Burbelo Peter D, Ching Kathryn H, Han Brian L, Bush Emily R, Reeves Westley H, Iadarola Michael J
Am J Transl Res. 2010 Mar 15;2(2):145-55.
Autoantibody levels to the SSA complex, composed of Ro52 and Ro60 proteins, are commonly measured in the diagnoses of Sjögren's Syndrome (SjS), as well as other rheumatological diseases. One of these proteins, Ro52, is an interferon-inducible member of the tripartite motif family bearing a RING motif functioning as an E3 ligase that ubiquitinates interferon regulatory factor 8 and other proteins. Using Luciferase Immunoprecipitation Systems (LIPS) we explored the antigenicity of Ro52 in detail. Analysis of antibody responses against Ro52 and 20 other established antigens revealed that Ro52 had the highest antibody titers and most likely represents one of the most immunogenic human proteins. While the antibody titers in many of the SjS patients were significantly and substantially higher than the controls, all healthy individuals had anti-Ro52 autoantibodies. N- and C-terminal fragments of Ro52 showed immunoreactivity in these serum samples, but the sums of these antibody titers were significantly lower than the antibody titers directed against the full-length Ro52. Antibody profiling of controls and SjS patients with three different N-terminal fragments of Ro52 revealed that the coiled-coil region was the most useful diagnostic (66% sensitivity), followed by the B-box (31% sensitivity), and then the RING-finger (24% sensitivity). The C-terminal region of Ro52, containing the B30.2 domain, showed higher antibody titers in SjS patients compared to controls and this region was responsible for the high level of Ro52 immunoreactivity in healthy individuals. Analysis of immunoreactivity to TRIM5, a Ro52-related protein, and the B30.2 domain from BTN1 and pyrin, failed to show significant antibody titers with the control or SjS patient serum. These results highlight the unusually high level of Ro52 antigenicity and demonstrate that autoantibodies are directed at both linear and conformational epitopes spanning the entire molecule.
在干燥综合征（SjS）以及其他风湿性疾病的诊断中，通常会检测针对由Ro52和Ro60蛋白组成的SSA复合物的自身抗体水平。其中一种蛋白Ro52是三重基序家族中干扰素诱导的成员，带有一个RING基序，作为E3连接酶发挥作用，可使干扰素调节因子8和其他蛋白发生泛素化。我们使用荧光素酶免疫沉淀系统（LIPS）详细探究了Ro52的抗原性。对针对Ro52和其他20种既定抗原的抗体反应进行分析后发现，Ro52具有最高的抗体滴度，很可能是免疫原性最强的人类蛋白之一。虽然许多干燥综合征患者的抗体滴度显著高于对照组，但所有健康个体都有抗Ro52自身抗体。Ro52的N端和C端片段在这些血清样本中显示出免疫反应性，但这些抗体滴度的总和明显低于针对全长Ro52的抗体滴度。用Ro52的三种不同N端片段对对照组和干燥综合征患者进行抗体谱分析发现，卷曲螺旋区域是最有用的诊断区域（敏感性为66%），其次是B盒（敏感性为31%），然后是指环结构域（敏感性为24%）。Ro52的C端区域包含B30.2结构域，与对照组相比，干燥综合征患者的该区域抗体滴度更高，并且该区域是健康个体中Ro52高免疫反应性的原因。对与Ro52相关的蛋白TRIM5以及BTN1和吡啉的B30.2结构域的免疫反应性分析未能在对照组或干燥综合征患者血清中显示出显著的抗体滴度。这些结果突出了Ro52异常高的抗原性，并表明自身抗体针对的是跨越整个分子的线性和构象表位。
