title: Distinct contributions of vacuolar Qabc- and R-SNARE proteins to membrane fusion specificity.
abstract: In eukaryotic endomembrane systems, Qabc-SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) on one membrane and R-SNARE on the opposing membrane assemble into a trans-QabcR-SNARE complex to drive membrane fusion. However, it remains ambiguous whether pairing of Qabc- and R-SNAREs mediates membrane fusion specificity. Here, we explored the fusion specificity of reconstituted proteoliposomes bearing purified SNAREs in yeast vacuoles and other organelles. We found that not only vacuolar R-SNARE Nyv1p but also the non-cognate R-SNAREs, endosomal Snc2p, and endoplasmic reticulum-Golgi Sec22p caused efficient fusion with vacuolar Qabc-SNAREs. In contrast, their fusion is blocked completely by replacing vacuolar Qc-SNARE Vam7p with the non-cognate endosomal Tlg1p and Syn8p, although these endosomal Qc-SNAREs fully retained the ability to form cis-SNARE complexes with vacuolar SNAREs in solution and on membranes. Thus, our current study establishes that an appropriate assembly of Qabc-SNAREs is crucial for regulating fusion specificity, whereas R-SNARE itself has little contribution to specificity.
authors.affiliation: Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Izawa
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Onoue
authors.forename: Noriko
authors.initials: N
authors.lastname: Furukawa
authors.forename: Joji
authors.initials: J
authors.lastname: Mima
mesh_terms: D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D011992:Endosomes / Q000235:genetics / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D008561:Membrane Fusion / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D050683:R-SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D050683:R-SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D050825:Synaptosomal-Associated Protein 25; C503584:Tlg1 protein, S cerevisiae; C494205:VAM7 protein, S cerevisiae