Abstract：
The transforming growth factor beta-activated kinase 1 (TAK1)/c-Jun N-terminal kinase (JNK) axis is an essential MAPK upstream mediator and regulates immune signaling pathways. However, whether the TAK1/JNK axis harnesses the strength in regulation of signal transduction in early vertebrate adaptive immunity is unclear. In this study, by modeling on Nile tilapia (Oreochromis niloticus), we investigated the potential regulatory function of TAK1/JNK axis on lymphocyte-mediated adaptive immune response. Both OnTAK1 and OnJNK exhibited highly conserved sequences and structures relative to their counterparts in other vertebrates. Their mRNA was widely expressed in the immune-associated tissues, while phosphorylation levels in splenic lymphocytes were significantly enhanced on the 4th day post-infection by Edwardsiella piscicida. In addition, OnTAK1 and OnJNK were significantly up-regulated in transcriptional level after activation of lymphocytes in vitro by phorbol 12-myristate 13-acetate plus ionomycin (P + I) or PHA, accompanied by a predominant increase in phosphorylation level. More importantly, inhibition of OnTAK1 activity by specific inhibitor NG25 led to a significant decrease in the phosphorylation level of OnJNK. Furthermore, blocking the activity of OnJNK with specific inhibitor SP600125 resulted in a marked reduction in the expression of T-cell activation markers including IFN-γ, CD122, IL-2, and CD44 during PHA-induced T-cell activation. In summary, these findings indicated that the conserved TAK1/JNK axis in Nile tilapia was involved in adaptive immune responses by regulating the activation of lymphocytes. This study enriched the current knowledge of adaptive immunity in teleost and provided a new perspective for understanding the regulatory mechanism of fish immunity.
摘要：
转化生长因子β激活激酶1（TAK1）/c-JunN末端激酶（JNK）轴是必需的MAPK上游介质，并调节免疫信号通路。然而,目前尚不清楚TAK1/JNK轴是否在早期脊椎动物适应性免疫中发挥调节信号转导的强度。在这项研究中,通过对尼罗罗非鱼（Oreochromisniloticus）建模，我们研究了TAK1/JNK轴对淋巴细胞介导的适应性免疫应答的潜在调节功能.相对于其他脊椎动物中的对应物，OnTAK1和OnJNK均表现出高度保守的序列和结构。它们的mRNA在免疫相关组织中广泛表达，而脾淋巴细胞的磷酸化水平在感染后第4天显着增强。此外,在佛波醇12-肉豆蔻酸酯13-乙酸酯加离子霉素（PI）或PHA体外激活淋巴细胞后，OnTAK1和OnJNK的转录水平显着上调，伴随着磷酸化水平的显著增加。更重要的是,特异性抑制剂NG25对OnTAK1活性的抑制导致OnJNK磷酸化水平显著降低。此外，用特异性抑制剂SP600125阻断OnJNK的活性导致T细胞活化标志物（包括IFN-γ）的表达显着降低，PHA诱导的T细胞活化期间的CD122、IL-2和CD44。总之,这些发现表明，尼罗罗非鱼中保守的TAK1/JNK轴通过调节淋巴细胞的激活而参与适应性免疫反应。本研究丰富了目前对硬骨鱼适应性免疫的认识,为理解鱼类免疫调节机制提供了新的视角。
