HEME A SYNTHESIS IS ESSENTIAL FOR Trypanosoma cruzi INFECTION AND INTRACELLULAR AMASTIGOTE REPLICATION

MARCELO L MERLI; BRENDA A CIRULLI; LUCAS PAGURA; JULIA A CRICCO

Buenos Aires

Congreso; XXVII Reunión Anual de la Scociedad Argentina de Protozoología; 2015

Sociedad Argentina de Protozoología

Trypanosoma cruzi presents nutritional requirements for heme. We are interested in studying how heme is transported to the parasite mitochondrion and how it is converted into heme A, a cofactor only seen in the cytochrome c oxidase complex (CcO) of the mitochondrial respiratory chain. In our laboratory we have identified the enzymes involved in heme A biosynthesis in T. cruzi: TcCox10 (heme O synthase) and TcCox15 (heme A synthase), both enzymes located in the mitochondrion. The genes encoding the WT and non-functional mutant proteins were cloned in the pTcINDEX vector and overexpressed in T. cruzi epimastigotes. We did not observe any effects when the mutant TcCOX10 genes were overexpressed but surprisingly the overexpression of the WT TcCOX10 gene caused a deleterious effect on epimastigotes' proliferation. On the other hand, the expression of mutant TcCOX15 genes caused a negative effect on epimastigotes proliferation together with a diminution on heme A levels and in the oxygen consumption. Also we tested how the expression of the mutant TcCOX15 genes affects the infection and the intracellular replication. In these cases, the presence of the mutant non-functional TcCox15 protein negatively affects the cellular infection by trypomastigotes and amastigotes intracellular replication. In summary, being Heme A ?like heme- an essential but toxic molecule, its synthesis must be regulated. The overexpression of the first enzyme of the pathway (TcCox10) altered the mitochondrion functions and -as consequence- the parasite proliferation. In addition, the expression of a non-functional TcCOX15 gene caused an inhibition of heme A synthesis (dominant negative effect) also affecting epimastigotes proliferation, trypomastigotes infection and amastigotes intracellular replication. Our results allows us to postulate that heme A synthesis is essential for T. cruzi, confirming that this parasite depends on mitochondrial respiratory chain along their different life-cycle stages.