The inhibitory kappa B kinase (IKK) is a critical regulator for the nuclear factor-κB (NF-κB) pathway. In this study, an IKKβ named as HLIKKβ was identified from the sea cucumber Holothuria leucospilota. The full-length cDNA of HLIKKβ is 4246 bp in size, containing a 132 bp 5′-untranslated region (UTR), a 1783 bp 3′-UTR and a 2331 bp open reading frame (ORF) encoding a protein of 776 amino acids with a deduced molecular weight of 89.66 kDa. HLIKKβ contains a kinase domain (KD) at its N-terminal, a leucine zipper (LZ) and a helix-loop-helix (HLH) motif at its C-terminal. In the KD, a conserved active loop (SXXXS) were identified. The results of luciferase reporter assay and ELISA assay showed that over-expressed HLIKKβ in HEK293T cells could activate the nuclear factor-κB (NF-κB) and induce the secretion of proinflammatory cytokines TNF-α and IL-1β. When HLIKKβ was silenced by siRNA, the apoptosis rate of sea cucumber coelomocytes was increased significantly, indicating the anti-apoptotic function of HLIKKβ. Moreover, the up-regulation of HLIKKβ mRNA was observed in the sea cucumber coelomocytes after polyriboinosinic polyribocytidylic acid [Poly (I:C)] or lipopolysaccharides (LPS) challenge, suggesting that the HLIKKβ might play important roles in the innate immune defense of sea cucumber against the viral and bacterial infections.

抑制性κB激酶（IKK）是核因子-κB（NF-κB）途径的关键调节剂。在这项研究中，从海参Holothuria leucospilota中鉴定出一个名为HLIKKβ的IKKβ 。HLIKKβ的全长cDNA大小为4246 bp，包含132 bp的5'-非翻译区（UTR），1783 bp的3'-UTR和2331 bp的开放阅读框（ORF），编码776个氨基酸的蛋白质，推导的分子量为89.66 kDa。HLIKKβ在其N端包含一个激酶结构域（KD），在其C端包含一个亮氨酸拉链（LZ）和一个螺旋-环-螺旋（HLH）基序。在KD中，确定了保守的活动环（SXXXS）。荧光素酶报告基因测定和ELISA测定的结果表明，HEK293T细胞中过表达的HLIKKβ可激活核因子-κB（NF-κB）并诱导促炎细胞因子TNF-α和IL-1β的分泌。siRNA沉默HLIKKβ后，海参系内皮细胞的凋亡率显着增加，提示HLIKKβ具有抗凋亡作用。此外，HLIKKβ的上调 在多核糖核酸聚核糖核酸[Poly（I：C）]或脂多糖（LPS）攻击后，在海参脐带内皮细胞中观察到mRNA，这表明HLIKKβ可能在海参对病毒和细菌感染的固有免疫防御中发挥重要作用。