title: Identification of IRAK-4 in grouper (Epinephelus coioides) that impairs MyD88-dependent NF-κB activation.
abstract: Interleukin 1 (IL-1) receptor-associated kinase (IRAK) family members are crucial signal transducer in the Toll-like receptor/IL-1R signal pathway, which mediates downstream signal cascades involved in the innate and adaptive immune responses. In this study, we identified an IRAK-4 protein (EcIRAK-4) in the orange-spotted grouper (Epinephelus coioides), with an N-terminal death domain, a proST domain, and a central kinase domain, similar to that of other fishes and mammals. A sequence alignment and phylogenic analysis demonstrated that full-length EcIRAK-4 shares a high degree of sequence identity with those of other fishes, especially the roughskin sculpin, and their death domains and kinase domains share greater identity than their proST domains. A conservation analysis indicated that most of the functional sites in mammalian IRAK-4 are conserved in IRAK-4 of the grouper and other fishes, with the exception of the sites of interaction with IRAK-2 and one autophosphorylation site within the activation loop. EcIRAK-4 is broadly expressed in all the tissues examined, with highest expression in the head kidney and liver. After infection with Cryptocaryon irritans, EcIRAK-4 expression was significantly upregulated, especially in the skin, which suggests that this molecule is involved in the host's defense against parasitic infection. Surprisingly, after cotransfection with grouper MyD88, EcIRAK-4 significantly impaired the NF-κB activity induced by MyD88. EcIRAK-4 was uniformly distributed throughout the cytoplasm in HeLa cells. These findings suggest that although IRAK-4 is evolutionarily conserved between fish and mammals, its signal transduction function is markedly different.
authors.affiliation: Key Laboratory of Aquatic Product Safety (Sun Yat-Sen University), Ministry of Education/ State Key Laboratory of Biocontrol, The School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, Guangdong Province, PR China.
authors.forename: Yan-Wei
authors.initials: YW
authors.lastname: Li
authors.affiliation: Key Laboratory of Aquatic Product Safety (Sun Yat-Sen University), Ministry of Education/ State Key Laboratory of Biocontrol, The School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, Guangdong Province, PR China.
authors.forename: Xu-Bing
authors.initials: XB
authors.lastname: Mo
authors.affiliation: College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong Province, PR China.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Aquatic Product Safety (Sun Yat-Sen University), Ministry of Education/ State Key Laboratory of Biocontrol, The School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, Guangdong Province, PR China.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.affiliation: College of Animal Science, South China Agricultural University, Guangzhou 510642, Guangdong Province, PR China.
authors.forename: Xue-Ming
authors.initials: XM
authors.lastname: Dan
authors.affiliation: School of Bioscience and Biotechnology, South China University of Technology, Guangzhou 510006, Guangdong Province, PR China.
authors.forename: Xiao-Chun
authors.initials: XC
authors.lastname: Luo
authors.affiliation: Key Laboratory of Aquatic Product Safety (Sun Yat-Sen University), Ministry of Education/ State Key Laboratory of Biocontrol, The School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, Guangdong Province, PR China. Electronic address: lianxing@mail.sysu.edu.cn.
authors.forename: An-Xing
authors.initials: AX
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016770:Ciliophora Infections / Q000201:enzymology / Q000276:immunology / Q000662:veterinary*; D005393:Fish Diseases / Q000201:enzymology* / Q000276:immunology / Q000469:parasitology; D029941:Fish Proteins / Q000502:physiology*; D015870:Gene Expression; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases / Q000502:physiology*; D008969:Molecular Sequence Data; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009928:Organ Specificity; D010473:Perciformes / Q000276:immunology / Q000378:metabolism* / Q000469:parasitology; D010802:Phylogeny; D015398:Signal Transduction; D015533:Transcriptional Activation / Q000276:immunology
chemical_list: D029941:Fish Proteins; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D053592:Interleukin-1 Receptor-Associated Kinases
keywords: Cryptocaryon irritans; Epinephelus coioides; IRAK-4; Overexpression