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Full-Text Articles in Medical Biochemistry
Interdependent Assembly Of Specific Regulatory Lipids And Membrane Fusion Proteins Into The Vertex Ring Domain Of Docked Vacuoles, Rutilio A. Fratti, Youngsoo Jun, Alexey J. Merz, Nathan Margolis, William Wickner
Interdependent Assembly Of Specific Regulatory Lipids And Membrane Fusion Proteins Into The Vertex Ring Domain Of Docked Vacuoles, Rutilio A. Fratti, Youngsoo Jun, Alexey J. Merz, Nathan Margolis, William Wickner
Dartmouth Scholarship
Membrane microdomains are assembled by lipid partitioning (e.g., rafts) or by protein-protein interactions (e.g., coated vesicles). During docking, yeast vacuoles assemble "vertex" ring-shaped microdomains around the periphery of their apposed membranes. Vertices are selectively enriched in the Rab GTPase Ypt7p, the homotypic fusion and vacuole protein sorting complex (HOPS)-VpsC Rab effector complex, SNAREs, and actin. Membrane fusion initiates at vertex microdomains. We now find that the "regulatory lipids" ergosterol, diacylglycerol and 3- and 4-phosphoinositides accumulate at vertices in a mutually interdependent manner. Regulatory lipids are also required for the vertex enrichment of SNAREs, Ypt7p, and HOPS. Conversely, SNAREs and actin …
Trans-Snare Interactions Elicit Ca2+ Efflux From The Yeast Vacuole Lumen, Alexey J. Merz, William T. Wickner
Trans-Snare Interactions Elicit Ca2+ Efflux From The Yeast Vacuole Lumen, Alexey J. Merz, William T. Wickner
Dartmouth Scholarship
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 …