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Gülcüler Balta GS, Monzel C, Kleber S, Beaudouin J, Balta E, Kaindl T, Chen S, Gao L, Thiemann M, Wirtz CR, Samstag Y, Tanaka M, Martin-Villalba A. 3D Cellular Architecture Modulates Tyrosine Kinase Activity, Thereby Switching CD95-Mediated Apoptosis to Survival. Cell Rep 2019; 29:2295-2306.e6. [DOI: 10.1016/j.celrep.2019.10.054] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 08/14/2019] [Accepted: 10/11/2019] [Indexed: 12/13/2022] Open
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Bamberg A, Redente EF, Groshong SD, Tuder RM, Cool CD, Keith RC, Edelman BL, Black BP, Cosgrove GP, Wynes MW, Curran-Everett D, De Langhe S, Ortiz LA, Thorburn A, Riches DWH. Protein Tyrosine Phosphatase-N13 Promotes Myofibroblast Resistance to Apoptosis in Idiopathic Pulmonary Fibrosis. Am J Respir Crit Care Med 2018; 198:914-927. [PMID: 29727583 PMCID: PMC6173065 DOI: 10.1164/rccm.201707-1497oc] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 05/04/2018] [Indexed: 01/11/2023] Open
Abstract
RATIONALE Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrotic interstitial lung disease characterized by (myo)fibroblast accumulation and collagen deposition. Resistance to Fas-induced apoptosis is thought to facilitate (myo)fibroblast persistence in fibrotic lung tissues by poorly understood mechanisms. OBJECTIVES To test the hypothesis that PTPN13 (protein tyrosine phosphatase-N13) is expressed by IPF lung (myo)fibroblasts, promotes their resistance to Fas-induced apoptosis, and contributes to the development of pulmonary fibrosis. METHODS PTPN13 was localized in lung tissues from patients with IPF and control subjects by immunohistochemical staining. Inhibition of PTPN13 function in primary IPF and normal lung (myo)fibroblasts was accomplished by: 1) downregulation with TNF-α (tumor necrosis factor-α)/IFN-γ, 2) siRNA knockdown, or 3) a cell-permeable Fas/PTPN13 interaction inhibitory peptide. The role of PTPN13 in the development of pulmonary fibrosis was assessed in mice with genetic deficiency of PTP-BL, the murine ortholog of PTPN13. MEASUREMENTS AND MAIN RESULTS PTPN13 was constitutively expressed by (myo)fibroblasts in the fibroblastic foci of patients with IPF. Human lung (myo)fibroblasts, which are resistant to Fas-induced apoptosis, basally expressed PTPN13 in vitro. TNF-α/IFN-γ or siRNA-mediated PTPN13 downregulation and peptide-mediated inhibition of the Fas/PTPN13 interaction in human lung (myo)fibroblasts promoted Fas-induced apoptosis. Bleomycin-challenged PTP-BL-/- mice, while developing inflammatory lung injury, exhibited reduced pulmonary fibrosis compared with wild-type mice. CONCLUSIONS These findings suggest that PTPN13 mediates the resistance of human lung (myo)fibroblasts to Fas-induced apoptosis and promotes pulmonary fibrosis in mice. Our results suggest that strategies aimed at interfering with PTPN13 expression or function may represent a novel strategy to reduce fibrosis in IPF.
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Affiliation(s)
- Alison Bamberg
- Program in Cell Biology, Department of Pediatrics
- Department of Immunology and Microbiology
| | - Elizabeth F. Redente
- Program in Cell Biology, Department of Pediatrics
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
- Department of Research, Veterans Affairs Eastern Colorado Health Care System, Denver, Colorado
| | - Steve D. Groshong
- Department of Medicine, and
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
| | - Rubin M. Tuder
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
| | - Carlyne D. Cool
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
| | - Rebecca C. Keith
- Department of Medicine, and
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
| | | | | | - Gregory P. Cosgrove
- Department of Medicine, and
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
| | - Murry W. Wynes
- Program in Cell Biology, Department of Pediatrics
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
| | | | - Stijn De Langhe
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
| | - Luis A. Ortiz
- Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Andrew Thorburn
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado
| | - David W. H. Riches
- Program in Cell Biology, Department of Pediatrics
- Department of Immunology and Microbiology
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, and
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado
- Department of Research, Veterans Affairs Eastern Colorado Health Care System, Denver, Colorado
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Site-Specific Detection of Tyrosine Phosphorylated CD95 Following Protein Separation by Conventional and Phospho-Protein Affinity SDS-PAGE. Methods Mol Biol 2018; 1557:173-188. [PMID: 28078592 DOI: 10.1007/978-1-4939-6780-3_16] [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: 03/10/2023]
Abstract
Phosphorylation of two tyrosines in the death domain of CD95 is a critical mechanism in determining the receptor's choices between cell death and survival signals. Recently, site-specific monoclonal antibodies against phosphorylated tyrosines of CD95 have been generated and used to successfully detect each phosphorylated death domain tyrosine of CD95 directly and separately by immunoblotting. Here we provide detailed protocols and useful tips for a successful site-specific detection of phosphorylated death domain tyrosine of CD95 following a protein separation by sizes (conventional SDS-PAGE) and by degrees of phosphorylation (phospho-protein affinity, mobility shift SDS-PAGE).
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Chakrabandhu K, Hueber AO. Fas Versatile Signaling and Beyond: Pivotal Role of Tyrosine Phosphorylation in Context-Dependent Signaling and Diseases. Front Immunol 2016; 7:429. [PMID: 27799932 PMCID: PMC5066474 DOI: 10.3389/fimmu.2016.00429] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 09/30/2016] [Indexed: 12/18/2022] Open
Abstract
The Fas/FasL system is known, first and foremost, as a potent apoptosis activator. While its proapoptotic features have been studied extensively, evidence that the Fas/FasL system can elicit non-death signals has also accumulated. These non-death signals can promote survival, proliferation, migration, and invasion of cells. The key molecular mechanism that determines the shift from cell death to non-death signals had remained unclear until the recent identification of the tyrosine phosphorylation in the death domain of Fas as the reversible signaling switch. In this review, we present the connection between the recent findings regarding the control of Fas multi-signals and the context-dependent signaling choices. This information can help explain variable roles of Fas signaling pathway in different pathologies.
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Chakrabandhu K, Huault S, Durivault J, Lang K, Ta Ngoc L, Bole A, Doma E, Dérijard B, Gérard JP, Pierres M, Hueber AO. An Evolution-Guided Analysis Reveals a Multi-Signaling Regulation of Fas by Tyrosine Phosphorylation and its Implication in Human Cancers. PLoS Biol 2016; 14:e1002401. [PMID: 26942442 PMCID: PMC4778973 DOI: 10.1371/journal.pbio.1002401] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 02/09/2016] [Indexed: 12/14/2022] Open
Abstract
Demonstrations of both pro-apoptotic and pro-survival abilities of Fas (TNFRSF6/CD95/APO-1) have led to a shift from the exclusive “Fas apoptosis” to “Fas multisignals” paradigm and the acceptance that Fas-related therapies face a major challenge, as it remains unclear what determines the mode of Fas signaling. Through protein evolution analysis, which reveals unconventional substitutions of Fas tyrosine during divergent evolution, evolution-guided tyrosine-phosphorylated Fas proxy, and site-specific phosphorylation detection, we show that the Fas signaling outcome is determined by the tyrosine phosphorylation status of its death domain. The phosphorylation dominantly turns off the Fas-mediated apoptotic signal, while turning on the pro-survival signal. We show that while phosphorylations at Y232 and Y291 share some common functions, their contributions to Fas signaling differ at several levels. The findings that Fas tyrosine phosphorylation is regulated by Src family kinases (SFKs) and the phosphatase SHP-1 and that Y291 phosphorylation primes clathrin-dependent Fas endocytosis, which contributes to Fas pro-survival signaling, reveals for the first time the mechanistic link between SFK/SHP-1-dependent Fas tyrosine phosphorylation, internalization route, and signaling choice. We also demonstrate that levels of phosphorylated Y232 and Y291 differ among human cancer types and differentially respond to anticancer therapy, suggesting context-dependent involvement of Fas phosphorylation in cancer. This report provides a new insight into the control of TNF receptor multisignaling by receptor phosphorylation and its implication in cancer biology, which brings us a step closer to overcoming the challenge in handling Fas signaling in treatments of cancer as well as other pathologies such as autoimmune and degenerative diseases. Signalling by the tumor necrosis factor receptor (TNFR) superfamily member Fas can promote either survival or death of a cell, but the mechanism underlying this choice is unclear. This study reveals that the outcome of Fas signalling (death versus survival) is determined by the tyrosine phosphorylation status of its death domain. The versatility of the tumor necrosis factor receptor superfamily members in cell fate regulation is well illustrated by the dual signaling generated by one of the most extensively studied members of the family, Fas (CD95/TNFSFR6). Upon binding its ligand, Fas is able to elicit both pro-death and pro-survival signals. Until now, we have lacked mechanistic knowledge about when and how one signaling output of Fas is favored over the other. We demonstrate here that the outcome of Fas signaling is determined by the phosphorylation status of two tyrosine residues (Y232 and Y291) within the death domain. Dephosphorylation of Fas tyrosines by SHP-1 tyrosine phosphatase turns on the pro-apoptotic signal whereas the tyrosine phosphorylation by Src family kinases (SFKs) turns off the pro-apoptotic signal and turns on the pro-survival signal. Furthermore, we provide evidence that Fas tyrosine phosphorylation status may vary among different cancer types and influence the response to anti-cancer treatments. This information reveals an opportunity to use the screening of Fas tyrosine phosphorylation, a newly discovered direct molecular indicator of Fas functional output, to aid the design of Fas-related cancer therapies.
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Affiliation(s)
| | - Sébastien Huault
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
| | - Jérôme Durivault
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
| | - Kévin Lang
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
| | - Ly Ta Ngoc
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
| | - Angelique Bole
- Centre d'Immunologie de Marseille-Luminy, Aix-Marseille Université, UM2, Marseille, France, INSERM, U1104, Marseille, France, and CNRS, UMR 7280, Marseille, France
| | - Eszter Doma
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
| | - Benoit Dérijard
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
| | | | - Michel Pierres
- Centre d'Immunologie de Marseille-Luminy, Aix-Marseille Université, UM2, Marseille, France, INSERM, U1104, Marseille, France, and CNRS, UMR 7280, Marseille, France
| | - Anne-Odile Hueber
- Univ. Nice Sophia Antipolis, CNRS, Inserm, iBV, 06100 Nice, France
- * E-mail: (AOH); (KC)
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Fouqué A, Debure L, Legembre P. The CD95/CD95L signaling pathway: a role in carcinogenesis. Biochim Biophys Acta Rev Cancer 2014; 1846:130-41. [PMID: 24780723 DOI: 10.1016/j.bbcan.2014.04.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 04/17/2014] [Accepted: 04/19/2014] [Indexed: 11/18/2022]
Abstract
Apoptosis is a fundamental process that contributes to tissue homeostasis, immune responses, and development. The receptor CD95, also called Fas, is a member of the tumor necrosis factor receptor (TNF-R) superfamily. Its cognate ligand, CD95L, is implicated in immune homeostasis and immune surveillance, and various lineages of malignant cells exhibit loss-of-function mutations in this pathway; therefore, CD95 was initially classified as a tumor suppressor gene. However, more recent data indicate that in different pathophysiological contexts, this receptor can transmit non-apoptotic signals, promote inflammation, and contribute to carcinogenesis. A comparison with the initial molecular events of the TNF-R signaling pathway leading to non-apoptotic, apoptotic, and necrotic pathways reveals that CD95 is probably using different molecular mechanisms to transmit its non-apoptotic signals (NF-κB, MAPK, and PI3K). As discussed in this review, the molecular process by which the receptor switches from an apoptotic function to an inflammatory role is unknown. More importantly, the biological functions of these signals remain elusive.
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Affiliation(s)
- Amélie Fouqué
- Université Rennes-1, 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; INSERM U1085, IRSET, 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; Equipe Labellisée Ligue Contre Le Cancer "Death Receptors and Tumor Escape", 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; Centre Eugène Marquis, rue bataille Flandres Dunkerque, Rennes, France
| | - Laure Debure
- Université Rennes-1, 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; INSERM U1085, IRSET, 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; Equipe Labellisée Ligue Contre Le Cancer "Death Receptors and Tumor Escape", 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; Centre Eugène Marquis, rue bataille Flandres Dunkerque, Rennes, France
| | - Patrick Legembre
- Université Rennes-1, 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; INSERM U1085, IRSET, 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; Equipe Labellisée Ligue Contre Le Cancer "Death Receptors and Tumor Escape", 2 Avenue du Professeur Léon Bernard, 35043 Rennes, France; Centre Eugène Marquis, rue bataille Flandres Dunkerque, Rennes, France.
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Kuo WH, Chen JH, Lin HH, Chen BC, Hsu JD, Wang CJ. Induction of apoptosis in the lung tissue from rats exposed to cigarette smoke involves p38/JNK MAPK pathway. Chem Biol Interact 2005; 155:31-42. [PMID: 15970277 DOI: 10.1016/j.cbi.2005.04.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Revised: 04/13/2005] [Accepted: 04/13/2005] [Indexed: 11/16/2022]
Abstract
Smoking is a major cause of human lung cancer. Past studies suggest that apoptosis might influence the malignant phenotype, but little is known about the association between apoptosis and cigarette smoke (CS)-induced lung pathogenesis. Using an in situ cell death detection kit (TA300), the association of CS with apoptosis was determined in a concentration-dependent manner. Furthermore, the expression of related proteins were investigated in the terminal bronchiole areas of the lung tissue from rats exposed to CS. Results showed that the expression of phosphotyrosine proteins was increased significantly in lung tissue of rats exposed to CS from 5 to 15 cigarettes. Using Western blotting and immunoprecipitation assay, Fas, a death receptor, was proved just be one of these phosphotyrosine proteins. CS triggered activation of MAP kinase (p38/JNK or ERK2) pathway, which led to Jun or p53 phosphorylation and FasL induction links Fas phosphorylation. Further, smoke treatment produced an increase in the level of proapoptotic proteins (Bax, t-Bid, cytochrome c and caspase-3), but a decline in Bcl-2, procaspase-8 and procaspase-9 proteins. Thus, CS-induced apoptosis may result from two main mechanisms, one is the activation of p38/JNK-Jun-FasL signaling, and the other is stimulated by the stabilization of p53, increase in the ratio of Bax/Bcl-2, release of cytochrome c; thus, leading to activation of caspase cascade.
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Affiliation(s)
- Wu-Hsien Kuo
- Institute of Biochemistry and Biotechnology, Chung Shan Medical University, No. 110, Sec. 1, Chien Kuo N. Road, Taichung 402, Taiwan
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Binah O, Shilkrut M, Yaniv G, Larisch S. The Fas Receptor-1,4,5-IP3Cascade: A Potential Target for Treating Heart Failure and Arrhythmias. Ann N Y Acad Sci 2004; 1015:338-50. [PMID: 15201173 DOI: 10.1196/annals.1302.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Activation of the Fas receptor in various cell types, including myocytes, triggers apoptotic as well as nonapoptotic effects. Recent studies suggest that Fas activation in the heart participates in the development of major pathologies such as myocarditis and ischemic/reperfusion insults, which are manifested by arrhythmias and mechanical dysfunction. To decipher the contribution of the Fas/FasL pathway to myocardial pathologies, we have investigated the functional consequences of Fas activation in normoxic and hypoxic ventricular myocytes. Our major findings were as follows. (1) Although Fas is constitutively expressed in ventricular myocytes, normoxic myocytes are resistant to Fas-mediated apoptosis. In contrast, hypoxia predisposes myocytes to apoptosis induced by Fas activation. The underlying mechanism is a shift in the balance between proapoptotic proteins (including Fas) and antiapoptotic proteins toward the former. (2) In normoxic myocytes, Fas activation causes a wide range of functional disturbances, which include reduction in resting potential and action potential amplitude, prolonged action potential duration, development of delayed and early after-depolarizations, occasionally culminating into arrhythmias, diastolic [Ca(2+)](i) level increase, decreased I(to) and increased I(Ca,L). (3) The above-mentioned effects in normoxic myocytes (but not Fas-mediated apoptosis in hypoxic myocytes) depend on the phospholipase C --> 1,4,5-IP(3) --> SR [Ca(2+)](i) release cascade. (4) Inhibition of tyrosine kinases with genistein blocks both the apoptotic and nonapoptotic consequences of Fas activation in ventricular myocytes. Based on these studies we propose that tyrosine phosphorylation in ventricular myocytes can serve as a novel potential target for attenuating Fas-mediated dysfunction in normoxic and hypoxic myocardium.
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Affiliation(s)
- Ofer Binah
- Rappaport Family Institute for Research in the Medical Sciences, Bruce Rappoport Faculty of Medicine, Bernard Katz Minerva Center for Cell Biophysics, Technion-Israel Institute of Technology, Haifa, 31096 Israel.
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Daigle I, Yousefi S, Colonna M, Green DR, Simon HU. Death receptors bind SHP-1 and block cytokine-induced anti-apoptotic signaling in neutrophils. Nat Med 2002; 8:61-7. [PMID: 11786908 DOI: 10.1038/nm0102-61] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Death domain-containing receptors of the tumor necrosis factor (TNF)/nerve growth factor (NGF) family can induce apoptosis upon activation in many cellular systems. We show here that a conserved phosphotyrosine-containing motif within the death domain of these receptors can mediate inhibitory functions. The Src homology domain 2 (SH2)-containing tyrosine phosphatase-1 (SHP-1), SHP-2 and SH2-containing inositol phosphatase (SHIP) bound to this motif in a caspase-independent but cell-dependent manner. We also found that stimulation of death receptors disrupted anti-apoptosis pathways initiated (at least under certain conditions) by survival factors in neutrophils. In these cells, activation of the tyrosine kinase Lyn, an important anti-apoptotic event, was prevented as a consequence of death-receptor stimulation, most likely through association of the receptor with activated SHP-1. Thus, we provide molecular and functional evidence for negative signaling by death receptors.
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Affiliation(s)
- Isabelle Daigle
- Swiss Institute of Allergy and Asthma Research (SIAF), Davos, Switzerland
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Role for Tyrosine Phosphorylation and Lyn Tyrosine Kinase in Fas Receptor-Mediated Apoptosis in Eosinophils. Blood 1998. [DOI: 10.1182/blood.v92.2.547] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Fas ligand/Fas receptor molecular interactions have been implicated as having an important function for the regulation of eosinophil apoptosis. The purpose of the present study was to investigate biochemical events triggered by the engagement of the Fas receptor in freshly isolated human and mouse eosinophils. Activation of the Fas receptor on eosinophils with the agonistic anti-Fas monoclonal antibody (MoAb) resulted in increased tyrosine phosphorylation of several intracellular proteins. The tyrosine kinase inhibitors lavendustin A and genistein inhibited Fas receptor-induced cell death in both human and mouse eosinophils in vitro and prevented, at least partially, Fas receptor-mediated resolution of eosinophilic inflammation in a mouse in vivo model of lung eosinophilia. In addition, in freshly purified human eosinophils, lavendustin A prevented anti-Fas MoAb-induced proteolytic cleavage of lamin B, suggesting that tyrosine kinases may amplify the proteolytic signaling cascade within interleukin-1β converting enzyme (ICE) family proteases. Moreover, the tyrosine kinase Lyn was identified as being involved in Fas receptor-mediated cell death. Collectively, these results demonstrate that tyrosine phosphorylation is an important step in the generation of the Fas receptor-linked transmembrane death signal in eosinophils and that Lyn participates in this pathway.
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Abstract
Fas ligand/Fas receptor molecular interactions have been implicated as having an important function for the regulation of eosinophil apoptosis. The purpose of the present study was to investigate biochemical events triggered by the engagement of the Fas receptor in freshly isolated human and mouse eosinophils. Activation of the Fas receptor on eosinophils with the agonistic anti-Fas monoclonal antibody (MoAb) resulted in increased tyrosine phosphorylation of several intracellular proteins. The tyrosine kinase inhibitors lavendustin A and genistein inhibited Fas receptor-induced cell death in both human and mouse eosinophils in vitro and prevented, at least partially, Fas receptor-mediated resolution of eosinophilic inflammation in a mouse in vivo model of lung eosinophilia. In addition, in freshly purified human eosinophils, lavendustin A prevented anti-Fas MoAb-induced proteolytic cleavage of lamin B, suggesting that tyrosine kinases may amplify the proteolytic signaling cascade within interleukin-1β converting enzyme (ICE) family proteases. Moreover, the tyrosine kinase Lyn was identified as being involved in Fas receptor-mediated cell death. Collectively, these results demonstrate that tyrosine phosphorylation is an important step in the generation of the Fas receptor-linked transmembrane death signal in eosinophils and that Lyn participates in this pathway.
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