Trypanosoma cruzi surface mucins with exposed variant epitopes

The protozoan parasite Trypanosoma cruzi, the agent of Chagas disease, has a large number of mucin molecules on its surface, whose expression is regul ated during the life cycle, These mucins are the main accepters of sialic a cid, a monosaccharide that is required by the parasite to infect and surviv e in the mammalian host. A large mucin-like gene family named TcMUC contain ing about 500 members has been identified previously in T. cruzi, TcMUC can be divided into two subfamilies according to the presence or absence of ta ndem repeats in the central region of the genes. In this work, T. cruzi par asites 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 b eta-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 glycosy lphosphatidylinositol to the plasma membrane and exposed to the medium. Ser a from infected mice recognized the recombinant product of one repeats-cont aining gene thus showing that they are expressed during the infection, TcMU C genes encode a hypervariable region at the N terminus. We now show that t he hypervariable region is indeed present in the exposed mature N termini o f the mucins because sera from infected hosts recognized peptides having se quences 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., Sanchez, D. O., and Frasch, A. C. C. (2000) J, Biol. Chem. 275, 10218-10227 ) which do not have variable regions.