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Li W, Li P, Li R, Yu Z, Sun X, Ji G, Yang X, Zhu L, Zhu S. GLP1R Single-Nucleotide Polymorphisms rs3765467 and rs10305492 Affect β Cell Insulin Secretory Capacity and Apoptosis Through GLP-1. DNA Cell Biol 2020; 39:1700-1710. [PMID: 32721233 DOI: 10.1089/dna.2020.5424] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The increased secretion of glucagon-like peptide-1 (GLP-1) after Roux-en-Y gastric bypass (RYGB) is regarded as the main reason for the improvement of blood glucose. However, the single-nucleotide polymorphisms (SNPs) of GLP-1 Receptor (GLP1R) impair receptor function, subsequently affecting β cell insulin secretion function, ultimately affecting the efficacy of RYGB. In this study, we revealed that two SNPs in GLP1R gene, rs3765467 and rs10305492, could significantly reduce the insulin secreted by β cells and the cyclic AMP concentration, whereas promote β cell apoptosis. Under high glucose exposure, rs3765467 and rs10305492 impaired β cell secretion of insulin and β cell viability in the same way; in other words, GLP1R rs3765467 and rs10305492 exert an effect on pancreatic β cell glucose-stimulated insulin secretion. Moreover, GLP-1 antagonist Exendin (9-39) further enhanced, whereas GLP-1 agonist Exendin-4 partially attenuated the effects of SNPs on the functions and apoptosis of β cells. In conclusion, the rs3765467 and rs10305492 SNPs in GLP1R show to exert a critical effect on regulating insulin secretory capacity of β cells and β cell mass. Through leading to the dysfunction and apoptosis of β cells, GLP1R rs3765467 and rs10305492 might also impair GLP-1 interaction with GLP1R, therefore attenuating the therapeutic effect of RYGB.
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Affiliation(s)
- Weizheng Li
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Pengzhou Li
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Rao Li
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Zhaomei Yu
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Xulong Sun
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Guangnian Ji
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Xiangwu Yang
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Liyong Zhu
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
| | - Shaihong Zhu
- Department of General Surgery, Third Xiangya Hospital, Central South University, Changsha, China
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Akiyama S, Ogiwara T, Aoki T, Tsunekawa K, Araki O, Murakami M. Glucagon-like peptide-1 stimulates type 3 iodothyronine deiodinase expression in a mouse insulinoma cell line. Life Sci 2014; 115:22-8. [PMID: 25241124 DOI: 10.1016/j.lfs.2014.09.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 08/14/2014] [Accepted: 09/08/2014] [Indexed: 12/25/2022]
Abstract
AIMS The pathophysiological roles of thyroid hormones in glucose metabolism remain uncertain. Type 3 iodothyronine deiodinase (D3) converts thyroxine (T4) and 3,5,3'-triiodothyronine (T3) to 3,3',5'-triiodothyronine (rT3) and 3,3'-diiodothyronine (T2), respectively, inactivating thyroid hormones in a cell-specific fashion. In the present study, we identified D3 expression in MIN6 cells derived from a mouse insulinoma cell line and examined the mechanisms regulating D3 expression in these cells. MAIN METHODS We characterized D3 activity using HPLC analysis, and examined the effect of GLP-1 or exendin-4 on D3 expression and cAMP accumulation in MIN6 cells. We also measured insulin secretion from MIN6 cells exposed to GLP-1 and T3. KEY FINDINGS We identified enzyme activity that catalyzes the conversion of T3 to T2 in MIN6 cells, which showed characteristics compatible with those for D3. D3 mRNA was identified in these cells using RT-PCR analysis. Forskolin rapidly stimulated D3 mRNA and D3 activity. Glucagon-like peptide-1 (GLP-1) increased D3 expression in a dose-dependent manner, and this effect was inhibited by the protein kinase A (PKA) inhibitor H-89. Exendin-4, a GLP-1 receptor agonist, also stimulated D3 expression in MIN6 cells. These results suggest that a cAMP-PKA-mediated pathway participates in GLP-1-stimulated D3 expression in MIN6 cells. Furthermore, GLP-1 stimulated insulin secretion was suppressed by the addition of T3 in MIN6 cells. SIGNIFICANCE Our findings indicate that GLP-1 regulates intracellular T3 concentration in pancreatic β cells via a cAMP-PKA-D3-mediated pathway that may also regulate β-cell function.
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Affiliation(s)
- Shigeo Akiyama
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Takayuki Ogiwara
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Tomoyuki Aoki
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Katsuhiko Tsunekawa
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Osamu Araki
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Masami Murakami
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan.
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Estrada JM, Soldin D, Buckey TM, Burman KD, Soldin OP. Thyrotropin isoforms: implications for thyrotropin analysis and clinical practice. Thyroid 2014; 24:411-23. [PMID: 24073798 PMCID: PMC3949435 DOI: 10.1089/thy.2013.0119] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Serum thyrotropin (TSH) is considered the single most sensitive and specific measure of thyroid function in the general population owing to its negative logarithmic association with free triiodothyronine and free thyroxine concentrations. It is therefore often the test of choice for screening, diagnosis, and monitoring of primary hypothyroidism. Serum TSH concentrations can be analyzed quantitatively using third-generation immunoassays, whereas its bioactivity can be measured by TSH activity assays in cell culture. Theoretically, if serum TSH concentrations are directly related to TSH activity, the two tests should yield comparable results. However, on occasion, the results are discordant, with serum concentrations being higher than TSH biological activity. This review focuses on the dissociation between the clinical state and serum TSH concentrations and addresses clinically important aspects of TSH analysis.
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Affiliation(s)
- Joshua M. Estrada
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia
| | - Danielle Soldin
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia
| | - Timothy M. Buckey
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia
| | - Kenneth D. Burman
- Endocrine Section, Medstar Washington Hospital Center, Washington, District of Columbia
| | - Offie P. Soldin
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia
- Department of Medicine, Georgetown University Medical Center, Washington, District of Columbia
- Department of Obstetrics and Gynecology, Georgetown University Medical Center, Washington, District of Columbia
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Ajjan RA, Weetman AP. Techniques to quantify TSH receptor antibodies. ACTA ACUST UNITED AC 2008; 4:461-8. [DOI: 10.1038/ncpendmet0886] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Accepted: 05/08/2008] [Indexed: 11/09/2022]
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Tsunekawa K, Onigata K, Morimura T, Kasahara T, Nishiyama S, Kamoda T, Mori M, Morikawa A, Murakami M. Identification and functional analysis of novel inactivating thyrotropin receptor mutations in patients with thyrotropin resistance. Thyroid 2006; 16:471-9. [PMID: 16756469 DOI: 10.1089/thy.2006.16.471] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE We identified and analyzed novel thyrotropin (TSH) receptor mutations in three Japanese families with resistance to TSH. DESIGN The TSH receptor gene was sequenced and the mutations were determined. The mutant TSH receptors were transfected into COS-7 cells, and their functions were analyzed. PATIENTS The patients were compound-heterozygotes for the R450H mutation and novel mutations in the TSH receptor gene. The first patient was a compound-heterozygote for R450H and V473I. The second sibling possessed R450H and R519C. The third sibling had R450H and R519G. RESULTS The R450H mutant exhibited moderately impaired receptor functions and a moderately decreased cell surface expression in agreement with previous results. The V473I mutant exhibited an almost normal TSH binding, a slightly decreased cyclic adenosine monophosphate (cAMP) response, a moderately decreased inositolphosphate (IP) response, and an almost normal cell surface expression. TSH binding and TSH stimulation of cAMP and IPs were markedly decreased in the R519C and R519G mutants. Cell surface expression was decreased in the R519C mutant and negligible in the R519G mutant. All of these mutants showed normal intracellular synthesis of TSH receptors. CONCLUSIONS These novel inactivating mutations contribute to understanding of the structure-function relationship of the TSH receptor. To date, all of the patients with TSH resistance resulting from TSH receptor mutations identified in Japan possessed the R450H mutation at least in one allele. These observations suggest that the R450H mutation is a commonly observed TSH receptor mutation in patients with TSH resistance in Japan.
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Affiliation(s)
- Katsuhiko Tsunekawa
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
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Morimura T, Tsunekawa K, Kasahara T, Seki K, Ogiwara T, Mori M, Murakami M. Expression of type 2 iodothyronine deiodinase in human osteoblast is stimulated by thyrotropin. Endocrinology 2005; 146:2077-84. [PMID: 15650076 DOI: 10.1210/en.2004-1432] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormones play important roles in bone growth, development, and turnover. To exert its biological activity, T(4) needs to be converted to T(3) by iodothyronine deiodinase. In human thyroid gland as well as rat brown adipose tissue, type 2 iodothyronine deiodinase (D2) expression is regulated by a TSH receptor-cAMP-mediated mechanism. TSH receptor knockout mice demonstrated the direct effects of TSH on bone via TSH receptors found on osteoblast and osteoclast precursors. In the present study we investigated the possible expression and function of iodothyronine deiodinase and TSH receptors in human osteoblast-like osteosarcoma (SaOS-2) cells and normal human osteoblast (NHOst) cells. Iodothyronine deiodinase activity was detected in SaOS-2 cells and NHOst cells, and all of the characteristics of deiodinating activity were compatible with those of D2. Northern analysis demonstrated D2 mRNA expression in SaOS-2 cells and NHOst cells. D2 mRNA levels as well as D2 activities were rapidly increased by dibutyryl cAMP or forskolin in SaOS-2 cells and NHOst cells. TSH receptor mRNA was demonstrated in SaOS-2 cells and NHOst cells, and D2 mRNA and D2 activity were stimulated by TSH in both cells. In addition, all T(3) receptor isoforms were detected by RT-PCR in SaOS-2 cells and NHOst cells. The present results indicate the expression of functional TSH receptors and D2 in human osteoblasts and suggest previously unrecognized roles of TSH receptors and local T(3) production by D2 in the pathophysiology of human osteoblasts.
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Affiliation(s)
- Tadashi Morimura
- Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
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Morrison BH, Bauer JA, Hu J, Grane RW, Ozdemir AM, Chawla-Sarkar M, Gong B, Almasan A, Kalvakolanu DV, Lindner DJ. Inositol hexakisphosphate kinase 2 sensitizes ovarian carcinoma cells to multiple cancer therapeutics. Oncogene 2002; 21:1882-9. [PMID: 11896621 PMCID: PMC2043497 DOI: 10.1038/sj.onc.1205265] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2001] [Revised: 12/11/2001] [Accepted: 12/18/2001] [Indexed: 12/29/2022]
Abstract
We recently identified inositol hexakisphosphate kinase 2 (IP6K2) as a positive regulator of apoptosis. Overexpression of IP6K2 enhances apoptosis induced by interferon-beta (IFN-beta) and cytotoxic agents in NIH-OVCAR-3 ovarian carcinoma cells. In this study, we contrast and compare IFN-beta and radiation-induced death, and show that IP6K2 expression sensitizes tumor cells. Unirradiated NIH-OVCAR-3 cells transfected with IP6K2 formed fewer colonies compared to unirradiated vector-expressing cells. IP6K2 overexpression caused increased radiosensitivity, evidenced by decreased colony forming units (CFU). Both IFN-beta and radiation induced caspase 8. IFN-beta, but not gamma-irradiation, induced TRAIL in NIH-OVCAR-3 cells. Gamma irradiation, but not IFN-beta, induced DR4 mRNA. Apoptotic effects of IFN-beta or gamma-irradiation were blocked by expression of a dominant negative mutant death receptor 5 (DR5Delta) or by Bcl-2. Caspase-8 mRNA induction was more pronounced in IP6K2-expressing cells compared to vector-expressing cells. These data suggest that overexpression of IP6K2 enhances sensitivity of some ovarian carcinomas to radiation and IFN-beta. IP6K2 may function to enhance the expression and/or function of caspase 8 and DR4 following cell injury. Both IFN-beta and gamma-irradiation induce apoptosis through the extrinsic, receptor-mediated pathway, IFN-beta through TRAIL, radiation through DR4, and both through caspase 8. The function of both death inducers is positively regulated by IP6K2.
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Affiliation(s)
- Bei H Morrison
- Center for Cancer Drug Discovery and Development, Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
| | - Joseph A Bauer
- Center for Cancer Drug Discovery and Development, Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
| | - Jiadi Hu
- Department of Microbiology and Immunology, Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland, MD 21201, USA
| | - Ronald W Grane
- Center for Cancer Drug Discovery and Development, Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
| | - Aylin M Ozdemir
- Center for Cancer Drug Discovery and Development, Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
| | - Mamta Chawla-Sarkar
- Center for Cancer Drug Discovery and Development, Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
| | - Bendi Gong
- Department of Cancer Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
| | - Alex Almasan
- Department of Cancer Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
- Department of Radiation Oncology, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
| | - Dhananjaya V Kalvakolanu
- Department of Microbiology and Immunology, Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland, MD 21201, USA
| | - Daniel J Lindner
- Center for Cancer Drug Discovery and Development, Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
- Department of Cancer Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio, OH 44195, USA
- Correspondence: DJ Lindner, 9500 Euclid Avenue, R40, Cleveland, OH 44195, USA; E-mail:
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Nagashima T, Murakami M, Onigata K, Morimura T, Nagashima K, Mori M, Morikawa A. Novel inactivating missense mutations in the thyrotropin receptor gene in Japanese children with resistance to thyrotropin. Thyroid 2001; 11:551-9. [PMID: 11442002 DOI: 10.1089/105072501750302859] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We describe Japanese siblings with resistance to thyrotropin (TSH) who are compound heterozygotes for two novel mutations in the TSH receptor gene. The affected siblings had increased serum TSH, normal serum thyroid hormones, and normal positioned but slightly hypoplastic thyroid glands. The mutated paternal allele has the substitution of His (CAC) in place of Arg (CGC) at codon 450 (R450H) of the TSH receptor. The mutated maternal allele has the substitution of Ser (AGT) in place of Gly (GGT) at codon 498 (G498S) of the TSH receptor. COS-7 cells transfected with the R450H mutant exhibited a slightly decreased TSH binding and a slightly decreased cyclic adenosine monophosphate (cAMP) response to TSH, whereas cells transfected with the G498S mutant exhibited a markedly decreased TSH binding and a markedly decreased cAMP response to TSH. Flow immunocytofluorometry analysis demonstrated that the G498S mutant resulted in extremely low expression at the cell surface as compared with the wild type receptor and the R450H mutant, in spite of a normal intracellular synthesis. The present cases are the first Japanese patients with TSH resistance in whom mutations in the TSH receptor gene have been identified. These novel mutations may contribute to understanding of the struc-ture-function relationship of the TSH receptor.
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Affiliation(s)
- T Nagashima
- Department of Pediatrics, Gunma University School of Medicine, Maebashi, Japan
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Khoo DH, Ho SC, Seah LL, Fong KS, Tai ES, Chee SP, Eng PH, Aw SE, Fok AC. The combination of absent thyroid peroxidase antibodies and high thyroid-stimulating immunoglobulin levels in Graves' disease identifies a group at markedly increased risk of ophthalmopathy. Thyroid 1999; 9:1175-80. [PMID: 10646655 DOI: 10.1089/thy.1999.9.1175] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Among Graves' Disease (GD) patients, we have observed an unexpectedly high prevalence of antithyroperoxidase antibody (TPOAb) and antithyroglobulin antibody (TgAb) negativity in those with severe ophthalmopathy. To study the possible role of thyroid autoantibodies in the pathogenesis of Graves' ophthalmopathy (GO), TPOAb, TgAb, thyroid-stimulating immunoglobulin (TSI), and thyrotropin-binding inhibitory immunoglobulin (TBII) levels were measured, and the presence or absence of GO was assessed by a single observer in 100 consecutive patients with newly diagnosed, untreated GD who were nonsmokers. Ophthalmopathy was present in 43 patients. TSI levels (p = 0.001), and the prevalence of TPOAb-negativity (p = 0.002) were significantly higher in patients with ophthalmopathy compared to those without. Logistic regression analysis showed that TSI levels (p = 0.005) and the absence of TPOAb (p = 0.0025) were independent predictors of GO. No correlation between TBII or TgAb and eye disease was found. The prevalence of GO increased with each quartile of TSI levels. The prevalence was 20%, 36%, 52%, and 64% in the first, second, third and fourth quartiles of TSI, respectively. The odds ratio of GO (with 95% confidence intervals) when TSI levels were above the median level (1640%) was 3.6 (1.5-8.0), when TPOAb was negative it was 5.0 (1.7-14.4), and with both risk factors it was 36.6 (4.3-313.5). The prevalence of ophthalmopathy in this last group was 92.9%. The combination of negative TPOAb and high TSI levels appears to be associated with a markedly increased risk of clinically evident ophthalmopathy.
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Affiliation(s)
- D H Khoo
- Department of Endocrinology, Singapore General Hospital.
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Hosoi Y, Murakami M, Minegishi T, Okano H, Ibuki Y, Takeuchi T, Mori M. Stimulation of Chinese hamster ovary cells expressing human thyrotropin receptors by serum human chorionic gonadotropin of patients with hydatidiform mole. Thyroid 1999; 9:1205-10. [PMID: 10646659 DOI: 10.1089/thy.1999.9.1205] [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: 11/13/2022]
Abstract
We evaluated the stimulation of Chinese hamster ovary cells expressing human thyrotropin receptors (CHO-hTSHR cell) by sera of five patients with hydatidiform mole before and after the evacuation of the mole, and compared the results with serum human chorionic gonadotropin (hCG) concentrations and serum free thyroid hormones in these patients. Significantly increased CHO-hTSHR cell stimulating activities were observed in sera from untreated patients, and the activity decreased promptly after the evacuation of the mole, concomitantly with the decrease in serum hCG and free thyroid hormones. CHO-hTSHR cell stimulating activity of sera of the untreated patients significantly correlated with serum hCG. Moreover, serum hCG stimulated CHO-hTSHR cells in a dose dependent manner similar to the dose-response curve of the stimulation by purified hCG. Sera of the patients and purified hCG did not stimulate nontransfected CHO-K1 cells. However, a significant correlation was not observed between serum-free thyroid hormones and serum hCG or between serum free thyroid hormones and CHO-hTSHR cell stimulating activities in untreated patients. These results indicate that serum hCG from patients with hydatidiform mole stimulates thyroid gland by interacting with TSH receptors, and suggest that the increase in thyroid hormones in patients may depend on both the increased serum hCG and the responsiveness of their thyroid glands to hCG.
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Affiliation(s)
- Y Hosoi
- First Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan
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Akamatsu W, Okano HJ, Osumi N, Inoue T, Nakamura S, Sakakibara S, Miura M, Matsuo N, Darnell RB, Okano H. Mammalian ELAV-like neuronal RNA-binding proteins HuB and HuC promote neuronal development in both the central and the peripheral nervous systems. Proc Natl Acad Sci U S A 1999; 96:9885-90. [PMID: 10449789 PMCID: PMC22305 DOI: 10.1073/pnas.96.17.9885] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hu proteins are mammalian embryonic lethal abnormal visual system (ELAV)-like neuronal RNA-binding proteins that contain three RNA recognition motifs. Although Drosophila ELAV is required for the correct differentiation and survival of neurons, the roles played by the Hu genes in the mammalian nervous system remain largely unknown. To explore the in vivo functions of mouse Hu proteins, we overexpressed them in rat pheochromocytoma PC12 cells, where they induced neuronal phenotype in the absence of nerve growth factor. We have characterized the functions of various forms of mHuB and mHuC bearing point mutations or deletions. Mutants of mHuC that had amino acid exchanges in the RNP1 domain of the first or second RNA recognition motifs (RRMs) lost biologic activity as well as RNA-binding activity. In addition, the mutants containing only the third RRM failed to induce the neuronal phenotype in PC12 cells and inhibited the biologic activity of cotransfected wild-type mHuB and mHuC, thus acting as a dominant-negative form. However, these mutants could not suppress the nerve growth factor-induced differentiation of PC12 cells. Further, we misexpressed wild-type and dominant-negative Hu in E9.5 mouse embryos, by using electroporation into the neural tube at the level of the rhombencephalon. mHuB and mHuC induced the ectopic expression of neuronal markers, whereas the dominant-negative forms of mHuB and mHuC suppressed the differentiation of central nervous system motor neurons. From these results, we suggest that Hu proteins are required for neuronal differentiation in the mammalian nervous system.
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Affiliation(s)
- W Akamatsu
- Department of Neuroanatomy, Biomedical Research Center, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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Rapoport B, Chazenbalk GD, Jaume JC, McLachlan SM. The thyrotropin (TSH) receptor: interaction with TSH and autoantibodies. Endocr Rev 1998; 19:673-716. [PMID: 9861544 DOI: 10.1210/edrv.19.6.0352] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- B Rapoport
- Autoimmune Disease Unit, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA
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Watson PF, Ajjan RA, Phipps J, Metcalfe R, Weetman AP. A new chemiluminescent assay for the rapid detection of thyroid stimulating antibodies in Graves' disease. Clin Endocrinol (Oxf) 1998; 49:577-81. [PMID: 10197071 DOI: 10.1046/j.1365-2265.1998.00619.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Thyroid stimulating antibodies (TSAb) are the cause of Graves' disease (GD). At present, these antibodies can only be measured using bioassays, which are generally time consuming and difficult to apply to whole serum. Here we describe a new chemiluminescent assay for the detection of TSAb in serum samples. METHODS A Chinese hamster ovary (CHO) cell line, stably transformed with a reporter plasmid containing the firefly luciferase gene under the transcriptional control of multiple cAMP responsive elements (CRE), was transfected with the human thyroid stimulating hormone (TSH) receptor. A clonal cell line, (NA-4), was obtained which showed a dose-dependent increase in luciferase activity in response to bovine and human TSH stimulation. NA-4 was subsequently used to study TSAb activity in 42 GD sera. RESULTS Of the GD sera 25 (60%) produced an increase in luciferase activity of 1.4-9 fold that obtained with control sera. Results were compared with an established bioassay for TSAb, based on the direct measurement of intracellular cAMP, and there was a significant correlation between the two assays (r = 0.8; P < 0.0001). IgG from GD patients, but not controls, also increased luciferase activity in NA-4 cells using concentrations as low as 3 mg/l in selected samples. CONCLUSION The present report describes a simple, sensitive and rapid assay for the detection of TSAb, with application both in the clinical analysis of GD patient sera and as a potential research tool for use in the isolation of TSAb monoclonal antibodies.
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Affiliation(s)
- P F Watson
- Division of Clinical Sciences Centre, University of Sheffield, Northern General Hospital, UK.
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Abstract
Graves' disease, one of the autoimmune thyroid diseases, is caused by the production of IgG autoantibodies directed against the thyrotropin receptor. These antibodies bind to and activate the receptor, causing the autonomous production of thyroid hormones. Despite recent improvements in our understanding of the cellular and molecular basis of autoimmunity, our currently available treatments for Graves' disease have remained largely unchanged over the last 50 years. Nevertheless, new concepts in immune system regulation hold out the prospect in the future for intervention designed to modify, and possibly cure, the underlying disease process.
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Affiliation(s)
- B McIver
- Mayo Graduate School of Medicine, Rochester, Minnesota, USA
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Sanders J, Oda Y, Roberts SA, Maruyama M, Furmaniak J, Smith BR. Understanding the thyrotropin receptor function-structure relationship. BAILLIERE'S CLINICAL ENDOCRINOLOGY AND METABOLISM 1997; 11:451-79. [PMID: 9532334 DOI: 10.1016/s0950-351x(97)80693-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The thyrotropin (TSH) receptor (TSHR) is a key protein in the control of thyroid function and a major thyroid autoantigen. Recently, molecular cloning of the receptor has been carried out and we now review the impact of this work on our understanding of the physiology and pathophysiology of the TSHR. Analysis of recombinant TSHR proteins expressed in prokaryotic and eukaryotic systems has indicated that post-translational processing is important for the formation of active receptors. Studies of TSHR glycosylation have shown that a 'mature' form of the receptor containing mainly complex-type sugar residues is principally involved in TSH and TSHR autoantibody (TRAb) binding. In addition, the processing of the TSHR peptide chain into two subunits observed with native TSHR has been confirmed using recombinant TSHR. However, despite considerable efforts in many laboratories, the binding site(s) for TSH and TRAb on the TSHR have not been well characterized as yet and lessons learned from the discovery of naturally occurring amino acid mutations of the TSHR confirm the complexity of the hormone and autoantibody binding sites. Future progress in producing large amounts of pure TSHR as well as monoclonal TRAbs, followed by crystallographic analysis of TSHR-TSH complexes and TSHR-TRAb complexes, should be helpful in providing a better insight into the relationship between TSHR structure and function.
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Affiliation(s)
- J Sanders
- FIRS Laboratories, RSR Ltd, Llanishen, Cardiff, UK
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Chazenbalk GD, Jaume JC, McLachlan SM, Rapoport B. Engineering the human thyrotropin receptor ectodomain from a non-secreted form to a secreted, highly immunoreactive glycoprotein that neutralizes autoantibodies in Graves' patients' sera. J Biol Chem 1997; 272:18959-65. [PMID: 9228077 DOI: 10.1074/jbc.272.30.18959] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Previous attempts to generate autoantibody-reactive, secreted thyrotropin receptor (TSHR) ectodomain in mammalian cells have failed because of retention within the cell of material with immature carbohydrate. We have overcome this difficulty by performing progressive carboxyl-terminal truncations of the human TSHR ectodomain (418 amino acid residues including signal peptide). Three ectodomain variants (TSHR-261, TSHR-289, and TSHR-309) were truncated at residues 261, 289, and 309, respectively. Unlike the full ectodomain, ectodomain variants were secreted with an efficiency inversely proportional to their size. Secreted ectodomain variants contained approximately 20 kDa of complex carbohydrate. TSHR-261 was chosen for further study because it was secreted very efficiently and neutralized autoantibodies in Graves' patients' sera. This ectodomain variant was partially purified using sequential lectin and nickel-chelate chromatography, permitting the first direct visualization and quantitation of the mammalian TSHR. Most important, very small (nanogram) quantities of this material neutralized 70-100% of TSHR autoantibody activity in all 18 Graves' sera studied. In summary, carboxyl-terminal truncation of the human TSHR ectodomain generates a secreted protein with complex carbohydrate that neutralizes autoantibodies in Graves' patients' sera. Antigenically active TSHR will be valuable for future studies on the diagnosis, pathogenesis, and immunotherapy of Graves' disease.
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Affiliation(s)
- G D Chazenbalk
- Thyroid Molecular Biology Unit, Veterans Administration Medical Center and the University of California, San Francisco, California 94121, USA
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18
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Kakinuma A, Chazenbalk GD, Jaume JC, Rapoport B, McLachlan SM. The human thyrotropin (TSH) receptor in a TSH binding inhibition assay for TSH receptor autoantibodies. J Clin Endocrinol Metab 1997; 82:2129-34. [PMID: 9215283 DOI: 10.1210/jcem.82.7.4092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Seven years after the molecular cloning of the human TSH receptor (TSHR), the porcine TSHR remains in general use in the TSH binding inhibition (TBI) assay for autoantibodies to the TSHR. We compared porcine and recombinant human TSHR in two types of TBI assays: one using intact Chinese hamster ovary cells expressing the recombinant human TSHR on their surface, and the other using soluble receptors extracted from these cells with detergent. In the intact cell TBI assay, monolayers expressing large numbers of TSHR were less effective than cells expressing few receptors. These findings are consistent with the very low concentration of TSHR autoantibodies in serum. Binding of [125I]human TSH was about 5-fold lower than that of [125I]bovine TSH to the intact cells. Nevertheless, TBI values with the two ligands were similar for most sera. However, a few sera produced greater inhibition of human than of bovine TSH binding. In the solubilized human TSHR TBI assay, in contrast to the intact cell TBI assay, cells expressing very large number of TSHR were an excellent source for detergent extraction of soluble human TSHR, but only if the cells were extracted while still on the dish and not after scraping. A 10-cm diameter dish of cells provided TSHR for 100-200 replicate determinations when substituted for solubilized porcine TSHR in a commercial TBI kit. TBI values in serum from 30 individuals with suspected Graves' disease correlated closely when tested with solubilized human and porcine TSHR (r = 0.954; P < 0.001). However, 2 sera that were negative with the porcine TSHR were positive with the human TSHR. TBI and thyroid-stimulating activity in these sera correlated weakly regardless of whether the TBI used human or porcine TSHR. These findings open the way to a practical TBI assay using recombinant human TSHR.
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Affiliation(s)
- A Kakinuma
- Thyroid Molecular Biology Unit, Veterans Administration Medical Center, San Francisco, California 94121, USA
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Suzuki T, Fujikura K, Takata K. Na(+)-dependent glucose transporter SGLT1 is localized in the apical plasma membrane upon completion of tight junction formation in MDCK cells. Histochem Cell Biol 1996; 106:529-33. [PMID: 8985740 DOI: 10.1007/bf02473267] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
SGLT1, an isoform of Na(+)-dependent glucose transporters, is localized at the apical plasma membrane in the epithelial cells of the small intestine and the kidney. In the present study we examined its location in SGLT1 cDNA-transfected MDCK cells, which form an epithelial sheet connected by tight junctions in culture. Formation of tight junctions was monitored by staining for occludin, an integral tight junction protein. In the cells demarcated by an uninterrupted occludin meshwork, SGLT1 was specifically localized at the apical plasma membrane, showing that SGLT1 has a signal to accomplish this restricted localization. In the cells with little or no occludin accumulation in the tight junction, however, SGLT1 was present along the entire aspect of the plasma membrane. Similar distribution of SGLT1 was observed in the cells as long as the occludin meshwork remained incomplete. These observations suggest that apical localization of SGLT1 occurs upon the completion of the uninterrupted meshwork of tight junctions.
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Affiliation(s)
- T Suzuki
- Department of Cell Biology, Gunma University, Japan
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