Identification of a modulator of the actin cytoskeleton, mitochondria, nutrient metabolism and lifespan in yeast

Abstract

In yeast, actin cables are F-actin bundles that are essential for cell division through their function as tracks for cargo movement from mother to daughter cell. Actin cables also affect yeast lifespan by promoting transport and inheritance of higher-functioning mitochondria to daughter cells. Here, we report that actin cable stability declines with age. Our genome-wide screen for genes that affect actin cable stability identified the open reading frame YKL075C. Deletion of YKL075C results in increases in actin cable stability and abundance, mitochondrial fitness, and replicative lifespan. Transcriptome analysis revealed a role for YKL075C in regulating branched-chain amino acid (BCAA) metabolism. Consistent with this, modulation of BCAA metabolism or decreasing leucine levels promotes actin cable stability and function in mitochondrial quality control. Our studies support a role for actin stability in yeast lifespan, and demonstrate that this process is controlled by BCAA and a previously uncharacterized ORF YKL075C, which we refer to as actin, aging and nutrient modulator protein 1 (AAN1).

Understanding the link between the actin cytoskeleton and prion biology

“…For example, healthy mitochondria tend to segregate to daughter cells while lower functioning oxidized mitochondria are spatially retained in the mother cell [ 36 ]. However, the ability to retain unhealthy mitochondria appears to decline with age through reduced stability of actin cables [ 37 ]. Damaged proteins and heat-induced aggregates are also spatially retained in mother cells through an Hsp104 and actin-dependent mechanism [ 38 , 39 ].…”

Mitochondrial protein and organelle quality control—Lessons from budding yeast

“…Consistent with this, our recent studies revealed that actin cables become functionally impaired with age and that stabilization of actin cables increases yeast cell fitness and extends lifespan. 117 These studies led to the identification of a novel modulator of the actin cytoskeleton that influences mitochondrial quality control and the aging process. Deletion of this gene, AAN1 (Actin, Aging, and Nutrient modulator protein 1), increases actin cable stability and abundance and results in an increase in mitochondrial fitness and extended replicative lifespan.…”

“…Deletion of this gene, AAN1 (Actin, Aging, and Nutrient modulator protein 1), increases actin cable stability and abundance and results in an increase in mitochondrial fitness and extended replicative lifespan. 117 Intriguingly, aan1Δ cells show altered branchedchain amino acid (BCAA) metabolism. Moreover, genetically modulating BCAA metabolism or decreasing leucine levels in the growth medium results in increased actin cable stability and mitochondrial quality.…”

“…Moreover, genetically modulating BCAA metabolism or decreasing leucine levels in the growth medium results in increased actin cable stability and mitochondrial quality. 117 Thus, Aan1 is a previously undescribed aging determinant that impacts yeast replicative lifespan and mitochondrial quality control in response to nutrient cues through effects on actin cable stability. These studies provide additional evidence for a role of the actin cytoskeleton in lifespan control, and are supported by findings that stabilization of the actin cytoskeleton affects cellular fitness and lifespan in C. elegans.…”

Enrichment of aging yeast cells and budding polarity assay in Saccharomyces cerevisiae

“…WGA-AlexaFlour or Calcofluor White can be used to assess buds scars and replicative aging or age-associated declines in polarity ( Figure 7 E) ( Yang et al., 2022 ). Isolated cells can be analyzed by light microscopy ( Sing et al., 2022 ; Yang et al., 2022 ) as well as transcriptomic, proteomic or epigenetic approaches ( Hendrickson et al., 2018 ).

Figure 6 Methods to determine cell viability Cells can be stained by trypan blue, methylene blue, propidium iodide + fluorescein diacetate, or LIVE/DEAD dye.

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