Receptor-mediated down regulation of the mating signaling cascade in Saccharomyces cerevisiae.
Item
-
Title
-
Receptor-mediated down regulation of the mating signaling cascade in Saccharomyces cerevisiae.
-
Identifier
-
AAI9732904
-
identifier
-
9732904
-
Creator
-
Couve, Andres Oscar.
-
Contributor
-
Adviser: Jeanne Hirsch
-
Date
-
1997
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Biology, Cell | Biology, Genetics | Biology, Molecular
-
Abstract
-
The yeast pheromone response pathway is mediated by two G protein-coupled receptors and a MAP kinase cascade. Three responses constitute the final outcome of the mating pathway. These include arrest at the G1 phase of the cell cycle, induction of transcription of mating specific genes and morphological changes that increase mating efficiency. The STE3{dollar}\sp{lcub}DAF{rcub}{dollar} mutation results in inappropriate expression of the a-factor receptor in MATa cells. Expression of this receptor in the inappropriate cell type confers resistance to pheromone-induced G1 arrest, a phenomenon termed receptor mediated inactivation. The ability of STE3{dollar}\sp{lcub}DAF{rcub}{dollar} cells to escape cell cycle arrest in the presence of pheromone was found to correlate with reduced phosphorylation of the cyclin-dependent kinase inhibitor Far1p. Measurement of Fus3p MAP kinase activity in wild type and STE3{dollar}\sp{lcub}DAF{rcub}{dollar} cells showed that induction of Fus3p activity was the same in both strains at times of up to one hour after pheromone treatment. However, after two or more hours, Fus3p activity declined in STE3{dollar}\sp{lcub}DAF{rcub}{dollar} cells but remained high in wild type cells. mRNA levels of the mating specific inducible gene FUS1 correlated with changes in Fus3p kinase activity. STE3{dollar}\sp{lcub}DAF{rcub}{dollar} was found to inhibit the pheromone response pathway at a step above the scaffolding protein Ste5p and above the Ste20p protein kinase. In addition, epistasis experiments demonstrated that STE3{dollar}\sp{lcub}DAF{rcub}{dollar} inhibited the mating pathway at the level or downstream of the G{dollar}\beta{dollar} subunit of the G protein. Mutational analysis of the G{dollar}\beta{dollar} subunit of the heterotrimeric G protein revealed that signaling through the mating pathway and receptor mediated inactivation could be uncoupled. STE3{dollar}\sp{lcub}DAF{rcub}{dollar} insensitive G{dollar}\beta{dollar} mutations mapped to essential domains for G{dollar}\beta{dollar}/G{dollar}\alpha{dollar} and G{dollar}\beta{dollar}/effector interactions. These findings indicate that receptor mediated inhibition is achieved by modification of G{dollar}\beta{dollar} function. Furthermore, they provide new evidence for the possible participation of G{dollar}\beta{dollar} and pheromone receptor in an adaptive response.;The observations significantly contribute to the understanding of the STE3{dollar}\sp{lcub}DAF{rcub}{dollar} mutation. They also provide new insights into the kinetics of the mating response and the relationship between the G protein coupled receptor and its effector molecules.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
