title: The synaptobrevin homologue Snc2p recruits the exocyst to secretory vesicles by binding to Sec6p.
abstract: A screen for mutations that affect the recruitment of the exocyst to secretory vesicles identified genes encoding clathrin and proteins that associate or colocalize with clathrin at sites of endocytosis. However, no significant colocalization of the exocyst with clathrin was seen, arguing against a direct role in exocyst recruitment. Rather, these components are needed to recycle the exocytic vesicle SNAREs Snc1p and Snc2p from the plasma membrane into new secretory vesicles where they act to recruit the exocyst. We observe a direct interaction between the exocyst subunit Sec6p and the latter half of the SNARE motif of Snc2p. An snc2 mutation that specifically disrupts this interaction led to exocyst mislocalization and a block in exocytosis in vivo without affecting liposome fusion in vitro. Overexpression of Sec4p partially suppressed the exocyst localization defects of mutations in clathrin and clathrin-associated components. We propose that the exocyst is recruited to secretory vesicles by the combinatorial signals of Sec4-GTP and the Snc proteins. This could help to confer both specificity and directionality to vesicular traffic.
authors.affiliation: Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: David
authors.initials: D
authors.lastname: Shen
authors.forename: Hua
authors.initials: H
authors.lastname: Yuan
authors.forename: Alex
authors.initials: A
authors.lastname: Hutagalung
authors.forename: Avani
authors.initials: A
authors.lastname: Verma
authors.forename: Daniel
authors.initials: D
authors.lastname: Kümmel
authors.forename: Xudong
authors.initials: X
authors.lastname: Wu
authors.forename: Karin
authors.initials: K
authors.lastname: Reinisch
authors.forename: James A
authors.initials: JA
authors.lastname: McNew
authors.forename: Peter
authors.initials: P
authors.lastname: Novick
mesh_terms: D001665:Binding Sites; D005089:Exocytosis; D011485:Protein Binding; D050683:R-SNARE Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D050683:R-SNARE Proteins; C490684:SEC6 protein, S cerevisiae; C083242:SNC2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
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