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A Modifying Autoantigen in Graves' Disease.

ABSTRACT: The TSH receptor (TSHR) is the major autoantigen in Graves' disease (GD). Bioinformatic analyses predict the existence of several human TSHR isoforms from alternative splicing, which can lead to the coexpression of multiple receptor forms. The most abundant of these is TSHRv1.3. In silico modeling of TSHRv1.3 demonstrated the structural integrity of this truncated receptor isoform and its potential binding of TSH. Tissue profiling revealed wide expression of TSHRv1.3, with a predominant presence in thyroid, bone marrow, thymus, and adipose tissue. To gain insight into the role of this v1.3 receptor isoform in thyroid pathophysiology, we cloned the entire open reading frame into a mammalian expression vector. Immunoprecipitation studies demonstrated that both TSHR-stimulating antibody and human TSH could bind v1.3. Furthermore, TSHRv1.3 inhibited the stimulatory effect of TSH and TSHR-Ab MS-1 antibody on TSHR-induced cAMP generation in a dose-dependent manner. To confirm the antigenicity of v1.3, we used a peptide ELISA against two different epitopes. Of 13 GD samples, 11 (84.6%) were positive for a carboxy terminal peptide and 10 (76.9%) were positive with a junction region peptide. To demonstrate that intracellular v1.3 could serve as an autoantigen and modulate disease, we used double-transfected Chinese hamster ovary cells that expressed both green fluorescent protein (GFP)-tagged TSHRv1.3 and full-length TSHR. We then induced cell stress and apoptosis using a TSHR monoclonal antibody and observed the culture supernatant contained v1.3-GFP protein, demonstrating the release of the intracellular receptor variant by this mechanism.

SUBMITTER: Latif R

PROVIDER: S-EPMC6455603 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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A Modifying Autoantigen in Graves' Disease.

Latif Rauf R Mezei Mihaly M Morshed Syed A SA Ma Risheng R Ehrlich Rachel R Davies Terry F TF

Endocrinology 20190501 5

The TSH receptor (TSHR) is the major autoantigen in Graves' disease (GD). Bioinformatic analyses predict the existence of several human TSHR isoforms from alternative splicing, which can lead to the coexpression of multiple receptor forms. The most abundant of these is TSHRv1.3. In silico modeling of TSHRv1.3 demonstrated the structural integrity of this truncated receptor isoform and its potential binding of TSH. Tissue profiling revealed wide expression of TSHRv1.3, with a predominant presence ...[more]

PMID: 30822352

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Project description:BackgroundA large gene region, called GD-1, was first described by this laboratory as linked to Graves' disease (GD) and included the gene for the thyroid-stimulating hormone receptor (TSHR). Recent studies have now suggested an association of TSHR intronic polymorphisms with GD. We have taken the opportunity to examine a population of well-characterized patients with autoimmune thyroid disease (AITD) typed for an additional thyroid susceptibility gene, the immunoregulatory gene for cytotoxic T-lymphocyte antigen 4 (CTLA-4), to examine its relationship with the susceptibility to GD endowed by TSHR gene polymorphisms.MethodsWe used TSHR-SNP-rs2268458, located in intron 1 of the TSHR gene, measured using standard PCR-RFLP procedures, as our marker for the TSHR gene association. We genotyped 200 patients with GD, 83 patients with Hashimoto's thyroiditis (HT), and 118 healthy controls (all female Caucasians).ResultsThe allele and genotype frequencies from GD patients, but not HT patients, were significantly different from controls. The frequency of the combined genotype (allele) CC + TC was significantly higher in GD patients versus controls, suggesting that the C-containing genotype increased the risk for GD in a dominant manner (p = 0.018, odds ratio [OR] = 1.8). When compared with CTLA-4 (A/G)(49) single-nucleotide polymorphism (SNP), we were unable to demonstrate additive risk in patients with established AITD. Further, subsetting the patients (n = 120) into those with clinically significant Graves' ophthalmopathy (GO) showed no association with the TSHR SNP.ConclusionsThese results demonstrated that the intronic TSHR-SNP-rs2268458 was associated with GD, but not with HT, thus indicating that the TSHR gene has the potential to increase susceptibility to GD. However, we were not able to demonstrate any additive risk with the CTLA-4 (A/G)(49) SNP, which is, therefore, an independent risk factor for AITD. This suggested that, within the limits of the study population, each of these two genes provided a small contribution to GD susceptibility and that neither was essential. In addition, there was no evidence for the TSHR gene association adding to the risk of developing GO. Direct functional analyses are now needed to help explain the mechanisms of this TSHR gene susceptibility to GD.

Dataset Information

A Modifying Autoantigen in Graves' Disease.

Publications

A Modifying Autoantigen in Graves' Disease.

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