Trypanosoma cruzi uses macropinocytosis as an additional entry pathway into mammalian host cell

Several intracellular pathogens are internalized by host cells via multiple endocytic pathways. It is no different with Trypanosoma cruzi. Evidences indicate that T. cruzi entry may occur by endocytosis/phagocytosis or by an active manner. Although macropinocytosis is largely considered an endocytic process where cells internalize only large amounts of solutes, several pathogens use this pathway to enter into host cells. To investigate whether T. cruzi entry into peritoneal macrophages and LLC-MK2 epithelial cells can be also mediated through a macropinocytosis-like process, we used several experimental strategies presently available to characterize macropinocytosis such as the use of different inhibitors. These macropinocytosis' inhibitors blocked internalization of T. cruzi by host cells. To further support this, immunofluorescence microscopy and scanning electron microscopy techniques were used. Field emission scanning electron microscopy revealed that after treatment, parasites remained attached to the external side of host cell plasma membrane. Proteins such as Rabankyrin 5, tyrosine kinases, Pak1 and actin microfilaments, which participate in macropinosome formation, were localized at T. cruzi entry sites. We also observed co-localization between the parasite and an endocytic fluid phase marker. All together, these results indicate that T. cruzi is able to use multiple mechanisms of penetration into host cell, including macropinocytosis.