作为白细胞介素-20(IL-20)亚家族的炎性细胞因子,IL-20在免疫防御中具有多种功能,炎症性疾病,组织再生,癌症,和新陈代谢。尽管已经阐明了哺乳动物IL-20的特征和功能,鱼IL-20的含量尚不清楚。在这项研究中,克隆了来自蛇头Channaargus(shIL-20)的IL-20基因并进行了功能表征。类似于其他物种的IL-20同源物,shIL-20在编码区具有5个外显子/4个内含子结构。shIL-20的开放阅读框由528个碱基对组成,编码175个氨基酸(aa),包括信号肽(aa1-24)和成熟肽(aa25-175)。成熟的shIL-20蛋白有6个保守的半胱氨酸残基,出现在所有被分析物种的IL-20蛋白中,和仅在几种硬骨鱼的IL-20蛋白中发现的额外半胱氨酸残基(Cys-82)。shIL-20的模型三级结构与智人IL-20的相似。shIL-20在所有分析的组织中组成型表达,并且其转录在体内由舒伯氏气单胞菌和诺卡氏菌在脾脏和头肾中诱导,在头肾白细胞(HKL)中由脂磷壁酸诱导,脂多糖,和聚肌苷酸-聚胞苷酸的体外研究。重组shIL-20蛋白诱导肿瘤坏死因子α1(TNF-α1)转录,TNF-α2,IL-1β,和内源性shIL-20,并促进HKLs的增殖。总之,这些发现表明,shIL-20参与对细菌入侵的免疫反应,并促进白细胞增殖,为鱼类IL-20在病原体入侵过程中的功能提供了新的见解。
As an inflammatory cytokine of the interleukin-20 (IL-20) subfamily, IL-20 has various functions in immune defenses, inflammatory diseases, tissue regeneration, cancer, and metabolism. Although the characteristics and functions of mammalian IL-20 have been clarified, those of fish IL-20 remain unclear. In this study, the IL-20 gene from the snakehead Channa argus (shIL-20) was cloned and functionally characterized. Similar to the IL-20 homologues of other species, the shIL-20 has a five exon/four intron structure in the coding region. The open reading frame of shIL-20 consists of 528 base pairs and encodes 175 amino acids (aa), including a signal peptide (aa 1-24) and a mature peptide (aa 25-175). The mature shIL-20 protein has six conserved cysteine residues, which occur in the IL-20 proteins of all species analyzed, and an additional cysteine residue (Cys-82) found only in the IL-20 proteins of several teleosts. The modeled tertiary structure of shIL-20 is similar with that of Homo sapiens IL-20. The shIL-20 was expressed constitutively in all the tissues analyzed, and its transcription was induced in the spleen and head kidney by Aeromonas schubertii and Nocardia seriolae in vivo and in head kidney leukocytes (HKLs) by lipoteichoic acid, lipopolysaccharide, and polyinosinic-polycytidylic acid in vitro. The recombinant shIL-20 protein induced the transcription of tumor necrosis factor α1 (TNF-α1), TNF-α2, IL-1β, and endogenous shIL-20, and promoted the proliferation of HKLs. In conclusion, these findings demonstrate that shIL-20 participates in the immune response to bacterial invasion and promotes leukocyte proliferation, offering new insights into the functions of fish IL-20 during pathogen invasion.