A. Hughes, DE Gottschling, An early age increase in vacuolar pH limits mitochondrial function and lifespan in yeast, Nature 492, 261–265 (13 December 2012), doi:10.1038/nature11654
Adam L. Hughes & Daniel E. Gottschling
2. 2
Saccharomyces cerevisiae (Budding yeast)
unicellular eukaryotic organism small genome comprising about 6000
genes, which has been completely
sequenced
molecular genetic tools
Cost effective model
Easy to manipulate
High throughput screening
31% of yeast gene has a human
homolog
3. 3
Introduction
S. cerevisiae
Aged yeast cells
- Mitochondria fragmentation
- Increase ROS
- Loss of mitochondrial DNA
AGEING
Chronological life span
Replicative life span
S. cerevisiae
4. 4
Introduction
S. cerevisiae
Aged yeast cells
- Mitochondria fragmentation
- Increase ROS
- Loss of mitochondrial DNA
AGEING
Chronological life span
Replicative life span
S. cerevisiae
Number of times an
individual cell divides
7. 7
Method: Mother enrichment program (MEP)
Daughter Cell
the transcription
factor Ace2
Sequester in the cytoplasm
Transported into the nucleus
8. 8
Method: Mother enrichment program (MEP)
Cre-
EBD78
SUMO-conjugating
enzyme
Activator of the
anaphase-promoting
complex (APC)
Arrest
in M-phase
9. 9
Results: Mitochondrial dysfunction in aged yeast
Calcofluor staining of
the bud scar
TOM70-GFP
Mitochondrial marker
Nr. Cell division
Characterization of age-associated mitochondrial phenotypes
10. 10
Results: Decreased of mitochondrial function
DiOC6 : ΔΨ-dependent mitochondrial
fluorescent dye
11. 11
Mitochondrial structure in young cells
250 genes1)
2) Overexpression of the 250 genes
MEP strain expressing Tom70-GFP
Delayed to the onset of altered mitochondrial
morphology in aged cells
12. 12
Results: VAM1 and VPH2
VAM1
VPH2
A Catalytic subunit of V-ATPase
V-ATPase assembly
V-ATPase : Acidification of the
vacuole
Overexpression of VMA suppressed
mitochondrial dysfunction in 93 %
Overexpression of VPH2 suppressed
mitochondrial dysfunction in 77 %
Suppression by VMA1 or VPH2 overexpression required V-ATPase activity
13. 13
Results: Vacuolar and mitochondrial function are linked
• Overexpression of VMA1 and
VPH2 increase both media and
maximal replicative lifespan.
14. 14
How vpH affects mitochondrial function?
vacuolar protein degradation?
Deletion of PEP4
No alteration of mitochondrial structure
15. 15
How vpH affects mitochondrial function?
Import of vacuolar metabolite?
Overexpression of vacuolar
importers
+
ConcA
ATV1 Neutral amino acid transporter
Prevent mitochondrial dysfunction
16. 16
Results: ATV1 prevents mitochondrial fragmentation
Overexpression of
ATV1
• Prevent alteration of mitochondrial structure
• No change in vacuolar acidification
17. 17
Results: ATV1 as aging modulator
Deletion of ATV1
Development of age-induced mitochondrial
dysfunction
Overexpression = Extending RLS
Deletion = Shortening of RLS
18. 18
Conclusion
o Yeast is a good model for aging
o Link between vacuolar pH and mitochondrial function
o Link between metabolite transport and aging
o Vacuole functionalion as aging modulator
o Reestablishment of acidification in the vacuole in the
daughter cells
Expression of the Cre recombinase is restricted by a daughter-specific promoter derived from SCW11 (PSCW11) (Figure 1A). Daughter-specific expression from PSCW11 is regulated by the transcription factor Ace2, which is asymmetrically distributed to daughter cell nuclei prior to cytokinesis
Cre activity is also post-transcriptionally regulated by fusion to the estradiol-binding domain (EBD) of the murine estrogen receptor (Cre-EBD78). The EBD sequesters the fusion protein in the cytoplasm until estradiol is introduced, at which point the fusion protein is transported into the nucleus where Cre can act upon its loxP DNA substrates
Mitochondria—which are
normally tubular—fragmented and ultimately aggregated in aged cells
(Fig. 1a). Mitochondrial fragmentation was present early in the ageing
process (86% of cells at 8 divisions), and progressed to large aggregates
and small fragments (93% of cells at 17 divisions) that persisted
throughout ageing (median lifespan of 28 divisions).
Mitochondrial membrane potential decreases in aged cells as indicated
by DiOC6 staining of aged cells expressing the mitochondrial outer membrane protein Tom70-
mCherry. c, Mitochondrial import is reduced in aged cells. Localization of mitochondrial matrix
marker preCox4-mCherry in aged cells that also express Tom70-GFP. pre-Cox4-mCherry is
localized to the cytoplasm in cells with reduced mitochondrial import.
dependent on the membrane potential for protein import, which is imported into mitochondria proportional to the MMP
Mitochondrial structure is regulated by 250 identified genes in
young cells
Vma1 is the catalytic subunit of
the peripheral-membrane-associated V1 sector of the V-ATPase14.
Vph2 is an endoplasmic-reticulum-localized integral membrane
protein required for V-ATPase assembly15. Overexpression of VMA1
or VPH2 from a high-copy promoter suppressed age-induced mitochondrial
dysfunction in 93% and 77% of aged cells, respectively (17 or
16 divisions) (Fig. 1b and Supplementary Fig. 3a). Importantly, suppression
by VMA1 or VPH2 overexpression required V-ATPase
activity, as treatment with the specific V-ATPase inhibitor concanamycin
A (concA)16 blocked their ability to produce normal, tubular
mitochondria (Fig. 1b and Supplementary Fig. 3a).
that resembled mitochondrial
phenotypes present in aged cells.
If reduced import of a particular amino acid or ion into the vacuole led
to mitochondrial dysfunction, then overexpressing the transporter
required for import of that metabolite into the vacuole might suppress
mitochondrial dysfunction in cells with a low vacuolar proton gradient.
To test this, we reduced the vacuolar proton gradient by treating
cells with low concentrations of concA, and measured mitochondrial
DYwith DiOC6 in cells overexpressing individual vacuolar amino acid
or ion transporters. Overexpressing most characterized V-ATPasedependent
vacuolar importers22–24 had no (NHX1, VBA1, VBA3) or little (VCX1, VBA2) effect on mitochondrial function. However, overexpressing
AVT1, a neutral amino acid transporter25, prevented mitochondrial
dysfunction in 60% of cells
If reduced import of a particular amino acid or ion into the vacuole led
to mitochondrial dysfunction, then overexpressing the transporter
required for import of that metabolite into the vacuole might suppress
mitochondrial dysfunction in cells with a low vacuolar proton gradient.
To test this, we reduced the vacuolar proton gradient by treating
cells with low concentrations of concA, and measured mitochondrial
DYwith DiOC6 in cells overexpressing individual vacuolar amino acid
or ion transporters. Overexpressing most characterized V-ATPasedependent
vacuolar importers22–24 had no (NHX1, VBA1, VBA3) or little (VCX1, VBA2) effect on mitochondrial function. However, overexpressing
AVT1, a neutral amino acid transporter25, prevented mitochondrial
dysfunction in 60% of cells