and neoplastic transformation was assessed by measuring colony formation in soft agar. Cyclin levels were measured by western blot. Results T51B cells readily internalized NTBI given as FAC. Within 1 week of treatment at 200 μM, there were significant but well-tolerated toxic effects including a decrease in cell proliferation (30% decrease, p < 0.01). FAC alone induced little or no colony formation in soft agar. In contrast, FAC addition to cells previously initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) resulted in a concentration dependent increase in colony formation. This was first detected at 12 weeks of FAC treatment and increased at longer times. At 16 weeks, colony formation increased more than 10 fold in cells treated with 200 μM FAC (p < 0.001). The iron chelator desferoxamine reduced both iron uptake and colony formation. Cells cultured with 200 μM FAC showed decreased cyclin D1, decreased cyclin A, and increased cyclin B1. Conclusion These results establish NTBI as a tumor promoter in T51B rat liver epithelial cells. Changes in cyclin proteins suggest cell cycle disregulation contributes to tumor promotion by NTBI in this liver cell model.
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23
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Monks NR, Liu S, Xu Y, Yu H, Bendelow AS, Moscow JA. Potent cytotoxicity of the phosphatase inhibitor microcystin LR and microcystin analogues in OATP1B1- and OATP1B3-expressing HeLa cells. Mol Cancer Ther 2007; 6:587-98. [PMID: 17308056 DOI: 10.1158/1535-7163.mct-06-0500] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Microcystins are a family of cyclic peptides that are potent inhibitors of the protein phosphatase families PP1 and PP2A. Only three human proteins are thought to be able to mediate the hepatic uptake of microcystins (the organic anion-transporting polypeptides OATP1B1, OATP1B3, and OATP1A2), and the predominant hepatic expression of these transporters accounts for the liver-specific toxicity of microcystins. A significant obstacle in the study of microcystins as anticancer drugs is the requirement of specific transport proteins for cellular uptake. We report that OATP1B3 mRNA is up-regulated in non-small cell lung cancer tumors in comparison with normal control tissues. This finding led to the exploration of microcystins as potential anticancer agents. We have developed a HeLa cell model with functional OATP1B1 and OATP1B3 activity. Transiently transfected HeLa cells are over 1,000-fold more sensitive to microcystin LR than the vector-transfected control cells, showing that transporter expression imparts marked selectivity for microcystin cytotoxicity. In addition, microcystin analogues showed variable cytotoxicities in the OATP1B1- and OATP1B3-transfected cells, including two analogues with IC(50) values <1 nmol/L. Cytotoxicity of microcystin analogues seems to correlate to the inhibition of PP2A in these cells and induces rapid cell death as seen by chromatin condensation and cell fragmentation. These studies show that microcystin-induced phosphatase inhibition results in potent cytotoxicity when microcystin compounds can gain intracellular access and are a potent novel class of therapeutic agents for tumors expressing these uptake proteins.
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Affiliation(s)
- Noel R Monks
- Department of Pediatrics, University of Kentucky, Room J457, 740 S. Limestone, Lexington, KY 40502, USA.
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24
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Chung CY, Koprich JB, Endo S, Isacson O. An endogenous serine/threonine protein phosphatase inhibitor, G-substrate, reduces vulnerability in models of Parkinson's disease. J Neurosci 2007; 27:8314-23. [PMID: 17670978 PMCID: PMC2074880 DOI: 10.1523/jneurosci.1972-07.2007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Relative neuronal vulnerability is a universal yet poorly understood feature of neurodegenerative diseases. In Parkinson's disease, dopaminergic (DA) neurons in the substantia nigra (SN) (A9) are particularly vulnerable, whereas adjacent DA neurons within the ventral tegmental area (A10) are essentially spared. Our previous laser capture microdissection and microarray study (Chung et al., 2005) demonstrated that molecular differences between these DA neurons may underlie their differential vulnerability. Here we show that G-substrate, an endogenous inhibitor of Ser/Thr protein phosphatases, exhibits higher expression in A10 compared with A9 DA neurons in both rodent and human midbrain. Overexpression of G-substrate protected dopaminergic BE(2)-M17 cells against toxins, including 6-OHDA and MG-132 (carbobenzoxy-L-leucyl- L-leucyl-L-leucinal), whereas RNA interference (RNAi)-mediated knockdown of endogenous G-substrate increased their vulnerability to these toxins. G-substrate reduced 6-OHDA-mediated protein phosphatase 2A (PP2A) activation in vitro and increased phosphorylated levels of PP2A targets including Akt, glycogen synthase kinase 3beta, and extracellular signal-regulated kinase 2 but not p38. RNAi to Akt diminished the protective effect of G-substrate against 6-OHDA. In vivo, lentiviral delivery of G-substrate to the rat SN increased baseline levels of phosphorylated Akt and protected A9 DA neurons from 6-OHDA-induced toxicity. These results suggest that inherent differences in the levels of G-substrate contribute to the differential vulnerability of DA neurons and that enhancing G-substrate levels may be a neuroprotective strategy for the vulnerable A9 (SN) DA neurons in Parkinson's disease.
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Affiliation(s)
- Chee Yeun Chung
- Neuroregeneration Laboratories, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
- Harvard Center for Neurodegeneration and Repair, Boston, Massachusetts 02114
- Udall Parkinson's Disease Research Center of Excellence, McLean Hospital and Harvard University, Belmont, Massachusetts 02478
| | - James B. Koprich
- Neuroregeneration Laboratories, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
- Harvard Center for Neurodegeneration and Repair, Boston, Massachusetts 02114
- Udall Parkinson's Disease Research Center of Excellence, McLean Hospital and Harvard University, Belmont, Massachusetts 02478
| | - Shogo Endo
- Okinawa Institute of Science and Technology, Okinawa 904-2234, Japan, and
| | - Ole Isacson
- Neuroregeneration Laboratories, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478
- Harvard Center for Neurodegeneration and Repair, Boston, Massachusetts 02114
- Udall Parkinson's Disease Research Center of Excellence, McLean Hospital and Harvard University, Belmont, Massachusetts 02478
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