First published online May 30, 2008
Journal of Experimental Biology 211, 1829-1840 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.000299
Mitochondria in energy-limited states: mechanisms that blunt the signaling of cell death
Steven C. Hand* and
Michael A. Menze
Division of Cellular, Developmental and Integrative Biology, Department
of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803,
USA
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Fig. 1. Comparison of pathways for programmed cell death (PCD) in
Caenorhabditis elegans, Drosophila melanogaster and mammalian cells.
For details see text.
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Fig. 2. Steps at which energy availability (shaded red) and calcium (shaded green)
may impact PCD. For further explanation see text.
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Fig. 3. Calcium does not open the MPTP in A. franciscana. Upper frame,
presence or absence of swelling induced by calcium plus phosphate in isolated
mitochondria from post-diapause embryos of A. franciscana and rat
liver. Mitochondrial absorbance (a.u.) at 540 nm (inversely related to
swelling) was measured after addition of 1 mmol l–1 calcium
to A. franciscana mitochondria and 0.1 mmol l–1 to
rat liver mitochondria. Mitochondria were energized with 5 mmol
l–1 succinate. Lower frame, Western blot analysis showing
lack of cytochrome c (cyt-c) release from A.
franciscana mitochondria in response to calcium. Blots were probed with
cyt-c antibody. Cyt-c Std, positive control, purified horse
heart cyt-c; Mito. extract, positive control, supernatant from
homogenized mitochondria; Control supern., supernatant from energized
mitochondria without Ca2+ addition; Plus Ca2+,
supernatant from energized mitochondria plus 1 mmol l–1
Ca2+ (modified from Menze et
al., 2005b ).
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Fig. 4. Calcium uptake and release by isolated mitochondria. Extra-mitochondrial
free calcium concentration was measured with the calcium probe fluo-5N. (A)
Energized mitochondria from A. franciscana lowered the concentration
of exogenously added Ca2+ at all concentrations investigated
compared with controls (no mitochondria present). Calcium-induced calcium
release was not observed, consistent with the lack of MPTP opening. (B) Rat
liver mitochondria reduced the free Ca2+ concentration only in the
case where no exogenous Ca2+ was added. Upon addition of 0.1 mmol
l–1 Ca2+, release of calcium was observed,
indicating MPTP opening. For further explanation, refer to text. Each bar
represents the mean ± s.d. of N=3 experiments.
*Significantly different from control (P<0.05)
(modified from Menze et al.,
2005b).
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Fig. 5. Impact of cytochrome c (cyt-c) addition on the activation
of caspase 3 and caspase 9 in cytosolic extracts from (A) human hepatoma cells
(C3A) and (B) diapause embryos of Artemia franciscana. Caspase
activities were measured following the increase in fluorescence (F;
in arbitrary units, a.u.) due to cleavage of Z-LEHD-R110 (caspase 9) or
Z-DEVD-R110 (caspase 3). Cyt-c additions were saturating for C3A
cells. No activation by cyt-c was observed for A.
franciscana extracts (modified from
Menze and Hand, 2007).
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Fig. 6. Influence of Mg-ADP on caspase 9 (Z-LEHD-R110) activity in cytosolic
extracts from diapause and post-diapause embryos of A. franciscana.
ADP inhibition was about 70% greater in diapause extracts at the approximate
physiological concentration of ADP (15–150 µmol l–1)
than in post-diapause extracts. Each bar is the mean ± s.d. of
N=4–7 experiments (modified from
Menze and Hand, 2007).
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© The Company of Biologists Ltd 2008
