Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mitochondrial oxidative phosphorylation involves five multimeric complexes imbedded in the inner membrane: complex I (Nicotinamide Adenine Dinucleotide (NADH) quinone oxidoreductase), II (succinate dehydrogenase), III (ubiquinol cytochrome c oxido reductase or bc1 complex), IV (cytochrome c oxidase), and V (ATP synthase). These respiratory complexes are conserved from the yeast Saccharomyces cerevisiae to human with the exception of complex I, which is replaced by three NADH dehydrogenases in S. cerevisiae. Here, we provide several protocols allowing an exhaustive characterization of each yeast complex: this chapter describes procedures from mitochondria preparation to measurement of the activity of each complex and analysis of their subunit composition and provides information on the interactions between different complexes.
...
PMID:Preparation of respiratory chain complexes from Saccharomyces cerevisiae wild-type and mutant mitochondria : activity measurement and subunit composition analysis. 1837 11

Nicotinamide, the principal form of niacin (vitamin B3), has been proposed to be neuroprotective in Parkinson's disease. However, the effects and mechanisms of nicotinamide on motor function in animals and on mitochondrial function in cellular systems have not been well studied. We hypothesized that niacin-derived NAD(P)H as antioxidants and enzyme cofactors could inhibit oxidative damage and improve mitochondrial function and thus protect neurodegeneration and improve motor function. In the present study, the effects of nicotinamide on mitochondrial function and oxidative stress were studied in a 1-methyl-4-phenylpyridinium (MPP(+))-induced cellular model of Parkinson's disease, and the effects of improving motor dysfunction were studied in an alpha-synuclein transgenic Drosophila Parkinson's model. Mitochondrial function was tested by measuring the activity of mitochondrial complex I and alpha-ketoglutarate dehydrogenase, and oxidative damage was tested by measuring reactive oxygen species, DNA damage (8-oxo-7,8-dihydro-2'-deoxyguanosine and Comet assay), and protein oxidation (protein carbonyls) levels. Nicotinamide at a relatively higher concentration, that is, 100-fold of the level in the cell culture medium (101 mg/L), significantly protected SK-N-MC human neuroblastoma cells from an MPP(+)-induced decrease in cell viability, complex I and alpha-ketoglutarate dehydrogenase activity, and an increase in oxidant generation, DNA damage, and protein oxidation. In the Drosophila model, nicotinamide at 15 and 30 mg/100 g diet significantly improved climbing ability. These results suggest that nutritional supplementation of nicotinamide at high doses decreases oxidative stress and improves mitochondrial and motor function in cellular and/or Drosophila models and may be an effective strategy for preventing and ameliorating Parkinson's disease.
...
PMID:High doses of nicotinamide prevent oxidative mitochondrial dysfunction in a cellular model and improve motor deficit in a Drosophila model of Parkinson's disease. 1838 61

Mutations in mitochondrial DNA (mtDNA) occur at high frequency in human tumors, but whether these mutations alter tumor cell behavior has been unclear. We used cytoplasmic hybrid (cybrid) technology to replace the endogenous mtDNA in a mouse tumor cell line that was poorly metastatic with mtDNA from a cell line that was highly metastatic, and vice versa. Using assays of metastasis in mice, we found that the recipient tumor cells acquired the metastatic potential of the transferred mtDNA. The mtDNA conferring high metastatic potential contained G13997A and 13885insC mutations in the gene encoding NADH (reduced form of nicotinamide adenine dinucleotide) dehydrogenase subunit 6 (ND6). These mutations produced a deficiency in respiratory complex I activity and were associated with overproduction of reactive oxygen species (ROS). Pretreatment of the highly metastatic tumor cells with ROS scavengers suppressed their metastatic potential in mice. These results indicate that mtDNA mutations can contribute to tumor progression by enhancing the metastatic potential of tumor cells.
...
PMID:ROS-generating mitochondrial DNA mutations can regulate tumor cell metastasis. 1838 60

Age-related glutamate excitotoxicity depends in an unknown manner on active mitochondria, which are key determinants of the cellular redox potential. Compared with embryonic and middle-aged neurons, old-aged rat hippocampal neurons have a lower resting reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and a lower redox ratio (NAD(P)H/flavin adenine nucleotide). Glutamate treatment resulted in an initial increase in NAD(P)H concentrations in all ages, followed by a profound calcium-dependent, age-related decline in NAD(P)H concentration and redox ratio. With complex I of the electron transport chain inhibited by rotenone, treatment with glutamate or ionomycin only resulted in the increase in NAD(P)H fluorescence. High-performance liquid chromatography analysis of adenine nucleotides in brain extracts showed 50% less nicotinamide adenine dinucleotide (NADH) and almost twice as much oxidized nicotinamide adenine dinucleotide, demonstrating a more oxidized ratio in old than middle-aged brain. Resting glutathione content also declined with age and further decreased with glutamate treatment without accompanying changes in adenosine triphosphate levels. We conclude that age does not affect production of NADH by dehydrogenases but that old-aged neurons consume more NADH and glutathione, leading to a catastrophic decline in redox ratio.
...
PMID:Age-related decreases in NAD(P)H and glutathione cause redox declines before ATP loss during glutamate treatment of hippocampal neurons. 1843 23

Traditional cuvette-based enzyme studies lack spatial information and do not allow real-time monitoring of the effects of modulating enzyme functions in vivo. In order to probe the realistic timescales of steric modifications in enzyme-substrate complexes and functional binding-unbinding kinetics in living cells without losing spatial information, it is imperative to develop sensitive imaging strategies that can report enzyme kinetics in real time over a wide dynamic range of timescales. Here we present a multi-photon excitation-based, ultra-fast photon detection using a streak camera and Laguerre expansion-based fast deconvolution approach for achieving high spatio-temporal resolution in monitoring real-time enzyme kinetics in single cells. In particular, we report spatially resolved, nanosecond-scale fluorescence dynamics associated with binding-unbinding kinetics of endogenous metabolic co-factor nicotinamide adenine dinucleotide with enzymes in intact living cells. By monitoring real-time kinetics of NAD(P)H-enzyme kinetics in primary hepatocytes isolated from young and aged mouse models, we observed that the mechanism of inhibition of mitochondrial respiration at complex I site is mediated by redistribution of free and protein-bound nicotinamide adenine dinucleotide pools and that this equilibrium redistribution is affected by age-related modifications in mitochondrial function. We describe unique advantages of Laguerre deconvolution algorithm in comparison with conventional lifetime analysis approaches. Non-invasive monitoring of metabolic dysfunctions in intact animal models is an attractive strategy for gaining insight into the dynamics of tissue metabolism in health and in various metabolic syndromes such as cancer, diabetes and aging-induced metabolic dysfunctions. Besides the example demonstrated above, we envisage that the proposed method can find applications in a variety of other situations where intensity-based approaches fall short owing to spectroscopic artefacts.
...
PMID:Spatially resolved fluorescence lifetime mapping of enzyme kinetics in living cells. 1850 58

Pancreatic islets express the superoxide-producing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system, but its role remains unknown. To address this, we studied the mechanisms of impaired insulin secretion induced by diphenyleneiodium (DPI), an NADPH oxidase inhibitor. We investigated the effects of DPI on glucose- and nonfuel-stimulated insulin secretion, islet glucose metabolism, and intracellular Ca2+ concentration ([Ca2+]i) dynamics in rat islets and beta-cell line RINm5F cells. DPI did not affect insulin secretion at 3.3 mm glucose but totally suppressed insulin secretion stimulated by 16.7 mm glucose (percentage of control, 9.2 +/- 1.2%; P <0.001). DPI also inhibited insulin release by high K+-induced membrane depolarization (percentage of control, 36.0 +/- 5.3%; P <0.01) and protein kinase C activation (percentage of control, 30.2 +/- 10.6% in the presence of extracellular Ca2+, P <0.01; percentage of control, 42.0 +/- 4.7% in the absence of extracellular Ca2+, P <0.01). However, DPI had no effect on mastoparan-induced insulin secretion at 3.3 and 16.7 mm glucose under Ca2+-free conditions. DPI significantly suppressed islet glucose oxidation and ATP content through its known inhibitory action on complex I in the mitochondrial respiratory chain. On the other hand, DPI altered [Ca2+]i dynamics in response to high glucose and membrane depolarization, and DPI per se dose-dependently increased [Ca2+]i. The DPI-induced [Ca2+]i rise was associated with a transient increase in insulin secretion and was attenuated by removal of extracellular Ca2+, by L-type voltage-dependent Ca2+ channel blockers, by mitochondrial inhibitors, or by addition of 0.1 or 1.0 microm H2O2 exogenously. Our results showed that DPI impairment of insulin secretion involved altered Ca2+ signaling, suggesting that NADPH oxidase may modulate Ca2+ signaling in beta-cells.
...
PMID:Impaired insulin secretion by diphenyleneiodium associated with perturbation of cytosolic Ca2+ dynamics in pancreatic beta-cells. 1861 20

Complex I or reduced nicotinamide adenine dinucleotide (NADH): ubiquinone oxydoreductase deficiency is the most common cause of respiratory chain defects. Molecular bases of complex I deficiencies are rarely identified because of the dual genetic origin of this multi-enzymatic complex (nuclear DNA and mitochondrial DNA) and the lack of phenotype-genotype correlation. We used a rapid method to screen patients with isolated complex I deficiencies for nuclear genes mutations by Surveyor nuclease digestion of cDNAs. Eight complex I nuclear genes, among the most frequently mutated (NDUFS1, NDUFS2, NDUFS3, NDUFS4, NDUFS7, NDUFS8, NDUFV1 and NDUFV2), were studied in 22 cDNA fragments spanning their coding sequences in 8 patients with a biochemically proved complex I deficiency. Single nucleotide polymorphisms and missense mutations were detected in 18.7% of the cDNA fragments by Surveyor nuclease treatment. Molecular defects were detected in 3 patients. Surveyor nuclease screening is a reliable method for genotyping nuclear complex I deficiencies, easy to interpret, and limits the number of sequence reactions. Its use will enhance the possibility of prenatal diagnosis and help us for a better understanding of complex I molecular defects.
...
PMID:Rapid screening for nuclear genes mutations in isolated respiratory chain complex I defects. 1916 55

Impaired mitochondrial activity has been linked to increased risk for clinical complications after injury. Furthermore, variant mitochondrial alleles have been identified and are thought to result in decreased mitochondrial activity. These include a nonsynonymous mitochondrial polymorphism (T4216C) in the nicotinamide adenine dinucleotide dehydrogenase 1 gene (ND1), encoding a key member of complex I within the electron transport chain, which is found almost exclusively among Caucasians. We hypothesized that burn patients carrying ND1 4216C are less able to generate the cellular energy necessary for an effective immune response and are at increased risk for infectious complications. The association between 4216C and outcome after burn injury was evaluated in a cohort of 175 Caucasian patients admitted to the Parkland Hospital with burns covering greater than or equal to 15% of their total body surface area or greater than or equal to 5% full-thickness burns under an institutional review board-approved protocol. To remove confounding unrelated to burn injury, individuals were excluded if they presented with significant non-burn-related trauma (Injury Severity Score > or =16), traumatic or anoxic brain injury, spinal cord injury, were HIV/AIDS positive, had active malignancy, or survived less than 48 h postadmission. Within this cohort of patients, carriage of the 4216C allele was significantly associated by unadjusted analysis with increased risk for sepsis-related organ dysfunction or septic shock (P = 0.011). After adjustment for full-thickness burn size, inhalation injury, age, and sex, carriage of the 4216C allele was associated with complicated sepsis (adjusted odds ratio = 3.7; 95% confidence interval, 1.5-9.1; P = 0.005), relative to carriers of the T allele.
...
PMID:Association of mitochondrial allele 4216C with increased risk for sepsis-related organ dysfunction and shock after burn injury. 1948 83

NADH:ubiquinone oxidoreductase (complex I) is a complicated respiratory chain enzyme that conserves the energy from NADH oxidation, coupled to ubiquinone reduction, as a proton motive force across the mitochondrial inner membrane. Alternatively, NADH oxidation, by the flavin mononucleotide in complex I, can be coupled to the reduction of hydrophilic electron acceptors, in non-energy-transducing reactions. The reduction of molecular oxygen and hydrophilic quinones leads to the production of reactive oxygen species, the reduction of nicotinamide nucleotides leads to transhydrogenation, and "artificial" electron acceptors are widely used to study the mechanism of NADH oxidation. Here, we use a combined modeling strategy to accurately describe data from three flavin-linked electron acceptors (molecular oxygen, APAD(+), and ferricyanide), in the presence and absence of a competitive inhibitor, ADP-ribose. Our combined ping-pong (or ping-pong-pong) mechanism comprises the Michaelis-Menten equation for the reactions of NADH and APAD(+), simple dissociation constants for nonproductive nucleotide-enzyme complexes (defined for specific flavin oxidation states), and second-order rate constants for the reactions of ferricyanide and oxygen. The NADH-dependent parameters are independent of the identity of the electron acceptor. In contrast, a further flavin-linked acceptor, hexaammineruthenium(III), does not obey ping-pong-pong kinetics, and alternative sites for its reaction are discussed. Our analysis provides kinetic and thermodynamic information about the reactions of the flavin active site in complex I that is relevant to understanding the physiologically relevant mechanisms of NADH oxidation and superoxide formation.
...
PMID:Reactions of the flavin mononucleotide in complex I: a combined mechanism describes NADH oxidation coupled to the reduction of APAD+, ferricyanide, or molecular oxygen. 1989 8

Tumor necrosis factor (TNF) is a pleiotropic molecule with a crucial role in cellular stress and inflammation during infection, tissue damage, and cancer. TNF signaling can lead to three distinct outcomes, each of which is initiated by different signaling complexes: the gene induction or survival mode, the apoptosis mode, and the necrosis mode. The kinases receptor-interacting protein 1 (RIP1) and RIP3 are key signaling molecules in necrosis and are regulated by caspases and ubiquitination. Moreover, TNF stimulation induces the formation of a necrosome in which RIP3 is activated and interacts with enzymes that control glycolytic flux and glutaminolysis. The necrosome induces mitochondrial complex I-mediated production of reactive oxygen species (ROS) and cytotoxicity, which suggest a functional link between increased bioenergetics and necrosis. In addition, other effector mechanisms also contribute to TNF-induced necrosis, such as recruitment of NADPH (the reduced form of nicotinamide adenine dinucleotide phosphate) oxidases and subsequent ROS production at the membrane-associated TNF receptor complex I; calcium mobilization; activation of phospholipase A(2), lipoxygenases, and acid sphingomyelinases; and lysosomal destabilization. However, the link between RIP1 and RIP3 and these subcellular events remains to be established. The regulation of RIP1 and RIP3 and their downstream signaling cascades opens new therapeutic avenues for treatment of pathologies associated with cell loss, such as ischemia-reperfusion damage and neurodegeneration, and ways to stimulate alternative immunogenic cell death pathways in cancer.
...
PMID:The role of the kinases RIP1 and RIP3 in TNF-induced necrosis. 2035 26


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---