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  • Phosphorylation of a membrane curvature-sensing motif switches function of the HOPS subunit Vps41 in membrane tethering.

Phosphorylation of a membrane curvature-sensing motif switches function of the HOPS subunit Vps41 in membrane tethering.

The Journal of cell biology (2010-11-17)
Margarita Cabrera, Lars Langemeyer, Muriel Mari, Ralf Rethmeier, Ioan Orban, Angela Perz, Cornelia Bröcker, Janice Griffith, Daniel Klose, Heinz-Jürgen Steinhoff, Fulvio Reggiori, Siegfried Engelbrecht-Vandré, Christian Ungermann
ABSTRACT

Tethering factors are organelle-specific multisubunit protein complexes that identify, along with Rab guanosine triphosphatases, transport vesicles and trigger their SNARE-mediated fusion of specific transport vesicles with the target membranes. Little is known about how tethering factors discriminate between different trafficking pathways, which may converge at the same organelle. In this paper, we describe a phosphorylation-based switch mechanism, which allows the homotypic vacuole fusion protein sorting effector subunit Vps41 to operate in two distinct fusion events, namely endosome-vacuole and AP-3 vesicle-vacuole fusion. Vps41 contains an amphipathic lipid-packing sensor (ALPS) motif, which recognizes highly curved membranes. At endosomes, this motif is inserted into the lipid bilayer and masks the binding motif for the δ subunit of the AP-3 complex, Apl5, without affecting the Vps41 function in endosome-vacuole fusion. At the much less curved vacuole, the ALPS motif becomes available for phosphorylation by the resident casein kinase Yck3. As a result, the Apl5-binding site is exposed and allows AP-3 vesicles to bind to Vps41, followed by specific fusion with the vacuolar membrane. This multifunctional tethering factor thus discriminates between trafficking routes by switching from a curvature-sensing to a coat recognition mode upon phosphorylation.

MATERIALS
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Brand
Product Description

Sigma-Aldrich
IGEPAL® CA-630, for molecular biology
Sigma-Aldrich
IGEPAL® CA-630, viscous liquid
Supelco
IGEPAL® CA-630
Sigma-Aldrich
Ergosterol, ≥75%