Final Report Summary - ENDOTOX (Endosomal dependent transport to the unique secretory organelles of apicomplexan parasites)
The aim of this proposal is to systematically dissect the secretory (and endocytic) pathway of the
obligate intracellular parasite Toxoplasma gondii, a model system for apicomplexans. These
parasites evolved a unique machinery in order to invade their host cells that is tightly linked to the
vesicular trafficking system. During invasion the parasite sequentially secretes the content of its
unique secretory organelles (micronemes and rhoptries) and employs its gliding machinery to
actively invade the host cell. The gliding machinery is tightly anchored at the Inner Membrane
Complex (IMC), which is derived from the Golgi and hence also linked to the secretory system of the
parasite. The aim of this proposal was to combine bioinformatics, biochemistry and reverse genetics to systematically analyse important trafficking factors that are required for the biogenesis, maintenance and regulation of these organelles. Our initial analysis revealed that ~150 genes are involved in this process. However, in a collaboration with Prof Joel Dacks (University of Alberta), who is an expert in evolution of endomembrane systems of eukaryotes, this candidate list significantly increased and is likely to do so in the future. In fact, we speculate that several of the identified essential “hypothetical genes” will turn out to be important for vesicular transport.
In order to characterise these genes, we developed novel reverse genetic tools, such as the DiCre
system (see Andenmatten et al., Nature Methods 2013), which has now also been established in
Plasmodium falciparum (see Collins et al., 2013). Furthermore, we adapted a novel system based on conditional cas9/CRISPR, which is currently used for a forward genetic screen.
In a complimentary approach, we performed an overexpression screen on Rab-GTPases and identified novel subsets of micronemes (Kremer et al., PLOS Pathogens 2013) and characterised other trafficking factors, such as Syntaxins (see Jackson et al., 2013), Clathrin (see Pieperhoff et al., 2014) or Dynamins (Melatti et al., accepted).
In the course of this project our attention also shifted towards the molecular motors involved in vesicular transport and found that parasite F-actin is important for material exchange between parasites within a parasitophorous vacuole (Periz et al., eLIFE 2017).
In future studies we aim to screen for drugs against some of the identified, essential trafficking factors, which we believe could lead to novel intervention strategies against these parasites, including human malaria.
obligate intracellular parasite Toxoplasma gondii, a model system for apicomplexans. These
parasites evolved a unique machinery in order to invade their host cells that is tightly linked to the
vesicular trafficking system. During invasion the parasite sequentially secretes the content of its
unique secretory organelles (micronemes and rhoptries) and employs its gliding machinery to
actively invade the host cell. The gliding machinery is tightly anchored at the Inner Membrane
Complex (IMC), which is derived from the Golgi and hence also linked to the secretory system of the
parasite. The aim of this proposal was to combine bioinformatics, biochemistry and reverse genetics to systematically analyse important trafficking factors that are required for the biogenesis, maintenance and regulation of these organelles. Our initial analysis revealed that ~150 genes are involved in this process. However, in a collaboration with Prof Joel Dacks (University of Alberta), who is an expert in evolution of endomembrane systems of eukaryotes, this candidate list significantly increased and is likely to do so in the future. In fact, we speculate that several of the identified essential “hypothetical genes” will turn out to be important for vesicular transport.
In order to characterise these genes, we developed novel reverse genetic tools, such as the DiCre
system (see Andenmatten et al., Nature Methods 2013), which has now also been established in
Plasmodium falciparum (see Collins et al., 2013). Furthermore, we adapted a novel system based on conditional cas9/CRISPR, which is currently used for a forward genetic screen.
In a complimentary approach, we performed an overexpression screen on Rab-GTPases and identified novel subsets of micronemes (Kremer et al., PLOS Pathogens 2013) and characterised other trafficking factors, such as Syntaxins (see Jackson et al., 2013), Clathrin (see Pieperhoff et al., 2014) or Dynamins (Melatti et al., accepted).
In the course of this project our attention also shifted towards the molecular motors involved in vesicular transport and found that parasite F-actin is important for material exchange between parasites within a parasitophorous vacuole (Periz et al., eLIFE 2017).
In future studies we aim to screen for drugs against some of the identified, essential trafficking factors, which we believe could lead to novel intervention strategies against these parasites, including human malaria.