scholarly journals IOP1, a novel hydrogenase-like protein that modulates hypoxia-inducible factor-1α activity

2006 ◽  
Vol 401 (1) ◽  
pp. 341-352 ◽  
Author(s):  
Jianhe Huang ◽  
Daisheng Song ◽  
Adrian Flores ◽  
Quan Zhao ◽  
Sharon M. Mooney ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Hypoxia Inducible Factor ◽  
Cell Types ◽  
Mrna Levels ◽  
Low Oxygen ◽  
Gene Expressions ◽  
Iron Sulfur Cluster ◽  
Α Subunit ◽  
Protein Levels ◽  
Hypoxic Conditions

A central means by which mammalian cells respond to low oxygen tension is through the activation of the transcription factor HIF-1 (hypoxia-inducible factor-1). Under normoxic conditions, HIF-1α (the α subunit of HIF-1) is targeted for rapid degradation by the ubiquitin–proteasome pathway. Under hypoxic conditions, this degradation is inhibited, thereby leading to the stabilization and activation of HIF-1α. Here, we report the identification of IOP1 (iron-only hydrogenase-like protein 1), a protein homologous with enzymes present in anaerobic organisms that contain a distinctive iron–sulfur cluster. IOP1 is present in a broad range of cell types. Knockdown of IOP1 using siRNA (small interfering RNA) in mammalian cells increases protein levels of HIF-1α under both normoxic and hypoxic conditions, and augments hypoxia-induced HRE (hypoxia response element) reporter gene and endogenous HIF-1α target gene expressions. We find that IOP1 knockdown up-regulates HIF-1α mRNA levels, thereby providing a mechanism by which knockdown induces the observed effects. The results collectively provide evidence that IOP1 is a component of the protein network that regulates HIF-1α in mammalian cells.

scholarly journals SDHC Promoter Methylation, a Novel Pathogenic Mechanism in Parasympathetic Paragangliomas

2017 ◽  
Vol 103 (1) ◽  
pp. 295-305 ◽  
Author(s):  
Cristóbal Bernardo-Castiñeira ◽  
Nuria Valdés ◽  
Marta I Sierra ◽  
Inés Sáenz-de-Santa-María ◽  
Gustavo F Bayón ◽  
...  
Keyword(s):  
Copy Number ◽  
Messenger Rna ◽  
Hypoxia Inducible Factor ◽  
Mrna Levels ◽  
Cluster Assembly ◽  
Iron Sulfur Cluster ◽  
Genetic Event ◽  
Protein Levels ◽  
First Case ◽  
Vhl Protein

Abstract Context Germline mutations in the succinate dehydrogenase A, B, C, and D genes (collectively, SDHx) predispose to the development of paragangliomas (PGLs) arising at the parasympathetic or sympathetic neuroendocrine systems. SDHx mutations cause absence of tumoral immunostaining for SDHB. However, negative SDHB immunostaining has also been found in a subset of PGLs that lack SDHx mutations. Settings Here, we report the comprehensive molecular characterization of one such a tumor of parasympathetic origin compared with healthy paraganglia and other PGLs with or without SDHx mutations. Results Integration of multiplatform data revealed somatic SDHC methylation and loss of the 1q23.3 region containing the SDHC gene. This correlated with decreased SDHC messenger RNA (mRNA) and protein levels. Furthermore, another genetic event found affected the VHL gene, which showed a decreased DNA copy number, associated with low VHL mRNA levels, and an absence of VHL protein detected by immunohistochemistry. In addition, the tumor displayed a pseudohypoxic phenotype consisting in overexpression of the hypoxia-inducible factor (HIF)-1α and miR-210, as well as downregulation of the iron-sulfur cluster assembly enzyme (ISCU) involved in SDHB maturation. This profile resembles that of SDHx- or VHL-mutated PGLs but not of PGLs with decreased VHL copy number, pointing to SDHC rather than VHL as the pathogenic driver. Conclusions Collectively, these findings demonstrate the potential importance of both the SDHC epigenomic event and the activation of the HIF-1α/miR-210/ISCU axis in the pathogenesis of SDHx wild-type/SDHB-negative PGLs. To our knowledge, this is the first case of a sporadic parasympathetic PGL that carries silencing of SDHC, fulfilling the two-hit Knudson’s model for tumorigenesis.

scholarly journals RSUME is implicated in HIF-1-induced VEGF-A production in pituitary tumour cells

2011 ◽  
Vol 19 (1) ◽  
pp. 13-27 ◽  
Author(s):  
B Shan ◽  
J Gerez ◽  
M Haedo ◽  
M Fuertes ◽  
M Theodoropoulou ◽  
...  
Keyword(s):  
Pituitary Adenoma ◽  
Hypoxia Inducible Factor ◽  
Pituitary Tumour ◽  
Mrna Levels ◽  
Human Pituitary ◽  
Human Pituitary Adenoma ◽  
Protein Levels ◽  
Hypoxic Conditions ◽  
Adaptive Processes ◽  
Endothelial Growth Factor

The recently cloned small RWD-domain containing protein RSUME was shown to increase protein levels of hypoxia-inducible factor-1α (HIF-1α). The latter is the oxygen-regulated subunit of HIF-1, the most important transcription factor of the cellular adaptive processes to hypoxic conditions. It is also a major regulator of vascular endothelial growth factor-A (VEGF-A), which is critically involved in the complex process of tumour neovascularisation. In this study, the expression and role of RSUME in pituitary tumours was studied. We found that RSUME mRNA was up-regulated in pituitary adenomas and significantly correlated with HIF-1α mRNA levels. Hypoxia (1% O2) or treatment with hypoxia-mimicking CoCl2enhanced RSUME and HIF-1α expression, induced translocation of HIF-1α to the nuclei and stimulated VEGF-A production both in pituitary tumour cell lines and primary human pituitary adenoma cell cultures. When RSUME expression was specifically down-regulated by siRNA, the CoCl2-induced increase VEGF-A secretion was strongly reduced which was shown to be a consequence of the RSUME knockdown-associated reduction of HIF-1α synthesis. Thus, RSUME plays an important role in initiating pituitary tumour neovascularisation through regulating HIF-1α levels and subsequent VEGF-A production and may therefore be critically involved in pituitary adenoma progression.

scholarly journals Regulation of hypoxia-inducible factor-1α by NF-κB

2008 ◽  
Vol 412 (3) ◽  
pp. 477-484 ◽  
Author(s):  
Patrick van Uden ◽  
Niall S. Kenneth ◽  
Sonia Rocha
Keyword(s):  
Hypoxia Inducible Factor ◽  
Nuclear Factor Κb ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Low Oxygen ◽  
Prolyl Hydroxylases ◽  
Hypoxic Conditions ◽  
Factor Α ◽  
Interfering Rna ◽  
Necrosis Factor

HIF (hypoxia-inducible factor) is the main transcription factor activated by low oxygen tensions. HIF-1α (and other α subunits) is tightly controlled mostly at the protein level, through the concerted action of a class of enzymes called PHDs (prolyl hydroxylases) 1, 2 and 3. Most of the knowledge of HIF derives from studies following hypoxic stress; however, HIF-1α stabilization is also found in non-hypoxic conditions through an unknown mechanism. In the present study, we demonstrate that NF-κB (nuclear factor κB) is a direct modulator of HIF-1α expression. The HIF-1α promoter is responsive to selective NF-κB subunits. siRNA (small interfering RNA) studies for individual NF-κB members revealed differential effects on HIF-1α mRNA levels, indicating that NF-κB can regulate basal HIF-1α expression. Finally, when endogenous NF-κB is induced by TNFα (tumour necrosis factor α) treatment, HIF-1α levels also change in an NF-κB-dependent manner. In conclusion, we find that NF-κB can regulate basal TNFα and, in certain circumstances, the hypoxia-induced HIF-1α.

Expression of hypoxia-inducible factor-1α in the brain of rats during chronic hypoxia

2000 ◽  
Vol 89 (5) ◽  
pp. 1937-1942 ◽  
Author(s):  
Juan C. Chávez ◽  
Faton Agani ◽  
Paola Pichiule ◽  
Joseph C. LaManna
Keyword(s):  
Mammalian Cells ◽  
Glucose Transporter ◽  
Hypoxia Inducible Factor ◽  
Arterial Oxygen Tension ◽  
Cell Types ◽  
Arterial Oxygen ◽  
Ependymal Cells ◽  
Mrna Levels ◽  
Adaptive Responses ◽  
Glucose Transporter 1

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that regulates adaptive responses to the lack of oxygen in mammalian cells. HIF-1 consists of two proteins, HIF-1α and HIF-1β. HIF-1α accumulates under hypoxic conditions, whereas HIF-1β is constitutively expressed. HIF-1α and HIF-1β expression were measured during adaptation to hypobaric hypoxia (0.5 atm) in rat cerebral cortex. Western blot analyses indicated that HIF-1α rapidly accumulated during the onset of hypoxia and did not fall for 14 days but fell to normal by 21 days despite the continuous low arterial oxygen tension. Immunostaining showed that neurons, astrocytes, ependymal cells, and possibly endothelial cells were the cell types expressing HIF-1α. Genes with hypoxia-responsive elements were activated under these conditions, as evidenced by elevated vascular endothelial growth factor and glucose transporter-1 mRNA levels. When 21-day-adapted rats were exposed to a more severe hypoxic challenge (8% oxygen), HIF-1α accumulated again. On the basis of these results, we speculate that the vascular remodeling and metabolic changes triggered during prolonged hypoxia are capable of restoring normal tissue oxygen levels.

scholarly journals Hypoxic induction of an HIF-1α–dependent bFGF autocrine loop drives angiogenesis in human endothelial cells

Blood ◽  
2006 ◽  
Vol 107 (7) ◽  
pp. 2705-2712 ◽  
Author(s):  
Maura Calvani ◽  
Annamaria Rapisarda ◽  
Badarch Uranchimeg ◽  
Robert H. Shoemaker ◽  
Giovanni Melillo
Keyword(s):  
Endothelial Cells ◽  
Mammalian Cells ◽  
Neutralizing Antibodies ◽  
Umbilical Vein ◽  
Hypoxia Inducible Factor ◽  
Transcriptional Response ◽  
Low Oxygen ◽  
Autocrine Loop ◽  
Hypoxic Induction ◽  
Hypoxic Conditions

AbstractHypoxia is a major pathophysiological condition for the induction of angiogenesis, which is a crucial aspect of growth in solid tumors. In mammalian cells, the transcriptional response to oxygen deprivation is largely mediated by hypoxia-inducible factor 1 (HIF-1), a heterodimer composed of HIF-1α and HIF-1β subunits. However, the response of endothelial cells to hypoxia and the specific involvement of HIF-α subunits in this process are still poorly understood. We show that human umbilical vein endothelial cells (HUVECs) cultured in the absence of growth factors survive and form tubelike structures when cultured under hypoxic, but not normoxic, conditions. HUVECs expressed both HIF-1α and HIF-2α when cultured under hypoxic conditions. Transfection of HIF-1α, but not HIF-2α, siRNA to HUVECs completely abrogated hypoxic induction of cords. Neutralizing antibodies to bFGF, but not IGF-1, VEGF, or PDGF-BB, blocked survival and sprouting of HUVECs under hypoxic conditions, suggesting the existence of an autocrine loop induced by low oxygen levels. Notably, bFGF-dependent induction of cord formation under normoxic conditions required HIF-1α activity, which was also essential for hypoxic induction of bFGF mRNA and protein expression. These results uncover the existence of an HIF-1α–bFGF amplification pathway that mediates survival and sprouting of endothelial cells under hypoxic conditions.

Transmembrane prolyl 4-hydroxylase is a fourth prolyl 4-hydroxylase regulating EPO production and erythropoiesis

Blood ◽  
2012 ◽  
Vol 120 (16) ◽  
pp. 3336-3344 ◽  
Author(s):  
Anu Laitala ◽  
Ellinoora Aro ◽  
Gail Walkinshaw ◽  
Joni M. Mäki ◽  
Maarit Rossi ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Mrna Level ◽  
Hypoxia Inducible Factor ◽  
Mrna Levels ◽  
Wild Type ◽  
Α Subunit ◽  
Hepcidin Expression ◽  
In The Wild ◽  
Hepcidin Mrna

AbstractAn endoplasmic reticulum transmembrane prolyl 4-hydroxylase (P4H-TM) is able to hydroxylate the α subunit of the hypoxia-inducible factor (HIF) in vitro and in cultured cells, but nothing is known about its roles in mammalian erythropoiesis. We studied such roles here by administering a HIF-P4H inhibitor, FG-4497, to P4h-tm−/− mice. This caused larger increases in serum Epo concentration and kidney but not liver Hif-1α and Hif-2α protein and Epo mRNA levels than in wild-type mice, while the liver Hepcidin mRNA level was lower in the P4h-tm−/− mice than in the wild-type. Similar, but not identical, differences were also seen between FG-4497–treated Hif-p4h-2 hypomorphic (Hif-p4h-2gt/gt) and Hif-p4h-3−/− mice versus wild-type mice. FG-4497 administration increased hemoglobin and hematocrit values similarly in the P4h-tm−/− and wild-type mice, but caused higher increases in both values in the Hif-p4h-2gt/gt mice and in hematocrit value in the Hif-p4h-3−/− mice than in the wild-type. Hif-p4h-2gt/gt/P4h-tm−/− double gene-modified mice nevertheless had increased hemoglobin and hematocrit values without any FG-4497 administration, although no such abnormalities were seen in the Hif-p4h-2gt/gt or P4h-tm−/− mice. Our data thus indicate that P4H-TM plays a role in the regulation of EPO production, hepcidin expression, and erythropoiesis.

Analysis by mRNA levels of the expression of six G protein α-subunit genes in mammalian cells and tissues

1991 ◽  
Vol 1094 (2) ◽  
pp. 193-199 ◽  
Author(s):  
Jermelina Linor R. Garibay ◽  
Tohru Kozasa ◽  
Hiroshi Itoh ◽  
Toshihiko Tsukamoto ◽  
Masaaki Matsuoka ◽  
...  
Keyword(s):  
G Protein ◽  
Mammalian Cells ◽  
Mrna Levels ◽  
Α Subunit ◽  
G Protein Α Subunit

scholarly journals Crosstalk in oxygen homeostasis networks: SKN-1/NRF inhibits the HIF-1 hypoxia-inducible factor in Caenorhabditis elegans

2021 ◽  
Author(s):  
Dingxia Feng ◽  
Zhiwei Zhai ◽  
Zhiyong Shao ◽  
Yi Zhang ◽  
Jo Anne Powell-Coffman
Keyword(s):  
Oxidative Stress ◽  
Hypoxia Inducible Factor ◽  
Regulatory Sequences ◽  
Low Oxygen ◽  
Transcriptional Responses ◽  
C Elegans ◽  
Protein Levels ◽  
Oxygen Homeostasis ◽  
Genome Wide ◽  
A Genome

AbstractDuring development, homeostasis, and disease, organisms must balance responses that allow adaptation to low oxygen (hypoxia) with those that protect cells from oxidative stress. The evolutionarily conserved hypoxia-inducible factors are central to these processes, as they orchestrate transcriptional responses to oxygen deprivation. Here, we employ genetic strategies in C. elegans to identify stress-responsive genes and pathways that modulate the HIF-1 hypoxia-inducible factor and facilitate oxygen homeostasis. Through a genome-wide RNAi screen, we show that RNAi-mediated mitochondrial or proteasomal dysfunction increases the expression of hypoxia-responsive reporter Pnhr-57:GFP in C. elegans. Interestingly, only a subset of these effects requires hif-1. Of particular importance, we found that skn-1 RNAi increases the expression of hypoxia-responsive reporter Pnhr-57:GFP and elevates HIF-1 protein levels. The SKN-1/NRF transcription factor has been shown to promote oxidative stress resistance. We present evidence that the crosstalk between HIF-1 and SKN-1 is mediated by EGL-9, the prolyl hydroxylase that targets HIF-1 for oxygen-dependent degradation. Treatment that induces SKN-1, such as heat, increases expression of a Pegl-9:GFP reporter, and this effect requires skn-1 function and a putative SKN-1 binding site in egl-9 regulatory sequences. Collectively, these data support a model in which SKN-1 promotes egl-9 transcription, thereby inhibiting HIF-1. We propose that this interaction enables animals to adapt quickly to changes in cellular oxygenation and to better survive accompanying oxidative stress.

scholarly journals Hypoxia-Induced Gene Expression Occurs Solely through the Action of Hypoxia-Inducible Factor 1α (HIF-1α): Role of Cytoplasmic Trapping of HIF-2α

2003 ◽  
Vol 23 (14) ◽  
pp. 4959-4971 ◽  
Author(s):  
Sang-ki Park ◽  
Agnes M. Dadak ◽  
Volker H. Haase ◽  
Lucrezia Fontana ◽  
Amato J. Giaccia ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcriptional Activity ◽  
Hypoxia Inducible Factor ◽  
Low Oxygen ◽  
Hypoxic Conditions ◽  
Show Evidence ◽  
Dependent Protein ◽  
A Cell ◽  
Cell Type Specific ◽  
Inducible Genes

ABSTRACT The hypoxia-inducible factors 1α (HIF-1α) and 2α (HIF-2α) have extensive structural homology and have been identified as key transcription factors responsible for gene expression in response to hypoxia. They play critical roles not only in normal development, but also in tumor progression. Here we report on the differential regulation of protein expression and transcriptional activity of HIF-1α and -2α by hypoxia in immortalized mouse embryo fibroblasts (MEFs). We show that oxygen-dependent protein degradation is restricted to HIF-1α, as HIF-2α protein is detected in MEFs regardless of oxygenation and is localized primarily to the cytoplasm. Endogenous HIF-2α remained transcriptionally inactive under hypoxic conditions; however, ectopically overexpressed HIF-2α translocated into the nucleus and could stimulate expression of hypoxia-inducible genes. We show that the factor inhibiting HIF-1 can selectively inhibit the transcriptional activity of HIF-1α but has no effect on HIF-2α-mediated transcription in MEFs. We propose that HIF-2α is not a redundant transcription factor of HIF-1α for hypoxia-induced gene expression and show evidence that there is a cell type-specific modulator(s) that enables selective activation of HIF-1α but not HIF-2α in response to low-oxygen stress.

scholarly journals Hypoxia-Inducible Factor 1α Is Essential for Cell Cycle Arrest during Hypoxia

2003 ◽  
Vol 23 (1) ◽  
pp. 359-369 ◽  
Author(s):  
Nobuhito Goda ◽  
Heather E. Ryan ◽  
Bahram Khadivi ◽  
Wayne McNulty ◽  
Robert C. Rickert ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Cell Cycle Arrest ◽  
Cellular Response ◽  
Hypoxia Inducible Factor ◽  
Growth Arrest ◽  
Cell Types ◽  
Low Oxygen ◽  
Double Knockout ◽  
Cycle Arrest

ABSTRACT A classical cellular response to hypoxia is a cessation of growth. Hypoxia-induced growth arrest differs in different cell types but is likely an essential aspect of the response to wounding and injury. An important component of the hypoxic response is the activation of the hypoxia-inducible factor 1 (HIF-1) transcription factor. Although this transcription factor is essential for adaptation to low oxygen levels, the mechanisms through which it influences cell cycle arrest, including the degree to which it cooperates with the tumor suppressor protein p53, remain poorly understood. To determine broadly relevant aspects of HIF-1 function in primary cell growth arrest, we examined two different primary differentiated cell types which contained a deletable allele of the oxygen-sensitive component of HIF-1, the HIF-1α gene product. The two cell types were murine embryonic fibroblasts and splenic B lymphocytes; to determine how the function of HIF-1α influenced p53, we also created double-knockout (HIF-1α null, p53 null) strains and cells. In both cell types, loss of HIF-1α abolished hypoxia-induced growth arrest and did this in a p53-independent fashion. Surprisingly, in all cases, cells lacking both p53 and HIF-1α genes have completely lost the ability to alter the cell cycle in response to hypoxia. In addition, we have found that the loss of HIF-1α causes an increased progression into S phase during hypoxia, rather than a growth arrest. We show that hypoxia causes a HIF-1α-dependent increase in the expression of the cyclin-dependent kinase inhibitors p21 and p27; we also find that hypophosphorylation of retinoblastoma protein in hypoxia is HIF-1α dependent. These data demonstrate that the transcription factor HIF-1 is a major regulator of cell cycle arrest in primary cells during hypoxia.

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