| Title: | Mitogen-activated protein kinases with distinct requirements for Ste5 scaffolding influence signaling specificity in Saccharomyces cerevisiae |
| Author(s): | Flatauer LJ; Zadeh SF; Bardwell L; |
| Address: | "Department of Developmental and Cell Biology, 5205 McGaugh Hall, University of California, Irvine, CA 92697-2300, USA" |
| DOI: | 10.1128/MCB.25.5.1793-1803.2005 |
| ISSN/ISBN: | 0270-7306 (Print) 1098-5549 (Electronic) 0270-7306 (Linking) |
| Abstract: | "Scaffold proteins are believed to enhance specificity in cell signaling when different pathways share common components. The prototype scaffold Ste5 binds to multiple components of the Saccharomyces cerevisiae mating pheromone response pathway, thereby conducting the mating signal to the Fus3 mitogen-activated protein kinase (MAPK). Some of the kinases that Ste5 binds to, however, are also shared with other pathways. Thus, it has been presumed that Ste5 prevents its bound kinases from transgressing into other pathways and protects them from intrusions from those pathways. Here we found that Fus3MAPK required Ste5 scaffolding to receive legitimate signals from the mating pathway as well as misdirected signals leaking from other pathways. Furthermore, increasing the cellular concentration of active Ste5 enhanced the channeling of inappropriate stimuli to Fus3. This aberrant signal crossover resulted in the erroneous induction of cell cycle arrest and mating. In contrast to Fus3, the Kss1 MAPK did not require Ste5 scaffolding to receive either authentic or leaking signals. Furthermore, the Ste11 kinase, once activated via Ste5, was able to signal to Kss1 independently of Ste5 scaffolding. These results argue that Ste5 does not act as a barrier that actively prevents signal crossover to Fus3 and that Ste5 may not effectively sequester its activated kinases away from other pathways. Rather, we suggest that specificity in this network is promoted by the selective activation of Ste5 and the distinct requirements of the MAPKs for Ste5 scaffolding" |
| Keywords: | "Adaptor Proteins, Signal Transducing/metabolism/*physiology Cell Cycle/physiology MAP Kinase Kinase Kinases/metabolism/physiology MAP Kinase Signaling System/*physiology Mitogen-Activated Protein Kinases/metabolism/*physiology Osmotic Pressure Saccharomyc;" |
| Notes: | "MedlineFlatauer, Laura J Zadeh, Sheena F Bardwell, Lee eng GM07311/GM/NIGMS NIH HHS/ R33 GM069013/GM/NIGMS NIH HHS/ GM60366/GM/NIGMS NIH HHS/ GM69013/GM/NIGMS NIH HHS/ T32 GM007311/GM/NIGMS NIH HHS/ R01 GM060366-06/GM/NIGMS NIH HHS/ R01 GM060366/GM/NIGMS NIH HHS/ R21 GM069013/GM/NIGMS NIH HHS/ Research Support, U.S. Gov't, P.H.S. 2005/02/17 Mol Cell Biol. 2005 Mar; 25(5):1793-803. doi: 10.1128/MCB.25.5.1793-1803.2005" |
