Broad Susceptibility of Nucleolar Proteins and Autoantigens to Complement C1 Protease Degradation
Broad Susceptibility of Nucleolar Proteins and Autoantigens to Complement C1 Protease Degradation
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DOI：
10.4049/jimmunol.1700728
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发表时间：
2017-12-15
影响因子：
4.4
通讯作者：
Lu, Jinhua
中科院分区：
文献类型：
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作者：
Cai, Yitian;Wee, Seng Yin Kelly;Lu, Jinhua
抗核自身抗体是系统性红斑狼疮（SLE）的致病标志，常靶向核仁。虽然这些抗体的原因仍然广泛和不明确，C1复合体（C1 qC 1（r）2C 1 s（2））或C4的遗传缺陷能够诱导这些抗体。考虑到最近的一项发现，在死细胞中，核仁被C1 q靶向，两个核仁自身抗原被C1 r/C1 s蛋白酶降解，我们认为C1可以通过广泛降解核仁蛋白或自身抗原来帮助对抗抗核自身免疫。将核仁分离至均一性并确定结构。C1处理后，裂解的核仁蛋白通过蛋白质组学二维荧光差异凝胶电泳和质谱鉴定，并通过使用特异性Abs的Western印迹进一步验证。使用SLE患者自身抗体估计C1治疗后核仁自身抗原降解的程度。分离的核仁与SLE患者自身抗体广泛反应。这些核仁缺乏显著的自身蛋白水解，但许多核仁蛋白和自身抗原被C1蛋白酶降解;超过20种核仁蛋白被鉴定为C1可裂解的。这些通过使用特异性Ab的Western印迹进一步验证。核仁广泛的自身抗原性可能归因于其自身蛋白水解不良，在坏死暴露时引起自体免疫刺激。然而，C1 q靶向这些核仁，导致C1蛋白酶活化和许多核仁蛋白或自身抗原的切割。这可能代表了对抗核自身免疫的一个重要监测机制，因为C1基因缺陷导致抗核自身抗体和SLE疾病。
Anti-nuclear autoantibodies, which frequently target the nucleoli, are pathogenic hallmarks of systemic lupus erythematosus (SLE). Although the causes of these Abs remain broad and ill-defined, a genetic deficiency in C1 complex (C1qC1(r)2C1s(2)) or C4 is able to induce these Abs. Considering a recent finding that, in dead cells, nucleoli were targeted by C1q and two nucleolar autoantigens were degraded by C1r/C1s proteases, we considered that C1 could help protect against antinuclear autoimmunity by broadly degrading nucleolar proteins or autoantigens. Nucleoli were isolated to homogeneity and structurally defined. After C1 treatment, cleaved nucleolar proteins were identified by proteomic two-dimensional fluorescence difference gel electrophoresis and mass spectrometry, and further verified by Western blotting using specific Abs. The extent of nucleolar autoantigen degradation upon C1 treatment was estimated using SLE patient autoantibodies. The isolated nucleoli were broadly reactive with SLE patient autoantibodies. These nucleoli lacked significant autoproteolysis, but many nucleolar proteins and autoantigens were degraded by C1 proteases; >20 nucleolar proteins were identified as C1 cleavable. These were further validated by Western blotting using specific Abs. The broad autoantigenicity of the nucleoli may attribute to their poor autoproteolysis, causing autologous immune stimulation upon necrotic exposure. However, C1q targets at these nucleoli to cause C1 protease activation and the cleavage of many nucleolar proteins or autoantigens. This may represent one important surveillance mechanism against antinuclear autoimmunity because C1 genetic deficiency causes anti-nuclear autoantibodies and SLE disease.