The N-terminal half of Cdc25 is essential for processing glucose signaling in Saccharomyces cerevisiae.
Saccharomyces cerevisiae Cdc25 is the prototype Ras GDP/GTP exchange protein. Its C-terminal catalytic domain was found to be highly conserved in the homologues p140(ras-GRF) and Sos. The regulatory domains in each Ras exchanger mediate the signals arriving from upstream elements such as tyrosine kinases for Sos, or Ca2+ and G proteins for p140.(Ras-GRF) In this study, we show that the N-terminal half (NTH) of S. cerevisiae Cdc25, as well as the C-terminal 37 amino acids, is essential for processing the elevation of cAMP in response to glucose. The mammalian p140(ras-GRF) catalytic domain (CGRF) restores glucose signaling in S. cerevisiae only if tethered between the N-terminal half (NTH) of S. cerevisiae Cdc25 and the C-terminal 37 amino acids. The glucose-induced transient elevation in cAMP is nullified or severely hampered by the deletion of domains within the NTH of Cdc25. These deletions, however, do not modify the intrinsic GDP/GTP exchange activity of mutant proteins as compared to native Cdc25. We also show that 7 Ser to Ala mutations at the cAMP-dependent protein kinase putative phosphorylation sites within the NTH of Cdc25 eliminate the descending portion of the glucose response curve, responsible for signal termination. These findings support a dual role of the NTH of Cdc25 in both enabling the glucose signal and being responsible for its attenuation.
Gross
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Department of Biological Chemistry, The Alexander Silverman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel.
Winograd
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S
Marbach
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Levitzki
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D000818:Animals; D020134:Catalytic Domain; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004789:Enzyme Activation; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005947:Glucose / Q000378:metabolism / Q000502:physiology*; D006150:Guanine Nucleotides / Q000502:physiology; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017384:Sequence Deletion; D015398:Signal Transduction / Q000235:genetics; D020666:ras-GRF1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D006150:Guanine Nucleotides; D010446:Peptide Fragments; D020666:ras-GRF1; D006162:Guanylate Cyclase; D005947:Glucose