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Schulte V, Sipol A, Burdach S, Rieger-Fackeldey E. The Truncated Splice Variant of the Granulocyte-Macrophage-Colony-Stimulating Factor Receptor β- Chain in Peripheral Blood Serves as Severity Biomarker of Respiratory Failure in Newborns. Neonatology 2021; 118:187-193. [PMID: 33784678 DOI: 10.1159/000513356] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 11/25/2020] [Indexed: 11/19/2022]
Abstract
BACKGROUND The granulocyte-macrophage-colony-stimulating factor (GM-CSF) plays an important role in surfactant homeostasis. βC is a subunit of the GM-CSF receptor (GM-CSF-R), and its activation mediates surfactant catabolism in the lung. βIT is a physiological, truncated isoform of βC and is known to act as physiological inhibitor of βC. OBJECTIVE The aim of this study was to determine the ratio of βIT and βC in the peripheral blood of newborns and its association with the degree of respiratory failure at birth. METHODS We conducted a prospective cohort study in newborns with various degrees of respiratory impairment at birth. Respiratory status was assessed by a score ranging from no respiratory impairment (0) to invasive respiratory support (3). βIT and βC expression were determined in peripheral blood cells by real-time PCR. βIT expression, defined as the ratio of βIT and βC, was correlated with the respiratory score. RESULTS βIT expression was found in all 59 recruited newborns with a trend toward higher βIT in respiratory ill (score 2, 3) newborns than respiratory healthy newborns ([score 0, 1]; p = 0.066). Seriously ill newborns (score 3) had significantly higher βIT than healthy newborns ([score 0], p = 0.010). Healthy preterm infants had significantly higher βIT expression than healthy term infants (p = 0.019). CONCLUSIONS βIT is expressed in newborns with higher expression in respiratory ill than respiratory healthy newborns. We hypothesize that βIT may have a protective effect in postnatal pulmonary adaptation acting as a physiological inhibitor of βC and, therefore, maintaining surfactant in respiratory ill newborns.
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Affiliation(s)
- Verena Schulte
- Department of Pediatrics, Division of Neonatology, Klinikum rechts der Isar, Technical University of Munich School of Medicine, Munich, Germany.,Department of Pediatrics, Children's Cancer Research Center, Kinderklinik München Schwabing, Technical University of Munich School of Medicine, Munich, Germany
| | - Alexandra Sipol
- Department of Pediatrics, Children's Cancer Research Center, Kinderklinik München Schwabing, Technical University of Munich School of Medicine, Munich, Germany
| | - Stefan Burdach
- Department of Pediatrics, Division of Neonatology, Klinikum rechts der Isar, Technical University of Munich School of Medicine, Munich, Germany.,Department of Pediatrics, Children's Cancer Research Center, Kinderklinik München Schwabing, Technical University of Munich School of Medicine, Munich, Germany
| | - Esther Rieger-Fackeldey
- Department of Pediatrics, Division of Neonatology, Klinikum rechts der Isar, Technical University of Munich School of Medicine, Munich, Germany
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Lee JH, Nam H, Um S, Lee J, Lee G, Seo BM. Upregulation of GM-CSF by TGF-β1 in epithelial mesenchymal transition of human HERS/ERM cells. In Vitro Cell Dev Biol Anim 2013; 50:399-405. [PMID: 24258001 DOI: 10.1007/s11626-013-9712-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 11/04/2013] [Indexed: 11/24/2022]
Abstract
Hertwig's epithelial root sheath/epithelial rests of Malassez (HERS/ERM) have been suggested to play an important role in tooth root formation, particularly in periodontal development. Epithelial mesenchymal transition (EMT) has been suggested to contribute to root development in tooth. However, the mechanism of interaction between HERS/ERM cells and dental mesenchymal cells has not been fully understood. In this study, we investigated the effect of exogenous transforming growth factor beta 1 (TGF-β1) in human HERS/ERM cells in order to verify the role of granulocyte macrophage colony-stimulating factor (GM-CSF) in EMT process. Antibody array was used to screen secretion factors by exogenous TGF-β1. Secretion of GM-CSF was increased by exogenous TGF-β1. Expression levels of EMT markers, vimentin, ZEB1 (zinc finger E-box binding homeobox 1), and E-cadherin, were confirmed using reverse transcription polymerase chain reaction and immunocytochemistry. Treatment with GM-CSF increased the expression of vimentin and ZEB1, similar to TGF-β1 treatment, and decreased the expression of E-cadherin. Our results suggest that GM-CSF could induce EMT in human HERS/ERM cells.
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Affiliation(s)
- Joo-Hee Lee
- Biotooth Engineering Lab, Department of Oral and Maxillofacial Surgery, School of Dentistry, Craniomaxillofacial Life Science, Dental Research Institute, Seoul National University, Seoul, South Korea
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Parajuli B, Sonobe Y, Kawanokuchi J, Doi Y, Noda M, Takeuchi H, Mizuno T, Suzumura A. GM-CSF increases LPS-induced production of proinflammatory mediators via upregulation of TLR4 and CD14 in murine microglia. J Neuroinflammation 2012; 9:268. [PMID: 23234315 PMCID: PMC3565988 DOI: 10.1186/1742-2094-9-268] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Accepted: 11/26/2012] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Microglia are resident macrophage-like cells in the central nervous system (CNS) and cause innate immune responses via the LPS receptors, Toll-like receptor (TLR) 4 and CD14, in a variety of neuroinflammatory disorders including bacterial infection, Alzheimer's disease, and amyotrophic lateral sclerosis. Granulocyte macrophage-colony stimulating factor (GM-CSF) activates microglia and induces inflammatory responses via binding to GM-CSF receptor complex composed of two different subunit GM-CSF receptor α (GM-CSFRα) and common β chain (βc). GM-CSF has been shown to be associated with neuroinflammatory responses in multiple sclerosis and Alzheimer's disease. However, the mechanisms how GM-CSF promotes neuroinflammation still remain unclear. METHODS Microglia were stimulated with 20 ng/ml GM-CSF and the levels of TLR4 and CD14 expression were evaluated by RT-PCR and flowcytometry. LPS binding was analyzed by flowcytometry. GM-CSF receptor complex was analyzed by immunocytochemistry. The levels of IL-1β, IL-6 and TNF-α in culture supernatant of GM-CSF-stimulated microglia and NF-κB nuclear translocation were determined by ELISA. Production of nitric oxide (NO) was measured by the Griess method. The levels of p-ERK1/2, ERK1/2, p-p38 and p38 were assessed by Western blotting. Statistically significant differences between experimental groups were determined by one-way ANOVA followed by Tukey test for multiple comparisons. RESULTS GM-CSF receptor complex was expressed in microglia. GM-CSF enhanced TLR4 and CD14 expressions in microglia and subsequent LPS-binding to the cell surface. In addition, GM-CSF priming increased LPS-induced NF-κB nuclear translocation and production of IL-1β, IL-6, TNF-α and NO by microglia. GM-CSF upregulated the levels of p-ERK1/2 and p-p38, suggesting that induction of TLR4 and CD14 expression by GM-CSF was mediated through ERK1/2 and p38, respectively. CONCLUSIONS These results suggest that GM-CSF upregulates TLR4 and CD14 expression in microglia through ERK1/2 and p38, respectively, and thus promotes the LPS receptor-mediated inflammation in the CNS.
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Affiliation(s)
- Bijay Parajuli
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Yoshifumi Sonobe
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Jun Kawanokuchi
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Yukiko Doi
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Mariko Noda
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
- Department of Anatomy, School of Medicine, Keio University, Shinanomachi, Tokyo, Japan
| | - Hideyuki Takeuchi
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Tetsuya Mizuno
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Akio Suzumura
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
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4
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Pradhan A, Lambert QT, Griner LN, Reuther GW. Activation of JAK2-V617F by components of heterodimeric cytokine receptors. J Biol Chem 2010; 285:16651-63. [PMID: 20363735 DOI: 10.1074/jbc.m109.071191] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The JAK2-V617F mutation is an important etiologic factor for the development of myeloproliferative neoplasms. The mechanism by which this mutated tyrosine kinase initiates deregulated signals in cells is not completely understood. It is believed that JAK2-V617F requires interactions with homodimeric cytokine receptors to elicit its transforming signal. In this study, we demonstrate that components of heterodimeric cytokine receptors can also activate JAK2-V617F. Expression of IL27Ra, a heterodimeric receptor component, enhanced the activation of JAK2-V617F and subsequent downstream signaling to activation of STAT5 and ERK. In addition, expression of components of the interleukin-3 receptor, IL3Ra and the common beta chain, activated JAK2-V617F as well as STAT5 and ERK. Importantly, expression of IL27Ra functionally replaced the requirement of a homodimeric cytokine receptor to promote the activation and transforming activity of JAK2-V617F in BaF3 cells. Tyrosine phosphorylation of IL27Ra was not required to induce activation of JAK2-V617F or STAT5, or to enhance the transforming activity of JAK2-V617F. Expression of IL3Ra or the common beta chain in BaF3 cells also enhanced the ability of JAK2-V617F to transform these hematopoietic cells. However, the heterodimeric receptor component IL12RB1 did not enhance the activation or transforming signals of JAK2-V617F in BaF3 cells. IL27Ra also activated the K539L and R683G JAK2 mutants. Together our data demonstrate that in addition to homodimeric receptors, some heterodimeric receptor components can support the activation and transforming signals of JAK2-V617F and other JAK2 mutants. Therefore, heterodimeric receptors may play unappreciated roles in JAK2 activation in the development of hematopoietic diseases including myeloproliferative neoplasms.
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Affiliation(s)
- Anuradha Pradhan
- Department of Molecular Oncology, Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, Florida 33612, USA
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Saulle E, Riccioni R, Coppola S, Parolini I, Diverio D, Riti V, Mariani G, Laufer S, Sargiacomo M, Testa U. Colocalization of the VEGF-R2 and the common IL-3/GM-CSF receptor beta chain to lipid rafts leads to enhanced p38 activation. Br J Haematol 2009; 145:399-411. [DOI: 10.1111/j.1365-2141.2009.07627.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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6
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Hansen G, Hercus TR, McClure BJ, Stomski FC, Dottore M, Powell J, Ramshaw H, Woodcock JM, Xu Y, Guthridge M, McKinstry WJ, Lopez AF, Parker MW. The structure of the GM-CSF receptor complex reveals a distinct mode of cytokine receptor activation. Cell 2008; 134:496-507. [PMID: 18692472 DOI: 10.1016/j.cell.2008.05.053] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 04/18/2008] [Accepted: 06/05/2008] [Indexed: 11/26/2022]
Abstract
Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic cytokine that controls the production and function of blood cells, is deregulated in clinical conditions such as rheumatoid arthritis and leukemia, yet offers therapeutic value for other diseases. Its receptors are heterodimers consisting of a ligand-specific alpha subunit and a betac subunit that is shared with the interleukin (IL)-3 and IL-5 receptors. How signaling is initiated remains an enigma. We report here the crystal structure of the human GM-CSF/GM-CSF receptor ternary complex and its assembly into an unexpected dodecamer or higher-order complex. Importantly, mutagenesis of the GM-CSF receptor at the dodecamer interface and functional studies reveal that dodecamer formation is required for receptor activation and signaling. This unusual form of receptor assembly likely applies also to IL-3 and IL-5 receptors, providing a structural basis for understanding their mechanism of activation and for the development of therapeutics.
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Affiliation(s)
- Guido Hansen
- Biota Structural Biology Laboratory, St. Vincent's Institute of Medical Research, 41 Victoria Parade, Fitzroy, Victoria 3065, Australia
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7
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Zaks-Zilberman M, Harrington AE, Ishino T, Chaiken IM. Interleukin-5 receptor subunit oligomerization and rearrangement revealed by fluorescence resonance energy transfer imaging. J Biol Chem 2008; 283:13398-406. [PMID: 18326494 DOI: 10.1074/jbc.m710230200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interleukin (IL)-5 exerts hematopoietic functions through binding to the IL-5 receptor subunits, alpha and betac. Specific assembly steps of full-length subunits as they occur in cell membranes, ultimately leading to receptor activation, are not well understood. We tracked the oligomerization of IL-5 receptor subunits using fluorescence resonance energy transfer (FRET) imaging. Full-length IL-5Ralpha and betac were expressed in Phoenix cells as chimeric proteins fused to enhanced cyan or yellow fluorescent protein (CFP or YFP, respectively). A time- and dose-dependent increase in FRET signal between IL-5Ralpha-CFP and betac-YFP was observed in response to IL-5, indicative of heteromeric receptor alpha-betac subunit interaction. This response was inhibited by AF17121, a peptide antagonist of IL-5Ralpha. Substantial FRET signals with betac-CFP and betac-YFP co-expressed in the absence of IL-5Ralpha demonstrated that betac subunits exist as preformed homo-oligomers. IL-5 had no effect on this betac-alone FRET signal. Interestingly, the addition of IL-5 to cells co-expressing betac-CFP, betac-YFP, and nontagged IL-5Ralpha led to further increase in FRET efficiency. Observation of preformed betac oligomers fits with the view that this form can lead to rapid cellular responses upon IL-5 stimulation. The IL-5-induced effects on betac assembly in the presence of nontagged IL-5Ralpha provide direct evidence that IL-5 can cause higher order rearrangements of betac homo-oligomers. These results suggest that IL-5 and perhaps other betac cytokines (IL-3 and granulocyte/macrophage colony-stimulating factor) trigger cellular responses by the sequential binding of cytokine ligand to the specificity receptor (subunit alpha), followed by binding of the ligand-subunit alpha complex to, and consequent rearrangement of, a ground state form of betac oligomers.
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Affiliation(s)
- Meirav Zaks-Zilberman
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA
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8
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Murphy JM, Young IG. IL-3, IL-5, and GM-CSF signaling: crystal structure of the human beta-common receptor. VITAMINS AND HORMONES 2006; 74:1-30. [PMID: 17027509 DOI: 10.1016/s0083-6729(06)74001-8] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The cytokines, interleukin-3 (IL-3), interleukin-5 (IL-5), and granulocyte-macrophage colony stimulating factor (GM-CSF), are polypeptide growth factors that exhibit overlapping activities in the regulation of hematopoietic cells. They appear to be primarily involved in inducible hematopoiesis in response to infections and are involved in the pathogenesis of allergic and inflammatory diseases and possibly in leukemia. The X-ray structure of the beta common (betac) receptor ectodomain has given new insights into the structural biology of signaling by IL-3, IL-5, and GM-CSF. This receptor is shared between the three ligands and functions together with three ligand-specific alpha-subunits. The structure shows betac is an intertwined homodimer in which each chain contains four domains with approximate fibronectin type-III topology. The two betac-subunits that compose the homodimer are interlocked by virtue of the swapping of beta-strands between domain 1 of one subunit and domain 3 of the other subunit. Site-directed mutagenesis has shown that the interface between domains 1 and 4 in this unique structure forms the functional epitope. This epitope is similar to those of other members of the cytokine class I receptor family but is novel in that it is formed by two different receptor chains. The chapter also reviews knowledge on the closely related mouse beta(IL-3) receptor and on the alpha-subunit-ligand interactions. The knowledge on the two beta receptors is placed in context with advances in understanding of the structural biology of other members of the cytokine class I receptor family.
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Affiliation(s)
- James M Murphy
- Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, Acton, ACT, Australia 0200
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Ebner K, Bandion A, Binder BR, de Martin R, Schmid JA. GMCSF activates NF-kappaB via direct interaction of the GMCSF receptor with IkappaB kinase beta. Blood 2003; 102:192-9. [PMID: 12637324 DOI: 10.1182/blood-2002-12-3753] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Granulocyte-macrophage colony-stimulating factor (GMCSF) has a central role in proliferation and differentiation of hematopoetic cells. Furthermore, it influences the proliferation and migration of endothelial cells. GMCSF elicits these functions by activating a receptor consisting of a ligand-specific alpha-chain and a beta-chain, which is common for GMCSF, interleukin-3 (IL-3), and IL-5. It is known that various signaling molecules such as Janus kinase 2 or transcription factors of the signal transducer and activator of transcription (STAT) family bind to the common beta-chain and initiate signaling cascades. However, alpha-chain-specific signal transduction adapters have to be postulated given that IL-3, IL-5, and GMCSF induce partly distinct biologic responses. Using a yeast 2-hybrid system, we identified the alpha-chain of the GMCSF receptor (GMRalpha) as putative interaction partner of IkappaB kinase beta, one of the central signaling kinases activating the transcription factor nuclear factor-kappaB (NF-kappaB). Using endogenous protein levels of endothelial cell extracts, we could verify the interaction by coimmunoprecipitation experiments. Fluorescence resonance energy transfer (FRET) microscopy confirmed the direct interaction of CFP-IKKbeta and YFPGMRalpha in living cells. Functional studies demonstrated GMCSF-dependent activation of IkappaB kinase activity in endothelial cells, degradation of IkappaB, and activation of NF-kappaB. Further biologic studies using GMCSF-dependent TF-1 cells indicated that GMCSF-triggered activation of NF-kappaB is important for cell survival and proliferation.
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Affiliation(s)
- Karin Ebner
- Department of Vascular Biology and Thrombosis Research, University of Vienna, Brunnerstrasse 59, A-1235 Vienna, Austria
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McClure BJ, Hercus TR, Cambareri BA, Woodcock JM, Bagley CJ, Howlett GJ, Lopez AF. Molecular assembly of the ternary granulocyte-macrophage colony-stimulating factor receptor complex. Blood 2003; 101:1308-15. [PMID: 12393492 DOI: 10.1182/blood-2002-06-1903] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine that stimulates the production and functional activity of granulocytes and macrophages, properties that have encouraged its clinical use in bone marrow transplantation and in certain infectious diseases. Despite the importance of GM-CSF in regulating myeloid cell numbers and function, little is known about the exact composition and mechanism of assembly of the GM-CSF receptor complex. We have now produced soluble forms of the GM-CSF receptor alpha chain (sGMRalpha) and beta chain (sbetac) and utilized GM-CSF, the GM-CSF antagonist E21R (Glu21Arg), and the betac-blocking monoclonal antibody BION-1 to define the molecular assembly of the GM-CSF receptor complex. We found that GM-CSF and E21R were able to form low-affinity, binary complexes with sGMRalpha, each having a stoichiometry of 1:1. Importantly, GM-CSF but not E21R formed a ternary complex with sGMRalpha and sbetac, and this complex could be disrupted by E21R. Significantly, size-exclusion chromatography, analytical ultracentrifugation, and radioactive tracer experiments indicated that the ternary complex is composed of one sbetac dimer with a single molecule each of sGMRalpha and of GM-CSF. In addition, a hitherto unrecognized direct interaction between betac and GM-CSF was detected that was absent with E21R and was abolished by BION-1. These results demonstrate a novel mechanism of cytokine receptor assembly likely to apply also to interleukin-3 (IL-3) and IL-5 and have implications for our molecular understanding and potential manipulation of GM-CSF activation of its receptor.
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Affiliation(s)
- Barbara J McClure
- Cytokine Receptor Laboratory and Protein Laboratory, Division of Human Immunology, Institute of Medical and Veterinary Science (IMVS), Adelaide, South Australia
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11
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Rossini A, Militi S, Sposi NM, Pelosi E, Testa U. Modulation by growth factors of the expression of interleukin 3 and granulocyte-macrophage colony-stimulating factor receptor common chain beta c. Leuk Lymphoma 2002; 43:1645-50. [PMID: 12400608 DOI: 10.1080/1042819021000002983] [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: 10/28/2022]
Abstract
Interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 5 (IL-5) exert their biological activities through interaction with cell-surface receptors that consist of two subunits, a specific a subunit and a common beta transducing subunit (beta c). We have evaluated the effect of growth factors on the expression of beta c in normal monocytes. Addition of either GM-CSF or M-CSF to monocytes elicited a marked increase of beta c chain expression, a phenomenon seemingly related to a stimulation of the transcriptional activity of this gene mediated through an enhancement of the PU.1 DNA binding activity. Interestingly, during the activation of beta c chain expression by growth factors a switch from the synthesis of the truncated betaIT to the full-length beta c was observed. Similar observations have been made also in the growth factor-dependent erythroleukemic cell line TF-1, showing that GM-CSF deprivation elicited a marked decrease of beta c chain expression.
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Affiliation(s)
- Annalisa Rossini
- Department of Hematology and Oncology, Istituto Superiore di Sanità, Rome, Italy
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12
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Watanabe S, Murakami T, Nakamura T, Morimoto C, Arai KI. Human GM-CSF induces HIV-1 LTR by multiple signalling pathways. Biochimie 2002; 84:633-42. [PMID: 12453635 DOI: 10.1016/s0300-9084(02)01433-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Human immunodeficiency virus type-1 (HIV-1) gene expression is known to be affected by numerous cytokines or growth factors. However, the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on long terminal repeat (LTR)-mediated transcription of HIV-1 still remains unknown. By transient transfection experiments with HIV-1 LTR reporter constructs, we showed that strong LTR-mediated activation was induced by GM-CSF in mouse Ba/F3 cells expressing human GM-CSF receptors (GM-CSFR). Mutational analysis of the HIV-1 LTR reporters revealed that both NF-kappaB and Sp1 binding sites play important roles as positive regulatory elements. Analysis of various mutants of the cytoplasmic region of GM-CSFR indicated that both the conserved membrane proximal region and tyrosine residues located in the distal part of the beta subunit were required for HIV-1 LTR activation. Possible involvement of MAPK and PI3-K signalling pathways was suggested by the partial inhibition by wortmannin, a specific inhibitor of the PI3-K pathway, and enhancement by constitutively active MEK1, of HIV-1 LTR activation. However, the MEK1 pathway is not essential since MEK1 inhibitor PD98059 did not suppress GM-CSF-induced HIV-1-LTR activation. Further analyses of GM-CSFR mutants suggested that some other unknown signalling pathway also participates in GM-CSF-induced HIV-1 LTR activation. Taken together, the data suggest that GM-CSF could upregulate the LTR-driven transcription of HIV-1 through modulation of NF-kappaB and SP1 by multiple signalling pathways.
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Affiliation(s)
- Sumiko Watanabe
- Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
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McClure B, Stomski F, Lopez A, Woodcock J. Perverted responses of the human granulocyte-macrophage colony-stimulating factor receptor in mouse cell lines due to cross-species beta-subunit association. Blood 2001; 98:3165-8. [PMID: 11698308 DOI: 10.1182/blood.v98.10.3165] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transfected murine cell lines are commonly used to study the function of many human cytokine or receptor mutants. This study reports the inappropriate activation of the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) receptor by the human GM-CSF antagonist, E21R, when the human receptor is introduced into the murine cell line BaF-B03. E21R-induced proliferation of the BaF-B03 cells is dependent on transfection with both hGM-CSF receptor alpha and beta(c) subunits. Studies on the underlying mechanism revealed constitutive association between human and mouse beta(c) and GM-CSF receptor-alpha, tyrosine phosphorylation of mouse and human beta(c), and association of phosphorylated mouse beta(c) into an activated human GM-CSF receptor complex in response to E21R and GM-CSF. This interspecies receptor cross-talk of receptor signaling subunits may produce misleading results and emphasizes the need to use cell lines devoid of the cognate endogenous receptors for functional analysis of ligand and receptor mutants.
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Affiliation(s)
- B McClure
- Cytokine Receptor Laboratory, Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Adelaide, South Australia
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Wagner K, Kafert-Kasting S, Heil G, Ganser A, Eder M. Inhibition of granulocyte-macrophage colony-stimulating factor receptor function by a splice variant of the common beta-receptor subunit. Blood 2001; 98:2689-96. [PMID: 11675339 DOI: 10.1182/blood.v98.9.2689] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 are composed of a ligand-specific alpha-chain (eg, alpha-GM-CSF receptor [alpha-GMR]) and a common beta-subunit (beta-GMR). Ligand binding is believed to induce assembly or conformational changes in preformed complexes containing more than one alpha- and beta-subunit in the activated receptor complex. To analyze the function of a splice variant of beta-GMR with a truncation in the intracellular domain (beta-GMR(IT)), BaF-3 cells expressing human alpha-GMR plus beta-GMR were transfected with beta-GMR(IT). In these cells, coexpression of beta-GMR(IT) inhibits GM-CSF-mediated survival and proliferation in a GM-CSF concentration-dependent manner. To analyze the effect of cytoplasmic assembly of truncated and full-length intracellular beta-GMR sequences, beta-GMR and beta-GMR(IT) were coexpressed with different chimeric alpha/beta-GMR constructs. Whereas both beta-GMR and beta-GMR(IT) generate high-affinity GMR complexes in the presence of alpha/beta-GMR, beta-GMR(IT) inhibits while beta-GMR supports proliferation and cell survival mediated by alpha/beta-GMR. Correspondingly, beta-GMR, but not beta-GMR(IT), generates functional GMR complexes when coexpressed with a defective alpha/beta-GMR construct. These data indicate that beta-GMR(IT) can inhibit survival and mitogenic signaling of the wild-type GMR and demonstrate that recruitment of alternatively spliced receptor subunits may regulate the function of heteromeric cytokine receptors.
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Affiliation(s)
- K Wagner
- Department of Hematology and Oncology, Hannover Medical School, and the Center for Cell Therapy/Cytonet, Hannover, Germany
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15
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Prassolov V, Meyer J, Brandenburg G, Hannemann J, Bergemann J, Ostertag W, Stocking C. Functional identification of secondary mutations inducing autonomous growth in synergy with a truncated interleukin-3 receptor Implications for multi-step oncogenesis. Exp Hematol 2001; 29:756-65. [PMID: 11378271 DOI: 10.1016/s0301-472x(01)00648-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE A truncated common beta chain (Deltabeta(C)) of the interleukin-3 (IL-3) receptor complex was previously identified as a key factor in inducing autonomous growth of IL-3-independent mutants. Expression of Deltabeta(C) in IL-3-dependent hematopoietic cells does not result in immediate factor-independent growth, but increases the frequency of obtaining autonomous mutants by three to four orders of magnitude. This study was designed to delineate the mechanisms by which Deltabeta(C) increases the frequency to autonomous growth. DESIGN AND METHODS Retroviral vectors were used to express Deltabeta(C) into IL-3-dependent myeloid cells, which were then tested for factor-independent growth. To determine if secondary genetic events were required for conversion to autonomous growth, elements of the Cre-loxP recombinant system were used to excise Deltabeta(C) in factor-independent clones. RESULTS Excision of Deltabeta(C) in factor-independent clones revealed two types of phenotypes: reversion to factor-dependent growth (1/8) or continued IL-3-dependent growth (7/8). Analysis of cells that remained factor independent revealed constitutive activation of STAT5, not observed in factor-dependent revertants. Analysis of revertant cells demonstrated the presence of interacting secondary mutations that synergize with Deltabeta(C)-induced proliferation. A cysteine residue within the truncated extracellular domain of Deltabeta(C) was also found to be required for its oncogenic potential, supporting a model of dimerization for receptor activation. CONCLUSIONS The high incidence of obtaining factor-independent mutants from cells expressing Deltabeta(C) results from the selection of mutations that either complement Deltabeta(C) expression to promote proliferation or that singly or in synergy with other secondary mutations negate the requirement of Deltabeta(C) expression for proliferation.
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Affiliation(s)
- V Prassolov
- Department of Cell and Virus Genetics, Heinrich-Pette-Institut für Experimentelle Immunologie und Virologie an der Universität Hamburg, Hamburg, Germany
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16
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Carr PD, Gustin SE, Church AP, Murphy JM, Ford SC, Mann DA, Woltring DM, Walker I, Ollis DL, Young IG. Structure of the complete extracellular domain of the common beta subunit of the human GM-CSF, IL-3, and IL-5 receptors reveals a novel dimer configuration. Cell 2001; 104:291-300. [PMID: 11207369 DOI: 10.1016/s0092-8674(01)00213-6] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The receptor systems for the hemopoietic cytokines GM-CSF, IL-3, and IL-5 consist of ligand-specific alpha receptor subunits that play an essential role in the activation of the shared betac subunit, the major signaling entity. Here, we report the structure of the complete betac extracellular domain. It has a structure unlike any class I cytokine receptor described thus far, forming a stable interlocking dimer in the absence of ligand in which the G strand of domain 1 hydrogen bonds into the corresponding beta sheet of domain 3 of the dimer-related molecule. The G strand of domain 3 similarly partners with the dimer-related domain 1. The structure provides new insights into receptor activation by the respective alpha receptor:ligand complexes.
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MESH Headings
- Amino Acid Sequence
- Animals
- Baculoviridae/genetics
- Blotting, Western
- Dimerization
- Humans
- Ligands
- Models, Molecular
- Molecular Sequence Data
- Protein Binding
- Protein Conformation
- Protein Folding
- Protein Structure, Quaternary
- Protein Structure, Tertiary
- Protein Subunits
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/chemistry
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/metabolism
- Receptors, Interleukin/chemistry
- Receptors, Interleukin/metabolism
- Receptors, Interleukin-3/chemistry
- Receptors, Interleukin-3/metabolism
- Receptors, Interleukin-5
- Sequence Alignment
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Affiliation(s)
- P D Carr
- Research School of Chemistry, Australian National University, Acton, ACT 0200, Australia
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17
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Prevost JM, Farrell PJ, Iatrou K, Brown CB. Determinants of the functional interaction between the soluble GM-CSF receptor and the GM-CSF receptor beta-subunit. Cytokine 2000; 12:187-97. [PMID: 10704245 DOI: 10.1006/cyto.1999.0527] [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: 12/14/2022]
Abstract
The GM-CSF receptor consists of a GM-CSF specific low affinity alpha-subunit (GMRalpha) and a beta-subunit (betac) that associates with GMRalpha in the presence of GM-CSF to form a high-affinity complex. A splice variant soluble isoform of GMRalpha (solalpha) consists of the extracellular domain of GMRalpha and a unique 16-amino acid C-terminal domain. Exogenously administered solalpha is unable to associate with betac on the cell surface either in the presence or absence of GM-CSF. However, paradoxically, co-expression of solalpha with betac results in the ligand-independent association of solalpha with betac on the cell surface via the C-terminal domain of solalpha. To study the interaction and functional characteristics of the solalpha-betac complex we engineered a soluble betac-subunit (ECDbeta) and expressed it alone and with solalpha. Co-expressed but not independent sources of solalpha and ECDbeta could be co-precipitated in the absence of ligand demonstrating the extracellular domain of betac was sufficient for association with solalpha upon co-expression. However, independent sources of solalpha could associate with ECDbeta in the presence of GM-CSF as could a C-terminal deficient solalpha mutant (ECDalpha) and the addition of ECDbeta to ECDalpha and GM-CSF was associated with a conversion from a low- to high-affinity ligand-receptor complex.
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Affiliation(s)
- J M Prevost
- Alberta Bone Marrow Transplant Program, Cancer Biology Research Group, Department of Medicine and Oncology, The University of Calgary, Calgary, Alberta, T2N 4N1, Canada
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18
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D'Andrea RJ, Gonda TJ. A model for assembly and activation of the GM-CSF, IL-3 and IL-5 receptors: insights from activated mutants of the common beta subunit. Exp Hematol 2000; 28:231-43. [PMID: 10720688 DOI: 10.1016/s0301-472x(99)00159-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Granulocyte-macrophage colony stimulating factor (GM-CSF), Interleukin-3 (IL-3) and Interleukin-5 (IL-5) have overlapping, pleiotropic effects on hematopoietic cells, including neutrophils, eosinophils, monocytes and early progenitor cells. The high-affinity receptors for human GM-CSF, IL-3, and IL-5 share a common beta-subunit (hbeta(c)), which is essential for signalling and plays a major role in recruiting intracellular signalling molecules. While activation of the cytoplasmic tyrosine kinase JAK2 appears to be the initiating event for signalling, the immediate events that trigger this are still unclear. We have isolated a number of activated mutants of hbeta(c), which can be grouped into classes defined by their state of receptor phosphorylation, their requirement for alpha subunit as a cofactor, and their activities in primary cells and cell lines. We discuss these findings with regard to the stoichiometry, activation, and signalling of the normal GM-CSF/IL-3/IL-5 receptor complexes. Specifically, this work has implications for the role of the ligand-specific alpha-subunits in initiating the signalling through the beta-subunit, the role of beta subunit dimerization as a receptor trigger, and the function of receptor tyrosine phosphorylation in generating growth and survival signals. Based on the properties of the activated mutants and the recent structures of erythropoietin receptor (Epo-R) complexes, we propose a model in which (1) activation of hbeta(c) can occur via alternative states that differ with respect to stoichiometry and subunit assembly, but which all mediate proliferative responses, and (2) each of the different classes of activated mutants mimics one of these alternative states.
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MESH Headings
- Amino Acid Sequence
- Animals
- Granulocyte-Macrophage Colony-Stimulating Factor/metabolism
- Humans
- Interleukin-3/metabolism
- Interleukin-5/metabolism
- Models, Biological
- Models, Molecular
- Molecular Sequence Data
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/chemistry
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/genetics
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/metabolism
- Receptors, Interleukin/chemistry
- Receptors, Interleukin/genetics
- Receptors, Interleukin/metabolism
- Receptors, Interleukin-3/chemistry
- Receptors, Interleukin-3/genetics
- Receptors, Interleukin-3/metabolism
- Receptors, Interleukin-5
- Signal Transduction
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Affiliation(s)
- R J D'Andrea
- Hanson Centre for Cancer Research and, Adelaide, South Australia, Australia
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19
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Kafert S, Luther S, Böll I, Wagner K, Ganser A, Eder M. Functional analysis of a single chain chimeric alpha/beta-granulocyte-macrophage colony-stimulating factor receptor. Importance of a glutamate residue in the transmembrane region. J Biol Chem 1999; 274:33064-71. [PMID: 10551876 DOI: 10.1074/jbc.274.46.33064] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To analyze the function of each subunit of the receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF), GMR, we previously generated a single-chain chimeric receptor by fusion of the extracellular and transmembrane domain from the alpha-subunit (alpha-GMR) to the intracellular part of the beta-subunit (beta-GMR) introducing an additional glutamate residue at the fusion site (alpha/beta-GMR). We demonstrated the capacity of alpha/beta-GMR to bind GM-CSF with low affinity and to induce GM-CSF-dependent activation of tyrosine kinase activity and proliferation in transfected Ba/F3 cells. To further compare the functions of wild type and chimeric receptors, we now report that this alpha/beta-GMR is sufficient to mediate morphological changes, expression of alpha(4)- and beta(1)-integrin receptor subunits, and serine-phosphorylation of Akt kinase. To analyze the function of the glutamate residue at the fusion region of alpha/beta-GMR various point mutants changing this amino acid and its position were expressed in Ba/F3 cells. None of these mutants was capable of supporting GM-CSF-dependent proliferation; however, when beta-GMR was coexpressed, GM-CSF mediated short and long term proliferation. Interestingly, some mutants but not alpha/beta-GMR can induce proliferation in the presence of an anti-alpha-GMR antibody. These data demonstrate the significance of a glutamate residue in the transmembrane region of alpha/beta-GMR for ligand-induced receptor activation.
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Affiliation(s)
- S Kafert
- Department of Hematology, Hannover Medical School, D-30625 Hannover, Germany
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20
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Woodcock JM, Bagley CJ, Lopez AF. The functional basis of granulocyte-macrophage colony stimulating factor, interleukin-3 and interleukin-5 receptor activation, basic and clinical implications. Int J Biochem Cell Biol 1999; 31:1017-25. [PMID: 10582336 DOI: 10.1016/s1357-2725(99)00084-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The cytokines granulocyte-macrophage colony stimulating factor, interleukin-3 and interleukin-5 have overlapping activities on cells expressing their receptors. This is explained by their sharing a receptor signal transduction subunit, beta c. This communal signaling subunit is also required for high affinity binding of all three cytokines. Therapeutic approaches attempting to interfere or modulate haemopoietic cells using cytokines or their analogues can in some instances be limited due to functional redundancy amongst cytokines using shared receptor signaling subunits. Therefore, a better approach would be to develop therapeutics against the shared subunit. Studies examining the GM-CSF, IL-3 and IL-5 receptors have identified the key events leading to functional receptor activation. With this knowledge, it is now possible to identify new targets for the development of a new class of antagonist that blocks the biological activity of all the cytokines utilizing beta c. This approach may be extended to other receptor systems such as IL-4 and IL-13 where receptor activation is dependent on a common signaling and binding subunit.
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MESH Headings
- Animals
- Binding Sites
- Humans
- Ligands
- Receptors, Cytokine/genetics
- Receptors, Cytokine/immunology
- Receptors, Cytokine/metabolism
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/genetics
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/immunology
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/metabolism
- Receptors, Interleukin/genetics
- Receptors, Interleukin/immunology
- Receptors, Interleukin/metabolism
- Receptors, Interleukin-3/genetics
- Receptors, Interleukin-3/immunology
- Receptors, Interleukin-3/metabolism
- Receptors, Interleukin-5
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Affiliation(s)
- J M Woodcock
- Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Adelaide, SA, Australia
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21
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Identification of a 14-3-3 Binding Sequence in the Common β Chain of the Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF), Interleukin-3 (IL-3), and IL-5 Receptors That Is Serine-Phosphorylated by GM-CSF. Blood 1999. [DOI: 10.1182/blood.v94.6.1933.418k10_1933_1942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The common β chain (βc) of the granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 receptors is the major signaling subunit of these receptors coupling ligand binding to multiple biological activities. It is thought that these multiple functions arise as a consequence of the recruitment of specific signaling molecules to tyrosine-phosphorylated residues in the cytoplasmic domain of βc. However, the contribution of serine phosphorylation in βc to the recruitment of signaling molecules is not known. We show here the identification of a phosphoserine motif in the cytoplasmic domain of βc that interacts with the adaptor protein 14-3-3ζ. Coimmunoprecipitation and pull-down experiments with a glutathione S-transferase (GST):14-3-3ζ fusion protein showed that 14-3-3 directly associates with βc but not the GM-CSF receptor chain. C-terminal truncation mutants of βcfurther showed that a region between amino acids 544 and 626 in βc was required for its association with 14-3-3ζ. This region contains the sequence 582HSRSLP587, which closely resembles the RSXSXP (where S is phosphorylated) consensus 14-3-3 binding site identified in a number of signaling molecules, including Raf-1. Significantly, substitution of582HSRSLP587 for EFAAAA completely abolished interaction of βc with GST–14-3-3ζ. Furthermore, the interaction of βc with GST–14-3-3 was greatly reduced in the presence of a peptide containing the 14-3-3 binding site, but only when 585Ser was phosphorylated. Direct binding experiments showed that the peptide containing phosphorylated 585Ser bound 14-3-3ζ with an affinity of 150 nmol/L. To study the regulation of 585S phosphorylation in vivo, we raised antibodies that specifically recognized 585Ser-phosphorylated βc. Using these antibodies, we showed that GM-CSF stimulation strongly upregulated 585Ser phosphorylation in M1 myeloid leukemic cells. The proximity of the SHC-binding site (577Tyr) to the 14-3-3–binding site (582HSRSLP587) and their conservation between mouse, rat, and human βc but not in other cytokine receptors suggest that they form a distinct motif that may subserve specialized functions associated with the GM-CSF, IL-3, and IL-5 receptors.
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22
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Identification of a 14-3-3 Binding Sequence in the Common β Chain of the Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF), Interleukin-3 (IL-3), and IL-5 Receptors That Is Serine-Phosphorylated by GM-CSF. Blood 1999. [DOI: 10.1182/blood.v94.6.1933] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe common β chain (βc) of the granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 receptors is the major signaling subunit of these receptors coupling ligand binding to multiple biological activities. It is thought that these multiple functions arise as a consequence of the recruitment of specific signaling molecules to tyrosine-phosphorylated residues in the cytoplasmic domain of βc. However, the contribution of serine phosphorylation in βc to the recruitment of signaling molecules is not known. We show here the identification of a phosphoserine motif in the cytoplasmic domain of βc that interacts with the adaptor protein 14-3-3ζ. Coimmunoprecipitation and pull-down experiments with a glutathione S-transferase (GST):14-3-3ζ fusion protein showed that 14-3-3 directly associates with βc but not the GM-CSF receptor chain. C-terminal truncation mutants of βcfurther showed that a region between amino acids 544 and 626 in βc was required for its association with 14-3-3ζ. This region contains the sequence 582HSRSLP587, which closely resembles the RSXSXP (where S is phosphorylated) consensus 14-3-3 binding site identified in a number of signaling molecules, including Raf-1. Significantly, substitution of582HSRSLP587 for EFAAAA completely abolished interaction of βc with GST–14-3-3ζ. Furthermore, the interaction of βc with GST–14-3-3 was greatly reduced in the presence of a peptide containing the 14-3-3 binding site, but only when 585Ser was phosphorylated. Direct binding experiments showed that the peptide containing phosphorylated 585Ser bound 14-3-3ζ with an affinity of 150 nmol/L. To study the regulation of 585S phosphorylation in vivo, we raised antibodies that specifically recognized 585Ser-phosphorylated βc. Using these antibodies, we showed that GM-CSF stimulation strongly upregulated 585Ser phosphorylation in M1 myeloid leukemic cells. The proximity of the SHC-binding site (577Tyr) to the 14-3-3–binding site (582HSRSLP587) and their conservation between mouse, rat, and human βc but not in other cytokine receptors suggest that they form a distinct motif that may subserve specialized functions associated with the GM-CSF, IL-3, and IL-5 receptors.
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23
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Heterodimerization of the and β Chains of the Interleukin-3 (IL-3) Receptor Is Necessary and Sufficient for IL-3–Induced Mitogenesis. Blood 1999. [DOI: 10.1182/blood.v94.5.1614] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe high-affinity receptor for interleukin-3 (IL-3) is a complex of the IL-3–binding subunit (IL-3) and a larger β chain—βc, or, in the mouse, βc or its close relative βIL-3. There is evidence that the critical event that initiates signaling is not the approximation of the cytoplasmic domains of IL-3 and βIL-3, but is, rather, the formation of a β-β homodimer. Many of these studies involved the analyses of receptor chimeras where the cytoplasmic domains were derived from IL-3, βc or βIL-3, and the extracellular domains were derived from other cytokine receptors, such as the erythropoietin receptor (EpoR). However, evidence that the EpoR may also associate with other receptors clouds the interpretation of these experiments. Therefore, we reevaluated the structure of the functional IL-3R using chimeric receptors with extracellular domains derived not from members of the cytokine-receptor family, but from CD8 or CD16. We show, by expression of these chimeras in Ba/F3 or CTLL-2 cells, that mitogenic signals were only generated by heterodimerization of the cytoplasmic domains of IL-3 and βIL-3. Homodimers of either IL-3 or βIL-3, alone or in combination, were nonfunctional. Furthermore, the ability of heterodimers to stimulate mitogenesis correlated with their ability to induce tyrosine phosphorylation of JAK-2. These data suggest that the physiological activation of the IL-3R involves the generation of simple heterodimers of IL-3 and βIL-3.
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24
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Heterodimerization of the and β Chains of the Interleukin-3 (IL-3) Receptor Is Necessary and Sufficient for IL-3–Induced Mitogenesis. Blood 1999. [DOI: 10.1182/blood.v94.5.1614.417k22_1614_1622] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The high-affinity receptor for interleukin-3 (IL-3) is a complex of the IL-3–binding subunit (IL-3) and a larger β chain—βc, or, in the mouse, βc or its close relative βIL-3. There is evidence that the critical event that initiates signaling is not the approximation of the cytoplasmic domains of IL-3 and βIL-3, but is, rather, the formation of a β-β homodimer. Many of these studies involved the analyses of receptor chimeras where the cytoplasmic domains were derived from IL-3, βc or βIL-3, and the extracellular domains were derived from other cytokine receptors, such as the erythropoietin receptor (EpoR). However, evidence that the EpoR may also associate with other receptors clouds the interpretation of these experiments. Therefore, we reevaluated the structure of the functional IL-3R using chimeric receptors with extracellular domains derived not from members of the cytokine-receptor family, but from CD8 or CD16. We show, by expression of these chimeras in Ba/F3 or CTLL-2 cells, that mitogenic signals were only generated by heterodimerization of the cytoplasmic domains of IL-3 and βIL-3. Homodimers of either IL-3 or βIL-3, alone or in combination, were nonfunctional. Furthermore, the ability of heterodimers to stimulate mitogenesis correlated with their ability to induce tyrosine phosphorylation of JAK-2. These data suggest that the physiological activation of the IL-3R involves the generation of simple heterodimers of IL-3 and βIL-3.
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25
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Okuda K, Foster R, Griffin JD. Signaling domains of the beta c chain of the GM-CSF/IL-3/IL-5 receptor. Ann N Y Acad Sci 1999; 872:305-12; discussion 312-3. [PMID: 10372132 DOI: 10.1111/j.1749-6632.1999.tb08474.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The granulocyte/macrophage colony-stimulating factor (GM-CSF)/interleukin-3 (IL-3)/IL-5 receptors are a family of heterodimeric transmembrane proteins expressed by myeloid lineage cells. Each receptor has a unique ligand-binding alpha chain and they share a common beta chain (beta c chain). Binding of GM-CSF activates at least one receptor-associated tyrosine kinase, JAK2, and rapidly induces tyrosine phosphorylation of the GMR beta c chain (GMR beta), but not the GMR alpha chain (GMR alpha). Mutation of each of the 8 tyrosine residues in the cytoplasmic domain of the human GMR beta to phenylalanine (GMR beta-F8) reduced tyrosine phosphorylation of GMR beta, SHP2 and SHC, but not JAK2 or STAT5. Interestingly, GMR beta-F8 was still capable of inducing at least short-term proliferation and enhancing viability. The role of each individual tyrosine residue was explored by replacing each mutated phenylalanine with the wild-type tyrosine residue. Tyrosine 577 was found to be sufficient to regenerate GM-CSF-dependent phosphorylation of SHC, and any of Y577, Y612, or Y695 were sufficient to regenerate GM-CSF-inducible phosphorylation of SHP2. Next, a series of four internal deletion mutants were generated, which deleted small sections from aa 518 to 626. One of these, deleting residues 566-589 was profoundly defective in signaling and supporting viability, and may identify an important viability signaling domain for this receptor family. Overall, these results indicate that GMR beta tyrosine residues are not necessary for activation of the JAK/STAT pathway, or for proliferation, viability, or adhesion signaling in Ba/F3 cells, although tyrosine residues significantly affect the magnitude of the response. However, internal deletion mutant studies identify critical domains for viability and proliferation.
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Affiliation(s)
- K Okuda
- Department of Adult Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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26
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Jenkins BJ, Le F, Gonda TJ. A cell type-specific constitutive point mutant of the common beta-subunit of the human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3, and IL-5 receptors requires the GM-CSF receptor alpha-subunit for activation. J Biol Chem 1999; 274:8669-77. [PMID: 10085105 DOI: 10.1074/jbc.274.13.8669] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The high affinity receptor for human granulocyte-macrophage colony-stimulating factor (GM-CSF) consists of a cytokine-specific alpha-subunit (hGMRalpha) and a common signal-transducing beta-subunit (hbetac) that is shared with the interleukin-3 and -5 receptors. We have previously identified a constitutively active extracellular point mutant of hbetac, I374N, that can confer factor independence on murine FDC-P1 cells but not BAF-B03 or CTLL-2 cells (Jenkins, B. J., D'Andrea, R. J., and Gonda, T. J. (1995) EMBO J. 14, 4276-4287). This restricted activity suggested the involvement of cell type-specific signaling molecules in the activation of this mutant. We report here that one such molecule is the mouse GMRalpha (mGMRalpha) subunit, since introduction of mGMRalpha, but not hGMRalpha, into BAF-B03 or CTLL-2 cells expressing the I374N mutant conferred factor independence. Experiments utilizing mouse/human chimeric GMRalpha subunits indicated that the species specificity lies in the extracellular domain of GMRalpha. Importantly, the requirement for mGMRalpha correlated with the ability of I374N (but not wild-type hbetac) to constitutively associate with mGMRalpha. Expression of I374N in human factor-dependent UT7 cells also led to factor-independent proliferation, with concomitant up-regulation of hGMRalpha surface expression. Taken together, these findings suggest a critical role for association with GMRalpha in the constitutive activity of I374N.
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Affiliation(s)
- B J Jenkins
- Hanson Centre for Cancer Research and Division of Human Immunology, Institute of Medical and Veterinary Science, Frome Road, Adelaide, South Australia 5000, Australia
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27
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Liu CB, Itoh T, Arai K, Watanabe S. Constitutive activation of JAK2 confers murine interleukin-3-independent survival and proliferation of BA/F3 cells. J Biol Chem 1999; 274:6342-9. [PMID: 10037724 DOI: 10.1074/jbc.274.10.6342] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Janus tyrosine kinase 2 (JAK2) plays an essential role of cytokine receptor signaling, including that of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor. We reported earlier that the activation of JAK2 is essential for all the examined signals induced by human GM-CSF through the box1 region of betac, such as promotion of cell survival and proliferation. To elucidate the role of JAK2 in cell survival and proliferation, we generated an artificial activation system by constructing a chimeric molecule (beta/JAK2) consisting of betac extracellular and transmembrane regions fused with JAK2, and we analyzed various signaling events in interleukin-3-dependent mouse pro-B cell, BA/F3. The beta/JAK2 was constitutively phosphorylated in the absence of human GM-CSF and murine interleukin-3, and this led to proliferation and cell survival. Western blot analysis showed that STAT5, Shc, and SHP-2 were not phosphorylated in the cells, and the consistent activation of beta-casein and c-fos promoters was not enhanced. In contrast, c-myc transcription was constitutively activated. We propose that the activation of beta/JAK2 suffices for survival and proliferation and that the activation of STAT5 and mitogen-activated protein kinase cascade is not required for these activities in BA/F3 cells.
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Affiliation(s)
- C B Liu
- Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Japan
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28
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Van Ostade X, Van der Heyden J, Verhee A, Vandekerckhove J, Tavernier J. The cell surface expression level of the human interleukin-5 receptor alpha subunit determines the agonistic/antagonistic balance of the human interleukin-5 E13Q mutein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 259:954-60. [PMID: 10092887 DOI: 10.1046/j.1432-1327.1999.00148.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The human interleukin-5 (IL-5) receptor consists of an alpha-chain that specifically binds the ligand with intermediate affinity, and a beta c-chain, that associates with the IL-5/IL-5R alpha complex, leading to a high-affinity, signal transducing receptor complex. Structure-function studies showed that modification of the putative beta c-chain binding site in IL-5 (E13Q mutein) converted the molecule into an antagonist. However, analysis of the effect of this mutant IL-5 on COS-1 cells transfected with both receptor subunits, did not show reduced interaction with the beta c subunit [Tavernier, J., Tuypens, T., Verhee, A., Plaetinck, G., Devos, R., Van der Heyden, J., Guisez, Y. & Oefner, C. (1995) Proc. Natl Acad. Sci. USA 89, 7041-7045]. To gain more insight into the mechanism of IL-5 antagonism by E13Q, we tested its biological activity on two FDC-P1 subclones that express clearly different numbers of alpha-subunits yet an almost constant number of murine beta c-subunits. Here we show that E13Q has a biological activity comparable to wild-type IL-5 only when a high number of alpha-chains is present on the cells. Confirming the critical role of the IL5R alpha cell-surface expression level, treatment with suboptimal doses of a neutralising anti-IL-5R alpha antibody results in reduced activity of the mutant but not of wild-type IL-5.
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Affiliation(s)
- X Van Ostade
- Flanders' Interuniversity Institute for Biotechnology, Department of Medical Protein Research, Faculty of Medicine, University of Ghent, Belgium
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de Groot RP, Coffer PJ, Koenderman L. Regulation of proliferation, differentiation and survival by the IL-3/IL-5/GM-CSF receptor family. Cell Signal 1998; 10:619-28. [PMID: 9794243 DOI: 10.1016/s0898-6568(98)00023-0] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The receptors for the I1-3/IL-5/GM-CSF cytokine family are composed of a heterodimeric complex of a cytokine-specific alpha chain and a common beta chain (betac). Binding of IL-3/IL-5/GM-CSF to their respective receptors rapidly induces activation of multiple intracellular signalling pathways, including the Ras-Raf-ERK, the JAK/STAT, the phosphatidylinositol 3-kinase PKB, and the JNK/SAPK and p38 signalling pathways. This review focuses on recent advancements in understanding how these different signalling pathways are activated by IL-3/IL-5/GM-CSF receptors, and how the individual pathways contribute to the pleiotropic effects of IL-3/IL-5/GM-CSF on their target cells, including proliferation, differentiation, survival, and effector functions.
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Affiliation(s)
- R P de Groot
- Department of Pulmonary Diseases, University Hospital Utrecht, The Netherlands.
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Saturation Mutagenesis of the β Subunit of the Human Granulocyte-Macrophage Colony-Stimulating Factor Receptor Shows Clustering of Constitutive Mutations, Activation of ERK MAP Kinase and STAT Pathways, and Differential β Subunit Tyrosine Phosphorylation. Blood 1998. [DOI: 10.1182/blood.v92.6.1989.418k18_1989_2002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The high-affinity receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 are heterodimeric complexes consisting of cytokine-specific subunits and a common signal-transducing β subunit (hβc). We have previously demonstrated the oncogenic potential of this group of receptors by identifying constitutively activating point mutations in the extracellular and transmembrane domains of hβc. We report here a comprehensive screen of the entire hβc molecule that has led to the identification of additional constitutive point mutations by virtue of their ability to confer factor independence on murine FDC-P1 cells. These mutations were clustered exclusively in a central region of hβc that encompasses the extracellular membrane-proximal domain, transmembrane domain, and membrane-proximal region of the cytoplasmic domain. Interestingly, most hβc mutants exhibited cell type-specific constitutive activity, with only two transmembrane domain mutants able to confer factor independence on both murine FDC-P1 and BAF-B03 cells. Examination of the biochemical properties of these mutants in FDC-P1 cells indicated that MAP kinase (ERK1/2), STAT, and JAK2 signaling molecules were constitutively activated. In contrast, only some of the mutant β subunits were constitutively tyrosine phosphorylated. Taken together, these results highlight key regions involved in hβc activation, dissociate hβc tyrosine phosphorylation from MAP kinase and STAT activation, and suggest the involvement of distinct mechanisms by which proliferative signals can be generated by hβc.© 1998 by The American Society of Hematology.
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Saturation Mutagenesis of the β Subunit of the Human Granulocyte-Macrophage Colony-Stimulating Factor Receptor Shows Clustering of Constitutive Mutations, Activation of ERK MAP Kinase and STAT Pathways, and Differential β Subunit Tyrosine Phosphorylation. Blood 1998. [DOI: 10.1182/blood.v92.6.1989] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe high-affinity receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 are heterodimeric complexes consisting of cytokine-specific subunits and a common signal-transducing β subunit (hβc). We have previously demonstrated the oncogenic potential of this group of receptors by identifying constitutively activating point mutations in the extracellular and transmembrane domains of hβc. We report here a comprehensive screen of the entire hβc molecule that has led to the identification of additional constitutive point mutations by virtue of their ability to confer factor independence on murine FDC-P1 cells. These mutations were clustered exclusively in a central region of hβc that encompasses the extracellular membrane-proximal domain, transmembrane domain, and membrane-proximal region of the cytoplasmic domain. Interestingly, most hβc mutants exhibited cell type-specific constitutive activity, with only two transmembrane domain mutants able to confer factor independence on both murine FDC-P1 and BAF-B03 cells. Examination of the biochemical properties of these mutants in FDC-P1 cells indicated that MAP kinase (ERK1/2), STAT, and JAK2 signaling molecules were constitutively activated. In contrast, only some of the mutant β subunits were constitutively tyrosine phosphorylated. Taken together, these results highlight key regions involved in hβc activation, dissociate hβc tyrosine phosphorylation from MAP kinase and STAT activation, and suggest the involvement of distinct mechanisms by which proliferative signals can be generated by hβc.© 1998 by The American Society of Hematology.
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JAK2 and JAK1 Constitutively Associate With an Interleukin-5 (IL-5) Receptor α and βc Subunit, Respectively, and Are Activated Upon IL-5 Stimulation. Blood 1998. [DOI: 10.1182/blood.v91.7.2264.2264_2264_2271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human interleukin-5 receptor (hIL-5R) consists of a unique α subunit (hIL-5Rα) and a common β subunit (βc) that activate two Janus kinases (JAK1 and JAK2) and a signal transducer and activator of transcription (STAT5). The precise stoichiometry of the hIL-5R subunits and the role of JAK kinases used in IL-5 signaling were investigated. We analyzed the interaction between hIL-5Rα and βc by immunoprecipitation using anti–hIL-5Rα and anti-βc monoclonal antibodies. The binding of JAK1 and JAK2 to each hIL-5R subunit was also evaluated in the hIL-5–responsive cell line, TF-h5Rα. It was observed that IL-5 stimulation induced the recruitment of βc to hIL-5Rα, although in the absence of IL-5 the subunits remain independent. In the absence of IL-5, JAK2 and JAK1 were associated with hIL-5Rα and βc, respectively. IL-5 stimulation resulted in tyrosine phosphorylation of JAK2, JAK1, βc, and STAT5. Moreover, IL-5–induced dimerization of IL-5R subunits caused JAK2 activation and βc phosphorylation even in the absence of JAK1 activation. Furthermore, tyrosine phosphorylation of JAK1 was dependent on the activation of JAK2. Detailed study of the C-terminal truncated cytoplasmic domain of hIL-5Rα revealed that the cytoplasmic stretch at position 346-387, containing the proline-rich region, is necessary for JAK2 binding. These observations suggest that activation of hIL-5Rα–associated JAK2 is indispensable for the IL-5 signaling event.
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JAK2 and JAK1 Constitutively Associate With an Interleukin-5 (IL-5) Receptor α and βc Subunit, Respectively, and Are Activated Upon IL-5 Stimulation. Blood 1998. [DOI: 10.1182/blood.v91.7.2264] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe human interleukin-5 receptor (hIL-5R) consists of a unique α subunit (hIL-5Rα) and a common β subunit (βc) that activate two Janus kinases (JAK1 and JAK2) and a signal transducer and activator of transcription (STAT5). The precise stoichiometry of the hIL-5R subunits and the role of JAK kinases used in IL-5 signaling were investigated. We analyzed the interaction between hIL-5Rα and βc by immunoprecipitation using anti–hIL-5Rα and anti-βc monoclonal antibodies. The binding of JAK1 and JAK2 to each hIL-5R subunit was also evaluated in the hIL-5–responsive cell line, TF-h5Rα. It was observed that IL-5 stimulation induced the recruitment of βc to hIL-5Rα, although in the absence of IL-5 the subunits remain independent. In the absence of IL-5, JAK2 and JAK1 were associated with hIL-5Rα and βc, respectively. IL-5 stimulation resulted in tyrosine phosphorylation of JAK2, JAK1, βc, and STAT5. Moreover, IL-5–induced dimerization of IL-5R subunits caused JAK2 activation and βc phosphorylation even in the absence of JAK1 activation. Furthermore, tyrosine phosphorylation of JAK1 was dependent on the activation of JAK2. Detailed study of the C-terminal truncated cytoplasmic domain of hIL-5Rα revealed that the cytoplasmic stretch at position 346-387, containing the proline-rich region, is necessary for JAK2 binding. These observations suggest that activation of hIL-5Rα–associated JAK2 is indispensable for the IL-5 signaling event.
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A Truncated Isoform of the Human β Chain Common to the Receptors for Granulocyte-Macrophage Colony-Stimulating Factor, Interleukin-3 (IL-3), and IL-5 With Increased mRNA Expression in Some Patients With Acute Leukemia. Blood 1998. [DOI: 10.1182/blood.v91.1.54] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractWe report here a naturally occurring isoform of the human β chain common to the receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 (GMRβC) with a truncated intracytoplasmic tail caused by deletion of a 104-bp exon in the membrane-proximal region of the chain. This β intracytoplasmic truncated chain (βIT) has a predicted tail of 46 amino acids, instead of 432 for βC, with 23 amino acids in common with βC and then a new sequence of 23 amino acids. In primary myeloid cells, βIT comprised approximately 20% of the total β chain message, but was increased up to 90% of total in blast cells from a significant proportion of patients with acute leukemia. Specific anti-βITantibodies demonstrated its presence in primary myeloid cells and cell lines. Coexpression of βIT converted low-affinity GMRα chains (KD 2.5 nmol/L) to higher-affinity αβ complexes (KD 200 pmol/L). These could bind JAK2 that was tyrosine-phosphorylated by stimulation with GM-CSF. βITdid not support GM-CSF–induced proliferation when cotransfected with GMRα into CTLL-2 cells. Therefore, it may interfere with the signal-transducing properties of the βC chain and play a role in the pathogenesis of leukemia.
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A Truncated Isoform of the Human β Chain Common to the Receptors for Granulocyte-Macrophage Colony-Stimulating Factor, Interleukin-3 (IL-3), and IL-5 With Increased mRNA Expression in Some Patients With Acute Leukemia. Blood 1998. [DOI: 10.1182/blood.v91.1.54.54_54_63] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report here a naturally occurring isoform of the human β chain common to the receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 (GMRβC) with a truncated intracytoplasmic tail caused by deletion of a 104-bp exon in the membrane-proximal region of the chain. This β intracytoplasmic truncated chain (βIT) has a predicted tail of 46 amino acids, instead of 432 for βC, with 23 amino acids in common with βC and then a new sequence of 23 amino acids. In primary myeloid cells, βIT comprised approximately 20% of the total β chain message, but was increased up to 90% of total in blast cells from a significant proportion of patients with acute leukemia. Specific anti-βITantibodies demonstrated its presence in primary myeloid cells and cell lines. Coexpression of βIT converted low-affinity GMRα chains (KD 2.5 nmol/L) to higher-affinity αβ complexes (KD 200 pmol/L). These could bind JAK2 that was tyrosine-phosphorylated by stimulation with GM-CSF. βITdid not support GM-CSF–induced proliferation when cotransfected with GMRα into CTLL-2 cells. Therefore, it may interfere with the signal-transducing properties of the βC chain and play a role in the pathogenesis of leukemia.
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36
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The Human Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF ) Receptor Exists as a Preformed Receptor Complex That Can Be Activated by GM-CSF, Interleukin-3, or Interleukin-5. Blood 1997. [DOI: 10.1182/blood.v90.8.3005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe granulocyte-macrophage colony-stimulating factor (GM-CSF ) receptor is expressed on normal and malignant hematopoietic cells as well as on cells from other organs in which it transduces a variety of functions. Despite the widespread expression and pleiotropic nature of the GM-CSF receptor, little is known about its assembly and activation mechanism. Using a combination of biochemical and functional approaches, we have found that the human GM-CSF receptor exists as an inducible complex, analogous to the interleukin-3 (IL-3) receptor, and also as a preformed complex, unlike the IL-3 receptor or indeed other members of the cytokine receptor superfamily. We found that monoclonal antibodies to the GM-CSF receptor α chain (GMRα) and to the common β chain of the GM-CSF, IL-3, and IL-5 receptors (βc ) immunoprecipitated both GMRα and βc from the surface of primary myeloid cells, myeloid cell lines, and transfected cells in the absence of GM-CSF. Further association of the two chains could be induced by the addition of GM-CSF. The preformed complex required only the extracellular regions of GMRα and βc , as shown by the ability of soluble βc to associate with membrane-anchored GMRα or soluble GMRα. Kinetic experiments on eosinophils and monocytes with radiolabeled GM-CSF, IL-3, and IL-5 showed association characteristics unique to GM-CSF. Significantly, receptor phosphorylation experiments showed that not only GM-CSF but also IL-3 and IL-5 stimulated the phosphorylation of GMRα-associated βc . These results indicate a pattern of assembly of the heterodimeric GM-CSF receptor that is unique among receptors of the cytokine receptor superfamily. These results also suggest that the preformed GM-CSF receptor complex mediates the instantaneous binding of GM-CSF and is a target of phosphorylation by IL-3 and IL-5, raising the possibility that some of the biologic activities of IL-3 and IL-5 are mediated through the GM-CSF receptor complex.
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Orchansky PL, Ayres SD, Hilton DJ, Schrader JW. An interleukin (IL)-13 receptor lacking the cytoplasmic domain fails to transduce IL-13-induced signals and inhibits responses to IL-4. J Biol Chem 1997; 272:22940-7. [PMID: 9278458 DOI: 10.1074/jbc.272.36.22940] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Interleukin (IL)-13 is a pleiotropic immunoregulatory cytokine that shares many, although not all, of the biological activities of IL-4. The overlapping biological properties of IL-4 and IL-13 appear to be due to the existence of shared components of the receptors, and we and others showed that the IL-4 receptor-alpha is involved in signal transduction paths activated by both. We show here that expression of the IL-13 receptor-alpha in two factor-dependent cell lines, the premyeloid FD5 and the T lymphoid CT4.S, conferred the ability to grow continuously in response to IL-13; to respond to IL-13 with tyrosine phosphorylation of JAK1, Tyk2, IL-4Ralpha, IRS-2, and STAT6; and to respond to IL-4 with tyrosine phosphorylation of Tyk2 in addition to those induced in parental cell lines. Expression of a truncated IL-13 receptor-alpha that lacked the cytoplasmic domain demonstrated that this domain was essential for IL-13-dependent growth and phosphorylation of the above substrates. Expression of this truncated IL-13 receptor also resulted in an inhibition of biochemical and biological responses to IL-4 that was exacerbated by the presence of IL-13. These dominant inhibitory effects indicate that the extracellular domain of the truncated IL-13 receptor competes with gammac for complexes of IL-4 and the IL-4 receptor-alpha, or, when itself bound to IL-13, competes with IL-4 for the IL-4 receptor-alpha.
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Affiliation(s)
- P L Orchansky
- The Biomedical Research Centre, 2222 Health Sciences Mall, University of British Columbia, Vancouver V6T 1Z3, Canada.
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Wiekowski M, Prosser D, Taremi S, Tsarbopoulos A, Jenh CH, Chou CC, Lundell D, Zavodny P, Narula S. Characterization of potential antagonists of human interleukin 5 demonstrates their cross-reactivity with receptors for interleukin 3 and granulocyte-macrophage colony-stimulating factor. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 246:625-32. [PMID: 9219518 DOI: 10.1111/j.1432-1033.1997.t01-2-00625.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The ligand-binding alpha-chain of the human interleukin 5 (IL-5) receptor was expressed in its soluble form, lacking the transmembrane and cytoplasmic domains, from recombinant baculovirus. The soluble receptor was used in a scintillation proximity assay to identify two chemical compounds that inhibit binding of human IL-5 to the soluble receptor alpha chain with IC50 of 8 microM and 11 microM. These compounds also inhibited the interaction of human IL-5 with its membrane-bound receptor, composed of the ligand-binding alpha chain and signal-transducing beta chain, and prevented signaling through the receptor. Analysis by surface plasmon resonance and matrix-assisted laser-desorption/ionization mass spectrometry showed that the identified compounds bound irreversibly to the receptor at a 1:1 (mol/mol) ratio, suggesting a covalent interaction with the alpha chain of the human IL-5 receptor. Both compounds also inhibited the interaction of the receptors for interleukin 3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), which are involved in hematopoietic differentiation and activation of immune cells, thus eliminating them as potential therapeutic agents. The inhibition of the structurally closely related receptors for IL-5, IL-3 and GM-CSF by both compounds, while binding of interleukin-4 to its receptor was not affected, suggests that a similar reactive site exists in the ligand-binding domains of the receptors for IL-5, IL-3 and GM-CSF.
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MESH Headings
- Animals
- Antigens, CD/metabolism
- Biosensing Techniques
- Cell Division/drug effects
- Cross Reactions
- Granulocyte-Macrophage Colony-Stimulating Factor/antagonists & inhibitors
- Granulocyte-Macrophage Colony-Stimulating Factor/metabolism
- Humans
- Interleukin-3/metabolism
- Interleukin-5/antagonists & inhibitors
- Interleukin-5/metabolism
- Mice
- Phenols/pharmacology
- Piperidines/pharmacology
- Receptors, Interleukin/antagonists & inhibitors
- Receptors, Interleukin/metabolism
- Receptors, Interleukin-3/antagonists & inhibitors
- Receptors, Interleukin-3/metabolism
- Receptors, Interleukin-4
- Receptors, Interleukin-5
- Recombinant Proteins/metabolism
- Solubility
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- Spodoptera
- Thiazoles/pharmacology
- Tumor Cells, Cultured
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Affiliation(s)
- M Wiekowski
- Department of Immunology, Schering Plough Research Institute, Kenilworth, NJ 07033, USA
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Muramatsu M, Yan J, Eto K, Tomoda T, Yamada R, Arai K. A chimeric serine/threonine kinase receptor system reveals the potential of multiple type II receptors to cooperate with transforming growth factor-beta type I receptor. Mol Biol Cell 1997; 8:469-80. [PMID: 9188099 PMCID: PMC276098 DOI: 10.1091/mbc.8.3.469] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Receptor-type serine/threonine kinases (RSKs) have been organized into two distinct classes known as types I and II on the basis of sequence similarity. However, experiments have shown ligand specificities in the two classes and as a result type I and type II receptors can often bind to a common ligand. The transforming growth factor-beta- (TGF-beta) specific receptors represent such a case, where both type I and II receptors (T beta RI and T beta RII) are observed. Of additional interest is the observation that heteromeric associations of type I and II receptors can also enable signaling. To further elucidate the function of various RSKs, the extracellular domains of both alpha and beta chains from human granulocyte-macrophage colony-stimulating factor receptors were linked to transmembrane cytoplasmic domains of RSKs. Chimeric receptors of human granulocyte-macrophage receptor (hGMR) alpha with T beta RI and hGMR beta with T beta RII were expressed in murine pre-B cell-derived Ba/F3 cells. These chimeras formed heteromeric complexes, transmitted TGF-beta signals, and were down-modulated in response to human granulocyte-macrophage colony-stimulating factor. However, experiments utilizing these chimeric receptors in different combinations revealed that only heteromeric associations of transmembrane cytoplasmic domains mediated signaling and down-modulation. Chimeric receptors with transmembrane cytoplasmic domains of activin receptor type II and bone morphogenetic protein receptor type II also provided signals in conjunction with chimeric T beta RI. As a result, these type II receptors may share a common potential to signal via T beta RI. hGMR-RSK chimeric receptors may be useful tools for the identification and characterization of the divergent signals mediated by individual RSKs.
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MESH Headings
- Activin Receptors, Type I
- Animals
- Bombyx
- COS Cells
- Cell Line
- Granulocyte-Macrophage Colony-Stimulating Factor/metabolism
- Granulocyte-Macrophage Colony-Stimulating Factor/pharmacology
- Growth Inhibitors/genetics
- Growth Inhibitors/metabolism
- Humans
- Mice
- Protein Binding/drug effects
- Protein Serine-Threonine Kinases/drug effects
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Receptor, Transforming Growth Factor-beta Type I
- Receptors, Cell Surface/biosynthesis
- Receptors, Cell Surface/drug effects
- Receptors, Growth Factor/drug effects
- Receptors, Growth Factor/genetics
- Receptors, Growth Factor/metabolism
- Receptors, Transforming Growth Factor beta/drug effects
- Receptors, Transforming Growth Factor beta/genetics
- Receptors, Transforming Growth Factor beta/metabolism
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/drug effects
- Recombinant Fusion Proteins/genetics
- Transcriptional Activation/drug effects
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Affiliation(s)
- M Muramatsu
- Department of Molecular and Developmental Biology, University of Tokyo, Japan
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40
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The Structural and Functional Basis of Cytokine Receptor Activation: Lessons From the Common β Subunit of the Granulocyte-Macrophage Colony-Stimulating Factor, Interleukin-3 (IL-3), and IL-5 Receptors. Blood 1997. [DOI: 10.1182/blood.v89.5.1471] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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41
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The Structural and Functional Basis of Cytokine Receptor Activation: Lessons From the Common β Subunit of the Granulocyte-Macrophage Colony-Stimulating Factor, Interleukin-3 (IL-3), and IL-5 Receptors. Blood 1997. [DOI: 10.1182/blood.v89.5.1471.1471_1471_1482] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Behrmann I, Janzen C, Gerhartz C, Schmitz-Van de Leur H, Hermanns H, Heesel B, Graeve L, Horn F, Tavernier J, Heinrich PC. A single STAT recruitment module in a chimeric cytokine receptor complex is sufficient for STAT activation. J Biol Chem 1997; 272:5269-74. [PMID: 9030599 DOI: 10.1074/jbc.272.8.5269] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We established a system of receptor chimeras that enabled us to induce heterodimerization of different cytoplasmic tails. Fusion constructs were created that are composed of the extracellular parts of the interleukin-5 receptor alpha and beta chains, respectively, and the transmembrane and intracellular parts of gp130, the signal transducing chain of the interleukin-6 receptor complex. In COS-7 transfectants we observed a dose-dependent interleukin-5-inducible STAT1 activation for which the presence of both the alpha and the beta chain chimera was needed. No STAT activity was detected if one of the cytoplasmic tails of the receptor complex was deleted, indicating that STAT activity resulted from a receptor dimer rather than from higher receptor aggregates. We further investigated whether dimerization of STAT1 depends on the juxtaposition of two STAT recruitment modules in a receptor complex. We show that a receptor dimer with only a single STAT1 docking site was still able to lead to STAT1 activation. This indicates that the formation of a paired set of STAT binding sites in a receptor complex is not the prerequisite for STAT factor dimerization. Our findings are discussed in view of alternative STAT dimerization models.
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Affiliation(s)
- I Behrmann
- Institute of Biochemistry, Rheinisch-Westfälische Technische Hochschule Aachen, 52057 Aachen, Germany.
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de Groot RP, van Dijk TB, Caldenhoven E, Coffer PJ, Raaijmakers JA, Lammers JW, Koenderman L. Activation of 12-O-tetradecanoylphorbol-13-acetate response element- and dyad symmetry element-dependent transcription by interleukin-5 is mediated by Jun N-terminal kinase/stress-activated protein kinase kinases. J Biol Chem 1997; 272:2319-25. [PMID: 8999940 DOI: 10.1074/jbc.272.4.2319] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Interleukin-5 (IL-5) is one of the major regulators of eosinophilic granulocytes in vivo. IL-5 exerts its pleiotropic effects by binding to the IL-5 receptor, which is composed of an IL-5-specific alpha chain and a common betac chain shared with the receptors for IL-3 and granulocyte-macrophage colony-stimulating factor. Previous studies have shown that binding of IL-5 to its receptor triggers the activation of multiple signaling cascades, including the Ras/mitogen-activated protein kinase, the phosphatidyl -3'-kinase, and the Janus kinase/signal transducer and activator of transcription pathways. Here we describe that IL-5 activates the serine/threonine protein kinase Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) pathway. We show that IL-5 activates TPA response element (TRE)-dependent transcription in transfection experiments. TRE activation by IL-5 is mediated by a region of the betac (577-581) that is also responsible for activation of JNK/SAPK and for activation of dyad symmetry element (DSE)-dependent transcription. Dominant-negative SAPK or ERK kinase-1 was used to demonstrate that JNK/SAPK activation is necessary for induction of DSE- and TRE-dependent transcription by IL-5, whereas extracellular signal-regulated kinase 2 was not essential for TRE- and DSE-dependent transcription. By contrast, IL-5-induced activation of the tyrosine kinase Janus kinase 2 seems to be a prerequisite for TRE- and DSE-dependent transcription. Taken together, we show for the first time that IL-5 activates kinases of the JNK/SAPK family, and that this activation is linked to IL-5-induced TRE- and DSE-dependent transcription.
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Affiliation(s)
- R P de Groot
- Department of Pulmonary Diseases, G03.550, University Hospital Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
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44
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Activating Mutations in Cytokine Receptors: Implications for Receptor Function and Role in Disease. Blood 1997. [DOI: 10.1182/blood.v89.2.355] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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45
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Li J, Cook R, Chaiken I. Mutants of single chain interleukin 5 show asymmetric recruitment of receptor alpha and betac subunits. J Biol Chem 1996; 271:31729-34. [PMID: 8940197 DOI: 10.1074/jbc.271.49.31729] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Dual asymmetric mutagenesis of single-chain interleukin 5 (scIL5) was used to obtain evidence that the normally homodimeric IL5 molecule, which contains two 4-helix bundle domains arranged symmetrically about a 2-fold axis, can recruit receptor alpha and betac subunits asymmetrically. Functionally active scIL5 was constructed using recombinant DNA methods by linking two IL5 monomers with a Gly-Gly linker. Mutants were constructed at residues Arg91, Glu110, and Trp111, previously shown to be involved in IL5 receptor alpha chain binding, and at residue Glu13, known to be involved in signal transduction presumably through interaction with the receptor betac chain. Mutants were examined for receptor alpha chain binding by an optical biosensor assay and for bioactivity using a cell proliferation assay. Substitution of the two binding site residues R91 and W111 in the same 4-helix bundle domain caused a 5-fold greater reduction in receptor binding affinity than when the two substitutions were distributed one in each domain. Substitution of E13 and R91 either in the same or in opposite domains gave comparable IL5Ralpha chain binding kinetics, essentially unchanged from those of scIL5. However, in contrast to the binding affinity pattern observed with R91A/W111A dual mutants, distributing the E13A/R91A mutations between the two 4-helix bundle domains caused a 5-6-fold greater loss of bioactivity than when the two changes were in the same domain, leaving the other domain unaltered. Taken with previous mutagenesis data, these results are consistent with a single shared-site model of IL5-IL5Ralpha chain recognition in which a single alpha chain can orientate in either of two modes, each one of which is stabilized preferentially by one of the two 4-helix bundles of IL5. Furthermore, the results suggest that a single betac molecule is activated for each IL5, through the Glu13 residue on the same helix bundle domain that dominates the IL5Ralpha interaction.
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Affiliation(s)
- J Li
- Molecular Immunology Department, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA
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46
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Watanabe S, Itoh T, Arai K. Roles of JAK kinases in human GM-CSF receptor signal transduction. J Allergy Clin Immunol 1996; 98:S183-91. [PMID: 8977526 DOI: 10.1016/s0091-6749(96)70065-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The receptors for human interleukin-3 (IL-3) and human granulocyte-macrophage colony-stimulating factor (GM-CSF), hIL-3R, hGM-CSFR, respectively, consists of two subunits, alpha and beta, both of which are members of the cytokine receptor superfamily. Phosphorylation of tyrosine residues in the hGMR beta subunit and several cellular proteins is observed after hGM-CSF stimulation. We analyzed the role of tyrosine residues in the hGMR beta subunit and the nature of tyrosine kinase, JAK2, in hGMR signal transduction using several hGMR beta subunit mutants. In addition to the box1 region, a membrane distal region (a.a. 544-589) of the hGMR beta was required for c-fos activation. Only one tyrosine residue (Tyr577) existed within the region 544 to 589, and substitution of Tyr577 to phenylalanine in GMR beta 589 resulted in loss of c-fos activation. In contrast, the same substitution in a wild type receptor did not affect GM-CSF induced activities such as c-fos messenger RNA (mRNA) induction and proliferation, but the substitution abolished Shc phosphorylation. These results suggest that the activation of Shc is not essential for c-fos activation and several tyrosine residues cooperate for c-fos activation. It is well documented that IL-3 or GM-CSF activate JAK2 in BA/F3 cells. The role of JAK2 in IL-3/GM-CSF functions, however, is largely unknown. We examined the role of JAK2 in GM-CSF induced signaling pathways. Dominant negative JAK2 (delta JAK2) lacking the C-terminus kinase domain suppressed IL-3/GM-CSF induced c-fos activation and c-myc activation and proliferation, suggesting that JAK2 was involved in both signaling pathways. Protein tyrosine phosphatase SHP-2 (also called PTP 1D) and Shc were phosphorylated by IL-3/GM-CSF in BA/F3 cells; however, these phosphorylation events were inhibited by the expression of delta JAK2. Taken together, these results indicate the JAK2 is a primary kinase regulating all the known activities of GM-CSF. JAK2 mediates GM-CSF induced c-fos activation through receptor phosphorylation and Shc/PTP 1D activation.
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Affiliation(s)
- S Watanabe
- Department of Molecular and Developmental Biology, University of Tokyo, Japan
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47
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Lia F, Rajotte D, Clark SC, Hoang T. A dominant negative granulocyte-macrophage colony-stimulating factor receptor alpha chain reveals the multimeric structure of the receptor complex. J Biol Chem 1996; 271:28287-93. [PMID: 8910448 DOI: 10.1074/jbc.271.45.28287] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The receptor for the hemopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF) is composed of two chains, both of which belong to the superfamily of cytokine receptors. The alpha chain confers low affinity binding only, whereas the beta chain (betac) confers high affinity binding when associated with alpha. Ectopic expression of both chains of the receptor in murine NIH-3T3 fibroblasts results in signal transduction, mitogenesis, and morphologic transformation. The cytoplasmic domain of the GM-CSF receptor alpha subunit (GMR-alpha) comprises 54 amino acids that have been shown to be important for signal transduction through the beta chain. The present study was designed to address the possibility of receptor oligomerization and its functional implication. Cross-linking studies with 125I-GM-CSF on NIH-3T3 transfectants is consistent with the presence of alpha and betac dimers and of receptor oligomers. We have, therefore, generated an inert alpha chain through polymerase chain reaction-mediated truncation of 47 amino acids of the COOH-terminal domain of alpha (alphat), and coexpressed alphat, alpha, and betac in NIH-3T3. In cells in which alphat and alpha are present in stoichiometric proportion within the GM-CSF-binding complex, we provide evidence that alphat is dominant negative over wild type alpha on the basis of two different functional assays: cell proliferation and foci formation. Hence, our results suggest the requirement for at least two functional alpha chains for signal transduction. Together with the cross-linking studies, our data indicate that the functional GMR is an oligomer that contains at least two alpha chains.
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Affiliation(s)
- F Lia
- Clinical Research Institute of Montreal, Montreal, Québec, Canada H2W 1R7.
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48
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Hara T, Miyajima A. Function and signal transduction mediated by the interleukin 3 receptor system in hematopoiesis. Stem Cells 1996; 14:605-18. [PMID: 8948019 DOI: 10.1002/stem.140605] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Interleukin 3 (IL-3) promotes development of hematopoietic cells through activation of the IL-3 receptor (IL-3R) complex consisting of alpha and beta subunits. The alpha subunit binds IL-3 with low affinity and forms a high-affinity receptor with the common beta subunit (beta c). The beta c subunit does not bind any cytokine by itself but is involved in the formation of high-affinity functional receptors for IL-5 and GM-CSF. As the alpha subunits provide the specificity to cytokines and beta c plays a major role in signal transduction, IL-3, GM-CSF and IL-5 exhibit similar functions when they act on the same cells. Surprisingly, no apparent hematological defect other than a reduced number of eosinophils was found in knock-out mice lacking an entire function of IL-3, GM-CSF and IL-5; this indicates a remarkable functional overlap with other cytokine systems for hematopoiesis. Binding of the cytokines to the receptor induces activation of the JAK2 tyrosine kinase that associates with beta c and triggers the signaling events. The membrane proximal region of beta c is responsible for activation of JAK2 and STAT5, as well as for induction of c-myc. The signals induced by this region are required for cell-cycle progression and DNA synthesis. Activation of the Ras pathway requires the distal region of beta c and is involved in the suppression of apoptosis. Proliferation of hematopoietic cells requires signals for both DNA synthesis and anti-apoptosis. In this review, we describe the recent findings of the function and signal transduction mediated by the IL-3R system.
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Affiliation(s)
- T Hara
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan
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