title: The Rho GTPase Rho3 has a direct role in exocytosis that is distinct from its role in actin polarity.
abstract: Budding yeast grow asymmetrically by the polarized delivery of proteins and lipids to specific sites on the plasma membrane. This requires the coordinated polarization of the actin cytoskeleton and the secretory apparatus. We identified Rho3 on the basis of its genetic interactions with several late-acting secretory genes. Mutational analysis of the Rho3 effector domain reveals three distinct functions in cell polarity: regulation of actin polarity, transport of exocytic vesicles from the mother cell to the bud, and docking and fusion of vesicles with the plasma membrane. We provide evidence that the vesicle delivery function of Rho3 is mediated by the unconventional myosin Myo2 and that the docking and fusion function is mediated by the exocyst component Exo70. These data suggest that Rho3 acts as a key regulator of cell polarity and exocytosis, coordinating several distinct events for delivery of proteins to specific sites on the cell surface.
authors.affiliation: Department of Cell Biology, Cell Biology, and Genetics, Weill Medical College of Cornell University, New York, New York 10021, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Adamo
authors.forename: G
authors.initials: G
authors.lastname: Rossi
authors.forename: P
authors.initials: P
authors.lastname: Brennwald
mesh_terms: D000199:Actins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D005656:Fungal Proteins / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D008854:Microscopy, Electron; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D018995:Myosin Heavy Chains; D024462:Myosin Type II; D024701:Myosin Type V; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D002352:Carrier Proteins; C103132:EXO70 protein, S cerevisiae; D005656:Fungal Proteins; C077512:MYO2 protein, S cerevisiae; C434211:MYO2 protein, S pombe; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D033921:Vesicular Transport Proteins; C489566:rho3 protein, S pombe; D024462:Myosin Type II; D024701:Myosin Type V; C064320:SEC4 protein, S cerevisiae; D018995:Myosin Heavy Chains; C074647:RHO3 protein, S cerevisiae; D020691:rab GTP-Binding Proteins; D020741:rho GTP-Binding Proteins