Autoantibodies directed to islet cell surface antigens and their pathologic roles in type-1 diabetes

胰岛自身抗体(AAs)是胰腺自身免疫的可靠生物标志物。血清中抗四种主要氨基酸 生化抗原(胰岛素、GAD、IA-2和ZnT8)在临床研究中经常被用作 1型糖尿病(T1D)患者的诊断和预后以及高危患者的疾病预测 T1D发病前的个体。已开发出可靠的生化分析方法来检测AAs识别 可溶性抗原或膜结合抗原的可溶性结构域。膜结合型氨基酸的检测 然而，抗原在其不溶性跨膜结构域的适配上受到技术困难的挑战。 (TMD)到基于溶液的分析平台。目前，我们还不知道这种疾病的流行情况和第一 出现以任何TMD抗原为靶点的AAs。在四种主要生化抗原中，胰岛特异的 ZnT8的独特之处在于它有一个主要的TMD，在一个全长的ZnT8中包含三分之二的蛋白质序列。我们的 最近的研究表明，随着胰岛素的分泌，锌离子被转运到胰腺β细胞的表面，并且 表面的TMD具有很强的抗原性，可被T1D患者血清中的ZnT8AAs识别。这些发现 提示ZnT8中的TMD是一种新的表面靶向AAs的免疫原域，其在 细胞表面可能促进抗体介导的细胞毒作用，直接导致β细胞自身免疫破坏。 为了验证这些假设，我们将(I)验证进展期患者中针对ZnT8的TMD(TMDA)的AAs T1D，以及(Ii)建立TMDA作为直接靶向AAs，因此，直接与活的胰腺β细胞结合 调节它们的功能和生存。这项拟议的研究有望验证一类全新的 以最近发现的胰岛细胞表面抗原为靶标的原子吸收光谱，阐明TMDAs在自然历史中的作用 T1D(目标1)和疾病发病机制(目标2)的关系。所获得的知识将转化为新的诊断 工具和潜在的治疗干预措施。

Islet autoantibodies (AAs) are reliable biomarkers of pancreatic autoimmunity. Serum AAs against four major biochemical antigens (insulin, GAD, IA-2, and ZnT8) are routinely used in clinical research as key metrics for diagnostics and prognostics in patients with type-1 diabetes (T1D), and for disease prediction in at-risk individuals before T1D onset. Robust biochemical assays have been developed to detect AAs recognizing soluble antigens or soluble domains of membrane-bound antigens. Detection of AAs to membrane-bound antigens, however, is challenged by technical difficulties in adaption of their insoluble transmembrane domains (TMD) to solution-based assay platforms. At present, we have no knowledge of the prevalence and first appearance of AAs targeting any TMD antigens. Among the four major biochemical antigens, the islet-specific ZnT8 is unique in having a major TMD that encompasses two thirds protein sequence in a full-length ZnT8. Our recent works showed that ZnT8 is trafficked to the surface of pancreatic β-cells following insulin secretion, and the surfaced TMD is highly antigenic, recognized by serum ZnT8 AAs in patients with T1D. These findings suggest that the TMD in ZnT8 is a novel immunogenic domain for surfaced-targeted AAs, and its display on the cell surface may promote antibody-mediated cytotoxicity contributing directly to β-cell autoimmune destruction. To test these hypotheses, we will (i) validate AAs directed to the TMD of ZnT8 (TMDAs) in patients progressing to T1D, and (ii) establish TMDAs as direct-targeting AAs, as such, bind directly to live pancreatic β cells to modulate their functions and survival. The proposed research is expected to validate a completely new class of AAs targeting a recently identified islet cell surface antigen, illuminating the roles of TMDAs in the natural history of T1D (Aim 1) and disease pathogenesis (Aim 2). The knowledge gained will be translated to novel diagnostic tools and potential therapeutic interventions.