Ssa1p chaperone interacts with the guanine nucleotide exchange factor of ras Cdc25p and controls the cAMP pathway in Saccharomyces cerevisiae

Mol Microbiol. 1998 Nov;30(4):855-64. doi: 10.1046/j.1365-2958.1998.01118.x.


We have found that the guanine nucleotide exchange factor for ras, Cdc25p, interacts with Ssa1p in Saccharomyces cerevisiae. This interaction was observed with GST-fused Cdc25p polypeptides and confirmed by coimmunoprecipitation with the endogenous Cdc25p. Hsp82 appeared also to be co-immunoprecipitated with Cdc25p, albeit to a lower level than Hsp70. In a strain deleted for SSA1 and SSA2, we observed a reduced cellular content of Cdc25p. Consistent with a reduced activity of the cAMP-dependent PKA pathway, the rate of accumulation of both trehalose and glycogen was stimulated in the ssa-deleted strain. Expression of SSA1 reversed these effects, whereas co-expression of SSA1 and PDE2 restored high accumulation. The expression of genes repressed by cAMP, GAC1 and TPS1, fused to beta-galactosidase, was also stimulated by deletion of SSA genes. The effect of ssa deletion on glycogen accumulation was lost in a strain deleted for CDC25 rescued by the RAS2ile152 allele. Altogether, these results lead to the conclusion that Ssa1p positively controls the cAMP pathway through Cdc25p. We propose that this connection plays a critical role in the adaptation of cells to stress conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / isolation & purification
  • Cell Cycle Proteins / metabolism*
  • Cyclic AMP / metabolism*
  • Epistasis, Genetic
  • Fungal Proteins / genetics
  • Fungal Proteins / isolation & purification
  • Fungal Proteins / metabolism*
  • Gene Expression
  • Glycogen / metabolism
  • Guanine Nucleotide Exchange Factors
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / isolation & purification
  • HSP70 Heat-Shock Proteins / metabolism*
  • HSP90 Heat-Shock Proteins
  • Heat-Shock Proteins / metabolism
  • Molecular Chaperones / metabolism
  • Mutagenesis
  • Proteins / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / isolation & purification
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins
  • Trehalose / metabolism
  • ras Guanine Nucleotide Exchange Factors
  • ras Proteins / genetics
  • ras-GRF1*


  • CDC25 protein, S cerevisiae
  • Cell Cycle Proteins
  • Fungal Proteins
  • Guanine Nucleotide Exchange Factors
  • HSP70 Heat-Shock Proteins
  • HSP82 protein, S cerevisiae
  • HSP90 Heat-Shock Proteins
  • Heat-Shock Proteins
  • Molecular Chaperones
  • Proteins
  • Recombinant Fusion Proteins
  • SSA2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • ras Guanine Nucleotide Exchange Factors
  • ras-GRF1
  • Glycogen
  • Trehalose
  • Cyclic AMP
  • Adenosine Triphosphatases
  • SSA1 protein, S cerevisiae
  • ras Proteins