Activation of yeast protein kinase C by Rho1 GTPase.

We have investigated the role of the essential Rho1 GTPase in cell integrity signaling in budding yeast. Conditional rho1 mutants display a cell lysis defect that is similar to that of mutants in the cell integrity signaling pathway mediated by protein kinase C (Pkc1), which is suppressed by overexpression of Pkc1.rho1 mutants are also impaired in pathway activation in response to growth at elevated temperature. Pkc1 co-immunoprecipitates with Rho1 in yeast extracts, and recombinant Rho1 associates with Pkc1 in vitro in a GTP-dependent manner. Recombinant Rho1 confers upon Pkc1 the ability to be stimulated by phosphatidylserine, indicating that Rho1 controls signal transmission through Pkc1.