title: The Schizosaccharomyces pombe Cdc42p GTPase signals through Pak2p and the Mkh1p-Pek1p-Spm1p MAP kinase pathway.
abstract: The Cdc42p GTPase is involved in many aspects of growth and cell-cycle regulation, including actin cytoskeletal rearrangements and activation of signal transduction pathways. To further investigate these functions, genetic interactions were examined between Schizosaccharomyces pombe Cdc42p, its effectors Pak1p and Pak2p, and the Mkh1p-Pek1p-Spm1p signal transduction pathway, which functions in cytokinesis and cell division. Expression of a truncated version of Pak2p lacking its N-terminal autoinhibitory domain led to a growth defect that was suppressed by deltamkh1 and deltaspm1 null mutations and an elongated cell phenotype indicative of a cell division defect that was suppressed by the deltamkh1 mutation. In addition, expression of the constitutively activated cdc42G12V mutant allele led to a growth defect that was rescued by the deltapak2 and deltamkh1 mutations. The deltapak2 mutation did not suppress the growth defect conferred by plasmid expression of Mkh1p, suggesting that Pak2p functions upstream of Mkh1p in this pathway. A two-hybrid protein interaction was observed between Pak2p and Mkh1p, but not between Pak1p and Mkh1p. These results are consistent with Cdc42p interacting with Pak2p to signal through the Mkh1p-Pek1p-Spm1p pathway.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05405, USA.
authors.forename: A
authors.initials: A
authors.lastname: Merla
authors.forename: D I
authors.initials: DI
authors.lastname: Johnson
mesh_terms: D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology*; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000378:metabolism*; D048369:MAP Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008853:Microscopy; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins; D020798:Two-Hybrid System Techniques; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D054462:p21-Activated Kinases
chemical_list: D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; C085569:GAL83 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C119549:Mek1 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020930:MAP Kinase Kinase Kinases; C106762:Mkh1 protein, S pombe; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae