Authors
A Zikova1; M Kunzová1; E Doleželová1; B Panicucci1; 1 Institute of Parasitology, Czech Academy of Sciences, České Budějovice, Czech Republic Discussion
Cellular differentiation of Trypanosoma brucei within its two distinct hosts includes at least five different life cycle forms. Their specific gene expression profiles point to differences in, for example, the cell surface proteome, carbohydrate metabolism, mitochondrial bioenergetics, and mitochondrial ultrastructure. The drivers and molecular mechanisms that control mitochondrial metabolic remodeling are still largely unknown. When characterizing the changes in mitochondrial metabolism of insect life cycle forms generated in vitro, we found that parasite differentiation from procyclics to epimastigotes and metacyclics is accompanied by an increase in mitochondrial reactive oxygen species (mROS), known signaling molecules. When mROS were reduced by genetically introduced scavengers (catalase, mitochondrial catalase, superoxide dismutase), parasite differentiation was severely impaired. In contrast, when mROS production was artificially increased, the parasite differentiated more efficiently from epimastigote to metacyclics. We linked mROS production to higher proline consumption in epimastigotes, which generates high levels of NADH, suggesting involvement of NADH dehydrogenases in mtROS production. We have also shown that mROS, rather than an increase in the AMP /ATP ratio, is critical for activation of AMP activated protein kinase (AMPK), a cellular energy sensor that promotes cell survival under environmental stress. Our data suggest that the parasite has adapted generic stress pathways to drive its differentiation into metabolically quiscent metacyclic cells. 
