Highly pathogenic natural monoclonal antibody B4-IgM recognizes a post-translational modification comprised of acetylated N-terminal methionine followed by aspartic or glutamic acid.
Highly pathogenic natural monoclonal antibody B4-IgM recognizes a post-translational modification comprised of acetylated N-terminal methionine followed by aspartic or glutamic acid.
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高致病性天然单克隆抗体 B4-IgM 可识别由乙酰化 N 末端蛋氨酸和天冬氨酸或谷氨酸组成的翻译后修饰。
DOI：
10.1016/j.molimm.2023.03.005
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发表时间：
2023
影响因子：
3.6
通讯作者：
MichaelHolers,V
中科院分区：
文献类型：
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作者：
Kulik,Liudmila;Renner,Brandon;Laskowski,Jennifer;Thurman,JoshuaM;MichaelHolers,V
天然单克隆抗体B4-IgM识别鼠膜联蛋白4（mAn 4）并在许多小鼠模型中加剧缺血再灌注损伤。在细胞凋亡过程中，细胞内mAn 4蛋白易位到膜表面，保持附着在外膜小叶上，在那里它被抗mAn 4 B4-IgM抗体识别。B4-IgM不识别人膜联蛋白4（hAn 4）。然而，B4-IgM抗体表位检测未知的人类蛋白质的蛋白质印迹，并通过流式细胞术对所有研究的人类细胞系进行细胞凋亡和健康细胞的一个小子集。B4-IgM抗体还识别胞质蛋白中坏死细胞上的表位，显然通过足够大的孔进入，以允许天然抗体穿透细胞并结合自身蛋白上表达的表位。使用蛋白质组学和定点突变，我们发现，B4-IgM结合到一个表位后修饰的乙酰化N-末端甲硫氨酸，其次是谷氨酸或天冬氨酸。该表位不是由细胞凋亡或损伤诱导的，因为这种修饰也可以在蛋白质翻译期间发生。这一发现揭示了一种额外的新机制，其中受损细胞被天然抗体检测到，天然抗体通过识别在可变细胞系中发现的多种蛋白质之间共享的表位来启动致病性补体激活。
The natural monoclonal antibody B4-IgM recognizes murine annexin 4 (mAn4) and exacerbates ischemia-reperfusion injury in many mouse models. During apoptosis, the intracellular mAn4 protein translocates to the membrane surface, remaining attached to the outer membrane leaflet where it is recognized by the anti-mAn4 B4-IgM antibody. B4-IgM does not recognize human annexin 4 (hAn4). However, the B4-IgM antibody epitope was detected by Western blot of unknown human proteins and by flow cytometry on all studied human cell lines undergoing apoptosis and on a minor subset of healthy cells. The B4-IgM antibody also recognizes the epitope on necrotic cells in cytoplasmic proteins, apparently entering through pores large enough to allow natural antibodies to penetrate the cells and bind to the epitope expressed on self-proteins. Using proteomics and site-directed mutagenesis, we found that B4-IgM binds to an epitope with post-translationally modified acetylated N-terminal methionine, followed by either glutamic or aspartic acid. The epitope is not induced by apoptosis or injury because this modification can also occur during protein translation. This finding reveals an additional novel mechanism whereby injured cells are detected by natural antibodies that initiate pathogenic complement activation through the recognition of epitopes that are shared across multiple proteins found in variable cell lines.