Coping with oxidative stress. The yeast model.

Saccharomyces cerevisiae is an optimal model to study stress responses for various reasons: i) budding yeast genome presents a high degree of homology with the human genome; ii) there are many proteins that show an elevated functional homology with specific human proteins; iii) it is a system whose genetic manipulation is reasonably easy and cheaper than other models; iv) the possibility of working with an haploid state facilitates the study of multiple processes; v) databases are the most complete of all the eukaryotic models. Due to the latest information derived from proteomic and genomic analyses, the genetic, biochemical and molecular information available relative to this biological system is extraordinarily big and complete. In this review, we present an overview of the mechanisms unravelling sensing and transducing oxidative stress. TOR, RAS/PKA, CWI, SNF1, and HOG are the main pathways involved both in the oxidative response and in the correct entry in stationary phase. In general, TOR and RAS/PKA dowregulation and SNF1 and CWI upregulation favour both a correct defence against oxidative damage and the entry in the quiescent state. All of these pathways have counterparts in humans. The actin cytoskeleton plays a dual function as sensor and target of oxidation, in tight connection with the former signalling cascades. In budding yeast, progression through stationary phase and quiescence constitute an accepted current model to study some of the mechanisms that determine life span. Aging is a process associated to oxidative stress and it is in tight relationship with bulk autophagy and mitophagy, both are mechanisms belonging to the oxidative defence and promoters of life extension when correctly regulated by, among other elements, the signalling cascades.