Phosphorylation of the S. cerevisiae Cdc25 in response to glucose results in its dissociation from Ras.
In the yeast Sacchromyces cerevisiae, addition of glucose to starved cells triggers a transient rise in the intracellular level of cyclic AMP that induces a protein phosphorylation cascade. The glucose signal is processed by the Cdc25/Ras/adenylyl cyclase pathway, where the role of Cdc25 is to catalyse the GDP-GTP exchange on Ras. The molecular mechanisms involved in the regulation of the activity of Cdc25 are unknown. We report here the use of highly selective anti-Cdc25 antibodies to demonstrate that Cdc25 is a phospho protein and that in response to glucose it is hyperphosphorylated, within seconds, by the cyclic AMP-dependent protein kinase. It is also demonstrated that, concomitantly with hyperphosphorylation, Cdc25 partially relocalizes to the cytoplasm, reducing its accessibility to membrane-bound Ras. These results are of general significance because of the highly conserved sequence of Ras-guanyl nucleotide exchange factors from yeasts to mammals.
Gross
E
E
Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
Goldberg
D
D
Levitzki
A
A
D000262:Adenylyl Cyclases / Q000378:metabolism; D018797:Cell Cycle Proteins; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007163:Immunosorbent Techniques; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins; D018631:ras Proteins; D020666:ras-GRF1
C542351:CDC25 protein, S cerevisiae; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D020666:ras-GRF1; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases; D019204:GTP-Binding Proteins; D018631:ras Proteins; D000262:Adenylyl Cyclases; D005947:Glucose