title: Yeast homotypic vacuole fusion requires the Ccz1-Mon1 complex during the tethering/docking stage.
abstract: The function of the yeast lysosome/vacuole is critically linked with the morphology of the organelle. Accordingly, highly regulated processes control vacuolar fission and fusion events. Analysis of homotypic vacuole fusion demonstrated that vacuoles from strains defective in the CCZ1 and MON1 genes could not fuse. Morphological evidence suggested that these mutant vacuoles could not proceed to the tethering/docking stage. Ccz1 and Mon1 form a stable protein complex that binds the vacuole membrane. In the absence of the Ccz1-Mon1 complex, the integrity of vacuole SNARE pairing and the unpaired SNARE class C Vps/HOPS complex interaction were both impaired. The Ccz1-Mon1 complex colocalized with other fusion components on the vacuole as part of the cis-SNARE complex, and the association of the Ccz1-Mon1 complex with the vacuole appeared to be regulated by the class C Vps/HOPS complex proteins. Accordingly, we propose that the Ccz1-Mon1 complex is critical for the Ypt7-dependent tethering/docking stage leading to the formation of a trans-SNARE complex and subsequent vacuole fusion.
authors.affiliation: Life Sciences Institute, Department of Molecular, Cellular and Developmental Biology and Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-2216, USA.
authors.forename: Chao-Wen
authors.initials: CW
authors.lastname: Wang
authors.forename: Per E
authors.initials: PE
authors.lastname: Stromhaug
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Kauffman
authors.forename: Lois S
authors.initials: LS
authors.lastname: Weisman
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Klionsky
mesh_terms: D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D046911:Macromolecular Substances; D008561:Membrane Fusion / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050600:SNARE Proteins; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; C441960:Ccz1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D046911:Macromolecular Substances; D008565:Membrane Proteins; C470635:Mon1 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C079005:YPT7 protein, S cerevisiae; D020691:rab GTP-Binding Proteins