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Abraham BG, Haikarainen T, Vuorio J, Girych M, Virtanen AT, Kurttila A, Karathanasis C, Heilemann M, Sharma V, Vattulainen I, Silvennoinen O. Molecular basis of JAK2 activation in erythropoietin receptor and pathogenic JAK2 signaling. SCIENCE ADVANCES 2024; 10:eadl2097. [PMID: 38457493 PMCID: PMC10923518 DOI: 10.1126/sciadv.adl2097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 02/06/2024] [Indexed: 03/10/2024]
Abstract
Janus kinase 2 (JAK2) mediates type I/II cytokine receptor signaling, but JAK2 is also activated by somatic mutations that cause hematological malignancies by mechanisms that are still incompletely understood. Quantitative superresolution microscopy (qSMLM) showed that erythropoietin receptor (EpoR) exists as monomers and dimerizes upon Epo stimulation or through the predominant JAK2 pseudokinase domain mutations (V617F, K539L, and R683S). Crystallographic analysis complemented by kinase activity analysis and atomic-level simulations revealed distinct pseudokinase dimer interfaces and activation mechanisms for the mutants: JAK V617F activity is driven by dimerization, K539L involves both increased receptor dimerization and kinase activity, and R683S prevents autoinhibition and increases catalytic activity and drives JAK2 equilibrium toward activation state through a wild-type dimer interface. Artificial intelligence-guided modeling and simulations revealed that the pseudokinase mutations cause differences in the pathogenic full-length JAK2 dimers, particularly in the FERM-SH2 domains. A detailed molecular understanding of mutation-driven JAK2 hyperactivation may enable novel therapeutic approaches to selectively target pathogenic JAK2 signaling.
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Affiliation(s)
| | - Teemu Haikarainen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
- Fimlab Laboratories, Tampere, Finland
| | - Joni Vuorio
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Mykhailo Girych
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Anniina T. Virtanen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Antti Kurttila
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Christos Karathanasis
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Frankfurt, Germany
| | - Mike Heilemann
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Frankfurt, Germany
| | - Vivek Sharma
- Department of Physics, University of Helsinki, Helsinki, Finland
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Olli Silvennoinen
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
- Fimlab Laboratories, Tampere, Finland
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
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2
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Havelange V, Constantinescu SN. Molecular pathogenesis of myeloproliferative neoplasms: Where do we stand in 2023? Am J Hematol 2023; 98:1512-1516. [PMID: 37635451 DOI: 10.1002/ajh.27062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 08/02/2023] [Indexed: 08/29/2023]
Affiliation(s)
- Violaine Havelange
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
- Department of Hematology, Cliniques universitaires Saint-Luc, Brussels, Belgium
| | - Stefan N Constantinescu
- Université catholique de Louvain and de Duve Institute, Brussels, Belgium
- Department of Hematology, Cliniques universitaires Saint-Luc, Brussels, Belgium
- Ludwig Institute for Cancer Research Brussels, Brussels, Belgium
- WelBio Department, Wel Research Institute, Wavre, Belgium
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, Oxford University, Oxford, UK
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3
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Levy G, Mambet C, Pecquet C, Bailly S, Havelange V, Diaconu CC, Constantinescu SN. Targets in MPNs and potential therapeutics. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 366:41-81. [PMID: 35153006 DOI: 10.1016/bs.ircmb.2021.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Philadelphia-negative classical Myeloproliferative Neoplasms (MPNs), including Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF), are clonal hemopathies that emerge in the hematopoietic stem cell (HSC) compartment. MPN driver mutations are restricted to specific exons (14 and 12) of Janus kinase 2 (JAK2), thrombopoietin receptor (MPL/TPOR) and calreticulin (CALR) genes, are involved directly in clonal myeloproliferation and generate the MPN phenotype. As a result, an increased number of fully functional erythrocytes, platelets and leukocytes is observed in the peripheral blood. Nevertheless, the complexity and heterogeneity of MPN clinical phenotypes cannot be solely explained by the type of driver mutation. Other factors, such as additional somatic mutations affecting epigenetic regulators or spliceosomes components, mutant allele burdens and modifiers of signaling by driver mutants, clonal architecture and the order of mutation acquisition, signaling events that occur downstream of a driver mutation, the presence of specific germ-line variants, the interaction of the neoplastic clone with bone marrow microenvironment and chronic inflammation, all can modulate the disease phenotype, influence the MPN clinical course and therefore, might be useful therapeutic targets.
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Affiliation(s)
- Gabriel Levy
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; Department of Pediatric Hematology and Oncology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Cristina Mambet
- Department of Cellular and Molecular Pathology, Stefan S. Nicolau Institute of Virology, Bucharest, Romania; Department of Hematology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
| | - Christian Pecquet
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; WELBIO (Walloon Excellence in Life Sciences and Biotechnology), Brussels, Belgium
| | - Sarah Bailly
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; Department of Hematology, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Violaine Havelange
- SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; Department of Hematology, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Carmen C Diaconu
- Department of Cellular and Molecular Pathology, Stefan S. Nicolau Institute of Virology, Bucharest, Romania
| | - Stefan N Constantinescu
- Ludwig Institute for Cancer Research, Brussels, Belgium; SIGN Unit, de Duve Institute, Université Catholique de Louvain, Brussels, Belgium; WELBIO (Walloon Excellence in Life Sciences and Biotechnology), Brussels, Belgium; Ludwig Institute for Cancer Research, Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom.
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4
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EndoBind detects endogenous protein-protein interactions in real time. Commun Biol 2021; 4:1085. [PMID: 34526658 PMCID: PMC8443649 DOI: 10.1038/s42003-021-02600-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 08/24/2021] [Indexed: 11/13/2022] Open
Abstract
We present two high-throughput compatible methods to detect the interaction of ectopically expressed (RT-Bind) or endogenously tagged (EndoBind) proteins of interest. Both approaches provide temporal evaluation of dimer formation over an extended duration. Using examples of the Nrf2-KEAP1 and the CRAF-KRAS-G12V interaction, we demonstrate that our method allows for the detection of signal for more than 2 days after substrate addition, allowing for continuous monitoring of endogenous protein-protein interactions in real time. Bill et al describe two high-throughput methods to detect protein-protein interactions in cells in real-time using the split-NanoLuciferase-complementation system. They demonstrate the methods can detect exogenously (RT-bind) or endogenously (EndoBind) expressed proteins, respectively.
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5
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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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6
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Hitchcock IS, Hafer M, Sangkhae V, Tucker JA. The thrombopoietin receptor: revisiting the master regulator of platelet production. Platelets 2021; 32:770-778. [PMID: 34097561 PMCID: PMC8292222 DOI: 10.1080/09537104.2021.1925102] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 04/27/2021] [Accepted: 04/28/2021] [Indexed: 12/25/2022]
Abstract
Thrombopoietin (TPO) and its receptor, MPL, are the primary regulators of platelet production and critical for hematopoietic stem cell (HSC) maintenance. Since TPO was first cloned in 1994, the physiological and pathological roles of TPO and MPL have been well characterized, culminating in the first MPL agonists being approved for the treatment of chronic immune thrombocytopenia in 2008. Dysregulation of the TPO-MPL signaling axis contributes to the pathogenesis of hematological disorders: decreased expression or function results in severe thrombocytopenia progressing to bone marrow failure, while hyperactivation of MPL signaling, either by mutations in the receptor or associated Janus kinase 2 (JAK2), results in pathological myeloproliferation. Despite its importance, it was only recently that the long-running debate over the mechanism by which TPO binding activates MPL has been resolved. This review will cover key aspects of TPO and MPL structure and function and their importance in receptor activation, discuss how these are altered in hematological disorders and consider how a greater understanding could lead to the development of better-targeted and more efficacious therapies.
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Affiliation(s)
- Ian S. Hitchcock
- York Biomedical Research Institute, Department of Biology, University of York, York, UK
| | - Maximillian Hafer
- Department of Biology and Center of Cellular Nanoanalytics, University of Osnabrück, Osnabrück, Germany
| | - Veena Sangkhae
- Center for Iron Disorders, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Julie A. Tucker
- York Biomedical Research Institute, Department of Biology, University of York, York, UK
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7
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Newton AS, Liosi ME, Henry SP, Deiana L, Faver JC, Krimmer SG, Puleo DE, Schlessinger J, Jorgensen WL. Indoloxytriazines as binding molecules for the JAK2 JH2 pseudokinase domain and its V617F variant. Tetrahedron Lett 2021; 77. [PMID: 34393283 DOI: 10.1016/j.tetlet.2021.153248] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Small molecules that selectively bind to the pseudokinase JH2 domain over the JH1 kinase domain of JAK2 kinase are sought. Virtual screening led to the purchase of 17 compounds among which 9 were found to bind to V617F JAK2 JH2 with affinities of 40 - 300 μM in a fluorogenic assay. Ten analogues were then purchased yielding 9 additional active compounds. Aminoanilinyltriazine 22 was particularly notable as it shows no detectable binding to JAK2 JH1, and it has a 65-μM dissociation constant K d with V617F JAK2 JH2. A crystal structure for 22 in complex with wild-type JAK2 JH2 was obtained to elucidate the binding mode. Additional de novo design led to the synthesis of 19 analogues of 22 with the most potent being 33n with K d values of 2-3 μM for WT and V617F JAK2 JH2, and with 16-fold selectivity relative to binding with WT JAK2 JH1.
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Affiliation(s)
- Ana S Newton
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107
| | - Maria-Elena Liosi
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107
| | - Sean P Henry
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107
| | - Luca Deiana
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107
| | - John C Faver
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107
| | - Stefan G Krimmer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107.,Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520-8066
| | - David E Puleo
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520-8066
| | - Joseph Schlessinger
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520-8066
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8
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Functional Consequences of Mutations in Myeloproliferative Neoplasms. Hemasphere 2021; 5:e578. [PMID: 34095761 PMCID: PMC8171364 DOI: 10.1097/hs9.0000000000000578] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 04/13/2021] [Indexed: 01/14/2023] Open
Abstract
Driver mutations occur in Janus kinase 2 (JAK2), thrombopoietin receptor (MPL), and calreticulin (CALR) in BCR-ABL1 negative myeloproliferative neoplasms (MPNs). From mutations leading to one amino acid substitution in JAK2 or MPL, to frameshift mutations in CALR resulting in a protein with a different C-terminus, all the mutated proteins lead to pathologic and persistent JAK2-STAT5 activation. The most prevalent mutation, JAK2 V617F, is associated with the 3 entities polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), while CALR and MPL mutations are associated only with ET and MF. Triple negative ET and MF patients may harbor noncanonical mutations in JAK2 or MPL. One major fundamental question is whether the conformations of JAK2 V617F, MPL W515K/L/A, or CALR mutants differ from those of their wild type counterparts so that a specific treatment could target the clone carrying the mutated driver and spare physiological hematopoiesis. Of great interest, a set of epigenetic mutations can co-exist with the phenotypic driver mutations in 35%–40% of MPNs. These epigenetic mutations, such as TET2, EZH2, ASXL1, or DNMT3A mutations, promote clonal hematopoiesis and increased fitness of aged hematopoietic stem cells in both clonal hematopoiesis of indeterminate potential (CHIP) and MPNs. Importantly, the main MPN driver mutation JAK2 V617F is also associated with CHIP. Accumulation of several epigenetic and splicing mutations favors progression of MPNs to secondary acute myeloid leukemia. Another major fundamental question is how epigenetic rewiring due to these mutations interacts with persistent JAK2-STAT5 signaling. Answers to these questions are required for better therapeutic interventions aimed at preventing progression of ET and PV to MF, and transformation of these MPNs in secondary acute myeloid leukemia.
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9
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Carreño-Tarragona G, Varghese LN, Sebastián E, Gálvez E, Marín-Sánchez A, López-Muñoz N, Nam-Cha S, Martínez-López J, Constantinescu SN, Sevilla J, Ayala R. A typical acute lymphoblastic leukemia JAK2 variant, R683G, causes an aggressive form of familial thrombocytosis when germline. Leukemia 2021; 35:3295-3298. [PMID: 33846542 DOI: 10.1038/s41375-021-01239-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 03/02/2021] [Accepted: 03/22/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Gonzalo Carreño-Tarragona
- Haematology and Haemotherapy Department, Hospital Universitario 12 de Octubre, I+12, CNIO, Complutense University, CIBERONC, Madrid, Spain
| | - Leila N Varghese
- Université Catholique de Louvain and de Duve Institute, Brussels, Belgium.,Ludwig Institute for Cancer Research, Brussels, Belgium.,WELBIO (Walloon Excellence in Life Sciences and Biotechnology), Brussels, Belgium
| | - Elena Sebastián
- Hematology and Hemotherapy Department, Hospital Infantil Universitario Niño Jesús, Fundación para la investigación Biomédica HIUNJ, CIBERER, Madrid, Spain
| | - Eva Gálvez
- Hematology and Hemotherapy Department, Hospital Infantil Universitario Niño Jesús, Fundación para la investigación Biomédica HIUNJ, CIBERER, Madrid, Spain
| | - Alberto Marín-Sánchez
- Haematology and Haemotherapy Department, Complejo Hospitalario Universitario de Albacete, Albacete, Spain
| | - Nieves López-Muñoz
- Haematology and Haemotherapy Department, Hospital Universitario 12 de Octubre, I+12, CNIO, Complutense University, CIBERONC, Madrid, Spain
| | - Syonghyun Nam-Cha
- Pathology Department, Complejo Hospitalario Universitario de Albacete, Albacete, Spain
| | - Joaquín Martínez-López
- Haematology and Haemotherapy Department, Hospital Universitario 12 de Octubre, I+12, CNIO, Complutense University, CIBERONC, Madrid, Spain
| | - Stefan N Constantinescu
- Université Catholique de Louvain and de Duve Institute, Brussels, Belgium. .,Ludwig Institute for Cancer Research, Brussels, Belgium. .,WELBIO (Walloon Excellence in Life Sciences and Biotechnology), Brussels, Belgium.
| | - Julián Sevilla
- Hematology and Hemotherapy Department, Hospital Infantil Universitario Niño Jesús, Fundación para la investigación Biomédica HIUNJ, CIBERER, Madrid, Spain
| | - Rosa Ayala
- Haematology and Haemotherapy Department, Hospital Universitario 12 de Octubre, I+12, CNIO, Complutense University, CIBERONC, Madrid, Spain.
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10
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Janus Kinases in Leukemia. Cancers (Basel) 2021; 13:cancers13040800. [PMID: 33672930 PMCID: PMC7918039 DOI: 10.3390/cancers13040800] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/05/2021] [Accepted: 02/09/2021] [Indexed: 01/12/2023] Open
Abstract
Janus kinases (JAKs) transduce signals from dozens of extracellular cytokines and function as critical regulators of cell growth, differentiation, gene expression, and immune responses. Deregulation of JAK/STAT signaling is a central component in several human diseases including various types of leukemia and other malignancies and autoimmune diseases. Different types of leukemia harbor genomic aberrations in all four JAKs (JAK1, JAK2, JAK3, and TYK2), most of which are activating somatic mutations and less frequently translocations resulting in constitutively active JAK fusion proteins. JAKs have become important therapeutic targets and currently, six JAK inhibitors have been approved by the FDA for the treatment of both autoimmune diseases and hematological malignancies. However, the efficacy of the current drugs is not optimal and the full potential of JAK modulators in leukemia is yet to be harnessed. This review discusses the deregulation of JAK-STAT signaling that underlie the pathogenesis of leukemia, i.e., mutations and other mechanisms causing hyperactive cytokine signaling, as well as JAK inhibitors used in clinic and under clinical development.
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11
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MPL mutations in essential thrombocythemia uncover a common path of activation with eltrombopag dependent on W491. Blood 2020; 135:948-953. [PMID: 31978223 DOI: 10.1182/blood.2019003240] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 01/10/2020] [Indexed: 12/26/2022] Open
Abstract
Mutations in the MPL gene encoding the human thrombopoietin receptor (TpoR) drive sporadic and familial essential thrombocythemias (ETs). We identified 2 ET patients harboring double mutations in cis in MPL, namely, L498W-H499C and H499Y-S505N. Using biochemical and signaling assays along with partial saturation mutagenesis, we showed that L498W is an activating mutation potentiated by H499C and that H499C and H499Y enhance the activity of the canonical S505N mutation. L498W and H499C can activate a truncated TpoR mutant, which lacks the extracellular domain, indicating these mutations act on the transmembrane (TM) cytosolic domain. Using a protein complementation assay, we showed that L498W and H499C strongly drive dimerization of TpoR. Activation by tryptophan substitution is exquisitely specific for position 498. Using structure-guided mutagenesis, we identified upstream amino acid W491 as a key residue required for activation by L498W or canonical activating mutations such as S505N and W515K, as well as by eltrombopag. Structural data point to a common dimerization and activation path for TpoR via its TM domain that is shared between the small-molecule agonist eltrombopag and canonical and novel activating TpoR mutations that all depend on W491, a potentially accessible extracellular residue that could become a target for therapeutic intervention.
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12
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Bose P, Verstovsek S. JAK Inhibition for the Treatment of Myelofibrosis: Limitations and Future Perspectives. Hemasphere 2020; 4:e424. [PMID: 32903304 PMCID: PMC7375176 DOI: 10.1097/hs9.0000000000000424] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 05/26/2020] [Indexed: 12/24/2022] Open
Abstract
The 2011 approval of ruxolitinib ushered in the Janus kinase (JAK) inhibitor era in the treatment of myelofibrosis (MF), and 2019 saw the US approval of fedratinib. The first therapeutic agents approved by regulatory authorities for MF, these drugs attenuate the overactive JAK-signal transducer and activator of transcription (STAT) signaling universally present in these patients, translating into major clinical benefits in terms of spleen shrinkage and symptom improvement. These, in turn, confer a survival advantage on patients with advanced disease, demonstrated in the case of ruxolitinib, for which long-term follow-up data are available. However, JAK inhibitors do not improve cytopenias in most patients, have relatively modest effects on bone marrow fibrosis and driver mutation allele burden, and clinical resistance eventually develops. Furthermore, they do not modify the risk of transformation to blast phase; indeed, their mechanism of action may be more anti-inflammatory than truly disease-modifying. This has spurred interest in rational combinations of JAK inhibitors with other agents that may improve cytopenias and drugs that could potentially modify the natural history of MF. Newer JAK inhibitors that are distinguished from ruxolitinib and fedratinib by their ability to improve anemia (eg, momelotinib) or safety and efficacy in severely thrombocytopenic patients (eg, pacritinib) are in phase 3 clinical trials. There is also interest in developing inhibitors that are highly selective for mutant JAK2, as well as "type II" JAK2 inhibitors. Overall, although current JAK inhibitors have limitations, they will likely continue to form the backbone of MF therapy for the foreseeable future.
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Affiliation(s)
- Prithviraj Bose
- Department of Leukemia, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Srdan Verstovsek
- Department of Leukemia, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
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13
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Raivola J, Haikarainen T, Silvennoinen O. Characterization of JAK1 Pseudokinase Domain in Cytokine Signaling. Cancers (Basel) 2019; 12:cancers12010078. [PMID: 31892268 PMCID: PMC7016850 DOI: 10.3390/cancers12010078] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 12/18/2019] [Accepted: 12/23/2019] [Indexed: 12/31/2022] Open
Abstract
The Janus kinase-signal transducer and activator of transcription protein (JAK-STAT) pathway mediates essential biological functions from immune responses to haematopoiesis. Deregulated JAK-STAT signaling causes myeloproliferative neoplasms, leukaemia, and lymphomas, as well as autoimmune diseases. Thereby JAKs have gained significant relevance as therapeutic targets. However, there is still a clinical need for better JAK inhibitors and novel strategies targeting regions outside the conserved kinase domain have gained interest. In-depth knowledge about the molecular details of JAK activation is required. For example, whether the function and regulation between receptors is conserved remains an open question. We used JAK-deficient cell-lines and structure-based mutagenesis to study the function of JAK1 and its pseudokinase domain (JH2) in cytokine signaling pathways that employ JAK1 with different JAK heterodimerization partner. In interleukin-2 (IL-2)-induced STAT5 activation JAK1 was dominant over JAK3 but in interferon-γ (IFNγ) and interferon-α (IFNα) signaling both JAK1 and heteromeric partner JAK2 or TYK2 were both indispensable for STAT1 activation. Moreover, IL-2 signaling was strictly dependent on both JAK1 JH1 and JH2 but in IFNγ signaling JAK1 JH2 rather than kinase activity was required for STAT1 activation. To investigate the regulatory function, we focused on two allosteric regions in JAK1 JH2, the ATP-binding pocket and the αC-helix. Mutating L633 at the αC reduced basal and cytokine induced activation of STAT in both JAK1 wild-type (WT) and constitutively activated mutant backgrounds. Moreover, biochemical characterization and comparison of JH2s let us depict differences in the JH2 ATP-binding and strengthen the hypothesis that de-stabilization of the domain disturbs the regulatory JH1-JH2 interaction. Collectively, our results bring mechanistic understanding about the function of JAK1 in different receptor complexes that likely have relevance for the design of specific JAK modulators.
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Affiliation(s)
- Juuli Raivola
- Faculty of Medicine and Life Sciences, Tampere University, 33014 Tampere, Finland; (J.R.); (T.H.)
| | - Teemu Haikarainen
- Faculty of Medicine and Life Sciences, Tampere University, 33014 Tampere, Finland; (J.R.); (T.H.)
| | - Olli Silvennoinen
- Faculty of Medicine and Life Sciences, Tampere University, 33014 Tampere, Finland; (J.R.); (T.H.)
- Institute of Biotechnology, Helsinki Institute of Life Science HiLIFE, University of Helsinki, 00014 Helsinki, Finland
- Fimlab Laboratories, Fimlab, 33520 Tampere, Finland
- Correspondence:
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14
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Vainchenker W, Plo I, Marty C, Varghese LN, Constantinescu SN. The role of the thrombopoietin receptor MPL in myeloproliferative neoplasms: recent findings and potential therapeutic applications. Expert Rev Hematol 2019; 12:437-448. [PMID: 31092065 DOI: 10.1080/17474086.2019.1617129] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Introduction: Classical Myeloproliferative Neoplasms (MPNs) include three disorders: Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF). MPNs are associated with constitutive activation of JAK2 leading to persistent cell signaling downstream of the dimeric myeloid cytokine receptors due to mutations in three genes encoding JAK2, calreticulin (CALR) and the thrombopoietin (TPO) receptor (MPL or TPOR). CALR and MPL mutants induce JAK2 activation that depends on MPL expression, thus explaining why they induce megakaryocyte pathologies including ET and PMF, but not PV. In contrast, JAK2 V617F drives all three diseases as it induces persistent signaling via EPOR, G-CSFR (CSF3R) and MPL. Areas Covered: Here, we review how different pathogenic mutations of MPL are translated into active receptors by inducing stable dimerization. We focus on the unique role of MPL on the hematopoietic stem cell (HSC), explaining why MPL is indispensable for the development of all MPNs. Last but not least, we describe how CALR mutants are pathogenic via binding and activation of MPL. Expert Opinion: Altogether, we believe that MPL is an important, but challenging, therapeutic target in MPNs that requires novel strategies to interrupt the specific conformational changes induced by each mutation or pathologic interaction without compromising the key functions of wild type MPL.
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Affiliation(s)
- William Vainchenker
- a UMR1170 , INSERM , Villejuif , France.,b Université Paris-Saclay , Villejuif , France
| | - Isabelle Plo
- a UMR1170 , INSERM , Villejuif , France.,b Université Paris-Saclay , Villejuif , France
| | - Caroline Marty
- a UMR1170 , INSERM , Villejuif , France.,b Université Paris-Saclay , Villejuif , France
| | - Leila N Varghese
- c Ludwig Institute for Cancer Research Brussels , Brussels , Belgium.,d de Duve Institute, Université catholique de Louvain , Brussels , Belgium
| | - Stefan N Constantinescu
- c Ludwig Institute for Cancer Research Brussels , Brussels , Belgium.,d de Duve Institute, Université catholique de Louvain , Brussels , Belgium.,e WELBIO (Walloon Excellence in Life Sciences and Biotechnology) , Brussels , Belgium
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