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Bao J, Tang Y, Chen Y, Jin J, Wang X, An G, Cao L, Zhang H, Cheng G, Pan G, Zhou Z. E. hellem Ser/Thr protein phosphatase PP1 targets the DC MAPK pathway and impairs immune functions. Life Sci Alliance 2024; 7:e202302375. [PMID: 38199846 PMCID: PMC10781585 DOI: 10.26508/lsa.202302375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 01/01/2024] [Accepted: 01/03/2024] [Indexed: 01/12/2024] Open
Abstract
Microsporidia are difficult to be completely eliminated once infected, and the persistence disrupts host cell functions. Here in this study, we aimed to elucidate the impairing effects and consequences of microsporidia on host DCs. Enterocytozoon hellem, one of the most commonly diagnosed zoonotic microsporidia species, was applied. In vivo models demonstrated that E. hellem-infected mice were more susceptible to further pathogenic challenges, and DCs were identified as the most affected groups of cells. In vitro assays revealed that E. hellem infection impaired DCs' immune functions, reflected by down-regulated cytokine expressions, lower extent of maturation, phagocytosis ability, and antigen presentations. E. hellem infection also detained DCs' potencies to prime and stimulate T cells; therefore, host immunities were disrupted. We found that E. hellem Ser/Thr protein phosphatase PP1 directly interacts with host p38α (MAPK14) to manipulate the p38α(MAPK14)/NFAT5 axis of the MAPK pathway. Our study is the first to elucidate the molecular mechanisms of the impairing effects of microsporidia on host DCs' immune functions. The emergence of microsporidiosis may be of great threat to public health.
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Affiliation(s)
- Jialing Bao
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Yunlin Tang
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Yebo Chen
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Jiangyan Jin
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Xue Wang
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Guozhen An
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Lu Cao
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Huarui Zhang
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Gong Cheng
- Tsinghua University-Peking University Joint Center for Life Sciences, School of Medicine, Tsinghua University, Beijing, China
| | - Guoqing Pan
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
| | - Zeyang Zhou
- https://ror.org/01kj4z117 The State Key Laboratory of Resource Insects, Southwest University, Chongqing, China
- https://ror.org/01kj4z117 Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Chongqing, China
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Umesalma S, Kaemmer CA, Kohlmeyer JL, Letney B, Schab AM, Reilly JA, Sheehy RM, Hagen J, Tiwari N, Zhan F, Leidinger MR, O'Dorisio TM, Dillon J, Merrill RA, Meyerholz DK, Perl AL, Brown BJ, Braun TA, Scott AT, Ginader T, Taghiyev AF, Zamba GK, Howe JR, Strack S, Bellizzi AM, Narla G, Darbro BW, Quelle FW, Quelle DE. RABL6A inhibits tumor-suppressive PP2A/AKT signaling to drive pancreatic neuroendocrine tumor growth. J Clin Invest 2019; 129:1641-1653. [PMID: 30721156 DOI: 10.1172/jci123049] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 01/24/2019] [Indexed: 12/15/2022] Open
Abstract
Hyperactivated AKT/mTOR signaling is a hallmark of pancreatic neuroendocrine tumors (PNETs). Drugs targeting this pathway are used clinically, but tumor resistance invariably develops. A better understanding of factors regulating AKT/mTOR signaling and PNET pathogenesis is needed to improve current therapies. We discovered that RABL6A, a new oncogenic driver of PNET proliferation, is required for AKT activity. Silencing RABL6A caused PNET cell-cycle arrest that coincided with selective loss of AKT-S473 (not T308) phosphorylation and AKT/mTOR inactivation. Restoration of AKT phosphorylation rescued the G1 phase block triggered by RABL6A silencing. Mechanistically, loss of AKT-S473 phosphorylation in RABL6A-depleted cells was the result of increased protein phosphatase 2A (PP2A) activity. Inhibition of PP2A restored phosphorylation of AKT-S473 in RABL6A-depleted cells, whereas PP2A reactivation using a specific small-molecule activator of PP2A (SMAP) abolished that phosphorylation. Moreover, SMAP treatment effectively killed PNET cells in a RABL6A-dependent manner and suppressed PNET growth in vivo. The present work identifies RABL6A as a new inhibitor of the PP2A tumor suppressor and an essential activator of AKT in PNET cells. Our findings offer what we believe is a novel strategy of PP2A reactivation for treatment of PNETs as well as other human cancers driven by RABL6A overexpression and PP2A inactivation.
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Affiliation(s)
| | | | | | | | | | | | - Ryan M Sheehy
- Department of Pharmacology.,Free Radical & Radiation Biology Training Program
| | | | | | | | - Mariah R Leidinger
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | | | | | | | - David K Meyerholz
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | - Abbey L Perl
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
| | | | | | | | | | - Agshin F Taghiyev
- Pediatrics, Colleges of Medicine, Engineering, or Public Health, University of Iowa, Iowa City, Iowa, USA
| | | | | | | | - Andrew M Bellizzi
- Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
| | - Goutham Narla
- Department of Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Benjamin W Darbro
- Pediatrics, Colleges of Medicine, Engineering, or Public Health, University of Iowa, Iowa City, Iowa, USA
| | | | - Dawn E Quelle
- Department of Pharmacology.,Molecular Medicine Graduate Program.,Free Radical & Radiation Biology Training Program.,Department of Pathology, in the College of Medicine, Holden Comprehensive Cancer Center, University of Iowa, Iowa City, Iowa, USA
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3
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Bastan R, Eskandari N, J Ardakani H, T Peachell P. Effects of fostriecin on β2-adrenoceptor-driven responses in human mast cells. J Immunotoxicol 2017; 14:60-65. [PMID: 28090813 DOI: 10.1080/1547691x.2016.1259277] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
As part of the intracellular processes leading to mast cell and basophil activation, phosphorylation of key substrates is likely to be important. These processes, mediated by phosphatases, are responsible for regulating phosphorylation. The aim of the present study was to determine effects fostriecin - a selective inhibitor of PP2A (protein phosphatase-2) - on β2-adrenoceptor-driven responses in human mast cells. Here, the effects of fostriecin (PP inhibitors) on the inhibition of histamine release from HLMC, on β-adrenoceptor-driven responses in mast cells and on desensitization were investigated. Long-term incubation (24 h) of mast cells with fostriecin (10-6 M) resulted in a significant (p < 0.001) reduction in the maximal response (from 41.2 [± 3.0] to 29.9 [± 4.2] %) to salbutamol following fostriecin treatment. The results showed that fostriecin pretreatment significantly attenuated the inhibitory effects of salbutamol. Overall, the present study suggested that PP2A has an important role in regulating mast cell β2-adrenoceptors.
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Affiliation(s)
- Reza Bastan
- a Department of Human Vaccines , Razi Serum and Vaccine Research Institute , Karaj , Iran
| | - Nahid Eskandari
- b Department of Immunology , Applied Physiology Research Center, Isfahan University of Medical Sciences , Isfahan , Iran
| | - Hamidrez J Ardakani
- b Department of Immunology , Applied Physiology Research Center, Isfahan University of Medical Sciences , Isfahan , Iran
| | - Peter T Peachell
- c Academic Unit of Respiratory Medicine , Medical School, University of Sheffield , Sheffield , UK
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4
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Song H, Pu J, Wang L, Wu L, Xiao J, Liu Q, Chen J, Zhang M, Liu Y, Ni M, Mo J, Zheng Y, Wan D, Cai X, Cao Y, Xiao W, Ye L, Tu E, Lin Z, Wen J, Lu X, He J, Peng Y, Su J, Zhang H, Zhao Y, Lin M, Zhang Z. ATG16L1 phosphorylation is oppositely regulated by CSNK2/casein kinase 2 and PPP1/protein phosphatase 1 which determines the fate of cardiomyocytes during hypoxia/reoxygenation. Autophagy 2016; 11:1308-25. [PMID: 26083323 DOI: 10.1080/15548627.2015.1060386] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Recent studies have shown that the phosphorylation and dephosphorylation of ULK1 and ATG13 are related to autophagy activity. Although ATG16L1 is absolutely required for autophagy induction by affecting the formation of autophagosomes, the post-translational modification of ATG16L1 remains elusive. Here, we explored the regulatory mechanism and role of ATG16L1 phosphorylation for autophagy induction in cardiomyocytes. We showed that ATG16L1 was a phosphoprotein, because phosphorylation of ATG16L1 was detected in rat cardiomyocytes during hypoxia/reoxygenation (H/R). We not only demonstrated that CSNK2 (casein kinase 2) phosphorylated ATG16L1, but also identified the highly conserved Ser139 as the critical phosphorylation residue for CSNK2. We further established that ATG16L1 associated with the ATG12-ATG5 complex in a Ser139 phosphorylation-dependent manner. In agreement with this finding, CSNK2 inhibitor disrupted the ATG12-ATG5-ATG16L1 complex. Importantly, phosphorylation of ATG16L1 on Ser139 was responsible for H/R-induced autophagy in cardiomyocytes, which protects cardiomyocytes from apoptosis. Conversely, we determined that wild-type PPP1 (protein phosphatase 1), but not the inactive mutant, associated with ATG16L1 and antagonized CSNK2-mediated phosphorylation of ATG16L1. Interestingly, one RVxF consensus site for PPP1 binding in the C-terminal tail of ATG16L1 was identified; mutation of this site disrupted its association with ATG16L1. Notably, CSNK2 also associated with PPP1, but ATG16L1 depletion impaired the interaction between CSNK2 and PPP1. Collectively, these data identify ATG16L1 as a bona fide physiological CSNK2 and PPP1 substrate, which reveals a novel molecular link from CSNK2 to activation of the autophagy-specific ATG12-ATG5-ATG16L1 complex and autophagy induction.
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Affiliation(s)
- Huiwen Song
- a Department of Cardiology ; Affiliated Baoan Hospital of Southern Medical University ; Shenzhen , China
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5
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Mahato P, Pandey S, Bhattacharyya S. Differential effects of protein phosphatases in the recycling of metabotropic glutamate receptor 5. Neuroscience 2015; 306:138-50. [DOI: 10.1016/j.neuroscience.2015.08.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 07/28/2015] [Accepted: 08/14/2015] [Indexed: 10/23/2022]
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6
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Pandey S, Mahato PK, Bhattacharyya S. Metabotropic glutamate receptor 1 recycles to the cell surface in protein phosphatase 2A-dependent manner in non-neuronal and neuronal cell lines. J Neurochem 2014; 131:602-14. [DOI: 10.1111/jnc.12930] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 07/30/2014] [Accepted: 08/08/2014] [Indexed: 02/03/2023]
Affiliation(s)
- Saurabh Pandey
- Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Punjab India
| | - Prabhat Kumar Mahato
- Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Punjab India
| | - Samarjit Bhattacharyya
- Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Punjab India
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Kranias G, Watt LF, Carpenter H, Holst J, Ludowyke R, Strack S, Sim ATR, Verrills NM. Protein phosphatase 2A carboxymethylation and regulatory B subunits differentially regulate mast cell degranulation. Cell Signal 2010; 22:1882-90. [PMID: 20688157 DOI: 10.1016/j.cellsig.2010.07.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Revised: 07/14/2010] [Accepted: 07/22/2010] [Indexed: 11/25/2022]
Abstract
Asthma is characterised by antigen-mediated mast cell degranulation resulting in secretion of inflammatory mediators. Protein phosphatase 2A (PP2A) is a serine/threonine protein phosphatase composed of a catalytic (PP2A-C) subunit together with a core scaffold (PP2A-A) subunit and a variable, regulatory (PP2A-B) subunit. Previous studies utilising pharmacological inhibition of protein phosphatases have suggested a positive regulatory role for PP2A in mast cell degranulation. In support of this we find that a high okadaic acid concentration (1μM) inhibits mast cell degranulation. Strikingly, we now show that a low concentration of okadaic acid (0.1μM) has the opposite effect, resulting in enhanced degranulation. Selective downregulation of the PP2A-Cα subunit by short hairpin RNA also enhanced degranulation of RBL-2H3 mast cells, suggesting that the primary role of PP2A is to negatively regulate degranulation. PP2A-B subunits are responsible for substrate specificity, and carboxymethylation of the PP2A-C subunit alters B subunit binding. We show here that carboxymethylation of PP2A-C is dynamically altered during degranulation and inhibition of methylation decreases degranulation. Moreover downregulation of the PP2A-Bα subunit resulted in decreased MK2 phosphorylation and degranulation, whilst downregulation of the PP2A-B'δ subunit enhanced p38 MAPK phosphorylation and degranulation. Taken together these data show that PP2A is both a positive and negative regulator of mast cell degranulation, and this differential role is regulated by carboxymethylation and specific PP2A-B subunit binding.
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Affiliation(s)
- Gregory Kranias
- School of Biomedical Sciences, Faculty of Health, University of Newcastle, Callaghan, NSW 2308, Australia
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Harrison CA, Bastan R, Peirce MJ, Munday MR, Peachell PT. Role of calcineurin in the regulation of human lung mast cell and basophil function by cyclosporine and FK506. Br J Pharmacol 2007; 150:509-18. [PMID: 17200674 PMCID: PMC2189730 DOI: 10.1038/sj.bjp.0707002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND AND PURPOSE Cyclosporine and FK506 are thought to act by targeting the Ca2+-dependent protein phosphatase, calcineurin. The aim of the present study was to determine whether cyclosporine and FK506 stabilize mast cells and basophils by interacting with calcineurin. EXPERIMENTAL APPROACH The effects of cyclosporine and FK506 on the IgE-mediated release of histamine from mast cells and basophils were evaluated. The presence of calcineurin in cells was determined by Western blotting. Ca2+-dependent protein phosphatase activities were assessed in cell extracts using a synthetic phosphorylated peptide that is known to serve as a substrate for calcineurin. KEY RESULTS FK506 was about 100-fold more potent than cyclosporine as an inhibitor of IgE-dependent histamine release from mast cells and basophils. Immunoblotting of solubilized preparations of purified cells demonstrated the presence of calcineurin in mast cells and basophils. In enzyme assays, mast cells expressed approximately 7-fold higher Ca2+-dependent protein phosphatase activity than basophils. Whereas cyclosporine effectively inhibited Ca2+-dependent protein phosphatase activity in cell extracts, FK506 was considerably less effective. CONCLUSIONS AND IMPLICATIONS FK506 and cyclosporine inhibit the stimulated release of histamine from mast cells and basophils. However, the ability of cyclosporine, but not FK506, to inhibit Ca2+-dependent protein phosphatase activity questions whether FK506 stabilizes mast cells and basophils by interacting with calcineurin.
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Affiliation(s)
- C A Harrison
- Department of Engineering Materials, Kroto Research Institute, University of Sheffield Sheffield, UK
| | - R Bastan
- Academic Unit of Molecular Pharmacology, University of Sheffield, Royal Hallamshire Hospital Sheffield, UK
| | - M J Peirce
- Section of Inflammation and Immunity, Division of Kennedy Institute of Rheumatology, Imperial College School of Medicine Hammersmith, London, UK
| | - M R Munday
- Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University of London London, UK
| | - P T Peachell
- Academic Unit of Molecular Pharmacology, University of Sheffield, Royal Hallamshire Hospital Sheffield, UK
- Author for correspondence:
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Sim ATR, Ludowyke RI, Verrills NM. Mast cell function: regulation of degranulation by serine/threonine phosphatases. Pharmacol Ther 2006; 112:425-39. [PMID: 16790278 DOI: 10.1016/j.pharmthera.2006.04.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 04/26/2006] [Indexed: 01/28/2023]
Abstract
Mast cells play both effector and modulatory roles in a range of allergic and immune responses. The principal function of these cells is the release of inflammatory mediators from mast cells by degranulation, which involves a complex interplay of signalling molecules. Understanding the molecular architecture underlying mast cell signalling has attracted renewed interest as the capacity for therapeutic intervention through controlling mast cell degranulation is now accepted as a viable proposition. The dynamic regulation of signalling by protein phosphorylation is a well-established phenomenon and many of the early events involved in mast cell activation are well understood. Less well understood however are the events further downstream of receptor activation that allow movement of granules through the cytoskeletal barrier and docking and fusion of granules with the plasma membrane. Whilst a potential role for the protein phosphatase family of signalling enzymes in mast cell function has been accepted for some time, the evidence has largely been derived from the use of broad specificity pharmacological inhibitors and results often depend upon the experimental conditions, leading to conflicting views. In this review, we present and discuss the pharmacological and recent molecular evidence that protein phosphatases, and in particular the protein phosphatase serine/threonine phosphatase type 2A (PP2A), have major regulatory roles to play and may be potential targets for the design of new therapeutic agents.
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Affiliation(s)
- Alistair T R Sim
- School of Biomedical Sciences and Hunter Medical Research Institute, Faculty of Health, The University of Newcastle, Callaghan, NSW, Australia.
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Boudreau RTM, Hoskin DW. The use of okadaic acid to elucidate the intracellular role(s) of protein phosphatase 2A: Lessons from the mast cell model system. Int Immunopharmacol 2005; 5:1507-18. [PMID: 16023602 DOI: 10.1016/j.intimp.2005.05.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 05/05/2005] [Accepted: 05/18/2005] [Indexed: 11/29/2022]
Abstract
In recent years a heightened appreciation has emerged for the role(s) that phosphatases play in regulating signal transduction pathways and other cellular processes. The tumor-promoting agent okadaic acid (OA) has been an invaluable tool in efforts aimed at delineating the contributions of the most abundant mammalian serine/threonine phosphatase, protein phosphatase 2A (PP2A), to intracellular signaling and cell function. PP2A, which is ubiquitous and vital in virtually every cell system studied, continues to be the focus of much research on phosphorylation control machinery. Mast cells represent an excellent in vitro model for the study of protein phosphorylation events because they possess a number of distinct signaling pathways that lead to the production and/or release of discreet mediators in response to different stimuli. The utility of OA in analyzing PP2A function has been demonstrated in mast cells across several species. Results of these studies have contributed to the current recognition that PP2A plays a crucial role in the biology of mast cells and other cell types.
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Affiliation(s)
- Robert T M Boudreau
- Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Sir Charles Tupper Medical Building, 5850 University Ave., Halifax, NS B3H 1X5, Canada
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Sim ATR, Baldwin ML, Rostas JAP, Holst J, Ludowyke RI. The role of serine/threonine protein phosphatases in exocytosis. Biochem J 2003; 373:641-59. [PMID: 12749763 PMCID: PMC1223558 DOI: 10.1042/bj20030484] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2003] [Revised: 05/09/2003] [Accepted: 05/16/2003] [Indexed: 10/27/2022]
Abstract
Modulation of exocytosis is integral to the regulation of cellular signalling, and a variety of disorders (such as epilepsy, hypertension, diabetes and asthma) are closely associated with pathological modulation of exocytosis. Emerging evidence points to protein phosphatases as key regulators of exocytosis in many cells and, therefore, as potential targets for the design of novel therapies to treat these diseases. Diverse yet exquisite regulatory mechanisms have evolved to direct the specificity of these enzymes in controlling particular cell processes, and functionally driven studies have demonstrated differential regulation of exocytosis by individual protein phosphatases. This Review discusses the evidence for the regulation of exocytosis by protein phosphatases in three major secretory systems, (1) mast cells, in which the regulation of exocytosis of inflammatory mediators plays a major role in the respiratory response to antigens, (2) insulin-secreting cells in which regulation of exocytosis is essential for metabolic control, and (3) neurons, in which regulation of exocytosis is perhaps the most complex and is essential for effective neurotransmission.
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Affiliation(s)
- Alistair T R Sim
- School of Biomedical Sciences, Faculty of Health, University of Newcastle, and Clinical Neuroscience Program, Hunter Medical Research Institute, Callaghan, NSW 2308, Australia.
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12
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Assari T, Cox S, Munday MR, Pearce B. Regulation of alpha(1)-adrenoceptor-linked phosphoinositide metabolism in cultured glia: involvement of protein phosphatases and kinases. Cell Signal 2003; 15:403-12. [PMID: 12618215 DOI: 10.1016/s0898-6568(02)00114-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Noradrenaline-stimulated phosphoinositide breakdown in cultured glia was found to be mediated by alpha(1A)-adrenoceptors. The alpha(1A)-selective agonist A61603 was as effective as noradrenaline in eliciting 3H-inositol phosphate (IP) accumulation but was approximately 50-fold more potent. In addition, the use of selective antagonists revealed a clear rank order of potency in the ability of these drugs to reverse the effect of noradrenaline on phosphoinositide breakdown: RS17053 (alpha(1A)-selective) >>AH11110A (alpha(1B)-selective)>BMY7378 (alpha(1D)-selective). Pre-treatment of cultured glia with the protein phosphatase inhibitor okadaic acid resulted in a concentration- and time-dependent reduction in noradrenaline-evoked 3H-IP accumulation. This effect was mimicked by, but was not additive with, a phorbol ester, was reversed by protein kinase C (PKC) inhibitors and was not evident in cells which had been PKC depleted. The ability of cell extracts to dephosphorylate radiolabelled glycogen phosphorylase revealed the presence of the phosphatases PP1 and PP2A in almost equal abundance. Okadaic acid pre-treatment of intact cultures elicited a marked reduction in total phosphatase activity, particularly that mediated by PP2A. We also determined the effect of okadaic acid pre-treatment on PKC and cyclic AMP-dependent protein kinase (PKA) activities in these cells. PKC and PKA activities in cell extracts were assessed by determining the incorporation of 32P into histone and kemptide, respectively. Okadaic acid elicited increases in both Ca(2+)-dependent and Ca(2+)-independent PKC activity; in addition, increases in both initial and total PKA activities were also recorded. The effect of okadaic acid on noradrenaline-stimulated 3H-IP accumulation were not, however, mimicked by either forskolin or 8-bromo-cyclic AMP, suggesting that this event is not regulated by PKA. Our data point to roles for both PKC and PP2A in the regulation of alpha(1A)-adrenoceptor-linked phosphoinositide metabolism in cultured cortical glia.
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Affiliation(s)
- Tracy Assari
- Department of Pharmacology, The School of Pharmacy, 29/39 Brunswick Square, London WC1N 1AX, UK
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13
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Boudreau RTM, Garduno R, Lin TJ. Protein phosphatase 2A and protein kinase Calpha are physically associated and are involved in Pseudomonas aeruginosa-induced interleukin 6 production by mast cells. J Biol Chem 2002; 277:5322-9. [PMID: 11706031 DOI: 10.1074/jbc.m108623200] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pulmonary infection with Pseudomonas aeruginosa is characterized by massive airway inflammation, which comprises significant cytokine production. Although mast cells are abundant in the lung and are potent sources of various cytokines, a role of mast cells in P. aeruginosa infection remains undefined, and P. aeruginosa-induced signaling mechanisms in mast cells have not been studied previously. Here we demonstrate that human cord blood-derived mast cells, mouse bone marrow-derived mast cells, and the mouse mast cell line MC/9 produce significant amounts of interleukin 6 (IL-6) in response to P. aeruginosa. This response was accompanied by a stimulation of protein kinase Calpha (PKCalpha) phosphorylation and PKC activity and was significantly blocked by the PKC inhibitors Ro 31-8220 and PKCalpha pseudosubstrate. Interestingly, mast cells treated with P. aeruginosa had reduced protein levels of phosphatase 2A catalytic unit (PP2Ac), which prompted us to determine whether a direct association between PKCalpha and PP2A occurs in mast cells. In mouse bone marrow-derived mast cells and MC/9 cells, as well as in the human mast cell line HMC-1, PP2A coimmunoprecipitated with PKCalpha either using PKCalpha- or PP2Ac-specific antibodies, suggesting that PKCalpha and PP2Ac are physically associated in mast cells. The PP2A inhibitor okadaic acid induced P. aeruginosa-like responses in mast cells including increased PKCalpha phosphorylation, stimulated PKC activity, and augmented IL-6 production, the last being blocked by the PKC inhibitor Ro 31-8220. Finally, okadaic acid potentiated the P. aeruginosa-induced IL-6 production. Collectively, these data provide, to our knowledge, the first evidence of both a direct physical association of PP2A and PKCalpha in mammalian cells and their coinvolvement in regulating mast cell activation in response to P. aeruginosa.
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Affiliation(s)
- Robert T M Boudreau
- Department of Microbiology, Dalhousie University, Halifax, Nova Scotia B3J 3G9, Canada
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Bastan R, Peirce MJ, Peachell PT. Regulation of immunoglobulin E-mediated secretion by protein phosphatases in human basophils and mast cells of skin and lung. Eur J Pharmacol 2001; 430:135-41. [PMID: 11698073 DOI: 10.1016/s0014-2999(01)01366-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A wide range of serine/threonine protein phosphatase (PP) inhibitors were studied for effects on the immunoglobulin E (IgE)-mediated release of histamine from human lung mast cells, human skin mast cells and basophils. Okadaic acid (OA) inhibited the release of histamine from all three cell types in a concentration-dependent manner. Two structural analogues of okadaic acid, okadaol and okadaone, known to be less active than the parent molecule as inhibitors of PP, were less active than okadaic acid as inhibitors of histamine release in these three cell types. A number of PP inhibitors, showing differences in selectivity for PP1 and PP2A, were also evaluated. Calyculin, which is roughly equipotent as a PP1 and PP2A inhibitor, attenuated the release of histamine from all three cell types. Similarly, tautomycin (TAU), which shows greater selectivity for PP1 over PP2A, was also effective at inhibiting histamine release in all three cell types. In contrast, fostriecin, which is very much more potent as an inhibitor of PP2A over PP1, was ineffective as an inhibitor in all three cell types. These data indicate that the regulation of mediator release by PPs is similar in lung mast cells, skin mast cells and basophils. Moreover, the data suggest that PP1 is important in the control of cellular activity.
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Affiliation(s)
- R Bastan
- Section of Molecular Pharmacology and Pharmacogenetics, University of Sheffield, The Royal Hallamshire Hospital (Floor L), Glossop Road, S10 2JF, Sheffield, UK
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Ludowyke RI, Holst J, Mudge LM, Sim AT. Transient translocation and activation of protein phosphatase 2A during mast cell secretion. J Biol Chem 2000; 275:6144-52. [PMID: 10692405 DOI: 10.1074/jbc.275.9.6144] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Okadaic acid inhibits secretion from mast cells, suggesting a regulatory role for protein Ser/Thr phosphatases type I (PP1) and/or 2A (PP2A) in the secretory process. In unstimulated RBL-2H3 cells, okadaic acid pretreatment inhibited PP2A activity in both cytosol and membrane fractions, but inhibition of secretion correlated with inhibition of membrane-bound rather than cytosolic PP2A activity. Okadaic acid had very little effect on PP1 activity. Stimulation of RBL-2H3 cells by antigen led to the activity and amount of PP2A in the membrane fraction increasing nearly 2-fold. In contrast, there was little change in the activity or distribution of PP1. Importantly, the translocation of PP2A was transient, coinciding with or marginally preceding the peak rate of secretion, suggesting a link between PP2A translocation, activity, and secretion. Phorbol 12-myristate 13-acetate plus the calcium ionophore A23187 induced a slower, prolonged rate of secretion that coincided with a similarly protracted translocation of PP2A to the membrane fraction. PP2A translocation is not the only event required for secretion as translocation was also induced by phorbol 12-myristate 13-acetate, without resulting in secretion. These results indicate that increased protein dephosphorylation in the membrane fraction mediated by PP2A is required for mast cell secretion. To our knowledge, this is the first demonstration of a signal-mediated, rapid, transient translocation and activation of PP2A in membranes in any system.
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Affiliation(s)
- R I Ludowyke
- Centre for Immunology, St. Vincent's Hospital, University of New South Wales, Sydney, New South Wales 2010, Australia.
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Peirce MJ, Munday MR, Peachell PT. Role of protein phosphatases in the regulation of human mast cell and basophil function. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:C1021-8. [PMID: 10600752 DOI: 10.1152/ajpcell.1999.277.6.c1021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Many extracellular stimuli mediate physiological change in target cells by altering the phosphorylation state of proteins. These alterations result from the dynamic interplay of protein kinases, which mediate phosphorylations, and protein phosphatases, which catalyse dephosphorylations. The antigen-mediated aggregation of high-affinity receptors for IgE on mast cells and basophils triggers rapid changes in the phosphorylation of many proteins and culminates in the generation of inflammatory mediators involved in allergic inflammatory diseases such as asthma. Although protein kinases have an established role in this process, less is known about the involvement of protein phosphatases. This imbalance has been redressed in recent years by the availability of phosphatase inhibitors, such as okadaic acid, that facilitate investigations of the role of protein phosphatases in intact cells. Here we review a number of studies in which inhibitors of protein phosphatases have been used to shed light on the potential importance of these enzymes in the regulation of human mast cell and human basophil function.
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Affiliation(s)
- M J Peirce
- Section of Molecular Pharmacology and Pharmacogenetics, University of Sheffield, Sheffield S10 2JF, United Kingdom
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Eltze M. Multiple mechanisms of action: the pharmacological profile of budipine. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1999; 56:83-105. [PMID: 10370904 DOI: 10.1007/978-3-7091-6360-3_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Four major components of the mechanism of action have been identified for the antiparkinsonian drug budipine up to now. 1) The primary action of budipine is an indirect dopaminergic effect as shown by facilitation of dopamine (DA) release, inhibition of monoamine oxidase type B (MAO-B) and of DA (re) up-take and stimulation of aromatic L-amino acid decarboxylase (AADC), which in sum might be responsible for enhancing the endogenous dopaminergic activity. 2) Radioligand and functional studies at the N-methyl-D-aspartate (NMDA) type glutamate receptor characterize budipine as a low-affinity, uncompetitive antagonist with fast kinetics and moderate voltage-dependency at the phencyclidine (PCP) binding site, comparable to that observed with amantadine, thereby counteracting an increased excitatory glutamatergic activity. 3) The antimuscarinic action of budipine, verified by functional and binding studies at native muscarinic M1-M3 and human recombinant m1-m5 receptor subtypes in vitro, is up to 125-fold weaker than that of biperiden and corresponds to its approximately 100-fold lower potency to cause experimentally-induced peripheral antimuscarinic effects and explains only part of its high potency, which equals biperiden, to suppress cholinergically evoked tremor. 4) An additional inhibition of striatal gamma-aminobutyric acid (GABA) release by budipine may be beneficial to suppress an increased striatal GABAergic output activity. The contribution of other observed effects to the therapeutic action of budipine, i.e. weak stimulation of noradrenaline and serotonin release, binding to brain sigma1 receptors and blockade of histamine H1 receptors, is not yet clear. By means of these multiple mechanisms, budipine might correct the imbalance of striatal output pathways by restoring DA levels in the striatum, and positively influence the secondary changes in other transmitter systems (glutamate, acetylcholine, GABA) observed in Parkinson's disease.
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Wang L, Correia I, Basu S, Theoharides TC. Ca2+ and phorbol ester effect on the mast cell phosphoprotein induced by cromolyn. Eur J Pharmacol 1999; 371:241-9. [PMID: 10357262 DOI: 10.1016/s0014-2999(99)00179-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Several phosphoproteins are involved in stimulus-secretion coupling. The beta and gamma subunits of immunoglobulin E binding protein (FC epsilonRI) and three other protein bands get phosphorylated during stimulation of mast cell secretion. These additional proteins of 42, 59 and 68 kDa are also phosphorylated when secretion is stimulated by compound 48/80 (C48/80). A 78 kDa band, however, is phosphorylated as secretion wanes after stimulation with C48/80 and by the anti-allergic drug disodium cromoglycate (cromolyn). Phosphorylation was blocked by protein kinase C inhibitors. We investigated the isozyme involved by first showing that a cation ionophore prevented the phosphorylation of the 78 kDa protein, while a Ca2+ chelator did not affect phosphorylation even though it enhanced the inhibitory effect of cromolyn. This protein was identified as moesin by immunoprecipitation. Protein kinase C activators had no effect on 78 kDa protein phosphorylation either in the presence or absence of Ca2+ ions, but prevented its phosphorylation by cromolyn. Protein phosphatase inhibitors prolonged the duration, but not the amount of phosphate incorporated in the 78 kDa protein band while cromolyn had no effect on protein phosphatase action in vitro. The insensitivity of the 78 kDa protein phosphorylation to calcium and protein kinase C activators suggests that an atypical protein kinase C isozyme may be involved. Western blot analysis identified the presence of isozymes alpha, beta, delta and zeta, of which only the latter fits the profile suggested by the present findings.
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Affiliation(s)
- L Wang
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA 02111, USA
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Peirce MJ, Munday MR, Peachell PT. Characterization of protein serine/threonine phosphatase activities in human lung mast cells and basophils. Br J Pharmacol 1998; 125:1095-101. [PMID: 9846650 PMCID: PMC1565675 DOI: 10.1038/sj.bjp.0702169] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The serine/threonine protein phosphatase (PP) inhibitors, okadaic acid and calyculin, attenuated the IgE-mediated release of histamine from human lung mast cells (HLMC) and basophils in a dose-dependent manner whereas an alternative PP inhibitor, microcystin, was ineffective. Calyculin was more potent than okadaic acid in both cell types. The concentration required to inhibit by 50% (IC50) the release of histamine was 15 (HLMC) and 50 nM (basophils) for calyculin and 200 (HLMC) and 300 nM (basophils) for okadaic acid. 2. Lysates of purified HLMC and basophils dephosphorylated radiolabelled glycogen phosphorylase, a substrate for both PP1 and PP2A. The PP activity in lysates of both cell types was inhibited in a dose-dependent fashion by the PP inhibitors with the following rank order of activity, calyculin (approximate IC50; 0.02-0.1 nM) > or = microcystin (0.1 nM) > okadaic acid (70 nM). 3. The PP1-selective inhibitor, inhibitor-2 (I-2), attenuated the dephosphorylation of glycogen phosphorylase in lysates of both HLMC and basophils. I-2 (20 nM) inhibited the glycogen phosphorylase PP activity by 71+/-3% and 49+/-13% in HLMC and basophil extracts, respectively. There were, approximately, 6 fold greater levels of I-2-sensitive activity in HLMC than in basophils. Qualitatively similar results were obtained with an alternative PP1-selective inhibitor, inhibitor-1 (I-1). 4. Lysates derived from HLMC and basophils dephosphorylated radiolabelled casein which is a PP2A-restricted substrate. HLMC lysates contained, approximately, 2.5 fold higher levels of casein PP activity than basophil lysates. 5. These data indicate that HLMC and basophils both contain PP1 and PP2A. The data suggest that, on a per cell basis, HLMC have higher levels of both PP1 and PP2A. Moreover, the ratio of PP1 to PP2A is higher in HLMC than in basophils.
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Affiliation(s)
- M J Peirce
- Section of Molecular Pharmacology & Pharmacogenetics, University of Sheffield, Royal Hallamshire Hospital
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