Project description:During their life cycle, trypanosomatids are exposed to stress conditions and adapt their energy and antioxidant metabolism to colonize their hosts. Strigomonas culicis is a monoxenous protist found in invertebrates with an endosymbiotic bacterium that completes essential biosynthetic pathways for the trypanosomatid. Our research group previously generated a wild-type H2O2-resistant (WTR) strain that showed improved mitochondrial metabolism and antioxidant defenses, which led to higher rates of Aedes aegypti infection. Here, we assess the biological contribution of the S. culicis endosymbiont and reactive oxygen species (ROS) resistance to oxidative and energy metabolism processes. Using high-throughput proteomics, several proteins involved in glycolysis and gluconeogenesis, the pentose phosphate pathway and glutathione metabolism were identified. The results suggest that ROS resistance decreases glucose consumption and indicate that the metabolic products from gluconeogenesis are key to supplying the protist with high-energy and reducing intermediates. Our hypothesis was confirmed by biochemical assays showing opposite profiles for glucose uptake and hexokinase and pyruvate kinase activity levels in the WTR and aposymbiotic strains, while the enzyme glucose-6P 1-dehydrogenase was more active in both strains. Regarding the antioxidant system, ascorbate peroxidase has an important role in H2O2 resistance and may be responsible for the high infection rates previously described for A. aegypti. In conclusion, our data indicate that the energy-related and antioxidant metabolic processes of S. culicis are modulated in response to oxidative stress conditions, providing new perspectives on the biology of the trypanosomatid-insect interaction as well as on the possible impact of resistant parasites in accidental human infection.
Project description:Strigomonas culicis is a kinetoplastid parasite of insects that maintains a mutualistic association with an intracellular symbiotic bacterium, that is highly integrated into the protozoa metabolism: it furnishes essential compounds and divides in synchrony with the nuclear host. The protozoa, conversely, can be rid of the endosymbiont, producing a cured cell line, which presents a diminished ability to colonize the insect host. This obligatory association can represent an intermediate step of the evolution towards the formation of a organelle, therefore representing an interesting model to understand the symbiogenesis theory. Here, we used shotgun proteomics to compare the S. culicis endosymbiont-containing and aposymbiotic strains, revealing a total of 11,305 peptides, and up to 2,213 proteins (2,029 and 1,452 for wild and aposymbiotic, respectively). Gene ontology associated to comparative analysis between both strains revealed that the biological processes most affected by the elimination of the symbiont were the amino acid metabolism, as well as protein synthesis and folding. This large-scale comparison of the protein expression in S. culicis marks a step forward in the comprehension of the role of endosymbiotic bacterium in monoxenic trypanosomatid biology, particularly because these organisms have a polycistronic open reading frame organization and post-transcriptional gene regulation.