title: Exo70p mediates the secretion of specific exocytic vesicles at early stages of the cell cycle for polarized cell growth.
abstract: In budding yeast, two classes of post-Golgi secretory vesicles carrying different sets of cargoes typified by Bgl2p and invertase are delivered to the plasma membrane for secretion. The exocyst is implicated in tethering these vesicles to the daughter cell membrane for exocytosis. In this study, we report that mutations in the exocyst component Exo70p predominantly block secretion of the Bgl2p vesicles. Furthermore, a defect in invertase vesicle trafficking caused by vps1Delta or pep12Delta in the exo70 mutant background is detrimental to the cell. The secretion defect in exo70 mutants was most pronounced during the early budding stage, which affected daughter cell growth. The selective secretion block does not occur at the vesicle formation or sorting stage because the exocytic vesicles are properly generated and protein processing is normal in the exo70 mutants. Our study suggests that Exo70p functions primarily at early stages of the cell cycle in Bgl2p vesicle secretion, which is critical for polarized cell growth.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: He
authors.forename: Fengong
authors.initials: F
authors.lastname: Xi
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Daniel
authors.initials: D
authors.lastname: TerBush
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
mesh_terms: D002453:Cell Cycle / Q000502:physiology*; D016764:Cell Polarity; D005089:Exocytosis / Q000502:physiology; D004693:Glucan Endo-1,3-beta-D-Glucosidase / Q000378:metabolism; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D022142:Secretory Vesicles / Q000502:physiology*; D033921:Vesicular Transport Proteins; D043324:beta-Fructofuranosidase / Q000378:metabolism
chemical_list: C103132:EXO70 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D043324:beta-Fructofuranosidase; C080389:BGL2 protein, S cerevisiae; D004693:Glucan Endo-1,3-beta-D-Glucosidase