ACTIVATION OF YEAST PROTEIN-KINASE-C BY RHO1 GTPASE

We have investigated the role of the essential Rho1 GTPase in cell int egrity signaling in budding yeast. Conditional rho1 mutants display a cell lysis defect that is similar to that of mutants in the cell integ rity signaling pathway mediated by protein kinase C (Pkc1), which is s uppressed by overexpression of Pkc1. rho1 mutants are also impaired in pathway activation in response to growth at elevated temperature. Pkc 1 co-immunoprecipitates with Rho1 in yeast extracts, and recombinant R ho1 associates with Pkc1 in vitro in a GTP-dependent manner. Recombina nt Rho1 confers upon Pkc1 the ability to be stimulated by phosphatidyl serine. indicating that Rho1 controls signal transmission through Pkc1 .