Kammanadiminti Srinivas J, Mann Barbara J, Dutil Lisa, Chadee Kris
Institute of Parasitology of McGill University Macdonald Campus,Ste. Anne de Bellevue, Quebec, Canada.
FASEB J. 2004 Jan;18(1):155-7. doi: 10.1096/fj.03-0578fje. Epub 2003 Nov 20.
The Gal/GalNAc lectin (Gal-lectin) of Entamoeba histolytica is a surface molecule involved in parasite adherence to host cells and is the most promising subunit vaccine candidate against amoebiasis. As macrophages are the major effector cells in host defense against amoebas, we studied the molecular mechanisms by which Gal-lectin activates macrophage. Microarray analysis showed that Gal-lectin up-regulated mRNAs of several cytokines and receptor genes involved in proinflammatory responses. The mechanism whereby the Gal-lectin regulates Toll-like receptor 2 (TLR-2) expression in macrophages was studied. Native Gal-lectin increased TLR-2 mRNA expression in a dose- and time-dependent fashion; peak response occurred with 1 microg/ml after 2 h stimulation. By immunoflourescence, enhanced surface expression of TLR-2 was observed after 12 h. With the use of nonoverlapping anti-Gal-lectin monoclonal antibodies that map to the carbohydrate recognition domain, amino acid 596-1082 was identified as the TLR-2 stimulating region. The Gal-lectin increased TLR-2 gene transcription, and the half-life of the mRNA transcripts was 1.4 h. Inhibition of nuclear factor (NF)-kappaB suppressed TLR-2 mRNA induction by the Gal-lectin. Moreover, cells pretreated with an inhibitor of p38 kinase (SB 208530) inhibited Gal-lectin induced TLR-2 mRNA expression by 40%. We conclude that the Gal-lectin activates NF-kappaB and MAP kinase-signaling pathways in macrophages culminating in the induction of several genes including TLR-2 and hypothesize that this could have a significant impact on macrophage activation and contribute to amoebic pathogenesis.
溶组织内阿米巴的半乳糖/ N - 乙酰半乳糖胺凝集素（Gal-凝集素）是一种参与寄生虫黏附宿主细胞的表面分子，是抗阿米巴病最有前景的亚单位疫苗候选物。由于巨噬细胞是宿主抵御阿米巴的主要效应细胞，我们研究了Gal-凝集素激活巨噬细胞的分子机制。基因芯片分析表明，Gal-凝集素上调了几种参与促炎反应的细胞因子和受体基因的mRNA。研究了Gal-凝集素调节巨噬细胞中Toll样受体2（TLR-2）表达的机制。天然Gal-凝集素以剂量和时间依赖性方式增加TLR-2 mRNA表达；刺激2小时后，1微克/毫升时出现峰值反应。通过免疫荧光法，12小时后观察到TLR-2的表面表达增强。使用定位到碳水化合物识别结构域的非重叠抗Gal-凝集素单克隆抗体，确定氨基酸596 - 1082为TLR-2刺激区域。Gal-凝集素增加了TLR-2基因转录，mRNA转录本的半衰期为1.4小时。核因子（NF）-κB的抑制抑制了Gal-凝集素对TLR-2 mRNA的诱导。此外，用p38激酶抑制剂（SB 208530）预处理的细胞抑制了Gal-凝集素诱导的TLR-2 mRNA表达的40%。我们得出结论，Gal-凝集素激活巨噬细胞中的NF-κB和丝裂原活化蛋白激酶信号通路，最终诱导包括TLR-2在内的几种基因，并推测这可能对巨噬细胞激活有重大影响，并有助于阿米巴发病机制。
