Novel conformation of histidyl-transfer RNA synthetase in the lung - The target tissue in Jo-1 autoantibody-associated myositis
Novel conformation of histidyl-transfer RNA synthetase in the lung - The target tissue in Jo-1 autoantibody-associated myositis
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DOI：
10.1002/art.22790
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发表时间：
2007-08-01
影响因子：
--
通讯作者：
Casciola-Rosen, Livia A.
中科院分区：
文献类型：
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作者：
Levine, Stuart M.;Raben, Nina;Casciola-Rosen, Livia A.
Objective.我们以前提出，新的表达和/或构象的自身抗原在靶组织中可能发挥作用，产生表型特异性免疫反应。组氨酰转移RNA合成酶（HisRS，Jo-1）自身抗体与肌炎患者间质性肺病的密切相关性促使我们研究肺中HisRS的表达和构象。正常人体组织标本探测一种新的抗HisRS抗体识别其颗粒酶B-可切割的构象免疫印迹和免疫组化。采用定点突变法定位了HisRS颗粒酶B位点，并在串联免疫沉淀/颗粒酶B切割研究中评价了其与抗体识别结构域的关系。自身抗体识别的HisRS α-螺旋卷曲螺旋N-末端结构域由颗粒酶B切割位点结合。在患者血清的免疫沉淀研究中，发现HisRS存在于2种构象中，通过对颗粒酶B切割的敏感性和自身抗体结合的修饰来定义。尽管HisRS在不同组织中的表达相似，但其颗粒酶B可切割形式在肺中的表达富集并定位于肺泡上皮。HisRS的蛋白水解敏感构象存在于肺中，肺是与该自身抗体应答相关的靶组织。因此，我们认为对HisRS的自身免疫是在肺中启动和传播的。
Objective. We previously proposed that novel expression and/or conformation of autoantigens in the target tissue may play a role in generating phenotype-specific immune responses. The strong association of autoantibodies to histidyl-transfer RNA synthetase (HisRS, Jo-1) with interstitial lung disease in patients with myositis led us to study HisRS expression and conformation in the lung.Methods. Normal human tissue specimens were probed with a novel anti-HisRS antibody recognizing its granzyme B-cleavable conformation by immunoblotting and immunohistochemistry. The HisRS granzyme B site was mapped using site-directed mutagenesis, and its relationship to the antibody recognition domain was evaluated in tandem immunoprecipitation/granzyme B cleavage studies.Results. The HisRS alpha-helical coiled-coil N-terminal domain recognized by autoantibodies is bounded by a granzyme B cleavage site. In immunoprecipitation studies with patient sera, HisRS was found to exist in 2 conformations, defined by sensitivity to cleavage by granzyme B and modification by autoantibody binding. Despite similar global expression of HisRS in different tissue, expression of its granzyme B-cleavable form was enriched in the lung and localized to the alveolar epithelium.Conclusion. A proteolytically sensitive conformation of HisRS exists in the lung, the target tissue associated with this autoantibody response. We thus propose that autoimmunity to HisRS is initiated and propagated in the lung.