scholarly journals Synergistic activation of retinoic acid (RA)-responsive genes and induction of embryonal carcinoma cell differentiation by an RA receptor alpha (RAR alpha)-, RAR beta-, or RAR gamma-selective ligand in combination with a retinoid X receptor-specific ligand.

1995 ◽  
Vol 15 (12) ◽  
pp. 6481-6487 ◽  
Author(s):  
B Roy ◽  
R Taneja ◽  
P Chambon
Keyword(s):  
Retinoic Acid ◽  
Cell Differentiation ◽  
Target Genes ◽  
Retinoic Acid Receptor ◽  
Significant Degree ◽  
Retinoid X Receptor ◽  
Embryonal Carcinoma Cell ◽  
Synergistic Activation ◽  
Selective Ligand

Retinoic acid receptor (RAR)-retinoid X receptor (RXR) heterodimers bind to cognate response elements in vitro more efficiently than do RAR or RXR homodimers, and both RAR and RXR partners have been shown to activate various promoters in transiently transfected cells. We have now investigated whether ligand-dependent activation of both heterodimeric partners is involved in induced expression of endogenous RA-responsive genes and in P19 and F9 cell differentiation. On their own, low concentrations of retinoids selective for either RAR alpha, RAR beta, or RAR gamma did not induce or very inefficiently induced the expression of several RA target genes or triggered differentiation. An RXR-specific synthetic retinoid was similarly inefficient at any concentration. In contrast, at the same concentrations, various combinations of RAR (RAR alpha, RAR beta, or RAR gamma) and RXR selective retinoids resulted in synergistic induction of all retinoic acid (RA) target genes examined, as well as in cell differentiation. However, the magnitude of this synergistic activation varied depending on both the RAR-RXR combination and the promoter context of the responsive genes. Promiscuous activation of the three RARs, or concomitant activation of RAR alpha and RAR gamma, at selective retinoid concentrations also resulted in induction of gene expression and cell differentiation. Taken together, our results are consistent with the conclusion that the RAR and RXR partners of RAR-RXR heterodimers can synergistically activate transcription of RA-responsive genes and can induce differentiation of P19 and F9 cells. Our results also indicate that there is a significant degree of functional redundancy between the three RAR types which, however, varies with the nature of the RA target genes.

scholarly journals Distinct retinoid X receptor-retinoic acid receptor heterodimers are differentially involved in the control of expression of retinoid target genes in F9 embryonal carcinoma cells.

1997 ◽  
Vol 17 (6) ◽  
pp. 3013-3020 ◽  
Author(s):  
H Chiba ◽  
J Clifford ◽  
D Metzger ◽  
P Chambon
Keyword(s):  
Retinoic Acid ◽  
Embryonal Carcinoma ◽  
Target Genes ◽  
Retinoic Acid Receptor ◽  
Retinoid X Receptor ◽  
Embryonal Carcinoma Cell ◽  
Retinoid Receptor ◽  
Embryonal Carcinoma Cell Line ◽  
Control Of Expression

The F9 murine embryonal carcinoma cell line represents a well-established system for the study of retinoid signaling in vivo. We have investigated the functional specificity of different retinoid X receptor (RXR)-retinoic acid (RA) receptor (RAR) isotype pairs for the control of expression of endogenous RA-responsive genes, by using wild-type (WT), RXR alpha(-/-), RAR alpha(-/-), RAR gamma(-/-), RXR alpha(-/-)-RAR alpha(-/-), and RXR alpha(-/-)-RAR gamma(-/-) F9 cells, as well as panRXR and RAR isotype (alpha, beta, and gamma)-selective retinoids. We show that in these cells the control of expression of different sets of RA-responsive genes is preferentially mediated by distinct RXR-RAR isotype combinations. Our data support the conclusion that RXR-RAR heterodimers are the functional units transducing the retinoid signal and indicate in addition that these heterodimers exert both specific and redundant functions on the expression of particular sets of RA-responsive genes. We also show that the presence of a given receptor isotype can hinder the activity of another isotype and therefore that functional redundancy between retinoid receptor isotypes can be artifactually generated by gene knockouts.

scholarly journals Sufu regulation of Hedgehog signaling in P19 cells is required for proper glial cell differentiation

2021 ◽  
Author(s):  
Danielle M. Spice ◽  
Joshua Dierolf ◽  
Gregory M. Kelly
Keyword(s):  
Retinoic Acid ◽  
Cell Differentiation ◽  
Glial Cell ◽  
Neural Differentiation ◽  
Hedgehog Signaling ◽  
Target Genes ◽  
Cell Model ◽  
Ectopic Expression ◽  
Negative Regulator ◽  
Embryonal Carcinoma Cell

AbstractHedgehog signaling is essential for vertebrate development, however, less is known about the negative regulators that influence this pathway during the differentiation of cell fates. Using the mouse P19 embryonal carcinoma cell model, Suppressor of Fused (SUFU), a negative regulator of the Hedgehog pathway, was investigated during retinoic acid-induced neural differentiation. We found Hedgehog signaling was activated in the early phase of neural differentiation and became inactive during terminal differentiation of neurons and astrocytes. SUFU, which regulates signaling at the level of GLI, remained relatively unchanged during the differentiation process, however SUFU loss through CRISPIR-Cas9 gene editing resulted in decreased cell proliferation and ectopic expression of Hedgehog target genes. Interestingly, SUFU-deficient cells were unable to differentiate in the absence of retinoic acid, but when differentiated in its presence they showed delayed and decreased astrocyte differentiation; neuron differentiation did not appear to be affected. Retinoic acid-induced differentiation also caused ectopic activation of Hh target genes in SUFU-deficient cells and while the absence of the GLI3 transcriptional inhibitor suggested the pathway was active, no full-length GLI3 was detected even though the message encoding Gli3 was present. Thus, the study would indicate the proper timing and proportion of glial cell differentiation requires SUFU, and its normal regulation of GLI3 to maintain Hh signaling in an inactive state.

The Combination of 9-cis Retinoic Acid Plus MEK Inhibitor Induces Apoptosis Via Dephosphorylation of Retinoid X Receptor α in HL-60R Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1927-1927
Author(s):  
Nobuhiro Kanemura ◽  
Hisashi Tsurumi ◽  
Senji Kasahara ◽  
Takeshi Hara ◽  
Toshiki Yamada ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Cell Differentiation ◽  
Retinoic Acid Receptor ◽  
Biological Activities ◽  
Combined Treatment ◽  
Mek Inhibitor ◽  
Retinoid X Receptor ◽  
Dominant Negative ◽  
Expression Level ◽  
Hcc Cells

Abstract Resistance against retinoic acid (RA) is a serious problem of differentiation-induction therapy for acute promyelocytic leukemia (APL) in clinical practice. RA exerts its biological activities primarily through the nuclear receptor dimmer, consisting of retinoic acid receptor (RAR) and retinoid X receptor (RXR). Both receptors consist of three subtypes (α, β and γ) and form heterodimeric RAR/RXR and homodimeric RXR/RXR complexes. 9-cis RA, which is a high-affinity ligand for RXR but also binds to RAR, induces cell differentiation in wild type HL-60 human myeloid leukemia cells. However, in HL-60R cells, the RA-resistant subclone of HL-60, 9-cis RA can not induce cell differentiation and apoptosis. We recently reported that malfunction of RXRα due to posttranslational modification by phosphorylation to be associated with carcinogenesis of hepatocellular carcinoma (HCC). Phosphorylated form of RXRα (p-RXRα) at serine 260 by Ras/MAPK is resistant to ubiquitin/proteasome-mediated degradation and the accumulation of p-RXRα interferes with the function of remaining normal RXRα in a dominant negative manner, thereby promoting growth of HCC cells. We also found that in the presence of MEK inhibitor PD98059, 9-cis RA can induce the degradation of p-RXRα and thus restoring the function of this receptor in RXRα-phosphorylated human HCC cells. Based on the results as described above, we initiated this study to examine whether 9-cis RA can exert growth inhibitory effects on RA-resistant HL-60R cells when combined with MEK inhibitor, with focusing on the inhibition of expression of p-RXRα protein. We found that RXRα protein was originally expressed in both HL-60 and HL-60R cells, and that the expression level of RXRα protein was inhibited by about 60% and 20%, respectively, when those cells were treated with 0.5 μM 9-cis RA. Not only total RXRα protein, but also the level of p-RXRα protein was constitutively expressed in both HL-60 and HL-60R cells, and was significantly decreased in HL-60 cells by treatment with 9-cis RA alone. On the other hand, in HL-60R cells, 9-cis RA alone nor 20 μM PD98059 alone did not cause a down regulation of these proteins. However, when HL-60R cells were treated with the combination of 9-cis RA plus PD98059, the expression level of p-RXRα protein was markedly decreased. Moreover, the combination of these agents induced apoptosis in HL-60R cells, whereas similar effect was not obtained when the cells were treated with either agent alone. The combined treatment of these agents also cooperatively inhibited the growth of HL-60 R cells. The present findings suggest that the accumulation of p-RXRα might impair the function of normal RXRα as a master regulator of nuclear receptors and, thus, contributing to the resistance to RA in HL-60R cells. Combination of 9-cis RA plus MEK inhibitor might be an effective regimen for patients with RA resistant APL.

scholarly journals The Corepressor CTBP2 Is a Coactivator of Retinoic Acid Receptor/Retinoid X Receptor in Retinoic Acid Signaling

2013 ◽  
Vol 33 (16) ◽  
pp. 3343-3353 ◽  
Author(s):  
Prashanth Kumar Bajpe ◽  
Guus J. J. E. Heynen ◽  
Lorenza Mittempergher ◽  
Wipawadee Grernrum ◽  
Iris A. de Rink ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Rna Interference ◽  
Nuclear Receptor ◽  
Transcriptional Control ◽  
Target Genes ◽  
Retinoic Acid Receptor ◽  
Retinoid X Receptor ◽  
Gene Promoters ◽  
Acid Receptor ◽  
Receptor Complexes

Retinoids play key roles in development, differentiation, and homeostasis through regulation of specific target genes by the retinoic acid receptor/retinoid X receptor (RAR/RXR) nuclear receptor complex. Corepressors and coactivators contribute to its transcriptional control by creating the appropriate chromatin environment, but the precise composition of these nuclear receptor complexes remains to be elucidated. Using an RNA interference-based genetic screen in mouse F9 cells, we identified the transcriptional corepressor CTBP2 (C-terminal binding protein 2) as a coactivator critically required for retinoic acid (RA)-induced transcription.CTBP2suppression by RNA interference confers resistance to RA-induced differentiation in diverse murine and human cells. Mechanistically, we find that CTBP2 associates with RAR/RXR at RA target gene promoters and is essential for their transactivation in response to RA. We show that CTBP2 is indispensable to create a chromatin environment conducive for RAR/RXR-mediated transcription by recruiting the histone acetyltransferase p300. Our data reveal an unexpected function of the corepressor CTBP2 as a coactivator for RAR/RXR in RA signaling.

scholarly journals Accumulation of Retinoid X Receptor-α in Uterine Leiomyomas Is Associated with a Delayed Ligand-Dependent Proteasome-Mediated Degradation and an Alteration of Its Transcriptional Activity

2007 ◽  
Vol 21 (3) ◽  
pp. 602-612 ◽  
Author(s):  
Debora Lattuada ◽  
Paola Viganó ◽  
Silvia Mangioni ◽  
Jenny Sassone ◽  
Stefania Di Francesco ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Target Genes ◽  
Specific Inhibitor ◽  
Retinoid X Receptor ◽  
Uterine Leiomyomas ◽  
Full Length ◽  
Molecular Alteration ◽  
Ubiquitin Proteasome

Abstract An alteration of the retinoid pathway can influence the development of uterine leiomyomas in animal models, and retinoids have shown efficacy in inhibiting the growth of this benign tumor both in vitro and in vivo. However, the underlying mechanisms and biological implications are unclear. The present study was based on the demonstration of an accumulation of full-length retinoid X receptor α (RXRα) in leiomyomas that was not associated with a modification of its gene expression. This accumulation was shown to increase the transcription of the RXR-responsive gene cellular retinoic acid binding protein II (CRABP-II) and to be linked to the cellular redistribution of the receptor and to its retarded degradation via the ubiquitin/proteasome pathway. Accordingly, treatment with a specific proteasome inhibitor but not with protease inhibitors strongly inhibited the degradation of full-length RXRα in cells deriving from both myometrium and leiomyoma, but the formation of RXRα/ubiquitin conjugates was differentially regulated between the two cell types. Moreover, full-length RXRα accumulated in leiomyomas was abnormally phosphorylated at serine/threonine residues relative to myometrial tissue. The ligand to RXRα, 9-cis-retinoic acid, induced the receptor breakdown in smooth muscle cells deriving from both normal and tumor tissue, whereas a MAPK-specific inhibitor was able to reduce RXRα levels only in leiomyoma cells. These results suggest that switching of the ubiquitin/proteasome-dependent degradation of RXRα by phosphorylation in leiomyomas may be responsible for the accumulation of the receptor and the consequent dysregulation of retinoic acid target genes. The ability of retinoids to modify this molecular alteration may be the rationale for their use in the treatment of leiomyomas.

scholarly journals Synergy against PML-RARa: targeting transcription, proteolysis, differentiation, and self-renewal in acute promyelocytic leukemia

2013 ◽  
Vol 210 (13) ◽  
pp. 2793-2802 ◽  
Author(s):  
Guilherme Augusto dos Santos ◽  
Lev Kats ◽  
Pier Paolo Pandolfi
Keyword(s):  
Retinoic Acid ◽  
Acute Promyelocytic Leukemia ◽  
Target Genes ◽  
Retinoic Acid Receptor ◽  
Promyelocytic Leukemia ◽  
Nuclear Bodies ◽  
Pml Nuclear Bodies ◽  
Molecular Events

Acute promyelocytic leukemia (APL) is a hematological malignancy driven by a chimeric oncoprotein containing the C terminus of the retinoic acid receptor-a (RARa) fused to an N-terminal partner, most commonly promyelocytic leukemia protein (PML). Mechanistically, PML-RARa acts as a transcriptional repressor of RARa and non-RARa target genes and antagonizes the formation and function of PML nuclear bodies that regulate numerous signaling pathways. The empirical discoveries that PML-RARa–associated APL is sensitive to both all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO), and the subsequent understanding of the mechanisms of action of these drugs, have led to efforts to understand the contribution of molecular events to APL cell differentiation, leukemia-initiating cell (LIC) clearance, and disease eradication in vitro and in vivo. Critically, the mechanistic insights gleaned from these studies have resulted not only in a better understanding of APL itself, but also carry valuable lessons for other malignancies.

scholarly journals The MS remyelinating drug bexarotene (an RXR agonist) promotes induction of human Tregs and suppresses Th17 differentiation in vitro

2021 ◽  
Author(s):  
Christof Gaunt ◽  
Daniel Rainbow ◽  
Ruairi Mackenzie ◽  
Lorna Jarvis ◽  
Hani Mousa ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Retinoic Acid ◽  
Retinoic Acid Receptor ◽  
Retinoid X Receptor ◽  
T Regulatory Cell ◽  
Regulatory Cell ◽  
All Trans Retinoic Acid ◽  
Th17 Differentiation ◽  
Treg Development

AbstractThe retinoid X receptor (RXR) agonist bexarotene has recently been shown to promote remyelination in individuals with multiple sclerosis. Murine studies demonstrated that RXR agonists can have anti-inflammatory effects by enhancing the ability of all-trans-retinoic acid (αtRA), the primary active metabolite of vitamin A, to promote T regulatory cell (Treg) induction and reduce Th17 differentiation in vitro, following stimulation of naïve CD4 cells in the presence of TGF-β.Stimulating naïve human CD4 T cells for 7 days, in the presence of either Treg or Th17 skewing cytokines ± bexarotene (1 μM), ± other RXR agonists (9CisRA and NRX 194204), or ± αtRA (100 nM) shows that RXR agonists, including bexarotene, are capable of tipping the human Treg/Th17 axis in favour of Treg induction. Furthermore, this occurs independently of αtRA and retinoic acid receptor (RAR) signalling. Tregs induced in the presence of bexarotene express many of the canonical markers of T cell regulation and are functionally suppressive in vitro.These findings support a potential immunomodulatory role for bexarotene and highlight the possible therapeutic application of RXR agonists in autoimmune disease, with bexarotene’s pro-remyelinating effects making multiple sclerosis a particularly attractive disease target.Significance StatementThe pan-retinoid X receptor (RXR) agonist bexarotene has recently been shown to promote remyelination in patients with multiple sclerosis. Here we demonstrate that bexarotene, and other RXR agonists have immunomodulating effects, tipping the Th17/T regulatory cell (Treg) differentiation axis in favour of Treg development.These findings lend support to the idea of developing RXR agonists as treatments of autoimmune diseases, in particular multiple sclerosis.

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