Cherepanov Igor, Sidorov Alexandr, Beduleva Liubov, Terentiev Alexey, Menshikova Daria, Khramova Tatyana, Menshikov Igor, Ivanov Pavel
Laboratory of Molecular and Cell Immunology, Department of Immunology and Cell Biology, Udmurt State University, 1 Universitetskaya St, Izhevsk, 426011, Russian Federation.
Department of Fundamental and Applied Chemistry, Udmurt State University, Izhevsk, Russian Federation.
Protein J. 2025 Feb;44(1):68-78. doi: 10.1007/s10930-024-10243-8. Epub 2024 Dec 4.
Thyroglobulin is a major autoantigen to which autoimmune response, destroying the thyroid gland in Hashimoto's thyroiditis, is directed. To detect a pathological autoimmune response to thyroglobulin, as well as the successful induction of experimental autoimmune thyroiditis, thyroglobulin carrying thyroiditogenic epitopes is necessary. It is not known which features of thyroglobulin structure determine the presence of thyroiditogenic epitopes and can serve as markers of their presence. We compared structure of thyroglobulin bearing thyroiditogenic epitopes (freshly isolated thyroglobulin) and thyroglobulin which had lost thyroiditogenic epitopes (lyophilized thyroglobulin). Fourier-transform infrared (FTIR) spectroscopy was used to elucidate the structure of thyroglobulin. The markers indicating the presence of thyroiditogenic epitopes on thyroglobulin are the vibrations of diiodotyrosine, monoiodotyrosine/diiodotyrosine relation in the range of 0.24-0.43 (95% confidence interval) and relatively high (> 32%) α-helix content. The loss of thyroiditogenic epitopes on thyroglobulin is associated with a weakening or complete disappearance of diiodotyrosine oscillations and a decrease in the proportion of α-helices in secondary structure. Thyroglobulin extracted with phenylmethylsulfonyl fluoride (PMSF) added is characterized by the same relatively high monoiodotyrosine/diiodotyrosine relation and low proportion of alpha helices as thyroglobulin without thyroiditogenic epitopes. Therefore, serine protease inhibitor PMSF is not suitable for extraction of native thyroglobulin bearing thyroiditogenic epitopes. FTIR spectroscopy can be used to detect thyroiditogenic epitopes on thyroglobulin.
甲状腺球蛋白是一种主要的自身抗原，自身免疫反应针对该抗原，会破坏桥本甲状腺炎中的甲状腺。为了检测对甲状腺球蛋白的病理性自身免疫反应以及成功诱导实验性自身免疫性甲状腺炎，携带致甲状腺炎表位的甲状腺球蛋白是必需的。尚不清楚甲状腺球蛋白结构的哪些特征决定了致甲状腺炎表位的存在，并可作为其存在的标志物。我们比较了携带致甲状腺炎表位的甲状腺球蛋白（新鲜分离的甲状腺球蛋白）和已失去致甲状腺炎表位的甲状腺球蛋白（冻干甲状腺球蛋白）的结构。采用傅里叶变换红外（FTIR）光谱法阐明甲状腺球蛋白的结构。表明甲状腺球蛋白上存在致甲状腺炎表位的标志物是二碘酪氨酸的振动、单碘酪氨酸/二碘酪氨酸比值在0.24 - 0.43范围内（95%置信区间）以及相对较高（>32%）的α-螺旋含量。甲状腺球蛋白上致甲状腺炎表位的丧失与二碘酪氨酸振荡减弱或完全消失以及二级结构中α-螺旋比例降低有关。添加苯甲基磺酰氟（PMSF）提取的甲状腺球蛋白与不具有致甲状腺炎表位的甲状腺球蛋白具有相同的相对较高的单碘酪氨酸/二碘酪氨酸比值和较低的α-螺旋比例。因此，丝氨酸蛋白酶抑制剂PMSF不适用于提取携带致甲状腺炎表位的天然甲状腺球蛋白。FTIR光谱可用于检测甲状腺球蛋白上的致甲状腺炎表位。
