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Abstract
The clinical availability of tissue-specific biomarkers of thyroid hormone (TH) action constitutes a "holy grail" for the field. Scientists have investigated several TH-dependent markers, including the tissue content of triiodothyronine (T3)-the active form of TH. The study of animal models and humans indicates that the T3 content varies among different tissues, mostly due to the presence of low-affinity, high-capacity cytoplasmic T3 binding proteins. Nonetheless, given that T3 levels in the plasma and tissues are in equilibrium, T3 signaling is defined by the intracellular free T3 levels. The available techniques to assess tissue T3 are invasive and not clinically applicable. However, the tracer kinetic studies revealed that serum T3 levels can accurately predict tissue T3 content and T3 signaling in most tissues, except for the brain and pituitary gland. This is true not only for normal individuals but also for patients with hypo or hyperthyroidism-but not for patients with non-thyroidal illness syndrome. Given this direct relationship between serum and tissue T3 contents and T3 signaling in most tissues, clinicians managing patients with hypothyroidism could refocus attention on monitoring serum T3 levels. Future clinical trials should aim at correlating clinical outcomes with serum T3 levels.
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Affiliation(s)
- Federico Salas-Lucia
- Section of Adult and Pediatric Endocrinology and Metabolism, The University of Chicago, Chicago, IL, United States
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2
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Abstract
µ-Crystallin is a NADPH-regulated thyroid hormone binding protein encoded by the CRYM gene in humans. It is primarily expressed in the brain, muscle, prostate, and kidney, where it binds thyroid hormones, which regulate metabolism and thermogenesis. It also acts as a ketimine reductase in the lysine degradation pathway when it is not bound to thyroid hormone. Mutations in CRYM can result in non-syndromic deafness, while its aberrant expression, predominantly in the brain but also in other tissues, has been associated with psychiatric, neuromuscular, and inflammatory diseases. CRYM expression is highly variable in human skeletal muscle, with 15% of individuals expressing ≥13 fold more CRYM mRNA than the median level. Ablation of the Crym gene in murine models results in the hypertrophy of fast twitch muscle fibers and an increase in fat mass of mice fed a high fat diet. Overexpression of Crym in mice causes a shift in energy utilization away from glycolysis towards an increase in the catabolism of fat via β-oxidation, with commensurate changes of metabolically involved transcripts and proteins. The history, attributes, functions, and diseases associated with CRYM, an important modulator of metabolism, are reviewed.
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Affiliation(s)
- Christian J Kinney
- Department of Physiology School of Medicine, University of Maryland, Baltimore, Baltimore, MD 21201
| | - Robert J Bloch
- Department of Physiology School of Medicine, University of Maryland, Baltimore, Baltimore, MD 21201
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3
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Reciprocal Control of Thyroid Binding and the Pipecolate Pathway in the Brain. Neurochem Res 2016; 42:217-243. [DOI: 10.1007/s11064-016-2015-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/15/2016] [Accepted: 07/22/2016] [Indexed: 12/21/2022]
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Suzuki S, Suzuki N, Mori JI, Oshima A, Usami S, Hashizume K. micro-Crystallin as an intracellular 3,5,3'-triiodothyronine holder in vivo. Mol Endocrinol 2007; 21:885-94. [PMID: 17264173 DOI: 10.1210/me.2006-0403] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Previously, we identified reduced nicotinamide adenine dinucleotide phosphate-dependent cytosolic T(3) binding protein in rat cytosol. Cytosolic T(3)-binding protein is identical to mu-crystallin (CRYM). Recently, CRYM mutations were found in patients with nonsyndromic hereditary deafness. Although it has been established that CRYM plays pivotal roles in reserving and transporting T(3) into the nuclei in vitro and has a clinical impact on hearing ability, the precise functions of CRYM remain to be elucidated in vivo. To further investigate the in vivo functions of CRYM gene products, we have generated mice with targeted disruption of the CRYM gene, which abrogates the production of CRYM. CRYM knockout loses the reduced nicotinamide adenine dinucleotide phosphate-dependent T(3) binding activity in the cytosol of the brain, kidney, heart, and liver. At the euthyroid state, knockout significantly suppresses the serum concentration of T(3) and T(4) despite normal growth, heart rate, and hearing ability. The disruption of the gene does not alter the expression of TSHbeta mRNA in the pituitary gland or glutathione-S-transferase alpha2 and deiodinase 1 mRNAs in either the liver or kidney. When radiolabeled T(3) is injected intravenously, labeled T(3) rapidly enters into and then escapes from the tissues in CRYM-knockout mice. These data suggest that because of rapid T(3) turnover, disruption of the CRYM gene decreases T(3) concentrations in tissues and serum without alteration of peripheral T(3) action in vivo.
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Affiliation(s)
- Satoru Suzuki
- Department of Aging Medicine and Geriatrics, Institute on Aging and Adaptation, Shinshu University, Graduate School of Medicine, 3-1-1, Asahi, Matsumoto, Nagano 390-8621, Japan.
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5
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McKinnon B, Li H, Richard K, Mortimer R. Synthesis of thyroid hormone binding proteins transthyretin and albumin by human trophoblast. J Clin Endocrinol Metab 2005; 90:6714-20. [PMID: 16159939 DOI: 10.1210/jc.2005-0696] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
CONTEXT Mechanisms regulating materno-fetal transfer of thyroid hormone are not well understood. Modulation of trophoblast type 3 iodothyronine deiodinase (D3) may play an important role. OBJECTIVE The objective of this study was to investigate trophoblast thyroid hormone binding proteins that may modulate interactions between D3 and T4. DESIGN Placentas were obtained by informed consent from women delivering normal infants by repeat cesarean section at 38-40 wk gestation. T4 and T3 binding was examined in human placenta. Serum thyroid hormone binding proteins were identified by Western blotting, and their mRNA was examined by RT-PCR. Presence of these proteins in trophoblast was determined by immunocytochemistry and immunofluorescence. Cytosol was progressively purified to reveal additional thyroid hormone binding proteins that were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry. Effects of mefenamic acid on placental deiodination were examined by HPLC. RESULTS We detected high-affinity T4 and T3 binding in human placental cytosol. All three major serum-binding proteins, T4 binding globulin (TBG), transthyretin (TTR), and albumin, were present in cytosol. TTR mRNA and albumin mRNA were detected in human placenta, and TTR and albumin were identified histochemically in syncytiotrophoblasts. Neither TBG mRNA nor TBG was detected, suggesting that plasma TBG had contaminated the cytosol preparation. Low-affinity thyroid hormone binding proteins alpha-1-antitrypsin and alpha-1-acid glycoprotein were also identified. Addition of mefenamic acid, a potent inhibitor of thyroid hormone binding, to placental cytosol significantly enhanced deiodination of T4 by D3. CONCLUSIONS Placenta produces a series of thyroid hormone binding proteins that may modify thyroid hormone deiodination and materno-fetal thyroid hormone transport.
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Affiliation(s)
- Brett McKinnon
- Conjoint Endocrine Laboratory, Clinical Research Centre, Royal Brisbane and Women's Hospital, Base Hospitals PO, Herston, Queensland 4029, Australia
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6
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Mori JI, Suzuki S, Kobayashi M, Inagaki T, Komatsu A, Takeda T, Miyamoto T, Ichikawa K, Hashizume K. Nicotinamide adenine dinucleotide phosphate-dependent cytosolic T(3) binding protein as a regulator for T(3)-mediated transactivation. Endocrinology 2002; 143:1538-44. [PMID: 11897713 DOI: 10.1210/endo.143.4.8736] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Nicotinamide adenine dinucleotide phosphate (NADPH)- dependent cytosolic T(3) binding protein (CTBP) plays a role in the regulation of nuclear transport of T(3) in vitro. However, it is not known whether CTBP regulates the T(3) action. In this study, we examined the effects of CTBP on cellular translocation of T(3) and on transcriptional activation using established CTBP-expressing CHO or GH3 cells. The expression of CTBP increased cellular and nuclear uptake of T(3) in the CTBP-expressing cells. The efflux rate was decreased by induction of CTBP. Efflux from nuclei also inhibited by induction of CTBP. Expression of CTBP suppressed the T(3)-regulated luciferase activity in GH3 cells. Suppression was observed to be related to the expression level of CTBP. T(3) induction of rat GH mRNA was lower in the cells expressing CTBP than that in CTBP-null cells. These results suggest that CTBP regulates the T(3)-induced gene expression, with which an increase in the nuclear content of the T(3) is associated. Because we observed that a part of CTBP could be transported into nuclei and that acceptor protein for CTBP is present in nuclei as previously reported, interaction of CTBP with certain proteins, including transcription factors or nuclear T(3) receptor, may contribute to the regulation.
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Affiliation(s)
- Jun-ichirou Mori
- Department of Aging Medicine and Geriatrics, Shinshu University School of Medicine, 3-1-1, Asahi, Matsumoto, 390-8621, Japan
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7
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Yamauchi K, Nakajima JI. Effect of coenzymes and thyroid hormones on the dual activities of Xenopus cytosolic thyroid-hormone-binding protein (xCTBP) with aldehyde dehydrogenase activity. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:2257-64. [PMID: 11985605 DOI: 10.1046/j.1432-1033.2002.02891.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A cytosolic thyroid-hormone-binding protein (xCTBP), predominantly responsible for the major binding activity of T3 in the cytosol of Xenopus liver, has been shown to be identical to aldehyde dehydrogenase class 1 (ALDH1) [Yamauchi, K., Nakajima, J., Hayashi, H., Horiuchi, R. & Tata, J.R. (1999) J. Biol. Chem. 274, 8460-8469]. Within this paper we surveyed which signaling, and other, compounds affect the thyroid hormone binding activity and aldehyde dehydrogenase activity of recombinant Xenopus ALDH1 (xCTBP/xALDH1) while examining the relationship between these two activities. NAD+ and NADH (each 200 microm), and two steroids (20 microm), inhibit significantly the T3-binding activity, while NADH and NADPH (each 200 microm), and iodothyronines (1 microm), inhibit the ALDH activity. Scatchard analysis and kinetic studies of xCTBP/xALDH1 indicate that NAD+ and T3 are noncompetitive inhibitors of thyroid-hormone-binding and ALDH activities, respectively. These results indicate the formation of a ternary complex consisting of the protein, NAD+ and thyroid hormone. Although the in vitro studies indicate that NAD+ and NADH markedly decrease T3-binding to xCTBP/xALDH1 at approximately 10-4 m, a concentration equal to the NAD content in various Xenopus tissues, photoaffinity-labeling of [125I]T3 using cultured Xenopus cells demonstrates xCTBP/xALDH1 bound T3 within living cells. These results raise the possibility that an unknown factor(s) besides NAD+ and NADH may modulate the thyroid-hormone-binding activity of xCTBP/xALDH1. In comparison, thyroid hormone, at its physiological concentration, would poorly modulate the enzyme activity of xCTBP/xALDH1.
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Affiliation(s)
- Kiyoshi Yamauchi
- Department of Biology and Geoscience, Faculty of Science, Shizuoka University, Shizuoka, Japan.
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8
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Yamauchi K, Tata JR. Characterization of Xenopus cytosolic thyroid-hormone-binding protein (xCTBP) with aldehyde dehydrogenase activity. Chem Biol Interact 2001; 130-132:309-21. [PMID: 11306054 DOI: 10.1016/s0009-2797(00)00274-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Multiple cytosolic thyroid-hormone-binding proteins (CTBPs) with varying characteristics, depending on the species and tissue, have been reported. We first purified a 59-kDa CTBP from Xenopus liver (xCTBP), and found that it is responsible for major [125I]T(3)-binding activity in Xenopus liver cytosol. Amino acid sequencing of internal peptide fragments derived from xCTBP demonstrated high identity to the corresponding sequence of mammalian aldehyde dehydrogenases 1 (ALDH1). To confirm whether or not xCTBP is identical to xALDH1, we isolated cDNAs encoding xALDH1 from an adult Xenopus hepatic cDNA library. The amino acid sequences deduced from the two isolated xALDH1 cDNAs were very similar to those of mammalian ALDH1 enzymes. The recombinant xALDH1 protein exhibited both T(3)-binding activity and ALDH activity converting retinal to retinoic acid (RA), which were similar to those of xCTBP purified from liver cytosol. The T(3)-binding activity was inhibited by NAD, while the ALDH activity was inhibited by thyroid hormones. Our results demonstrate that xCTBP is identical to ALDH1 and suggest that this protein might modulate RA synthesis and intracellular concentration of free T(3). Communications between thyroid hormone and retinoid pathways are discussed.
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Affiliation(s)
- K Yamauchi
- Department of Biology, Faculty of Science, Shizuoka University, 836 Oya, 422-8529, Shizuoka, Japan.
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Yamauchi K, Nakajima J, Hayashi H, Horiuchi R, Tata JR. Xenopus cytosolic thyroid hormone-binding protein (xCTBP) is aldehyde dehydrogenase catalyzing the formation of retinoic acid. J Biol Chem 1999; 274:8460-9. [PMID: 10085078 DOI: 10.1074/jbc.274.13.8460] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amino acid sequencing of an internal peptide fragment derived from purified Xenopus cytosolic thyroid hormone-binding protein (xCTBP) demonstrates high similarity to the corresponding sequence of mammalian aldehyde dehydrogenase 1 (ALDH1) (Yamauchi, K., and Tata, J. R. (1994) Eur. J. Biochem. 225, 1105-1112). Here we show that xCTBP was co-purified with ALDH and 3,3',5-triiodo-L-thyronine (T3) binding activities. By photoaffinity labeling with [125I]T3, a T3-binding site in the xCTBP was estimated to reside in amino acid residues 93-114, which is distinct from the active site of the enzyme but present in the NAD+ binding domain. The amino acid sequences deduced from the two isolated xALDH1 cDNAs (xALDH1-I and xALDH1-II) were 94.6% identical to each other and very similar to those of mammalian ALDH1 enzymes. The two recombinant xALDH1 proteins exhibit both T3 binding activity and ALDH activity converting retinal to retinoic acid (RA), which are similar to those of xCTBP. The mRNAs were present abundantly in kidney and intestine of adult female Xenopus. Interestingly, their T3 binding activities were inhibited by NAD+ and NADH but not by NADP+ and NADPH, whereas NAD+ was required for their ALDH activities. Our results demonstrate that xCTBP is identical to ALDH1 and suggest that this protein might modulate RA synthesis and intracellular level of free T3.
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Affiliation(s)
- K Yamauchi
- Department of Biology, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
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10
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Yamauchi K, Tata JR. Tissue-dependent and developmentally regulated cytosolic thyroid-hormone-binding proteins (CTBPs) in Xenopus. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1997; 118:27-32. [PMID: 9366033 DOI: 10.1016/s0742-8413(97)00077-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Xenopus cytosolic thyroid-hormone-binding proteins (CTBPs) were examined by a photoaffinity labeling and [125I]T3-binding assay. An affinity-labeled protein of 59 kDa, which was responsible for the major T3-binding activity in adult tissues, was predominant in liver. The 59-kDa CTBP first appeared in significant amounts at the metamorphic climax stage in liver cytosol and continued to be expressed after metamorphosis. Another affinity-labeled CTBP of 38 kDa appeared at the metamorphic climax stage in cytosol from head region, but disappeared after this stage. T3-binding assay using whole cytosol showed that a distinct CTBP, although not photoaffinity-labeled, was present in cytosol from hindlimb bud and gradually disappeared as the hindlimb grew. The cytosol from liver, head region, and hindlimb bud contained high affinity binding sites for T3 with Kd values ranging from 10(-9) to 10(-8) M. These results suggest that there are at least three distinct CTBPs in Xenopus cytosol, which are expressed in a tissue-dependent and developmentally regulated manner.
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Affiliation(s)
- K Yamauchi
- Department of Biology, Faculty of Science, Shizuoka University, Japan.
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11
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Guthapfel R, Gueguen P, Quemeneur E. Reexamination of hormone-binding properties of protein disulfide-isomerase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 242:315-9. [PMID: 8973649 DOI: 10.1111/j.1432-1033.1996.0315r.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Protein disulfide-isomerase (PDI), an abundant multifunctional protein, has been described as a 3,3',5-triiodo-L-thyronine (T3)-binding protein. As pointed out by several authors, the physiological significance of this hormone-binding property has not been fully addressed. To clarify this point, we have analyzed the T3-binding properties of purified PDI. At equilibrium, T3 binds PDI at two binding sites: first, at a high-affinity site with a Kd of 21 nM and a Bmax of 1.8 x 10(-3) mol T3/mol PDI monomer, and second at a very low affinity site that is unsaturated up to 100 microM T3. Thus, T3 binding is mainly non-specific and the specific part represents only about 0.2% of the protein monomer. Cross-linking experiments at a concentration where mainly specific binding occurs indicate that PDI does not bind L-T3 exclusively; a wide variety of analogs are also bound. Refolding of reduced denatured ribonuclease A by PDI is inhibited by T3 and analogs, and the inhibition profile reflects the binding properties very closely. Since purified PDI displays neither the specificity expected for a physiological receptor, nor significant T3-binding activity, results are discussed in terms of a necessary PDI association with another component to form a T3 receptor.
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Affiliation(s)
- R Guthapfel
- Commissariat à l'Energie Atomique, Département d'Ingénierie et d'Etudes des Protéines, Gif-sur-Yvette, France
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Yamauchi K, Tata JR. Purification and characterization of a cytosolic thyroid-hormone-binding protein (CTBP) in Xenopus liver. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 225:1105-12. [PMID: 7957201 DOI: 10.1111/j.1432-1033.1994.1105b.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A variety of cytosolic thyroid-hormone-binding proteins with different characteristics have previously been reported. Here, we first describe the thyroid-hormone-binding characteristics of adult Xenopus liver cytosol, then a novel procedure for purifying cytosolic thyroid-hormone-binding protein (CTBP) from Xenopus liver (xCTBP). The procedure consists of combining preparative isoelectrofocusing, FPLC cation-exchange chromatography, HPLC hydrophobic-interaction chromatography and ultraviolet light cross-linking of 125I-labeled 3,3'5-triiodo-L-thyronine (T3). The isolated xCTBP thus prepared retained all the characteristics of the major thyroid- hormone-(TH)-binding component of the unfractionated cytosol. It is a monomeric protein of approximately 59 kDa with an isoelectric point of 7.0 +/- 0.1, binds T3 with a higher affinity than its analogs with a Kd of approximately 9 nM, and is sensitive to sulfhydryl agents but not to NADPH. In several respects, xCTBP differs from most CTBP-like preparations from other sources described hitherto. Microsequencing of a 23-amino-acid peptide generated from xCTBP by cyanogen bromide digestion revealed 92-100% identity of a 23-amino-acid sequence of several mammalian (amino acids 236-258) and avian (amino acids 245-267) cytosolic aldehyde dehydrogenases (ALDH); xCTBP also exhibited significant similarity of amino acid composition with rat ALDH. This novel finding of sequence identity between a CTBP and ALDH, and the diversity of CTBPs from different sources, suggest that a variety of cytosolic proteins, depending on the species and tissue, can function as thyroid-hormone-binding proteins.
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Affiliation(s)
- K Yamauchi
- Laboratory of Developmental Biochemistry, National Institute for Medical Research, London, England
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13
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Soboll S. Thyroid hormone action on mitochondrial energy transfer. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1144:1-16. [PMID: 8347656 DOI: 10.1016/0005-2728(93)90024-a] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- S Soboll
- Institut für Physiologische Chemie I, Universität Düsseldorf, Germany
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14
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Lennon AM. Purification and characterization of rat brain cytosolic 3,5,3'-triiodo-L-thyronine-binding protein. Evidence for binding activity dependent on NADPH, NADP and thioredoxin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 210:79-85. [PMID: 1446686 DOI: 10.1111/j.1432-1033.1992.tb17393.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A rat brain cytosolic 3,5,3'-triiodo-L-thyronine-(T3)-binding protein (CTBP) was purified using, successively, carboxymethyl-Sephadex, DEAE-Spherodex, T3-Sepharose-4B affinity chromatography and Sephacryl S-200. The molecular mass determined by SDS/PAGE wa 58 kDa. The binding characteristics determined by Scatchard analysis revealed a single class of binding sites with a Ka of 1.56 nM-1 and a maximal binding capacity of 7500 nmol T3/g protein. The relative binding affinities of iodothyronine analogues were D-T3 > L-T3 > L-T4 > 3,3'-5-triiodothyroacetic acid > reverse T3. The optimum pH for binding was 7.5. Purified brain CTBP was reversibly inactivated by charcoal. NADPH, NADP and thioredoxin restored binding activity to a level higher than that of the control; this effect was concentration dependent. Maximal activation was observed at 25 nM NADPH. NADP was effective only in the presence of 1 mM dithiothreitol; maximal activity was obtained at 10 nM NADP. At concentrations higher than 50 nM NADP, the binding gradually decreased. Thioredoxin in the presence of 1 mM dithiothreitol activated CTBP; maximal binding was obtained with 4 microM thioredoxin. In the presence of NADPH, NADP or thioredoxin the maximal binding capacity increased 2-4 times and the Ka was 2.6 nM-1. These results show that the activity of purified cytosolic brain T3-binding protein may be modulated by NADPH, NADP or thioredoxin.
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Affiliation(s)
- A M Lennon
- Unité de Recherche sur la Glande Thyroide et la Régulation Hormonale, Institut National de la Santé et de la Recherche Médicale, Le Kremlin Bicêtre, France
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15
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Macaulay JO, Warne GL, Krozowski ZS. The methyltrienolone binding protein of JEG-3 cells and human placenta is localized within the nucleus and is tightly associated with chromatin. J Steroid Biochem Mol Biol 1992; 42:259-65. [PMID: 1606039 DOI: 10.1016/0960-0760(92)90128-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Human placenta contains the methyltrienolone binding protein (MTBP), an androgen binding protein which is distinct from the androgen receptor. This study demonstrates that the human choriocarcinoma cell line (JEG-3) also contains the MTBP and that in both human placenta and JEG-3 cells the MTBP is located exclusively in the nucleus and in particular is associated with DNase 1 resistant chromatin.
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Affiliation(s)
- J O Macaulay
- Department of Endocrinology and Diabetes, Royal Children's Hospital, Parkville, Australia
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16
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Barlow JW, Raggatt LE, Lim CF, Topliss DJ, Stockigt JR. Characterization of cytoplasmic T3 binding sites by adsorption to hydroxyapatite: effects of drug inhibitors of T3 and relationship to glutathione-S-transferases. Thyroid 1992; 2:39-44. [PMID: 1326362 DOI: 10.1089/thy.1992.2.39] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
To facilitate studies of thyroid hormone (T3) binding to cytoplasmic proteins, we prepared monkey (M. fascicularis) liver cytosol (100,000g supernatant) and examined T3 binding using hydroxyapatite (HAP) separation. HAP adsorbs cytoplasmic and nuclear binding sites but not serum T4 binding proteins. Cytosol was incubated with [125I]T3 for 30 min at 4 degrees C and separated by adding an equal volume of HAP (15 g/100 mL). After a further incubation of 10 min, the HAP pellet was washed three times in buffer containing Triton X-100, 0.5%. With this method, a single class of T3 binding site was observed with Kd 15.8 +/- 1.2 nM, concentration 0.62 +/- 0.17 pmol/mg protein (n = 3, mean +/- SD). We used this assay to assess potential drug inhibitors of cytoplasmic binding and to evaluate the proposal that glutathione-S-transferases (GST) and cytoplasmic T3 binding proteins are identical. Displacement of [125I]T3 by unlabeled iodothyronines relative to T3 (100) was T4 58, Triac 7, rT3 7, Tetrac less than or equal to 1. This hierarchy indicates that this binding site is distinct from nuclear or serum binding sites. T3 binding was displaceable by nonsteroidal anti-inflammatory drugs (NSAID) and nonbile acid cholephils (NBAC). Half-inhibitory concentrations (microM, mean +/- SD, n greater than or equal to 3) were diclofenac 4.9 +/- 1.3, mefenamic acid 13.6 +/- 0.6, bromosulphthalein 45 +/- 3, iopanoic acid approximately 200. Amiodarone and furosemide were inactive up to 100 microM. No displacement was observed with cortisol or the bile acid taurocholate, up to 100 microM. Dithiothreitol, 5 mM, did not change binding affinity or capacity.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J W Barlow
- Ewen Downie Metabolic Unit, Alfred Hospital, Melbourne, Australia
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Novel cold-sensitive cytosolic 3,5,3'-triiodo-L-thyronine-binding proteins in human red blood cell. Isolation and characterization. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55314-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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18
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Hashizume K, Suzuki S, Ichikawa K, Takeda T, Kobayashi M. Effect of active vitamin D3 on the levels of NADPH-dependent cytosolic 3,5,3'-triiodo-L-thyronine-binding protein. Biochem Biophys Res Commun 1991; 177:388-94. [PMID: 2043122 DOI: 10.1016/0006-291x(91)91995-o] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Effect of 1 alpha-OH-vitamin D3 (1 alpha-OH-D3) and 1,25-(OH)2-vitamin D3 (1,25-(OH)2-dihydroxycholecalciferol)(1,25-(OH)2-D3) on the levels of NADPH-dependent cytosolic 3,5,3'-triiodo-L-thyronine (T3)-binding protein (CTBP) was studied in rats and cultured dRLh cells. Deprivation of rats from vitamin D decreased the activity of cytosolic NADPH-dependent T3 binding in rat kidney and liver. The decrease was restored by administration of 1 alpha-OH-D3(0.2 micrograms/kg). The activity of cytosolic NADPH-dependent T3 binding was increased in the dRLh cells by addition of 1,25-(OH)2-D3 to the culture medium. The maximal binding capacity (MBC) was increased by 1,25-(OH)2-D3 without changes in the affinity constant. These results suggested that active vitamin D3 plays an important role in the regulation of cellular T3 translocation through increasing the binding capacity of NADPH-dependent cytosolic T3-binding protein.
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Affiliation(s)
- K Hashizume
- Department of Geriatrics, Endocrinology and Metabolism, Shinshu University School of Medicine, Matsumoto, Japan
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Abstract
Cellular binding proteins of thyroid hormones are present in the cell nucleus, cytosol, cell membrane, and mitochondria. While nuclear binding is proven to mediate hormone action, the exact roles of the other binding sites remain to be established. Nuclear receptor associates with DNA, core histone, and nuclear matrix and preferentially distributes in transcriptionally active chromatin due to interaction with H1 histone. Of particular importance is the binding of nuclear receptor to specific DNA sequences of target genes, termed thyroid-responsive elements. The binding is stabilized by non-receptor nuclear protein. Upon binding thyroid hormone, nuclear receptor is activated through alterations in the steric configuration, leading to changes in the rate of transcription of the target genes. Multiple nuclear receptor forms exist with likely distinct functional roles. Cytosolic thyroid hormone binding proteins are also heterogeneous. One form is under the control of cell metabolism (NADP and NADPH) and it may have a role in transport of the hormone to mitochondria and nucleus. Membrane-linked thyroid hormone binding proteins may have dual functional roles: one is to mediate hormone action and the other is to support active uptake of hormones by cells. Mitochondrial function may be regulated by thyroid hormone through mitochondrial binding sites in cooperation with nuclear receptor-mediated pathway. Further studies are required to elucidate the exact functional roles of non nuclear thyroid hormone binding proteins.
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Affiliation(s)
- K Ichikawa
- Department of Geriatrics, Shinshu University School of Medicine, Nagano, Japan
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Affiliation(s)
- L J DeGroot
- Department of Medicine, University of Chicago, IL 60637
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Hashizume K, Miyamoto T, Ichikawa K, Yamauchi K, Sakurai A, Ohtsuka H, Kobayashi M, Nishii Y, Yamada T. Evidence for the Presence of Two Active Forms of Cytosolic 3,5,3′-Triiodo-L-thyronine (T3)-binding Protein (CTBP) in Rat Kidney. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83671-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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