Remodeling of organelle-bound actin is required for yeast vacuole fusion.
Actin participates in several intracellular trafficking pathways. We now find that actin, bound to the surface of purified yeast vacuoles in the absence of cytosol or cytoskeleton, regulates the last compartment mixing stage of homotypic vacuole fusion. The Cdc42p GTPase is known to be required for vacuole fusion. We now show that proteins of the Cdc42p-regulated actin remodeling cascade (Cdc42p --> Cla4p --> Las17p/Vrp1p --> Arp2/3 complex --> actin) are enriched on isolated vacuoles. Vacuole fusion is dramatically altered by perturbation of the vacuole-bound actin, either by mutation of the ACT1 gene, addition of specific actin ligands such as latrunculin B or jasplakinolide, antibody to the actin regulatory proteins Las17p (yeast Wiskott-Aldrich syndrome protein) or Arp2/3, or deletion of actin regulatory genes. On docked vacuoles, actin is enriched at the "vertex ring" membrane microdomain where fusion occurs and is required for the terminal steps leading to membrane fusion. This role for actin may extend to other trafficking systems.
Eitzen
Gary
G
Department of Biochemistry, Dartmouth Medical School, 7200 Vail Building, Hanover, NH 03755-3844, USA.
Wang
Li
L
Thorngren
Naomi
N
Wickner
William
W
D000199:Actins / Q000235:genetics / Q000502:physiology*; D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D047630:Depsipeptides; D005656:Fungal Proteins / Q000276:immunology; D008024:Ligands; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology*; D021962:Membrane Microdomains / Q000378:metabolism; D009154:Mutation; D010456:Peptides, Cyclic / Q000494:pharmacology; D011485:Protein Binding; D029701:Saccharomyces cerevisiae Proteins; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D015534:Trans-Activators / Q000235:genetics; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; D014617:Vacuoles / Q000502:physiology*; D051316:Wiskott-Aldrich Syndrome Protein; D015003:Yeasts; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000378:metabolism*
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D047630:Depsipeptides; D005656:Fungal Proteins; C480361:LAS17 protein, S cerevisiae; D008024:Ligands; D010456:Peptides, Cyclic; D029701:Saccharomyces cerevisiae Proteins; C414202:TRAF3IP2 protein, human; D013844:Thiazoles; D053778:Thiazolidines; D015534:Trans-Activators; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; D051316:Wiskott-Aldrich Syndrome Protein; C057531:jasplakinolide; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; C037068:latrunculin B