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Identification of novel membrane-binding domains in multiple yeast Cdc42 effectors.

The Rho-type GTPase Cdc42 is a central regulator of eukaryotic cell polarity and signal transduction. In budding yeast, Cdc42 regulates polarity and mitogen-activated protein (MAP) kinase signaling in part through the PAK-family kinase Ste20. Activation of Ste20 requires a Cdc42/Rac interactive binding (CRIB) domain, which mediates its recruitment to membrane-associated Cdc42. Here, we identify a separate domain in Ste20 that interacts directly with membrane phospholipids and is critical for its function. This short region, termed the basic-rich (BR) domain, can target green fluorescent protein to the plasma membrane in vivo and binds PIP(2)-containing liposomes in vitro. Mutation of basic or hydrophobic residues in the BR domain abolishes polarized localization of Ste20 and its function in both MAP kinase-dependent and independent pathways. Thus, Cdc42 binding is required but is insufficient; instead, direct membrane binding by Ste20 is also required. Nevertheless, phospholipid specificity is not essential in vivo, because the BR domain can be replaced with several heterologous lipid-binding domains of varying lipid preferences. We also identify functionally important BR domains in two other yeast Cdc42 effectors, Gic1 and Gic2, suggesting that cooperation between protein-protein and protein-membrane interactions is a prevalent mechanism during Cdc42-regulated signaling and perhaps for other dynamic localization events at the cell cortex.

Pubmed ID: 17914055

Authors

  • Takahashi S
  • Pryciak PM

Journal

Molecular biology of the cell

Publication Data

December 28, 2007

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM57769
  • Agency: NIGMS NIH HHS, Id: R01 GM057769

Mesh Terms

  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Binding Sites
  • Carrier Proteins
  • Cell Membrane
  • Hydrophobic and Hydrophilic Interactions
  • Intracellular Signaling Peptides and Proteins
  • MAP Kinase Kinase Kinases
  • Molecular Sequence Data
  • Protein Binding
  • Protein-Serine-Threonine Kinases
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • cdc42 GTP-Binding Protein