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Hu M, Yang T, Yang L, Niu L, Zhu J, Zhao A, Shi M, Yuan X, Tang M, Yang J, Pei H, Yang Z, Chen Q, Ye H, Niu T, Chen L. Preclinical studies of Flonoltinib Maleate, a novel JAK2/FLT3 inhibitor, in treatment of JAK2 V617F-induced myeloproliferative neoplasms. Blood Cancer J 2022; 12:37. [PMID: 35256594 PMCID: PMC8901636 DOI: 10.1038/s41408-022-00628-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Revised: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 02/05/2023] Open
Abstract
Janus kinase 2 (JAK2) hyperactivation by JAK2V617F mutation leads to myeloproliferative neoplasms (MPNs) and targeting JAK2 could serve as a promising therapeutic strategy for MPNs. Here, we report that Flonoltinib Maleate (FM), a selective JAK2/FLT3 inhibitor, shows high selectivity for JAK2 over the JAK family. Surface plasmon resonance assays verified that FM had a stronger affinity for the pseudokinase domain JH2 than JH1 of JAK2 and had an inhibitory effect on JAK2 JH2V617F. The cocrystal structure confirmed that FM could stably bind to JAK2 JH2, and FM suppressed endogenous colony formation of primary erythroid progenitor cells from patients with MPNs. In several JAK2V617F-induced MPN murine models, FM could dose-dependently reduce hepatosplenomegaly and prolong survival. Similar results were observed in JAK2V617F bone marrow transplantation mice. FM exhibited strong inhibitory effects on fibrosis of the spleen and bone marrow. Long-term FM treatment showed good pharmacokinetic/pharmacodynamic characteristics with high drug exposure in tumor-bearing tissues and low toxicity. Currently, FM has been approved by the National Medical Products Administration of China (CXHL2000628), and this study will guide clinical trials for patients with MPNs.
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Affiliation(s)
- Mengshi Hu
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Tao Yang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Linyu Yang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Lu Niu
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Jinbing Zhu
- Department of Hematology and Research Laboratory of Hematology, West China Hospital of Sichuan University, Chengdu, China
| | - Ailin Zhao
- Department of Hematology and Research Laboratory of Hematology, West China Hospital of Sichuan University, Chengdu, China
| | - Mingsong Shi
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Xue Yuan
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Minghai Tang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Jianhong Yang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Heying Pei
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Zhuang Yang
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Qiang Chen
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Haoyu Ye
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China
| | - Ting Niu
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China.
- Department of Hematology and Research Laboratory of Hematology, West China Hospital of Sichuan University, Chengdu, China.
| | - Lijuan Chen
- State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital of Sichuan University, Chengdu, China.
- Chengdu Zenitar Biomedical Technology Co., Ltd, Chengdu, China.
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Sekine Y, Kikkawa K, Witthuhn BA, Kashiwakura JI, Muromoto R, Kitai Y, Fujimuro M, Oritani K, Matsuda T. A novel intramolecular negative regulation of mouse Jak3 activity by tyrosine 820. Int Immunol 2022; 34:303-312. [PMID: 35192696 DOI: 10.1093/intimm/dxac005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 02/21/2022] [Indexed: 11/13/2022] Open
Abstract
Jak3, a member of the Janus kinase family, is essential for the cytokine receptor common gamma (γ) chain-mediated signaling. During activation of Jak3, tyrosine residues are phosphorylated and potentially regulate its kinase activity. We identified a novel tyrosine phosphorylation site within mouse Jak3, Y820, which is conserved in human Jak3, Y824. IL-2-induced tyrosine phosphorylation of Jak3 Y824 in human T cell line HuT78 cells was detected by using a phosphospecific, pY824, antibody. Mutation of mouse Jak3 Y820 to alanine (Y820A) showed increased autophosphorylation of Jak3 and enhanced STAT5 tyrosine phosphorylation and transcriptional activation. Stably expressed Jak3 Y820A in F7 cells, an IL-2 responsive mouse pro-B cell line Ba/F3, exhibited enhanced IL-2-dependent cell growth. Mechanistic studies demonstrated that interaction between Jak3 and STAT5 increased in Jak3 Y820A compared to Jak3 WT. These data suggest that Jak3 Y820 plays a role in negative regulation of Jak3-mediated STAT5 signaling cascade upon IL-2-stimulation. We speculate that this occurs through an interaction promoted by the tyrosine phosphorylated Y820 or a conformational change by Y820 mutation with either the STAT directly or with the recruitment of molecules such as phosphatases via a SH2 interaction. Additional studies will focus on these interactions as Jak3 plays a crucial role in disease and health.
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Affiliation(s)
- Yuichi Sekine
- Department of Cell Biology, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Kazuna Kikkawa
- Department of Cell Biology, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Bruce A Witthuhn
- Center for Mass Spectrometry and Proteomics, University of Minnesota, Minneapolis, MN, USA
| | - Jun-Ichi Kashiwakura
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Ryuta Muromoto
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Yuichi Kitai
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Masahiro Fujimuro
- Department of Cell Biology, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Kenji Oritani
- Department of Hematology, International University of Health and Welfare, 4-3 Kouzunomori, Narita, Chiba, Japan
| | - Tadashi Matsuda
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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JAK2S523L, a novel gain-of-function mutation in a critical autoregulatory residue in JAK2V617F- MPNs. Blood Adv 2021; 4:4554-4559. [PMID: 32956452 DOI: 10.1182/bloodadvances.2019001283] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 08/21/2020] [Indexed: 12/12/2022] Open
Abstract
The SH2-JH2 linker domain of JAK2 has been implicated in the negative regulation of JAK2 activity. In 2 patients with myeloproliferative neoplasms (MPNs), we identified and characterized the novel JAK2 mutation S523L, which occurs in a key residue in the linker region. In 1 case, acquisition of JAK2S523L was associated with thrombocytosis and bone marrow megakaryocytic hyperplasia, and there were no other somatic alterations in this patient. The second patient with JAK2S523Lmutation presented with increased hematocrit and had concurrent mutations in RUNX1 and BCORL1. Consistent with the genetic and clinical data, expression of JAK2S523L causes interleukin-3-independent growth in Ba/F3 cells transduced with the erythropoietin receptor by constitutively active Jak2/Stat5 signaling.
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Strous GJ, Almeida ADS, Putters J, Schantl J, Sedek M, Slotman JA, Nespital T, Hassink GC, Mol JA. Growth Hormone Receptor Regulation in Cancer and Chronic Diseases. Front Endocrinol (Lausanne) 2020; 11:597573. [PMID: 33312162 PMCID: PMC7708378 DOI: 10.3389/fendo.2020.597573] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 10/14/2020] [Indexed: 12/14/2022] Open
Abstract
The GHR signaling pathway plays important roles in growth, metabolism, cell cycle control, immunity, homeostatic processes, and chemoresistance via both the JAK/STAT and the SRC pathways. Dysregulation of GHR signaling is associated with various diseases and chronic conditions such as acromegaly, cancer, aging, metabolic disease, fibroses, inflammation and autoimmunity. Numerous studies entailing the GHR signaling pathway have been conducted for various cancers. Diverse factors mediate the up- or down-regulation of GHR signaling through post-translational modifications. Of the numerous modifications, ubiquitination and deubiquitination are prominent events. Ubiquitination by E3 ligase attaches ubiquitins to target proteins and induces proteasomal degradation or starts the sequence of events that leads to endocytosis and lysosomal degradation. In this review, we discuss the role of first line effectors that act directly on the GHR at the cell surface including ADAM17, JAK2, SRC family member Lyn, Ubc13/CHIP, proteasome, βTrCP, CK2, STAT5b, and SOCS2. Activity of all, except JAK2, Lyn and STAT5b, counteract GHR signaling. Loss of their function increases the GH-induced signaling in favor of aging and certain chronic diseases, exemplified by increased lung cancer risk in case of a mutation in the SOCS2-GHR interaction site. Insight in their roles in GHR signaling can be applied for cancer and other therapeutic strategies.
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Affiliation(s)
- Ger J. Strous
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
- BIMINI Biotech B.V., Leiden, Netherlands
| | - Ana Da Silva Almeida
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Joyce Putters
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Julia Schantl
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Magdalena Sedek
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Johan A. Slotman
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Tobias Nespital
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Gerco C. Hassink
- Department of Cell Biology, Centre for Molecular Medicine, University Medical Centre Utrecht, Utrecht, Netherlands
| | - Jan A. Mol
- Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands
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Hammarén HM, Virtanen AT, Raivola J, Silvennoinen O. The regulation of JAKs in cytokine signaling and its breakdown in disease. Cytokine 2019; 118:48-63. [DOI: 10.1016/j.cyto.2018.03.041] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 03/29/2018] [Accepted: 03/30/2018] [Indexed: 01/12/2023]
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Benton CB, Boddu PC, DiNardo CD, Bose P, Wang F, Assi R, Pemmaraju N, KC D, Pierce S, Patel K, Konopleva M, Ravandi F, Garcia‐Manero G, Kadia TM, Cortes J, Kantarjian HM, Andreeff M, Verstovsek S. Janus kinase 2 variants associated with the transformation of myeloproliferative neoplasms into acute myeloid leukemia. Cancer 2019; 125:1855-1866. [DOI: 10.1002/cncr.31986] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 12/20/2018] [Indexed: 01/12/2023]
Affiliation(s)
- Christopher B. Benton
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Prajwal C. Boddu
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Courtney D. DiNardo
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Prithviraj Bose
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Feng Wang
- Department of Genomic Medicine The University of Texas MD Anderson Cancer Center Houston Texas
| | - Rita Assi
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Naveen Pemmaraju
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Devendra KC
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Sherry Pierce
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Keyur Patel
- Department of Hematopathology The University of Texas MD Anderson Cancer Center Houston Texas
| | - Marina Konopleva
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Farhad Ravandi
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | | | - Tapan M. Kadia
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Jorge Cortes
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Hagop M. Kantarjian
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Michael Andreeff
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
| | - Srdan Verstovsek
- Department of Leukemia The University of Texas MD Anderson Cancer Center Houston Texas
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7
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Soendergaard C, Bergenheim FH, Bjerrum JT, Nielsen OH. Targeting JAK-STAT signal transduction in IBD. Pharmacol Ther 2018; 192:100-111. [PMID: 30048708 DOI: 10.1016/j.pharmthera.2018.07.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
An unmet medical need exists for novel targeted therapies for inflammatory bowel disease (IBD) as many patients experience inadequate responses to antibody-based biologics. An oral drug formulation with reduced production costs and redundancy for healthcare staff to administer therapy ideally should result in diminished healthcare expenses and improved patient compliance. A new drug class of small molecules, the Janus kinase (JAK) inhibitors (jakinibs), fulfills these criteria and has recently shown efficacy in IBD. Here we provide an overview of the mode of action of jakinibs and provide a comprehensive overview of existing clinical studies. Convincing clinical data show that a complex cytokine-driven inflammation can efficiently be modulated by therapeutic inhibition of the JAK proteins.
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Affiliation(s)
| | | | | | - Ole Haagen Nielsen
- Department of Gastroenterology, Herlev Hospital, University of Copenhagen, Denmark.
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8
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Abstract
The JAK (Janus kinase) family members serve essential roles as the intracellular signalling effectors of cytokine receptors. This family, comprising JAK1, JAK2, JAK3 and TYK2 (tyrosine kinase 2), was first described more than 20 years ago, but the complexities underlying their activation, regulation and pleiotropic signalling functions are still being explored. Here, we review the current knowledge of their physiological functions and the causative role of activating and inactivating JAK mutations in human diseases, including haemopoietic malignancies, immunodeficiency and inflammatory diseases. At the molecular level, recent studies have greatly advanced our knowledge of the structures and organization of the component FERM (4.1/ezrin/radixin/moesin)-SH2 (Src homology 2), pseudokinase and kinase domains within the JAKs, the mechanism of JAK activation and, in particular, the role of the pseudokinase domain as a suppressor of the adjacent tyrosine kinase domain's catalytic activity. We also review recent advances in our understanding of the mechanisms of negative regulation exerted by the SH2 domain-containing proteins, SOCS (suppressors of cytokine signalling) proteins and LNK. These recent studies highlight the diversity of regulatory mechanisms utilized by the JAK family to maintain signalling fidelity, and suggest alternative therapeutic strategies to complement existing ATP-competitive kinase inhibitors.
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Montresor A, Bolomini-Vittori M, Toffali L, Rossi B, Constantin G, Laudanna C. JAK tyrosine kinases promote hierarchical activation of Rho and Rap modules of integrin activation. ACTA ACUST UNITED AC 2014; 203:1003-19. [PMID: 24368807 PMCID: PMC3871442 DOI: 10.1083/jcb.201303067] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Lymphocyte recruitment is regulated by signaling modules based on the activity of Rho and Rap small guanosine triphosphatases that control integrin activation by chemokines. We show that Janus kinase (JAK) protein tyrosine kinases control chemokine-induced LFA-1- and VLA-4-mediated adhesion as well as human T lymphocyte homing to secondary lymphoid organs. JAK2 and JAK3 isoforms, but not JAK1, mediate CXCL12-induced LFA-1 triggering to a high affinity state. Signal transduction analysis showed that chemokine-induced activation of the Rho module of LFA-1 affinity triggering is dependent on JAK activity, with VAV1 mediating Rho activation by JAKs in a Gαi-independent manner. Furthermore, activation of Rap1A by chemokines is also dependent on JAK2 and JAK3 activity. Importantly, activation of Rap1A by JAKs is mediated by RhoA and PLD1, thus establishing Rap1A as a downstream effector of the Rho module. Thus, JAK tyrosine kinases control integrin activation and dependent lymphocyte trafficking by bridging chemokine receptors to the concurrent and hierarchical activation of the Rho and Rap modules of integrin activation.
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Affiliation(s)
- Alessio Montresor
- Department of Pathology and Diagnostics, Division of General Pathology, School of Medicine, and 2 The Center for Biomedical Computing, University of Verona, Verona 37134, Italy
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New insights into the structure and function of the pseudokinase domain in JAK2. Biochem Soc Trans 2013; 41:1002-7. [PMID: 23863170 DOI: 10.1042/bst20130005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
JAK (Janus kinase) 2 plays a critical role in signal transduction through several cytokine receptors. JAKs contain a typical tyrosine kinase domain preceded by a pseudokinase [JH2 (JAK homology 2)] domain which has been considered to be catalytically inactive. Identification of activating mutations in the JH2 domain of JAK2 as the major cause for polycythaemia vera and other MPNs (myeloproliferative neoplasms) demonstrate the critical regulatory function for this domain, but the underlying mechanisms have remained elusive. We have performed biochemical and functional analysis on the JH2 domain of JAK2. The results indicate that JH2 functions as an active protein kinase and phosphorylates two residues in JAK2 (Ser523 and Tyr570) that have been shown previously to be negative regulatory sites for JAK2 activity. The crystal structure of the JAK2 JH2 domain provides an explanation for the functional findings and shows that JH2 adopts a prototypical kinase fold, but binds MgATP through a non-canonical mode. The structure of the most prevalent pathogenic JH2 mutation V617F shows a high level of similarity to wild-type JH2. The most notable structural deviation is observed in the N-lobe αC-helix. The structural and biochemical data together with MD (molecular dynamics) simulations show that the V617F mutation rigidifies the αC-helix, which results in hyperactivation of the JH1 domain through an as yet unidentified mechanism. These results provide structural and functional insights into the normal and pathogenic function of the JH2 domain of JAK2.
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11
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Stec W, Vidal O, Zeidler MP. Drosophila SOCS36E negatively regulates JAK/STAT pathway signaling via two separable mechanisms. Mol Biol Cell 2013; 24:3000-9. [PMID: 23885117 PMCID: PMC3771960 DOI: 10.1091/mbc.e13-05-0275] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The low-complexity Drosophila genome includes previously uncharacterized SOCS36E, an ancestral SOCS4/5 homologue. It is shown that SOCS36E suppresses JAK/STAT signaling through two separate mechanisms: via receptor stability, mediated by the conserved SOCS-box domain, and via suppression of receptor phosphorylation that requires the N-terminal domain. Conserved from humans to Drosophila, the Janus kinase/signal transducer and activators of transcription (JAK/STAT) signaling cascade is essential for multiple developmental and homeostatic processes, with regulatory molecules controlling pathway activity also highly conserved. We characterize the Drosophila JAK/STAT pathway regulator SOCS36E and show that it functions via two independent mechanisms. First, we show that Drosophila Elongin B/C and Cullin-5 act via the SOCS-box of SOCS36E to reduce pathway activity specifically in response to ligand stimulation—a process that involves endocytic trafficking and lysosomal degradation of the Domeless (Dome) receptor. Second, SOCS36E also suppresses both stimulated and basal pathway activity via an Elongin/Cullin-independent mechanism that is mediated by the N-terminus of SOCS36E, which is required for the physical interaction of SOCS36E with Dome. Although some human SOCS proteins contain N-terminal kinase-inhibitory domains, we do not identify such a region in SOCS36E and propose a model wherein the N-terminal of SOCS36E blocks access to tyrosine residues in Dome. Our biochemical analysis of a SOCS-family regulator from a lower organism highlights the fundamental conserved roles played by regulatory mechanisms in signal transduction.
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Affiliation(s)
- Wojciech Stec
- MRC Centre for Development and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
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12
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Nespital T, Strous GJ. The Jak/STAT signaling pathway is downregulated at febrile temperatures. PLoS One 2012; 7:e49374. [PMID: 23166650 PMCID: PMC3498154 DOI: 10.1371/journal.pone.0049374] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 10/08/2012] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The Janus family of kinases (JAKs), Jak1, Jak2, Jak3, and Tyk2, constitute a subgroup of non-receptor protein tyrosine kinases. Upon cytokine binding, the receptor-associated kinases are activated and phosphorylate tyrosine residues in their cognate cytokine receptors. Their activities are controlled at several levels and include cellular concentration, auto-activation, and degradation. PRINCIPAL FINDINGS Our findings show that elevated temperatures in the fever range irreversibly aggregate Jak2 and considerably reduce functional Jak2 protein levels. Jak2 synthesis remains unaltered. We observed that also the protein level of the signal transducer and activator of transcription, STAT5b, is transiently decreased at temperatures above 37°C. Consequently, the signaling response, e.g. via the growth hormone receptor, is reduced. CONCLUSIONS/SIGNIFICANCE These findings predict that elevated body temperatures lower the responsiveness of cytokine receptors.
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Affiliation(s)
| | - Ger J. Strous
- Department of Cell Biology and Institute of Biomembranes, University Medical Center Utrecht, Utrecht, The Netherlands
- * E-mail:
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13
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Zhou C, Baltz JM. JAK2 mediates the acute response to decreased cell volume in mouse preimplantation embryos by activating NHE1. J Cell Physiol 2012; 228:428-38. [DOI: 10.1002/jcp.24147] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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14
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The pseudokinase domain of JAK2 is a dual-specificity protein kinase that negatively regulates cytokine signaling. Nat Struct Mol Biol 2011; 18:971-6. [PMID: 21841788 DOI: 10.1038/nsmb.2099] [Citation(s) in RCA: 205] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 06/14/2011] [Indexed: 12/13/2022]
Abstract
Human JAK2 tyrosine kinase mediates signaling through numerous cytokine receptors. The JAK2 JH2 domain functions as a negative regulator and is presumed to be a catalytically inactive pseudokinase, but the mechanism(s) for its inhibition of JAK2 remains unknown. Mutations in JH2 lead to increased JAK2 activity, contributing to myeloproliferative neoplasms (MPNs). Here we show that JH2 is a dual-specificity protein kinase that phosphorylates two negative regulatory sites in JAK2: Ser523 and Tyr570. Inactivation of JH2 catalytic activity increased JAK2 basal activity and downstream signaling. Notably, different MPN mutations abrogated JH2 activity in cells, and in MPN (V617F) patient cells phosphorylation of Tyr570 was reduced, suggesting that loss of JH2 activity contributes to the pathogenesis of MPNs. These results identify the catalytic activity of JH2 as a previously unrecognized mechanism to control basal activity and signaling of JAK2.
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Sanz A, Ungureanu D, Pekkala T, Ruijtenbeek R, Touw IP, Hilhorst R, Silvennoinen O. Analysis of Jak2 catalytic function by peptide microarrays: the role of the JH2 domain and V617F mutation. PLoS One 2011; 6:e18522. [PMID: 21533163 PMCID: PMC3078918 DOI: 10.1371/journal.pone.0018522] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Accepted: 03/10/2011] [Indexed: 12/27/2022] Open
Abstract
Janus kinase 2 (JAK2) initiates signaling from several cytokine receptors and is required for biological responses such as erythropoiesis. JAK2 activity is controlled by regulatory proteins such as Suppressor of Cytokine Signaling (SOCS) proteins and protein tyrosine phosphatases. JAK2 activity is also intrinsically controlled by regulatory domains, where the pseudokinase (JAK homology 2, JH2) domain has been shown to play an essential role. The physiological role of the JH2 domain in the regulation of JAK2 activity was highlighted by the discovery of the acquired missense point mutation V617F in myeloproliferative neoplasms (MPN). Hence, determining the precise role of this domain is critical for understanding disease pathogenesis and design of new treatment modalities. Here, we have evaluated the effect of inter-domain interactions in kinase activity and substrate specificity. By using for the first time purified recombinant JAK2 proteins and a novel peptide micro-array platform, we have determined initial phosphorylation rates and peptide substrate preference for the recombinant kinase domain (JH1) of JAK2, and two constructs comprising both the kinase and pseudokinase domains (JH1-JH2) of JAK2. The data demonstrate that (i) JH2 drastically decreases the activity of the JAK2 JH1 domain, (ii) JH2 increased the Km for ATP (iii) JH2 modulates the peptide preference of JAK2 (iv) the V617F mutation partially releases this inhibitory mechanism but does not significantly affect substrate preference or Km for ATP. These results provide the biochemical basis for understanding the interaction between the kinase and the pseudokinase domain of JAK2 and identify a novel regulatory role for the JAK2 pseudokinase domain. Additionally, this method can be used to identify new regulatory mechanisms for protein kinases that provide a better platform for designing specific strategies for therapeutic approaches.
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Affiliation(s)
- Arturo Sanz
- Department of Hematology, Erasmus MC, Rotterdam, Netherlands
| | - Daniela Ungureanu
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
| | - Tuija Pekkala
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
| | | | - Ivo P. Touw
- Department of Hematology, Erasmus MC, Rotterdam, Netherlands
| | - Riet Hilhorst
- PamGene International BV, 's-Hertogenbosch, The Netherlands
| | - Olli Silvennoinen
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- Tampere University Hospital, Tampere, Finland
- * E-mail:
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Togi S, Ikeda O, Kamitani S, Nakasuji M, Sekine Y, Muromoto R, Nanbo A, Oritani K, Kawai T, Akira S, Matsuda T. Zipper-interacting protein kinase (ZIPK) modulates canonical Wnt/beta-catenin signaling through interaction with Nemo-like kinase and T-cell factor 4 (NLK/TCF4). J Biol Chem 2011; 286:19170-7. [PMID: 21454679 DOI: 10.1074/jbc.m110.189829] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Zipper-interacting protein kinase (ZIPK) is a widely expressed serine/threonine kinase that has been implicated in apoptosis and transcriptional regulation. Here, we identified Nemo-like kinase (NLK) as a novel ZIPK-binding partner and found that ZIPK regulates NLK-mediated repression of canonical Wnt/β-catenin signaling. Indeed, siRNA-mediated reduction of endogenous ZIPK expression reduced Wnt/β-catenin signaling. Furthermore, ZIPK affected the formation of NLK-T-cell factor 4 (TCF4) complex. Importantly, ZIPK siRNA treatment in human colon carcinoma cells resulted in a reduction of β-catenin/TCF-mediated gene expression and cell growth. These results indicate that ZIPK may serve as a transcriptional regulator of canonical Wnt/β-catenin signaling through interaction with NLK/TCF4.
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Affiliation(s)
- Sumihito Togi
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
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17
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Ikeda O, Sekine Y, Mizushima A, Nakasuji M, Miyasaka Y, Yamamoto C, Muromoto R, Nanbo A, Oritani K, Yoshimura A, Matsuda T. Interactions of STAP-2 with Brk and STAT3 participate in cell growth of human breast cancer cells. J Biol Chem 2010; 285:38093-103. [PMID: 20929863 DOI: 10.1074/jbc.m110.162388] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
STAP-2 (signal transducing adaptor protein-2) is a recently identified adaptor protein that contains pleckstrin homology (PH) and Src homology 2-like domains, as well as a STAT3-binding motif in its C-terminal region. STAP-2 is also a substrate of breast tumor kinase (Brk). In breast cancers, Brk expression is deregulated and promotes STAT3-dependent cell proliferation. In the present study, manipulated STAP-2 expression demonstrated essential roles of STAP-2 in Brk-mediated STAT3 activation. STAP-2 interacts with both Brk and STAT3. In addition, small interfering RNA-mediated reduction of endogenous STAP-2 expression strongly decreased Brk-mediated STAT3 activation in T47D breast cancer cells. The PH domain of STAP-2 is involved in multiple steps: the binding between Brk and STAP-2, the activation and tyrosine phosphorylation of STAT3, and the activation of Brk. Notably, a STAP-2 PH-Brk fusion protein exhibited robust kinase activity and increased activation and tyrosine phosphorylation of STAT3. Finally, STAP-2 knockdown in T47D cells induced a significant decrease of proliferation, as strong as that of Brk or STAT3 knockdown. Taken together, our findings are likely to inform the development of a novel therapeutic strategy, as well as the determination of novel prognostic values, in breast carcinomas.
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Affiliation(s)
- Osamu Ikeda
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
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18
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Argetsinger LS, Stuckey JA, Robertson SA, Koleva RI, Cline JM, Marto JA, Myers MG, Carter-Su C. Tyrosines 868, 966, and 972 in the kinase domain of JAK2 are autophosphorylated and required for maximal JAK2 kinase activity. Mol Endocrinol 2010; 24:1062-76. [PMID: 20304997 DOI: 10.1210/me.2009-0355] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Janus kinase 2 (JAK2) is activated by a majority of cytokine family receptors including receptors for GH, leptin, and erythropoietin. To identify novel JAK2-regulatory and/or -binding sites, we set out to identify autophosphorylation sites in the kinase domain of JAK2. Two-dimensional phosphopeptide mapping of in vitro autophosphorylated JAK2 identified tyrosines 868, 966, and 972 as sites of autophosphorylation. Phosphorylated tyrosines 868 and 972 were also identified by mass spectrometry analysis of JAK2 activated by an erythropoietin-bound chimeric erythropoietin receptor/leptin receptor. Phosphospecific antibodies suggest that the phosphorylation of all three tyrosines increases in response to GH. Compared with wild-type JAK2, which is constitutively active when overexpressed, JAK2 lacking tyrosine 868, 966, or 972 has substantially reduced activity. Coexpression with GH receptor and protein tyrosine phosphatase1B allowed us to investigate GH-dependent activation of these mutated JAK2s in human embryonic kidney 293T cells. All three mutated JAK2s are activated by GH, although to a lesser extent than wild-type JAK2. The three mutated JAK2s also mediate GH activation of signal transducer and activator of transcription 3 (Stat3), signal transducer and activator of transcription 5b (Stat5b) and ERK1, but at reduced levels. Coexpression with Src-homology 2B1beta (SH2B1beta), like coexpression with GH-bound GH receptor, partially restores the activity of all three JAK2 mutants. Based on these results and the crystal structure of the JAK2 kinase domain, we hypothesize that small changes in the conformation of the regions of JAK2 surrounding tyrosines 868, 966, and 972 due to e.g. phosphorylation, binding to a ligand-bound cytokine receptor, and/or binding to Src-homology 2B1, may be essential for JAK2 to assume a maximally active conformation.
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Affiliation(s)
- Lawrence S Argetsinger
- Department of Molecular and Integrative Physiology, The University of Michigan Medical School, Ann Arbor, Michigan 48109-5622, USA
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19
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Regulation of Jak2 function by phosphorylation of Tyr317 and Tyr637 during cytokine signaling. Mol Cell Biol 2009; 29:3367-78. [PMID: 19364823 DOI: 10.1128/mcb.00278-09] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Jak2, the cognate tyrosine kinase for numerous cytokine receptors, undergoes multisite phosphorylation during cytokine stimulation. To understand the role of phosphorylation in Jak2 regulation, we used mass spectrometry to identify numerous Jak2 phosphorylation sites and characterize their significance for Jak2 function. Two sites outside of the tyrosine kinase domain, Tyr(317) in the FERM domain and Tyr(637) in the JH2 domain, exhibited strong regulation of Jak2 activity. Mutation of Tyr(317) promotes increased Jak2 activity, and the phosphorylation of Tyr(317) during cytokine signaling requires prior activation loop phosphorylation, which is consistent with a role for Tyr(317) in the feedback inhibition of Jak2 kinase activity after receptor stimulation. Comparison to several previously identified regulatory phosphorylation sites on Jak2 revealed a dominant role for Tyr(317) in the attenuation of Jak2 signaling. In contrast, mutation of Tyr(637) decreased Jak2 signaling and activity and partially suppressed the activating JH2 V617F mutation, suggesting a role for Tyr(637) phosphorylation in the release of JH2 domain-mediated suppression of Jak2 kinase activity during cytokine stimulation. The phosphorylation of Tyr(317) and Tyr(637) act in concert with other regulatory events to maintain appropriate control of Jak2 activity and cytokine signaling.
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20
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Thompson BR, Mazurkiewicz-Muñoz AM, Suttles J, Carter-Su C, Bernlohr DA. Interaction of adipocyte fatty acid-binding protein (AFABP) and JAK2: AFABP/aP2 as a regulator of JAK2 signaling. J Biol Chem 2009; 284:13473-13480. [PMID: 19318353 DOI: 10.1074/jbc.m900075200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Adipocyte fatty acid-binding protein (AFABP/aP2) facilitates the intracellular solubilization and trafficking of lipids within the aqueous environment of the cell. Studies in the AFABP/aP2 knock-out mouse suggest that the protein may have roles in cellular processes broader than lipid transport. We present herein the finding that AFABP/aP2 interacts with JAK2 in a fatty acid-dependent manner. This interaction was established using yeast two-hybrid analysis, co-immunoprecipitation from adipose tissue, and 3T3-L1 adipocytes as well as in 293 cells overexpressing JAK2 and AFABP/aP2. Mutational analysis of AFABP/aP2 (R126L/Y128F) revealed that fatty acid binding activity is necessary for the interaction and that Asp(18) of the helix-turn-helix motif forms a component of the interaction domain. Mutational analysis of JAK2 (Y1007F/Y1008F) revealed that AFABP/aP2 associates with the basal unphosphorylated form of the protein. Interleukin-6, but not interleukin-10, stimulated phosphorylation of STAT3, and induction of SOCS3 mRNA expression were potentiated in a time- and dose-dependent manner in macrophage cell lines derived from AFABP/aP2-EFABP/mal1 double knock-out mice relative to cells from wild type animals. These results suggest that ligand-bound AFABP/aP2 binds to and attenuates JAK2 signaling and establishes a new role for AFABP/aP2 as a fatty acid sensor affecting cellular metabolism via protein-protein interactions.
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Affiliation(s)
- Brian R Thompson
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455
| | - Anna M Mazurkiewicz-Muñoz
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Jill Suttles
- Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, Kentucky 40292
| | - Christin Carter-Su
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - David A Bernlohr
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455.
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21
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Abstract
The BCR-ABL-negative myeloproliferative neoplasms (MPNs), polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF), entered the spotlight in 2005 when the unique somatic acquired JAK2 V617F mutation was described in >95% of PV and in 50% of ET and PMF patients. For the very rare PV patients who do not harbor the JAK2 V617F mutation, exon 12 JAK2 mutants were discovered also to result in activated forms of JAK2. A minority of ET and PMF patients harbor mutations that constitutively activate the thrombopoietin receptor (TpoR). In bone marrow reconstitution models based on retroviral transduction, the phenotype induced by JAK2 V617F is less severe and different from the rapid fatal myelofibrosis induced by TpoR W515L. The reasons for these differences are unknown. Exactly by which mechanism(s) one acquired somatic mutation, JAK2 V617F, can promote three different diseases remains a mystery, although gene dosage and host genetic variation might have important functions. We review the recent progress made in deciphering signaling anomalies in PV, ET and PMF, with an emphasis on the relationship between JAK2 V617F and cytokine receptor signaling and on cross-talk with several other signaling pathways.
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Robertson SA, Leinninger GM, Myers MG. Molecular and neural mediators of leptin action. Physiol Behav 2008; 94:637-42. [PMID: 18501391 PMCID: PMC2516921 DOI: 10.1016/j.physbeh.2008.04.005] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 04/02/2008] [Indexed: 01/17/2023]
Abstract
The adipose tissue-derived hormone, leptin, acts via its receptor (LepRb) in the brain to regulate energy balance and neuroendocrine function. Parsing the biology of leptin requires understanding LepRb signaling and the roles for specific signaling pathways in neural and physiological leptin action. Since the leptin acts via a broadly distributed network of LepRb-expressing neurons, understanding the function of each of these LepRb neural populations will also be crucial. Here, we review the status of knowledge regarding the molecular mediators of leptin action and the neural substrate via which leptin acts to regulate physiologic processes.
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Affiliation(s)
- Scott A. Robertson
- Division of Metabolism, Endocrinology and Diabetes, Department of Medicine and Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Gina M. Leinninger
- Division of Metabolism, Endocrinology and Diabetes, Department of Medicine and Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Martin G. Myers
- Division of Metabolism, Endocrinology and Diabetes, Department of Medicine and Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
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23
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McDoom I, Ma X, Kirabo A, Lee KY, Ostrov DA, Sayeski PP. Identification of tyrosine 972 as a novel site of Jak2 tyrosine kinase phosphorylation and its role in Jak2 activation. Biochemistry 2008; 47:8326-34. [PMID: 18636744 DOI: 10.1021/bi800867d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Jak2 is a 130 kDa tyrosine kinase that is important in a number of cellular signaling pathways. Its function is intrinsically regulated by the phosphorylation of a handful of its 49 tyrosines. Here, we report that tyrosine 972 (Y972) is a novel site of Jak2 phosphorylation and, hence, autoregulation. Specifically, we found that Y972 is phosphorylated and confirmed that this residue resides on the surface of the protein. Using expression plasmids that expressed either wild-type Jak2 or a full-length Jak2 cDNA containing a single Y972F substitution mutation, we investigated the consequences of losing Y972 phosphorylation on Jak2 function. We determined that the loss of Y972 phosphorylation significantly reduced the levels of both Jak2 total tyrosine phosphorylation and phosphorylation of Y1007/Y1008. Additionally, Y972 phosphorylation was shown to be important for maximal kinase function. Interestingly, in response to classical cytokine activation, the Jak2 Y972F mutant exhibited a moderately impaired level of activation when compared to the wild-type protein. However, when Jak2 was activated via a GPCR ligand, the ability of the Y972F mutant to be activated was completely lost, therefore suggesting a differential role of Y972 in Jak2 activation. Finally, we found that phosphorylation of Y972 enhances Jak2 kinase function via a mechanism that appears to stabilize the active conformation of the protein. Collectively, our results suggest that Y972 is a novel site of Jak2 phosphorylation and plays an important differential role in ligand-dependent Jak2 activation via a mechanism that involves stabilization of the Jak2 active conformation.
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Affiliation(s)
- Issam McDoom
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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24
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The saga of JAK2 mutations and translocations in hematologic disorders: pathogenesis, diagnostic and therapeutic prospects, and revised World Health Organization diagnostic criteria for myeloproliferative neoplasms. Hum Pathol 2008; 39:795-810. [PMID: 18538168 DOI: 10.1016/j.humpath.2008.02.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 02/08/2008] [Accepted: 02/11/2008] [Indexed: 12/22/2022]
Abstract
JAK2 is a tyrosine kinase involved in cytokine signaling. The JAK2V617F point mutation, first described in 2005, results in constitutive activation of JAK2 and is now widely used as a diagnostic marker for Philadelphia chromosome negative myeloproliferative neoplasms. In recent years, more novel JAK2 mutations and fusion genes have been discovered in myeloproliferative neoplasms and other hematologic malignancies. This review aims to summarize the discovery and use of the JAK2V617F point mutation, other novel JAK2 mutations, and JAK2 translocations in diagnosing myeloproliferative neoplasms, acute myeloid leukemia, and acute lymphoid leukemia. JAK2 mutation testing is addressed, including the sensitivity and specificity of the different JAK2 mutation testing methods, clinical indications for use, and the use of quantitative JAK2 mutation testing for routine pathologic diagnosis, prognosis, and monitoring response to therapy. The relationship of JAK2 mutation to endogenous erythroid colony formation, thrombopoietin receptor mutation, polycythemia rubra vera-1 overexpression, and thrombopoietin receptor underexpression in myeloproliferative neoplasms are explored. Also discussed are the JAK2 inhibitors for clinical trials. Finally, the advantages of the newly proposed World Health Organization classification for myeloproliferative neoplasms are reviewed.
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25
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Abstract
The adipose tissue-derived hormone leptin acts via its receptor (LRb) in the brain to regulate energy balance and neuroendocrine function. LRb signaling via STAT3 and a number of other pathways is required for the totality of leptin action. The failure of elevated leptin levels to suppress feeding and mediate weight loss in common forms of obesity defines a state of so-called leptin resistance. A number of mechanisms, including the leptin-stimulated phosphorylation of Tyr(985) on LRb and the suppressor of cytokine signaling 3, attenuate leptin signaling and promote a cellular leptin resistance in obesity. Several unique features of the arcuate nucleus of the hypothalamus may contribute to the severity of cellular leptin resistance in this region. Other mechanisms that govern feeding behavior and food reward may also underlie the inception of obesity.
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Affiliation(s)
- Martin G Myers
- Division of Metabolism, Endocrinology and Diabetes, Department of Medicine, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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26
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Leinninger GM, Myers MG. LRb signals act within a distributed network of leptin-responsive neurones to mediate leptin action. Acta Physiol (Oxf) 2008; 192:49-59. [PMID: 18171429 DOI: 10.1111/j.1748-1716.2007.01784.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The adipose tissue-derived hormone, leptin, acts via its receptor (LRb) in the brain to regulate energy balance and neuroendocrine function. In order to understand leptin action we have explored the physiological function of LRb signalling pathways, defining important roles for signal transducer and activator of transcription-3 (STAT3) in positive signalling and for LRbTyr(985)-mediated feedback inhibition in leptin signal attenuation. As the cells on which leptin acts are not homogeneous, but rather represent a broadly distributed network of neurones with divergent projections and functions, it is also crucial to consider how each of these populations responds to LRb signals to contribute to leptin action. While well-known LRb-expressing neurones within the arcuate nucleus of the hypothalamus mediate crucial effects on satiety and energy expenditure, other populations of LRb-expressing neurones in the ventral tegmental area and elsewhere likely control the mesolimbic dopamine system. Additional populations of LRb-expressing neurones likely contribute to other aspects of neuroendocrine regulation. It will be important to define the molecular mechanisms by which leptin acts to regulate neurophysiology in each of these LRb-expressing neural populations in order to understand the totality of leptin action.
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Affiliation(s)
- G M Leinninger
- Division of Metabolism, Endocrinology and Diabetes, Department of Medicine, University of Michigan Medical School, Ann Arbor, MI 48109-0678, USA
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27
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Jak2 FERM domain interaction with the erythropoietin receptor regulates Jak2 kinase activity. Mol Cell Biol 2007; 28:1792-801. [PMID: 18160720 DOI: 10.1128/mcb.01447-07] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Janus kinases are essential for signal transduction by a variety of cytokine receptors and when inappropriately activated can cause hematopoietic disorders and oncogenesis. Consequently, it can be predicted that the interaction of the kinases with receptors and the events required for activation are highly controlled. In a screen to identify phosphorylation events regulating Jak2 activity in EpoR signaling, we identified a mutant (Jak2-Y613E) which has the property of being constitutively activated, as well as an inactivating mutation (Y766E). Although no evidence was obtained to indicate that either site is phosphorylated in signaling, the consequences of the Y613E mutation are similar to those observed with recently described activating mutations in Jak2 (Jak2-V617F and Jak2-L611S). However, unlike the V617F or L611S mutant, the Y613E mutant requires the presence of the receptor but not Epo stimulation for activation and downstream signaling. The properties of the Jak2-Y613E mutant suggest that under normal conditions, Jak2 that is not associated with a receptor is locked into an inactive state and receptor binding through the FERM domain relieves steric constraints, allowing the potential to be activated with receptor engagement.
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28
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Elsasser TH, Li CJ, Caperna TJ, Kahl S, Schmidt WF. Growth hormone (GH)-associated nitration of Janus kinase-2 at the 1007Y-1008Y epitope impedes phosphorylation at this site: mechanism for and impact of a GH, AKT, and nitric oxide synthase axis on GH signal transduction. Endocrinology 2007; 148:3792-802. [PMID: 17510232 DOI: 10.1210/en.2006-1736] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A generalized increase in liver protein tyrosine nitration (3'-nitrotyrosine, 3'-NT) occurs after GH injection in a time frame consistent with observed acute GH hyporesponsiveness. Here we investigated whether the GH-associated nitration process might be targeted to the (1007)Y-(1008)Y-phosphorylation epitope of Janus kinase (JAK)-2 because of its homology to a defined peptide nitration motif. Using antibodies we developed to the 3'NT-substituted peptide analog of the (1007)Y-(1008)Y-JAK2 site (nitro-JAK2), we demonstrated a rapid increase in membrane-associated nitro-JAK2 after GH. In vivo (bovine liver) and in vitro (porcine hepatocytes), GH-induced cellular levels of nitro-(1007)Y-(1008)Y-JAK2 persisted significantly longer after a stimulatory GH pulse than did levels of phospho-JAK2. Treatment of cultured cells with inhibitors of AKT or endothelial nitric oxide synthase prior to GH challenge attenuated the increases in nitro-JAK2 predominantly in the membrane subcellular fraction. In instances in which GH effected orthophosphorylation of (694)Y-signal transducer and activator of transcription (STAT)-5b, the addition of AKT and endothelial nitric oxide synthase inhibitors prior to GH significantly increased the levels of phospho-(694)Y-STAT5b and phospho-(1007)Y-JAK2 over those arising from GH alone. Nuclear magnetic resonance molecular modeling of natural and 3'-NT- and orthophosphate-substituted peptide analogs of the (1007)Y-(1008)Y site demonstrated significant effects of 3'-nitration on the planar orientation and intramolecular stabilizing points of the affected tyrosines. When these peptides were used as substrates for in vitro tyrosine kinase phosphorylation reactions, 3'-NT in the (1007)Y and/or (1008)Y positions blocked the generation of (1007)Y-phosphotyrosine. The data suggest that the nitration of JAK2 may act as an inhibitory counterpart to phosphorylation activation, reflecting a very localized break on the progression of GH signal transduction processes spanning JAK-STAT-AKT interactions.
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Affiliation(s)
- Ted H Elsasser
- US Department of Agriculture, Agricultural Research Service, Growth Biology Laboratory, Beltsville, Maryland 20705, USA.
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29
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Elsasser TH, Kahl S, Li CJ, Sartin JL, Garrett WM, Rodrigo J. Caveolae nitration of Janus kinase-2 at the 1007Y-1008Y site: coordinating inflammatory response and metabolic hormone readjustment within the somatotropic axis. Endocrinology 2007; 148:3803-13. [PMID: 17510231 DOI: 10.1210/en.2006-1737] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Life-threatening proinflammatory response (PR) induces severe GH resistance. Although low-level PR is much more commonly encountered clinically, relatively few studies have investigated the accompanying change in GH signal transduction progression and, in particular, the impact of low-level PR on Janus kinase (JAK)-2. Using a low-level, in vivo endotoxin [lipopolysaccharide (LPS)] challenge protocol, we demonstrated that the liver tissue content of JAK2 declined 24 h (62%, P < 0.02) after LPS and that tyrosine-nitrated JAK2 could be immunoprecipitated from post-LPS liver biopsy homogenates. With antibodies developed to probe specifically for nitration at the (1007)Y-(1008)Y phosphorylation epitope of JAK2, we demonstrated that the nitrated (1007)Y-(1008)Y-JAK-2 (nitro-JAK2) coimmunoprecipitated with caveolin-1 and (1177)phospho-SER-endothelial nitric oxide synthase when post-LPS liver homogenates were treated with anticaveolin-1 and protein A/G. The magnitude of increase in nitro-JAK2 was attenuated in animals treated with vitamin E prior to LPS. The increase in nitro-JAK2 after LPS was greater in a line of experimental animals with a genetic propensity for higher PR at the given LPS dose than responses measured in their normal counterparts. The development and remission of nitro-JAK2 was temporally concordant with changes in plasma concentrations of IGF-I; hepatocellular IGF-I mRNA content was inversely proportional to nitro-JAK2 content. Localized changes in the state of nitration of regulatory phosphorylation domains of JAK2 in caveolar microenvironments and tissue content of JAK2 during PR suggest a unique mechanism through which discrete signal transduction switching might occur in the liver to fine tune cellular responses to the endocrine-immune signals that develop during low-level, transient proinflammatory stress.
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Affiliation(s)
- Ted H Elsasser
- Growth Biology Laboratory, US Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705, USA.
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30
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Funakoshi-Tago M, Pelletier S, Matsuda T, Parganas E, Ihle JN. Receptor specific downregulation of cytokine signaling by autophosphorylation in the FERM domain of Jak2. EMBO J 2006; 25:4763-72. [PMID: 17024180 PMCID: PMC1618111 DOI: 10.1038/sj.emboj.7601365] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Accepted: 08/30/2006] [Indexed: 01/17/2023] Open
Abstract
The tyrosine kinase, Janus kinase-2 (Jak2), plays a pivotal role in signal transduction through a variety of cytokine receptors, including the receptor for erythropoietin (Epo). Although the physiological relevance of Jak2 has been definitively established, less is known about its regulation. In studies assessing the roles of sites of tyrosine phosphorylation, we identified Y(119) in the FERM (band 4.1, Ezrin, radixin and moesin) domain as a phosphorylation site. In these studies, we demonstrate that the phosphorylation of Y(119) in response to Epo downregulates Jak2 kinase activity. Using a phosphorylation mimic mutation (Y(119)E), downregulation is shown to involve dissociation of Jak2 from the receptor complex. Conversely, a Y(119)F mutant is more stably associated with the receptor complex. Thus, in cytokine responses, ligand binding induces activation of receptor associated Jak2, autophosphorylation of Y(119) in the FERM domain and the subsequent dissociation of the activated Jak2 from the receptor and degradation. This regulation occurs with the receptors for Epo, thrombopoietin and growth hormone but not with the receptor for interferon-gamma.
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Affiliation(s)
| | - Stephane Pelletier
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Tadashi Matsuda
- Department of Immunology, Hokkaido University, Sapporo, Japan
| | - Evan Parganas
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - James N Ihle
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN 38120, USA. Tel.: +1 901 495 3422; Fax: +1 901 525 8025; E-mail:
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31
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Grandage VL, Everington T, Linch DC, Khwaja A. Gö6976 is a potent inhibitor of the JAK 2 and FLT3 tyrosine kinases with significant activity in primary acute myeloid leukaemia cells. Br J Haematol 2006; 135:303-16. [PMID: 16956345 DOI: 10.1111/j.1365-2141.2006.06291.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aberrant activation of Janus kinase/signal transducers and activators of transcription (JAK/STAT) signalling is implicated in a number of haematological malignancies and effective JAK inhibitors may be therapeutically useful. We found that Gö6976, an indolocarbazole inhibitor of the calcium-dependent isozymes of protein kinase C (PKC), inhibited interleukin 3/granulocyte-macrophage colony-stimulating factor-induced signalling, proliferation and survival whereas Gö6983, a broad spectrum PKC inhibitor, had no such effects. Gö6976 was found to be a direct and potent inhibitor of JAK2 in vitro. Gö6976 also inhibited signalling, survival and proliferation in cells expressing the leukaemia-associated TEL-JAK2 fusion protein and the myeloproliferative disorder (MPD)-associated JAK2 V617F mutant. In primary acute myeloid leukaemia (AML) cells, incubation with Gö6976 reduced constitutive STAT activity in all cases studied. In addition, Akt and mitogen-activated protein kinase phosphorylation were reduced in 4/5 FLT3-internal tandem duplication (ITD) positive AML cases and 7/13 FLT3-wild-type (WT) cases. Expression of FLT3-WT, ITD and D835Y in 32D cells showed that Gö6976 is also a potent inhibitor of WT and mutant FLT3. In AML cells, Gö6976 reduced the survival to 55 +/- 5% of control in FLT3-ITD cases and to 69 +/- 5% in FLT3-WT samples. These data may help identify clinically useful compounds based on the structure of Gö6976, which can be employed for the treatment of MPDs as well as AML.
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Affiliation(s)
- Victoria L Grandage
- Department of Haematology, Royal Free and University College London Medical School, London, UK
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Abstract
The production of blood cells is regulated by a number of protein growth factors and cytokines that influence cell survival, proliferation and differentiation. Many of these molecules bind to cell surface receptors, which belong to a family of closely related cytokine receptors that lack intrinsic catalytic activity but are intimately associated with tyrosine kinases of the Janus kinase (JAK) family. Ligand binding induces the activation of JAKs, which sit at the apex of a signalling cascade in which a key role is played by members of the signal transducers and activators of transcription (STAT) group. Congenital deficiencies in JAK-STAT signalling are associated with immunodeficiency states and acquired activating mutations and translocations are involved in the pathophysiology of haematological malignancy. The latter findings have raised hopes that drugs that target aberrant JAK-STAT signalling may be useful for the treatment of human disease.
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Affiliation(s)
- Asim Khwaja
- Department of Haematology, Royal Free and University College Medical School, London, UK.
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Mazurkiewicz-Munoz AM, Argetsinger LS, Kouadio JLK, Stensballe A, Jensen ON, Cline JM, Carter-Su C. Phosphorylation of JAK2 at serine 523: a negative regulator of JAK2 that is stimulated by growth hormone and epidermal growth factor. Mol Cell Biol 2006; 26:4052-62. [PMID: 16705159 PMCID: PMC1489095 DOI: 10.1128/mcb.01591-05] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The tyrosine kinase JAK2 is a key signaling protein for at least 20 receptors in the cytokine/hematopoietin receptor superfamily and is a component of signaling for multiple receptor tyrosine kinases and several G-protein-coupled receptors. In this study, phosphopeptide affinity enrichment and mass spectrometry identified serine 523 (Ser523) in JAK2 as a site of phosphorylation. A phosphoserine 523 antibody revealed that Ser523 is rapidly but transiently phosphorylated in response to growth hormone (GH). MEK1 inhibitor UO126 suppresses GH-dependent phosphorylation of Ser523, suggesting that extracellular signal-regulated kinases (ERKs) 1 and/or 2 or another kinase downstream of MEK1 phosphorylate Ser523 in response to GH. Other ERK activators, phorbol 12-myristate 13-acetate and epidermal growth factor, also stimulate phosphorylation of Ser523. When Ser523 in JAK2 was mutated, JAK2 kinase activity as well as GH-dependent tyrosyl phosphorylation of JAK2 and Stat5 was enhanced, suggesting that phosphorylation of Ser523 inhibits JAK2 kinase activity. We hypothesize that phosphorylation of Ser523 in JAK2 by ERKs 1 and/or 2 or other as-yet-unidentified kinases acts in a negative feedback manner to dampen activation of JAK2 in response to GH and provides a mechanism by which prior exposure to environmental factors that regulate Ser523 phosphorylation might modulate the cell's response to GH.
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Affiliation(s)
- Anna M Mazurkiewicz-Munoz
- Graduate Program in Cellular and Molecular Biology, The University of Michigan Medical School, Ann Arbor, MI 48109-0622, USA
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Sekine Y, Yumioka T, Yamamoto T, Muromoto R, Imoto S, Sugiyma K, Oritani K, Shimoda K, Minoguchi M, Akira S, Yoshimura A, Matsuda T. Modulation of TLR4 signaling by a novel adaptor protein signal-transducing adaptor protein-2 in macrophages. THE JOURNAL OF IMMUNOLOGY 2006; 176:380-9. [PMID: 16365431 DOI: 10.4049/jimmunol.176.1.380] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Signal-transducing adaptor protein-2 (STAP-2) is a recently identified adaptor protein that contains pleckstrin and Src homology 2-like domains as well as a YXXQ motif in its C-terminal region. Our previous studies have demonstrated that STAP-2 binds to STAT3 and STAT5, and regulates their signaling pathways. In the present study, STAP-2 was found to positively regulate LPS/TLR4-mediated signals in macrophages. Disruption of STAP-2 resulted in impaired LPS/TLR4-induced cytokine production and NF-kappaB activation. Conversely, overexpression of STAP-2 enhanced these LPS/TLR4-induced biological activities. STAP-2, particularly its Src homology 2-like domain, bound to both MyD88 and IkappaB kinase (IKK)-alphabeta, but not TNFR-associated factor 6 or IL-1R-associated kinase 1, and formed a functional complex composed of MyD88-STAP-2-IKK-alphabeta. These interactions augmented MyD88- and/or IKK-alphabeta-dependent signals, leading to enhancement of the NF-kappaB activity. These results demonstrate that STAP-2 may constitute an alternative LPS/TLR4 pathway for NF-kappaB activation instead of the TNFR-associated factor 6-IL-1R-associated kinase 1 pathway.
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Affiliation(s)
- Yuichi Sekine
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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Kaur S, Uddin S, Platanias LC. The PI3' Kinase Pathway in Interferon Signaling. J Interferon Cytokine Res 2005; 25:780-7. [PMID: 16375606 DOI: 10.1089/jir.2005.25.780] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Interferons (IFNs) are pleiotropic cytokines with important immunomodulatory, antitumor, antiviral, and growth inhibitory properties. Consistent with the multiplicity of their effects, the IFNs activate several cellular cascades after they bind to their receptors. Although the Jak-Stat pathway is the most studied pathway, it appears that additional signaling cascades play roles in IFN signaling. The phosphatidylinositol 3'-kinase (PI3'K) pathway has emerged as one of the critical players in IFN signal transduction and is the focus of this review. This pathway is activated distinctively from the Stat pathway but plays important roles in the regulation of IFN-dependent gene transcription and initiation of mRNA translation.
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Affiliation(s)
- Surinder Kaur
- Robert H. Lurie Comprehensive Cancer Center and Division of Hematology-Oncology, Northwestern University Medical School, 303 East Superior Street, Chicago, IL 60611, USA
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Sato N, Kamada N, Muromoto R, Kawai T, Sugiyama K, Watanabe T, Imoto S, Sekine Y, Ohbayashi N, Ishida M, Akira S, Matsuda T. Phosphorylation of threonine-265 in Zipper-interacting protein kinase plays an important role in its activity and is induced by IL-6 family cytokines. Immunol Lett 2005; 103:127-34. [PMID: 16325270 DOI: 10.1016/j.imlet.2005.10.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 10/20/2005] [Accepted: 10/20/2005] [Indexed: 01/18/2023]
Abstract
Zipper-interacting protein kinase (ZIPK) is a widely expressed serine/threonine kinase that has been implicated in cell death and transcriptional regulation, but its mechanism of regulation remains unknown. Here, we identified threonine-265 (Thr265) in ZIPK as a major autophosphorylation site. Mutational analyses revealed that autophosphorylation of Thr265 were essential for its full catalytic activity toward an exogenous substrate as well as for cell death induction. Furthermore, leukemia inhibitory factor (LIF) stimulated Thr265 phosphorylation of ZIPK, thereby leading to phosphorylation and activation of signal transducer and activator of transcription (STAT3). Taken together, our findings demonstrate that ZIPK is positively regulated through Thr265 phosphorylation and that this phosphorylation is essential for its function.
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Affiliation(s)
- Noriko Sato
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-Ku Kita 12 Nishi 6, Sapporo 060-0812, Japan
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Sato N, Kawai T, Sugiyama K, Muromoto R, Imoto S, Sekine Y, Ishida M, Akira S, Matsuda T. Physical and functional interactions between STAT3 and ZIP kinase. Int Immunol 2005; 17:1543-52. [PMID: 16219639 DOI: 10.1093/intimm/dxh331] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Signal transducer and activator of transcription 3 (STAT3) is a latent cytoplasmic transcription factor that can be activated by cytokines and growth factors. It plays important roles in cell growth, apoptosis and cell transformation, and is constitutively active in a variety of tumor cells. In this study, we provide evidence that zipper-interacting protein kinase (ZIPK) interacts physically with STAT3. ZIPK specifically interacted with STAT3, and did not bind to STAT1, STAT4, STAT5a, STAT5b or STAT6. ZIPK phosphorylated STAT3 on serine 727 (Ser727) and enhanced STAT3 transcriptional activity. Small interfering RNA-mediated reduction of ZIPK expression decreased leukemia inhibitory factor (LIF)- and IL-6-induced STAT3-dependent transcription. Furthermore, LIF- and IL-6-mediated STAT3 activation stimulated ZIPK activity. Taken together, our data suggest that ZIPK interacts with STAT3 within the nucleus to regulate the transcriptional activity of STAT3 via phosphorylation of Ser727.
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Affiliation(s)
- Noriko Sato
- Department of Immunology, Graduate School of Pharmaceutical Sciences Hokkaido University, Kita-Ku Kita 12 Nishi 6, Sapporo 060-0812, Japan
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