Identification of Entamoeba histolytica thiol-specific antioxidant as a GalNAc lectin-associated protein

Mol Biochem Parasitol. 2003 Apr 3;127(2):113-20. doi: 10.1016/s0166-6851(02)00326-2.


Entamoeba histolytica is a human intestinal parasite that causes amebic dysentery. A cell surface amebic adhesin, the galactose and N-acetyl-D-galactosamine inhibitable (GalNAc) lectin mediates amebic adherence to and contact-dependent killing of host cells. Previous work has suggested that the GalNAc lectin transduces signals via protein interactions with its short cytoplasmic domain. We used a yeast two-hybrid system to screen an E. histolytica cDNA library for proteins that interact with the GalNAc lectin cytoplasmic domain. One isolate was the E. histolytica thiol-specific antioxidant (TSA). TSA is an enzyme that detoxifies hydrogen peroxide. TSA did not interact in yeast two-hybrid experiments with a mutant version of the lectin cytoplasmic domain, confirming the specificity of the lectin-TSA interaction. Furthermore, mutational analyses of the TSA isolate demonstrated that an in-frame five amino acid sequence introduced between amino acids 61-62 yielded a TSA mutant that did not interact with the lectin cytoplasmic domain upon expression in the yeast two-hybrid system. The association of TSA and GalNAc lectin was further supported by co-immunoaffinity purification. Confocal microscopy demonstrated co-localization of TSA and GalNAc lectin at sites of ameba:host cell contact. Recruitment of TSA by the GalNAc lectin suggests a novel mechanism of parasite defense against reactive oxygen intermediates generated by host peripheral mononuclear cells.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylgalactosamine / metabolism*
  • Animals
  • Caco-2 Cells
  • Entamoeba histolytica / enzymology*
  • Entamoeba histolytica / growth & development
  • Entamoeba histolytica / pathogenicity
  • Humans
  • Lectins / chemistry
  • Lectins / genetics
  • Lectins / metabolism*
  • Mutagenesis, Insertional / methods
  • Mutation
  • Neutrophils / metabolism
  • Peroxidases / genetics
  • Peroxidases / isolation & purification
  • Peroxidases / metabolism*
  • Peroxiredoxins
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / metabolism*
  • Two-Hybrid System Techniques


  • Igl2 protein, Entamoeba histolytica
  • Lectins
  • Protozoan Proteins
  • Peroxidases
  • Peroxiredoxins
  • Acetylgalactosamine