Genetic Basis of Non-Familial IgA Nephropathy

非家族性 IgA 肾病的遗传基础

• 批准号: 7812064
• 负责人: Tongzhong Ju
• 金额: $ 30.29万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-16 至 2013-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7812064
• 关键词: 7p13; Address; Amino Acids; Anabolism; Antibodies; Antigens; Autoantibodies; Autoimmune Diseases; B-Lymphocytes; Binding; Biological Assay; Blood Cells; Cell Line; Cell surface; Cells; Complementary DNA; Deposition; Diagnosis; Embryo; Enzyme-Linked Immunosorbent Assay; Enzymes; Evaluation; Exons; Galactose; Galactosyltransferases; Genes; Genetic; Glomerulonephritis; Glycopeptides; Glycoproteins; Goals; Hematopoietic stem cells; Human; IGA Glomerulonephritis; IgA1; Immunoglobulin A; Immunoglobulins; In Vitro; Inflammation; Kidney Diseases; Kidney Failure; Light; Link; Mammals; Maps; Masks; Membrane Glycoproteins; Methods; Molecular; Molecular Chaperones; Mono-S; Mus; Mutate; Mutation; O-Glycans Biosynthesis Pathway; Pathogenesis; Pathway interactions; Patients; Plasma Cells; Polysaccharides; Prevention; Proteins; Recombinants; Sampling; Serum; Severities; Site; Somatic Mutation; Structure; Syndrome; Testing; Therapeutic; Tn antigen; Tumor Cell Line; Xq24; base; glycosylation; in vivo; inhibitor/antagonist; insight; multicatalytic endopeptidase complex; novel; novel diagnostics; peripheral blood; prevent; public health relevance; sialosyl-Tn antigen

DESCRIPTION (provided by applicant): Immunoglobulin A (IgA) nephropathy (IgAN) or Berger's disease is an autoimmune disease resulting from the abnormal deposit of IgA in the glomerulus. Primary IgAN is the most common form of primary glomerulonephritis, leading to progressive renal failure in almost one third of the patients. Numerous studies have suggested that IgAN results from abnormal O-glycosylation of IgA1. Normal IgA1 is unique among immunoglobulins in that it contains ~5 Ser/Thr-linked O-glycans with mono-sialylated and di-sialylated core 1 structures. The pathogenesis of the IgAN is associated with a deficiency of galactose in O-glycans and concomitant expression of the Tn antigen (GalNAc?-Ser/Thr) in its hinge region of IgA1. Tn antigen is normally masked through addition of galactose by the T-synthase to generate the core 1 structure (Gal(3GalNAc-R). We discovered that T-synthase requires a unique molecular chaperone we termed Cosmc that helps to fold the T-synthase during its biosynthesis in the ER. Cosmc is encoded on Xq24 and is an ER chaperone that prevents the aggregation/proteasomal degradation of the T-synthase. Preliminary studies show that somatic mutations in Cosmc cause expression of the Tn antigen. We now hypothesize that somatic mutations of Cosmc in IgA-secreting B cells cause undergalactosylation of IgA1 and result in non-familial or sporadic IgAN. In this proposal, we will focus on three Specific Aims. Aim 1: We will analyze Cosmc in Tn/CD19(+) B lymphocytes from peripheral blood of patient with IgAN. For all mutations found, the effects of mutation on Cosmc chaperone toward the T-synthase will be examined by in vitro complementation assays. We will isolate, immortalize and establish the Tn/CD19(+) or Tn/IgA(+) Blymphocytes from patients with IgAN, examine the cDNA and gene for Cosmc; introduce wild type Cosmc into the B cells to restore T-synthase activity; and test whether Cosmc expression corrects O-glycosylation of cell surface glycoproteins and IgA1. Aim 2: We will define the structures of O-glycans on each site of the hinge region in IgA from patients with IgAN. Aim 3: We will characterize the autoantibodies in sera of patients with IgAN using a glycan microarray including various glycans and synthetic glycopeptides representing the IgA1 hinge region, and establish an ELISA method for potential diagnosis of IgAN from serum samples. Understanding the genetic basis for IgAN will shed light on developing new diagnostics and therapeutic treatments for IgAN. PUBLIC HEALTH RELEVANCE Our goal of this project is to investigate the genetic basis or molecular mechanism of non-familial IgA nephropathy (IgAN), the most common form of primary glomerulonephritis leading to progressive renal failure in almost one third of the patients. IgAN is caused by the deposit of IgA1 in glomerulus because the IgA1 carries aberrant O-glycans such as Tn antigen. O-glycan biosynthesis is regulated by Cosmc, core 1 (3-galactosyltransferase specific molecular chaperone, through assisting the folding of core 1 (3- galactosyltrasferase (T-synthase) which is a key enzyme guarding the pathway. Human Cosmc is encoded by a single-Exon gene Cosmc on Xq24. Somatic mutation in Cosmc is responsible for the abnormal expression of Tn and sialylTn antigens in human tumor cell lines and blood cells of patients with Tn syndrome. We hypothesize that the somatic mutation of X-linked Cosmc in IgA1 secreting B cell is associated with IgAN. To test our hypothesis, we will focus on three Aims for this proposal: 1) Examine Cosmc gene in Tn(+), IgA1 secreting B cells or plasma cells isolated from patients with IgAN and matched healthy controls; examine the Cosmc gene from immortalized Tn(+), IgA1 secreting B cells or plasma cells; correct the O-glycan structure on IgA1 by introducing the wild type Cosmc into these cells; 2) Define the O-glycan structure on each site of hinge region in IgA1; 3) Characterize the autoimmune antibody in sera of patients with IgAN. These studies will directly address the molecular mechanism of IgAN, which will have an important impact on our understanding of the pathogenesis of IgA1, and provide new diagnostics and avenues of treatment or prevention for sporadic IgAN.

描述（申请人提供）： 免疫球蛋白 A (IgA) 肾病 (IgAN) 或伯杰氏病是一种因 IgA 在肾小球中异常沉积而导致的自身免疫性疾病。原发性 IgAN 是原发性肾小球肾炎最常见的形式，导致近三分之一的患者出现进行性肾衰竭。大量研究表明 IgAN 是 IgA1 异常 O-糖基化的结果。正常 IgA1 在免疫球蛋白中是独特的，因为它含有约 5 个 Ser/Thr 连接的 O 聚糖，具有单唾液酸化和二唾液酸化核心 1 结构。 IgAN 的发病机制与 O-聚糖中半乳糖的缺乏以及 IgA1 铰链区 Tn 抗原 (GalNAc?-Ser/Thr) 的同时表达有关。 Tn 抗原通常通过 T 合酶添加半乳糖来掩蔽，以生成核心 1 结构 (Gal(3GalNAc-R)。我们发现 T 合酶需要一种独特的分子伴侣，我们称为 Cosmc，它有助于在 ER 中生物合成过程中折叠 T 合酶。Cosmc 在 Xq24 上编码，是一种 ER 伴侣，可防止 T-合酶的聚集/蛋白酶体降解。初步研究表明，Cosmc 的体细胞突变会导致 Tn 抗原的表达。我们现在假设 IgA 分泌 B 细胞中 Cosmc 的体细胞突变导致 IgA1 半乳糖基化不足，并导致非家族性或散发性 IgAN。在本提案中，我们将重点关注三个具体目标。目标 1： 我们将分析 IgAN 患者外周血 Tn/CD19(+) B 淋巴细胞中的 Cosmc。对于发现的所有突变，将通过体外互补测定来检查 Cosmc 分子伴侣对 T 合酶的突变影响。我们将分离、永生化并建立 Tn/CD19(+) 或 Tn/IgA(+) B 淋巴细胞 IgAN 患者，检查 Cosmc 的 cDNA 和基因；将野生型Cosmc引入B细胞以恢复T-合酶活性；并测试 Cosmc 表达是否纠正细胞表面糖蛋白和 IgA1 的 O-糖基化。目标 2：我们将定义 IgAN 患者 IgA 铰链区每个位点的 O-聚糖结构。目标 3：我们将描述 使用聚糖微阵列（包括代表 IgA1 铰链区的各种聚糖和合成糖肽）检测 IgAN 患者血清中的自身抗体，并建立一种 ELISA 方法，用于从血清样本中诊断 IgAN。了解 IgAN 的遗传基础将为开发新的 IgAN 诊断和治疗方法提供线索。 公共卫生相关性 我们这个项目的目标是调查遗传因素 非家族性 IgA 肾病 (IgAN) 的基础或分子机制，IgAN 是原发性肾小球肾炎的最常见形式，导致近三分之一的患者进行性肾功能衰竭。 IgAN 是由 IgA1 沉积在肾小球中引起的，因为 IgA1 携带异常的 O-聚糖，例如 Tn 抗原。 O-聚糖生物合成受 Cosmc 调控， 核心1（3-半乳糖基转移酶）特异性分子伴侣，通过协助核心1（3-半乳糖基转移酶（T-合酶）的折叠，这是保护该通路的关键酶。人类Cosmc由Xq24上的单外显子基因Cosmc编码。Cosmc的体细胞突变导致Tn和唾液酸Tn抗原的异常表达 人类肿瘤细胞系和 Tn 综合征患者的血细胞中。我们推测分泌IgA1的B细胞中X连锁Cosmc的体细胞突变与IgAN有关。为了检验我们的假设，我们将重点关注该提案的三个目标：1）检查从 IgAN 患者和匹配的健康对照中分离的 Tn（+）、IgA1 分泌 B 细胞或浆细胞中的 Cosmc 基因；检查 来自永生化Tn(+)、IgA1分泌B细胞或浆细胞的Cosmc基因；通过将野生型 Cosmc 引入这些细胞来纠正 IgA1 上的 O-聚糖结构； 2) 定义IgA1铰链区各位点的O-聚糖结构； 3) 表征 IgAN 患者血清中的自身免疫抗体。这些研究将直接解决IgAN的分子机制，对我们理解IgA1发病机制产生重要影响，并为散发性IgAN提供新的诊断和治疗或预防途径。