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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
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Regulation of Longevity and
Stress Resistance by Sch9 in
Yeast
Paola Fabrizio,
1
Fabiola Pozza,
1
Scott D. Pletcher,
2
Christi M. Gendron,
2
Valter D. Longo
1
*
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
2
-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:
sch9
K441A
and sch9
D556R
(15). Transformation
of sch9 with wild-type SCH9 reversed the
life-span extension, whereas transformation
1
Division of Biogerontology, Andrus Gerontology
Center, and Department of Biological Sciences, Uni-
versity of Southern California, Los Angeles, CA
90089 0191, USA.
2
Max Planck Institute for Demo-
graphic Research, Rostock, 18057 Germany.
*To whom correspondence should be addressed. E-
mail: vlongo@usc.edu
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
K441A
, Sch9
D556R
). 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)].
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with the genes encoding for the inactive
Sch9
K441A
or Sch9
D556R
kinases did not (Fig.
1C).
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
2
-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
(19).
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
T(T/A)AG
3
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/
H
2
O
2
-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
mutants.
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
600
(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
600
of 0.1 in potassium phos-
phate buffer and treated with 20 Mofthe
superoxide/H
2
O
2
-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
shown.
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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
SHC
gene
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;
101126/science.1059497
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-
mail: rauschej@georgetown.edu
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
2
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.
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... Promote autophagy Enhanced cell resistance to hightemperature and oxidative stress, increasing survival rates by 60% and 50%, respectively [132] Oxidative stress Overexpress ATG8 ATG11 ATG32 ...
... Disrupting ATG13 Inhibit autophagy Ethanol production increased by 38% [145] Yeast atg32D Inhibit mitophagy During sake brewing, the maximum rate of CO 2 production increased by 7.50%; final ethanol concentration increased by 2.12% The final ethanol concentration of minimal synthetic medium incubated with the atg32D strain was 2.76% increased relative to its parent sake yeast strain [146] The 2,3-butanediol (23BD) titer was 23.6 times higher than that in the control strain [147] replication life (defined as the number of maternal cells divided into offspring cells). Compared with the wildtype DBY746, the cell survival rate of the sch9D strain increased by 60% under heat stress and increased by 50% under oxidative stress [132]. sch9D can induce autophagy in yeast [133], and the regulation of sch9 on the autophagy or proteasome pathway can accelerate the degradation of ubiquitinated proteins under yeast heat stress, reduce the level of ubiquitination, and improve the high-temperature tolerance of yeast [132,134]. ...
... Compared with the wildtype DBY746, the cell survival rate of the sch9D strain increased by 60% under heat stress and increased by 50% under oxidative stress [132]. sch9D can induce autophagy in yeast [133], and the regulation of sch9 on the autophagy or proteasome pathway can accelerate the degradation of ubiquitinated proteins under yeast heat stress, reduce the level of ubiquitination, and improve the high-temperature tolerance of yeast [132,134]. With oxidative stimulation, overexpression of atg8 and atg11 genes significantly reduced the intracellular ROS content of the strain, which was only 52.05% and 22.57% of the initial state, and helped the strain to maintain mitochondrial activity [135]. ...
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Historically, plant derived natural products and their crude extracts have been used to treat a wide range of ailments across the world. Biogerontology research aims to explore the molecular basis of aging and discover new anti-aging therapeutic compounds or formulations to combat the detrimental effects of aging and promote a healthy life span. The budding yeast Saccharomyces cerevisiae has been, and continues to be, an indispensable model organism in the field of biomedical research for discovering the molecular basis of aging S. cerevisiae has preserved nutritional signaling pathways (such as the target of rapamycin (TOR)-Sch9 and the Ras-AC-PKA (cAMP-dependent protein kinase) pathways, and shows two distinct aging paradigms chronological life span (CLS) and replicative life span (RLS). This review explores the anti-aging properties of natural products, predominantly derived from plants, and phytoextracts using S. cerevisiae as a model organism.
... Early studies using both unicellular yeast [1,2] and multicellular invertebrates, such as Caenorhabditis elegans [3][4][5] and Drosophila melanogaster [6,7], have demonstrated positive correlations between the degree of stress resistance and lifespan. Specifically, long-lived individuals are significantly more resistant to the lethal effects of various agents, such as heat and oxidizing chemicals, than were short-lived individuals [1][2][3][4][5][6][7]. ...
... Early studies using both unicellular yeast [1,2] and multicellular invertebrates, such as Caenorhabditis elegans [3][4][5] and Drosophila melanogaster [6,7], have demonstrated positive correlations between the degree of stress resistance and lifespan. Specifically, long-lived individuals are significantly more resistant to the lethal effects of various agents, such as heat and oxidizing chemicals, than were short-lived individuals [1][2][3][4][5][6][7]. Since then, this finding has been extended to include multiple vertebrate species, such as fishes [8] and turtles [9], as well as both mammals and birds (reviewed in Alper et al., [10]) using primary fibroblast cell cultures as the model system, rather than intact individuals, for both practical and ethical reasons [11]. ...
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Small-breed dogs live significantly longer lives than large-breed dogs, while having higher mass-specific metabolic rates and faster growth rates. Underlying this observed physiological difference across domestic dogs, there must also be differences at other levels of organization that could lead to elucidating what accounts for the disparity in aging rates and life span within this species. At the cellular level, a clear mechanism underlying whole animal traits has not been fully elucidated. Here, we cultured dermal fibroblasts from large and small breed dogs from both young and old age categories and examined the degree of resistance to multiple sources of cytotoxic stress. This included heat (42 °C), paraquat, cadmium, and hydrogen peroxide for increasing amounts of time (heat) or increasing concentrations (chemical stressors). We hypothesized that small breed dogs, with longer lifespans, would have greater cellular resistance to stress compared with large breed dogs. Final sample sizes include small puppies (N = 18), large puppy (N = 32), small old (N = 11), and large old (N = 23) dogs. Using a 2 (donor size) by 2 (donor age) between-subjects multivariate analysis of variance, we found that the values for the dose that killed 50% of the cells (LD50) were not significantly different based on donor size (p = 0.45) or donor age (p = 0.20). The interaction was also not significant (p = 0.47). Interestingly, we did find that the degree of resistance to cadmium toxicity was significantly correlated with the degree of resistance to both heat and hydrogen peroxide, but not paraquat (p < 0.01 for both). These data suggest that cellular stress resistance does not differ among domestic dogs as a function of size or age, pointing to other cellular pathways as the mechanistic basis for the observed differences in lifespan.
... Identifying factors which regulate aging-associated epigenetics will be important for predicting, diagnosing, and/or treating age-related ailments. To investigate the fundamental molecular basis behind aging, chronological aging (CLS) in yeast is a well-established model system to identify conserved factors that affect cellular mortality (Fabrizio et al. 2001). CLS is a measure of how long a cell maintains its viability after it stops dividing at the stationary phase. ...
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Aging is a complex phenomenon that is characterized by the altered regulation of various biological processes over time. One of these, epigenetics, play a crucial role throughout the different stages of eukaryotic life and its alteration is considered a key molecular hallmark of aging. However, the epigenetic factors which are important for lifespan control remain elusive. Here, we used S. pombe as a model organism to study the epigenetic basis of aging. Our study reveals that loss of the epe1 + gene, encoding for the JmjC domain protein Epe1 , extends chronological lifespan and increases H3K9me3 in aged S. pombe cells .
... Sch9 is an AGC family protein kinase that is among the most evolutionarily conserved kinases. 1 It is involved in various cellular processes, including growth, 2,3 metabolism, 4 stress response, [5][6][7][8] and lifespan. 9,10 Similar to typical AGC family kinases, its activation requires the phosphorylation of its regulatory motifs. The C-terminus of Sch9, which contains hydrophobic motifs, is phosphorylated by the target of rapamycin complex 1 (TORC1), a highly conserved protein kinase complex. 1 Additionally, the C-terminus of Sch9 is also phosphorylated by Bur1/2 and Pho85/Pho80. ...
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The regulation of cellular metabolism is crucial for cell survival, with Sch9 in Saccharomyces cerevisiae serving a key role as a substrate of TORC1. Sch9 localizes to the vacuolar membrane through binding to PI(3,5)P2, which is necessary for TORC1-dependent phosphorylation. This study demonstrates that cytosolic pH regulates Sch9 localization. Under stress conditions that induce cytosolic acidification, Sch9 detached from the vacuolar membrane. In vitro experiments confirmed that Sch9’s affinity for PI(3,5)P2 is pH-dependent. This pH-dependent localization switch is essential for regulating the TORC1–Sch9 pathway. Impairment of the dissociation of Sch9 from the vacuolar membrane in response to cytosolic acidification resulted in the deficient induction of stress response gene expression and delayed the adaptive response to acetic acid stress. These findings indicate the importance of proper Sch9 localization for metabolic reprogramming and stress response in yeast cells.
... A number of yeast oncogene orthologues, including Ras and Sch9 (which is the functional orthologue of human S6K), have the ability to decrease the organism's tolerance to stress in experimentation (Jordan et al. 2019). Additionally, mutations that activate IGF1R, RAS, PI3KCA, or AKT, or mutations that inactivate PTEN, are seen in the great majority of breast cancers and other forms of human cancer (Fabrizio et al. 2001). This concept posits that hunger might exert an opposing influence on cancer cells, impeding their capacity to endure cellular stresses such as chemotherapy in comparison to healthy cells. ...
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The number of studies that have been conducted on the possible benefits of different types of fasting or calorie restriction on cancer therapy, including the likelihood that these treatments lessen side effects, has been limited. However, the results are nevertheless promising. Chemotherapy’s adverse effects have led to a quest for options that reduce reliance on it. The susceptibility of tumorous cells to specific metabolites and nutrient deficiency is increasingly recognized as a key characteristic of the disease. This review delves into the data on various fasting methods and calorie restriction in rodents and humans, with a focus on biological adaptations that could potentially lower cancer risk or enhance cancer treatment results. We also emphasize recent scientific developments regarding the use of prolonged fasting and fasting-mimicking diets as a possible additional treatment for patients receiving immunotherapy or other treatments. This approach shows promise in enhancing treatment effectiveness, preventing resistance, and minimizing side effects. This study proposes that combining fasting and calorie restriction with chemotherapy, immunotherapy, or other therapies might be a potential technique to improve treatment efficacy, avoid resistance, and reduce adverse effects.
... Thus, NUMT formation in early stationary phase cells is not associated with overall loss of mtDNA or loss of viability. Another argument against dead cells being a source of mtDNA for NUMT formation is that sch9Δ mutant maintains 100% viability even at 8 days stationary phase (Supplementary Fig. 3f) 33 , yet the number of insertions is similar when compared to wild-type. Finally, mtDNA fragments could originate from a cell's own mitochondria, including connected mother-daughter pairs, or from other live cells in culture. ...
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In metazoans mitochondrial DNA (mtDNA) or retrotransposon cDNA released to cytoplasm are degraded by nucleases to prevent sterile inflammation. It remains unknown whether degradation of these DNA also prevents nuclear genome instability. We used an amplicon sequencing-based method in yeast enabling analysis of millions of DSB repair products. In non-dividing stationary phase cells, Pol4-mediated non-homologous end-joining increases, resulting in frequent insertions of 1–3 nucleotides, and insertions of mtDNA (NUMTs) or retrotransposon cDNA. Yeast EndoG (Nuc1) nuclease limits insertion of cDNA and transfer of very long mtDNA ( >10 kb) to the nucleus, where it forms unstable circles, while promoting the formation of short NUMTs (~45–200 bp). Nuc1 also regulates transfer of extranuclear DNA to nucleus in aging or meiosis. We propose that Nuc1 preserves genome stability by degrading retrotransposon cDNA and long mtDNA, while short NUMTs originate from incompletely degraded mtDNA. This work suggests that nucleases eliminating extranuclear DNA preserve genome stability.
... These ancient signaling cascades are the main regulators of metabolism and growth. However, a myriad of molecular pathways and biological processes downstream of IIS and TOR are involved in lifespan determination [12,13]. Disruptions of genes encoding positive regulators of IIS and mTOR signaling extend the lifespan. ...
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Studies on numerous species have demonstrated strikingly conserved mechanisms that determine the aging process, from yeasts to worms, flies, zebrafish, mice, and humans. The fruit fly Drosophila melanogaster is an excellent model organism for studying the biological basis of normal aging and etiology of age-related diseases. Since its inception in 1967, the Bloomington Drosophila Stock Center (BDSC) has grown into the largest collection of documented D. melanogaster strains (currently > 91,000). This paper aims to briefly review conserved mechanisms of aging and provides a guide to help users understand the organization of stock listings on the BDSC website and familiarize themselves with the search functions on BDSC and FlyBase, with an emphasis on using genes in conserved pathways as examples to find stocks for aging studies.
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This chapter aims to provide an overview of the most recent studies aimed at unravelling the reason why some populations living in areas known as blue zones (BZ) exhibit much longer survival at old ages than others, such as the people of Okinawa (Japan), Sardinia (Italy), Nicoya (Costa Rica) and Ikaria (Greece). After presenting some historical details on the identification of these long-lived populations, it will discuss hypotheses and findings concerning the potential biological determinants (genetics, epigenetics and hormones) of these exceptional longevities, as well as the environmental context (lifestyle and nutrition) and social-cultural factors (such as socialization through family ties and solidarity).
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Tumor immunotherapy has significantly transformed the field of oncology over the past decade. An optimal tumor immunotherapy would ideally elicit robust innate and adaptive immune responses within tumor immune microenvironment (TIME). Unfortunately, immune system experiences functional decline with chronological age, a process termed “immunosenescence,” which contributes to impaired immune responses against pathogens, suboptimal vaccination outcomes, and heightened vulnerability to various diseases, including cancer. In this context, we will elucidate hallmarks and molecular mechanisms underlying immunosenescence, detailing alterations in immunosenescence at molecular, cellular, organ, and disease levels. The role of immunosenescence in tumorigenesis and senescence‐related extracellular matrix (ECM) has also been addressed. Recognizing that immunosenescence is a dynamic process influenced by various factors, we will evaluate treatment strategies targeting hallmarks and molecular mechanisms, as well as methods for immune cell, organ restoration, and present emerging approaches in immunosenescence for tumor immunotherapy. The overarching goal of immunosenescence research is to prevent tumor development, recurrence, and metastasis, ultimately improving patient prognosis. Our review aims to reveal latest advancements and prospective directions in the field of immunosenescence research, offering a theoretical basis for development of practical anti‐immunosenescence and anti‐tumor strategies.
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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.
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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.
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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.
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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.
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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.
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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.