A Caenorhabditis elegans Glycolipid-binding Galectin Functions in Host Defense against Bacterial Infection
A Caenorhabditis elegans Glycolipid-binding Galectin Functions in Host Defense against Bacterial Infection
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DOI：
10.1074/jbc.m109.038257
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发表时间：
2009-09-25
影响因子：
4.8
通讯作者：
Yamashita, Katsuko
中科院分区：
文献类型：
--
作者：
Ideo, Hiroko;Fukushima, Keiko;Yamashita, Katsuko
半乳糖凝集素是β -半乳糖苷结合蛋白的一个家族，广泛存在于动物物种中，并调节多种生物现象。为了研究糖脂结合凝集素的生物学功能，我们纯化了重组秀丽隐杆线虫凝集素（LEC-1-11），并研究了其与秀丽隐杆线虫糖脂的结合。我们发现LEC-8通过碳水化合物识别与秀丽隐杆线虫的糖脂结合。据报道，产Cry5B的苏云金芽孢杆菌菌株可感染秀丽隐杆线虫，而秀丽隐杆线虫的Cry5B受体分子为糖脂类。我们发现Cry5B和LEC-8以剂量依赖的方式结合到线虫糖脂包被板上，并且添加LEC-8可以抑制Cry5B与糖脂的结合。LEC-8通常在咽肠瓣膜和肠直瓣膜中表达强烈，在肠中表达较弱。然而，当饲喂表达Cry5B的大肠杆菌时，秀丽隐杆线虫肠道中LEC-8::EGFP蛋白水平显著升高。相比之下，由Cry5B触发的LEC-8::EGFP表达在具有抗毒素的秀丽隐杆线虫突变体中降低，这些突变体涉及糖脂生物合成的基因发生突变。此外，lec -8缺陷突变体比野生型蠕虫对Cry5B更敏感。这些结果表明，糖脂结合凝集素LEC-8通过与目标糖脂分子的竞争性结合，有助于宿主防御细菌感染。
Galectins are a family of beta-galactoside-binding proteins that are widely found among animal species and that regulate diverse biological phenomena. To study the biological function of glycolipid-binding galectins, we purified recombinant Caenorhabditis elegans galectins (LEC-1-11) and studied their binding to C. elegans glycolipids. We found that LEC-8 binds to glycolipids in C. elegans through carbohydrate recognition. It has been reported that Cry5B-producing Bacillus thuringiensis strains can infect C. elegans and that the C. elegans Cry5B receptor molecules are glycolipids. We found that Cry5B and LEC-8 bound to C. elegans glycolipid-coated plates in a dose-dependent manner and that Cry5B binding to glycolipids was inhibited by the addition of LEC-8. LEC-8 is usually expressed strongly in the pharyngeal-intestinal valve and intestinal-rectal valve and is expressed weakly in intestine. However, when C. elegans were fed Escherichia coli expressing Cry5B, intestinal LEC-8::EGFP protein levels increased markedly. In contrast, LEC-8::EGFP expression triggered by Cry5B was reduced in toxin-resistant C. elegans mutants, which had mutations in genes involved in biosynthesis of glycolipids. Moreover, the LEC-8-deficient mutant was more susceptible to Cry5B than wild-type worms. These results suggest that the glycolipid-binding lectin LEC-8 contributes to host defense against bacterial infection by competitive binding to target glycolipid molecules.