Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Strial marginal cells are known to take up and metabolize glucose as their main source of metabolic energy. The membrane transport mechanisms for glucose uptake into strial marginal cells, however, are largely unknown. Two types of glucose transporters in mammalian cells have been described, the facilitated glucose transporter GLUT and the sodium/glucose cotransporter SGLT. The goal of the present study was to determine which of these represent the main glucose uptake mechanism in strial marginal cells. Glucose uptake into strial marginal cells was assessed by monitoring the cellular concentration of the reduced form of nicotinamide adenine dinucleotide (NADH) fluorometrically. The relation between the autofluorescence from marginal cells and cellular metabolism was verified as follows. The autofluorescence (excitation: 340 nm, emission: 450-490 nm) decreased when oxidative phosphorylation in the mitochondria was uncoupled with carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and increased when cytochrome oxidase was inhibited with cyanide. These effects indicate that the autofluorescence is dependent on the mitochondrial metabolic state, and more specifically on the level of NADH in mitochondria. Glucose removal from the bath solution elicited a 39% decrease in the autofluorescence intensity within 5 min. Similarly, cytochalasin B (10 microM) reduced the fluorescence intensity by 34% in 5 min. In contrast, neither phlorizin (0.1 mM) nor Na+ removal from the bath solution caused any appreciable change in the autofluorescence intensity. These results indicate that glucose depletion affects the metabolic state of the marginal cell within a few minutes, and that marginal cells take up glucose via GLUT, but not via SGLT. Since the excitation and emission wavelengths of several fluorescent dyes used in physiological studies (e.g., Fura-2 and SBFI) are similar to those of NADH, possible effects of autofluorescence on recording signals should always be taken into account when these dyes are utilized.
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PMID:Marginal cells of the stria vascularis of gerbils take up glucose via the facilitated transporter GLUT: application of autofluorescence. 944 20

Long-chain polyunsaturated (n-3) fatty acids have been reported to influence the efficiency of membrane receptors, transporters and enzymes. Because the brain is particularly rich in docosahexaenoic acid (DHA, 22:6 n-3), the present study addresses the question of whether the 22:6 n-3 fatty acid deficiency induces disorder in regulation of energy metabolism in the CNS. Three brain regions that share a high rate of energy metabolism were studied: fronto-parietal cortex, hippocampus and suprachiasmatic nucleus. The effect of the diet deficient in n-3 fatty acids resulted in a 30-50% decrease in DHA in membrane phospholipids. Moreover, a 30% decrease in glucose uptake and a 20-40% decrease in cytochrome oxidase activity were observed in the three brain regions. The n-3 deficient diet also altered the immunoreactivity of glucose transporters, namely GLUT1 in endothelial cells and GLUT3 in neurones. In n-3 fatty acid deficient rats, GLUT1-immunoreactivity readily detectable in microvessels became sparse, whereas the number of GLUT3 immunoreactive neurones was increased. However, western blot analysis showed no significant difference in GLUT1 and GLUT3 protein levels between rats deficient in n-3 fatty acids and control rats. The present results suggest that changes in energy metabolism induced by n-3 deficiency could result from functional alteration in glucose transporters.
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PMID:Glucose transport and utilization are altered in the brain of rats deficient in n-3 polyunsaturated fatty acids. 1206 80

We sought to test the hypothesis that monocarboxylate transporter isoform 1 (MCT1) is the inner mitochondrial membrane lactate/pyruvate transporter, and, as such, contributes to functioning of the intracellular lactate shuttle. However, presence of a mammalian mitochondrially localized MCT1 (mMCT1) has been contested. We sought to confirm by Western blotting the mitochondrial localization of MCT1 in rat cardiac, soleus, and extensor digitorum longus muscles utilizing three different cell fractionation methods and three different antibodies. We performed Western blotting using antibodies to cell membrane glucose transporter isoform GLUT1, inner mitochondrial constituent cytochrome oxidase, the monocarboxylate transporter protein chaperone CD147, as well as custom and commercially available MCT1 antibodies. Western blots demonstrated similar results with each MCT1 antibody and two of three methods of fractionation. MCT1 was found in the mitochondria, as well as in the sarcolemmal membrane and whole muscle homogenates. Probing with GLUT1 and CD147 demonstrated that mitochondrial fractions were not contaminated with sarcolemmal remnants. Probing with cytochrome oxidase showed mitochondrial localization of MCT1. Comparison of these results to the findings of others indicates that the most likely source of discrepancy is the cell fractionation procedure utilized.
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PMID:MCT1 confirmed in rat striated muscle mitochondria. 1512 43

The middle portion of Meckel's cartilage resembles endochondral bone formation accompanied by chondrocyte hypertrophy and death, cartilaginous matrix calcification, and chondroclastic resorption. We examined Meckel's cartilage specimens from mice mandibles taken on embryonic days 14-16 (E14-E16) using immunohistochemistry for hypoxia-inducible factor-1alpha (HIF-1alpha), glucose transporter 1 (GLUT1), glucose transporter 3 (GLUT3), and glucose transporter 5 (GLUT5), and using enzyme histochemistry for glucose-6-phosphate isomerase (GPI), lactate dehydrogenase (LDH), and cytochrome oxidase (COX), along with the periodic acid-Schiff (PAS) reaction, and compared the results with those of endochondral bones from E16 hind limbs. Periodic acid-Schiff-positive glycogen, HIF-1alpha, and GLUT immunoreactivity, and GPI, LDH, and COX activities were observed in Meckel's cartilage in E14 and E15 mandibles. In E16 mandibles, hypertrophic chondrocytes showed a transitory loss of HIF-1alpha immunoreactivity and consumed glycogen, while those closest to the resorption front showed intense immunoreactivity for HIF-1, GLUT3, and GLUT5. Hypertrophic chondrocytes of metatarsals possessed HIF-1alpha immunoreactivity in the nuclei and diminished COX activity, whereas developing tibias showed weak HIF-1alpha immunoreactivity even in hypoxic regions characterized by little or no COX activity. These findings suggest that HIF-1alpha becomes stabilized independently of the concentration of oxygen, and largely contributes to the development and resorption of Meckel's cartilage, probably through shifting the predominant metabolic mode from aerobic to anaerobic glycolysis.
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PMID:Metabolic mode peculiar to Meckel's cartilage: immunohistochemical comparisons of hypoxia-inducible factor-1alpha and glucose transporters in developing endochondral bones in mice. 1870 2

Several evidence indicate that metabolic alterations play a pivotal role in cancer development. Here, we report that the mitochondrial uncoupling protein 2 (UCP2) sustains the metabolic shift from mitochondrial oxidative phosphorylation (mtOXPHOS) to glycolysis in pancreas cancer cells. Indeed, we show that UCP2 sensitizes pancreas cancer cells to the treatment with the glycolytic inhibitor 2-deoxy-D-glucose. Through a bidimensional electrophoresis analysis, we identify 19 protein species differentially expressed after treatment with the UCP2 inhibitor genipin and, by bioinformatic analyses, we show that these proteins are mainly involved in metabolic processes. In particular, we demonstrate that the antioxidant UCP2 induces the expression of hnRNPA2/B1, which is involved in the regulation of both GLUT1 and PKM2 mRNAs, and of lactate dehydrogenase (LDH) increasing the secretion of L-lactic acid. We further demonstrate that the radical scavenger N-acetyl-L-cysteine reverts hnRNPA2/B1 and PKM2 inhibition by genipin indicating a role for reactive oxygen species in the metabolic reprogramming of cancer cells mediated by UCP2. We also observe an UCP2-dependent decrease in mtOXPHOS complex I (NADH dehydrogenase), complex IV (cytochrome c oxidase), complex V (ATPase) and in mitochondrial oxygen consumption, suggesting a role for UCP2 in the counteraction of pancreatic cancer cellular respiration. All these results reveal novel mechanisms through which UCP2 promotes cancer cell proliferation with the concomitant metabolic shift from mtOXPHOS to the glycolytic pathway.
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PMID:The antioxidant uncoupling protein 2 stimulates hnRNPA2/B1, GLUT1 and PKM2 expression and sensitizes pancreas cancer cells to glycolysis inhibition. 2798 50