Department of Biochemistry, University of Turku, Turku, Finland.
Structural Bioinformatics Laboratory, Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
Sci Rep. 2017 Aug 15;7(1):8246. doi: 10.1038/s41598-017-08597-4.
We report the extent, specific sites and structural requirements of joint inflammation related citrullination in extracellular proteins. A total of 40 synovial fluid samples derived from chronically inflamed human joints were analysed by heparin-agarose fractionation and LC-MS/MS. Citrullination of 55 arginines in extracellular proteins was detected. Importantly, 20% of the sites have a characterized function related to the hallmarks of destructive joint inflammation. E.g. four arginine residues, shown here to be citrullinated, are also affected by mutations in inherited diseases causing haemolysis or blood clotting dysfunction. Citrullination of integrin ligands was selected for further studies since fibronectin R234 in isoDGR was among the most frequently citrullinated arginines in synovial fluid. Assays with synovial fibroblasts and integrin αVβ3 indicated decreased affinity to the enzymatically citrullinated integrin binding sites. To conclude, our data indicate that in inflamed joints extensive citrullination affects the functional arginine residues in extracellular proteins.
我们报告了关节炎症相关瓜氨酸化在细胞外蛋白质中的程度、特定部位和结构要求。总共分析了 40 份来自慢性炎症关节的滑液样本，采用肝素琼脂糖分级分离和 LC-MS/MS。检测到细胞外蛋白质中 55 个精氨酸的瓜氨酸化。重要的是，20%的位点具有与破坏性关节炎症特征相关的特征功能。例如，四个精氨酸残基，这里显示被瓜氨酸化，也受到导致溶血或凝血功能障碍的遗传性疾病突变的影响。整合素配体的瓜氨酸化被选择进行进一步研究，因为在同型 DGR 中，纤维连接蛋白 R234 是滑液中最常被瓜氨酸化的精氨酸之一。用滑膜成纤维细胞和整合素 αVβ3 进行的测定表明，对酶促瓜氨酸化整合素结合位点的亲和力降低。总之，我们的数据表明，在炎症关节中，广泛的瓜氨酸化会影响细胞外蛋白质中功能精氨酸残基。
