Cell adhesion and Ca2+ signaling activity in stably transfected trypanosoma cruzi epimastigotes expressing the metacyclic stage-specific surface molecule gp82

Metacyclic trypomastigotes of Trypanosoma cruzi express a developmentally regulated 82-kDa surface glycoprotein (gp82) that has been implicated in host cell invasion. gp82-mediated interaction of metacyclic forms with target cells induces in both cells activation of the signal transduction pathways, leading to intracellular Ca2+ mobilization, which is required for parasite internalization. Noninfective epimastigotes do not express detectable levels of gp82 and are unable to induce a Ca2+ response. We stably transfected epimastigotes with a T. cruzi expression vector carrying the metacyclic stage gp82 cDNA. These transfectants produced a functional gp82, which bound to and triggered a Ca2+ response in HeLa cells, in the same manner as the metacyclic trypomastigote gp82. Such properties were not found in epimastigotes transfected with the plasmid vector alone. Epimastigotes expressing gp82 on the surface adhered to HeLa cells but were not internalized. Treatment of gp82-expressing epimastigotes with forskolin, an activator of adenylyl cyclase that increases the metacyclic trypomastigote entry into target cells, did not promote parasite internalization. P175, an intracellular tyrosine phosphorylated protein, which appears to play a role in gp82-dependent signaling cascade in metacyclic forms, was undetectable in epimastigotes, either transfected or not with pTEX-gp82. Overall, our results indicate that gp82 is required but not sufficient for target cell invasion.Universidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biofis, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biofis, BR-04023062 São Paulo, BrazilWeb of Scienc

CHARACTERIZATION OF A CDNA CLONE ENCODING THE CARBOXY-TERMINAL DOMAIN OF A 90-KILODALTON SURFACE-ANTIGEN OF TRYPANOSOMA-CRUZI METACYCLIC TRYPOMASTIGOTES

We have cloned and sequenced a cDNA for a metacyclic trypomastigote-specific glycoprotein, with a molecular mass of 90 kDa, termed MTS-gp90. By immunoblotting, antibodies to the MTS-gp90 recombinant protein reacted exclusively with a 90-kDa antigen of metacyclic trypomastigotes. The insert of the MTS-gp90 cDNA clone strongly hybridized with a single 3.0-kb mRNA of metacyclic forms, whereas the hybridization signal with epimastigote mRNA was weak and those with RNAs from other developmental stages were negative, indicating that transcription of the MTS-gp90 gene is developmentally regulated. A series of experiments showed that the MTS-gp90 gene is present in multiple copies in the Trypanosoma cruzi genome, arranged in a nontandem manner, and that there are at least 40 copies of the gene per haploid genome. Sequence analysis of recombinant MTS-gp90 revealed 40 to 60% identity at the amino acid level with members of a family of mammalian stage-specific, 85-kDa surface antigens of T. cruzi. However, there are considerable differences in the amino acid compositions outside the homology region.ESCOLA PAULISTA MED,DEPT MICROBIOL IMMUNOL & PARASITOL,BR-04023 SAO PAULO,BRAZILBIOMERIEUX,BIOL CELLULAIRE LAB,LYON,FRANCEESCOLA PAULISTA MED,DEPT MICROBIOL IMMUNOL & PARASITOL,BR-04023 SAO PAULO,BRAZILWeb of Scienc