[Frontiers in Bioscience 15, 913-933, June 1, 2010]
Genetic defects, thyroid growth and malfunctions of the TSHR in pediatric patients
Heike Biebermann1, Franziska Winkler1, Gunnar Kleinau2
1Institute of Experimental Pediatric Endocrinology, Charite Universitatsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany, 2Leibniz-Institut fur Molekulare Pharmakologie (FMP), Robert-Rossle-Straße 10, 13125 Berlin, Germany
TABLE OF CONTENTS
1. ABSTRACT
Naturally occurring activating and inactivating mutations of the thyrotropin receptor (TSHR) were found as a molecular cause of diseases in patients suffering from non-autoimmune hyperthyroidism and syndromes of thyrotropin resistance, respectively. These mutations are mostly functionally characterized in vitro and therefore, they represent an excellent tool to study structure-function relationships of this G-protein-coupled receptor. In this review, we summarize published germline mutations of the TSHR with focus on 1) the phenotype of (pediatric) patients, 2) potential genotype/phenotype correlations, 3) structural implications for receptor activation and inactivation, 4) the impact on thyroid growth, and 5) finally on aspects of TSHR dimerization. In conclusion, this comprehensive analysis of medical and biological data opens an avenue to understand genetic defects and malfunctions of the TSHR in molecular detail and in their entirety. This knowledge is important to refine our insights in non-autoimmune diseases caused by defects of the TSHR gene and it might help to develop pharmacological means for compensation of uncontrolled thyroid growth.
2. INTRODUCTION
Thyroid stimulating hormone (TSH, also called Thyrotropin) is the most important factor for thyroid growth and function (reviewed in (1, 2)). TSH exerts its action via binding to and activating of the TSH receptor (TSHR) a member of the large superfamily of G-protein-coupled receptors (GPCR). These receptors share the common structural feature of a serpentine domain (SD) consisting of seven membrane-spanning alpha-helices (TMHs) that are connected by three intracellular and three extracellular loops (ICLs and ECLs). The N-terminal part of the receptor is extracellular and the C-terminus is intracellular located. The TSHR belongs to the subfamily of glycoprotein hormone receptors (GPHRs) together with the lutropin (LHCGR) and the follitropin receptor (FSHR). Binding of TSH to the large extracellular region of the receptor forces a conformational change in the protein resulting in G-protein activation (reviewed in (3)).
The TSHR is promiscuous with regard to its ability to activate all four G-protein families (4-6). So far activation of the Gs/adenylyl cyclase pathway seems to be of highest importance for thyroid growth and function (2), however, recently it was shown that activation of the Gq/11 pathway is obligatory for thyroid growth and thyroid hormone synthesis also (7, 8). The physiological relevance of Gi and G12/13 activation is poorly understood, although it was recently shown that MAPK activation is dependent on G13 signaling (9). Disturbance of thyroid function, resulting in a hyper- or hypo-functioning thyroid, results in disease conditions due to excess or lack of thyroid hormones, respectively.
Genetic defects in the TSHR were found as molecular causes of non-autoimmune hyperthyroidism (in cases of thyroid hormone excess) and of resistance to TSH (in cases of complete or partial lack of thyroid hormones) (10). In this review, we will focus on previously (reviews (11-13)) and recently published naturally occurring mutations in the TSHR gene leading to gain- or loss-of-function of thyroid hormone production. We will reflect also on the functional characterization of these mutations in vitro, which is a helpful tool to improve and to support the molecular diagnosis in patients. Moreover, these mutations are an excellent tool to obtain deeper insights into molecular details of TSHR structure and regulatory mechanisms of inter- as well as intramolecular interactions. This knowledge is necessary to learn more about the mechanisms of receptor activation and inactivation, which is a prerequisite to develop new ideas concerning therapeutic concepts (agents) for potential optimized treatment of thyroid diseases caused by malfunction of the TSHR.
3. GENETIC DEFECTS OF THE TSHR
It is known for a very long time that auto-antibodies to the TSHR in patients with Graves disease result in hyperfunction of the thyroid gland (14, 15). Additionally blocking antibodies of the TSHR were found in patients with congenital hypothyroidism (16). Shortly after cloning of the TSHR (17-22) it became obvious that not only immunological reactions lead to malfunction, but also mutations in the coding region were found to be responsible for disturbed thyroid function (23).
The gene of the TSHR is located on chromosome 14q31 (24), and the protein is encoded by 10 exons. Exon 1 to 9 encode for the extracellular region of the TSHR and exon 10 is encoding the serpentine domain and the C-terminal part (reviewed in (25)). Genetic defects of the TSHR include nonsense mutations, missense mutations, frame shift mutations, small deletions and insertions.
The molecular etiology of thyroid dysgenesis is poorly understood and in rare cases mutations in thyroid transcription factors (Pax-8, NKX2.1 and FoxE1) were identified (26-28). So far, mutations in the TSHR gene are the most common genetic cause of congenital hypothyroidism with hypoplasia of the thyroid gland in patients (16) were no further defects like kidney or lung involvement were identified, although also TSHR mutations in these patients are rare.
3.1. Somatic mutations
In 1993 the first mutations in the TSHR were found as somatic mutations in toxic thyroid adenomas (23). These mutations result in constitutive activation of the Gs/adenylyl cyclase signaling pathway (constitutively activating mutations, CAMs). This first report was followed by a huge variety of others, where heterozygous mutations in the TSHR gene were found as the molecular cause of hyperfunctioning adenomas (Figure 1B). The frequency of these somatic mutations varies largely (between below 10% up to 80 % (29)) depending on the study performance, e.g. patients origin and mutation screening procedure. As result of these mutations thyroid hormones in these patients were elevated and TSH levels were suppressed. Furthermore, some rare mutations (e.g. D633H,C (30) in TMH 6, I486F (31) in ECL 1) also activate both the Gs/adenylyl cyclase and the Gq/11 phospholipase C pathway.
No inactivating somatic TSHR mutation has been reported yet and somatic activating TSHR mutations in pediatric patients are extremely rare. Only one case has been reported so far (32). Therefore, this review will focus on germline mutations.
3.2. Germline mutations
Shortly after the first report of a somatic CAM in the TSHR gene, germline mutations were found in two large pedigrees with hyperfunctioning thyroid glands (33). These heterozygous CAMs were identified as the molecular cause of non-autoimmune hyperthyroidism and were described in familial as well as sporadic cases. So far, in all carriers of germline TSHR CAMs the thyroid gland was enlarged, which was addressed as an effect of Gs activation (2).
Besides CAMs, inactivating mutations in the TSHR gene were found also. These mutations occur homo- or compound heterozygously and result in hyperthyrotropinemia or congenital hyperthyroidism in the mutation carriers (34, 35). Clinical and functional aspects of inactivating and activating TSHR mutations will be discussed in the following sections.
4. INACTIVATING TSHR MUTATIONS AS THE MOLECULAR CAUSE OF HYPERTHYROTROPINEMIA AND CONGENITAL HYPERTHYROIDISM
4.1. Clinical aspects
The first patients in whom inactivating TSHR mutations were found are three siblings suffering from hyperthyrotropinemia (36). In these patients the thyroid gland was normal in size and position and thyroid hormone levels were in the normal range, a condition referred to as fully compensated resistance to thyroid hormones. The patients were compound heterozygous carriers of two mutations in exon 6 of the TSHR gene, which both result in a partial loss-of-function (37). Based on these findings, it was likely that more drastic mutations with complete loss-of-function might lead to congenital hypothyroidism. Indeed, the first patient with congenital hypothyroidism was a compound heterozygous carrier of a frameshift mutation leading to a complete loss-of-function and a missense mutation, C390W. The thyroid gland of the patient was located normally but hypoplastic (35). Noteworthy, this mutation resulted in partial loss-of-function of TSHR signaling when it was studied in vitro in a COS-7 cell overexpressing system. The functional effect of this mutation was even more severe when the mutation was investigated in a stable CHO-K1 cell line that reflects better the physiological level of TSHR expression. These findings demonstrate the difficulties to transfer results of functional in vitro characterization to the phenotype of patients. In often used heterologous overexpressing systems the degree of TSHR expression is much higher than in thyrocytes (34), which could lead to signal transduction levels that are not so severely affected as under physiologically relevant conditions. In addition to difficulties in the assessment of data of functional in vitro characterization, the phenotype of the patients carrying comparable TSHR mutations can vary between hyperthyrotropinemia and congenital hypothyroidism (35, 38). Reasons for this could be multi-factorial ranging from environmental factors to genetic susceptibility. After the first reports many more homo-, hetero- and compound heterozygous mutations were described as the molecular cause of different degrees of thyroid hormone resistance (Figure 1A, for references see Table 1).
4.2. Molecular and structural aspects of receptor inactivation
The wild type amino acids of loss-of-function mutants are involved in the maintenance of important TSHR properties like correct protein folding, the intrinsic signaling-capability, or the predisposition for interaction with TSH and G-protein. Molecular reasons for aberant signaling activity (partial or complete loss-of-function) of the TSHR caused by mutations can be grouped in the following categories:
1. Most of the known inactivating mutations lead to intracellularly retained TSHRs. This is the case for all nonsense and frame shift mutations, but also for mutations that result in complete misfolding of the receptor (Table 1B).
2. Mutations that maintain the receptor in the TSH unoccupied state and hinder a shift to the active conformation after TSH binding. These mutations are located in the N-terminus (e.g. D403N), serpentine domain (e.g. D460N, TMH2), or the ECLs (e.g. Q489H, ECL1) of the receptor (for references see Table 1).
3. Mutations that are incompatible with TSH binding. These mutations are extremely rare and they are located in the extracellular Leucine-rich repeat domain (LRRD) (8, 39). Most likely they directly influence TSH binding by disruption of potential intermolecular contact interfaces between TSH and TSHR.
4. Mutations at positions (Figure 1A) at the intracellular loops and intracellular transitions to the helices of the TSHR (e.g. R450H, TMH2; or M527T, ICL2), which are potentially important for receptor/G-protein contact.
The most drastic phenotype is loss-of-function caused by mutations leading to intracellularly retained TSHRs (nonsense mutations, frameshift mutations, missense mutations). In terms of partial loss-of-function it has to be assumed that functional properties of the receptor are partially preserved. This could be explained by the recently published finding of a multiply induced activation of the TSHR (40), which means, the full activation process is characterized by modification of the basal conformation at several spatially diversely located activation points. In a reverse conclusion, an interruption of "multi-component" signaling by single substitutions only leads to a locally restricted and therefore partial inactivation. Interestingly, mutations with a decreased basal activity (inverse agonistic mutations) are also under discussion to cause malfunction of GPCRs (like the TSHR) with a loss-of-function phenotype (41, 42).
Mapping of known loss-of-function mutations and the available 3-dimensional model of the TSHR reveal (Figure 2) that the majority of substitutions are localized in peripherical spatial regions like the LRRD, ECLs, and ICLs. We conclude that the loops and the extracellular part of the TSHR are most important for receptor trafficking, cell-surface expression, intermolecular contacts, and stabilization of the active conformation. The relevance and sensitivity of this "functional package" is exemplarily demonstrated by the recently reported mutation Q489H in extracellular loop 1 (ECL1), leading to high receptor expression levels on the cell surface and is able to bind TSH. However, it is suggested by the authors of this recent study that this mutation leads to a receptor that bypasses the endoplasmatic reticulum and golgi apparatus control system and reaches the cell surface as an immature receptor that impedes complete glycosylation and abolishes intramolecular cleavage. This altogether blocks the molecular changes to reach an active conformation (43).
The ECL1 of TSHR has been found to be important for keeping the receptor in its basal state (40, 44). This finding was underlined by data obtained with the closely related FSHR (45). Moreover, the ECL1 is extracellularly exposed and should be a determinant of assumed interaction between the serpentine domain and the hinge region (40, 46-48). Such interactions are involved in regulation of basal TSHR activity and in control of the transition between basal and activated receptor conformations. Mutation Q489H is localized in the middle part of ECL1 and is one out of several identified naturally occurring mutations in ECL1 (Figure 3): inactivating mutations - W488R, Q489H (43, 49, 50), activating mutations - A485V, I486M,F,N (31, 51, 52). While W488 most likely stabilizes ECL1 and the inactivating mutation W488R disturbs the folding of ECL1, Q489 might establish contacts to an interaction partner in spatial proximity that should be located in the hinge region according to the exposed location of ECL1. This interaction might be relevant for signaling related processes like stabilization of the activated TSHR conformation or justification of the receptor components serpentine domain/hinge region/LRRD to each other. In contrast, the mutation Q489H is unable to keep the molecular functions of the wild type side-chain. These conclusions are supported by mutagenesis studies at the ECL1, where the Q489A mutation and different W488 side-chain variations always lead to TSHR inactivation (40). The mechanism of CAMs at residues A485 and I486 will be discussed in more detail in section 5.2.
5. ACTIVATING GERMLINE MUTATIONS
5.1. Clinical aspects
The first patients diagnosed with a constitutive activating mutation as the molecular cause of non-autoimmune hyperthyroidism came from two large pedigrees from Belgium, known as the Reims and Nancy family (33). Already in this study it became obvious that severity and onset of disease vary between members of one family. It was speculated that environmental factors and the genetic background are responsible for this phenotypic variability (33). In addition to familial cases, sporadic cases were described (53, 54). There is some overlap between mutations found in toxic thyroid nodules or adenomas and as germline mutations. In the beginning it was assumed that these somatic mutations could be also found in severe sporadic cases. But over time this assumption did not hold true as these somatic mutations were also found in familial cases (54-56). For treatment options, the identification of a heterozygous TSHR mutation is of extreme importance if the subsequent functional characterization affirms the constitutive TSHR activation caused by the mutation. For patients, especially children, in whom hyperthyroidism can only be poorly controlled by anti-thyroid drugs, total thyroidectomy is the treatment of choice to avoid long-term sequela and complications like premature craniosynostosis (10). However, thyroidectomy is not necessary in all patients (51, 57, 58) as in the younger patients hyperthyroidism can be controlled by ant-thyroid drug treatment.
For activating mutations a correlation of the degree of constitutive Gs activation in vitro and the phenotype of the patient is not appropriate. One reason for this is the heterologous overexpression cell system standardly used for functional in vitro characterization of mutated receptors. Comparison of cAMP (cyclic adenosine monophosphate) accumulation in COS-7 cells and different thyroid cell systems demonstrated a discrepancy between cAMP formation between thyroid and non-thyroid cell lines indicating that the cellular context is important for the biological effects of the mutations (59).
5.2. Molecular and structural aspects of TSHR activation by mutation
The TSHR is characterized by a physiologically relevant basal (ligand independent) signaling activity (between 5-10 percent compared to TSH induced maximum of activation), which can be increased by mutations of single amino acids or deletions of receptor portions (60, 61). As described in section 5.1., this increase of basal activity can cause disease conditions like described for many other GPCRs (62-64). Two principle molecular reasons of non-autoimmune TSHR activation by mutation which lead to gain-of-function phenotypes can be distinguished:
(1) constitutive activation of the TSHR in absence of the endogenous ligand TSH,
(2) abrogated specificity for glycoprotein-hormones (reviewed in (65)).
For abrogated glycoprotein-hormone specificity one mutation, K183R in the LRRD, is reported so far (66) that displays promiscuous ligand binding (binding affinity for CG is increased). In contrast, somatic and germline mutations that constitutively activate the TSHR are published in around 70 reports (Figure 4). What are the molecular mechanisms of TSHR activation caused by mutations? Two possible modes of molecular action for CAMs are under discussion (67): 1. CAMs disrupt an interaction network important for stabilization of the basal conformation (most of the reported CAMs), or 2. substituted side-chains create new interactions (wild type amino acids are not involved in the maintenance of the basal state) and thereby shift the equilibrium between the inactive and active states towards the activated conformation (e.g. Y601N (68, 69)).
It can be assumed, that the majority of the CAMs are acting according to scenario 1. Examples are two positions of naturally occurring CAMs in the ECL1 (Figure 3): A485V, I486M,F;N (31, 51, 52). These side-chain substitutions and related constitutive TSHR activation suggest that tight hydrophobic interactions of the wild type amino acids are essential to keep the ECL1 in its conformation, which is crucial for maintenance of the basal state (40, 44). The exposed extracellular location of ECL1 in combination with its functional importance (see also section 4.4.) designate this loop as a candidate for potential interaction with the hinge region. Interestingly, naturally occurring CAMs in the ECLs or the hinge region have been reported only for the TSHR, but not for the closely related FSHR and LHCGR. Characterization of CAMs observed for the TSHR at corresponding positions of the FSHR or the LHCGR could help to answer the question of similarities or differences in resulting mutant properties and could provide further mechanistic and evolutionary insights into the group of GPHRs.
The distribution of naturally occurring gain-of-function mutations in the TSHR provides insights in the interrelation between structural and functional aspects of signaling mechanisms. CAMs of the TSHR are cumulatively localized in the centre of the transmembrane helix-core (Figure 4). The helices 3, 6 and 7 are hot-spots for CAMs. Several of the sensitive wild type amino acids interact directly with each other, e.g. A593 (TMH5) with V509 (TMH3) (70). Breakage of interactions or specific modifications at these positions releases the TSHR in its active conformation, which is confirmed in numerous mutagenesis studies (30, 71-75). In conclusion, the basal receptor conformation is constraint by interactions between residues at the helices with preferences for certain helices and regions in the central core of the helical-bundle. For activation of the TSHR these constraints must be released, which leads to structural shifts between receptor components (LRRD/hinge region/serpentine domain) and also between particular helices like TMH5, TMH6, and TMH7.
6. DIMERIZATION OF THE TSHR
Di- or oligomerization is an accepted structural and functional feature of G-protein-coupled receptors and has been shown for numerous GPCRs (76, 77). Dimerization of GPCRs can affect processes like trafficking to the cell surface, ligand binding, ligand-induced signaling and ligand-induced internalization. Moreover, as GPCRs are potent targets for therapeutical intervention, homo- and heterodimerization with unrelated GPCRs have to be taken into account (78).
For the TSHR first reports of potential organization in oligomers where revealed by the use of different antibodies raised against the N-terminus, the midportion and the C-terminus of the ectodomain (79). By using a fluorescence based technology (fluorescence resonance energy transfer, FRET) TSHR dimerization was first shown after expression in Chinese hamster ovary cells in which TSHR is expressed at a more physiologically relevant density (80). The effect of TSH binding for dimer formation seems to be controversial (80, 81) as it was first shown that TSH binding inhibits receptor oligomerization, however the degree of inhibition was low (80) and this finding was not reproduced in a second study (81).
Detailed characterization of TSHR di- or oligomerization by bioluminescence resonance energy transfer (BRET) and homogenous time resolved fluorescence (HTRF) point to the important role of the heptahelical domain of the receptor for intermolecular protein-protein interaction. The extracellular part might modulate the interaction (81). TSHR di-oligomerization seems to be constitutive and occurs early in the endoplasmatic reticulum (like also shown for the homologous LHCGR and FSHR (82, 83)) and is discussed to be obligatory for proper receptor expression (84).
For some patients who are diagnosed with TSH insensitivity only one heterozygous mutation could be identified (36). No second mutation in the coding region of the TSHR could be identified. One could speculate that the second mutation might be located in the promoter or the intronic region. However, dominant-negative effects for some mutations are likely also. This has been shown recently for partially inactivating TSHR mutations. These mutations (C41S, L467P, C600R) were identified in patients with autosomal dominant inheritance of TSH resistance (85). For all mutations intracellular trapping of the wild-type/mutant complex was demonstrated. This early TSHR dimerization could be an explanation for the dominant occurrence of heterozygous inactivating TSHR mutations (36, 85) that lead to a mild form of hyerthyrotropinemia. Moreover, the problems in correlation of genotype (functional characteristics of a mutation) and the phenotype of the patients (congenital hypothyroidism or hyperthyrotropinemia) may also be due to the fact, that GPCRs are not only able to homo-dimerize, but also to hetero-dimerize with other (unrelated) GPCRs, in particular in overexpression systems. Therefore, it might be valuable to test partial loss-of-function mutations in human thyrocytes, in which the TSHR is expressed at physiologically relevant levels.
The formation of tetrameric complexes has been shown for beta-2 adrenergic receptors (86). If this also holds true for the TSHR, five different variants of tetrameric complexes could be formed consisting of: 1. wild-type receptors only, 2. mutant receptors only, 3. one wild-type and three mutant receptors, 4. two wild-type and two mutant receptors or 5. three wild-type and 1 mutant receptor. The consequences of this mixture in vivo and in vitro should be responsible for signaling properties that also depend on interacting molecules like chaperones which could strongly differ between thyroid follicular cell and in vitro cell systems.
So far, only few inactivating mutations were examined in co-transfection experiments showing complementation of two inactivating mutations (81). For heterozygous constitutively activating mutations such interaction has not yet been investigated, however, it is also likely that activating mutation influence wild-type receptor function.
Interestingly, for the LHCGR it is demonstrated that a signaling inactive LHCGR mutant (that is trafficked normally to the plasma membrane) decreases the signaling of the wild type or the constitutively active LHCGR due to receptor heterodimerization (87).
6.1. Hypothetical TSHR dimer-interface
The FSHR is like the TSHR a member of the homologous GPHRs (88) and fragments of this gonadotrophic receptor were crystallized in 2005 (89-91). This structure of the LRRD is complexed with the hormone FSH and provided deep insights in the interaction between receptor and the glycoprotein hormone (92). Interestingly, in this crystal structure two LRRD monomers were arranged in a dimer conformation. In consequence, contacts between the extracellular regions of two receptor monomers in a dimer were discussed to be of importance for dimerization of GPHRs (90-92). Indeed, this hypotheses (but not the suggested participating detailed amino acids like Y110) for the FSHR has been refined by current studies of Guan and co-workers (83), who showed both the extracellular region and the serpentine domain as competent for oligomer-arrangements. A similar potential for oligomerization is also assumed for the extracellular and transmembrane regions of the LHCGR (93). For the TSHR interactions between the transmembrane regions are responsible to stabilize the dimer contact and the extracellular parts might modulate the interaction (81). Anyway, the detailed contacts between the monomers in dimer-oligomer arrangements and the functional significance of TSHR oligomers are still under discussion (80, 84, 94, 95).
For TSHR, FSHR, LHCGR and the Leucine-rich repeat containing G-protein-coupled receptors (LGRs) 7 and 8 (binding of peptide-hormones relaxins 1 to 3 and insulin-like 3/relaxin-like factor) an additional hint for dimer-arrangement and functionality is given by the fact that these receptors can be trans-activated by ligand binding (81, 96, 97) and negative cooperative effects were observed ((81, 98, 99), reviewed in (3)). This mechanism of receptor activation allows the conclusion of at least close distances between receptor monomers.
With respect to naturally occurring mutations one phenomenon is still unexplained and should be included in the discussion of TSHR dimer-arrangement and the dimer-interface (contact(s)). In detail, a microdomain of 5 consecutive amino acid positions (L629, I630, F631, T632, D633) were CAMs have been identified is localized in TMH6 (Figures 1 and 4). Because these residues are in an alpha-helix, where one turn is constituted by 3.6 amino acids per definition, at least one residue side-chain must point into the membrane. Homology models of the TSHR favour the side-chain of F631 to stick into the membrane. Furthermore, a similar observation can be made for I635 one turn above F631, but also for F666 at TMH7 (Figure 5). At these positions, naturally occurring CAMs are known. The question arises, how the increased basal activity by mutation can be explained in these particular cases? The side-chains do not interact directly with other amino acids and therefore mutations can not lead to a disruption (released basal conformation) or to constitution (stabilization of the activated conformation) of constraining interactions. In our here suggested hypothetical dimer arrangement of the TSHR with a main contact-interface between TMH6 and TMH7 these residues would interact with each other (Figure 5). Naturally occurring mutations F631V, I635V (TMH6), or F666L (TMH7) should interrupt hydrophobic and aromatic interactions constraining this potential dimer-interaction by introduction of shorter or non-aromatic side-chains. In a reverse interpretation, TMH6 and TMH7, which are known to be strongly involved in receptor activation are constraint in this dimer-arrangement and a release of such constraint could participate in TSHR activation. This suggestion is underlined by the extraordinary high number of CAMs in TMH6 (Figure 4). Additionally, ECL3 connects TMH6 and TMH7 and should be involved in this dimer-model by forming intermolecular interactions between receptor monomers. Therefore, known gain-of-function mutations like N650Y (100), V656F (60), or deletion del658-661 (101) probably modify this proposed dimer-interface also. However, without experimental evidence and exact knowledge of the in vivo dimer-interface the question of a relation between TSHR activation and complete interruption of the dimer-contact, a dimer-rearrangement, or dimer-constitution can not be answered yet.
7. TSHR MUTATIONS AND THYROID GROWTH
The first identified inactivating TSHR mutations led to a phenotype with a normal size of the thyroid gland (37). This was due to the fact that high TSH levels in the patients can overcome the partial inactivation of the mutation resulting in normal function of the thyroid gland. If high TSH levels can not rescue inactivating mutations, congenital hypothyroidism with hypoplasia of the thyroid gland occurs (43). This hypoplasia can be mild (102) or could result in apparent athyrosis (103, 104). For inactivating mutations, effects on cell surface expression, ligand binding and Gs activation were investigated only because higher amounts of TSH for activation of Gq/11 are needed (see Table 1). Interestingly, one TSHR mutation was identified in three siblings who suffer from congenital hyperthyrotropinemia and increased radio-iodine uptake. The identified homozygous L653V mutation showed normal cell surface expression and ligand binding, as well as normal basal cAMP and IP accumulation levels. Strikingly, TSH-induced EC50 levels for cAMP were slightly enhanced and TSH-induced IP levels were markedly reduced (8). This was the first report that demonstrated the important role of the Gq/11 pathway in thyroid hormone production, because the TSH levels needed to overcome the defect of TSHR signaling are much higher than for the slight defect in Gs/adenylyl cyclase signaling (8).
So far, all reported CAMs have been identified in patients with non-autoimmune hyperthyroidism and goiter. Growing of the thyroid gland was assumed to be the result of constitutive activation of the Gs/adenylyl cyclase pathway (2). However, it has been shown that constitutive activation of the Gs/adenylyl cyclase pathway is not sufficient to generate toxic thyroid nodules or adenomas (105). This could be also true for goiter formation in patients carrying constitutively activating germline TSH mutations pointing to more complex mechanisms in goiter formation.
Only a few mutations constitutively activate the Gq/11-mediated pathway. The activation of both signaling pathways did not lead to a more severe phenotype than Gs activating mutations alone (106). So far, only a few mutations with reduced or impaired IP formation were reported (see Table 1). For these mutations a reduction in cell surface expression or maximal binding properties could be responsible for reduction of bTSH-stimulated IP accumulation. For mutations M463V, A485V, I568T, F631S, C672Y an effect of IP impairment, measured in in vitro studies, on goiter formation in vivo is not clear, but can not be excluded. This is also the case for two TSHR mutations (S505R, N670S) that are expressed on the cell surface comparable to wild-type receptor, but are characterized by a decreased IP accumulation. In general, for the above mentioned mutations the onset of goiter formation is unclear.
Furthermore, attention on the physiological relevance of the Gq-mediated IP signaling pathway was drawn in previous studies (107). The recent view on thyroid growth probably has to be reconsidered now, because it was shown in 2007 that mice lacking Gq/11 proteins suffer from hypothyroidism and are protected of goitrogenous thyroid growth (7). In this line, we detected a patient with mild non-autoimmune hyperthyroidism. The child only presented with elevated thyroid hormone and repressed TSH levels. The size of the thyroid gland was normal and anti-thyroid drug treatment was not considered for a long time. Functional characterization of the identified mutation (C636W) showed the expected constitutive activity of the Gs pathway, however, the Gq/11 pathway induced by TSH was nearly completely inactivated (108) although cell surface expression and binding properties were not affected. We here suppose that loss-of-function of the Gq/11 pathway might participate in the mild phenotype of the patient and the current lack of goiter (age 11.5 years). Therefore, this condition should be termed non-autoimmune, non-goitrogenous hyperthyroidism. To verify the hypothesis that a lack of Gq/11 activation should protect from uncontrolled thyroid growth, more young patients with a similar phenotype have to be investigated.
8. CONCLUDING REMARKS
The knowledge concerning medical and biological aspects related to the thyrotropin receptor has been exponentially accumulated in the last decades, also the role of the TSHR in non-thyroidal tissues (109, 110). This includes occurrence and prevalence of naturally occurring mutations, phenotypes and understanding of diseases related to TSHR malfunctions, but also mechanisms of signaling processes at this protein are of high interest (1, 2, 14, 15, 25, 63, 64, 93, 111). Regulation of TSHR function is studied intensively and a few findings can be generalized for other GPCRs characterized by similar structural and functional features like elevated basal signaling activity or multiple and synergistic signal induction (40). Understanding of structural features causally related to functional properties is a prerequisite and of high interest for optimized treatment of patients. The investigation of antibodies (agonistic, antagonistic, inverse agonistic (14, 15, 112-114)) and the development of allosterically bound synthetic drug-like agonists and antagonists for the TSHR (115-117) are topics of high priority in this field (118). Major goals are the understanding of TSHR signaling and the specific pharmacological modulation of signaling pathways.
9. ACKNOWLEDGEMENT
This work was supported by the graduate college 1208, TP1. We thank Susanne Neumann, NIDDK, NIH, Bethesda, US, for critical reading of the manuscript and her constructive suggestions.
10. REFERENCES
1. Garcia-Jimenez, C., and Santisteban, P.: TSH signalling and cancer. Arq Bras. Endocrinol. Metabol., 51, 654-671 (2007)
doi:10.1590/S0004-27302007000500003
2. Vassart, G., and Dumont, J. E: The thyrotropin receptor and the regulation of thyrocyte function and growth. Endocr. Rev., 13, 596-611 (1992)
doi:10.1210/edrv-13-3-596
3. Kleinau, G., and Krause, G.: Thyrotropin and homologous glycoprotein hormone receptors: structural and functional aspects of extracellular signaling mechanisms. Endocr. Rev., 30, 133-151 (2009)
doi:10.1210/er.2008-0044
4. Allgeier, A., Laugwitz, K. L., Van Sande, J., Schultz, G., and Dumont, J. E.: Multiple G-protein coupling of the dog thyrotropin receptor. Mol. Cell Endocrinol., 127, 81-90 (1997)
doi:10.1016/S0303-7207(96)03996-2
5. Laugwitz, K. L., Allgeier, A., Offermanns, S., Spicher, K., Van Sande, J., Dumont, J. E., and Schultz, G.: The human thyrotropin receptor: a heptahelical receptor capable of stimulating members of all four G protein families. Proc. Natl. Acad. Sci. U. S. A 93, 116-120 (1996)
doi:10.1073/pnas.93.1.116
6. Laurent, E., Mockel, J., Van Sande, J., Graff, I., and Dumont, J. E.: Dual activation by thyrotropin of the phospholipase C and cyclic AMP cascades in human thyroid. Mol. Cell Endocrinol. 52, 273-278 (1987)
doi:10.1016/0303-7207(87)90055-4
7. Kero, J., Ahmed, K., Wettschureck, N., Tunaru, S., Wintermantel, T., Greiner, E., Schutz, G., and Offermanns, S.: Thyrocyte-specific Gq/G11 deficiency impairs thyroid function and prevents goiter development. J. Clin. Invest, 117, 2399-2407 (2007)
doi:10.1172/JCI30380
8. Grasberger, H., Van Sande, J., Hag-Dahood, M. A., Tenenbaum-Rakover, Y., and Refetoff, S.: A familial thyrotropin (TSH) receptor mutation provides in vivo evidence that the inositol phosphates/Ca2+ cascade mediates TSH action on thyroid hormone synthesis. J. Clin. Endocrinol. Metab, 92, 2816-2820 (2007)
doi:10.1210/jc.2007-0366
9. Buch, T. R., Biebermann, H., Kalwa, H., Pinkenburg, O., Hager, D., Barth, H., Aktories, K., Breit, A., and Gudermann, T.: G13-dependent activation of MAPK by thyrotropin. J. Biol. Chem., 283, 20330-20341 (2008)
doi:10.1074/jbc.M800211200
10. Gruters, A., Schoneberg, T., Biebermann, H., Krude, H., Krohn, H. P., Dralle, H., and Gudermann, T.: Severe congenital hyperthyroidism caused by a germ-line neo mutation in the extracellular portion of the thyrotropin receptor. J. Clin. Endocrinol. Metab, 83, 1431-1436 (1998)
doi:10.1210/jc.83.5.1431
11. Rodien, P., Ho, S. C., Vlaeminck, V., Vassart, G., and Costagliola, S.: Activating mutations of TSH receptor. Ann. Endocrinol. (Paris), 64, 12-16 (2003)
doi: AE-02-2003-64-1-0003-4266-101019-ART05
12. Farid, N. R., Kascur, V., and Balazs, C.: The human thyrotropin receptor is highly mutable: a review of gain-of-function mutations. Eur. J. Endocrinol., 143, 25-30 (2000)
doi:10.1530/eje.0.1430025
13. Corvilain, B., Van Sande, J., Dumont, J. E., and Vassart, G.: Somatic and germline mutations of the TSH receptor and thyroid diseases. Clin. Endocrinol. (Oxf) 55, 143-158 (2001)
doi:10.1046/j.1365-2265.2001.01365.x
14. Rapoport, B., and McLachlan, S. M.: The thyrotropin receptor in Graves' disease. Thyroid, 17, 911-922 (2007)
doi:10.1089/thy.2007.0170
15. Davies, T. F., Ando, T., Lin, R. Y., Tomer, Y., and Latif, R.: Thyrotropin receptor-associated diseases: from adenomata to Graves disease. J. Clin. Invest, 115, 1972-1983 (2005)
doi:10.1172/JCI26031
16. Bogner, U., Gruters, A., Sigle, B., Helge, H., and Schleusener, H.: Cytotoxic antibodies in congenital hypothyroidism. J. Clin. Endocrinol. Metab, 68, 671-675 (1989)
doi:10.1210/jcem-68-3-671
17. Parmentier, M., Libert, F., Maenhaut, C., Lefort, A., Gerard, C., Perret, J., Van Sande, J., Dumont, J. E., and Vassart, G.: Molecular cloning of the thyrotropin receptor. Science, 246, 1620-1622 (1989)
doi:10.1126/science.2556796
18. Nagayama, Y., Kaufman, K. D., Seto, P., and Rapoport, B.: Molecular cloning, sequence and functional expression of the cDNA for the human thyrotropin receptor. Biochem. Biophys. Res. Commun., 165, 1184-1190 (1989)
doi:10.1016/0006-291X(89)92727-7
19. Misrahi, M., Loosfelt, H., Atger, M., Sar, S., Guiochon-Mantel, A., and Milgrom, E.: Cloning, sequencing and expression of human TSH receptor. Biochem. Biophys. Res. Commun., 166, 394-403 (1990)
doi:10.1016/0006-291X(90)91958-U
20. Huang, G. C., Page, M. J., Roberts, A. J., Malik, A. N., Spence, H., McGregor, A. M., and Banga, J. P.: Molecular cloning of a human thyrotropin receptor cDNA fragment. Use of highly degenerate, inosine containing primers derived from aligned amino acid sequences of a homologous family of glycoprotein hormone receptors. FEBS Lett., 264, 193-197 (1990)
doi:10.1016/0014-5793(90)80246-F
21. Frazier, A. L., Robbins, L. S., Stork, P. J., Sprengel, R., Segaloff, D. L., and Cone, R. D.: Isolation of TSH and LH/CG receptor cDNAs from human thyroid: regulation by tissue specific splicing. Mol. Endocrinol., 4, 1264-1276 (1990)
doi:10.1210/mend-4-8-1264
22. Akamizu, T., Ikuyama, S., Saji, M., Kosugi, S., Kozak, C., McBride, O. W., and Kohn, L. D.: Cloning, chromosomal assignment, and regulation of the rat thyrotropin receptor: expression of the gene is regulated by thyrotropin, agents that increase cAMP levels, and thyroid autoantibodies. Proc. Natl. Acad. Sci. U. S. A, 87, 5677-5681 (1990)
doi:10.1073/pnas.87.15.5677
23. Parma, J., Duprez, L., Van Sande, J., Cochaux, P., Gervy, C., Mockel, J., Dumont, J., and Vassart, G.: Somatic mutations in the thyrotropin receptor gene cause hyperfunctioning thyroid adenomas. Nature, 365, 649-651 (1993)
doi:10.1038/365649a0
24. Rousseau-Merck, M. F., Misrahi, M., Loosfelt, H., Atger, M., Milgrom, E., and Berger, R.: Assignment of the human thyroid stimulating hormone receptor (TSHR) gene to chromosome 14q31. Genomics, 8, 233-236 (1990)
doi:10.1016/0888-7543(90)90276-Z
25. Szkudlinski, M. W., Fremont, V., Ronin, C., and Weintraub, B. D.: Thyroid-stimulating hormone and thyroid-stimulating hormone receptor structure-function relationships. Physiol Rev., 82, 473-502 (2002)
doi: 10.1152/physrev.00031.2001
26. Macchia, P. E., Lapi, P., Krude, H., Pirro, M. T., Missero, C., Chiovato, L., Souabni, A., Baserga, M., Tassi, V., Pinchera, A., Fenzi, G., Gruters, A., Busslinger, M., and Di Lauro, R.: PAX8 mutations associated with congenital hypothyroidism caused by thyroid dysgenesis. Nat. Genet., 19, 83-86 (1998)
doi:10.1038/ng0598-83
27. Krude, H., Schutz, B., Biebermann, H., von Moers, A., Schnabel, D., Neitzel, H., Tonnies, H., Weise, D., Lafferty, A., Schwarz, S., DeFelice, M., von Deimling, A., van Landeghem, F., DiLauro, R., and Gruters, A.: Choreoathetosis, hypothyroidism, and pulmonary alterations due to human NKX2-1 haploinsufficiency. J. Clin. Invest, 109, 475-480 (2002)
doi: 10.1172/JCI0214341
28. Clifton-Bligh, R. J., Wentworth, J. M., Heinz, P., Crisp, M. S., John, R., Lazarus, J. H., Ludgate, M., and Chatterjee, V. K.: Mutation of the gene encoding human TTF-2 associated with thyroid agenesis, cleft palate and choanal atresia. Nat. Genet., 19, 399-401 (1998)
doi:10.1038/1294
29. Russo, D., Arturi, F., Suarez, H. G., Schlumberger, M., Du Villard, J. A., Crocetti, U., and Filetti, S.: Thyrotropin receptor gene alterations in thyroid hyperfunctioning adenomas. J. Clin. Endocrinol. Metab, 81, 1548-1551 (1996)
doi:10.1210/jc.81.4.1548
30. Neumann, S., Krause, G., Chey, S., and Paschke, R.: A free carboxylate oxygen in the side chain of position 674 in transmembrane domain 7 is necessary for TSH receptor activation. Mol. Endocrinol., 15, 1294-1305 (2001)
doi:10.1210/me.15.8.1294
31. Parma, J., Van Sande, J., Swillens, S., Tonacchera, M., Dumont, J., and Vassart, G.: Somatic mutations causing constitutive activity of the thyrotropin receptor are the major cause of hyperfunctioning thyroid adenomas: identification of additional mutations activating both the cyclic adenosine 3',5'-monophosphate and inositol phosphate-Ca2+ cascades. Mol. Endocrinol., 9, 725-733 (1995)
doi:10.1210/me.9.6.725
41. Tao, Y. X.: Constitutive activation of G protein-coupled receptors and diseases: insights into mechanisms of activation and therapeutics. Pharmacol. Ther. 120, 129-148 (2008) 81. Urizar, E., Montanelli, L., Loy, T., Bonomi, M., Swillens, S., Gales, C., Bouvier, M., Smits, G., Vassart, G., and Costagliola, S.: Glycoprotein hormone receptors: link between receptor homodimerization and negative cooperativity. EMBO J., 24, 1954-1964 (2005)
32. Kopp, P., Muirhead, S., Jourdain, N., Gu, W. X., Jameson, J. L., and Rodd, C.: Congenital hyperthyroidism caused by a solitary toxic adenoma harboring a novel somatic mutation (serine281-->isoleucine) in the extracellular domain of the thyrotropin receptor. J. Clin. Invest, 100, 1634-1639 (1997)
doi:10.1172/JCI119687
33. Duprez, L., Parma, J., Van Sande, J., Allgeier, A., Leclere, J., Schvartz, C., Delisle, M. J., Decoulx, M., Orgiazzi, J., Dumont, J.: Germline mutations in the thyrotropin receptor gene cause non-autoimmune autosomal dominant hyperthyroidism. Nat. Genet., 7, 396-401 (1994)
doi:10.1038/ng0794-396
34. Supornsilchai, V., Sahakitrungruang, T., Wongjitrat, N., Wacharasindhu, S., Suphapeetiporn, K., and Shotelersuk, V.: Expanding clinical spectrum of non-autoimmune hyperthyroidism due to an activating germline mutation, p.M453T, in the thyrotropin receptor gene. Clin. Endocrinol. (Oxf), 70, 623-628 (2009)
doi:10.1111/j.1365-2265.2008.03367.x
35. Biebermann, H., Schoneberg, T., Krude, H., Schultz, G., Gudermann, T., and Gruters, A.: Mutations of the human thyrotropin receptor gene causing thyroid hypoplasia and persistent congenital hypothyroidism. J. Clin. Endocrinol. Metab, 82, 3471-3480 (1997)
doi:10.1210/jc.82.10.3471
36. Tenenbaum-Rakover, Y., Grasberger, H., Mamanasiri, S., Ringkananont, U., Montanelli, L., Barkoff, M. S., Dahood, A. M., and Refetoff, S.: Loss-of-function mutations in the thyrotropin receptor gene as a major determinant of hyperthyrotropinemia in a consanguineous community. J. Clin. Endocrinol. Metab, 94, 1706-1712 (2009)
doi:10.1210/jc.2008-1938
37. Refetoff, S., Sunthornthepvarakul, T., Gottschalk, M. E., and Hayashi, Y.: Resistance to thyrotropin and other abnormalities of the thyrotropin receptor. Recent Prog. Horm. Res., 51, 97-120 (1996)
No DOI found
38. de Roux, N., Misrahi, M., Brauner, R., Houang, M., Carel, J. C., Granier, M., Le Bouc, Y., Ghinea, N., Boumedienne, A., Toublanc, J. E., and Milgrom, E.: Four families with loss of function mutations of the thyrotropin receptor. J. Clin. Endocrinol. Metab, 81, 4229-4235 (1996)
doi:10.1210/jc.81.12.4229
39. Clifton-Bligh, R. J., Gregory, J. W., Ludgate, M., John, R., Persani, L., Asteria, C., Beck-Peccoz, P., and Chatterjee, V. K.: Two novel mutations in the thyrotropin (TSH) receptor gene in a child with resistance to TSH. J. Clin. Endocrinol. Metab, 82, 1094-1100 (1997)
doi:10.1210/jc.82.4.1094
40. Kleinau, G., Jaeschke, H., Mueller, S., Raaka, B. M., Neumann, S., Paschke, R., and Krause, G.: Evidence for cooperative signal triggering at the extracellular loops of the TSH receptor. FASEB J., 22, 2798-2808 (2008)
doi:10.1096/fj.07-104711
doi:10.1016/j.pharmthera.2008.07.005
42. Kleinau, G., Jaeschke, H., Mueller, S., Worth, C. L., Paschke, R., and Krause, G.: Molecular and structural effects of inverse agonistic mutations on signaling of the thyrotropin receptor--a basally active GPCR. Cell Mol. Life Sci., 65, 3664-3676 (2008)
doi:10.1007/s00018-008-8450-2
43. Sura-Trueba, S., Aumas, C., Carre, A., Durif, S., Leger, J., Polak, M., and de Roux, N.: An inactivating mutation within the first extracellular loop of the thyrotropin receptor impedes normal posttranslational maturation of the extracellular domain. Endocrinology, 150, 1043-1050 (2009)
doi:10.1210/en.2008-1145
44. Mizutori, Y., Chen, C. R., McLachlan, S. M., and Rapoport, B.: The thyrotropin receptor hinge region is not simply a scaffold for the leucine-rich domain but contributes to ligand binding and signal transduction. Mol. Endocrinol., 22, 1171-1182 (2008)
doi:10.1210/me.2007-0407
45. Agrawal, G., and Dighe, R. R.: Critical involvement of the hinge region of the follicle-stimulating hormone receptor in the activation of the receptor. J. Biol. Chem., 284, 2636-2647 (2009)
doi:10.1074/jbc.M808199200
46. Zhang, M., Tong, K. P., Fremont, V., Chen, J., Narayan, P., Puett, D., Weintraub, B. D., and Szkudlinski, M. W.: The extracellular domain suppresses constitutive activity of the transmembrane domain of the human TSH receptor: implications for hormone-receptor interaction and antagonist design. Endocrinology, 141, 3514-3517 (2000)
doi:10.1210/en.141.9.3514
47. Neumann, S., Claus, M., and Paschke, R.: Interactions between the extracellular domain and the extracellular loops as well as the 6th transmembrane domain are necessary for TSH receptor activation. Eur. J. Endocrinol. 152, 625-634 (2005)
doi:10.1530/eje.1.01891
48. Vlaeminck-Guillem, V., Ho, S. C., Rodien, P., Vassart, G., and Costagliola, S.: Activation of the cAMP pathway by the TSH receptor involves switching of the ectodomain from a tethered inverse agonist to an agonist. Mol. Endocrinol., 16, 736-746 (2002)
doi:10.1210/me.16.4.736
49. Camilot, M., Teofoli, F., Gandini, A., Franceschi, R., Rapa, A., Corrias, A., Bona, G., Radetti, G., and Tato, L.: Thyrotropin receptor gene mutations and TSH resistance: variable expressivity in the heterozygotes. Clin. Endocrinol. (Oxf), 63, 146-151 (2005)
doi:10.1111/j.1365-2265.2005.02314.x
50. De Marco, G., Agretti, P., Camilot, M., Teofoli, F., Tato, L., Vitti, P., Pinchera, A., and Tonacchera, M.: Functional studies of new TSH receptor (TSHr) mutations identified in patients affected by hypothyroidism or isolated hyperthyrotrophinaemia. Clin. Endocrinol. (Oxf), 70, 335-338 (2009)
doi:10.1111/j.1365-2265.2008.03333.x
51. Akcurin, S., Turkkahraman, D., Tysoe, C., Ellard, S., De Leener, A., Vassart, G., and Costagliola, S.: A family with a novel TSH receptor activating germline mutation (p.Ala485Val). Eur. J. Pediatr., 167, 1231-1237 (2008)
doi:10.1007/s00431-007-0659-9
52. Gozu, H., Avsar, M., Bircan, R., Claus, M., Sahin, S., Sezgin, O., Deyneli, O., Paschke, R., Cirakoglu, B., and Akalin, S.: Two novel mutations in the sixth transmembrane segment of the thyrotropin receptor gene causing hyperfunctioning thyroid nodules. Thyroid, 15, 389-397 (2005)
doi:10.1089/thy.2005.15.389
53. Van Sande, J., Parma, J., Tonacchera, M., Swillens, S., Dumont, J., and Vassart, G.: Somatic and germline mutations of the TSH receptor gene in thyroid diseases. J. Clin. Endocrinol. Metab, 80, 2577-2585 (1995)
doi:10.1210/jc.80.9.2577
54. Kopp, P., Van Sande, J., Parma, J., Duprez, L., Gerber, H., Joss, E., Jameson, J. L., Dumont, J. E., and Vassart, G.: Brief report: congenital hyperthyroidism caused by a mutation in the thyrotropin-receptor gene. N. Engl. J. Med., 332, 150-154 (1995)
doi:10.1056/NEJM199501193320304
55. Schwab, K. O., Gerlich, M., Broecker, M., Sohlemann, P., Derwahl, M., and Lohse, M. J. Constitutively active germline mutation of the thyrotropin receptor gene as a cause of congenital hyperthyroidism. J. Pediatr., 131, 899-904 (1997)
doi:10.1016/S0022-3476(97)70040-4
56. Biebermann, H., Schoneberg, T., Krude, H., Gudermann, T., and Gruters, A.: Constitutively activating TSH-receptor mutations as a molecular cause of non-autoimmune hyperthyroidism in childhood. Langenbecks Arch. Surg., 385, 390-392 (2000)
doi:10.1007/s004230000145
57. Claus, M., Maier, J., Paschke, R., Kujat, C., Stumvoll, M., and Fuhrer, D.: Novel thyrotropin receptor germline mutation (Ile568Val) in a Saxonian family with hereditary nonautoimmune hyperthyroidism. Thyroid, 15, 1089-1094 (2005)
doi:10.1089/thy.2005.15.1089
58. Nishihara, E., Nagayama, Y., Amino, N., Hishinuma, A., Takano, T., Yoshida, H., Kubota, S., Fukata, S., Kuma, K., and Miyauchi, A.: A novel thyrotropin receptor germline mutation (Asp617Tyr) causing hereditary hyperthyroidism. Endocr. J., 54, 927-934 (2007)
doi:10.1507/endocrj.K07-088
59. Fuhrer, D., Lewis, M. D., Alkhafaji, F., Starkey, K., Paschke, R., Wynford-Thomas, D., Eggo, M., and Ludgate, M.: Biological activity of activating thyroid-stimulating hormone receptor mutants depends on the cellular context. Endocrinology, 144, 4018-4030 (2003)
doi:10.1210/en.2003-0438
60. Fuhrer, D., Holzapfel, H. P., Wonerow, P., Scherbaum, W. A., and Paschke, R.: Somatic mutations in the thyrotropin receptor gene and not in the Gs alpha protein gene in 31 toxic thyroid nodules. J. Clin. Endocrinol. Metab, 82, 3885-3891 (1997)
doi:10.1210/jc.82.11.3885
61. Duprez, L., Hermans, J., Van Sande, J., Dumont, J. E., Vassart, G., and Parma, J.: Two autonomous nodules of a patient with multinodular goiter harbor different activating mutations of the thyrotropin receptor gene. J. Clin. Endocrinol. Metab, 82, 306-308 (1997)
doi:10.1210/jc.82.1.306
62. Kenakin, T.: The physiological significance of constitutive receptor activity. Trends in Pharmacological Sciences, 26, 603-605 (2005)
doi:10.1016/j.tips.2005.10.007
63. Schoneberg, T., Schulz, A., Biebermann, H., Hermsdorf, T., Rompler, H., and Sangkuhl, K.: Mutant G-protein-coupled receptors as a cause of human diseases. Pharmacol. Ther., 104, 173-206 (2004)
doi:10.1016/j.pharmthera.2004.08.008
64. Schoneberg, T., Schulz, A., and Gudermann, T.: The structural basis of G-protein-coupled receptor function and dysfunction in human diseases. Rev. Physiol Biochem. Pharmacol., 144, 143-227 (2002)
doi: 10.1007/BFb0116587
65. Costagliola, S., Urizar, E., Mendive, F., and Vassart, G.: Specificity and promiscuity of gonadotropin receptors. Reproduction., 130, 275-281 (2005)
doi:10.1530/rep.1.00662
66. Rodien, P., Bremont, C., Sanson, M. L., Parma, J., Van Sande, J., Costagliola, S., Luton, J. P., Vassart, G., and Duprez, L.: Familial gestational hyperthyroidism caused by a mutant thyrotropin receptor hypersensitive to human chorionic gonadotropin. N. Engl. J. Med., 339, 1823-1826 (1998)
doi:10.1056/NEJM199812173392505
67. Parnot, C., Miserey-Lenkei, S., Bardin, S., Corvol, P., and Clauser, E.: Lessons from constitutively active mutants of G protein-coupled receptors. Trends Endocrinol. Metab, 13, 336-343 (2002)
doi:10.1016/S1043-2760(02)00628-8
68. Arseven, O. K., Wilkes, W. P., Jameson, J. L., and Kopp, P.: Substitutions of tyrosine 601 in the human thyrotropin receptor result in increase or loss of basal activation of the cyclic adenosine monophosphate pathway and disrupt coupling to Gq/11. Thyroid, 10, 3-10 (2000)
doi:10.1089/thy.2000.10.3
69. Biebermann, H., Schoneberg, T., Schulz, A., Krause, G., Gruters, A., Schultz, G., and Gudermann, T.: A conserved tyrosine residue (Y601) in transmembrane domain 5 of the human thyrotropin receptor serves as a molecular switch to determine G-protein coupling. FASEB J., 12, 1461-1471 (1998)
No DOI found
70. Karges, B., Krause, G., Homoki, J., Debatin, K. M., de Roux, N., and Karges, W.: TSH receptor mutation V509A causes familial hyperthyroidism by release of interhelical constraints between transmembrane helices TMH3 and TMH5. J. Endocrinol. 186, 377-385 (2005)
doi:10.1677/joe.1.06208
71. Claus, M., Jaeschke, H., Kleinau, G., Neumann, S., Krause, G., and Paschke, R.: A hydrophobic cluster in the center of the third extracellular loop is important for thyrotropin receptor signaling. Endocrinology, 146, 5197-5203 (2005)
doi:10.1210/en.2005-0713
72. Claus, M., Neumann, S., Kleinau, G., Krause, G., and Paschke, R.: Structural determinants for G-protein activation and specificity in the third intracellular loop of the thyroid-stimulating hormone receptor. J. Mol. Med., 84, 943-954 (2006)
doi:10.1007/s00109-006-0087-8
73. Kleinau, G., Brehm, M., Wiedemann, U., Labudde, D., Leser, U., and Krause, G.: Implications for molecular mechanisms of glycoprotein hormone receptors using a new sequence-structure-function analysis resource. Mol. Endocrinol., 21, 574-580 (2007)
doi:10.1210/me.2006-0309
74. Kleinau, G., Claus, M., Jaeschke, H., Mueller, S., Neumann, S., Paschke, R., and Krause, G. Contacts between extracellular loop two and transmembrane helix six determine basal activity of the thyroid-stimulating hormone receptor. J. Biol. Chem., 282, 518-525 (2007)
doi:10.1074/jbc.M606176200
75. Wonerow, P., Chey, S., Fuhrer, D., Holzapfel, H. P., and Paschke, R.: Functional characterization of five constitutively activating thyrotrophin receptor mutations. Clin. Endocrinol. (Oxf), 53, 461-468 (2000)
doi:10.1046/j.1365-2265.2000.01119.x
76. Bouvier, M.: Oligomerization of G-protein-coupled transmitter receptors. Nat. Rev. Neurosci., 2, 274-286 (2001)
doi:10.1038/35067575
77. George, S. R., O'Dowd, B. F., and Lee, S. P.: G-protein-coupled receptor oligomerization and its potential for drug discovery. Nat. Rev. Drug Discov., 1, 808-820 (2002)
doi:10.1038/nrd913
78. Barnes, P. J.: Receptor heterodimerization: a new level of cross-talk. J. Clin. Invest, 116, 1210-1212 (2006)
doi:10.1172/JCI28535
79. Graves, P. N., Vlase, H., Bobovnikova, Y., and Davies, T. F.: Multimeric complex formation by the thyrotropin receptor in solubilized thyroid membranes. Endocrinology, 137, 3915-3920 (1996)
doi:10.1210/en.137.9.3915
80. Latif, R., Graves, P., and Davies, T. F.: Oligomerization of the human thyrotropin receptor: fluorescent protein-tagged hTSHR reveals post-translational complexes. J. Biol. Chem., 276, 45217-45224 (2001)
doi:10.1074/jbc.M103727200
doi:10.1038/sj.emboj.7600686
82. Guan, R., Wu, X., Feng, X., Zhang, M., Hebert, T. E., and Segaloff, D. L.: Structural determinants underlying constitutive dimerization of unoccupied human follitropin receptors. Cell Signal., 22, 247-56 (2009)
doi:10.1016/j.cellsig.2009.09.023
83. Guan, R., Feng, X., Wu, X., Zhang, M., Zhang, X., Hebert, T. E., and Segaloff, D. L.: Bioluminescence resonance energy transfer studies reveal constitutive dimerization of the human lutropin receptor and a lack of correlation between receptor activation and the propensity for dimerization. J. Biol. Chem., 284, 7483-7494 (2009)
doi:10.1074/jbc.M809150200
84. Persani, L., Calebiro, D., and Bonomi, M.: Technology Insight: modern methods to monitor protein-protein interactions reveal functional TSH receptor oligomerization. Nat. Clin. Pract. Endocrinol. Metab, 3, 180-190 (2007)
doi:10.1038/ncpendmet0401
85. Calebiro, D., de Filippis, T., Lucchi, S., Covino, C., Panigone, S., Beck-Peccoz, P., Dunlap, D., and Persani, L.: Intracellular entrapment of wild-type TSH receptor by oligomerization with mutants linked to dominant TSH resistance. Hum. Mol. Genet., 14, 2991-3002 (2005)
doi:10.1093/hmg/ddi329
86. Fung, J. J., Deupi, X., Pardo, L., Yao, X. J., Velez-Ruiz, G. A., Devree, B. T., Sunahara, R. K., and Kobilka, B. K:.Ligand-regulated oligomerization of beta(2)-adrenoceptors in a model lipid bilayer. EMBO J., 28, 3315-3328 (2009)
doi:10.1038/emboj.2009.267
87. Zhang, M., Feng, X., Guan, R., Hebert, T. E., and Segaloff, D. L.: A cell surface inactive mutant of the human lutropin receptor (hLHR) attenuates signaling of wild-type or constitutively active receptors via heterodimerization. Cell Signal., 21, 1663-1671 (2009)
doi:10.1016/j.cellsig.2009.07.003
88. Vassart, G., Pardo, L., and Costagliola, S.: A molecular dissection of the glycoprotein hormone receptors. Trends Biochem. Sci., 29, 119-126 (2004)
doi:10.1016/j.tibs.2004.01.006
89. Fan, Q. R., and Hendrickson, W. A.: Structure of human follicle-stimulating hormone in complex with its receptor. Nature, 433, 269-277 (2005)
doi:10.1038/nature03206
90. Fan, Q. R., and Hendrickson, W. A.: Assembly and structural characterization of an authentic complex between human follicle stimulating hormone and a hormone-binding ectodomain of its receptor. Mol. Cell Endocrinol., 260-262, 73-82 (2007)
doi:10.1016/j.mce.2005.12.055
91. Fan, Q. R., and Hendrickson, W. A.: Comparative structural analysis of the binding domain of follicle stimulating hormone receptor. Proteins, 72, 393-401 (2008)
doi:10.1002/prot.21937
92. Dias, J. A.: Endocrinology: fertility hormone in repose. Nature, 433, 203-204 (2005)
doi:10.1038/433203a
93. Latif, R., Morshed, S. A., Zaidi, M., and Davies, T. F.: 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., 38, 319-41 (2009)
doi:10.1016/j.ecl.2009.01.006
94. Davies, T., Marians, R., and Latif, R.: The TSH receptor reveals itself. J. Clin. Invest, 110, 161-164 (2002)
doi:10.1172/JCI16234
95. Latif, R., Graves, P., and Davies, T. F.: Ligand-dependent inhibition of oligomerization at the human thyrotropin receptor. J. Biol. Chem., 277, 45059-45067 (2002)
doi:10.1074/jbc.M206693200
96. Jeoung, M., Lee, C., Ji, I., and Ji, T. H.: Trans-activation, cis-activation and signal selection of gonadotropin receptors. Mol. Cell Endocrinol., 260-262, 137-143 (2007)
doi:10.1016/j.mce.2005.09.015
97. Svendsen, A. M., Vrecl, M., Ellis, T. M., Heding, A., Kristensen, J. B., Wade, J. D., Bathgate, R. A., De Meyts, P., and Nohr, J.: Cooperative binding of insulin-like Peptide 3 to a dimeric relaxin family peptide receptor 2. Endocrinology, 149, 1113-1120 (2008)
doi:10.1210/en.2007-0412
98. Powell-Jones, C. H., Thomas, C. G., Jr., and Nayfeh, S. N.: Contribution of negative cooperativity to the thyrotropin-receptor interaction in normal human thyroid: kinetic evaluation. Proc. Natl. Acad. Sci., 76, 705-709 (1979)
doi:10.1073/pnas.76.2.705
99. Chazenbalk, G. D., Kakinuma, A., Jaume, J. C., McLachlan, S. M., and Rapoport, B.: Evidence for negative cooperativity among human thyrotropin receptors overexpressed in mammalian cells. Endocrinology, 137, 4586-4591 (1996)
doi:10.1210/en.137.11.4586
100. Tonacchera, M., Van Sande, J., Cetani, F., Swillens, S., Schvartz, C., Winiszewski, P., Portmann, L., Dumont, J. E., Vassart, G., and Parma, J.: Functional characteristics of three new germline mutations of the thyrotropin receptor gene causing autosomal dominant toxic thyroid hyperplasia. J. Clin. Endocrinol. Metab, 81, 547-554 (1996)
doi:10.1210/jc.81.2.547
101. Parma, J., Duprez, L., Van Sande, J., Hermans, J., Rocmans, P., Van Vliet, G., Costagliola, S., Rodien, P., Dumont, J. E., and Vassart, G.: Diversity and prevalence of somatic mutations in the thyrotropin receptor and Gs alpha genes as a cause of toxic thyroid adenomas. J. Clin. Endocrinol. Metab, 82, 2695-2701 (1997)
doi:10.1210/jc.82.8.2695
102. Nagashima, T., Murakami, M., Onigata, K., Morimura, T., Nagashima, K., Mori, M., and Morikawa, A.: Novel inactivating missense mutations in the thyrotropin receptor gene in Japanese children with resistance to thyrotropin. Thyroid, 11, 551-559 (2001)
doi:10.1089/105072501750302859
103. Abramowicz, M. J., Duprez, L., Parma, J., Vassart, G., and Heinrichs, C.: Familial congenital hypothyroidism due to inactivating mutation of the thyrotropin receptor causing profound hypoplasia of the thyroid gland. J. Clin. Invest, 99, 3018-3024 (1997)
doi:10.1172/JCI119497
104. Gagne, N., Parma, J., Deal, C., Vassart, G., and Van Vliet, G.: Apparent congenital athyreosis contrasting with normal plasma thyroglobulin levels and associated with inactivating mutations in the thyrotropin receptor gene: are athyreosis and ectopic thyroid distinct entities? J. Clin. Endocrinol. Metab, 83, 1771-1775 (1998)
doi:10.1210/jc.83.5.1771
105. Derwahl, M., Hamacher, C., Russo, D., Broecker, M., Manole, D., Schatz, H., Kopp, P., and Filetti, S.: Constitutive activation of the Gs alpha protein-adenylate cyclase pathway may not be sufficient to generate toxic thyroid adenomas. J. Clin. Endocrinol. Metab, 81, 1898-1904 (1996)
doi:10.1210/jc.81.5.1898
106. Biebermann, H., Schoneberg, T., Hess, C., Germak, J., Gudermann, T., and Gruters, A.: The first activating TSH receptor mutation in transmembrane domain 1 identified in a family with nonautoimmune hyperthyroidism. J. Clin. Endocrinol. Metab, 86, 4429-4433 (2001)
doi:10.1210/jc.86.9.4429
107. Van Sande, J., Dequanter, D., Lothaire, P., Massart, C., Dumont, J. E., and Erneux, C.: Thyrotropin stimulates the generation of inositol 1,4,5-trisphosphate in human thyroid cells. J. Clin. Endocrinol. Metab, 91, 1099-1107 (2006)
doi:10.1210/jc.2005-1324
108. Kleinau, G., Winkler, F., Krause, G., Gruters, A., and Biebermann, H.: Pathogenic constitutive activation of the thyrotropin receptor caused by a newly identified single substitution in transmembrane helix 6. Hormones, 7, 43 (2008)
109. De Lloyd, A., Bursell, J., Gregory, J., Rees, D., and Ludgate, M.: Thyrotropin Receptor Activation and Body Composition. J. Endocrinol., 204, 13-20 (2009)
doi: 10.1677/JOE-09-0262
110. Sun, S. C., Hsu, P. J., Wu, F. J., Li, S. H., Lu, C. H., and Luo, C. W.: Thyrostimulin, but not thyroid-stimulating hormone, acts as a paracrine regulator to activate thyroid-stimulating hormone receptor in the mammalian ovary. J. Biol. Chem., (2009)
doi: 10.1074/jbc.M109.066266
111. Eckstein, A. K., Johnson, K. T., Thanos, M., Esser, J., and Ludgate, M.: Current insights into the pathogenesis of Graves' orbitopathy. Horm. Metab Res., 41, 456-464 (2009)
doi:10.1055/s-0029-1220935
112. Morshed, S. A., Latif, R., and Davies, T. F.: Characterization of thyrotropin receptor antibody-induced signaling cascades. Endocrinology, 150, 519-529 (2009)
doi:10.1210/en.2008-0878
113. Michalek, K., Morshed, S. A., Latif, R., and Davies, T. F.: TSH receptor autoantibodies. Autoimmun. Rev., 9, 113-116 (2009)
doi:10.1016/j.autrev.2009.03.012
114. Chen, C. R., McLachlan, S. M., and Rapoport, B.: Suppression of thyrotropin receptor constitutive activity by a monoclonal antibody with inverse agonist activity. Endocrinology, 148, 2375-2382 (2007)
doi:10.1210/en.2006-1754
115. Neumann, S., Huang, W., Titus, S., Krause, G., Kleinau, G., Alberobello, A. T., Zheng, W., Southall, N. T., Inglese, J., Austin, C. P., Celi, F. S., Gavrilova, O., Thomas, C. J., Raaka, B. M., and Gershengorn, M. C.: Small-molecule agonists for the thyrotropin receptor stimulate thyroid function in human thyrocytes and mice. Proc. Natl. Acad. Sci. U. S. A, 106, 12471-12476 (2009)
doi:10.1073/pnas.0904506106
116. Neumann, S., Kleinau, G., Costanzi, S., Moore, S., Jiang, J. K., Raaka, B. M., Thomas, C. J., Krause, G., and Gershengorn, M. C.: A Low Molecular Weight Antagonist for the Human Thyrotropin Receptor with Therapeutic Potential for Hyperthyroidism. Endocrinology, 149, 5943-4 (2008)
doi:10.1210/en.2008-0836
117. Neumann, S., Raaka, B. M., and Gershengorn, M. C.: Human TSH receptor ligands as pharmacological probes with potential clinical application. Expert Review of Endocrinology & Metabolism, 4, 669-679 (2009)
doi:10.1586/eem.09.36
118. Beck-Peccoz, P.: Antithyroid drugs are 65 years old: time for retirement? Endocrinology, 149, 5943-5944 (2008)
doi:10.1210/en.2008-1349
119. Sanders, J., Chirgadze, D. Y., Sanders, P., Baker, S., Sullivan, A., Bhardwaja, A., Bolton, J., Reeve, M., Nakatake, N., Evans, M., Richards, T., Powell, M., Miguel, R. N., Blundell, T. L., Furmaniak, J., and Smith, B. R.: Crystal structure of the TSH receptor in complex with a thyroid-stimulating autoantibody. Thyroid, 17, 395-410 (2007)
doi:10.1089/thy.2007.0034
120. Duprez, L., Parma, J., Costagliola, S., Hermans, J., Van Sande, J., Dumont, J. E., and Vassart, G.: Constitutive activation of the TSH receptor by spontaneous mutations affecting the N-terminal extracellular domain. FEBS Lett., 409, 469-474 (1997)
doi:10.1016/S0014-5793(97)00532-2
121. Borgel, K., Pohlenz, J., Koch, H. G., and Bramswig, J. H.: Long-term carbimazole treatment of neonatal nonautoimmune hyperthyroidism due to a new activating TSH receptor gene mutation (Ala428Val). Horm. Res., 64, 203-208 (2005)
doi:10.1159/000089348
122. Gozu, H. I., Bircan, R., Krohn, K., Muller, S., Vural, S., Gezen, C., Sargin, H., Yavuzer, D., Sargin, M., Cirakoglu, B., and Paschke, R.: Similar prevalence of somatic TSH receptor and Gsalpha mutations in toxic thyroid nodules in geographical regions with different iodine supply in Turkey. Eur. J. Endocrinol., 155, 535-545 (2006)
doi:10.1530/eje.1.02253
123. de Roux, N., Polak, M., Couet, J., Leger, J., Czernichow, P., Milgrom, E., and Misrahi, M.: A neomutation of the thyroid-stimulating hormone receptor in a severe neonatal hyperthyroidism. J. Clin. Endocrinol. Metab, 81, 2023-2026 (1996)
doi:10.1210/jc.81.6.2023
124. Fuhrer, D., Warner, J., Sequeira, M., Paschke, R., Gregory, J., and Ludgate, M.: Novel TSHR germline mutation (Met463Val) masquerading as Graves' disease in a large Welsh kindred with hyperthyroidism. Thyroid, 10, 1035-1041 (2000)
doi:10.1089/thy.2000.10.1035
125. Holzapfel, H. P., Wonerow, P., von Petrykowski, W., Henschen, M., Scherbaum, W. A., and Paschke, R.: Sporadic congenital hyperthyroidism due to a spontaneous germline mutation in the thyrotropin receptor gene. J. Clin. Endocrinol. Metab, 82, 3879-3884 (1997)
doi:10.1210/jc.82.11.3879
126. Tonacchera, M., Agretti, P., Rosellini, V., Ceccarini, G., Perri, A., Zampolli, M., Longhi, R., Larizza, D., Pinchera, A., Vitti, P., and Chiovato, L.: Sporadic nonautoimmune congenital hyperthyroidism due to a strong activating mutation of the thyrotropin receptor gene. Thyroid, 10, 859-863 (2000)
doi:10.1089/thy.2000.10.859
127. Esapa, C. T., Duprez, L., Ludgate, M., Mustafa, M. S., Kendall-Taylor, P., Vassart, G., and Harris, P. E.: A novel thyrotropin receptor mutation in an infant with severe thyrotoxicosis. Thyroid, 9, 1005-1010 (1999)
doi:10.1089/thy.1999.9.1005
128. Alberti, L., Proverbio, M. C., Costagliola, S., Weber, G., Beck-Peccoz, P., Chiumello, G., and Persani, L.: A novel germline mutation in the TSH receptor gene causes non-autoimmune autosomal dominant hyperthyroidism. Eur. J. Endocrinol., 145, 249-254 (2001)
doi:10.1530/eje.0.1450249
129. Paschke, R., Tonacchera, M., Van Sande, J., Parma, J., and Vassart, G.: Identification and functional characterization of two new somatic mutations causing constitutive activation of the thyrotropin receptor in hyperfunctioning autonomous adenomas of the thyroid. J. Clin. Endocrinol. Metab, 79, 1785-1789 (1994)
doi:10.1210/jc.79.6.1785
130. Ringkananont, U., Van Durme, J., Montanelli, L., Ugrasbul, F., Yu, Y. M., Weiss, R. E., Refetoff, S., and Grasberger, H.: Repulsive separation of the cytoplasmic ends of transmembrane helices 3 and 6 is linked to receptor activation in a novel thyrotropin receptor mutant (M626I). Mol. Endocrinol., 20, 893-903 (2006)
doi:10.1210/me.2005-0339
131. Fuhrer, D., Wonerow, P., Willgerodt, H., and Paschke, R.: Identification of a new thyrotropin receptor germline mutation (Leu629Phe) in a family with neonatal onset of autosomal dominant nonautoimmune hyperthyroidism. J. Clin. Endocrinol. Metab, 82, 4234-4238 (1997)
doi:10.1210/jc.82.12.4234
132. Nwosu, B. U., Gourgiotis, L., Gershengorn, M. C., and Neumann, S.: A novel activating mutation in transmembrane helix 6 of the thyrotropin receptor as cause of hereditary nonautoimmune hyperthyroidism. Thyroid, 16, 505-512 (2006)
doi:10.1089/thy.2006.16.505
133. Khoo, D. H., Parma, J., Rajasoorya, C., Ho, S. C., and Vassart, G.: A germline mutation of the thyrotropin receptor gene associated with thyrotoxicosis and mitral valve prolapse in a Chinese family. J. Clin. Endocrinol. Metab, 84, 1459-1462 (1999)
doi:10.1210/jc.84.4.1459
134. Tonacchera, M., Chiovato, L., Pinchera, A., Agretti, P., Fiore, E., Cetani, F., Rocchi, R., Viacava, P., Miccoli, P., and Vitti, P.: Hyperfunctioning thyroid nodules in toxic multinodular goiter share activating thyrotropin receptor mutations with solitary toxic adenoma. J. Clin. Endocrinol. Metab, 83, 492-498 (1998)
doi:10.1210/jc.83.2.492
135. Liu, Z., Sun, Y., Dong, Q., He, M., Cheng, C. H., and Fan, F.: A novel TSHR gene mutation (Ile691Phe) in a Chinese family causing autosomal dominant non-autoimmune hyperthyroidism. J. Hum. Genet, 53, 475-478 (2008)
doi:10.1007/s10038-008-0257-3
136. Nicoletti, A., Bal, M., De Marco, G., Baldazzi, L., Agretti, P., Menabo, S., Ballarini, E., Cicognani, A., Tonacchera, M., and Cassio, A.: Thyrotropin-stimulating hormone receptor gene analysis in pediatric patients with non-autoimmune subclinical hypothyroidism. J. Clin. Endocrinol. Metab, 94, 4187-4194 (2009)
doi:10.1210/jc.2009-0618
137. Alberti, L., Proverbio, M. C., Costagliola, S., Romoli, R., Boldrighini, B., Vigone, M. C., Weber, G., Chiumello, G., Beck-Peccoz, P., and Persani, L.: Germline mutations of TSH receptor gene as cause of nonautoimmune subclinical hypothyroidism. J. Clin. Endocrinol. Metab, 87, 2549-2555 (2002)
doi:10.1210/jc.87.6.2549
138. Costagliola, S., Sunthorntepvarakul, T., Migeotte, I., Van Sande, J., Kajava, A. M., Refetoff, S., and Vassart, G.: Structure-function relationships of two loss-of-function mutations of the thyrotropin receptor gene., Thyroid 9, 995-1000 (2004)
doi:10.1089/thy.1999.9.995
139. Tonacchera, M., Perri, A., De Marco, G., Agretti, P., Banco, M. E., Di Cosmo, C., Grasso, L., Vitti, P., Chiovato, L., and Pinchera, A.: Low prevalence of thyrotropin receptor mutations in a large series of subjects with sporadic and familial nonautoimmune subclinical hypothyroidism. J. Clin. Endocrinol. Metab, 89, 5787-5793 (1999)
doi:10.1210/jc.2004-1243
140. Russo, D., Betterle, C., Arturi, F., Chiefari, E., Girelli, M. E., and Filetti, S.: A novel mutation in the thyrotropin (TSH) receptor gene causing loss of TSH binding but constitutive receptor activation in a family with resistance to TSH. J. Clin. Endocrinol. Metab, 85, 4238-4242 (2000)
doi:10.1210/jc.85.11.4238
141. Mizuno, H., Kanda, K., Sugiyama, Y., Imamine, H., Ito, T., Kato, I., Togari, H., Kamoda, T., and Onigata, K.: Longitudinal evaluation of patients with a homozygous R450H mutation of the TSH receptor gene. Horm. Res., 71, 318-323 (2009)
doi:10.1159/000223415
142. Tsunekawa, K., Onigata, K., Morimura, T., Kasahara, T., Nishiyama, S., Kamoda, T., Mori, M., Morikawa, A., and Murakami, M.: Identification and functional analysis of novel inactivating thyrotropin receptor mutations in patients with thyrotropin resistance. Thyroid, 16, 471-479 (2006)
doi:10.1089/thy.2006.16.471
143. Tonacchera, M., Agretti, P., Pinchera, A., Rosellini, V., Perri, A., Collecchi, P., Vitti, P., and Chiovato, L.: Congenital hypothyroidism with impaired thyroid response to thyrotropin (TSH) and absent circulating thyroglobulin: evidence for a new inactivating mutation of the TSH receptor gene. J. Clin. Endocrinol. Metab, 85, 1001-1008 (2000)
doi:10.1210/jc.85.3.1001
144. Fricke-Otto, S., Pfarr, N., Muhlenberg, R., and Pohlenz, J.: Mild congenital primary hypothyroidism in a Turkish family caused by a homozygous missense thyrotropin receptor (TSHR) gene mutation (A593V). DE">Exp. Clin. Endocrinol. Diabetes, 113, 582-585 (2005)
doi:10.1055/s-2005-865914
Abbreviations: GPHR, glycoprotein hormone receptor; LHCGR, lutropin/choriogonadotropin receptor, lutropin receptor; FSHR, follicle stimulating hormone receptor, follitropin receptor; TSHR, thyroid stimulating hormone receptor, thyrotroin receptor; bTSH, bovine thyroid stimulating hormone; LH, luteinizing hormone; CG, choriogonadotropin; FSH, follicle stimulating hormone; GPCR, G-protein coupled receptor; TMH, transmembrane helix; ECL1/2/3, extracellular loops 1/2/3; ICLs 1/2/3, intracellular loops 1/2/3; LRRD, Leucine-rich repeat domain; SD, serpentine domain; CAM, constitutively activating mutation; wt, wild type; N-tt, N-terminal tail; C-tt, C-terminal tail; cAMP, cyclic adenosine monophosphate; IP, Inositolphosphat; FRET, fluorescence resonance energy transfer; BRET, bioluminescence resonance energy transfer; HTRF, homogenous time resolved fluorescence; COS-7, Cercopithecus aethiops (CV1 Origin SV-40); CHO, Chinese hamster ovary; Leucine-rich repeat containing G-protein-coupled receptors, LGRs
Key Words: Thyrotropin Receptor, Naturally Occurring Mutations, Pathogenic Mutations, Germline Mutations, Somatic Mutations, Dimerization, Glycoprotein Hormone Receptors, Review
Send correspondence to: PD Heike Biebermann, Charite Campus Virchow Klinikum, Institut fur Experimentelle Padiatrische Endokrinologie, Ostring 3, Augustenburgerplatz 1, 13353 Berlin, Germany, Tel: 49-30-450 559 828, Fax: 49-30-450 566 941, E-mail:heike.biebermann@charite.de