Tc HRG plays a central role in orchestrating heme uptake in Trypanosoma cruzi epimastigotes.

Trypanosoma cruzi , a heme auxotrophic parasite, can control intracellular heme content by modulating Tc HRG expression when a free heme source is added to axenic culture. Herein, we explore the role of Tc HRG protein in regulating the uptake of heme derived from hemoglobin in epimastigotes. It was found that the parasite’s endogenous Tc HRG (protein and mRNA) responds similarly to bound (hemoglobin) and free (hemin) heme. Additionally, the overexpression of Tc HRG leads to an increase in intracellular heme content. The localization of Tc HRG is also not affected in parasites supplemented with hemoglobin as the sole heme source. Endocytic null epimastigotes do not show a significant difference in growth profile, intracellular heme content and Tc HRG protein accumulation compared to WT when feeding with hemoglobin or hemin as a source of heme. These results suggest that the uptake of hemoglobin-derived heme likely occurs through extracellular proteolysis of hemoglobin via the flagellar pocket, and this process is governed by Tc HRG. In sum, T. cruzi epimastigotes controls heme homeostasis by modulating Tc HRG expression independently of the source of available heme.