Qu Yifan, Gao Yan, Cui Jie, Zhang Haikun, Liu Fengchen, Lin Xiaoxue, Chu Zhongyi, Liu Yaqiong, Han Yijing, Huang Baoyu, Wang Xiaotong
School of Fisheries, Ludong University, Yantai, 264025, China.
Yantai Marine Economic Research Institute, Yantai, 264003, China.
Fish Shellfish Immunol. 2025 Oct;165:110478. doi: 10.1016/j.fsi.2025.110478. Epub 2025 Jun 3.
The large-scale death of cultured sea urchins due to pathogenic infections has profoundly affected the aquaculture sector. However, the exact details of the innate immune mechanisms in these organisms are unclear and associated research remains limited. The transcription factor nuclear factor-kappa B (NF-κB) plays a key role in the immune process of animals, thereby significantly influencing cellular regulation, development, and diverse biological functions. The inhibitor of NF-κB (IκB) protein interacts directly with the transcription factor to suppress its activity. However, this regulatory process has not been fully explored in sea urchins. In this study, a newly identified IκB gene (designated SiIκB) from the sea urchin Strongylocentrotus intermedius was extensively characterized. SiIκB comprises a 1140 bp open reading frame, producing a 379-amino-acid protein that contains six conserved ankyrin repeats. Phylogenetic analysis indicated that SiIκB grouped with IκB proteins from other echinoderms. The expression of SiIκB mRNA in various tissues was assessed using the quantitative real-time polymerase chain reaction, identifying the highest expression levels in the intestine and coelomocytes. Moreover, the SiIκB protein was located primarily in the cytoplasm of transfected eukaryotic cells. Lipopolysaccharide and polyinosinic: polycytidylic acid stimulation triggered a substantial increase in SiIκB gene expression, which showed a pattern of initial suppression followed by upregulation. The interaction between SiIκB and SiRel, part of the sea urchin NF-κB family, was verified through co-immunoprecipitation experiments. Furthermore, dual-luciferase reporter assays showed that SiIκB suppressed several SiRel-activated reporter genes (AP-1, IFN-α/γ, and IL-6) in a dose-dependent manner. These findings indicate that SiIκB is essential for regulating SiRel activity, therefore facilitating sea urchin innate immunity. This study advances our theoretical understanding of echinoderm immunity and provides a foundation for the development of disease-resistant sea urchins.
养殖海胆因致病性感染而大规模死亡，这对水产养殖行业产生了深远影响。然而，这些生物体内先天免疫机制的确切细节尚不清楚，相关研究仍然有限。转录因子核因子-κB（NF-κB）在动物免疫过程中起关键作用，从而显著影响细胞调节、发育和多种生物学功能。NF-κB抑制剂（IκB）蛋白直接与转录因子相互作用以抑制其活性。然而，这一调节过程在海胆中尚未得到充分研究。在本研究中，对新鉴定出的中间球海胆IκB基因（命名为SiIκB）进行了广泛表征。SiIκB包含一个1140 bp的开放阅读框，产生一种379个氨基酸的蛋白质，该蛋白质含有六个保守的锚蛋白重复序列。系统发育分析表明，SiIκB与其他棘皮动物的IκB蛋白归为一类。使用定量实时聚合酶链反应评估SiIκB mRNA在各种组织中的表达，结果表明在肠和体腔细胞中的表达水平最高。此外，SiIκB蛋白主要位于转染真核细胞的细胞质中。脂多糖和聚肌苷酸：聚胞苷酸刺激引发SiIκB基因表达大幅增加，呈现出先抑制后上调的模式。通过免疫共沉淀实验验证了SiIκB与海胆NF-κB家族成员SiRel之间的相互作用。此外，双荧光素酶报告基因检测表明，SiIκB以剂量依赖性方式抑制多个SiRel激活的报告基因（AP-1、IFN-α/γ和IL-6）。这些发现表明，SiIκB对于调节SiRel活性至关重要，从而促进海胆的先天免疫。本研究推进了我们对棘皮动物免疫的理论认识，并为培育抗病海胆奠定了基础。
