As a key molecule in innate immune signalling pathway, interleukin (IL)-1 receptor-associated kinase 1 (IRAK1) mediates downstream signalling cascades in immune response. In the present study, an IRAK1 orthologue was characterized from rainbow trout (Oncorhynchus mykiss), with a 2115 bp open reading frame (ORF), encoding a protein of 704 amino acids (aa). Multiple alignments showed that IRAK1 contains highly conserved features among different species, with a conservative N-terminal death domain (DD) and a C-terminal conserved serine/threonine protein kinase (STKc) domain. Expression analysis indicated that IRAK1 was widely expressed in examined organs/tissues, with the highest level observed in muscle and lowest in stomach. In RTG-2 cell line, the induced expression of IRAK1 was observed following the stimulation by the fish bacterial pathogen Flavobacterium columnare. Luciferase activity assays revealed that IRAK1 induced significantly the activity of NF-κB in Human embryonic kidney 293T (HEK293T) cell line; but after co-transfected with rainbow trout IL-1 receptor-associated kinase 4 (IRAK4), the induction was significantly down-regulated when compared with the expression of IRAK1 alone. Co-immunoprecipitation (Co-IP) assays indicated that IRAK1 was associated with rainbow trout myeloid differentiation factor 88 (MyD88), IRAK4 and TNF receptor associated factor 6 (TRAF6) in transfected HEK293T cells, and may form a complex with MyD88, IRAK4 and TRAF6 during the signalling pathway.

作为先天免疫信号通路中的关键分子，白细胞介素 (IL)-1 受体相关激酶 1 (IRAK1) 在免疫反应中介导下游信号级联反应。在本研究中，IRAK1 直系同源物从虹鳟鱼（Oncorhynchus mykiss)，具有 2115 bp 的开放阅读框 (ORF)，编码 704 个氨基酸 (aa) 的蛋白质。多重比对显示 IRAK1 在不同物种中包含高度保守的特征，具有保守的 N 端死亡结构域 (DD) 和 C 端保守的丝氨酸/苏氨酸蛋白激酶 (STKc) 结构域。表达分析表明，IRAK1在检查的器官/组织中广泛表达，在肌肉中观察到最高水平，在胃中观察到最低水平。在 RTG-2 细胞系中，在鱼细菌病原体Flavobacterium columnare的刺激下观察到 IRAK1 的诱导表达. 荧光素酶活性测定显示，IRAK1 显着诱导人胚肾 293T (HEK293T) 细胞系中 NF-κB 的活性；但与虹鳟鱼 IL-1 受体相关激酶 4 (IRAK4) 共转染后，与单独 IRAK1 的表达相比，诱导显着下调。免疫共沉淀 (Co-IP) 测定表明，IRAK1 与转染的 HEK293T 细胞中的虹鳟骨髓分化因子 88 (MyD88)、IRAK4 和 TNF 受体相关因子 6 (TRAF6) 相关，并可能与 MyD88、IRAK4 和TRAF6 在信号通路中。