TRYPANOSOMA-CRUZI 175-KDA PROTEIN-TYROSINE PHOSPHORYLATION IS ASSOCIATED WITH HOST-CELL INVASION

We examined the requirement of Trypanosoma cruzi protein tyrosine phos phorylation for parasite entry into mammalian cells and analyzed the p rofile of phosphorylated proteins in infective trypomastigotes. Treatm ent of metacyclic or tissue culture trypomastigotes with genistein, an inhibitor of protein tyrosine kinase activity, significantly inhibite d invasion of cultured HeLa cells. A soluble factor, contained in HeLa cell extract and absent in the extract or T. cruzi-resistant K562 cel ls, greatly enhanced phosphorylation levels of a 175-kDa protein (p175 ) in trypomastigotes. Genistein inhibited p175 tyrosine phosphorylatio n. P175 was undetectable in noninvasive epimastigotes. The phosphoryla tion-inducing activity of HeLa cell extract was abrogated by adsorptio n with metacyclic trypomastigotes but not with epimastigotes or when i t was mixed with recombinant protein Jig, which contains the entire pe ptide sequence of gp82, a metacyclic stage-specific surface glycoprote in implicated in target cell invasion. These data suggest ttl;it. in m etacyclic trypomastigotes, gp82 is the signaling receptor that mediate s protein tyrosine phosphorylation necessary for host cell invasion. ( C) 1998 Academic Press.