title: Trans-SNARE interactions elicit Ca2+ efflux from the yeast vacuole lumen.
abstract: Ca2+ transients trigger many SNARE-dependent membrane fusion events. The homotypic fusion of yeast vacuoles occurs after a release of lumenal Ca2+. Here, we show that trans-SNARE interactions promote the release of Ca2+ from the vacuole lumen. Ypt7p-GTP, the Sec1p/Munc18-protein Vps33p, and Rho GTPases, all of which function during docking, are required for Ca2+ release. Inhibitors of SNARE function prevent Ca2+ release. Recombinant Vam7p, a soluble Q-SNARE, stimulates Ca2+ release. Vacuoles lacking either of two complementary SNAREs, Vam3p or Nyv1p, fail to release Ca2+ upon tethering. Mixing these two vacuole populations together allows Vam3p and Nyv1p to interact in trans and rescues Ca2+ release. Sec17/18p promote sustained Ca2+ release by recycling SNAREs (and perhaps other limiting factors), but are not required at the release step itself. We conclude that trans-SNARE assembly events during docking promote Ca2+ release from the vacuole lumen.
authors.affiliation: Dept. of Biochemistry, 7200 Vail Bldg., Dartmouth Medical School, Hanover, NH 03755-3844, USA.
authors.forename: Alexey J
authors.initials: AJ
authors.lastname: Merz
authors.forename: William T
authors.initials: WT
authors.lastname: Wickner
mesh_terms: D002118:Calcium / Q000378:metabolism*; D007700:Kinetics; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D050600:SNARE Proteins; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25; D014617:Vacuoles / Q000502:physiology*; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins; D002118:Calcium