Cloning of a surface membrane glycoprotein specific for the infective formof Trypanosoma cruzi having adhesive properties to laminin

Trypomastigotes of Trypanosoma cruzi express a set of surface glycoproteins known, collectively, as Tc-85. A monoclonal antibody to these proteins, na med H1A10, inhibits (50-90%) in vitro parasite interiorization into host ce lls, thus implicating these glycoproteins in the infection process. Two DNA inserts, a genomic DNA fragment and a full-length cDNA encoding the H1A10 epitope, have now been cloned and characterized. Results show that both hav e high sequence identity with all reported members of the gp85/trans-sialid ase gene family, although the H1A10 epitope exists only in the Tc-85 subset of the family. The epitope has been mapped by competition of antibody bind ing to a Tc-85 recombinant protein with peptides having sequences predicted by the Tc-85 DNA sequence, which contains also putative N-glycosylation si tes and COOH-terminal glycosylphosphatidylinositol anchor insertion sites, as expected, since an N-glycan chain and a glycosylphosphatidylinositol anc hor have been characterized previously in the Tc-85 subset. The protein enc oded by the full-length cDNA insert binds to cells and in vitro to laminin, but not to gelatin or fibronectin, in a saturable manner. For the first time it was possible to assign a defined ligand to a sequence d glycoprotein belonging to the gp85 family, This fact, together with the r eported binding of family members to cell surfaces, reinforces the hypothes is that this family encodes glycoproteins with similar sequences but differ ing enough as to bind to different ligands and thus forming a family of adh esion glycoproteins enabling the parasite to overcome the barriers interpos ed by cell membranes, extracellular matrices, and basal laminae.