Signal transduction through the Gal-GalNAc lectin of Entamoeba histolytica involves a spectrin-like protein

Capping followed by uroid formation in Entamoeba histolytica has been implicated in resistance against the host immune response during development of amoebiasis. The amebic actomyosin cytoskeleton is essential for such a process. A protein from the spectrin family co-localizes with the Gal-GalNAc lectin during capping of this surface protein complex. Co-localization is not observed when capping of the Gal-GalNAc lectin is specifically inhibited by production of the carboxyl-terminal region of its heavy chain that includes the lectin cytoplasmic tail. A peptide encompassing the lectin last 77 amino acids fused to glutathione-S-transferase interacts in vitro with purified spectrin. The spectrin-binding site was narrowed down to a stretch of 21 amino acids within the lectin cytoplasmic domain. This is the first report identifying an amino acid sequence involved in the interaction between the Gal-GalNAc lectin and cytoskeletal spectrin.