Thyroid stimulating antibodies (TSAB) cause Graves’ disease and contribute to Graves’ Orbitopathy (GO) pathogenesis. We hypothesise that the presence of TSH binding proteins (truncated TSHR variants (TSHRv)) and/or nonclassical ligands such as thyrostimulin (α2β5) might provide a mechanism to protect against or exacerbate GO. We analysed primary human orbital preadipocyte-fibroblasts (OF) from GO patients and people free of GO (non-GO). Transcript (QPCR) and protein (western blot) expression levels of TSHRv were measured through an adipogenesis differentiation process. Cyclic-AMP production by TSHR activation was studied using luciferase-reporter and RIA assays. After differentiation, TSHRv levels in OF from GO were significantly higher than non-GO (p = 0.039), and confirmed in ex vivo analysis of orbital adipose samples. TSHRv western blot revealed a positive signal at 46 kDa in cell lysates and culture media (CM) from non-GO and GO-OF. Cyclic-AMP decreased from basal levels when OF were stimulated with TSH or Monoclonal TSAB (M22) before differentiation protocol, but increased in differentiated cells, and was inversely correlated with the TSHRv:TSHR ratio (Spearman correlation: TSH r = −0.55, p = 0.23, M22 r = 0.87, p = 0.03). In the bioassay, TSH/M22 induced luciferase-light was lower in CM from differentiated GO-OF than non-GO, suggesting that secreted TSHRv had neutralised their effects. α2 transcripts were present but reduced during adipogenesis (p < 0.005) with no difference observed between non-GO and GO. β5 transcripts were at the limit of detection. Our work demonstrated that TSHRv transcripts are expressed as protein, are more abundant in GO than non-GO OF and have the capacity to regulate signalling via the TSHR.
Expression of endogenous putative tsh binding protein in orbit / M.S. Draman, F. Grennan-Jones, P. Taylor, I. Muller, S. Evans, A. Haridas, D.S. Morris, D.A. Rees, C. Lane, C. Dayan, L. Zhang, M. Ludgate. - In: CURRENT ISSUES IN MOLECULAR BIOLOGY. - ISSN 1467-3037. - 43:3(2021), pp. 1794-1804. [10.3390/cimb43030126]
|Titolo:||Expression of endogenous putative tsh binding protein in orbit|
|Parole Chiave:||Binding protein; Graves’ Orbitopathy; Thyrostimulin; Thyrotropin receptor; Variant|
|Settore Scientifico Disciplinare:||Settore MED/13 - Endocrinologia|
|Data di pubblicazione:||2021|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.3390/cimb43030126|
|Appare nelle tipologie:||01 - Articolo su periodico|