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Hassan M, Yasir M, Shahzadi S, Chun W, Kloczkowski A. Molecular Role of Protein Phosphatases in Alzheimer's and Other Neurodegenerative Diseases. Biomedicines 2024; 12:1097. [PMID: 38791058 PMCID: PMC11117500 DOI: 10.3390/biomedicines12051097] [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: 03/22/2024] [Revised: 05/02/2024] [Accepted: 05/14/2024] [Indexed: 05/26/2024] Open
Abstract
Alzheimer's disease (AD) is distinguished by the gradual loss of cognitive function, which is associated with neuronal loss and death. Accumulating evidence supports that protein phosphatases (PPs; PP1, PP2A, PP2B, PP4, PP5, PP6, and PP7) are directly linked with amyloid beta (Aβ) as well as the formation of the neurofibrillary tangles (NFTs) causing AD. Published data reported lower PP1 and PP2A activity in both gray and white matters in AD brains than in the controls, which clearly shows that dysfunctional phosphatases play a significant role in AD. Moreover, PP2A is also a major causing factor of AD through the deregulation of the tau protein. Here, we review recent advances on the role of protein phosphatases in the pathology of AD and other neurodegenerative diseases. A better understanding of this problem may lead to the development of phosphatase-targeted therapies for neurodegenerative disorders in the near future.
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Affiliation(s)
- Mubashir Hassan
- The Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children’s Hospital, Columbus, OH 43205, USA;
| | - Muhammad Yasir
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (M.Y.); (W.C.)
| | - Saba Shahzadi
- The Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children’s Hospital, Columbus, OH 43205, USA;
| | - Wanjoo Chun
- Department of Pharmacology, Kangwon National University School of Medicine, Chuncheon 24341, Republic of Korea; (M.Y.); (W.C.)
| | - Andrzej Kloczkowski
- The Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children’s Hospital, Columbus, OH 43205, USA;
- Department of Pediatrics, The Ohio State University, Columbus, OH 43205, USA
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH 43210, USA
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Ke W, Zhou Y, Lai Y, Long S, Fang L, Xiao S. Porcine reproductive and respiratory syndrome virus nsp4 positively regulates cellular cholesterol to inhibit type I interferon production. Redox Biol 2021; 49:102207. [PMID: 34911669 PMCID: PMC8758914 DOI: 10.1016/j.redox.2021.102207] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 11/26/2021] [Accepted: 12/07/2021] [Indexed: 02/07/2023] Open
Abstract
Cellular cholesterol plays an important role in the life cycles of enveloped viruses. Previous studies by our group and other groups have demonstrated that the depletion of cellular cholesterol by methyl-β-cyclodextrin (MβCD) reduces the proliferation of porcine reproductive and respiratory syndrome virus (PRRSV), a porcine Arterivirus that has been devastating the swine industry worldwide for over two decades. However, how PRRSV infection regulates cholesterol synthesis is not fully understood. In this study, we showed that PRRSV infection upregulated the activity of protein phosphatase 2 (PP2A), which subsequently activated 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), the rate-limiting enzyme in the cholesterol synthesis pathway, to increase the levels of cellular cholesterol. By screening the PRRSV-encoded proteins, we showed that nsp4 dominated the upregulation of cellular cholesterol, independently of the 3C-like protease activity of nsp4. A mutation analysis showed that domain I (amino acids 1–80) of PRRSV nsp4 interacted with PR65 alpha (PR65α), the structural subunit, and PP2Ac, the catalytic subunit, of PP2A. Importantly, domain I of nsp4 inhibited Sendai virus-induced interferon β production, and this inhibitory effect was eliminated by Lovastatin, an HMGCR inhibitor, indicating that the upregulation of cellular cholesterol by nsp4 is a strategy used by PRRSV to suppress the antiviral innate immunity of its host. Collectively, we here demonstrated the mechanism by which PRRSV regulates cellular cholesterol synthesis and reported a novel strategy by which PRRSV evades its host's antiviral innate immune response. PRRSV nsp4 up-regulates cellular cholesterol via the PP2A-HMGCR pathway. Nsp4 domain I (amino acids 1–80) interacts with A and C subunits of PP2A. Nsp4 domain I inhibits IFN-I production by upregulating cellular cholesterol. The HMGCR inhibitor Lovastatin inhibits PRRSV proliferation.
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Affiliation(s)
- Wenting Ke
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; The Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Yanrong Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; The Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Yinan Lai
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; The Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Siwen Long
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; The Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Liurong Fang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; The Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China.
| | - Shaobo Xiao
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; The Key Laboratory of Preventive Veterinary Medicine in Hubei Province, Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China.
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Schuhmacher D, Sontag JM, Sontag E. Protein Phosphatase 2A: More Than a Passenger in the Regulation of Epithelial Cell-Cell Junctions. Front Cell Dev Biol 2019; 7:30. [PMID: 30895176 PMCID: PMC6414416 DOI: 10.3389/fcell.2019.00030] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 02/22/2019] [Indexed: 12/17/2022] Open
Abstract
Cell–cell adhesion plays a key role in the maintenance of the epithelial barrier and apicobasal cell polarity, which is crucial for homeostasis. Disruption of cell–cell adhesion is a hallmark of numerous pathological conditions, including invasive carcinomas. Adhesion between apposing cells is primarily regulated by three types of junctional structures: desmosomes, adherens junctions, and tight junctions. Cell junctional structures are highly regulated multiprotein complexes that also serve as signaling platforms to control epithelial cell function. The biogenesis, integrity, and stability of cell junctions is controlled by complex regulatory interactions with cytoskeletal and polarity proteins, as well as modulation of key component proteins by phosphorylation/dephosphorylation processes. Not surprisingly, many essential signaling molecules, including protein Ser/Thr phosphatase 2A (PP2A) are associated with intercellular junctions. Here, we examine how major PP2A enzymes regulate epithelial cell–cell junctions, either directly by associating with and dephosphorylating component proteins, or indirectly by affecting signaling pathways that control junctional integrity and cytoskeletal dynamics. PP2A deregulation has severe consequences on the stability and functionality of these structures, and disruption of cell–cell adhesion and cell polarity likely contribute to the link between PP2A dysfunction and human carcinomas.
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Affiliation(s)
- Diana Schuhmacher
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia
| | - Jean-Marie Sontag
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - Estelle Sontag
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
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Abstract
Small viral proteins with cationic domains can be involved in multiple biological processes including cell penetration or interaction with intracellular targets. Within the last two decades several reports indicated that the C-terminus of HIV-1 Vpr is a cell penetrating sequence, a PP2A-dependent death domain and also displays toxicity against Gram-negative E. coli. Interestingly, HIV-1 Vpr, as well as some cationic proteins encoded by different viruses, share similar physical properties with the unique anti-microbial human cathelicidin LL37 peptide. Consistent with these observations, the Viral Quinta Columna Hypothesis predicts that virally-encoded cationic peptides encoded by multiple viruses may at the same time i) behave as new cathelicidin-like viral positive effectors of innate immunity, mainly through electrostatic interactions with microbial walls, and also display specific toxic cellular effects through interactions with specific intracellular targets such as PP2A proteins. In this context, virally-encoded cationic peptides, potentially detectable in biological fluids, may define a new paradigm for a viral control of homeostasis. Finally, we can also predict that characterization of virally encoded sequences with anti-infective effects may serve as template for the design of new efficient therapeutics polypeptides.
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Affiliation(s)
- Alphonse Garcia
- Laboratoire E3 Phosphatases, Unité RMN, Institut Pasteur, 25 rue du Dr. Roux, 75015 Paris, France.
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Chiang HS, Zhao Y, Song JH, Liu S, Wang N, Terhorst C, Sharpe AH, Basavappa M, Jeffrey KL, Reinecker HC. GEF-H1 controls microtubule-dependent sensing of nucleic acids for antiviral host defenses. Nat Immunol 2013; 15:63-71. [PMID: 24270516 PMCID: PMC4066330 DOI: 10.1038/ni.2766] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 10/08/2013] [Indexed: 12/15/2022]
Abstract
Detailed understanding of the signaling intermediates that confer the sensing of intracellular viral nucleic acids for induction of type I interferons is critical for strategies to curtail viral mechanisms that impede innate immune defenses. Here we show that the activation of the microtubule-associated guanine nucleotide exchange factor GEF-H1, encoded by Arhgef2, is essential for sensing of foreign RNA by RIG-I-like receptors. Activation of GEF-H1 controls RIG-I and Mda5-dependent phosphorylation of IRF3 and induction of interferon-β expression in macrophages. Generation of Arhgef2−/− mice revealed a pronounced signaling defect that prevented antiviral host responses to encephalomyocarditis virus and influenza A virus. Microtubule networks sequester GEF-H1 that upon activation is released to enable antiviral signaling by intracellular nucleic acid detection pathways.
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Affiliation(s)
- Hao-Sen Chiang
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School
| | - Yun Zhao
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School
| | - Joo-Hye Song
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School
| | - Song Liu
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School
| | - Ninghai Wang
- Division of Immunology, Beth Israel Deaconess Medical Center and Center for the Study of Inflammatory Bowel Disease, Harvard Medical School
| | - Cox Terhorst
- Division of Immunology, Beth Israel Deaconess Medical Center and Center for the Study of Inflammatory Bowel Disease, Harvard Medical School
| | - Arlene H Sharpe
- Department of Microbiology, Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Megha Basavappa
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School
| | - Kate L Jeffrey
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School
| | - Hans-Christian Reinecker
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School
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Identification of cellular proteome using two-dimensional difference gel electrophoresis in ST cells infected with transmissible gastroenteritis coronavirus. Proteome Sci 2013; 11:31. [PMID: 23855489 PMCID: PMC3734006 DOI: 10.1186/1477-5956-11-31] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 06/23/2013] [Indexed: 01/05/2023] Open
Abstract
Background Transmissible gastroenteritis coronavirus (TGEV) is an enteropathogenic coronavirus that causes diarrhea in pigs, which is correlated with high morbidity and mortality in suckling piglets. Information remains limited about the comparative protein expression of host cells in response to TGEV infection. In this study, cellular protein response to TGEV infection in swine testes (ST) cells was analyzed, using the proteomic method of two-dimensional difference gel electrophoresis (2D DIGE) coupled with MALDI-TOF-TOF/MS identification. Results 33 differentially expressed protein spots, of which 23 were up-regulated and 10 were down-regulated were identified. All the protein spots were successfully identified. The identified proteins were involved in the regulation of essential processes such as cellular structure and integrity, RNA processing, protein biosynthesis and modification, vesicle transport, signal transduction, and the mitochondrial pathway. Western blot analysis was used to validate the changes of alpha tubulin, keratin 19, and prohibitin during TGEV infection. Conclusions To our knowledge, we have performed the first analysis of the proteomic changes in host cell during TGEV infection. 17 altered cellular proteins that differentially expressed in TGEV infection were identified. The present study provides protein-related information that should be useful for understanding the host cell response to TGEV infection and the underlying mechanism of TGEV replication and pathogenicity.
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Shio MT, Olivier M. Editorial: Leishmania survival mechanisms: the role of host phosphatases. J Leukoc Biol 2010; 88:1-3. [PMID: 20591873 DOI: 10.1189/jlb.0210088] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Malur AG, Wells G, McCoy A, Banerjee AK. Evidence for phosphorylation of human parainfluenza virus type 3 C protein: mutant C proteins exhibit variable inhibitory activities in vitro. Virus Res 2009; 144:180-7. [PMID: 19410612 DOI: 10.1016/j.virusres.2009.04.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 04/16/2009] [Accepted: 04/26/2009] [Indexed: 11/16/2022]
Abstract
The P mRNA of human parainfluenza virus type 3, like other members of the subfamily Paramyxovirinae, gives rise to several polypeptides, one amongst them, the C protein, which is involved in inhibition of viral RNA synthesis as well as counteracting the host interferon signaling pathway. As a further step towards characterizing the function of C protein we present evidence to demonstrate the phosphorylation of C protein. Evidence for this observation emerged from deletion mapping studies coupled with mass spectroscopy analysis confirming residues S7, S22, S47T48 and S81 residues as the phosphorylation sites within the NH(2)-terminus of C protein. Here, we utilized a HPIV 3 minigenome replication assay and real time RT-PCR analysis to measure the relative RNA levels synthesized in the presence of mutant C proteins. Mutants S7A and S81A displayed low levels of RNA while mutant 5A that was devoid of all these phosphorylation sites exhibited high RNA level in comparison to wild type C during transcription. Interestingly, high levels of RNA were observed in the presence of S81A and mutant 5A during replication. Taken together, our results indicate that phosphorylation may differentially affect the inhibitory activity of C protein thereby regulating viral RNA synthesis.
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Affiliation(s)
- Achut G Malur
- Department of Microbiology and Immunology, Brody School of Medicine, Biotech 124, East Carolina University, 600 Moye Boulevard, Greenville, NC 27834, USA.
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Santamaría E, Mora MI, Potel C, Fernández-Irigoyen J, Carro-Roldán E, Hernández-Alcoceba R, Prieto J, Epstein AL, Corrales FJ. Identification of replication-competent HSV-1 Cgal+ strain signaling targets in human hepatoma cells by functional organelle proteomics. Mol Cell Proteomics 2008; 8:805-15. [PMID: 19098277 DOI: 10.1074/mcp.m800202-mcp200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
In the present work, we have attempted a comprehensive analysis of cytosolic and microsomal proteomes to elucidate the signaling pathways impaired in human hepatoma (Huh7) cells upon herpes simplex virus type 1 (HSV-1; Cgal(+)) infection. Using a combination of differential in-gel electrophoresis and nano liquid chromatography/tandem mass spectrometry, 18 spots corresponding to 16 unique deregulated cellular proteins were unambiguously identified, which were involved in the regulation of essential processes such as apoptosis, mRNA processing, cellular structure and integrity, signal transduction, and endoplasmic-reticulum-associated degradation pathway. Based on our proteomic data and additional functional studies target proteins were identified indicating a late activation of apoptotic pathways in Huh7 cells upon HSV-1 Cgal(+) infection. Additionally to changes on RuvB-like 2 and Bif-1, down-regulation of Erlin-2 suggests stimulation of Ca(2+)-dependent apoptosis. Moreover, activation of the mitochondrial apoptotic pathway results from a time-dependent multi-factorial impairment as inferred from the stepwise characterization of constitutive pro- and anti-apoptotic factors. Activation of serine-threonine protein phosphatase 2A (PP2A) was also found in Huh7 cells upon HSV-1 Cgal(+) infection. In addition, PP2A activation paralleled dephosphorylation and inactivation of downstream mitogen-activated protein (MAP) kinase pathway (MEK(1/2), ERK(1/2)) critical to cell survival and activation of proapoptotic Bad by dephosphorylation of Ser-112. Taken together, our results provide novel molecular information that contributes to define in detail the apoptotic mechanisms triggered by HSV-1 Cgal(+) in the host cell and lead to the implication of PP2A in the transduction of cell death signals and cell survival pathway arrest.
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Affiliation(s)
- Enrique Santamaría
- Division of Hepatology and Gene Therapy, Proteomics Unit, Centre for Applied Medical Research, University of Navarra, 31008 Pamplona, Spain
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Yang Z, Zhang F, Zhu L, He G. Identification of differentially expressed genes in brown planthopper Nilaparvata lugens (Hemiptera: Delphacidae) responding to host plant resistance. BULLETIN OF ENTOMOLOGICAL RESEARCH 2006; 96:53-9. [PMID: 16441905 DOI: 10.1079/ber2005400] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The brown planthopper Nilaparvata lugens Stål is one of the major insect pests of rice Oryza sativa L. The host resistance exhibits profound effects on growth, development and propagation of N. lugens. To investigate the molecular response of N. lugens to host resistance, a cDNA-amplified fragment length polymorphism (cDNA-AFLP) technique was employed to identify the differentially expressed genes in the nymphs feeding on three rice varieties. Of the 2,800 cDNA bands analysed, 54 were up-regulated and seven down-regulated qualitatively in N. lugens when the ingestion sources were changed from susceptible rice plants to resistant ones. Sequence analysis of the differential transcript-derived fragments showed that the genes involved in signalling, stress response, gene expression regulation, detoxification and metabolism were regulated by host resistance. Four of the transcript-derived fragments corresponding to genes encoding for a putative B subunit of phosphatase PP2A, a nemo kinase, a cytochrome P450 monooxygenase and a prolyl endopeptidase were further characterized in detail. Northern blot analysis confirmed that the expression of the four genes was enhanced in N. lugens feeding on resistant rice plants. The roles of these genes in the defensive response of N. lugens to host plant resistance were discussed.
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Affiliation(s)
- Zhifan Yang
- Key Laboratory of Ministry of Education for Plant Development Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
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Georgopoulou U, Tsitoura P, Kalamvoki M, Mavromara P. The protein phosphatase 2A represents a novel cellular target for hepatitis C virus NS5A protein. Biochimie 2006; 88:651-62. [PMID: 16460864 DOI: 10.1016/j.biochi.2005.12.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 12/16/2005] [Indexed: 01/15/2023]
Abstract
It is well established that HCV NS5A protein when expressed in mammalian cells perturbs the extracellular signal regulated kinase (ERK) pathway. The protein serine/threonine phosphatase 2A controls the phosphorylation of numerous proteins involved in cell signaling and one characterized function is the regulation of Ras-Raf mitogen activated protein (MAP) kinase signaling pathways. Our results showed that expression of HCV NS5A protein stimulates phosphatase 2A (PP2A) activity in cells, indicating the relevance of NS5A as a regulator of PP2A in vivo. We found that transient expression of the full length NS5A protein in different cell lines leads to a significant increase of the PP2A activity and this activity is specifically inhibited by the addition of okadaic acid, a PP2A inhibitor, in living cells. Further investigation showed that NS5A protein interacts in vivo and in vitro with the scaffolding A and the catalytic C subunits of PP2A. We propose that HCV NS5A represents a viral PP2A regulatory protein. This is a novel function for the NS5A protein which may have a key role in the ability of the virus to deregulate cell growth and survival.
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Affiliation(s)
- Urania Georgopoulou
- Molecular Virology Laboratory, Hellenic Pasteur Institute, 127, Vas. Sofias Avenue, Athens 11521, Greece.
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Guergnon J, Dessauge F, Dominguez V, Viallet J, Bonnefoy S, Yuste VJ, Mercereau-Puijalon O, Cayla X, Rebollo A, Susin SA, Bost PE, Garcia A. Use of penetrating peptides interacting with PP1/PP2A proteins as a general approach for a drug phosphatase technology. Mol Pharmacol 2005; 69:1115-24. [PMID: 16387795 DOI: 10.1124/mol.105.019364] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Protein phosphatase types 1 (PP1) and 2A (PP2A) represent two major families of serine/threonine protein phosphatases that have been implicated in the regulation of many cellular processes, including cell growth and apoptosis in mammalian cells. PP1 and PP2A proteins are composed of oligomeric complexes comprising a catalytic structure (PP1c or PP2AC) containing the enzymatic activity and at least one more interacting subunit. The binding of different subunits to a catalytic structure generates a broad variety of holoenzymes. We showed here that casein kinase 2alpha (Ck2alpha) and simian virus 40 small t antigen share a putative common beta-strand structure required for PP2A1 trimeric holoenzyme binding. We have also characterized DPT-sh1, a short basic peptide from Ck2alpha that interacted only in vitro with the PP2A-A subunit and behaves as a nontoxic penetrating shuttle in several cultivated human cell lines and chick embryos. In addition, DPT-sh1 specifically accumulated in human red cells infected with Plasmodium falciparum malaria parasites. We therefore designed bipartite peptides containing DPT-sh1 and PP1- or PP2A-interacting sequences. We found that DPT-5, a DPT-sh1-derived peptide containing a short sequence identified in CD28 antigen, interacts with PP2A-Balpha, and DPT-7, another DPT-sh1-derived peptide containing a short sequence identified in Bad as a PP1 catalytic consensus docking motif, induce apoptosis in cultivated cell lines. These results clearly indicate that the rational design of PP1/PP2A interacting peptides is a pertinent strategy to deregulate intracellular survival pathways.
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Affiliation(s)
- Julien Guergnon
- Equipe Phosphatases, Unité de Chimie Organique, Institut Pasteur, 25 rue du Dr Roux, 75015 Paris, France
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Kray AE, Carter RS, Pennington KN, Gomez RJ, Sanders LE, Llanes JM, Khan WN, Ballard DW, Wadzinski BE. Positive regulation of IkappaB kinase signaling by protein serine/threonine phosphatase 2A. J Biol Chem 2005; 280:35974-82. [PMID: 16126728 DOI: 10.1074/jbc.m506093200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription factor NF-kappaB plays a key regulatory role in the cellular response to pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF). In the absence of TNF, NF-kappaB is sequestered in the cytoplasm by inhibitory IkappaB proteins. Phosphorylation of IkappaBby the beta-catalytic subunit of IKK, a multicomponent IkappaB kinase, targets the inhibitor for proteolytic destruction and facilitates nuclear translocation of NF-kappaB. This pathway is initiated by TNF-dependent phosphorylation of T loop serines in IKKbeta, which greatly stimulates IkappaB kinase activity. Prior in vitro mixing experiments indicate that protein serine/threonine phosphatase 2A (PP2A) can dephosphorylate these T loop serines and inactivate IKK, suggesting a negative regulatory role for PP2A in IKK signaling. Here we provided several in vivo lines of evidence indicating that PP2A plays a positive rather than a negative role in the regulation of IKK. First, TNF-induced degradation of IkappaB is attenuated in cells treated with okadaic acid or fostriecin, two potent inhibitors of PP2A. Second, PP2A forms stable complexes with IKK in untransfected mammalian cells. This interaction is critically dependent on amino acid residues 121-179 of the IKKgamma regulatory subunit. Third, deletion of the PP2A-binding site in IKKgamma attenuates T loop phosphorylation and catalytic activation of IKKbeta in cells treated with TNF. Taken together, these data provide strong evidence that the formation of IKK.PP2A complexes is required for the proper induction of IkappaB kinase activity in vivo.
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Affiliation(s)
- Arlene E Kray
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600, USA
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Morinobu S, Kawano KI, Yamawaki S. Lithium and protein phosphatases: apoptosis or neurogenesis? ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.cnr.2004.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Viallet J, Garcia A, Weydert A. Protein phosphatase 2A as a new target for morphogenetic studies in the chick limb. Biochimie 2004; 85:753-62. [PMID: 14585542 DOI: 10.1016/j.biochi.2003.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The family of ser/thr protein phosphatases 2A (PP2A) is a major regulator of cell proliferation and cell death and is critically involved in the maintenance of homeostasis. In order to analyse the importance of PP2A proteins in apoptotic and developmental processes, this review focuses on previous studies concerning the role of PP2A in morphogenesis. We first analyse wing formation in Drosophila, a model for invertebrates, then chick limb bud, a model for vertebrates. We also present a pioneer experiment to illustrate the potential relevance of PP2A studies in BMP signalling during chicken development and we finally discuss the BMP downstream signalling pathways.
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Affiliation(s)
- Jean Viallet
- Faculté de Médecine, LEDAC UMR 5538 Institut Albert Bonniot, Rond Point de la Chantourne, 38706 La Tronche cedex, France
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Morinobu S, Fujimaki K, Kawano KI, Tanaka K, Takahashi J, Ohkawa M, Yamawaki S, Kato N. Influence of immobilization stress on the expression and phosphatase activity of protein phosphatase 2A in the rat brain. Biol Psychiatry 2003; 54:1060-6. [PMID: 14625148 DOI: 10.1016/s0006-3223(03)00417-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Protein phosphatase 2A (PP2A) is a major kinase phosphatase that plays an important role in regulating the activities of protein kinase cascades. It has been revealed that stress changes neuronal gene expression by activating these cascades. We examined the expression of the catalytic subunit C and serine and threonine phosphatase activity of PP2A in the rat frontal cortex and hippocampus following various immobilization stress paradigms. METHODS Immunoblot and immunohistochemical analyses were performed to examine the expression of PP2A. The level of phosphatase activity of PP2A was determined as the amount of free phosphate generated from a synthetic phosphopeptide. RESULTS Immunoblot analysis revealed no significant change in the level of PP2A immunoreactivity in response to either a single or repeated stress. Immunohistochemical analysis revealed that neither a single nor repeated stress changed PP2A immunoreactivity in the hippocampus; however, the levels of serine and threonine phosphatase activity in the frontal cortex and hippocampus were significantly upregulated in response to a single or repeated stress. CONCLUSIONS These results demonstrated that both a single and repeated immobilization stress upregulated the activity of PP2A in the rat brain, suggesting that PP2A may be involved, at least in part, in the downregulation of protein kinase activation induced by stress.
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Affiliation(s)
- Shigeru Morinobu
- Department of Psychiatry and Neurosciences, Hiroshima University School of Medicine, Hiroshima, Japan
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Garcia A, Cayla X, Guergnon J, Dessauge F, Hospital V, Rebollo MP, Fleischer A, Rebollo A. Serine/threonine protein phosphatases PP1 and PP2A are key players in apoptosis. Biochimie 2003; 85:721-6. [PMID: 14585537 DOI: 10.1016/j.biochi.2003.09.004] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The reversible phosphorylation of proteins controlled by protein kinases and protein phosphatases is a major mechanism that regulates a wide variety of cellular processes. In contrast to C. elegans, recent studies in mammalian cells have highlighted a major role of serine/threonine protein phosphorylation in apoptosis. To illustrate the importance of dephosphorylation processes in apoptosis, this review will focus on recent studies suggesting that the interaction of the serine/threonine protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) with certain regulators of the Bcl-2 family is critically involved in the control of apoptosis.
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Affiliation(s)
- Alphonse Garcia
- URA CNRS 2581, Département de Parasitologie, Institut Pasteur, 25, rue du Dr Roux, 75015 Paris, France.
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Gentry MS, Hallberg RL. Localization of Saccharomyces cerevisiae protein phosphatase 2A subunits throughout mitotic cell cycle. Mol Biol Cell 2002; 13:3477-92. [PMID: 12388751 PMCID: PMC129960 DOI: 10.1091/mbc.02-05-0065] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2002] [Accepted: 07/10/2002] [Indexed: 11/11/2022] Open
Abstract
Protein phosphatase 2A (PP2A) regulates a broad spectrum of cellular processes. This enzyme is a collection of varied heterotrimeric complexes, each composed of a catalytic (C) and regulatory (B) subunit bound together by a structural (A) subunit. To understand the cell cycle dynamics of this enzyme population, we carried out quantitative and qualitative analyses of the PP2A subunits of Saccharomyces cerevisiae. We found the following: the level of each subunit remained constant throughout the cell cycle; there is at least 10 times more of one of the regulatory subunits (Rts1p) than the other (Cdc55p); Tpd3p, the structural subunit, is limiting for both catalytic and regulatory subunit binding. Using green fluorescent protein-tagged forms of each subunit, we monitored the sites of significant accumulation of each protein throughout the cell cycle. The two regulatory subunits displayed distinctly different dynamic localization patterns that overlap with the A and C subunits at the bud tip, kinetochore, bud neck, and nucleus. Using strains null for single subunit genes, we confirmed the hypothesis that regulatory subunits determine sites of PP2A accumulation. Although Rts1p and Tpd3p required heterotrimer formation to achieve normal localization, Cdc55p achieved its normal localization in the absence of either an A or C subunit.
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Affiliation(s)
- Matthew S Gentry
- Department of Biology, Syracuse University, Syracuse, New York 13244, USA
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Modrof J, Mühlberger E, Klenk HD, Becker S. Phosphorylation of VP30 impairs ebola virus transcription. J Biol Chem 2002; 277:33099-104. [PMID: 12052831 DOI: 10.1074/jbc.m203775200] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription of the highly pathogenic Ebola virus (EBOV) is dependent on VP30, a constituent of the viral nucleocapsid complex. Here we present evidence that phosphorylation of VP30, which takes place at six N-terminal serine residues and one threonine residue, is of functional significance. Replacement of the phosphoserines by alanines resulted in an only slightly phosphorylated VP30 (VP30(6A)) that is still able to activate EBOV-specific transcription in a plasmid-based minigenome system. VP30(6A), however, did not bind to inclusions that are induced by the major nucleocapsid protein NP. Three intracellular phosphatases (PP1, PP2A, and PP2C) have been determined to dephosphorylate VP30. The presence of okadaic acid (OA), an inhibitor of PP1 and PP2A, had the same negative effect on transcription activation by VP30 as the substitution of the six phosphoserines for aspartate residues. OA, however, did not impair transcription when VP30 was replaced by VP30(6A). In EBOV-infected cells, OA blocked virus growth dose-dependently. The block was mediated by the extensive phosphorylation of VP30, which is evidenced by the result that expression of VP30(6A), in trans, led to the progression of EBOV infection in the presence of OA. In conclusion, phosphorylation of VP30 was shown to regulate negatively transcription activation and positively binding to the NP inclusions.
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Affiliation(s)
- Jens Modrof
- Institut für Virologie der Philipps-Universität Marburg, Robert-Koch-Strasse 17, Marburg 35037, Germany
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Abstract
Dynamic phosphorylation and dephosphorylation of proteins are fundamental mechanisms utilized by cells to transduce signals. Whereas transduction by protein kinases has been a major focus of studies in the last decade, protein phosphatase 2A (PP2A) enzymes emerge in this millenium as the most fashionable players in cellular signaling. Viral proteins target specific PP2A enzymes in order to deregulate chosen cellular pathways in the host and promote viral progeny. The observation that a variety of viruses utilize PP2A to alienate cellular behavior emphasizes the fundamental importance of PP2A in signal transduction. This review will primarily focus on discussing the uniqueness of PP2A regulation and uncovering the critical role played by protein-protein interactions in the modulation of PP2A signaling. Moreover, the place of PP2A in signaling pathways and its functional significance for human diseases will be discussed.
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Affiliation(s)
- E Sontag
- Department of Pathology/Neuropathology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9073, USA.
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Lecuona E, Garcia A, Sznajder JI. A novel role for protein phosphatase 2A in the dopaminergic regulation of Na,K-ATPase. FEBS Lett 2000; 481:217-20. [PMID: 11007967 DOI: 10.1016/s0014-5793(00)02009-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Stimulation of dopaminergic type 1 (D(1)) receptors increases lung edema clearance by regulating Na,K-ATPase function in the alveolar epithelium. We studied the role of serine/threonine protein phosphatases in the Na,K-ATPase regulation by D(1) agonists in A549 cells. We found that low doses of the type 1/2A protein phosphatase inhibitor okadaic acid as well as SV40 small t antigen transiently transfected into A549 cells prevented the D(1) agonist-induced increase in Na,K-ATPase activity and translocation from intracellular pools to the plasma membrane. This was associated with a rapid and transient increase in protein phosphatase 2A activity. We conclude that D(1) stimulation regulates Na,K-ATPase activity by promoting recruitment of Na,K-ATPases from intracellular pools into the basolateral membranes of A549 cells via a type 2A protein phosphatase.
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Affiliation(s)
- E Lecuona
- Division of Pulmonary and Critical Care Medicine, Northwestern University, 300 East Superior Street, Tarry Building 14-707, Chicago, IL 60611, USA
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