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Visualizing Intracellular SNARE Trafficking by Fluorescence Lifetime Imaging Microscopy
Published on: December 29, 2017
HOPS initiates vacuole docking by tethering membranes before trans-SNARE complex assembly
Christopher M Hickey1, William Wickner
1Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, USA.
Molecular Biology of the Cell
|May 14, 2010
Summary
The homotypic fusion and vacuole protein sorting (HOPS) complex directly tethers membranes during vacuole fusion. Rab proteins and lipids support HOPS membrane association, facilitating subsequent fusion steps.
Area of Science:
- Cell Biology
- Molecular Biology
- Membrane Trafficking
Background:
- Vacuole homotypic fusion is essential for cellular function and requires numerous purified protein components.
- The precise roles of individual components, particularly the homotypic fusion and vacuole protein sorting (HOPS) complex, in the fusion process remain incompletely understood.
Purpose of the Study:
- To elucidate the direct role of the HOPS complex in the early stages of vacuole homotypic fusion, specifically membrane tethering.
- To determine how other factors, including Rab proteins and lipids, contribute to HOPS-mediated tethering and subsequent fusion.
Main Methods:
- Reconstitution of vacuole homotypic fusion using purified components including lipids, SNAREs, Sec17p, Sec18p, Ypt7p (Rab), and the HOPS complex.
- Analysis of proteoliposome clustering and fusion subreactions to identify the direct tethering agent.
Main Results:
- The HOPS complex was identified as the direct mediator of membrane tethering during vacuole fusion.
- Rab proteins and vacuolar lipids were shown to support the membrane association of HOPS, thereby contributing to tethering.
- HOPS-mediated tethering indirectly promotes trans-SNARE complex formation, which is further stabilized by SNAREs and protected from disassembly by Sec17p/Sec18p.
Conclusions:
- HOPS acts as the primary tethering factor in vacuole homotypic fusion.
- The study clarifies the sequential roles of HOPS, Rab proteins, lipids, and SNAREs in achieving membrane fusion.
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