The HOPS/class C Vps complex tethers membranes by binding to one Rab GTPase in each apposed membrane

Article
Authors:Ho, Ruoya, Department of Molecular Phys and Biological PhysicsUniversity of Virginia Stroupe, Christopher, Department of Molecular Phys and Biological PhysicsUniversity of Virginia
Abstract:

Many Rab GTPase effectors are membrane-tethering factors, that is, they physically link two apposed membranes before intracellular membrane fusion. In this study, we investigate the distinct binding factors needed on apposed membranes for Rab effector– dependent tethering. We show that the homotypic fusion and protein-sorting/class C vacuole protein-sorting (HOPS/class C Vps) complex can tether low-curvature membranes, that is, liposomes with a diameter of ∼100 nm, only when the yeast vacuolar Rab GTPase Ypt7p is present in both tethered membranes. When HOPS is phosphorylated by the vacuolar casein kinase I, Yck3p, tethering only takes place when GTP-bound Ypt7p is present in both tethered membranes. When HOPS is not phosphorylated, however, its tethering activity shows little specificity for the nucleotide-binding state of Ypt7p. These results suggest a model for HOPS-mediated tethering in which HOPS tethers membranes by binding to Ypt7p in each of the two tethered membranes. Moreover, because vacuole-associated HOPS is presumably phosphorylated by Yck3p, our results suggest that nucleotide exchange of Ypt7p on multivesicular bodies (MVBs)/late endosomes must take place before HOPS can mediate tethering at vacuoles.

Keywords:
Rab effector–dependent tethering, HOPS/class C Vps complex tethers, membrane fusio
Rights:
All rights reserved (no additional license for public reuse)
Language:
English
Source Citation:

Ho, Ruoya, and Christopher Stroupe. "The HOPS/class C Vps complex tethers membranes by binding to one Rab GTPase in each apposed membrane." Molecular Biology of the Cell 26.14 (2015): 2655-2663. Available: ["http://doi.org/10.1091/mbc.E14-04-0922"].

Publisher:
American Society for Cell Biology
Published Date:
2015