The role of beta-cell crinophagy in generating diabetogenic neoepitopes

摘要 自身免疫性疾病在美国影响超过2000万人， 正在上升病人通常遭受一生的不断恶化的疾病，因为没有治愈大多数 自身免疫性疾病，包括1型糖尿病。应对这一艰巨挑战需要更好的 了解引起自身反应的致病因素。尽管大量的研究表明， 研究了天然抗原的作用，新抗原/新表位是否起驱动自身免疫的作用， 这一过程仍然不太清楚。新抗原的鉴定，特别是翻译后修饰 负责产生免疫原性新表位的PTMs需要严格检查。 内分泌组织通常是自身免疫的目标。不同的内分泌细胞利用 处理过量分泌蛋白以维持细胞内稳态的途径。在这一过程中， 规则的分泌颗粒直接与溶酶体融合。由此产生的囊泡，食毛体，或 分泌体富含分解代谢的肽段。在1型糖尿病中， 一种靶向胰岛中产生胰岛素的β细胞的疾病， 提供天然肽以供病原性CD 4 T细胞识别。我们最近的检查， 免疫肽组学揭示了多种多样的PTM在crinosome衍生的肽，表明crinosomes是一个 与1型糖尿病相关的潜在新抗原和新表位的专门储存库。 一种新型新表位家族C19 S（胰岛素B链中的半胱氨酸至丝氨酸转化）逐渐成为 沿着糖尿病自身免疫过程的发展。最重要的是，我们高度认同 在患有T1 D的小鼠和人类中C19 S的相容序列。在小鼠中，C19 S可以被先前的 未鉴定的CD 4 T细胞不同于对天然表位有反应性的那些。因此，有必要确定 靶向C19 S的自身反应性T细胞的致病性。此外，作为代表性的新表位家族， C19 S提供了一个设定点，用于描述β细胞分泌吞噬如何作为一种新的致病成分在哺乳动物中发挥作用。 T1D C19 S可能通过将β细胞应激与自身免疫联系起来而启动T1 D发病机制中的“前馈”回路。 我们还建议评估C19 S在人类分泌吞噬和T细胞病理学中的翻译应用。 这些分析可能导致对由人类分泌物吞噬产生的新表位的广泛鉴定，其可能 作为T1 D发病机制和治疗的有价值的靶标。分析潜在的C19 S-反应性T细胞， 人PBMC可能扩展我们对自身免疫发病机制的认识， 天然抗原。

ABSTRACT Autoimmune diseases affect more than 20 million people in the United States, and the worldwide prevalence is rising. Patients usually suffer from a lifetime of deteriorating illness because no cures are available for most autoimmune diseases, including type 1 diabetes. Addressing this formidable challenge requires a better understanding of the pathogenic elements eliciting autoreactive responses. Although extensive studies have examined the role of native antigens, whether neoantigens/neoepitopes function to drive the autoimmune process remains poorly understood. The identity of neoantigens, especially post-translational modifications (PTMs) responsible for generating immunogenic neoepitopes, requires a critical examination. Endocrine tissues are commonly targeted by autoimmunity. Diverse endocrine cells use the crinophagic pathway to dispose of excessive amounts of secretory proteins to maintain cellular homeostasis. In this process, the regular secretory granules are directly fused to lysosomes. The resulting vesicle, crinophagic bodies, or crinosomes, are enriched with catabolized peptide segments. In type 1 diabetes, a deteriorating autoimmune disease targeting the insulin-producing β cells in pancreatic islets, crinosomes function as an antigen source providing native peptides for recognition by pathogenic CD4 T cells. Our recent examination by immunopeptidomics uncovered diverse PTMs in crinosome-derived peptides, indicating that crinosomes are a specialized repository of potential neoantigens and neoepitopes related to type 1 diabetes. A novel neoepitope family, C19S (cysteine-to-serine conversion in the insulin B-chain), became progressively prominent along with the development of the diabetic autoimmune process. Most importantly, we identified highly compatible sequences of C19S in mice and humans with T1D. In mice, C19S can be recognized by previously unidentified CD4 T cells distinct from those reactive to the native epitope. It is therefore necessary to determine the pathogenicity of the autoreactive T cells targeting C19S. Furthermore, as a representative neoepitope family, C19S provides a setpoint for delineating how β-cell crinophagy functions as a novel pathogenic component in T1D. C19S may initiate a "feed-forward" loop in T1D pathogenesis by linking β-cell stress with autoimmunity. We also propose to assess translational applications of C19S in human crinophagy and T cell pathobiology. These analyses may lead to a broad identification of neoepitopes generated by human crinophagy, which may serve as valuable targets for T1D pathogenesis and therapeutics. Analysis of potential C19S-reactive T cells in human PBMCs may extend our knowledge of autoimmune pathogenesis beyond the current paradigm defined by native antigens.