Tang Xueying, Huang Baoyu, Zhang Linlin, Li Li, Zhang Guofan
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, China; University of Chinese Academy of Sciences, Beijing 100039, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong 266071, China; National & Local Joint Engineering Laboratory of Ecological Mariculture, Qingdao, Shandong 266071, China.
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong 266071, China; National & Local Joint Engineering Laboratory of Ecological Mariculture, Qingdao, Shandong 266071, China.
Dev Comp Immunol. 2017 Jul;72:21-29. doi: 10.1016/j.dci.2017.02.004. Epub 2017 Feb 13.
Interleukin-1 receptor-associated kinases (IRAKs) play important roles in MyD88-dependent TLR signaling, the crucial innate immune pathway in molluscs. In this study, we examined the full-length IRAK4 genetic sequence in the Pacific oyster (Crassostrea gigas) by molecular cloning. Phylogenetic analysis revealed that CgIRAK4 is most closely related to Mytilus edulis, and forms a clade with other molluscs. CgIRAK4 transcripts are widely expressed in all tissues, with the highest expression observed in the hemocytes and gill. Moreover, CgIRAK4 is significantly upregulated after Oyster herpesvirus-1 microvariant (OsHV-1 μvar), Vibrio alginolyticus, and poly I:C challenge. Yeast two-hybrid and co-immunoprecipitation assays reveal that the CgIRAK4 death domain is necessary to mediate interaction between CgIRAK4 and two CgMyD88 isoforms. In addition, CgIRAK4 overexpression cannot induce NF-κB transcriptional activity, but blocks that induced by CgMyD88 in HEK293T cells. These findings elucidate the mechanisms of MyD88-dependent TLR signaling in molluscs, and the differences in IRAK-mediated pathway activation between invertebrates and vertebrates.
白细胞介素-1受体相关激酶（IRAKs）在MyD88依赖的TLR信号通路中发挥重要作用，这是软体动物至关重要的天然免疫途径。在本研究中，我们通过分子克隆检测了太平洋牡蛎（Crassostrea gigas）中IRAK4的全长基因序列。系统发育分析表明，CgIRAK4与紫贻贝（Mytilus edulis）关系最为密切，并与其他软体动物形成一个进化枝。CgIRAK4转录本在所有组织中广泛表达，在血细胞和鳃中表达量最高。此外，在受到牡蛎疱疹病毒-1微变体（OsHV-1 μvar）、溶藻弧菌（Vibrio alginolyticus）和聚肌苷酸:聚胞苷酸（poly I:C）刺激后，CgIRAK4显著上调。酵母双杂交和免疫共沉淀试验表明，CgIRAK4死亡结构域对于介导CgIRAK4与两种CgMyD88异构体之间的相互作用是必需的。此外，CgIRAK4过表达不能诱导NF-κB转录活性，但在HEK293T细胞中可阻断由CgMyD88诱导的NF-κB转录活性。这些发现阐明了软体动物中MyD88依赖的TLR信号通路的机制，以及无脊椎动物和脊椎动物在IRAK介导的途径激活方面的差异。
