title: Molecular characterization of Pacific oyster (Crassostrea gigas) IRAK4 gene and its role in MyD88-dependent pathway.
abstract: 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.
authors.affiliation: 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.
authors.forename: Xueying
authors.initials: X
authors.lastname: Tang
authors.affiliation: 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.
authors.forename: Baoyu
authors.initials: B
authors.lastname: Huang
authors.affiliation: 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.
authors.forename: Linlin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, China; Laboratory for Marine Fisheries and Aquaculture, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong 266071, China; National & Local Joint Engineering Laboratory of Ecological Mariculture, Qingdao, Shandong 266071, China.
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.affiliation: 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. Electronic address: gfzhang@qdio.ac.cn.
authors.forename: Guofan
authors.initials: G
authors.lastname: Zhang
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D049896:Crassostrea / Q000276:immunology*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006434:Hemocytes / Q000276:immunology*; D006564:Herpesviridae / Q000276:immunology*; D006566:Herpesviridae Infections / Q000276:immunology*; D006801:Humans; D007113:Immunity, Innate; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010802:Phylogeny; D011070:Poly I-C / Q000276:immunology; D011485:Protein Binding; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D014735:Vibrio Infections / Q000276:immunology*
chemical_list: D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; C507773:IRAK4 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases; D011070:Poly I-C
keywords: Crassostrea gigas; IRAK4; MyD88; NF-κB; TLR