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Kazzaz SA, Tawil J, Harhaj EW. The aryl hydrocarbon receptor-interacting protein in cancer and immunity: Beyond a chaperone protein for the dioxin receptor. J Biol Chem 2024; 300:107157. [PMID: 38479600 PMCID: PMC11002312 DOI: 10.1016/j.jbc.2024.107157] [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: 01/09/2024] [Revised: 03/04/2024] [Accepted: 03/06/2024] [Indexed: 04/04/2024] Open
Abstract
The aryl hydrocarbon receptor (AhR)-interacting protein (AIP) is a ubiquitously expressed, immunophilin-like protein best known for its role as a co-chaperone in the AhR-AIP-Hsp90 cytoplasmic complex. In addition to regulating AhR and the xenobiotic response, AIP has been linked to various aspects of cancer and immunity that will be the focus of this review article. Loss-of-function AIP mutations are associated with pituitary adenomas, suggesting that AIP acts as a tumor suppressor in the pituitary gland. However, the tumor suppressor mechanisms of AIP remain unclear, and AIP can exert oncogenic functions in other tissues. While global deletion of AIP in mice yields embryonically lethal cardiac malformations, heterozygote, and tissue-specific conditional AIP knockout mice have revealed various physiological roles of AIP. Emerging studies have established the regulatory roles of AIP in both innate and adaptive immunity. AIP interacts with and inhibits the nuclear translocation of the transcription factor IRF7 to inhibit type I interferon production. AIP also interacts with the CARMA1-BCL10-MALT1 complex in T cells to enhance IKK/NF-κB signaling and T cell activation. Taken together, AIP has diverse functions that vary considerably depending on the client protein, the tissue, and the species.
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Affiliation(s)
- Sarah A Kazzaz
- Department of Microbiology and Immunology, Penn State College of Medicine, Hershey, Pennsylvania, USA; Medical Scientist Training Program, Penn State College of Medicine, Hershey, Pennsylvania, USA
| | - John Tawil
- Department of Microbiology and Immunology, Penn State College of Medicine, Hershey, Pennsylvania, USA
| | - Edward W Harhaj
- Department of Microbiology and Immunology, Penn State College of Medicine, Hershey, Pennsylvania, USA.
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2
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Huang W, Rui K, Wang X, Peng N, Zhou W, Shi X, Lu L, Hu D, Tian J. The aryl hydrocarbon receptor in immune regulation and autoimmune pathogenesis. J Autoimmun 2023; 138:103049. [PMID: 37229809 DOI: 10.1016/j.jaut.2023.103049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/10/2023] [Accepted: 04/18/2023] [Indexed: 05/27/2023]
Abstract
As a ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR) is activated by structurally diverse ligands derived from the environment, diet, microorganisms, and metabolic activity. Recent studies have demonstrated that AhR plays a key role in modulating both innate and adaptive immune responses. Moreover, AhR regulates innate immune and lymphoid cell differentiation and function, which is involved in autoimmune pathogenesis. In this review, we discuss recent advances in understanding the mechanism of activation of AhR and its mediated functional regulation in various innate immune and lymphoid cell populations, as well as the immune-regulatory effect of AhR in the development of autoimmune diseases. In addition, we highlight the identification of AhR agonists and antagonists that may serve as potential therapeutic targets for the treatment of autoimmune disorders.
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Affiliation(s)
- Wei Huang
- Institute of Medical Immunology, Affiliated Hospital of Jiangsu University, Zhenjiang, China; Department of Laboratory Medicine, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Ke Rui
- Institute of Medical Immunology, Affiliated Hospital of Jiangsu University, Zhenjiang, China; Department of Laboratory Medicine, Affiliated Hospital of Jiangsu University, Zhenjiang, China.
| | - Xiaomeng Wang
- Institute of Medical Immunology, Affiliated Hospital of Jiangsu University, Zhenjiang, China; Department of Laboratory Medicine, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Na Peng
- Department of Rheumatology and Nephrology, The Second People's Hospital, China Three Gorges University, Yichang, China
| | - Wenhao Zhou
- Department of Laboratory Medicine, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Xiaofei Shi
- Department of Rheumatology and Immunology, The First Affiliated Hospital and School of Medicine, Henan University of Science and Technology, Luoyang, China
| | - Liwei Lu
- Department of Pathology and Shenzhen Institute of Research and Innovation, The University of Hong Kong, Chongqing International Institute for Immunology, China
| | - Dajun Hu
- Department of Rheumatology and Nephrology, The Second People's Hospital, China Three Gorges University, Yichang, China.
| | - Jie Tian
- Institute of Medical Immunology, Affiliated Hospital of Jiangsu University, Zhenjiang, China; Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China.
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Ortiz NR, Guy N, Garcia YA, Sivils JC, Galigniana MD, Cox MB. Functions of the Hsp90-Binding FKBP Immunophilins. Subcell Biochem 2023; 101:41-80. [PMID: 36520303 DOI: 10.1007/978-3-031-14740-1_2] [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] [Indexed: 12/23/2022]
Abstract
The Hsp90 chaperone is known to interact with a diverse array of client proteins. However, in every case examined, Hsp90 is also accompanied by a single or several co-chaperone proteins. One class of co-chaperone contains a tetratricopeptide repeat (TPR) domain that targets the co-chaperone to the C-terminal region of Hsp90. Within this class are Hsp90-binding peptidylprolyl isomerases, most of which belong to the FK506-binding protein (FKBP) family. Despite the common association of FKBP co-chaperones with Hsp90, it is abundantly clear that the client protein influences, and is often influenced by, the particular FKBP bound to Hsp90. Examples include Xap2 in aryl hydrocarbon receptor complexes and FKBP52 in steroid receptor complexes. In this chapter, we discuss the known functional roles played by FKBP co-chaperones and, where possible, relate distinctive functions to structural differences between FKBP members.
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Affiliation(s)
- Nina R Ortiz
- Border Biomedical Research Center and Department of Biological Sciences, University of Texas at El Paso, El Paso, TX, USA
| | - Naihsuan Guy
- Border Biomedical Research Center and Department of Biological Sciences, University of Texas at El Paso, El Paso, TX, USA
| | - Yenni A Garcia
- Border Biomedical Research Center and Department of Biological Sciences, University of Texas at El Paso, El Paso, TX, USA
| | - Jeffrey C Sivils
- Border Biomedical Research Center and Department of Biological Sciences, University of Texas at El Paso, El Paso, TX, USA
| | - Mario D Galigniana
- Departamento de Química Biológica/IQUIBICEN, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Biología y Medicina Experimental/CONICET, Buenos Aires, Argentina
| | - Marc B Cox
- Border Biomedical Research Center and Department of Biological Sciences, University of Texas at El Paso, El Paso, TX, USA.
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Texas at El Paso, El Paso, TX, USA.
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4
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Engin AB, Engin ED, Engin A. The effect of environmental pollution on immune evasion checkpoints of SARS-CoV-2. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2021; 81:103520. [PMID: 33132153 PMCID: PMC7580701 DOI: 10.1016/j.etap.2020.103520] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 10/15/2020] [Accepted: 10/18/2020] [Indexed: 05/04/2023]
Abstract
Many diverse strategies allow and facilitate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to evade antiviral innate immune mechanisms. Although the type I interferon (IFN) system has a critical role in restricting the dissemination of viral infection, suppression of IFN receptor signals by SARS-CoV-2 constitutes a checkpoint that plays an important role in the immune escape of the virus. Environmental pollution not only facilitates SARS-CoV-2 infection but also increases infection-associated fatality risk, which arises due to Systemic Aryl hydrocarbon Receptor (AhR) Activation Syndrome. The intracellular accumulation of endogenous kynurenic acid due to overexpression of the indoleamine 2,3-dioxygenase (IDO) by AhR activation induces AhR-interleukin-6 (IL-6)-signal transducers and activators of the transcription 3 (STAT3) signaling pathway. The AhR-IDO1-Kynurenine pathway is an important checkpoint, which leads to fatal consequences in SARS-CoV-2 infection and immune evasion in the context of Treg/Th17 imbalance and cytokine storm.
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Affiliation(s)
- Ayse Basak Engin
- Gazi University, Faculty of Pharmacy, Department of Toxicology, Ankara, Turkey.
| | - Evren Doruk Engin
- Ankara University, Biotechnology Institute, Gumusdere Campus, Kecioren, Ankara, Turkey
| | - Atilla Engin
- Gazi University, Faculty of Medicine, Department of General Surgery, Ankara, Turkey
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Parasar B, Chang PV. Engineered Th17 Cell Differentiation Using a Photoactivatable Immune Modulator. J Am Chem Soc 2020; 142:18103-18108. [PMID: 32975936 PMCID: PMC11100974 DOI: 10.1021/jacs.0c07485] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
T helper 17 (Th17) cells, an important subset of CD4+ T cells, help to eliminate extracellular infectious pathogens that have invaded our tissues. Despite the critical roles of Th17 cells in immunity, how the immune system regulates the production and maintenance of this cell type remains poorly understood. In particular, the plasticity of these cells or their dynamic ability to trans-differentiate into other CD4+ T cell subsets remains mostly uncharacterized. Here, we report a synthetic immunology approach using a photoactivatable immune modulator (PIM) to increase Th17 cell differentiation on demand with spatial and temporal precision to help elucidate this important and dynamic process. In this chemical strategy, we developed a latent agonist that upon photochemical activation releases a small-molecule ligand that targets the aryl hydrocarbon receptor (AhR) and ultimately induces Th17 cell differentiation. We used this chemical tool to control AhR activation with spatiotemporal precision within cells and to modulate Th17 cell differentiation on demand using UV light illumination. We envision that this approach will enable an understanding of the dynamic functions and behaviors of Th17 cells in vivo during immune responses and in mouse models of inflammatory disease.
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Baldwin WS. Phase 0 of the Xenobiotic Response: Nuclear Receptors and Other Transcription Factors as a First Step in Protection from Xenobiotics. NUCLEAR RECEPTOR RESEARCH 2019; 6:101447. [PMID: 31815118 PMCID: PMC6897393 DOI: 10.32527/2019/101447] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
This mini-review examines the crucial importance of transcription factors as a first line of defense in the detoxication of xenobiotics. Key transcription factors that recognize xenobiotics or xenobiotic-induced stress such as reactive oxygen species (ROS), include AhR, PXR, CAR, MTF, Nrf2, NF-κB, and AP-1. These transcription factors constitute a significant portion of the pathways induced by toxicants as they regulate phase I-III detoxication enzymes and transporters as well as other protective proteins such as heat shock proteins, chaperones, and anti-oxidants. Because they are often the first line of defense and induce phase I-III metabolism, could these transcription factors be considered the phase 0 of xenobiotic response?
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Affiliation(s)
- William S Baldwin
- Clemson University, Biological Sciences/Environmental Toxicology, 132 Long Hall, Clemson, SC 29634
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7
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Fock V, Gudmundsson SR, Gunnlaugsson HO, Stefansson JA, Ionasz V, Schepsky A, Viarigi J, Reynisson IE, Pogenberg V, Wilmanns M, Ogmundsdottir MH, Steingrimsson E. Subcellular localization and stability of MITF are modulated by the bHLH-Zip domain. Pigment Cell Melanoma Res 2018; 32:41-54. [PMID: 29938923 DOI: 10.1111/pcmr.12721] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 06/01/2018] [Accepted: 06/19/2018] [Indexed: 12/15/2022]
Abstract
Microphthalmia-associated transcription factor (MITF) is a member of the basic helix-loop-helix leucine zipper (bHLH-Zip) family and functions as the master regulator of the melanocytic lineage. MITF-M is the predominant isoform expressed in melanocytes and melanoma cells, and, unlike other MITF isoforms, it is constitutively nuclear. Mutational analysis revealed three karyophilic signals in the bHLH-Zip domain of MITF-M, spanning residues 197-206, 214-217, and 255-265. Structural characterization of the MITF protein showed that basic residues within these signals are exposed for interactions in the absence of DNA. Moreover, our data indicate that neither DNA binding nor dimerization of MITF-M are required for its nuclear localization. Finally, dimerization-deficient MITF-M mutants exhibited a significantly reduced stability in melanoma cells when compared to the wild-type protein. Taken together, we have shown that, in addition to its well-established role in DNA binding and dimer formation, the bHLH-Zip domain of MITF modulates the transcription factor's subcellular localization and stability.
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Affiliation(s)
- Valerie Fock
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Sigurdur Runar Gudmundsson
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Hilmar Orn Gunnlaugsson
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Jon August Stefansson
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Vivien Ionasz
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Alexander Schepsky
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Jade Viarigi
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Indridi Einar Reynisson
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | | | | | - Margret Helga Ogmundsdottir
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
| | - Eirikur Steingrimsson
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, BioMedical Center, University of Iceland, Reykjavik, Iceland
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Hernández-Ramírez LC, Morgan RM, Barry S, D’Acquisto F, Prodromou C, Korbonits M. Multi-chaperone function modulation and association with cytoskeletal proteins are key features of the function of AIP in the pituitary gland. Oncotarget 2018; 9:9177-9198. [PMID: 29507682 PMCID: PMC5823669 DOI: 10.18632/oncotarget.24183] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 01/01/2018] [Indexed: 11/25/2022] Open
Abstract
Despite the well-recognized role of loss-of-function mutations of the aryl hydrocarbon receptor interacting protein gene (AIP) predisposing to pituitary adenomas, the pituitary-specific function of this tumor suppressor remains an enigma. To determine the repertoire of interacting partners for the AIP protein in somatotroph cells, wild-type and variant AIP proteins were used for pull-down/quantitative mass spectrometry experiments against lysates of rat somatotropinoma-derived cells; relevant findings were validated by co-immunoprecipitation and co-localization. Global gene expression was studied in AIP mutation positive and negative pituitary adenomas via RNA microarrays. Direct interaction with AIP was confirmed for three known and six novel partner proteins. Novel interactions with HSPA5 and HSPA9, together with known interactions with HSP90AA1, HSP90AB1 and HSPA8, indicate that the function/stability of multiple chaperone client proteins could be perturbed by a deficient AIP co-chaperone function. Interactions with TUBB, TUBB2A, NME1 and SOD1 were also identified. The AIP variants p.R304* and p.R304Q showed impaired interactions with HSPA8, HSP90AB1, NME1 and SOD1; p.R304* also displayed reduced binding to TUBB and TUBB2A, and AIP-mutated tumors showed reduced TUBB2A expression. Our findings suggest that cytoskeletal organization, cell motility/adhesion, as well as oxidative stress responses, are functions that are likely to be involved in the tumor suppressor activity of AIP.
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Affiliation(s)
- Laura C. Hernández-Ramírez
- Centre for Endocrinology, Barts and The London School of Medicine, Queen Mary University of London, London, EC1M 6BQ, UK
- Present address: Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD 20892-1862, USA
| | - Rhodri M.L. Morgan
- Genome Damage and Stability Centre, University of Sussex, Brighton, Falmer, BN1 9RQ, UK
- Present address: Protein Crystallography Facility, Centre for Structural Biology, Flowers Building, Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Sayka Barry
- Centre for Endocrinology, Barts and The London School of Medicine, Queen Mary University of London, London, EC1M 6BQ, UK
| | - Fulvio D’Acquisto
- Centre for Microvascular Research, Barts and The London School of Medicine, Queen Mary University of London, London, EC1M 6BQ, UK
| | | | - Márta Korbonits
- Centre for Endocrinology, Barts and The London School of Medicine, Queen Mary University of London, London, EC1M 6BQ, UK
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Ligand-mediated cytoplasmic retention of the Ah receptor inhibits macrophage-mediated acute inflammatory responses. J Transl Med 2017; 97:1471-1487. [PMID: 28892097 PMCID: PMC5711556 DOI: 10.1038/labinvest.2017.92] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 07/12/2017] [Accepted: 07/18/2017] [Indexed: 12/25/2022] Open
Abstract
The Ah receptor (AHR) has been shown to exhibit both inflammatory and anti-inflammatory activity in a context-specific manner. In vivo macrophage-driven acute inflammation models were utilized here to test whether the selective Ah receptor modulator 1-allyl-7-trifluoromethyl-1H-indazol-3-yl]-4-methoxyphenol (SGA360) would reduce inflammation. Exposure to SGA360 was capable of significantly inhibiting lipopolysaccharide (LPS)-mediated endotoxic shock in a mouse model, both in terms of lethality and attenuating inflammatory signaling in tissues. Topical exposure to SGA360 was also able to mitigate joint edema in a monosodium urate (MSU) crystal gout mouse model. Inhibition was dependent on the expression of the high-affinity allelic AHR variant in both acute inflammation models. Upon peritoneal MSU crystal exposure SGA360 pretreatment inhibited neutrophil and macrophage migration into the peritoneum. RNA-seq analysis revealed that SGA360 attenuated the expression of numerous inflammatory genes and genes known to be directly regulated by AHR in thioglycolate-elicited primary peritoneal macrophages treated with LPS. In addition, expression of the high-affinity allelic AHR variant in cultured macrophages was necessary for SGA360-mediated repression of inflammatory gene expression. Mechanistic studies revealed that SGA360 failed to induce nuclear translocation of the AHR and actually enhanced cytoplasmic localization. LPS treatment of macrophages enhanced the occupancy of the AHR and p65 to the Ptgs2 promoter, whereas SGA360 attenuated occupancy. AHR ligand activity was detected in peritoneal exudates isolated from MSU-treated mice, thus suggesting that the anti-inflammatory activity of SGA360 is mediated at least in part through AHR antagonism of endogenous agonist activity. These results underscore an important role of the AHR in participating in acute inflammatory signaling and warrants further investigations into possible clinical applications.
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10
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Sakurai S, Shimizu T, Ohto U. The crystal structure of the AhRR-ARNT heterodimer reveals the structural basis of the repression of AhR-mediated transcription. J Biol Chem 2017; 292:17609-17616. [PMID: 28904176 DOI: 10.1074/jbc.m117.812974] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 09/12/2017] [Indexed: 12/19/2022] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin and related compounds are extraordinarily potent environmental toxic pollutants. Most of the 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicities are mediated by aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor belonging to the basic helix-loop-helix (bHLH) Per-ARNT-Sim (PAS) family. Upon ligand binding, AhR forms a heterodimer with AhR nuclear translocator (ARNT) and induces the expression of genes involved in various biological responses. One of the genes induced by AhR encodes AhR repressor (AhRR), which also forms a heterodimer with ARNT and represses the activation of AhR-dependent transcription. The control of AhR activation is critical for managing AhR-mediated diseases, but the mechanisms by which AhRR represses AhR activation remain poorly understood, because of the lack of structural information. Here, we determined the structure of the AhRR-ARNT heterodimer by X-ray crystallography, which revealed an asymmetric intertwined domain organization presenting structural features that are both conserved and distinct among bHLH-PAS family members. The structures of AhRR-ARNT and AhR-ARNT were similar in the bHLH-PAS-A region, whereas the PAS-B of ARNT in the AhRR-ARNT complex exhibited a different domain arrangement in this family reported so far. The structure clearly disclosed that AhRR competitively represses AhR binding to ARNT and target DNA and further suggested the existence of an AhRR-ARNT-specific repression mechanism. This study provides a structural basis for understanding the mechanism by which AhRR represses AhR-mediated gene transcription.
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Affiliation(s)
- Shunya Sakurai
- From the Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan and
| | - Toshiyuki Shimizu
- From the Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan and .,the Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Umeharu Ohto
- From the Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan and
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Sharma RP, Schuhmacher M, Kumar V. Review on crosstalk and common mechanisms of endocrine disruptors: Scaffolding to improve PBPK/PD model of EDC mixture. ENVIRONMENT INTERNATIONAL 2017; 99:1-14. [PMID: 27697394 DOI: 10.1016/j.envint.2016.09.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 09/18/2016] [Accepted: 09/19/2016] [Indexed: 06/06/2023]
Abstract
Endocrine disruptor compounds (EDCs) are environment chemicals that cause harmful effects through multiple mechanisms, interfering with hormone system resulting in alteration of homeostasis, reproduction and developmental effect. Many of these EDCs have concurrent exposure with crosstalk and common mechanisms which may lead to dynamic interactions. To carry out risk assessment of EDCs' mixture, it is important to know the detailed toxic pathway, crosstalk of receptor and other factors like critical window of exposure. In this review, we summarize the major mechanism of actions of EDCs with the different/same target organs interfering with the same/different class of hormone by altering their synthesis, metabolism, binding and cellular action. To show the impact of EDCs on life stage development, a case study on female fertility affecting germ cell is illustrated. Based on this summarized discussion, major groups of EDCs are classified based on their target organ, mode of action and potential risk. Finally, a conceptual model of pharmacodynamic interaction is proposed to integrate the crosstalk and common mechanisms that modulate estrogen into the predictive mixture dosimetry model with dynamic interaction of mixture. This review will provide new insight for EDCs' risk assessment and can be used to develop next generation PBPK/PD models for EDCs' mixture analysis.
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Affiliation(s)
- Raju Prasad Sharma
- Center of Environmental Food and Toxicological Technology (TecnATox), Departament d'Enginyeria Química, Universitat Rovira i Virgili, Tarragona, Catalonia, Spain
| | - Marta Schuhmacher
- Center of Environmental Food and Toxicological Technology (TecnATox), Departament d'Enginyeria Química, Universitat Rovira i Virgili, Tarragona, Catalonia, Spain
| | - Vikas Kumar
- Center of Environmental Food and Toxicological Technology (TecnATox), Departament d'Enginyeria Química, Universitat Rovira i Virgili, Tarragona, Catalonia, Spain.
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12
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Occhi G, Barollo S, Regazzo D, Bertazza L, Galuppini F, Guzzardo V, Jaffrain-Rea ML, Vianello F, Ciato D, Ceccato F, Watutantrige-Fernando S, Bisognin A, Bortoluzzi S, Pennelli G, Boscaro M, Scaroni C, Mian C. A constitutive active MAPK/ERK pathway due to BRAFV600E positively regulates AHR pathway in PTC. Oncotarget 2016; 6:32104-14. [PMID: 26392334 PMCID: PMC4741662 DOI: 10.18632/oncotarget.5194] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 09/03/2015] [Indexed: 12/29/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor mediating the toxicity and tumor-promoting properties of dioxin. AHR has been reported to be overexpressed and constitutively active in a variety of solid tumors, but few data are currently available concerning its role in thyroid cancer. In this study we quantitatively explored a series of 51 paired-normal and papillary thyroid carcinoma (PTC) tissues for AHR-related genes. We identified an increased AHR expression/activity in PTC, independently from its nuclear dimerization partner and repressor but strictly related to a constitutive active MAPK/ERK pathway. The AHR up-regulation followed by an increased expression of AHR target genes was confirmed by a meta-analysis of published microarray data, suggesting a ligand-independent active AHR pathway in PTC. In-vitro studies using a PTC-derived cell line (BCPAP) and HEK293 cells showed that BRAFV600E may directly modulate AHR localization, induce AHR expression and activity in an exogenous ligand-independent manner. The AHR pathway might represent a potential novel therapeutic target for PTC in the clinical practice.
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Affiliation(s)
- Gianluca Occhi
- Department of Biology, University of Padova, Padova, Italy
| | - Susi Barollo
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Daniela Regazzo
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Loris Bertazza
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Francesca Galuppini
- Surgical Pathology & Cytopathology Unit, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Vincenza Guzzardo
- Surgical Pathology & Cytopathology Unit, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Marie Lise Jaffrain-Rea
- Department of Clinical and Biotechnological Sciences, University of L'Aquila, L'Aquila, Italy.,Neuromed Institute, Department of Neurological Sciences, University of L'Aquila, L'Aquila, Italy
| | - Federica Vianello
- Department of Radiotherapy, Istituto Oncologico del Veneto, IOV-IRCCS, Padova, Italy
| | - Denis Ciato
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Filippo Ceccato
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | | | | | | | - Gianmaria Pennelli
- Surgical Pathology & Cytopathology Unit, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Marco Boscaro
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Carla Scaroni
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
| | - Caterina Mian
- Endocrinology Division, Department of Medicine, Hospital/University of Padova, Padova, Italy
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Zhou Q, Lavorgna A, Bowman M, Hiscott J, Harhaj EW. Aryl Hydrocarbon Receptor Interacting Protein Targets IRF7 to Suppress Antiviral Signaling and the Induction of Type I Interferon. J Biol Chem 2015; 290:14729-39. [PMID: 25911105 DOI: 10.1074/jbc.m114.633065] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Indexed: 12/25/2022] Open
Abstract
The transcription factor IRF7 (interferon regulatory factor 7) is a key regulator of type I interferon and plays essential roles in restricting virus infection and spread. IRF7 activation is tightly regulated to prevent excessive inflammation and autoimmunity; however, how IRF7 is suppressed by negative regulators remains poorly understood. Here, we have identified AIP (aryl hydrocarbon receptor interacting protein) as a new binding partner of IRF7. The interaction between AIP and IRF7 is enhanced upon virus infection, and AIP potently inhibits IRF7-induced type I IFN (IFNα/β) production. Overexpression of AIP blocks virus-induced activation of IFN, whereas knockdown of AIP by siRNA potentiates virally activated IFN production. Consistently, AIP-deficient murine embryonic fibroblasts are highly resistant to virus infection because of increased production of IFNα/β. AIP inhibits IRF7 function by antagonizing the nuclear localization of IRF7. Together, our study identifies AIP as a novel inhibitor of IRF7 and a negative regulator of innate antiviral signaling.
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Affiliation(s)
- Qinjie Zhou
- From the Department of Microbiology and Immunology, The University of Miami, Miller School of Medicine, Miami, Florida 33136
| | - Alfonso Lavorgna
- the Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland 21287
| | - Melissa Bowman
- the Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland 21287, the Graduate Program in Cellular and Molecular Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, and
| | - John Hiscott
- the Division of Infectious Diseases, Vaccine & Gene Therapy Institute of Florida, Port Saint Lucie, Florida 34987
| | - Edward W Harhaj
- the Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Baltimore, Maryland 21287,
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Romano S, D'Angelillo A, Romano MF. Pleiotropic roles in cancer biology for multifaceted proteins FKBPs. Biochim Biophys Acta Gen Subj 2015; 1850:2061-8. [PMID: 25592270 DOI: 10.1016/j.bbagen.2015.01.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 01/05/2015] [Accepted: 01/06/2015] [Indexed: 12/18/2022]
Abstract
BACKGROUND FK506 binding proteins (FKBP) are multifunctional proteins highly conserved across the species and abundantly expressed in the cell. In addition to a well-established role in immunosuppression, FKBPs modulate several signal transduction pathways in the cell, due to their isomerase activity and the capability to interact with other proteins, inducing changes in conformation and function of protein partners. Increasing literature data support the concept that FKBPs control cancer related pathways. SCOPE OF THE REVIEW The aim of the present article is to review current knowledge on FKBPs roles in regulation of key signaling pathways associated with cancer. MAJOR CONCLUSIONS Some family members appear to promote disease while others are protective against tumorigenesis. GENERAL SIGNIFICANCE FKBPs family proteins are expected to provide new biomarkers and small molecular targets, in the near future, increasing diagnostic and therapeutic opportunities in the cancer field. This article is part of a Special Issue entitled Proline-Directed Foldases: Cell Signaling Catalysts and Drug Targets.
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Affiliation(s)
- Simona Romano
- Department of Molecular Medicine and Medical Biotechnologies, Federico II University, Naples, Italy
| | - Anna D'Angelillo
- Department of Molecular Medicine and Medical Biotechnologies, Federico II University, Naples, Italy; Department of Advanced Biomedical Sciences, Federico II University, Naples, Italy
| | - Maria Fiammetta Romano
- Department of Molecular Medicine and Medical Biotechnologies, Federico II University, Naples, Italy.
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15
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Guy NC, Garcia YA, Sivils JC, Galigniana MD, Cox MB. Functions of the Hsp90-binding FKBP immunophilins. Subcell Biochem 2015; 78:35-68. [PMID: 25487015 DOI: 10.1007/978-3-319-11731-7_2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Hsp90 functionally interacts with a broad array of client proteins, but in every case examined Hsp90 is accompanied by one or more co-chaperones. One class of co-chaperone contains a tetratricopeptide repeat domain that targets the co-chaperone to the C-terminal region of Hsp90. Within this class are Hsp90-binding peptidylprolyl isomerases, most of which belong to the FK506-binding protein (FKBP) family. Despite the common association of FKBP co-chaperones with Hsp90, it is now clear that the client protein influences, and is influenced by, the particular FKBP bound to Hsp90. Examples include Xap2 in aryl hydrocarbon receptor complexes and FKBP52 in steroid receptor complexes. In this chapter, we discuss the known functional roles played by FKBP co-chaperones and, where possible, relate distinctive functions to structural differences between FKBP members.
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Affiliation(s)
- Naihsuan C Guy
- Department of Biological Sciences, Border Biomedical Research Center, University of Texas at El Paso, 79968, El Paso, TX, USA,
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16
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Ohno M, Kanayama T, Moore R, Ray M, Negishi M. The roles of co-chaperone CCRP/DNAJC7 in Cyp2b10 gene activation and steatosis development in mouse livers. PLoS One 2014; 9:e115663. [PMID: 25542016 PMCID: PMC4277317 DOI: 10.1371/journal.pone.0115663] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 11/16/2014] [Indexed: 11/18/2022] Open
Abstract
Cytoplasmic constitutive active/androstane receptor (CAR) retention protein (CCRP and also known as DNAJC7) is a co-chaperone previously characterized to retain nuclear receptor CAR in the cytoplasm of HepG2 cells. Here we have produced CCRP knockout (KO) mice and demonstrated that CCRP regulates CAR at multiple steps in activation of the cytochrome (Cyp) 2b10 gene in liver: nuclear accumulation, RNA polymerase II recruitment and epigenetic modifications. Phenobarbital treatment greatly increased nuclear CAR accumulation in the livers of KO males as compared to those of wild type (WT) males. Despite this accumulation, phenobarbital-induced activation of the Cyp2b10 gene was significantly attenuated. In ChIP assays, a CAR/retinoid X receptor-α (RXRα) heterodimer binding to the Cyp2b10 promoter was already increased before phenobarbital treatment and further pronounced after treatment. However, RNA polymerase II was barely recruited to the promoter even after phenobarbital treatment. Histone H3K27 on the Cyp2b10 promoter was de-methylated only after phenobarbital treatment in WT but was fully de-methylated before treatment in KO males. Thus, CCRP confers phenobarbital-induced de-methylation capability to the promoter as well as the phenobarbital responsiveness of recruiting RNA polymerase II, but is not responsible for the binding between CAR and its cognate sequence, phenobarbital responsive element module. In addition, KO males developed steatotic livers and increased serum levels of total cholesterol and high density lipoprotein in response to fasting. CCRP appears to be involved in various hepatic regulations far beyond CAR-mediated drug metabolism.
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Affiliation(s)
- Marumi Ohno
- Pharmacogenetics Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, United States of America
| | - Tomohiko Kanayama
- Pharmacogenetics Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, United States of America
| | - Rick Moore
- Pharmacogenetics Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, United States of America
| | - Manas Ray
- Knockout Core, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, United States of America
| | - Masahiko Negishi
- Pharmacogenetics Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, United States of America
- * E-mail:
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17
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Novel role of hnRNP-A2/B1 in modulating aryl hydrocarbon receptor ligand sensitivity. Arch Toxicol 2014; 89:2027-38. [PMID: 25224401 DOI: 10.1007/s00204-014-1352-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 08/25/2014] [Indexed: 10/24/2022]
Abstract
The aryl hydrocarbon receptor (AHR) is responsible for susceptibility to its ligand-dependent responses. However, the effect of non-AHR factors is less clear. To explore the non-AHR factors, we used two mouse strains with different AHR genetic variants, namely C3H/lpr and MRL/lpr strains with Ala and Val as the 375th amino acid residue, respectively. To assess the contribution of AHR alone, COS-7 cells transiently expressing AHR from each strain were treated with 6-formylindolo[3,2-b]carbazole (FICZ) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and xenobiotic-responsive element (XRE)-driven reporter gene activities were measured. FICZ-EC50 values for the C3H/lpr and MRL/lpr AHR-mediated transactivation were 0.023 and 0.046 nM, respectively, indicating a similar susceptibility in both AHR genotypes. In contrast, C3H/lpr AHR was fourfold more sensitive to TCDD than MRL/lpr AHR. By a pull-down assay using a XRE-containing PCR product as bait and the hepatic nuclear extracts of both FICZ-treated mouse strains, we identified two interacting proteins as heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP-A2) and its splicing variant (hnRNP-A2b). Immunoprecipitation assays demonstrated the AHR interaction with hnRNP-A2/B1. When hnRNP-A2 was co-expressed with the MRL/lpr or C3H/lpr AHR in COS-7, FICZ treatment decreased EC50 to about threefold in both AHR genotypes, compared with EC50 in AHR alone. Similarly, hnRNP-A2b co-expression also lowered the FICZ-EC50 values. In TCDD-treated COS-7, responses depended on the AHR genotype; while no change in TCDD-EC50 was observed for C3H/lpr AHR when hnRNP-A2 was co-expressed, the value was reduced to nearly tenfold for MRL/lpr AHR. Co-transfection with hnRNP-A2b attenuated the AHR sensitivity to TCDD. In conclusion, the hnRNP-A2/B1 interacting with AHR may be a modulator of the AHR ligand sensitivity.
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Schimmack G, Eitelhuber AC, Vincendeau M, Demski K, Shinohara H, Kurosaki T, Krappmann D. AIP augments CARMA1-BCL10-MALT1 complex formation to facilitate NF-κB signaling upon T cell activation. Cell Commun Signal 2014; 12:49. [PMID: 25245034 PMCID: PMC4222456 DOI: 10.1186/s12964-014-0049-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 07/15/2014] [Indexed: 11/11/2022] Open
Abstract
Background The CARMA1-BCL10-MALT1 (CBM) complex bridges T cell receptor (TCR) signaling to the canonical IκB kinase (IKK)/NF-κB pathway. The CBM complex constitutes a signaling cluster of more than 1 Mio Dalton. Little is known about factors that facilitate the rapid assembly and maintenance of this dynamic higher order complex. Findings Here, we report the novel interaction of the aryl hydrocarbon receptor (AHR) interacting protein (AIP) and the molecular scaffold protein CARMA1. In T cells, transient binding of CARMA1 and AIP enhanced formation of the CBM complex. Thereby, AIP promoted optimal IKK/NF-κB signaling and IL-2 production in response to TCR/CD28 co-stimulation. Conclusions Our data demonstrate that AIP acts as a positive regulator of NF-κB signaling upon T cell activation.
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19
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Zhou Y, Zhang X, Klibanski A. Genetic and epigenetic mutations of tumor suppressive genes in sporadic pituitary adenoma. Mol Cell Endocrinol 2014; 386:16-33. [PMID: 24035864 PMCID: PMC3943596 DOI: 10.1016/j.mce.2013.09.006] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 09/03/2013] [Indexed: 12/28/2022]
Abstract
Human pituitary adenomas are the most common intracranial neoplasms. Approximately 5% of them are familial adenomas. Patients with familial tumors carry germline mutations in predisposition genes, including AIP, MEN1 and PRKAR1A. These mutations are extremely rare in sporadic pituitary adenomas, which therefore are caused by different mechanisms. Multiple tumor suppressive genes linked to sporadic tumors have been identified. Their inactivation is caused by epigenetic mechanisms, mainly promoter hypermethylation, and can be placed into two groups based on their functional interaction with tumor suppressors RB or p53. The RB group includes CDKN2A, CDKN2B, CDKN2C, RB1, BMP4, CDH1, CDH13, GADD45B and GADD45G; AIP and MEN1 genes also belong to this group. The p53 group includes MEG3, MGMT, PLAGL1, RASSF1, RASSF3 and SOCS1. We propose that the tumor suppression function of these genes is mainly mediated by the RB and p53 pathways. We also discuss possible tumor suppression mechanisms for individual genes.
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Affiliation(s)
- Yunli Zhou
- Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States
| | - Xun Zhang
- Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States
| | - Anne Klibanski
- Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, United States.
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20
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Lee C, Mullen Grey AK, Riddick DS. Loss of hepatic aryl hydrocarbon receptor protein in adrenalectomized rats does not involve altered levels of the receptor's cytoplasmic chaperones. Can J Physiol Pharmacol 2013; 91:1154-7. [PMID: 24289088 DOI: 10.1139/cjpp-2013-0238] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aryl hydrocarbon receptor (AHR) plays physiological roles and mediates adaptive and toxic responses to environmental pollutants. Adrenalectomized rats display decreased hepatic AHR protein levels, with no change in mRNA, and selectively impaired induction of cytochrome P450 1B1. This is similar to reported phenotypes for mice with hepatocyte-specific conditional deletion of AHR-interacting protein (AIP), a chaperone protein of the cytoplasmic AHR complex. In this study, we demonstrated that adrenalectomy (ADX) and acute dexamethasone (DEX) treatment do not alter hepatic AIP mRNA or protein levels. Also, hepatic protein levels of the 90 kDa heat shock protein and p23 were not altered by ADX or acute DEX treatment. These results suggest that the loss of rat hepatic AHR protein following ADX cannot be explained by changes in the levels of the receptor's cytoplasmic chaperone proteins.
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Affiliation(s)
- Chunja Lee
- Department of Pharmacology and Toxicology, Medical Sciences Building, University of Toronto, Toronto, ON M5S 1A8, Canada
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21
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MacPherson L, Tamblyn L, Rajendra S, Bralha F, McPherson JP, Matthews J. 2,3,7,8-Tetrachlorodibenzo-p-dioxin poly(ADP-ribose) polymerase (TiPARP, ARTD14) is a mono-ADP-ribosyltransferase and repressor of aryl hydrocarbon receptor transactivation. Nucleic Acids Res 2012; 41:1604-21. [PMID: 23275542 PMCID: PMC3562000 DOI: 10.1093/nar/gks1337] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)-inducible poly(ADP-ribose) polymerase (TiPARP/ARTD14) is a member of the PARP family and is regulated by the aryl hydrocarbon receptor (AHR); however, little is known about TiPARP function. In this study, we examined the catalytic function of TiPARP and determined its role in AHR transactivation. We observed that TiPARP exhibited auto-mono-ADP-ribosyltransferase activity and ribosylated core histones. RNAi-mediated knockdown of TiPARP in T-47D breast cancer and HuH-7 hepatoma cells increased TCDD-dependent cytochrome P450 1A1 (CYP1A1) and CYP1B1 messenger RNA (mRNA) expression levels and recruitment of AHR to both genes. Overexpression of TiPARP reduced AHR-dependent increases in CYP1A1-reporter gene activity, which was restored by overexpression of AHR, but not aryl hydrocarbon receptor nuclear translocator. Deletion and mutagenesis studies showed that TiPARP-mediated inhibition of AHR required the zinc-finger and catalytic domains. TiPARP and AHR co-localized in the nucleus, directly interacted and both were recruited to CYP1A1 in response to TCDD. Overexpression of Tiparp enhanced, whereas RNAi-mediated knockdown of TiPARP reduced TCDD-dependent AHR proteolytic degradation. TCDD-dependent induction of AHR target genes was enhanced in Tiparp−/− mouse embryonic fibroblasts compared with wildtype controls. Our findings show that TiPARP is a mono-ADP-ribosyltransferase and a transcriptional repressor of AHR, revealing a novel negative feedback loop in AHR signalling.
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Affiliation(s)
- Laura MacPherson
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
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22
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Chen Y, Tang Y, Guo C, Wang J, Boral D, Nie D. Nuclear receptors in the multidrug resistance through the regulation of drug-metabolizing enzymes and drug transporters. Biochem Pharmacol 2012; 83:1112-26. [PMID: 22326308 PMCID: PMC3339266 DOI: 10.1016/j.bcp.2012.01.030] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 01/23/2012] [Accepted: 01/25/2012] [Indexed: 01/18/2023]
Abstract
Chemotherapy is one of the three most common treatment modalities for cancer. However, its efficacy is limited by multidrug resistant cancer cells. Drug metabolizing enzymes (DMEs) and efflux transporters promote the metabolism, elimination, and detoxification of chemotherapeutic agents. Consequently, elevated levels of DMEs and efflux transporters reduce the therapeutic effectiveness of chemotherapeutics and, often, lead to treatment failure. Nuclear receptors, especially pregnane X receptor (PXR, NR1I2) and constitutive androstane activated receptor (CAR, NR1I3), are increasingly recognized for their role in xenobiotic metabolism and clearance as well as their role in the development of multidrug resistance (MDR) during chemotherapy. Promiscuous xenobiotic receptors, including PXR and CAR, govern the inducible expressions of a broad spectrum of target genes that encode phase I DMEs, phase II DMEs, and efflux transporters. Recent studies conducted by a number of groups, including ours, have revealed that PXR and CAR play pivotal roles in the development of MDR in various human carcinomas, including prostate, colon, ovarian, and esophageal squamous cell carcinomas. Accordingly, PXR/CAR expression levels and/or activation statuses may predict prognosis and identify the risk of drug resistance in patients subjected to chemotherapy. Further, PXR/CAR antagonists, when used in combination with existing chemotherapeutics that activate PXR/CAR, are feasible and promising options that could be utilized to overcome or, at least, attenuate MDR in cancer cells.
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Affiliation(s)
- Yakun Chen
- Department of Medical Microbiology, Immunology, and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL 62794, United States
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Abstract
Germline mutations in the aryl hydrocarbon receptor-interacting protein gene (AIP) predispose to young-onset pituitary tumours, most often to GH- or prolactin-secreting adenomas, and most of these patients belong to familial isolated pituitary adenoma families. The molecular pathway initiated by the loss-of-function AIP mutations leading to pituitary tumour formation is unknown. AIP, a co-chaperone of heat-shock protein 90 and various nuclear receptors, belongs to the family of tetratricopeptide repeat (TPR)-containing proteins. It has three antiparallel α-helix motifs (TPR domains) that mediate the interaction of AIP with most of its partners. In this review, we summarise the known interactions of AIP described so far. The identification of AIP partners and the understanding of how AIP interacts with these proteins might help to explain the specific phenotype of the families with heterozygous AIP mutations, to gain deeper insight into the pathological process of pituitary tumour formation and to identify novel drug targets.
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Affiliation(s)
- Giampaolo Trivellin
- Department of Endocrinology, Bart's and the London School of Medicine, Queen Mary University of London, London EC1M 6BQ, UK
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24
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Craig Rowlands J, Urban JD, Wikoff DS, Budinsky RA. An Evaluation of Single Nucleotide Polymorphisms in the Human Aryl Hydrocarbon Receptor-Interacting Protein (AIP) Gene. Drug Metab Pharmacokinet 2011; 26:431-9. [DOI: 10.2133/dmpk.dmpk-11-sc-013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Klein K, Winter S, Turpeinen M, Schwab M, Zanger UM. Pathway-Targeted Pharmacogenomics of CYP1A2 in Human Liver. Front Pharmacol 2010; 1:129. [PMID: 21918647 PMCID: PMC3171976 DOI: 10.3389/fphar.2010.00129] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 09/28/2010] [Indexed: 01/08/2023] Open
Abstract
The human drug metabolizing cytochrome P450 (CYP) 1A2, is one of the major P450 isoforms contributing by about 5–20% to the hepatic P450 pool and catalyzing oxidative biotransformation of up to 10% of clinically relevant drugs including clozapine and caffeine. CYP1A2 activity is interindividually highly variable and although twin studies have suggested a high heritability, underlying genetic factors are still unknown. Here we adopted a pathway-oriented approach using a large human liver bank (n = 150) to elucidate whether variants in candidate genes of constitutive, ligand-inducible, and pathophysiological inhibitory regulatory pathways may explain different hepatic CYP1A2 phenotypes. Samples were phenotyped for phenacetin O-deethylase activity, and the expression of CYP1A2 protein and mRNA was determined. CYP1A2 expression and function was increased in smokers and decreased in patients with inflammation and cholestasis. Of 169 SNPs in 17 candidate genes including the CYP1A locus, 136 non-redundant SNPs with minor allele frequency >5% were analyzed by univariate and multivariate methods. A total of 13 strong significant associations were identified, of which 10 SNPs in the ARNT, AhRR, HNF1α, IL1β, SRC-1, and VDR genes showed consistent changes for at least two phenotypes by univariate analysis. Multivariate linear modeling indicated that the polymorphisms and non-genetic factors together explained 42, 38, and 33% of CYP1A2 variation at activity, protein and mRNA levels, respectively. In conclusion, we identified novel trans-associations between regulatory genes and hepatic CYP1A2 function and expression, but additional genetic factors must be assumed to explain the full extent of CYP1A2 heritability.
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Affiliation(s)
- Kathrin Klein
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, University of Tuebingen Stuttgart, Germany
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26
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Nukaya M, Lin BC, Glover E, Moran SM, Kennedy GD, Bradfield CA. The aryl hydrocarbon receptor-interacting protein (AIP) is required for dioxin-induced hepatotoxicity but not for the induction of the Cyp1a1 and Cyp1a2 genes. J Biol Chem 2010; 285:35599-605. [PMID: 20829355 DOI: 10.1074/jbc.m110.132043] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) plays an essential role in the toxic response to environmental pollutants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin), in the adaptive up-regulation of xenobiotic metabolizing enzymes, and in hepatic vascular development. In our model of AHR signaling, the receptor is found in a cytosolic complex with a number of molecular chaperones, including Hsp90, p23, and the aryl hydrocarbon receptor-interacting protein (AIP), also known as ARA9 and XAP2. To understand the role of AIP in adaptive and toxic aspects of AHR signaling, we generated a conditional mouse model where the Aip locus can be deleted in hepatocytes. Using this model, we demonstrate two important roles for the AIP protein in AHR biology. (i) The expression of AIP in hepatocytes is essential to maintain high levels of functional cytosolic AHR protein in the mammalian liver. (ii) Expression of the AIP protein is essential for dioxin-induced hepatotoxicity. Interestingly, classical AHR-driven genes show differential dependence on AIP expression. The Cyp1b1 and Ahrr genes require AIP expression for normal up-regulation by dioxin, whereas Cyp1a1 and Cyp1a2 do not. This differential dependence on AIP provides evidence that the mammalian genome contains more than one class of AHR-responsive genes and suggests that a search for AIP-dependent, AHR-responsive genes may guide us to the targets of the dioxin-induced hepatotoxicity.
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Affiliation(s)
- Manabu Nukaya
- McArdle Laboratory for Cancer Research, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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27
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Cain JW, Miljic D, Popovic V, Korbonits M. Role of the aryl hydrocarbon receptor-interacting protein in familial isolated pituitary adenoma. Expert Rev Endocrinol Metab 2010; 5:681-695. [PMID: 30764022 DOI: 10.1586/eem.10.42] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Pituitary adenomas are typically sporadic benign tumors. However, approximately 5% of cases have been found to be familial in origin. Of these, approximately 40% occur in the absence of multiple endocrine neoplasia type 1 or Carney complex and have been termed 'familial isolated pituitary adenoma' (FIPA). Recently, germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene have been described in 15-20% of these families, identifying an autosomal dominant condition with incomplete penetrance termed 'pituitary adenoma predisposition'. Pituitary adenoma predisposition cohorts show a marked disposition to develop large, aggressive somatotroph, somatolactotroph or lactotroph adenomas, typically presenting at a young age. AIP mutation families have a distinct clinical phenotype compared with AIP mutation-negative FIPA families. Current evidence suggests that AIP is a tumor-suppressor gene. AIP has been demonstrated to interact with a number of cellular proteins, including several nuclear receptors, heat-shock protein 90 and survivin, although the mechanism of the tumor-suppressor effect is unknown. This article summarizes available data regarding the role of AIP in pituitary tumorigenesis and the clinical features of FIPA.
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Affiliation(s)
- Joshua W Cain
- a Department of Endocrinology, Barts and the London School of Medicine, Queen Mary University of London, EC1M 6BQ, UK
| | - Dragana Miljic
- b Institute of Endocrinology, School of Medicine, University Belgrade Belgrade, Serbia
| | - Vera Popovic
- b Institute of Endocrinology, School of Medicine, University Belgrade Belgrade, Serbia
| | - Márta Korbonits
- a Department of Endocrinology, Barts and the London School of Medicine, Queen Mary University of London, EC1M 6BQ, UK
- c
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28
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Zhou SF, Wang B, Yang LP, Liu JP. Structure, function, regulation and polymorphism and the clinical significance of human cytochrome P450 1A2. Drug Metab Rev 2010; 42:268-354. [PMID: 19961320 DOI: 10.3109/03602530903286476] [Citation(s) in RCA: 183] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human CYP1A2 is one of the major CYPs in human liver and metabolizes a number of clinical drugs (e.g., clozapine, tacrine, tizanidine, and theophylline; n > 110), a number of procarcinogens (e.g., benzo[a]pyrene and aromatic amines), and several important endogenous compounds (e.g., steroids). CYP1A2 is subject to reversible and/or irreversible inhibition by a number of drugs, natural substances, and other compounds. The CYP1A gene cluster has been mapped on to chromosome 15q24.1, with close link between CYP1A1 and 1A2 sharing a common 5'-flanking region. The human CYP1A2 gene spans almost 7.8 kb comprising seven exons and six introns and codes a 515-residue protein with a molecular mass of 58,294 Da. The recently resolved CYP1A2 structure has a relatively compact, planar active site cavity that is highly adapted for the size and shape of its substrates. The architecture of the active site of 1A2 is characterized by multiple residues on helices F and I that constitutes two parallel substrate binding platforms on either side of the cavity. A large interindividual variability in the expression and activity of CYP1A2 has been observed, which is largely caused by genetic, epigenetic and environmental factors (e.g., smoking). CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR) and CYP1A2 is induced through AhR-mediated transactivation following ligand binding and nuclear translocation. Induction or inhibition of CYP1A2 may provide partial explanation for some clinical drug interactions. To date, more than 15 variant alleles and a series of subvariants of the CYP1A2 gene have been identified and some of them have been associated with altered drug clearance and response and disease susceptibility. Further studies are warranted to explore the clinical and toxicological significance of altered CYP1A2 expression and activity caused by genetic, epigenetic, and environmental factors.
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Affiliation(s)
- Shu-Feng Zhou
- Discpline of Chinese Medicine, School of Health Sciences, RMIT University, Bundoora, Victoria 3083, Australia.
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Mukai R, Shirai Y, Saito N, Fukuda I, Nishiumi S, Yoshida KI, Ashida H. Suppression mechanisms of flavonoids on aryl hydrocarbon receptor-mediated signal transduction. Arch Biochem Biophys 2010; 501:134-41. [PMID: 20450880 DOI: 10.1016/j.abb.2010.05.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 04/23/2010] [Accepted: 05/01/2010] [Indexed: 10/19/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates biological and toxicological effects by binding to its agonists such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Previously we demonstrated that flavonoids suppressed the TCDD-induced DNA-binding activity of the AhR in a structure-dependent manner. In this study, we investigated the mechanisms by which flavonoids suppressed the AhR-mediated signal transduction in mouse hepatoma Hepa-1c1c7 cells. Flavones and flavonols suppressed the TCDD-induced nuclear translocation of the AhR and dissociation of its partner proteins, heat shock protein 90 and X-associated protein 2, whereas flavanones and catechins did not. Flavonoids of all these four subclasses suppressed the phosphorylation of both AhR and Arnt and the formation of a heterodimer consisting of these proteins. Since certain flavonoids are known to inhibit mitogen-activated protein kinases (MAPKs), we confirmed the contribution of MAPK/ERK kinase (MEK) to the AhR-mediated signal transduction by using U0126, an inhibitor of MEK1/2. U0126 suppressed TCDD-induced phosphorylation of the AhR and Arnt followed by the DNA-binding activity of the AhR. Flavanones and catechins suppressed the TCDD-induced phosphorylation of ERK1/2. The inhibition of MEK/ERK phosphorylation is one of the mechanisms by which flavanones and catechins suppress the AhR-mediated signal transduction in Hepa-1c1c7 cells.
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Affiliation(s)
- Rie Mukai
- Department of Agrobioscience, School of Agricultural Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
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Molecular genetics of the aip gene in familial pituitary tumorigenesis. PROGRESS IN BRAIN RESEARCH 2010; 182:229-53. [PMID: 20541668 DOI: 10.1016/s0079-6123(10)82010-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Pituitary adenomas usually occur as sporadic tumors, but familial cases are now increasingly identified. As opposed to multiple endocrine neoplasia type 1 and Carney complex, in familial isolated pituitary adenoma (FIPA) syndrome no other disease is associated with the familial occurrence of pituitary adenomas. It is an autosomal dominant disease with incomplete variable penetrance. Approximately 20% of patients with FIPA harbour germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene located on 11q13. Patients with AIP mutations have an overwhelming predominance of somatotroph and lactotroph adenomas, which often present in childhood or young adulthood. AIP, originally identified as a molecular co-chaperone of several nuclear receptors, is thought to act as a tumor suppressor gene; overexpression of wild-type, but not mutant AIP, reduces cell proliferation while knockdown of AIP stimulates it. AIP is shown to bind various proteins, including the aryl hydrocarbon receptor, Hsp90, phosphodiesterases, survivin, RET and the glucocorticoid receptor, but currently it is not clear which interaction has the leading role in pituitary tumorigenesis. This chapter summarizes the available clinical and molecular data regarding the role of AIP in the pituitary gland.
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The active form of human aryl hydrocarbon receptor (AHR) repressor lacks exon 8, and its Pro 185 and Ala 185 variants repress both AHR and hypoxia-inducible factor. Mol Cell Biol 2009; 29:3465-77. [PMID: 19380484 DOI: 10.1128/mcb.00206-09] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) repressor (AHRR) inhibits AHR-mediated transcription and has been associated with reproductive dysfunction and tumorigenesis in humans. Previous studies have characterized the repressor function of AHRRs from mice and fish, but the human AHRR ortholog (AHRR(715)) appeared to be nonfunctional in vitro. Here, we report a novel human AHRR cDNA (AHRRDelta8) that lacks exon 8 of AHRR(715). AHRRDelta8 was the predominant AHRR form expressed in human tissues and cell lines. AHRRDelta8 effectively repressed AHR-dependent transactivation, whereas AHRR(715) was much less active. Similarly, AHRRDelta8, but not AHRR(715), formed a complex with AHR nuclear translocator (ARNT). Repression of AHR by AHRRDelta8 was not relieved by overexpression of ARNT or AHR coactivators, suggesting that competition for these cofactors is not the mechanism of repression. AHRRDelta8 interacted weakly with AHR but did not inhibit its nuclear translocation. In a survey of transcription factor specificity, AHRRDelta8 did not repress the nuclear receptor pregnane X receptor or estrogen receptor alpha but did repress hypoxia-inducible factor (HIF)-dependent signaling. AHRRDelta8-Pro(185) and -Ala(185) variants, which have been linked to human reproductive disorders, both were capable of repressing AHR or HIF. Together, these results identify AHRRDelta8 as the active form of human AHRR and reveal novel aspects of its function and specificity as a repressor.
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Laenger A, Lang-Rollin I, Kozany C, Zschocke J, Zimmermann N, Rüegg J, Holsboer F, Hausch F, Rein T. XAP2 inhibits glucocorticoid receptor activity in mammalian cells. FEBS Lett 2009; 583:1493-8. [PMID: 19375531 DOI: 10.1016/j.febslet.2009.03.072] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 03/19/2009] [Accepted: 03/31/2009] [Indexed: 11/18/2022]
Abstract
XAP2 is member of a protein family sharing the TPR protein interaction motif. It displays close homology to the immunophilins FKBP51 and FKBP52 that act via the Hsp90 folding machinery to regulate the glucocorticoid receptor (GR). We show that XAP2 inhibits GR by reducing its responsiveness to hormone in transcriptional activation. The effect of XAP2 on GR requires its interaction with Hsp90 through the TPR motif. The PPIase-like region turned out to be enzymatically inactive. Thus, PPIase activity is not essential for the action of XAP2 on GR, similarly to FKBP51 and FKBP52.
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Affiliation(s)
- Anna Laenger
- Max Planck Institute of Psychiatry, Kraepelinstrasse 10, 80804 Munich, Germany
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Peng TL, Chen J, Mao W, Song X, Chen MH. Aryl hydrocarbon receptor pathway activation enhances gastric cancer cell invasiveness likely through a c-Jun-dependent induction of matrix metalloproteinase-9. BMC Cell Biol 2009; 10:27. [PMID: 19371443 PMCID: PMC2680824 DOI: 10.1186/1471-2121-10-27] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 04/16/2009] [Indexed: 02/05/2023] Open
Abstract
Background Abberant aryl hydrocarbon receptor (AhR) expression and AhR pathway activation are involved in gastric carcinogenesis. However, the relationship between AhR pathway activation and gastric cancer progression is still unclear. In present study, we used 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD), a classic and most potent ligand of AhR, to activate AhR pathway and investigated the effect of AhR pathway activation on human gastric cancer AGS cell invasion and explored the corresponding mechanism. Results To determine whether AhR pathway can be activated in AGS cells, we examined the expression of CYP1A1, a classic target gene of AhR pathway, following TCDD exposure. RT-PCR and western blot analysis showed that both CYP1A1 mRNA and protein expression were increased in a dose-dependent manner following TCDD treatment and AhR antagonist resveratrol (RSV) could reverse this TCDD-induced CYP1A1 expression. To determine whether TCDD treatment of AGS cells results in an induction of MMP-9 expression, we detected MMP-9 mRNA using RT-PCR and detected MMP-9 enzymatic activity using gelatin zymography. The results showed that both MMP-9 mRNA expression and enzymatic activity were gradually increased with the concentration increase of TCDD in media and these changes could be reversed by RSV treatment in a dose-dependent manner. To examine whether AhR activation-induced MMP-9 expression and activity in AGS cells results in increased migration and invasion, we performed wound healing migration assay and transwell migration and invasion assay. After TCDD treatment, the migration distance and the migration and invasion abilities of AGS cells were increased with a dose-dependent manner. To demonstrate AhR activation-induced MMP-9 expression is mediated by c-Jun, siRNA transfection was performed to silence c-Jun mRNA in AGS cells. The results showed that MMP-9 mRNA expression and activity in untreated control AGS cells were very weak; After TCDD (10 nmol/L) treatment, MMP-9 mRNA expression and activity were significant increased; This TCDD-induced MMP-9 expression and activity increase could be abolished by c-Jun siRNA transfection. Conclusion AhR pathway activation enhances gastric cancer cell invasiveness likely through a c-Jun-dependent induction of MMP-9. Our results provide insight into the mechanism and function of the AhR pathway and its impact on gastric cancer progression.
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Affiliation(s)
- Tie-Li Peng
- Department of Gastroenterology, the First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, PR China.
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Mukai R, Fukuda I, Nishiumi S, Natsume M, Osakabe N, Yoshida KI, Ashida H. Cacao polyphenol extract suppresses transformation of an aryl hydrocarbon receptor in C57BL/6 mice. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2008; 56:10399-10405. [PMID: 18928297 DOI: 10.1021/jf802453t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Dioxins enter the body through the diet and cause various toxicological effects through transformation of an aryl hydrocarbon receptor (AhR). Plant extracts and phytochemicals including flavonoids are reported to suppress this transformation. This paper investigates the suppression by a cacao polyphenol extract (CPE) of AhR transformation in vivo. The CPE was administered orally to C57BL/6 mice at 100 mg/kg of body weight, followed 1 h later by 3-methylcholanthrene (MC), an AhR agonist, injected intraperitoneally at 10 mg/kg of body weight. CPE suppressed the MC-induced transformation to the control level by inhibiting the formation of a heterodimer between AhR and an aryl hydrocarbon receptor nuclear translocator in the liver at 3 h postadministration. It also suppressed MC-induced cytochrome P4501A1 expression and NAD(P)H:quinone-oxidoreductase activity, whereas it increased glutathione S-transferase activity at 25 h. CPE constituents and their metabolites might contribute, at least in part, to the suppression of AhR transformation. The results indicate that the intake of CPE suppressed the toxicological effects of dioxins in the body.
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Affiliation(s)
- Rie Mukai
- Department of Agrobioscienec, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
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Oesch-Bartlomowicz B, Oesch F. Role of cAMP in mediating AHR signaling. Biochem Pharmacol 2008; 77:627-41. [PMID: 19013136 DOI: 10.1016/j.bcp.2008.10.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Revised: 10/11/2008] [Accepted: 10/13/2008] [Indexed: 01/30/2023]
Abstract
Regulation of the nuclear import of many transcription factors represents a step in gene regulation which is crucial for a number of cellular processes. The aryl hydrocarbon receptor (AHR), a basic helix-loop-helix protein of the PAS (PER-ARNT-SIM) family of transcriptional regulators is a cytosol-associated and ligand-activated receptor. The environmental toxin dioxin binds with high affinity to AHR rendering it nuclear and leading to the activation of AHR sensitive genes. However, the fact, that the AHR mediates a large variety of physiological events without the involvement of any known exogenous ligand, including liver and vascular system development, maturation of the immune system, regulation of genes involved in cellular growth, cell differentiation and circadian rhythm, speaks for an important role of AHR in cell biology independent of the presence of an exogenous ligand. Different approaches were applied to study mechanism(s) which render AHR nuclear and design its function in absence of exogenous ligands. We found that AHR is sensitive to cAMP signaling mediated by cAMP-dependent protein kinase (PKA) which fundamentally differs from AHR signaling mediated by the exogenous ligand dioxin. It has been shown that PKA mediated signaling can be confined by compartmentalization of signaling components in microdomains conferring specificity to signaling by the ubiquitous second messenger cAMP. Moreover, A-kinase-anchoring proteins (AKAPs) and newly discovered cAMP receptors, Epac (exchange protein directly activated by cAMP), may give us a further chance to enter into new dimensions of cAMP signal transmissions that potentially may bring us closer to AHR physiology.
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Vogel CFA, Matsumura F. A new cross-talk between the aryl hydrocarbon receptor and RelB, a member of the NF-kappaB family. Biochem Pharmacol 2008; 77:734-45. [PMID: 18955032 DOI: 10.1016/j.bcp.2008.09.036] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 09/19/2008] [Accepted: 09/25/2008] [Indexed: 11/17/2022]
Abstract
The discovery of the new crosstalk between the aryl hydrocarbon receptor (AhR) and the NF-kappaB subunit RelB may extend our understanding of the biological functions of the AhR and at the same time raises a number of questions, which will be addressed in this review. The characteristics of this interaction differ from that of AhR with RelA in that the latter appears to be mostly negative unlike the collaborative interactions of AhR/RelB. The AhR/RelB dimer is capable of binding to DNA response elements including the dioxin response element (DRE) as well as NF-kappaB binding sites supporting the activation of target genes of the AhR as well as NF-kappaB pathway. Further studies show that AhR/RelB complexes can be found not only in lymphoid cells but also in a human hepatoma cell line (HepG2) or breast cancer cell line (MDA-MB-231). RelB has been implicated in carcinogenesis of breast cancer for instance and RelB is known to be a critical factor for the function and differentiation of dendritic cells; interestingly the participation of AhR in both processes has been suggested recently, which offers the great potential to expand the scope of the physiological roles of the AhR. There is evidence indicating that RelB may serve as a pro-survival factor, including its ability to promote "inflammation resolution" besides the association of RelB with inflammatory disorders. Based on such information, a hypothesis has been proposed in this review that AhR together with RelB functions as a coordinator of inflammatory responses.
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Affiliation(s)
- Christoph F A Vogel
- Department of Environmental Toxicology, University of California Davis, Davis, CA 95616, USA.
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Ohtake F, Fujii-Kuriyama Y, Kato S. AhR acts as an E3 ubiquitin ligase to modulate steroid receptor functions. Biochem Pharmacol 2008; 77:474-84. [PMID: 18838062 DOI: 10.1016/j.bcp.2008.08.034] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 08/28/2008] [Accepted: 08/28/2008] [Indexed: 10/21/2022]
Abstract
The arylhydrocarbon receptor (AhR) mediates the adverse effects of dioxins, including modulation of sex steroid hormone signaling. The role of AhR as a transcription factor is well described. AhR regulates the expression of target genes such as CYP1A1; however, the mechanisms of AhR function through other target-selective systems remain elusive. Accumulating evidence suggests that AhR modulates the functions of other transcription factors. The ligand-activated AhR directly associates with estrogen or androgen receptors (ERalpha or AR) and modulates their function both positively and negatively. This may, in part explain the sex steroid hormone-related adverse effects of dioxins. AhR has recently been shown to promote the proteolysis of ERalpha/AR through assembling a ubiquitin ligase complex, CUL4B(AhR). In the CUL4B(AhR) complex, AhR acts as a substrate-recognition subunit to recruit ERalpha/AR. This action defines a novel role for AhR as a ligand-dependent E3 ubiquitin ligase. We propose that target-specific regulation of protein destruction, as well as gene expression, is modulated by environmental toxins through the E3 ubiquitin ligase activity of AhR.
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Affiliation(s)
- Fumiaki Ohtake
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo, Japan
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de Oliveira SK, Smolenski A. Phosphodiesterases link the aryl hydrocarbon receptor complex to cyclic nucleotide signaling. Biochem Pharmacol 2008; 77:723-33. [PMID: 18805402 DOI: 10.1016/j.bcp.2008.08.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 08/26/2008] [Accepted: 08/26/2008] [Indexed: 11/16/2022]
Abstract
The aryl hydrocarbon receptor (AHR) is a major transcription factor regulated by different mechanisms. The classical view of AHR activation by xenobiotics needs to be amended by recent findings on the regulation of AHR by endogenous ligands and by crosstalk with other signaling pathways. In the cytosol the AHR recruits a large number of binding partners, including HSP90, p23, XAP2 and the ubiquitin ligases cullin 4B and CHIP. Furthermore, XAP2 binds the cyclic nucleotide phosphodiesterases PDE2A and PDE4A5. PDE2A inhibits nuclear translocation of AHR suggesting an important regulatory role of cyclic nucleotides in AHR trafficking. Signaling involving cAMP is organized in subcellular compartments and a distinct cAMP compartment might be required for proper AHR mobility and function. We conclude that the AHR complex integrates ligand binding and cyclic nucleotide signaling to generate an adequate transcriptional response.
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Beischlag TV, Luis Morales J, Hollingshead BD, Perdew GH. The aryl hydrocarbon receptor complex and the control of gene expression. Crit Rev Eukaryot Gene Expr 2008; 18:207-50. [PMID: 18540824 DOI: 10.1615/critreveukargeneexpr.v18.i3.20] [Citation(s) in RCA: 530] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that controls the expression of a diverse set of genes. The toxicity of the potent AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin is almost exclusively mediated through this receptor. However, the key alterations in gene expression that mediate toxicity are poorly understood. It has been established through characterization of AhR-null mice that the AhR has a required physiological function, yet how endogenous mediators regulate this orphan receptor remains to be established. A picture as to how the AhR/ARNT heterodimer actually mediates gene transcription is starting to emerge. The AhR/ARNT complex can alter transcription both by binding to its cognate response element and through tethering to other transcription factors. In addition, many of the coregulatory proteins necessary for AhR-mediated transcription have been identified. Cross talk between the estrogen receptor and the AhR at the promoter of target genes appears to be an important mode of regulation. Inflammatory signaling pathways and the AhR also appear to be another important site of cross talk at the level of transcription. A major focus of this review is to highlight experimental efforts to characterize nonclassical mechanisms of AhR-mediated modulation of gene transcription.
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Affiliation(s)
- Timothy V Beischlag
- Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA
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Leontiou CA, Gueorguiev M, van der Spuy J, Quinton R, Lolli F, Hassan S, Chahal HS, Igreja SC, Jordan S, Rowe J, Stolbrink M, Christian HC, Wray J, Bishop-Bailey D, Berney DM, Wass JAH, Popovic V, Ribeiro-Oliveira A, Gadelha MR, Monson JP, Akker SA, Davis JRE, Clayton RN, Yoshimoto K, Iwata T, Matsuno A, Eguchi K, Musat M, Flanagan D, Peters G, Bolger GB, Chapple JP, Frohman LA, Grossman AB, Korbonits M. The role of the aryl hydrocarbon receptor-interacting protein gene in familial and sporadic pituitary adenomas. J Clin Endocrinol Metab 2008; 93:2390-401. [PMID: 18381572 DOI: 10.1210/jc.2007-2611] [Citation(s) in RCA: 222] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
CONTEXT Mutations have been identified in the aryl hydrocarbon receptor-interacting protein (AIP) gene in familial isolated pituitary adenomas (FIPA). It is not clear, however, how this molecular chaperone is involved in tumorigenesis. OBJECTIVE AIP sequence changes and expression were studied in FIPA and sporadic adenomas. The function of normal and mutated AIP molecules was studied on cell proliferation and protein-protein interaction. Cellular and ultrastructural AIP localization was determined in pituitary cells. PATIENTS Twenty-six FIPA kindreds and 85 sporadic pituitary adenoma patients were included in the study. RESULTS Nine families harbored AIP mutations. Overexpression of wild-type AIP in TIG3 and HEK293 human fibroblast and GH3 pituitary cell lines dramatically reduced cell proliferation, whereas mutant AIP lost this ability. All the mutations led to a disruption of the protein-protein interaction between AIP and phosphodiesterase-4A5. In normal pituitary, AIP colocalizes exclusively with GH and prolactin, and it is found in association with the secretory vesicle, as shown by double-immunofluorescence and electron microscopy staining. In sporadic pituitary adenomas, however, AIP is expressed in all tumor types. In addition, whereas AIP is expressed in the secretory vesicle in GH-secreting tumors, similar to normal GH-secreting cells, in lactotroph, corticotroph, and nonfunctioning adenomas, it is localized to the cytoplasm and not in the secretory vesicles. CONCLUSIONS Our functional evaluation of AIP mutations is consistent with a tumor-suppressor role for AIP and its involvement in familial acromegaly. The abnormal expression and subcellular localization of AIP in sporadic pituitary adenomas indicate deranged regulation of this protein during tumorigenesis.
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Affiliation(s)
- Chrysanthia A Leontiou
- Department of Endocrinology, Barts and the London School of Medicine, London, United Kingdom
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Lin BC, Sullivan R, Lee Y, Moran S, Glover E, Bradfield CA. Deletion of the Aryl Hydrocarbon Receptor-associated Protein 9 Leads to Cardiac Malformation and Embryonic Lethality. J Biol Chem 2007; 282:35924-32. [DOI: 10.1074/jbc.m705471200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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Evans BR, Karchner SI, Allan LL, Pollenz RS, Tanguay RL, Jenny MJ, Sherr DH, Hahn ME. Repression of aryl hydrocarbon receptor (AHR) signaling by AHR repressor: role of DNA binding and competition for AHR nuclear translocator. Mol Pharmacol 2007; 73:387-98. [PMID: 18000031 DOI: 10.1124/mol.107.040204] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of the aryl hydrocarbon receptor (AHR) by 2,3,7,8-tetrachlorodibenzo-p-dioxin causes altered gene expression and toxicity. The AHR repressor (AHRR) inhibits AHR signaling through a proposed mechanism involving competition with AHR for dimerization with AHR nuclear translocator (ARNT) and binding to AHR-responsive enhancer elements (AHREs). We sought to delineate the relative roles of competition for ARNT and AHREs in the mechanism of repression. In transient transfections in which AHR2-dependent transactivation was repressed by AHRR1 or AHRR2, increasing ARNT expression failed to reverse the repression, suggesting that AHRR inhibition of AHR signaling does not occur through sequestration of ARNT. An AHRR1 point mutant (AHRR1-Y9F) that could not bind to AHREs but that retained its nuclear localization was only slightly reduced in its ability to repress AHR2, demonstrating that AHRR repression does not occur solely through competition for AHREs. When both proposed mechanisms were blocked (AHRR1-Y9F plus excess ARNT), AHRR remained functional. AHRR1 neither blocked AHR nuclear translocation nor reduced the levels of AHR2 protein. Experiments using AHRR1 C-terminal deletion mutants showed that amino acids 270 to 550 are dispensable for repression. These results demonstrate that repression of AHR transactivation by AHRR involves the N-terminal portion of AHRR; does not involve competition for ARNT; and does not require binding to AHREs, although AHRE binding can contribute to the repression. We propose a mechanism of AHRR action involving "transrepression" of AHR signaling through protein-protein interactions rather than by inhibition of the formation or DNA binding of the AHR-ARNT complex.
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Affiliation(s)
- Brad R Evans
- Department of Biology, MS#32, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
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Vogel CFA, Sciullo E, Li W, Wong P, Lazennec G, Matsumura F. RelB, a new partner of aryl hydrocarbon receptor-mediated transcription. Mol Endocrinol 2007; 21:2941-55. [PMID: 17823304 PMCID: PMC2346533 DOI: 10.1210/me.2007-0211] [Citation(s) in RCA: 238] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The nuclear factor-kappaB (NF-kappaB) transcription factor family has a crucial role in rapid responses to stress and pathogens. We show that the NF-kappaB subunit RelB is functionally associated with the aryl hydrocarbon receptor (AhR) and mediates transcription of chemokines such as IL-8 via activation of AhR and protein kinase A. RelB physically interacts with AhR and binds to an unrecognized RelB/AhR responsive element of the IL-8 promoter linking two signaling pathways to activate gene transcription. We found a time-dependent recruitment of AhR to the RelB/AhR responsive element site of IL-8 mediated by the AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) and via activation of protein kinase A. Furthermore, NF-kappaB-binding sites that are preferentially recognized by RelB/p52 are a target for RelB/AhR complexes without addition of any stimuli, implicating the endogenous function of the AhR. RelB/AhR complexes are also found to bind on xenobiotic responsive element, and RelB drastically increases the 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced xenobiotic responsive element reporter activity. The interaction of RelB with AhR signaling, and AhR with NF-kappaB RelB signaling pathways represent a new mechanism of cross talk between the two transcription factors.
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Affiliation(s)
- Christoph F A Vogel
- Department of Environmental Toxicology, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.
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44
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Specific blockage of ligand-induced degradation of the Ah receptor by proteasome but not calpain inhibitors in cell culture lines from different species. Biochem Pharmacol 2007; 74:131-43. [PMID: 17445780 DOI: 10.1016/j.bcp.2007.03.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 03/18/2007] [Accepted: 03/20/2007] [Indexed: 11/28/2022]
Abstract
To firmly establish the pathway involved in ligand-induced degradation of the AHR, cell lines derived from mouse rat or human tissues were exposed to inhibitors specific to the proteasome or calpain proteases and exposed to TCDD. The level of endogenous AHR and CYP1A1 protein was then evaluated by quantitative Western blotting. Treatment of cells with the calpain inhibitors: calpeptin, calpain inhibitor III, or PD150606 either individually or in combinations up to 75 microM did not reduce TCDD-induced degradation of the AHR, the induction of endogenous CYP1A1 or the nuclear accumulation of the AHR. The activity of the inhibitors was verified with an in vivo calpain assay. In contrast, exposure of cells to the specific proteasome inhibitors: epoxomicin (1-5 microM), proteasome inhibitor I (5-10 microM) or lactacystin (5-15 microM) completely inhibited TCDD-induced degradation of the AHR. Inhibition of AHR degradation with these compounds did not reduce the induction of endogenous CYP1A1. In addition, exposure of the Hepa-1 line to the various proteasome inhibitors caused an accumulation of the AHR in the nucleus in the absence of TCDD exposure. Finally, Western blot analysis of the DNA bound AHR showed that its molecular mass was unchanged in comparison to the unliganded (cytoplasmic) AHR. Thus, these studies conclusively implicate the proteasome and not calpain proteases in the ligand-induced degradation of the mouse, rat and human AHR and suggest that the pharmacological use of proteasome inhibitors may impact the time course and magnitude of gene regulatory events mediated through the AHR.
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45
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Hollingshead BD, Patel RD, Perdew GH. Endogenous hepatic expression of the hepatitis B virus X-associated protein 2 is adequate for maximal association with aryl hydrocarbon receptor-90-kDa heat shock protein complexes. Mol Pharmacol 2006; 70:2096-107. [PMID: 16988012 DOI: 10.1124/mol.106.029215] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor that acts as an environmental sensor by binding to a variety of xenobiotics. AHR activation serves to combat xenotoxic stress by inducing metabolic enzyme expression in the liver. The hepatitis B virus X-associated protein (XAP2) is a component of the cytosolic AHR complex and modulates AHR transcriptional properties in vitro and in cell culture and yeast systems. Expression of XAP2 is low in liver compared with other nonhepatic tissues and the AHR exhibits high ligand-induced transcriptional activity. Because XAP2 has been demonstrated to repress AHR activity, we hypothesized that XAP2 may be limiting in liver and that increasing XAP2 levels would attenuate AHR transcriptional activity. To this end, transgenic mice were generated that exhibit hepatocyte-specific elevation in XAP2 expression. Transgenic XAP2 expression was restricted to liver, and its ability to complex with the AHR was verified. Gene expression experiments were performed by inducing AHR transcriptional activity with beta-naphthoflavone via intraperitoneal injection, and mRNA quantification was done by real-time polymerase chain reaction. Wild-type and transgenic animals showed little difference in constitutive or ligand-induced CYP1A1; CYP1A2; UDP glucuronosyltransferase 1A2; NAD(P)H dehydrogenase, quinone 1; constitutive androstane receptor; or nuclear factor erythroid 2-related factor 2 mRNA expression. Sucrose density fractionation and AHR immunoprecipitation experiments found little or no stoichiometric increase in bound XAP2 to the AHR between genotypes. Gene array studies were performed to identify novel XAP2-regulated targets. Taken together, this work shows that despite the relatively low level of XAP2 in liver, it is not a limiting component in AHR regulation.
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Affiliation(s)
- Brett D Hollingshead
- Graduate Program in Biochemistry, Microbiology, and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Ramadoss P, Marcus C, Perdew GH. Role of the aryl hydrocarbon receptor in drug metabolism. Expert Opin Drug Metab Toxicol 2006; 1:9-21. [PMID: 16922649 DOI: 10.1517/17425255.1.1.9] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that regulates the transcription of certain key enzymes involved in the metabolism of xenobiotic substances including some drugs. The AhR can be activated by a wide range of classes of compounds (e.g. polycyclic aromatic hydrocarbons, benzimidazoles and flavonoids), and interacts with a number of other proteins, including nuclear hormone receptors such as the oestrogen and androgen receptors. Activation of the AhR antagonises the oestrogen receptor and can lead to modulation of its transcriptional activity; thus, activating the AhR may serve as a target for breast cancer therapy. Disruption of normal signalling by drug interactions with the AhR or downstream components of this pathway could result in adverse effects, such as the bioactivation of procarcinogens or the disruption of normal homeostasis. The cytochrome P450s CYP1A1, -1B1, -1A2 and -2S1 are regulated by the AhR, and they are all involved in the metabolism of endogenous substrates as well as xenobiotics. Polymorphisms in the AhR, or polymorphisms in enzymes regulated by the AhR, may cause variations in response to certain drugs in different individuals; this needs to be taken into consideration when administering drugs that interact with this pathway.
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Affiliation(s)
- Preeti Ramadoss
- The Pennsylvania State University, Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary Science, University Park, PA 16802, USA
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47
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Kang BH, Altieri DC. Regulation of Survivin Stability by the Aryl Hydrocarbon Receptor-interacting Protein. J Biol Chem 2006; 281:24721-7. [PMID: 16807248 DOI: 10.1074/jbc.m603175200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Survivin is a multifunctional member of the IAP (inhibitor of apoptosis) family, but its molecular interactions in protection from cell death and regulation of cell division have not been completely elucidated. In a proteomics screening to identify novel survivin-binding partners, we found that the aryl hydrocarbon receptor-interacting protein (AIP) directly associates with survivin in vitro and in co-immunoprecipitation experiments in vivo. This interaction is mediated by the carboxyl-terminal end of AIP, which contains three tetratricopeptide motifs, and involves the carboxyl terminus coiled coil in survivin with critical roles of Asp(142) in AIP recognition. A survivin mutant lacking only Asp(142) fails to bind AIP and exhibits accelerated degradation in vivo in a reaction reversed by a proteasome inhibitor. Acute knock-down of AIP by short interference RNA or competition of the survivin-AIP complex by peptidyl mimicry destabilizes survivin levels in cells, with enhanced apoptosis but no changes in cell cycle progression. Therefore, AIP regulates survivin stability, thus elevating a cellular anti-apoptotic threshold. The survivin-AIP complex may influence the cellular xenobiotic response to environmental toxin(s) and contribute to subcellular chaperone trafficking during cell death regulation.
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Affiliation(s)
- Byoung Heon Kang
- Department of Cancer Biology and the Cancer Center, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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Pollenz RS, Wilson SE, Dougherty EJ. Role of endogenous XAP2 protein on the localization and nucleocytoplasmic shuttling of the endogenous mouse Ahb-1 receptor in the presence and absence of ligand. Mol Pharmacol 2006; 70:1369-79. [PMID: 16835354 DOI: 10.1124/mol.106.027672] [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] [Indexed: 11/22/2022] Open
Abstract
Studies using transient expression systems have implicated the hepatitis B virus X-associated protein (XAP2) in the control of aryl hydrocarbon receptor (AHR) stability and subcellular location. Studies were performed in Hepa-1 cells to evaluate these functions of XAP2 on the mouse Ahb-1 receptor under endogenous stoichiometry. The Ahb-1 receptor is cytoplasmic, and it becomes predominantly nuclear after 30 to 60 min of ligand exposure with minimal degradation. During this time, XAP2 coprecipitates with the AHR, suggesting that it does not affect the nuclear localization of the liganded receptor. Overexpression of XAP2 in Hepa-1 cells does not result in increased association with the endogenous Ahb-1 complex or influence the receptors cytoplasmic localization. Knockdown of endogenous XAP2 by small interfering RNA results in >or=90% reduction in the amount of XAP2 associated with the endogenous Ahb-1 receptor complex. Despite the reduction in XAP2, the unliganded Ahb-1 receptor complex remains cytoplasmic, although inhibition of nuclear export results in accumulation of the receptor in the nucleus. Truncation of the C-terminal 305 amino acids of the Ahb-1 receptor (AHR500) results in proteins that exhibit a predominantly nuclear localization and remain associated with the same level of endogenous XAP2 as full-length AHRs. Together, these results support a model in which the majority of the unliganded Ahb-1 receptor complexes are associated with XAP2, and the association prevents dynamic nucleocytoplasmic shuttling in the unliganded state. After ligand binding, XAP2 remains associated with the Ahb-1 receptor complex, and it does not impair nuclear translocation but may function to limit receptor "transformation".
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Affiliation(s)
- Richard S Pollenz
- Department of Biology, BSF 110, 4202 E. Fowler Ave., University of South Florida, Tampa, FL 33620, USA.
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Dunham EE, Stevens EA, Glover E, Bradfield CA. The Aryl Hydrocarbon Receptor Signaling Pathway Is Modified through Interactions with a Kelch Protein. Mol Pharmacol 2006; 70:8-15. [PMID: 16582008 DOI: 10.1124/mol.106.024380] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor with important roles in metabolic adaptation, dioxin toxicology, and vascular development. To understand the details of this signal transduction pathway, we have used the yeast two-hybrid system to identify proteins that physically interact with the AHR in a ligand-dependent manner. Using this strategy, we identified a novel modifier of the AHR signaling pathway that we named Ah-receptor associated protein 3 (ARA3). Coexpression of ARA3 with an AHR chimera in yeast and mammalian cells enhances signaling in response to agonists. The human full-length cDNA previously was described as influenza virus nonstructural protein-1 binding protein (NS1BP). This protein contains four apparent domains-a "broad complex/tramtrack/bric-a-brac" (BTB) domain, a "kelch" domain, a "BTB and C-terminal kelch" (BACK) domain, and an intervening region (IVR). The carboxyl terminus of the AHR "Per-ARNT-Sim" (periodicity/AHR nuclear translocator/simple-minded) domain and the BACK/IVR domains of ARA3 mediate the AHR-ARA3 interaction. The BACK/IVR domains of ARA3 also are sufficient to modify AHR signaling in yeast and mammalian cells. In an effort to provide a preliminary model of NS1BP activity in AHR signaling, we demonstrate that NS1BP regulates the concentration of functional AHR in mammalian cells.
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Affiliation(s)
- Elizabeth E Dunham
- McArdle Laboratory for Cancer Research, 1400 University Avenue, Madison, WI 53706-1599, USA
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50
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Murray IA, Reen RK, Leathery N, Ramadoss P, Bonati L, Gonzalez FJ, Peters JM, Perdew GH. Evidence that ligand binding is a key determinant of Ah receptor-mediated transcriptional activity. Arch Biochem Biophys 2005; 442:59-71. [PMID: 16137638 DOI: 10.1016/j.abb.2005.07.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2005] [Revised: 07/19/2005] [Accepted: 07/22/2005] [Indexed: 11/20/2022]
Abstract
The aryl hydrocarbon receptor (AhR) mediates the biological activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Whether the AhR can mediate enhanced transcriptional activity in the absence of ligand binding has not been established. Hepatocytes from AhR-null (AhR-KO) and wild-type (AhR-WT) neonatal mice were immortalized with Simian virus 40. Two point mutants of the AhR, A375I and A375F, were generated to test the hypothesis that the AhR requires ligand binding to exhibit significant transcriptional activity, both mutants fail to bind ligand or exhibit enhanced activity in cells exposed to AhR ligands. Upon transient, co-expression of ARNT with AhR-A375I or AhR-A375F in AhR-KO cells, these mutants exhibited significant ligand-independent transcriptional activity. However, in CV-1 cells, which others have previously shown to contain relatively high levels of AhR ligand(s), these AhR mutants exhibit essentially no constitutive activity. These results indicate that while the AhR can potentially exhibit activity in the absence of ligand binding, the high constitutive receptor activity observed in many cell lines appears to be due to the presence of endogenous AhR ligands.
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Affiliation(s)
- Iain A Murray
- Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary Science, The Pennsylvania State University, University Park, PA 16802, USA
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