Mayampurath Anoop, Song Ehwang, Mathur Abhinav, Yu Chuan-Yih, Hammoud Zane, Mechref Yehia, Tang Haixu
School of Informatics & Computing, Indiana University , 901 East 10th Street, Bloomington, Indiana 47408, United States.
J Proteome Res. 2014 Nov 7;13(11):4821-32. doi: 10.1021/pr500242m. Epub 2014 Jul 7.
Glycan moieties of glycoproteins modulate many biological processes in mammals, such as immune response, inflammation, and cell signaling. Numerous studies show that many human diseases are correlated with quantitative alteration of protein glycosylation. In some cases, these changes can occur for certain types of glycans over specific sites in a glycoprotein rather than on the global abundance of the glycoprotein. Conventional analytical techniques that analyze the abundance of glycans cleaved from glycoproteins cannot reveal these subtle effects. Here we present a novel statistical method to quantify the site-specific glycosylation of glycoproteins in complex samples using label-free mass spectrometric techniques. Abundance variations between sites of a glycoprotein as well as different glycoforms, that is, glycopeptides with different glycans attached to the same site, can be detected using these techniques. We applied our method to an esophageal cancer study based on blood serum samples from cancer patients in an attempt to detect potential biomarkers of site-specific N-linked glycosylation. A few glycoproteins, including vitronectin, showed significantly different site-specific glycosylations within cancer/control samples, indicating that our method is ready to be used for the discovery of glycosylated biomarkers.
糖蛋白的聚糖部分调节哺乳动物体内的许多生物学过程，如免疫反应、炎症和细胞信号传导。大量研究表明，许多人类疾病与蛋白质糖基化的定量改变相关。在某些情况下，这些变化可能发生在糖蛋白特定位点上的某些类型聚糖，而非糖蛋白的整体丰度上。分析从糖蛋白上裂解下来的聚糖丰度的传统分析技术无法揭示这些细微影响。在此，我们提出一种新颖的统计方法，使用无标记质谱技术对复杂样品中糖蛋白的位点特异性糖基化进行定量。使用这些技术可以检测糖蛋白位点之间以及不同糖型（即同一位点连接不同聚糖的糖肽）之间的丰度变化。我们将我们的方法应用于一项基于癌症患者血清样本的食管癌研究，试图检测位点特异性N-连接糖基化的潜在生物标志物。包括玻连蛋白在内的一些糖蛋白在癌症/对照样本中显示出显著不同的位点特异性糖基化，表明我们的方法已可用于发现糖基化生物标志物。
