In vertebrates, TANK Binding Kinase 1 (TBK1) plays an important role in innate immunity, mainly because it can mediate production of interferon to resist the invasion of pathogens. In mammals, cell division cycle-25a (Cdc25a) is a member of the Cdc25 family of cell division cycle proteins. It is a phosphatase that plays an important role in cell cycle regulation by dephosphorylating its substrate proteins. Currently, many phosphatases are reported to play a role in innate immunity. This is because the phosphatases can shut down or reduce immune signaling pathways by down-regulating phosphorylation signals. However, there are no reports on fish Cdc25a in innate immunity. In this paper, we conducted a preliminary study on the involvement of grass carp Cdc25a in innate immunity. First, we cloned the full-length cDNA of grass carp Cdc25a (CiCdc25a), and found that it shares the highest genetic relationship with that of Anabarilius grahami through phylogenetic tree comparison. In grass carp tissues and CIK cells, the expression of CiCdc25a mRNA was up-regulated under poly (I:C) stimulation. Therefore, CiCdc25a can respond to poly (I:C). The subcellular localization results showed that CiCdc25a is distributed both in the cytoplasm and nucleus. We also found that CiCdc25a can down-regulate the expression of IFN 1 with or without poly (I:C) stimulation. In other words, the down-regulation of IFN1 by CiCdc25a is independent of poly (I:C) stimulation. Further functional studies have shown that the inhibition of IFN1 expression by CiCdc25a may be related to decrease of TBK1 activity. We also confirmed that the phosphorylation of TBK1 at Ser¹⁷² is essential for production of IFN 1. In short, CiCdc25a can interact with TBK1 and subsequently inhibits the phosphorylation of TBK1, thereby weakens TBK1 activity. These results indicated that grass carp Cdc25a down-regulates IFN 1 expression by reducing TBK1 phosphorylation.

在脊椎动物中，TANK结合激酶1（TBK1）在先天免疫中发挥着重要作用，主要是因为它可以介导干扰素的产生以抵抗病原体的入侵。在哺乳动物中，细胞分裂周期 25a (Cdc25a) 是细胞分裂周期蛋白 Cdc25 家族的成员。它是一种磷酸酶，通过使其底物蛋白去磷酸化而在细胞周期调节中起重要作用。目前，据报道许多磷酸酶在先天免疫中发挥作用。这是因为磷酸酶可以通过下调磷酸化信号来关闭或减少免疫信号通路。然而，没有关于鱼Cdc25a在先天免疫中的报道。在本文中，我们对草鱼Cdc25a在先天免疫中的参与进行了初步研究。首先，我们克隆了草鱼的全长cDNACdc25a（CiCdc25a ），通过系统发育树比较发现它与Anabarilius grahami的亲缘关系最高。在草鱼组织和 CIK 细胞中，CiCdc25a mRNA 的表达在 poly (I:C) 刺激下上调。因此，CiCdc25a可以响应聚（I：C）。亚细胞定位结果表明CiCdc25a同时分布在细胞质和细胞核中。我们还发现 CiCdc25a 可以在有或没有多聚 (I:C) 刺激的情况下下调 IFN 1 的表达。换句话说，CiCdc25a 对 IFN1 的下调与多 (I:C) 刺激无关。进一步的功能研究表明，CiCdc25a 对 IFN1 表达的抑制可能与 TBK1 活性的降低有关。我们还证实了 TBK1 在 Ser ¹⁷²的磷酸化对于产生 IFN 1 是必不可少的。简而言之，CiCdc25a 可以与 TBK1 相互作用并随后抑制 TBK1 的磷酸化，从而削弱 TBK1 的活性。这些结果表明草鱼 Cdc25a 通过减少 TBK1 磷酸化来下调 IFN 1 的表达。