Trypanosome TOR as a major regulator of cell growth and autophagy

Trypanosomatid protozoa parasites are responsible for tropical diseases, and undergo complex life cycles involving developmental forms adapted to insect vectors and vertebrate hosts. During their life cycle these parasites proceed through different forms in response to dramatic environmental changes and/or developmentally regulated programs. Successful progression of the parasite through its life cycle is highly dependent on the capacity of adaptation to distinct stresses involving processes such as autophagy. In eukaryotes, Target Of Rapamycin (TOR) protein kinases act as a sensor, which integrates the nutritional and energetic status, adjusting cell metabolism and growth. Compromising cell viability in yeast and mammals leads to a reduction of TOR function, triggering processes aimed to overcome unfavourable conditions. This is partly achieved by TOR-mediated regulation of protein synthesis and recycling of cellular components by autophagy. In the last few years, autophagy has been described during developmental differentiation processes in Trypanosomatids. However, no link between TOR signalling, autophagy and differentiation has been described so far. This addendum is a commentary to the work published by our group,¹ where we discuss the possible role of TOR kinases, as a controller of cell growth and autophagy, in the regulation of differentiation processes during Trypanosomatids life cycles.