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The mitochondrial ribosomal protein of the large subunit, Afo1p, determines cellular longevity through mitochondrial back-signaling via TOR1.

Heeren G, Rinnerthaler M, Laun P, von Seyerl P, Kössler S, Klinger H, Hager M, Bogengruber E, Jarolim S, Simon-Nobbe B, Schüller C, Carmona-Gutierrez D, Breitenbach-Koller L, Mück C, Jansen-Dürr P, Criollo A, Kroemer G, Madeo F, Breitenbach M - Aging (Albany NY) (2009)

Bottom Line: Despite the respiratory deficiency the mutant has paradoxical increase in growth rate compared to generic petite mutants.A comparison of the single and double mutant strains for afo1 and fob1 shows that the longevity phenotype of afo1 is independent of the formation of ERCs (ribosomal DNA minicircles).AFO1/MRPL25 function establishes a new connection between mitochondria, metabolism and aging.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Division of Genetics, University of Salzburg, 5020 Salzburg, Austria.

ABSTRACT
Yeast mother cell-specific aging constitutes a model of replicative aging as it occurs in stem cell populations of higher eukaryotes. Here, we present a new long-lived yeast deletion mutation,afo1 (for aging factor one), that confers a 60% increase in replicative lifespan. AFO1/MRPL25 codes for a protein that is contained in the large subunit of the mitochondrial ribosome. Double mutant experiments indicate that the longevity-increasing action of the afo1 mutation is independent of mitochondrial translation, yet involves the cytoplasmic Tor1p as well as the growth-controlling transcription factor Sfp1p. In their final cell cycle, the long-lived mutant cells do show the phenotypes of yeast apoptosis indicating that the longevity of the mutant is not caused by an inability to undergo programmed cell death. Furthermore, the afo1 mutation displays high resistance against oxidants. Despite the respiratory deficiency the mutant has paradoxical increase in growth rate compared to generic petite mutants. A comparison of the single and double mutant strains for afo1 and fob1 shows that the longevity phenotype of afo1 is independent of the formation of ERCs (ribosomal DNA minicircles). AFO1/MRPL25 function establishes a new connection between mitochondria, metabolism and aging.

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Lifespans of                                            isogenic strains afo1Δ, wild type                                            BY4741 and BY4741 ρ0. Lifespans were determined as                                            described previously [2] by micromanipulating daughter cells and counting                                            generations of at least 45 yeast mother cells on synthetic complete (SC)                                            media with 2% glucose as carbon source.
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Figure 1: Lifespans of isogenic strains afo1Δ, wild type BY4741 and BY4741 ρ0. Lifespans were determined as described previously [2] by micromanipulating daughter cells and counting generations of at least 45 yeast mother cells on synthetic complete (SC) media with 2% glucose as carbon source.

Mentions: We compared the transcriptome of senescent yeast mother cells (fraction V) with young daughter cells (fraction II) after separating them by elutriation centrifugation [2]. Senescent cells were found to upregulate 39 genes and to down-regulate 53 transcripts. Deletion mutants [12] corresponding to these 92 genes were tested for their resistance or hypersensitivity to five different oxidants (hydrogen peroxide, tert-butyl hydroperoxide (t-BHP), diamide, cumene hydroperoxide, and menadione). Only two mutants were found to be consistently resistant against more than one oxidant (and not hypersensitive to any other oxidant). Among these two mutants only one, deleted for YGR076C/MRPL25 (later termed AFO1, see below) caused a mother cell-specific lifespan expansion on the standard media used by us (SC + 2% glucose) (Figure 1). This deletion mutation conferred resistance to diamide and t-BHP and a somewhat weaker resistance to hydrogen peroxide, as well as a 50% reduced ROS production (as compared to the BY4741 ρ0mutant). ROS production was measured by quantitation of fluorescence signals obtained after dihydroethidium (DHE) staining. The mutant displayed a 60% increase in the median and a 71% increase in the maximum lifespan (Figure 1). The mutant only grew on media containing fermentable carbon sources and hence is respiration deficient. We therefore asked if the respiratory deficiency caused the increased replicative life span. However, a bona fide BY4741 ρ0mutant did not show any extension in replicative life span (as compared to BY4741 WT cells), meaning that lack of respiration is not sufficient to confer longevity to mother cells (Figure 1). We also tested if afo1Δ cells displayed the retrograde response [3,13] by measuring CIT2 transcription and no effect of the afo1Δ mutation could be discerned (see Supplementary Figure 1). We conclude that the elongation of lifespan observed here is not caused by respiratory deficiency and is independent of the retrograde response as defined by Jazwinski [14] and Butow [15].


The mitochondrial ribosomal protein of the large subunit, Afo1p, determines cellular longevity through mitochondrial back-signaling via TOR1.

Heeren G, Rinnerthaler M, Laun P, von Seyerl P, Kössler S, Klinger H, Hager M, Bogengruber E, Jarolim S, Simon-Nobbe B, Schüller C, Carmona-Gutierrez D, Breitenbach-Koller L, Mück C, Jansen-Dürr P, Criollo A, Kroemer G, Madeo F, Breitenbach M - Aging (Albany NY) (2009)

Lifespans of                                            isogenic strains afo1Δ, wild type                                            BY4741 and BY4741 ρ0. Lifespans were determined as                                            described previously [2] by micromanipulating daughter cells and counting                                            generations of at least 45 yeast mother cells on synthetic complete (SC)                                            media with 2% glucose as carbon source.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2806038&req=5

Figure 1: Lifespans of isogenic strains afo1Δ, wild type BY4741 and BY4741 ρ0. Lifespans were determined as described previously [2] by micromanipulating daughter cells and counting generations of at least 45 yeast mother cells on synthetic complete (SC) media with 2% glucose as carbon source.
Mentions: We compared the transcriptome of senescent yeast mother cells (fraction V) with young daughter cells (fraction II) after separating them by elutriation centrifugation [2]. Senescent cells were found to upregulate 39 genes and to down-regulate 53 transcripts. Deletion mutants [12] corresponding to these 92 genes were tested for their resistance or hypersensitivity to five different oxidants (hydrogen peroxide, tert-butyl hydroperoxide (t-BHP), diamide, cumene hydroperoxide, and menadione). Only two mutants were found to be consistently resistant against more than one oxidant (and not hypersensitive to any other oxidant). Among these two mutants only one, deleted for YGR076C/MRPL25 (later termed AFO1, see below) caused a mother cell-specific lifespan expansion on the standard media used by us (SC + 2% glucose) (Figure 1). This deletion mutation conferred resistance to diamide and t-BHP and a somewhat weaker resistance to hydrogen peroxide, as well as a 50% reduced ROS production (as compared to the BY4741 ρ0mutant). ROS production was measured by quantitation of fluorescence signals obtained after dihydroethidium (DHE) staining. The mutant displayed a 60% increase in the median and a 71% increase in the maximum lifespan (Figure 1). The mutant only grew on media containing fermentable carbon sources and hence is respiration deficient. We therefore asked if the respiratory deficiency caused the increased replicative life span. However, a bona fide BY4741 ρ0mutant did not show any extension in replicative life span (as compared to BY4741 WT cells), meaning that lack of respiration is not sufficient to confer longevity to mother cells (Figure 1). We also tested if afo1Δ cells displayed the retrograde response [3,13] by measuring CIT2 transcription and no effect of the afo1Δ mutation could be discerned (see Supplementary Figure 1). We conclude that the elongation of lifespan observed here is not caused by respiratory deficiency and is independent of the retrograde response as defined by Jazwinski [14] and Butow [15].

Bottom Line: Despite the respiratory deficiency the mutant has paradoxical increase in growth rate compared to generic petite mutants.A comparison of the single and double mutant strains for afo1 and fob1 shows that the longevity phenotype of afo1 is independent of the formation of ERCs (ribosomal DNA minicircles).AFO1/MRPL25 function establishes a new connection between mitochondria, metabolism and aging.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Division of Genetics, University of Salzburg, 5020 Salzburg, Austria.

ABSTRACT
Yeast mother cell-specific aging constitutes a model of replicative aging as it occurs in stem cell populations of higher eukaryotes. Here, we present a new long-lived yeast deletion mutation,afo1 (for aging factor one), that confers a 60% increase in replicative lifespan. AFO1/MRPL25 codes for a protein that is contained in the large subunit of the mitochondrial ribosome. Double mutant experiments indicate that the longevity-increasing action of the afo1 mutation is independent of mitochondrial translation, yet involves the cytoplasmic Tor1p as well as the growth-controlling transcription factor Sfp1p. In their final cell cycle, the long-lived mutant cells do show the phenotypes of yeast apoptosis indicating that the longevity of the mutant is not caused by an inability to undergo programmed cell death. Furthermore, the afo1 mutation displays high resistance against oxidants. Despite the respiratory deficiency the mutant has paradoxical increase in growth rate compared to generic petite mutants. A comparison of the single and double mutant strains for afo1 and fob1 shows that the longevity phenotype of afo1 is independent of the formation of ERCs (ribosomal DNA minicircles). AFO1/MRPL25 function establishes a new connection between mitochondria, metabolism and aging.

Show MeSH