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Begitt A, Krause S, Cavey JR, Vinkemeier DE, Vinkemeier U. A family-wide assessment of latent STAT transcription factor interactions reveals divergent dimer repertoires. J Biol Chem 2023; 299:104703. [PMID: 37059181 DOI: 10.1016/j.jbc.2023.104703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 04/04/2023] [Accepted: 04/06/2023] [Indexed: 04/16/2023] Open
Abstract
The conversion of STAT proteins from latent to active transcription factors is central to cytokine signalling. Triggered by their signal-induced tyrosine phosphorylation, it is the assembly of a range of cytokine-specific STAT homo- and heterodimers that marks a key step in the transition of hitherto latent proteins to transcription activators. In contrast, the constitutive self-assembly of latent STATs and how it relates to the functioning of activated STATs, is understood less well. To provide a more complete picture, we developed a co-localization-based assay and tested all 28 possible combinations of the seven unphosphorylated STAT (U-STAT) proteins in living cells. We identified five U-STAT homodimers -STAT1, STAT3, STAT4, STAT5A and STAT5B- and two heterodimers -STAT1:STAT2 and STAT5A:STAT5B- and performed semi-quantitative assessments of the forces and characterizations of binding interfaces that support them. One STAT protein -STAT6- was found to be monomeric. This comprehensive analysis of latent STAT self-assembly lays bare considerable structural and functional diversity in the ways that link STAT dimerization before and after activation.
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Affiliation(s)
- Andreas Begitt
- The University of Nottingham, School of Life Sciences, Nottingham, UK
| | - Sebastian Krause
- The University of Nottingham, School of Life Sciences, Nottingham, UK
| | - James R Cavey
- The University of Nottingham, School of Life Sciences, Nottingham, UK
| | | | - Uwe Vinkemeier
- The University of Nottingham, School of Life Sciences, Nottingham, UK
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2
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Dimri S, Malhotra R, Shet T, Mokal S, Gupta S, De A. Noncanonical pS727 post translational modification dictates major STAT3 activation and downstream functions in breast cancer. Exp Cell Res 2020; 396:112313. [PMID: 33002501 DOI: 10.1016/j.yexcr.2020.112313] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 09/15/2020] [Accepted: 09/27/2020] [Indexed: 12/25/2022]
Abstract
Activation of STAT3 via Y705-phosphorylation is well documented across multiple cancer types and thus forms the basis of canonical pathway to judge STAT3 activation. Recently, important roles of two other post translational modification (PTM) sites, i.e. S727-phosphorylation and K685-acetylation, leading to STAT3 activation are reported. However, their critical mode of function in controlling STAT3 dimerization and signaling, independent of canonical activation remains elusive. Therefore, to understand the functional relevance of each STAT3 PTMs in breast cancer (BC), cell models are developed by stable overexpression of PTM-site specific point mutants, i.e. Y705F, S727A or K685R, in a 3'UTR-STAT3 knockdown BC cell background. Results using this model system reveal novel findings showing that phosphorylation at S727 can lead to STAT3 activation independent of phosphoY705. We also demonstrate that loss of pS727 or K685ac significantly affects functional phenotypes such as cell survival and proliferation as well as downstream transcriptional activity (Twist 1, Socs3, c-Myc, Bcl-1 and Mcl-1) of STAT3. Thereafter, by utilizing a BRET biosensor for measuring STAT3 phosphorylation in live cells, a crucial role of pS727 in dictating STAT3 activation and homodimerization formation is uncovered. Further by performing retrospective IHC analysis of total and phospho-forms of STAT3 in a cohort of 76 triple negative breast cancer (TNBC) patient samples, a significant dominant expression of phosphoS727 over phosphoY705 PTM (p < 0.001) is found in STAT3 positive cases. We also focus on validating known STAT3 inhibitor molecules for their action against both pY705 and pS727 activation. This study for the first time demonstrates that an anti-helminth drug compound, Niclosamide, is capable of inactivating both phospho-PTM sites on STAT3 and exhibits excellent anticancer efficacy in preclinical TNBC tumour model.
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Affiliation(s)
- Shalini Dimri
- Molecular Functional Imaging Lab, Advanced Centre for Treatment, Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, India; Homi Bhabha National Institute, Mumbai, India.
| | - Renu Malhotra
- Molecular Functional Imaging Lab, Advanced Centre for Treatment, Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, India.
| | - Tanuja Shet
- Tata Memorial Hospital, Mumbai, India; Homi Bhabha National Institute, Mumbai, India.
| | - Smruti Mokal
- Tata Memorial Hospital, Mumbai, India; Homi Bhabha National Institute, Mumbai, India.
| | - Sudeep Gupta
- Tata Memorial Hospital, Mumbai, India; Advanced Centre for Treatment, Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, India; Homi Bhabha National Institute, Mumbai, India.
| | - Abhijit De
- Molecular Functional Imaging Lab, Advanced Centre for Treatment, Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, India; Homi Bhabha National Institute, Mumbai, India.
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Letra‐Vilela R, Cardoso B, Silva‐Almeida C, Maia Rocha A, Murtinheira F, Branco‐Santos J, Rodriguez C, Martin V, Santa‐Marta M, Herrera F. Can asymmetric post-translational modifications regulate the behavior of STAT3 homodimers? FASEB Bioadv 2020; 2:116-125. [PMID: 32123861 PMCID: PMC7003655 DOI: 10.1096/fba.2019-00049] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 06/14/2019] [Accepted: 12/10/2019] [Indexed: 01/16/2023] Open
Abstract
Signal transducer and activator of transcription 3 (STAT3) is a ubiquitous and pleiotropic transcription factor that plays essential roles in normal development, immunity, response to tissue damage and cancer. We have developed a Venus-STAT3 bimolecular fluorescence complementation assay that allows the visualization and study of STAT3 dimerization and protein-protein interactions in living cells. Inactivating mutations on residues susceptible to post-translational modifications (PTMs) (K49R, K140R, K685R, Y705F and S727A) changed significantly the intracellular distribution of unstimulated STAT3 dimers when the dimers were formed by STAT3 molecules that carried different mutations (ie they were "asymmetric"). Some of these asymmetric dimers changed the proliferation rate of HeLa cells. Our results indicate that asymmetric PTMs on STAT3 dimers could constitute a new level of regulation of STAT3 signaling. We put forward these observations as a working hypothesis, since confirming the existence of asymmetric STAT3 homodimers in nature is extremely difficult, and our own experimental setup has technical limitations that we discuss. However, if our hypothesis is confirmed, its conceptual implications go far beyond STAT3, and could advance our understanding and control of signaling pathways.
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Affiliation(s)
- Ricardo Letra‐Vilela
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
- Cell Structure and Dynamics LaboratoryFaculdade de CiênciasUniversidade de LisboaLisbonPortugal
| | - Beatriz Cardoso
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
| | - Catarina Silva‐Almeida
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
| | - Ana Maia Rocha
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
| | - Fernanda Murtinheira
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
- Cell Structure and Dynamics LaboratoryFaculdade de CiênciasUniversidade de LisboaLisbonPortugal
| | - Joana Branco‐Santos
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
| | - Carmen Rodriguez
- Instituto Universitario de Oncología del Principado de Asturias (IUOPA) and Departamento de Morfología y Biología CelularFacultad de MedicinaUniversity of OviedoOviedoSpain
| | - Vanesa Martin
- Instituto Universitario de Oncología del Principado de Asturias (IUOPA) and Departamento de Morfología y Biología CelularFacultad de MedicinaUniversity of OviedoOviedoSpain
| | - Mariana Santa‐Marta
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
| | - Federico Herrera
- Cell Structure and Dynamics LaboratoryInstituto de Tecnologia Quimica e Biologica (ITQB‐NOVA)Universidade Nova de LisboaOeirasPortugal
- Cell Structure and Dynamics LaboratoryFaculdade de CiênciasUniversidade de LisboaLisbonPortugal
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Visualization and quantification of dynamic STAT3 homodimerization in living cells using homoFluoppi. Sci Rep 2018; 8:2385. [PMID: 29402895 PMCID: PMC5799161 DOI: 10.1038/s41598-018-20234-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 01/15/2018] [Indexed: 12/23/2022] Open
Abstract
Dimerization in signal transduction is a dynamically regulated process and a key regulatory mechanism. Signal transducer and activator of transcription 3 (STAT3) dimerizes after tyrosine phosphorylation upon cytokine stimulation. Because only the STAT3 dimer possesses the trans-activation activity, dimerization is an indispensable process for cytokine signaling. Here we report the detection of dynamic STAT3 dimerization in living cells using the homoFluoppi system. This method allowed us to validate the presence of an intact Src homology 2 domain and STAT3 Tyr705 phosphorylation, which facilitate puncta formation and homodimerization. Puncta formation was reversible, as determined by a decreased punctate signal after washout of oncostatin M. We analyzed STAT3 mutants, which have been reported in patients with hyper IgE syndrome and inflammatory hepatocellular adenoma (IHCA). Analysis of the IHCA mutants using homoFluoppi revealed constitutive activity independent of cytokine stimulation and novel insight into kinetics of dimer dissociation process. Next, we used homoFluoppi to screen for inhibitors of STAT3 dimerization, and identified 3,4-methylenedioxy-β-nitrostyrene as a novel inhibitor. The results of this study show that homoFluoppi is a useful research tool for the analysis of proteins like STAT3 that dynamically dimerize, and is applicable for the screening of dimerization modulators.
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Gao J, Chen J, Cai M, Xu H, Jiang J, Tong T, Wang H. Clustered localization of STAT3 during the cell cycle detected by super-resolution fluorescence microscopy. Methods Appl Fluoresc 2017; 5:024004. [DOI: 10.1088/2050-6120/aa6ab5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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4-Carbonyl-2,6-dibenzylidenecyclohexanone derivatives as small molecule inhibitors of STAT3 signaling pathway. Bioorg Med Chem 2016; 24:6174-6182. [PMID: 27816267 DOI: 10.1016/j.bmc.2016.09.070] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/20/2022]
Abstract
Inhibition of STAT3 signaling pathway is proposed to be a promising strategy for cancer treatment. In this study, a series of 4-carbonyl-2,6-dibenzylidenecyclohexanone derivatives were prepared and evaluated as anticancer agents. The most potent compound 13r was discovered to exhibit antiproliferative activity against a broad rang of cancer cell lines and relatively low cytotoxicity against normal human cells. Besides, 13r effectively suppressed STAT3 expression as well as phosphorylation, and surface plasmon resonance analysis confirmed the direct interaction of 13r with STAT3. Docking simulation showed that 13r could inhibit STAT3 by targeting SH2 domain. This study provided evidence for these compounds to be further developed as antitumor agents through inhibition of the STAT3 pathway.
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Abstract
Application of bioluminescence resonance energy transfer (BRET) assay has been of special value in measuring dynamic events such as protein-protein interactions (PPIs) in vitro or in vivo. It was only in the late 1990s the BRET assay using RLuc-YFP was introduced for biological research showing its use in determining interaction of two proteins involved in circadian rhythm. Several inherent attributes such as rapid and fairly sensitive ratiometric measurements, assessment of PPI irrespective of protein location in cellular compartment, and cost-effectiveness consenting to high-throughput assay development make BRET a popular genetic reporter-based assay for PPI studies. In BRET-based screening, within a defined proximity range of 10-100 Å, excited state energy of the luminescence molecule can excite the acceptor fluorophore in the form of resonance energy transfer, causing it to emit at its characteristic emission wavelength. Based on this principle, several such donor-acceptor pairs, using the Renilla luciferase or its mutants as donor and either GFP2, YFP, mOrange, TagRFP, or TurboFP as acceptor, have been reported for use.In recent years, BRET-related research has become significantly versatile in the assay format and its applicability by adopting the assay on multiple detection devices such as small-animal optical imaging platform or bioluminescence microscope. Beyond the scope of quantitative measurement of PPIs and protein dimerization, molecular optical imaging applications based on BRET assays have broadened its scope for screening of pharmacological compounds by unifying in vitro, live cell, and in vivo animal/plant measurement all on one platform. Taking examples from the literature, this chapter contributes to in-depth methodological details on how to perform in vitro and in vivo BRET experiments, and illustrates its advantages as a single-format assay.
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Affiliation(s)
- Shalini Dimri
- Molecular Functional Imaging Lab, ACTREC, Tata Memorial Centre, Kharghar, Navi Mumbai, 410210, India
| | - Soumya Basu
- Molecular Functional Imaging Lab, ACTREC, Tata Memorial Centre, Kharghar, Navi Mumbai, 410210, India
| | - Abhijit De
- Molecular Functional Imaging Lab, ACTREC, Tata Memorial Centre, Kharghar, Navi Mumbai, 410210, India.
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Domoszlai T, Martincuks A, Fahrenkamp D, Schmitz-Van de Leur H, Küster A, Müller-Newen G. Consequences of the disease-related L78R mutation for dimerization and activity of STAT3. J Cell Sci 2014; 127:1899-910. [DOI: 10.1242/jcs.137422] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
STAT3 (signal transducer and activator of transcription 3) is a transcription factor centrally involved in diverse processes including hematopoiesis, immunity and cancer progression. In response to cytokine stimulation STAT3 is activated through phosphorylation of a single tyrosine residue. The phosphorylated STAT3 dimers are stabilized by intermolecular SH2 domain/phosphotyrosine interactions. These activated dimers accumulate in the nucleus and bind to specific DNA sequences resulting in target gene expression. We analysed and compared the structural organizations of the unphosphorylated latent and phosphorylated activated STAT3 dimers using Förster resonance energy transfer (FRET) in fixed and living cells. The latent dimers are stabilized by homotypic interactions between the N-terminal domains. A somatic mutation (L78R) found in inflammatory hepatocellular adenomas (IHCA) which is located in the N-terminal domain of STAT3 disturbs latent dimer formation. Applying intramolecular FRET we verify a functional role of the SH2 domain in latent dimer formation suggesting the parallel orientation of the protomers in the latent STAT3 dimer similar to activated STAT3 dimers but in contrast to the latent dimers of STAT1 and STAT5. Our findings reveal unique structural characteristics of STAT3 within the STAT family and contribute to the understanding of the L78R mutation found in IHCA.
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9
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Mohr A, Chatain N, Domoszlai T, Rinis N, Sommerauer M, Vogt M, Müller-Newen G. Dynamics and non-canonical aspects of JAK/STAT signalling. Eur J Cell Biol 2011; 91:524-32. [PMID: 22018664 DOI: 10.1016/j.ejcb.2011.09.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 09/05/2011] [Accepted: 09/12/2011] [Indexed: 11/25/2022] Open
Abstract
The Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway directly links ligand-binding to a membrane-bound receptor with the activation of a transcription factor. This signalling module enables the cell to rapidly initiate a transcriptional response to external stimulation. The main components of this evolutionary conserved module are cytokines that specifically bind to cytokine receptors leading to the activation of receptor-associated Janus tyrosine kinases (JAKs). The receptor-bound JAKs activate STAT transcription factors through phosphorylation of a single tyrosine residue. Activated STAT dimers translocate into the nucleus to induce target gene expression. In this article we will review current opinions on the molecular mechanism and on intracellular dynamics of JAK/STAT signalling with a special focus on the cytokine receptor glycoprotein 130 (gp130) and STAT3. In particular we will concentrate on non-canonical aspects of Jak/STAT signalling including preassembled receptor complexes, preformed STAT dimers, STAT trafficking and non-canonical functions of STATs.
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Affiliation(s)
- Anne Mohr
- Institut für Biochemie und Molekularbiologie, RWTH Aachen University, Aachen, Germany
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10
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Fletcher S, Page BDG, Zhang X, Yue P, Li ZH, Sharmeen S, Singh J, Zhao W, Schimmer AD, Trudel S, Turkson J, Gunning PT. Antagonism of the Stat3-Stat3 protein dimer with salicylic acid based small molecules. ChemMedChem 2011; 6:1459-70. [PMID: 21618433 PMCID: PMC3192013 DOI: 10.1002/cmdc.201100194] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Indexed: 12/15/2022]
Abstract
More than 50 new inhibitors of the oncogenic Stat3 protein were identified through a structure-activity relationship (SAR) study based on the previously identified inhibitor S3I-201 (IC₅₀ =86 μM, K(i) >300 μM). A key structural feature of these inhibitors is a salicylic acid moiety, which, by acting as a phosphotyrosine mimetic, is believed to facilitate binding to the Stat3 SH2 domain. Several of the analogues exhibit higher potency than the lead compound in inhibiting Stat3 DNA binding activity, with an in vitro IC₅₀ range of 18.7-51.9 μM, and disruption of Stat3-pTyr peptide interactions with K(i) values in the 15.5-41 μM range. One agent in particular exhibited potent inhibition of Stat3 phosphorylation in both breast and multiple myeloma tumor cells, suppressed the expression of Stat3 target genes, and induced antitumor effects in tumor cells harboring activated Stat3 protein.
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Affiliation(s)
- Steven Fletcher
- Department of Chemistry, University of Toronto Mississauga, Mississauga, ON, L5L 1C6 (Canada)
| | - Brent D. G. Page
- Department of Chemistry, University of Toronto Mississauga, Mississauga, ON, L5L 1C6 (Canada)
| | - Xialoei Zhang
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Sciences, University of Central Florida, Orlando, FL, 32826 (USA)
| | - Peibin Yue
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Sciences, University of Central Florida, Orlando, FL, 32826 (USA)
| | - Zhi Hua Li
- Division of Medical Oncology and Hematology, University Health Network, Princess Margaret Hospital, McLaughlin Centre of Molecular Medicine, 620 University Ave, Toronto, ON, M5G 2C1 (Canada)
| | - Sumaiya Sharmeen
- Ontario Cancer Institute/Princess Margaret Hospital, 610 University Avenue, Toronto, ON, M5G 2M9 (Canada)
| | - Jagdeep Singh
- Department of Chemistry, University of Toronto Mississauga, Mississauga, ON, L5L 1C6 (Canada)
| | - Wei Zhao
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Sciences, University of Central Florida, Orlando, FL, 32826 (USA)
| | - Aaron D. Schimmer
- Ontario Cancer Institute/Princess Margaret Hospital, 610 University Avenue, Toronto, ON, M5G 2M9 (Canada)
| | - Suzanne Trudel
- Division of Medical Oncology and Hematology, University Health Network, Princess Margaret Hospital, McLaughlin Centre of Molecular Medicine, 620 University Ave, Toronto, ON, M5G 2C1 (Canada)
| | - James Turkson
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Sciences, University of Central Florida, Orlando, FL, 32826 (USA)
| | - Patrick T. Gunning
- Department of Chemistry, University of Toronto Mississauga, Mississauga, ON, L5L 1C6 (Canada)
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Cimica V, Chen HC, Iyer JK, Reich NC. Dynamics of the STAT3 transcription factor: nuclear import dependent on Ran and importin-β1. PLoS One 2011; 6:e20188. [PMID: 21625522 PMCID: PMC3098288 DOI: 10.1371/journal.pone.0020188] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 04/27/2011] [Indexed: 01/05/2023] Open
Abstract
The signal transducer and activator of transcription-3 (STAT3) induces transcription of genes that control differentiation, inflammation, proliferation, and tumor cell invasion. Cytokines such as interleukin-6 and interferon stimulate the specific tyrosine phosphorylation of STAT3, which confers its ability to bind consensus DNA targets. In addition, unphosphorylated STAT3 has been demonstrated to induce specific gene expression. STAT3 must gain entrance to the nucleus to impact transcription, however access to the nucleus is a tightly regulated process. Because nuclear trafficking is critical to the function of STAT3, we investigated the molecular mechanisms by which STAT3 is imported to the nucleus. Live cell imaging techniques were used with STAT3 tagged with green fluorescence protein (GFP) or photoactivatable GFP to follow the cellular dynamics of both unphosphorylated and tyrosine phosphorylated forms. Cytokine activation did not alter the rate of STAT3 nuclear import or nuclear export. In addition, Förster resonance energy transfer experiments revealed homomeric interaction of unphosphorylated STAT3 dependent on its amino terminus, but this dimerization is not necessary for its nuclear import. Previous work demonstrated the adapter importin-α3 binds to STAT3 and is required for nuclear import. To determine whether STAT3 nuclear import is mediated by the importin-α/importin-β1 heterodimer, the effects of siRNA to importin-β1 were evaluated. Results indicate STAT3 nuclear import is dependent on the function of importin-β1. Since the Ran GTPase is necessary to bind importin-β1 in the nucleus for release of importin-α-cargo, the effect of a GTPase deficient mutant of Ran was tested. Expression of the Ran interfering mutant inhibited STAT3 nuclear import. This study defines importin-α/importin-β1/Ran as the molecular mechanism by which STAT3 traffics to the nucleus.
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Affiliation(s)
- Velasco Cimica
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Hui-Chen Chen
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Janaki K. Iyer
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Nancy C. Reich
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail:
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Raptis L, Arulanandam R, Geletu M, Turkson J. The R(h)oads to Stat3: Stat3 activation by the Rho GTPases. Exp Cell Res 2011; 317:1787-95. [PMID: 21619876 DOI: 10.1016/j.yexcr.2011.05.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 05/09/2011] [Accepted: 05/10/2011] [Indexed: 02/09/2023]
Abstract
The signal transducer and activator of transcription-3 (Stat3) is a member of the STAT family of cytoplasmic transcription factors. Overactivation of Stat3 is detected with high frequency in human cancer and is considered a molecular abnormality that supports the tumor phenotype. Despite concerted investigative efforts, the molecular mechanisms leading to the aberrant Stat3 activation and Stat3-mediated transformation and tumorigenesis are still not clearly defined. Recent evidence reveals a crosstalk close relationship between Stat3 signaling and members of the Rho family of small GTPases, including Rac1, Cdc42 and RhoA. Specifically, Rac1, acting in a complex with the MgcRacGAP (male germ cell RacGAP), promotes tyrosine phosphorylation of Stat3 by the IL6-receptor family/Jak kinase complex, as well as its translocation to the nucleus. Studies have further revealed that the mutational activation of Rac1 and Cdc42 results in Stat3 activation, which occurs in part through the upregulation of IL6 family cytokines that in turn stimulates Stat3 through the Jak kinases. Interestingly, evidence also shows that the engagement of cadherins, cell to cell adhesion molecules, specifically induces a striking increase in Rac1 and Cdc42 protein levels and activity, which in turn results in Stat3 activation. In this review we integrate recent findings clarifying the role of the Rho family GTPases in Stat3 activation in the context of malignant progression.
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Affiliation(s)
- Leda Raptis
- Department of Microbiology and Immunology and Pathology, Queen's University, Kingston, Ontario, Canada.
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Sabat R, Grütz G, Warszawska K, Kirsch S, Witte E, Wolk K, Geginat J. Biology of interleukin-10. Cytokine Growth Factor Rev 2010; 21:331-44. [PMID: 21115385 DOI: 10.1016/j.cytogfr.2010.09.002] [Citation(s) in RCA: 714] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Robert Sabat
- Interdisciplinary Group of Molecular Immunopathology, Dermatology/Medical Immunology, University Hospital Charité, Berlin, Germany.
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Characterization of a dominant-active STAT that promotes tumorigenesis in Drosophila. Dev Biol 2010; 344:621-36. [PMID: 20501334 DOI: 10.1016/j.ydbio.2010.05.497] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Accepted: 05/15/2010] [Indexed: 01/08/2023]
Abstract
Little is known about the molecular mechanisms by which STAT proteins promote tumorigenesis. Drosophila is an ideal system for investigating this issue, as there is a single STAT (Stat92E), and its hyperactivation causes overgrowths resembling human tumors. Here we report the first identification of a dominant-active Stat92E protein, Stat92E(DeltaNDeltaC), which lacks both N- and C-termini. Mis-expression of Stat92E(DeltaNDeltaC)in vivo causes melanotic tumors, while in vitro it transactivates a Stat92E-luciferase reporter in the absence of stimulation. These gain-of-function phenotypes require phosphorylation of Y(711) and dimer formation with full-length Stat92E. Furthermore, a single point mutation, an R(442P) substitution in the DNA-binding domain, abolishes Stat92E function. Recombinant Stat92E(R442P) translocates to the nucleus following activation but fails to function in all assays tested. Interestingly, R(442) is conserved in most STATs in higher organisms, suggesting conservation of function. Modeling of Stat92E indicates that R(442) may contact the minor groove of DNA via invariant TC bases in the consensus binding element bound by all STAT proteins. We conclude that the N- and C- termini function unexpectedly in negatively regulating Stat92E activity, possibly by decreasing dimer dephosphorylation or increasing stability of DNA interaction, and that Stat92E(R442) has a nuclear function by altering dimer:DNA binding.
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15
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Zhang X, Yue P, Fletcher S, Zhao W, Gunning PT, Turkson J. A novel small-molecule disrupts Stat3 SH2 domain-phosphotyrosine interactions and Stat3-dependent tumor processes. Biochem Pharmacol 2010; 79:1398-409. [PMID: 20067773 DOI: 10.1016/j.bcp.2010.01.001] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Revised: 12/10/2009] [Accepted: 01/04/2010] [Indexed: 10/20/2022]
Abstract
The molecular modeling of the phosphotyrosine (pTyr)-SH2 domain interaction in the Stat3:Stat3 dimerization, combined with in silico structural analysis of the Stat3 dimerization disruptor, S3I-201, has furnished a diverse set of analogs. We present evidence from in vitro biochemical and biophysical studies that the structural analog, S3I-201.1066 directly interacts with Stat3 or the SH2 domain, with an affinity (K(D)) of 2.74microM, and disrupts the binding of Stat3 to the cognate pTyr-peptide, GpYLPQTV-NH(2), with an IC(50) of 23microM. Moreover, S3I-201.1066 selectively blocks the association of Stat3 with the epidermal growth factor receptor (EGFR), and inhibits Stat3 tyrosine phosphorylation and nuclear translocation in EGF-stimulated mouse fibroblasts. In cancer cells that harbor aberrant Stat3 activity, S3I-201.1066 inhibits constitutive Stat3 DNA-binding and transcriptional activities. By contrast, S3I-201.1066 has no effect on Src activation or the EGFR-mediated activation of the Erk1/2(MAPK) pathway. S3I-201.1066 selectively suppresses the viability, survival, and malignant transformation of the human breast and pancreatic cancer lines and the v-Src-transformed mouse fibroblasts harboring persistently active Stat3. Treatment with S3I-201.1066 of malignant cells harboring aberrantly active Stat3 down-regulated the expression of c-Myc, Bcl-xL, Survivin, the matrix metalloproteinase 9, and VEGF. The in vivo administration of S3I-201.1066-induced significant antitumor response in mouse models of human breast cancer, which correlates with the inhibition of constitutively active Stat3 and the suppression of known Stat3-regulated genes. Our studies identify a novel small-molecule that binds with a high affinity to Stat3, blocks Stat3 activation and function, and thereby induces antitumor response in human breast tumor xenografts harboring persistently active Stat3.
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Affiliation(s)
- Xiaolei Zhang
- University of Central Florida College of Medicine, Orlando, 32827, USA
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Abstract
BACKGROUND Aberrant activation of the signal transducer and activator of transcription (STAT)3 occurs in many human tumors. Moreover, studies utilizing genetic and pharmacological approaches to modulate constitutive STAT3 activity have provided compelling evidence for the critical role of aberrant STAT3 activity in malignant transformation and tumor progression, and thereby validated STAT3 as a novel cancer drug target. OBJECTIVE This review is intended to be a full coverage of the efforts to develop direct STAT3 inhibitors and will provide a discussion on the inhibitory modalities developed to date. METHODS Review of the literature focused on the modalities and mechanisms that directly target and inhibit the STAT protein or its functions. RESULTS/CONCLUSION While a variety of STAT3 inhibitors have been identified that induce antitumor cell effects in vitro and in vivo, the landscape remains murky. With a few exceptions, most of the STAT3 inhibitors reported to date have not undergone an in vivo efficacy, pharmacology or toxicity testing. Also, there is no evidence, per the published literature of an impending clinical development for the few agents that were reported to exhibit in vivo efficacy. Overall, there is the need for a reassessment of the ongoing strategies to target STAT3 intended not only for refinement, but also for incorporating some new technologies to strengthen our efforts and ensure the success - sooner, rather than later - of identifying suitable anti-STAT3 agents for development into clinically useful anticancer therapeutics.
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Affiliation(s)
- Peibin Yue
- University of Central Florida College of Medicine, Burnett School of Biomedical Sciences, Biomolecular Science Center, Department of Molecular Biology and Microbiology, 12722 Research Parkway, Orlando, FL 32826, USA
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Singh R, Kesarwani P, Ahirwar DK, Kapoor R, Mittal RD. Interleukin 8 −251T>A and Interferon gamma +874A>T polymorphism: Potential predictors of allograft outcome in renal transplant recipients from north India. Transpl Immunol 2009; 21:13-7. [DOI: 10.1016/j.trim.2009.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 12/26/2008] [Accepted: 01/09/2009] [Indexed: 11/25/2022]
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18
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Mahdavi A, Davey RE, Bhola P, Yin T, Zandstra PW. Sensitivity analysis of intracellular signaling pathway kinetics predicts targets for stem cell fate control. PLoS Comput Biol 2008; 3:e130. [PMID: 17616983 PMCID: PMC1913098 DOI: 10.1371/journal.pcbi.0030130] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Accepted: 05/22/2007] [Indexed: 01/16/2023] Open
Abstract
Directing stem cell fate requires knowledge of how signaling networks integrate temporally and spatially segregated stimuli. We developed and validated a computational model of signal transducer and activator of transcription-3 (Stat3) pathway kinetics, a signaling network involved in embryonic stem cell (ESC) self-renewal. Our analysis identified novel pathway responses; for example, overexpression of the receptor glycoprotein-130 results in reduced pathway activation and increased ESC differentiation. We used a systematic in silico screen to identify novel targets and protein interactions involved in Stat3 activation. Our analysis demonstrates that signaling activation and desensitization (the inability to respond to ligand restimulation) is regulated by balancing the activation state of a distributed set of parameters including nuclear export of Stat3, nuclear phosphatase activity, inhibition by suppressor of cytokine signaling, and receptor trafficking. This knowledge was used to devise a temporally modulated ligand delivery strategy that maximizes signaling activation and leads to enhanced ESC self-renewal.
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Affiliation(s)
- Alborz Mahdavi
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Ryan E Davey
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Patrick Bhola
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Ting Yin
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Peter W Zandstra
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
- * To whom correspondence should be addressed. E-mail:
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Sehgal PB. Paradigm shifts in the cell biology of STAT signaling. Semin Cell Dev Biol 2008; 19:329-40. [PMID: 18691663 DOI: 10.1016/j.semcdb.2008.07.003] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 07/15/2008] [Accepted: 07/17/2008] [Indexed: 01/25/2023]
Abstract
In recent years several of the key tenets of the original cytokine-STAT-signaling paradigm had to be revised. First, the notion that nonphosphorylated "inactive" STATs are present in the cytoplasm as free monomers which dimerized only subsequent to Tyr-phosphorylation has been replaced by the understanding that nonphosphorylated STATs in the cytoplasm exist largely as dimers and high molecular mass "statosome" complexes. Second, the notion that phosphorylation, either of Tyr or Ser residues or both, in STAT species is required for transcriptional activation has been replaced by the realization that nonphosphorylated STATs can be transcriptionally active albeit with respect to sets of target genes distinct from phosphorylated STATs. Third, the notion that it is the activation by phosphorylation of STATs at the plasma membrane that then leads to their import into the nucleus has been replaced by the recognition that even nonphosphorylated STATs shuttle between the cytoplasm and nucleus at all times in a constitutive manner. Fourth, the notion that the trans-cytoplasmic transit of STATs from the plasma membrane to the nuclear import machinery takes place exclusively as a free cytosolic process has been replaced by the understanding that at least a portion of this trans-cytoplasmic transit is mediated via membrane-associated caveolar and endocytic trafficking (the "signaling endosome" hypothesis). Fifth, the targeting and sequestration of activated STAT3 to long-lived endosomes in the cytoplasm requires consideration of STAT3-mediated "signal transduction" from the plasma membrane to cytoplasmic membrane destinations potentially for function(s) in the cytoplasm. Indeed, in tissue sections many discrete histologic cell types display PY-STAT3 almost exclusively in the cytoplasm with little, if any, in the nucleus. New challenges include determining the structural bases for the recruitment of nonphosphorylated dimeric STAT species to the cytosolic face of membranes including at the cytoplasmic tails of respective receptor complexes, the conformational changes subsequent to phosphorylation and the structural bases for the targeting and functions of STAT proteins within the cytoplasm per se.
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Affiliation(s)
- Pravin B Sehgal
- Department of Cell Biology & Anatomy, New York Medical College, Valhalla, NY 10595, United States.
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Abstract
Interferons (IFNs) were discovered 50 years ago independently by Isaacs and Lindemann and by Nagata and Kojima. When it was later realized that IFNs are active at very low concentrations, research began to determine how their powerful effects were generated from such a small initial signal. It has since been established that interferons, as well as all other cytokines, employ cell surface receptors to translate their presence in the serum to a potent cellular response to a viral infection. These receptor complexes are composed of multiple distinct glycosylated transmembrane polypeptides, a number of protein tyrosine kinases, and interact transiently with a large variety of other proteins including transcription factors, phosphatases, signaling repressors, and adaptor proteins coupling the receptor to alternative signaling pathways. Three major receptor complexes exist that are exclusive to each of three major classes of interferon. Even though the effects of each major class of interferon vary physiologically, each receptor complex interacts with its ligand in similar ways and activates similar signaling cascades. In this mini-review, we take a historical perspective at the major events in the characterization of interferon receptors, discussing interesting results that still need to be explained.
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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, Piscataway, NJ 08854, USA
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21
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STAT3 expression in salivary gland tumours. Oral Oncol 2007; 44:439-45. [PMID: 17826306 DOI: 10.1016/j.oraloncology.2007.05.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 05/23/2007] [Accepted: 05/24/2007] [Indexed: 11/27/2022]
Abstract
The aim of the present study was to evaluate the signal transducer and activator of transcription (STAT3) expression, which is constitutively active in different types of malignant tumours, in salivary gland tumours. Fifty biopsies of salivary gland tumours (9 pleomorphic adenomas, 12 adenoid cystic carcinomas, 7 epithelial-myoepithelial carcinomas, 10 polymorphous low-grade adenocarcinomas and 12 mucoepidermoid carcinomas) and 10 normal salivary glands were immunohistochemically labeled for STAT3 and Phospho-STAT3 (STAT3P). The labeled sections were qualitatively and quantitatively evaluated. The results showed that, in normal salivary gland, STAT3 was expressed in cytoplasm and STAT3P in nuclei of all tissue cells, except in large mucous acinar cells for which both antibodies were negative. In pleomorphic adenoma, the expression was the same as in normal glands. In malignant tumours, there were variations in the expression of these antibodies. The most important one was the presence of STAT3 in the nuclei of the malignant tumour cells, most evident in the cribriform-type of adenoid cystic carcinoma. Both loss and variation of STAT3P expression were also observed. The presence of STAT3 in the nuclei of malignant salivary gland tumours may represent an important event in oncogenesis probably contributing to tumour cell proliferation while blocking apoptosis. However, further investigation will be necessary to support this hypothesis.
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22
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Li L, Shaw PE. Elevated activity of STAT3C due to higher DNA binding affinity of phosphotyrosine dimer rather than covalent dimer formation. J Biol Chem 2006; 281:33172-81. [PMID: 16956893 DOI: 10.1074/jbc.m606940200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Signal transducer and activator of transcription (STAT) proteins are involved in cell proliferation and survival, aspects of tissue differentiation and immune function. STAT3 appears to be fundamentally important for vertebrate organisms, being required for the self-renewal of embryonal stem cells in response to leukemia inhibitory factor signaling and for proliferation of some somatic cell types. Moreover, STAT3 is up-regulated in a range of tumors, and a modified version of STAT3 (STAT3C) has been shown to function as an oncogene, whereas inhibition of STAT3 can suppress tumor cell growth. The constitutive activity of oncogenic STAT3C was reported to depend on spontaneous dimerization directed by disulfide bonds in the absence of tyrosine phosphorylation. In fact, tyrosine phosphorylation consequent upon cytokine or mitogen-induced signaling events remains obligatory for STAT3C activation. Instead, the DNA-binding affinity of phospho-STAT3C is elevated resulting in a faster on-rate and slower off-rate. The faster on-rate sensitizes STAT3C to cytokine stimulation, and the slower off-rate protects it from inactivation by nuclear phosphatases. These changes account for the ability of STAT3C to up-regulate persistently the expression of STAT3 target genes and promote cell cycle progression.
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Affiliation(s)
- Li Li
- Centre for Biochemistry and Cell Biology, School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
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23
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Zhang L, Badgwell DB, Bevers JJ, Schlessinger K, Murray PJ, Levy DE, Watowich SS. IL-6 signaling via the STAT3/SOCS3 pathway: functional analysis of the conserved STAT3 N-domain. Mol Cell Biochem 2006; 288:179-89. [PMID: 16718380 PMCID: PMC2441693 DOI: 10.1007/s11010-006-9137-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 01/17/2006] [Indexed: 10/24/2022]
Abstract
The conserved N-domain of the STAT proteins has been implicated in several activities crucial to cytokine signaling including receptor recruitment and STAT activation, cooperative DNA binding and STAT-dependent gene expression. We evaluated the role of the STAT3 N-domain in the IL-6 signal transduction pathway leading to Socs3 gene expression, an essential mechanism that controls the quality and magnitude of IL-6-dependent transcriptional responses. Based on the model for STAT N-domain function in cooperative gene expression and the presence of tandem STAT binding motifs in the murine Socs3 promoter, we anticipated that stabilizing interactions between adjacent STAT3 dimers via N-domain sequences might be essential for Socs3 gene expression. This was underscored by the tight conservation in the location and sequence of the tandem STAT binding sites between the murine and human Socs3 promoters. Using reconstitution into Stat3-/- mouse embryonic fibroblasts (Stat3-/- MEFs), we find that a STAT3 N-domain deletion mutant (Delta 133STAT3) is activated by tyrosine phosphorylation in response to IL-6 and then undergoes dephosphorylation with kinetics similar to full-length STAT3. These results highlight important differences compared to other STATs where the N-domain has been shown to mediate activation (STAT4) or dephosphorylation (STAT1). STAT3 binds predominantly to a single STAT consensus site in the Socs3 promoter, despite the presence of an adjacent STAT motif. Significantly, Delta 133STAT3 stimulates expression of the endogenous Socs3 gene in Stat3-/- MEFs upon IL-6 treatment with an activity similar to reconstituted STAT3, demonstrating that the N-domain is dispensable for Socs3 gene expression. We propose that the Socs3 gene in its chromosomal context is activated by the IL-6/STAT3 pathway independent of STAT3 N-domain sequences.
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Affiliation(s)
- Ling Zhang
- Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
| | - Donna B. Badgwell
- Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
- The Graduate School of Biomedical Sciences, University of Texas, Houston, Texas 77030
| | - Jack J. Bevers
- Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
- The Graduate School of Biomedical Sciences, University of Texas, Houston, Texas 77030
| | - Karni Schlessinger
- New York University School of Medicine, New York, NY 10016
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT
| | - Peter J. Murray
- Department of Infectious Diseases, St. Jude Children’s Research Hospital, Memphis, TN 38105
| | - David E. Levy
- New York University School of Medicine, New York, NY 10016
| | - Stephanie S. Watowich
- Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030
- The Graduate School of Biomedical Sciences, University of Texas, Houston, Texas 77030
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Shah M, Patel K, Mukhopadhyay S, Xu F, Guo G, Sehgal PB. Membrane-associated STAT3 and PY-STAT3 in the Cytoplasm. J Biol Chem 2006; 281:7302-8. [PMID: 16407171 DOI: 10.1074/jbc.m508527200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signal transduction from the plasma membrane to the nucleus by STAT proteins is widely represented as exclusively a soluble cytosolic process. Using cell-fractionation methods, we observed that approximately 5% of cytoplasmic STAT3 was constitutively associated with the purified early endosome (EE) fraction in human Hep3B liver cells. By 15-30 min after interleukin-6 (IL-6) treatment, up to two-thirds of cytoplasmic Tyr-phosphorylated STAT3 can be associated with the purified early endosome fraction (Rab-5-, EEA1-, transferrin receptor-, and clathrin-positive fraction). Electron microscopy, immunofluorescence, and detergent dissection approaches confirmed the association of STAT3 and PY-STAT3 with early endosomes. STAT3 was constitutively associated with clathrin heavy chain in membrane and in the 1- to 2-MDa cytosolic complexes. The membrane association was dynamic in that, within 15 min of treatment with the vicinal-thiol cross-linker phenylarsine oxide, there was a dramatic increase in bulk STAT3 association with sedimentable membranes. The functional contribution of PY-STAT3 association with the endocytic pathway was evaluated in transient transfection assays using IL-6-inducible STAT3-reporter-luciferase constructs and selective regulators of this pathway. STAT3-transcriptional activation was inhibited by expression constructs for dominant negative dynamin K44A, epsin 2a, amphiphysin A1, and clathrin light chain but enhanced by that for the active dynamin species MxA. Taken together, these studies emphasize the contribution of the endocytic pathway to productive IL-6/STAT3 signaling.
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Affiliation(s)
- Mehul Shah
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA
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25
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Krause CD, Mei E, Mirochnitchenko O, Lavnikova N, Xie J, Jia Y, Hochstrasser RM, Pestka S. Interactions among the components of the interleukin-10 receptor complex. Biochem Biophys Res Commun 2006; 340:377-85. [PMID: 16364239 DOI: 10.1016/j.bbrc.2005.11.182] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Accepted: 11/29/2005] [Indexed: 11/18/2022]
Abstract
We used fluorescence resonance energy transfer previously to show that the interferon-gamma (IFN-gamma) receptor complex is a preformed entity mediated by constitutive interactions between the IFN-gammaR2 and IFN-gammaR1 chains, and that this preassembled entity changes its structure after the treatment of cells with IFN-gamma. We applied this technique to determine the structure of the interleukin-10 (IL-10) receptor complex and whether it undergoes a similar conformational change after treatment of cells with IL-10. We report that, like the IFN-gamma receptor complex, the IL-10 receptor complex is preassembled: constitutive but weaker interactions occur between the IL-10R1 and IL-10R2 chains, and between two IL-10R2 chains. The IL-10 receptor complex undergoes no major conformational changes when cells are treated with cellular or Epstein-Barr viral IL-10. Receptor complex preassembly may be an inherent feature of Class 2 cytokine receptor complexes.
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Affiliation(s)
- Christopher D Krause
- Department of Molecular Genetics, Microbiology, and Immunology, The University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA
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26
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Neculai D, Neculai AM, Verrier S, Straub K, Klumpp K, Pfitzner E, Becker S. Structure of the Unphosphorylated STAT5a Dimer*. J Biol Chem 2005; 280:40782-7. [PMID: 16192273 DOI: 10.1074/jbc.m507682200] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
STAT proteins have the function of signaling from the cell membrane into the nucleus, where they regulate gene transcription. Latent mammalian STAT proteins can form dimers in the cytoplasm even before receptor-mediated activation by specific tyrosine phosphorylation. Here we describe the 3.21-A crystal structure of an unphosphorylated STAT5a homodimer lacking the N-terminal domain as well as the C-terminal transactivation domain. The overall structure of this fragment is very similar to phosphorylated STATs. However, important differences exist in the dimerization mode. Although the interface between phosphorylated STATs is mediated by their Src-homology 2 domains, the unphosphorylated STAT5a fragment dimerizes in a completely different manner via interactions between their beta-barrel and four-helix bundle domains. The STAT4 N-terminal domain dimer can be docked onto this STAT5a core fragment dimer based on shape and charge complementarities. The separation of the dimeric arrangement, taking place upon activation and nuclear translocation of STAT5a, is demonstrated by fluorescence resonance energy transfer experiments in living cells.
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Affiliation(s)
- Dante Neculai
- Department for NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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Stable expression of constitutively-activated STAT3 in benign prostatic epithelial cells changes their phenotype to that resembling malignant cells. Mol Cancer 2005; 4:2. [PMID: 15647107 PMCID: PMC546221 DOI: 10.1186/1476-4598-4-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2004] [Accepted: 01/12/2005] [Indexed: 12/15/2022] Open
Abstract
Background Signal transducers and activators of transcription (STATs) are involved in growth regulation of cells. They are usually activated by phosphorylation at specific tyrosine residues. In neoplastic cells, constitutive activation of STATs accompanies growth dysregulation and resistance to apoptosis through changes in gene expression, such as enhanced anti-apoptotic gene expression or reduced pro-apoptotic gene expression. Activated STAT3 is thought to play an important role in prostate cancer (PCA) progression. Because we are interested in how persistently-activated STAT3 changes the cellular phenotype to a malignant one in prostate cancer, we used expression vectors containing a gene for constitutively-activated STAT3, called S3c, into NRP-152 rat and BPH-1 human benign prostatic epithelial cells. Results We observed that prostatic cell lines stably expressing S3c required STAT3 expression for survival, because they became sensitive to antisense oligonucleotide for STAT3. However, S3c-transfected cells were not sensitive to the effects of JAK inhibitors, meaning that STAT3 was constitutively-activated in these transfected cell lines. NRP-152 prostatic epithelial cells lost the requirement for exogenous growth factors. Furthermore, we observed that NRP-152 expressing S3c had enhanced mRNA levels of retinoic acid receptor (RAR)-α, reduced mRNA levels of RAR-β and -γ, while BPH-1 cells transfected with S3c became insensitive to the effects of androgen, and also to the effects of a testosterone antagonist. Both S3c-transfected cell lines grew in soft agar after stable transfection with S3c, however neither S3c-transfected cell line was tumorigenic in severe-combined immunodeficient mice. Conclusions We conclude, based on our findings, that persistently-activated STAT3 is an important molecular marker of prostate cancer, which develops in formerly benign prostate cells and changes their phenotype to one more closely resembling transformed prostate cells. That the S3c-transfected cell lines require the continued expression of S3c demonstrates that a significant phenotypic change occurred in the cells. These conclusions are based on our data with respect to loss of growth factor requirement, loss of androgen response, gain of growth in soft agar, and changes in RAR subunit expression, all of which are consistent with a malignant phenotype in prostate cancer. However, an additional genetic change may be required for S3c-transfected prostate cells to become tumorigenic.
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Lopez-Ilasaca MA, Bernabe-Ortiz JC, Na SY, Dzau VJ, Xavier RJ. Bioluminescence resonance energy transfer identify scaffold protein CNK1 interactions in intact cells. FEBS Lett 2004; 579:648-54. [PMID: 15670823 DOI: 10.1016/j.febslet.2004.12.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2004] [Revised: 10/08/2004] [Accepted: 12/05/2004] [Indexed: 11/16/2022]
Abstract
Connector enhancer of KSR (CNK) proteins have been proposed to act as scaffolds in the Ras-MAPK pathway. In this work, using in vivo bioluminescence resonance energy transfer (BRET) assays and in vitro co-immunoprecipitation, we show that hCNK1 interacts with the active form of Rho A (G14V) proteins. The domain of hCNK1 that allows binding to Rho proteins involves the C-terminal PH domain. Overexpression of hCNK1 does not affect the actin cytoskeleton and does not modify the appearance of stress fibers in cells overexpressing a constitutively active form of RhoA. In contrast, hCNK1 was able to significantly decrease the RhoA-induced transcriptional activity of the serum response element (SRE) without effect on the Ras-induced SRE activation. These results identify hCNK1 as a specific partner of Rho proteins both in vitro and in vivo and suggest a role of hCNK1 in the signal transduction of Rho proteins.
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Affiliation(s)
- Marco A Lopez-Ilasaca
- Cardiovascular Research Laboratories, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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29
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Grütz G. New insights into the molecular mechanism of interleukin-10-mediated immunosuppression. J Leukoc Biol 2004; 77:3-15. [PMID: 15522916 DOI: 10.1189/jlb.0904484] [Citation(s) in RCA: 219] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Interleukin-10 (IL-10) is an important immunomodulatory cytokine, which has attracted much attention because of its anti-inflammatory properties. It reduces antigen presentation and inhibits T cell activation. IL-10-treated myeloid cells lose their ability to respond toward the endotoxin lipopolysaccharide (LPS) with the production of several proinflammatory mediators. Thereby, IL-10 limits excessive inflammatory reactions in response to endotoxin as it occurs in colitis or endotoxin shock. Mice can be tolerized toward endotoxin shock when pretreated with a sublethal dose of LPS. This can be mimicked in vitro as LPS desensitization, resulting in a similar LPS hyporesponsiveness as observed with IL-10 pretreatment. However, an early block in LPS signaling characterizes LPS desensitization, whereas IL-10 seems to target late events. Controversial reports have been published where IL-10 would interfere with the induction of proinflammatory mediators, and little is known about the molecular mechanisms behind the anti-inflammatory activities of IL-10. Some recent publications have tried to gain more insight into the molecular mechanism of IL-10 by gene-expression profiling and functional studies in myeloid-derived cells. These results are reviewed here and compared with the progress that has been made to understand the induction of endotoxin tolerance by LPS itself.
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Affiliation(s)
- Gerald Grütz
- Charité Berlin, Institute of Medical Immunology, Luisenstr. 6-8, Berlin, Germany.
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30
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Li L, Shaw PE. A STAT3 dimer formed by inter-chain disulphide bridging during oxidative stress. Biochem Biophys Res Commun 2004; 322:1005-11. [PMID: 15336564 DOI: 10.1016/j.bbrc.2004.08.014] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2004] [Indexed: 01/02/2023]
Abstract
Signal transducer and activator of transcription (STAT) proteins are activated by cytokines and growth factors to play distinct roles in immune responses and developmental processes. STATs were thought to exist as latent, cytoplasmic monomers and activation to require dimer formation was mediated exclusively by reciprocal phospho-tyrosine/SH2-domain interactions, but recent evidence of cytoplasmic STAT complexes, including dimers, and unphosphorylated STATs in the nucleus has challenged these notions. STAT complexes detected by conventional SDS-PAGE, including a STAT3 dimer, have been reported. We show that such complexes can form during cell lysis and be disrupted with DTT, suggesting inter-chain disulphide bridging. STAT3 also forms a related complex in cells upon oxidative stress. We map the interaction to the amino-terminal domain of STAT3 and use mass spectrometry to implicate cysteine 259 as the reactive residue. The redox sensitivity of STAT3 may be significant, given its activation in cells in response to reactive oxygen species.
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Affiliation(s)
- Li Li
- School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK
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