State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Fish Shellfish Immunol. 2012 Jun;32(6):1022-31. doi: 10.1016/j.fsi.2012.02.024. Epub 2012 Mar 3.
Toll-like receptor 22 (TLR22) is a fish-specific TLR which recognizes double-strand (ds) RNA and participates in the innate immune response through the Toll-IL-1R homology domain-containing adaptor protein 1 (TICAM-1). To further investigate how the innate immune system of teleosts responds to viral infections, we cloned the full-length cDNA sequence of grass carp (Ctenopharyngodon idella) TLR22 (CiTLR22). The complete cDNA sequence of CiTLR22 was 3647 bp and encodes a polypeptide of 954 amino acids. Analysis of the deduced amino acid sequence indicated that CiTLR22 has typical structural features of proteins belonging to the TLR family. These included 17 LRR domains (residues 88-634) and one C-terminal LRR domain (LRR-CT, residues 694-745) in the extracellular region, and a TIR domain (residues 801-944) in the cytoplasmic region. Comparison with homologous proteins showed that the deduced CiTLR22 has the highest sequence identity to common carp TLR22 (82.9%). Genomic DNA of CiTLR22 was obtained by long-distance (Ld) PCR and structure analysis revealed that the CiTLR22 gene is encoded by uninterrupted exons. Reverse transcriptase-PCR (RT-PCR) revealed that CiTLR22 is a non-maternal gene. It is prominently expressed in immune relevant tissues such as spleen and head kidney. Quantitative RT-PCR analysis showed that CiTLR22 transcripts were upregulated significantly in immune relevant tissues and blood following grass carp reovirus (GCRV) infection. In the whole genomic sequence, nine single nucleotide polymorphisms (SNPs) were detected. Seven of them were sited in the coding region, and the other two located in the 5' and 3' untranslated region (UTR) respectively. None of the SNPs was associated with the resistance of grass carp to GCRV. These results suggested a role for CiTLR22 in mediating immune protection against viral infection in grass carp.
Toll 样受体 22（TLR22）是一种鱼类特异性 TLR，它可以识别双链 RNA，并通过 Toll-IL-1R 同源结构域包含衔接蛋白 1（TICAM-1）参与固有免疫反应。为了进一步研究硬骨鱼类的固有免疫系统如何对病毒感染做出反应，我们克隆了草鱼（Ctenopharyngodon idella）TLR22（CiTLR22）的全长 cDNA 序列。CiTLR22 的完整 cDNA 序列长 3647bp，编码一个 954 个氨基酸的多肽。对推导的氨基酸序列分析表明，CiTLR22 具有 TLR 家族蛋白的典型结构特征。这些特征包括胞外区的 17 个 LRR 结构域（残基 88-634）和一个 C 端 LRR 结构域（LRR-CT，残基 694-745），以及胞质区的一个 TIR 结构域（残基 801-944）。与同源蛋白的比较表明，推导的 CiTLR22 与鲤鱼 TLR22 的序列同一性最高（82.9%）。通过长距离（Ld）PCR 获得了 CiTLR22 的基因组 DNA，结构分析表明 CiTLR22 基因由不连续的外显子编码。逆转录 PCR（RT-PCR）显示 CiTLR22 是一种非母源性基因。它在免疫相关组织（如脾脏和头肾）中表达明显。定量 RT-PCR 分析显示，在草鱼呼肠孤病毒（GCRV）感染后，CiTLR22 转录本在免疫相关组织和血液中显著上调。在整个基因组序列中，检测到九个单核苷酸多态性（SNP）。其中七个位于编码区，另外两个分别位于 5'和 3'非翻译区（UTR）。这些 SNP 均与草鱼对 GCRV 的抗性无关。这些结果表明 CiTLR22 在介导草鱼抗病毒感染的免疫保护中发挥作用。
