scholarly journals A Feedback Loop Involving the Phd3 Prolyl Hydroxylase Tunes the Mammalian Hypoxic Response In Vivo

2009 ◽  
Vol 29 (21) ◽  
pp. 5729-5741 ◽  
Author(s):  
Yoji Andrew Minamishima ◽  
Javid Moslehi ◽  
Robert F. Padera ◽  
Roderick T. Bronson ◽  
Ronglih Liao ◽  
...  

ABSTRACT Hypoxia-inducible factor (HIF), consisting of a labile α subunit and a stable β subunit, is a master regulator of hypoxia-responsive mRNAs. HIFα undergoes oxygen-dependent prolyl hydroxylation, which marks it for polyubiquitination by a complex containing the von Hippel-Lindau protein (pVHL). Among the three Phd family members, Phd2 appears to be the primary HIF prolyl hydroxylase. Phd3 is induced by HIF and, based on findings from in vitro studies, may participate in a HIF-regulatory feedback loop. Here, we report that Phd3 loss exacerbates the HIF activation, hepatic steatosis, dilated cardiomyopathy, and premature mortality observed in mice lacking Phd2 alone and produces a closer phenocopy of the changes seen in mice lacking pVHL than the loss of Phd2 alone. Importantly, the degree to which Phd3 can compensate for Phd2 loss and the degree to which the combined loss of Phd2 and Phd3 resembles pVHL loss appear to differ for different HIF-responsive genes and in different tissues. These findings highlight that the responses of different HIF target genes to changes in prolyl hydroxylase activity differ, quantitatively and qualitatively, in vivo and have implications for the development of paralog-specific prolyl hydroxylase inhibitors as therapeutic agents.

2004 ◽  
Vol 24 (20) ◽  
pp. 9038-9047 ◽  
Author(s):  
Mangatt P. Biju ◽  
Aaron K. Neumann ◽  
Steven J. Bensinger ◽  
Randall S. Johnson ◽  
Laurence A. Turka ◽  
...  

ABSTRACT The von Hippel-Lindau gene product (pVHL) targets the α subunit of basic helix-loop-helix transcription factor hypoxia-inducible factor (HIF) for proteasomal degradation. Inactivation of pVhl in the mouse germ line results in embryonic lethality, indicating that tight control of Hif-mediated adaptive responses to hypoxia is required for normal development and tissue function. In order to investigate the role of pVhl in T-cell development, we generated mice with thymocyte-specific inactivation of Vhlh resulting in constitutive transcriptional activity of Hif-1, as well as mice with thymocyte-specific repression of Hif-1 in a wild-type and Vhlh-deficient background. Thymi from Vhlh-deficient mice were small due to a severe reduction in the total number of CD4/CD8-double-positive thymocytes which was associated with increased apoptosis in vivo and in vitro. Increased apoptosis was a result of enhanced caspase 8 activity, while Bcl-2 and Bcl-XL transgene expression had little effect on this phenotype. Inactivation of Hif-1 in Vhlh-deficient thymocytes restored thymic cellularity as well as thymocyte viability in vitro. Our data suggest that tight regulation of Hif-1 via pVhl is required for normal thymocyte development and viability and that an increase in Hif-1 transcriptional activity enhances caspase 8-mediated apoptosis in thymocytes.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Guodong Li ◽  
Chung-Nga Ko ◽  
Dan Li ◽  
Chao Yang ◽  
Wanhe Wang ◽  
...  

AbstractImpaired wound healing and ulcer complications are a leading cause of death in diabetic patients. In this study, we report the design and synthesis of a cyclometalated iridium(III) metal complex 1a as a stabilizer of hypoxia-inducible factor-1α (HIF-1α). In vitro biophysical and cellular analyses demonstrate that this compound binds to Von Hippel-Lindau (VHL) and inhibits the VHL–HIF-1α interaction. Furthermore, the compound accumulates HIF-1α levels in cellulo and activates HIF-1α mediated gene expression, including VEGF, GLUT1, and EPO. In in vivo mouse models, the compound significantly accelerates wound closure in both normal and diabetic mice, with a greater effect being observed in the diabetic group. We also demonstrate that HIF-1α driven genes related to wound healing (i.e. HSP-90, VEGFR-1, SDF-1, SCF, and Tie-2) are increased in the wound tissue of 1a-treated diabetic mice (including, db/db, HFD/STZ and STZ models). Our study demonstrates a small molecule stabilizer of HIF-1α as a promising therapeutic agent for wound healing, and, more importantly, validates the feasibility of treating diabetic wounds by blocking the VHL and HIF-1α interaction.


2002 ◽  
Vol 22 (6) ◽  
pp. 1947-1960 ◽  
Author(s):  
William J. Hansen ◽  
Michael Ohh ◽  
Javid Moslehi ◽  
Keiichi Kondo ◽  
William G. Kaelin ◽  
...  

ABSTRACT We examined the biogenesis of the von Hippel-Lindau (VHL) tumor suppressor protein (pVHL) in vitro and in vivo. pVHL formed a complex with the cytosolic chaperonin containing TCP-1 (CCT or TRiC) en route to assembly with elongin B/C and the subsequent formation of the VCB-Cul2 ubiquitin ligase. Blocking the interaction of pVHL with elongin B/C resulted in accumulation of pVHL within the CCT complex. pVHL present in purified VHL-CCT complexes, when added to rabbit reticulocyte lysate, proceeded to form VCB and VCB-Cul2. Thus, CCT likely functions, at least in part, by retaining VHL chains pending the availability of elongin B/C for final folding and/or assembly. Tumor-associated mutations within exon II of the VHL syndrome had diverse effects upon the stability and/or function of pVHL-containing complexes. First, a pVHL mutant lacking the entire region encoded by exon II did not bind to CCT and yet could still assemble into complexes with elongin B/C and elongin B/C-Cul2. Second, a number of tumor-derived missense mutations in exon II did not decrease CCT binding, and most had no detectable effect upon VCB-Cul2 assembly. Many exon II mutants, however, were found to be defective in the binding to and subsequent ubiquitination of hypoxia-inducible factor 1α (HIF-1α), a substrate of the VCB-Cul2 ubiquitin ligase. We conclude that the selection pressure to mutate VHL exon II during tumorigenesis does not relate to loss of CCT binding but may reflect quantitative or qualitative defects in HIF binding and/or in pVHL-dependent ubiquitin ligase activity.


Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2896-2896
Author(s):  
Anita Hollenbeck ◽  
Stefanie Weber ◽  
Kathrin Händschke ◽  
Mandy Necke ◽  
Bertram Opalka ◽  
...  

Abstract Early thymic progenitors enter the thymus and are exposed to regional hypoxia while they develop in a step-wise manner to mature functional T-cells. Therefore, hypoxia might represent an important component of the highly specialized thymic microenvironment. On the molecular level the hypoxia-inducible factor pathway controls the cellular response to hypoxia. In this pathway, the von-Hippel-Lindau protein (pVHL) continuously mediates the destruction of the transcription factor hypoxia-inducible factor-1α (HIF-1α) under normoxic conditions. Under hypoxia HIF-1α degradation is inhibited leading to the activation of HIF-1α target genes. Others used lck-Cre transgene-mediated conditional in vivo deletion of the Vhl gene to study the role of the oxygen-sensing pathway in developing thymocytes and found normal numbers of early double-negative (DN; CD4-CD8-) thymocytes (Biju et al., Mol Cell Biol, 2004). However, lck-Cre deletion initiates at the DN3 (CD25+CD44-) stage leaving the Vhl locus of very early DN1 (CD25-CD44+), DN2 (CD25+CD44+) and DN3 thymocytes unaltered. Therefore, we here used the ubiquitous hematopoietic deleter strain vav-Cre to investigate the role of pVHL in very early thymocytes (vav-Cre;VhlloxP;loxP mice). Using a PCR-based strategy we confirmed complete deletion of the Vhl gene in this model. We observed unaltered DN1 and DN2 progenitor numbers, however in contrast to the published lck-cre-mediated system we consistently observed an up to twofold expansion of the DN3 cellular compartment. As the hypoxia-inducible factor pathway was shown to modulate NOTCH1 signaling we studied Notch1 expression on Vhl-deficient thymocytes. Strikingly, Notch1 expression was significantly increased on expanded Vhl null DN3 thymocytes. At the DN3 developmental stage selection of cells with an accurately re-arranged T-cell receptor β-locus occurs. Thus, we analyzed pre- and post-β-selection DN3 cells by CD28 staining. Interestingly, we found both pre- and post-β-selection DN3 subpopulations expanded. In order to investigate whether the progenitor expansion is mediated by the lack of HIF-1α inhibition in the Vhl-deficient context we studied DN3 thymocytes in a conditional hematopoietic HIF-1α gain-of-function model (vav-Cre;HIF1dPA). Overexpression of HIF-1α, which is insensitive to pVHL-mediated degradation in vav-Cre;HIF1dPAmice, also resulted in expanded DN3 thymocytes. In summary, we describe novel conditional models to genetically alter the hypoxia-inducible factor pathway within very early thymic progenitors. Genetic Vhl loss led to an expansion of DN3 thymocytes. This DN3 expansion is most likely due to the absence of HIF-1α-inhibition, because HIF-1α overexpression phenocopied the Vhl-deficient DN3 thymocyte expansion. Disclosures Dührsen: Celgene: Honoraria, Research Funding.


2013 ◽  
Vol 305 (12) ◽  
pp. F1697-F1704 ◽  
Author(s):  
Jacob Richards ◽  
Kit-Yan Cheng ◽  
Sean All ◽  
George Skopis ◽  
Lauren Jeffers ◽  
...  

The circadian clock plays an important role in the regulation of physiological processes, including renal function and blood pressure. We have previously shown that the circadian protein period (Per)1 regulates the expression of multiple Na+ transport genes in the collecting duct, including the α-subunit of the renal epithelial Na+ channel. Consistent with this finding, Per1 knockout mice exhibit dramatically lower blood pressure than wild-type mice. We have also recently demonstrated the potential opposing actions of cryptochrome (Cry)2 on Per1 target genes. Recent work by others has demonstrated that Cry1/2 regulates aldosterone production through increased expression of the adrenal gland-specific rate-limiting enzyme 3β-dehydrogenase isomerase (3β-HSD). Therefore, we tested the hypothesis that Per1 plays a role in the regulation of aldosterone levels and renal Na+ retention. Using RNA silencing and pharmacological blockade of Per1 nuclear entry in the NCI-H295R human adrenal cell line, we showed that Per1 regulates 3β-HSD expression in vitro. These results were confirmed in vivo: mice with reduced levels of Per1 had decreased levels of plasma aldosterone and decreased mRNA expression of 3β-HSD. We postulated that mice with reduced Per1 would have a renal Na+-retaining defect. Indeed, metabolic cage experiments demonstrated that Per1 heterozygotes excreted more urinary Na+ compared with wild-type mice. Taken together, these data support the hypothesis that Per1 regulates aldosterone levels and that Per1 plays an integral role in the regulation of Na+ retention.


2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Antonella Falconieri ◽  
Giovanni Minervini ◽  
Raissa Bortolotto ◽  
Damiano Piovesan ◽  
Raffaele Lopreiato ◽  
...  

Abstract Mutations of the von Hippel–Lindau (pVHL) tumor suppressor are causative of a familiar predisposition to develop different types of cancer. pVHL is mainly known for its role in regulating hypoxia-inducible factor 1 α (HIF-1α) degradation, thus modulating the hypoxia response. There are different pVHL isoforms, including pVHL30 and pVHL19. However, little is known about isoform-specific functions and protein–protein interactions. Integrating in silico predictions with in vitro and in vivo assays, we describe a novel interaction between pVHL and mouse double minute 2 homolog (MDM2). We found that pVHL30, and not pVHL19, forms a complex with MDM2, and that the N-terminal acidic tail of pVHL30 is required for its association with MDM2. Further, we demonstrate that an intrinsically disordered region upstream of the tetramerization domain of MDM2 is responsible for its isoform-specific association with pVHL30. This region is highly conserved in higher mammals, including primates, similarly to what has been already shown for the N-terminal tail of pVHL30. Finally, we show that overexpression of pVHL30 and MDM2 together reduces cell metabolic activity and necrosis, suggesting a synergistic effect of these E3 ubiquitin ligases. Collectively, our data show an isoform-specific interaction of pVHL with MDM2, suggesting an interplay between these two E3 ubiquitin ligases.


2019 ◽  
Vol 131 (4) ◽  
pp. 1106-1114 ◽  
Author(s):  
Matthew J. Shepard ◽  
Alejandro Bugarini ◽  
Nancy A. Edwards ◽  
Jie Lu ◽  
Qi Zhang ◽  
...  

OBJECTIVEVon Hippel-Lindau disease (VHL) is a tumor predisposition syndrome characterized by CNS hemangioblastomas (HBs) and clear cell renal cell carcinomas (RCCs) due to hypoxia-inducible factor activation (pseudohypoxia). Because of the lack of effective medical therapies for VHL, HBs and RCCs account for significant morbidity and mortality, ultimately necessitating numerous neurological and renal surgeries. Propranolol is an FDA-approved pan-beta adrenergic antagonist with antitumor effects against infantile hemangiomas (IHs) and possibly VHL HBs. Here, the authors investigated the antitumor efficacy of propranolol against pseudohypoxia-driven VHL-HBs and VHL-RCCs.METHODSPatient-derived VHL-associated HBs (VHL-HBs) or 786-O-VHL−/− RCC cells were treated with clinically relevant concentrations of propranolol in vitro and assessed with viability assays, flow cytometry, quantitative real-time polymerase chain reaction, and western blotting. In vivo confirmation of propranolol antitumor activity was confirmed in athymic nude mice bearing 786-O xenograft tumors. Lastly, patients enrolled in a VHL natural history study (NCT00005902) were analyzed for incidental propranolol intake. Propranolol activity against VHL-HBs was assessed retrospectively with volumetric HB growth kinetic analysis.RESULTSPropranolol decreased HB and RCC viability in vitro with IC50 (half maximal inhibitory concentration) values of 50 µM and 200 µM, respectively. Similar to prior reports in infantile hemangiomas, propranolol induced apoptosis and paradoxically increased VEGF-A mRNA expression in patient-derived VHL-HBs and 786-O cells. While intracellular VEGF protein levels were not affected by propranolol treatment, propranolol decreased HIF expression in 786-O cells (7.6-fold reduction, p < 0.005). Propranolol attenuated tumor progression compared with control (33% volume reduction at 7 days, p < 0.005) in 786-O xenografted tumor-bearing mice. Three patients (harboring 25 growing CNS HBs) started propranolol therapy during the longitudinal VHL-HB study. HBs in these patients tended to grow slower (median growth rate 27.1 mm3/year vs 13.3 mm3/year) during propranolol treatment (p < 0.0004).CONCLUSIONSPropranolol decreases VHL-HB and VHL-related RCC viability in vitro likely by modulation of VEGF expression and by inducing apoptosis. Propranolol abrogates 786-O xenograft tumor progression in vivo, and retrospective clinical data suggest that propranolol curtails HB growth. These results suggest that propranolol may play a role in the treatment of VHL-related tumors.


Author(s):  
Xu Liu ◽  
Kun Qiao ◽  
Kaiyuan Zhu ◽  
Xianglan Li ◽  
Chunbo Zhao ◽  
...  

In recent years, an increasing number of studies have reported that long noncoding RNAs (lncRNAs) play crucial roles in breast cancer (BC) progression and metastasis. Another study group of our research center reported that lncRNA HCG18 was one of the 30 upregulated lncRNAs in BC tissues compared with normal tissues in The Cancer Genome Atlas database. However, the exact biological roles of HCG18 in BC remain unclear. In this study, we demonstrated that HCG18 is significantly upregulated in BC tissues and cells and that BC patients with high HCG18 expression tend to have poor prognosis. In vitro assays indicated that HCG18 promotes BC cell proliferation and invasion and endows BC cells with cancer stemness properties. In vivo assays revealed that reducing HCG18 expression in the BC cell line MDA-MB-231 markedly decreased tumor growth and lung metastasis in xenograft mouse models. In terms of mechanism, we found that HCG18 positively regulated the expression of BC-related ubiquitin-conjugating enzyme E2O (UBE2O) by sponging miR-103a-3p, and our previous research verified that UBE2O could promote the malignant phenotypes of BC cells through the UBE2O/AMPKα2/mTORC1 axis. Furthermore, as a downstream target of the HCG18/miR-103a-3p/UBE2O/mTORC1 axis, hypoxia-inducible factor 1α transcriptionally promoted HCG18 expression and then formed a positive feedback loop in BC. Taken together, these results confirm that HCG18 plays an oncogenic role in BC and might serve as a prognostic biomarker and a potential therapeutic target for BC treatment.


2013 ◽  
Vol 394 (4) ◽  
pp. 435-448 ◽  
Author(s):  
Johanna Myllyharju ◽  
Peppi Koivunen

Abstract Hypoxia-inducible transcription factor (HIF), an αβ dimer, is the key inducer of hypoxia-responsive genes that operate both during normal development and pathological processes in association with decreased oxygen availability. The products of HIF target genes function in, e.g., hematopoiesis, angiogenesis, iron transport, glucose utilization, resistance to oxidative stress, cell proliferation, survival and apoptosis, extracellular matrix homeostasis, and tumorigenesis and metastasis. HIF is accumulated in hypoxia, whereas it is rapidly degraded in normoxic cells. The oxygen-sensing mechanism behind this phenomenon is provided by HIF prolyl 4-hydroxylases (HIF-P4Hs, commonly known as PHDs and EglNs) that require oxygen in their reaction. In normoxia, two prolines in the oxygen-dependent degradation domain of the HIFα subunit become hydroxylated by the HIF-P4Hs. The 4-hydroxyproline residues formed serve as recognition sites for the von Hippel-Lindau E3 ubiquitin ligase complex and result in subsequent ubiquitination and instant proteasomal degradation of HIFα in normoxia. The HIF-P4H reaction is inhibited in hypoxia. HIFα evades degradation and forms a functional dimer with HIFβ, leading to activation of the HIF target genes. The central role of HIF-P4Hs in the regulation of the hypoxia response pathway has provided an attractive possibility as a drug candidate for treatment of, e.g., severe anemias and ischemic conditions, and several companies are currently carrying out clinical studies on the use of HIF-P4H inhibitors to treat anemia in patients with a kidney disease. Therefore, it is important to understand the effects of individual HIF-P4H isoenzymes on the hypoxia response and potential other pathways in vivo. The common and specific functions of the HIF-P4H isoenzymes are discussed in this review on the basis of available data from cell biological studies and gene-modified animals.


2017 ◽  
Vol 24 (9) ◽  
pp. C9-C19 ◽  
Author(s):  
Rodrigo Almeida Toledo

Two recent independent studies published in Nature show robust responses of clear cell renal cell carcinoma (ccRCC) cell lines, preclinical ccRCC xenograft models and, remarkably, a patient with progressive ccRCC despite receiving multiple lines of treatment, to the long-awaited, recently developed inhibitors of hypoxia-inducible factor 2-alpha (HIF2α). This commentary published in Endocrine-Related Cancer is based on the recognition of similar molecular drivers in ccRCC and the endocrine neoplasias pheochromocytomas and paragangliomas (PPGLs), ultimately leading to stabilization of HIFs. HIF-stabilizing mutations have been detected in the von Hippel–Lindau (VHL) gene, as well as in other genes, such as succinate dehydrogenase (SDHx), fumarate hydratase (FH) and transcription elongation factor B subunit 1 (TCEB1), as well as the gene that encodes HIF2α itself: EPAS1HIF2α. Importantly, the recent discovery of EPAS1 mutations in PPGLs and the results of comprehensive in vitro and in vivo studies revealing their oncogenic roles characterized a hitherto unknown direct mechanism of HIF2α activation in human cancer. The now available therapeutic opportunity to successfully inhibit HIF2α pharmacologically with PT2385 and PT2399 will certainly spearhead a series of investigations in several types of cancers, including patients with SDHB-related metastatic PPGL for whom limited therapeutic options are currently available. Future studies will determine the efficacy of these promising drugs against the hotspot EPAS1 mutations affecting HIF2α amino acids 529–532 (in PPGLs) and amino acids 533–540 (in erythrocytosis type 4), as well as against HIF2α protein activated by VHL, SDHx and FH mutations in PPGL-derived chromatin cells.


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