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Stable endocytic structures navigate the complex pellicle of apicomplexan parasites
Ludek Koreny1, Brandon N Mercado-Saavedra1, Christen M Klinger2
1Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK.
Nature Communications
|April 15, 2023
Summary
Apicomplexan parasites use unique, fixed endocytic structures called micropores for plasma membrane maintenance, not nutrition. These ancient structures, conserved across species like those causing malaria, evolved early in Alveolata.
Area of Science:
- Cell biology
- Parasitology
- Eukaryotic evolution
Background:
- Apicomplexan parasites significantly impact human health, yet their fundamental cellular processes, including endocytosis, remain poorly understood.
- Key questions persist regarding the location, conservation, and function of endocytosis within this diverse phylum.
Purpose of the Study:
- To investigate the molecular composition and behavior of endocytic structures in the apicomplexan model *Toxoplasma*.
- To determine the conserved nature and evolutionary origins of these structures within the Apicomplexa.
- To elucidate the primary functions of endocytosis in *Toxoplasma*.
Main Methods:
- Utilized *Toxoplasma* as a model organism to study endocytosis.
- Characterized the molecular makeup and dynamics of fixed endocytic protein complexes.
- Compared these structures with known endocytic machinery in other eukaryotes.
Main Results:
- Identified unusual, stable endocytic protein complexes in *Toxoplasma*, contrasting with dynamic machinery in other eukaryotes.
- Correlated these structures with the 'micropore' observed across Apicomplexa.
- Found conserved molecular adaptations, including the kelch-domain protein K13 (linked to malaria drug resistance).
- Determined that endocytosis in *Toxoplasma* primarily serves plasma membrane homeostasis, not nutrition.
Conclusions:
- Specialized, fixed endocytic structures (micropores) are a conserved feature of Apicomplexa.
- These structures likely originated early in infrakingdom Alveolata, possibly as an adaptation to the complex pellicle.
- The primary role of endocytosis in *Toxoplasma* is maintaining plasma membrane integrity.
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