College of Life Science, Henan Normal University, Xinxiang, Henan, 453007, China; East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, 200090, China.
College of Life Science, Henan Normal University, Xinxiang, Henan, 453007, China.
Fish Shellfish Immunol. 2018 Nov;82:258-266. doi: 10.1016/j.fsi.2018.08.021. Epub 2018 Aug 9.
Mannose receptor (MR), a member of pattern-recognition receptors (PRRs), is the first MR family member to be discovered that plays a critical role in immunity. The function of MRs has been reported in mammals and teleosts while none in invertebrates. In the present study, we identified a MR-like gene (designated as PcMR) from red swamp crayfish, Procambarus clarkii. The PcMR cDNA is 6848 bp long with a 6288 bp open reading frame that encodes a polypeptide with 2095 amino acid residues. PcMR transcripts were mainly detected in hepatopancreas and hemocytes, and upregulated by Vibrio anguillarum challenge. The PcMR protein contained 14 C-type lectin domains (CTLDs) and they were divided into four fragments (CTLD 1-3, CTLD 4-6, CTLD 7-10, CTLD 11-14). The four recombinant proteins encoded by the four fragments were all expressed and purified. Microorganism-binding and sugar-binding assay showed that CTLD 1-3, CTLD 4-6, CTLD 7-10, CTLD 11-14 could bind to a variety of bacteria, as well as glycoconjugates on the bacterial surface. Moreover, they agglutinated bacteria in a calcium-dependent manner. Bacteria clearance experiment manifested that the mixed proteins facilitated the clearance of injected bacteria in crayfish. PcMR silencing by siRNA interference impaired the bacterial clearance ability. These results suggest PcMR is involved in the antibacterial defense of crayfish, and this study will help us better understand the functions of invertebrate MRs.
甘露糖受体（MR）是模式识别受体（PRRs）的成员之一，是第一个被发现的在免疫中起关键作用的 MR 家族成员。MR 的功能已在哺乳动物和硬骨鱼中得到报道，而在无脊椎动物中尚未报道。本研究从克氏原螯虾（Procambarus clarkii）中鉴定出一种类似 MR 的基因（命名为 PcMR）。PcMR cDNA 长 6848bp，开放阅读框长 6288bp，编码一个含有 2095 个氨基酸残基的多肽。PcMR 转录本主要在肝胰腺和血细胞中检测到，并在鳗弧菌刺激下上调。PcMR 蛋白含有 14 个 C 型凝集素结构域（CTLDs），分为 4 个片段（CTLD 1-3、CTLD 4-6、CTLD 7-10、CTLD 11-14）。由这 4 个片段编码的 4 个重组蛋白均被表达和纯化。微生物结合和糖结合试验表明，CTLD 1-3、CTLD 4-6、CTLD 7-10、CTLD 11-14 可以与多种细菌以及细菌表面的糖缀合物结合。此外，它们以钙离子依赖的方式凝集细菌。细菌清除实验表明，混合蛋白促进了螯虾体内注射细菌的清除。通过 siRNA 干扰沉默 PcMR 会损害细菌清除能力。这些结果表明 PcMR 参与了螯虾的抗菌防御，本研究将有助于我们更好地理解无脊椎动物 MR 的功能。
