The Interdependence of Nutrient and Pheromone Sensing Pathways in Yeast
Funded by the National Science Foundation (MCB-0952519)
March 1, 2010 - May 31, 2013
Institutions and Faculty Participating in the Program
Carson Newman College - Dr. Steve Wright - firstname.lastname@example.org
Tennessee Wesleyan College - Dr. Grant Wilhite - email@example.com
Maryville College - Dr. Jennifer Brigati - firstname.lastname@example.org
The University of Tennessee, Knoxville - Dr. Jeff Becker - email@example.com
Cell division and fusion are resource intensive activities, and thus the ability of the yeast cell to coordinate the availability of nutrients in its environment with reproduction is of great physiological importance. This project will examine the role that glucose availability plays in yeast mating by testing the hypothesis that glucose sensing and mating are interdependent. The glucose sensor and the pheromone receptor are the only G protein coupled receptors (GPCR) in yeast. The aims of this project include 1) assessing the effects of pheromone stimulation on the glucose sensor, 2) examining the direct physical interactions of the glucose sensing and pheromone receptors, and 3) identifying interactions between components of the signaling pathways downstream of these receptors.
We have been working on how the membrane environment of the pheromone receptor Ste2p affects its activity for many years. This receptor is involved in the mating process of bakers/brewers yeast which is a complex but relatively well understood system of transmitting a signal from the cell surface into and throughout the cell interior. The receptor belongs to a large class of membrane proteins called G protein coupled receptors, of which there are hundreds of examples in humans. In recent years these receptors have been found to reside in certain regions of the cell membrane and even pair up with each other or with other GPCRs. Yeast express only two types of these receptors at any one time so it makes for a much less complicated system to study than with mammalian cells. If these two proteins pair up or dimerize in yeast then removal of one might affect the activity of the other. We found that if cells did not express the protein Gpr1p then the activity of the mating pathway beginning with Ste2p was compromised. Gpr1 is a glucose sensor that helps the yeast cell set its metabolic program based on available nutrients. The Ste2p/pheromone pathway is based mainly on a group of proteins known as MAPKs whereas the Gpr1/glucose pathway is based on cAMP production and activation of PKA. We have been looking at what happens to either pathway when components of the other are missing. We have found that the two pathways are dependent upon each other for full activity.