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Liao W, Waisayanand N, Fanhchaksai K, Visser WE, Meima ME, Wejaphikul K. Resistance to Thyroid Hormone Beta Due to THRB Mutation in a Patient Misdiagnosed With TSH-Secreting Pituitary Adenoma. JCEM CASE REPORTS 2024; 2:luae140. [PMID: 39091608 PMCID: PMC11291949 DOI: 10.1210/jcemcr/luae140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Indexed: 08/04/2024]
Abstract
Elevated concentrations of T3 and T4 concomitant with nonsuppressed TSH are found in both TSH-producing tumors and resistance to thyroid hormone beta (RTHβ), posing a diagnostic challenge. We demonstrate here a 54-year-old female who presented with palpitations, goiter, and elevated free T4 with nonsuppressed TSH concentrations (TSH 2.2 mIU/L [normal range, NR 0.27-4.2 mIU/L] and FT4 59.08 pmol/L [NR 12.0-22.0 pmol/L]). Because magnetic resonance imaging revealed a pituitary microadenoma (4 mm), she was diagnosed with TSH-secreting pituitary adenoma and underwent transsphenoidal surgery. Pathological reports showed no tumor cells. Subsequent genetic testing revealed a pathogenic variant in the THRB gene resulting in a His435Arg amino acid substitution in the T3 receptor isoform beta 1 (TRβ1), suggestive of RTHβ. In vitro and ex vivo studies revealed that the His435Arg mutated TRβ1 (TRβ1-H435R) completely abolishes the T3-induced transcriptional activation, nuclear receptor corepressor 1 release, steroid receptor coactivator 1 recruitment, and T3-induced thyroid hormone target gene expression, confirming the pathogenicity of this variant. The identification of a pituitary microadenoma in a patient with RTHβ led to a misdiagnosis of a TSH-producing tumor and unnecessary surgery. Genetic testing proved pivotal for an accurate diagnosis, suggesting earlier consideration in similar clinical scenarios.
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Affiliation(s)
- Wenjun Liao
- Department of Internal Medicine, Academic Center for Thyroid Diseases, Erasmus MC, 3015 CN, Rotterdam, the Netherlands
| | - Nipawan Waisayanand
- Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand
| | - Kanda Fanhchaksai
- Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand
| | - W Edward Visser
- Department of Internal Medicine, Academic Center for Thyroid Diseases, Erasmus MC, 3015 CN, Rotterdam, the Netherlands
| | - Marcel E Meima
- Department of Internal Medicine, Academic Center for Thyroid Diseases, Erasmus MC, 3015 CN, Rotterdam, the Netherlands
| | - Karn Wejaphikul
- Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand
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Li Q, Yao B, Zhao S, Lu Z, Zhang Y, Xiang Q, Wu X, Yu H, Zhang C, Li J, Zhuang X, Wu D, Li Y, Xu Y. Discovery of a Highly Selective and H435R-Sensitive Thyroid Hormone Receptor β Agonist. J Med Chem 2022; 65:7193-7211. [PMID: 35507418 DOI: 10.1021/acs.jmedchem.2c00144] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The design and development of agonists selectively targeting thyroid hormone receptor β (TRβ) and TRβ mutants remain challenging tasks. In this study, we first adopted the strategy of breaking the "His-Phe switch" to solve two problems, simultaneously. A structure-based design approach was successfully utilized to obtain compound 16g, which is a potent TRβ agonist (EC50: 21.0 nM, 85.0% of the maximum efficacy of 1) with outstanding selectivity for TRβ over TRα and also effectively activates the TRβH435R mutant. Then, we developed a highly efficient synthetic method for 16g. Our serials of cocrystal structures revealed detailed structural mechanisms in overcoming subtype selectivity and rescuing the H435R mutation. 16g also showed excellent lipid metabolism, safety, metabolic stability, and pharmacokinetic properties. Collectively, 16g is a well-characterized selective and mutation-sensitive TRβ agonist for further investigating its function in treating dyslipidemia, nonalcoholic steatohepatitis (NASH), and resistance to thyroid hormone (RTH).
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Affiliation(s)
- Qiu Li
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,University of Chinese Academy of Sciences, No. 19 Yuquan Road, Beijing 100049, China
| | - Benqiang Yao
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen 361005, China
| | - Shiting Zhao
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,University of Chinese Academy of Sciences, No. 19 Yuquan Road, Beijing 100049, China
| | - Zhou Lu
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen 361005, China
| | - Yan Zhang
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Qiuping Xiang
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Xishan Wu
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Haonan Yu
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Cheng Zhang
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Junhua Li
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Xiaoxi Zhuang
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | - Donghai Wu
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,China-New Zealand Joint Laboratory on Biomedicine and Health, Guangzhou 510530, China
| | - Yong Li
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Xiamen 361005, China
| | - Yong Xu
- Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China.,China-New Zealand Joint Laboratory on Biomedicine and Health, Guangzhou 510530, China.,Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
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Yao B, Wei Y, Zhang S, Tian S, Xu S, Wang R, Zheng W, Li Y. Revealing a Mutant-Induced Receptor Allosteric Mechanism for the Thyroid Hormone Resistance. iScience 2019; 20:489-496. [PMID: 31655060 PMCID: PMC6806671 DOI: 10.1016/j.isci.2019.10.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 09/19/2019] [Accepted: 09/30/2019] [Indexed: 12/13/2022] Open
Abstract
Resistance to thyroid hormone (RTH) is a clinical disorder without specific and effective therapeutic strategy, partly due to the lack of structural mechanisms for the defective ligand binding by mutated thyroid hormone receptors (THRs). We herein uncovered the prescription drug roxadustat as a novel THRβ-selective ligand with therapeutic potentials in treating RTH, thereby providing a small molecule tool enabling the first probe into the structural mechanisms of RTH. Despite a wide distribution of the receptor mutation sites, different THRβ mutants induce allosteric conformational modulation on the same His435 residue, which disrupts a critical hydrogen bond required for the binding of thyroid hormones. Interestingly, roxadustat retains hydrophobic interactions with THRβ via its unique phenyl extension, enabling the rescue of the activity of the THRβ mutants. Our study thus reveals a critical receptor allosterism mechanism for RTH by mutant THRβ, providing a new and viable therapeutic strategy for the treatment of RTH. We identified a novel THR ligand that effectively binds to THRβ mutants Structures revealed mechanisms for the RTH controlled by a key residue switch Roxadustat retains unique hydrophobic interactions with THRβ mutants We provide a promising approach to design THR ligands in treating RTH
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Affiliation(s)
- Benqiang Yao
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China
| | - Yijuan Wei
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China
| | - Shuchi Zhang
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China
| | - Siyu Tian
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China
| | - Shuangshuang Xu
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China
| | - Rui Wang
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China
| | - Weili Zheng
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Signaling Network, School of Life Sciences, Xiamen University, Fujian 361005, China
| | - Yong Li
- 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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Vela A, Pérez-Nanclares G, Ríos I, Rica I, Portillo N, Castaño L. Thyroid hormone resistance from newborns to adults: a Spanish experience. J Endocrinol Invest 2019; 42:941-949. [PMID: 30707410 DOI: 10.1007/s40618-019-1007-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 01/09/2019] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Thyroid hormone resistance (RTH β) is a rare genetic disorder characterized by an altered response of target tissue to the action of thyroid hormone. Few studies on RTH β have been carried out in southern European populations. We aimed to describe the clinical and genetic characteristics at the time of diagnosis in a Spanish cohort of patients with genetically confirmed RTH β, with ages ranging from newborns to adults. METHODS Retrospective multicenter study of 28 patients who were genetically confirmed as RTH β. Clinical and biochemical data were collected from the reference centers, and the studied variables included age, sex, anthropometric data, clinical characteristics and biochemical results. In the Basque country, a simultaneous analysis of TSH and T4 is carried out in the program for the screening of inborn errors of metabolism. A molecular analysis of the thyroid hormone beta (THRB) gene was performed. RESULTS The total cohort included 20 adults and eight pediatric patients (six newborns). Of the total, 5 (17.8%) were diagnosed by clinical characteristics (goiter, hypertension or tachycardia), 13 (46.4%) were analyzed in the context of a family study and 10 (35.7%) were diagnosed after obtaining an altered fT4 and/or TSH level in a biochemical analysis performed due to clinical symptoms unrelated to RTH β. Four of the newborns included in the series were diagnosed by the result of neonatal screening, which allows us to estimate a minimum local incidence of RTH β of 1/18,750 live newborns. The genetic analysis showed the presence of 12 different heterozygous mutations in the THRB gene. CONCLUSIONS We report the clinical and genetic characteristics of a Spanish RTH β cohort, from neonates to adults. We also describe one novel mutation in the THRB gene as the cause of the disease. The simultaneous analysis of TSH and T4 carried out in the program for the screening of inborn errors of metabolism facilitates the early diagnosis of RTH β in newborns and has allowed us to estimate a minimum local incidence of RTH of 1/18,750 live newborns.
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Affiliation(s)
- A Vela
- Biocruces Health Research Institute, Cruces University Hospital, CIBERER, CIBERDEM, UPV-EHU, Barakaldo, Basque Country, Spain
| | - G Pérez-Nanclares
- Biocruces Health Research Institute, Cruces University Hospital, CIBERER, CIBERDEM, UPV-EHU, Barakaldo, Basque Country, Spain
| | - I Ríos
- Biocruces Health Research Institute, Cruces University Hospital, CIBERER, CIBERDEM, UPV-EHU, Barakaldo, Basque Country, Spain
| | - I Rica
- Biocruces Health Research Institute, Cruces University Hospital, CIBERER, CIBERDEM, UPV-EHU, Barakaldo, Basque Country, Spain
| | - N Portillo
- Biocruces Health Research Institute, Alto Deba Hospital, Gipuzkoa, Basque Country, Spain
| | - L Castaño
- Biocruces Health Research Institute, Cruces University Hospital, CIBERER, CIBERDEM, UPV-EHU, Barakaldo, Basque Country, Spain.
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Braun D, Lelios I, Krause G, Schweizer U. Histidines in potential substrate recognition sites affect thyroid hormone transport by monocarboxylate transporter 8 (MCT8). Endocrinology 2013; 154:2553-61. [PMID: 23592749 DOI: 10.1210/en.2012-2197] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mutations in monocarboxylate transporter 8 (MCT8; SLC16A2) cause the Allan-Herndon-Dudley syndrome, a severe X-linked psychomotor retardation syndrome. MCT8 belongs to the major facilitator superfamily of 12 transmembrane-spanning proteins and transports thyroid hormones across the blood-brain barrier and into neurons. How MCT8 distinguishes thyroid hormone substrates from structurally closely related compounds is not known. The goal of this study was to identify critical amino acids along the transport channel cavity, which participate in thyroid hormone recognition. The fact that T3 is bound between a His-Arg clamp in the crystal structure of the T3 receptor/T3 complex prompted us to investigate whether such a motif might potentially be relevant for T3 recognition in MCT8. We therefore replaced candidate histidines and arginines by site-directed mutagenesis and performed activity assays in MDCK-1 cells and Xenopus oocytes. Histidines were replaced by alanine, phenylalanine, and glutamine to probe for molecular properties like aromatic ring structure and H-bonding properties. It was found that some mutations in His192 and His415 significantly changed substrate transport kinetics. Arg301 at the intracellular end of the substrate channel is at an ideal distance to His415 to participate in a His-Arg clamp and mutation to alanine-abrogated hormone transport. Molecular modeling demonstrates a perfect fit of T3 poised into the substrate channel between His415 and Arg301 and observing the same geometry as in the T3 receptor.
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Affiliation(s)
- Doreen Braun
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, D-13353, Berlin, Germany
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6
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Hirano T, Kagechika H. Thyromimetics: a review of recent reports and patents (2004 – 2009). Expert Opin Ther Pat 2010; 20:213-28. [DOI: 10.1517/13543770903567069] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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7
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Hassan A, Koh J. Selective Chemical Rescue of a Thyroid-Hormone-Receptor Mutant, TRβ(H435Y), Identified in Pituitary Carcinoma and Resistance to Thyroid Hormone. Angew Chem Int Ed Engl 2008; 47:7280-3. [DOI: 10.1002/anie.200801742] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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8
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Hassan A, Koh J. Selective Chemical Rescue of a Thyroid-Hormone-Receptor Mutant, TRβ(H435Y), Identified in Pituitary Carcinoma and Resistance to Thyroid Hormone. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200801742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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9
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Tsui KH, Hsieh WC, Lin MH, Chang PL, Juang HH. Triiodothyronine modulates cell proliferation of human prostatic carcinoma cells by downregulation of the B-cell translocation gene 2. Prostate 2008; 68:610-9. [PMID: 18196550 DOI: 10.1002/pros.20725] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Studies suggest that triiodothyronine (T3) and cognate nuclear receptors (hTR) are involved in regulation of prostatic cell growth and differentiation. To probe mechanisms for T3 effects, we studied prostate carcinoma cells, investigating the effect of T3 on expression of the B-cell translocation gene 2 (BTG2), which regulates the G1/S transition of the cell cycle. METHODS Effects of T3 on cell proliferation were determined by (3)H-thymidine incorporation. T3 modulation of BTG2 expression was investigated using immunoblots, Northern blots, and transient gene expression assays. The putative T3 response element was determined by electrophoretic mobility shift assay. RESULTS T3 (0.1-1,000 nM) enhanced threefold the proliferation of prostate carcinoma cells and human androgen-dependent prostate carcinoma cells (LNCaP), but not PC-3 cells. T3 also inhibited BTG2 gene expression in LNCaP cells. Reporter assays showed that T3 downregulates by 50% promoter activity of the BTG2 gene in LNCaP cells but not PC-3 cells or thyroid-hormone receptor (TRbeta1)-overexpression PC-3 cells. Deleting the putative thyroid hormone response element (TRE; AGCGATGACCTCAGCG) blocked the inhibitory effect of T3 on BTG2 promoter activity. Electrophoretic mobility shift assays with purified TRbeta1 from in vitro translation, or with nuclear extracts from LNCaP cells and PC-3 cells, demonstrated the presence of T3 receptor binding sites in the TRE region. CONCLUSIONS These results suggested that the T3 upregulates proliferation of LNCaP cells by downregulating BTG2 gene expression through the consensus TRE pathway.
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Affiliation(s)
- Ke-Hung Tsui
- Department of Urology, Chang Gung Memorial Hospital, Kwei-Shan, Tao-Yuan, Taiwan, ROC
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Hassan AQ, Koh JT. A functionally orthogonal ligand-receptor pair created by targeting the allosteric mechanism of the thyroid hormone receptor. J Am Chem Soc 2006; 128:8868-74. [PMID: 16819881 PMCID: PMC2515387 DOI: 10.1021/ja060760v] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Nuclear receptors are ligand-dependent transcription factors that are of interest as potential tools to artificially regulate gene expression. Ligand binding induces a conformational change involving helix-12 which forms part of the dimerization interface used to bind transcriptional coactivators. When triiodothyronine (T3) binds the thyroid hormone receptor (TR) it indirectly contacts helix-12 through intermediary residues His(435) and Phe(451) termed a His-Phe switch. The mutant TRbeta(H435A) is nonresponsive to physiological concentrations of T3 but can be activated by the synthetic hormone analogue QH2 which potently activates His435-->Ala mutant at concentrations that do not activate the wild-type receptors TRalpha and TRbeta. QH2 does not show antagonist behavior with the wild-type TRs. QH2's functionally orthogonal behavior with TRbeta(H435A) is preserved on the three consensus thyroid hormone response elements.
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Affiliation(s)
- A. Quamrul Hassan
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - John T. Koh
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
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Jurutka PW, MacDonald PN, Nakajima S, Hsieh JC, Thompson PD, Whitfield GK, Galligan MA, Haussler CA, Haussler MR. Isolation of baculovirus-expressed human vitamin D receptor: DNA responsive element interactions and phosphorylation of the purified receptor. J Cell Biochem 2002; 85:435-57. [PMID: 11948698 DOI: 10.1002/jcb.10134] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Two controversial aspects in the mechanism of human vitamin D receptor (hVDR) action are the possible significance of VDR homodimers and the functional role of receptor phosphorylation. To address these issues, milligram quantities of baculovirus-expressed hVDR were purified to 97% homogeneity, and then tested for binding to the rat osteocalcin vitamin D responsive element (VDRE) via electrophoretic mobility shift and half-site competition assays in the presence or absence of a CV-1 nuclear extract containing retinoid X receptor (RXR). Methylation interference analysis revealed that both the hVDR homodimer and the VDR-RXR heterodimer display similar patterns of VDRE G-base protection. However, in competition studies, the relative dissociation of the homodimeric hVDR complex from the VDRE was extremely rapid (t1/2 < 30 s) compared to the dissociation of the heteromeric complex (t1/2 > 5 min), thus illustrating the relative instability and low affinity of homodimeric VDR binding to DNA. These results indicate that VDR-RXR heterodimers are the preferred VDRE binding species. Further, two dimensional gel electrophoresis of hVDR demonstrated several isoelectric forms of the receptor, suggesting that it is subject to multiple phosphorylation events. In vitro kinase assays confirmed that purified hVDR is an efficient substrate for protein kinases A and Cbeta, as well as casein kinase II. In vivo studies of the expressed receptor in intact cells, namely baculovirus vector infected Sf9 insect cells and transfected mammalian COS-7 cells, demonstrated that hVDR was phosphorylated in a hormone-enhanced fashion. Functional consequences of hVDR phosphorylation were suggested by the observations that: (i) potato acid phosphatase (PAP)-treated hVDR no longer interacted with the VDRE as either a homodimer or a heteromeric complex with RXR, and (ii) treatment of transfected COS-7 cells with a phosphatase inhibitor (okadaic acid) along with 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) resulted in a synergistic enhancement of both hVDR phosphorylation and transactivation of a VDRE-linked reporter gene, compared to the effect of treatment with either agent alone. These studies point to a significant role for phosphorylation of VDR in regulating high-affinity VDR-RXR interactions with VDREs, and also in modulating 1,25(OH)2D3-elicited transcriptional activation in target cells.
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Affiliation(s)
- Peter W Jurutka
- Department of Biochemistry and Molecular Biophysics, College of Medicine, University of Arizona, Tucson, Arizona 85724, USA
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Nomura Y, Nagaya T, Yamaguchi S, Katunuma N, Seo H. Cleavage of RXRalpha by a lysosomal enzyme, cathepsin L-type protease. Biochem Biophys Res Commun 1999; 254:388-94. [PMID: 9918848 DOI: 10.1006/bbrc.1998.9941] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study, we characterized a protease responsible for the cleavage of RXRalpha in two human derived cell lines, HepG2 and JEG-3 cells. Electrophoretic mobility shift assay (EMSA) combined with antibody supershift analysis suggested that contamination of cytoplasmic components during nuclear extract preparation could result in complete cleavage of RXRalpha at its N-terminus in JEG-3 cells, while such proteolytic activity was much less evident in HepG2. When the nuclei were purified in the presence of leupeptin, only full-length RXRalpha was found in the extracts prepared from both JEG-3 and HepG2 cells, suggesting a member of cysteine protease family is responsible for the cleavage. The presence of the protease in the cytoplasm, but not in the nucleus, was confirmed by incubating full-length 35S-labeled RXRalpha with each fraction. The cytoplasmic fraction from JEG-3 and HepG2 cells cleaved RXRalpha into smaller sizes with molecular mass of 45, 43, and 31 kD. Immunoprecipitation with antibodies recognizing distinct epitopes indicated that the cleaved RXRalpha with the size of 45 and 43 kD were truncated at N-terminus in which most of the A/B domain was absent. Using a series of protease inhibitors, the enzyme cleaving RXRalpha was characterized as cathepsin L-type protease. The enzyme activity in JEG-3 cells was much higher than that in HepG2 cells. This is the first demonstration that RXRalpha is cleaved by a lysosomal enzyme, cathepsin L-type protease.
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Affiliation(s)
- Y Nomura
- Division of Molecular and Cellular Adaptation, Nagoya University, Nagoya, 464-8601, Japan
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Mammen M, Choi SK, Whitesides GM. Polyvalente Wechselwirkungen in biologischen Systemen: Auswirkungen auf das Design und die Verwendung multivalenter Liganden und Inhibitoren. Angew Chem Int Ed Engl 1998. [DOI: 10.1002/(sici)1521-3757(19981016)110:20<2908::aid-ange2908>3.0.co;2-2] [Citation(s) in RCA: 522] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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