Classic or modified phagocytosis is the main mechanism of entrance into host cells displayed by several intracellular pathogens. Phagosomes constitute the first, and sometimes, the last stop for the pathogen; they modulate the initial or final pathogens micro-environment, allow pathogen differentiation into different evolutive forms, controll the passage of nutrients and enzimatic substrates (by the presence of channels and by fusion with other host cell vesicles), regulate the antigen presentation by infected cells or the entrance/activity of chemotherapics. Each phagosome is unique, developed from a conjoint of host cell signals triggered by the recognition of the particle/pathogen and from a series of fusion/fission events between phagosome and other selected vesicles. Once internalized by host cells, some pathogens escape from phagosomes and lodge in the citosol. Other are capable of interfere in the maturation of phagosomes, leading to the formation of specialized phagosomes (called parasitophorous vacuoles), customized, displaying selective fusogenicity with host cell vesicles from endocytic and secretory pathways. Parasite of Leishmania genus are examples of pathogens lodged within parasitophorous vacuoles (PVs) during all their intracellular lifecycle inside mammalian host cells. The morphological and biochemical diversity of Leishmania vacuoles is poorly understood. On the other hand, parasites from Trypanosoma cruzi species only transiently live within PVs during their intracellular lifecycle, escaping to host cell citosol (a process which molecular mechanisms are not established). By coinfecting cells in vitro with these two parasites, we investigate the possibility of fusion between Leishmania and T. cruzi PVs and the consequences for both parasites of this intravacuolar cohabitation (chimeric PV). As models of host cells, we will use cell lines transfected with interference RNA for endossomal and lisossomal proteins (LAMPs and Rabs), proteins involved in membrane fusion (SNAREs) and proteins involved in vacuolar acidification (V-ATPases). The participation of these molecules in the transference of T. cruzi to Leishmania PVs, in the differentiation of T. cruzi within chimeric PVs and in the escape of T. cruzi from the chimeric PVs to the citosol will be investigated.
News published in Agência FAPESP Newsletter about the scholarship: