Department of Biomolecular Chemistry, Institute for Molecules and Materials, Nijmegen Center for Molecular Life Sciences, Radboud University Nijmegen, P,O, Box 9101, 6500 HB Nijmegen, The Netherlands.
Arthritis Res Ther. 2012 Feb 17;14(1):R35. doi: 10.1186/ar3744.
Fibronectin is one of the most abundant proteins present in the inflamed joint. Here, we characterized the citrullination of fibronectin in the joints of rheumatoid arthritis (RA) patients and studied the prevalence, epitope specificity and human leukocyte antigen (HLA) association of autoantibodies against citrullinated fibronectin in RA.
Citrullinated residues in fibronectin isolated from RA patient synovial fluid were identified by mass spectrometry. The corresponding citrullinated and non-citrullinated peptides were synthesized and used to analyze the presence of autoantibodies to these peptides in RA sera and sera from other diseases and healthy controls by ELISA. The data were compared with risk factors like shared epitope HLA alleles and smoking, and with clinical features.
Five citrullinated residues were identified in fibronectin from RA synovial fluid. RA sera reacted in a citrulline-dependent manner with two out of four citrullinated fibronectin peptides, one of which contains two adjacent citrulline residues, in contrast to non-RA sera, which were not reactive. The most frequently recognized peptide (FN-Cit1035,1036, LTVGLTXXGQPRQY, in which × represents citrulline) was primarily targeted by anti-CCP (cyclic citrullinated peptide) 2-positive RA patients. Anti-FN-Cit1035,1036 autoantibodies were detected in 50% of established anti-CCP2-positive RA patients and in 45% of such patients from a early arthritis clinic. These antibodies appeared to be predominantly of the immunoglobulin G (IgG) isotype and to be associated with HLA shared epitope alleles (odds ratio = 2.11).
Fibronectin in the inflamed synovia of RA patients can be citrullinated at least at five positions. Together with the flanking amino acids, three of these citrullinated residues comprise two epitopes recognized by RA autoantibodies. Anti-citrullinated fibronectin peptide antibodies are associated with HLA shared epitope alleles.
纤维连接蛋白是存在于炎症关节中的最丰富的蛋白质之一。在这里，我们对类风湿关节炎 (RA) 患者关节中的纤维连接蛋白的瓜氨酸化进行了表征，并研究了 RA 中针对瓜氨酸化纤维连接蛋白的自身抗体的流行率、表位特异性和人类白细胞抗原 (HLA) 相关性。
通过质谱法鉴定从 RA 患者滑膜液中分离的纤维连接蛋白中的瓜氨酸化残基。合成相应的瓜氨酸化和非瓜氨酸化肽，并通过 ELISA 分析 RA 血清和其他疾病血清以及健康对照血清中这些肽的自身抗体的存在。将数据与共享表位 HLA 等位基因和吸烟等危险因素以及临床特征进行比较。
从 RA 滑膜液中的纤维连接蛋白中鉴定出 5 个瓜氨酸化残基。RA 血清以瓜氨酸依赖性方式与四个瓜氨酸化纤维连接蛋白肽中的两个反应，其中一个含有两个相邻的瓜氨酸残基，而与非 RA 血清不同，非 RA 血清没有反应。最常被识别的肽（FN-Cit1035,1036，LTVGLTXXGQPRQY，其中×代表瓜氨酸）主要由抗 CCP（环状瓜氨酸肽）2 阳性 RA 患者靶向。抗 FN-Cit1035,1036 自身抗体在 50%的已建立的抗 CCP2 阳性 RA 患者和早期关节炎诊所的此类患者中检测到。这些抗体似乎主要是免疫球蛋白 G (IgG) 同种型，并且与 HLA 共享表位等位基因相关（比值比=2.11）。
RA 患者炎症滑膜中的纤维连接蛋白至少可以在五个位置瓜氨酸化。与侧翼氨基酸一起，这三个瓜氨酸化残基包含两个 RA 自身抗体识别的表位。抗瓜氨酸化纤维连接蛋白肽抗体与 HLA 共享表位等位基因相关。
