Department of Medical Biochemistry, Institute of Biomedicine, University of Gothenburg, Medicinaregatan 9A, 405 30, Gothenburg, Sweden.
Mol Cell Proteomics. 2013 Apr;12(4):921-31. doi: 10.1074/mcp.M113.028878. Epub 2013 Mar 1.
Rheumatoid arthritis is a common and debilitating systemic inflammatory condition affecting up to 1% of the world's population. This study aimed to investigate the immunological significance of O-glycans in chronic arthritis at a local and systemic level. O-Glycans released from synovial glycoproteins during acute and chronic arthritic conditions were compared and immune-reactive glycans identified. The sulfated core 1 O-glycan (Galβ1-3GalNAcol) was immune reactive, showing a different isomeric profile in the two conditions. From acute reactive arthritis, three isomers could be sequenced, but in patients with chronic rheumatoid arthritis, only a single 3-Gal sulfate-linked isomer could be identified. The systemic significance of this glycan epitope was investigated using the salivary mucin MUC7 in patients with rheumatoid arthritis and normal controls. To analyze this low abundance glycan, a selected reaction monitoring (SRM) method was developed to differentiate and relatively quantitate the core 1 O-glycan and the sulfated core 1 O-glycan Gal- and GalNAc-linked isomers. The acquisition of highly sensitive full scan linear ion trap MS/MS spectra in addition to quantitative SRM data allowed the 3- and 6-linked Gal isomers to be differentiated. The method was used to relatively quantitate the core 1 glycans from MUC7 to identify any systemic changes in this carbohydrate epitope. A statistically significant increase in sulfation was identified in salivary MUC7 from rheumatoid arthritis patients. This suggests a potential role for this epitope in chronic inflammation. This study was able to develop an SRM approach to specifically identify and relatively quantitate sulfated core 1 isomers and the unsulfated structure. The expansion of this method may afford an avenue for the high throughput investigation of O-glycans.
类风湿关节炎是一种常见且使人虚弱的全身性炎症性疾病，影响全球多达 1%的人口。本研究旨在探究局部和全身性慢性关节炎中 O-聚糖的免疫学意义。对急性和慢性关节炎条件下从滑膜糖蛋白中释放的 O-聚糖进行了比较，并鉴定了免疫反应性聚糖。在两种情况下，具有硫酸化核心 1 O-聚糖（Galβ1-3GalNAcol）的免疫反应性不同，其异构型谱也不同。从急性反应性关节炎中可以测序出三种异构型，但在慢性类风湿关节炎患者中，只能鉴定出一种单一的 3-半乳糖硫酸化异构型。使用类风湿关节炎患者和正常对照者的唾液黏蛋白 MUC7 研究了该糖基表位的系统意义。为了分析这种低丰度聚糖，开发了一种选择反应监测 (SRM) 方法，以区分和相对定量核心 1 O-聚糖以及硫酸化核心 1 O-聚糖的 Gal 和 GalNAc 连接异构型。除了定量 SRM 数据外，还获得了高灵敏度全扫描线性阱 MS/MS 谱，从而可以区分 3-和 6-连接的半乳糖异构型。该方法用于相对定量 MUC7 中的核心 1 聚糖，以鉴定该碳水化合物表位的任何系统变化。从类风湿关节炎患者的唾液 MUC7 中鉴定出硫酸化的统计学显著增加。这表明该表位在慢性炎症中具有潜在作用。本研究能够开发出一种 SRM 方法，专门鉴定和相对定量硫酸化核心 1 异构型和非硫酸化结构。该方法的扩展可能为 O-聚糖的高通量研究提供途径。
