Attachment of flagellum to the cell body is important to the kinetics of transferrin uptake by Trypanosoma cruzi.

The flagellar pocket and the cytostome are surface domains of Trypanosoma cruzi epimastigote involved in acquisition of nutrients. The cytostome is physically connected to the flagellar complex. To investigate if this association plays a role in endocytosis in T. cruzi, the endocytic activity in wild type and gp72 null mutant (flagellum-cell body attachment region is absent) epimastigotes was compared. Both wild type and mutant cells were incubated with transferrin conjugated with Alexa 543 or gold particles over different time periods and thereafter qualitatively and quantitatively analyzed by flow cytometry and transmission electron microscopy. Flow cytometry analysis showed a reduction in transferrin uptake by null mutant after 30 min of incubation. In addition, at this time period, signals detected by fluorescence microscopy were slightly lower in null mutant cells. At lower incubation times, no differences between wild type and mutant epimastigotes could be observed. Quantitative data obtained by morphometric and flow cytometry analysis suggested that the speed of the endocytic process in the null mutant was similar to wild type cells, although null mutants were not able to bind cargo and therefore internalize as much as wild type epimastigotes. Our observations suggest that the physical association between cytostome and the flagellar complex plays a role in endocytosis efficiency by epimastigotes of T. cruzi.
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