Low-pH response in Saccharomyces cerevisiae : implication of the RhoGAP Rgd1p and the PKC pathway.
Xavier Gatti, Sandra Claret, Helder Fernandes, Olivier Roumanie, François Doignon, Marc Crouzet, Didier Thoraval
LBMS, IBGC UMR CNRS/U Bordeaux2 5095, 146 rue léo saignat, Bordeaux, 33076, France
The yeast Saccharomyces cerevisiae senses from its environment various stress signals such as temperature, pH, osmotic pressure, nutrient starvation, ... We highlighted the important role of Rgd1p, the RhoGAP of Rho3p and Rho4p, in cell survival after acidic shock. Indeed the transcription of RGD1 gene is controlled by the pH of the medium through the transcription factors Msn2p and Msn4p, implied in the general stress response, and the STRE box. In addition, we showed that PKC pathway was activated during acidic stress, and that this activation depended on Rgd1p and Mid2p, a cell wall sensor. Moreover the components of the PKC-MAPK cascade were also shown to be essential in cell survival at low-pH. These results allowed us to propose a model for the response to acidic shock in the yeast Saccharomyces cerevisiae, connecting the small G proteins Rho3p and Rho4p through their RhoGAP Rgd1p on one hand, and the PKC pathway on the other hand. A physical partner of Rgd1p which could be the link between these two pathways is under study. Key words : acid shock, stress response, PKC pathway, RhoGAP.