A Caenorhabditis elegans Glycolipid-binding Galectin Functions in Host Defense against Bacterial Infection

• DOI: 10.1074/jbc.m109.038257
• Publication Date: 2009-07-28T01:09:41Z
• Authors: Hiroko Ideo; Keiko Fukushima; Keiko Gengyo-Ando; Shohei Mitani; Katsufumi Dejima; Kazuya Nomura; Katsuko Yamashita
• Keywords: 0301 basic medicine; Bacillus thuringiensis Toxins; Galectins; Green Fluorescent Proteins; Bacillus thuringiensis; Enzyme-Linked Immunosorbent Assay; Recombinant Proteins; 3. Good health; Endotoxins; Hemolysin Proteins; 03 medical and health sciences; Bacterial Proteins; Host-Pathogen Interactions; Mutation; Animals; Protein Isoforms; Glycolipids; Intestinal Mucosa; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Chromatography, High Pressure Liquid; Protein Binding

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.