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Ortiga-Carvalho TM, Chiamolera MI, Pazos-Moura CC, Wondisford FE. Hypothalamus-Pituitary-Thyroid Axis. Compr Physiol 2016; 6:1387-428. [PMID: 27347897 DOI: 10.1002/cphy.c150027] [Citation(s) in RCA: 213] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The hypothalamus-pituitary-thyroid (HPT) axis determines the set point of thyroid hormone (TH) production. Hypothalamic thyrotropin-releasing hormone (TRH) stimulates the synthesis and secretion of pituitary thyrotropin (thyroid-stimulating hormone, TSH), which acts at the thyroid to stimulate all steps of TH biosynthesis and secretion. The THs thyroxine (T4) and triiodothyronine (T3) control the secretion of TRH and TSH by negative feedback to maintain physiological levels of the main hormones of the HPT axis. Reduction of circulating TH levels due to primary thyroid failure results in increased TRH and TSH production, whereas the opposite occurs when circulating THs are in excess. Other neural, humoral, and local factors modulate the HPT axis and, in specific situations, determine alterations in the physiological function of the axis. The roles of THs are vital to nervous system development, linear growth, energetic metabolism, and thermogenesis. THs also regulate the hepatic metabolism of nutrients, fluid balance and the cardiovascular system. In cells, TH actions are mediated mainly by nuclear TH receptors (210), which modify gene expression. T3 is the preferred ligand of THR, whereas T4, the serum concentration of which is 100-fold higher than that of T3, undergoes extra-thyroidal conversion to T3. This conversion is catalyzed by 5'-deiodinases (D1 and D2), which are TH-activating enzymes. T4 can also be inactivated by conversion to reverse T3, which has very low affinity for THR, by 5-deiodinase (D3). The regulation of deiodinases, particularly D2, and TH transporters at the cell membrane control T3 availability, which is fundamental for TH action. © 2016 American Physiological Society. Compr Physiol 6:1387-1428, 2016.
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Affiliation(s)
- Tania M Ortiga-Carvalho
- Institute of Biophysics Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro, Brazil
| | - Maria I Chiamolera
- Department of Medicine, Escola Paulista de Medicina, Universidade Federal de Sao Paulo, Sao Paulo, Brazil
| | - Carmen C Pazos-Moura
- Institute of Biophysics Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro, Brazil
| | - Fredic E Wondisford
- Department of Medicine, Rutgers-Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA
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Decherf S, Seugnet I, Becker N, Demeneix BA, Clerget-Froidevaux MS. Retinoic X receptor subtypes exert differential effects on the regulation of Trh transcription. Mol Cell Endocrinol 2013; 381:115-23. [PMID: 23896434 DOI: 10.1016/j.mce.2013.07.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 07/19/2013] [Accepted: 07/19/2013] [Indexed: 02/07/2023]
Abstract
How Retinoid X receptors (RXR) and thyroid hormone receptors (TR) interact on negative TREs and whether RXR subtype specificity is determinant in such regulations is unknown. In a set of functional studies, we analyzed RXR subtype effects in T3-dependent repression of hypothalamic thyrotropin-releasing hormone (Trh). Two-hybrid screening of a hypothalamic paraventricular nucleus cDNA bank revealed specific, T3-dependent interaction of TRs with RXRβ. In vivo chromatin immuno-precipitation showed recruitment of RXRs to the TRE-site 4 region of the Trh promoter in the absence of T3. In vivo overexpression of RXRα in the mouse hypothalamus heightened T3-independent Trh transcription, whereas RXRβ overexpression abrogated this activity. Loss of function of RXRα and β by shRNAs induced inverse regulations. Thus, RXRα and RXRβ display specific roles in modulating T3-dependent regulation of Trh. These results provide insight into the actions of these different TR heterodimerization partners within the context of a negatively regulated gene.
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Affiliation(s)
- Stéphanie Decherf
- CNRS UMR 7221-USM 501, «Evolution of Endocrine Regulations», «Regulations, Development and Molecular Diversity» Department, Muséum National d'Histoire Naturelle, 57 rue Cuvier, CP 32, 75231 Paris Cedex 5, France
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Chiappini F, Ramadoss P, Vella KR, Cunha LL, Ye FD, Stuart RC, Nillni EA, Hollenberg AN. Family members CREB and CREM control thyrotropin-releasing hormone (TRH) expression in the hypothalamus. Mol Cell Endocrinol 2013; 365:84-94. [PMID: 23000398 PMCID: PMC3572472 DOI: 10.1016/j.mce.2012.09.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 09/05/2012] [Accepted: 09/11/2012] [Indexed: 01/19/2023]
Abstract
Thyrotropin-releasing hormone (TRH) in the paraventricular nucleus (PVN) of the hypothalamus is regulated by thyroid hormone (TH). cAMP response element binding protein (CREB) has also been postulated to regulate TRH expression but its interaction with TH signaling in vivo is not known. To evaluate the role of CREB in TRH regulation in vivo, we deleted CREB from PVN neurons to generate the CREB1(ΔSIM1) mouse. As previously shown, loss of CREB was compensated for by an up-regulation of CREM in euthyroid CREB1(ΔSIM1) mice but TSH, T₄ and T₃ levels were normal, even though TRH mRNA levels were elevated. Interestingly, TRH mRNA expression was also increased in the PVN of CREB1(ΔSIM1) mice in the hypothyroid state but became normal when made hyperthyroid. Importantly, CREM levels were similar in CREB1(ΔSIM1) mice regardless of thyroid status, demonstrating that the regulation of TRH by T₃ in vivo likely occurs independently of the CREB/CREM family.
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Affiliation(s)
- Franck Chiappini
- Division of Endocrinology, Diabetes and Metabolism. Beth Israel Deaconess Medical Center and Harvard Medical School. Center of Life Science, Boston, MA, 02115. ; ; ; ; ;
- Address correspondence and reprint request to: Dr. Franck Chiappini or Dr. Anthony Hollenberg, MD, 330 Brookline Avenue, E/CLS 0728, MA, 02215. Tel: 617-735-3268. Fax: 617-735-3323; ,
| | - Preeti Ramadoss
- Division of Endocrinology, Diabetes and Metabolism. Beth Israel Deaconess Medical Center and Harvard Medical School. Center of Life Science, Boston, MA, 02115. ; ; ; ; ;
| | - Kristen R. Vella
- Division of Endocrinology, Diabetes and Metabolism. Beth Israel Deaconess Medical Center and Harvard Medical School. Center of Life Science, Boston, MA, 02115. ; ; ; ; ;
| | - Lucas L. Cunha
- Division of Endocrinology, Diabetes and Metabolism. Beth Israel Deaconess Medical Center and Harvard Medical School. Center of Life Science, Boston, MA, 02115. ; ; ; ; ;
| | - Felix D. Ye
- Division of Endocrinology, Diabetes and Metabolism. Beth Israel Deaconess Medical Center and Harvard Medical School. Center of Life Science, Boston, MA, 02115. ; ; ; ; ;
| | - Ronald C. Stuart
- Division of Endocrinology, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Providence, RI 02903. ;
| | - Eduardo A. Nillni
- Division of Endocrinology, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Providence, RI 02903. ;
| | - Anthony N. Hollenberg
- Division of Endocrinology, Diabetes and Metabolism. Beth Israel Deaconess Medical Center and Harvard Medical School. Center of Life Science, Boston, MA, 02115. ; ; ; ; ;
- Address correspondence and reprint request to: Dr. Franck Chiappini or Dr. Anthony Hollenberg, MD, 330 Brookline Avenue, E/CLS 0728, MA, 02215. Tel: 617-735-3268. Fax: 617-735-3323; ,
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Jiang X, Cai Z, Zhao X, Zhang L, Chen Z, Wang Y, Guo X, Xu N. Mapping, CDNA Cloning and Tissue Expression of the Porcine Thyrotropin-Releasing Hormone Receptor Gene. Anim Biotechnol 2011; 22:30-6. [DOI: 10.1080/10495398.2011.547745] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Matre V, Høvring PI, Fjeldheim AK, Helgeland L, Orvain C, Andersson KB, Gautvik KM, Gabrielsen OS. The human neuroendocrine thyrotropin-releasing hormone receptor promoter is activated by the haematopoietic transcription factor c-Myb. Biochem J 2003; 372:851-9. [PMID: 12628004 PMCID: PMC1223435 DOI: 10.1042/bj20030057] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2003] [Revised: 03/03/2003] [Accepted: 03/10/2003] [Indexed: 01/14/2023]
Abstract
Thyrotropin-releasing hormone (TRH) receptor (TRHR) is a G-protein-coupled receptor playing a crucial role in the anterior pituitary where it controls the synthesis and secretion of thyroid-stimulating hormone and prolactin. Its widespread presence not only in the central nervous system, but also in peripheral tissues, including thymus, indicates other important, but unknown, functions. One hypothesis is that the neuropeptide TRH could play a role in the immune system. We report here that the human TRHR promoter contains 11 putative response elements for the haematopoietic transcription factor c-Myb and is highly Myb-responsive in transfection assays. Analysis of Myb binding to putative response elements revealed one preferred binding site in intron 1 of the receptor gene. Transfection studies of promoter deletions confirmed that this high-affinity element is necessary for efficient Myb-dependent transactivation of reporter plasmids in CV-1 cells. The Myb-dependent activation of the TRHR promoter was strongly suppressed by expression of a dominant negative Myb-Engrailed fusion. In line with these observations, reverse transcriptase PCR analysis of rat tissues showed that the TRHR gene is expressed both in thymocytes and bone marrow. Furthermore, specific, high-affinity TRH agonist binding to cell-surface receptors was demonstrated in thymocytes and a haematopoietic cell line. Our findings imply a novel functional link between the neuroendocrine and the immune systems at the level of promoter regulation.
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Affiliation(s)
- Vilborg Matre
- Department of Biochemistry, University of Oslo, P.O. Box 1041 Blindern, Norway.
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Harder S, Dammann O, Buck F, Zwiers H, Lederis K, Richter D, Bruhn TO. Cloning of two thyrotropin-releasing hormone receptor subtypes from a lower vertebrate (Catostomus commersoni): functional expression, gene structure, and evolution. Gen Comp Endocrinol 2001; 124:236-45. [PMID: 11703088 DOI: 10.1006/gcen.2001.7709] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A PCR approach was used to clone thyrotropin-releasing hormone receptors (TRH-R) from the brain and anterior pituitary of the teleost Catostomus commersoni (cc), the white sucker. Two distinct TRH-R, designated ccTRH-R1 and ccTRH-R2, were identified. ccTRH-R1 was similar to mammalian TRH-R of the subtype 1, whereas ccTRH-R2 exhibited the highest identity (61% at the amino acid level) with the recently discovered rat TRH-R2. It is postulated that ccTRH-R2 and rat TRH-R2 are members of the same TRH-R subfamily 2. Functional expression of ccTRH receptors in human embryonic kidney cells and in Xenopus laevis oocytes demonstrated that both ccTRH receptors were fully functional in both systems. Oocytes expressing either receptor responded to the application of TRH by an induction of membrane chloride currents, indicating that ccTRH-R of both subtypes are coupled to the inositol phosphate/calcium pathway. The analysis of genomic clones revealed, for the first time, both similarities and differences in the structure of TRH-R subtype genes. Both ccTRH-R genes contained an intron within the coding region at the beginning of transmembrane domain (TM) 6. The position of this intron is highly conserved, as it was found at an identical position in the human TRH-R1 gene. The ccTRH-R2 gene contained an additional intron at the end of TM 3 that was not found in any of the TRH-R1 genes identified so far. The analysis of the gene structure of ccTRH-R and the amino acid sequence comparisons of mammalian and teleost TRH-R of both subtypes suggest that TRH receptors have been highly conserved during the course of vertebrate evolution. A common ancestral TRH receptor gene that could be found much earlier in evolution, possibly in invertebrates, might be the origin of ccTRH-R genes.
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Affiliation(s)
- S Harder
- Institut für Zellbiochemie und klinische Neurobiologie, Universität Hamburg, Martinistrasse 52, Hamburg, D-20246, Germany
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Kim K, Arai K, Sanno N, Teramoto A, Shibasaki T. The expression of thyrotrophin-releasing hormone receptor 1 messenger ribonucleic acid in human pituitary adenomas. Clin Endocrinol (Oxf) 2001; 54:309-16. [PMID: 11298082 DOI: 10.1046/j.1365-2265.2001.01237.x] [Citation(s) in RCA: 15] [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
OBJECTIVE Thyrotrophin-releasing hormone (TRH) paradoxically induces the release of growth hormone (GH) when injected intravenously into acromegalic patients, although the mechanism of this action is unknown at present. Several research groups have reported that the level of TRH receptor-1 (TRHR-1) mRNA expression is variable in pituitary adenomas, and does not correlate with the degree of paradoxical GH response to TRH administration in a limited number of acromegalic patients. We aimed to compare the expression levels of TRHR-1 mRNA among various types of pituitary adenoma and to clarify whether these levels correlate with the degree of pituitary hormone response to TRH. PATIENTS Pituitary adenoma tissue was obtained by surgery from 14 patients with acromegaly, four with prolactinomas, nine with nonfunctioning adenomas and one with a TSH-producing adenoma. METHODS The level of human TRHR-1 mRNA expression in each adenoma was quantified using the competitive reverse transcription polymerase chain reaction (RT-PCR) METHOD: For amplification of a TRHR-1 cDNA fragment, a sense primer was designed according to the sequence in exon 2 and an antisense primer designed according to the sequence located at the region in exon 3 that does not encode for the alternative splicing-generated short form of TRHR-1 mRNA. RESULTS TRHR-1 mRNA was detected in all pituitary adenomas examined and did not correlate with their size. The mean level of TRHR-1 mRNA expression was significantly lower in GH-producing adenomas than in prolactinomas and nonfunctioning adenomas (1.4 +/- 0.4 x 10(-2) attomol/microg total RNA, 10.7 3.4 x 10(-2) attomol/microg total RNA, and 7.2 +/- 3.3 x 10(-2) attomol/g total RNA, respectively). The ratio of plasma peak GH induced by TRH administration to the basal level of plasma GH in the patients with acromegaly correlated positively with the level of TRHR-1 mRNA expression in their GH-producing adenomas (r = 0.620, P = 0.0179). The responsiveness of plasma PRL and gonadotrophin to TRH in the patients with prolactinoma and nonfunctioning pituitary adenoma did not significantly correlate with the levels of TRHR-1 mRNA expression in their pituitary adenomas, respectively. CONCLUSIONS The findings of the present study suggest that the level of TRHR-1 mRNA expression varies among different types of pituitary adenoma. Furthermore, in acromegaly, the responsiveness of plasma GH to TRH administration appears to at least partially depend on the level of TRHR-1 mRNA expression in the GH-producing pituitary adenoma.
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Affiliation(s)
- K Kim
- Department of Physiology, Nippon Medical School, Tokyo, Japan. Kim_Kyongsong/
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8
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Geiger A, Decaux JF, Burcelin R, Le Cam A, Salazar G, Charron MJ, Girard J, Kervran A. Structural and functional characterizations of the 5'-flanking region of the mouse glucagon receptor gene: comparison with the rat gene. Biochem Biophys Res Commun 2000; 272:912-21. [PMID: 10860851 DOI: 10.1006/bbrc.2000.2876] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A putative proximal promoter was defined previously for the mouse glucagon receptor (GR) gene. In the present study, a distal promoter was characterized upstream from a novel non-coding exon revealed by the 5'-rapid amplification of cDNA ends from mouse liver tissue. The 5'-flanking region of the mouse GR gene was cloned up to 6 kb and the structural organization was compared to the 5' untranslated region of the rat gene cloned up to 7 kb. The novel exon, separated by an intron of 3.8 kb from the first coding exon, displayed a high homology (80%) with the most distal of the two untranslated exons found in the 5' region of the rat GR gene. The mouse distal promoter region, extending up to -1 kb from the novel exon, displayed 85% identity with the rat promoter. Both contain a highly GC-rich sequence with five putative binding sites for Sp1, but no consensus TATA or CAAT elements. To evaluate basal promoter activities, 5'-flanking sequences of mouse or rat GR genes were fused to a luciferase reporter gene and transiently expressed in a mouse and in a rat cell line, respectively or in rat hepatocytes. Both mouse and rat distal promoter regions directed a high level of reporter gene activity. Deletion of the Sp1 binding sites region or mutation of the second proximal Sp1 sequence markedly reduced the distal promoter activity of the reporter gene. The mouse proximal promoter activity was 2- to 3-fold less than the distal promoter, for which no functional counterpart was observed in the similar region of the rat gene.
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Affiliation(s)
- A Geiger
- INSERM U376, CHU Arnaud de Villeneuve, Montpellier, France
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Bauer K, Schomburg L, Heuer H, Schäfer MK. Thyrotropin releasing hormone (TRH), the TRH-receptor and the TRH-degrading ectoenzyme; three elements of a peptidergic signalling system. Results Probl Cell Differ 1999; 26:13-42. [PMID: 10453458 DOI: 10.1007/978-3-540-49421-8_2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Affiliation(s)
- K Bauer
- Max-Planck-Institut für experimentelle Endokrinologie, Hannover, Germany
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10
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Høvring PI, Matre V, Fjeldheim AK, Loseth OP, Gautvik KM. Transcription of the human thyrotropin-releasing hormone receptor gene-analysis of basal promoter elements and glucocorticoid response elements. Biochem Biophys Res Commun 1999; 257:829-34. [PMID: 10208868 DOI: 10.1006/bbrc.1999.0545] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The gene for the human thyrotropin-releasing hormone receptor (TRHR) spans 35 kb and contains three exons and two introns (Matre et al. (1999) J. Neurochem. 72, 1-11). Despite a reported transcription start site (TSS) mapped to position -885 upstream of the translation initiation codon (Iwasaki et al. (1996) J. Biol. Chem. 271, 22183-8), we found cell type specific promoter activity directed by a fragment downstream of this site (-770 to +1). To elucidate the basis for this unexpected activity, we analyzed basal promoter elements in this region of the gene. One divergent TATA box, TTTAAA in position -759, was found by mutational analysis to be critical for promoter activity, providing a likely explanation for the basal activity observed. This proximal region apparently contains several promoter elements, including Pit-1 binding sequences within the first intron of the TRHR gene as previously reported. Here we describe the analysis of two putative glucocorticoid response elements (GREs) that we identified in this region, one (distal) half site overlapping the proposed TSS at -885 and one (proximal) full site within the first intron at position -624. Accordingly, stimulation of rat pituitary GH3 and GH4C1 cells with dexamethasone strongly enhanced transcription activity of a reporter construct containing the distal GRE half site and the proximal GRE site. Both sites bound the glucocorticoid receptor (GR) in a specific manner. Deletion of the distal GRE half site abolished the dexamethasone induction of CAT transcription, as did mutations in the proximal site. We therefore conclude that both sites are necessary for regulation of the TRHR gene transcription by glucocorticoids.
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Affiliation(s)
- P I Høvring
- Institute of Medical Biochemistry, University of Oslo, Blindern, Oslo, 0317, Norway.
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11
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Matre V, Høvring PI, Orstavik S, Frengen E, Rian E, Velickovic Z, Murray-McIntosh RP, Gautvik KM. Structural and functional organization of the gene encoding the human thyrotropin-releasing hormone receptor. J Neurochem 1999; 72:40-50. [PMID: 9886052 DOI: 10.1046/j.1471-4159.1999.0720040.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The thyrotropin-releasing hormone (TRH) receptor (TRHR) is widely distributed throughout the central and peripheral nervous systems. In addition to its role in controlling the synthesis and secretion of thyroid-stimulating hormone and prolactin from the anterior pituitary, TRH is believed to act as a neurotransmitter as well as a neuromodulator. We have isolated genomic lambda and P1-derived artificial chromosome clones encoding the human TRHR. The gene was found to be 35 kb with three exons and two introns. A 541-bp intron 1 (-629 to -89 relative to the translation start site) is conserved between human and mouse. A large intron 2 of 31 kb disrupts the open reading frame (starting in position +790) in the sequence encoding the supposed junction between the third intracellular loop and the putative sixth transmembrane domain. A similar intron was found in chimpanzee and sheep but not in rat and mouse. Promoter analysis of upstream regions demonstrated cell type-specific reporter activation, and sequencing of 2.5 kb of the promoter revealed putative cis-acting regulatory elements for several transcription factors that may contribute to the regulation of the TRHR gene expression. Functional analysis of potential response elements for the anterior pituitary-specific transcription factor Pit-1 revealed cell type-specific binding that was competed out with a Pit-1 response element from the GH gene promoter.
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Affiliation(s)
- V Matre
- Institute of Medical Biochemistry, University of Oslo, Norway
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12
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Kaji H, Tai S, Okimura Y, Iguchi G, Takahashi Y, Abe H, Chihara K. Cloning and characterization of the 5'-flanking region of the human growth hormone secretagogue receptor gene. J Biol Chem 1998; 273:33885-8. [PMID: 9852035 DOI: 10.1074/jbc.273.51.33885] [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: 12/28/2022] Open
Abstract
Recently, the growth hormone secretagogue receptor (GHS-R) cDNA has been isolated from the pituitary and hypothalamus. To evaluate the regulation of human (h) GHS-R gene expression, we cloned the hGHS-R gene containing the 5'-flanking region of 0.6-2.9 kilobase pairs. Analysis of the hGHS-R transcripts with 5'-rapid amplification of cDNA ends suggested that the putative transcription initiation site was approximately -453 base pairs upstream of the translation initiation site (+1). There is no typical TATA, CAAT, or GC box but an initiator-like sequence and putative binding sites for several transcription factors around the putative transcription start site. The 5'-flanking region inserted into a luciferase reporter vector had promoter activity in GH3 cells but had activity indistinguishable from background in HeLa or EP1 cells. The hGHS-R promoter activity in GH3 cells increased by deletion of nucleotides from -1224 to -734, whereas it was decreased by further deletion from -734 to -608. Knowledge of the promoter region of the hGHS-R gene will facilitate elucidation of its transcriptional control.
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Affiliation(s)
- H Kaji
- Third Division, Department of Medicine, Kobe University School of Medicine, Kobe 650-0017, Japan.
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13
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Sun YM, Millar RP, Ho H, Gershengorn MC, Illing N. Cloning and characterization of the chicken thyrotropin-releasing hormone receptor. Endocrinology 1998; 139:3390-8. [PMID: 9681487 DOI: 10.1210/endo.139.8.6133] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We report on the cloning of the full-length complementary DNA for the chicken TRH receptor. Although the TRH receptor has been cloned from several mammalian species, this is the first report from another vertebrate class. The ligand binding pocket, which is situated in the transmembrane helices of the mouse and rat TRH receptors, is completely conserved in the chicken receptor. Pharmacological studies (receptor binding and signaling) employing several TRH analogs revealed that there are no significant differences between the chicken and mouse receptors. These findings show that there have been considerable evolutionary constraints on TRH receptor structure and function. Several truncated forms of the chicken TRH receptor that appear to retain a part of an intron and are truncated in the putative third intracellular loop were also cloned, but were nonfunctional. This study provides a useful tool for further studies on the roles of TRH in avian growth and TSH regulation.
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Affiliation(s)
- Y M Sun
- Medical Research Council/University of Cape Town Research Unit for Molecular Reproductive Endocrinology, University of Cape Town, South Africa
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14
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Nakaar V, Bermudes D, Peck KR, Joiner KA. Upstream elements required for expression of nucleoside triphosphate hydrolase genes of Toxoplasma gondii. Mol Biochem Parasitol 1998; 92:229-39. [PMID: 9657328 DOI: 10.1016/s0166-6851(97)00220-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Nucleoside triphosphate hydrolase is an abundant protein secreted by the obligate protozoan parasite Toxoplasma gondii. The protein has apyrase activity, degrading ATP to the di- and mono-phosphate forms. Because T. gondii is incapable of de novo synthesis of purines, it is postulated that NTPase may be used by the parasite to salvage purines from the host cell for survival and replication. To elucidate the molecular mechanisms of NTP gene expression, we isolated from the virulent RH strain of T. gondii the putative promoter region of three tandemly repeated NTP genes (NTP1, 2, 3). Using deletion constructs linked to the chloramphenicol acetyl transferase (CAT) reporter gene, we defined an active promoter within the first 220 bp. Sequence analysis of this region reveals the lack of a TATA box, but the promoter region is associated with a sequence which resembles an initiator element (Inr) in the NTP1 and NTP3 genes. This sequence which is similar to other Inrs known to regulate the expression of a wide variety of RNA polymerase II genes, is required for NTP expression. The NTP3 promoter contains sufficient information for developmentally regulated expression of CAT activity when the actively replicating stage tachyzoite differentiates into the dormant bradyzoite form.
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Affiliation(s)
- V Nakaar
- Department of Internal Medicine 808 LCI, Yale University School of Medicine, New Haven, CT 06520-8022, USA
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Satoh T, Yamada M, Feng P, Hashimoto K, Wilber JF, Mori M. Postnatal ontogeny of the thyrotropin-releasing hormone receptor messenger ribonucleic acids in the rat forebrain. Neuropeptides 1997; 31:351-5. [PMID: 9308023 DOI: 10.1016/s0143-4179(97)90071-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Postnatal developmental change of the thyrotropin-releasing hormone receptors (TRHR) in the rat forebrain was investigated using TRH binding assays and Northern blot analyses from postnatal day 8 to the age of 2 years. TRH binding assays, with [3H]MeHisTRH as the radioactive ligand, demonstrated that the binding capacity in the forebrain was lowest at postnatal day 8 and increased to a maximum level at postnatal day 20. The TRH binding significantly decreased to adult levels between days 20 and 35, and no significant change was observed thereafter. Northern blot analysis, with a 32P-labeled TRHR cRNA probe, revealed that expression of the TRHR gene in the forebrain was not detectable on day 8 after birth, whereas apparent gene expression could be detected in the anterior pituitary. In contrast to the binding capacities, TRHR mRNA levels were very low until postnatal day 20, and increased significantly between days 20 and 35. No significant alteration in mRNA levels was observed after day 35. These results indicated that: (1) TRH binding capacities in the forebrain increased to a maximum levels between the second and third postnatal week and thereafter decreased to adult level, (2) the levels of TRHR mRNA and the TRH-binding capacities did not correlate in that period, suggesting that the TRHR number in the immature forebrain might be regulated by a posttranscriptional mechanism, and (3) expression of the TRHR gene in the forebrain and pituitary seemed to be regulated differentially during development.
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Affiliation(s)
- T Satoh
- First Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan
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16
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Reinhart J, Xiao S, Arora KK, Catt KJ. Structural organization and characterization of the promoter region of the rat gonadotropin-releasing hormone receptor gene. Mol Cell Endocrinol 1997; 130:1-12. [PMID: 9220016 DOI: 10.1016/s0303-7207(97)00064-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The gene encoding the rat gonadotropin-releasing hormone (GnRH) receptor was isolated, and its structural organization and promoter region were characterized. The gene was found to consist of three exons that encode the receptor protein, and spanned about 20 kb. Of two genomic clones analyzed, one contained the 5'-untranslated region and the first exon, and the other contained the second and third exons. The sizes of the first, second, and third exons are 625, 217, and 1476 nt, respectively. The first intron is at least 12 kb in length and is located between nucleotides 522 and 523 of the cDNA reading frame, in the middle of the fourth transmembrane domain. The second intron is about 2.5 kb and is also located in the reading frame between nucleotides 739 and 740, separating the fifth and sixth transmembrane domains. Genomic blots in combination with cloning and sequencing suggested that a single GnRH receptor gene is present in the rat genome. Primer extension indicated that the transcription start site is located 103 nt upstream of the translational start codon. A putative TATA box is positioned 23 nt in front of the transcription initiation site. The 1.8 kb 5' flanking sequence contains an SF-1 site, an AP-1 site, CCAAT sequences, a Pit-1 binding site, and a potential CRE-like sequence. To evaluate promoter activity, the 1.8 kb and two 5' deleted fragments of 1.2 and 0.6 kb were fused to the luciferase reporter gene and transiently expressed in immortalized pituitary gonadotrophs (alphaT3-1 cells) and hypothalamic neurons (GT1-7 cells), and in nonpituitary (COS-7) cells. Luciferase gene expression was significantly increased by all three fragments in pituitary and hypothalamic cells, but not in COS-7 cells. The promoter activity of the 1.2 kb fragment was higher than that of the other fragments. Forskolin and cAMP analogs increased luciferase gene expression in both alphaT3-1 and GT1-7 cells, but activation of protein kinase C by phorbol myristate acetate had no effect. These studies indicate that positive and negative regulatory elements are present within the 1.8 kb 5' flanking sequence of the GnRH receptor. Knowledge of the genomic organization and analysis of the promoter region of the rat GnRH receptor gene will facilitate the elucidation of its transcriptional control in pituitary gonadotrophs and hypothalamic neurons.
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Affiliation(s)
- J Reinhart
- Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Penhoat A, Naville D, Jaillard C, Durand P, Bégeot M. Presence of multiple functional polyadenylation signals in the 3'-untranslated region of human corticotropin receptor cDNA. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1356:249-52. [PMID: 9194567 DOI: 10.1016/s0167-4889(97)00031-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We present 2.59 kb of the 3'-non-coding region of the ACTH receptor cDNA that contains seven potential polyadenylation signals. Among these signals, five are functional as detected by 3'-RACE and are consistent with the transcripts of 1.8, 3.4 and 4 kb visualized on Northern blots. We propose that the most likely molecular mechanism for the multiple ACTH-R mRNA transcripts is the alternative use of polyadenylation signals.
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Affiliation(s)
- A Penhoat
- INSERM-INRA U 418, Hôpital Debrousse, Lyon, France.
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