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Trypanosoma cruzi, the etiological agent of Chagas' disease, is an early divergent eukaryote in which control of gene expression relies mainly in post-transcriptional mechanisms. Transcription levels are globally up and down regulated during the transition between proliferating and non-proliferating life-cycle stages. In this work we characterized a nuclear adenylate kinase isoform (TcADKn) that is involved in ribosome biogenesis. Nuclear adenylate kinases have been recently described in a few organisms, being all related to RNA metabolism. Depending on active transcription and translation, TcADKn localizes in the nucleolus or the cytoplasm. A non-canonical nuclear localization signal was mapped towards the N- terminal of the protein, being the phosphate-binding loop essential for its localization. In addition, TcADKn nuclear exportation depends on the nuclear exportation adapter CRM1. TcADKn nuclear shuttling is governed by nutrient availability, oxidative stress and by the equivalent in T. cruzi of the mammalian TOR (Target of Rapamycin) pathway. One of the biological functions of TcADKn is ribosomal 18S RNA processing by direct interaction with ribosomal protein TcRps14. Finally, TcADKn expression is regulated by its 39 UTR mRNA. Depending on extracellular conditions, cells modulate protein translation rates regulating ribosome biogenesis and nuclear adenylate kinases are probably key components in these processes. [ABSTRACT FROM AUTHOR]

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l-Cysteine and methionine are unique amino acids that act as sulfur donors in all organisms. In the specific case of Trypanosomatids,l-cysteine is particularly relevant as a substrate in the synthesis of trypanothione. Although it can be synthesized de novo,l-cysteine is actively transported in Trypanosoma cruzi epimastigote cells.l-Cysteine uptake is highly specific; none of the amino acids assayed yield significant differences in terms of transport rates.l-Cysteine is transported by epimastigote cells with a calculated apparent Km of 49.5 μM and a Vmax of about 13 pmol min−1 per 107 cells. This transport is finely regulated by amino acid starvation, extracellular pH, and between the parasite growth phases. In addition,l-cysteine is incorporated post-translationally into proteins, suggesting its role in iron–sulfur core formation. Finally, the metabolic fates ofl-cysteine were predicted in silico. [ABSTRACT FROM AUTHOR]

Abstract: Aspartate is one of the compounds that induce the differentiation process of the non-infective epimastigote stage to the infective trypomastigote stage of the protozoan parasite Trypanosoma cruzi. l-aspartate is transported by both epimastigote and trypomastigote cells at the same rate, about 3.4 pmolmin−1 per 107 cells. Aspartate transport is only competed by glutamate suggesting that this transport system is specific for anionic amino acids. Aspartate uptake rates increase along the parasite growth curve, by amino acids starvation or pH decrease. The metabolic fate of the transported aspartate was predicted in silico by identification of seven putative genes coding for enzymes involved in aspartate metabolism that could be related to the differentiation process. [Copyright &y& Elsevier]

Trypanosoma cruzi, the etiological agent of Chagas disease, uses arginine for several metabolic processes, including energy reserves management. In the present work, a novel low-affinity arginine transport system has been studied. Maximum velocity (97 pmol min-1 per 107 cells), and an estimate for the apparent Km value (350 μM) of this arginine transporter, were 6-fold and 80-fold higher respectively, when compared with the previously described high-affinity arginine transport system. This transport activity seems to be H+-mediated, presents a broad specificity by other amino acids such as methionine, and is regulated along the parasite growth curve and life cycle. [Copyright &y& Elsevier]