Recently, a lectin-like activity that binds to sulphated polysaccharides has been identi®ed in lysates of Toxoplasma (Ortega-Barria and Boothroyd, 1999). This lectinlike activity agglutinates erythrocytes and may mediate attachment to host cell glycosaminoglycans (GAGs). In support of this model, parasite infectivity was modulated by soluble GAGs or decreased expression of host cell surface GAGs on human foreskin (HFF) ®broblasts or CHO cells (Ortega-Barria and Boothroyd, 1999). Independently, we have also observed that high concentrations of soluble GAGs block parasite invasion into a wide range of different lineages of mammalian host cells (V. B. Carruthers and L. D.Sibley,inpreparation).While several potential molecules with heparin-binding activity were identi®ed in lysates of Toxoplasma, their intracellular location and exact role in cell adhesion has not been established (Ortega-Barria and Boothroyd, 1999). Nonetheless, indirect results suggest that heparin-binding proteins are localized within an apical but intracellular compartment within the parasite and that they are translocated to the cell surface during attachment (Ortega-Barria and Boothroyd, 1999).
Recently, a lectin-like activity that binds to sulphated polysaccharides has been identi®ed in lysates of Toxoplasma (Ortega-Barria and Boothroyd, 1999). This lectinlike activity agglutinates erythrocytes and may mediate attachment to host cell glycosaminoglycans (GAGs). In support of this model, parasite infectivity was modulated by soluble GAGs or decreased expression of host cell surface GAGs on human foreskin (HFF) ®broblasts or CHO cells (Ortega-Barria and Boothroyd, 1999). Independently, we have also observed that high concentrations of soluble GAGs block parasite invasion into a wide range of different lineages of mammalian host cells (V. B. Carruthers and L. D.Sibley,inpreparation).While several potential molecules with heparin-binding activity were identi®ed in lysates of Toxoplasma, their intracellular location and exact role in cell adhesion has not been established (Ortega-Barria and Boothroyd, 1999). Nonetheless, indirect results suggest that heparin-binding proteins are localized within an apical but intracellular compartment within the parasite and that they are translocated to the cell surface during attachment (Ortega-Barria and Boothroyd, 1999).
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