Heme A synthesis is essential for the survival and infectivity of Trypanosoma cruzi.

MERLI ML; CRICCO JA; MEDIAVILLA MG; TEVERE E; CIRULLI BA; PAGURA L

Caxambu

Congreso; XXXIII Reuniao Anual da Sociedade Brasileira de Protozoologia; 2017

Sociedade Brasileira de Protozoologia

Although Trypanosoma cruzi is an aerobic organism, it does not produce heme. Heme is acquired from the hosts, distributed and inserted into heme-proteins such as respiratory complexes in the parasite?s mitochondrion. It has been proposed that T. cruzi?s energy metabolism relies on a branched respiratory chain with a cytochrome c oxidase (CcO) as the main terminal oxidase, which contains two molecules of heme A as cofactors. Two enzymes, heme O synthase (HOS) and heme A synthase (HAS), are involved in heme A synthesis. We present here our results on heme A synthesis and its relevance in T. cruzi.We identified the HOS and HAS enzymes in T. cruzi, named TcCox10 and TcCox15, respectively. TcCox15 was differentially detected in T. cruzi?s stages by Western blot assays, being more abundant in the replicative forms, reflecting the necessity of more heme A synthesis and therefore more CcO activity at these stages. We designed and constructed TcCox15 mutants replacing conserved His residues by Ala. The overexpression of these non-functional mutants caused a reduction in heme A content with a concomitant drop in CcO activity in epimastigotes, confirming TcCox15 as HAS in T. cruzi. Also, the overexpression of these non-functional mutants negatively affects trypomastigotes? infection and intracellular amastigotes? replication. Interestingly, the over-expression of TcCox10 protein caused a negative effect on epimastigotes growth, suggesting that heme A synthesis should be regulated at the first step of this pathway. Our results clearly showed that a drawback in heme A synthesis provoked a reduction on CcO activity and, in consequence, an impairment on T. cruzi survival, proliferation and infectivity. This evidence supports that T. cruzi depends on the respiratory chain activity along its life cycle, being CcO an essential terminal oxidase. This reinforces the idea of parasite energy metabolism as an attractive therapeutic target to control infection and transmission.