Rho5p downregulates the yeast cell integrity pathway.
The Rho family of proteins and their effectors are key regulators involved in many eukaryotic cell functions. In Saccharomyces cerevisiae the family consists of six members, Rho1p to Rho5p and Cdc42p. With the exception of Rho5p, these enzymes have been assigned different biological functions, including the regulation of polar growth, morphogenesis, actin cytoskeleton, budding and secretion. Here we show that a rho5 deletion results in an increased activity of the protein kinase C (Pkc1p)-dependent signal transduction pathway. Accordingly, the deletion shows an increased resistance to drugs such as caffeine, Calcofluor white and Congo red, which indicates activation of the pathway. In contrast, overexpression of an activated RHO5Q91H mutant renders cells more sensitive to these drugs. We conclude that Rho5p acts as an off-switch for the MAP-kinase cascade, which differentiates between MAP-kinase-dependent and -independent functions of Pkc1p. Kinetics of actin depolarisation and repolarisation after heat treatment of rho5 deletions as well as strains overexpressing the activated RHO5Q91H allele provide further evidence for such a function.
Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, Geb. 26. 12, D-40225 Düsseldorf, Germany. heinisch@uni-hohenheim.de
Hans-Peter
HP
Schmitz
Stefanie
S
Huppert
Anja
A
Lorberg
Jürgen J
JJ
Heinisch
D000199:Actins / Q000096:biosynthesis / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D006358:Hot Temperature / Q000009:adverse effects; D020935:MAP Kinase Signaling System / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D020741:rho GTP-Binding Proteins / Q000172:deficiency* / Q000235:genetics
D000199:Actins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; C097993:Pkc1 protein, Trichoderma reesei; D011493:Protein Kinase C; C474618:RHO5 protein, S cerevisiae; D020741:rho GTP-Binding Proteins