title: Organelle size control - increasing vacuole content activates SNAREs to augment organelle volume through homotypic fusion.
abstract: Cells control the size of their compartments relative to cell volume, but there is also size control within each organelle. Yeast vacuoles neither burst nor do they collapse into a ruffled morphology, indicating that the volume of the organellar envelope is adjusted to the amount of content. It is poorly understood how this adjustment is achieved. We show that the accumulating content of yeast vacuoles activates fusion of other vacuoles, thus increasing the volume-to-surface ratio. Synthesis of the dominant compound stored inside vacuoles, polyphosphate, stimulates binding of the chaperone Sec18/NSF to vacuolar SNAREs, which activates them and triggers fusion. SNAREs can only be activated by lumenal, not cytosolic, polyphosphate (polyP). Control of lumenal polyP over SNARE activation in the cytosol requires the cytosolic cyclin-dependent kinase Pho80-Pho85 and the R-SNARE Nyv1. These results suggest that cells can adapt the volume of vacuoles to their content through feedback from the vacuole lumen to the SNAREs on the cytosolic surface of the organelle.
authors.affiliation: Département de Biochimie, Université de Lausanne, Chemin des Boveresses 155, Epalinges 1066, Switzerland.
authors.forename: Yann
authors.initials: Y
authors.lastname: Desfougères
authors.affiliation: GZMB, Institut für Molekulare Strukturbiologie, Georg-August-Universität Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
authors.forename: Heinz
authors.initials: H
authors.lastname: Neumann
authors.affiliation: Département de Biochimie, Université de Lausanne, Chemin des Boveresses 155, Epalinges 1066, Switzerland andreas.mayer@unil.ch.
authors.forename: Andreas
authors.identifier: 0000-0001-6131-313X
authors.initials: A
authors.lastname: Mayer
mesh_terms: D003600:Cytosol / Q000378:metabolism; D008561:Membrane Fusion; D008954:Models, Biological; D053141:Organelle Size; D011122:Polyphosphates / Q000378:metabolism; D011485:Protein Binding; D050600:SNARE Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D011122:Polyphosphates; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
keywords: Lysosome; Membrane fusion; Organelle size; Polyphosphate; SNAREs; Vacuole