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Regulation of Longevity and Stress Resistance by Sch9 in Yeast


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The protein kinase Akt/protein kinase B (PKB) is implicated in insulin signaling in mammals and functions in a pathway that regulates longevity and stress resistance in Caenorhabditis elegans. We screened for long-lived mutants in nondividing yeastSaccharomyces cerevisiae and identified mutations in adenylate cyclase and SCH9, which is homologous to Akt/PKB, that increase resistance to oxidants and extend life-span by up to threefold. Stress-resistance transcription factors Msn2/Msn4 and protein kinase Rim15 were required for this life-span extension. These results indicate that longevity is associated with increased investment in maintenance and show that highly conserved genes play similar roles in life-span regulation in S. cerevisiae and higher eukaryotes.
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DOI: 10.1126/science.1059497
, 288 (2001); 292Science
et al.Paola Fabrizio,
Sch9 in Yeast
Regulation of Longevity and Stress Resistance by (this information is current as of January 13, 2009 ):
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Regulation of Longevity and
Stress Resistance by Sch9 in
Paola Fabrizio,
Fabiola Pozza,
Scott D. Pletcher,
Christi M. Gendron,
Valter D. Longo
The protein kinase Akt/protein kinase B (PKB) is implicated in insulin signaling
in mammals and functions in a pathway that regulates longevity and stress
resistance in Caenorhabditis elegans. We screened for long-lived mutants in
nondividing yeast Saccharomyces cerevisiae and identified mutations in ade-
nylate cyclase and SCH9, which is homologous to Akt/PKB, that increase re-
sistance to oxidants and extend life-span by up to threefold. Stress-resistance
transcription factors Msn2/Msn4 and protein kinase Rim15 were required for
this life-span extension. These results indicate that longevity is associated with
increased investment in maintenance and show that highly conserved genes
play similar roles in life-span regulation in S. cerevisiae and higher eukaryotes.
Mutations that extend life-span in C. elegans,
Drosophila melanogaster, and mice are asso-
ciated with increased resistance to oxidative
stress (1, 2). However, the mechanisms that
regulate aging in these multicellular organ-
isms are poorly understood. As in higher
eukaryotes, the unicellular yeast Saccharo-
myces cerevisiae undergoes an age-depen-
dent increase in cell dysfunction and mortal-
ity rates (3, 4 ). Aging in yeast is associated
with an enlargement of the cell and a slowing
in the budding rate, and is commonly mea-
sured by counting the number of buds gener-
ated by a single mother cell (replicative life-
span) (5, 6 ). The replicative life-span of yeast
is regulated by the Sir2 protein, which medi-
ates chromatin silencing in a nicotinamide
adenine dinucleotide– dependent manner (6,
7). However, yeast can also age chronologi-
cally as a population of nondividing cells (2,
4, 6). Saccharomyces cerevisiae grown in
complete glucose medium [synthetic com-
plete (SC) medium] stop dividing after 24 to
48 hours and survive for 5 to 7 days while
maintaining high metabolic rates (2, 8, 9), a
situation more akin to their experience in
nature where they are likely to survive as
nondividing populations exposed to scarce
nutrients. For these reasons, and to avoid
extended growth and entry into the hypo-
metabolic stationary phase induced by incu-
bation in the nutrient-richer yeast extract/
peptone/dextrose (YPD) medium (10), our
studies were performed exclusively in SC
medium. The survival of nondividing yeast is
shortened by null mutations in either or both
superoxide dismutases (SODs) (2, 11, 12)
and is modestly extended by overexpressing
the antiapoptotic protein Bcl-2 (8).
To understand the molecular mechanism
that regulates yeast longevity, we transposon-
mutagenized yeast cells and isolated long-lived
mutants (13). Because of the association be-
tween stress resistance and longevity in higher
eukaryotes, we screened for mutants that sur-
vived both a 1-hour heat stress at 52°C and a
9-day treatment with the superoxide-generating
agent paraquat (1 mM). From 2 billion cells
screened, we isolated 4000 thermotolerant col-
onies and 40 paraquat-resistant colonies carry-
ing transposons. From the 4040 stress-resistant
mutants, we isolated nine that were able to
survive to day 9, when most of the wild-type
cells are dead. The only two long-lived mutants
isolated independently in both the paraquat and
heat shock selections, designated Tn3-5 and
Tn3-24, were also the longest lived (Fig. 1A),
suggesting that resistance to multiple stresses is
associated with increased longevity. Allele res-
cue of the mutants revealed that transposons
had integrated in the promoter region of the
Sch9 protein kinase gene (sch9::mTn) (Tn3-5)
(33 base pairs upstream of the start codon) and
in the NH
-terminal regulatory region of ade-
nylate cyclase (cyr1::mTn) (Tn3-24) (between
codon 208 and 209). The mean life-spans of
sch9::mTn and cyr1::mTn were extended by 30
and 90%, respectively. Transformation of
Tn3-5 cells with wild-type SCH9, and of Tn3-
24 cells with CYR1, abolished the survival ex-
tension, strongly suggesting that the decreased
expression or activity of Sch9 and Cyr1 extends
survival (not shown).
To investigate further the role of SCH9 in
chronological survival, we deleted the SCH9
gene (14). The sch9 mutants grew slowly, but
survived three times longer than wild-type cells
(Fig. 1B). To determine whether the protein
kinase activity of Sch9 accelerates mortality in
nondividing yeast, we transformed mutants
with either wild-type SCH9 or with forms of
SCH9 bearing kinase-inactivating mutations:
and sch9
(15). Transformation
of sch9 with wild-type SCH9 reversed the
life-span extension, whereas transformation
Division of Biogerontology, Andrus Gerontology
Center, and Department of Biological Sciences, Uni-
versity of Southern California, Los Angeles, CA
90089 0191, USA.
Max Planck Institute for Demo-
graphic Research, Rostock, 18057 Germany.
*To whom correspondence should be addressed. E-
Fig. 1. Mutations in CYR1 and in SCH9
increase chronological life-span of S.
cerevisiae. Survival of (A) the wild
type (DBY746), and transposon-mu-
tagenized cyr1::mTn (Tn3-24) and
sch9::mTn (Tn3-5); (B) the wild type
and sch9;(C) sch9 transformed
with vector alone wild-type SCH9
or with a mutated sch9 encoding
for a catalytically inactive proteins
, Sch9
). Cell viability
was measured every 2 days starting at
day3(14). Experiments were repeat-
ed between three and seven times
with two or more samples per exper-
iment with similar results. The aver-
age of all experiments is shown. The
mean life-span increase in cyr1::mTn
(90%), sch9::mTn (30%), and sch9
(300%) is significant [P 0.05, anal-
ysis of variance (ANOVA)].
13 APRIL 2001 VOL 292 SCIENCE www.sciencemag.org288
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with the genes encoding for the inactive
or Sch9
kinases did not (Fig.
Both Sch9 and Cyr1 function in path-
ways that mediate glucose-dependent sig-
naling, stimulate growth and glycolysis,
and decrease stress resistance, glycogen ac-
cumulation, and gluconeogenesis (16). The
COOH-terminal region of Sch9 is highly
homologous to the AGC family of serine/
threonine kinases, which includes Akt/
PKB, whereas the NH
-terminal region
contains a C2 phospholipid and calcium-
binding motif. The 327–amino acid serine/
threonine kinase domain of yeast Sch9 is,
respectively, 47 and 45% identical to that
of C. elegans AKT-2 and AKT-1, which
function downstream of the insulin-recep-
tor homolog DAF-2 in a longevity/diapause
regulatory pathway (14, 17, 18). In this
domain conserved from yeast to mammals,
Sch9 is also 49% identical to human AKT-
1/AKT-2/PKB, which are implicated in bi-
ological functions including insulin signal-
ing, the translocation of glucose transport-
er, apoptosis, and cellular proliferation
The CYR1 gene encodes for adenylate
cyclase, which stimulates cyclic adenosine
monophosphate (cAMP)–dependent protein
kinase (PKA) activity required for cell cycle
progression and growth. The catalytic sub-
units of PKA are also 35 to 42% identical to
C. elegans and human AKT-1/AKT-2, al-
though PKA belongs to a different family of
serine/threonine kinase. The inactivation of
the Ras/cAMP/PKA pathway in S. cerevisiae
increases resistance to thermal stress, in part,
by activating transcription factors Msn2 and
Msn4, which induce the expression of genes
encoding for several heat shock proteins,
catalase (CTT1), and the DNA damage induc-
ible gene DDR2 (14, 16). MnSOD also ap-
pears to be regulated in a similar manner (20).
To determine whether MSN2/MSN4 mediate
survival extension, we deleted both genes in
the cyr1::mTn mutants. The absence of both
transcription factors abolished the life-span
extension conferred by cyr1::mTn, but did
not affect the survival of wild-type cells (Fig.
2A). By contrast, the deletion of MSN2/
MSN4 did not reverse the survival extension
in sch9 cells (Fig. 2B).
The protein kinase Rim15 regulates genes
containing a PDS ( postdiauxic shift) element
AT involved in the induction of
thermotolerance and starvation resistance by
a Msn2/Msn4-independent mechanism (21).
To test the role of Rim15 in survival, we
generated sch9 rim15 mutants. The life-
span of the double mutant was decreased
compared to sch9 (Fig. 2B). The deletion of
RIM15 also abolished the life-span extension
in cyr1::mTn cells (Fig. 2A). However, it is
difficult to establish whether Rim15 mediates
the survival extension in these mutants, be-
cause rim15 single mutants are short-lived
(Fig. 2A).
To test whether the long-lived strains
were stress-resistant, we exposed the mutants
to hydrogen peroxide, menadione, or heat.
All mutants were resistant to a 1-hour heat
shock treatment at 55°C (Fig. 3A). Similarly,
3- to 5-day-old mutants were resistant to a
30-min treatment with 100 mM hydrogen
peroxide (Fig. 3B) or with the superoxide/
-generating agent menadione (20 M)
(Fig. 3C).
In yeast sod2 mutants, superoxide specif-
ically inactivates aconitase and other [4Fe-4S]
cluster enzymes and causes the loss of mito-
chondrial function and cell death (11, 12). To
investigate further the role of superoxide toxic-
ity in aging, we monitored the activity and
reactivation of mitochondrial aconitase, which
can also serve as an indirect measure of super-
oxide concentration (22). In agreement with the
pattern of resistance to superoxide toxicity (Fig.
3C), aconitase specific activity decreased by
50% in wild-type cells, and by 30% in
cyr1::mTn mutants, but did not decrease in
sch9::mTn and sch9 mutants at day 7 com-
pared to day 3 (14 ). The percent reactivation of
aconitase was lowest in the long-lived sch9
mutants and highest in wild-type cells (Fig. 4A)
and correlated with death rates (Fig. 4B), sug-
gesting that cyr1 and sch9 mutants increase
survival, in part, by preventing superoxide tox-
icity. However, the overexpression of both
SOD1 and SOD2 only increases survival by
30% (9), indicating that additional systems, reg-
ulated by Msn2, Msn4, and Rim15, are respon-
sible for the major portion of chronological
life-span extension in cyr1::mTn and sch9
There are many phenotypic similarities
between long-lived mutants in S. cerevisiae,
C. elegans, Drosophila, and mice (1, 2). Cae-
Fig. 2. Transcription factors Msn2,
Msn4, and protein kinase Rim15 are
required for the chronological life-
span extension of cyr1::mTn and
sch9 mutants. (A) Survival of the
wild type and cyr1::mTn mutants lack-
ing either the stress-resistance genes
MSN2/MSN4 or RIM15.(B) Survival of
the wild type and sch9 mutants
lacking either MSN2/MSN4 or RIM15.
Experiments were repeated between
three and seven times with two or
more samples per experiment with
similar results. The average of all ex-
periments is shown.
Fig. 3. Heat-shock and oxidative stress resis-
tance are increased in long-lived mutants. (A)
Serial dilutions (1:1 to 1:1000, left to right) of
cells removed from day 1 postdiauxic phase
cultures were spotted onto YPD plates and
incubated at 30°C (control) or 55°C (heat-
shocked) for 1 hour. Pictures were taken after a
4-day incubation at 30°C. The experiment was
performed twice with two or more samples per
experiment with similar results. Cells removed
from days 3 or 5 in the postdiauxic phase were
(B) diluted to an OD
(optical density at 600
nm) of 1 in expired medium and incubated with
hydrogen peroxide (100 mM) for 30 min or (C)
diluted to an OD
of 0.1 in potassium phos-
phate buffer and treated with 20 Mofthe
-generating agent menadione
for 60 min. Viability was measured by plating
cells onto YPD plates after the treatment. The
experiments were performed twice with similar
results. The average of the two experiments is
on January 13, 2009 www.sciencemag.orgDownloaded from
norhabditis elegans age-1 and daf-2 mutations
extend the life-span in adult organisms by 65 to
100%, by decreasing AKT-1/AKT2 signaling
and activating transcription factor DAF-16 (14,
18, 23). These changes are associated with the
induction of superoxide dismutase (MnSOD),
catalase, and the heat shock proteins HSP70
and HSP90 (14, 17). A role for oxidants in the
aging of C. elegans was confirmed by the ex-
tended survival of wild-type worms treated
with small synthetic SOD/catalase mimetics
(24). Thus, the yeast Gpr1/Cyr1/PKA/Msn2/4-
Sch9/Rim15 and the C. elegans DAF-2/AGE-
1/AKT/DAF16 pathways play similar roles in
regulating longevity and stress resistance (14 ).
Analogously, a Drosophila line with a mutation
in the heterotrimeric guanosine triphosphate–
binding protein (G protein)–coupled receptor
homolog MTH gene displays a 35% increase in
life-span and is resistant to starvation and para-
quat toxicity (25). Furthermore, in flies,
aconitase undergoes age-dependent oxidation
and inactivation (26), and the overexpression
of SOD1 increases survival by up to 40% (27,
28). A mutation in a signal-transduction gene
also increases resistance to stress and length-
ens survival in mammals. A knockout muta-
tion in the signal transduction p66
increases resistance to paraquat and hydrogen
peroxide and extends survival by 30% in
mice (29).
We propose that yeast Sch9 and PKA and
worm AKT-1/AKT-2 evolved from common
ancestors that regulated metabolism, stress re-
sistance, and longevity in order to overcome
periods of starvation. Analogous mechanisms
triggered by low nutrients may be responsible
for the extended longevity of dietary restricted
rodents (3). The phenotypic similarities of long-
lived mutants ranging from yeast to mice (1, 2),
and the role of the conserved yeast Sch9 and
PKA and mammalian Akt/PKB in glucose me-
tabolism, raise the possibility that the funda-
mental mechanism of aging may be conserved
from yeast to humans.
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1 February 2001; accepted 15 March 2001
Published online 5 April 2001;
Include this information when citing this paper.
Functional Specialization in
Rhesus Monkey Auditory Cortex
Biao Tian, David Reser, Amy Durham, Alexander Kustov,
Josef P. Rauschecker*
Neurons in the lateral belt areas of rhesus monkey auditory cortex prefer complex
sounds to pure tones, but functional specializations of these multiple maps in the
superior temporal region have not been determined. We tested the specificity
of neurons in the lateral belt with species-specific communication calls pre-
sented at different azimuth positions. We found that neurons in the anterior
belt are more selective for the type of call, whereas neurons in the caudal belt
consistently show the greatest spatial selectivity. These results suggest that
cortical processing of auditory spatial and pattern information is performed in
specialized streams rather than one homogeneously distributed system.
Hearing plays a dual role in the identification
of sounds and in their localization. Although
it is undisputed that auditory cortex partici-
pates in the analysis of spectro-temporal pat-
terns for the identification of complex sound
objects, including speech and music, the neu-
ral basis of auditory spatial perception re-
mains a matter of controversy. Brainstem-
structures play a significant role in the pro-
cessing of binaural cues, which contain im-
portant information for sound localization
(1). However, lesions of auditory cortex also
impair auditory spatial analysis (2, 3). With
the recent discovery of multiple cochleotopic
maps in nonprimary auditory cortex of the
rhesus monkey (4, 5), the question arises
whether neurons in some of these areas show
greater specificity for sound source location
than in others. This could indicate the exis-
tence of a specialized cortical stream for the
processing of auditory space, similar to what
Georgetown Institute for Cognitive and Computa-
tional Sciences, Department of Physiology and Bio-
physics, Georgetown University Medical Center,
Washington, DC 20007, USA.
*To whom correspondence should be addressed. E-
Fig. 4. Mutations in cyr1
and sch9 delay the re-
versible inactivation of
the superoxide-sensitive
enzyme aconitase in the
mitochondria. (A) Mito-
chondrial aconitase per-
cent reactivation after
treatment of whole-cell
extracts of yeast re-
moved from cultures at
day 5 through 7 with
agents (iron and Na
S) able to reactivate superoxide inactivated [4Fe-4S] clusters. (B) Death rate
reported as the fraction of cells that lose viability in the 24-hour period following the indicated day.
13 APRIL 2001 VOL 292 SCIENCE www.sciencemag.org290
on January 13, 2009 www.sciencemag.orgDownloaded from
... These lifespan-determining genes, age-1, daf-2 and daf-16 act in a singular pathway and are orthologous to mammalian insulin and insulin-like signalling (ILS) pathway components: phosphatidylinositol-3 kinase (P13K), insulin-like receptor and FOXO respectively. Further studies in yeast (Fabrizio et al. 2001a), flies (Clancy et al. 2001;Tatar et al. 2001) and mice (Bartke 2008) indicated this was not a mechanism unique to worms, but one that is evolutionarily conserved to regulate lifespan. Further still, the relevance of the ILS pathway to humans has been confirmed by studying human Willcox et al. 2008) and insulin/insulin-like growth factor I receptor (IGF1R) (Suh et al. 2008) The TOR pathway regulates cell proliferation, autophagy and protein synthesis in response to growth factors, amino acids and energy. ...
... Target of Rapamycin (TOR) has been described as a central regulator of lifespan, originally identified through studies in yeast and C. elegans in which reduced expression of TOR signalling doubled chronological lifespan in yeast (Fabrizio et al. 2001b) and extends lifespan in C. elegans (Jia, Chen, and Riddle 2004). TOR forms part of the mTORC1 complex which drives cell growth in response to nutrient levels. ...
The reduction of activity of RNA polymerase I and III (Pol I and III) extends lifespan and these effects can be mediated by one organ; the gut. This thesis explores how reduced activity of Pol I or III in Drosophila impacts health. I explored the effect of reduced Pol I or Pol III activity on neuromuscular health through observing changes in climbing behaviour. Reduced activity of Pol I in the gut, and in particular, the intestinal stem cells, mediates the amelioration of neuromuscular decline through non-cell autonomous effects. Furthermore, I investigated the impact of reduced Pol I or III activity on quantity and quality of sleep and activity through Drosophila activity monitoring assays. Pol III mutants are hyperactive relative to controls and protect against age-related increase in sleep fragmentation. Pol I mutants are hyperactive during the day and ameliorate age-related decline in day activity; the former phenotype is recapitulated by enterocyte specific knockdown of Pol I. Pol I mutants also protect against age-related increase in total sleep which again is recapitulated by gut specific knockdown of Pol I. Additionally, I conducted an exploratory investigation of gene expression changes in Drosophila with reduced Pol III activity in the gut with the aim of elucidating how the gut can alter wider organismal health. This analysis identified genes encoding secreted proteins including neuroendocrine peptides, as well as genes involved in lipid metabolism, autophagy and immune signalling that were differentially regulated in this intervention. Finally, I analysed nucleolar size in guts of Pol I and Pol III mutants. Pol I mutants have reduced nucleolar size relative to controls whilst Pol III mutants’ nucleoli are not significantly altered. The reduced activity of Pol I or Pol III can improve indices of health in older flies. These effects are not the same between the Pols or on different aspects of health and some may be mediated by non-cell autonomous mechanisms.
... A central role in the nutrient-responsive network of the yeast Saccharomyces cerevisiae is played by the protein kinase Sch9, which was suggested to combine the functions of the mammalian S6-kinase (S6K) [1] and protein kinase B (PKB)/Akt [2]. Sch9 controls several processes, including the regulation of transcription and translation [3][4][5], cellular stress responses [6][7][8][9], sphingolipid metabolism [10], pH homeostasis [11], and chronological as well as replicative lifespan [12,13]. Sch9 receives input from several upstream players. ...
Full-text available
Yeast cells maintain an intricate network of nutrient signaling pathways enabling them to integrate information on the availability of different nutrients and adjust their metabolism and growth accordingly. Cells that are no longer capable of integrating this information, or that are unable to make the necessary adaptations, will cease growth and eventually die. Here, we studied the molecular basis underlying the synthetic lethality caused by loss of the protein kinase Sch9, a key player in amino acid signaling and proximal effector of the conserved growth-regulatory TORC1 complex, when combined with either loss of the cyclin-dependent kinase (CDK) Pho85 or loss of its inhibitor Pho81, which both have pivotal roles in phosphate sensing and cell cycle regulation. We demonstrate that it is specifically the CDK-cyclin pair Pho85-Pho80 or the partially redundant CDK-cyclin pairs Pho85-Pcl6/Pcl7 that become essential for growth when Sch9 is absent. Interestingly, the respective three CDK-cyclin pairs regulate the activity and distribution of the phosphatidylinositol-3 phosphate 5-kinase Fab1 on endosomes and vacuoles, where it generates phosphatidylinositol-3,5 bisphosphate that serves to recruit both TORC1 and its substrate Sch9. In addition, Pho85-Pho80 directly phosphorylates Sch9 at Ser726, and to a lesser extent at Thr723, thereby priming Sch9 for its subsequent phosphorylation and activation by TORC1. The TORC1-Sch9 signaling branch therefore integrates Pho85-mediated information at different levels. In this context, we also discovered that loss of the transcription factor Pho4 rescued the synthetic lethality caused by loss of Pho85 and Sch9, indicating that both signaling pathways also converge on Pho4, which appears to be wired to a feedback loop involving the high-affinity phosphate transporter Pho84 that fine-tunes Sch9-mediated responses.
... By target mutation, the gene study encoding the invertebrate life has made significant progress, and the research elucidates the inhibition of signal pathway of insulin or insulin-like growth factor-1 can significantly increase the lifespan [5] In fruit flies, yeast and mammals, insulin like signaling cascade, similarly to the DAF-2 signaling pathway, can increase the lifespan by altering the IGF-1 signal pathway. There are a large number of results show that the IGF system plays a significant role in the aging process [6][7][8]. ...
... Active mTORC1 promotes rapid cell growth, ribosome biogenesis, transcription, protein translation, and cellular nutrient import, and it inhibits organismal maintenance mechanisms such as autophagy and several stress response mechanisms [22,35]. Inhibition of mTORC1 can be achieved by AMPK activation, genetic manipulations, or the use of rapamycin, leading to lifespan extension in yeast, nematodes, water flea, flies, and mice, together indicating that metabolism is shifted towards better maintenance [36][37][38][39][40][41]. DNA damage can also suppress mTOR, and further mTOR inhibition causes upregulation of 8-oxoguanine glycosylase 1 (OGG1), a DNA repair enzyme, and fails to extend lifespan in DNA-repair-deficient mice, pointing to the ability of organisms to repair DNA better in the absence of mTOR activity [42][43][44]. ...
We propose a two-mode (pursuit/maintenance) model of metabolism defined by usable resource availability. Pursuit, consisting of anabolism and catabolism, dominates when usable resources are plentiful and leads to the generation of metabolic waste. In turn, maintenance of a system is activated by elevated metabolic waste during resource depletion. Interaction with the environment results in pendulum-like swings between these metabolic states in thriveless attempts to maintain the least deleterious organismal state – ephemeral homeostasis. Imperfectness of biological processes during these attempts supports the accumulation of the deleteriome, driving organismal aging. We discuss how metabolic adjustment by the environment and resource stabilization may modulate healthspan and lifespan.
... This suggested that a yeast kinase was able to phosphorylate Bax in a similar way as AKT. Interestingly, when BaxWT was expressed in a yeast strain deleted for Sch9, a yeast homolog of AKT (26), BaxWT displayed a greater mitochondrial localization than in a wild-type yeast ( Figure 2A). We have previously extensively characterized a P168A mutant, that displays both a strong constitutive mitochondrial localization ( Figure 2A) and a large cytochrome c release capacity ( Figure 3B) (27)(28)(29). ...
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The S184 residue of Bax is the target of several protein kinases regulating cell fate, including AKT. It is well-established that, in cellulo , the substitution of S184 by a non-phosphorylatable residue stimulates both the mitochondrial localization of Bax, cytochrome c release, and apoptosis. However, in in vitro experiments, substituted mutants did not exhibit any increase in their binding capacity to isolated mitochondria or liposomes. Despite exhibiting a significant increase of the 6A7 epitope exposure, substituted mutants remain limited in their ability to form large oligomers, suggesting that they high capacity to promote apoptosis in cells was more related to a high content than to an increased ability to form large pores in the outer mitochondrial membranes.
... Because of this, fasting is being investigated as a potential augmentative therapy during cancer therapies [167]. Autophagy impairment has been linked to several diseases, such as Alzheimer's and Parkinson's diseases, diabetes, cancer, chronic inflammatory diseases, depression and chronic fatigue syndrome [168,169]. Increased enthusiasm about fasting and its associated benefits [170] has prompted interest from clinical researchers. A recent study found that short-term, time-restricted feeding is safe and feasible in non-obese healthy midlife and older adults [171]. ...
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Background: An increasing number of studies suggest that diet plays an important role in regulating aging processes and modulates the development of the most important age-related diseases. Objective: The aim of this review is to provide an overview of the relationship between nutrition and critical age-associated diseases. Methods: A literature review was conducted to survey recent pre-clinical and clinical findings related to the role of nutritional factors in modulation of fundamental cellular and molecular mechanisms of aging and their role in prevention of the genesis of the diseases of aging. Results: Studies show that the development of cardiovascular and cerebrovascular diseases, neurodegenerative diseases, cognitive impairment and dementia can be slowed down or prevented by certain diets with anti-aging action. The protective effects of diets, at least in part, may be mediated by their beneficial macro- (protein, fat, carbohydrate) and micronutrient (vitamins, minerals) composition. Conclusions: Certain diets, such as the Mediterranean diet, may play a significant role in healthy aging by preventing the onset of certain diseases and by improving the aging process itself. This latter can be strengthened by incorporating fasting elements into the diet. As dietary recommendations change with age, this should be taken into consideration as well, when developing a diet tailored to the needs of elderly individuals. Future and ongoing clinical studies on complex anti-aging dietary interventions translating the results of preclinical investigations are expected to lead to novel nutritional guidelines for older adults in the near future.
... Paradigm-shifting work in the worm Caenorhabditis elegans has identified single-gene mutations that significantly extend lifespan, thereby demonstrating a clear contribution of genetics to lifespan determination. Since the first genes to increase lifespan were identified in C. elegans (Friedman & Johnson, 1988;Kenyon et al., 1993;Klass, 1977;Wong et al., 1995), single-gene mutations have also been shown to extend lifespan in other model organisms including yeast, flies, and mice (Clancy et al., 2001;Fabrizio et al., 2001;Holzenberger et al., 2003). Importantly, many of the genes or interventions that extend lifespan are evolutionarily conserved (Kenyon, 2005). ...
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Mutations that extend lifespan are associated with enhanced resistance to stress. To better understand the molecular mechanisms underlying this relationship, we directly compared lifespan extension, resistance to external stressors, and gene expression in a panel of nine long-lived Caenorhabditis elegans mutants from different pathways of lifespan extension. All of the examined long-lived mutants exhibited increased resistance to one or more types of stress. Resistance to each of the examined types of stress had a significant, positive correlation with lifespan, with bacterial pathogen resistance showing the strongest relationship. Analysis of transcriptional changes indicated that all of the examined long-lived mutants showed a significant upregulation of multiple stress response pathways. Interestingly, there was a very significant overlap between genes highly correlated with stress resistance and genes highly correlated with longevity, suggesting that the same genetic pathways drive both phenotypes. This was especially true for genes correlated with bacterial pathogen resistance, which showed an 84% overlap with genes correlated with lifespan. To further explore the relationship between innate immunity and longevity, we disrupted the p38-mediated innate immune signaling pathway in each of the long-lived mutants and found that this pathway is required for lifespan extension in eight of nine mutants. Overall, our results demonstrate a strong correlation between stress resistance and longevity that results from the high degree of overlap in genes contributing to each phenotype. Moreover, these findings demonstrate the importance of the innate immune system in lifespan determination and indicate that the same underlying genes drive both immunity and longevity.
... More recent work used multi-dimensional linear regression (Bielby et al. 2007) to connect multiple traits such as brain size with longevity (Sacher 1959;Hofman 1983;Austad & Fischer 1991;Schoenemann 2004;Isler & van Schaik 2012). The diversity of lifespan is of interest, since it may point to ways of understanding the regulation of longevity in which stress resistance plays a major role (Fabrizio et al. 2001;Morley & Morimoto 2004;Kozłowski 2006;Curran & Ruvkun 2007;Pan & Chang 2012;Tian et al. 2013;Gorbunova et al. 2014;Szekely et al. 2015;see Heininger 2022, part 17). Life history traits such as longevity and reproductive parameters are closely linked with the ecological niche and environmental interactions of each species (Southwood 1988;Linden & Møller 1989;Martin 1995;Spor et al. 2009;Kostikova et al. 2013). ...
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We extend techniques and learnings about the stochastic properties of nonlinear responses from finance to medicine, particularly oncology, where it can inform dosing and intervention. We define antifragility. We propose uses of risk analysis for medical problems, through the properties of nonlinear responses (convex or concave). We (1) link the convexity/concavity of the dose-response function to the statistical properties of the results; (2) define “antifragility” as a mathematical property for local beneficial convex responses and the generalization of “fragility” as its opposite, locally concave in the tails of the statistical distribution; (3) propose mathematically tractable relations between dosage, severity of conditions, and iatrogenics. In short, we propose a framework to integrate the necessary consequences of nonlinearities in evidence-based oncology and more general clinical risk management.
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Toward a genetic dissection of the processes involved in aging, a screen for gene mutations that extend life-span in Drosophila melanogaster was performed. The mutant line methuselah(mth) displayed approximately 35 percent increase in average life-span and enhanced resistance to various forms of stress, including starvation, high temperature, and dietary paraquat, a free-radical generator. The mth gene predicted a protein with homology to several guanosine triphosphate–binding protein–coupled seven–transmembrane domain receptors. Thus, the organism may use signal transduction pathways to modulate stress response and life-span.
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Reactive oxygen (RO) has been identified as an important effector in ageing and lifespan determination. The specific cell types, however, in which oxidative damage acts to limit lifespan of the whole organism have not been explicitly identified. The association between mutations in the gene encoding the oxygen radical metabolizing enzyme CuZn superoxide dismutase (SOD1) and loss of motorneurons in the brain and spinal cord that occurs in the life-shortening paralytic disease, Familial Amyotrophic Lateral Sclerosis (FALS; ref. 4), suggests that chronic and unrepaired oxidative damage occurring specifically in motor neurons could be a critical causative factor in ageing. To test this hypothesis, we generated transgenic Drosophila which express human SOD1 specifically in adult motorneurons. We show that overexpression of a single gene, SOD1, in a single cell type, the motorneuron, extends normal lifespan by up to 40% and rescues the lifespan of a short-lived Sod null mutant. Elevated resistance to oxidative stress suggests that the lifespan extension observed in these flies is due to enhanced RO metabolism. These results show that SOD activity in motorneurons is an important factor in ageing and lifespan determination in Drosophila.
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Gene mutations in invertebrates have been identified that extend life span and enhance resistance to environmental stresses such as ultraviolet light or reactive oxygen species. In mammals, the mechanisms that regulate stress response are poorly understood and no genes are known to increase individual life span. Here we report that targeted mutation of the mouse p66shc gene induces stress resistance and prolongs life span. p66shc is a splice variant of p52shc/p46shc (ref. 2), a cytoplasmic signal transducer involved in the transmission of mitogenic signals from activated receptors to Ras. We show that: (1) p66shc is serine phosphorylated upon treatment with hydrogen peroxide (H2O2) or irradiation with ultraviolet light; (2) ablation of p66shc enhances cellular resistance to apoptosis induced by H2O2 or ultraviolet light; (3) a serine-phosphorylation defective mutant of p66shc cannot restore the normal stress response in p66shc-/- cells; (4) the p53 and p21 stress response is impaired in p66shc-/- cells; (5) p66shc-/- mice have increased resistance to paraquat and a 30% increase in life span. We propose that p66shc is part of a signal transduction pathway that regulates stress apoptotic responses and life span in mammals.
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The rapid inactivation of aconitase by O2-, previously seen to occur in vitro, was explored in vivo. A fraction of the aconitase in growing, aerobic, Escherichia coli is inactive at any instant but can be activated by imposition of anaerobic conditions. This reactivation occurred in the absence of protein synthesis and was inhibited by the ferrous chelator alpha,alpha'-dipyridyl. This fraction of inactive, but activatable, aconitase was increased by augmenting O2- production with paraquat, decreased by elevation of superoxide dismutase, and increased by inhibiting reactivation with alpha,alpha'-dipyridyl. The balance between inactive and active aconitase thus represented a pseudoequilibrium between inactivation by O2- and reactivation by restoration of Fe(II), and it provided, for the first time, a measure of the steady-state concentration of O2- within E. coli. On this basis, [O2-] was estimated to be approximately 20-40 pM in aerobic log phase E. coli containing wild type levels of superoxide dismutase and approximately 300 pM in a mutant strain lacking superoxide dismutase.
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Yeast lacking copper-zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (SOD), catalase T, or metallothionein were studied using long term stationary phase (10-45 days) as a simple model system to study the roles of antioxidant enzymes in aging. In well aerated cultures, the lack of either SOD resulted in dramatic loss of viability over the first few weeks of culture, with the CuZnSOD mutant showing the more severe defect. The double SOD mutant died within a few days. The severity reversed in low aeration; the CuZnSOD mutant remained viable longer than the manganese SOD mutant. To test whether reactive oxygen species generated during respiration play an important role in the observed cellular death, growth in nonfermentable carbon sources was measured. All strains grew under low aeration, indicating respiratory competence. High aeration caused much reduced growth in single SOD mutants, and the double mutant failed to grow. However, removal of respiration via another mutation dramatically increased short term survival and reversed the known air-dependent methionine and lysine auxotrophies. Our results suggest strongly that mitochondrial respiration is a major source of reactive oxygen species in vivo, as has been shown in vitro, and that these species are produced even under low aeration.
We tested the theory that reactive oxygen species cause aging. We augmented the natural antioxidant systems ofCaenorhabditis elegans with small synthetic superoxide dismutase/catalase mimetics. Treatment of wild-type worms increased their mean life-span by a mean of 44 percent, and treatment of prematurely aging worms resulted in normalization of their life-span (a 67 percent increase). It appears that oxidative stress is a major determinant of life-span and that it can be counteracted by pharmacological intervention.
SOD2, encoding manganese superoxide dismutase (MnSOD), is essential for stationary-phase survival of yeast cells. In addition, stationary-phase cells are more resistant to oxidative stress than exponential-phase cells. The use of a SOD2::lacZfusion construct in this study shows that transcription of SOD2 increases 6.5-fold as cells enter stationary phase in rich, glucose medium. The increase in SOD2 expression appears to be due to two phenomena - the switch to a non-fermentable carbon source and nutrient limitation. Analysis of SOD2 transcription in mutant Saccharomyces cerevisiae strains showed that the gene was negatively regulated by intracellular cAMP levels which decrease as cells enter stationary phase. Mutation of 'stress-responsive' (STRE) elements in the SOD2 promoter which respond to cAMP levels resulted in the loss of cAMP-dependent expression but only partially reduced the increase in expression as cells entered stationary phase. A putative Yap1p-binding site was found to be inactive and mutation of YAP1 had no effect on the STRE-mediated expression. To fully eliminate the stationary-phase response, it was necessary to mutate a HAP2/3/4/5 complex binding site in addition to the STRE elements. It is postulated that the effects of the STRE sites and the HAP2/3/4/5 complex binding site are additive.
A mutation in the age-1 gene of the nematode Caenorhabditis elegans has been shown to result in a 65 percent increase in mean life-span and a 110 percent increase in maximum life-span at 25 degrees. One of the hallmarks of organismic aging and senescent processes is an exponential acceleration of age-specific mortality rate with chronological age. This exponential acceleration is under genetic control: age-1 mutant hermaphrodites show a 50 percent slower rate of acceleration of mortality with chronological age than wild-type strains. Mutant males also show a lengthening of life and a slowing of the rate of acceleration of mortality, although age-1 mutant males still have significantly shorter life-spans than do hermaphrodites of the same genotype. The slower rates of acceleration of mortality are recessive characteristics of the age-1 mutant alleles examined.
The life spans of individual Saccharomyces cerevisiae cells were determined microscopically by counting the number of buds produced by each cell to provide a measure of the number of cell generations (age) before death. As the cells aged, their generation times increased five- to sixfold. The generation times of daughter cells were virtually identical to those of their mothers throughout the life spans of the mothers. However, within two to three cell divisions after the daughters were detached from their mothers by micromanipulation, their generation times reverted to that characteristic of their own age. Recovery from the mother cell effect was also observed when the daughters were left attached to their mothers. The results suggest that senescence, as manifested by the increase in generation time, is a phenotypically dominant feature in yeast cells and that it is determined by a diffusible cytoplasmic factor(s) that undergoes turnover. This factor(s) appeared to be transmitted by a cell not only to its daughter, but also indirectly to its granddaughter. In separate studies, it was determined that the induced deposition of chitin, the major component of the bud scar, in the yeast cell wall had no appreciable effect on life span. We raise the possibility that the cytoplasmic factor(s) that appears to mediate the "senescent phenotype" is a major determinant of yeast life span. This factor(s) may be the product of age-specific gene expression.
Like other microorganisms, the yeast Saccharomyces cerevisiae responds to starvation by arresting growth and entering stationary phase. Because most microorganisms exist under conditions of nutrient limitation, the ability to tolerate starvation is critical for survival. Molecular analyses have identified changes in transcription, translation, and protein modification in stationary-phase cells. At the level of translation, the pattern of newly synthesized proteins in stationary-phase cells is surprisingly similar to the pattern of proteins synthesized during exponential growth. When limited for different nutrients, yeast strains may not enter stationary phase but opt for pathways such as pseudohyphal growth. If nutrient limitation continues, the end-point is likely to be a stationary-phase cell. Based on the results of recent studies, we propose a model for entry into stationary phase in which G(o) arrest is separable from acquisition of the ability to survive long periods of time without added nutrients.