Galectin-3 binds lactosaminylated lipooligosaccharides from Neisseria gonorrhoeae and is selectively expressed by mucosal epithelial cells that are infected.
Galectins are a family of beta-galactoside binding proteins that have been proposed as host receptors for bacteria because beta-galactoside carbohydrates are common in bacterial membrane glycolipid lipooligosaccharides (LOS) and lipopolysaccharides. We investigated the interaction of galectin-3 with gonococcal LOS that make lactosyl (Lc2 or Lac), paraglobosyl (nLc4; LNnT; lacto-N-neotetraose), gangliosyl (IV3GalNAcnLc4), and neolactohexaosyl (nLc6, lactonorhexaosyl) oligosaccharides. All but gangliosyl LOS terminate in beta-galactoside. Galectin-3 had the highest affinity for the nLc6 LOS, which is made by a strain that is highly infectious for the male urethra, but also bound nLc4 LOS and to a Lac LOS. The lacto-N-neotetraose tetrasaccharide was a more potent inhibitor of galectin-3 binding to LOS than either lactose or N-acetyllactosamine. The relative affinity of galectin-3 for gonococci mirrored its affinity for purified LOS. Western blot analysis revealed expression of galectin-3 by human endometrial adenocarcinoma and prostatic epithelial cells that can be invaded by gonococci. Immunohistochemistry of human fallopian tube epithelium showed localized expression of galectin-3 by non-ciliated cells, the specific cell gonococci invade in this tissue. We conclude that because of its location and affinity for gonococcal LOS galectin-3 could play a role in gonococcal infection.
D002240:Carbohydrate Sequence; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005187:Fallopian Tubes / Q000166:cytology / Q000378:metabolism*; D005260:Female; D037502:Galectin 3 / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007797:Laminin / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009092:Mucous Membrane / Q000166:cytology / Q000378:metabolism*; D009344:Neisseria gonorrhoeae / Q000235:genetics / Q000378:metabolism*; D009924:Organ Culture Techniques; D011485:Protein Binding; D012044:Regression Analysis; D014407:Tumor Cells, Cultured
D037502:Galectin 3; D007797:Laminin; D008070:Lipopolysaccharides; C023023:lipid-linked oligosaccharides