A Human Monoclonal Autoantibody to the Thyrotropin Receptor with Thyroid-Stimulating Blocking Activity

Sanders, Jane; Evans, Michele K.; Betterle, Corrado; Sanders, Paul G.; Bhardwaja, Anshu; Young, Stuart; Roberts, Emma; Wilmot, Jane; Richards, Tonya; Kiddie, Angela; Small, Kasemsri; Platt, Hayley; Summerhayes, Sara; Harris, Rebecca; Reeve, Magnus; Coco, Graziella; Zanchetta, R.; Shu, Chen; Furmaniak, Jadwiga; Smith, Bernard Rees

doi:10.1089/thy.2007.0327

Cited by 57 publications

(101 citation statements)

References 40 publications

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“…Interestingly, one of the blocking TSHR-Abs (RSR-B2) induced a small increase in cAMP levels that was paralleled by increased cell proliferation, indicating that c-Raf/ERK and cAMP/CREB activation may have contributed to this proliferation. Recently, two independent groups identified blocking antibodies that suppress the constitutive activity of TSHR and cAMP generation (52,55). Indeed, these findings together with ours are in agreement with the hypothesis that the blocking antibodies may have influenced thyrocyte functions by altering multiple signaling mechanisms.…”

Section: Discussionsupporting

confidence: 90%

“…There are also antibodies that reduce TSH action at the TSHR or decrease its constitutive activity without a potent signaling capacity (51,52). Igs from Graves' and autoimmune (Hashimoto's) thyroiditis patients have also recently been shown to compete with a blocking monoclonal antibody to the N terminus of the TSHR ␤-subunit (amino acids 382-415) (53).…”

Section: Discussionmentioning

confidence: 99%

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Characterization of Thyrotropin Receptor Antibody-Induced Signaling Cascades

2008

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The TSH receptor (TSHR) is constitutively active and is further enhanced by TSH ligand binding or by stimulating TSHR antibodies (TSHR-Abs) as seen in Graves' disease. TSH is known to activate the thyroid epithelial cell via both Galphas-cAMP/protein kinase A/ERK and Galphaq-Akt/protein kinase C coupled signaling networks. The recent development of monoclonal antibodies to the TSHR has enabled us to investigate the hypothesis that different TSHR-Abs may have unique signaling imprints that differ from TSH ligand itself. We have, therefore, performed sequential studies, using rat thyrocytes (FRTL-5, passages 5-20) as targets, to examine the signaling pathways activated by a series of monoclonal TSHR-Abs in comparison with TSH itself. Activation of key signaling molecules was estimated by specific immunoblots and/or enzyme immunoassays. Continuing constitutive TSHR activity in thyroid cells, deprived of TSH and serum for 48 h, was demonstrated by pathway-specific chemical inhibition. Under our experimental conditions, TSH ligand and TSHR-stimulating antibodies activated both Galphas and Galphaq effectors. Importantly, some TSHR-blocking and TSHR-neutral antibodies were also able to generate signals, influencing primarily the Galphaq effectors and induced cell proliferation. Most strikingly, antibodies that used the Galphaq cascades used c-Raf-ERK-p90RSK as a unique signaling cascade not activated by TSH. Our study demonstrated that individual TSHR-Abs had unique molecular signatures which resulted in sequential preferences. Because downstream thyroid cell signaling by the TSHR is both ligand dependent and independent, this may explain why TSHR-Abs are able to have variable influences on thyroid cell biology.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Characterization of Thyrotropin Receptor Antibody-Induced Signaling Cascades

2008

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“…M22 interactions with the TSHR LRD observed in the M22-TSHR crystal structure are in good agreement with extensive experimental studies carried out with full-length TSHRs and therefore it would be expected that small molecules acting on the LRD would also inhibit antibody binding to intact TSHRs , 2007a,b, Rees Smith et al 2007. However, these molecules may or may not have an effect on binding and biological activity of at least some of TSHR autoantibodies with blocking activity (Rees Smith et al 2007, Sanders et al 2008b. Consequently, our results on M22 and TSH interactions with the TSHR suggest new possibilities to control ligand induced TSHR activity in Graves' disease.…”

Section: Discussionsupporting

confidence: 80%

Thyroid stimulating autoantibody M22 mimics TSH binding to the TSH receptor leucine rich domain: a comparative structural study of protein–protein interactions

Miguel¹,

Sanders²,

Chirgadze³

et al. 2009

Journal of Molecular Endocrinology

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The TSH receptor (TSHR) ligands M22 (a thyroid stimulating human monoclonal antibody) and TSH, bind to the concave surface of the leucine rich repeats domain (LRD) of the TSHR and here, we show that M22 mimics closely the binding of TSH. We compared interactions produced by M22 with the TSHR in the M22-TSHR crystal structure (2 . 55 Å resolution) and produced by TSH with the TSHR in a TSH-TSHR comparative model. The crystal structure of the TSHR and a comparative model of TSH based on the crystal structure of FSH were used as components to build the TSH-TSHR model. This model was built based on the FSH-FSH receptor structure (2 . 9 Å ) and then the structure of the TSHR in the model was replaced by the TSHR crystal structure. The analysis shows that M22 light chain mimics the TSHb chain in its interaction with TSHR LRD, while M22 heavy chain mimics the interactions of the TSHa chain. The M22-TSHR complex contains a greater number of hydrogen bonds and salt bridges and fewer hydrophobic interactions than the TSH-TSHR complex, consistent with a higher M22 binding affinity. Furthermore, the surface area formed by TSHR residues N208, Q235, R255, and N256 has been identified as a candidate target region for small molecules which might selectively block binding of autoantibodies to the TSHR.

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“…It is difficult to envisage how such a difference in clearance rate could occur unless the former were of subclass IgG3, which has a shorter half-life than IgG1, IgG2, or IgG4 (41). Serum TSAb are of subclass IgG1 (42), sometimes IgG4 (43), and the monoclonal human TSAb and TBAb isolated to date are IgG1 (5,44,45). Although IgG1 was the predominant subclass, in some patients, TBAb activity was detected in subclasses IgG2, 3, and 4 (46).…”

Section: Pregnancy and Postpartum Tsab/tbab Switchesmentioning

confidence: 99%