College of Life Science, Qingdao Agricultural University, 700 Changcheng Road, Qingdao 266109, China.
Fish Shellfish Immunol. 2011 Jun;30(6):1223-9. doi: 10.1016/j.fsi.2011.04.014. Epub 2011 Apr 27.
Cell adhesion factors are important immune components for invertebrate to immobilize, phagocytose or encapsulate invasive microorganisms and foreign particles. In this study, a new cell adhesion factor, peroxinectin (refered as Pcpxin) was isolated from hemocytes of red swamp crayfish (Procambarus clarkii). The full-length cDNA of Pcpxin was 3014 bp encoding a protein of 819 amino acid residues with a predicted molecular weight of 89.0 kDa and a calculational isoelectric point of 6.93. The putative amino acid sequence contained a peroxidase domain and a signal peptide of 21 amino acid residues, and exhibited high identity to peroxinectin from Pacifastacus leniusculus (85%), Fenneropenaeus chinensis (62%) and Scylla serrata (58%), as well as peroxidase from Camponotus floridanus (40%), Pediculus humanus corporis (39%), and Culex quinquefasciatus (38%). Quantitative real time PCR revealed that mRNA expression of Pcpxin in hemocytes could be inhibited by challenge with heat-killed Aeromonas hydrophila, suggesting that Pcpxin was involved in immune responses to A. hydrophila. RNA interference (RNAi) experiment demonstrated that silencing Pcpxin significantly reduced the survival rate of red swamp crayfishes after challenge with A. hydrophila, which indicated that Pcpxin was important for P. clarkii to survive A. hydrophila infection. Moreover, silencing Pcpxin inhibited the up-regulation of crustin1 and lysozyme expression in response to challenge with heat-killed A. hydrophila. This result suggested that Pcpxin might participate in antibacterial peptide gene expression and thereby might be involved in signal transduction pathway regulating the expression of antibacterial peptide gene.
细胞黏附因子是无脊椎动物固定、吞噬或包裹入侵微生物和外来颗粒的重要免疫成分。本研究从克氏原螯虾（Procambarus clarkii）血细胞中分离到一种新的细胞黏附因子，命名为过氧化物酶连接蛋白（peroxinectin，Pcpxin）。Pcpxin 的全长 cDNA 为 3014 bp，编码一个 819 个氨基酸残基的蛋白质，预测分子量为 89.0 kDa，理论等电点为 6.93。该蛋白含有一个过氧化物酶结构域和一个 21 个氨基酸残基的信号肽，与美洲螯龙虾（Pacifastacus leniusculus）、中国对虾（Fenneropenaeus chinensis）和锯缘青蟹（Scylla serrata）的过氧化物酶连接蛋白具有高度同源性（85%、62%和 58%），与佛罗里达切叶蚁（Camponotus floridanus）、人虱（Pediculus humanus corporis）和致倦库蚊（Culex quinquefasciatus）的过氧化物酶同源性分别为 40%、39%和 38%。定量实时 PCR 显示，Pcpxin 在血细胞中的 mRNA 表达可被热灭活的嗜水气单胞菌（Aeromonas hydrophila）抑制，表明 Pcpxin 参与了对 A. hydrophila 的免疫反应。RNA 干扰（RNAi）实验表明，沉默 Pcpxin 可显著降低克氏原螯虾在受到 A. hydrophila 攻击后的存活率，表明 Pcpxin 对 P. clarkii 抵抗 A. hydrophila 感染非常重要。此外，沉默 Pcpxin 抑制了抗菌肽基因 crustin1 和溶菌酶表达的上调。这一结果表明，Pcpxin 可能参与抗菌肽基因表达，并可能参与调节抗菌肽基因表达的信号转导通路。
