Protein phosphatase PPP3CA (calcineurin A) down-regulates hypoxia-inducible factor transcriptional activity

AbstractUnderstanding the mechanisms underlying evasive resistance in cancer is an unmet medical need to improve the efficacy of current therapies. In hepatocellular carcinoma (HCC), aberrant expression of hypoxia-inducible factor 1 α (HIF1α) and increased aerobic glycolysis metabolism are drivers of resistance to therapy with the multi-kinase inhibitor Sorafenib. However, it has remained unknown how HIF1α is activated and how its activity and the subsequent induction of aerobic glycolysis promote Sorafenib resistance in HCC. Here, we report the ubiquitin-specific peptidase USP29 as a new regulator of HIF1α and of aerobic glycolysis during the development of Sorafenib resistance in HCC. In particular, we identified USP29 as a critical deubiquitylase (DUB) of HIF1α, which directly deubiquitylates and stabilizes HIF1α and, thus, promotes its transcriptional activity. Among the transcriptional targets of HIF1α is the gene encoding hexokinase 2 (HK2), a key enzyme of the glycolytic pathway. The absence of USP29, and thus of HIF1α transcriptional activity, reduces the levels of aerobic glycolysis and restores sensitivity to Sorafenib in Sorafenib-resistant HCC cells in vitro and in xenograft transplantation mouse models in vivo. Notably, the absence of USP29 and high HK2 expression levels correlate with the response of HCC patients to Sorafenib therapy. Together, the data demonstrate that, as a DUB of HIF1α, USP29 promotes Sorafenib resistance in HCC cells, in parts by upregulating glycolysis, thereby opening new avenues for therapeutically targeting Sorafenib-resistant HCC in patients.

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Calcineurin, a calcium/calmodulin-regulated protein phosphatase, in mammalian neuroendocrine cells and neoplasms

Neuroscience Letters ◽

10.1016/0304-3940(92)90231-u ◽

1992 ◽

Vol 143 (1-2) ◽

pp. 51-54 ◽

Cited By ~ 6

Author(s):

Satoshi Goto ◽

Shinji Nagahiro ◽

Yukitaka Ushio ◽

Asao Hirano

Keyword(s):

Protein Phosphatase ◽

Neuroendocrine Cells ◽

Calcineurin A

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Nitric oxide modulates hypoxia-inducible factor-1 and poly(ADP-ribose) polymerase-1 cross talk in response to hypobaric hypoxia

Journal of Applied Physiology ◽

10.1152/japplphysiol.00898.2011 ◽

2012 ◽

Vol 112 (5) ◽

pp. 816-823 ◽

Cited By ~ 14

Author(s):

Rubén Martínez-Romero ◽

Ana Cañuelo ◽

Eva Siles ◽

F. Javier Oliver ◽

Esther Martínez-Lara

Keyword(s):

Nitric Oxide ◽

Hypobaric Hypoxia ◽

Reactive Oxygen Species Production ◽

Transcriptional Activity ◽

Hypoxia Inducible Factor ◽

No Production ◽

Oxygen Species ◽

Hypoxia Inducible Factor 1 ◽

Species Production ◽

Parp 1

The physiological response to hypobaric hypoxia represents a complex network of biochemical pathways in which the nitrergic system plays an important role. Previous studies have provided evidence for an interplay between the hypoxia-inducible factor-1 (HIF-1) and poly(ADP-ribose) polymerase-1 (PARP-1) under hypoxia. Here, we evaluate the potential involvement of nitric oxide (NO) in the cross talk between these two proteins. With this aim, we studied comparatively the effect of pharmacological inhibitors of NO production or PARP activity in the response of the mouse cerebral cortex to 4 h of exposure to a simulated altitude of 31,000 ft. Particularly, we analyzed the NO and reactive oxygen species production, the expression of NO synthase (NOS) isoforms, PARP-1 activity, HIF-1α expression and HIF-1 transcriptional activity, the protein level of the factor inhibiting HIF, and, finally, beclin-1 and fractin expression, as markers of cellular damage. Our results demonstrate that the reduction of NO level did not affect reactive oxygen species production but significantly 1) dampened the posthypoxic increase in neuronal NOS and inducible NOS expression without altering endothelial NOS protein level; 2) prevented PARP activation; 3) decreased HIF-1α response to hypoxia; 4) achieved a higher long-term HIF-1 transcriptional activity by reducing factor inhibiting HIF expression; and 5) reduced hypoxic damage. The pharmacological inhibition of PARP reproduced the NOS expression pattern and the HIF-1α response observed in NOS-inhibited mice, supporting its involvement in the NO-dependent regulation of hypoxia. As a whole, these results provide new data about the molecular mechanism underlying the beneficial effects of controlling NO production under hypobaric hypoxic conditions.

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

Molecular and Cellular Biology ◽

10.1128/mcb.23.14.4959-4971.2003 ◽

2003 ◽

Vol 23 (14) ◽

pp. 4959-4971 ◽

Cited By ~ 115

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.

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The calmodulin-dependent protein phosphatase catalytic subunit (calcineurin A) is an essential gene in Aspergillus nidulans.

The EMBO Journal ◽

10.1002/j.1460-2075.1994.tb06703.x ◽

1994 ◽

Vol 13 (16) ◽

pp. 3917-3924 ◽

Cited By ~ 38

Author(s):

C. Rasmussen ◽

C. Garen ◽

S. Brining ◽

R.L. Kincaid ◽

R.L. Means ◽

...

Keyword(s):

Aspergillus Nidulans ◽

Protein Phosphatase ◽

Essential Gene ◽

Catalytic Subunit ◽

Calcineurin A ◽

Dependent Protein

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Arabidopsis PP6 phosphatases dephosphorylate PIF proteins to repress photomorphogenesis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1907540116 ◽

2019 ◽

Vol 116 (40) ◽

pp. 20218-20225

Author(s):

Xiaodan Yu ◽

Jie Dong ◽

Zhaoguo Deng ◽

Yaping Jiang ◽

Chong Wu ◽

...

Keyword(s):

Protein Phosphatase ◽

Transcriptional Activity ◽

Light Exposure ◽

Whole Genome ◽

Wild Type ◽

Catalytic Subunits ◽

Genes Encoding ◽

The Stability

The PHYTOCHROME-INTERACTING FACTORs (PIFs) play a central role in repressing photomorphogenesis, and phosphorylation mediates the stability of PIF proteins. Although the kinases responsible for PIF phosphorylation have been extensively studied, the phosphatases that dephosphorylate PIFs remain largely unknown. Here, we report that seedlings with mutations in FyPP1 and FyPP3, 2 genes encoding the catalytic subunits of protein phosphatase 6 (PP6), exhibited short hypocotyls and opened cotyledons in the dark, which resembled the photomorphogenic development of dark-grown pifq mutants. The hypocotyls of dark-grown sextuple mutant fypp1 fypp3 (f1 f3) pifq were shorter than those of parental mutants f1 f3 and pifq, indicating that PP6 phosphatases and PIFs function synergistically to repress photomorphogenesis in the dark. We showed that FyPPs directly interacted with PIF3 and PIF4, and PIF3 and PIF4 proteins exhibited mobility shifts in f1 f3 mutants, consistent with their hyperphosphorylation. Moreover, PIF4 was more rapidly degraded in f1 f3 mutants than in wild type after light exposure. Whole-genome transcriptomic analyses indicated that PP6 and PIFs coregulated many genes, and PP6 proteins may positively regulate PIF transcriptional activity. These data suggest that PP6 phosphatases may repress photomorphogenesis by controlling the stability and transcriptional activity of PIF proteins via regulating PIF phosphorylation.

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