Cell-surface carbohydrates of Entamoeba invadens

Abstract

Cell-surface carbohydrates of Entamoeba invadens trophozoites were analyzed using (a) a panel of highly purified lectins specific for molecules containing N-acetylglucosamine or sialic acid, N-acetylgalactosamine, galactose, mannose-like residues, and fucose; (b) Escherichia coli K-12 with mannose-sensitive fimbria; (c) enzymatic digestion; and (d) scanning electron microscopy. The presence of galactose (D-Gal) and N-acetylgalactosamine (D-GalNAc) was detected in the amoeba. Previous trypsinization induced the appearance of Glycine max (SBA, specific for D-GalNAc residues)-binding sites, whereas such treatment completely abolished the ability of Ricinus communis (RCAI) and Axinalla polypoides (APP, specific for D-Gal) lectins and partially abolished that of Euonymus europaeus (EEL, specific for D-Gal) lectins to agglutinate the trophozoites. The agglutinating activity of E. coli K-12 adheans with the amoeba was markedly increased after trypsin digestion, indicating that mannose units become exposed after enzyme treatment. These findings were essentially confirmed by scanning electron microscopy. After neuraminidase treatment the parasites became strongly agglutinated with SBA and Arachis hypogaea (PNA, specific for D-Gal) and the cell interaction with Wisteria floribunda (WFH, specific for D-GalNAc) was markedly increased. These results suggest that in E. invadens trophozoites, sialic acid residues are linked to D-Gal and D-GalNAc.

Analysis of Acanthamoeba polyphaga surface carbohydrate exposure by FITC-lectin binding and fluorescence evaluation

“…The specific avidity exhibited by FITC-lectins employed is well documented (Van Damme et al 1998), hence the nature of cyst and trophozoite carbohydrate cell surface exposure, rather than mere carbohydrate composition alone may be elucidated. In contrast with the trophozoites of Entamoeba invadens (Ribeiro et al 1997), acanthamoebal trophozoites investigated showed somewhat less avidity for galactose-and N-acetylgalactosamine-specific lectins compared with Nacetylglucosamine-specific WGA, potentially indicative of their different surface composition and nature. Acanthamoebal cysts and trophozoites, although their cell wall and plasma membrane composition differs greatly, also show some degree of similarity in cell surface carbohydrate exposure, as lectins specific for N-acetylglucosamine, N-acetylgalactosamine and mannose/glucose readily bind to both their surfaces.…”

“…In turn, FITC-lectin avidity of Acanthamoeba and Naegleria strains differed between morphological forms, species and pathogenic or nonpathogenic strains of the same species (Bose et al 1989). More sophisticated Entamoeba studies have not only demonstrated further the experimental potential of fluorescent lectins in elucidating protozoan cell surface nature and dynamics (Ribeiro et al 1997), but also the natural role of lectins as encystation-specific glycoproteins in cyst-wall maturation (Frisardi et al 2000). The studies outlined below employ the techniques of flow cytometry and a panel of FITC-lectins and concepts developed from ligand-receptor studies, to characterize Acanthamoeba polyphaga cyst and trophozoite lectin avidity, hence surface carbohydrate nature.…”

“…Attachment of L. pneumophilia to a surface galactose/N-acetylgalactose exposed by Hartmannella vermiformis induces tyrosine dephosphorylation, as part of a signal cascade, resulting in bacterial phagocytosis (Abu Kwaik et al 1998). In particular, Ribeiro et al 1997 suggested that Escherichia coli became attached to mannose exposed by trophozoites prior to their internalization. Comprehensive quantification and comparison of carbohydrate exposure including mannose residues amongst trophozoites, combined with compromising such exposure, through lectin binding and hapten blocking, may further furnish understanding of particle internalization and phagocytosis by trophozoites.…”

“…Bose et al 1989;Ribeiro et al 1997) that rely on fluorescence microscopy, direct observation of FITC-lectin binding or agglutination, limited scoring and lacking statistical analysis must be viewed with caution, particularly if an attempt to relate carbohydrate exposure to the likes of acanthamoebal pathogenicity be envisaged. However, further and more subtle comparison of comparative lectin binding by acanthamoebal forms, hence their cell surface nature can be obtained from such surfacebinding determinants as lectin-trophozoite/cyst K d and B max values (Table 2).…”

Effect of lectins on the invasion of Ichthyophthirius theront to channel catfish tissue

“…(Vommaro et at. 1997, Feng & Woo 1998, Entamoeba invadens (Ribeiro et al 1997), Glugea plecoglossi (Kim et al 1999), Leishmania spp. (Grogl et al 1987, Jaffe & McMahon-Pratt 1988, Sphaerospora sp.…”