Chen Da-Yong, Li Bang-Ze, Xu Wen-Bin, Zhang Yan-Mei, Li Bing-Wu, Cheng Yuan-Xin, Xiao Yi, Lin Chen-Yang, Dong Wei-Ren, Shu Miao-An
College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
Dev Comp Immunol. 2023 Feb;139:104585. doi: 10.1016/j.dci.2022.104585. Epub 2022 Nov 9.
Interleukin-1 receptor associated kinases (IRAK) is the most important downstream kinases of TLRs/IL-1R signaling pathway for signal transduction and activation of inflammatory response against pathogen infections. However, the molecular identification and function characterization of IRAK2 homologs in lower vertebrate remains obscure. In this study, three IRAK2 genes (AdIRAK2a, AdIRAKb and AdIRAK2c) and their respective transcripts were identified from the Chinese giant salamander Andrias davidianus. This is the first evidence that three different IRAK2 genes exist in an ancient amphibian species, which has never been reported in other vertebrates. The complete open reading frames (ORFs) of AdIRAK2a, AdIRAK2b and AdIRAK2c were 2112 bp, 1917 bp and 816 bp encoding deduced proteins of 703 amino acids (aa), 628 aa and 271 aa, respectively. All three AdIRAK2 proteins contained two predicted conserved functional domains, including a death domain (DD) and a serine/threonine protein kinases domain (KD). Phylogenetic analysis showed that the three AdIRAK2s clustered together with other known IRAK2 of vertebrates. The three AdIRAK2s were ubiquitously expressed in all tested tissues with a similar tissues distribution pattern. After challenge of Aeromonas hydrophila (A. hydrophila), Staphylococcus aureus (S.aureus), giant salamander iridovirus (GSIV, belonging to the genus Ranavirus in the family Iridoviridae) and polyinosinic:polycytidylic acid (poly(I:C)), the expression levels of all AdIRAK2s in blood were significantly altered, however, they exhibited distinct response patterns. Moreover, the results of over-expression and RNAi of AdIRAK2s implied the involvement of AdIRAK2s in triggering NF-κB-mediated signaling pathways and inflammatory responses. This study might provide a better understanding of the presence and immune regulation function of IRAK2 in amphibians and even in vertebrates.
白细胞介素-1受体相关激酶（IRAK）是Toll样受体（TLRs）/白细胞介素-1受体（IL-1R）信号通路中最重要的下游激酶，负责信号转导以及激活针对病原体感染的炎症反应。然而，低等脊椎动物中IRAK2同源物的分子鉴定和功能表征仍不清楚。在本研究中，从中国大鲵（Andrias davidianus）中鉴定出了三个IRAK2基因（AdIRAK2a、AdIRAKb和AdIRAK2c）及其各自的转录本。这是首次证明在一种古老的两栖动物物种中存在三种不同的IRAK2基因，其他脊椎动物中从未有过相关报道。AdIRAK2a、AdIRAK2b和AdIRAK2c的完整开放阅读框（ORF）分别为2112 bp、1917 bp和816 bp，分别编码703个氨基酸（aa）、628个aa和271个aa的推导蛋白。所有三种AdIRAK2蛋白都包含两个预测的保守功能域，包括一个死亡结构域（DD）和一个丝氨酸/苏氨酸蛋白激酶结构域（KD）。系统发育分析表明，三种AdIRAK2与脊椎动物的其他已知IRAK2聚集在一起。三种AdIRAK2在所有测试组织中均有广泛表达，且组织分布模式相似。在用嗜水气单胞菌（A. hydrophila）、金黄色葡萄球菌（S.aureus）、大鲵虹彩病毒（GSIV，属于虹彩病毒科蛙病毒属）和聚肌苷酸:聚胞苷酸（poly(I:C)）进行刺激后，血液中所有AdIRAK2的表达水平均发生了显著变化，然而，它们表现出不同的反应模式。此外，AdIRAK2的过表达和RNA干扰结果表明AdIRAK2参与触发NF-κB介导的信号通路和炎症反应。本研究可能有助于更好地理解IRAK2在两栖动物乃至脊椎动物中的存在及其免疫调节功能。
