Nutrient Uptake Portals in Toxoplasma gondii Tachyzoites

Abstract

The process of nutrient acquisition by Toxoplasma gondii tachyzoites is an attractive target for developing and designing drugs against toxoplasmosis, however, just recently it was revealed to be an important process to be understood. The present work helps address the lack of information about the exact sites where nutrient uptake in T. gondii. The endocytosis of proteins by tachyzoites of T. gondii was measured using both fluid-phase and receptor-mediated endocytic tracers. Quantitative analysis by flow cytometry revealed important differences in the percentage of labeled parasites, incubated with BSA, dextran, or transferrin. The analysis by confocal microscopy showed that the anterior portion of the conoid is one preferential site for binding BSA and transferrin to the tachyzoite, later localized within elongated structures present in the anterior region of the parasite. The ultrastructural analysis of multiple ultrathin sections displayed the endocytic markers at the following: (i) conoid, within rhoptries, (ii) in cup-shaped invagination of the parasite membrane (micropore) and, (iii) posterior pore. The present study brings data revealing three possible nutrient uptake portals in Toxoplasma tachyzoites that may contribute in the future to a therapeutic design with a view to treatment of toxoplasmosis.