Phosphorylation of human progesterone receptors at serine-294 by mitogen-activated protein kinase signals their degradation by the 26 S proteasome. Proc Natl Acad Sci USA

Department of Medicine, The Molecular Biology Program, and The Colorado Cancer Center, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 02/2000; 97(3):1032-7. DOI: 10.1073/pnas.97.3.1032
Source: PubMed


Ligand-dependent down-regulation that leads to rapid and extensive loss of protein is characteristic of several nuclear steroid receptors, including human progesterone receptors (PRs). In breast cancer cells, >95% of PRs are degraded 6 h after the start of progestin treatment. The mechanism for down-regulation is unknown. We examined the role of PR phosphorylation by mitogen-activated protein kinases (MAPKs) in this process. Lactacystin and calpain inhibitor I, specific inhibitors of the 26S proteasome, blocked progestin-induced down-regulation, and ubiquitinated conjugates of PR accumulated in cells. Ligand-dependent PR degradation was also blocked by specific inhibition of p42 and p44 MAPKs. To define the targets of phosphorylation by this kinase, two serine/proline MAPK consensus sites on PR were mutated. We demonstrate that mutation of PR serine-294 to alanine (S294A) specifically and completely prevents ligand-dependent receptor down-regulation. We also find that rapid, ligand-independent degradation of immature PR intermediates occurs by a proteasome-mediated pathway. These results demonstrate that PR destruction, by either of two alternate routes, is mediated by the 26S proteasome. Specifically, down-regulation of mature PRs occurs by a mechanism in which ligand binding activates PR phosphorylation by MAPKs at a unique serine residue, which then targets the receptors for degradation.

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    • "A number of EDCs have been shown to cause a nonmonotonic response in a number of vertebrate species. These responses can be from different molecular responses, such as proliferation versus apoptosis (Sonnenschein et al., 1989; Geck et al., 1997), a change in selectivity of a receptor or interaction at various doses or time points (Sohoni and Sumpter, 1998; Tilghman et al., 2010), desensitization of a receptor (Hoeck et al., 1989; Lange et al., 2000), or negative feedback as the case with estrogen-dependent dopamine release (Peter et al., 1986; Peter et al., 1986Peter et al., 1986; Vachar et al., 2002, Vetillard et al., 2003). Another possibility is that bifenthrin may alter different molecular pathways at differing time points. "
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    ABSTRACT: Bifenthrin is a type I pyrethroid pesticide, which has been shown to increase plasma estrogen concentrations in several fish models. The mechanism of action by which bifenthrin alters 17β-estradiol (E2) is unclear. E2 biosynthesis is regulated through pituitary follicle stimulating hormone, which is directly controlled by hypothalamic gonadotropin releasing hormone (GnRH2). Since dopaminergic signaling significantly influences GnRH2 release in fish, the goal of the study was to determine the effect of a 96h and 2 weeks exposure to bifenthrin on dopaminergic signaling in juvenile rainbow trout (Oncorhynchus mykiss) (RT). Our results indicated that a decrease in dopamine receptor 2A (DR2A) expression was associated with a trend toward an increase in plasma E2 following exposure at 96h and 2 weeks, and a significant increase in the relative expression of vitellogenin mRNA at 2 weeks. DR2A mRNA expression decreased 426-fold at 96h and 269-fold at 2 weeks in the brains of 1.5ppb (3.55pM) bifenthrin treated RT. There was an increase in tyrosine hydroxylase transcript levels at 96h, which is indicative of dopamine production in the brains of the 1.5ppb (3.55pM) bifenthrin treated RT. A significant increase in the relative expression of GnRH2 was observed at 96h but a significant decrease was noted after 2 weeks exposure indicating potential feedback loop activation. These results indicate that the estrogenic-effects of bifenthrin may result in part from changes in signaling within the dopaminergic pathway, but that other feedback pathways may also be involved. Copyright © 2015 Elsevier B.V. All rights reserved.
    Aquatic toxicology (Amsterdam, Netherlands) 03/2015; 162. DOI:10.1016/j.aquatox.2015.03.005 · 3.45 Impact Factor
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    • "These receptor modifications dramatically alter PR function, receptor localization and turnover, and promoter selectivity. The PR can be phosphorylated basally in the absence of the hormonal ligand, but is potently modified after ligand treatment, in response to local growth factors or in a cell cycle-dependent manner [12,13,15-17] (G. Dressing and C. Lange, unpublished data). "
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    ABSTRACT: The ovarian steroid hormone, progesterone, and its nuclear receptor, the progesterone receptor, are implicated in the progression of breast cancer. Clinical trial data on the effects of hormone replacement therapy underscore the importance of understanding how progestins influence breast cancer growth. The progesterone receptor regulation of distinct target genes is mediated by complex interactions between the progesterone receptor and other regulatory factors that determine the context-dependent transcriptional action of the progesterone receptor. These interactions often lead to post-translational modifications to the progesterone receptor that can dramatically alter receptor function, both in the normal mammary gland and in breast cancer. This review highlights the molecular components that regulate progesterone receptor transcriptional action and describes how a better understanding of the complex interactions between the progesterone receptor and other regulatory factors may be critical to enhancing the clinical efficacy of anti-progestins for use in the treatment of breast cancer.
    BMC Medicine 02/2014; 12(1):32. DOI:10.1186/1741-7015-12-32 · 7.25 Impact Factor
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    • "Interestingly, hormone-dependent down-regulation that leads to rapid and extensive loss of receptor is characteristic of other nuclear steroid receptors, including human progesterone receptors (PRs). In particular, in breast cancer cells, it has been demonstrated that PR is phosphorylated by ERK in Ser294 and degraded by a 26S proteasome-mediated pathway 6 hrs after treatment with progestin [18]. These results indicate that steroid hormones evoke surprising similar mechanisms to trigger receptor down-regulation. "
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    ABSTRACT: 17β-estradiol (E2)-dependent estrogen receptor (ER) α intracellular concentration is a well recognized critical step in the pleiotropic effects elicited by E2 in several target tissues. Beside E2, a class of synthetic and plant-derived chemicals collectively named endocrine disruptors (EDs) or xenoestrogens bind to and modify both nuclear and extra-nuclear ERα activities. However, at the present no information is available on the ability of EDs to hamper ERα intracellular concentration. Here, the effects of bisphenol A (BPA) and naringenin (Nar), prototypes of synthetic and plant-derived ERα ligands, have been evaluated on ERα levels in MCF-7 cells. Both EDs mimic E2 in triggering ERα Ser118 phosphorylation and gene transcription. However, only E2 or BPA induce an increase of cell proliferation; whereas 24 hrs after Nar stimulation a dose-dependent decrease in cell number is reported. E2 or BPA treatment reduces ERα protein and mRNA levels after 24 hrs. Contrarily, Nar stimulation does not alter ERα content but reduces ERα mRNA levels like other ligands. Co-stimulation experiments indicate that 48 hrs of Nar treatment prevents the E2-induced ERα degradation and hijacks the physiological ability of E2:ERα complex to regulate gene transcription. Mechanistically, Nar induces ERα protein accumulation by preventing proteasomal receptor degradation via persistent activation of p38/MAPK pathway. As a whole these data demonstrate that ERα intracellular concentration is an important target through which EDs hamper the hormonal milieu of E2 target cells driving cells to different outcomes or mimicking E2 even in the absence of the hormone.
    PLoS ONE 02/2014; 9(2):e88961. DOI:10.1371/journal.pone.0088961 · 3.23 Impact Factor
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