Discovery and Analysis of Invertebrate IgV(J)-C2 Structure from Amphioxus Provides Insight into the Evolution of the Ig Superfamily

文献类型： 外文期刊

第一作者： Chen, Rong

作者： Chen, Rong;Zhang, Lijie;Zhang, Nianzhi;Zhang, Ling;Yao, Shugang;Wu, Yanan;Jiang, Bo;Wang, Zhenbao;Yuan, Hongyu;Xia, Chun;Chen, Rong;Qi, Jianxun;Zhang, Qiujin;Xia, Chun

作者机构：

期刊名称：JOURNAL OF IMMUNOLOGY （ 影响因子：5.422； 五年影响因子：6.029 ）

ISSN： 0022-1767

年卷期： 2018 年 200 卷 8 期

页码：

收录情况： SCI

摘要： The emergence of adaptive immunity in jawed vertebrates depended on the appearance of variable immune receptors, BCRs and TCRs, which exhibit variable-J constant (V-J-C) type Ig superfamily folds. Hitherto, however, the structures of IgV-J-IgC type molecules had never been characterized in invertebrates, leaving the origin of BCR/TCR-type molecules unknown. Using x-ray crystallography, the structure of a V-J-C2 molecule, named AmpIgV(J)-C2, was determined in amphioxus (Branchiostoma floridae). The first domain shows typical V folding, including the hydrophobic core, CDR analogs, and eight conserved residues. The second domain is a C2-type Ig superfamily domain, as defined by its short length and the absence of beta-strand D- and C1-typical motifs. AmpIgV(J)-C2 molecules form homodimers, using "three-layer packing dimerization," as described for TCRs and BCRs. The AmpIgV(J)-C2 V domain harbors a diglycine motif in beta-strand G and forms a beta-bulge structure participating in V-V intermolecular interaction. By immunohistochemistry, AmpIgV(J)-C2 molecules were primarily found in mucosal tissues, whereas PCR and sequence analysis indicated considerable genetic variation at the single-gene level; these findings would be consistent with an immune function and a basic ability to adapt to binding different immune targets. Our results show a BCR/TCR-ancestral like molecule in amphioxus and help us to understand the evolution of the adaptive immune system.

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