Heterologous expression of a Trypanosoma cruzi surface glycoprotein (gp82)in mammalian cells indicates the existence of different signal sequence requirements and processing

Metacyclic trypomastigotes of Trypanosoma cruzi express a developmentally r egulated 82 kDa surface glycoprotein (gp82) that has been implicated in the mammalian cell invasion. When the non-infective epimastigote stage of the parasite was transfected with a vector containing the gp82 gene, an 82 kDa surface glycoprotein, which was indistinguishable from the metacyclic stage protein, was expressed. In contrast, when the same gene was expressed in t ransfected mammalian cells, although a large amount of protein was produced , it was not imported into the endoplasmic reticulum and glycosylated. This blockage in targeting and processing could be partially compensated for by the addition of a virus haemagglutinin signal peptide to the amino terminu s of gp82. Thus, the requirements for membrane protein processing are disti nct in mammals and T cruzi, and an intrinsic feature of the gp82 prevents s ubsequent sorting to the mammalian cell surface. These results could be use ful in the development of new DNA vaccines against T. cruzi employing paras ite genes encoding immunodominant surface glycoproteins.