Horm Metab Res 2015; 47(10): 735-752
DOI: 10.1055/s-0035-1559648
Review

Mechanisms of Action of TSHR Autoantibodies

Authors

  • J. Furmaniak

    1   FIRS Laboratories, RSR Ltd, Parc Ty Glas, Llanishen, Cardiff, UK
  • J. Sanders

    1   FIRS Laboratories, RSR Ltd, Parc Ty Glas, Llanishen, Cardiff, UK
  • R. Núñez Miguel

    1   FIRS Laboratories, RSR Ltd, Parc Ty Glas, Llanishen, Cardiff, UK
  • B. Rees Smith

    1   FIRS Laboratories, RSR Ltd, Parc Ty Glas, Llanishen, Cardiff, UK

Abstract

The availability of human monoclonal antibodies (MAbs) to the TSHR has enabled major advances in our understanding of how TSHR autoantibodies interact with the receptor. These advances include determination of the crystal structures of the TSHR LRD in complex with a stimulating autoantibody (M22) and with a blocking type autoantibody (K1-70). The high affinity of MAbs for the TSHR makes them particularly suitable for use as ligands in assays for patient serum TSHR autoantibodies. Also, M22 and K1–70 are effective at low concentrations in vivo as TSHR agonists and antagonists respectively. K1-70 has important potential in the treatment of the hyperthyroidism of Graves’ disease and Graves’ ophthalmopathy. Small molecule TSHR antagonists described to date do not appear to have the potency and/or specificity shown by K1-70. New models of the TSHR ECD in complex with various ligands have been built. These models suggest that initial binding of TSH to the TSHR causes a conformational change in the hormone. This opens a positively charged pocket in receptor-bound TSH which attracts the negatively charged sulphated tyrosine 385 on the hinge region of the receptor. The ensuing movement of the receptor's hinge region may then cause activation. Similar activation mechanisms seem to take place in the case of FSH and the FSHR and LH and the LHR. However, stimulating TSHR autoantibodies do not appear to activate the TSHR in the same way as TSH.



Publication History

Received: 09 April 2015

Accepted: 24 July 2015

Article published online:
11 September 2015

Georg Thieme Verlag
Rüdigerstraße 14, 70469 Stuttgart, Germany