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1 Department of Biochemistry, College of Science, Yonsei University, Seoul 120-749, Republic of Korea
2 School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea
3 Department of Biochemistry, School of Medicine and Department of Molecular Science and Technology, The Graduate School, Ajou University, Suwon 443-721, Republic of Korea
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Abstract |
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Introduction |
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We showed previously that Caenorhabditis elegans DIC-1 is present in the inner membrane (especially cristae) of mitochondria and its knockdown induces the formation of numerous vesicles inside the mitochondria (Han et al. 2006). Besides this morphological change in the mitochondria, the knockdown caused embryonic lethality and apoptosis, and inhibited oogenesis. The human homologue of DIC-1, DICE-1 (Deleted In Cancer 1) is responsible for non-small cell lung carcinoma, and localizes to nuclei (Wieland et al. 1999, 2001, 2004), unlike the C. elegans homologue. To examine the mode of action of DIC-1 in cristae formation, we generated a transgenic C. elegans line in which dic-1 over-expression was inducible. After over-expression, mitochondria were observed by electron microscopy. From a comparison of the resulting intra-mitochondrial structure with the mitochondria of the wild type and dic-1 knockdown strains, we suggest a basis for the control of mitochondrial cristae by DIC-1. In addition, we measured various physiological properties related to mitochondria, such as oxygen consumption rate, ATP content and reactive oxygen species (ROS) level, after over-expression or knockdown of dic-1. The relationship between these physiological properties and intra-mitochondrial morphology is discussed.
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Results |
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We showed previously that DIC-1 knockdown resulted in the formation of a number of vesicles inside mitochondria and the absence of normal cristae (Fig. 1B; Han et al. 2006). To better understand the role of DIC-1 in cristae formation, we induced DIC-1 over-expression by heat shock in the transgenic C. elegans line ykIs53, in which the DIC-1 cDNA under the control of hsp-16.2 is integrated into the chromosome. After inducing DIC-1 over-expression, we observed a marked increase in the number and width of the cristae in the mitochondria of muscle cells, as shown in the cryo-electron micrograph of Fig. 1D. To quantitate the increase in the area taken up by cristae, the whole area of a mitochondrial cross-section and of each crista in the cross-section was measured using the IMAGEJ program (National Institutes of Health). The sum of the crista area in the mitochondrial cross-section was divided by the total area of the cross-section to obtain the fractional area occupied by cristae. As illustrated in Table 1, the wild-type N2 strain with or without heat shock treatment, and the DIC-1 over-expressing line ykIs53 without heat shock, were all similar in average mitochondrial size and fractional area of cristae. However, after heat shock the average cross-sectional area of a mitochondrion in ykIs53 increased by 60% (P < 0.001). A much greater change was found in the percent area of the cristae, which was 3.7-fold increased, suggesting that DIC-1 actively participates in the formation of cristae. Although there are changes in the average cross-sectional area of a mitochondrion and the fractional area of cristae, biogenesis of mitochondria did not appear to have increased on the basis of a mitochondrial protein level. The levels of mitochondrial proteins (cytochrome C oxidase subunit 1 and F1 ATP synthase β-subunit in the inner membrane, VDAC in the outer membrane and manganese superoxide dismutase in the matrix) did not change significantly after DIC-1 over-expression, as shown by the Western blot in Fig. S1A in Supporting Information. In contrast, the level of DIC-1 increased slightly after inducing expression of the dic-1 transgene by heat shock (Fig. S1B in Supporting Information). The mitochondria of the dic-1 knockdown strain contained numerous vesicles (Fig. 1B), as in our previous work (Han et al. 2006), although the two layers of lipid membrane enveloping the vesicles can be more clearly observed than in our previous report.
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In order to see whether mitochondrial activity is affected by the altered intra-mitochondrial structure, the oxygen consumption of worms was measured after dic-1 over-expression or knockdown. In accord with the increased fractional area of cristae in mitochondria, oxygen consumption increased by 16% (P < 0.001) as a result of dic-1 over-expression (Fig. 2A). In contrast, no clear changes (P = 0.22) in oxygen consumption rate resulted from dic-1 knockdown. Changes in the respiratory activity of adult worms did not occur despite the striking vesicular inner structure of the mitochondria after dic-1 knockdown. When a subunit of ubiquinol–cytochrome C reductase (encoded by the open reading frame T02H6.11) was targeted by RNAi as a negative control, oxygen consumption rate greatly decreased, as reported by Lee et al. (2003).
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To examine if oxygen consumption rate affects ATP content, we measured ATP content in extracts of adult worms after knockdown and over-expression of dic-1 (Fig. 2B). Intriguingly, heat shock increased the ATP level in the wild-type N2 strain by 31% (P = 0.112). dic-1 over-expression also increased ATP by 44% (P = 0.006) compared to the wild-type N2 (+heat) control, with the ATP level in the wild-type N2 (–heat) set at 100%. This result agrees with the increased oxygen consumption after dic-1 over-expression. After dic-1 knockdown, ATP decreased by 31% (P < 0.001) unlike oxygen consumption, which did not change significantly. The decreased level of ATP after dic-1 knockdown might have contributed to the observed inhibition of oogenesis and the embryonic lethality (Han et al. 2006).
dic-1 Over-expression and knockdown decrease and increase ROS level, respectively
We measured levels of ROS in extracts of adult worms after knockdown and over-expression of dic-1 (Fig. 3A). To detect hydrogen peroxide-related ROS, DCF-DA was incubated with the extracts and the fluorescence of the reaction product measured. ROS level decreased by 14% (P < 0.001) as a result of dic-1 over-expression, which was not expected on the basis of the increased oxygen consumption rate. Nevertheless, dic-1 knockdown increased ROS level by 14% (P < 0.001), in line with the opposite change after dic-1 over-expression.
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To see how the changes in ROS level affected the sensitivity of worms to exogenous oxidative stress, adult worms were exposed to paraquat for 1 day and their survival was scored (Fig. 3B). Heat shock increased the survival rate of wild-type N2 worms by 6% (P = 0.17) at 50 mM paraquat, and by 12% (P = 0.006) at 100 mM paraquat. Compared with the wild-type (+heat) control, the survival rate of the over-expression line was decreased by 10% (P = 0.029) at 50 mM paraquat significantly and by 8% (P = 0.065) at 100 mM paraquat. An opposite and much greater effect was observed in the dic-1 knockdown strain, where worm survival increased by 17% (P = 0.001) and 41% (P < 0.001) at 50 and 100 mM paraquat, respectively. The hyposensitivity of the knockdown strain to paraquat was unexpected, as it had a normal oxygen consumption rate and slightly increased ROS level. However, the mitochondrial membrane potential, as assessed using JC-1 dye, was unaffected by dic-1(RNAi) (data not shown), excluding the possibility that the permeation of paraquat cation into mitochondria was decreased. One possible explanation is that the slightly higher ROS level pre-induced a mechanism of defense against the sudden exogenous oxidative stress. Indeed, the level of sod-3 (mitochondrial superoxide dismutase) transcripts increased after dic-1 knockdown (Fig. 4, P = 0.001 vs. the control), as did the GFP-tagged protein, as reported by Curran & Ruvkun (2007). Heat shock to the wild-type N2 strain also increased the sod-3 transcript level by 35% (P = 0.001), whereas the dic-1 over-expression line (+heat) gave a similar increase of 27% (P = 0.022) relative to the over-expression line (–heat), with the transcript level in wild-type N2 (–heat) set at 100%. Thus, dic-1 over-expression does not appear to affect sod-3 expression, although it is not known why sod-3 transcripts are elevated in the dic-1 over-expression line (–heat) even without heat shock. In order to see if the relationship between paraquat resistance and sod-3 expression held true for other mitochondrial proteins, we tested four C. elegans genes, knockdown of which was shown by Kim & Sun (2007) to increase paraquat-resistance and life span. The four genes Y56A3A.19, F54D8.2, T27E9.1 and Y57G11C.12 encode the mitochondrial polypeptides, acyl carrier protein/NADH-ubiquinone oxidoreductase, cytochrome C oxidase subunit VIa, ADP/ATP translocase and NADH ubiquinone oxidoreductase (nuo-1), respectively. Knockdown of three of these four genes tested (the exception being F54D8.2 with P = 0.272 vs. the control) resulted in increased sod-3 transcripts (Fig. 4).
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Discussion |
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In accord with the increased area of cristae as a result of dic-1 over-expression, oxygen consumption rate and ATP content also increased after the over-expression. Heat shock by itself increased ATP content slightly in the wild-type strain, but dic-1 over-expression additionally increased ATP content with respect to the heat control. Heat shock decreases ATP levels in mammalian cells and tissues (Lilly et al. 1984), but in bacteria an initial rapid increase of ATP is followed by a gradual decrease (Soini et al. 2005). The increased level of ATP even 4 h after heat shock in the wild-type strain could have resulted from the relatively long (1 h) period of heat shock so that the animals might not yet have recovered fully. Although respiration was enhanced by dic-1 over-expression, ROS levels were unexpectedly lowered. In the case of dic-1 knockdown, ATP levels decreased and ROS levels increased, which were effects opposite to the over-expression phenotypes.
dic-1 over-expression and knockdown also resulted in opposite effects on the sensitivity of worms to paraquat. Generally, but not always, a higher endogenous ROS level is associated with hypersensitivity to exogenous ROS. However, as in the work of Lee et al. (2003), knockdown of C. elegans mitochondrial proteins resulting in a longer life span, associated with low oxygen consumption rate and ATP content, but also with hypersensitivity to paraquat. Thus, reduced ROS levels which are expected to result from the knockdown of mitochondrial proteins appear to be associated with hypersensitivity to paraquat. In agreement with this hypothesis, we showed in this study that the hyposensitivity to paraquat induced by dic-1 knockdown is correlated with an increased level of sod-3 transcripts. A similar correlation between paraquat-resistance and sod-3 expression was also previously observed for isp-1, which encodes the iron–sulfur protein of ubiquinone cytochrome C oxidoreductase in C. elegans (Feng et al. 2001). These observations support the argument that a slightly increased level of ROS induces the expression of genes whose products confer increased resistance to subsequent exposure to such oxidative stress. Nevertheless, knockdown of C. elegans mitochondrial proteins resulted in increased resistance to hydrogen peroxide, which contrasts with the hypersensitivity to paraquat (Lee et al. 2003). However, mitochondrial proteins, a majority of which are involved in oxidative phosphorylation, comprised one-third of the C. elegans proteins identified in an RNAi screen for resistance to paraquat and for longer life span (Kim & Sun 2007). Thus, knockdown of mitochondrial proteins yielding longer life spans can lead to hyper- or hypo-sensitivity to exogenous oxidative stress depending on the protein and the type of exogenously induced ROS. A more comprehensive study of the relationship between oxidative phosphorylation and C. elegans life span has been recently carried out by Rea et al. (2007); several genes involved in oxidative phosphorylation were knocked down to gradually increasing extents. Life span first increased, but then began to decrease as the extent of knockdown was increased. No correlation between life span and endogenous oxidative stress level, as represented by protein carbonylation, was found.
In summary, C. elegans DIC-1 promotes cristae formation in mitochondria and its role might be related to lengthening and widening of cristae tubules. The enhanced cristae formation is accompanied by increased mitochondrial activity, as assayed by oxygen consumption and ATP levels. This suggests that this protein might be used to augment defective oxidative phosphorylation as a result of aging or genetic defects. Additional studies will be needed to map the protein regions essential for this function, so that small domains or peptides can be developed to control mitochondrial activity.
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Experimental procedures |
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A 2.6 kb DNA fragment containing the dic-1 open reading frame was amplified from the yk293c3 EST cDNA clone using Top-pfu DNA polymerase (CoreBioSystem). The amplified DNA fragment was cloned into pPD49.78 under the hsp-16.2 promoter and DNA of the resulting recombinant plasmid pLTH34 (2 µg/mL) was microinjected into the gonads of young adult C. elegans N2, together with pRF4 plasmid DNA (50 µg/mL) (Kramer et al. 1990). Transgenic worms among the F1 progeny were selected by observing their rolling (rol-6) phenotype and confirming the presence of the recombinant plasmid in the worms by PCR amplification. Transgenic worms containing extra-chromosomal copies of pLTH34 and pRF4 were irradiated at the young adult stage with UV (254 nm, 300 J/m2) using a germicidal lamp to generate an integrated line of dic-1, referred to as ykIs53. The ykIs53 line was backcrossed with N2 four times to remove possible unrelated mutations. To induce over-expression of dic-1, ykIs53 worms at the young adult stage were incubated at 30 °C for 1 h.
For the over-expression of the VWF domain, a 447-bp DNA fragment (1–149 amino acids) of dic-1 was amplified and cloned as above to obtain the recombinant plasmid pLTH64. pLTH64 DNA (10 µg/mL) was microinjected into the gonads of young adult C. elegans N2, together with pPD118.33 plasmid DNA (20 µg/mL). Transgenic worms containing extra-chromosomal copies of the plasmid DNAs were named ykEx64 and maintained by observing GFP expression in pharyngeal muscle cells.
Fluorescence microscopy
The Pmyo-3::mitochondrial signal sequence::gfp transgenic line, in which muscle cell mitochondria are marked by GFP (Labrousse et al. 1999), was crossed with the ykIs53 [Phsp-16.2::dic-1] or ykEx64 [Phsp16.2::vwf] line to generate double transgenic lines. dic-1 and vwf over-expressions were induced as above. Caenorhabditis elegans adult worms were mounted on a slide overlaid with 2% agarose and observed with a fluorescence microscope (DMR HC, Leica).
Bacteria-mediated RNAi
RNAi was performed by feeding C. elegans worms Escherichia coli HT115(DE3) cells expressing double-stranded RNA (dsRNA) of dic-1 from the L1 stage, as described previously (Han et al. 2006). For control RNAi experiments, E. coli HT115(DE3) cells transformed with control pPD129.36(L4440) plasmid DNA were fed to C. elegans. To obtain a negative control strain defective in respiration, a subunit (the open reading frame T02H6.11) of ubiquinol–cytochrome C reductase, part of oxidative phosphorylation complex III, was knocked down using E. coli HT115(DE3) cells expressing dsRNA of the 430 bp-long EcoRI-XhoI fragment of EST clone yk1715b03.
Cryo-electron microscopy
We prepared adult N2 worms in which dic-1 RNAi had been induced from the L1 stage, and ykIs53 worms with dic-1 over-expressed. For dic-1 over-expression, young adult ykIs53 worms were incubated at 30 °C for 1 h and then at 20 °C for 4 h before harvesting for electron microscopy. The worms were frozen at –180 °C, substituted with a resin, sectioned (RMC MTXL), and stained with uranyl acetate and lead citrate, as described previously (Han et al. 2006). The sections were viewed under a Tecnai 12 electron microscope (Philips, Netherlands) or a JEM-ARM 1300S high voltage electron microscope (Jeol, Japan, installed at the Korea Basic Science Institute). The entire areas of 45 randomly chosen mitochondria in two-dimensional electron micrographs, and the summed areas of cristae in each mitochondrion were obtained with the IMAGE J program (National Institutes of Health).
Oxygen consumption rate
We measured oxygen consumption rates by the procedures described by Lee et al. (2003) and Braeckman et al. (2002), with slight modifications. Approximately, 5000 hatched L1 worms were grown to the young adult stage on large nematode growth medium (NGM) plates containing E. coli HT115(DE3) cells. Young adults were collected in S-basal buffer and washed four times in the buffer to remove bacteria. Approximately 1500 worms in 200 µL of S basal buffer were placed into a Mitocell chamber equipped with a Clark-type oxygen electrode (782 Oxygen Meter, Strathkelvin Instruments, Glasgow, UK), and the oxygen concentration was measured for a few minutes. The worms were then removed from the chamber, resuspended in 600 µL of 1x PBS, and sonicated. The cell lysate was centrifuged at 20 000 g in a microcentrifuge for 20 min and the supernatant was taken to determine protein concentration with the Advanced Protein Assay reagent (ADV01, Cytoskeleton). Oxygen consumption rate was normalized to total protein content. The measurements were performed five times.
Reactive oxygen species (ROS)
To measure intracellular levels of H2O2-related ROS, young adult worms were collected in M9 buffer and washed four times in the buffer. Cell extracts were prepared by freezing the worms in liquid nitrogen, thawing and sonicating in 1x PBS. The cell extracts were spun in a microcentrifuge (4 °C) at 20 000 g for 30 min, and the protein concentration of the supernatant was measured. Supernatant samples containing 5 µg of protein was pre-incubated with 50 µM of 2,7-dichlorofluorescein diacetate (DCF-DA, Molecular Probes) in 100 µL of PBS at 37 °C for 1 h. Fluorescence intensity was measured with a fluorometer (Spectra Fluor Plus, Tecan) every 10 min for 1 h at excitation wavelength 485 nm and emission wavelength 535 nm. We arbitrarily took the fluorescence intensity at the 1 h time point and divided its value by the fluorescence intensity of the N2 strain (without heat shock) to obtain relative fluorescence intensities. The measurements were performed seven times.
ATP assay
We measured ATP content as described previously, with slight modifications (Braeckman et al. 2002; Dillin et al. 2002; Lee et al. 2003). Approximately, 5000 hatched L1 worms were grown to the young adult stage on large NGM plates containing E. coli HT115(DE3) cells. They were collected in M9 buffer and washed four times. Cell extracts were prepared by freezing the worms under liquid nitrogen, thawing, and sonicating in TE buffer (100 mM Tris–Cl, pH 7.6, 4 mM EDTA). The sonicated samples were boiled for 7 min to release ATP and destroy ATPase activity, and spun in a microcentrifuge (4 °C) at 20 000 g for 30 min. Fifty microliters of serially diluted ATP (1–100 µM) was reacted with 50 µL of the luciferase reagent provided with the ATP Bioluminescent HSII kit (Roche Applied Science) and light intensities were measured using a luminometer (Spectra Fluor Plus, Tecan) to provide a standard curve of ATP concentration. The ATP dilution series was replaced by the C. elegans extracts (1 µg/µL) and the ATP levels obtained were normalized to the protein content of each extract. The measurements were repeated seven times.
Survival in paraquat
To measure sensitivity to paraquat (Sigma), young adults were transferred from NGM agar plates to microtubes containing 50 or 100 mM paraquat in M9 solution and incubated at 20 °C for 24 h, after which dead worms were counted based on sustained absence of motility. The measurements were performed four times.
Measurement of mRNA expression levels by real-time RT-PCR
Real-time RT-PCR was used to measure levels of sod-3 mRNA in worms, in which mitochondrial protein expressions were inhibited by RNAi or induced. For dic-1 over-expression, young adult ykIs53 worms were incubated at 30 °C for 1 h and then at 20 °C for 4 h before harvest. To knockdown the expressions of Y56A3A.19, F54D8.2, T27E9.1 and Y57G11C.12 (nuo-1), we used E. coli transformants from the C. elegans RNAi v1.1 Feeding Library (Open Biosystems) that express the appropriate double-stranded RNAs. We grew approximately 1000 hatched L1 worms to the young adult stage on an NGM plate seeded with E. coli cells expressing a given double-stranded RNA. The worms were washed three times in M9 solution to free them of bacteria. Total RNA was prepared using an Easy-Blue RNA Extraction kit (iNtRON Biotechnology, Korea), followed by extraction with chloroform and then isopropyl alcohol. The RNA was ethanol-precipitated, resuspended in DEPC-treated distilled water, and reverse transcribed using a Power cDNA synthesis kit (iNtRON) with oligo(dT). Real-time PCR was carried out with a SYBR Premix Ex Taq (Perfect Real Time) kit (TaKaRa) and gene-specific primers in a thermal cycler (PTC-200, MJ Research) with a Chromo4 detection system (CFB-3240, Bio-Rad). Primers used for amplification of sod-3 were 5'-CAGATCTCCCATTCGACTATGC and 5'-GTGTCCACCACCATTGAATTTC, and those for tbg-1 (
-tubulin) were 5'-CGTCATCAGCCTGGTAGAACA and 5'-TGATGACTGTCCACGTTGGA. The cDNA amplification kinetics of the sod-3 gene was analyzed using Opticon Monitor3 software (Bio-Rad) and normalized to that of the tbg-1 gene.
Western blot analysis
Cell extracts were prepared by freezing young adult worms in liquid nitrogen, thawing, and sonicating in 1x PBS as for ATPase assay above. Samples of equal total protein concentration were mixed with 1 volumes of 2x sample loading buffer (200 mM Tris–Cl, pH 8.0, 500 mM NaCl, 0.1 mM EDTA, 0.1% Triton X-100 and 0.4 mM PMSF) and boiled for 5 min. The worm lysate was electrophoresed on a 10% SDS polyacrylamide gel and electroblotted onto a nitrocellulose transfer membrane. The membrane was incubated in blocking solution containing an antibody against either cytochrome C oxidase subunit I (Molecular Probes, 1 : 2000 dilution), mitochondrial ATP synthase subunit β (Abcam, 1 : 3000 dilution), voltage-dependent anion-selective channel 1 (Santa Cruz Biotechnology, 1 : 300 dilution), manganese superoxide dismutase 2 (Abcam, 1 : 6000 dilution), DIC-1 (1 : 1500), or 
-tubulin (Developmental Studies Hybridoma Bank, 1 : 5000 dilution) at 4 °C overnight. The membrane was then incubated with anti-mouse, anti-goat, anti-rat or anti-rabbit horseradish peroxidase antibody (Jackson Bioresearch, 1 : 5000 dilution) for 1 h at 25 °C. The WestSaveUp kit (Abfrontier, Korea) was used to detect the secondary antibody on the membrane. Luminescence of the blot was captured using an LAS-3000 imaging system (Fujifilm). To prepare antiserum against DIC-1, the polypeptide (amino acids 400–654) was amplified from EST clone yk293c3 and cloned into pENTR/D-TOPO (Gateway system, Invitrogen). The recombinant plasmid DNA was recombined with pDEST15 using a Gateway LR Clonase II Enzyme Mix, and transformed into E. coli BL21AI. The E. coli cells were cultured at 37 °C to an optical density 0.5 at 600 nm, at which time arabinose was added to 0.2%, followed by incubation for 4 h. The over-expressed protein was used to immunize rats.
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Acknowledgements |
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Footnotes |
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The authors made equal contributions to the work. 
* Correspondence: kooh{at}yonsei.ac.kr or sshan{at}korea.ac.kr |
References |
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Celotto, A.M., Frank, A.C., McGrath, S.W., Fergestad, T., Van Voorhies, W.A., Buttle, K.F., Mannella, C.A. & Palladino, M.J. (2006) Mitochondrial encephalomyopathy in Drosophila. J. Neurosci. 26, 810–820.
Curran, S.P. & Ruvkun, G. (2007) Lifespan regulation by evolutionarily conserved genes essential for viability. PLoS Genet. 3, 479–487.
Dillin, A., Hsu, A.-L., Arantes-Oliveira, N., Lehrer-Graiwer, J., Hsin, H., Fraser, A.G., Kamath, R.S., Ahringer & J., Kenyon, C. (2002) Rates of behavior and aging specified by mitochondrial function during development. Science 298, 2398–2401.
Feng, J., Bussière, F. & Hekimi, S. (2001) Mitochondrial electron transport is a key determinant of life span in Caenorhabditis elegans. Dev. Cell 1, 633–644.[CrossRef][Medline]
Frezza, C., Cipolat, S., de Brito, O.M., Micaroni, M., Beznoussenko, G.V., Rudka, T., Bartoli, D., Polishuck, R.S., Danial, N.N., Strooper, B.D. & Scorrano, L. (2006) OPA1 controls apoptotic cristae remodeling independently from mitochondrial fusion. Cell 126, 177–189.[CrossRef][Medline]
Han, S.M., Lee, T.H., Mun, J.Y., Kim, M.J., Kritikou, E., Lee, S.-J., Han, S.S., Hengartner, M.O. & Koo, H.-S. (2006) Deleted-In-Cancer-1 (DICE-1) is an essential protein controlling the topology of the inner mitochondrial membrane in C. elegans. Development 133, 3597–3606.
Heath-Engel, H.M. & Shore, G.C. (2006) Mitochondrial membrane dynamics, cristae remodelling and apoptosis. Biochim. Biophy. Acta 1763, 549–560.
Hoppins, S., Lackner, L. & Nunnari, J. (2007) The machines that divide and fuse mitochondria. Annu. Rev. Biochem. 76, 751–780.[CrossRef][Medline]
John, G.B., Shang, Y., Li, L., Renken, C., Mannella, C.A., Selker, J.M.L., Rangell, L., Bennett, M.J. & Zha, J. (2005) The mitochondrial inner membrane protein mitofilin controls cristae morphology. Mol. Biol. Cell 16, 1543–1554.
Kim, Y. & Sun, H. (2007) Functional genomic approach to identify novel genes involved in the regulation of oxidative stress resistance and animal lifespan. Aging Cell 6, 489–503.[CrossRef][Medline]
Kramer, J.M., French, R.P., Park, E.-C. & Johnson, J.J. (1990) The Caenorhabditis elegans rol-6 gene, which interacts with the sqt-1 collagen gene to determine organismal morphology, encodes a collagen. Mol. Cell. Biol. 10, 2081–2089.
Labrousse, A.M., Zappaterra, M.D., Rube, D.A. & van der Bliek, A.M. (1999) Caenorhabditis elegans dynamin-related protein DRP-1 controls severing of the mitochondrial outer membrane. Mol. Cell 4, 815–826.[CrossRef][Medline]
Lee, S.S., Lee, R.Y.N., Fraser, A.G., Kamath, R.S., Ahringer, J. & Ruvkun, G. (2003) A systematic RNAi screen identifies a critical role for mitochondria in C. elegans longevity. Nat. Genet. 33, 40–48.[CrossRef][Medline]
Lilly, M.B., Ng, T.C., Evanochko, W.T., Katholi, C.R., Kumar, N.G., Elgavish, G.A., Durant, J.R., Hiramoto, R., Ghanta, V. & Glickson, J.D. (1984) Loss of high-energy phosphate following hyperthermia demonstrated by in vivo 31P-nulear magnetic resonance spectroscopy. Cancer Res. 44, 633–638.
Mannella, C.A. (2006) Structure and dynamics of the mitochondrial inner membrane cristae. Biochim. Biophys. Acta 1763, 542–548.
Paumard, P., Vaillier, J., Coulary, B., Schaeffer, J., Soubannier, V., Mueller, D.M., Brèthes, D., di Rago, J.-P. & Velours, J. (2002) The ATP synthase is involved in generating mitochondrial cristae morphology. EMBO J. 21, 221–230.[CrossRef][Medline]
Rea, S.L., Ventura, N. & Johnson, T.E. (2007) Relationship between mitochondrial electron transport chain dysfunction, development, and life extension in Caenorhabditis elegans. PLoS Biol. 5, 2312–2319.
Soini, J., Falschlehner, C., Mayer, C., Böhm, D., Weinel, S., Panula, J., Vasala, A. & Neubauer, P. (2005) Transient increase of ATP as a response to temperature up-shift in Escherichia coli. Microb. Cell Fact. 4, 9.[Medline]
Whittaker, C.A. & Hynes, R.O. (2002) Distribution and evolution of von Willebrand/integrin A domains: widely dispersed domains with roles in cell adhesion and elsewhere. Mol. Biol. Cell 13, 3369–3387.
Wieland, I., Arden, K.C., Michels, D., Klein-Hitpass, L., Böhm, M., Viars, C.S. & Weidle, U.H. (1999) Isolation of DICE1: a gene frequently affected by LOH and downregulated in lung carcinomas. Oncogene 18, 4530–4537.[CrossRef][Medline]
Wieland, I., Röpke, A., Stumm, M., Sell, C., Weidle, U.H. & Wieacker, P.F. (2001) Molecular characterization of the DICE1 (DDX26) tumor suppressor gene in lung carcinoma cells. Oncol. Res. 12, 491–500.[Medline]
Wieland, I., Sell, C., Weidle, U.H. & Wieacker, P.F. (2004) Ectopic expression of DICE1 suppresses tumor cell growth. Oncol. Rep. 12, 207–211.[Medline]
Received: 18 July 2008
Accepted: 24 November 2008
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