Molecular characterization of Pacific oyster (Crassostrea gigas) IRAK4 gene and its role in MyD88-dependent pathway

• Published in: Developmental & Comparative Immunology
• Main Authors: Tang, Xueying, Huang, Baoyu, Zhang, Linlin, Li, Li, Zhang, Guofan
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Crassostrea Gigas; Irak4; Myd88; Tlr; Nf-kappa b; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: http://ir.qdio.ac.cn/handle/337002/137057; https://doi.org/10.1016/j.dci.2017.02.004

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 Glade 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 (0sHV-1 mu var), 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-kappa B 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. (C) 2017 Elsevier Ltd. All rights reserved.