Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan.
College of Aquaculture and Fisheries, Can Tho University, Can Tho, Vietnam.
Front Immunol. 2022 Jul 19;13:940877. doi: 10.3389/fimmu.2022.940877. eCollection 2022.
Nile tilapia () is one of the most important food fish in the world. However, the farming industry has encountered significant challenges, such as pathogen infections. Toll-like receptors (TLRs) play an essential role in the initiation of the innate immune system against pathogens. Sterile alpha and TIR motif-containing protein 1 (SARM1) is one of the most evolutionarily conserved TLR adaptors, and its orthologs are present in various species from worms to humans. SARM1 plays an important role in negatively regulating TIR domain-containing adaptor proteins inducing IFNβ (TRIF)-dependent TLR signaling in mammals, but its immune function remains poorly understood in fish. In this study, SARM1 () was cloned and its evolutionary status was verified using bioinformatic analyses. mRNA expression of was found at a higher level in the trunk kidney and muscle in healthy fish. The examination of its subcellular location showed that the OnSARM1 was detected only in the cytoplasm of THK cells, and colocalized with OnMyD88, OnTRIF and OnTRIF in small speckle-like condensed granules. The transcript levels of , , , and downstream effectors, including ()-, , and type I (), were regulated conversely to the expression of in the head kidney from and infected fish. Moreover, the treatment of THK cells with lysates from and enhanced the activity of the NF-κB promoter, but the effects were inhibited in the OnSARM1 overexpressed THK cells. Overexpression of OnSARM1 alone did not activate the NF-κB-luciferase reporter, but it suppressed OnMyD88- and OnTIRAP-mediated NF-κB promoter activity. Additionally, OnSARM1 inhibited the mRNA expression of proinflammatory cytokines and hepcidin in lysate stimulated THK cells. Taken together, these findings suggest that OnSARM1 serves as a negative regulator by inhibiting NF-κB activity, thereby influencing the transcript level of proinflammatory cytokines and antimicrobial peptides in the antibacterial responses.
尼罗罗非鱼（）是世界上最重要的食用鱼类之一。然而，水产养殖行业面临着重大挑战，例如病原体感染。Toll 样受体（TLRs）在对抗病原体的先天免疫系统启动中起着至关重要的作用。无菌α和 TIR 基序包含蛋白 1（SARM1）是最进化保守的 TLR 接头之一，其同源物存在于从蠕虫到人等各种物种中。SARM1 在负调控 TIR 结构域包含接头蛋白诱导 IFNβ（TRIF）依赖性 TLR 信号传导中在哺乳动物中起着重要作用，但在鱼类中其免疫功能仍知之甚少。在这项研究中，克隆了 SARM1（），并通过生物信息学分析验证了其进化地位。在健康鱼的 trunk kidney 和肌肉中，发现 mRNA 的表达水平更高。对其亚细胞定位的检查表明，OnSARM1 仅在 THK 细胞的细胞质中被检测到，并与 OnMyD88、OnTRIF 和 OnTRIF 在小斑点状浓缩颗粒中共定位。感染 和 后，头肾中 的转录水平与 的表达呈相反调节，下游效应物，包括 （）-、 、 和 I 型 （）。此外，来自 和 的裂解物处理 THK 细胞增强了 NF-κB 启动子的活性，但在过表达 OnSARM1 的 THK 细胞中，该作用被抑制。单独过表达 OnSARM1 本身不会激活 NF-κB-luciferase 报告基因，但它抑制了 OnMyD88 和 OnTIRAP 介导的 NF-κB 启动子活性。此外，OnSARM1 抑制了 裂解物刺激的 THK 细胞中促炎细胞因子和抗菌肽的 mRNA 表达。总之，这些发现表明，OnSARM1 作为一种负调节剂，通过抑制 NF-κB 活性，从而影响抗菌反应中促炎细胞因子和抗菌肽的转录水平。
