title: Membrane targeting of the yeast exocyst complex.
abstract: The exocytosis is a process of fusion of secretory vesicles with plasma membrane, which plays a prominent role in many crucial cellular processes, e.g. secretion of neurotransmitters, cytokinesis or yeast budding. Prior to the SNARE-mediated fusion, the initial contact of secretory vesicle with the target membrane is mediated by an evolutionary conserved vesicle tethering protein complex, the exocyst. In all eukaryotic cells, the exocyst is composed of eight subunits - Sec5, Sec6, Sec8, Sec10, Sec15, Exo84 and two membrane-targeting landmark subunits Sec3 and Exo70, which have been described to directly interact with phosphatidylinositol (4,5)-bisphosphate (PIP2) of the plasma membrane. In this work, we utilized coarse-grained molecular dynamics simulations to elucidate structural details of the interaction of yeast Sec3p and Exo70p with lipid bilayers containing PIP2. We found that PIP2 is coordinated by the positively charged pocket of N-terminal part of Sec3p, which folds into unique Pleckstrin homology domain. Conversely, Exo70p interacts with the lipid bilayer by several binding sites distributed along the structure of this exocyst subunit. Moreover, we observed that the interaction of Exo70p with the membrane causes clustering of PIP2 in the adjacent leaflet. We further revealed that PIP2 is required for the correct positioning of small GTPase Rho1p, a direct Sec3p interactor, prior to the formation of the functional Rho1p-exocyst-membrane assembly. Our results show the critical importance of the plasma membrane pool of PIP2 for the exocyst function and suggest that specific interaction with acidic phospholipids represents an ancestral mechanism for the exocyst regulation.
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02 Prague, Czech Republic; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague, Czech Republic. Electronic address: pleskot@ueb.cas.cz.
authors.forename: Roman
authors.initials: R
authors.lastname: Pleskot
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague, Czech Republic; J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague, Czech Republic.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Cwiklik
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague, Czech Republic; Department of Physics, Tampere University of Technology, FI-33101 Tampere, Finland.
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02 Prague, Czech Republic; Department of Experimental Plant Biology, Charles University in Prague, 128 44 Prague, Czech Republic.
authors.forename: Viktor
authors.initials: V
authors.lastname: Žárský
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02 Prague, Czech Republic. Electronic address: potocky@ueb.cas.cz.
authors.forename: Martin
authors.initials: M
authors.lastname: Potocký
mesh_terms: D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D005089:Exocytosis; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D009154:Mutation; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055571:Secretory Pathway; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: C103132:EXO70 protein, S cerevisiae; D019269:Phosphatidylinositol 4,5-Diphosphate; D021122:Protein Subunits; C103130:SEC3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C051302:RHO1 protein, S cerevisiae; D020741:rho GTP-Binding Proteins
keywords: Exo70p; Molecular dynamics simulation; Phosphatidylinositol (4,5)-bisphosphate; Rho1p; Sec3p; The exocyst complex