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The rab exchange factor Sec2p reversibly associates with the exocyst
Martina Medkova1, Y Ellen France, Jeff Coleman
1Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA.
Sec2p, a regulator of secretory vesicle transport, binds to the exocyst complex via Sec15p. This interaction is crucial for vesicle exocytosis and recycling, with mutations disrupting release and causing vesicle accumulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Interactions
Background:
- Sec4p activation by its exchange factor, Sec2p, is essential for polarized transport and exocytosis of secretory vesicles.
- A specific C-terminal region of Sec2p governs its localization, and its absence causes temperature-sensitive growth and vesicle mislocalization.
Purpose of the Study:
- To investigate the interaction between Sec2p and the exocyst complex.
- To elucidate the mechanism by which Sec2p localization regulates vesicle transport and exocytosis.
Main Methods:
- Co-immunoprecipitation assays to detect protein-protein interactions.
- Analysis of Sec2p localization in wild-type and mutant strains.
- Assessment of secretory vesicle distribution and exocytosis.
Main Results:
- Sec2p directly interacts with the exocyst subunit Sec15p on secretory vesicles.
- Mutations in Sec2p that cause mislocalization lead to increased binding to the exocyst complex.
- This interaction couples nucleotide exchange on Sec4p to effector recruitment.
Conclusions:
- Sec2p associates with the exocyst complex, specifically Sec15p, to regulate secretory vesicle transport.
- Normal Sec2p function requires its release from the exocyst after vesicle tethering to enable recycling.
- Failure to release Sec2p from Sec15p in mutants blocks this recycling pathway, leading to depolarized vesicle accumulation.
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