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

Hypoxia-inducible factor 1 (HIF-1) regulates transcription in response to changes in O(2) concentration. O(2)-dependent degradation of the HIF-1alpha subunit is mediated by prolyl hydroxylase (PHD), the von Hippel-Lindau (VHL)/Elongin-C/Elongin-B E3 ubiquitin ligase complex, and the proteasome. Inhibition of heat-shock protein 90 (HSP90) leads to O(2)/PHD/VHL-independent degradation of HIF-1alpha. We have identified the receptor of activated protein kinase C (RACK1) as a HIF-1alpha-interacting protein that promotes PHD/VHL-independent proteasomal degradation of HIF-1alpha. RACK1 competes with HSP90 for binding to the PAS-A domain of HIF-1alpha in vitro and in human cells. HIF-1alpha degradation induced by the HSP90 inhibitor 17-allylaminogeldanamycin is abolished by RACK1 loss of function. RACK1 binds to Elongin-C and promotes ubiquitination of HIF-1alpha. Elongin-C-binding sites in RACK1 and VHL show significant sequence similarity. Thus, RACK1 is an essential component of an O(2)/PHD/VHL-independent mechanism for regulating HIF-1alpha stability through competition with HSP90 and recruitment of the Elongin-C/B ubiquitin ligase complex.
Mol Cell 2007 Jan 26
PMID:RACK1 competes with HSP90 for binding to HIF-1alpha and is required for O(2)-independent and HSP90 inhibitor-induced degradation of HIF-1alpha. 1724 29

Succinate dehydrogenase (SDH) and fumarate hydratase (FH) are components of the tricarboxylic acid (TCA) cycle and tumor suppressors. Loss of SDH or FH induces pseudohypoxia, a major tumor-supporting event, which is the activation of hypoxia-inducible factor (HIF) under normoxia. In SDH- or FH-deficient cells, HIF activation is due to HIF1alpha stabilization by succinate or fumarate, respectively, either of which, when in excess, inhibits HIFalpha prolyl hydroxylase (PHD). To reactivate PHD, we focused on its substrate, alpha-ketoglutarate. We designed and synthesized cell-permeating alpha-ketoglutarate derivatives, which build up rapidly and preferentially in cells with a dysfunctional TCA cycle. This study shows that succinate- or fumarate-mediated inhibition of PHD is competitive and is reversed by pharmacologically elevating intracellular alpha-ketoglutarate. Introduction of alpha-ketoglutarate derivatives restores normal PHD activity and HIF1alpha levels to SDH-suppressed cells, indicating new therapy possibilities for the cancers associated with TCA cycle dysfunction.
Mol Cell Biol 2007 May
PMID:Cell-permeating alpha-ketoglutarate derivatives alleviate pseudohypoxia in succinate dehydrogenase-deficient cells. 1732 41

We investigated a molecular mechanism underlying quercetin-mediated amelioration of colonic mucosal injury and analyzed chemical structure contributing to the quercetin's effect. Quercetin up-regulated vascular endothelial growth factor (VEGF), an ulcer healing factor, not only in colon epithelial cell lines but also in the inflamed colonic tissue. VEGF derived from quercetin-treated colon epithelial cells promoted tube formation. The VEGF induction was dependent on quercetin-mediated hypoxia-inducible factor-1 (HIF-1) activation. Quercetin delayed HIF-1alpha protein disappearance, which occurred by inhibiting HIF-prolyl hydroxylase (HPH), the key enzyme for HIF-1alpha hydroxylation and subsequent von Hippel Lindau-dependent HIF-1alpha degradation. HPH inhibition by quercetin was neutralized significantly by an elevated dose of iron. Consistent with this, cellular induction of HIF-1alpha by quercetin was abolished by pretreatment with iron. Two iron-chelating moieties in quercetin, -OH at position 3 of the C ring and/or -OH at positions 3' and 4' of the B ring, enabled the flavonoid to inhibit HPH and subsequently induce HIF-1alpha. Our data suggest that the clinical effect of quercetin may be partly attributed to the activation of an angiogenic pathway HIF-1-VEGF via inhibiting HPH and the chelating moieties of quercetin were required for inhibiting HPH.
Mol Pharmacol 2007 Jun
PMID:Quercetin activates an angiogenic pathway, hypoxia inducible factor (HIF)-1-vascular endothelial growth factor, by inhibiting HIF-prolyl hydroxylase: a structural analysis of quercetin for inhibiting HIF-prolyl hydroxylase. 1737 63

The hypoxia-inducible factor HIF-1 is the key regulator in cellular adaptation to hypoxia. Acting through a complex pathway, interconnected with VHL and kinases, it regulates a large number of genes, such as those involved in erythropoiesis, glycolysis, pH regulation, and angiogenesis. Recently, a missense mutation [c.950C>G (p.Pro317Arg)] in the prolyl hydroxylase domain protein 2 (PHD2) gene, whose encoded protein has HIF-1alpha as a substrate, provided evidence of the PHD2 role in a case of familial erythrocytosis. In this study, we looked for mutations in the PHD2 gene, in 74 patients with unidentified erythrocytosis. We found two heterozygous carriers of frameshift mutations [c.606delG (p.Met202IlefsX71) and c.840_841insA (p.Arg281ThrfsX3)]; both located in exon 1 and a heterozygous carrier of a nonsense mutation [c.1129C>T (p. Gln377X)] in exon 3. As a result of these mutations the encoded PHD2, if synthesized, would lose its catalytic activity. The genetic defects herein described are the first frameshift and nonsense mutations reported in the PHD2 gene and, as the previous missense mutation described, suggest that a decreased prolyl hydroxylase activity disturbing the oxygen-sensing pathway might be the cause of erythrocytosis. In addition to erythrocytosis, other complications, such as inflammatory arthromyalgia, have been observed in one case.
Blood Cells Mol Dis
PMID:Disturbance in the HIF-1alpha pathway associated with erythrocytosis: further evidences brought by frameshift and nonsense mutations in the prolyl hydroxylase domain protein 2 (PHD2) gene. 1793 62

Cell culture studies have implicated the oxygen-sensitive hypoxia-inducible factor (HIF) prolyl hydroxylase PHD3 in the regulation of neuronal apoptosis. To better understand this function in vivo, we have created PHD3(-/-) mice and analyzed the neuronal phenotype. Reduced apoptosis in superior cervical ganglion (SCG) neurons cultured from PHD3(-/-) mice is associated with an increase in the number of cells in the SCG, as well as in the adrenal medulla and carotid body. Genetic analysis by intercrossing PHD3(-/-) mice with HIF-1a(+/-) and HIF-2a(+/-) mice demonstrated an interaction with HIF-2alpha but not HIF-1alpha, supporting the nonredundant involvement of a PHD3-HIF-2alpha pathway in the regulation of sympathoadrenal development. Despite the increased number of cells, the sympathoadrenal system appeared hypofunctional in PHD3(-/-) mice, with reduced target tissue innervation, adrenal medullary secretory capacity, sympathoadrenal responses, and systemic blood pressure. These observations suggest that the role of PHD3 in sympathoadrenal development extends beyond simple control of cell survival and organ mass, with functional PHD3 being required for proper anatomical and physiological integrity of the system. Perturbation of this interface between developmental and adaptive signaling by hypoxic, metabolic, or other stresses could have important effects on key sympathoadrenal functions, such as blood pressure regulation.
Mol Cell Biol 2008 May
PMID:Abnormal sympathoadrenal development and systemic hypotension in PHD3-/- mice. 1833 18

We have confirmed that the NO donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP) stabilizes the transactive form of hypoxia-inducible factor-1alpha (HIF-1alpha), leading to the induction of HIF-1alpha target genes such as vascular endothelial growth factor and carbonic anhydrase 9. Activation of HIF-1alpha should require inhibition of the dual system that keeps it inactive. One is ubiquitination, which is triggered by hydroxylation of HIF-1alpha-proline and the subsequent binding of E3 ubiquitin ligase, the von Hippel Lindau (VHL) protein. The other is hydroxylation of HIF-1alpha-asparagine, which reduces the affinity of HIF-1alpha for its coactivator, cAMP responsive element binding protein/p300. We examined the effects of the NO donor SNAP on proline and asparagine hydroxylation of HIF-1alpha peptides by measuring the activities of the corresponding enzymes, HIF-1alpha-specific proline hydroxylase 2 (PHD2) and the HIF-1alpha-specific asparagine hydroxylase, designated factor inhibiting HIF-1alpha (FIH-1), respectively. We found that the SNAP did not prevent PHD2 from hydroxylating the proline of HIF-1alpha. Instead, it blocked the interaction between VHL and the proline-hydroxylated HIF-1alpha, but only when the reducing agents Fe(II) and vitamin C were limiting. The fact that the absence of cysteine 520 of HIF-1alpha abolishes its responsiveness to SNAP suggests that this residue mediates the inhibition by SNAP of the interaction between VHL and HIF-1alpha, presumably by S-nitrosylation of HIF-1alpha. Un-like PHD2, asparagine hydroxylation by FIH-1 was directly inhibited by SNAP, but again only when reducing agents were limiting. Substitution of cysteine 800 of HIF-1alpha with alanine failed to reverse the inhibitory effects of SNAP on asparagine hydroxylation, implying that FIH-1, not its substrate HIF-1alpha, is inhibited by SNAP.
Mol Pharmacol 2008 Jul
PMID:Nitric oxide donor, (+/-)-S-nitroso-N-acetylpenicillamine, stabilizes transactive hypoxia-inducible factor-1alpha by inhibiting von Hippel-Lindau recruitment and asparagine hydroxylation. 1842 57

The serine/threonine kinase-15 (STK15) acts as a cell cycle regulator being overexpressed in various tumors. One mechanism that could contribute to overexpression of STK15 is tumor hypoxia where hypoxia-inducible factor-1 (HIF-1) is a major regulator of transcription. Therefore, we analyzed whether hypoxia and HIF-1 could contribute to overexpression of STK15. We found that hypoxia increased STK15 expression and STK15 promoter activity in HepG2 tumor cells. Overexpression of HIF-1 alpha induced STK15 gene transcription, whereas HIF-1 alpha siRNA and overexpression of prolyl hydroxylase 2 (PHD-2), a negative regulator of HIF-1 alpha, reversed this effect. In addition, site-directed mutagenesis experiments and chromatin immunoprecipitation revealed that from the three putative hypoxia responsive elements (HRE) within the STK15 promoter only HRE-2 was functional and bound HIF-1. Further, siRNA against STK15 inhibited proliferation of HepG2 cells induced by hypoxia. These results show that STK15 gene transcription can be regulated by hypoxia and HIF-1 via HRE-2 of the STK15 promoter. Thus, tumor hypoxia may trigger overexpression of STK15 observed in various tumors.
Mol Biol Cell 2008 Sep
PMID:Transcriptional regulation of serine/threonine kinase-15 (STK15) expression by hypoxia and HIF-1. 1856 94

Exposure to environmental pollutants such as polychlorinated biphenyls (PCBs) is now taken into account to partly explain the worldwide decline of amphibians. PCBs induce deleterious effects on developing amphibians including deformities and delays in metamorphosis. However, the molecular mechanisms by which they express their toxicity during the development of tadpoles are still largely unknown. A proteomics analysis was performed on developing Xenopus laevis tadpoles exposed from 2 to 5 days postfertilization to either 0.1 or 1 ppm Aroclor 1254, a PCB mixture. Two-dimensional DIGE with a minimal labeling method coupled to nanoflow liquid chromatography-tandem mass spectrometry was used to detect and identify proteins differentially expressed under PCBs conditions. Results showed that 59 spots from the 0.1 ppm Aroclor 1254 condition and 57 spots from the 1 ppm Aroclor 1254 condition displayed a significant increase or decrease of abundance compared with the control. In total, 28 proteins were identified. The results suggest that PCBs induce mechanisms against oxidative stress (peroxiredoxins 1 and 2), adaptative changes in the energetic metabolism (enolase 1, glycerol-3-phosphate dehydrogenase, and creatine kinase muscle and brain types), and the implication of the unfolded protein response system (glucose-regulated protein, 58 kDa). They also affect, at least at the highest concentration tested, the synthesis of proteins involved in normal cytogenesis (alpha-tropomyosin, myosin heavy chain, and alpha-actin). For the first time, proteins such as aldehyde dehydrogenase 7A1, CArG binding factor-A, prolyl 4-hydroxylase beta, and nuclear matrix protein 200 were also shown to be up-regulated by PCBs in developing amphibians. These data argue that protein expression reorganization should be taken into account while estimating the toxicological hazard of wild amphibian populations exposed to PCBs.
Mol Cell Proteomics 2009 Apr
PMID:Protein expression profiling in the African clawed frog Xenopus laevis tadpoles exposed to the polychlorinated biphenyl mixture aroclor 1254. 1901 Dec 58

Neurotrophins are critical for the survival of neurons during development and insufficient access to neurotrophins later in life may contribute to the loss of neurons in neurodegenerative disease, spinal cord injury, and stroke. The prolyl hydroxylase inhibitors ethyl 3,4-dihydroxybenzoic acid (DHB) and dimethyloxalylglycine (DMOG) were shown to inhibit cell death in a model of neurotrophin deprivation that involves depriving sympathetic neurons of nerve growth factor (NGF). Here we show that treatment with DMOG or DHB reverses the decline in 2-deoxyglucose uptake caused by NGF withdrawal and suppresses the NGF deprivation-induced accumulation of reactive oxygen species. Neither DMOG nor DHB prevented death when NGF deprivation was carried out under conditions of glucose starvation, and both compounds proved toxic to NGF-maintained neurons deprived of glucose, suggesting that their survival-promoting effects are mediated through the preservation of glucose metabolism. DHB and DMOG are well known activators of hypoxia-inducible factor (HIF), but whether activation of HIF underlies their survival-promoting effects is not known. Using gene disruption and RNA interference, we provide evidence that DMOG and, to a lesser extent, DHB require HIF-2alpha expression to inhibit NGF deprivation-induced death. Furthermore, suppressing basal HIF-2alpha expression, but not HIF-1alpha, in NGF-maintained neurons is sufficient to promote cell death. These results implicate HIF-2alpha in the neuroprotective mechanisms of prolyl hydroxylase inhibitors and in an endogenous cell survival pathway activated by NGF in developing neurons.
Mol Pharmacol 2009 May
PMID:Prolyl hydroxylase inhibitors depend on extracellular glucose and hypoxia-inducible factor (HIF)-2alpha to inhibit cell death caused by nerve growth factor (NGF) deprivation: evidence that HIF-2alpha has a role in NGF-promoted survival of sympathetic neurons. 1920 94

At least 28 proteins have now been defined as collagens (Trends Genet. 20:33-43, 2004; J. Biol. Chem. 281:3494-3504, 2006), but many of those recently discovered are present in tissues in such small amounts that their isolation for characterization at the protein level has so far been impossible. Some of the fibrilforming collagens are used as a biomaterial in numerous medical applications and as a delivery system for various drugs (3, 4). The collagens used in all these applications have been isolated from animal tissues and are liable to cause allergic reactions in some subjects and carry a risk of disease-causing contaminants (3,4). An efficient recombinant expression system for collagens can thus be expected to have numerous scientific and medical applications. The systems commonly used for expressing other proteins in lower organisms are not suitable as such for the production of recombinant collagens, however, as bacteria and yeast have no prolyl 4-hydroxylase activity and insect cells have insufficient levels of it. Prolyl 4-hydroxylase, an alpha 2 beta 2 tetramer in vertebrates, plays a central role in the synthesis of all collagens, as 4-hydroxyproline-deficient collagen polypeptide chains cannot form triple helices that are stable at 37 degrees C (5,6). All attempts to assemble an active prolyl 4-hydroxylase tetramer from its subunits in vitro have been unsuccessful, but active recombinant human prolyl 4-hydroxylase has been produced in insect cells, yeast, and Escherichia coli by coexpression of its alpha - and beta -subunits (7-9).
Methods Mol Biol 2009
PMID:Recombinant collagen trimers from insect cells and yeast. 1924 4


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