IgA1 glycosylation and receptor interactions in IgA nephropathy

描述(申请人提供)：IgA肾病(IgAN)是肾小球肾炎最常见的形式，是肾脏的一种炎症性疾病。IGAN的特征是lgA1抗体沉积在肾小球系膜，随后炎症免疫细胞渗透，最终导致肾功能丧失。在很大比例的IgAN患者中，lgA1抗体表现出糖基化和聚合状态的改变。这些改变被认为在改变lgA1和IgA特异性受体之间的相互作用中发挥作用，特别是FcalphaRI(CD89)和转铁蛋白受体(TFR)，尽管有相互矛盾的数据报道。这项研究的长期目标是确定导致系膜中lgA1沉积的准确分子事件。中心假设是，lgA1糖基化和聚合的修饰导致关键的IgA结合受体(特别是FcalphaRI和TFR)的亲和力增加。这些异常的相互作用被认为直接导致lgA1在肾系膜沉积和随后的炎症反应。这一建议的具体目的包括：1)使用具有明确糖基化状态的重组lgA1来表征lgA1糖基化和聚合对其与FcalphaRI和TfR相互作用的影响；2)表征从健康人和IgAN患者血清中纯化的lgA1的受体相互作用，并将受体亲和力与lgA1糖基化和聚合状态相关联；以及3)确定FcalphaRI N-糖基化对其与lgA1和TfR相互作用的贡献。与lgA1、FcalphaRI和TFR的结合研究将通过表面等离子体共振和分析超速离心法进行。LgA1糖基化将通过凝集素亲和力分析进行表征，并通过傅立叶变换-离子回旋共振质谱仪对感兴趣的样品进行彻底分析。这项研究将有助于确定IgA肾病(IgAN)的分子基础，这是一种在美国影响大约10万名患者的肾脏疾病。IGAN是终末期肾脏疾病的主要原因，每年在医疗保健上花费180亿美元。了解IgAN背后的分子相互作用将是开发这种代价高昂且使人虚弱的疾病治疗方法的第一步。

DESCRIPTION (provided by applicant): IgA nephropathy (IgAN) is the most common form of glomerulonephritis, an inflammatory disease of the kidney. IgAN is characterized by deposition of lgA1 antibodies in the glomerular mesangium of the kidney, followed by infiltration of inflammatory immune cells and eventual loss of kidney function. lgA1 antibodies show altered glycosylation and polymerization states in a large percentage of IgAN patients. These alterations have been suggested to play a role in modifying the interactions between lgA1 and IgA-specific receptors, particularly, FcalphaRI (CD89) and transferrin receptor (TfR), although conflicting data have been reported. The long-term goal of this research effort is to ascertain the precise molecular events that lead to lgA1 deposition in the mesangium. The central hypothesis is that modifications in lgA1 glycosylation and polymerization lead to increased affinity for critical IgA-binding receptors (specifically, FcalphaRI and TfR). These aberrant interactions are proposed to lead directly to deposition of lgA1 in the kidney mesangium and the ensuing inflammatory response. Specific Aims for this proposal include: 1) Characterize the effects of lgA1 glycosylation and polymerization on its interaction with FcalphaRI and TfR, using recombinant lgA1 with defined glycosylation states; 2) Characterize the receptor interactions of lgA1 purified from serum of healthy and IgAN patients and correlate the receptor affinity with lgA1 glycosylation and polymerization state; and 3) Determine the contribution of FcalphaRI N-glycosylation to its interaction with lgA1 and TfR. Binding studies with lgA1, FcalphaRI, and TfR will be carried out by surface plasmon resonance and analytical ultracentrifugation. lgA1 glycosylation will be characterized by lectin affinity assays along with thorough analysis of samples of interest by Fourier transform-ion cyclotron resonance mass spectrometry. This research will help determine the molecular basis for IgA nephropathy (IgAN), a kidney disease affecting approximately 100,000 patients in the US. IgAN is a primary cause of end-stage renal disease, which costs $18 billion per year in medical care. Understanding the molecular interactions underlying IgAN will be the first step towards developing treatments for this costly and debilitating disease.