Rho5 GTPase is necessary for oxidant-induced cell death in budding yeast

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-02, Vol.105 (5), p.1522-1527
• Main Authors: Singh, Komudi, Kang, Pil Jung, Park, Hay-Oak
• Format: Article
• Language: English
• Subjects: Apoptosis; Biological Sciences; Cell death; Cells; DNA damage; Enzymes; Fluorescence; Gene Deletion; Green Fluorescent Proteins - analysis; Green Fluorescent Proteins - genetics; Guanosine Triphosphate - metabolism; guanosinetriphosphatase; hydrogen peroxide; Hydrogen Peroxide - pharmacology; mutants; Mutation; Oxidants - pharmacology; Oxidative Stress; oxidoreductases; phenotype; Plasmids; Reactive Oxygen Species; rho GTP-Binding Proteins - analysis; rho GTP-Binding Proteins - genetics; rho GTP-Binding Proteins - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae Proteins - analysis; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Saccharomycetales; Thioredoxin; thioredoxin reductase; Thioredoxin-Disulfide Reductase - metabolism; Viability; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0707359105

In both animal and yeast cells, reactive oxygen species (ROS) are produced as byproducts of metabolism and upon exposure to diverse environmental stresses. Cellular defense systems operate to avoid molecular damage caused by ROS, but the redox balance is disturbed under excessive stress. Cells of the budding yeast Saccharomyces cerevisiae undergo apoptotic-like cell death upon exposure to hydrogen peroxide (H₂O₂). Here, we report that the Rho5 GTPase of budding yeast is necessary for H₂O₂-induced cell death, which accompanies ROS accumulation and DNA fragmentation. Unlike WT, a rho5 deletion mutant (rho5Δ) exhibits little cell death, whereas the constitutively active rho5G¹²V mutant exhibits excess ROS accumulation and increased cell death upon H₂O₂ treatment. Consistent with a role in the oxidative stress response, Rho5 interacts with the thioredoxin reductase Trr1, a key component of the cytoplasmic thioredoxin antioxidant system, in a GTP-dependent manner. This interaction occurs on the vacuolar membrane before exposure to H₂O₂ but also in the vacuolar lumen after H₂O₂ treatment. Trr1 levels are elevated in rho5Δ cells but are elevated only slightly in WT and not in the rho5G¹²V cells after H₂O₂ treatment. Taken together, these data suggest that Rho5 mediates H₂O₂-induced cell death by regulating the level of Trr1 or by excluding Trr1 from its cytoplasmic substrate.