Autoantibodies to calpastatin (an endogenous inhibitor for calcium-dependent neutral protease, calpain) in systemic rheumatic diseases.
Autoantibodies to calpastatin (an endogenous inhibitor for calcium-dependent neutral protease, calpain) in systemic rheumatic diseases.
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系统性风湿病中钙蛋白酶抑制剂（钙依赖性中性蛋白酶钙蛋白酶的内源性抑制剂）的自身抗体。
DOI：
10.1073/pnas.92.16.7267
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发表时间：
1995
影响因子：
11.1
通讯作者：
Masashi Akizuki
中科院分区：
文献类型：
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作者：
Tsuneyo Mimori;Kazuhiro Suganuma;Yutaka Tanami;T. Nojima;Mami Matsumura;Takao Fujii;Toshio Yoshizawa;Koichi Suzuki;Masashi Akizuki
我们鉴定出一种自身抗体，可以与钙调蛋白(一种钙依赖的中性蛋白钙蛋白酶(EC 3.4.22.17)的抑制蛋白)发生反应。在早期的免疫印迹研究中，类风湿性关节炎(RA)患者的血清在HeLa细胞提取液中识别出未知的60、45和75 kDa蛋白质。为了鉴定这些自身抗原，我们使用患者血清从lambda gt11表达文库中克隆了cDNA。我们分离了四个表达RA血清识别的融合蛋白的基因的克隆。1.2kb的cDNA插入片段(称为RA-6)似乎编码与HeLa细胞的60 kDa抗原相对应的多肽，因为与RA-6融合蛋白结合的抗体也与60 kDa的HeLa蛋白反应。其推导的氨基酸序列与人Calastatin的C端178个氨基酸序列完全一致，只有1个氨基酸发生替换。与RA-6反应的患者血清也与猪肌肉Calastatin结合，抗人Calastatin的单抗识别RA-6融合蛋白，证实了RA-6与Calastatin的同一性。此外，纯化的RA-6融合蛋白抑制了Calain的蛋白分解活性，而从含有抗Calastatin抗体的血清中提取的Ig G阻断了RA-6融合蛋白的Calastatin活性。RA-6产品的免疫印迹在57%的RA患者中检测到Calastatin的自身抗体；这一发生率显著高于其他系统性风湿性疾病，包括系统性红斑狼疮(27%)、多发性肌炎/皮肌炎(24%)、系统性硬化症(38%)和重叠综合征(29%)。因此，抗钙调蛋白抗体在类风湿性关节炎患者中最常见，并可能参与风湿性疾病的发病机制。
We identified an autoantibody that reacts with calpastatin [an inhibitor protein of the calcium-dependent neutral protease calpain (EC 3.4.22.17)]. In early immunoblot studies, sera from patients with rheumatoid arthritis (RA) recognized unidentified 60-, 45-, and 75-kDa proteins in HeLa cell extracts. To identify these autoantigens, we used patient sera to clone cDNAs from a lambda gt11 expression library. We isolated clones of four genes that expressed fusion proteins recognized by RA sera. The 1.2-kb cDNA insert (termed RA-6) appeared to encode a polypeptide corresponding to the 60-kDa antigen from HeLa cells, since antibodies bound to the RA-6 fusion protein also reacted with a 60-kDa HeLa protein. The deduced amino acid sequence of the RA-6 cDNA was completely identical with the C-terminal 178 amino acids of human calpastatin except for one amino acid substitution. Patient sera that reacted with the RA-6 also bound pig muscle calpastatin, and a monoclonal antibody to human calpastatin recognized the RA-6 fusion protein, confirming the identity of RA-6 with calpastatin. Moreover, the purified RA-6 fusion protein inhibited the proteolytic activity of calpain, and IgG from a serum containing anti-calpastatin antibodies blocked the calpastatin activity of the RA-6 fusion protein. Immunoblots of the RA-6 product detected autoantibodies to calpastatin in 57% of RA patients; this incidence was significantly higher than that observed in other systemic rheumatic diseases, including systemic lupus erythematosus (27%), polymyositis/dermatomyositis (24%), systemic sclerosis (38%), and overlap syndrome (29%). Thus, anti-calpastatin antibodies are present most frequently in patients with RA and may participate in pathogenic mechanisms of rheumatic diseases.