Abstract
All endo- and exocytosis in the African trypanosome Trypanosoma brucei occurs at a single subdomain of the plasma membrane. This subdomain, the flagellar pocket, is a small vase-shaped invagination containing the root of the cell’s single flagellum. Several cytoskeleton-associated multiprotein complexes are coiled around the neck of the flagellar pocket on its cytoplasmic face. One of these, the hook complex, may affect macromolecule entry into the flagellar pocket lumen. In previous work, knockdown of the hook complex component TbMORN1 resulted in larger cargo being unable to enter the flagellar pocket. In this study, the hook complex component TbSmee1 was characterised in bloodstream form Trypanosoma brucei and was found to be essential for cell viability. TbSmee1 knockdown resulted in flagellar pocket enlargement, and impaired access to the pocket membrane by surface-bound cargo. Inhibition of endocytosis by knockdown of clathrin phenocopied TbSmee1 knockdown, suggesting that endocytic activity itself is a prerequisite for the entry of surface-bound cargo into the flagellar pocket.
Summary Characterisation of the essential trypanosome protein TbSmee1 suggests that endocytosis is required for flagellar pocket access of surface-bound cargo
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
↵3 Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, Vienna Biocenter (VBC) Vienna, Austria
↵4 Francisco de Vitoria University, Madrid, Spain
↵5 Department of Structural and Computational Biology, Max Perutz Labs, University of Vienna, Vienna Biocenter (VBC), Vienna, Austria
↵6 Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
↵7 Center for Medical Biochemistry, Max Perutz Labs, Medical University of Vienna, Vienna Biocenter (VBC) Vienna, Austria