Serum tests have become a partial alternative to renal biopsy for diagnosing primary membranous nephropathy (pMN). However, urine tests, due to their non-invasive nature and ability to more accurately reflect glomerular diseases, hold great promise for the detection of pMN. However, the low protein concentration and the time-consuming sample preparation procedure of urine samples challenges the proteomic and glycoproteomic analysis to find urine-derived signatures associated with pMN. In this study, we presented a microparticle-assisted protein capture (MAPC) method to efficiently prepare urine samples. It was found that proteins and N-linked intact glycopeptides can be sensitively identified from urine samples of pMN patients and healthy controls by using this method. For comparison, proteins and N-linked intact glycopeptides from serum were also analyzed. Interestingly, discrepancy was found in the changing trends for proteins/intact glycopeptides between serum and urine. Moreover, urine derived proteins, N-linked intact glycopeptides, and glycans exhibited more pronounced changes between pMN and healthy control compared to serum sample. Notably, urine IgG4 not only up-regulated in pMN at global peptide level, its corresponding site-specific glycans were specifically identified in pMN urine with significantly up-regulations, suggested the potential of using glycosylated urine IgG4 for the non-invasive diagnosis of pMN.

中文翻译：

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微粒辅助蛋白质捕获方法有助于对尿液样品进行蛋白质组学和糖蛋白组学分析


血清检测已成为肾活检诊断原发性膜性肾病 （pMN） 的部分替代方法。然而，由于其非侵入性和更准确地反映肾小球疾病的能力，尿液检测在 pMN 的检测方面具有很大的前景。然而，尿液样品的低蛋白质浓度和耗时的样品制备过程对蛋白质组学和糖蛋白组学分析提出了挑战，难以找到与 pMN 相关的尿液衍生特征。在这项研究中，我们提出了一种高效制备尿液样本的微粒辅助蛋白质捕获 （MAPC） 方法。研究发现，使用该方法可以从 pMN 患者和健康对照者的尿液样本中灵敏地鉴定蛋白质和 N-连接完整糖肽。为了进行比较，还分析了血清中的蛋白质和 N-连接完整糖肽。有趣的是，在血清和尿液之间蛋白质/完整糖肽的变化趋势中发现了差异。此外，与血清样品相比，尿液衍生蛋白、N-连接完整糖肽和聚糖在 pMN 和健康对照之间表现出更明显的变化。值得注意的是，尿液 IgG4 不仅在整体肽水平上调在 pMN 中上调，其相应的位点特异性聚糖在 pMN 尿液中被特异性鉴定，并且显着上调，这表明使用糖基化尿液 IgG4 进行 pMN 无创诊断的潜力。