The human HIF (hypoxia-inducible factor)-3α gene is a HIF-1 target gene and may modulate hypoxic gene induction

2009 ◽  
Vol 424 (1) ◽  
pp. 143-151 ◽  
Author(s):  
Tetsuhiro Tanaka ◽  
Michael Wiesener ◽  
Wanja Bernhardt ◽  
Kai-Uwe Eckardt ◽  
Christina Warnecke

HIF (hypoxia-inducible factor)-3α is the third member of the HIF transcription factor family. Whereas HIF-1α and -2α play critical roles in the cellular and systemic adaptation to hypoxia, little is known about the regulation and function of HIF-3α. At least five different splice variants may be expressed from the human HIF-3α locus that are suggested to exert primarily negative regulatory effects on hypoxic gene induction. In the present paper, we report that hypoxia induces the human HIF-3α gene at the transcriptional level in a HIF-1-dependent manner. HIF-3α2 and HIF-3α4 transcripts, the HIF-3α splice variants expressed in Caki-1 renal carcinoma cells, rapidly increased after exposure to hypoxia or chemical hypoxia mimetics. siRNA (small interfering RNA)-mediated HIF-α knockdown demonstrated that HIF-3α is a specific target gene of HIF-1α, but is not affected by HIF-2α knockdown. In contrast with HIF-1α and HIF-2α, HIF-3α is not regulated at the level of protein stability. HIF-3α protein could be detected under normoxia in the cytoplasm and nuclei, but increased under hypoxic conditions. Promoter analyses and chromatin immunoprecipitation experiments localized a functional hypoxia-responsive element 5′ to the transcriptional start of HIF-3α2. siRNA-mediated knockdown of HIF-3α increased transactivation of a HIF-driven reporter construct and mRNA expression of lysyl oxidase. Immunohistochemistry revealed an overlap of HIF-1α-positive and HIF-3α-positive areas in human renal cell carcinomas. These findings shed light on a novel aspect of HIF-3α as a HIF-1 target gene and point to a possible role as a modulator of hypoxic gene induction.

2011 ◽  
Vol 301 (3) ◽  
pp. C550-C552 ◽  
Author(s):  
Gregg L. Semenza

A fundamental physiological property of mammalian cells is the regulation of proliferation according to O2 availability. Progression through the cell cycle is inhibited under hypoxic conditions in many, but not all, cell types, and this G1 arrest is dependent on hypoxia-inducible factor (HIF) 1α. Components of the hexameric MCM helicase, which binds to replication origins before the onset of DNA synthesis, are present in large excess in mammalian cells relative to origins, suggesting that they may have additional functions. Screens for HIF-1α interacting proteins revealed that MCM7 binds to the amino-terminal PER-SIM-ARNT (PAS) domain of HIF-1α and stimulates prolyl hydroxylation-dependent ubiquitination and degradation of HIF-1α, whereas MCM3 binds to the carboxyl terminus of HIF-1α and enhances asparaginyl hydroxylation-dependent inhibition of HIF-1α transactivation domain function. Thus MCM proteins inhibit HIF activity via two distinct O2-dependent mechanisms. Under prolonged hypoxic conditions, MCM mRNA expression is inhibited in a HIF-1α-dependent manner. Thus HIF and MCM proteins act in a mutually antagonistic manner, providing a novel molecular mechanism for homeostatic regulation of cell proliferation based on the relative levels of these proteins.


Blood ◽  
2008 ◽  
Vol 111 (6) ◽  
pp. 3131-3136 ◽  
Author(s):  
Dong Hoon Shin ◽  
Yang-Sook Chun ◽  
Dong Soon Lee ◽  
L. Eric Huang ◽  
Jong-Wan Park

Abstract Bortezomib (PS-341), a proteasome inhibitor, has been examined clinically for the treatment of multiple myeloma and several solid tumors. Bortezomib directly induces tumor cell death and has also been reported to inhibit tumor adaptation to hypoxia by functionally inhibiting hypoxia-inducible factor-1α (HIF-1α). However, the mechanism underlying HIF-1 inhibition by bortezomib remains obscure. In the present study, we demonstrated that bortezomib attenuated the hypoxic induction of erythropoietin and vascular endothelial growth factor at subnanomolar concentrations in multiple myeloma and liver cancer cell lines, regardless of cytotoxic concentrations of bortezomib. Bortezomib repressed HIF-1α activity by inhibiting the recruitment of p300 coactivator. Specifically, bortezomib targeted HIF-1α C-terminal transactivation domain (CAD) but not the CAD lacking Asn803, which is a hydroxylation site by the factor inhibiting HIF-1 (FIH). Accordingly, this effect of bortezomib on CAD was augmented by FIH expression and abolished by FIH knock-down. Furthermore, bortezomib stimulated the interaction between CAD and FIH under hypoxic conditions, and FIH inhibition reversed the suppressions of erythropoietin and vascular endothelial growth factor by bortezomib. We propose that the mechanism underlying the inhibitory effects of bortezomib on tumor angiogenesis and hypoxic adaptation involves the repression of HIF-1α transcriptional activity by reinforcing the FIH-mediated inhibition of p300 recruitment.


Antioxidants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 48
Author(s):  
Naoko Kida ◽  
Yoshiyuki Matsuo ◽  
Yoshiko Hashimoto ◽  
Kenichiro Nishi ◽  
Tomoko Tsuzuki-Nakao ◽  
...  

Cigarette smoking (CS) is a major contributing factor in the development of a large number of fatal and debilitating disorders, including degenerative diseases and cancers. Smoking and passive smoking also affect the establishment and maintenance of pregnancy. However, to the best of our knowledge, the effects of smoking on the human endometrium remain poorly understood. In this study, we investigated the regulatory mechanism underlying CS-induced hypoxia-inducible factor (HIF)-1α activation using primary human endometrial stromal cells and an immortalized cell line (KC02-44D). We found that the CS extract (CSE) increased reactive oxygen species levels and stimulated HIF-1α protein stabilization in endometrial stromal cells, and that CS-induced HIF-1α-dependent gene expression under non-hypoxic conditions in a concentration- and time-dependent manner. Additionally, we revealed the upregulated expression of a hypoxia-induced gene set following the CSE treatment, even under normoxic conditions. These results indicated that HIF-1α might play an important role in CS-exposure-induced cellular stress, inflammation, and endometrial remodeling.


2021 ◽  
Vol 22 (16) ◽  
pp. 8596
Author(s):  
Ji Young Kim ◽  
Eun Jung Lee ◽  
Yuri Ahn ◽  
Sujin Park ◽  
Yu Jeong Bae ◽  
...  

Hypoxic conditions induce the activation of hypoxia-inducible factor-1α (HIF-1α) to restore the supply of oxygen to tissues and cells. Activated HIF-1α translocates into the nucleus and binds to hypoxia response elements to promote the transcription of target genes. Cathepsin L (CTSL) is a lysosomal protease that degrades cellular proteins via the endolysosomal pathway. In this study, we attempted to determine if CTSL is a hypoxia responsive target gene of HIF-1α, and decipher its role in melanocytes in association with the autophagic pathway. The results of our luciferase reporter assay showed that the expression of CTSL is transcriptionally activated through the binding of HIF1-α at its promoter. Under autophagy-inducing starvation conditions, HIF-1α and CTSL expression is highly upregulated in melan-a cells. The mature form of CTSL is closely involved in melanosome degradation through lysosomal activity upon autophagosome–lysosome fusion. The inhibition of conversion of pro-CTSL to mature CTSL leads to the accumulation of gp100 and tyrosinase in addition to microtubule-associated protein 1 light chain 3 (LC3) II, due to decreased lysosomal activity in the autophagic pathway. In conclusion, we have identified that CTSL, a novel target of HIF-1α, participates in melanosome degradation in melanocytes through lysosomal activity during autophagosome–lysosome fusion.


Hypertension ◽  
2013 ◽  
Vol 62 (suppl_1) ◽  
Author(s):  
Weiru Zhang ◽  
Yujin Zhang ◽  
Wei Wang ◽  
Renna Luo ◽  
Cheng Zhao ◽  
...  

Hypertension is the most prevalent life-threatening disease worldwide and is frequently associated with chronic kidney disease (CKD). However, the molecular basis underlying hypertensive CKD is not fully understood. We sought to identify specific factors and signaling pathways that contribute to hypertensive CKD and thereby exacerbate disease progression. Using high throughput quantitative RT-PCR profiling, we discovered that the expression level of 5’-ectonucleotidase (CD73), a key enzyme that produces extracellular adenosine, was significantly increased in the kidneys of angiotensin II (Ang II)-infused mice, an animal model of hypertensive nephropathy. Using both CD73 and A2B adenosine receptor (ADORA2B)-deficient mice coupled with pharmacological studies, we found that elevated CD73-mediated excess renal adenosine preferentially induced the ADORA2B expression and enhanced kidney ADORA2B signaling contributes to Ang II-induced hypertension. Similarly, in humans, we found that both CD73 and ADORA2B levels were significantly elevated in the kidneys of CKD patients compared to normal individuals and further elevated in hypertensive CKD patients. These findings led us to further discover that elevated renal CD73 contributes to excess adenosine signaling via ADORA2B activation that directly stimulates endothelin-1 (ET-1) production in a hypoxia inducible factor-α (HIF-1α)-dependent manner and underlies the pathogenesis of the disease. Lastly, we revealed that HIF-1α is an important factor responsible for Ang II-induced CD73 and ADORA2B expression at the transcriptional level. Overall, our studies reveal that Ang II-induced renal CD73 promotes the production of renal adenosine that is a prominent driver of hypertensive CKD by enhanced ADORA2B signaling-mediated ET-1 induction in a HIF-1α dependent manner. The inhibition of excess adenosine-mediated ADORA2B signaling represents a novel therapeutic target for the disease.


2009 ◽  
Vol 29 (16) ◽  
pp. 4467-4483 ◽  
Author(s):  
Nils Halberg ◽  
Tayeba Khan ◽  
Maria E. Trujillo ◽  
Ingrid Wernstedt-Asterholm ◽  
Alan D. Attie ◽  
...  

ABSTRACT Adipose tissue can undergo rapid expansion during times of excess caloric intake. Like a rapidly expanding tumor mass, obese adipose tissue becomes hypoxic due to the inability of the vasculature to keep pace with tissue growth. Consequently, during the early stages of obesity, hypoxic conditions cause an increase in the level of hypoxia-inducible factor 1α (HIF1α) expression. Using a transgenic model of overexpression of a constitutively active form of HIF1α, we determined that HIF1α fails to induce the expected proangiogenic response. In contrast, we observed that HIF1α initiates adipose tissue fibrosis, with an associated increase in local inflammation. “Trichrome- and picrosirius red-positive streaks,” enriched in fibrillar collagens, are a hallmark of adipose tissue suffering from the early stages of hypoxia-induced fibrosis. Lysyl oxidase (LOX) is a transcriptional target of HIF1α and acts by cross-linking collagen I and III to form the fibrillar collagen fibers. Inhibition of LOX activity by β-aminoproprionitrile treatment results in a significant improvement in several metabolic parameters and further reduces local adipose tissue inflammation. Collectively, our observations are consistent with a model in which adipose tissue hypoxia serves as an early upstream initiator for adipose tissue dysfunction by inducing a local state of fibrosis.


2008 ◽  
Vol 412 (3) ◽  
pp. 477-484 ◽  
Author(s):  
Patrick van Uden ◽  
Niall S. Kenneth ◽  
Sonia Rocha

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.


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