Arsenic trioxide inhibits nuclear receptor function via SEK1/JNK-mediated RXRα phosphorylation
Koren K. Mann, … , Jonathan M. Kurie, Wilson H. Miller Jr.
Koren K. Mann, … , Jonathan M. Kurie, Wilson H. Miller Jr.
Published October 3, 2005
Citation Information: J Clin Invest. 2005;115(10):2924-2933. https://doi.org/10.1172/JCI23628.
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Research Article Oncology

Arsenic trioxide inhibits nuclear receptor function via SEK1/JNK-mediated RXRα phosphorylation

Abstract

We have previously published that 2 proven treatments for acute promyelocytic leukemia, As2O3 and retinoic acid, can be antagonistic in vitro. We now report that As2O3 inhibits ligand-induced transcription of the retinoic acid receptor, as well as other nuclear receptors that heterodimerize with the retinoid X receptor α (RXRα). As2O3 did not inhibit transactivation of the estrogen receptor or the glucocorticoid receptor, which do not heterodimerize with RXRα. We further show that As2O3 inhibits expression of several target genes of RXRα partners. Phosphorylation of RXRα has been reported to inhibit nuclear receptor signaling, and we show by in vivo labeling and phosphoamino acid detection that As2O3 phosphorylated RXRα in the N-terminal ABC region exclusively on serine residues. Consistent with our previous data implying a role for JNK in As2O3-induced apoptosis, we show that pharmacologic or genetic inhibition of JNK activation decreased As2O3-induced RXRα phosphorylation and blocked the effects of As2O3 on RXRα-mediated transcription. A mutational analysis indicated that phosphorylation of a specific serine residue, S32, was primarily responsible for inhibition of RXRα-mediated transcription. These data may provide some insight into the rational development of chemotherapeutic combinations involving As2O3 as well as into molecular mechanisms of arsenic-induced carcinogenesis resulting from environmental exposure.

Authors

Koren K. Mann, Alessandra M.S. Padovani, Qi Guo, April L. Colosimo, Ho-Young Lee, Jonathan M. Kurie, Wilson H. Miller Jr.

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Figure 7

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Endogenous nuclear receptor target induction is inhibited by As2O3 cotre...
Endogenous nuclear receptor target induction is inhibited by As2O3 cotreatment. (A) NB4 cells were treated for 8 hours with media, 10–5 M 9-cis RA plus 4 μg/ml 22(R)-hydroxycholesterol, 5 μM As2O3, or the combination of all 3 treatments. Cytoplasmic extracts (top 2 blots) were used in immunoblotting with anti-ABCA1 antibody or anti–β-actin antibody. Total RNA (bottom 2 blots) was used in Northern blotting for either ABCA1 or β-actin mRNA. (B) HepG2 cells were treated with media, 50 μM rifampicin, 5 μM As2O3, or the combination for 24 hours. Microsomes were isolated and used in immunoblotting experiments with anti-CYP3A4 antibody. Ponceau-stained band of microsomal extracts is presented as a loading control. (C) MCF-7 cells were treated with media, 10–9 M vitamin D3, 5 μM As2O3, or the combination for 24 hours. RNA was isolated and used in Northern blotting experiments with probes for vitamin D3 24-hydroxylase (top) and β-actin (bottom). (D) NB4 cells were treated for 24 hours with 10–6 M RA, 5 μM As2O3, or the combination. Total RNA was used in either RPAs (RARβ) or Northern blotting experiments (C/EBPε). β-Actin was used as a control in both RPA and Northern blot experiments.