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Updated: Feb 16, 2026

In Vitro Polymerization of F-actin on Early Endosomes
Published on: August 28, 2017
Vps34 and the Armus/TBC-2 Rab GAPs: Putting the brakes on the endosomal Rab5 and Rab7 GTPases
Fiona Law1,2, Christian E Rocheleau1,2
1Division of Endocrinology and Metabolism, Department of Medicine and the Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada.
Abstract:
Rab5 and Rab7 GTPases are key regulators of endosome maturation and lysosome fusion. They activate the class III phosphoinositide 3-kinase (PI3K) Vps34 to generate pools of phosphatidylinositol-3 phosphate [PI(3)P] on endosomes. Together PI(3)P and the GTP-bound Rabs coordinate the recruitment of endosomal regulators to drive early to late endosome maturation and ultimately lysosome fusion. Counterintuitively, loss of Vps34 results in enlarged endosomes, like those seen from expressing activated Rab GTPases. Two recent papers in the Journal of Cell Science, Jaber et al., 2016 and Law, Seo et al., 2017, demonstrate that a function of Vps34 is to inactive the Rab5 and Rab7 GTPases via recruitment of the TBC1D2 family of Rab GTPase Activating Proteins (GAPs).
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