The Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Rd., Qingdao 266071, China.
Fish Shellfish Immunol. 2010 Apr;28(4):687-94. doi: 10.1016/j.fsi.2010.01.005. Epub 2010 Jan 14.
IkappaB is an important member of NF-kappaB pathway in the innate immune system. In the present study, the full-length cDNA sequence encoding IkappaB protein (designated AiIkappaB) was isolated from bay scallop Argopecten irradians. The complete sequence of AiIkappaB cDNA containing a 5' untranslated region (UTR) of 237 bp, a 3' UTR of 1023 bp with a poly (A) tail, and an open reading frame (ORF) of 1086 bp encoding a polypeptide of 361 amino acids with the predicted molecular weight of 39.9 kDa and theoretical isoelectric point of 4.7. Six ankyrin repeats which were necessary for specific binding to NF-kappaB and two potential phosphorylation sites responsible for IkappaB degradation were identified in the N-terminus of AiIkappaB. No PEST domain but a phosphorylation site motif (S(357)DSD(360)) was present at the C-terminus of AiIkappaB. Predicted three-dimensional structure of AiIkappaB shared high similarity with mammalian IkappaBalpha. Similarity and phylogenetic analysis revealed that AiIkappaB was clustered into IkappaBs from invertebrate. All these typical characteristics indicated that the AiIkappaB should be classified into IkappaB family proteins. Quantitative real-time RT-PCR was employed to assess the mRNA expression of AiIkappaB in various tissues and its temporal expression in haemocytes of scallops challenged with Listonella anguillarum. The mRNA transcript of AiIkappaB could be detected in all the examined tissues with highest expression level in hepatopancreas. Bacteria infection inhibited the transcription level of AiIkappaB. The results suggested the involvement of AiIkappaB in responses against bacterial infection and further highlighted its functional importance in the immune system of A. irradians.
IkappaB 是天然免疫系统中 NF-kappaB 途径的重要成员。在本研究中，从海湾扇贝 Argopecten irradians 中分离出编码 IkappaB 蛋白的全长 cDNA 序列（命名为 AiIkappaB）。AiIkappaB cDNA 的完整序列包含一个 237bp 的 5'非翻译区（UTR）、一个 1023bp 的 3'UTR 带有 poly(A)尾巴和一个 1086bp 的开放阅读框（ORF），编码一个 361 个氨基酸的多肽，预测分子量为 39.9kDa，理论等电点为 4.7。在 AiIkappaB 的 N 端鉴定到六个必需与 NF-kappaB 特异性结合的锚蛋白重复和两个负责 IkappaB 降解的潜在磷酸化位点。在 AiIkappaB 的 C 端没有 PEST 结构域，但存在一个磷酸化位点模体（S(357)DSD(360)）。AiIkappaB 的预测三维结构与哺乳动物 IkappaBalpha 具有高度相似性。相似性和系统发育分析表明，AiIkappaB 聚类为来自无脊椎动物的 IkappaBs。所有这些典型特征表明，AiIkappaB 应归类为 IkappaB 家族蛋白。定量实时 RT-PCR 用于评估 AiIkappaB 在各种组织中的 mRNA 表达及其在扇贝血淋巴细胞中对鳗弧菌刺激的时间表达。AiIkappaB 的 mRNA 转录本可在所有检测组织中检测到，在肝胰腺中表达水平最高。细菌感染抑制了 AiIkappaB 的转录水平。结果表明 AiIkappaB 参与了对细菌感染的反应，并进一步强调了其在 A. irradians 免疫系统中的功能重要性。
