胰岛锌转运体8抗原的翻译后修饰在1型糖尿病发病机制中的作用

Type 1 diabetes (T1D) is an autoimmune disease in which islet β cells are targeted by autoreactive T cells. Many physiological and environmental triggers associated with T1D increase the potential for abnormal folding, aggregation, and post-translational modification (PTM) of proteins. In the context of genetic susceptibility to autoimmunity and failure of peripheral tolerance, the presentation of abnormally-modified proteins (neo-antigens) by antigen presenting cells initiates T cell-mediated pathogenesis in T1D. In this research, we use human islet cells to prove that PTMs of proteins leads islet β cells to the formation of a highly antigenic epitope for diabetic T cells. And then, we analyze the differences between the naturally occurring and PTM form of the epitope at the molecular level, and explore the possible mechanism how peptide fills the T cell receptor binding groove well after PTM. Not only the pathogenesis might be gained, but also novel diagnostic and therapeutic approaches could be developed for type 1 diabetes if protein modifications were shown to play a critical role in the loss of immune tolerance of the disease.

1型糖尿病(T1D)是自身反应性T细胞靶向破坏胰岛β细胞的自身免疫性疾病，CD8+T细胞在其发病机制中起重要作用。预实验结果已证实锌转运体8(ZnT8)是T1D致病性CD8+T细胞的靶抗原。作为胰岛自身抗原的ZnT8为何及如何被机体致病性T细胞识别而打破免疫耐受机制？本研究首先通过检测ZnT8抗原特异性CD8+T细胞对内质网应激状态下人胰岛细胞的免疫反应强度，证明ZnT8在功能异常的内质网经翻译后修饰(PTM)激活了致病性T细胞对新抗原表位的识别和靶向攻击；再利用氨基酸测序、分子筛色谱分析等手段进一步分析ZnT8抗原PTM表位肽的分子结构和蛋白多肽聚集情况，探讨ZnT8经PTM改变蛋白构象、暴露隐匿表位肽结构，增强抗原性及与致病性T细胞亲和力的可能机制。本研究从胰岛抗原PTM激活致病性T细胞靶向识别和免疫攻击的新视角为揭示T1D免疫耐受缺陷机制奠定了基础，也为T1D的防治打开了新思路。

1 型糖尿病 (T1D) 是自身反应性 T 细胞靶向破坏胰岛 β 细胞的自身免疫性疾病，锌转运体8 (ZnT8) 是 T1D 致病性 T 细胞的靶抗原。本课题围绕翻译后修饰致胰岛 ZnT8 抗原免疫耐受缺陷在 T1D 发病机制中的作用展开研究。通过筛选和制备 ZnT8 抗原 HLA-A*0201 限制性 T 细胞表位肽，利用 Tgase 处理获得 ZnT8 的 PTM表位肽；同时构建人 ZnT8 (268-369) cDNA，将其免疫 HLA-A*0201 β2m null HHD 转基因鼠，之后分离纯化小鼠脾细胞，与 ZnT8 自然表位肽和 ZnT8 的 PTM 表位肽进行 ELISPORT，初步证明翻译后修饰增强了 ZnT8 表位肽的抗原性；并对 T1D 患者 ZnT8 自然肽与 PTM 多肽特异性自身反应 T 细胞分析。课题阐述了胰岛抗原 ZnT8 翻译后修饰致 β 细胞免疫耐受缺陷在 T1D 发病机制中的关键作用，不仅帮助我们更好的理解疾病的发生和胰岛 β 细胞衰竭的机制，通过预防 β 细胞抗原 PTM 异常修饰新抗原的产生及后继识别，阻止致病性 T 细胞对胰岛 β 细胞的靶向破坏，也为 T1D 临床干预疗打开了新思路。