Functional analyses of the Tetraspanin 6 membrane protein during Trichomonas vaginalis migration and pathogenesis

NATALIA DE MIGUEL

Woods Hole

Congreso; XX Molecular Parasitology Meeting; 2009

The unicellular parasitic Trichomonas vaginalis is the causative agent of trichomoniasis, the most prevalent non-viral sexually transmitted disease in humans. Because T. vaginalis is an obligate extracellular pathogen, proteins on the surface may play a critical role host-parasite interaction and the consequent pathogenesis. Here, we report the identification and functional characterization of T. vaginalis Tetraspanin-6 (TSP6). TSP6 is member of the tetraspanin family, which comprises a large superfamily of cell surface-associated membrane proteins that has been implicated in fundamental biological processes, including cell adhesion, migration, fusion and proliferation. Our studies showed that TSP6 targets to both the plasma membrane and the flagella of free living parasites. The protein relocalizes during  exposure to vaginal epithelial cells (VECs). Moreover, qPCR analysis of parasites exposed to VECs revealed a dual upregulation over the time. The complex localization and expression pattern of TSP6 suggests that its intracellular trafficking and distribution must be tightly regulated during parasite pathogenesis. In order to evaluate TSP6 function, cell adhesion and migration assays were performed using parasites that over-express full length and C-terminal truncated version of TSP6. Although no effect was observed on parasite that overexpress full length TSP6, when the C-terminal tail is removed (TSP6DCt), exogenous TSP6 exerted a dominant negative effect, as it significantly reduced migration through matrigel invasion chambers compared with parasites transfected with empty plasmid. No effect was observed in adhesion experiments. In addition, TSP6DCt does not relocalize upon exposure to VECs as observed for the full length protein. In conclusion, TSP6 appears to influence cellular migration, with the TSP6 tail being of particular importance in determining the “outside-in” signals that follow ligand engagement. The elucidation of determinants involved in the process of migration may reveal virulence factors and novel therapeutic targets to combat disease.