Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to test for the presence of liver hypoxia and recovery after reperfusion when blood alcohol levels (BAL) are high. Male rats were fed ethanol intragastrically at a constant rate for 1 month. The pO(2) levels were then measured on the liver surface of these rats, in vivo during laparatomy under isoflurane anesthesia. To measure the response to acute hypoxia, the hepatic blood flow was clamped off at the porta hepatis. When the clamp was released, recovery from hypoxia was measured. A number of hypoxic-inducible genes in the liver were analyzed by means of quantitative RT-PCR as a measure of increased activation of hypoxia initiated transcription. The mRNA levels of genes for adrenomedullin, adrenergic receptor alpha, 1a and 1d, CDK inhibitor 1a, and erythropoietin were all significantly higher at the peaks than troughs. Expression of these same genes in the livers of control rats fed dextrose was lower than at the troughs. Although the mRNA level of the hypoxia-inducible factor (HIF-1alpha) was higher at the trough than at the peak, its protein concentration in the nuclear fraction was not increased at the troughs compared with the peaks. In fact, the nuclear protein level of HIF-1alpha at the peak was significantly higher than in control samples, which is consistent with the presence of hypoxia at the peaks. Further analysis of the HIF-alpha degradation regulation revealed that prolyl 4-hydroxylase (P4ha1) and von Hippel-Lindau syndrome homolog (Vhl) were both up-regulated at the troughs compared with the peaks. The liver surface oxygen levels at the peaks were reduced compared with the control samples. The pO(2) levels fell abruptly when the vessels at the porta hepatis were clamped. When the clamp was removed, allowing reperfusion of the liver, pO(2) returned to baseline levels in the control, and at the troughs but not at the peaks. These results support the hypothesis that hypoxia occurs at the peaks of the BAL cycle and recovery from ischemia is impaired at the peaks.
Exp Mol Pathol 2004 Dec
PMID:Liver hypoxia and lack of recovery after reperfusion at high blood alcohol levels in the intragastric feeding model of alcohol liver disease. 1550 34

Oxygen-dependent proteolysis is the primary means of regulating the hypoxia-inducible factor (HIF) family of transcription factors. The alpha-subunit of HIF factor 1 (HIF-1) contains two highly conserved oxygen-dependent degradation domains (402 ODD and 564 ODD), each of which includes a proline that is hydroxylated in the presence of oxygen, allowing the von Hippel-Lindau (VHL) E3 ubiquitin ligase to interact and target HIF-1alpha to the proteasome for degradation. Mutation of either proline is sufficient to partially stabilize HIF-1alpha under conditions of normoxia, but the specific contributions of each hydroxylation event to the regulation of HIF-1alpha are unknown. Here we show that the two ODDs of HIF-1alpha have independent yet interactive roles in the regulation of HIF-1alpha protein turnover, with the relative involvement of each ODD depending on the levels of oxygen. Using hydroxylation-specific antibodies, we found that under conditions of normoxia proline 564 is hydroxylated prior to proline 402, and mutation of proline 564 results in a significant reduction in the hydroxylation of proline 402. Mutation of proline 402, however, has little effect on the hydroxylation of proline 564. To determine whether the more rapid hydroxylation of the proline 564 under conditions of normoxia is due to a preference for the particular sequence surrounding proline 564 or for that site within the protein, we exchanged the degradation domains within the full-length HIF-1alpha protein. In these domain-swapping experiments, prolyl hydroxylase domain 1 (PHD1) and PHD2 preferentially hydroxylated the proline located in the site of the original 564 ODD, while PHD3 preferred the proline 564 sequence, regardless of its location. At limiting oxygen tensions, we found that proline 402 exhibits an oxygen-dependent decrease in hydroxylation at higher oxygen tensions relative to proline 564 hydroxylation. These results indicate that hydroxylation of proline 402 is highly responsive to physiologic changes in oxygen and, therefore, plays a more important role in HIF-1alpha regulation under conditions of hypoxia than under conditions of normoxia. Together, these findings demonstrate that each hydroxylated proline of HIF-1alpha has a distinct activity in controlling HIF-1alpha stability in response to different levels of oxygenation.
Mol Cell Biol 2005 Aug
PMID:Coordinate regulation of the oxygen-dependent degradation domains of hypoxia-inducible factor 1 alpha. 1602 80

Iron and copper are essential nutrients, excesses or deficiencies of which cause impaired cellular functions and eventually cell death. The metabolic fates of copper and iron are intimately related. Systemic copper deficiency generates cellular iron deficiency, which in humans results in diminished work capacity, reduced intellectual capacity, diminished growth, alterations in bone mineralization, and diminished immune response. Copper is required for the function of over 30 proteins, including superoxide dismutase, ceruloplasmin, lysyl oxidase, cytochrome c oxidase, tyrosinase and dopamine-beta-hydroxylase. Iron is similarly required in numerous essential proteins, such as the heme-containing proteins, electron transport chain and microsomal electron transport proteins, and iron-sulfur proteins and enzymes such as ribonucleotide reductase, prolyl hydroxylase phenylalanine hydroxylase, tyrosine hydroxylase and aconitase. The essentiality of iron and copper resides in their capacity to participate in one-electron exchange reactions. However, the same property that makes them essential also generates free radicals that can be seriously deleterious to cells. Thus, these seemingly paradoxical properties of iron and copper demand a concerted regulation of cellular copper and iron levels. Here we review the most salient characteristics of their homeostasis.
Mol Aspects Med
PMID:Iron and copper metabolism. 1611 86

Soluble nickel compounds are likely human carcinogens. The mechanism by which soluble nickel may contribute to carcinogenesis is unclear, though several hypotheses have been proposed. Here we verify the ability of nickel to enter the cell via the divalent metal ion transporter 1 (DMT1) and disturb cellular iron homeostasis. Nickel may interfere with iron at both an extracellular level, by preventing iron from being transported into the cell, and at an intracellular level, by competing for iron sites on enzymes like the prolyl hydroxylases that modify hypoxia inducible factor-1alpha (HIF-1alpha). Nickel was able to decrease the binding of the Von Hippel-Lindau (VHL) protein to HIF-1alpha, indicating a decrease in prolyl hydroxylase activity. The ability of nickel to affect various iron dependent processes may be an important step in nickel dependent carcinogenesis. In addition, understanding the mechanisms by which nickel activates the HIF-1alpha pathway may lead to new molecular targets in fighting cancer.
Mol Cell Biochem 2005 Nov
PMID:Soluble nickel interferes with cellular iron homeostasis. 1628 25

Hypoxia-inducible factor 1 (HIF-1) is controlled through stability regulation of its alpha subunit, which is expressed under hypoxia but degraded under normoxia. Degradation of HIF-1alpha requires association of the von Hippel Lindau protein (pVHL) to provoke ubiquitination followed by proteasomal digestion. Besides hypoxia, nitric oxide (NO) stabilizes HIF-1alpha under normoxia but destabilizes the protein under hypoxia. To understand the role of NO under hypoxia we made use of pVHL-deficient renal carcinoma cells (RCC4) that show a high steady state HIF-1alpha expression under normoxia. Exposing RCC4 cells to hypoxia in combination with the NO donor DETA-NO (2,2'-(hydroxynitrosohydrazono) bis-ethanimine), but not hypoxia or DETA-NO alone, decreased HIF-1alpha protein and attenuated HIF-1 transactivation. Mechanistically, we noticed a role of calpain because calpain inhibitors reversed HIF-1alpha degradation. Furthermore, chelating intracellular calcium attenuated HIF-1alpha destruction by hypoxia/DETA-NO, whereas a calcium increase was sufficient to lower the amount of HIF-1alpha even under normoxia. An active role of calpain in lowering HIF-1alpha amount was also evident in pVHL-containing human embryonic kidney cells when the calcium pump inhibitor thapsigargin reduced HIF-1alpha that was stabilized by the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG). We conclude that calcium contributes to HIF-1alpha destruction involving the calpain system.
Mol Biol Cell 2006 Apr
PMID:Calpain mediates a von Hippel-Lindau protein-independent destruction of hypoxia-inducible factor-1alpha. 1642 Dec 54

Development of lung microvasculature is critical for distal airway formation. Both processes are arrested in the lungs of preterm newborns with bronchopulmonary dysplasia (BPD), a chronic form of lung disease. We hypothesized that activation of hypoxia-inducible factors (HIFs) augments lung vascular development. Pulmonary angiogenic factors were assessed by quantitative real-time PCR, Western blot, and immunohistochemistry in preterm baboons (125 days+14 days pro re nata O2 model) treated for 14 days with intravenous FG-4095, an inhibitor of prolyl hydroxylase domain-containing proteins (PHDs) that initiates HIF degradation. HIF-1alpha, but not HIF-2alpha, mRNA and protein were increased (8- and 3-fold, respectively) in FG-4095-treated baboons relative to untreated controls. Expression of PHD-1, -2, and -3 was unchanged. Of note, mRNA and/or protein for platelet-endothelial cell adhesion molecule 1 (PECAM-1) and vascular endothelial growth factor (VEGF) were increased by FG-4095. Moreover, PECAM-1-expressing capillary endothelial cells detected by immunohistochemistry were augmented in FG-4095-treated baboons to levels comparable to those in fetal age-matched controls. Alveolar septal cell expression of Ki67, a proliferative marker, and VEGF were similar in untreated controls and FG-4095-treated neonates. These results indicate that HIF stimulation by PHD inhibition enhances lung angiogenesis in the primate model of BPD.
Am J Physiol Lung Cell Mol Physiol 2006 Oct
PMID:Enhancement of angiogenic effectors through hypoxia-inducible factor in preterm primate lung in vivo. 1667 81

The phosphoinositide 3-kinase (PI3K)/Akt pathway is commonly activated in cancer; therefore, we investigated its role in hypoxia-inducible factor-1alpha (HIF-1alpha) regulation. Inhibition of PI3K in U87MG glioblastoma cells, which have activated PI3K/Akt activity secondary to phosphatase and tensin homologue deleted on chromosome 10 (PTEN) mutation, with LY294002 blunted the induction of HIF-1alpha protein and its targets vascular endothelial growth factor and glut1 mRNA in response to hypoxia. Introduction of wild-type PTEN into these cells also blunted HIF-1alpha induction in response to hypoxia and decreased HIF-1alpha accumulation in the presence of the proteasomal inhibitor MG132. Akt small interfering RNA (siRNA) also decreased HIF-1alpha induction under hypoxia and its accumulation in normoxia in the presence of dimethyloxallyl glycine, a prolyl hydroxylase inhibitor that prevents HIF-1alpha degradation. Metabolic labeling studies showed that Akt siRNA decreased HIF-1alpha translation in normoxia in the presence of dimethyloxallyl glycine and in hypoxia. Inhibition of mammalian target of rapamycin (mTOR) with rapamycin (10-100 nmol/L) had no significant effect on HIF-1alpha induction in a variety of cell lines, a finding that was confirmed using mTOR siRNA. Furthermore, neither mTOR siRNA nor rapamycin decreased HIF-1alpha translation as determined by metabolic labeling studies. Therefore, our results indicate that Akt can augment HIF-1alpha expression by increasing its translation under both normoxic and hypoxic conditions; however, the pathway we are investigating seems to be rapamycin insensitive and mTOR independent. These observations, which were made on cells grown in standard tissue culture medium (10% serum), were confirmed in PC3 prostate carcinoma cells. We did find that rapamycin could decrease HIF-1alpha expression when cells were cultured in low serum, but this seems to represent a different pathway.
Mol Cancer Res 2006 Jul
PMID:Akt1 activation can augment hypoxia-inducible factor-1alpha expression by increasing protein translation through a mammalian target of rapamycin-independent pathway. 1684 22

PHD1, PHD2, and PHD3 are prolyl hydroxylase domain proteins that regulate the stability of hypoxia-inducible factor alpha subunits (HIF-alpha). To determine the roles of individual PHDs during mouse development, we disrupted all three Phd genes and found that Phd2(-/-) embryos died between embryonic days 12.5 and 14.5 whereas Phd1(-/-) or Phd3(-/-) mice were apparently normal. In Phd2(-/-) mice, severe placental and heart defects preceded embryonic death. Placental defects included significantly reduced labyrinthine branching morphogenesis, widespread penetration of the labyrinth by spongiotrophoblasts, and abnormal distribution of trophoblast giant cells. The expression of several trophoblast markers was also altered, including an increase in the spongiotrophoblast marker Mash2 and decreases in the labyrinthine markers Tfeb and Gcm1. In the heart, trabeculae were poorly developed, the myocardium was remarkably thinner, and interventricular septum was incompletely formed. Surprisingly, while there were significant global increases in HIF-alpha protein levels in the placenta and the embryo proper, there was no specific HIF-alpha increase in the heart. Taken together, these data indicate that among all three PHD proteins, PHD2 is uniquely essential during mouse embryogenesis.
Mol Cell Biol 2006 Nov
PMID:Placental but not heart defects are associated with elevated hypoxia-inducible factor alpha levels in mice lacking prolyl hydroxylase domain protein 2. 1696 70

Prolyl hydroxylation of hypoxible-inducible factor alpha (HIF-alpha) proteins is essential for their recognition by pVHL containing ubiquitin ligase complexes and subsequent degradation in oxygen (O(2))-replete cells. Therefore, HIF prolyl hydroxylase (PHD) enzymatic activity is critical for the regulation of cellular responses to O(2) deprivation (hypoxia). Using a fusion protein containing the human HIF-1alpha O(2)-dependent degradation domain (ODD), we monitored PHD activity both in vivo and in cell-free systems. This novel assay allows the simultaneous detection of both hydroxylated and nonhydroxylated PHD substrates in cells and during in vitro reactions. Importantly, the ODD fusion protein is regulated with kinetics identical to endogenous HIF-1alpha during cellular hypoxia and reoxygenation. Using in vitro assays, we demonstrated that the levels of iron (Fe), ascorbate, and various tricarboxylic acid (TCA) cycle intermediates affect PHD activity. The intracellular levels of these factors also modulate PHD function and HIF-1alpha accumulation in vivo. Furthermore, cells treated with mitochondrial inhibitors, such as rotenone and myxothiazol, provided direct evidence that PHDs remain active in hypoxic cells lacking functional mitochondria. Our results suggest that multiple mitochondrial products, including TCA cycle intermediates and reactive oxygen species, can coordinate PHD activity, HIF stabilization, and cellular responses to O(2) depletion.
Mol Cell Biol 2007 Feb
PMID:Multiple factors affecting cellular redox status and energy metabolism modulate hypoxia-inducible factor prolyl hydroxylase activity in vivo and in vitro. 1710 81

Oxidative stress has been implicated in the pathogenesis of neuronal degenerative diseases. It is also widely known that oxidative stress induces mitogen-activated protein kinase (MAPK) signaling cascades. In this study, we used proteomic analysis to investigate the role of the MAPK pathway in oxidative stress-induced neuronal cell death. The results demonstrated that several proteins, including eukaryotic translation elongation factor 2 (eEF2) and enolase I, showed a differential expression pattern during the neuronal cell death process, and this was MAPK pathway dependent. Several chaperone and cytoskeletal proteins including heat shock protein 70, calreticulin, vimentin, prolyl 4-hydroxylase beta polypeptide, and transgelin 2 were up-or down-regulated, despite their expressions not depending on the MAPK pathway. These findings strongly suggest that the expressions of proteins which play protective roles are independent of the MAPK pathway. On the other hand, eEF2 and enolase I may be the downstream targets of the MAPK pathway.
Cell Mol Biol Lett 2007
PMID:A proteomic analysis of the effect of MAPK pathway activation on L-glutamate-induced neuronal cell death. 1712 46


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