The Rho3 and Rho4 small GTPases interact functionally with Wsc1p, a cell surface sensor of the protein kinase C cell-integrity pathway in Saccharomyces cerevisiae

Laboratoire de Biologie Moléculaire et de Séquençage, Institut de Biochimie et Génétique Cellulaires, UMR Université Victor Segalen Bordeaux 2-CNRS 5095, box 64, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France Correspondence François Doignon doignon{at}u-bordeaux2.fr Rgd1, a GTPase-activating prot...

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Veröffentlicht in:Microbiology (Society for General Microbiology) 2006-03, Vol.152 (3), p.695-708
Hauptverfasser: Fernandes, Helder, Roumanie, Olivier, Claret, Sandra, Gatti, Xavier, Thoraval, Didier, Doignon, Francois, Crouzet, Marc
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Sprache:eng
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Zusammenfassung:Laboratoire de Biologie Moléculaire et de Séquençage, Institut de Biochimie et Génétique Cellulaires, UMR Université Victor Segalen Bordeaux 2-CNRS 5095, box 64, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France Correspondence François Doignon doignon{at}u-bordeaux2.fr Rgd1, a GTPase-activating protein, is the only known negative regulator of the Rho3 and Rho4 small GTPases in the yeast Saccharomyces cerevisiae . Rho3p and Rho4p are involved in regulating cell polarity by controlling polarized exocytosis. Co-inactivation of RGD1 and WSC1 , which is a cell wall sensor-encoding gene, is lethal. Another plasma membrane sensor, Mid2p, is known to rescue the rgd1 wsc1 synthetic lethality. It has been proposed that Wsc1p and Mid2p act upstream of the protein kinase C (PKC) pathway to function as mechanosensors of cell wall stress. Analysis of the synthetic lethal phenomenon revealed that production of activated Rho3p and Rho4p leads to lethality in wsc1 cells. Inactivation of RHO3 or RHO4 was able to rescue the rgd1 wsc1 synthetic lethality, supporting the idea that the accumulation of GTP-bound Rho proteins, following loss of Rgd1p, is detrimental if the Wsc1 sensor is absent. In contrast, the genetic interaction between RGD1 and MID2 was not due to an accumulation of GTP-bound Rho proteins. It was proposed that simultaneous inactivation of RGD1 and WSC1 constitutively activates the PKC–mitogen-activated protein kinase (MAP kinase) pathway. Moreover, it was shown that the activity of this pathway was not involved in the synthetic lethal interaction, which suggests the existence of another mechanism. Consistent with this idea, it was found that perturbations in Rho3-mediated polarized exocytosis specifically impair the abundance and processing of Wsc1 and Mid2 proteins. Hence, it is proposed that Wsc1p participates in the regulation of a Rho3/4-dependent cellular mechanism, and that this is distinct from the role of Wsc1p in the PKC–MAP kinase pathway. Abbreviations: ASR, arrest of secretion response; 5-FOA, 5-fluoroorotic acid; GAP, GTPase-activating protein; HA, haemagglutinin; MAP kinase, mitogen-activated protein kinase; PKC, protein kinase C; WT, wild type Supplementary Fig. S1, available with the online version of this paper, shows the detection of phosphorylated and total Slt2p in isogenic WT and rho3-V51 strains grown in synthetic medium, the detection of phosphorylated and total Slt2p in a WT strain co-producing WT, GDP-blocked or GTP-blocked forms of R
ISSN:1350-0872
1465-2080
DOI:10.1099/mic.0.28231-0