Chagas disease (also
called American trypanosomiasis) is caused by the protozoan parasite Trypanosoma
i. The infection is mostly
spread by triatomine insects but congenital and transfusional transmission is
also common. Similarly to T. brucei
and Leishmania spp
lacks for a heme synthesis route but present several heme-proteins
involved in the respiratory chain complexes and other essential metabolic
pathways (Tripodi, 2011
). For this reason, trypanosomatids must scavenge this
molecule from the host or vector. Being heme an
essential cofactor for T. cruzi
heme homeostasis represents a promising target to inhibit T. cruzi
proliferation and infectivity.
is able to import
heme from the hosts during the replicative stages and a protein we named Tc
is essential for heme transport activity (Merli, 2016
). We observed that the
expression of Tc
HRG is modulated by heme availability. Heme is also a
highly toxic molecule, then this parasite must present a strict control on heme
homeostasis (import, trafficking, and detoxification) where Tc
other unknown proteins are directly involved. Therefore, it was postulated that
may sense intracellular heme and adjust Tc
and accumulation to promote or reduce heme transport activity (Pagura, 2020
In order to assess the puzzle pieces of heme homeostasis we designed a
transcriptome experiment where we evaluated the effect of hemin and hemoglobin
supplementation as heme source in previously heme-starved epimastigotes of T.
during a time course of 24hs.
The parasites were cultures for 48 h in LIT-10% BFS medium without heme
supplementation. Cultures were then washed and resuspended in fresh medium with
5 uM heme as hemin or hemoglobin and in medium without heme as control. Samples
from 3 biological replicas were taken at 0, 4 and 24 h after treatment.
Total RNA samples were sent to the NGS service and raw data were analysed to obtain
the differentially expressed genes (DEG).
Reads were mapped to the T. cruzi
DM28c 2018 genome from
TriTrypDB platform where 17197 genes are annotated (Berna, 2018
). We detected a
total of 303 DEG in both hemin and hemoglobin supplemented cultures 4 hours
post-treatment and 171 DEG after 24 hours of heme supplementation. Among the
down-regulated genes in treated epimastigotes we pointed these cellular
functions: flagellum structure, protein modification, transporters, and signal
transduction. We also observed a down regulation of several genes encoded for
respiratory complex and electron transfer. The processes up
regulated in supplemented epimastigotes were gene expression regulation,
translation and protein synthesis, protein transport, protein-protein
interaction, protein folding and modification, transporters, cystathionine
synthesis and NAD(P)+/NAD(P)H metabolism.
These results denote that changes in heme availability in epimastigotes
have a general effect on the metabolic state of the parasite. We observed
modifications in gene expression with specific down-regulated and up-regulated
metabolic pathways. Biochemical assays should be performed in order to validate
the data obtained from this transcriptome analysis.
Our results reinforce the statement that heme homeostasis is essential
for the parasite. Puzzling over the heme transport and utilization will
contribute to find an Aquiles’ heel of the parasite as well as discover new
target molecules to control T. cruzi