Recent developments in yeast aging

Abstract

In the last decade, research into the molecular determinants of aging has progressed rapidly and much of this progress can be attributed to studies in invertebrate eukaryotic model organisms. Of these, single-celled yeast is the least complicated and most amenable to genetic and molecular manipulations. Supporting the use of this organism for aging research, increasing evidence has accumulated that a subset of pathways influencing longevity in yeast are conserved in other eukaryotes, including mammals. Here we briefly outline aging in yeast and describe recent findings that continue to keep this "simple" eukaryote at the forefront of aging research.

Figure 1. Schematic for Yeast Replicative and Chronological Aging

(A) RLS in yeast is measured by the number of mitotic divisions that can arise from a single mother cell. Replicative viability is calculated as the mean number of daughters produced from mothers of a particular strain background before senescence. (B) CLS is measured by the length of time cells in a stationary culture can remain viable. Viability is calculated by the fraction of the culture able to reenter the cell cycle after an extended state of quiescence.

Figure 2. TOR Kinase Mediates Important Cellular Responses Implicated in Extended Longevity

During periods of nutrient availability, TOR kinase is activated, leading to G1 progression, translation initiation, increased ribosome biogenesis, and a suppression of autophagy and the stress response. When TOR is inactivated, either by DR or by the TOR inhibitor rapamycin, a cellular response is initiated that turns down protein translation and cell growth, and increases protein turnover and genes involved in the stress response. The conserved cellular regime that is the result of inactivated TOR kinase increases both replicative and chronological life span in yeast.