Hypoxia induces hexokinase II gene expression in human lung cell line A549 (original) (raw)
Related papers
Journal of Hepatology, 2005
Background/Aims: In a hypoxic state, a glycolytic system is operating as a salvage pathway of generating ATP, and hexokinase II, the first enzyme in this system, might be over-expressed in hepatocellular carcinomas (HCCs). This study was to evaluate if hexokinase II is participating in HCC cell survival in a hypoxic state, and to analyze the mechanism of cell death caused by hexokinase II-specific inhibition.
Transcriptional regulation of genes encoding glycolytic enzymes by hypoxia-inducible factor 1
Journal of biological …, 1994
Hypoxia-inducible factor 1 (HIF-1) activates erythropoietin gene transcription in Hep3B cells subjected to hypoxia. HIF-1 activity is also induced by hypoxia in non-erythropoietin-producing cells, suggesting a more general regulatory role. W e now report that RNAs encoding the glycolytic enzymes aldolase A (ALDA), phosphoglycerate kinase 1 (PGKl), and pyruvate kinase M were induced by exposure of Hep3B or HeLa cells to inducers of HIF-1 (1% 0,, cobalt chloride, or desferrioxamine), whereas cycloheximide blocked induction of glycolytic RNAs and HIF-1 activity. Oligonucleotides from the ALDA, PGK1, enolase 1, lactate dehydrogenase A, and phosphofructokinase L (PFKL) genes, containing sequences similar to the HIF-1 binding site in the erythropoietin enhancer, specifically bound HIF-1 present in crude nuclear extracts or affinity-purified preparations. Sequences from the ALDA, PFKL, and PGKl genes containing HIF-1 binding sites mediated hypoxia-inducible transcription in transient expression assays. These results support the role of HIF-1 as a mediator of adaptive responses to hypoxia that underlie cellular and systemic oxygen homeostasis.
American journal of physiology. Lung cellular and molecular physiology, 2002
Increased glucose utilization and hexokinase (HK)-II expression are adaptive features of lung cells exposed to hypoxia or hyperoxia. HK-II is the most regulated isoform of HK. Whether its overexpression could be protective against oxidative stress was explored in human lung epithelial-like (A549) cells. HK-II was overexpressed in A549 cells in a tetracycline-repressible retroviral vector system. Elevated expression of HK-II was confirmed by Western blot and activity measurements. Cell death caused by exposure to hyperoxia was decreased in HK-II-overexpressing cells. This effect was reversed when HK-II expression was suppressed with doxycycline. A similar protective effect was observed in HK-II-overexpressing cells after treatment with 1 mM hydrogen peroxide for 48 h. At baseline, fluorescence microscopy showed that overexpressed HK-II was localized to mitochondria. Electron microscopic studies showed that hyperoxia-exposed HK-II overexpressors had better-preserved and quantitatively...
Clinica Chimica Acta, 2008
Cells experiencing lowered O 2 levels (hypoxia) undergo a variety of biological responses in order to adapt to these unfavorable conditions. The master switch, orchestrating the cellular response to low O 2 levels, is the transcription factor, termed hypoxia-inducible factor (HIF). The α subunits of HIF are regulated by 2-oxoglutarate-dependent oxygenases that, in the presence of O 2 , hydroxylate specific prolyl and asparaginyl residues of HIF-α, inducing its proteasome-dependent degradation and repression of transcriptional activity, respectively. Hypoxia inhibits oxygenases, stabilized HIFα translocates to the nucleus, dimerizes with HIF-β, recruits the coactivators p300/CBP, and induces expression of its transcriptional targets via binding to hypoxia-responsive elements (HREs). HREs are composite regulatory elements, comprising a conserved HIF-binding sequence and a highly variable flanking sequence that modulates the transcriptional response. In summary, the transcriptional response of a cell is the end product of two major functions. The first (trans-acting) is the level of activation of the HIF pathway that depends on regulation of stability and transcriptional activity of the HIF-α. The second (cis-acting) comprises the characteristics of endogenous HREs that are determined by the availability of transcription factors cooperating with HIF and/or individual HIF-α isoforms.
2007
The hypoxic accumulation of the transcription factor subunit hypoxia-inducible factor-1α (HIF-1α), a potential endogenous hypoxia marker and therapeutic target, has recently been shown to strongly depend on glucose availability. The aim of this study was to investigate the underlying mechanism of this effect. Material and Methods: HIF-1α protein levels were studied by Western blotting in HT 1080 human fibrosarcoma cells and in a hypoxia-responsive element green fluorescent protein (HRE-GFP) reporter assay in stably transfected HT 1080 cells treated with hypoxia (0.1% O 2 , 12 h) and glycolysis inhibitors 2-deoxyglucose (2-DG) or iodoacetate (IAA). HIF-1α mRNA expression was quantified via real-time polymerase chain reaction (RT-PCR). Results: Both inhibitors drastically reduced hypoxic HIF-1α accumulation (2-DG + hypoxia 2% mean HIF-1α protein level vs. 59% hypoxia alone; IAA + hypoxia 13% mean HIF-1α protein level vs. 96% hypoxia alone), an effect not rescued by the addition of pyruvate and confirmed in an HRE-GFP reporter assay in stably transfected HT 1080 cells. RT-PCR under identical conditions showed no effect of glycolysis inhibition on HIF-1α mRNA levels, suggesting a translational or posttranslational mechanism. Conclusion: The effect of glycolysis modulation on the HIF-1α levels in tumor cells may provide a novel approach to therapeutically target HIF-1α.
Effect of hypoxia on gene expression by human hepatocytes (HepG2)
Physiological Genomics, 2002
The full extent to which hypoxia produces gene expression changes in human cells is unknown. We used late-generation oligonucleotide arrays to catalog hypoxia-induced changes in gene expression in HepG2 cells. Five paired sets of cultures were subjected to either control (room air-5% CO2) or hypoxic (1% O2-5% CO2) conditions for 24 h, and RNA was analyzed on an Affymetrix cDNA array containing ∼12,600 sequences. A statistically significant change in expression was shown by 2,908 sequences (1,255 increased and 1,653 decreased). The observed changes were highly concordant with published literature on hypoxic stress but showed relatively little overlap (12–22%) with changes in gene expression that have been reported to occur after heat stress in other systems. Of note, of these 2,908 sequences, only 387 (213 increased and 174 decreased) both exhibited changes in expression of twofold or greater and were highly expressed in at least three of the five experiments. We conclude that the ef...
Roles Of HIF and 2-Oxoglutarate Dependent Enzymes in Controlling Gene Expression In Hypoxia
2020
Hypoxia — reduction in oxygen availability—plays key roles in both physiological and pathological processes. Given the importance of oxygen for cell and organism viability, mechanisms to sense and respond to hypoxia are in place. A variety of enzymes utilise molecular oxygen, but of particular importance to oxygen sensing are the 2-oxoglutarate (2-OG) dependent dioxygenases (2OGDs). Of these, Prolyl-hydroxylases have long been recognised to control the levels and function of Hypoxia Inducible Factor (HIF), a master transcriptional regulator in hypoxia, via their hydroxylase activity. However, recent studies are revealing that dioxygenases are involved in almost all aspects of gene regulation, including chromatin organisation, transcription and translation. We highlight the relevance of HIF and 2-OG dioxyenases in the control of gene expression in response to hypoxia and their relevance to human cancers.
Regulation of gene expression by hypoxia
Biochemical Journal, 2008
Hypoxia induces profound changes in the cellular gene expression profile. The discovery of a major transcription factor family activated by hypoxia, HIF (hypoxia-inducible factor), and the factors that contribute to HIF regulation have greatly enhanced our knowledge of the molecular aspects of the hypoxic response. However, in addition to HIF, other transcription factors and cellular pathways are activated by exposure to reduced oxygen. In the present review, we summarize the current knowledge of how additional hypoxia-responsive transcription factors integrate with HIF and how other cellular pathways such as chromatin remodelling, translation regulation and microRNA induction, contribute to the co-ordinated cellular response observed following hypoxic stress.
The FASEB Journal, 2002
Cellular responses to oxygen are increasingly recognized as critical in normal development and physiology, and are implicated in pathological processes. Many of these responses are mediated by the transcription factors HIF-1 and HIF-2. Their regulation occurs through oxygen-dependent proteolysis of the alpha subunits HIF-1α and HIF-2α, respectively. Both are stabilized in cell lines exposed to hypoxia, and recently HIF-1α was reported to be widely expressed in vivo. In contrast, regulation and sites of HIF-2α expression in vivo are unknown, although a specific role in endothelium was suggested. We therefore analyzed HIF-2α expression in control and hypoxic rats. Although HIF-2α was not detectable under baseline conditions, marked hypoxic induction occurred in all organs investigated, including brain, heart, lung, kidney, liver, pancreas, and intestine. Time course and amplitude of induction varied between organs. Immunohistochemistry revealed nuclear accumulation in distinct cell populations of each tissue, which were exclusively non-parenchymal in some organs (kidney, pancreas, and brain), predominately parenchymal in others (liver and intestine) or equally distributed (myocardium). These data indicate that HIF-2 plays an important role in the transcriptional response to hypoxia in vivo, which is not confined to the vasculature and is complementary to rather than redundant with HIF-1.