Transcription profiling by array of a human breast cancer cell line treated with small molecule inhibitors of the Hypoxia inducible factor (HIF) hydroxylases
ABSTRACT: The hypoxia inducible factor (HIF) system orchestrates cellular responses to hypoxia in animals. HIF is an α/β-heterodimeric transcription factor that regulates the expression of hundreds of genes in a context dependent manner. A hypoxia-sensing component of the HIF system involves oxygen-dependent catalysis by the HIF hydroxylases; in humans there are three HIF prolyl hydroxylases (PHD1-3) and an asparaginyl hydroxylase (FIH). PHD catalysis regulates HIFα levels and FIH catalysis regulates HIF activity. How differences in HIFα hydroxylation status relate to variations in the induction of HIF target gene transcription is unknown. We report studies using small molecule inhibitors of the HIF hydroxylases to investigate the extent to which HIF target gene upregulation is induced by reduced PHD catalysis. The results reveal substantial differences in the role of prolyl- and asparaginyl-hydroxylation in regulating hypoxia responsive genes in cells. Selective PHD inhibitors with different structural scaffolds behave similarly. However, under the tested conditions, a broad-spectrum 2OG dioxygenase inhibitor is a better mimic of the transcriptional response to hypoxia than the selective PHD inhibitors, consistent with an important role for FIH in the hypoxic transcriptional response. Indeed, combined application of selective PHD and FIH inhibitors resulted in transcriptional induction of a subset of genes that were not fully responsive to PHD inhibition alone. Thus, for the therapeutic regulation of HIF target genes, it is important to consider both PHD and FIH activity, and in the case of some sets of target genes, simultaneous inhibition of the PHDs and FIH catalysis may be preferable.
Project description:The hypoxia inducible factor (HIF) system orchestrates cellular responses to hypoxia in animals. HIF is an /-heterodimeric transcription factor that regulates the expression of hundreds of genes in a context dependent manner. A hypoxia-sensing component of the HIF system involves oxygen-dependent catalysis by the HIF hydroxylases; in humans there are three HIF prolyl hydroxylases (PHD1-3) and an asparaginyl hydroxylase (FIH). PHD catalysis regulates HIF levels and FIH catalysis regulates HIF activity. How differences in HIF hydroxylation status relate to variations in the induction of HIF target gene transcription is unknown. We report studies using small molecule inhibitors of the HIF hydroxylases to investigate the extent to which HIF target gene upregulation is induced by reduced PHD catalysis. The results reveal substantial differences in the role of prolyl- and asparaginyl-hydroxylation in regulating hypoxia responsive genes in cells. Selective PHD inhibitors with different structural scaffolds behave similarly. However, under the tested conditions, a broad-spectrum 2OG dioxygenase inhibitor is a better mimic of the transcriptional response to hypoxia than the selective PHD inhibitors, consistent with an important role for FIH in the hypoxic transcriptional response. Indeed, combined application of selective PHD and FIH inhibitors resulted in transcriptional induction of a subset of genes that were not fully responsive to PHD inhibition alone. Thus, for the therapeutic regulation of HIF target genes, it is important to consider both PHD and FIH activity, and in the case of some sets of target genes, simultaneous inhibition of the PHDs and FIH catalysis may be preferable.
Project description:This a model from the article:
Hypoxia-dependent sequestration of an oxygen sensor by a widespread structural motif can shape the hypoxic response - a predictive kinetic model
Bernhard Schmierer, Béla Novák1 and Christopher J Schofield
BMC Systems Biology2010, 4:139
The activity of the heterodimeric transcription factor hypoxia inducible factor (HIF) is regulated by the post-translational, oxygen-dependent hydroxylation of its α-subunit by members of the prolyl hydroxylase domain (PHD or EGLN)-family and by factor inhibiting HIF (FIH). PHD-dependent hydroxylation targets HIFα for rapid proteasomal degradation; FIH-catalysed asparaginyl-hydroxylation of the C-terminal transactivation domain (CAD) of HIFα suppresses the CAD-dependent subset of the extensive transcriptional responses induced by HIF. FIH can also hydroxylate ankyrin-repeat domain (ARD) proteins, a large group of proteins which are functionally unrelated but share common structural features. Competition by ARD proteins for FIH is hypothesised to affect FIH activity towards HIFα; however the extent of this competition and its effect on the HIF-dependent hypoxic response are unknown.
To analyse if and in which way the FIH/ARD protein interaction affects HIF-activity, we created a rate equation model. Our model predicts that an oxygen-regulated sequestration of FIH by ARD proteins significantly shapes the input/output characteristics of the HIF system. The FIH/ARD protein interaction is predicted to create an oxygen threshold for HIFα CAD-hydroxylation and to significantly sharpen the signal/response curves, which not only focuses HIFα CAD-hydroxylation into a defined range of oxygen tensions, but also makes the response ultrasensitive to varying oxygen tensions. Our model further suggests that the hydroxylation status of the ARD protein pool can encode the strength and the duration of a hypoxic episode, which may allow cells to memorise these features for a certain time period after reoxygenation.
The FIH/ARD protein interaction has the potential to contribute to oxygen-range finding, can sensitise the response to changes in oxygen levels, and can provide a memory of the strength and the duration of a hypoxic episode. These emergent properties are predicted to significantly shape the characteristics of HIF activity in animal cells. We argue that the FIH/ARD interaction should be taken into account in studies of the effect of pharmacological inhibition of the HIF-hydroxylases and propose that the interaction of a signalling sensor with a large group of proteins might be a general mechanism for the regulation of signalling pathways.
There are there models described in the paper. 1) Skeleton Model 1 (SKM1) - HIFα CAD-hydroxylation in the absence of the FIH/AR-interaction. 2) Skeleton Model 2 (SKM2) - FIG sequestration by ARD proteins and oxygen-dependent FIH-release. 3) Full Model (Fusion of SKM1 and SKM2) - the effects of the FIH/ARD proteins interaction on HIFα CAD-hydroxylation.
This model corresponds to the "Full Model" described in the paper. The model reproduces figure 5 of the publication.
This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2011 The BioModels.net Team.
To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.
Project description:The response of cells to hypoxia is characterised by co-ordinated regulation of many genes. Studies of the regulation of the expression of many of these genes by oxygen has implicated a role for the heterodimeric transcription factor hypoxia inducible factor (HIF). The mechanism of oxygen sensing which controls this heterodimeric factor is via oxygen dependent prolyl and asparaginyl hydroxylation by specific 2-oxoglutarate dependent dioxygenases (PHD1, PHD2, PHD3 and FIH-1). Whilst HIF appears to have a major role in hypoxic regulation of gene expression, it is unclear to what extent other transcriptional mechanisms are also involved in the response to hypoxia. The extent to which 2-oxoglutarate dependent dioxygenases are responsible for the oxygen sensing mechanism in HIF-independent hypoxic gene regulation is also unclear. Both the prolyl and asparaginyl hydroxylases can be inhibited by dimethyloxalylglycine (DMOG). Such inhibition can produce activation of the HIF system with enhanced transcription of target genes and might have a role in the therapy of ischaemic disease. We have examined the extent to which the HIF system contributes to the regulation of gene expression by hypoxia, to what extent 2-oxoglutarate dependent dioxygenase inhibitor can mimic the hypoxic response and the nature of the global transcriptional response to hypoxia. We have utilised microarray assays of mRNA abundance to examine the gene expression changes in response to hypoxia and to DMOG. We demonstrate a large number of hypoxically regulated genes, both known and novel, and find a surprisingly high level of mimicry of the hypoxic response by use of the 2-oxoglutarate dependent dioxygenase inhibitor, dimethyloxalylglycine. We have also used microarray analysis of cells treated with small interfering RNA (siRNA) targeting HIF-1alpha and HIF-2alpha to demonstrate the differing contributions of each transcription factor to the transcriptional response to hypoxia. Candidate transcripts were confirmed using an independent microarray platform and real-time PCR. The results emphasise the critical role of the HIF system in the hypoxic response, whilst indicating the dominance of HIF-1alpha and defining genes that only respond to HIF-2alpha. Keywords: Hypoxia response, gene knockdown, chemical treatment Overall design: MCF7 breast cancer cell lines were grown under conditions of either normoxia (21% oxygen) or hypoxia (1% oxygen) for 16 hours in an Invivo2 Hypoxia Workstation (Ruskin Technologies, UK). All culture media comprised DMEM, 2mM L-Glutamine and 10% Fetal Bovine Serum. Total RNA was extracted from each sample using the Absolutely RNA RT-PCR Miniprep kit (Stratagene). In total, 7 different types of sample were analysed by microarray technology. These were: ‘normoxia’ - cells grown in normoxic (21% oxygen) conditions; ‘hypoxia’ - cells grown in hypoxic conditions (1% oxygen) for 16 hours; ‘DMOG’ - cells grown in normoxic conditions and exposed to the 2-oxoglutarate dependent dioxygenase inhibitor dimethyloxalylglycine, DMOG (2 mM) for 16 hours; ‘OF’ - cells grown in hypoxic conditions as above and exposed to oligofectamine transfection reagent (Invitrogen) alone; ‘HIF1’ - cells grown in hypoxic conditions as above and exposed to HIF-1alpha siRNA; ‘HIF2’ - cells grown in the same hypoxic conditions with HIF-2alpha siRNA and ‘HIF12’ - cells grown in the same hypoxic conditions with both HIF-1alpha and HIF-2alpha siRNA. Three independent samples were analysed for each experimental condition. All of the analyses for the hypoxia and DMOG samples were compared to the normoxia samples whilst the siRNA transfected samples were compared against the OF samples. The normoxia, hypoxia and DMOG samples (replicates 1-3) were arrayed to HG-U133A Genechips and sample types OF, HIF1, HIF2 and HIF12 (replicates 1-3) were arrayed to HG-U133 plus 2 Genechips (Affymetrix). The normoxia, hypoxia and DMOG samples (replicates 2-3) along with the samples OF, HIF1, HIF2 and HIF12 (replicates 4-6) were arrayed to the ‘whole genome’ Sentrix Human-6 Expression BeadChips (Illumina). All labelling, hybridisation and scanning steps were performed according to the manufacturers’ instructions.
Project description:Protein hydroxylases are oxygen and alpha-ketoglutarate-dependent enzymes that catalyze hydroxylation of amino acids such as proline, thus linking oxygen and metabolism to enzymatic activity. Prolyl hydroxylation is a dynamic post-translational modification that regulates protein stability and protein-protein interactions; however, the extent of this modification is largely uncharacterized. The goals of this study are to investigate the biological consequences of prolyl hydroxylation and to identify new targets which undergo prolyl hydroxylation in human cardiomyocytes.
Project description:Skeletal muscle has an impressive ability to repair itself after a damaging insult and this response is essential to the process of muscle adaptation. In conditions such as muscular dystrophy and the sarcopenia of old age, repair is compromised leading to fibrosis and fatty tissue accumulation. Hypoxia-inducible factors (HIFs) are highly conserved regulators of gene transcription under conditions of low oxygen tension and HIF target genes such as EPO and VEGF have been associated with muscle protection and repair. We sought to interrogate the importance of HIF activation to skeletal muscle repair through the use of prolyl hydroxylase inhibitors (PHI) that stabilize HIF and activate target gene transcription in a mouse eccentric exercise limb damage model. We used microarrays to detail the global effects of prolyl hydroxylase inhibitors (PHI) in a mouse eccentric exercise limb damage model. Overall design: Normal C57Bl6/NJ mice were housed individually and fed standard chow and water ad libitum. Right hind limbs were injured while left hind limbs were used as control. Animals were treated either with PHI or vehicle. Gastrocnemius samples were collected after 3 hrs, 6hrs, and 9hrs, respectively.
Project description:The asparagine hydroxylase, factor inhibiting HIF (FIH) confers oxygen-dependence upon the hypoxia-inducible factor (HIF), a master regulator of the cellular adaptive response to hypoxia. Studies investigating whether asparagine hydroxylation is a general regulatory oxygen-dependent modification have identified multiple non-HIF targets for FIH. However the functional consequences of this outside of the HIF pathway remain unclear. Here, we demonstrate that the deubiquitinase ovarian tumor domain containing, ubiquitin aldehyde binding protein 1 (OTUB1) is a substrate for hydroxylation by endogenous FIH on N22. Mutation of N22 leads to a profound change in the interaction of OTUB1 with proteins important in cellular metabolism. Furthermore, mutant OTUB1 (lacking the hydroxylation site) impairs cellular metabolic processes when compared to wild type. Based on these data, we hypothesize that OTUB1 is a target for functional hydroxylation by FIH, and propose that this provides new insight into the regulation of cellular energy metabolism during hypoxia.
Project description:Hypoxia results in the changes in expression of many genes, the majority of which are mediated via the transcriptional activity of the hypoxia inducible factor (HIF) complex. However, other mechanisms of gene regulation by hypoxia are likely and include control of mRNA stability, regulation of mRNA translation and regulation mediated by micrornas. The aim of this study is to identify microRNAs which expression is regulated by hypoxia. We chose the breast cancer line MCF7 for study as we had previously characterised the expression of the components of the HIF system in that cell line and undertaken an extensive study of the gene expression profile in response to hypoxia, a prolyl hydroxylase inhibitor dimethyloxalylglycine and HIF-1a isoform manipulations (Eldvidge. G.P. et al. (2006) JBC, vol. 281, 22, 15215-15226).
Project description:In this study we report the gene expression profile and MISO analysis for alternative splicing events such as exon skipping in iPSC-derived cardiomyocytes which were treated with a drug inhibiting α-ketoglutarate-dependent hydroxylases (dimethyloxalylglycine) and compared to vehicle control. α-ketoglutarate-dependent hydroxylase inhibition plays a central role in cardiac hypoxia and the goal of this study was to identify new pathways in hypoxia beyond HIF-1α. Overall design: Biological replicates of RNA-seq data from iPSC-derived cardiomyocytes treated with dimethyloxalylglycine or vehicle control
Project description:Hypoxia occurs when tissue or cellular oxygen demand exceeds its supply and is a frequent condition in health and disease. Metazoans have developed a regulatory system that allows them to sense changes in oxygen levels in their microenvironment and adapt to them. The asparagine hydroxylase factor inhibiting HIF (FIH) regulates the transcriptional activity of the hypoxia-inducible factor (HIF), the master regulator of the cellular adaptive response to hypoxia [1, 2]. We recently identified the deubiquitinating enzyme ovarian tumour domain containing, ubiquitin aldehyde binding protein 1 (OTUB1) as novel bona fide FIH target protein with the hydroxylation occurring at the asparagine residue N22 [3, 4]. Surprisingly, in a follow-up investigation we observed a SDS-PAGE resistant interaction between FIH and OTUB1, resulting in a FIH-OTUB1 heterodimer (HD). Further analysis of the FIH-OTUB1 HD demonstrated that it is not linked by a disulfide bond, oxyester or thioester but likely through an amide bond. Interestingly, mutation of the hydroxylation acceptor site N22 in OTUB1 and genetic and pharmacologic inhibition of FIH prevented the formation of the heterodimer, demonstrating that HD formation is a consequence of FIH activity. To investigate if FIH-dependent stable protein complex formation was exclusive for OTUB1, we carried out a mass spectrometry (MS)-based FIH interactome analyses with denatured and non-denatured cell lysates (with or without SDS treatment and boiling). The results indicate the existence of further novel denaturing condition resistant protein complexes. 1. Mahon, P.C., K. Hirota, and G.L. Semenza, FIH-1: a novel protein that interacts with HIF-1alpha and VHL to mediate repression of HIF-1 transcriptional activity. Genes & development, 2001. 15(20): p. 2675-86. 2. Lando, D., et al., FIH-1 is an asparaginyl hydroxylase enzyme that regulates the transcriptional activity of hypoxia-inducible factor. Genes & development, 2002. 16(12): p. 1466-71. 3. Scholz, C.C., et al., Regulation of IL-1beta-induced NF-kappaB by hydroxylases links key hypoxic and inflammatory signaling pathways. Proc Natl Acad Sci U S A, 2013. 110(46): p. 18490-5. 4. Scholz, C.C., et al., FIH Regulates Cellular Metabolism through Hydroxylation of the Deubiquitinase OTUB1. PLoS biology, 2016. 14(1): p. e1002347.
Project description:Recently, hypoxia via the transcription factor HIF-1a has been implicated to play an important role for the fate of the adaptive immune response by regulatory T cells (Treg) and T helper 17 cells (TH17) in the mouse model. However, the reports on the effect of HIF-1a are conflicting and so far no functional data in the human system are available. Therefore, we analyzed the effect of hypoxia and HIF-1a on Treg and TH17 in the human system. FACS, western blot and reporter assays clearly demonstrated that hypoxia does not up-regulate the level of HIF-1a in CD4+ T cells (THC) and microarray analysis revealed no change of the transcriptome comparing normoxia vs. hypoxia. Furthermore, we could show that HIF-1a is almost exclusively regulated via NF-kB and NFAT, whereas hydroxylation and subsequent degradation of HIF-1a had little to no effect. In addition, we showed that HIF-1a is essential for nTreg mediated suppression and for IL-17A secretion of TH17, but not for TH17 lineage commitment measured by RORγt expression. In conclusion, our results demonstrated that THC have a distinct regulation of HIF-1a protein levels, which was absolutely essential for Treg and TH17 function. 3 patients, 2 cell type, 2 treatments = 12 arrays