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Davis PJ, Mousa SA, Lin HY. Nongenomic Actions of Thyroid Hormone: The Integrin Component. Physiol Rev 2020; 101:319-352. [PMID: 32584192 DOI: 10.1152/physrev.00038.2019] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The extracellular domain of plasma membrane integrin αvβ3 contains a cell surface receptor for thyroid hormone analogues. The receptor is largely expressed and activated in tumor cells and rapidly dividing endothelial cells. The principal ligand for this receptor is l-thyroxine (T4), usually regarded only as a prohormone for 3,5,3'-triiodo-l-thyronine (T3), the hormone analogue that expresses thyroid hormone in the cell nucleus via nuclear receptors that are unrelated structurally to integrin αvβ3. At the integrin receptor for thyroid hormone, T4 regulates cancer and endothelial cell division, tumor cell defense pathways (such as anti-apoptosis), and angiogenesis and supports metastasis, radioresistance, and chemoresistance. The molecular mechanisms involve signal transduction via mitogen-activated protein kinase and phosphatidylinositol 3-kinase, differential expression of multiple genes related to the listed cell processes, and regulation of activities of other cell surface proteins, such as vascular growth factor receptors. Tetraiodothyroacetic acid (tetrac) is derived from T4 and competes with binding of T4 to the integrin. In the absence of T4, tetrac and chemically modified tetrac also have anticancer effects that culminate in altered gene transcription. Tumor xenografts are arrested by unmodified and chemically modified tetrac. The receptor requires further characterization in terms of contributions to nonmalignant cells, such as platelets and phagocytes. The integrin αvβ3 receptor for thyroid hormone offers a large panel of cellular actions that are relevant to cancer biology and that may be regulated by tetrac derivatives.
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Affiliation(s)
- Paul J Davis
- Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Rensselaer, New York; Department of Medicine, Albany Medical College, Albany, New York; Ph.D. Program for Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; Taipei Cancer Center, Taipei Medical University, Taipei, Taiwan; and Traditional Herbal Medicine Research Center of Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan
| | - Shaker A Mousa
- Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Rensselaer, New York; Department of Medicine, Albany Medical College, Albany, New York; Ph.D. Program for Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; Taipei Cancer Center, Taipei Medical University, Taipei, Taiwan; and Traditional Herbal Medicine Research Center of Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan
| | - Hung-Yun Lin
- Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Rensselaer, New York; Department of Medicine, Albany Medical College, Albany, New York; Ph.D. Program for Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; Taipei Cancer Center, Taipei Medical University, Taipei, Taiwan; and Traditional Herbal Medicine Research Center of Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan
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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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Hallen A, Jamie JF, Cooper AJL. Lysine metabolism in mammalian brain: an update on the importance of recent discoveries. Amino Acids 2013; 45:1249-72. [PMID: 24043460 DOI: 10.1007/s00726-013-1590-1] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 08/29/2013] [Indexed: 12/23/2022]
Abstract
The lysine catabolism pathway differs in adult mammalian brain from that in extracerebral tissues. The saccharopine pathway is the predominant lysine degradative pathway in extracerebral tissues, whereas the pipecolate pathway predominates in adult brain. The two pathways converge at the level of ∆(1)-piperideine-6-carboxylate (P6C), which is in equilibrium with its open-chain aldehyde form, namely, α-aminoadipate δ-semialdehyde (AAS). A unique feature of the pipecolate pathway is the formation of the cyclic ketimine intermediate ∆(1)-piperideine-2-carboxylate (P2C) and its reduced metabolite L-pipecolate. A cerebral ketimine reductase (KR) has recently been identified that catalyzes the reduction of P2C to L-pipecolate. The discovery that this KR, which is capable of reducing not only P2C but also other cyclic imines, is identical to a previously well-described thyroid hormone-binding protein [μ-crystallin (CRYM)], may hold the key to understanding the biological relevance of the pipecolate pathway and its importance in the brain. The finding that the KR activity of CRYM is strongly inhibited by the thyroid hormone 3,5,3'-triiodothyronine (T3) has far-reaching biomedical and clinical implications. The inter-relationship between tryptophan and lysine catabolic pathways is discussed in the context of shared degradative enzymes and also potential regulation by thyroid hormones. This review traces the discoveries of enzymes involved in lysine metabolism in mammalian brain. However, there still remain unanswered questions as regards the importance of the pipecolate pathway in normal or diseased brain, including the nature of the first step in the pathway and the relationship of the pipecolate pathway to the tryptophan degradation pathway.
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Affiliation(s)
- André Hallen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Balaclava Road, North Ryde, NSW, 2109, Australia,
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Eguchi R, Ishihara A, Yamauchi K. Interaction of diethylstilbestrol and ioxynil with transthyretin in chicken serum. Comp Biochem Physiol C Toxicol Pharmacol 2008; 147:345-50. [PMID: 18243807 DOI: 10.1016/j.cbpc.2008.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Revised: 12/23/2007] [Accepted: 01/03/2008] [Indexed: 11/28/2022]
Abstract
The association of suspected endocrine-disrupting chemicals (EDCs), diethylstilbestrol (DES), ioxynil and pentachlorophenol (PCP), with chicken serum proteins was investigated in relation to thyroid system disruption. All of these chemicals strongly inhibited l-[(125)I]thyroxine ([(125)I]T(4)) binding to purified transthyretin (TTR) whereas PCP was less potent inhibitor than DES and ioxynil of [(125)I]T(4) binding to diluted whole chicken serum. This result suggested that PCP interacted with serum proteins other than TTR in whole chicken serum. Following the incubation of chicken serum with each chemical (final concentrations 0.25-1.0 microM), serum proteins were fractionated by gel filtration chromatography (Cellulofine GCL-1000) and affinity chromatography (human retinol-binding protein coupled to Sepharose 4B). Although all chemicals were detected in the gel filtration chromatography 50-100 kDa fractions, DES and ioxynil, but not PCP, were co-eluted with TTR during affinity chromatography. Our results indicated that a significant proportion of DES and ioxynil, but a low proportion of PCP, interacted with TTR in whole chicken serum.
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Affiliation(s)
- Ryoji Eguchi
- Graduate School of Science and Engineering; Shizuoka University, Shizuoka, 422-8529, Japan
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Kudo Y, Yamauchi K, Fukazawa H, Terao Y. In vitro and in vivo analysis of the thyroid system-disrupting activities of brominated phenolic and phenol compounds in Xenopus laevis. Toxicol Sci 2006; 92:87-95. [PMID: 16627555 DOI: 10.1093/toxsci/kfj204] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigated the effects of the brominated phenolic and phenol compounds, some of which are brominated flame retardants, on the binding of (125)I-3,3',5-L-triiodothyronine ((125)I-T(3)) to purified Xenopus laevis transthyretin (xTTR) and to the ligand-binding domain of X. laevis thyroid hormone receptor beta (xTR LBD), on the induction of a T(3)-responsive reporter gene in a recombinant X. laevis cell line (XL58-TRE-Luc) and on T(3)-induced or spontaneous metamorphosis in X. laevis tadpoles. Of the brominated phenolic and phenol compounds tested, 3,3',5-tribromobisphenol A and 3,3'-dibromobisphenol A were the most potent competitors of (125)I-T(3) binding to xTTR and the xTR LBD, respectively. Structures with a bromine in either ortho positions with respect to the hydroxy group competed more efficiently with T(3) binding to xTTR and the xTR LBD. 3,3',5-Tribromobisphenol A and 3,3',5,5'-tetrabromobisphenol A, at 0.1-1.0 microM, exerted both T(3) agonist and antagonist activities in the T(3)-responsive reporter gene assay. Sera obtained from fetal bovine and bullfrog tadpoles weakened the T(3) agonist and antagonist activities of 3,3',5-tribromobisphenol A, but not the T(3) antagonist activity of o-t-butylphenol, for which xTTR has no significant affinity. The T(3) agonist and antagonist activities of 0.5 microM 3,3',5-tribromobisphenol A were confirmed in the in vivo, short-term gene expression assay in premetamorphic X. laevis tadpoles using endogenous, T(3)-responsive genes as molecular markers. Our results suggest that 3,3',5-tribromobisphenol A affects T(3) binding to xTTR and xTR and that it interferes with the intracellular T(3) signaling pathway.
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Affiliation(s)
- Yumiko Kudo
- Department of Biology, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan
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Murata T, Yamauchi K. Low-temperature arrest of the triiodothyronine-dependent transcription in Rana catesbeiana red blood cells. Endocrinology 2005; 146:256-64. [PMID: 15471964 DOI: 10.1210/en.2004-1090] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We examined possible molecular mechanisms for the low-temperature arrest of T3-induced Rana catesbeiana metamorphosis. Scatchard plots revealed that the ratios of maximum binding capacity/dissociation constant for high-affinity sites of tadpole serum proteins for T3 at 20 and 28 C was 3.3-4.6 times less than that at 4 C, due to the decrease in maximum binding capacity values. Kinetic studies of T3 uptake into tadpole red blood cells demonstrated that the ratio of maximum uptake rate/Michaelis constant at 23 C was approximately 13 times greater than that at 4 C. The process of intracellular transport of T3 into the nucleus was not arrested at 4 C. The ratio of T3 incorporated into nuclei to that taken up into red blood cells was not significantly different at 4, 20, and 28 C, indicating the absence of temperature-sensitive sites in this process. T3 binding to the T3 receptors alpha and beta were not temperature sensitive at least at 4 and 20 C. Transcription of the tr genes, early primary T3 response genes, was activated by 10 nM T3 at 20 and 28 C but was barely detected at 4 C. These results indicate that the major molecular event causing the low-temperature arrest of amphibian metamorphosis occurs after T3 entry into the nucleus but before or during the transcriptional activation of the tr genes. Plasma proteins binding T3 and the cellular thyroid hormone uptake system on the plasma membrane may contribute to the slowing of the incorporation of T3 into nucleus at 4 C by decreasing the uptake velocity of T3.
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Affiliation(s)
- Tomonori Murata
- Department of Biology, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
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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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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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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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Reymond MJ, Lemarchand-Béraud T. Effects of thyroid hormones on the hypothalamic dopaminergic neurons. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1990; 274:257-70. [PMID: 2239427 DOI: 10.1007/978-1-4684-5799-5_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- M J Reymond
- Department of Internal Medicine, C.H.U.V., Lausanne, Switzerland
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Ishigaki S, Abramovitz M, Listowsky I. Glutathione-S-transferases are major cytosolic thyroid hormone binding proteins. Arch Biochem Biophys 1989; 273:265-72. [PMID: 2774553 DOI: 10.1016/0003-9861(89)90483-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Thyroid hormone binding proteins of rat liver cytosol were characterized. Glutathione-S-transferases were identified among major cytosolic proteins adsorbed by thyroxine affinity matrices. The Ya and Yb subunits of the glutathione-S-transferases were also principal proteins of cytosol covalently labeled with 3,3',5-triiodo-L-thyronine (T3) or 3,3',5,5'-tetraiodo-L-thyronine (T4) by photoaffinity methods. T3 and T4, but not L-thyronine or iodinated tyrosines, were bound with high affinity to purified glutathione-S-transferases and were potent inhibitors of their enzymatic activities. These results suggest that glutathione-S-transferases have the potential to function in the intracellular binding and transport of thyroid hormones. The proteins provide a means for regulating the action and metabolism of thyroid hormones by acting as high capacity binding components.
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Affiliation(s)
- S Ishigaki
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
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Blondeau JP, Osty J, Francon J. Characterization of the thyroid hormone transport system of isolated hepatocytes. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)69122-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Chapter 5 Mechanism of action of thyroid hormone. ACTA ACUST UNITED AC 1988. [DOI: 10.1016/s0167-7306(08)60640-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Francon J, Osty J, Chantoux F, Lennon AM. Cellular location of cytosolic triiodothyronine binding protein in primary cultures of fetal rat brain. Mol Cell Endocrinol 1985; 39:197-207. [PMID: 2984063 DOI: 10.1016/0303-7207(85)90063-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The evolution of a cytosolic triiodothyronine (T3) binding protein was studied in primary cultures of fetal rat brain. These cultures exhibited neuronal characteristics during the first week. T3 binding activity in cell supernatants increased during this period from 39 +/- 7 (mean +/- SD) to 159 +/- 24 fmoles T3/culture flask. A similar increase was observed in the soluble proteins. After day 8, neuronal death occurred and glial cells multiplied and differentiated. On day 11 an 86% drop in the binding activity was observed (24 +/- 7 fmoles T3/culture flask); the pool of soluble proteins remained stable. Scatchard analysis revealed two types of binding site in both 7- and 14-day cultured cell cytosols. Binding affinities were similar in both cytosols (KA1 approximately 1.5 X 10(9) M-1, KA2 approximately 1 X 10(8) M-1); in contrast, the number of sites was 4-fold smaller in 14-day cytosols. In subcultures mostly composed of glial cells, almost the same affinities were measured, but the numbers of both types of sites were 20 times smaller than in 7-day cells. These results show that in cell cultures from embryonic rat telencephalon, cytosolic T3 binding protein is mainly located in the neurons.
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Puymirat J. Effects of dysthyroidism on central catecholaminergic neurons. Neurochem Int 1985; 7:969-77. [DOI: 10.1016/0197-0186(85)90145-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/1984] [Accepted: 10/22/1984] [Indexed: 10/27/2022]
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Nunez J. Microtubules and brain development: The effects of thyroid hormones. Neurochem Int 1985; 7:959-68. [DOI: 10.1016/0197-0186(85)90144-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/1984] [Accepted: 10/17/1984] [Indexed: 11/30/2022]
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Lennon AM, Chantoux F, Osty J, Francon J. A high affinity thyroid hormone binding protein in the cytosol of embryonic rat brain cells in primary cultures. Biochem Biophys Res Commun 1983; 116:901-8. [PMID: 6316973 DOI: 10.1016/s0006-291x(83)80227-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A thyroid hormone binding protein(s) has been characterized in the cytosol of fetal rat brain cells in primary cultures. This protein is closely related to the one described in brain supernatants with respect to its electrophoretic mobility, binding kinetic parameters and estimated molecular weight (65 000 daltons). However, in contrast to the brain cytosolic binding protein, two classes of affinity sites for triiodothyronine (T3) and thyroxine (T4) have been demonstrated: a high affinity site (KA = 1.2-3.7(3) X 10(9) M-1 for T3 and KA = 3.7-5 X 10(8) M-1 for T4) and a low affinity site (KA = 0.8-1.4 X 10(8) M-1 for T3 and 1.6-2.9 X 10(7) M-1 for T4). The results are discussed with respect to their cellular significance.
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