Characterize the Landscape and Origin of Hybrid Peptides in Beta Cells

在1型糖尿病中，自身反应性T细胞介导了产生胰岛素的β细胞的破坏。研究这种疾病的一个关键问题是，为什么用来保护我们免受病毒等病原体侵袭的T细胞会转而攻击人体自身的细胞。细胞内形成的蛋白质修饰为这种误导性攻击提供了一个看似合理的解释，因为蛋白质的组成发生了变化，使它们看起来像是免疫系统的外来物质。利用对β细胞提取物的质谱分析，我们最近发现了一个新的蛋白质修饰家族，它在β细胞中形成，并在一种主要的1型糖尿病动物模型中作为疾病驱动T细胞的靶点。此外，我们还证明，从1型糖尿病器官捐赠者的残余胰岛中分离出来的自身反应性T细胞也可以靶向携带这种修饰的蛋白质。这种修饰是胰岛素片段与其他蛋白质片段交叉连接的结果，导致杂交肽的形成。在交界处，这些多肽包含新的氨基酸序列，而这些氨基酸序列不是由生物体的基因组编码的。这些非生殖系编码序列为自身反应性T细胞提供了可信的靶点，介导了对β细胞的破坏。在这里，我们将(1)通过质谱学在人类β细胞中搜索杂交肽，(2)研究导致杂交肽形成的机制，以及(3)设计新的生物信息学工具，使我们能够通过搜索质谱学数据集来自信地快速识别贝塔细胞中的杂交肽。鉴定人体组织中的杂交肽将为我们提供有价值的工具，以设计新的策略来预测、预防或逆转1型糖尿病。了解导致杂交肽形成的机制将使我们能够测试防止杂交肽形成的策略，使疾病驱动的T细胞看不到β细胞。生物信息学工具将使我们能够表征在β细胞中可能形成的大量潜在的杂交肽，以及在其他自身免疫性疾病中靶向的其他细胞类型。总而言之，这笔赠款的任何一个目标的成功都将为我们提供宝贵的工具和试剂，以前所未有的详细研究1型糖尿病。

In type 1 diabetes autoreactive T cells mediate the destruction of insulin producing beta cells. A key question in the study of this disease is why T cells, which are there to protect us from pathogens such as viruses, turn against the body’s own cells. Protein modifications that form within cells provide a plausible explanation for this misguided attack as the composition of proteins is altered, making them appear foreign to the immune system. Using mass spectrometric analyses on beta cell extracts, we recently identified a new family of protein modifications that forms in beta cells and is targeted by disease driving T cells in a major animal model of type 1 diabetes. Furthermore, we demonstrated that autoreactive T cells, that were isolated from the residual islets of type 1 diabetic organ donors, also target proteins carrying this type of modification. The modification is a result of insulin fragments that are cross-linked to other protein fragments, leading to the formation of hybrid peptides. At the junction those peptides contain new amino acid sequences that are not encoded by the organism’s genome. These non-germline encoded sequences deliver plausible targets for autoreactive T cells that mediate the destruction of beta cells. Here we will (1) search for hybrid peptides in human beta cells by mass spectrometry, (2) study the mechanism that leads to the formation of hybrid peptides, and (3) devise new bioinformatics tools that will allow us to confidently and rapidly identify hybrid peptides in beta cells by searching mass spectrometric datasets. Identification of hybrid peptides in human tissue will provide us with valuable tools to devise new strategies to predict, prevent or reverse type 1 diabetes. Understanding the mechanism that leads to the formation of hybrid peptides will allow us to test strategies which prevent the formation of those peptides, rendering beta cells invisible to disease driving T cells. Bioinformatics tools will allow us to characterize the vast number of potential hybrid peptides that may form in beta cells as well as additional cells types that are targeted in other autoimmune diseases. In summary, success in any of the aims of this grant will provide us with valuable tools and reagents to study type 1 diabetes in unprecedented detail.