title: Membrane association and functional regulation of Sec3 by phospholipids and Cdc42.
abstract: The exocyst is an octameric protein complex implicated in tethering post-Golgi secretory vesicles at the plasma membrane in preparation for fusion. However, it is not clear how the exocyst is targeted to and physically associates with specific domains of the plasma membrane and how its functions are regulated at those regions. We demonstrate that the N terminus of the exocyst component Sec3 directly interacts with phosphatidylinositol 4,5-bisphosphate. In addition, we have identified key residues in Sec3 that are critical for its binding to the guanosine triphosphate-bound form of Cdc42. Genetic analyses indicate that the dual interactions of Sec3 with phospholipids and Cdc42 control its function in yeast cells. Disrupting these interactions not only blocks exocytosis and affects exocyst polarization but also leads to defects in cell morphogenesis. We propose that the interactions of Sec3 with phospholipids and Cdc42 play important roles in exocytosis and polarized cell growth.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Zhang
authors.forename: Kelly
authors.initials: K
authors.lastname: Orlando
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: Allison
authors.initials: A
authors.lastname: Zajac
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D005089:Exocytosis / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000032:analysis; D016297:Mutagenesis, Site-Directed; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D053778:Thiazolidines / Q000494:pharmacology; D014335:Tropomyosin / Q000235:genetics; D033921:Vesicular Transport Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002352:Carrier Proteins; C103132:EXO70 protein, S cerevisiae; C109253:GIC2 protein, S cerevisiae; D019269:Phosphatidylinositol 4,5-Diphosphate; C103130:SEC3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D053778:Thiazolidines; D014335:Tropomyosin; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; C037068:latrunculin B