How much (ATP) does it cost to build a trypanosome? A theoretical study on the quantity of ATP needed to maintain and duplicate a bloodstream-form Trypanosoma brucei cell.

ATP hydrolysis is required for the synthesis, transport and polymerization of monomers for macromolecules as well as for the assembly of the latter into cellular structures. Other cellular processes not directly related to synthesis of biomass, such as maintenance of membrane potential and cellular shape, also require ATP. The unicellular flagellated parasite Trypanosoma brucei has a complex digenetic life cycle. The primary energy source for this parasite in its bloodstream form (BSF) is glucose, which is abundant in the host's bloodstream. Here, we made a detailed estimation of the energy budget during the BSF cell cycle. As glycolysis is the source of most produced ATP, we calculated that a single parasite produces 6.0 x 1011 molecules of ATP/cell cycle. Total biomass production (which involves biomass maintenance and duplication) accounts for ~63% of the total energy budget, while the total biomass duplication accounts for the remaining ~37% of the ATP consumption, with in both cases translation being the most expensive process. These values allowed us to estimate a theoretical YATP of 10.1 (g biomass)/mole ATP and a theoretical [Formula: see text] of 28.6 (g biomass)/mole ATP. Flagellar motility, variant surface glycoprotein recycling, transport and maintenance of transmembrane potential account for less than 30% of the consumed ATP. Finally, there is still ~5.5% available in the budget that is being used for other cellular processes of as yet unknown cost. These data put a new perspective on the assumptions about the relative energetic weight of the processes a BSF trypanosome undergoes during its cell cycle.

Genome-scale metabolic models highlight stage-specific differences in essential metabolic pathways in Trypanosoma cruzi.

Chagas disease is a neglected tropical disease and a leading cause of heart failure in Latin America caused by a protozoan called Trypanosoma cruzi. This parasite presents a complex multi-stage life cycle. Anti-Chagas drugs currently available are limited to benznidazole and nifurtimox, both with severe side effects. Thus, there is a need for alternative and more efficient drugs. Genome-scale metabolic models (GEMs) can accurately predict metabolic capabilities and aid in drug discovery in metabolic genes. This work developed an extended GEM, hereafter referred to as iIS312, of the published and validated T. cruzi core metabolism model. From iIS312, we then built three stage-specific models through transcriptomics data integration, and showed that epimastigotes present the most active metabolism among the stages (see S1-S4 GEMs). Stage-specific models predicted significant metabolic differences among stages, including variations in flux distribution in core metabolism. Moreover, the gene essentiality predictions suggest potential drug targets, among which some have been previously proven lethal, including glutamate dehydrogenase, glucokinase and hexokinase. To validate the models, we measured the activity of enzymes in the core metabolism of the parasite at different stages, and showed the results were consistent with model predictions. Our results represent a potential step forward towards the improvement of Chagas disease treatment. To our knowledge, these stage-specific models are the first GEMs built for the stages Amastigote and Trypomastigote. This work is also the first to present an in silico GEM comparison among different stages in the T. cruzi life cycle.

L-Glutamine uptake is developmentally regulated and is involved in metacyclogenesis in Trypanosoma cruzi.

Trypanosoma cruzi, the aetiological agent of Chagas disease, can obtain L-glutamine (Gln) through the enzyme glutamine synthetase (GS) using glutamate (Glu) and ammonia as substrates. In this work, we show additional non-canonical roles for this amino acid: its involvement in ATP maintenance and parasite survival under severe metabolic stress conditions and its participation in the differentiation process occurring in the insect vector (metacyclogenesis). These roles are dependent on the supply of Gln from an extracellular source. We show that T. cruzi incorporates Gln through a saturable and specific transport system, which results in unusual stability at elevated temperatures. The activity was moderately higher at pH values between 6 and 7 and was sensitive to the dissipation of the H+ gradient at the plasma membrane. When analysed in the different life cycle stages, we found that Gln transport is developmentally regulated. In fact, Gln uptake and GS activity seem to be finely regulated at most stages: when GS activity is increased, transport is decreased and vice versa, with the exception of trypomastigotes, where both sources of Gln are diminished. This metabolic adaptation reflects the relevance of Gln in T. cruzi biology and the plasticity of these parasites to adjust their metabolism to changing environments.