Unravelling of protein trafficking in Trypanosoma cruzi, the agent of Chagas disease. - In Argentina it is estimated that around 1,600,000 people are infected with Trypanosoma cruzi, the causative agent of Chagas disease. In this proposal we face two main challenges associated with the glycobiology of the parasite and its relevance to cell biology and in the interaction with the mammalian and insect hosts. The final purpose is not only to gain knowledge about biology of the parasite but mainly to determine targets for the development for urgently needed new chemotherapies since the available ones are from the ‘70s and highly toxic. We have recently determined that, in T. cruzi, the contractile vacuole complex (CVC) is involved in protein trafficking to the parasite surface. Here we propose to fully understand protein trafficking through CVC, in particular that mediated by Rab proteins. Because the CVC is an organelle absent in mammals, it could provide with an interesting target for chemotherapies. Unlike mammalian cells, trypanosomes exhibit a significant proportion of GPI-anchored proteins on their surface. Its precursors are synthesized in the endoplasmic reticulum by successive transfer of monosaccharides to a phosphatidylinositol molecule. Our recent studies have revealed that trans-sialidase (TS) and mucins exhibit a distinct and ordered domain distribution on the parasite surface, forming patch regions. A possible explanation for this peculiar organization may be that the proteins have glycosylphosphatidylinositol (GPI) anchors with different lipids: mucins have alkyl-acylglycerol, while TS has ceramide. The role of ceramide in GPI anchoring remains poorly understood. The partitioning of proteins into distinct domains may have significant implications for parasite cell biology, infectivity, and pathogenicity. The enzyme responsible of transfer the ceramide is the ceramide remodelase. We identified the T. cruzi gene orthologue of the encoding gene in yeast. This gene was able to complement the corresponding Saccharomyces cerevisiae mutant. Based on these significant findings, we propose to investigate ceramide acquisition at the GPI-anchoring in T. cruzi and its relevance to the protein traffic and localization on the parasite’s surface. Furthermore, considering that mammalian cells lack ceramides in their GPI, this pathway of incorporation becomes into another promising target for drug development.
