Genetic relationships between the G protein beta gamma complex, Ste5p, Ste20p and Cdc42p: investigation of effector roles in the yeast pheromone response pathway.
The Saccharomyces cerevisiae G protein beta gamma dimer, Ste4p/Ste18p, acts downstream of the alpha subunit, Gpa1p, to activate the pheromone response pathway and therefore must interact with a downstream effector. Synthetic sterile mutants that exacerbate the phenotype of ste4-ts mutations were isolated to identify proteins that functionally interact with Ste4p. The identification of a ste18 mutant indicated that this screen could identify proteins that interact directly with Ste4p. The other mutations were in STE5 and the STE20 kinase gene, which act near Ste4p in the pathway, and a new gene called STE21. ste20 null mutants showed residual mating, suggesting that another kinase may provide some function. Overexpression of Ste5p under galactose control activated the pheromone response pathway. This activation was dependent on Ste4p and Ste18p and partially dependent on Ste20p. These results cannot be explained by the linear pathway of Ste4p-->Ste20p-->Ste5p. Overexpression of Cdc42p resulted in a slight increase in pheromone induction of a reporter gene, and overexpression of activated forms of Cdc42p resulted in a further twofold increase. Mutations in pheromone response pathway components did not suppress the lethality associated with the activated CDC42 mutations, suggesting that this effect is independent of the pheromone response pathway.
Akada
R
R
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05405, USA.
Kallal
L
L
Johnson
D I
DI
Kurjan
J
J
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D005838:Genotype; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D016296:Mutagenesis; D010641:Phenotype; D010675:Pheromones / Q000502:physiology*; D010957:Plasmids; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010675:Pheromones; C080321:STE5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D019204:GTP-Binding Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae