Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.11.2 (prolyl hydroxylase)
 1,814 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neutrophils are key mediators of the innate immune response and are required to function at sites of low oxygenation. We have shown that in hypoxia neutrophils are protected from apoptosis via a mechanism dependent on prolyl hydroxylase domain/hypoxia-inducible factor 1alpha (PHD/HIF-1alpha). This response would be predicted to involve the von Hippel Lindau protein (pVHL)-dependent ubiquitination and degradation of HIF-1alpha. Patients with VHL disease inherit a mutation in one VHL allele, which allows us to study the effects of heterozygous VHL expression in human neutrophils. Neutrophils exhibited a striking "partial hypoxic" pheno-type, with delayed rates of apoptosis and enhanced bacterial phagocytosis under normoxic conditions and preserved responses to low levels of oxygen. This provides direct evidence that the HIF-1alpha/VHL pathway regulates the innate immune response in humans. It also establishes that heterozygous VHL defects are sufficient to perturb normal responses and illustrates the potential to use this to address the role of HIF and VHL in human biology.
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PMID:Neutrophils from patients with heterozygous germline mutations in the von Hippel Lindau protein (pVHL) display delayed apoptosis and enhanced bacterial phagocytosis. 1680 12

The hypoxia-inducible transcription factor-1 (HIF-1) is central to a number of pathological processes through the induction of specific genes such as vascular endothelial growth factor (VEGF). Even though HIF-1 is highly regulated by cellular oxygen levels, other elements of the inflammatory and tumor microenvironment were shown to influence its activity under normal oxygen concentration. Among others, recent studies indicated that transforming growth factor (TGF) beta increases the expression of the regulatory HIF-1alpha subunit, and induces HIF-1 DNA binding activity. Here, we demonstrate that TGFbeta acts on HIF-1alpha accumulation and activity by increasing HIF-1alpha protein stability. In particular, we demonstrate that TGFbeta markedly and specifically decreases both mRNA and protein levels of a HIF-1alpha-associated prolyl hydroxylase (PHD), PHD2, through the Smad signaling pathway. As a consequence, the degradation of HIF-1alpha was inhibited as determined by impaired degradation of a reporter protein containing the HIF-1alpha oxygen-dependent degradation domain encompassing the PHD-targeted prolines. Moreover, inhibition of the TGFbeta1 converting enzyme, furin, resulted in increased PHD2 expression, and decreased basal HIF-1alpha and VEGF levels, suggesting that endogenous production of bioactive TGFbeta1 efficiently regulates HIF-1-targeted genes. This was reinforced by results from HIF-1alpha knock-out or HIF-1alpha-inhibited cells that show impairment in VEGF production in response to TGFbeta. This study reveals a novel mechanism by which a growth factor controls HIF-1 stability, and thereby drives the expression of specific genes, through the regulation of PHD2 levels.
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PMID:Transforming growth factor beta1 induces hypoxia-inducible factor-1 stabilization through selective inhibition of PHD2 expression. 1681 40

Hypoxic preconditioning can protect the brain against a subsequent damaging ischaemic insult. Mild hypoxia alone seems not sufficient to cause neuronal injury, but can induce changes in gene expression and intracellular signalling pathways and the hypoxia-inducible transcription factor (HIF-1) is a key modulator of these genes. Recently, a family of HIF prolyl hydroxylase enzymes (PHDs) has been shown to regulate HIF-1 function by controlling its degradation. Since PHD-2 is thought to be the predominant isoform which regulates HIF-1, we have investigated whether preconditioning with hypoxia can affect levels of PHD-2 and HIF-1alpha proteins to elucidate roles for the HIF-1/PHD-2 system in the neuroprotection conferred by hypoxic preconditioning. Sprague-Dawley rats (postnatal Day 6 (p6)) were exposed to preconditioning with hypoxia (3 h, 8% oxygen) or normoxia (3 h, room air) at various times (0, 0.5, 2, 4, 16 and 24 h) after reoxygenation, brains were obtained for Western blot and immunohistochemical analyses of PHD-2 and HIF-1alpha proteins. Western blotting studies demonstrate a significant increase in the expression of PHD-2 ( approximately 1.8-2-fold increase, at 0.5, 16 and 24 h after reoxygenation; p < 0.01) and HIF-1alpha (approximately 1.7-fold increase immediately after hypoxia; p < 0.05) proteins following hypoxic preconditioning relative to normoxic control tissue. Similar results were observed in immunohistochemical studies examining PHD-2 and HIF-1alpha proteins. Our study demonstrated for the first time that in vivo exposure to systemic hypoxia elevates the expression of PHD-2 protein in brain and it is likely that enhancing HIF-1 function by inhibition of PHD activity is involved in the protective effect conferred by hypoxic preconditioning in neonatal rat brain.
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PMID:Hypoxic preconditioning produces differential expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and its regulatory enzyme HIF prolyl hydroxylase 2 in neonatal rat brain. 1682 26

Recently resolved X-ray crystal structure of HIF-1alpha prolyl hydroxylase was used to design and develop a novel series of pyrazolopyridines as potent HIF-1alpha prolyl hydroxylase inhibitors. The activity of these compounds was determined in a human EGLN-1 assay. Structure-based design aided in optimizing the potency of the initial lead (2, IC(50) of 11 microM) to a potent (11l, 190 nM) EGLN-1 inhibitor. Several of these analogs were potent VEGF inducers in a cell-based assay. These pyrazolopyridines were also effective in stabilizing HIF-1alpha.
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PMID:Design and synthesis of a series of novel pyrazolopyridines as HIF-1alpha prolyl hydroxylase inhibitors. 1690 45

Structure-guided de novo drug design led to the identification of a novel series of substituted pyridine derivatives as HIF-1alpha prolyl hydroxylase inhibitors. Pyridine carboxyamide derivatives bearing a substituted aryl group at the 5-position of the pyridine ring show appreciable activity, while constraining the side chain by placing a pyrazole carboxylic acid generated a potent lead series with consistent activity against EGLN-1.
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PMID:Design and synthesis of substituted pyridine derivatives as HIF-1alpha prolyl hydroxylase inhibitors. 1690 49

A new series of potent 8-hydroxyquinolines was designed based on the newly resolved X-ray crystal structure of EGLN-1. Both alkyl and aryl 8-hydroxyquinoline-7-carboxyamides were good HIF-1alpha prolyl hydroxylase (EGLN) inhibitors. In subsequent VEGF induction assays, these exhibited potent VEGF activity. In addition, this class of compounds did show the ability to stabilize HIF-1alpha.
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PMID:Structure-based design, synthesis, and SAR evaluation of a new series of 8-hydroxyquinolines as HIF-1alpha prolyl hydroxylase inhibitors. 1693 Oct 7

The activity and levels of the metazoan HIF (hypoxia-inducible factor) are regulated by its hydroxylation, catalysed by 2OG (2-oxoglutarate)- and Fe(II)-dependent dioxygenases. An oxygen consumption assay was developed and used to study the relationship between HIF hydroxylase activity and oxygen concentration for recombinant forms of two human HIF hydroxylases, PHD2 (prolyl hydroxylase domain-containing protein 2) and FIH (factor inhibiting HIF), and compared with two other 2OG-dependent dioxygenases. Although there are caveats on the absolute values, the apparent K(m) (oxygen) values for PHD2 and FIH were within the range observed for other 2OG oxygenases. Recombinant protein substrates were found to have lower apparent K(m) (oxygen) values compared with shorter synthetic peptides of HIF. The analyses also suggest that human PHD2 is selective for fragments of the C-terminal over the N-terminal oxygen-dependent degradation domain of HIF-1alpha. The present results, albeit obtained under non-physiological conditions, imply that the apparent K(m) (oxygen) values of the HIF hydroxylases enable them to act as oxygen sensors providing their in vivo capacity is appropriately matched to a hydroxylation-sensitive signalling pathway.
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PMID:Studies on the activity of the hypoxia-inducible-factor hydroxylases using an oxygen consumption assay. 1695 79

Utilizing modeling information from a recently resolved structure of human HIF-1alpha prolyl hydroxylase (EGLN1) and structure-based design, a novel series of imidazo[1,2-a]pyridine derivatives was prepared. The activity of these compounds was determined in a human EGLN1 assay and a limited SAR was developed.
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PMID:A novel series of imidazo[1,2-a]pyridine derivatives as HIF-1alpha prolyl hydroxylase inhibitors. 1696 72

The mechanisms controlling the expression of the gene encoding for the hormone erythropoietin (EPO) are exemplary for oxygen-regulated gene expression. In humans and other mammals, hypoxia modulates EPO levels by increasing expression of the EPO gene. An association between polycythaemia and people living at high altitudes was first reported more than 100 years ago. Since the identification of EPO as the humoral regulator of red blood cell production and the cloning of the EPO gene, considerable progress has been made in understanding the regulation of EPO gene expression. This has finally led to the identification of a widespread cellular oxygen-sensing mechanism. Central to this mechanism is the transcription factor complex hypoxia-inducible factor (HIF)-1. The abundance and activity of HIF-1, a heterodimer of an alpha- and beta-subunit, is predominantly regulated by oxygen-dependent post-translational hydroxylation of the alpha-subunit. Non-heme ferrous iron containing hydroxylases use dioxygen and 2-oxoglutarate to specifically target proline and an asparagine residue in HIF-1alpha. As such, the three prolyl hydroxylases (prolyl hydroxylase domain-containing protein (PHD) 1, PHD2 and PHD3) and the asparagyl hydroxylase (factor inhibiting HIF (FIH)-1) act as cellular oxygen sensors. In addition to erythropoiesis, HIF-1 regulates a broad range of physiologically relevant genes involved in angiogenesis, apoptosis, vasomotor control and energy metabolism. Therefore, the HIF system is implicated in the pathophysiology of many human diseases. In addition to the tight regulation by oxygen tension, temporal and tissue-specific signals limit expression of the EPO gene primarily to the fetal liver and the adult kidney.
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PMID:Hypoxia-induced erythropoietin production: a paradigm for oxygen-regulated gene expression. 1700 76

The overall goal of the current study was to examine the functional activity of the prolyl hydroxylases (PHDs) in maturing chondrocytes. Herein, we show for the first time that the PHDs are expressed in the maturing zone of the growth plate, and by a chondrocytic cell line. We determined if this protein and its substrate, hypoxia inducible factor (HIF)-1alpha, modulated the induction of apoptosis. Using a chondrocyte cell line that matured in culture, we inhibited HIF-1alpha expression using siRNA technology and pharmacologically blocked PHD activity. We noted that PHD suppression sensitized the cells to an apoptotic challenge with H(2)O(2). We next examined the interplay between the PHDs and HIF-1alpha by suppressing HIF-1alpha and blocking PHD activity. We noted reduced killing when the mature HIF-silenced cells were challenged with H(2)O(2). In contrast, there was limited change in the viability of immature cells. Based on these differences in chondrocyte susceptibility, it is concluded that HIF-1alpha sensitizes maturing cells to H(2)O(2)-mediated killing. We next determined if this change in the viability of the PHD-inhibited cells was linked to changes in activation of caspase-3. It was noted that there was a minimal change in enzyme activity of the PHD-inhibited HIF-1alpha suppressed cells. Finally, we found that as the chondrocytes mature, the activities of catalase and SOD were significantly reduced and that there was a decrease in the levels of Bcl-2 and Bcl(XL). This loss of protective activity together with the changes mediated by HIF would be expected to generate conditions that would favor the induction of chondrocyte apoptosis.
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PMID:Expression of HIF prolyl hydroxylase isozymes in growth plate chondrocytes: relationship between maturation and apoptotic sensitivity. 1704 72


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