Deutsch
    Lehrstuhl für Zell- und Entwicklungsbiologie

    We found that trypanosomes recycle their plasma membrane with unprecedented speed through a tiny invagination of the cell surface called flagellar pocket. Unlike most eucaryotes the parasites endocytose exclusively via clathrin-coated vesicles. Our aim is to provide a molecular blueprint of the highly efficient trypanosome membrane recycling machinery.

    T. brucei internalizes all membrane via clathrin-coated vesicles. The endocytosed membrane along with fluid cargo is transported with bi-phasic kinetics via early endosomes to recycling endosomes. Strikingly, the Rab11-positive recycling endosomes are the place of VSG sorting: small clathrin-coated vesicles bud from extended, fenestrated structures, carrying the cargo via late endosomes to the single lysosomes. These vesicles are devoid of VSG. Thus, by a negative mechanism, i.e. the subtraction of membrane in the form of clathrin-vesicles, the GPI-anchored protein is passively (i.e by default) concentrated in recycling endosomes. This novel mechanism differs to models postulated for the mechanism of sorting of GPI-proteins. Interestingly, the recycling endosomes that carry the increasingly concentrated VSG, eventually give rise to small, disk-shaped carriers that fuse with the flagellar pocket. These Rab11-positive exocytic carriers (EXCs) are abundantly found within the cell and were the first example for an endosome-derived structure fusing with the plasma membrane in any eukaryote.


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