Membrane association and functional regulation of Sec3 by phospholipids and Cdc42

J Cell Biol. 2008 Jan 14;180(1):145-58. doi: 10.1083/jcb.200704128.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Adaptor Proteins, Signal Transducing
  • Binding Sites
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Cell Membrane / metabolism*
  • Cell Membrane / ultrastructure
  • Exocytosis / physiology
  • Green Fluorescent Proteins / analysis
  • Mutagenesis, Site-Directed
  • Phosphatidylinositol 4,5-Diphosphate / metabolism*
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Saccharomyces cerevisiae Proteins / physiology
  • Thiazolidines / pharmacology
  • Tropomyosin / genetics
  • Vesicular Transport Proteins
  • cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / metabolism*

Substances

  • Actins
  • Adaptor Proteins, Signal Transducing
  • Bridged Bicyclo Compounds, Heterocyclic
  • Carrier Proteins
  • EXO70 protein, S cerevisiae
  • GIC2 protein, S cerevisiae
  • Phosphatidylinositol 4,5-Diphosphate
  • SEC3 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Thiazolidines
  • Tropomyosin
  • Vesicular Transport Proteins
  • Green Fluorescent Proteins
  • cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
  • latrunculin B