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Roy A, Shrivastva S, Naseer S. In and out: Traffic and dynamics of thrombopoietin receptor. J Cell Mol Med 2021; 25:9073-9083. [PMID: 34448528 PMCID: PMC8500957 DOI: 10.1111/jcmm.16878] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/27/2021] [Accepted: 08/04/2021] [Indexed: 12/17/2022] Open
Abstract
Thrombopoiesis had long been a challenging area of study due to the rarity of megakaryocyte precursors in the bone marrow and the incomplete understanding of its regulatory cytokines. A breakthrough was achieved in the early 1990s with the discovery of the thrombopoietin receptor (TpoR) and its ligand thrombopoietin (TPO). This accelerated research in thrombopoiesis, including the uncovering of the molecular basis of myeloproliferative neoplasms (MPN) and the advent of drugs to treat thrombocytopenic purpura. TpoR mutations affecting its membrane dynamics or transport were increasingly associated with pathologies such as MPN and thrombocytosis. It also became apparent that TpoR affected hematopoietic stem cell (HSC) quiescence while priming hematopoietic stem cells (HSCs) towards the megakaryocyte lineage. Thorough knowledge of TpoR surface localization, dimerization, dynamics and stability is therefore crucial to understanding thrombopoiesis and related pathologies. In this review, we will discuss the mechanisms of TpoR traffic. We will focus on the recent progress in TpoR membrane dynamics and highlight the areas that remain unexplored.
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Affiliation(s)
- Anita Roy
- Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, India
| | - Saurabh Shrivastva
- Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, India
| | - Saadia Naseer
- Kusuma School of Biological Sciences, Indian Institute of Technology, New Delhi, India
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2
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Reprogramming signal transduction through a designer receptor tyrosine kinase. Commun Biol 2021; 4:752. [PMID: 34140621 PMCID: PMC8211861 DOI: 10.1038/s42003-021-02287-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 06/01/2021] [Indexed: 11/30/2022] Open
Abstract
Controlling signal transduction with artificial designer receptors is a promising approach to realize future medicine for intractable diseases. Although several functional artificial receptors have been reported by domain engineering, more sophisticated engineering within domains has yet to be thoroughly investigated. Here we demonstrate motif-based engineering of a receptor tyrosine kinase for reprogramming signal transduction. We design a scaffold-less tyrosine kinase domain that does not recruit any signal transducers but retains its kinase function. The resultant scaffold-less tyrosine kinase domain is linked to a tyrosine motif that recruits a target signaling molecule upon its phosphorylation. The engineered tyrosine motif–kinase fusion protein is further connected to a small molecule- or light-dependent dimerizing domain that can switch on the kinase activity in response to an external stimulus. The resultant designer receptors attain specific chemical- or photo-activation of signaling molecules of interest in mammalian cells. Thus, our designer receptor tyrosine kinase proves the possibility of rationally reprogramming intracellular signal transduction on a motif basis. The motif-based receptor engineering may realize tailor-made functional receptors useful in the fields of biology and medicine. Kongkrongtong et al. present motif-based engineering of tyrosine kinase receptor for reprogramming signal transduction. Here, by swapping internal tyrosine of receptor with those that bind intracellular STAT signaling proteins, they demonstrate that specificity of this receptor can be reprogrammed with this approach.
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Szabo M, Kowalczyk W, Tarasova A, Andrade J, Be CL, Mulder R, White J, Meyer AG, Schwab KE, Cartledge K, Le TC, Arachchilage AW, Wang X, Hoffman R, Nilsson SK, Haylock DN, Winkler DA. Potent In Vitro Peptide Antagonists of the Thrombopoietin Receptor as Potential Myelofibrosis Drugs. ADVANCED THERAPEUTICS 2021. [DOI: 10.1002/adtp.202000241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Monika Szabo
- CSIRO Manufacturing Research Way Clayton 3168 Australia
| | | | - Anna Tarasova
- CSIRO Manufacturing Research Way Clayton 3168 Australia
| | | | - Cheang Ly Be
- CSIRO Manufacturing Research Way Clayton 3168 Australia
| | - Roger Mulder
- CSIRO Manufacturing Research Way Clayton 3168 Australia
| | - Jacinta White
- CSIRO Manufacturing Research Way Clayton 3168 Australia
| | - Adam G. Meyer
- CSIRO Manufacturing Research Way Clayton 3168 Australia
| | | | | | - Tu C. Le
- School of Engineering RMIT University Melbourne 3000 Australia
| | | | - Xiaoli Wang
- Icahn School of Medicine Mt Sinai School of Medicine New York NY 10029 USA
| | - Ronald Hoffman
- Icahn School of Medicine Mt Sinai School of Medicine New York NY 10029 USA
| | - Susan K. Nilsson
- CSIRO Manufacturing Research Way Clayton 3168 Australia
- Australian Regenerative Medicine Institute Monash University Melbourne 3800 Australia
| | - David N. Haylock
- La Trobe Institute for Molecular Science La Trobe University Kingsbury Drive Bundoora 3086 Australia
| | - David A. Winkler
- CSIRO Manufacturing Research Way Clayton 3168 Australia
- La Trobe Institute for Molecular Science La Trobe University Kingsbury Drive Bundoora 3086 Australia
- Monash Institute of Pharmaceutical Sciences Monash University 392 Royal Parade Parkville 3052 Australia
- School of Pharmacy University of Nottingham Nottingham NG7 2RD UK
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Rommel MGE, Hoerster K, Milde C, Schenk F, Roser L, Kohlscheen S, Heinz N, Modlich U. Signaling properties of murine MPL and MPL mutants after stimulation with thrombopoietin and romiplostim. Exp Hematol 2020; 85:33-46.e6. [PMID: 32417303 DOI: 10.1016/j.exphem.2020.04.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 04/24/2020] [Accepted: 04/29/2020] [Indexed: 01/01/2023]
Abstract
Thrombopoietin (THPO) and its receptor myeloproliferative leukemia virus oncogene (MPL) regulate hematopoietic stem cell (HSC) quiescence and maintenance, but also megakaryopoiesis. Thrombocytopenias or aplastic anemias can be treated today with THPO peptide mimetics (romiplostim) or small-molecule THPO receptor agonists (e.g., eltrombopag). These THPO mimetics were designed for human application; however, many preclinical studies are performed in murine models. We investigated the activation of wild-type murine MPL (mMPL) by romiplostim. Romiplostim stimulated AKT, ERK1/2, and STAT5 phosphorylation without preference for one of these pathways, however, with a four- to fivefold lower phosphorylation intensity at high concentration. Faster internalization of mMPL after romiplostim binding could be one explanation of reduced signaling. In vitro megakaryocyte differentiation, proliferation, and maturation by romiplostim was less efficient compared with stimulation with mTHPO. We further dissected mMPL signaling by lentiviral overexpression of mMPL mutants with tyrosine (Y)-to-phenylalanine (F) substitutions in the distal cytoplasmic tyrosines 582 (Y582F), 616 (Y616F), and 621 (Y621F) individually and in combination (Y616F_Y621F) and in truncated receptors lacking 53 (Δ53) or 69 (Δ69) C-terminal amino acids. Mutation at tyrosine residue Y582F caused a gain-of-function with baseline activation and increased ERK1/2 phosphorylation upon stimulation. In agreement with this, proliferation in Y582F-32D cells was increased, yet did not rescue in vitro megakaryopoiesis from Mpl-deficient cells. Y616F and Y621F mutated receptors exhibited strongly impaired ERK1/2 and decreased AKT signaling and conferred reduced proliferation to 32D cells upon mTHPO stimulation but a partial correction of immature megakaryopoiesis in vitro.
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Affiliation(s)
- Marcel G E Rommel
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Keven Hoerster
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany; Institute for Transfusion Medicine, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Christian Milde
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Franziska Schenk
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Luise Roser
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Saskia Kohlscheen
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Niels Heinz
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany
| | - Ute Modlich
- Research Group for Gene Modification in Stem Cells, Division of Veterinary Medicine, Paul-Ehrlich-Institut, Langen, Germany.
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Wang B, Mehta H. Cytokine receptor splice variants in hematologic diseases. Cytokine 2019; 127:154919. [PMID: 31816579 DOI: 10.1016/j.cyto.2019.154919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 10/08/2019] [Accepted: 11/04/2019] [Indexed: 12/13/2022]
Abstract
Cytokine and cytokine receptors are important regulators of hematopoiesis. Hematopoietic stem cells (HSCs) and progenitors differentiate into the myeloid or lymphoid lineage in response to specific cytokines. Cell-type specific receptors are expressed on committed progenitors that bind to other late-acting cytokines that are involved in terminal differentiation of hematopoietic cells. In normal hematopoiesis, these receptors undergo alternative splicing and are developmentally regulated. Splicing changes can significantly affect the structure and function of the receptors resulting in alterations of either the extracellular ligand binding domain or the cytoplasmic signaling domain responsible for cellular growth and differentiation. Most alternatively spliced isoforms generally lose the ability to promote differentiation. Evidently, overexpression of naturally occurring cytokine receptor alternate isoforms are observed in multiple myeloid diseases such as myelodysplastic syndromes (MDS), acute myeloid leukemia (AML), and polycythemia vera (PV). The purpose of this review is to introduce the various isoforms of key cytokine receptors that play a crucial role in myeloid development and their potential role in myeloid diseases.
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Affiliation(s)
- Borwyn Wang
- Center for Clinical and Translational Research, Virginia Commonwealth University, Richmond, VA, United States; Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Hrishikesh Mehta
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
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Saka K, Lai CY, Nojima M, Kawahara M, Otsu M, Nakauchi H, Nagamune T. Dissection of Signaling Events Downstream of the c-Mpl Receptor in Murine Hematopoietic Stem Cells Via Motif-Engineered Chimeric Receptors. Stem Cell Rev Rep 2018; 14:101-109. [PMID: 28948469 PMCID: PMC5801400 DOI: 10.1007/s12015-017-9768-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Hematopoietic stem cells (HSCs) are a valuable resource in transplantation medicine. Cytokines are often used to culture HSCs aiming at better clinical outcomes through enhancement of HSC reconstitution capability. Roles for each signal molecule downstream of receptors in HSCs, however, remain puzzling due to complexity of the cytokine-signaling network. Engineered receptors that are non-responsive to endogenous cytokines represent an attractive tool for dissection of signaling events. We here tested a previously developed chimeric receptor (CR) system in primary murine HSCs, target cells that are indispensable for analysis of stem cell activity. Each CR contains tyrosine motifs that enable selective activation of signal molecules located downstream of the c-Mpl receptor upon stimulation by an artificial ligand. Signaling through a control CR with a wild-type c-Mpl cytoplasmic tail sufficed to enhance HSC proliferation and colony formation in cooperation with stem cell factor (SCF). Among a series of CRs, only one compatible with selective Stat5 activation showed similar positive effects. The HSCs maintained ex vivo in these environments retained long-term reconstitution ability following transplantation. This ability was also demonstrated in secondary recipients, indicating effective transmission of stem cell-supportive signals into HSCs via these artificial CRs during culture. Selective activation of Stat5 through CR ex vivo favored preservation of lymphoid potential in long-term reconstituting HSCs, but not of myeloid potential, exemplifying possible dissection of signals downstream of c-Mpl. These CR systems therefore offer a useful tool to scrutinize complex signaling pathways in HSCs.
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Affiliation(s)
- Koichiro Saka
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Chen-Yi Lai
- Division of Stem Cell Therapy, Center for Stem Cell Biology and Regenerative Medicine, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan.,Division of Stem Cell Processing / Stem Cell Bank, Center for Stem Cell Biology and Regenerative Medicine, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan
| | - Masanori Nojima
- Division of Advanced Medicine Promotion, Advanced Clinical Research Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan
| | - Masahiro Kawahara
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Makoto Otsu
- Division of Stem Cell Therapy, Center for Stem Cell Biology and Regenerative Medicine, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan. .,Division of Stem Cell Processing / Stem Cell Bank, Center for Stem Cell Biology and Regenerative Medicine, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan.
| | - Hiromitsu Nakauchi
- Division of Stem Cell Therapy, Center for Stem Cell Biology and Regenerative Medicine, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan.,Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Teruyuki Nagamune
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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Varghese LN, Defour JP, Pecquet C, Constantinescu SN. The Thrombopoietin Receptor: Structural Basis of Traffic and Activation by Ligand, Mutations, Agonists, and Mutated Calreticulin. Front Endocrinol (Lausanne) 2017; 8:59. [PMID: 28408900 PMCID: PMC5374145 DOI: 10.3389/fendo.2017.00059] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 03/17/2017] [Indexed: 12/13/2022] Open
Abstract
A well-functioning hematopoietic system requires a certain robustness and flexibility to maintain appropriate quantities of functional mature blood cells, such as red blood cells and platelets. This review focuses on the cytokine receptor that plays a significant role in thrombopoiesis: the receptor for thrombopoietin (TPO-R; also known as MPL). Here, we survey the work to date to understand how this receptor functions at a molecular level throughout its lifecycle, from traffic to the cell surface, dimerization and binding cognate cytokine via its extracellular domain, through to its subsequent activation of associated Janus kinases and initiation of downstream signaling pathways, as well as the regulation of these processes. Atomic level resolution structures of TPO-R have remained elusive. The identification of disease-causing mutations in the receptor has, however, offered some insight into structure and function relationships, as has artificial means of receptor activation, through TPO mimetics, transmembrane-targeting receptor agonists, and engineering in dimerization domains. More recently, a novel activation mechanism was identified whereby mutated forms of calreticulin form complexes with TPO-R via its extracellular N-glycosylated domain. Such complexes traffic pathologically in the cell and persistently activate JAK2, downstream signal transducers and activators of transcription (STATs), and other pathways. This pathologic TPO-R activation is associated with a large fraction of human myeloproliferative neoplasms.
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Affiliation(s)
- Leila N. Varghese
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Jean-Philippe Defour
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- Department of Clinical Biology, Cliniques universitaires St Luc, Université catholique de Louvain, Brussels, Belgium
| | - Christian Pecquet
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Stefan N. Constantinescu
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- SIGN Pole, de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- *Correspondence: Stefan N. Constantinescu,
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8
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Du C, Xu Y, Yang K, Chen S, Wang X, Wang S, Wang C, Shen M, Chen F, Chen M, Zeng D, Li F, Wang T, Wang F, Zhao J, Ai G, Cheng T, Su Y, Wang J. Estrogen promotes megakaryocyte polyploidization via estrogen receptor beta-mediated transcription of GATA1. Leukemia 2016; 31:945-956. [DOI: 10.1038/leu.2016.285] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 09/13/2016] [Accepted: 09/14/2016] [Indexed: 12/21/2022]
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A thrombopoietin receptor antagonist is capable of depleting myelofibrosis hematopoietic stem and progenitor cells. Blood 2016; 127:3398-409. [PMID: 27114459 DOI: 10.1182/blood-2015-10-674465] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 04/21/2016] [Indexed: 01/12/2023] Open
Abstract
Recently, interactions between thrombopoietin (TPO) and its receptor, the myeloproliferative leukemia (MPL) virus oncogene, have been shown to play a role in the development and progression of myeloproliferative neoplasms including myelofibrosis (MF). These observations have led to the development of strategies to disrupt the association of TPO with its receptor as a means of targeting MF hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs). In this report, we show that although both splenic and peripheral blood MF CD34(+) cells expressed lower levels of MPL than normal CD34(+) cells, TPO promoted the proliferation of MF CD34(+) cells and HPCs in a dose-dependent fashion. Furthermore, the treatment of MF but not normal CD34(+) cells with a synthesized MPL antagonist, LCP4, decreased the number of CD34(+)Lin(-) cells and all classes of assayable HPCs (colony-forming unit-megakaryocyte [CFU-MK], CFU-granulocyte/macrophage, burst-forming unit-erythroid/CFU-erythroid, and CFU-granulocyte/erythroid/macrophage/MK) irrespective of their mutational status. In addition, LCP4 treatment resulted in the depletion of the number of MF HPCs that were JAK2V617F(+) Moreover, the degree of human cell chimerism and the proportion of malignant donor cells were significantly reduced in immunodeficient mice transplanted with MF CD34(+) cell grafts treated with LCP4. These effects of LCP4 on MF HSCs/HPCs were associated with inhibition of JAK-STAT activity, leading to the induction of apoptosis. These findings demonstrate that such specific anti-cytokine receptor antagonists represent a new class of drugs that are capable of targeting MF HSCs.
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10
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Saeidi K. Myeloproliferative neoplasms: Current molecular biology and genetics. Crit Rev Oncol Hematol 2015; 98:375-89. [PMID: 26697989 DOI: 10.1016/j.critrevonc.2015.11.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Revised: 09/10/2015] [Accepted: 11/09/2015] [Indexed: 12/16/2022] Open
Abstract
Myeloproliferative neoplasms (MPNs) are clonal disorders characterized by increased production of mature blood cells. Philadelphia chromosome-negative MPNs (Ph-MPNs) consist of polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). A number of stem cell derived mutations have been identified in the past 10 years. These findings showed that JAK2V617F, as a diagnostic marker involving JAK2 exon 14 with a high frequency, is the best molecular characterization of Ph-MPNs. Somatic mutations in an endoplasmic reticulum chaperone, named calreticulin (CALR), is the second most common mutation in patients with ET and PMF after JAK2 V617F mutation. Discovery of CALR mutations led to the increased molecular diagnostic of ET and PMF up to 90%. It has been shown that JAK2V617F is not the unique event in disease pathogenesis. Some other genes' location such as TET oncogene family member 2 (TET2), additional sex combs-like 1 (ASXL1), casitas B-lineage lymphoma proto-oncogene (CBL), isocitrate dehydrogenase 1/2 (IDH1/IDH2), IKAROS family zinc finger 1 (IKZF1), DNA methyltransferase 3A (DNMT3A), suppressor of cytokine signaling (SOCS), enhancer of zeste homolog 2 (EZH2), tumor protein p53 (TP53), runt-related transcription factor 1 (RUNX1) and high mobility group AT-hook 2 (HMGA2) have also identified to be involved in MPNs phenotypes. Here, current molecular biology and genetic mechanisms involved in MNPs with a focus on the aforementioned factors is presented.
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Affiliation(s)
- Kolsoum Saeidi
- Department of Medical Genetics, Kerman University of Medical Sciences, Kerman, Iran.
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11
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Abstract
Major progress has been recently made in understanding the molecular pathogenesis of myeloproliferative neoplasms (MPN). Mutations in one of four genes-JAK2, MPL, CALR, and CSF3R-can be found in the vast majority of patients with MPN and represent driver mutations that can induce the MPN phenotype. Hyperactive JAK/STAT signaling appears to be the common denominator of MPN, even in patients with CALR mutations and the so-called "triple-negative" MPN, where the driver gene mutation is still unknown. Mutations in epigenetic regulators, transcription factors, and signaling components modify the course of the disease and can contribute to disease initiation and/or progression. The central role of JAK2 in MPN allowed development of small molecular inhibitors that are in clinical use and are active in almost all patients with MPN. Advances in understanding the mechanism of JAK2 activation open new perspectives of developing the next generation of inhibitors that will be selective for the mutated forms of JAK2.
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Lee EJ, Be CL, Vinson AR, Riches AG, Fehr F, Gardiner J, Gengenbach TR, Winkler DA, Haylock D. Immobilisation of a thrombopoietin peptidic mimic by self-assembled monolayers for culture of CD34+ cells. Biomaterials 2015; 37:82-93. [DOI: 10.1016/j.biomaterials.2014.10.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 10/02/2014] [Indexed: 01/25/2023]
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13
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Lan H, Li W, Fu Z, Yang Y, Wu T, Liu Y, Zhang H, Cui H, Li Y, Hong P, Liu J, Zheng X. Differential intracellular signalling properties of the growth hormone receptor induced by the activation of an anti-GHR antibody. Mol Cell Endocrinol 2014; 390:54-64. [PMID: 24755421 DOI: 10.1016/j.mce.2014.04.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Revised: 03/16/2014] [Accepted: 04/11/2014] [Indexed: 11/27/2022]
Abstract
A series of studies have reported that anti-GHR antibody can function as a GHR agonist and may serve as an attractive tool for studying the mechanisms of GHR activation. However, to date, there is relatively little information about intracellular signalling triggered by anti-GHR antibody. Therefore, in this work, we have developed a panel of monoclonal antibodies to GHBP, among which one Mab, termed CG-172, was selected for further characterisation because of its signalling properties. The results from FACS assays, receptor binding and immunoprecipitation assays and western blotting demonstrated that CG-172 specifically binds to GHR expressed on target cells. Subsequently, epitope mapping studies that used receptor binding analysis showed that CG-172 specifically binds subdomain 1 of GHR ECD. We next examined the resulting signal transduction pathways triggered by this antibody in CHO-GHR638 cells and rat hepatocytes. We found that CG-172 can activate JAK2, AKT, ERK1/2 and STAT1/3 but not STAT5. The phosphorylation kinetics of STAT1/3, AKT and ERK1/2 induced by either GH or CG-172 were analysed in dose-response and time course experiments. Our observations demonstrated that an anti-GHR monoclonal antibody (CG-172) can serve as an attractive tool to study the mechanism(s) of GHR-mediated intracellular signalling pathways and may lead to the production of signal-specific molecules that are capable of inducing different biochemical responses.
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Affiliation(s)
- Hainan Lan
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Wei Li
- State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, PR China
| | - Zhiling Fu
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Yanhong Yang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Tiancheng Wu
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Yu Liu
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Hui Zhang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Huanzhong Cui
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Yumeng Li
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Pan Hong
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Jingsheng Liu
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China
| | - Xin Zheng
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Xincheng Street 2888, Changchun 130118, PR China.
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14
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Jagya N, Varma SPK, Thakral D, Joshi P, Durgapal H, Panda SK. RNA-seq based transcriptome analysis of hepatitis E virus (HEV) and hepatitis B virus (HBV) replicon transfected Huh-7 cells. PLoS One 2014; 9:e87835. [PMID: 24505321 PMCID: PMC3914852 DOI: 10.1371/journal.pone.0087835] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Accepted: 12/30/2013] [Indexed: 12/11/2022] Open
Abstract
Pathogenesis of hepatitis B virus (HBV) and hepatitis E virus (HEV) infection is as varied as they appear similar; while HBV causes an acute and/or chronic liver disease and hepatocellular carcinoma, HEV mostly causes an acute self-limiting disease. In both infections, host responses are crucial in disease establishment and/or virus clearance. In the wake of worsening prognosis described during HEV super-infection over chronic HBV hepatitis, we investigated the host responses by studying alterations in gene expression in liver cells (Huh-7 cell line) by transfection with HEV replicon only (HEV-only), HBV replicon only (HBV-only) and both HBV and HEV replicons (HBV+HEV). Virus replication was validated by strand-specific real-time RT-PCR for HEV and HBsAg ELISA of the culture supernatants for HBV. Indirect immunofluorescence for the respective viral proteins confirmed infection. Transcription profiling was carried out by RNA Sequencing (RNA-Seq) analysis of the poly-A enriched RNA from the transfected cells. Averages of 600 million bases within 5.6 million reads were sequenced in each sample and ∼15,800 genes were mapped with at least one or more reads. A total of 461 genes in HBV+HEV, 408 in HBV-only and 306 in HEV-only groups were differentially expressed as compared to mock transfection control by two folds (p<0.05) or more. Majority of the significant genes with altered expression clustered into immune-associated, signal transduction, and metabolic process categories. Differential gene expression of functionally important genes in these categories was also validated by real-time RT-PCR based relative gene-expression analysis. To our knowledge, this is the first report of in vitro replicon transfected RNA-Seq based transcriptome analysis to understand the host responses against HEV and HBV.
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Affiliation(s)
- Neetu Jagya
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Satya Pavan Kumar Varma
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Deepshi Thakral
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Prashant Joshi
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Hemlata Durgapal
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Subrat Kumar Panda
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
- * E-mail:
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15
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Saka K, Kawahara M, Teng J, Otsu M, Nakauchi H, Nagamune T. Top-down motif engineering of a cytokine receptor for directing ex vivo expansion of hematopoietic stem cells. J Biotechnol 2013; 168:659-65. [PMID: 24070902 DOI: 10.1016/j.jbiotec.2013.09.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 09/12/2013] [Indexed: 12/12/2022]
Abstract
The technique to expand hematopoietic stem cells (HSCs) ex vivo is eagerly anticipated to secure an enough amount of HSCs for clinical applications. Previously we developed a scFv-thrombopoietin receptor (c-Mpl) chimera, named S-Mpl, which can transduce a proliferation signal in HSCs in response to a cognate antigen. However, a remaining concern of the S-Mpl chimera may be the magnitude of the cellular expansion level driven by this molecule, which was significantly less than that mediated by endogenous wild-type c-Mpl. In this study, we engineered a tyrosine motif located in the intracellular domain of S-Mpl based on a top-down approach in order to change the signaling properties of the chimera. The truncated mutant (trunc.) and an amino-acid substitution mutant (Q to L) of S-Mpl were constructed to investigate the ability of these mutants to expand HSCs. The result showed that the truncated and Q to L mutants gave higher and considerably lower number of the cells than unmodified S-Mpl, respectively. The proliferation level through the truncated mutant was even higher than that of non-transduced HSCs with the stimulation of a native cytokine, thrombopoietin. Moreover, we analyzed the signaling properties of the S-Mpl mutants in detail using a pro-B cell line Ba/F3. The data indicated that the STAT3 and STAT5 activation levels through the truncated mutant increased, whereas activation of the Q to L mutant was inhibited by a negative regulator of intracellular signaling, SHP-1. This is the first demonstration that a non-natural artificial mutant of a cytokine receptor is effective for ex vivo expansion of hematopoietic cells compared with a native cytokine receptor.
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Affiliation(s)
- Koichiro Saka
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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16
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Saka K, Kawahara M, Nagamune T. Reconstitution of a cytokine receptor scaffold utilizing multiple different tyrosine motifs. Biotechnol Bioeng 2013; 110:3197-204. [DOI: 10.1002/bit.24973] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 05/20/2013] [Accepted: 06/03/2013] [Indexed: 12/23/2022]
Affiliation(s)
- Koichiro Saka
- Department of Chemistry and Biotechnology, School of Engineering; The University of Tokyo; 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8656 Japan
| | - Masahiro Kawahara
- Department of Chemistry and Biotechnology, School of Engineering; The University of Tokyo; 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8656 Japan
| | - Teruyuki Nagamune
- Department of Chemistry and Biotechnology, School of Engineering; The University of Tokyo; 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8656 Japan
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17
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Tarasova A, Haylock DN, Meagher L, Be CL, White J, Nilsson SK, Andrade J, Cartledge K, Winkler DA. Potent Agonists of a Hematopoietic Stem Cell Cytokine Receptor, c-Mpl. ChemMedChem 2013; 8:763-71. [DOI: 10.1002/cmdc.201300089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Indexed: 11/12/2022]
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18
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Sugita M, Kalota A, Gewirtz AM, Carroll M. Eltrombopag inhibition of acute myeloid leukemia cell survival does not depend on c-Mpl expression. Leukemia 2012. [PMID: 23183425 DOI: 10.1038/leu.2012.310] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- M Sugita
- Division of Hematology and Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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19
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Ohashi H, Morita H, Tahara T, Tsunakawa H, Matsumoto A, Ogami K, Kato T, Miyazaki H. Thrombopoietin stimulates proliferation and megakaryocytic differentiation of mouse pro-B cell line BF-TE22. Cytotechnology 2012; 26:199-206. [PMID: 22358617 DOI: 10.1023/a:1007915809529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have isolated and characterized a thrombopoietin (TPO)-dependent BF-TE22 cell line endogenously expressing murine Mpl, which is a subclone of murine pro-B Ba/F3 cells. TPO stimulated the proliferation of BF-TE22 cells in a dose-dependent manner, and also induced the expression of megakaryocyte lineage-specific AP-51 and CD61 cell surface antigens. The results indicate that the murine Mpl on BF-TE22 cells can transmit both proliferation and megakaryocyte lineage-specific differentiation signals to cells. Furthermore, it was shown that IL-3 inhibits the TPO-induced differentiation signals of BF-TE22 cells. These results suggest that the signals mediated by IL-3 predominate over those of TPO in BF-TE22 cells. Thus, BF-TE22 cells will be useful for the biological and biochemical studies of the TPO-Mpl signal transduction mechanism.
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Affiliation(s)
- H Ohashi
- Pharmaceutical Research Laboratory, Kirin Brewery Co., Ltd, Miyahara 3, Takasaki, Gunma, 370, Japan
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20
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Thrombopoietin receptor down-modulation by JAK2 V617F: restoration of receptor levels by inhibitors of pathologic JAK2 signaling and of proteasomes. Blood 2012; 119:4625-35. [PMID: 22378845 DOI: 10.1182/blood-2011-08-372524] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The constitutively active JAK2 V617F mutant is the major determinant of human myeloproliferative neoplasms (MPNs). We show that coexpression of murine JAK2 V617F and the murine thrombopoietin (Tpo) receptor (TpoR, c-MPL) in hematopoietic cell lines or heterozygous knock-in of JAK2 V617F in mice leads to down-modulation of TpoR levels. Enhanced TpoR ubiquitinylation, proteasomal degradation, reduced recycling, and maturation are induced by the constitutive JAK2 V617F activity. These effects can be prevented in cell lines by JAK2 and proteasome inhibitors. Restoration of TpoR levels by inhibitors could be detected in platelets from JAK2 inhibitor-treated myelofibrosis patients that express the JAK2 V617F mutant, and in platelets from JAK2 V617F knock-in mice that were treated in vivo with JAK2 or proteasome inhibitors. In addition, we show that Tpo can induce both proliferative and antiproliferative effects via TpoR at low and high JAK2 activation levels, respectively, or on expression of JAK2 V617F. The antiproliferative signaling and receptor down-modulation by JAK2 V617F were dependent on signaling via TpoR cytosolic tyrosine 626. We propose that selection against TpoR antiproliferative signaling occurs by TpoR down-modulation and that restoration of down-modulated TpoR levels could become a biomarker for the treatment of MPNs.
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21
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Saka K, Kawahara M, Ueda H, Nagamune T. Activation of target signal transducers utilizing chimeric receptors with signaling-molecule binding motifs. Biotechnol Bioeng 2012; 109:1528-37. [DOI: 10.1002/bit.24421] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 12/15/2011] [Accepted: 12/19/2011] [Indexed: 12/22/2022]
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22
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Ghanima W, Junker P, Hasselbalch HC, Boiocchi L, Geyer JT, Feng X, Gudbrandsdottir S, Orazi A, Bussel JB. Fibroproliferative activity in patients with immune thrombocytopenia (ITP) treated with thrombopoietic agents. Br J Haematol 2011; 155:248-55. [DOI: 10.1111/j.1365-2141.2011.08845.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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23
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Orientation-specific signalling by thrombopoietin receptor dimers. EMBO J 2011; 30:4398-413. [PMID: 21892137 DOI: 10.1038/emboj.2011.315] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 08/04/2011] [Indexed: 02/08/2023] Open
Abstract
Ligand binding to the thrombopoietin receptor is thought to stabilize an active receptor dimer that regulates megakaryocyte differentiation and platelet formation, as well as haematopoietic stem cell renewal. By fusing a dimeric coiled coil in all seven possible orientations to the thrombopoietin receptor transmembrane (TM)-cytoplasmic domains, we show that specific biological effects and in vivo phenotypes are imparted by distinct dimeric orientations, which can be visualized by cysteine mutagenesis and crosslinking. Using functional assays and computational searches, we identify one orientation that represents the inactive dimeric state and another similar to a physiologically activated receptor. Several other dimeric orientations are identified that induce proliferation and in vivo myeloproliferative and myelodysplastic disorders, indicating the receptor can signal from several dimeric interfaces. The set of dimeric thrombopoietin receptors with different TM orientations may offer new insights into the activation of distinct signalling pathways by a single receptor and suggests that subtle differences in cytokine receptor dimerization provide a new layer of signalling regulation that is relevant for disease.
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24
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Chou FS, Mulloy JC. The thrombopoietin/MPL pathway in hematopoiesis and leukemogenesis. J Cell Biochem 2011; 112:1491-8. [PMID: 21360575 DOI: 10.1002/jcb.23089] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hematopoietic stem cells (HSC) comprise a small percentage of total hematopoietic cells. Their ability to self-renewal is key to the continuous replenishment of the hematopoietic system with newly formed functional blood cell types while maintaining their multipotential capacity. Understanding the extrinsic signals that are essential to HSC maintenance will provide insights into the regulation of hematopoiesis at its most primitive stage, and with the knowledge applied, will potentially lead to improved clinical transplantation outcomes. In this review, we will summarize the current understanding of the role of the thrombopoietin/MPL signaling pathway in HSC maintenance during adult and fetal hematopoiesis. We will also speculate on the downstream key players in the pathway based on published data, and summarize the role of this pathway in leukemia.
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Affiliation(s)
- Fu-Sheng Chou
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA
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25
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Tarasova A, Haylock D, Winkler D. Principal signalling complexes in haematopoiesis: Structural aspects and mimetic discovery. Cytokine Growth Factor Rev 2011; 22:231-53. [DOI: 10.1016/j.cytogfr.2011.09.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 09/06/2011] [Indexed: 11/17/2022]
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26
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Tarasova A, Winkler DA. Modelling atypical small-molecule mimics of an important stem cell cytokine, thrombopoietin. ChemMedChem 2010; 4:2002-11. [PMID: 19810084 DOI: 10.1002/cmdc.200900340] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We report the first comprehensive 3D QSAR study of a large, structurally diverse set of compounds that act as atypical thrombopoietin (TPO) mimics by interacting with the transmembrane domain of the TPO receptor, c-MPL. These agonists of c-MPL were superimposed according to a pharmacophore hypothesis, resulting in 3D QSAR models of high statistical significance. The pharmacophore-based superimposition and comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were used to derive the QSAR models relating structure to the published in vitro bioactivities of the TPO mimics. The CoMFA and CoMSIA models gave high correlation coefficients of the bioactivities with the derived fields, resulting in robust prediction of agonist activity of the superimposed compounds. The models have been interpreted in terms of the requirements for binding to the transmembrane domain of the TPO receptor.
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Affiliation(s)
- Anna Tarasova
- Molecular and Health Technologies, CSIRO, Bag 10, Clayton South MDC, 3169, Australia
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27
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Induction of myeloproliferative disorder and myelofibrosis by thrombopoietin receptor W515 mutants is mediated by cytosolic tyrosine 112 of the receptor. Blood 2010; 115:1037-48. [DOI: 10.1182/blood-2008-10-183558] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Constitutively active JAK2V617F and thrombopoietin receptor (TpoR) W515L/K mutants are major determinants of human myeloproliferative neoplasms (MPNs). We show that a TpoRW515 mutation (W515A), which we detected in 2 myelofibrosis patients, and the Δ5TpoR active mutant, where the juxtamembrane R/KW515QFP motif is deleted, induce a myeloproliferative phenotype in mouse bone marrow reconstitution experiments. This phenotype required cytosolic Y112 of the TpoR. Phosphotyrosine immunoprofiling detected phosphorylated cytosolic TpoR Y78 and Y112 in cells expressing TpoRW515A. Mutation of cytosolic Y112 to phenylalanine prevented establishment of the in vivo phenotype and decreased constitutive active signaling by Δ5TpoR and TpoRW515A, especially via the mitogen-activated protein (MAP)–kinase pathway, without decreasing Janus kinase 2 (JAK2) activation. In contrast, mutation of cytosolic Y78 to phenylalanine enhanced the myeloproliferative syndrome induced by the TpoRW515 mutants, by enhancing receptor-induced JAK2 activation. We propose that TpoR cytosolic phosphorylated Y112 and flanking sequences could become targets for pharmacologic inhibition in MPNs.
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28
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Metjian A, Abrams CS. New advances in the treatment of adult chronic immune thrombocytopenic purpura: role of thrombopoietin receptor-stimulating agents. Biologics 2009; 3:499-513. [PMID: 20054440 PMCID: PMC2802075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Decades of basic science and clinical research have led to an increased understanding of the pathophysiology of immune thrombocytopenic purpura (ITP), the processes underlying thrombopoiesis, and the treatment of chronic ITP. Now, new agents are available to treat ITP in a nonimmunosuppressive fashion. Lessons learned from the clinical trials of recombinant human thrombopoietin (TPO) have led to the development of a novel class of compounds: nonimmunogenic agonists of the thrombopoietin receptor. Representing the first nonimmunosuppressive agents to treat chronic refractory ITP in decades, medications such as romiplostim and eltrombopag were recently approved by the US Food and Drug Administration. These new agents offer physicians a new tool for treating difficult cases of ITP in their medical armamentarium. Additional TPO mimetics are also being developed that show promise in vitro, and await future development.
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Affiliation(s)
- Ara Metjian
- Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Charles S Abrams
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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29
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Arnold DM, Nazi I, Kelton JG. New treatments for idiopathic thrombocytopenic purpura: rethinking old hypotheses. Expert Opin Investig Drugs 2009; 18:805-19. [PMID: 19426124 DOI: 10.1517/13543780902905848] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND The efficacy of thrombopoietin (TPO) mimetics in patients with idiopathic thrombocytopenic purpura (ITP) reaffirms that impaired platelet production is an important mechanism. New strategies to reduce platelet destruction, like rituximab, are also effective. OBJECTIVES To describe the efficacy and safety of rituximab and the TPO mimetics, romiplostim and eltrombopag, and how they relate to ITP pathogenesis. METHODS Narrative review summarizing full publications and meeting abstracts. RESULTS/CONCLUSIONS A 4-week course of rituximab is associated with a platelet count response in 60% of patients with ITP, and durable responses have been observed. Subtle increases in infection have been reported. Romiplostim and eltrombopag are each associated with a 60 - 85% response while on treatment. Transient bone marrow reticulin with romiplostim and elevated liver enzymes with eltrombopag are rare side effects. The application of these agents in non-splenectomized patients requires further study.
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Affiliation(s)
- Donald M Arnold
- Michael G DeGroote School of Medicine, Medicine and Pathology and Molecular Medicine, McMaster University, 1200 Main Street W, Hamilton, Ontario, Canada.
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30
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Abstract
Primary immune thrombocytopenic purpura (ITP) remains a diagnosis of exclusion both from nonimmune causes of thrombocytopenia and immune thrombocytopenia that develops in the context of other disorders (secondary immune thrombocytopenia). The pathobiology, natural history, and response to therapy of the diverse causes of secondary ITP differ from each other and from primary ITP, so accurate diagnosis is essential. Immune thrombocytopenia can be secondary to medications or to a concurrent disease, such as an autoimmune condition (eg, systemic lupus erythematosus [SLE], antiphospholipid antibody syndrome [APS], immune thyroid disease, or Evans syndrome), a lymphoproliferative disease (eg, chronic lymphocytic leukemia or large granular T-lymphocyte lymphocytic leukemia), or chronic infection, eg, with Helicobacter pylori, human immunodeficiency virus (HIV), or hepatitis C virus (HCV). Response to infection may generate antibodies that cross-react with platelet antigens (HIV, H pylori) or immune complexes that bind to platelet Fcγ receptors (HCV), and platelet production may be impaired by infection of megakaryocyte (MK) bone marrow–dependent progenitor cells (HCV and HIV), decreased production of thrombopoietin (TPO), and splenic sequestration of platelets secondary to portal hypertension (HCV). Sudden and severe onset of thrombocytopenia has been observed in children after vaccination for measles, mumps, and rubella or natural viral infections, including Epstein-Barr virus, cytomegalovirus, and varicella zoster virus. This thrombocytopenia may be caused by cross-reacting antibodies and closely mimics acute ITP of childhood. Proper diagnosis and treatment of the underlying disorder, where necessary, play an important role in patient management.
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Affiliation(s)
- Douglas B Cines
- University of Pennsylvania School of Medicine, Department of Pathology and Laboratory Medicine, Philadelphia, PA 19104, USA.
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31
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Ballmaier M, Germeshausen M. Advances in the understanding of congenital amegakaryocytic thrombocytopenia. Br J Haematol 2009; 146:3-16. [PMID: 19388932 DOI: 10.1111/j.1365-2141.2009.07706.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Congenital amegakaryocytic thrombocytopenia (MIM #604498) is an extremely rare inherited bone marrow failure syndrome, usually presenting as a severe thrombocytopenia at birth due to ineffective megakaryocytopoiesis and no characteristic physical anomalies. Usually the isolated thrombocytopenia progresses to pancytopenia during the first years of life. The only curative therapy to date is haematopoietic stem cell transplantation. Most of the cases of congenital amegakaryocytic thrombocytopenia are caused by defective expression or function of the thrombopoietin receptor due to homozygous or compound heterozygous mutations in the gene MPL. The essential roles of thrombopoietin as a lineage specific regulator of platelet production and as a regulator of haematopoietic stem cell function are reflected in the haematological defects seen in affected individuals.
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Affiliation(s)
- Matthias Ballmaier
- Department of Paediatric Haematology and Oncology, Hannover Medical School, Hannover, Germany.
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32
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Screening of proteins that interact with human thrombopoietin receptor c-Mpl using yeast two-hybrid system. SCIENCE IN CHINA. SERIES C, LIFE SCIENCES 2008; 43:239-44. [PMID: 18726378 DOI: 10.1007/bf02879282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/1999] [Indexed: 10/22/2022]
Abstract
Thrombopoietin (TPO) is the major cytokine involved in platelet production and exerts its effects via the receptor c-Mpl. The yeast two-hybrid system has been used to screen the proteins interacting with c-Mpl. First, the cDNA fragment of c-Mpl intracellular domain was cloned into two-hybrid vector pAS2, and the resulting plasmid is designated as pASMM. Then a human placenta cDNA library was screened using the pASMM as a target plasmid. Seven positive clones were isolated from 150 000 independent transformants. Sequence analysis of one of the positive clones demonstrates that a part of coding sequence of vimentin from 611 bp to 3' end and flanking non-translation region was obtained. Therefore, there is an interaction between vimentin and TPO receptor. The results suggest that cytoskeletal protein may play an important role in TPO signal transduction pathway.
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33
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Kuter DJ. New drugs for familiar therapeutic targets: thrombopoietin receptor agonists and immune thrombocytopenic purpura. Eur J Haematol 2008:9-18. [DOI: 10.1111/j.1600-0609.2007.00999.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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34
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Metjian A, Abrams CS. New insights and therapeutics for immune-mediated thrombocytopenia. Expert Rev Cardiovasc Ther 2008; 6:71-84. [DOI: 10.1586/14779072.6.1.71] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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35
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Dillon M, Minear J, Johnson J, Lannutti BJ. Expression of the GPI-anchored receptor Prv-1 enhances thrombopoietin and IL-3-induced proliferation in hematopoietic cell lines. Leuk Res 2007; 32:811-9. [PMID: 17980909 DOI: 10.1016/j.leukres.2007.09.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 09/25/2007] [Accepted: 09/27/2007] [Indexed: 12/20/2022]
Abstract
Prv-1 is a hematopoietic cell surface receptor that has been shown to be overexpressed in patients diagnosed with polycythemia vera (PV) and essential thrombocythemia (ET), yet its cellular function remains unclear. In this study, we assessed the role of Prv-1 in thrombopoietin (Tpo)/Mpl signaling with the goal of identifying molecular mechanisms which augment Tpo-induced proliferation. By engineering the cytokine-dependent hematopoietic cell line BaF3 to express both Prv-1 and wild-type or mutant forms of Mpl, we were able to follow the time course of Tpo-dependent proliferation. We report that the overexpression of Prv-1 increased Tpo as well as IL-3-induced proliferation of BaF3/Mpl and BaF3 cells. Cells co-expressing Prv-1 and an Mpl receptor containing a Box 1 motif mutation, which fails to activate Jak2, was completely deficient in Tpo-dependent proliferation. In addition, BaF3 and BaF3/Prv-1 cells stimulated with IL-3 in the presence of the Jak2 inhibitor, AG490, abrogated the proliferative response, indicating that Prv-1 requires a functional Jak2 for its signaling activities. Western blot analysis showed an increase in Tpo and IL-3-induced Stat3 and Stat5 tyrosine phosphorylation in BaF3/Mpl and BaF3 cells expressing Prv-1. These results indicate a novel function for Prv-1 as a signaling molecule in cytokine signaling cascades and may lead to a greater understanding of the mechanism of overexpression of Prv-1 in myeloproliferative disorders.
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Affiliation(s)
- Megan Dillon
- Puget Sound Blood Center, Seattle, WA 98104, United States
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36
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Baker JE, Su J, Hsu A, Shi Y, Zhao M, Strande JL, Fu X, Xu H, Eis A, Komorowski R, Jensen ES, Tweddell JS, Rafiee P, Gross GJ. Human thrombopoietin reduces myocardial infarct size, apoptosis, and stunning following ischaemia/reperfusion in rats. Cardiovasc Res 2007; 77:44-53. [PMID: 18006466 DOI: 10.1093/cvr/cvm026] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
AIMS Thrombopoietin (Tpo) is known for its ability to stimulate platelet production. However, it is currently unknown whether Tpo plays a physiological function in the heart. METHODS AND RESULTS We assessed the potential protective role of Tpo in vitro and in vivo in two rat models of myocardial ischaemia/reperfusion. Tpo receptor (c-mpl) message was detected in the heart using RT-PCR, and the Tpo receptor protein was detected using western blotting and immunohistochemistry. Tpo treatment immediately before ischaemia reduced myocardial necrosis, apoptosis, and decline in ventricular function following ischaemia/reperfusion in the rat in a concentration- and dose-dependent manner with an optimal concentration of 1.0 ng/mL in vitro and an optimal dose of 0.05 microg/kg iv in vivo. Tpo also reduced infarct size when given after the onset of ischaemia or at reperfusion. Tpo activated JAK-2 (Janus kinase-2) and p44 MAPK (mitogen-activated protein kinase) during reperfusion but not prior to ischaemia. Inhibition of JAK-2 (AG-490), p42/44 MAPK (PD98059), mitochondrial K(ATP) channels (5-HD), and sarcolemmal K(ATP) channels (HMR 1098) abolished Tpo-induced resistance to injury from myocardial ischaemia/reperfusion. AG-490, PD98059, 5-HD, and HMR1098 alone had no effect on cardioprotection. Treatment with a single dose of Tpo (0.05 or 1.0 microg/kg iv) did not result in the elevation of platelet count or haematocrit over a 16-day period. CONCLUSION A single treatment of Tpo confers cardioprotection through JAK-2, p42/44 MAPK, and K(ATP) channels, suggesting a potential therapeutic role of Tpo in the treatment of injury resulting from myocardial ischaemia and reperfusion.
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Affiliation(s)
- John E Baker
- Division of Cardiothoracic Surgery, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
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Tong W, Ibarra YM, Lodish HF. Signals emanating from the membrane proximal region of the thrombopoietin receptor (mpl) support hematopoietic stem cell self-renewal. Exp Hematol 2007; 35:1447-55. [PMID: 17637498 PMCID: PMC2062518 DOI: 10.1016/j.exphem.2007.05.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Revised: 05/14/2007] [Accepted: 05/15/2007] [Indexed: 01/17/2023]
Abstract
OBJECTIVE Studies using thrombopoietin -/- (TPO(-/-)) or TPO receptor, mpl(-/-) mice have established a critical role for TPO/mpl signaling in hematopoietic stem cell (HSC) development. In this study, we further dissected mpl signaling in both megakaryopoiesis and HSC function, using mice bearing a truncated mpl receptor lacking the distal 60 amino acids (Delta60). This deletion removes three major signaling tyrosines on the mpl cytoplasmic domain, but retains the membrane proximal Box1 and Box2 domains required for JAK2 activation. MATERIALS AND METHODS Competitive bone marrow transplantations (BMT) and serial BMTs were performed to study HSC function. Western blot analysis was used to study TPO-stimulated signaling pathways. BM cell cultures in the presence of TPO were used to study megakaryocyte development. RESULTS In agreement with prior findings, we show that Delta60 BM cells cultured in TPO generated normal numbers of megakaryocytes, but with greatly reduced ploidy. As expected from the deletion of three signaling tyrosine residues, freshly isolated Delta60 megakaryocytes showed marked reduction in all known TPO-stimulated signaling pathways tested, including signal transducers and activators of transcription (Stat) 5, Stat3, Akt, and p42/44 mitogen-activated kinase. We found that Delta60 mice displayed normal short-term (ST-HSC) activities and marginally compromised long-term (LT-HSC) stem cell activities in primary transplantation. In addition, Delta60 mice supported HSC self-renewal for at least two serial BMTs. CONCLUSION Our data reveal a pivotal role for an unknown signal emanating from the membrane proximal region of the mpl receptor or from JAK2 itself in maintaining stem cell activity and self-renewal, in addition to its role in megakaryocytopoiesis and thrombopoiesis.
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Affiliation(s)
- Wei Tong
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts, USA.
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Abstract
Although development of first-generation thrombopoietic growth factors (recombinant human thrombopoietin [TPO] and pegylated recombinant human megakaryocyte growth and development factor [PEG-rHuMGDF]) was stopped due to development of antibodies to PEG-rHuMGDF, nonimmunogenic second-generation thrombopoietic growth factors with unique pharmacologic properties have been developed. TPO peptide mimetics contain TPO receptor-activating peptides inserted into complementarity-determining regions of Fab (Fab 59), attached to the IgG Fc region (AMG 531), or pegylated (Peg-TPOmp). Orally available, TPO nonpeptide mimetics (eltrombopag, AKR-501) bind and activate the TPO receptor by a mechanism different from TPO and may have an additive effect to TPO. TPO agonist antibodies are monoclonal antibodies activating the TPO receptor but modified in size [TPO minibodies; ie, VB22B sc(Fv)(2)] or immunoglobuln type (domain subclass-converted TPO agonist antibodies; ie, MA01G4G344). All second-generation thrombopoietic growth factors stimulate growth of TPO-dependent cell lines via JAK2/STAT signaling pathways and increase platelet counts in animals. When tested in healthy humans, TPO peptide and nonpeptide mimetics produced a dose-dependent rise in platelet count. AMG 531 and eltrombopag markedly increase platelet counts in patients with immune thrombocytopenic purpura, without significant adverse effects. One or more second-generation thrombopoietic growth factors should soon be clinically available for treating thrombocytopenic disorders.
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Affiliation(s)
- David J Kuter
- Hematology Division, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA.
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Aggarwal BB, Sethi G, Ahn KS, Sandur SK, Pandey MK, Kunnumakkara AB, Sung B, Ichikawa H. Targeting signal-transducer-and-activator-of-transcription-3 for prevention and therapy of cancer: modern target but ancient solution. Ann N Y Acad Sci 2007; 1091:151-69. [PMID: 17341611 DOI: 10.1196/annals.1378.063] [Citation(s) in RCA: 331] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent evidence indicates a convergence of molecular targets for both prevention and therapy of cancer. Signal-transducer-and-activator-of-transcription-3 (STAT3), a member of a family of six different transcription factors, is closely linked with tumorigenesis. Its role in cancer is indicated by numerous avenues of evidence, including the following: STAT3 is constitutively active in tumor cells; STAT3 is activated by growth factors (e.g., EGF, TGF-alpha, IL-6, hepatocyte growth factor) and oncogenic kinases (e.g., Src); STAT3 regulates the expression of genes that mediate proliferation (e.g., c-myc and cyclin D1), suppress apoptosis (e.g., Bcl-x(L) and survivin), or promote angiogenesis (e.g, VEGF); STAT3 activation has been linked with chemoresistance and radioresistance; and chemopreventive agents have been shown to suppress STAT3 activation. Thus inhibitors of STAT3 activation have potential for both prevention and therapy of cancer. Besides small peptides and oligonucleotides, numerous small molecules have been identified as blockers of STAT3 activation, including synthetic molecules (e.g., AG 490, decoy peptides, and oligonucleotides) and plant polyphenols (e.g., curcumin, resveratrol, flavopiridol, indirubin, magnolol, piceatannol, parthenolide, EGCG, and cucurbitacin). This article discusses these aspects of STAT3 in more detail.
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Affiliation(s)
- Bharat B Aggarwal
- Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
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Tong W, Sulahian R, Gross AW, Hendon N, Lodish HF, Huang LJS. The Membrane-proximal Region of the Thrombopoietin Receptor Confers Its High Surface Expression by JAK2-dependent and -independent Mechanisms. J Biol Chem 2006; 281:38930-40. [PMID: 17052978 DOI: 10.1074/jbc.m607524200] [Citation(s) in RCA: 31] [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
Janus tyrosine kinase 2 (JAK2) is essential for signaling by the thrombopoietin (TpoR) and erythropoietin (EpoR) receptors. In the absence of JAK2 most EpoR molecules are retained in the endoplasmic reticulum in an Endo H-sensitive form. In contrast, we show that in the absence of JAK2 a large fraction of the TpoR is processed to the mature Endo H-resistant form and reaches the cell surface. By studying chimeras of the TpoR and EpoR we show that high surface expression of the TpoR is entirely conferred by the membrane-proximal region of the intracellular domain that includes the juxtamembrane, Box 1, and Box 2 regions. The TpoR intracellular domain shows similar effects on receptor endocytosis rate as that of the EpoR, but does stabilize the mature receptor isoform from degradation. Co-expression of JAK2 further stabilizes mature TpoR and thus further increases its surface expression. This JAK2 effect depends on the Box 1 region, the only JAK2 interacting site in the TpoR. By contrast, EpoR requires Box 1 as well as the flanking 20 residues on the C-terminal side for JAK2 interaction and JAK2-dependent surface expression. Our study suggests that whereas cell surface expression of type I cytokine receptors requires their cognate JAKs, the mechanisms governing receptor-JAK interactions differ among receptors interacting with the same JAK protein.
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Affiliation(s)
- Wei Tong
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
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41
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Chanprasert S, Geddis AE, Barroga C, Fox NE, Kaushansky K. Thrombopoietin (TPO) induces c-myc expression through a PI3K- and MAPK-dependent pathway that is not mediated by Akt, PKCzeta or mTOR in TPO-dependent cell lines and primary megakaryocytes. Cell Signal 2005; 18:1212-8. [PMID: 16380230 DOI: 10.1016/j.cellsig.2005.09.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Accepted: 09/28/2005] [Indexed: 01/30/2023]
Abstract
Thrombopoietin (TPO) and its receptor (c-Mpl) are the major regulators of megakaryocyte and platelet production and serve a critical and non-redundant role in hematopoietic stem cell (HSC) biology. TPO signals through the Jak-STAT, Ras-Raf-MAPK, and PI3K pathways, and promotes survival, proliferation, and polyploidization in megakaryocytes. The proto-oncogene c-myc also plays an important role in many of these same processes. In this work we studied the regulated expression of c-myc in megakaryocytic cell lines and primary cells by quantitative real-time RT-PCR. We found that TPO induced expression of c-myc in 1 h in both hematopoietic cell lines (UT-7 and BaF3/Mpl) and mature murine megakaryocytes. The TPO-induced expression of c-myc was blocked by a phosphatidylinositol 3-kinase (PI3K) inhibitor, suggesting that TPO stimulated c-myc expression through a PI3K-dependent pathway. Of interest, our study showed that overexpression of active Akt did not rescue the effect of PI3K blockade on c-myc expression, rather, enhanced it. In addition, inhibitors of protein kinase C (PKC)zeta and the target of rapamycin (mTOR) also failed to affect c-myc mRNA expression, while c-myc mRNA expression was reduced by inhibition of the mitogen activated protein kinase (MAPK) pathway. Therefore, we conclude that TPO stimulates c-myc expression in primary megakaryocytes through a PI3K- and MAPK-dependent pathway that is not mediated by Akt, PKCzeta or mTOR.
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Affiliation(s)
- Supantitra Chanprasert
- Department of Clinical Microscopy, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand
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Zheng H, Hu P, Quinn DF, Wang YK. Phosphotyrosine Proteomic Study of Interferon α Signaling Pathway Using a Combination of Immunoprecipitation and Immobilized Metal Affinity Chromatography. Mol Cell Proteomics 2005; 4:721-30. [PMID: 15659558 DOI: 10.1074/mcp.m400077-mcp200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyrosine phosphorylation is a type of post-translational modification that plays a crucial role in signal transduction. Thus, the study of this modification at the proteomic level has great biological significance. However, because of the low abundance of tyrosine-phosphorylated proteins in total cell lysate, it is difficult to evaluate the dynamics of tyrosine phosphorylation at a global level. In this work, proteins carrying phosphotyrosine (pTyr) were first purified from whole cell lysate by immunoprecipitation using anti-pTyr monoclonal antibodies. After tryptic digestion, phosphopeptides were further enriched by IMAC and analyzed by LC-MS. Quantitative changes of tyrosine phosphorylation at the global level were evaluated using isotopic labeling (introduced at the methyl esterification step prior to IMAC). Using this double enrichment approach, we characterized interferon alpha (IFNalpha)-induced pTyr proteomic changes in Jurkat cells. We observed induced phosphorylation on several well documented as well as novel tyrosine phosphorylation sites on proteins involved in IFNalpha signal transduction, such as Tyk2, JAK1, and IFNAR subunits. A specific site on alpha-tubulin (Tyr-271) was observed to be phosphorylated upon treatment as well. Furthermore, our results suggest that LOC257106, a CDC42 GAP-like protein, is potentially involved in this pathway.
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Affiliation(s)
- Haiyan Zheng
- Discovery Technologies, Novartis Institute for Biomedical Research, Inc., Cambridge, MA 02139, USA
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Ahr B, Denizot M, Robert-Hebmann V, Brelot A, Biard-Piechaczyk M. Identification of the cytoplasmic domains of CXCR4 involved in Jak2 and STAT3 phosphorylation. J Biol Chem 2004; 280:6692-700. [PMID: 15615703 DOI: 10.1074/jbc.m408481200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The chemokine SDF-1alpha transduces G(i)-dependent and -independent signals through CXCR4. Activation of Jak2/STAT3, a G(i)-independent signaling pathway, which plays a major role in survival signals, is known to be activated after SDF-1alpha binding to CXCR4 but the domains of CXCR4 involved in this signaling remain unexplored. Using human embryonic kidney HEK-293 cells stably expressing wild-type or mutated forms of CXCR4, we demonstrated that STAT3 phosphorylation requires the N-terminal part of the third intracellular loop (ICL3) and the tyrosine 157 present at the end of the second intracellular loop (ICL2) of CXCR4. In contrast, neither the conserved Tyr(135) in the DRY motif at the N terminus of ICL2 nor the Tyr(65) and Tyr(76) in the first intracellular loop (ICL1) are involved in this activation. ICL3, which does not contain any tyrosine residues, is needed to activate Jak2. These results demonstrate that two separate domains of CXCR4 are involved in Jak2/STAT3 signaling. The N-terminal part of ICL3 is needed to activate Jak2 after SDF-1alpha binding to CXCR4, leading to phosphorylation of only one cytoplasmic Tyr, present at the C terminus of ICL2, which triggers STAT3 activation. This work has profound implications for the understanding of CXCR4-transduced signaling.
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Affiliation(s)
- Barbara Ahr
- Laboratoire Infections Rétrovirales et Signalisation Cellulaire, CNRS UMR 5121, Institut de Biologie, 4, Bd Henri IV, CS 89508, 34960 Montpellier Cedex 2, France
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Sivakumar PV, Foster DC, Clegg CH. Interleukin-21 is a T-helper cytokine that regulates humoral immunity and cell-mediated anti-tumour responses. Immunology 2004; 112:177-82. [PMID: 15147560 PMCID: PMC1782493 DOI: 10.1111/j.1365-2567.2004.01886.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Cytokines and their receptors represent key targets for therapeutic intervention. Ligands are being used to supplement cell numbers that become depleted as a result of disease (organ failure, infection) or subsequent disease treatments (i.e. chemotherapy). Conversely, the inhibition of target cell binding by cytokines is an established strategy for abrogating pathologic cellular activities common to many immunological diseases. Considerable effort in biomedical research is being focused on the cytokine families that play a dominant role in regulating immunity and then prioritizing each member for its therapeutic potential. Currently, the interleukin-2 (IL-2) family of cytokines is widely recognized for its central involvement in controlling lymphocyte function and is the most explored for medical utility. Collectively, these proteins (or their antagonists) are either marketed drugs or have received advanced testing for an impressive array of indications including cancer, infectious disease, transplantation, inflammation and allergic asthma. Here we review the current understanding of IL-21, the most recent member of this cytokine family to be discovered. As will be discussed, IL-21 shares many of the same attributes as its relatives in that it has broad immunoregulatory activity and can modulate both humoral and cell-mediated responses. Its ability to stimulate durable anti-tumour responses in mice defines one therapeutic indication that merits clinical development.
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Affiliation(s)
- Pallavur V Sivakumar
- Department of Immunology and the Program of Cytokine Biology, ZymoGenetics Inc., Seattle, WA 98102, USA
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Lannutti BJ, Shim MH, Blake N, Reems JA, Drachman JG. Identification and activation of Src family kinases in primary megakaryocytes. Exp Hematol 2004; 31:1268-74. [PMID: 14662334 DOI: 10.1016/j.exphem.2003.09.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
OBJECTIVES We have recently shown that the Src family of tyrosine kinases (SFKs) are activated by TPO stimulation in both primary megakaryocytic progenitors and a hematopoietic cells line (BaF3) expressing the TPO receptor (Mpl). In this study, we examine which of the eight Src family members are expressed in primary megakaryocytes (MKs) and determine which of these become activated in response to TPO. MATERIALS AND METHODS High-density oligonucleotide microarrays were used to compare the gene expression profiles of Src kinases from undifferentiated hematopoietic progenitors (CD34+/CD38(lo)) and after in vitro megakaryocytic differentiation. Western blot analysis of lysates from purified, mature murine MKs identified which of SFKs are present. Finally, in vitro kinase assays determined which of the SFKs in primary MKs are activated by TPO stimulation. RESULTS Array profiles demonstrate that Fyn, Lyn, Fgr, Hck, Src, and Yes are all expressed in cultured human MKs (Fyn, Lyn>Src, Yes, Fgr, Hck). Similarly, Western blots of murine MKs identified the same six SFKs (Fyn, Fgr, Hck, Lyn, Src, and Yes). Of these, only Fyn and Lyn demonstrate increased kinase activity after TPO stimulation. Interestingly, gene expression analysis indicates that, among the SFKs, Fyn expression is uniquely upregulated during MK development. CONCLUSION These results provide the first direct evidence that two Src kinases are activated in primary MKs, Fyn and Lyn. The fact that only Fyn expression is significantly upregulated during MK differentiation suggests variable gene regulation. Specificity of the TPO signaling cascade is demonstrated by the selective activation of Fyn and Lyn.
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Affiliation(s)
- Brian J Lannutti
- Puget Sound Blood Center, 921 Terry Avenue, Seattle, WA 98104-1256, USA.
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Feese MD, Tamada T, Kato Y, Maeda Y, Hirose M, Matsukura Y, Shigematsu H, Muto T, Matsumoto A, Watarai H, Ogami K, Tahara T, Kato T, Miyazaki H, Kuroki R. Structure of the receptor-binding domain of human thrombopoietin determined by complexation with a neutralizing antibody fragment. Proc Natl Acad Sci U S A 2004; 101:1816-21. [PMID: 14769915 PMCID: PMC357010 DOI: 10.1073/pnas.0308530100] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cytokine thrombopoietin (TPO), the ligand for the hematopoietic receptor c-Mpl, acts as a primary regulator of megakaryocytopoiesis and platelet production. We have determined the crystal structure of the receptor-binding domain of human TPO (hTPO(163)) to a 2.5-A resolution by complexation with a neutralizing Fab fragment. The backbone structure of hTPO(163) has an antiparallel four-helix bundle fold. The neutralizing Fab mainly recognizes the C-D crossover loop containing the species invariant residue Q111. Titration calorimetric experiments show that hTPO(163) interacts with soluble c-Mpl containing the extracellular cytokine receptor homology domains with 1:2 stoichiometry with the binding constants of 3.3 x 10(9) M(-1) and 1.1 x 10(6) M(-1). The presence of the neutralizing Fab did not inhibit binding of hTPO(163) to soluble c-Mpl fragments, but the lower-affinity binding disappeared. Together with prior genetic data, these define the structure-function relationships in TPO and the activation scheme of c-Mpl.
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Affiliation(s)
- Michael D Feese
- Central Laboratories for Key Technology, Kirin Brewery Co. Ltd., 1-13-5 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan
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Lannutti BJ, Drachman JG. Lyn tyrosine kinase regulates thrombopoietin-induced proliferation of hematopoietic cell lines and primary megakaryocytic progenitors. Blood 2004; 103:3736-43. [PMID: 14726379 DOI: 10.1182/blood-2003-10-3566] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this study we demonstrate that thrombopoietin (TPO)-stimulated Src family kinases (SFKs) inhibit cellular proliferation and megakaryocyte differentiation. Using the Src kinase inhibitors pyrolopyrimidine 1 and 2 (PP1, PP2), we show that TPO-dependent proliferation of BaF3/Mpl cells was enhanced at concentrations that are specific for SFKs. Similarly, proliferation is increased after introducing a dominant-negative form of Lyn into BaF3/Mpl cells. Murine marrow cells from Lyn-deficient mice or wild-type mice cultured in the presence of the Src inhibitor, PP1, yielded a greater number of mature megakaryocytes and increased nuclear ploidy. Truncation and targeted mutation of the Mpl cytoplasmic domain indicate that Y112 is critical for Lyn activation. Examining the molecular mechanism for this antiproliferative effect, we determined that SFK inhibitors did not affect tyrosine phosphorylation of Janus kinase 2 (JAK2), Shc, signal transducer and activator of transcription (STAT)5, or STAT3. In contrast, pretreatment of cells with PP2 increased Erk1/2 (mitogen-activated protein kinase [MAPK]) phosphorylation and in vitro kinase activity, particularly after prolonged TPO stimulation. Taken together, our results show that Mpl stimulation results in the activation of Lyn kinase, which appears to limit the proliferative response through a signaling cascade that regulates MAPK activity. These data suggest that SFKs modify the rate of TPO-induced proliferation and are likely to affect cell cycle regulation during megakaryocytopoiesis.
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Dahlen DD, Broudy VC, Drachman JG. Internalization of the thrombopoietin receptor is regulated by 2 cytoplasmic motifs. Blood 2003; 102:102-8. [PMID: 12623841 DOI: 10.1182/blood-2002-11-3468] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Receptor-mediated internalization appears to be the primary mean of regulating the plasma level of thrombopoietin (TPO). However, the processes that regulate Mpl internalization have not previously been described. Using the cytokine-dependent cell line BaF3, we have identified 2 distinct motifs within the cytoplasmic domain of Mpl that underlie ligand-dependent internalization. Removal of the fourth cytoplasmic tyrosine residue by deletion or truncation results in a significant decrease in maximal internalization. The remaining receptor internalization is abrogated by deletion of cytoplasmic residues 54-69, which include the core box2 region (L54L55E56I57L58) and the only dileucine motifs (L54L55 and I57L58) within the cytoplasmic domain of Mpl. Receptor internalization mediated by this latter subdomain does not require Jak2 activation. Furthermore, TPO-stimulated cellular proliferation appears to be directly correlated with receptor internalization, indicating that internalization of the TPO/Mpl complex may be essential for normal signal transduction. Finally, we have demonstrated that upon removal of TPO from the supernatant, Mpl promptly reappears on the cell surface, suggesting that a pool of intracellular Mpl can be rapidly recycled to the cell surface. These data help identify the receptor motifs involved in TPO-induced internalization of Mpl and suggest that Mpl translocation may be necessary for normal cellular proliferation.
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Affiliation(s)
- Debra D Dahlen
- Division of Hematology, University of Washington, Seattle, WA 98104, USA.
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Abstract
Although first proposed to be the primary regulator of platelet production 45 years ago, the gene for thrombopoietin was cloned only within the last decade. Since then, our understanding of megakaryocyte and platelet production has increased substantially, and it is now appreciated that in addition to its critical role in regulating thrombopoiesis, the hormone affects multiple aspects of hematopoiesis, including playing a non-redundant role in stem cell survival, self-renewal and expansion. In addition to this greater physiological understanding of thrombopoietin biology, the molecular mechanisms by which the hormone affects cell survival and proliferation are coming under increased scrutiny. At least four signaling pathways have been identified that play important and non-overlapping roles in stem cell and megakaryocyte growth and development, potentially providing new strategies to therapeutically intervene in hematopoiesis. This review will focus on our current understanding of these processes.
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Affiliation(s)
- K Kaushansky
- Department of Medicine, University of California San Diego, San Diego, CA, USA.
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Tefferi A. Thrombopoietin expression and plasma concentrations in chronic myeloproliferative disorders. Leuk Res 2003; 27:121-3. [PMID: 12526917 DOI: 10.1016/s0145-2126(02)00088-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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