Pathogen-Specific Binding Soluble Down Syndrome Cell Adhesion Molecule (Dscam) Regulates Phagocytosis via Membrane-Bound Dscam in Crab.
Pathogen-Specific Binding Soluble Down Syndrome Cell Adhesion Molecule (Dscam) Regulates Phagocytosis via Membrane-Bound Dscam in Crab.
复制标题
病原体特异性结合可溶性唐氏综合症细胞粘附分子 (Dscam) 调节吞噬作用
DOI：
10.3389/fimmu.2018.00801
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发表时间：
2018
影响因子：
7.3
通讯作者：
Li WW
中科院分区：
文献类型：
--
作者：
Li XJ;Yang L;Li D;Zhu YT;Wang Q;Li WW
唐氏综合症细胞粘附分子（Dscam）基因是一个非凡的多样性例子，可以产生数千种同种型，迄今为止只在昆虫和甲壳类动物中发现。累积的证据表明，Dscam可能有助于昆虫特异性免疫反应的机制基础。然而，Dscam与病原体和免疫相关的机制和功能在很大程度上仍然未知。本研究对中华绒螯蟹（Eriocheir sinensis）的基因组结构和Dscam外显子进行了分析。这些变体，命名为EsDscam，由于三个可变剪接的免疫球蛋白（IG）结构域和一个跨膜结构域，可能产生30，600种同种型。EsDscam在mRNA和蛋白质水平上在细菌挑战后显著上调。此外，发现细菌特异性EsDscam同种型与原始细菌特异性结合以促进有效清除。此外，细菌特异性结合的可溶性EsDscam通过完整的Ig 1-Ig 4结构域显着增强消除原始细菌通过吞噬血细胞，这一功能被废除的部分Ig 1-Ig 4结构域截断。进一步的研究表明，敲除膜结合的EsDscam抑制了具有相同胞外区的EsDscam促进细菌吞噬的能力。免疫细胞化学显示EsDscam的可溶性和膜结合形式在血细胞表面共定位。远Western和免疫共沉淀分析表明EsDscam亚型之间的同型相互作用。这项研究提供了一种机制，通过这种机制，可溶性Dscam调节血细胞的吞噬作用，通过细菌特异性结合和特异性相互作用与膜结合的Dscam作为吞噬受体。
The Down syndrome cell adhesion molecule (Dscam) gene is an extraordinary example of diversity that can produce thousands of isoforms and has so far been found only in insects and crustaceans. Cumulative evidence indicates that Dscam may contribute to the mechanistic foundations of specific immune responses in insects. However, the mechanism and functions of Dscam in relation to pathogens and immunity remain largely unknown. In this study, we identified the genome organization and alternative Dscam exons from Chinese mitten crab, Eriocheir sinensis. These variants, designated EsDscam, potentially produce 30,600 isoforms due to three alternatively spliced immunoglobulin (Ig) domains and a transmembrane domain. EsDscam was significantly upregulated after bacterial challenge at both mRNA and protein levels. Moreover, bacterial specific EsDscam isoforms were found to bind specifically with the original bacteria to facilitate efficient clearance. Furthermore, bacteria-specific binding of soluble EsDscam via the complete Ig1–Ig4 domain significantly enhanced elimination of the original bacteria via phagocytosis by hemocytes; this function was abolished by partial Ig1–Ig4 domain truncation. Further studies showed that knockdown of membrane-bound EsDscam inhibited the ability of EsDscam with the same extracellular region to promote bacterial phagocytosis. Immunocytochemistry indicated colocalization of the soluble and membrane-bound forms of EsDscam at the hemocyte surface. Far-Western and coimmunoprecipitation assays demonstrated homotypic interactions between EsDscam isoforms. This study provides insights into a mechanism by which soluble Dscam regulates hemocyte phagocytosis via bacteria-specific binding and specific interactions with membrane-bound Dscam as a phagocytic receptor.