title: Homotypic vacuole fusion in yeast requires organelle acidification and not the V-ATPase membrane domain.
abstract: Studies of homotypic vacuole-vacuole fusion in the yeast Saccharomyces cerevisiae have been instrumental in determining the cellular machinery required for eukaryotic membrane fusion and have implicated the vacuolar H(+)-ATPase (V-ATPase). The V-ATPase is a multisubunit, rotary proton pump whose precise role in homotypic fusion is controversial. Models formulated from in vitro studies suggest that it is the proteolipid proton-translocating pore of the V-ATPase that functions in fusion, with further studies in worms, flies, zebrafish, and mice appearing to support this model. We present two in vivo assays and use a mutant V-ATPase subunit to establish that it is the H(+)-translocation/vacuole acidification function, rather than the physical presence of the V-ATPase, that promotes homotypic vacuole fusion in yeast. Furthermore, we show that acidification of the yeast vacuole in the absence of the V-ATPase rescues vacuole-fusion defects. Our results clarify the in vivo requirements of acidification for membrane fusion.
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Coonrod
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Graham
authors.forename: Lindsay N
authors.initials: LN
authors.lastname: Carpp
authors.forename: Tom M
authors.initials: TM
authors.lastname: Carr
authors.forename: Laura
authors.initials: L
authors.lastname: Stirrat
authors.forename: Katherine
authors.initials: K
authors.lastname: Bowers
authors.forename: Nia J
authors.initials: NJ
authors.lastname: Bryant
authors.forename: Tom H
authors.initials: TH
authors.lastname: Stevens
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D043564:Inorganic Pyrophosphatase / Q000378:metabolism*; D008561:Membrane Fusion / Q000502:physiology*; D051379:Mice; D009154:Mutation / Q000235:genetics; D017494:Proton Pumps; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D017494:Proton Pumps; D025262:Vacuolar Proton-Translocating ATPases; C505048:AVP1 protein, Arabidopsis; D043564:Inorganic Pyrophosphatase