Identification of a new C-type lectin, TES-70, secreted by infective larvae of Toxocara canis, which binds to host ligands
Identification of a new C-type lectin, TES-70, secreted by infective larvae of Toxocara canis, which binds to host ligands
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DOI：
10.1017/s0031182099006721
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发表时间：
2000-11-01
期刊：
影响因子：
2.4
通讯作者：
Maizels, RM
中科院分区：
文献类型：
--
作者：
Loukas, A;Doedens, A;Maizels, RM
犬蛔虫的感染幼虫在发育停滞状态下在宿主的组织中存活较长时间，成功地逃避了免疫破坏。这种生存策略被认为是由犬绦虫排泄/分泌（TES）产物介导的，这些产物下调或转移免疫反应。我们纯化了TES的主要产物之一TES-70，并获得了4个色氨酸肽的氨基酸序列。通过小鼠抗tes血清对犬T. cDNA文库进行表达筛选，这些肽与cDNA中预测的蛋白相匹配。预测的蛋白（Tc-CTL-4）与犬t幼虫分泌的32 kda c型凝集素Tc-CTL-1相似，但大于Tc-CTL-1。Tc-CTL-4具有信号肽、2个富含cys结构域和c端钙依赖性c型凝集素结构域，与宿主免疫细胞受体如巨噬细胞甘露糖受体和CD23具有序列相似性。凝集素结构域在细菌中表达，纯化的重组蛋白的抗血清证实Tc-ctl-4确实编码了天然的TES-70糖蛋白。体外实验表明，TES-70以钙依赖的方式选择性结合到Madin-Darby犬肾细胞表面的配体上，被哺乳动物血清抑制，表明宿主聚糖是这种新的寄生虫凝集素的天然配体。
Infective larvae of the dog roundworm Toxocara canis survive in the tissues of their hosts for extended periods in a state of developmental arrest, successfully evading immune destruction. This survival strategy is thought to be mediated by T. canis excretory/secretory (TES) products which downregulate or divert the immune response. We purified one of the major TES products, TES-70 and gained amino acid sequence from 4 tryptic peptides. These peptides were matched to a predicted protein from a cDNA that was isolated by expression screening a T. canis cDNA library with mouse anti-TES serum. The predicted protein (Tc-CTL-4) is similar to, but larger than, Tc-CTL-1, a 32-kDa C-type lectin secreted by T. canis larvae. Tc-CTL-4 has a signal peptide, 2 Cys-rich domains and a C-terminal calcium-dependent C-type lectin domain that shares sequence similarity with host immune cell receptors such as macrophage mannose receptor and CD23. The lectin domain was expressed in bacteria and antiserum to the purified recombinant protein was used to confirm that Tc-ctl-4 did encode the native TES-70 glycoprotein. TES-70 selectively bound to ligands on the surface of Madin-Darby Canine Kidney cells in vitro in a calcium-dependent manner, inhibitable by mammalian serum, indicating that a host glycan is the native ligand for this new parasite lectin.