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Expression of prolyl hydroxylases (PHDs) is selectively controlled by HIF-1 and HIF-2 proteins in nucleus pulposus cells of the intervertebral disc: distinct roles of PHD2 and PHD3 proteins in controlling HIF-1? activity in hypoxia.

ABSTRACT: Adaptive response to hypoxia in nucleus pulposus cells of the intervertebral disc is regulated by the hypoxia-inducible factors, HIF-1? and HIF-2?. Moreover, oxygen-dependent turnover of HIF-1? in these cells is controlled by the prolyl-4-hydroxylase domain (PHD) family of proteins. Whether HIF homologues control expression of PHDs and whether PHDs control hypoxia-inducible factor (HIF) turnover and/or activity under hypoxia is not known. Here, we show that in nucleus pulposus cells, hypoxia robustly induces PHD3 expression and, to a lesser extent, of PHD2 and PHD1. Reporter analysis shows that the hypoxic induction of the PHD2 promoter is HIF-1? dependent, whereas PHD3 promoter/enhancer activity is dependent on both HIF-1? and HIF-2?. Lentiviral delivery of HIF-1?, ShHIF-1?, and ShHIF-1? confirmed these observations. Noteworthy, HIF-1? maintains basal expression of PHD1 in hypoxia at the posttranscriptional level. Finally, loss of function studies using lentiviral transduction of ShPHDs clearly shows that even at 1% O(2), PHD2 selectively degrades HIF-1?. In contrast, in hypoxia, PHD3 enhances HIF-1? transcriptional activity without affecting protein levels. To correlate these observations with disc disease, a condition characterized by tissue vascularization, we analyzed human tissues. Increased PHD1 mRNA expression but decreased PHD2 and PHD3 expression is observed in degenerate tissues. Interestingly, the hypoxic responsiveness of all the PHDs is maintained in isolated nucleus pulposus cells regardless of the disease state. We propose that PHD2 and PHD3 can be used as a biomarker of tissue oxygenation in the disc and that, as such, it may have important clinical implications.

SUBMITTER: Fujita N

PROVIDER: S-EPMC3351286 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Expression of prolyl hydroxylases (PHDs) is selectively controlled by HIF-1 and HIF-2 proteins in nucleus pulposus cells of the intervertebral disc: distinct roles of PHD2 and PHD3 proteins in controlling HIF-1α activity in hypoxia.

Fujita Nobuyuki N Markova Dessislava D Anderson D Greg DG Chiba Kazuhiro K Toyama Yoshiaki Y Shapiro Irving M IM Risbud Makarand V MV

The Journal of biological chemistry 20120326 20

Adaptive response to hypoxia in nucleus pulposus cells of the intervertebral disc is regulated by the hypoxia-inducible factors, HIF-1α and HIF-2α. Moreover, oxygen-dependent turnover of HIF-1α in these cells is controlled by the prolyl-4-hydroxylase domain (PHD) family of proteins. Whether HIF homologues control expression of PHDs and whether PHDs control hypoxia-inducible factor (HIF) turnover and/or activity under hypoxia is not known. Here, we show that in nucleus pulposus cells, hypoxia rob ...[more]

PMID: 22451659

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Project description:BackgroundColorectal cancer (CRC) is one of the most common and comprehensively studied malignancies. Hypoxic conditions during formation of CRC may support the development of more aggressive cancers. Hypoxia inducible factor (HIF), a major player in cancerous tissue adaptation to hypoxia, is negatively regulated by the family of prolyl hydroxylase enzymes (PHD1, PHD2, PHD3) and asparaginyl hydroxylase, called factor inhibiting HIF (FIH).MethodsPHD1, PHD2, PHD3 and FIH gene expression was evaluated using quantitative RT-PCR and western blotting in primary colonic adenocarcinoma and adjacent histopathologically unchanged colonic mucosa from patients who underwent radical surgical resection of the colon (n=90), and the same methods were used for assessment of PHD3 gene expression in HCT116 and DLD-1 CRC cell lines. DNA methylation levels of the CpG island in the promoter regulatory region of PHD1, PHD2, PHD3 and FIH were assessed using bisulfite DNA sequencing and high resolution melting analysis (HRM) for patients and HRM analysis for CRC cell lines.ResultsWe found significantly lower levels of PHD1, PHD2 and PHD3 transcripts (p=0.00026; p<0.00001; p<0.00001) and proteins (p=0.004164; p=0.0071; p<0.00001) in primary cancerous than in histopathologically unchanged tissues. Despite this, we did not observe statistically significant differences in FIH transcript levels between cancerous and histopathologically unchanged colorectal tissue, but we found a significantly increased level of FIH protein in CRC (p=0.0169). The reduced PHD3 expression was correlated with significantly increased DNA methylation in the CpG island of the PHD3 promoter regulatory region (p<0.0001). We did not observe DNA methylation in the CpG island of the PHD1, PHD2 or FIH promoter in cancerous and histopathologically unchanged colorectal tissue. We also showed that 5-Aza-2'-deoxycytidine induced DNA demethylation leading to increased PHD3 transcript and protein level in HCT116 cells.ConclusionWe demonstrated that reduced PHD3 expression in cancerous tissue was accompanied by methylation of the CpG rich region located within the first exon and intron of the PHD3 gene. The diminished expression of PHD1 and PHD2 and elevated level of FIH protein in cancerous tissue compared to histopathologically unchanged colonic mucosa was not associated with DNA methylation within the CpG islands of the PHD1, PHD2 and FIH genes.

Project description:STUDY DESIGN:Profiling proteins expressed in the nucleus pulposus of fetal intervertebral disc (IVD). PURPOSE:To evaluate the molecular complexity of fetal IVDs not exposed to mechanical, traumatic, inflammatory, or infective insults to generate improved knowledge on disc homeostasis. OVERVIEW OF LITERATURE:Low back pain is the most common musculoskeletal disorder, causing a significant reduction in the quality of life, and degenerative disc disorders mainly contribute to the increasing socioeconomic burden. Despite extensive research, the causative pathomechanisms behind degenerative disc disorders are poorly understood. Precise molecular studies on the intricate biological processes involved in maintaining normal disc homeostasis are needed. METHODS:IVDs of nine fetal specimens obtained from medical abortions were used to dissect out the annulus fibrosus and nucleus pulposus under sterile operating conditions. Dissected tissues were transferred to sterile Cryovials and snap frozen in liquid nitrogen before transporting to the research laboratory for protein extraction and further liquid chromatography tandem mass spectrometry (LC-MS/ MS) analysis. Collected data were further analyzed using Gene Functional Classification Tool in DAVID and STRING databases. RESULTS:A total of 1,316 proteins were identified through LC-MS/MS analysis of nine fetal IVD tissues. Approximately 247 proteins present in at least four fetal discs were subjected to further bioinformatic analysis. The following 10 clusters of proteins were identified: collagens, ribosomal proteins, small leucine-rich proteins, matrilin and thrombospondin, annexins, protein disulfide isomerase family proteins and peroxiredoxins, tubulins, histones, hemoglobin, and prolyl 4-hydroxylase family proteins. CONCLUSIONS:This study provides fundamental information on the proteome networks involved in the growth and development of healthy fetal discs in humans. Systematic cataloging of proteins involved in various structural and regulatory processes has been performed. Proteins expressed most abundantly (collagen type XIV alpha 1 chain, biglycan, matrilin 1, and thrombospondin 1) in their respective clusters also elucidate the possibility of utilizing these proteins for potential regenerative therapies.

Dataset Information

Expression of prolyl hydroxylases (PHDs) is selectively controlled by HIF-1 and HIF-2 proteins in nucleus pulposus cells of the intervertebral disc: distinct roles of PHD2 and PHD3 proteins in controlling HIF-1? activity in hypoxia.

Publications

Expression of prolyl hydroxylases (PHDs) is selectively controlled by HIF-1 and HIF-2 proteins in nucleus pulposus cells of the intervertebral disc: distinct roles of PHD2 and PHD3 proteins in controlling HIF-1α activity in hypoxia.

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