The location of Trypanosoma cruzi glycoproteins in the plasma membrane is determined by their GPI anchor acceptor sequence.

CARLEVARO, GIANNINA; MUCCI, JUAN; BURGOS, JUAN; CAMPETELLA, OSCAR

Evento virtual

Encuentro; Molecular Parasitology Meeting XXXI; 2020

Genetics Society of America

At variance with mammals, trypanosomatids have a high percentage of proteins anchored by Glycosyl-Phosphatidyl-Inositol (GPI) into their plasma membrane. In Trypanosoma cruzi, GPI-anchored proteins such as trans-sialidase (TS) and mucins have a crucial role in the infection establishment. Despite being functionally related as an enzyme-substrate pair, these virulence factors are ordered in domains spatially separated from each other. We found mucins are located in detergent-resistant areas, whereas TSs are not. Currently, there is only scarce information concerning the signals that determine this arrangement on the plasma membrane. It is known that these two proteins have different GPI-lipidic composition, because of that we evaluated the involvement of GPI anchors in determining this membrane assortment. In order to investigate that, we constructed several recombinant genes fused to the MucII-GPI or the TS-GPI signal coding sequence and cloned into a tetracycline-inducible expression vector. Using this regulated system allowed us to study both the final disposition in the plasma membrane as well as the intracellular trafficking of these recombinant proteins at different times post-induction. By analyzing the arrangement of these proteins on the cell surface, we observed a different protein domain pattern both in size and distribution. Besides, this correlated with the detection of proteins in detergent-resistant or non-detergent-resistant domains, depending on whether they carried the GPI anchor signal of MucII or TS, respectively, highlighting the relevance of GPI anchors in the final destination of surface proteins. Concerning the intracellular trafficking, we also observed these proteins initially arranged in domains in the endoplasmic reticulum (ER) endomembrane and detected them segregated in detergent-resistant regions in the ER-Golgi intermediate compartment (ERGIC). This early arrangement and sorting of proteins in different lipidic domains in the ER/ERGIC endomembranes could be essential to reach the high degree of order of the T. cruzi plasma membrane. Therefore, these results are relevant to understand how the paradoxical segregation of these virulence factors on the cell surface is achieved and reveal aspects of the organization of membrane proteins in T. cruzi early from its insertion into the cellular endomembranes.