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T细胞，这是为了保护我们免受病原体，如病毒，转向对身体自己的细胞。细胞内形成的蛋白质修饰为这种误导性攻击提供了一个合理的解释，因为蛋白质的组成发生了改变，使它们对免疫系统来说似乎是外来的。使用β细胞提取物的质谱分析，我们最近确定了一个新的蛋白质修饰家族，该家族在β细胞中形成，并在1型糖尿病的主要动物模型中被疾病驱动T细胞靶向。此外，我们证明了从1型糖尿病器官供体的残余胰岛中分离的自身反应性T细胞也靶向携带这种类型修饰的蛋白质。这种修饰是胰岛素片段与其他蛋白质片段交联的结果，导致形成杂合肽。在连接处，这些肽含有不是由生物体基因组编码的新氨基酸序列。这些非生殖系编码序列为介导β细胞破坏的自身反应性T细胞提供合理的靶标。在这里，我们将（1）通过质谱法在人类β细胞中搜索杂合肽，（2）研究导致杂合肽形成的机制，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数据集自信而快速地识别β细胞中的杂合肽。在人体组织中鉴定杂合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。了解导致杂合肽形成的机制将使我们能够测试防止这些肽形成的策略，使β细胞对疾病驱动T细胞不可见。生物信息学工具将使我们能够表征可能在β细胞中形成的大量潜在杂合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，任何一项资助目标的成功都将为我们提供有价值的工具和试剂，以前所未有的细节研究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.