Xiong Xunhao, Feng Qiaoli, Chen Lei, Xie Liping, Zhang Rongqing
Institute of Marine Biotechnology, Department of Biological Science and Biotechnology, Tsinghua University, Beijing, 100084, China.
Dev Comp Immunol. 2008;32(1):15-25. doi: 10.1016/j.dci.2007.03.013. Epub 2007 Apr 26.
IkappaB kinase (IKK) play central roles in cell signaling by regulating nuclear factor-kappaB (NF-kappaB) activation, which is involved in inflammatory response, proliferation, development and bone homeostasis. We report here for the first time that an IKK homologue was cloned and functionally characterized in pearl oyster, Pinctada fucata. The full-length cDNA consists of 2546bp with an ORF encoding a 737 amino acids protein. The putative pearl oyster IKK protein (Pf-IKK) possesses the characteristic organization of the mammalian IKK proteins, namely an amino-terminal kinase domain followed by a leucine zipper region and a carboxylterminal helix-loop-helix motif. Real-time PCR (RT-PCR) analysis indicated that Pf-IKK was ubiquitously expressed in pearl oyster. We also found that lipopolysaccharides (LPS) transiently stimulates IkappaBalpha degradation, but not expression levels of Pf-IKK. When transfected into NIH3T3 cells, Pf-IKK activated the expression of NF-kappaB-controlled reporter gene and induced NF-kappaB translocation, whereas the activation was greatly deduced by pyrrolidine dithiocarbamate (PDTC). We also found that overexpression of Pf-IKK increased the alkaline phosphatase (ALP) activity significantly. Based on the results and the homology to the vertebrate NF-kappaB cascade, these studies help to highlight a potentially important regulatory pathway to the study of the related functions in mollusks.
IκB激酶（IKK）通过调节核因子-κB（NF-κB）的激活在细胞信号传导中发挥核心作用，NF-κB参与炎症反应、增殖、发育和骨稳态。我们在此首次报道在珍珠贝（Pinctada fucata）中克隆并鉴定了一种IKK同源物的功能。其全长cDNA由2546个碱基对组成，开放阅读框编码一个737个氨基酸的蛋白质。推测的珍珠贝IKK蛋白（Pf-IKK）具有哺乳动物IKK蛋白的典型结构，即一个氨基末端激酶结构域，后面跟着一个亮氨酸拉链区域和一个羧基末端螺旋-环-螺旋基序。实时PCR（RT-PCR）分析表明Pf-IKK在珍珠贝中广泛表达。我们还发现脂多糖（LPS）可短暂刺激IκBα降解，但不影响Pf-IKK的表达水平。当转染到NIH3T3细胞中时，Pf-IKK激活了NF-κB控制的报告基因的表达并诱导NF-κB易位，而吡咯烷二硫代氨基甲酸盐（PDTC）可大大降低这种激活作用。我们还发现Pf-IKK的过表达显著增加了碱性磷酸酶（ALP）的活性。基于这些结果以及与脊椎动物NF-κB级联的同源性，这些研究有助于突出一条潜在的重要调控途径，以用于研究软体动物中的相关功能。
