Trypanosoma cruzi Surface Mucins with Exposed Variant Epitopes

Abstract

The protozoan parasite Trypanosoma cruzi, the agent of Chagas disease, has a large number of mucin molecules on its surface, whose expression is regulated during the life cycle. These mucins are the main acceptors of sialic acid, a monosaccharide that is required by the parasite to infect and survive in the mammalian host. A large mucin-like gene family named TcMUC containing about 500 members has been identified previously in T. cruzi. TcMUC can be divided into two subfamilies according to the presence or absence of tandem repeats in the central region of the genes. In this work, T. cruzi parasites were transfected with one tagged member of each subfamily. Only the product from the gene with repeats was highly O-glycosylated in vivo. The O-linked oligosaccharides consisted mainly of beta-d-Galp(1-->4)GlcNAc and beta-d-Galp(1-->4)[beta-d-Galp(1-->6)]-d-GlcNAc. The same glycosyl moieties were found in endogenous mucins. The mature product was anchored by glycosylphosphatidylinositol to the plasma membrane and exposed to the medium. Sera from infected mice recognized the recombinant product of one repeats-containing gene thus showing that they are expressed during the infection. TcMUC genes encode a hypervariable region at the N terminus. We now show that the hypervariable region is indeed present in the exposed mature N termini of the mucins because sera from infected hosts recognized peptides having sequences from this region. The results are discussed in comparison with the mucins from the insect stages of the parasite (Di Noia, J. M., D'Orso, I., Sánchez, D. O., and Frasch, A. C. C. (2000) J. Biol. Chem. 275, 10218-10227) which do not have variable regions.

Action of Trypanosoma rangeli in infections with virulent Trypanosoma cruzi populations

“…Antibodies recognizing the parasite mucins (Pollevick et al 2000) and those neutralizing the trans-sialidase activity have been found in sera from T. cruzi infected humans and animals (Leguizamón et al 1994a, b). Therefore, we can speculate that cross-reactive antibodies induced by the homologous mucins and sialidases expressed in T. rangeli might be involved in the protective effect of T. rangeli infection on evolution of Chagas disease.…”

Relationship of Sialyl-Lewisx/a Underexpression and E-Cadherin Overexpression in the Lymphovascular Embolus of Inflammatory Breast Carcinoma

“…Presumably much of this surface sLe x occurs on MUC1 because it is overexpressed in wild-type MARY-X but undoubtedly other sialylated surface molecules are also fucosylated by these two approaches. 24,25 FucT-III transfection was . SLe x/a -MARY-X exhibits a similar enlargement.…”

Procyclin Null Mutants ofTrypanosoma bruceiExpress Free Glycosylphosphatidylinositols on Their Surface

“…Tetramethylrhodamine B isothiocyanate-conjugated anti-mouse antibody (Sigma) was used at 1:400 and fluorescein isothiocyanate-conjugated anti-rabbit antibody (Sigma) at 1:2000. (Pollevick et al, 2000).…”

“…To investigate whether the free GPI is exposed on the surface of the null mutant, living procyclic forms were incubated in serum-free medium, resulting in the removal of sialic acid residues by the endogenous trans-sialidase (Pollevick et al, 2000). The cells were subsequently treated with galactose oxidase and the oxidized terminal ␤-galactose residues were reduced with [ 3 H]borohydride.…”