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

Following traumatic injury, the formation of a glial scar and deposition of extracellular matrix (ECM) contributes to the regeneration failure in the adult mammalian central nervous system (CNS). Using a postcommissural fornix transection as a brain lesion model in rat, we have previously shown that the collagenous basement membrane (BM) at the lesion site is a major impediment for axon regeneration. Deposition of BM in this lesion model can be delayed by administration of the iron chelator 2,2'-bipyridine (BPY), an inhibitor of prolyl 4-hydroxylase (PH), a key enzyme of collagen biosynthesis. To examine whether this potential therapeutic approach is transferable to other CNS regions, we have chosen the mechanically lesioned rat spinal cord to investigate the effects of BPY administration on BM formation. Due to the close proximity of the lesion zone to meningeal fibroblasts, a cell-type secreting large amounts of collagen IV, BM deposition was much more extensive in the spinal cord than in the brain lesion. Neither immediate injections nor continuous application of BPY resulted in a detectable reduction of BM formation in the spinal cord. Only a combination of anti-scarring treatments including (i) injection of the more potent PH inhibitor [2,2'-bipyridine]-5,5'-dicarboxylic acid (BPY-DCA), (ii) selective inhibition of fibroblast proliferation and ECM production by 8-Br-cAMP, and (iii) continuous application of BPY-DCA, reduced the lesion-induced BM significantly. The present results clearly demonstrate, that the exclusive application of BPY according to a protocol designed for treatment of brain lesions is not sufficient to reduce BM formation in the lesioned adult rat spinal cord.
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PMID:A reliable method to reduce collagen scar formation in the lesioned rat spinal cord. 1156 34

HIF is a transcriptional complex that plays a central role in mammalian oxygen homeostasis. Recent studies have defined posttranslational modification by prolyl hydroxylation as a key regulatory event that targets HIF-alpha subunits for proteasomal destruction via the von Hippel-Lindau ubiquitylation complex. Here, we define a conserved HIF-VHL-prolyl hydroxylase pathway in C. elegans, and use a genetic approach to identify EGL-9 as a dioxygenase that regulates HIF by prolyl hydroxylation. In mammalian cells, we show that the HIF-prolyl hydroxylases are represented by a series of isoforms bearing a conserved 2-histidine-1-carboxylate iron coordination motif at the catalytic site. Direct modulation of recombinant enzyme activity by graded hypoxia, iron chelation, and cobaltous ions mirrors the characteristics of HIF induction in vivo, fulfilling requirements for these enzymes being oxygen sensors that regulate HIF.
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PMID:C. elegans EGL-9 and mammalian homologs define a family of dioxygenases that regulate HIF by prolyl hydroxylation. 1159 78

Hypoxia-inducible factor (HIF)-1alpha is the oxygen-sensitive subunit of HIF-1, a transcriptional master regulator of oxygen homeostasis. Oxygen-dependent prolyl hydroxylation targets HIF-1alpha for ubiquitinylation and proteasomal degradation. Unexpectedly, we found that exposing mice to elevated temperatures resulted in a strong HIF-1alpha induction in kidney, liver, and spleen. To elucidate the molecular mechanisms responsible for this effect, HepG2 hepatoma cells were exposed to different temperatures (34-42 degrees C) under normoxic (20% O(2)) or hypoxic (3% O(2)) conditions. Heat was sufficient to stabilize mainly a phosphatase-resistant, low molecular weight form of HIF-1alpha (termed HIF-1alpha(a)). Heat-induced HIF-1alpha(a) accumulated in the nucleus but neither bound to DNA nor trans-activated reporter or target gene expression, demonstrating the need for post-translational modifications for these functions. The protein banding pattern of heat-induced HIF-1alpha in immunoblot analyses was clearly distinct from the HIF-1alpha pattern after prolyl hydroxylase inhibition (by hypoxia or iron chelation/replacement) or following proteasome inhibition, suggesting that heat stabilizes HIF-1alpha by a novel mechanism. Inhibition of the ATP-dependent chaperone activity of HSP90 by novobiocin or geldanamycin prevented heat-induced as well as hypoxia-induced HIF-1alpha accumulation, indicating a common role of the HSP90 chaperone activity in HIF-1alpha stabilization by these two environmental parameters.
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PMID:Heat induction of the unphosphorylated form of hypoxia-inducible factor-1alpha is dependent on heat shock protein-90 activity. 1177 66

Hypoxia-inducible factor (HIF) is central in coordinating many of the transcriptional adaptations to hypoxia. Composed of a heterodimer of alpha and beta subunits, the alpha subunit is rapidly degraded in normoxia, leading to inactivation of the hypoxic response. Many models for a molecular oxygen sensor regulating this system have been proposed, but an important finding has been the ability to mimic hypoxia by chelation or substitution of iron. A key insight has been the recognition that HIF-alpha is targeted for degradation by the ubiquitin-proteasome pathway through binding to the von Hippel-Lindau tumour suppressor protein (pVHL), which forms the recognition component of an E3 ubiquitin ligase complex leading to ubiquitylation of HIF-alpha. Importantly, the classical features of regulation by iron and oxygen availability are reflected in regulation of the HIF-alpha/pVHL interaction. It has recently been shown that HIF-alpha undergoes an iron- and oxygen-dependent modification before it can interact with pVHL, and that this results in hydroxylation of at least one prolyl residue (HIF-1alpha, Pro 564). This modification is catalysed by an enzyme termed HIF-prolyl hydroxylase (HIF-PH), and compatible with all previously described prolyl-4-hydroxylases HIF-PH also requires 2-oxoglutarate as a cosubstrate. The key position of this hydroxylation in the degradation pathway of HIF-alpha, together with its requirement for molecular dioxygen as a co-substrate, provides the potential for HIF-PH to function directly as a cellular oxygen sensor. However, the ability of these enzyme(s) to account for the full range of physiological regulation displayed by the HIF system remains to be defined.
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PMID:Regulation of HIF by the von Hippel-Lindau tumour suppressor: implications for cellular oxygen sensing. 1179 92

To examine the potential role of particle iron in fibrogenicity, we loaded nonfibrogenic fine (0.12micro) TiO(2) with increasing amounts of Fe(II)-Fe(III) chloride. Dusts were applied to rat tracheal explants, which were maintained in air organ culture for 1 wk. Iron-loaded dust increased procollagen gene expression and tissue hydroxyproline. The active oxygen species (AOS) scavenger tetramethylthiourea prevented these effects. Iron loading caused nuclear factor (NF)-kappaB activation, decreased levels of total IkappaBalpha, but relatively increased levels of both IkappaBalpha-phosphoserine 32/36 and IkappaBalpha-phosphotyrosine. A citrate extract of iron-loaded dust increased procollagen expression. Gel shift using a probe consisting of the NF-kappaB consensus sequence from the prolyl-4-hydroxylase promoter and adjacent bases showed increased nuclear binding, and RT-PCR examination showed increased prolyl-hydroxylase alpha-chain gene expression after iron loading. We conclude that addition of surface iron can convert a nonreactive model air pollutant particle into a fibrogenic particle via AOS- and NF-kappaB-dependent pathways, probably through two different NF-kappaB activation pathways in two different anatomic compartments. This process may proceed in vivo through iron extracted from the dust into the cytoplasm. NF-kappaB activation may directly increase expression of prolyl hydroxylase, an enzyme involved in collagen synthesis. These findings suggest that air pollutant particles containing significant quantities of transition metals may produce airway wall fibrosis and lead to chronic obstructive pulmonary disease.
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PMID:Iron loading makes a nonfibrogenic model air pollutant particle fibrogenic in rat tracheal explants. 1203 67

The hypusine biosynthetic steps represent novel targets for intervention in cell proliferation. Hypusine is a rare amino acid, formed posttranslationally in one cellular protein, eIF5A, and is essential for cell proliferation. Deoxyhypusine hydroxylase, the metalloenzyme catalyzing the final step in hypusine biosynthesis, and prolyl 4-hydroxylase, a non-heme iron enzyme critical for collagen processing, can be inhibited by small chelating molecules that target their essential metal atom. We examined the effects of 5 compounds (ciclopirox, deferiprone, deferoxamine, mimosine and 2,2'-dipyridyl) on these protein hydroxylases in HUVECs, on cell proliferation and on angiogenesis using 2 model assays: tube-like vessel formation on Matrigel and the chick aortic arch sprouting assay. These compounds inhibited cellular deoxyhypusine hydroxylase in a concentration-dependent manner, but their efficacy varied widely in the following order: ciclopirox--> deferoxamine-->2,2'-dipyridyl-->deferiprone-->mimosine (IC(50) 5-200 microM). Inhibition of DNA synthesis, following the same order (IC(50) 10-450 microM), correlated with G(1) arrest of the cell cycle. These compounds also inhibited proline hydroxylation and maturation of collagen in HUVECs and caused inhibition of angiogenesis in vitro. Of the compounds tested, ciclopirox was by far the most effective inhibitor of HUVEC proliferation and angiogenesis. The strong antiangiogenic activity of this readily available antifungal drug along with its antiproliferative effects suggests a new potential application for ciclopirox in the treatment of solid tumors.
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PMID:The antifungal drug ciclopirox inhibits deoxyhypusine and proline hydroxylation, endothelial cell growth and angiogenesis in vitro. 1284 89

Iron (Fe) is an obligate requirement for life and it is well known that Fe depletion leads to G(1)/S arrest and apoptosis. These facts, together with studies showing that Fe chelators can inhibit the growth of aggressive tumours such as neuroblastoma, suggest that Fe-deprivation may be an important therapeutic strategy. To optimise the anti-proliferative effects of Fe chelators, the role of Fe in cell cycle control requires intense investigation. For many years, Fe chelators were known to prevent the activity of the R2 subunit of ribonucleotide reductase (RR) that catalyzes the conversion of ribonucleotides into deoxyribonucleotides (dNTPs) for DNA synthesis. In addition, Fe depletion may also inhibit the newly identified p53-inducible form of this molecule called p53R2. This protein has the same Fe-binding sites as found in R2, and its activity is thought to supply dNTPs for the critical process of DNA repair. Iron chelation also causes hypophosphorylation of the retinoblastoma protein (pRb) and decreases the expression of cyclins A, B and D, which are vital for cell cycle progression. Other regulatory molecules whose expression is affected by Fe depletion include p53 and hypoxia inducible factor-1alpha (HIF-1alpha). The levels of p53 increase following Fe chelation via the ability of HIF-1alpha to bind and stabilize p53. The activity of HIF-1alpha is controlled by an Fe-dependent enzyme known as HIF-alpha prolyl hydroxylase (PH). Chelation of Fe from this enzyme inhibits its activity, leading to stabilization of HIF-1alpha and the subsequent effects on downstream targets critical for angiogenesis and tumour growth. The levels of p53 may also increase after Fe chelation by phosphorylation of this protein at serine-15 and -37. This prevents the interaction of p53 with murine double minute-2 (mdm-2) and its degradation. Iron chelation also markedly increases the mRNA levels of the p53-inducible cyclin-dependent kinase (cdk) inhibitor, p21(WAF1/CIP1). Surprisingly, the increase in p21(WAF1/CIP1) mRNA was not reciprocated at the protein level, and this may result in cell cycle dysregulation. This review will focus on the molecular mechanisms induced following Fe chelation and the role of Fe in cell cycle progression.
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PMID:The role of iron in cell cycle progression and the proliferation of neoplastic cells. 1224 9

Recently, work on the mechanism of action of the von Hippel-Lindau tumour suppressor protein (pVHL) and studies on hypoxic gene regulation have converged, providing insights into both cellular oxygen sensing and cancer pathogenesis. pVHL is the recognition component of the E3-ubiquitin ligase complex involved in the degradation of hypoxia-inducible factor-1 (HIF) alpha-subunits, a process regulated by oxygen availability and blocked by disease causing pVHL mutations. In normoxic cells, pVHL targeting of HIF-alpha subunits follows hydroxylation of critical HIF prolyl residues by a group of oxygen, 2-oxoglutarate- and iron-dependent enzymes. In this review, we outline current understanding of HIF/pVHL/prolyl hydroxylase pathway and consider the implications for VHL-associated cancer.
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PMID:The von Hippel-Lindau tumor suppressor, hypoxia-inducible factor-1 (HIF-1) degradation, and cancer pathogenesis. 1250 60

Sensing of ambient dioxygen levels and appropriate feedback mechanisms are essential processes for all multicellular organisms. In animals, moderate hypoxia causes an increase in the transcription levels of specific genes, including those encoding vascular endothelial growth factor and erythropoietin. The hypoxic response is mediated by hypoxia-inducible factor (HIF), an alphabeta heterodimeric transcription factor in which both the HIF subunits are members of the basic helix-loop-helix PAS (PER-ARNT-SIM) domain family. Under hypoxic conditions, levels of HIFalpha rise, allowing dimerization with HIFbeta and initiating transcriptional activation. Two types of dioxygen-dependent modification to HIFalpha have been identified, both of which inhibit the transcriptional response. Firstly, HIFalpha undergoes trans -4-hydroxylation at two conserved proline residues that enable its recognition by the von Hippel-Lindau tumour-suppressor protein. Subsequent ubiquitinylation, mediated by an ubiquitin ligase complex, targets HIFalpha for degradation. Secondly, hydroxylation of an asparagine residue in the C-terminal transactivation domain of HIFalpha directly prevents its interaction with the co-activator p300. Hydroxylation of HIFalpha is catalysed by enzymes of the iron(II)- and 2-oxoglutarate-dependent dioxygenase family. In humans, three prolyl hydroxylase isoenzymes (PHD1-3) and an asparagine hydroxylase [factor inhibiting HIF (FIH)] have been identified. The role of 2-oxoglutarate oxygenases in the hypoxic and other signalling pathways is discussed.
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PMID:The role of iron and 2-oxoglutarate oxygenases in signalling. 1277 46

The present investigation provides for the first time, unambiguous information on the occurrence of hypoxia-inducible factors (HIF-1alpha and HIF-1beta proteins) in normoxia (Nx) and their interaction with hypoxia (Hx) and intracellular Fe(2+) chelation in the rat carotid body (CB) glomus cells. HIF-1alpha bound to HIF-1beta translocated into the nucleus is identified on the basis of immunohistochemistry and immunofluorescence. In Nx, a weak expression of HIF-1alpha was observed in CB glomus cells. However, exposure of CB and glomus cells to Hx (Po(2) approximately 7 Torr) and Nx with ciclopirox olamine (CPX, 5 microM) for 1 h showed a significant ( P<0.001) increase in HIF-1alpha protein. The CBs and glomus cells exposed to Nx, Hx, and Nx with CPX showed a constant level of HIF-1beta protein expression. HIF-1alpha subunit is continuously synthesized and degraded under normoxic conditions, while it accumulates rapidly following exposure to low oxygen tensions. Hydroxylation of HIF-1alpha by prolyl hydroxylase for proteasomal degradation was dependent on iron, 2-oxoglutarate, and oxygen concentration. The intracellular iron that acts as a cofactor for prolyl hydroxylase activity belongs to the labile iron pool and can be easily chelated. Thus, chelation of intracellular labile iron by CPX in Nx significantly increased HIF-1alpha in CB glomus cells. Thus, the results are consistent with the hypothesis that HIF-1alpha which is present in the glomus cells translocates to the nucleus during exposure to Hx and to CPX in Nx.
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PMID:Effects of hypoxia and intracellular iron chelation on hypoxia-inducible factor-1alpha and -1beta in the rat carotid body and glomus cells. 1460 Aug 37


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