Identification of D ck1 and L mo1 as upstream regulators of the small GTP ase R ho5 in S accharomyces cerevisiae

Summary The exact function and regulation of the small GTP ase Rho5 , a putative homolog of mammalian Rac1 , in the yeast S accharomyces cerevisiae have not yet been elucidated. In a genetic screen initially designed to identify novel regulators of cell wall integrity signaling, we identified the homologs of mammalian DOCK1 ( Dck1 ) and ELMO ( Lmo1 ) as upstream components which regulate Rho5. Deletion mutants in any of the encoding genes ( DCK 1 , LMO 1 , RHO 5 ) showed hyper‐resistance to cell wall stress agents, demonstrating a function in cell wall integrity signaling. Live‐cell fluorescence microscopy showed that Dck1 , Lmo1 and Rho5 quickly relocate to mitochondria under oxidative stress and cell viability assays indicate a role of Dck1 / Lmo1 / Rho5 signaling in triggering cell death as a response to hydrogen peroxide treatment. A regulatory role in autophagy/mitophagy is suggested by the colocalization of Rho5 with autophagic markers and the decreased mitochondrial turnover observed in dck1 , lmo1 and rho5 deletion mutants. Rho5 activation may thus serve as a central hub for the integration of different signaling pathways.