title: Identification of novel membrane-binding domains in multiple yeast Cdc42 effectors.
abstract: 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.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Satoe
authors.initials: S
authors.lastname: Takahashi
authors.forename: Peter M
authors.initials: PM
authors.lastname: Pryciak
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D008969:Molecular Sequence Data; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C109252:GIC1 protein, S cerevisiae; C109253:GIC2 protein, S cerevisiae; D047908:Intracellular Signaling Peptides and Proteins; D029701:Saccharomyces cerevisiae Proteins; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D020764:cdc42 GTP-Binding Protein