The Stationary-Phase Cells of Saccharomyces cerevisiae Display Dynamic Actin Filaments Required for Processes Extending Chronological Life Span

Abstract

Stationary-growth-phase Saccharomyces cerevisiae yeast cultures consist of nondividing cells that undergo chronological aging. For their successful survival, the turnover of proteins and organelles, ensured by autophagy and the activation of mitochondria, is performed. Some of these processes are engaged in by the actin cytoskeleton. In S. cerevisiae stationary-phase cells, F actin has been shown to form static aggregates named actin bodies, subsequently cited to be markers of quiescence. Our in vivo analyses revealed that stationary-phase cultures contain cells with dynamic actin filaments, besides the cells with static actin bodies. The cells with dynamic actin displayed active endocytosis and autophagy and well-developed mitochondrial networks. Even more, stationary-phase cell cultures grown under calorie restriction predominantly contained cells with actin cables, confirming that the presence of actin cables is linked to successful adaptation to stationary phase. Cells with actin bodies were inactive in endocytosis and autophagy and displayed aberrations in mitochondrial networks. Notably, cells of the respiratory activity-deficient cox4⌬ strain displayed the same mitochondrial aberrations and actin bodies only. Additionally, our results indicate that mitochondrial dysfunction precedes the formation of actin bodies and the appearance of actin bodies corresponds to decreased cell fitness. We conclude that the F-actin status reflects the extent of damage that arises from exponential growth.O nce glucose and other external nutrients are exhausted, cell division stops and Saccharomyces cerevisiae cells are able to survive for extended periods of time. This period of survival has been termed chronological aging and has become a model for aging of postmitotic tissues (1, 2). The cells in these nondividing stationary-phase cell cultures are often termed quiescent (Q) cells (3, 4). Some authors claim that stationary-phase yeast cell populations are heterogeneous and only a portion of them have characteristics of quiescence (5, 6). The ability to survive the period of scarcity of external nutrition and reproduce again upon refeeding is influenced by several life span-extending genetic and environmental interventions. One of the most cited is calorie restriction (CR) (7).In general, cells that are in a nutrient-poor environment activate processes that help them to efficiently utilize inner resources and thus prolong the life span. A catabolic process that has a positive impact on chronological aging is autophagy, which provides nutrients by the vacuolar degradation of damaged or superfluous macromolecules and organelles (8, 9). In addition, Fabrizio et al. demonstrated that the deletion of several genes encoding endosomal functions also shortens the life span (8). Note that some of them have not been directly implicated in autophagy (8). The efficient utilization of resources is ensured by the activation of mitochondrial respiration. It has been proved that the utilization of carbohydrate stores by respiration instead...

Effect of Ethanol-Derived Clove Leaf Extract on the Oxidative Stress Response in Yeast Schizosaccharomyces pombe

“…Such data indicate that clove leaf extract is likely capable of modulating oxidative stress response in a way that is more effective than CR conditions. A previous study had reported that in addition to the autophagy and mitochondrial activities, the dynamic actin cytoskeleton is involved in the survival of stationary phase, thus extending the life span of the yeast S. cerevisiae [28]. To our knowledge, this is the first report of the use of clove leaf extract to promote cell viability of yeast cells, which suggest its potential as an antiaging agent.…”

Mitochondria reorganization upon proliferation arrest predicts individual yeast cell fate

“…We have previously reported that upon carbon source exhaustion, the actin cytoskeleton reorganizes into Actin Bodies (AB) and the proteasome re-localizes from the nucleus into proteasome storage granules (PSG) ( Sagot et al, 2006 ; Laporte et al, 2008 ; Laporte et al, 2015 ). Whether these rearrangements are specific of the quiescent state has been challenged ( Vasicova et al, 2015 ), but never tested directly. To tackle this question, we used our individual cell tracking approach with cells expressing both Ilv3-RFP and either Abp1-3xGFP (AB) or Scl1-3xGFP (PSG).…”

Misfolding-prone proteins are reversibly sequestered to an Hsp42-associated granule upon chronological aging

“…Since the sources of energy and materials are restricted in stationary phase cells, formation of protein granules is often regarded as a mechanism to store crucial proteins that will later be used for mitosis re-entry (Laporte et al, 2008;Narayanaswamy et al, 2009;Sagot et al, 2006). However, a few recent studies indicate that some granule structures only appear in cells with inferior physiological states (Lee et al, 2016;Vasicova et al, 2015), suggesting that the storage model is oversimplified. In log phase cells, misfolded or damaged proteins are often collected to specific compartments or deposition sites.…”