Sho1 and Pbs2 act as coscaffolds linking components in the yeast high osmolarity MAP kinase pathway

Mol Cell. 2004 Jun 18;14(6):825-32. doi: 10.1016/j.molcel.2004.06.011.


Scaffold proteins mediate efficient and specific signaling in several mitogen-activated protein (MAP) kinase cascades. In the yeast high osmolarity response pathway, the MAP kinase kinase Pbs2 is thought to function as a scaffold, since it binds the osmosensor Sho1, the upstream MAP kinase kinase kinase Ste11, and the downstream MAP kinase Hog1. Nonetheless, previous work has shown that Ste11 can be activated even when Pbs2 is deleted, resulting in inappropriate crosstalk to the mating pathway. We have found a region in the C terminus of Sho1 that binds Ste11 independently of Pbs2 and is required for crosstalk. These data support a model in which Sho1 has at least two separable interaction regions: one that binds Ste11 and mediates its activation, and one that binds Pbs2, directing Ste11 to act on Pbs2. Thus, a network of interactions provided by both Sho1 and Pbs2 appears to direct pathway information flow.

MeSH terms

  • MAP Kinase Kinase Kinases / chemistry
  • MAP Kinase Kinase Kinases / metabolism
  • MAP Kinase Signaling System*
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism
  • Membrane Proteins / physiology*
  • Mitogen-Activated Protein Kinase Kinases / chemistry
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Mitogen-Activated Protein Kinase Kinases / physiology*
  • Models, Molecular
  • Osmolar Concentration
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / physiology*
  • src Homology Domains


  • Membrane Proteins
  • SHO1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • MAP Kinase Kinase Kinases
  • Ste11 protein, S cerevisiae
  • Mitogen-Activated Protein Kinase Kinases
  • PBS2 protein, S cerevisiae