Kurzbeschreibung
(Englisch)
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Autophagy, a particular form of programmed cell death, has recently been proposed to play an important role during differentiation of protozoan parasites. The present grant application proposes to study key steps during autophagy in Trypanosoma brucei, a protozoan parasite responsible for human sleeping sickness, and a related animal disease, in Africa. Our work will focus on the dependency of early key events in autophagy on membrane lipid homeostasis in T. brucei. The possibility to study autophagy by generating inducible RNAi or knock-out mutant parasites in T. brucei and to use trypanosomes defective in different steps in phospholipid synthesis offers unique possibilities to advance the knowledge in autophagy in general, and to study its role during the parasite cell cycle.
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Partner und Internationale Organisationen
(Englisch)
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BE, CH, DE, DK, ES, FR, GR, IL, IT, NL, PT, UK
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Abstract
(Englisch)
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African trypanosomes are protozoan parasites causing African sleeping sickness in humans and nagana in domestic animals. These diseases have a major impact on human and animal health by severely affecting social and economic development among the poorest, mostly rural, populations in sub-Saharan Africa. During its complex life cycle, Trypanosoma brucei alternates between the mammalian bloodstream and the insect host, the tsetse fly. One prerequisite for the parasite to change between the different life cycle forms is its ability to rapidly degrade macromolecules and organelles that are no longer needed in the new environment. This process, which has not been studied in detail in T. brucei, has been suggested to involve autophagy, a mechanism of self-digestion of cellular components that usually occurs without destruction of the cell. Autophagy is an evolutionary conserved mechanism involving approximately 40 gene products in most eukaryotes. Interestingly, due to the apparent lack of several putative autophagy genes in the genome, T. brucei parasites likely possess a machinery consisting of considerably fewer proteins. Atg8, a key protein for autophagy, marks the onset and progression of autophagy in most eukaryotes. In the yeast, Saccharomyces cerevisiae, the role of Atg8 has been well characterized: upon induction of autophagy, Atg8 becomes covalently modified by attachment of the phospholipid, phosphatidylethanolamine, providing Atg8 with a hydrophobic anchor. As a result, the localization of Atg8 changes from the cytosol to the membrane of autophagic vesicles (autophagosomes), where it is involved in membrane expansion and hemifusion. Within the framework of COST action BM0802, we have been studying autophagy in T. brucei by generating several parasite cell lines expressing tagged forms of Atg8 in both procyclic (insect stage) and bloodstream forms. In addition, we have generated knock-out cell lines for two of the key proteins involved in autophagy. We are using these mutant parasites to study the role of autophagy during metabolic starvation and its possible involvement during differentiation of T. brucei.
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