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Updated: May 4, 2026

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Published on: August 28, 2017
The ancient small GTPase Rab21 functions in intermediate endocytic steps in trypanosomes
Moazzam Ali1, Ka Fai Leung, Mark C Field
1Department of Pathology, University of Cambridge, Cambridge, United Kingdom.
African trypanosome Rab21 protein is essential for cell division and lysosomal traffic. Its function is linked to the endosomal sorting complex required for transport (ESCRT) system, suggesting a conserved role in endocytosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Parasitology
Background:
- Endocytosis is a fundamental cellular process conserved across eukaryotes.
- African trypanosomes (Trypanosoma brucei) utilize exclusively clathrin-mediated endocytosis, with unique features.
- Rab GTPases are key regulators of vesicular transport, including endocytosis.
Purpose of the Study:
- To investigate the role of Trypanosoma brucei Rab21 (TbRab21) in endocytosis and cellular processes.
- To determine the localization and functional interactions of TbRab21 within the trypanosome endocytic pathway.
Main Methods:
- Immunofluorescence microscopy to determine TbRab21 localization.
- RNA interference (RNAi) to knockdown TbRab21 and ESCRT components.
- Analysis of protein expression and localization following knockdown.
Main Results:
- TbRab21 localizes to endosomes, partially overlapping with Rab5A, Rab28, and Vps23.
- TbRab21 is essential for Trypanosoma brucei proliferation and lysosomal trafficking.
- TbRab21 knockdown affects ESCRT component and TbRab28 expression, while Vps23 knockdown affects TbRab21 expression.
Conclusions:
- TbRab21 functions downstream of TbRab5A in the endocytic pathway.
- TbRab21 interacts closely with the trypanosome endosomal sorting complex required for transport (ESCRT) machinery.
- TbRab21 plays a crucial role in regulating endosomal sorting and cellular viability in African trypanosomes.
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