Increased Life Span due to Calorie Restriction in Respiratory-Deficient Yeast

Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America.
PLoS Genetics (Impact Factor: 7.53). 12/2005; 1(5):e69. DOI: 10.1371/journal.pgen.0010069
Source: PubMed


A model for replicative life span extension by calorie restriction (CR) in yeast has been proposed whereby reduced glucose in the growth medium leads to activation of the NAD+-dependent histone deacetylase Sir2. One mechanism proposed for this putative activation of Sir2 is that CR enhances the rate of respiration, in turn leading to altered levels of NAD+ or NADH, and ultimately resulting in enhanced Sir2 activity. An alternative mechanism has been proposed in which CR decreases levels of the Sir2 inhibitor nicotinamide through increased expression of the gene coding for nicotinamidase, PNC1. We have previously reported that life span extension by CR is not dependent on Sir2 in the long-lived BY4742 strain background. Here we have determined the requirement for respiration and the effect of nicotinamide levels on life span extension by CR. We find that CR confers robust life span extension in respiratory-deficient cells independent of strain background, and moreover, suppresses the premature mortality associated with loss of mitochondrial DNA in the short-lived PSY316 strain. Addition of nicotinamide to the medium dramatically shortens the life span of wild type cells, due to inhibition of Sir2. However, even in cells lacking both Sir2 and the replication fork block protein Fob1, nicotinamide partially prevents life span extension by CR. These findings (1) demonstrate that respiration is not required for the longevity benefits of CR in yeast, (2) show that nicotinamide inhibits life span extension by CR through a Sir2-independent mechanism, and (3) suggest that CR acts through a conserved, Sir2-independent mechanism in both PSY316 and BY4742.

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Available from: Matt Kaeberlein, Oct 06, 2015
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    • "In this study, we endeavored to systematically study synergistic interactions with target of rapamycin (TOR) kinase activity. TOR is a primary integrator of proliferative signals, and aberrant signaling by this kinase contributes to cancer (Casadio et al., 1999; Inoki et al., 2005; Kaeberlein et al., 2005; Martin and Hall, 2005; Tee and Blenis, 2005; Tischmeyer et al., 2003). As clinical use of selective inhibitors of TOR complex 1 (TORC1; rapamycin and its derivatives, rapalogs) becomes more widespread in cancer treatment and ATP-competitive inhibitors of both TORC1 and TORC2 (including BEZ235, INK- 128/MLN0128, KU-0063794, and WYE-354) reach the clinic, the search for secondary targets to use in combination therapy will gain urgency. "
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    ABSTRACT: Current approaches for identifying synergistic targets use cell culture models to see if the combined effect of clinically available drugs is better than predicted by their individual efficacy. New techniques are needed to systematically and rationally identify targets and pathways that may be synergistic targets. Here, we created a tool to screen and identify molecular targets that may synergize with new inhibitors of target of rapamycin (TOR), a conserved protein that is a major integrator of cell proliferation signals in the nutrient-signaling pathway. Although clinical results from TOR complex 1 (TORC1)-specific inhibition using rapamycin analogs have been disappointing, trials using inhibitors that also target TORC2 have been promising. To understand this increased therapeutic efficacy and to discover secondary targets for combination therapy, we engineered Tor2 in S. cerevisiae to accept an orthogonal inhibitor. We used this tool to create a chemical epistasis miniarray profile (ChE-MAP) by measuring interactions between the chemically inhibited Tor2 kinase and a diverse library of deletion mutants. The ChE-MAP identified known TOR components and distinguished between TORC1- and TORC2-dependent functions. The results showed a TORC2-specific interaction with the pentose phosphate pathway, a previously unappreciated TORC2 function that suggests a role for the complex in balancing the high energy demand required for ribosome biogenesis.
    Cell Reports 12/2013; 5(6). DOI:10.1016/j.celrep.2013.11.040 · 8.36 Impact Factor
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    • "Another important observation from this study is that, in addition to the magnitude and direction of effect, the mechanisms by which DR influences longevity can change depending on genetic context. For example, in sod2Δ cells, induction of mitochondrial respiration dramatically shortens lifespan while in wild-type (Kaeberlein et al. 2005a) or prohibitin mutant cells (this study) induction of respiration has little or no effect on RLS "
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    ABSTRACT: Dietary restriction (DR) increases lifespan and attenuates age-related phenotypes in many organisms; however, the effect of DR on longevity of individuals in genetically heterogeneous populations is not well characterized. Here we describe a large-scale effort to define molecular mechanisms that underlie genotype-specific responses to DR. The effect of DR on lifespan was determined for 166 single-gene deletion strains in Saccharomyces cerevisiae. Resulting changes in mean lifespan ranged from a reduction of 79% to an increase of 103%. Vacuolar pH homeostasis, superoxide dismutase activity, and mitochondrial proteostasis were found to be strong determinants of the response to DR. Proteomic analysis of cells deficient in prohibitins revealed induction of a mitochondrial unfolded protein response (mtUPR) which has not previously been described in yeast. Mitochondrial proteotoxic stress in prohibitin mutants was suppressed by DR via reduced cytoplasmic mRNA translation. A similar relationship between prohibitins, the mtUPR, and longevity was also observed in Caenorhabditis elegans. These observations define conserved molecular processes that underlie genotype-dependent effects of DR that may be important modulators of DR in higher organisms. This article is protected by copyright. All rights reserved.
    Aging cell 07/2013; 12(6). DOI:10.1111/acel.12130 · 6.34 Impact Factor
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    • "Lin et al. [10] first proposed that the effect of CR in yeast replicative lifespan was dependent on an increase in respiratory rates promoted by this intervention, although later results questioned the specific need for respiratory enhancements for the extension of replicative lifespan [11], [12]. Subsequently, many different groups and experimental approaches clearly demonstrated enhanced respiratory rates are necessary for the increment of chronological lifespan promoted by CR. "
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    ABSTRACT: Calorie restriction (CR) is an intervention known to extend the lifespan of a wide variety of organisms. In S. cerevisiae, chronological lifespan is prolonged by decreasing glucose availability in the culture media, a model for CR. The mechanism has been proposed to involve an increase in the oxidative (versus fermentative) metabolism of glucose. Here, we measured wild-type and respiratory incompetent (ρ(0)) S. cerevisiae biomass formation, pH, oxygen and glucose consumption, and the evolution of ethanol, glycerol, acetate, pyruvate and succinate levels during the course of 28 days of chronological aging, aiming to identify metabolic changes responsible for the effects of CR. The concomitant and quantitative measurements allowed for calculations of conversion factors between different pairs of substrates and products, maximum specific substrate consumption and product formation rates and maximum specific growth rates. Interestingly, we found that the limitation of glucose availability in CR S. cerevisiae cultures hysteretically increases oxygen consumption rates many hours after the complete exhaustion of glucose from the media. Surprisingly, glucose-to-ethanol conversion and cellular growth supported by glucose were not quantitatively altered by CR. Instead, we found that CR primed the cells for earlier, faster and more efficient metabolism of respiratory substrates, especially ethanol. Since lifespan-enhancing effects of CR are absent in respiratory incompetent ρ(0) cells, we propose that the hysteretic effect of glucose limitation on oxidative metabolism is central toward chronological lifespan extension by CR in this yeast.
    PLoS ONE 02/2013; 8(2):e56388. DOI:10.1371/journal.pone.0056388 · 3.23 Impact Factor
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