IGA CELLULAR RECEPTOR INTERACTIONS IN IGA NEPHROPATHY

免疫球蛋白肾病(IgAN)是肾小球疾病的主要原因。 世界。IgA1在肾小球系膜上的显著沉积是 疾病。尽管经过了25年的调查，LGA之所以 定位于系膜以及这种沉积与系膜的关系 慢性肾功能不全的部分患者进展缓慢 伊根仍然不为人知。在这个提案中，我们将检验一般假设 在lgAN中，循环lgA1结构的异常导致 不成比例的LGA部分绕过正常的分解代谢 和/或选择性地与肾小球系膜细胞结合。 肾脏。该项目将专注于O-连接的低聚糖结合 LgA1的铰链区多肽，因为这些结构 区分lgA1和lgA2以及其他主要的IGS同工型。的约束性 LgA1对两种细胞受体、去唾液酸糖蛋白受体的影响 肝癌细胞与系膜细胞原代培养的FcalphaR受体 将对细胞进行详细检查。这些受体是从一些 LGA受体，因为它们最有可能参与LGA 分解代谢缺陷(ASGPR)或将异常的LGA靶向肾脏 (系膜FcalphaR)。这两种受体都需要低聚糖在其 用于结合的配体。三个具体的假设将被检验：1) 一些IgAN患者的lgA1会相对更好地绑定到恐惧 2)某些lgAN患者的lgA1的结合 诱导更多的FcalphaR的表达和细胞因子的产生 来自培养的系膜细胞的生长因子，以及3)一些 L和2中定义的功能异常可归因于异常 LgA1铰链区的糖基化。要在此中使用的方法 研究内容包括用凝集素亲和层析法从沙门氏菌中分离出lgA1。 20例狼疮性肾炎患者、10例正常人和10例狼疮性肾炎患者的血清 其他形式的肾小球肾炎。对结合的详细研究， 选定的lgA1的内化和细胞内命运 将进行准备工作。不同制剂对人免疫球蛋白A1的影响 通过Northern杂交和释放FcalphaR来评估FcalphaR的表达 转化生长因子、血小板衍生生长因子和IL-6 免疫分析。碳水化合物结构分析将由Beta执行 消除和高效液相色谱、凝集素结合和酶降解。铰链 用免疫球蛋白特异的酶和胰酶产生的糖蛋白将是 已提交进行AA序列分析。成功完成这些研究 应识别LGA结构和功能的一个或多个异常 使部分IGAN患者易发生LGA系膜沉积。这些 研究最终应该能够确定有风险的患者 Igan的发展或进展。用于治疗的特定地点 这些研究也可能建议采取干预措施。

lgA nephropathy (IgAN) is the leading cause of glomerulonephrits in the world. Prominent deposition of IgA1 in the mesangium is the hallmark of the disease. Despite over 25 years of investigation, the reason why lgA localizes to the mesangium and the relationship between this deposition and slow but progressive development of renal dysfunction in some patients with IgAN remains unknown. In this proposal, we will test the general hypothesis that in lgAN, abnormalities in the structure of the circulating lgA1 cause a disproportionate fraction of the lgA to bypass the normal catabolic pathway in the liver and/or to bind selectively to the mesangial cells in the kidney. The project will focus on the O-linked oligosaccharides bound the hinge region peptide of lgA1, since these are the structures that distinguish lgA1 from lgA2 and the other major Igs isotypes. The binding of lgA1 to two cellular receptors, the asialoglycoprotein receptor on cultured hepatoma cells and the FcalphaR receptor of primary cultures of mesangial cells will be examined in detail. These receptors were chosen from a number of lgA receptors, since they are most likely to be involved in an lgA catabolic defect (ASGPR) or in targeting of the abnormal lgA to the kidney (mesangial FcalphaR). Both receptors require oligosaccharides on their ligands for binding. Three specific hypotheses will be tested: 1) that the lgA1 from some patients with IgAN will bind relatively better to the FeaR than the ASGPR, 2) that binding of the lgA1 from some patients with lgAN induces the expression of more FcalphaR and the production of cytokines and growth factors from cultured mesangial cells, and 3) that some of the functional abnormalities defined in l and 2 can be attributed to aberrant glycosylation of the hinge region of lgA1. The methods to be used in this study include isolation by lectin affinity chromatography of lgA1 from the serum of 20 patients with lgAN, 10 normals subjects and 10 patients with other forms of glomerulonephritis. Detailed studies of the binding, internalization and the intracellular fate of the selected lgA1 preparations will be undertaken. The effect of various preparations of lgA1 on FcalphaR expression will be assessed by Northern blotting and release of transforming growth factor, platelet derived growth factor and lL-6 by immunoassays. Carbohydrated structural analysis will be performed by beta elimination and HPLC, lectin binding and enzymatic degradation. The hinge glycoproteins produced with lgA-specific proteases and trypsin will be submitted for aa sequence analysis. Successful completion of these studies should identify one or more abnormalities of lgA structure and function predispose some patients with lgAN to mesangial deposition of lgA. These studies should eventually allow identification of patients at risk for development or progression of lgAN. Specific sites for therapeutic interventions may also be suggested by these studies.