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Mesev EV, Lin AE, Guare EG, Heller BL, Douam F, Adamson B, Toettcher JE, Ploss A. Membrane-proximal motifs encode differences in signaling strength between type I and III interferon receptors. Sci Signal 2023; 16:eadf5494. [PMID: 37816090 PMCID: PMC10939449 DOI: 10.1126/scisignal.adf5494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 09/09/2023] [Indexed: 10/12/2023]
Abstract
Interferons (IFNs) play crucial roles in antiviral defenses. Despite using the same Janus-activated kinase (JAK)-signal transducer and activator of transcription (STAT) signaling cascade, type I and III IFN receptors differ in the magnitude and dynamics of their signaling in terms of STAT phosphorylation, gene transcription, and antiviral responses. These differences are not due to ligand-binding affinity and receptor abundance. Here, we investigated the ability of the intracellular domains (ICDs) of IFN receptors to differentiate between type I and III IFN signaling. We engineered synthetic, heterodimeric type I and III IFN receptors that were stably expressed at similar amounts in human cells and responded to a common ligand. We found that our synthetic type I IFN receptors stimulated STAT phosphorylation and gene expression to greater extents than did the corresponding type III IFN receptors. Furthermore, we identified short "box motifs" within ICDs that bind to JAK1 that were sufficient to encode differences between the type I and III IFN receptors. Together, our results indicate that specific regions within the ICDs of IFN receptor subunits encode different downstream signaling strengths that enable type I and III IFN receptors to produce distinct signaling outcomes.
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Affiliation(s)
- Emily V. Mesev
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Aaron E. Lin
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Emma G. Guare
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Brigitte L. Heller
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Florian Douam
- Department of Microbiology, Boston University Chobanian and Avedisian School of Medicine, Boston, MA 02118, USA
- National Emerging Infectious Diseases Laboratories, Boston University, Boston, MA 02118, USA
| | - Britt Adamson
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
- Lewis Sigler Center for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Jared E. Toettcher
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
- Omenn-Darling Bioengineering Institute, Princeton University, Princeton, NJ 08544, USA
| | - Alexander Ploss
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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2
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Mesev EV, Guare EG, Ploss A, Toettcher JE. Synthetic Heterodimers of Type III Interferon Receptors Require TYK2 for STAT Activation. J Interferon Cytokine Res 2023; 43:414-426. [PMID: 37725008 PMCID: PMC10517332 DOI: 10.1089/jir.2023.0039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 07/10/2023] [Indexed: 09/21/2023] Open
Abstract
Type III interferons (IFN-λ) are central to host defense against viral infection of epithelial barrier surfaces. IFN-λ binding to its receptor induces a JAK-STAT cascade through kinases Janus-associated kinase 1 (JAK1) and tyrosine kinase 2 (TYK2), which are associated on either subunit of the heterodimeric type III IFN receptor. Recent studies have shown that TYK2 is not necessary for IFN-λ to signal, in contrast to IFN-α, which uses the same JAK-STAT pathway activated by the type I IFN receptor. The mechanism for this differential TYK2 requirement is unknown. Our study uses synthetic IFN receptors in TYK2-deficient U2OS epithelial cells to define the processes in type I and III IFN signaling that require TYK2. We find that TYK2 deficiency reduces signaling equally from heterodimers of either type I or III IFN receptor intracellular domains. In contrast, JAK1-associated homodimers of IFNAR2 or IFNLR1 are both fully signaling competent even in the absence of TYK2. These results suggest that heterodimerization of the type III IFN receptor is insufficient to confer TYK2-independent signaling. Thus, we propose that noncanonical receptor complexes may participate in endogenous type III IFN signaling to confer TYK2-independent signaling downstream of IFN-λ stimulation.
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Affiliation(s)
- Emily V. Mesev
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Emma G. Guare
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Alexander Ploss
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Jared E. Toettcher
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
- Omenn-Darling Bioengineering Institute, Princeton University, Princeton, New Jersey, USA
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3
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Zhang X, Wu N, Huang H, Li S, Liu S, Zhang R, Huang Y, Lyu H, Xiao S, Ali DW, Michalak M, Chen XZ, Zhou C, Tang J. Phosphorylated PTTG1 switches its subcellular distribution and promotes β-catenin stabilization and subsequent transcription activity. Oncogene 2023; 42:2439-2455. [PMID: 37400529 DOI: 10.1038/s41388-023-02767-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 06/18/2023] [Accepted: 06/26/2023] [Indexed: 07/05/2023]
Abstract
The Wnt/β-catenin signaling is usually abnormally activated in hepatocellular carcinoma (HCC), and pituitary tumor-transforming gene 1 (PTTG1) has been found to be highly expressed in HCC. However, the specific mechanism of PTTG1 pathogenesis remains poorly understood. Here, we found that PTTG1 is a bona fide β-catenin binding protein. PTTG1 positively regulates Wnt/β-catenin signaling by inhibiting the destruction complex assembly, promoting β-catenin stabilization and subsequent nuclear localization. Moreover, the subcellular distribution of PTTG1 was regulated by its phosphorylation status. Among them, PP2A induced PTTG1 dephosphorylation at Ser165/171 residues and prevented PTTG1 translocation into the nucleus, but these effects were effectively reversed by PP2A inhibitor okadaic acid (OA). Interestingly, we found that PTTG1 decreased Ser9 phosphorylation-inactivation of GSK3β by competitively binding to PP2A with GSK3β, indirectly leading to cytoplasmic β-catenin stabilization. Finally, PTTG1 was highly expressed in HCC and associated with poor patient prognosis. PTTG1 could promote the proliferative and metastasis of HCC cells. Overall, our results indicated that PTTG1 plays a crucial role in stabilizing β-catenin and facilitating its nuclear accumulation, leading to aberrant activation of Wnt/β-catenin signaling and providing a feasible therapeutic target for human HCC.
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Affiliation(s)
- Xuewen Zhang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Nianping Wu
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Huili Huang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Shi Li
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Shicheng Liu
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Rui Zhang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Yuan Huang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Hao Lyu
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Shuai Xiao
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
| | - Declan William Ali
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G2R3, Canada
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6G2R3, Canada
| | - Xing-Zhen Chen
- Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, T6G2R3, Canada
| | - Cefan Zhou
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China.
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G2R3, Canada.
| | - Jingfeng Tang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering (Ministry of Education), Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China.
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Wong GL, Manore SG, Doheny DL, Lo HW. STAT family of transcription factors in breast cancer: Pathogenesis and therapeutic opportunities and challenges. Semin Cancer Biol 2022; 86:84-106. [PMID: 35995341 PMCID: PMC9714692 DOI: 10.1016/j.semcancer.2022.08.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/08/2022] [Accepted: 08/10/2022] [Indexed: 02/07/2023]
Abstract
Breast cancer is the most commonly diagnosed cancer and second-leading cause of cancer deaths in women. Breast cancer stem cells (BCSCs) promote metastasis and therapeutic resistance contributing to tumor relapse. Through activating genes important for BCSCs, transcription factors contribute to breast cancer metastasis and therapeutic resistance, including the signal transducer and activator of transcription (STAT) family of transcription factors. The STAT family consists of six major isoforms, STAT1, STAT2, STAT3, STAT4, STAT5, and STAT6. Canonical STAT signaling is activated by the binding of an extracellular ligand to a cell-surface receptor followed by STAT phosphorylation, leading to STAT nuclear translocation and transactivation of target genes. It is important to note that STAT transcription factors exhibit diverse effects in breast cancer; some are either pro- or anti-tumorigenic while others maintain dual, context-dependent roles. Among the STAT transcription factors, STAT3 is the most widely studied STAT protein in breast cancer for its critical roles in promoting BCSCs, breast cancer cell proliferation, invasion, angiogenesis, metastasis, and immune evasion. Consequently, there have been substantial efforts in developing cancer therapeutics to target breast cancer with dysregulated STAT3 signaling. In this comprehensive review, we will summarize the diverse roles that each STAT family member plays in breast cancer pathobiology, as well as, the opportunities and challenges in pharmacologically targeting STAT proteins and their upstream activators in the context of breast cancer treatment.
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Affiliation(s)
- Grace L Wong
- Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Sara G Manore
- Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Daniel L Doheny
- Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Hui-Wen Lo
- Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, NC, USA; Breast Cancer Center of Excellence, Wake Forest University School of Medicine, Winston-Salem, NC, USA; Wake Forest Baptist Comprehensive Cancer Center, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
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5
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Manokaran G, Audsley MD, Funakoda H, David CT, Garnham KA, Rawlinson SM, Deffrasnes C, Ito N, Moseley GW. Deactivation of the antiviral state by rabies virus through targeting and accumulation of persistently phosphorylated STAT1. PLoS Pathog 2022; 18:e1010533. [PMID: 35576230 PMCID: PMC9135343 DOI: 10.1371/journal.ppat.1010533] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 05/26/2022] [Accepted: 04/19/2022] [Indexed: 12/25/2022] Open
Abstract
Antagonism of the interferon (IFN)-mediated antiviral state is critical to infection by rabies virus (RABV) and other viruses, and involves interference in the IFN induction and signaling pathways in infected cells, as well as deactivation of the antiviral state in cells previously activated by IFN. The latter is required for viral spread in the host, but the precise mechanisms involved and roles in RABV pathogenesis are poorly defined. Here, we examined the capacity of attenuated and pathogenic strains of RABV that differ only in the IFN-antagonist P protein to overcome an established antiviral state. Importantly, P protein selectively targets IFN-activated phosphorylated STAT1 (pY-STAT1), providing a molecular tool to elucidate specific roles of pY-STAT1. We find that the extended antiviral state is dependent on a low level of pY-STAT1 that appears to persist at a steady state through ongoing phosphorylation/dephosphorylation cycles, following an initial IFN-induced peak. P protein of pathogenic RABV binds and progressively accumulates pY-STAT1 in inactive cytoplasmic complexes, enabling recovery of efficient viral replication over time. Thus, P protein-pY-STAT1 interaction contributes to ‘disarming’ of the antiviral state. P protein of the attenuated RABV is defective in this respect, such that replication remains suppressed over extended periods in cells pre-activated by IFN. These data provide new insights into the nature of the antiviral state, indicating key roles for residual pY-STAT1 signaling. They also elucidate mechanisms of viral deactivation of antiviral responses, including specialized functions of P protein in selective targeting and accumulation of pY-STAT1. Following viral infection, the host activates multiple antiviral defenses. The ability of viruses to overcome these defenses is critical to disease. The earliest antiviral response involves the production of interferon messenger molecules. Interferons act on infected cells to inhibit viral proliferation, as well as on non-infected cells to establish an antiviral state before infection and so limit viral spread through the host organism. Many strategies used by viruses to overcome the former are well understood, but mechanisms important to the latter, and their importance to disease, are less well defined. In this study, we investigated how rabies virus overcomes a pre-established antiviral state in target cells. We found that the capacity to disable the antiviral state correlates with the ability to cause disease, and involves binding of a viral protein to cellular signaling proteins, which our data indicate are responsible for the maintenance of a prolonged antiviral state. This advances our understanding of antiviral responses, and identifies a key step in lethal infection by rabies virus that causes approximately 60,000 human deaths per year. The findings may contribute to new approaches for the development of vaccines or antivirals.
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Affiliation(s)
- Gayathri Manokaran
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Michelle D. Audsley
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Haruka Funakoda
- Laboratory of Zoonotic Diseases, Joint Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
| | - Cassandra T. David
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Katherine A. Garnham
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Stephen M. Rawlinson
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Celine Deffrasnes
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Naoto Ito
- Laboratory of Zoonotic Diseases, Joint Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
- * E-mail: (NI); (GWM)
| | - Gregory W. Moseley
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Melbourne, Australia
- * E-mail: (NI); (GWM)
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6
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Tanaka T, Konishi Y, Ichise H, Tsukiji S, Matsuda M, Terai K. A Dual Promoter System to Monitor IFN-γ Signaling in vivo at Single-cell Resolution. Cell Struct Funct 2021; 46:103-111. [PMID: 34744115 PMCID: PMC10511040 DOI: 10.1247/csf.21052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 10/27/2021] [Indexed: 11/11/2022] Open
Abstract
IFN-γ secreted from immune cells exerts pleiotropic effects on tumor cells, including induction of immune checkpoint and antigen presentation, growth inhibition, and apoptosis induction. We combined a dual promoter system with an IFN-γ signaling responsive promoter to generate a reporter named the interferon sensing probe (ISP), which quantitates the response to IFN-γ by means of fluorescence and bioluminescence. The integration site effect of the transgene is compensated for by the PGK promoter-driven expression of a fluorescent protein. Among five potential IFN-γ-responsive elements, we found that the interferon γ-activated sequence (GAS) exhibited the best performance. When ISP-GAS was introduced into four cell lines and subjected to IFN-γ stimulation, dose-dependency was observed with an EC50 ranging from 0.2 to 0.9 ng/mL, indicating that ISP-GAS can be generally used as a sensitive biosensor of IFN-γ response. In a syngeneic transplantation model, the ISP-GAS-expressing cancer cells exhibited bioluminescence and fluorescence signals in an IFN-γ receptor-dependent manner. Thus, ISP-GAS could be used to quantitatively monitor the IFN-γ response both in vitro and in vivo.Key words: in vivo imaging, tumor microenvironment, interferon-gamma, dual promoter system.
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Affiliation(s)
- Taisei Tanaka
- Laboratory of Bioimaging and Cell Signaling, Research Center for Dynamic Living Systems, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Yoshinobu Konishi
- Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Hiroshi Ichise
- Lymphocyte Biology Section, Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Shinya Tsukiji
- Department of Nanopharmaceutical Sciences, Nagoya Institute of Technology, Nagoya, Japan
| | - Michiyuki Matsuda
- Laboratory of Bioimaging and Cell Signaling, Research Center for Dynamic Living Systems, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto, Japan
| | - Kenta Terai
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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7
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Awasthi N, Liongue C, Ward AC. STAT proteins: a kaleidoscope of canonical and non-canonical functions in immunity and cancer. J Hematol Oncol 2021; 14:198. [PMID: 34809691 PMCID: PMC8607625 DOI: 10.1186/s13045-021-01214-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 11/09/2021] [Indexed: 12/24/2022] Open
Abstract
STAT proteins represent an important family of evolutionarily conserved transcription factors that play key roles in diverse biological processes, notably including blood and immune cell development and function. Classically, STAT proteins have been viewed as inducible activators of transcription that mediate cellular responses to extracellular signals, particularly cytokines. In this 'canonical' paradigm, latent STAT proteins become tyrosine phosphorylated following receptor activation, typically via downstream JAK proteins, facilitating their dimerization and translocation into the nucleus where they bind to specific sequences in the regulatory region of target genes to activate transcription. However, growing evidence has challenged this paradigm and identified alternate 'non-canonical' functions, such as transcriptional repression and roles outside the nucleus, with both phosphorylated and unphosphorylated STATs involved. This review provides a revised framework for understanding the diverse kaleidoscope of STAT protein functional modalities. It further discusses the implications of this framework for our understanding of STAT proteins in normal blood and immune cell biology and diseases such as cancer, and also provides an evolutionary context to place the origins of these alternative functional modalities.
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Affiliation(s)
- Nagendra Awasthi
- School of Medicine, Deakin University, Pigdons Road, Geelong, VIC, 3216, Australia.,Institue of Mental and Physical Health and Clinical Translation (IMPACT), Deakin University, Geelong, VIC, Australia
| | - Clifford Liongue
- School of Medicine, Deakin University, Pigdons Road, Geelong, VIC, 3216, Australia.,Institue of Mental and Physical Health and Clinical Translation (IMPACT), Deakin University, Geelong, VIC, Australia
| | - Alister C Ward
- School of Medicine, Deakin University, Pigdons Road, Geelong, VIC, 3216, Australia. .,Institue of Mental and Physical Health and Clinical Translation (IMPACT), Deakin University, Geelong, VIC, Australia.
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8
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Yang J, Kunimoto H, Katayama B, Zhao H, Shiromizu T, Wang L, Ozawa T, Tomonaga T, Tsuruta D, Nakajima K. Phospho-Ser727 triggers a multistep inactivation of STAT3 by rapid dissociation of pY705-SH2 through C-terminal tail modulation. Int Immunol 2020; 32:73-88. [PMID: 31555812 PMCID: PMC10689346 DOI: 10.1093/intimm/dxz061] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 09/18/2019] [Indexed: 12/21/2022] Open
Abstract
Signal transducer and activator of transcription 3 (STAT3) is involved in many biological processes, including immunity and cancer. STAT3 becomes phosphorylated at Tyr705 and Ser727 on IL-6 stimulation. Phospho-Tyr705 (pY705) stabilizes the STAT3 dimer with reciprocal interactions between pY705 and the SH2 of the other molecule and phospho-Ser727 (pS727) accelerates pY705 dephosphorylation. We study how pS727 regulates STAT3 in both structural and biological perspectives. Using STAT3 reconstituted in HepG2-stat3-knockout cells, we show that pS727, together with a handshake N-terminal domain (NTD) interaction, causes rapid inactivation of STAT3 for pY705 dephosphorylation and a chromosome region maintenance 1 (CRM1)-independent nuclear export, which is critical for faithful STAT3 response to the cellular signals. The various N-terminal tags, GFP-related Ruby and FLAG, rendered the export CRM1-dependent and especially FLAG-tag caused nuclear accumulation of STAT3, indicating the presence of conformational changes in inactivation. Impaired reactivation of STAT3 by S727A or FLAG-tag delayed or inhibited the IL-6-induced saa1 mRNA expression, respectively. The detailed analysis of the pY705-SH2 structure identified the C-terminal tail (CTT) from L706 to P715 as a key regulator of the CTT-CTT intermolecular and the CTT-SH2 intramolecular interactions that support pY705-SH2 association. The functional studies using multiple STAT3 mutants indicated that the degree of the two interactions determines the stability of pY705-SH2 interaction. Importantly, Pro715 was critical for the pS727's destabilizing activity and the known phosphorylation and acetylation at the CTT structurally inhibited the pY705-SH2 interaction. Thus, pS727 triggers pY705-SH2 dissociation by weakening the supportive interactions likely through CTT modulation, inducing rapid cycles of STAT3 activation-inactivation for proper function of STAT3.
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Affiliation(s)
- Junhao Yang
- Department of Immunology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Hiroyuki Kunimoto
- Department of Immunology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Bumpei Katayama
- Department of Dermatology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Hong Zhao
- Department of Immunology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Takashi Shiromizu
- Laboratory of Proteome Research, National Institute of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka, Japan
| | - Lingyu Wang
- Department of Immunology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Toshiyuki Ozawa
- Department of Dermatology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Takeshi Tomonaga
- Laboratory of Proteome Research, National Institute of Biomedical Innovation, Health and Nutrition, Ibaraki, Osaka, Japan
| | - Daisuke Tsuruta
- Department of Dermatology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Koichi Nakajima
- Department of Immunology, Osaka City University Graduate School of Medicine, Osaka, Japan
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9
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Nast R, Staab J, Meyer T, Lüder CGK. Toxoplasma gondii stabilises tetrameric complexes of tyrosine-phosphorylated signal transducer and activator of transcription-1 and leads to its sustained and promiscuous DNA binding. Cell Microbiol 2018; 20:e12887. [PMID: 29968354 DOI: 10.1111/cmi.12887] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 06/07/2018] [Accepted: 06/25/2018] [Indexed: 11/29/2022]
Abstract
Toxoplasma gondii is an obligate intracellular parasite that infects up to 30% of humans worldwide. It can lead to severe diseases particularly in individuals with immature or defective immune responses. Control of T. gondii relies on the IFN-γ-induced signal transducer and activator of transcription-1 (STAT1) pathway. T. gondii, however, largely inactivates STAT1-mediated gene transcription by T. gondii inhibitor of STAT1-dependent transcription (TgIST), a parasite effector protein binding to STAT1. Here, we have analysed requirements of STAT1 to bind TgIST and characterised downstream effects on STAT1 signalling. TgIST bound to STAT1 dimers but more efficiently assembled with STAT1 tetramers, which are essential for effective IFN-γ responsiveness. Such binding was abrogated in N-terminal, but not C-terminal deletion mutants of STAT1. Furthermore, TgIST did not bind to the STAT1F77A substitution mutant that cannot form STAT1 tetramers, resulting in a complete unresponsiveness of parasite-infected STAT1F77A -expressing cells to IFN-γ. Remarkably, binding of TgIST considerably increased the affinity of the aberrant STAT1 tetramers for DNA consensus sequence binding motifs and even enabled binding to nonconsensus sequences. Consistent with the increased DNA binding, STAT1 from parasite-infected cells remained phosphorylated at Tyr701 and Ser727 and was retained within the nucleus in a DNA-bound state. The sustained and promiscuous binding activity particularly of STAT1 tetramers to unspecific DNA sites lacking a consensus STAT1-binding motif is an as yet unrecognised mechanism contributing to the defective IFN-γ-mediated signalling in T. gondii-infected cells.
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Affiliation(s)
- Roswitha Nast
- Institute for Medical Microbiology, University Medical Center Goettingen, Georg-August University, Göttingen, Germany
| | - Julia Staab
- Psychosomatic Medicine and Psychotherapy, University Medical Center Goettingen, Georg-August University, Göttingen, Germany
| | - Thomas Meyer
- Psychosomatic Medicine and Psychotherapy, University Medical Center Goettingen, Georg-August University, Göttingen, Germany
| | - Carsten G K Lüder
- Institute for Medical Microbiology, University Medical Center Goettingen, Georg-August University, Göttingen, Germany
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10
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Nan Y, Wu C, Zhang YJ. Interferon Independent Non-Canonical STAT Activation and Virus Induced Inflammation. Viruses 2018; 10:v10040196. [PMID: 29662014 PMCID: PMC5923490 DOI: 10.3390/v10040196] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/07/2018] [Accepted: 04/11/2018] [Indexed: 02/06/2023] Open
Abstract
Interferons (IFNs) are a group of secreted proteins that play critical roles in antiviral immunity, antitumor activity, activation of cytotoxic T cells, and modulation of host immune responses. IFNs are cytokines, and bind receptors on cell surfaces to trigger signal transduction. The major signaling pathway activated by IFNs is the JAK/STAT (Janus kinase/signal transducer and activator of transcription) pathway, a complex pathway involved in both viral and host survival strategies. On the one hand, viruses have evolved strategies to escape from antiviral host defenses evoked by IFN-activated JAK/STAT signaling. On the other hand, viruses have also evolved to exploit the JAK/STAT pathway to evoke activation of certain STATs that somehow promote viral pathogenesis. In this review, recent progress in our understanding of the virus-induced IFN-independent STAT signaling and its potential roles in viral induced inflammation and pathogenesis are summarized in detail, and perspectives are provided.
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Affiliation(s)
- Yuchen Nan
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, China.
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine and Maryland Pathogen Research Institute, University of Maryland, College Park, MD 20742, USA.
| | - Chunyan Wu
- Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, China.
| | - Yan-Jin Zhang
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine and Maryland Pathogen Research Institute, University of Maryland, College Park, MD 20742, USA.
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Human Cytomegalovirus Utilizes a Nontraditional Signal Transducer and Activator of Transcription 1 Activation Cascade via Signaling through Epidermal Growth Factor Receptor and Integrins To Efficiently Promote the Motility, Differentiation, and Polarization of Infected Monocytes. J Virol 2017; 91:JVI.00622-17. [PMID: 29021395 DOI: 10.1128/jvi.00622-17] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 09/18/2017] [Indexed: 12/12/2022] Open
Abstract
Human cytomegalovirus (HCMV) infects peripheral blood monocytes and triggers biological changes that promote viral dissemination and persistence. We have shown that HCMV induces a proinflammatory state in infected monocytes, resulting in enhanced monocyte motility and transendothelial migration, prolonged monocyte survival, and differentiation toward a long-lived M1-like macrophage phenotype. Our data indicate that HCMV triggers these changes, in the absence of de novo viral gene expression and replication, through engagement and activation of epidermal growth factor receptor (EGFR) and integrins on the surface of monocytes. We previously identified that HCMV induces the upregulation of multiple proinflammatory gene ontologies, with the interferon-associated gene ontology exhibiting the highest percentage of upregulated genes. However, the function of the HCMV-induced interferon (IFN)-stimulated genes (ISGs) in infected monocytes remained unclear. We now show that HCMV induces the enhanced expression and activation of a key ISG transcriptional regulator, signal transducer and activator of transcription (STAT1), via an IFN-independent but EGFR- and integrin-dependent signaling pathway. Furthermore, we identified a biphasic activation of STAT1 that likely promotes two distinct phases of STAT1-mediated transcriptional activity. Moreover, our data show that STAT1 is required for efficient early HCMV-induced enhanced monocyte motility and later for HCMV-induced monocyte-to-macrophage differentiation and for the regulation of macrophage polarization, suggesting that STAT1 may serve as a molecular convergence point linking the biological changes that occur at early and later times postinfection. Taken together, our results suggest that HCMV reroutes the biphasic activation of a traditionally antiviral gene product through an EGFR- and integrin-dependent pathway in order to help promote the proviral activation and polarization of infected monocytes.IMPORTANCE HCMV promotes multiple functional changes in infected monocytes that are required for viral spread and persistence, including their enhanced motility and differentiation/polarization toward a proinflammatory M1 macrophage. We now show that HCMV utilizes the traditionally IFN-associated gene product, STAT1, to promote these changes. Our data suggest that HCMV utilizes EGFR- and integrin-dependent (but IFN-independent) signaling pathways to induce STAT1 activation, which may allow the virus to specifically dictate the biological activity of STAT1 during infection. Our data indicate that HCMV utilizes two phases of STAT1 activation, which we argue molecularly links the biological changes that occur following initial binding to those that continue to occur days to weeks following infection. Furthermore, our findings may highlight a unique mechanism for how HCMV avoids the antiviral response during infection by hijacking the function of a critical component of the IFN response pathway.
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Ganesan N, Li J, Sharma V, Jiang H, Compagnoni A. Process Simulation of Complex Biological Pathways in Physical Reactive Space and Reformulated for Massively Parallel Computing Platforms. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2016; 13:365-379. [PMID: 27045833 DOI: 10.1109/tcbb.2015.2443784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Biological systems encompass complexity that far surpasses many artificial systems. Modeling and simulation of large and complex biochemical pathways is a computationally intensive challenge. Traditional tools, such as ordinary differential equations, partial differential equations, stochastic master equations, and Gillespie type methods, are all limited either by their modeling fidelity or computational efficiency or both. In this work, we present a scalable computational framework based on modeling biochemical reactions in explicit 3D space, that is suitable for studying the behavior of large and complex biological pathways. The framework is designed to exploit parallelism and scalability offered by commodity massively parallel processors such as the graphics processing units (GPUs) and other parallel computing platforms. The reaction modeling in 3D space is aimed at enhancing the realism of the model compared to traditional modeling tools and framework. We introduce the Parallel Select algorithm that is key to breaking the sequential bottleneck limiting the performance of most other tools designed to study biochemical interactions. The algorithm is designed to be computationally tractable, handle hundreds of interacting chemical species and millions of independent agents by considering all-particle interactions within the system. We also present an implementation of the framework on the popular graphics processing units and apply it to the simulation study of JAK-STAT Signal Transduction Pathway. The computational framework will offer a deeper insight into various biological processes within the cell and help us observe key events as they unfold in space and time. This will advance the current state-of-the-art in simulation study of large scale biological systems and also enable the realistic simulation study of macro-biological cultures, where inter-cellular interactions are prevalent.
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Gao J, Wang F, Liu Y, Cai M, Xu H, Jiang J, Wang H. Revealing the cellular localization of STAT1 during the cell cycle by super-resolution imaging. Sci Rep 2015; 5:9045. [PMID: 25762114 PMCID: PMC4356954 DOI: 10.1038/srep09045] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 02/16/2015] [Indexed: 01/30/2023] Open
Abstract
Signal transducers and activators of transcription (STATs) can transduce cytokine signals and regulate gene expression. The cellular localization and nuclear trafficking of STAT1, a representative of the STAT family with multiple transcriptional functions, is tightly related with transcription process, which usually happens in the interphase of the cell cycle. However, these priority questions regarding STAT1 distribution and localization at the different cell-cycle stages remain unclear. By using direct stochastic optical reconstruction microscopy (dSTORM), we found that the nuclear expression level of STAT1 increased gradually as the cell cycle carried out, especially after EGF stimulation. Furthermore, STAT1 formed clusters in the whole cell during the cell cycle, with the size and the number of clusters also increasing significantly from G1 to G2 phase, suggesting that transcription and other cell-cycle related activities can promote STAT1 to form more and larger clusters for fast response to signals. Our work reveals that the cellular localization and clustering distribution of STAT1 are associated with the cell cycle, and further provides an insight into the mechanism of cell-cycle regulated STAT1 signal transduction.
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Affiliation(s)
- Jing Gao
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Feng Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
| | - Yanhou Liu
- Institute of Immunology, The First Bethune Hospital Academy of Translational Medicine, Jilin University, Changchun, Jilin, China
| | - Mingjun Cai
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
| | - Haijiao Xu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
| | - Junguang Jiang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
| | - Hongda Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
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14
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Reich NC. STATs get their move on. JAKSTAT 2013; 2:e27080. [PMID: 24470978 PMCID: PMC3891633 DOI: 10.4161/jkst.27080] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 11/01/2013] [Accepted: 11/04/2013] [Indexed: 12/18/2022] Open
Abstract
Understanding the mechanisms that regulate dynamic localization of a protein within a cell can provide critical insight to its functional molecular interactions. Signal transducers and activators of transcription (STATs) play essential roles in development, proliferation, and immune defense. However the consequences of STAT hyperactivity can predispose to diseases including autoimmunity and cancer. To function as transcription factors STATs must gain access to the nucleus, and knowledge of the mechanisms that regulate STAT nuclear trafficking can provide a means to control STAT action. This review presents a synopsis of some of the studies that address the nuclear dynamics of the STAT proteins. Evidence suggests that not all STATs are the same. Nuclear import of STAT1 and STAT4 appears linked to their tyrosine phosphorylation and the formation of parallel dimers via reciprocal phosphotyrosine and Src homology 2 domain interactions. This dimer arrangement generates a conformational nuclear localization signal. STAT2 is imported continually to the nucleus in an unphosphorylated state due to its association with IRF9, but the dominant nuclear export signal of STAT2 shuttles the complex back to the cytoplasm. Following STAT2 tyrosine phosphorylation, it can form dimers with STAT1 to affect nuclear import as the trimeric complex (ISGF3). Distinctly, STAT3, STAT5, and STAT6 are continually imported to the nucleus independent of tyrosine phosphorylation. Mutational studies indicate the nuclear localization signals in these STATs require the conformational structure of their coiled-coil domains. Increases in STAT nuclear accumulation following cytokine stimulation appear coordinate with their ability to bind DNA.
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Affiliation(s)
- Nancy C Reich
- Department of Molecular Genetics and Microbiology; Stony Brook University; Stony Brook, NY USA
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15
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Dittrich A, Siewert E, Schaper F. Determination of protein turnover rates in the JAK/STAT pathway using a radioactive pulse-chase approach. Methods Mol Biol 2013; 967:69-80. [PMID: 23296722 DOI: 10.1007/978-1-62703-242-1_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The turnover rate of different protein species in a signal transduction network strongly affects the impact of the given species on the outcome of a stimulus. Whereas stable, long-lived proteins mainly account for the transmission of a signal, unstable short-lived species often comprise regulatory functions. Here, we describe a method to determine the half-lives of proteins of the JAK/STAT pathway by a pulse-chase approach in cell culture. First, radioactive labeling with (35)S-methionine is carried out to label newly synthesized proteins (pulse). Subsequently, the dynamics of the decay of these proteins is monitored in the absence of labeled amino acids over a defined time period (chase). For this purpose the protein of interest is isolated by immunoprecipitation from total cell lysates, separated on an SDS-polyacrylamide gel, and subsequently visualized by autoradiography.
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Affiliation(s)
- Anna Dittrich
- Department of Systems Biology, Institute of Biology, Otto-von-Guericke-University, Magdeburg, Germany
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16
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Qi YF, Huang YX, Wang HY, Zhang Y, Bao YL, Sun LG, Wu Y, Yu CL, Song ZB, Zheng LH, Sun Y, Wang GN, Li YX. Elucidating the crosstalk mechanism between IFN-gamma and IL-6 via mathematical modelling. BMC Bioinformatics 2013; 14:41. [PMID: 23384097 PMCID: PMC3599299 DOI: 10.1186/1471-2105-14-41] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 02/03/2013] [Indexed: 11/10/2022] Open
Abstract
Background Interferon-gamma (IFN-gamma) and interleukin-6 (IL-6) are multifunctional cytokines that regulate immune responses, cell proliferation, and tumour development and progression, which frequently have functionally opposing roles. The cellular responses to both cytokines are activated via the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. During the past 10 years, the crosstalk mechanism between the IFN-gamma and IL-6 pathways has been studied widely and several biological hypotheses have been proposed, but the kinetics and detailed crosstalk mechanism remain unclear. Results Using established mathematical models and new experimental observations of the crosstalk between the IFN-gamma and IL-6 pathways, we constructed a new crosstalk model that considers three possible crosstalk levels: (1) the competition between STAT1 and STAT3 for common receptor docking sites; (2) the mutual negative regulation between SOCS1 and SOCS3; and (3) the negative regulatory effects of the formation of STAT1/3 heterodimers. A number of simulations were tested to explore the consequences of cross-regulation between the two pathways. The simulation results agreed well with the experimental data, thereby demonstrating the effectiveness and correctness of the model. Conclusion In this study, we developed a crosstalk model of the IFN-gamma and IL-6 pathways to theoretically investigate their cross-regulation mechanism. The simulation experiments showed the importance of the three crosstalk levels between the two pathways. In particular, the unbalanced competition between STAT1 and STAT3 for IFNR and gp130 led to preferential activation of IFN-gamma and IL-6, while at the same time the formation of STAT1/3 heterodimers enhanced preferential signal transduction by sequestering a fraction of the activated STATs. The model provided a good explanation of the experimental observations and provided insights that may inform further research to facilitate a better understanding of the cross-regulation mechanism between the two pathways.
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Affiliation(s)
- Yun-feng Qi
- National Engineering Laboratory for Druggable Gene and Protein Screening, Northeast Normal University, Changchun 130024, China
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Cimica V, Reich NC. Nuclear trafficking of STAT proteins visualized by live cell imaging. Methods Mol Biol 2013; 967:189-202. [PMID: 23296731 DOI: 10.1007/978-1-62703-242-1_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The ability to observe the dynamic localization of a protein in living cells can provide critical insight to its mode of action and functional molecular interactions. To this purpose, green fluorescent protein (GFP) has served as a powerful tool to tag STAT proteins for microscopic visualization. Live cell imaging with STAT-GFP proteins has contributed to our understanding of signal transduction and the complexities of nuclear transport of STAT proteins. In this report we summarize recent approaches that use GFP-based techniques with live cell imaging to study the mechanisms of STAT nuclear import and export: photoactivation, fluorescence recovery after photobleaching (FRAP), and fluorescence loss in photobleaching (FLIP).
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Affiliation(s)
- Velasco Cimica
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
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18
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Han F, Fan L, Wang X, Li W. Sulforhodamine B restaining as a whole-cell label allows visualizing one more fluorochrome and its application in assaying protein nucleocytoplasmic distribution. Cytometry A 2012; 81:532-40. [DOI: 10.1002/cyto.a.22057] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 03/03/2012] [Accepted: 03/28/2012] [Indexed: 11/10/2022]
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19
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Han F, Liang P, Wang F, Zeng L, Zhang B. Automated analysis of time-lapse imaging of nuclear translocation by retrospective strategy and its application to STAT1 in HeLa cells. PLoS One 2011; 6:e27454. [PMID: 22125613 PMCID: PMC3220678 DOI: 10.1371/journal.pone.0027454] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 10/17/2011] [Indexed: 11/19/2022] Open
Abstract
Cell-based image analysis of time-lapse imaging is mainly challenged by faint fluorescence and dim boundaries of cellular structures of interest. To resolve these bottlenecks, a novel method was developed based on “retrospective” analysis for cells undergoing minor morphological changes during time-lapse imaging. We fixed and stained the cells with a nuclear dye at the end of the experiment, and processed the time-lapse images using the binary masks obtained by segmenting the nuclear-stained image. This automated method also identifies cells that move during the time-lapse imaging, which is a factor that could influence the kinetics measured for target proteins that are present mostly in the cytoplasm. We then validated the method by measuring interferon gamma (IFNγ) induced signal transducers and activators of transcription 1 (STAT1) nuclear translocation in living HeLa cells. For the first time, automated large-scale analysis of nuclear translocation in living cells was achieved by our novel method. The responses of the cells to IFNγ exhibited a significant drift across the population, but common features of the responses led us to propose a three-stage model of STAT1 import. The simplicity and automation of this method should enable its application in a broad spectrum of time-lapse studies of nuclear-cytoplasmic translocation.
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Affiliation(s)
- Fujun Han
- Laboratory for RNA Chemical Biology, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, People's Republic of China
- Department of Otorhinolaryngology, People's Liberation Army No. 458 Hospital, Guangzhou, China
- School of Biochemistry, Medical Sciences, University Walk, Bristol, United Kingdom
- * E-mail: (FH); (BZ)
| | - Peizhou Liang
- Laboratory for RNA Chemical Biology, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Feifei Wang
- Laboratory for RNA Chemical Biology, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Lingyun Zeng
- Department of Neuroendocrine, People's Liberation Army No. 458 Hospital, Guangzhou, China
| | - Biliang Zhang
- Laboratory for RNA Chemical Biology, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, People's Republic of China
- State Key Laboratory of Respiratory Diseases, Guangzhou Institute of Respiratory Diseases, Guangzhou, China
- * E-mail: (FH); (BZ)
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Datta S, Hazari S, Chandra PK, Samara M, Poat B, Gunduz F, Wimley WC, Hauser H, Koster M, Lamaze C, Balart LA, Garry RF, Dash S. Mechanism of HCV's resistance to IFN-α in cell culture involves expression of functional IFN-α receptor 1. Virol J 2011; 8:351. [PMID: 21756311 PMCID: PMC3156775 DOI: 10.1186/1743-422x-8-351] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 07/14/2011] [Indexed: 01/12/2023] Open
Abstract
The mechanisms underlying the Hepatitis C virus (HCV) resistance to interferon alpha (IFN-α) are not fully understood. We used IFN-α resistant HCV replicon cell lines and an infectious HCV cell culture system to elucidate the mechanisms of IFN-α resistance in cell culture. The IFN-α resistance mechanism of the replicon cells were addressed by a complementation study that utilized the full-length plasmid clones of IFN-α receptor 1 (IFNAR1), IFN-α receptor 2 (IFNAR2), Jak1, Tyk2, Stat1, Stat2 and the ISRE- luciferase reporter plasmid. We demonstrated that the expression of the full-length IFNAR1 clone alone restored the defective Jak-Stat signaling as well as Stat1, Stat2 and Stat3 phosphorylation, nuclear translocation and antiviral response against HCV in all IFN-α resistant cell lines (R-15, R-17 and R-24) used in this study. Moreover RT-PCR, Southern blotting and DNA sequence analysis revealed that the cells from both R-15 and R-24 series of IFN-α resistant cells have 58 amino acid deletions in the extracellular sub domain 1 (SD1) of IFNAR1. In addition, cells from the R-17 series have 50 amino acids deletion in the sub domain 4 (SD4) of IFNAR1 protein leading to impaired activation of Tyk2 kinase. Using an infectious HCV cell culture model we show here that viral replication in the infected Huh-7 cells is relatively resistant to exogenous IFN-α. HCV infection itself induces defective Jak-Stat signaling and impairs Stat1 and Stat2 phosphorylation by down regulation of the cell surface expression of IFNAR1 through the endoplasmic reticulum (ER) stress mechanisms. The results of this study suggest that expression of cell surface IFNAR1 is critical for the response of HCV to exogenous IFN-α.
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Affiliation(s)
- Sibnarayan Datta
- Department of Pathology and Laboratory Medicine, Tulane University Health Sciences Center, New Orleans, LA, USA
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Meyer T, Vinkemeier U. Assessing sequence-specific DNA binding and transcriptional activity of STAT1 transcription factor. Methods Mol Biol 2010; 647:139-59. [PMID: 20694665 DOI: 10.1007/978-1-60761-738-9_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Continuous nucleocytoplasmic shuttling of signal transducer and activator of transcription (STAT) proteins is a key to understand their function as cytokine-responsive transcription factors. STATs enter the nucleus both by carrier-dependent and carrier-independent transport pathways, and it was previously shown that STAT1 exits the nucleus only after its prior enzymatic dephosphorylation by nuclear phosphatases. The identification of different transport pathways for unphosphorylated and tyrosine-phosphorylated STAT dimers was made possible by a combination of a diverse set of experimental approaches in the field of molecular biology. In the following, we will summarize some of the techniques that have been successfully used to decipher molecular mechanisms engaged in STAT1 dynamics.
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Affiliation(s)
- Thomas Meyer
- Department of Cardiology, University of Marburg, Baldingerstrasse, Marburg, Germany
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22
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Poat B, Hazari S, Chandra PK, Gunduz F, Alvarez X, Balart LA, Garry RF, Dash S. Intracellular expression of IRF9 Stat fusion protein overcomes the defective Jak-Stat signaling and inhibits HCV RNA replication. Virol J 2010; 7:265. [PMID: 20939906 PMCID: PMC2964675 DOI: 10.1186/1743-422x-7-265] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2010] [Accepted: 10/12/2010] [Indexed: 01/05/2023] Open
Abstract
Interferon alpha (IFN-α) binds to a cell surface receptor that activates the Jak-Stat signaling pathway. A critical component of this pathway is the translocation of interferon stimulated gene factor 3 (a complex of three proteins Stat1, Stat2 and IRF9) to the nucleus to activate antiviral genes. A stable sub-genomic replicon cell line resistant to IFN-α was developed in which the nuclear translocation of Stat1 and Stat2 proteins was prevented due to the lack of phosphorylation; whereas the nuclear translocation of IRF9 protein was not affected. In this study, we sought to overcome defective Jak-Stat signaling and to induce an antiviral state in the IFN-α resistant replicon cell line by developing a chimera IRF9 protein fused with the trans activating domain (TAD) of either a Stat1 (IRF9-S1C) or Stat2 (IRF9-S2C) protein. We show here that intracellular expression of fusion proteins using the plasmid constructs of either IRF9-S1C or IRF9-S2C, in the IFN-α resistant cells, resulted in an increase in Interferon Stimulated Response Element (ISRE) luciferase promoter activity and significantly induced HLA-1 surface expression. Moreover, we show that transient transfection of IRF9-S1C or IRF9-S2C plasmid constructs into IFN-α resistant replicon cells containing sub-genomic HCV1b and HCV2a viruses resulted in an inhibition of viral replication and viral protein expression independent of IFN-α treatment. The results of this study indicate that the recombinant fusion proteins of IRF9-S1C, IRF9-S2C alone, or in combination, have potent antiviral properties against the HCV in an IFN-α resistant cell line with a defective Jak-Stat signaling.
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Affiliation(s)
- Bret Poat
- Department of Pathology and Laboratory Medicine, Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA-70112, USA
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Finley SD, Gupta D, Cheng N, Klinke DJ. Inferring relevant control mechanisms for interleukin-12 signaling in naïve CD4+ T cells. Immunol Cell Biol 2010; 89:100-10. [PMID: 20479776 DOI: 10.1038/icb.2010.69] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Interleukin-12 (IL-12) is a key cytokine involved in shaping the cell-mediated immunity to intracellular pathogens. IL-12 initiates a cellular response through the IL-12 signaling pathway, a member of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) family of signaling networks. The JAK/STAT pathway includes several regulatory elements; however, the dynamics of these mechanisms are not fully understood. Therefore, the objective of this study was to infer the relative importance of regulatory mechanisms that modulate the activation of STAT4 in naïve CD4(+) T cells. Dynamic changes in protein expression and activity were measured using flow cytometry and these data were used to calibrate a mathematical model of IL-12 signaling. An empirical Bayesian approach was used to infer the relative strengths of the different regulatory mechanisms in the system. The model predicted that IL-12 receptor expression is regulated by a dynamic, autonomous program that was independent of STAT4 activation. In summary, a mathematical model of the canonical IL-12 signaling pathway used in conjunction with a Bayesian framework provided high-confidence predictions of the system-specific control mechanisms from the available experimental observations.
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Affiliation(s)
- Stacey D Finley
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA
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Abstract
To support and guide an extensive experimental research into systems biology of signaling pathways, increasingly more mechanistic models are being developed with hopes of gaining further insight into biological processes. In order to analyze these models, computational and statistical techniques are needed to estimate the unknown kinetic parameters. This chapter reviews methods from frequentist and Bayesian statistics for estimation of parameters and for choosing which model is best for modeling the underlying system. Approximate Bayesian computation techniques are introduced and employed to explore different hypothesis about the JAK-STAT signaling pathway.
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Toni T, Stumpf MPH. Simulation-based model selection for dynamical systems in systems and population biology. ACTA ACUST UNITED AC 2009; 26:104-10. [PMID: 19880371 PMCID: PMC2796821 DOI: 10.1093/bioinformatics/btp619] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
MOTIVATION Computer simulations have become an important tool across the biomedical sciences and beyond. For many important problems several different models or hypotheses exist and choosing which one best describes reality or observed data is not straightforward. We therefore require suitable statistical tools that allow us to choose rationally between different mechanistic models of, e.g. signal transduction or gene regulation networks. This is particularly challenging in systems biology where only a small number of molecular species can be assayed at any given time and all measurements are subject to measurement uncertainty. RESULTS Here, we develop such a model selection framework based on approximate Bayesian computation and employing sequential Monte Carlo sampling. We show that our approach can be applied across a wide range of biological scenarios, and we illustrate its use on real data describing influenza dynamics and the JAK-STAT signalling pathway. Bayesian model selection strikes a balance between the complexity of the simulation models and their ability to describe observed data. The present approach enables us to employ the whole formal apparatus to any system that can be (efficiently) simulated, even when exact likelihoods are computationally intractable.
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Affiliation(s)
- Tina Toni
- Division of Molecular Biosciences, Imperial College London, Wolfson Building, SW72AZ London, UK.
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Han F, Luo Y, Ge N, Xu J. Construction of fluorescence resonance energy transfer vectors and their application in study of structure and function of signal transducers and activators of transcription 1. Acta Biochim Biophys Sin (Shanghai) 2008; 40:934-42. [PMID: 18989574 DOI: 10.1111/j.1745-7270.2008.00480.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Protein-protein interactions have been studied extensively by green fluorescent protein-based fluorescence resonance energy transfer (FRET). The fluorescent proteins (FP) can be fused either to the N- or C-terminus of a host protein, but it is difficult to predict which order will perturb the host protein the least and provide the largest FRET. Therefore, a researcher needs to fuse host proteins with FP at both the N- and C-termini and test every possible combination (N-N, N-C, or C-C) to promote the energy transfer efficiency. Consequently, researchers required to do many subclonings. Herein, we designed FRET vectors to make them more efficient. The expression vectors of pCFP-YFP and pYFP-CFP were constructed with both cyan fluorescent protein (CFP)-yellow fluorescent protein (YFP) and YFP-CFP coding sequences flanked by two restriction enzyme sites, and with multiple cloning regions in the middle of both coding sequences. To select an optimal combination for FRET detection, we created plasmids encoding various fusion proteins of FP and signal transducers and activators of transcription 1 (STAT1) . We found that the nuclear:cytoplasmic fluorescence intensity ratios of STAT1-FP were significantly higher than those of FP-STAT1 at steady state, and fluorescence redistribution was only observed for STAT1-FP upon interferon gamma (IFNgamma) stimulation. In addition, positive FRET signals were only detected in the C-C interactions of STAT1 homodimer. Taken together, these data indicate that fusing STAT1 at the N-terminus with FP impairs the interactions of unphosphorylated STAT1 homodimers and possibly diminishes its binding with DNA. In contrast, STAT1-FP was functional with respect to its activation. Moreover, the FRET vectors are able to facilitate FRET studies.
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Affiliation(s)
- Fujun Han
- Guangzhou Medical College, Guangzhou Institute of Respiratory Diseases, Guangzhou 510120, China
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27
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Krejci P, Prochazkova J, Bryja V, Jelinkova P, Pejchalova K, Kozubik A, Thompson LM, Wilcox WR. Fibroblast growth factor inhibits interferon gamma-STAT1 and interleukin 6-STAT3 signaling in chondrocytes. Cell Signal 2008; 21:151-60. [PMID: 18950705 DOI: 10.1016/j.cellsig.2008.10.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 09/24/2008] [Accepted: 10/08/2008] [Indexed: 01/10/2023]
Abstract
Activation of fibroblast growth factor receptor 3 (FGFR3) leads to attenuation of cartilage growth. The members of the STAT family of transcription factors are believed to participate in FGFR3 signaling in cartilage, however the molecular mechanism of this action is poorly understood. Here, we demonstrate that a chronic FGF stimulus leads to accumulation of STAT1, 3, 5 and 6, evident in both in vitro chondrocyte model and murine limb explant cultures. Despite the accumulation, both endogenous and cytokine-induced activation of STAT1 and STAT3 is impaired by FGF, as demonstrated by imaging of active STAT nuclear translocation and analyses of STAT activatory phosphorylation and transcriptional activation. Further, we demonstrate that FGF induces expression of CIS, SOCS1 and SOCS3 inhibitors of gp130, a common receptor for the IL6-family of cytokines. Since cytokine-gp130 signaling represents an important positive regulator of cartilage, its inhibition may contribute to the growth-inhibitory effect of FGFR3 in cartilage.
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Affiliation(s)
- Pavel Krejci
- Institute of Experimental Biology, Masaryk University, 61137 Brno, Czech Republic.
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28
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Abstract
Signalling in multicellular organisms is mediated by complex networks that integrate extracellular and intracellular signals to generate appropriate responses regulating cell proliferation, differentiation and survival. Downstream of many cytokine and growth hormone receptors, receptor-associated JAKs (Janus kinases) activate transcription factors of the STAT (signal transducer and activator of transcription) protein family and thereby mediate signal transduction from the plasma membrane to the nucleus. The JAK/STAT pathway has been shown to be constitutively activated in a wide array of human malignancies. To elucidate mechanisms contributing to tumour formation and identify system properties of the JAK/STAT signalling pathway, a systems biology approach can be employed. So far the majority of studies available have focused on down-regulation of the signalling pathway based on simulations. However, a data-based model of the core module of the JAK2/STAT5 signalling pathway showed that rapid nucleocytoplasmic cycling of STAT5 is an essential pathway property. In the future, combining assays for quantitative analysis at different levels will be important to gain deeper insight into molecular mechanisms regulating intracellular communication mediated by such complex dynamic systems as signalling pathways and their targets.
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Krejci P, Salazar L, Goodridge HS, Kashiwada TA, Schibler MJ, Jelinkova P, Thompson LM, Wilcox WR. STAT1 and STAT3 do not participate in FGF-mediated growth arrest in chondrocytes. J Cell Sci 2008; 121:272-81. [DOI: 10.1242/jcs.017160] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Activating mutations in fibroblast growth factor receptor 3 (FGFR3) cause several human skeletal dysplasias as a result of attenuation of cartilage growth. It is believed that FGFR3 inhibits chondrocyte proliferation via activation of signal transducers and activators of transcription (STAT) proteins, although the exact mechanism of both STAT activation and STAT-mediated inhibition of chondrocyte growth is unclear. We show that FGFR3 interacts with STAT1 in cells and is capable of activating phosphorylation of STAT1 in a kinase assay, thus potentially serving as a STAT1 kinase in chondrocytes. However, as demonstrated by western blotting with phosphorylation-specific antibodies, imaging of STAT nuclear translocation, STAT transcription factor assays and STAT luciferase reporter assays, FGF does not activate STAT1 or STAT3 in RCS chondrocytes, which nevertheless respond to a FGF stimulus with potent growth arrest. Moreover, addition of active STAT1 and STAT3 to the FGF signal, by means of cytokine treatment, SRC-mediated STAT activation or expression of constitutively active STAT mutants does not sensitize RCS chondrocytes to FGF-mediated growth arrest. Since FGF-mediated growth arrest is rescued by siRNA-mediated downregulation of the MAP kinase ERK1/2 but not STAT1 or STAT3, our data support a model whereby the ERK arm but not STAT arm of FGF signaling in chondrocytes accounts for the growth arrest phenotype.
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Affiliation(s)
- Pavel Krejci
- Institute of Experimental Biology, Masaryk University, 61137 Brno, Czech Republic
- Department of Cytokinetics, Institute of Biophysics ASCR, 61265 Brno, Czech Republic
| | - Lisa Salazar
- Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92697, USA
| | - Helen S. Goodridge
- Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Tamara A. Kashiwada
- Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92697, USA
| | - Matthew J. Schibler
- Brain Research Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Petra Jelinkova
- Institute of Experimental Biology, Masaryk University, 61137 Brno, Czech Republic
| | - Leslie Michels Thompson
- Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92697, USA
| | - William R. Wilcox
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
- Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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30
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Abstract
The ability of transcription factors to gain entrance to the nucleus is critical to their role in gene expression. Signal transducers and activators of transcription (STATs) are latent DNA binding factors activated by specific tyrosine phosphorylation. There are seven mammalian STAT genes encoding proteins that display constitutive nuclear localization and/or conditional nuclear localization. This review will focus on STAT1 and STAT2 that are activated in response to interferon and exhibit conditional nuclear localization. The dynamic redistribution of STAT1 and STAT2 between the cytoplasm and the nucleus is coordinate with their gain of ability to bind DNA.
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Affiliation(s)
- Nancy C Reich
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794-5222, United States.
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31
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Meyer T, Begitt A, Vinkemeier U. Green fluorescent protein-tagging reduces the nucleocytoplasmic shuttling specifically of unphosphorylated STAT1. FEBS J 2007; 274:815-26. [PMID: 17288561 DOI: 10.1111/j.1742-4658.2006.05626.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) and related techniques using green fluorescent protein (GFP)-tagged proteins are widely used to study the subcellular trafficking of proteins. It was concluded from these experiments that the cytokine-induced nuclear import of tyrosine-phosphorylated (activated) signal transducer and activator of transcription 1 (STAT1) was rapid, while the constitutive shuttling of unphosphorylated STAT1 was determined to be inefficient. However, unrelated experiments came to different conclusions concerning the constitutive translocation of STAT1. Because these discrepancies have not been resolved, it remained unclear whether or not unphosphorylated STAT1 is a relevant regulator of cytokine-dependent gene expression. This study was initiated to examine the influence of GFP-tagging on the nucleocytoplasmic shuttling of phosphorylated and unphosphorylated STAT1. In accordance with previous findings our results confirm the undisturbed rapid nuclear import of GFP-tagged activated STAT1. However, we reveal an inhibitory influence of GFP specifically on the constitutive nucleocytoplasmic cycling of the unphosphorylated protein. The decreased shuttling of unphosphorylated STAT1-GFP significantly reduced the activation level while nuclear accumulation was prolonged. Importantly, despite unimpaired nuclear import of activated STAT1 the transcription of a STAT1-dependent reporter gene was more than halved after GFP-tagging, which could be linked directly to reduced nucleocytoplasmic shuttling. In conclusion, it is demonstrated that GFP-based techniques considerably underestimate the actual shuttling rate of unphosphorylated native STAT1. The results confirm that the activation of STAT1 and hence its transcriptional activity is proportional to the nucleocytoplasmic shuttling rate of the unphosphorylated protein. Moreover, our data indicate that GFP-tagging may differently affect the mechanistically distinct translocation pathways of a shuttling protein.
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Affiliation(s)
- Thomas Meyer
- Abteilung Psychosomatische Medizin und Psychotherapie, Philipps-Universität Marburg, Germany
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32
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Chen W, Khurana Hershey GK. Signal transducer and activator of transcription signals in allergic disease. J Allergy Clin Immunol 2007; 119:529-41; quiz 542-3. [PMID: 17336608 DOI: 10.1016/j.jaci.2007.01.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2006] [Revised: 01/03/2007] [Accepted: 01/05/2007] [Indexed: 01/05/2023]
Abstract
Signal transducer and activator of transcription (STAT) proteins are a group of transcription factors that transmit signals from the extracellular milieu of cells to the nucleus. They are crucial for the signaling of many cytokines that are mediators of allergic inflammation and impact various cell types critical to allergy including epithelial cells, mast cells, lymphocytes, dendritic cells, and eosinophils. Dysregulation of STAT signaling has been implicated in allergic disease, highlighting the importance of these ubiquitous molecules in allergic inflammation and the potential of these pathways as a target for therapeutic intervention. This review will summarize the current understanding of the roles of STAT signaling in allergic disease and the potential of targeting STATs for the treatment of allergic disorders, emphasizing recent observations.
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Affiliation(s)
- Weiguo Chen
- Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
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33
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Marq JB, Brini A, Kolakofsky D, Garcin D. Targeting of the Sendai virus C protein to the plasma membrane via a peptide-only membrane anchor. J Virol 2007; 81:3187-97. [PMID: 17229713 PMCID: PMC1866060 DOI: 10.1128/jvi.02465-06] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Several cellular proteins are synthesized in the cytosol on free ribosomes and then associate with membranes due to the presence of short peptide sequences. These membrane-targeting sequences contain sites to which lipid chains are attached, which help direct the protein to a particular membrane domain and anchor it firmly in the bilayer. The intracellular concentration of these proteins in particular cellular compartments, where their interacting partners are also concentrated, is essential to their function. This paper reports that the apparently unmodified N-terminal sequence of the Sendai virus C protein (MPSFLKKILKLRGRR . . .; letters in italics represent hydrophobic residues; underlined letters represent basic residues, which has a strong propensity to form an amphipathic alpha-helix in a hydrophobic environment) also function as a membrane targeting signal and membrane anchor. Moreover, the intracellular localization of the C protein at the plasma membrane is essential for inducing the interferon-independent phosphorylation of Stat1 as part of the viral program to prevent the cellular antiviral response.
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Affiliation(s)
- Jean-Baptiste Marq
- Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, 11 Ave de Champel, CH-1211 Geneva, Switzerland
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34
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Abstract
Accurate cellular localization is crucial for the effective function of most signalling molecules and nuclear translocation is central to the function of transcription factors. The passage of large molecules between the cytoplasm and nucleus is restricted, and this restriction affords a mechanism to regulate transcription by controlling the access of transcription factors to the nucleus. In this Review, we focus on the signal transducer and activator of transcription (STAT) family of transcription factors. The regulation of the nuclear trafficking of STAT-family members is diverse. Some STAT proteins constitutively shuttle between the nucleus and cytoplasm, whereas others require tyrosine phosphorylation for nuclear localization. In either case, the regulation of nuclear trafficking can provide a target for therapeutic intervention.
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Affiliation(s)
- Nancy C Reich
- Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11777, USA.
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35
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Lang C, Algner M, Beinert N, Gross U, Lüder CGK. Diverse mechanisms employed by Toxoplasma gondii to inhibit IFN-gamma-induced major histocompatibility complex class II gene expression. Microbes Infect 2006; 8:1994-2005. [PMID: 16824778 DOI: 10.1016/j.micinf.2006.02.031] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Revised: 02/14/2006] [Accepted: 02/24/2006] [Indexed: 10/24/2022]
Abstract
The intracellular parasite Toxoplasma gondii is able to establish persistent infections in immunocompetent hosts and this may be facilitated by different immune evasion mechanisms. In the present study, we describe that infection of murine monocyte/macrophage RAW 264.7 cells with T. gondii blocks the IFN-gamma-induced upregulation of major histocompatibility complex (MHC) class II mRNAs and proteins. Heat inactivation of the parasites prior to host cell invasion, but not inhibition of the intracellular replication of T. gondii abolished the inhibition of MHC class II upregulation. Interestingly, a T. gondii lysate (TL) mimicked the inhibitory effect of viable parasites on MHC class II expression. Nuclear translocation of the signal transducer and activator of transcription in response to IFN-gamma were normal both in cells incubated with TL or infected with viable parasites. Transcript levels of the class II transactivator and consequently H2-Ab were nevertheless diminished by both viable parasites and TL. In contrast, interferon regulatory factor-1 mRNA was only decreased in response to viable T. gondii. Luciferase reporter assays confirmed differential effects of viable parasites and TL on minimal or complex IFN-gamma-responsive promoters. Furthermore, only TL, and not viable parasites, strongly induced the secretion of IL-10 by murine macrophages. Whereas TL also inhibited MHC class II expression in macrophages from IL-10-deficient mice, increased IL-10 secretion by wild type macrophages did not mediate the block in MHC class II upregulation. In conclusion, T. gondii employs different mechanisms to inhibit MHC class II expression, suggesting a complex regulation of this immune evasion strategy.
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Affiliation(s)
- Christine Lang
- Institute for Medical Microbiology, Georg-August-University, Kreuzbergring 57, D-37075 Goettingen, Germany
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36
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Frahm T, Hauser H, Köster M. IFN-type-I-mediated signaling is regulated by modulation of STAT2 nuclear export. J Cell Sci 2006; 119:1092-104. [PMID: 16507591 DOI: 10.1242/jcs.02822] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Signaling through the IFN type I receptor is mediated by assembly of the ISGF3 complex consisting of STAT1, STAT2 and IRF9. Whereas STAT1 is instrumentalized by many cytokines, STAT2 is specifically used by type I IFNs. Here, we report that the main regulatory mechanism of nuclear accumulation of STAT2 is nuclear export. We determined the kinetics of nucleocytoplasmic shuttling of STAT2 in living cells. In the absence of IFN, a virtually exclusive cytoplasmic localisation of STAT2 can be detected. Nevertheless, STAT2 is permanently and rapidly shuttling between the cytoplasm and the nucleus. The steady-state localization is explained by a very efficient nuclear export. Our studies indicate that at least two pathways (one of which is CRM1-dependent, the other not yet identified) are responsible for clearing the nucleus from STAT2. The constitutive nucleocytoplasmic shuttling of STAT2 does neither depend on the presence of IRF9 or STAT1, nor does it require tyrosine phosphorylation. Upon treatment with IFN type I, nuclear export of STAT2 is completely abolished in cells used within this study, whereas nuclear import is functioning. This explains the observed nuclear accumulation of STAT2. We have identified a region in the C-terminus of STAT2 that is essential for its almost exclusively cytoplasmic localization in the absence of IFN and responsible for CRM1-specific export. In comparative studies we show that nucleocytoplasmic shuttling of STAT2 is significantly different from that of STAT1. STAT1 is also shuttling in the absence of IFN, but the exchange rate in unstimulated cells is more than ten times lower. We further show that the latent STAT2 protein has stronger intrinsic nuclear-export activity than STAT1. Together, these observations lead to a model for IFN-type-I-induction in which the receptor-mediated heterodimerization overcomes the slow nuclear import of STAT1 and blocks the strong STAT2 export activity that leads to the accumulation of both signal transducers in the nucleus.
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Affiliation(s)
- Thomas Frahm
- Department of Gene Regulation and Differentiation, GBF--German Research Centre for Biotechnology, Mascheroder Weg 1, 38124 Braunschweig, Germany
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37
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Krause CD, He W, Kotenko S, Pestka S. Modulation of the activation of Stat1 by the interferon-gamma receptor complex. Cell Res 2006; 16:113-23. [PMID: 16467883 DOI: 10.1038/sj.cr.7310015] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The activation of Stat1 by the interferon-gamma (IFN-gamma) receptor complex is responsible for the transcription of a significant portion of IFN-gamma induced genes. Many of these genes are responsible for the induction of an apoptotic state in response to IFN-gamma. In the absence of Stat1 activation, IFN-gamma instead induces a proliferative response. Modifying Stat1 activation by IFN-gamma may have pharmacological benefits. We report that the rate of activation of Stat1 can be altered in HeLa cells by overexpressing either the IFN-gammaR1 chain or the IFN-gammaR2 chain. These alterations occur in hematopoietic cell lines: Raji cells and monocytic cell lines, which have average and above-average IFN-gammaR2 surface expression, activate Stat1 similarly to HeLa cells and HeLa cells overexpressing IFNgammaR2, respectively. The rapid Stat1 activation seen in HeLa cells can be inhibited by overexpressing a chimeric IFN-gammaR2 chain that does not bind Jak2 or (when high concentrations of IFN-gamma are used) by overexpressing IFN-gammaR1. These data are consistent with a model in which the recruitment of additional Jak2 activity to a signaling complex accelerates the rate of Stat1 activation. We conclude that the rate of activation of Stat1 in cells by IFN-gamma can be modified by regulating either receptor chain and speculate that pharmacological agents which modify receptor chain expression may alter IFN-gamma receptor signal transduction.
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Affiliation(s)
- Christopher D Krause
- Department of Molecular Genetics, Microbiology and Immunology, Robert Wood Johnson Medical School, The University of Medicine and Dentistry of New Jersey, 675 Hoes Lane West, Piscataway, 08855, USA
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38
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Köster M, Frahm T, Hauser H. Nucleocytoplasmic shuttling revealed by FRAP and FLIP technologies. Curr Opin Biotechnol 2005; 16:28-34. [PMID: 15722012 DOI: 10.1016/j.copbio.2004.11.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Protein mobility within cells is of key importance for many cellular functions. Although immunostaining can reveal protein locations in the steady-state, this might not represent the full picture and provides no information about protein movements. Fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) are two techniques that enable the dynamics of intracellular protein mobility to be studied. These technologies have been successfully used to analyze the nucleocytoplasmic shuttling of STAT1, an intracellular signal transducer and activator of transcription, and can applied to the study of other proteins. Furthermore, FRAP and FLIP approaches have the added advantage of not affecting cell viability and might find application in the imaging of intracellular events in certain tissues and live animals.
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Affiliation(s)
- Mario Köster
- Department of Gene Regulation and Differentiation, GBF, Mascheroder Weg 1, D-38124 Braunschweig, Germany
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39
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Truchet S, Chebrout M, Djediat C, Wietzerbin J, Debey P. Presence of permanently activated signal transducers and activators of transcription in nuclear interchromatin granules of unstimulated mouse oocytes and preimplantation embryos. Biol Reprod 2004; 71:1330-9. [PMID: 15189833 DOI: 10.1095/biolreprod.104.029405] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
We previously described that mouse oocytes and preimplantation embryos express the two subunits of interferon-gamma receptor. We now report that, despite the presence of STAT1 (signal transducer and activator of transcription 1) at both the mRNA and protein levels, interferon gamma (IFNgamma) as well as IFNalpha are unable to trigger massive nuclear translocation of STAT1 in these cells, even at high cytokine concentrations. Conversely, nuclear accumulation of STAT1 was readily observed in murine L929 somatic cells under the same conditions. However, in the absence of any stimulation, both tyrosine (Y701p) and serine (S727p) phosphorylated forms of STAT1 were already detected in the nuclei of oocytes and early embryos. Phosphorylated STAT1 appeared concentrated in large nuclear dots, which were identified by indirect immunofluorescence and electron microscopy as clusters of interchromatin granules (IGCs or speckles). A similar distribution was also observed for the serine (S727p) phosphorylated form of STAT3 as well as for tyrosine (Y689p) phosphorylated STAT2. Western blot analysis confirmed that STAT factors present in mouse oocytes are predominantly phosphorylated. In parallel, we showed that the transcription of two IFNgamma-target genes, namely interferon regulatory factor-1 (IRF-1) and suppressor of cytokine signaling-1 (SOCS-1) is indeed increased in two-cell embryos in response to IFNgamma. Altogether, our results suggest that, despite the lack of massive nuclear accumulation of STAT1 in response to exogenous IFNs and the permanent presence of phosphorylated STATs in the nucleus, JAK/ STAT pathways are functional during early development.
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Affiliation(s)
- Sandrine Truchet
- USM 503 MNHN, UMR 8646 CNRS-MNHN, U565 INSERM, Département Régulation, Développement et Diversité Moléculaire, Muséum National d'Histoire Naturelle, 75005 Paris, France.
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40
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Fischer P, Lehmann U, Sobota RM, Schmitz J, Niemand C, Linnemann S, Haan S, Behrmann I, Yoshimura A, Johnston JA, Müller-Newen G, Heinrich PC, Schaper F. The role of the inhibitors of interleukin-6 signal transduction SHP2 and SOCS3 for desensitization of interleukin-6 signalling. Biochem J 2004; 378:449-60. [PMID: 14611646 PMCID: PMC1223960 DOI: 10.1042/bj20030893] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Revised: 11/10/2003] [Accepted: 11/11/2003] [Indexed: 01/06/2023]
Abstract
The immediate early response of cells treated with IL-6 (interleukin-6) is the activation of the signal transducer and activator of transcription (STAT)3. The Src homology domain 2 (SH2)-containing protein tyrosine phosphatase SHP2 and the feedback inhibitor SOCS3 (suppressor of cytokine signalling) are potent inhibitors of IL-6 signal transduction. Impaired function of SOCS3 or SHP2 leads to enhanced and prolonged IL-6 signalling. The inhibitory function of both proteins depends on their recruitment to the tyrosine motif 759 within glycoprotein gp130. In contrast to inactivation, desensitization of signal transduction is regarded as impaired responsiveness due to prestimulation. Usually, after activation the sensing receptor becomes inactivated by modifications such as phosphorylation, internalization or degradation. We designed an experimental approach which allows discrimination between desensitization and inactivation of IL-6 signal transduction. We observed that pre-stimulation with IL-6 renders cells less sensitive to further stimulation with IL-6. After several hours, the cells become sensitive again. We show that not only signal transduction through previously activated receptors is affected by desensitization but signalling through receptors which were not targeted by the first stimulation was also attenuated ( trans -desensitization). Interestingly, in contrast to inhibition, desensitization does not depend on the presence of functional SHP2. Furthermore, cells lacking SOCS3 show constitutive STAT3 activation which is not affected by pre-stimulation with IL-6. All these observations suggest that desensitization and inhibition of signalling are mechanistically distinct.
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Affiliation(s)
- Patrick Fischer
- Department of Biochemistry, Faculty of Medicine, RWTH Aachen, Pauwelsstrasse 30, D-52074 Aachen, Germany
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41
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Schroder K, Hertzog PJ, Ravasi T, Hume DA. Interferon-gamma: an overview of signals, mechanisms and functions. J Leukoc Biol 2003; 75:163-89. [PMID: 14525967 DOI: 10.1189/jlb.0603252] [Citation(s) in RCA: 2907] [Impact Index Per Article: 138.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Interferon-gamma (IFN-gamma) coordinates a diverse array of cellular programs through transcriptional regulation of immunologically relevant genes. This article reviews the current understanding of IFN-gamma ligand, receptor, signal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophage function during infection. The current model for IFN-gamma signal transduction is discussed, as well as signal regulation and factors conferring signal specificity. Cellular effects of IFN-gamma are described, including up-regulation of pathogen recognition, antigen processing and presentation, the antiviral state, inhibition of cellular proliferation and effects on apoptosis, activation of microbicidal effector functions, immunomodulation, and leukocyte trafficking. In addition, integration of signaling and response with other cytokines and pathogen-associated molecular patterns, such as tumor necrosis factor-alpha, interleukin-4, type I IFNs, and lipopolysaccharide are discussed.
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Affiliation(s)
- Kate Schroder
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Brisbane 4072, Australia.
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42
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McBride KM, Reich NC. The ins and outs of STAT1 nuclear transport. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2003; 2003:RE13. [PMID: 12915721 DOI: 10.1126/stke.2003.195.re13] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
There is an inherent elegance in being in the right place at the right time. The STAT1 transcription factor possesses regulatory signals that ensure its distribution to the right cellular location at the right time. Latent STAT1 resides primarily in the cytoplasm, and there it responds to hormone signaling through tyrosine phosphorylation by Janus kinases or growth factor receptors. After phosphorylation, STAT1 dimerizes, and this conformational change reveals a nuclear import signal that is recognized by a specific nuclear import carrier. In the nucleus, the STAT1 dimer dissociates from the import carrier and binds to specific DNA target sites in the promoters of regulated genes. STAT1 is subsequently dephosphorylated in the nucleus by a constitutively active tyrosine phosphatase, leading to its dissociation from DNA. A nuclear export signal of STAT1 appears to be masked when dimers are bound to DNA, but it becomes accessible to the CRM1 export carrier after dissociation from DNA. CRM1 binds STAT1 and transports the transcription factor back to the cytoplasm. Studies show that the regulatory trafficking signals that guide the nuclear import and export of STAT1 reside within its DNA binding domain. The location of these signals indicates that their function has coevolved with the ability of STAT1 to bind DNA and regulate gene expression. The nuclear import and subsequent recycling of STAT1 to the cytoplasm are integral to its function as a signal transducer and activator of transcription.
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Affiliation(s)
- Kevin M McBride
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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43
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44
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Abstract
Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling is essential but not sufficient for full responses to the interferons (IFNs), most cytokines and some growth factors. The IFN-gamma and interleukin-6 (IL-6) response pathways have been used as model systems to investigate both the signals involved and their organisation. Activated STAT1 diffuses freely in the cytoplasmic and nuclear compartments of the cell providing a 'random walk' element in the IFN-gamma response. Completely foreign chimeric receptors and, remarkably, in the absence of STAT3, the endogenous IL-6 receptor can efficiently mediate an IFN-gamma-like response. Accordingly all of the signals required for an IFN-gamma response can be generated through physiological levels of a foreign ligand. JAK/STAT signalling, therefore, appears 'soft-wired', modular and highly flexible with substantial overlap between different response pathways. The data are consistent with a generic or 'core' set of signals from JAK/receptor complexes with 'add-on' modulation through specific receptor motifs. The cellular background likely profoundly affects the nature of the response.
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Affiliation(s)
- Ian M Kerr
- Cancer Research UK London Research Institute, Lincoln's Inn Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.
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45
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Köster M, Lykke-Andersen S, Elnakady YA, Gerth K, Washausen P, Höfle G, Sasse F, Kjems J, Hauser H. Ratjadones inhibit nuclear export by blocking CRM1/exportin 1. Exp Cell Res 2003; 286:321-31. [PMID: 12749860 DOI: 10.1016/s0014-4827(03)00100-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In addition to previously isolated ratjadone A we describe three new members of this family, ratjadones B, C, and D, from another strain of the myxobacterium Sorangium cellulosum. We have investigated the properties of these ratjadones with respect to their activity on mammalian cell lines. We found IC(50) values in the picomolar range and a significant increase in the size of nuclei. A further examination showed that they inhibit the export of the leucine-rich nuclear export signal (LR-NES) containing proteins in different cell lines. Ratjadones are able to inhibit the formation of the nuclear export complex composed of the CRM1, RanGTP, and the cargo protein, as shown by two different in vitro assays. Finally, the binding of ratjadone C to CRM1 was demonstrated. These ratjadone activities are in the same concentration range as described for the polyketide leptomycin B (LMB) from Streptomyces sp. Like LMB, it seems that the ratjadones covalently bind to CRM1, inhibit cargo protein binding via LR-NES, and thereby block nuclear export. Thus, the ratjadones represent a new class of natural compounds which inhibit proliferation in eukaryotes by blocking nuclear export.
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Affiliation(s)
- Mario Köster
- Department of Gene Regulation and Differentiation, GBF-German Research Centre for Biotechnology, Mascheroder Weg 1, D-38124 Braunschweig, Germany
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46
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Ivaska J, Bosca L, Parker PJ. PKCepsilon is a permissive link in integrin-dependent IFN-gamma signalling that facilitates JAK phosphorylation of STAT1. Nat Cell Biol 2003; 5:363-9. [PMID: 12640464 DOI: 10.1038/ncb957] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2002] [Revised: 12/22/2002] [Accepted: 01/31/2003] [Indexed: 02/07/2023]
Abstract
The critical dependence of receptor-triggered signals on integrin-mediated cell-substrate interactions represents a fundamental biological paradigm in health and disease. However, the molecular connections of these permissive inputs, which operate through integrin-matrix interactions, has remained largely obscure. Here we show that the serine-threonine kinase protein kinase C epsilon (PKCepsilon) functions as a signal integrator between cytokine and integrin signalling pathways. Integrins are shown to control PKCepsilon phosphorylation acutely by determining complex formation with protein phosphatase 2A (PP2A) and the upstream kinase PDK1 (phosphoinositide-dependent kinase 1). The PP2A-induced loss of PKCepsilon function results in attenuated interferon gamma (INF-gamma)-induced phosphorylation of STAT1 (signal transducer and activator of transcription 1) downstream of Janus kinase 1/2 (JAK1/2). PKCepsilon function and the IFN-gamma response can be recovered by inhibition of PP2A if PDK1 is associated with PKCepsilon in this complex. More directly, a PP2A-resistant mutant of PKCepsilon is sufficient for restoration of the IFN-gamma response in suspension culture. Thus, PKCepsilon functions as a central point of integration through which integrin engagement exerts a permissive input on IFN-gamma signalling.
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Affiliation(s)
- Johanna Ivaska
- Protein Phosphorylation Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, UK
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Swameye I, Muller TG, Timmer J, Sandra O, Klingmuller U. Identification of nucleocytoplasmic cycling as a remote sensor in cellular signaling by databased modeling. Proc Natl Acad Sci U S A 2003; 100:1028-33. [PMID: 12552139 PMCID: PMC298720 DOI: 10.1073/pnas.0237333100] [Citation(s) in RCA: 261] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Considerable progress has been made in identifying the molecular composition of complex signaling networks controlling cell proliferation, differentiation, and survival. However, to discover general building principles and predict the dynamic behavior of signaling networks, it is necessary to develop quantitative models based on experimental observations. Here we report a mathematical model of the core module of the Janus family of kinases (JAK)-signal transducer and activator of transcription (STAT) signaling pathway based on time-resolved measurements of receptor and STAT5 phosphorylation. Applying the fitted model, we can determine the quantitative behavior of STAT5 populations not accessible to experimental measurement. By in silico investigations, we identify the parameters of nuclear shuttling as the most sensitive to perturbations and verify experimentally the model prediction that inhibition of nuclear export results in a reduced transcriptional yield. The model reveals that STAT5 undergoes rapid nucleocytoplasmic cycles, continuously coupling receptor activation and target gene transcription, thereby forming a remote sensor between nucleus and receptor. Thus, dynamic modeling of signaling pathways can promote functional understanding at the systems level.
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Affiliation(s)
- I Swameye
- Max-Planck-Institut für Immunbiologie, Stübeweg 51, D-79108 Freiburg, Germany
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48
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Abstract
Suppressor of cytokine signaling-1 (SOCS1) was identified as the negative regulator of Janus kinase (JAK) and signal transducer and activator of transcription (STAT) signal transduction pathway. However, the kinetics and control mechanism of the pathway have not yet been fully understood. We have developed the computer simulation of the JAK/STAT pathway. Without nuclear phosphatase, SOCS1's binding to JAK did not cause the decrease in nuclear phosphorylated STAT1. However, without SH2 domain-containing tyrosine phosphatase 2 (SHP-2) or cytoplasmic phosphatase, it did. So nuclear phosphatase is considered to be the most important in this system. By changing parameters of the model, dynamical characteristics and control mechanism were investigated.
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Affiliation(s)
- Satoshi Yamada
- Advanced Technology R&D Center, Mitsubishi Electric Corporation, 8-1-1, Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661, Japan.
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49
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Abstract
The spectral resolution of fluorescence microscope images in living cells is achieved by using a confocal laser scanning microscope equipped with grating optics. This capability of temporal and spectral resolution is especially useful for detecting spectral changes of a fluorescent dye; for example, those associated with fluorescence resonance energy transfer (FRET). Using the spectral imaging fluorescence microscope system, it is also possible to resolve emitted signals from fluorescent dyes that have spectra largely overlapping with each other, such as fluorescein isothiocyanate (FITC) and green fluorescent protein (GFP).
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Affiliation(s)
- Tokuko Haraguchi
- CREST Research Project, Kansai Advanced Research Center, Communications Research Laboratory, 588-2 Iwaoka, Iwaoka-cho, Nishi-ku, Kobe 651-2492, Japan
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50
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Zeng R, Aoki Y, Yoshida M, Arai KI, Watanabe S. Stat5B shuttles between cytoplasm and nucleus in a cytokine-dependent and -independent manner. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:4567-75. [PMID: 11971004 DOI: 10.4049/jimmunol.168.9.4567] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In response to cytokine stimuli, Stats are phosphorylated and translocated to the nucleus to activate target genes. Then, most are dephosphorylated and returned to the cytoplasm. Using Ba/F3 cells, we found that the nuclear export of Stat5B by cytokine depletion was inhibited by leptomycin B (LMB), a specific inhibitor of nuclear export receptor chromosome region maintenance 1. Interestingly, LMB treatment in the absence of cytokine led to the accumulation of Stat5B in the nucleus, suggesting that Stat5B shuttles between the nucleus and the cytoplasm as a monomer without cytokine stimulation. This notion is supported by the observation that LMB-induced accumulation of Stat5B in the nucleus was also observed with Stat5B having a mutated tyrosine 699, which is essential for dimer formation. Using a series of mutant Stat5Bs, we identified a part of the coiled coil domain to be a critical region for monomer nuclear import and a more N-terminal region to be critical for the cytokine stimulation dependent import of Stat5B. Taken together, we propose a model in which Stat5B shuttles between the nucleus and cytoplasm by two different mechanisms, one being a factor-independent constitutive shuttling by monomeric form, and the other, a factor stimulation-dependent one regulated by tyrosine phosphorylation and subsequent dimerization.
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Affiliation(s)
- Rong Zeng
- Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Tokyo, Japan
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