Abstract
Trypanosoma cruzi, the etiological agent of Chagas' disease, has a metabolism largely based on the consumption of glucose and proline. This amino acid is essential for host cells infection and intracellular differentiation. In this work we identified a proline transporter (TcAAAP069) by yeasts complementation assays and overexpression in Trypanosoma cruzi epimastigotes. TcAAAP069 is mono-specific for proline but presents an unusual feature; the lack of stereospecificity, because it is competitively inhibited by the D- enantiomer. Parasites overexpressing TcAAAP069 have an increased intracellular proline concentration, 2.6-fold higher than controls, as a consequence of a higher proline transport rate. Furthermore, augmented proline concentration correlates with an improved resistance to trypanocidal drugs and also to reactive oxygen species including hydrogen peroxide and nitric oxide, emulating natural physiological situations. The IC50s for nifurtimox, benznidazole, H2O2 and NO. were 125%, 68%, 44% and 112% higher than controls, respectively. Finally, proline metabolism generates a higher concentration (48%) of ATP in TcAAAP069 parasites. Since proline participates on essential energy pathways, stress and drug resistance responses, these results provide a novel target for the development of new drugs for the treatments for Chagas' disease.
Highlights
Trypanosoma cruzi, the etiological agent of Chagas’ disease, has a metabolism largely based on the consumption of amino acids, mainly proline, which constitutes the main carbon and energy source in the insect stage of the parasite life cycle
Expression of the T. cruzi proline transporter in yeasts With the aim of identifying a T. cruzi proline transporter, ten genes from the previously characterized TcAAAP family have been subcloned in yeast expression vectors for complementation assays
As figure 1A shows, only yeasts expressing the transporter TcAAAP069 were able to grow under these conditions
Summary
Trypanosoma cruzi, the etiological agent of Chagas’ disease, has a metabolism largely based on the consumption of amino acids, mainly proline, which constitutes the main carbon and energy source in the insect stage of the parasite life cycle. The ability of proline to suppress reactive oxygen species (ROS) and apoptosis in mammalian cells involves the secondary amine of its pyrrolidine ring, and it was demonstrated manipulating intracellular proline concentration by adding the amino acid to the medium or endogenously by altering proline dehydrogenase levels [6,7]. Osmotic stress that occurs within the gut of the triatomine vector and in the vertebrate host, initially causes swelling, but this is rapidly adjusted by a compensatory volume reversal associated with a selective amino acid efflux, mainly alanine and proline [8]
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