Solving the puzzle of copper trafficking in Trypanosoma cruzi : candidate genes that can balance uptake and toxicity

Trypanosoma cruzi, the causative agent of Chagas disease, depends on acquiringnutrients and cofactors, such as copper (Cu), from different hosts. Cu isessential for aerobic organisms, but it can also be toxic, and so its transportand storage must be regulated. In the present study, we characterized theeffects of changes in Cu availability on growth behavior, intracellular ioncontent and oxygen consumption. Our results show that copper is essentialfor epimastigote proliferation and for the metacyclogenesis process. On theother hand, intracellular amastigotes suffered copper stress during infection.In addition, we identify gene products potentially involved in copper metabolism.Orthologs of the highly conserved P-type Cu ATPases involved in copperexport and loading of secreted enzymes were identified and named T.cruzi Cu P-type ATPase (TcCuATPase). TcCuATPase transcription is upregulatedduring infective stages and following exposure to copper chelators inthe epimastigote stage. Homolog sequences for the high affinity import proteinCTR1 were not found. Instead, we propose that the T. cruzi iron transporter(TcIT), a ZIP family transporter, could be involved in copper uptakebased on transcriptional response to copper availability. Further canonicalcopper targets (based on homology to yeast and mammals) such as the T.cruzi ferric reductase (TcFR) and the cupro-oxidase TcFet3 are upregulatedduring infective stages and under conditions of intracellular copper deficiency.In sum, copper metabolism is essential for the life cycle of T. cruzi.Even though cytosolic copper chaperons were not identified, we propose apreviously undescribed model for copper transport and intracellular distributionin T. cruzi, including some conserved factors such as TcCuATPase, aswell as others such as TcFR and TcIT, playing novel functions.