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Results for “Electron Transport Complex II”

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At least 145 records · Page 8Linked to original sources
PubMed2002

Ceramide-induced apoptosis of D283 medulloblastoma cells requires mitochondrial respiratory chain activity but occurs independently of caspases and is not sensitive to Bcl-xL overexpression.

Ceramides are potent lipid second messengers that are involved in apoptotic and hypoxic/ischaemic neurone death. We investigated the role of mitochondria and the mitochondrial apoptosis pathway in ceramide-induced cell death using human D283 medulloblastoma cells with a reduced mitochondrial DNA copy number (rho- cells) and a corresponding defect in mitochondrial respiration. Treatment with the complex I inhibitor rotenone, C2- or C8-ceramide induced cell death in D283 control cells, while rho- cells were significantly protected. In contrast, activation of the mitochondrial apoptosis pathway by transient overexpression of the pro-apoptotic Bax protein or exposure to the kinase inhibitor staurosporine induced apoptosis to a similar extent in control and rho- cells. Overexpression of the antiapoptotic protein Bcl-xL failed to inhibit the toxic effect of C2-ceramide in D283 control cells, and no significant increase in caspase-3-like protease activity could be detected during the death process. Despite this, C2-ceramide induced significant chromatin condensation and cell shrinkage in D283 control cells, reminiscent of apoptosis. These morphological alterations were associated with the activation of calpains. Both apoptotic morphology and calpain activation were attenuated in rho- cells. Our data indicate that the apoptosis-inducing effect of C2-ceramide may require mitochondrial respiratory chain activity and can occur independently of the mitochondrial apoptosis pathway, but involves the activation of calpains.

Apoptosis↗
PubMed2002

Mitochondrial electron transport chain complex dysfunction in a transgenic mouse model for amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis is a fatal neurodegenerative disease that causes degeneration of motoneurons. Mutation of Cu,Zn superoxide dismutase (SOD1) is one cause for this disease. In mice, expression of mutant protein causes motoneuron degeneration and paralysis resembling the human disease. Morphological change, indicative of mitochondrial damage, occurs at early stages of the disease. To determine whether mitochondrial function changes during the course of disease progression, enzyme activities of mitochondrial electron transport chain in spinal cords from mice at different disease stages were measured using three different methods: spectrophotometric assay, in situ histochemical enzyme assay, and blue native gel electrophoresis combined with in-gel histochemical reaction. The enzyme activities were decreased in the spinal cord, particularly in the ventral horn, beginning at early disease stages. This decrease persisted throughout the course of disease progression. This decrease was not detected in the spinal cords of non-transgenic animals, of mice expressing the wild-type protein, and in cerebellum and dorsal horn of the spinal cords from mice expressing mutant protein. These results demonstrate a functional defect in mitochondria in the ventral horn region and support the view that mitochondrial damage plays a role in mutant SOD1-induced motoneuron degeneration pathway.

Amyotrophic Lateral Sclerosis↗
PubMed2004

"Respirasome"-like supercomplexes in green leaf mitochondria of spinach.

Higher plant mitochondria have many unique features compared with their animal and fungal counterparts. This is to a large extent related to the close functional interdependence of mitochondria and chloroplasts, in which the two ATP-generating processes of oxidative phosphorylation and photosynthesis, respectively, take place. We show that digitonin treatment of mitochondria contaminated with chloroplasts from spinach (Spinacia oleracea) green leaves at two different buffer conditions, performed to solubilize oxidative phosphorylation supercomplexes, selectively extracts the mitochondrial membrane protein complexes and only low amounts of stroma thylakoid membrane proteins. By analysis of digitonin extracts from partially purified mitochondria of green leaves from spinach using blue and colorless native electrophoresis, we demonstrate for the first time that in green plant tissue a substantial proportion of the respiratory complex IV is assembled with complexes I and III into "respirasome"-like supercomplexes, previously observed in mammalian, fungal, and non-green plant mitochondria only. Thus, fundamental features of the supramolecular organization of the standard respiratory complexes I, III, and IV as a respirasome are conserved in all higher eukaryotes. Because the plant respiratory chain is highly branched possessing additional alternative enzymes, the functional implications of the occurrence of respiratory supercomplexes in plant mitochondria are discussed.

Animals↗
PubMed2005

Characterization of mitochondrial respiratory chain energetics in the vestibular nucleus complex.

CONCLUSIONS: Despite having very high neuronal firing rates, the VNC does not have unusually high mitochondrial activity in vitro. This study is the first in which functionally active mitochondria from the hindbrain have been isolated and characterized. OBJECTIVE: Neurons in the vestibular nucleus complex (VNC) have exceptionally high spontaneous firing rates. Neuronal mitochondria generate adenosine triphosphate critical for maintaining the membrane potentials required for axon firing. We therefore hypothesized a high rate of mitochondrial activity in the VNC. MATERIAL AND METHODS: To test this hypothesis, we compared mitochondrial activity in the VNC with mitochondrial activity from another area of the hindbrain, the cerebellum. Mitochondrial respiratory activity was assessed by measuring oxidative phosphorylation and mitochondrial respiratory enzyme complex activity. RESULTS: Assay results were not significantly different in the VNC compared to those obtained with the cerebellum or with rat brain mitochondria in previous studies.

Adenosine Triphosphate↗
PubMed2005

Mitochondrial complex I, II/III, and IV activities in familial and sporadic Parkinson's disease.

A possible role of mitochondrial respiratory chain dysfunction in the pathogenesis of sporadic Parkinson's disease (PD) has been described. There are only a few reports concerning mitochondrial involvement in familial Parkinson's disease. The present study investigated mitochondrial complex I-IV activity in patients with sporadic and familial PD, compared to controls. Platelets were isolated from venous blood and platelet mitochondria were obtained through sonication and differential centrifugation. Complex I, II/III, and IV activities were measured in 17 patients with family history of Parkinson's disease (PDF), 15 patients with sporadic Parkinson disease (PDS), and 17 age-matched, healthy controls. The mitochondrial enzyme activities did not differ significantly between patient groups and controls. In addition, there was no correlation between mitochondrial complex activities and age, severity of disease, or age at onset of disease in the patient groups. In this study, the data indicate no significant differences in mitochondrial complex I-IV activities in PDF and PDS.

Aged↗
PubMed1999

Absence of mitochondrial dysfunction in polymyalgia rheumatica. Evidence based on a simultaneous molecular and biochemical approach.

OBJECTIVE: To investigate the molecular and biochemical profile of skeletal muscle mitochondria of patients with isolated polymyalgia rheumatica (PMR). PATIENTS AND METHODS: We included patients with a recent diagnosis of PMR and as control healthy individuals submitted to orthopedic surgery. Skeletal muscle was obtained from quadriceps, thus was mitochondria immediately isolated. Long polymerase chain reaction and Southern blot transference were performed to detect deleted mtDNA molecules. Mitochondrial oxidative activity using different substrates and individual enzyme activity of respiratory chain complexes were assessed to search for any biochemical dysfunction. RESULTS: Fifty-one individuals (PMR=25, controls=26) were included. Mean age was 72 (11) years; 45% were females. We found no significant increase of deleted mtDNA molecules in PMR patients compared to controls. Both groups differed neither on oxygen consumption (p=NS for all substrates) nor enzymatic activity (p=NS for all complexes). CONCLUSIONS: Skeletal muscle mitochondria are molecularly and biochemically unaffected in PMR.

Adenosine Triphosphatases↗
PubMed1996

Effects of ubiquinone enriched diet on deterioration of mitochondrial respiratory function caused by fried beef derived mutagenic factor in rats.

2-Amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP), a potent mutagenic agent produced during thermal processing of meats, shows detrimental effects on mitochondrial respiratory function. Effects of dietary ubiquinone-10 was examined on PhIP-induced mitochondrial respiratory dysfunction in rats. Rats fed with 0.2% ubiquinone-10 diet mitigated the PhIP-induced decrease in mitochondrial complex I activities observed in rat heart, diaphragm, and psoai major. Therefore, dietary anti-oxidants such as ubiquinone-10 could cancel out the unfavorable effects of PhIP and contribute to the preservation of mitochondrial function.

Animals↗
PubMed1998

A high rate (20%-30%) of parental consanguinity in cytochrome-oxidase deficiency.

By studying a large series of 157 patients, we found that complex I (33%), complex IV (28%), and complex I+IV (28%) deficiencies were the most common causes of respiratory chain (RC) defects in childhood. Truncal hypotonia (36%), antenatal (20%) and postnatal (31%) growth retardation, cardiomyopathy (24%), encephalopathy (20%), and liver failure (20%) were the main clinical features in our series. No correlation between the type of RC defect and the clinical presentation was noted, but complex I and complex I+IV deficiencies were significantly more frequent in cases of cardiomyopathy (P<.01) and hepatic failure (P<.05), respectively. The sex ratio (male/female) in our entire series was mostly balanced but was skewed toward males being affected with complex I deficiency (sex ratio R=1.68). Interestingly, a high rate of parental consanguinity was observed in complex IV (20%) and complex I+IV (28%) deficiencies. When parental consanguinity was related to geographic origin, an even higher rate of inbreeding was observed in North African families (76%, P<.01). This study gives strong support to the view that an autosomal recessive mode of inheritance is involved in most cases of mitochondrial disorders in childhood, a feature that is particularly relevant to genetic counseling for this devastating condition.

Abnormalities, Multiple↗
PubMed2001

Effect of hypoenergetic feeding and refeeding on muscle and mononuclear cell activities of mitochondrial complexes I--IV in enterally fed rats.

BACKGROUND: Previous studies suggested that cell energetics are altered by malnutrition. OBJECTIVE: We hypothesized that nutritional manipulations influence mitochondrial enzyme activities of the electron transport chain in both skeletal muscle and blood mononuclear cells. DESIGN: After a gastrostomy tube was inserted, 44 rats were randomly assigned to 1 of 4 experimental groups: control fed (CF; 364 kJ/d for 7 d), hypoenergetic fed (HF; 92 kJ/d for 7 d), hypoenergetic protein refed (HPR; 92 kJ/d for 7 d and then 129 kJ/d for 1 d), and hypoenergetic glucose refed (HGR; 92 kJ/d for 7 d and then 129 kJ/d for 1 d). The protein and glucose contents of the liquid formulas were different for the HPR and HGR groups. After mitochondria were isolated from the soleus muscle, the activities of complexes I--IV were measured spectrophotometrically. Because of the lack of available tissue, only the activity of complex I was measured in the mononuclear cell extract. RESULTS: The recovery of complex activities in the CF and HF groups was not significantly different in the mitochondrial fraction of the soleus muscle. Compared with that in the CF group, the activities of complexes I--III in the mitochondrial fraction of the soleus muscle and the activity of complex I in mononuclear cells were significantly lower in the HF group. The activities of complexes I--III in the mitochondrial fraction of the soleus muscle and the activity of complex I in mononuclear cells were significantly higher in the HPR than in the HF group. The activity of complex IV was generally not affected by nutritional manipulations. CONCLUSION: Malnutrition decreases activities of mitochondrial complexes, which are restored by protein but not glucose refeeding.

Adenosine Triphosphate↗
PubMed1998

Mutations in the membrane anchor of yeast cytochrome c1 compensate for the absence of Oxa1p and generate carbonate-extractable forms of cytochrome c1.

Oxa1p is a mitochondrial inner membrane protein that is mainly required for the insertion/assembly of complex IV and ATP synthase and is functionally conserved in yeasts, humans, and plants. We have isolated several independent suppressors that compensate for the absence of Oxa1p. Molecular cloning and sequencing reveal that the suppressor mutations (CYT1-1 to -6) correspond to amino acid substitutions that are all located in the membrane anchor of cytochrome c1 and decrease the hydrophobicity of this anchor. Cytochrome c1 is a catalytic subunit of complex III, but the CYT1-1 mutation does not seem to affect the electron transfer activity. The double-mutant cyt1-1,164, which has a drastically reduced electron transfer activity, still retains the suppressor activity. Altogether, these results suggest that the suppressor function of cytochrome c1 is independent of its electron transfer activity. In addition to the membrane-bound cytochrome c1, carbonate-extractable forms accumulate in all the suppressor strains. We propose that these carbonate-extractable forms of cytochrome c1 are responsible for the suppressor function by preventing the degradation of the respiratory complex subunits that occur in the absence of Oxa1p.

Adenosine Triphosphatases↗
PubMed2004

Differential expression of mitochondrial electron transport chain proteins in cardiac tissues of broilers from pulmonary hypertension syndrome-resistant and -susceptible lines.

Pulmonary hypertension syndrome (PHS) is a metabolic disease associated with the rapid growth rate of modern broilers. Broilers susceptible to PHS experience sustained elevation of pulmonary arterial pressure leading to right ventricular hypertrophy and ultimately heart failure. Previous studies have shown that mitochondrial function is defective in broilers with PHS; they use oxygen less efficiently than broilers without PHS. In this study mitochondrial electron transport chain (ETC) protein levels were compared in cardiac tissues from PHS resistant and susceptible line broilers using quantitative immunoblots. Seven of 9 anti-mammalian mitochondrial ETC protein antibodies tested exhibited cross-species reactivity. Six ETC proteins were differentially expressed in the right ventricles of broilers raised under simulated high altitude conditions (2,900 m above sea level). Four ETC proteins were present at higher levels in resistant line birds without PHS than in resistant line birds with PHS or in susceptible line birds with or without PHS. One ETC protein was present at higher levels in broilers without PHS than in broilers with PHS in both lines, and one ETC protein was present at lower levels in susceptible line birds without PHS than in susceptible line birds with PHS or in resistant line birds with or without PHS. Interestingly, differential expression of mitochondrial ETC proteins was not observed in the right ventricles of broilers raised at local altitude (390 m above sea level) nor was it observed in the left ventricles of broilers exposed to simulated high altitude. These results suggest that higher levels of mitochondrial ETC proteins in right ventricle cardiac muscle may be correlated with resistance to PHS in broilers.

Animals↗