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Wang L, Zhang M, Wang Y, Shi B. Graves' Orbitopathy Models: Valuable Tools for Exploring Pathogenesis and Treatment. Horm Metab Res 2023; 55:745-751. [PMID: 37903495 DOI: 10.1055/a-2161-5417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2023]
Abstract
Graves' orbitopathy (GO) is the most common extrathyroidal complication of Graves' disease (GD) and severely affects quality of life. However, its pathogenesis is still poorly understood, and therapeutic options are limited. Animal models are important tools for preclinical research. The animals in some previous models only exhibited symptoms of hyperthyroidism without ocular lesions. With the improvements achieved in modeling methods, some progressive animal models have been established. Immunization of mice with A subunit of the human thyroid stimulating hormone receptor (TSHR) by either adenovirus or plasmid (with electroporation) is widely used and convincing. These models are successful to identify that the gut microbiota influences the occurrence and severity of GD and GO, and sex-related risk factors may be key contributors to the female bias in the occurrence of GO rather than sex itself. Some data provide insight that macrophages and CD8+ T cells may play an important pathogenic role in the early stage of GO. Our team also replicated the time window from GD onset to GO onset and identified a group of CD4+ cytotoxic T cells. In therapeutic exploration, TSHR derived peptides, fingolimod, and rapamycin offer new potential options. Further clinical trials are needed to investigate these drugs. With the increasing use of these animal models and more in-depth studies of the new findings, scientists will gain a clearer understanding of the pathogenesis of GO and identify more treatments for patients.
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Affiliation(s)
- Ling Wang
- Department of Endocrinology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Meng Zhang
- Department of Endocrinology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Yue Wang
- Department of Endocrinology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Bingyin Shi
- Department of Endocrinology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
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2
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Kieber-Emmons T. Antibodies and Structure. Monoclon Antib Immunodiagn Immunother 2020; 39:193-194. [DOI: 10.1089/mab.2020.29003.tke] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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McLachlan SM, Rapoport B. A transgenic mouse that spontaneously develops pathogenic TSH receptor antibodies will facilitate study of antigen-specific immunotherapy for human Graves' disease. Endocrine 2019; 66:137-148. [PMID: 31560118 DOI: 10.1007/s12020-019-02083-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Accepted: 09/04/2019] [Indexed: 12/13/2022]
Abstract
Graves' hyperthyroidism can be treated but not cured. Antigen-specific immunotherapy would accomplish this goal, for which purpose an animal model is an invaluable tool. Two types of animal models are available. First, pathogenic TSHR antibodies (TSHRAb) can be induced by injecting mice with fibroblasts co-expressing the human TSHR (hTSHR) and MHC class II, or in mammals using plasmid or adenovirus vectors encoding the hTSHR or its A-subunit. Second, a mouse model that spontaneously develops pathogenic TSHRAb resembling those in human disease was recently described. This outcome was accomplished by transgenic intrathyroidal expression of the hTSHR A-subunit in NOD.H2h4 mice that are genetically predisposed to develop thyroiditis but, without the transgene, do not generate TSHRAb. Recently, novel approaches to antigen-specific immunotherapy have been tested, primarily in the induced model, by injecting TSHR A-subunit protein or cyclic TSHR peptides. T-cell tolerance has also been induced in "humanized" HLA-DR3 mice by injecting synthetic peptides predicted in silico to mimic naturally processed TSHR T-cell epitopes. Indeed, a phase 1 study based on the latter approach has been conducted in humans. In the spontaneous model (hTSHR/NOD.H2h mice), injection of soluble or nanoparticle-bearing hTSHR A-subunits had the unwanted effect of exacerbating pathogenic TSHRAb levels. A promising avenue for tolerance induction, successful in other conditions and yet to be tested with the TSHR, involves encapsulating the antigen. In conclusion, these studies provide insight into the potential outcome of immunotherapeutic approaches and emphasize the importance of a spontaneous model to test future novel, antigen-specific immunotherapies for Graves' disease.
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Affiliation(s)
- Sandra M McLachlan
- Department of Medicine, University of California Los Angeles, 100 Medical Plaza Driveway, Los Angeles, CA, 90095, USA
| | - Basil Rapoport
- Department of Medicine, University of California Los Angeles, 100 Medical Plaza Driveway, Los Angeles, CA, 90095, USA.
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4
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Miller-Gallacher J, Sanders P, Young S, Sullivan A, Baker S, Reddington SC, Clue M, Kabelis K, Clark J, Wilmot J, Thomas D, Chlebowska M, Cole F, Pearson E, Roberts E, Holly M, Evans M, Núñez Miguel R, Powell M, Sanders J, Furmaniak J, Rees Smith B. Crystal structure of a ligand-free stable TSH receptor leucine-rich repeat domain. J Mol Endocrinol 2019; 62:117-128. [PMID: 30689545 DOI: 10.1530/jme-18-0213] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 01/28/2019] [Indexed: 12/19/2022]
Abstract
The crystal structures of the thyroid-stimulating hormone receptor (TSHR) leucine-rich repeat domain (amino acids 22-260; TSHR260) in complex with a stimulating human monoclonal autoantibody (M22TM) and in complex with a blocking human autoantibody (K1-70™) have been solved. However, attempts to purify and crystallise free TSHR260, that is not bound to an autoantibody, have been unsuccessful due to the poor stability of free TSHR260. We now describe a TSHR260 mutant that has been stabilised by the introduction of six mutations (H63C, R112P, D143P, D151E, V169R and I253R) to form TSHR260-JMG55TM, which is approximately 900 times more thermostable than wild-type TSHR260. These six mutations did not affect the binding of human TSHR monoclonal autoantibodies or patient serum TSHR autoantibodies to the TSHR260. Furthermore, the response of full-length TSHR to stimulation by TSH or human TSHR monoclonal autoantibodies was not affected by the six mutations. Thermostable TSHR260-JMG55TM has been purified and crystallised without ligand and the structure solved at 2.83 Å resolution. This is the first reported structure of a glycoprotein hormone receptor crystallised without ligand. The unbound TSHR260-JMG55TM structure and the M22 and K1-70 bound TSHR260 structures are remarkably similar except for small changes in side chain conformations. This suggests that neither the mutations nor the binding of M22TM or K1-70TM change the rigid leucine-rich repeat domain structure of TSHR260. The solved TSHR260-JMG55TM structure provides a rationale as to why the six mutations have a thermostabilising effect and provides helpful guidelines for thermostabilisation strategies of other soluble protein domains.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Jill Clark
- FIRS Laboratories, RSR Ltd, Cardiff, CF14 5DUUK
| | - Jane Wilmot
- FIRS Laboratories, RSR Ltd, Cardiff, CF14 5DUUK
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5
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Kleinau G, Worth CL, Kreuchwig A, Biebermann H, Marcinkowski P, Scheerer P, Krause G. Structural-Functional Features of the Thyrotropin Receptor: A Class A G-Protein-Coupled Receptor at Work. Front Endocrinol (Lausanne) 2017; 8:86. [PMID: 28484426 PMCID: PMC5401882 DOI: 10.3389/fendo.2017.00086] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 04/03/2017] [Indexed: 12/21/2022] Open
Abstract
The thyroid-stimulating hormone receptor (TSHR) is a member of the glycoprotein hormone receptors, a sub-group of class A G-protein-coupled receptors (GPCRs). TSHR and its endogenous ligand thyrotropin (TSH) are of essential importance for growth and function of the thyroid gland and proper function of the TSH/TSHR system is pivotal for production and release of thyroid hormones. This receptor is also important with respect to pathophysiology, such as autoimmune (including ophthalmopathy) or non-autoimmune thyroid dysfunctions and cancer development. Pharmacological interventions directly targeting the TSHR should provide benefits to disease treatment compared to currently available therapies of dysfunctions associated with the TSHR or the thyroid gland. Upon TSHR activation, the molecular events conveying conformational changes from the extra- to the intracellular side of the cell across the membrane comprise reception, conversion, and amplification of the signal. These steps are highly dependent on structural features of this receptor and its intermolecular interaction partners, e.g., TSH, antibodies, small molecules, G-proteins, or arrestin. For better understanding of signal transduction, pathogenic mechanisms such as autoantibody action and mutational modifications or for developing new pharmacological strategies, it is essential to combine available structural data with functional information to generate homology models of the entire receptor. Although so far these insights are fragmental, in the past few decades essential contributions have been made to investigate in-depth the involved determinants, such as by structure determination via X-ray crystallography. This review summarizes available knowledge (as of December 2016) concerning the TSHR protein structure, associated functional aspects, and based on these insights we suggest several receptor complex models. Moreover, distinct TSHR properties will be highlighted in comparison to other class A GPCRs to understand the molecular activation mechanisms of this receptor comprehensively. Finally, limitations of current knowledge and lack of information are discussed highlighting the need for intensified efforts toward TSHR structure elucidation.
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Affiliation(s)
- Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin, Berlin, Germany
- Group Protein X-Ray Crystallography and Signal Transduction, Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany
| | | | - Annika Kreuchwig
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Heike Biebermann
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin, Berlin, Germany
| | | | - Patrick Scheerer
- Group Protein X-Ray Crystallography and Signal Transduction, Institute of Medical Physics and Biophysics, Charité-Universitätsmedizin, Berlin, Germany
| | - Gerd Krause
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
- *Correspondence: Gerd Krause,
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Abstract
Hyperthyroidism is a form of thyrotoxicosis in which there is excess thyroid hormone synthesis and secretion. Multiple etiologies can lead to a common clinical state of "thyrotoxicosis," which is a consequence of the high thyroid hormone levels and their action on different tissues of the body. The most common cause of thyrotoxicosis is Graves' disease, an autoimmune disorder in which stimulating thyrotropin receptor antibodies bind to thyroid stimulating hormone (TSH) receptors on thyroid cells and cause overproduction of thyroid hormones. Other etiologies include: forms of thyroiditis in which inflammation causes release of preformed hormone, following thyroid gland insult that is autoimmune, infectious, mechanical or medication induced; secretion of human chorionic gonadotropin in the setting of transient gestational thyrotoxicosis and trophoblastic tumors; pituitary thyrotropin release, and exposure to extra-thyroidal sources of thyroid hormone that may be endogenous or exogenous. © 2017 American Physiological Society. Compr Physiol 7:67-79, 2017.
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Affiliation(s)
- Ishita Singh
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare Systems, Los Angeles, California, USA
| | - Jerome M Hershman
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare Systems, Los Angeles, California, USA
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Rapoport B, Banuelos B, Aliesky HA, Hartwig Trier N, McLachlan SM. Critical Differences between Induced and Spontaneous Mouse Models of Graves' Disease with Implications for Antigen-Specific Immunotherapy in Humans. THE JOURNAL OF IMMUNOLOGY 2016; 197:4560-4568. [PMID: 27913646 DOI: 10.4049/jimmunol.1601393] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 10/14/2016] [Indexed: 01/20/2023]
Abstract
Graves' hyperthyroidism, a common autoimmune disease caused by pathogenic autoantibodies to the thyrotropin (TSH) receptor (TSHR), can be treated but not cured. This single autoantigenic target makes Graves' disease a prime candidate for Ag-specific immunotherapy. Previously, in an induced mouse model, injecting TSHR A-subunit protein attenuated hyperthyroidism by diverting pathogenic TSHR Abs to a nonfunctional variety. In this study, we explored the possibility of a similar diversion in a mouse model that spontaneously develops pathogenic TSHR autoantibodies, NOD.H2h4 mice with the human (h) TSHR (hTSHR) A-subunit transgene expressed in the thyroid and (shown in this article) the thymus. We hypothesized that such diversion would occur after injection of "inactive" hTSHR A-subunit protein recognized only by nonpathogenic (not pathogenic) TSHR Abs. Surprisingly, rather than attenuating the pre-existing pathogenic TSHR level, in TSHR/NOD.H2h4 mice inactive hTSHR Ag injected without adjuvant enhanced the levels of pathogenic TSH-binding inhibition and thyroid-stimulating Abs, as well as nonpathogenic Abs detected by ELISA. This effect was TSHR specific because spontaneously occurring autoantibodies to thyroglobulin and thyroid peroxidase were unaffected. As controls, nontransgenic NOD.H2h4 mice similarly injected with inactive hTSHR A-subunit protein unexpectedly developed TSHR Abs, but only of the nonpathogenic variety detected by ELISA. Our observations highlight critical differences between induced and spontaneous mouse models of Graves' disease with implications for potential immunotherapy in humans. In hTSHR/NOD.H2h4 mice with ongoing disease, injecting inactive hTSHR A-subunit protein fails to divert the autoantibody response to a nonpathogenic form. Indeed, such therapy is likely to enhance pathogenic Ab production and exacerbate Graves' disease in humans.
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Affiliation(s)
- Basil Rapoport
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Medical Center and UCLA School of Medicine, Los Angeles, CA 90048; and
| | - Bianca Banuelos
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Medical Center and UCLA School of Medicine, Los Angeles, CA 90048; and
| | - Holly A Aliesky
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Medical Center and UCLA School of Medicine, Los Angeles, CA 90048; and
| | - Nicole Hartwig Trier
- Department of Autoimmunology and Biomarkers, Statens Serum Institut, DK-2300 Copenhagen S, Denmark
| | - Sandra M McLachlan
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Medical Center and UCLA School of Medicine, Los Angeles, CA 90048; and
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Inaba H, De Groot LJ, Akamizu T. Thyrotropin Receptor Epitope and Human Leukocyte Antigen in Graves' Disease. Front Endocrinol (Lausanne) 2016; 7:120. [PMID: 27602020 PMCID: PMC4994058 DOI: 10.3389/fendo.2016.00120] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 08/12/2016] [Indexed: 11/13/2022] Open
Abstract
Graves' disease (GD) is an organ-specific autoimmune disease, and thyrotropin (TSH) receptor (TSHR) is a major autoantigen in this condition. Since the extracellular domain of human TSHR (TSHR-ECD) is shed into the circulation, TSHR-ECD is a preferentially immunogenic portion of TSHR. Both genetic factors and environmental factors contribute to development of GD. Inheritance of human leukocyte antigen (HLA) genes, especially HLA-DR3, is associated with GD. TSHR-ECD protein is endocytosed into antigen-presenting cells (APCs), and processed to TSHR-ECD peptides. These peptide epitopes bind to HLA-class II molecules, and subsequently the complex of HLA-class II and TSHR-ECD epitope is presented to CD4+ T cells. The activated CD4+ T cells secrete cytokines/chemokines that stimulate B-cells to produce TSAb, and in turn hyperthyroidism occurs. Numerous studies have been done to identify T- and B-cell epitopes in TSHR-ECD, including (1) in silico, (2) in vitro, (3) in vivo, and (4) clinical experiments. Murine models of GD and HLA-transgenic mice have played a pivotal role in elucidating the immunological mechanisms. To date, linear or conformational epitopes of TSHR-ECD, as well as the molecular structure of the epitope-binding groove in HLA-DR, were reported to be related to the pathogenesis in GD. Dysfunction of central tolerance in the thymus, or in peripheral tolerance, such as regulatory T cells, could allow development of GD. Novel treatments using TSHR antagonists or mutated TSHR peptides have been reported to be effective. We review and update the role of immunogenic TSHR epitopes and HLA in GD, and offer perspectives on TSHR epitope specific treatments.
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Affiliation(s)
- Hidefumi Inaba
- The First Department of Medicine, Wakayama Medical University, Wakayama, Japan
- *Correspondence: Hidefumi Inaba,
| | - Leslie J. De Groot
- Department of Cellular and Molecular Biology, University of Rhode Island, Providence, RI, USA
| | - Takashi Akamizu
- The First Department of Medicine, Wakayama Medical University, Wakayama, Japan
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Banga JP, Moshkelgosha S, Berchner-Pfannschmidt U, Eckstein A. Modeling Graves' Orbitopathy in Experimental Graves' Disease. Horm Metab Res 2015; 47:797-803. [PMID: 26287396 DOI: 10.1055/s-0035-1555956] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Graves' orbitopathy (GO), also known as thyroid eye disease is an inflammatory disease of the orbital tissue of the eye that arises as a consequence of autoimmune thyroid disease. The central feature of the disease is the production of antibodies to the thyrotropin hormone receptor (TSHR) that modulate the function of the receptor leading to autoimmune hyperthyroidism and GO. Over the years, all viable preclinical models of Graves' disease have been incomplete and singularly failed to progress in the treatment of orbital complications. A new mouse model of GO based upon immunogenic presentation of human TSHR A-subunit plasmid by close field electroporation is shown to lead to induction of prolonged functional antibodies to TSHR resulting in chronic disease with subsequent progression to GO. The stable preclinical GO model exhibited pathologies reminiscent of human disease characterized by orbital remodeling by inflammation and adipogenesis. Inflammatory lesions characterized by CD3+ T cells and macrophages were localized in the orbital muscle tissue. This was accompanied by extensive adipogenesis of orbital fat in some immune animals. Surprisingly, other signs of orbital involvement were reminiscent of eyelid inflammation involving chemosis, with dilated and congested orbital blood vessels. More recently, the model is replicated in the author's independent laboratories. The pre-clinical model will provide the basis to study the pathogenic and regulatory roles of immune T and B cells and their subpopulations to understand the initiation, pathophysiology, and progression of GO.
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Affiliation(s)
- J P Banga
- Faculty of Life Sciences & Medicine, King's College London, The Rayne Institute, London, UK
| | - S Moshkelgosha
- Faculty of Life Sciences & Medicine, King's College London, The Rayne Institute, London, UK
| | | | - A Eckstein
- Department of Ophthalmology, University of Duisburg-Essen, Essen, Germany
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Chen CR, Salazar LM, McLachlan SM, Rapoport B. Deleting the Redundant TSH Receptor C-Peptide Region Permits Generation of the Conformationally Intact Extracellular Domain by Insect Cells. Endocrinology 2015; 156:2732-8. [PMID: 25860033 PMCID: PMC4475722 DOI: 10.1210/en.2015-1154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The TSH receptor (TSHR) extracellular domain (ECD) comprises a N-terminal leucine-rich repeat domain and an hinge region (HR), the latter contributing to ligand binding and critical for receptor activation. The crystal structure of the leucine-rich repeat domain component has been solved, but previous attempts to generate conformationally intact complete ECD or the isolated HR component for structural analysis have failed. The TSHR HR contains a C-peptide segment that is removed during spontaneous TSHR intramolecular cleavage into disulfide linked A- and B-subunits. We hypothesized that deletion of the redundant C-peptide would overcome the obstacle to generating conformationally intact TSHR ECD protein. Indeed, lacking the C-peptide region, the TSHR ECD (termed ECD-D1) and the isolated HR (termed HR-D1) were secreted into medium of insect cells infected with baculoviruses coding for these modified proteins. The identities of TSHR ECD-D1 and HR-D1 were confirmed by ELISA and immunoblotting using TSHR-specific monoclonal antibodies. The TSHR-ECD-D1 in conditioned medium was folded correctly, as demonstrated by its ability to inhibit radiolabeled TSH binding to the TSH holoreceptor. The TSHR ECD-D1 purification was accomplished in a single step using a TSHR monoclonal antibody affinity column, whereas the HR-D1 required a multistep protocol with a low yield. In conclusion, we report a novel approach to generate the TSHR ECD, as well as the isolated HR in insect cells, the former in sufficient amounts for structural studies. However, such studies will require previous complexing of the ECD with a ligand such as TSH or a thyroid-stimulating antibody.
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Affiliation(s)
- Chun-Rong Chen
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and University of California, Los Angeles School of Medicine, Los Angeles, California 90048
| | - Larry M Salazar
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and University of California, Los Angeles School of Medicine, Los Angeles, California 90048
| | - Sandra M McLachlan
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and University of California, Los Angeles School of Medicine, Los Angeles, California 90048
| | - Basil Rapoport
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and University of California, Los Angeles School of Medicine, Los Angeles, California 90048
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Rapoport B, Aliesky HA, Chen CR, McLachlan SM. Evidence that TSH Receptor A-Subunit Multimers, Not Monomers, Drive Antibody Affinity Maturation in Graves' Disease. J Clin Endocrinol Metab 2015; 100:E871-5. [PMID: 25856215 PMCID: PMC4454809 DOI: 10.1210/jc.2015-1528] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT The TSH receptor (TSHR) A-subunit shed from the cell surface contributes to the induction and/or affinity maturation of pathogenic TSHR autoantibodies in Graves' disease. OBJECTIVE This study aimed to determine whether the quaternary structure (multimerization) of shed A-subunits influences pathogenic TSHR autoantibody generation. DESIGN The isolated TSHR A-subunit generated by transfected mammalian cells exists in two forms; one (active) is recognized only by Graves' TSHR autoantibodies, the second (inactive) is recognized only by mouse monoclonal antibody (mAb) 3BD10. Recent evidence suggests that both Graves' TSHR autoantibodies and mAb 3BD10 recognize the A-subunit monomer. Therefore, if the A-subunit monomer is an immunogen, Graves' sera should have antibodies to both active and inactive A-subunits. Conversely, restriction of TSHR autoantibodies to active A-subunits would be evidence of a role for shed A-subunit multimers, not monomers, in the pathogenesis of Graves' disease. Therefore, we tested a panel of Graves' sera for their relative recognition of active and inactive A-subunits. RESULTS Of 34 sera from unselected Graves' patients, 28 were unequivocally positive in a clinical TSH binding inhibition assay. None of the latter sera, as well as 8/9 sera from control individuals, recognized inactive A-subunits on ELISA. In contrast to Graves' sera, antibodies induced in mice, not by shedding from the TSHR holoreceptor, but by immunization with adenovirus expressing the free human A-subunit, were directed to both the active and inactive A-subunit forms. CONCLUSIONS The present study supports the concept that pathogenic TSHR autoantibody affinity maturation in Graves' disease is driven by A-subunit multimers, not monomers.
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Affiliation(s)
- Basil Rapoport
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and UCLA School of Medicine, Los Angeles, California 90048
| | - Holly A Aliesky
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and UCLA School of Medicine, Los Angeles, California 90048
| | - Chun-Rong Chen
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and UCLA School of Medicine, Los Angeles, California 90048
| | - Sandra M McLachlan
- Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and UCLA School of Medicine, Los Angeles, California 90048
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