title: Role of Cdc42-Cla4 interaction in the pheromone response of Saccharomyces cerevisiae.
abstract: In Saccharomyces cerevisiae, the highly conserved Rho-type GTPase Cdc42 is essential for cell division and controls cellular development during mating and invasive growth. The role of Cdc42 in mating has been controversial, but a number of previous studies suggest that the GTPase controls the mitogen-activated protein (MAP) kinase cascade by activating the p21-activated protein kinase (PAK) Ste20. To further explore the role of Cdc42 in pheromone-stimulated signaling, we isolated novel alleles of CDC42 that confer resistance to pheromone. We find that in CDC42(V36A) and CDC42(V36A, I182T) mutant strains, the inability to undergo pheromone-induced cell cycle arrest correlates with reduced phosphorylation of the mating MAP kinases Fus3 and Kss1 and with a decrease in mating efficiency. Furthermore, Cdc42(V36A) and Cdc42(V36A, I182T) proteins show reduced interaction with the PAK Cla4 but not with Ste20. We also show that deletion of CLA4 in a CDC42(V36A, I182T) mutant strain suppresses pheromone resistance and that overexpression of CLA4 interferes with pheromone-induced cell cycle arrest and MAP kinase phosphorylation in CDC42 wild-type strains. Our data indicate that Cla4 has the potential to act as a negative regulator of the mating pathway and that this function of the PAK might be under control of Cdc42. In conclusion, our study suggests that control of pheromone signaling by Cdc42 not only depends on Ste20 but also involves interaction of the GTPase with Cla4.
authors.affiliation: Department of Biology, Molecular Genetics, Philipps University, D-35032 Marburg, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Heinrich
authors.forename: Tim
authors.initials: T
authors.lastname: Köhler
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Mösch
mesh_terms: D002453:Cell Cycle; D025141:Drug Resistance, Fungal; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D020935:MAP Kinase Signaling System / Q000187:drug effects; D000072235:Mating Factor; D020928:Mitogen-Activated Protein Kinases; D010455:Peptides; D010675:Pheromones / Q000494:pharmacology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D001616:beta-Galactosidase / Q000378:metabolism; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D010455:Peptides; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; D000072235:Mating Factor; C105722:SKM1 protein, S cerevisiae; C095212:CLA4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D001616:beta-Galactosidase; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae