Department of Nephrology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan.
J Nephrol. 2010 Jan-Feb;23(1):70-6.
Although many reports have described the abnormal structures of O-glycan in the IgA1 hinge region in IgA nephropathy (IgAN), the specific glycopeptide that can be used as a diagnostic biomarker for IgAN has not yet been identified. To pursue this diagnostic approach, we used mass spectrometric analysis to search for specific structures in IgA1 hinge glycopeptides in 30 IgAN patients contrasted with 30 healthy controls.
IgA1 hinge glycopeptides were individually purified from the sera of 30 biopsy-proven IgAN patients and 30 healthy controls. The structure of each glycopeptide was analyzed by ion trap mass spectrometry. Sugar conformations in each glycopeptide were estimated by collision-induced dissociation tandem mass spectrometry. Furthermore, to search for specific O-glycans in IgAN patients with a statistical significance, the identified hinge glycopeptides were analyzed by Fisher exact test.
A total of 57 hinge glycopeptides were identified from each of the 2 sample groups. Among the structures of the hinge glycopeptides identified, statistical significance was found for 6 glycopeptides (O-glycan compositions were 33-mer hinge core peptides + xGalNAc + yGal + zNeu5Ac; x:y:z = 5:3:3, 5:3:0, 5:2:1, 4:2:2, 3:1:1, 3:1:0) by Fisher exact test (p<0.05). In these 6 O-glycan compositions, 3 compositions (x:y:z = 4:2:2, 3:1:1, 3:1:0) were only observed in IgAN patients and were absent in the 30 controls.
Statistically specific O-glycans were identified in 30 IgAN patients compared with 30 controls. These results open the possibility for preparation of lectin and/or antibodies binding to specific glycopeptides in IgAN.
虽然许多报道描述了 IgA 肾病（IgAN）中 IgA1 铰链区 O-聚糖的异常结构，但尚未确定可作为 IgAN 诊断生物标志物的特定糖肽。为了寻求这种诊断方法，我们使用质谱分析在 30 例活检证实的 IgAN 患者和 30 例健康对照者的 IgA1 铰链糖肽中寻找特异性结构。
从 30 例活检证实的 IgAN 患者和 30 例健康对照者的血清中分别纯化 IgA1 铰链糖肽。通过离子阱质谱分析分析每种糖肽的结构。通过碰撞诱导解离串联质谱法估计每种糖肽中的糖构象。此外，为了寻找具有统计学意义的 IgAN 患者中特定的 O-聚糖，通过 Fisher 精确检验分析鉴定的铰链糖肽。
从每组的 2 个样本中鉴定出总共 57 个铰链糖肽。在所鉴定的铰链糖肽结构中，通过 Fisher 精确检验发现 6 种糖肽具有统计学意义（O-聚糖组成 33 -mer 铰链核心肽+xGalNAc+yGal+zNeu5Ac；x：y：z=5：3：3，5：3：0，5：2：1，4：2：2，3：1：1，3：1：0）（p<0.05）。在这 6 种 O-聚糖组成中，仅在 IgAN 患者中观察到 3 种组成（x：y：z=4：2：2，3：1：1，3：1：0），在 30 名对照者中未见。
与 30 名对照者相比，在 30 名 IgAN 患者中鉴定出具有统计学意义的特异性 O-聚糖。这些结果为制备与 IgAN 中特定糖肽结合的凝集素和/或抗体开辟了可能性。
