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Makkonen K, Jännäri M, Crisóstomo L, Kuusi M, Patyra K, Melnyk V, Linnossuo V, Ojala J, Ravi R, Löf C, Mäkelä JA, Miettinen P, Laakso S, Ojaniemi M, Jääskeläinen J, Laakso M, Bossowski F, Sawicka B, Stożek K, Bossowski A, Kleinau G, Scheerer P, FinnGen F, Reeve MP, Kero J. Mechanisms of thyrotropin receptor-mediated phenotype variability deciphered by gene mutations and M453T-knockin model. JCI Insight 2024; 9:e167092. [PMID: 38194289 PMCID: PMC11143923 DOI: 10.1172/jci.insight.167092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 01/05/2024] [Indexed: 01/10/2024] Open
Abstract
The clinical spectrum of thyrotropin receptor-mediated (TSHR-mediated) diseases varies from loss-of-function mutations causing congenital hypothyroidism to constitutively active mutations (CAMs) leading to nonautoimmune hyperthyroidism (NAH). Variation at the TSHR locus has also been associated with altered lipid and bone metabolism and autoimmune thyroid diseases. However, the extrathyroidal roles of TSHR and the mechanisms underlying phenotypic variability among TSHR-mediated diseases remain unclear. Here we identified and characterized TSHR variants and factors involved in phenotypic variability in different patient cohorts, the FinnGen database, and a mouse model. TSHR CAMs were found in all 16 patients with NAH, with 1 CAM in an unexpected location in the extracellular leucine-rich repeat domain (p.S237N) and another in the transmembrane domain (p.I640V) in 2 families with distinct hyperthyroid phenotypes. In addition, screening of the FinnGen database revealed rare functional variants as well as distinct common noncoding TSHR SNPs significantly associated with thyroid phenotypes, but there was no other significant association between TSHR variants and more than 2,000 nonthyroid disease endpoints. Finally, our TSHR M453T-knockin model revealed that the phenotype was dependent on the mutation's signaling properties and was ameliorated by increased iodine intake. In summary, our data show that TSHR-mediated disease risk can be modified by variants at the TSHR locus both inside and outside the coding region as well as by altered TSHR-signaling and dietary iodine, supporting the need for personalized treatment strategies.
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Affiliation(s)
- Kristiina Makkonen
- Department of Clinical Sciences, Faculty of Medicine, and
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Meeri Jännäri
- Department of Clinical Sciences, Faculty of Medicine, and
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Luís Crisóstomo
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Matilda Kuusi
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Konrad Patyra
- Department of Clinical Sciences, Faculty of Medicine, and
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | | | - Veli Linnossuo
- Department of Clinical Sciences, Faculty of Medicine, and
| | - Johanna Ojala
- Department of Clinical Sciences, Faculty of Medicine, and
| | - Rowmika Ravi
- Department of Clinical Sciences, Faculty of Medicine, and
| | - Christoffer Löf
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Juho-Antti Mäkelä
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Päivi Miettinen
- New Children’s Hospital, Helsinki University Hospital, Helsinki, Finland
| | - Saila Laakso
- New Children’s Hospital, Helsinki University Hospital, Helsinki, Finland
| | - Marja Ojaniemi
- Department of Pediatrics and Adolescence, PEDEGO Research Unit and Medical Research Center, University and University Hospital of Oulu, Oulu, Finland
| | | | - Markku Laakso
- Institute of Clinical Medicine, Internal Medicine, University of Eastern Finland, Kuopio, Finland
| | - Filip Bossowski
- Department of Pediatrics, Endocrinology, Diabetes with a Cardiology Unit, Medical University in Białystok, Bialystok, Poland
| | - Beata Sawicka
- Department of Pediatrics, Endocrinology, Diabetes with a Cardiology Unit, Medical University in Białystok, Bialystok, Poland
| | - Karolina Stożek
- Department of Pediatrics, Endocrinology, Diabetes with a Cardiology Unit, Medical University in Białystok, Bialystok, Poland
| | - Artur Bossowski
- Department of Pediatrics, Endocrinology, Diabetes with a Cardiology Unit, Medical University in Białystok, Bialystok, Poland
| | - Gunnar Kleinau
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, and
- Humboldt - Universität zu Berlin, Institute of Medical Physics, Biophysics, Group Structural Biology of Cellular Signaling, Berlin, Germany
| | - Patrick Scheerer
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, and
- Humboldt - Universität zu Berlin, Institute of Medical Physics, Biophysics, Group Structural Biology of Cellular Signaling, Berlin, Germany
| | - FinnGen FinnGen
- Institute for Molecular Medicine Finland, HiLIFE, University of Helsinki, Helsinki, Finland
- FinnGen is detailed in Supplemental Acknowledgments
| | - Mary Pat Reeve
- Institute for Molecular Medicine Finland, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Jukka Kero
- Department of Clinical Sciences, Faculty of Medicine, and
- Department of Pediatrics and Adolescent Medicine, Turku University Hospital, Turku, Finland
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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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3
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Press O, Zvagelsky T, Vyazmensky M, Kleinau G, Engel S. Construction of Structural Mimetics of the Thyrotropin Receptor Intracellular Domain. Biophys J 2016; 111:2620-2628. [PMID: 28002738 PMCID: PMC5192603 DOI: 10.1016/j.bpj.2016.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 10/26/2016] [Accepted: 11/02/2016] [Indexed: 10/20/2022] Open
Abstract
The signaling of a G protein-coupled receptor (GPCR) is dictated by the complementary responsiveness of interacting intracellular effectors such as G proteins. Many GPCRs are known to couple to more than one G protein subtype and induce a multitude of signaling pathways, although the in vivo relevance of particular pathways is mostly unrecognized. Dissecting GPCR signaling in terms of the pathways that are activated will boost our understanding of the molecular fundamentals of hormone action. The structural determinants governing the selectivity of GPCR/G protein coupling, however, remain obscure. Here, we describe the design of soluble GPCR mimetics to study the details of the interplay between G-proteins and activators. We constructed functional mimetics of the intracellular domain of a model GPCR, the thyrotropin receptor. We based the construction on a unique scaffold, 6-Helix, an artificial protein that was derived from the elements of the trimer-of-hairpins structure of HIV gp41 and represents a bundle of six α-helices. The 6-Helix scaffold, which endowed the substituted thyrotropin receptor intracellular domain elements with spatial constraints analogous to those found in native receptors, enabled the reconstitution of a microdomain that consists of intracellular loops 2 and 3, and is capable of binding and activating Gα-(s). The 6-Helix-based mimetics could be used as a platform to study the molecular basis of GPCR/G protein recognition. Such knowledge could help investigators develop novel therapeutic strategies for GPCR-related disorders by targeting the GPCR/G protein interfaces and counteracting cellular dysfunctions via focused tuning of GPCR signaling.
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Affiliation(s)
- Olga Press
- Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Tatiana Zvagelsky
- Department of Chemistry, Faculty of Natural Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Maria Vyazmensky
- Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin, Berlin, Germany
| | - Stanislav Engel
- Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
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4
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Derkach KV, Moiseyuk IV, Shpakova EA, Shpakov AO. The thyroid status of rats immunized with peptides derived from the extracellular regions of the types 3 and 4 melanocortin receptors and the 1B-subtype 5-hydroxytryptamine receptor. J EVOL BIOCHEM PHYS+ 2015. [DOI: 10.1134/s0022093015040031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Intranasal and Intramuscular Administration of Lysine-Palmitoylated Peptide 612–627 of Thyroid-Stimulating Hormone Receptor Increases the Level of Thyroid Hormones in Rats. Int J Pept Res Ther 2015. [DOI: 10.1007/s10989-014-9452-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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6
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Banerjee AA, Mahale SD. Role of the Extracellular and Intracellular Loops of Follicle-Stimulating Hormone Receptor in Its Function. Front Endocrinol (Lausanne) 2015; 6:110. [PMID: 26236283 PMCID: PMC4505104 DOI: 10.3389/fendo.2015.00110] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/03/2015] [Indexed: 12/20/2022] Open
Abstract
Follicle-stimulating hormone receptor (FSHR) is a leucine-rich repeat containing class A G-protein coupled receptor belonging to the subfamily of glycoprotein hormone receptors (GPHRs), which includes luteinizing hormone/choriogonadotropin receptor (LH/CGR) and thyroid-stimulating hormone receptor. Its cognate ligand, follicle-stimulating hormone binds to, and activates FSHR expressed on the surface of granulosa cells of the ovary, in females, and Sertoli cells of the testis, in males, to bring about folliculogenesis and spermatogenesis, respectively. FSHR contains a large extracellular domain (ECD) consisting of leucine-rich repeats at the N-terminal end and a hinge region at the C-terminus that connects the ECD to the membrane spanning transmembrane domain (TMD). The TMD consists of seven α-helices that are connected to each other by means of three extracellular loops (ELs) and three intracellular loops (ILs) and ends in a short-cytoplasmic tail. It is well established that the ECD is the primary hormone binding domain, whereas the TMD is the signal transducing domain. However, several studies on the ELs and ILs employing site directed mutagenesis, generation of chimeric receptors and in vitro characterization of naturally occurring mutations have proven their indispensable role in FSHR function. Their role in every phase of the life cycle of the receptor like post translational modifications, cell surface trafficking, hormone binding, activation of downstream signaling, receptor phosphorylation, hormone-receptor internalization, and recycling of hormone-receptor complex have been documented. Mutations in the loops causing dysregulation of these processes lead to pathophysiological conditions. In other GPHRs as well, the loops have been convincingly shown to contribute to various aspects of receptor function. This review article attempts to summarize the extensive contributions of FSHR loops and C-terminal tail to its function.
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Affiliation(s)
- Antara A. Banerjee
- Division of Structural Biology, National Institute for Research in Reproductive Health, Indian Council of Medical Research, Mumbai, India
| | - Smita D. Mahale
- Division of Structural Biology, National Institute for Research in Reproductive Health, Indian Council of Medical Research, Mumbai, India
- ICMR Biomedical Informatics Centre, National Institute for Research in Reproductive Health, Indian Council of Medical Research, Mumbai, India
- *Correspondence: Smita D. Mahale, Division of Structural Biology, ICMR Biomedical Informatics Centre, National Institute for Research in Reproductive Health, Indian Council of Medical Research, Jehangir Merwanji Street, Parel, Mumbai 400 012, India,
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Kleinau G, Biebermann H. Constitutive activities in the thyrotropin receptor: regulation and significance. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 70:81-119. [PMID: 24931193 DOI: 10.1016/b978-0-12-417197-8.00003-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The thyroid-stimulating hormone receptor (TSHR, or thyrotropin receptor) is a family A G protein-coupled receptor. It not only binds thyroid-stimulating hormone (TSH, or thyrotropin) but also interacts with autoantibodies under pathological conditions. The TSHR and TSH are essential for thyroid growth and function and thus for all thyroid hormone-associated physiological superordinated processes, including metabolism and development of the central nervous system. In vitro studies have found that the TSHR permanently stimulates ligand-independent (constitutive) activation of Gs, which ultimately leads to intracellular cAMP accumulation. Furthermore, a vast variety of constitutively activating mutations of TSHR-at more than 50 different amino acid positions-have been reported to enhance basal signaling. These lead in vivo to a "gain-of-function" phenotype of nonautoimmune hyperthyroidism or toxic adenomas. Moreover, many naturally occurring inactivating mutations are known to cause a "loss-of-function" phenotype, resulting in resistance to thyroid hormone or hyperthyrotropinemia. Several of these mutations are also characterized by impaired basal signaling, and these are designated here as "constitutively inactivating mutations" (CIMs). More than 30 amino acid positions with CIMs have been identified so far. Moreover, the permanent TSHR signaling capacity can also be blocked by inverse agonistic antibodies or small drug-like molecules, which both have a potential for clinical usage. In this chapter, information on constitutive activity in the TSHR is described, including up- and downregulation, linked protein conformations, physiological and pathophysiological conditions, and related intracellular signaling.
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Affiliation(s)
- Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
| | - Heike Biebermann
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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Kleinau G, Neumann S, Grüters A, Krude H, Biebermann H. Novel insights on thyroid-stimulating hormone receptor signal transduction. Endocr Rev 2013; 34:691-724. [PMID: 23645907 PMCID: PMC3785642 DOI: 10.1210/er.2012-1072] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The TSH receptor (TSHR) is a member of the glycoprotein hormone receptors, a subfamily of family A G protein-coupled receptors. The TSHR is of great importance for the growth and function of the thyroid gland. The TSHR and its endogenous ligand TSH are pivotal proteins with respect to a variety of physiological functions and malfunctions. The molecular events of TSHR regulation can be summarized as a process of signal transduction, including signal reception, conversion, and amplification. The steps during signal transduction from the extra- to the intracellular sites of the cell are not yet comprehensively understood. However, essential new insights have been achieved in recent years on the interrelated mechanisms at the extracellular region, the transmembrane domain, and intracellular components. This review contains a critical summary of available knowledge of the molecular mechanisms of signal transduction at the TSHR, for example, the key amino acids involved in hormone binding or in the structural conformational changes that lead to G protein activation or signaling regulation. Aspects of TSHR oligomerization, signaling promiscuity, signaling selectivity, phenotypes of genetic variations, and potential extrathyroidal receptor activity are also considered, because these are relevant to an understanding of the overall function of the TSHR, including physiological, pathophysiological, and pharmacological perspectives. Directions for future research are discussed.
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Affiliation(s)
- Gunnar Kleinau
- Institute of Experimental Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, Ostring 3, Augustenburger Platz 1, 13353 Berlin, Germany.
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9
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Moreira IS. Structural features of the G-protein/GPCR interactions. Biochim Biophys Acta Gen Subj 2013; 1840:16-33. [PMID: 24016604 DOI: 10.1016/j.bbagen.2013.08.027] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 01/07/2023]
Abstract
BACKGROUND The details of the functional interaction between G proteins and the G protein coupled receptors (GPCRs) have long been subjected to extensive investigations with structural and functional assays and a large number of computational studies. SCOPE OF REVIEW The nature and sites of interaction in the G-protein/GPCR complexes, and the specificities of these interactions selecting coupling partners among the large number of families of GPCRs and G protein forms, are still poorly defined. MAJOR CONCLUSIONS Many of the contact sites between the two proteins in specific complexes have been identified, but the three dimensional molecular architecture of a receptor-Gα interface is only known for one pair. Consequently, many fundamental questions regarding this macromolecular assembly and its mechanism remain unanswered. GENERAL SIGNIFICANCE In the context of current structural data we review the structural details of the interfaces and recognition sites in complexes of sub-family A GPCRs with cognate G-proteins, with special emphasis on the consequences of activation on GPCR structure, the prevalence of preassembled GPCR/G-protein complexes, the key structural determinants for selective coupling and the possible involvement of GPCR oligomerization in this process.
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Affiliation(s)
- Irina S Moreira
- REQUIMTE/Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.
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10
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Cassio A, Nicoletti A, Rizzello A, Zazzetta E, Bal M, Baldazzi L. Current loss-of-function mutations in the thyrotropin receptor gene: when to investigate, clinical effects, and treatment. J Clin Res Pediatr Endocrinol 2013; 5 Suppl 1:29-39. [PMID: 23154162 PMCID: PMC3608004 DOI: 10.4274/jcrpe.864] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Thyroid-stimulating hormone receptor (TSHR) loss-of-function (LOF) mutations lead to a wide spectrum of phenotypes, ranging from severe congenital hypothyroidism (CH) to mild euthyroid hyperthyrotropinemia. The degree of TSH resistance depends on the severity of the impairment of the receptor function caused by the mutation and on the number of mutated alleles In this review data about genotype-phenotype correlation and criteria for clinical work-up will be presented and discussed. Complete TSH resistance due to biallelic LOF TSHR mutations must be suspected in all patients with severe not syndromic CH and severe thyroid hypoplasia diagnosed at birth by neonatal screening. Partial forms of TSH resistance show a more heterogeneous hormonal and clinical pattern . In these cases TSH serum levels are above the upper limit of normal range for the age but with a very variable pattern, free thyroxine (T4) concentrations are within the normal range and thyroid size can be normal or hypoplastic at ultrasound scan. An early substitutive treatment with L-T4 must be mandatory in all patients with severe CH due to complete uncompensated TSH resistance diagnosed at birth by neonatal screening. The usefulness of substitutive treatment appears much more controversial inpatients with subclinical hypothyroidism due to partial TSH resistance in whom the increased TSH concentration should be able to compensate the mild functional impairment of the mutant receptor. Together with standard criteria we recommend also an accurate clinical work-up to select patients who are candidates for a LOF TSHR mutation.
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Affiliation(s)
- Alessandra Cassio
- Department of Gynaecologic, Obstetric and Paediatric Sciences, S Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
| | - Annalisa Nicoletti
- Department of Gynaecologic, Obstetric and Paediatric Sciences, S.Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Angela Rizzello
- Department of Gynaecologic, Obstetric and Paediatric Sciences, S.Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Emanuela Zazzetta
- Department of Gynaecologic, Obstetric and Paediatric Sciences, S.Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Milva Bal
- Department of Gynaecologic, Obstetric and Paediatric Sciences, S.Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Lilia Baldazzi
- Department of Gynaecologic, Obstetric and Paediatric Sciences, S.Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
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Shpakova EA, Shpakov AO, Chistyakova OV, Moyseyuk IV, Derkach KV. Biological activity in vitro and in vivo of peptides corresponding to the third intracellular loop of thyrotropin receptor. DOKL BIOCHEM BIOPHYS 2012; 443:64-7. [PMID: 22562627 DOI: 10.1134/s1607672912020020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Indexed: 11/23/2022]
Affiliation(s)
- E A Shpakova
- Institute of Macromolecular Compounds, Russian Academy of Sciences, Bol'shoi proezd 31, St. Petersburg, 119004 Russia
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12
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Hull JJ, Lee JM, Matsumoto S. Identification of specific sites in the third intracellular loop and carboxyl terminus of the Bombyx mori pheromone biosynthesis activating neuropeptide receptor crucial for ligand-induced internalization. INSECT MOLECULAR BIOLOGY 2011; 20:801-811. [PMID: 21955122 DOI: 10.1111/j.1365-2583.2011.01110.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Sex pheromone production in most moths is mediated by the pheromone biosynthesis activating neuropeptide receptor (PBANR). Using fluorescent Bombyx mori PBANR (BmPBANR) chimeras to study PBANR regulation, we previously showed that BmPBANR undergoes rapid ligand-induced internalization, that the endocytotic motif resides between residues 358-367 of the BmPBANR C terminus, and that the internalization pathway is clathrin-dependent. Here, we sought to expand our understanding of the molecular mechanisms underlying BmPBANR function and regulation by transiently expressing a series of fluorescent BmPBANR chimeric constructs in cultured Spodoptera frugiperda (Sf9) cells and assaying for internalization of a fluorescently labelled ligand. Pharmacological inhibition of phospholipase C significantly reduced internalization, suggesting that BmPBANR regulation proceeds via a conventional G-protein-dependent pathway. This was further supported by impaired internalization following site-directed mutagenesis of R263 and R264, two basic residues at the transmembrane 6 intracellular junction that are thought to stabilize G-protein coupling via electrostatic interactions. Ala substitution of S333 and S366, two consensus protein kinase C sites in the C terminus, likewise impaired internalization, as did RNA interference-mediated knockdown of Sf9 protein kinase C. N-terminal truncations of BmPBANR indicate that the first 27 residues are not necessary for cell surface trafficking or receptor functionality.
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Affiliation(s)
- J J Hull
- Molecular Entomology Laboratory, RIKEN Advanced Science Institute, Wako, Saitama, Japan.
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13
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Kleinau G, Hoyer I, Kreuchwig A, Haas AK, Rutz C, Furkert J, Worth CL, Krause G, Schülein R. From molecular details of the interplay between transmembrane helices of the thyrotropin receptor to general aspects of signal transduction in family a G-protein-coupled receptors (GPCRs). J Biol Chem 2011; 286:25859-71. [PMID: 21586576 PMCID: PMC3138303 DOI: 10.1074/jbc.m110.196980] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 05/10/2011] [Indexed: 12/24/2022] Open
Abstract
Transmembrane helices (TMHs) 5 and 6 are known to be important for signal transduction by G-protein-coupled receptors (GPCRs). Our aim was to characterize the interface between TMH5 and TMH6 of the thyrotropin receptor (TSHR) to gain molecular insights into aspects of signal transduction and regulation. A proline at TMH5 position 5.50 is highly conserved in family A GPCRs and causes a twist in the helix structure. Mutation of the TSHR-specific alanine (Ala-593⁵·⁵⁰) at this position to proline resulted in a 20-fold reduction of cell surface expression. This indicates that TMH5 in the TSHR might have a conformation different from most other family A GPCRs by forming a regular α-helix. Furthermore, linking our own and previous data from directed mutagenesis with structural information led to suggestions of distinct pairs of interacting residues between TMH5 and TMH6 that are responsible for stabilizing either the basal or the active state. Our insights suggest that the inactive state conformation is constrained by a core set of polar interactions among TMHs 2, 3, 6, and 7 and in contrast that the active state conformation is stabilized mainly by non-polar interactions between TMHs 5 and 6. Our findings might be relevant for all family A GPCRs as supported by a statistical analysis of residue properties between the TMHs of a vast number of GPCR sequences.
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Affiliation(s)
- Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie, 13125 Berlin, Germany.
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Lado-Abeal J, Quisenberry LR, Castro-Piedras I. Identification and evaluation of constitutively active thyroid stimulating hormone receptor mutations. Methods Enzymol 2011; 484:375-95. [PMID: 21036242 DOI: 10.1016/b978-0-12-381298-8.00019-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
Abstract
Thyroid stimulating hormone receptor (TSHR) is a guanine nucleotide-binding protein-coupled seven-transmembrane-domain receptor that controls the differentiation, growth, and function of the thyroid gland through stimulation of adenylyl cyclase and phospholipase C pathways. Thyroid stimulating hormone (TSH) is the main TSHR ligand, and unliganded receptor remains silent due to the interaction of its large extracellular domain with the extracellular loops of the serpentine. The TSHR gene is highly mutagenic and constitutively active mutations have been extensively described. Naturally occurring TSHR-activating mutations can affect any part of the receptor, but most activating mutations affect the serpentine region, and the majority of these are located in the third intracellular loop or transmembrane domain six. We describe several simple and relatively cheap methods used in our laboratory to study constitutive TSHR mutations that include (1) screening of TSHR gene mutations in paraffin-embedded thyroid tissue samples, (2) measurement of TSHR constitutive activity in vitro, (3) measurement of TSHR expression at cell surface by flow cytometry analysis, (4) TSH binding to TSHR, and (5) TSHR phosphorylation analysis.
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Affiliation(s)
- Joaquin Lado-Abeal
- Department of Internal Medicine, Tech University Health Sciences Center-SOM, Lubbock, Texas, USA
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15
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Constitutive activation of the thyroid-stimulating hormone receptor (TSHR) by mutating Ile691 in the cytoplasmic tail segment. PLoS One 2011; 6:e16335. [PMID: 21283701 PMCID: PMC3025015 DOI: 10.1371/journal.pone.0016335] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 12/10/2010] [Indexed: 11/24/2022] Open
Abstract
Background Autosomal dominant non-autoimmune hyperthyroidism (ADNAH) is a rare genetic disorder of the endocrine system. Molecular genetic studies in ADNAH have revealed heterozygous germline mutations in the TSHR. To data, mutations leading to an increase in the constitutive activation of the TSHR have been described in the transmembrane segments, exoloops and cytoplasmic loop of TSHR. These mutations result in constitutive activation of the Gαs/cAMP or Gαq/11/inositol phosphate (IP) pathways, which stimulate thyroid hormone production and thyroid proliferation. Methodology/Principal Findings In a previous study, we reported a new TSHR mutation located in the C-terminal domain of TSHR, which results in a substitution of the conserved Ile691 for Phe. In this study, to address the question of whether the I691F mutated receptor could be responsible for Gαs/cAMP or Gαq/11/IP constitutive activity, wild-type and TSHR mutants were expressed in COS-7 cells to determine cAMP constitutive activity and IP formation. Compared to the cell surface with expression of the A623V mutated receptor as positive control, the I691F mutated receptor showed a slight increase of cAMP accumulation. Furthermore, I691F resulted in constitutive activation of the Gαq/11/IP signaling pathway. Conclusions/Significance Our results indicate that Ile691 not only contributes to keeping TSHR inactive in the Gαs/cAMP pathways but also in the Gαq/11/IP cascade.
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Hai MTV, Radu A, Ghinea N. The cleavage of thyroid-stimulating hormone receptor is dependent on cell-cell contacts and regulates the hormonal stimulation of phospholipase c. J Cell Mol Med 2010; 13:2253-2260. [PMID: 18627427 DOI: 10.1111/j.1582-4934.2008.00422.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Thyroid-stimulating hormone receptor (TSHR) consists of a hormone-binding extracellular subunit and a seven-transmembrane spanning subunit that interacts with the G proteins G(alphas) and G(alphaq). The two subunits, generated by proteolytic cleavage of a single polypeptide chain, are held together by disulphide bridges. The receptor is completely cleaved in thyroid tissue, while in cultured cells (thyrocytes and non-thyroid cells) the cleaved and uncleaved forms coexist. The reasons for these divergent data are not understood. Here we provide an explanation by showing that cleavage depends on cell-cell contacts. An almost complete cleavage was observed in confluent cells, while in sparse cells most of the receptor was in the uncleaved form. We also show that coupling of TSHR to G(alphaq) (as measured by inositolphosphate generation) is markedly reduced when the receptor is not cleaved. In contrast, coupling to G(alphas) [as measured by cyclic adenosine 3',5'-monophosphate (cAMP) synthesis] is unaffected by cleavage of the receptor. These results suggest that the cell-cell contacts are necessary for cleavage of the receptor, which acts as a regulatory step in inositolphosphate production via phospholipase C activation. The latter observation was confirmed using cells that express the uncleavable mutant TSHR-delta50-NET, for which the TSH-stimulated inositolphosphate production was completely abolished.
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Affiliation(s)
- Mai-Thu Vu Hai
- INSERM U841-Eq07, UniversitéParis, Faculté de Médicine, Créteil, France
| | - Aurelian Radu
- Mount Sinai School of Medicine, Department of Developmental and Regenerative Biology, New York, NY, USA
| | - Nicolae Ghinea
- INSERM U841-Eq07, UniversitéParis, Faculté de Médicine, Créteil, France
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17
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Kleinau G, Jaeschke H, Worth CL, Mueller S, Gonzalez J, Paschke R, Krause G. Principles and determinants of G-protein coupling by the rhodopsin-like thyrotropin receptor. PLoS One 2010; 5:e9745. [PMID: 20305779 PMCID: PMC2841179 DOI: 10.1371/journal.pone.0009745] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 02/19/2010] [Indexed: 11/23/2022] Open
Abstract
In this study we wanted to gain insights into selectivity mechanisms between G-protein-coupled receptors (GPCR) and different subtypes of G-proteins. The thyrotropin receptor (TSHR) binds G-proteins promiscuously and activates both Gs (cAMP) and Gq (IP). Our goal was to dissect selectivity patterns for both pathways in the intracellular region of this receptor. We were particularly interested in the participation of poorly investigated receptor parts. We systematically investigated the amino acids of intracellular loop (ICL) 1 and helix 8 using site-directed mutagenesis alongside characterization of cAMP and IP accumulation. This approach was guided by a homology model of activated TSHR in complex with heterotrimeric Gq, using the X-ray structure of opsin with a bound G-protein peptide as a structural template. We provide evidence that ICL1 is significantly involved in G-protein activation and our model suggests potential interactions with subunits Gα as well as Gβγ. Several amino acid substitutions impaired both IP and cAMP accumulation. Moreover, we found a few residues in ICL1 (L440, T441, H443) and helix 8 (R687) that are sensitive for Gq but not for Gs activation. Conversely, not even one residue was found that selectively affects cAMP accumulation only. Together with our previous mutagenesis data on ICL2 and ICL3 we provide here the first systematically completed map of potential interfaces between TSHR and heterotrimeric G-protein. The TSHR/Gq-heterotrimer complex is characterized by more selective interactions than the TSHR/Gs complex. In fact the receptor interface for binding Gs is a subset of that for Gq and we postulate that this may be true for other GPCRs coupling these G-proteins. Our findings support that G-protein coupling and preference is dominated by specific structural features at the intracellular region of the activated GPCR but is completed by additional complementary recognition patterns between receptor and G-protein subtypes.
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Affiliation(s)
- Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Holger Jaeschke
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | | | - Sandra Mueller
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | - Jorge Gonzalez
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | - Ralf Paschke
- Department for Internal Medicine, Neurology and Dermatology, University of Leipzig, Leipzig, Germany
| | - Gerd Krause
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin, Germany
- * E-mail:
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18
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Nicoletti A, Bal M, De Marco G, Baldazzi L, Agretti P, Menabò S, Ballarini E, Cicognani A, Tonacchera M, Cassio A. Thyrotropin-stimulating hormone receptor gene analysis in pediatric patients with non-autoimmune subclinical hypothyroidism. J Clin Endocrinol Metab 2009; 94:4187-94. [PMID: 19820021 DOI: 10.1210/jc.2009-0618] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Mutations in TSH receptor (TSHR) are notoriously associated with congenital hypothyroidism as well as with non-autoimmune subclinical hypothyroidism, a mild form of TSH resistance that is not as well characterized by diagnostic procedures. OBJECTIVE The genetic analysis of the TSHR gene was performed to determine the prevalence of TSHR gene mutations in non-autoimmune subclinical hypothyroidism during the pediatric age. The new mutations were studied for genotypic-phenotypic correlation. PATIENTS Thirty-eight children (ages 0.5-18.0 yr) affected by non-autoimmune subclinical hypothyroidism diagnosed in our center (follow-up from 1 to 11.5 yr) and normal at neonatal screening were enrolled in the genetic study. In 11 cases, the relatives were included in the genetic analysis. RESULTS Eleven different mutations of the TSHR gene were identified in 11 of the 38 patients. Two are new: the nonsense mutation C31X and the missense mutation P68S, which shows a decrease in TSH binding capacity but not in biological activity. In all cases the carrier parent was identified. CONCLUSIONS To date, this study demonstrates the highest prevalence (29%) of TSHR gene mutations in children and adolescents with non-autoimmune subclinical hypothyroidism not selected by neonatal screening. Functional studies show that some mutations cause a slight inactivation of the TSHR. This reveals a possible limit of the in vitro study or of the knowledge of mechanisms involving TSHR, or that other candidate genes must be considered.
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Affiliation(s)
- Annalisa Nicoletti
- Department of Gynaecologic, Obstetric, and Paediatric Sciences, S Orsola-Malpighi Hospital, University of Bologna, 40138 Bologna, Italy
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Latif R, Morshed SA, Zaidi M, Davies TF. The thyroid-stimulating hormone receptor: impact of thyroid-stimulating hormone and thyroid-stimulating hormone receptor antibodies on multimerization, cleavage, and signaling. Endocrinol Metab Clin North Am 2009; 38:319-41, viii. [PMID: 19328414 DOI: 10.1016/j.ecl.2009.01.006] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The thyroid-stimulating hormone receptor (TSHR) has a central role in thyrocyte function and is also one of the major autoantigens for the autoimmune thyroid diseases. We review the post-translational processing, multimerization, and intramolecular cleavage of TSHR, all of which may modulate its signal transduction. The recent characterization of monoclonal antibodies to the TSHR, including stimulating, blocking, and neutral antibodies, have also revealed unique biologic insights into receptor activation and the variety of these TSHR antibodies may help explain the multiple clinical phenotypes seen in autoimmune thyroid diseases. Knowledge of the structure/function relationship of the TSHR is beginning to provide a greater understanding of thyroid physiology and thyroid autoimmunity.
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Affiliation(s)
- Rauf Latif
- Thyroid Research Unit, Mount Sinai School of Medicine and the James J. Peters VA Medical Center, New York, NY 10468, USA.
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Gao F, Harikumar KG, Dong M, Lam PCH, Sexton PM, Christopoulos A, Bordner A, Abagyan R, Miller LJ. Functional importance of a structurally distinct homodimeric complex of the family B G protein-coupled secretin receptor. Mol Pharmacol 2009; 76:264-74. [PMID: 19429716 DOI: 10.1124/mol.109.055756] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Oligomerization of G protein-coupled receptors has been described, but its structural basis and functional importance have been inconsistent. Here, we demonstrate that the agonist occupied wild-type secretin receptor is predominantly in a guanine nucleotide-sensitive high-affinity state and exhibits negative cooperativity, whereas the monomeric receptor is primarily in a guanine nucleotide-insensitive lower affinity state. We previously demonstrated constitutive homodimerization of this receptor through the lipid-exposed face of transmembrane (TM) IV. We now use cysteine-scanning mutagenesis of 14 TM IV residues, bioluminescence resonance energy transfer (BRET), and functional analysis to map spatial approximations and functional importance of specific residues in this complex. All, except for three helix-facing mutants, trafficked to the cell surface, where secretin was shown to bind and elicit cAMP production. Cells expressing complementary-tagged receptors were treated with cuprous phenanthroline to establish disulfide bonds between spatially approximated cysteines. BRET was measured as an indication of receptor oligomerization and was repeated after competitive disruption of oligomers with TM IV peptide to distinguish covalent from noncovalent associations. Although all constructs generated a significant BRET signal, this was disrupted by peptide in all except for single-site mutants replacing five residues with cysteine. Of these, covalent stabilization of receptor homodimers through positions of Gly(243), Ile(247), and Ala(250) resulted in a GTP-sensitive high-affinity state of the receptor, whereas the same procedure with Ala(246) and Phe(240) mutants resulted in a GTP-insensitive lower affinity state. We propose the existence of a functionally important, structurally specific high-affinity dimeric state of the secretin receptor, which may be typical of family B G protein-coupled receptors.
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Affiliation(s)
- Fan Gao
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, USA
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21
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Kleinau G, Krause G. Thyrotropin and homologous glycoprotein hormone receptors: structural and functional aspects of extracellular signaling mechanisms. Endocr Rev 2009; 30:133-51. [PMID: 19176466 DOI: 10.1210/er.2008-0044] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The TSH receptor (TSHR) together with the homologous lutropin/choriogonadotropin receptor and the follitropin receptor are glycoprotein hormone receptors (GPHRs). They constitute a subfamily of the rhodopsin-like G protein-coupled receptors with seven transmembrane helices. GPHRs and their corresponding hormones are pivotal proteins with respect to a variety of physiological functions. The identification and characterization of intra- and intermolecular signaling determinants as well as signaling mechanisms are prerequisites to gaining molecular insights into functions and (pathogenic) dysfunctions of GPHRs. Knowledge about activation mechanisms is fragmentary, and the specific aspects have still not been understood in their entirety. Therefore, here we critically review the data available for these receptors and bring together structural and functional findings with a focus on the important large extracellular portion of the TSHR. One main focus is the particular function of structural determinants in the initial steps of the activation such as: 1) hormone binding at the extracellular site; 2) hormone interaction at a second binding site in the hinge region; 3) signal regulation via sequence motifs in the hinge region; and 4) synergistic signal amplification by cooperative effects of the extracellular loops toward the transmembrane region. Comparison and consolidation of data from the homologous glycoprotein hormone receptors TSHR, follitropin receptor, and lutropin/choriogonadotropin receptor provide an overview of extracellular mechanisms of signal initiation, conduction, and regulation at the TSHR and homologous receptors. Finally, we address the issue of structural implications and suggest a refined scenario for the initial signaling process on GPHRs.
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Affiliation(s)
- Gunnar Kleinau
- Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany
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García-Jiménez C, Santisteban P. Thyroid-stimulating hormone/cAMP-mediated proliferation in thyrocytes. Expert Rev Endocrinol Metab 2008; 3:473-491. [PMID: 30290436 DOI: 10.1586/17446651.3.4.473] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Current research on thyrotropin-activated proliferation in the thyrocyte needs to be aimed at a better understanding of crosstalk and negative-feedback mechanisms with other proliferative pathways, especially the insulin/IGF-1-induced phosphoinositol-3 kinase pathway and the serum-induced MAPK or Wnt pathways. Convergence of proliferative pathways in mTOR is a hotspot of current research, and combined treatment using double class inhibitors for thyroid cancer may bring some success. New thyroid-stimulating hormone receptor (TSHR)-interacting proteins, a better picture of cAMP targets, a deeper knowledge of the action of the protein kinase A regulatory subunits, especially their interactions with the replication machinery, and a further understanding of mechanisms that lead to cell cycle progression through G1/S and G2/M checkpoints are areas that need further elucidation. Finally, massive information coming from microarray data analysis will prompt our understanding of thyroid-stimulating hormone-promoted thyrocyte proliferation in health and disease.
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Affiliation(s)
- Custodia García-Jiménez
- a Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Avda Atenas s/n, 28922 Alcorcón, Madrid, Spain.
| | - Pilar Santisteban
- b Instituto de Investigaciones Biomédicas 'Alberto Sols', CSIC, C/Arturo Duperier, 4, 28932 Madrid, Spain.
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Feng X, Müller T, Mizrachi D, Fanelli F, Segaloff DL. An intracellular loop (IL2) residue confers different basal constitutive activities to the human lutropin receptor and human thyrotropin receptor through structural communication between IL2 and helix 6, via helix 3. Endocrinology 2008; 149:1705-17. [PMID: 18162522 PMCID: PMC2276707 DOI: 10.1210/en.2007-1341] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The human lutropin receptor (hLHR) and human TSH receptor (hTSHR) are G protein-coupled receptors that play key roles in reproductive and thyroid physiology, respectively. We show using a quantitative assessment of cAMP production as a function of cell surface receptor expression that the hTSHR possesses greater basal constitutive activity than the hLHR. Further studies were undertaken to test the hypothesis that different potential Gs-coupling motifs identified in IL2 of the hTSHR and hLHR contribute to their different basal constitutive activities. Although mutating the receptors to interchange their potential Gs-coupling motifs reversed their relative activities, we show this to be due to the swapping of one IL2 residue (Q476 in the hLHR; R531 in the hTSHR). Molecular dynamics simulations show that the effect of the hLHR(Q476R) mutation, switching the structural features of the hLHR toward those of the hTSHR, is greater than the switching effect of the hTSHR(R531Q) mutant toward the hLHR. The structural model of the hLHR(Q476R) mutant can be considered as a hybrid of wild-type (wt) hTSHR and constitutively active mutant hLHR forms. In this hLHR(Q476R) mutant, IL2 adopts a structure similar to IL2 of the wt hTSHR, but it shares with the hLHR constitutively active mutant the solvent exposure and the reciprocal arrangement of helices 3, 5, and 6, including the weakening of the wt native R3.50-D6.30 interaction. Our results suggest a H3-mediated structural connection between IL2 and the cytosolic extension of H6. Thus, IL2 contributes significantly to the inactive and active state ensembles of these G protein-coupled receptors.
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Affiliation(s)
- Xiuyan Feng
- Department of Molecular Physiology and Biophysics, The Roy J. and Lucille R. Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA
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