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Kaushansky K. Thrombopoietin, the Primary Regulator of Platelet Production: From Mythos to Logos, a Thirty-Year Journey. Biomolecules 2024; 14:489. [PMID: 38672505 PMCID: PMC11047867 DOI: 10.3390/biom14040489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 04/08/2024] [Accepted: 04/09/2024] [Indexed: 04/28/2024] Open
Abstract
Thrombopoietin, the primary regulator of blood platelet production, was postulated to exist in 1958, but was only proven to exist when the cDNA for the hormone was cloned in 1994. Since its initial cloning and characterization, the hormone has revealed many surprises. For example, instead of acting as the postulated differentiation factor for platelet precursors, megakaryocytes, it is the most potent stimulator of megakaryocyte progenitor expansion known. Moreover, it also stimulates the survival, and in combination with stem cell factor leads to the expansion of hematopoietic stem cells. All of these growth-promoting activities have resulted in its clinical use in patients with thrombocytopenia and aplastic anemia, although the clinical development of the native molecule illustrated that "it's not wise to mess with mother nature", as a highly engineered version of the native hormone led to autoantibody formation and severe thrombocytopenia. Finally, another unexpected finding was the role of the thrombopoietin receptor in stem cell biology, including the development of myeloproliferative neoplasms, an important disorder of hematopoietic stem cells. Overall, the past 30 years of clinical and basic research has yielded many important insights, which are reviewed in this paper.
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Affiliation(s)
- Kenneth Kaushansky
- Renaissance School of Medicine, Stony Brook University, Stony Brook, NY 11794, USA
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2
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Scheller L, Strittmatter T, Fuchs D, Bojar D, Fussenegger M. Generalized extracellular molecule sensor platform for programming cellular behavior. Nat Chem Biol 2018; 14:723-729. [DOI: 10.1038/s41589-018-0046-z] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 03/02/2018] [Indexed: 12/13/2022]
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Kish WS, Sachi H, Naik AD, Roach MK, Bobay BG, Blackburn RK, Menegatti S, Carbonell RG. Design, selection, and development of cyclic peptide ligands for human erythropoietin. J Chromatogr A 2017; 1500:105-120. [DOI: 10.1016/j.chroma.2017.04.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 03/28/2017] [Accepted: 04/10/2017] [Indexed: 11/26/2022]
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5
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Analysis of the Asymmetry of Activated EPO Receptor Enables Designing Small Molecule Agonists. VITAMINS AND HORMONES 2017. [DOI: 10.1016/bs.vh.2017.03.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Hinou H, Abe Y, Hayakawa S, Naruchi K, Fujitani N, Nishimura SI. Solid-phase synthesis of C-mannosylated glycopeptide on WSXWS motif of human erythropoietin receptor. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.01.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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7
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Abstract
Erythropoietin (EPO) is a protein made by the kidneys in response to low red blood cell count that is secreted into the bloodstream and binds to a receptor on hematopoietic stem cells in the bone marrow inducing them to become new red blood cells. EPO made with recombinant DNA technology was brought to market in the 1980s to treat anemia caused by kidney disease and cancer chemotherapy. Because EPO infusion was able to replace blood transfusions in many cases, it rapidly became a multibillion dollar per year drug and as the first biologic created with recombinant technology it launched the biotech industry. For many years intense research was focused on creating a small molecule orally available EPO mimetic. The Robert Wood Johnson (RWJ) group seemed to definitively establish that only large peptides with a minimum of 60 residues could replace EPO, as anything less was not a full agonist. An intense study of the published work led me to hypothesize that the size of the mimetic is not the real issue, but the symmetry making and breaking of the EPO receptor induced by the ligand is the key to activating the stem cells. This analysis meant that residues in the binding site of the receptor deemed absolutely essential for ligand binding and activation from mutagenesis experiments, were probably not really that important. My fundamental hypotheses were: (a) the symmetric state of the homodimeric receptor is the most stable state and thus must be the off-state, (b) a highly localized binding site exists at a pivot point where the two halves of the receptor meet, (c) small molecules can be created that have high potency for this site that will be competitive with EPO and thus can displace the protein-protein interaction, (d) small symmetric molecules will stabilize the symmetric off-state of the receptor, and (e) a key asymmetry in the small molecule will stabilize a mirror image asymmetry in the receptor resulting in the stabilization of the on-state and proliferation of the stem cells into red blood cells. Researchers at Amgen published a co-crystal structure of EPO bound to the EPO receptor, which has a beautiful twofold symmetry-it was argued that this is the active state of the receptor. Activating the EPO receptor with EPO induces an almost instantaneous shutdown mechanism to sharply curtail any proliferative signal transduction, and thus, my hypotheses lead to the conclusion that the Amgen co-crystal is actually the state after receptor downregulation and thus an off-state. To put these hypotheses to the test, my computational method of Simulated Annealing of Chemical Potential was run using the co-crystal created at RWJ, which is the receptor trapped in a partial agonist state. The simulations predicted a previously unknown high affinity binding site at the pivot point where the two halves of the dimeric receptor meet, and detailed analysis of the fragment patterns led to the prediction of a molecule less than 300 MW that is basically twofold symmetric with a chiral center on one side and not the other. Thus, to the degree that computer simulations can be taken seriously, these results support my hypotheses on small molecule receptor activation. When this small molecule was synthesized and tested it indeed induced human hematopoietic stems cells to become red blood cells. When the predicted chiral center of this molecule was removed eliminating its one asymmetric feature, the resulting molecule was an antagonist-it could potently displace hot EPO but could no longer induce stem cell proliferation and differentiation. These results provided strong support for my theories on how to create potent small molecule EPO agonists and were used to launch the new company Locus Pharmaceuticals. These molecules, however, required significant chemical changes in order to make them stable in other in vitro assays and to be in vivo active, but these alterations had to be done in a way that maintained the symmetry-asymmetry considerations that led to the creation of an in vitro active molecule. The combination of changing functional groups to enable good pharmacokinetics, while not changing the key intrinsic symmetry properties were never seriously pursued at Locus and the program died. Investigations into how red blood cells are created have occupied many prominent researchers for the entire twentieth century. In the second half of the century EPO was discovered and by the end of the century it became a blockbuster commercial product that launched the biotech revolution.
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Affiliation(s)
- Frank Guarnieri
- Department of Physiology & Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA, 23298, USA,
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Varghese LN, Zhang JG, Young SN, Willson TA, Alexander WS, Nicola NA, Babon JJ, Murphy JM. Functional characterization of c-Mpl ectodomain mutations that underlie congenital amegakaryocytic thrombocytopenia. Growth Factors 2014; 32:18-26. [PMID: 24438083 DOI: 10.3109/08977194.2013.874347] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Activation of the cell surface receptor, c-Mpl, by the cytokine, thrombopoietin (TPO), underpins megakaryocyte and platelet production in mammals. In humans, mutations in c-Mpl have been identified as the molecular basis of Congenital Amegakaryocytic Thrombocytopenia (CAMT). Here, we show that CAMT-associated mutations in c-Mpl principally lead to defective receptor presentation on the cell surface. In contrast, one CAMT mutant c-Mpl, F104S, was expressed on the cell surface, but showed defective TPO binding and receptor activation. Using mutational analyses, we examined which residues adjacent to F104 within the membrane-distal cytokine receptor homology module (CRM) of c-Mpl comprise the TPO-binding epitope, revealing residues within the predicted Domain 1 E-F and A-B loops and Domain 2 F'-G' loop as key TPO-binding determinants. These studies underscore the importance of the c-Mpl membrane-distal CRM to TPO-binding and suggest that mutations within this CRM that perturb TPO binding could give rise to CAMT.
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Affiliation(s)
- Leila N Varghese
- The Walter and Eliza Hall Institute of Medical Research , Parkville, Victoria , Australia and
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Chen WM, Yu B, Zhang Q, Xu P. Identification of the residues in the extracellular domain of thrombopoietin receptor involved in the binding of thrombopoietin and a nuclear distribution protein (human NUDC). J Biol Chem 2010; 285:26697-709. [PMID: 20529857 PMCID: PMC2924112 DOI: 10.1074/jbc.m110.120956] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 06/06/2010] [Indexed: 11/06/2022] Open
Abstract
Thrombopoietin (TPO) and its receptor (Mpl) have long been associated with megakaryocyte proliferation, differentiation, and platelet formation. However, studies have also shown that the extracellular domain of Mpl (Mpl-EC) interacts with human (h) NUDC, a protein previously characterized as a human homolog of a fungal nuclear migration protein. This study was undertaken to further delineate the putative binding domain on the Mpl receptor. Using the yeast two-hybrid system assay and co-immunoprecipitation, we identified that within the Mpl-EC domain 1 (Mpl-EC-D1), amino acids 102-251 were strongly involved in ligand binding. We subsequently expressed five subdomains within this region with T7 phage display. Enzyme-linked immunosorbent binding assays identified a short stretch of peptide located between residues 206 and 251 as the minimum binding domain for both TPO and hNUDC. A series of sequential Ala replacement mutations in the region were subsequently used to identify the specific residues most involved in ligand binding. Our results point to two hydrophobic residues, Leu(228) and Leu(230), as having substantial effects on hNUDC binding. For TPO binding, mutations in residues Asp(235) and Leu(239) had the largest effect on binding efficacy. In addition, deletion of the conservative motif WGSWS reduced binding capacity for hNUDC but not for TPO. These separate binding sites on the Mpl receptor for TPO and hNUDC raise interesting implications for the cytokine-receptor interactions.
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Affiliation(s)
- Wei-Min Chen
- From the Key Laboratory of Gene Engineering of Education Ministry, Zhongshan University, Guangzhou 510275, China
| | - Bo Yu
- From the Key Laboratory of Gene Engineering of Education Ministry, Zhongshan University, Guangzhou 510275, China
| | - Qing Zhang
- From the Key Laboratory of Gene Engineering of Education Ministry, Zhongshan University, Guangzhou 510275, China
| | - Peilin Xu
- From the Key Laboratory of Gene Engineering of Education Ministry, Zhongshan University, Guangzhou 510275, China
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Lim AC, Ketchem RR, Borges L, Carabeo T, Carter J, Hoover JE, Hu Z, Wittekind M, Zhou H, Mehlin C. A diversity of antibody epitopes can induce signaling through the erythropoietin receptor. Biochemistry 2010; 49:3797-804. [PMID: 20337434 DOI: 10.1021/bi1001147] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Stimulation of red cell production through agonism of the erythropoietin receptor (EpoR) has historically been accomplished through administration of erythropoietin (EPO), the native ligand. The short half-life of EPO has led to the development of a variety of other agonists, including antibodies. It is of considerable interest to understand how these agents might activate the EpoR and whether or not it is important to bind in a manner similar to the native ligand. The binding epitopes of a panel of eight agonistic, single-chain antibody (scFv-Fc) constructs were determined through scanning alanine mutagenesis as well as more limited arginine mutagenesis of the receptor. It was found that while some of these constructs bound to receptor epitopes shared by the ligand, others bound in completely unique ways. The use of a panel of agonists and scanning mutagenesis can define the critical binding regions for signaling; in the case of the EpoR, these regions were remarkably broad.
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Affiliation(s)
- Ai Ching Lim
- Amgen, Inc., 1201 Amgen Court West AW2/3152, Seattle, Washington 98119-3105, USA
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11
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Yoon SI, Jones BC, Logsdon NJ, Harris BD, Deshpande A, Radaeva S, Halloran BA, Gao B, Walter MR. Structure and mechanism of receptor sharing by the IL-10R2 common chain. Structure 2010; 18:638-48. [PMID: 20462497 PMCID: PMC2879597 DOI: 10.1016/j.str.2010.02.009] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Revised: 02/12/2010] [Accepted: 02/15/2010] [Indexed: 01/07/2023]
Abstract
IL-10R2 is a shared cell surface receptor required for the activation of five class 2 cytokines (IL-10, IL-22, IL-26, IL-28, and IL-29) that play critical roles in host defense. To define the molecular mechanisms that regulate its promiscuous binding, we have determined the crystal structure of the IL-10R2 ectodomain at 2.14 A resolution. IL-10R2 residues required for binding were identified by alanine scanning and used to derive computational models of IL-10/IL-10R1/IL-10R2 and IL-22/IL-22R1/IL-10R2 ternary complexes. The models reveal a conserved binding epitope that is surrounded by two clefts that accommodate the structural and chemical diversity of the cytokines. These results provide a structural framework for interpreting IL-10R2 single nucleotide polymorphisms associated with human disease.
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Affiliation(s)
- Sung-il Yoon
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Brandi C. Jones
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Naomi J. Logsdon
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Bethany D. Harris
- Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Ashlesha Deshpande
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Svetlana Radaeva
- Section on Liver Biology, Laboratory of Physiologic Studies, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892
| | - Brian A. Halloran
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Bin Gao
- Section on Liver Biology, Laboratory of Physiologic Studies, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892
| | - Mark R. Walter
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
- Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, Alabama 35294
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12
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Fox NE, Lim J, Chen R, Geddis AE. F104S c-Mpl responds to a transmembrane domain-binding thrombopoietin receptor agonist: proof of concept that selected receptor mutations in congenital amegakaryocytic thrombocytopenia can be stimulated with alternative thrombopoietic agents. Exp Hematol 2010; 38:384-91. [PMID: 20188141 DOI: 10.1016/j.exphem.2010.02.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 02/10/2010] [Accepted: 02/16/2010] [Indexed: 12/22/2022]
Abstract
OBJECTIVE To determine whether specific c-Mpl mutations might respond to thrombopoietin receptor agonists. MATERIALS AND METHODS We created cell line models of type II c-Mpl mutations identified in congenital amegakaryocytic thrombocytopenia. We selected F104S c-Mpl for further study because it exhibited surface expression of the receptor. We measured proliferation of cell lines expressing wild-type or F104S c-Mpl in response to thrombopoietin receptor agonists targeting the extracellular (m-AMP4) or transmembrane (LGD-4665) domains of the receptor by 1-methyltetrazole-5-thiol assay. We measured thrombopoietin binding to the mutant receptor using an in vitro thrombopoietin uptake assay and identified F104 as a potentially critical residue for the interaction between the receptor and its ligand by aligning thrombopoietin and erythropoietin receptors from multiple species. RESULTS Cells expressing F104S c-Mpl proliferated in response to LGD-4665, but not thrombopoietin or m-AMP4. Compared to thrombopoietin, LGD-4665 stimulates signaling with delayed kinetics in both wild-type and F104S c-Mpl-expressing cells. Although F104S c-Mpl is expressed on the cell surface in our BaF3 cell line model, the mutant receptor does not bind thrombopoietin. Comparison to the erythropoietin receptor suggests that F104 engages in hydrogen-bonding interactions that are critical for binding to thrombopoietin. CONCLUSIONS These findings suggest that a small subset of patients with congenital amegakaryocytic thrombocytopenia might respond to treatment with thrombopoietin receptor agonists, but that responsiveness will depend on the type of mutation and agonist used. We postulate that F104 is critical for thrombopoietin binding. The kinetics of signaling in response to a transmembrane domain-binding agonist are delayed in comparison to thrombopoietin.
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Affiliation(s)
- Norma E Fox
- Pediatric Hematology-Oncology, University of California, San Diego, La Jolla, Calif. 92017, USA
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Karchin R, Monteiro ANA, Tavtigian SV, Carvalho MA, Sali A. Functional impact of missense variants in BRCA1 predicted by supervised learning. PLoS Comput Biol 2006; 3:e26. [PMID: 17305420 PMCID: PMC1797820 DOI: 10.1371/journal.pcbi.0030026] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Accepted: 12/27/2006] [Indexed: 11/19/2022] Open
Abstract
Many individuals tested for inherited cancer susceptibility at the BRCA1 gene locus are discovered to have variants of unknown clinical significance (UCVs). Most UCVs cause a single amino acid residue (missense) change in the BRCA1 protein. They can be biochemically assayed, but such evaluations are time-consuming and labor-intensive. Computational methods that classify and suggest explanations for UCV impact on protein function can complement functional tests. Here we describe a supervised learning approach to classification of BRCA1 UCVs. Using a novel combination of 16 predictive features, the algorithms were applied to retrospectively classify the impact of 36 BRCA1 C-terminal (BRCT) domain UCVs biochemically assayed to measure transactivation function and to blindly classify 54 documented UCVs. Majority vote of three supervised learning algorithms is in agreement with the assay for more than 94% of the UCVs. Two UCVs found deleterious by both the assay and the classifiers reveal a previously uncharacterized putative binding site. Clinicians may soon be able to use computational classifiers such as those described here to better inform patients. These classifiers can be adapted to other cancer susceptibility genes and systematically applied to prioritize the growing number of potential causative loci and variants found by large-scale disease association studies.
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Affiliation(s)
- Rachel Karchin
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- Institute of Computational Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail: (RK); (AS)
| | - Alvaro N. A Monteiro
- Risk Assessment, Detection, and Intervention Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, United States of America
| | | | - Marcelo A Carvalho
- Risk Assessment, Detection, and Intervention Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, United States of America
| | - Andrej Sali
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
- California Institute for Quantitative Biomedical Research, University of California San Francisco, San Francisco, California, United States of America
- * To whom correspondence should be addressed. E-mail: (RK); (AS)
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14
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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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Murphy JM, Ford SC, Olsen JE, Gustin SE, Jeffrey PD, Ollis DL, Young IG. Interleukin-3 Binding to the Murine βIL-3 and Human βc Receptors Involves Functional Epitopes Formed by Domains 1 and 4 of Different Protein Chains. J Biol Chem 2004; 279:26500-8. [PMID: 15060062 DOI: 10.1074/jbc.m402705200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interleukin-3 (IL-3) is a cytokine produced by activated T-cells and mast cells that is active on a broad range of hematopoietic cells and in the nervous system and appears to be important in several chronic inflammatory diseases. In this study, alanine substitutions were used to investigate the role of residues of the human beta-common (hbetac) receptor and the murine IL-3-specific (beta(IL-3)) receptor in IL-3 binding. We show that the domain 1 residues, Tyr(15) and Phe(79), of the hbetac receptor are important for high affinity IL-3 binding and receptor activation as shown previously for the related cytokines, interleukin-5 and granulocyte-macrophage colony-stimulating factor, which also signal through this receptor subunit. From the x-ray structure of hbetac, it is clear that the domain 1 residues cooperate with domain 4 residues to form a novel ligand-binding interface involving the two protein chains of the intertwined homodimer receptor. We demonstrate by ultracentrifugation that the beta(IL-3) receptor is also a homodimer. Its high sequence homology with hbetac suggests that their structures are homologous, and we identified an analogous binding interface in beta(IL-3) for direct IL-3 binding to the high affinity binding site in hbetac. Tyr(21) (A-B loop), Phe(85), and Asn(87) (E-F loop) of domain 1; Ile(320) of the interdomain loop; and Tyr(348) (B'-C' loop) and Tyr(401) (F'-G' loop) of domain 4 were shown to have critical individual roles and Arg(84) and Tyr(317) major secondary roles in direct murine IL-3 binding to the beta(IL-3)receptor. Most surprising, none of the key residues for direct IL-3 binding were critical for high affinity binding in the presence of the murine IL-3 alpha receptor, indicating a fundamentally different mechanism of high affinity binding to that used by hbetac.
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Affiliation(s)
- James M Murphy
- Division of Molecular Bioscience, John Curtin School of Medical Research and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
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16
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Stroud RM, Wells JA. Mechanistic diversity of cytokine receptor signaling across cell membranes. Sci Signal 2004; 2004:re7. [PMID: 15126678 DOI: 10.1126/stke.2312004re7] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Circulating cytokines bind to specific receptors on the cell outer surface to evoke responses inside the cell. Binding of cytokines alters the association between receptor molecules that often cross the membrane only once in a single alpha-helical segment. As a consequence, association of protein domains on the inside of the membrane are also altered. Increasing evidence suggests that an initial "off-state" of associated receptors is perturbed, and brought to an activated state that leads to intracellular signaling and eventually effects a change in DNA transcription. The initial detection event that transduces the change in receptor association is sensitive to both proximity and orientation of the receptors, and probably also to the time that the activated state or receptor association is maintained. Ultimately, a cascade of phosphorylation events is triggered. The initial kinases are sometimes part of the intracellular domains of the receptors. The kinases can also be separate proteins that may be pre-associated with intracellular domains of the receptors, or can be recruited after the intracellular association of the activated receptors. We focus here on each of the cases for which structures of the activated cytokine-receptor complexes are known, in a search for underlying mechanisms. The variations in modes of association, stoichiometries of receptors and cytokines, and orientations before and after activation of these receptors are almost as great as the number of complexes themselves. The principles uncovered nevertheless illustrate the basis for high specificity and fidelity in cytokine-mediated signaling.
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Affiliation(s)
- Robert M Stroud
- Department of Biochemistry and Biophysics, UCSF Genentech Hall, 600 16th Street, University of California, San Francisco, CA 94143-2240, USA
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Murphy JM, Ford SC, Wiedemann UM, Carr PD, Ollis DL, Young IG. A novel functional epitope formed by domains 1 and 4 of the human common beta-subunit is involved in receptor activation by granulocyte macrophage colony-stimulating factor and interleukin 5. J Biol Chem 2003; 278:10572-7. [PMID: 12525483 DOI: 10.1074/jbc.m211664200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The receptors for human interleukins 3 and 5 and granulocyte macrophage colony-stimulating factor are composed of ligand-specific alpha-subunits and a common beta-subunit (betac), the major signaling entity. The way in which betac interacts with ligands in the respective activation complexes has remained poorly understood. The recently determined crystal structure of the extracellular domain of betac revealed a possible ligand-binding interface composed of domain 1 of one chain of the betac dimer and the adjacent domain 4 of the symmetry-related chain. We have used site-directed mutagenesis, in conjunction with ligand binding and proliferation studies, to demonstrate the critical requirement of the domain 1 residues, Tyr(15) (A-B loop) and Phe(79) (E-F loop), in high affinity complex formation and receptor activation. The novel ligand-receptor interface formed between domains 1 and 4 represents the first example of a class I cytokine receptor interface to be composed of two noncontiguous fibronectin III domains.
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Affiliation(s)
- James M Murphy
- Division of Molecular Bioscience, John Curtin School of Medical Research and the Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
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Maxwell AP. Novel erythropoiesis-stimulating protein in the management of the anemia of chronic renal failure. Kidney Int 2002; 62:720-9. [PMID: 12110039 DOI: 10.1046/j.1523-1755.2002.00474.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- A Peter Maxwell
- Belfast City Hospital and Queen's University of Belfast, Belfast, Northern Ireland.
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19
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Olosz F, Malek TR. Structural basis for binding multiple ligands by the common cytokine receptor gamma-chain. J Biol Chem 2002; 277:12047-52. [PMID: 11815609 DOI: 10.1074/jbc.m110520200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The common gamma-chain (gamma(c)) that functions both in ligand binding and signal transduction is a shared subunit of the multichain receptors for interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21. The structural basis by which the ectodomain of gamma(c) contributes to binding six distinct cytokines is only partially defined. In the present study, epitope mapping of antagonistic anti-gamma(c) monoclonal antibodies led to the identification of Asn-128 of mouse gamma(c) that represents another potential contact residue that is required for binding IL-2, IL-7, and IL-15 but not IL-4. In addition, Tyr-103, Cys-161, Cys-210, and Cys-211, previously identified to contribute to binding IL-2 and IL-7, were also found to be involved in binding IL-4 and IL-15. Collectively, these data favor a model in which gamma(c) utilizes a common mechanism for its interactions with multiple cytokines, and the binding sites are largely overlapping but not identical. Asn-128 and Tyr-103 likely act as contact residues whereas Cys-161, Cys-210, and Gly-211 may stabilize the structure of the proposed ligand-interacting surface formed by the two extracytoplasmic domains.
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Affiliation(s)
- Ferenc Olosz
- Department of Microbiology and Immunology, University of Miami School of Medicine, Miami, Florida 33101, USA
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20
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Affiliation(s)
- H A Blacklock
- Department of Haematology, Middlemore Hospital, Auckland 6, New Zealand.
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21
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Bagley CJ, Woodcock JM, Guthridge MA, Stomski FC, Lopez AF. Structural and functional hot spots in cytokine receptors. Int J Hematol 2001; 73:299-307. [PMID: 11345195 DOI: 10.1007/bf02981954] [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: 10/21/2022]
Abstract
The activation of cytokine receptors is a stepwise process that depends on their specific interaction with cognate cytokines, the formation of oligomeric receptor complexes, and the initiation of cytoplasmic phosphorylation events. The recent determination of the structure of extracellular domains of several cytokine receptors allows comparison of their cytokine-binding surfaces. This comparison reveals a common structural framework that supports considerable diversity and adaptability of the binding surfaces that determine both the specificity and the orientation of subunits in the active receptor complex. These regions of the cytokine receptors have been targeted for the development of specific agonists and antagonists. The physical coupling of signaling intermediates to the intracellular domains of their receptors plays a major role in determining biological responses to cytokines. In this review, we focus principally on the receptors for cytokines of the granulocyte-macrophage colony-stimulating factor (GM-CSF) family and, where appropriate, compare them with related cytokine receptors. Several paradigms are beginning to emerge that focus on the ability of the extracellular portion of the cytokine receptor to recognize the appropriate cytokine and on a phosphorylated motif in the intracellular region of the GM-CSF receptor that couples to a specific signaling pathway.
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MESH Headings
- Amino Acid Motifs
- Animals
- Cell Division
- Cytokines/pharmacology
- Granulocyte-Macrophage Colony-Stimulating Factor/drug effects
- Granulocyte-Macrophage Colony-Stimulating Factor/physiology
- Hematopoietic Stem Cells/cytology
- Hematopoietic Stem Cells/metabolism
- Humans
- Interleukin-3/physiology
- Interleukin-5/physiology
- Ligands
- Models, Molecular
- Phosphatidylinositol 3-Kinases/physiology
- Phosphorylation
- Phosphoserine/chemistry
- Phosphotyrosine/physiology
- Protein Conformation
- Protein Processing, Post-Translational
- Receptors, Cytokine/chemistry
- Receptors, Cytokine/drug effects
- Receptors, Cytokine/physiology
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/chemistry
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/drug effects
- Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/physiology
- Receptors, Interleukin/chemistry
- Receptors, Interleukin/drug effects
- Receptors, Interleukin/physiology
- Receptors, Interleukin-3/chemistry
- Receptors, Interleukin-3/drug effects
- Receptors, Interleukin-3/physiology
- Receptors, Interleukin-5
- Signal Transduction
- Structure-Activity Relationship
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Affiliation(s)
- C J Bagley
- Division of Human Immunology, Hanson Centre for Cancer Research, the Institute of Medical and Veterinary Science, Adelaide, Australia
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22
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Olosz F, Malek TR. Three loops of the common gamma chain ectodomain required for the binding of interleukin-2 and interleukin-7. J Biol Chem 2000; 275:30100-5. [PMID: 10887198 DOI: 10.1074/jbc.m004976200] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The common gamma chain (gammac), a subunit of the interleukin (IL)-2, IL-4, IL-7, IL-9, and IL-15 receptors, contributes to both cytokine binding and subsequent signal transduction. Using a model-based site-directed mutagenesis strategy, we have identified residues of the mouse gammac extracellular domain that are required for normal gammac-dependent enhancement of IL-2 and IL-7 binding. One of these sites, Tyr-103, is homologous to key ligand-interacting residues in the growth hormone and erythropoietin receptors, whereas Cys-161, Cys-210, and Gly-211 may function indirectly by maintaining the functional conformation of gammac via formation of an intramolecular disulfide bond. These two cysteines are also required for the integrity of a putative epitope recognized by TUGm2, an antagonistic monoclonal antibody that blocks gammac-dependent cytokine binding and bioactivity. These results are consistent with the involvement of three predicted loops in gammac that contribute to the binding of both IL-2 and IL-7. Mutations in these loops have also been noted in the gammac gene of patients with X-linked severe combined immunodeficiency.
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Affiliation(s)
- F Olosz
- Department of Microbiology and Immunology, University of Miami School of Medicine, Miami, Florida 33101, USA
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23
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Yoon C, Johnston SC, Tang J, Stahl M, Tobin JF, Somers WS. Charged residues dominate a unique interlocking topography in the heterodimeric cytokine interleukin-12. EMBO J 2000; 19:3530-41. [PMID: 10899108 PMCID: PMC313992 DOI: 10.1093/emboj/19.14.3530] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Human interleukin-12 (IL-12, p70) is an early pro-inflammatory cytokine, comprising two disulfide-linked subunits, p35 and p40. We solved the crystal structures of monomeric human p40 at 2.5 A and the human p70 complex at 2.8 A resolution, which reveals that IL-12 is similar to class 1 cytokine-receptor complexes. They also include the first description of an N-terminal immunoglobulin-like domain, found on the p40 subunit. Several charged residues from p35 and p40 intercalate to form a unique interlocking topography, shown by mutagenesis to be critical for p70 formation. A central arginine residue from p35 projects into a deep pocket on p40, which may be an ideal target for a small molecule antagonist of IL-12 formation.
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MESH Headings
- Arginine/genetics
- Arginine/metabolism
- Binding Sites
- Crystallography, X-Ray
- Dimerization
- Disulfides/chemistry
- Disulfides/metabolism
- Drug Design
- Epitopes/chemistry
- Epitopes/metabolism
- Growth Hormone/chemistry
- Growth Hormone/metabolism
- Humans
- Interleukin-12/antagonists & inhibitors
- Interleukin-12/chemistry
- Interleukin-12/genetics
- Interleukin-12/metabolism
- Models, Molecular
- Molecular Weight
- Mutagenesis, Site-Directed
- Protein Binding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, Cytokine/antagonists & inhibitors
- Receptors, Cytokine/chemistry
- Receptors, Cytokine/genetics
- Receptors, Cytokine/metabolism
- Receptors, Somatotropin/chemistry
- Receptors, Somatotropin/metabolism
- Signal Transduction
- Static Electricity
- Structure-Activity Relationship
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Affiliation(s)
- C Yoon
- Departments of Musculoskeletal Sciences and Biological Chemistry, Wyeth Research, 87 Cambridge Park Drive, Cambridge, MA 02140, USA
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24
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Czabotar PE, Holland J, Sanderson CJ. Identification of regions within the third FnIII-like domain of the IL-5Ralpha involved in IL-5 interaction. Cytokine 2000; 12:867-73. [PMID: 10880230 DOI: 10.1006/cyto.1999.0663] [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: 11/22/2022]
Abstract
Previously, two binding sites for interleukin 5 (IL-5) were identified on the IL-5 receptor alpha chain (IL-5Ralpha). They are located within the CD loop of the first fibronectin type III (FnIII)-like domain and the EF loop of the second FnIII-like domain. The first binding site was identified by exploiting the different abilities of human IL-5Ralpha (hIL-5Ralpha) and mouse IL-5Ralpha (mIL-5Ralpha) to bind hIL-5. Here we show that ovine IL-5 (oIL-5) has the ability to activate the hIL-5Ralpha but not the mIL-5Ralpha. By using chimeras of the mIL-5Ralpha and hIL-5Ralpha we demonstrate that residues within the first and third FnIII-like domains of mIL-5Ralpha are responsible for this lack of activity. Furthermore, mutation of residues on hIL-5Ralpha to mIL-5Ralpha within the predicted DE and FG loop regions of the third FnIII domain reduces oIL-5 activity. These results show that regions of the third FnIII domain of IL-5Ralpha are involved in binding, in addition to the regions in domains one and two of the IL-5Ralpha that were identified in an earlier study.
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Affiliation(s)
- P E Czabotar
- Molecular Immunology Group, Curtin University of Technology, Perth, Australia.
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25
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Pearson PL, Smith TP, Sonstegard TS, Klemcke HG, Christenson RK, Vallet JL. Porcine erythropoietin receptor: molecular cloning and expression in embryonic and fetal liver. Domest Anim Endocrinol 2000; 19:25-38. [PMID: 10962196 DOI: 10.1016/s0739-7240(00)00062-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The full coding sequence for porcine erythropoietin receptor (EPOR) was elucidated using reverse transcription polymerase chain reaction (PCR) (rtPCR) and 3' and 5' rapid amplification of cDNA ends (RACE) procedures. Total RNA collected from Day 30 fetal liver was used as starting material. A 1843 bp sequence was obtained from which could be inferred a 509 amino acid protein which was 79-85% identical to the amino acid sequence of erythropoietin receptor from other species. Total RNA samples collected from white crossbred intact, white crossbred UHO and Meishan gilts on Days 24, 30 and 40 of gestation were subjected to Northern blotting using porcine EPOR cDNA as probe. Results indicated that (1) a major and two minor forms of mRNA are present, (2) fetal liver mRNA concentrations for EPOR are low on Day 24 of gestation and increase dramatically by Day 30 and (3) mRNA concentrations for EPOR tended to be decreased by intrauterine crowding.
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Affiliation(s)
- P L Pearson
- USDA, ARS, Roman L. Hruska US Meat Animal Research Center, Clay Center, NE 68933, USA
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26
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Olivier C, Auguste P, Chabbert M, Lelièvre E, Chevalier S, Gascan H. Identification of a gp130 cytokine receptor critical site involved in oncostatin M response. J Biol Chem 2000; 275:5648-56. [PMID: 10681548 DOI: 10.1074/jbc.275.8.5648] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gp130 cytokine receptor is involved in the formation of multimeric functional receptors for interleukin-6 (IL-6), IL-11, leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor, and cardiotrophin-1. Cloning of the epitope recognized by an OSM-neutralizing anti-gp130 monoclonal antibody identified a portion of gp130 receptor localized in the EF loop of the cytokine binding domain. Site-directed mutagenesis of the corresponding region was carried out by alanine substitution of residues 186-198. To generate type 1 or type 2 OSM receptors, gp130 mutants were expressed together with either LIF receptor beta or OSM receptor beta. When positions Val-189/Tyr-190 and Phe-191/Val-192 were alanine-substituted, Scatchard analyses indicated a complete abrogation of OSM binding to both type receptors. Interestingly, binding of LIF to type 1 receptor was not affected, corroborating the notion that in this case gp130 mostly behaves as a converter protein rather than a binding receptor. The present study demonstrates that positions 189-192 of gp130 cytokine binding domain are essential for OSM binding to both gp130/LIF receptor beta and gp130/OSM receptor beta heterocomplexes.
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MESH Headings
- Alanine/chemistry
- Amino Acid Sequence
- Animals
- Antibodies, Monoclonal/metabolism
- Antigens, CD/chemistry
- Antigens, CD/metabolism
- Binding Sites
- COS Cells
- Cytokine Receptor gp130
- Cytokines/metabolism
- Dose-Response Relationship, Drug
- Enzyme-Linked Immunosorbent Assay
- Epitopes/metabolism
- Flow Cytometry
- Growth Inhibitors
- Humans
- Interleukin-6
- Kinetics
- Leukemia Inhibitory Factor
- Leukemia Inhibitory Factor Receptor alpha Subunit
- Lymphokines
- Membrane Glycoproteins/chemistry
- Membrane Glycoproteins/metabolism
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Oncostatin M
- Peptide Library
- Peptides/metabolism
- Protein Binding
- Protein Structure, Secondary
- Receptors, Cytokine/metabolism
- Receptors, OSM-LIF
- Recombinant Proteins/metabolism
- Sequence Homology, Amino Acid
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Affiliation(s)
- C Olivier
- INSERM E 9928, CHU d'Angers, 49033 Angers Cedex, France
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27
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Sabath DF, Lin N, Sabath DE, Kaushansky K, Broudy VC. Tyrosine 462 of the membrane-proximal F'-G' loop of murine Mpl is not essential for high-affinity binding of thrombopoietin. Cytokine 2000; 12:127-33. [PMID: 10671297 DOI: 10.1006/cyto.1999.0531] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ligand binding site of Mpl, the thrombopoietin (Tpo) receptor, has not been determined. Tyr(462)of murine Mpl corresponds to Tyr(421)of the common beta chain of the human IL-3, IL-5 and GM-CSF receptors. Tyr(421)has been identified as essential for high-affinity ligand binding. To determine whether Tyr(462)is similarly required for Tpo binding, wild-type murine Mpl (Mpl-WT) or mutant receptors containing an alanine (Y462A) or lysine (Y462K) in place of Tyr(462)were expressed in BaF3 cells. In proliferation studies, the Y462A mutation had no effect on Tpo-induced growth. In contrast, the Y462K mutation led to an attenuated proliferative response to Tpo. In single-point binding studies, both Mpl-WT and Y462A cells were able to bind [(125)I]Tpo in a specific manner. In contrast, there was a marked reduction in binding of [(125)I]Tpo by Y462K cells. Mpl-WT cells bound Tpo with a K(d)of approximately 330 pM, while Y462A cells bound Tpo with a K(d)of approximately 268 pM. The binding affinity of Y462K cells was below that quantifiable by Scatchard analysis. This study suggests that unlike the corresponding Tyr(421)of the common human beta chain, Tyr(462)of murine Mpl is not required for high-affinity ligand binding, although it may be located in proximity to the ligand binding site.
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Affiliation(s)
- D F Sabath
- Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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28
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Wilson IA, Jolliffe LK. The structure, organization, activation and plasticity of the erythropoietin receptor. Curr Opin Struct Biol 1999; 9:696-704. [PMID: 10607675 DOI: 10.1016/s0959-440x(99)00032-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Dimerization of the erythropoietin receptor has long been accepted as the singular step in its mechanism of activation. Recent studies have revealed a regulator process for activation that is dependent on the actual configuration of the receptor-ligand dimer assembly. This aspect of the receptor subunit assembly appears to extend to the unliganded receptor, which can dimerize on the cell surface and diminish any spontaneous background signaling in the absence of ligand. This self-recognition, as well as the multiple ligand binding capabilities of the receptor binding site, is consistent with an emerging theme of plasticity in protein-protein and ligand-receptor interactions.
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Affiliation(s)
- I A Wilson
- Department of Molecular Biology, Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla 92037, USA.
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29
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Haman A, Cadieux C, Wilkes B, Hercus T, Lopez A, Clark S, Hoang T. Molecular determinants of the granulocyte-macrophage colony-stimulating factor receptor complex assembly. J Biol Chem 1999; 274:34155-63. [PMID: 10567387 DOI: 10.1074/jbc.274.48.34155] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor (GMR) is composed of two chains that belong to the superfamily of cytokine receptors typified by the growth hormone receptor. A common structural element found in cytokine receptors is a module of two fibronectin-like domains, each characterized by seven beta-strands denoted A-G and A'-G', respectively. The alpha-chain (GMRalpha) confers low affinity GM-CSF binding (K(d) = 1-5 nM), whereas the beta-chain (beta(c)) does not bind GM-CSF by itself but confers high affinity binding when associated with alpha (K(d) = 40-100 pM). In the present study, we define the molecular determinants required for ligand recognition and for stabilization of the complex through a convergence of several approaches, including the construction of chimeric receptors, the molecular dynamics of our three-dimensional model of the GM.GMR complex, and site-directed mutagenesis. The functional importance of individual residues was then investigated through ligand binding studies at equilibrium and through determination of the kinetic constants of the GM.GMR complex. Critical to this tripartite complex is the establishment of four noncovalent bonds, three that determine the nature of the ligand recognition process involving residues Arg(280) and Tyr(226) of the alpha-chain and residue Tyr(365) of the beta-chain, since mutations of either one of these residues resulted in a significant decrease in the association rate. Finally, residue Tyr(365) of beta(c) serves a dual function in that it cooperates with another residue of beta(c), Tyr(421) to stabilize the complex since mutation of Tyr(365) and Tyr(421) result in a drastic increase in the dissociation rate (Koff). Interestingly, these four residues are located at the B'-C' and F'-G' loops of GMRalpha and of beta(c), thus establishing a functional symmetry within an apparently asymmetrical heterodimeric structure.
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Affiliation(s)
- A Haman
- The Clinical Research Institute of Montreal, Montréal, Québec H2W 1R7, Canada
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30
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Miller BA, Barber DL, Bell LL, Beattie BK, Zhang MY, Neel BG, Yoakim M, Rothblum LI, Cheung JY. Identification of the erythropoietin receptor domain required for calcium channel activation. J Biol Chem 1999; 274:20465-72. [PMID: 10400674 DOI: 10.1074/jbc.274.29.20465] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Erythropoietin (Epo) activates a voltage-independent Ca2+ channel that is dependent on tyrosine phosphorylation. To identify the domain(s) of the Epo receptor (Epo-R) required for Epo-induced Ca2+ influx, Chinese hamster ovary (CHO) cells were transfected with wild-type or mutant Epo receptors subcloned into pTracer-cytomegalovirus vector. This vector contains an SV40 early promoter, which drives expression of the green fluorescent protein (GFP) gene, and a cytomegalovirus immediate-early promoter driving expression of the Epo-R. Successful transfection was verified in single cells by detection of GFP, and intracellular Ca2+ ([Ca]i) changes were simultaneously monitored with rhod-2. Transfection of CHO cells with pTracer encoding wild-type Epo-R, but not pTracer alone, resulted in an Epo-induced [Ca]i increase that was abolished in cells transfected with Epo-R F8 (all eight cytoplasmic tyrosines substituted). Transfection with carboxyl-terminal deletion mutants indicated that removal of the terminal four tyrosine phosphorylation sites, but not the tyrosine at position 479, abolished Epo-induced [Ca]i increase, suggesting that tyrosines at positions 443, 460, and/or 464 are important. In CHO cells transfected with mutant Epo-R in which phenylalanine was substituted for individual tyrosines, a significant increase in [Ca]i was observed with mutants Epo-R Y443F and Epo-R Y464F. The rise in [Ca]i was abolished in cells transfected with Epo-R Y460F. Results were confirmed with CHO cells transfected with plasmids expressing Epo-R mutants in which individual tyrosines were added back to Epo-R F8 and in stably transfected Ba/F3 cells. These results demonstrate a critical role for the Epo-R cytoplasmic tyrosine 460 in Epo-stimulated Ca2+ influx.
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Affiliation(s)
- B A Miller
- Department of Pediatrics, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033, USA.
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31
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Middleton SA, Barbone FP, Johnson DL, Thurmond RL, You Y, McMahon FJ, Jin R, Livnah O, Tullai J, Farrell FX, Goldsmith MA, Wilson IA, Jolliffe LK. Shared and unique determinants of the erythropoietin (EPO) receptor are important for binding EPO and EPO mimetic peptide. J Biol Chem 1999; 274:14163-9. [PMID: 10318834 DOI: 10.1074/jbc.274.20.14163] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown previously that Phe93 in the extracellular domain of the erythropoietin (EPO) receptor (EPOR) is crucial for binding EPO. Substitution of Phe93 with alanine resulted in a dramatic decrease in EPO binding to the Escherichia coli-expressed extracellular domain of the EPOR (EPO-binding protein or EBP) and no detectable binding to full-length mutant receptor expressed in COS cells. Remarkably, Phe93 forms extensive contacts with a peptide ligand in the crystal structure of the EBP bound to an EPO-mimetic peptide (EMP1), suggesting that Phe93 is also important for EMP1 binding. We used alanine substitution of EBP residues that contact EMP1 in the crystal structure to investigate the function of these residues in both EMP1 and EPO binding. The three largest hydrophobic contacts at Phe93, Met150, and Phe205 and a hydrogen bonding interaction at Thr151 were examined. Our results indicate that Phe93 and Phe205 are important for both EPO and EMP1 binding, Met150 is not important for EPO binding but is critical for EMP1 binding, and Thr151 is not important for binding either ligand. Thus, Phe93 and Phe205 are important binding determinants for both EPO and EMP1, even though these ligands share no sequence or structural homology, suggesting that these residues may represent a minimum epitope on the EPOR for productive ligand binding.
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Affiliation(s)
- S A Middleton
- R. W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey 08869, USA.
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32
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Hendrix DK, Klein TE, Kuntz ID, Klien TE. Macromolecular docking of a three-body system: the recognition of human growth hormone by its receptor. Protein Sci 1999; 8:1010-22. [PMID: 10338012 PMCID: PMC2144328 DOI: 10.1110/ps.8.5.1010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Human growth hormone (hGH) binds to its receptor (hGHr) in a three-body interaction: one molecule of the hormone and two identical monomers of the receptor form a trimer. Curiously, the hormone-receptor interactions in the trimer are not equivalent and the formation of the complex occurs in a specific kinetic order (Cunningham BC, Ultsch M, De Vos AM, Mulkerrin MG, Clauser KR, Wells JA, 1991, Science 254:821-825). In this paper, we model the recognition of hGH to the hGHr using shape complementarity of the three-dimensional structures and macromolecular docking to explore possible binding modes between the receptor and hormone. The method, reported previously (Hendrix DK, Kuntz ID, 1998, Pacific symposium on biocomputing 1998, pp 1234-1244), is based upon matching complementary-shaped strategic sites on the molecular surface. We modify the procedure to examine three-body systems. We find that the order of binding seen experimentally is also essential to our model. We explore the use of mutational data available for hGH to guide our model. In addition to docking hGH to the hGHr, we further test our methodology by successfully reproducing 16 macromolecular complexes from X-ray crystal structures, including enzyme-inhibitor, antibody-antigen, protein dimer, and protein-DNA complexes.
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Affiliation(s)
- D K Hendrix
- Department of Pharmaceutical Chemistry, University of California, San Francisco, 94143-0446, USA
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33
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Hage T, Sebald W, Reinemer P. Crystal structure of the interleukin-4/receptor alpha chain complex reveals a mosaic binding interface. Cell 1999; 97:271-81. [PMID: 10219247 DOI: 10.1016/s0092-8674(00)80736-9] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Interleukin-4 (IL-4) is a principal regulatory cytokine during an immune response and a crucial determinant for allergy and asthma. IL-4 binds with high affinity and specificity to the ectodomain of the IL-4 receptor alpha chain (IL4-BP). Subsequently, this intermediate complex recruits the common gamma chain (gamma c), thereby initiating transmembrane signaling. The crystal structure of the intermediate complex between human IL-4 and IL4-BP was determined at 2.3 A resolution. It reveals a novel spatial orientation of the two proteins, a small but unexpected conformational change in the receptor-bound IL-4, and an interface with three separate clusters of trans-interacting residues. Novel insights on ligand binding in the cytokine receptor family and a paradigm for receptors of IL-2, IL-7, IL-9, and IL-15, which all utilize gamma c, are provided.
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Affiliation(s)
- T Hage
- Institut für Physiologische Chemie II, Theodor-Boveri-Institut für Biowissen Schaften (Biozentrum), Universität Würzburg, Germany
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34
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Livnah O, Stura EA, Middleton SA, Johnson DL, Jolliffe LK, Wilson IA. Crystallographic evidence for preformed dimers of erythropoietin receptor before ligand activation. Science 1999; 283:987-90. [PMID: 9974392 DOI: 10.1126/science.283.5404.987] [Citation(s) in RCA: 460] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Erythropoietin receptor (EPOR) is thought to be activated by ligand-induced homodimerization. However, structures of agonist and antagonist peptide complexes of EPOR, as well as an EPO-EPOR complex, have shown that the actual dimer configuration is critical for the biological response and signal efficiency. The crystal structure of the extracellular domain of EPOR in its unliganded form at 2.4 angstrom resolution has revealed a dimer in which the individual membrane-spanning and intracellular domains would be too far apart to permit phosphorylation by JAK2. This unliganded EPOR dimer is formed from self-association of the same key binding site residues that interact with EPO-mimetic peptide and EPO ligands. This model for a preformed dimer on the cell surface provides insights into the organization, activation, and plasticity of recognition of hematopoietic cell surface receptors.
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Affiliation(s)
- O Livnah
- Department of Molecular Biology and Skaggs Institute of Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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Syed RS, Reid SW, Li C, Cheetham JC, Aoki KH, Liu B, Zhan H, Osslund TD, Chirino AJ, Zhang J, Finer-Moore J, Elliott S, Sitney K, Katz BA, Matthews DJ, Wendoloski JJ, Egrie J, Stroud RM. Efficiency of signalling through cytokine receptors depends critically on receptor orientation. Nature 1998; 395:511-6. [PMID: 9774108 DOI: 10.1038/26773] [Citation(s) in RCA: 418] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Human erythropoietin is a haematopoietic cytokine required for the differentiation and proliferation of precursor cells into red blood cells. It activates cells by binding and orientating two cell-surface erythropoietin receptors (EPORs) which trigger an intracellular phosphorylation cascade. The half-maximal response in a cellular proliferation assay is evoked at an erythropoietin concentration of 10 pM, 10(-2) of its Kd value for erythropoietin-EPOR binding site 1 (Kd approximately equal to nM), and 10(-5) of the Kd for erythropoietin-EPOR binding site 2 (Kd approximately equal to 1 microM). Overall half-maximal binding (IC50) of cell-surface receptors is produced with approximately 0.18 nM erythropoietin, indicating that only approximately 6% of the receptors would be bound in the presence of 10 pM erythropoietin. Other effective erythropoietin-mimetic ligands that dimerize receptors can evoke the same cellular responses but much less efficiently, requiring concentrations close to their Kd values (approximately 0.1 microM). The crystal structure of erythropoietin complexed to the extracellular ligand-binding domains of the erythropoietin receptor, determined at 1.9 A from two crystal forms, shows that erythropoietin imposes a unique 120 degrees angular relationship and orientation that is responsible for optimal signalling through intracellular kinase pathways.
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Affiliation(s)
- R S Syed
- Amgen Inc., Thousand Oaks, California 91320-1789, USA.
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Klumb LA, Chu V, Stayton PS. Energetic roles of hydrogen bonds at the ureido oxygen binding pocket in the streptavidin-biotin complex. Biochemistry 1998; 37:7657-63. [PMID: 9601024 DOI: 10.1021/bi9803123] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The high-affinity streptavidin-biotin complex is characterized by an extensive hydrogen-bonding network. A study of hydrogen-bonding energetics at the ureido oxygen of biotin has been conducted with site-directed mutations at Asn 23, Ser 27, and Tyr 43. A new competitive biotin binding assay was developed to provide direct equilibrium measurements of the alterations in Kd. S27A, Y43F, Y43A, N23A, and N23E mutants display DeltaDeltaG degrees at 37 degrees C relative to wild-type streptavidin of 2.9, 1.2, 2.6, 3.5, and 2.6 kcal/mol, respectively. The equilibrium-binding enthalpies for all of the mutants were measured by isothermal titration calorimetry, and the Y43A and N23A mutants display large decreases in the equilibrium binding enthalpy at 25 degrees C of 8.9 and 6.9 kcal/mol, respectively. The S27A and N23E mutants displayed small decreases in binding enthalpy of 1.6 and 0.9 kcal/mol relative to wild-type, while the Y43F mutant displayed a -2.6 kcal/mol increase in the binding enthalpy at 25 degrees C. At 37 degrees C, the Y43A and N23A mutants display decreases of 7.8 and 7.9 kcal/mol, respectively, while the S27A, N23E, and Y43F mutants displayed decreases of 4.9, 3.7, and 1.2 kcal/mol relative to wild-type. Kinetic analyses were also conducted to probe the contributions of the hydrogen bonds to the activation barrier. Wild-type streptavidin at 37 degrees C displays a koff of (4.1 +/- 0.3) x 10(-5) s-1, and the conservative Y43F, S27A, and N23A mutants displayed increases in koff to (20 +/- 1) x 10(-5) s-1, (660 +/- 40) x 10(-5) s-1, and (1030 +/- 220) x 10(-)5 s-1, respectively. The Y43A and N23E mutants displayed 93-fold and 188-fold increases in koff, respectively. Activation energies and enthalpies for each of the mutants were determined by transition-state analysis of the dissociation rate temperature dependence. All of the mutants except Y43F display large reductions in the activation enthalpy. The Y43F mutant has a more positive activation enthalpy, and thus a more favorable activation entropy that underlies the overall reduction in the activation barrier. For the most conservative mutant at each ureido oxygen hydrogen-bonding position, bound-state alterations account for most of the energetic changes in a single transition-state model, suggesting that the ureido oxygen hydrogen-bonding interactions are broken in the dissociation transition state.
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Affiliation(s)
- L A Klumb
- Department of Bioengineering, University of Washington, Seattle 98195, USA
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37
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Abstract
AbstractErythropoietin (EPO) is a factor essential for erythroid cell proliferation, differentiation, and survival. The production of EPO by the kidneys in response to hypoxia and anemia is well documented. To determine whether EPO is also produced by hematopoietic cells, we analyzed the expression of EPO in normal human hematopoietic progenitors and in their progeny. Undifferentiated CD34+lin− hematopoietic progenitors do not have detectable EPO mRNA. Differentiating CD34+ cells that are stimulated with recombinant human EPO in serum-free liquid cultures express both EPO and EPO receptor (EPOR). Because CD34+ cells represent a heterogeneous cell population, we analyzed individual burst-forming units–erythroid (BFU-E) and nonerythroid colony-forming unit–granulocyte-macrophage colonies for EPO mRNA. Only BFU-E colonies were positive for EPO mRNA. Lysates from pooled BFU-E colonies stained positively for EPO by immunoblotting. To further confirm the intrinsic nature of erythroid EPO, we replaced extrinsic EPO in erythroid colony cultures with EPO-mimicking peptide (EMP). We show EPO expression in the EMP-stimulated BFU-Es at both mRNA and protein levels. Stimulation of bone marrow mononuclear cells (BMMCs) with EMP upregulated EPO expression. Furthermore, we found EPO and EPOR mRNAs as well as EPO protein in K562 cells, a human erythroleukemia cell line. Stimulation of K562 cells with EMP upregulated EPO expression. We suggest that EPO of erythroid origin may have a role in the regulation of erythropoiesis.
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Abstract
Erythropoietin (EPO) is a factor essential for erythroid cell proliferation, differentiation, and survival. The production of EPO by the kidneys in response to hypoxia and anemia is well documented. To determine whether EPO is also produced by hematopoietic cells, we analyzed the expression of EPO in normal human hematopoietic progenitors and in their progeny. Undifferentiated CD34+lin− hematopoietic progenitors do not have detectable EPO mRNA. Differentiating CD34+ cells that are stimulated with recombinant human EPO in serum-free liquid cultures express both EPO and EPO receptor (EPOR). Because CD34+ cells represent a heterogeneous cell population, we analyzed individual burst-forming units–erythroid (BFU-E) and nonerythroid colony-forming unit–granulocyte-macrophage colonies for EPO mRNA. Only BFU-E colonies were positive for EPO mRNA. Lysates from pooled BFU-E colonies stained positively for EPO by immunoblotting. To further confirm the intrinsic nature of erythroid EPO, we replaced extrinsic EPO in erythroid colony cultures with EPO-mimicking peptide (EMP). We show EPO expression in the EMP-stimulated BFU-Es at both mRNA and protein levels. Stimulation of bone marrow mononuclear cells (BMMCs) with EMP upregulated EPO expression. Furthermore, we found EPO and EPOR mRNAs as well as EPO protein in K562 cells, a human erythroleukemia cell line. Stimulation of K562 cells with EMP upregulated EPO expression. We suggest that EPO of erythroid origin may have a role in the regulation of erythropoiesis.
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Johnson DL, Farrell FX, Barbone FP, McMahon FJ, Tullai J, Hoey K, Livnah O, Wrighton NC, Middleton SA, Loughney DA, Stura EA, Dower WJ, Mulcahy LS, Wilson IA, Jolliffe LK. Identification of a 13 amino acid peptide mimetic of erythropoietin and description of amino acids critical for the mimetic activity of EMP1. Biochemistry 1998; 37:3699-710. [PMID: 9521688 DOI: 10.1021/bi971956y] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To obtain information about the functional importance of amino acids required for effective erythropoietin (EPO) mimetic action, the conserved residues of a peptide mimetic of EPO, recently discovered by phage display, were subjected to an alanine replacement strategy. Further, to identify a minimal mimetic peptide sequence, a series of truncation peptides has been generated. One EPO mimetic peptide sequence, EMP1, was targeted and more than 25 derivatives of this sequence were evaluated for their ability to compete with [125I]EPO for receptor binding and for their ability to support the proliferation of two EPO-responsive cell lines. Two hydrophobic amino acids, Tyr4 and Trp13, appear essential for mimetic action, and aromatic residues appear to be important at these sites. These findings are consistent with the previously reported X-ray crystal structure of EMP1 complexed with the extracellular domain of the EPO receptor (EPO binding protein; EBP). In our efforts to define the structural elements required for EPO mimetic action, a 13 amino acid peptide was identified which possesses mimetic properties and contains a minimal agonist epitope. The ability of this peptide to effectively serve as a mimetic capable of the induction of EPO-responsive cell proliferation appears to reside within a single residue, equivalent to position Tyr4 of EMP1, when present in a sequence that includes the cyclic core peptide structure. Although these peptides are less potent than EPO, they should serve as an excellent starting point for the design of compounds with EPO mimetic activity.
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Affiliation(s)
- D L Johnson
- R. W. Johnson Pharmaceutical Research Institute, Drug Discovery Research, Raritan, New Jersey 08869, USA.
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Johnson DL, Farrell FX, Barbone FP, McMahon FJ, Tullai J, Kroon D, Freedy J, Zivin RA, Mulcahy LS, Jolliffe LK. Amino-terminal dimerization of an erythropoietin mimetic peptide results in increased erythropoietic activity. CHEMISTRY & BIOLOGY 1997; 4:939-50. [PMID: 9427659 DOI: 10.1016/s1074-5521(97)90302-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Erythropoietin (EPO), the hormone involved in red blood cell production, activates its receptor by binding to the receptor's extracellular domain and presumably dimerizing two receptor monomers to initiate signal transduction. EPO-mimetic peptides, such as EMP1, also bind and activate the receptor by dimerization. These mimetic peptides are not as potent as EPO, however. The crystal structure of the EPO receptor (EBP) bound to EMP1 reveals the formation of a complex consisting of two peptides bound to two receptors, so we sought to improve the biological activity of EPO-mimetic peptides by constructing covalent dimers of EMP1 and other peptide mimetics linked by polyethylene glycol (PEG). RESULTS The potency of the PEG-dimerized EPO peptide mimetics both in vitro and in vivo was improved up to 1,000-fold compared to the corresponding peptide monomers. The dimers were constructed using peptide monomers which have only one reactive amine per molecule, allowing us to conclude that the increase in potency can be attributed to a structure in which two peptides are linked through their respective amino termini to the difunctional PEG molecule. In addition, an inactive peptide was converted into a weak agonist by PEG-induced dimerization. CONCLUSIONS The potency of previously isolated peptides that are modest agonists of the EPO receptor was dramatically increased by PEG-induced dimerization. The EPO receptor is thought to be dimerized during activation, so our results are consistent with the proposed 2:2 receptor : peptide stoichiometry. The conversion of an inactive peptide into an agonist further supports the idea that dimerization can mediate receptor activation.
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Affiliation(s)
- D L Johnson
- Drug Discovery Research, R.W. Johnson Pharmaceutical Research Institute, Route 202, Box 300, Raritan, NJ 08869, USA. . com
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41
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Layton JE, Iaria J, Smith DK, Treutlein HR. Identification of a ligand-binding site on the granulocyte colony-stimulating factor receptor by molecular modeling and mutagenesis. J Biol Chem 1997; 272:29735-41. [PMID: 9368043 DOI: 10.1074/jbc.272.47.29735] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Granulocyte colony-stimulating factor (G-CSF) initiates its effects on cells of the neutrophil lineage by inducing formation of a homodimeric receptor complex. The structure of the G-CSF receptor has not yet been determined, therefore we used molecular modeling to identify regions of the receptor that were likely to be involved in ligand binding. The G-CSF receptor sequence was aligned with all the available sequences of the gp130 and growth hormone receptor families and a model of the cytokine receptor homologous domain was constructed, based on the growth hormone receptor structure. Alanine substitution mutagenesis was performed on loops and individual residues that were predicted to bind ligand. Mutant receptors were expressed in factor-dependent Ba/F3 cells and assessed for proliferation response and ligand binding. Six residues were identified that significantly reduced receptor function, with Arg288 in the F'-G' loop having the greatest effect. These residues formed a binding face on the receptor model resembling the growth hormone receptor site, which suggests that the model is reasonable. However, electrostatic analysis of the model provided further evidence that the mechanism of receptor dimerization is different from that of the growth hormone receptor.
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Affiliation(s)
- J E Layton
- Ludwig Institute for Cancer Research, Melbourne Tumour Biology Branch, P. O. Box 2008, Royal Melbourne Hospital, Parkville, Australia 3050.
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42
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Rajotte D, Cadieux C, Haman A, Wilkes BC, Clark SC, Hercus T, Woodcock JA, Lopez A, Hoang T. Crucial role of the residue R280 at the F'-G' loop of the human granulocyte/macrophage colony-stimulating factor receptor alpha chain for ligand recognition. J Exp Med 1997; 185:1939-50. [PMID: 9166423 PMCID: PMC2196330 DOI: 10.1084/jem.185.11.1939] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The receptor for granulocyte/macrophage colony-stimulating factor (GM-CSF) is composed of two chains, alpha and betac. Both chains belong to the superfamily of cytokine receptors characterized by a common structural feature, i.e., the presence of at least two fibronectin-like folds in the extracellular domain, which was first identified in the growth hormone receptor. The GM-CSF receptor (GMR)-alpha chain confers low affinity binding only (5-10 nM), whereas the other chain, betac, does not bind GM-CSF by itself but confers high affinity binding when associated with GMR-alpha (25-100 pM). The present study was designed to define the assembly of the GMR complex at the molecular level through site-directed mutagenesis guided by homology modeling with the growth hormone receptor complex. In our three-dimensional model, R280 of GMR-alpha, located in the F'-G' loop and close to the WSSWS motif, is in the vicinity of the ligand Asp112, suggesting the possibility of electrostatic interaction between these two residues. Through site directed mutagenesis, we provide several lines of evidence indicating the importance of electrostatic interaction in ligand-receptor recognition. First, mutagenesis of GMR-alphaR280 strikingly ablated ligand binding in the absence of beta common (betac); ligand binding was restored in the presence of betac with, nonetheless, a significant shift from high (26 pM) toward low affinity (from 2 to 13 nM). The rank order of the dissociation constant for the different GMR-alphaR280 mutations where Lys > Gln > Met > Asp, suggesting the importance of the charge at this position. Second, a mutant GM-CSF with charge reversal mutation at position Asp112 exhibited a 1,000-fold decrease in affinity in receptor binding, whereas charge ablation or conservative mutations were the least affected (10-20-fold). Third, removal of the charge at position R280 of GMR-alpha introduced a 10-fold decrease in the association rate constant and only a 2-fold change in the dissociation rate constant, suggesting that R280 is implicated in ligand recognition, possibly through interaction with Asp112 of GM-CSF. For all R280 mutants, the half-efficient concentrations of GM-CSF required for membrane (receptor binding) to nuclear events (c-fos promoter activation) and cell proliferation (thymidine incorporation) were in the same range, indicating that the threshold for biologic activity is governed mainly by the affinity of ligand-receptor interaction. Furthermore, mutation of other residues in the immediate vicinity of R280 was less drastic. Sequence alignment and modeling of interleukin (IL)-3R and IL-5R identified an arginine residue at the tip of a beta turn in a highly divergent context at the F'-G' loop, close to a conserved structural element, the WSXWS motif, suggesting the possibility of a ligand association mechanism similar to the one described herein for GMR.
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Affiliation(s)
- D Rajotte
- Clinical Research Institute of Montréal, Laboratory of Hemopoiesis and Leukemia, Montréal, Quebec, Canada
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Deane CM, Kroemer RT, Richards WG. A structural model of the human thrombopoietin receptor complex. J Mol Graph Model 1997; 15:170-8, 185-8. [PMID: 9457620 DOI: 10.1016/s1093-3263(97)00102-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Thrombopoietin (TPO) is a glycoprotein hormone that regulates red blood cell production. Presented here is a modeling study of the extracellular region of the human thrombopoietin receptor complex, in particular the TPO-receptor interface. The models were developed from structural homology to other cytokines and their receptors. Experimental evidence suggests that the receptor is homodimeric and it was modeled accordingly. Key interactions are shown that correlate with previous cytokine receptor complexes, and the pattern of cysteine bonding (Cys7-Cys151 and Cys29-Cys85) agrees with that experimentally determined for thrombopoietin. These models pave the way for possible mutagenesis experimentation and the design of (ant)agonists.
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Affiliation(s)
- C M Deane
- Physical and Theoretical Chemistry Laboratory, University of Oxford, United Kingdom
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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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45
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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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46
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Barbone FP, Middleton SA, Johnson DL, McMahon FJ, Tullai J, Gruninger RH, Schilling AE, Jolliffe LK, Mulcahy LS. Mutagenesis studies of the human erythropoietin receptor. Establishment of structure-function relationships. J Biol Chem 1997; 272:4985-92. [PMID: 9030560 DOI: 10.1074/jbc.272.8.4985] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Mutagenesis of the erythropoietin receptor (EPOR) permits analysis of the contribution that individual amino acid residues make to erythropoietin (EPO) binding. We employed both random and site-specific mutagenesis to determine the function of amino acid residues in the extracellular domain (referred to as EPO binding protein, EBP) of the EPOR. Residues were chosen for site-specific alanine substitution based on the results of the random mutagenesis or on their homology to residues that are conserved or have been reported to be involved in ligand binding in other receptors of the cytokine receptor family. Site-specific mutants were expressed in Escherichia coli as soluble EBP and analyzed for EPO binding in several different assay formats. In addition, selected mutant proteins were expressed as full-length EPOR on the surface of COS cells and analyzed for 125I-EPO binding in receptor binding assays. Using these methods, we have identified residues that appear to be involved in EPO binding as well as other residues, most of which are conserved in receptors of the cytokine receptor family, that appear to be necessary for the proper folding and/or stability of the EPOR. We present correlations between these mutagenesis data and the recently solved crystal structure of the EBP with a peptide ligand.
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Affiliation(s)
- F P Barbone
- The R. W. Johnson Pharmaceutical Research Institute, Drug Discovery Research, Raritan, New Jersey 08869, USA.
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47
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Livnah O, Stura EA, Johnson DL, Middleton SA, Mulcahy LS, Wrighton NC, Dower WJ, Jolliffe LK, Wilson IA. Functional mimicry of a protein hormone by a peptide agonist: the EPO receptor complex at 2.8 A. Science 1996; 273:464-71. [PMID: 8662530 DOI: 10.1126/science.273.5274.464] [Citation(s) in RCA: 501] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The functional mimicry of a protein by an unrelated small molecule has been a formidable challenge. Now, however, the biological activity of a 166-residue hematopoietic growth hormone, erythropoietin (EPO), with its class 1 cytokine receptor has been mimicked by a 20-residue cyclic peptide unrelated in sequence to the natural ligand. The crystal structure at 2.8 A resolution of a complex of this agonist peptide with the extracellular domain of EPO receptor reveals that a peptide dimer induces an almost perfect twofold dimerization of the receptor. The dimer assembly differs from that of the human growth hormone (hGH) receptor complex and suggests that more than one mode of dimerization may be able to induce signal transduction and cell proliferation. The EPO receptor binding site, defined by peptide interaction, corresponds to the smaller functional epitope identified for hGH receptor. Similarly, the EPO mimetic peptide ligand can be considered as a minimal hormone, and suggests the design of nonpeptidic small molecule mimetics for EPO and other cytokines may indeed be achievable.
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MESH Headings
- Amino Acid Sequence
- Binding Sites
- Crystallography, X-Ray
- Drug Design
- Erythropoietin/chemistry
- Erythropoietin/metabolism
- Growth Hormone/chemistry
- Growth Hormone/metabolism
- Humans
- Hydrogen Bonding
- Models, Molecular
- Molecular Mimicry
- Molecular Sequence Data
- Peptides, Cyclic/chemistry
- Peptides, Cyclic/metabolism
- Protein Conformation
- Protein Folding
- Protein Structure, Secondary
- Receptors, Erythropoietin/agonists
- Receptors, Erythropoietin/chemistry
- Receptors, Erythropoietin/metabolism
- Receptors, Somatotropin/chemistry
- Receptors, Somatotropin/metabolism
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Affiliation(s)
- O Livnah
- Department of Molecular Biology and the Skaggs Institute of Chemical Biology, The Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, CA 92037, USA
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