title: Regulation of exocytosis by the exocyst subunit Sec6 and the SM protein Sec1.
abstract: Trafficking of protein and lipid cargo through the secretory pathway in eukaryotic cells is mediated by membrane-bound vesicles. Secretory vesicle targeting and fusion require a conserved multisubunit protein complex termed the exocyst, which has been implicated in specific tethering of vesicles to sites of polarized exocytosis. The exocyst is directly involved in regulating soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor (SNARE) complexes and membrane fusion through interactions between the Sec6 subunit and the plasma membrane SNARE protein Sec9. Here we show another facet of Sec6 function-it directly binds Sec1, another SNARE regulator, but of the Sec1/Munc18 family. The Sec6-Sec1 interaction is exclusive of Sec6-Sec9 but compatible with Sec6-exocyst assembly. In contrast, the Sec6-exocyst interaction is incompatible with Sec6-Sec9. Therefore, upon vesicle arrival, Sec6 is proposed to release Sec9 in favor of Sec6-exocyst assembly and to simultaneously recruit Sec1 to sites of secretion for coordinated SNARE complex formation and membrane fusion.
authors: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors: Francesca
authors: F
authors: Morgera
authors: Margaret R
authors: MR
authors: Sallah
authors: Michelle L
authors: ML
authors: Dubuke
authors: Pallavi
authors: P
authors: Gandhi
authors: Daniel N
authors: DN
authors: Brewer
authors: Chavela M
authors: CM
authors: Carr
authors: Mary
authors: M
authors: Munson
mesh_terms: D005089:Exocytosis; D008561:Membrane Fusion; D051938:Munc18 Proteins / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D051938:Munc18 Proteins; D021122:Protein Subunits; D050767:Qc-SNARE Proteins; C497931:SEC1 protein, S cerevisiae; C490684:SEC6 protein, S cerevisiae; C090117:SEC9 protein, S cerevisiae; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins