A full biological response to autoantibodies in Graves' disease requires a disulfide-bonded loop in the thyrotropin receptor N terminus homologous to a laminin epidermal growth factor-like domain

被引:50
作者
Chen, CR
Tanaka, K
Chazenbalk, GD
McLachlan, SM
Rapoport, B
机构
[1] Univ Calif Los Angeles, Sch Med, Los Angeles, CA 90048 USA
[2] Univ Calif Los Angeles, Cedars Sinai Res Inst, Autoimmune Dis Unit, Los Angeles, CA 90048 USA
关键词
D O I
10.1074/jbc.M008001200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
We observed amino acid homology between the cysteine-rich N terminus of the thyrotropin receptor (TSHR) ectodomain and epidermal growth factor-like repeats in the laminin yl chain, Thyroid-stimulating autoantibodies (TSAb), the cause of Graves' disease, interact with this region of the TSHR in a manner critically dependent on antigen conformation. We studied the role of the cluster of four cysteine (Cys) residues in this region of the TSHR on the functional response to TSAb in Graves' patients' sera. As a benchmark we also studied TSH binding and action. Removal in various permutations of the four cysteines at TSHR positions 24, 29, 31, and 41 (signal peptide residues are 1-21) revealed Cys(41) to be the key residue for receptor expression Forced pairing of Cys(41) with any one of the three upstream Cys residues was necessary for trafficking to the cell surface of a TSHR with high affinity TSH binding similar to the wild-type receptor. However, for a full biological response to TSAb, forced pairing of Cys(41) with Cys(29) or with Cys(31), but not with Cys(24), retained functional activity comparable with the wild-type TSHR, These data suggest that an N-terminal disulfide-bonded loop between Cys(41) and Cys(29) or its close neighbor Cys(31) comprises, in part, the highly conformational epitope for TSAb at the critical N terminus of the TSHR, Amino acid homology, as well as cysteine pairing similar to the laminin gamma1 chain epidermal growth factor-like repeat 11, suggests conformational similarity between the two molecules and raises the possibility of molecular mimicry in the pathogenesis of Graves' disease.
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页码:14767 / 14772
页数:6
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