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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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Schernthaner-Reiter MH, Trivellin G, Stratakis CA. Chaperones, somatotroph tumors and the cyclic AMP (cAMP)-dependent protein kinase (PKA) pathway. Mol Cell Endocrinol 2020; 499:110607. [PMID: 31586652 DOI: 10.1016/j.mce.2019.110607] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 09/28/2019] [Accepted: 09/30/2019] [Indexed: 02/08/2023]
Abstract
The cAMP-PKA pathway plays an essential role in the pituitary gland, governing cell differentiation and survival, and maintenance of endocrine function. Somatotroph growth hormone transcription and release as well as cell proliferation are regulated by the cAMP-PKA pathway; cAMP-PKA pathway abnormalities are frequently detected in sporadic as well as in hereditary somatotroph tumors and more rarely in other pituitary tumors. Inactivating variants of the aryl hydrocarbon receptor-interacting protein (AIP)-coding gene are the genetic cause of a subset of familial isolated pituitary adenomas (FIPA). Multiple functional links between the co-chaperone AIP and the cAMP-PKA pathway have been described. This review explores the role of chaperones including AIP in normal pituitary function as well as in somatotroph tumors, and their interaction with the cAMP-PKA pathway.
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Affiliation(s)
| | - Giampaolo Trivellin
- Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, USA
| | - Constantine A Stratakis
- Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, USA
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3
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The aryl hydrocarbon receptor: an environmental sensor integrating immune responses in health and disease. Nat Rev Immunol 2019; 19:184-197. [PMID: 30718831 DOI: 10.1038/s41577-019-0125-8] [Citation(s) in RCA: 670] [Impact Index Per Article: 134.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The environment, diet, microbiota and body's metabolism shape complex biological processes in health and disease. However, our understanding of the molecular pathways involved in these processes is still limited. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that integrates environmental, dietary, microbial and metabolic cues to control complex transcriptional programmes in a ligand-specific, cell-type-specific and context-specific manner. In this Review, we summarize our current knowledge of AHR and the transcriptional programmes it controls in the immune system. Finally, we discuss the role of AHR in autoimmune and neoplastic diseases of the central nervous system, with a special focus on the gut immune system, the gut-brain axis and the therapeutic potential of targeting AHR in neurological disorders.
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4
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Yelamanchi SD, Tyagi A, Mohanty V, Dutta P, Korbonits M, Chavan S, Advani J, Madugundu AK, Dey G, Datta KK, Rajyalakshmi M, Sahasrabuddhe NA, Chaturvedi A, Kumar A, Das AA, Ghosh D, Jogdand GM, Nair HH, Saini K, Panchal M, Sarvaiya MA, Mohanraj SS, Sengupta N, Saxena P, Subramani PA, Kumar P, Akkali R, Reshma SV, Santhosh RS, Rastogi S, Kumar S, Ghosh SK, Irlapati VK, Srinivasan A, Radotra BD, Mathur PP, Wong GW, Satishchandra P, Chatterjee A, Gowda H, Bhansali A, Pandey A, Shankar SK, Mahadevan A, Prasad TSK. Proteomic Analysis of the Human Anterior Pituitary Gland. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2019; 22:759-769. [PMID: 30571610 DOI: 10.1089/omi.2018.0160] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The pituitary function is regulated by a complex system involving the hypothalamus and biological networks within the pituitary. Although the hormones secreted from the pituitary have been well studied, comprehensive analyses of the pituitary proteome are limited. Pituitary proteomics is a field of postgenomic research that is crucial to understand human health and pituitary diseases. In this context, we report here a systematic proteomic profiling of human anterior pituitary gland (adenohypophysis) using high-resolution Fourier transform mass spectrometry. A total of 2164 proteins were identified in this study, of which 105 proteins were identified for the first time compared with high-throughput proteomic-based studies from human pituitary glands. In addition, we identified 480 proteins with secretory potential and 187 N-terminally acetylated proteins. These are the first region-specific data that could serve as a vital resource for further investigations on the physiological role of the human anterior pituitary glands and the proteins secreted by them. We anticipate that the identification of previously unknown proteins in the present study will accelerate biomedical research to decipher their role in functioning of the human anterior pituitary gland and associated human diseases.
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Affiliation(s)
| | - Ankur Tyagi
- 2 Center for Systems Biology and Molecular Medicine, Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore, India
| | - Varshasnata Mohanty
- 2 Center for Systems Biology and Molecular Medicine, Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore, India
| | - Pinaki Dutta
- 3 Department of Endocrinology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Márta Korbonits
- 4 Department of Endocrinology, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom
| | - Sandip Chavan
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India
| | - Jayshree Advani
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India.,5 Manipal Academy of Higher Education, Manipal, India
| | - Anil K Madugundu
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India.,5 Manipal Academy of Higher Education, Manipal, India.,6 Center for Molecular Medicine, National Institute of Mental Health & Neurosciences, Bangalore, India.,7 Department of Laboratory Medicine and Pathology and Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
| | - Gourav Dey
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India.,5 Manipal Academy of Higher Education, Manipal, India
| | - Keshava K Datta
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India
| | - M Rajyalakshmi
- 8 Department of Biotechnology, BMS College of Engineering, Bangalore, India
| | | | - Abhishek Chaturvedi
- 9 Department of Biochemistry, Melaka Manipal Medical College, Manipal Academy of Higher Education, Manipal, India
| | - Amit Kumar
- 10 Institute of Life Sciences, Nalco Square, Bhubaneswar, India
| | - Apabrita Ayan Das
- 11 Cell Biology and Physiology Division, Indian Institute of Chemical Biology, Kolkata, India
| | - Dhiman Ghosh
- 12 Protein Engineering and Neurobiology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology, Bombay, India
| | | | - Haritha H Nair
- 13 Division of Cancer Research, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Keshav Saini
- 14 Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India
| | - Manoj Panchal
- 15 Department of Life Science, Central University of South Bihar, Gaya, India
| | | | - Soundappan S Mohanraj
- 17 Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Nabonita Sengupta
- 18 Neuroinflammation Laboratory, National Brain Research Centre, Manesar, India
| | - Priti Saxena
- 14 Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India
| | | | - Pradeep Kumar
- 20 Department of Biotechnology, VBS Purvanchal University, Jaunpur, India
| | - Rakhil Akkali
- 21 Department of Biotechnology, Indian Institute of Technology, Madras, India
| | | | | | - Sangita Rastogi
- 24 Microbiology Laboratory, National Institute of Pathology, New Delhi, India
| | - Sudarshan Kumar
- 25 Proteomics and Structural Biology Laboratory, Animal Biotechnology Center, National Dairy Research Institute, Karnal, India
| | - Susanta Kumar Ghosh
- 19 Department of Molecular Parasitology, National Institute of Malaria Research, Bangalore, India
| | | | - Anand Srinivasan
- 27 Department of Pharmacology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Bishan Das Radotra
- 28 Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Premendu P Mathur
- 29 Department of Biochemistry and Molecular Biology, School of Life Sciences, Pondicherry University, Pondicherry, India
| | - G William Wong
- 30 Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | | | - Aditi Chatterjee
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India
| | - Harsha Gowda
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India
| | - Anil Bhansali
- 3 Department of Endocrinology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Akhilesh Pandey
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India.,5 Manipal Academy of Higher Education, Manipal, India.,6 Center for Molecular Medicine, National Institute of Mental Health & Neurosciences, Bangalore, India.,7 Department of Laboratory Medicine and Pathology and Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota.,32 McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.,33 Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland.,34 Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland.,35 Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Susarla K Shankar
- 36 Department of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bangalore, India.,37 Human Brain Tissue Repository, National Institute of Mental Health and Neuro Sciences, Neurobiology Research Centre, Bangalore, India
| | - Anita Mahadevan
- 36 Department of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bangalore, India.,37 Human Brain Tissue Repository, National Institute of Mental Health and Neuro Sciences, Neurobiology Research Centre, Bangalore, India
| | - T S Keshava Prasad
- 1 Institute of Bioinformatics, International Technology Park, Bangalore, India.,2 Center for Systems Biology and Molecular Medicine, Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore, India
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5
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p23 protects the human aryl hydrocarbon receptor from degradation via a heat shock protein 90-independent mechanism. Biochem Pharmacol 2018; 152:34-44. [PMID: 29555469 DOI: 10.1016/j.bcp.2018.03.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/14/2018] [Indexed: 01/29/2023]
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated signaling molecule which is involved in diverse biological functions ranging from cancer metastasis to immune regulation. This receptor forms a cytoplasmic complex with Hsp90, p23, and XAP2. We have previously reported that down-regulation of p23 triggers degradation of the AHR protein, uncovering a potentially dynamic event which controls the cellular AHR levels without ligand treatment. Here we investigate the underlying mechanisms for this p23 effect using wild-type HeLa and the p23 knockdown HeLa cells. Reduction of the Hsp90 and XAP2 contents, however, did not affect the AHR protein levels, implying that this p23 effect on AHR is more than just alteration of the cytoplasmic complex dynamics. Association of p23 with Hsp90 is not important for the modulation of the AHR levels since exogenous expression of p23 mutants with modest Hsp90-binding affinity effectively restored the AHR message and protein levels. The protein folding property of p23 which resides at the terminal 50-amino acid region is not involved for this p23 effect. Results from our interaction study using the affinity purified thioredoxin fusion proteins and GST fusion proteins showed that p23 directly interacts with AHR and the interaction surface lies within AHR amino acid 1-216 and p23 amino acid 1-110. Down-regulation of the p23 protein content promotes the ubiquitination of AHR, indicating that p23 protects AHR from the ubiquitin-meditated protein degradation.
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6
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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: 29] [Impact Index Per Article: 4.8] [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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7
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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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8
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Formosa R, Vassallo J. The Complex Biology of the Aryl Hydrocarbon Receptor and Its Role in the Pituitary Gland. Discov Oncol 2017. [PMID: 28634910 DOI: 10.1007/s12672-017-0300-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor best known for its ability to mediate the effects of environmental toxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin), polycyclic aromatic hydrocarbons (PAHs), benzene, and polychlorinated biphenyls (PCBs) through the initiation of transcription of a number of metabolically active enzymes. Therefore, the AHR has been studied mostly in the context of xenobiotic signaling. However, several studies have shown that the AHR is constitutively active and plays an important role in general cell physiology, independently of its activity as a xenobiotic receptor and in the absence of exogenous ligands. Within the pituitary, activation of the AHR by environmental toxins has been implicated in disruption of gonadal development and fertility. Studies carried out predominantly in mouse models have revealed the detrimental influence of several environmental toxins on specific cell lineages of the pituitary tissue mediated by activation of AHR and its downstream effectors. Activation of AHR during fetal development adversely affected pituitary development while adult models exposed to AHR ligands demonstrated varying degrees of pituitary dysfunction. Such dysfunction may arise as a result of direct effects on pituitary cells or indirect effects on the hypothalamic-pituitary-gonadal axis. This review offers in-depth analysis of all aspects of AHR biology, with a particular focus on its role and activity within the adenohypophysis and specifically in pituitary tumorigenesis. A novel mechanism by which the AHR may play a direct role in pituitary cell proliferation and tumor formation is postulated. This review therefore attempts to cover all aspects of the AHR's role in the pituitary tissue, from fetal development to adult physiology and the pathophysiology underlying endocrine disruption and pituitary tumorigenesis.
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Affiliation(s)
- Robert Formosa
- Department of Medicine, Faculty of Medicine and Surgery, University of Malta, MSD 2080, Msida, Malta
| | - Josanne Vassallo
- Department of Medicine, Faculty of Medicine and Surgery, University of Malta, MSD 2080, Msida, Malta. .,Neuroendocrine Clinic, Department of Medicine, Mater Dei Hospital, Msida, Malta.
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9
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Hernández-Ramírez LC, Trivellin G, Stratakis CA. Role of Phosphodiesterases on the Function of Aryl Hydrocarbon Receptor-Interacting Protein (AIP) in the Pituitary Gland and on the Evaluation of AIP Gene Variants. Horm Metab Res 2017; 49:286-295. [PMID: 28427099 DOI: 10.1055/s-0043-104700] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Familial isolated pituitary adenoma (FIPA) is caused in about 20% of cases by loss-of-function germline mutations in the AIP gene. Patients harboring AIP mutations usually present with somatotropinomas resulting either in gigantism or young-onset acromegaly. AIP encodes for a co-chaperone protein endowed with tumor suppressor properties in somatotroph cells. Among other mechanisms proposed to explain this function, a regulatory effect over the 3',5'-cyclic adenosine monophosphate (cAMP) signaling pathway seems to play a prominent role. In this setting, the well-known interaction between AIP and 2 different isoforms of phosphodiesterases (PDEs), PDE2A3 and PDE4A5, is of particular interest. While the interaction with over-expressed AIP does not seem to affect PDE2A3 function, the reported effect on PDE4A5 is, in contrast, reduced enzymatic activity. In this review, we explore the possible implications of these molecular interactions for the function of somatotroph cells. In particular, we discuss how both PDEs and AIP could act as negative regulators of the cAMP pathway in the pituitary, probably both by shared and independent mechanisms. Moreover, we describe how the evaluation of the AIP-PDE4A5 interaction has proven to be a useful tool for testing AIP mutations, complementing other in silico, in vitro, and in vivo analyses. Improved assessment of the pathogenicity of AIP mutations is indeed paramount to provide adequate guidance for genetic counseling and clinical screening in AIP mutation carriers, which can lead to prospective diagnosis of pituitary adenomas.
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Affiliation(s)
- Laura C Hernández-Ramírez
- Section on Endocrinology and Genetics (SEGEN), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Giampaolo Trivellin
- Section on Endocrinology and Genetics (SEGEN), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Constantine A Stratakis
- Section on Endocrinology and Genetics (SEGEN), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, MD, USA
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10
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Signaling network map of the aryl hydrocarbon receptor. J Cell Commun Signal 2016; 10:341-346. [PMID: 27465749 DOI: 10.1007/s12079-016-0341-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 07/21/2016] [Indexed: 01/09/2023] Open
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11
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Lecoq AL, Viengchareun S, Hage M, Bouligand J, Young J, Boutron A, Zizzari P, Lombès M, Chanson P, Kamenický P. AIP mutations impair AhR signaling in pituitary adenoma patients fibroblasts and in GH3 cells. Endocr Relat Cancer 2016; 23:433-43. [PMID: 27080473 DOI: 10.1530/erc-16-0041] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 04/14/2016] [Indexed: 12/30/2022]
Abstract
Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene predispose humans to pituitary adenomas through unknown molecular mechanisms. The best-known interacting partner of AIP is the aryl hydrocarbon receptor (AhR), a transcription factor that mediates the effects of xenobiotics implicated in carcinogenesis. As 75% of AIP mutations disrupt the physical and/or functional interaction with AhR, we postulated that the tumorigenic potential of AIP mutations might result from altered AhR signaling. We evaluated the impact of AIP mutations on the AhR signaling pathway, first in fibroblasts from AIP-mutated patients with pituitary adenomas, by comparison with fibroblasts from healthy subjects, then in transfected pituitary GH3 cells. The AIP protein level in mutated fibroblasts was about half of that in cells from healthy subjects, but AhR expression was unaffected. Gene expression analyses showed significant modifications in the expression of the AhR target genes CYP1B1 and AHRR in AIP-mutated fibroblasts, both before and after stimulation with the endogenous AhR ligand kynurenine. Kynurenine increased Cyp1b1 expression to a greater extent in GH3 cells overexpressing wild type compared with cells expressing mutant AIP Knockdown of endogenous Aip in these cells attenuated Cyp1b1 induction by the AhR ligand. Both mutant AIP expression and knockdown of endogenous Aip affected the kynurenine-dependent GH secretion of GH3 cells. This study of human fibroblasts bearing endogenous heterozygous AIP mutations and transfected pituitary GH3 cells shows that AIP mutations affect the AIP protein level and alter AhR transcriptional activity in a gene- and tissue-dependent manner.
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Affiliation(s)
- Anne-Lise Lecoq
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France
| | - Say Viengchareun
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France
| | - Mirella Hage
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France
| | - Jérôme Bouligand
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France Assistance Publique-Hôpitaux de ParisService de Génétique Moléculaire, Pharmacogénétique et Hormonologie, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Jacques Young
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France Assistance Publique-Hôpitaux de ParisService d'Endocrinologie et des Maladies de la Reproduction, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Audrey Boutron
- Assistance Publique-Hôpitaux de ParisService de Biochimie, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Philippe Zizzari
- Inserm U894Centre de Psychiatrie et Neurosciences, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Marc Lombès
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France Assistance Publique-Hôpitaux de ParisService d'Endocrinologie et des Maladies de la Reproduction, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Philippe Chanson
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France Assistance Publique-Hôpitaux de ParisService d'Endocrinologie et des Maladies de la Reproduction, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Peter Kamenický
- Institut National de la Santé et de la Recherche Médicale (Inserm) U1185Le Kremlin-Bicêtre, France Université Paris-SudFaculté de Médecine Paris-Sud, Université Paris Saclay, Le Kremlin-Bicêtre, France Assistance Publique-Hôpitaux de ParisService d'Endocrinologie et des Maladies de la Reproduction, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
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Amara IE, Anwar-Mohamed A, Abdelhamid G, El-Kadi AO. Mercury modulates the cytochrome P450 1a1, 1a2 and 1b1 in C57BL/6J mice: in vivo and in vitro studies. Toxicol Appl Pharmacol 2013; 266:419-29. [DOI: 10.1016/j.taap.2012.11.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 11/17/2012] [Accepted: 11/30/2012] [Indexed: 10/27/2022]
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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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Amara IE, Anwar-Mohamed A, El-Kadi AO. Mercury modulates the CYP1A1 at transcriptional and posttranslational levels in human hepatoma HepG2 cells. Toxicol Lett 2010; 199:225-33. [DOI: 10.1016/j.toxlet.2010.09.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 09/03/2010] [Accepted: 09/06/2010] [Indexed: 10/19/2022]
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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
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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: 14] [Impact Index Per Article: 1.0] [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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Anwar-Mohamed A, Elbekai RH, El-Kadi AOS. Regulation of CYP1A1 by heavy metals and consequences for drug metabolism. Expert Opin Drug Metab Toxicol 2009; 5:501-21. [DOI: 10.1517/17425250902918302] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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18
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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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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: 543] [Impact Index Per Article: 33.9] [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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20
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Flaveny C, Reen RK, Kusnadi A, Perdew GH. The mouse and human Ah receptor differ in recognition of LXXLL motifs. Arch Biochem Biophys 2008; 471:215-23. [PMID: 18242161 PMCID: PMC2293825 DOI: 10.1016/j.abb.2008.01.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 01/17/2008] [Accepted: 01/17/2008] [Indexed: 02/04/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand inducible transcription factor that exhibits interspecies differences, with the human and mouse AhR C-terminal transactivation domain sharing only 58% amino acid sequence identity. The AhR has a transactivation domain comprised of proline/serine/threonine-rich, glutamine-rich, and acidic amino acid subdomains. A truncated mAhR and hAhR containing only the acidic subdomain displayed widely differing transactivation potentials. Whether the glutamine-rich subdomain of the mouse AhR and the human AhR differentially recruit LXXLL-motif coactivators was investigated. Transiently expressed GAL4 DNA binding domain (GAL4DBD)-LXXLL-motif fusion proteins were used to map the critical LXXLL binding sequence of the hAhR to amino acid residues 663-688. Several LXXLL-motif GAL4DBD fusion proteins dramatically differed in their ability to influence the transactivation potential of the mAhR and hAhR. These findings suggest that the human and mouse AhR may display differential recruitment of coactivators and hence may exhibit divergent regulation of target genes.
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Affiliation(s)
- Colin Flaveny
- Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Rashmeet K. Reen
- Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Ann Kusnadi
- Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Gary H. Perdew
- Center for Molecular Toxicology and Carcinogenesis and the Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802
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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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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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Morales JL, Perdew GH. Carboxyl terminus of hsc70-interacting protein (CHIP) can remodel mature aryl hydrocarbon receptor (AhR) complexes and mediate ubiquitination of both the AhR and the 90 kDa heat-shock protein (hsp90) in vitro. Biochemistry 2007; 46:610-21. [PMID: 17209571 PMCID: PMC2527729 DOI: 10.1021/bi062165b] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The regulation of the aryl hydrocarbon receptor (AhR) protein levels has been an area of keen interest, given its important role in mediating the cellular adaptation and toxic response to several environmental pollutants. The carboxyl terminus of hsc70-interacting protein (CHIP) ubiquitin ligase was previously associated with the regulation of the aryl hydrocarbon receptor, although the mechanisms were not directly demonstrated. In this study, we established that CHIP could associate with the AhR at cellular levels of these two proteins, suggesting a potential role for CHIP in the regulation of the AhR complex. The analysis of the sucrose-gradient-fractionated in vitro translated AhR complexes revealed that CHIP can mediate hsp90 ubiquitination while cooperating with unidentified factors to promote the ubiquitination of mature unliganded AhR complexes. In addition, the immunophilin-like protein XAP2 was able to partially protect the AhR from CHIP-mediated ubiquitination in vitro. This protection required the direct interaction of the XAP2 with the AhR complex. Surprisingly, CHIP silencing in Hepa-1c1c7 cells by siRNA methods did not reveal the function of CHIP in the AhR complex, because it did not affect well-characterized activities of the AhR nor affect its steady-state protein levels. However, the presence of potential compensatory mechanisms may be confounding this particular observation. Our results suggest a model where the E3 ubiquitin ligase CHIP cooperates with other ubiquitination factors to remodel native AhR-hsp90 complexes and where co-chaperones such as the XAP2 may affect the ability of CHIP to target AhR complexes for ubiquitination.
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Affiliation(s)
- J Luis Morales
- Graduate Program in Biochemistry, Microbiology, and Molecular Biology, The 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: 112] [Impact Index Per Article: 6.2] [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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Pollenz RS, Buggy C. Ligand-dependent and -independent degradation of the human aryl hydrocarbon receptor (hAHR) in cell culture models. Chem Biol Interact 2006; 164:49-59. [PMID: 16978595 DOI: 10.1016/j.cbi.2006.08.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 08/04/2006] [Accepted: 08/17/2006] [Indexed: 11/27/2022]
Abstract
Studies have shown that zebrafish and rodent aryl hydrocarbon receptors (AHRs) are degraded following ligand exposure and that reductions in AHR protein can impact growth and development in vivo. The current study was designed to evaluate the degradation of the AHR in seven human cell lines that were derived from various carcinomas or from normal tissue. Consistent with studies in other species, the results show that the human AHR (hAHR) is degraded in a ligand dependent manner following exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin for up to 16h. However, the hAHRs expressed in the various cell lines show differences in the time course and magnitude of degradation. The ligand dependent degradation is completely blocked by treatment with the proteasome inhibitor, MG-132. Ligand-independent degradation of the hAHR following exposure to geldanamycin (GA) is also observed in the different cell lines, although the magnitude of hAHR degradation is also is variable. These findings are significant since they indicate that ligand-dependent and independent degradation of the AHR is a conserved aspect of this signal transduction cascade from fish to human. In addition, the study identifies several cell lines that may provide novel models to further assess the regulation of AHR-mediated signaling and degradation of the human AHR.
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Affiliation(s)
- Richard S Pollenz
- Department of Biology, University of South Florida, 4202 E Fowler Avenue SCA 110, Tampa, FL 33620-5200, United States.
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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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27
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Nohara K, Ao K, Miyamoto Y, Ito T, Suzuki T, Toyoshiba H, Tohyama C. Comparison of the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1 gene expression profile in lymphocytes from mice, rats, and humans: most potent induction in humans. Toxicology 2006; 225:204-13. [PMID: 16839655 DOI: 10.1016/j.tox.2006.06.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Revised: 06/02/2006] [Accepted: 06/06/2006] [Indexed: 11/27/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exerts its toxicity by binding a transcription factor, the aryl hydrocarbon receptor (AhR). C57BL/6 (C57) mice express AhRs that have high affinity for TCDD, and they strongly express target genes and develop severe toxic effects upon TCDD exposure. By contrast, DBA/2 (DBA) mice have a low-affinity form of AhR, weakly express target genes, and are resistant to TCDD. Although humans express low-affinity AhRs and have been assumed to be refractory to TCDD, their sensitivity to TCDD has yet to be determined. In this study we compared the TCDD-induced CYP1A1 gene expression profiles in lymphocytes from humans, C57 mice, DBA mice, and SD rats to obtain data as a basis for estimating human sensitivity to TCDD. Lymphocyte fractions prepared from the blood of individual humans and animals were cultured with TCDD. Their mRNAs for CYP1A1 and housekeeping genes were measured by RT-PCR or real-time PCR with primers designed for regions that are 100% homologous among each of the genes of all species/strains tested to obtain similar PCR efficiency. TCDD-induced CYP1A1 expression peaked at 2h in DBA mice and SD rats and at 6h in C57 mice and humans. At the peak times human lymphocytes showed the most potent CYP1A1 mRNA induction of the four species/strains tested. These results suggest that human lymphocytes are more sensitive to TCDD than the lymphocytes of mice and rats. Since the AhR-dependent gene expression did not reflect the AhR affinity for TCDD, these results also suggest that AhR-dependent gene expression in lymphocytes is modulated by an as yet unidentified mechanism in addition to the AhR affinity.
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Affiliation(s)
- Keiko Nohara
- Environmental Health Sciences Division, National Institute for Environmental Studies, Tsukuba 305-8506, Japan.
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28
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Reichard JF, Dalton TP, Shertzer HG, Puga A. Induction of oxidative stress responses by dioxin and other ligands of the aryl hydrocarbon receptor. Dose Response 2006; 3:306-31. [PMID: 18648615 DOI: 10.2203/dose-response.003.03.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
TCDD and other polyhalogenated aromatic hydrocarbon ligands of the aryl hydrocarbon receptor (AHR) have been classically considered as non-genotoxic compounds because they fail to be directly mutagenic in either bacteria or most in vitro assay systems. They do so in spite of having repeatedly been linked to oxidative stress and to mutagenic and carcinogenic outcomes. Oxidative stress, on the other hand, has been used as a marker for the toxicity of dioxin and its congeners. We have focused this review on the connection between oxidative stress induction and the toxic effects of fetal and adult dioxin exposure, with emphasis on the large species difference in sensitivity to this agent. We examine the roles that the dioxin-inducible cytochromes P450s play in the cellular and toxicological consequences of dioxin exposure with emphasis on oxidative stress involvement. Many components of the health consequences resulting from dioxin exposure may be attributable to epigenetic mechanisms arising from prolonged reactive oxygen generation.
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Affiliation(s)
- John F Reichard
- Center for Environmental Genetics and Department of Environmental Health, University of Cincinnati Medical Center, Cincinnati, OH 45267, USA
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Karchner SI, Franks DG, Kennedy SW, Hahn ME. The molecular basis for differential dioxin sensitivity in birds: role of the aryl hydrocarbon receptor. Proc Natl Acad Sci U S A 2006; 103:6252-7. [PMID: 16606854 PMCID: PMC1435364 DOI: 10.1073/pnas.0509950103] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related halogenated aromatic hydrocarbons (HAHs) are highly toxic to most vertebrate animals, but there are dramatic differences in sensitivity among species and strains. Aquatic birds including the common tern (Sterna hirundo) are highly exposed to HAHs in the environment, but are up to 250-fold less sensitive to these compounds than the typical avian model, the domestic chicken (Gallus gallus). The mechanism of HAH toxicity involves altered gene expression subsequent to activation of the aryl hydrocarbon receptor (AHR), a basic helix-loop-helix-PAS transcription factor. AHR polymorphisms underlie mouse strain differences in sensitivity to HAHs and polynuclear aromatic hydrocarbons, but the role of the AHR in species differences in HAH sensitivity is not well understood. Here, we show that although chicken and tern AHRs both exhibit specific binding of [3H]TCDD, the tern AHR has a lower binding affinity and exhibits a reduced ability to support TCDD-dependent transactivation as compared to AHRs from chicken or mouse. We further show through use of chimeric AHR proteins and site-directed mutagenesis that the difference between the chicken and tern AHRs resides in the ligand-binding domain and that two amino acids (Val-325 and Ala-381) are responsible for the reduced activity of the tern AHR. Other avian species with reduced sensitivity to HAHs also possess these residues. These studies provide a molecular understanding of species differences in sensitivity to dioxin-like compounds and suggest an approach to using the AHR as a marker of dioxin susceptibility in wildlife.
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Affiliation(s)
- Sibel I. Karchner
- *Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543; and
| | - Diana G. Franks
- *Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543; and
| | - Sean W. Kennedy
- Environment Canada, Canadian Wildlife Service/National Wildlife Research Centre, Ottawa, ON, Canada K1A 0H3
| | - Mark E. Hahn
- *Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543; and
- To whom correspondence should be addressed. E-mail:
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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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Pollenz RS, Dougherty EJ. Redefining the role of the endogenous XAP2 and C-terminal hsp70-interacting protein on the endogenous Ah receptors expressed in mouse and rat cell lines. J Biol Chem 2005; 280:33346-56. [PMID: 16085934 DOI: 10.1074/jbc.m506619200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Studies using transient expression systems have implicated the XAP2 protein in the control of aryl hydrocarbon receptor (AHR) stability and subcellular location. Thus, studies were performed in cell lines that expressed endogenous rat or mouse Ah(b-1) (C57BL/6) or Ah(b-2) (C3H) AHRs with similar levels of endogenous XAP2. Unliganded rat and mouse Ah(b-2) receptor complexes associated with reduced levels of XAP2 and exhibited dynamic nucleocytoplasmic shuttling in comparison with Ah(b-1) receptors. Rat and mouse Ah(b-2) receptors also exhibited a greater magnitude of ligand-induced degradation than Ah(b-1) receptors. Small interfering RNA reduction of endogenous XAP2 by >80% had minimal impact on the level of Ah(b-2) receptors but resulted in a 25-30% reduction of Ah(b-1) receptors. XAP2 reduction resulted in increased susceptibility of the Ah(b-1) receptor to ligand-induced degradation yet produced higher levels of endogenous CYP1A1 induction. Stable expression of the Ah(b-2) receptor in the C57BL/6 background resulted in a protein with reduced association with XAP2, dynamic nucleocytoplasmic shuttling, and increased levels of ligand-induced degradation. Small interfering RNA reduction of endogenous XAP2 in a C-terminal hsp70-interacting protein knockout mouse cell line, exhibited a 25-30% reduction in the level of endogenous Ah(b-1) AHR and showed high levels of ligand-induced degradation. Thus, endogenous XAP2 exerts a negative function on a small fraction of the endogenous Ah(b-1) receptor complex but appears to have a minimal impact on endogenous rat or Ah(b-2) receptors. This implies that the analysis of the AHR-mediated signaling via rat and mouse Ah(b-2) receptors may better represent the physiology of this signal transduction pathway.
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Affiliation(s)
- Richard S Pollenz
- Department of Biology, University of South Florida, Tampa, Florida 33620, USA.
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Riggs DL, Cox MB, Cheung-Flynn J, Prapapanich V, Carrigan PE, Smith DF. Functional specificity of co-chaperone interactions with Hsp90 client proteins. Crit Rev Biochem Mol Biol 2005; 39:279-95. [PMID: 15763706 DOI: 10.1080/10409230490892513] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
A wide array of proteins in signal transduction pathways depend on Hsp90 and other chaperone components for functional maturation, regulation, and stability. Among these Hsp90 client proteins are steroid receptors, members from other classes of transcription factors, and representatives of both serine/threonine and tyrosine kinase families. Typically, dynamic complexes form on the client protein, and these consist of Hsp90- plus bound co-chaperones that often have enzymatic activities. In addition to its direct influence on client folding, Hsp90 locally concentrates co-chaperone activity within the client complex, and dynamic exchange of co-chaperones on Hsp90 facilitates sampling of co-chaperone activities that may, or may not, act on the client protein. We are just beginning to understand the nature of biochemical and molecular interactions between co-chaperone and Hsp90-bound client. This review focuses on the differential effects of Hsp90 co-chaperones toward client protein function and on the specificity that allows co-chaperones to discriminate between even closely related clients.
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Affiliation(s)
- Daniel L Riggs
- Department of Biochemistry and Molecular Biology, Mayo Clinic Scottsdale, Scottsdale, AZ 85259, USA
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Hollingshead BD, Petrulis JR, Perdew GH. The Aryl Hydrocarbon (Ah) Receptor Transcriptional Regulator Hepatitis B Virus X-associated Protein 2 Antagonizes p23 Binding to Ah Receptor-Hsp90 Complexes and Is Dispensable for Receptor Function. J Biol Chem 2004; 279:45652-61. [PMID: 15322122 DOI: 10.1074/jbc.m407840200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To further understand the role that the hepatitis B virus X-associated protein 2 (XAP2) plays in regulating aryl hydrocarbon receptor (AhR) function, a point mutation was introduced at tyrosine 408 of the AhR, changing the residue to an alanine or lysine. These mutations resulted in the loss of AhR binding to endogenous XAP2 in COS-1 cells and reduced binding of exogenously expressed XAP2. Cellular localization of the mutant AhR-yellow fluorescent protein fusion proteins remained nuclear when XAP2 was co-expressed, while the non-mutant receptor was redistributed to the cytoplasm. XAP2 expression caused an overall repression of constitutive and ligand-induced AhR transcriptional activity. However, increased expression of XAP2 had no effect on the AhRY408A mutant transcriptional activity. Additionally the XAP2 binding-deficient AhR mutants showed overall higher transcriptional activity when compared with the non-mutant receptor. Interestingly reduced incorporation of the Hsp90 associated co-chaperone p23 in the unliganded AhR complex was observed with increasing XAP2 expression. The displacement of p23 from Hsp90 did not occur when increasing levels of XAP2 were introduced in COS-1 cells in the absence of the AhR; thus this displacement event occurs specifically within an AhR complex. Finally XAP2 itself was capable of existing in multimeric complexes, and these complexes did not require Hsp90 or AhR to form. However, it is not yet clear whether XAP2 can exist within the AhR complex in more than one copy.
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Affiliation(s)
- Brett D Hollingshead
- 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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Ramadoss P, Perdew GH. Use of 2-azido-3-[125I]iodo-7,8-dibromodibenzo-p-dioxin as a probe to determine the relative ligand affinity of human versus mouse aryl hydrocarbon receptor in cultured cells. Mol Pharmacol 2004; 66:129-36. [PMID: 15213304 DOI: 10.1124/mol.66.1.129] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [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-induced transcription factor that is activated by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other related compounds, leading to toxicity. There is considerable variation in the response to TCDD among different species, and this may be correlated to differences in the AhR. Variations in the structure of the AhR could result in altered biochemical properties of the receptor, such as ligand affinity or transactivation potential. The difference between the mouse AhR b-1 allele (mAhR(b-1)) and human AhR (hAhR), in terms of their relative affinity for a photoaffinity ligand (2-azido-3-[(125)I]iodo-7,8-dibromodibenzo-p-dioxin), was assessed using both in vitro assays and assays performed directly in cell culture. Results revealed that the hAhR has a lower affinity for the photoaffinity ligand compared with mAhR(b-1). In contrast with a previous study, we found that a single amino acid (valine 381) in hAhR is responsible for the lower ligand affinity, and mutating this residue to alanine results in restoration of high ligand affinity in hAhR. In vitro ligand binding assays are limited by the low concentrations of protein in the assays, and it is not appropriate to compare ligand affinities of different receptors using this method without performing a competition assay or increasing the protein concentration in the assay. Because of the limitation of the in vitro assay, the relative ligand occupancy of mAhR(b-1) and hAhR was compared most effectively within cells, revealing that mAhR(b-1) has a 10-fold higher relative ligand affinity in cells, whereas mAhR(d) has a 2-fold higher relative ligand affinity than hAhR.
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Affiliation(s)
- Preeti Ramadoss
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary Science, Graduate Program in Biochemistry, Microbiology and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA
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