Cdc42p GDP/GTP cycling is necessary for efficient cell fusion during yeast mating.
The highly conserved small Rho G-protein, Cdc42p plays a critical role in cell polarity and cytoskeleton organization in all eukaryotes. In the yeast Saccharomyces cerevisiae, Cdc42p is important for cell polarity establishment, septin ring assembly, and pheromone-dependent MAP-kinase signaling during the yeast mating process. In this study, we further investigated the role of Cdc42p in the mating process by screening for specific mating defective cdc42 alleles. We have identified and characterized novel mating defective cdc42 alleles that are unaffected in vegetative cell polarity. Replacement of the Cdc42p Val36 residue with Met resulted in a specific cell fusion defect. This cdc42[V36M] mutant responded to mating pheromone but was defective in cell fusion and in localization of the cell fusion protein Fus1p, similar to a previously isolated cdc24 (cdc24-m6) mutant. Overexpression of a fast cycling Cdc42p mutant suppressed the cdc24-m6 fusion defect and conversely, overexpression of Cdc24p suppressed the cdc42[V36M] fusion defect. Taken together, our results indicate that Cdc42p GDP-GTP cycling is critical for efficient cell fusion.
Institute of Signaling, Developmental Biology, and Cancer, Centre National de la Recherche Scientifique UMR 6543, Université de Nice, Faculté des Sciences-Parc Valrose, 06108 Nice Cedex 2, France.
Sophie
S
Barale
Derek
D
McCusker
Robert A
RA
Arkowitz
D000595:Amino Acid Sequence; D002459:Cell Fusion; D016764:Cell Polarity; D005838:Genotype; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000502:physiology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000502:physiology*
D029701:Saccharomyces cerevisiae Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae