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Ortiga-Carvalho TM, Chiamolera MI, Pazos-Moura CC, Wondisford FE. Hypothalamus-Pituitary-Thyroid Axis. Compr Physiol 2016; 6:1387-428. [PMID: 27347897 DOI: 10.1002/cphy.c150027] [Citation(s) in RCA: 214] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The hypothalamus-pituitary-thyroid (HPT) axis determines the set point of thyroid hormone (TH) production. Hypothalamic thyrotropin-releasing hormone (TRH) stimulates the synthesis and secretion of pituitary thyrotropin (thyroid-stimulating hormone, TSH), which acts at the thyroid to stimulate all steps of TH biosynthesis and secretion. The THs thyroxine (T4) and triiodothyronine (T3) control the secretion of TRH and TSH by negative feedback to maintain physiological levels of the main hormones of the HPT axis. Reduction of circulating TH levels due to primary thyroid failure results in increased TRH and TSH production, whereas the opposite occurs when circulating THs are in excess. Other neural, humoral, and local factors modulate the HPT axis and, in specific situations, determine alterations in the physiological function of the axis. The roles of THs are vital to nervous system development, linear growth, energetic metabolism, and thermogenesis. THs also regulate the hepatic metabolism of nutrients, fluid balance and the cardiovascular system. In cells, TH actions are mediated mainly by nuclear TH receptors (210), which modify gene expression. T3 is the preferred ligand of THR, whereas T4, the serum concentration of which is 100-fold higher than that of T3, undergoes extra-thyroidal conversion to T3. This conversion is catalyzed by 5'-deiodinases (D1 and D2), which are TH-activating enzymes. T4 can also be inactivated by conversion to reverse T3, which has very low affinity for THR, by 5-deiodinase (D3). The regulation of deiodinases, particularly D2, and TH transporters at the cell membrane control T3 availability, which is fundamental for TH action. © 2016 American Physiological Society. Compr Physiol 6:1387-1428, 2016.
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Affiliation(s)
- Tania M Ortiga-Carvalho
- Institute of Biophysics Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro, Brazil
| | - Maria I Chiamolera
- Department of Medicine, Escola Paulista de Medicina, Universidade Federal de Sao Paulo, Sao Paulo, Brazil
| | - Carmen C Pazos-Moura
- Institute of Biophysics Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro, Brazil
| | - Fredic E Wondisford
- Department of Medicine, Rutgers-Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA
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Jung KK, Kim SY, Kim TG, Kang JH, Kang SY, Cho JY, Kim SH. Differential regulation of thyroid hormone receptor-mediated function by endocrine disruptors. Arch Pharm Res 2007; 30:616-23. [PMID: 17615682 DOI: 10.1007/bf02977657] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
It is well known that endocrine disruptors (EDs) act as anti-estrogenic agents and affect the function of reproductive organ. EDs are also thought to affect thyroid hormone (TH) system which is important for biological functions such as growth, development and metabolism. However, it is still not clear how EDs are able to regulate TH receptor (TR)-mediated functions. In this study, therefore, the modulatory effects of representative EDs such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polychlorinated biphenyl (Aroclor 1254) and bisphenol A (BPA) were examined using TR-expressing GH3 cells (a rat pituitary gland epithelial tumor cell line) activated by triiodothyronine (T3). EDs tested significantly blocked T3 binding to TR in a dose-dependent manner. Biochemical characterization by Scatchard and Lineweaver-Burk plot analyses indicated that TCDD and aroclor 1254 bound to TH receptors in a competitive inhibitory manner, whereas BPA bound to TH receptors in a non-competitive pattern. The different inhibitory mode of action by EDs was also found in regulating TR-mediated production of prolactin (PRL). Aroclor 1254 exposure for 48 h enhanced T3-mediated PRL production, but BPA down-regulated. These results suggest that the EDs (TCDD, Aroclor 1254 and BPA) could differentially bind to TR and distinctly regulate the action of TR function, even though EDs are structurally similar.
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Affiliation(s)
- Ki Kyung Jung
- Department of Pharmacology, Biochemical Pharmacology Team, National Institute of Toxicological Research, Seoul 122-704, Korea
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Maruvada P, Baumann CT, Hager GL, Yen PM. Dynamic shuttling and intranuclear mobility of nuclear hormone receptors. J Biol Chem 2003; 278:12425-32. [PMID: 12506123 DOI: 10.1074/jbc.m202752200] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We expressed green fluorescent protein (GFP) chimeras of estrogen, retinoic acid, and thyroid hormone receptors (ERs, RARs, and TRs, respectively) in HeLa cells to examine nucleocytoplasmic shuttling and intranuclear mobility of nuclear hormone receptors (NRs) by confocal microscopy. These receptors were predominantly in the nucleus and, interestingly, underwent intranuclear reorganization after ligand treatment. Nucleocytoplasmic shuttling was demonstrated by heterokaryon experiments and energy-dependent blockade of nuclear import and leptomycin-dependent blockade of nuclear export. Ligand addition decreased shuttling by GFP-ER, whereas heterodimerization with retinoid X receptor helped maintain TR and RAR within the nucleus. Intranuclear mobility of the GFP-NRs was studied by fluorescence recovery after photo-bleaching +/- cognate ligands. Both GFP-TR and GFP-RAR moved rapidly in the nucleus, and ligand binding did not significantly affect their mobility. In contrast, estrogen binding decreased the mobility of GFP-ER and also increased the fraction of GFP-ER that was unable to diffuse. These effects were even more pronounced with tamoxifen. Co-transfection of the co-activator, SRC-1, further slowed the mobility of liganded GFP-ER. Our findings suggest estradiol and tamoxifen exert differential effects on the intranuclear mobility of GFP-ER. They also show that ligand-binding and protein-protein interactions can affect the intracellular mobility of some NRs and thereby may contribute to their biological activity.
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Affiliation(s)
- Padma Maruvada
- Molecular Regulation and Neuroendocrinology Section, Clinical Endocrinology Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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Takeshita A, Taguchi M, Koibuchi N, Ozawa Y. Putative role of the orphan nuclear receptor SXR (steroid and xenobiotic receptor) in the mechanism of CYP3A4 inhibition by xenobiotics. J Biol Chem 2002; 277:32453-8. [PMID: 12072427 DOI: 10.1074/jbc.m111245200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytochrome P450 monooxygenase 3A4 (CYP3A4) is responsible for the metabolism of endogenous steroids and drugs in liver. Many inducers of human CYP3A4, such as rifampicin, bind to the orphan nuclear receptor SXR (steroid and xenobiotic receptor) as ligands and stimulate transcription on xenobiotic response elements located in the CYP3A4 promoter. Conversely, it is not known whether SXR mediates the transcriptional repression. We thus examined transcriptional repression of SXR and its interaction with corepressors, NCoR (nuclear receptor corepressor) and SMRT (silencing mediator for retinoid and thyroid receptors) using reporter assays in the absence and presence of ligand. Cotransfection of SMRT, but not NCoR, inhibited not only basal but also rifampicin-induced transcriptional activity of SXR on the CYP3A4 promoter through specific SMRT-SXR interaction in HepG2 cells. Interestingly, rifampicin also increased the interaction of SXR with SMRT as well as with coactivator SRC-1. On the other hand, the anti-fungal agent ketoconazole decreased SXR interaction with both SRC-1 and SMRT. Ketoconazole partially inhibited corticosterone-induced SXR-mediated transcription on the CYP3A4 promoter. Taken together, our results suggest that the differential interaction of coactivators and corepressors induced by various xenobiotics may alter SXR-mediated transcription. Further, the effects of ketoconazole on the CYP3A4 gene suppression may explain, in part, drug-induced inhibition of the CYP3A4 action at the transcriptional level.
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Affiliation(s)
- Akira Takeshita
- Division of Endocrinology and Metabolism, Toranomon Hospital, Okinaka Memorial Institute for Medical Research, Tokyo 105-8470, Japan.
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Wu Y, Delerive P, Chin WW, Burris TP. Requirement of helix 1 and the AF-2 domain of the thyroid hormone receptor for coactivation by PGC-1. J Biol Chem 2002; 277:8898-905. [PMID: 11751919 DOI: 10.1074/jbc.m110761200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although PGC-1 (peroxisome proliferator-activated receptor-gamma coactivator-1) has been previously shown to enhance thyroid hormone receptor (TR)/retinoid X receptor-mediated ucp-1 gene expression in a ligand-induced manner in rat fibroblast cells, the precise mechanism of PGC-1 modulation of TR function has yet to be determined. In this study, we show that PGC-1 can potentiate TR-mediated transactivation of reporter genes driven by natural thyroid hormone response elements both in a ligand-dependent and ligand-independent manner and that the extent of coactivation is a function of the thyroid hormone response element examined. Our data also show that PGC-1 stimulation of TR activity in terms of Gal4 DNA-binding domain fusion is strictly ligand-dependent. In addition, an E457A AF-2 mutation had no effect on the ligand-induced PGC-1 enhancement of TR activity, indicating that the conserved charged residue in AF-2 is not essential for this PGC-1 function. Furthermore, GST pull-down and mammalian two-hybrid assays demonstrated that the PGC-1 LXXLL motif is required for ligand-induced PGC-1/TR interaction. This agonist-dependent PGC-1/TR interaction also requires both helix 1 and the AF-2 region of the TR ligand-binding domain. Taken together, these results support the notion that PGC-1 is a bona fide TR coactivator and that PGC-1 modulates TR activity via a mechanism different from that utilized with peroxisome proliferator activator receptor-gamma.
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Affiliation(s)
- Yifei Wu
- Gene Regulation, Bone, and Inflammation Research, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, Indiana 46285, USA
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Ko L, Cardona GR, Henrion-Caude A, Chin WW. Identification and characterization of a tissue-specific coactivator, GT198, that interacts with the DNA-binding domains of nuclear receptors. Mol Cell Biol 2002; 22:357-69. [PMID: 11739747 PMCID: PMC134202 DOI: 10.1128/mcb.22.1.357-369.2002] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gene activation mediated by nuclear receptors is regulated in a tissue-specific manner and requires interactions between nuclear receptors and their cofactors. Here, we identified and characterized a tissue-specific coactivator, GT198, that interacts with the DNA-binding domains of nuclear receptors. GT198 was originally described as a genomic transcript that mapped to the human breast cancer susceptibility locus 17q12-q21 with unknown function. We show that GT198 exhibits a tissue-specific expression pattern in which its mRNA is elevated in testis, spleen, thymus, pituitary cells, and several cancer cell lines. GT198 is a 217-amino-acid nuclear protein that contains a leucine zipper required for its dimerization. In vitro binding and yeast two-hybrid assays indicated that GT198 interacted with nuclear receptors through their DNA-binding domains. GT198 potently stimulated transcription mediated by estrogen receptor alpha and beta, thyroid hormone receptor beta1, androgen receptor, glucocorticoid receptor, and progesterone receptor. However, the action of GT198 was distinguishable from that of the ligand-binding domain-interacting nuclear receptor coactivators, such as TRBP, CBP, and SRC-1, with respect to basal activation and hormone sensitivity. Furthermore, protein kinase A, protein kinase C, and mitogen-activated protein kinase can phosphorylate GT198 in vitro, and cotransfection of these kinases regulated the transcriptional activity of GT198. These data suggest that GT198 is a tissue-specific, kinase-regulated nuclear receptor coactivator that interacts with the DNA-binding domains of nuclear receptors.
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Affiliation(s)
- Lan Ko
- Department of Gene Regulation, Bone and Inflammation Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
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Baumann CT, Maruvada P, Hager GL, Yen PM. Nuclear cytoplasmic shuttling by thyroid hormone receptors. multiple protein interactions are required for nuclear retention. J Biol Chem 2001; 276:11237-45. [PMID: 11152480 DOI: 10.1074/jbc.m011112200] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this report, we have studied the intracellular dynamics and distribution of the thyroid hormone receptor-beta (TRbeta) in living cells, utilizing fusions to the green fluorescent protein. Wild-type TRbeta was mostly nuclear in both the absence and presence of triiodothyronine; however, triiodothyronine induced a nuclear reorganization of TRbeta. By mutating defined regions of TRbeta, we found that both nuclear corepressor and retinoid X receptor are involved in maintaining the unliganded receptor within the nucleus. A TRbeta mutant defective in DNA binding had only a slightly altered nuclear/cytoplasmic distribution compared with wild-type TRbeta; thus, site-specific DNA binding is not essential for maintaining TRbeta within the nucleus. Both ATP depletion studies and heterokaryon analysis demonstrated that TRbeta rapidly shuttles between the nuclear and the cytoplasmic compartments. Cotransfection of nuclear corepressor and retinoid X receptor markedly decreased the shuttling by maintaining unliganded TRbeta within the nucleus. In summary, our findings demonstrate that TRbeta rapidly shuttles between the nucleus and the cytoplasm and that protein-protein interactions of TRbeta with various cofactors, rather than specific DNA interactions, play the predominant role in determining the intracellular distribution of the receptor.
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Affiliation(s)
- C T Baumann
- Laboratory of Receptor Biology and Gene Expression, NCI and Molecular Regulation and Neuroendocrinology Section, Clinical Endocrinology Branch, NIDDKD, National Institutes of Health, Bethesda, Maryland 20892, USA
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Safer JD, Cohen RN, Hollenberg AN, Wondisford FE. Defective release of corepressor by hinge mutants of the thyroid hormone receptor found in patients with resistance to thyroid hormone. J Biol Chem 1998; 273:30175-82. [PMID: 9804773 DOI: 10.1074/jbc.273.46.30175] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
On positive thyroid hormone response elements (pTREs), thyroid hormone receptor (TR) binding to DNA in the absence of ligand (thyroid hormone, T3) decreases transcription (silencing). Silencing is due to a family of recently described nuclear corepressor proteins (NCoR and SMRT) which bind to the CoR box in the hinge region of TR. Ligand-dependent activation of TR is associated with displacement of corepressors and recruitment of coactivating proteins. Resistance to thyroid hormone (RTH) is due to mutations in the beta isoform of the thyroid hormone receptor (TR-beta). To date, three RTH mutations reportedly with near-normal T3 binding (A234T, R243Q, and R243W) have been described in or near the CoR box. To determine the mechanism of RTH caused by these mutants, the interaction of wild type (wt) and mutant TRs with the corepressor, NCoR, and the coactivator, SRC-1, was tested in gel-shift assays. As expected, NCoR bound wt TR in the absence of T3 and dissociated from TR with increasing T3 concentration. SRC-1 failed to bind wt TR in the absence of T3, but bound to TR with increasing avidity as T3 concentrations rose. At no T3 concentration did both NCoR and SRC-1 bind to wt TR, indicating that their binding to TR was mutually exclusive. Hinge mutants bound NCoR normally in the absence of T3; however, dissociation of NCoR and recruitment of SRC-1 was markedly impaired except at very high T3 concentrations. Importantly, hinge mutant TRs when complexed to DNA bound T3 poorly despite their near-normal T3 binding in solution. These binding studies correlated with functional assays showing defective transactivation of pTREs by hinge mutants except at high T3 concentrations. Thus, we describe a novel mechanism of RTH whereby TR hinge mutants selectively affect T3 binding when complexed to DNA, and prevent NCoR dissociation from TR. Our data also suggest that solution T3 binding by RTH mutants may not accurately reflect physiologically relevant T3 binding by TR when bound to DNA.
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Affiliation(s)
- J D Safer
- Thyroid Unit, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Takeshita A, Yen PM, Ikeda M, Cardona GR, Liu Y, Koibuchi N, Norwitz ER, Chin WW. Thyroid hormone response elements differentially modulate the interactions of thyroid hormone receptors with two receptor binding domains in the steroid receptor coactivator-1. J Biol Chem 1998; 273:21554-62. [PMID: 9705285 DOI: 10.1074/jbc.273.34.21554] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ligand-dependent transcriptional activation by nuclear receptors is mediated by interactions with coactivators. Recently, a consensus interaction motif (LXXLL) has been identified in a number of coactivators such as steroid receptor coactivator-1 (SRC-1). SRC-1 contains three such motifs in the central (nuclear receptor binding domain-1, NBD-1) and a single one in the C-terminal (NBD-2) regions. To define the nature and role of the two NBDs in SRC-1, interaction studies between the two NBDs and thyroid hormone receptor (TR) were performed. Although NBD-1 and NBD-2 showed similar ligand- and AF-2-dependent interactions with TR in solution, these two NBDs possessed distinct interaction properties with TR when TR is bound to a thyroid hormone-response element (TRE). Both in vitro and in vivo interaction studies demonstrate that NBD-1, but not NBD-2, exhibits ligand-dependent interaction with TR in the presence of TREs. In addition, a natural isoform of SRC-1, SRC-1E, which lacks NBD-2, preserved TR as well as progesterone receptor-mediated coactivator function on reporter gene expression. Finally, we found that NBD-1 failed to interact with a TR and retinoid X receptor heterodimer complex on a transcriptionally inactive direct repeat +4 TRE in electrophoretic mobility shift assays. These observations indicate that DNA-induced, as well as ligand-induced, conformational change(s) of TR may influence the nature of its binding to SRC-1, and that the two NBDs of SRC-1 may play different roles to regulate ligand-dependent transactivation of TRs.
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Affiliation(s)
- A Takeshita
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
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