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Yao B, Yang C, Pan C, Li Y. Thyroid hormone resistance: Mechanisms and therapeutic development. Mol Cell Endocrinol 2022; 553:111679. [PMID: 35738449 DOI: 10.1016/j.mce.2022.111679] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 05/03/2021] [Accepted: 05/09/2022] [Indexed: 10/18/2022]
Abstract
As an essential primary hormone, thyroid hormone (TH) is indispensable for human growth, development and metabolism. Impairment of TH function in several aspects, including TH synthesis, activation, transportation and receptor-dependent transactivation, can eventually lead to thyroid hormone resistance syndrome (RTH). RTH is a rare syndrome that manifests as a reduced target cell response to TH signaling. The majority of RTH cases are related to thyroid hormone receptor β (TRβ) mutations, and only a few RTH cases are associated with thyroid hormone receptor α (TRα) mutations or other causes. Patients with RTH suffer from goiter, mental retardation, short stature and bradycardia or tachycardia. To date, approximately 170 mutated TRβ variants and more than 20 mutated TRα variants at the amino acid level have been reported in RTH patients. In addition to these mutated proteins, some TR isoforms can also reduce TH function by competing with primary TRs for TRE and RXR binding. Fortunately, different treatments for RTH have been explored with structure-activity relationship (SAR) studies and drug design, and among these treatments. With thyromimetic potency but biochemical properties that differ from those of primary TH (T3 and T4), these TH analogs can bypass specific defective transporters or reactive mutant TRs. However, these compounds must be carefully applied to avoid over activating TRα, which is associated with more severe heart impairment. The structural mechanisms of mutation-induced RTH in the TR ligand-binding domain are summarized in this review. Furthermore, strategies to overcome this resistance for therapeutic development are also discussed.
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Affiliation(s)
- Benqiang Yao
- The State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian, 361005, China
| | - Chunyan Yang
- The State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian, 361005, China.
| | - Chengxi Pan
- The State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian, 361005, China
| | - Yong Li
- The State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian, 361005, China.
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Rekawiecki R, Dobrzyn K, Kowalik MK. Steroid Receptor Coregulators Can Modulate the Action of Progesterone Receptor during the Estrous Cycle in Cow Endometrium. Animals (Basel) 2021; 11:ani11113217. [PMID: 34827948 PMCID: PMC8614263 DOI: 10.3390/ani11113217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/23/2021] [Accepted: 11/08/2021] [Indexed: 11/17/2022] Open
Abstract
Simple Summary Proper functioning of the endometrium is necessary for the implantation of the embryo after fertilization and its development throughout pregnancy. The key role in this process plays appropriate action of progesterone through the nuclear receptor isoforms. The action of the receptor is regulated by the attachment of receptor modulators called coregulators which include coactivators and corepressors. Their improper expression in humans causes a malfunction of progesterone receptors and leads to disorders of pregnancy. However, in farm animals, such disorders may be one of the reasons leading up to early embryonic lethality, which in cows reaches up to 40%. Obtained results indicate the important role of the studied coregulators in regulating progesterone activity in endometrial cells, especially during the preimplantation period. Therefore, they can be helpful in better understanding the regulation and expression of the coactivators and corepressors in cow endometrium during the estrous cycle and can contribute to reducing this problem. They can also be of significant practical importance, making for the increased efficiency of breeding these animals. Abstract Nuclear receptor coregulators include coactivators and corepressors which associate with the progesterone receptor (PGR) during its activation. Fluctuations in the transcription levels of their respective genes and subsequent protein production as well as in related activities for histone acetyltransferase (HAT) and histone deacetylase (HDAC) can affect PGR function and thus change the action of progesterone (P4) in bovine endometrium during the estrous cycle. Endometrial tissue on days 2–5, 6–10, 11–16, and 17–20 of the estrous cycle was used for determination of the mRNA expression levels of coactivators P300, CREB, and SRC-1 along with corepressor NCOR-2 using Real-Time PCR, with protein levels by Western blot. Coregulators cellular localizations were assessed by immunohistochemistry whereas the activities of HAT and HDAC by using EIA. The highest levels of mRNA and proteins for all of the investigated coregulators, as well as the highest levels of activity for HAT and HDAC, were detected over days 2–16 of the estrous cycle. All of the tested coregulatory proteins were localized in the nuclei of endometrial cells. This research indicates the important role of coregulators of the PGR receptor in regulating P4 activity in endometrial cells, especially during the pre-implantation period.
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Rekawiecki R, Dobrzyn K, Kotwica J, Kowalik MK. Progesterone Receptor Coregulators as Factors Supporting the Function of the Corpus Luteum in Cows. Genes (Basel) 2020; 11:genes11080923. [PMID: 32806523 PMCID: PMC7465684 DOI: 10.3390/genes11080923] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 08/06/2020] [Accepted: 08/07/2020] [Indexed: 11/16/2022] Open
Abstract
Progesterone receptor (PGR) for its action required connection of the coregulatory proteins, including coactivators and corepressors. The former group exhibits a histone acetyltransferase (HAT) activity, while the latter cooperates with histone deacetylase (HDAC). Regulations of the coregulators mRNA and protein and HAT and HDAC activity can have an indirect effect on the PGR function and thus progesterone (P4) action on target cells. The highest mRNA expression levels for the coactivators—histone acetyltransferase p300 (P300), cAMP response element-binding protein (CREB), and steroid receptor coactivator-1 (SRC-1)—and nuclear receptor corepressor-2 (NCOR-2) were found in the corpus luteum (CL) on days 6 to 16 of the estrous cycle. The CREB protein level was higher on days 2–10, whereas SRC-1 and NCOR-2 were higher on days 2–5. The activity of HAT and HDAC was higher on days 6–10 of the estrous cycle. All of the coregulators were localized in the nuclei of small and large luteal cells. The mRNA and protein expression levels of the examined coactivators and corepressor changed with the P4 level. Thus, P4 may regulate CL function via the expression of coregulators, which probably affects the activity of the PGR.
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Concolino P, Costella A, Paragliola RM. Mutational Landscape of Resistance to Thyroid Hormone Beta (RTHβ). Mol Diagn Ther 2020; 23:353-368. [PMID: 30976996 DOI: 10.1007/s40291-019-00399-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Resistance to thyroid hormone beta (RTHβ) is a syndrome characterized by reduced responsiveness of peripheral tissues to thyroid hormone (TH). In most cases, the disorder is associated with germline pathogenic variants in the thyroid hormone receptor beta (THRB) gene. This paper summarizes the clinical and biochemical presentation of the disease, providing a comprehensive overview on molecular genetic features. Particular care is given in reporting all identified THRB variants with an assessed or unknown clinical significance. Our aim is to offer a useful tool for clinical and genetic specialists in order to ease clinical diagnosis and genetic counseling.
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Affiliation(s)
- Paola Concolino
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy.
| | - Alessandra Costella
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo A. Gemelli 8, 00168, Rome, Italy
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Li JE, Futawaka K, Yamamoto H, Kasahara M, Tagami T, Liu TH, Moriyama K. Cinnamaldehyde Contributes to Insulin Sensitivity by Activating PPARδ, PPARγ, and RXR. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2015; 43:879-92. [PMID: 26227398 DOI: 10.1142/s0192415x15500512] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cinnamon is a traditional folk herb used in Asia and has been reported to have antidiabetic effects. Our previous study showed that cinnamaldehyde (CA), a major effective compound in cinnamon, exhibited hypoglycemic and hypolipidemic effects together in db/db mice. The aim of the present study was to elucidate the molecular mechanisms of the effects of CA on the transcriptional activities of three peroxisome proliferator-activated receptors, (PPAR) α, δ, and γ. We studied the effects of CA through a transient expression assay with TSA201 cells, derivatives of human embryonic kidney cell line (HEK293). Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis was also performed to evaluate mRNA expression levels. We show here that CA induced PPARδ, PPARγ and retinoid X receptor (RXR) activation. CA may activate PPARγ in a different manner than pioglitazone, as CA selectively stimulated PPARγ S342A mutant while pioglitazone did not. In addition, CA and L-165041 had a synergistic effect on PPARδ activation. To gather the biological evidence that CA increases PPARs transcription, we further measured the expressions of PPARδ and PPARγ target genes in 3T3-L1 adipocytes. The data showed CA induced the expression of PPARδ and PPARγ target genes, namely aP2 and CD36, in differentiated adipocytes. As a result, PPARδ, PPARγ and their heterodimeric partner RXR appear to play a part in the CA action in the target tissues, thereby enhancing insulin sensitivity and fatty acid β-oxidation and energy uncoupling in skeletal muscle and adipose tissue.
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Affiliation(s)
- Juan-E Li
- Department of Chinese Medicine, Shaanxi Provincial People's Hospital, Xi'an 710068, China.,Graduate School, Beijing University of Chinese Medicine, Beijing 100029, China
| | - Kumi Futawaka
- Department of Medicine and Clinical Science, School of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan
| | - Hiroyuki Yamamoto
- Department of Medicine and Clinical Science, School of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan
| | - Masato Kasahara
- Department of Nephrology and Blood Purification, Institute of Biomedical Research and Innovation, Kobe Medical Frontier Center, Kobe 650-0047, Japan
| | - Tetsuya Tagami
- Clinical Research Institute, Kyoto Medical Center, National Hospital Organization, Kyoto 612-8555, Japan
| | - Tong-Hua Liu
- Graduate School, Beijing University of Chinese Medicine, Beijing 100029, China
| | - Kenji Moriyama
- Department of Medicine and Clinical Science, School of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan.,Clinical Research Institute, Kyoto Medical Center, National Hospital Organization, Kyoto 612-8555, Japan
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Fattori J, Campos JLO, Doratioto TR, Assis LM, Vitorino MT, Polikarpov I, Xavier-Neto J, Figueira ACM. RXR agonist modulates TR: corepressor dissociation upon 9-cis retinoic acid treatment. Mol Endocrinol 2014; 29:258-73. [PMID: 25541638 DOI: 10.1210/me.2014-1251] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Transcriptional regulation controlled by thyroid hormone receptor (TR) drives events such as development, differentiation, and metabolism. TRs may act either as homodimers or as heterodimers with retinoid X receptor (RXR). Thyroid hormone T3 preferentially binds TR-RXR heterodimers, which activate transcription through coactivator recruitment. However, it is unclear whether TR-RXR heterodimers may also be responsive to the canonical RXR agonist 9-cis retinoic acid (9C) in the context of physiological gene regulation. New structural studies suggest that 9C promotes the displacement of bound coactivators from the heterodimer, modifying TR-RXR activity. To shed light on the molecular mechanisms that control TR-RXR function, we used biophysical approaches to characterize coregulator recruitment to TR-TR or to TR-RXR in the presence of T3 and/or 9C as well as cell-based assays to establish the functional significance of biophysical findings. Using cell-based and fluorescence assays with mutant and wild-type TR, we show that 9C does indeed have a function in the TR-RXR heterodimer context, in which it induces the release of corepressors. Furthermore, we show that 9C does not promote detectable conformational changes in the structure of the TR-RXR heterodimer and does not affect coactivator recruitment. Finally, our data support the view that DNA binding domain and Hinge regions are important to set up NR-coactivator binding interfaces. In summary, we showed that the RXR agonist 9C can regulate TR function through its modulation of corepressor dissociation.
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Affiliation(s)
- Juliana Fattori
- Centro Nacional de Pesquisa em Energia e Materiais (J.F., J.L.O.C., T.R.D., L.M.A., M.T.V., J.X.-N., A.C.M.F.), Laboratório Nacional de Biociências, Campinas SP, 13083-970, Brazil; and Instituto de Física de São Carlos (I.P.), Universidade de São Paulo, São Carlos SP, 13560-970, Brazil
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A novel 1297-1304delGCCTGCCA mutation in the exon 10 of the thyroid hormone receptor β gene causes resistance to thyroid hormone. ACTA ACUST UNITED AC 2013; 8:163-9. [PMID: 23315966 DOI: 10.1007/bf03260060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Resistance to the thyroid hormone (RTH) is an inherited syndrome of reduced tissue responsiveness to hormonal action caused by mutations located in the ligand-binding domain and adjacent hinge region of the thyroid hormone receptor β (TRβ) gene. PATIENT The patient in this study, a 42-year-old Caucasian male, came to medical attention because he experienced atrial fibrillation. Clinical evaluation showed a small and diffuse goiter and biochemical tests revealed markedly elevated concentrations of total T(4), total T(3), and free T(4), normal thyroid-stimulating hormone (TSH) values and slightly increased I(131) thyroid uptake at 24 hours. The thyroperoxidase, thyroglobulin, and TSH receptor antibodies were positive. He was treated with cabergoline plus methimazole. This treatment was stopped because of the inconsistent response, monotherapy with tri-iodothyroacetic acid (TRIAC) was then prescribed after molecular diagnosis confirmed RTH syndrome. METHODS The exons 9 and 10 of the TRβ gene, including splicing signals and the flanking intronic regions of each intron, were amplified with PCR. DNA sequences from each amplified fragment were performed with the Taq polymerase-based chain terminator method and using the specific TRβ forward and reverse primers. RESULTS Direct sequence analysis of the exons 9 and 10 of the TRβ gene revealed an eight basepair deletion, 1297-1304delGCCTGCCA in exon 10. The mutation produces a frameshift at amino acid 433 and introduces a stop codon TGA at position 461, 85 nucleotides downstream from deletion. This alteration was not detected in either the father or mother of the patient, suggesting a de novo mutation that was confirmed by DNA fingerprint analysis. CONCLUSIONS In the present study we have identified a novel sporadic mutation corresponding to 1297-1304delGCCTGCCA deletion in the activating function 2 (AF-2) region of TRβ. To our knowledge, this is the first time that the presence of a partial deletion of eight nucleotides in the TRβ has been reported.
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Mavinakere MS, Powers JM, Subramanian KS, Roggero VR, Allison LA. Multiple novel signals mediate thyroid hormone receptor nuclear import and export. J Biol Chem 2012; 287:31280-97. [PMID: 22815488 PMCID: PMC3438959 DOI: 10.1074/jbc.m112.397745] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Thyroid hormone receptor (TR) is a member of the nuclear receptor superfamily that shuttles between the cytosol and nucleus. The fine balance between nuclear import and export of TR has emerged as a critical control point for modulating thyroid hormone-responsive gene expression; however, sequence motifs of TR that mediate shuttling are not fully defined. Here, we characterized multiple signals that direct TR shuttling. Along with the known nuclear localization signal in the hinge domain, we identified a novel nuclear localization signal in the A/B domain of thyroid hormone receptor α1 that is absent in thyroid hormone receptor β1 and inactive in the oncoprotein v-ErbA. Our prior studies showed that thyroid hormone receptor α1 exits the nucleus through two pathways, one dependent on the export factor CRM1 and the other CRM1-independent. Here, we identified three novel CRM1-independent nuclear export signal (NES) motifs in the ligand-binding domain as follows: a highly conserved NES in helix 12 (NES-H12) and two additional NES sequences spanning helix 3 and helix 6, respectively. Mutations predicted to disrupt the α-helical structure resulted in a significant decrease in NES-H12 activity. The high degree of conservation of helix 12 suggests that this region may function as a key NES in other nuclear receptors. Furthermore, our mutagenesis studies on NES-H12 suggest that altered shuttling of thyroid hormone receptor β1 may be a contributing factor in resistance to thyroid hormone syndrome. Taken together, our findings provide a detailed mechanistic understanding of the multiple signals that work together to regulate TR shuttling and transcriptional activity, and they provide important insights into nuclear receptor function in general.
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Affiliation(s)
- Manohara S Mavinakere
- Department of Biology, College of William and Mary, Williamsburg, Virginia 23187, USA
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Sar P, Peter R, Rath B, Mohapatra AD, Mishra SK. 3, 3'5 Triiodo L thyronine induces apoptosis in human breast cancer MCF-7 cells, repressing SMP30 expression through negative thyroid response elements. PLoS One 2011; 6:e20861. [PMID: 21687737 PMCID: PMC3110202 DOI: 10.1371/journal.pone.0020861] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 05/14/2011] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Thyroid hormones regulate cell proliferation, differentiation as well as apoptosis. However molecular mechanism underlying apoptosis as a result of thyroid hormone signaling is poorly understood. The antiapoptotic role of Senescence Marker Protein-30 (SMP30) has been characterized in response to varieties of stimuli as well as in knock out model. Our earlier data suggest that thyroid hormone 3, 3'5 Triiodo L Thyronine (T(3)), represses SMP30 in rat liver. METHODOLOGY/PRINCIPAL FINDINGS In highly metastatic MCF-7, human breast cancer cell line T3 treatment repressed SMP30 expression leading to enhanced apoptosis. Analysis by flow cytometry and other techniques revealed that overexpression and silencing of SMP30 in MCF-7 resulted in decelerated and accelerated apoptosis respectively. In order to identify the cis-acting elements involved in this regulation, we have analyzed hormone responsiveness of transiently transfected hSMP30 promoter deletion reporter vectors in MCF-7 cells. As opposed to the expected epigenetic outcome, thyroid hormone down regulated hSMP30 promoter activity despite enhanced recruitment of acetylated H3 on thyroid response elements (TREs). From the stand point of established epigenetic concept we have categorised these two TREs as negative response elements. Our attempt of siRNA mediated silencing of TRβ, reduced the fold of repression of SMP30 gene expression. In presence of thyroid hormone, Trichostatin- A (TSA), which is a Histone deacetylase (HDAC) inhibitor further inhibited SMP30 promoter activity. The above findings are in support of categorisation of both the thyroid response element as negative response elements as usually TSA should have reversed the repressions. CONCLUSION This is the first report of novel mechanistic insights into the remarkable downregulation of SMP30 gene expression by thyroid hormone which in turn induces apoptosis in MCF-7 human breast cancer cells. We believe that our study represents a good ground for future effort to develop new therapeutic approaches to challenge the progression of breast cancer.
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Affiliation(s)
- Pranati Sar
- Cancer Biology Lab, Department of Gene Function and Regulation, Institute of Life Sciences, Chandrasekharpur, Bhubaneswar, India
| | - Rosalima Peter
- Cancer Biology Lab, Department of Gene Function and Regulation, Institute of Life Sciences, Chandrasekharpur, Bhubaneswar, India
| | - Bandita Rath
- Cancer Biology Lab, Department of Gene Function and Regulation, Institute of Life Sciences, Chandrasekharpur, Bhubaneswar, India
| | - Alok Das Mohapatra
- Vector Born Disease Lab, Department of Infectious Disease Biology, Institute of Life Sciences, Chandrasekharpur, Bhubaneswar, India
| | - Sandip K. Mishra
- Cancer Biology Lab, Department of Gene Function and Regulation, Institute of Life Sciences, Chandrasekharpur, Bhubaneswar, India
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Tagami T, Usui T, Shimatsu A, Beniko M, Yamamoto H, Moriyama K, Naruse M. Aberrant expression of thyroid hormone receptor beta isoform may cause inappropriate secretion of TSH in a TSH-secreting pituitary adenoma. J Clin Endocrinol Metab 2011; 96:E948-52. [PMID: 21430027 DOI: 10.1210/jc.2010-2496] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Patients with TSH-secreting pituitary adenomas (TSHoma) show inappropriate secretion of TSH; serum TSH levels are not suppressed despite high serum free thyroid hormone levels. The mechanism of a defect in negative regulation of TSH in a TSHoma is still unclear. OBJECTIVE Recently, we cloned a novel thyroid hormone receptor β isoform (TRβ4) from a human pituitary library. To elucidate the clinical significance of TRβ4, we investigated the expression of this isoform in TSHoma. METHODS RT-PCR was performed to detect TRβ isoforms such as TRβ1, TRβ2, and TRβ4 using RNA obtained from surgically resected TSHoma. The effects of TRβ4 on the TSH gene expression were examined in the transient gene expression experiments. RESULTS Quantitative analysis using a real-time PCR revealed that relative expression of TRβ4 to TRβ1+2 was higher in three TSHoma than in a prolactinoma or a nonfunctioning pituitary adenoma. TRβ4 construct did not mediate T(3)-dependent gene regulation but inhibited the negative regulation of TSHα mediated by TRβ1 or TRβ2. CONCLUSIONS Aberrant expression of TRβ4 may partly contribute to the inappropriate secretion of TSH in a TSHoma.
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Affiliation(s)
- Tetsuya Tagami
- Division of Endocrinology and Metabolism, Clinical Research Institute, National Hospital Organization Kyoto Medical Center, Mukaihata-cho 1-1, Fukakusa, Fushimi-ku, Kyoto 612-8555, Japan.
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Tagami T, Yamamoto H, Moriyama K, Sawai K, Usui T, Shimatsu A, Naruse M. Identification of a novel human thyroid hormone receptor β isoform as a transcriptional modulator. Biochem Biophys Res Commun 2010; 396:983-8. [DOI: 10.1016/j.bbrc.2010.05.038] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 05/07/2010] [Indexed: 10/19/2022]
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Thyroid hormone receptor beta mutation causes severe impairment of cerebellar development. Mol Cell Neurosci 2010; 44:68-77. [PMID: 20193766 DOI: 10.1016/j.mcn.2010.02.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 12/28/2009] [Accepted: 02/19/2010] [Indexed: 11/21/2022] Open
Abstract
Cerebellar development on the postnatal period is mainly characterized by cellular proliferation in the external granular layer (EGL) followed by migration of granular cells in the molecular layer through the Bergmann glia (BG) fibers in order to form the granular layer in the adult. All these events are drastically affected by thyroid hormones (TH), which actions are mainly mediated by alpha (TRalpha) and beta (TRbeta) nuclear receptor isoforms. Here, we analyzed the effects of a natural human mutation (337T) in the TRbeta locus, which impairs T3 binding to its receptor, on the mouse cerebellum ontogenesis. We report that target inactivation of TRbeta-TH binding leads to a smaller cerebellum area characterized by impaired lamination and foliation. Further, TRbeta mutant mice presented severe deficits in proliferation of granular precursors, arborization of Purkinje cells and organization of BG fibers. Together, our data suggest that the action of TH via TRbeta regulates important events of cerebellar ontogenesis contributing to a better understanding of some neuroendocrine disorders. Further, our data correlate TRbeta with cerebellar foliation, and provide, for the first time, evidence of a receptor-mediated mechanism underlying TH actions on this event.
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Ferreira Azevedo M, Barra GB, Medeiros LDD, Simeoni LA, Naves LA, Neves FDAR. A novel mutation of thyroid hormone receptor beta (I431V) impairs corepressor release, and induces thyroid hormone resistance syndrome. ACTA ACUST UNITED AC 2009; 52:1304-12. [PMID: 19169485 DOI: 10.1590/s0004-27302008000800016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Accepted: 10/14/2008] [Indexed: 11/22/2022]
Abstract
Resistance to thyroid hormone (RTH) is a rare disorder characterized by variable tissue hyporesponsiveness to thyroid hormone, usually caused by mutations in the thyroid hormone receptor beta (TRbeta). We describe a large Brazilian family harboring a novel mutation affecting TRbeta gene and inducing RTH. A 14-year-old girl was found to have elevated free T4 and free T3 plasma concentrations in coexistence with unsuppressed TSH and a questionable goiter. The diagnosis of RTH was verified by identification of a novel mutation (I431V) in the TRbeta gene. Sixteen asymptomatic relatives of the proposita are also affected by the mutation. Functional studies showed that I431V mutation exerts dominant-negative effect on wild type TRbeta, mainly by impairment of ligand-dependent release of corepressor SMRT. The presence of this mutation reduces potency, but does not affect efficacy of thyroid hormone action, in accordance with the clinical picture of eumetabolism of the affected individuals.
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Alonso M, Goodwin C, Liao X, Ortiga-Carvalho T, Machado DS, Wondisford FE, Refetoff S, Weiss RE. In vivo interaction of steroid receptor coactivator (SRC)-1 and the activation function-2 domain of the thyroid hormone receptor (TR) beta in TRbeta E457A knock-in and SRC-1 knockout mice. Endocrinology 2009; 150:3927-34. [PMID: 19406944 PMCID: PMC2717870 DOI: 10.1210/en.2009-0093] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The activation function-2 (AF-2) domain of the thyroid hormone (TH) receptor (TR)-beta is a TH-dependent binding site for nuclear coactivators (NCoA), which modulate TH-dependent gene transcription. In contrast, the putative AF-1 domain is a TH-independent region interacting with NCoA. We determined the specificity of the AF-2 domain and NCoA interaction by evaluating thyroid function in mice with combined disruption of the AF-2 domain in TRbeta, due to a point mutation (E457A), and deletion of one of the NCoAs, steroid receptor coactivator (SRC)-1. The E457A mutation was chosen because it abolishes NCoA recruitment in vitro while preserving normal TH binding and corepressor interactions resulting in resistance to TH. At baseline, disruption of SRC-1 in the homozygous knock-in (TRbeta(E457A/E457A)) mice worsened the degree of resistance to TH, resulting in increased serum T(4) and TSH. During TH deprivation, disruption of AF-2 and SRC-1 resulted in a TSH rise 50% of what was seen when AF-2 alone was removed, suggesting that SRC-1 was interacting outside of the AF-2 domain. Therefore, 1) during TH deprivation, SRC-1 is necessary for activating the hypothalamic-pituitary-thyroid axis; 2) ligand-dependent repression of TSH requires an intact AF-2; and 3) SRC-1 may interact with the another region of the TRbeta or the TRalpha to regulate TH action in the pituitary. This report demonstrates the dual interaction of NCoA in vivo: the TH-independent up-regulation possibly through another domain and TH-dependent down-regulation through the AF-2 domain.
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Affiliation(s)
- Manuela Alonso
- Department of Medicine, Committees on Genetics, The University of Chicago, Chicago, Illinois 60637, USA
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Tagami T, Yamamoto H, Moriyama K, Sawai K, Usui T, Shimatsu A, Naruse M. A selective peroxisome proliferator-activated receptor-gamma modulator, telmisartan, binds to the receptor in a different fashion from thiazolidinediones. Endocrinology 2009; 150:862-70. [PMID: 19147680 DOI: 10.1210/en.2008-0502] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Angiotensin type 1 receptor blockers are widely used for the treatment of hypertension, and one angiotensin type 1 receptor blocker, telmisartan, specifically activates the peroxisome proliferator-activated receptor (PPAR)-gamma. We studied the impact of PPARgamma mutants on transcriptional control and interaction with cofactors to elucidate differences in the molecular mechanism between telmisartan and other PPARgamma agonists, thiazolidinediones (TZDs). We created several amino acid substitutions in the ligand binding domain of PPARgamma that, based on molecular modeling, may affect the binding of these agents. In transient expression experiments, wild-type PPARgamma-mediated transcription stimulated by telmisartan was more than one third of that stimulated by TZDs. The activation stimulated by TZDs was impaired, whereas activation stimulated by telmisartan was retained, in the H323Y, S342A, and H449A mutants. In the Y473A mutant, the TZD-induced activation was further impaired and lower than that of telmisartan-induced activation. Coexpression of coactivators enhanced the activation by both telmisartan and TZDs, but activation by telmisartan always exceeded that of TZDs in the Y473A mutant. Based on a mammalian two-hybrid assay, the interaction with corepressors was retained in Y473A. Telmisartan and TZDs, but not 9cis retinoic acid, dissociated corepressors from the wild-type PPARgamma. Telmisartan most effectively dissociated corepressors from Y473A. The interaction with coactivators was enhanced by TZD activation of wild-type PPARgamma and both telmisartan and TZD activation of Y473A. Thus, the Y473A mutant is selectively stimulated by telmisartan but not TZDs, suggesting that telmisartan and TZDs have differential effects on the transcriptional control. In conclusion, these PPARgamma mutants could be powerful tools for developing novel therapeutic agents that retain the metabolic efficacy of PPARgamma activation with fewer adverse effects, such as the increase in body weight associated with TZDs.
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Affiliation(s)
- Tetsuya Tagami
- Clinical Research Institute, Kyoto Medical Center, National Hospital Organization, Fukakusa, Kyoto, Japan.
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Liu MH, Li J, Shen P, Husna B, Tai ES, Yong EL. A natural polymorphism in peroxisome proliferator-activated receptor-alpha hinge region attenuates transcription due to defective release of nuclear receptor corepressor from chromatin. Mol Endocrinol 2008; 22:1078-92. [PMID: 18292238 DOI: 10.1210/me.2007-0547] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a central regulator of lipid metabolism. Fibrate drugs act on PPARalpha to modulate dyslipidemias. A natural variant (V227A) affecting the PPARalpha hinge region was associated with perturbations in blood lipid levels in Asian populations. In this study, we investigated the functional significance of the V227A substitution. The variant significantly attenuated PPARalpha-mediated transactivation of the cytochrome P450 4A6 and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) genes in the presence of fibrate ligands. Screening of a panel of PPARalpha coregulators revealed that V227A enhanced recruitment of the nuclear corepressor NCoR. Transactivation activity of V227A could be restored by silencing NCoR or by inhibition of its histone deacetylase activity. Deletion studies indicated that PPARalpha interacted with NCoR receptor-interacting domain 1 (ID1) but not ID2 or ID3. These interactions were dependent on the intact consensus nonapeptide nuclear receptor interaction motif in NCoR ID1 and were enhanced by the adjacent 24 N-terminal residues. Novel corepressor interaction determinants involving PPARalpha helices 1 and 2 were identified. In hepatic cells, the V227A substitution stabilized PPARalpha/NCoR interactions and caused defective release of NCoR in the presence of agonists on the HMGCS2 promoter. These results provide the first indication that defective function of a natural PPARalpha variant was due, at least partially, to increased corepressor binding. Our data suggest that the PPARalpha/NCoR interaction is physiologically relevant and can produce a discernable phenotype when the magnitude of the interaction is altered by a naturally occurring variation.
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Affiliation(s)
- Mei Hui Liu
- Department of Obstetrics and Gynecology, National University Hospital, Yong Loo Lin School of Medicine, Republic of Singapore
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17
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Moriyama K, Tagami T, Usui T, Naruse M, Nambu T, Hataya Y, Kanamoto N, Li YS, Yasoda A, Arai H, Nakao K. Antithyroid drugs inhibit thyroid hormone receptor-mediated transcription. J Clin Endocrinol Metab 2007; 92:1066-72. [PMID: 17192293 DOI: 10.1210/jc.2006-1621] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
CONTEXT Methimazole (MMI) and propylthiouracil (PTU) are widely used as antithyroid drugs (ATDs) for the treatment of Graves' disease. Both MMI and PTU reduce thyroid hormone levels by several mechanisms, including inhibition of thyroid hormone synthesis and secretion. In addition, PTU decreases 5'-deiodination of T(4) in peripheral tissues. ATDs may also interfere with T(3) binding to nuclear thyroid hormone receptors (TRs). However, the effect of ATDs on the transcriptional activities of T(3) mediated by TRs has not been studied. OBJECTIVE The present study was undertaken to determine whether ATDs have an effect on the gene transcription regulated by T(3) and TRs in vitro. METHODS Transient gene expression experiments and GH secretion assays were performed. To elucidate possible mechanisms of the antagonistic action of ATDs, the interaction between TR and nuclear cofactors was examined. RESULTS In the transient gene expression experiments, both MMI and PTU significantly suppressed transcriptional activities mediated by the TR and T(3) in a dose-dependent manner. In mammalian two-hybrid assays, both drugs recruited one of the nuclear corepressors, nuclear receptor corepressor, to the TR in the absence of T(3). In addition, PTU dissociated nuclear coactivators, such as steroid receptor coactivator-1 and glucocorticoid receptor interacting protein-1, from the TR in the presence of T(3). Finally, MMI decreased the GH release that was stimulated by T(3). CONCLUSIONS ATDs inhibit T(3) action by recruitment of transcriptional corepressors and/or dissociation of coactivators. This is the first report to show that ATDs can modulate T(3) action at the transcriptional level.
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Affiliation(s)
- Kenji Moriyama
- Division of Endocrinology and Metabolism, Clinical Research Institute, Kyoto Medical Center, National Hospital Organization, Kyoto 612-8555, Japan
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18
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Wu SY, Cohen RN, Simsek E, Senses DA, Yar NE, Grasberger H, Noel J, Refetoff S, Weiss RE. A novel thyroid hormone receptor-beta mutation that fails to bind nuclear receptor corepressor in a patient as an apparent cause of severe, predominantly pituitary resistance to thyroid hormone. J Clin Endocrinol Metab 2006; 91:1887-95. [PMID: 16464943 DOI: 10.1210/jc.2005-2428] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Resistance to thyroid hormone (RTH) is a dominantly inherited syndrome of variable tissue hyporesponsiveness to thyroid hormone (TH). OBJECTIVE We report a newborn who presented with severe RTH (Mkar) with serum TSH 1500 mU/liter and free T(3) greater than 50 pm (normal 3.1-9.4) and free T(4) 25.3 pm (normal 12-22). We hypothesized that the RTH was due to reduced ligand binding and/or abnormal interaction with nuclear cofactors. DESIGN These were prospective in vivo and in vitro studies. SETTING The study was conducted at a tertiary care university hospital. PATIENTS Patients included a newborn child and two other subjects with RTH. INTERVENTION The effect of various TH-lowering agents in the subject with RTH was studied. In vitro studies including EMSA and mammalian two-hybrid assay as well as in vitro transfection studies were conducted. MAIN OUTCOME MEASURES Sequencing of the TH receptor (TR)beta and in vitro measurements of receptor-cofactor interaction were measured. RESULTS Sequencing of the TRbeta demonstrated a de novo heterozygous mutation, 1590_1591insT, resulting in a frameshift producing a mutant TRbeta (mutTR)-beta with a 28-amino acid (aa) nonsense sequence and 2-amino acid carboxyl-terminal extension. The Mkar mutation was evaluated in comparison to three other TRbeta frameshift mutations in the carboxyl terminus. EMSA demonstrated that the Mkar mutTRbeta1 had impaired ability to recruit nuclear receptor corepressor but intact association with silencing mediator of retinoid and thyroid receptor (SMRT). CONCLUSION Our data suggest that alterations in codons 436-453 in helix 11 result in significantly diminished association with nuclear receptor corepressor but not SMRT. This novel mutTRbeta demonstrates nuclear corepressor specificity that results in severe predominantly pituitary RTH due to impaired release of SMRT.
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Affiliation(s)
- Sharon Y Wu
- Department of Medicine, University of Chicago, 5841 South Maryland Avenue, Mail Code 3090, Chicago, Illinois 60645, USA
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19
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Ortiga-Carvalho TM, Shibusawa N, Nikrodhanond A, Oliveira KJ, Machado DS, Liao XH, Cohen RN, Refetoff S, Wondisford FE. Negative regulation by thyroid hormone receptor requires an intact coactivator-binding surface. J Clin Invest 2005; 115:2517-23. [PMID: 16100573 PMCID: PMC1184039 DOI: 10.1172/jci24109] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Accepted: 05/31/2005] [Indexed: 11/17/2022] Open
Abstract
Thyroid hormone (TH) action is mediated by TH receptors (TRs), which are members of the nuclear hormone receptor superfamily. In vitro studies have demonstrated that TR activity is regulated by interactions with corepressor and coactivator proteins (CoRs and CoAs, respectively). TH stimulation is thought to involve dissociation of CoRs and recruitment of CoAs to the liganded TR. In contrast, negative regulation by TH is thought to occur via recruitment of CoRs to the liganded TR. The physiological role of CoAs bound to TRs, however, has yet to be defined. In this study, we used gene-targeting techniques to mutate the TR-beta locus within its activation function-2 (AF-2) domain (E457A). This mutation was chosen because it completely abolished CoA recruitment in vitro, while preserving normal triiodothyronine (T3) binding and CoR interactions. As expected, TH-stimulated gene expression was reduced in homozygous E457A mice. However, these animals also displayed abnormal regulation of the hypothalamic-pituitary-thyroid axis. Serum thyroxine, T3, and thyroid-stimulating hormone (TSH) levels and pituitary Tshb mRNA levels were inappropriately elevated compared with those of WT animals, and L-T3 treatment failed to suppress serum TSH and pituitary Tshb mRNA levels. Therefore, the AF-2 domain of TR-beta is required for positive and, paradoxically, for negative regulation by TH in vivo.
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Affiliation(s)
- Tania M Ortiga-Carvalho
- Department of Medicine and Committee on Molecular Metabolism and Nutrition, Pritzker School of Medicine, The University of Chicago, Chicago, Illinois, USA
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20
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Torre P, Bertoli M, Di Giovanni S, Scommegna S, Conte C, Novelli G, Cianfarani S. Endocrine and neuropsychological assessment in a child with a novel mutation of thyroid hormone receptor: response to 12-month triiodothyroacetic acid (TRIAC) therapy. J Endocrinol Invest 2005; 28:657-62. [PMID: 16218051 DOI: 10.1007/bf03347267] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
OBJECTIVE To determine the endocrine, neuropsychological and genetic features of a child with resistance to thyroid hormone (RTH), and his response to long-term triiodothyroacetic acid (TRIAC) therapy. METHODS Growth, thyroid function, and neuropsychology were assessed at baseline and during 12-month TRIAC therapy. Genetic analysis was performed by PCR and denaturing high performance liquid chromatography. RESULTS The main clinical finding was the attention deficit-hyperactivity disorder (ADHD). A novel mutation in exon 10 (phenylalanine to isoleucine in codon 455) was found. Long-term TRIAC therapy was effective in the management of the endocrine and neuropsychological manifestations of the syndrome. CONCLUSIONS ADHD was the only phenotypic manifestation of this novel mutation of thyroid hormone (TH) receptor. TRIAC is an effective and safe drug in the long-term treatment of children with RTH.
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Affiliation(s)
- P Torre
- Rina Balducci Center of Pediatric Endocrinology, Department of Public Health and Cell Biology; Tor Vergata University, Rome, Italy
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21
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Michalik L, Feige JN, Gelman L, Pedrazzini T, Keller H, Desvergne B, Wahli W. Selective expression of a dominant-negative form of peroxisome proliferator-activated receptor in keratinocytes leads to impaired epidermal healing. Mol Endocrinol 2005; 19:2335-48. [PMID: 15890673 DOI: 10.1210/me.2005-0068] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Many nuclear hormone receptors are involved in the regulation of skin homeostasis. However, their role in the epithelial compartment of the skin in stress situations, such as skin healing, has not been addressed yet. The healing of a skin wound after an injury involves three major cell types: immune cells, which are recruited to the wound bed; dermal fibroblasts; and epidermal and hair follicle keratinocytes. Our previous studies have revealed important but nonredundant roles of PPARalpha and beta/delta in the reparation of the skin after a mechanical injury in the adult mouse. However, the mesenchymal or epithelial cellular compartment in which PPARalpha and beta/delta play a role could not be determined in the null mice used, which have a germ line PPAR gene invalidation. In the present work, the role of PPARalpha was studied in keratinocytes, using transgenic mice that express a PPARalpha mutant with dominant-negative (dn) activity specifically in keratinocytes. This dn PPARalpha lacks the last 13 C terminus amino acids, binds to a PPARalpha agonist, but is unable to release the nuclear receptor corepressor and to recruit the coactivator p300. When selectively expressed in keratinocytes of transgenic mice, dn PPARalphaDelta13 causes a delay in the healing of skin wounds, accompanied by an exacerbated inflammation. This phenotype, which is similar to that observed in PPARalpha null mice, strongly suggests that during skin healing, PPARalpha is required in keratinocytes rather than in other cell types.
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Affiliation(s)
- L Michalik
- Center for Integrative Genomics, National Center of Competence in Research Frontiers in Genetics, University of Lausanne, Lausanne, Switzerland.
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22
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Danzi S, Klein I. Posttranscriptional regulation of myosin heavy chain expression in the heart by triiodothyronine. Am J Physiol Heart Circ Physiol 2005; 288:H455-60. [PMID: 15650152 DOI: 10.1152/ajpheart.00896.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Triiodothyronine (T3) regulates cardiac contractility in part by regulating the expression of several important cardiac myocyte genes. In the rat, the T3-mediated induction of alpha-myosin heavy chain (MHC) transcription in hypothyroid hearts is rapid, exhibiting zero-order kinetics, whereas the repression of beta-MHC in these same hearts is much slower. To elucidate the mechanism for T3 transcriptional as well as posttranscriptional regulation of both MHC gene isoforms, we used an RT-PCR-based transcription assay and the RNA polymerase II inhibitor actinomycin D in an in vivo model to simultaneously measure specific alpha- and beta-MHC heterogeneous nuclear RNA (hnRNA), mRNA kinetics, and MHC antisense RNA. In vivo actinomycin D treatment blocked alpha-MHC transcription in euthyroid rats by >80% at 2 h and suggested a half-life of alpha-MHC hnRNA of approximately 1 h, whereas actinomycin D inhibited beta-MHC transcription in hypothyroid rats by >75% at 6 h, suggesting a significantly longer hnRNA half-life of approximately 4 h. The effect of actinomycin D on beta-MHC transcription was independent of T3. T3 treatment in hypothyroid animals caused beta-MHC mRNA to decline more rapidly than beta-MHC hnRNA, demonstrating, for the first time, a posttranscriptional mechanism(s). The measured change in beta-MHC mRNA half-life indicates a T3-mediated destabilization of beta-MHC mRNA. To understand the mechanism by which T3 destabilizes beta-MHC mRNA, we measured beta-MHC antisense RNA. beta-MHC antisense RNA is present in euthyroid myocytes, but levels are not significant in hypothyroid myocytes. This differential expression may explain some of the effects of T3 on MHC posttranscriptional regulation.
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Affiliation(s)
- Sara Danzi
- Division of Endocrinology and Department of Medicine, North Shore University Hospital/New York University School of Medicine and North Shore-LIJ Research Institute, Manhasset, New York, USA
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23
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Nakano K, Matsushita A, Sasaki S, Misawa H, Nishiyama K, Kashiwabara Y, Nakamura H. Thyroid-hormone-dependent negative regulation of thyrotropin beta gene by thyroid hormone receptors: study with a new experimental system using CV1 cells. Biochem J 2004; 378:549-57. [PMID: 14611644 PMCID: PMC1223958 DOI: 10.1042/bj20031592] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2003] [Accepted: 11/12/2003] [Indexed: 11/17/2022]
Abstract
The molecular mechanism involved in the liganded thyroid hormone receptor suppression of the TSHbeta (thyroid-stimulating hormone beta, or thyrotropin beta) gene transcription is undetermined. One of the main reasons is the limitation of useful cell lines for the experiments. We have developed an assay system using non-pituitary CV1 cells and studied the negative regulation of the TSHbeta gene. In CV1 cells, the TSHbeta-CAT (chloramphenicol acetyltransferase) reporter was stimulated by Pit1 and GATA2 and suppressed by T3 (3,3',5-tri-iodothyronine)-bound thyroid hormone receptor. The suppression was dependent on the amounts of T3 and the receptor. Unliganded receptor did not stimulate TSHbeta activity, suggesting that the receptor itself is not an activator. Analyses using various receptor mutants revealed that the intact DNA-binding domain is crucial to the TSHbeta gene suppression. Co-activators and co-repressors are not necessarily essential, but are required for the full suppression of the TSHbeta gene. Among the three receptor isoforms, beta2 exhibited the strongest inhibition and its protein level was the most predominant in a thyrotroph cell line, TalphaT1, in Western blotting. The dominant-negative effects of various receptor mutants measured on the TSHbeta-CAT reporter were not simple mirror images of those in the positive regulation under physiological T3 concentration.
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Affiliation(s)
- Keiko Nakano
- Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan
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24
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Hu X, Cherbas L, Cherbas P. Transcription activation by the ecdysone receptor (EcR/USP): identification of activation functions. Mol Endocrinol 2003; 17:716-31. [PMID: 12554759 DOI: 10.1210/me.2002-0287] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The ecdysone receptor is a heterodimer of the two nuclear receptors EcR and ultraspiracle (USP). We have identified the regions of Drosophila EcR and USP responsible for transcriptional activation of a semisynthetic Eip71CD promoter in Kc cells. The isoform-specific A/B domains of EcR-B1 and B2, but not those of EcR-A or USP, exhibit strong activation activity [activation function 1 (AF1)], both in isolation and in the context of the intact receptor. AF1 activity in isoform B1 derives from dispersed elements; the B2-specific AF1 consists of a 17-residue amphipathic helix. AF2 function was studied using a two-hybrid assay in Kc cells, based on the observation that potent hormone-dependent activation by the EcR/USP ligand-binding domain heterodimer requires the participation of both partners. Mutagenesis reveals that AF2 function depends on EcR helix 12, but not on the cognate USP region. EcR helix 12 mutants (F645A and W650A) exhibit a dominant negative phenotype. Thus, in the setting tested, the ecdysone receptor can activate transcription using the AF1 regions of EcR-B1 or -B2 and the AF2 region of EcR. USP acts as an allosteric effector for EcR, but does not contribute any intrinsic function.
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Affiliation(s)
- Xiao Hu
- Department of Biology, Jordan Hall, 1001 East Third Street, Bloomington, Indiana 47405, USA
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25
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Park Y, Freedman BD, Lee EJ, Park S, Jameson JL. A dominant negative PPARgamma mutant shows altered cofactor recruitment and inhibits adipogenesis in 3T3-L1 cells. Diabetologia 2003; 46:365-77. [PMID: 12687335 DOI: 10.1007/s00125-003-1037-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2002] [Revised: 11/12/2002] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS PPARgamma, a member of the nuclear hormone receptor family of transcription factors, plays a key role in adipocyte differentiation and insulin sensitivity. The aim of this study was to identify a potential dominant negative murine PPARgamma mutant and to characterize the in vitro functional properties of this mutant. METHODS In vitro transient transfections and mammalian two-hybrid assays in TSA201 cells were used to characterize the transcriptional activity of the L466A mutant and to study the molecular interaction of transcriptional cofactors with the L466A mutant in an attempt to elucidate the mechanism of its dominant negative activity. Adenoviral constructs expressing PPARgamma wild-type (AdWT) or the L466A mutant (AdL466A) were infected into the murine 3T3-L1 cell line to study the mutant's effect on adipogenesis. RESULTS The L466A mutant alone is transcriptionally defective. However, it retains DNA binding and inhibits the ligand-dependent and -independent activity of the wild-type receptor, consistent with dominant negative properties. In mammalian two-hybrid studies, the L466A mutant does not bind nuclear receptor coactivators. However, it more avidly recruits corepressors due to enhanced binding to the corepressor ID1 domain, leading to pronounced transcriptional repression. The AdL466A mutant inhibits adipogenesis induced by either a differentiation cocktail or by thiazolidinedione ligand. AdL466A infection also blocked the upregulation of the adipocyte marker genes aP2 and adipsin. CONCLUSION We conclude that the L466A PPARgamma mutant possesses potent dominant negative activity based on preferential corepressor recruitment and it inhibits adipogenesis and the expression of adipocyte-specific genes.
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Affiliation(s)
- Y Park
- Division of Endocrinology, Metabolism and Molecular Medicine, Northwestern University Medical School, Chicago, USA
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26
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Cherbas L, Hu X, Zhimulev I, Belyaeva E, Cherbas P. EcR isoforms in Drosophila: testing tissue-specific requirements by targeted blockade and rescue. Development 2003; 130:271-84. [PMID: 12466195 DOI: 10.1242/dev.00205] [Citation(s) in RCA: 251] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The three Drosophila EcR isoforms differ only at their N termini; thus, they share the conserved ligand-binding domain transcriptional activation function (AF2) and only differ in the unconserved A/B region, which contains a second, isoform-specific, activation function (AF1). We have developed a dominant-negative mutant EcR (EcR-DN), expressed it in flies with the GAL4/UAS system, and used it to block ecdysone signaling in eight tissues or groups of tissues. Localized EcR-DN arrests ecdysone-dependent development in the target cells and often--because of a molting checkpoint--arrests development globally. Simultaneously expressing individual wild-type EcR isoforms in the same target tissues suppresses the EcR-DN phenotype and identifies the rescuing isoform as sufficient to support the development of the target. Every isoform, and even an N-terminal truncated EcR that lacks any AF1, supports development in the fat body, eye discs, salivary glands, EH-secreting neurosecretory cells and in the dpp expression domain, implying that AF1 is dispensable in these tissues. By contrast, only EcR-A is able to support development in the margins of the wing discs, and only EcR-B2 can do so in the larval epidermis and the border cells of the developing egg chamber. In light of our results, the simplest explanations for the widespread spatial and temporal variations in EcR isoform titers appear untenable.
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Affiliation(s)
- Lucy Cherbas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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27
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Moriyama K, Tagami T, Akamizu T, Usui T, Saijo M, Kanamoto N, Hataya Y, Shimatsu A, Kuzuya H, Nakao K. Thyroid hormone action is disrupted by bisphenol A as an antagonist. J Clin Endocrinol Metab 2002; 87:5185-90. [PMID: 12414890 DOI: 10.1210/jc.2002-020209] [Citation(s) in RCA: 546] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Bisphenol A (BPA), a monomer of polycarbonate plastics, has been shown to possess estrogenic properties and act as an agonist for the estrogen receptors. Although an epidemiologically based investigation has suggested that some chemicals could disrupt thyroid function in animals, the effects on thyroid hormone receptors (TRs) are unknown. We show here that BPA inhibits TR-mediated transcription by acting as an antagonist. In the transient gene expression experiments, BPA suppressed transcriptional activity that is stimulated by thyroid hormone (T(3)) in a dose-dependent manner. The inhibitory effects were observed in the presence of physiological concentrations of T(3). In contrast, in the case of negatively regulated TSHalpha promoter, BPA activated the gene transcription that is suppressed by T(3). To elucidate possible mechanisms of the antagonistic action of BPA, the effects on T(3) binding and cofactor interaction with TR were examined. The K(i) value for BPA was 200 micro M when assessed by inhibition of [(125)I]T(3) binding to rat hepatic nuclear TRs. In a mammalian two-hybrid assay, BPA recruited the nuclear corepressor to the TR. These results suggest that BPA could displace T(3) from the TR and recruit a transcriptional repressor, resulting in gene suppression. This is the first report that BPA can antagonize T(3) action at the transcriptional level. BPA may disrupt the function of various types of nuclear hormone receptors and their cofactors to disturb our internal hormonal environment.
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Affiliation(s)
- Kenji Moriyama
- Department of Medicine and Clinical Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
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Côté S, Rosenauer A, Bianchini A, Seiter K, Vandewiele J, Nervi C, Miller WH. Response to histone deacetylase inhibition of novel PML/RARalpha mutants detected in retinoic acid-resistant APL cells. Blood 2002; 100:2586-96. [PMID: 12239173 DOI: 10.1182/blood-2002-02-0614] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Resistance to all-trans retinoic acid (ATRA) remains a clinical problem in the treatment of acute promyelocytic leukemia (APL) and provides a model for the development of novel therapies. Molecular alterations in the ligand-binding domain (LBD) of the PML/RARalpha fusion gene that characterizes APL constitute one mechanism of acquired resistance to ATRA. We identified missense mutations in PML/RARalpha from an additional ATRA-resistant patient at relapse and in a novel ATRA-resistant cell line, NB4-MRA1. These cause altered binding to ligand and transcriptional coregulators, leading to a dominant-negative block of transcription. These mutations are in regions of the LBD that appear to be mutational hot spots occurring repeatedly in ATRA-resistant APL patient cells. We evaluated whether histone deacetylase (HDAC) inhibition could overcome the effects of these mutations on ATRA-induced gene expression. Cotreatment with ATRA and TSA restored RARbeta gene expression in NB4-MRA1 cells, whose PML/RARalpha mutation is in helix 12 of the LBD, but not in an APL cell line harboring the patient-derived PML/RARalpha mutation, which was between helix 5 and 6. Furthermore, ATRA combined with TSA increases histone 4 acetylation on the RARbeta promoter only in NB4-MRA1 cells. Consistent with these results, the combined treatment induces differentiation of NB4-MRA1 only. Thus, the ability of an HDAC inhibitor to restore ATRA sensitivity in resistant cells may depend on their specific molecular defects. The variety of PML/RARalpha mutations arising in ATRA-resistant patients begins to explain how APL patients in relapse may differ in response to transcription therapy with HDAC inhibitors.
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Affiliation(s)
- Sylvie Côté
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and McGill University Department of Oncology and Medicine, Montreal, Quebec, Canada
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Dussault I, Lin M, Hollister K, Fan M, Termini J, Sherman MA, Forman BM. A structural model of the constitutive androstane receptor defines novel interactions that mediate ligand-independent activity. Mol Cell Biol 2002; 22:5270-80. [PMID: 12101224 PMCID: PMC133936 DOI: 10.1128/mcb.22.15.5270-5280.2002] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2002] [Revised: 03/07/2002] [Accepted: 04/25/2002] [Indexed: 11/20/2022] Open
Abstract
Unlike classical nuclear receptors that require ligand for transcriptional activity, the constitutive androstane receptor (CAR) is active in the absence of ligand. To determine the molecular contacts that underlie this constitutive activity, we created a three-dimensional model of CAR and verified critical structural features by mutational analysis. We found that the same motifs that facilitate ligand-dependent activity in classical receptors also mediated constitutive activity in CAR. This raises a critical question: how are these motifs maintained in an active conformation in unliganded CAR? The model identified several novel interactions that account for this activity. First, CAR possesses a short loop between helix 11 and the transactivation domain (helix 12), as well as a short carboxy-terminal helix. Together, these features favor ligand-independent docking of the transactivation domain in a position that is characteristic of ligand-activated receptors. Second, this active conformation is further stabilized by a charge-charge interaction that anchors the carboxy-terminal activation domain to helix 4. Mutational analysis of these interactions provides direct experimental support for this model. We also show that ligand-mediated repression of constitutive activity reflects both a displacement of coactivator and a recruitment of corepressor. Our data demonstrate that CAR utilizes the same conserved structural motifs and coregulator proteins as originally defined for classical nuclear receptors. Despite these remarkable similarities, our model demonstrates how a few critical changes in CAR can dramatically reverse the transcriptional activity of this protein.
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Affiliation(s)
- Isabelle Dussault
- Division of Molecular Medicine, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA 91010, USA
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Jung DJ, Lee SK, Lee JW. Agonist-dependent repression mediated by mutant estrogen receptor alpha that lacks the activation function 2 core domain. J Biol Chem 2001; 276:37280-3. [PMID: 11487586 DOI: 10.1074/jbc.m106860200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Nuclear receptor corepressor (N-CoR) and silencing mediator of retinoid and thyroid hormone receptors (SMRT) form heterogeneous complexes with various histone deacetylases (HDACs). In this report, we found that ER alpha-Delta AF2, a mutant estrogen receptor alpha (ER alpha) deleted for the C-terminal activation function 2 (AF2) core domain, directs estradiol (E(2))-dependent repression and impairs E(2)-induced transactivation by wild type ER alpha. This repression required coexpressed BRG1 in SW-13 cells that lack BRG1, the ATPase constituent of the chromatin-remodeling SWI.SNF complex, and was abolished by HDAC inhibitor trichostatin A. We further demonstrated that ER alpha-Delta AF2 constitutively associates with SMRT but binds DNA in an E(2)-dependent manner in vivo. These results suggest that ER alpha-Delta AF2 and similar mutant receptors recently found associated with certain tumors may actively perturb the normal E(2) signaling via SWI/SNF, N-CoR/SMRT, and HDAC.
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Affiliation(s)
- D J Jung
- Center for Ligand and Transcription, Pohang University of Science and Technology, Pohang 790-784, Korea
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31
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Collingwood TN, Urnov FD, Chatterjee VK, Wolffe AP. Chromatin remodeling by the thyroid hormone receptor in regulation of the thyroid-stimulating hormone alpha-subunit promoter. J Biol Chem 2001; 276:34227-34. [PMID: 11454868 DOI: 10.1074/jbc.m105172200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The chromatin architecture of a promoter is an important determinant of its transcriptional response. For most target genes, the thyroid hormone receptor (TR) activates gene expression in response to thyroid hormone (T(3)). In contrast, the thyroid-stimulating hormone alpha-subunit (TSH alpha) gene promoter is down-regulated by TR in the presence of T(3). Here we utilize the capacity for the Xenopus oocyte to chromatinize exogenous nuclear- injected DNA to analyze the chromatin architecture of the TSH alpha promoter and how this changes upon TR-mediated regulation. Interestingly, in the oocyte, the TSH alpha promoter was positively regulated by T(3). In the inactive state, the promoter contained six loosely positioned nucleosomes. The addition of TR/retinoid X receptor together had no effect on the chromatin structure, but the inclusion of T(3) induced strong positioning of a dinucleosome in the TSH alpha proximal promoter that was bordered by regions that were hypersensitive to cleavage by methidiumpropyl EDTA. We identified a novel thyroid response element that coincided with the proximal hypersensitive region. Furthermore, we examined the consequences of mutations in TR that impaired coactivator recruitment. In a comparison with the Xenopus TR beta A promoter, we found that the effects of these mutations on transactivation and chromatin remodeling were significantly more severe on the TSH alpha promoter.
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Affiliation(s)
- T N Collingwood
- Laboratory of Molecular Embryology, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Abstract
Thyroid hormones (THs) play critical roles in the differentiation, growth, metabolism, and physiological function of virtually all tissues. TH binds to receptors that are ligand-regulatable transcription factors belonging to the nuclear hormone receptor superfamily. Tremendous progress has been made recently in our understanding of the molecular mechanisms that underlie TH action. In this review, we present the major advances in our knowledge of the molecular mechanisms of TH action and their implications for TH action in specific tissues, resistance to thyroid hormone syndrome, and genetically engineered mouse models.
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Affiliation(s)
- P M Yen
- Molecular Regulation and Neuroendocrinology Section, Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Affiliation(s)
- M L Privalsky
- Section of Microbiology, Division of Biological Sciences, One Shield Avenue, University of California at Davis, Davis, CA 95616, USA
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34
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Lin KH, Wu YH, Chen SL. Impaired interaction of mutant thyroid hormone receptors associated with human hepatocellular carcinoma with transcriptional coregulators. Endocrinology 2001; 142:653-62. [PMID: 11159836 DOI: 10.1210/endo.142.2.7927] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormone (T(3)) exerts its many biological activities through interaction with specific nuclear receptors (TRs) that function as ligand-dependent transcription factors at genes that contain a thyroid hormone response element (TRE). Mutant TRs have been detected in human hepatocellular carcinoma cell lines and tissue, but their contribution to carcinogenesis has remained unclear. The interaction of four such mutant TRs (J7-TRalpha1, J7-TRbeta1, H-TRalpha1, and L-TRalpha1) with transcriptional coregulators has now been investigated. With the exception of J7-TRalpha1, which in the absence of T(3) exhibited transcriptional silencing activity with a TRE-reporter gene construct in transfected cells, the mutant TRs had little effect (compared with that of wild-type receptors) on transcriptional activity of the reporter gene in the absence or presence of T(3), of the transcriptional corepressors SMRT, NCoR or of the transcriptional coactivator SRC. Electrophoretic mobility-shift assays revealed that, in the presence of T(3), the J7-TRss1 mutant did not interact with SRC, whereas J7-TRalpha1 and H-TRalpha1 exhibited reduced abilities to associate with this coactivator and L-TRalpha1 showed an ability to interact with SRC similar to that of wild-type TRalpha1. The dominant negative activity of the mutant TRs in transfected cells appeared inversely related to the ability of the receptors to interact with SRC. Whereas J7-TRss1, H-TRalpha1, and L-TRalpha1 did not interact with SMRT, and NCoR. J7-TRalpha1 bind to corepressors but failed to dissociate from them in the presence of T(3). These aberrant interactions between the mutant TRs and transcriptional coregulators may contribute to the highly variable clinical characteristics of human hepatocellular carcinoma.
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Affiliation(s)
- K H Lin
- Department of Biochemistry, Chang-Gung University, Taoyuan, Taiwan 333, Republic of China.
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35
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Taniyama M, Ishikawa N, Momotani N, Ito K, Ban Y. Toxic multinodular goitre in a patient with generalized resistance to thyroid hormone who harbours the R429Q mutation in the thyroid hormone receptor beta gene. Clin Endocrinol (Oxf) 2001; 54:121-4. [PMID: 11167935 DOI: 10.1046/j.1365-2265.2001.01033.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The association of resistance to thyroid hormone (RTH) due to a receptor defect with toxic multinodular goitre or with carcinoma of the thyroid has not been previously reported. Previous histopathological studies of the thyroid gland in patients with RTH have revealed changes similar to multinodular goitre, probably due to continuous stimulation by TSH. We report here a case of generalized resistance to thyroid hormone associated with a multinodular goitre, which became toxic. The patient was a 46-year-old Japanese woman who noticed a goitre although she had no symptoms of thyrotoxicosis. Initial examination revealed elevated serum thyroid hormone levels and a normal TSH level. Ultrasonography disclosed a multinodular goitre with cystic lesions. Three years later, the patient complained that the goitre had become larger and that she had developed symptoms of thyrotoxicosis such as palpitation and hyperhydrosis. Progressive hyperthyroxinaemia with relatively suppressed TSH, increased radioiodine uptake and negative anti-TSH receptor antibodies led to the diagnosis of toxic multinodular goitre. Subtotal thyroidectomy was performed, and pathological examination revealed a micropapillary carcinoma within the multinodular goitre. Occurrence of thyroid carcinoma should be considered in RTH because its incidence is high in multinodular goitre. Molecular examination revealed the R429Q mutation in the thyroid hormone receptor beta gene, which is one of the mutations usually manifesting as the pituitary resistance phenotype. That thyrotoxic manifestations appeared only during toxic stage of multinodular goitre in this case suggests that the phenotype of this type of mutation can be dependent on the amount of thyroid hormone.
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MESH Headings
- Amino Acids/urine
- Biomarkers/blood
- Biomarkers/urine
- Carcinoma, Papillary, Follicular/complications
- Carcinoma, Papillary, Follicular/genetics
- Carcinoma, Papillary, Follicular/metabolism
- Female
- Goiter, Nodular/complications
- Goiter, Nodular/genetics
- Goiter, Nodular/metabolism
- Humans
- Middle Aged
- Mutation
- Receptors, Thyroid Hormone/genetics
- Sex Hormone-Binding Globulin/analysis
- Tetrahydrocortisol/urine
- Tetrahydrocortisone/urine
- Thyroid Neoplasms/complications
- Thyroid Neoplasms/genetics
- Thyroid Neoplasms/metabolism
- Thyroidectomy
- Thyroxine/metabolism
- Triiodothyronine
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Affiliation(s)
- M Taniyama
- Division of Endocrinology and Metabolism, Showa University Hospital and Third Department of Internal Medicine, Showa University, School of Medicine, 1-5-8, Hatanodai, Shinagawa, Tokyo, Japan
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36
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Abstract
The prohormone convertases (PCs) PC1 and PC2 are key enzymes capable of processing a variety of prohormones to their bioactive forms. In this study, we demonstrated that 6-n-propyl-2-thiouracil (PTU)-induced hypothyroidism stimulated, whereas triido-L-thyronine (T(3))-induced hyperthyroidism suppressed, PC1 mRNA levels in the rat anterior pituitary. Using 5' deletions of the human PC1 (hPC1) promoter transiently transfected into GH3 (a somatotroph cell line) cells, we found that T(3) negatively regulated hPC1 promoter activity and that this regulation required the region from -82 to +19 bp relative to the transcription start site. Electrophoretic mobility shift assays (EMSAs) using purified thyroid hormone receptor-alpha1 (TR alpha 1) and retinoid X receptor-beta (RXRbeta) proteins and GH3 nuclear extracts demonstrated that the region from -10 to +19 bp of the hPC1 promoter bound TR alpha 1 as both a monomer and a homodimer and bound TR alpha 1/RXR beta as a heterodimer and multimer. EMSAs with oligonucleotides containing point mutations of the putative negative thyroid response elements (TREs) exhibited diminished homodimer and loss of multimer binding. We conclude that there are multiple novel TRE-like sequences in the hPC1 promoter located from -10 to +19 bp.
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MESH Headings
- Alitretinoin
- Animals
- Antineoplastic Agents/pharmacology
- Aspartic Acid Endopeptidases/genetics
- Aspartic Acid Endopeptidases/metabolism
- Cells, Cultured
- Gene Deletion
- Gene Expression Regulation, Enzymologic/drug effects
- Gene Expression Regulation, Enzymologic/physiology
- Genes, Reporter
- Hypothyroidism/chemically induced
- Hypothyroidism/metabolism
- Luciferases/genetics
- Male
- Mutagenesis, Insertional/physiology
- Oligonucleotides/genetics
- Oligonucleotides/metabolism
- Peptide Fragments/metabolism
- Pituitary Gland, Anterior/metabolism
- Promoter Regions, Genetic/physiology
- Proprotein Convertases
- Protein Processing, Post-Translational/drug effects
- Protein Processing, Post-Translational/physiology
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Retinoic Acid/metabolism
- Retinoid X Receptors
- Transcription Factors/metabolism
- Tretinoin/pharmacology
- Triiodothyronine/metabolism
- Uracil/analogs & derivatives
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Affiliation(s)
- Q L Li
- Division of Endocrinology, Department of Medicine, Cedars-Sinai Research Institute--University of California at Los Angeles School of Medicine, Los Angeles, 90048, USA
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37
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Davis PJ, Shih A, Lin HY, Martino LJ, Davis FB. Thyroxine promotes association of mitogen-activated protein kinase and nuclear thyroid hormone receptor (TR) and causes serine phosphorylation of TR. J Biol Chem 2000; 275:38032-9. [PMID: 10982791 DOI: 10.1074/jbc.m002560200] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activated nongenomically by l-thyroxine (T(4)), mitogen-activated protein kinase (MAPK) complexed in 10-20 min with endogenous nuclear thyroid hormone receptor (TRbeta1 or TR) in nuclear fractions of 293T cells, resulting in serine phosphorylation of TR. Treatment of cells with the MAPK kinase inhibitor, PD 98059, prevented both T(4)-induced nuclear MAPK-TR co-immunoprecipitation and serine phosphorylation of TR. T(4) treatment caused dissociation of TR and SMRT (silencing mediator of retinoid and thyroid hormone receptor), an effect also inhibited by PD 98059 and presumptively a result of association of nuclear MAPK with TR. Transfection into CV-1 cells of TR gene constructs in which one or both zinc fingers in the TR DNA-binding domain were replaced with those from the glucocorticoid receptor localized the site of TR phosphorylation by T(4)-activated MAPK to a serine in the second zinc finger of the TR DNA-binding domain. In an in vitro cell- and hormone-free system, purified activated MAPK phosphorylated recombinant human TRbeta1 (). Thus, T(4) activates MAPK and causes MAPK-mediated serine phosphorylation of TRbeta1 and dissociation of TR and the co-repressor SMRT.
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Affiliation(s)
- P J Davis
- Samuel S. Stratton Veterans Affairs Medical Center and the Molecular and Cellular Medicine Program, Department of Medicine and the Center for Cell Biology and Cancer Research, Albany Medical College, Albany, New York 12208, USA.
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38
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Kaneshige M, Kaneshige K, Zhu X, Dace A, Garrett L, Carter TA, Kazlauskaite R, Pankratz DG, Wynshaw-Boris A, Refetoff S, Weintraub B, Willingham MC, Barlow C, Cheng S. Mice with a targeted mutation in the thyroid hormone beta receptor gene exhibit impaired growth and resistance to thyroid hormone. Proc Natl Acad Sci U S A 2000; 97:13209-14. [PMID: 11069286 PMCID: PMC27204 DOI: 10.1073/pnas.230285997] [Citation(s) in RCA: 198] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Patients with mutations in the thyroid hormone receptor beta (TRbeta) gene manifest resistance to thyroid hormone (RTH), resulting in a constellation of variable phenotypic abnormalities. To understand the molecular basis underlying the action of mutant TRbeta in vivo, we generated mice with a targeted mutation in the TRbeta gene (TRbetaPV; PV, mutant thyroid hormone receptor kindred PV) by using homologous recombination and the Cre/loxP system. Mice expressing a single PV allele showed the typical abnormalities of thyroid function found in heterozygous humans with RTH. Homozygous PV mice exhibit severe dysfunction of the pituitary-thyroid axis, impaired weight gains, and abnormal bone development. This phenotype is distinct from that seen in mice with a null mutation in the TRbeta gene. Importantly, we identified abnormal expression patterns of several genes in tissues of TRbetaPV mice, demonstrating the interference of the mutant TR with the gene regulatory functions of the wild-type TR in vivo. These results show that the actions of mutant and wild-type TRbeta in vivo are distinct. This model allows further study of the molecular action of mutant TR in vivo, which could lead to better treatment for RTH patients.
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Affiliation(s)
- M Kaneshige
- Laboratory of Molecular Biology, National Cancer Institute, and Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
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39
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Furlanetto TW, Kopp P, Peccin S, Gu WX, Jameson JL. A novel mutation (M310L) in the thyroid hormone receptor beta causing resistance to thyroid hormone in a Brazilian kindred and a neonate. Mol Genet Metab 2000; 71:520-6. [PMID: 11073720 DOI: 10.1006/mgme.2000.3088] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Resistance to thyroid hormone (RTH) is an inherited syndrome of reduced tissue responsiveness to thyroid hormone (T3) caused by mutations in the thyroid hormone receptor beta (TRbeta). The index patient of the family reported here, a 17-year-old woman, came to medical attention because of a diffuse goiter, short stature, and learning disabilities. Biochemical tests revealed an elevated free T4 of 5.2 ng/dl (0.8-2.1), a T3 of 270 ng/dl (80-220), and a nonsuppressed TSH of 1.79 mU/l (0.4-4). Administration of exogenous T4 or T3 did not result in the usual TSH suppression, prompting the clinical diagnosis of RTH. Her father and one of her brothers also had clinical and biochemical findings consistent with RTH. Direct sequence analysis of the TRbeta gene revealed a heterozygous transition 928A>G in exon 9 resulting in substitution of methionine 310 by leucine (M310L). This novel receptor mutant has a reduced affinity for T3 ( approximately 10% of normal) and dominant negative properties that are similar in comparison to other RTH mutations. The index patient had a normal pregnancy and delivery. At birth, the female neonate had no goiter, a significantly elevated T4, and increased TSH. The diagnosis of RTH was confirmed by sequencing the TRbeta gene. She was underweight at birth and her length was between the 5th and 10th percentile. At 26 months, her height remained at the 10th percentile but her bone age was 18 months, suggesting mild hypothyroidism at the level of the bone. In contrast, increased heart rate and restlessness are consistent with hyperthyroidism in other tissues, such as the heart and possibly the brain.
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Affiliation(s)
- T W Furlanetto
- Division of Endocrinology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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40
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van Beeren HC, Bakker O, Wiersinga WM. Desethylamiodarone interferes with the binding of co-activator GRIP-1 to the beta 1-thyroid hormone receptor. FEBS Lett 2000; 481:213-6. [PMID: 11007966 DOI: 10.1016/s0014-5793(00)01970-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Ligand binding to the thyroid hormone nuclear receptor beta1 (TRbeta(1)) is inhibited by desethylamiodarone (DEA), the major metabolite of the widely used anti-arrhythmic drug amiodarone. Gene expression of thyroid hormone (triiodothyronine, T(3))-regulated genes can therefore be affected by amiodarone due to less ligand binding to the receptor. Previous studies have indicated the possibility of still other explanations for the inhibitory effects of amiodarone on T(3)-dependent gene expression, probably via interference with receptor/co-activator and co-repressor complex. The binding site of DEA is postulated to be on the outside surface of the receptor protein overlapping the regions where co-activator and co-repressor bind. Here we show the effect of a drug metabolite on the interaction of TRbeta(1) with the co-activator GRIP-1 (glucocorticoid receptor interacting protein-1). The T(3)-dependent binding of GRIP-1 to the TRbeta(1) is disrupted by DEA. A DEA dose experiment showed that the drug metabolite acts like an antagonist under 'normal' conditions (at 10(-7) M T(3) and 5x10(-6)-->10(-3) M DEA), but as an agonist under extreme conditions (at 0 and 10(-9) M T(3) and >10(-4) M DEA). To our knowledge, these results show for the first time that a metabolite of a drug which was not devised for this purpose can interfere with nuclear receptor/co-activator interaction.
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Affiliation(s)
- H C van Beeren
- Department of Endocrinology, Academic Medical Centre F5-171, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
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41
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Li QL, Jansen E, Brent GA, Naqvi S, Wilber JF, Friedman TC. Interactions between the prohormone convertase 2 promoter and the thyroid hormone receptor. Endocrinology 2000; 141:3256-66. [PMID: 10965896 DOI: 10.1210/endo.141.9.7674] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The majority of prohormones are cleaved at paired basic residues to generate bioactive hormones by prohormone convertases (PCs). As PC1 and PC2, two neuroendocrine-specific PCs, appear to be the key enzymes capable of processing a variety of prohormones, alterations of PC2 and/or PC1 levels will probably have a profound effect on hormonal homeostasis. We investigated the regulation of PC2 messenger RNA (mRNA) by thyroid hormone using GH3 cells to demonstrate that T3 negatively regulated PC2 mRNA levels in a dose- and time-dependent fashion. Functional analysis of progressive 5'-deletions of the human (h) PC2 promoter luciferase constructs in GH3 cells demonstrated that the regulation probably occurs at the transcriptional level, and that putative negative thyroid hormone response elements were located within the region from -44 to + 137 bp relative to the transcriptional start site. Transient transfections in JEG-3 cells and COS-1 cells showed that the suppressive effect of T3 was equally mediated by the thyroid hormone receptor (TR) isoforms TRalpha1 and TRbeta1. Electrophoretic mobility shift assays using purified TRal and retinoid X receptor-beta protein as well as GH3 nuclear extracts showed that regions from +51 to +71 bp and from +118 to +137 bp of the hPC2 promoter bind to TRalpha1 as both a monomer and a homodimer and with TRalpha1/retinoid X receptor-beta as a heterodimer. Finally, the in vivo regulation of pituitary PC2 mRNA by thyroid status was demonstrated in rats. These results demonstrate that T3 negatively regulates PC2 expression at the transcriptional level and that functional negative thyroid hormone response elements exist in the hPC2 promoter. We postulate that the alterations of PC2 activity may mediate some of the pathophysiological consequences of hypo- or hyperthyroidism.
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Affiliation(s)
- Q L Li
- Department of Medicine, Cedars-Sinai Research Institute, University of California School of Medicine, Los Angeles 90048, USA
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42
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Lim J, Ghadessy FJ, Abdullah AA, Pinsky L, Trifiro M, Yong EL. Human androgen receptor mutation disrupts ternary interactions between ligand, receptor domains, and the coactivator TIF2 (transcription intermediary factor 2). Mol Endocrinol 2000; 14:1187-97. [PMID: 10935543 DOI: 10.1210/mend.14.8.0499] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The androgen receptor (AR) is a ligand-dependent X-linked nuclear transcription factor regulating male sexual development and spermatogenesis. The receptor is activated when androgen binds to the C-terminal ligand-binding domain (LBD), triggering a cascade of molecular events, including interactions between the LBD and the N-terminal transactivation domain (TAD), and the recruitment of transcriptional coactivators. A nonconservative asparagine to lysine substitution in AR residue 727 was encountered in a phenotypically normal man with subfertility and depressed spermatogenesis. This N727K mutation, although located in the LBD, did not alter any ligand-binding characteristic of the AR in the patient's fibroblasts or when expressed in heterologous cells. Nonetheless, the mutant AR displayed only half of wild-type transactivation capacity when exposed to physiological or synthetic androgens. This transactivation defect was consistently present when examined with two different reporter systems in three cell lines, using three androgen-driven promoters (including the complex human prostate-specific antigen promoter), confirming the pathogenicity of the mutation. In mammalian two-hybrid assays, N727K disrupted LBD interactions with the AR TAD and with the coactivator, transcription intermediary factor 2 (TIF2). Strikingly, the transactivation defect of the mutant AR can be rectified in vitro with mesterolone, consistent with the ability of this androgen analog to restore sperm production in vivo. Mesterolone, but not the physiological androgen dihydrotestosterone, restored mutant LBD interactions with the TAD and with TIF2, when expressed as fusion proteins in the two-hybrid assay. Our data support an emerging paradigm with respect to AR mutations in the LBD and male infertility: pathogenicity is transmitted through reduced interdomain and coactivator interactions, and androgen analogs that are corrective in vitro may indicate hormonal therapy.
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Affiliation(s)
- J Lim
- Department of Obstetrics and Gynecology, National University of Singapore, Republic of Singapore
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43
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Andersson ML, Vennström B. A choice between transcriptional enhancement and repression by the v-erbA oncoprotein governed by one nucleotide in a thyroid hormone responsive half site. Oncogene 2000; 19:3563-9. [PMID: 10951561 DOI: 10.1038/sj.onc.1203692] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The v-erbA oncoprotein (P75gag-v-erbA) can repress thyroid hormone receptor induced transcriptional activation of target genes. A central question is how hormone responsive elements in a target gene determine the transcriptional regulation mediated by P75gag-v-erbA. We addressed this with receptors chimeric between P75gag-v-erbA and thyroid hormone receptor (TR) by testing their regulatory activities on thyroid hormone response elements (TREs) differing in the sequence of the consensus core recognition motif AGGTCA. We report here that enhances, TR dependent transcriptional activation is conferred by P75gag-v-erbA when the thymidine in the half site recognition motif is exchanged for an adenosine. The enhancement was independent of the DNA binding region of P75gag-v-erbA, whereas increased expression of corepressor abolished the enhancing effect. The data indicate that the enhancement results from an impaired DNA binding by the oncoprotein combined with an effective scavenging of corepressors. Our data thus suggest the P75gag-v-erbA indirectly can contribute to enhancement of thyroid hormone induced gene expression.
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Affiliation(s)
- M L Andersson
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
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44
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Oesterreich S, Zhang Q, Hopp T, Fuqua SA, Michaelis M, Zhao HH, Davie JR, Osborne CK, Lee AV. Tamoxifen-bound estrogen receptor (ER) strongly interacts with the nuclear matrix protein HET/SAF-B, a novel inhibitor of ER-mediated transactivation. Mol Endocrinol 2000; 14:369-81. [PMID: 10707955 DOI: 10.1210/mend.14.3.0432] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The estrogen receptor (ER) is a ligand-dependent transcription factor that acts in a cell- and promoter-specific manner. Evidence suggests that the activity of the ER can be regulated by a number of other stimuli (e.g. growth factors) and that the effects of the ER are modulated by nuclear factors termed coregulators. While the interplay among these factors may in part explain the pleiotropic effects elicited by the ER, there are several other less well described mechanisms of control, such as interactions with the nuclear matrix. Here we report that the nuclear matrix protein/scaffold attachment factor HET/SAF-B is an ER-interacting protein. ER and HET/SAF-B interact in in vitro binding assays, with HET binding to both the ER DNA-binding domain and the hinge region. Coimmunoprecipitation experiments reveal that HET/SAF-B and ER associate in cell lines in the presence or absence of estradiol, but binding is increased by the antiestrogen tamoxifen. HET/SAF-B enhances tamoxifen antagonism of estrogen-induced ER-mediated transactivation, but at high concentrations can inhibit both estrogen and tamoxifen-induced ER activity. HET/SAF-B-mediated repression of ER activity is dependent upon interaction with the ER-DBD. While the existence of high-affinity binding sites for the ER in the nuclear matrix has been known for some time, we now provide evidence of a specific nuclear matrix protein binding to the ER. Furthermore, our data showing that HET/SAF-B binds to ER particularly strongly in the presence of tamoxifen suggests that it may be important for the antagonist effect of tamoxifen.
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Affiliation(s)
- S Oesterreich
- Department of Medicine, University of Texas Health Science Center, San Antonio 78284, USA.
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Gurnell M, Wentworth JM, Agostini M, Adams M, Collingwood TN, Provenzano C, Browne PO, Rajanayagam O, Burris TP, Schwabe JW, Lazar MA, Chatterjee VK. A dominant-negative peroxisome proliferator-activated receptor gamma (PPARgamma) mutant is a constitutive repressor and inhibits PPARgamma-mediated adipogenesis. J Biol Chem 2000; 275:5754-9. [PMID: 10681562 DOI: 10.1074/jbc.275.8.5754] [Citation(s) in RCA: 227] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) promotes adipocyte differentiation, exerts atherogenic and anti-inflammatory effects in monocyte/macrophages, and is believed to mediate the insulin-sensitizing action of antidiabetic thiazolidinedione ligands. As no complete PPARgamma antagonists have been described hitherto, we have constructed a dominant-negative mutant receptor to inhibit wild-type PPARgamma action. Highly conserved hydrophobic and charged residues (Leu(468) and Glu(471)) in helix 12 of the ligand-binding domain were mutated to alanine. This compound PPARgamma mutant retains ligand and DNA binding, but exhibits markedly reduced transactivation due to impaired coactivator (cAMP-response element-binding protein-binding protein and steroid receptor coactivator-1) recruitment. Unexpectedly, the mutant receptor silences basal gene transcription, recruits corepressors (the silencing mediator of retinoid and thyroid receptors and the nuclear corepressor) more avidly than wild-type PPARgamma, and exhibits delayed ligand-dependent corepressor release. It is a powerful dominant-negative inhibitor of cotransfected wild-type receptor action. Furthermore, when expressed in primary human preadipocytes using a recombinant adenovirus, this PPARgamma mutant blocks thiazolidinedione-induced differentiation, providing direct evidence that PPARgamma mediates adipogenesis. Our observations suggest that, as in other mutant nuclear receptor contexts (acute promyelocytic leukemia, resistance to thyroid hormone), dominant-negative inhibition by PPARgamma is linked to aberrant corepressor interaction. Adenoviral expression of this mutant receptor is a valuable means to antagonize PPARgamma signaling.
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Affiliation(s)
- M Gurnell
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QQ, United Kingdom
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Chien PY, Ito M, Park Y, Tagami T, Gehm BD, Jameson JL. A fusion protein of the estrogen receptor (ER) and nuclear receptor corepressor (NCoR) strongly inhibits estrogen-dependent responses in breast cancer cells. Mol Endocrinol 1999; 13:2122-36. [PMID: 10598586 DOI: 10.1210/mend.13.12.0394] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Nuclear receptor corepressor (NCoR) mediates repression (silencing) of basal gene transcription by nuclear receptors for thyroid hormone and retinoic acid. The goal of this study was to create novel estrogen receptor (ER) mutants by fusing transferable repressor domains from the N-terminal region of NCoR to a functional ER fragment. Three chimeric NCoR-ER proteins were created and shown to lack transcriptional activity. These fusion proteins silenced basal transcription of the ERE2-tk-Luc reporter gene and inhibited the activity of co-transfected wild-type ER (wtER), indicating that they possess dominant negative activity. One of the fusion proteins (CDE-RD1), containing the ER DNA-binding and ligand-binding domains linked to the NCoR repressor domain (RD1), was selected for detailed examination. Its hormone affinity, intracellular localization, and level of expression in transfected cells were similar to wtER, and it bound to the estrogen response element (ERE) DNA in gel shift assays. Glutathione-S-transferase pull-down assays showed that CDE-RD1 retains the ability to bind to steroid receptor coactivator-1. Introduction of a DNA-binding domain mutation into the CDE-RD1 fusion protein eliminated silencing and dominant negative activity. Thus, the RD1 repressor domain prevents transcriptional activation despite the apparent ability of CDE-RD1 to bind DNA, ligand, and coactivators. Transcriptional silencing was incompletely reversed by trichostatin A, suggesting a histone deacetylase-independent mechanism for repression. CDE-RD1 inhibited ER-mediated transcription in T47D and MDA-MB-231 breast cancer cells and repressed the growth of T47D cells when delivered to the cells by a retroviral vector. These ER-NCoR fusion proteins provide a novel means for inhibiting ER-mediated cellular responses, and analogous strategies could be used to create dominant negative mutants of other transcription factors.
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Affiliation(s)
- P Y Chien
- Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA
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47
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Tagami T, Park Y, Jameson JL. Mechanisms that mediate negative regulation of the thyroid-stimulating hormone alpha gene by the thyroid hormone receptor. J Biol Chem 1999; 274:22345-53. [PMID: 10428804 DOI: 10.1074/jbc.274.32.22345] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A group of transcriptional cofactors for nuclear hormone receptors, referred to as corepressors (CoRs) and coactivators (CoAs), has been shown to induce transcriptional silencing and hormone-induced activation, respectively, of genes that contain positive hormone response elements. Transcriptional silencing by CoRs involves the recruitment of histone deacetylases (HDACs), whereas ligand-dependent activation is associated with the recruitment of CoAs, which possess or recruit histone acetyltransferases (HATs). In a reciprocal manner, negatively regulated genes are stimulated by nuclear receptors in the absence of ligand and are repressed in response to ligand binding to receptors. We show here that negative regulation of the thyroid-stimulating hormone alpha (TSHalpha) promoter by the thyroid hormone receptor (TR) involves a novel mechanism in which the recruitment of CoRs by TR is associated with transcriptional stimulation and histone acetylation. Expression of excess HDAC reverses the stimulation mediated by the TR.CoR complex, consistent with a pivotal role for acetylation in this event. Addition of the ligand, 3,5,3'-triiodothyronine (T3), induces transcriptional repression of the TSHalpha promoter and is associated with the loss of histone acetylation. T3-dependent repression is blocked by phosphorylation of cAMP response element binding protein, or by inhibition of HDAC, indicating that receptor action is subverted by maneuvers that stimulate histone acetylation of the target gene. We propose that negative regulation of a subset of genes by TR involves the active exchange of CoRs and CoAs with intrinsic promoter regulatory elements that normally strongly induce histone acetylation and transcriptional activation.
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Affiliation(s)
- T Tagami
- Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA
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Weiss RE, Xu J, Ning G, Pohlenz J, O'Malley BW, Refetoff S. Mice deficient in the steroid receptor co-activator 1 (SRC-1) are resistant to thyroid hormone. EMBO J 1999; 18:1900-4. [PMID: 10202153 PMCID: PMC1171275 DOI: 10.1093/emboj/18.7.1900] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Steroid receptor co-activator 1 (SRC-1) is a transcription co-factor that enhances the hormone-dependent action, mediated by the thyroid hormone (TH) receptor (TR) and other nuclear receptors. In vitro studies have shown that SRC-1 is necessary for the full expression of TH effect. SRC-1 knockout mice (SRC-1(-/-)) provide a model to examine the role of this co-activator on TH action in vivo. At baseline, SRC-1(-/-) mice display resistance to TH (RTH) as evidenced by a 2.5-fold elevation of serum TSH levels, despite a 50% increase in serum free TH levels as compared with wild-type (SRC-1(+/+)) mice. When mice were made hypothyroid, TSH levels increased, obliterating the difference between SRC-1(+/+) and SRC-1(-/-) mice observed at baseline. In contrast, the decline of TSH by treatment with L-triiodothyronine was severely blunted in SRC-1(-/-) mice. These data indicate that SRC-1 is not required for the upregulation of TSH in TH deficiency. However, SRC-1 enhances the sensitivity of TSH downregulation by TH. This is the first demonstration of RTH caused by a deficient co-factor other than TR. It supports the hypothesis that a putative defect in the SRC-1 gene or another co-factor could be the cause of RTH in humans without mutations in the TR genes.
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Affiliation(s)
- R E Weiss
- Department of Medicine,Jr Mental Retardation Research Center, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA.
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