TURNOVER AND SHEDDING OF THE TC-85 SURFACE GLYCOPROTEIN OF TRYPANOSOMA-CRUZI TRYPOMASTIGOTES

Tc-85 is an 85-kDa surface glycoprotein specific for the trypomastigot e stage of Trypanosoma cruzi which has been implicated in the invasion of host cells by the parasite, Tc-85 has a half-life of 3.5-4 h and i s synthesized as a 95-kDa precursor. Processing of the 95-kDa precurso r is inhibited by N-p-tosyl-L-lysine chloromethyl ketone, p-chloromerc uriphenylsulfonic acid, iodoacetamide or N-ethyl-maleimide, but not by aprotinin, antipain or phenylmethylsulfonil fluoride. Tc-85, but not the precursor, is rapidly shed into the medium, allowing a correlation between the decrease of Tc-85 in trypomastigotes and its increase in the culture medium. The shedding of Tc-85 was inhibited 50% by 1 mu M tunicamycin, but not by 10 mu M swainsonine or 10 mu M 1-deoxynojirimy cin under the experimental conditions employed. This suggests that N-l inked oligosaccharides are important for the shedding phenomenon, alth ough it appears that they do not have to be fully processed for sheddi ng to occur.