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Updated: Oct 12, 2025

In Vitro Polymerization of F-actin on Early Endosomes
Published on: August 28, 2017
Capping protein regulates endosomal trafficking by controlling F-actin density around endocytic vesicles and
Dawei Wang1,2, Zuodong Ye1,2, Wenjie Wei3
1City University of Hong Kong Shenzhen Research Institute, Shenzhen, China.
Abstract:
Actin filaments (F-actin) have been implicated in various steps of endosomal trafficking, and the length of F-actin is controlled by actin capping proteins, such as CapZ, which is a stable heterodimeric protein complex consisting of α and β subunits. However, the role of these capping proteins in endosomal trafficking remains elusive. Here, we found that CapZ docks to endocytic vesicles via its C-terminal actin-binding motif. CapZ knockout significantly increases the F-actin density around immature early endosomes, and this impedes fusion between these vesicles, manifested by the accumulation of small endocytic vesicles in CapZ-knockout cells. CapZ also recruits several RAB5 effectors, such as Rabaptin-5 and Rabex-5, to RAB5-positive early endosomes via its N-terminal domain, and this further activates RAB5. Collectively, our results indicate that CapZ regulates endosomal trafficking by controlling actin density around early endosomes and recruiting RAB5 effectors.
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